Sealing means for a longitudinally displaceable rod

#This invention relates to sealing means for a longitudinally displaceable rod extending from a zone under pressure and the objects of the invention include the provision of sealing means the effectiveness of which increases upon an increase in the pressure of said zone relative to its surroundings.

#According to the invention, the rod passes through a flexible annular sealing element a part of which is bent or folded back to form a cavity which receives fluid under pressure, said cavity being so positioned that the pressure of the fluid urges the sealing element into engagement with the rod.

#The invention will now be described by way of example with reference to the accompanying drawings which illustrate an embodiment of sealing means for a hydraulic shock absorber, this being a preferred application of the invention. In the drawings:

#FIG. 1 is an axial sectional view of the upper part of a hydraulic shock absorber which includes two coaxial tubes, and

#FIG. 2 is a sectional view of a sealing element forming part of the shock absorber prior to incorporation of the sealing element in the shock absorber.

#The shock absorber includes a rod 3 that is axially reciprocable within a tube 1 filled with a liquid 2, for example, oil. The rod 3 carries a piston 3a formed with a plurality of passages so that movement of the rod 3 and piston 3a causes displacement of the liquid through the passages which are controlled by valves shown schematically in FIG. 1 and comprising thin steel sheets 3b and 3c.

#At the upper end of the tube 1, there is a guide member 4 which surrounds the rod 3 and is formed of an anti-friction metal in order to facilitate sliding of the rod 3. An annular cavity 5 is provided at the outer end of the guide member 4, i.e. the end thereof remote from the zone containing the liquid under pressure. A sealing element 6 of an elastomeric material is supported on the guide member 4 by means of a metallic washer 7 which is of dished form so as to obtain adequate rigidity without having to increase the thickness of a washer 7. The washer 7 is intended to act as a strengthening member for the whole of the elastic mass of the sealing element 6 which has a thin flange 8 thermally bonded to the outwardly facing surface of the washer 7.

#An outer washer 9 of annular form rests on the flange 8 and is pressed against the flange 8 to effect compression thereof in order to obtain a peripheral fluid-tight seal between the sealing element 6 and the outer tube 1a of the shock absorber. The diameter of the flange 8 is sufficient to obtain this sealing action. Pressing of the outer washer 9 into engagement with the flange 8 is obtained, in the particular embodiment shown in FIG. 1, by bending over the end portion of the outer tube 1a. In an alternative arrangement (not shown), a screw-threaded element is provided which engages the outer tube 1a and can be tightened to effect the required compression of the flange 8.