GB986860A - Valve and dash-pot assembly - Google Patents

Abstract

986,860. Valves; dashpots. DOMINION ENGINEERING WORKS Ltd. Nov. 21, 1962, No. 44038/62 Headings F2S and F2V. A valve and dashpot assembly comprises a housing 5 with a pivotally mounted valve 6 which is closable against a seat 8 and a dashpot assembly including a closed hydraulic circuit filled with damping fluid and an operative member 12 positioned in the housing 5 to be engaged and moved, against the resistance of the damping fluid, by the valve 6 during a final opening or closing movement sealing means 15 being arranged to prevent mixing of fluid in the valve housing and damping fluid by leakage past the operative member 12 and transfer barrier means 31, 32 being included for maintaining the pressure of the damping fluid substantially the same as that of the fluid passing through the housing 5. The operative member 12 constitutes the rod of a piston 17 which is loaded by a spring 22 in a working cylinder 18 the chambers of which, at either side of the piston 17, are connected by passages 25, 28, 26 which include a throttling valve 27 and preferably a by-pass 29 with a one-way valve 30. The pressure equalizing means comprises a cylinder 32 whose ends communicate respectively through ducts 34, 33 with the hydraulic fluid passage 28 and the interior space of the valve housing 5 and which accommodates a separating piston 31. As shown, Fig. 2, a piston rod 12, with sealing rings 43 and with a stop ring 52 which co-operates with a stop collar 51 secured in a recess 53 in an end cover 37 for the cylinder 38 containing a spring-loaded piston 40, has its outer end located in the valve housing 5. The pressure equalizing means comprises a casing 65 with a bellows 66 which communicates with the valve housing space through a duct 72 the casing 65 communicating through a poppet valve assembly 87 with the hydraulic fluid in a port 57, Fig. 3, in a valve unit 55 which has a throttle valve 60 and which is connected to the end chambers of the cylinder 38 by means of pipes 62, 63. In a modification, Fig. 5, the transfer barrier of the pressure equalizing means comprises two metal bellows 101, 102 which encircle the push rod 12 the outer end of the larger open-ended bellows 101 being welded to a sealing ring 103 for one end of the cylinder 38 and the inner end being welded to a guide piston 106 working in the cylinder 38 and provided with through ports 107. The open end of the smaller bellows 102, which is received in a recess 112 in the piston 40, is welded around an opening 108 in the guide piston 106 the other closed end capping the end of the push rod 12. A fluid transfer bore 113 with a throttling valve 114 is provided in the wall of the cylinder 38, fluid from the valve housing being delivered, through a spiral groove 115 in a piston rod sleeve 36 to the interior of the bellows 101, 102.