| 主权项 |
1. A writing instrument, comprising:
a main body; a working cam rotatably connected to a rear portion of the main body to undergo rotation within a predetermined range and forming part of a screw-shaped cam groove; a refill inserted in a non-rotatable fashion into the main body and having a guide pin slidably engageable with the cam groove to advance or retract the refill in the axial direction of the main body when the working cam rotates; a sealing section that seals the front end of the refill when the refill retracts and the front end of the refill is housed in the main body and that releases the sealing to let the front end of the refill protrude when the refill advances; and a regulating member that regulates the rotation of the working cam so that the working cam rotates between one end position at which rotation starts and the refill is fully retracted and another end position at which the rotation ends and the front end of the refill protrudes from the main body, wherein the cross section of the main body and the cross section of the working cam have a shape different from a circle so that when the working cam is located at the position at which the rotation starts, the outer configurations of the main body and the working cam coincide with each other, and when the working cam rotates, the outer configurations are shifted and do not coincide with each other, whereby the rotation of the working cam can be discerned by the coincidence or non-coincidence of the outer configurations. |
