* GB785398 (A)

Description: GB785398 (A) ? 1957-10-30

The method for indirectly heating a fluid

Description of GB785398 (A)

PATENT SPECIFICATION 4 ', __ Date of Applic, No 30882/55. Application m -Complete Spec 7859398 ation and filing Complete Specification: Oct 28, 1955. lade in United States of America on Nov 16, 1954. ification Published: Oct 30, 1957. Index at acceptance:-Class 1 ( 1), A 3 (AIA: B 1); 51 ( 1), B 28 A, BA 8 (A 2: A 4: B 4: E: J: 53: X), BA 26; and 123 ( 2), A 9 82. International Classification-13 B Olj F 22 b F 23 c. COMPLETE SPECIFICATION The method for Indirectly Heating a Fluid We, COMBUSTION ENGINEERING, INC, a corporation organised under the laws of the State of Delaware, United States of America, of 200, Madison Avenue, New York, 16, State of New York, 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 lto be performed, to be particularly described in and by the following statement: - This invention relates to a new and improved method for the indirect heating of fluids, and is particularly concerned with the generation and/or heating of steam. In conventional boilers and in similar apparatus a suitable fuel is burned by flame combustion and the heat released then transferred indirectly to the water or other fluid to be heated In such an operation there is necessarily required, in order to maintain efficient combustion of the fuel, a separate space for the oxidation or combustion of the fuel, commonly termed the furnace portion, with the heat exchange surface usually arranged partly in surrounding relation to the combustion space, and partly in a separate space of its own beyond the furnace The heat exchange surface surrounding the combustion space and exposed to radiation from the flame is ordinarily

termed the radiant section of the boiler, while the exchange surface beyond the furnace space, which is exposed only to the hot gases leaving the boiler, is usually termed the convection section. In, a great majority of present boiler furnaces and in similar equipment, a relatively large volume is provided for combustion of the fuel, this being made necessary by nractical design considerations such as that of providing for proper flame travel, etc, so that in most boilers the maximum rate of heat release in the furnace or combustion space is only of the order of, for example, 14,000 to 36,000 BTU/cu ft depending upon the particular fuel being fired as well as other considerations In comparatively large boilers, lPl because of this relatively low rate of heat release per unit volume of combustion space, (the size and cost of the furnace section of the boiler becomes a considerable factor. With respect to the rate of heat transfer, that is the rate at which heat produced in the furnace portion is transferred to the fluid flowing within the boiler tubes, even in conventional boilers relatively high rates of transfer may be obtained in the radiant section while much lower rates are obtained in the convection section with the latter being in the order of 8 to 13 BTU/hr /sq ft / 1 F In practice, however, only a limited amount of heat can be recovered in the radiant section where the heat transfer rates are relatively high, since the gases pass out of the furnace at a relatively high temperature of, for example, 1800 'F to 20000 F, leaving a major portion of the heat to be recovered in the convection section where the heat transfer rate is low. A further aspect of the operation of a conventional boiler furnace where the combustion of the fuel takes place by flame combustion is that the fuel must be consumed at a high temperature, usually reaching a minimum of about 30001 F These temperatures are usually above the fusion temperature of ash which may be present in the fuel giving rise to the familiar problems of slagging the furnace walls and the banks of convection tubes, with the resultant erosion and corrosion problems and lowering of heat transfer efficiency. It is an object of the present invention to provide a system for indirectly heating a fluid by means of heat released by the oxidation of a fuel, in which the oxidation of the fuel and at least a substantial portion of the heat transfer to the fluid takes place in the same space, thus obviating the need for a separate furnace or other space primarily for ithe combustion of the fuel and thereby considerably reducing the overall size of the equipment. It ijs a further object of the invention to provide a system of these characteristics which is characterized by very high rates of r heat release per unit volume, thus making possible further reduction in the

overall size of the equipment needed. It is another object of the invention to provide such a system wlihich is further characterized by high rates of transfer of the heat produced by oxidation of the fuel to the fluid being heated, thereby reducing considerably the area of heat exchange surface required. It is still another object of the invention to provide such a system in which the maximum temperature obtained during oxidation of the fuel is maintained well below 'the flame temperatures ordinarily involved in the combustion of fuels in conventional furnaces, while at the same rtime providing for efficient utilization of the fuel, thereby avoiding problems such as ash fusion, which attend the high temperatures incident ito, flame combustion. In its broad aspect, the present invention involves the oxidation of a suitable fuel-air mixture within a fluidized bed of particles, at least a portion of which are particles composed of an active oxidation catalyst, so that the oxidation of the fuel which releases heat within the bed takes place through the agency of the catalyst at maximum temperatures well below those required for efficient flame combustion. Immersed within the fluidized bed are water tubes, steam tubes, or other suitable heat exchange members through which flows the fluid to be heated, the heat exchange surface being in direct and intimate contact with the particles making up the bed and with the gases flowing therethrough Fluid flowing through the immersed tubes or the like absorbs heat from the bed and itself becomes heated The rate of heat absorption from the bed may be regulated by controlling the bed temperature which in turn may be controlled by the rate of supply of fuel and -air to the bed, the composition of the fuel-air mixture being oxidised within the bed and by other means, in a manner to be outlined more in detail hereafter. In order to effectively oxidize -fuel catalytically at temperatures well below those normally attained in flame combustion, as is required in the system outlined above, it is necessary to employ oxidation catalysts that have high activity in comparison with inert materials such as sand, clays, etc Such active catalysts as are contemplated by the present invention -owe their acteivity to a particular physical structure and/or chemical constitution and -must be used under conditions which are not destructive of these special characteristics Thus in the use of active oxidation catalysts maximum temperature limits 5 below ordinary flame: temperatures, must be observed in-order to avoid deactivation or loss of activity through the alteration of the physical structure -or chemical constitution responsible for their relatively high activity. This requires the control of maximum bed temperatures to avoid deactivation of the catalyst as will be explained and illustrated more

in detail below. Examples of oxidation catalysts which are particularly suitable for use in the system of 70 the invention include activated forms of metal oxides impregnated with a minor amount of a metal in finely divided form In particular, activated forms of alumina, beryllia, thoria, zirconia, or magnesia, or mixtures of these 75 oxides, impregnated with minor amounts of finely divided metals such as platinum, palladium, rhodium, ruthenium, silver, copper, chromium, manganese, nickel, cobalt, or combinations of these metals such as a silver 80 chromium, copper-chromium, copper-manganese combination, have been found to be especially suitable. As well known in the art of catalysis, the so-called activated forms of these metal oxides, 85 such as activated alumina, are those forms which are characterized by a porous structure which possesses a large internal pore volume and surface area The activated form is prepared by controlled dehydration of a hydrated 90 form of the oxide, control of temperature during the dehydration being essential to prevent destruction of the pore structure Activated alumina, for example, may be prepared by precipitating a hydrous alumina gel from a 95 solution of an aluminum salt, drying the gel, and thereafter heating carefully at a temperature not higher than about 2000 CF to expel the combined water and produce a partially anhydrous or substantially anhydrous oxide 100 often referred to as gamma alumina Catalytically active alumina may also be prepared from the naturally occurring bauxite, which contains hydrated alumina, by removal of the impurities which it contains, such as iron and 105 silicates, followed by heating at a temperature below about 20000 F to drive off the combined water In contrast to the activated form, other forms of alumina and similar oxides, such as so-called alpha alumina, also fre 110 quently referred to as corundum oralundum, are characterized by relatively dense structures having little or no internal pore volume or surface area Such materials, either by themselves or even coated with metals selected from 115 the list above, relatively speaking, have little or no oxidation activity The amount of metal impregnating the activated oxide may vary considerably and the optimum amount depends to some extent upon 120 the particular metal chosen In the case of platinum or palladium, for example, very small amounts are required to produce an oxidation catalyst of excellent activity, such as from 0.1 % to 10 % by weight based on the weight 125 of the activated metal oxide In the case of other materials, such as a silver-chromiumcombination, a somewhat higher percentage of the metal such as from 2 O % to 5 0 ', may be more desirable 130 785,398 785,398 3 Impregnation of the active oxide may be accomplished by any desirable method which will result in the depositing of the metal upon the surface of the oxide in finely

divided form. Impregnation is most conveniently accomplished by dipping the metal oxide, such as activated alumina, into a solution of a salt of the desired metal and then decomposing tlhe salt Thus for example, activated alumina may be dipped into a 1 0 % by weight aqueous solution of chloroplatinic acid, dried, and then the platinum salt decomposed into metallic platinum by heat As a result of this type of impregnation, the platinum is distributed over the surface of the alumina in extremely finely divided form. The maximum temperature at which the catalysts of the type discussed above may be used varies somewhat depending upon the particular catalyst employed, but in general ranges below about 20000 F For a platinum on alumina catalyst, for example, the maximum operating temperature is of the order of 18002000 F, while a catalyst consisting of alumina impregnated with a metal combination such as silver-chromium or copper-chromium becomes deactivated at temperatures -of the order of 16000 F. While oxidation catalysts of the type described above are particularly suitable for use in the system of the invention, it is to be understood that other types having similar activity and similar properties with respect to deactivation temperature may also be employed In general, it may be stated -that suitable oxidation catalysts for use in accordance with the invention should have the following characteristics: Good activity, that is the ability to promote the oxidation of fuels at high rates per unit catalyst surface area; wide range of effective operating temperatures, that is, the ability to promote the oxidation of fuels at significant rates at relatively low operating temperatures such as temperatures from 6000 F to 10000 F coupled with the ability to operate at high temperatures, such as from 1300 'F to 1800 'F without undergoing deactivation; and finally, good physical stability such as resistance to' erosion, attrition or other types of disintegration. The phenomenon of fluidization is of course well known, being in extensive commercial use in some industrial applications such as the catalytic cracking of hydrocarbons for the production of high octane gasoline Extensive pilot plant and semi-commercial plant investigation has also been made of the application of fluidization bed technique to processes such as the Fischer-Tropsch, coal gasification, coal carbonization, coal drying, ore roasting, shale distillation and the like. According to these investigations, te excellent temperature distribution throughout the fluidized bed, and consequent ease of temperature control, in contrast to the use of a fixed bed, have been the main advantages which have led to the use or extensive

