GB1329562A - Fluid operated actuator for movable members - Google Patents

Abstract

1329562 Fluid pressure actuator SPERRY RAND AUSTRALIA Ltd 16 Sept 1970 [25 Sept 1969] 44171/70 Heading F1D In a double-acting actuator, Fig. 1, a pair of relief valves 46, 47, Fig. 9, in passageways through a piston assembly 2, 3, connecting the chambers 5, 6 of a cylinder 4 prevent a build-up of pressure behind the piston assembly except at the end of each stroke when relative movement between parts of the piston assembly 2, 3 closes the respective passageway, Fig. 9. The pressure buildup is detected by a pressure senser 86 Fig.17 which produces a signal at some remote point. A pressure source and drain are connected via a selector valve 85 to lines 31, 32 which are respectively connected to the chambers 5, 6 via ducts 28, 29, spring-loaded valves 23a, 23b, and ducts 25, 24, Fig. 11 the duct 25 linking with the chamber 5 via a conduit 15, Fig. 1. The pressurized fluid in, e.g. duct 28 as shown, opens the associated valve 23a and also acts on a shuttle 27 which opens the other valve 23b. The piston assembly comprises an inner portion 2 having a rod 7 for connection to, e.g. a valve member 9, and an outer portion 3 comprising a pair of inner sleeves 38, 39 each having an end shoulder 42, 43, and an outer sleeve 41, slidable on the sleeves 38, 39 between the shoulders 42, 43. Near the end of each stroke, the sleeve 41 engages an abutment 67, 68, the sleeves 38, 39 and the inner portion 2 continuing to move until the sleeve 41 engages one of the shoulders 42, 43, closing the relief passage opening 63, or 64. Safety valves (71, 72) Figs. 15, 16 (not shown) prevent pressure build-up in the chambers 5, 6 when the actuator is idle and are located respectively in a passageway 77 connecting duct 25 with duct 29 and in a passageway 83 connecting ducts 24 and 28, Fig. 11. In a second embodiment, for actuating rotary members via a rack on the piston, and a pinion, a pair of cylinder heads 111, 118 each has an inlet-outlet opening 128, 129 communicating with a valve 123a, 123b and pipe 192, 193 leading to the space behind a shuttle 127b, 127a on the opposite head, so that pressurized fluid opens the associated valve to enter one chamber and acts on the shuttle in the opposite head to open the other valve to allow the fluid to escape from the other chamber. The relief valves are located externally of the cylinder and are rendered inoperative when the piston heads 189 engage adjustable axial abutments 202, 203 through which the relief passages extend. It is stated that the operating fluid may be gas or liquid, and the invention is also applicable to diaphragm or bellows actuators.