JP2006103288A - Pipe type ball-point pen tip, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pipe type ball-point pen tip which solves the trouble occurring by the punching process which is peculiar to the pipe type ball-point pen tip, has a sufficient sealability between the inner peripheral surface of a caulked section and a ball, has ink flowability without directivity, and can obtain a smooth writing feeling, and to provide a manufacturing method of the pipe type ball-point pen tip. <P>SOLUTION: A tapered edge section 31 is formed on the distal end of a metal tubule 3. By a punching process, a plurality of inward protruding sections 34 for a ball receiving seat are formed circumferentially in the inner peripheral surface of the tubule 3 behind the edge section 31 with an equal interval. The caulked section 35 is formed by bending the distal end of the edge section 31 inward into a circumferential shape. The ball 2 is rotatably embraced between the inward protruding sections 34 and the caulked section 35. The ball 2 is urged forward and is constituted to be closely joinable to the inner peripheral surface of the caulked section 35. By pressing the ball 2 to the inner peripheral surface of the caulked section 35, a spherical surface-like recess section 35a having a curvature being equivalent to the ball 2 is formed in the inner peripheral surface of the caulked section 35. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pipe-type ballpoint pen tip in which a plurality of inward protruding portions for ball receiving seats are formed by punching on the inner surface in the vicinity of the tip of a metal thin tube, and a method for manufacturing the same. In the present invention, “front” refers to the ball side, and “rear” refers to the opposite side.

  Conventionally, in this type of pipe-type ballpoint pen tip, Patent Document 1 discloses that a ball receiving seat comprising a plurality of inwardly projecting portions is formed by plastic deformation on the inner surface near the tip of a metal thin tube, and the ball is attached to the front by a spring. A pipe-type ballpoint pen tip having a structure in which the ball is brought into close contact with the inner peripheral surface of the crimping portion is disclosed.

  The conventional pipe-type ballpoint pen tip has a tapered shape due to the punching effect when a plurality of recesses are formed on the outer peripheral surface of the thin tube by punching in order to obtain a plurality of inward protruding portions for a ball receiving seat. The cross-sectional shape of the inner peripheral surface of the caulking portion at the tip of the edge portion tends to be a shape distorted from a circle. In such a case, the sealing performance between the outer peripheral surface of the ball and the inner peripheral surface of the crimping portion is reduced, and ink leaks out from between the inner peripheral surface of the crimping portion and the ball in the downward direction of the pen tip, or directionality occurs in the ink discharge. There is a possibility that a difference in ink discharge amount depending on the writing direction becomes large, or that the rotation of the ball becomes non-uniform so that the writing feeling is lowered.

  Further, in the pipe-type ballpoint pen tip of Patent Document 2, for the purpose of avoiding that the straight portion of the spring that urges the ball forward enters the peripheral edge portion of the radial ink outflow hole between the inward protruding portions, The amount of inward deformation (that is, the concave portion formed by punching) when forming the inward protruding portion is relatively large. For this reason, the pipe-type ballpoint pen tip of Patent Document 2 is likely to have a shape in which the cross-sectional shape of the inner peripheral surface of the crimping portion is distorted from a circular shape.

  Further, in Patent Document 3, for the purpose of improving the sealing performance between the inner peripheral surface of the crimping portion and the ball, the inner wall of the crimping portion that is in contact with the ball has the same diameter as the ball by performing crimping processing in which the crimping portion is pressed against the ball. A method of manufacturing a ballpoint pen tip formed on the spherical surface is disclosed. In Patent Document 3, when the inner wall of the crimping part is formed into a spherical surface having the same diameter as the ball (that is, when crimping is performed to press the ball against the inner peripheral surface of the crimping part), a method of pushing up the ball with the ball support rod (A) and a method (b) of supporting a ball by a ball receiving seat are disclosed.

  In the method (a) in which the ball is pushed up by the ball support rod of Patent Document 3, the ball pen tip employed has an ink circulation hole (capillary hole) in the ball receiving seat having a circular cross section. However, the ballpoint pen tip of the present application is a pipe type, and the ink circulation hole of the ball receiving seat has a non-circular cross-sectional shape (that is, the cross-sectional shape of the ink circulation hole formed between the inward projecting portions is the central portion. Radial extending outward in the radial direction). Therefore, it is not easy to press the center of the rear surface of the ball with the ball support rod of the method (a). Therefore, when the method (a) is adopted for a pipe-type ballpoint pen tip, a spherical surface having the same diameter as the ball cannot be properly formed on the inner circumferential surface of the crimped portion, and sufficient sealing performance between the crimped portion and the ball is obtained. May not be obtained.

