GB1431641A - Valve mechanism - Google Patents

Abstract

1431641 Valves I CHIVARI 4 Jan 1974 [18 Jan 1973] 00399/74 Heading F2V A valve assembly for controlling the rate of lowering of a load supported by a double-acting fluid motor, comprises a control piston 14, Fig. 1, and a valve member 58 including a throttle tube 48 having elongated openings or arrays of bores 54 therein. The openings may become narrower towards their lower ends and may communicate with tapering recesses in the peripheral surface of the tube. The assembly in use is connected between a change-over valve (46), Fig. 2 (not shown), and the motor (34). With the change-over valve positioned to deliver pressure fluid to the valve via line 44, the fluid passes into chamber 20 and through bores 50 and 110 into a chamber 12 where it forces control piston 14 upwardly and also acts on convex surface 68 of the tube to force the latter downwardly and unseat valve head 58. Thus the fluid passes from chamber 20 through the tube into a chamber 24 and thence through a line 30 to the underside of motor piston to exert a lifting or holding force thereon. Fluid exhausted from the chamber 94 above control piston 14 returns to a reservoir via bore 92, adjustable restrictor 90, bores 80, 74 and line 72. With the change-over valve position to lower the load, the pressure fluid is delivered to a line (70) leading directly to the upper side of motor piston and is also delivered to the line 72, the return flow from the underside of the motor piston passes into the valve assembly via line 30 and out via line 44, whereby the speed of lowering is controlled by the degree of throttling of the return flow by the throttling tube, the position of the latter being controlled by the control piston 14 in response to the fluid pressure delivered to chamber 94 from line 72. To enable the chamber 94 to be exhausted quickly when the changeover valve is subsequently moved to its neutral or load lifting position, a by-pass duct is arranged adjacent the restrictor and is controlled by a slide valve actuated by a solenoid 106.