ballpoint pen

Abstract

This ballpoint pen (1) comprises: a barrel (2); a cylindrical tip (30) having a front edge (30b) at the front end thereof; a cylindrical body (70) disposed behind the first edge (30b); a ball receiving seat (71b) formed at the front end of the cylindrical body (70); a ball (40) held rotatably between the front edge (30b) and the ball receiving seat (71b); a restriction portion (10k) that restricts the rearward movement of the cylindrical body (70); and an elastic member (60) that urges the cylindrical body (70) forward, wherein the cylindrical body (70) has an elastic deformation portion (71d) made of a synthetic resin and has an ink passage (71t) uniformly formed along the axial direction, and the expression 1.02X<Y<1.30X is satisfied, where X denotes the outer diameter of the elastic deformation portion (71d) and Y denotes the minimum inner diameter of the tip 30.

Description

[Technical Field]

[0001] The present invention relates to a ballpoint pen. [Background technology]

[0002] JP2017-185774A discloses a ballpoint pen that can obtain an appropriate amount of ink ejection regardless of the magnitude of writing pressure, and can produce handwriting with varying width and intonation depending on the magnitude of writing pressure.

[0003] The ballpoint pen disclosed in JP2017-185774A comprises a front edge portion formed at the front end of a cylindrical body, a pressing member housed within the cylindrical body so as to be movable in the front-rear direction and having a ball receiving seat at its front end, a first restriction wall portion that restricts the forward movement of the pressing member, a second restriction wall portion that restricts the rearward movement of the pressing member, a ball rotatably held between the front edge portion and the receiving seat member, a first resilient member that urges the ball forward, and a second resilient member that urges the pressing member forward.When writing with weak writing pressure, the pressing member abuts against the first restriction wall portion and the first resilient member is compressed and deformed, so that the ball abuts against the ball receiving seat of the pressing member, and when writing with strong writing pressure, the first and second resilient bodies are compressed and deformed, so that the pressing member abuts against the second restriction wall portion, and therefore the amount of retraction of the ball can be changed depending on the strength of the writing pressure. Therefore, in the ballpoint pen of JP2017-185774A, the gap between the ball and the front edge changes depending on the writing pressure, so that when the writing pressure is low, the amount of ink ejected decreases, allowing for writing with a narrow line width, and when the writing pressure is high, the amount of ink ejected increases, allowing for writing with a wide line width. Furthermore, when writing with strong writing pressure, the pressing member abuts against the second restricting wall portion and cannot retract, so the gap between the ball and the front edge of the cylindrical body remains constant, resulting in a stable amount of ink ejection and enabling writing with a uniform thickness.

[0004] However, in the structure of the ballpoint pen of JP2017-185774A, when writing with an awareness of applying a strong writing pressure, there is a risk of applying too much writing pressure more than necessary. In this case, since the pressing member cannot retreat further due to the second restricting wall portion, the ball is strongly pressed against the ball receiving seat of the pressing member. For this reason, there is a risk that the wear of the ball and the ball receiving seat is promoted, or scratches are generated and the writing feel deteriorates.

[0005] Based on various prototypes and evaluations through intensive studies, the inventor of the present case has found that making the member having a ball receiving seat behind the ball elastically deformable is effective in reducing the load applied to the ball and the member having the ball receiving seat even under a strong writing pressure.

Summary of the Invention

[0006] The present invention has been made based on the above background, and an object thereof is to provide a ballpoint pen capable of changing the protruding amount of ink according to the writing pressure and arbitrarily changing the line width of the handwriting, and reducing the load applied to the ball and the ball receiving seat even when a strong writing pressure is applied.

[0007] [1] The ballpoint pen according to the present invention includes a shaft cylinder, a cylindrical tip at least partially disposed in the shaft cylinder and having an inward front edge portion at the front end, a cylindrical body disposed behind the front edge portion and at least partially housed in the tip so as to be movable back and forth, a ball receiving seat formed at the front end portion of the cylindrical body, a ball rotatably held between the front edge portion and the ball receiving seat, a restricting portion disposed behind the cylindrical body for restricting the backward movement of the cylindrical body, and an elastic member for biasing the cylindrical body forward. The cylindrical body has an elastically deformable portion formed of a synthetic resin and an ink passage formed uniformly along the axial direction. When the outer diameter of the elastically deformable portion is X and the minimum inner diameter of the inner peripheral portion of the tip at a position axially opposite to the elastically deformable portion is Y, it satisfies the relational expression of 1.02X < Y < 1.30X, which is a ballpoint pen.

[0008] [2] The ballpoint pen of this embodiment is a ballpoint pen of [1] that includes an outer tube attached to the rear of the tip, and an inner tube attached inside the outer tube and movable axially relative to the outer tube, and has an engaging portion on the outer surface of the inner tube for attaching it so that it can be moved axially relative to the outer tube, an engaging portion on the inner surface of the outer tube for engaging with the inner tube, and a regulating portion on the front of the inner tube.

[0009] [3] The ballpoint pen of this embodiment is the ballpoint pen of [2], in which the locking portion is a male thread portion and the locked portion is a female thread portion.

