4456 4460.output

* GB784863 (A)

Description: GB784863 (A) ? 1957-10-16

Improvements in or relating to electron discharge devices employing photo-conductivetargets

Description of GB784863 (A)

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PATENT SPECIFICATION 78 Inventors: -HANS GERHARD LUBSZYNSKI and JOHN WARDLEY. Date of filing Complete Specification: July 7, 1955. Application Date: July 27, 1954 No 21832154. Complete Specification Published: Oct 16,1957. Index at Acceptance-Classes 37, K( 1 DUA: 2: 3 D: 3 R); and 39 ( 1), D( 41 H: 7 F 2). International Classification:-H Olj, I. COMPLETE SPECIFICATION. Improvements in or relating to Electron Discharge Devices Employing Photo-Conductive Targets. We, ELECTRIC & MUSICAL INDUSTRIES LIMITED, a British Company, of Blyth Road, Hayes, Middlesex, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following

statement:- This invention relates to electron discharge devices employing photo-conductive targets. Devices of this kind have been proposed for television and similar purposes in which the target comprises a layer of photo-conductive material which is deposited on a transparent signal electrode formed on a glass window of the envelope of the device and the target is arranged to be scanned by a cathode ray tube so as to generate signals in accordance with the point-to-point conductivity of the target when an optical image is projected thereon In one form of device the photoconductive layer is composed of antimony trisulphide which is deposited in the form of a spongy layer The glass window of the envelope in such devices is usually circular and the photo-conductive layer is usually deposited over the whole area of the window. In use, however, of such devices it is usually the practice to scan a rectangular raster the orientation of which relatively to the window depends on the disposition of the scanning means, which usually comprise scanning coils surrounding the envelope of the device. It is found when such devices are initially used or tested that if a rectangular raster is scanned on the target whilst the latter is illuminated uniformly, the scanned area has a lower resistance in the dark and a greater sensitivity compared with the unscanned area Furthermore, if a checker board image is projected on to the target and scanned in lPrice 3 s 6 d l a rectangular raster, it is found that the lighter areas of the scanned pattern have a lower resistance in the dark and higher sensitivity compared with the darker areas of the pattern These effects are permanent and are undesirable since it is obvious that a uniform sensitivity and dark resistance should be present over the whole of the area of the target, particularly since after initial use of the device re-orientation of the scanned area may occur. The object of the present invention is to provide a method of treating a photo-conductive target with a view to reducing the above-mentioned effects. According to the present invention there is provided a method of treating a photoconductive target arranged on an electrically conducting signal electrode with a view to imparting a substantially uniform sensitivity and dark resistance to the target which comprises bombarding substantially the whole area of the photo-conductive target with a high beam current whilst setting up a voltage gradient through the thickness of said target and whilst the target is illuminated with a uniform illumination. A voltage of the order of 150 volts with respect to the cathode may be applied to the signal electrode in order to set up a high voltage

gradient through the thickness of said target, although preferably, during treatment of the tube in accordance with the invention the voltage of the signal electrode is varied from a low voltage to a high voltage of the order of 150 volts and vice versa, In order that the said invention may be clearly understood and readily carried into effect, it will now be more fully described with reference to the accompanying drawing which illustrates a typical form of electron 1,363 784,863 discharge device employing a photo-conductive target. As shown in the drawing the reference numeral 1 indicates an evacuated envelope having a glass end wall 2 on which is formed a transparent signal electrode 3 having deposited thereon a photo-conductive target 4 which may consist of zinc sulphide or cadmium sulphide but preferably consists of a spongy layer of antimony trisulphide having a superimposed solid layer of antimony trisulphide Within the envelope 1 there is provided an anode 5, the end of which adjacent to the photo-conductive target 4 is provided with a mesh 6 At the end of the envelope 1 remote from the window 2 there is provided an electron gun comprising a cathode 7, a cathode screen 8 and a limiter electrode 9 The cathode 1 serves to generate a beam of electrons which can be scanned over the photo-conductive target 4 by means of scanning coils 10 The electron beam is maintained in focus by means of a solenoid coil 11 The device shown in the drawing is 2 ' also provided with the usual alignment coils 12. In order to avoid the undesirable effects hereinbefore referred to, the following procedure is adopted The device is conditioned for operation by connecting the cathode 7 to a source at zero voltage, the cathode shield to a source of voltage which may vary from 100 to zero volts, the limiter electrode 9 to a positive source of 300 volts and 3.5 the anode 5 to a similar source of voltage. The signal electrode 3 is connected to a source of voltage which can be varied from 0 to 150 volts positive whereby a voltage gradient can be set up through the thickness of the target 4 The usual current supply is applied to the coil 11 and to the alignment coil 12 and a suitable scanning waveform is applied to the coil 10 so as to enable the whole of the target area to be bombarded with electrons The electron beam is also defocused either by varying the normal current supply of the solenoid 11 or by varying the voltage of the electrode 8 or both and the beam current is adjusted to a high value. -50 With the device operating in this manner the whole of the target area is then illuminated with a uniform illumination from a light source indicated conventionally at 13, this illumination being of the order of 15 to -5 200 foot candles, and the voltage applied to the signal electrode 3 is then slowly made positive up to 150 volts and down to zero volts several times, say 2 to 6 times during a period of

20 seconds whilst the whole area of the target is scanned with said defocused beam The same process is then repeated with the target in the dark The scanning beam may employ a beam current of several microamperes, say up to 10 microamperes which is high compared with the normal operating beam current of, say, one to two microamperes Instead of applying a voltage to the signal plate 3 in order to set up the voltage gradient through the target 4 a similar voltage gradient can be established through the thickness of the photo-conductive target 4 by applying a suitable negative voltage to the cathode 7 It is desirable during the treatment of the device in the above manner to ensure that the impedance of the photo-conductive target 4 does not become too low, say as low as a few megohms (say 10), by employing too much illumination from the source 13 The method described above is found to result in an overall sensitivity gain of between 3 and 9 db over an untreated target and retention of images is found to be substantially avoided. ( 5 i O

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* GB784864 (A)

Description: GB784864 (A) ? 1957-10-16

Improvements in or relating to a device for supplying an electric out-putquantity in dependence upon an electric in-put quantity


PATENT SPECIFICATION 7849864 Date of Application and filing Complete Specification July 27, 1954. No 21987/54.

Application made in Germany on July 27, 1953. Application made in Germany on July 1, 1954. Complete Specification Published Oct 16, 1957. I Ldex at Act u,:-Classes 38 ( 2), TIF, T 7 (A 3: A 7 A 9: C 2: CS); 38 ( 4), R( 4: 21 B 3: 67); and ( 4), lr 93 International Classification: -GO Of H 02,L H 03 f. COMPLETE SPECIFICATION Improvements in or relating to a Device for Supplying an Electric Out-Put Quantity in Dependence upon an Electric In-Put Quantity We, SIEMENS-SCEUCKERTWERKE ARTIENGESELLSCHAFT, a German company, of Berlin and Erlangen, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to a device for supplying an output, in the form of an electric control quantity in dependence upon deviations from a standard value of an electric quantity which is to be regulated and is supplied as an input to the device. According to the present invention there is provided a device for supplying an output, in the form of an electric control quantity, in dependence upon deviations from a standard value of an electric quantity which is to be regulated and is supplied as an input to the device, wherein a magnetic bridge is provided, the arms of the bridge including a permanent magnet acting as a source of a magnetic standard value and an electromagnet arranged to be energised by said electric quantity and to furnish a unidirectional flux accordingly, there being provided a choke having a doublelimbed core arranged to act as a diagonal of the bridge in such manner that the core carries, in the same direction in each limb, a flux determined by the difference between the flux of the permanent magnet and that of the electromagnet, and wherein each limb of the chokce core is provided with a winding so that the effective impedance of such windings is controlled by said difference, said windings being arranged to carry alternating current which constitutes, or is arranged to furnish, said electric control quantity and, in consequence of the control upon said effective impedance, is controllable in dependence upon the deviation of said electric quantity from a standard value, the choke windings being so connected that the alternating fluxes which they produce are substanlly confined to the magnetic circlit which is constituted by the choke core and which includes both limbs thereof. Preferably, the two windings of the choke are electrically series-connected Since the two alternating fluxes tend to become equal owing to the use of a common core, the normal behaviour of a series choke is disturbed, and a small alternating flux remains which flows

through the magnetic path provided by the arms of the bridge However, this does not affect the satisfactory operation of the choke. In the known arrangements the whole alternating flux must pass through the arms of the bridge. The effective permeability of the choke core, and hence the impedances of the choke windings, varies according to the flux passing through the choke Thus if an alternating auxiliary voltage is applied to the choke windings, the alternating current which is set up in the choke windings depends not only upon the value of that voltage but also upon the value of the input quantity (that is, for example, the value of a quantity to be regulated) which is converted in the electromagnet of the bridge into a magnetic measurement value In order to obviate the dependence upon the auxiliary voltage a second choke is preferably employed to which is applied the input quantity (by means of an electromagnet) and an auxiliary alternating voltage of the same value as that applied: in the first choke and preferably being obtained from the same source The difference between the alternating currents of the two chokes, if necessary after rectification thereof, or a quantity the value of which depends on such difference is employed as the output quantity of control quantity of the device The second choke may be pre-magnetised in dependence upon the quantity to be regulated In this case, if the permanent magnet of the first choke develops a flux greater than that of the associated electromagnet, and if 'the second choke has no permanent magnet whereby the 784,864 advantage is afforded that as the quantity to be regulated increases, a decrease in the premagnetisation of the first choke core occurs, while an increase in the premagnetisation of the core of the second choke occurs, so that when the quantity to be regulated has a certain value the premagnetisations of the two chokes and consequently also the alternating currents in the windings of the chokes are equal The differential effect of the currents in the windings of the two respective chokes is then zero. In order to obtain a substantially linear relationship between the premagnetisation of the choke core and the quantity to be regulated, one or more air-gaps are preferably provided in the magnetic circuit and are formed in the second choke in the core thereof and in the core of the electromagnet. A simplification may be effected by employing an electromagnet, which is energised in dependence upon the quantity to be regulated and is common to both the magnetic circuit of the bridge and to the magnetic circuit of the second choke. For increasing the sensitivity of regulation, it may prove expedient to energise the electromagnet additionally in dependence upon the output quantity of the system, that is to say, to use a form of

