JPS5923858Y2 - Tatsu pin screw - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a tapping screw designed to prevent loosening.

Conventionally, when a self-tapping screw is tightened into a prepared hole in a viscoelastic material such as a thermoplastic resin, the tightening elastically recovers over time and the tightening force decreases, causing the self-tapping screw to tighten. This made it easier to remove, and it often fell off easily due to vibration or impact.

Such a decrease in the tightening force over time, which occurs when tightening a self-tapping screw into a viscoelastic material, cannot be prevented.

The purpose of the present invention is to provide a self-tapping screw that utilizes the elastic resilience of the thermoplastic resin mentioned above to prevent it from coming off even if the tightening force is lost, and that will not fall off due to vibration or impact. .

Furthermore, another object of the present invention is to provide a self-tapping screw that is effective in preventing loosening not only when tightening onto viscoelastic materials but also when tightening into die casting and the like.

Hereinafter, the present invention will be explained with reference to the drawings which are examples.

FIG. 1 shows a first embodiment of a self-tapping screw 10 according to the present invention, in which a head 13 with a driving tool engaging means, in the figure a cross recess 12, is provided at one end of a main rod portion 11, and an introduction portion 14 at the other end. , and form continuous two thread threads 15 and 16 across the main rod part 11 and the introduction part 14, and the common root diameter of these two thread threads 15 and 16 is at least as large as the main rod part 11. The outer diameters of these two helical ridges 15 and 16 lie on a common tapered conical surface on the introduction part 14, but on the main rod part 11, The first threaded thread 15 tapers to a positive angle α, and the second threaded thread 16 tapers to a negative angle β, starting from the vicinity of the joining portion 17 with the portion 14.

In other words, the outer diameter of the first threaded thread 15 increases as it approaches the head 13, and conversely, the outer diameter of the second threaded thread 16 decreases as it approaches the head 13. It is configured.

Since the self-tapping screw 10 according to the present invention is configured as described above, as shown in FIG. When the tapping screw 10 is screwed into the pilot hole 21 provided in the hole 21, first, as shown in FIG.

Then, the two threaded threads 15 and 1 on these introduction portions 14
Since the outer diameters of 6 are on the same conical surface, these two threads will ultimately form internal threads of the same depth.

Further, when screwing continues, the introduction part 14 and the main rod part 11
5, the first thread 15 continues to form a deeper internal thread, but the second
As the diameter of Noneshiyama 16 gradually decreases,
A gap 22 will be created between it and the previously formed female thread.

By the way, in order for the first screw thread 15 to continue forming a deep female thread, the material of the mating member 20 must be removed, and this removed material moves to fill the gap 22.

Furthermore, the viscoelastic material acts to fill this gap 22 due to its characteristic elastic restoration over time (see FIG. 6).

Therefore, depending on the material of the mating member 20, the diameter of the pilot hole 21, the length of the threaded part fitting with the tapping screw 10, the thread pitch P of the tapping crocodile 10, the thread angle θ, and the main rod part 11.
Valley diameter on top, first threaded crest 1 on main rod part 11
By appropriately selecting specifications such as the taper angle α of 5 and the taper angle β of the second thread 16, the gap 22 can be almost completely filled.

Generally, a tapping screw is prevented from rotating by the frictional force generated by the tightening force, so if this tightening force is lost for some reason, the frictional force also disappears and it becomes free, and it is easily affected by vibrations and shocks. It will eave and fall off.

However, the tapping screw 10 according to the present invention is fitted to the mating member 20 with almost no gap 22 as described above.

Therefore, even if the tightening force of the mating member 20 is lost, in order for the tapping screw to loosen, the internal thread formed on the mating member 20 must be reworked to allow the thicker thread 16 to pass through. First, it is impossible for the tapping screw to rotate naturally due to vibration or impact and fall off.

Since the tapping screw according to the present invention has the above-mentioned effects, it has elastic recovery properties like thermoplastic resin,
It is particularly suitable for mating parts that tend to lose tightening force, but even for materials that do not have elastic recovery properties such as die-casting, it is necessary to appropriately select the above specifications and take advantage of the movement of the material during screwing. For example, the same effect can be obtained, so it can be applied to usage conditions where vibrations and shocks are severe.

As an embodiment of the present invention, the tapping screw of Hirako has been described above, but the same applies to the tapping screw in which the introduction part is a pointed tip, as shown in FIG.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a front view of the self-tapping screw according to the present invention, FIG. 2 is a plan view, FIG. 3 is a partially cutaway front view showing how the screw is used, and FIG. 4 is a front view of the self-tapping screw according to the present invention. 5 is a partially enlarged view showing the fitted state of the screw during screwing. FIG. 6 is a partially enlarged view showing the fitted state of the screw after screwing is completed. The enlarged view, FIG. 7, is a front view showing another embodiment of the self-tapping screw according to the present invention. 10...Tapping, 11...Main rod, 14...Introduction, 15.16...
2 thread threads, 20...Mating member, 21...
... Pilot hole, 30... Member to be tightened.

Claims (3)

[Scope of utility model registration request] (1) A head equipped with a driving tool engagement means is provided at one end of the main rod, an introduction section is provided at the other end, and a continuous double thread thread is formed across the main rod section and the introduction section. The root diameter of the two-thread thread on the rod is substantially uniform, and the outer diameter of the thread on the main rod starts from the vicinity of the joint between the introduction part and the main rod and extends toward the head side. A tapping screw characterized in that the first threaded thread tapers at a positive angle and the second threaded thread tapers at a negative angle. (2) The tapping pin according to claim 1 of the utility model registration claim, characterized in that the diameter of the thread of the double thread screw provided in the introduction portion gradually decreases toward the tip. Neshi. (3) The tapping machine according to claim 1, wherein the introducing portion has a pointed shape.