Ball-point pen tip

Abstract

To provide a ball-point pen tip capable of obtaining a writing line with inflection.SOLUTION: A ball-point pen tip includes: a ball 10; a ball holding chamber 24 for rotatably storing the ball 10; and a tip body 20 having an ink flow passage 28 communicating with the ball holding chamber 24. The ball holding chamber 24 includes: a ball receiving seat 26 that defines a part of the ball holding chamber 24; and a distal end opening 23 that exposes a part of the ball 10 to the outside while holding the ball 10 between the ball receiving seat 26 and the distal end opening. When the ball 10 seated on the ball receiving seat 26 is viewed in a cross section that is perpendicular to a central axis CL of the tip body 20 and that includes the distal end opening 23, a dimension of a gap g formed between an outer peripheral surface of the ball 10 and the distal end opening 23 periodically increases and decreases along a circumferential direction around the central axis CL of the tip body 20.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, as a 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 receiving 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, when 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, since the gap dimension between the outer peripheral surface of the ball and the tip opening during writing is substantially constant regardless of the direction in which the ball pen tip runs on the writing surface, the line width of the writing line written on the writing surface is also almost constant. Naturally, the written font also has a constant line width. However, when compared with, for example, a font written with a brush, there is inevitably a lack of cadence.

[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 obtain a wavy writing line.

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 chip body having a ball holding chamber that rotatably houses the ball and an ink flow passage communicating with the ball holding chamber, and is provided with the ball holding chamber has 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 seated on the ball seat is viewed in a cross-section perpendicular to the central axis of the chip body and including the tip opening, the gap dimension formed between the outer peripheral surface of the ball and the tip opening periodically increases and decreases along the circumferential direction centered on the central axis of the chip body.

[0008] According to the ballpoint pen tip described in (1) above, a gap distribution that periodically increases and decreases along the circumferential direction is provided in advance in the gap between the outer peripheral surface of the ball seated on the ball seat and the tip opening. Then, when writing, the ballpoint pen tip is run along the writing surface while pressing the ball against the writing surface. Then, the ink supplied into the ball holding chamber through the ink flow passage flows out from the chip body to the outside through the gap between the outer peripheral surface of the rolling ball and the tip opening, moves to the writing surface, and becomes a writing line. At this time, when writing by moving the ball pen tip so that the gap dimension is relatively larger and faces forward in the writing direction, the amount of ink coming out of the gap and moving onto the writing surface is relatively large, so the writing line becomes thick. On the other hand, when writing by moving the ball pen tip so that the gap dimension is relatively smaller and faces forward in the writing direction, the amount of ink coming out of the gap is relatively small, so the writing line becomes thin. Thus, just by changing the writing direction, it becomes possible to freely change the thickness of the writing line.

[0009] (2) The ball pen tip according to (1) above may be configured as follows: When viewed in the cross section, the caulking portion of the chip body that defines the tip opening has a constant wall thickness at each position in the circumferential direction, and a first outer peripheral surface whose radius from the central axis in the circumferential direction periodically increases and decreases in proportion to the increase and decrease of the gap. In the case of the ballpoint pen tip described in the above (2), the radius from the central axis to the first outer peripheral surface periodically increases and decreases along the circumferential direction, so that a dimensional distribution that periodically increases and decreases along the circumferential direction is imparted to the gap between the outer peripheral surface of the ball seated on the ball receiving seat and the tip opening. That is, at the position on the first outer peripheral surface where the radius from the central axis is the smallest, the position of the tip opening inside thereof through a certain wall thickness is closest to the central axis, so the gap formed between the tip opening and the outer peripheral surface of the ball is the narrowest. And starting from here, when looking at it as moving along the circumferential direction, in proportion to the fact that the radius of the first outer peripheral surface centered on the central axis of the chip body gradually expands, the gap dimension also gradually expands. Further moving along the circumferential direction, it reaches the position on the first outer peripheral surface where the radius from the central axis is the largest, and the position of the tip opening inside thereof through a certain wall thickness is also farthest from the central axis, so the gap formed between the tip opening and the outer peripheral surface of the ball is the widest. Taking this as the turning-back position and further looking at it as moving along the circumferential direction, in proportion to the fact that the radius of the first outer peripheral surface centered on the central axis gradually decreases, the gap dimension also gradually narrows. And finally, it returns to the starting position, and both the radius of the first outer peripheral surface and the gap dimension become the smallest. Note that the relationship between the increase and decrease of the gap dimension and the increase and decrease of the radius of the first outer peripheral surface is not limited to only a directly proportional relationship, and it may be slightly deviated from the directly proportional relationship, but it is most preferable to use the directly proportional relationship because the change of the writing line can be most effectively expressed.

