JP2024094078A - Thermochromic writing implements - Google Patents

Abstract

To provide a thermochromic writing instrument that ensures airtight performance inside the barrel with a small number of parts, allows easy attachment of a friction body, and provides stable friction without the friction body wobbling during friction.
[Solution] The thermochromic writing instrument of the present invention comprises a barrel, a pen tip, an ink occlusion body, thermochromic ink contained in the ink occlusion body, and a friction body that is removably screwed onto the rear of the barrel. The barrel is provided with a female thread portion and a first airtight portion on the inner surface of the rear end. The friction body is provided with a male thread portion that is screwed into the female thread portion, a second airtight portion, and a friction portion. The first airtight portion and the second airtight portion provide an airtight structure for ensuring airtight performance inside the barrel.
[Selected figure] Figure 2

Description

The present invention relates to a thermochromic writing instrument. More specifically, the present invention relates to a thermochromic writing instrument that is equipped with a friction body that can thermally discolor a thermochromic ink mark by rubbing the mark and generating frictional heat.

Patent Document 1 discloses a writing instrument in which a plug is press-fitted and fixed to the inner surface of a cylinder, the plug blocks air circulation inside the cylinder between the front and rear openings, and ink is stored inside the cylinder in front of the plug. A protruding member (friction body) is inserted forward from the rear into the writing instrument as a friction-discoloring member made of an elastic material that rubs thermochromic handwriting and thermally discolors the handwriting with the frictional heat generated.

Patent Document 2 also discloses a thermochromic writing instrument that can reliably block ventilation between the inside and outside of the barrel at the rear end opening of the barrel to which the friction body is attached. In detail, the friction body is composed of a front bulge with an annular outer seal on its outer surface, an engaging recess connected to the rear of the front bulge, and a rear bulge connected to the rear of the engaging recess, and the engaging protrusion on the barrel engages with the engaging recess on the friction body, causing the rear bulge to protrude rearward from the rear end of the barrel, and fitting the outer seal and inner seal airtightly. This blocks ventilation between the inside and outside of the barrel at the rear end opening of the barrel.

JP 2010-6055 A JP 2011-79206 A

In the technology disclosed in Patent Document 1, a plug is press-fitted and fixed to the inner surface of the cylinder, and the plug can reliably block air circulation inside the cylinder between the front and rear openings. However, two parts, the plug and the friction body, are provided at the rear end of the barrel, and reducing the number of parts to improve productivity was an issue.

In addition, with the technology disclosed in Patent Document 2, a large force is required when the rear bulge of the friction body overcomes the engaging protrusion on the inner surface of the rear end opening of the barrel from the front to the rear, which may make assembly difficult. Also, if the dimensions are set so that a large force is not required to overcome from the front to the rear, the friction body may wobble and may not provide stable, appropriate friction.

The present invention was made in light of the above findings, and aims to provide a thermochromic writing instrument that realizes a configuration that can reliably block ventilation inside the barrel with a small number of parts, that allows the friction body to be easily attached, and that provides stable and appropriate friction without the friction body wobbling during friction. In the present invention, "front" refers to the pen tip side, and "rear" refers to the opposite side.

The present invention is a thermochromic writing instrument comprising a barrel, a nib provided at the front end of the barrel, an ink occlusion body connected to the nib and housed inside the barrel, thermochromic ink housed in the ink occlusion body, and a friction body removably screwed into the rear of the barrel, the barrel having a female threaded portion and a first airtight portion on the inner surface of the rear end, the friction body having a male threaded portion that screws into the female threaded portion, a second airtight portion, and a friction portion that rubs the handwriting of the thermochromic ink and can thermally discolor the handwriting of the thermochromic ink with the frictional heat generated at that time, and an airtight structure is provided for maintaining airtightness between the barrel and the friction body by the first airtight portion and the second airtight portion.

