Writing instrument

Abstract

In a writing instrument (1), a front shaft (5) is provided on a rear shaft (6) in which an ink reservoir (7) is housed in a detachable manner. A fitting portion (51) is provided on the rear outer surface of the front shaft (5), and the fitting portion (51) is latched in a fitted portion (61) formed on the inner surface of an opening portion of the rear shaft (6) in a detachable manner. The fitting portion (51) has an outward press contact portion (53) and a slit (54) provided through in the radial direction. The fitted portion (61) has an inward press contact portion (63). When the front shaft (5) and the rear shaft (6) are connected, the front shaft (5) and the rear shaft (6) are pressed in the radial direction.

Description

Technical Field

[0001] This invention relates to a writing instrument. Specifically, the writing instrument has a front shaft that is detachably mounted on a rear shaft that houses an ink reservoir, allowing the ink reservoir to be replaced or replenished with ink while the front shaft is detached from the rear shaft. Background Technology

[0002] Patent Document 1 discloses a writing instrument configured such that a detachable cartridge can be engaged or disengaged axially relative to a main body, and the ink reservoir inside the main body and / or the detachable cartridge is detachable. On one of the main body and the detachable cartridges, a plurality of radially protruding protrusions are partially provided in the circumferential direction, and on the other cartridge, a smooth, non-protruding pressing surface is provided that contacts the plurality of protrusions. When the two cartridges are connected, the protrusions and the pressing surface press against each other radially. According to this writing instrument, the detachable cartridge is easily engaged or disengaged relative to the main body, and the main body and the detachable cartridge are not excessively (firmly) fastened as in a screw-on connection, thus facilitating easy replacement of the ink reservoir.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Publication No. 2006-142559 Summary of the Invention

[0006] In the structure disclosed in Patent Document 1, the main body and the disassembly tube are connected (fitted) only by radial pressing of the protrusion and the pressing surface. Therefore, when the main body and the disassembly tube are resin components, the fitting force becomes smaller than desired due to the creep of the resin components, raising concerns that the disassembly tube may accidentally detach from the main body. Conversely, the fitting force becomes larger than desired due to the fastening (so-called blocking) of the resin components, raising concerns that it may be difficult to remove the disassembly tube from the main body with the desired force. In other words, in the structure disclosed in Patent Document 1, it is difficult to set and maintain a suitable fitting force when connecting (fitting) the main body and the disassembly tube in a freely detachable manner.

[0007] This invention addresses the problems of the prior art by providing a suitable engagement force that is relatively easy to set and maintain when the front shaft (equivalent to the disassembly sleeve in Patent Document 1) and the rear shaft (equivalent to the main body sleeve in Patent Document 1) are connected (fitted) in a freely detachable manner. Furthermore, in this invention, "front" refers to the tip side, and "rear" refers to the side opposite the tip side.

[0008] This invention relates to a writing instrument in which the front shaft is detachably mounted on a rear shaft that houses an ink reservoir. The ink reservoir can be replaced or replenished with ink while the front shaft is detached from the rear shaft. The instrument is characterized in that the rear portion of the front shaft and the front portion of the rear shaft are detachably fitted together. One of the rear portion of the front shaft and the front portion of the rear shaft has: a cylindrical small-diameter base; an outwardly pressing portion that protrudes radially from the outer surface of the small-diameter base; and at least one slit extending parallel to the axial direction. Furthermore, the front axle rear portion and the rear axle front portion are arranged in a manner that at least a portion of the front axle overlaps with at least a portion of the outward pressing portion in the axial direction, and are radially penetrating through the small-diameter base. The other of the front axle rear portion and the rear axle front portion has: a cylindrical large-diameter base with a diameter larger than the small-diameter base and inserted by the small-diameter base; and an inward pressing portion disposed on the inner surface of the large-diameter base. When the front axle rear portion and the rear axle front portion are fitted together, the outward pressing portion and the inward pressing portion are radially pressed together with each other.

[0009] According to the present invention, at least one slit extending radially through the small-diameter base extends parallel to the axial direction, and at least a portion of its position in the axial direction overlaps with at least a portion of the outward pressing portion in the axial direction. Therefore, when the small-diameter base is inserted into the large-diameter base (during pressing), the small-diameter base deforms in such a way that the width of the slit decreases, thereby facilitating insertion. On the other hand, after insertion (after pressing), due to the restoring force required to restore the width of the slit, the outward and inward pressing portions are pressed together radially with sufficient force. Accordingly, it is relatively easy to set and maintain a suitable engagement force when connecting (fitting) the front and rear axles in a freely detachable manner.

[0010] Preferably, the outward pressing portion extends circumferentially except for the portion through which the gap is provided. In this case, the connection between the front and rear axles is more stable, resulting in better writing feel and performance.

[0011] Furthermore, preferably, the outward pressing portion is positioned at a predetermined distance inward from the top end of the small-diameter base, such that when the rear portion of the front axle and the front portion of the rear axle are engaged, the outer surface of the small-diameter base and the inner surface of the large-diameter base do not contact each other radially at the top end of the small-diameter base. In this case, high dimensional accuracy is not required for the portion other than the pressing portion, and it is easier to set and maintain a suitable engagement force when connecting the front and rear axles in a freely detachable manner. Additionally, the productivity of the components (front and rear axles) is also improved.

[0012] Furthermore, preferably, the small-diameter base has an outward locking portion that is axially away from the outward pressing portion, and the large-diameter base has an inward locking portion that is axially away from the inward pressing portion. When the rear portion of the front axle and the front portion of the rear axle are engaged, the outward locking portion and the inward locking portion lock each other axially. In this case, due to the axial locking function applied to the front and rear axles, the connection between the front and rear axles is more stable, resulting in better writing feel and writing performance.

[0013] Furthermore, in this case, it is more preferable that the outward pressing portion extends circumferentially except through the portion where the gap is provided, the inward pressing portion extends circumferentially and presses against the outward pressing portion radially, and the outward locking portion extends circumferentially except through the portion where the gap is provided, and the inward locking portion extends circumferentially and locks against the outward locking portion axially. In this case, the connection between the front and rear axles is more stable, thus resulting in better writing feel and writing performance.

[0014] Furthermore, in this case, it is more preferable that the inward locking portion is radially recessed on the inner surface of the large-diameter base, and the inward pressing portion is composed of a cylindrical surface that is smoothly continuous along the inner surface of the large-diameter base and has the same curvature as the inner surface of the large-diameter base. In this case, no special processing is required for the inward pressing portion, thus improving the manufacturability of the component.

[0015] Alternatively, preferably, when the rear portion of the front axle and the front portion of the rear axle are engaged, the outward pressing portion and the inward pressing portion lock each other in the axial direction. In this case, the locking function in the axial direction of the front and rear axles is also applied, thus the connection between the front and rear axles is more stable, resulting in better writing feel and writing performance.

