JP4655855B2 - Ballpoint pen tip - Google Patents

Description

  The present invention is composed of at least a ball as an application member and a ball holder that rotatably holds the ball in a state where a part of the ball protrudes from the opening. The opening on the front side is made smaller in diameter than the diameter of the ball, and an inward protruding portion that forms an inscribed circle having a diameter smaller than the diameter of the ball is arranged in the middle of the communication hole. Is related to a ballpoint pen tip.

Patent Document 1 discloses that the rotation of a ball is smoothed by applying spherical processing by driving a member having a spherical tip into a ball receiving seat portion of a ball holder.
Patent Document 2 discloses that spherical processing is formed by pressing a ball serving as a writing member.
JP 53-082532 A JP-A-63-252799

  However, when writing, if the writing angle is small or the writing speed is fast, the center of the ball is displaced from the axis of the ball holder, so that the portion close to the side of the ball holding chamber receives the ball. . This part is in a state close to point contact or line contact, and the load received from the ball does not disperse. Therefore, the resistance to the rotation of the ball is greatly influenced by the surface state. In particular, the side surface of the ball holding chamber is rough due to cutting. In the case of the surface, the ball does not rotate smoothly, resulting in poor writing such as a heavy writing feel and blurring at the writing tip.

As an improvement measure, the present invention comprises at least a ball as an application member and a ball holder that rotatably holds the ball in a state where a part of the ball protrudes from the opening, and the ball holder serves as an ink passage. The inwardly projecting portion that forms the inscribed circle having a diameter smaller than the diameter of the ball in the middle of the communication hole and having the opening at the both ends communicated by the communication hole, the front opening being made smaller than the diameter of the ball. In the ballpoint pen tip disposed between the ball holding chambers, a transfer surface on which the surface state of the ball is transferred by pressing the ball is formed on the inner wall of the bottom of the ball holding chamber. The diameter A of the largest inscribed circle, the diameter B of the smallest inscribed circle, and the diameter D of the ball at the rear side portion of the center position of the ball when the ball is in contact with the inward projecting portion and positioned at the rearmost portion. But, .92 ≦ A / D ≦ 1.05 and the gist of the ballpoint pen tip is the relationship 0.25 ≦ B / D ≦ 0.75.

On the transfer surface of the ball surface formed on the inner wall of the ball holding chamber, a thin film of ink is formed between the ball and the ball. The smoother the surface state of the transfer surface, the lower the frictional resistance against rotation of the ball even if direct contact with the ball occurs. Further, since the movement resistance between the ink film and the wall surface is also suppressed, the ink can easily move and the smooth ink flow is guaranteed.
The diameter A of the maximum inscribed circle, the diameter B of the minimum inscribed circle, and the diameter of the ball on the rear side of the center position of the ball when the ball is in contact with the inward protruding portion and positioned at the rearmost portion of the transfer surface When D has a relationship of 0.92 ≦ A / D ≦ 1.05 and 0.25 ≦ B / D ≦ 0.75, this transfer surface has a small writing angle when writing, When the writing speed is high, the center of the ball will be a part that receives the ball even if it deviates from the axis of the ball holder, and a thin film of ink is formed between the ball and the ball so that the ball rotates smoothly. It can be maintained.
Further, since the area of the transfer surface is large, the load applied to the outside can be dispersed, and smooth rotation of the ball is facilitated.

The ball-point pen tip of the present invention facilitates the rotation of the ball during writing, and is particularly effective for ink that has a shear thinning viscosity that tends to intervene between the ball and the transfer surface, and has a medium to high viscosity when standing. It is. Since these inks are stationary when not in use, the viscosity is maintained high, and the viscosity decreases as the ball rotates by writing, especially when it receives a shearing force at the contact portion between the ball and the ball holding chamber. It helps to rotate the ball smoothly.
As a form of the writing instrument using the ballpoint pen tip of the present invention, the ink stored in the ink storage body such as a fiber bundling body is arranged in the ink containing portion, or the container is used without using such an ink storage body. It can be used for a so-called raw ink type in which ink in a free state is directly filled therein, and a pressure type for supporting discharge by pressing the back of the ink with compressed air or the like.
In addition to the cap type having an elastic material such as rubber that contacts the opening that is the ink discharge port of the ballpoint pen tip, a refill that does not have such a cap and that has a ballpoint tip at the tip by operation is provided on the exterior body. It can also be a retractable ballpoint pen that can be retracted from the tip.

