Ballpoint pen

Abstract

A ballpoint pen (10) includes a ballpoint pen tip (30), the ballpoint pen tip (30) includes a pipe (40) including a deformed portion (42) and a ball holding chamber (46) formed in front of the deformed portion (42), a ball (32) disposed in the ball holding chamber (46), a center core (50) at least a part of which is disposed in the pipe (40), a gap (34) formed between the ball (32) and a front end (57) of the center core (50), and an ink channel (60) formed between the center core (50) and the pipe (40), in which the ballpoint pen tip (30) includes a first region (A1) and a second region (A2) positioned to the rear of the first region (A1), and a cross-sectional area of the ink channel (60) in the first region (A1) is larger than a cross-sectional area of the ink channel (60) in the second region (A2).

Description

TECHNICAL FIELD

[0001] The present invention relates to a ballpoint pen.BACKGROUND ART

[0002] Conventionally, a ballpoint pen including a pipe provided at a tip end portion thereof and a ball disposed in a ball holding chamber provided at a tip end of the pipe is known. In a ballpoint pen disclosed in JP6345403B, an ink guide core is disposed in a pipe (narrow tube), and a gap between an outer surface of the ink guide core and an inner surface of the pipe is an ink flow gap. Ink stored in an ink tank is supplied to a ball through the ink flow gap.

[0003] JP6345403B discloses a ballpoint pen in which a difference between an inner diameter of the pipe and an outer diameter of the ink guide core is larger than an axial distance between a front end of the ink guide core and the ball. This ballpoint pen is advantageous in that, even if air is mixed into a ballpoint pen tip from a ball side at a time of writing or attaching or detaching a cap, and the mixed air stagnates in the ink flow gap between the outer surface of the ink guide core and the inner surface of the pipe, smooth ink flowability from a rear to the ball is maintained.

[0004] The inventor of the present application has further studied such a ballpoint pen, and has found the following problems. In a case where the gap between the outer surface of the ink guide core and the inner surface of the pipe is large, a flow rate of the ink passing through the gap is sufficiently secured. However, in this case, an ink suction force due to capillarity generated in the ink in the gap decreases. As a result, particularly at a start of use of the ballpoint pen, the ink may not be sufficiently supplied from the rear to the ball. Meanwhile, in a case where the gap between the outer surface of the ink guide core and the inner surface of the pipe is reduced, the ink suction force due to capillarity generated in the ink in the gap increases. However, in this case, the flow rate of the ink passing through the gap decreases, and particularly when a writing speed is high, ink supply from the rear to the ball decreases, and handwriting may be faint.SUMMARY OF THE INVENTION

[0005] The present invention has been made in consideration of such points, and an object thereof is to supply ink sufficiently to a ball at a start of use of a ballpoint pen and during writing with the ballpoint pen.

[0006] A ballpoint pen according to the present invention is [1] a ballpoint pen including a ballpoint pen tip, the ballpoint pen tip includes: a pipe including a deformed portion and a ball holding chamber formed in front of the deformed portion; a ball disposed in the ball holding chamber; a center core at least a part of which is disposed in the pipe; a gap formed between the ball and a front end of the center core; and an ink channel formed between the center core and the pipe, in which the ballpoint pen tip includes a first region and a second region positioned to the rear of the first region, and a cross-sectional area of the ink channel in the first region is larger than a cross-sectional area of the ink channel in the second region.

[0007] The ballpoint pen according to the present invention is [2] the ballpoint pen according to [1], in which the ink channel in the first region has a cylindrical shape extending along a central axis of the pipe, and the ink channel in the second region has a cylindrical shape extending along a central axis of the pipe.

[0008] The ballpoint pen according to the present invention is the ballpoint pen according to [2], in which an inner diameter of the ink channel in the first region is smaller than an inner diameter of the ink channel in the second region.

[0009] The ballpoint pen according to the present invention is [4] the ballpoint pen according to any one of [1] to [3], in which the center core includes a small diameter part disposed in the first region and a large diameter part disposed in the second region, and a diameter of the small diameter part is smaller than a diameter of the large diameter part.

[0010] The ballpoint pen according to the present invention is the ballpoint pen according to [4], in which a radius of the small diameter part is larger than a distance between a central axis of the pipe and a top portion of the deformed portion.

[0011] The ballpoint pen according to the present invention is the ballpoint pen according to [4] or [5], in which a step portion formed between the small diameter part and the large diameter part has a curved-surface shape protruding toward an inside of the center core.

[0012] The ballpoint pen according to the present invention is the ballpoint pen according to any one of [1] to [6], in which at least a part of the first region is positioned to the rear of a top portion of the deformed portion.

[0013] The ballpoint pen according to the present invention is the ballpoint pen according to [7], in which the entire first region is positioned to the rear of a top portion of the deformed portion.