[0010] (3) The ballpoint pen tip described in the above (1) may be configured as follows: When viewed in the cross section, the caulked portion of the chip body that defines the tip opening has a wall thickness that periodically increases and decreases in inverse proportion to the increase and decrease of the gap in the circumferential direction, and a second outer peripheral surface having the same radius from the central axis at each position in the circumferential direction. And it has these. In the case of the ball pen tip described in the above (3), the thickness of the caulked portion periodically increases and decreases along the circumferential direction, so that a dimensional distribution that periodically increases and decreases along the circumferential direction is imparted to the gap between the ball seated in the ball receiving seat and the tip opening. That is, at the position where the thickness of the caulked portion is the thickest, the position of the tip opening, which is the inner peripheral edge thereof, is closest to the central axis, so the gap formed between the tip opening and the outer peripheral surface of the ball is the narrowest. And starting from here, when looking at it as moving along the circumferential direction, in inverse proportion to the fact that the thickness gradually becomes thinner, the gap dimension gradually widens. Further moving along the circumferential direction, the position where the thickness is the thinnest is reached, and since the position of the tip opening, which is the inner peripheral edge thereof, is farthest from the central axis, the gap formed between the tip opening and the outer peripheral surface of the ball becomes the widest. Regarding this as the turning-back position and further looking at it as moving along the circumferential direction, in inverse proportion to the fact that the thickness gradually increases, the gap dimension gradually narrows. And finally, it returns to the starting position, where the thickness is the thickest and the gap is the narrowest. Incidentally, the relationship between the increase and decrease of the gap and the increase and decrease of the thickness is not limited to only a direct or inverse proportional relationship, and it may be slightly deviated from the direct or inverse proportional relationship, but it is most preferable that it is a direct or inverse proportional relationship because the change in the writing line can be most effectively expressed.

Advantages of the Invention

[0011] According to the ball pen tip according to the above aspect of the present invention, by changing the writing direction, the thickness of the writing line can be freely changed, and a writing line full of cadence can be obtained.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

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

[0014] As shown in Fig. 1, the ballpoint pen tip of this embodiment has a ball 10 and a tip body 20. The ball 10 is a metal sphere with an outer diameter of, for example, 0.7 mm. In the following figures after Fig. 1, in order to clearly show the internal structure of the tip body 20 and the position of the ball 10 within the tip body 20, the ball 10 may be shown by a two-dot chain line. Also, in the following description, the state of pressing the ball 10 against a writing surface such as a piece of paper for writing is referred to as the "writing state", and the state of not pressing the ball 10 against a writing surface such as a piece of paper for writing is sometimes referred to as the "state before starting writing".

[0015] The tip body 20 is a metal cylindrical part that tapers towards the tip direction, which is above the plane of the paper in Fig. 1. The tip body 20 has an outer peripheral surface 21 in a substantially frustum shape that is coaxial with the central axis CL. At the tip of the outer peripheral surface 21, a caulking part 22 is formed. The caulking part 22 is formed by caulking the tip of the tip body 20 after accommodating the ball 10, and its outer diameter is bent more angularly towards the radially inner side than other parts. The outer peripheral surface 21 and the outer peripheral surface 22a of the caulking part 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, within the tip body 20, in the direction from the tip towards the rear end, a tip opening 23, a ball holding chamber 24, an ink flow groove 27, an ink flow path 28, and a rear hole 29 are formed in this order and arranged in line. The tip opening 23 is a circular opening formed within the caulked portion 22. As shown in FIG. 1, its center line CL1 is slightly shifted toward the right side of the paper surface from the central axis CL of the chip body 20. On the other hand, in the state before starting writing shown in FIG. 1, the ball 10 is coaxial with the central axis CL within the ball holding chamber 24, and a part of it is arranged to protrude and be exposed outside the chip body 20. In the state before starting writing, an annular gap g is formed along the circumferential direction 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 within a virtual plane that includes the tip opening 23 and is perpendicular to the central axis CL.

