Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Reexamination Certificate
2001-08-27
2004-04-13
Knight, Anthony (Department: 3677)
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
C277S496000
Reexamination Certificate
active
06719297
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a piston ring for use in a vibration damper (shock absorber), having a covering surface which covers a circumferential surface of a piston, and supporting surfaces with retaining segments which engage upper and lower sides of the piston. The piston ring has a butt joint formed by a tongue which is circumferentially movable in a cutout so that the piston ring can expand radially.
2. Description of the Related Art
U.S. Pat. No. 5,615,756 discloses a piston ring including a covering surface which covers a circumferential surface of a piston, and supporting segments having retaining surfaces which engage on the upper and lower sides of the piston. The piston ring has a butt joint which enables the piston ring to be elastically deformable radially, the butt joint being designed at one end of the covering surface with at least one tongue which engages in a cutout in the other end of the covering surface.
The design, which is simple in principle, and the problem-free installation are features of this piston ring. When piston rings are used in vibration dampers, it is possible, at very high damping forces, to detect relatively large dispersions of the damping forces which can be attributed to the piston ring. The tongue at one end of the piston ring tends to lift radially from the piston enabling a flow connection of undefined size between the upper and lower side of the piston to occur.
Under some circumstances, a remedy would be possible by using a radially effective clamping ring, as is disclosed, for example, U.S. Pat. No. 6,186,512. Either a groove or at least one shoulder is provided in the piston for the mounting of the clamping ring. Neither solution is suitable for a piston ring in conjunction with a flat piston, as is described in U.S. Pat. No. 5,615,756, since the production advantage described in that patent would no longer be usable.
SUMMARY OF THE INVENTION
The object of the present invention is to realize a piston ring, in particular for a flat piston, which is constantly leakproof even when subjected to a large hydraulic load.
According to the invention, the object is achieved by providing the tongue with at least one retaining segment which runs in the circumferential direction and engages in a supporting manner in each case on the upper and lower side of the piston.
The retaining segments not only prevent deformation of the tongue of the piston ring when subjected to pressure, but also ensure closure of the open butt joint.
In a further advantageous refinement of the invention, at least in some sections in the circumferential direction of the piston ring, the cutout is designed with bearing segments which fix the end of the piston ring axially with respect to the piston. Both ends of the piston ring are thereby defined in their position.
In order to be able to keep to a spatial refinement which is as simple as possible for the piston ring, the bearing segments are supported in the axial direction of the piston on the retaining segments.
The more uniformly the piston ring is able to keep to its circular shape, in particular in the region of the tongue, the better the sealing function is carried out. Therefore, the one end of the covering surface has, in the region of the butt joint, at least one centering web which aligns the tongue radially with respect to the cutout of the butt joint.
According to a further advantageous embodiment, the retaining segments are designed such that they are larger radially inward in relation to the piston ring than the bearing segments, so that the centering web engages, as part of the retaining segment, radially inward on the bearing segments. The centering web ensures that the tongue is not able to protrude radially from the circumferential surface of the piston ring. In practice, the centering web forms a locking means.
Furthermore, the piston ring can have at least one clamping ring which is arranged outside the circumferential surface of the piston and prestresses the piston ring against a cylindrical wall. The piston does not require any adaptation whatsoever for the clamping ring, so that a simple piston contour can be retained.
In this connection, the at least one clamping ring is accommodated in a groove, the supporting segment forming a groove side wall of the groove.
A second groove side wall is formed by a sealing lip of the piston ring. In the end, no additional axial construction space has to be used for the clamping ring.
In order to be able to optimally use the clamping action of the clamping ring, the groove width for the clamping ring is designed such that it is larger than the height of the clamping ring.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.
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Asadi Hassan
Fenn Gerald
Höhn Matthias
Wirth Peter
Cohen & Pontani, Lieberman & Pavane
Jackson André L.
Knight Anthony
Mannesmann Sachs AG
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