Patent GB-1413450-A (GB)
Title: Fluid control valve and pressure compensating mechanism therefor
IPC: F15B13/04
Filed: 1974-05-22
Abstract: 1413450 Valves KOEHRING CO 22 May 1974 [21 Sept 1973] 22919/74 Heading F2V A valve 10, Fig. 1, for controlling the speed and direction of an hydraulic motor C1 comprises a body 9 slidably containing a control spool 13 and a pressure compensating plunger 14 to regulate the flow of fluid from inlet 18 to service passages 21 or 22 in response to the pressure differential across spool 13. Plunger 14 has a bore 34 containing a check valve 47 which permits flow from inlet 18 via ports 37, bore 34 and ports 46 to feeder passage 20 but prevents reverse flow. The pressure within bore 34 is communicated via passage 36 to a chamber 32 to tend to urge plunger 14 leftwards to decrease the flow from inlet 18 through ports 37 but to increase the by-pass flow through plunger groove 33 to outlet 19. Plunger 14 is biased in the opposite direction by spring 38 assisted by service pressure communicated to chamber 31. Such communication is effected from the operative service passage 21 or 22 via ports 60 or 61, passages 59, 57 in an end face of body 9, a passage 56 leading to chamber 55 and thence through plunger port 41 into chamber 31. In the neutral position of spool 13, ports 60, 61 and consequently chamber 31 are vented to drain via port 64 and passages 63, 65 in the spool. Lands 26, 27 on the latter are provided with throttling notches 29, 30 to meter the flow from feeder passage 20 to respective service passages 21 or 22. Compensating plunger 14 thus acts to maintain a constant pressure drop across the operative throttling notches 29 or 30 corresponding to any given setting of spool 13 by varying the by-pass flow to outlet 19 as required. The desired speed of motor C1 can thus be maintained. In a modification (Fig. 8, not shown) chamber 32 of the compensating mechanism is communicated via passages (142, 143) with the pressure downstream rather than upstream of check valve 47. Four similar valves 110, 210, 310, 410, Fig. 7, may be arranged in a bank between inlet and outlet sections 66, 67 to control respective motors (C2, to C5, Figs. 1a, 1b, not shown). Valves 110, 210 are identical but differ from valve 10 in that their compensating plungers (114, 214) each include a frusto-conical surface (68) adjacent inlet 18 so that the flow to outlet 19 can never be fully blocked. Valves 110, 210 can thus be used for parallel operation. Valve 310 has a compensating plunger 14 the same as in valve 10 but its spool 313 is modified such that exhaust fluid flowing from motor (C4) to service passage 22 is directed via passage (324) to the valve outlet 19, rather than to drain, and thence to the inlet 18 of final valve 410. Valve 310 thus functions as a series-parallel valve with its spool 313 in a leftwards position and as a series valve with its spool in a rightwards position. Final valve 410 has a compensating plunger 14, the same as in valve 10, which controls the pressure drop across its own spool 413 but in addition acts to build up operating pressure at the inlets 18 of the valves 110, 210 since the frusto-conical portions (68) prevent the plungers 114, 214 of the latter from performing this function. To enable plunger 14 of valve 410 to so act, the chamber 31 thereof communicates via passages 56, 57, 59, when spool 413 is in the neutral position, with spool ports (102, Fig. 1b) leading into an internal chamber 75 which itself communicates via spool ports (101) and a passage 100 with a passage 85 extending through all the valve bodies and containing shuttle valves 87. Each of the latter is associated with a passage 89 leading to the chamber 31 of the respective compensating plunger, and with a depression 88, Fig. 5, which cannot be wholly closed by the shuttle 87. The latter ensure that the motor operating at the higher pressure always receives sufficient fluid.