JP3956469B2 - Writing instrument - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention has an inner cylinder that accommodates ink and a backflow preventive body that is in contact with the interface of the ink, and an outer cylinder that houses the inner cylinder, and a gap space is provided between the outer cylinder and the inner cylinder. And a writing instrument in which an air circulation hole is provided on the side surface of the outer cylinder to communicate the gap space with the outside air.
[0002]
[Prior art]
Conventional writing tools that contain ink and the backflow preventer in contact with the ink interface in the ink tank prevent backflow by following the ink interface that moves due to a decrease in the ink storage volume in the ink tank due to ink consumption by writing. The body moves and keeps the ink tank at atmospheric pressure. That is, in such a writing instrument, it is necessary that the space on the side opposite to the ink of the backflow preventer communicates with the outside air. If the backflow prevention body does not move, the ink tank will be depressurized as the ink is consumed, and the ink discharge from the ink tank will be excluded, and the space on the opposite side of the backflow prevention body from the ink will not communicate with the outside air. In this case, the space is reduced in pressure, and the movement of the backflow preventer is alienated, eventually reducing the pressure in the ink tank.
[0003]
[Problems to be solved by the invention]
As described above, the backflow preventer must follow a relatively small force of negative pressure due to the volumetric phenomenon of the ink, and must be easily movable. Usually, a cylindrical body or a cylindrical member is wrapped with a high-viscosity fluid such as α-olefin or polybutene so as not to come into direct contact with the inner wall of the ink tank so as to be easily moved. However, this easy movement may cause another problem. That is, when an external force is applied to the writing instrument, such as when an impact is applied by dropping the writing instrument, the backflow prevention body in the ink tank may move backward. When the backflow prevention body suddenly moves backward, the high-viscosity fluid film that fills the gap between the backflow prevention body and the inner wall of the ink tank may be broken and ink may leak out. In particular, with a writing instrument that opens the valve linked to the pen tip by pressing the pen tip, when using the pen tip upward, opening the valve causes the ink weight to be applied to the backflow prevention body, and the rear end of the ink tank. Ink may leak out. In addition, when the ink tank and the exterior body that accommodates it are made of a transparent material, the temperature inside the ink tank tends to rise when left in the sun, etc., increasing the pressure in the ink tank and causing backflow It may also occur that the prevention body is pushed up in the direction opposite to the pen tip. When such a backflow of ink occurs, there is a problem that the back of the backflow prevention body communicates with the outside air as described above and leaks to the outside and may stain hands and clothes.
[0004]
That is, the present invention has an inner cylinder that accommodates ink and a backflow preventive body that is in contact with the interface of the ink, and an outer cylinder that houses the inner cylinder, and the inner cylinder is interposed between the outer cylinder and the inner cylinder. A writing instrument that secures a gap space and has an air flow hole that communicates the gap space with the outside air on the side surface of the outer cylinder, wherein the minimum diameter of the air flow hole is a portion where the opening of the air flow hole is located The gist of the writing instrument is larger than the gap width of the gap space.
[0005]
[Action]
The liquid basically does not move in the wide space unless an external force such as gravity acts, and moves in the narrow space by the capillary force. In particular, in a low-viscosity liquid having a viscosity of several to several tens cps, the ink moves to the side where the capillary force is large in a narrow space. Therefore, the capillary force that can act on the air circulation hole is made smaller than the capillary force that can act on the gap space, and even if ink leaks from the ink tank, the ink is prevented from reaching the air circulation hole as much as possible.
[0006]
【Example】
Hereinafter, an example will be described with reference to the drawings.
1 basically includes an outer cylinder 3 that houses an inner cylinder 2 filled with ink 1 in a free state therein, and is fixed to the tip of the outer cylinder 3 by concave and convex fitting. A pen core holder 5 is slidably inserted into the pen core 4 made of a fiber bundling body. An elastic valve 6 having a slit-like ink passage which is closed in a normal state where no external force is applied is installed in the inner hole of the pen core holder 5, and the inner cylinder which is press-fitted and fixed to the rear portion of the pen core holder 5. 2 is connected to the inner hole. The rear end of the pen core 4 slidable back and forth can contact the elastic valve 6 to open the slit-shaped ink passage. Although the ink volume in the inner cylinder 2 decreases as the ink is consumed, the backflow preventer composition 7 comprising a high-viscosity fluid such as polybutene or α-olefin oil in the inner cylinder 2 at the interface position with the ink 1. And a stopper plug 8 made of a material smaller than the specific gravity of the backflow prevention body composition, and the backflow prevention body composition 7 and the floating stopper 8 are arranged on the pen core 4 side together with the ink interface due to the ink loss accompanying ink consumption. Move to.