[0016] Furthermore, preferably, the pen also includes a cap that covers the front axle when not writing, with a portion of the inner surface of the cap adhering to the full circumference of a portion of the outer surface of the rear axle. In this case, the front axle is not removed when the pen cap is removed. Accordingly, it is not necessary to securely engage the front and rear axles, making it easier to set a suitable engagement force between them. Additionally, the shape and outer diameter of the outer surface of the rear axle are generally stable, thus ensuring reliable airtightness during the engagement of the inner surface of the pen cap with the outer surface of the rear axle.

[0017] Alternatively, preferably, when the front shaft is detached from the rear shaft, the ink reservoir is detached from the rear shaft and housed inside the front shaft. In this case, the workability of replacing the ink reservoir or replenishing ink to the ink reservoir is improved.

[0018] Furthermore, preferably, the slit opens at the top end of the small-diameter base and tapers inward from the top end of the small-diameter base. In this case, when the small-diameter base is inserted into the large-diameter base (during pressing), the wider portion of the slit at the top end is used efficiently, while after insertion (after pressing), the narrower portion of the slit at the inside increases the rigidity against bending. Additionally, with this slit shape, the front axle is easier to manufacture using a die, thereby reducing manufacturing costs.

[0019] Furthermore, it is preferable that the slits are provided at approximately equal intervals of three or more in an odd number along the circumference. In this case, even if the width of each slit is reduced, the workability when inserting the small-diameter base into the large-diameter base can be maintained at a high level. On the other hand, by reducing the width of each slit, the rigidity against bending is increased.

[0020] Furthermore, it is preferable to provide ribs that insert into the gap on the inner surface of the large-diameter base. In this case, the rigidity against bending is increased. Additionally, it is possible to provide a function that prevents relative rotation between the front and rear axles.

[0021] Invention Effects

[0022] According to the writing instrument of the present invention, it is easier to set and maintain a suitable engagement force when the front and rear shafts are connected (fitted) in a freely detachable manner. Attached Figure Description

[0023] Figure 1 This is a longitudinal sectional view showing the first embodiment of the present invention.

[0024] Figure 2 yes Figure 1 Enlarged view of the main parts.

[0025] Figure 3A This is a longitudinal sectional view of the retaining member according to the first to sixth embodiments of the present invention.

[0026] Figure 3B yes Figure 3A AA sectional view.

[0027] Figure 3C yes Figure 3A BB cross-sectional view.

[0028] Figure 4A This is a front view of the pen tip according to the first to sixth embodiments of the present invention.

[0029] Figure 4B yes Figure 4A A three-dimensional image of the pen tip.

[0030] Figure 5 yes Figure 2 Enlarged longitudinal section view of the main part.

[0031] Figure 6A This is a front view of the front axis of the first embodiment of the present invention.

[0032] Figure 6B This is a longitudinal sectional view of the rear axle according to the first embodiment of the present invention.

[0033] Figure 6C yes Figure 6A CC section view.

[0034] Figure 7 This is an enlarged longitudinal sectional view of the main part of the second embodiment of the present invention.

[0035] Figure 8A This is a front view of the front axis of the second embodiment of the present invention.

[0036] Figure 8B This is a longitudinal sectional view of the rear axle according to the second embodiment of the present invention.

[0037] Figure 8C yes Figure 8A DD sectional view.

[0038] Figure 9A This is the front view of the front axis of the third embodiment of the present invention.

[0039] Figure 9B This is a longitudinal sectional view of the rear axle according to the third embodiment of the present invention.

[0040] Figure 9C yes Figure 9A EE sectional view.

[0041] Figure 10A This is the front view of the front axis of the fourth embodiment of the present invention.

[0042] Figure 10B This is a longitudinal sectional view of the rear axle according to the fourth embodiment of the present invention.

[0043] Figure 10C yes Figure 10A FF sectional view.

[0044] Figure 11A This is an enlarged longitudinal sectional view of the main part of the fifth embodiment of the present invention.

[0045] Figure 11B yes Figure 11A HH sectional view.

[0046] Figure 12A This is a front view of the front axis of the fifth embodiment of the present invention.

[0047] Figure 12B This is a longitudinal sectional view of the rear axle according to the fifth embodiment of the present invention.

[0048] Figure 12C yes Figure 12A GG cross-sectional view.

[0049] Figure 12D yes Figure 12B KK sectional view.

[0050] Figure 13A This is an enlarged longitudinal sectional view of the main part of the sixth embodiment of the present invention.

[0051] Figure 13B yes Figure 13A Section II.

[0052] Figure 14A This is the front view of the front axis of the sixth embodiment of the present invention.

[0053] Figure 14B This is a longitudinal sectional view of the rear axle according to the sixth embodiment of the present invention.

[0054] Figure 14C yes Figure 14A JJ sectional view.

[0055] Figure 14D yes Figure 14B LL sectional view.

[0056] Figure 15A This is the front view of the front axis of the seventh embodiment of the present invention.

[0057] Figure 15B This is a longitudinal sectional view of the rear axle according to the seventh embodiment of the present invention.

[0058] Figure 15C yes Figure 15A NN cross-sectional view. Detailed Implementation

[0059] Hereinafter, six embodiments of the present invention will be described with reference to the accompanying drawings.

[0060] <First Embodiment>

[0061] The writing instrument 1 mainly consists of a pen cap 2, a pen nib 3, a retaining component 4 for holding the pen nib 3, an ink reservoir 7, a front shaft 5 and a rear shaft 6 that internally house the ink reservoir 7. The retaining component 4 is pressed into a retaining component fitting part 58 that fits into the front shaft 5. The writing instrument 1 is a writing instrument in which the front shaft 5 is detachably mounted on the rear shaft 6 that houses the ink reservoir 7, allowing the ink reservoir 7 to be replaced or ink to be added to the ink reservoir 7 while the front shaft 5 is detached from the rear shaft 6.

[0062] ·nib

[0063] One end of the pen tip 3, serving as the writing section 31, protrudes forward from the front edge 44 of the front opening of the holding member 4. The other end (rear part 35) of the pen tip 3 is inserted into the front end of the ink reservoir 7. For example, the writing section 31 is machined into a chisel shape. However, the writing section 31 is not limited to a chisel shape; it can also be machined into other shapes corresponding to the purpose, such as a cannonball shape, a rectangular shape, a square prism shape, or a plate shape. Furthermore, the form of the writing instrument of the present invention is not limited to the example shown in the figure; it can also be a double-ended writing instrument in which pen tips of different shapes are installed at both ends of the ink reservoir 7.

