Ball-point pen tip

Abstract

To provide a ball-point pen tip which can achieve both prevention of ball burning and improvement of writing feeling.SOLUTION: In this ball-point pen tip, when a ball receiving seat 26 is viewed in an opposite view from a direction along a center axis CL of a tip body 20, in a circumferential direction around the center axis CL, the ball receiving seat 26 includes a range R1 in which a width dimension c along the radial direction of the center axis CL is c1 and a range R2 in which the width dimension c adjacent to the range R1 and along the radial direction around the center axis CL is c2 which is shorter than c1. The range R1 and the range R2 are provided two or more at the ball receiving seat 26 respectively, and they are arranged alternately side by side in the circumferential direction around the center axis CL. The space between the ranges R1 adjacent to each other via the range R2 is connected by a recess part S which has the width dimension of a difference between c1 and c2.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a ball pen tip.

Background Art

[0002] Conventionally, as the tip structure of a ball pen, for example, a ball pen tip shown in Patent Document 1 below is known. The ball pen tip has a ball and a tip body. In the tip body, a ball holding chamber for holding the ball, a tip opening that communicates with the ball holding chamber and exposes a part of the ball to the outside, and an ink flow path for supplying ink into the ball holding chamber are formed. In the ball holding chamber, a ball seating seat on which the ball sits and a plurality of ink flow grooves communicating with the ink flow path are formed. In the ball pen tip having the above configuration, during writing, the ball pen tip is moved while pressing the ball against the writing surface and rolling it. Then, as the ball rolls, the ink in the ink flow path is guided into the ball holding chamber through each ink flow groove, and further transferred to the writing surface through the gap between the outer peripheral surface of the ball and the tip opening to form a writing line.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, in the conventional ball pen tip, there was a case where the rolling of the ball became sluggish during writing, and the writing line became blurred due to so-called "sticking". In addition, in the conventional ball pen tip, the ball during writing did not behave stably in the ball holding chamber, so the writing feel deteriorated in some cases. Since these two problems are in a mutually contradictory relationship, there was a risk that if one was improved, the other problem would become prominent.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a ballpoint pen tip that can achieve both prevention of ball seizure and improvement of writing feel.

Means for Solving the Problems

[0006] The present invention adopts the following aspects in order to solve the above problems and achieve the related object.

[0007] (1) A ballpoint pen tip according to an aspect of the present invention includes a ball, a ball holding chamber that rotatably houses the ball, and a tip body having an ink flow passage communicating with the ball holding chamber, and is provided with the ball holding chamber includes a ball seat that defines a part of the ball holding chamber, and a tip opening that holds the ball between the ball seat and exposes a part of the ball to the outside, and has when the ball seat is viewed in a direction facing the center axis of the tip body, the ball seat has a first region in a circumferential direction centered on the center axis and having a first width dimension along a radial direction of the center axis, and a second region adjacent to the first region and having a second width dimension shorter than the first width dimension along a radial direction centered on the center axis, two or more of the first regions and the second regions are provided in the ball seat respectively, and are alternately arranged side by side in the circumferential direction around the center axis, adjacent first regions adjacent to each other via the second region are connected by a recess having a width dimension equal to a difference between the first width dimension and the second width dimension.

[0008] According to the ball pen tip described in the above (1), in the ball receiving seat, a first region having a relatively long radial width dimension and a second region having a relatively short radial width dimension are alternately arranged along the circumferential direction. And at the position where the second region is arranged on the ball receiving seat, a recess is arranged by using the space created by making the second region shorter than the first region. During writing, in the second region, the ink flowing from the ink flow path toward the tip opening reaches the gap between the outer peripheral surface of the ball and the inner peripheral surface of the tip opening after going through the process of being temporarily stored in the recess. On the other hand, in the first region that is longer in the radial direction than the second region, a wider support range for the ball is ensured than in the second region. Therefore, since the ink temporarily stored in the recess of the second region can be supplied to the gap between the outer peripheral surface of the ball and the inner peripheral surface of the tip opening, it is possible to suppress the blurring of the writing line due to the sticking of the ball. Also, since the outer peripheral surface of the ball can be stably supported over a wide range by the first region, the rolling of the ball can be made more stable and a good writing feel can be obtained. During writing, usually, the writing direction of the ball pen tip changes randomly, so the above-described anti-sticking effect and writing feel improvement effect are manifested so as to complement each other. Therefore, it is possible to achieve both prevention of the ball from sticking and improvement of the writing feel.

[0009] (2) In the ball pen tip described in the above (1), the depth of the recess may be deeper than both the first region and the second region. In the case of the ball pen tip described in the above (2), since a sufficient amount of ink can be stored in the recess, it is possible to more effectively suppress the sticking of the ball and the blurring of the writing line.

[0010] (3) The ball pen tip described in the above (1) or the above (2) may be configured as follows: An ink flow groove that communicates between the ink flow path and the ball holding chamber is within the second region, or at the boundary position between the first region and the second region, and leads to the recess. In the case of the ball pen tip described in the above (3), since the ink flow groove communicates with the recess within the second region or via the boundary position between the first region and the second region, the ink supplied from the ink flow path can be fed into the recess smoothly without stagnation. Therefore, the ink amount in the recess can always be ensured sufficiently, so that smudging of the writing line due to ball sticking can be suppressed more effectively.