[0014] The ballpoint pen according to the present invention is the ballpoint pen according to any one of [1] to [8], in which the front end of the center core is positioned to the rear of a top portion of the deformed portion.

[0015] According to the present invention, ink can be sufficiently supplied to a ball both at a start of use of a ballpoint pen and during writing with the ballpoint pen.BRIEF DESCRIPTION OF DRAWINGS

[0016] [Fig. 1] Fig. 1 is a view for describing a first embodiment of the present invention, and is a longitudinal sectional view illustrating an example of a ballpoint pen. [Fig. 2] Fig. 2 is an enlarged longitudinal sectional view illustrating a part of Fig. 1. [Fig. 3] Fig. 3 is a longitudinal sectional view illustrating a part of Fig. 2 in a further enlarged manner. [Fig. 4] Fig. 4 is an external view illustrating a center core of a ballpoint pen tip. [Fig. 5] Fig. 5 is a transverse sectional view taken along line V-V in Fig. 3. [Fig. 6] Fig. 6 is a transverse sectional view taken along line VI-VI in Fig. 3. [Fig. 7] Fig. 7 is a transverse sectional view taken along line VII-VII in Fig. 3. [Fig. 8] Fig. 8 is a view for describing a second embodiment of the present invention, and is a longitudinal sectional view illustrating an example of a ballpoint pen. [Fig. 9] Fig. 9 is an enlarged longitudinal sectional view illustrating a part of Fig. 8. [Fig. 10] Fig. 10 is a longitudinal sectional view illustrating a part of Fig. 9 in a further enlarged manner. MODE FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in the drawings attached herein, scales, vertical and horizontal dimensional ratios, and the like are appropriately changed and exaggerated from the actual ones for convenience of illustration and ease of understanding.

[0018] In addition, terms such as "parallel", "orthogonal", "same", and the like, values of length and angle, and the like, which specify shapes and geometric conditions and degrees thereof, used in the present specification are interpreted including a range in which similar functions can be expected without being bound by a strict meaning.

[0019] In the present specification, a direction in which a central axis A of a ballpoint pen 10 extends (a longitudinal direction and a vertical direction in a longitudinal sectional view) is defined as an axial direction da, a direction orthogonal to the axial direction da is defined as a radial direction, and a direction along a circumference around a central axis A is defined as a circumferential direction. In addition, along the axial direction da, a pen point side is defined as front, and a side opposite to the pen point is defined as rear. In addition, along the radial direction, a side approaching the central axis A is defined as an inside or inward, and a side away from the central axis A is defined as an outside or outward.First Embodiment

[0020] Fig. 1 is a view for describing a first embodiment of the present invention, and is a longitudinal sectional view illustrating an example of a ballpoint pen 10. Fig. 2 is a view illustrating a part of a front portion of the ballpoint pen 10, and is a longitudinal sectional view illustrating a portion denoted by II in Fig. 1 in an enlarged manner. The ballpoint pen 10 includes a barrel 11, an ink storage part 12, and a ballpoint pen tip 30. The ballpoint pen 10 may further include at least one of a tail plug 13, an ink stopper 15, a first guide member 21, a second guide member 23, and a holding member 25.

[0021] The barrel 11 is a member that forms an outer shell of the ballpoint pen 10, and has a substantially cylindrical shape. A central axis of the barrel 11 coincides with the central axis A of the ballpoint pen 10. The barrel 11 of the present embodiment is intended to be gripped by fingers when a user writes with the ballpoint pen 10. The barrel 11 may be formed of, for example, a material such as resin or metal. When the ballpoint pen 10 is not used, a cap covering the ballpoint pen tip 30 may be attached to a front portion of the barrel 11. The tail plug 13 may be attached to a rear end portion of the barrel 11.

[0022] The ink storage part 12 is provided in the barrel 11. The ink storage part 12 is a space that stores ink for writing. The ink stopper 15 is disposed in front of the ink storage part 12. A rear portion of the ink stopper 15 is inserted into the barrel 11 from the front, whereby the ink stopper 15 is coupled to the barrel 11. The ink stopper 15 has a function of suppressing leakage of the ink in the ink storage part 12 to outside of the ballpoint pen 10.

[0023] The ink stopper 15 includes a plurality of fins 16, a plurality of ink holding grooves 17, and a through hole 18. Each of the fins 16 has a disk shape extending in a direction orthogonal to the central axis A. The ink holding grooves 17 are spaces formed between two fins 16 adjacent to each other in the axial direction da. The ink holding grooves 17 have a function of temporarily holding the ink leaking from the ink storage part 12. The fins 16 may be formed with air guide grooves that extend in the axial direction da and allow two ink holding grooves 17 adjacent to each other in the axial direction da to communicate with each other. In addition, an air guide groove extending in the axial direction da may also be formed in flange portions of the fins 16, flange portions being engaged with the barrel 11. Gaps may be formed between radially outer ends of the fins 16 and an inner surface of the barrel 11. The through hole 18 penetrates a center of the ink stopper 15 in the axial direction da. The ink stopper 15 may be formed by, for example, injection molding of resin.