[0010] [4] The ballpoint pen of this embodiment is a ballpoint pen of [2] or [3], in which an inner cylinder seal portion is provided on the outer surface of the inner cylinder to provide an airtight seal between the inner cylinder and the outer cylinder, and an outer cylinder seal portion is provided on the inner surface of the outer cylinder to provide an airtight seal between the inner cylinder and the outer cylinder, and an airtight seal is provided between the inner cylinder seal portion and the outer cylinder seal portion.

[0011] [5] The ballpoint pen of this embodiment is the ballpoint pen of [4], in which the airtight seal 90 is an O-ring, the outer cylinder seal portion 20s is cylindrical, and the inner cylinder seal portion 10s has an annular groove in which the O-ring is accommodated.

[0012] [6] The ballpoint pen of this embodiment is any one of the ballpoint pens [1] to [5], in which at least a part of the cylindrical body 70 is formed by extrusion molding.

[0013] [7] The ballpoint pen of this embodiment is any one of the ballpoint pens [1] to [6], wherein the ink passage has, in cross section, a central inner hole 71c and a plurality of groove-like portions 71m connected to the central inner hole 71c and extending radially. [Effects of the Invention]

[0014] According to the present invention, it has been possible to provide a ballpoint pen that can change the amount of ink protrusion according to the writing pressure, thereby allowing the line width of the handwriting to be changed as desired, and that can reduce the load on the ball and ball receiving seat even when strong writing pressure is applied. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a vertical cross-sectional view of a ballpoint pen according to an embodiment of the present invention. [Figure 2] 2 is a vertical cross-sectional view showing the state in which the refill of the ballpoint pen of FIG. 1 is advanced. FIG. [Figure 3] 3 is an enlarged vertical cross-sectional view showing the front part of the ballpoint pen of FIG. 2. [Figure 4] FIG. 4 is an enlarged view of the vicinity of the ball in FIG. 3. [Figure 5] 2 is an enlarged vertical cross-sectional view showing the cylindrical body of the ballpoint pen of FIG. 1. FIG. [Figure 6] FIG. 6 is an enlarged end view showing the AA end face in FIG. 5. [Figure 7] 3 is an enlarged vertical cross-sectional view of the front part of the ballpoint pen of FIG. 2, showing the state when writing with a relatively low writing pressure. FIG. [Figure 8] FIG. 8 is an enlarged view of the vicinity of the ball in FIG. 7. [Figure 9] 8 is an enlarged vertical cross-sectional view of the front part of the ballpoint pen of FIG. 7, showing a state when writing is performed with a further increased writing pressure. FIG. [Figure 10] FIG. 10 is an enlarged view of the vicinity of the ball in FIG. 9. [Figure 11] 3 is a vertical cross-sectional view showing the ballpoint pen of FIG. 2 in a state where the outer cylinder body is rotated relative to the inner cylinder body and moved relatively forward. FIG. [Figure 12] 12 is an enlarged vertical cross-sectional view of the front part of the ballpoint pen of FIG. 11, showing the state when writing with a relatively low writing pressure. FIG. [Figure 13] FIG. 13 is an enlarged view of the vicinity of the ball in FIG. [Figure 14] 13 is an enlarged vertical cross-sectional view of the front part of the ballpoint pen of FIG. 12, showing a state in which writing is performed with a further increased writing pressure. FIG. [Figure 15]FIG. 15 is an enlarged view of the vicinity of the ball in FIG. [Figure 16] FIG. 10 is an enlarged view of the vicinity of the ball in a modified example of the ballpoint pen. [Figure 17] 17 is a view of the hollow tube of FIG. 16 as seen from the front end side. [Figure 18] FIG. 10 is an enlarged view of the vicinity of the ball in another modified example of the ballpoint pen. [Figure 19] 19 is a view of the hollow tube of FIG. 18 as seen from the front end side. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings attached to this specification, the scale and aspect ratios may be appropriately changed and exaggerated from those of the actual objects for the sake of convenience in illustration and understanding.

[0017] Terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​of lengths and angles, are not to be construed as being bound by strict meanings but should be interpreted to include a range within which similar functions can be expected.

[0018] In this specification, the direction in which the central axis of the ballpoint pen 1 extends (longitudinal direction) is referred to as the axial direction or longitudinal direction, the direction perpendicular to the axial direction is referred to as the radial direction, and the direction along the circumference around the central axis is referred to as the circumferential direction. Also, along the axial direction, the side where the front edge of the tip is located is referred to as the front, and the opposite direction is referred to as the rear. Also, along the radial direction, the direction toward the axis center (central axis) of the barrel is referred to as the inside or inward, and the opposite direction is referred to as the outside or outward.

