JP4669111B2 - Writing instrument shaft - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an improvement of a shaft cylinder of a writing instrument having a grip for preventing slip.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a writing instrument in which a soft material such as rubber is fitted to the grip part has been known in order to eliminate the fact that the grip part slips or the finger hurts when writing for a long time. However, rubbers such as silicon rubber, EPDM, and NBR require a vulcanization process or are difficult to handle due to long parts and difficult to manufacture parts. There was a problem that it was difficult to do so and it could not be provided at a low cost. In order to solve the problem, recently, a method of integrally forming an elastomer by two-color molding on a shaft cylinder has been adopted. In addition, a normal shaft cylinder obtained by two-color molding is formed with stepped portions on the front and back of the shaft tube peripheral surface as a gripping position, and a grip is provided on a recessed portion formed between the stepped portions. ing.
[0003]
Also, during molding of the elastomer, when the molten elastomer flows into the molding space of the mold including the shaft cylinder surface that has already been solidified, the entrainment of air and gases such as generated gas cannot be released. It remains in the corner of the step formed on the shaft cylinder, resulting in a gap between the peripheral surface of the shaft cylinder and the elastomer, resulting in peeling of the grip, and appearance such as traces and gas burns due to bubbles There is a problem that causes defects.
In particular, when a transparent or colored transparent elastomer is used, the appearance defect becomes more prominent.
[0004]
[Problems to be solved by the invention]
In the molding process of non-slip grip elastomers molded by two-color molding, such as poor grip appearance and peeling due to residual air such as entrained air and water vapor or gas generated in the resin material Prevent problems.
[0005]
The present invention has the following configuration in order to achieve the above-described problems. The shaft tube of the writing instrument according to the invention of claim 1 is a two-color molding, and is a shaft tube of a writing tool formed by integrally forming a grip such as an elastomer or rubber on the shaft tube. curve substantially perpendicular step portion with respect to the peripheral surface of the peripheral surface and front and rear end surfaces of the grip inner surface of the grip to contact abutment with the barrel are formed respectively, at least one of the stepped portion to expand from the peripheral surface Are connected and formed on the entire circumference (a curved surface).
[0006]
The shaft cylinder of the writing instrument according to the invention described in claim 2 is the shaft cylinder of the writing instrument according to claim 1, wherein the curved line includes two or more circles sandwiching one circle or two or more circles or straight lines. A circle is formed such that the circle is provided smoothly and continuously, and the peripheral surface and the stepped portion are substantially tangent.
[0007]
The shaft cylinder of the writing instrument according to the invention described in claim 3 is the shaft cylinder of the writing instrument according to claim 2, wherein the contact point between the curve and the step portion has a height of the step portion from the circumferential surface of 1. Sometimes it is in the range of 0.5 to 0.7.
[0008]
The shaft cylinder of the writing instrument according to the invention described in claim 4 is the axial cylinder of the writing instrument according to claim 2, wherein the height of the step portion from the peripheral surface is 0.7, and the extension line of the peripheral surface The contact point of the circle in the circumferential direction is set to 1 and the contact point of the circle in the step direction is set to 0.4, with the intersection of the extension line of the step and the origin as the origin.
[0009]
【Example】
The shaft cylinder of the writing instrument of the present invention is a cylinder body that projects the writing part at the tip or accommodates the writing part so that the writing part can be projected and retracted, and a grip is provided at a position that becomes the grip part position of the shaft cylinder in writing. FIG. 1 shows a conventional example in which a grip 2 is provided on the shaft tube 1, but the appearance is shown in the same manner as the shaft tube 7 of the present invention shown in FIG. 4 provided with a grip. is there.
[0010]
As shown in FIGS. 2 and 3, the conventional shaft cylinder 1 is formed with stepped portions 5 and 6 at the front and rear portions of the circumferential surface 4 serving as a gripping portion position, and the corner portion where the stepped portion 6 and the circumferential surface 4 intersect is formed. A small chamfer 6a or an edge is formed. Further, as shown in FIG. 1, a grip 2 formed of an elastomer or rubber is provided in a concave portion surrounded by the peripheral surface 4 and the step portions 5 and 6. That is, by the two-color molding, the grip 2 is integrally molded with the shaft cylinder 1 as a base, and the grip 2 is prevented from coming off and rotating with respect to the shaft cylinder 1 (welding each other or For example, an engagement portion is provided) and is firmly fixed.
Further, the material of the shaft cylinder 1 is polycarbonate, and the material of the grip 2 is a thermoplastic elastomer. The material of the barrel 1 may be a thermoplastic resin such as AS, PS, PP.
[0011]
The non-slip grip elastomer is filled from the gate 3 on the front side of the shaft cylinder by two-color molding. In the conventional example, when the melted elastomer flows into the molding space of the mold including the peripheral surface of the shaft cylinder, the peripheral surface of the shaft cylinder, the elastomer and the gas cannot be released due to air entrainment or generated gas. There was a problem of poor adhesion such as a gap between the two and the grip peeled off, and defects in appearance such as traces of gas and gas burns. In particular, when a transparent or colored transparent elastomer is used, the appearance defect becomes more prominent.
