Patent ID: 7101102

Claim:
A capless writing instrument, wherein a writing element is arranged inside a barrel cylinder so that a pen point of the writing element can come out and retract through a front end opening of the barrel cylinder, wherein an inner cap formed of rubber or elastic resin is provided at the front end opening of the barrel cylinder, and the inner cap is composed of: a closing portion disposed on the pen point projecting side with respect to the axial direction of the barrel cylinder for closing the front end opening and having a slit for allowing the pen point to project and retract; and forward projected portions that are projected from the outer periphery of the closing portion toward the front end opening, and projections are formed on the outer periphery of the forward projected portions or on the inner surface of the barrel cylinder opposing and in contact with the outer periphery of the forward projected portions, so that, in the slit closed state, force which is directed approximately perpendicular to the slit surfaces will act inward from the outer periphery of the forward projected portions by the function of the projections; wherein when the inner cap is not positioned in the inner end of the barrel cylinder the inner cap has a first position where the forward projected portions are a first distance apart from one another thereby creating a first force in a direction perpendicular to the surfaces of the slits, and when the inner cap is positioned in the end of the barrel cylinder the inner cap has a second position where the forward projected portions are a second distance apart from one another thereby creating a second force in a direction perpendicular to the surfaces of the slits, the second distance being smaller than the first distance, and the second force being larger than the first force.