JPS62179996A - Manufacture of ball pen tip - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a ballpoint pen tip formed from a metal capillary.

(Prior art) The conventional method for manufacturing a ballpoint pen tip from a thin metal tube includes: ■ Pressing inward multiple points on the same circumference of the outer circumferential surface near the tip of a thin metal tube made of stainless steel to form a ball on the inner wall. One in which a ball is inserted into the tip of a thin metal tube with a protruding catch, and the tip edge is caulked; ■ A hole is formed in the tip of the thin metal tube from the opening direction to form a ball catch, and the ball is inserted. There are some that have their tip edge crimped afterwards. However, according to these methods, the inner diameter of the metal thin tube is required to be slightly larger than the ball diameter, or slightly smaller than the ball diameter by the amount of hole cleaning. When forming a chip or the like, there is a problem that the outer diameter of the metal tube becomes extremely small, resulting in insufficient strength against bending. Furthermore, when dispensing the tip of a water-based ballpoint pen, etc., the outer diameter of the ink supply wick is limited by the inner diameter of the metal tube, so there is the problem that sufficient ink cannot be supplied to the tip.

Therefore, as a method to solve this problem, the outer circumferential surface of only the tip of a thin metal tube having an inner diameter sufficiently larger than the ball diameter, which is the part where the ball seat is formed, is pressed inward to form a tapered narrowed part. A ball holding hole and a pole seat are formed by drilling the inner surface of this narrowed part from the tip opening side, and an axial ink guide groove is formed in the rear part of the pole seat by broaching etc. A method has been considered in which the ball is formed, and then the ball is inserted into the ball holding hole, and the tip edge of the ball holding hole is caulked inward to prevent the ball from being pulled out.

(Problem to be Solved by the Invention) According to the method (2) above, the diameter of the metal capillary tube is not limited by the ball diameter and it is possible to have a sufficient diameter, so it is possible to create an ultra-fine ballpoint pen for Japanese writing. Even when forming a chip or the like, there is no need to worry about strength, and it is also possible to mount an ink supply core with a sufficient outer diameter.

By the way, it is desirable to use a hard material such as stainless steel for the metal thin tube for the ballpoint pen tip in order to prevent deterioration of life due to wear of the ball seat, provide durability, and maintain high quality. Conventionally, small diameter (outer diameter is 3W)
Stainless steels used for thin metal tubes (less than m) are mainly austenitic, such as 5USJO4.
It is relatively easy to weld, has high tensile strength, and can be made into small-diameter drawn tubes, so it is widely used as industrial thin tubes. However, when a ballpoint pen tip is formed using this 5US304 according to the method (2) above, 5US304 is used.
US304 has high work hardening properties (work hardening index is n=0
．． 53, whereas the hardening index of mild steel is n=0.25. ), the following problems arise. First, in (A) narrowing the tip, if the cross-section reduction rate exceeds 40 to 60 inches, the narrow part becomes brittle due to work hardening, and the axial direction from the end surface The problem is that fine cracks occur in parallel to
In the case of (b), the diameter of the metal capillary is twice the diameter of the ball. When forming ultra-fine ballpoint pen tips with small ball diameters, the bending strength and stable ink supply are somewhat insufficient, and in the case of (b), the process The technical difficulty of heat treatment during the process is high, resulting in high costs. Next (B) When performing cutting such as drilling holes to form a pole seat in the sharp part,
Since this cutting process is precision processing and requires a minute cutting feed, the hardened layer produced by the cutting process is repeatedly cut, which significantly reduces the durability of the cutting tool. Particularly in broaching to form ink guiding grooves, the higher the hardness of the material, the more difficult the processing becomes, so heat treatment is required to lower the hardness of the material.
Since the hardness of SUS 304 cannot be adjusted by heat treatment, it must be processed in a so-called annealed state, which tends to cause cracks, which creates the contradictory problem of making it impossible to process ballpoint pen tips that require dimensional accuracy. Furthermore (C
) SUS 30 is also used in the caulking process after inserting the ball.
No. 4 has a problem in that the springback is large and the gap between the ball and the inner surface of the ball holding hole is not stable, causing variations in the amount of ink flowing out. The purpose of the present invention is to solve such problems.

(Means for Solving the Problems) The method for manufacturing a ballpoint pen tip of the present application, which was devised to solve the above problems, is as follows:
5-20 cm, Ti 0.1-1%, Sl 0.01-1%
The tip of a thin metal tube of the required diameter made of ferritic stainless steel containing 1% ferritic stainless steel is narrowed, the tip is creped, and the crepe is cut to create various parts such as ball seats and ink guiding grooves. It is characterized by forming.