feedback. For obtaining a large working range with a changing value of an auxiliary alternating voltage feeding the choke, and of the frequency thereof, it is desirable to employ for the choke cores a material having a magnetisation curve or hysteresis loop of approximately rectangular form. The permanent magnet is preferably constructed of high-grade permanent-magnet material, such for example as the known aluminium-nickel-cobalt alloys, with a view to reducing the space occupied For the remaining parts of the magnetic circuits, apart from the choke core and the permanent magnet, a magnetic material of low coercivity, such for example as carbonyl iron, is preferably employed. If a second choke is used for obviating the influences of fluctuations of the auxiliary alternating voltage with which the first choke is fed, and the second choke is fed with an alternating voltage of the same value as the first voltage, and if the differential effect of the alternating currents in the tvw chokes are employed as a control quantity after rectification, an arrangement may be used in which a separate rectifier is not required to rectify the current flowing through each of the chokes, but, instead, a rectifier system common to the two chokes may be employed, which feeds a control winding. Thus, while, for example, a rectifier comprising four rectifying elements can be employed in a bridge connection for each choke, a total of only four rectifying elements need be utilised if the two sets of leads by which the two chokes are fed with alternating voltages, or windings generating these voltages, are connected together at one pole In this case, like terminals, referred to the direction 70 of the alternating voltages, can be coupled together, or opposite terminals can be connected together A control winding, for example which form part of a magnetic amplifier, is provided with a centre tapping which 75 is joined to the connection point of the two voltage sources or windings. If like terminals of the windings or voltage sources are connected together the whole current of each choke flows through the control 80 winding The difference between the two choke currents in the control widding is thus effective as an ampere-turns difference at the amplifier On the other hand, if a coupling between opposite terminals of the windings or 85 alternating-voltage sources is employed, the difference between the two rectified alternating currents flows direclly through the control winding The control winding therefore only requires to be designed for the difference of 90 the currents of the chokes in this case. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made to the

accompanying drawings in which: 95 Fig 1 is a diagrammatic drawing of an electromagnetic crontrolling device, Fig 2 is a diagrammatic drawing of an electromagnetic controlling device with associated circuits, 100 Fig 3 is a diagrammatic drawing of an electro-magnetic controlling device with associated circuits, and Figs 4, 5 and 6 are electric control circuits. Referring now to the drawings, ln Figure 105 1, 1 designates a clhoki core asszmbly with two working windings 2 and 3, tih of which are arranged to carry alteona:ins current This choke assembly forms ahe diagonal branch of a magnetic bridge, the arms of the bridge com 110 prising a permanent magnet 4, an electromagnet serving as an actual-value converter and comprising a core 5 and a w-vinding 6, two yoke pieces 7 and 3, and two air gaps 9 and 10. The winding 6 carries a controlling d c 115 current derived from the actual value, i e the quantity to be regulated The difference between the magnetic fluxes prcluzed by the permanent magnet 4 and the electromagnet ( 5-6) produces a premagnetising unidirec 120 tional flux in the choke core 1, this flux acting in the same direction in each limb of the choke. However, the flux produced by the alternating current windings circulates around the choke so that in any half-cycle, the unidirectional and 125 alternating fluxes are additive in one limb and oppositely directed in the other. In one half-cycle of the alternating current, one limb of the choke core therefore remains substantially saturated, and at the same time 130 784,864 the other limb is unsaturated and is capable of producing a reactive voltage in the choke wind ing thereon The value of the premagnetising unidirectional flux in the choke core depends upon the value of the input quantity, that is, for example, on the quantity to be regulated, due to the formation of the difference between the unidirection fluxes of the permanent magnet and of the electromagnet, so that an alternating current in the choke windings varies in accordance with the in-put quantity. In Figure 2, A is a controlling device corresponding to the one shown in Figure 1, the same references have therefore been retained for like parts for the sake of simplicity. Associated with the device A is a second controlling device 13 in which the core 11 of a choke has windings 12 and 13 Two yoke pieces 14 and 15 co-operate through air gaps 16 and 17 with the core 18 of an electromagnet, the associated winding of which is designated by 19 The winding 6 of the converter for the actual measurement value in the form of the electromagnet ( 5-6) is fed, through a resistance 20, with a current which depends upon, for example the quantity to be regulated, from conductors 21 A current is produced, by the same

voltage as e:ists between conductors 21, and fed to the winding 19 of the electromagnet ( 18-19) of the device B through the resistance 22. The windings ( 2 and 3) of the device A are fed from secondary winding 23 a of a transformer 23, at the primary winding 23 b of which an alternating voltage exists The windings 12 and 13 of the device B are fed from another secondary winding 23 c of the transformer 23, which winding supplies a voltage of the same value as that supplied by the winding 23 a The choke current of the device A is rectified by a fourelement rectifier 24 and Passed through a load The choke current of the device B is rectified by a four-element rectifier 26 and passed through a load 27 The two loads 25 and 27 may be, for example, control windings of a magnetic amplifier which is to be controlled. Alternatively, a separate control winding of a magnetic amplifier may be connected to the terminals 28 and 29, and be supplied with a feed voltage equal to the difference between the voltages across the load resistances 25 and 27. The device B co-operates with the device A so that a difference voltage corresponding to the two altertating currents in the chokes of the devices A and B is set up at the output, for examples at the terminals 28 and 29 If the chokes of devices A and B are equally premagnetised, the two choke currents are equal, regardless of the value of the auxiliary alternating voltage applied to the transformer or of the frequency of this voltage. In Figure 3, like narts are again designated by the same reference numerals, insofar as they are equivalent to the parts shown in Figures 1 and 2, with the exception of the two electromagnets ( 5-6) and ( 18-19) of the devices A and B. In Figure 2 the devices A and B are spati 70 ally independent units, but in Fig 3 they are shown as permanently associated together as units A' and B', and they now have a common electromagnet with a core 30 and a winding 31 which is fed from terminals 21 through a 75 resistance 32 with a current derived from the actual value The electromagnet has a further winding 33 which is fed with a current derived from an output quantity of the system at the ends of load resistances 25 and 27, so that the 80 output quantity is fed back to the device. The expenditure in a device as shown in Figure 3 is reduced in relation to that of the device shown in Figure 2. With an actual quantity of a predetermined 85 value at the terminals 21, the premagnetisation in the two chokices units A' and B' is equal in value, so that the difference between their rectified alternating currents is zero If the flux produced by the permanent magnet 4 is greater 90 than that produced by the electromagnet, an increase of the actual value at the terminals 21 brings about a decrease of unidirectional flux in the choke core 1 so that the permeability of

this core increases Thus the impedance of 95 the windings 2 and 3 increases so that the chokice current of the unit A' decreases That of the choke in unit B' also increases Conversely, if the actual value at the terminals 21 decreases, the choke current of the unit A'100 increases, while that of the unit B' simultaneously decreases The differential effect of the output currents acting through the loads 25 and 27 accordingly varies in value and direction in dependence upon the deviation of the 105 actual value from a reference value, predetermined by the permanent magnet. It is expedient to employ a material for the choke cores, for example 1 and 11, having a hysteresis loop which is as far as possible rect 110 angular The yoke pieces 7, 8, 14 and 15 and the core of the electromagnet 30 are preferably constructed of a material having low coercivity. The permanent magnet preferably consists of a material of high coercivity with high remanent 115 induction, for example of an aluminium-nickelcobalt alloy. In Figure 4, 101 designates a transformer which feeds the windings of two chokes 102 and 103 corresponding to the chokes of the 120 units previously described Only the working windings of the chokes 102 and 103, which chokes correspond to the chokes A, B and A' B' of Figures 2 and 3 respectively, are shown. One terminal of one secondary winding of the 125 transformer 101 is connected to a like terminal of the other secondary winding The two chokes are connected to a common rectifier system comprising rectifying elements 104 a to 104 d The control winding 105 of a 130 784,864 magnetic amplifier is connected to the output of this rectifier system 104 A centre tapping a of winding 105 is connected to the common connection of the two secondary windings of the transformer 101 During one halfcycle of the alternating current, the current of the choke 102 flows through the element 104 b and the upper half of the control winding 105 to the common connecting point of the two secondary windings of the transformer At the same time, the current in the choke 103 flows through the element 104 d and the lower part of the control winding 105 to the common connecting point of the two secondary windings of the transformer 101 The arrows indicate the magnetic energisations produced by the windings For the above described halfcycle, the arrows are drawn as continuous lines. During the other half-cycle, the currents flowing through the windings produce magnetisations in the two halves of the winding 105 as indicated by the broken-lined arrows. In Figure 5, the same references have again been used for the same parts as in Figure 4. As will be seen from the figure, opposite terminals of the two

secondary windings of the transformer 101 are connected together in this case In one half-cycle of the alternating current, the current flows through the choke 102 and through the rectifier element 104 b, and back through the upper half of the control winding 105 to the common point of the two secondary windings At the same time, the current flows by way of the choke 103 through the upper half of the winding 105 and the rectifying element 104 c, back to that terminal on the secondary side of the transformer which is associated with the choke 103 This is indicated by the arrows drawn in continuous lines in the figure. It will be seen from this that only the difference between the currents in the tw Vo chokes 102 and 103 flows through the upper half of the control winding 105 In the other half43 cycle of the alternating current, this difference current similarly flows through the lower half of the control winding 105, as indicated by the broken-lined arrows. In this arrangement, the reztifie: elements are only subjected to a very small inverse voltage, because the inverse voltage which the elements 104 a and 104 d have to block in common is equal to the volt drop in the forward direction across the elements 104 b and 104 e. Figure 6 of the drawings illustrates a complete arrangement in which a regulating arrangement as shown in Figures 4 or 5 is employed In this arrangement, 106 is a device 6 C for supplying an electrical control quantity which includes the arrangement shown in Figure 4 or Figure 5 with the exception of lthe control winding 105, which is formed in this figure by two windings 107 and 108 109, 110 and 111 are connecting conductors leading to a three-phase current supply system, from which a load is fed through saturable regulating chokes 112 and a transformer 113, through a rectifier 114 having a smoothing device 115 connected thereto and through the 70 terminals 116 and 117 The voltage at the load terminals 116 and 117 is fed, as a quantity to be regulated, through the conductors 118 and 119 to the regulating arrangement 106 The actual value may be adjusted by variation of 75 the resistance 120 The aforesaid windings 107 and 108 form a control winding of a magnetic amplifier 121 The said amnlifier also comprises two working windings 123 and 124 fed by an alternating-current source 122, which 80 is so connected with rectifying elements 125 to 128 that a direct voltage is supplied at the output terminals 129 and 130 of the arrangement The amplifier feeds, through a resistance 131 a control winding 132 having the terminal 85 connections a-b This control winding is associated with the chokes 112, as may be seen fromn the illustration this winding also being shown at the choke 112 The winding 132 is shown twice for ease of illustration A 90 further winding 133 having the terminals c and d is fed in the oppsite

