PURPOSE: To stabilize the supply amount of ink, in a writing utensil such as a white market, by making the receding stroke of a slide plug due to a pump mechanism larger than the width of the elastomer seal provided to the outer peripheral part of the slide plug when standard equal pressure is applied to a pen body.
CONSTITUTION: When writing pressure is applied to a felt tip 4, the felt tip 4 recedes and the piston body 7 of a pump mechanism 5 is deformed to pressurize the ink in an ink chamber 2. At this time, a slide plug 9 recedes but an ink film is not bonded to the inner peripheral surface of the ink chamber 2 on the side of a tail plug 11 from a seal part 10 and the slide plug 9 slides in a direct contact state. Therefore, the pressure in the ink chamber 2 becomes relatively high corresponding to the slide resistance at the receding time of the slide plug 9 and ink is sent to the felt tip 4 in the amount corresponding to the amount of the ink consumed in one stroke of writing. The receding quantity of the slide plug 9 exceeds the seal width of the seal part. Therefore, the part where the seal part 10 is in a close contact state before the receding of the slide plug 9 of the inner peripheral surface of the ink chamber 2 is wetted with ink.