| 摘要 |
In a rotational drive mechanism employed for a mechanical pencil, a cam structure is simplified, the number of components is reduced, and the rotational drive mechanism is allowed to be easily assembled. A large number of cam faces 24a and 24b are continuously formed in a circle on upper and lower faces which are perpendicular to an axial direction of a rotatable cam 24 which constitutes the rotational drive mechanism 21. Elastic members 23b are formed integrally with a holder member 23 for rotatably supporting the rotatable cam 24 so as to extend in the axial direction, and the first fixed cam and second fixed cam 23c and 23d having a small number of cam faces at butts and tips of the elastic members are arranged to face each other via the upper and lower cam faces 24a and 24b of the rotatable cam 24. It is arranged that the rotatable cam 24 is retreated and moved forward in the axial direction by writing pressure applied to a writing lead so as to be rotationally driven in one direction and rotational motion of the rotatable cam 24 is transmitted to the writing lead. |
