Barrel and method for manufacturing barrel

Abstract

To provide a shaft cylinder in which a step amount of mismatch does not become large unintentionally, and the step amount of mismatch is small more easily with high accuracy.SOLUTION: The present invention is summarized as a barrel 2 of a writing instrument, the barrel including at least a cylindrical portion and a cutout portion that is continuous with the cylindrical portion in an axial direction and has a discontinuous portion in a circumferential direction, wherein a mismatch is provided on an outer wall surface of the cylindrical portion, and a large diameter portion, a small diameter portion, and a step portion that connects the large diameter portion and the small diameter portion are formed with the mismatch as a boundary.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a barrel of a writing instrument. [Background technology]

[0002] Writing instrument barrels are primarily molded parts made of resin. Various inventions have been disclosed for manufacturing methods for writing instrument barrels. Patent Document 1 (JP 2010-111083 A) discloses an invention in which a mismatch is intentionally created, that is, a difference is created in the outer diameter dimensions formed by the insert and the main cavity, in order to suppress burrs on the printing layer and perform transfer printing on the outer wall surface of the barrel. Patent Document 2 (JP 2003-80880 A) also discloses an invention in which the insert lines that appear due to the mismatch are made less noticeable by covering them with a grip. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-111083 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-80880 Summary of the Invention [Problem to be solved by the invention]

[0004] When mismatching is performed as in Patent Document 1, the larger the mismatch step, the more useful it is for avoiding undercuts that must be considered in mold operation. However, the larger the mismatch step, the more noticeable the nesting lines, which detracts from the appearance of the molded product. Also, unlike Patent Document 2, nesting lines may appear in locations that cannot be covered by other components such as grips. Therefore, the size of the mismatch step must be minimized. However, when the shapes of the opposing end faces of the insert and main cavity are complex (for example, shapes that must be machined by electrical discharge rather than by lathe), the mold machining accuracy is relatively low, and it is difficult to measure and evaluate the finished dimensions of the mold, making it difficult to machine the mold further. As a result, the mismatch step can unintentionally become large.

[0005] An object of the present invention is to provide a barrel that can be easily and accurately fitted with a small mismatch step. [Means for solving the problem]

[0006] The gist of the present invention is a barrel for a writing instrument, which is composed of at least a cylindrical portion and a cutout portion that is connected to the cylindrical portion in the axial direction and has a discontinuous portion in the circumferential direction, and a mismatch is provided on the outer wall surface of the cylindrical portion, and a large diameter portion, a small diameter portion, and a step portion connecting the large diameter portion and the small diameter portion are formed on either side of the mismatch. [Effects of the Invention]

[0007] The present invention can provide a barrel that makes it easy to reduce the radial height of the step from the small diameter portion by forming the mismatch on the outer wall surface of the cylindrical portion, which avoids cutout portions with complex shapes and makes it relatively easy to control the dimensions in the mold. [Brief explanation of the drawings]

[0008] [Figure 1] (a) An external view of the ballpoint pen 1, (b) a perspective view of the ballpoint pen 1 [Figure 2] Knock 5 external perspective view [Figure 3] An external perspective view of the grip 8 [Figure 4] An external perspective view of the rear axle 4 [Figure 5] Schematic cross-sectional view of a mold for manufacturing the rear axle 4 [Figure 6] (a) An external view of the crown 6, (b) a perspective view of the external view of the crown 6 [Figure 7] Longitudinal cross section of rear axle 5 [Figure 8] (a) An external view of the clip 7, (b) an external view of the clip 7 from the barrel 2 side, and (c) an external perspective view of the clip 7. [Figure 9] Enlarged view of the attachment portion 7b of the clip 7 [Figure 10] A-A' cross-sectional view of Figure 8(b) [Figure 11] Appearance of crown 6 after clip 7 is attached [Figure 12] Cross-sectional view of the arrows B-B' in Figure 11 DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the applicator according to the present invention will be described with reference to the drawings as appropriate. The present invention is not limited to the embodiment, and various modifications can be made without departing from the spirit and scope of the present invention.

[0010] The barrel of the present invention is applicable to barrels of writing implements, which can be widely used for general writing implements such as ballpoint pens, mechanical pencils, and marking pens, as well as barrels of cosmetic products such as eyeliners and eyebrow pencils.