[0019] (First embodiment) 1 is a longitudinal cross-sectional view of a ballpoint pen 1 in a first embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view showing a state in which the refill 3 of the ballpoint pen of FIG. 1 has been advanced, FIG. 3 is an enlarged longitudinal cross-sectional view showing the front part of the ballpoint pen of FIG. 2, FIG. 4 is an enlarged view of the vicinity of the ball of FIG. 3, FIG. 5 is an enlarged longitudinal cross-sectional view showing the cylindrical body of the ballpoint pen of FIG. 1, FIG. 6 is an enlarged end view showing the AA end face in FIG. 5, FIG. 7 is an enlarged longitudinal cross-sectional view of the front part of the ballpoint pen of FIG. 2 when writing with a relatively low writing pressure, FIG. 8 is an enlarged view of the vicinity of the ball of FIG. 7, and FIG. 9 is an enlarged view of the vicinity of the ball of the ballpoint pen of FIG. 7 when writing with a further low writing pressure. FIG. 10 is an enlarged vertical cross-sectional view of the front part showing the state when writing with increased pressure, FIG. 9 is an enlarged view of the vicinity of the ball, FIG. 11 is a vertical cross-sectional view of the ballpoint pen of FIG. 2 showing the state when the outer cylinder is rotated relative to the inner cylinder and moved forward relatively, FIG. 12 is an enlarged vertical cross-sectional view of the front part of the ballpoint pen of FIG. 11 showing the state when writing with a relatively low writing pressure, FIG. 13 is an enlarged view of the vicinity of the ball in FIG. 12, FIG. 14 is an enlarged vertical cross-sectional view of the front part of the ballpoint pen of FIG. 12 showing the state when writing with a further increased writing pressure, and FIG. 15 is an enlarged view of the vicinity of the ball in FIG. 14.

[0020] The ballpoint pen 1 of this embodiment shown in Figure 1 is a retractable ballpoint pen and includes a barrel 2 with an opening at its front end. A refill 3 that is movable in the axial direction of the barrel 2 is replaceably housed inside the barrel 2. The refill 3 has an ink storage tube 80 at its rear that stores writing ink, and an inner cylinder 10 is fixed to the front end of the ink storage tube 80. A tip 30 is connected to the inner cylinder 10 via an outer cylinder 20, as described below, and the tip 30 can be protruded and retracted from the opening of the barrel 2 as the refill 3 moves.

[0021] The retraction mechanism (not shown) of this embodiment is a rear-end knock type retraction mechanism using a rotary cam mechanism. The retraction mechanism includes a cam portion formed on the inner surface of the rear of the barrel 2, a rotating member that engages with the cam portion and abuts against the rear end of the refill 3, an operating portion 4 that engages with the rotating member and protrudes from the rear opening of the barrel 2, and a coil spring 5 (e.g., a compression coil spring) that is housed in the barrel 2 and biases the refill 3 rearward.

[0022] Furthermore, the retraction mechanism of this embodiment is a double-knock type in which the operating unit 4 is pressed forward for both the pen tip extension operation and the pen tip retraction operation. Specifically, when the operating unit 4 is pressed forward in the state shown in FIG. 1 in which the refill 3 is retracted into the barrel 2, the refill 3 is moved forward, and the tip 30 connected to the front portion of the outer barrel 20 protrudes from the front opening of the barrel 2, as shown in FIG. 2. This protruding state is maintained by the engagement between a cam portion (not shown) and a rotating member. When the operating unit 4 is pressed forward with the tip 30 protruding (as shown in FIG. 2), the engagement between the cam portion and the rotating member is released. As a result, the refill 3 is returned to the rear side by the action of the coil spring 5, and the tip 30 retracts from the front opening of the barrel 2.

[0023] 3 to 15, the outer cylindrical body 20 is threadedly engaged (one embodiment of attachment) with the front part of the inner cylindrical body 10. Specifically, a male threaded portion 10t (one embodiment of a locking portion) for threadingly engaging with the outer cylindrical body 20 is provided on the outer surface of the inner cylindrical body 10, and a female threaded portion 20t (one embodiment of a locked portion) for threadingly engaging with the inner cylindrical body 10 is provided on the inner surface of the outer cylindrical body 20, and the male threaded portion 10t and the female threaded portion 20t are threadedly engaged with each other.

[0024] As a result, the inner cylinder 10 and the outer cylinder 20 can be rotated relative to each other, thereby adjusting the relative positions in the axial direction.

[0025] In addition, an inner cylinder seal portion 10s is provided on the outer surface of the inner cylinder 10 to provide an airtight seal between it and the outer cylinder 20, and an outer cylinder seal portion 20s is provided on the inner surface of the outer cylinder 20 to provide an airtight seal between it and the inner cylinder 10, providing an airtight seal between the two.

[0026] In this embodiment, the inner cylinder seal portion 10s and the outer cylinder seal portion 20s are located rearward of the male thread portion 10t and the female thread portion 20t, respectively. The outer cylinder seal portion 20s has a cylindrical surface. An annular groove is provided in the inner cylinder seal portion 10s. An O-ring 90 made of, for example, nitrile rubber is provided in the annular groove as an airtight seal. This prevents ink flowing inside the inner cylinder 10 from leaking to the outside. Furthermore, by accommodating the O-ring in the annular groove, the O-ring can be prevented from falling off and an airtight state can be easily maintained even when the outer cylinder 20 is moved axially relative to the inner cylinder 10.

[0027] A tip 30 is connected to the front side of the outer cylindrical body 20, and holds a ball 40 at its front end.

[0028] The tip 30 has a front edge 30b that protrudes inward at the front end of the tip 30 and is capable of making annular contact with a portion of the front side of the ball 40. This allows the tip 30 to function as a holder for holding the ball 40. The size and shape of the front edge 30b are selected according to the size of the ball 40. In this embodiment, the diameter of the ball 40 is φ0.5 mm, so the inner diameter of the tip of the front edge 30b is φ0.485 mm. The inner surface of the front edge 30b is shaped like a truncated cone.

