JP2010221408A - Applicator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent poor ink discharge caused by the narrowing of radial grooves by recessing work and the deformation of the cross sectional shape of a ball holding chamber by a cutting force used for forming radial grooves. <P>SOLUTION: After the formation of the radial grooves, an impact force is given between those radial grooves, and thereby the width of an opening is expanded to the ball holding chamber of the radial groove, and the recessed part is formed at a stepped part by transferring the shape of a ball by the impact force given to the ball. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a step of forming a ball holding chamber which is a large-diameter portion and a small-diameter hole opened in the ball holding chamber as an ink passage which is a through-hole in a cylindrical metal member, and radial cutting Inserting a cutting jig having a blade from the ball holding chamber side, cutting a step between the ball holding chamber, which is a large diameter portion, and the small diameter hole to form a radial groove communicating with the small diameter hole; Applying impact force to the writing ball placed in the ball holding chamber in a partially protruding state from the tip to form a recess in which the shape of the ball is transferred to the step, and crimping the tip of the opening from the diameter of the ball The present invention relates to a method of manufacturing a ballpoint pen tip having a step of preventing a ball from coming out by reducing the diameter.

Conventionally, a ballpoint pen tip that is a pen point member of a ballpoint pen is basically composed of a ball that is a writing member and a ball holder that rotatably holds a part of the ball in a state of protruding from the tip opening. This ball holder is processed by cutting with a cutting jig having a cutting blade such as a drill or a bite, or by plastic deformation to transfer the shape of the ball by applying an impact force or to reduce the diameter by pressing a roller. Has been.
Since the inside of the ball holder holds the ball and also serves as an ink passage, it greatly affects the quality of the ballpoint pen, so the dimensional accuracy of processing is extremely important.

  Therefore, Japanese Patent Application Laid-Open No. 2000-015979 (Patent Document 1) inserts a stepped core pin inside a metal thin tube, presses the entire tip of the outer surface of the metal pin while overheating, and receives a uniform ball seat. After forming the surface, punch out multiple vertical grooves from the ball seat along the ink holes or stop halfway to make ink grooves, install the balls, and caulk until the upper edge is in close contact with the balls Further, a manufacturing method is disclosed in which a ball is sunk to create an appropriate gap, thereby improving a defect in which the amount of ink outflow varies depending on the writing direction of the writing line.

JP 2000-015979 A

However, in the invention described in Patent Document 1, it may be possible to form a uniform receiving seat. However, after forming a plurality of longitudinal grooves, the ball is sunk into the receiving seat surface, so that the receiving force is received by the impact force. The width of the radial groove, which is the vertical groove provided in the seat, is deformed to be narrow, the flow of ink supplied to the ball holding chamber is controlled, the ink discharge amount varies, the density of the handwriting In some cases, the line width was not uniform, and the handwriting was blurred.
In addition, due to the impact force and pressing force when forming the radial groove, only the periphery of the portion corresponding to the extension line of the processed portion of the inner groove of the wall portion of the ball holding chamber is caused to fall inside, The cross-sectional shape of the ball holding chamber is deformed and the roundness is impaired. Thereby, since the annular gap between the ball and the tip opening differs depending on the position of the ball-point pen tip, the amount of ink discharge varies depending on the writing direction when writing with a constant grip, the density of the handwriting, There were cases where the line width was not uniform and the writing was blurred.

  The present invention provides a step of forming a ball holding chamber which is a large diameter portion and a small diameter hole which opens in the ball holding chamber as an ink passage which is a through hole in a cylindrical metal member, and a radially arranged cutting Inserting a cutting jig having a blade from the ball holding chamber side, cutting a step between the ball holding chamber, which is a large diameter portion, and the small diameter hole to form a radial groove communicating with the small diameter hole; Applying impact force to the writing ball placed in the ball holding chamber in a partially protruding state from the tip to form a recess in which the shape of the ball is transferred to the step, and crimping the tip of the opening from the diameter of the ball In the method of manufacturing a ballpoint pen tip having a step of preventing a ball from falling out of a small diameter, after the radial groove is formed, an impact force is applied between the radial grooves to thereby prevent the radial groove from being held in the ball holding chamber. Widened the opening , The gist of the method for manufacturing a ballpoint pen tip for forming a recess the impact force imparted by transferring the shape of a ball in the stepped portion to the ball.

