GB672969A - Improvements relating to control valves for liquids and gases - Google Patents

Abstract

672,969. Valves. CLIMAX ROCK DRILL & ENGINEERING WORKS, Ltd. Nov. 21, 1949 [Oct. 21, 1948], No. 27399/48. Class 135. In a piston slide valve having a ported liner and a landed piston slidable therein, at least one of the piston lands has a seal between it and the liner comprising a pair of rubber rings mounted in grooves and so spaced that on one of the rings passing a port the other still makes sealing contact. As shown, for controlling the supply and exhaust of pressure fluid to and from a double-acting cylinder, the valve comprises a casing 1, Fig. 1, having ports 2 ... 6 and an axial bore 7 housing spaced liners 8, 9 within which is slidably mounted a piston valve 19 having lands 20. A sealing ring 21 of synthetic rubber is mounted in a groove in each of the outer lands whilst a pair of similar rings are mounted in grooves in the ports' inner lands and so spaced apart that on movement of the piston to control radial ports 12, 13 in the liners 8, 9 a seal is formed at all times, between the piston and the liner even when one of the rings is passing its associated port. The piston is biased to the right by a spring 22 and operated by a pivotally mounted lever 26 having a projection 27 pivotally mounting a rod 28 engaging a recess 29 in the end of the piston. A projection 31 on a plate 32 secured to the lever 26 engages stops on a plate 24 secured to the casing to limit the movement of the piston in both directions. In a modification, the plate 32 is replaced by a plate 46, Fig. 3, of different shape formed with an arcuate slot 50 engaging a pin 49 fixed on the lever 42 and connected by a spring 48 to a casing plate 43. In this arrangement, on continued anti-clockwise movement of the lever 42, after the pin 49 engages the upper end of the slot 50, the lever 42 and plate 46 both move against the spring 48 to move the piston 19 into a third position. In another arrangement, the piston 19 is operated by a cam engaging a roller mounted on the piston. In a further modification, the right-hand end of the casing is fitted with an adaptor to which compressed air is supplied to or exhausted from the cylinder to operate the piston. In a still further arrangement, adaptors may be fitted to both ends of the casing and bleed passages in the piston connect the central pressure port 3 to spaces at either end of the piston. The pressure in these spaces may be relieved to atmosphere by solenoid-actuated pilot valves to operate the piston. The casing may have three ports instead of five to control a single-acting cylinder.