Writing instruments

Abstract

A writing instrument (1) has a tubular inner tube (20) having a first opening end (29) and a second opening end (18), and has a tubular rear shaft (10) in which the first opening end (29) is inserted into the interior of the second opening end (18) and fits with the inner tube (20), and at least one adjacent portion (30) is provided at the opening edge or near the opening edge of the first opening end (29), which is formed to be thinner than other parts at the opening edge or near the opening edge.

Description

Technology Field

[0001] The present invention relates to a writing instrument. Background Technology

[0002] A writing instrument having an inner tube as a first tube-shaped member and a rear shaft as a second tube-shaped member is known (Patent Document 1). In the writing instrument described in Patent Document 1, the front end of the inner tube, which is the first opening end, is inserted into the rear end of the rear shaft, which is the second opening end, so that the inner tube and the rear shaft are fitted together. Specifically, in the fitted state, a concave portion provided on the outer surface near the front end of the inner tube and a convex portion provided on the inner surface of the rear shaft are engaged in the direction of pulling out the inner tube. Prior art literature

[0003] Japanese Patent Publication No. 2021-30669 The problem to be solved

[0004] During assembly, when the front end of the inner tube is inserted into the rear end of the rear shaft, the front end of the inner tube undergoes elastic deformation as it passes over the convex portion of the rear shaft. The greater the force required to elastically deform the front end of the inner tube—that is, the greater the amount of elastic deformation—the more difficult it becomes to assemble, or fit, the inner tube and the rear shaft. If the height of the convex portion of the rear shaft is reduced to decrease the amount of elastic deformation, thereby allowing for easier assembly with less force, the engagement with the concave portion of the inner tube weakens, making it easier for the inner tube and the rear shaft to come loose.

[0005] On the other hand, if the depth of the concave portion of the inner tube and the height of the convex portion of the rear shaft are increased to make it difficult for the inner tube and rear shaft to loosen, the amount of elastic deformation increases, requiring greater force for assembly. Furthermore, since the front portion of the inner tube is circular and has a uniform thickness along its entire circumference, it is resistant to elastic deformation. Conversely, stress tends to concentrate particularly at the shear edge corresponding to the location where the concave portion is formed, and there is a risk of damage such as cracking due to elastic deformation.

[0006] Patent Document 1 describes a fitting between a convex portion of the rear axis and a concave portion of the inner cylinder, but the same applies to a writing instrument in which, for example, a ring-shaped first convex portion is formed on the outer surface of a first cylinder-shaped member inserted inside, and a plurality of second convex portions arranged along the circumferential direction are formed on the inner surface of a second cylinder-shaped member. That is, in such a writing instrument, the first convex portion and the second convex portion slide over each other to fit, but even in this case, there is a risk that the front edge of the first cylinder-shaped member may be damaged due to elastic deformation.

[0007] The present invention aims to provide a writing instrument having easy assembly, sufficient fitting force, and durability. means of solving the problem

[0008] According to one aspect of the present invention, a writing instrument is provided having a first tubular member having a first opening end and a second tubular member having a second opening end, wherein the first opening end is inserted into the interior of the second opening end and is compatible with the first tubular member, and at least one thin portion is provided at the opening edge or near the opening edge of the first opening end, the thickness of which is thinner than that of other parts at the opening edge or near the opening edge.

[0009] The above at least one contact portion may have at least two contact portions, and each of the at least two contact portions may be arranged at equal intervals around the central axis of the first cylindrical member. The boundary between the at least one contact portion and the other portion may be formed in a stepped shape. The first cylindrical member is an inner tube, and the second cylindrical member is a shaft or rear shaft into which the inner tube is inserted from the rear end, and a bulging portion is formed at the rear end of the inner tube, and the front end surface of the bulging portion contacts the rear end surface of the shaft or rear shaft, and the inner tube has a clip, and on the inner surface of the shaft or rear shaft, at least one first interlocking portion is provided at a position rotated by a predetermined angle around the central axis with respect to the clip in a fitted state, and on the outer surface of the inner tube, a second interlocking portion capable of interlocking with the first interlocking portion is provided. A guide projection may be provided on the outer surface of the first cylindrical member, and the second cylindrical member may be provided with a groove or notch that extends from the second opening end toward the interior of the second cylindrical member and receives the guide projection to guide the insertion of the first cylindrical member. The device may further provide a writing element, a spring that presses the writing element backward, an outer cam provided on the inner surface of the first cylindrical member or the second cylindrical member, a cylindrical operating member, and an insertion part that can be inserted into the front opening of the operating member, a rotor that is pressed backward through the writing element by the spring, and configured to cooperate with the outer cam by the operation of the operating member, and a pressing means provided between the writing element and the rotor, wherein the pressing means may be configured to make the central axis of the rotor inclined with respect to the central axis of the first cylindrical member or the second cylindrical member.The above-mentioned pressure means may be a pressure surface inclined with respect to a plane perpendicular to the central axis of the rotor provided on the front surface of the rotor, or a pressure projection provided on the front surface of the rotor. Effects of the invention

[0010] According to an embodiment of the present invention, a common effect is achieved by providing a writing instrument having easy assembly, sufficient fitting force, and durability. Brief explanation of the drawing

