Notebook

Abstract

To provide a writing instrument that maintains its fitting force even after repeated attachment and detachment of the barrel and cap, and that suppresses wobbling between the barrel and cap over a long period of time. [Solution] The writing instrument 1 comprises a barrel 2 and a cap 7. On the inner surface of the cap 7, a first inward projection 71, a second inward projection 72, and a third inward projection 73 are provided at different positions in the axial direction. When the cap 7 is attached to the front of the barrel 2, the first inward projection 71 fits into the barrel 2, the second inward projection 72 is close to or in contact with the barrel 2, and the third inward projection 73 is not in contact with the barrel 2. When the cap 7 is attached to the rear of the barrel 2, the first inward projection 71 and the second inward projection 72 are not in contact with the barrel 2, and the third inward projection 73 fits into the barrel 2.

Description

Technical Field

[0001] The present invention relates to a writing instrument having caps that are detachable from both ends of a barrel.

Background Art

[0002] In Patent Document 1, in a writing instrument in which caps 8 are detachable from both ends of a shaft body 4, on the back side of a first protrusion 8b for fitting formed at the opening end of the cap 8, a second protrusion 8d having an inscribed circle diameter substantially equal to or smaller than the inscribed circle diameter of the first protrusion 8b is formed, so that a writing instrument with less wobbling when attaching and detaching the cap 8 to the shaft body 4 is described.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the cap 8 is attached to the front of the shaft body 4, the first protrusion 8b gets over the circumferential rib 2a and the cap 8 and the shaft body 4 are fitted together. When the cap 8 is attached to the rear of the shaft body 4, the first protrusion 8b and the rear part of the shaft body 4 are fitted together, and the second protrusion 8d and the outer peripheral surface of the shaft body 4 come into contact or abut.

[0005] That is, in the writing instrument disclosed in Patent Document 1, in both cases where the cap 8 is attached to the front of the shaft body 4 and where the cap 8 is attached to the rear of the shaft body 4, since the first protrusion 8b and the shaft body 4 are fitted together, by attaching and detaching the cap 8 to the front and rear of the shaft body 4, the first protrusion 8b may be worn, and the fitting force between the first protrusion 8b and the shaft body 4 may decrease.

[0006] Furthermore, even when the cap 8 is attached to the front of the shaft 4, there is a risk that the second projection 8d and the shaft 4 will come into contact. In such cases, whether the cap 8 is attached to the front of the shaft 4 or to the rear of the shaft 4, the second projection 8d and the shaft 4 are fitted together, so attaching and detaching the cap 8 to the front and rear of the shaft 4 may cause wear on the second projection 8d, and the second projection 8d may no longer be able to prevent the shaft 4 and the cap 8 from wobbling.

[0007] Furthermore, since the first protrusion 8b is formed at the open end of the cap 8, when the cap 8 is attached to the rear of the shaft 4, the first protrusion 8b may engage with the vicinity of the axial center of the rear shaft 3, potentially scratching the outer surface of the rear shaft 3. If the vicinity of the axial center of the rear shaft 3 is scratched, the scratch will be noticeable.

[0008] The present invention aims to solve the aforementioned problems of the conventional method, and provides a writing instrument equipped with detachable caps at both ends of the barrel, in which the fitting force between the barrel and the cap is maintained even after repeated attachment and detachment of the barrel and the cap, and which can suppress wobbling between the barrel and the cap when the cap is attached to the barrel over a long period of time. In this invention, in the writing instrument, "front" refers to the pen tip side, and "rear" refers to the opposite side. In the cap, "rear" refers to the open end side, and "front" refers to the opposite side. [Means for solving the problem]

[0009] The writing instrument of the first invention of this application comprises a barrel and a cylindrical cap with one end open, wherein a pen tip is provided at one end of the barrel, the cap is detachable from both ends of the barrel, and the inner surface of the cap is provided with a first inward projection, a second inward projection, and a third inward projection, each at different positions in the axial direction. When the cap is attached to the tip end of the barrel, the first inward projection and the barrel are fitted together, the second inward projection and the barrel are close to or in contact with each other, and the third inward projection and the barrel are not in contact. When the cap is attached to the end of the barrel opposite to the pen tip, the first inward projection and the second inward projection are in a non-contact state with the barrel, and the third inward projection is fitted with the barrel.

