JPH0125771Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention is screwed into a member to be fastened by rotation, and fastening is performed by cutting a female thread that matches the own thread into the member to be fastened. This invention relates to the improvement of so-called tatsupin screws.

(Prior Art) Various proposals have been made for reducing the screwing torque for this type of tuft pin screw. For example, as in Japanese Patent Publication No. 37-4608, the cross section of the screw shaft is triangular and non-circular so that there is contact at three points when screwing, and as in Japanese Patent Publication No. 39-14383,
Some have a conical tip shaft with a plurality of protrusions that are large enough to protrude from the threads. however,
The former has the disadvantage that the tightening force is reduced because the tightening is done by three-point contact, and the latter has the disadvantage that the projections cause variations in the female thread that is plastically worked, resulting in the clearance between the female thread and the tatsupin screw being reduced. The problem was that it became larger and caused a decrease in tightening force and variations in the tightening force.

(Purpose of the invention) Therefore, the object of the present invention is to improve the drawbacks of the prior art described above, reduce the screwing torque, and provide a tuft pin screw that does not reduce the tightening force.

(Structure and operation of the invention) The tatsupin screw of the invention has at least a thread near the joint between the parallel screw shaft and the tip screw shaft.
The gist is that a large number of small diameter recesses are provided on the flange surface. In other words, as the shaft diameter and thread height gradually increase, the threading torque is reduced by reducing the surface area of the thread that comes into contact with the fastened member near the joint where the maximum threading torque is required. This is what I did.

(Example) Examples of the present invention will be described below with reference to the drawings.
FIG. 1 is an overall front view of a tuft pin screw 1, which is composed of a head 2, a parallel screw shaft 3, and a tip screw shank 4, like a normal tatu pin screw. The head 2 has an engagement groove 5 for engaging a rotating means such as a screwdriver, and a cylindrical shaft 7 extending from the seat surface 6 side of the head.
A contour screw thread 8 is provided on the top of the parallel screw shaft portion 3.
is formed. Further, a tapered thread 10 is provided on a conical shaft 9 continuous with the cylindrical shaft 7 in a manner continuous with the same-height thread 8, thereby forming a tip threaded shaft portion 4. As shown in the enlarged sectional view of FIG. 2, a large number of small-diameter recesses 12 are provided on the flank surface of the thread 11 near the joint between the parallel screw shaft 3 and the tip screw shaft 4. There is.
The small diameter recesses 12 are hemispherical recesses like dimples provided on the surface of a golf ball, and are scattered at a substantially uniform depth. Further, these small diameter recesses 12 can be formed by providing small diameter protrusions having a shape compatible with the small diameter recesses at appropriate locations on the die during rolling. In addition, as another embodiment, a small diameter recessed portion may be provided over almost the entire area of the screw thread, as in the case of the tuft pin screw 13 shown in FIG.

(Effects of the invention) According to the tatsupin screw of the invention, the following effects can be expected.

By providing the small-diameter recess for the screw thread that cuts into the fastened member to form a female thread during screwing, the surface area that comes into contact with the fastened member is substantially reduced, thereby reducing the screwing torque. It is possible to reduce this and prevent burn-in and the like.

The basic shape of the other parts except for the small-diameter recess is completely the same as that of a normal Tatsupin screw, so there is no clearance between the plastically worked female thread and the male thread of the Tatsupin screw when tightening the screw. It is possible to obtain excellent tightening performance.

When a lubricant or the like is used, the small-diameter recess functions as a kind of oil dam and helps improve performance.

As shown in FIG. 4, when the fastened member 14 is an elastic member such as synthetic resin, a part of the fastened member elastically restores after screw fastening and comes into close contact with the inner surface of the small diameter recess, preventing loosening and reducing the tightening force. Contribute to improvement.

It has a simple configuration and can be manufactured at low cost using the same rolling process as regular tatsu pin screws.

[Brief explanation of the drawing]

FIG. 1 is an overall front view of a tut pin screw according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of essential parts of the same tut pin screw, FIG. The figure is a sectional view showing a fastened state applied to a synthetic resin fastened member. 1, 13...Tatsupin screw, 2...Head, 3...
...Parallel threaded shaft part, 4...Tip threaded shaft part, 5...Engagement groove, 6...Seat surface, 7...Cylindrical shaft, 8...Contour thread, 9...Conical shaft, 10... Tapered thread, 1
1... Joint part, 14... Member to be fastened.

Claims (1)

[Scope of utility model registration request] a head that engages with the rotation means; a parallel screw shaft portion having a cylindrical shaft extending from the head and having equal height threads; and a conical shaft continuous with the cylindrical shaft having the same height threads. In a tatsupin screw consisting of a distal screw shaft portion having a continuous tapered thread, at least the thread near the joint of the parallel screw shaft portion and the distal screw shaft portion has a large number of A tatsu pin screw characterized by having a small diameter recess.