By retracting the part by applying an impact force such as cutting or pressing between the adjacent radial grooves of the stepped part between the ball holding chamber which is the large diameter part and the small diameter hole, radial Since the recess is formed by applying an impact force to the ball after expanding the width of the opening of the groove, the narrowing of the radial groove due to the formation of the recess is suppressed, the amount of ink that can be circulated is ensured, and the scatter of the handwriting is reduced. Ink discharge defects such as can be suppressed as much as possible.
In addition, since the wall of the ball holding chamber corresponding to the portion to which the impact force is applied to the stepped portion also falls down in a minute amount, the ball pen closes to the deformation of the inner shape of the ballpoint pen tip due to the formation of the radial groove. The inner and outer diameters of the tip can be corrected to a shape close to a circle, there is no difference in the annular gap between the ball and the tip opening, and there is no variation in the amount of ink that can be circulated. The problem can be prevented.

The principal part expansion longitudinal cross-sectional view of the ball-point pen tip processed with the manufacturing method of this invention. FIG. 2 is a cross-sectional view taken along line I-I ′ of FIG. 1. Process drawing of small diameter hole and rear hole forming process. Tip portion outer surface forming process machining diagram. Radial groove formation process processing drawing. The principal part longitudinal cross-sectional view of the ball-point pen tip processed by the radial groove formation process. FIG. 7 is a cross-sectional view taken along line II-II ′ in FIG. 6. Process drawing of impact force application process. The principal part longitudinal cross-sectional view of the ball-point pen tip processed by the impact-force provision process. FIG. 10 is a cross-sectional view taken along the line III-III ′ of FIG. 9. Caulking process processing diagram. FIG. The principal part longitudinal cross-sectional view of the ball-point pen chip processed at the recessed part formation process. FIG. 14 is a sectional view taken along the line IV-IV ′ in FIG. 13. FIG. 6 is a process drawing of an impact force application process of Example 2. FIG. 4 is a longitudinal sectional view of a main part of a ballpoint pen chip processed in an impact force application process of Example 2. FIG. 17 is a cross-sectional view taken along line V-V ′ in FIG. 16. The principal part enlarged vertical sectional view of the ball-point pen tip processed by the conventional manufacturing method. FIG. 18 is a sectional view taken along the line VI-VI ′ of FIG. 17.

  The ballpoint pen tip manufacturing method of the present invention includes a step of forming a radial groove by cutting in a step between a ball holding chamber and a small-diameter hole, and a ball placed in the ball holding chamber is impacted from above. A step of applying an impact force between the radial grooves between the step of applying a force and forming the recess in the stepped portion.