According to the present invention, a friction body is provided that is detachably screwed from the rear of the barrel, and an airtight structure is provided to maintain airtightness between the barrel and the friction body by a first airtight section and a second airtight section. This allows for a configuration that can reliably block airflow inside the barrel with a small number of parts, and the friction body can be easily attached, so that the friction body does not wobble during friction and provides stable, appropriate friction.

Preferably, the friction body is formed integrally with the friction portion, the male thread portion, and the second airtight portion, which are made of a material different from that of the friction portion, by two-color molding.

In this case, the friction part, the male thread part made of a material different from that of the friction part, and the second airtight part are made of materials suitable for each part, so that the desired friction performance can be obtained, and reliable screwing performance and airtight structure can be obtained. In addition, the friction part, the male thread part made of a material different from that of the friction part, and the second airtight part are integrally formed by two-color molding, so that it is possible to further prevent the friction body from wobbling during friction.

Preferably, the first airtight portion is an inwardly facing smooth surface, and the second airtight portion is an outwardly facing annular protrusion. In this case, the first airtight portion and the second airtight portion are in line contact, and a local force is applied to the contact portion of the outwardly facing annular protrusion, which is suitable for obtaining reliable airtight performance.

Preferably, a slit is provided on the outer surface of the friction body, or a through hole is provided that communicates with the inside of the friction body in the axial direction. In this case, the air inside the barrel is not compressed when the friction body is attached, which improves assembly.

Preferably, when the friction body is screwed into the barrel, the front end of the friction part is located forward of the rear end of the barrel. In this case, the boundary of the two-color molding is hidden inside the barrel, making it possible to realize a friction part with excellent aesthetics.

In addition, preferably, the friction body has a flange at the front end of the friction part, and the front end of the flange abuts against the rear end of the barrel when the friction body is screwed onto the barrel. In this case, the outer diameter of the rear end of the barrel and the maximum outer diameter of the friction part (outer diameter of the flange) can be made to be approximately the same dimension, so that a shape with almost no steps from the rear end of the barrel to the friction part can be achieved, and the area around the friction part can be made to have an excellent aesthetic appearance.

The present invention realizes a configuration that can reliably block ventilation inside the barrel using a small number of parts, and also allows the friction body to be easily attached, so that the friction body does not wobble during friction and can provide stable and appropriate friction.

1 is a schematic front view showing a thermochromic writing instrument of the present invention. 1 is an enlarged longitudinal sectional view of a main portion of a thermochromic writing instrument according to a first embodiment of the present invention. FIG. FIG. 2 is a perspective view of a friction body according to the first embodiment of the present invention. FIG. 5 is an enlarged longitudinal sectional view of a main portion of a thermochromic writing instrument according to a second embodiment of the present invention. FIG. 11 is a perspective view of a friction body according to a second embodiment of the present invention. FIG. 11 is an enlarged longitudinal sectional view of a main portion of a thermochromic writing instrument according to a third embodiment of the present invention. FIG. 11 is a perspective view of a friction body according to a third embodiment of the present invention. FIG. 11 is an enlarged longitudinal sectional view of a main portion of a thermochromic writing instrument according to a fourth embodiment of the present invention. FIG. 13 is a perspective view of a friction body according to a fourth embodiment of the present invention.

Four embodiments of the present invention will be described below with reference to the drawings.

<First embodiment>

A thermochromic writing instrument 1 according to a first embodiment of the present invention is shown in Figs. 1 to 3. As shown in Fig. 1, the thermochromic writing instrument 1 according to this embodiment comprises a barrel 3, a nib 4 provided at the front end of the barrel 3, an ink absorbing body 5 connected to the nib 4 and housed inside the barrel, thermochromic ink housed in the ink absorbing body 5, a friction body 2 removably screwed onto the rear of the barrel 3, and a cap (not shown) removably attached to the outer surface of the barrel 3 on the nib 4 side.