[0017] When the caulked portion 22 having the above-described configuration is viewed in a cross section that includes the tip opening 23 and is perpendicular to the central axis CL, the radius from the central axis CL periodically increases and decreases along the circumferential direction. Regarding this, as shown in FIG. 1, the center line CL1 of the circle formed by the outer diameter of the caulked portion 22 is shifted with a shift amount s toward the right side of the paper surface with respect to the central axis CL. That is, as shown in FIG. 8(a) described later, when viewed in a cross section that includes the tip opening 23 and is perpendicular to the central axis CL, the point indicating the center line CL1 is arranged at a position shifted by the shift amount s directly beside the point indicating the central axis CL. Note that since FIG. 8(a) has the left-right relative position reversed with respect to FIG. 1, the shift direction of the center line CL1 is exactly reversed when compared with FIG. 1.

[0018] Here, as shown in Fig. 8(a), the radius R1 from the center line CL1 to the outer peripheral surface (first outer peripheral surface) 22a of the caulking portion 22 is the same at each position in the circumferential direction. On the other hand, the radius R2 from the central axis CL to the outer peripheral surface 22a of the caulking portion 22 periodically increases and decreases along the circumferential direction. That is, when the position a in Fig. 8(a) is taken as the starting position, at this position a, the outer peripheral surface 22a approaches the central axis CL by the amount of the shift s. And the wall thickness t1 of the caulking portion 22 is constant at each position in the circumferential direction. Also, since the central position of the ball 10 in the state before starting to write is on the central axis CL regardless of the shift amount s, when viewed in the cross section of the figure, the gap g between the outer peripheral surface of the ball 10 and the tip opening 23 is the narrowest.

[0019] Then, between starting from the position a and reaching the position b along the circumferential direction, the radius R2 seen from the central axis CL gradually increases, and proportionally, the gap g also gradually widens. When further advancing in the circumferential direction beyond the position b, the radius R2 further increases, and proportionally, the gap g also further widens. And at the position c, the radius R2 becomes the maximum and the gap g is also the widest. When further advancing in the circumferential direction with the position c as the turning point, conversely, the radius R2 gradually decreases, and proportionally, the gap g also gradually narrows. This tendency continues even beyond the position d, and when returning to the position a, the gap g becomes the narrowest again. Thus, when viewed along the circumferential direction, with the wall thickness t1 being constant, the gap g also periodically increases and decreases in proportion to the periodic increase and decrease of the radius R2.

[0020] Returning to the description of Fig. 1. The ball holding chamber 24 is a space that rotatably holds the ball 10 between it and the tip opening 23. In the ball holding chamber 24, a circumferential groove 25 arranged on the rear end side of the tip opening 23 and a ball receiving seat 26 arranged on the rear end side of the circumferential groove 25 are formed.

[0021] The circumferential groove 25 is an annular concave groove formed along the circumferential direction centered on the central axis CL between the edge 26a of the ball receiving seat 26 closest to the tip opening 23 and the tip opening 23. The circumferential groove 25 has an inner peripheral surface 25a at its tip portion communicating with the tip opening 23, which is formed to taper toward the tip opening 23. The inner peripheral surface 25a is formed during the caulking process that forms the caulking portion 22, and in synchronization with the tip opening 23, the radial dimension centered on the central axis CL along the circumferential direction periodically increases and decreases along the circumferential direction.

[0022] That is, as shown in FIG. 2, on the right side of the drawing plane, the gap g between the tip opening 23 and the outer peripheral surface of the ball 10 is the widest in the circumferential direction. In synchronization with this, the gap between the inner peripheral surface 25a and the ball 10 is also the widest in the circumferential direction. Starting from this position and advancing in the circumferential direction, the gap g formed in the tip opening 23 gradually narrows, and in synchronization with this, the gap between the inner peripheral surface 25a and the ball 10 also gradually narrows. Then, at the position on the left side of the drawing plane in FIG. 2, the gap g formed in the tip opening 23 becomes the narrowest, and in synchronization with this, the gap between the inner peripheral surface 25a and the ball 10 also becomes the narrowest. In the middle of this process, at the position viewed along the A-A arrow in FIG. 2, the gap g shown on the right side of the drawing plane in FIG. 3 is formed in the tip opening 23, and that gap g has a dimension approximately in the middle of the two gaps g on the left and right sides of the drawing plane in FIG. 2. The same applies to the inner peripheral surface 25a. As shown on the right side of the drawing plane in FIG. 3, it has a dimension approximately in the middle of the gaps formed in each of the two inner peripheral surfaces 25a on the left and right sides of the drawing plane in FIG. 2.

