JP3924904B2 - Writing instrument - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a writing instrument in which a synthetic resin pipe body having a rear end opened as an ink tank is used, and a backflow prevention body that can move as the ink interface moves is disposed inside.
[0002]
[Prior art]
A writing instrument that uses a pipe body obtained by cutting an extruded product made of polypropylene resin as an ink tank is used for a ballpoint pen or the like. There is no problem if a fairly high-viscosity ink is used, but if a relatively low-viscosity ink is used, the ink will flow out from the opening at the rear end, so it will flow back to the ink interface. What arrange | positions the prevention body as a movable stopper is known. In order to prevent the backflow of ink, this backflow prevention body has an outer diameter that is as close as possible to the inner diameter of the pipe body, but does not move along with the ink interface that moves as the ink is consumed. Since the inside of the ink tank is depressurized and ink discharge from the nib is obstructed, a slight gap is usually formed between the pipe wall and the inner wall of the pipe body, wrapped in a highly viscous fluid such as α-olefin or polybutene. The movement is not inhibited by direct contact.
[0003]
[Problems to be solved by the invention]
However, it is difficult to make the inner wall dimensions of the pipe body, which is a molded product of synthetic resin, the same over the entire length, and there may be a portion with a narrow diameter due to dimensional variations on the inner wall. In addition, since the outer diameter of the backflow prevention body may vary, the backflow prevention body may come into contact with the inner wall of the pipe body while the backflow prevention body is moving. Especially when the pipe body is housed in the exterior body and the rear end of the pipe body is in contact with the bottom of the exterior body, when external pressure is applied in the direction of reducing the diameter of the pipe body, the desired pipe body inner diameter cannot be obtained. Similarly, while the backflow prevention body is moving, it sometimes comes into contact with the inner wall of the pipe body and stops moving .
[0004]
That is, the present invention uses a synthetic resin pipe body having an open rear end as an ink tank, and a writing instrument in which a backflow prevention body that can move in accordance with the movement of the ink interface is disposed inside the ink tank. The gist of the writing instrument is characterized in that pressure input is applied to the opening at the rear end of the pipe body to expand the opening, and the inner diameter of the pipe body is expanded .
[0005]
【Example】
Hereinafter, an example will be described with reference to the drawings . Each drawing shows only the rear part of the writing instrument, but the front part structure of the writing instrument is not particularly limited, and a conventionally known appropriate structure can be adopted.
In FIG. 1, the pipe body 2 made of polypropylene resin as an ink tank is sandwiched in the longitudinal direction in an outer casing 1 of a bottomed cylindrical body which is an injection-molded product of acrylonitrile styrene resin having transparency. FIG. That is, in the pipe body 2, the backflow prevention body composition 4 of the high-viscosity fluid made of α-olefin, polybutene and the like that follows the movement of the ink 3 and the ink interface and the backflow prevention body composition 4 are placed on the inner wall of the pipe body. Floating plug 5 which is a backflow preventer disposed so as to be interposed therebetween is accommodated. Although not shown in the drawings, the pipe body 2 is sandwiched between the front member of the writing instrument to which the exterior body 1 is connected and the rear end abutting against the bottom of the exterior body 1.
[0006]
The rear end opening edge 2a of the pipe body 2 is a tapered wall that gradually increases in diameter toward the rear. . Since the rear end of the pipe body 2 is deformed and expanded, the diameter of the pipe body as a whole is slightly expanded. Therefore, even if a portion with a somewhat narrow diameter is formed in the inner diameter of the pipe body 2, it can be absorbed by this expanded diameter, and inhibiting the movement of the float 5 is suppressed as much as possible. Here, the press-contact part 1a of the exterior body 1 has a notch part 1b indicated by a dotted line in the drawing, not a circumferential step part. That is, the space 6 behind the pipe body 2 is not sealed. This space 6 communicates with the outside air through an air hole (not shown) formed in the exterior body 1.
[0007]
FIG. 2 shows another example. It is an example of what has a plurality of press-fitting pieces 1c as a press-contact portion of the outer package 1. The press-fitting piece 1c has a tapered tip portion 1d that gradually goes toward the center toward the tip. Since the tapered wall of the tip end portion 1d abuts against and is pressed against the opening edge of the pipe body 2, the press-fitting piece 1c is inserted while being pressed into the inner hole of the pipe body 2. The press-fitting piece 1c is less likely to be deformed than the pipe body 2, whereby the rear end of the pipe body 2 is deformed and expanded. Therefore, similarly to the above-described example, the diameter of the entire pipe body is slightly increased, and the movement of the floating plug 5 that is the backflow preventing body is suppressed as much as possible.
[0008]
FIG. 3 shows still another example.
As a means for expanding the diameter of the rear end portion of the pipe body 2, a tail plug 7 is press-fitted into the rear end of the pipe body 2. The tail plug 7 has a ventilation center hole 7a in the pipe body 2 for preventing the space 6 behind the floating plug 5 that is a backflow prevention body from being sealed, and has an annular pressure contact portion 7b. A portion protruding rearward from the pipe body 2 is in contact with the bottom of the exterior body 1 at the rear end 7d, and a slit 7c communicating with the ventilation center hole 7a is formed. The ventilation center hole 7a and the slit 7c communicate with the outside air through the air hole of the exterior body 1 described in the above example. That is, the positional relationship is adjusted so that the outer wall of the expanded pipe body 1 does not circumferentially contact the inner wall of the exterior body 1 by contacting the bottom of the exterior body 1 at the rear end 7d of the tail plug 7 is doing.
[0009]
【The invention's effect】
As described above, the writing instrument of the present invention can suppress as much as possible the inhibition of the movement of the backflow preventer that follows the ink interface.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part showing an example.
FIG. 2 is a cross-sectional view of a main part showing another example.
FIG. 3 is a cross-sectional view of a main part showing still another example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exterior body 1a Press-contact part 1b Notch part 1c Press-fitting piece 1d Tip part 2 Pipe body 2a Rear end opening edge 3 Ink 4 Backflow prevention body composition 5 Floating plug 6 Space 7 Tail plug 7a Vent center hole 7b Press-in part 7c Slit 7d rear end

Claims (5)

In a writing instrument that uses a synthetic resin pipe body that opens the rear end as an ink tank, and a backflow prevention body that can move in accordance with the movement of the ink interface, the back of the pipe body that becomes the ink tank A writing instrument, wherein a pressure input is applied to an open port at an end to widen the open port, and an inner diameter of the pipe body is expanded .   2. The writing instrument according to claim 1, wherein the pipe body as the ink tank is accommodated in an exterior body, and a pressure contact portion with respect to the opening of the pipe body is formed at the bottom of the exterior body.   3. An opening portion at the rear end of the pipe body is formed as a tapered wall that gradually widens toward the rear side, and the pressure contact portion formed on the bottom portion of the exterior body is brought into contact with the tapered wall to widen the opening. Writing instrument as described.   The pressure contact portion of the exterior body is a pressure contact piece having a front end portion whose outer diameter is gradually reduced toward the front end side, and the pressure contact piece is press-fitted from the rear end opening of the pipe body to be expanded. The writing instrument according to claim 2.   2. The writing instrument according to claim 1, wherein a press-fit tail plug having an air circulation hole is inserted into a rear end opening of the pipe body as the ink tank to expand the mouth.

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