As shown in Fig. 1, the barrel 3 includes a cylindrical front axle 3a and a cylindrical rear axle 3b attached to the rear outer surface of the front axle 3a. The front axle 3a and the rear axle 3b are obtained from a molded body of synthetic resin (e.g., polypropylene, etc.). Examples of the structure in which the rear axle 3b is attached to the rear outer surface of the front axle 3a include a climbing-over fitting in which a protrusion on the outer surface of the front axle 3a climbs over a protrusion on the inner surface of the rear axle 3b, a concave-convex fitting in which a concave on the outer surface of the front axle 3a fits over a convex on the inner surface of the rear axle 3b, a press-fit fitting in which the outer surface of the front axle 3a and the inner surface of the rear axle 3b are pressed together, and a screw fitting in which a male screw portion on the outer surface of the front axle 3a and a female screw portion on the inner surface of the rear axle 3b are screwed together.

Front Shaft As shown in FIG. 1, the front barrel 3a comprises a tapered portion to which the pen tip 4 is fixed, a cylindrical front tube portion connected integrally to the rear of the tapered portion, a disk-shaped flange portion connected integrally to the rear end of the front tube portion so as to protrude radially outward, and a cylindrical rear tube portion (not shown) connected integrally to the rear of the flange portion.

The front end of the front shaft 3a is formed with a tapered section that narrows in diameter as it moves forward. A nib attachment hole is provided axially through the tapered section of the front shaft 3a. The nib 4 is press-fitted and fixed into the nib attachment hole. An ink occluder 5 is housed inside the front shaft 3a, and the front end of the ink occluder 5 is connected to the rear end of the nib 4.

Rear axle As shown in Figure 1, the rear axle 3b has an outer surface that tapers toward the rear. The rear axle 3b is open at both ends and has an inner hole that penetrates in the axial direction. The friction body 2 is inserted into the rear end opening of the rear axle 3b. The front inner surface of the rear axle 3b and the outer surface of the rear cylinder part of the front axle 3a are airtightly fitted together. A decorative portion is provided on the outer surface of the rear axle 3b by transfer printing.

As shown in FIG. 2, the barrel 3 (rear barrel 3b) has a female thread 31 and a first airtight portion on the inner surface of the rear end. The friction body 2 can be screwed to the female thread 31. The first airtight portion has an inwardly smooth surface, and the first airtight portion and the second airtight portion 23 of the friction body 2 provide an airtight structure for maintaining airtightness between the barrel 3 and the friction body 2.

As shown in FIG. 2, the barrel 3 (rear barrel 3b) has an abutment portion 33 that abuts against the abutment portion 24 of the friction body 2, which will be described later. In this embodiment, the abutment portion 33 is a flat surface that is perpendicular to the axial direction and is provided in front of the female thread portion 31 and behind the first airtight portion.

Pen tip The pen tip 4 is a resin-processed body of a synthetic resin (e.g., polyester) fiber bundle. The front end of the pen tip 4 is formed in a chisel shape. The rear end of the pen tip 4 has a tapered surface that narrows in diameter toward the rear. The rear end of the pen tip 4 is pierced and connected to the front end of the ink occlusion body 5.

Other examples of the pen tip 4 include a ballpoint pen tip in which a ball is rotatably held at the front end, a pen body made of a porous synthetic resin with continuous pores, a plastic pen body made by extrusion molding of a synthetic resin with an axial ink lead-out passage, and a calligraphy pen body. An ink guide member may be interposed between the pen tip 4 and the ink occlusion body 5, or the pen tip 4 and the ink occlusion body 5 may be directly connected.

Ink Occluder The ink occluder 5 is made of a synthetic resin fiber bundle (e.g., polyester fiber bundle) and a cylindrical outer skin surrounding the outer periphery. The outer skin is made of a synthetic resin cylinder (e.g., an extrusion molded body of polypropylene resin). In this embodiment, the ink occluder 5 is impregnated with a thermochromic ink.

