Patent ID: 9145941
Filing Date: 2015-09-29
Classification: B21D,B21F,F16F,Y10T

Abstract:
1. A method for manufacturing a hollow coil spring, comprising: sealing opposite ends of a hollow spring member by gathering a core material of each respective end of the hollow spring member by machining, the machining including relatively rotating the hollow spring member and a tool; and forming the hollow spring member into a coil shape after the sealing step, wherein in the sealing step, the ends of the hollow spring member are each formed in a hemispherical shape, and in the forming step, the hollow spring members is wound around a rod by moving a chuck portion, which grips one end of the hollow spring member, in an axial direction of the rod while relatively rotating around an outer circumference of the rod, thereby forming a hollow body in the coiled shape.