5376 5380.output

* GB785784 (A)

Description: GB785784 (A) ? 1957-11-06

Improvements in or relating to werner type complexes and compositionscontaining thesame

Description of GB785784 (A)

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PATENT SPECIFICATION Inventors: RICHARD LEE DALTON and FRANK BRITT HAUSERMAN 785,784 ___ | Date of Application and filing Complete Specification: Feb 8, 1954. No 29428156. (Divided out of No 776,156). Complete Specification Published: Nov 6, 1957. Index at acceptance:-Classes 1 ( 3), AID 10, A 1 (G 1 O: Gl OD 10: NIOA); 2 ( 3), C 1 E 3 K( 1: 8), C 2 B 2 (A 1: A 2: D: F: G 1 A: G 8: K), C 2 B( 20: 29), C 3 A 7 (A 1: A 2: B: D: El: E 2: F 2: G 1), C 3 A 1 OA 4 (A: B: C: D: G), C 3 A 10 A 5 A 1, C 3 C 5 (A 1: B: C 2: El); and 15 ( 2), GAX, GB 2 (A 1: Bi: BX), GB 1 ( 3: 4 D), GIB 5 (A: B: C), GC 2 A( 4: 6 A: 8: 10: 12 B 2: 13 B: X), GC 2 C( 4: 6: 9: X). International Classification:-CO 1 g CO 8 f DO 6 m. COMPLETE SPECIFICATION

Improvements in or relating to Werner Type Complexes' and Compositions containing the same We, E I Du PONT DE NEMOURS AND COMPANY, a Corporation organised and existing under the laws of the State of Delaware, United States of America, of 10th and Market Streets, Wilmington, State of Delaware, 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: - In specification No 776,156 we have described compositions comprising a polymerized Werner type chromium complex in which a trivalent nuclear chromium atom is coordinated with a carboxylic acido group having from 2 to, 8 carbon atoms, and which compositions have a basicity of at least 70 % The aforesaid specification describes the preparation of the compositions in question, their use in the treatment of siliceous surfaces such as glass fibres end the production of articles of manufacture comprising the glass fibres so treated which are bonded to plastics such as polyester resins. Size compositions that are useful for the treatment of glass fibres to, impart good abrasion resistance thereto are also, described, these size compositions including the polymerized Werner type chromium complex associated with polyvinyl acetate. The polymerized Werner type chromium complexes having a basicity of at least 70 % are prepared in accordance with the aforesaid specification, preferably in the form of colloidal dispersions, by treating an aqueous solution of a Werner type complex with an anion exchanger for a period of time sufficient to raise the basicity of the Werner type complex to the desired degree. According to the present invention solutions or dispersions of unpolymerized Wemer type complexes are treated with a nitrogen base to adjust the p H value of the solution or dispersion to 4 to 7; this treatment leads to the formation of water-soluble, polymerized Werner type complexes. Suitable nitrogen-coirtaining bases for use in this invention include ammonia, organic arnines and quaternary ammonium hydroxides in which each organic constituent on the nitrogen atom contains no carbon atom farther removed from the nitrogen atom than 4 consecutive carbon atoms and the total number of carbon atoms attached to the nitrogen exclusively through carbon is not more than twelve. Hydrous chromia may be used in association with the modified Werner type acido chromic complexes of this invention. The Werner type complexes which are modified in accordance with this invention are similar to those used as the parent materials in the aforesaid specification No 776,156, that is, they comprise a trivalent nuclear chromium atom which is coordinated with a carbo'xylic acido

group having from 2 to, 8 and preferably from 2 to 6 carbon atoms, the acido group being coordinated with the trivalent chromium atom through the carboxyl radical These complexes may contain any of a very wide variety of acido groups, for example, parahydroxybenzoato; unsaturated acido groups such as acrylato, crotonato, sf Tbato', isocrotonato, alpha L and beta-ethylacrylato, angellato, tiglato, beta furyl-acrylato, cyanacetato, or chloroacetato, groups The groups in the complex other than those acido groups co2 785,784 ordinated with the chromium nucleus are of secondary importance; they are preferably neutral or monovalent There may, however, be present such other groups as aqua or hydroxyl groups as well as monovalent inorganic acid radicals such as chloro, bromo, or nitrato Examples of suchchromiumcomplexes include the following: p-Aminobenzoato Chromic Chloride Benzoato Chromic Chloride Crotonato Chromic Chloride Cyanoacetato Chromic Chloride 2,4-Dihydroxybenzoato Chromic Chloride Furoato Chromic Chloride Gallato Chromic Chloride Glycinato Chromic Chloride Gluhonato Chromic Chloride Nitrobenzoate Chromic Chloride Profionato Chromiic Chloride Salicylato Chromic Chloride Thioglycolato Chromic Chloride Trichloroacetato Chromic Chloride Trimethylacetato Chromic Chloride The preferred Werner type complex employed in the practice of the present invention is methacrylato chromic chloride and, when used, the preferred basic chromium salt is basic chromium chloride. The ratio of chromium to acido groups in the Werner complex may vary from 1: 1 to 100:1, but is preferably from 2:1 to 5:1. These ratios can be adjusted by a suitable selection of the reactants; alternatively Werner type complexes having a fairly low chromium ratio can be given an effectively higher ratio by addition or combination of basic chromic chloride A 2: 1 ratio is preferred when the chrome complex is to be used as a coupling agent between unsaturated resins and glass fibres, but if the composition is to be used to dnsolubilize polymers such as polyvinyl alcohol or polyvinyl acetate, then a much higher ratio is desired. Fibres, in general, when treated with the compositions of this invention are rendered abrasion-resistant while glass fibres so coated form strong bonds with polyester and similar resins, the bonding being unaffected on prolonged exposure to water or high humidities. The preparations are-very stable and may contain up to 10 % of polymerized Werner type chromium complex in the form, of an aqueous solution. In the practice of this invention the aqueous solution of the parent material is in effect neutralized to the point where the p H of the solution is adjusted to 4 to 7, preferably from to 6 at 250 C The p H of the Werner complex solution so neutralized drifts downward as the