[0024] The first guide member 21 and the second guide member 23 have a function of guiding the ink in the ink storage part 12 toward the ballpoint pen tip 30. The first guide member 21 and the second guide member 23 are disposed in the through hole 18 of the ink stopper 15. The first guide member 21 may be, for example, a member having a pipe shape. In this case, the ink in the ink storage part 12 can flow toward the second guide member 23 through a cavity inside the first guide member 21. The first guide member 21 may be formed of, for example, a material such as resin or metal. The second guide member 23 may be, for example, a fiber bundle formed by bundling a large number of fibers extending substantially along the axial direction da. In the example illustrated in Figs. 1 and 2, the first guide member 21 and the second guide member 23 are connected to each other by a front end of the first guide member 21 being inserted into the second guide member 23 from the rear. In a case where the second guide member 23 is formed of a fiber bundle, the ink flowing from the first guide member 21 into the second guide member 23 can flow toward the ballpoint pen tip 30 through gaps between fibers due to capillarity.

[0025] The holding member 25 is a member that holds the ballpoint pen tip 30. A rear end portion of the holding member 25 is inserted from the front into the through hole 18 of the ink stopper 15. As a result, the holding member 25 is attached to the ink stopper 15. The holding member 25 has a through hole 26. The through hole 26 penetrates a center of the holding member 25 in the axial direction da. A front end portion of the second guide member 23 is inserted into the through hole 26 from the rear. As a result, the second guide member 23 and the holding member 25 are coupled to each other. A rear end portion of a pipe 40 of the ballpoint pen tip 30 is inserted into the through hole 26 from the front. As a result, the holding member 25 and the pipe 40 are coupled to each other. In addition, as a result, the pipe 40 is held by the holding member 25. The holding member 25 may be formed of, for example, a material such as resin or metal.

[0026] Next, the ballpoint pen tip 30 of the present embodiment will be described with reference to Figs. 3 to 7. Fig. 3 is a view illustrating a part of the ballpoint pen tip 30, and is a longitudinal sectional view illustrating a portion denoted by III in Fig. 2 in an enlarged manner. Fig. 4 is an external view illustrating a center core 50 of the ballpoint pen tip 30. Fig. 5 is a transverse sectional view taken along line V-V in Fig. 3. Fig. 6 is a transverse sectional view taken along line VI-VI in Fig. 3. Fig. 7 is a transverse sectional view taken along line VII-VII in Fig. 3.

[0027] The ballpoint pen tip 30 includes a ball 32, the pipe 40, and the center core 50. The pipe 40 is a member that holds the ball 32 and has a function of supplying the ink to the ball 32. The pipe 40 is a substantially cylindrical member extending along the central axis A of the ballpoint pen 10. A central axis of the pipe 40 coincides with the central axis A of the ballpoint pen 10. Therefore, the central axis A is the central axis of the ballpoint pen 10 and is also the central axis of the pipe 40. The pipe 40 may be formed of, for example, metal such as stainless steel. The pipe 40 includes a deformed portion 42 and a ball holding chamber 46. The deformed portion 42 is a portion where a wall portion of the pipe 40 is deformed inward. The deformed portion 42 is formed by, for example, the wall portion of the pipe 40 being pressed inward. The pipe 40 may have a plurality of deformed portions 42 arranged in the circumferential direction. The plurality of deformed portions 42 may be arranged at equal angular pitches in the circumferential direction. The pipe 40 of the present embodiment has four deformed portions 42 arranged in the circumferential direction (see Fig. 7). The four deformed portions 42 may be arranged at an angular pitch of 90 degrees in the circumferential direction. Note that the pipe 40 may have two or three deformed portions 42, or may have five or more deformed portions 42.

[0028] The ball holding chamber 46 is formed in front of the deformed portions 42. A front inner surface of the deformed portions 42 constitutes a ball reception seat in the ball holding chamber 46. The ball holding chamber 46 has a function of holding the ball 32, and a function of holding the ink in the ball holding chamber 46 and applying the ink to the ball 32. In the illustrated example, after the ball 32 is disposed in the ball holding chamber 46, the ball 32 is held in the ball holding chamber 46 by a front end edge of the pipe 40 being crimped so as to deform inward in the radial direction. In this state, the ball 32 is rotatable in the ball holding chamber 46. Note that a part of the ball 32 protrudes forward from the ball holding chamber 46.

[0029] The center core 50 is a substantially rod-shaped member extending along the central axis A. At least a part of the center core 50 is disposed inside the pipe 40. The center core 50 may be a solid member or a hollow member. In the example illustrated in Figs. 1 and 2, a rear end of the center core 50 is inserted into the second guide member 23 from the front, whereby the center core 50 and the second guide member 23 are connected to each other. The center core 50 may be formed of, for example, a material such as resin or metal. In particular, the center core 50 is preferably formed of a resin material such as polyacetal (POM).

