JP6084380B2 - Intrusion ballpoint pen - Google Patents

Description

  The present invention relates to a retractable ballpoint pen including a retracting mechanism that allows a tip end portion of a ballpoint pen tip to protrude from a tip opening portion of a shaft tube.

  Conventionally, a ballpoint pen tip formed by rotatably holding a ball is attached to the tip of an ink storage cylinder directly or via a chip holder, and ink for ballpoint pen is directly stored in the ink storage cylinder. The ballpoint pen refill is stored in the shaft tube by being biased toward the rear end side of the shaft tube by a coil spring, and the tip portion of the ballpoint pen tip can be protruded and retracted from the tip opening portion of the shaft tube. It is well known for the penetrating ballpoint pen.

  In such a retractable ball-point pen tip, as disclosed in Japanese Patent Application Laid-Open No. 07-204567, “Applicator”, a coil spring is provided at the back of the ball, and the ball is pressed against the inner wall of the tip of the tip to cause ink leakage from the tip of the tip. Many structures have been proposed that prevent this.

  Also, many proposals have been made to increase the vertical clearance of a ball for the purpose of increasing the amount of ink consumption as disclosed in JP-A-06-15218 “Method for producing applicator”.

Japanese Patent Laid-Open No. 07-204567 Japanese Patent Laid-Open No. 06-15218

  However, when used in a retractable ballpoint pen, the tip of the tip may be dented due to an impact when dropped from the desk onto the floor. This dent is intended to increase the amount of ink supplied. If the longitudinal clearance of the ball is increased, ink leakage may occur even if the ball is pressed against the inner wall of the tip end of the chip. In particular, even with a dent of the same size, the smaller the ball, such as φ0.4 mm or less, the smaller the caulking inner diameter and the caulking outer diameter tend to be, and the greater the influence of the dent on the inner diameter.

In order to solve the above-described problem, the present invention provides a ballpoint pen tip which is formed by holding a ball having a diameter of 0.4 mm or less at the tip of an ink storage cylinder by a caulking portion at the tip tip, or a tip holder. A ballpoint pen refill that contains thermochromic ink directly in the ink storage cylinder is urged and stored in the axial cylinder by the coil spring toward the rear end side of the axial cylinder, A retractable ballpoint pen comprising a retracting mechanism that allows the tip of the ballpoint pen tip to protrude from the tip opening of the shaft tube by operating an operation part of an operating body provided on the shaft tube, the rear end of the barrel, and frictional handwriting of the thermochromic ink, the handwriting of the thermochromic ink at a frictional heat generated when possible thermochromic, Shore a hardness of 40 or more, 100 or less rubber Wear-like elasticity A coil spring that presses the ball against the inner wall of the tip of the tip with a pressing force higher than the total weight of the retractable ballpoint pen, and is arranged in the longitudinal direction of the ball. The clearance is 30 to 40 μm, the caulking part outer diameter is 1.0 to 1.2 times the ball diameter, and the operation part is composed of a plate piece provided with a transparent or translucent hole, and the shaft cylinder When projecting outwardly from the outer peripheral surface of the rear end portion, the tangent line between the friction body and the operation portion faces the friction body downward, and the axis of the shaft cylinder is perpendicular to the writing surface. The angle from the writing surface is 60 degrees or more, and the position of the center of gravity in a state where the ball-point pen tip protrudes is located in the middle of the writing instrument or in the rear thereof.

  By the way, when verifying the phenomenon that the writing instrument falls from the desk, the hand holding the writing instrument may slip and drop, but most of them are written on the desk with the hand, elbow, book or notebook. It hits and falls.

  The present invention has been made in view of these prior arts, and it is difficult to make a dent on the tip of the tip due to an impact when a writing instrument placed sideways on a desk is accidentally dropped, and stable ink outflow. The object is to provide a retractable ballpoint pen capable of obtaining a quantity.

