Patent ID: 6928846
Filing Date: 2005-08-16
Classification: B21F

Abstract:
1. A method of manufacturing a coil spring having a straight and oblique axial line, comprising the steps of: feeding a rod member along an axial line thereof; applying an outer diameter control roller to said rod member from a first direction which is substantially perpendicular to said axial line; applying a pitch control tool from a second direction substantially perpendicular to both said axial line of said rod member and said first direction; displacing said outer diameter control roller cyclically so as to form a first section having a relatively large effective radius of curvature and a second section having a relatively small effective radius of curvature in each turn of said coil spring; and displacing said pitch control tool in said second direction in synchronism with the displacement of said outer diameter control roller so as to maintain a pitch of said coil wire substantially constant substantially over an entire length thereof; wherein said pitch control tool is displaced such that ΔP=A(ΔD/D)P holds, where P is an offset of said pitch control tool with respect to a reference plane corresponding to a zero pitch, ΔP is the displacement of said pitch control tool, D is the distance between said pitch control tool and outer diameter control roller, ΔD is the displacement of said outer diameter control roller, and A is a constant value.