Ink In this embodiment, the ink contained in the ink occlusion body 5 is a thermochromic ink. The thermochromic ink is preferably a reversible thermochromic ink. The reversible thermochromic ink may be of various types, such as a thermal decolorization type that is decolorized by heating from a colored state, a color memory retention type that alternately retains a colored state or a decolored state in a specific temperature range, or a thermal color development type that is colored by heating from a decolored state and returns to the decolored state by cooling from the colored state, either alone or in combination.

As a coloring material contained in the reversible thermochromic ink, for example, a reversible thermochromic pigment in which a reversible thermochromic composition containing at least the three essential components of (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the reaction (coloring reaction) in which the two chemically bind together occurs is encapsulated in a microcapsule is preferably used.

Friction Body As shown in Figs. 2 and 3, the friction body 2 of this embodiment includes a cylindrical small diameter portion, a friction portion 21 having a convex curved surface and integrally connected to the rear of the small diameter portion, a male thread portion 22 formed on the small diameter portion, a second airtight portion 23 formed in front of the male thread portion 22, a contact portion 24 that contacts the abutted portion 33 of the barrel 3, and a ventilation portion communicating in the axial direction.

The male threaded portion 22 is screwed into the female threaded portion 31 of the rear axle 3b, thereby allowing the friction body 2 to be detachably attached to the barrel 3. The second airtight portion 23 is an outward annular protrusion that protrudes radially outward. The first airtight portion 32, which is made of the inwardly smooth surface described above, and the second airtight portion 23, which is the outward annular protrusion, provide an airtight structure for maintaining airtightness between the barrel 3 and the friction body 2.

The second airtight portion 23 may also be an outwardly facing smooth surface. In this case, it is preferable that the first airtight portion 32 is an inwardly facing annular protrusion. In addition, when the second airtight portion 23 is an outwardly facing smooth surface, the first airtight portion 32 may also be an inwardly facing smooth surface.

In addition, in this embodiment, the abutment portion 24 is a plane that is provided in front of the male thread portion 22 and behind the second airtight portion 23 and is perpendicular to the axial direction.

The friction portion 21 rubs the mark of thermochromic ink, and the frictional heat generated during the friction can thermally discolor the mark of thermochromic ink. The friction portion 21 protrudes rearward from the rear end of the rear barrel 3b. The maximum outer diameter of the portion (friction portion 21) protruding rearward from the rear end of the rear barrel 3b is set to be equal to or smaller than the outer diameter of the rear end of the rear barrel 3b.

In this embodiment, the material constituting the friction body 2 is preferably a synthetic resin (rubber, elastomer) having elasticity, such as silicone resin, SBS resin (styrene-butadiene-styrene copolymer), SEBS resin (styrene-ethylene-butylene-styrene copolymer), fluorine-based resin, chloroprene resin, nitrile resin, polyester-based resin, ethylene propylene diene rubber (EPDM), a mixture of two or more rubber elastic materials, and a mixture of a rubber elastic material and a synthetic resin. The synthetic resin having elasticity constituting the friction body 2 is not a highly abrasive elastic material (e.g., eraser, etc.), but a low-abrasive elastic material that generates almost no abrasion debris (eraser debris) during friction. The friction body 2 can be combined with a writing implement and a friction implement that is a separate member of any shape to obtain a writing implement set, but providing the friction body 2 to the writing implement makes it highly portable.

The friction body 2 may be formed from a mixture of polypropylene resin and a styrene-based thermoplastic elastomer, or a mixture of polypropylene resin and a polypropylene-based thermoplastic elastomer. The blending ratio of the mixture is 1:1 to 1:4 by weight, and the material does not contain abrasives, plasticizers, or fillers, and has a durometer hardness type A of 70 to 100 as specified in JIS K6251. The friction body 2 is formed from a low-wear elastic material that does not contain plasticizers and has a pencil line erasing ability (erasing rate) of 70% or less as specified in JIS S 6050-2002. As a result, the friction body 2 is effective because it is less likely to produce eraser shavings when rubbed and has excellent thermal discoloration resistance.