[0007]
Since the backflow preventer composition 7 and the float plug 8 move together with the ink interface due to the reduction of the ink volume accompanying ink consumption, the outer cylinder 3 is decompressed and the ink supply to the pen core 4 is not hindered. An air circulation hole 10 is provided between the inner cylinder 2 and the inner cylinder 2 to communicate the gap space 9 and the outside air formed on the side surface of the outer cylinder 3 communicating with the gap space 9. Air is taken in from the air circulation hole 10 to smoothly supply ink to the pen core 4.
[0008]
As shown in FIG. 2, which is a cross-sectional view taken along the line AA ′ in FIG. 1, the air circulation hole 10 is a tapered through hole that gradually expands outward, and the minimum diameter portion extends to the gap space 9. It is the opening edge of. The minimum diameter (x) of the air circulation hole 10 is set larger than the gap width (y) that is the distance between the inner cylinder 2 and the outer cylinder 3 in the cross section (x> y). Furthermore, in this example, the minimum diameter of the air circulation hole 10 is set to be larger than twice the gap width of the gap space 9 (x> 2y). This is because even when the installation position of the inner cylinder 2 is deviated from the center position of the outer cylinder 3, the space width of the gap space is made narrower. That is, when ink leaks from the rear end opening of the inner cylinder 2 due to an unexpected impact or the like and ink enters the gap space 9, the air circulation hole 10 is prevented from leaking outside from the air circulation hole 10. If the minimum diameter of the ink is larger than the gap width of the gap space where the opening is located and the ink flows backward, the capillary force acting on the ink works in the gap space with a small diameter. Even if the ink leaks from the ink tank, the ink is prevented from reaching the outside through the air circulation hole as much as possible. However, the air circulation hole needs to have a minimum diameter that allows the ink film to be attached, and has a size that can exert a capillary force, although it varies depending on the ink.
[0009]
FIG. 3 shows another example. It is shown as a drawing corresponding to FIG. 2 of the above example. The point etc. which were made into an example of the writing instrument which has an inner cylinder which accommodates ink and an ink backflow prevention body inside, and an outer cylinder which accommodates this inner cylinder are the same as the above-mentioned example. The difference is that the width (y2) of the area corresponding to the portion where the air circulation hole 10 is located in the gap space 9 is secured wider than the width (y) of the area of the other gap space 9. That is, the recess 3a is formed in the inner wall of the outer cylinder 3 continuously to the air circulation hole 9, so that the capillary force is not exerted to the outside as much as possible. As a result, it is difficult for ink to flow into the recess 3a, which is a gap space near the air circulation hole, and ink leakage from the air circulation hole 10 can be suppressed.
[0010]
【The invention's effect】
The writing instrument of the present invention can prevent ink leakage from the flow hole to the outside air when ink flows backward from the inner cylinder.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example.
FIG. 2 is a cross-sectional view taken along line AA ′ of FIG.
FIG. 3 shows another example of FIG. 2 equivalent part.
DESCRIPTION OF SYMBOLS 1 Ink 2 Inner cylinder 3 Outer cylinder 3a Concave part 4 Pen core 5 Pen core holder 6 Elastic valve 7 Backflow prevention body composition 8 Floating stopper 9 Crevice space 10 Air circulation hole x Minimum value y of air circulation hole 10 Gap width

Claims (3)

An inner cylinder that houses the ink and the backflow preventive body that is in contact with the interface of the ink, and an outer cylinder that houses the inner cylinder, and a gap space is secured between the outer cylinder and the inner cylinder In the writing instrument in which an air circulation hole is provided on the side surface of the outer cylinder to communicate the outside air with the gap space, the minimum diameter of the air circulation hole is the gap width of the gap space in the portion where the opening of the air circulation hole is located. Writing instrument characterized by being larger.   The writing instrument according to claim 1, wherein the diameter of the air circulation hole gradually increases toward the outside.   The writing instrument according to claim 1 or 2, wherein a gap width of the gap space in a portion where the air circulation hole is located is larger than a space width of another gap space.

Images