| 摘要 |
PURPOSE:To facilitate the manufacture and to reduce the cost, by providing a plurality of projections on one outercircumference of a yoke plate while providing the same number of grooves helically on the adjusting ring with correspondense to said projection then engaging said projection with said grooves. CONSTITUTION:Three projections 15, for example, are provided on one yoke plate 16 while three grooves 17 engaging with said projections 15 are provided helically on the adjusting ring 18. Said projections 15 and the helical grooves 17 are engaged to perform the function similar to the conventional screw section. With such structure the working of the male thread to the innercircumferential face of the adjusting ring and the working of the male thread to the outercircumferential face of the yoke plate are not required, while the yoke plate can be manufactured through single punching work by means of the press resulting in the cost reduction. |