investigation of the fluidized bed technique This uniformity of bed temperature, coupled with the also recognized advantage of relatively high 70 rates of heat exchange to surfaces immersed within the fluidized bed, has led to the further suggestion of heating a bed of inert solids by the introduction of hot combustion gases therein and absorbing heat from the bed by means 75 of heat exchange surface immersed within the bed. In accordance with the present invention, the principle of the fluidized bed is also employed, but in the present case, as distin 80 guished from prior systems, the oxidation of the fuel, instead of occurring by flame combustion, takes place catalytically at the surface of an active oxidation catalyst which itself comprises the entire or at least a substantial 85 part of the fluidized bed of particles In addition to providing high rates of heat exchange, which of course is a valuable advantage in steam generating and similar types of operation, the invention makes possible very high 90 rates of heat release; and also makes possible operation outside the ordinary limits of flammability thus making feasible the utilization of waste fuel gases which are impossible or difficult xto burn under condi 95 tions of ordinary flame combustion; all at temperatures well below those attained in ordinary flame combustioni processes, thus eliminating all of the difficulties ordinarily associated with such high temperatures 100 As is well known, the fluidization of la bed of solid particles is accomplished by passing a gas stream upwardly through the bed of particles at a velocity which is adjusted so as to expand the bed at least to a condition where 105 the individual particles become disengaged from one another sufficiently to circulate at least in a limited manner throughout the bed, the velocity being however less than that which would cause entrainment of any except a small 110 amount of relatively undersized particles that may be present in the bed A bed of fluidized particles resembles in many respects a boiling liquid, having a turbulent upper surface where the gaseous phase becomes disengaged from 115 the bed and exerting a pseudo-hydrostatic pressure on the walls and bottom of the vessel in which it is contained In accordance with the invention, the degree or violence of fluidization may vary considerably from a con 120 dition where the bed is expanded only enough to allow limited circulation of the 'particles throughout the bed to a condition of more violent fluidization where much more active circulation obtains The size of the particles 125 making up the bed may vary over a considerable range, including particle sizes of the order of 100 to 200 microns such as are commonly used where fluidized bed techniques are employed, to particles of considerably larger 130 785,398 size such as those ranging from 500 to 5000 microns Superficial velocities (linear

velocity of the fluidizing gas stream in an empty vessel under standard conditions) necessary to maintain the bed in a fluidized condition will of course vary with the particles size, ranging from the usual 1 to 2 feet per second required for fluidized beds containing particles of 100 to 200 microns in size, to velocities of 20 feet per second for particles of the order of 5000 microns in size It is to be understood that the specific size ranges mentioned are illustrative only of those that may be used, and the invention is not to be limited to particles of any particular size or size range. According to the invention, there is provided a method for indirectly heating a fluid by means of flowing fluid through a conduit immersed in a fluidized bed of solid particles thereby heating said fluid and absorbing heat from said bed, comprising the steps of completely oxidizing a fuel-air mixture catalytically within said fluidized bed, said bed comprising at least in part particles of an active oxidation catalyst, whereby contact of said fuel_ air mixture with said particles of oxidation catalyst results in release of heat within said bed, and maintaining the maximum temperature of said bed well below ordinary flame temperatures. For increased clarity of discussion, reference is now made to the accompanying drawings in which: Figure 1 is a perspective view of one forns of apparatus suitable for carrying out the invention with portions thereof being broken away and the fluidized material removed therefrom in order to show construction details; and Figure 2 is a vertical sectional view of this apparatus taken generally along line 2-2 of Figure 1. Referring now to Figure 1, the reference numeral 10 refers to a housing composed of fire brick or other refractory material Within the housing 10 a perforate grid 12 is disposed forming a support and air distributor for a fluidized bed 14 having a turbulent upper surface 16. The bed 14 is maintained in a fluidized condition by means of air supplied beneath the bed by 'a blower 17 and line 19 with this air being preheated to a desired temperature by means of burner 18 which is supplied with fuel and air through lines 20 and 22 respectively and with this fuel and air supply being regulated by valves 24 The preheated air enters plenum chamber 25 from line 19 and passes through perforate grid 12 which evenly distributes it throughout ithe crosssection of the bed with the rate of air thus supplied being regulated bv valve 26 Fuel or a fuel-air mixture is supplied by means of a distributor which includes manifold 30 to one end of which is connected supply line 32 and from which project distributor conduits 34 the latter extending across the bed at uniformly spaced intervals and at a location immediately above grid 12 The fuel passes out

through the many openings provided along the length of 70 the distributor conduits 34 and mixes with the preheated air passing upwardly through grid 12 into bed 14. Positioned within the fluidized bed is a tube bank consisting of laterally spaced tube coils 75 36 with each coil comprising a bent tube in a single plane to form a panel with the inlet of the tube communicating with an inlet header 38 and the outlet communicating with an outlet header 40 through the medium of connect 80 ing tubes 42 Water or other suitable fluid to be heated is supplied to the inlet header 38 through supply conduit 44 and in order to more effectively control the distribution of this fluid to the various coils 36, header 38 is 85 divided into three separate sections each of which communicates with conduit 44 through a valved connection 46 The fluid, after entering header 38, flows into the connecting tubes 42, each of which is provided with a meter 90 ing orifice at its inlet, and then into and through the respective tube coils from which the fluid flows into header 40 through connecting tubes 42 and is then conveyed to any desired location In order to provide a more 95 even temperature distribution from the front to the back of the bed the tube coils are connected to the headers so the direction of fluid flow across the bed through adjacent coils is respectively reversed 100 While not shown in the illustrated embodiment the combustion gases generated by the catalytic oxidation of fuel within bed 14, after becoming disengaged from the bed at surface 16, may be conveyed over additional heat ex 105 change surface or passed throudh a fluidized bed of inert material within which heat exchange surface is disposed in order to further reduce the temperature of these gases prior to discharging the same up the usual stack 110 A suitable cyclone senarator (not sl-own) Pl qv be employed to collect fines such as small catalyst particles carried from the bed or ash particles resulting from the oxidation of ashcontaining fuels 115 Referring to Ficure 1, on start ur the Preheat burrer 18 is ignited and the hot preheated air forced un through bed 14 to bring the bed consisting entirely or Dartiallv of narticles of oxidation catalvst to a temnerature, 120 such as from 700 to 1200 F at which tbhe oxidation of the fuel-air mixture suhlseauentlv sunulied to the bed at the surface of the particles of oxidation catalyst takes place at a sufficiendly higb rate to sustnin the minimum 125 operating temnerature of the catalyst under operating conditions The minimum operating temnerature of the catalvst will vary somewvlhat depending upon the activity of the catalvst, the more active the catalyst in general, the 130 785,398 factor since the continued activity of the oxidation catalyst requires that the bed temperature be maintained below its deactivation temperature, which in the case of the catalysts mentioned heretofore, may vary, for example, 70 from 15000 F to 2000 '

F in practice, the control of bed temperature will be effected chiefly by providing a sufficient density of heat exchange surface immersed within the bed, at the chosen rate of heat input to the 75 bed, to maintain the bed temperature at all times below the deactivation temperature of the catalyst but above its minimum activation temperature The greater the rate of heat input to the bed (as expressed, for example, in cubic 80 feet of a given fuel-air mixture per second per square foot of horizontal cross-sectional bed area,) the greater will be the required density of heat exchange surface in the bed (as expressed, for example, in square feet of 85 immersed heat exchange surface per cubic foot of bed volume) to provide the required rate of heat absorption to maintain the desired temperature For a given rate of heat input to the bed, the required density of heat 90 exchange surface will depend also upon the coefficient of heat exchange across the immersed surface and the average temperature of the fluid within the heat exchange tubes. Thus, for example, when the system is used 95 for heating water to 180 F less heat exchange surface will be required for a given rate of heat input to maintain a predetermined bed temperature than when the system is employed for superheating steam to 'a tempera 100 ture of 10000 F. In the more usual situation, where a fuelair mixture in theoretical or near theoretical proportions is oxidized in the bed, the bed temperature, in the absence of cooling, would 105 reach flame temperatures such as 3000 F. and above By immersing the proper amount of heat exchange surface in the bed and absorbing heat therefrom by means of the fluid circulated in indirect heat exchange therewith, 110 the bed temperature may be maintained at the desired level below the deactivation temperature of the catalyst,;such as at a level of from 1000 " F to 15000 F. Regulation of the output of the invention 115 may be achieved by adjusting the rate of flow of the fuel-air mixture per unit horizontal cross-sectional bed area Regulation of the output in this manner is limited by the necessity of maintaining the bed in a fluidized con 120 dition and by the added necessity of maintaining the bed temperature within certain limits, as determined by the minimum activation temperature of the catalyst and the maximum temperature at which the catalyst may operate 125 without undergoing deactivation Thus, at peak loads, the flow of fuel-air miiixture through the bed may be increased to the point at which the bed reaches its maximum permissible operating temperature or until the maximum 130 lower the minimum operating temperature under given operating conditions During the preheat period, the bed of particles need not necessarily be fluidized, and in fact, in some cases it may prove desirable, particularly with respect to heat economy, to preheat the bed with a

