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; 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; and a circumferential groove 25 that is formed along a circumferential direction around a central axis CL of the tip body 20 between an edge 26a closest to the distal end opening 23 of the ball receiving seat 26 and the distal end opening 23. A groove-width w1 of the circumferential groove 25 periodically increases and decreases along the circumferential direction.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 seats 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, 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 is moved on the writing surface, the line width of the writing line written on the writing surface is also substantially 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 enables writing with intonation.

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) The ballpoint pen tip according to one 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 path 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, a tip opening that holds the ball between the ball seat and exposes a part of the ball to the outside, a circumferential groove formed along the circumferential direction centered on the central axis of the tip body between the edge of the ball seat closest to the tip opening and the tip opening, and has the groove width of the circumferential groove periodically increases and decreases along the circumferential direction.

[0008] According to the ballpoint pen tip described in (1) above, during 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 path flows out of the tip body to the outside through the gap between the outer peripheral surface of the rolling ball and the tip opening, and moves to the writing surface. When writing, the ball is supported in a state slightly retracted with respect to the writing direction by the rear part entering the circumferential groove when viewed with the writing direction as the front. In that state, the ink is transferred to the writing surface from the gap between the front side of the ball and the tip opening when viewed with the writing direction as the front. When the writing direction, that is, the advancing direction of the ballpoint pen tip, is changed, the contact position of the ball in the circumferential direction on the circumferential groove also changes. Here, since the groove width of the circumferential groove periodically increases and decreases along the circumferential direction, the amount of backward movement of the ball with respect to the writing direction also increases and decreases depending on the contact position of the ball. That is, at the contact position where the groove width is wide and the ball enters deeper into the circumferential groove, the amount of backward movement of the ball becomes large. Therefore, the gap between the front side and the tip opening when looking at the writing direction as the front becomes wider, and the amount of ink passing through here increases, so the writing line also becomes thicker. Conversely, at the contact position where the groove width is narrow and the ball enters shallower into the circumferential groove, the amount of backward movement of the ball becomes small. Then, the gap between the front side along the writing direction of the ball and the tip opening also becomes narrow, so the amount of ink passing through here decreases, and the writing line also becomes thinner. Therefore, it is possible to freely change the thickness of the writing line only by changing the writing direction.

[0009] (2) The ballpoint pen tip described in (1) above may be configured as follows: When viewing the ball seat along the central axis in a front view, the seat width along the cross-section including the central axis periodically increases and decreases along the circumferential direction so as to be inversely proportional to the increase and decrease of the groove width.

[0010] In the case of the ballpoint pen tip described in (2) above, conversely, the seat width is the widest at the position where the groove width of the circumferential groove is the narrowest. And starting from here and looking at it as moving along the circumferential direction, the seat width gradually narrows in inverse proportion to the fact that the groove width of the circumferential groove gradually widens. Further moving along the circumferential direction, the groove width of the circumferential groove becomes the widest, and the seat width at the same position conversely becomes the narrowest. Taking this as the turning-back position and further looking at it as moving along the circumferential direction, the seat width gradually widens in inverse proportion to the fact that the groove width of the circumferential groove gradually narrows. And finally, it returns to the starting position, where the groove width of the circumferential groove is the narrowest and the seat width is the widest. In this way, by increasing or decreasing the seat width along the circumferential direction, the groove width can be increased or decreased along the circumferential direction in inverse proportion to this. Therefore, the amount of retraction of the ball during writing at each position in the circumferential direction of the circumferential groove can be appropriately adjusted, so that the gap between the front side along the writing direction of the ball and the tip opening can also be appropriately increased or decreased according to the writing direction. Note that the relationship between the increase and decrease of the seat width and the increase and decrease of the groove width is not limited to only the direct and inverse proportional relationships as described above, and it may be slightly deviated from the direct and inverse proportional relationships. However, it is most preferable to use the direct and inverse proportional relationships because the change of the writing line can be most effectively expressed.

