Writing instrument part and writing instrument equipped therewith

Abstract

To provide a writing instrument part and a writing instrument equipped with the writing instrument part, in which the occurrence of sink marks in the vicinity of a protrusion is suppressed in a cylindrical writing instrument part with the protrusion formed on an outer surface thereof.SOLUTION: An inner cylinder 3 having a cylindrical member that is an injection molded product has at least a cam protrusion section 21 having a first wall thickness t1 that extends in the axial direction and a part of a first groove section 22 having a second wall thickness t2 that extends in the axial direction and is thinner than the first wall thickness t1. A connection section 11 is formed on the outer surface of the inner cylinder 3, and the shape of the cross section of the cylindrical member including the first wall thickness part, the second wall thickness part and the protrusion is linearly symmetrical.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a writing instrument part and a writing instrument equipped with a writing instrument part. [Background technology]

[0002] In injection molding, the molding shrinkage of the material may cause depressions, so-called "sink marks", on the surface of the molded product, which may impair the appearance. Sink marks may occur due to differences in thickness of the molded product. For example, Patent Document 1 discloses a writing instrument part in which a tube part and a clip part are integrally injection molded. On the inner peripheral surface of the tube part, a plurality of ribs extending in the axial direction are formed at equal intervals along the circumferential direction. Since the tube part has parts with different thicknesses, such as the clip part provided on the outer peripheral surface of the tube part and the plurality of ribs provided on the inner peripheral surface of the tube part, sink marks may occur on the outer peripheral surface of the tube part around the clip part, for example.

[0003] Incidentally, there is known a knock-type writing instrument that has a barrel with multiple outer cams formed on its inner circumferential surface and a rotor with multiple inner cams formed on its outer circumferential surface, and that can switch between a writing state and a non-writing state by engaging or disengaging the outer cams with the inner cams in response to a knock operation of a knock member. Here, the relationship between conventional writing instrument parts and sink marks will be described with reference to Figs. 9 and 10.

[0004] FIG. 9 is a vertical cross-sectional view of the rear end of an inner tube 103 of a conventional knock-type writing implement, and FIG. 10 is a horizontal cross-sectional view taken along line CC in FIG. 9. In FIG. 9 and FIG. 10, a barrel is used as a writing implement part that is a cylindrical member, specifically, an inner tube 103 that constitutes the barrel, is used as an example. A clip 110 is integrally provided on the outer peripheral surface of the inner tube 103. The clip 110 has a connecting portion 111 and a clip body 112. The clip body 112 is provided on the outer peripheral surface of the inner tube 103 via the connecting portion 111. Four outer cams 120 are provided on the inner peripheral surface of the inner tube 103 at equal intervals along the circumferential direction. Each of the outer cams 120 has a cam protrusion portion 121 extending in the axial direction. A first groove portion 122 extending in the axial direction is defined by adjacent outer cams 120. A second groove portion 123 extending in the axial direction is formed in the outer cam 120, that is, in the center in the width direction, that is, in the circumferential direction, of the cam protrusion portion 121.

[0005] If the cam protrusion 121 is a first thick portion having a first thickness t11, the first groove 122 is a second thick portion having a second thickness t12, and the second groove 123 is a third thick portion having a third thickness t13, the second thickness t12 is thinner than the first thickness t11, and the third thickness t13 is thinner than the first thickness t11 and thicker than the second thickness t12. The inner cylinder 103 in the portion where the outer cam 120 is not provided mainly has the second thickness t12. In the knock member having eight sliding protrusions provided at equal intervals along the circumferential direction on the outer peripheral surface, each of the sliding protrusions is configured to be movable in the front-rear direction within the first groove 122 and the second groove 123 of the outer cam 120 formed in the inner cylinder 103 by the knock operation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2002-103882 A Summary of the Invention [Problem to be solved by the invention]

[0007] The thickness of the portion of the outer cam 120, i.e., the first thickness t11 and the third thickness t13, is thicker than the thickness of the portion of the inner tube 103 where the outer cam 120 is not provided, i.e., the second thickness t12, and therefore sink marks are likely to occur. In particular, as shown in Fig. 10, in the cross section of the inner tube 103, the symmetry line S of the connection portion 111 with respect to the inner tube 103 does not coincide with the symmetry line of the outer cam, and the shapes of the respective portions in the cross section are not line-symmetrical. As a result, in Fig. 10, the thickness or amount of synthetic resin near the connection portion 111 on the counterclockwise side with respect to the connection portion 111 (portions indicated by reference characters t11 and t13) is larger than the thickness or amount of synthetic resin near the connection portion 111 on the clockwise side with respect to the connection portion 111 (portion indicated by reference character t12). That is, the synthetic resin between the connection portion 111 and the thick portion adjacent to the connection portion 111 is more likely to shrink during injection molding, and sink marks are more likely to occur. In other words, if a protruding portion exists on the outer surface, the synthetic resin in that portion is more likely to shrink in relation to the shape of the inner surface, and sink marks are more likely to occur.

