BACKGROUND ART A writing instrument is generally used for writing or drawing. Such writing instrument is designed to permit smooth flow of ink from ink reservoir to the writing tip.

Various types of writing instruments and ink for the writing instrument have been provided. Ink for gel type pen has a higher fluidity than oil based ink, because its viscosity is lower than oil based ink. Therefore, in case of gel type pen using ink of which viscosity is low, ink overflows easily due to the condition of use, impact from the outside, change of temperature, etc.

The structure of a conventional gel type pen is shown in Fig. l.

As shown in Fig. l, the conventional gel type pen comprises an ink reservoir 100 having an ink-storing chamber 120 for storing ink, a housing 200 which has an ink channel made at the center portion thereof and is fixed to the lower end of the ink reservoir 100, and a writing tip 300 fixed to the lower end of the housing 200. An ink follower 500 is placed in the ink reservoir 100 to prevent ink therein from flowing backward. The ink follower 500 is formed by injected gel after ink is injected into the ink reservoir 100. The writing tip 300 has a writing tip channel 320 made at the center portion thereof, and a ball 340 is provided to the end of the writing tip channel 320.

However, a disadvantage of the conventional writing instrument is that ink in the ink

reservoir 100 overflows to the writing tip if the internal pressure of the ink reservoir 100 is increased improperly due to some reason or other. That is, if the internal pressure of the ink reservoir 100 is increased, the increased pressure applies to the inner wall of the ink- storing chamber 120 and to the inner wall of the ink channel 220 uniformly. Thus, the increased pressure is transmitted to the writing tip 300 directly through the ink channel 220, and ink in the ink reservoir 100 is over-transmitted to the writing tip 300 in proportion to the increased pressure. If the ink is over-transmitted to the writing tip 300, the writing tip 300 is over-saturated with ink and drips.

DETAILED DESCRIPTION OF THE INVENTION In view of the prior art described above, including the disadvantages and deficiencies of the prior art, it is an object of the present invention to provide a writing instrument which prevents the increased pressure from overflowing to the writing tip 300 directly even if the internal pressure of the ink reservoir 100 is increased improperly.

The writing instrument according to the present invention comprises an ink reservoir for storing ink; a housing having an ink channel made at the center portion thereof, the housing being fixed to the lower end of the ink reservoir; a writing tip fixed to the lower end of the housing; and a decompression member for preventing the pressure in the ink reservoir from being transmitted to the writing tip directly, the decompression member being disposed in the housing, wherein an ink flow clearance is made between the inner wall of the housing and the decompression member when the decompression member is disposed in the housing.

The decompression member has a horizontal portion being in contact with the ink in

the ink reservoir and a vertical portion protruding from the bottom side thereof.

The horizontal portion has a clearance projection protruding from the bottom side thereof, and the vertical portion has a clearance projection protruding from the outer surface thereof in order to define the ink flow clearance.

The housing can have a clearance projection protruding from the upper end thereof and the inner wall thereof.

It is desirable that the ink flow clearance is 0. 2-1 mm (millimeter).

The clearance projection can be a plurality of hemispherical projections, and can be a plurality of ribs, which are continuously formed along the ink flowing direction to the writing tip.

The decompression member can have the shape corresponding to the inner wall of the housing. The decompression member has a clearance projection protruding from the outer surface thereof in order to define the ink flow clearance. The housing has a clearance projection protruding from the inner wall thereof.

It is desirable that the ink flow clearance is 0. 2-0. 5 mm (millimeter).

The clearance projection can be a plurality of hemispherical projections, or can be a plurality of ribs, which are continuously formed along the longitudinal direction thereof.

In the meanwhile, a clearance member can be disposed between the housing and the decompression member in order to define the ink flow clearance.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a vertical sectional view showing an embodiment of a conventional writing instrument.

Fig. 2 is a vertical sectional view showing a writing instrument according to the first embodiment of the present invention.

Fig. 3 is a fragmentary expanded sectional view showing the flow of ink of the writing instrument shown in Fig. 2.

Figs. 4A and 4B are sectional views taken along lines A-A and B-B of Fig. 2 respectively.

Figs. 5A and 5B are perspective views showing embodiments of the decompression member of the writing instrument shown in Fig. 2.

Fig. 6 is a vertical sectional view showing a writing instrument according to the second embodiment of the present invention.

Fig. 7 is a fragmentary expanded sectional view showing the flow of ink of the writing instrument shown in Fig. 6.

Figs. 8A and 8B are sectional views taken along lines C-C and D-D of Fig. 6 respectively.

Fig. 9 is a vertical sectional view showing a writing instrument according to the third embodiment of the present invention.

Fig. 10 is a fragmentary expanded sectional view showing the flow of ink of the writing instrument shown in Fig. 9.

Figs. 11A and 11B are perspective views showing embodiments of the decompression member of the writing instrument shown in Fig. 9.

