Patent GB-1470686-A (GB)
Title: Fluid valve structures
IPC: F16K31/40
Filed: 1974-04-05
Abstract: 1470686 Valves KOEHRING CO 5 April 1974 [16 Aug 1973] 15262/74 Heading F2V [Also in Division G3] A valve assembly comprises a valve member movable between an open and a closed position, and means responsive to initial movement of the valve member towards the closed position for initially imparting to the valve member an acceleration which increases as the valve member moves towards the closed position. In one arrangement, Fig. 1, the valve assembly forms a high speed shut off and dump valve 10 having a main hydraulic metering reaction 16 pilot operated by an electric force motor 14. Metering section 16 comprises a valve spool 48 slidable within a bore 50 in body 38 and normally biased leftwards by spring 76 to a position in which piston land 52 engages a conical or cylindrical floating seat 56. In this position liquid from a high pressure source can flow from conduit 104 through chamber 60 and bore 50 to a high pressure outlet conduit 108. The latter is isolated from a chamber 112 and drain conduit 114 by lands 64, 66 spaced apart by an annular groove 70 which communicates through radial holes 78, 80 with stepped bore 72, 82 within land 66. The coils 22, 24 of force motor 14 are normally energized by an electric signal supplied via terminals 28 to hold armature 30 in the position shown in which flapper 140 blocks pilot valve nozzle 126 while leaving nozzle 124 fully open. The nozzles 124, 126 are supplied with pressure liquid via restrictions 130, 132 respectively and consequently a higher pressure exists in duct 122 than in duct 120, the latter pressures acting respectively on the right and left ends of spool 48. Should there now be a failure of the electric signal, the bias of magnet 26 causes flapper 140 to swing leftwards and restrict nozzle 124, consequently by increasing the pressure in duct 120 while reducing that in duct 122. Thus spool 48 starts to move rightwards. As land 52 moves away from seat 56 the high pressure in chamber 60 can increasingly act on the left face of the land, thus increasing the rightwards acceleration of spool 48 towards a position (Fig. 2, not shown) in which supply conduit 104 is isolated from outlet conduit 108 and the latter is connected to drain conduit 114. Simultaneously the pressure acting on the right end of spool 48 is vented to drain 114 via holes 78, 80 and groove 70, thus further increasing the rightwards acceleration. The axial position of floating seat 56 can be adjusted by a screw 90. The shut off and dump valve 10 may form part of an electrohydraulic system, Fig. 3, wherein supply conduit 104 is fed by pump 156 and outlet conduit 108 is connected to an electrohydraulic servovalve 160. The latter controls flow to and from a hydraulic actuator 166 via lines 168, 170 and is itself positioned by comparison at summing junction 178 of an output signal 180 with an electric feedback signal 184. Should a failure detector 186 note the loss of the latter signal then valve 10 operates as previously described to shut off supply conduit 104 and connect conduit 108 to drain conduit 114 in order to dump hydraulic fluid from actuator 166. In further modifications (Figs. 4, 5 not shown), the valve 10 is positioned between the servovalve and the hydraulic actuator and the arrangement of lands on the main metering spool is altered.