Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1999-03-23
2002-01-01
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S559000, C277S569000
Reexamination Certificate
active
06334618
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to industrial sealing parts which are used in those such as car vehicles, electric instruments, machine tools or the like. More particularly, the present invention relates to sealing devices for establishing a seal between relatively movable shaft and housing. More particularly, the present invention relates to sealing devices with a harder portion on an inner surface of a sealing lip, to provide said sealing lip with hydrodynamic pumping effects to pump back oil or fluid to be sealed to the oil or fluid side.
The present invention also relates to a process to make a sealing device having a sealing lip comprising harder helical or circular or screw portions on the inner surface of the sealing lip, the hardened portions are made by irradiation of radiation ray.
2. Description of the Related Art
Conventionally, a sealing device of this type, for example, as is shown in
FIG. 10
has been used so far.
FIG. 10
is a fragmentary cross-sectional view showing a conventional sealing device which is mounted on a shaft.
As shown in
FIG. 10
, the sealing device is used to seal a distance or a gap between a housing
500
and a shaft
600
, preventing a fluid (oil or the like:) to be sealed from leaking from a fluid (oil or the like) side O to an air-side A.
The sealing device
400
has a rigid (metal) annular casing
401
with a sealing member such as a sealing lip (
402
,
405
) which is formed on the rigid annular casing
401
in one body. A radially inwardly tip portion of an inner periphery of the sealing lip is urged toward the shaft
600
to make the tip portion slidably and sealingly engage with the shaft
600
, by a garter spring
403
in a spring holder
404
(as shown in FIG.
10
).
A secondary sealing lip (dust sealing lip)
405
in
FIG. 10
is additionally formed in the air-side A of the sealing device for preventing contaminants from entering into the oil-side O from the air-side A.
In such a conventional sealing device
400
, in order to secure more effective sealing properties, the main sealing lip
402
has an important element, such as a helical pumping rib
406
(as shown in
FIG. 11 and 12
) on the inner surface of the sealing lip.
FIG. 11
is a fragmentary cross-sectional view showing a conventional sealing device, and
FIG. 12
is a cross-sectional view taken along the line Y-Y′. As shown in
FIG. 11
, on the inner surface of the main sealing lip
402
a plurarity of helical pumping ribs
406
are formed. By providing these helical pumping ribs, pumping functions to pump back fluid or oil to be sealed to the oil-side O is effectively secured.
Conventional sealing device mentioned above has following shortages.
1. In order to provide such helical pumping ribs on the inner surface of the sealing lip, sealing devices are transfer or injection molded in a mold having helical pumping ribs thereof. To provide helical pumping ribs in the mold, however, causes shortages such as an increase of a burden in designing or processing, to cause increase in cost.
2. On the other hand, in the case that these convexo-concave portions
406
of helical pumping ribs are provided on the inner surface of the sealing lip, the convex portions tend to be exposed to a severe friction with the shaft
600
compared with portions other than the convex portions of the inner surface of the sealing lip, causing severe abrasion especially at the convex portions to bring the initial configuration (shape) of the helical ribs into other configuration (shape) with proceeding of abrasion. These phenomena cause unstable sealing properties of conventional sealing devices in long use.
To cope with these problems mentioned above, it is necessary for us, by estimating the change of the configuration (shape) of the helical ribs with proceeding of the abrasion at the portion of the ribs, to design the shape of the helical ribs precisely, so that the sealing devices have stable sealing properties even in the long use. It is, however, very difficult to estimate accurate abrasion mode, as well as to design the shape of the ribs based on the estimated abrasion mode in long use.
Another type of conventional sealing device is shown in FIG.
13
. As is shown in
FIG. 13
, another type of conventional sealing device
700
is designed to seal a distance or a gap between an annular housing
900
and a shaft
800
, preventing a fluid (oil or the like) to be sealed from leaking from a fluid (oil or the like) side O to an air-side A.
The conventional sealing device
700
has a rigid (metal) annular casing
701
with a rubber sealing member
702
in one body, and with a resin sealing member
703
which is placed between and held by the annular rigid casing
701
and the rubber sealing member
702
.
The rubber sealing member
702
comprises a radially outer peripheral sealing portion
702
b
which firmly contacts with the hausing to seal a fluid, a sealing lip
702
a
which slides on and seals the shaft
800
, and a radially extending portion
702
c
which connects to the radially outer peripheral sealing portion
702
b
, in one body.
The resin sealing member
703
backs up a base portion
702
d of the sealing lip
702
a
of the rubber sealing member
702
to prevent the base portion
702
d
from over deformation caused by pressure from the oil-side O, and also slides on and seals the shaft
800
.
Accordingly, the resin sealing member
703
is preferably made of a resin material having certain degree of bending resistance (or flexibility) in order to secure the shape thereof and the engagement with the shaft
800
. Examples of such resin materials having specific flexibility (which means not so rigid), are fluoro polymers such as PTFE (Polytetrafluoroethylene) or the like.
Moreover, differing from the sealing lip or the like made of rubber which has sufficient elasticity, the resin sealing member
703
can not give a strong tension to all over the sealing periphery of the surface of the shaft. Oil leakage tends to occur due to the lack of tension in resin sealing member. In order to prevent oil leakage, grooves
704
having a pumping property are usually formed on the sealingly engaging surface of the resin sealing member
703
.
The groove
704
has a structure to give the resin sealing member
703
a pumping function to pump oil back to oil-side O at the time there is relative rotational movement between the sealing device
700
and the shaft
800
.
When the sealing device
700
is used in such a place where the shaft
800
is only driven in one rotational direction (not in reverse rotational direction) relative to the sealing device, the grooves
704
are preferably formed in a screw type manner, thereby providing the sealing device
700
with one way pumping effect. On the other hand, when the shaft
800
is driven in both normal and reverse rotational directions, a plurality of grooves
704
are preferably formed in a concentric circular manner, thereby exerting moderate pumping effect on the sealing device even in both normal and reverse rotations of the shaft
800
. The distance or the gap between the shaft
800
and the hausing
900
is effectively sealed by the sealing device mentioned above.
As is shown in
FIG. 14A and 14B
(Japanese Patent Tokosho 60-56618), the resin sealing member
703
has been prepared to form the helical groove by using thread cutting means, on a surface
707
of an end portion of a resin tubular body
705
, which has a predetermined inner and outer diameter made of resin material such as PTFE (Polytetrafluoroethylene or the like); and then cutting off the end portion by a cutting means
706
from the resin tubular body
705
to make a washer-like plain sealing member
703
with helical groove (as shown in FIG.
14
A). Helical groove can be made by press forming processes as well as cutting processes.
A pressing tool
800
J, which has an approximately same outer diameter as that of the shaft
800
to be sealed, is inserted, by using a press machine or the like, into an inner hollow bore of the thus obt
Minagawa Hironori
Ohta Takashi
Knight Anthony
NOK Corporation
Peavey Enoch E.
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