JP3918081B2 - Writing instrument - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a writing instrument in which a circumferential recess is formed in the outer wall of a shaft cylinder of a writing instrument, and a cylindrical elastic body is fitted as a gripping member in the recess.
[0002]
[Prior art]
Conventionally, a cylindrical elastic body such as a cross-linked elastomer such as silicon rubber, NBR rubber, or butyl rubber or a non-cross-linked elastomer such as polyethylene, polystyrene, or polyisobutylene is fitted to the grip of the writing instrument to prevent slipping during writing. Is known. A press-fitting method is generally used as a method of fitting the gripping member made of an elastic body. In the case where a circumferential concave portion is formed on the outer wall of the shaft cylinder and an elastic body is fitted into the concave portion and is fixed using the concave / convex fitting force, the shaft cylinder is fixed using the concave / convex fitting force. The elastic body climbs over the collar and is fitted into the recess, minimizing the front-rear deviation and obtaining a high fixing force.
[0003]
[Problems to be solved by the invention]
However, on the other hand, it is necessary to get over the large-diameter collar, and it is difficult to attach the gripping member, which is an elastic body. The wall surface of the inner hole of the gripping member comes into contact with the outer peripheral surface of the collar portion to generate frictional resistance, making it difficult to fit the elastic body to the shaft body.
[0004]
[Means for Solving the Problems]
That is, the present invention provides a writing instrument in which a circumferential recess is formed in the outer wall of the shaft cylinder of the writing instrument, and a cylindrical elastic body is fitted as a gripping member in the recess, and the pendulum direction of the shaft cylinder with respect to the gripping member The gist of the writing instrument is characterized in that a collar is formed at the position and the outer peripheral shape of the collar is a polygon or an ellipse .
[0005]
【Example】
Hereinafter, an example will be described with reference to the drawings.
FIG. 1 shows a stainless steel ballpoint pen tip 4 for applying ink onto a paper pipe on a polypropylene pipe 3 containing ink 2 in a shaft cylinder 1 made of acrylonitrile styrene, and the ballpoint pen tip 4. A refill 6 comprising a polybutylene terephthalate chip holder 5 as a joint with the pipe 3 is arranged, and a brass tip 7 for fixing the refill 6 is screwed onto the tip of the shaft tube 1. This is an example of a ballpoint pen with a polyethylene sealing tail plug 8 attached to the rear end of the barrel 1. Reference numeral 9 is a high-viscosity fluid based on polybutene that moves in close contact with the ink interface that moves with ink consumption due to writing and prevents backflow of ink. A groove-like air hole 10 formed in the shaft cylinder 1 is formed between the tip of the shaft cylinder 1 and the tip 7 and communicates with the rear end of the pipe 3 of the refill 6 to reduce ink by writing. Accompanied with the outside air. As a means for supplying the outside air into the shaft cylinder (the rear end opening portion of the pipe) in this way, an appropriate number and an appropriately sized hole may be directly formed in the shaft cylinder 1.
[0006]
As shown also in FIG. 2 which is a cross-sectional view taken along the line AA ′ of FIG. 1, a circumferential recess for fitting a cylindrical elastic body 11 made of styrene elastomer to the outer wall of the shaft cylinder 1. 12 is formed. And the collar part 13 is arrange | positioned adjacent to this recessed part 12 at the front end side of the axial cylinder 1. As shown in FIG.
[0007]
The recess 12 is formed with a plurality of longitudinal ribs 14 extending in the longitudinal direction leaving the foremost part and the last part of the recess 12, and the longitudinal ribs 14 are substantially formed on the inner wall of the cylindrical elastic body 11. As a result, the cylindrical elastic body 11 is restrained from moving (displaced) in the longitudinal and circumferential directions. In addition, a circumferential groove 15 is formed in the front portion of the concave portion 12 and is fitted to a circumferential inward convex portion 16 formed on the inner wall of the front portion of the cylindrical elastic body 11 so as to hold a grip portion for writing. When the cylindrical elastic body 11 is written, the displacement due to the gripping force being applied in the direction of the pen tip is suppressed and the fixing is ensured.
[0008]
As shown in FIG. 3, which is a cross-sectional view taken along the line BB ′ in FIG. 1, the outer shape of the cross section of the collar portion 13 formed on the distal end side of the shaft tube 1 is hexagonal, and the corner is chamfered. It consists of an R shape. When the cylindrical elastic body 11 is fitted into the concave portion 12 of the shaft cylinder 1, the inner wall surface of the cylindrical elastic body 11 passes through the outer peripheral surface of the collar portion 13 and is fitted into the concave portion 12. At this time, if the cross-sectional shape of the flange portion 13 is circular, the inner wall surface of the cylindrical elastic body 11 and the entire outer peripheral surface of the flange portion 13 are brought into contact with uniform pressure input due to the maximum diameter. Thus, a frictional resistance force is applied between overcoming the flange portion 13 and fitting into the recess 12. However, in the case of this example, the cross-sectional shape of the flange 13 is hexagonal so that the contact area with the inner wall surface of the cylindrical elastic body 11 is reduced or the size of the pressure input hits the corner of the hexagon. It can divide | segment into the strong press-fit part of the part of a diameter, and the weak press-fit part applicable to a edge | side, and can reduce frictional resistance. Therefore, the ease of fitting of the cylindrical elastic body 11 is improved.
