GB982087A - Hydraulic control valves - Google Patents

Abstract

982,087. Valves. NEW YORK AIR BRAKE CO. Sept. 3, 1963 [Dec. 28, 1962], No. 34811/63. Heading F2V. With the spool valve 17 in the spring-centred neutral position shown, the pump 41 is connected to a tank 43 by way of inlet port 2, passage 13, annular grooves 7, 9, plunger grooves 18, 19, annular groove 8 and exhaust port 3 whilst annular motor grooves 6, 11, connected to the top and bottom of the motor cylinder 45, are isolated by spool lands 21, 23 whereby the motor is hydraulically locked. The spool is moved to the left to raise a load W connected to the motor 45, in which position of the spool pressure fluid flows to the rod end of the motor via passage 13, annular groove 9, radial spool passages 32, and groove 11. Fluid exhausting from the head end of the motor to the tank 43 passes through groove 6, radial spool passages 29, spool bore 24, a check valve 31, radial spool passages 28, an annular groove 5 and exhaust manifold 14. The spool is moved to the right to lower the load W, in which position fluid is transmitted to the head end of the motor 45 by passage 13, groove 7, passages 29, check valve 31, passages 28 and groove 6. Fluid displaced from the rod end of the motor flows to groove 11, and, if the pump can supply the demand of the motor, via radial spool passages 33, a check valve 34, passages 32 and an annular groove 12 to the tank; if the load W tends to move the motor at a rate that exceeds the supply capacity of the pump then the check valve 34 partially or completely closes so that some or all of the fluid displaced from the rod end is directed to the head end through an extension 15 of groove 11, radial spool passages 39, undercut 37 and groove 9 so forming a regenerative flow path. The weight W may be oppositely disposed so as to tend to retract the motor. Check valve 34, which is more heavily loaded than the other valve 31, also serves to prevent falling of the load when the pump is building up to operating pressure. The spool is provided with conical undercuts 36, 37 and radial passages 38, 39 to reduce the axial components of the dynamic reaction forces acting thereon; the undercut 37 and passage 39 also form part of the regenerative flow path. A relief valve 16 is associated with the supply passage 13. Specification 812,490 is referred to.