  Further, in the method (b) of supporting the ball by the ball receiving seat of Patent Document 3, the back surface of the ball is at the opening edge of the ink circulation hole of the ball receiving seat during the caulking process in which the ball is pressed against the inner peripheral surface of the caulking portion. Press contact. In the method (b), the opening edge of the ink circulation hole of the ball-point pen chip has an unstable edge shape. Therefore, it is difficult to support the ball by always matching the center of the ball and the center of the ball receiving seat (that is, the axis of the chip body) without variation.

Conventionally, in a pipe-type ballpoint pen tip, fine irregularities are likely to occur on the inner peripheral surface of the thin tube. 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, In the state where the pen tip is downward, the ink may leak out from between the inner peripheral surface of the crimping portion and the ball. In particular, in the case of low viscosity ink, the ink leakage is likely to occur.
Utility model registration No. 2577544 JP 2003-136877 A Japanese Patent No. 2770148

  The present invention solves the above-mentioned conventional problems, solves the problems caused by the punching process peculiar to the pipe-type ballpoint pen tip, and has sufficient sealing performance between the inner peripheral surface of the crimped portion and the ball, and ink having no directionality. It is an object of the present invention to provide a pipe-type ballpoint pen tip and a method for manufacturing the pipe-type ballpoint pen tip that can provide a flowability and a smooth writing feeling.

The present invention is characterized by the following requirements.

(Claim 1)
A tapered edge portion is formed at the tip of the metal thin tube, and a punching process is performed on the outer peripheral surface of the thin tube behind the edge portion. The protrusions are formed at equal intervals in the circumferential direction, the crimping part is formed by bending the tip of the edge part inwardly, and the ball is rotated between the inward protrusion and the crimping part. A pipe-type ballpoint pen tip that is configured to be held so that the ball is urged forward and can be brought into close contact with the inner peripheral surface of the caulking portion, and the ball is pressed against the inner peripheral surface of the caulking portion; A pipe-type ballpoint pen tip comprising a spherical recess having a curvature equivalent to that of a ball on the inner peripheral surface of the crimping portion.

(Claim 2)
2. The pipe-type ballpoint pen tip according to claim 1, wherein an inner peripheral surface of the caulking portion and an inner peripheral surface of the edge portion behind the caulking portion are smoother than an inner peripheral surface of the thin tube behind the inward protruding portion.

(Claim 3)
An edge portion forming step for forming a tapered edge portion at the tip of the metal thin tube, and punching at a plurality of locations on the outer peripheral surface near the tip of the metal thin tube at equal intervals in the circumferential direction, A ball receiving seat forming step for forming a plurality of inward protruding portions for a ball receiving seat on an inner peripheral surface, and after the ball receiving seat forming step, a ball is inserted into the front side of the inward protruding portion, By bending the tip of the edge portion inwardly in a circular shape and pressing the inner peripheral surface of the edge portion against the ball, a crimped portion having a spherical concave portion with the same curvature as the ball is formed. And a caulking step formed by correcting the inner peripheral surface of the tip of the caulking portion into a circular cross-section, and after the caulking step, the ball is pressed backward with a hammer to thereby form a ball and an inner peripheral surface of the caulking portion. Forming a gap in the front-rear direction Pipe type ballpoint pen tip manufacturing method characterized by comprising the hammering step of forming a spherical recess of the ball equivalent curvature to the front of the inwardly projecting portion.

(Claim 4)
In the ball receiving seat forming step, or between immediately after the ball receiving seat forming step and immediately before the caulking step, a pressing pin having a conical or spherical tip surface is inserted from the tip opening of the capillary tube, The pipe-type ballpoint pen tip according to claim 3, wherein the tip surface of the pressing pin presses the front surface of the inward projecting portion to form a temporary conical or spherical concave portion on the front surface of the inward projecting portion. Production method.

(Claim 5)
The method of manufacturing a pipe-type ballpoint pen tip according to claim 4, wherein the ball is sandwiched in the front-rear direction by the temporary recess and the ball support pin during the caulking step.