solution ages but it does not reduce the effectiveness of the product Additional neutralizer should not, however, thereafter be added because the further addition of neutralizer decreases the effectiveness of the treating solution. While it has been stated above that when the nitrogen-containing base employed to neutralize the solution is an organic amine or a quaternary ammonium compound the total number of carbon atoms attached to the nitro 70 gen atom exclusively through carbon should not be more than 12, it will nevertheless be understood that there may be more than 12 carbon atoms if the carbons are not consecutive but are joined through other atoms such as oxygen 75 Thus amines or quaternary ammonium bases substituted with polyethylene oxide groups in which the carbon groups are separated by oxygen atoms according to the arrangement N-(C-C-0), are operable 80 Among the quaternary ammonium bases which may be used are those in which the substituents on the nitrogen atom are aliphatic, alicyclic, aromatic or heterocyclic groups The groups may all be the same or may be differ 85 ent Specific quaternary ammonium hydroxides which mav be used are these in which the substituents are tetramethyl, tetraethyl, tetraisopropyl, tetra-n-propyl or combinations of the foregoing; also, dimethyldiallyl, tetra 90 ethanol, tri-methylethanol, phenyltrhnethyl, trimethylcyclohexyl, N metllyl-pyridinium, N,N-dimethylpiperidin ium and NN-dimethylmiorpholinium. Among the amine bases which may be used 95 are those in which the substituents on the nitrogen are aliphatic, aromatic, alicyclic and heterocyclic groups They may be primary, secondary and tertiary The groups may all be the same or may be different 100 Specific amines which may be used in the processes of the invention are those in which the substituents are: mone-, di-, or trimethyl; monoc-, di-, or triethyl; mono-, di-, or triisopropyl; mono-, di-, or n-propyl; mono-, di-, or 105 triisobutyl or combinations of the foregoing substituents; diethanolphenyl, mono-cyclopropyl, mono-, di or triethanolamine Also useful are pyridine, piperidine, morpholine, pyrazine and similar cyclic compounds in which the nitrogen 110 is in the ring. In operation of processes of the invention, an aqueous treating solution containing methacrylate chromic chloride, for example, is first prepared The aqueous treating solution 115 should contain from about 0 1 %, to about 1.0 % by weight of methacrylato chromic chloride. A suitable method of preparing such a treating solution consists of adding a stock solution 120 of methacrylato chromic chloride to the required amount of water. It is preferred to employ a dilute aqueous solution of the nitrogen-containing base With more concentrated solution, an insoluble

pre 125 cipitate may be formed during the addition of the nitrogen-containing base A 1 I% aqueous solution of the nitrogen-containing base is especially preferred. The nitrogen-containing base can be added 130 785,734 785,784 at a reasonably fast rate so, long as there is sufficient agitation to prevent formation of a permanent precipitate The neutralized solution should be clear Turbid solutions should never be used for treating glass fibres. The invention also includes improved size compositions which contain the improved modified chromic composition and polyvinyl acetate These sfize composition may also contain a lubricant of the conventional type such as a petroleum, vegetable or animal oil, a wax, which may be natural or synthetic, or a fat such as tristearin; certain organic materials which are oil-like may also be used such as the amine acetates which are water-soluble but which have a very effective lubricating action. The lubricants are generally used in amounts varying from 5 % to 10 % by weight of the weight of the polyvinyl acetate These sizes may also include other substances such as starch and gelatine. In order that the invention may be more fully understood, the following examples are given by way of illustration only: EXAMPLE 1. The preparation of methacrylato chromic chloride was carried out as follows: A solution of a basic trivalent chromium salt having a basicity of 33 3,% was made by reducing the hexavalent chromium compound chromic oxide, (Cr O,), using isopropanol as the reducing agent Thus a solution of 33 6 parts of weight of chromic oxide in 66 4 parts of 36 % hydrochloric acid was slowly added tc' a refluxing soluton of 5 4 parts of hydrochloric acid in 94 6 parts of isopropanol Analysis of the resulting solution showed 8 35 % chloride, and 7 43 % chromium The Cl: Cr ratio was adjusted to 2: 1 by the addition of 4 92 parts of hydrochloric acid. Coordination of methacrylato groups with this basic trivalent chromium salt was effected by adding 4 97 parts of methacrylic acid and 9.26 parts of isopropanol to 85 76 parts of the basic chromic chloride solution The isopropanol acted as a solvent in: this step of the reaction The solution was heated to reflux and allowed to cool The resulting methacrylato chromic chloride contained 6 % chromium and was soluble in water. The treating solution for applying the methacrylato chromic chloride to the glass fabric was prepared by mixing 980 grams of water with 20 grams of the stock methacrylato, chromic chloride solution described above. The p H of this solution was adjusted to al value of 5 9 with a dilute

aqueous solution (l,% active ingredient) of piperidine. A sample of heat cleaned glass fabric, 181 weave (described in United States Air Force Specification No 12051, 3rd August, 1949), was then immersed in the solution for a period of five minutes The excess liquid was re, moved from the fabric by passing it through a rubber rolled hand wringer to, give a 30 per cent wet pick-up The fabric was then dried for a period of 10 minutes in an oven at a temperature of 1500 C The fabric was cooled to room temperature, removed from the oven, and soaked in pure water for a period of five 70 minutes in order to remove harmful salts. After the fabric was allowed to dry, it was suitable for laminate preparation. The laminates were prepared by impregnating the treated fabric with a low pressure 75 polyester resin containing 1 % benzoyl peroxide as the curing catalyst A sandwich containing twelve layers of resin-impregnated fabric was formed and cured under a pressure of fifteen pounds per square inch in a 80 hydraulic press The platens of the press were heated at such a rate that they reached a tempterature of 600 C after a period of 30 minutes, 80 C after 45 minutes and 120 C. after 60 minutes The laminate was then re 85 moved from the press. The laminate was transparent and had a dry flexural strength (determined according to United States Federal Specification L-P- 406 a) of 76,700 lbs /sq in After the laminate 90 was soaked for a period of three hours in boiling water, it had a flexural strength of 63,600 lbs /sq in The completed laminate was 0 137 inches thick and contained 41 4 % resin. EXAMPLE 2 95 54 grams of the stock solution (prepared in Example 1) of methacrylato, chromic chloride was diluted with 2046 grams of water Then 600 grams of a 1;% aqueous solution of morpholine was added After the resulting solu 100 tion was stirred for a period of five minutes, it had a p H of 5 68. Segments of heat-cleaned glass fabric, 181 weave, were immersed in the treating solution for a period of one minute The excess liquor 105 was removed from the fabric by means of a rubber rolled wringer (wet pick-up was 301 %). The fabric was dried at a temperature of 1500 C for a period of ten minutes. The dried fabric was immersed in water for 110 a period of one minute in order to remove harmful salts The fabric was dried at a temperature of 1500 C for a period of ten minutes. A twelve ply laminate was then prepared as described in Example 1 The cured laminate 115 had a dry flexural strength of 68,000 lbs /sq in.

