JPH0448335Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a tuft pin screw, particularly to a tuft pin screw for thin plates.

Prior art and its problems In general, a tapping screw is screwed directly into a prepared hole in a plate material, and is tightened to the plate material while forming an internal thread.For example, there is a tapping screw having a single thread. .

However, since the longitudinal section of a tapping screw with a single thread is not symmetrical,
It is easy to screw in an inclined position during screwing work.

Moreover, if the pitch of the threads is made smaller in order to mesh as many male and female threads as possible to obtain the desired holding force, the amount of screw-in per revolution will decrease, resulting in the problem of longer screw-in work. There is.

In order to solve this problem, tapping having two threads has been developed.

However, even if the tapping screw has two threads, when the plate material is thin, it is necessary to mesh as many male and female threads as possible, so it is necessary to reduce the thread pitch of the tapping screw. One method of reducing the thread pitch is to make the thread angle of the tapping screw sharp, for example, 30°. However, if the thread angle is made sharp in this way, the thread of the tapping screw itself cannot ensure a certain strength, so there is a problem that the thread of the tapping screw itself breaks down during the screwing operation, making it impossible to screw in.

On the other hand, the thread angle of the tatsupin screw, for example,
If you try to make the thread pitch 60° like a normal thread and make the thread pitch smaller, the thread height of the tatsu pin screw will become lower. Therefore, the thread height of the female threaded portion formed in the thin plate is also reduced, and the amount of mutual bite between the male threaded portion and the female threaded portion is reduced.
As a result, the tightening and breaking torque decreases, so if the tuft pin screw is overtightened, the threads of the female thread formed in the prepared hole are often destroyed, and the screw loses its original tightening function.

Therefore, in order to prevent idling due to over-tightening of the Tatsupin screw, for example, a locking pawl is provided on the seat surface of the screw head, as in the Tatsupin screw described in Japanese Utility Model Publication No. 57-50575. A mechanism has been proposed that prevents idling due to over-tightening of the tuft pin screw by locking it to the surface of the plate material. However, this method has the problem of scratching the surface of the plate material.

In view of the above-mentioned problems, the present invention aims to provide a tatsu pin screw that can be screwed into a thin plate accurately and quickly while ensuring a predetermined tightening and breaking torque without damaging the surface of the plate material. .

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a tuft pin screw having two threads, and the height of at least one of the two threads. is configured to increase and decrease periodically around the thread reference height.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings of FIGS. 1 to 9.

As shown in FIG. 1, the tuft pin screw according to the first embodiment has a screw head 1, two threads 31,
32.

The screw head 1 has a slot 1a on its upper end surface for inserting and rotating the tip of a screwdriver (not shown).

The shaft part 2 consists of a lower neck part 21 and a tip part 22,
The lower neck portion 21 is a parallel thread, and the tip portion 22 is a tapered thread. Therefore, the tip portion 22 gradually forms a female thread in the pilot hole of the plate material, and the lower neck portion 21 is screwed into the plate material with a high tightening torque.

Among the two threads 31 and 32, the thread height of one thread 31 is a uniform thread height (thread thread reference height), while the thread height of the other thread 32 is equal to the thread height of the thread 31. 120 around the standard mountain height
It increases and decreases periodically with each degree. The thread reference height according to the present application refers to, for example, the height of the thread defined for the shaft diameter of the screw in JIS or the like.

The maximum thread height of the thread 32 is 140% of the thread reference height, while the minimum thread height is 60% of the thread reference height. In order to compare the heights of the threads 31 and 32 for each rotation angle, cross-sectional views of the threads 31 and 32 taken along the indicated lines -, - and - shown in Fig. 2 are shown in Figs. As shown in FIG.

From the viewpoint of mechanical strength, the maximum thread height of the thread 32 is preferably 140% or less of the thread reference height, and the minimum thread height is preferably 60% or more of the thread reference height. Further, the increase/decrease in the thread height may be in simple direct proportion to the rotation angle, or may be a parabolic increase/decrease.

In this embodiment, there is a step between the portion of the thread 32 having the maximum thread height and the portion having the minimum thread height, and this step is connected to form one discontinuous groove 33. However, in this embodiment, the height of the thread 32 increases and decreases periodically every 120 degrees, so three discontinuous grooves 33 are formed. However, if the number of grooves 33 is large, the portion that engages with the thread of the female thread formed in the prepared hole will be reduced, and the tightening and breaking torque will be reduced. For this reason,
It is preferable that the height of the thread 32 is periodically increased or decreased so that the number of the grooves 33 is from 2 to 9.

Furthermore, if the thread angles of the threads 31 and 32 are too small, the thread angle of the female threaded portion formed in the prepared hole of the plate material will be small, and the thread of the female thread portion will be easily damaged. For this reason, the screw threads 31, 32 and the thread (not shown) of the female thread portion formed in the plate material are designed so that they have the same mechanical strength.
It is preferable that the thread angle of No. 2 is around 60°.

The second embodiment, as shown in FIG.
1 and 32 are provided, and only the threads 31 are provided on the intermediate portion 23 and the tip portion 22.
The lower neck portion 21 and the intermediate portion 23 have parallel threads, and the tip portion 22 has a tapered thread.

The rest is the same as the previous embodiment, so the explanation will be omitted.