[0029] A cylindrical body 70 abutting the rear side of the ball 40 extends in the axial direction of the tip 30. As shown in FIG. 3, the cylindrical body 70 is composed of a cylindrical hollow tube 71 made of synthetic resin and a cylindrical connecting tube 72 press-fitted into the rear portion of the hollow tube 71. The rear end of the connecting tube 72 of the cylindrical body 70 is constantly abutting against a coil spring 60 (an example of an elastic member). The coil spring 60 is housed inside the inner cylindrical body 10 and extends in the axial direction, with the rear end of the coil spring 60 abutting against an inner step 10n of the inner cylindrical body 10. This urges the ball 40 forward by the repulsive force of the coil spring 60, improving the seal between the ball 40 and the front edge 30b formed at the front end of the tip 30, and preventing the ink at the writing tip (pen tip) from drying out.

[0030] Here, a clearance C1 remains between the rear surface of the flange portion 72f of the connecting tube 72, which can abut against the front end of the coil spring 60, and the restricting portion 10k at the front end of the inner cylindrical body 10. In the state shown in FIG. 3, the size of the clearance C1 is relatively small (0.02 mm). This clearance C1 disappears when the cylindrical body 70 retracts due to the writing pressure applied during writing, causing the flange portion 72f to abut against the restricting portion 10k (see FIG. 7). At this time, the appropriate repulsive force of the coil spring 60 stably supports the ball 40 circumferentially at the tip of the hollow tube 71 via the connecting tube 72, providing a pleasant writing experience.

[0031] The hollow tube 71 (cylindrical body 70) has a central bore 71c that is generally cylindrical and penetrates from front to back. As shown in Figure 6, the central bore 71c is connected to multiple (four in this embodiment) grooves 71m that extend radially from the central bore 71c. The central bore 71c and the multiple grooves 71m function as ink passages 71t through which ink passes and is supplied to the ball 40. A ball seat 71b that abuts against and supports the ball 40 is provided at the tip of the hollow tube 71. The groove width of the grooves 71m is narrower than the diameter of the central bore 71c, so that the capillary force acting on the ink in the grooves 71m is strong. This improves the fluidity of the ink, and the ink that passes through groove portion 71m is supplied to ball 40. Even if the amount of ink ejected from the gap between ball 40 and front edge portion 30b increases, sufficient ink is still supplied to ball 40 and the front end of the tip. Hollow tube 71 has, for example, an outer diameter of 0.45 mm, an inner diameter (central bore 71c) of 0.20 mm, and a length of 12 mm. Hollow tube 71 is made of a synthetic resin. Suitable synthetic resins include polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), polyacetal, polyamide, and nylon. PEEK is particularly preferred because it has excellent mechanical strength, such as abrasion resistance and impact resistance, and also has good dimensional stability. Furthermore, the hollow tube 71 is formed by extrusion molding, which allows the central inner hole 71c and groove-like portion 71m of the inner diameter portion of the hollow tube 71 and the outer diameter portion to be formed uniformly along the axial direction, and allows for inexpensive production.

[0032] Since the entire hollow tube 71 is made of synthetic resin, when an unduly high writing pressure is transmitted to the hollow tube 71 via the ball 40 during writing, it functions as an elastic deformation part 71d that elastically deforms within a range where it does not plastically deform. In the present embodiment, when the elastic deformation part 71d elastically deforms, the central part of the hollow tube 71 protruding from the front end of the connecting cylinder 72 protrudes in the axial diameter direction (deforms in an arcuate shape), thereby absorbing the writing pressure. For this reason, since a gap is required in the inner peripheral part 30a of the tip 30 for the hollow tube 71 of the cylindrical body 70 to flex in the axial diameter direction, as shown in FIG. 3, when the outer diameter of the elastic deformation part 71d of the cylindrical body 70 is X and the minimum inner diameter of the inner peripheral part 30a of the tip 30 at a position axially opposite to the elastic deformation part 71d is Y, it is preferable that the relational expression 1.02X < Y < 1.30X holds. Thereby, the elastic deformation part 71d of the cylindrical body 70 can elastically deform and flex in the axial diameter direction. Further, when the elastic deformation part 71d elastically deforms, the elastic deformation part 71d and the inner surface of the tip 30 are restricted from contacting and deforming more than a certain level, thereby preventing plastic deformation of the elastic deformation part 71d and reducing the influence on the central inner hole 71c and the groove-like part 71m, thus preventing the ink passage from being blocked. And a gap is formed between the inner peripheral part 30a of the tip 30 and the hollow tube 71, and the gap functions as an ink parallel passage 31 through which the ink flows. In the present embodiment, since the minimum inner diameter Y of the tip 30 is formed to be 0.480 mm and the outer diameter X of the elastic deformation part 71d of the cylindrical body 70 is formed to be 0.45 mm, the above relational expression is satisfied.

[0033] The internal spaces of the inner cylindrical body 10, the outer cylindrical body 20, the tip 30, and the cylindrical body 70 serve as an ink supply path leading to the ball 40. The inner cylindrical body 10 has an ink connection path 50 leading from the inside of the ink storage cylinder 80 to the inside of the outer cylindrical body 20, and a coil spring 60 is accommodated in the ink connection path 50.