(Claim 6)
In the edge portion forming step, a center pin whose outer peripheral surface is previously smoothed is inserted into a metal thin tube, and a tapered edge portion is formed at the tip of the thin tube by plastic working in which a rotating roller is pressed against the outer peripheral surface of the thin tube. Forming an annular smooth surface that is smoother than the inner peripheral surface of the thin tube behind the edge portion on the inner peripheral surface of the tip of the edge portion, and at the same time, the hardness of the outer peripheral surface of the edge portion from the hardness of the outer peripheral surface of the thin tube 6. The method for producing a pipe-type ballpoint pen tip according to claim 3, 4 or 5, wherein the height is increased.

According to the first aspect, the cross-sectional shape of the inner peripheral surface of the caulking portion is corrected from a non-circular shape to a circular shape, and there is obtained a smooth writing feeling due to non-directional ink outflow and uniform ball rotation. Further, the sealing performance between the inner peripheral surface of the crimping portion and the ball is improved, and even if the pen tip is kept downward for a long period of time, there is no possibility that the ink leaks from between the crimping portion and the ball.

According to the second aspect, the sealing performance between the inner peripheral surface of the crimping portion and the ball is further improved, and smooth rotation of the ball can be obtained. Furthermore, it is not necessary to smooth the entire inner peripheral surface of the thin tube, and the manufacturing cost can be reduced.

According to the third aspect, the inner peripheral surface of the tip of the edge portion is corrected to a circular cross section in the caulking process, so that there is no directionality and the smooth writing feeling due to uniform ball rotation. Can provide a pipe-type ballpoint pen tip. In addition, the seal between the inner surface of the crimping part and the ball is improved, and a pipe-type ballpoint pen tip that does not cause ink to leak outside between the crimping part and the ball even if stored for a long time with the pen tip facing downward. Obtainable. In addition, a pipe-type ballpoint pen tip that can suppress wear of the ball receiving seat accompanying rotation of the ball can be obtained.

According to the fourth aspect, the spherical concave portion can be appropriately formed on the inner peripheral surface of the caulking portion.

According to the fifth aspect, the spherical concave portion can be appropriately formed on the inner peripheral surface of the crimping portion.

According to the sixth aspect, the spherical concave portion can be easily smoothed. Furthermore, the durability of the crimped portion is improved, and a pipe-type ballpoint pen tip is obtained in which there is no possibility that the ball will drop off in a short period from the start of writing.

The best mode for carrying out the present invention will be described.

  The pipe-type ballpoint pen tip 1 according to the embodiment of the present invention forms a tapered edge portion 31 at the tip of a metal thin tube 3 and punches the outer peripheral surface of the thin tube 3 behind the edge portion 31. A plurality of inwardly projecting portions 34 for ball receiving seats are formed at equal intervals in the circumferential direction on the inner peripheral surface of the narrow tube 3 behind the edge portion 31, and the tip of the edge portion 31 is bent inwardly in a circumferential shape. A caulking portion 35 is formed, and the ball 2 is rotatably held between the inwardly projecting portion 34 and the caulking portion 35, and the ball 2 is biased forward to the inner peripheral surface of the caulking portion 35. A pipe-type ballpoint pen tip configured to be in close contact with a ball 2 having a curvature equivalent to that of the ball 2 on the inner circumferential surface of the caulking portion 35 by pressing the ball 2 against the inner circumferential surface of the caulking portion 35. Forming the recess 35a And (claim 1) the requirement.

  The pipe-type ballpoint pen tip (Claim 1) has a spherical recess 35a having a curvature equivalent to that of the ball 2 on the inner peripheral surface of the crimping portion 35 by pressing the ball 2 against the inner peripheral surface of the crimping portion 35. By being formed, the cross-sectional shape of the inner peripheral surface of the crimping portion 35 is corrected from a non-circular shape to a circular shape, and there is no ink directivity and smooth writing feeling due to the uniform rotation of the ball 2. It is done.

  Further, the pipe-type ballpoint pen tip (Claim 1) has the inner peripheral surface of the caulking portion 35 because the forward-biased ball 2 is reliably brought into annular contact with the spherical concave portion 35a of the inner peripheral surface of the caulking portion 35. And the ball 2 are improved in sealing performance, and even if the pen nib is kept downward for a long period of time, there is no possibility that the ink leaks from between the caulking portion 35 and the ball 2 to the outside.

  In other words, the pipe-type ballpoint pen tip (Claim 1) eliminates problems caused by punching (directional ink outflow, uneven rotation of the ball 2, and deterioration in the sealing performance between the crimping portion 35 and the ball 2). it can.

