GB1449961A - Earth working machines - Google Patents

Abstract

1449961 Hydrostatic transmissions POCLAIN 28 Jan 1974 [9 Feb 1973] 03874/74 Heading F2W [Also in Division E1] An earth working machine comprises a frame 4, Fig. 1, front and rear wheels 5, 7 driven respectively by first and second hydraulic motors 21, 22, Fig. 3, working equipment 3 articulated to the frame, a double-acting jack 8 coupled between the frame and working equipment, and an hydraulic control system which automatically adjusts the working equipment in dependence of the torques opposing the front and rear wheels. Included in the control system is a three-position distributer 14 which, in a first position connects one chamber 12 of the jack 8 to a supply 19 of pressurized fluid 17 and the other chamber 13 to a discharge reservoir 20, in a second position reverses the arrangement, and in a third position disconnects the chambers. Automatic selection of the distributer position is achieved by means of a double-acting jack having chambers 37, 38, which can, by means of a second distributer 39, be placed in communication with the fluid lines 31, 33 to the motors 21 and 22. If, for example, the front wheels 5 were to lift off the ground (Fig. 1) pressure in the supply line 31 would drop and distributer 14 in communication therewith would be moved into its second position wherein fluid would be fed to the chamber 13 to extend the jack 8 and lower the front wheels. A spring 36 tends to maintain the distributer 14 in its third position when the pressures in the chambers 37 and 38 are equal. In an alternative embodiment, Fig. 4 (not shown), the position of the distributer 14 is selected automatically by means of a pilot fluid from a low-pressure source (57). A second three-position distributer (49) has its position governed by the highpressure supply to the motors 21, 22, and this distributer (49) supplies the low pressure fluid to one of the chambers 37, 38 of the distributer 14 in one position and supplies the fluid to the other chamber in another position. In each hydrostatic transmission a reversing valve 25, 26 has a position in which the wheels are hydrostatically braked, and these valves 25, 26 may be operated separately or together.