JP2009073133A - Ink tank interchange type writing utensil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink tank interchange type writing utensil which can restrain the leakage of ink to the outside by the careless removal of a tail plug and an ink tank before the ink in the ink tank is completely consumed. <P>SOLUTION: A writing utensil body 2 has a journal 5 providing a pen point 3 at a front end, and a cylindrical tail plug 7 installed freely detachably by connecting to the rear end opening part of the journal 5. The front end part of the ink tank 8 is inserted from the rear end opening part of the journal 5 into the interior thereof, and the rear end part of the ink tank 8 is projected backward from the rear end opening part of the journal 5. The tail plug 7 is installed in the rear end opening part of the journal 5, and the rear end part of the ink tank 8 is accommodated in the interior of the tail plug 7. The rear end part outer circumference surface of the journal 5 and the outer circumference surface of the tail plug 7 are coated with a cylindrical heat shrinkable film 9. The front end of the cylindrical heat shrinkable film 9 is positioned on the rear end part outer circumference surface of the journal 5, and the rear end of the heat shrinkable film 9 is positioned on the outer circumference surface of the tail plug 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink tank exchangeable writing instrument.

Conventionally, in this type of writing instrument, Patent Document 1 includes at least an ink tank made of a transparent material so that the ink accommodated in the interior can be externally seen, and an attachment part that can be attached to and detached from the writing instrument body. In the refill exchange type writing instrument in which the refill is attached to the writing instrument body, the refill exchange type writing instrument is disclosed in which an opening hole is formed in the rear portion of the writing instrument body and the ink tank protrudes from the opening hole.

Japanese Utility Model Publication No. 6-86975

In the writing instrument of Patent Document 1, since the ink tank protrudes rearward from the writing instrument body, the ink tank is detached from the coupling part with the writing instrument body due to impact such as dropping or inadvertent contact. The ink inside may leak out.

The present invention solves the above-mentioned conventional problems, and can prevent the ink tank from coming off from the joint with the writing instrument body due to a drop impact or inadvertent contact, and the ink in the ink tank can be completely removed. The present invention is intended to provide an ink tank exchangeable writing instrument that can prevent the leakage of ink to the outside due to careless removal of the tail plug and ink tank before consumption. In the present invention, “front” refers to the pen tip side, and “rear” refers to the ink tank side.

1st invention of this application is the ink tank exchange-type writing instrument which accommodated the ink tank 8 in the inside of the writing instrument main body 2 so that replacement | exchange was possible, Comprising: The writing instrument main body 2 is equipped with the axial cylinder 5 provided with the nib 3 at the front end, A cylindrical tail plug 7 is detachably attached to the rear end opening of the shaft cylinder 5, and the front end of the ink tank 8 is inserted into the shaft cylinder 5 from the rear end opening of the shaft cylinder 5. The rear end portion of the ink tank 8 protrudes rearward from the rear end opening portion of the shaft cylinder 5, the tail plug 7 is attached to the rear end opening portion of the shaft cylinder 5, and the ink tank 8 is placed inside the tail plug 7. The rear end portion is accommodated, the outer peripheral surface of the rear end portion of the shaft cylinder 5 and the outer peripheral surface of the tail plug 7 are covered with a cylindrical heat-shrinkable film 9, and the front end of the heat-shrinkable film 9 is the rear end of the shaft cylinder 5. It is located on the outer peripheral surface of the end, and the rear end of the heat-shrinkable film 9 is positioned on the outer peripheral surface of the tail plug 7 (claim) 1) and the requirements.

The ink tank replaceable writing instrument 1 according to the first aspect of the present invention has a configuration in which the tail plug 7 is attached to the rear end opening of the shaft tube 5 and the rear end of the ink tank 8 is accommodated inside the tail plug 7. It is possible to prevent the ink tank 8 from falling off due to inadvertent contact. In addition, the ink tank replaceable writing instrument 1 according to the first aspect of the invention makes it easy to remove the ink tank 8 by the configuration in which the rear end portion of the ink tank 8 projects rearward from the rear end opening of the shaft cylinder 5.

