JP2005119281A - Pipe-type ballpoint pen chip and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve sealability between the inner circumferential surface of a caulked portion and a ball without multiplying manufacturing steps. <P>SOLUTION: A manufacturing method of a pipe-type ballpoint pen comprises an edge portion forming step, a ball swivel forming step, and a caulking step. In the edge portion forming step, a center pin 4 is inserted into a metal tube 3, and tapered edge portions 31 are formed at distal ends of the tube 3 through plastic deformation carried out by subjecting a rotation roller 5 to pressure welding with the outer circumferential surface of the tube 3. In the ball swevel forming step, a ball swevel is formed by subjecting the inner surface of the tube 3 at vicinity of the distal end of it to pressure deformation toward inside. In the caulking step, after a ball is inserted into the front side of the ball swevel, the distal end of the edge portion 31 is bent toward inside such that it rotatably holds the ball. In the edge portion forming step, by use of the center pin 4 having a preliminary-smoothed outer peripheral surface, the edge portions 31 are formed at the outer peripheral surfaces of the distal ends of the tube 3, and, at the same time, at the inner circumferential surface of the distal end of the edge portion 31, an annular smooth surface which is smooth is formed from the inner surface of the tube 3 which is at a rear portion of the edge portion 31. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pipe-type ballpoint pen tip and a manufacturing method thereof. Specifically, the present invention relates to a pipe-type ballpoint pen tip obtained by plastically deforming a metal thin tube and a method for manufacturing the same.

  Conventionally, in a method for manufacturing a pipe-type ballpoint pen tip, Patent Document 1 discloses that a center pin is inserted into a metal thin tube, and a plastic roller is pressed against the outer peripheral surface of the thin tube to cause a tip of the thin tube. An edge portion forming step for forming a tapered edge portion, a ball receiving seat forming step for forming a ball receiving seat by pressing deformation inward in the vicinity of the tip of the thin tube, and a ball inserted into the front side of the ball receiving seat Thereafter, a pipe-type ballpoint pen tip manufacturing method comprising a caulking process in which the tip of the edge portion is bent inward to hold the ball rotatably is disclosed.

  However, in the manufacturing method of Patent Document 1, fine irregularities are likely to occur on the inner peripheral surface of the thin tube. In particular, the fine irregularities are more likely to occur in a type that does not cut the inner surface of the ball house as in the present application, as compared to a type in which the inner surface of the ball house that accommodates the ball is obtained by cutting. If the fine irregularities are present on the inner peripheral surface of the edge portion, the sealing property (adhesiveness) between the inner peripheral surface of the crimped portion (the portion where the tip of the edge portion is bent inward) and the ball decreases, There is a possibility that ink may leak out from between the caulking portion and the ball in the state where the pen tip is downward. In particular, in the case of low viscosity ink, the ink leakage is likely to occur.

  Further, in Patent Document 2, a cutting process for forming a ball house capable of storing a ball is formed in the vicinity of one end of the holder, a cylindrical shape, and a mirror finish is applied to the outer peripheral surface. A first caulking step in which a mirror surface is transferred to the inner peripheral surface near the tip of the ball house by applying a caulking process to the open end of the ball house side of the holder with the pin being inserted into the ball house; A ballpoint pen including a second caulking step in which a ball is housed inside the ball house after one caulking step, and then a caulking portion having an inner diameter smaller than the diameter of the ball is provided at the open end of the holder on the ball house side. A method for manufacturing a chip is disclosed.

However, in the manufacturing method of Patent Document 2, the mirror surface is transferred to the inner peripheral surface near the tip of the ball house (first caulking process) before the normal caulking process (second caulking process) for providing the caulking portion. )is required. Therefore, there is a possibility that the manufacturing process increases and the manufacturing cost increases.
JP-A-9-123663 JP 2002-321484 A

  The present invention solves the above-mentioned conventional problems, and provides a method for manufacturing a pipe-type ballpoint pen tip capable of improving the sealing performance between the inner peripheral surface of the crimping portion and the ball without increasing the number of manufacturing steps. In addition, an object of the present invention is to provide a pipe-type ballpoint pen tip that improves the sealing performance between the inner peripheral surface of the crimping portion and the ball and can obtain a smooth rotation of the ball during writing.