The basic structure of a ballpoint pen tip consists of a ball that becomes a writing member that contacts the writing surface such as paper and transfers the ink, and a ball holder that rotatably holds the ball. Ink is applied to the writing surface through the through hole of the ball holder.
The ball holder is formed by subjecting a cylindrical member obtained by cutting a wire made of an alloy such as stainless steel, brass, or white to an appropriate length to various processes.
The through hole of the ball holder is an ink flow path and is formed by a drill or the like. First, a portion that becomes a small-diameter hole is formed over the entire length of the cylindrical member with a relatively small-diameter drill, and then a large-diameter hole that serves as a ball holding chamber is formed with a predetermined dimension at one end with a large-diameter drill. Dig up to. At this time, it is preferable that the opening angle of the tip portion of the drill is approximated to the step angle between the ball holding chamber and the small-diameter hole to be finally formed because less processing is required. The reason for forming the small diameter hole is to form a step portion for regulating the retraction of the ball installed in the ball holding chamber between the ball holding chamber and the small diameter hole. It is a part that limits the amount of circulation. In particular, when another member such as a coil spring that urges the ball forward is inserted, the effective cross-sectional area through which ink can flow is reduced by the amount of the insert, so the design dimension value is also taken into consideration. Therefore, it is possible to obtain an appropriate ink flow rate by adjusting the diameter and length of the small-diameter hole. The length of the small diameter hole can be adjusted by forming a large diameter rear hole with a large diameter drill from the end side opposite to the ball holding chamber. As the ballpoint pen tip, the total length of the ballpoint pen tip is determined for convenience such as the length of the connecting part to be connected to the ink tank member. Therefore, the length of the small diameter hole is adjusted by adjusting the depth of the rear hole accordingly. Will be adjusted. When it is necessary to dig deeper in the rear hole, a large force is required to dig deeper with a large-diameter drill, and the burden on the drill becomes large. It is preferable to gradually dig deeper by changing the drill so that the diameter gradually becomes smaller. Further, when a coil spring or the like that biases the ball forward is inserted and disposed after the ball is disposed, a step portion of a difference in diameter formed between the small diameter hole and the rear hole is formed on an acute angle. It is preferable that the coil spring is not easily caught and does not hinder insertion.
Further, by using a pipe-shaped member instead of a wire as the material, the process of forming a through hole can be omitted, but a process of forming an inward protruding portion that serves as a ball retraction restricting portion is required.
In addition, re-cutting with a cutting blade such as a drill or a bite on the stepped surface corresponding to the inner wall surface and the bottom surface of the ball holding chamber, and finishing it is done in terms of the accuracy of the finished dimensions and on the inner surface. It can also be said to be a preferable process in order not to leave unnecessary things such as burrs and scraps.

  Next, a cutting jig having cutting blades arranged radially is inserted into the rear hole from the ball holding chamber side, and the inward protruding portion is partially extended from the step side between the ball holding chamber and the small diameter hole. And a radial groove communicating with the small-diameter hole is formed in the portion. This radial groove is a portion that serves as a passage for supplying ink to the ball holding chamber from a small-diameter hole that is blocked by the writing ball, and there is a portion that opens to the ball holding chamber even when the ball is retracted. Formed as follows. In addition, when the groove penetrates the rear hole, there is no part that hinders the ink flow, but on the other hand, the ink tends to recede, and when the coil spring is installed as described above, Cutting burrs may occur in the opening of the coil, which may hinder the insertion of the coil spring. However, if it is a non-penetrating groove, the ink retraction is suppressed and the coil spring is guided to the small-diameter hole. In some cases, it is preferable.

  The cutting blade to be used has a shape in which the cutting blade is formed radially from the central portion, but the overall outer shape is a shape in which a cone of the bottom surface of the same diameter is connected to the tip of a cylinder. If the part corresponding to the cylindrical part has a so-called back taper that has a slightly smaller diameter in the rear, the resistance during cutting can be reduced, but there is a so-called spring back that is a reaction to cutting stress. May be sacrificed by the dimensional system. However, it can be said that with a material such as free-cutting stainless steel used for ballpoint pen tips, there is relatively little spring back against shearing such as cutting. High quality materials such as die steel, cemented carbide, ultrafine particle cemented carbide are suitable for the cutting blade material, and it is better to have a coating of TiC, TiCN, etc. to improve durability. .

After the step of forming the radial groove, before the step of forming the concave portion in the stepped portion, a cutting jig having the same number of cutting blades as the number of grooves of the radial groove or a pointed multiple having the same number of corners as the number of grooves A pyramid pressing jig is inserted from the ball holding chamber side toward the rear hole and is made to collide between the radial grooves, and a small-diameter radial groove or dent as an impact mark is formed by the impact force at that time.
The step between the radial grooves receives an impact force from the cutting jig or the pressing jig, so that the force for retracting the part in the direction of the rear hole works, and the step of the portion not directly contacting the jig is on the small-diameter hole side. As a result, the width of the opening on the ball holding side of the radial groove is widened.
In addition, due to the impact force due to cutting when forming the radial groove, the wall portion of the ball holding chamber on the extension line of the portion where the radial groove is processed falls inward, and the cross-sectional shape of the ball holding chamber is Deformation and roundness are impaired, but by forming the collision mark by cutting or pressing, the stepped portion of the portion that does not directly contact the jig by the impact force in the processing is on the small-diameter hole side Therefore, the wall portion of the ball holding chamber on the extension line of the portion to which the impact force is applied is also allowed to fall down in a minute amount. Therefore, the inner diameter and outer diameter of the ball-point pen tip can be corrected to a shape close to a circle in close proximity to the deformation of the inner shape of the ball-point pen tip due to the formation of the radial grooves.
In addition, as for the impact mark, the one that communicates with the rear hole and the one that does not communicate with the rear hole are appropriately adopted so that the radial groove width becomes the design value, and the shape, size, and depth are appropriately combined.
The material of the jig to be used is suitable for high hardness such as die steel, cemented carbide, ultrafine particle cemented carbide as well as radial grooves as ink flow passages, and coating such as TiC / TiCN is also required for durability improvement It is better to apply according to. The cutting jig can also be provided with a back taper.

