Pressurized pen

A pressurized pen including a pen refill unit loaded in a barrel, a pen tip disposed on a front end portion of a medium containing tube for containing ink and the like in the pen refill unit, a press pump mechanism for pressing an inside of a rear opening portion of the medium containing tube, and a knock mechanism disposed on a rear end section of the barrel, said knock mechanism enables the pen tip to protrude and retreat from the front end section of the barrel, wherein the press pump mechanism includes a pressurizing member having a pressurizing chamber communicating with the inside of the medium containing tube and being disposed on the rear opening portion of the medium containing tube so as to freely expand and contract in an axial direction, and a pressing member which is configured to press the pressurizing member in a pressing direction and which interlocks with a pressing operation of the knock mechanism, and

• wherein the pressurizing member includes an elastic cylindrical member, said elastic cylindrical member includes a large-diameter front cylinder portion of which a front end in air-tight manner communicates directly with the rear opening portion of the medium containing tube and which forms the pressurizing chamber, and a small-diameter rear cylinder portion which is coaxially connected to a rear end of the front cylinder portion and in which the front end portion of the pressing member is pressed into a rear aperture thereof,
• whereby the inside of the medium containing tube is pressurized by allowing the pressing member to press the rear cylinder portion into the front cylinder portion and compressing the elastic cylindrical member in the axial direction with the pressing chamber air-tight, and
• whereby the elastic cylindrical member is decompressed so as to elongate in the axial direction and the inside of the medium containing tube communicates with the outside air, by a pressing and opening operation of the pressing member.