[1] In the present invention, the center pin 4 is inserted into the metal thin tube 3, and the tapered edge portion 31 is formed at the tip of the thin tube 3 by plastic deformation in which the rotating roller 5 is pressed against the outer peripheral surface of the thin tube 3. An edge portion forming step to be formed, a ball receiving seat forming step in which a ball receiving seat 11 is formed on the inner surface in the vicinity of the tip of the thin tube 3 by inward pressing deformation, and the ball 2 is inserted into the front side of the ball receiving seat 11 Thereafter, a pipe-type ballpoint pen tip manufacturing method comprising a caulking step of bending the tip of the edge portion 31 inward and holding the ball 2 rotatably, wherein the outer peripheral surface is preliminarily formed in the edge portion forming step. The smoothed center pin 4 is used to form the edge portion 31 on the outer peripheral surface at the tip of the thin tube 3, and at the same time, the inner surface of the tip of the edge portion 31 is connected to the inner surface of the thin tube 3 behind the edge portion 31. Forming a smooth annular smooth surface 32 (claim 1) and requirements.

  According to the manufacturing method of claim 1, when the edge portion 31 is formed on the outer peripheral surface of the tip of the thin tube 3 by plastic deformation from the straight outer peripheral surface (straight tubular outer peripheral surface) of the thin tube 3 in the edge portion forming step. At the same time, the outer peripheral surface of the center pin 4 smoothed in advance is brought into pressure contact with the inner peripheral surface of the thin tube 3, so that the fine irregularities on the inner peripheral surface of the thin tube 3 are crushed and the inner peripheral surface of the thin tube 3 is smoothed. As a result, an annular smooth surface 32 that is smoother than the inner surface of the thin tube 3 behind the edge portion 31 is formed on the inner peripheral surface at the tip of the edge portion 31. As a result, the sealing performance between the inner peripheral surface of the crimping portion 12 and the ball 2 is improved, and even if a low-viscosity ink is applied, the ink leaks from between the crimping portion 12 and the ball 2 when the pen tip is directed downward. Can be sufficiently prevented, and the increase in manufacturing cost can be suppressed without increasing the number of manufacturing steps.

[2] In the method for manufacturing a pipe-type ballpoint pen tip according to claim 1, the surface roughness of the outer peripheral surface of the center pin 4 is set larger than the surface roughness of the annular smooth surface 32 formed on the inner peripheral surface of the edge portion 31. (Claim 2) is preferable. Thereby, it is not necessary to smooth the outer peripheral surface of the center pin 4 with high accuracy, and the center pin 4 can be obtained at a low cost.

[3] In the method for manufacturing a pipe-type ballpoint pen tip according to claim 1 or 2, it is preferable that the hardness of the center pin 4 is set higher than the hardness of the thin tube 3 immediately before the edge portion forming step (claim 3). As a result, the convex and concave portions on the inner peripheral surface of the thin tube 3 are crushed by the pressure contact of the center pin 4, and the inner peripheral surface at the tip of the edge portion 31 can be easily smoothed.