[0011] (3) The ballpoint pen tip described in the above (1) or (2) may be configured as follows: In a state where the ball is seated in surface contact with the ball receiving seat, The gap dimension between the outer peripheral surface of the ball and the tip opening periodically increases and decreases along the circumferential direction so as to be inversely proportional to the increase and decrease of the groove width. In the case of the ballpoint pen tip described in the above (3), at the time of non-writing when the ball is seated in surface contact with the ball receiving seat, the gap dimension is the widest at the position where the groove width of the circumferential groove is the narrowest. And starting from here and looking at it as moving along the circumferential direction, in inverse proportion to the gradual widening of the groove width of the circumferential groove, the gap dimension gradually narrows. Further moving along the circumferential direction, the groove width of the circumferential groove becomes the widest, and the gap dimension at the same position becomes the narrowest instead. Taking this as the turning-back position and further looking at it as moving along the circumferential direction, in inverse proportion to the gradual narrowing of the groove width of the circumferential groove, the gap dimension gradually widens. And finally, it returns to the starting position, while the groove width of the circumferential groove becomes the narrowest and the gap dimension becomes the widest. In this way, in the case of this configuration, at the time of the state before the start of writing, the gap between the outer peripheral surface of the ball and the tip opening is adjusted in advance to increase and decrease in the circumferential direction. Here, for example, when writing such that the groove width is widest during non-writing and narrowest on the rear side in the writing direction, on the front side in the writing direction, since the gap dimension is adjusted wider in advance, this widening is added to the widening of the gap dimension accompanying the backward movement amount of the ball during writing. As a result, the gap on the front side in the writing direction becomes wider, and since the amount of ink passing through this gap further increases, a thicker writing line can be drawn. Conversely, when writing such that the groove width is narrowest on the front side in the writing direction and widest on the rear side in the writing direction, on the front side of the ball, since the gap dimension is adjusted narrower in advance, due to this narrowing, the gap dimension on the front side in the writing direction is suppressed to be smaller. As a result, since the amount of ink passing through this gap becomes less, a thinner writing line can be drawn. Therefore, it is possible to more strongly emphasize the increase and decrease in the line width of the writing line depending on the writing direction. Note that the relationship between the increase and decrease in the gap dimension and the increase and decrease in the groove width is not limited to only the directly proportional relationship as described above, and it may be slightly deviated from the direct proportionality, but it is most preferable to use the direct proportionality as the change in the writing line can be most effectively exhibited.

Advantages of the Invention

[0012] 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, so it is possible to obtain a writing line full of intonation.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0014] [First Embodiment] Hereinafter, with reference to FIGS. 1 to 7, a ballpoint pen tip according to the first embodiment of the present invention will be described. In the following description, the central axis CL of the ballpoint 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 ballpoint pen tip is referred to as the "tip direction", the direction along the central axis CL toward the rear end side of the ballpoint pen tip is referred to as the "rear end direction", and the direction including both the "tip direction" and the "rear end direction" is referred to as the "axial direction". Further, in a cross-section perpendicular to the central axis CL, the direction away from the central axis CL is referred to as the "radial outer side", the direction approaching the central axis CL in a cross-section perpendicular to the central axis CL is referred to as the "radial inner side", and the circumferential direction around the central axis CL is referred to as the "circumferential direction".

[0015] As shown in FIG. 1, the ballpoint pen tip of the present 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 referred to as 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 referred to as the "state before starting writing".

[0016] The tip body 20 is a metal cylindrical component that tapers toward the tip direction, which is above the paper surface of FIG. 1. The chip body 20 has a frustum-shaped outer peripheral surface 21 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 radially inward with a further angle compared to other portions. Both the outer peripheral surface 21 and the caulking portion 22 have a circular outer shape in a cross-section perpendicular to the central axis CL at each position on the central axis CL. In addition, as can be seen by comparing FIGS. 1 and 2, both the outer peripheral surface 21 and the caulking portion 22 have the same longitudinal cross-sectional shape including the central axis CL at any longitudinal cross-sectional position in the circumferential direction.

[0017] As shown in FIG. 1, inside the chip body 20, in the rear end direction, 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 side by side. The tip opening 23 is a circular opening formed inside the caulking portion 22, which is coaxial with the central axis CL and perpendicular to the central axis CL. The radius from the central axis CL of the tip opening 23 is the same at any position in the circumferential direction. Also, in the state before starting writing shown in FIGS. 1 and 2, 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 and is exposed outside the chip body 20. Therefore, in the state before starting writing, an annular gap g with a substantially constant width is formed at each position in 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 in a virtual plane perpendicular to the central axis CL and including the tip opening 23.

