JPH088332Y2 - Tapping screw for thin plate - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tapping screw which is screwed into a preformed hole while forming a screw thread, and more particularly to a thin plate tapping screw for fixing a component to a relatively thin work piece.

[0002]

2. Description of the Related Art Conventionally, when a component is fixed to such a relatively thin plate-like work, the work is prevented from escaping in the axial direction or cracking and the female screw of the work shown in FIG. 5 is destroyed. In order to increase the maximum screw tightening torque TM immediately before the threading as much as possible, a screw is used in which the angle of the flank surface forming the screw thread is asymmetric even when the screw thread angle is made smaller than that of a normal screw. Further, a tapping screw having a fine thread pitch is used in order to maximize the contact portion between the thread and the work. Furthermore,
In some cases, in order to increase the contact area between the work and the screw thread, two threads are formed in the portion close to the head seat surface of the screw.

[0003]

However, in the case where all the threads of the legs are asymmetric and the intervals of the valleys are the same as described above, female threads are continuously formed on the workpiece during screwing, so that the workpiece is Although it is difficult to crack, the frictional resistance of the screw in the axial direction and the radial direction is small, and the maximum screw tightening torque (torque just before breaking the female screw) cannot be improved and a sufficient locking action cannot be obtained. The same applies to the case where the thread pitch is fine. Furthermore, in the case of a double thread formed on the leg that is close to the seat surface,
Since the second thread is formed on the work during the screwing operation, the first female screw formed on the work is easily broken, and various problems such as insufficient fixation of parts to the work occur.

The present invention has been devised for the purpose of solving the above problems and providing a tapping screw for a thin plate which can obtain a proper screwing action, and which can improve the maximum screw tightening torque and surely prevent loosening. It is a thing.

[0005]

The present invention achieves such an object, and has a leg portion 3 on a seat surface of a head portion 2, and the leg portion 3 has a pressure side flank surface 21 and a leg portion. In a tapping screw 1 having an asymmetric thread 20 composed of an idle flank 22 that is less than the angle formed by a plane that intersects the axis of the portion 3, the asymmetry of the leg 3 that is close to the seat surface is formed. At least the base side of the thread 20 on the play side flank 22 of the plurality of threads 20 is formed with a gentle inclination, and the interval of the valleys 23 in the base is set to the interval of the valleys 24 on the tip side of the leg 3. It is a narrow thin plate tapping screw.

[0006]

As described above, the tapping screw 1 is formed so as to be asymmetric with respect to the plurality of threads 20 close to the head seat surface, and at least the base side of the threads 20 on the play side flank 22 is formed with a gentle inclination. Since the interval between the valley portions 23 is narrowed, the female screw of the work 30 is drawn into the valley portion 23 by the pressure side flank surface 21, is sandwiched by the play side flank surface 22, and the maximum screw tightening torque is improved. At the same time, the loosening of the screws is prevented.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 3 denotes a leg portion formed on the seating surface of the head 2 of the thin plate tapping screw 1. The leg portion 3 is composed of a straight portion 10 and a conical portion 11 continuous with the straight portion 10. Has been done. Threads 20 are formed on the straight portion 10 and the conical portion 11, and the height of the threads 20 decreases as they reach the tip. Further, this screw thread 20 is asymmetrical in that the pressure flank 21 from the tip end is a steep slope having an inclination angle α with respect to the plane crossing the leg 3, and the play flank 22 is a slope having a gentler inclination angle β. There are 20 threads. Further, as shown in FIG.
The plurality of threads 20 at a position close to the seat surface of the head 2 of the leg portion 3 are the so-called pressure flanks 21 on the head seat surface side, that is, the pressure side flanks 21 are inclined with respect to the plane crossing the axis. On the other hand, the play side flank 22 on the opposite side of this slope has a compound angle of a slant angle β on the thread tip side and a gentle slope on the base side with a slant angle γ. A slope is formed. These angles are in the relationship of α <β <γ, and further, the interval of the valley portions 23 between the screw threads 20 is relatively larger than the interval of the valley portions 24 on the tip end side of the leg due to the slope of the inclination angle γ. It is getting narrower.

