GB1086662A - Improvements relating to self-propelled traction vehicles, more particularly agricultural tractors - Google Patents

Abstract

1,086,662. Tractor power lift mechanism. LINDE A.G. Dec. 3, 1964 [Dec. 3, 1963; March 4, 1964], No. 48915/64. Heading A1P. [Also in Division B7] A tractor is provided with means whereby the engine output, the ratio of a continuously variable transmission gear or an operational characteristic of a mounted or trailed implement is controlled in response to the magnitude of the tractive load or to the occurrence of wheel spin. In Fig. 1 the resistance of a plough carried by a three-point linkage depresses the upper link 4 against spring loading 14 to actuate a lever 10 linked to a lever 16 which regulates the engine output or adjusts the ratio of a continuously variable transmission gear. If the lever 16 controls the transmission gear ratio, it may also, as at predetermined position during its travel, alter the engine speed from that associated with lowest specific fuel consumption to the maximum speed or to that providing greatest torque. In a tractor provided with a continuously variable hydrostatic transmission (Fig. 2, not shown) comprising a variable output pump (22) driven by the engine and connected by pipes (24, 25) to a hydrostatic motor, one of valves (28, 29) is opened when the adjustable portion (23) of the pump is positioned to provide maximum output, whereupon fluid from one of pipes (24, 25) is supplied to a cylinder (34) containing a piston (35) displaceable against spring loading to regulate the engine output. An exhaust pipe (38) restricted by a capillary bore enables fluid to be exhausted from the cylinder (34) when both valves (28, 29) are closed so that the piston (35) is restored to its initial position by the spring (36). In Fig. 3 the output of a hydrostatic transmission pump 22 is reduced should a traction wheel spin by a hydraulic ram 47 communicating through a valve 43 with a flow circuit 52 between a gear pump 53 coupled to a driven wheel and a gear pump 54 coupled to an undriven reference wheel. When the driven wheel slips the output of fluid from the gear pump 53 exceeds that returned by the gear pump 54 to a reservoir 56 and the excess fluid is supplied to the cylinder 47 to reduce the output of the transmission pump 22. Should the wheel continue to slip when the output from the pump 22 reaches a minimum, a projection 39 on the adjustable portion 23 of the pump depresses a spring-loaded contact plate 40 to displace the valve 43 and divert excess fluid from the gear pump 53 to a power device 50 which reduces the depth of furrow of a plough or adjusts the cutting angle of the ploughshare and/or mould board about a vertical or inclined axis.