Advantages of the Invention

[0011] According to the ball pen tip according to the above aspect of the present invention, it is possible to provide a ball pen tip that can achieve both prevention of ball sticking and improvement of writing feel.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0013] Hereinafter, with reference to the drawings, the ball pen tip according to each embodiment of the present invention will be described. In the following description, the central axis CL of the ball pen tip is used as a reference for indicating directions. That is, the direction along the central axis CL toward the tip side of the ball pen tip is called the "tip direction", the direction along the central axis CL toward the rear end side of the ball pen tip is called the "rear end direction", and the direction including both the "tip direction" and the "rear end direction" is called the "axial direction". Further, in a cross section perpendicular to the central axis CL, the direction away from the central axis CL is called the "radial outer side", the direction approaching the central axis CL in a cross section perpendicular to the central axis CL is called the "radial inner side", and the circumferential direction around the central axis CL is called the "circumferential direction".

[0014] [First Embodiment] The first embodiment of the present invention will be described below with reference to FIGS. 1 to 4. As shown in FIG. 1, the ball pen tip of this embodiment has a ball 10 and a tip body 20. The ball 10 is a metal sphere having an outer diameter of, for example, 0.7 mm. In FIGS. 1 and subsequent figures, in order to clearly show the internal structure of the tip body 20 and the position of the ball 10 in the tip body 20, the ball 10 may be shown by a two-dot chain line. Further, in the following description, the state of pressing the ball 10 against a writing surface such as a sheet of paper for writing is called the "writing state", and the state of not pressing the ball 10 against a writing surface such as a sheet of paper for writing is sometimes called the "state before starting writing".

[0015] The chip body 20 is a metallic cylindrical component that tapers toward the tip direction, which is above the plane of the paper in FIG. 1. The chip body 20 has an outer peripheral surface 21 in a substantially frustum - like shape that is coaxial with the central axis CL. At the tip of the outer peripheral surface 21, a caulking portion 22 is formed. The caulking portion 22 is formed by caulking the tip of the chip body 20 after accommodating the ball 10, and its outer diameter is bent more angularly toward the radially inner side than other portions. The outer peripheral surface 21 and the outer peripheral surface 22a of the caulking portion 22 both have a circular cross - sectional shape perpendicular to the central axis CL at each position on the central axis CL.

[0016] As shown in FIG. 1, inside the chip body 20, in the direction from the tip toward the rear end, a tip opening 23, a ball holding chamber 24, an ink flow groove 27, an ink flow passage 28, and a rear hole 29 are formed in this order side by side. The tip opening 23 is a circular opening formed inside the caulking portion 22 and is coaxial with the central axis CL. In the state before starting writing shown in FIG. 1, the ball 10 is coaxial with the central axis CL inside the ball holding chamber 24 and is arranged such that a part of it protrudes outside the chip body 20 and is exposed. In the state before starting writing, an annular gap g having a constant width dimension at each circumferential position is formed between the outer peripheral surface of the ball 10 and the tip opening 23. Note that the gap g indicates the dimension along the radial direction centered on the central axis CL in a virtual plane including the tip opening 23 and perpendicular to the central axis CL.

[0017] As shown in FIG. 1, the ball holding chamber 24 is a space that rotatably holds the ball 10 between it and the tip opening 23. The ball holding chamber 24 has a circumferential groove 25 formed on the rear end side of the tip opening 23 and a ball receiving seat 26 formed on the rear end side of the circumferential groove 25.

[0018] The circumferential groove 25 is an annular concave groove that communicates with the tip opening 23 and is formed along the circumferential direction centered on the central axis CL. The circumferential groove 25 has an inner circumferential surface 25a that is formed tapered toward the tip opening 23 and communicates with the tip opening 23, an inner side surface 25b that is continuously formed on the rear end side of the inner circumferential surface 25a, and a bottom surface 25c that is continuously formed on the rear end side of the inner side surface 25b.

[0019] The inner circumferential surface 25a is formed during the caulking process that forms the caulking portion 22, and the radial dimension centered on the central axis CL is constant (the same) at each position in the circumferential direction. Also, the width dimension along the central axis CL of the inner circumferential surface 25a is constant (the same) at each position in the circumferential direction centered on the central axis CL.

[0020] The inner side surface 25b is a cylindrical surface centered on the central axis CL, and the radial dimension from the central axis CL is constant (the same) at each position in the circumferential direction. The inner side surface 25b has a width dimension a along the axial direction that varies at each position in the circumferential direction. That is, as shown in FIG. 1, the width dimension a of the inner side surface 25b is relatively small on the left side of the paper surface with respect to the central axis CL, and conversely, is relatively large on the right side of the paper surface with respect to the central axis CL. On the other hand, when viewed in the cross section of FIG. 2, the width dimension a of the inner side surface 25b is relatively large on the left side of the paper surface with respect to the central axis CL, and conversely, is relatively small on the right side of the paper surface with respect to the central axis CL.

[0021] Here, when the relatively small width dimension a is set as a1 and the relatively large width dimension a is set as a2, as shown in FIG. 3, a range R1 where the width dimension a is a1 and a range R2 where the width dimension a is a2 are arranged alternately along the circumferential direction. Each of the range R1 where the width dimension a is a1 and the range R2 where the width dimension a is a2 has a range of 90° centered on the central axis CL. That is, with the central axis CL as the center, in the 90° range R2 in the upper right of the paper surface of FIG. 3, the width dimension a is large and is a2, and in the 90° range R1 adjacent to the range R2 in the circumferential direction and in the lower right of the paper surface of FIG. 3, the width dimension a is small and is a1. In the 90° range R2 further adjacent to the range R1 in the circumferential direction and in the lower left of the paper surface of FIG. 3, the width dimension a is large and is a2, and in the 90° range R1 further adjacent to the range R2 in the circumferential direction and in the upper left of the paper surface of FIG. 3, the width dimension a is small and is a1. That is, when FIG. 3 is viewed clockwise with the central axis CL as the center, the range R1 where the width dimension a is a1 and the range R2 where the width dimension a is a2 are arranged alternately at 90° intervals. In other words, a pair of ranges R1 where the width dimension a is a1 are arranged opposite each other with the central axis CL in between, and a pair of ranges R2 where the width dimension a is a2 are arranged opposite each other with the central axis CL in between. Thus, the inner surface 25b is composed of ranges R1 and R2 that are divided into four along the circumferential direction.