[0011] 1(a) and 1(b) are diagrams showing the appearance of a ballpoint pen 1, which is a writing instrument to which a barrel according to the present invention is applied; FIG. 2 is an external perspective view of a knock 5; and FIG. 3 is an external perspective view of a grip 8. The ballpoint pen 1 is composed of at least a barrel 2, a ballpoint pen refill disposed inside the barrel 2, a spring member, a cam mechanism, the knock 5, a crown 6, a clip 7, and a grip 8. The barrel 2 is composed of a front barrel 3 and a rear barrel 4. The grip 8 covers the rear of the front barrel 3, and its rear end is in contact with the front end of the rear barrel 4. The ballpoint pen refill is urged rearward by the spring member inside the barrel 2. When a user presses the knock 5, the knock 5 and the ballpoint pen refill advance inside the barrel 2. The advancing knock 5 activates the cam mechanism inside the barrel 2. The cam mechanism locks the ballpoint pen refill in place, and the writing part located at the front end of the ballpoint pen refill protrudes from the front opening of the front barrel 3, making it possible to write. When the user presses the knock 5 again, the knock 5 and ballpoint pen refill 2 move forward inside the barrel 2. The forward-moving knock 5 activates the cam mechanism. When the user releases the pressure on the knock 5, the ballpoint pen refill 2 moves backward inside the barrel 2 due to the biasing force of the elastic member, and the writing part retracts from the front opening of the front barrel 3, making it impossible to write.

[0012] FIG. 4 is an external perspective view of the rear axle 4. The rear axle 4, which constitutes the barrel 2 according to the present invention, is a cylindrical resin molded product that penetrates in the axial direction, and in this embodiment is made of polycarbonate resin. The rear axle 4 is composed of at least a cylindrical portion 4a and a cutout portion 4b. In a cross section perpendicular to the axial direction, the cylindrical portion 4a has an approximately circular inner and outer shape. The approximately circular shape does not only mean a perfect circle centered on the axis, but also allows for some distortion due to molding tolerances. The cutout portion 4b is connected to the cylindrical portion 4a in the axial direction and has a discontinuous portion in the circumferential direction.

[0013] A mismatch 4c is provided on the outer wall surface of the cylindrical portion 4a. The mismatch 4c is formed by the boundary between the main cavity 8 and the insert 9 during the manufacturing process of the rear body 4, which will be described later.

[0014] On the outer wall surface of the cylindrical portion 4a, a large diameter portion 4aa, a small diameter portion 4ab, and a step portion 4ac (mismatch 4c) connecting the large diameter portion 4aa and the small diameter portion 4ab are formed with a mismatch 4c as a boundary.

[0015] The mismatch 4c is preferably formed on the outer wall surface of the cylindrical portion 4a, which avoids the complex-shaped cutout portion 4b and allows for relatively easy control of the dimensions in the mold, thereby making it easier to reduce the radial height of the step portion 4ac from the small diameter portion 4ab. In this embodiment, the cutout portion 4b is provided 2.50 mm axially rearward of the mismatch 4c.

[0016] The rear axle 4 is also provided with a locking hole 4d that penetrates radially. The locking hole 4d is formed by a slide pin 12 that is incorporated into the main cavity 9 during the manufacturing process of the rear axle 4, which will be described later. In this embodiment, a mismatch 4c is provided 3.15 mm axially rearward of the rear end of the locking hole 4d. By providing the mismatch 4c further axially rearward of the locking hole 4d, which is located in a position close to the axial rear end in the axial direction of the rear axle 4, it is possible to ensure a sufficient mold thickness for the main cavity 9 rearward of the slide pin 12, which increases the mold strength, which is more preferable.

[0017] It is more preferable that the large diameter portion 4aa does not have a parting line at least along the axial direction. A parting line is a linear protrusion that occurs at the joint between molds. If a parting line occurs in a resin molded product, it becomes difficult to apply decoration such as transfer printing or stickers to that area, and it can even ruin the appearance. By using the manufacturing method for the rear axle 4 described below, it is possible to mold a rear axle 4 of any shape without forming a parting line on the outer wall surface of the rear axle 4.

