Patent GB-563339-A (GB)
Title: Improvements in or relating to endless track vehicles
IPC: B62D11/10
Filed: 1940-12-27
Abstract: 563,339. Driving and steering endlesstrack vehicles. AUTOMOTIVE PRODUCTS CO., Ltd., and GATES, G. R. G. Dec. 27, 1940, No. 18169. [Classes 79 (ii) and 79 (v)] The track sprockets 24 are driven from a change-speed gear 10 through a shaft 14 and two clutches 16, the driven elements of the clutches being geared at 17, 18 to differential half-axles 21, a friction clutch 71 being provided for connecting the differential casing 27 to the engine through gearing 74, 73 of a different ratio from that between the engine and the half-axles. Thus, the vehicle can be steered by disconnecting one or other of the clutches 16 and causing the clutch 71 to be more or less fully engaged. In the construction shown in Fig. 1, the driven clutch shafts 15 are connected by the gears 17, 18 to the shafts 21 which drive the track sprockets 24 through reduction gear 22, 23. Normally, the clutches 16 are engaged and the clutch 71 is disengaged so that the tracks are driven through the clutches at equal speeds and the vehicle is driven in a straight path. To steer the vehicle to one side, the clutch 16 on that side is released bv means of a corresponding hydraulic cylinder 41 and the clutch 71 is engaged to a greater or lesser degree by a cylinder 75, the cylinders 41 and 75 being controlled by a hand-operated steering valve 46. When the clutch on one side is disengaged, the corresponding track slows down, and the engagement of the clutch 71 causes the differential casing 27 to be driven at a lower speed, say, half, than the track that is still driven. Thus, if the clutch 71 is fully engaged the undriven track becomes stationary and the vehicle will pivot about it, whilst if the clutch is only partially engaged the track which has its clutch 16 disconnected will be driven through the differential gear at a speed lower than that of the other track. Thus, the radius of turning can be controlled by varying the degree of engagement of the clutch 71, the differential casing of the tracks will be driven at equal speeds in opposite directions so that the vehicle will pivot about its centre. Hydraulic pressure for operating the clutches and brake is supplied by a master cylinder 44, the piston in which is operated from the gear-box 10 by a frictional mechanism 45 which may be of the kind described in Specification 525,415, [Group XXXIV]. When the hand-operated steering valve 46 is rotated in either direction from the central position shown by means of a handle 56, a cam disc 63 acts on, the piston-rod 61 of a control cylinder 57 which transmits pressure to a cylinder 58 bringing the mechanism 45 into action to apply pressure to the clutch cylinder 71 and the steering valve. At the same time the valve 46 connects one of the clutch pipe-lines 52, 53 to the cylinder 44 and the corresponding clutch is disengaged. The extent to which the clutch 71 is engaged depends on the pressure in the control cylinder 57 and therefore on the rotation of the valve 46. The clutch 71 can be independently controlled to brake the vehicle by means of a pedal (not shown) operating a fork 64 which engages a collar 65 on the piston-rod 61. Modifications are described in which (1) the clutch 71 is mounted on the shaft 14 and connects the gearwheel 74 to the shaft 14, and (2) the track sprockets 24 are coaxial with the shafts 14, 15. According to the Provisional Specification, the differential casing 27 may be controlled by a brake so that it can either be retarded or held stationary ; in the latter case the two tracks rotate in opposite directions.