[0018] As shown in FIGS. 1 and 2, the ball holding chamber 24 is a space that rotatably holds the ball 10 between it and the tip opening 23. Inside 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.

[0019] The circumferential groove 25 is an annular concave groove formed around the central axis CL between the tip opening 23 and the ball receiving seat 26. The circumferential groove 25 is a groove formed along the circumferential direction around the central axis CL between the edge 26a of the ball receiving seat 26 that is closest to the tip opening 23 and the tip opening 23. Here, as shown in FIG. 1, since the edge 26a is inclined with respect to the plane perpendicular to the central axis CL, the groove width w1 formed between the edge 26a and the tip opening 23 periodically increases and decreases along the circumferential direction. That is, as shown in FIG. 3, at the position on the right end of the paper surface, the groove width w1 of the circumferential groove 25 is the widest, and as it moves along the circumferential direction from that position toward the left side of the paper surface, the groove width w1 gradually narrows, and at the position on the left end of the paper surface, the groove width w1 is the narrowest. Although not shown in the figure, if we continue to advance counterclockwise in the circumferential direction with the position on the left end of the paper surface as the turning point, the groove width w1 gradually widens, and when it reaches the position on the right end of the paper surface shown in FIG. 3, the groove width w1 becomes the widest again. In this way, the groove width w1 of the circumferential groove 25 increases and decreases while making one full turn around the central axis CL. Therefore, the groove width w1 periodically increases and decreases along the circumferential direction.

[0020] Returning to FIGS. 1 and 2 for further explanation, the tip portion of the circumferential groove 25 that communicates with the tip opening 23 has an inner peripheral surface 25a that tapers toward the tip opening 23. The inner peripheral surface 25a is formed during the caulking process that forms the caulking portion 22, and like the outer peripheral surface of the caulking portion 22, the axial width dimension is constant at each position in the circumferential direction. Subsequently, between the rear end edge of the inner peripheral surface 25a and the edge 26a of the ball receiving seat 26, an inner peripheral surface 25b is formed whose axial width dimension increases and decreases along the circumferential direction. The inner peripheral surface 25b has a bottom surface 25b1 and a side surface 25b2. Here, since the bottom surface 25b1 is inclined with respect to the plane perpendicular to the central axis CL, the axial width dimension of the side surface 25b2 increases and decreases along the circumferential direction in accordance with this inclination. As a result, the groove width w1 of the circumferential groove 25 increases and decreases along the circumferential direction.

[0021] The inclination of the bottom surface 25b1 described above is realized by periodically increasing and decreasing the seat width w2 of the ball receiving seat 26 shown in FIG. 4 in the circumferential direction. That is, the seat width w2 of the ball receiving seat 26 shown in FIG. 4 becomes narrower toward the right side of the paper surface, so that the position of the edge 26a becomes lower as shown in FIG. 3. Conversely, the seat width w2 of the ball receiving seat 26 shown in FIG. 4 becomes wider toward the left side of the paper surface, so that the position of the edge 26a becomes higher as shown in FIG. 3. By increasing and decreasing the seat width w2 of the ball receiving seat 26 along the circumferential direction in this way, the height position of the edge 26a is changed, and thereby the groove width w1 is increased and decreased along the circumferential direction.

[0022] As shown in FIG. 1, when the circumferential groove 25 is viewed in a cross section including the central axis CL, two ridge lines are formed between the inner peripheral surface 25a and the side surface 25b2 and between the side surface 25b2 and the bottom surface 25b1 between the tip opening 23 and the edge 26a. The portion between these two ridge lines is at the position farthest from the radial outside from the entrance of the circumferential groove 25, so it becomes the bottom surface of the circumferential groove 25. Explaining this with reference to FIG. 3, on the right side of the paper surface of FIG. 3, a virtual straight line connecting points P4 and P5 to be described later becomes the entrance of the circumferential groove 25, and the bottom surface is at the deepest position farthest from the radial outside (right side of the paper surface) with this entrance as the depth reference. Similarly, on the left side of the paper surface of FIG. 3, a virtual straight line connecting points P2 and P3 to be described later becomes the entrance of the circumferential groove 25, and the bottom surface is at the deepest position farthest from the radial outside (left side of the paper surface) with this entrance as the depth reference. And when comparing the two bottom surfaces on the left and right of the paper surface in the cross section of FIG. 3, the bottom surface on the right side of the paper surface where the groove width w1 is wide is farther from the radial outside from the entrance of the circumferential groove 25 than the bottom surface on the left side of the paper surface where the groove width w1 is narrow, and the groove is deeper. In this way, the depth of the circumferential groove 25 from its entrance to the bottom surface becomes deeper in direct proportion to the groove width w1.

