Patent ID: 6866436

Claim:
A writing instrument comprising: a tubular member having a longitudinal axis and an aperture at an end thereof; a writing component mounted in the tubular member and having a writing tip at an end portion thereof, the tubular member and the writing component being movable relative to one another in an axial direction along the longitudinal axis of the tubular member between a writing position at which the writing tip protrudes from the aperture of the tubular member and a housed position at which the writing tip is disposed in the tubular member; an airtight sleeve connected to the end portion of the writing component for movement between an advanced position and a retracted position, the airtight sleeve having a bore through which the end portion of the writing component passes during movement of the writing component between the writing position and the housed position; a cap plate pivotally connected to the airtight sleeve for opening and closing the bore of the airtight sleeve; and a projecting rib connected to the cap plate so that when the airtight sleeve moves from the advanced position to the retracted position, the projecting rib abuts an inner surface of the tubular member so as to pivot the cap plate in such a direction that the cap plate closes the bore of the airtight sleeve; wherein the tubular member has a window hole into which the projecting rib projects when the airtight sleeve moves from the retracted position to the advanced position to allow the cap plate to pivot in a direction to open the bore of the airtight sleeve.