  FIG. 1 is a longitudinal sectional view of a ballpoint pen tip showing an example of the present invention. Further, FIG. 2 shows the ball in the enlarged view of the J portion in FIG. A ball 1 serving as an application member is rotatably held at the tip, with a portion protruding from the tip of the ball holder 2, and the tip opening 2 a prevents the ball 1 from falling off. The outer diameter is slightly smaller than the outer diameter. In addition, an inward protruding portion 2 b installed in the vicinity of the tip of the ball holder 2 restricts the movement of the ball 1 backward. The ball holder 2 has a through-hole as an ink passage. The through-hole has a ball holding chamber 2d in which movement of the ball 1 in the front-rear direction is restricted by the front end opening 2a and the inward projecting portion 2b. It consists of a small-diameter portion 2e of the communication hole formed by the inward projecting portion 2b, which has a smaller diameter than the ball 1 immediately behind, and a rear hole 2f disposed at the rear portion of the inward projecting portion.

  In the inward projecting portion 2b, a plurality of grooves 3 through which ink can flow is opened to the small diameter portion 2e and the ball holding chamber 2d. This groove 3 does not communicate with the rear hole 2f, but this is to suppress the ink that has reached the ball holding chamber 2d from flowing back as much as possible. When it is desired to increase the discharge amount, the groove 3 may be formed to penetrate to the rear hole 2f.

  On the inner surface of the ball holding chamber 2d, there are formed transfer surfaces 2g and 2g 'to which the surface state of the ball 1 is transferred by pressing the ball 1. The surface roughness Ra of the ball 1 is about 0.002 μm to 0.030 μm, and as a result, the surface roughness Ra of the transfer surface is 1 μm or less. The transfer surfaces 2g and 2g 'are divided in the circumferential direction by the grooves 3, and further divided in the front-rear direction by a circumferential recess 3a. The groove 3 and the circumferential recess 3 a actually supply ink to the transfer surfaces 2 g and 2 g ′ that form a narrow gap between the ball 1 and a thin ink film between the ball 1 and the ball holder 2. Form. The opening of the small diameter portion 2e to the ball holding chamber 2d protrudes inward, and the inscribed circle diameter formed in the portion is slightly smaller than the small diameter portion 2e. Then, as shown in FIG. 3, which corresponds to FIG. 2 and shows the ball in broken lines, the center of the transfer surface 2g, 2g ′ when the ball is in contact with the inward projecting portion and positioned at the rearmost portion. Also, the diameter of the maximum inscribed circle in the rear side portion is the inscribed circle diameter (φA portion) formed in the outer shape of the front transfer surface 2g, and the minimum inscribed circle diameter is the rear transfer surface 2g ′. Is the inscribed circle diameter (φB portion) formed in the inner shape.

  The opening to the small diameter portion 2e of the groove 3 is gradually narrowed toward the front. This is because when the transfer surface 2g is formed, the wall surface of the inward projecting portion 2b formed substantially in parallel collapses due to composition deformation. The shape of the groove 3 is not limited to the shape of the present example, and the completed groove 3 is made substantially parallel by reducing the amount of pressing of the ball 1 or by forming a groove having a wider space in advance toward the inner side. Alternatively, it may be formed so as to be wider toward the inside.

