Patent GB-850633-A (GB)
Title: Motors for hydrostatic power transmission systems
Inventor: HAMBLIN HENRY JOEL
IPC: F03C1/40
Filed: 1958-06-24
Abstract: 850,633. Hydraulic transmission of power. NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 8, 1959 [June 24, 1958], No. 20243/58. Class 69 (2). An hydraulic motor for an hydraulic power transmission system comprises at least five cylinders 18, Fig. 1, provided with cut-off valve devices 27, Fig. 4, adapted to be operable so that when one cylinder is supplied with fluidpressure, at least one succeeding cylinder is cut-off from the supply during what would have been the operative stroke of its piston 19. The five cylinders 18, Fig. 1, are fixed to a rotatable casing 17 of a tractor wheel, and the pistons 19 are connected by rods 20 to pressure pads engaging an eccentric 12 integral with a stub shaft 13, Fig. 3, fixed to a frame portion of the tractor. During low-speed, high-pressure operation, fluid is supplied sequentially to the inlets 29 of the cylinders from a pump connected to an inlet channel 22 which communicates with a passage 30 in a valve member 23 fixed to the stub shaft 13. The passage 30 communicates in turn with passages 26 in the casing 17 to supply the fluid to the inlets of all the cylinders as the wheel rotates. Exhaust fluid from the cylinders passes through a passage 31 in the valve member to a bore 32 in the stub shaft leading to an outlet which is maintained at a controlled backpressure. Reverse rotation of the wheel may be effected by reversing the connections to the channel 22 and bore 32. The supply from the pump is also connected by a one-way valve 36 to a chamber 34 to assist a spring 37 to press the valve member 23 against the face 25 of the casing. During the low-speed, high-pressure operation, the controlled back-pressure is communicated by a passage 52, a sliding valve 44 and a passage 56 to inlet grooves 62 in rotary valves 59 respectively connected by pipes 64 to chambers 43, Fig. 4, associated with the cut-off valve devices 27 of each cylinder. The pressure in the chambers 43 causes detents 40 to engage recesses 41 in the spools 38 of the valves to maintain communication between the supply passages 26, connected to the inlets 49 of the valves, and ports 28 connected to the inlets 29 of the cylinders, so that each cylinder is supplied with fluid during each rotation of the wheel and maximum torque is transmitted. The inlet groove 62, Fig. 3, of each valve 59 and a groove 65 connected to an exhaust chamber 67, during rotation of the valves 59, alternately connect pipes 77, 78 leading to opposite ends of their associated cut-off valves to the controlled backpressure of the outlet and to exhaust, respectively, but with the detents engaged in the recesses, the valve spools 38 remain stationary. During high-speed, and low-load operation, however, the controlled back pressure is reduced and is not sufficient to retain the detents in the recesses and the valve spools reciprocate to, in one position, connect the supply to the inlets to the cylinders, and in the other position, block the flow. As the valves 59 are rotated by gearing 57, 76 at half the speel of the wheel, each cylinder is cut-off from the supply during alternate revolutions of the whee, two and a half power strokes thus being provi led for each revolution. In an alternative embodiment, each spool 38 is reciprocated against spring-pressure by fluid-pressure supplied from the cylinder immediately preceding the valve. If the embodiments have 7 or more cylinders, every second and third cylinder may be cut-off for high-speed operation.