[0034] The ink passage 71t of the hollow tube 71 communicates with the ink communication passage 50 via the inner hole of the connecting tube 72, thereby allowing ink in the ink reservoir 80 to be supplied to the ball 40 via the ink communication passage 50. At the same time, an ink communication passage 73 is formed between the hollow tube 71 and the connecting tube 72 of the cylindrical body 70, and the ink communication passage 73 connects the ink communication passage 50 with the ink parallel passage 31. As a result, the ink parallel passage 31 also becomes part of the ink supply passage, and ink in the ink reservoir 80 is supplied via the ink communication passage 50 and the ink communication passage 73. The ink that has passed through the ink passage 71t and the ink parallel passage 31 is then supplied to the ball 40 from the rear side and is ejected from an ink supply gap between the ball 40 and the front edge portion 30b, which will be described later, to write on a writing surface such as paper. In this embodiment, ink is supplied to the ball 40, which is the writing tip, from multiple routes, so that even if the ink supply gap changes during writing and the amount of ink ejected temporarily increases, as described below, sufficient ink can be supplied without interruption.

[0035] The ballpoint pen 1 configured as above operates as follows.

[0036] 7, when ball 40 is brought into contact with writing surface P and subjected to writing pressure during writing, ball 40 retracts tubular body 70 (hollow tube 71 and connecting tube 72) against the repulsive force of coil spring 60, and the clearance between flange portion 72f of connecting tube 72 and restricting portion 10k of inner cylindrical body 10 disappears (they come into contact). At this time, the appropriate repulsive force of coil spring 60 stably supports ball 40 circumferentially on ball receiving seat 71b of hollow tube 71 via connecting tube 72, providing a good writing feel.

[0037] However, because the size of the clearance has been adjusted to be relatively small, ball 40 only penetrates to a relatively shallow position relative to front edge 30b, which is the narrowed portion at the front end of tip 30. As a result, as shown in Figure 8, the ink supply gap S1 formed between ball 40 and front edge 30b becomes small, allowing writing with a relatively narrow line width on writing surface P.

[0038] 7, as shown in Fig. 9, the cylindrical body 70 cannot move back because it is in contact with the restricting portion 10k of the inner cylindrical body 10, and so the elastically deforming portion 71d of the hollow tube 71 made of synthetic resin deforms so as to bend (arcuate) in the axial direction, and as a result, the overall axial length of the hollow tube 71 is shortened by the amount of bending, so that the ball 40 penetrates relatively deep into the front edge portion 30b. As a result, as shown in Fig. 10, the ink supply gap S2 between the ball 40 and the front edge portion 30b becomes larger than the ink supply gap S1 in Fig. 7, and the amount of ink discharged from the ink supply gap S2 increases, allowing writing with a relatively thick line width on the writing surface P. Furthermore, even if one does not intend to write with a relatively thick line width, it is conceivable that the writing pressure may temporarily increase when writing. Even in this case, the elastic deformation portion 71d of the cylindrical body 70 will flex, thereby reducing excessive load on the ball 40 and the ball receiving seat 71b of the cylindrical body 70 and preventing scratches, deformation, and wear, and the appropriate flex deformation of the elastic deformation portion 71d will provide a good writing feel even if the writing pressure varies when writing.

[0039] Furthermore, by changing the size of the clearance, the ink supply gap formed between the ball 40 and the leading edge 30b can be changed as desired, and the line width of the handwriting can be changed accordingly.

[0040] Specifically, by rotating the outer tube body 20 (with the tip 30) relative to the inner tube body 10 from the state shown in Figure 3 and changing the threaded state (threaded position) between the male thread portion 10t and the female thread portion 20t to the state shown in Figure 11, the clearance can be increased from C1 to C2.

[0041] In the state shown in FIG. 11, the size of the clearance C2 is relatively large (0.10 mm). This clearance C2 also disappears when the hollow tube 71 and the connecting tube 72 retract due to the writing pressure during writing and abut against the restricting portion 10k (see FIG. 12). At this time, as shown in FIG. 13, the ink supply gap S3 becomes even larger than the ink supply gap S1 in FIG. 8 and the ink supply gap S2 in FIG. 10, allowing writing with a thicker line width on the writing surface P. Then, due to the appropriate repulsive force of the coil spring 60, the ball 40 is stably supported circumferentially at the tip of the hollow tube 71 via the connecting tube 72, providing a good writing feel.

[0042] Furthermore, when further writing pressure is applied from the state shown in Figure 12, as shown in Figure 14, cylindrical body 70 cannot retract because it abuts against restricting portion 10k of inner cylindrical body 10, so elastic deformation portion 71d of hollow tube 71 made of synthetic resin deforms so as to bend in the axial direction, and as a result, the overall axial length of hollow tube 71 is shortened by the amount of bending, so that ball 40 penetrates even deeper into front edge 30b. As a result, as shown in Figure 15, ink supply gap S4 between ball 40 and front edge 30b becomes larger than ink supply gap S3 in Figure 13, and the amount of ink discharged from the tip 30 increases, allowing for writing with even thicker lines.