[0008] The present invention aims to provide a cylindrical writing instrument part having a protrusion formed on its outer surface, in which the occurrence of sink marks near the protrusion is suppressed, and a writing instrument equipped with the writing instrument part. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a writing instrument part having a tubular member which is an injection-molded product, wherein the tubular member has at least a first thick portion having a first thickness extending in the axial direction, and a second thick portion extending in the axial direction and having a second thickness thinner than the first thickness, a protrusion is formed on the outer surface of the tubular member, and the cross-sectional shape of the tubular member including the first thick portion, the second thick portion, and the protrusion is line-symmetrical.

[0010] In the cross section, a portion other than the first thick portion may be arranged in radial alignment with the protruding portion. The first thick portion may have a plurality of first thick portions and a plurality of second thick portions, and each of the first thick portions and each of the second thick portions may be arranged at equal intervals along the circumferential direction. The tubular member may have a cylindrical outer peripheral surface. The first thick portions may be a plurality of protruding outer cams cooperating with a rotor, and a first groove portion in which a sliding protrusion of a knock member is arranged may be defined by adjacent outer cams, and a portion of the first groove portion may be the second thick portion. The outer cam may be formed with a second groove portion extending in the axial direction and in which a sliding protrusion of the knock member is arranged, and a portion of the second groove portion may be a third thick portion having a third thickness extending in the axial direction, and the third thickness may be thinner than the first thickness and thicker than the second thickness. In the cross section, a portion of the third thick portion may be arranged in radial alignment with the protruding portion.

[0011] There is also provided a knock-type writing instrument comprising the above-mentioned writing instrument component, a rotor that cooperates with the outer cam, and a knock member that cooperates with the rotor. Effect of the Invention

[0012] According to the aspects of the present invention, a common effect is achieved in that a cylindrical writing instrument part having a protrusion formed on its outer surface is provided, in which the occurrence of sink marks near the protrusion is suppressed, and a writing instrument equipped with the writing instrument part is provided. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a knock-type writing instrument according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a side view of the knock-type writing instrument of FIG. [Diagram 3] FIG. 3 is a vertical cross-sectional view of the knock-type writing instrument of FIG. [Figure 4] FIG. 4 is an exploded perspective view of the knock mechanism. [Diagram 5] FIG. 5 is a vertical cross-sectional view of the barrel. [Figure 6]FIG. 6 is an enlarged view of part A in FIG. [Figure 7] FIG. 7 is a vertical cross-sectional view of the rear end portion of the inner cylinder. [Figure 8] FIG. 8 is a cross-sectional view taken along line BB in FIG. [Figure 9] FIG. 9 is a vertical cross-sectional view of the rear end portion of the inner barrel of a conventional knock-type writing instrument. [Figure 10] FIG. 10 is a cross-sectional view taken along line CC in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Corresponding components are designated by common reference numerals throughout the drawings.

[0015] Fig. 1 is a perspective view of a knock type writing instrument 1 according to an embodiment of the present invention, Fig. 2 is a side view of the knock type writing instrument 1 of Fig. 1, and Fig. 3 is a vertical cross-sectional view of the knock type writing instrument 1 of Fig. 1. In addition, Fig. 4 is an exploded perspective view of the knock mechanism, and Fig. 5 is a vertical cross-sectional view of the barrel 2.

[0016] The knock type writing instrument 1 has a barrel 2 and an inner barrel 3 formed in a cylindrical shape, a refill 5 which is a writing body disposed in the barrel 2 and has a writing part 5a at one end, and a spring 6 which urges the refill 5 rearward. A through hole 2a is formed at the front end of the barrel 2 to allow the writing part 5a of the refill 5 to protrude. In this specification, in the axial direction of the knock type writing instrument 1, the side of the writing part 5a is defined as the "front" side, and the side opposite the writing part 5a is defined as the "rear" side.