The friction body 2 is made of a low-wear elastic material that produces almost no wear debris (eraser debris) when rubbed, but depending on the type or condition of the rubbing surface or the method of rubbing, it may gradually wear down or become damaged. A worn or damaged friction body 2 cannot provide appropriate friction, and it may become difficult to rub the thermochromic ink marks and thermally discolor the thermochromic ink marks with the frictional heat generated during the process.

In addition, if there is handwriting written with a pencil or the like on the friction surface of the friction body 2, or if the friction surface is dirty, pencil lead residue or dirt may be transferred to the friction body 2, causing the friction body 2 to become dirty. If the friction body 2 is dirty, when another paper surface or the like is rubbed, the dirt or the like that has adhered to the friction body 2 may be transferred to the paper surface, causing the paper surface to become dirty.

If the friction body 2 becomes worn, damaged, or soiled, it is possible to provide appropriate friction again by replacing the worn, damaged, or soiled friction body 2 with a new friction body 2. The friction body 2 of this embodiment is attached detachably by screwing, so it can be easily replaced with a new friction body 2.

The friction body 2 of this embodiment may have a rotation operation part formed of a two-sided width part or a knurled part on the outer surface of the friction part 21. By rotating the rotation operation part, the screwed state between the shaft tube 3 and the friction body 2 can be easily released, making it easier to attach and detach the shaft tube 3 and the friction body 2. Examples of the rotation operation part include a two-sided width part such as a hexagon or octagon that can be hung with a wrench, or a knurled part.

As shown in Figs. 2 and 3, in this embodiment, a slit penetrating the outer surface of the friction body 2 in the axial direction is provided as a ventilation part. Note that the ventilation part 25 may be a through hole that communicates with the inside of the friction body 2 in the axial direction, other than a slit.

As shown in Figures 2 and 3, the friction body 2 of this embodiment is formed by two-color molding of the friction part 21 and the small diameter part (male thread part 22 and second airtight part 23) made of a material different from that of the friction part 21. In this embodiment, the front end of the friction part 21 is located forward of the rear end of the barrel 3 when the friction body 2 is screwed into the barrel 3.

In addition, in this embodiment, the friction body 2 has an inner hole that opens forward, located at the axis. This allows the thickness of the small diameter portion (the male thread portion 22 and the second airtight portion 23) to be reduced, preventing the shape from becoming unstable due to molding sink marks.

The thermochromic writing instrument 1 configured as above functions as follows.

According to the thermochromic writing instrument 1 of this embodiment, the friction body 2 is screwed from the rear of the barrel 3, so that the friction body 2 can be easily and firmly attached to the barrel 3, and the friction body 2 does not wobble during friction, allowing for stable and appropriate friction.

In addition, the first airtight part 32 and the second airtight part 23 provide airtight performance between the barrel 3 and the friction body 2. In other words, no additional parts are required to provide airtight performance between the inside and outside of the barrel 3, and the thermochromic writing instrument 1 can be constructed with a small number of parts.

In addition, since the first airtight portion 32 is an inwardly facing smooth surface and the second airtight portion 23 is an outwardly facing annular protrusion, the first airtight portion 32 and the second airtight portion 23 are in line contact, and localized force is applied to the contact portion of the outwardly facing annular protrusion, which is suitable for obtaining reliable airtight performance.

In addition, the friction body 2 is formed by two-color molding of the friction part 21 and the small diameter part (male thread part 22 and second airtight part 23) made of a different material from the friction part 21, which are integrally formed. As a result, the friction part 21 and the small diameter part (male thread part 22 and second airtight part 23) made of a different material from the friction part 21 are formed of materials suitable for each part, and it is possible to obtain the desired friction performance, as well as reliable screwing performance and an airtight structure. It also has the effect of increasing the rigidity of the friction body 2, which prevents the friction body 2 from wobbling during friction and allows for more stable and appropriate friction.