[2] In the pipe-type ballpoint pen tip according to the first aspect, the inner peripheral surface of the caulking portion 35 and the inner peripheral surface of the edge portion 31 behind the caulking portion 35 are smoother than the inner peripheral surface of the narrow tube 3 behind the inward projecting portion 34. (Claim 2) is preferable. As a result, the sealing performance between the inner peripheral surface of the crimping portion 35 and the ball 2 is further improved and smooth rotation of the ball is obtained, and it is not necessary to smooth the entire inner peripheral surface of the thin tube 3, thereby reducing the manufacturing cost. Can be suppressed. The surface roughness (Ra) of the inner peripheral surface of the caulking portion 35 and the edge portion 31 rearward of the caulking portion 35 is preferably 0.25 μm or less, and the surface of the inner peripheral surface of the narrow tube 3 behind the inward protruding portion 34. The roughness (Ra) is preferably 0.4 μm or more.

[3] In addition, the pipe-type ballpoint pen tip manufacturing method according to the embodiment of the present invention includes an edge portion forming step for forming the tapered edge portion 31 at the tip of the metal thin tube 3, and the vicinity of the tip of the metal thin tube 3. A ball receiving seat forming step for forming a plurality of inwardly projecting portions 34 for the ball receiving seat on the inner peripheral surface in the vicinity of the tip of the thin tube 3 by punching a plurality of locations on the outer peripheral surface at equal intervals in the circumferential direction; After the ball receiving seat forming step, the ball 2 is inserted in front of the inward projecting portion 34, the tip of the edge portion 31 of the thin tube 3 is bent inwardly, and the tip of the edge portion 31 is bent. By pressing the inner peripheral surface against the ball 2, a crimped portion 35 having a spherical concave portion 35 a having the same curvature as that of the ball 2 is formed on the inner peripheral surface, and the inner peripheral surface at the tip of the crimped portion 35 is circular in cross section. A caulking process that is straightened into a shape; After the crimping process, the ball 2 is pressed backward with the hammer 10 to form a front-rear gap between the ball 2 and the inner circumferential surface of the crimping portion 35 and the ball 2 on the front surface of the inward projecting portion 34. And a hammering step for forming a spherical concave portion 34b having the same curvature as the above (claim 3).

  By the manufacturing method of the pipe-type ballpoint pen tip (Claim 3), the inner peripheral surface (that is, the inner peripheral surface of the caulking portion 35) at the tip of the edge portion 31 having a non-circular cross section due to the punching process is By correcting the circular cross section to a circular shape, it is possible to provide a pipe-type ball-point pen tip that can obtain a smooth writing feeling due to non-directional ink outflow and uniform rotation of the ball 2.

  Further, the pipe-type ballpoint pen tip manufacturing method (Claim 3) ensures that the forward-biased ball 2 is brought into close annular contact with the spherical concave portion 35a on the inner peripheral surface of the caulking portion 35. Even if the sealability between the inner peripheral surface and the ball 2 is improved and the pen tip is kept downward for a long time, there is no possibility that the ink leaks from between the caulking portion 35 and the ball 2 to the outside.

  That is, the pipe ballpoint pen tip manufacturing method (Claim 3) causes defects caused by punching (directional ink outflow, uneven rotation of the ball 2, and reduction in sealing performance between the crimping portion 35 and the ball 2). ) Can be eliminated.

  Further, by forming the spherical concave portion 34b having the same curvature as the ball 2 on the front surface of the inward projecting portion 34 by the manufacturing method of the pipe-type ballpoint pen tip (Claim 3), the ball 2 and the ball receiving seat A pipe-type ballpoint pen tip capable of increasing the contact area and suppressing the wear of the ball seat (the increase in the amount of movement of the ball 2 in the front-rear direction) accompanying the rotation of the ball 2 is obtained.

[4] In the manufacturing method (Claim 3), in the ball receiving seat forming step, or immediately after the ball receiving seat forming step to immediately before the caulking step, a conical or spherical tip surface is formed. The provided pressing pin 6 is inserted from the tip opening of the thin tube 3, and the tip surface of the pressing pin 6 presses the front surface of the inward projecting portion 34, so that the front surface of the inward projecting portion 34 has a conical or spherical shape. It is preferable that a temporary recess 34a is formed (claim 4).

  According to the manufacturing method (Claim 4), at the time of the caulking process, the portion that supports the rear surface of the ball 2 is a conical surface formed on the front surface of the inward projecting portion 34 instead of the opening edge of the ink outflow hole as in the prior art. It is a spherical concave portion 34a. Therefore, at the time of the caulking process, the center of the ball 2 can be surely matched with the center of the inward projecting portion 34 group (the axis of the narrow tube 3), and the ball 2 can be supported stably. As a result, the spherical concave portion 35 a can be appropriately formed on the inner peripheral surface of the crimping portion 35. The temporary recess 34a is formed to be shallower than the spherical recess 34b formed on the front surface of the inward projecting portion 34 group in the hammering process.