[0010] The first invention of this application, with the above configuration, allows the cap to be supported at two points, the first inward projection and the second inward projection, when the cap is attached to the front of the barrel, thereby suppressing wobbling between the barrel and the cap. Furthermore, when the cap is attached to the front of the barrel, the third inward projection does not interfere with the barrel, and when the cap is attached to the rear of the barrel, the first and second inward projections do not interfere with the barrel, thus suppressing wear on the first, second, and third inward projections and maintaining the fitting force between the barrel and the cap. Moreover, wobbling between the barrel and the cap can be suppressed over a long period of time.

[0011] The writing instrument of the second invention of the present application is provided in the first invention, wherein the outer surface of the barrel on the pen tip side is provided with an outward projection that overcomes the first inward projection and engages with the first inward projection, and a support portion that is close to or in contact with the second inward projection. The outer surface of the barrel opposite to the pen tip is provided with an annular smooth surface that presses against and fits with the third inward projection.

[0012] The second invention of this application allows the cap to be securely attached to the front of the barrel with the above configuration. Furthermore, it can reliably suppress any wobbling of the cap relative to the barrel when the cap is attached to the front of the barrel. Moreover, it allows the cap to be securely attached to the rear of the barrel.

[0013] The writing instrument of the third invention of this application is characterized in that, in either the first or second invention, the support portion is made from the annular, smooth outer surface of the barrel, and the second inward projection is a group of multiple projections arranged circumferentially at equal intervals.

[0014] The third invention of this application, with the above configuration, can absorb radial variations in the outer diameter of the support portion and the height of the second inward projection. Furthermore, because the outer surface of the barrel is smooth, it does not impair the grip feel or design when holding the writing instrument.

[0015] The fourth invention of this application is characterized in that, in any of the first to third inventions, the first inward projection, the second inward projection, and the third inward projection are arranged in the order of the first inward projection, the second inward projection, and the third inward projection in the order of the first inward projection, the second inward projection, and the third inward projection is greater than the inscribed circle diameter of the first inward projection and the third inward projection.

[0016] The writing instrument of the fourth invention of this application, with the above configuration, makes it easy to control the axial position of the outward projection that engages with the first inward projection when the cap is attached to the front of the barrel. Furthermore, when the cap is attached to the rear of the barrel, the barrel engages with the third inward projection located at the innermost part of the cap, allowing the barrel to be inserted all the way into the cap, thus keeping the overall length of the barrel and cap together short.

[0017] Furthermore, because the inscribed circle diameters of the first, second, and third inward-facing projections are different, it is possible to avoid the first, second, and third inward-facing projections always fitting into the shaft cylinder at the same time. Note that the inscribed circle diameter refers to the diameter of the smallest inscribed circle of the inward-facing projection.

[0018] The fifth invention of this application is characterized in that, in the first to fourth inventions, a locking portion is provided on the inner surface of the cap, which contacts the end of the barrel when the cap is attached to the end of the barrel opposite to the pen tip.

[0019] In the writing instrument of the fifth invention of this application, with the above configuration, when the cap is attached to the rear of the barrel, the locking part and the end of the barrel come into contact, thus preventing the cap from being fitted too far in. [Effects of the Invention]

[0020] The present invention relates to a writing instrument provided with caps that can be attached to and detached from both ends of a barrel. Even if the attachment and detachment of the barrel and the cap are repeated, the fitting force between the barrel and the cap is maintained, and the wobbling between the barrel and the cap when the cap is attached to the barrel can be suppressed over a long period of time.

