Electrofusion of electrofusion joint, method of confirming state of fusion and fusion joint suitable for use in the methods

Abstract

An electrofusion joint includes an electrical heating wire embedded in its inner peripheral region. The electrofusion joint can be fitted to an end of a plastic pipe. By supplying electrical current to the electrical resistance heating wire the interface between the joint and the pipe are fusion bonded. In order to allow easy determination of the completion of fusion bonding, the electrofusion joint is provided with an annular groove in the outer peripheral surface extending to a region of the joint near the electrical resistance heating wire. A pin or bar-like core member is located at and extends upwardly from the center of the groove. A stopper member is provided above the core to control the extent of projection of the pin or bar-like core such that any rise in pressure due to flow of molten resin in the groove of the joint which is transfered to the pin or bar-like core member enables confirmation that the fusion has been successfully accomplished by the observation of the limited movement of the stopping member with minimal flow of resin. Furthermore, as the stopper member is lifted by this pressure the electrical contact between the heating wire and electrical current supply is broken and further heating is terminated.

Dependencies are inferred from the claim text.