| 摘要 |
PROBLEM TO BE SOLVED: To provide a plate-like contact spring used for a key switch for a keyboard of a portable telephone or the like, capable of remarkably enhancing the limit of fatigue breakdown as compared with a conventional one by preventing stress concentration in a peripheral part and by reducing stress amplitude in use so as to prevent the fatigue breakdown even if it is repeatedly used 106 times or more, or semipermanently. SOLUTION: This contact spring is formed by bending a thin plate-like conductive spring material so as to project its front face 11a side and to recess its back face 11b side, and by arranging small projections 11d projecting in the back face direction at some positions in its circumferential part 11c.
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