Furthermore, the ink tank replaceable writing instrument 1 according to the first invention covers the outer peripheral surface of the rear end portion of the shaft cylinder 5 and the outer peripheral surface of the tail plug 7 with a cylindrical heat-shrinkable film 9, and heats the entire writing instrument. Since the structure is not covered with the shrinkable film 9, the user can make a trial write before purchase, and after the purchase, the ink in the ink tank 8 is completely consumed before the tail plug 7 and the ink tank. It is possible to prevent the ink from leaking to the outside due to inadvertent removal of 8. The outer peripheral surface of the tail plug 7 where the rear end of the heat-shrinkable film 9 is located may be the front end portion outer peripheral surface of the tail plug 7 or the rear end outer peripheral surface of the tail plug 7. In the present invention, the shaft cylinder 5 and the tail plug 7 are detachably attached by means such as screwing, press-fitting, fitting, and engagement.

According to a second invention of the present application, in the first invention, the outer diameter of the rear end of the shaft tube 5 is larger than the outer diameter of the outer peripheral surface of the rear end portion of the shaft tube 5 where the front end of the heat-shrinkable film 9 is located. The requirement is that the outer diameter of the front end of the tail plug 7 is set larger than the outer diameter of the outer peripheral surface of the tail plug 7 where the rear end of the heat-shrinkable film 9 is located (Claim 2). To do.

In the ink tank replaceable writing instrument 1 according to the second invention, the outer diameter of the rear end of the shaft cylinder 5 is larger than the outer diameter of the outer peripheral surface of the rear end portion of the shaft cylinder 5 where the front end of the heat-shrinkable film 9 is located. By setting, the rearward movement of the heat-shrinkable film 9 can be prevented. Further, in the ink tank replaceable writing instrument 1 of the second invention, the outer diameter of the front end of the tail plug 7 is set larger than the outer diameter of the outer peripheral surface of the tail plug 7 where the rear end of the heat-shrinkable film 9 is located. As a result, the forward movement of the heat-shrinkable film 9 can be prevented. That is, the ink tank replaceable writing instrument 1 according to the second invention is such that the heat-shrinkable film 9 in the covering state on the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7 moves back and forth. The heat shrinkable film 9 can be prevented from falling off the rear end portion of the shaft tube 5 and the tail plug 7. In the present invention, the outer diameter of the outer peripheral surface of the rear end portion of the shaft cylinder 5 and the outer diameter of the outer peripheral surface of the tail plug 7 include a plurality of protrusions (including ribs) distributed in the circumferential direction on the outer peripheral surface. ) Is the diameter of the circumscribed circle of the protrusion.

According to a third invention of the present application, in the second invention, the protrusions 73 and 74 that are discontinuous in the circumferential direction are provided on the outer peripheral surface of the rear end portion of the shaft tube 5 or the outer peripheral surface of the tail plug 7. Is covered with a heat shrinkable film 9 (Claim 3).

The ink tank replaceable writing instrument 1 according to the third aspect of the present invention is provided with protrusions 73 and 74 that are discontinuous in the circumferential direction on the outer peripheral surface of the rear end portion of the barrel 5 or the outer peripheral surface of the tail plug 7. By covering with the heat-shrinkable film 9, the circumferentially discontinuous protrusions 73 and 74 bite into the heat-shrinkable film 9, and the heat-shrinkable film 9 is against the shaft tube 5 or the tail plug 7. To prevent idling. In the fifth aspect, discontinuous protrusions in the circumferential direction may be provided on both the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7. The protrusions discontinuous in the circumferential direction are non-annular protrusions, and examples thereof include protrusions or ribs formed at one place in the circumferential direction and a plurality of protrusions or ribs distributed in the circumferential direction.

According to a fourth invention of the present application, in the invention of the third aspect, one of the outer peripheral surface of the rear end portion of the shaft tube 5 or the outer peripheral surface of the tail plug 7 does not include the protrusions 73 and 74, and the protrusion 73. It is a requirement that the outer peripheral surface on the side not provided with 74 and the inner peripheral surface of the heat-shrinkable film 9 are bonded via a thermoplastic adhesive 91 (Claim 4).

