JPS5884211A - Torque regulating screw and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torque regulating screw used in a conduit connecting device and a method for manufacturing the same.

Conduit connecting devices use torque regulating screws that break and scatter their heads when the tightening resistance exceeds a certain value. As shown in FIG. 13, for example, as shown in FIG. It has a part 3a and a threaded shaft part 4a, and a constriction part 11a is formed between the head part 2a and the rotating part 3a.
It is known that the head part 2a breaks off and one head part 2a is scattered. However, such a torque regulating screw is manufactured by forming the m part and drawing the shaft, and then roll drawing the shaft to form the constricted part 1.
1a must be formed, the number of steps and man-hours increases, and the manufacturing cost increases accordingly. Furthermore, since the cross-sectional area of the constriction formed by roll drawing varies widely, the setting of the breaking torque is severely restricted, and it is extremely difficult to manufacture products with particularly small breaking torque without variation. Incidentally, the breaking torque of the torque regulating screw used in the above-mentioned conduit connecting device is regulated to be within the range of 5 to 3/3-#.

In view of the above-mentioned problems, the present inventor created a columnar hole 8 extending from the head 2b to the rotating part 3b, as shown in FIG.
b is provided concentrically with the rotating part 3b and the screw shaft part 4b, and a cylindrical thin-walled part 1 is provided at the connecting part between the head 2b and the rotating part 3b.
A torque regulating screw was proposed in Utility Model Application No. 1986-01 (tlI), which formed a head 2b and was designed to cover the thin-walled portion 11b when the tightening torque exceeded a certain value. However, since the thin wall portion 11b of this torque regulating screw has a cylindrical shape, even if the thickness is made relatively thin, it will not break.
If the thickness of the thin wall portion 11b is made extremely thin, the punch and die used to form the columnar hole 8b may be damaged, so there is a limit to how thin the thin wall portion 11b can be made. It has proven difficult to manufacture torque-limiting screws with small breaking torques limited to .

The present invention is aimed at solving these difficulties, and has been made as a countermeasure.The columnar hole 8b provided from the head 2b to the turn portion 3b in order to form the thin wall portion 11b is made into a square hole. , a thin wall portion is formed by the square hole at the connection point between the head and the rotating portion, and a breaking portion for dividing the thin wall portion is formed at a corner of the square hole, thereby causing the thin wall portion to To provide a torque regulating screw having a small breaking torque and having a small breaking torque with little variation.

Further, the present invention provides a method for manufacturing the above-mentioned upper torque regulating screw, in which the breaking portion that divides the thin wall portion as described above can be processed at the same time as the molding of the screw head and shaft portion without adding extra steps or increasing the number of man-hours. The purpose is to

Hereinafter, one embodiment of the present invention will be described based on the drawings. 1st b! ! l indicates a metal wire material with a circular cross section. The raw material 1 obtained by cutting the wire into a predetermined size is preformed using a preforming punch 20 and a die 21 as shown in FIG. Shaft diameter d
The threaded shaft portion 4 that has been drawn to a smaller size is processed. At the same time, a recess 6 is formed at the lower end of the screw shaft 4 using a forming pin 22 .

Next, the enlarged portion 21 is compression-molded to form the outline of the head, and at the same time, a retaining groove for a rotary tool such as a driver is machined. It has characteristics. In other words, as shown in FIG. 1M8 and FIG. It has a protrusion 26 for forming a rotary tool engagement groove that also serves as a flathead screwdriver.

The die 26 has a chamfered portion 2 with a large radius of curvature on the periphery of the opening.
7.

Using the above-mentioned head forming punch 23 and die 26,
When 2 is molded, a projecting portion 6 having a diameter larger than the shaft diameter d is formed along the chamfered portion 27 on the outer periphery of the connecting portion between the head 2 and the rotating portion 3, and the rotating portion 3, the hole diameter in the diagonal direction is slightly larger than the shaft diameter d of the rotating part 3, and the effective depth L extends slightly below the lower surface 7 of the head 2.
is formed, and a rotary tool engagement groove 9 that can be used for both a differential screwdriver and a flathead screwdriver is formed in the opening of the square hole 8 by the protrusion 26 .

Subsequently, as shown in FIGS. 5 and 6, the trimming punch 28 having a hexagonal hole 29 and trimming are performed in a step of trimming the outer periphery of the head 2 into a hexagonal shape 10 using a cutting die 30. The opening edge 31 of the die 30 is used to squeeze and remove the overhanging portion 6 by crushing it. When the overhanging part 6 is removed in this way, as shown in FIGS. 6 and 7, a thin wall part 11 is formed at the connection point between the head 2 and the rotating part 3 due to the presence of the square hole 8. , the thin wall portion 11 is partially fractured at the four corners of the bottom of the square hole 8, and a minute fracture portion 12 is formed 66, and the thin wall portion 11 is divided by the fracture portion 12, and breaks with a small torque. . Furthermore, the fracture tortoise is determined by the cross-sectional area of the square hole 8 and the shaft diameter d.
Since it is determined by the cross-sectional area of the thin-walled portion 11, a small breaking torque with little variation can be easily obtained. In the figure, 32 is a recess for absorbing the excess meat crushed by the opening edge 31, and 33 is a knockout punch.

