GB841902A - Improved sealing assembly - Google Patents

Abstract

841,902. Piston packing; joint-making packing. PARKER-HANNIFIN CORPORATION. Sept. 27, 1957 [Sept. 28, 1956], No. 30291/57. Classes 122 (1) and 122 (3). Sealing means between cylindrical inner and outer members 10, 21, Fig. 2, comprises a resilient packing ring 17 mounted in a groove 11 in one member (the inner 10, as shown) and a continuous back-up ring 22 of a relatively harder material than the ring 17 mounted in a stepped recess 15 formed at one side of the groove 11. As shown in Fig. 2, applied to a piston 10, the packing ring 17, which may be of rubber, is a close fit between the walls 12, 14 of the groove 11 and has an inside diameter which, when the ring is initially assembled, may or may not contact the bottom 18 of the groove since, under pressure, sealing contact is provided between the ring and the wall 14. The back-up ring, which prevents extrusion of the packing ring, may be made of " Teflon " (Registered Trade Mark) and has an inside diameter at least equal to the mean diameter of the packing ring 17 so that, on assembly, a part of the ring may be passed over the flanged end 24 of the piston into the groove 11, thereby allowing the remainder to clear the flange and thus permit the fitting of the ring on to the step. Any undue twisting of the packing ring within the groove 11 during reciprocation of the piston is prevented by providing in the bottom of the groove recesses 26, 27 into which the ring may be deformed. As shown in Fig. 5, a packing ring 32 and back-up ring 33 are mounted in the closure ring 31 of an hydraulic cylinder 30 or, alternatively, both rings may be mounted within the cylinder wall and cooperate with an internal closure plug.