Pipe joint

Details Pipe joint Pipe joint

1998-06-12

2001-01-09

Browne, Lynne H. (Department: 3629)

Pipe joints or couplings

Packed

Gasket retainer

C285S328000, C285S917000

Reexamination Certificate

active

06170890

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to pipe joints, and more particularly to pipe joints suitable, for example, for use in manufacturing semiconductors of which extremely high cleanliness is required.
The present inventor has already proposed a pipe joint suited, for example, to use in fabricating semiconductors of which extremely high cleanliness is required. With reference to
FIG. 6
, the proposed pipe joint comprises a pair of tubular joint members
1
,
2
, an annular gasket
3
interposed between abutting end faces of the joint members
1
,
2
and threaded means for joining the joint members
1
,
2
, the abutting end faces of the joint members
1
,
2
being formed with annular seal projections
37
,
38
respectively, so that when the threaded means is completely tightened up, recesses corresponding to the respective seal projections
37
,
38
are created in end faces of the gasket
3
, with respective inner peripheries
1
a,
2
a
of the abutting end faces of the joint members
1
,
2
becoming approximately flush with an inner periphery
3
a
of the gasket
3
. The pipe joint is characterized in that each of the seal projections
37
,
38
has a sectional contour which comprises a circular-arc portion
37
b
(
38
b
) extending radially outward from the abutting end face, and a straight portion
37
a
(
38
a
) extending from the circular-arc portion
37
b
(
38
b
) (see JP-A-32984/1997). Referring to the same drawing, the abutting end faces have respective inner flat portions
15
,
16
formed inwardly of the seal projections
37
,
38
, and respective outer flat portions
17
,
18
positioned outwardly of the projections
37
,
38
. Indicated at
9
and
10
are overtightening preventing annular ridges formed at the outer peripheries of the respective abutting end faces.
The pipe joint described has no liquid trapping cavity, is unlikely to develop in the inner periphery of the gasket creases which would permit deposition of dirt and further enables the worker, while tightening the threaded member, to perceive an altered reaction which indicates the completion of tightening. Thus, the pipe joint has features suitable for use in manufacturing semiconductors. However, the joint has the following problem. While such pipe joints as assembled once are frequently disassembled and assembled again, the joint shown in
FIG. 6
has the drawback that the gasket
3
is difficult to remove from the joint members
1
,
2
for disassembly because when the gasket
3
is to be moved axially relative to the first and second joint members
1
,
2
, the straight portions
37
a,
38
a
of the seal projections
37
,
38
biting in the gasket
3
give increased friction against the movement of the gasket.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a pipe joint which is easy to disassemble and assemble again and which nevertheless has no liquid trapping cavity, is unlikely to develop any dirt accumulating creases in the inner periphery of its gasket and is adapted to notify completion of tightening by an altered reaction, the pipe joint thus having features suitable for use in fabricating semiconductors.
The present invention provides a pipe joint comprising a pair of tubular joint members, an annular gasket interposed between abutting end faces of the joint members and threaded means for joining the joint members, the abutting end face of each the joint members being formed with an annular seal projection, so that when the threaded means is completely tightened up, a recess corresponding to the seal projection is created in the end face of the gasket opposed thereto, with the inner periphery of the abutting end face of each joint member becoming approximately flush with an inner periphery the gasket, the pipe joint being characterized in that the seal projection is positioned radially outward of the inner periphery of the abutting end face of the joint member and has in section a contour which comprises a circular-arc portion extending radially outward from the abutting end face, and a straight portion extending from the circular-arc portion, the circular-arc portion having a center positioned radially inward of the point of intersection of the circular-arc portion and the straight portion, the straight portion being inclined at 30 to 60 degrees with respect to the direction of axis of the joint.
As the threaded means is tightened, the seal projections of the joint members come into intimate contact with the respective end faces of the gasket, opposed thereto, and the inner peripheral portion of the abutting end face of each joint member then comes into intimate contact with the inner peripheral portion of the gasket end face opposed thereto, producing a sealing effect and eliminating any liquid trapping cavity. Although the gasket deforms most greatly at the position where each seal projection is located, this position is not the inner periphery of the gasket end face but is outward of the inner periphery, so that the gasket portion deforming most greatly is outward of the inner peripheral portion. Consequently no crease is formed in the inner periphery of the gasket, obviating the likelihood of dirt collecting in creases. If the straight portion included in the contour of the projection extends axially of the joint, there arises the problem that the gasket is difficult to remove when the pipe joint is to be disassembled, whereas the straight portion, which is inclined, obviates this problem. Moreover, the projection permits the worker to perceive an altered reaction more easily than when it is wholly in the form of a circular arc. Thus, the projection has an advantage of a projection which is entirely in the form of a circular arc and that of a projection which has an axial straight portion.
If the inclination is smaller than 30 degrees, the projection will have the drawback of rendering the gasket difficult to remove, i.e., the problem attributable to the presence of the axial straight portion, while if the inclination is greater than 60 degrees, there arises a problem attributable to the projection which is arcuate in its entirety, i.e., the drawback that an altered reaction is difficult to perceive. Accordingly, the inclination is preferably 30 to 60 degrees, more preferably about 45 degrees.


REFERENCES:
patent: 1537755 (1925-05-01), Dowling
patent: 1595310 (1926-08-01), Mueller et al.
patent: 1715854 (1929-06-01), McKenzie-Martyn
patent: 4838583 (1989-06-01), Babuder et al.
patent: 5340170 (1994-08-01), Shinohara et al.
patent: 5409270 (1995-04-01), Shinohara et al.
patent: 5720505 (1998-02-01), Ohmi et al.
patent: 5887876 (1999-03-01), Aldridge et al.
patent: 0 758 067 A1 (1997-02-01), None
patent: 0 837 278 (1998-04-01), None
patent: 2 038 972 (1980-07-01), None
patent: 6011079 (1994-01-01), None
patent: 9-032984 (1997-02-01), None
Patent Abstracts of Japan, vol. 097, No. 006, Jun. 30, 1997.

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