In this case, MO may be added to improve the corrosion resistance of the stainless steel used, and small amounts of other elements such as Nb, which are usually added, may be added to improve workability and weldability. Of course, I don't mind that. In general, ferritic stainless steel (for example, SUS 43) has weaknesses such as high-temperature brittleness and 475°C brittleness, which makes it inconvenient for welding, so small diameter metal tubes (outer diameter of 3 mm or less) are not often manufactured. However, since the ferritic stainless steel containing the composition shown in the present invention has improved weldability, it is possible to manufacture small diameter pipes.

(Examples and effects) C 0.03%, Cr 16~IQ%, Ti 0.1~
1.0%, Sl 0.8%, Mn 1.0%, P 0θ
The tip of the metal tube (1) (outer diameter 3 ws or less) shown in Fig. 1, which is made of ferritic stainless steel containing 0.03% S and 0.2 to 0.5% MO, is The entire circumference is pressed inward and narrowed several times to gradually taper, and the final shape is as shown in Figure 2, i.e., the narrowed part (2) with a reduced diameter at the tip. Finish it into the shape you want.

The hardness distribution in each part at this stage is SUS 304.
Fig. 3 shows a comparison with the one using . As is clear from this graph, the hardness increases in the narrowed part (2) of the one using SUS 304, whereas
In the case using this example, cracks occurred in the narrowed portion (2), but no cracks occurred in the case of this example. Although ferritic stainless steel (SUS 430 series) is inferior in mechanical properties to SUS 304 in terms of elongation and reduction of area, it does not crack, and BUS304 has better mechanical properties than ferritic stainless steel. The reason why cracks occur despite being superior to steel is due to this increase in hardness. Next, the parts surrounded by broken lines in FIG. 2, namely the ball seat forming part (3) and the ball holding hole forming part (4)
) from the tip side by cutting and then chamfering. At this time, the material according to this example has low work hardenability, and even if a small cutting feed is applied, the hardened layer will not be cut, so the wear of the tool is small, and the 5U830
It was confirmed through actual testing that the durability was significantly improved and the tool life was approximately 10 times longer than when cutting materials made of No. 4.

Furthermore, in the subsequent broaching process of the ink guide groove forming portion (the area surrounded by the dashed line in FIG. 2) (5), there was almost no increase in the hardness of the material in this example, so 5US304 was used.
There was no need for heat treatment as in the case of using . Furthermore, as a result of measuring the gap between the ball and the inner surface of the ball holding hole after the ball is caulked to prevent the ball from being pulled out after insertion, the gap was approximately 20 mm in this example, as shown in Figures 4 and 5. It is stable between ~40 microns, whereas S
Using US 304, very variable results were obtained between 0 and 50 microns.

Furthermore, when the relationship between the recording distance and the amount of ink flowing out was measured using several samples, the results shown in the graphs of FIGS. 6 and 7 were obtained. That is, in this example, there is little variation in the amount of ink flowing out of each sample, whereas in the case of the sample using SUS 304, the variation is extremely large.

(Effects of the Invention) The present invention has the following effects due to the above-described configuration and operation. First, ferritic stainless steel (8U8
430 steel series) has work hardening properties compared to austenitic stainless steels (S
It is possible to prevent the occurrence of cracks due to narrowing of the rounded tip, which is lower than that of the US 304 steel series), and for the same reason, heat treatment is not required during the machining amount, streamlining the process, and improving the durability of the tool during cutting. Improved productivity and processing accuracy, resulting in improved productivity, stable quality, and reduced costs. Further, the caulking accuracy of the tip portion is improved, variations in the gap between the ball and the inner surface of the ball holding hole are suppressed, and the amount of ink flowing out is stabilized. As described above, the present invention has the remarkable effect of being able to mass-produce high-quality ballpoint pen tips with excellent workability at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a metal pipe before processing according to an embodiment of the present invention;
Fig. 2 is a vertical cross-sectional view of a metal pipe that has been subjected to a narrowing process according to an embodiment of the present invention, and Fig. 3 is a hardness distribution at various parts of the tip including the sharply processed part of an embodiment of the present invention and a conventional example. Graph diagram showing 4th
The figure is a graph showing the measured gap between the ball after caulking in this example and the inner surface of the ball holding hole, and Figure 5 shows the measured gap between the ball after caulking in the conventional example and the inner surface of the ball holding hole. 6 is a graph showing the relationship between the positioning distance and the amount of ink flowing out in this embodiment, and FIG. 7 is a graph showing the relationship between the marking distance and the amount of ink flowing in the conventional example. (l),...Metal tube, (2)...Narrowed part, (3)...
...Ball seat forming part, (4)...Ball holding hole forming part, (5)...Ink guiding groove forming part.

Claims (1)

[Claims] C 0.1% or less, Cr 15-20%, Ti 0.1
The tip of a metal capillary tube of the desired diameter made of ferritic stainless steel containing ~1% and 0.01~1% Si is narrowed to reduce its diameter, and the reduced diameter section is cut. A method for manufacturing a ballpoint pen tip, which comprises forming various parts such as a ball seat and an ink guiding groove using the same method.