| 摘要 |
PROBLEM TO BE SOLVED: To perform uniform fusion connection by a method wherein the protrusion of an indicator is normally protruded from the outer surface of a coupling and a fusion state is reliably sensed through visual observation, even in an electric fusion coupling formed of a resin material having defective fluidity. SOLUTION: In case of an indicator 4 for an electric fusion coupling formed of a thermoplastic resin material having a linear expansion factor of 8-13×10<-5> / deg.C and/or a melt flow rate of 0.05-0.15 g/10 min, an opening hole 5 with a bottom is formed in the outer periphery of a coupling body 1, and a protrusion 6 with a given height integrally protruded in the opening hole 5 from a bottom 8 and having a tip positioned lower than the outer peripheral surface of the coupling body is provided. A thick section part 7 formed in an inclination-form manner and stair-form manner integrally with the side wall 9 of the opening hole is formed at the bottom 8 of the opening hole, and this constitution forms an electric fusion coupling. |