[0012]
It has been confirmed that the gas cannot easily escape in the case of a chamfer 6a or an edge where the corner portion which is the intersection of the step portion 6 and the peripheral surface 4 is very small. It has also been clarified that the gas is surely escaped by forming an appropriate curved surface at the corner.
Conventionally, in the case where a grip is fitted in the recess of the shaft tube, it is common sense to secure a contact area with the end surface of the grip so that the soft grip does not float from the peripheral surface of the shaft tube However, in the two-color molding, since the grip can be firmly fixed to the shaft tube, a step within the necessary limit is secured at the corner and a gas escape passage is formed with a smooth curve. As a result, the flow and filling of the elastomer became smooth, and it was found effective because no gas remained.
[0013]
4 and 5 show an embodiment of the present invention.
In the shaft cylinder 7 of the embodiment, as shown in the figure, step portions 9 and 10 are formed on the front and rear portions of the peripheral surface 8 to be the grip portion position, and the corner portion where the step portion 10 and the peripheral surface 8 intersect is an appropriate curved surface. 11 is formed. In addition, a grip formed of elastomer or rubber is provided in the concave portion surrounded by the peripheral surface 8 and the step portions 9 and 10 as in the conventional example.
[0014]
By the way, in the above-mentioned embodiment, the gate is on the front side of the shaft cylinder, and the curved surface is formed only at the corner of the step portion which is the flow end portion of the elastomer away from the gate, but of course the curved surface is formed on both sides. May be. If the gate is the central part of the cylinder, the curved surface is formed on both sides.
[0015]
In addition, as a condition for forming an effective curved surface at the corner between the substantially perpendicular peripheral surface and the stepped portion, a curved line is smoothly composed of one circle, two or more circles, or two or more circles sandwiching a straight line. It is provided continuously, and a circle is formed so that the peripheral surface and the step portion are substantially tangent. Further, the contact point between the curve and the step portion should be provided in the range of 0.5 to 0.7 when the height of the step portion from the peripheral surface is 1 . Further preferably, the height 0.7 ungated stepped portion from the peripheral surface as shown in FIG. 6, as the origin of the intersection of the extension of the extension and the stepped portion of the circumferential surface, the circumferential direction of a circle The contact position is 1 and the circle contact position in the step direction is 0.4.
[0016]
Also, as shown in FIG. 6, when connecting with two or more circles, it is effective to change the radius R from the large Ra to the small Rb in the flow direction of the elastomer.
At the same time, the effect is further amplified by appropriately installing a gas vent (air escape groove) on the parting surface connected to the step of the molding die.
[0017]
【The invention's effect】
The embodiments of the present invention are as described above, and in the molding process of the non-slip grip elastomer molded by two-color molding, the entrained air and the gas such as water vapor and generated gas contained in the resin material are sure. This makes it possible to prevent problems such as poor appearance and peeling of the grip, and provide a writing instrument shaft that is durable, of good quality and of good appearance.
[Brief description of the drawings]
FIG. 1 is a longitudinal half sectional view showing a structure of a shaft cylinder of a writing instrument provided with a grip.
FIG. 2 is an external view of a conventional shaft cylinder.
FIG. 3 is an enlarged view of a part A in FIG. 2;
FIG. 4 is an external view of a shaft cylinder that is an embodiment of the present invention.
5 is an enlarged view of a portion B in FIG. 4. FIG.
FIG. 6 is an enlarged view of a main part showing a desirable state of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shaft cylinder 2 Grip 3 Gate 4 Peripheral surface 5 Step part 6 Step part 6a Chamfer 7 Shaft cylinder 8 Peripheral surface 9 Step part 10 Step part 11 Curved surface 12 Peripheral surface 13 Step part

Claims (4)

In a two-color molding, a shaft of a writing instrument formed by integrally molding a grip such as an elastomer or rubber on a shaft, the peripheral surface of the grip closely contacting the inner surface of the grip and the front and rear end surfaces of the grip There substantially formed perpendicular step portion, respectively with respect to the peripheral surface of the abutment and the barrel, at least on one of the stepped portion curves to extend from the peripheral surface (be curved) All over the circumference be connected form A writing instrument shaft. The curve is formed such that one circle, two or more circles, or two or more circles sandwiching a straight line are provided smoothly and continuously, and the circumferential surface and the step portion are substantially tangent. The shaft cylinder of the writing instrument according to claim 1. The shaft cylinder of the writing instrument according to claim 2, wherein the contact point between the curved line and the step portion is provided in the range of 0.5 to 0.7 when the height of the step portion from the peripheral surface is 1 . The height of the step portion from the peripheral surface is 0.7, the intersection of the peripheral surface extension line and the step extension line is the origin, the circle contact in the circumferential direction is 1, the circle in the step direction The shaft cylinder of the writing instrument according to claim 2, wherein the contacts are provided as 0.4.

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