Patent GB-786590-A (GB)
Title: Tractor having driven rear-wheels
IPC: B62D49/08
Filed: 1955-10-11
Abstract: 786,590. Tractors. VAN DER LELY N.V., C. Oct. 11, 1955 [Oct. 14, 1954], No. 28953/55. Classes 79(1) and 79(2) [Also in Group XXXII] Relates to tractors of the kind in which a frame carries an engine and in which the distance between the centre of gravity of the engine and the ground can be changed by means of an adjusting device on the frame. According to the invention, the adjusting device comprises adjusting members which are arranged to support the axles of the rear wheels and adjusting means which are arranged to move the axles from one working position in which the axles lie in front, relative to the intended direction of movement of the tractor, of a line joining the axles when they are in a central position to another working position in which the axles lie behind the line the arrangement permitting the tractor to have different wheel-base-lengths. In the arrangement according to Fig. 2, engine-driven rear wheels 3, 4 are carried at the free ends of crank members 12 which at their other ends are provided with crank parts 8, 9 by which the crank members are pivotally mounted on rearwardly extending parts 6, 7 of the tractor frame 1. Each crank part 8 and 9 is provided with a toothed wheel 11 which engages a toothed rack 18 movable in either direction by a hydraulic piston and cylinder device 14, 16 and 15, 16, whereby to effect adjustment of the wheel base of the tractor and the height above ground of the tractor and of an implement fastened thereto by fastening members 37 and 38. The rear wheels may be driven by a chain located within the crank members 12. Front steerable wheels 20, 21 are carried by shafts 22 on steering pivots supported by vertical elements 23 the upper ends of which are interconnected by a member 24 pivoted on a pin 25 about the longitudinal axis of the tractor. The member 24 is hingedly connected to the tractor frame 1 by bars 27, 27. The pin 25 also connects the lower end 28 of a forked arm 29 to the member 24 the other end of the arm 29 being connected through arms 30, 32 of a hydraulically operated piston and cylinder device 34, 35. The arrangement is such that adjustment of the height above ground of the front of the tractor frame may be effected by the piston and cylinder device, while permitting swinging movement of the member 24 about the pin 25. The cylinders 14, 15 and 35 may include gas under pressure of the hydraulic liquid, to provide a resilient suspension for the tractor wheels. In another arrangement, Fig. 4, a member 40A at each side of the tractor frame 39, is rotatably supported by an axle 40 and is connected through parallel arms 43, 44, pivoted about parallel axes 41, 42 and 47, 48 to a wheel supporting member 45. A hydraulic piston and cylinder device 49 pivotally connected between the axes 42 and 47 is operative to selectively adjust the distance of the road wheel 46 or 51 laterally of the tractor frame, the height of the frame, above ground being adjustable by rotation of the member 40A. Each road wheel is driven by a pressure oil driven motor built into the wheel hub and supplied through flexible pipings 53, 54. The parallel arm arrangement of Fig. 4 may replace the crank members of the Fig. 2 arrangement. In Fig. 4, the parts 40A may be replaced by a vertically movable paralellogram construction. The implement attached to the tractor may be carried adjustably about the axis of the power takeoff of the tractor.