| 摘要 |
The present invention provides a counter gear mechanism which comprises the following elements. A large gear (10) comprises a disk-like portion and a circumferentially extending portion continuously extending on a peripheral portion of the disk-like portion. The circumferentially extending portion has a larger width than a thickness of the disk-like portion. The circumferentially extending portion has a circumferential outer surface on which first gear teeth (14) are provided. A small gear (20) is coaxially engaged with the large gear (10). The small gear (20) comprises a disk-like plate and a body being cyrindrically shaped to have a circumferential outer surface on which second gear teeth (23) are provided. A tubular member (12) is provided at a center of the disk-like portion. The tubular member (12) defines a hole and extends along a rotation axis around which the large gear (10) rotates. The tubular member (12) projects from the large gear (10) on its one side where the small gear (20) is provided. At least a recessed portion (13a,13b) is formed in the disk-like portion. The recessed portion (13a,13b) is shaped to draw a part of a circle coaxially encompassing the tubular member (12). At least a projection (24a,24b) is fixed on the disk-like plate of the small gear (20) but on an opposite side to the side on which the body is provided. The projection (24a,24b) inserts into the recessed portion (13a,13b) to move along a longitudinal direction of the recessed portion (13a,13b). First and second spring members (15) are provided within the recessed portion (13a,13b) at opposite sides of the projection (24a,24b) so that the first spring member pushes the projection (24a,24b) toward the second spring member whilst the second spring member pushes the projection (24a,24b) toward the first spring member. <IMAGE> |