[0030] The center core 50 includes a small diameter part 51 and a large diameter part 53. Each of the small diameter part 51 and the large diameter part 53 has a columnar shape. A diameter D 51 of the small diameter part 51 is smaller than a diameter D 53 of the large diameter part 53 (see Fig. 4). The large diameter part 53 is positioned to the rear of the small diameter part 51. In particular, the large diameter part 53 is positioned adjacent to the small diameter part 51 and positioned to the rear of the small diameter part 51. The small diameter part 51 defines a first region A1 extending in the axial direction da, and the large diameter part 53 defines a second region A2 extending in the axial direction da. Therefore, it can be said that the small diameter part 51 is disposed in the first region A1, and the large diameter part 53 is disposed in the second region A2. The second region A2 is positioned to the rear of the first region A1. In particular, the second region A2 is positioned adjacent to the first region A1 and positioned to the rear of the first region A1.

[0031] An ink channel 60 is formed between an outer surface of the center core 50 and an inner surface of the pipe 40. A rear end of the ink channel 60 communicates with the second guide member 23. The ink flowing from the second guide member 23 into the ballpoint pen tip 30 flows toward the ball holding chamber 46 through the ink channel 60. In particular, in the ink channel 60, the ink flows toward the ball holding chamber 46 due to capillarity generated in the ink.

[0032] The ink channel 60 in the first region A1 has a cylindrical shape extending along the central axis A of the pipe 40. In addition, the ink channel 60 in the second region A2 has a cylindrical shape extending along the central axis A of the pipe 40. As a result, the ink smoothly flows along the ink channel 60 having a cylindrical shape.

[0033] In the present embodiment, an inner diameter D 1 of the ink channel 60 in the first region A1 coincides with the diameter D 51 of the small diameter part 51 of the center core 50. In addition, an inner diameter D 2 of the ink channel 60 in the second region A2 coincides with the diameter D 53 of the large diameter part 53 of the center core 50. Here, as described above, the diameter D 51 of the small diameter part 51 of the center core 50 is smaller than the diameter D 53 of the large diameter part 53. Therefore, the inner diameter D 1 of the ink channel 60 in the first region A1 is smaller than the inner diameter D 2 of the ink channel 60 in the second region A2 (see Figs. 5 and 6).

[0034] As a result, a cross-sectional area of the ink channel 60 in the first region A1 and a cross-sectional area of the ink channel 60 in the second region A2 can be differentiated from each other without changing the inner diameter D of the pipe 40 along the axial direction da. Therefore, it is possible to suppress complication of a structure of the pipe 40. In particular, the cross-sectional area of the ink channel 60 in the first region A1 and the cross-sectional area of the ink channel 60 in the second region A2 can be differentiated from each other without changing a shape and dimensions of the pipe 40 from the conventional ballpoint pen 10.

[0035] In addition, by configuring the diameter D 51 of the small diameter part 51 of the center core 50 to be smaller than the diameter D 53 of the large diameter part 53, the cross-sectional area of the ink channel 60 in the first region A1 and the cross-sectional area of the ink channel 60 in the second region A2 can be easily differentiated from each other only by changing a shape of the center core 50. Specifically, by differentiating the diameter D 51 of the small diameter part 51 and the diameter D 53 of the large diameter part 53 of the center core 50 from each other, the cross-sectional area of the ink channel 60 in the first region A1 and the cross-sectional area of the ink channel 60 in the second region A2 can be differentiated from each other.

[0036] In the present embodiment, an inner diameter D of the pipe 40 in the first region A1 is equal to an inner diameter D of the pipe 40 in the second region A2. In this case, a cross-sectional area S 1 of the ink channel 60 in the first region A1 (see Fig. 6) is larger than a cross-sectional area S 2 of the ink channel 60 in the second region A2 (see Fig. 5). The cross-sectional area S 1 of the ink channel 60 in the first region A1 is an area of a space between an outer surface of the small diameter part 51 and the inner surface of the pipe 40, at a cross section orthogonal to the central axis A. In addition, the cross-sectional area S 2 of the ink channel 60 in the second region A2 is an area of a space between an outer surface of the large diameter part 53 and the inner surface of the pipe 40, at the cross section orthogonal to the central axis A.

[0037] Because the cross-sectional area S 1 of the ink channel 60 in the first region A1 is larger than the cross-sectional area S 2 of the ink channel 60 in the second region A2, a sufficient amount of the ink can be held in the ink channel 60 in the first region A1. As a result, even when a writing speed with the ballpoint pen 10 is high, the ink can be sufficiently supplied from the ink channel 60 to the ball 32. Therefore, even when the writing speed with the ballpoint pen 10 is high, it is possible to sufficiently suppress the handwriting from being faint.