Other shape examples of the transfer surfaces 2g and 2g ′ will be described with reference to FIGS. 4 and 5 corresponding to FIG.
In the example of FIG. 4, the transfer surfaces 2g and 2g ′ are the same in the front-rear direction divided by the recesses 3a, but the transfer surface behind the recesses 3a is divided in the circumferential direction by the grooves 3. 2g ′ only, and the transfer surface 2g in front of the recess 3a is continuous in the circumferential direction. This is effective when it is desired to suppress the ink discharge amount, and the ink passage amount is adjusted by the gap between the front transfer surface 2 g and the ball 1.
In the example of FIG. 5, the transfer surface is not divided in the front-rear direction, but is divided only in the circumferential direction by the grooves 3. This is effective when a wide transfer surface is desired. As a result, the writing feeling becomes smooth. In the case of such a shape, when the transfer surface 2g is formed, it is strongly pressed by the ball 1, and as a result, the amount of plastic deformation increases, and the springback phenomenon and the wedge-like expansion occur. Depending on the phenomenon, the transfer surface 2g may spread away from the ball. In this case, the maximum inscribed circle diameter of the transfer surface 2g is larger than the diameter of the ball 1 even though the ball 1 is pressing. Further, when the pressing distance is long, the tip of the transfer surface 2g may be positioned in front of the center of the ball 1 that has retreated last.

A method for processing the ballpoint pen tip of this example will be described.
First, the coil material is cut to an appropriate length by shearing, corners and burrs at the end are removed by barreling, dried after washing to obtain a workpiece that is the basis of a ballpoint pen tip (not shown).
With respect to this work, a taper part is formed at the front part by one or a plurality of times by a cutting tool such as a cutting tool, and a flat part is formed by cutting at the tip of the work with a cutting tool and an end mill. Next, a center reference hole serving as a guide for cutting is formed with a cutting tool and a drill toward the rear side from the front end surface of the workpiece. Next, the small diameter portion 2e is formed with a drill, and the prepared hole of the ball holding chamber 2d is cut with a drill or a bite. At the same time as the above-described series of cutting operations, rear hole machining is performed from the rear to the front of the workpiece so as to communicate with the small diameter portion 2e (by gradually reducing the diameter in a plurality of times). Further, if necessary, a reduced diameter portion 2h (see FIG. 1) is provided on the outer end portion of the workpiece for press-fitting positioning with a coating liquid storage member or a connection member (not shown) with the coating liquid storage member. It may be formed.

  Next, the bottom surface portion and the side wall portion of the ball holding chamber 2d in which the ball 1 is held are cut by one ball house bite, and an angle closer to the outer end of the outer shape of the ball holding chamber 2d than the tapered portion. The caulking taper portion 2i opened is cut and formed with a chamfering tool. At the same time, the tip surface 2j of the ball holding chamber 2d is cut with a surface tool. By performing these processes simultaneously with a processing tool to which three types of processing tools are attached, uneven thickness and center deviation near the tip of the ball holder 2 in the cutting process can be prevented.

Next, a radial groove 3 is formed in the small diameter portion 2e by a shearing tool in which a radial cutting blade is formed. At this time, burrs are generated in the small-diameter portion 2e due to the shearing process, but if necessary, cutting is performed again with a drill having the same diameter or a slightly smaller diameter, or shearing is performed with a pin having a slightly smaller diameter than the small-diameter part 2e. If this is applied, the burr can be removed to the extent that it does not affect the ink ejection.
In this way, the ball holder material before holding the ball as shown in FIG. 6 is obtained.

  Next, as shown in FIG. 7, the ball 1 is disposed so as to contact the bottom surface of the ball holding chamber 2d, and the ball 1 is struck rearward by a hammer tool F having a smooth bottom surface. Transfer surfaces 2g and 2g ′ of the ball 1 are formed (see FIG. 8).