[0023] The ink flow channel 27 is a channel that guides the ink in the ink flow path 28 into the ball holding chamber 24. As shown in FIGS. 3 and 4, a plurality of ink flow channels 27 are arranged at equal angular intervals around the central axis CL. In the illustrated example, a case where four ink flow channels 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 only. Each ink flow channel 27 is formed from the ink flow path 28 to the ball receiving seat 26 in the ball holding chamber 24. Each ink flow channel 27 is a slit formed long in the axial direction, and is formed such that the groove width becomes wider toward the radially outer side. Here, since the bottom surface 25b1 is inclined as described above, as shown in FIG. 1, the groove length in the axial direction of each ink flow channel 27 is different depending on its formation position. That is, the groove length of the ink flow channel 27 formed at a position where the groove width w1 is wide and the seat width w2 is narrow is short, and conversely, the groove length of the ink flow channel 27 formed at a position where the groove width w1 is narrow and the seat width w2 is wide is long.

[0024] When the ratio obtained by dividing the minimum value of the groove width w1 by the maximum value is defined as R1, it is preferable to select R1 from within the range of 0.5 to 0.8. If the upper limit value of this range is exceeded, the change in the line width depending on the writing direction becomes poor. Conversely, if the lower limit value of this range is fallen below, the gap g becomes excessively small depending on the writing direction, the ink supply cannot catch up with the writing, and there is a risk of causing streaks in the handwriting. Therefore, it is preferable to select R1 from within the range of 0.5 to 0.8.

[0025] 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 channel 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 channel 27. The rear hole 29 is a substantially cylindrical space coaxial with the central axis CL and has an inner diameter dimension larger than that of the ink flow passage 28. The upper part of the rear hole 29 is reduced in diameter toward the tip direction, and at the upper end position, it has the same inner diameter dimension as the ink flow passage 28.

[0026] The operation and effect of the ballpoint pen tip having the configuration described above will be described below with reference to FIGS. 5 and 6. Before that, the schematic diagrams of FIGS. 5 and 6 will be explained. Note that FIGS. 5 and 6 are schematically shown with their respective dimensions appropriately adjusted for the purpose of explanation. FIG. 5 is a schematic cross-sectional view showing the ballpoint pen tip shown in the cross-section of FIG. 3 upside down, indicating the state before starting writing. Points P1 to P6 in FIG. 5 indicate the points where the ball 10 contacts within the ball holding chamber 24 and correspond to points P1 to P6 in FIG. 3.

[0027] Among these points P1 to P6, the arc connecting points P1 and P2 indicates the cutting line on the left side of the paper surface of the ball seat 26 shown in FIG. 3. Also, the arc connecting points P5 and P6 indicates the cutting line on the right side of the paper surface of the ball seat 26 shown in FIG. 3. That is, points P1, P2, P5, and P6 indicate the respective end positions of the cutting line when the ball seat 26 is cut in the cross-section of FIG. 3. As shown in FIG. 5, the seat width w2 is wider on the one side on the right side of the paper surface with respect to the central axis CL than on the other side on the left side of the paper surface with respect to the central axis CL.

[0028] Also, the two-dot chain line passing through points P2, P3, P4, and P5 in FIG. 5 indicates the contour of the circumferential groove 25 when viewed in the cross-section of FIG. 3. Here, the two-dot chain line connecting points P2 and P3 indicates the cutting line on the left side of the paper surface of the circumferential groove 25 shown in FIG. 3. Also, the two-dot chain line connecting points P4 and P5 indicates the cutting line on the right side of the paper surface of the circumferential groove 25 shown in FIG. 3. As shown in FIG. 5, the groove width w1 is narrower on the one side on the right side of the paper surface with respect to the central axis CL than on the other side on the left side of the paper surface with respect to the central axis CL.