direction through the resistance 134 by the voltage across the terminals 116, 117 This winding is also again shown with the same reference 133 at the 95 chokes By reason of the fact that the chokes 112 are designed as so-called rectifier chokes, with which a rectifying element is connected in series with each of the alternating-current lworking windings, so that only one half-cycle 100 fisws through one of the working windings and only the other half-cycle throuah the other workzing winding, a load-dependent pre-magnetisation of the choke is obtained It will be assumed by way of example in accordance with 105 the arrows placed above and below of the windings 132 andl 133 and in accordance with the rectifier s-ymbol placed ab:ve the winding 132 that in the hai,-cele of the alternating current considered the rectifvin elements hay 11 C ing the forward direction is effective for the load current The rectifying element thus determnines the direction of the rremagnetisation, which is '3 roduced at the choke 112 in depnsdepne upon lead At the same time, the 115 winding 132 surplics, in the case assumed, a minagnetisation in the direction of the arrow indicated above by this winding When the voltage across the load terminals ( 116-117) increases, the arrangement 10 supplies a con 120 trol current through the windings ( 107-108) to the amnlifier 121 in the sense that the outnut voltage across the terminals ( 129 130) and consequentlv the current through the w.inding 132 in the direction rb-) increases 125 Thus thle effective premagnertisation of the chokse 112 decreases so that the impedance of its load windings increases This brings about an increase in the voltage drop across the load windings of the choke 112 and consequently 130 arms of the bridge including a permanent magnet acting as a source of a magnetic standard value and an electromagnet arranged to be energised by said electric quantity and to furnish a unidirectional flux accordingly, there 70 being provided a choke having a doublelimbed core arranged to act as a diagonal of the bridge in such manner that the core car-. ries, in the same direction in each limb, a flux determined by the difference between the flux 75 of the permanent magnet and that of the electromagnet, and wherein each limb of the choke core is provided with a winding so that the effective impedance of such windings, is controlled by said difference, said windings being 80 arranged to carry alternating current which constitutes, or is arranged to furnish, said electric control quantity and, in consequence of the control upon said effective impedance, is controllable in dependence upon the devia 85 tion of said electric quantity from a standard value, the choke windings being so connected that the alternating fluxes which they produce are substantially confined to the magnetic circuit which is constituted by the choke core 90 and which includes

both limbs thereof.


* GB784865 (A)

Description: GB784865 (A) ? 1957-10-16

Improvements in or relating to quick cooking rice

Description of GB784865 (A) Translate this text into Tooltip



c; -% I N -, ' q 41 ' -7 4 4 PATENT SPE Ci FICATION 7894,g 5 Date of,, i tion and Filing Ccmplet 6 Specification: Aug31, 1954 1 N'o2522/54. Application made in United States of America on Sept IQ,; 953. f Patent of Addition to No 657,691 dated April 22, 19 X 8 as imprc'er use or modified by No 737,372 dated Feb 8, 195 'L Complete Specification Published: Oct 16, 1957. Index at Acceptance:-Class 58, A 3 B, AH( 3: 4 A: 4 C: 6 D). International Classification:-B 02 b. COMPLETE SPECIFICATION Improvements in or relating to Quick Cooking Rice. E Ri ATA SPECIFICATION NO 784, 865

Page 3, line 42, for irt read air,. Page 4, line 68, for,isomewhate read "scaeiat THE PAT Ei NT OFFICE, 25th A Tovember, 1957 in the external portions or sheath of the rice grain should comprise moist, substantially completely gelatinized starch in a completely pliable condition, as set forth in the above-mentioned specification, the internal portions or core of the grain need not be relatively brittle but may range from this condition (i e, partially gelatinized and relatively brittle) to a condition of substantially complete gelatinization and pliability. If the internal portions have not been gelatinized at all, the degree of brittleness is too high for the purpose of the present invention But rice which has been soaked to 'n about 30 % moisture and then steamed to fully gelatinize the exterior portions while the interior portions are only slightly gelatinized, and also rice which has been fully gelatinized, dried and then steamed briefly to moisten only the exterior portions of the grain, are both suitable for application of the step of mechanical compression So also is a rice grain having fully pliable exterior portions along with interior portions of substantially equal pliability Thus it will be seen further that the moisture content of 34 ,% mentioned in the above specification is not a limiting value. According to the present invention there DB 00840/1 ( 22)/3606 150 111/57 R increase its moisture cunot Lrut LU a uuataial degree, say, 17-36 %, preferably 25 %, and steamed to partially or completely gelatinize the rice and further increase its 65 moisture content, say, by 1-8 %, but as a rule not to exceed 40,/o The rice is coimpressed and then dried in any suitable manner. 2 Ungelatinized, milled rice is soaked to 70 increase its moisture content to a substantial degree, say, 17-36 %, preferably 25 35 %, and steamed to completely gelatinize the rice and further increase its moisture content, say, by 1-8 %, but as a rule not to ex 75 ceed 40 % The rice is mechanically compressed and placed in water to increase its moisture content to 60-70 % On the other hand, after steaming as above described, the rice may be soaked in water to raise its 80 moisture content to 60-70 % as above and thereafter compressed Preferably, the rice is contacted with the soaking water while still hot from the steaming since this provides the rice in an enlarged condition which 85 greatly facilitates soaking At a moisture content appreciably above 70 % the advantages of compression are not as great as when the rice contains less moisture The rice is then dried in any suitable manner, 90 PATENT SPECIFICATION Dcte of Appiication and Filing Complete Specification: Aug31, 1954 No 25239/54. Application made in United States of America on Sept 10, 1953.

(Patent of Addition to No 657,691 dated April 22, 1948 as improved upon or modified by No 737,372 dated Feb 8, 1951). Complete Specification Published: Oct 16, 1957. Index at Acceptance:-Class 58, A 3 B, AH( 3: 4 A: 4 C: 6 D). International Classification:-BO 2 b. COMPLETE SPECIFICATION Improvements in or relating to Quick Cooking Rice. 1, A 1 AULLAH KHAN OZAI-DURRANI, a citizen of the United States of America, of 7th Street, and Grand Avenue, Stuttgart, Arkansas, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to a method of preparing a quick cooking rice product and to the rice product itself. The present invention is an improvement in or modification of earlier Specification Serial No 737,372. It has been found that while the starch in the external portions or sheath of the rice grain should comprise moist, substantially completely gelatinized starch in a completely pliable condition, as set forth in the above-mentioned specification, the internal portions or core of the grain need not be relatively brittle but may range from this condition (i e, partially gelatinized and relatively brittle) to a condition of substantially complete gelatinization and pliability. If the internal portions have not been gelatinized at all, the degree of brittleness is too high for the purpose of the present invention But rice which has been soaked to about 30 ,,, moisture and then steamed to fully gelatinize the exterior portions while the interior portions are only slightly gelatinized, and also rice which has been fully gelatinized, dried and then steamed briefly to moisten only the exterior portions of the grain, are both suitable for application of the step of mechanical compression So also is a rice grain having fully pliable exterior portions along with interior portions of substantially equal pliability Thus it will be seen further that the moisture content of 34 %,h mentioned in the above specification is not a limiting value. According to the present invention there is provided a process for preparing qui 2 cooking rice which comprises suijectini rice grains, having exterior portions of moist, substantially completely gelantinized starch in a completely pliable condition and 50 interior portions ranging from relatively brittle, at least partially gelatinized starch to substantially completely gelatinized starch in a completely pliable condition, to mechanical compression to distort and

modify 55 the structure of the rice grains without ducing them to a flaked condition. The following procedures illustrate by way of example various ways in which the invention can be carried out: 60 1 Ungelatinized, milled rice is soaked ti increase its moisture content to a substantial degree, say, 17-36 %, preferably 25%, and steamed to partially or completely gelatinize the rice and further increase its 65 moisture content, say, by 1-8 %, but as a rule not to exceed 40 % The rice is compressed and then dried in any suitable manner. 2 Ungelatinized, milled rice is soaked to 70 increase its moisture content to a substantial degree, say, 17-36 %, preferably 25 35 %, and steamed to completely gelatinize th 3 rice and further increase its moisture content, say, by 1-8 %, but as a rule not to ex 75 ceed 40 % The rice is mechanically compressed and placed in water to increase its moisture content to 60-70 % On the other hand, after steaming as above described, the rice may be soaked in water to raise its 80 moisture content to 60-70 % as above and thereafter compressed Preferably, the rice is contacted with the soaking water while still hot from the steaming since this provides the rice in an enlarged condition which 85 greatly facilitates soaking At a moisture content appreciably above 70 % the advantages of compression are not as great as when the rice contains less moisture The rice is then dried in any suitable manner,90 preferably at relatively high temperature cient to raise the moisture content to about and air velocities 30 % Such soaked grains have the non3 Ungelatinized, milled rice is soaked to uniform moisture distribution described in increase its moisture content to a substant our above specification, and when they are ial degree, say, 17-36 %o, preferably 25-35 %, heated for brief periods, the pliable sheath 70 and steamed briefly to render only the sur and brittle core described in our above face portion of the grains pliable and gelat specification are produced, as well as the inized The rice is compressed, steamed for results of compression and drying therein an additional period to complete gelatini described The same results are obtained zation throughout the rice grains and then when parboiled or otherwise pregelatinized 75 dried in any suitable manner Before dry dry rice grains are moistened, compressed ing the rice may be soaked in hot or cold and dried as in procedures 5 and 7 outwater as desired to increase its moisture lined above. content to 60-70 %O in which case it is pre But relatively long periods of heating the ferably dried using relatively high tempera soaked grains will produce grains that ares O tures and air velocities substantially completely pliable throughout. 4 Dried, milled rice, either ungelatinized A similar condition is produced when the or parboiled or otherwise gelatinized, is grains,