Brief Description of the Drawings

[0021] [Figure 1] It is a side view showing the writing instrument with the cap attached to the front side of the barrel. [Figure 2] It is a side view showing the barrel. [Figure 3] It is an enlarged longitudinal sectional view showing the cap. [Figure 4] It is a bottom view of the cap. [Figure 5] (A) is a view showing the arrow direction of the A - A cross section in FIG. 3, and (B) is a view showing the arrow direction of the B - B cross section in FIG. 3. [Figure 6] It is a longitudinal sectional view of FIG. 1. [Figure 7] (C) is an enlarged view of part C in FIG. 6, and (D) is an enlarged view of part D in FIG. 6. [Figure 8] It is a side view showing the writing instrument with the cap attached to the rear side of the barrel. [Figure 9] It is a longitudinal sectional view of FIG. 8. [Figure 10] (E) is an enlarged view of part E in FIG. 9, and (F) is an enlarged view of part F in FIG. 9.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0023] Embodiments of the present invention are shown in FIGS. 1 to 10. The writing instrument 1 of the present embodiment includes a barrel 2, a writing body 6 housed in the barrel 2, and caps 7 that can be attached to and detached from both ends of the barrel 2. In the present embodiment, with the cap 7 attached to the front side of the barrel 2, the total length of the writing instrument 1 in the axial direction is 139 mm.

[0024] ·Shaft cylinder Figure 2 shows the shaft cylinder 2. The shaft cylinder 2 consists of a cylindrical front shaft 3, a cylindrical rear shaft 4 connected to the rear end of the front shaft 3, and a tail plug 5 provided at the rear end of the rear shaft 4.

[0025] The front shaft 3 is made of a cylindrical molded body of synthetic resin (e.g., polycarbonate resin). The outer surface of the front shaft 3 is provided with a gripping portion 31 made of an elastic material. The gripping portion 31 is provided by two-color molding or attached to the outer surface of the front shaft 3. A tip portion 32 is provided at the front of the front shaft 3. The outer diameter of the tip portion 32 decreases towards the front. The front end of the tip portion 32 is open. A flange portion 33 is provided at the rear of the front shaft 3. The outer diameter of the flange portion 33 is larger than the outer diameter of the front shaft 3 in front of the flange portion 33. A guide portion 34 is provided in front of the flange portion 33. The outer diameter of the guide portion 34 increases from front to rear. The outer diameter of the rear end of the guide portion 34 is set to be approximately the same as, or slightly smaller than, the inner diameter of the rear end of the cap 7.

[0026] Outward-facing projections 35 are provided on the outer surface of the front shaft 3. The outward-facing projections 35 are a group of multiple projections (four in this embodiment) arranged at equal intervals around the circumference. More than four outward-facing projections 35 may be provided. As shown in Figures 6 and 7(D), when the cap 7 is attached to the front side of the shaft cylinder 2, the outward-facing projections 35 and the first inward-facing projection 71 engage. Subsequently, the rear end surface of the cap 7 and the front end surface of the flange portion 33 come into contact. The axial dimensional relationship between the flange portion 33 and the outward-facing projections 35 is important when attaching the cap 7 to the shaft cylinder 2. Because the outward-facing projections 35 are provided behind the gripping portion 31, the distance between the flange portion 33 and the outward-facing projections 35 becomes shorter, making it easier to control the axial position of the outward-facing projections 35.

[0027] A support portion 36 is provided on the outer surface of the front shaft 3. In this embodiment, the outer diameter of the support portion 36 is 8.6 mm. The support portion 36 has an annular and smooth outer surface. The outer diameter of the support portion 36 is approximately constant. The outer diameter of the support portion 36 may be constant. The outer diameter of the annular smooth surface 43 may change from rear to front. As shown in Figure 7(C), when the cap 7 is attached to the front side of the shaft 2, the support portion 36 and the second inward projection 72 are in close proximity. When the cap 7 is attached to the front side of the shaft 2, the support portion 36 and the second inward projection 72 may be in contact. Because the support portion 36 is provided in front of the gripping portion 31, a large distance can be secured between the first inward projection 71 and the second inward projection 72 that support the cap 7. Since the cap 7 is supported at two points, the outward projection 35 and the support portion 36, which are at a distance from each other, the wobbling of the cap 7 can be suppressed more effectively. Since the support portion 36 is located behind the tip portion 32, the outer diameter of the support portion 36 can be made larger. By making the outer diameter of the support portion 36 larger, the inscribed circle diameter of the second inward projection 72 can be made larger, and even when the cap 7 is attached to the rear side of the shaft cylinder 2, the second inward projection 72 can be set so that it does not come into contact with the shaft cylinder 2.

