Patent GB-1466022-A (GB)
Title: Pilot-controlled pressure relief valves
IPC: F16K17/10
Filed: 1975-01-23
Abstract: 1466022 Valves ZAHNRADFABRIK FRIEDRICH AG 23 Jan 1975 [23 Jan 1974 8 Jan 1975 (2)] 2969/75 Heading F2V [Also in Division G3] In a pilot-operated relief valve the pilot valve has two opposed surfaces subject to inlet pressure and a further surface axially intermediate the two opposed surfaces, subject to outlet pressure. In a first embodiment, Fig. 1, the pilot valve 9 is in the form of a stepped piston with an axial passage so that inlet pressure acts on the two end faces of the piston and outlet pressure acts on a stepped face 11. In a second embodiment, Fig. 2 (not shown), the pilot valve comprises a loose ball closure member (16) seating on a main valve sliding piston (201) actuated by a plenum (14) sliding in the main piston and having an extension pin (15) of smaller diameter which lifts the ball off its seat. The end of the piston (14) opposite the ball is subject to inlet pressure via a deformable plastics seal (20) fixed in the bore (19) in which the piston (14) slides, the surface intermediate the piston and its extension pin is subject to outlet pressure and the ball is subject to outlet pressure on its surface within the seat orifice and the remaining surface of the ball is subject to inlet pressure via a passage (210) through the main valve piston (201). In a third embodiment, Fig. 3 (not shown) and similar to Fig. 2, the pilot valve (24) is a conical lift valve and a filter (22), surrounding the bore in which the plunger slides, filters not only the fluid applied to the plastics seal but also filters the supply of inlet pressure to the pilot lift valve via a bore (310) in the main valve piston. In fourth and fifth embodiments, Figs. 4 and 5 (not shown) the pilot valve member is a conical lift valve and in a sixth embodiment, Fig. 6 (not shown) having a loose-ball pilot valve a further passage (28) is provided communicating with the chamber (307) behind the main valve so that the pilot valve, and hence the main valve, may be opened by remote control of a pressure supply to the passage (28). In a seventh embodiment Fig. 7 (not shown) the pilot valve is a sliding piston valve actuated by a smaller diameter plunger, inlet pressure being applied to the opposed ends of the plunger and piston and outlet pressure being applied to the differential area where these two members are in contact. In an eighth embodiment, Fig. 8 (not shown) the pilot valve, similar in construction to that of Fig. 4, is fixed in the end of the chamber, in which the main valve moves, remote from the inlet. In a sixth embodiment, Fig. 9, the pilot valve comprises a hollow tubular moving closure member 928 which seats on a ball 929 in non-closing contact with a tubular part 930 in communication with outlet pressure. The closure member 928 slides on the tube 930 by means of a ring 933, a seal 934 being provided between the tube and closure member. The closure member moves under the combined influence of a spring 906 and inlet and outlet pressures operating on the various surfaces of the member and the ring 933 and seal 934 as influenced by the pressure of the ball seat 929. In a tenth embodiment, Fig. 10 (not shown) and generally similar to Fig. 9, the main relief valve is a lift-type whereas all the others are sliding piston-type.