In order to solve the above-described problem, the present invention provides a ballpoint pen tip which is formed by holding a ball having a diameter of 0.4 mm or less at the tip of an ink storage cylinder by a caulking portion at the tip tip, or a tip holder. A ballpoint pen refill that contains thermochromic ink directly in the ink storage cylinder is urged and stored in the axial cylinder by the coil spring toward the rear end side of the axial cylinder, A retractable ballpoint pen comprising a retracting mechanism that allows the tip of the ballpoint pen tip to protrude from the tip opening of the shaft tube by operating an operation part of an operating body provided on the shaft tube, Rubbing the handwriting of the thermochromic ink on the rear end portion of the shaft cylinder, comprising a friction body having rubber-like elasticity capable of thermally discoloring the handwriting of the thermochromic ink by the frictional heat generated at that time, Behind the ball, front A coil spring that presses the ball on the inner wall of the tip of the tip with a pressing force higher than the total weight of the retractable ballpoint pen is disposed, and the vertical clearance of the ball is 30 to 40 μm, and the caulking portion outer diameter is The center of gravity in the state where the ball-point pen tip protrudes is located at the middle part of the writing instrument or at the rear thereof.
In the present invention, “front” indicates the ball-point pen tip side in the longitudinal direction of the pen writing instrument, and “rear” indicates the friction body side. Moreover, the intermediate part of the writing instrument full length is not limited to the position equidistant from both ends of the writing instrument full length, but includes the vicinity thereof.

  The total weight of the retractable ballpoint pen is 10 g or less.

  Further, the operation portion of the operation body is provided to project outward from the outer peripheral surface of the shaft cylinder, and the maximum circumferential width of the operation portion is made smaller than the maximum circumferential width of the friction body, The pressing force of the coil spring that urges the ball-point pen refill toward the rear end side of the shaft tube is 100 to 200 g.

  According to the first configuration of the present invention, it is a retractable ballpoint pen using a ball of φ0.4 mm or less, and the handwriting of the thermochromic ink is rubbed against the rear end portion of the shaft tube. A friction body having a rubber-like elasticity capable of thermally discoloring the handwriting of the thermochromic ink by the generated frictional heat; the ball on the inner wall of the tip end of the ball behind the ball; and the total weight of the retractable ballpoint pen A coil spring that presses with a higher pressing force, a vertical clearance of the ball of 30 to 40 μm, an outer diameter of the caulking portion of 1.0 to 1.2 times the ball diameter, By placing the position of the center of gravity in a state where the ball-point pen tip protrudes in the middle part of the entire length of the writing instrument or behind it, the drop impact can be effectively reduced.

  This is because the position of the center of gravity in the state where the ball-point pen tip protrudes is located in the middle part of the writing instrument full length or behind it, even if the writing instrument placed sideways on the desk accidentally drops, from the tip end side, It can be made difficult to fall on the floor. Furthermore, since the friction body attached to the rear end portion of the cylinder has rubber-like elasticity, even if it falls and collides with the floor surface from the friction body, the impact can be mitigated. Preferably it is located.

  If a ball with a small diameter of φ0.4 mm or less is used and the vertical clearance of the ball is 30 to 50 μm as described above, the ball moves due to an impact when the tip of the tip protrudes and retracts or when a friction body is used. There is a risk of air stagnation. Therefore, in the present invention, in addition to the above-described configuration, the ball is pressed against the inner wall of the tip end portion with a pressing force higher than the total weight of the retractable ballpoint pen to suppress the ball from being easily moved, It is also important to make the outer diameter of the part 1.0 to 1.2 times the ball diameter, preferably 1.05 to 1.1 times to prevent paper hitting and ball drop. If the outer diameter of the caulking portion is smaller than 1.0 times the ball diameter, the ball holding force tends to decrease. If the outer diameter exceeds 1.2 times, the desired clearance is difficult to obtain and a paper hit phenomenon occurs. It tends to be easy.

According to the first configuration of the present invention, the writing instrument placed sideways on the desk is accidentally dropped by locating the center of gravity position in the state where the ball-point pen tip protrudes at the middle part or the rear of the writing instrument. However, it can be made difficult to fall to the floor surface from the tip end portion side, and damage to the tip end portion can be suppressed. In particular, even with a dent of the same size, the smaller the ball, such as φ0.5 mm or less, the smaller the caulking inner diameter tends to be, and the greater the influence of the dent on the inner diameter, the more remarkable the effect of this configuration. It is. In addition, since the friction body provided at the rear end of the shaft cylinder has rubber-like elasticity, if it falls and collides with the floor surface from the friction body, there is an effect that can reduce the impact. It is preferable to be located rearward. In addition, in this invention, an intermediate part is not limited to the position equidistant from both ends of a writing instrument full length, but the vicinity is included.

  In the present invention, the thermochromic ink is preferably a reversible thermochromic ink. The reversible thermochromic ink is a heat decoloring type that decolors by heating from a colored state, a color memory retaining type that reversibly stores and retains a colored state or a decolored state in a specific temperature range, or from a decolored state Various types such as a heating coloring type that develops color by heating and returns to a decolored state by cooling from the colored state can be used alone or in combination.