[0064] like Figure 2 As shown in Figure 4, the pen tip 3 has: a front portion 33 with a writing section 31 at its top; a cylindrical central portion 34 whose outer surface is held in the front-rear direction by a retaining member 4 and a front shaft 5; and a cylindrical rear portion 35, which is inserted into the front end of the ink reservoir 7. The front portion 33 of the pen tip 3 has a generally rectangular cross-section. When writing, the front portion 33 of the pen tip 3 can bend and deform towards the long side of the generally rectangular cross-section (possessing this flexibility).

[0065] The pen tip 3 is made of a porous material of synthetic resin with continuous air bubbles. Furthermore, the pen tip 3 should be able to flow ink and be flexible. Specifically, examples include fiber pen tips, felt pen tips, brush pen tips, and plastic pen tips with capillary passages in the axial direction.

[0066] ·Ink storage body

[0067] The ink reservoir 7 is composed of a component having continuous pores capable of impregnating ink. Examples include a thermally fused fiber bundle, a resin-processed fiber bundle, a resin-processed felt, a needle-punched felt, and a porous material (e.g., a continuous bubble body of synthetic resin such as a sponge). Additionally, the ink reservoir 7 may have an outer skin made of a synthetic resin film or the like on its outer peripheral surface.

[0068] When the front shaft 5 is removed from the rear shaft 6, the ink reservoir 7 is removed from the rear shaft 6 while being held on a retaining rib 59 extending rearward in the axial direction from the rear end of the longitudinal rib 57 of the front shaft 5, and is housed and held inside the front shaft 5. This improves the workability of replacing the ink reservoir 7 or replenishing ink to it. Furthermore, the retaining rib 59 of the front shaft 5 can also extend to the inner surface of the fitting portion 51 of the front shaft 5.

[0069] Pen cap

[0070] When not writing, the pen cap 2, which covers the front shaft 5, is a cylindrical, bottomed body with an open rear end and a closed front end, consisting of a bottom wall and a peripheral wall. The pen cap 2 is obtained, for example, by injection molding of a synthetic resin (e.g., polypropylene).

[0071] In this embodiment, the pen cap 2 is detachably connected to the rear shaft 6. Specifically, the rear shaft fitting portion 22, located on the inner surface of the pen cap 2, fits into the pen cap fitting portion 65, located on the outer surface of the rear shaft 6. Simultaneously, the annular sealing portion 21, located in front of the rear shaft fitting portion 22, is airtightly fitted into the airtight portion 64, located in front of the pen cap fitting portion 65. That is, when not writing, the pen cap 2 covers the front shaft 5, a portion of the inner surface of the pen cap 2 (rear shaft fitting portion 22) fits into a portion of the outer surface of the rear shaft 6 (pen cap fitting portion 65), and a portion of the inner surface of the pen cap 2 (annular sealing portion 21) completely covers and tightly adheres to the portion of the outer surface of the rear shaft 6 (airtight portion 64).

[0072] Here, as illustrated in Patent Document 1, when three protrusions are provided at predetermined intervals, the cross-sectional shape of the main body tube with the detachable tube is approximately triangular. In this case, suitable airtightness may not be achieved between the pen cap and the main body tube, raising concerns about poor writing quality due to the pen tip drying out.

[0073] In this embodiment, to avoid this problem, as described later, the outward-facing working portions (outward-facing locking portions 53a and outward-facing pressing portions 53b) of the front shaft 5 and the inward-facing working portions (inward-facing locking portions 63a and inward-facing pressing portions 63b) of the rear shaft 6 extend continuously in the circumferential direction. Therefore, when the front shaft 5 and the rear shaft 6 are engaged, the cross-sectional shape of the outer surface of the rear shaft 6 is approximately circular. Accordingly, suitable airtightness can be obtained between the pen cap 2 and the rear shaft 6.

[0074] Front axle

[0075] The front axle 5 is a cylindrical body open at both ends, for example, obtained by injection molding of synthetic resin. Figure 2 As shown, a retaining member fitting portion 58 is formed on the inner surface of the front end of the front shaft 5 for pressing into the outer surface of the rear end of the retaining member 4 (second rib 43b: see Figure 3). Furthermore, behind the retaining member fitting portion 58 of the front shaft 5, multiple (here, eight) longitudinal ribs 57 extending along the axial direction are formed at equal intervals in the circumferential direction. The central portion 34 of the pen tip 3 is clamped in the front-rear direction by the first abutting wall portion 42 of the retaining member 4 and the second abutting wall portion 56a on the front end side of the longitudinal ribs 57. This prevents the pen tip 3 from falling off the retaining member 4 or from being buried in the retaining member 4 (front shaft 5). Additionally, the amount of protrusion of the pen tip 3 from the retaining member 4 can be accurately limited. Furthermore, the third abutting wall portion 56b on the rear end side of the longitudinal ribs 57 restricts the front end of the ink reservoir 7 in the front-rear direction.

[0076] The rear part of the front axle 5 becomes the fitting part 51, which fits into the fitting part 61 of the opening of the rear axle 6 in a freely detachable manner. Figure 6A As shown, the fitting portion 51 includes: a cylindrical small-diameter base 52; an outwardly locking portion 53a that protrudes radially from the outer surface of the small-diameter base 52; an outwardly pressing portion 53b that also protrudes radially from the outer surface of the small-diameter base 52 and is located away from the outwardly locking portion 53a in the axial direction; and a slit 54 that extends parallel to the axial direction and penetrates the small-diameter base 52 radially. The outwardly locking portion 53a extends circumferentially (circumferential except for the portion where the slit 54 is provided), and the outwardly pressing portion 53b also extends circumferentially (circumferential except for the portion where the slit 54 is provided). The slit 54 is formed in a pattern where the position of a portion of its axial direction overlaps with the positions of the outwardly locking portion 53a and the outwardly pressing portion 53b in the axial direction (the slit 54 is formed in a pattern that spans the outwardly locking portion 53a and the outwardly pressing portion 53b).

[0077] According to this structure, when the small-diameter base 52 is inserted into the large-diameter base 62 (see reference) Figure 6B During insertion (pressing), the small-diameter base 52 deforms by reducing the width of the gap 54, thereby facilitating the insertion operation. On the other hand, after insertion (pressing), due to the restoring force required to restore the width of the gap 54, the outward pressing portion 53b and the inward pressing portion 63b (see reference)... Figure 6B They are pressed together radially with sufficient force. Accordingly, it is relatively easy to set and maintain the appropriate engagement force when the front axle 5 and the rear axle 6 are connected (fitted) in a freely detachable manner.

[0078] In this embodiment, the outward pressing portion 53b is provided behind the outward locking portion 53a (on the side near the top of the small diameter base portion 52). In addition, the front axle 5 has a stepped portion 55 for the opening of the rear axle 6 to abut.

[0079] Alternatively, the front shaft 5 may also have a direction recognition section on its outer surface for identifying the orientation of the pen tip 3. For example, the direction recognition section may be provided by a protrusion extending along the axial direction. In this case, it is not necessary to visually confirm the orientation of the pen tip 3 before writing, and writing can be started immediately after the pen tip 3 is exposed.

