JPH025992Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to the structure of a cap that is fitted over the tip of a writing instrument barrel to prevent the tip of the writing instrument from drying out.

(Prior art) A conventional cap 1 of this type has a shaft cylinder 2 on its inner surface.
A sealing protrusion 3 is provided around the outer circumferential surface of the cylinder, and the sealing protrusion 3 is located on the same cross section perpendicular to the axial direction as shown in FIGS. 4 and 5. .

(Problem to be solved by the invention) Therefore, if the fit between the inner diameter of the sealing protrusion of the cap and the outer diameter of the writing instrument barrel facing the sealing protrusion is not appropriate, the sealing performance may be impaired. Otherwise, the fitting force becomes excessive, making attachment and detachment difficult. Particularly when the wall thickness of the cap is large, the variation in the fitting force is large and the allowable range of interference error becomes narrow. As described above, conventional structures require high dimensional accuracy, making it difficult to provide inexpensive products.

The present invention aims to solve these problems.

(Means for Solving the Problems) In order to solve the above problems, the present invention is made of elastic synthetic resin and has a sealing protrusion on its inner surface that is displaceable in the axial direction. The purpose is to provide a cap for a writing instrument that is provided with a writing instrument.

(Function) In other words, in the conventional structure, the seal point was concentrated at one point in the axial direction, so the size of the interference, which is the difference between the inner diameter of the sealing protrusion at the same location and the outer diameter of the shaft cylinder opposite to the sealing protrusion, was This was a major factor in determining the magnitude of the fitting force, which necessitated strict dimensional control.However, with this invention, the sealing points are dispersed within the required range in the axial direction, so At one point in the axial direction of the cap, the entire circumference is not restricted by the sealing protrusion, so it is possible to extend the protrusion in the circumferential direction and deform the cap. Since it is a factor that determines the resultant force, the influence of the interference between the seal protrusion and the shaft cylinder on the fitting force is reduced, and the allowable dimensions can be increased accordingly, making it easier to mold overall and shortening the molding cycle. It is what it is.

(Embodiment) Figures 1 and 2 show the first embodiment of the present invention, in which Figure 1 is a diagram of the fitted state of the cap 1 and the barrel 2, and Figure 2 is an expanded inner view of the cap. The cap 1 is made of an elastic synthetic resin, and is provided with a sealing protrusion 3 on its inner surface that is displaced in a straight step in the axial direction. In the figure, reference numeral 4 denotes an inner surface protrusion provided on the inner surface of the opening end of the cap to prevent the cap from coming off, and 5 an outer surface protrusion of the shaft cylinder that engages with the inner protrusion 4 when the cap 1 is fitted.

Next, FIG. 3 shows an expanded inner view of the cap of the second embodiment of the present invention, in which the sealing protrusion 3 provided on the inner surface of the cap 1 has a straight stepped shape in the axial direction, unlike the first embodiment. It is constructed so that it is not displaced in the axial direction, but in a curved manner in the axial direction.

(Effects of the invention) The present invention has the above-described structure and function, and the dimensional tolerance of the sealing protrusion provided on the inner surface of the cap and the interference between the shaft cylinder is expanded, and molding is facilitated, resulting in an inexpensive product. This has the effect of making it possible to provide such services.

[Brief explanation of the drawing]

Figures 1 and 2 show the first embodiment of the present invention, and Figure 1 is a diagram of the fitted state of the cap and barrel;
FIG. 2 is an exploded inner view of the cap, and FIG. 3 is an exploded inner view of the cap, showing a second embodiment of the present invention. Figures 4 and 5 show conventional examples; Figure 4 is a diagram of the fitted state of the cap and barrel;
The figure is an expanded inner view of the cap. 1... Cap, 2... Shaft cylinder, 3... Seal protrusion,
4...Inner surface protrusion, 5...Outer surface protrusion.

Claims (1)

[Scope of utility model registration request] A cap for a writing instrument that is made of elastic synthetic resin and has a sealing protrusion on its inner surface that is displaceable in the axial direction and that is in close contact with the outer surface of the barrel.