  The coloring material contained in the reversible thermochromic ink includes conventionally known (a) electron donating color-forming organic compounds, (b) electron-accepting compounds, and (c) color reactions of both. A reversible thermochromic microcapsule pigment in which a reversible thermochromic composition containing at least three essential components of a reaction medium for determining the occurrence temperature of the microcapsule is preferably used.

The size of the above-described microcapsule pigment particles is preferably 0.1 to 30 μm. The size of the particles, which merely refers to the average size of can and this determined by volume-based centrifugal sedimentation or laser diffraction. The pigment content is preferably 3 to 15% by mass with respect to the total amount of the ink composition.

  The friction body used in the present invention includes rubber-like elastic members such as silicone rubber, fluorine rubber, chloroprene rubber, nitrile rubber, polyester rubber, ethylene propylene diene rubber (EPDM), styrene elastomer, ester elastomer. Examples thereof include rubber having elasticity like rubber, elastomer, and the like, and can be appropriately selected and used. Further, the friction body described above may be formed integrally with the rear end portion of the shaft tube, or a separate member may be mounted by two-color molding or fitting. Moreover, Shore A hardness 40 or more and 100 or less are preferable.

According to the 2nd structure of this invention, in addition to the above-mentioned center-of-gravity position, a drop impact can be relieve | moderated further by making a product weight into 10 g or less. This is because the impact due to dropping is F = mV / t (impact force F [N], the mass of the object is m [kg], the deceleration time is t [s], V = √ (2 gh) (g is gravitational acceleration = 9.8 [m / s ² ], h is the height [m]), and greatly depends on the mass of the object (product weight), especially when using small diameter balls of φ0.4 mm or less Therefore, it is important to suppress the drop impact by setting the product weight to 10 g or less, because the thickness of the caulking portion at the tip end of the chip is thin and easily dents are formed at the time of dropping. If the product weight is too small, it will be easy to move when the hands, elbows, books, notebooks, etc. hit the retractable writing instrument placed sideways on the desk, and as a result it will be easy to drop, so the product weight will be It is preferable to set it as 5 g or more.

  According to the third configuration of the present invention, the operating portion of the operating body is provided so as to protrude outward from the outer peripheral surface of the shaft cylinder, and the circumferential width of the operating portion is set to the circumferential width of the friction body. By making it smaller than this, there is an effect that it is easy to visually recognize the handwriting on the writing surface when the friction body is used and when the friction body is used. However, since it becomes difficult to operate when the width of the operation portion is reduced, it is preferable that the pressing force of the coil spring that urges the ballpoint pen refill toward the rear end side of the shaft cylinder is 100 to 200 g. If it is less than 100 g, the tip end of the tip may inadvertently protrude, and if it exceeds 200 g, the operability is reduced and the above-mentioned knock impact tends to increase. Is 100 to 200 g, preferably 120 to 180 g.

  The present invention has been able to provide a retractable ballpoint pen that is less likely to have a dent on the tip end due to an impact such as dropping, and can obtain a stable ink outflow amount.

It is a longitudinal cross-sectional view which shows the retractable ball-point pen of Embodiment 1. FIG. It is a figure which shows the state which the ball-point pen tip in FIG. 1 protruded. It is the principal part expanded sectional view in which a part of ball-point pen tip in Drawing 1 was omitted. It is the external view seen from the upper surface direction in FIG. It is an external view which shows the state which uses the friction body in FIG.

  1-5, the retractable ball-point pen 1 of Embodiment 1 is shown. The retractable ballpoint pen 1 includes a front pen 2 and an intermediate shaft 3 screwed together, and a ballpoint pen refill contained in a shaft cylinder body obtained by fitting the rear shaft 4 over the rear end of the intermediate shaft 3. 2 is housed by being slidably urged toward the rear end of the rear shaft 4 by a coil spring 8 disposed between the spring receiving member 7 and the rotary cam 6 disposed at the rear end. Further, in the intermediate shaft 3, a retracting mechanism including a rotating cam 6 is provided. Although not shown, a cam groove is provided on the inner surface of the intermediate shaft 3.

  Further, an elongated window hole 4A extending in the longitudinal direction is provided in the outer peripheral surface of the rear shaft 4 so as to communicate with the inside and the outside in the radial direction. The outer surface of the rear shaft 4 extends outward from the window hole 4A. A transparent operation body 5 is disposed so as to protrude. The operation body 5 is formed with an operation portion 5A protruding outward from the window hole 4A, and a plurality of serrated cam portions (not shown) at the tip so as to move the rotating cam 6 forward and induce rotation. And a shaft portion 5B.

