GB974751A - Seals for rods and shafts - Google Patents

Abstract

974,751. Seals. PARKER-HANNIFIN CORPORATION. March 17, 1961, No. 9892/61. Heading F2B. A combined sealing and wiping device for use between the piston rod 24 and the casing 26 of an hydraulic cylinder, Fig. 1, comprises a gland 28 surrounding the rod at one end of the cylinder and incorporating spaced sealing and wiper rings 46, 48, the space between these rings comprising an initial portion 72 and an additional portion for receiving leakage fluid beyond the normal capacity of the portion 72 in order to reduce pressure build-up of leakage fluid in the latter portion, the entry of the leakage fluid into the additional portion being progressively resisted by resilient means which provide self-restoring force for returning the fluid to the portion 72 to prevent escape of leakage fluid past the wiping ring 48. The rings 46, 48 are of resilient rubber or rubberlike material and have in the free state a crosssection comprising a base portion 50 with oppositely diverging lips having tapered end faces. Extrusion of the ring 46 is prevented by a leather washer 66. The ring 48 is resiliently mounted in a recess 68 in the gland 28 by means of a coiled or wave-like spring 74 interposed between a backing washer 76 and a stop spring ring 78. An annular fin 70 engages between the lips of the ring 48 to prevent them from abutting against the end face 69 of the recess 68. In operation, on the outstroke of the rod 24 pressure build-up in the space 72 is prevented by movement of the ring 48 against the spring 74 whereby additional space is provided to receive the excess leakage fluid, the latter being returned to the space 72 under the biasing force of the spring as the rod 24 on its inward stroke carries back into the cylinder some of the leakage fluid. The spring 74 may be replaced by a thick rubber washer. In another embodiment, Fig. 7, the wiping ring 90 rests against the end wall of the gland 110 and has a rear lip 106 extending beyond the gland for wiping dirt off the rod 24. The space 72 communicates with a cylinder 114 screwed into the gland and incorporating a spring-loaded piston 116. Alternatively, in a vertical cylinder, Fig. 17, the space 72 is in communication with a standpipe 238 extending above the ring 90 and in which the excess fluid accumulates and is returned by gravity to the space 72. In a further embodiment, Fig. 8, the excess fluid enters through radial passages 132 into axial blind passages 128 in the gland 126 and is resisted by air trapped therein. The sealing and/or the wiping rings of the above embodiments may be replaced by a resilient 0-ring. The sealing ring may also consist of a number of V-section rings 192, Fig. 16, of leather or rubber-like material and held in the cylinder casing 194 between correspondingly shaped backing rings 206, 208 by a gland 212 screwed in the casing. In a still further embodiment, Fig. 13, the wiping ring 156, which may alternatively be similar to that of Fig. 1, is made resiliently axially compressible by providing in its base portion an annular groove or a number of holes 160 and in its peripheral surfaces recesses 162, 164. Specification 974,752 is referred to.