PURPOSE: To prevent a spacer from becoming off positioned and falling off by fixing it in such a manner as to provide an insulting cylinder with an engaging section and fit an insulating piece in it.

CONSTITUTION: An insulation covered 8 lead wire 7 is provided with spacers 9 and 9', and a barrier 11 is concentrically arranged on this. Further, spacers 10 and 10' are arranged on this, and then, a barrier 12 is also concentrically arranged. A hole 18 is bored on the end sections of the spacers 9 and 9', and another penetrating hole of the same diameter is bored on the same position of the barrier 11. After assembling, stoppers 16 and 16' having the same shape as the holes are fit into the holes to prevent them from becoming off positioned. The other end section is also provided with a stopper in the same manner. And then, the spacers 10 and 10' and the barrier 12 are also provided with stoppers 17 and 17' in the same manner. In this case, since the spacers 9 and 9' and also 10 and 10' are located in the same radial position, the stoppers 16 and 16' are covered by the spacers 10 and 10' and prevented from coming off. In this mechanism, it is possible to prevent the spacers from being off positioned and falling off, to arrange the insulation cylinder barrier on the lead wire at a required interval and to improve insulating strength.