[0028] The rear axle 4 is made of a cylindrical molded body of synthetic resin (for example, polycarbonate resin). The rear axle 4 is attached to the rear of the front axle 3 by screwing. The rear axle 4 only needs to be fixed to the front axle 3, and may be provided on the front axle 3 by press-fitting, engagement, screwing, fitting, bonding, two-color molding, etc. A stepped portion 41 is provided at the rear end of the rear axle 4. An inward projection 42 is integrally formed on the inner surface of the rear end of the rear axle 4.

[0029] An annular smooth surface 43 is provided at the rear end of the outer surface of the rear shaft 4. The annular smooth surface 43 has an annular and smooth outer surface. The outer diameter of the annular smooth surface 43 increases from the rear to the front. The outer diameter of the annular smooth surface 43 may be constant. As shown in Figures 9 and 10(F), when the cap 7 is attached to the rear side of the barrel 2, the annular smooth surface 43 and the third inward projection 73 are pressed together and fitted. Because the annular smooth surface 43 is provided at the rear end of the rear shaft 4, even if the rear shaft 4 is scratched when the rear shaft 4 and the third inward projection 73 are fitted together, the scratches will not be large and noticeable. In addition, when decoration such as transfer printing is applied to the outer surface of the rear shaft 4, the decoration will not be scratched even when the cap 7 is attached to the rear side of the barrel 2 by avoiding the annular smooth surface 43.

[0030] As shown in Figure 10(E), with the cap 7 attached to the rear of the shaft 2, the outer diameter of the rear shaft 4 radially inward of the first inward projection 71 is set to be smaller than the inscribed circle diameter of the first inward projection 71. Similarly, as shown in Figure 10(F), the outer diameter of the rear shaft 4 radially inward of the second inward projection 72 is set to be smaller than the inscribed circle diameter of the second inward projection 72. With this configuration, when the cap 7 is attached to the rear of the shaft 2, the outer surface of the shaft 2 is not scratched by the first inward projection 71 and the second inward projection 72.

[0031] In this embodiment, the outer diameter of the rear shaft 4 gradually increases towards the front. The shape of the rear shaft 4 can be anything as long as it does not come into contact with the first inward projection 71 and the second inward projection 72 when the cap 7 is attached to the rear side of the shaft cylinder 2.

[0032] The tail plug 5 is equipped with an outward projection 51. The tail plug 5 is connected to the rear shaft 4 by the outward projection 51 overcoming and fitting into the inward projection 42. The tail plug 5 only needs to be connected to the rear shaft 4, and may be provided on the rear shaft 4 by press-fitting, engagement, screwing, fitting, bonding, two-color molding, etc. If the ink 64 is a thermochromic ink, the tail plug 5 may be a friction body that erases the ink's writing by frictional heat.

[0033] The circumscribed diameter of the portion of the tail plug 5 that is exposed to the outer surface is smaller than the outer diameter of the rear end of the rear axle 4. When the tail plug 5 is attached to the rear axle 4, a portion of the stepped portion 41 is exposed to the outer surface.

[0034] ·cap Figure 3 shows the cap 7. The cap 7 is made of a cylindrical body. As shown in Figures 1 and 8, the cap 7 is detachable from both ends of the shaft 2. The inner diameter of the cylindrical body constituting the cap 7 is larger than the outer diameter of the front shaft 3 in front of the flange 33, and smaller than the outer diameter of the flange 33. The inner surface of the cap 7 is provided with a first inward projection 71, a second inward projection 72, a third inward projection 73, and a locking portion 74, in order from the rear to the front. A crown cap 75 is provided at the front end of the cap 7.

[0035] The first inward projection 71 is an annular projection. The first inward projection 71 is provided on the inner surface near the opening end of the cap 7. The inscribed circle diameter of the first inward projection 71 is set to be slightly smaller than the circumscribed circle diameter of the outward projection 35 and larger than the outer diameter of the front shaft 3. As shown in Figures 6 and 7(D), when the cap 7 is attached to the front side of the shaft 2, the first inward projection 71 overcomes the outward projection 35, causing the first inward projection 71 and the outward projection 35 to engage, and the cap 7 is attached to the shaft 2.

[0036] The first inward projection 71 and the outward projection 35 can be a combination of an annular projection and a group of projections arranged circumferentially at equal intervals. The outward projection 35 may be an annular projection, and the first inward projection 71 may be a group of projections arranged circumferentially at equal intervals. By having either the first inward projection 71 or the outward projection 35 be a group of projections arranged circumferentially at equal intervals, radial variations in the height of the projections can be absorbed.