[0011] FIG. 1 is a cross-sectional view of a writing instrument according to an embodiment of the present invention. Figure 2 is a longitudinal section of the rear axis. FIG. 3 is another longitudinal section of the rear axis corresponding to line AA in FIG. 2. Figure 4 is a perspective view of the internal passage. Figure 5 is a longitudinal section of the inner tube. FIG. 6 is another longitudinal section of the inner tube corresponding to line BB of FIG. 5. Figure 7 is a cross-sectional view of the inner tube corresponding to line CC of Figure 5. Fig. 8 is an exploded perspective view of the rear shaft and inner tube. FIG. 9 is a longitudinal section view of the assembly part of the rear shaft and inner tube. FIG. 10 is a cross-sectional view of another assembly part of the rear shaft and inner tube corresponding to line DD of FIG. 9. FIG. 11 is a longitudinal cross-sectional view of the rear portion of a writing instrument in a non-writing state according to another embodiment of the present invention. FIG. 12 is a longitudinal section of the latter part of the writing instrument of FIG. 11 in a writing state. Fig. 13 is a perspective view of the internal passage. Fig. 14 is a longitudinal section of the inner tube. FIG. 15 is an exploded perspective view of the rear shaft and inner tube. FIG. 16 is a perspective view of the rotor. Fig. 17 is a side view of the rotor. Specific details for implementing the invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Throughout all drawings, corresponding components are denoted by common reference numerals.

[0013] FIG. 1 is a cross-sectional view of a writing instrument (1) according to an embodiment of the present invention. The writing instrument (1) is a ballpoint pen, which is a so-called click-type writing instrument.

[0014] The writing instrument (1) has a shaft (2) having a front shaft (3) and a rear shaft (10) that is screw-coupled to the outer surface of the rear end of the front shaft (3); an inner tube (20) that is fitted to the inner surface of the rear end of the shaft (2), that is, the rear end of the rear shaft (10), and is also equipped with a clip (21); a refill (4) which is a writing instrument disposed within the shaft (2) and has a writing part (4a) at one end; and a spring (5) which is an elastic member that presses the refill (4) backward. In this embodiment, the refill (4) is a ballpoint pen refill. In this specification, regarding the axial direction of the writing instrument (1), the side of the writing part (4a) is defined as the "front" side, and the side opposite to the writing part (4a) is defined as the "rear" side. Additionally, the inner tube (20) may also be referred to as the shaft (2).

[0015] On the outer surface of the radiator (3), a grip (3a) is provided by two-color molding so that the user can easily grip it. The radiator (3) is formed from a semi-rigid or rigid resin material, such as polypropylene or polycarbonate. The grip (3a) is formed from a material having rubber elasticity, such as a thermoplastic elastomer, or a soft resin material.

[0016] The grip (3a) may be provided to extend forward beyond the front end of the front shaft (3) and to cover the front end surface of the front shaft (3), as disclosed, for example, in Japanese Patent Publication No. 2013-52678. By doing so, a good writing instrument (1) can be provided for all users with different gripping positions of the grip (3a). Additionally, the grip (3a) may be provided on the outer circumference of the front shaft (3) and extend backward beyond the flange portion (3b) that hooks the front end surface of the rear shaft (10), as disclosed, for example in Japanese Patent Publication No. 2014-46639, and may also have a convex portion that protrudes outward in the radial direction from the extended portion. By doing so, when the front shaft (3) and the rear shaft (10) are screw-coupled, the convex portion is compressed by the inner circumference of the rear shaft (10), thereby preventing the screw coupling from being released.

[0017] A known knock mechanism is disposed inside the rear end of the inner tube (20). The knock mechanism has a rotor (40) disposed within the inner tube (20) so as to be movable in the forward and backward directions, and an operating member (7) that protrudes rearward from the rear end opening of the rear shaft (10) and is disposed at the rear of the rotor (40) so as to be movable in the forward and backward directions. The operating member (7) is a tube-shaped member with a closed rear end, and a cam surface (7a) is provided on the ring-shaped front end surface. The rotor (40) consists of an insertion part (41) that is inserted into the front end opening of the operating member (7) and used for core fitting, and a main body part (42) formed in front of the insertion part (41). On the outer surface of the main body part (42), four inner cams (43) that are arranged in the forward and backward directions are provided at equal intervals in the circumferential direction. On the ring-shaped rear end surface of the main body (42), a cam support surface (44) is provided that cooperates with the cam surface (7a) of the operating member (7). The rotor (40) and the operating member (7) are pressed backward together with the refill (4) by the spring (5). That is, the rear end surface of the refill (4) is always in contact with the front end surface of the rotor (40). The rotor (40) is configured to rotate in the circumferential direction by the cooperation of the cam surface (7a) of the operating member (7) and the cam support surface (44) of the rotor (40).

