Electric heating – Inductive heating – With heat exchange
Patent
1992-08-28
1994-08-16
Leung, Philip H.
Electric heating
Inductive heating
With heat exchange
219611, 219643, 285 21, 1562742, H05B 610, F16L 4702
Patent
active
053389204
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an electro-fusion fitting. More particularly, it relates to an electro-fusion fitting used for joining a synthetic resin pipe or the like, and a joining method using the electro-fusion fitting and a method of manufacturing the electro-fusion fitting.
PRIOR ART
The applicant of the present invention has proposed in Japanese Utility Model Laying-open No. 86847/1990 an electro-fusion fitting which is used for joining a pipe made of a synthetic resin material such as polyethylene, polybutene and etc. and is the background of the present invention.
An electro-fusion fitting 1 shown in FIG. 17 which is the background of the present invention includes a hollow cylindrical body 2 made of a synthetic resin material, and a cylindrical magnetic alloy member is embedded in the vicinity of the inner surface of the body 2 excluding a cold zone 6. Resin pipes 4 are inserted from both ends of the body 2. A high frequency current is applied to the magnetic alloy member 3 by a high frequency power supply 5, so that the magnetic alloy member 3 generates heat. Consequently, joint surfaces of the body 2 and the resin pipe 4 are fused, so that the body 2 and the resin pipe 4 are joined to each other.
Such an electro-fusion fitting 1 has the disadvantages of being inferior in productivity and high in manufacturing costs because it is manufactured by injection molding due to the necessity of forming the cold zone 6.
On the other hand, if the body 2 is formed by extrusion molding, it is possible to improve the productivity. However, the cold zone 6 cannot be formed by the extrusion molding because the magnetic alloy member 3 is continuous.
Meanwhile, the cold zone means a region where the body 2 is not fused. If such the cold zone 6 is not formed, the body 2 in a portion where no cold zone is formed is fused at the time of fusing, and molten resin flows out of a gap between the body 2 and the pipe 4 consequently, pressure for fusing and joining both the body 2 and the pipe 4 is reduced, so that joint defects occur. The cold zone 6 is required to prevent such joint defects.
SUMMARY OF THE INVENTION
Therefore, a principal object of the present invention is to provide a new electro-fusion fitting, and a joining method using the electro-fusion fitting and a method of manufacturing the electro-fusion fitting.
Another object of the present invention is to provide an electro-fusion fitting in which a cold zone can be formed at the time of fusing even if a magnetic alloy member embedded in the electro-fusion fitting is continuous and a joining method using the electro-fusion fitting.
Still another object of the present invention is to provide a method of manufacturing an electro-fusion fitting, in which it is possible to simply manufacture an electro-fusion fitting in which a cold zone can be formed.
An electro-fusion fitting according to the present invention is an electro-fusion fitting to which a member to be jointed made of a first synthetic resin material and having a first joint surface is joined, which comprises: a body made of a second synthetic resin material and having a second joint surface along the first joint surface of the member to be jointed, the first and second synthetic resin materials respectively having first and second fusion temperatures; a magnetic alloy member so formed as to be continuous in the axial direction on the inner surface of the body or the vicinity thereof, the magnetic alloy member having a curie temperature equal to or higher than the first and second fusion temperatures; and a shield member provided on the outer surface of a portion, where a cold zone is to be formed, of the body and for shielding electromagnetic induction from a high frequency power supply to the magnetic alloy member.
The body and the member to be joined are so fixed to each other that the second joint surface of the body is along the first joint surface of the member to be joined. If current is applied from the high frequency power supply to the magnetic alloy member by the
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Kasa Hideki
Kyomen Junsuke
Okusaka Shigeru
Sakaguchi Masayuki
Tago Takashi
Kubota Corporation
Leung Philip H.
Metcal Inc.
Rose Howard L.
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