After three hours exposure to boiling water, the laminate had a flexural strength of 59,000 lbs /sq in The finished laminate was 0 138 inches; thick and had a resin content of 404 % 120 EXAMPLE 3. To a stainless steel mixing tank containing gallons of water, there was added 3 33 pounds of stock methacrylato, chromic chloride solution prepared as described in Example 1 125 After the stock solution and water were thoroughly mixed, 7 30 lbs of 1 % aqueous ammonia was added with vigorous stirring. The p H of the resulting solution was 5 63 and its temperature was 270 C 130 A treating solution was then pumped to the dip tank of a conventional textile slasher The slasher was equipped with a rubber squeeze roll to regulate wet pick-up and seven steam heated drying cans The glass fabric, 181 weave, was treated by passing it into the dip tank where the solution was applied ( 10 seconds immersion), through the squeeze rolls to get a wet-pick of 35 % and onto the drying cans all -10 heated to a temperature of 2000 C The cloth travelled at three yards per minute through the treating equipment. After drying, the fabric was washed to remove harmful salts The washing was accomplished by passing the fabric through a slasher which contained pure water in the dip tank. Drying was effected by regulating the first two cans at temperatures of 130 C and 1600 C. respectively, while the remaining five cans were retained at a temperature of 200 C. Laminates prepared from this fabric according to, the procedure in Example 1, were very transparent and had dry flexural strengths of 65,000 lbs /sq in After three hours boiling in, water the laminates still retained a flexural strength of 53,100 lbs /sq in. EXAMPLES 4-14. The procedure for these examples consisted of the steps of placing the water in a suitable container, adding the specific quantity of methacrylato chromic chlcride (prepared according to Example 1), stirring the mixture for a period of five minutes, adding a 1 %' aqueous solution of the specified amine and stirring the resulting solution for a period of six minutes The recorded p H corresponds to that of the final treating solution. Pieces of heat-cleaned glass fabric, 181 weave, were immersed in the treating solution for a period of five minutes and then passed through a wringer in order to reduce the wet pick-up to 30 % The fabric was then dried. for a period of ten minutes at a temperature of 150 C. After the fabric was dried, the harmful salts were removed therefrom by immersing the fabric in pure water for a period of one minute, removing the excess wash water with a wringer and drying the fabric

for a period of ten minutes at a temperature of 150 C. Laminates were then prepared as described in Example 1 and treated according to U S. Federal Specification L-P-406 a The wet flexural strength refers to the strength of the test specimen after boiling for three hours in water. Treating Solution Example Amine Grams Grams Methacrylato Water Chromic Chloride Grams 1 % p H of Amine Treating > Solution Solution 4 Ammonia 2526 54 120 5 30 Aniline 582 18 300 5 02 6 Diethylene triamine 796 18 86 5 38 7 Dimethylamine 2361 54 285 5 60 8 NN-Dimethylethanolamine 718 18 164 5 40 9 NN'-Dimethylethylene 754 18 128 5 95 diamine Ethanol amine 730 18 152 5 65 11 Hexamethylene tetramine 2466 54 180 5 30 12 Pyridine 582 18 300 5 45 13 Tetramethyl ammonium 682 18 197 5 69 hydroxide 14 Trimethylamine 2328 54 318 5 40 Used 10 % Hexamethylene tetramine stock solution -85,784 785,784 Laminate Properties Dry Wet Flexural Flexural Resin Example X 1000 X 1000 Content 4 71 6 46 8 6 69 0 7 67 8 8 60 4 9 50 9 65 9 11 72 3 12 57 5 13 63 5 14 64 3 61.3 42.3 51.6 58.6 57.1 43.7 49.5 51.1 49.0 57.0 56.3 38.8 % 40.4 36.0 38.5 38.0 39.6 37.5 39.7 39.6 37.0 41.0 EXAMPLE 15. Twenty-seven grams of methacrylato chromic chloride prepared according to the method described in Example 1 were added to 2573 grams of water 99 grams of 1 % aqueous ammonia were added thereto The resulting solution was stirred for a period of five minutes It had a p H of 5 85. Portions of heat-cleaned glass fabric, 181 weave, were immersed in the treating solution for a period of one minute The excess liquor was removed from the fabric with a rubber roll wringer (wet pick-up, was 30;%) The fabric was; dried for a period of ten minutes at a temperature of 1500 C. Laminates prepared from this fabric according to the directions in, Example 1 had dry flexural strengths of 68,200 lbs /sq in and wet flexural strengths, after three hours exposure to boiling water, of 56,400 lbs /sq in. EXAMPLE 16. A sizing composition for glass fibres was prepared by mixing 94 77 parts of water with 0.66 parts of methacrylato chromic chloride and thei diluted methacrylato, chromic chloride neutralized with 1 46 parts of 1 % ammonia in order to convert it into a polymerized form. To the dilute polymerized methacrylato chromic solution is added 3 2 parts of plasticized polyvinyl acetate, and 0 09 parts of an amine acetato lubricant This composition was effective for sizing glass fibres and could be applied to the glass fibres by merely running the fibres through the solution The treated fibres were then dried for 30