  In order to use the retractable ballpoint pen 1, the operating body 5 is disposed so as to protrude outward from the outer peripheral surface of the rear shaft 4 from the state in which the tip portion of the ballpoint pen tip 12 is immersed in the tip opening 2 </ b> A of the front shaft 2. When the operating portion 5A is slid in the direction of the front end opening 2A of the front shaft 2 along the window hole 4A provided in the rear shaft 4 against the urging force of the coil spring 8, the shaft portion 5B of the operating body 5 is moved. The rotary cam 6 is actuated so that the tip of the ball-point pen tip 12 can be written while maintaining the state of protruding from the tip opening 2A of the front shaft 2. The above-described in / out mechanism is a conventionally in-and-out mechanism composed of the rotating cam 6, and allows the ball-point pen tip 12 to enter and exit from the front end opening 2 </ b> A of the front shaft 2. The urging force of the coil spring 8 that urges the ballpoint pen refill toward the rear end side of the rear shaft 4 was 150 gf as a result of measurement with a push-pull scale, and the ink consumption per 100 m was 180 mg.

  A friction body 9 made of a polyester elastomer is mounted on the rear end portion of the rear shaft 4 by fitting, and as shown in FIG. 5, the friction body 9 is pressed against the writing surface and rubbed. The handwriting of the thermochromic ink can be thermally decolored or discolored by heat. With the ball-point pen tip 12 immersed in the front shaft 2, the angle β of the tangent S between the operation portion 5 </ b> A of the operation body 5 and the friction body 9 was 78 degrees with respect to the axis J.

  The total length L of the retractable ballpoint pen in the present embodiment is 144.0 cm with the tip of the ballpoint pen tip 12 projecting from the front shaft 2, and with the tip of the ballpoint pen tip 12 projecting from the front shaft 2. The center-of-gravity position G was 71.5 cm from the tip of the ballpoint pen tip 12 and 72.5 mm from the rear end of the friction body 9. In order to confirm the state of falling from the desk, the drop-type ballpoint pen 1 was placed in a parallel state with respect to the ground, and as a result of a drop test of dropping from a height of 1 m, the tip 13 was not dropped and the caulking portion 13A was There was no damage.

  The maximum width (outer diameter) A of the friction body 9 is 6 mm, and the maximum width E in the circumferential direction of the operation portion 5A is 2 mm (A> E). The maximum width (outer diameter) A of the friction body 9 is smaller (A> B) than the maximum width (outer diameter) B (7 mm) of the rear end portion of the rear shaft 4. The total weight of the retractable writing instrument 1 is 9.0 g, the maximum width D (outer diameter) of the front shaft is 9.0 mm, the maximum width (outer diameter) of the intermediate shaft is 9.0 mm, and the maximum width C of the rear shaft ( The outer diameter was 8 mm. Further, the longitudinal distance Q from the rear end of the friction body 9 to the operation portion 5A was 2.7 times the longitudinal length R of the friction body 9 exposed from the rear end of the rear shaft 4 to the outside.

  The ballpoint pen refill extends to a chip body 13 made of a stainless steel wire, a ball holding chamber 14, an ink circulation hole 17 in the center of the ball holding chamber 14, and a radial shape communicating with the ink circulation hole 17. A ball 19 made of tungsten carbide having a diameter of 0.38 mm is placed on the bottom wall 15 of the ball holding chamber 14 and the caulking portion 13A at the tip of the tip is caulked inward. Thus, the ball-point pen tip 12 that is rotatably held so that a part of the ball 19 protrudes from the tip end edge of the ball 19 is attached to the tip end portion of the ink containing cylinder 10 via the tip holder 11.

  The ballpoint pen tip 12 is formed by cutting a stainless steel wire having a diameter of 2.3 mm and a hardness of 230 Hv to 280 Hv into a desired length, and producing a ball holding chamber 14, an ink circulation groove 16, an ink circulation hole 17, and a rear hole 18. A ball 19 is placed on the bottom wall 15 of the ball holding chamber 14, and a sealing surface substantially the same shape as the ball 19 is formed on the inner wall of the caulking portion 13 </ b> A at the tip end of the tip by rear hammering.