[0017] The front end of the inner tube 3 is inserted into the rear end of the barrel 2 and is fitted by screwing. The barrel 2 may be composed of two parts, a front shaft and a rear shaft, including the inner tube 3. A knock mechanism is disposed inside the inner tube 3. The knock mechanism has an outer cam 20 formed on the inner circumferential surface of the inner tube 3, a knock member 30, and a rotor 40. The knock member 30 is configured to cooperate with the rotor 40, and the rotor 40 is configured to cooperate with the outer cam 20. The refill 5 moves in the front-rear direction inside the barrel 2 by the knock mechanism. At this time, the state in which the writing part 5a is immersed in the barrel 2 is called a non-writing state (FIGS. 1 to 3), and the state in which the writing part 5a protrudes from the barrel 2 is called a writing state. In the knock-type writing instrument 1, each component except for the refill 5 and the spring 6 is a writing instrument part that is an injection-molded product manufactured by injection molding of a synthetic resin material, and in particular, the barrel 2, the inner barrel 3 and the knock member 30 are cylindrical components.

[0018] A clip 10 is provided integrally on the outer surface of the inner tube 3, i.e., the cylindrical outer peripheral surface 7. The clip 10 has a connection portion 11 and a clip body 12. The clip body 12 is provided on the outer peripheral surface 7 of the inner tube 3 via the connection portion 11. As shown in FIG. 4, a male thread portion 8 is formed on the outer peripheral surface of the front end portion of the inner tube 3 that is inserted into the rear end portion of the shaft tube 2. Behind the male thread portion 8, an annular fitting portion 9, which is an annular protrusion, is formed.

[0019] Referring to FIG. 5, a female threaded portion 14 that screws into the male threaded portion 8 of the inner tube 3 is formed on the inner peripheral surface of the rear end of the barrel 2. Four fitting projections 15 are formed at equal intervals along the circumferential direction behind the female threaded portion 14. A first reduced diameter portion 16 is formed on the inner peripheral surface of the barrel 2 in front of the female threaded portion 14 so that the inner diameter gradually decreases toward the front. A plurality of ribs 17 that extend in the axial direction and are equally spaced along the circumferential direction are formed on the inner peripheral surface near the front end of the barrel 2. A sloping surface 18 that slopes toward the rear is formed on the rear end of each of the plurality of ribs 17. A second reduced diameter portion 19 is formed on the inner peripheral surface of the barrel 2 near the through hole 2a so that the inner diameter gradually decreases toward the front.

[0020] The barrel 2 has the first reduced diameter portion 16, the inclined surface 18, and the second reduced diameter portion 19, all of which are inclined surfaces facing rearward, which facilitates demolding during injection molding and ensures moldability. For this reason, it is preferable that these inclination angles are less than 45 degrees. During assembly, in which the spring 6 is inserted into the barrel 2 from its rear end, the front end of the spring 6 is guided by the inclined surfaces 18 of the multiple ribs 17. As a result, the front end of the spring 6 is positioned by being surrounded by the multiple ribs 17, and the spring 6 can expand and contract without buckling.

[0021] The surface of the clip body 12 is provided with a step portion 13 so that it appears S-shaped or wavy in a plan view as shown in FIG. 2. The step portion 13 is provided so that the height gradually increases from the center of the clip body 12 toward the outside in the axial direction. The step portion 13 located further back faces the left side in the figure, and the step portion 13 located further forward faces the right side in the figure. That is, the step portion 13 is formed in the clip body 12 so that the inner part of the curve is higher than the outer part of the curve in the up and down curve of the S shape. By having the step portion 13 in the clip 10, it becomes easier for fingers to be caught when the inner tube 3 is screwed into the shaft tube 2, improving the ease of assembly. In addition, the S-shaped appearance presented by the step portion 13 reminds us that the knock-type writing instrument 1 is a sustainable product.

[0022] 5, the knock member 30 is a cylindrical member with a closed rear end and an open front end. Eight sliding protrusions 31 are provided at equal intervals along the circumferential direction on the outer circumferential surface of the front side of the knock member 30. A cam surface 32 is formed on the front end surface of the knock member 30. The cam surface 32 has eight peaks and valleys aligned along the circumferential direction.