According to this embodiment, the tip portion 22 and the intermediate portion 2
3 is provided with only one thread 31, which has the advantage that the initial screwing torque is small and workability is improved.

In addition, in the above-mentioned embodiment, the two threads 31,
32, the case where only the thread height of the thread 32 is periodically increased or decreased around the thread reference height has been described, but this is not necessarily the case.
Of course, the thread heights of the threads 31 and 32 of the strips may also be periodically increased or decreased.

Experimental Example 1 As shown in Figure 7, the Tatsupin screw used in the experiment had an outer diameter of the thread of the shaft portion 2 of 4 mm and a length of 12 mm.
The sample was mm.

The tatsupin screw has a diameter of 10 mm on the underside of the screw head 1.
A collar portion 1b with a thickness of 0.9 mm and a thickness of 0.9 mm is provided.

Further, the tuft pin screw is attached to the lower neck portion 2 of the shaft portion 2.
1 is provided with threads 31 and 32 in parallel, and a thread 31 is provided on the intermediate portion 23 and the tip portion 22.

The threads 31 and 32 of the lower neck part 21 have a thread angle
60 degrees, pitch 1.41mm, maximum thread height 0.53mm (110% of thread reference height), minimum thread height 0.31mm (65% of thread reference height) %) in 120 degree increments,
It extends to a position 4.9 mm from the lower surface of the flange portion 1b.

On the other hand, the threads 3 of the intermediate portion 23 and the tip portion 22
1 has a uniform thread height (0.48 mm), a thread angle of 60 degrees, and a pitch of 1.41 mm.

Then, screw the above-mentioned tatsupin screw into a prepared hole of 2.90 mm in diameter provided in a steel plate (SPCC) 4 with a thickness of 0.5 mm, and tighten the plate material to be tightened (SPCC) 5 with a thickness of 5 mm and having a blank hole 5a with a diameter of 5 mm. The tightening and breaking torque of the tuft pin screw was measured.

The number of samples is 10, and the graph of the tightening and breaking torque of three representative samples is shown in Figure 8.
As shown in the figure.

Comparative Example 1 Screw thread 31 without thread 32 and having uniform thread height (0.48 mm) on all shaft portions 21
A single tuft pin screw having the same external dimensions as in Experimental Example 1 described above was used as a sample, except for the provision of a screw, and the tightening and breaking torque was measured in the same manner as in Experimental Example 1.

The number of samples is 10, and the graph of the tightening and breaking torque of three representative samples is shown in Figure 9.
As shown in the figure.

As a result of the above measurements, the average value of the tightening and breaking torque of the 10 tuft pin screws in Experimental Example 1 was 24.0Kg.
f・cm, whereas that of Comparative Example 1 was 12.8
It was Kgf・cm.

From this, it was found that Experimental Example 1 had approximately twice the tightening and breaking torque of Comparative Example 1.

As mentioned above, the reason why the tightening and breaking torque of Experimental Example 1 is larger than that of Comparative Example 1 is that the female thread is accurately cut without tilting the two threads, and the height of the threads increases and decreases periodically. The tip of the thread that is higher than the standard thread height digs deeply into the pilot hole of the plate material, increasing the tightening and breaking torque, while the part that is lower than the thread reference height digs deeply into the pilot hole of the plate material, while the tip of the thread part that is lower than the thread reference height digs deeply into the pilot hole of the plate material. This is thought to be to alleviate stress on the threads and prevent damage to the threads.

Effects of the Invention As is clear from the above explanation, according to the present invention, even when the Tatsupin screw according to the present application is screwed into a thin plate, the thread of the female thread formed in the prepared hole is not easily damaged, so the tightening breaking torque is low. increases, and fully demonstrates the original function of the screw.

Moreover, since no locking pawl is provided on the seat surface of the screw head, the surface of the plate material will not be scratched.

Furthermore, since the tuft pin screw according to the present invention has two threads and its longitudinal section is symmetrical, the screw can be screwed in accurately without being forcefully screwed in in an inclined state during the screwing operation.

Furthermore, since the tatsu pin screw according to the present invention has two threads, even if the distance between adjacent threads is small, the pitch of each thread itself is equal to or less than the distance.
There are twice as many. Therefore, according to the tuft pin screw according to the invention of the present invention, the amount of screwing in per one rotation is larger than that of the tutu pin screw having a single thread having the distance of one pitch, so that the screwing work is faster.

[Brief explanation of the drawing]

1 to 5 show a first embodiment of the present invention, in which FIG. 1 is a front view, FIG. 2 is a sectional view of the shaft, and FIGS. 6 is a front view of the second embodiment of the present invention, and FIG. 7 shows the tightening state of Experimental Example 1. The cross-sectional views shown, and FIGS. 8 and 9 are graphs showing the measurement results of Experimental Example 1 and Comparative Example 1. 1... Screw head, 2... Shaft part, 31, 32...
screw thread.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a tuft pin screw having two threads, the height of at least one of the two threads is centered on the reference thread height. A tatsu pin screw that is characterized by increasing and decreasing periodically. (2) The tuft pin screw according to claim 1, wherein the rate at which the thread height increases or decreases is at least two cycles per rotation. (3) The maximum thread height of the thread that periodically increases and decreases is 140% or less of the thread reference height, and the minimum thread height is 60% or more of the thread reference height. The tuft pin screw according to claim 1 or 2 of the utility model registration claim, characterized by: