JPS633451Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention provides a screw that is inserted into a pilot hole while forming an internal thread, and the tip of the shaft of the screw has a diameter smaller than the inner diameter of the pilot hole. In addition to forming a spherical retaining part with a larger diameter, a smooth shaft part is formed between the spherical retaining part and the shank of the screw, which has a smaller diameter than the internal thread forming hole that is present in the female thread forming hole when the screw is released. Regarding set screws.

Conventional locking screws of this type are, for example,
As disclosed in Japanese Patent Publication No. 53-43967, a ring-shaped projection with a sharp ridge and a diameter slightly larger than the pilot hole diameter is formed at the tip of the shank of the screw to prevent it from coming out.
Therefore, when the retaining portion is inserted into the pilot hole, if the axis of the screw is inclined relative to the axis of the pilot hole,
There is a problem in that the ridge line of the anti-pullout portion damages and deforms the inner wall of the pilot hole, which interferes with the formation of the female thread. Furthermore, when the screw engagement is released after the female thread is formed, the axis of the screw is inclined relative to the axis of the female tapped hole, and this inclination of the screw causes the ridge line of the anti-pullout portion to damage and deform the female thread on the exit side of the female tapped hole which is in engagement with the anti-pullout portion.

The present invention was devised to solve the above-mentioned conventional drawbacks, and its specific configuration will be explained below with reference to the drawings showing one embodiment.

1A and 1B are a front view and an end view showing the shape of a screw material 1 constituting the retaining screw of the present invention, in which the screw material 1 includes a head 2 and a shaft portion connected to the head 2. 3, and a flat portion 4 parallel to the axis is formed at each portion of the circumference of the outer peripheral surface of the front half of the shaft portion 3 divided into three equal parts. As shown in FIGS. 2 to 4, the shaft portion 3 of the screw material 1 formed in this way is formed with a male thread for forming a preliminary female thread, leaving a portion where a spherical retaining portion 7 and a smooth shaft portion 8, which will be described later, be formed. A spherical retaining portion 7 is formed at the tip of the shaft portion 3 of the screw, and this spherical retaining portion 7 has a “ The relationship is "prepared hole diameter ≧ maximum diameter part of spherical retaining part 7", and after screwing (after forming female thread), the relationship is "hole diameter of female thread part < maximum diameter part of spherical retaining part 7". At the same time, a smooth shaft portion 8 having a smaller diameter than the hole diameter of the female thread ridge portion is formed between the spherical retaining portion 7 and the male thread portion 9 for forming a preliminary female thread, and the female thread is formed. The spherical retaining portion 7 is configured to engage with the female thread portion 11b on the exit side of the pilot hole 11a in the spherical region before reaching its maximum diameter when the screw is unscrewed later, and furthermore, the spherical retaining portion 7 and the screw The above-mentioned smooth shaft portion 8 is configured to reside within the female thread forming hole 11c in the above-mentioned engaged state between the shaft portion 3 and the shaft portion 3. Due to the presence of the flat part 4 formed in the front half of the thread material 1, the maximum diameter part of the spherical retaining part 7 and the thread 9a of the male thread part 9 for forming a preliminary female thread have recessed notches 7a and 9b. is formed. Reference numeral 11 indicates a mating member having a pilot hole 11a having the above-mentioned relationship with the maximum diameter part of the spherical retaining portion 7, and reference numeral 11c indicates the male thread portion 9 for forming a preliminary female thread and the reference female thread forming member in the pilot hole 11a. The internally threaded hole plastically formed in the threaded portion 10 is shown.

As shown in FIG. 3, the spherical retaining portion 7 of the retaining screw is slid into the pilot hole 11a of the mating member 11, and while rotating the retaining screw in the screwing direction, a preliminary female thread is formed in the pilot hole 11a. A preliminary female thread is formed in the male thread part 9, and a reference female thread 11c is formed in this preliminary female thread in the male thread part 10 for forming a reference female thread, and the part to be attached is formed between the head 2 and the mating member 11. Tighten members (not shown). Next, when the tightened retaining screw is rotated in the opposite direction to the previous direction to release the screw, the smooth shaft portion 8 is inserted into the female thread forming hole 11c as shown in FIG. , the spherical area in front of the maximum diameter part of the spherical retaining part 7 is a female thread 11.
It engages with the female threaded portion 11b on the exit side of c, and prevents the retaining screw from coming out.

According to the present invention, since a spherical retaining portion is formed at the tip of the shaft of the screw to be screwed into the prepared hole while forming a female thread, the spherical retaining portion can be lowered regardless of the screwing position. It can slide smoothly into the hole, and even if the axis of the screw is tilted with respect to the axis of the pilot hole, because the spherical retaining part is a spherical surface, the pilot hole will not be damaged or deformed. It is possible to form an accurate female thread in the prepared hole without any fear, and furthermore, when the screw is released after forming the female thread, the spherical retaining part can be formed in the spherical area just before reaching its maximum diameter. Since it is configured to engage with the female thread ridge on the exit side of the female thread forming hole, there is no risk of damaging or deforming the female thread, and therefore, the screw thread for the next female thread can be tightened. Furthermore, according to the present invention, when the spherical retaining part is in the above-mentioned engaged state, the smooth shaft part is inside the female thread forming hole, and the end of the male thread part is inside the female thread forming hole. The locking screw is placed in a state where it is released from the entrance side, and the locking screw is in a completely free state (the state in which the restraint during screwing is released), so you can clearly and reliably recognize the completion of unscrewing by feeling it. This eliminates the problem of unnecessary rotation without noticing the unscrewing, and even if excessive rotation occurs, damage to the thread can be prevented.

In addition, FIG. 5 shows the surface of the above-mentioned spherical retaining part 7 coated with a lubricant 7b, and according to this embodiment, the spherical retaining part 7 can be inserted into the above-mentioned pilot hole 11a very smoothly and without resistance. Furthermore, the lubricant 7b is adhered to the inner diameter of the prepared hole during the insertion, so that it has the advantage that female thread forming can be easily performed.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1A is a front view of the material shape of the retaining screw, Fig. 1B is an end view of Fig. 1A, and Fig. 2A is a partially cutaway view. A front view of the retaining screw shown in FIG. 2B is an end view of FIG. 2A,
Figure 3 is a front view showing the state in which the spherical retaining part of the retaining screw is inserted into the pilot hole of the mating member, Figure 4 is a front view showing the unscrewed state of the retaining screw, and Figure 5 is the retaining screw. FIG. 3 is a partially cutaway front view of another embodiment of the present invention. 7... Spherical retaining part, 8... Smooth shaft part, 9... Male thread part for forming preliminary female thread, 10... Male thread part for forming reference female thread, 11... Mating member, 11a... Pilot hole, 11b...Female thread, 11c...Female thread forming hole.

Claims (1)

[Scope of utility model registration request] For screws that are screwed into a prepared hole while forming a female thread, a spherical retaining portion is formed at the tip of the shaft portion of the screw, and the spherical retaining portion is attached to the hole diameter ≧ spherical retaining portion before forming the female thread into the prepared hole. The maximum diameter of the spherical retaining part is formed so that the relationship is ``the diameter of the female thread < the maximum diameter of the spherical retaining part'' after screwing into the prepared hole, and when the screw is released, the spherical retaining part The part is configured to engage with the female thread on the exit side of the prepared hole in the spherical area before reaching its maximum diameter part, and furthermore, in the engaged state, between the spherical retaining part and the shaft part of the screw. A retaining screw characterized in that a smooth shaft portion is formed in the thread forming hole with a smaller diameter than the internal thread forming hole.