After the above trimming process is completed, see Figure 8.

l! As shown in FIG. 9, the rotating portion 3 is knurled 13 and the screw shaft portion 4 is rolled with threads 14 to complete the torque regulating screw.

FIG. 10 shows an example of use of the torque regulating screw configured as described above. Insert the conduit tubes 17 and 17 from both sides of the joint pipe 160, which has a screw tube 16 protruding from both ends of the outer periphery, and insert a screwdriver into the tool engagement groove 9 of the head 2 of the torque regulating screw screwed into the screw tube 16. Engage and rotate to tighten, and attach the tip of the screw shaft 4 to the conduit 1.
When the two electric conduit tubes 17 and 17 are connected to each other via the joint tube 16 by press-fitting the conduit tubes 17 to 7, and the screws are tightened to a certain level, the thin walled portion 11 breaks, as shown in FIG. The head 2 is scattered as shown on the right side. If it is necessary to remove the above screws that have been tightened in this way.

The screw can be removed by engaging a tool such as a bench with the rotating portion 3 and rotating the screw in the axial direction.

Note that due to excessive tightening, the screwing depth of the tip of the screw shaft portion 4 is limited.

11 and 12 illustrate another embodiment of the present invention, in which the diagonal hole diameter of the square hole 81 is smaller than the shaft diameter d of the rotating part 3. An annular groove 1 with a V-shaped cross section is formed by cutting or plastic processing on the outer periphery of the rotating part 3 directly below the rotating part 2.
By providing 8.

A thin wall portion 11 is formed at the connection point between the part 2 and the rotating portion 3, and the thin wall portion 11 is partially divided at the four corners of the square hole 81 to form a minute broken portion 12. It is.

As described in detail above, the torque regulating screw of the present invention has a rectangular hole provided from one head to the rotating portion, and a thin wall portion is formed at the connecting portion between the head and the rotating portion, and Since a breaking portion is formed at the corner of the hole to separate the thin walled portion, the thin wall portion can be broken with a relatively small tightening torque, and there is little variation in the breaking torque, making it possible to improve the conduit connection device. Suitable for use as screws.

Furthermore, according to the method of the present invention, the torque regulating screw having the above-mentioned structure can be mass-produced at low cost using the same process and number of man-hours as for ordinary screw machining.

[Brief explanation of the drawing]

Figure 1 is a front view of the material, Figure 2 is a partially vertical front view of the preforming process, Figure 8 is a partial vertical front view of the head forming process, and Figure 4 is a punch and die in the head forming process. Plan view of 5th
Figure 6 is a partially longitudinal front view of the trimming process, Figure 7 is a plan view of the trimmed head, Figure 8 is a front view of the completed torque regulating screw of the present invention, and the wJs figure is @8 10 is a partially cutaway front view showing the same usage example, FIG. 11 is a partially cutaway front view showing another embodiment, and FIG. 12 is a partially cutaway front view showing another example. FIG. 11 is a cross-sectional view taken along the line I[-I[, and FIGS. 18 and 14 are front views showing different conventional examples. 2...Head 3...Rotation
Part 4... Screw shaft part 6... Overhanging part 7... Bottom 1ii9.8 of head 2... Corner Hole 9... Rotating tool Engagement groove 11...Thin wall portion 12...Broken portion (Patent applicant: Tosuma Nakayama, Toyodai Miyake)
Figure 4 (in

Claims (1)

[Scope of Claims] 1. A square hole drilled from the part of the screw body to the rotary part, in which a rotating part and a screw shaft part are integrally formed below the head having a retaining groove of a rotary tool. is provided approximately concentrically with the rotating part, and the square hole forms a thin-walled part at the connection point between the head and the rotating part, and the thin-walled part is formed at the corner of the square hole. Torque regulating screw with a broken part that separates the parts. 2. The friction regulating screw according to claim 1, wherein the opening of the square hole is formed in an engagement groove of a rotary tool. 6. A head having a one-turn tool 6 engagement groove is formed by forging a material obtained by cutting a wire rod into a predetermined size, and a rotating part with a shaft diameter d and a screw shaft part connected below the head are integrated. When forming the
An overhang is formed on the outer periphery of the connection point between the head and the rotating part, and the diameter of the hole in the diagonal direction from the head to the rotating part is slightly larger than the shaft diameter d of the rotating part. A square hole with a depth L extending slightly below the lower surface of the head is provided concentrically with the rotating part, and in the next head trimming step, the overhanging part is crushed using a cutting die. and forming a thin walled portion by the square hole at a connection point between the head and the rotating portion, and a breaking portion for dividing the thin walled portion at a corner of the bottom of the square hole. A manufacturing method for torque regulating screws.