[5] In the manufacturing method of claim 4, it is preferable that the ball 2 is sandwiched between the temporary recess 34a and the ball support pin 9 in the caulking step (claim 5). That is, in the manufacturing method (Claim 5), the front surface of the ball 2 is supported by the ball support pin 9 and the rear surface of the ball 2 is supported by the temporary recess 34a at the time of the caulking process. Thereby, the backlash of the ball 2 in the front-rear direction is suppressed, the ball 2 is securely supported by the temporary recess 34a, and the center of the ball 2 and the center of the inward projecting portions 34 group (the axis of the narrow tube 3) are further increased. Can be matched. As a result, the spherical concave portion 35 a can be appropriately formed on the inner peripheral surface of the caulking portion 35.

[6] In the manufacturing method according to claim 3, 4 or 5, in the edge portion forming step, a center pin 4 whose outer peripheral surface is smoothed in advance is inserted into the metal thin tube 3, and the outer surface of the thin tube 3 is inserted. A tapered edge portion 31 is formed at the tip of the thin tube 3 by plastic working to press the rotating roller 5, and the inner peripheral surface of the tip of the edge portion 31 is smoother than the inner peripheral surface of the thin tube 3 behind the edge portion 31. It is preferable that the hardness of the outer peripheral surface of the edge portion 31 is made higher than the hardness of the outer peripheral surface of the narrow tube 3 behind the edge portion 31 simultaneously with the formation of the annular smooth surface 33 (Claim 6).

  In the manufacturing method (Claim 6), since the annular smooth surface 33 is formed in advance on the inner peripheral surface of the edge portion 31 before the caulking process, the spherical smooth surface 33 on the inner peripheral surface of the edge portion 31 is spherical on the caulking process. The concave portion 35a is formed. Thereby, the spherical recess 35a can be easily smoothed. Further, in the manufacturing method (Claim 6), since the hardness of the outer peripheral surface of the edge portion 31 is higher than the hardness of the outer peripheral surface of the thin tube 3 behind the edge portion 31, the durability of the edge portion 31 (ie, the caulking portion 35) is improved. The pipe-type ball-point pen tip which improves and does not have a possibility that the ball | bowl 2 may drop | omit in a short period after writing start is obtained.

  An embodiment of a method for producing the pipe-type ballpoint pen tip 1 of the present invention will be described in order with reference to the drawings (see FIGS. 1 to 10). The manufacturing method of the pipe-type ballpoint pen tip 1 of the present embodiment includes an edge portion forming step (first step), a ball receiving seat forming step (second step), a caulking step (third step), and a hammering step ( 4 steps).

[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 adopted. 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 slightly smaller than the inner diameter of the thin tube 3 and slightly larger than the outer diameter of the ball 2. In this embodiment, the outer diameter of the thin tube 3 is set to 0.5 mm, the inner diameter of the thin tube 3 is set to 0.32 mm, the outer diameter of the ball 2 is set to 0.3 mm, and the outer diameter of the center pin 4 is set to 0.31 mm.

  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 32 having an angle α at the end of each thin tube 3. The angle α is set in a range of 30 ° to 90 ° (preferably in a range of 40 ° to 80 °), whereby an edge portion 31 having an appropriate shape can be formed and at the same time, an inner peripheral surface of the edge portion 31 can be formed. It is possible to reliably form the annular smooth surface 33 that provides sufficient sealing performance with the ball 2. If the angle α is smaller than 30 degrees, it becomes difficult to form the annular smooth surface 33 having a sufficiently small surface roughness on the inner peripheral surface of the edge portion 31. Also, if the angle α is greater than 90 degrees, the thickness of the tip portion of the edge portion 31 increases, and it is difficult to form the crimped portion 35 (that is, to bend the tip of the edge portion 31 inward). It becomes.

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

  In the edge portion forming step, the edge portion 31 is formed at the tip of the thin tube 3, and at the same time, the smoothed outer peripheral surface of the center pin 4 is pressed against the inner peripheral surface of the edge portion 31. An annular smooth surface 33 having an inner diameter smaller than the other part of the inner surface of the thin tube 3 is formed. The surface roughness of the annular smooth surface 33 is set smaller than the surface roughness of the other part of the inner surface of the thin tube 3. The inner diameter of the annular smooth surface 33 is 0.31 mm which is the same as the outer diameter of the center pin 4.

