Patent GB-533452-A (GB)
Title: Improvements in and relating to hydraulic power transmissions
IPC: B60K17/10
Filed: 1939-08-26
Abstract: 533,452. Hydraulic transmission of power. LEWIS, L. G. Aug. 26, 1939, No. 24619. [Class 69 (ii)] [Also in Group XXXI] In driving-gear, particularly for motor vehicles, comprising a motor-operated pump in circuit with one or more motors through a reversing-valve, the shaft of each motor is coupled to a driven member through changespeed gearing operated by the motive fluid under control of a valve. As applied to endlesstrack vehicles, the system may include means for controlling the flow to either pump for steering purposes. An engine-driven pump 1, Fig. 1, is connected by pipes 6, 7, 8, 9 to rotary motors 2, 3 for driving the wheels or endless tracks of a vehicle. The pipes 6, 9 have branches 6<SP>1</SP>, 6<SP>2</SP> and 91, 9<SP>2</SP> leading to the casing 16 of a reversing-valve 14 secured to a spindle 15 and formed with passages 21, 22. Normally, liquid flows straight through the pipes 6, 9, and the motors are driven forwards. The motors are started and controlled by means of a valve 12 arranged in a byepass 11. For relieving excessive pressure, a chamber 48 in the pipe 9 communicates with a chamber 49 containing a spring-urged piston. When the valve 14 is adjusted, the passages 21 and 22 establish communication between the branches 6<SP>1</SP>, 9<SP>1</SP> and 6<SP>2</SP>, 92 respectively, valves 18 on the spindle 15 prevent liquid from flowing straight through the pipes 6, 9, and the motors are reversed. During the change from forward to reverse drive and vice versa, delivery of liquid to the motors is stopped and then gradually reestablished by means of byepass grooves 23, 24, Fig. 3, in the valve 14. To provide for steering endless-track vehicles, the pipe-system may include a pair of rotary valves for reducing or stopping the flow of liquid to either motor 2. Each motor-shaft 45 is coupled to a driven member 25 by means of change-speed gearing comprising a clutch-member 26 secured to the driven member and co-operating for direct drive with a member 31 on a slide 30. The gear is changed down by shifting the slide to bring a pinion 32 thereon into engagement with a pinion 29 on a shaft 28 provided with another pinion 27 engaging the member 26. The slide may be provided with a hydraulic coupling 46. Pistons 35 for shifting the slides work in cylinders 36 which are inter-connected by a pipe 37 and are connected by pipes 38 to chamber 39 containing valves 40 which are secured to the spindle 15. The chambers are inter-connected by pipes 41, 42, and are connected by branches 6<SP>3</SP>, 9<SP>3</SP> to the pipes 6, 9. When the valve 14 is in reversing position, the valves 40 permit communication between the pipes 38 and the pipes 41, 42, and the pistons 35 hold in the low gear. When the valve 14 is moved into forward position, low gear is maintained until the pipes 41, 42 are cut off, and the pistons 35 then shift the gears into high-gear position. The valve 14 is formed with by-pass grooves 43, 44, Fig. 3, for stopping delivery of liquid to the motors during gearchanging. Specification 503,742 is referred to.