Piston ring for shock absorber

Details Piston ring for shock absorber Piston ring for shock absorber

1998-08-10

2001-01-23

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Piston ring or piston ring expander or seat therefor

C277S498000, C188S322180

Reexamination Certificate

active

06176492

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a shock absorber construction and more particularly to an improved sealing piston ring arrangement for a shock absorber.
A common type of shock absorber used for suspension systems and other purposes employs a piston that is slidably supported within a hydraulic cylinder. The piston and/or cylinder are provided with passages that extend between opposite sides of the piston and which include an arrangement for damping the flow therethrough. This provides a hydraulic damping action, as is well known in the art.
With this type of arrangement, however, there is also provided a seal on the exterior surface of the piston which engages and seals with the cylinder so as to preclude fluid leakage past the seal that would permit fluid to bypass the damping arrangement mentioned. However, these types of arrangements provide certain problems, as may be best understood by reference to
FIG. 1
which shows a conventional seal of the type utilized in shock absorbers.
FIG. 1
shows a portion of a shock absorber arrangement of the prior art type and this shock absorber mechanism is shown only partially and in cross-section to indicate the problems associated with the seal therein. The overall construction of the shock absorber in which the sealing mechanism is employed may be of any known type and such structures will be shown later in describing the preferred embodiment of the invention in FIG.
2
.
Nevertheless, the shock absorber includes an outer cylinder
21
which defines a cylinder bore
22
in which a piston
23
reciprocates. The cylinder
22
is filled with hydraulic fluid so as to form chambers above and below the piston
23
. In addition, flow passages are provided between the two chambers, normally in the body of the piston
23
, through which fluid may flow in a damped fashion so as to damp the suspension movement with which the shock absorber is associated.
In order to provide a seal and insure against leakage around this shock absorbing passage arrangement, at least one piston ring groove
24
is formed in the outer peripheral surface of the piston
23
. A piston ring
25
is provided in this piston ring groove
24
. This piston ring
25
may be of any type of construction and is pressed by its own resilience and by that of an O-ring
26
into sealing engagement with the cylinder surface
22
. The O-ring
26
is received in a groove
27
formed in the exterior surface of the piston
23
at the base of the ring groove
24
.
As may be seen in this Figure, if the piston
23
is forced downwardly relative to the cylinder
21
in the direction indicated by the force arrow F, the piston ring
25
will slide slightly upwardly and bottom against the upper side of the ring groove
24
of the piston
23
.
Thus, some fluid under pressure may enter into this area through a gap G that exists between the exterior surface of the piston
23
and the cylinder
22
. This pressure can then flow into a further gap area G
1
behind the piston ring
25
.
Thus, a hydraulic pressure is exerted which acts in conjunction with the pressure of ring
25
and the O-ring
26
to force the piston ring
25
into tight engagement with the surface
22
of the cylinder
21
. This restricts motion and can cause imprecise action of the shock absorber.
Arrangements have been proposed for reducing this effect by permitting a passage that will communicate the exterior surface of the piston ring with its interior surface. However, such passages then provide a path through which fluid may leak from one end of the piston ring to the other. Thus the shock absorbing system will be partially bypassed.
It is, therefore, a principal object of this invention to provide an improved piston ring arrangement that can be utilized with shock absorbers or other similar arrangements.
It is a further object of this invention to provide an improved piston ring arrangement wherein compressive pressure in one of the fluid chambers defined by the associated piston will not act on the piston ring to vary its sealing force with the cylinder in which it is received.
SUMMARY OF THE INVENTION
This invention is adapted to be embodied in a piston sealing arrangement for a shock absorber having a hydraulic cylinder in which a piston is slidably supported. The piston is provided with a peripheral groove in which a sealing piston ring is provided. A communicating passage arrangement is formed in the piston ring that communicates the exterior surface of the piston ring which engages the cylinder bore with the interior surface of the piston which faces the ring groove so as to balance therebetween. A seal is provided between the piston ring groove and the piston ring so as to preclude fluid flow from one fluid chamber to the other through the piston ring groove and the communicating passage arrangement.


REFERENCES:
patent: 3814445 (1974-06-01), Bitzan
patent: 4422649 (1983-12-01), Howarth
patent: 4592559 (1986-06-01), Harvey
patent: 4785922 (1988-11-01), Kiehart

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