[0009]
Then, the cylindrical elastic body 11 once fitted is locked by the collar portion 13 so as not to be displaced in the pen tip direction, and the same difficulty as that obtained when the collar portion is circular is obtained. The cross-sectional shape of the collar portion 13 may be a polygonal shape, and may be four or eight. However, the smaller the contact area, the easier it is to insert, so it is preferably 10 or less, and the corner portion R is also small. That's good.
[0010]
Further, the inner wall shape of the portion of the shaft tube 1 where the flange portion 13 is formed is a hexagonal shape that matches the shape of the flange portion 13. Although it is preferable not to form the undercut portion as much as possible with the injection mold in relation to the shape with other portions, in this example, the inner wall shape of the shaft tube 1 is the same as the portion corresponding to the flange 13 shown in the figure. It has a square shape. In particular, the flange portion 13 which is a large diameter portion is a portion where uneven thickness portions (so-called sink phenomenon) due to shrinkage of the synthetic resin are easily generated during injection molding. By doing so, the thickness of the molded product is reduced as much as possible. It can be made uniform, and the above-mentioned uneven thickness portion is not formed on the appearance. Further, when the shaft cylinder 1 is formed of a transparent synthetic resin, a visual effect due to light refraction can be obtained by the six corners of the inner surface.
[0011]
In addition, the cylindrical elastic body 11 is apparently attached to the recess 12 of the shaft cylinder 1 without a front and rear gap, but in this example, the length of the recess 12 is 95 to 98% of the length of the elastic body 11. It is a length. If the lengths of the concave portion 12 and the elastic body 11 are the same, the flange portion 13 is slight due to variations in pressure applied when the elastic body 11 is attached to the concave portion 12 and the elasticity of the elastic body 11. There may be a gap between the elastic body 11 and the elastic body 11. If the pressure input is always uniform, there is no problem, but if this is assembled by hand, the variation will be large and the ratio of gaps will be high. In addition, in the state where the elastic body 11 is mounted in the recess 12, the outer diameter of the recess 12 is slightly larger than the inner diameter of the elastic body 11 in order to increase the mounting force, so the elastic body 11 extends in the warp direction. Under the force, it inevitably contracts in the longitudinal direction to form a gap. Further, the elastic body 11 deteriorates due to secular change, and a gap is inevitably generated when the elastic body 11 contracts. These not only impair the appearance of the appearance, but also cause the elastic body 11 to shift in the front-rear direction due to the generated gap and impair the grip feeling during writing. These problems can be solved by making the length of the recess 12 slightly shorter than the length of the elastic body 11 .
[0012]
FIG. 4 shows another example. It shows as a figure equivalent to FIG. 3 about the above-mentioned example. It is an example which made the cross-sectional shape of the collar part 13 the ellipse which reduced the large diameter part used as a strong press-fit with an elastic body as much as possible.
[0013]
FIG. 5 shows still another example. It shows as a figure equivalent to FIG. 3 about the above-mentioned example. A recess 17 is formed on the collar 13 as a non-contact portion with the cylindrical elastic body 11. Since the contact area with the cylindrical elastic body 11 can be reduced, the force required for fitting can be reduced. Also in this example, the thickness of the molded product is made as uniform as possible so that uneven thickness portions are not formed on the appearance, but the corners are aligned with the portion where the outer diameter is the largest. It is assumed that the polygonal shape is located (the one shown is a pentagon).
[0014]
【The invention's effect】
According to the present invention, when the gripping member of the writing instrument is fitted, the pressure input (friction resistance) that is always generated when the cylindrical elastic body that is the gripping member gets over the large-diameter collar of the shaft body is reduced, In addition to being able to be easily fitted, and after the gripping member is fitted, it is displaced in the direction of the pen tip and is difficult to come off.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example.
FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.
FIG. 3 is a cross-sectional view taken along the line BB ′ in FIG. 1;
FIG. 4 is a view corresponding to FIG. 3 showing another example.
FIG. 5 is a view corresponding to FIG. 3 and showing another example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shaft cylinder 2 Ink 3 Pipe 4 Ball-point pen tip 5 Tip holder 6 Refill 7 Tip 8 Tail plug 9 High-viscosity fluid 10 Vent hole 11 Cylindrical elastic body 12 Concave part 13 Ridge part 14 Vertical rib 15 Circumferential groove 16 Inward convex part 17 Recess

Claims (2)

In a writing instrument in which a circumferential recess is formed in the outer wall of the shaft cylinder of the writing instrument, and a cylindrical elastic body is fitted as a gripping member in the recess, a collar is provided at a position closer to the pen tip direction than the gripping member. A writing instrument characterized in that the outer peripheral shape of the collar is formed into a polygon or an ellipse .   The writing instrument according to claim 1, wherein a non-contact portion with a gripping member when the gripping member is mounted is formed on the collar portion.

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