[0018] The knock operation is performed by pressing the operating member (7) forward while resisting the pressure of the spring (5). As the operating member (7) moves due to the knock operation, the rotor (40) and the refill (4) are pressed and move forward within the inner tube (20). Next, when the force applied to the operating member (7) is released, the rotor (40) rotates around the central axis, and the rear end surface of the inner cam (43) formed on the outer surface of the rotor (40) and the front end surface of the outer cam (9) formed on the inner surface of the inner tube (20) engage. As a result, the writing instrument (1) maintains a writing state in which the writing part (4a) protrudes from the front end of the shaft (2). When a knock operation is performed in the writing state of the writing instrument (1), the rotor (40) and the refill (4) are pressed together with the movement of the operating member (7) and move forward within the inner tube (20), and the locking between the rear end surface of the inner cam (43) of the rotor (40) and the front end surface of the outer cam (9) of the inner tube (20) is released. Next, when the force applied to the operating member (7) is released, the rotor (40) rotates around the central axis, and the refill (4) moves backward by the pressure of the spring (5). As a result, the writing instrument (1) becomes a non-writing state (Fig. 1) in which the writing part (4a) is immersed within the shaft tube (2). That is, the rotor is configured to cooperate with the outer cam.

[0019] The refill (4) may be a type of writing instrument other than a ballpoint pen, such as a marking pen, a touch pen, or an eraser. Additionally, part or all of the operating member (7) may be an erasing part that erases the handwriting of the writing instrument (1). The refill (4) may contain thermochromic ink containing a thermochromic colorant. In this case, the writing instrument (1) is a thermochromic writing instrument, and the handwriting of the writing instrument (1) can be thermochromically changed by frictional heat generated when it is rubbed by a frictional body as an erasing member.

[0020] Here, thermochromic ink refers to ink that maintains a predetermined color (first color) at room temperature (e.g., 25°C), changes to a different color (second color) when heated to a predetermined temperature (e.g., 60°C), and then returns to the original color (first color) when cooled to a predetermined temperature (e.g., -5°C). In a writing instrument using thermochromic ink, the process of making the second color colorless and heating a line drawn in the first color (e.g., red) to colorless is referred to as "erasing" in this context. Accordingly, frictional heat is generated by a frictional body abrading the writing surface, etc., on which the line is written, thereby changing the line to colorless, i.e., erasing it. Furthermore, naturally, the second color may be a colored color other than colorless.

[0021] FIG. 2 is a longitudinal section of the rear axis (10), and FIG. 3 is another longitudinal section of the rear axis (10) corresponding to line AA of FIG. 2.

[0022] The rear shaft (10) is a cylindrical member. The rear end surface (10a) of the rear shaft (10) is formed in the shape of an inclined surface inclined at about 45 degrees with respect to the central axis. The rear end surface (10a) is not a strictly inclined surface, but is formed in the shape of a slightly convex curve. On the inner surface of the rear shaft (10) that is rearward from the center in the axial direction, a small diameter portion (11) is formed with a smaller inner diameter than the inner surface of the front.

[0023] On the inner surface of the rear shaft (10), a first guide groove (12) of approximately rectangular shape is formed, extending forward from the rear end surface (10a). The first guide groove (12) is formed in the part closest to the front of the inclined rear end surface (10a). The first guide groove (12) may be a notch extending forward from the rear end surface (10a) of the rear shaft (10). Additionally, on the inner surface of the rear shaft (10), two second guide grooves (13) of approximately rectangular shape are formed, extending forward from the rear end surface (10a). Each of the two second guide grooves (13) is positioned at a location rotated approximately 90 degrees around the central axis of the rear shaft (10) relative to the first guide groove (12). Each of the two second guide grooves (13) faces each other. In the shear portion inside the second guide groove (13), a first interlocking portion (14) is formed, which is a groove shallower than other parts of the second guide groove (13). In other words, the first interlocking portion (14) is a projection provided inside the second guide groove (13).

[0024] On the inner surface of the rear shaft (10), two convex portions (15) are formed extending toward the rear from the front edge of the small diameter portion (11). The convex portions (15) protrude from the inner surface of the rear shaft (10) at a uniform height. Each of the two convex portions (15) is positioned at a location rotated approximately 90 degrees around the central axis of the rear shaft (10) with respect to the first guide groove (12). The two convex portions (15) face each other. Accordingly, each of the two convex portions (15) is aligned in the axial direction with the corresponding second guide groove (13). An inclined surface (16) is provided at the rear end of the convex portion (15). A forward-facing locking surface (17) is formed on the front end of the convex portion (15).

[0025] FIG. 4 is a perspective view of the inner tube (20), FIG. 5 is a longitudinal section view of the inner tube (20), FIG. 6 is another longitudinal section view of the inner tube (20) corresponding to line BB of FIG. 5, and FIG. 7 is a cross section view of the inner tube (20) corresponding to line CC of FIG. 5.