[0029] Since it is in the state before starting writing, ball 10 is seated in surface contact with ball seat 26, and the outer peripheral surface of ball 10 is in contact with the positions of points P1, P2, P5, and P6 (solid circles with hatching). On the other hand, since ball 10 is not in contact with tip opening 23 at this time, it is not in contact with points P3 and P4 (solid circles without hatching), and a gap g is formed between each of them. Since the center X of ball 10 in the seated state on ball seat 26 is located on central axis CL, the left and right gaps g shown in FIG. 5 are equal to each other.

[0030] FIG. 6 is a schematic diagram showing the writing state of the ball pen tip, where (a) shows the case of writing along one direction D1 with respect to writing surface P, and (b) shows the case of writing along the other direction D2 with respect to writing surface P. Also, among points P1 to P6, those in contact with ball 10 are indicated by solid circles with hatching, and those not in contact are indicated by solid circles without hatching.

[0031] As shown in FIG. 6(a), when ball 10 is written in one direction D1 of writing surface P, ball 10 moves away from ball seat 26 and rolls counterclockwise in a two-point support state by points P2 and P3 of circumferential groove 25. At this time, since ball 10 is displaced to the rear side in the writing direction within ball holding chamber 24, axis CLb passing through its center X and perpendicular to writing surface P is also displaced to the rear side in the writing direction. That is, a part of the outer peripheral surface of ball 10 enters between points P2 and P3 and slightly retreats to the rear side in the writing direction. However, since the interval between points P2 and P3 is set narrower than the interval between points P4 and P5, the retreat amount of ball 10 is restricted to be relatively small. As a result, the gap g formed between point P4 on the front side in the writing direction and the outer peripheral surface of ball 10 is restricted to be relatively small. Since the gap g on the front side in the writing direction is restricted to be relatively small in this way, the amount of ink moving through here to writing surface P is restricted to be relatively small, and the writing line becomes thin.

[0032] Subsequently, as shown in Fig. 6(b), when the ball 10 is written in the other direction D2 of the writing surface P, the ball 10 rolls clockwise in a two-point support state by the points P4 and P5 of the circumferential groove 25 while remaining separated from the ball receiver seat 26. At this time, since the ball 10 is displaced rearward in the writing direction within the ball holding chamber 24, its axis CLb is also displaced rearward in the writing direction. That is, a part of the outer peripheral surface of the ball 10 enters between the points P4 and P5 and retreats slightly more rearward in the writing direction. Here, since the interval between the points P4 and P5 is set wider than the interval between the points P2 and P3, the amount of retreat of the ball 10 becomes larger than that in Fig. 6(a). As a result, the gap g formed between the point P3 on the front side in the writing direction and the outer peripheral surface of the ball 10 is formed wider. Since the gap g on the front side in the writing direction is thus opened wider, the amount of ink transferred to the writing surface P through here becomes larger, and the writing line becomes thicker. As described above, the circumferential groove 25 has a groove depth from its groove opening to the bottom surface that increases in proportion to the groove width w1. Therefore, even when the ball 10 retreats deeply as shown in Fig. 6(b), since the bottom surface of the circumferential groove 25 is also formed deeply, it does not prevent the retreat of the ball 10. Thus, the gap g can be surely widened.

[0033] On the other hand, when writing by moving the ball pen tip in a direction orthogonal to the one direction D1 in Fig. 6(a) and the other direction D2 in Fig. 6(b) (i.e., the direction perpendicular to the paper surface of Fig. 6), the left or right direction in the paper surface of Fig. 2 becomes the writing direction. In this case, as shown in Fig. 2, since the shape of the circumferential groove 25 is symmetric about the central axis CL, the width dimension between the two points supporting the ball 10 rolling in the circumferential groove 25 is the same whether the left direction in the paper surface of Fig. 2 is the writing direction or the right direction in the paper surface of Fig. 2. Therefore, the gap g is approximately in the middle between the gap g shown in Fig. 6(a) and the gap g shown in Fig. 6(b), and the amount of ink transferred to the writing surface through here is also approximately in the middle. Thus, the thickness of the writing line is also in the middle (medium-thick line) between the writing line (thin line) in Fig. 6(a) and the writing line (thick line) in Fig. 6(b).