[4] Further, in the present invention, the tapered edge portion 31 is formed at the distal end of the metal thin tube 3, and the crimped portion 12 is formed by bending the distal end of the edge portion 31 inwardly in a circumferential shape. A ball receiving seat 11 is formed on the inner surface of the narrow tube 3 behind the crimping portion 12 by inward pressing deformation, and the ball 2 is rotatably held between the ball receiving seat 11 and the crimping portion 12. It is a pipe type ball-point pen tip to be formed, and an annular smooth surface 32 smoother than the inner surface of the thin tube 3 behind the edge portion 31 is formed on the inner peripheral surface of the tip of the edge portion 31 (Claim 4). The present invention is of a type in which the inner surface of the ball house (the inner surface of the narrow tube 3 between the ball receiving seat 11 and the crimping portion 12) is formed without cutting, and fine irregularities tend to exist on the inner surface of the ball house. In addition, since the annular smooth surface 32 is formed at least on the inner peripheral surface of the tip of the edge portion 31, the sealing performance between the inner peripheral surface of the crimping portion 12 and the ball 2 is improved, and even if a low-viscosity ink is applied, the pen The ink can be sufficiently prevented from leaking between the caulking portion 12 and the ball 2 when facing downward, and the contact between the inner peripheral surface of the edge portion 31 and the ball 2 becomes smooth, and a smooth ball at the time of writing 2 rotations (ie smooth writing feeling) are obtained.

[5] In the pipe-type ballpoint pen tip of claim 4, the width M of the annular smooth surface 32 is 50% to 90% of the axial length L of the tapered portion 33 of the outer peripheral surface of the edge portion 31. (Claim 5) is preferable. Thereby, the rotation of the ball 2 during writing becomes smoother and the annular smooth surface 32 can be easily formed. If the width M of the annular smooth surface 32 is less than 50% of the axial length L of the tapered portion 33 of the outer peripheral surface of the edge portion 31, the ball 2 is behind the annular smooth surface 32 during writing. There is a risk that smooth rotation of the ball 2 is hindered by contact with the inner surface of the thin tube 3 where fine irregularities are present. On the other hand, when the width M of the annular smooth surface 32 exceeds 90% of the axial length L of the tapered portion 33 of the outer peripheral surface of the edge portion 31, it becomes difficult to manufacture the annular smooth surface 32. The surface 32 cannot be easily formed.

[6] The pipe-type ballpoint pen tip according to claim 4 or 5, wherein the surface roughness (Ra) of the annular smooth surface 32 is 0.25 μm or less, and the surface of the inner surface of the thin tube 3 behind the annular smooth surface 32 The roughness (Ra) is preferably 0.4 μm or more (Claim 6). Thereby, sufficient sealing performance between the inner peripheral surface of the crimping portion 12 and the ball 2 can be obtained, and at the same time, it is not necessary to smooth the inner surface of the thin tube 3 with high accuracy in advance. If the surface roughness (Ra) of the annular smooth surface 32 exceeds 0.25 μm, the sealing property between the inner peripheral surface of the crimped portion 12 and the ball 2 becomes insufficient. If the surface roughness (Ra) of the inner surface of the thin tube 3 behind the annular smooth surface 32 is less than 0.4 μm, it is necessary to make the inner surface of the thin tube 3 a smooth surface with high accuracy in advance. Cost increases.

By the pipe ballpoint pen tip manufacturing method according to the first aspect, sufficient sealing performance between the inner peripheral surface of the crimping portion and the ball can be obtained without increasing the number of manufacturing steps.

The pipe ballpoint pen tip manufacturing method of claim 2 eliminates the need for smoothing the outer peripheral surface of the center pin with high accuracy.

According to the manufacturing method of the pipe-type ballpoint pen tip of claim 3, the inner peripheral surface of the tip of the edge portion can be easily smoothed.

According to the pipe-type ballpoint pen tip of claim 4, a sufficient sealing property between the inner peripheral surface of the crimping portion and the ball is obtained, and smooth rotation of the ball at the time of writing is obtained.

According to the pipe-type ballpoint pen tip of the fifth aspect, the rotation of the ball at the time of writing becomes smoother and the annular smooth surface can be easily formed.

According to the pipe-type ballpoint pen tip of the sixth aspect, it is possible to obtain a reliable sealing performance between the caulking portion inner peripheral surface and the ball, and at the same time, it is not necessary to smooth the inner surface of the thin tube in advance with high accuracy.

The best mode for carrying out the present invention will be described below with reference to the drawings.