[0022] As shown in Fig. 3, when viewed along the central axis CL, the bottom surface 25c is roughly divided into four ranges. When comparing these four ranges with each other, their outer diameter dimensions are the same, but the inner diameter dimensions are different between adjacent ones in the circumferential direction such that they alternate between larger and smaller along the circumferential direction. And due to this difference in inner diameter dimensions, the radial width dimension b is divided into two types: a relatively small b1 and a relatively large b2. That is, with the central axis CL as the center, in the 90° range R2 located in the upper right of the paper of Fig. 3, the width dimension b is large and is b2. In the 90° range R1 adjacent to the range R2 in the circumferential direction and located in the lower right of the paper of Fig. 3, the width dimension b is small and is b1. In the 90° range R2 adjacent to the range R1 in the circumferential direction and located in the lower left of the paper of Fig. 3, the width dimension b is large and is b2. In the 90° range R1 adjacent to the range R2 in the circumferential direction and located in the upper left of the paper of Fig. 3, the width dimension b is small and is b1. That is, when viewing Fig. 3 clockwise with the central axis CL as the center, the ranges R1 with the width dimension b being b1 and the ranges R2 with the width dimension b being b2 are arranged alternately at 90° intervals. In other words, a pair of ranges R1 with the width dimension b being b1 are arranged opposite each other with the central axis CL in between, and a pair of ranges R2 with the width dimension b being b2 are arranged opposite each other with the central axis CL in between. Thus, the bottom surface 25c is composed of the ranges R1 and R2 that are divided into four parts along the circumferential direction.

[0023] And the ranges R1 and R2 that are divided into four parts on the bottom surface 25c and the ranges R1 and R2 that are divided into four parts on the inner surface 25b described above are arranged with their circumferential positions synchronized. That is, as shown in Fig. 3, when viewed along the circumferential direction, the position of the range R1 where the width dimension a of the inner surface 25b is a1 completely coincides with the position of the range R1 where the width dimension b of the bottom surface 25c is b1. Similarly, when viewed along the circumferential direction, the position of the range R2 where the width dimension a of the inner surface 25b is a2 completely coincides with the position of the range R2 where the width dimension b of the bottom surface 25c is b2. As shown in FIG. 3, in a range R2 where the width dimension a of the inner surface 25b is a2 and the width dimension b of the bottom surface 25c is b2, since both the width dimension a and the width dimension b are large, an arc-shaped recess S having a relatively large capacity is formed at a position sandwiched between the pair of ranges R1, R1. This recess S, due to the combination of the wide width dimension b2 and the wide width dimension a2, constitutes a large-capacity ink storage portion having a wide width dimension in the radial direction and a deep depth dimension in the axial direction, as shown in FIG. 4. When supporting the outer peripheral surface of the rolling ball 10 in the range R2, this ink storage portion can sufficiently secure the amount of ink supplied to the support location. As shown in FIG. 4, both circumferential ends of the recess S are partitioned by vertical walls 25d formed in the respective ranges R1, R1 adjacent to both sides thereof. Further, as shown in FIG. 3, a pair of the recesses S are arranged to face each other with the central axis CL interposed therebetween.

[0024] As shown in FIGS. 1 and 2, the ball seat 26 is a concave curved surface on which the outer peripheral surface shape of the ball 10 is transferred by hammering, and is a portion where the ball 10 in the state before the start of writing seats in surface contact. Then, as shown in FIG. 3, the ball seat 26 has a width dimension c along the radial direction that varies at each position in the circumferential direction. Here, when the relatively large width dimension c is designated as c1 and the relatively small width dimension c is designated as c2, a range R1 where the width dimension c is c1 and a range R2 where the width dimension c is c2 are arranged alternately along the circumferential direction. Each of the range R1 where the width dimension c is c1 and the range R2 where the width dimension c is c2 has a 90° range centered on the central axis CL. That is, with the central axis CL as the center, in the 90° range R2 located in the upper right of the drawing plane of FIG. 3, the width dimension c is small and is c2, and in the 90° range R1 adjacent to the range R2 in the circumferential direction and located in the lower right of the drawing plane of FIG. 3, the width dimension c is large and is c1. In the 90° range R2 further adjacent to the range R1 in the circumferential direction and located in the lower left of the drawing plane of FIG. 3, the width dimension c is small and is c2, and in the 90° range R1 further adjacent to the range R2 in the circumferential direction and located in the upper left of the drawing plane of FIG. 3, the width dimension c is large and is c1. That is, when viewing FIG. 3 clockwise with the central axis CL as the center, the range R1 where the width dimension c is c1 and the range R2 where the width dimension c is c2 are arranged alternately at 90° intervals. In other words, a pair of ranges R1 where the width dimension c is c1 are arranged opposite each other with the central axis CL in between, and a pair of ranges R2 where the width dimension c is c2 are arranged opposite each other with the central axis CL in between. Thus, the ball seat 26 is composed of ranges divided into four along the circumferential direction.