[0023] When further advancing in the circumferential direction with the left side of the drawing plane in FIG. 2 as the turning point, the gap g formed at the tip opening 23 gradually widens, and in synchronization with this, the gap between the inner peripheral surface 25a and the ball 10 also gradually widens. Then, it returns to the starting position on the right side of the drawing plane in FIG. 2, the gap g formed in the tip opening 23 becomes the widest again, and in synchronization with this, the gap between the inner peripheral surface 25a and the ball 10 also becomes the widest again. In the middle of this process, at the position viewed along the A-A arrow in FIG. 2, the gap g shown on the left side of the drawing plane in FIG. 3 is formed in the tip opening 23, and that gap g has a dimension approximately in the middle of the two gaps g on the left and right sides of the drawing plane in FIG. 2. The same applies to the inner peripheral surface 25a. As shown on the left side of the drawing plane in FIG. 3, it has a dimension approximately in the middle of the gaps formed in each of the two inner peripheral surfaces 25a on the left and right sides of the drawing plane in FIG. 2.

[0024] Also, as shown in FIGS. 2 and 3, when the width dimension along the central axis CL of the inner peripheral surface 25a is w, the width dimension w also periodically increases and decreases along the circumferential direction. That is, on the right side of the paper surface of FIG. 2, the width dimension w is the narrowest in the circumferential direction, and conversely, on the left side of the paper surface of FIG. 2, the width dimension w is the widest in the circumferential direction. On the other hand, at the position of the A-A arrow view in FIG. 2, as shown in FIG. 3, the width dimensions w at the left and right positions of the paper surface are each approximately in the middle between the maximum value and the minimum value of the width dimension w shown in FIG. 2. As shown in FIG. 2, at the position on the left end of the paper surface where the width dimension w of the inner peripheral surface 25a is the widest, the position where it is caulked and bent is closer to the rear end side than on the right side of the paper surface. Therefore, the range of the inner peripheral surface 25a visible on the left side of the paper surface is larger than the range of the inner peripheral surface 25a visible on the right side of the paper surface. As a result, the gap g between the tip opening 23 and the outer peripheral surface of the ball 10 becomes smaller. On the other hand, at the position on the right end of the paper surface where the width dimension w of the inner peripheral surface 25a is the narrowest, the position where it is caulked and bent is farther from the rear end side than on the left side of the paper surface. Therefore, the range of the inner peripheral surface 25a visible on the right side of the paper surface is smaller than the range of the inner peripheral surface 25a visible on the left side of the paper surface, and the gap g between the tip opening 23 and the outer peripheral surface of the ball becomes larger. Therefore, the gap g and the width dimension w are in a directly proportional relationship, and each increases and decreases along the circumferential direction.

[0025] As shown in FIG. 4, the ink flow groove (channel) 27 is a flow path that guides the ink in the ink flow path 28 into the ball holding chamber 24. A plurality of ink flow grooves 27 are arranged at equal angular intervals around the central axis CL. In the illustrated example, the case where four ink flow grooves 27 are arranged at 90° intervals 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 path 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. The groove lengths of each ink flow groove 27 in the axial direction are all the same.

[0026] As shown in FIG. 1, the ink flow path (capillary) 28 is a cylindrical space coaxial with the central axis CL, and four openings communicating with each ink flow groove 27 are formed on the upper inner peripheral surface thereof. The ink flow path 28 supplies the ink in the rear hole 29 into the ball holding chamber 24 mainly 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 has the same inner diameter dimension as the ink flow path 28 at its upper end position.