As for the material suitable for each part, for the friction body 2, the soft material synthetic resin (rubber, elastomer) described above is particularly preferable. Also, for the small diameter part (male thread part 22 and second airtight part 23), it is preferable to form it from a hard material synthetic resin (particularly polypropylene) in order to obtain an airtight structure that maintains airtightness more reliably.

In addition, when the friction body 2 is screwed into the barrel 3, the front end of the friction part 21 is positioned forward of the rear end of the barrel 3, so that the boundary of the two-color molding is hidden inside the barrel 3. This makes it possible to realize a friction part 21 with excellent aesthetics.

When the friction body 2 is attached, the abutted portion 33 and the abutting portion 24 come into contact with each other, which functions as a stopper when the friction body 2 is screwed together, making it possible to screw it together without loosening. In addition, the amount of protrusion of the friction body 2 from the shaft tube 3 is always constant, making it possible to easily and stably assemble it.

In addition, a slit penetrating in the axial direction is provided on the outer surface of the friction body 2 as a ventilation section 25. This allows the air inside the shaft tube 3 to escape to the outside through the ventilation section 25 when the friction body 2 is attached. Therefore, the air inside the shaft tube 3 is not compressed, improving the ease of assembly.

This also makes it possible to use the slit as a rotation operating part, and as mentioned above, the threaded engagement between the barrel 3 and the friction body 2 can be easily released, making it easier to attach and detach the barrel 3 and the friction body 2.

As described above, the thermochromic writing instrument 1 of this embodiment realizes a configuration that can reliably block ventilation inside the barrel 3 with a small number of parts, and the friction body 2 can be easily attached, so that the friction body 2 does not wobble during friction and can provide stable and appropriate friction.

Second Embodiment
4 and 5 show a second embodiment of the present invention. This is a modification of the first embodiment, and differs from the first embodiment in the shapes of the contact portion 24 and the contacted portion 33. The other configurations and effects are the same as those of the first embodiment, so a description thereof will be omitted.

As shown in Figures 4 and 5, in this embodiment, the abutment portion 33 of the shaft tube 3 is provided in front of the female thread portion 31 and behind the first airtight portion 32, and is a truncated cone surface tapered toward the axial front. The abutment portion 24 of the friction body 2 is provided in front of the male thread portion 22 and behind the second airtight portion 23, and is a truncated cone surface tapered toward the axial front.

As a result, the truncated cone surfaces of the abutting portion 24 and the abutted portion 33 bite into each other as they are screwed together, allowing the friction body 2 to be screwed together more firmly. In addition, the friction body 2 does not wobble during friction, allowing for more stable and appropriate friction.

In addition, as the abutting portion 24 and the abutted portion 33 are screwed together, the truncated cone surfaces of the abutting portion 24 and the abutted portion 33 bite into each other, resulting in an airtight structure between the abutting portion 24 and the abutted portion 33. In other words, in addition to the airtight structure between the first airtight portion 32 and the second airtight portion 23, an airtight structure can also be provided between the abutting portion 24 and the abutted portion 33, which is suitable for obtaining more reliable airtight performance.

Third Embodiment
6 and 7 show a third embodiment of the present invention. This is a modification of the first embodiment, and differs from the first embodiment in the positions of the contact portion 24 and the contacted portion 33. The other configurations and effects are the same as those of the first embodiment, so a description thereof will be omitted.

As shown in Figures 6 and 7, in this embodiment, the abutted portion 33 of the barrel 3 is the rear end surface of the barrel 3. The abutting portion 24 of the friction body 2 is a flat surface that is provided in front of the friction portion 21 and behind the male threaded portion 22, and is perpendicular to the axial direction. In detail, a flange portion is provided behind the male threaded portion 22, and the front end surface of the flange portion is the abutting portion 24 in this embodiment.