[0043] As described above, in this embodiment, the amount of clearance that allows the ball 40 to retract can be increased or decreased by rotating the outer cylinder 20 relative to the inner cylinder 10, and therefore the ink discharge amount can be adjusted by adjusting the ink supply gap at the front end of the tip 30, thereby changing the line width of the handwriting. In addition, the ink supply gap can also be adjusted by adjusting the amount of deformation of the elastic deformation portion 71d of the cylindrical body 70 by adjusting the writing pressure during writing, so it is possible to provide a ballpoint pen that allows the user to finely adjust the line width of the handwriting to suit their preferences.

[0044] Also, in the present embodiment, even if the ball receiving seat 71b at the front end of the cylindrical body 70 (hollow tube 71) that abuts on the ball 40 due to the rotation of the ball 40 during writing wears out, by rotating the outer cylinder 2 with respect to the inner cylinder 10 by the amount of wear, the repulsive force acting on the ball 40 by the coil spring 60 can be kept constant in a state where no writing pressure is applied. Therefore, writing with the same writing feeling can be maintained.

[0045] Furthermore, even when writing is performed in a state where the clearance disappears by the contact of the flange portion 72f and the regulating portion 10k due to the backward movement of the cylindrical body 70 by the writing pressure during writing, the elastic deformation portion 71d of the cylindrical body 70 elastically deforms, thereby reducing the load applied to the ball 40 and the ball receiving seat 71b. Also, since the ball 40 is supported by the appropriate bending deformation of the elastic deformation portion 71d, a good writing feeling can be provided even if the writing pressure varies.

[0046] The ballpoint pen 1 of the present embodiment includes a shaft cylinder 2, a cylindrical tip 30 at least partially disposed within the shaft cylinder 2 and having an inward front edge portion 30b at the front end, a cylindrical body 70 disposed behind the front edge portion 30b and at least partially housed within the tip 30 so as to be movable back and forth, a ball receiving seat 71b formed at the front end portion of the cylindrical body 70, a ball 40 rotatably held between the front edge portion 30b and the ball receiving seat 71b, a regulating portion 10k disposed behind the cylindrical body 70 for regulating the backward movement of the cylindrical body 70, and an elastic member 60 for biasing the cylindrical body 70 forward. The cylindrical body 70 has an elastic deformation portion 71d formed of a synthetic resin and an ink passage 71t formed uniformly along the axial direction. When the outer diameter of the elastic deformation portion 71d is X and the minimum inner diameter of the inner peripheral portion of the tip 30 at a position axially opposite to the elastic deformation portion 71d is Y, the relational expression 1.02X < Y < 1.30X is satisfied. [?]

[0047] [?] [?]According to such a ballpoint pen 1, since the cylindrical body 70 is housed in the chip 30 so as to be movable back and forth, when the ball 40 receives writing pressure during writing, the ball 40 presses the ball seat 71b backward, and thereby the cylindrical body 70 retreats against the elastic force of the elastic member 60, so that a gap is generated between the ball 40 and the front edge portion of the cylindrical body 70. For this reason, the ink discharge amount during writing can be increased, and it is possible to adjust the line width of the handwriting according to the strength of the writing pressure. Further, the cylindrical body 70 has an elastically deformable portion 71d formed of a synthetic resin. Further, when the outer diameter of the elastically deformable portion 71d is X and the minimum inner diameter of the inner peripheral portion of the chip 30 at a position facing the elastically deformable portion 71d in the axial direction is Y, by satisfying the relational expression of 1.02X < Y < 1.30X, a gap for the elastically deformable portion 71d to deform when writing pressure is applied is formed between the elastically deformable portion 71d and the inner peripheral portion of the chip 30, and the deformation of the elastically deformable portion 71d can be restricted so as not to deform more than a certain amount. For this reason, even if excessive writing pressure is applied to the cylindrical body 70 via the ball 40, the load applied to the ball 40 and the ball seat 71b can be reduced by the elastic deformation of the cylindrical body 70, and it is possible to prevent the elastically deformable portion 71d of the cylindrical body 70 from deforming too much and undergoing plastic deformation. Incidentally, the elastically deformable portion 71d may function as the elastically deformable portion 71d for the entire cylindrical body 70, or a part of the cylindrical body 70 may function as the elastically deformable portion 71d. And, as long as the ink passage is not blocked by the deformation, the deformation of the elastically deformable portion 71d may be such that the entire or a part of the cylindrical body 70 is deformed so as to warp in the axial diameter direction, or may be deformed so as to bulge in the axial diameter direction.

[0048] As the material constituting the cylindrical body 70 of the present invention, PEEK, PTFE, polyacetal, polyamide or nylon, etc. can be preferably used. In particular, when PEEK is used, it is excellent in mechanical strength such as wear resistance and impact resistance, and has good dimensional stability, so it can be more preferably used. Further, in order to improve the mechanical strength of the material and make it last longer as a writing body, it may be compounded and strengthened with glass fiber, carbon fiber, etc., a material excellent in self-lubricity such as graphite may be added, or a hard film such as a fluororesin or diamond-like carbon may be coated.

[0049] The ballpoint pen 1 of this embodiment comprises an outer cylinder 20 attached to the rear of the tip 30, and an inner cylinder 10 attached inside the outer cylinder 20 and movable axially relative to the outer cylinder 20, with an engaging portion 10t provided on the outer surface of the inner cylinder 10 for attachment so as to be movable axially relative to the outer cylinder 20, an engaging portion 20t provided on the inner surface of the outer cylinder 20 for engaging with the inner cylinder 10, and a regulating portion 10k provided at the front of the inner cylinder 10.