  The outer peripheral surface of the edge portion 31 is composed of a conical tapered portion 32, and a straight outer peripheral surface is continuously provided from the rear end of the tapered portion 32 to the rear. The annular smooth surface 33 is formed on the inner peripheral surface of the edge portion 31 in a range from the tip of the edge portion 31 (tip of the taper portion 32) to the front position from the rear end of the taper portion 32 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 32). That is, the width M of the annular smooth surface 33 is set shorter than the axial length L of the tapered portion 32 of the outer peripheral surface of the tapered edge portion 31 (that is, L> M). Thereby, the annular smooth surface 33 is efficiently and surely provided on the inner peripheral surface of the edge portion 31 where smoothness is required (that is, the inner peripheral surface of the crimped portion 35 after the crimping process and the inner peripheral surface of the ball house behind the crimped portion 35). Formed. Incidentally, fine irregularities 36 are present on the inner peripheral surface of the thin tube 3 behind the annular smooth surface 33.

  The width M of the annular smooth surface 33 is set to 50% to 90% (preferably 60% to 85%) of the axial length L of the tapered portion 32 of the outer peripheral surface of the tapered edge portion 31. . Thereby, the rotation of the ball 2 during writing becomes smoother, and the annular smooth surface 33 can be easily formed. If the width M of the annular smooth surface 33 is less than 50% of the axial length L of the tapered portion 32 of the outer peripheral surface of the edge portion 31, the ball 2 is behind the annular smooth surface 33 during writing. There is a risk that smooth rotation of the ball 2 may be hindered by contact with the inner surface of the thin tube 3 where the fine irregularities 36 exist. On the other hand, when the width M of the annular smooth surface 33 exceeds 90% of the axial length L of the tapered portion 32 of the outer peripheral surface of the edge portion 31, it becomes difficult to manufacture the annular smooth surface 33. The surface 33 cannot be easily formed.

  In this example, the surface roughness (Ra) of the outer peripheral surface of the center pin 4 was 0.26 μm or more (specifically, 0.26 μm to 0.6 μm) immediately before the edge portion forming step. The surface roughness (Ra) of the inner peripheral surface of the thin tube 3 was 0.4 μm or more (specifically, 0.4 μm to 2 μm) immediately before the edge portion forming step. The surface roughness (Ra) of the annular smooth surface 33 was 0.25 μm or less (specifically 0.05 μm to 0.25 μm) immediately after the edge portion forming step. The surface roughness (Ra) of the inner peripheral surface of the thin tube 3 where the fine irregularities 36 on the rear side of the annular smooth surface 33 exist is immediately after the edge portion forming step and immediately after 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 surface roughness (Ra).

  That is, the surface roughness of the annular smooth surface 33 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 33 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 the Vickers hardness (Hv) of the thin tube 3 internal peripheral surface just before an edge part formation process is 200-240. 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.

  Moreover, the Vickers hardness (Hv) of the outer surface of the edge part 31 of a present Example is set to 300-500 (preferably 350-450), and the Vickers hardness of the thin tube 3 outer surface behind the inward protrusion part 34 of a present Example (Hv) is set to 200-240. That is, the hardness of the outer surface of the edge portion 31 is set to be higher than the hardness of the outer surface of the thin tube 3 behind the inward projecting portion 34. Thereby, durability of the edge part 31 (namely, crimping part 35) improves, and generation | occurrence | production of a ball | bowl omission can be suppressed.

  In this embodiment, 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 33 formed on the inner peripheral surface of the tip 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 36 are crushed, and the annular smooth surface 332 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, 4 and 5)
A point-like pressing 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 pressed and plastically deformed inward in the radial direction, and three inwardly protruding portions 34 serving as ball receiving seats are formed at equal intervals in the circumferential direction. The pressing pin 6 includes a conical tip end surface. When the front end surface of the pressing pin 6 is pressed against the front surface of the inward projecting portion 34 group, a temporary recess 34 a is formed in the front surface of the inward projecting portion 34 group. In this embodiment, the ball receiving seat forming step is performed after the edge portion forming step. However, other than this, it can be performed before the edge portion forming step.

  The axial length L of the tapered portion 32 of the edge portion 31 is set to be shorter than the axial length N from the tip of the edge portion 31 to the inward protruding portion 34 (that is, L <N To be set). As a result, punching can be performed on the side wall of the straight tubule 3 behind the tapered portion 32 of the edge portion 31, and the inward protruding portion 34 can be appropriately formed.