  One embodiment of a method for manufacturing a pipe-type ballpoint pen tip of the present invention will be described in order with reference to the drawings (see FIGS. 1 to 6). That is, the manufacturing method of the pipe-type ball-point pen tip of the present embodiment includes three steps: an edge portion forming step (first step), a ball receiving seat forming step (second step), and a crimping step (third step). .

[Edge part formation process]
The edge portion forming process will be described. (See Figs. 1 and 2)
As the metal thin tube 3, a straight cylindrical body (straight tubular cylindrical body) of stainless steel (specifically, austenitic stainless steel such as SUS304 or SUS321) is employed. The center pin 4 is a cylindrical rod-shaped body made of metal (specifically, stainless steel such as SUS304). The outer peripheral surface of the center pin 4 is smoothed in advance.

  The center pin 4 is inserted into the narrow tube 3. The outer diameter of the center pin 4 is set substantially equal to the inner diameter of the narrow tube 3.

  Then, in a state where the center pin 4 is inserted into the narrow tube 3, two rotating rollers 5 having tapered portions are brought into pressure contact with the center of the outer peripheral surface of the narrow tube 3. The rotation roller 5 is set to have the same rotation direction and rotation speed, rolls the thin tube 3 between the two rotation rollers 5, and cuts the thin tube 3 into two equal parts at the center by plastic deformation (see FIG. 1). ). Thereafter, the center pin 4 is extracted from the narrow tube 3.

  The tapered portion of the rotating roller 5 forms a conical tapered edge portion 31 having a tapered portion 33 having an angle α at the end of each thin tube 3 (see FIG. 2). The angle α is set in a range of 30 ° to 90 ° (preferably in a range of 40 ° to 80 °), whereby the crimped portion 12 can be easily formed, and at the same time, the ball is formed on the inner peripheral surface of the edge portion 31. Therefore, the annular smooth surface 32 can be reliably formed. If the angle α is smaller than 30 degrees, it becomes difficult to form the annular smooth surface 32 having a sufficiently small surface roughness on the inner peripheral surface of the edge portion 31. Further, if the angle α is larger than 90 degrees, the thickness of the tip portion of the edge portion 31 becomes large, and it is difficult to form the crimped portion 12 (that is, to bend the tip of the edge portion 31 inward). It becomes.

  In this embodiment, the center of the thin tube 3 is cut into two equal parts, so that a tapered portion 33 is formed on the straight outer peripheral surface from the single thin tube 3 and an annular smooth surface 32 is formed on the inner peripheral surface. Two thin tubes 3 having the edge portion 31 can be manufactured at the same time. In addition, in the present invention, in the state where the center pin 4 is inserted at the tip of the thin tube 3, the taper is formed by plastic deformation in which the taper portion of the rotating roller 5 is pressed against the straight outer peripheral surface of one end of the thin tube 3. It is also possible to provide the portion 33 and form the tapered edge portion 31.

  In the edge portion forming step, a taper portion 33 (tapered edge portion 31) is formed on the straight outer peripheral surface of the thin tube 3, and at the same time, the center pin 4 is formed on the tip inner peripheral surface of the edge portion 31. An annular smooth surface 32 is formed by press-contacting the smoothed outer peripheral surface. The outer peripheral surface of the edge portion 31 is composed of a conical tapered portion 33, and a straight outer peripheral surface is continuously provided from the rear end of the tapered portion 33 to the rear. The annular smooth surface 32 is formed in the range of the inner peripheral surface of the edge portion 31 from the tip of the edge portion 31 (tip of the taper portion 33) to the front position from the rear end of the taper portion 33 of the edge portion 31. It is not formed up to the inner peripheral surface of the thin tube 3 behind the portion 31 (tapered portion 33). That is, the width M of the annular smooth surface 32 is set to be shorter than the length L in the axial direction of the tapered portion 33 of the outer peripheral surface of the tapered edge portion 31 (that is, L> M). Thereby, the annular smooth surface 32 is efficiently and reliably formed on the inner peripheral surface of the tip of the edge portion 31 (that is, the inner peripheral surface of the crimped portion 12 after the crimping process) that requires sealing performance with the ball 2. In addition, fine irregularities 34 are present on the inner peripheral surface of the thin tube 3 behind the annular smooth surface 32. The width M of the annular smooth surface 32 is set to 50% to 90% (preferably 60% to 85%) of the axial length L of the tapered portion 33 of the outer peripheral surface of the tapered edge portion 31. Is done.