[0080] If we give a specific example of the dimensions, the length of the minor diameter base 52 (from the step 55 to the rear) is 15mm, and the inner diameter of the minor diameter base 52 is... The outer diameter of the base 52 of the small diameter is The gap 54 is 14.5 mm long and 1 mm wide. The outward locking portion 53a is circumferential (annular except for the gap 54) in the axial direction within a distance of 3.8 mm to 5.2 mm from the step portion 55, forming a raised portion with an arc-shaped cross-section (the raised height from the small diameter base 52 is 0.15 mm). The outward pressing portion 53b is circumferential (annular except for the gap 54) in the axial direction within a distance of 11.3 mm to 12.7 mm from the step portion 55, forming a raised portion with an arc-shaped cross-section (the raised height from the small diameter base 52 is 0.15 mm).

[0081] Rear axle

[0082] The rear axle 6, which is detachably connected to the rear end of the front axle 5, is a cylindrical, bottomed body with an open front end and a closed rear end, consisting of a bottom wall and a peripheral wall. The rear axle 6 is obtained, for example, by injection molding of a synthetic resin (e.g., polypropylene).

[0083] like Figure 6B As shown, the fitting portion 61 has: a cylindrical large-diameter base 62, the diameter of which is larger than that of the small-diameter base 52 and is inserted into the small-diameter base 52; an inward locking portion 63a, which is radially recessed on the inner surface of the large-diameter base 62; and an inward pressing portion 63b, which is composed of a cylindrical surface that is smoothly continuous along the inner surface of the large-diameter base 62 and has the same curvature as the inner surface of the large-diameter base 62.

[0084] In this embodiment, the inward pressing part 63b is disposed behind the inward locking part 63a.

[0085] Outward crimping portion 53b and inward crimping portion 63b (see reference) Figure 6B In addition to being pressed together by sufficient force in the radial direction, the outward locking part 53a and the inward locking part 63a (see reference) Figure 6B The front axle 5 and the rear axle 6 are locked together in the axial direction, so that they are connected without "wobbling" in both the radial and axial directions. Therefore, writing with a good feel and stability is possible.

[0086] Furthermore, in this embodiment, the outward pressing portion 53b is positioned at a predetermined distance from the top end of the small-diameter base 52 towards the inward (front) side. Accordingly, when the front shaft 5 and the rear shaft 6 are engaged, the outer surface of the engaging portion 51 (outer surface of the small-diameter base 52) and the inner surface of the top end of the rear shaft 6 (inner surface of the large-diameter base 62) do not contact each other radially at the top end of the small-diameter base 52.

[0087] If we assume that when the current shaft 5 and the rear shaft 6 are engaged, the outer surface of the engaging portion 51 and the inner surface of the top of the rear shaft 6 are in radial contact at the top of the small diameter base 52, then the outer diameter of the rear shaft 6 after connection (i.e., the outer diameter of the airtight portion 64) may become too large. When the pen cap 2 is engaged on the outer surface of the rear shaft 6 in this state, there is a concern that the engaging force between the pen cap 2 and the rear shaft 6 may become too high (tight).

[0088] In contrast, according to this embodiment, when the front shaft 5 and the rear shaft 6 are engaged, the outer surface of the engaging portion 51 at the top end of the small-diameter base 52 does not contact the inner surface of the top end of the rear shaft 6 in the radial direction. Therefore, the engaging portion 51 does not affect the outer diameter of the airtight portion 64. Accordingly, for portions other than the outward pressing portion 53b (and the outward locking portion 53a), the small-diameter base 52 does not require high dimensional accuracy, and it becomes easier to set and maintain a suitable engaging force when connecting the front shaft 5 and the rear shaft 6 in a freely detachable manner. In addition, the manufacturability of the components (front shaft 5 and rear shaft 6) is also improved. Furthermore, since the shape and outer diameter of the outer surface of the rear shaft 6 are generally stable, reliable airtightness and engaging force can be obtained when the inner surface of the pen cap 2 is engaged with the outer surface of the rear shaft 6.

[0089] Furthermore, in this embodiment, the inward locking portion 63a is formed as an annular groove that can engage with the outward locking portion 53a. On the other hand, the inward pressing portion 63b is formed as a smooth, continuous pressing surface (a cylindrical surface that is smoothly continuous along the inner surface of the large-diameter base 62 and has the same curvature as the inner surface of the large-diameter base 62) that can contact the outward pressing portion 53b. Accordingly, when the front axle 5 and the rear axle 6 are engaged, the opening and the stepped portion 55 of the rear axle 6 abut against each other, the outward locking portion 53a and the inward locking portion 63a (annular groove) engage in the axial direction, and the outward pressing portion 53b and the inward pressing portion 63b (pressing surface) press against each other in the radial direction. Accordingly, the front axle 5 and the rear axle 6 are engaged in a suitable locking position, and therefore, a suitable engagement force can be obtained more reliably when the front axle 5 and the rear axle 6 are connected in a freely detachable manner. In addition, users can easily understand and identify that the front axle 5 and the rear axle 6 are properly connected.

[0090] Regarding this point, in the structure disclosed in Patent Document 1, it is not easy to apply a sense of locking when the main body and the disassembly tube are engaged. That is, it has the disadvantage of not giving the user a sense of reassurance that the main body and the disassembly tube are properly connected.

[0091] In contrast, the writing instrument 1 according to this embodiment can make the engagement of the front axle 5 and the rear axle 6 a click-like engagement. Therefore, it can give the user a sense of reassurance that the front axle 5 and the rear axle 6 are properly connected.

[0092] Furthermore, the outward locking portion 53a and the inward locking portion 63a lock in the axial direction, while the outward pressing portion 53b and the inward pressing portion 63b press in the radial direction. Therefore, the two positions of the front axle 5 and the rear axle 6 in the axial direction interact with each other. Accordingly, the front axle 5 and the rear axle 6 are connected without "wobbling" in both the axial and radial directions during writing, thus enabling writing with a good feel and stability.

[0093] For specific examples of dimensions, the inner diameter of the major diameter base 62 is... The outer diameter of the large-diameter base 62 is The inward locking portion 63a is circumferentially shaped in a region 4.1 mm to 5.5 mm from the top (front end) of the large-diameter base 62 along the axial direction, forming a concave portion with a trapezoidal or arc-shaped cross-section (maximum depth 0.15 mm). The pen cap fitting portion 65 is circumferentially shaped as an arc-shaped raised portion (raised height 0.3 mm) at approximately four equally spaced points (four positions) along the axial direction in a region 8.6 mm to 10.4 mm from the top of the large-diameter base 62.