[0025] And the ranges R1 and R2 divided into four in the ball seat 26 and the ranges R1 and R2 divided into four on the bottom surface 25c described above are arranged in synchronization in the circumferential direction. That is, as shown in FIG. 3, when viewed along the circumferential direction, the position of the range R1 where the width dimension c of the ball seat 26 is c1 completely coincides with the position of the range R1 where the width dimension b of the bottom surface 25c is b1. Similarly, when viewed along the circumferential direction, the position of the range R2 where the width dimension c of the ball seat 26 is c2 completely coincides with the position of the range R2 where the width dimension b of the bottom surface 25c is b2. As a result, as shown in FIG. 3, in the range R1 where the width dimension a of the inner surface 25b is a1 and the width dimension b of the bottom surface 25c is b1, since both the width dimension a and the width dimension b are formed to be relatively small, accordingly, the width dimension c of the ball receiving seat 26 becomes wider and a relatively large surface area is ensured. Therefore, in the range R1, a relatively large range for supporting the outer peripheral surface of the ball 10 can be ensured, so that the rolling ball 10 can be stably supported.

[0026] As shown in FIG. 1, the ink flow groove (channel) 27 is a flow path that guides the ink in the ink flow passage 28 into the ball holding chamber 24. As shown in FIG. 3, a plurality of ink flow grooves 27 are arranged at equal angular intervals around the central axis CL. In the illustrated example, a case where four ink flow grooves 27 are arranged at intervals of 90° around the central axis CL is exemplified, but the number and the angular interval of the arrangement are not limited to this example. As shown in FIG. 1, each ink flow groove 27 is formed from the ink flow passage 28 to the ball receiving seat 26 in the ball holding chamber 24. Each ink flow groove 27 is a slit formed long in the axial direction, and is formed such that the groove width becomes wider toward the outer side in the radial direction. As shown in FIG. 3, each ink flow groove 27 is arranged at the circumferential center position of the ball receiving seat 26 within the same ranges R1 and R2 that divide the ball receiving seat 26 into four parts. That is, in the range R1, since the angle between one side edge and the other side edge in the circumferential direction is 90°, the ink flow groove 27 is formed such that the circumferential position of 45° from one side edge or the other side edge toward the other side becomes the center position. Similarly, in the range R2, since the angle between one side edge and the other side edge in the circumferential direction is 90°, the ink flow groove 27 is formed such that the circumferential position of 45° from one side edge or the other side edge toward the other side becomes the center position.

[0027] As shown in Fig. 1, each ink flow groove 27 has a groove length in the axial direction that is different from that of the other ink flow grooves 27 adjacent to it in the circumferential direction centered on the central axis CL. That is, in the ranges R2 in the upper right and lower left of the drawing in Fig. 3, since the width dimension c of the ball receiving seat 26 is short, the length dimension of the ink flow groove 27 is accordingly shortened. Conversely, in the ranges R1 in the lower right and upper left of the drawing, since the width dimension c of the ball receiving seat 26 is long, the length dimension of the ink flow groove 27 is accordingly lengthened. Therefore, in the range R1, a pair of longer ink flow grooves 27 are arranged opposite each other with the central axis CL in between. Also, in the range R2, a pair of shorter ink flow grooves 27 are arranged opposite each other with the central axis CL in between. All of the ink flow grooves 27 have their rear ends communicating with the ink flow path 28, and their front ends opening through the bottom surface 25c. And out of these four ink flow grooves 27, only the two ink flow grooves 27 formed shorter directly communicate with the recess S forming the ink storage part. That is, through these shorter ink flow grooves 27, the ink flow path 28 and the recess S are directly connected.

[0028] Returning to Fig. 1, the ink flow path (capillary) 28 is a cylindrical space coaxial with the central axis CL, and four openings communicating with each of the ink flow grooves 27 are formed on its upper inner peripheral surface. The ink flow path 28 supplies the ink in the rear hole 29 mainly into the ball holding chamber 24 through each ink flow groove 27. The rear hole 29 is a substantially cylindrical space coaxial with the central axis CL and has an inner diameter dimension wider than that of the ink flow path 28. The upper part of the rear hole 29 is reduced in diameter toward the tip direction, and at its upper end position, it has the same inner diameter dimension as the ink flow path 28.

[0029] The operation and effect of the ball pen tip having the configuration described above will be described. As described above, according to the ballpoint pen tip of the present embodiment, in the ball receiving seat 26, a range (first region) R1 having a relatively long radial width dimension c and a range (second region) R2 having a relatively short width dimension c are alternately arranged along the circumferential direction. And, in the range R2 on the ball receiving seat 26, a concave portion S is arranged by using the space created by making the width dimension c shorter than that in the range R1.

[0030] During writing, in the range R2, the ink flowing from the ink flow path 28 toward the tip opening 23 reaches the gap between the outer peripheral surface of the ball 10 and the inner peripheral surface 25a of the tip opening after passing through the process of being temporarily stored in the concave portion S. Also, in the range R1 that is longer in the radial direction than the range R2, a support range for the ball 10 is secured wider than that in the range R2. Therefore, since the ink temporarily stored in the concave portion S in the range R2 can be supplied to the gap between the outer peripheral surface of the ball 10 and the inner peripheral surface 25a of the tip opening 23, it is possible to suppress the fading of the writing line due to the sticking of the ball 10. Also, since the outer peripheral surface of the ball 10 can be stably supported over a wide range by the range R1, the rolling of the ball 10 can be made more stable and a good writing feeling can be obtained. During writing, usually, the writing direction of the ballpoint pen tip changes randomly, so the above-described anti-sticking effect and writing feeling improvement effect are manifested so as to complement each other. Therefore, it is possible to achieve both prevention of sticking of the ball 10 and improvement of the writing feeling.