relatively low flow of the gases while in a static condition. After preheating ithe bed to the minimum activation temperature of the catalyst under the chosen operating conditions, fuel is delivered to the bed through distribution conduits 34 and the rate of fuel and air supply is adjusted to maintain the bed of particles in a fluidized condition The fuel-air mixture thus produced reacts catalytically at the surface of the catalyst, thus oxidizing the fuel and releasing heat within the bed Simultaneously water, steam or other fluid to be heated is passed through coils 36 with the fluid absorbing heat from the bed during such passage and itself becoming heated The gases leaving the fluidized bed, which may be at an elevated temperature of, for example 600 to 12000 F, may have additional heat extracted therefrom in any desired manner before being exhausted to atmosphere through a sitack. The minimum depth of the fluidized bed necessary to give efficient operation is affected by a number of factors, particularly the rate of introduction of the fuel and air and the activity of the catalyst Generally speaking, the less active the catalyst the greater the rate of flow of fuel mixture through the bed, the greater the depth is required 'to provide complete oxidation of the fuel within the confines of the bed Another factor affecting the minimum depth is the required density of heat exchange surface immersed within the bed in order to provide the desired operating temperature under particular conditions or range of conditions chosen With these factors in mind, it may be stated generally that the fluidized bed may vary in depth from as little as 6 " to as much, for example, as 3 ' or 4 '. The bed need not be comprised entirely of particles of oxidation catalyst but may have included therein particles of other material which are substantially inert under conditions of operation, such as particles of fused silica, sands, clays, etc The inclusion of such particles in the bed tends to reduce the overall activity of the bed In some 'cases however it actually may prove desirable to reduce the overall activity of the bed, as for example, in a situation where a highly active catalyst is used requiring only a small fluidized bed depth, such as 9 ", to provide sufficient catalytic surface, it being impossible without interfering with the fluidization characteristics to provide a sufficiently high density of heat exchange surface immersed within the fluidized bed to maintain the bed at the desired temperature level. Control of the temperature is an important M 8,390 Is fluidization velocity is reached whichever limiting condition is reached first under the particular circumstances of operation At minimum loads, the flow of the fuel-air mix-. ture through the bed may be reduced until the minimum permissible bed

temperature is reached or the minimum fluidization velocity is reached, whichever limiting condition occurs first. It is also possible to vary the heat input to the system, and consequently the heat output, by varying the relative proportions of the fuel and air or in other words, the composition of the fuel-air mixture delivered to the bed By varying the amount of excess air for example, the heat input may be varied independently of the fluidization velocity In all operations, however, where the maximum efficiency is desired, the amount of excess air should be held to the minimum required for sufficient oxidation of the fuel Using the invention, in which ithe oxidation of the fueloccurs catalytically, excess air requirements are reduced lto a minimum relative to thoseordinarily required in normal, flame combustion systems Thus, excess air of the order of 2 to 5 %, as contrasted to the usual ideal requirements of 10 to 30 %/,, required in con ventional boilers will provide for complete oxidation of the fuel. Suitable fuels for use with the fluidized. bed of oxidation catalyst include gaseous fuels such as natural gas, water gas, producer gasetc: liquid fuels such as fuel oils; and finely divided solid fuels such as powdered coal. When charging liquid fuels or solid fuels such as coal, the fuel should be preferably first reducel to a finely divided condition before introduction into the bed In the case of oil, for example, provision should preferably be made for pre-atomization or vaporization to insure rapid and complete oxidation at the surface of the catalyst In the case of coal or other solid fuels, the coal should be reduced to a very finely divided condition, such as ground through 200mesh or finer, to permit the catalytic reaction to take place efficiently In some cases it may be desirable to introduce mixtures of fuel, such as mixture of coal in a fuel gas The fuel may be premixed with the air necessary for oxidation, or introduced separately into the fluidized bed by direct injection within the bed by means of a distributing device immersed therein as shown in the illustrative embodiment. Although atmospheric air will ordinarily be used in the invention, it is to be understood that other oxygen-containing gases such as oxygen-enriched air, mixtures of air and gases returned from the stack, or even pure oxygen, may be used in its stead, and that the term htair" in ithis description and in the claims which follow is intended to include both atmospheric air and these other oxygen-containing gases. The invention is also capable of operating efficiently on waste gases of low BTU content that are difficult or impossible to burn. under conditions of flame combustion One example of such waste gases

that may be 70 utilized in the invention are those obtained from the regeneration kilns in the catalytic cracking process as a result of buring off of the coke deposit on the cracking catalyst under controlled temperature conditions Such gases 75 ordinarily leave the regeneration kiln {at temperatures of 500 F Rand contain 3 % to 8 % carbon monoxide Such mixtures, being outside the limits of flammability, will burn by flame combustion only when preheated to 80 very high temperatures such as 2200 F to 2600 F Such fuel mixtures, however, may be oxidised with complete efficiency in the invention at much lower temperatures. The invention will find its chief application 85 for the generation and superheating of steam to replace conventional boilers for this purpose It may be used, however, for the indirect heating of other fluids, such as the heating of hot water or the preheating of oil 90 as is common in the petroleum refineries prior to the delivery of the oil to distillation towers or other treating units. The invention makes possible, on an economical and practical scale, heat release rates far 95 greater than those obtained in normal boiler furnace aperation Thus, with catalysts of the type hereinbefore mentioned, heat release rate of the order of 100,000 to 1,000,000 BTU per cubic foot ef fluidized bed volume per 100 hour and above can readily be obtained The maximum heat release rate per cubic foot of bed volume depends upon the activity of the catalyst, the more active ithe catalyst, in general, the higher the heat release rate pos 105 sible This factor, combined with the fact that excellent heat transfer rates within the fluidized bed, of, for example, from 30 to 70 BTU per square foot of heat exchange surface, per degree of temperature differential, per 110 hour, obtained in normal operation, results in great reductions in the overall size of the boiler. The following example illustrates the results obtainable through the use of the invention 115 A catalyst was employed consisting of pellets of activated alumina impregnated with 0 2 % by weight of platinum, the pellets being in the shape of cylinders having a diameter and length of about 086 " A bed of such pellets 120 was employed in a cylindrical vessel having a settled depth of 9 inches Fuel-air mixtures consisting of city gas or propane with approximatefy 2 % excess air were passed upwardly through such a bed of pellets at a rate suffi 125 cient to maintain the bed in a boiling or fluidized condition, superficial velocities through the bed at bed temperatures being of the order of 7 ft per second The depth of the bed in -the fluidized condition was about 101 130 6 785,398 perature of said bed well below ordinary flame temperatures. 2 The method according to claim 1, wherein said oxidation catalyst has a minimum activation temperature under operating conditions and a

maximum operating temperature above which said catalyst becomes deactivated, the temperature of said bed being maintained above said minimum activation temperature of said catalyst under operating conditions but below the deactivation temperature thereof. 3 The method according to claim 1 or 2, wherein said active oxidation catalyst has a deactivation temperature below ordinary flame temperatures, iand that said fuel is oxidized at the surface of said oxidation catalyst under conditions and at such a rate as to raise the temperature of said bed, in the absence of cooling, beyond the deactivation temperature of said catalyst, with the fluid being passed through said conduit at a rate adjusted to maintain the temperature of said bed below the deactivation temperature of said catalyst. 4 The method according to claim 1, 2 or 3, wherein water is jpassed through said conduit and converted into steam, the rate of steam generation being regulated by varying the rate of supply of said fuel-air mixture to said bed while at all times maintaining the rate of supply of said fuel-air mixture within the limitation required to maintain said bed in a fluidized condition. The method for indirectly heating a fluid substantially as described with reference to the accompanying drawings. STEVENS, LANGNER, PARRY & ROLLINSON, Chartered Patent Agents, Agents for the Applicants. inches Heat exchange surface consisting of a tubular coil was immersed within the bed through which water was passed at varying rates for the production of hot water or the generation of steam By proper adjustment of the area of heat exchange surface immersed within the bed, the temperature of the bed was maintained within the range of from 11000 F to 1550 F Under such conditions, complete oxidation of the fuel within the bed rat the surface of the catalyst was obtained The rate of heat release within the bed was approximately 900,000 BTU per cubic foot of bed volume, per hour, while the heat ex1 D change coefficients to the coil were of the order of 35 to 49 BTU per square foot of coil area, per degree temperature differential between the bed and fluid within the tube, per hour. It is to be understood of course that the above desciption and illustrative examples given are intended for the purpose of illustration, and that many modifications such as will occur to those skilled in the art are possible within the scope of the invention as set forth in the appended claims.

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* GB785399 (A)

Description: GB785399 (A)

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Description of GB785399 (A)

PATENT SPECIFICATION Date of Application and filing Complete Specification: Nov 2, 1955. 7859399 No 31353155. Application made in United States of America on Nov 15, 1954. Complete Specification Published: Oct 30, 1957. Index at acceptance:-Class 97 ( 3), C 7. International Classification:-GO 1 c. COMPLETE SPECIFICATION Gyroscopic Rate of Turn Indicator We, BENDIX AVIATION CORPORATION, a Corporation of the State of Delaware, United States of America, of Fisher Building, Detroit, Michigan, 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:- The invention relates to gyroscopes and more particularly to gyroscopes adapted to indicate rate of angular motion, such as rate of turn of the craft on which the gyroscope is mounted. An angular rate gyroscope has two degrees of freedom and includes a rotor support rotatably supported in a frame for rotation about an axis at right angles to the spin axis of the rotor When the craft on which the gyroscope is mounted executes a turn, the gyroscope precesses in one direction or the other from its neutral position, as determined by the direction of the turn, and in some instances, coil springs are used to oppose precession of the gyroscope from its neutral position, but such springs are sensitive to friction and do not return the gyroscope to its neutral position Also, such springs usually are non-linear.

