| 摘要 |
PROBLEM TO BE SOLVED: To restrain fluctuation of a tripping load due to variations of an engaging point of a latch and a latch hook in a cutoff mechanism, which locks the latch with the latch hook and maintains a movable contact in a closing state, and opens the movable contact by rotating the latch hook with a tripping device to unlock the latch in an abnormality. SOLUTION: An engagement face 11b with the latch hook 20 of the latch 11 is formed as a convexity arc face 11b. An engagement face 20b of the latch hook 20 which is engaged with this arc face 11b is formed a concave arc face having larger curvature radius than the convexity arc face 11b. A center of curvature X is matched exactly with a center of a shaft Y of a shaft 21 which supports a latch hook 20. The load to drive a latch hook 20 by the tripping device is not changed even if an engagement position S is changed, because the line of action of an engaging force T which acts on from the latch 11 to the latch hook 20 goes through the center of the shaft Y.
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