Pipe joints or couplings – Particular interface – Tapered
Reexamination Certificate
1999-03-19
2001-01-30
Nicholson, Eric K. (Department: 3629)
Pipe joints or couplings
Particular interface
Tapered
C285S354000, C285S386000
Reexamination Certificate
active
06179348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a fitting or a fitting structure of a synthetic resinous material mainly used in a tubing system in a high technology field or industry such as fabrication of semiconductors, for example, for transferring a high-temperature, high-pressurized special chemical fluid which should be under strict control because of its environmental impact, for example.
2. Prior Art
There are known fitting structures for plastic pipes or tubes, which use fluid-tight screws, ferrules, or a variety of other fluid-tight structures. Because of inherent natures of fluoroplastics, fitting structures made of a fluoroplastic material, for example, TFE (tetrafluoroethylene), PFA (copolymer of polytetrafluoroethylene and perfluoroalkylvinylether), or FEP (copolymer of polytetrafluoropropylene), are often used for transferring high-temperature, high-pressurized chemical fluids, particularly chemical liquids which need careful handling. However, conventional fluoroplastic fitting structures involve the problem of leakage of fluids. Namely, these fitting structures repeatedly experience expansion and contraction during the heat cycle, and creeps are produced in the fitting structures. These creeps result in making microscopic gaps between connected elements, and this is a major reason of the leakage problem. It is extremely difficult to prevent these gaps from being made.
To solve the problem a tube fitting as shown in
FIG. 7
has been proposed. The prior art fitting shown in
FIG. 7
is used for connecting a tube to an associated device, for example. In
FIG. 7
, the reference numeral
1
represents a tube made of a fluoroplastic material. One end or a forward end section of the tube
1
is folded back to outwardly overlap the remainder main portion of the tube
1
to form a folded-back portion of a predetermined length. As a result, the tube
1
, in the folded shape, defines a folded-back end which is U-shaped in its cross section.
A fitting for connecting the tube
1
is made up of an insert
10
, a fitting body
6
and a ring member
8
which are all made of a fluoroplastic material.
The insert
10
has a tubular shape and it is mounted on the tube
1
such that one end section (lower end section in
FIG. 7
) of the insert
10
sits between the main body of the tube
1
and the foldedback portion thereof.
The fitting body
6
includes an annular groove
6
a
whose bottom is U-shaped in its cross section to fit the U-shaped forward end of the tube
1
; a cylindrical portion
6
c
encircling the annular groove
6
a
to define an inner wall surface
6
b
for contact with the outer wall of the folded-back portion of the tube
1
and an outer wall surface threaded to form a threaded portion
6
f
; and a connecting portion
6
e
threaded on its outer circumferential surface to form a threaded portion
6
d
for connecting the fitting body
6
to an associated device or apparatus.
The ring member
8
includes an inner ring portion
8
a
for engagement with the other end (upper end in
FIG. 7
) of the insert
10
, and an outer cylindrical portion
8
b
whose inner wall surface is threaded to form a threaded portion
8
c
for threading engagement with the threaded portion
6
f
of the fitting body
6
.
For fabricating the fitting structure, one end section of the tube
1
is first folded back outwardly by a predetermined length, and the insert
10
is inserted between the main portion and the folded-back portion of the tube
1
. Then, the semi-assembly of the tube
1
and the insert
10
is joined to the fitting body
6
. After that, the portion
6
f
of the fitting body
6
is threadedly engaged with the portion
8
c
of the ring member
8
until the insert
10
tightly compresses the U-shaped forward end of the tube
1
onto the annular groove
6
a
of the fitting body
6
.
As a result, the tube
1
is firmly connected to the fitting, and the above-mentioned leakage problem is removed.
However, the prior art fitting structure is bulky in diameter because of the radially overlapped arrangement of the insert
10
, the cylindrical portion
6
c
of the fitting body
6
and the outer cylindrical portion
8
b
of the ring member
8
around the tube
1
with threads being formed on the portions
6
c
and
8
b
for firm engagement between the fitting body
6
and the ring member
8
. With the prior art fitting, the diametrical bulkiness of the fitting will make it impossible to arrange a plurality of tubes closely side by side for connection with the associated device.
SUMMARY OF THE INVENTION
The invention overcomes the above-mentioned problems by providing a fitting for connecting one tube to another tube or an associated device, said fitting comprising a fastener for engagement a two-plied section including a folded-back portion which is formed by folding or turning back one end section of said tube outwardly, and a fitting body for fitting into said fastener;
said fastener having an engaging portion for receiving said two-plied section of said tube, a contact portion for contact with the outer surface of said folded-back portion of said tube, and a threaded portion formed on the inner surface thereof;
said engaging portion, said contact portion and said threaded portion being axially aligned;
said fitting body including a cylindrical section which has an end for abutting against the U-shaped end of said two-plied section of said tube, said cylindrical section being provided with a threaded portion on the outer surface thereof.
The fitting according to the invention may include a insert having one end section to be inserted between the main body of the tube and the folded-back portion in the two-plied section. In this case, the fastener preferably has an engaging portion which is engageable with the other end of the insert.
According to the fitting of the invention, since the threaded portion is arranged axially offset from the engaging portion and the contact portion, it is possible for the fastener to have a decreased outer diameter in comparison with the prior art fitting.
REFERENCES:
patent: 431816 (1890-07-01), Lomasney
patent: 509743 (1893-11-01), Lane
patent: 771682 (1904-10-01), Sussman
patent: 1880638 (1932-10-01), Wood et al.
patent: 1925937 (1933-09-01), Schultis
patent: 2445702 (1948-07-01), Weyenberg et al.
patent: 3380764 (1968-04-01), Wilson
patent: 3501171 (1970-03-01), Baron
patent: 4133565 (1979-01-01), Shutt
patent: 5439259 (1995-08-01), Taga et al.
patent: 1091 (1889-06-01), None
patent: 1238867 (1960-07-01), None
patent: 351829 (1931-07-01), None
patent: 3229089 (1991-10-01), None
patent: 5322083 (1993-12-01), None
Lipsitz Barry R.
Nicholson Eric K.
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