One object of the present invention is to provide an improved spring means for opposing precession of the gyroscope from neutral position. Another object is to provide an improved spring means which exerts a substantially linear force on the gyroscope in opposing precession and which is cheap and simple to construct and positive in its action in returning the gyroscope to neutral position. According to the invention thereisprovided an angular rate gyroscope, comprising a rotor supporting member mounted for rotation relatively to a frame member, and rotation restraining means for said rotor supporting member comprising a resiliently flexible elonlPrice 3/6 l gated element secured to one of said members and slidable relatively to the other member, which element is arranged to extend through the axis of rotation of the supporting member in the centered condition of the latter and is 50 resiliently flexed in one or the other sense upon precession of said supporting member in one or the other direction from its centered condition, to exert a centering torque thereon. The invention will now be described by 55 way of example with reference to the accompanying drawings in which:Fig 1 is a horizontal section of an angular rate indicator constructed according to the invention and taken approximately on the 6 m line 1-1 of Fig 2; Fig 2 is in part a front view and in part a vertical section with portions of the indicator removed; 1 Fig 3 is a detail of another embodiment 65 of the novel spring mechanism for opposing precession of the gyroscope. The novel angular rate gyroscope of the invention is shown embodied in an angular rate indicator and comprises a rotor 1 70 rotatably supported in a rotor support or casing 3, mounted for rotation in a frame 5 by bearings 7, 9 A cover 11 is secured to frame 5 A bracket 13 is secured to casing 3 and is pivotally connected to an arm 15 75 attached to the plunger of dash pot 17. A pointer 19 is pivoted to frame 5 by a pivot 21 and is drivably connected to rotor casing 3 to indicate angular rate of turn on a dial 23 A pin 25 on bracket 13 is received 80 between the ends of a forked member 27 secured to a pin 29 mounted on pointer 19. A rod-like spring element 31 is secured at one end to bracket 13 and extends through the axis of rotation of rotor casing 3 and the 85 other end of element 31 is slidably received in ajewel bearing 33 mounted in a member 35 threaded to frame 5 This provides for adjusting the bearing lengthwise of element 31 to vary the effective length of element 31 and 90 785,399 thus vary the sensitivity of the gyroscope. A lock nut 37 prevents rotation of member 35 relative to frame 5 after adjustment. Upon precession of the gyroscope rotor casing 3 pivots in frame 5 and moves pointer 19 over associated dial 23 and such movement is opposed

by dash pot 17 and spring element 31 Spring element 31 flexes in one direction or the other, as determined by the direction of angular movement of rotor casing 3 from neutral position, and as it flexes, it slides in bearing 33 Element 31 exerts an angular force on rotor casing 3 opposing precession of the gyroscope and returns the casing to neutral position when the precessing forces are withdrawn. The housing may be provided with a suitable cover glass 39 at its forward end for viewing pointer 19 and dial 23 and the instrument may also include an inclinometer assembly 41. The embodiment shown in Fig 3 operates in substantially the same manner as the embodiment in Figs 1 and 2 except that jewel bearing 33 a is fixed to bracket i 3 a and slidingly receives one end of rod-like element 31 a, the other end of the rod-like element being seated in a block 35 a rotatable in frame 5 a for adjusting the effective length of element 31 a A lock nut 37 a is provided to prevent movement of block 35 a after adjustment. The centering arrangement embodied in the angular rate gyroscope shown and described herein is positive in its action in returning the rotor support to neutral position. It is cheap and simple to manufacture and may readily be adjusted to vary the sensitivity of the gyroscope Also, the centering arrangement provides for substantially linear precession of the gyroscope from neutral position.

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* GB785400 (A)

Description: GB785400 (A) ? 1957-10-30

Coarse and fine follow-up measuring systems

Description of GB785400 (A)

PATENT SPECIFICATION Inven hz: THOFDPORE JUL 7 IPS MESH 785400 Date of Application and filing Complete Specification Nov 7 1955. No 31127/55. Complete Specification Published Oct 30,1957. Index at acceptance: -Classes 37, A 9 (A 5: B 9: Cl: C 5); and 40 ( 1), NI(A 3 C 1: B 2: D 1), N 3 ( 54: 55: 57 G: V 3). International Classification: -G Oir G 08 c. COMPLETE SPECIFICATION Coarse and Fine Follow-up Measuring Systems We, GILBERT & BARKER MANUFACTURING COMPANY, a corporation organized and existing under the laws of the State of Massachusetts, United States of America, located at West Springfield, State 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 improvements in telemetric systems. More particularly, the invention is directed to an improved null-balance measuring system, having transmitters and receivers interconnected in a normally-balanced circuit network, which becomes unbalanced by minute variations in unidirectional voltage produced in the transmitter by variations in the condition being measured and which automatically rebalances by suitable means such as a reversible twophase alternating-current servo-mator, actuated in one direction or the other, depending on the direction of unbalance, by alternating-current voltages suitably converted from the unidirectional unbalance voltages and suitably amplified, the motor serving to move the indicator of a measuring instrument to show in suitable units the variations in the condition being measured. The invention, while capable of general application, finds one advantageous use in the measurement of liquid level in a storage tank and in the indication of such measurement at a remote point For exam-ple, in the petroleum industry, it is desired to be able to ascertain at one receiving station, the level of liquid in any one of a plurality of storage tanks, and this invention has been directed especially to the accomplishment of this work with precision and in a fool-proof manner, tlthough it may be used for many other purposes, as will be readily understood by those skilled in the art. The invention has for one object the provision in a measuring system of the class des 45 cribed of a means for automatically returning the indicator of a measuring instrument to its initial or zero position,

whenever there is an interruption in the self-balancing circuit network, by means of a small but constant alter 50 nating-current signal introduced into the amplifier of the system and tending, when permitted by the absence of a larger and overpowering signal, to turn the indicator back to zero 55 Tle foregoing provision, while not limited thereto, is especially useful in connection with the fractions measuring instrument used in a receiver which is adapted to be selectively connected by suitable switching means to a 60 plurality of transmitters, as for one example, in the case of a " farm " of petroleum storage tanks The fractions transmitter usually has a continuously rotatable slider This slider can stop in the gap between the two ends of the 65 potentiometer winding and thereby break the circuit network and prevent the receiving fracticns potentiometer of the receiver from rebalancing at the proper level Because of this it Would be possible, under some conditions, 70 for the measuring instrument to give a false indication, except for the provision which automatically restores the indicator to zero, whenever the circuit network is broken in the manner set forth 75 Another object of the invention is the provision in a measuring system of the class described, wherein there are two measuring instruments, both actuated by the same variations in the condition being measured but at 80 different rates, so that one shows unis and the other fractions of units of such condition, of means controlled by and in proportion to the movement of the fractions indicator for opposing movement of the units indicator by its 85 actuating force to maintain the units indicator stationary at one unit position, while the fractions indicator moves gradually from between 785,400 zero and its full unit position Wiecn tbe fr. tions indicator resets to zero the opposing force is released, allowing the units indicator to be suddenly moved one full unit from said one unit position tc; a next adjacent unit position. These and other objects will best be understood from the detailed description of one illustrative embodiment of the invention in the accompanying drawing in which, The figure is an electrical diagram of a measuring apparatus embodying the invention. In this drawing, the invention has been shown, by way of illustrative example, as embodied in a null-balance system for measuring the liquid level in any one of a plurality of storage tanks and for indicating such level at a remote location on suitable instruments, which may indicate or record the level in feet and inches, for example This adaptation of the invention is desirable for use in the vetroleum industry to enable an operator at a receiving, station, remote from a tank farm, to be able to readily ascertain the level of liquid in any one of the large number of storage tannls which usually comprise such

a farnm While this Invention is desirable for this narticular use it is nevertheless adapted for mranv other uses, wherever the condition to be measured is to be expressed in units and fractions thereef, as will readily be understood by those skilled in the art. At each tank is a transmitting station, such as 1 ' and T 2, and at each such station are a pair of transmitters Each such pair may for example consist of two Precision potentiometers 1 and 2, the movable elements 3 2nd 4 of which are actuated by variations in the level of liquid in the tank In this case the potentiometer l has a circular resistance wfinding and its movable element 3 will be rotated one complete revolution by a twelve-inch variation in level of liauid in the tank The rotent ometer 2 has an helical resistance winding and its movable element 4 will traverse its ranfie (ten revolutions) by a variation in level eaqul to the total depth of liquid that the tank hil hold, say for exa-mule, 50 feet Either pair of these transmitters mav be connected by a switch S, usually snap-acting and orerated in any suitable way and Preferably from the receiving station R to a pair of receivers consisting of precision potentiomreters 5 and 6. The movable elements 7 and 8 of the potentiometers 5 and 6 are respectivelv actuated by suitable servo-motors Ml and M' through the intermediary of a suitable transmission 9 which includes reduation gearing 10 and wiv Nch is herein indicated merely in conventional form The servo-motors in this examrle are 115 volt, two-nhase alternatinz-ulrrent induction motors having a synchronous speed of 3600 r m p, which is reduced b ear in to 8 r m p The two inch rotentio-ireers l and 5 antd the tvwo foot potentiometers 2 and 6 are include in a measuring crcnit net i Oi of the null-baiance typ Te, whereby the movement of the movable element 3 or 4 wil' unbalance the particular circuit network that it controls The unbalance signal, which is a small micro-ampere D C current or nmilli-volt 70 D.C voltage, is converted in a suitable converter C' or C', as the case may be, into phasesensitive alternating-current that is amplified by a suitable electronic amplifier A' or A 2, as the case may be, and transmitted to the motors 75 MW or M 2, whn ich move the elements 7 or 8, respectively, to rebalance the respective systems The measurements are shown by indicators such for example as pointers 11 and 12, which may be driven from the shafts of h O elements 7 and 8, respectively, and show on scales 13 and 14 the measurement in inches and feet respectively. Broadly considered, each receiver includes a measurement indicator movable by electrical 85 means, which include the servo-motor, receiving potentiometer, amplifier and converter and which is actuated by a variation in voltage produced by the transmitter The converter constih tes an input portion of such electrical 90 means, receiving