The ink tank replaceable writing instrument 1 according to the fourth aspect of the present invention includes an outer peripheral surface of the rear end portion outer peripheral surface of the shaft cylinder 5 or an outer peripheral surface of the tail plug 7 that does not include the protrusions 73 and 74, and heat shrinkability. By bonding between the inner peripheral surface of the film 9 via a thermoplastic adhesive 91, it is possible to prevent the heat-shrinkable film 9 from spinning around the shaft tube 5 or the tail plug 7, As a result, even if the tail plug 7 is to be removed from the shaft tube 5, it cannot be easily removed unless the heat-shrinkable film 9 is broken, and the tail plug 7 can be prevented from being inadvertently removed. In addition, the ink tank replaceable writing instrument 1 according to the fourth aspect of the invention employs the thermoplastic adhesive 91 as the adhesive 91 so that the adhesive 91 is heated by heat-shrinking the heat-shrinkable film 9. The heat-shrinkable film 9 can be properly bonded by being activated. In the fourth invention, the thermoplastic adhesive 91 may be provided between the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7 and the inner peripheral surface of the heat-shrinkable film 9. Good.

According to a fifth invention of the present application, in the first invention, the protrusions 73 and 74 that are discontinuous in the circumferential direction are provided on the outer peripheral surface of the rear end portion of the shaft tube 5 or the outer peripheral surface of the tail plug 7. Is covered with a heat shrinkable film 9 (Claim 5).

The ink tank replaceable writing instrument 1 according to the fifth aspect of the present invention is provided with protrusions 73 and 74 that are discontinuous in the circumferential direction on the outer peripheral surface of the rear end portion of the shaft cylinder 5 or the outer peripheral surface of the tail plug 7. By covering with the heat-shrinkable film 9, the circumferentially discontinuous protrusions 73 and 74 bite into the heat-shrinkable film 9, and the heat-shrinkable film 9 is against the shaft tube 5 or the tail plug 7. To prevent idling. In the fifth aspect, discontinuous protrusions in the circumferential direction may be provided on both the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7.

According to a sixth invention of the present application, in the first invention, a thermoplastic adhesive is provided between the outer peripheral surface of the rear end portion of the shaft tube 5 or the outer peripheral surface of the tail plug 7 and the inner peripheral surface of the heat-shrinkable film 9. It is a requirement to be bonded via the agent 91 (Claim 6).

The ink tank replaceable writing instrument 1 according to the sixth aspect of the present invention has a thermoplastic adhesive 91 between the outer peripheral surface of the rear end portion of the barrel 5 or the outer peripheral surface of the tail plug 7 and the inner peripheral surface of the heat-shrinkable film 9. The heat shrinkable film 9 can be prevented from idling with respect to the shaft tube 5 or the tail plug 7 by adhering via. The ink tank replaceable writing instrument 1 according to the sixth aspect of the invention employs the thermoplastic adhesive 91 as the adhesive 91, so that the adhesive 91 is heated by heat when the heat-shrinkable film 9 is thermally contracted. The heat-shrinkable film 9 can be properly bonded by being activated.

In the sixth invention, both the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7 and the inner peripheral surface of the heat-shrinkable film 9 are bonded via a thermoplastic adhesive 91. It may be configured as follows. Thereby, even if it is going to remove the tail plug 7 with respect to the axial cylinder 5, unless the heat-shrinkable film 9 is fractured | ruptured, it cannot be removed easily and the careless removal of the tail plug 7 can be prevented.

The present invention can prevent the ink tank from dropping off due to a drop impact or inadvertent contact, and the user can make a trial write before purchase, and the ink in the ink tank can be completely removed even after purchase. Before consumption, it is possible to prevent the ink from leaking out due to careless removal of the tail plug and the ink tank.

An ink tank replaceable writing instrument 1 according to an embodiment of the present invention is shown in FIGS.
The ink tank replaceable writing instrument 1 according to this embodiment includes a pen tip 3, an ink occlusion body 4 connected to the rear end of the pen nib 3, and an intermediate member 6 disposed behind the ink occlusion body 4. The ink tank 8 disposed behind the intermediate member 6, the pen tip 3 is held at the front end portion, and the ink storage body 4, the intermediate member 6, and the ink tank 8 front portion are accommodated therein. The shaft tube 5, the tail plug 7 that is removably screwed into the rear end opening of the shaft tube 5, and the heat shrinkability that covers the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7. Film 9. In the present embodiment, the writing instrument body 2 includes a shaft cylinder 5 and a tail plug 7, and the ink tank 8 is accommodated inside the writing instrument body 2 in a replaceable manner.

