Patent GB-847918-A (GB)
Title: Control means for road vehicle hydraulic power transmission systems
Inventor: BOTTOMS CHARLES HERBERT
IPC: F16H61/42
Filed: 1955-06-29
Abstract: 847,918. Motor vehicle hydraulic driving gear. LUCAS (INDUSTRIES) Ltd., J. Sept. 26, 1956 [June 29, 1955], No. 18766/55. Classes 79(2) and 79(5). [Also in Group XXIX] In a road vehicle power transmission system having a variabledelivery and reversible pump a connectable either in series or in parallel with motors t, u connected to the road wheels, control means are provided comprising a manually operable mechanism having a rotatable and axially movable member n connected by a quick - pitch helical connection m to a member j capable of only rotary motion and connected to a liquid-operable servo-mechanism for controlling the output of the Dump. As shown the motors can be connected either in series or in parallel with the pump through valves r, s, and the output and direction of the pump can be varied by a rod e connected to the swash plate . t, the rod e and valves r, s being controlled by a hand lever o co-operating with a gate p. The lever o carries the can member n and the pinion member j meshes with a rack i. A rod g carrying the rack i also carries a valve member h co-operating with a seat in the hollow rod e which carries a piston d in a cylinder c, the ends of the cylinder being in communication through a restricted orifice f in the pistons (or alternatively in the cylinder wall) and the bore in the rod e serving to connect one end of the cylinder c through the pump housing to a sump. The valves r,s are actuated by a slidable rod q attached to the lever o. Control lever actions. Normally the pump a delivers through a pipe 2 past a spring loaded valve w to a point 15, the hydraulic system being replenished by a pump 4 through spring loaded valves 5, 6, 7 and relief valves 8, 9 being provided. With the lever o in the position shown the motors are connected in series, the liquid flowing from the point 15 as indicated by the full line arrows (i.e. to motor u, valves r, s, motor t and back to the pump). Movement of the lever o along a slot 10 in the gate p from the position shown will cause the valve member h, piston d and rod e to move to the left increasing the obliquity of the plate b and hence the pump output. Movement of the lever o along a slot 12 in the gate p from the position shown will increase the obliquity of the plate b and hence the pump output and will also move the rod q axially to turn the valves r, s through 90 degrees when the flow of liquid from the pump will be as indicated by the dotted line arrows (i,e. the liquid dividing into two streams at the point 15, one flow passing through the valve s and the motor t to the pump and the other flow through the motor u and valve r to the pump). Movement of the lever o from the slot 12 along a slot 13 will reduce the obliquity of the plate b to zero at a neutral position 14. Further movement of the lever o along the slot 13 past the position 14 impart an opposite obliquity to the blade b hence causing the action of the pump and motors to be reversed. The system includes a non-return relief valve comprising a spring loaded closure member 16, the spring 17 abutting a member 18 connected by a rod 19 to a roller 20 engaging the cam n and the cam being tapered axially, whereby the spring force acting on the member 16 can be varied. Differential action. When the motors are connected in series, the system includes means for obtaining a differential action between the driven road wheels. The means comprises a normally closed by-pass valve associated with each motor, the valve comprising a piston 21 in a cylinder 22 normally closing a by-pass pipe 23 connected to the associated motor and the cylinder 22 being connected by a pipe 24 to the motor. One end of the piston 21 carries a piston 25 in a cylinder portion 26, the piston 25 (or the portion 26) carrying a restricted orifice 27 inter-connecting the ends of the portion 26. The portions 26 are connected by pipes 35, 38 to seatings 39, 36 adapted to be closed by members 40, 41 on a T-shaped lever 42 loaded by a spring 43. A stem 44 on a pivoted lever 45 engages the lever 42 and the opposite ends of the lever 45 are acted on by pistons 46, 47 in cylinders 48, 49. Each cylinder 48, 49 is connected on opposite sides of the associated piston by pipes 50, 51 to the inlet and outlet of the associated hydraulic motor. In operation, unequal loading on the motors (such as the vehicle rounding a bend) causes the pressure acting on one of the pistons 46, 47 to exceed the other, thereby tilting the lever 42 to cause motive liquid for the lighter loaded motor to bypass that motor. Associated with the lever 42 is a pivoted lever 55 engaging a cam 54 connected to the lever o whereby the lever 42 is lifted when the lever o moves from slot 13 to slot 10 or vice versa. The lever 55 can also be manually operated through a flexible cable 56 connected to a knob 57 carried by the lever o.