Valves for controlling fluid flow

摘要

905,572. Valves. CLARK EQUIPMENT CO. April 19, 1961 [May 5, 1960], No. 14085/61. Class 135. A regulating valve for controlling the flow of fluid from the motor of a hoist, comprises a valve sleeve 44, closed at one end and provided with axially spaced circumferential openings 48, 50, the openings 50 may be arranged as two sets of staggered openings 50, 52. A valve member 44 is located in the sleeve and is loaded by a spring 70 towards the closed end of the sleeve. The valve member is provided with a series of openings 56 and carries a plate 60 having a fixed orifice 62. The end of the valve member is provided with an orifice 80 and a spring-loaded plate 82 provided with a small orifice 88. In operation, fluid supplied to the hoist flows from an inlet 32 and through openings 48 and 56, 50 and 52 in an unrestricted manner to a motor port 46, the valve member 44 being in the position shown. When the hoist is being lowered, fluid from the port 46 flows through ports 50, 52 and 56 to a chamber 54 and through orifice 80 to a chamber 78, by lifting a plate 82, to cause the valve member 44 to move against the spring loading 70. Such movement of the valve member 44 reduces the area of the openings 52, 50 and 48 and continues until the pressure in the chamber 54 is constant in response to the pressure drop required by the fixed orifice 62. In practice, the member 44 moves past this position and moves back to the required position by slow leakage from the chamber 78 through the small orifice 88, thus preventing hunting. The rate of descent of the hoist under the control of such a valve varies inversely with the load on the hoist.