[0094] • Retaining components

[0095] The retaining component 4 is a cylindrical body with openings at both ends, for example, obtained by injection molding of synthetic resin.

[0096] like Figures 3A to 3C As shown, on the inner surface of the rear portion (circular cross-section) of the retaining member 4, multiple (four in this case) first ribs 43a extending along the axial direction are formed. These multiple first ribs 43a are used to press into the central portion 34 of the pen tip 3. On the other hand, on the outer surface of the rear portion (circular cross-section) of the retaining member 4, multiple (six in this case) second ribs 43b extending along the axial direction are formed at equal intervals. These multiple second ribs 43b are pressed into the retaining member fitting portion 58 fitted into the front shaft 5. In addition, the connecting hole formed by the second ribs 43b and the retaining member fitting portion 58 of the front shaft 5 functions as an air passage hole, allowing ink to be smoothly discharged from the pen tip 3.

[0097] In addition, refer to Figure 2 The retaining member 4 has a retaining portion 41 on the front side that surrounds the front portion 33 of the pen tip 3 and has a generally rectangular cross-section. The writing portion 31 protrudes forward from the front edge 44 of the retaining portion 41 of the retaining member 4.

[0098] The tip 32 of the pen tip 3 protrudes forward from the front edge 44 of the retaining member 4, but the amount of protrusion is greater than 0.2 mm and less than 6.0 mm, preferably greater than 1.0 mm and less than 5.0 mm. Within this preferred range, a firm and stable pen feel can be obtained when the amount of protrusion is small, and a soft pen feel can be obtained when the amount of protrusion is large.

[0099] The front edge 44 of the retaining member 4 is provided with a chamfer or rounding. In particular, it is preferable to provide a chamfer or rounding at least on the edge of the pen tip 3 that may come into contact with the pen tip 3. Accordingly, even if the pen tip 3 is excessively bent and comes into contact with the front edge 44 of the retaining member 4, the load applied to the front part 33 of the pen tip 3 can be minimized, thereby more reliably preventing the pen tip 3 from breaking or being damaged.

[0100] like Figure 2 and Figure 3A As shown, the front edge 44 of the retaining member 4 is formed in a generally straight shape, and the top 32 of the writing part 31 is formed in a generally straight shape. The angle of the front edge 44 of the retaining member 4 relative to the axial direction is approximately the same as the angle of the top 32 of the writing part 31 relative to the axial direction. Accordingly, even if the pen tip 3 is excessively bent, the load applied to the pen tip 3 by the front edge 44 of the retaining member 4 is evenly applied to the front part 33 of the pen tip 3, thereby reliably preventing the pen tip 3 from breaking or being damaged.

[0101] Here, the angle of the front edge 44 of the retaining member 4 relative to the axial direction refers to an angle of 90 degrees or less among the angles formed by the front edge 44 of the retaining member 4 and the axial direction, and the angle of the top 32 of the writing part 31 relative to the axial direction refers to an angle of 90 degrees or less among the angles formed by the top 32 of the writing part 31 and the axial direction. Furthermore, these two angles are approximately the same, meaning that the front edge 44 of the retaining member 4 and the top 32 are approximately parallel. These angles are set to be 30 degrees or more and 90 degrees or less, preferably 45 degrees or more and 90 degrees or less.

[0102] like Figure 2 As shown, when the writing instrument is viewed as a whole along the extension of the short side of the writing section 31 that contacts the paper, the shape of the pen tip 3 exposed from the holding member 4 is approximately a parallelogram or rectangle. Therefore, the shape and orientation of the writing section 31 can be determined based on the shape of the front edge 44. Thus, it is not necessary to directly visually confirm the orientation of the pen tip 3 before writing, and writing can be started immediately after the pen tip 3 is exposed.

[0103] Furthermore, it is preferable that the color of the retaining component 4 is different from the color of the pen tip 3 (i.e., the ink color). Accordingly, the orientation of the front edge 44 is more obvious, making it easier to identify the shape and orientation of the writing section 31. In addition, when the pen tip 3 itself is colored with a dark color such as black, while the retaining component 4 is colored with a bright color different from the pen tip 3, the orientation of the front edge 44 is more obvious, making it easier to identify the shape and orientation of the writing section 31.

[0104] Furthermore, the structure that allows the front shaft 5 and rear shaft 6 of this embodiment to be freely detached and fitted together can also be applied to the fitting structure of the retaining member 4 and the front shaft 5. Accordingly, since the retaining member 4 and the front shaft 5 can be freely detached and fitted together with a suitable fitting force, it can provide a comfortable feeling for the user. In addition, the user can easily understand and recognize that the retaining member 4 and the front shaft 5 are properly connected, thus making it easier to change the pen tip.

[0105] <Second Implementation>

[0106] Figure 7 This is an enlarged longitudinal sectional view of the main part of the second embodiment of the present invention. Figure 8A This is a front view of the front axle of the second embodiment of the present invention. Figure 8B This is a longitudinal sectional view of the rear axle according to the second embodiment of the present invention. Figure 8C yes Figure 8A DD sectional view.

[0107] In the second embodiment of the present invention, the fitting portion 251 of the front axle 205 and the fitted portion 261 of the rear axle 206 differ from those in the first embodiment. The other structures of the second embodiment are substantially the same as those of the writing instrument 1 in the first embodiment. Figures 7 to 8C In this document, structural parts that are the same as those in the first embodiment are marked with the same labels, and their detailed descriptions are omitted.

[0108] Front axle

[0109] The front axle 205 is also a cylindrical body with openings at both ends, for example, obtained by injection molding of synthetic resin. The rear part of the front axle 205 becomes a fitting part 251, which fits into the fitting part 261 of the opening of the rear axle 206 in a detachable manner. Figure 7 and Figure 8A As shown, the fitting portion 251 includes: a cylindrical small-diameter base 252; a first outward pressing portion 253a, which protrudes radially from the outer surface of the small-diameter base 252; a second outward pressing portion 253b, which is formed by a cylindrical surface that is smoothly continuous along the outer surface of the small-diameter base 252 and has the same curvature as the outer surface of the small-diameter base 252; and a slit 254, which extends parallel to the axial direction and penetrates the small-diameter base 252 radially. The first outward pressing portion 253a extends circumferentially (circumferentially except for the portion where the slit 254 is provided). The slit 254 is formed in a pattern where the position of a portion of its axial direction overlaps with the position of the first outward pressing portion 253a in the axial direction (in a pattern where the slit 254 spans the first outward pressing portion 253a).

[0110] According to this structure, when the small-diameter base 252 is inserted into the large-diameter base 262 (see reference) Figure 8BDuring insertion (pressing), the small-diameter base 252 deforms by reducing the width of the gap 254, thereby facilitating the insertion operation. On the other hand, after insertion (pressing), due to the restoring force required to restore the width of the gap 254, the first outward pressing portion 253a and the first inward pressing portion 263a (see reference)... Figure 8B They are pressed together radially with sufficient force. Accordingly, it is relatively easy to set and maintain a suitable engagement force when the front axle 205 and the rear axle 206 are connected (fitted) in a freely detachable manner.

