Improvements in vehicles adapted to carry material handling attachments

摘要

871, 287. Motor vehicles. GENERAL MOTORS CORPORATION. April 14, 1960 [May 13, 1959], No. 13340/60. Addition to 819,954. Classes 79(3) and 79(5). A vehicle comprises a forward section which is equipped with a material handling attachment, e.g. a digger bucket, and which is articulated to the rear section about a vertical axis provided by ball-and-socket joints 26, 28 and about a longitudinal axis provided by ball-and-socket joints 26 and 30 as described in the parent Specification, the vehicle being rotated about the vertical axis for steering purposes by a pair of hydraulic jacks 32. The front and rear wheels of the vehicle are driven as in the parent Specification, and a follow up device is provided which is operative at a given angle of turn determined by the extent of turn of the steering wheel to stop the mechanism from turning the front section further, the follow up device being little affected by relative movements of the two sections about the longitudinal axis. A steering worm 36 is driven through splines 46 allowing axial movement of the worm, from a steering shaft 48. The worm is engaged by a follower 52 mounted on a crank 54 rigid with a shaft 56 with which a crank 58 is also rigid. A rod 62 is pin jointed to the crank 58 and to a member 29 of the front section to which parts of the ball-andsocket joints 28 and 30 are attached. Centering springs 44 are provided on the worm. A valve, having ports 76 and 78 communicating with the hydraulic cylinders 32, an exhaust port 68 connected with a tank 70 and an inlet port 72 connected with a pump 74, has a spool 86 moved axially by a link 92 in response to axial movements of the worm 36. At the commencement of a turn, the pivot points 28, 30 and 26 'are in the longitudinal vertical plane of the vehicle. The steering wheel is turned and because of the position of the follower 52 and its associated links prevents the follower-from moving, the worm moves axially in one direction. Because of the geometry of the mechanism, as the front section turns, the rod 62 causes the follower to move and thus the worm 36 in a direction opposite to which the worm has previously moved to the point at which the hydraulic system is inoperative. As shown in Fig. 4, the valve is in the inoperative position. When the spool moves downwards the inlet port 72 is opened to the port 76 leading to the cylinders 32 and return line 78 communicates with the return 68 through apertures 88 and a central bore of the spool. In the upper position, inlet port 72 is opened to port 78 and port 76 is connected to port 68. Because the rod 62 is close to the longitudinal axis of turn, relative movements of the sections about that axis do not substantially affect the follow up device.