[0027] The operation and effect of the ballpoint pen tip having the configuration described above will be described. First, with the ball 10 pressed against a writing surface such as paper (not shown), the ballpoint pen tip is run so that the C direction in FIG. 1 becomes the writing direction. Then, since the gap g in front of the writing direction is adjusted to be narrow in advance, the amount of ink flowing out through this gap g is restricted to be small, and the writing line becomes thin. Conversely, the ballpoint pen tip is run so that the D direction in FIG. 1 becomes the writing direction. Then, since the gap g in front of the writing direction is adjusted to be wide in advance, the amount of ink flowing out through this gap g becomes large, and the writing line becomes thick. Furthermore, when the ballpoint pen tip is run so that the direction perpendicular to the paper surface in FIG. 1, that is, the left - right direction of the paper surface in FIG. 3, becomes the writing direction, since the gap g in front of the writing direction is adjusted to have a medium - sized dimension exactly, the amount of ink flowing out through this gap g also becomes medium - sized, and the writing line becomes a medium - thick line. Furthermore, by changing the writing direction, a writing line having a line width between a thin line and a medium - thick line or a writing line having a line width between a thick line and a medium - thick line can be drawn. Thus, according to the ballpoint pen tip of the present embodiment, by simply changing the writing direction, the line width of the writing line can be continuously controlled from a thin line to a thick line. Therefore, compared with the conventional ballpoint pen tip having a constant line width, it is possible to draw a writing line with rich variations in line width and a cadenced feeling.

[0028] As described above, the line width of the writing line is controlled by controlling the gap g. The simulation results of specific numerical examples of the gap g are shown in FIG. 5. FIGS. 5(a) to 5(c) are longitudinal sectional views showing the writing state of the ballpoint pen tip. Here, (a) shows the case of writing while running slightly inclined in the direction of arrow C in FIG. 1 (the case of writing in the direction from the wider gap g to the narrower gap g). Further, FIG. 5(b) shows the case of writing while running slightly inclined in the direction perpendicular to the paper surface in FIG. 1 (the case of writing in the direction from the medium-width gap g to the medium-width gap g). And FIG. 5(c) shows the case of writing while running slightly inclined in the direction of arrow D in FIG. 1 (the case of writing in the direction from the narrower gap g to the wider gap g). The angles with respect to the writing surface P in FIGS. 5(a) to 5(c) are all set to 70°.

[0029] In the case of FIG. 5(a), the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 was 0.018 mm. In the case of FIG. 5(b), the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 was 0.022 mm. Therefore, the gap g increased by 0.004 mm compared to FIG. 5(a). In the case of FIG. 5(c), the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 was 0.027 mm. Therefore, the gap g increased by 0.009 mm compared to FIG. 5(a). From the above, a thin line can be written in the writing direction of FIG. 5(a) where the gap g is the narrowest, a medium-thick line can be written in the writing direction of FIG. 5(b) where the gap g is medium, and a thick line can be written in FIG. 5(c) where the gap g is the widest.

[0030] Next, the caulking method for forming the gap g will be described below with reference to FIGS. 6 to 8. FIG. 6 is a longitudinal sectional view for explaining caulking in the manufacturing process of the ballpoint pen tip shown in FIG. 1 and the like, and the processing proceeds in the order of (a), (b), (c), and (d). FIG. 7 is a longitudinal sectional view for explaining caulking in the manufacturing process of the ballpoint pen tip according to a modified example, and the processing proceeds in the order of (a), (b), (c), and (d). Then, FIG. 8 is a sectional view taken along a section orthogonal to the central axis CL and including the tip opening 23 of the chip body 20. (a) shows the shape when the caulking of FIG. 6 is performed, and (b) shows the shape when the caulking of FIG. 7 is performed.

[0031] As shown in FIG. 6(a), the tip (upper end) of the chip body 20 before caulking has the same wall thickness at each position along the circumferential direction. The ball 10 is disposed in the ball holding chamber 24, and the ball receiving seat 26 has also been processed by transferring the shape of the ball 10. As shown in FIG. 6(b), the caulking tool T is disposed above the chip body 20. At this time, the caulking tool T is disposed such that the center line CLT of the caulking tool T is shifted in a direction parallel to the central axis CL of the chip body 20 and perpendicular to the central axis CL (leftward in the paper plane). The shift amount sT of the center line CLT along the horizontal direction with respect to the central axis CL can be exemplified by 5 μm. A pair of caulking surfaces ck for caulking the tip portion of the chip body 20 are disposed at the lower portion of the caulking tool T.

