METHOD TO STRENGTHEN CYLINDRICAL HELICAL SPRINGS Russian patent published in 2017 - IPC B21F35/00 C21D9/02 F16F1/06 

FIELD: machine engineering.

SUBSTANCE: method involves winding the spring with a pitch which exceeds the pitch of the finished spring, lumocontrol, grinding the ends of the heat-treated spring, shot blasting and predeformation. In the final stage, after predeformation, the outer and inner surfaces of the spring are hardened in one operation by pressing using a hardening device when the spring is in the die hole by swelling the spring coils to the surface of the die hole by the punch entering it. The gap between the die hole and the punch surface is chosen to be less than the diameter of the spring coil by 0.2…5 mm.

EFFECT: increased stability of the spring elastic properties.

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