Next, a ball serving as a writing member is placed in the ball holding chamber, and a so-called hammer process is performed to apply an impact force to the ball with a hammer tool, so that the ball is placed between the ball holding chamber and the small-diameter hole. The center of the step is plastically deformed into a ball shape to form a recess. This plastic deformation causes the radial groove to become narrower, and the larger the deformation volume, the larger the amount of the radial groove that can be reduced. Since the width of the opening to the ball holding chamber of the radial groove is widened by forming an impact mark between the radial grooves, the narrowing of the radial groove can be suppressed even if the recess is formed. The amount of ink that can be distributed can be secured, and ink ejection defects can be suppressed as much as possible.
Further, since the concave portion is a portion where the ball is pressed and plastically deformed, the surface thereof is in a state where the surface of the ball is transferred. If the ball to be used is a surface with little unevenness close to a mirror surface, the surface of the concave portion is also a surface state close to the mirror surface, and the factor that inhibits the rotation of the ball can be reduced.
The hardness of the hammer tool used here is preferably a material slightly lower than the ball hardness so that cracks do not occur on the surface of the ball during hammering.

The edge of the tip opening of the ball holder is reduced in diameter to a smaller diameter than that of the ball by plastic deformation called caulking with a pressure welding tool, thereby preventing the ball from coming off. Since the crimped tip part may come into contact with the paper surface during writing, if there are edges or burrs in the part, the writing quality will be lost, or the paper fiber will be scraped off and the paper fiber will be Since it may enter the inside of the ball holding chamber with rotation and block a part of the radial groove, it is preferable to form an R chamfered shape or to mirror the surface roughness of the caulking portion.
In addition, by this caulking process, the tip of the ball holder can be pressed against the ball, and in this case, a belt-like portion having a width that is the same curvature as the ball can be formed in the portion of the ball holder that contacts the ball. . If the surface of the band-like portion is a mirror surface with very few irregularities, the ball can rotate smoothly, and a coil spring that urges the ball forward is inserted into the ball holder, and one of the coil springs is inserted. When the ball is pressed by the part to prevent the ink from drying when not written, the belt-like part is in close contact with the ball, so that the sealing property is maintained, and a ballpoint pen that is stable over time is obtained. Can do. In addition, you may perform this process before the process of forming a recessed part in a step part.

  Next, a pin is inserted from the rear hole and the ball is pushed up, and the above-mentioned crimped ball holder tip portion is slightly expanded to form a space in which the ball can move back and forth. As a result, when writing, the ball comes into contact with the paper and moves backward, thereby forming a gap through which ink is ejected. When the caulking process is performed before the step of forming the concave portion in the stepped portion, the size of the concave portion to be formed can be adjusted to form an annular gap that can discharge an appropriate amount of ink.