Fig. 12 is a vertical sectional view showing a writing instrument according to the fourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

Referring now to the drawings, wherein like reference characters and element name designate like or corresponding parts throughout the several views.

Hereinafter, a writing instrument according to the first embodiment will be described in detail.

Fig. 2 is a vertical sectional view showing a writing instrument according to the first embodiment of the present invention, Fig. 3 is a fragmentary expanded sectional view showing the flow of ink of the writing instrument shown in Fig. 2, and Figs. 4A and 4B are sectional views taken along lines A-A and B-B of Fig. 2 respectively.

As shown in Fig. 2, the writing instrument according to the first embodiment consists of an ink reservoir 10, a housing 20, a writing tip 30, a decompression member 40, and an ink follower 50.

The ink reservoir 10 is a hollow cylinder-like structure that stores ink. Ink is injected into an ink-storing chamber 12 of the ink reservoir 10, and then the ink follower 50 is formed in the ink-storing chamber 12 by injection of gel. The ink follower prevents the ink in the ink-storing chamber 12 from flowing backward.

The housing 20 has an ink channel 22 made at the center portion thereof and a housing hole 26 made at the lower end thereof. The decompression member 40 is disposed into the housing 20. The housing 20 is fixed to the lower end of the ink reservoir 10.

The writing tip 30 is a part that is in contact with a paper during writing on the paper.

The writing tip 30 has a writing tip channel 32, and a ball 34 installed in the end of the

writing tip channel 32. The writing tip 30 is fixed to the housing hole 26 so that it protrudes from the lower end of the housing 20. The present embodiment discloses the writing tip 30 with the ball 34. However, the writing tip 30 can be substituted with other conventional writing tip.

The decompression member 40 is a part that prevents the internal pressure of the ink reservoir 10 from transmitting to the writing tip 30 directly. The decompression member 40 consists of a horizontal portion 42 having a shape of disc and a vertical portion 44 having a shape of a column. The vertical portion 44 protrudes perpendicularly from the bottom side of the horizontal portion 42. Clearance projections 46,48 are formed at the bottom side of the horizontal portion 42 and at the outer surface of the vertical portion 44.

The embodiments of the decompression member 40 are disclosed in Figs. 5A and 5B.

As shown in Fig. 5A, the clearance projection 46 formed at the bottom side of the horizontal portion 42 is a plurality of ribs continuously formed toward the center of the horizontal portion 42. The clearance projection 48 formed at the outer surface of the vertical portion 44 is a plurality of ribs continuously formed along the longitudinal direction thereof. As shown in Fig. 5B, the clearance projection 46,48 can be a plurality of hemispherical projections.

In the meantime, the clearance projection 46,48 is not restricted only to the shape shown in Fig. 5A or 5B, and may be practiced or embodied in other ways as well if an ink flow clearance is made.

The decompression member 40 is disposed in the ink channel 22 of the housing 20.

That is, a manufacturer inserts the vertical portion 44 into the ink channel 22, and then pushes it so that the horizontal portion 42 is in contact with the upper end of the housing 20.

When the decompression member 40 is fitted into the ink channel 22 perfectly, a horizontal

ink flow clearance 23 is defined between the bottom side of the horizontal portion 42 and the upper end of the housing 20, and a vertical ink flow clearance 24 is defined between the inner wall of the housing 20 and the outer surface of the vertical portion 44. The vertical ink flow clearance 24 is communicated with the horizontal ink flow clearance 23.

It is desirable that the ink flow clearances are about 0.2 mm-1 mm. That is, it is desirable that the clearance projection 46,48 rises to a height of about 0.2 mm-1 mm.

If the ink flow clearances 23,24 are smaller, it enhances the effect of pressure drop.

However, if the ink flow clearances 23,24 become too small, almost to the limit, it becomes not possible for the inlc to flow. According to the experiment, it has been known that if the ink flow clearances 23,24 are below 0.2 mm, the ink cannot flow effectively, and if the ink flow clearances 23,24 are over 1 mm, the effect of pressure drop is reduced.

The overall operation of the first embodiment is as follows.

As shown in Figs. 2 or 3, the pressure in the ink reservoir 10 applies uniformly to the inner wall thereof. In the meanwhile, if the internal pressure of the ink reservoir 100 is increased improperly due to increase of temperature or impact from the outside, the increased pressure is applied to the inner wall of the ink reservoir 10 and to the topside of the horizontal portion 42 of the decompression member 40 directly. Thus, the above- described increased pressure is decreased first.

The decreased pressure by the operation of the top side of the decompression member 40 is applied to the ink flow clearance 23 made between the bottom side of the horizontal portion 42 and the top side of the housing 20, and then is applied to the ink flow clearance 24 made between the outer surface of the vertical portion 44 and the inner wall of the housing 20. The decreased pressure by the operation of the topside of the decompression member 40 is decreased more and more while going through the ink flow

clearance 23,24 bent at right angles. That is, the pressure applied to the writing tip 30 is decreased due to the flow loss caused by the flow of ink through the ink flow clearance 23, 24 and by the friction loss caused at the inner wall of the housing 20 and the outer surface of the decompression member 40.