This allows the outer diameter of the rear end of the barrel 3 and the maximum outer diameter of the friction part 21 (outer diameter of the flange) to be approximately the same dimension, making it possible to create a shape with almost no steps from the rear end of the barrel 3 to the friction part 21, and achieving an area around the friction part with excellent aesthetics.

Fourth Embodiment
8 and 9 show a fourth embodiment of the present invention. This is a modified example of the second embodiment, and differs from the second embodiment in three points. The first point is that a part (plug body 6) is provided to obtain airtight performance between the inside and outside of the barrel 3. The second point is that the friction body 2 does not include the second airtight portion 23. The third point is the shape of the ventilation portion 25. The other configurations and effects are the same as those of the second embodiment, so a description thereof will be omitted.

The thermochromic writing instrument 1 of this embodiment is provided with a plug 6 on the inner surface of the barrel 3 to obtain airtight performance between the inside and outside of the barrel 3. By providing airtight sections on the outer surface of the plug 6 and the inner surface of the barrel 3, an airtight structure can be obtained. Therefore, an airtight section (second airtight section 23) is not required for the friction body 2.

In detail, as shown in FIG. 8, an annular seal and a locking wall located behind the annular seal are integrally formed on the inner surface of the rear part of the rear axle 3b. The annular seal and the outer surface of the plug 6 are airtightly fitted together in the radial direction, and the locking wall and the rear end of the plug 6 are in axial contact.

However, even in this embodiment in which the plug body 6 is provided, the friction body 2 may be provided with a second airtight portion 23. This allows more reliable airtight performance to be obtained. Also, as shown in FIG. 8, the front surface of the plug body 6 functions as a filling abutment portion against which the filling abuts.

In this embodiment, the ventilation portion 25 is a through hole located at the axis of the friction body 2. The associated action and effect are the same as those of the above-described embodiments 1 to 3. Note that, in this embodiment, the ventilation portion may also be a slit that penetrates the outer surface of the friction body 2 in the axial direction.

Reference Signs List 1 Thermochromic writing implement 2 Friction body 21 Friction portion 22 Male thread portion 23 Second airtight portion 24 Contact portion 25 Ventilation portion 3 Barrel tube 3a Front barrel 3b Rear barrel 31 Female thread portion 32 First airtight portion 33 Contact portion 4 Pen tip 5 Ink occluding body 6 Plug

Claims (6)

A shaft cylinder,
a pen tip provided at a front end of the barrel;
an ink occlusion body connected to the pen tip and housed inside the barrel;
a thermochromic ink contained in the ink occlusion body;
a friction body that is detachably screwed to the rear of the barrel,
The barrel has an internal thread portion and a first airtight portion on an inner surface of a rear end thereof,
the friction body includes a male screw portion that is screwed into the female screw portion, a second airtight portion, and a friction portion that rubs the handwritten mark of the thermochromic ink and can thermally discolor the handwritten mark of the thermochromic ink by frictional heat generated at the time,
A thermochromic writing instrument, in which an airtight structure is provided by the first airtight portion and the second airtight portion to maintain airtightness between the barrel and the friction body. 2. The thermochromic writing instrument according to claim 1, wherein the friction body is formed by two-color molding, integrally with the friction portion, the male screw portion and the second airtight portion, which are made of a material different from that of the friction portion. 3. The thermochromic writing implement according to claim 2, wherein the first airtight portion is an inwardly facing smooth surface, and the second airtight portion is an outwardly facing annular protrusion. 4. The thermochromic writing implement according to claim 3, wherein a slit is provided on the outer surface of the friction body, or a through hole is provided which communicates with the inside of the friction body in the axial direction. 5. The thermochromic writing instrument according to claim 1, wherein a front end of the friction portion is located forward of a rear end of the barrel when the friction body is screwed into the barrel. The friction body includes a flange portion at a front end of the friction portion,
5. The thermochromic writing implement according to claim 1, wherein the front end of the flange abuts against the rear end of the barrel when the friction body is screwed onto the barrel.