Vehicle transmission systems

911,850. Hydraulic transmission of power. LUCAS (INDUSTRIES) Ltd., JOSEPH. April 19, 1961 [April 26, 1960], No. 14539/60. Class 69 (2). [Also in Group XXXI] A motor vehicle transmission having an engine-driven pump 1 of the swash plate-type supplying a fluid activated motor 3 which drives the vehicle wheels comprises a servo cylinder 13, the piston 14 of which varies the angle of the cam plate 2 of the pump, a spring 15 biasing the piston 14 towards the position of maximum obliquity of the cam plate, there being a line 10 connecting the output and input sides of the pump having a pair of restricting orifices 11 and 12, the end of cylinder 13 remote from the spring 15 being connected to the line 10 between the orifices 11 and 12 and the other end of the cylinder being connected to the line 10 on the pump return side of the orifices, the orifice 11 being bridged by a variable orifice or valve 16 connected to the engine throttle control 17 whereby, as the engine throttle is closed the valve 16 is opened, so submitting the one end of cylinder 13 to a greater proportion of the pump output pressure and narrowing the obliquity of the earn plate 2, increasing the transmission ratio. The arrangement also provides that when the engine is operating at a fixed intermediate throttle setting, the transmission ratio will vary according to the required torque. The pump-motor circuit includes the pump output line 6, and return line 5 and reversing valve 9 which may also be put in a neutral position wherein the lines 5 and 6 are connected. A reservoir 8 is connected through non-return valves 7 to the lines 5 and 6 and to the pump and motor.