[0034] Furthermore, when writing in a direction between the left - right direction of the paper of FIG. 6 and the direction orthogonal to the paper of FIG. 6, that is, when writing with the Y - direction and Z - direction in FIG. 4 as the writing direction, writing lines having a line width between the above - mentioned thin line and medium - thick line, or writing lines having a line width between the above - mentioned medium - thick line and thick line can be drawn. Thus, according to the ball - pen tip of this embodiment, the line width of the writing line can be continuously controlled from a thin line to a thick line just by changing the writing direction. Therefore, compared with the conventional ball - pen tip with a constant line width, it is possible to draw a writing line with rich variations in line width and with cadence.

[0035] 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. 7. FIGS. 7(a) to (c) are longitudinal sectional views showing the writing state of the ball - pen tip. Here, (a) shows the case of writing while running slightly inclined in the direction of arrow C in FIG. 1 (when writing in the direction from the wider seat width w2 to the narrower one). Also, FIG. 7(b) shows the case of writing while running slightly inclined in the direction perpendicular to the paper surface of FIG. 2 (when writing in the direction from the medium - width seat width w2 to the medium - width one). And FIG. 7(c) shows the case of writing while running slightly inclined in the direction of arrow D in FIG. 1 (when writing in the direction from the narrower seat width w2 to the wider one). The angles with respect to the writing surface P in FIGS. 7(a) to (c) are all set to 70°.

[0036] In the case of FIG. 7(a), the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 was 0.025 mm. In the case of FIG. 7(b), 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 0.002 mm compared with FIG. 7(a). In the case of FIG. 7(c), the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 was 0.033 mm. Therefore, the gap g increased by 0.008 mm compared with FIG. 7(a). From the above, a thin line can be written in the writing direction of Fig. 7(a) where the gap g is the narrowest, a medium-thick line can be written in the writing direction of Fig. 7(b) where the gap g is medium, and a thick line can be written in Fig. 7(c) where the gap g is the widest.

[0037] [Second Embodiment] Hereinafter, with reference to Figs. 8 to 10, the ballpoint pen tip according to the second embodiment of the present invention will be described. In the following description, the differences from the ballpoint pen tip of the first embodiment will be mainly described, and for the rest, the description will be omitted as being the same as the configuration of the first embodiment.

[0038] Fig. 8 is a view showing the ballpoint pen tip of this embodiment, and is an enlarged cross-sectional view of a portion corresponding to a part of Fig. 1. Further, Fig. 9 is a longitudinal sectional view seen from the E-E arrow direction of Fig. 8. In this embodiment, a caulking portion 122 is formed at the tip of the outer peripheral surface 21 of the chip body 20. This caulking portion 122 is formed by caulking the tip of the chip body 20 after accommodating the ball 10, similar to the caulking portion 22 of the first embodiment, and its outer diameter is bent more angularly and radially inward than other portions. A tip opening 123 is formed at the tip of the caulking portion 122, and an inner peripheral surface 125a is formed inside the caulking portion 122.

[0039] Here, in the ballpoint pen tip of this embodiment, the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 123 periodically increases and decreases along the circumferential direction even in the state before the start of writing, which is particularly different from the configuration of the first embodiment. In this embodiment, there is no change in the shape or arrangement of the ball 10 itself. The outer peripheral surface of the ball 10 sitting on the ball seat 26 has a constant radius dimension along the circumferential direction when viewed in a cross-section perpendicular to the central axis CL. However, unlike the tip opening 23, the tip opening 123 has a radius from the central axis CL that increases and decreases in the circumferential direction. Specifically, in FIG. 8, the gap g1 on the left side of the paper surface is the widest in the circumferential direction of the tip opening 123. Starting from here and looking at the movement along the circumferential direction, the gap g gradually narrows. The gap g in the middle is one of the gaps g3 shown in FIG. 9. Further moving along the circumferential direction, it becomes the gap g2 on the right side of the paper surface in FIG. 8 and is the narrowest. Taking this as the turning-back position and looking at the further movement along the circumferential direction, the gap g gradually widens. The gap g in the middle is the other of the gaps g3 shown in FIG. 9. And finally, it returns to the starting position and becomes the widest gap g1. Thus, in this embodiment, at the time of the state before starting to write, the gap g between the outer peripheral surface of the ball 10 and the tip opening 123 is adjusted to increase and decrease in the circumferential direction.