[0031] The essence of the first embodiment described above is summarized below. (1) As illustrated in FIG. 1, the ballpoint pen tip of the present embodiment includes a ball 10, a chip body 20 having a ball holding chamber 24 that rotatably houses the ball 10 and an ink flow path 28 that communicates with the ball holding chamber 24, and is provided with the ball holding chamber 24 includes a ball receiving seat 26 that defines a part of the ball holding chamber 24, a tip opening 23 that holds the ball 10 between the ball receiving seat 26 and exposes a part of the ball 10 to the outside, and has. And, as shown in FIG. 3, when the ball seat 26 is viewed from the direction along the central axis CL of the chip body 20, the ball seat 26 has a range (first region) R1 in which the width dimension c along the radial direction of the central axis CL is c1 (first width dimension) in the circumferential direction centered on the central axis CL, and a range (second region) R2 that is adjacent to the range (first region) R1 and in which the width dimension c along the radial direction centered on the central axis CL is shorter than c1 (first width dimension) and is c2 (second width dimension), two of the ranges (first regions) R1 and two of the ranges (second regions) R2 are respectively provided in the ball seat 26, and are alternately arranged side by side in the circumferential direction around the central axis CL, the ranges (first regions) R1 adjacent to each other via the range (second region) R2 are connected by a recess S having a width dimension that is the difference between c1 (first width dimension) and c2 (second width dimension). According to the ballpoint pen chip described in (1) above, it is possible to cause the anti-sticking effect and the writing feeling improvement effect to be exhibited so as to complement each other.

[0032] (2) As illustrated in FIG. 4, the depth of the recess S is formed deeper than both the surface of the ball seat 26 in the range (first region) R1 and the surface of the ball seat 26 in the range (second region) R2. According to the configuration described in (2) above, since a sufficient amount of ink can be stored in the recess S, it is possible to more effectively suppress the sticking of the ball 10 and the blurring of the writing line.

[0033] (3) As illustrated in FIG. 4, a pair of the ink flow grooves 27 that communicate between the ink flow path 28 and the ball holding chamber 24 lead to the recess S through the circumferential center position of the ball seat 26 in the range (second region) R2. According to the configuration described in (3) above, the ink supplied from the ink flow path 28 can be sent into the recess S without stagnation. Therefore, since the ink amount in the recess S can always be sufficiently ensured, it is possible to more effectively suppress the blurring of the writing line due to the sticking of the ball 10.

[0034] [Second Embodiment] In the above-described first embodiment, the case where each ink flow groove 27 is disposed at the circumferential center position of each of the ranges R1 and R2 has been illustrated. However, the formation position of each ink flow groove 27 is not limited to this position only. As another arrangement example of each ink flow groove 27, it will be described below with reference to FIGS. 5 and 6. Since this second embodiment corresponds to a modification of the above-described first embodiment, the description will be centered on the differences from the above-described first embodiment, and redundant descriptions of other configurations will be omitted assuming that they are the same as those in the above-described first embodiment.

[0035] Each ink flow groove 27 of the present embodiment is formed at the boundary position between the range (first region) R1 and the range (second region) R2. That is, as shown in FIG. 5, the first one of the four ink flow grooves 27 is arranged so as to overlap the boundary line between the range R2 in the upper right of the drawing and the range R1 in the upper left of the drawing. Similarly, the second one of the four ink flow grooves 27 is arranged so as to overlap the boundary line between the range R2 in the upper right of the drawing and the range R1 in the lower right of the drawing. Similarly, the third one of the four ink flow grooves 27 is arranged so as to overlap the boundary line between the range R1 in the lower right of the drawing and the range R2 in the lower left of the drawing. Similarly, the fourth one of the four ink flow grooves 27 is arranged so as to overlap the boundary line between the range R2 in the lower left of the drawing and the range R1 in the upper left of the drawing.

[0036] All of the ink flow grooves 27 have the same length dimension. That is, as shown in FIG. 5, when viewed along the central axis CL, the radial dimensions of all the ink flow grooves 27 are equal to each other, and the dimensions in the direction parallel to the central axis CL are also equal to each other. And as shown in FIG. 6, the rear end sides of the respective ink flow grooves 27 all open so as to communicate with the ink flow path 28. Also, two of the ink flow grooves 27 open directly toward one of the pair of recesses S, and the other two of the ink flow grooves 27 open directly toward the other of the pair of recesses S. Therefore, also in the present embodiment, the ink in the ink flow path 28 can be supplied to the recess S without stagnation through the respective ink flow grooves 27. In addition, in the present embodiment, since the ink is supplied from two ink flow grooves 27 to one recess S, the ink supply to the recess S can be performed more smoothly. Also, similar to the first embodiment, since a wide support range of the ball 10 can be ensured in the range R1 and stable support can be achieved, the rolling of the ball 10 can be stabilized and a good writing feeling can be obtained. As described above, also in the ballpoint pen tip of the present embodiment, it is possible to cause the anti-burnishing effect and the writing feeling improvement effect to be manifested so as to complement each other.

[0037] [Third Embodiment] In the first embodiment described above, the number of divisions of the ball seat 26 is four, but in the present embodiment, as shown in FIGS. 7 to 10, the number of divisions is six. As shown in FIG. 7, the ballpoint pen tip of the present embodiment has a ball 10 and a tip body 120. Since the ball 10 is the same as that of the first embodiment, the same reference numerals are used and redundant description is omitted.

[0038] The tip body 120 is a metal cylindrical component that tapers toward the tip direction, which is above the plane of FIG. 1. The tip body 120 has an outer peripheral surface 121 having a substantially frustum shape that is coaxial with the central axis CL. A caulking portion 122 is formed at the tip of the outer peripheral surface 121. The caulking portion 22 is formed by caulking the tip of the tip body 120 after accommodating the ball 10, and the outer diameter is bent further radially inward with an angle compared to the other portions. The outer peripheral surface 121 and the outer peripheral surface 122a of the caulking portion 122 both have a circular cross-sectional shape perpendicular to the central axis CL at each position on the central axis CL.