[0037] As shown in Figure 10(E), when the cap 7 is attached to the rear of the shaft 2, the first inward projection 71 and the shaft 2 do not come into contact. This configuration suppresses wear of the first inward projection 71 and maintains the dimensional relationship between the shaft 2 and the first inward projection 71. As a result, the fitting force between the shaft 2 and the cap 7 can be maintained over a long period of time.

[0038] As shown in Figures 3 and 4, the second inward projection 72 is a group of multiple projections (four in this embodiment) arranged circumferentially at equal intervals. More than four second inward projections 72 may be provided. The cross-sectional shape of the second inward projection 72 is as shown in Figure 5(B). The inscribed circle diameter of the second inward projection 72 is set to be approximately the same as, or slightly larger than, the outer diameter of the support portion 36. The inscribed circle diameter of the second inward projection 72 is smaller than the inscribed circle diameter of the first inward projection 71. The inscribed circle diameter of the second inward projection 72 is 8.7 mm. Because the inscribed circle diameter of the second inward projection 72 is constant in the axial direction, even if there are variations in the axial dimensions of the cap 7 and the shaft cylinder 2, the second inward projection 72 and the support portion 36 can be reliably brought close to or in contact with each other. As shown in Figures 6 and 7(C), when the cap 7 is attached to the front of the shaft 2, the second inward projection 72 is located radially outward of the support portion 36, and the second inward projection 72 and the support portion 36 are in close proximity or in contact. The cap 7 is supported by the shaft 2 at two points, the first inward projection 71 and the second inward projection 72, thereby suppressing wobbling of the cap 7 relative to the shaft 2.

[0039] As shown in Figure 10(F), when the cap 7 is attached to the rear of the shaft 2, the second inward projection 72 and the shaft 2 do not come into contact. This configuration suppresses wear of the second inward projection 72 and maintains the dimensional relationship between the shaft 2 and the second inward projection 72. As a result, wobbling between the shaft 2 and the cap 7 can be suppressed over a long period of time.

[0040] As shown in Figures 3 and 4, the third inward projection 73 is a group of multiple projections (four in this embodiment) arranged circumferentially at equal intervals. There may be four or more third inward projections 73. The cross-sectional shape of the third inward projection 73 is as shown in Figure 5(A). The inscribed circle diameter of the third inward projection 73 is set to be slightly smaller than the outer diameter of the annular smooth surface 43. The inscribed circle diameter of the third inward projection 73 is smaller than the inscribed circle diameter of the second inward projection. As shown in Figures 9 and 10(F), when the cap 7 is attached to the rear side of the shaft 2, the annular smooth surface 43 and the third inward projection 73 are pressed together and fitted, thereby attaching the cap 7 to the shaft 2.

[0041] As shown in Figure 7(C), when the cap 7 is attached to the front of the shaft 2, the third inward projection 73 and the shaft 2 do not come into contact. This configuration suppresses wear of the third inward projection 73 and maintains the dimensional relationship between the shaft 2 and the third inward projection 73. As a result, the fitting force between the shaft 2 and the cap 7 can be maintained over a long period of time.

[0042] As shown in Figure 7(C), when the cap 7 is attached to the front of the barrel 2, the third inward projection 73 is located radially outward of the tip portion 32. This configuration creates a relatively large gap between the third inward projection 73 and the tip portion 32, so that even if the inscribed circle diameter of the third inward projection 73 is smaller than the inscribed circle diameters of the first inward projection 71 and the second inward projection 72, the third inward projection 73 will not interfere with the barrel 2.

[0043] The cap 7 may be provided with a pen tip sealing member made of an elastic material. The pen tip sealing member makes close contact with the pen tip 61 to prevent the evaporation of the ink 64. The close contact of the pen tip sealing member with the pen tip 61 further reduces the wobbling of the cap 7 relative to the barrel 2.