[0038] In addition, because the cross-sectional area S 2 of the ink channel 60 in the second region A2 is smaller than the cross-sectional area S 1 of the ink channel 60 in the first region A1, a large suction force is generated in the ink positioned in the second region A2 due to capillarity. With this large suction force, a sufficient amount of ink can flow from the ink storage part 12 toward the ball 32. As a result, the ink can be sufficiently supplied from the ink storage part 12 to the ball 32 particularly at a start of use of the ballpoint pen 10.

[0039] The cross-sectional area S 1 of the ink channel 60 in the first region A1 may be, for example, 0.07 mm 2< or more and 0.49 mm 2< or less. Preferably, the cross-sectional area S 1 may be 0.13 mm 2< or more and 0.32 mm 2< or less. More preferably, the cross-sectional area S 1 may be 0.25 mm 2< or more and 0.32 mm 2< or less. In addition, the cross-sectional area S 2 of the ink channel 60 in the second region A2 may be, for example, 0.03 mm 2< or more and 0.24 mm 2< or less. Preferably, the cross-sectional area S 2 may be 0.05 mm 2< or more and 0.17 mm 2< or less. More preferably, the cross-sectional area S 2 may be 0.12 mm 2< or more and 0.17 mm 2< or less. A ratio (S 2 / S 1 ) of the cross-sectional area S 2 of the ink channel 60 in the second region A2 to the cross-sectional area S 1 of the ink channel 60 in the first region A1 may be 0.26 or more and 0.87 or less. Preferably, the ratio (S 2 / S 1 ) may be 0.26 or more and 0.65 or less. More preferably, the ratio (S 2 / S 1 ) may be 0.39 or more and 0.65 or less. In addition, a length of the first region A1 along the axial direction da may be, for example, 0.2 mm or more and 3.5 mm or less. Preferably, the length of the first region A1 along the axial direction da may be 1.0 mm or more and 1.4 mm or less.

[0040] As illustrated in Fig. 7, a radius Rs 1 of the small diameter part 51 may be greater than a distance L between the central axis A of the pipe 40 and top portions 44 of the deformed portions 42. In other words, the radius R 51 of the small diameter part 51 may be larger than a radius of a circle (inscribed circle) C inscribed in the top portions 44 of the deformed portions 42, at a cross section (see Fig. 7) orthogonal to the central axis A. In this case, as illustrated in Fig. 3, the entire small diameter part 51 is positioned to the rear of the top portions 44 of the deformed portions 42. At this time, a position of the center core 50 in the axial direction da can be determined by bringing a front end 57 of the center core 50 into contact with rear inner surfaces of the deformed portions 42.

[0041] At least a part of the first region A1 is positioned to the rear of the top portions 44 of the deformed portions 42. In particular, in the example illustrated in Fig. 3, the entire first region A1 is positioned to the rear of the top portions 44 of the deformed portions 42. Dimensions of the pipe 40 are relatively generous to the rear of the top portions 44 of the deformed portions 42. Therefore, a volume of the ink channel 60 in the first region A1 can be sufficiently secured by disposing the first region A1 at a portion to the rear of the top portions 44 of the deformed portions 42. Therefore, a sufficient amount of the ink can be held in the ink channel 60 in the first region A1.

[0042] As illustrated in Fig. 3, the front end 57 of the center core 50 may be positioned to the rear of the top portions 44 of the deformed portions 42. The front end 57 may be in contact with the rear inner surfaces of the deformed portions 42. In the present embodiment, a gap 34 in the axial direction da is formed between the rear end of the ball 32 and the front end 57 of the center core 50. That is, the front end 57 of the center core 50 is not in contact with the ball 32. As a result, the center core 50 does not hinder rotation of the ball 32 at a time of writing. Therefore, feel of writing with the ballpoint pen 10 can be made smooth.

[0043] As illustrated in Figs. 3 and 4, a step portion 55 formed between the small diameter part 51 and the large diameter part 53 may have a curved-surface shape protruding toward an inside of the center core 50. In this case, in the step portion 55, the ink smoothly flows along the curved surface. Therefore, in the ink channel 60, the ink can be smoothly supplied from the second region A2 toward the first region A1. In a longitudinal section (see Fig. 3) including the central axis A, a curvature radius of the curved surface of the step portion 55 may be, for example, 0.05 mm or more and 1.0 mm or less.

[0044] As described above, a large suction force is generated in the ink positioned in the second region A2 due to capillarity. In the ballpoint pen 10, the ink stored in the ink storage part 12 flows toward the ball holding chamber 46 with the suction force generated in the ink positioned in the second region A2. In the ballpoint pen 10 of the present embodiment, a suction force due to capillarity is also generated in the ink positioned in the first region A1. In the ballpoint pen 10 of the present embodiment, moreover, a suction force due to capillarity is also generated in the ink positioned in the first guide member 21 and / or the second guide member 23. With these suction forces, the ink stored in the ink storage part 12 flows toward the ball holding chamber 46. Note that the ink positioned in the first region A1 flows toward the ball holding chamber 46 through passages 62 (see Fig. 7) formed between the deformed portions 42 adjacent to each other in the circumferential direction.

