| 摘要 |
A writing instrument has a tubular casing having a longitudinal axis, a through-hole extending in a longitudinal direction of the longitudinal axis, a wall surface, and an aperture formed in the wall surface. A writing refill is inserted in the through-hole of the tubular casing for extension out of the casing to a writing position and retraction into the casing to a retracted position. A rotary cam mechanism is accommodated in the through-hole of the casing for extending and retracting the writing refill between the writing position and the retracted position. The rotary cam mechanism comprises a cam cylinder having a projection engaging the aperture of the casing and a stationary cam, a rotary cam engageable with the stationary cam of the cam cylinder, and a knocking cam engageable with the stationary cam of the cam cylinder and the rotary cam. A knocking member is integrally connected to the knocking cam and is connected to the cam cylinder in a non-rotatable state while permitting movement of the knocking member relative to the cam cylinder in the longitudinal direction.
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