An example of the ball-point pen tip thus obtained is shown in FIG. For convenience of explanation, the outer shape of the ball 1 is indicated by a broken line, and shows a state seen through. 2 is a cross-sectional view taken along the line II ′ of FIG.
The writing member includes a ball 1 and a ball holder 2 that holds the ball 1 rotatably. However, the writing member is not limited thereto, and may be a combination of other members such as a coil spring. .
The ball 1 is formed of a ceramic sintered body or a super hard material such as tungsten carbide or silicon carbide, and is manufactured by, for example, polishing and spheronizing a pressed blank sphere and stabilizing it by heat treatment. . By polishing, heat treatment, chemical treatment, etc., those with appropriate surface roughness can be manufactured, but for example by polishing the ball surface to a mirror surface state and smoothing the rotation of the ball and ball seat during writing, When writing on a paper surface that the ball skips, such as on paper with a hand grease or coated paper, roughen the surface of the ball and make the surface of the ball uneven. You can get a stable handwriting by turning the ball and turning the ball.
Further, the ball 1 can be appropriately manufactured with a diameter, and the one used as a ballpoint pen is approximately 0.25 to 2.0 mm. In the case of a relatively large-diameter ball, the ball holding chamber naturally becomes larger, so that the impact surface is applied to the ball in the hammer process, the concave surface that transfers the shape of the ball to the stepped portion becomes larger, and the deformation volume increases. The effect of the present invention is sufficiently exhibited because the width of the radial groove is large and the width of the radial groove is large.

The ball holder 2 has a ball holding chamber 3, a small diameter hole 4, and a rear hole 5 from the front end side as a passage for ink penetrating through the above-described manufacturing method for forming a through hole in the cylindrical metal member. A step portion 6 is formed between the ball holding chamber 3 and the rear hole 5 due to a difference in hole diameter.
The tip opening 7 of the ball holding chamber 3 is reduced in diameter by caulking, and the ball 1 moves in the front-rear direction by the tip opening 7 reduced in diameter and the step portion 6. It defines the range to obtain.

  Further, a plurality of radial grooves 8 are formed in the step portion 6 (five in the figure) and are annularly cut at equal intervals. The radial grooves 8 communicate with the small diameter hole 4. A concave portion 9 that is an impact mark is formed by a manufacturing method in which an impact force is applied between the radial grooves 8 to form an impact mark. By applying this impact force, the width of the opening of the radial groove 8 that is an ink flow path with respect to the ball holding chamber 3 is widened. Further, the step portion of the portion that does not directly contact the jig forming the impact mark is pulled to the small diameter hole side, and the portion of the wall portion 3a of the ball holding chamber 3 on the extension line of the portion to which the impact force is applied, that is, Then, the wall portion corresponding to the portion between the radial grooves 8 is also tilted inwardly, and the inner and outer diameters of the ball holding chamber 3 are corrected to a shape close to a circle.

  The step 6 is formed with a recess 10 formed by applying an impact force to the ball after the radial groove 8 and the recess 9 which is an impact mark are formed and the ball is set. The recess 10 stabilizes the position of the ball when the ball 1 is in a state of being retracted by abutting against the paper surface at the time of writing, and ensures smooth rotation with little unnecessary vibration. Thus, the ink in a layered form can be used as a lubricant for the rotation of the ball. Further, the aforementioned radial groove 8 has an opening 8 a outside the concave portion 10 of the step portion 6, and ensures ink supply to the ball holding chamber 3.

As the ink applied to the ballpoint pen using the ballpoint pen tip obtained in the present invention, either water-based ink using water as a main medium or oil-based ink using an organic solvent such as alcohol as a main medium can be used. Pigments and dyes that are coloring components, high-boiling organic solvents for preventing freezing, resin components that provide fixability to the writing surface, surfactants that adjust surface tension, viscoelasticity, lubricity, etc. Saccharides, rust preventives, and antifungal agents are blended, and may be blended with a white hiding component such as titanium oxide for the purpose of correcting typographical errors.
Also, if necessary, such as checking the viscosity or remaining amount of the ink, contact the ink interface and follow the ink interface with highly viscous fluids such as polybutene, its gelled products, and silicone oil that are not compatible with the ink. It can also be arranged in layers to move. This high-viscosity fluid can also serve to suppress the backflow of ink.

Example 1
Hereinafter, an example will be described with reference to the drawings. In addition, a process shall transfer in order of the number in the parenthesis which bears each process.