[0045] The ballpoint pen 10 of the present embodiment includes a ballpoint pen tip, the ballpoint pen tip includes the pipe 40 including the deformed portions 42 and the ball holding chamber 46 formed in front of the deformed portions 42, the ball 32 disposed in the ball holding chamber 46, the center core 50 at least a part of which is disposed in the pipe 40, the gap 34 formed between the ball 32 and the front end 57 of the center core 50, and the ink channel 60 formed between the center core 50 and the pipe 40, in which the ballpoint pen tip 30 includes the first region A1 and the second region A2 positioned to the rear of the first region A1, and the cross-sectional area of the ink channel 60 in the first region A1 is larger than the cross-sectional area of the ink channel 60 in the second region A2.

[0046] According to such a ballpoint pen 10, because the cross-sectional area S 1 of the ink channel 60 in the first region A1 is larger than the cross-sectional area S 2 of the ink channel 60 in the second region A2, a sufficient amount of ink can be held in the ink channel 60 in the first region A1. As a result, even when a writing speed with the ballpoint pen 10 is high, the ink can be sufficiently supplied from the ink channel 60 to the ball 32. Therefore, even when the writing speed with the ballpoint pen 10 is high, it is possible to sufficiently suppress the handwriting from being faint.

[0047] In addition, because the cross-sectional area S 2 of the ink channel 60 in the second region A2 is smaller than the cross-sectional area S 1 of the ink channel 60 in the first region A1, a large suction force is generated in the ink positioned in the second region A2 due to capillarity. With this large suction force, a sufficient amount of ink can flow from the ink storage part 12 toward the ball 32. As a result, the ink can be sufficiently supplied from the ink storage part 12 to the ball 32 particularly at a start of use of the ballpoint pen 10.

[0048] Therefore, the ink can be sufficiently supplied to the ball 32 both at a start of use of the ballpoint pen 10 and during writing with the ballpoint pen 10.

[0049] In the ballpoint pen 10 of the present embodiment, the ink channel 60 in the first region A1 has a cylindrical shape extending along the central axis A of the pipe 40, and the ink channel 60 in the second region A2 has a cylindrical shape extending along the central axis A of the pipe 40.

[0050] According to such a ballpoint pen 10, the ink smoothly flows along the ink channel 60 having a cylindrical shape.

[0051] In the ballpoint pen 10 of the present embodiment, the inner diameter D 1 of the ink channel 60 in the first region A1 is smaller than the inner diameter D 2 of the ink channel 60 in the second region A2.

[0052] According to such a ballpoint pen 10, the cross-sectional area of the ink channel 60 in the first region A1 and the cross-sectional area of the ink channel 60 in the second region A2 can be differentiated from each other without changing the inner diameter D of the pipe 40 along the axial direction da. Therefore, it is possible to suppress complication of a structure of the pipe 40. In particular, the cross-sectional area of the ink channel 60 in the first region A1 and the cross-sectional area of the ink channel 60 in the second region A2 can be differentiated from each other without changing a shape and dimensions of the pipe 40 from the conventional ballpoint pen 10.

[0053] In the ballpoint pen 10 of the present embodiment, the center core 50 includes the small diameter part 51 disposed in the first region A1 and the large diameter part 53 disposed in the second region A2, and the diameter D 51 of the small diameter part 51 is smaller than the diameter D 53 of the large diameter part 53.

[0054] According to such a ballpoint pen 10, the cross-sectional area of the ink channel 60 in the first region A1 and the cross-sectional area of the ink channel 60 in the second region A2 can be differentiated from each other easily, only by changing the shape of the center core 50. Specifically, by differentiating the diameter D 51 of the small diameter part 51 and the diameter D 53 of the large diameter part 53 of the center core 50 from each other, the cross-sectional area of the ink channel 60 in the first region A1 and the cross-sectional area of the ink channel 60 in the second region A2 can be differentiated from each other.

[0055] In the ballpoint pen 10 of the present embodiment, the radius R 51 of the small diameter part 51 is larger than the distance L between the central axis A of the pipe 40 and the top portions 44 of the deformed portions 42.

[0056] According to such a ballpoint pen 10, the entire small diameter part 51 is positioned to the rear of the top portions 44 of the deformed portions 42. At this time, a position of the center core 50 in the axial direction da can be determined by bringing a front end 57 of the center core 50 into contact with rear inner surfaces of the deformed portions 42.

[0057] In the ballpoint pen 10 of the present embodiment, the step portion 55 formed between the small diameter part 51 and the large diameter part 53 has a curved-surface shape protruding toward an inside of the center core 50.