[0039] As shown in Fig. 7, inside the chip body 120, in the direction from the tip to the rear end, a tip opening 123, a ball holding chamber 124, an ink flow groove 127, an ink flow path 128, and a rear hole 129 are formed in this order side by side. The tip opening 123 is a circular opening formed in the caulking portion 22 and is coaxial with the central axis CL. In the state before starting writing shown in Fig. 1, the ball 10 is coaxial with the central axis CL in the ball holding chamber 124 and is arranged such that a part of it protrudes outside the chip body 120 and is exposed. In the state before starting writing, an annular gap g having a constant width dimension at each circumferential position is formed between the outer peripheral surface of the ball 10 and the tip opening 123. Note that the gap g indicates a dimension along the radial direction centered on the central axis CL in a virtual plane including the tip opening 123 and orthogonal to the central axis CL.

[0040] As shown in Fig. 7, the ball holding chamber 124 is a space for rotatably holding the ball 10 between it and the tip opening 123. The ball holding chamber 124 has a circumferential groove 125 formed on the rear end side of the tip opening 23 and a ball receiving seat 126 formed on the rear end side of the circumferential groove 125.

[0041] The circumferential groove 125 is an annular concave groove that communicates with the tip opening 123 and is formed along the circumferential direction centered on the central axis CL. The circumferential groove 125 has an inner peripheral surface 125a that tapers toward the tip opening 123 and communicates with the tip opening 123, an inner side surface 125b that is continuous with the rear end side of the inner peripheral surface 125a, and a bottom surface 125c that is continuous with the rear end side of the inner side surface 125b.

[0042] The inner peripheral surface 125a is formed during the caulking process for forming the caulking portion 122, and the radius dimension centered on the central axis CL is constant (the same) at each circumferential position. Also, the width dimension of the inner peripheral surface 125a along the central axis CL is constant (the same) at each circumferential position centered on the central axis CL.

[0043] The inner surface 125b is a cylindrical surface centered on the central axis CL, and the radial dimension from the central axis CL is constant (the same) at each position in the circumferential direction. The inner surface 125b has a width dimension a along the axial direction that varies at each position in the circumferential direction. That is, as shown in Fig. 7, the width dimension a of the inner surface 125b is relatively small at the leftmost position on the paper surface compared to the central axis CL, and conversely, it is relatively large at the position overlapping the central axis CL on the paper surface. Also, when viewed in the cross-section of Fig. 8, the width dimension a of the inner surface 125b is relatively small at the position shifted to the right side of the paper surface from the central axis CL, and conversely, it is relatively large at the position shifted to the left side of the paper surface from the central axis CL. Thus, the inner surface 125b is divided into six parts by being divided into a range where the width dimension a is large and a range where it is small.

[0044] Here, when the relatively small width dimension a is designated as a1 and the relatively large width dimension a is designated as a2, as shown in Fig. 9, a range R1 where the width dimension a is a1 and a range R2 where the width dimension a is a2 are arranged alternately along the circumferential direction. As an example of the opening angle of the range R1, 75° can be cited with the central axis CL as the center. Also, as an example of the opening angle of the range R2, 45° can be cited with the central axis CL as the center. In Fig. 9, three ranges R1 and three ranges R2 are arranged alternately along the circumferential direction. In other words, with the central axis CL in between, the ranges R1 and R2 are arranged opposite to each other.

[0045] As shown in Fig. 9, when viewed along the central axis CL, the bottom surface 125c is largely divided into six ranges. When these six ranges are compared with each other, the outer diameter dimensions are the same, but the inner diameter dimensions are different between adjacent ones in the circumferential direction so that they alternately become larger and smaller along the circumferential direction. And due to this difference in the inner diameter dimension, the radial width dimension b is divided into two, a relatively small b1 and a relatively large b2. Therefore, when Fig. 9 is viewed clockwise with the central axis CL as the center, a range R1 where the width dimension b is b1 and a range R2 where the width dimension b is b2 are arranged alternately. In other words, with the central axis CL in between, a range R1 where the width dimension b is b1 and a range R2 where the width dimension b is b2 are arranged opposite to each other.

[0046] And the ranges R1 and R2 that are divided into six parts on the bottom surface 125c and the ranges R1 and R2 that are divided into six parts on the inner surface 125b described above are arranged with their circumferential positions synchronized. That is, as shown in FIG. 9, when viewed along the circumferential direction, the position of the range R1 where the width dimension a of the inner surface 125b is a1 and the position of the range R1 where the width dimension b of the bottom surface 125c is b1 completely coincide. Similarly, when viewed along the circumferential direction, the position of the range R2 where the width dimension a of the inner surface 125b is a2 and the position of the range R2 where the width dimension b of the bottom surface 125c is b2 completely coincide. As shown in FIG. 9, in the range R2 where the width dimension a of the inner surface 25b is a2 and the width dimension b of the bottom surface 25c is b2, since both the width dimension a and the width dimension b are large, an arc-shaped recess S having a relatively large capacity is formed in the range R2 sandwiched between the pair of ranges R1 and R1. This recess S forms a large-capacity ink storage portion having a wide width dimension in the radial direction and a deep depth dimension in the axial direction, as shown in FIG. 10, due to the combination of b2 with a wide width dimension b and a2 with a wide width dimension a. With this ink storage portion, when the outer peripheral surface of the rolling ball 10 is supported in the range R2, a sufficient amount of ink supply to this support portion can be ensured. As shown in FIG. 10, both circumferential ends of the recess S are partitioned by vertical walls 125d formed in the respective adjacent ranges R1 and R1. Further, the recesses S are arranged at 120° intervals around the central axis CL as shown in FIG. 9.