  Thereafter, the tip of the ball holder 2 is caulked. At the lower end of the caulking tool, a roller capable of rotating is installed at a position facing the roller and in the vicinity of the tip of the ball holder 2, and the roller has a tapered surface. By this caulking tool, the tip of the ball holder 2, specifically, the roller is pressed against the caulking taper portion 2i, and the vicinity of the portion is plastically deformed inward with some springback. . This caulking process prevents the ball 1 from coming off from the ball holder 2 (ball holding chamber 2d). This step may be performed before the step of hitting the ball 1 backward.

  Using the ballpoint pen tip created as shown in Table 1, the diameter A of the maximum inscribed circle, the diameter B of the minimum inscribed circle, and the width and number of the grooves 3 on the transfer surface 2g are actually written by hand. Performed sensory evaluation. The inks used in the writing test are as follows.

Spiron Black GMH Special (Dye, manufactured by Hodogaya Chemical Co., Ltd.) 15.0 parts
Bali First Violet # 1701 (dye, manufactured by Orient Chemical Co., Ltd.)
15.0 parts
Ethylene glycol monophenyl ether 40.0 parts
Benzyl alcohol 12.5 parts
Resin SK (ketone resin, manufactured by Huls (Germany)) 13.5 parts
PVP K-90 (polyvinylpyrrolidone, manufactured by ISP Japan Co., Ltd.) 2.0 parts
Priceurf A208B (phosphate ester derivative, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2.0 parts
The above components were heated and stirred with a stirrer (80 ° C., 4 hours) and then filtered with warm pressure to obtain a black oil-based ink composition for ballpoint pens. The viscosity of this ink was 10500 mPa · s at 25 ° C. The viscosity of the ink was measured at 25 ° C. and 5 rpm (shear rate 3.5 [1 / sec]) using an ST rotor of an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.).

  In the ballpoint pen tip, a contact surface of the ball with the inner surface of the ball holder is used as a transfer surface of the ball, and further, the outer diameter is increased to obtain a smooth and slick writing.

The longitudinal cross-sectional view which shows an example of this invention. The j section expanded sectional view which abbreviate | omitted illustration of the ball | bowl of the thing of FIG. FIG. 2 is a view corresponding to FIG. The expanded sectional view equivalent to FIG. 3 which shows another example. Furthermore, the expanded sectional view equivalent to FIG. 3 which shows another example. The expanded sectional view equivalent to j section in the middle of manufacture processing of a ball-point pen tip. The expanded sectional view equivalent to j section in the middle of manufacture processing of a ball-point pen tip. The expanded sectional view equivalent to j section in the middle of manufacture processing of a ball-point pen tip.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball | bowl 2 Ball | bowl holder 2a Front opening part 2b Inward protrusion part 2d Ball holding chamber 2e Small diameter part 2f Rear hole 2g Transfer surface 2g 'Transfer surface 2h Reduced diameter part 2i Caulking taper part 2j Front end surface 3 Groove 3a Concave F Hammer tool

Claims (2)

It is composed of at least a ball as an application member and a ball holder that rotatably holds the ball with a part of the ball protruding from the opening. The ball holder has openings at both ends by communication holes as ink passages. The front opening is made smaller than the diameter of the ball, and an inward protruding portion that forms an inscribed circle with a diameter smaller than the diameter of the ball is arranged in the middle of the communication hole, and the ball is held between them. In the ballpoint pen tip used as a chamber, a transfer surface to which the surface state of the ball is transferred by pressing the ball is formed on the inner wall of the bottom of the ball holding chamber , and the ball of the transfer surface has an inward protruding portion. The diameter A of the largest inscribed circle, the diameter B of the smallest inscribed circle, and the diameter D of the ball in the rear side part of the center position of the ball when abutting and positioned at the rearmost part are 0.92 ≦ A / D ≦ 1.05 , Ballpoint pen tip is the relationship 0.25 ≦ B / D ≦ 0.75. The area C of the transfer surface and the surface area S of the ball on the rear side of the center position of the ball when the ball is in contact with the inward protruding portion and positioned at the rearmost portion are 0.21 ≦ C / S ≦ 0. The ball-point pen tip according to claim 1, which has a relationship of .40.

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