[0058] According to such a ballpoint pen 10, in the step portion 55, the ink smoothly flows along the curved surface. Therefore, in the ink channel 60, the ink can be smoothly supplied from the second region A2 toward the first region A1.

[0059] In the ballpoint pen 10 of the present embodiment, at least a part of the first region A1 is positioned to the rear of the top portions 44 of the deformed portions 42.

[0060] In the ballpoint pen 10 of the present embodiment, the entire first region A1 is positioned to the rear of the top portions 44 of the deformed portions 42.

[0061] According to such a ballpoint pen 10, the volume of the ink channel 60 in the first region A1 can be sufficiently secured by disposing the first region A1 in a portion, the dimensions of which are relatively generous, to the rear of the top portions 44 of the deformed portions 42. Therefore, a sufficient amount of the ink can be held in the ink channel 60 in the first region A1.

[0062] In the ballpoint pen 10 of the present embodiment, the front end 57 of the center core 50 is positioned to the rear of the top portions 44 of the deformed portions 42.

[0063] According to such a ballpoint pen 10, the gap 34 in the axial direction da can be more reliably formed between the ball 32 and the front end 57 of the center core 50. As a result, the center core 50 does not hinder rotation of the ball 32 at a time of writing. Therefore, feel of writing with the ballpoint pen 10 can be made smooth.Second Embodiment

[0064] A second embodiment of the present invention will be described with reference to Figs. 8 to 10. In the following description and the drawings used in the following description, the same reference signs as those used in the description of the first embodiment are used for portions that may be configured similarly to those in the first embodiment, and redundant description will be omitted.

[0065] Fig. 8 is a view for describing the second embodiment of the present invention, and is a longitudinal sectional view illustrating an example of a ballpoint pen 10. Fig. 9 is a view illustrating a part of a front portion of the ballpoint pen 10, and is a longitudinal sectional view illustrating a portion denoted by IX in Fig. 8 in an enlarged manner. Fig. 10 is a view illustrating a part of a ballpoint pen tip 30, and is a longitudinal sectional view illustrating a portion denoted by X in Fig. 9 in an enlarged manner.

[0066] The ballpoint pen tip 30 of the present embodiment includes a ball 32, a pipe 140, and a center core 50. The pipe 140 is a member that holds the ball 32 and has a function of supplying ink to the ball 32. The pipe 140 extends along a central axis A of the ballpoint pen 10. A central axis of the pipe 140 coincides with the central axis A of the ballpoint pen 10. Therefore, the central axis A is the central axis of the ballpoint pen 10 and is also the central axis of the pipe 140. The pipe 140 may be formed of, for example, metal such as stainless steel.

[0067] The pipe 140 of the present embodiment includes a small diameter part 141, a large diameter part 143, and an intermediate part 145. The small diameter part 141 has a substantially cylindrical shape and extends along the central axis A. The small diameter part 141 includes a deformed portion 42 and a ball holding chamber 46. The large diameter part 143 is positioned to the rear of the small diameter part 141 and has a substantially cylindrical shape. An outer diameter of the large diameter part 143 is larger than an outer diameter of the small diameter part 141. In addition, an inner diameter of the large diameter part 143 is larger than an inner diameter of the small diameter part 141.

[0068] The intermediate part 145 is positioned between the small diameter part 141 and the large diameter part 143. A front end of the intermediate part 145 is connected to a rear end of the small diameter part 141, and a rear end of the intermediate part 145 is connected to a front end of the large diameter part 143. In the present embodiment, the small diameter part 141, the intermediate part 145, and the large diameter part 143 are integrally formed. That is, the pipe 140 is formed of a single member. The intermediate part 145 is configured such that an outer diameter thereof and inner diameter thereof increase toward rear. Therefore, an outer peripheral surface and inner peripheral surface of the intermediate part 145 extend in directions inclined with respect to an axial direction da and a radial direction, so as to be directed radially outward as being directed rearward. In the present embodiment, in a cross section passing through the central axis A, the outer peripheral surface and inner peripheral surface of the intermediate part 145 linearly extend so as to be directed radially outward as being directed rearward.

[0069] The ballpoint pen 10 of the present embodiment includes a holding member 125 instead of the holding member 25 of the first embodiment. The holding member 125 has a through hole 26. A coupling portion between an ink stopper 15 and the holding member 125, and a coupling portion between a second guide member 23 and the holding member 125 are both configured similarly to those in the first embodiment. A rear end portion of the pipe 140 of the ballpoint pen tip 30 is attached to a step portion 127 provided on an outer periphery of a front end portion of the holding member 125. In particular, a rear end portion of the large diameter part 143 of the pipe 140 is attached to the step portion 127. As a result, the holding member 125 and the pipe 140 are coupled to each other.