  In this example, the surface roughness (Ra) of the outer peripheral surface of the center pin 4 immediately before the edge portion forming step was 0.26 μm or more (specifically 0.26 μm to 0.6 μm). The surface roughness (Ra) of the inner peripheral surface of the thin tube 3 immediately before the edge portion forming step was 0.4 μm or more (specifically, 0.4 μm to 2 μm). The surface roughness (Ra) of the annular smooth surface 32 immediately after the edge portion forming step was 0.25 μm or less (specifically 0.05 μm to 0.25 μm). The surface roughness (Ra) of the inner peripheral surface of the thin tube 3 where the fine irregularities 34 are present behind the annular smooth surface 32 immediately after the edge portion forming step is the surface roughness of the inner peripheral surface of the thin tube 3 immediately before the edge portion forming step. It was 0.4 μm or more (specifically, 0.4 μm to 2 μm), which is the same as the roughness (Ra).

  That is, the surface roughness of the annular smooth surface 32 immediately after the edge portion forming step is smaller than the surface roughness of the inner peripheral surface of the thin tube 3 immediately before the edge portion forming step. Further, the surface roughness of the outer peripheral surface of the center pin 4 is set to a value larger than the surface roughness of the annular smooth surface 32 formed on the inner peripheral surface of the edge portion 31. The surface roughness was measured using a non-contact three-dimensional measuring device (NH-3) manufactured by Mitaka Kogyo Co., Ltd.

  Moreover, the Vickers hardness (Hv) of the center pin 4 of a present Example is 400-500, and is the Vickers hardness (Hv) 200-240 of the internal peripheral surface of the thin tube 3 just before an edge part formation process. That is, the hardness of the center pin 4 is set higher than the hardness of the inner peripheral surface of the thin tube 3 immediately before the edge portion forming step.

  Further, the Vickers hardness (Hv) of the outer surface of the edge portion 31 of this embodiment is set to 300 to 500 (preferably 350 to 450), and the Vickers hardness of the outer surface of the narrow tube 3 behind the ball receiving seat 11 of this embodiment ( Hv) is set to 200-240. That is, the hardness of the outer surface of the edge portion 31 is set higher than the hardness of the outer surface of the thin tube 3 behind the ball receiving seat 11. Thereby, durability of the edge part 31 (namely, crimping part 12) improves, and generation | occurrence | production of the fall-off | omission of the ball | bowl 2 can be suppressed.

  In this embodiment, the surface roughness of the outer peripheral surface of the center pin 4 is set to be larger than the surface roughness of the annular smooth surface 32 formed on the inner peripheral surface of the edge portion 31, and the hardness of the center pin 4 is It is set to be higher than the hardness of the narrow tube 3 immediately before the edge portion forming step. Thereby, it becomes unnecessary to smooth the outer peripheral surface of the center pin 4 with high accuracy, the center pin 4 can be obtained at a low cost, and the inner peripheral surface of the thin tube 3 is pressed by the press contact of the outer peripheral surface of the center pin 4. The convex portions of the fine irregularities 34 are crushed, and the annular smooth surface 32 can be easily formed on the inner peripheral surface of the tip of the thin tube 3.

[Ball receiving seat formation process]
The ball seat formation process will be described. (See Figs. 3 and 4)
A pointed guide pin 6 is inserted into the inside of the thin tube 3 obtained in the edge portion forming step on the edge portion 31 side, and the side wall behind the edge portion 31 of the thin tube 3 is formed into three pointed shapes. The punch 7 is plastically deformed inward in the radial direction, and three inward projections to be the ball receiving seat 11 are formed at equal intervals in the circumferential direction. In the present embodiment, the ball receiving seat forming step is performed after the edge portion forming step, but other than this, it may be performed before the edge portion forming step.