[0044] • Locking part The locking portion 74 is a group of longitudinal ribs (eight in this embodiment) arranged circumferentially at equal intervals. The rear end of the locking portion 74 has a plane perpendicular to the axial direction. The inscribed circle diameter of the rear end of the locking portion 74 is smaller than the inscribed circle diameter of the third inward projection 73. Furthermore, the inscribed circle diameter of the locking portion 74 is larger than the circumscribed circle diameter of the tail plug 5 and smaller than the outer diameter of the stepped portion 41. With this configuration, as shown in Figures 9 and 10(F), when the cap 7 is attached to the rear side of the shaft cylinder 2, the stepped portion 41 and the locking portion 74 come into contact, preventing the cap 7 from being fitted too far in. Also, since the locking portion 74 and the tail plug 5 do not interfere with each other, the tail plug 5 is not damaged.

[0045] In this embodiment, the outer diameter of the rear axle 4 increases from the rear to the front. If the cap 7 is fitted too far in, there is a risk that the rear axle 4 will come into contact with the first inward projection 71 and the second inward projection 72. However, since the locking portion 74 and the stepped portion 41 come into contact first, the rear axle 4 will not come into contact with the first inward projection 71 and the second inward projection 72.

[0046] When the cap 7 is attached to the front of the shaft 2, the locking portion 74 is located radially outward of the front shaft 3 at or in front of the front end portion 32. This configuration creates a relatively large gap between the locking portion 74 and the front end portion 32, so that even if the inscribed circle diameter of the locking portion 74 is smaller than the inscribed circle diameters of the first inward projection 71, the second inward projection 72, and the third inward projection 73, the locking portion 74 and the shaft 2 do not interfere with each other.

[0047] ·Cursive Figure 6 shows the cursive writing style 6. The cursive writing style 6 consists of a pen tip 61, an ink reservoir tube 62, a cursive end cap 63, and ink 64 contained within the ink reservoir tube 62.

[0048] The cursive pen 6 is equipped with a pen tip 61. The pen tip 61 may consist of, for example, only a metal ballpoint pen tip that rotatably holds a ball at its front end, or a synthetic resin pen tip holder that holds the rear outer surface of the ballpoint pen tip. The pen tip 61 is attached to the front end opening of the ink reservoir tube 62. A cursive pen end plug 63, which has a vent hole that allows air to pass between the ink reservoir tube 62 and the outside, is attached to the rear end opening of the ink reservoir tube 62. Inside the pen tip 61 is a spring that presses the ball at the front end forward. The spring is a compression coil spring with a rod portion at its front end, and the front end of the rod portion is in contact with the rear surface of the ball. When not writing, the forward biasing force of the spring causes the ball to be in close contact with the inner surface of the inwardly facing front edge of the front end of the ballpoint pen tip, preventing ink 64 from leaking from the front end of the pen tip 61 and preventing the ink 64 from evaporating.

[0049] ·Friction body The elastic material constituting the friction body is preferably an elastic synthetic resin (rubber, elastomer), such as silicone resin, SBS resin (styrene-butadiene-styrene copolymer), SEBS resin (styrene-ethylene-butadiene-styrene copolymer), fluororesin, chloroprene resin, nitrile resin, polyester resin, ethylene propylene diene rubber (EPDM), etc. The elastic synthetic resin constituting the friction part 14 is preferably a low-wear elastic material that produces almost no wear debris (eraser shavings) during friction, rather than a high-wear elastic material (e.g., an eraser).

[0050] • Heat-change color ink In this embodiment, the ink 64 may be a reversible thermochromic ink. The reversible thermochromic ink can be configured using various types, either alone or in combination, such as a heat-decolorizing type that decolorizes from a colored state by heating, a color-memory-holding type that alternately stores and maintains a colored state or a decolorized state within a specific temperature range, or a heat-developing type that develops color from a decolorized state by heating and returns to a decolorized state by cooling from the colored state. Handwriting using the reversible thermochromic ink can easily change color due to frictional heat from the friction body.

[0051] The writing instrument 1 of this embodiment comprises a barrel 2 and a cylindrical cap 7 with one end open, a pen tip 61 provided at one end of the barrel 2, the cap 7 being detachable from both ends of the barrel 2, and the inner surface of the cap 7 having a first inward projection 71, a second inward projection 72, and a third inward projection 73, each at different positions in the axial direction. When the cap 7 is attached to the end of the barrel 2 on the nib side 61, the first inward projection 71 and the barrel 2 are fitted together, the second inward projection 72 and the barrel 2 are close to or in contact with each other, and the third inward projection 73 and the barrel 2 are not in contact. When the cap 7 is attached to the end of the barrel 2 opposite to the nib 61, the first inward projection 71 and the second inward projection 72 are in a non-contact state with the barrel 2, and the third inward projection 73 is fitted with the barrel 2.

