JPH11210728A - Male screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-weighted, strong screw. SOLUTION: A screw has a shank 11 and a head 12, while a spiral screw thread 13 is formed on an outer periphery of the shaft 11. Its based material is aluminum or an aluminum alloy. A nickel metal film 14 is formed on whole of the screw by electroless plating. The base material itself is aluminum or an aluminum alloy which has strength to some extent. It is coated with the nickel metal film 14 to form a hard shell. Twisting strength of the male screw is thus improved. A light-weighted, strong male screw can thus be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a male screw including a self-tapping screw, and more particularly to a lightweight and strong male screw.

[0002]

2. Description of the Related Art Cellular phones, portable tape recorders and C
There are many portable industrial products such as D players and cameras, but it is not too much to say that reducing their weight is directly linked to sales promotion. For this reason, each manufacturer is greatly committed to reducing the weight. The object of this weight reduction includes screws used in these assemblies, and there is an extremely strong demand for weight reduction of screws, particularly male screws. In response to such a request, attempts have been made to make the external thread made of plastic or aluminum or an aluminum alloy.

[0003]

However, most of the screws used in the above-mentioned portable telephones and the like have a small diameter of 2.6φ or less, which is called a miniature screw. When it comes to plastics, those that are satisfactory in strength cannot be obtained. On the other hand, those made of aluminum or aluminum alloy are more durable than plastics, but still do not provide sufficient strength and lack reliability. Of course, some of these materials have an increased hardness when subjected to heat treatment, but the heat treatment is extremely labor-intensive and increases the production cost.

The present invention has been made in view of the above-described circumstances, and has as its first object to provide a lightweight and strong screw. Further, a second object of the present invention is to provide a male screw capable of preventing loosening without increasing a tightening torque, in addition to the above objects.

[0005]

SUMMARY OF THE INVENTION In order to achieve the first object, the present invention has a head portion at one end of a shaft portion, and a helical thread at least on the outer periphery of the shaft portion at the distal end side. In the formed screw, the shaft and the head are formed of a lightweight metal, and a metal film is formed on the entire screw including the head by plating for surface hardening.

The light metal may be aluminum or an aluminum alloy, and the metal film may include a nickel plating layer or a hard chromium plating layer, or the plating may be formed by electroless plating.

In order to achieve the second object, the male screw according to the present invention, in addition to the above-mentioned configuration, has a crest width of the male screw wider than a valley width at a threaded portion of the female screw, and a foot width of the male screw is smaller than that of the female screw. It is characterized in that the width is less than the width of the joint.

Alternatively, the peak width of the male screw is made equal to the root width of the threaded portion of the female screw, and a contact surface overlapping with the slope of the threaded portion of the female screw is formed on at least one of the two slopes at the peak. In other portions, a gap may be formed in the sense with the female screw.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the screw of the present invention.
As shown in the drawing, the screw 10 of the present invention has a head portion 12 at one end of a shaft portion 11, and a spiral screw thread 13 reaching the tip of the shaft portion 11 is formed on the outer periphery of the shaft portion 11. ing. The screw having the above configuration is formed by rolling from aluminum or various aluminum alloys. The head 12 is provided with a recess 12a formed of a cross hole or the like. In the embodiment of FIG. 1, the thread 13 is formed up to the head 12, but it is not necessarily formed up to the head, and it is sufficient that the thread 13 is formed at least on the tip side of the shaft 11.

[0010] The screw of the present invention is characterized in that the entire screw is covered with a metal film 14 by nickel plating. In FIG. 1, the head 12 is shown by a virtual line and the metal film 14 is not shown, but a nickel metal film 14 is also formed on this portion similarly to the screw thread.

[0011] Nickel plating, besides corrosion resistance and beautification,
It is used for the purpose of surface hardening. By forming a hard nickel metal film 14 on a material made of soft aluminum or aluminum alloy, the advantage of aluminum and aluminum alloy is that the lightweight point is maintained. It is possible to compensate for the disadvantage of insufficient strength, and to obtain a light and strong screw.

In other words, by using aluminum or an aluminum alloy instead of plastic as the material, the material can have a certain level of strength. By forming the nickel metal film 14 thereon, a hard shell can be formed. With this structure, the strength of the male screw including the torsional strength is improved, and the required strength can be achieved.

In the screw of the present invention, the thickness of the metal film 14 is
The thickness is 5 to 10 μm. If it is less than 5 μm, improvement in strength cannot be expected, and if it exceeds 10 μm, it takes too much time for plating and the cost is increased. The screw on which the nickel metal film 14 having the thickness in the above range was formed was measured using a micro Vickers hardness meter.
4 has a hardness of about Hv500,
At the same time as the surface hardens, the mechanical strength also increases, in particular it is resistant to torsion.

[0014] It is sufficient that the plating is provided only on the thread portion. However, if the plating is provided on other shaft portions or the head, the strength of the entire screw is increased, and at the same time, the screw is beautified and the corrosion resistance is improved. Is also improved.

The method for manufacturing a screw according to the present invention will be briefly described. First, an aluminum wire having a desired diameter is cut to a predetermined length, a recess such as a head and a cross hole is formed, and a thread is formed from a tip of a shaft to a predetermined position by a rolling machine. Up to this point, the screw is the same as the conventional screw. However, depending on the accuracy required for the male screw as a finished product, the screw may be formed as thin as the thickness of the metal film 14.

