Oil seal

Details Oil seal Oil seal

1999-03-01

2001-08-21

Sandy, Robert J. (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Diverse and distinct dynamic seals

C264S161000

Reexamination Certificate

active

06276691

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to oil seals for establishing a seal between relatively movable shaft and housing. More particularly, the present invention relates to lip-type oil seals having hydrodynamic pumping means, which is used in an automobile or in a general industrial machinery.
2. Description of the Prior Art
Conventionally, as shown in
FIG. 15
, there has been known an oil seal having helical pumping ribs
52
at around a tip portion of a seal lip
51
to improve seal functions. The pumping ribs provide oil seals with a pumping function to pump fluid to be sealed toward fluid side. This type of oil seals has a sharp edge
53
at a tip of the seal lip
51
, and the helical pumping ribs
52
starts from the sharp edge
53
.
The sharp edge
53
, however, tends to be abraded comparatively rapidly by sliding on a member to be sealed such as a shaft (not shown in FIG.
15
).
Therefor, in these conventional oil seals mentioned above, the tip of the helical pumping ribs
52
tend to be comparatively rapidly disappeared with comparatively rapidly being abraded at the sharp edge
53
, causing changes of contact conditions of the helical pumping ribs
52
with the member to be sealed.
Accordingly, there have been a defect of comparatively rapidly decrease in pumping function of the helical pumping ribs
52
, by comparatively rapidly abrasion phenomenon mentioned above.
Japan unexamined laid open patent 7-301339 discloses an oil seal having, in the seal lip
101
, a third frustoconical surface (so called a “flat” surface)
106
between a frustoconical air-side surface
103
and a frustoconical oil-side surface
102
(as is shown in
FIG. 16
) to avoid such a defect as described above. There are an edge line
104
and
107
, which is a juncture line between the flat surface
106
and the frustoconical oil-side surface
102
, and between the flat surface
106
and the frustoconical air-side surface
103
, respectively as shown in FIG.
16
. As is shown in
FIG. 16
, the flat surface has a width W in actual size, which is a width in the direction of a central axis line
0
of the oil seal. The oil seal also has angles a, &bgr;, and &ggr; as is shown in
FIG. 16
; the &agr;, &bgr; and &ggr; is an angle between the central axis of the oil seal and the frustoconical oil-side surface
102
, the frustoconical air-side surface
103
, and the so-called flat surface
106
, respectively. The patent of 7-301339 also discloses uniform helical grooves providing the seal lip with a pumping function pumping oil (or fluid, not shown in
FIG. 16
) back from the air-side to the oil-side. In this regard, the terms “oil-side” and “air-side” refer, respectively, to being situated closer to the oil-side A and the air-side B indicated in FIG.
16
.
The oil seal also has a garter spring
105
placed in a groove formed on an outer periphery of the seal lip
101
, and a rigid annular casing
108
which supports the seal lip
101
in the lower part of the oil seal, as is shown in FIG.
16
.
The 7-301339 patent, however, has such a wider projection area which is placed between a groove and an another adjacent groove, that a deformation of the groove is not so large at the time when the third frustoconical surface is fitted on a member (or shaft, not shown in
FIG. 16
) to be sealed. This type of oil seals show sometimes some disadvantages such as some oil leakage from the oil-side A to the air-side B through a portion between the seal lip and the member (shaft) to be sealed, at the time of the state that there is no relative rotational movement between the seal lip and the member (shaft) to be sealed, because of the groove being usually little deformed to cause some apertures between the seal lip and the shaft.
SUMMARY OF THE INVENTION
It is therefore that, from the view point mentioned above, an object of the present invention is to provide an oil seal having a property not to be decreased in pumping function of the ribs at around the edge of the seal lip in its long use, and having an excellent sealing property even at the time there is no relative movement between the seal lip and the shaft, resulting an excellent sealing properties for a long period of time as well as at an initial stage in use.
Another object of the present invention is to provide an oil seal having an improved wearability.
A still another object of the present invention is to provide an oil seal having a static and dynamic sealing performance.
A still another object of the present invention is to provide an oil seal having an improved hydrodynamic pumping function even at the time of the counter member to be sealed is counterrotated.
These objects are achieved by providing a third annular substantially frustoconical (or flat) surface between a frustoconical air-side surface and a frustoconical oil-side surface of a seal lip, and providing a plurality of helical pumping ribs on the third annular flat surface to pump back oil in the sliding portion of the seal lip, to the oil-side. The cross-sectional shape of each ribs provided on the third annular flat surface, are similar to a triangular or bilge or mountainous shape in its cross section and the height of the ribs are uniformly controlled throughout its entire length.
Each ribs is formed from the edge on the oil (or fluid) side to another edge on the air-side of the third annular flat surface with a predetermined crisscross angle &thgr; to an edge line, which is a juncture line between the third annular flat surface and the frustoconical oil-side surface. These first ribs are placed equally around the surface of the third surface.
Some of the first ribs can be placed equally around the surface of the third surface with a predetermined crisscross angle (180° minus &thgr; or 180-&thgr;) to the edge line, so as to prevent oil from leaking at the time of reverse revolution of the shaft. Each first ribs do not cross over each other.
These first helical ribs mentioned above are designed to be deformed when the seal lip
1
is mounted on the shaft, so that the third surface having the first helical ribs is snugly fitted on the shaft to prevent oil from leaking through the portion between the shaft and the third surface at the time there is no relative movement between the shaft and the third annular flat surface.
And also these objects are achieved by further providing a second helical pumping ribs on the frustoconical air-side surface. Each second helical pumping ribs have a bilge type or a triangular type in cross section thereof. And the height and the width of the second pumping ribs, at least partially, progressively increases from the oil-side to the air-side.
These second ribs are placed equally around the surface of the frustoconical air-side surface with a predetermined crisscross angle to an edge line, which is a juncture line of the third annular flat surface and the frustoconical air-side surface. These features and advantages of the invention, as well as other features and advantages thereof, will become apparent from the following description.


REFERENCES:
patent: 3930655 (1976-01-01), Fern
patent: 3973781 (1976-08-01), Grorich
patent: 4288083 (1981-09-01), Braconier
patent: 5759466 (1998-06-01), Onuma et al.
patent: 7-301339 (1995-11-01), None

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