JPS6059445B2 - Torque-regulated type removal prevention screw - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a torque-regulated removal prevention screw equipped with a tip that breaks when tightened to a specified torque or higher.

(Prior art) In general, removal prevention screws are broadly classified into those whose tightening part is threaded with a specified torque and those whose tightening part has directionality (one-way). For example, there is a prior art disclosed in Utility Model Application Publication No. 48-51957.

As something similar to this prior art, the applicant of the present invention studied a torque regulating type removal prevention screw shown in FIG. 3, and the present invention improves the drawbacks of the screw, so this will be described as a conventional example. The screw 30 is formed by a round-shaped head 31 and a screw shaft portion 32, and a circular groove 33 of a predetermined depth is provided on the upper surface of the head 31. Each cutting tip 34, 35 is provided at a symmetrical position on the inner peripheral surface 33a of the circular groove 33.
are respectively provided to protrude in the axial direction. Sending chip 34,
35 is made to protrude when forming the head 31 or the circular groove 33, and its lower surface is integrally joined to the bottom surface 33b of the circular groove 33. The screw 30 with the above configuration has a fourth
The tightening operation is performed by a shearing driver 40 as shown in the figure. This shedding driver 40 has notches 42 and 43 at the tip of a cylindrical body 41 having an outer diameter that can fit into the circular groove 33 of the screw 30, and which can engage with the shearing tips 34 and 35, respectively. It has been established. The circular concave groove 3 of the screw 30 is attached to a predetermined rotary tool of the shearing driver 40 and inserted into a screw hole of a member to be tightened.
3 and rotate it, the notches 42 and 43
The screw 30 is screwed in while it is engaged with the cutting tips 34 and 35. Then, the head bearing surface 31a of the screw 30 comes into contact with the surface of the screw hole of the member to be tightened, and then a tightening force exceeding a preset specified torque is applied to the shear tips 3j4, 3.
5, the cutting tip is sheared and removed from both bases joining the circumferential surface 33a and bottom surface 33 of the circular groove 33, as shown in FIG. In this case, it goes without saying that the specified torque is an appropriate value to obtain a complete tightening force, and to prevent excessive tightening.
Furthermore, due to the shear removal of the shear chips 34 and 35, they cannot be removed by normal means. (Problems to be Solved by the Invention) In the case of the screw 30, each cutting tip 34, 35 is joined to the inner peripheral surface 33a and bottom surface 33b of the circular groove 33, and has an L-shaped connecting portion. are doing.

For this reason, a large shearing torque is required, which makes it difficult to set the specified torque in consideration of the appropriate tightening force, and the shearing points are not constant, causing variations in the tightening force. There were drawbacks, such as the possibility that the remaining sheared chip would not function to prevent removal. (Means for Solving the Problems) Therefore, in the present invention, the cutting tip protruding into the circular groove is joined only on the inner peripheral surface, and a gap is formed between it and the bottom surface of the circular groove. The gist of this is that they are provided and separated.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a screw 10 according to a first embodiment of the invention.
The screw 10 is formed by a round-shaped head 11 and a screw shaft 12, and a circular groove 13 of a predetermined depth is provided on the upper surface of the head 11. At symmetrical positions on the inner circumferential surface 13a of the circular groove 13, cutting tips 14 and 15 are provided to protrude in the axial direction. Gaps 16 and 17 are provided between the lower surfaces of the cutting chips 14 and 15 and the bottom surface 13b of the circular groove 13, respectively, to separate them. It is joined only to a part of the inner peripheral surface 13a. Next, FIG. 2 shows a screw according to a second embodiment of the present invention. 20 is shown.

As in the first embodiment, the screw 20 is formed by a head 21 and a screw shaft 22, and each cutting tip 24 is provided on the inner circumferential surface 13a of the circular groove 13 provided on the upper surface of the head. , 25 are provided protrudingly. Similar to the screw 10, this screw 20 has gaps 26 and 27 separating the bottom surface of each cutting tip 24 and 25 from the bottom surface 23b of the circular groove 23, and in addition, The upper surfaces of the cutting tips 24 and 25 have steps 28 and 29 relative to the head 11. Due to the voids 16, 17 and 26, 27 of the first and second embodiments, the joint of each shearing tip is only in one direction, so the shearing torque can be set small and variations are reduced. At the same time, no chips remain after cutting, and the removal prevention function is not impaired.

Further, the steps 28 and 29 in the second embodiment are provided to properly shear chips that tend to remain at the opening edge of the circular groove 23. Note that the number, shape, dimensions, etc. of the shearing tips of the present invention are appropriately selected depending on the set value of the specified torque.

The screws 20 and 30 according to the embodiments described above are tightened and the tips are sheared using a shearing driver 40 shown in FIG. 4, as in the case of the conventional example.

- (Effect of the invention) As is clear from the above embodiments, in the screw of the present invention, the cutting tip is joined only on the inner circumferential surface of the circular groove, and there is a gap between it and the bottom surface of the circular groove. Separated.

Therefore, compared to the conventional screw described above, the shearing torque can be arbitrarily set within a wide range from a small shearing torque to a large shearing torque, and its design is also easy. Furthermore, there is little variation in the shearing torque that varies from screw to screw, and stable fastening can be achieved with uniform tightening force.
Furthermore, since only a small amount of the cutting chip remains, the removal prevention function is not impaired, and intentional removal can be reliably prevented.

[Brief explanation of drawings]

Fig. 1 is a front view and a partially cutaway side view of a screw according to a first embodiment of the present invention, and Fig. 2 is a front view and a partially cutaway side view of a screw according to a second embodiment of the present invention. Main part side view shown as
Fig. 3 is a front view and a partially cutaway side view of the main part of a conventional screw, Fig. 4 is a front view and a side view of the main part of a shearing screwdriver, and Fig. 5 is a shearing of a shearing tip. It is an explanatory diagram showing a state. [Explanation of symbols], 10, 20...Screw, 11, 21
...Head, 12, 22...Screw shaft, 13
, 23...Circular groove, 13a, 23a...Inner peripheral surface, 13b, 23b...Bottom surface, 14, 15,
24, 25... Sending chip, 16, 17, 2
6, 27... air gap, 28, 29... level difference.

Claims (1)

[Claims] 1 A circular concave groove is provided in the head, and a plurality of shearing tips protruding in the axial direction are provided on the inner circumferential surface of the circular concave groove, and can be engaged with a tightening tool and sheared with a specified torque. Further, a torque regulating type removal prevention screw is provided, characterized in that a gap is provided between the lower surface of the shearing tip and the bottom surface of the circular groove to separate the two.