| 摘要 |
PROBLEM TO BE SOLVED: To enable manufacture of an electrofusion type pipe joint with no inner defective such as void and small molding deformation by reducing depth of a groove in which an electrothermal wire is spirally embedded compared to the diameter of the wire. SOLUTION: An inner member layer 4 is formed by injection molding from thermoplastic resin, such as polyethyrene resin, polypropyrene resin, polyvinyl chloride resin, or polybutene resin. Depth (h) of a groove 4a of the inner member layer 4 is less than a wire diameter (d) of an electrothermal wire 2, in particular, less than half of the wire diameter (d). Since the groove 4a is thus filled with the electrowire 2, air included in molten resin in a die and gas generated from the molten resin are not sealed in the groove 4a. An air reservoir is not generated, so that void is not generated which may be caused by concentration of the gas in pressure holding process and cooling process. Inner defectives are eliminated with certainty. |