minutes at C. A similar size can be made using other conventianal lubricants in equivalent amount and there can be used, for example, 0 09 parts of octyl amino acetate. EXAMPLE 17. A mixture of basic chromic chloride and methacrylato chromic chloride was prepared by mixing appropriate quantities of basic chromic chloride and methacrylato chromic chloride to give a composition having a chromium content of 6 22 % and a methacrylic acid content of 2 14 % The ratio of chromium atoms to methacrylic acid molecules was 4.8:1. In order to prepare a composition for sizing glass fibres, 0 50 parts of the mixture of basic chromic chloride and methacrylato chromic chloride was mixed with 81 3 parts of water and the dilute solution neutralized with 16 60 parts of 0 08 S% ammonia To the polymerized chrome solution is added 1 51 parts of plasticized polyvinyl acetate emulsion containing % solids and 0 09 parts of an amine acetate lubricant This composition was applied to glass fibres by passing the fibres through a bath of the solution The treated fibres are then dried at 1250 C for 30 minutes. A similar size can be made using other conventional lubricants in equivalent amount and there can be used, for example, 0 09 parts of octyl amine acetate. The calculated probable basicity of the Werner type complexes after treatment with nitrogen-containing bases as described in the foregoing Examples is shown in the final column of the following Table. Basicities of Methacrylato Chromic Chloride After Neutralization Max Basic IonizaBasicity tion Constant Base Probable p H Basicity 1 Piperidine 2 Morpholine 3 NH 3 4 NH, Aniline 6 Diethylenetriamine 7 Dimethylamine 8 NN-Dimethylethanolamine 9 N N'-Dimethylethylenediamine Ethanolamine 11 Hexamethylenetetramine 12 Pyridine 13 Tetramethylammonium hydroxide 14 Trimethylamine Ammonia 16,, 17,, Insuff. data 53 % 54 % 54 % 68 % 57 % % % 1.6 x 10 5 9 not available 1.8 x 10-5 3.8 X l Q-1 not available 5.1 X 10-4 not available 63 % not available 57 % 2 8 x 10-5 44 % not available 77 % 1 4 x 10- 51 % Strong base % 79 % 54 % 52 % 5.3 x 10-5 1.8 X 10-5 ,3 , 5.68 < 53 % 5.63 54 % 5.30 54 % 5.02 31 % 5.38 ca 50 % 5.60 50 % 5.40 ca 45 % 5.95 ca 60 % 5.65 57 % 5.30 < 44 % 5.45 37 % 5.69 51 % 5.40 45 % 5.85 79 % 54 % 52 % The assumptions made in calculating the maximum basicity are: 1) Methacrylato chromic chloride has a basicity of 17 % 2 Cr(OH)C 12 + HA -a lCr 2 (OH)AlC 1 + H 20 2) All stock complex solutions contain 6 % Cr unless otherwise stated 3) All bases completely ionized.

Basicity corrected by calculating the percent ionization of the base from the ionization constant, concentration, and measured p H value. The products above described can be used for the modification of adhesive and filmforming, compositions such as those containing polyvinyl alcohol, polyvinyl acetate, alkyd resins and various other natural or synthetic gums and resins They may also be used in addition to the described use with glass fibres and products, for the treatment of fibres, sliver, yarns or fabrics of nylon, acrylic fibres, polyester fibres, cellulose acetate and natural fibres such as wool, cotton, and ramie, as well as of mixtures thereof.

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* GB785785 (A)

Description: GB785785 (A) ? 1957-11-06

Improvements in or relating to docks for loading and unloading vehicles


COMPLETE SPECIFICATION. Improvements in or relating to Docks for Loading and Unloading Vehicles. I, GREGORY SPENCER JINICS, a British Subject, of Cleco Works, Foundry Square, Leicester, 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 is for improvements in or relating to loading and unloading arrangements for vehicles and while it is particularly applicable to the loading of road vehicles is can also be applied to

use with rail vehicles. In the loading and unloading of goods vehicles such as lorries it is common practice to back the vehicle up to a dock as normally provided on a warehouse building so that transfer of goods between the dock and the vehicle may be effected. In some cases a gate or flap is provided for example at the forward end of the dock, and is pivoted about its lower edge so that it may be swung down to form a loading ramp or bridge along which the goods may be trundled On to or off a vehicle. With such loading or unloading arrangements it is naturally desired to transport the goods in considerable bulk so that rapid loading may be effected and when goods, for example in a container, are moved from the dock on to the platform of the vehicle the weight transferred on to the vehicle causes its platform to drop by deflection of the suspension springs thereby introducing difficulties in the loading operation, due to undue tilting of the ramp or bridge. The invention has for one of its objects to reduce or eliminate this disadvantage. In accordance with the invention there is provided for a vehicle loading or unloading dock at which goods are transferred over a movable ramp or bridge extending between a loading or unloading shelf and the floor of a vehicle, means for varying the heightwise distance between said shelf and the vehicle floor and control apparatus actuated by movements of the ramp or bridge and when so actuated to operate said means in such manner as to maintain the relative heightwise positions of said shelf and vehicle floor substantially unaltered despite variations in the loading of the vehicle. Conveniently this arrangement of parts is provided in combination with a ramp or bridge adapted to extend between the loading or unloading shelf and the vehicle floor and arranged to be pivoted along one end to one of said members and to rest at its other end against the other member the control apparatus being arranged to be actuated by pivotal movements of said ramp or bridge. Thus the relative positions heightwise of said shelf and floor will be controlled in accordance with the angular position of the ramp or bridge with respect to its pivotal axis and any changes in such angular position will cause compensating adjustment of the relative heights of the shelf and floor in order to maintain them substantially unaltered. During the loading or unloading of a vehicle the tendency for changes in the loading of the suspension springs thereof will consequently give rise to little or no variations in the relative heights of the shelf and floor and as a result the transport of goods on to or away from the vehicle will be considerably facilitated. The said distance varying means conveniently comprises power operated means (e.g. hydraulic mechanism) for restoring the relative heightwise positions of said shelf and floor on the occurrence of a change in

their relative levels. The invention according to another aspect provides for a vehicle loading or unloading dock whereat goods are adapted to be moved between a loading or unloading shelf and a platform of a vehicle over a flap or gate pivoted at one end to one of such members for heightwise swinging movement and arranged to rest at its other end against the other of such members, means adapted to be actuated by pivotal movement of said flap or gate for controlling the relative heightwise positions of said shelf and platform in such manner as to tend to maintain said flap or gate in a substantially horizontal attitude. With such arrangement goods may conveniently be trundled over the flap or gate for loading or unloading of a vehicle without there being any undesirable canting of the flap or gate such as would interfere with the loading or unloading operation due to changes in the load on the vehicle springs. In a preferred arrangement the relative heightwise positions of the said shelf and platform are adjusted by means of a heightwise adjustable road platform on which at least a part of the vehicle is adapted to rest at the loading or unloading station, which platform is arranged to be raised or lowered as required by the aforesaid control apparatus. The invention includes, for use at a vehicle loading or unloading dock, an assembly of parts comprising a loading or unloading ramp or bridge adapted for mounting in a heightwise movable manner at said dock, a control apparatus adapted for actuation by heightwise movements of said ramp or bridge and power operated means controlled by said control apparatus for effecting relative heightwise movement between the floor of a vehicle alongside the dock and a loading or unloading shelf of the dock in such manner as to tend to maintain the relative heightwise position of such floor and shelf substantially unaltered. The invention may conveniently be carried into effect in a loading or unloading arrangement as illustrated in the accompanying drawings which will now be described by way of example with reference to these drawings. In the drawings: Figure 1 is a somewhat diagrammatic view in side elevation and partly in cross-section illustrating a loading arrangement in accordance with the invention; Figure 2 is an end elevation as seen from the right of Fig. 1 of certain of the parts shown therein; Figure 3 is a detailed view on an enlarged scale of part of the arrangement in Fig. 1; Figure 4 is a side elevation with certain parts removed illustrating control apparatus provided at a loading doc1;. drawn awn to a scale

