Patent GB-1222372-A (GB)
Title: Improvements in or relating to supply and control mechanism for hydraulically-driven vehicles
Inventor: TAYLOR NORMAN CHARLES FRANK
IPC: B60K7/00
Filed: 1967-06-03
Abstract: 1,222,372. Hydraulic reciprocating pumps. LANGDALE ENG. CO. Ltd. Aug.30, 1968 [June 3, 1967], No.25752/67. Heading F1A. [Also in Division F2] A control system for a motor vehicle hydrostatic transmission having a variable displacement pump 20 providing separate deliveries 43X, 43Y to circuits 2A, 2B, 4A, 4B supplying at least two motors 3, 5 which drive and brake the vehicle wheels comprises a reversing valve 15 in each circuit, a valve 16 which connects the high-pressure lines 32X, 32Y of the two circuits to permit differential action between the motors and a brake valve 43 to throttle the return line 33 for vehicle braking. The valves 15, 16 are controlled by hand levers 18, 19 whilst the brake valve 43, and pump displacement are controlled by pedals 8, 9 which actuate master cylinders 10 connected to slave cylinders 12, 13 operating with servo assistance the brake valve and pump displacement controls. The reversing valves may, as shown, be a combined reversing valve 15, additionally or alternately separate reversing valves may be provided in each circuit to permit differential operation for steering. As shown the circuit 2A, 2B supplies two motors 3 driving the front wheels whilst the circuit 4A, 4B supplies two motors 5 driving the rear wheels. An additional valve 17 linked to the valve 15 blocks the supply to the front motors 3 when the valve 15 is moved to a position connecting the high-pressure lines 32X, 32Y whereupon both deliveries are supplied to the rear motors 5 for high speed travel. Relief valves 28 limit the pump delivery pressure whilst a relief valve 35 in parallel with the brake valve 34 limits the back pressure in the line 33 during braking. In Fig. 10 (not shown) the circuit (2A, 2B) supplies the wheel motors (3A) on one side of the vehicle whilst the other circuit (4A, 4B) supplies the wheel motors (5A) on the other side of the vehicle. The valve 17 is omitted and an additional reversing valve (112) is provided in each circuit for steering. In Fig. 11 (not shown) the two circuits provide independent drives to the two front wheels only. Pump construction. The pump, Fig.6, comprises pistons 46 slidable in radial cylinders 40 fed from a common inlet 42 through one-way valves 44. Alternate cylinders are connected through oneway valves 45 to the delivery ducts 43X, 43Y respectively. The pistons 46 are urged by springs 47 into engagement with the outer race of a bearing 50 whose inner race 63 is rotatable with a driving shaft 21. The bearing 50 is biased by springs 68 to a position concentric with the shaft 21 for zero pump delivery and is moved to an eccentric position by a piston 66 radially slidable in a chamber 65 in the shaft 21. Pump displacement control. On depression of the pedal 9 a piston 76 of the slave cylinder 13 moves left a pilot valve 78 whereupon pressure liquid is supplied to the rear face 80 of a piston 71 which follows the movement of the pilot valve 78. On initial leftward movement of the piston 71 a ball 84 closes an exhaust duct 74 from a chamber 69 connected to the chamber 65. Further leftward movement of the piston 71 forces the liquid from the chamber 69 into the chamber 65 to cause outward movement of the piston 66 and corresponding eccentricity of the bearing 50. On release of the pedal 9 the piston 76 opens an exhaust duct 87 to vent the rear of the piston 71 which is returned by a spring 89. Cooling and make-up circuit. A make-up pump 24 draws liquid from a reservoir 7 through a filter 25 and supplies liquid at a pressure determined by a relief valve 27 to the low-pressure pump inlet duct 42 and through one-way valves 57 to the servocontrol system. A cooling fan 23 driven by the driving shaft 21 directs air over the reservoir 7 which has cooling fins 104.