GB1410406A - Valves - Google Patents

Abstract

1410406 Valves BERINGER-HYDRAULIK GmbH 8 Nov 1973 [9 Nov 1972] 51847/73 Heading F2V [Also in Division G3] An hydraulic self-closing valve for connection to an hydraulic rotary unit or a lifting piston and cylinder unit H via a port 4, Fig. 1, and to a supply pump P and return line R via a port 5, has a spool 2 which remains in the open position shown for normal fluid flow in either direction. However, in the event of excessive lowering speeds and consequent high flow rate through the valve to the line R, due, e.g. to a fracture in the pump line, it moves against the action of spring 3 towards a closed position thereby progressively throttling the flow via partcircular recesses 7 therein. The consequent rise in the pressure differential across the spool 2 is communicated through passages 10, 12 to opposite ends of an auxiliary spool 8 which, when the differential reaches a predetermined value, moves downwardly to throttle the flow exhausting from spring chamber 16 and thereby dampen the final part of the movement of the spool 2 to its closed position wherein flange 20 thereon abuts a seating 21. The spool 8 carries an 0-ring 17 which co-operates with a seating 22 when the spool 8 is moved to its maximum throttling position. The maximum flow via spool 2 and the minimum flow via the spool 8 are adjustable via screws 6 and 19 respectively. In an alternative embodiment, Fig. 2 (not shown), the auxiliary spool is omitted and the spool (2) has a coaxial passage therein communicating the spring chamber (16) with the port (5), the passage becoming throttled by a fixed needle (25) when spool (2) has moved partway towards its closed position. An additional throttling passage (28) between chamber (16) and port (5) may be provided in the valve housing, the degree of throttling being adjustable by a screw (29).