JP2001124039A - Multiple thread tapping screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple thread tapping screw capable of stabilizing the thread bite-in when female threads are formed while the merit of tapping screw having non-circular threads is well made use of, enlarge the contacting area with the molded female threads, increasing the fastening ruptural torque and retaining shaft force, and performing stable fastening even if the work consists of a very thin steel sheet. SOLUTION: The tapping screw has a head 12 furnished with a rotary tool engagement part 13 at one end of a body threaded portion 11 to serve for fastening, and also at the other end, an intrusion end threaded part 14 thinning toward the tip where femal threads are formed, wherein the intrusion end threaded part 14 consists of non-circular multiple threads 14a and 14b while the body threaded portion 11 consists of circular, parallel multiple threads 11a continued to the non-circular multiple threads 14a and 14b. The intrusion end threaded part 14 is composed of non-circular tapered multiple threads 14a and non-circular multiple threads 14a continued to the tapered ones 14 and having approximately the same rotational diameter as the outside diameter of the mentioned parallel ones 11a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-threaded tapping screw having a thread portion formed into a multi-thread thread.

[0002]

2. Description of the Related Art As a conventional self-tapping screw, FIG.
As shown in FIG. 5, the contour of the thread 1 is substantially equilateral triangular, each side 2 has an arc shape, and is formed in a non-circular shape having three protrusions 3 at the intersection of the two sides 2. A non-circular thread tapping screw in which a female screw 4 is formed by three projections 3 is widely used.

[0003]

The above-mentioned conventional tapping screw has a great advantage in that the screwing resistance is small and the fastening operation can be performed efficiently, but the formed female screw 4 and the non-circular thread 1 have a great advantage. The contact area 5 is small, so that there is a disadvantage that the tightening breaking torque and the holding axial force are low.
In addition, since the non-circular thread 1 has one thread, FIG.
And (b), the metal sheet 6 which is the member to be fastened.
When the female screw is formed by screwing into the prepared hole 7 provided in the hole, the screwing is unstable, the shaft core is inclined as shown in the drawing, and the biting is likely to occur, especially when fastening to a thin plate, Since the pilot hole 7 tends to be a fool hole due to poor biting, accurate torque control is required during the fastening operation. For this reason, a tightening tool with an electric torque control is used. However, in the case of a thin plate, even if a tightening tool with a torque control is used, an idiot is formed, so that there are restrictions on use conditions such as a reduction in a fastening speed. Therefore, the conventional non-circular thread tapping screw has a limit at which a thin plate having a thickness of about 0.6 mm can be stably fastened.

On the other hand, in the case of home electric appliances and the like, there is a tendency to reduce the total cost of the products by using thinner steel plates.

[0005] The present invention has been made in view of the above-described circumstances, and while taking advantage of the conventional tapping screw having a non-circular thread, the threading at the time of forming an internal thread is stable, and The object of the present invention is to provide a multi-threaded tapping screw which has a large contact area with a formed female screw, can increase a tightening breaking torque and a holding axial force, and can perform a stable fastening even on an extremely thin steel plate. I have.

[0006]

In order to achieve the above-mentioned object, the present invention has a head provided with an engaging portion of a rotary tool at one end of a main body screw portion for fastening, and a female screw at the other end. A tapping screw having a tapered entry end thread portion to be formed, wherein the entry end thread portion is formed as a non-circular multi-start thread, and wherein the main body thread portion is continuous with the non-circular multi-start thread. It is characterized by being formed in a parallel multi-thread thread.

The entry end thread portion has a non-circular tapered multi-threaded thread, a continuous diameter of the non-circular tapered multi-threaded thread, and a rotation diameter substantially equal to the outer diameter of the circular parallel multi-threaded thread. And a non-circular multi-thread thread.

In the multi-thread tapping screw of the present invention, since the entire thread including the entry end thread portion is formed as a multi-thread thread, two or more threads bite into the prepared hole so that a stable bite is formed. Adhesion is obtained, and no pit is formed in the pilot hole. Moreover, since the entry end thread portion is formed in a non-circular thread, the female screw can be efficiently formed with a small screwing resistance. Further, since the main body thread portion screwed to the formed female screw and provided for fastening is formed as a normal thread, that is, a circular parallel thread, the contact area with the female screw is large, and the conventional non-circular screw is used. Higher tightening breaking torque and holding axial force can be obtained as compared with a mountain tapping screw. Therefore, the multi-thread tapping screw of the present invention can perform stable fastening even to a thin metal plate having a thickness of 0.6 mm or less, and can be expected to expand the field of use.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a multiple tapping screw according to the present invention, and FIG. 2 is an explanatory diagram showing a threaded state of the multiple tapping screw according to the present invention.

