Patent ID: 8177447

Claim:
A writing tool having a dryness prevention unit, comprising: a hollow shaft ( 10 ) having at a first end thereof a nib hole ( 13 ), with a shutter shaft seat ( 12 ) protruding from an inner wall of the shaft; a cartridge ( 20 ) secured to an interior of the shaft ( 10 ) to correspond to a center of the nib hole ( 13 ), and comprising a knock part ( 29 ) inserted into an insert hole ( 14 ) formed in a second end of the shaft ( 10 ), and a pair of pressing parts ( 22 ) provided on an end of a nib extension shaft ( 23 ) of the cartridge; a rear O-ring ( 30 ) surrounding the end of the nib extension shaft ( 23 ) of the cartridge ( 20 ); a spherical shutter ( 40 ) having a shape of a hollow sphere, held in the rear O-ring ( 30 ), and having a spherical shutter part ( 43 ) to isolate a nib ( 24 ) from an exterior; wherein the rear O-ring ( 30 ) comprises: a sealing part ( 32 ) having a shape of a cylinder which has a diameter corresponding to a diameter of the nib extension shaft ( 23 ) such that the sealing part air-tightly surrounds an outer circumference of the nib extension shaft ( 23 ) of the cartridge ( 20 ); and a spherical-shutter support part ( 31 ) having a diameter which is larger than the diameter of the sealing part ( 32 ), and supporting the spherical shutter ( 40 ), the spherical-shutter support part ( 31 ) having a first side and a second side of an end of the spherical-shutter support part; a front O-ring ( 50 ) contacting the shutter part ( 43 ), and coming into contact with the nib hole ( 13 ); and a spring ( 7 ) contacting at a first end thereof a lower end of a step of the cartridge ( 20 ), and contacting at a second end thereof a step of the rear O-ring ( 30 ), thus axially biasing either the rear O-ring ( 30 ) or the cartridge ( 20 ) within a stroke distance of the cartridge ( 20 ), whereby the spherical shutter ( 40 ) is rotated by the pressing parts ( 22 ), so that the shutter part ( 43 ) opens the front O-ring ( 50 ), and thus the nib ( 24 ) is projected from the nib hole ( 13 ); wherein the spherical-shutter support part ( 31 ) comprises half-moon-shaped wings protruding from both sides of the end of the spherical-shutter support part, thus supporting the spherical shutter ( 40 ) so that the spherical shutter rotates around a pair of protrusions without being dislodged from a predetermined position, and causing the nib ( 24 ) to be sealed by the spherical shutter ( 40 ).