A tightly winding coil spring is used as the bending relieving tool 10, and its screw shaft part 23 is installed on the wire deriving end of both the first and second wire holders 6 and 7. 屈曲緩和具10には密巻状のコイルばねを用い、そのねじ軸部23を第1・第2の両ワイヤーホルダー6・7のワイヤー導出端に装着する。 - 特許庁