[0026] The inner tube (20) is a cylindrical member. On the inner surface of the rear end of the inner tube (20), the aforementioned outer cam (9), which consists of a plurality of protrusions extending in the front-rear direction, is formed. On the outer surface of the rear end of the inner tube (20), a protruding portion (22) that protrudes outward in the diameter direction is formed. The outer surface of the protruding portion (22) is formed to be integral with the outer surface of the rear shaft (10) when the inner tube (20) is fitted with the rear shaft (10), for example, to be a single surface. On the front end surface of the protruding portion (22), a fitting surface (22a) is formed that fits with the rear end surface (10a) of the rear shaft (10) when the inner tube (20) is fitted with the rear shaft (10). For this reason, the fitting surface (22a) is formed in a concave curved shape that is complementary to the rear end surface (10a) of the rear shaft (10). A clip (21) is integrally provided in the protruding portion (22). The clip (21) is formed to be positioned at the furthest rear portion of the rear end surface (10a) of the rear shaft (10) when the inner tube (20) is fitted with the rear shaft (10). On the rear end surface of the inner tube (20) near the source of the clip (21), a rear end concave portion (22b) is provided so as to be adjacent to and connected to the opening through which the operating member (7) protrudes. The bottom surface (22c) of the rear end concave portion (22b) is formed to be approximately flat.

[0027] On the outer surface of the center in the axial direction of the inner tube (20), a roughly rectangular guide projection (23) is formed. The guide projection (23) is provided on the side opposite to the clip (21) with respect to the central axis of the inner tube (20). The circumferential width of the guide projection (23) is only slightly smaller than the width of the first guide groove (12) of the rear axis (10). On the outer surface of the inner tube (20) near the rear of the guide projection (23), two roughly rectangular second engaging parts (24) are formed. The two second engaging parts are roughly rectangular projections. Each of the two second engaging parts (24) is positioned at a location rotated approximately 90 degrees around the central axis of the inner tube (20) with respect to the guide projection (23). Each of the two second engaging parts (24) faces each other. The width of the second interlocking part (24) in the circumferential direction is only slightly smaller than the width of the second guide groove (13) of the rear shaft (10).

[0028] Two rectangular concave portions (25) are formed on the front outer surface of the inner tube (20). The concave portions (25) are concave portions of uniform depth from the outer surface of the inner tube (20). Each of the two concave portions (25) is positioned at a location rotated approximately 90 degrees around the central axis of the inner tube (20) relative to the clip (21). Each of the two concave portions (25) faces each other. Accordingly, each of the two concave portions (25) is aligned in the axial direction with the corresponding second interlocking portion (24). In the rectangular concave portions (25), a roughly U-shaped U-shaped hole (26) is formed, consisting of a through hole along the rear edge portion and two through holes extending forward from each of the ends of the through hole. An elastic deformation portion (27) is formed inside the concave portion (25) by means of a U-shaped hole (26). The elastic deformation portion (27) is cantilever-shaped and extends toward the rear within the concave portion (25). On the outer surface of the elastic deformation portion (27), a roughly spherical projection (28) is formed that protrudes outward in the radial direction.

[0029] On the outer surface near the first opening end (29) at the front of the inner tube (20), a ring-shaped surface (29a) formed with a smaller diameter than other parts is formed. On the inner surface near the first opening end (29), an inclined surface (29b) inclined toward the front is formed. On the inner surface of the first opening end (29), two proximate sections (30) extending toward the rear from the front end surface of the inner tube (20) are formed. The proximate sections (30) are formed in a concave shape that is thinner than other parts including the inclined surface (29b) in the first opening end (29). The boundary between the proximate sections (30) and other parts of the inner tube (20) is formed in a stepped shape (Fig. 7). Each of the two proximate sections (30) is positioned in a radial alignment with respect to the clip (21). In other words, each of the two approaching parts (30) is positioned at a location rotated about 90 degrees around the central axis of the inner tube (20) with respect to the two concave parts (25). Each of the two approaching parts (30) faces each other.

[0030] With reference to FIGS. 8 to 10, the assembly of the rear shaft (10) and the inner tube (20) will be described. FIG. 8 is an exploded perspective view of the rear shaft (10) and the inner tube (20), FIG. 9 is a longitudinal cross-sectional view of the assembly part of the rear shaft (10) and the inner tube (20), and FIG. 10 is a longitudinal cross-sectional view of another assembly part of the rear shaft (10) and the inner tube (20) corresponding to line DD in FIG. 9.

[0031] The first opening end (29) of the inner tube (20) is inserted into the second opening end (18) at the rear of the rear shaft (10). At this time, the position of the inner tube (20) around the central axis line is aligned so that the guide projection (23) of the inner tube (20) enters into the first guide groove (12) of the rear shaft (10). When the insertion of the first opening end (29) continues while the guide projection (23) has entered into the first guide groove (12), next, each of the two second interlocking parts (24) of the inner tube (20) enters into the corresponding second guide groove (13) of the rear shaft (10).

[0032] Additionally, as the insertion of the first opening end (29) continues, the first opening end (29) reaches the convex portion (15) of the rear shaft (10). Here, the outer diameter of the first opening end (29) of the inner tube (20), that is, the outer diameter of the portion of the ring-shaped surface (29a), is only slightly larger than the diameter of the inscribed circle of the two opposing convex portions (15) of the rear shaft (10). Therefore, when the inner tube (20) is pressed against the rear shaft (10), the first opening end (29) is elastically deformed as it travels over the inclined surface (16) provided at the rear end of the convex portion (15). By doing so, the first opening end (29) of the inner tube (20) can be further inserted into the interior of the rear shaft (10). Finally, the convex portion (15) of the rear shaft (10) is received within the concave portion (25) of the inner tube (20), and the two second interlocking portions (24) of the inner tube (20) are interlocked in the radial direction with the first interlocking portion (14) of the rear shaft (10) corresponding to the second guide groove (13), so that the assembly, i.e., fitting, of the rear shaft (10) and the inner tube (20) is completed.

