| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that since the hitherto known positioning mechanism has a shape of a portion in contact with a follower wheel which is set in a bilaterally symmetrical shape, a rotation load in a forward direction and a reverse direction is substantially the same, and thus it is difficult to simply establish convenience by a positioning mechanism alone that a driving in the forward rotation side makes a load as much as small and the reverse rotation side performs a positioning with much stronger force.SOLUTION: The positioning mechanism includes a rigid part for performing a positioning of a follower wheel. A contacting relationship between this rigid body and a follower gear provided in the follower wheel is configured such that a length of an arm of moments of a force which rotates the rigid body is extremely long in the forward direction relative to the reverse direction, and a load of the gear toward the rotational direction is small relative to the reverse direction. The rigid body of the positioning mechanism sets angle α formed by a perpendicular component of a tangent line of a point at which a vertex of the rigid body and the follower gear comes in contact with each other and a component toward a rotational center direction of a contact point with the follower gear of the vertex of the rigid body to equal to or more than 0°, and when a strong shock is applied, the rigid body acting as a reverse rotation preventive mechanism prevents a damage of detached components. |