[0070] In the present embodiment, entire small diameter part 51 and step portion 55 of the center core 50 are disposed in the small diameter part 141 of the pipe 140. In addition, a large diameter part 53 of the center core 50 is disposed so as to extend over the small diameter part 141, intermediate part 145, and large diameter part 143 of the pipe 140. That is, a part on a front side of the large diameter part 53 of the center core 50 is positioned in the small diameter part 141 of the pipe 140, and a part on a rear side of the large diameter part 53 of the center core 50 is positioned in the large diameter part 143 of the pipe 140. As illustrated in Fig. 10, in the present embodiment, a first region A1 and a second region A2 are defined in the small diameter part 141.

[0071] In addition, in the present embodiment, a third region A3 is defined in the intermediate part 145 and large diameter part 143 of the pipe 140. The third region A3 is a region between the front end of the intermediate part 145 and the front end of the holding member 125. The third region A3 is positioned to the rear of the second region A2. In particular, the third region A3 is positioned adjacent to the second region A2 and positioned to the rear of the second region A2. A part of the large diameter part 53 of the center core 50 is disposed in the third region A3. A cross-sectional area S 3 of an ink channel 60 in the third region A3 is larger than a cross-sectional area S 1 of the ink channel 60 in the first region A1 and a cross-sectional area S 2 of the ink channel 60 in the second region A2.

[0072] With the ballpoint pen 10 of the present embodiment also, because the cross-sectional area S 1 of the ink channel 60 in the first region A1 is larger than the cross-sectional area S 2 of the ink channel 60 in the second region A2, a sufficient amount of the ink can be held in the ink channel 60 in the first region A1. As a result, even when a writing speed with the ballpoint pen 10 is high, the ink can be sufficiently supplied from the ink channel 60 to the ball 32. Therefore, even when the writing speed with the ballpoint pen 10 is high, it is possible to sufficiently suppress the handwriting from being faint.

[0073] In addition, because the cross-sectional area S 2 of the ink channel 60 in the second region A2 is smaller than the cross-sectional area S 1 of the ink channel 60 in the first region A1, a large suction force is generated in the ink positioned in the second region A2 due to capillarity. With this large suction force, a sufficient amount of ink can flow from the ink storage part 12 toward the ball 32. As a result, the ink can be sufficiently supplied from the ink storage part 12 to the ball 32 particularly at a start of use of the ballpoint pen 10.

[0074] In addition, because the cross-sectional area S 3 of the ink channel 60 in the third region A3 is larger than the cross-sectional area S 1 of the ink channel 60 in the first region A1 and the cross-sectional area S 2 of the ink channel 60 in the second region A2, a more sufficient amount of the ink can be held in the ink channel 60 in the third region A3. As a result, the ink can be sufficiently and quickly supplied to the ink channel 60 in the second region A2. Therefore, even when the writing speed with the ballpoint pen 10 is high, it is possible to more effectively suppress handwriting from being faint.

[0075] Therefore, the ink can be sufficiently supplied to the ball 32 both at a start of use of the ballpoint pen 10 and during writing with the ballpoint pen 10.

Claims

1. A ballpoint pen comprising a ballpoint pen tip, the ballpoint pen tip includes: a pipe including a deformed portion and a ball holding chamber formed in front of the deformed portion; a ball disposed in the ball holding chamber; a center core at least a part of which is disposed in the pipe; a gap formed between the ball and a front end of the center core; and an ink channel formed between the center core and the pipe, wherein the ballpoint pen tip includes a first region and a second region positioned to rear of the first region, and a cross-sectional area of the ink channel in the first region is larger than a cross-sectional area of the ink channel in the second region.

2. The ballpoint pen according to claim 1, wherein the ink channel in the first region has a cylindrical shape extending along a central axis of the pipe, and the ink channel in the second region has a cylindrical shape extending along a central axis of the pipe.

3. The ballpoint pen according to claim 2, wherein an inner diameter of the ink channel in the first region is smaller than an inner diameter of the ink channel in the second region.

4. The ballpoint pen according to claim 1, wherein the center core includes a small diameter part disposed in the first region and a large diameter part disposed in the second region, and a diameter of the small diameter part is smaller than a diameter of the large diameter part.

5. The ballpoint pen according to claim 4, wherein a radius of the small diameter part is larger than a distance between a central axis of the pipe and a top portion of the deformed portion.

6. The ballpoint pen according to claim 4, wherein a step portion formed between the small diameter part and the large diameter part has a curved-surface shape protruding toward an inside of the center core.

7. The ballpoint pen according to claim 1, wherein at least a part of the first region is positioned to rear of a top portion of the deformed portion.

8. The ballpoint pen according to claim 7, wherein the entire first region is positioned to rear of a top portion of the deformed portion.

9. The ballpoint pen according to claim 1, wherein the front end of the center core is positioned to rear of a top portion of the deformed portion.

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