[0033] When the assembly of the rear shaft (10) and the inner tube (20) is complete, even if a force is applied to the inner tube (20) to pull it out from the rear shaft (10), as shown in FIG. 10, the catch surface (17) of the convex portion (15) of the rear shaft (10) catches on the front end (25a) of the concave portion (25) of the inner tube (20), thereby preventing the inner tube (20) from coming out from the rear shaft (10). In addition, the protrusion (28) of the elastic deformation portion (27) comes into contact with the surface of the convex portion (15) of the rear shaft (10), thereby elastically deforming the elastic deformation portion (27) so that it bends inward in the radial direction. Because of this, the rear end edge (27a) of the inner surface of the elastic deformation portion (27) protrudes inward in the radial direction within the inner tube (20). As a result, for example, when replacing the refill (4), the rotor (40) positioned at the rear inside the inner tube (20) is caught on the rear edge (27a) of the inner surface of the elastic deformation part (27), thereby preventing the rotor (40) from falling off.

[0034] When the first opening end (29) undergoes elastic deformation, the portion of the approaching portion (30) is thinner than other portions, so its rigidity is lowered, making it easy to undergo elastic deformation. In other words, if the opening end has a uniform thickness over the entire circumference, the opening end becomes difficult to undergo elastic deformation due to the circular cross-sectional shape of the opening end. Therefore, according to the inner tube (20) having the first opening end (29) equipped with the approaching portion (30), compared to the case of the same inner tube and rear shaft where the approaching portion is not provided at the opening end, it can be assembled with less force, and sufficient fitting force can be maintained between the rear shaft (10) and the inner tube (20). In addition, because the stress in the first opening end (29) and its vicinity is absorbed and relieved by the elastic deformation of the approaching portion (30), the durability of the inner tube (20) is improved. In short, in the writing instrument (1), easy assembly, sufficient fitting force, and durability can be realized.

[0035] Additionally, the aforementioned approach portion (30) is formed in a concave shape on the inner surface of the first opening end portion (29) of the inner tube (20), but it may also be formed in a concave shape on the outer surface of the first opening end portion (29). In the approach portion (30), the boundary with other parts of the inner tube (20) is formed in a stepped shape, but it may also be formed so that the approach portion (30) and other parts of the inner tube (20) are smoothly and continuously connected. At least one approach portion (30) may be provided, and three or more may be provided. When at least two approach portions (30) are provided, it is preferable that they be arranged at equal intervals around the central axis of the inner tube (20), but they do not need to be arranged at equal intervals. The approach portion (30) may be provided at least at the opening edge of the first opening end portion (29) or near the opening edge.

[0036] It is preferable that the approach portion (30) be positioned in a location where elastic deformation is likely to be greater. For example, in the inner tube (20), a pair of concave portions (25) and a pair of approach portions (30) are positioned at a location rotated approximately 90 degrees around the central axis of the inner tube (20). When assembling the rear shaft (10) and the inner tube (20), if the convex portion (15) of the rear shaft (10) passes over the part of the first opening end (29) of the inner tube (20) corresponding to the concave portion (25), the corresponding part undergoes elastic deformation inward in the radial direction. Meanwhile, the part of the first opening end (29) rotated approximately 90 degrees around the central axis of the inner tube (20) from that part has a maximum radius of curvature, and therefore the stress is also maximum. In the inner tube (20), since a contact portion (30) is provided in the part where stress is maximum, stress is absorbed by elastic deformation, thereby preventing damage to the first opening end portion (29). In short, depending on the shape, form, or number of the fitting portions, the shape (e.g., width in the circumferential direction, length extending in the axial direction, depth from the inner surface of the inner tube (20)), and number of contact portions (30) can be appropriately configured.

[0037] When the assembly of the rear shaft (10) and the inner tube (20) is completed, as described above, each of the two second interlocking parts (24) of the inner tube (20) is engaged with the corresponding first interlocking part (14) within the second guide groove (13). By the engagement of the first interlocking part (14) and the second interlocking part (24), the inner tube (20) is prevented from coming off the rear shaft (10) by the use of the clip (21). That is, when gripping an item by the clip (21), the clip (21) opens up at the point of connection with the protruding part (22). At this time, the force of the clip (21) opening acts on the rear end surface (10a) of the rear shaft (10) through the bulging part (22), and a force is applied to the inner tube (20) to pull it out from the rear shaft (10) by the “lever principle” of pulling out a stopper using a bottle opener. However, since the two second interlocking parts (24) of the inner tube (20) are in the second guide groove (13) and are engaged with the first interlocking part (14), the movement of the inner tube (20) against the rear shaft (10) is restricted as part of the force action by the lever principle, and the inner tube (20) is prevented from coming out of the rear shaft (10).

