| 摘要 |
A ratchet mechanism for enabling motion to be transferred in one direction but not in the opposite direction as disclosed which does not require springs. The mechanism includes an engagement member (16, 50, 100, 250, 330) which has teeth for engaging teeth on an outer member (12, 70, 200, 300). The engaging member (16, 50, 100, 250, 330) is mounted on an inner member (30, 80, 220, 320). A drive surface (120, 255, 323) on the engagement member (16, 50, 100, 250, 330) contacts teeth of the outer member (12, 70, 200, 300) when rotated in one direction so as to move the engagement member into position whereby a tooth (18, 110, 258, 335) can engage teeth of the outer member. When rotated in the opposite direction, the engagement member is moved out of engagement with the outer member to enable the ratchet to freewheel. In other arrangements, a cam (34, 321) either alone or in engagement with a drive surface causes engagement or disengagement of the teeth of the engagement member with the outer member.
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