the unbalance voltage from the transmitting potentiometer. All the potentiometers described are energied from a suitable power source, usually Located at the receiving statieon such source 95 supplying direct current by way of line wires and 16, which are respectively connectri to the positive and negative terminals of the potentiometers The line wire 16 connects wit'l the negative terminals of all the potentiometers 100 at all the tanks, wvhereas the line wire 15 may be selectively connected by switch S to various line w vire extensions 15 ', which extend one to each tank and connect with the positive terminals ef both transmitting potentiometers At 105 each transmitting station, line-balancing variable resistors 17 and 18 are respectively interposed between the line wires 15 ' and 16 and the Positive and negative terminals of the potentiometers The inch and foot transmitting 110 patentiometers are connected in parallel and one set of variable resistors 17 and 18 suffices for both The receiring potentiometers 5 and 6 'nave individual line-balancing va-iable-resistors 19 and 20, respectively The various line 115 balancing resistors are adjusted so that the potential across the positive and negative termina L of each potentiometer is exactly the same The movable elements, or sliders 3 apt' 4, of the transmitting potentiometers are con 120 nectel through the converters C' and C 2 to the mnov a'e ele ents 7 and 8 o respectivelv of the receiving Potentiometers 5 and 6 When the element 3 is in the same position as element 7 and the element 4 is in the same posi 125 tion as element 8, no current will flow in the connection between the elements 4 and 8 Each element 3 is connected by a wire 211 to a terminal of Switch S and each element 4 is connected by a wire 22 ' to another terminal of 130 785,400 3 switch S This switch can connect any pair r of wires 21 ' and 22 ' to wires 21 and 22, res t pectively, which lead to the converter Cl and c a foot-stepping means ST, respectively, such ( means being connected by a wire 23 to the 1 converter C 2, as will later be described in i detail 1 The direct-current power source for the e potentiometers may be of any suitable kind i There has been shown herein a power source l P, which supplies a direct-current potential of 1 volts to the line wires 15 and 16 This source P includes the secondary 24 of a transformer 25, the primary 26 of which is connected by line wires 27 and 28 to a suitable source of alternating current, in this case of volts and 60 cycles frequency The secondary 24 is connected to line wires 15 and 16 by wires 29 and 30, the wire 29 having interposed therein a rectifier 30 ', a choke coil 31 and a variable resistor 32 (herein of 200 ohms resistance) The wire 29 is connected at points on opposite sides of coil 31 and a point between resistor 32 and wire 15 to wire 30 by filter capacitors 33 Connecting the wire 30 to the wire 29 at a point between resistor 32

and the connection to the adjacent capacitor 33, is a resistor 34 (herein having a resistance of 2000 ohms) This power source rectifies alter-nating current at 120 volts and delivers direct current to the line wires 15 and 16 at 80 volts, the last named voltage being adjustable by the variable resistor 32. Direct current for the amplifiers A' and A 2 is derived from a full-wave rectifier 261 supplied from a secondary 27 ' of transformer 25, which secondary has its mid point grounded and its terminals connected one to each of the plates of the rectifier The cathode of the rectifier is connected by a wire 28 ' to both the amplifiers A' and A' and its filament is supplied with heating current from a secondary 291 of transformer 25. The converters C' and C 2 may be of any suitable type In the example herein shown, each converter comprises a bridge circuit having resistors 35, 36, 37 and 38, one in each branch of the bridge, and a variable resistor 39, the movable element 40 of which constitutes one output terminal of the bridge, the other output terminal being designated 41. The input terminals 42 and 43 of the bridge circuit are connected by wires 44 and 45 to a secondary 46 of transformer 25, herein sunplying 60 cycle alternating-current at 8 volt. The converter C' has a separate supply at the same voltage and frequency from a secondary 47 of transformer 25 by way of wires 48 and 49 The resistors 35 and 36 are ordinary linear resistors of substantially equal resistance, in this case 33 ohms The resistors 37 and 38, however, are non-linear resistors, which are semi-conductors exhibiting some degree of polarization and have the special characteristic that their ohmic esistance varies with the current flowing hrough them and with the direction of flow f the current Germanium, selenium and silicon are examples of material that have been found suitable An ordinary dry type rectifier 70 s suitable provided that it is operated at a voltage below that at which it will function efliciently as a rectifier because the rectifier does not function as a rectifier in the converter. Rather, it allows current to flow in both direc 75 lions but to different degrees The output terminals 40 and 41 of the bridge circuit are respectively connected by wires 50 and 51 and coupling capacitors 52 and 53 to the input terminals of the amplifier The wire 21, which V 3 connects with the slider 3 of the transmitting inch potentiometer is connected through a loading resistor 54 to wire 50 and thus to output terminal 40 of the converter bridge The slider 7 of the receiving inch potentiometer is 85 connected by a wire 55 to wire 51 and thus to the output terminal 41 The wire 21 is also connected by a capacitor 56 to a grounded input wire 511 of the amplifier Al.

It will thus be seen that the inch sliders 3 90 and 7 and the converter bridge C' are connected in series by the wires 21, 211 and 55. With no current flowing in this series connection the converter bridge C' is balanced by adjustment of the slider 40 until no AC vol 95 tage appears in its output circuit A movement of the inch slider 3 of the transmitting inch potentiometer will unbalance the measuring system and a small voltage, of the order of milli-volts, will be applied across the output 100 terminals of the converter bridge, causing a micro-ampere unidirectional current to flow through the bridge The current will divide and flow part through one branch, which includes resistors 35 and 37, and part 105 through the other branch which includes resistors 36 and 38 The arrow heads of the symbols for the non-linear resistors 37 and 38, indicate the direction in which the resistors are most conductive It will be seen that direct 110 current will flow through one non-linear resistor in its more conductive direction and through the other non-linear resistor in the less conductive direction The resistance of one non-linear resistor will increase and the resis 1 5 tance of the other will increase, causing a change in current through the bridge The bridge becomes unbalanced and a 60-cycle alternating-current appears across the outmut terminals of the bridge This current is either 120 in phase or entirely out of phase with the line current depending on the polarity of the unbalanced voltage The small unbalance alternating-current signal is amplified to a suitable extent by an amplifier A', which may be 125 of any suitable type well known in the art, and the amplified signal is transmitted by wires 57 and 58 to one winding 59 of the two-phase servo-motor M' The other winding 60 of motor M' is connected to the alternating-cur 130 785,400 785,400 rent supply wires 27 and 28 A suitable capacitor 61 is interposed in one of such wires to secure proper phase displacement When the unbalance voltage is of one polarity, the motor M' will turn in one direction and when the unbalance voltage is opposite polarity, the motor will turn in the opposite direction When the measuring system is in balance there is no 60 cycle output current from the bridge and the motor remains stationary. In the case of the transmitting foot potentiometer, the unbalance voltage is applied to converter C 2, changed into alternating current, which is amplified by an amplifier A and transmitted to a motor M' to actuate the slider 8 and pointer 12 in the same general way as described in connection with the inch potentiometer, except that the pointer 12 and the slider 8 are moved step by step The pointer 12 is LO moved by increments equal to the distance between two successive graduations on scale 14 and never comes to rest in an intermediate

position It is desired to have the pointer 12 remain stationary at a foot graduation, while the point 11 moves up or down between 0 and 12 inches To accomplish this, is the purpose of the stepping arrangement ST, heretofore referred to as being interposed between the wire 22, which connects with the slider 4 of the transmitting foot potentiometer, and the wire 23, which connects with output terminal 40 of the converter bridge C 2 The other output terminal 41 of bridge C' is connected by a wire 62 with the slider 8 of the receiving foor potentiometer. This stepping arrangement ST comprises means for producing in the series circuit that interconnects the sliders 4 and 8 of the transmitting and receiving foot potentiometer 2 and 6, a unidirectional voltage, which will equal and oppose the voltage produced by movement of the foot slider 4 and cancel it, so that no movement of the slider 8 or pointer 12 will result The production of this bucking voltage is controlled from the slider 7 of the receiving inch potentiometer 5 and is directly proportional to the voltage produced as this slider moves from 0 to 12 inches or vice versa. Movement of the slider 8 and pointer 12 of wt) the receiving foot potentiometer occurs only when the slider 3 passes from one end to the other of the resistance winding of the transmitting inch potentiometer 1 There is a small gap between such ends that has been shown conventionally and not its actual size, which is very small, a matter of about 2 degrees in angular extent When the slider 3 passes from one end to the other of its winding the slider 7 rebalances and the indicator 11 is reset, moving to zero and causing the bucking voltage to drop to zero Then the slider 8 and pointer 12 will be moved by the voltage derived from the foot potentiometer in one step such that the pointer is carried to the next foot graduation on the scale 14 The bucking voltage must be isolated from the potentiometer voltages although it must be controlled by and in proportion to the change of voltage produced by the movement of the slider of one of the inch potentiometers and preferably that of the 70 receiving inch potentiometer. In order to effect isolation of the bucking voltage, a transformer 64 is utilized and the bucking voltage is produced in the secondary and a circuit, conneced thereto, as will be 75 later described The primary 66 of transformer 64 is supplied with current, in this case at 120 volts, 60 cycles, from a secondary 67 of the power supply transformer 25 The primary 66 is included in a series circuit comprising the 80 wire 68, secondary 67, a wire 72, load resistor 71 (in this case of 100,000 ohms resistance), triode 70 and a wire 69 The primary 65, while shown connected to the plate of triode 70, could equally well be in the cathode side with 85 resistor 71 The latter is by-passed by a