[0018] It is more preferable that the radial height from the small diameter portion 4ab to the step portion 4ac be 0.02 mm or less along the entire circumference, because even if there is a mismatch 4c, the printing is less likely to peel off after transfer printing and the appearance is less likely to be marred. The radial height from the small diameter portion 4ab to the step portion 4ac is preferably 0.02 mm or less along the entire circumference, rather than being 0.04 mm or less in total at two circumferentially opposing points. In other words, by preventing the occurrence of locally high radial heights from the small diameter portion 4ab to the step portion 4ac, the transfer printing is applied uniformly, the printing is less likely to peel off, and the appearance is less likely to be marred.

[0019] This section describes a manufacturing method for the rear axle 4 that constitutes the barrel 2 according to the present invention. FIG. 5 is a schematic cross-sectional view of a mold for manufacturing the rear axle 4. A substantially cylindrical insert 10 is placed in the space formed by the inner wall surface of the substantially cylindrical main cavity 9. Similar to the cylindrical portion 4a, the substantially cylindrical shape does not only mean a perfect circle centered on the axis, but also allows for some distortion due to molding tolerances. A slide pin 12 is incorporated inside the main cavity 9, slightly axially forward of the front end of the insert 10. The rear axle 4 that constitutes the barrel 2 is molded by pouring resin into the mold shown in FIG. 5. This embodiment employs a so-called internal gate method, in which resin flows into the axially forward inner wall surface of the rear axle 4 via a core pin 11 located axially forward. There are two gates, which serve as resin inlet ports, spaced equally apart circumferentially, and located 90° rotated left and right from the circumferential position of the locking hole 4d. The main cavity 9 and the insert 10 form the outer wall surface of the rear body 4, the slide pin 12 forms the locking hole 4d, and two core pins 11 facing each other along the axial direction form the inner wall surface of the rear body 4. The step 4ac is formed at the boundary between the main cavity 9 and the insert 10. Because the main cavity 8 and the insert 9 are both roughly cylindrical and have shapes that make it easy to control the dimensions in the mold, it is possible to manufacture a barrel in which the radial height of the step 4ac formed at the boundary between them from the small diameter portion is reduced.

[0020] The material of the rear axle 4 can be selected appropriately, taking into consideration moldability and durability, from polycarbonate resin, polypropylene resin, acrylic resin, polyethylene resin, polyamide resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polyethylene naphthalate resin, vinyl chloride resin, ethylene vinyl alcohol copolymer, polyacrylonitrile resin, fluororesin, polyacetal resin, polyethylene terephthalate resin, polystyrene resin, ABS resin, silicone resin, elastomer, or composites containing these resins. In this embodiment, the outer surface of the rear axle 4 is finished to an arithmetic mean roughness Ra of 0.16 μm, so it can be printed using appropriate methods such as transfer printing, pad printing, hot stamp printing, and silk screen printing. In addition, in the case of transfer printing, the transfer foil is generally configured such that an adhesive layer, a printed pattern layer, and a release layer are layered in that order on the printing substrate. However, if the printed pattern layer or release layer is finished with an uneven surface, the outer surface of the rear axle 4 can be decorated entirely or partially with a less glossy appearance. Furthermore, if a medium layer made of highly transparent ink is placed on the printing substrate so as to cover the printed pattern layer, the appearance of the print will remain the same while preventing the ink in the printed pattern layer from peeling off due to external rubbing, which is preferable.

[0021] 6(a) and (b) are diagrams showing the appearance of the crown 6, and Fig. 7 is a vertical cross-sectional view of the rear body 4. A locking protrusion 6a is provided on the outer wall on the opening side of the crown 6. The locking protrusion 6a fits into the locking hole 4d, allowing the crown 6 to be attached to the rear body 4.

[0022] An attachment projection 6b for attaching clip 7 is provided on the outer wall opposite the opening side of crown 6. Clip 7 can be attached to crown 6 by clamping attachment projection 6b with attachment projection 7ba of clip 7, which will be described later.