  Further, the axial length L of the tapered portion 33 of the edge portion 31 is set shorter than the axial length N from the tip of the edge portion 31 to the ball seat 11 shown in FIG. L <N is set). Thereby, punch processing can be given to the straight thin tube 3 side wall behind the taper portion 33 of the edge portion 31, and the ball receiving seat 11 can be appropriately formed.

[Caulking process]
The caulking process will be described. (See FIGS. 5 and 6)
The ball 2 is inserted into the front side of the ball receiving seat 11 of the thin tube 3 obtained in the ball receiving seat forming step, and then the conical inner surface 81 of the caulking die 8 is brought into pressure contact with the outer peripheral surface of the tapered edge portion 31 to taper. The tip of the edge portion 31 is bent inward in a tapered shape to form the crimped portion 12. Thereby, the pipe-type ball-point pen tip 1 in which the ball 2 is rotatably held between the crimping portion 12 and the ball receiving seat 11 is obtained. In this embodiment, the angle β of the conical inner surface 81 of the caulking die 8 (that is, the angle β of the outer surface of the caulking portion 12) is set in the range of 85 degrees to 120 degrees.

[Application example]
FIG. 7 shows an example of a ballpoint pen 9 to which the ballpoint pen tip 1 obtained by the manufacturing method of the present invention is applied. The ball-point pen 9 of this application example includes the ball-point pen tip 1 that rotatably holds the ball 2 at the tip, a holder 91 in which the rear portion of the ball-point pen tip 1 is press-fitted and fixed to the front, and a rear portion of the holder 91. Ink receiving cylinder 92 press-fitted and fixed to the front end opening, ink 92a and follower 92b accommodated in ink accommodating cylinder 92, and bullets accommodated and disposed inside ballpoint pen tip 1 and holder 91 It comprises a member 93 (specifically, a compression coil spring) and a tail plug 94 provided with a vent hole 94a that is press-fitted and fixed to the rear end opening of the ink containing cylinder 92.

  The ink containing cylinder 92 is filled with ink 92a and a follower 92b made of a high-viscosity fluid that is disposed at the rear end of the ink 92a and moves forward as the ink 92a is consumed. Examples of the ink 92a include a low-viscosity aqueous or oil-based ink, or an aqueous or oil-based gel ink having shear thinning viscosity. Examples of the follower 92b include a configuration made of only a high-viscosity fluid, or a configuration in which a solid is contained in a high-viscosity fluid.

  The elastic member 93 includes a front rod portion 93a and a rear coil portion 93b that are integrally connected. A bulging portion 93c is formed at the rear end portion of the coil portion 93b. The bulging portion 93c is a tightly wound portion whose outer diameter is set larger than that of the front coil portion 93b. The bulging portion 93c gets over the locking projection 91a on the inner peripheral surface of the holder 91 from behind and is locked to the locking projection 91a. Thereby, the elastic member 93 is held in a compressed state.

  The tip of the rod portion 93a is brought into contact with the rear surface of the ball 2 and presses the ball 2 forward, whereby the ball 2 is brought into close contact with the inner peripheral surface (that is, the annular smooth surface 32) of the caulking portion 12 of the ballpoint pen tip 1. The pen nib (that is, between the ball 2 and the caulking portion 12 inner peripheral surface) is sealed. Even if the ball 2 is brought into close contact with the annular smooth surface 32 on the inner peripheral surface of the crimping portion 12, even if the ball 2 is stored in the pen tip downward state, ink leakage from the pen tip is prevented, and the pen tip is stored in the upward state. Even if this is done, air contamination from the pen tip is prevented. In addition, the ball-point pen tip 1 obtained by the present invention can be applied to a type of ball-point pen that does not include the resilient member 93 that urges the ball 2 forward, in addition to the application example described above. Ink leakage from the nib in the tip-down state is prevented.