[0111] In this embodiment, the second outward pressing portion 253b is provided behind the first outward pressing portion 253a (on the side near the top of the small-diameter base portion 252). In addition, the front axle 205 has a stepped portion 255 for the opening of the rear axle 206 to abut.

[0112] To provide a specific example of the dimensions, the length of the minor diameter base 252 (from the step 255 to the rear) is 15mm, and the inner diameter of the minor diameter base 252 is... The outer diameter of the base 252 of the minor diameter is The length of the gap 254 is 8 mm, and the width of the gap 254 is uniform, being 1 mm. The first outward pressing part 253a is circumferential in the axial direction in the region at a distance of 9.8 mm to 11.2 mm from the step part 255 (except for the part of the gap 254, it is annular), forming a raised part with an arc-shaped cross section (the raised part has a height of 0.15 mm).

[0113] Rear axle

[0114] The rear axle 206, which is detachably connected to the rear end of the front axle 205, is also a cylindrical bottomed body with an open front end and a closed rear end, consisting of a bottom wall and a peripheral wall. The rear axle 206 is also obtained by injection molding of a synthetic resin (e.g., polypropylene).

[0115] like Figure 8B As shown, the fitting portion 261 has: a cylindrical (strictly speaking, a step with a change in inner diameter is provided in the middle) large-diameter base 262, which has a larger diameter than the small-diameter base 252 and is inserted into the small-diameter base 252; a first inward pressing portion 263a, which is provided radially protruding from the inner surface of the large-diameter base 262; and a second inward pressing portion 263b, which is also provided radially protruding from the inner surface of the large-diameter base 262.

[0116] In this embodiment, the second inward crimping portion 263b is disposed behind the first inward crimping portion 263a.

[0117] In addition to being pressed together radially with sufficient force, the first outward pressing portion 253a and the first inward pressing portion 263a are also pressed together radially with the second outward pressing portion 253b and the second inward pressing portion 263b. Therefore, the front axle 205 and the rear axle 206 are connected radially without "wobbling". Furthermore, in this embodiment, as... Figure 7 As shown, the first outward pressing part 253a and the first inward pressing part 263a are locked together in the axial direction (acting as an outward locking part and an inward locking part), so the front axle 205 and the rear axle 206 are connected without "wobbling" in the axial direction. Therefore, writing with a good writing feel and stability is possible.

[0118] Furthermore, in this embodiment, the second outward pressing portion 253b is also provided at a predetermined distance from the top end of the small-diameter base 252 towards the inward (front) side. Accordingly, when the front shaft 205 and the rear shaft 206 are engaged, the outer surface of the engaging portion 251 (outer surface of the small-diameter base 252) and the inner surface of the top end of the rear shaft 206 (inner surface of the large-diameter base 262) do not contact each other radially at the top end of the small-diameter base 252.

[0119] That is, in this embodiment, the small-diameter base 252 does not require high dimensional accuracy for the portions other than the first outward pressing portion 253a and the second outward pressing portion 253b. Therefore, setting and maintaining a suitable engagement force when connecting the front shaft 205 and the rear shaft 206 in a freely detachable manner becomes easier. Furthermore, the manufacturability of the components (front shaft 205 and rear shaft 206) is also improved. Moreover, since the shape and outer diameter of the outer surface of the rear shaft 206 are generally stable, reliable airtightness and engagement force can be obtained during the engagement of the inner surface of the pen cap 2 with the outer surface of the rear shaft 206.

[0120] Furthermore, in this embodiment, when the front axle 205 and the rear axle 206 are engaged, the opening and the stepped portion 255 of the rear axle 206 abut against each other. The first outward pressing portion 253a and the first inward pressing portion 263a are locked in the axial direction and pressed radially, while the second outward pressing portion 253b and the second inward pressing portion 263b are both pressed radially. Accordingly, the front axle 205 and the rear axle 206 are engaged at a suitable locking position, thus providing a more reliable and suitable engagement force for easy disassembly and reassembly of the front axle 205 and the rear axle 206. Additionally, the user can easily and clearly recognize that the front axle 205 and the rear axle 206 are properly connected. Therefore, the user can feel reassured that the front axle 205 and the rear axle 206 are properly connected.

[0121] For example, the inner diameter of the base 262 is... (Strictly speaking, at a length of 5.5mm from the top side is) On its inner side (With steps)), the outer diameter of the large-diameter base 262 is... The first inward pressing portion 263a is circumferentially shaped in a region 3 mm to 4 mm from the top (front end) of the large-diameter base 262 along the axial direction, forming a raised portion with an arc-shaped cross-section (raised height of 0.15 mm). The second inward pressing portion 263b is circumferentially shaped in a region 9.8 mm to 11.2 mm from the top (front end) of the large-diameter base 262 along the axial direction, forming a raised portion with an arc-shaped cross-section (raised height of 0.15 mm). The pen cap fitting portion 265 is formed with raised portions with an arc-shaped cross-section (raised height of 0.3 mm) at approximately four equally spaced points along the circumferential direction in a region 8.6 mm to 10.4 mm from the top of the large-diameter base 262 along the axial direction.

[0122] <Third Implementation>

[0123] Figure 9A This is a front view of the front axle of the third embodiment of the present invention. Figure 9B This is a longitudinal sectional view of the rear axle according to the third embodiment of the present invention. Figure 9C yes Figure 9A EE sectional view.

[0124] In the third embodiment of the present invention, the shape of the slit 354 differs from that in the first embodiment. Specifically, the slit 354 tapers inward from the top end of the small-diameter base 52. The other structures of the third embodiment are substantially the same as those of the writing instrument 1 in the first embodiment. Figures 9A to 9C In this document, the same markings are used for structural parts that are the same as those in the first embodiment, and detailed descriptions of them are omitted.

[0125] According to this embodiment, when the small-diameter base 52 is inserted into the large-diameter base 62 (during pressing), the wider portion of the top side of the slit 354 is used efficiently. On the other hand, after insertion (after pressing), the narrower portion of the inner side of the slit 354 increases the rigidity against bending. Furthermore, with this shape of the slit 354, the front axle 5 is easily manufactured by a die, thereby reducing manufacturing costs.

[0126] To give a specific example of the dimensions, the length of the gap 354 is 14.5mm, the width of the gap 354 is 1.5mm at the top, and tapers at a 2° cone angle towards the inside.

[0127] <Fourth Implementation>

[0128] Figure 10A This is a front view of the front axle according to the fourth embodiment of the present invention. Figure 10BThis is a longitudinal sectional view of the rear axle according to the fourth embodiment of the present invention. Figure 10C yes Figure 10A FF sectional view.