The aluminum screw thus formed is plated with nickel. The plating method is preferably an electroless plating method. That is, the above-mentioned rolled, necessary pre-processed external thread is thrown into the solution and crushed, without passing an electric current from the outside, the nickel ions in the solution are chemically reduced by a reducing agent, A plating film is formed on the surface of the screw. The solution is heated to about 90 ° C., and the thickness of the plating layer (metal film 14) can be controlled by adjusting the time during which the screw is immersed in the solution. By electroless plating, there is no pinhole and a highly pure nickel metal film is formed. As described above, about 500 Hv,
The metal film 14 having high hardness can be obtained.
It is simpler than heat treatment. Instead of nickel plating, another metal such as hard chrome plating may be plated.

FIG. 2 shows a second embodiment of the present invention. The unplated configuration is the same as the male screw described in Japanese Patent Application Laid-Open No. Hei 5-71524 filed by the applicant of the present application, and is a cross-sectional view showing a state where the male screw 20 of the present invention is screwed to the female screw 21. . Although not particularly shown, the metal film 14 formed by plating is formed in the same manner as in FIG.

The arrow shown in FIG. 2 indicates the traveling direction of the male screw when the male screw is screwed. The top of the screw thread 22 is parallel to the direction of travel of the male screw and is a plane along the spiral of the screw. The width W of the crest of the screw thread 22 is larger than the root width w of the female screw 21 to which this crest is screwed, and the width D at the foot of the screw thread is smaller than the corresponding root width d of the female screw 21. Further, the slope on the front side in the traveling direction of the screw thread has the same inclination as the slope of the female screw, and the slope on the rear side is steeper than the slope of the female screw.

The male screw 20 having such a configuration is connected to the female screw 21.
Then, the rear end 22a of the crest of the male screw bites into the female screw 21, and the auxiliary female screw 24 is screwed in while tapping. By this tapping, the male and female screws 20, 21 are screwed tightly and are hardly loosened. Further, tapping is performed only at the rear end of the crest of the male screw 20, and only a small part of the entire screw is viewed. Therefore, the screwing can be performed with almost no increase in the screwing torque.

As described above, despite the fact that the male screw is made of a relatively soft metal such as aluminum or an aluminum alloy, the auxiliary female screw 24 can be tapped only when the metal film 14 is made of nickel, which is a hard material. Because they use it.

FIGS. 3 and 4 are sectional views of a third embodiment of the present invention. The configuration without plating is described in the prior application filed by the applicant of the present application, Japanese Patent Application No. 9-281543. The male screw 30 in this embodiment has a thread 3
The width of the crest 1 is the same as the width of the valley at the threaded portion of the female screw 32, and at least one of the two slopes at the ridge has a contact surface 33 overlapping the slope of the female screw at the threaded portion.
A gap is formed between the female screw 32 and the portion other than the contact surface 33 of the male screw 30.

With such a configuration, the male screw 30 comes into contact with the female screw 32 only on the outermost contact surface 33 of the outer diameter of the screw thread 31, and the slack can be prevented most efficiently. Further, in this embodiment, since the auxiliary female screw 24 is not formed, even if it is repeatedly used, the effect of preventing loosening is not reduced. Furthermore, the tightening torque is lower than in the case of the second embodiment shown in FIG.

Since the male screw of the second and third embodiments has a strong connection with the female screw, even if the tightening is interrupted halfway,
There is little loosening, and it can be used as a screw for adjustment.

[0024]

As described above, the male screw according to the present invention has a head portion at one end of a shaft portion and a helical thread formed at least on the outer periphery of the shaft portion at the distal end side. The shaft and head are made of lightweight metal, and the entire screw including the head is coated with a metal film by plating for surface hardening, so it has a light and hard surface, and the overall strength of the screw Ascending, it is possible to obtain a male screw that is resistant to twisting.

If the plating is made by electroless plating of nickel, a harder metal film with higher purity can be obtained, which is more effective.

Further, in addition to the above-described configuration, a configuration in which the crest width of the male screw is wider than the root width of the screw portion of the female screw and the foot width of the male screw is smaller than the width of the screw portion of the female screw, or the crest width of the male screw Is formed to be the same as the valley width at the threaded portion of the female screw, and a contact surface overlapping with the slope of the threaded portion of the female screw is formed on at least one of the two slopes at the peak, and a gap other than the contact surface is provided to feel the female screw. Is formed, it is possible to obtain a screw that is not easily loosened without increasing the tightening torque.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a male screw of the present invention.

FIG. 2 is a sectional view of a main part showing a state in which a male screw is screwed with a female screw according to a second embodiment of the present invention.

FIG. 3 is a partial perspective view showing a configuration of a right half of a male screw according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a main part showing a state where the male screw of FIG. 3 is screwed into the female screw.

[Explanation of symbols]

 Reference Signs List 10 Male thread 11 Shaft 12 Head 13, 22, 30 Thread 14 Metal film 21, 32 Female thread 33 Contact surface W Width of thread crest w Width of corresponding female thread D Width of corresponding thread c Thread width

Claims (5)

[Claims] 1. A screw having a head at one end of a shaft portion and a helical thread formed at least on the outer periphery of the shaft portion at the distal end side, wherein the shaft portion and the head are formed of a lightweight metal. A male screw formed by forming a metal film by plating for surface hardening on the entire screw including the head. 2. The male screw according to claim 1, wherein the lightweight metal is aluminum or an aluminum alloy, and the metal film includes a nickel plating layer or a hard chrome plating layer. 3. The male screw according to claim 1, wherein the plating is performed by electroless plating. 4. The method according to claim 1, wherein the crest width of the male screw is wider than the root width of the screw portion of the female screw, and the foot width of the male screw is less than the width of the screw portion of the female screw. Male screw described in Crab. 5. A crest width of the male screw is made equal to a root width of a screw portion of the female screw, and a contact surface overlapping with a slope of the screw portion of the female screw is formed on at least one of both slopes at the crest. A gap is formed in a portion other than the portion in a sense with the female screw.
The male screw according to any one of the above.