Patent GB-896399-A (GB)
Title: Hydraulic transmission systems for vehicles
Inventor: SKINNER ROBERT THOMAS JOHN
IPC: F16H61/42
Filed: 1959-11-11
Abstract: 896,399. Hydraulic transmission of power. LUCAS (INDUSTRIES) Ltd., JOSEPH Nov. 8, 1960 [Nov. 11, 1959], No. 38188/59. Class 69 (2). [Also in Group XXXI] An hydraulic power-transmission for a motor vehicle comprises a variable-stroke fluidactuated motor for driving the vehicle, a variable - stroke engine-driven pump for supplying motive fluid to the motor and means for changing the speed ratio between the engine and motor whereby the stroke of the pump can be varied between a maximum and a minimum with the stroke of the motor constant and whereby after the stroke of the motor has reached one of its limits during a change in a given sense, the speed ratio can be changed in the same sense by varying the stroke of the motor. A pump 1 comprises a rotor 3 having cylindrical bores and plungers 4 co-operating through slippers 5 with a swash-plate 6, driven by an engine 15. The pump has an inlet 7 and outlet 8 and fluid is supplied from a reservoir 13 by an engine-driven boost pump 14 at a pressure determined by a relief valve 16. The motor 9, of similar construction to the pump but of smaller capacity, drives the wheels or tracks of the vehicle through an output shaft 10, the outlet 8 of the pump being connected to an inlet 11 of the motor and an outlet 12 of the motor being connected to the inlet 7 of the pump. The swashplates 6 and 17 are provided with rollers cooperating with cam surfaces 18, 19 which are movable transversely relatively to the axes of the rotors. As shown, they are on the same member and are disposed such that while the roller of swash-plate 6 bears against the inclined part of the cam surface whereby angular movement is imparted to the swash-plate, the roller of swash-plate 17 is at maximum angularity, bearing against a flat part of the cam surface 19, and when the swash-plate 6 is moved to the position of maximum angularity, the angularity of roller of swash-plate 17 will be reduced while maintaining the angularity of swash-plate 6 constant by any further movement of the cam member in the same direction. The movement of cam member 20 over the positions whereby angular movement is imparted to swash-plate 6 gives a continuously variable gear change over the range of normal gears whereas the continued movement imparting movement to swash-plate 17 provides an '' overdrive," and the cam surface is so shaped that when the member 20 is moved to the extreme position opposite to the " overdrive " positions, it has passed the position of zero delivery of the pump and the motor is driven in reverse. The cam member 20 is provided with pistons operating in cylinders 21 and 22 so that the cam 20 may be positioned by hydraulic control, the piston-and-cylinder 22 being larger so that when the pressures in both cylinders are equal the cam is moved to the position of zero delivery of the pump determined by an hydraulically-operable stop 23 which may be moved to obtain the " reverse " position. The swash-plates may be adjusted by separate cammembers operated hydraulically in synchronism and the pump 1 may supply two or more motors for driving different wheels of the vehicle. Specification 896,400 is referred to.