Thus, the structure concerning the decompression member 40 prevents the increased pressure from overflowing to the writing tip 30 directly ever if the internal pressure of the ink reservoir 12 is increased improperly.

Hereinafter, a writing instrument according to the second embodiment will be described in detail.

Fig. 6 is a vertical sectional view showing a writing instrument according to the second embodiment of the present invention, Fig. 7 is a fragmentary expanded sectional view showing the flow of ink of the writing instrument shown in Fig. 6, and Figs. 8A and 8B are sectional views taken along lines C-C and D-D of Fig. 6 respectively.

As shown in Figs. 8A and 8B, the writing instrument according to the second embodiment has the same structure as that of the first embodiment, except that the clearance projection 46, 48 is made at the housing 20. That is, the clearance projection 46, 48 is made at the top side and the inner wall of the housing 20, and the decompression member 40 has a smooth horizontal portion 42 and a smooth vertical portion 44.

A maker inserts the decompression member 40 into the ink channel 22 of the housing 20, and then pushes it so that the horizontal portion 42 is in contact with the upper end of the housing 20.

When the decompression member 40 is fitted into the housing 20 perfectly, a horizontal ink flow clearance 23 is defined between the bottom side of the horizontal portion 42 and the top side of the housing 20, and a vertical ink flow clearance 24 is

defined between the inner wall of the housing 20 and the outer surface of the vertical portion 44 by the clearance projection 46,48 made at the top side and the inner wall of the housing 20. The vertical ink flow clearance 24 is communicated with the horizontal ink flow clearance 23.

The operation of the second embodiment is almost the same as that of the first embodiment. That is, the increased pressure in the ink-storing chamber 12 is decreased while going through the ink flow clearance 23,24. Thus, the structure concerning the decompression member 40 prevents the ink in the inlc reservoir 10 from overflowing to the writing tip 30, because the decreased pressure is applied to the writing tip 30.

Hereinafter, a writing instrument according to the third embodiment will be described in detail.

Fig. 9 is a vertical sectional view showing a writing instrument according to the third embodiment of the present invention, Fig. 10 is a fragmentary expanded sectional view showing flow of ink in the writing instrument shown in Fig. 9, and Figs. 11A and 11B are perspective views showing embodiments of the decompression member of the writing instrument shown in Fig. 9.

The writing instrument according to the third embodiment has the same structure as that of the first embodiment, except for the shape of the decompression member 40.

The decompression member 40 has a shape like a column. That is, the decompression member 40 does not have a horizontal portion.

The horizontal portion 44 has a clearance projection 48 made at the outer surface thereof. As shown in Fig. 8, the clearance projection 48 consists of a plurality of ribs continuously protruding along the longitudinal direction of the vertical portion 44. In the meanwhile, as shown in Fig. llB, the clearance projection 48 can be a plurality of

hemispherical projections.

In the meanwhile, the clearance projection 48 can be formed at the inner wall of the housing 20 as that of the second embodiment.

It is desirable that the ink flow clearance, which is defined between the inner wall of the housing 20 and the outer surface of the decompression member 40, is about 0.2 mm- 0.5 mm. That is, it is desirable that the clearance projection 48 rises to a height of about 0.2 mm-0. 5 mm.

The ink flow clearance according to the present embodiment should be smaller than that of the first embodiment because the decompression member 40 according to the present embodiment does not have a horizontal portion having a shape of a disc and thus the pressure in the ink reservoir chamber 12 is applied to the ink flow clearance 24 directly.

If the decompression member 40 is disposed in the ink channel 22 of the housing 20, a minute ink flow clearance 24, of which the size is 0. 2mm-0. 5mm, is defined between the outer surface of the decompression member 40 and the inner wall of the housing 20.

If the pressure in the ink-storing chamber 12 is increased improperly, the increased pressure is transmitted to the writing tip 30 through the ink flow clearance 24. The increased pressure is decreased while going through the ink flow clearance 24, because the ink flow clearance 24 is minute thereby causing flow loss. In addition, The increased pressure is decreased while going through the ink flow clearance 24, because there is friction loss caused by the flow friction at the inner wall of the housing 20 and at the outer surface of the decompression member 40.

Hereinafter, a writing instrument according to the fourth embodiment will be described in detail.

Fig. 12 is a vertical sectional view showing a writing instrument according to the

fourth embodiment of the present invention.

The writing instrument according to the fourth embodiment has the same structure as that of the first embodiment or the third embodiment, except that a clearance member 49 for defining the ink flow clearance 23,24 is disposed between the decompression member 40 and the housing 20. That is, clearance projections are formed neither at the decompression member 40 nor at the housing 20.

According to the fourth embodiment, the decompression member 40 or the housing 20 can be manufactured easily.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.