Patent GB-594007-A (GB)
Title: Improvements in or relating to hydraulic shock absorbers
IPC: F16F9/36
Filed: 1943-11-03
Abstract: 594,007. Shock-absorbers. FOCHT, N, S. Nov. 3, 1943, No. 27115/46. Convention date, Oct. 30, 1942. Divided out of 593,954. [Class 108 (iii)] [Also in Group XXVI] Relates to a hydraulic shock-absorber of the piston-and-cylinder type in which the piston-rod 44, Fig. 1, passes through a head 13 at one end of the cylinder 10, inward movement of the rod into the cylinder causing liquid to be expelled therefrom into a reservoir c, from which liquid returns to the cylinder as the rod moves outwardly. According to the invention, the cylinder head 13 is formed with a recess 94. in communication with the. reservoir, and the portion of the pistonrod extending through the recess is surrounded by a gasket 95, Fig. 2, formed in one or more pieces and having two annular lips 99, 100 extending obliquely inwardly towards the piston, both lips being in wiping engagement with the rod at their free inner edges, the lip 100 nearer the piston containing at least one hole 106, while means are provided for the admission of atmospheric air to the annular space 101 between the lip 99 and the rod. As shown, a third lip 98 extends inwardly from the body portion 96 of the gasket. The cylinder head 13 .consists of a shell 91 and a plug 92 which is held in position by the shell 91 screwing on the upper end of the cylinder 10, a groove 15 in the shell accommodating the upper end of a tube 12 forming the outer wall of the reservoir. A second annular space 102 is formed in the shell 91 above the gasket and communicates respectively with the atmosphere and with the space 101 through one or more holes' 103, 104 respectively in the shell and gasket. The gasket is held tightly in the cylinder head recess 94 by being engaged underneath by the upper edge of a ring 97 which rests on the plug.92. A further annular space 105 between the lips 99, 100 communicates with the reservoir c through the hole 106 in the lip 100, the interior of the ring 97, grooves 107 extending across the top of the plug 92, an annular channel 108 in the shell 91, and holes 109. In the lower portion of the plug 92, a rubber or like ring 111 is disposed in a channel 110 in sealing engagement with the piston-rod and contains a V-shaped groove 112 extending from end to end, which while the shock-absorber is being filled with liquid, acts as a vent to permit escape of air from the cylinder chamber a and which, under low working pressures in the chamber a, allows a small amount of liquid together with any further air in the chamber a to escape into the recess 94. As the pressure in chamber a increases, the groove 112 closes and escape of liquid is prevented. On rebound, as the piston 11 moves upwardly in the cylinder 10, liquid flows from the reservoir into the cylinder chamber b through valve mechanism at the lower end of the cylinder, as described in Specification 594,006. As the level of the liquid in the reservoir drops, the resulting tendency to produce a partial vacuum in the reservoir causes the gasket lip 99 to flex outwardly permitting air to enter the reservoir through the holes 103, space 101, holes 106, grooves 107 and holes 109. Simultaneously, any liquid escaping from the cylinder chamber a along the piston-rod is scraped off by the lips 98, 99, 100 into the recess 94 and returns to the reservoir with the vacuum 1 preventing air. A dirtexcluding tube 114 may be fixed to the piston-rod, e.g., by being carried by a head 115, on an upward extension 44<1> of the rod. The piston valvemechanism is as described in Specification 593,954.