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 exceeding the pitch of the finished spring, heat treatment, wheel blasting, lumo control, grinding the ends of the heat-treated spring, spring hardening. In the final stage, the spring is hardened and compressed prior to contacting the coils, and pressing of compressed spring outer and inner surfaces is performed by means of hardening device when the compressed spring is located in the matrix opening. Pressing of outer and inner surfaces of compressed spring is carried out in one operation by stamping when compressed spring is in the matrix opening by spreading spring coils to the matrix opening surface with a punch entering therein, the diameter of the matrix opening equals the diameter of the compressed spring. The gap between the matrix opening and the punch surface is chosen less than the diameter of the spring coil by 0.2…5 mm.

EFFECT: increased productivity of hardening and the stability of the spring elastic properties.

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