  4 and 5 show the thin tube 3 immediately after the ball receiving seat forming step. As shown in FIG. 5, immediately after the ball seat forming step, the cross-sectional shape of the tip of the edge portion 31 of the thin tube 3 is distorted from a circle due to the influence of punching.

[Caulking process]
The caulking process will be described. (See Figure 6)
The ball 2 (outer diameter 0.3 mm) is inserted into the front side of the inward protruding portion 34 of the thin tube 3 obtained in the ball receiving seat forming step. Thereafter, the front surface of the ball 2 is supported by the ball support pins 9 and the rear surface of the ball 2 is supported by the temporary recesses 34a (that is, the ball 2 is sandwiched in the front-rear direction by the ball support pins 9 and the temporary recesses 34a). The conical surface inner surface 81 of the caulking die 8 is brought into pressure contact with the outer peripheral surface of the edge portion 31, and the tip of the tapered edge portion 31 is bent inwardly in a tapered shape to form the caulking portion 35. When forming the crimping portion 35, the ball 2 is strongly pressed against the inner peripheral surface of the crimping portion 35. Thereby, a spherical recess 35 a having a curvature equivalent to that of the ball 2 is formed on the inner peripheral surface of the crimping portion 35. The spherical concave portion 35a is smoother than the inner peripheral surface of the thin tube 3 behind the inward projecting portion 34. In the caulking process, since the smooth surface of the surface of the ball 2 is transferred to the annular smooth surface 33 obtained in the edge portion forming process, the spherical concave portion 35a can obtain a more reliable smooth surface. In the present 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 35) is set in the range of 85 to 120 degrees.

[Hammer ring process]
The hammering process will be described. (See Figure 7)
After the caulking step, the ball 2 protruding from the tip opening of the thin tube 3 is pressed backward by the hammer 10. Thereby, a spherical recess 34b having a curvature equivalent to that of the ball 2 is formed in the front surface of the inward projecting portion 34 group, and a clearance in the front-rear direction between the inner peripheral surface of the crimping portion 35 and the ball 2 (that is, the crimping portion). The amount of play in the front-rear direction of the ball 2 between 35 and the inward projecting portion 34 is ensured.

  Through the four steps, the pipe-type ballpoint pen tip 1 of the present invention is obtained.

8, 9 and 10 show the pipe-type ballpoint pen tip 1 obtained in this embodiment.
A spherical recess 35a is formed on the inner circumferential surface of the crimping portion 35 by pressure contact with the ball 2 during the crimping process, so that the cross-sectional shape of the inner circumferential surface of the crimping portion 35 is corrected to a circular shape (FIG. 9). reference). Further, since the annular smooth surface 33 is also present on the inner peripheral surface of the ball house behind the caulking portion, an even smoother rotation of the ball can be obtained.

[Application example]
FIG. 11 shows an example of a ballpoint pen to which the pipe-type ballpoint pen tip 1 obtained by the manufacturing method of the present invention is applied. The ballpoint pen 11 of this application example includes the pipe-type ballpoint pen tip 1 having a ball 2 rotatably held at the tip, a holder 111 in which the rear portion of the pipe-type ballpoint pen tip 1 is press-fitted and fixed to the front, and the holder An ink storage tube 112 whose rear portion 111 is press-fitted and fixed to the front end opening, an ink 112a and a follower 112b stored in the ink storage tube 112, the inside of the pipe-type ballpoint pen tip 1 and the holder 111 An elastic member 113 (specifically, a compression coil spring) to be accommodated and a tail plug 114 having a vent hole 114a that is press-fitted and fixed to the rear end opening of the ink accommodating cylinder 112.

  The ink storage cylinder 112 is filled with an ink 112a and a follower 112b made of a high-viscosity fluid that is disposed at the rear end of the ink 112a and moves forward as the ink 112a is consumed. Examples of the ink 112a 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 112b 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 113 includes a front straight portion 113a and a rear coil portion 113b that are integrally connected. A bulging portion 113c is formed at the rear end portion of the coil portion 113b. The bulging portion 113c gets over the locking projection 111a on the inner peripheral surface of the holder 111 from behind and is locked to the locking projection 111a. Thereby, the elastic member 113 is held in a compressed state.