FIG. 3 is a sectional view of a leg portion showing another embodiment, in which a plurality of threads 2 of the leg portion 3 approaching the head seat surface.
0 is the flank surface on the pressure side with respect to the surface crossing the axis.
No. 1 is formed with an angle of inclination α as in the above-mentioned embodiment, while the play side flank 22 on the opposite side of the flank 21 is provided with a small portion on the thread tip side with an angle of inclination β. In addition, a slope having a compound angle having a gentle inclination angle γ is formed on the base side longer than that in the above embodiment.

Therefore, the tip end of the leg portion 3 of the tapping screw 1 for fixing the component 31 has a preset work 30.
When the screwing operation is started by pressing the screw into the hole, the screw is screwed in while the female screw is formed in the hole of the work 30. At this time, the female thread of the hole is formed into a normal shape with the screwing torque TS by the thread 20 on the tip end side of the leg.
When the compound angle screw thread 20 formed at a position close to the head seat surface is screwed in, the work piece 30 is deformed along the screw thread 20, and as shown in FIG. The flank surface 21 pulls it toward the head side so that it is sandwiched between the flank surface 22 and the play side flank surface 22. On the other hand, the work 30 sandwiched between the screw threads 20 in this way enters the narrow valley portion 23, and the maximum screw tightening torque TM is significantly improved as shown in FIG. When the screw tightening work is completed in this way, a complete screw loosening prevention effect is obtained.

In these embodiments, the play side flanks are all formed with compound angles. However, the present invention is not limited to this, and the flanks are loose and straight from the tip to the base. Good.

[0011]

As is apparent from the above-described embodiments, the present invention has the inclined pressure side flank surface 21 close to the head seat surface of the tapping screw 1, while the pressure side flank surface is provided. At least 2 threads on the opposite side of surface 21
Since the base side of 0 is formed with the play side flank surface 22 formed with a gentle angle of inclination, and the interval between the valleys 23 in the base is narrower than the interval between the valleys 24 on the tip side of the leg 3, At the beginning of screwing, the screw is relatively easy to screw into the work, and when the work approaches the head seat surface, the part with the flank on the play side is screwed in, so the frictional force between this thread and the work increases. However, the maximum screw tightening torque is improved, and the function of preventing the screw from loosening after the completion of tightening is surely obtained. Further, since the screw thread is not formed in the work midway, a peculiar effect such as preventing the female screw of the work from being crushed can be obtained.

[0012]

[Brief description of drawings]

FIG. 1 is a front view showing a tightened state of the present invention.

FIG. 2 is an enlarged cross-sectional front view of essential parts showing an embodiment of the present invention.

FIG. 3 is a cross-sectional front view of essential parts showing another embodiment of the present invention.

FIG. 4 shows a screw tightening characteristic according to the present invention.

FIG. 5 shows screw tightening characteristics of a conventional screw.

[Explanation of symbols]

 1 tapping screw 2 head 3 leg 10 straight part 11 conical part 20 screw thread 21 pressure side flank surface 22 play side flank surface 23, 24 valley part 30 work part 31

Claims (1)

[Scope of utility model registration request] 1. A leg portion (3) is provided on a seating surface of the head portion (2),
The leg (3) has an asymmetric screw formed by a pressure side flank surface (21) and a play side flank surface (22) having an angle less than the angle formed by this surface and the surface traversing the leg portion (3). In the tapping screw (1) having the thread (20), at least the thread (20) is provided at the play flank (22) of the asymmetric threads (20) of the leg (3) close to the seat surface. ) Is formed on the base side with a gentle inclination, and the interval between the valleys (23) in the base is set to the leg (3).
A tapping screw for a thin plate, characterized in that it is narrower than the interval between the troughs (24) on the tip side of the.