either ungelatinized or parboiled, placed in hot or boiling water to raise the are placed in hot or boiling water to inmoisture content to 60-70 %, and in the crease their moisture content to about 60-85 case of the former, effect gelatinization The 700, as in the fourth procedure, and when rice is compressed and thereafter dried, pre previously gelatinized rice is steamed long ferably at relatively high temperatures and enough to increase its moisture content to air velocities 17-25 /as in the sixth procedure in the 5 Dried, milled, parboiled or otherwise eighth procedure on the other hand the 90 gelatinized rice is contacted briefly with external portions after drying may be somewater to moisten the surface of the grains what less moist and hence less pliable than and then steamed for a short period, the the internal portions but are still sufficiently moistening and steaming serving to increase pliable to prevent disintegration of the the overall moisture content of the rice by grains during compression 95 1-5 %, the bulk of the moisture being con In the preferred e-ibodilment of the incentrated at the surface of the grains The vention, ungelatinized milled white rice (the rice is then mechanically compressed and ordinary rice of commerce) is treawed subdried in any suitable manner stantially as set foth in our above specifica6 Dried, parboiled or otherwise gelatin tion except that the moisture content after 100 ized rice is steamed for a sufficient time to soaking ma sometimes be hioher than increase the overall moisture content of the specified therein say 36 and mray somerice to 17-25 %' and render the entire grain times be inceased during steaming by as fully pliable The rice is then mechanically much as 8-,; at such higher moisture concompressed and dried in any suitable man tents the steaming period may be as little 105 ner In the case of rough rice, the com as 3 minutes Compression of the grains pression step serves to crack and loosen the then takes place between rolls as set forth hulls which may be separated from the in our above specification. grains in any conventional manner in the case of grains having relatively 7 Dried, milled, parboiled or otherwise high moisture contents, e g, in the neigh 10 gelatinized rice is placed in cold water for a bourhood of 65 %, a press may be preperiod of time sufficient fo raise its moisture ferred to rolls in order to avoid undue disto 30-70 %, say, 30-60 minutes The rice is integration of the grains. then compressed and dried While any suitable drying method can be 8 Ungelatinized, milled rice is soaked to employed, circulation of heated air through 115 increase its moisture content to a substanial a bed of rice is highly efficient and usually degree, say 30 %,0, steamed to substantially to be preferred Any temperature may be fully gelatinize the grains throughout and used below that at which

scorching or disincrease its moisture content to about 350,', coloration occurs say 375 4 f J O F ShrinkThe rice is then dried in any conventional age may occur at temperatures of the order 120 manner to 17-25 %, compressed and dried of 150 '-200 F, however and when the It is preferred that a tempering step be em moisture content of the rice is high, say ployed after the first drying step so that the 55-70 %, temperatures and air velocities of moisture distribution within the grains may the order of 280 F and 200 ft /mill are be uniform and the moisture of the exterior preferred In the case of relatively low 125 portions be thereby increased so that said moisture content, say 17-40 K, still higher portions will have greater pliability temperatures of the order of 325 '-350 'F. When it is desired to soak the rice prior have the advantage of producing a slight ento steaming or cooking, 30 minutes soak largement of the grains. ing at room temperature is generally suffi EXAMPLE I 130 784,865 784,865 pounds of ungelatinized white rice ith a moisture content of about 12 are placed in a 100 gallon vessel or tank together with about 60 gallons of water and allowed to soak for 30 minutes at room Temperature ( 75 F) Thereafter the rice is transferred from the tank to a screen and allowed to drain for 15 minutes At this point the rice contains about 30 %,' of moisl: ture Satisfactory results are obtained in accordance with this embodiment of the invention if the conditions of soaking are varied so that the moisture content may range from about 17 %, to about 36 %, preferable results are obtained at 25-35 %. Then the rice is transferred to an 80 gallon autoclave and treated with dry steam at 8 pounds gauge pressure for 5 minutes at the end of which time the outer portions of the rice grains are substantially completely gelatinized containing no birefringent material and the inner portions while somewhat gelatinized still contain an appreciable amount of ungelatinized starch granules or birefringent material The overall moisture content of the grains after steaming is about 34 %- 7 Generally, rice prepared in this manner may have a moisture content of about 17-40 %, and be suitable for compression The rice grains are then removed from the cooker and transferred to a conveyor belt, being spread out thereon in a layer about one grain thick The grains are thus conveyed to and passed between smooth rolls set to reduce the thickness of the grain to about % of their thickness before compression. After passing through the rolls the rice is dried in any conventional manner to a stable moisture content of 10 to 14 % A convenient and rapid way of effecting drying is to employ a forced draft, hot air drier using ir at 325 -350 F, the drying being effected in 5-10 minutes The product has a density of 0 70 g /cc It is then packaged

and distributed in the usual commercial manner. EXAMPLE II pounds of ungelatinized white rice with a moisture content of about 12 % is placed in a 100 gallon vessel or tank together with about 60 gallons of water and allowed to soak for 30 minutes at room temperature ( 75 F) Thereafter, it is transferred from the tank to another tank containing boiling water and boiled for about 10 minutes to fully gelatinize an hydrate the grains raising their moisture content to 65 % The rice is then cooled and transferred to a horizontally moving screen o 60 from the end of which it falls onto one of a pair of smooth compression rolls spaced apart sufficiently to compress the grains to about 70 %, of their thickness before compression In order to facilitate handling at to this point a stream of cold water is played onto the same roll onto which the rice grains are deposited so that at the time of compression the grains are in effect slurriel in water this prevents the grains from sticking to the rolls so that disintegration is 70 prevented oi at least minimized From the rolls the compressed rice grains and the water fall onto a horizontally moving screen The rice grains are drained in the first tfew feet of their travel on the con-75 veyor Thereafter, hot air at a temperature of about 285 F is blown upwardly through the bed of rice grains at an air velocity of about 200 feet per minute If desired, at a subsequent point in the screen's travels the 80 hot air may be passed downwardly through the bed of rice grains In this manner, the relatively enlarged size of the grains resulting from the complete gelatinization and hydration of the rice is preserved to a great 85 degree and the rice is reduced to a stable moisture content of 10,14 %, the final product having a density of 0 25-0 45 g /cc. EXAMPLE III 90 pounds of milled, parboiled or otherwise gelatinized, dried rice with a moisture content of about 12,', are placed in an 80 gallon autoclave and steamed at 8 lbs,'sq. in (gauge) for 8-10 mrinutes to raise the 95 moisture content thereof to 22 % and render said grains completely pliable throughout Thereafter, said grains are compressed by passing the same through rolls, spaced so as to reduce the grains to about 60 %, of 100 their thickness before compression, and the rice is dried to a stable moisture content of 10-14 %, in the manner described in detail in Example I above, the final product having a density of 0 70-0 75 g /cc 105 EXAMPLE IV pounds of milled, parboiled or otherwise gelatinized, dried rice with a moisture content of about 12 % are placed in about gallons of water contained in a 100 gal-110 lon tank at room temperature ( 75 F) and allowed to soak in the water for two minutes The soaked rice is then removed from the water, drained for a half minute and placed in an 80 gallon autoclave and 15 steamed at 8 Ibs /sq in (gauge) for 1-2 minutes to render the surface portion of the

grains pliable and increase the overall moisture content of the grains by about %, the interior portions of the grains re-120 maining substantially unchanged Therearter, said grains are compressed by passing the same through rolls, spaced so as to reduce the grains to about 80 % of their thickness before compression, and dried to 125 a stable moisture content of 10-14 % in the manner described in detail in Example I above. EXAMPLE V pounds of milled, parboiled or other 130 wise gelatinized, dried rice With a moisture content of about 12 'o are placed in about gallons of water in a 100 gallon tank and allowed to remain therein for about one hour at room temperature ( 75 F) and raise the moisture content of the rice to 50, The rice is then drained for 15 minutes Thereafter said grains are compressed by passing the same through rolls, spaced so as to reduce the grains to about 80 ' of their thickness before compression, and dried to a stable moisture content of 10-14 ', in the manner described in detail in Example I above The density of this product is O 65-0 75 g /cc. EXAMPLE V 1 pounds of ungelatinized rice with a moisture content of 12 %, is placed in a 100 gallon tank together with 60 gallons of water and soaked for 30 minutes at room temperature ( 75 F) Thereafter it is transferred from the tank to a screen and allowed to drain for 15 minutes At this point the rice contains 30 %, moisture The rice is transferred to an 80 gallon autoclave and treated w.ith steam at 8 lbs /sq in for 10 minutes and completely gelatinized Thereafter the rice is returned to the soaking tank and allowed to soak in the water for an additional period of 20 minutes which serves to increase the moisture content of the rice to about 65 ',, The rice is then removed from the soaking water, drained for 15 minutes. blasted with cold air to toughen the surfaces of the grains and then subjected to mechanical compression by passing the same through rolls spaced so as to reduce the grains to about 70, of their thickness before compression and dried to a stable moisture content of 10-14-, as described in detail in Example 11 above The density of this product is 0 4 g /cc. If desired, the rice may be soaked and 45steamed to fully gelatinize the same, compressed and then soaked in water to fully hydrate the same to 60-70, moisture and then dried. Also, the rice may simply be soaked, steamed to fully gelatinize the same, and then compressed and dried. EXAMPLE Vli pounds of ungelatinized white rice with a moisture content of about 12 %, is placed in a 100 gallon vessel or tank together with about 60 gallons of water and allowed to soak for 30 minutes at room temperature ( 75 F) Thereafter the rice is transferred from the tank to a screen and allowed to drain for 15 minutes At this point the rice

contains about 30 % of moisture The rice is then transferred to an 80 gallon autoclave and steamed at 8 Ibs /sq. in (gauge) for 5 minutes at the end of which time the outer portions oi ile rice grains a,: completely gelatinized ailnd the inner p):tions:h:ile some;haic gelatinzedl still contain an appreciable amount of ungelatinizec starch granules The rice grains are then 70 compressed by passing the same through rolls spaced so as to reduce the grains tc about 70 ',, of their thickneses before compression as described in detail in Examples I and 11 above The rice is then returned 75 to the 80 gallon autoclave and steamed for an additional 5-10 minutes to render the same completely gelatinized throughout. after which it is removed from the autoclave and dried to a stable moisture content of 80 about 10-14 ', using the drying condition described in Example 1 The density of this product is 0 50-0 70 g /cc. I will be evident that at any appropriate stage in the process the rice grains can be 85 washed with water or solvent extracted te decrease their fat content and thereby decrease any problemn of rancidificazion thamight exist Also any suitable antioxidant catn be added if desired One very eff-90 ective method of eliminating any possibility of a rancidity problem is to soak the rice il. hot water, say, at 175 '-30 n F for 5-10 minutes This may be employed at any stage of the process, but it is preferred that 95 it should follow the preliminary soaking step which is employed in many of the embodiments of the invention described above.