[0050] According to this ballpoint pen 1, the outer cylinder 20 to which the tip 30 is attached can be moved relative to the inner cylinder 10 in the axial direction, and the position of the restricting portion 10k can be moved back and forth relative to the tip 30, thereby adjusting the distance that the cylindrical body 70 housed inside the tip 30 can be retracted. Therefore, the amount of retraction of the ball 40 that abuts against the ball receiving seat 71b of the cylindrical body 70 can also be adjusted, and the amount of retraction of the ball 40 can be adjusted to a constant amount even if the ball receiving seat 71b of the cylindrical body 70 wears due to the rotation of the ball 40 during writing.

[0051] In the ballpoint pen 1 of this embodiment, the locking portion 10t is a male screw portion, and the locked portion 20t is a female screw portion.

[0052] According to such a ballpoint pen 1, the outer cylinder 20 is fixed to the inner cylinder 10 with a screw, so that the amount of retraction of the ball 40 can be easily adjusted by rotating the outer cylinder 20 relative to the inner cylinder 10.

[0053] In the ballpoint pen 1 of this embodiment, an inner cylinder seal portion 10s is provided on the outer surface of the inner cylinder 10 to provide an airtight seal between it and the outer cylinder 20, and an outer cylinder seal portion 20s is provided on the inner surface of the outer cylinder 20 to provide an airtight seal between it and the inner cylinder 10, and an airtight seal 90 is provided between the inner cylinder seal portion 10s and the outer cylinder seal portion 20s.

[0054] According to such a ballpoint pen 1, the airtight seal 90 can prevent the ink flowing inside the inner cylinder 10 from leaking out to the outside.

[0055] In the ballpoint pen 1 of this embodiment, the airtight seal 90 is an O-ring, the outer cylinder seal portion 20s has a cylindrical surface, and the inner cylinder seal portion 10s is provided with an annular groove in which the O-ring is housed.

[0056] According to such a ballpoint pen 1, an O-ring is housed in the annular groove, so that even if the outer cylinder body 20 is moved axially relative to the inner cylinder body 10, the O-ring is prevented from falling off, and an airtight state between the inner cylinder body 10 and the outer cylinder body 20 can be easily maintained.

[0057] In the ballpoint pen 1 of this embodiment, at least a part of the cylindrical body 70 is formed by extrusion molding.

[0058] Such a ballpoint pen 1 is preferable because it is easy to form the ink passage inside the cylindrical body 70 in a uniform state along the axial direction.

[0059] In the ballpoint pen 1 of this embodiment, the ink passage 71t has, in cross section, a central inner hole 71c and a plurality of groove-like portions 71m that are connected to the central inner hole 71c and extend radially.

[0060] With this ballpoint pen 1, the capillary force inside the cylindrical body 70 is strengthened by the groove-like portions 71m, thereby improving the fluidity of the ink inside the cylindrical body 70. Furthermore, since ink is supplied not only from the central inner hole 71c located in the center of the ball 40 but also from the radially formed groove-like portions 71m when writing, even if a strong writing pressure is applied to increase the gap between the ball 40 and the tip edge and increase the amount of ink ejected, it is possible to prevent the ink from running out and the handwriting from becoming smeared.

[0061] Next, a modified example of the ballpoint pen 1 will be described with reference to Figures 16 and 17. Figure 16 is an enlarged view of the vicinity of the ball 40 in the modified example of the ballpoint pen 1, and Figure 17 is a view of the hollow tube 71 in Figure 16 as seen from the front end side.

[0062] In this modification, the minimum inner diameter Y of the inner circumferential portion 30a of the tip 30 at a position facing the elastic deformation portion 71d in the axial direction is larger than the diameter of the ball 40. In addition, the outer diameter X of the elastic deformation portion 71d of the cylindrical body 70 is larger than the diameter of the ball 40. The distance Z between the inner walls 71m1 of the groove-like portion 71m of the cylindrical body 70 is smaller than the diameter of the ball 40. The inner diameter of the central inner hole 71c of the cylindrical body 70 is smaller than the diameter of the ball 40.

[0063] The diameter of the ball 40 may be, for example, 0.5 mm. The inner diameter of the central inner hole 71c of the cylindrical body 70 may be, for example, 0.32 mm. The outer diameter X of the elastically deformable portion 71d may be, for example, 0.55 mm. The minimum inner diameter Y of the inner peripheral portion 30a of the tip 30 may be, for example, 0.58 mm. The distance Z between the inner walls 71m1 of the groove-shaped portion 71m may be 0.45 mm. In this case, Y≈1.055X.

[0064] Next, a modified example of the ballpoint pen 1 will be described with reference to Figures 18 and 19. Figure 18 is an enlarged view of the vicinity of the ball 40 in another modified example of the ballpoint pen 1, and Figure 19 is a view of the hollow tube 71 in Figure 18 as seen from the front end side.

