Patent GB-544739-A (GB)
Title: Improvements in or relating to hydraulic transmissions
IPC: F16H61/42
Filed: 1940-08-14
Abstract: 544,739. Hydraulic transmission of power. WAHLMARK, G. A. Aug. 14, 1940, No. 13010. Convention date, Sept. 12, 1939. [Class 69 (ii)] A transmission comprising a variable-displacement pump and motor is provided with hydraulic means for simultaneously controlling the displacement of the pump and motor to obtain any one of a number of predetermined motor-speeds. The apparatus shown in Figs. 4, 7 and 10 includes a variable-displacement pump 30 and motor 31, the pump-shaft 32 being driven by an electromotor and the motor-shaft 92 being connected to an output shaft 28 by variable-speed gearing 25. The gearing comprises a sun-wheel 201 on the shaft 92, planet-wheels 203 mounted on a flange 197 on the shaft 28, and an annulus 206 which is shiftable by means of a piston 211, mounted in a cylinder 212, to bring clutch-teeth on the annulus into engagement with the flange 197 or the frame for direct or low-speed drive. The pump 30 and motor 31 consist of blocks 37, 97 formed with cylinders 38, 98 co-operating with wobble-plates 39, 99 pivoted on the shafts 32, 92. Liquid flow to and from ports 80, 140 in the cylinders 36, 96 is controlled by valves 70, 130 (constructed as described in Specifications 516,721 and 516,764) arranged in chambers 73, 82 which communicate through passages 81, 85, the valves causing the ports 80, 140 to communicate alternately with the passages 81, 85. The wobble-plates 39, 99 are adjustable by means of slides 50, 110 mounted in the shafts 32, 92 and coupled by ball-bearings 55, 116 to axially movable sleeves 58, 118 which are coupled by levers 60, 120 to pistons 63, 122 mounted in cylinders 64, 123. The cylinder 64 communicates through a recess 157 with another cylinder 154 containing a piston 155 which is geared by a pinion 151 to the piston 63. The cylinders communicate through ports 158, 159 with a casing containing a valve 160 formed with ports 168, 169 which communicate through a passage 166 and a groove 165 with a supply-passage 163. The pistons 63, 155 abut on a plunger 175 provided with a screw 177 abutting on the piston 122, the arrangement causing the wobble-plate 99 to be moved counterclockwise by each piston 63, 155. When the handle 170 of the valve 160 is set in stop- or mid-position, both ports 168, 159 are closed, the pistons 63, 155 are held in mid-position by liquidpressure in the cylinder 123, and the wobbleplates 39, 99 are in zero-stroke and maximumstroke position. When the handle 170 is set in forward or reverse position, the piston 155 or 63 is moved towards the right to adjust the wobbleplates. The piston 122 may be provided with a dashpot for retarding movement of the wobbleplates, and consequently retarding acceleration of the output shaft. The dashpot may consist of a piston connected to the piston 122 and mounted in the end of the cylinder 123, this being in communication through a check-valve and a conduit with the valve 326. At low speeds, movement of the piston is retarded by an adjustable outlet in the cylinder. At higher speeds, delayed acceleration not being required, the dashpot piston moves further towards the right, and the outlet is byepassed through a port in the cylinder. The piston 122 is geared by a cross-shaft 230 to a plunger 238, Figs. 7 and 10, mounted in a bore 239 in a housing 233 and urged upwards by a piston 270. Pistons 246, mounted in bores 245 in the housing, co-operate with adjustable stopscrews 2401 and are each formed with a shoulder 248 for engaging a flange 250 on the plunger 238. The bores 245 communicate through passages 281 and ports 280 with a rotary valve 275. The valve is formed with grooves 278, 279 for causing a supply-line 328 to communicate with one of the ports 289, the selected piston 246 being thereby caused to move into engagement with its stop 2401, and the previously selected piston being released. The shoulder 248 of the selected piston co-operates with the flange 250 to limit the stroke of the pistons 122, 63, 155 and thereby determine the speed of the motor 31. The plunger 238 moves upwards or downwards according as to whether the new speed is lower or higher than the previous speed. One of the stops 2401 may correspond to the " stop " or mid-adjustment. The valve 275 may be adjusted by means of a handle, or, as shown in Fig. 10, the valve may be geared to a tool-turret 366 so that selection of each tool effects corresponding adjustment of the valve. The speed of the motor is indicated by graduated rings 285, Fig. 7, each geared to one of the stop-screws 2401, the graduations being visible through a slot 293 in a cap 289 for the housing 233. The apparatus is in circuit with a gearpump 87, Fig. 10, for supplying oil to the cylinders 64, 154, 123, 212, and also for supplying make-up oil to the pump and motor cylinders 38, 98 and for lubricating the wobble-plates 39, 99. The circuit includes a reversing-valve 312 mounted in a bore 311 and formed with annular grooves 320, 321, and ports 322, 323. The bore communicates (1) through conduits 316, 317 with the passages 85, 81 between the pump 30 and motor 31, (2) through conduits 327, 328 and 330 with the valves 160, 275 and a manually-operated valve 331 for directing oil to either end of the cylinder 212 to shift the gear-annulus 206, and (3) with relief-valves 326, 346 and a conduit 349 leading to the cylinder 123. When the valve 160 is moved into forward or reverse position, the valve 312 is shifted upwards or downwards by pressure in the conduit 317 or 316, and make-up oil is supplied to the pump and motor cylinders through the conduit 316 or 317 respectively. A relief-valve 305 byepasses excess oil to nozzles 307, 308 for lubricating the wobble-plates 39, 99. The stop-mechanism shown in Fig. 7 may be replaced by a single adjustable stop mounted adjacent the right-hand end of the cylinder 123 and co-operating with a pivoted dog arranged in the path of a pin on the end of the piston 122. The stop may consist of a headed pin abutting on a ball in a sleeve which is threaded into a bushing and is provided with an adjusting-knob.