[0129] In the fourth embodiment of the present invention, the shape and number of slits 454 differ from those in the first embodiment. Specifically, as shown in... Figure 10C As shown, the three slits 454 are arranged at approximately equal intervals along the circumference; however, the width of each slit 454 is narrower than the width of the slit 54 in the first embodiment. The other structures of the fourth embodiment are substantially the same as those of the writing instrument 1 in the first embodiment. Figures 10A to 10C In this document, structural parts that are the same as those in the first embodiment are marked with the same labels, and their detailed descriptions are omitted.

[0130] According to this embodiment, even if the width of each slit 454 is reduced, the overall flexural deformation of the small-diameter base 52 can be ensured. Therefore, the workability when the small-diameter base 52 is inserted into the large-diameter base 62 can be maintained at a high level. On the other hand, by reducing the width of each slit 454, the rigidity against bending can be improved.

[0131] To give a specific example of the dimensions, the length of each gap 454 is 14.5mm, and the width of each gap 454 is uniform at 0.3mm.

[0132] The number of slots is not limited to 3; any odd number of slots, 3 or more, is acceptable. On the other hand, when an even number of slots are arranged at approximately equal intervals along the axial direction, the rigidity relative to the directional bending of two slots arranged opposite each other is insufficient, and therefore this is not preferred.

[0133] <Fifth Implementation>

[0134] Figure 11A This is an enlarged longitudinal sectional view of the main part of the fifth embodiment of the present invention. Figure 11B yes Figure 11A HH sectional view, Figure 12A This is a front view of the front axle according to the fifth embodiment of the present invention. Figure 12B This is a longitudinal sectional view of the rear axle according to the fifth embodiment of the present invention. Figure 12C yes Figure 12A GG sectional view, Figure 12D yes Figure 12B KK sectional view.

[0135] In the fifth embodiment of the present invention, the shape of the slit 554 differs from that in the first embodiment. Specifically, the slit 554 tapers from the top end of the small-diameter base 52 to the rear end of the outward pressing portion 53b, and has a uniform width at a position inward (front) from the rear end of the outward pressing portion 53b. Furthermore, a rib 569 for insertion into the slit 554 of the rear axle 6 is provided on the inner surface of the large-diameter base 62. The rib 569 extends rearward along the axial direction from a position slightly in front of the inward locking portion 63a, crossing the inward locking portion 63a. The other structures of the fifth embodiment are substantially the same as those of the writing instrument 1 of the first embodiment. Figures 11A to 12D In this document, structural parts that are the same as those in the first embodiment are marked with the same labels, and their detailed descriptions are omitted.

[0136] According to this embodiment, a large-diameter base 62 is inserted into the small-diameter base 52 (see reference). Figure 12B During insertion (pressing), the small-diameter base 52 deforms by reducing the width of the gap 554, thereby facilitating the insertion process. Then, the rib 569 is inserted into the gap 554 during the insertion process, significantly improving rigidity against bending. At this time, the top of the gap 554 is conical (or chamfered or rounded, etc., can be used instead of a conical shape), thus ensuring smooth insertion of the rib 569. After insertion (pressing), the outward pressing portion 53b and the inward pressing portion 63b press against each other radially with sufficient force, making it easier to set and maintain a suitable engagement force when connecting (fitting) the front axle 5 and the rear axle 6 in a freely detachable manner.

[0137] In addition, according to this embodiment, by inserting the rib 569 into the gap 554, a function is added to prevent the front axle 5 and the rear axle 6 from rotating relative to each other.

[0138] Specific examples of dimensions include: the length of slit 554 is 14.5 mm, the width of slit 554 at the top is 5 mm, the cone angle of the tapered portion is 90°, and the width of the uniformly wide portion is 1 mm. Additionally, the rib 569 has a uniform width of 1 mm, a uniform bulge height of 0.7 mm, and its front end is located 3 mm behind the front end of the large-diameter base 62.

[0139] <Sixth Implementation>

[0140] Figure 13A This is an enlarged longitudinal sectional view of the main part of the sixth embodiment of the present invention. Figure 13B yes Figure 13A Sectional view II, Figure 14A This is a front view of the front axle of the sixth embodiment of the present invention. Figure 14B This is a longitudinal sectional view of the rear axle according to the sixth embodiment of the present invention. Figure 14C yes Figure 14A JJ sectional view, Figure 14D yes Figure 14B LL sectional view.

[0141] In the sixth embodiment of the present invention, the three points provided in both the gap 654 and the rib 669 differ from those in the fifth embodiment. Specifically, as shown in... Figure 14C As shown, the three slits 654 are arranged at approximately equal intervals along the circumference; on the other hand, as... Figure 14D As shown, the three ribs 669 are also arranged at approximately equal intervals along the circumference. The other structures of the sixth embodiment are largely the same as those of the writing instrument in the fifth embodiment. Figures 13A to 14D In this document, the same markings are used for structural parts that are the same as those in the fifth embodiment, and their detailed descriptions are omitted.

[0142] According to this embodiment, a large-diameter base 62 is inserted into the small-diameter base 52 (see reference). Figure 14B During insertion (pressing), the small-diameter base 52 deforms by reducing the width of each slot 654, thereby facilitating the insertion process. Then, the corresponding ribs 669 are inserted into each slot 654 during the insertion process, thereby significantly improving rigidity against bending. At this time, the top of the slot 654 is tapered (or chamfered or rounded, etc., can be used instead of tapered), thus ensuring smooth insertion of the ribs 669. After insertion (pressing), the outward pressing portion 53b and the inward pressing portion 63b press against each other radially with sufficient force, thus making it easier to set and maintain a suitable engagement force when connecting (fitting) the front axle 5 and the rear axle 6 in a freely detachable manner.

[0143] Furthermore, according to this embodiment, by inserting the rib 669 into the gap 654, a function is added to prevent the front axle 5 and the rear axle 6 from rotating relative to each other.

[0144] Specific examples of dimensions include: the length of each slit 654 is 14.5 mm, the width of each slit 654 at the top is 5 mm, the cone angle of the tapered portion is 90°, and the width of the uniformly wide portion is 1 mm. Furthermore, the width of each rib 669 is uniform at 0.8 mm, the height of each rib 669 is uniform at 0.7 mm, and the position of the front end of each rib 669 is 3 mm behind the front end of the large-diameter base 62.

[0145] <Seventh Implementation>

[0146] Figure 15A This is a front view of the front axle of the seventh embodiment of the present invention. Figure 15B This is a longitudinal sectional view of the rear axle according to the seventh embodiment of the present invention. Figure 15C yes Figure 15A NN cross-sectional view.