[0052] In this embodiment, the writing instrument 1 has an outward projection 35 on the outer surface of the barrel 2 on the pen tip side that overcomes the first inward projection 71 and engages with the first inward projection 71, and a support portion 36 that is close to or in contact with the second inward projection 72. The outer surface of the barrel 2 opposite to the pen tip 61 is provided with an annular smooth surface 43 that presses against and fits with the third inward projection 73.

[0053] The writing instrument 1 of this embodiment is characterized in that the support portion 36 is made from the annular and smooth outer surface of the barrel 2, and the second inward projection 72 is a group of multiple projections arranged at equal intervals around the circumference.

[0054] The writing instrument 1 of this embodiment is characterized in that the first inward projection 71, the second inward projection 72, and the third inward projection 73 are arranged in the order of the first inward projection 71, the second inward projection 72, and the third inward projection 73 from the opening end side of the cap 7 in the axial direction forward, and the inscribed circle diameter of the first inward projection 71 is larger than the inscribed circle diameter of the second inward projection 72, and the inscribed circle diameter of the second inward projection 72 is larger than the inscribed circle diameter of the third inward projection 73.

[0055] The writing instrument 1 of this embodiment is characterized in that a locking portion 74 is provided on the inner surface of the cap 7, which contacts the end of the barrel 2 when the cap 7 is attached to the end of the barrel 2 opposite to the pen tip 61. [Explanation of symbols]

[0056] 1 writing implements 2 shaft cylinder 3 Front axle 31 Gripping part 32 Tip part 33. Tsuba (guard) 34 Information Department 35 Extrovert process 36 Support part 4 Rear axle 41 Stepped section 42 Introvert process 43 Annular smooth surface 5. Tail plug 51 External process 6 Cursive 61 nib 62 Ink storage tubes 63 Cursive Tail Plug 64 Ink 7 caps 71 First inward process 72 Second inward process 73 Third inward process 74 Locking part 75 Head crown

Claims

1. A writing instrument comprising a barrel and a cylindrical cap with one end open, wherein a pen tip is provided at one end of the barrel, the cap is detachable from both ends of the barrel, and the inner surface of the cap is provided with a first inward projection, a second inward projection, and a third inward projection, each at different positions in the axial direction. When the cap is attached to the tip end of the barrel, the first inward projection and the barrel are fitted together, the second inward projection and the barrel are close to or in contact with each other, and the third inward projection and the barrel are not in contact. A writing instrument characterized in that, when the cap is attached to the end of the barrel opposite to the pen tip, the first inward projection and the second inward projection are in a non-contact state with the barrel, and the third inward projection is fitted with the barrel.

2. The outer surface of the barrel on the pen tip side is provided with an outward projection that overcomes the first inward projection and engages with the first inward projection, and a support portion that is close to or in contact with the second inward projection. The writing instrument according to claim 1, characterized in that the outer surface of the barrel opposite to the pen tip is provided with an annular smooth surface that presses against and fits with the third inward projection.

3. The writing instrument according to claim 1 or 2, characterized in that the support portion is made of the annular, smooth outer surface of the barrel, and the second inward projection is a group of projections arranged circumferentially at equal intervals.

4. The writing instrument according to any one of claims 1 to 3, characterized in that the first inward projection, the second inward projection, and the third inward projection are arranged in the order of the first inward projection, the second inward projection, and the third inward projection in the order of the first inward projection, the second inward projection, and the third inward projection, in axial direction forward from the opening end of the cap, and the inscribed circle diameter of the first inward projection is larger than the inscribed circle diameter of the second inward projection, and the inscribed circle diameter of the second inward projection is larger than the inscribed circle diameter of the third inward projection.

5. The writing instrument according to any one of claims 1 to 4, characterized in that the inner surface of the cap is provided with a locking portion that contacts the end of the barrel when the cap is attached to the end of the barrel opposite to the pen tip.

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