GB560981A - Improvements in and relating to the steering of vehicles having endless tracks - Google Patents

Abstract

560,981. Change-speed gearing. WILSON, W. G. Sept. 16, 1939, No. 26007. [Class 80 (ii)] [Also in Group XXXI] In power driving and steering mechanism for endless-track vehicles each track is driven through a combined epicyclic driving and steering gear with small ratio differences, both sets of such gears being driven by a main change-speed gear common to both, so that both tracks can be driven through the usual speed changes of the main gear, and the steering gears can be separately controlled to drive the tracks at equal speeds or to drive one track at a speed differing only slightly from that of the other. The difference in speed of the two tracks can be modified by allowing slip in the drive to one track. In the construction shown the engine unit a drives the tracks p through bevel gearing d, a transverse shaft e, two independent compound epicyclic two-speed gears g, spur gearing m and track sprockets o. Each end of the driving shaft e carries the sun pinion t of a first epicyclic train r and the toothed annulus 12 of a second epicyclic train s. The planet carrier v of the planet pinions u, of the first train may be held by a brake z and carries the sun pinion y of the second train, this pinion being loose on the driven shaft h to which is fixed the planet carrier 11 of the planet pinions of this second train. When the annulus w of the first train is held by a brake x, the brake z being free, the shaft e drives the shaft h through the two epicyclic trains compounded. When the brake x is released and the brake z applied the shaft h is driven through the second train only, the ratio of this train being sufficiently close to that of the compound train for steering purposes. In order to render the steering action more smooth and gradual the brake band z may be loosened to allow slip, the drum v and the band being of increased width for this purpose. For sharp turns either track can be retarded or held stationary by independent brakes k<1>. The gear and steering brakes may be controlled either by hand or hydraulic or pneumatic servo-motor. In the latter case the engine a drives an air compressor 23 to supply a receiver 24, the three brakes x, z, k<1> on each side being controlled through valves 25 operated by levers 26. Normally, when both brakes x are applied the vehicle is driven in a straight path ; to steer the vehicle gradually one brake x is released and the corresponding brake z applied, while to make a sharp turn the brake z on that side is or may be released and the corresponding brake k<1> applied. In a modified construction of epicyclic gear the driving shaft e carries the sun pinion of the first train and the planet carrier of the second train, and the annulus of the second train is fixed to the driven shaft h, the planet carrier of the first train being fixed to the sun pinion and the brake of the first train as in the construction shown in Fig. 2.