[0040] As such adjustments for increasing and decreasing the gap g in the circumferential direction when the ball 10 is sitting, various modes can be considered. For example, during caulking, by creating a difference in the caulking amount on the left and right sides of the paper surface in FIG. 8, a gap g that increases and decreases in the circumferential direction can be formed. Alternatively, on the left and right sides of the paper surface in FIG. 8, before forming the caulked portion 122 by caulking, the wall thickness is increased and decreased in the circumferential direction, and then caulking with an equal caulking amount in the circumferential direction is applied, whereby a gap g that increases and decreases in the circumferential direction can also be formed. Of course, as long as the gap g can be increased and decreased in the circumferential direction, adjustments may be made using other processing methods.

[0041] However, when increasing or decreasing the gap g, it is necessary to adjust the circumferential positional relationship so that it is directly proportional to the increase or decrease of the groove width w1. That is, as shown in Fig. 8, it is adjusted so that the widest gap g1 is formed at the position on the left side of the paper where the groove width w1 is the narrowest. As a result, the narrowest gap g2 is formed at the position on the right side of the paper where the groove width w1 is the widest. Note that this adjustment can also be made based on the seat width w2. In this case, when increasing or decreasing the gap g, it is necessary to adjust so that it is directly proportional to the increase or decrease of the seat width w2. That is, as shown in Fig. 8, it is adjusted so that the widest gap g1 is formed at the position on the left side of the paper where the seat width w2 is the widest. As a result, the narrowest gap g2 is formed at the position on the right side of the paper where the seat width w2 is the narrowest.

[0042] As described above, by previously imparting an increase or decrease along the circumferential direction to the gap g formed in the state where the ball 10 is seated in surface contact with the ball seat 26, the increase or decrease in the circumferential direction of the gap g based on the groove width w1 (seat width w2) imparted in the first embodiment can be further increased. That is, by making the dimensional difference of the gap g caused by the difference in the writing direction larger, the difference in the thickness of the writing line due to the difference in the writing direction can be made larger, and it becomes possible to draw a writing line that is more full of undulations.

[0043] Also in the case of this embodiment, a simulation of specific numerical examples for the gap g was performed. The results are shown in Fig. 10. Figs. 10(a) to (c) are longitudinal sectional views showing the writing state of the ballpoint pen tip. Here, Fig. 10(a) shows the case of writing while running slightly inclined in the direction of arrow F in Fig. 8 (writing in the direction from the wider seat width w2 to the narrower one), Fig. 10(b) shows the case of writing while running slightly inclined in the direction perpendicular to the paper surface in Fig. 8 (writing in the direction from the medium seat width w2 to the medium seat width w2), and Fig. 10(c) shows the case of writing while running slightly inclined in the direction of arrow G in Fig. 8 (writing in the direction from the narrower seat width w2 to the wider one). The angles with respect to the writing surface P in Figs. 10(a) to (c) are all set to 70°.

[0044] In the case of Fig. 10(a), the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 was 0.017 mm. This is narrower than the gap g of 0.025 mm shown in Fig. 7(a). In the case of Fig. 10(b), the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 was 0.019 mm. Therefore, the gap g increased by 0.002 mm compared to Fig. 10(a). In the case of Fig. 10(c), the gap g formed between the outer peripheral surface of the ball 10 and the tip opening 23 was 0.030 mm. Therefore, the gap g increased by 0.013 mm compared to Fig. 10(a). In the case of Fig. 7(c), the increase was 0.008 mm, so the difference in the gap g was further widened by 0.005 mm. Therefore, compared to the configuration of the first embodiment, it is possible to write with more undulation.

[0045] The gist of each of the embodiments described above is summarized below.