[0047] As shown in FIG. 7, the ball seat 126 is a concave curved surface on which the outer peripheral surface shape of the ball 10 is transferred by hammering, and is the portion where the ball 10 in the state before the start of writing seats in surface contact. Then, as shown in Fig. 9, the ball seat 126 has a width dimension c along the radial direction that varies at each position in the circumferential direction. Here, when the relatively large width dimension c is designated as c1 and the relatively small width dimension c is designated as c2, a range R1 where the width dimension c is c1 and a range R2 where the width dimension c is c2 are arranged alternately along the circumferential direction. That is, when Fig. 9 is viewed clockwise around the central axis CL, the range R1 where the width dimension c is c1 and the range R2 where the width dimension c is c2 are arranged alternately. From another perspective, the ranges R1 where the width dimension c is c1 are arranged at 120° intervals along the circumferential direction around the central axis CL. Also, the ranges R2 where the width dimension c is c2 are arranged at 120° intervals along the circumferential direction around the central axis CL. Thus, the ball seat 126 is composed of ranges R1 and R2 that are circumferentially divided into six parts.

[0048] Then, the ranges R1 and R2 that are divided into six parts in the ball seat 126 and the ranges R1 and R2 that are divided into six parts on the bottom surface 125c described above are arranged in circumferential synchronization. As a result, as shown in Fig. 9, in the range R1 where the width dimension a of the inner surface 125b is a1 and the width dimension b of the bottom surface 125c is b1, since both the width dimension a and the width dimension b are formed to be relatively small, accordingly, the width dimension c of the ball seat 126 becomes wider and a relatively large surface area is ensured. Therefore, in the range R1, a relatively large area for supporting the outer peripheral surface of the ball 10 can be ensured, so that the rolling ball 10 can be stably supported.

[0049] As shown in Fig. 7, the ink flow groove (channel) 127 is a flow path that guides the ink in the ink flow passage 128 into the ball holding chamber 124. Each ink flow groove 127 is formed from the ink flow passage 128 to the ball seat 126 in the ball holding chamber 124. Each ink flow groove 127 is a slit formed long in the axial direction, and is formed such that the groove width becomes wider toward the radially outer side. As shown in Fig. 9, a plurality of ink flow grooves 127 are arranged at equal angular intervals around the central axis CL. In the illustrated example, six ink flow grooves 127 are formed. Each ink flow groove 127 is disposed at the circumferential center position of the ball seat 26 within the same range in each of the ranges R1 and R2 that divide the ball seat 26 into six parts.

[0050] As shown in Fig. 7, each ink flow groove 127 has a groove length in the axial direction that is different from that of the other ink flow grooves 127 adjacent to it on both circumferential sides centered on the central axis CL. That is, in the range R2 of Fig. 9, since the width dimension c of the ball seat 126 is short, the length dimension of the ink flow groove 127 is accordingly shortened. Conversely, in the range R1, since the width dimension c of the ball seat 126 is long, the length dimension of the ink flow groove 127 is accordingly lengthened. All of the ink flow grooves 127 have their rear end sides communicating with the ink flow path 128, and their front end sides penetrate the bottom surface 125c and open. Among these six ink flow grooves 127, only the three ink flow grooves 127 formed with a longer length directly communicate with the concave portion S forming the ink storage portion. That is, the ink flow path 128 and the concave portion S are directly connected by these longer ink flow grooves 127.

[0051] Returning to Fig. 7, the ink flow path (capillary) 128 is a cylindrical space coaxial with the central axis CL, and six openings communicating with each of the ink flow grooves 127 are formed on the upper inner circumferential surface thereof. The ink flow path 128 supplies the ink in the rear hole 129 mainly into the ball holding chamber 124 through each ink flow groove 127. The rear hole 129 is a substantially cylindrical space coaxial with the central axis CL and has an inner diameter dimension larger than that of the ink flow path 128. The upper part of the rear hole 129 is reduced in diameter toward the tip direction, and has the same inner diameter dimension as the ink flow path 128 at its upper end position.

[0052] The operation and effect of the ballpoint pen tip having the configuration described above will be described. Also in the ballpoint pen tip of the present embodiment, the same operational effects as those of the ballpoint pen tip of the first embodiment can be obtained. That is, since the ink temporarily stored in the recess S in the range R2 can be supplied to the gap between the outer peripheral surface of the ball 10 and the inner peripheral surface 125a of the tip opening 123, it is possible to suppress blurring of the writing line due to sticking of the ball 10. Further, since the range R1 can stably support the outer peripheral surface of the ball 10 over a wide range, the rolling of the ball 10 can be made more stable and a good writing feel can be obtained. Therefore, it is possible to achieve both prevention of sticking of the ball 10 and improvement of the writing feel.

[0053] [Fourth Embodiment] In the above third embodiment, the case where each ink flow groove 127 is arranged at the circumferential center position of each of the ranges R1 and R2 is illustrated. However, the formation position of each ink flow groove 127 is not limited to this position only. As another arrangement example of each ink flow groove 127, it will be described below with reference to FIGS. 11 and 12. Since the present fourth embodiment corresponds to a modification of the above third embodiment, the description will be centered on the differences from the above third embodiment, and redundant descriptions of other configurations will be omitted assuming that they are the same as those of the above third embodiment.

