Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Reexamination Certificate
1998-05-14
2001-08-14
Brittain, James R. (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
C277S560000, C277S565000
Reexamination Certificate
active
06273430
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an oil seal for use in a gas spring, hydraulic shock absorber or the like device to provide a hermetic seal between a cylinder and a piston rod thereof.
2. Description of the Related Art
In a gas spring, a piston rod is reciprocally disposed in a cylinder. Within the cylinder is filled high pressure gas together with lube oil. Accordingly, at the end of the cylinder is provided a fluid seal or oil seal so as to provide a seal between the cylinder and the piston rod.
The oil seal has an annular seal lip extending radially inward so as to fit closely, at an inner circumferential surface thereof, the outer circumferential surface of the piston rod. In this instance, in order that the seal lip can prevent leakage of oil and gas assuredly, it needs to retain a predetermined contact pressure under which it is urged for contact with the piston rod. However, if it is tried to simply make higher the contact pressure of the seal lip, the contact area at which the seal lip is brought into contact with the piston rod is increased with increase of the contact pressure, thus causing the oil film covering the circumferential surface of the piston rod to be liable to be cut or removed by the seal lip at the time of movement of the piston rod relative to the oil seal. Thus, when the piston rod is out of lube oil, the resistance of the oil seal to movement of the piston rod increases while the lubrication at the seal lip becomes worse, thus deteriorating the durability of the oil seal.
From the foregoing reasons, an oil seal capable of solving such a problem has been proposed as is disclosed in Japanese utility model second publication (after examined) No. 7-36210.
This oil seal is shown in FIG.
5
and generally indicated by
1
. The oil seal
1
includes an annular seal lip
2
having an inclined inner circumferential surface
3
which is inclined with respect to a center axis of the oil seal
1
when observed in a longitudinal section, i.e., the annular seal lip
2
has a conical inner circumferential surface
3
. At the inner circumferential surface
3
, the seal lip
1
is formed with a plurality of annular projections
4
a
to
4
e
which are arranged in sequence axially of the oil seal
1
. The annular projections
4
a
to
4
e
have end portions brought into contact with the outer circumferential surface of the piston rod
5
. Such an oil seal
1
can be higher in the contact pressure of each of the annular projections
4
a
to
4
e
but smaller in the continuous or consecutive contact surface area, thus allowing the oil film formed on the outer circumferential surface of the piston rod
5
to be hard to be cut or removed by the seal lip
2
. In the meantime, in
FIG. 5
, indicated by
6
is a cylinder and by
7
is a metallic reinforcement ring attached to the oil seal
1
.
However, in the above described oil seal
1
, the annular projections
4
a
to
4
e
are formed so as to be simply of the same height above the inner circumferential surface
3
. Thus, when the seal lip
2
is subjected to the high pressure within the cylinder
6
, the annular projections
4
a
to
4
e
located axially more inside of the cylinder
6
receives more of the cylinder inside pressure. By this, the contact pressure of the annular projection
4
a
becomes larger as compared with those of the other annular projections. As a result, the annular projection
4
a
located axially more inside of the cylinder
6
is deformed axially outside of the cylinder
6
more largely and its contact area also becomes larger. For this reason, a problem of the prior art oil seal
1
is that when the cylinder inside pressure is high the annular projection
4
a
located axially more inside possibly cuts or removes the oil film on the outer circumferential surface of the piston rod
5
.
SUMMARY OF DTHE INVENTION
According to an aspect of the present invention, there is provided a novel and improved oil seal which is attached to an end of a cylinder filled with high pressure fluid together with oil and having an annular seal lip slidably fitted on an outer circumferential surface of a piston rod which is reciprocal in while protruding from the cylinder. The seal lip has on an inner circumferential surface thereof a plurality of annular projections at which it is brought into contact with the outer circumferential surface of the piston rod. One of the annular projections which is located more axially outside of the cylinder is larger in the height above the inner circumferential surface than one of the annular projections which is located more axially inside of the cylinder. The annular projections which are located more axially inside of the cylinder are subjected to more of the high pressure within the cylinder. However, since the annular projections which are located more radially outside of the cylinder are larger in the height above the inner circumferential surface than those which are located more axially inside of the cylinder, the annular projections are all nearly equal in the contact pressure with respect to the piston rod. As a result, it never occurs such a case in which the amount of deformation of the annular projections which are located more axially inside of the cylinder becomes excessively large, thus causing all of the annular projections to become nearly equal in the contact area with respect to the piston while allowing the grooves in which oil is collected to be formed between adjacent two of the annular projections assuredly.
According to a further aspect of the present invention, the annular projections are variable in the height multi-stepwise in a way as to increase in the height in order from one that is located more axially inside to one that is located more axially outside of the cylinder By this, the annular projections all have a nearly equal surface area for contact with the piston rod.
It is accordingly an object of the present invention to provide a novel and improved fluid seal or oil seal which can assuredly prevent shortage or lack of its lube oil on the outer circumferential surface of a piston rod of a hydraulic device such as a gas spring, hydraulic shock absorber, etc.
It is a further aspect of the present invention to provide a novel and improved fluid seal or oil seal of the foregoing character which can improve its lubrication as well as the lubrication of the associated piston rod or the like and elongate its durability assuredly.
REFERENCES:
patent: 2316713 (1943-04-01), Procter
patent: 2568056 (1951-09-01), Corder
patent: 2977138 (1961-03-01), Brittain, Jr.
patent: 3119624 (1964-01-01), Freed
patent: 3144256 (1964-08-01), Wright
patent: 3183009 (1965-05-01), Kunel
patent: 3368650 (1968-02-01), Wasdell
patent: 4061346 (1977-12-01), Coleman et al.
patent: 4534239 (1985-08-01), Heimann
patent: 5178243 (1993-01-01), Hamada et al.
patent: 5478091 (1995-12-01), Gardner
patent: 7-36210 (1995-08-01), None
Hiramoto Michiya
Kanari Issei
Beres John L.
Brittain James R.
Foley & Lardner
Unisia Jecs Corporation
LandOfFree
Oil seal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Oil seal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oil seal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2521091