[0023] 8(a), 8(b), and 8(c) are diagrams showing the appearance of clip 6, and FIG. 9 is an enlarged view of the vicinity of mounting portion 7b of clip 7. Clip 7 is a component composed of clip body 7a, mounting portion 7b, and ball portion 7c. Clip 7 is made of carbon steel, and plate-shaped clip body 7a is appropriately bent and processed by a method such as press working to form mounting portion 7b and ball portion 7c. After bending, clip 7 is nickel-plated, tin-cobalt-plated, and chromate-treated. Mounting portion 7b is formed by bending both longitudinal edges of clip body 7a toward barrel 2. Mounting portion 7b is formed in two pieces, positioned opposite each other across clip body 7a.

[0024] The mounting portion 7b is formed with a mounting protrusion 7ba and an intrusion prevention wall portion 7bb. The mounting protrusion 7ba is formed by further bending the end of the mounting portion 7b that is along the longitudinal direction of the clip body 7a. The mounting protrusion 7ba is formed in two pieces and is the portion that clamps the mounting protrusion 6b of the crown 6. The mounting protrusion 7ba contacts the mounting protrusion 6b sequentially from the front end side, and the clip 7 is attached to the crown 6.

[0025] FIG. 10 is a cross-sectional view taken along the line A-A' in FIG. 8(a). The longitudinal ends of the clip 7 on the ball portion 7c side of the attachment portion 7b are further bent toward each other to form an intrusion prevention wall portion 7bb. The intrusion prevention wall portion 7bb prevents parts of other clips 7 from entering the area enclosed by the clip body 7a and the attachment portion 7b and causing entanglement of the clips 7, for example, in an automated machine that applies slight vibrations to the clips 7 while moving them along a narrow path to align the orientation of a large number of clips 7 during the assembly process of the ballpoint pen 1, or in a container that stirs the clips 7 during a polishing process or heat treatment process during plating. This prevents the clips 7 from accidentally entangling with each other during each process, facilitating optional processing in each process, thereby improving the ease of assembly of the ballpoint pen 1.

[0026] The intrusion prevention wall portion 7bb has a shape in which a portion on the barrel 2 side is recessed toward the clip body 7a. Figure 11 is an external view of the crown 6 after the clip 7 has been attached, and Figure 12 is a cross-sectional view taken along the line B-B' in Figure 11. Because the shape of the intrusion prevention wall portion 7bb prevents it from coming into contact with the locking projection 6a when the clip 7 is attached to the crown 6 from the axial front, it is possible to prevent the intrusion prevention wall portion 7bb from bending unexpectedly. [Explanation of symbols]

[0027] 1 ballpoint pen 2 shaft cylinder 3 Front axle 4 Rear axle 4a Cylindrical part 4aa Large diameter part 4ab Small diameter section 4ac stepped section 4b Notch 4c Mismatch 4d locking hole 5 Knock 6 crown 6a Locking protrusion 6b Mounted protrusion 7 clips 7a Clip body 7b Mounting part 7ba Mounting protrusion 7bb Intrusion prevention wall 7c Tamabe 8 Grip 9 Main Cavity 10 Nesting 11 Core pin 12 Slide pin

Claims

1. A barrel of a writing instrument, The bearing is at least composed of a cylindrical portion and a cutout portion that is continuous with the cylindrical portion in the axial direction and has a discontinuous portion in the circumferential direction, A mismatch is provided on the outer wall surface of the cylindrical portion, and a large diameter portion, a small diameter portion, and a step portion connecting the large diameter portion and the small diameter portion are formed on either side of the mismatch. Axial tube.

2. At least a parting line is not formed in the large diameter portion. The barrel according to claim 1.

3. The height of the step portion from the small diameter portion in the radial direction is 0.02 mm or less over the entire circumference. The barrel according to claim 1 or claim 2.

4. A method for manufacturing a barrel according to claim 1 or claim 2, a substantially cylindrical nest is disposed in a space formed by an inner wall surface of the substantially cylindrical main cavity; The shaft tube is molded by allowing resin to flow between the inner wall surfaces of the main cavity and the insert and the outer wall surface of the core pin, The step is formed at the boundary between the main cavity and the insert. Manufacturing method of barrel.

5. A method for manufacturing a barrel according to claim 3, a substantially cylindrical nest is disposed in a space formed by an inner wall surface of the substantially cylindrical main cavity; The shaft tube is molded by allowing resin to flow between the inner wall surfaces of the main cavity and the insert and the outer wall surface of the core pin, The step is formed at the boundary between the main cavity and the insert. Manufacturing method of barrel.

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