| 摘要 |
PROBLEM TO BE SOLVED: To ensure simplification of a cam structure, reduction in the number of parts, as well as easiness of assembling of a rotary driving mechanism in rotary driving mechanisms to be used for mechanical pencils.SOLUTION: Many torus-like continuous cam faces 24a and 24b are respectively formed at upper and lower faces perpendicular to the axial direction of a rotary cam 24 constituting a rotary driving mechanism 21. On a holder member 23 rotatably supporting the rotary cam 24, an elastic member 23b is integrally molded long in the axial direction, and on a proximal part and on a distal part of the elastic member, first and second fixed cams 23c and 23d equipped with a few cam faces are arranged by standing face to face so that the upper and lower cam faces 24a and 24b of the rotary cam 24 are pinched. The rotary cam 24 is rotated and driven in one direction by being retreated and advanced in the axial direction by the writing pressure received by a writing core, and the rotational movement of the rotary cam 24 is transmitted to the writing core. |
