| 摘要 |
A ratchet drive comprises a support in which the trunnions of a ratchet gear are mounted. A pair of transversely spaced drive plates are also mounted on the support for tilting movement about the axis of the ratchet gear between an active stroke and a return stroke so that front ends of a pair of drive pawls connected to the drive plates engage, during each active stroke of the latter, adjacent teeth of the ratchet gear to turn the latter through a predetermined angle during each active stroke. A member is mounted between the drive plates for pivoting movement about a pivot axis extending parallel and spaced from the axis of the ratchet gear and the rear ends of the drive pawls are mounted on the member respectively to opposite sides of the pivot axis, so that if during the active stroke of the drive plates the front end of only one of the pawls should, due to manufacturing tolerances, engage the respective tooth, the thrust imparted by the one drive pawl will turn the member about its pivot axis to bring the front end of the other pawl in engagement with the adjacent tooth to equalize the load on the two teeth during each active stroke of the drive plates. |
