| 摘要 |
PURPOSE:A thin band steel for forming a spring is shaped so as to cause its edge portion to be directed inwardly in respect to a center of the spring and a life for fatigue is improved. CONSTITUTION:Warpings 8 and 8 are formed in advance at both edges of a thin band steel. When this thin band steel is used as a coil spring, the warpings 8, 8 made at both edges curved at 5 are found at the middle of the drums 1 and 2, and the inwardly directed warpings 9, 9 are formed at both edges on the winding drum 1. The portion 10 generating a maximum tensile stress corresponds to a top end of the inwardly directed warping 8 rather than its edges and so no cracks are generated from the edges of he band due to its fatigue. When the band is to be used at its wound condition, a compression stress is generated at a top end of the warping and thus it is possible to extend the life of the band up to its rapture. |