  The tip of the straight portion 113a 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 of the caulking portion 35 of the pipe-type ballpoint pen tip 1, and the pen tip (ie Between the ball 2 and the caulking portion 35 inner peripheral surface) is sealed. Since the ball 2 is in close contact with the inner peripheral surface of the crimping portion 35, ink leakage from the pen tip is prevented even if the pen 2 is stored in a downward state. Air contamination from the front is prevented.

  When the ballpoint pen 11 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, and the ball was not dropped, and the ball seat was less worn, I was able to use it for a long time.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pipe-type ball-point pen tip 2 Ball 3 Narrow tube 31 Edge part 32 Tapered part 33 Annular smooth surface 34 Inner protrusion 34a Temporary recessed part 34b Spherical recessed part 35 Caulking part 35a Spherical recessed part 36 Fine unevenness 4 Center pin 5 Rotating roller 6 Pressing pin 7 Punch 8 Caulking die 81 Conical surface inner surface 9 Ball support pin 10 Hammer 11 Ball pen 111 Holder 111a Locking projection 112 Ink receiving cylinder 112a Ink 112b Following body 113 Ejection member 113a Straight part 113b Coil part 113c Bumping part 114 Tail Plug 114a Ventilation hole α Angle of taper portion of edge portion β Angle of caulking portion outer surface L Length of taper portion of edge portion in axial direction M Width of annular smooth surface N In the axial direction from the tip of edge portion to inward protruding portion length

Claims (6)

A tapered edge portion is formed at the tip of the metal thin tube, and a punching process is performed on the outer peripheral surface of the thin tube behind the edge portion. The protrusions are formed at equal intervals in the circumferential direction, the crimping part is formed by bending the tip of the edge part inwardly, and the ball is rotated between the inward protrusion and the crimping part. A pipe-type ballpoint pen tip that is configured to be held so that the ball is urged forward and can be brought into close contact with the inner peripheral surface of the caulking portion, and the ball is pressed against the inner peripheral surface of the caulking portion; A pipe-type ballpoint pen tip comprising a spherical recess having a curvature equivalent to that of a ball on the inner peripheral surface of the crimping portion. 2. The pipe-type ballpoint pen tip according to claim 1, wherein an inner peripheral surface of the caulking portion and an inner peripheral surface of the edge portion behind the caulking portion are smoother than an inner peripheral surface of the thin tube behind the inward protruding portion. An edge portion forming step for forming a tapered edge portion at the tip of the metal thin tube, and punching at a plurality of locations on the outer peripheral surface near the tip of the metal thin tube at equal intervals in the circumferential direction, A ball receiving seat forming step for forming a plurality of inward protruding portions for a ball receiving seat on an inner peripheral surface, and after the ball receiving seat forming step, a ball is inserted into the front side of the inward protruding portion, By bending the tip of the edge portion inwardly in a circular shape and pressing the inner peripheral surface of the edge portion against the ball, a crimped portion having a spherical concave portion with the same curvature as the ball is formed. And a caulking step formed by correcting the inner peripheral surface of the tip of the caulking portion into a circular cross-section, and after the caulking step, the ball is pressed backward with a hammer to thereby form a ball and an inner peripheral surface of the caulking portion. Forming a gap in the front-rear direction Pipe type ballpoint pen tip manufacturing method characterized by comprising the hammering step of forming a spherical recess of the ball equivalent curvature to the front of the inwardly projecting portion. In the ball receiving seat forming step, or between immediately after the ball receiving seat forming step and immediately before the caulking step, a pressing pin having a conical or spherical tip surface is inserted from the tip opening of the capillary tube, The pipe-type ballpoint pen tip according to claim 3, wherein the tip surface of the pressing pin presses the front surface of the inward projecting portion to form a temporary conical or spherical concave portion on the front surface of the inward projecting portion. Production method. The method of manufacturing a pipe-type ballpoint pen tip according to claim 4, wherein the ball is sandwiched in the front-rear direction by the temporary recess and the ball support pin during the caulking step. In the edge portion forming step, a center pin whose outer peripheral surface is previously smoothed is inserted into a metal thin tube, and a tapered edge portion is formed at the tip of the thin tube by plastic working in which a rotating roller is pressed against the outer peripheral surface of the thin tube. Forming an annular smooth surface that is smoother than the inner peripheral surface of the thin tube behind the edge portion on the inner peripheral surface of the tip of the edge portion, and at the same time, the hardness of the outer peripheral surface of the edge portion from the hardness of the outer peripheral surface of the thin tube 6. The method for producing a pipe-type ballpoint pen tip according to claim 3, 4 or 5, wherein the height is increased.

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