* GB784866 (A)

Description: GB784866 (A) ? 1957-10-16

Improvements in and relating to electric circuit breakers


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PATENT SPECIFICATION __ 784,866 Date of Application and Filing Complete b 7 i $&' Date of Applicatio Specification: Sept16, 1954 No 26877154. y Application made in United States of America on Oct16, 1953. Complete Specification Published: Oct 16, 1957. Index at Acceptance: Class 38 ( 5), Bl L( 2 A: 5: 7 A 2: 7 86: 13), Bl NID, International Classification:-HO In H 02 c B 2 (A 5 A 2: B 3: Bl O: Bl I: C 6 X: C 8 B). COMPLETE SPECIFICA Ti ON Improvements in and relating to Electric Circuit Breakers. We, IGRANIC ELECTRIC COMPANY LIMITED a British Company, of Elstow Road, Bedford, in the County of Bedford, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to electric circuit breakers, particularly small circuit breakers adapted for use as motor starters. The invention seeks to provide a simple, reliable and inexpensive circuit breaker of this character. A further object is the provision of a circuit breaker which is easy to assemble, requires a relatively small number of working parts, and is fully protected against deleterious effects from sparking and external dust and dirt particles. Other objects and advantages of the invention will appear hereinafter. The invention consists broadly of an electric circuit breaker having a movable contact mounted on and movable with an insulating contact carrier and constantly biased towards closed circuit position, an

overcentre spring action manually operable to one position to overcome said bias and move said contact carrier and contact to open circuit position, and manually operable to another position to permit said contact carrier and contact to move to closed circuit position under said bias, current responsive means for moving said contact carrier and contact to open circuit position in opposition to said bias, independently of said overcentre spring action, and a housing for said spring action, said housing having a guide for said contact carrier. A preferred circuit breaker according to the invention has the following general characteristics: the movable contact carrying bridging members are loosely mounted 43 on an insulating contact carrier which is slidably guided in the base and cover forming the circuit breaker housing Such members are spring biased toward closed circuk and with the contact carrier move back and forth in a path substantially perpendicular 556 to the dividing plane between cover and base This facilitates assembly of the circuit breaker The contact carrier is moved toward the cover to open the normally closed contacts by a manually controlled 5 overcentre spring action carried in the base. This action is installed in the base by the simple expedient of axially sliding its main pivot into a bearing in the base while such action is momentarily held in place The 60 action includes a contact operating lever which engages with the contact carrier to move it to opened position Such lever has an overload bar which in overload conditions is engageable by an overload lock and 65 reset lever also included in such action. These levers, a spring support and a manually operated lever are all mounted on the same pin in such action While there is a slight tolerance built into the mechanism 70 to provide for wear of the contacts, this is not sufficient to impart a hammer blow in the opening of the contacts Instead the over-centre spring action imparts a positive and instantaneous opening to the contacts 75 without the necessity of damaging hammer blows which soon wear and break down such small lightly constructed circuit breakers The base and the cover completely enclose the contacts and all operating mem 80 bers, except the handle of the manually operated lever, to protect them from dust and dirt and to keep harmful sparking fully shielded. For a more detail description of the said 8 $ preferred circuit breaker reference should be made to the following description of a specific embodiment read in connection with the accompanying drawings, in which: Fig 1 is a top plan view of a circuit 9 784,866 breaker embodying the present invention with the manually operated lever in "offposition; Fig 2 is a sectional view taken on the ine 2-2 of Fig 1; Fig 3 is a

sectional view taken on the line 2-2 of Fig 1 showing the parts as positioned with the manually operated lever in "on" position; Fig 4 is a sectional view taken on the line 2-2 of Fig I with the parts shown in the osition assumed when the contacts have been opened by the operation of the overload mechanism; Fig 5 is a sectional view taken on the line 5-5 of Fig 3; Fig 6 is a sectional view taken on the line 6-6 of Fig 3; Fig 7 is a sectional view taken on the line 207-7 of Fig 5; Fig 8 is a sectional view taken on the line 8-8 of Fig 5; and Fig 9 is an exploded prospective view of the circuit breaker shown in Figs 1-8 (incl). The circuit breaker illustrated in the drawings is a multiple pole starter rated at approximately 1 horsepower, single phase on 115 and 230 volts Completely assembled it is approximately 1 inches wide, 21 inches 301 long and 2 inches high Such small circuit breaker has a base 10 and a cover 12 formed of molded insulating material which are secured to provide a housing for the complete circuit breaker operating mechanism except the handle of the manually operated lever On a flat portion of the base 10 facing the cover 12 there are mounted fixed contacts 14 into the threaded supports of which are threaded exterior ter4 Opinal screws 16 Between these contacts is a groove 18 for guiding the contact carrier. Slots 20 transverse to such groove guide the finger of the contact operating lever A projection 22 on the base 10 houses the 45thermal release assembly A rectangular hole 24 accommodates the handle of the manually operated lever and provides shoulders limiting the extreme movements of such handle The overcentre spring action is held in the base 10 during assembly of the circuit breaker by having an extending end of the pivot of such action project into a bearing 26 in such base Opposite this bearing is a cylindrical groove 27 which co-operates with a similar cylinder groove in the cover to form the other bearing for such pin. The cover 12 has a recess 28 which accommodates the swinging elements of the overcentre spring action At the bottom of this recess is a groove 30 which guides the end of an overload lever The right hand w all of such recess has a semi-cylindrical groove 32 (see Figs 4 and 8) which pro-ides an abutment for the spring of the overcentre spring action Adjacent to the recess 28 are a pair of spaced recesses 34 (see Figs 6 and 7) terminating in cylindrical wells 36 which provide operating space for the contact bridging members and their compression springs Slots 38 co-operating 70 with the grooves 18 in tile base 10 provide the complete guide for the contact carrier bar A semi-cylindrical bearing 40 in the cover 12 (see Fig 5) co-operates with the semi-cylindrical bearing 27 in the base 1075 to form the outer bearing for the main pivot of the overcentre spring action.

The movable contacts of the circuit breaker are mounted on a pair of bridges 42 apertured loosely to slide on tongues 4480 on a contact carrier 46 The carrier 46 is made of insulating material such as melamine and is slidably guided in the groove i 8 and slots 38 simultaneously to mo-ve the bridges 42 in the recesses 34 with the con-85 tacts thereon in alignment with respective pairs of the fixed contacts 14 The bridges 42 are continuously urged toward the closed circuit position shown in Figs 3, 6 and 7 by compression springs 48 It is relatixely 90 simple to assemble the bridges 42, carrier 46 and springs 48 The springs 48 are seated in the wells 36 of the cover The bridges 42 are placed on the tongues 44 and the contact carrier 46 fitted in the grooves 95 18 of the base 10 When the cover 12 is placed on the base i 0, the springs 48 will be properly compressed Tihe contact carrier -46 has a centrally located slot 50 which engages a giner on the coi;at operating 100 lever To aid in effecting its movenent towa d circvit opned positicn Thb o vcrcentre spring a tio intcltdes a manually cacrat d eet 52 to which is pivoted by a single main pivot 74 a sprin 105 suport 70, a contact operating lever 82 and an overload and reset lever 90 An overcentre spring 76 e:te-nds beweel the brid Be of the spring support 70 and a spring yoke 62 pivoted to the manually operated lever I 10 52 The manually operated lever 52 is made of insulating material and has a hand engageable finger which in the assembled condition projects outwardly of the lousing through the hole 24 A pair of spaced l S shoulders 54 alternati rely en-ae the en of hole 24 to establish the "off" and "on" position of the lever 52 A pair of trunnions 56 with bearings 58 therein are saced by a groove 60 The latter slidably guides 120 the spring yoke 62 pivoted to the lever 52 by a pin 64 fitting in an elongated bearing 66 in the lever 52 and passing through a hole 68 in such spring yoke The spring support 70 is U-shaped and has a connect 125 ing bridge and a pair of legs terminating in apertured ends 72 These ends straddle the trunnions 56 with the apertures aligned with bearings 58 and mounted on the main pivot 74 The tension spring 76 has one end 130 784,866 anchored to the bridge of support 70 and its other end engaged in a hole 78 in the yoke 62 This yoke has an arcuate slot 80 fitting over the pin 74 which permits it to swing about the pin 64 without interfering with the main pivot 74 Such linkage will cause the spring support 70 to move back and forth between its limit position of Fig. 2 and its limit position of Fig 3 upon swinging the lever 52 back and forth between its open circuit position of Fig 2 and its closed circuit position of Fig 3 Such motion after dead centre is reached is very rapid. In normal operation the motion of the spring support 70 is transmitted to the contact carrier 46 by the contact operating lever 82 This lever