[0032] As shown in FIG. 6(c), the caulking tool T is lowered toward the chip body 20, and caulking is performed along the circumferential direction while pressing each caulking surface ck against the tip of the chip body 20. At this time, as described above, since caulking is performed with the caulking tool T slightly shifted with respect to the tip of the chip body 20, when comparing the caulking amounts on the left and right sides of the paper surface in FIG. 6(c), the caulking amount of the portion on the right side of the paper surface is larger than that of the portion on the left side of the paper surface. As a result, as shown in FIG. 6(d), on the left side of the paper surface, since the caulking amount is relatively small, the inclination of the caulking portion 22 at this position is also smaller, and the gap g becomes larger. On the other hand, on the right side of the paper surface, since the caulking amount is relatively large, the inclination of the caulking portion 22 at this position is also larger, and the gap g becomes smaller. As described above, by preparing the chip body 20 having a tip with a constant wall thickness in the circumferential direction and performing caulking after slightly shifting the caulking tool T from the coaxial state, it is possible to form the caulking portion 22 that periodically increases and decreases along the circumferential direction.

[0033] The caulking portion 22 and the gap g after caulking are shown in FIG. 8(a). As shown in the figure, at the position a along the circumferential direction, since the caulking by the caulking tool T is applied more strongly, the gap g is narrowed. On the other hand, at the position c along the circumferential direction, since the caulking by the caulking tool T is applied more weakly, the gap g is widened. And at the positions b and d along the circumferential direction, since the caulking by the caulking tool T is applied moderately, the dimension of the gap g is also moderate. Thus, the gap g periodically increases and decreases along the circumferential direction. Here, as described above, the center line CL1 of the outer shape of the caulking portion 22 is shifted with a shift amount s with respect to the central axis CL of the chip body 20. Since this shift amount s is approximately equal to the shift amount sT when the caulking tool T is arranged, 5 μm can be exemplified as its specific numerical value.

[0034] Subsequently, as a modification of the above embodiment, FIGS. 7 and 8(b) will be described. In this modified example, as shown in Fig. 7(a), a thickness that periodically increases and decreases along the circumferential direction is pre-formed at the tip (upper end) of the chip body 20 before caulking. Therefore, the thickness is the thickest on the right side of the paper in Fig. 7(a) and the thinnest on the left side of the paper. Hereinafter, the difference dimension between the maximum thickness and the minimum thickness of this thickness is defined as td. Also, in order to distinguish it from the outer peripheral surface (first outer peripheral surface) 22a in Fig. 8(a), a new reference numeral 22a1 is given to the outer peripheral surface of the caulking portion 22 for explanation. The ball 10 is arranged in the ball holding chamber 24 of the chip body 20, and the ball seat 26 is also processed by transferring the shape of the ball 10. As shown in Fig. 7(b), the caulking tool T is arranged above the chip body 20. At this time, the caulking tool T is arranged so that the center line CLT of the caulking tool T is coaxial with the central axis CL of the chip body 20. A pair of caulking surfaces ck for caulking the tip of the chip body 20 are arranged at the lower part of the caulking tool T. That is, the caulking tool T used in this modified example is exactly the same as the one shown in Fig. 6, and only its arrangement is different.

[0035] As shown in Fig. 7(c), the caulking tool T is lowered toward the chip body 20, and caulking is performed along the circumferential direction while pressing each caulking surface ck against the tip of the chip body 20. At this time, as described above, since caulking is performed with the caulking tool T coaxially arranged with respect to the tip of the chip body 20, when the caulking amounts are compared in the left-right direction of the paper in Fig. 7(c), the caulking amounts are equal on the left and right. That is, the tilting angles of the outer peripheral surface (second outer peripheral surface) 22a1 of the caulking portion 22 are equal on the left and right. However, as described above, since a thickness that periodically increases and decreases along the circumferential direction is pre-formed at the tip of the chip body 20 before caulking, when the inner peripheral surface 25a after caulking is compared on the left and right of the paper, on the right side of the paper, it is closer to the outer peripheral surface of the ball 10 by the difference dimension td, and on the left side of the paper, it is farther from the outer peripheral surface of the ball 10 by the difference dimension td. As a result, as shown in Fig. 7(d), the gap g becomes larger by the difference dimension td on the left side of the paper and smaller by the difference dimension td on the right side of the paper. As described above, by preparing the chip body 20 having a tip whose wall thickness periodically increases and decreases along the circumferential direction, and performing caulking processing on the caulking tool T in a coaxial state, it is possible to form a gap g that periodically increases and decreases along the circumferential direction.

