Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
2000-11-28
2003-12-09
Eashoo, Mark (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S271100, C264S295000, C264S296000
Reexamination Certificate
active
06660206
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, and 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 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 baked 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 are 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 lip formed of a rubber-like elastic material and a resin seal lip. A further object of the present invention is to provide a method of manufacturing the compound type sealing device capable of preventing the resin seal lip from interfering with the rubber seal lip. A further object of the present invention is to effectively prevent the rubber material from intruding during the manufacturing process. A further object of the present invention is to make the thickness of the resin seal lip relatively thin in order to improve the follow-up performance of the resin seal lip. A further object of the present invention is to reduce heat generation. A further object of the invention is to form the resin seal lip simultaneously with the rubber seal lip molding process.
SUMMARY OF THE INVENTION
The present invention provides a sealing device for sealing two members which are disposed to be relatively rotated mutually concentrically, the sealing device being provided with a first seal member having a seal lip formed of a rubber-like elastic material and a second seal member having a seal lip formed of a resin material to be assembled integrally with the first seal member, and characterized in that an annular space is formed between the rubber seal lip and the resin seal lip so as to prevent the resin seal lip from interfering with the rubber seal lip.
Accordingly, the resin seal lip becomes flexible following up the operation of a shaft without interfering with the rubber seal lip, thus improving the sealing performance.
It is characterized in that the annular space is formed between the resin seal lip and a side of the lip facing radially inward, facing the shaft and the resin seal lip of the rubber seal lip. This is because, in a conventional product, the side of the lip facing radially inward, facing the shaft and facing the resin seal lip of the rubber seal lip is most interfered with.
It is characterized in that an annular groove is formed to a side surface on the side of said annular space of the resin seal lip.
It is characterized in that a plurality of the annular grooves are formed in an axial direction.
Matsushima Noboru
Yamanaka Satoshi
Armstrong Westerman & Hattori
Eashoo Mark
NOK Corporation
Shipsides Geoffrey P.
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