has a pair of supporting legs straddling the spring support 70 and 2 S pivoted on the main pivot 74 Such contact operating lever 82 has an extending finger 84 slidable in the slots 20 and seated in the slot 50 of the contact carrier 46 The bridge of lever 9 has an arcuate recess 86 which fits around the spring 76 to permit the clockwise edges of the bridge to be engaged by the legs of the spring support 70 in the normally operating "off" position of the circuit breaker of Fig 2 The contact operating lever 82 also has an overload bar ,8 which is engaged by the overload and reset lever 90 when the latter is released upon an overload. The overload and reset lever 90 has a main bridge with spaced supporting leas 92 straddling the contact operating lever 82 and pivoted on the main pivot 74 The lever 90 also has a spring anchor 94 with an outer supporting leg 96 also pivoted on the main pivot 74 A tensioned overload spring 98 extends from the anchor 94 to a pin 100 secured in the base 10 A locking arm 102 formed as part of the lever 90 has a spring finger 104 normally engaged with a ratchet 106 of a thermal release assembly 108. Such -assembly is welr known The ratchet 106 is normally held against rotation until the heater coil, connected to a terminal 110 and the adjacent terminal 16, melts the eutectic solder upon occurrence of an overload The ratchet 106 will then rotate and release the overload and reset lever 90 which will, under influence of spring 98, operate to open the circuit The terminal 110 is carried in a plate 112 to which is threadedly fitted a terminal 114 for external connection. To assemble the overcentre spring action, the spring yoke 62 is placed in the groove and pin 64 inserted in bearing 66 through hole 68 Then the spring 76 is secured to the anchor 78 The spring support 70, contact operating lever 82 and overload and reset lever 90 are then fitted over the trunnions 56 and the main pivot 74 inserted 65through them and the bearings 58 until its inner end (left as viewed in Fig 9) is flush with the inner of the legs 92 The spring 76 is then connected to the support 70 The action is assembled as a unit into the base with the handle of the lever'52 project 70 ing out of hole 24 The main pivot 74 is then moved inwardly, so that its inner end slides into the bearing 26 thus holding the action in place After the contact bar 46 and spring 98 are assembled in the base 10,75 the cover 12, with bridges 42 and sorings 48 in place, is placed on the base 10 and secured by screws 116 which are threaded into mounting strips 118. Starting with the circuit breaker in the 80 "off" position, shown in Figs I and 2 assume that the handle of the operating lever 52 is swung from the "off" position to the "on" position shown in Fin 3 During the first part of such movement the contact 85 operating lever 82 holds the s Wring support 70 in the position shown in Fig 2 As the pin 64

moves clockwise about the main pivot 74, such pin pivot and anchoring hole 78 approach a position of alignment with 90 the central axis of spring 76 Before such alignment position is reached the force exerted by springs 48 is sufficient to overcome the then opposing force of spring 76, and movement of the contact carrier toward 95 closed position results in the forced movement of lever 70 thr Jugh the aforementioned aligned position to its opposite extreme position shown in Fig 3 During the aforementioned movement pin 64 moves to en too gage with the other end of slot 66 in lever 52. Starting with the parts shown in the "on" position of Fig 3, movement of operating lever 52 in the counter-clockwise direction 105 to the "off" position shown in Fin 2 will cause pin 64, pivot 74 and hole 78 to be brought toward the aforementioned alignment position During such movement pin 64 moves from the right end to the left end 110 of slot 66 thereby providing a slight lost motion action, offsetting any retarding tendency caused by the speed or manner of movement of lever 52 Spring support 70 is held against the groove 32 as shown in 115 Fig 3 during the initial part of such movement As the alignment position is passed, the tension of the spring 76 moves spring support 70 rapidly in the clockwise direction from such position, to the position shown 120 in Fig 2 The legs of the spring support will contact the bridge of operating lever 82 and swing it clockwise to the position shown in Fig 2 with a rapid motion but without hammer action The finger 84 in 125 stantly depresses the contact bar 46 with the consequent opening of the contacts as the effective force of spring 76 is considerably greater than the combined effective force of springs 48 130 784,866 With the circuit breaker in the normall) "on" position shown in Fig 3, an overloac will release the ratchet 106 and the overload and reset lever 90 will instantly pivol under the influence of spring 98 to the position shown in Fig 4 Its arm 102 will engage the overload bar 88 and swing the contact operating lever 82 to the circuit open position shown in Fig 4 This takes place without any interference to or from the manually operated lever 52, the overcentre spring 76, and the spring support 70 After the overload has been removed and the solder in the thermal element hardened, the circuit breaker may be reset This is accomplished by swinging the manually operated lever 52 from the "on" position of Fig 4 to the "off" position of Fig 2 This movement causes the left hand lower edge of such lever to engage the bridge of the lever 90 and swing such lever counter-clockwise to carry the arm 102 to the position shown in Fig 2, so that the spring finger 104 will again engage with the ratchet 106 and hold such lever with energy stored in spring 98. Lever 90 in so moving disengages from lever 82 and the latter momentarily freed rotates a slight amount in the counter-clockwise

direction thereby permitting contact carrier 3046 to move a slight amount toward contact closed position During the aforementioned "resetting" operation, spring support 70 is caused to snap overcentre to the position shown in Fig 2, and in so doing engages with lever 82 to drive the latter in the clockwise direction before it can move freely any appreciable amount in the counter-clockwise direction. It will be observed that because lever 90 can move lever 82, to contact opening position independently of lever 52 and spring carrier 70, that the circuit breaker is of the "trip-free" type, that is to say, the contacts cannot be closed by movement of lever 52 to "on" position, following "resetting" operation of the latter if the thermal element has not rehardened.


* GB784867 (A)

Description: GB784867 (A) ? 1957-10-16

Improvements in or relating to travelling-wave electron tubes


PATENT SPECIFICATION Date of Application and filing Complete Specification: Sept 23, 1954. g W i rt i 9 No 27566/54. Application made in United States of America on Sept 24, 1953. Application made in United States of America on Oct 19, 1953. Complete Specification Published: Oct 16, 1957. Index at acceptance:-Classes 39 ( 1), D( 1 OD: 1 OF: 11: 16 A 1: 18 A: 40 F: 46 A); and 40 ( 8), WG. International Classification:-H Olb, j. COMPLETE SPECIFICATION

Improvements in or relating to Travelling-Wave Electron Tubes We, RAYTHEON MANUFACTURING COMPANY, a corporation organised under the laws of the State of Delaware, United States of America, of Waltham, County of Middlesex, Commonwealth of Massachusetts, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to a travelling-wave electron tube. One of the commonly employed anode structures forming the signal wave transmission network of a travelling-wave tube is a strapped solid vane structure This anode structure includes an electrically conductive supporting plate to which a plurality of equally spaced substantially rectangular planar members or vanes, positioned substantially normal to the supporting plate, are attached. At points on the edges of alternate vanes near the free ends thereof are connected two pairs of conductive straps which extend longitudinally along the structure This anode structure is enclosed within an evacuated envelope of a travelling-wave tube which includes a negative electrode, a collector electrode, means for producing an electron beam and necessary connections. All other things being equal, it is desirable that the characteristic impedance of a periodic anode network for use in a travelling-wave tube amplifier or oscillator be as high as possible. The characteristic impedance Zo normalized with respect to the characteristic impedance Z, of each cavity or network section formed between two adjacent anode vanes is a function of a design parameter a For the strapped vane structure, xc is defined as coo Ls a = _ ( 1) zoo where lr is the cutoff frequency lPrice 3 s 6 d l L, is the strap inductance per network section Zo is the characteristic impedance of the parallel conductor network section or cavity formed by two adjacent vanes. It is known that in the aforesaid prior structure it is not practically feasible to increase the impedance by increasing a indefinitely A value of a must be selected and maintained, for a particular periodic delay network, which will permit that network to transmit waves at all frequencies within the pass band at phase velocities which are less than the phase velocity Vpx of the lower cutoff or,, mode frequency. The ratio of Z to Z O is a constant, for a given value of a and wavelength In order to increase the characteristic impedance ZO, therefore, it is necessary to increase Z also. For the strapped vane network, Zo is given by S Zo=kh where s is the spacing between vanes and h is the height of the vanes. ( 2) Since the separation of the vanes (i e, the pitch) determines the

velocity at cutoff and, hence, the velocity everywhere in the operating range, the amount of separation is dictated by operating voltage considerations It is undesirable to increase Zo by increasing s since this increases the phase velocity and voltage of the amplifier If h is reduced, on the other hand, the width of the vanes and the electron beam is narrowed and it is difficult to obtain the desired beam current. According to the invention there is provided a travelling-wave electron tube including a delay line having two ends between which electromagnetic waves can travel on a route along said line but not substantially on any other route, the line being adapted to propagate electromagnetic waves and thereby produce an ultra-high frequency field, the delay line com- 2 784,867 prising an electrically-conductive base and a plurality of U-shaped electrical conductors which are arranged in a row along the base and are each connected at both ends to the base so that said conductors form with said base a series of delay line sections, the tube further including means for producing a stream of electrons which move in a path along the line but to one side of said delay line sections so that there will be interaction between the electrons and said field. As compared with the conventional strapped vane network, the provision of U-shaped conductive loops increases the impedance of the delay line without changing the pitch or the height of the vanes. In order to overcome the problem of heat dissipation resulting from the smaller surface area of the vanes, the latter are preferably made in the form of U-shaped tubular loops through which a cooling fluid can be circulated Although the straps may be located externally or internally near the ends of the loops, it is preferable to use a single pair of spaced straps located near the centres of the loops The decreased area of the opposing faces of adjacent loops can be achieved by reducing the loop dimensions within limits compatable with physical strength and efficient internal flow of cooling fluid. A further improvement of this periodic delay network when used as an anode in travellingwave tubes, may be effected by providing flat surfaces on the outer surface of the loop cross arms, that is, along the surface of the loop facing the electron stream. From equations ( 1) and ( 2), it is evident that is the value of Z is to increase and that of a is to remain constant, the strap inductance L, or the cutoff frequency too must be increased Usually it is not feasible to vary the cutoff frequency so that it is necessary to increase the value of L O This may be accomplished in at least two ways The number of straps may be reduced from four, as used in the known periodic structures, for example, to a single pair of straps The