[0023] The rotor 40 is composed of an insertion portion 41 formed in a cylindrical shape, which is inserted into the inside of the knock member 30 from the front end portion thereof for centering, and a cam portion 42 formed in a cylindrical shape and disposed in front of the insertion portion 41. The cam portion 42 has a larger outer diameter than the insertion portion 41. A cam receiving surface 43 is formed on the rear end surface of the cam portion 42, which cooperates with the cam surface 32 of the knock member 30 and has a complementary shape. Four inner cams 44, which are protrusions extending in the axial direction, are provided at equal intervals along the circumferential direction on the outer peripheral surface of the cam portion 42. The rear end surface of the refill 5, which is biased rearward by the spring 6, abuts against the front end surface of the rotor 40. A thin groove 45 extending in the radial direction is formed on the rear end surface of the refill 5 to ensure ventilation between the inside and outside of the refill 5.

[0024] FIG. 6 is an enlarged view of part A in FIG. 3. FIG. 6 shows the engagement between the engagement projection 15 of the shaft tube 2 and the annular engagement portion 9 of the inner tube 3. When the front end of the inner tube 3 is inserted and screwed into the inside of the rear end of the shaft tube 2, the female thread portion 14 of the shaft tube 2 and the male thread portion 8 of the inner tube 3 gradually screw together. When the inner tube 3 is gradually inserted into the inside of the shaft tube 2 by continuing to screw it in, eventually, the engagement projection 15 of the shaft tube 2 and the annular engagement portion 9 of the inner tube 3 overcome each other while undergoing elastic deformation, and the rear end surface of the shaft tube 2 abuts against the annular surface of the inner tube 3, completing the screwing and engagement. As a result, the shaft tube 2 and the inner tube 3 are locked in the axial direction by the female thread portion 14 of the shaft tube 2 and the male thread portion 8 of the inner tube 3.

[0025] Generally, when writing with a writing instrument, the entire instrument is subjected to vibrations due to the writing action, and the vibrations may cause the screwing at the screwed portion to gradually loosen. In the knock-type writing instrument 1, the fitting protrusion 15 of the barrel 2 and the annular fitting portion 9 of the inner barrel 3 are engaged in the axial direction, thereby preventing the screwing between the barrel 2 and the inner barrel 3 from loosening.

[0026] Conversely, the fitting protrusion 15 of the barrel 2 and the annular fitting portion 9 of the inner barrel 3 may be provided on the barrel 2 side and the fitting protrusion on the inner barrel 3 side, or annular fitting portions may be provided on both the barrel 2 side and the inner barrel 3 side. Also, a protruding convex portion may be formed on one of the barrel 2 side and the inner barrel 3 side, and a concave portion that fits into the convex portion may be formed on the other of the barrel 2 side and the inner barrel 3 side.

[0027] Fig. 7 is a vertical cross-sectional view of the rear end of the inner cylinder 3, and Fig. 8 is a horizontal cross-sectional view taken along line BB in Fig. 7. Four outer cams 20 constituting part of the knock mechanism are provided at equal intervals along the circumferential direction on the inner peripheral surface of the rear end of the inner cylinder 3. Each of the outer cams 20 has a cam protrusion 21 extending in the axial direction. Adjacent outer cams 20 define a first groove 22 extending in the axial direction. A second groove 23 extending in the axial direction is formed in the center of the outer cam 20, i.e., the cam protrusion 21, in the width direction, i.e., in the circumferential direction.

[0028] If the cam protrusion 21 is a first thick portion having a first thickness t1, the first groove 22 is a second thick portion having a second thickness t2, and the second groove 23 is a third thick portion having a third thickness t3, the second thickness t2 is thinner than the first thickness t1, and the third thickness t3 is thinner than the first thickness t1 and thicker than the second thickness t2. The inner cylinder 3 in the portion where the outer cam 20 is not provided mainly has the second thickness t2.

[0029] In an assembled state, each of the sliding protrusions 31 of the knock member 30 is configured to be movable in the front-rear direction within the first groove portion 22 and the second groove portion 23 of the outer cam 20 formed in the inner cylinder 3. In the knock type writing instrument 1 in the non-writing state, each of the inner cams 44 is disposed in the first groove portion 22 of the outer cam 20, and in the knock type writing instrument 1 in the writing state, each of the inner cams 44 is engaged with the outer cam 20 in the axial direction. The cam surface 32 of the knock member 30 and the cam receiving surface 43 of the rotor 40 are configured such that, when the inner cam 44 is engaged with the outer cam 20 or accommodated in the first groove portion 22 between the outer cams 20, the peaks of the cam surface 32 are positioned on the slope between the adjacent peaks and valleys of the cam receiving surface 43 in the circumferential direction. Therefore, when the inclined surface of the cam surface 32 presses the inclined surface of the cam receiving surface 43 by a knock operation, the rotor 40 receives a circumferential component force due to this operation load and the biasing force of the spring 6, and rotates in the circumferential direction.

