| 摘要 |
PROBLEM TO BE SOLVED: To minimize the necessary spring force of a cam returning spring device of a press die corresponding to the stroke position of a cam. SOLUTION: A weak coil spring 21 with small permissible load and large permissible deflection and a storage coil spring 22 with large permissible load and small permissible deflection are fitted to a guide pin 30 in an expandable manner and connected to each other in series. A deflection stopper 31 for regulating the maximum deflection of the weak coil spring 21 is formed in the guide pin 30. During the pressing work, the strong coil spring 22 and the weak coil spring 21 are compressed as a composite spring, and after the deflection of the weak coil spring 21 reaches the regulated compressive deflection, only the strong coil spring 22 is compressed. In the first half of the cam return, only the strong coil spring 22 is expanded. In the second half, both the strong oil spring 22 and the weak coil spring 21 are expanded to achieve the cam return with two-stage strong-weak spring characteristics.
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