JPH038469Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a writing instrument cartridge for a knock-type writing instrument, which is housed in a barrel and has a pen tip that can be moved out and out from the tip of the barrel by an appropriate mechanism.

Notsuku-style writing instruments have excellent operability, but only writing instruments that use extremely viscous ink, such as oil-based ink ballpoint pens, are in practical use, and the handwriting does not penetrate to the back side of the paper or is not very clear. Although there have been many inventions and ideas for writing instruments using water-based ink, which have the advantage of producing fine handwriting and are preferred for general writing, they have not yet been put into practical use. The current situation is that this is not the case. The main reason for this is when the pen tip dries out when the cartridge is not in use (when the cartridge is stored in the barrel) and air flows in through the air hole provided at the front of the writing instrument cartridge, causing the ink inside to dry and causing ink smearing. In order to prevent this, a sealing structure was required within the tip of the shaft cylinder, and this sealing structure was technically extremely advanced, making it impossible to achieve the intended purpose.

Therefore, the applicant came to the conclusion that in order to obtain a practical writing instrument using water-based ink, there was a technical limit to the pursuit of a sealed structure.
As a countermeasure, we previously proposed installing an air hole in the tail plug at the rear of the writing instrument cartridge, but subsequent research revealed that the diameter and length of the air hole are extremely delicate, and that Air hole provided in the section (diameter is approximately 0.5 to 1 mm)
It has been found that relatively preferable results can be obtained when the diameter is smaller, for example, 0.5 mm or less. However, in order to form air holes in the tail plug, cutting using a cutting tool such as a drill or reamer, which is a conventional method for forming holes, is required.
When special processing such as electrical discharge machining, laser processing, or injection molding was used, the following problems occurred.

In other words, in the case of , the limit for drilling micro holes is 3 to 5 times the depth of the diameter of the cutter, and drilling holes deeper than that may damage the cutter and make it impossible to machine, or the workpiece may be made of resin. In the case of , the problem is that the hole melts due to the heat generated by the cutter, causing it to become clogged or bent. This is possible if the processing is focused on the following, but the problem is that the surface becomes rough due to processing heat, resulting in poor accuracy, and it takes a lot of processing time and setup time. On the mold, a core pin is required for forming micropores, but it is technically impossible to maintain such a core pin so that it does not bend due to the internal pressure of the resin. Micropores become bent due to contraction,
The problem is that it gets blocked.

Therefore, we pursued how to form air holes with small diameter and appropriate length in the tail plug with high precision.
It was also proposed to place a tail plug at the rear of the writing instrument cartridge, which is composed of an external material and an internal material, and where the non-contact part formed between the two is used as an air hole when the internal material is fixed to the external material. It turns out that there is room for improvement. In other words, when the inner and outer members are made of the same material with poor flexibility and there are variations in dimension, when the two are fixed together, the air holes, which are the non-contact parts formed between them, The size also varies, which means that optimal air circulation cannot be guaranteed.

Therefore, the present invention attempts to minimize variations in the size of the air holes even if the dimensions vary by using a harder resin as the inner material than the outer material.

The present invention will be described in detail below based on embodiments shown in the accompanying drawings.

Reference numeral 1 denotes a writing instrument cartridge made of metal or the like, in which an ink storage body 2 for storing water-based ink is housed, and a tail plug 3 is disposed at the rear of the writing instrument cartridge 1. This tail plug 3 is composed of an outer member 4 and an inner member 5. The front part 4 of the outer member 4 is made of a resin such as soft polyethylene, vinyl acetate, vinyl chloride, and solvent-resistant heat-resistant rubber, and has a through hole 4 a bored inside.
b is fixed to the rear part of the writing instrument cartridge 1 by an appropriate fastening means such as press-fitting. The internal material 5 is made of a resin harder than the external material, such as polypropylene, polyacetal, or polyester terephthalate, has approximately the same outer diameter as the through hole 4a of the external material 4, and is further formed with a linear notch 5a. The rod-shaped portion 5b is press-fitted and fixed into the through-hole 4a of the external member 4, and when the rod-shaped portion 5b is press-fitted and fixed, the longitudinal direction formed between the linear notch 5a of the rod-shaped portion 5b and the through-hole 4a is The linear non-contact portion 6 serves as an air hole. 4c is a ventilation slit formed in the front part of the outer member 4, and this slit 4c
The reason why the space 7 behind the slit 4c is stepped is that when an impact is applied to the cartridge, the ink impregnated in the ink storage body 2 flows into the linear non-contact part 6 (air hole). This is to prevent

As described above, the present invention consists of a tail plug made of an outer material made of resin and an inner material made of a harder resin than the outer material, and when the inner material is press-fitted and fixed to the outer material, the inner material and the outer material are bonded together. Since the linear non-contact part formed in the longitudinal direction is made to be an air hole, there is no problem like the above-mentioned processing methods, and if the dimensions of the internal material and external material are controlled, minute If you can easily obtain an air hole with a diameter (equivalent cross-sectional area) and sufficient length, and if the dimensions of the internal material are made somewhat larger, even if some variation occurs in the dimension management, Since the outer material, which is softer than the inner material, expands outward when the two are fixed together, variations in the air holes themselves can be minimized, and the problem of ink smearing caused by drying of the ink inside the writing instrument cartridge can be avoided. This is something that can be prevented as much as possible.

In the example, a notch was provided in the rod-shaped part to form a linear non-contact part, but it is also possible to press-fit a rod-shaped part with a circular cross section into a through hole with an elliptical cross section to form a non-contact part. Alternatively, the non-contact portion may be formed not in a straight line but in a curved shape.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal cross-sectional view of a main part, and FIG. 2 is a cross-sectional view taken along the line A--A in FIG. 1. 1... Writing instrument cartridge, 2... Ink absorber, 3... Tail plug, 4... External material, 5... Internal material,
6...Non-contact part.

Claims (1)

[Scope of utility model registration request] A knob-type writing instrument is housed in a barrel and has a retractable mechanism in which the pen tip protrudes and retracts from the tip of the barrel.The ink absorber that absorbs water-based ink is housed inside, and an external material made of resin and a retractable material are installed at the rear. A writing instrument cartridge for a lock-type writing instrument, which is composed of an inner material made of a harder resin than the outer material, and has a tail plug that uses a non-contact part formed between the two as an air hole when the inner material is fixed to the outer material.