[0030] That is, when a knock operation is performed to press the knock member 30 forward, the cam surface 32 of the knock member 30 and the cam receiving surface 43 of the rotor 40 cooperate to rotate the rotor 40. In response to the rotation of the rotor 40, the inner cam 44 engages with the outer cam 20 formed on the inner cylinder 3 or is accommodated in the first groove portion 22 between the outer cams 20. When the inner cam 44 is accommodated in the first groove portion 22 between the outer cams 20, the outer cam 20 is accommodated between the inner cams 44. In short, the knock type writing instrument 1 can be switched between a writing state and a non-writing state by the outer cam 20 and the inner cam 44 engaging or disengaging with each other in response to the knock operation of the knock member 30.

[0031] Unlike the conventional inner cylinder 103 shown in FIG. 10, the inner cylinder 3 of the knock-type writing instrument 1 has a symmetry line S of the connection part 11 with respect to the inner cylinder 3 and a symmetry line of the outer cam, as shown in the cross section of FIG. 8. That is, the shape of each part in the cross section of the inner cylinder 3 is linearly symmetrical with respect to the symmetry line S. Specifically, with respect to the symmetry line S passing through the center of the connection part 11 and the axial center of the inner cylinder 3 in the cross section, the second groove part 23 is divided symmetrically for the outer cam 20 closest to the connection part 11 and the outer cam 20 furthest from the connection part 11 among the four outer cams 20, the cam protrusion part 21 is arranged symmetrically, and the other two outer cams 20 are arranged symmetrically with respect to each other. Therefore, in particular, in the outer cam 20 closest to the connection part 11, biased shrinkage that is likely to occur in the conventional inner cylinder 10 shown in FIG. 10 is unlikely to occur due to the relationship between the connection part 11 and the shape of the inner surface of the inner cylinder 3 near the connection part 11 during injection molding of a synthetic resin material. As a result, the occurrence of sink marks in the inner cylinder 3 can be suppressed.

[0032] In the shape of the inner surface of the inner tube 3, a symmetric line that symmetrically divides the first groove portion 22 may be considered in addition to the symmetric line S that symmetrically divides the second groove portion 23, but it is preferable that the second groove portion 23 is arranged in radial alignment with the connection portion 11 as shown in Fig. 8. That is, since the second thickness t2 of the first groove portion 22 is thinner than the third thickness t3 of the second groove portion 23, the second groove portion 23 is aligned in the radial direction with the connection portion 11, and therefore the thinner first groove portion 22 is arranged on the circumferential outside of the connection portion 11, and the occurrence of sink marks can be further suppressed. However, the first groove portion 22 may be arranged in radial alignment with the connection portion 11.

[0033] In addition, sink marks can also be suppressed by increasing the axial length of the outer cam 20, i.e., the cam protrusion 21, particularly the length of the rear end side of the inner tube 3, and by making the first thickness t1 of the cam protrusion 21 thicker.

[0034] In the knock-type writing instrument 1, the synthetic resin members forming each part are all made of the same material and grade, which makes it easy to reuse them. The spring 6 may also be made of the same material as the knock member 30 and the like. It is preferable to use recycled plastic as the synthetic resin in order to reduce the environmental impact. Recycled plastic refers to plastics that are recycled as plastic raw materials for molding by melting and kneading separately collected plastics, and plastics that are recycled as plastic molded products by molding the plastic raw materials for molding. Specific examples of recycled plastics include recycled products such as polypropylene and polycarbonate. Additives such as antioxidants, ultraviolet absorbers, light stabilizers, lubricants, and compatibilizers are added for the purpose of stabilizing the quality of plastics produced. It is particularly preferable to use additives with excellent light resistance. By adding a colorant, the appearance of the resin surface, which has variations, can be stabilized.

[0035] The separated and collected plastic may be marine plastic collected from the sea. In particular, when marine plastic is used for injection molding, sink marks are likely to occur due to the fluidity during molding. In this case, the occurrence of sink marks can be suppressed by configuring the inner cylinder 3 as in the above-described embodiment.

[0036] The refill 5 may be a writing instrument of other types, such as a ballpoint pen, a marking pen, a touch pen, an eraser, etc. Also, a part or the whole of the knock member 30 may be an erasing portion that erases handwriting made by a knock-type writing instrument.