larger than that of Fi. 1: and Figure 5 is a front elevation viewed as seen from the left of Fig. 4 illustrating parts of the control arrangement. Referring firstly to Figs. 1 and 2, there is shown a loading dock having a shelf 10 (arranged above ground level ll) such as is commonly provided at warehouses for the loading and unloading of goods on to and from vehicles which are adapted to be drawn up against the dock. Generally in the case of a lorry the latter is backed towards the dock so that loading and unloading is effected at the rear of the body of the vehicle across a small space between it and the shelf 10 of the dock. The dock is provided with a gate or flap 12 pivoted at 13 alongside the forward edge of the shelf 10 so as to swing heightwise and be adapted to form a ramp or bridge which can be lowered with its free edge resting on the floor of the vehicle. Goods may then be trundled to or from the vehicle over the flap 12 on a suitable wheeled canier. ks goods are unloaded from or loaded on to a vehide the loading of the vehicle springs is varied and the floor of the vehicle rises or falls relatively to the wheels so that normally the flap 12 would become canted and recesses or humps formed between it and the vehicle and the dock, rendering bulk transport of goods over it extremely difficult. As a consequence it is usual to manhandle the goods in loading and unloading and this occupies a considerable amount of labour and time. In accordance with the invention the flap 12 co-operates with control mechanism containted in a box indicated generally at 14 in Fig. 1 which control mechanism by its operation actuates power operated means for correcting any departure from the required relative heightwise position of the shelf 10 and the fioor of a vehicle being loaded or unloaded. Te this end the ground immediately in front of the dock is formed with a well 15, there being mounted across the ton of the well a heightwise movable table or floor panel 16 which is pivoted at 17 along its forward edge and forms a platform on to which the vehicle is run in bringing it to the loading or unloading station against the dock. The table 16 may for instance support the rear wheels of the lorry which is backed to a position adjacent to the dock. Within the well 15 are disposed one or more hydraulic jacks 18 coupled to the underside of the table 16 and anchored ta a fixed abutment 19 within the well 15. To provide lateral rigidity the table 16 carries depending arcuate plates 20 curved about the pivotal axis 17 and strene-thened by transverse weh-like gussets 71. The plates 90 straddle an upstanding pl2teR e column 22 secured to the bottom of a deepened recess 33 formed in the well 15 adjacent to the dock. The plates 20 on their inner

faces carry rollers 24 supported by suitable brackets 25 and bearing against the opposite face of the column 22. The hinged mounting of The table 16 is shown more clearly in Fig. 3 in which the table 16 which may be formed by an assem bly of channel lii;e members welded together has welded at 28 to its end remote from the dock a curved plate 26 having bearing engagement with a rod 27 at the pivotal axis 17. The rod 27 is welded at 29 to an upstanding bar 30 secured as by welding to a base plate 31. The latter is conveniently secured by foundation bolts 32 and nuts 33 to a mounting block 34 (see Fig. 1) provided near the top of the well 15 at its outer side. Also secured to the plate 31 is an upstand ing plate 134 to which is removably attached by fixing screws 35 a cover plate 36 serving to retain the arcuate plate 26 in bearing engagement with the rod 27. By removal of the cover plate 36 the table 16 may be removed from its well, after detachment from its jacks 18, to afford access to the parts contained in the well. The control box 14 and parts contained therein are shown in detail in Figs. 4 and 5 wherein the casing of the box is indicated at 37. The top of the box 37 is closed by an inverted channel section bar 39 from which there are upstanding at spaced inter vals bearing lugs 38 forming supports for the flap 12. The latter has attached to it spaced bearing brackets 40 embraced by and pivoted to the pairs of brackets 38 and it will be seen that there is a central bracket 40 aligned with a plunger 41 slidably mounted in a bearing bush 42 provided centrally on the channel bar 39. The plunger 41 is anchored at its lower end at 45 to the shorter end of a transverse lever 43 mounted on a pivot spindle 44 supported in internal bosses provided on the front and rear walls of the casing 37. The anchorage 45 is dis

posed at only a short distance from the pivot 44, while the opposite end of the lever 43 extends substantially further from the pivot 44. Its extremity is anchored at 46 to a downwardly extending adjustable link 47 coupled at its lower end at 48 to a further transverse lever 49 pivoted at 50 between bearing brackets 51 upstanding from a casing 52 of a hydraulic control valve. The lever 49 has a detachable extension 53 on the same side of its pivot as is the link 47. This extension 53 carries near its extremity a mercury switch 54 in a slanting attitude, preferably adjustable, having electrical con nections 55 extending to a connection box 56 within the casing 37. The opposite end of the lever 49 is coupled by a pin and slot connection indicated at 57 to a vertically slideable stem 58 of a hydraulic control valve of known type. The mercury switch 54 is adapted to be connected in the control circuit of an electric motor (not shown) for driving an hydraulic pump (not shown) for supplying operating liquid under pressure from a reservoir to the jacks 18 and the hydraulic control valve in the casing 52 is arranged to control such liquid supply and also the release of the operating liquid from the jacks for return to the reservoir. The apparatus illustrated Operates in the following manner. With a lorry or similar vehicle backed so that its rear wheels rest on the table 16 and the rear end of the lorry open for loading or unloading the pivot flap 12 is swung downwardly to cause its free end to rest on the rear end of the floor of the lorry. If the table 16 holds the rear end of the lorry in a position in which the flap 12 rests in an approximately horizontal attitude the hydraulic control mechanism will remain inactive with the mercury switch 54 open and the pump motor out of operate tion. if however the table 16 is depressed partly into the well by the weight of the lorry to an extent such that the flap 12 falls below the horizontal the plunger 41 will be depressed causing the lever 43 to turn antI- clockwise as viewed in Fig. 5 raising the link 47 and causing the lever 49 to turn clockwise as seen in that Figure. The effect of such movement of lever 49 is first to close the mercury switch and bring the pump motor into operation and then, by moving the valve spindle 58 to a sufficient extent downwardly, to cause liquid to be forced into the jacks 18 thereby raising the table