capacitor 73 The heater of this triode is supplied with 6 3 volts from a secondary 74 of transformer 25 Grid bias is secured by way of a wire 75, which connects with a tap of a vol 90 tage divider 76 The latter is connected across the direct current supply wires 15 and 16, and said tap, in this case, is 20 volts above the negative power supply terminal The grid of triode 70 is connected through a resistor 77 95 and a wire 78 to the wire 55 and thus to the slider 7 of the receiving inch potentiometer. The secondary 65 is connected in series with a rectifier 79 and a variable resistor 80 which in this example has a resistance of 1000 ohms 100 The wire 22 from the slider 4 which is the positive output terminal of the transmitting foot potentiometer is connected to the positive terminal, which in this case, is the movable contact of the variable resistor 80 The nega 105 tive terminal of resistor 80 is connected to the wire 23, which, as above described, connects with the converter C 2 and through the latter and wire 62 with the slider 8 of the receiving foot potentiometer 6 The voltage produced in 110 the circuit of the secondary 65 is rectified by rectifier 79 and its pulsations are smoothed out by an electrolytic capacitor 81 A part of this voltage, in this case about a third, is applied in the circuit between the sliders 4 and 8 in 115 opposition to the voltage derived from the transmitting foot potentiometer 2. The circuit associated with triode 70 is basically a form of " cathode follower ", which has characteristics making it suitable for the par 120 ticular work here involved Specifically, the circuit is highly degenerative and thus has a high degree of negative feed back This makes for excellent linearity, so that the output voltage is very closely proportional to the input 125 voltage Therefore, the circuit is independent of tube aging or differences between individual tubes While there is an actual loss in voltage (the output voltage being about 95 % of the input voltage), there is a gain in power because 13 (' 785,400 the input impedance becomes so high that ne; appreciable power is drawn from the input source Loss of voltage is not important since a maximum of only about 1 5 volts is required for the bucking voltage This circuit permits the use of input voltages as high as 75 volts while retaining good output proportionality. These are the usual attributes of cathode follower circuits As differentiated from the conventional cathode-flollower circuits, the present one is supplied with alternating plate voltage of 120 volts and the triode operates in self-rectifying fashion The output voltage is in series with the input voltage and bucking it. The circuit operates to cause a direct-current voltage to appear across the cathode resistor 71 which voltage is practically the same as that across the input The input voltage to the cathode follower is

taken between the slider of the receiving inch potentiometer and the tap in the voltage divider 76 and in this case, varies from approximately -20 to + 55 volts. The maximum bucking voltage required is only about 1 5 volts 5 assuming the foot transmitting potentiometer voltage to vary from 0 to 75 volts with a variation of from 0 to 50 feet in the depth of liquid in the tank The necessary reduction in voltage to from 0 to 1 5 is effected with the step down transformer 64 (having a 5 to 1 ratio) and the variable resistor 80, which is adjusted to exactly the proper voltage That is, the bucking voltage produced will vary from 0 to the maximum as the voltage of the transmitting foot potentiometer varies, when moved by a one foot difference in level. The input voltage varying as above set forth, causes the output voltage (across the terminals of variable resistor 80) to vary from 0 to 1 5 volts in direct proportion. It will therefore be seen that as the slider 4 of the transmitting foot potentiometer moves from any foot position toward another the variation in voltage effected by its movement over this foot range is offset by an opposing voltage which varies in the same manner and to the same extent, whereby the pointer 12 of the receiving foot potentiometer will remain stationary at said one foot position on scale 14 The pointer 12 will not move until the opposing voltage ceases which happens when the slider 7 of the receiving inch potentiometer resets to zero Then, the one foot change in voltage built up by movement of the transmitting foot potentiometer through a one foot range will cause the motor M 2 to move pointer 12 up or down as the case may be to the next one foot graduation on scale 14 and the slider 8 to rebalance the network. The invention, as thus far described, is applicable for the remote indications of liquid level in a single tank However, when a plurality of tanks are employed and the receiver is switched from one transmitter to the other, as for example by the switch S, there is a possibility of error under certain conditions unless means are provided to prevent it The difficulty arises from the necessity of using a continuously rotatable inch potentiometer 1, where the slider 3 must move from one end of the potentiometer winding to the other across 70 a dead spot or gap 63 This gap represents about half of one per cent of the winding space of the potentiometer and usually about /J on the scale 13 This will means a variation of '/3 J 2 at the zero point, which is not too 75 serious The serious factor is that about half of one per cent of the time or about once in times, the slider 3 will stop in gap 63, thereby opening the null-balance circuit and making it inoperative 80 In the case of a single tank system, the inch indicator 11 will follow down with the tank level to within 1/, inch

of zero level and remain there in an inoperative condition until the tank level changes sufficiently to cause the 85 slider 3 of the transmitting inch potentiometer to remake contact with either the top or the bottom of its resistance winding and thus no serious error will occur However, in a multitank system, trouble can arise, when the opera 90 tor switches the pair of receivers from one pair of transmitters, as at T', to another pair of transmitters as at T 2 Suppose that the first tank has a level of 25 feet 6-4 inches and that this level has been read and recorded Suppose 95 also that the second tank has a level of 41 feet 0 inches and that the slider 3 of its inch potentiometer is on the dead spot 63 When the operator switches to the second tank, the foot indicator 12 will attempt to rebalance to the 10 op proper foot graduation on scale 14 but the inch pointer 11 will remain in error at the 63 " reading Moreover, the stepping signal, which was correct for the first tank, or of the proper amplitude for an inch reading of 6 k"', is now 105 incorrectly applied to the foot indicator 12 and will position it about midway between the 40 foot and 41 foot positions on scale 14. To overcome this difficulty, a relativelysmall 60 cycle alternating-current signal, which 110 is called a " creep " signal, is injected into the amplifier in such a manner as to actuate the motor Ml in the direction necessary to turn the indicator 11 back to zero, whenever the measuring circuit network is opened because 115 of the slider 3 stopping in the gap 63 While this creep signal may be injected into the amplifier A' at various locations, it is herein shown as injected into the cathode circuit of the first stage amplifier tube 85 This creep 120 signal is derived from a secondary 82 of transformer 25 that supplies the 6 volts needed for the heaters of the various tubes One terminal of such secondary is customarily grounded and the other terminal is connected by a wire 83 125 and a 150,000 ohm resistor 84 to the cathode terminal of the first stage tube 85 of ampifier A' This tube has an input resistor 86 (in this example having a resistance of 1 megohm) and a cathode bias resistor 87 (in this example 130 having a resistance of 330 ohms) The resistors 84 and 87 constitute a voltage divider and the voltage across the terminals of resistor 87 will be about 129 A C volts in this example This creep signal is applied to the cathode circuit of tube 85, and assuming an amplification of 10 in the first stage of the amplifier, this signal would be balanced by an input signal of 0129 A.C volts in the direction tending to turn the motor M 1 to move the indicator away from zero This creep signal, in this example, is amplified about 150 times, and provides at the motor MA about 19 volts, which is sufficiently above the average motor starting voltage of around 8 volts, to accomplish the purpose Thepolarity or phase of this

alternating creep voltage is such as to turn the motor in the direction necessary to move the indicator 11 back to zero A stop, indicated conventionally at 88, is provided to arrest indicator 11 at zero Similar stops 89 are provided to prevent the slider 7 from running off either end of the resistance winding of potentiometer 5 Consequently, under the circumstances above described, where the receivers are switched from the transmitters at one tank which has a level of feet 6 inches, to the Iransmitters at another tank, which has a level of 41 feet O inches, the transmitter inch potentiometer will be open because its slider 3 is in gap 63 and the creep signal will cause the pointer 11 to move back to zero position As the slider 7 of the inch potentiometer 5 resets to zero, the stepping signal will decrease to zero and be cancelled The slider 8 of the receiving foot potentiometer will rebalance at the 41 foot position and indicator 8 will be moved to the 41 foot indication on scale 14. The use of the creep signal necessarily means that balancing of the measuring circuit will occur when the indicator 11 is at a point slightly offset from zero, assuming that this circuit has been reclosed This offset will, however, always be in the same direction and by the same amount Compensation may be made by shifting the scale by the amount of the offset or by adjustment of the line resistors 19 and 20 Since balance takes place, strictly speaking, at a false null point, it is necessary that a very minute line current flow, just sufficient to produce an output voltage from the converter bridge circuit of equal amplitude and opposite phase to overcome the injected creep signal The error introduced by the use of this creep signal is well within the permissible tolerance and represents a difference in level of only 002 inch. In operation, assuming switch S to be positioned as shown, the transmitters at 'P are coupled to the receivers at R and any variation in the condition being measured, such as level of liquid in a storage tank, will cause movement of the units and fraction sliders 4 and 3, respectively The movement of the fractions slider 3 unbalances the fractions measuring circuit network and causes the motor M' to be actuated to move slider 7 of the fractions rezeiving potentiometer 5 to rebalance the network and also move indicator 11 to indicate on scale 13 the new level in fractions, in this 70 case inches The movement of the slider 4 of the units or foot potentiometer 2 does not, however, cause the slider 8 of the units receiving potentiometer 6 to follow it As the foot slider 4 moves and effects a change in voltage, 75 an equal but opposite voltage is created by the stepping means ST, with the result that the slider 8 remains stationary and the indicator 12 likewise remains stationary at a unit or foot graduation on scale 14 The stepping means 80 ST is controlled by the movement of