size of the straps may be decreased to achieve the desired increase in L, In addition, the strap inductance may be increased by keeping the straps as far away from the loops as possible except at the points of connection In the case of linear straps, slotted portions may exist therein over which the portion of the loop not connected thereto may pass; the loops may also be bent to achieve the same result. In a further construction, the shorted lines, which may be a half wave length long at the lower cutoff frequency of the network, are made with a triangular cross section which permits a high impedance circuit to be maintained, as in the case of the interdigital delay line, while providing the additional advantages of a more uniform direct current electric field in the interaction space, a stronger radio frequency field in the desired space harmonic, higher inductance of the strapped coupling for a given strap size, and greater uniformity in the manufacture of the circuit loops Moreover, by making the loops hollow, the delay 70 network has advantages over the interdigital delay structure in that it may be adapted for fluid cooling, thereby permitting high thermal dissipation and high power capability. Another construction involves an open wave 75 guide loaded at the open face by a series of shorted transmission lines or loops of the type previously described, each of which is substantially one half wave length long at the upper cutoff wave length This loaded wave 80 guide delay structure has been found to possess a higher impedance than that of the strapped vane anode delay line of the first embodiment, with resulting advantages in tube optics gain and efficiency Furthermore, assembly of 85 the loaded wave guide structure is simpler than that of the strapped vane structure, and the structural uniformity of the loaded wave guide structure is superior to that of the strapped vane structure This construction, 90 too, is amenable to fluid cooling and consequently is capable of operation at relatively high power levels. For a better understanding of the invention and to show how it may be carried into effect, 95 the same will now be described with reference to the accompanying drawings, in which: Figures 1 and 2 are isometric views of two different periodic delay networks, parts being broken away in each Figure for ease of illus 100 tration, Figure 3 is a longitudinal cross-sectional view of a travelling-wave electron tube utilizing the period delay network of Figure 1 as the anode, 105 Figure 4 (drawn in the inverted position with respect to Figure 3) is a view corresponding to a part of Figure 3 and illustrating a modification of the periodic delay networks shown in Figures 1 and 2, 110 Figure 5 shows diagrammatically a network representing the equivalent circuit of the periodic delay network of Figure 1, Figure 6 shows diagrammatically the equivalent circuit of a single section of the net 115 Figures 7 to 9 are graphs illustrating

various characteristics of a periodic delay netFigure 10 is an isometric view of a further 120 periodic delay network, part being broken away for ease of illustration, Figure 11 is a detailed isometric view showing a modification of the network shown in Figure 10, 125 Figure 12 is a cross-sectional view of a modified version of the network shown in Figure 10, Figure 13 is an isometric view of a further periodic delay network, part being broken 130 784,867 Instead of resorting to an attenuative coating, the loops themselves may be constructed of a material, such as iron, having a high attenuation factor. A pair of trough-shaped headers 20 and 21 70 are secured in substantial alignment with the opposite ends of the network loops 14 and 14 ' to the under side of base 11, as by soldering, so as to form a fluid-tight seal One end of each header is closed while the other end is 75 connected to a fluid circulating pump (not shown) The fluid is used for cooling the network and it passes along one header, through each loop in parallel and back along the other header 80 Although the periodic delay network 10 has been shown as linear, it should be understood that the network may also be circular to conform to the usual practice in magnetron design. In Fig 3, a travelling-wave tube amplifier 85 is shown which includes as its anode the periodic network 10, previously described. The structure serving as the anode of the travelling-wave amplifier comprises a base 11 which forms one of the walls of an evacuated 90 envelope further including an oppositely disposed wall 27, end walls 28 and 29 and a pair of side walls, not shown Base 11 may be fastened to the contiguous walls of the envelope by soldering or by means of fastening 95 devices such as screws. The inner conductor 31 of a coaxial input coupling device 30 extends through an aperture 32 in the base 11 and is attached, as by soldering, to one end of the first loop 14 a at 100 the input end of the anode structure This loop, as well as the loop 14 N at the other end of the structure, is solid as contrasted with the tubular loops in between An output coupling device 40 is similarly attached to one end of 105 the loop 14 N at the output end of the anode structure, as shown in Fig 3 Positioned adjacent the input end of the anode 10 is a cathode structure 35 having an electron emissive surface 36 The cathode 110 structure 35 is supported by a hollow supporting cylinder 37 extending through an aperture in wall 27 of the tube envelope Cylinder 37 surrounds a central conductor 38 which is connected to one end of a heater coil, not shown, 115 positioned in thermal proximity to the emissive surface 36. An auxiliary electrode 44 is positioned substantially parallel to the anode structure and spaced therefrom, as shown in Fig 3 120 Electrode

44 which is otherwise referred to as a ",sole," is trough-like and of U-shaped cross-section, the bottom surface thereof being positioned somewhat lower than the electron emissive surface 36 of the cathode 125 Sole 44 is supported relative to the remainder of the tube envelope by means of a pair of supporting rods 46 rigidly attached to the sole These rods are insulatedly supported with respect to wall 27 by means of metallic 130 away for ease of illustration, Figure 14 is a cross-sectional view of the network shown in Figure 13, Figure 15 is a detailed view of a portion of the network shown in Figure 13, Figure 16 is a cross-sectional view of a modified version of the network shown in Figure 13, Figure 17 is a central longitudinal crosssectional view of a travelling-wave tube incorporating a periodic delay network as shown in Figure 10, Figure 18 is a central longitudinal crosssectional view of a travelling-wave tube incorporating a periodic delay network as shown in Figure 13, and Figure 19 illustrates a cooling arrangement for a periodic delay network. Referring now to the drawings, in Figure 1 a periodic delay network 10 includes an electrically conductive base 11 containing two rows of aligned circular apertures 12 positioned adjacent opposite edges of the base and extending clear through the same A plurality of electrically conductive tubular U-shaped transmission loops 14 and 141 are disposed in a row along the base The pitch or spacing between adjacent loops is preferably uniform throughout the length of the structure The ends of each loop are inserted in oppositely disposed apertures 12 in the base in a manner clearly shown in Fig 1. A pair of spaced straps 15 and 15 ' extend along paths which pass near the centres of the loop and they are attached to alternately arranged loops 14 and 14 ', respectively These loops are preferably constructed of straps of metal having a high thermal and electrical conductivity Each of the straps 15, 151 is formed with a plurality of spaced projecting portions 16, the spacing between centres of such portions being substantially equal to the pitch of the loops 14 or the loop 14 ' The portions of a strap between adjacent projecting portions will be referred to as slotted portions The straps are connected at the projecting portions, to the transmission loops, as by soldering In order to couple together the odd numbered loops with one strap and the even numbered loops with the other strap, the projecting portions of one strap fall opposite the slotted portions of the other, as shown in Fig 1 The straps 15 and 151 may, alternatively, be in the form of loops of metal strip, as shown in Fig 2 The centre of each strap loop of Fig 2 or the slotted portion of each of the straps of Fig 1, as the case may be, is thus separated from the U-shaped loops 14 or 14 ', as the case may be, by a relatively large amount, whereby a substantial strap inductance is obtained.

Attenuation may be introduced into network 10 by means of a metallic attenuating coating 18, such as graphite, deposited near the ends of some of the transmission loops. 784,867 members 47 sealed, in turn, to ceramic seals 48 The latter are each connected to an electrically conductive cylinder 49 which surrounds rods 46 and is, in turn, fitted in a recess in wall 27. Positioned beyond that end of sole 44 which is remote from the cathode, and in substantial alignment with the sole is a collector electrode 50 rigidly supported by means of a lead-in rod 51 extending through an aperture in wall 27 and spaced from the wall Rod 51 is supported relative to wall 27 by means of a conductive cup 52, a ceramic cylinder 53 and a metallic cylinder 54 surrounding rod 51, the parts being sealed together like the sole supporting devices previously described. A direct current electric field may be established between the anode and the sole by connecting a source of direct current voltage, not shown, therebetween The cathode is negative with respect to the anode but may or may not be at the same potential as the sole. A transverse magnetic field is produced in the space between the periodic anode structure and the sole in a direction normal to the electric field therebetween, that is to say, in a direction perpendicular to the plane of the paper By proper adjustment of the magnetic field, the electrons emitted from the cathode will be directed along a path adjacent the loops of the anode structure Interaction of the electron beam with a wave traversing the anode structure will result in amplification within the travelling-wave tube. It is possible to eliminate the transverse magnetic field and to operate the travellingwave tube as a non-magnetic amplifier. The cathode-sole assembly shown in Fig 3 may be replaced by a continuous cathode extending the length of the tube This is true regardless of whether or not the tube utilizes a transverse magnetic field. An improvement in the periodic structure of Figs 1 to 3 is shown in Fig 4 in which flat plates 60 are attached, as by brazing, each to the outer edge of the cross arm of a corresponding transmission loop, that is to say on that surface of the loop which is nearest the electron stream These plates are substantially rectangular and may be approximately the length of the loop cross arm The tubes may, alternatively, be formed with flat surfaces instead of having flat pieces attached thereto. For example, the surface of the tubular loops facing the -electron stream may be filed or machined down flat, provided, of course, that the wall thickness of the loops is sufficiently large The composite

surface of the periodic structure formed by the several plates 60 which is presented to the interaction space of the travelling-wave tube is substantially flat in the construction shown in Fig 4 rather than a series of rounded surfaces, and the gap between adjacent plates is quite small compared with the average distance between the rounded surfaces of adjacent tubular loops of Figs 1 to 3 Since this composite surface approaches a solid plane substantially equidistant at all points from the sole of the travelling-wave tube, the direct current electric field in the interaction space is comparatively uniform Because of this uniform direct current field, a more uniform electron beam is attained. An analysis of the strapped loop periodic structure of Figs 1 to 3 may be had by constructing a linear array of said loops which have been straightened out, as schematically illustrated in Fig 5 The length of the loops included between the two points of connection to base 11 is designated as d while the distance of the straps from the ends of the loop is designated as f The ratio of f to d, which is a feature of the strap separation, is designated as k For example, if both straps were located at the centre of the loops, the value of k would be 0 5. A single network section is shown schematically in Fig 6 and may be considered to be a parallel-plane shorted transmission line of characteristic impedance Zen It is divided into two parallel paths by the dotted line through point mn at which the strap 15 is connected to loop 14 The impedances looking in both directions away from m are Z, and Z The impedance Z between point m and point n, the point of connection of strap 151 to loop 14 ', is equal to the parallel combination of impedances Z, and Z 2, where and j Zc rn 2 'r Id A Z =j Z c Pan _ 2 A LI-kd) A ( 3) ( 4) the impedance Z thus becomes j 7 C ra,7 Ot Tkd Aran 2 ir f-kei) A tan 2,7 d t tan gff l-kd) A A ( 5) 105 The effect of the network design parameter z on the normalized impedance of the Z. periodic network of Fig 1, for a given wave length, normalized with respect to the upper cutoff wave length A,, is shown in the graph 110 of Fig 7 The network impedance is increased as x is increased from 0 1 to 1 For example, at a normalized wave length of 09, the normalized impedance increases from about 0 9 when =- 1 to approximately 2 7 115 when x = 1 This graph represents a periodic network having a value k= 0 4, as will be shown later The shape of the curves of Fig. 7 will be changed somewhat as the strap separation, or value k, changes, as will be 120 784,867 held constant The curves of Fig 9 indicate that the impedance level of the system is 65 reduced when k is reduced Since the value of k, as well as the value of a, affects the shape of the curves, suitable values of k and a should be chosen simultaneously in order to secure desirable network characteristics 70