[0046] (1) As illustrated in Fig. 1, a ball pen tip according to one aspect of the present invention includes a ball 10, a chip body 20 having a ball holding chamber 24 that rotatably houses the ball 10 and an ink flow passage 28 that communicates with the ball holding chamber 24, and is provided with the ball holding chamber 24 includes a ball seat 26 that defines a part of the ball holding chamber 24, a tip opening 23 that exposes a part of the ball 10 while holding the ball 10 between the ball seat 26, a circumferential groove 25 formed along the circumferential direction centered on the central axis CL of the chip body 20 between the edge 26a of the ball seat 26 closest to the tip opening 23 and the tip opening 23, and has the groove width w1 of the circumferential groove 25 periodically increases and decreases along the circumferential direction. According to the ball pen tip described in (1) above, by changing the writing direction, the thickness of the writing line can be freely changed, so it is possible to obtain a writing line full of undulation.

[0047] (2) As illustrated in Fig. 4, the ballpoint pen tip described in (1) above may be configured as follows: When the ball receiving seat 26 is viewed in a direction facing the central axis CL, the seat width w2 along the cross-section including the central axis CL periodically increases and decreases in the circumferential direction so as to be inversely proportional to the increase and decrease of the groove width w1. In the case of the ballpoint pen tip described in (2) above, since the retraction amount of the ball 10 at each position of the circumferential groove 25 during writing can be appropriately ensured, the gap g between the outer peripheral surface of the ball 10 and the tip opening 23 on the front side along the writing direction can also be increased and decreased more appropriately according to the writing direction.

[0048] (3) As illustrated in Fig. 8, the ballpoint pen tip described in (1) or (2) above may be configured as follows: In a state where the ball 10 is seated in surface contact with the ball receiving seat 26, the gap dimension between the outer peripheral surface of the ball 10 and the tip opening 23 periodically increases and decreases in the circumferential direction so as to be inversely proportional to the increase and decrease of the groove width w1. In the case of the ballpoint pen tip described in (3) above, a writing line with more prominent differences between the thin line and the thick line and more cadence can be obtained.

[0049] As a supplement, (1) above can also be summarized as follows: The 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, is provided, the ball holding chamber 24 has a ball receiving seat 26 defining 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, when the chip body 20 is viewed in a cross-section including the central axis CL of the chip body 20, The ball receiving seat 26 has a first cutting line on one side with respect to the central axis line CL (the cutting line extending from point P5 to point P6 in FIG. 5), a second cutting line on the other side (the cutting line extending from point P1 to point P2 in FIG. 5), a first seat radius point on the first cutting line where the seat radius from the central axis line CL is the longest (point P5 in FIG. 5), and a second seat radius point on the second cutting line where the seat radius from the central axis line CL is the longest (point P2 in FIG. 5). The tip opening 23 has a first tip point on the one side with respect to the central axis line CL (point P4 in FIG. 5) and a second tip point on the other side (point P3 in FIG. 5). The seat radius of the second seat radius point from the central axis line CL is longer than that of the first seat radius point. The distance between the first seat radius point and the first tip point is longer than the distance between the second seat radius point and the second tip point. The first tip point is radially outside the virtual arc obtained by extending the first cutting line. The second tip point is radially outside the virtual arc obtained by extending the second cutting line. Ball pen tip.

Explanation of reference numerals

[0050] 10 Ball 20 Chip body 23 Tip opening 24 Ball holding chamber 25 Circumferential groove 26 Ball receiving seat 26a Edge 28 Ink flow passage CL Central axis line g Gap w1 Groove width w2 Seat width

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; comprising the ball holding chamber having 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; a circumferential groove formed along the circumferential direction centered on the central axis of the chip body between the edge of the ball seat closest to the tip opening and the tip opening; having the groove width of the circumferential groove periodically increasing and decreasing along the circumferential direction. A ball pen tip, characterized in that.

2. When the ball seat is viewed in a facing direction along the central axis, the seat width along the cross-section including the central axis periodically increases and decreases along the circumferential direction so as to be inversely proportional to the increase and decrease of the groove width. The ball pen tip according to claim 1, characterized in that.

3. In a state where the ball is seated in surface contact with the ball seat, the gap dimension between the outer peripheral surface of the ball and the tip opening periodically increases and decreases along the circumferential direction so as to be inversely proportional to the increase and decrease of the groove width. The ball pen tip according to claim 1 or 2, characterized in that.

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