Patent GB-635231-A (GB)
Title: Improvements in hydraulic power transmission
IPC: F15B11/04
Filed: 1946-12-21
Abstract: 635,231. Hydraulic transmission of power; liquid-pressure engines. VICKERS, Inc. Dec. 21, 1946, No. 37625. Convention date, Dec. 21, 1945. [Class 69 (ii)] A unitary panel for controlling a hydraulic transmission comprising a hydraulic pump and a double-acting hydraulic motor, to give rapid advance, feed and rapid return movements to and for stopping the motor, comprises a valve block having external connection ports including pressure and exhaust ports and a pair of motor ports, valve ports including a pair of motor ports, a pressure port between the motor ports, an exhaust port adjoining one of the motor ports and a first port adjoining the other motor port, liquid connections between each external port and each corresponding valve port, a device in the block for limiting liquid flow to a predetermined adjustable feed rate, a bore connecting the flow limiting device to one of the external motor ports and to the first valve port, and a first shiftable valve member in the block co-operating with the valve ports to provide rapid advance, feed and rapid return action, the construction being such as to permit the use of one of a plurality of alternative, shiftable valve members, one of which latter connects the valve pressure port to the valve exhaust port to stop the motor, whilst a second shiftable valve member blocks the valve pressure port from communication with all other ports to stop the motor. The first valve member 30 is of the open centre type and is slidable in a bore 14, whilst the device for limiting liquid flow comprises a throttle valve 80, provided with a dial and knob assembly for obtaining both fine and coarse adjustment of the throttling effect. A compensating valve 86 is provided for maintaining a uniform pressure drop across the throttle valve 80. To produce a rapid advance movement of the piston of motor 250, the first valve 30 is moved to the extreme leftward position by liquid pressure under the control of a pilot valve 268 so that liquid from a tank 240 is forced, by the pump 242, through a relief valve 278, a conduit 246 to the valve pressure-port 16 in bore 14, a groove 224 in the first valve 30, and a valve motor-port 18 in bore 14 to the upper end of the piston of motor 250. The liquid discharging from the other end of the motor 250 is conducted by a conduit 256, valve motor-port 20 in bore 14 and a groove 228 to the tank 240. To obtain a rapid return movement of the motor 250, the first valve 30 is hydraulically moved to its extreme rightward position, whereupon motor port 20 now carries the pressure liquid and motor port 18 the exhaust liquid. After the piston or motor 250 has shifted a predetermined distance during rapid advance, the first valve 30 is moved to the feed position shown by rotating a shaft mechanically or manually, which shaft has a diametrical lever with a ball end secured to the valve 30 so that pressure liquid from the pump 242 is directed through groove 224 and motor port 18 to the upper end of motor 250. Discharging liquid will flow through compensating valve 86, throttle valve 80, and throttle port 22 in valve bore 14, groove 218, transverse ports 234, bore 232, transverse ports 236 and groove 228, the five latter being in the valve 30, and tank port 24 to the tank 240. When the valve 30 is moved to a position just to the right of that shown, the motor '250 is stopped since the pressure from pump 242 is conducted from pressure port 16 to motor port 18, groove 218, bore 234, groove 228 and thence to the tank. In a modification, one of the alternative valve members of the closed-centre type is used when it is desired to control another load device as well as motor 250. The closed-centre valve differs from the open-centre type in that the grooves 218 and 224 have a decreased length. The operation is identical in both instances, except that in the stop position of the closedcentre valve, communication between the pressure port 16 and all the other ports along the bore 14 is prevented by the valve body covering this port. In another modification, another alternative valve member of the differential type is used which differs from the first valve in that it has an additional groove, whilst groove 228 has a decreased length so that during rapid advance the differential valve connects the pressure port 16 to both the motor ports 18 and 20 to provide a differential movement of the motor 250. The movement of the valve may be effected by combinations of manual and automatic operations, the automatic shift, being completed by tappets on the motor or machine-tool, or by solenoids. A conduit 282 connecting the right and left-hand ends of the valve bore has a plug inserted in it when any of the valves 30 are hydraulically operated under the control of a pilot valve.