Although the travelling-wave tube shown in Figure 3 is of linear configuration, the principle of its construction can be applied to other than linear travelling-wave tubes For example, a circular tube may be used 75 Referring to Fig 10, a portion of a strapped loop periodic relay structure 110 is shown which, like that shown in the foregoing Figures 1 to 3, inclusive, consists of a plurality of cavities or network sections formed by 80 adjacent U-shaped transmission loops shorted at both ends by an electrically-conductive member and having alternate loops interconnected by a pair of metal straps In this case, however, the cross section of the loops 85 is made substantially triangular, as shown in Figs 10 to 12. The end portions 122 of each loop 112 and 1121 are inserted in corresponding apertures 113 and 1131 in an electrically-conductive 90 base 111 and are secured thereto, as by brazing Since circular apertures are readily obtainable by drilling holes in the base, the end portions of the loops are preferably machined round It is possible, of course, to 95 utilize triangular apertures in the base plate or, in the event that fluid cooling is not desired, as in the construction illustrated in Figure 10, to secure the ends of the loops at the surface of the base 100 The first set of alternate loops are interconnected by an electrically-conductive strap 114 while a second set of alternate loops 112 ' are interconnected by a similar strap 114 '. These straps may take the form shown in 105 Fig 10 in which alternately disposed projecting portions 115 and 115 ' may be attached to the under side of the corresponding loops, as by soldering Alternatively, the straps may contain V-slots 117 into which the apex of 110 the triangular loops may be inserted prior to soldering, as shown in Fig 11. The spacing of the straps 114 and 1141 partially determines the characteristic impedance and velocity dispersion character 115 istics of the network and the spacing selected will be governed by circuit design considerations. The reasons underlying the use of transmission loops of triangular cross section will 120 now be stated As pointed out earlier, the characteristic impedance Z of the strapped loop delay structure is related to the characteristic impedance Z O of the cavity formed by adjacent loops by a constant factor, at a given 125 wave length. In order to increase Z and consequently the gain of a travelling-wave amplifier utilizing evident from inspection of Fig 9, to be described later. The dispersion curve of the space harmonic of the travelling-wave suitable for amplification, that is, the relationship between the wave length and the phase velocity of the first harmonic of a wave

travelling along the periodic network 10 of the travelling-wave tube of Fig 3 is shown in Fig 8 for various values of a The portion of the dispersion curve representative of the component of the travelling-wave suitable for operation of the travelling-wave tube as an oscillator is not shown in Fig 8 but the two portions of the dispersion curve representative of the fundamental and first space harmonic are symmetrically located about a line passing VAT A, through the origin ( = 0 and = 0) of the V A, curve and unity on the normalized phase velocity axis and having a slope equal to the reciprocal of twice the pitch of the periodic network. As shown in Fig 8, the curves 81 and 82 for respective values of a of 0 1 and 0 2 are relatively flat over a wide range However, the required phase velocity for most of the wave lengths in the pass band is greater than that necessary for i-, mode oscillations so that undesirable oscillations may be set up in the travelling-wave tube For high values of a, for example for values of the order of 0 6 to 1, the curves 86 to 90 are not flat over any substantial portion thereof and the gain of an amplifier tube operating on these curves, even assuming that oscillations will not occur, will vary considerably with operating wave lengths. For values of v in the range of 0 3 to 0 5, the curves are relatively flat over a wide range of wave lengths, for example, between the normalized wave lengths of approximately 75 and 95, as shown in curves 83 to 85 Hence, the degree of interaction between the electron beam and the waves propagating along the anode structure, and consequently the gain of the travelling-wave tube when used as an amplifier, remain substantially constant over a wide band of frequencies when curves 83 to obtain In practice this means that the desired gain may be accomplished over a wide band of frequencies using the same anode voltage or the same magnetic field strength, if the tube utilizes a transverse magnetic field. A value of a equal to about 0 4 or 0 5 is satisfactory for the periodic network represented in Fig 8. As evidenced by equation ( 5), infra, the factor k of the strapped loop periodic network has an effect upon the impedance level of the network The effect of k on the impedance is shown in Fig 9 in which graphs of normalized impedance versus normalized wave length for various values of k from 0 1 to 0 5 are shown by curves 95 and 99, respectively, when a is 784,867 6 784,867 this network as an anode, it is necessary to increase the value of Z O A high impedance is also desirable for a travelling-wave oscillator. An expression for Ze, has been given earlier (equation 1) and it will be seen that since a constant value of 7 is desirable, it is necessary to increase the value of the strap inductance L, For the same pitch,

the average gap or distance between adjacent loops of triangular cross section is considerably less than the average spacing in the case of loops of circular or rectangular cross section The area of metallic surfaces of the loop near the strap in the case of triangular loops is decreased, that is, the effective length of the strap between adjacent loops is increased As the spacing between adjacent loops is increased, the inductance of the strap interconnecting the adjacent loops is increased, for a given strap size, so that a higher impedance network may be obtained The use of heavier straps is permitted as a result of this increase in L. In this connection, the strap' inductance may be further increased, as pointed out in the first part of this specification, by keeping the slotted portion 116 of the strap which is bridged by alternate loops as far from the loop as possible The capacitance between a triangular-section loop and a corresponding slotted portion of a strap is less than that between a circular or rectangular-section loop and the same slotted portion The inductance, which varies inversely as the capacitance is consequently increased. A further advantage of an anode periodic structure having triangular-section loops is that a more uniform direct current electric field in the interaction space of a travelling wave tube utilizing the same may be obtained With loops of triangular cross section, the composite surface of a periodic structure formed by the several loops of the structure which is presented to the interaction space of the travellingwave tube is substantially flat, rather than a series of rounded surfaces as in the case of a structure using loops of circular cross section. Because the series of the loops facing the interaction space are flat, the gap between adjacent network loops at said surface (in the average gap) is considerably less than in the case of adjacent loops of circular cross section In other words, the aforesaid composite surface of the triangular loop network more nearly approaches a solid plane substantially equdistant at all points from the cathode or sole of the travelling wave tube Because of this comparative surface uniformity of the triangular loop structure, the direct current electric field in the interaction space is much more uniform than that obtainable when the loops ofthe anode periodic structure are round. Still another advantage of the anode structure using loops of triangular cross section over structures using round loops is that the space harmonic content of the electromagnetic wave in the interaction space is made stronger. A Fourier analysis of the radio frequency field between adjacent network loops indicates that the amplitude of the space harmonics of the field, relative to the fundamental, at a given 70 distance from

the anode increases as the space between said adjacent loops is decreased Since the radio frequency electric field at the anode can exist only across the gap between network sections (loops), the decrease in spacing be 75 tween adjacent network loops, brought about by the use of loops of triangular cross section, results in the production of a stronger radio frequency field in the harmonic most effective for amplification (first space harmonic) and im 80 proved interaction between the electron beam and the aforesaid harmonic propagating along the anode network. A final advantage of loops of triangular cross section is that they may be formed readily from 85 standard tubing or rods of various size by means of a conventional die so that all loops are uniform and in the case where tubing is used, capable of receiving a fluid coolant In the construction shown in Fig 12, the 90 transmission loops are made hollow to permit the passage therethrough of a coolant such as water A continuous fluid-circulating path is provided which includes a pair of headers 118 and 119 and the several ducts 120, one within 95 each loop 112 or 1121 These ducts are connected in parallel A fluid pump (not shown) is connected to one end of each of the headers. A possible direction of flow of the cooling fluid is shown by arrows in Fig 12, although the flow 100 may be in the reverse direction if the connections to the pump are reversed The header, as shown in Fig 12, consists of a U-shaped trough which may be soldered or otherwise joined to the bottom of base 111 so as to form a fluid 105 tight seal The fluid cooling system shown is illustrative of one of several possible cooling systems. When hollow loops are used instead of the solid loops of Figs 10 and 11, the end portions 110 of the loop are preferably of the same configuration as the remainder of the loop, and the apertures 113 in base 111 are triangular rather than circular It is possible, however, to make the ends of the hollow, triangular-section loops 115 circular, as in the case of the solid loops of Figs 10 and 11. A travelling wave amplifier 130 is shown in Fig 17 which incorporates as its anode the periodic structure 110 of Fig 10 The ampli 120 fier is otherwise the same as that described with reference to Figure 3. Although the loops 112 and 112 ' of the anode structure shown in Fig 17 are solid, it should be understood that tubular loops, such 125 as shown in Fig 12 may be used in conjunction with a fluid cooling system. The anode structure may also be used in a travelling-wave oscillator as well as in a travelling-wave amplifier In either case, the in 130 784,867 triangular die. Although triangular tubular loops are preferable to loops of other cross section, for reasons already explained, the loaded wave guide

structure may operate satisfactorily with 70 loops of round or square cross section; in other words, the cross-sectional configuration of the loops used with the loaded wave guide structure need not be triangular. In Fig 18 a travelling wave oscillator is 75 shown incorporating the periodic structure just described The elements of the tube of Fig 18 which correspond to those of Fig 17 are indicated by the same reference numerals. Since the tube is an oscillator, only one co 80 axial connector is shown It is possible to use the periodic wave guide anode structure in a travelling wave amplifier, in which case an input and an output connector must be provided in the manner shown in Fig 17 85 The tube of Fig 18 is shown as having a cathode and sole and, like that of Fig 17, is adapted for use with a transverse magnetic field-producing means If an oscillator of the non-magnetic type is contemplated, the cathode 90 and sole may be replaced by the continuous cathode previously referred to in connection with Fig 17. The end loop 112 a of Fig 18 is made solid and is connected to the inner conductor 131 of 95 a coaxial connector 130 If the tube were to operate as an amplifier using both an input and an output connector, the loop 112 m at the other end of the periodic structure would be made solid and would be connected to a co 100 axial connector, as in the case of Fig 17 The remaining loops are hollow and, together with headers 170 and 171 mounted along the wall of the tube, as more clearly shown in Fig. 20, form a continuous path for the circulation 105 of a cooling fluid One end of each header is closed while the other end is connected to one of the connections of a fluid circulating pump 175.


Law

4456 4460.output