Pen nib The nib 3 is a rod-like body obtained by resin processing of synthetic resin fibers (for example, polyester fiber, acrylic fiber, nylon fiber, etc.). The front end of the nib 3 is ground like a bullet. The outer peripheral surface of the rear end portion of the nib 3 is chamfered in a tapered shape.

Ink occlusion body The ink occlusion body 4 is made of a processed body of cylindrical synthetic resin fibers (for example, polyester fibers). The rear end of the pen tip 3 is inserted into the axial center of the front end surface of the ink storage body 4, and the rear end of the pen tip 3 is positioned in front of the ink storage body 4. In the present invention, instead of providing the ink occlusion body 4, comb-like ink that temporarily holds overflow ink corresponding to an increase in the internal pressure of the ink tank 8 between the nib 3 and the ink tank 8. A retaining member may be provided.

The shaft cylinder 5 is a cylindrical body obtained by injection molding of a synthetic resin (for example, polypropylene, polyethylene, etc.). An outer peripheral surface of the pen tip 3 is held at the tapered front end portion of the shaft tube 5, and a female screw portion 51 is formed on the inner peripheral surface of the rear end opening of the shaft tube 5. The outer peripheral surface of the rear end portion of the shaft tube 5 is a tapered surface whose outer diameter gradually increases toward the rear. That is, the outer diameter of the rear end of the shaft tube 5 is set larger than the outer diameter of the outer peripheral surface of the rear end portion of the shaft tube 5 where the front end of the heat-shrinkable film 9 is located.

Intermediate member The intermediate member 6 is obtained by injection molding of a synthetic resin (for example, polypropylene, polyethylene, etc.). The intermediate member 6 includes a partition wall 61 that partitions the ink storage body 4 and the ink tank 8, and a plurality of intermediate members that protrude forward from the front surface of the partition wall 61 and are pierced and connected to the inside of the ink storage body 4 (specifically 2) connecting pipes 62, a connecting pipe 63 protruding rearward from the rear surface of the partition wall 61 and inserted into the front end opening of the ink tank 8, and forward of the front surface of the partition wall 61 or the partition wall 61. And an attachment cylinder portion 64 that protrudes rearward from the rear surface and is fixed to the inner surface of the shaft tube 5 (inner surface of the main body). The connecting pipe 63 is integrally formed with a protruding piece 63a for pressing one side of the plug 81. On the front surface of the partition wall 61, a regulating wall portion 61a made of a plate-like rib is integrally formed. The restriction wall portion 61 a comes into contact with the rear end surface of the ink storage body 44.

Ink tank The ink tank 8 is a bottomed cylindrical body having a front end opened and a rear end closed, and is obtained by injection molding or blow molding of a transparent or translucent synthetic resin (for example, polypropylene). Ink is directly stored in the ink tank 8. Specifically, the ink stored in the ink tank 8 is ink for writing instruments (for example, water-based ink, oil-based ink) or coating liquid (for example, cosmetic liquid, correction liquid, adhesive, paint, liquid medicine, etc.). Is mentioned.

The outer surface of the connecting pipe 63 of the intermediate member 6 is detachably fitted to the inner surface of the front end opening of the ink tank 8. When ink in the ink tank 8 is consumed and writing becomes impossible, the ink tank 8 is removed from the connection pipe 63 and a new ink tank 8 filled with ink is removed from the rear end opening of the shaft cylinder 5. The connecting pipe 63 is inserted into the front end opening of the new ink tank 8. Thereby, writing becomes possible again. The front end opening of the new ink tank 8 is closed by a plug 81 before the connection pipe 63 is inserted. When the connecting pipe 63 is inserted into the front end opening of the ink tank 8, the protruding piece 63a of the connecting pipe 63 presses the plug 81 backward, removes the plug 81, and the front end opening of the ink tank 8 opens. It is plugged. In a state where the ink tank 8 is inserted into the shaft cylinder 5, the rear end portion of the ink tank 8 projects rearward from the rear end opening of the shaft cylinder 5.

-Tail plug The tail plug 7 is formed of a bottomed cylindrical body having a front end opened and a rear end closed, and is obtained by injection molding of a transparent or translucent synthetic resin (for example, polypropylene). In a state where the tail plug 7 is attached to the rear end opening of the shaft cylinder 5, the rear end of the ink tank 8 is accommodated in the tail plug 7.