16 and the rear end of the vehicle. Such raising movement continues until the flap 12 reaches an approximately horizontal position. At this stage the plunger 41 will have risen with the flap being urged against it by the weight of the levers 43 and 49 assisted if necessary by a suitable spring so that the control valve stem 58 will have become raised to a position in which both the inlet to and the outlet from the jacks 18 are closed and the mercury switch 54 has been tilted sufficiently to interrupt the circuit of the pump motor. Loading or unloading of the vehicle may then proceed, the goods being trundled in container across the pivoted flap 12. As the load On the vehicle is increased or reduced the suspension springs of the vehicle will cause its floor to be lowered or raised, thereby causing heightwise movement of the flap 12 about its divot 13. Raising movement of the flap will permit the plunger 41 to rise further with the result that the stem 58 of the control valve will be raised to a position in which the inlet to the jacks remains closed and an escape outlet from them is open to allow liquid to flow from the iacks to the reservoir. This action permits the table 16 to fall under the weight of the vehicle until the flap 12 resumes a horizontal position whereupon the lowering of the flap will cause the outlet from the jacks 18 to be closed and the table 16 will again become steady. If on the other hand the pivot flap drops its movement by actuating the plunger 41 and levers 43 and 49 will cause the mercury switch to close and start up the compressor motor and at the same time move the control valve stem 58 to a position in which the liquid is forced into the jacks 18, thereby raising the table 16 until a position of equilibrium is again reached with the flap 12 in a horizontal position. It will be thus appreciated that the arrangement described provides for automatic self levelling of a loading ramp or bridge during loading or unloading operations thus facilitating rapid transfer of goods between a dock and a vehicle. The relative level between the vehicle and the dock need not necessarily be such that a loading ramp or bridge such as 12 is caused to occupy a horizontal position as the arrangement can readily be adjusted by adjusting link 47 and the angular setting of switch 53 to arrange that the neutralized setting of the control arrangement (i.e. that in which the rams 18 are shut off from the pump and reservoir and the pump motor is inoperative) will occur when the loading ramp or bridge is slightly inclined upwardly or downwardly. When. a lorry is backed on to the road platform 16 before the hinged flap or gate is lowered the rams 18 would normally be permitted to contract and cause the rear end of the lorry to become lowered. The lowering of the hinged flap or gate 12 will however operate the mechanism to cause the rear end of the lorry to be raised again.

However, if desired a manually operable stop valve may be inserted in the exhaust from the rams 18 so that by closing the stop valve the rams may be prevented from collapsing when the lorry is first backed on to the road platform. After the hinged flap or gate 12 has then been lowered the manually operable stop valve will be opened. In applying the invention to the loading of rail vehicles the platform referred to as a road platform would of course, be one carrying rails on which the vehicle to be loaded may be Tun. The invention is applicable to side loading as well as end loading of vehicles. For side loading the road platform 16 would preferably be made of sufficient width to enable the side wheels of a vehicle adjacent to the dock to be run on to it so that the rams 18 would act to raise and lower the whole of one side of the vehicle as required. Further the shelf 19 need not be a fixed shelf but could be substituted bv a shelf jutting out from the dock. Surk shelf could be pivoted to the dock and have a pivoted flap such as 12 carried at its extremity and arranged by operation of the control apparatus to vary the heightwise setting of the shelf in a required manner in which case a fixed floor would replace the platform 16. Instead of having the pivoted flap 12 mounted on the dock or a shelf extending therefrom, it may if desired be replaced by a ramp or bridge pivoted to the vehicle and arranged to rest at its free edge on the shelf of the dock and arranged by heightwise movement to actuate suitable mechanism on the shelf or its support for operating the control apparatus to effect self levelling adjustment. It is to be understood that the invention is not necessarily restricted to a hydraulic control arrangement, as other forms of control operable by a pivot flap or gate mounted either on the dock or on the loading end or side of a vehicle may be employed to achieve the same result. What I claim is: 1. For a vehicle loading or unloading dock at which goods are transferred over a movable ramp or bridge extending between a loading or unloading shelf and the floor of a vehicle, the provision of means for varying the heightwise distance between said shelf and the vehicle floor and control apparatus adapted to be actuated by movements of the said ramp or bridge and adapted when so actuated to operate said means in such manner as to maintain the relative heightwise positions of said shelf and vehicle floor substantially unaltered despite variations in the loading of the vehicle. 2. An arrangement of parts according to Claim 1 in combination with a ramp or bridge adapted to extend between the loading or unloading shelf and the vehicle floor and arranged to be pivoted along one end to one of said members and to rest at its

other end against the other member, the control apparatus being arranged to be actuated by pivotal movements of said ramp or bridge. 3. An arrangement of parts according to Claim 1 or Claim 2 wherein the said distance varying means comprises power operated means (e.g. hydraulic mechanism) for restoring the relative heightwise positions of said shelf and floor on the occurrence of a change in their relative levels. 4. For a vehicle loaning or unloading dock whereat goods are adapted to be movec' between a loading or unloading shelf anC a platform of a vehicle over a flap or gate pivoted at one end to one of such member for heightwise swinging movement and arranged to rest at its other end against. the other of such members, the provision of means adapted to be actuated by pivot'

* GB785786 (A)

Description: GB785786 (A) ? 1957-11-06

Improvements in or relating to domestic fire fronts and grates


PATENT SPECIFICATION Date of filing Complete Specification: Aug 17, 1954. Application Date: May 18, 1953 No 13616/53. Complete Specification Published: Nov 6, 1957. Index at Acceptance:-Class 126, B( 4 A:13 E:13 H 16 A). International Clasasification:-F 24 b. COMPLETE SPECIFICATION. Improvements in or relating to Domestic Fire Fronts and Grates. We, CASTLE CASTINGS LIMITED, Brooks Works, Clitheroe, in the County of Lancaster, a British Company, and EDWARD LAWRENSON, of the Company's address, a British Subject, 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 domestic fire fronts and grates particularly of the so called continuous burning type.