[0038] In the above-described embodiment, the second guide groove (13) of the rear shaft (10) and the first engaging part (14) formed therein, and the second engaging part (24) of the inner tube (20) are each positioned opposite each other, that is, at a position rotated about 90 degrees around the center axis line with respect to the clip (21), but, for example, they may be positioned at a position rotated in the range of 45 to 135 degrees with respect to the clip (21).

[0039] The first engaging portion (14) of the rear shaft (10) and the second engaging portion (24) of the inner tube (20) may be configured arbitrarily, provided that they engage when the rear shaft (10) and the inner tube (20) are fitted together and that the release of the fitting is prevented by the expansion of the clip (21). For example, a key groove extending in the axial direction may be formed on the inner surface of the rear shaft, and a key projection extending in the axial direction corresponding to the key groove may be formed on the outer surface of the inner tube. When the rear shaft and the inner tube are fitted together, the key projection may be received in the key groove, thereby restricting the movement of the inner tube relative to the rear shaft when the clip is used.

[0040] In the above-described embodiment, the inner tube of the writing instrument is described as the first tube-shaped member and the shaft, i.e., the rear shaft, is described as the second tube-shaped member, and the assembly thereof is described; however, the above-described configuration may also be applied to the assembly of two other tube-shaped members in the writing instrument. For example, the above-described configuration may also be applied to the assembly of the front shaft and the rear shaft. Furthermore, the above-described configuration may also be applied to writing instruments other than click-type writing instruments, such as cap-type writing instruments.

[0041] In the above-described embodiment, the configuration was such that a concave portion provided in the first cylindrical member and a convex portion provided in the second cylindrical member were fitted together; however, the above configuration may also be applied to a configuration in which, for example, a ring-shaped first convex portion provided on the outer surface of the first cylindrical member inserted inside and a plurality of second convex portions provided along the circumferential direction on the inner surface of the second cylindrical member are fitted together. The above configuration may also be applied to a configuration in which one or both of the first cylindrical member and the second cylindrical member are fitted without having one or both of the convex portions or concave portions. In short, the above configuration may be applied to any configuration of a writing instrument having a first cylindrical member having a first opening end and a second cylindrical member having a second opening end, wherein the first opening end is inserted into the interior of the second opening end and is capable of fitting with the first cylindrical member.

[0042] On the surface of the shaft (2) excluding the grip (3a), that is, the surface of the rear shaft (10) and the inner shaft (20), a surface finishing process, known as pear-shaped processing, is performed to prevent scratches on the surface and to express a matte finish. The arithmetic mean roughness (Ra) of the pear-shaped surface is preferably in the range of 5㎛ to 50㎛. If the value is smaller than 5㎛, the surface becomes close to a mirror surface, making scratches more noticeable, while if the value is larger than 50㎛, mold release during resin molding becomes difficult. Furthermore, in order to obtain good design quality, particularly a matte finish, it is even more preferable for the arithmetic mean roughness (Ra) to be in the range of 10㎛ to 25㎛. The above-mentioned pear-shaped surface can be obtained by performing treatments such as etching, sandblasting, or polishing rather than mirror finishing on the mold surface. In addition, the surface of the mold part after electrical discharge machining can be made into a different surface by leaving it unpolished. The arithmetic mean roughness (Ra) of the different surface refers to the arithmetic mean roughness (Ra) defined in JIS B0601:2013, and the measurement of surface roughness is performed using (Mitsutoyo product model name SJ-301). Furthermore, instead of the grip (3a) of the front axis (3), the surface of the front axis (3) is made of the same material and has the same surface roughness as the rear axis (10), thereby obtaining a design that gives a sense of unity as the entire shaft (2).

[0043] Hereinafter, with reference to FIGS. 11 to 17, a writing instrument (100) according to another embodiment of the present invention, which achieves the same effect as the embodiment described above, will be described. As described above, since common reference numerals are attached to corresponding components, the description of these components is omitted.

[0044] FIG. 11 is a cross-sectional view of the rear portion of a writing instrument (100) in a non-writing state according to another embodiment of the present invention, and FIG. 12 is a cross-sectional view of the rear portion of the writing instrument (100) of FIG. 11 in a writing state. The writing instrument (100) differs from the writing instrument (1) described above only in the shape of the inner tube (120) and the rotor (140), and is identical in the shape of other parts. In the non-writing state shown in FIG. 11, the rear end surface of the inner cam (43) of the rotor (140) and the front end surface of the outer cam (9) of the inner tube (20) are not engaged, so the rotor (140) is retracted together with the refill (4). In the writing state shown in FIG. 12, since the rear end surface of the inner cam (43) of the rotor (140) and the front end surface of the outer cam (9) of the inner tube (20) are engaged, the rotor (140) advances together with the refill (4), and the writing part (4a) protrudes from the front end of the shaft (2).

[0045] FIG. 13 is a perspective view of the inner tube (120), FIG. 14 is a longitudinal cross-sectional view of the inner tube (120), and FIG. 15 is an exploded perspective view of the rear shaft (10) and the inner tube (120). The inner tube (120) differs from the inner tube (20) of the writing instrument (1) in that it does not have a ring-shaped surface (29a) formed on the outer surface near the first opening end (29) at the front of the inner tube (20), has a third interlocking part (31) in addition to the second interlocking part (24), and has a bottom surface (122c) instead of a rear concave part (22b). Additionally, the inner tube (120) may have a ring-shaped surface (29a).