Further, the ball protrusion H where the ball 19 protrudes from the tip end of the state where the ball 19 is placed on the bottom wall 15 is 30% of the ball diameter, the caulking angle α is 110 degrees, and the longitudinal direction of the ball 19 (in FIG. 3). The clearance in the left and right direction of the ball 19 is 35 μm, and the caulking portion outer diameter K is 1.05 times the ball diameter. Further, a coil spring 20 is disposed behind the ball 19, and the ball 19 is pressed against the inner wall sealing surface side of the caulking portion 13A by this pressing force. The pressing force of the coil spring 20 that presses the ball 19 is 20 gf.

  By setting the pressing force of the coil spring 20 that presses the ball 19 to be larger than the entire (product) weight of the retractable ballpoint pen 1 and 30 g or less, good writing and impact resistance can be obtained. This is because if the pressing force of the coil spring 20 that presses the ball 19 is smaller than the product weight, it is difficult to suppress the movement of the ball due to impact, and ink leakage is likely to occur. Further, if the pressing force of the coil spring 20 that presses the ball 19 is larger than 30 g, the writing performance and writing quality are deteriorated.

  If the ball protrusion H that protrudes from the tip end of the ball 19 placed on the bottom wall 15 is less than 25% of the ball diameter, the tip end is on the writing surface such as the writing surface during writing. It becomes easy to hit and it is easy to damage the tip end. If it is larger than 40%, the ball holding force becomes weak, and the impact resistance performance such as dropping falls. Further, by forming the caulking angle α to be an obtuse angle, there is an effect of increasing the ball holding force of the caulking portion 13A. However, when the caulking angle α exceeds 120 degrees, the tip end of the chip easily hits a writing surface such as a writing surface during writing. 90 degrees to 120 degrees is preferable.

  The ink containing cylinder 10 contains a reversible thermochromic microcapsule pigment having an average particle size of 0.5 μm, and an ink viscosity at 1 rpm in an EM type rotational viscometer is 1020 mPa · s (25 ° C.), A thermochromic water-based ballpoint pen ink (not shown) having an ink viscosity at 100 rpm of 84 mPa · s (25 ° C.) and a shear thinning index of 0.48, and a grease-like ink at the rear end of the ink A follower (not shown) is accommodated directly. The ink viscosity is preferably 40 to 200 mPa · s at 100 rpm in an EM rotational viscometer.

  Further, the tangent S between the friction body 9 and the operation portion 5A is such that the friction pen 9 faces downward and the axis J of the shaft cylinder is perpendicular to the writing surface in a state where the ballpoint pen tip 12 is immersed in the front shaft 2. By setting it to 45 degrees or more, when the user uses the friction body 9, it can be used without worrying about the contact between the writing surface and the operation unit 5 </ b> A. In particular, since the handwriting having a diameter of φ0.4 mm or less is small, when the friction body 9 is directed downward and the axis J of the shaft cylinder is perpendicular to the writing surface, the tangent S between the friction body 9 and the operation portion 5A is The angle is preferably 60 degrees or more with respect to the writing surface, and most preferably 70 degrees or more.

  In this embodiment, a ball of 0.38 mm is used for convenience, but the diameter of the ball is not particularly limited as long as it is φ0.4 mm or less, but φ0.3 mm to φ0.4 mm is preferable.

  Further, in this embodiment, the operation portion 5A which is a protruding portion is a plate piece having an arc-shaped vertical section that also serves as a rolling prevention protrusion when the writing instrument is placed on the desk in a horizontal direction, and is provided with a hole for attaching a charm. However, it is also possible to form or attach the clip integrally.

  Moreover, in this embodiment, although the axial cylinder main body is comprised by the front axis | shaft, the center axis | shaft, and the rear axis | shaft, it is not specifically limited. The front shaft, the middle shaft, the rear shaft, and the operation body are made of synthetic resin or metal such as polycarbonate, polyethylene, ABS, polypropylene, etc., but at least the operation body is made of transparent or translucent synthetic resin. Is preferred. This is because by making the operating body transparent or translucent, the visibility of the handwriting can be made difficult to deteriorate even when the operating body enters the field of view when the friction body is used.