the slider 7 of the fractions or inch receiving potentiometer 5 The fractions indicator 11 will move up or down the scale 13 without any resulting movement of the units indicator 12 until the 85 slider 3 of the fractions transmitting potentiometer moves from one end of the winding of the latter to the other end When this occurs, the slider 7 will rebalance and reset indicator ii from zero to full scale ( 12 inch) position or 90 vice versa In either case, the bucking signal will be caused to drop to zero, whereupon, the units slider 8 will rebalance and move the indicator 12 to a position one unit higher or lower on the scale 14 95 In switching the receivers from one pair of transmitters to another pair, the creep signal comes into play, whenever the slider 3 of the fractions potentiometer of the second transmitter is in the gap 63 The measuring circuit 100 is then broken preventing the fractions receiving potentiometer from rebalancing and its indicator from showing the proper value On such a break in the measuring circuit and in the event that the slider 7 and indicator 11 are 105 in other than their zero positions, the motor Ml will be actuated to move them to such positions. The invention thus provides an improved telemetric system which is particularly adapted 110 for use where the measuring instruments must show units and fractions of the condition being measured It is characterized by improved means for maintaining the units indicator stationary at one unit position during 115 the movement of the fractions indicator between the two extreme positions of its range and for moving the units indicator by one unit increments only when the fractions indicator reaches either of its extreme positions The 120 invention also is characterized by means for moving the fractions indicator to its zero position, whenever, on switching from one fractions transmitter to another, the slider of the latter transmitter is on its dead spot whereby 125 the measuring network is temporarily inoperative The invention is particularly useful in systems where there are a plurality of transmitters that are to be successively connected to a single receiver and enables the switching 130 785,400 t 785,400 7 from one transmitter to another to be effected without introducing any possibility of any substantial error occurring.

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* GB785401 (A)

Description: GB785401 (A) ? 1957-10-30

Improvements in or relating to switching devices for record players

Description of GB785401 (A)

PATENT SPECIFICATION Date of Application and filing Complete Specification: Nov 9, 1955. 785,401 No 32041/55. Application made in Germany on Nov 12, 1954. Complete Specification Published: Oct 30, 1957. Index at acceptance:-Classes 38 ( 5), Bl F( 1 X:8), B 2 A 5 A 5; and 40 ( 2), D 2 BU. International Classification:-G 10 j, HO 2 c. COMPLETE SPECIFICATION Improvements in or relating to Switching Devices for Record Players We, PHILIPS ELECTRICAL INDUSTRIES LIMITED, of Spencer House, South Place, Finsbury, London, E C 2, a British Company, 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:- The invention relates to switching devices for record players provided with a support, longitudinally movable by spring means, for the pick-up arm, which support in the loaded condition occupies a position which is different from the position in the unloaded condition and which according to these positions controls a switch included in the circuit of the driving motor of the turn-table, which switch can also be controlled by a separate switching lever which is adapted to be operated manually and acts upon a switch actuating member, associated with the pick-up arm support and provided with a switch contact, without the position of the support being changed. In the known devices of this type a switch lever actuates the mains switch by means of a lever system which also acts upon the pick-up support by means of a coupling member. However, such a device occupies a comparatively large amount of space, which is not available in modern record-players andlor. record-changers due to their small sizes.

It is an object of the invention to provide a switching device for record-players of the kind described in the preamble which has a very compact and space-saving construction, the switch actuating member being adjustable over the pick-up support and, when it has been moved by the switch lever, being held in this position by the support when the pick-up arm has been raised from the support, whilst to the switch actuating member a restoring force is applied such that, after the pick-up has again been returned to the support, said switch actuating member opens the switch to lPrice 3/61 stop the motor. This method consequently eliminates the need for a separate lever system appertaining to the system for the transmission of movement, so that the size of the switching device 50 in the horizontal plane is determined substantially exclusively by the cross-sectional area of the coupling member together with the switching contact. Preferably the lower end of the pick-up arm 55 support is provided with a projection by means of which the switch actuating member is supported in switch actuating position, which member carries one part of the switch comprising a snap spring having a switch 60 contact thereon. The restoring force which acts upon the switch actuating member and opposes the spring action of the pick-up arm support is exerted by a weight or a resilient member and 65 is smaller than the spring force exerted by the support but greater than the force required for -operating the switch. In order that the invention may readily be carried into effect, one example will now be 70 described in detail with reference to the accompanying drawings, in which:Fig 1 is a cross-sectional view of a switch device in accordance with the invention, the pick-up arm being disposed on the support 75 whilst the switch actuating member is in the rest-position; Fig 2 is a side elevation of the sectional view according to Fig 1; Fig 3 shows the switch device shown in 80 Fig 1 the switch actuating member being raised; and Fig 4 shows the switch device shown in Fig 3 the pick-up arm being raised. Through a frame plate 1 of a record-player 85 a support 3 shaped into the form of a hollow cylinder is passed from below in the proximity of a turn-table (not shown) which is driven by an electric motor 2, which support is secured to the frame plate 1 Below the 90 r_ X am 785,401 frame plate 1 the support 3 is designed as a housing 4 for the switch of the driving motor 2. In Figs 1 to 3 the pick-up arm 5 is located on the support 3 of the record-player in its S rest position and by its weight presses a support 7, which is adapted to be moved vertically in the support 3 in a hollow cylinder and which is acted upon by a compression spring 6 abutting against a base plate 8 of the switch housing 4 The support 7

is provided at its lower end with a flange 9 upon which a switch actuating member 10 made of insulating material bears The switch actuating member 10 has a cylindrical aperture formed in its upper portion which slightly exceeds the outer diameter of the support 7, so that the switch actuating member 10 is vertically displaceable over the support 7 by means of a lever 12 of a push-button device 13, which lever engages a projection 11 of the switch actuating member 10 The lower portion of the switch actuating member 10 passes through the frame plate 8 and is bifurcated, the bifurcated part holding a weight 14 which tends to restore the switch actuating member 10 to its rest position. The upper portion of the switch actuating member 10 in addition is provided with two opposed wedge-shaped grooves 15, which are adapted to engage with one end of a snap spring 16 which is used to operate a switch contact In the rest position of the switch actuating member 10 the snap spring 16 engages an insulated pin 17 of the switch housing 4 This spring is connected to one end of the winding of the driving motor 2, the other end of which is connected to a mains terminal. When the push-button device 13 (Fig 2) is actuated, the switch actuating member 10 is raised by the lever 12, so that the contact spring 16 is snapped over (Fig 3) and engages an insulated contact 18 which is provided on the switch housing 4 and is also connected to a mains terminal, with the result that the driving motor 2 starts. By the driving motor 2 the pick-up arm 5 is automatically lifted from the support 3 and the support 7 and lowered onto a record arranged on the turn-table by means of a mechanism (not shown) Simultaneously the compression spring 6 raises the support 7 so that it engages, with its flange 9, the switch actuating member 10 which has been supported by the lever 12 and is now held in the raised position by the support 7 (Fig 4). Consequently the thrust force of the spring 6 must be stronger than the weight of the switch actuating member 10 inclusive of the counterweight 14 The push-button device 13 can now be released so that the lever 12 returns to the initial position. When the record has been played, the pick-up arm 5 is again located on the support 3 and by its weight presses down the support 765 against the force of the spring 6, whilst the switch actuating member 10 is also moved down under the influence of the counterweight 11 so that the contact spring 16 is suddenly caused to snap over, with the result that the 70 circuit of the driving motor 2 is interrupted (Fig 1) It will be obvious that the weight 14 must be great enough to be able to snap over the contact spring 16.

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* GB785402 (A)

Description: GB785402 (A) ? 1957-10-30

Improvements in loaders for sugar cane or the like

Description of GB785402 (A)