[0046] In the inner tube (120), a rear end recess (122b) is provided on the rear end surface of the inner tube (120) near the source of the clip (21), so as to be adjacent to and connected to the opening through which the operating member (7) protrudes. The bottom surface (122c) of the rear end recess (122b) is formed in a convex curved shape that protrudes toward the rear and slopes overall toward the opening. By having the rear end recess (122b) and having the bottom surface (122c) formed in a convex curved shape, the inner tube (120) can obtain good design quality. Furthermore, by having the bottom surface (122c) in a convex curved shape, the accumulation of dust, etc. can be prevented, and even if dust, etc. is accumulated, it can be easily removed. Additionally, the bottom surface (122c) may be a flat inclined surface that slopes toward the opening through which the operating member (7) protrudes, in addition to a convex curved shape.

[0047] On the outer surface of the inner tube (120) at the rear of each second interlocking part (24), a third interlocking part (31) is formed integrally with the second interlocking part (24). The two third interlocking parts (31) are trapezoidal projections with their rear portions connected to the fitting surface (22a). The circumferential width of the third interlocking part (31) is greater than the width of the second interlocking part (24). Additionally, the height of the third interlocking part (31) is lower than the height of the second interlocking part (24). In the assembly of the rear shaft (10) and the inner tube (120), as described above, the second interlocking part (24) of the inner tube (120) is interlocked with the first interlocking part (14) of the corresponding rear shaft (10) in the radial direction within the second guide groove (13). At this time, the circumferential width of the third interlocking part (31) is greater than the width of the second guide groove (13) of the rear shaft (10). Therefore, the portion of the third interlocking part (31) that is larger than the width of the second guide groove (13) fits with the inner surface of the rear shaft (10) near the second guide groove (13). As a result, rattling of the inner tube (120) relative to the rear shaft (10) can be more reliably prevented, for example, when gripping an item by the clip (21) as described above.

[0048] Additionally, the third interlocking part (31) of the inner tube (120) can be in any location and shape as long as it can be fitted with the inner surface of the rear shaft (10). Accordingly, the third interlocking part (31) does not need to be aligned in the axial direction with the second interlocking part (24). The third interlocking part (31) may be one or three or more.

[0049] FIG. 16 is a perspective view of the rotor (140), and FIG. 17 is a side view of the rotor (140). The rotor (140) differs from the rotor (40) of the writing instrument (1) only in the shape of the front surface. Accordingly, the rotor (140) consists of an insertion part (41) that is inserted into the front opening of the operating member (7) and used by fitting it in place, and a main body part (42) formed in front of the insertion part (41). On the outer surface of the main body part (42), four inner cams (43) extending in the front-rear direction are provided at equal intervals in the circumferential direction. On the ring-shaped rear end surface of the main body part (42), a cam receiving surface (44) that cooperates with the cam surface (7a) of the operating member (7) is provided. Additionally, on the ring-shaped front surface of the rotor (140), a pressure surface (145) is provided, which is a plane inclined with respect to a plane perpendicular to the central axis of the rotor (140). A pressure projection (146) is provided at the rearmost portion of the inclined pressure surface (145). The pressure projection (146) has a flat and inclined side surface (146a) provided near the central axis and a flat front surface (146b) provided at the tip of the pressure projection (146). The outer surface of the pressure projection (146) opposite to the central axis is provided as a plane with the main body (42). A ventilation groove (147) is provided on the pressure surface (145) along the same straight line passing through the central axis. By means of the ventilation groove (147), the interior of the refill (4) is prevented from being sealed between the front surface of the rotor (140) and the ventilation groove (147).

[0050] The pressure surface (145) and the pressure projection (146) constitute a pressure means for applying pressure to the rotor (140) so as to incline it with respect to the central axis of the writing instrument (100). This will be explained with reference to FIGS. 11 and FIGS. 12.

[0051] When the writing instrument (100) is in a non-writing state as shown in FIG. 11, the operating member (7) is pressed backward by the spring (5) via the refill (4) and the rotor (140). Therefore, the rattling of the operating member (7) is minimal or almost non-existent. On the other hand, when the writing instrument (100) is in a writing state as shown in FIG. 12, the rear end surface of the inner cam (43) of the rotor (40) and the front end surface of the outer cam (9) of the inner tube (120) are engaged, so the pressing force of the refill (4) is not transmitted to the operating member (7). Therefore, when the operating member (7) is not fixed, there is a possibility that the operating member (7) will rattle by the distance between the position shown in FIG. 11 and the position shown in FIG. 12. In other words, since writing typically involves the continuous up-and-down movement of the writing instrument, if the operating member is not fixed, it may rattle up and down in accordance with the writing motion. This rattling of the operating member causes unpleasant sounds or vibrations for the user.