[0065] In this modification, the minimum inner diameter Y of the inner circumferential portion 30a of the tip 30 at a position facing the elastic deformation portion 71d in the axial direction is larger than the diameter of the ball 40. In addition, the outer diameter X of the elastic deformation portion 71d of the cylindrical body 70 is larger than the diameter of the ball 40. The distance Z between the inner walls 71m1 of the groove-like portion 71m of the cylindrical body 70 is larger than the diameter of the ball 40. The inner diameter of the central inner hole 71c of the cylindrical body 70 is smaller than the diameter of the ball 40.

[0066] The diameter of the ball 40 may be, for example, 0.5 mm. The inner diameter of the central inner hole 71c of the cylindrical body 70 may be, for example, 0.39 mm. The outer diameter X of the elastic deformation part 71d may be, for example, 0.65 mm. The minimum inner diameter Y of the inner peripheral part 30a of the chip 30 may be, for example, 0.68 mm. The distance Z between the back walls 71m1 of the groove-shaped part 71m may be 0.55 mm. In this case, Y≒1.046X.

[0067] In the example shown in FIGS. 16 and 18, the ball seat 71b has a chamfered shape. In particular, in the illustrated example, the ball seat 71b has a spherical shape along the outer shape of the ball 40. Thereby, when the ball 40 and the ball seat 71b slide relative to each other, wear of the ball seat 71b is suppressed.

[0068] Also in the example shown in FIGS. 16 to 19, when the outer diameter of the elastic deformation part 71d is X and the minimum inner diameter of the inner peripheral part of the chip 30 at a position axially opposite to the elastic deformation part 71d is Y, the relational expression of 1.02X < Y < 1.30X is satisfied. Therefore, the same effect as the example described with reference to FIGS. 1 to 15 can be exhibited.

[0069] In the example shown in FIGS. 16 to 19, since the outer diameter X of the hollow tube 71 is larger than the diameter of the ball 40, it is possible to increase the size (cross-sectional area) of the ink passage 71t formed in the hollow tube 71. In this case, the amount of ink supplied from the hollow tube 71 to the ball 40 can be increased. Thereby, the width of the handwriting formed by the ballpoint pen 1 can be thickened or the handwriting can be darkened. In particular, when the outer diameter X of the hollow tube 71 is larger than the diameter of the ball 40, the degree of freedom in designing the dimensions and shape of the ink passage 71t can be improved. For example, the degree of freedom in designing the dimensions and shape of the central inner hole 71c and the groove-shaped part 71m included in the ink passage 71t can be improved.

[0070] Furthermore, hollow tube 71 is biased forward by coil spring 60 via connecting tube 72. As a result, hollow tube 71 is subjected to an axial compressive force. In the example shown in FIGS. 16 to 19, the outer diameter X of hollow tube 71 is larger than the diameter of ball 40, so the thickness of the wall of hollow tube 71 can be increased. This ensures sufficient strength of hollow tube 71. This makes it possible to prevent unintended deformation, such as buckling, of hollow tube 71 due to the compressive force generated in hollow tube 71 by being biased by coil spring 60.

Claims

1. A shaft cylinder and a cylindrical tip at least partially disposed within the barrel and having an inwardly facing front edge at its front end; a cylindrical body disposed rearward of the front end edge portion, at least a portion of which is accommodated within the tip so as to be movable back and forth; a ball receiving seat formed at the front end of the cylindrical body; a ball rotatably held between the front edge and the ball seat; a restricting portion disposed behind the cylindrical body and restricting rearward movement of the cylindrical body; an elastic member that biases the cylindrical body forward, the cylindrical body has an elastically deformable portion made of synthetic resin and an ink passage formed uniformly along the axial direction, A ballpoint pen characterized in that the relationship 1.02X<Y<1.30X is satisfied, where X is the outer diameter of the elastically deforming portion and Y is the minimum inner diameter of the inner periphery of the tip at a position opposite to the elastically deforming portion in the axial direction.

2. an outer cylindrical body attached to a rear portion of the tip; and an inner cylindrical body attached inside the outer cylindrical body and movable relative to the outer cylindrical body in the axial direction, an engaging portion is provided on an outer surface of the inner cylindrical body to be attached to the outer cylindrical body so as to be movable relative to the outer cylindrical body in the axial direction; an inner surface of the outer cylindrical body is provided with a locking portion for locking with the inner cylindrical body; 2. The ballpoint pen according to claim 1, wherein the restricting portion is provided at a front portion of the inner cylinder.

3. the locking portion is a male thread portion, The locked portion is a female screw portion.

3. The ballpoint pen according to claim 2.

4. an inner cylinder seal portion is provided on the outer surface of the inner cylinder to provide an airtight seal between the inner cylinder and the outer cylinder; an outer cylinder seal portion for airtightly sealing the outer cylinder with the inner cylinder, 3. The ballpoint pen according to claim 2, wherein an airtight seal is provided between the inner barrel seal and the outer barrel seal.

5. the airtight seal is an O-ring; The outer cylinder seal portion has a cylindrical surface shape, 5. The ballpoint pen according to claim 4, wherein the inner cylindrical seal portion is provided with an annular groove for accommodating the O-ring.

6. 2. The ballpoint pen according to claim 1, wherein at least a portion of the cylindrical body is formed by extrusion molding.

7. 7. The ballpoint pen according to claim 1, wherein the ink passage has, in cross section, a central bore and a plurality of grooves that are connected to the central bore and extend radially.

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