[0036] The caulked portion 22 and the gap g formed in this modified example are shown in Fig. 8(b). As shown in the figure, at the position a1 along the circumferential direction, since the wall thickness of the tip of the chip body 20 is thick, even if the caulking amount by the caulking tool T is the same in the circumferential direction, the tip opening 23 approaches the outer peripheral surface of the ball 10, so the gap g becomes narrow. On the other hand, at the position c1 along the circumferential direction, since the wall thickness of the tip of the chip body 20 is thin, even if the caulking amount by the caulking tool T is the same in the circumferential direction, the tip opening 23 moves away from the outer peripheral surface of the ball 10, so the gap g becomes wide. And at the positions b1 and d1 along the circumferential direction, since the wall thickness of the tip of the chip body 20 is medium, the dimension of the gap g is also medium. In this way, the gap g periodically increases and decreases along the circumferential direction.

[0037] As shown in Fig. 8(b), the outer peripheral surface 22a1 of the caulked portion 22 forms a circle coaxial with the central axis CL of the chip body 20. On the other hand, the tip opening 23 has a circular shape with a center line CL2 eccentric to the left side of the drawing and a radius R3 because a wall thickness distribution that periodically increases and decreases along the circumferential direction is imparted to the portion that becomes the caulked portion before caulking processing. Here, the radius R3 from the center line CL2 to the tip opening 23 is the same at each position in the circumferential direction. On the other hand, the radius R3 from the central axis CL to the tip opening 23 periodically increases and decreases along the circumferential direction. That is, when the position a1 in Fig. 8(b) is taken as the starting position, at this position a1, the tip opening 23 approaches the central axis CL by the differential dimension td. And since the center position of the ball 10 in the state before starting writing is on the central axis CL regardless of the differential dimension td, when viewed in the cross-section of the figure, the gap g between the outer peripheral surface of the ball 10 and the tip opening 23 is the narrowest.

[0038] Then, between starting from position a1 and reaching position b1 along the circumferential direction, the radius R4 as seen from the central axis CL gradually increases, and proportionally, the gap g also gradually widens. When further advancing in the circumferential direction beyond position b1, the radius R4 further increases, and proportionally, the gap g further widens. And at position c1, the radius R4 becomes maximum and the gap g becomes widest. When further advancing in the circumferential direction with position c1 as the turning point, conversely, the radius R4 gradually decreases, and proportionally, the gap g gradually narrows. This tendency continues even beyond position d1, and when returning to position a1, the gap g becomes narrowest again. Thus, when viewed along the circumferential direction, the gap g periodically increases and decreases in proportion to the periodic increase and decrease of the radius R4. Here, the center line CL2 of the tip opening 23 is shifted with respect to the central axis CL of the chip body 20. This shift amount is approximately equal to the dimension difference td previously given to the tip of the chip body 20 in FIG. 7(a), and as a specific numerical value, 5 μm can be exemplified.

[0039] The gist of each of the embodiments described above is summarized below. (1) As illustrated in FIGS. 1 to 3, a ballpoint pen tip according to one aspect of the present invention includes a ball 10, a chip body 20 having a ball holding chamber 24 for rotatably accommodating the ball 10 and an ink flow passage 28 communicating with the ball holding chamber 24, and is provided with the ball holding chamber 24 having a ball seat 26 defining a part of the ball holding chamber 24, a tip opening 23 that holds the ball 10 between the ball seat 26 and exposes a part of the ball 10 to the outside, and having When the ball 10 seated on the ball seat 26 is viewed in a cross-section perpendicular to the central axis CL of the chip body 20 and including the tip opening 23, the dimension of the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 periodically increases and decreases along the circumferential direction centered on the central axis CL of the chip body 20. According to the ballpoint pen tip described in the above (1), since the thickness of the writing line can be freely changed by changing the writing direction, it is possible to obtain a writing line full of cadence.

[0040] (2) As illustrated in Fig. 8(a), the ballpoint pen tip described in the above (1) may be configured as follows: When viewed in the cross-section, the caulking portion 22 of the chip body 20 that defines the tip opening 23 has a constant wall thickness t1 at each position in the circumferential direction, and an outer peripheral surface (first outer peripheral surface) 22a whose radius from the central axis CL in the circumferential direction periodically increases and decreases in proportion to the increase and decrease of the gap g. In the case of the ballpoint pen tip described in the above (2), while keeping the wall thickness t1 of the caulking portion 22 constant in the circumferential direction, the caulking portion 22 is eccentrically arranged, so that the gap g is increased and decreased along the circumferential direction. Thereby, the gap g can be appropriately increased and decreased according to the writing direction.