[0147] In the seventh embodiment of the present invention, the outward locking portion 753a, in a region 3.8 mm to 5.2 mm away from the step portion 55 along the axial direction, is formed as a generally dome-shaped raised portion (0.15 mm in height from the small diameter base 52) at approximately equal intervals at eight points (eight positions) along the circumferential direction, without overlapping with the gap 54. In this configuration, a portion of the gap 54 overlaps with the position of the outward pressing portion 753b along the axial direction. The outward pressing portion 753b, in a region 11.3 mm to 12.7 mm away from the step portion 55 along the axial direction, is also formed as a generally dome-shaped raised portion (0.15 mm in height from the small diameter base 52) at approximately equal intervals at eight points (eight positions) along the circumferential direction, without overlapping with the gap 54. The other structures of the seventh embodiment are substantially the same as those of the writing instrument 1 of the first embodiment. Figures 15A to 15C In this document, structural parts that are the same as those in the first embodiment are marked with the same labels, and their detailed descriptions are omitted.

[0148] According to this embodiment, the same effects as in the first embodiment can be obtained. Specifically, when the front axle 5 and rear axle 6 are engaged, the opening and stepped portion 55 of the rear axle 6 abut against each other, the outward locking portion 753a and the inward locking portion 63a (annular groove) lock in the axial direction, and the outward pressing portion 753b and the inward pressing portion 63b (pressing surface) press against each other in the radial direction. Accordingly, the front axle 5 and rear axle 6 are engaged in a suitable locking position, thus providing a more reliable and appropriate engagement force when connecting the front axle 5 and rear axle 6 in a freely detachable manner. Furthermore, it allows the user to easily understand and identify that the front axle 5 and rear axle 6 are properly connected.

[0149] Furthermore, the modifications described in embodiments 3 to 6 can also be implemented in this embodiment.

[0150] Explanation of reference numerals in the attached figures

[0151] 1: Writing instrument; 2: Pen cap; 21: Annular seal; 22: Rear axle fitting part; 3: Pen tip; 31: Writing part; 32: Top; 33: Front part; 34: Central part; 35: Rear part; 4: Holding part; 41: Holding part; 42: First abutting wall part; 43a: First rib; 43b: Second rib; 44: Front edge part; 5: Front axle; 51: Fitting part; 52: Small diameter base part; 53a: Outward locking part; 53b: Outward pressing part; 54: Gap; 55: Step part; 56a: Second abutting wall part; 56b: Third abutting wall part; 57: Longitudinal rib; 58: Holding part fitting part; 59: Holding rib; 6: Rear axle; 61: Fitted part; 62: Large diameter Base; 63a: Inward locking part; 63b: Inward pressing part; 64: Airtight part; 65: Pen cap fitting part; 7: Ink reservoir; 205: Front axis; 206: Rear axis; 251: Fitting part; 252: Small diameter base; 253a: First outward pressing part; 253b: Second outward pressing part; 254: Gap; 255: Stepped part; 261: Fitted part; 262: Large diameter base; 263a: First inward pressing part; 263b: Second inward pressing part; 265: Pen cap fitting part; 354: Gap; 454: Gap; 554: Gap; 569: Rib; 654: Gap; 669: Rib; 753a: Outward locking part; 753b: Outward pressing part.

Claims

1. A writing instrument, wherein the front shaft of the writing instrument is detachably mounted on a rear shaft that houses an ink reservoir, and the ink reservoir can be replaced or refilled with ink while the front shaft is detached from the rear shaft. Its features are, The rear portion of the front axle and the front portion of the rear axle can be easily detached and fitted together. One of the rear portion of the front axle and the front portion of the rear axle has: Cylindrical base with small diameter; An outwardly pressed portion, which protrudes radially from the outer surface of the small-diameter base; At least one slit, extending parallel to the axial direction and overlapping at least a portion of the outwardly pressing portion in the axial direction with at least a portion of the outwardly pressing portion in the axial direction, is provided to penetrate the small-diameter base radially. The other of the rear portion of the front axle and the front portion of the rear axle has: A cylindrical large-diameter base, whose diameter is larger than that of the small-diameter base and is inserted into the small-diameter base; and An inwardly pressed portion is provided on the inner surface of the large-diameter base. When the rear portion of the front axle and the front portion of the rear axle are engaged, the outward pressing portion and the inward pressing portion press against each other radially. The small-diameter base has an outward locking portion that is located away from the outward pressing portion in the axial direction. The large-diameter base has an inward locking portion that is located away from the inward pressing portion in the axial direction. When the rear portion of the front axle and the front portion of the rear axle are engaged, the outward locking portion and the inward locking portion lock each other in the axial direction. The gap is formed in a pattern in which the position of a portion of its axial direction overlaps with the position of the outward locking portion's axial direction.

2. The writing instrument according to claim 1, characterized in that, When the front shaft is removed from the rear shaft, the ink reservoir is removed from the rear shaft and housed inside the front shaft.

3. The writing instrument according to claim 1, characterized in that, The slit opens at the top of the small diameter base and tapers inward from the top of the small diameter base.

4. The writing instrument according to claim 1, characterized in that, Ribs that insert into the gap are provided on the inner surface of the large-diameter base.

5. The writing instrument according to claim 1, characterized in that, The outward pressing portion extends circumferentially except for the portion through which the gap is provided. The inward pressing portion extends circumferentially and presses against the outward pressing portion radially. The outward locking portion extends circumferentially except for the portion through which the gap is provided. The inward locking portion extends circumferentially and locks against the outward locking portion in the axial direction.

6. The writing instrument according to claim 5, characterized in that, The inward locking portion is radially recessed on the inner surface of the large-diameter base. The inward pressing portion is composed of a cylindrical surface that is smoothly continuous along the inner surface of the large-diameter base and has the same curvature as the inner surface of the large-diameter base.

7. The writing instrument according to any one of claims 1 to 6, characterized in that, The outward pressing portion extends circumferentially except for the portion through which the gap is provided.

8. The writing instrument according to any one of claims 1 to 6, characterized in that, The outward pressing part is located at a predetermined distance from the top end of the small diameter base. When the rear part of the front axle and the front part of the rear axle are engaged, the outer surface of the small diameter base and the inner surface of the large diameter base do not contact each other radially at the top end of the small diameter base.

9. The writing instrument according to any one of claims 1 to 6, characterized in that, When the rear portion of the front axle and the front portion of the rear axle are engaged, the outward pressing portion and the inward pressing portion are locked together in the axial direction.

10. The writing instrument according to any one of claims 1 to 6, characterized in that, It also has a pen cap that covers the front axle when not writing. A portion of the inner surface of the pen cap is in close contact with a portion of the outer surface of the rear axle around its entire circumference.

11. The writing instrument according to any one of claims 1 to 6, characterized in that, The slits are arranged in an odd number of three or more at approximately equal intervals along the circumference.

Images