A male screw portion 71 is formed on the front outer peripheral surface of the tail plug 7, and the male screw portion 71 is detachably screwed with a female screw portion 51 on the inner peripheral surface of the rear end opening of the shaft cylinder 5. An annular flange 72 is formed on the outer peripheral surface of the tail plug 7 behind the male screw portion 71. A protrusion 73 (that is, a discontinuous protrusion in the circumferential direction) is formed on a part of the outer peripheral surface of the flange 72. A plurality of (for example, four) ribs 74 (that is, discontinuous protrusions in the circumferential direction) extending in the axial direction are formed at equal intervals on the outer peripheral surface of the tail plug 7 behind the collar portion 72. The outer diameter of the front end of the tail plug 7 (that is, the outer diameter of the flange 72) is the outer diameter of the outer peripheral surface of the tail plug 7 where the rear end of the heat-shrinkable film 9 is located (the outer diameter of the circumscribed circle of the rib 74). Set larger than.

Since the tail plug 7 and the ink tank 8 are made of a transparent or translucent synthetic resin, the inside of the ink tank 8 can be visually recognized from the outside, and the ink color and the remaining amount of ink in the ink tank 8 can be visually confirmed.

The rib 74 prevents slipping when the tail plug 7 is screwed into the shaft cylinder 5. The protrusion 73 has a rolling prevention function and protrudes radially outward from an extension line extending rearward from the outer peripheral surface of the shaft tube 5.

-Heat-shrinkable film The heat-shrinkable film 9 consists of a film made of a cylindrical transparent synthetic resin (for example, polyethylene terephthalate). A thermoplastic adhesive is attached to a part of the inner peripheral surface of the heat-shrinkable film 9. The adhesive is in a solidified state at normal temperature, and is activated by heating when the heat-shrinkable film 9 is heat-shrinked. The heat-shrinkable film 9 covers the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7 (region including the flange portion 72, the protrusion 73, and the rib 74) by heat shrinkage. It is in close contact with the outer peripheral surface of the rear end portion and the outer peripheral surface of the tail plug 7. The outer peripheral surface of the rear end portion of the shaft cylinder 5 is not provided with a discontinuous protrusion in the circumferential direction, and the space between the outer peripheral surface of the rear end portion of the shaft cylinder 5 and the inner peripheral surface of the heat-shrinkable film 9 is thermoplastic. Bonded via an adhesive.

In a state where the heat shrinkable film 9 is covered on the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7, the front end of the heat shrinkable film 9 is positioned on the outer peripheral surface of the rear end portion of the shaft tube 5. The rear end of the heat-shrinkable film 9 is located on the outer peripheral surface of the tail plug 7.

In the embodiment of the present invention, the outer peripheral surface of the rear end portion of the shaft tube 5 and the outer peripheral surface of the tail plug 7 are covered with the cylindrical heat-shrinkable film 9, and the entire writing instrument is not covered with the heat-shrinkable film 9, The user can make a trial write before purchase, and even after purchase, before the ink in the ink tank 8 is completely consumed, the ink leaks to the outside due to inadvertent removal of the tail plug 7 and the ink tank 8. Can be prevented.

In the embodiment of the present invention, the outer diameter of the rear end of the shaft tube 5 is set larger than the outer diameter of the outer peripheral surface of the rear end portion of the shaft tube 5 where the front end of the heat-shrinkable film 9 is located. The outer diameter of the front end of the plug 7 (the outer diameter of the flange 72) is set larger than the outer diameter of the outer peripheral surface of the tail plug 7 where the rear end of the heat-shrinkable film 9 is located (the diameter of the circumscribed circle of the rib 74). Thus, the heat-shrinkable film 9 in a covering state on the outer peripheral surface of the rear end portion of the shaft cylinder 5 and the outer peripheral surface of the tail plug 7 can be prevented from moving back and forth, and the heat-shrinkable film 9 is It can prevent falling off from the rear end and the tail plug 7.