[0041] (3) As illustrated in Fig. 8(b), the ballpoint pen tip described in the above (1) may be configured as follows: When viewed in the cross-section, the caulking portion 22 of the chip body 20 that defines the tip opening 23 has a wall thickness t2 that periodically increases and decreases in inverse proportion to the increase and decrease of the gap g, and an outer peripheral surface (second outer peripheral surface) 22a1 whose radius from the central axis CL in the circumferential direction is the same at each position in the circumferential direction. It has. In the case of the ballpoint pen tip described in the above (3), the tip opening 23 is eccentrically arranged by periodically increasing and decreasing the wall thickness t2 of the caulking portion 22 along the circumferential direction. Thereby, the gap g can be appropriately increased and decreased according to the writing direction.

[0042] Note that, as specific numerical values of the shift amount s and the differential dimension method td described above, 5 μm was exemplified in the above embodiments and modified examples, but it is not limited thereto. As the shift amount s (or differential dimension method td) required to realize a wavy writing line, it is preferably appropriately selected from within the range of 3 μm to 20 μm. If it is below the lower limit value of this range, the undulation of the writing line becomes poor. Conversely, if it exceeds the upper limit value of this range, depending on the writing direction, the gap g becomes excessively small, the ink supply cannot keep up with the writing, and there is a risk of streaks in the handwriting. Therefore, it is preferable that the shift amount s and the differential dimension method td are within the above range.

[0043] Note that the configurations of the above (2) and the above (3) may be partially modified and combined. Specifically, referring to FIG. 8(a) for explanation, in this figure, the wall thickness t1 is constant in the circumferential direction, but this may be changed so that it is not constant, the wall thickness t1 is the thickest at position a, the wall thickness t1 is the thinnest at position c, and the wall thickness t1 at positions b and c is intermediate between the wall thickness t1 at position a and the wall thickness t1 at position b. That is, in FIG. 8(a), only the position of the tip opening 23 may be slightly moved toward the left side of the paper surface. In this case, the increase and decrease of the gap g along the circumferential direction become more prominent, and a more undulating writing line can be obtained. Alternatively, referring to FIG. 8(b) for explanation, in this figure, the radius from the central axis CL to the outer peripheral surface 22a1 is constant at each position in the circumferential direction, but this may be changed so that it is not constant, the radius is the largest at position a1, the radius is the smallest at position c1, and the radius at positions b1 and c1 is intermediate between the radius at position a1 and the radius at position b1. That is, in FIG. 8(b), while maintaining the circumferential distribution of the wall thickness t2, the position of the caulking portion 22 may be slightly moved toward the left side of the paper surface. Also in this case, the increase and decrease of the gap g along the circumferential direction become more prominent, and a more undulating writing line can be obtained.

Explanation of Signs

[0044] 10 Ball 20 Chip Body 22 Caulking Portion 22a Outer peripheral surface (first outer peripheral surface) 22a1 Outer peripheral surface (second outer peripheral surface) 23 Tip opening 24 Ball holding chamber 26 Ball receiving seat 28 Ink flow passage CL Central axis g Gap t1 Wall thickness

Claims

1. A ball, a ball holding chamber that rotatably houses the ball, and a chip body having an ink flow passage communicating with the ball holding chamber, are provided, wherein the ball holding chamber has 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 when the ball seated on the ball seat is viewed in a cross section perpendicular to the central axis of the chip body and including the tip opening, the dimension of the gap formed between the outer peripheral surface of the ball and the tip opening periodically increases and decreases along the circumferential direction centered on the central axis of the chip body. The ballpoint pen tip is characterized by this.

2. When viewed in the cross section, the caulked portion of the chip body that defines the tip opening has a constant wall thickness at each position in the circumferential direction, and a first outer peripheral surface whose radius from the central axis in the circumferential direction periodically increases and decreases in proportion to the increase and decrease of the gap. It has The ballpoint pen tip according to claim 1, characterized by this.

3. When viewed in the cross section, the caulked portion of the chip body that defines the tip opening has a wall thickness that periodically increases and decreases in inverse proportion to the increase and decrease of the gap in the circumferential direction, and a second outer peripheral surface whose radius from the central axis is the same at each position in the circumferential direction. It has The ballpoint pen tip according to claim 1, characterized by this.

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