  When the ballpoint pen 9 of the application example was written, there was no backlash of the ball 2 and a smooth writing feeling due to the smooth rotation of the ball 2 was obtained.

It is explanatory drawing of the edge part formation process of the Example of this invention. It is a principal part expanded longitudinal cross-sectional view of the thin tube obtained at the edge part formation process of FIG. It is expansion explanatory drawing of the ball receiving seat formation process of the said Example. It is sectional drawing which follows the AA line of FIG. It is expansion explanatory drawing of the crimping process of the said Example. It is a principal part expanded longitudinal cross-sectional view of the ball-point pen tip obtained with the manufacturing method of the said Example. It is a longitudinal cross-sectional view which shows the example of the ball-point pen to which the ball-point pen tip obtained by this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball-point pen tip 11 Ball seat 12 Caulking part 2 Ball 3 Narrow tube 31 Edge part 32 Annular smooth surface 33 Tapered part 34 Fine unevenness 4 Center pin 5 Rotating roller 6 Guide pin 7 Punch 8 Caulking die 81 Conical surface inner surface 9 Ball-point pen 91 Holder 91a Locking projection 92 Ink receiving cylinder 92a Ink 92b Follower 93 Repelling member 93a Rod part 93b Coil part 93c Bulging part 94 Tail plug 94a Vent hole α Angle of taper part of edge part β Angle L of caulking part outer surface Edge part Length M of taper part in the axial direction Width N of the annular smooth surface Length in the axial direction from the tip of the edge part to the ball seat

Claims (6)

An edge portion forming step for forming a tapered edge portion at the tip of the thin tube by plastic deformation in which a center pin is inserted into the metal thin tube and a rotating roller is pressed against the outer peripheral surface of the thin tube, and the vicinity of the tip of the thin tube Ball receiving seat forming process that forms a ball receiving seat by inward pressure deformation on the inner surface, and after inserting the ball on the front side of the ball receiving seat, the tip of the edge portion can be bent inward to rotate the ball A pipe-type ballpoint pen tip manufacturing method comprising a caulking process to be held in
In the edge portion forming step, a center pin whose outer peripheral surface is previously smoothed is used to form an edge portion on the outer peripheral surface of the tip of the thin tube, and at the same time, a narrow tube behind the edge portion is formed on the inner peripheral surface of the tip of the edge portion. A method of manufacturing a pipe-type ballpoint pen tip, wherein an annular smooth surface smoother than an inner surface is formed. 2. The method of manufacturing a pipe-type ballpoint pen tip according to claim 1, wherein the surface roughness of the outer peripheral surface of the center pin is set larger than the surface roughness of the annular smooth surface formed on the inner peripheral surface of the edge portion. The pipe type ball-point pen tip manufacturing method according to claim 1 or 2, wherein the hardness of the center pin is set higher than the hardness of the narrow tube immediately before the edge portion forming step. A tapered edge portion is formed at the tip of the metal thin tube, and a crimped portion is formed by bending the tip of the edge portion inwardly to the inside, and the inner surface of the capillary tube at the rear of the crimped portion is inwardly formed. A pipe-type ballpoint pen tip formed by pressing deformation to form a ball receiving seat and holding the ball rotatably between the ball receiving seat and the crimping portion,
An annular smooth surface that is smoother than the inner surface of the thin tube behind the edge portion is formed on the inner peripheral surface of the tip of the edge portion. The pipe-type ballpoint pen tip according to claim 4, wherein a width M of the annular smooth surface is 50% to 90% of an axial length L of the tapered portion of the outer peripheral surface of the edge portion. 6. The surface roughness (Ra) of the annular smooth surface is 0.25 [mu] m or less, and the surface roughness (Ra) of the inner surface of the capillary tube behind the annular smooth surface is 0.4 [mu] m or more. Pipe-type ballpoint pen tip.

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