The multi-thread tapping screw 10 of the present invention has a head portion 12 provided with an engaging portion 13 of a rotary tool at one end of a main body screw portion 11 for fastening, and a tapered entry for forming a female screw at the other end. The configuration having the end screw portion 14 is the same as the conventional tapping screw, but the entire thread from the main body screw portion 11 to the entry end screw portion 14 is a multi-thread screw (two-thread screw in the illustrated embodiment). Is formed. Then, the main body screw portion 11 has a circular parallel multi-start thread 1 similar to a normal thread over the entire area.
On the other hand, the entry end threaded portion 14 is formed over the entire area by non-circular multi-threaded threads 14a and 14b having the same shape as the non-circular thread 1 shown in FIG.
The entry end screw portion 14 is continuous with the non-circular tapered multi-thread thread 14a on the distal end side and the non-circular tapered multi-thread thread 14a,
And a non-circular multi-start thread 14 having a rotation diameter substantially equal to the outer diameter of the circular parallel multi-start thread 11a of the main body thread portion 11.
b, and the non-circular multi-start thread 14b is continuous with the circular parallel multi-start thread 11a. With such a configuration, the internal thread partially formed by the tapered multi-threaded thread 14a is formed into a complete internal thread by the non-circular multi-threaded thread 14b. The circular parallel multi-threaded thread 11a of the portion 11 is screwed very smoothly.

On the other hand, as shown in FIG. 2, when a non-circular tapered multi-thread screw 14a and a non-circular multi-thread screw 14b following this are screwed into the prepared hole 7 of the thin metal plate 6 to be fastened, a female screw is formed. Since two or more screw threads 14a and 14b bite into the prepared hole 7, stable biting is obtained, and no pitted holes are generated in the prepared hole 7. Further, the female thread is efficiently formed with a small screwing resistance by the tapered multi-thread thread 14a formed in the non-circular thread and the non-circular multi-thread thread 14b following the tapered multi-thread thread 14b. Then, when the circular parallel thread 11a of the main body screw 11 is screwed into the formed female screw, the thread 11a is a normal thread, so that the contact area with the female screw is large, and the conventional non-circular thread tapping screw is used. Larger tightening breaking torque and holding axial force can be obtained. Therefore, the multi-starting screw 10 according to the present invention
Can stably connect thin steel sheets with a thickness of 0.6 mm or less, which has been the limit for the use of conventional tapping screws. The use in industrial fields, where reductions in emissions can be achieved, will be greatly expanded.

[0012]

As described above, according to the multi-thread tapping screw of the present invention, the biting of the internal thread with respect to the member to be fastened when forming the internal thread is stable, and the formed internal thread and the main body thread portion used for fastening are formed. Has a large contact area, and a large tightening breaking torque and holding axial force can be obtained. Therefore, stable fastening can be performed even on a very thin steel plate, and the field of use is greatly expanded.

[Brief description of the drawings]

FIG. 1 is a front view showing a multiple tapping screw according to the present invention.

FIG. 2 is an explanatory view showing a threaded state of a multi-threaded tapping screw according to the present invention.

FIG. 3 is a sectional view of a main part of a tapping screw having a non-circular thread.

FIG. 4 is an explanatory view showing a threaded state of a conventional tapping screw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-circular thread 6 Metal thin plate 7 Prepared hole 10 Multi-threaded tapping screw 11 Body thread part 11a Circular parallel thread 12 Head 13 Engaging part 14 Entry end thread part 14a Non-circular tapered multi-thread thread 14b Non-circular multi-thread Thread

Claims (2)

[Claims] 1. A tapping screw having a head portion provided with an engaging portion of a rotary tool at one end of a main body screw portion provided for fastening, and a tapered entry end screw portion forming a female screw at the other end, The entry end thread portion is formed in a non-circular multi-thread thread, and the main body thread portion is formed in a circular parallel multi-thread thread continuous with the non-circular multi-thread thread. Threaded tapping screw. 2. The non-circular taper multi-thread thread, wherein the entry end thread portion is continuous with the non-circular taper multi-thread thread, and
The multi-thread tapping screw according to claim 1, comprising a non-circular multi-thread having substantially the same rotation diameter as an outer diameter of the circular parallel multi-thread.