In the embodiment of the present invention, discontinuous protrusions (that is, protrusions 73 and ribs 74) are provided on the outer peripheral surface of the tail plug 7 in the circumferential direction, and the discontinuous protrusions 73 and 74 are covered with the heat-shrinkable film 9. By doing so, it is possible to prevent the protrusions 73 and 74 discontinuous in the circumferential direction from biting the heat-shrinkable film 9 and causing the heat-shrinkable film 9 to idle around the shaft tube 5 or the tail plug 7. .

In the embodiment of the present invention, the heat shrinkability is obtained by adhering between the outer peripheral surface of the rear end portion of the shaft tube 5 and the inner peripheral surface of the heat shrinkable film 9 via a thermoplastic adhesive. The film 9 can be prevented from spinning around the shaft tube 5. As a result, even if the tail plug 7 is removed from the shaft tube 5, it is easily removed unless the heat-shrinkable film 9 is broken. Inadvertent removal of the tail plug 7 can be prevented.

In the embodiment of the present invention, when replacing the ink tank, the tail plug 7 is removed from the rear end portion of the shaft cylinder 5 by loosening the screwed state, and after the ink tank 8 is removed, a new ink tank 8 is attached to the shaft. While being inserted into the cylinder 5, the tail plug 7 is screwed into the rear end portion of the shaft cylinder 5 again.

It is a front view of an embodiment of the invention. It is a longitudinal cross-sectional view of FIG. It is the sectional view on the AA line of FIG. FIG. 3 is a sectional view taken along line B-B in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ink tank exchange-type writing instrument 2 Writing instrument main body 3 Pen tip 4 Ink occlusion body 5 Shaft cylinder 51 Female thread part 6 Intermediate member 61 Bulkhead 61a Restriction wall part 62 Communication pipe 63 Connection pipe 63a Projection piece 64 Mounting cylinder part 7 End plug 71 Male Screw part 72 Hook part 73 Projection 74 Rib 8 Ink tank 81 Plug body 9 Heat-shrinkable film 91 Adhesive

Claims (6)

An ink tank exchangeable writing instrument in which the ink tank can be exchanged inside the writing instrument body, and the writing instrument body is detachably attached to the shaft cylinder having a pen tip at the front end and the rear end opening of the shaft cylinder. The front end of the ink tank is inserted into the shaft cylinder from the rear end opening of the shaft cylinder, and the rear end of the ink tank is rearward of the rear end opening of the shaft cylinder. A tail plug is attached to the rear end opening of the shaft cylinder, the rear end portion of the ink tank is accommodated inside the tail plug, and the outer peripheral surface of the rear end portion of the shaft cylinder and the outer peripheral surface of the tail plug are tubular. The heat-shrinkable film is coated, and the front end of the heat-shrinkable film is positioned on the outer peripheral surface of the rear end of the shaft tube, and the rear end of the heat-shrinkable film is positioned on the outer peripheral surface of the tail plug Ink tank replaceable writing instrument. The outer diameter of the rear end of the shaft tube is set to be larger than the outer diameter of the outer peripheral surface of the rear end portion of the shaft tube where the front end of the heat-shrinkable film is located, and the outer diameter of the front end of the tail plug is heat-shrinkable. The ink tank replaceable writing instrument according to claim 1, which is set to be larger than the outer diameter of the outer peripheral surface of the tail plug where the rear end of the film is located. The ink tank replaceable writing instrument according to claim 2, wherein a discontinuous protrusion in the circumferential direction is provided on the outer peripheral surface of the rear end portion of the shaft tube or the outer surface of the tail plug, and the protrusion is covered with a heat-shrinkable film. Adhesion between the outer peripheral surface of the rear end portion of the shaft tube or the outer peripheral surface of the tail plug without the projection and the inner peripheral surface of the heat-shrinkable film via a thermoplastic adhesive The ink tank replaceable writing instrument according to claim 3. The ink tank replaceable writing instrument according to claim 1, wherein a discontinuous protrusion is provided in the circumferential direction on the outer peripheral surface of the rear end portion of the shaft tube or the outer surface of the tail plug, and the protrusion is covered with a heat-shrinkable film. 2. The ink tank replaceable writing instrument according to claim 1, wherein the outer peripheral surface of the rear end portion of the shaft tube or the outer peripheral surface of the tail plug and the inner peripheral surface of the heat-shrinkable film are bonded via a thermoplastic adhesive. .

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