Patent GB-646791-A (GB)
Title: Improvements in or relating to hydraulic pumps or motors
IPC: F04C14/00
Filed: 1947-07-11
Abstract: 646,791. Single-acting multiple-suction or multiple-delivery pumps. OILGEAR CO. July 11, 1947, No. 18470/47. Convention date, Aug. 18, 1939. [Class 102(i)] ,[Also in Group XXIX] A control for a hydraulic pump or motor having a displacement varying member shiftable between zero and maximum displacement positions comprises means for moving the member from its zero displacement position to a maximum displacement position which moves it at high speed and tends to move it at high speed during the whole of its travel between these positions interrupting means effective only at a point between the positions for interrupting the high speed movement of the member which tends completely to stop the movement and means for modifying the effect of the interrupting means to enable the moving means to move the member at slow speed past the point whereby the displacement of the machine is suddenly increased a predetermined amount and then maintained nearly constant for a predetermined period of time and then suddenly increased to a predetermined maximum. Fig. 1 shows a hydraulic pump 1 including a rotary cylinder block 2 having radially arranged cylinders in which operate pistons which bear against an annular reaction surface 4 in a separate rotatable thrust member carried by a slide block 5. The pump will supply liquid at a rate and in a direction dependent on the direction and distance the axis of the reaction surface 4 is offset from the axis of the cylinder barrel 2. Liquid flows to and from the cylinder through ports in a stationary shaft 3, pipes 7, 8 being delivery or return pipes or vice versa according to the direction of displacement of the block 5. If pipe 8 is being supplied with liquid a valve 15 is automatically moved to the left to disconnect this pipe from a chamber 22 and connect the pipe 7 to this chamber so that any deficiency of liquid supplied by the return pipe 7 can be made up by suction through the valve 23 from a reservoir 9 or any excess discharged into the reservoir through a relief valve 24. When the pipe 7 becomes the pressure pipe the valve 15 is automatically moved to the right to cut off this pipe and connect pipe 8 to the reservoir. The slide block 5 is operated by liquid supplied by a hydraulic pump 27 and controlled by a valve 39. When. the control valve is shifted into a position in which it connects pipes 41 and 42 to a drain pipe 40 liquid from the pump flows through a passage 55 bore 48 (best shown in Fig. 2) port 56.to a cylinder 46 to cause a piston 45 to move the slide block 5 to the right at high speed until a piston 53 on a valve 51 connected to the block 5 closes an orifice 58. Liquid then flows through an adjustable passage 59 at a slow speed to move the block to the right at slow speed. As soon as the piston has moved past the orifice 58 the block moves to the right again at high speed until a stop rod 36 contacts an adjusting screw 35. When the block is in this position and the valve 39 is moved to its normal position in which pipe 41 is opened to gear pump pressure liquid from the pump will flow to a cylinder 30 and cause a piston 33 to shift the slide block to the left at high speed until the piston is stopped by a collar 38 on a rod 36 at which time the slide block is in its neutral position and further movement to the left is prevented due to piston 45 being continuously subjected to gear pump pressure. When the valve 39 is shifted to a position to connect channel 42 to a pipe 28 liquid from the pump 27 will flow to cylinder 30 and cause piston 32 to shift the block 5 to the left. The block will move at high speed and liquid will flow freely from cylinder 46 through port 56, bore 48 and port 55 into pipe 28 until the piston 53 blocks the flow of liquid through the bore 48. Liquid expelled from the cylinder must then flow through the passage 59 so that the block moves slowly until the piston 53 moves away from an orifice 57 and permits liquid again to flow freely through the bore 48 when the block moves at high speed until valve 51 engages an adjusting screw 50. When the slide block is at the limit of its movement to the left and the control valve is returned to its neutral position so that the pipe 41 is open to gear pump pressure and the pipe 42 is open to drain, liquid from the gear pump will move the slide block towards the right at high speed until stopped in the neutral position by the piston 33.