GB1366669A - Fluid flow controlling device for reversible fluid motors - Google Patents

Abstract

1366669 Hydraulic motor control circuits KOEHRING Co 20 Oct 1971 [18 Jan 1971] 48740/71 Heading F1P [Also in Division F2] A flow control valve connecting opposite ends (17, 18) Fig.1 (not shown) of a reversible hydraulic motor (5) with motor ports of a conventional main distribution valve (10) comprises a body 20 Fig.2 having an axial bore 21 intersected by service passages 38, 39 a spool 22 biased by spring 26 to the central passage-blocking position shown and movable to an operating position e.g. to the right, by pump pressure in an inlet 40 of passage 38 being transmitted through bores 52, 53 of an end 23 of the spool to the spring chamber 50 whereby a central land 33 opens a connection between a portion 41 of passage 38 with a lateral port 43 connected to the motor end 17 whilst a spool land 35 opens a connection between a lateral port 47 connected to motor end (18) to an outlet 44 of passage 39 connected to the return motor port of valve (10); the shift of the spool 22 towards its working position being determined by the pressure of the pump delivery which when decreased causes partial return of the spool to a position wherein motor exhaust is restricted by means of metering notches 36 on land 35. Each passage 38, 39 contains a check-valve 42, 46 which when its associated passage is connected to the exhaust end of the motor is by-passed and remains closed. In a modification, the flow control valve 54 Fig. 4 throttles the exhaust from one end only of the motor, e.g., a double acting lift cylinder 60. In operation, and with distributing valve 61 moved to the right of its neutral position shown, pump pressure is directed through a line 73, a lateral part 77 of valve 64 and an orifice 83 Fig. 5 to a chamber 82 where it acts against the end of the valve spool 67 and moves it to the right against a spring 70 a sufficient distance for lands 86, 87 to uncover portions 79, 80 of service passages 71, 72 connected to the upper and lower ends of cylinder 60 thereby lowering the load. In the event of fast descent resulting in near cavitation the pressure drop in chamber 82 results in partial return of spool 67 to a position in which exhaust from the cylinder bottom is restricted by notches 90 in land 87 and at the same time pump delivery is restricted by notches 89 in land 86. To lift the load, valve 61 is moved to the left and pump pressure in a line 74 by-passes valve 64 and opens a check-valve 93 to gain access to the lower end of cylinder 60, the upper end of which is connected through a check-valve 95 to the valve 61.