[0052] In the writing instrument (100) according to the present embodiment, particularly as shown in FIG. 12, the pressing surface (145) of the rotor (140) is pressed by the rear end surface of the refill (4) which is pressed backward by the spring (5). While the rear end surface of the refill (4) is a surface perpendicular to the central axis of the writing instrument (100), the pressing surface (145) is a plane inclined with respect to the surface perpendicular to the central axis of the rotor (140). Therefore, due to the pressing force of the spring (5), a force is applied in a direction inclined with respect to the central axis of the rotor (140) so that the front of the pressing surface (145) and the front of the rear end surface of the refill (4) come into contact. As a result, the central axis of the rotor (140) is inclined with respect to the central axis of the writing instrument (100). In addition, at this time, the perimeter edge of the rear end surface of the refill (4) comes into contact with the pressure projection (146), specifically the side (146a), thereby restricting the rear end of the refill (4) from moving in the radial direction along the pressure surface (145). As a result, the central axis of the refill (4) is aligned with the central axis of the writing instrument (100), so that the rotor (140) can be tilted more reliably.

[0053] The insertion part (41) of the inclined rotor (140) presses the operating member (7) into which the insertion part (41) is inserted from the inside. That is, the operating member (7) is pressed against the inner surface of the shaft (2) by the insertion part (41) of the rotor (140), specifically against the inner surface of the opening of the inner tube (120) from which the operating member (7) protrudes. Because of this, the operating member (7) is held and fixed between the insertion part (41) of the rotor (140) and the inner surface of the shaft (2), thereby preventing rattling of the operating member (7). As a result, the occurrence of sound or vibration during writing operation can be prevented, and the writing sensation for the user can be improved.

[0054] Additionally, either the pressure surface (145) or the pressure projection (146) may be omitted. Additionally, a configuration corresponding to the pressure surface (145) and the pressure projection (146) may be provided on the rear end surface of the refill (4). That is, as a pressure means, a pressure projection may be provided on the rear end surface of the refill (4), or a pressure surface may be provided on the rear end surface of the refill (4) that is a plane inclined with respect to a plane perpendicular to the central axis of the refill (4). The pressure means may be a separate member mounted on the refill (4) or the rotor (140). Explanation of the symbols

[0055] 1 : Writing instruments 2 : Anterior pain 3 : Record player 4 : Refill 5 : Spring 40: Rotor 7 : Absence of operation 9 : External Campus 10 : Rear Axel 11 : Blind 12 : Guide Home 1 13 : 2nd Guide Home 14: First interlocking part 15: Convex part 16 : Slope 17 : Hanging surface 18: Second opening end 20 : Collusion 21 : Clip 22 : Swelling part 23 : Guide protrusion 24 : Second interlocking part 25: Concave part 26: U-shaped hole 27 : Elastic deformation part 28: Protrusion 29 : First opening end 30 : Close Combat

Claims

Claim 1 A writing instrument having a first tubular member having a first opening end, and a second tubular member having a second opening end, wherein the first opening end is inserted into the interior of the second opening end and is compatible with the first tubular member, and at least one thin portion is provided at the opening edge or near the opening edge of the first opening end, the thickness of which is thinner than that of the opening edge or other portion near the opening edge. Claim 2 A writing instrument according to claim 1, wherein the at least one proximate part has at least two proximate parts, and each of the at least two proximate parts is arranged at equal intervals around the central axis of the first cylindrical member. Claim 3 A writing instrument according to claim 1 or claim 2, wherein the boundary between the at least one adjacent part and the other part is formed in a stepped shape. Claim 4 A writing instrument according to claim 1 or claim 2, wherein the first tube-shaped member is an inner tube, the second tube-shaped member is a shaft or rear shaft into which the inner tube is inserted from the rear end, a bulging portion is formed at the rear end of the inner tube, the front end surface of the bulging portion contacts the rear end surface of the shaft or rear shaft, the inner tube has a clip, at least one first engaging portion is provided on the inner surface of the shaft or rear shaft at a position rotated by a predetermined angle around the center axis line with respect to the clip in a fitted state, and a second engaging portion capable of engaging with the first engaging portion is provided on the outer surface of the inner tube. Claim 5 A writing instrument according to claim 1 or claim 2, wherein a guide projection is provided on the outer surface of the first cylindrical member, and the second cylindrical member is provided with a groove or notch that extends from the second opening end toward the interior of the second cylindrical member and receives the guide projection to guide the insertion of the first cylindrical member. Claim 6 A writing instrument according to claim 1 or claim 2, further comprising a writing element, a spring for pressing the writing element backward, an outer cam provided on the inner surface of the first cylindrical member or the second cylindrical member, a cylindrical operating member, and an insertion portion insertable into the front opening of the operating member, a rotor that is pressed backward via the writing element by the spring and configured to cooperate with the outer cam by the operation of the operating member, and a pressing means provided between the writing element and the rotor, wherein the pressing means is configured to cause the central axis of the rotor to be inclined with respect to the central axis of the first cylindrical member or the second cylindrical member. Claim 7 A writing instrument according to claim 6, wherein the pressing means is a pressing surface inclined with respect to a plane orthogonal to the central axis of the rotor provided on the front surface of the rotor, or a pressing projection provided on the front surface of the rotor.

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