Patent GB-909934-A (GB)
Title: Improved traction for earth movers and the like
IPC: E02F3/65
Filed: 1961-05-26
Abstract: 909,934. Earth-moving machines. M-R-S MANUFACTURING CO. May 26, 1961 [May 27, 1960], No. 19112/61. Class 68 (1). [Also in Groups XXXI and XXXII] A machine for. moving earth and the like comprises a tractor having wheels 28 drivable from a power source 30 on the tractor, a trailer having a pair of wheels 53, 132, at each end, draw gear 88 interconnecting the trailer and tractor, means 98 connecting the rear of the tractor with one end of the trailer and operable to transfer at least part of the weight of the trailer from the wheels 53 at the one end to the driven wheels of the tractor, power means on the trailer for driving at least wheels 132, and means at an operator's station 42 on the tractor for controlling the weight transfer means and the power means. The trailer comprises a goosenecked frame member 52 supported on wheels 53 and pivoted at 55 to a bowl 54 which is also connected to a frame 56 (Figs. 1 and 3), supported on the rear wheels. Hydraulic means 87 can raise and lower the bowl from and to the scraping position, in which a scraper blade 58 is operative. For dumping the contents of the bowl, its floor 62 and rear wall 64 are pivoted on the blade at 66, and to a lever 68 which is supported on frame 56 by a lever 74 and jack 82, the latter being extended for dumping. The weight transfer means is an hydraulic jack 98, which when extended tends to lift the trailer front wheels, throwing additional weight on to the tractor drive wheels 28 and the trailer drive wheels 132, to improve traction. The trailer has its own internal combustion engine 116, driving wheels 132 through lockable differential gearing. The trailer change-speed gearing is controlled remotely as shown in Fig. 4, where the gear shift element 138 is pneumatically moved to reverse, neutral, first, second, third, or fourth gear positions in accordance with manual choice of forward, neutral, or reverse, and an axial-driven governor 198. A crosshead 136 on element 138 is urged by a spring 140 towards the reverse position, and may abut the piston-rods 150, 158, 162, 168, 170 of cylinders 144, 152, 160, 164 and 166, of which the former contains a spring 148, stronger than spring 140, urging element 138 to the neutral position, and the remainder contain springs such as 156 urging their piston rods inwardly. The governor 198 raises a rod 216, shown in its lowest position, as the vehicle speed rises. The rod has a flange 222 working in cylinder 196 to connect ports 230, 232, 234, 236, to a source of pressure in pipe 194 or to atmosphere. With lever 180 in the (forward) position shown, air under pressure is admitted from pipe 174 through valve 172 to pipe 184 and pipe 194. Cylinder 152 is connected to pressure through port 230 and pipe 238, and piston-rod 158 moves cross-head 136 to place element 138 in first gear position. As the vehicle speed rises, ports 232, 234 and 236 are successively connected by flange 222 to pressure, and pressurize cylinders 160, 164 and 166 in succession, moving element 138 through second and third to fourth gear position. If lever 180 is placed in reverse position, valve 172 connects an exhaust pipe 239 to pipe 184, cylinder 196, and cylinders 152, 160, 164 and 166. Pipe 174 is connected to pipe 190, to pressurize cylinder 144 and withdraw its piston-rod. Spring 140 then moves element 138 to reverse position. With lever 180 in the neutral position, pipes 184 and 190 are connected to exhaust pipes 239 and 192 respectively. Spring 148 then moves element 138 to the neutral position. The compressed-air supply in pipe 184 when lever 180 is in the forward position, is fed to a manuallycontrolled four-position valve 20, which can supply air to either, both, or neither of cylinders 256, 266, controlling respectively the trailer differential lock and the weight transfer jack 98. A manually-controlled valve 195 enables these devices to be operated without governorcontrolled gear shifting. It is preferred that the weight transfer means shall be inoperative and the differential locked above a certain road speed, and therefore a valve (not shown) is included between pipe 184 and valve 20, and operated by a servo cylinder when compressedair reaches a tap X on the pipe 242 leading from port 234 to cylinder 164, so that the valve is closed when the road speed is such that third or fourth gear is engaged. When maximum speed is attained, the trailer gear box is automatically put in neutral by a servo cylinder (not shown) acting on valve 172 and operated from a port 237 in cylinder 196. The accelerator pedal controlling the tractor engine may also control the trailer engine by a pneumatic relay comprising a valve operated by the pedal to control the pressure of air admitted to a cylinder, the piston-rod of which moves against a spring to operate the trailer throttle. Alternatively, the trailer wheels may be driven by individual electric motors supplied from a generator on the tractor, the control pedal then operating a variable resistor to control the field energization of the generator. This pedal may be locked to the tractor engine accelerator pedal, or the two pedals may be disposed so as to be operable by one foot. In a further embodiment, the wheels 132 are driven from the tractor prime mover through bevel gearing and universally jointed shafting, which extends along the draw-bar 88 and frame member 52. This shafting also drives the front trailer wheels 53 through worm gearing. The rear wheel drive may be disconnected by a clutch, and both front and rear wheel drives may be disconnected by a further clutch which is put out when the weight transfer means is disabled, above a certain speed. An electrically-driven trailer may have provision for coupling to a tractor at either end. Each end then has a draw-bar, a bracket for attachment to the weight transfer means, and a socket for receiving an electric plug on a cable from the generator on the tractor. Specification 891,689 is referred to.