Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1995-03-07
2001-02-06
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S560000, C277S565000, C277S569000
Reexamination Certificate
active
06182975
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a sealing device, and more particularly, to a compound-type sealing device having a combination of seal lips, wherein a first seal lip is formed of a rubber-like elastic material and a second seal lip is formed of a resin material. The present invention also more particularly relates to a method of manufacturing such a compound-type sealing device.
BACKGROUND OF THE INVENTION
It is well known in the art of sealing devices which have seal lips, to provide a sealing device which utilizes a seal lip formed of a rubber-like elastic material or a resin material such as PTFE (polytetrafluoroethylene). In a conventional sealing device where a seal lip formed only of a rubber-like elastic material is used, the seal lip may be damaged by contact with the fluid which is to be sealed, such as, oil or other chemicals. This may be very inconvenient. On the other hand, where a seal lip is used that is formed only of a resin material, the seal lip has the problem that the seal lip does not suitably follow-up the operation of a rotational shaft to be sealed due to a lack of elasticity of the resin of the seal lip and due to a leakage of fluid such as oil from a small gap.
The prior art has attempted to solve the aforementioned problems by providing a sealing device
100
, as shown in
FIG. 10
, having only a resin seal lip
101
, in which the elasticity of the resin seal lip
101
is improved.
In such a sealing device
100
, the resin seal lip
101
has outer diameter side end portions
102
which are nip-supported by a pair of reinforcing rings
103
and
104
. In order to improve the follow-up performance of the resin seal lip
101
to the rotation of the shaft and to prevent an oil leakage through the small gap, grooves
107
and
108
are formed so as to provide a bellows shape on the peripheral surfaces of the resin seal lip
101
on a side of the resin seal lip opposite the fluid to be sealed and on a side of the resin seal lip opposite a fluid side not to be sealed. These grooves
107
and
108
are formed by an upper die
111
and a lower die
112
, as shown in
FIG. 11
, and are provided with mutually opposing projections
109
and
110
on the die's pressing surfaces so as to provide grooves
107
and
108
on the upper and lower surfaces of the seal lip
101
as shown in FIG.
12
.
Although the resin seal lip
101
of the conventional sealing device
100
has improved elasticity, the improvement in the elasticity is limited. The resin seal lip
101
still does not have as much elasticity as that of the seal lip formed of the rubber-like elastic material.
Furthermore, a sealing device
400
, such as is shown in
FIG. 13
, is also well known. The conventional sealing device
400
includes a resin liner
407
which is bonded on a sliding surface
405
of a seal lip
402
formed of a rubber-like elastic material extending from a seal body
401
to the side of the seal lip opposite the fluid side to be sealed. The sealing device
400
thereby provides the elasticity of the rubber-like elastic material and improves durability of the sliding surface. The liner
407
has a sliding surface
403
on which is formed a helical groove
403
having a pumping function.
In such a conventional sealing device
400
, however, the unsolved problem is that oil leaks through the small gap between the resin liner
407
and the rotation shaft
406
.
In order to prevent the problems encountered in both the above-described conventional sealing devices, there have been further proposed various sealing devices of a compound type. Compound type sealing devices have a combination of a seal lip formed of a rubber-like material and a seal lip formed of a resin material.
A conventional sealing device
300
of a compound type is shown in FIG.
14
. The sealing device
300
is for sealing a gap between a housing
301
and a rotation shaft
302
. The sealing device
300
has outer diameter side end portions of a seal lip
303
on the side of the seal lip opposite the fluid side to be sealed formed of the rubber-like elastic material, of a resin seal lip
304
disposed on an atmosphere side on the back surface side of the seal lip
303
and of a back-up ring
305
disposed on a further atmosphere side of the resin seal lip
304
are all assembled together into a recessed portion
307
of a fit ring
306
.
In this type of the sealing device, however, the resin seal lip
304
interferes with the back surface of the seal lip
303
of the rubber-like elastic material, providing the problem that there is poor follow-up performance of the resin seal lip
304
to the swing-rotation of the rotation shaft
302
. Additionally, this type of sealing device is costly to assemble due to the requirement of m any assembling processes and many workings involved.
On the other hand, a sealing device
200
, such as is shown in
FIG. 15
, is one provided with a resin seal lip
203
formed of the rubber-like elastic material which are integrally formed for eliminating the assembling processes such as mentioned above in the former example of FIG.
14
. That is, the sealing device
200
is one for sealing the gap between a housing
201
and a rotation shaft
202
. A reinforcing ring
205
is interposed between the rubber seal lip
203
on the side of the seal lip opposite the fluid side to be sealed and the resin seal lip
204
on the atmosphere side, and the rubber seal lip
203
is bonded integrally with the resin seal lip
204
through a plurality of perforations
206
formed in the reinforcing ring
205
.
Furthermore, a back-up ring
207
is press-fitted to an inner periphery of the reinforcing ring
205
on the atmosphere side of the resin seal lip
204
to hold the resin seal lip
204
between the reinforcing ring
205
and the back-up ring
207
.
FIG. 16
illustrates manufacturing processes of the aforementioned integral-compound type sealing device.
That is, a resin material
204
A for forming a resin seal lip
204
is disposed in a mold cavity
507
of a rubber formation mold
506
constructed by upper first and second mold parts
501
and
502
and lower first, second and third mold parts
503
,
504
and
505
. The reinforcing ring
205
having the perforations
206
is disposed on the resin material
204
A so as to abut against it, and under this state, a rubber material is vulcanized for forming the seal lip
203
of the rubber-like elastic material. Simultaneously with the formation of the rubber seal lip
203
, the rubber material is backed integrally with a portion of the resin material
204
A intruded into the cavity
507
and bonded thereto (refer to FIG.
16
(
a
)).
Thereafter, as shown in FIG.
16
(
b
), the upper first and second mold parts
501
and
502
are opened (in the direction of the arrow) to open the mold
506
, and as shown in FIG.
16
(
c
), the lower mold part
503
is pushed up in the direction of the arrow to form a lip front end portion. Then, as shown in FIG.
16
(
d
), the lower second mold part
504
, against which the resin material
204
A abuts, is pushed up in the direction of the arrow, thereby separating the mold product from the mold
506
.
However, even in the conventional compound type sealing device described above, a side of the lip facing radially inwardly, facing the shaft and the resin lip
204
of the seal lip
203
formed of the rubber-like elastic material is disposed adjacent to the resin seal lip
204
, so that the resin seal lip
204
interferes with the rubber seal lip
203
, thus providing the problem of poor follow-up performance with respect to the rotation shaft
202
.
Furthermore, countermeasures for preventing the rubber material from rotating during manufacturing as well as the problems of dimensional performance in the formation of the resin seal lip
204
should be considered.
An object of the present invention is to solve the problems encountered in the prior art described above. A further object of the present invention is to provide a sealing device of a compound type having a combination of a seal l
Matsushima Noboru
Yamanaka Satoshi
Armstrong, Westerman Hattori, McLeland & Naughton
Beres John L.
Knight Anthony
NOK Corporation
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