| 摘要 |
PROBLEM TO BE SOLVED: To prevent thermal deformation such as expansion and contraction by doing high temperature heat treatment which is done at a temperature of the melting point of a thermoplastic resin or above and low temperature heat treatment which is done at a temperature within a range of use conditions after the molding of a joint of the resin with a heating body embedded. SOLUTION: An electric fusion joint (socket) 1 comprises a joint main body of a thermoplastic resin, a heating body 12 made of a heating body wire 22 coated with a thermoplastic resin 21 which is wound spirally in the same depth in the neighbourhood of the inner surface of the main body and embedded, and terminal pins 13 for feeding a current from both ends of the heating body. The joint 1 is subjected to high temperature heat treatment which is done at a temperature of the melting point of the resin or above and low temperature heat treatment which is done at a temperature within a range of use conditions. Preferably, the high temperature heat treatment is done at a temperature close to the melting point, a temperature as high as possible within a range not to cause the deformation of the joint main body, and the low temperature heat treatment is done at a temperature as low as possible within the range of use conditions. In Japan, it is preferably about -10 deg.C. The heating body, for example, is made of a nickrome wire, etc. |
