GB942552A - Spool valve assembly - Google Patents

Abstract

942,552. Valves. PARKER-HANNIFIN CORPORATION. May 10, 1960 [May 12, 1959; Aug. 6, 1959; Feb. 3, 1960], No. 16498/60. Heading F2V. A spool valve assembly includes a housing having a bore 7 intersected along its axis by two inlet ports 8, 9 connected with an inlet passage 4, three exhaust ports 11, 12, 14 in communication with an exhaust passage 10, and two service ports 15, 16 connected to a piston and cylinder 19, and a valve spool 45 with a passageway 46 and alternating lands and grooves, the assembly having a neutral position in which an inlet and an exhaust port are in communication and the service ports are blocked, two operating positions in which one service port communicates with an inlet port while the other communicates with an exhaust port, and a float position in which the service ports communicate with each other and with exhaust. A perforated sleeve 70 restricts the flow from the service port 15 to the exhaust port 11 in one of the operating positions to prevent cavitation when the piston is driven by its load. The valve is shown in the neutral position in which fluid from the pressure port 4 flows around a relief valve 32 into the two ports 8 and 9, past two grooves 57 and 58 on the valve spool 45 and into the port 14 leading to the exhaust passage 10, the two service ports 15, 16 being blocked by lands 53, 54 and 50, 51. When the valve is moved to the raised position, R, lands 52 and 53 arrest the flow into the port 14 so that the rise in pressure causes a spring- loaded non-return valve (not shown) to allow fluid to pass into a space 21 and through a groove 59 into the service port 15. Exhaust from the motor flows out of the port 16 and through a groove 56 into the port 12. In the lower position, L, lands 51 and 52 close the port 14 and fluid passes through a second non- return valve (not shown) into a space 23 placed in communication with the port 16 by the groove 56. Exhaust from the port 15 passes through a groove 59 and orifices 71, 72 into a port 11. The spool 45 may be moved to its float position, F, by compressing a centring spring 83 and raising a detent member 85 until a groove 86 is engaged by a spring ring 89 when slots 60 and 61 are in alignment with the service ports 15 and 16 and an orifice 62 with the port 14, whereby fluid may flow from one end of the motor to the other through the bore 46 in the spool 45, the difference in fluid volumes displaced passing through the orifice 62. The groove 57 provides communication between the passages 4 and 10. The two non- return valves are housed in a common bore having a central connection with the passage 4. If the pressure in the latter becomes excessive it acts on an annular face A to lift the relief valve 32 against a spring 34. Both the spool 45 and the valve 32 may be inverted in the housing. A wiper seal 107 is provided for the spool which has metering slots in its lands and co-operates with a sleeve 100 to shorten its stroke. Specification 942,553 is referred to.