<(1) Wire cutting process (not shown)>
A metal wire bundled in a coil shape is attached to a cold forging machine (header machine) manufactured by Nakashimada Iron Works Co., Ltd., and the total length of the finished ball holder is sheared to a total length of about 0.1 mm on both ends. To form a cylindrical metal member. After this cutting step, in order to make the member flow of the so-called parts feeder of the member supply device to the chip processing machine in the next step lubricate, the oil is removed by washing. Further, in order to improve the member supply performance to the so-called collet chuck of the member fixing tool of the chip processing machine, the corner of the shearing surface of the wire rod is chamfered by barrel polishing as necessary.

<(2) Small diameter hole and rear hole forming step>
Next, the cylindrical metal member to be the chip holder 2 is put into a chip processing machine, the cylindrical metal member is fixed by a collet chuck (not shown), and the front and rear ends are adjusted in order to adjust the total length to a predetermined length. After cutting with a cutting tool, it is cut into a plurality of cutting tools with a cutting tool to form a tapered portion 2a whose outer diameter is reduced toward the tip.
Next, an auxiliary hole (not shown) serving as a center guide for forming the through-hole is formed with a cutting tool or a drill, and a small-diameter hole 4 is formed with a drill from the tip side, and then, as shown in FIG. The ball holding chamber 3 is formed with the drill A and the stepped portion 6 is formed between the ball holding chamber 3 and the small diameter hole 4, and the rear hole 5 'is further formed into the small diameter hole with the larger diameter drill A'. 4 is formed up to a position not penetrating through 4.
Thereafter, as shown in FIG. 4, the inner wall surface 3b, the bottom surface 3c, and the tip surface 3d of the ball holding chamber 3 are finished with a cutting tool and the tip outer chamfered portion 3e is also finished with a cutting tool. Further, the rear hole 5 is passed through the small-diameter hole 4 with a drill that gradually decreases the diameter from the rear end side of the ball holder to a larger diameter to a smaller diameter.
Next, an ink tank member and a small-diameter outer step portion (not shown) serving as a press-fit portion for coupling to an ink tank connecting member (both not shown) are formed by cutting with a cutting tool.

<(3) Radial groove forming step>
As shown in FIG. 5, the step 6 formed by processing the small-diameter hole 4 and the ball holding chamber 3 is cut with a cutting jig B having cutting blades arranged radially, and ink distribution holes are formed. The radial groove 8 is formed. In this embodiment, the cutting jig B is stopped in the middle of the small diameter hole 4 so as not to penetrate the rear hole 5.
FIG. 6 shows a longitudinal sectional view of the main part of the product obtained up to this step. 7 is a cross-sectional view taken along the line II-II ′ of FIG.

<(4) Impact force application process>
As shown in FIG. 8, the radial grooves 9 are formed as impact marks by cutting with a cutting jig K in which the same number of radial blades as the radial grooves 8 are arranged between the radial grooves 8. As a result, the width of the opening of the radial groove 8 with respect to the ball holding chamber 3 is widened, and the wall portion 3a of the ball holding chamber 3 corresponding to the portion to which the impact force is applied to the stepped portion 6 is also slightly inside. Therefore, the inner diameter and outer diameter of the ball-point pen tip are corrected to a shape close to a circle in close proximity to the deformation of the inner shape of the ball-point pen tip due to the formation of the radial grooves 8.
FIG. 9 shows a longitudinal sectional view of the main part of the product obtained up to this step. 10 is a cross-sectional view taken along the line III-III ′ of FIG.

<(5) Caulking process>
Next, as shown in FIG. 11, after the ball 1 is placed in the ball holding chamber 3, the tip outer chamfered portion 3 e of the ball holder 2 is plastically deformed inward by a pressing tool R such as a roller. Caulking is performed to prevent the ball 1 from coming out of the ball holding chamber 3.