[0054] Each ink flow groove 127 of the present embodiment is formed at the boundary position between the range (first region) R1 and the range (second region) R2. That is, as shown in FIG. 11, the first one of the six ink flow grooves 127 is arranged so as to overlap the boundary line between the ranges R2 and R1, which is in the upper right of the paper surface of the figure. Similarly, the second one of the six ink flow grooves 127 is arranged so as to overlap the boundary line between the ranges R1 and R2, which is at the right end of the paper surface of the figure. Hereinafter, in the same manner, the remaining four ink flow grooves 127 are each arranged so as to overlap the boundary line between the ranges R1 and R2.

[0055] All of the ink flow grooves 127 have the same length dimension. That is, as shown in FIG. 11, all the ink flow grooves 127 have the same radial dimension when viewed along the central axis CL, and also have the same dimension in the direction parallel to the central axis CL. And, as shown in FIG. 12, the rear end sides of all the ink flow grooves 127 are open so as to communicate with the ink flow path 128. Also, all of the inside of each ink flow groove 127 directly opens into the three recesses S, respectively. Therefore, also in the present embodiment, the ink in the ink flow path 128 can be supplied to the recess S without stagnation through each ink flow groove 127. In addition, in the present embodiment, since the ink is supplied from two ink flow grooves 127 to one recess S, the ink supply to the recess S can be performed more smoothly. Also, similar to the third embodiment, in the range R1, a wide support range of the ball 10 can be secured and stable support can be achieved, so that the rolling of the ball 10 can be stabilized and a good writing feeling can be obtained. As described above, also in the ballpoint pen tip of the present embodiment, it is possible to cause the anti-baking effect and the writing feeling improvement effect to be manifested so as to complement each other.

[0056] As described above, each embodiment of the present invention has been described, but appropriate modifications may be made as necessary. For example, in the first embodiment and the second embodiment, the recess S is provided at the boundary position between the circumferential groove 25 and the ball receiving seat 26, but the position of the recess S may be moved to the rear end side in the axial direction. Specifically, the recess S may be provided at the boundary position between the ball receiving seat 26 and the ink flow path 28, or at an intermediate position in the axial direction of the ball receiving seat 26. Similarly, in the case of the third embodiment and the fourth embodiment, the recess S may be provided at the boundary position between the ball receiving seat 126 and the ink flow path 128, or at an intermediate position in the axial direction of the ball receiving seat 126.

[0057] In the above (1) of the first embodiment, when defining the range (first region) R1 and the range (second region) R2, the width dimensions c (c1, c2) along the radial direction of the ball receiving seat 26 were used. Here, instead of the width dimension c, the length dimension along the axial direction of the ball receiving seat 26, or the circumference of the arc line forming the surface when the ball receiving seat 26 is cut by a cross section including the central axis CL may be used to define in the same manner. For example, in the case of the former, it may be defined as follows: "When the ball seat 26 is cut along a cross-section including the central axis line CL, there are a range (first region) R1 where the length dimension along the axial direction of the ball seat 26 is the first length dimension, and a range (second region) R2 that is adjacent to the range (first region) R1 and where the length dimension along the axial direction of the ball seat 26 is the second length dimension shorter than the first length dimension. The range (first region) R1 and the range (second region) R2 are each provided in two or more on the ball seat 26, arranged alternately in the circumferential direction around the central axis line CL, and the ranges (first regions) R1 adjacent to each other via the range (second region) R2 are connected by a recess S having a length dimension equal to the difference between the first length dimension and the second length dimension." In the case of the latter, it may be defined as follows: "When the ball seat 26 is cut along a cross-section including the central axis line CL, there are a range (first region) R1 where the circumferential length of the arc forming the surface of the ball seat 26 is the first circumferential length, and a range (second region) R2 that is adjacent to the range (first region) R1 and where the circumferential length along the surface of the ball seat 26 is the second circumferential length shorter than the first circumferential length. The range (first region) R1 and the range (second region) R2 are each provided in two or more on the ball seat 26, arranged alternately in the circumferential direction around the central axis line CL, and the ranges (first regions) R1 adjacent to each other via the range (second region) R2 are connected by a recess S having a dimension equal to the difference between the first circumferential length and the second circumferential length."

Explanation of Reference Signs

[0058] 10 Ball 20, 120 Chip Body 22, 122 Crimping Portion 23, 123 Tip Opening 24, 124 Ball Holding Chamber 26, 126 Ball Seat 28, 128 Ink Flow Path c Width Dimension Along the Radial Direction of the Central Axis Line c1 First Width Dimension c2 Second Width Dimension CL Central Axis Line R1 Range (First Region) R2 Range (Second Region) S recess

Claims

1. A ball, a chip body having a ball holding chamber for rotatably accommodating the ball, and an ink flow passage communicating with the ball holding chamber, are provided, wherein the ball holding chamber has a ball seat defining a part of the ball holding chamber, a tip opening that holds the ball between the ball seat and exposes a part of the ball to the outside, and has when the ball seat is viewed facing the direction along the central axis of the chip body, the ball seat has a first region having a first width dimension along the radial direction of the central axis in the circumferential direction centered on the central axis, and a second region adjacent to the first region and having a second width dimension shorter than the first width dimension along the radial direction centered on the central axis, the first region and the second region are each provided with two or more on the ball seat and are arranged alternately in the circumferential direction around the central axis, each of the first regions adjacent to each other via the second region is connected by a recess having a width dimension equal to the difference between the first width dimension and the second width dimension. A ball pen tip characterized by the above.

2. The depth of the recess is deeper than both the first region and the second region. The ball pen tip according to claim 1, characterized by the above.

3. An ink flow groove for communicating between the ink flow passage and the ball holding chamber is inside the second region, or at the boundary position between the first region and the second region, and communicates with the recess through the above. The ball pen tip according to claim 1 or 2, characterized by the above.

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