GB1425820A - Device for feeding fluid - Google Patents

Abstract

1425820 Hydrostatic transmissions POCLAIN 25 Jan 1974 [12 Feb 1973 14 Dec 1973] 03619/74 Heading F2W In a hydrostatic transmission having two motors 7, 8 (Fig. 1), 312, 316 (Fig. 5) supplied from a single pump 1 through a fluid divider 5 (Fig. 1) or from separate pumps 301, 302 (Fig. 6) a discharge valve 21 (Fig. 1), 322 (Fig. 5) is disposed in a line connected to the pump output (or the output of the pump supplying the higher pressure), the discharge valve being operated by the sum of the pressures in the input lines 13, 14, 306, 307 to the motors. In the embodiment shown in Fig. 1 the pressures in lines 13 and 14 are sensed by lines 15 and 16 connected thereto, the pressures passing through restrictors 18 and 19 and combining in a pilot line 22 of valve 21. The system used in Fig. 6 consists of a piston 221 having a surface S 1 acted on by the pressure in line 306 and a surface S 2 acted on by the pressure in line 307 to operate valve 322 through a fluid column in line 332, which system may be used in the single-pump arrangement of Fig. 1 (Fig. 2, not shown). The piston 221 may operate the valve 322 directly through a piston rod (Figs. 3 and 7, not shown). In the embodiment shown in Fig. 6 the higher pressure pump output line is connected to the discharge valve through a shuttle valve 318. In each embodiment a pressure relief valve 25, 325 is provided, this opening at a pressure greater than the pressure which exists in each of the input lines to the motors to open the discharge valve when these input lines are at the same pressure, but less than twice this pressure to protect the system in the event of one motor having an input at substantially zero pressure. Three position reversing valves 308, 309 are provided for the motors in Fig. 6. In a further embodiment (Fig. 4, not shown) the pump (102) is variable displacement and reversible in its pumping direction, the motors here being supplied in closed circuit with one-way and shuttle valves permitting the operation of the invention in both directions. A feed pump is also provided which provides fluid pressure to operate a selector valve (107) against a spring (133). Operation.-The operation of the discharge valve by the sum of the pressures to the motors allows one pressure to rise above the maximum allowed pressure for equal supplies to the motors when one wheel (if the system is in a vehicle with motors driving wheels on opposite sides) slips to reduce the pressure supplied thereto, and so the system permits a certain transfer of torque to the non-slipping wheel.