[0037] The refill 5 may be a ballpoint pen containing thermochromic ink. Here, the thermochromic ink refers to ink that has the property of maintaining a predetermined color (first color) at room temperature (e.g., 25°C), changing to another color (second color) when heated to a predetermined temperature (e.g., 60°C), and then returning to the original color (first color) when cooled to a predetermined temperature (e.g., -5°C). In a thermochromic writing instrument using thermochromic ink, the second color is made colorless, and the term "erasing" refers to heating a line drawn in the first color (e.g., red) to make it colorless. Therefore, the friction member, which is the erasing part, rubs against the writing surface on which the line was drawn to generate frictional heat, thereby changing the drawn line to colorless, that is, erasing it. It should be noted that the second color may be a color other than colorless.

[0038] Although the embodiment of the present invention has been described using the knock-type writing instrument 1 as an example, the present invention may be applied to other writing instruments, such as cap-type writing instruments and multi-core writing instruments. In short, the present invention may be applied arbitrarily as long as the writing instrument part has at least a first thick portion having a first thickness extending in the axial direction and a second thick portion having a second thickness extending in the axial direction and thinner than the first thickness, a protrusion is formed on the outer surface of the cylindrical member, and the cross-sectional shape of the cylindrical member including the first thick portion, the second thick portion, and the protrusion is line-symmetrical.

[0039] For example, the outer cam 20 may be configured without the second groove portion 23. Also, instead of the outer cam, the first thick portion and the second thick portion may be configured by a protrusion for fitting purposes and other portions. The inner surface may be formed into a cylindrical surface, and the first thick portion and the second thick portion may be formed so as to protrude radially outward. In this case, it is preferable that the portion other than the first thick portion is aligned radially with the protrusion in the cross section. Also, it is preferable that the outer cam has a plurality of first thick portions and a plurality of second thick portions, and each of the first thick portions and each of the second thick portions are arranged at equal intervals along the circumferential direction.

[0040] The tubular member may be, for example, a polygonal tubular member other than the inner tube 3 having a cylindrical outer peripheral surface. The protrusion formed on the outer or outer peripheral surface of the tubular member may be any protrusion, for example, a decorative protrusion, other than the connection portion 11 of the clip 10. The protrusion may be configured line-symmetrically in the vicinity of the outer surface of the tubular member, and may not be symmetric in a portion separated from the outer surface to an extent that does not affect the sink mark, as shown in the shape of the clip body 12, for example.

[0041] As described above, in a cylindrical writing instrument part having a protrusion formed on its outer surface, by optimizing the internal shape and arrangement and reducing unevenness in the thickness of the part, it is possible to provide a writing instrument part and a writing instrument equipped with a writing instrument part in which the occurrence of sink marks near the protrusion is suppressed. [Explanation of symbols]

[0042] 1. Knock-type writing implement 2 shaft cylinder 3 Inner cylinder 5 Refills 7 Outer surface 10 Clips 11 Connection 12 Clip body 20 Outer Cam 21 Cam protrusion 22 First groove 23 Second groove

Claims

1. A writing implement part having a cylindrical member which is an injection molded product, the cylindrical member has at least a first thick portion extending in an axial direction and having a first thickness, and a second thick portion extending in the axial direction and having a second thickness thinner than the first thickness, A protrusion is formed on the outer surface of the cylindrical member, A component for a writing instrument, characterized in that the cross-sectional shape of the tubular member including the first thick portion, the second thick portion and the protruding portion is line-symmetrical.

2. 2. The writing implement component according to claim 1, wherein in the cross section, a portion other than the first thick portion is aligned radially with the protruding portion.

3. 3. A writing instrument part as described in claim 1 or 2, comprising a plurality of the first thick portions and a plurality of the second thick portions, each of the first thick portions and each of the second thick portions being arranged at equal intervals along the circumferential direction.

4. 2. The writing instrument part according to claim 1, wherein the first thick portion is a plurality of protruding outer cams cooperating with a rotor, adjacent outer cams define a first groove portion in which a sliding protrusion of a knock member is disposed, a portion of the first groove portion is the second thick portion, the outer cam is formed with a second groove portion extending in the axial direction and in which the sliding protrusion of the knock member is disposed, and a portion of the second groove portion is a third thick portion having a third thickness extending in the axial direction, the third thickness is thinner than the first thickness and thicker than the second thickness, and in the cross section, a portion of the third thick portion is disposed in radial alignment with the protrusion.

5. A knock-type writing implement comprising: the writing implement component according to claim 4; a rotor that cooperates with the outer cam; and a knock member that cooperates with the rotor.

Images