COMPLETE SPECIFICATION Improvements in Loaders for Sugar Cane or the like I, ALLAN MACSPORRAN, of Redbank, near Brisbane, in the State of Queensland, Commonwealth of Australia, a Subject of the Queen of Great Britain, 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 improvements in loaders for sugar cane or the like, the term "cane or the like"embracing cane stalks and other rod like articles. A loader for sugar cane or the like may be applied to the front of a hydraulically operated front-end lifting frame mounted on a tractor, the loader in such a case ordinarily including a loading fork hinged to the front of the lifting frame in advance of the tractor. and adapted, when the frame is lowered, to lie close to the ground, releasable locking means being provided to retain it in such operative position. Also pivoted to the front part of the lifting frame, above the fork, is a grab device including arms curving forwardly and downwardly and means adapted to cause these arms to descend to gather and hold cane under which the fork has been driven upon the advance of the tractor. The cane, supported by the loader and held by the grab. may be lifted by elevating the lifting frame, and carried by

manoeuvering the tractor over a truck, and when a trip or lock release mechanism is operated by the tractor driver, the fork drops to shed the load into the truck. The principal object of my present invention is to provide a loader for cane or the like having a grab device which is particu- larly efficient in gathering cane on to a loader fork, and holding it so that none of the load will be inadvertently shed whilst it is being raised, or during manoeuvering of the tractor. Other objects of the invention are to provide a loader having a grab device which ----a ., is simple and economical to manufacture, easy to operate, and sturdy and durable in use. With the foregoing and other objects in view, my invention resides broadly in a loader for cane or the like including a fork adapted to be mounted on a lifting frame of a tractor and adapted, when in operative position, to be driven by the tractor under a load of cane or the like ; releasable locking means adapted to retain the fork in operative position, a grab including a grab arm having a down-turned front end and adapted to be pivotally mounted at or near its rear end above the fork : a flexible member extending rearwardly from the lower front part of the grab arm ; means for raising the grab arm to inoperative position ; means for lowering the grab arm to operative position; and means adapted to cause tensioning of the flexible member as the grab arm is moved to or near to operative position. Preferably spring-loaded means are provided for raising the grab arm to inoperative position, and preferably, for lowering the grab arm to operative position there is provided a hydraulic ram connected between the grab arm and one arm of a bell-crank, to the other arm of which is connected the flexible member, the parts being so made and arranged that as the grab arm is brought to or near to operative position, the ram, on extending, moves pivotally beyond a dead-centre position in relation to the bell-crank while the bell-crank is held by the ram against a stop, further extension of the ram moving the bell-crank to tension the flexible member. Other optional features of the invention will become apparent from the following description. In order that a preferred embodiment of the invention may be readily understood and put into practical effect, I now refer to the accompanying drawings, wherein : Fig. 1 is a side elevational view of a cane loader according to the invention, the fork being in operative position and the grab be- ing in inoperative position ; Fig. 2 is a plan view of the loader shown in Fig. 1 ; and Fig. 3 is a side elevational view of the loader, the fork being in operative position, and the grab being lowered to operative position. The cane loader shown in the drawings is adapted to be applied to a

pair of lifting arms. the front portions of which are indicated at 10, of a front-end lifting frame, these lifting arms being adapted to be pivoted at their rear ends to either side of the chassis of a tractor, hydraulically operable means (not shown) being provided for raising or lowering the lifting arms. The lifting arms are rigidly interconnected, at their downwardly-inclining front parts, by two transverse bars 11 on which are fitted rear and front spacer tubes 12 and 13 respectively. A lifting fork assembly 14 is mounted at the lower front parts of the lifting arms 10, this assembly including a transverse shoe spacer tube 15 from each end of which there extend radially a pair of spaced lugs 16 pivoted at 17 to either side of the front extremity of one of the lifting arms 10. Normally inclining forwardly and downwardly from the said shoe spacer tube 15, near to each end, are a pair of spaced shoe mounting brackets 18, and between each pair of these brackets the rear end of a lifting fork shoe 19 is pivoted by a bolt 20. A shoe adjustment bolt 21 passing through corresponding arcuate slots 22 in each pair of brackets and the interposed upper rear part of the hoe 19 acts to hold each shoe in desired sagulady adjusted position. In order to retain the lifting fork assembly 14 in operative position, as shown, there are provided a pair of shoe lock assemblies 23 between the shoe spacer tube 15 and the front lifting arm spacer tube 13, these shoe locks being adapted to be released, to permit the lifting fork 14 to drop gravitationally to inoperative position, upon the tensioning, by the driver of the tractor, of a cable 24 connected to a trip mechanism 25. The nature of the shoe locks and the associated trip mechanism does not form part of my present invention. A forwardly extending grab mounting bracket, indicated generally at 26, is mounted upon the rear and front lifting arm spacer tubes 12 and 13. This mounting bracket includes a pair of stays 27 which, for the greater part are parallel, but which, towards the rear, converge and are secured by a bolt 28 to either side of an apertured lux 29 extending forwardly from the lifting frame rear spacer tube I2. A grab shaft 30 has its reduced and threaded ends passed through apertures in the front ends of the stays 27 and through registered apertures in the front ends of a pair of supports 31, the threaded ends of the said shaft then being engaged by nuts 32. The rear ends of the said supports 31, and also the lower ends of a pair of braces 33, are secured by bolts 34 to lugs 35 extending from the front lifting frame spacer tube 13. Welded to the grab shaft are a pair of parallel grab arms 36 which, for some distance from the grab shaft are straight, and are then, at their forward part, curved more or less arcuately downwards to straight tips 37, pointed at their extremities. The curved part of

each grab arm 36 consists of two spaced parallel members, of which the inner members, rearwardly of the curved part, extend to the rear above and at an angle to the rear straight parts of the grab arms 36, and constitute ram mounting bracket stays 38. The said ram mounting bracket stays converge to the rear, where they are welded to the upper ends of a pair of spaced angled ram mounting brackets 39, secured at their lower ends to the grab shaft 30. Tie bolts 40 and 41 interconnect the straight parts of the grab arms 36, the front tie bolt 41 serving also to hold the ram mounting bracket stays 38 ; and a sheave pin 42 vis secured between the two members of the curved part of each grab arm 36. At the tip 37 of each grab arm 36, the two members forming the forward part of that grab arm are curved arcuately in cross-section, so that they meet longitudinally and are welded together for strength. The interconnected grab arms are normally urged to raised inoperative position. as shown in Fig. 1, by a leaf spring 43, anchored at one end to a transverse leaf spring box 44 secured between the two grab mounting bracket stays 27, and extending forwardly and under the front grab arm tie bolt 41. The grab arms may be brought downwardly to operative position, as shown in Fig. 3, by means of a hydraulic ram 45, adapted to be supplied with hydraulic fluid under pressure from the hydraulic installation of the tractor by a line 46. At its front end, the ram is pivotally connected at 47 between the two ram mounting brackets 39, and at its rear end it is pivotally connected at 48 to one arm 49 of a bell-crank 50. This bell-crank is formed of two similar spaced and rigidly interconnected members between which the rear end of the ram is pivoted : and the other arm 51 of the bell-crank has a bolt 52 en- gaged in any selected pair of a number of pairs of holes 53 through the two members formin, the said arm 51. The bell-crank 50 is fulcrumed on a spacer shaft 54 between the stays 27 of the grab mounting bracket 26 ; and normally, with the grab in raised inoperative position, as shown in Fig. 1, the arm 49 of the bell-crank inclines upwardlv and forwardly, the bell-crank arm 51 inclin ing downwardly and rearwardly, and a prolongation of the axis of the ram 45 passes above the fulcrum of the bell-crank. Thrust exerted by the ram, then, at this stage will urge the bell-crank 50 to rotate so that the arm 49 is raised ; but a stop bolt 55 in a stop bracket 56 secured between the stays 27 limits the upward movement of the said arm 49. A helical torsion spring 57 about the spacer shaft 54 and anchored at one end on the said shaft and engaged at the other end with the bell-crank 50, urges the bell-crank to the position shown in Fig. 1, the bellcrank arm 49 against the stop bolt 55. A cable 58 is passed around the bolt 52 in the arm 51 of the

bell-crank 50. Each end of the cable is then carried forwardly, around the sheave pin 42 of one of the grab arms 36, and then made fast about the front tie bolt 41 between the two members of the forward part of the grab arm. Downward movement of the grab is limited by a pair of stops 59 welded to the grab shaft 30 and adapted, when the grab has been lowered to operative position, as shown in Fig. 3, to be brought to rest in contact with the undersides of the stays 27 of the grab mounting bracket 26. In use, the tractor to which the cane loader is fitted is driven forward with the lifting arms 10 lowered so that the lifting fork assembly 14 is in operative position, the shoes 19 riding along on the ground and the grab arms raised to inoperative position. The shoes are driven under a load of cane to be loaded, and the hydraulic ram 45 is then operated to cause the grab arms 36 to be moved pivotally downwards, against the action of the leaf spring 43. Owing to the nature of the ram mounting brackets 39, as the ram 45 is extended, its front end is raised until it passes dead-centre position in relation to the bell-crank 50 ; that is the rearward prolongation of its axis passes below the fulcrum of the said bell-crank. This occurs about the time the grab arms 36 have been brought down between the shoes 19 to separate the cane to be lifted ; and thereupon the bellcrank 50 is turned about its fulcrum, against the action of the torsion spring 57, as the ram extends. This action of the bell-crank serves to tension the cable 58, the two parts of which are consequently brought tightly across the load of cane, indicated in broken outline at 60 in Fig. 2. If the load of cane 60 should be more bulky to one side of the cane loader than to the other, the cable 58 will slide in one direction or the other over the bolt 52, so that the pressure exerted by the two parts of the cable will be more or less equalized, and the cane load will be firmly held in place. The lifting arms 10 are raised, and the tractor is manoeuvered to bring the load above a truck to be loaded, whereupon the tractor driver tensions the trip cable 24, the shoe locks 23 are released, and the shoes 19 drop gravitationally to shed the load into the truck. The lifting frame is then lowered, the lifting fork is brought to operative position, and the grab is raised, whereupon the procedure as described may be recommenced. It will be found that loaders for sugar cane or the like made in accordance with the invention will be very effective in achieving the objects for which the invention has been devised. It will, of course, be understood that the preferred embodiment herein described may be subject to many modifications of constructional detail and design which will be readily apparent to persons skilled in the art without departing from the scope and ambit of the invention defined by the

appended claims. What I claim is :- 1. A loader for cane or the like including a fork adapted to be mounted on a lifting frame of a tractor and adapted, when in operative position, to be driven by the tractor under a load of cane or the like, releasable locking means adapted to retain the fork in operative position ; a grab including a grab arm having a down-turned front end and adapted to be pivotally mounted at or near its rear end above the fork ; a flexible member extending rearwardly from the lower part of the grab arm ; means for raising the grab arm to inoperative position, means for lowering the grab arm to operative position; and means adapted to cause tensioning of the flexible member as the grab arm is moved to or near to operative position.

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