The main object of this invention is to provide means for accurately positioning the grate in relation to the front or fret and to provide a simple means for inserting bricks to protect the front. According to this invention a front of the kind referred to is formed with holes in a base portion, which holes are adapted to receive projections on the underside of the grate to ensure that the grate is fixed in the correct position relative to the front. A suitable aperture is preferably provided in the edge of the base portion of the front in conjunction with each hole for extracting dust from the relevant hole when the grate is removed as otherwise this operation is made difficult. According to a further feature of this invention the rear of the front is protected by a refractory brick which is made in two parts to allow the brick to be inserted after the front has been secured in the fireplace. The two parts of the brick are preferably adapted to pivot around their outer ends on the front of the grate and at the front are bevelled down the edges which form the joint to allow of easy turning about their pivots. According to a still further feature of this invention the grate when in position is also so fixed that when a gas burner is incorporated in the front, each projected gas flame is so lPrice 3 s 6 d l directed that it comes through a hole or 45 space in the grate and therefore does not impinge upon the grate. One construction in accordance with this invention will now be particularly described with reference to the accompanying drawings 50 in which:Fig 1 is a rear perspective view of a front or fret; Fig 2 is a view from underneath of a front or fret and grate combined; 55 Fig 3 is a perspective view from above of the front or fret and grate combined. In this construction the fire front or fret 1 is formed with holes 3 at each side in the base portion 5 and the holes are arranged to 60 break through the edge of the base portion to allow dust to be easily removed as indicated at 7 in Fig 1. The grate 9 is provided with projections having circular feet 11 adapted to engage 65 the holes 3 in the front or fret 1 and to locate the grate in position. The grate 9 is also provided with pivots (not shown) at each end near the front on which are mounted the two halves 13 and 70 of the protecting brick This brick is made of refractory material and is split as shown in Fig 3 to allow the two halves 13 and 15 to be swung about their pivoted ends 17 and 19 into position 75 When a gas burner is incorporated in the front or fret it is necessary to maintain its position in relation to the spacing of the holes or spaces 21 in the

grate 9 and also the direction of the projected gas flames This 80 is secured by the provision of two corner brackets 23 cast integral with the fire front or fret 1. The gas burner 27 is located between the two brackets and locked in position by nuts 85 on the outside The arrangement of the two corner brackets ensures that the holes 785,786 785,786 29 in the burner are opposite the spaces 21 in the grate. When it is desired to assemble the fire the front or fret is first secured to the fireplace in any suitable manner, e g by means of studs, bolts or the like passing through holes 25 formed in the base portion of the front or fret The grate is then placed in position locating the projections 11 in the holes 3 in the front or fret The two halves of the brick are then placed on their pivots and swung round to meet each other in which position they may be cemented together.


* GB785787 (A)

Description: GB785787 (A) ? 1957-11-06

Improvements in and relating to the construction of the walls of buildings


PATENT SPECIFICATION Date of filing Complete Specification: Jan 13, 1955. Application Date: Nov 4, 1953 No 30449/53. Complete Specification Published: Nov 6, 1957. Index at Acceptance:-Classes 20 ( 4), V 5: and 87 ( 1), B 1 A 3 B, Bl F( 1 B: X: 7). International Classification:-E 04 b, c.

COMPLETE SPECIFICATION. Improvements in and relating to the Construction of the Walls of Buildings. I, ROBERT B Ruc E, a British Subject, of 121 West Regent Street, Glasgow, C 2, Scotland, 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 has reference to the construction of the walls of buildings wherein the walls are formed of pre-formed gypsum panels which do not require a plaster surface. The present invention has for its object to provide improvements whereby walls formed of such panels will have better uniformity and continuity of load transmission and the panels will be more effectively bonded in position. According to the present invention in the construction of the walls of buildings wherein the walls are formed of pre-formed gypsum panels which do not require a plaster surface and wherein the adjacent vertical edges of aligned panels form vertical channels therebetween and their upper and lower sides have cavities extending the length thereof, gypsum or the like is introduced into an upper channel extending over aligned panels, said channel being formed of parallel joists and a runner having openings therein at spaced distances apart, the gypsum or the like forming a bed in the upper channel and upper cavities and also filling and flowing through the vertical channels to form a bed in a channel formed in a lower runner positioned below the panels, the load on the upper floor or roof being transmitted through the first bed to the panels, and the second bed serving to receive the load transmitted through the panels both beds acting to ensure uniform continuity of load transmission and also serving as dowels to prevent displacement of the panels. lPrice 3 s 6 d l In the construction of the walls of buildings of two or more storeys as set forth ini the preceding paragraph the lower runners of the upper storey or storeys may be supported by dwangs secured between the joists. The panels may have a honeycomb interior and provided with openings in their upper and lower sides to give access to pockets formed by the honeycomb interior, such pockets forming the cavities of the panels. The invention will now be described with reference to the annexed drawings wherein: Figure 1 is a section through a ground floor, wall and the first floor of a building, the panel forming the wall being shown cut away. Figure 2 is a perspective view showing part of a ground floor, part of the first floor, part of the intervening wall and the lower part of

the wall immediately above; and Figure 3 is a section on the line 3-3 of Figure 1. The invention as applied to a multi-storey building will be described with reference to Figures 1 to 3. As shown in said Figures the ground floor 12 a is provided with a series of horizontally extending runners 10, one for each wall, the upper face of each runner having a longitudinally extending channel 11 Such runners are supported by brickwork or other under building 12 The ground floor 12 a is supported in the usual manner by timber joists 12 b. Between the joists 13 supporting the first floor 13 a are secured upper runners 14 having longitudinally extending channels 15 formed in their under faces and vertical passages 16 communicating with said channels Located between and secured to the said joists and bearing on the upper 785,787 runners are timber dwangs 17 positioned at spaced distances apart, the upper sides of the dwangs being flush with the upper faces of the joists 13 The panels 18 forming the walls are formed of gypsum the outer faces of which do not require a plaster surface. The interior of each panel is of honeycomb formation and along the top and bottom thereof is a series of aligned port holes 19 communicating with a series of upper and lower pockets 20 formed by the honeycomb interior, such pockets forming upper and lower cavities The vertical sides of each panel are channelled as at 20 a so that adjacent panels form vertical cavities 20 b open at their ends The runners are of substantially the same thickness as the panels. The construction of the walls of the first storey will now be described After the upper and lower runners 14 and 10 respectively are secured in position the panels are fitted in place so that they rest on the lower runners and form a small gap between their upper sides and the upper runner, such gap being the thickness of the usual plaster board 21 which forms the ceiling The sides of said gap are then pointed as at 2 ak and liquid gypsum or the like poured through the holes 16 in the upper runners, the gypsum or the like flowing into the cavities in the upper part of the panels as well as the cavity formed between the top side of the panels and the underside of the runner The gypsum or the like also flows through the cavities 20 b formed between adjacent panels, the cavities formed in the lower sides of the panels and the channel in the lower runner. Consequently the gypsum or the like, when hard, forms a bed 22 which extends into the cavity of the upper runner, the cavities in the upper end of the panels and the cavity between the said runner and the upper end of the panels. The gypsum or the like also forms a bed 23 which extends into the

cavity of the lower runner, the cavities in the lower end of the panels and the cavity between the lower runner and the panels The beds ensure uniformity and continuity of load transmission. Further said beds form dowels which, in combination with the vertical columns of gypsum 23 a in the vertical cavities, prevent displacement of the panels. aa Skirting boards 24 can be nailed to the lower runners and the plaster board ceiling applied to the under faces of the joists of the first floor. After the liquid gypsum or the like has been introduced as aforesaid a runner 25 is 60 placed on the aforesaid dwangs 17, this runner likewise having a channel on its upper face Upper runners similar to the upper runner already described are secured between joists carrying the next floor and the 65 panels supported between said runners and liquid gypsum or the like introduced into the cavities as already described In like manner the walls of further storeys are constructed. The walls of single storey buildings may 70 be constructed in like manner.