<(6) Concave formation process>
As shown in FIG. 12, an impact force is applied to the ball 1 by a hammer tool M, and a concave portion 10 in which the shape of the ball 1 is transferred to the step portion 6 is formed by the plastic deformation, and a hammer to the step portion 6 is formed. By adjusting the pressing depth of the tool M, a space in which the ball can move back and forth is formed. As a result, when writing, the ball comes into contact with the paper and moves backward, thereby forming a gap through which ink is ejected.
As described above, since the concave portion 10 is formed after the width of the opening portion of the radial groove 8 is widened, the narrowing of the radial groove 8 due to the formation of the concave portion 10 can be suppressed, and the amount of ink that can be distributed is ensured. In addition, ink discharge defects can be suppressed as much as possible.
FIG. 13 shows a vertical cross-sectional view of the main part (ball 1 is indicated by a broken line) obtained by the steps so far. 14 is a cross-sectional view taken along the line IV-IV ′ of FIG. 13 (the ball 1 is omitted).

Example 2
Since the wire rod cutting process or radial groove forming process, caulking process, and recess forming process are the same as those in the first embodiment, description thereof is omitted.
<(4) Impact force application process>
As shown in FIG. 15, pressing is performed by a pressing tool K ′ having a polygonal pyramid shape having a pointed tip and a number of corners equal to the number of the radial grooves 8 between the radial grooves 8. As shown in FIG. 16 which is a longitudinal cross-sectional view of the product obtained after this processing and FIG. 17 which is a cross-sectional view taken along the line III-III ′ of FIG. 16, a recess 9 which is an impact mark is formed by this processing. As a result, the width of the opening of the radial groove 8 with respect to the ball holding chamber 3 is widened, and the wall portion 3a of the ball holding chamber 3 corresponding to the portion to which the impact force is applied to the stepped portion 6 is also slightly inside. Therefore, the inner diameter and outer diameter of the ball-point pen tip are corrected to a shape close to a circle in close proximity to the deformation of the inner shape of the ball-point pen tip due to the formation of the radial grooves 8.
In this example, unlike the application of impact force with a cutting jig having a cutting blade, the pointed tip polygonal surface having no cutting blade is positioned at the step 6 between the radial grooves 8 and pushed in. Since it is a plastic deformation process, when the processing volume is the same as that of the cutting process, the impact force to the stepped portion 6 is increased, so that the width of the opening of the radial groove 8 with respect to the ball holding chamber 3 can be increased. In addition, the collapse of the ball holding chamber wall portion 3a corresponding to the portion to which the impact force is applied to the stepped portion increases, and the inner diameter and outer diameter of the ballpoint pen tip are corrected to a shape close to a circle. Will also increase.
Further, unlike cutting, no chips are generated, and it is possible to prevent the ink flow path from being obstructed by the remaining chips in the chip holder 2.

DESCRIPTION OF SYMBOLS 1 Ball 2 Ball holder 2a Tapered part 3 Ball holding chamber 3a Wall part 3b Inner wall surface 3c Bottom surface 3d Tip surface 3e Tip outer chamfered part 4 Small diameter hole 5 Rear hole 5 Rear hole '
6 Stepped portion 7 Tip opening portion 8 Radial groove 8a opening portion 9 Impact mark 10 Recessed portion 11 Narrow width portion A Drill A 'Drill B Cutting jig K Cutting jig K' Pressing tool R Pressure welding tool M Hammer tool

Claims (1)

  A step of forming a ball holding chamber which is a large-diameter portion and a small-diameter hole opened in the ball holding chamber as an ink passage which is a through-hole in a cylindrical metal member, cutting which has cutting blades arranged radially Inserting a jig from the ball holding chamber side, cutting the step between the ball holding chamber which is the large diameter portion and the small diameter hole to form a radial groove communicating with the small diameter hole, part from the tip Applying impact force to the writing ball placed in the ball holding chamber in a protruding state to form a recess that transfers the shape of the ball to the stepped portion, and crimping the tip of the opening to make it smaller than the diameter of the ball In the ballpoint pen tip manufacturing method including the step of preventing the ball from slipping out, the width of the opening of the radial groove with respect to the ball holding chamber is formed by applying an impact force between the radial grooves after the radial grooves are formed. After spreading the ball Ballpoint pen tip manufacturing method of the impact force imparted to form a recess to transfer the shape of the ball in the stepped portion.