| 摘要 |
<p>PURPOSE:To detect the pressure without the efflux of molten resin from fused part and prevent the short circuiting of heating wire and the lowering of fusion efficiency and the like from occurring by a method wherein a pin or bar-like core for transmitting pressure is formed at the center of an annular groove, which is cut so deep as to reach near the heating wire on a joint, so as to stop energizing by detecting the pressure of the molten resin at the fused part through the core. CONSTITUTION:A bar-like core 53 for transmitting pressure is formed by cutting an annular groove 52, which is so deep as to reach near heating wire 57, in the neighborhood of the electrical outlet 51 of an electro-fusion joint. On the other hand, a pressure switch 55 is provided on a connector 54 so as to engage the piston 56 of the pressure switch 55, when the connector 54 is inserted in the outlet 51. When internal pressure is developed through the expansion of the resin surrounding the heating wire 57 due to its thermal fusion after the start of energizing, the pressure is transmitted to the core so as to be detected with the pressure switch 55 in order to open the switch of an energizing circuit and stop energizing. Further, blind holes 14 reaching near the heating wire 11 are formed and plugged with transparent heat-resistant glass sheets 15 inside electrical outlets 13 so as to inspect the molten resin flowing in the blind hole 14 in order to confirm the fusion of a joint.</p> |