* GB785788 (A)

Description: GB785788 (A) ? 1957-11-06

Improvements in or relating to electrical speed detection systems


COMPLETE SPECIEfICATION Improvements in or relating to Electrical Speed Detection Systems. We, IGRANIC ELECTRIC COMPANY LIMITED, a British Company, of Elstow Road, Bedford in the County of Bedford, do hereby declare the

invention, for which we pray that a patent may be granted to us, and-the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to electrical speed detection systems, and more particularly to systems for the detection of zero speeds in a variable speed device. A primary object of the invention is to provide such a system which is reliable in operation and inexpensive to manufacture. According to the invention there is provided an electrical system for detecting when a variable speed device is at zero speed, comprising an electro-responsive device, and a switch device which effects circuit commutation at a frequency corresponding to the speed of said variable speed device, and which ceases such commutation when said speed is zero, said switch device and the sensitive circuit of said electro-responsive device being included, together with rectifier means and capacitor means, in a network supplied from an alternating current source, so that said capacitor means are charged, through said rectifier means, and discharge through said sensitive circuit, so long, and only so long, as such commutation of said switch device is taking place whereby said electro-responsive device detects when said variable speed device is at zero speed. In order that the invention may be more readily understood, an embodiment thereof is illustrated schematically and diagrammatically in the accompariying drawing. Referring to the drawing, the system there illustrated comprises a pair of supply lines L1 and L2 for connection to an alternating current source of power. Connected to line L1 is the conducting arm 10 of a single pole, double-throw switch which comprises in addition, stationary contacts 12 and 14. The switch actuating mechanism selected for illustration includes, as a part of arm 10, a cam follower 16 which rides upon a rotating cam 1-8. Upon rotation cam 18 imparts a cyclic, oscillatory-motion to arm- 10, causing it to make connection alternately with con tacts 12 and 14. Contact 12 is connected to line L2 through the series circuit combination of a half wave rectifying element 20 and a capacitor 22. Contact 14 is connected to line L2 through the series circuit combination of a half-wave rectifying element 24 and a capa

citor 26. The rectifiers 20 and 24 are connected in inverse directions of conduc tivity with respect to the supply lines L1 and L2. Bridging the connection between rectifier 20 and capacitor 22 with the connection between rectifier 24 and capacitor 26; is the operating winding 28a of an electromagnetic relay 28. The relay is provided with contacts 28b which may be normally open or normally closed according to the requirements of a control system including contacts 28b at X-X. In addition, a smoothing capacitor 30 may be connected, as shown, in parallel with winding 28" to reduce chattering of the relay when the oscillation frequency of arm 10 is low. In operation cam 18 is rotated, and thus arm 10 is oscillated, at a speed which is equal or proportional to the speed of a device, of which zero speed is to be detected. It is arranged that arm 10 will always be oscillated at a lower frequency than that of the alternating current supply. During the period when line L1 is posi tive with respect to line L2 and arm 10 is in contact with contact 12, capacitor 22 is charged to a higher or positive potential with respect to line L2 through rectifier 20. When line L1 is negative with respect to line L2 and arm 10 is in contact with contact 14, capacitor 26 is charged through rectifier 24 to a lower or negative potential with respect to line L2. Capacitors 22 and 26 are connected in series with one another across winding 28a so that their respective potentials are additive and so that together they discharge unidirectional current through winding 28a and maintain relay 28 in an energized condition. These capacitors have sufficiently large capacitance, and winding 28a has sufficient impedance, to make the time constant of the discharge path large. As long as arm 10 continues to oscillate it will make contact with contacts 12 and 14 at times when the supply lines have proper polarity to cause charging current to flow into capacitors 22 and 26 thereby renewing and maintaining their charge. Thus the flow of current in winding 28a will continue as long as arm 10 oscillates. When arm 10 comes to rest, however, the current flow will cease, relay

28 will be de-energized, and normally open contacts 28 will be opened. This action is not dependent upon the position in which the arm 10 comes to rest. If the arm stops intermediate contacts 12 and 14, capacitors 22 and 26 will completely discharge; but if it comes to rest in contact with either contact 12 or 14, capacitors 22 and 26 will be charged to equal, like potentials. In either event, current will cease flowing in winding 28. The system is applicable for use with a wide variety of control systems in which the detection of zero speed is required. The invention may be used, for example, in systems for plugging motors or with interlock circuits for use with conveyors, rotating or oscillating laundry equipment and other apparatus. The single-pole double-throw switch and cam illustrated and described is intended to be representative only. While such an arrangement is suitable for some applications it will be readily apparent that various other well known types of actuators, commutating devices and the like may be used in other applications of the invention. Since it is immaterial whether arm 10 comes to rest between or in contact with one of contacts 12 or 14, the duration of the open period of the switch is not critical. What we claim is: 1. An electrical system for detecting when a variable speed device is at zero s p e e d, - comprising an - electro-responsive device, and a switch device which effects circuit commutation at a frequency corresponding to the speed of said variable speed device,- and which ceases such commutation when said speed is zero, said switch device and the sensitive circuit of said electroresponsive device being included, together with rectifier means and capacitor means, in a network supplied from an alternating current source, so that said capacitor means are charged, through said rectifier means, and discharged through said sensitive circuit, so long, and only so long, as such commutation of said switch device is taking place, whereby said electro-responsive d e v i c e detects when said variable speed device is at zero speed. 2. An electrical system according to claim 1, wherein the frequency of commutation is always less than the frequency of the alternation current. 3. An electrical system according to any of the preceding claims, wherein said capacitor means comprise two capacitors and said rectifier means comprise two respective rectifiers, and, except when said commutation has ceased, said capacitors are intermittently charged through their respective rectifers, as said switch device makes it circuit commutations, and said capacitors are connected in series across said sensitive circuit with their potentials additive,

so that they together discharge through said sensitive circuit. 4. An electrical system for detecting when a variable speed device is at zero speed, substantially as herein described, with reference to the accompanying drawings.

Internet

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