GB880408A - Pressure relief valve - Google Patents

Abstract

880,408. Hydraulic pit-props. BECORIT GRUBENAUSBAU G.m.b.H. Nov. 5, 1957 [Nov. 7, 1956; May 15, 1957], No. 34488/57. Class 20(2) [Also in Group XXIX] A spring loaded pressure relief valve includes a storage chamber having a restricted inlet for the pressure fluid to be controlled and an outlet controlled by the valve element. In the first example, Fig. 1, the ball valve 8 is loaded by an adjustable spring 10 into a conical seating 7 in the outlet passage 6 from a storage chamber 2 one wall of which is formed by a flexible plate spring 3 and which is connected through a restriction 4 and a passage 5 to the pressure line, e.g. a pit prop compression chamber. In operation, when the valve 8 is closed the pressure in the chamber 2 is the same as that in the pressure line. As the pressure increases the wall 3 flexes upwardly until the pressure within the chamber 2 is sufficient to open the ball valve 8 against the force of the spring 10 and the frictional force between the ball and seat. The sudden disappearance of the frictional force gives the valve a high lift characteristic. The pressure within the chamber 2 falls and the wall 3 flexes inwardly and the valve re-seats. The ball 8 may be magnetic so that magnetic action tends to maintain it in its seat. In another example, Fig. 4, the ball valve 18 is loaded by a coiled spring 21 and by flexible plate spring 20 to seat on a member 19 carried by a flexible plate spring 17. As the pressure in the chamber 16 increases the plate spring 17 flexes upwardly taking with it the valve seat 19 and the spring 21 and causing upward flexing of the spring 20. When the spring 20 snaps over its dead centre position the ball valve is opened by the fluid pressure in the chamber 16 whereupon the spring 17 returns to its initial position. In another example, Fig. 6, the storage chamber 28 has a flexible wall 29, a restricted inlet 30 and is connected by a passage 31 to a cylinder bore 32 containing a piston 33 from which extends a rod 34 into a passage 36 having a seat 35 for a ball 37 loaded by a spring 38 which acts through a plunger 41. The bore 32 has an enlarged portion 32a and the piston has a flow passage 43 extending part way along its length. When the pressure in the chamber 32a is sufficient to raise the valve the resulting pressure drop across the piston causes upward movement of the piston and the rod 34 raises the ball 37 fully and allows direct flow of fluid via piston flow passage 43.