  In addition, if the maximum outer diameter of the rear end portion of the rear shaft exceeds 1.5 times the maximum outer diameter of the friction body, the rear end portion of the shaft cylinder may block the handwriting from being recognized when the friction body is used. If the maximum outer diameter of the friction body is larger than the maximum outer diameter of the rear end portion of the shaft cylinder (less than 1.0 times), the operation body may be difficult to operate. The maximum outer diameter is 1.0 to 1.5 times the maximum outer diameter of the friction body, and when using the friction body, the rear end portion of the shaft tube is prevented from blocking the handwriting, and is visible to the handwriting. It is preferable to improve the property. Further, not only the rear end portion of the rear shaft but also the rear end of the shaft cylinder of the friction body is 1/3 or more of the entire length of the writing instrument, more preferably 1/2 or more, and most preferably the maximum outer diameter of the entire writing is determined by the friction. By making the maximum outer diameter of the body 1.0 to 1.5 times, the handwriting visibility can be further enhanced. Note that many common notebooks are provided with horizontal ruled lines at a pitch of 7 mm, and a large number of 8 mm and 10 mm pitches are commercially available. Therefore, it is preferable that the maximum outer diameter of the friction body is 7.0 mm or less.

Further, in this embodiment, for the sake of convenience, a retractable ballpoint pen provided with a retractable mechanism including a rotating cam is illustrated, but the retractable mechanism is not particularly limited. And Mochiiruko a retractable mechanism consisting of the rotating cam in consideration of operability and the like are preferable.

  Since the retractable ballpoint pen of the present invention can be used without limiting the retractable mechanism, it can be widely used as a retractable ballpoint pen.

DESCRIPTION OF SYMBOLS 1 Retractable ball-point pen 2 Front shaft 2A Front opening 3 Intermediate shaft 4 Rear shaft 4A Sliding hole 5 Operation body 5A Operation portion 5B Shaft portion 5C Hole portion 6 Rotating cam 7 Spring receiving member 8 Coil spring 9 Friction body 10 Ink receiving cylinder DESCRIPTION OF SYMBOLS 11 Tip holder 12 Ball-point pen tip 13 Tip body 13A Caulking part 14 Ball holding chamber 15 Bottom wall 16 Ink flow groove 17 Ink flow hole 18 Rear hole 19 Ball 20 Coil spring 21 Writing surface A Maximum outer diameter of friction body B Rear rear axis Maximum outer diameter of the end C Maximum outer diameter of the rear shaft D Maximum outer diameter of the front shaft and the intermediate shaft E Width of the operation section G Center of gravity H Out of the ball J Center axis K Caulking outer diameter L With the tip of the tip protruding M Distance from tip end to center of gravity N Distance from rear end of friction body to center of gravity Q Distance from rear end of friction body to operation section R After friction body Tangent of the angle length exposed from the rear end to the outside S tangent α caulking angle β friction body and the operating portion

Claims (3)

A ball-point pen tip that rotatably holds a ball of φ0.4 mm or less by a caulking portion at the tip end of the tip is mounted directly or via a tip holder on the tip of the ink containing tube, The ballpoint pen refill that directly contains the thermochromic ink is stored inside the shaft cylinder by biasing it toward the rear end side of the shaft cylinder with a coil spring, and the operation part of the operating body provided on the shaft cylinder is operated. The ballpoint pen tip includes a retractable mechanism that allows the tip end of the ballpoint pen to protrude from the tip opening of the shaft tube, and the thermochromic property is provided at the rear end portion of the shaft tube. rubbing handwriting ink, the handwriting of the thermochromic ink at a frictional heat generated when possible thermochromic, Shore a hardness of 40 or more, comprising a friction body having a 100 following rubber-like elasticity, the ball Behind, before A coil spring that presses the ball on the inner wall of the tip of the tip with a pressing force higher than the total weight of the retractable ballpoint pen is disposed, and the vertical clearance of the ball is 30 to 40 μm, and the caulking portion outer diameter is The operation part is composed of a plate piece provided with a transparent or translucent hole, and protrudes outward from the outer peripheral surface of the rear end part of the shaft tube. The angle from the writing surface is 60 degrees or more when the tangent line between the friction body and the operating portion faces the friction body downward and the axis of the shaft cylinder is perpendicular to the writing surface. A retractable ballpoint pen , wherein the position of the center of gravity in a state in which the ballpoint pen tip protrudes is located at the middle part of the writing instrument or at the rear thereof. 2. The retractable ballpoint pen according to claim 1, wherein the total weight of the retractable ballpoint pen is 10 g or less. The maximum width of the circumferential direction of the front SL operating body, as well as smaller than the maximum width in the circumferential direction of the friction body, and 100~200g the pressing force of the coil spring biasing the ballpoint pen refill in the barrel rear end The retractable ballpoint pen according to claim 1 or 2, wherein

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