JPS6249488B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blind nut, and particularly to a rotation prevention mechanism thereof.

A member that is thin and difficult to operate from both sides, such as the reinforcing member 4 that fixes the bumper 2 of an automobile as shown in FIG. 1, is difficult to thread and insert and position a nut inside. Therefore, it is difficult to fasten the above members using ordinary nuts and bolts. Therefore, a nut 10 (herein referred to as a blind nut) that can be fixed from one side is used. The blind nut 10 is comprised of a hollow cylindrical body made of a plastically deformable material, has a female thread 12 cut in its front inner diameter portion, and has a radially outwardly extending flange at its rear end. This blind nut 10 is inserted into the mounting hole of one fastened member 16 from one side and then compressed in the axial direction, causing the nut to bulge outward as shown in FIG. 2, thereby being caulked and fixed. Thereafter, the bolt 8 passed through the other fastened member 18 is screwed together to perform the fastening operation.

However, with conventional blind nuts, the outer circumferential surface of the nut and the inner circumferential surface of the mounting hole of the fastened member are only in concentric surface contact, so a large torque is applied to the blind nut when tightening the bolt using an impact wrench, etc. If the bolt ends are brought into contact with each other and an axial force is applied, the blind nut, which has been secured by caulking, may spin idly.

Therefore, an object of the present invention is to further stabilize the caulking of the blind nut.

In order to achieve the above object, according to the present invention, a concave groove cut out in the radially outward direction is provided on the outer peripheral surface of the mounting hole of the fastened member, and a blind nut is inserted into the mounting hole in the radially outward direction including the mounting hole. The intermediate wall portion of the blind nut is bulged out, and the member to be fastened is held under pressure between the bulged portion and the flange portion. This groove can be formed in a pre-formed mounting hole (usually a round hole) using the tool described below. That is, a tool for forming a grooved mounting hole for a blind nut includes a rod-shaped guide portion that contacts the inner circumferential surface of a blind nut mounting hole formed in advance on a member to be fastened, and a rod-shaped guide portion disposed behind the guide portion. It consists of a flange portion that can be inserted into the mounting hole, and a blade that is formed on the front edge of the outer periphery of the flange portion to protrude radially outward and has a cutting edge angle of 15 to 40 degrees.

According to the present invention, since a concave groove notched radially outward is provided on the circumferential surface of the mounting hole of the fastened member, the nut mounting hole becomes irregularly shaped, and when the nut is swaged, the nut outer circumferential surface (intermediate wall portion) becomes plastic. Since it deforms and bulges and fits into the groove, it will not slip even if a large torque is applied during bolt tightening.

Forming the groove using the above tool does not require a receiving die, and there is almost no surface deformation of the fastened member.
A concave groove can be formed from the outside on a hollow member to be fastened with a blind nut.

The present invention will be described below with reference to the accompanying drawings.

First, with reference to FIGS. 3 and 4, the tool 2
0 and the blind nut mounting hole 22 will be explained. The irregularly shaped mounting hole 22 as shown in the figure is first drilled into the fastened member 1 using a drill (not shown).
A round hole is formed in 6 from one side, and then a groove 24 notched radially outward is formed in the circumferential surface of the round hole using a tool 20 shown in FIGS. 3 and 4. The grooves 24 shown in the figure have a semicircular shape, and a total of four grooves are formed, but it is also possible to have a shape other than this, such as a triangle, or a number other than the above, for example, 1 to 3 or 5 or more. .

The tool 20 includes a guide portion 26 located at the front;
It mainly consists of a grip section 28 located at the rear, a flange section 30 located between the two, and a cutting edge 32 located at the front edge of the outer periphery of the flange section 30.
The guide portion 26 has a truncated conical tip for easy insertion, and the rest of the guide portion 26 has a substantially quadrangular prism shape. Each corner of the square column is rounded so as to make surface contact with the inner peripheral surface of the round hole. Therefore, alignment of the tool 20 is completed by inserting the guide portion 26 into the round hole. This flange portion 30 has an outer diameter approximately equal to the inner diameter of the round hole so that it can be inserted into the round hole of the member to be fastened 16, and a cutting edge 32 is provided at the front edge of the outer periphery. One or more cutting edges 32 are provided along the outer periphery of the flange portion 30. The cutting edge or rake angle of the cutting edge 32 is 15 to 40 degrees, preferably 30 degrees, allowing cutting from one side. The grip portion 28 is formed in a cylindrical shape so that it can be easily attached to a predetermined punching device (not shown). When the tool 20 with the guide portion 26 inserted into the round hole of the member 16 to be fastened is struck by a predetermined punch device, the cutting blade 32 comes into contact with the periphery of the round hole of the member 16 to be fastened, and the tool 20 is inserted into the round hole of the member 16 to be fastened. is notched, and the round hole is used as the irregularly shaped mounting hole 22.

As shown in FIG. 6, the blind nut 10 is inserted into the mounting hole 22 thus modified from one side. The blind nut 10 is a hollow, substantially cylindrical member made of a plastically deformable material, and has a flange portion 14 extending radially outward at one end. The inner diameter portion 12 of the blind nut 10 is composed of a female threaded portion 12 provided near the end opposite to the flange portion 14, and a bolt guide portion 34 located on the flange portion 14 side. The bolt guide portion 34 has an inner diameter slightly larger than that of the female thread portion 12 as shown in the figure, and therefore the wall portion 36 corresponding to the bolt guide portion 34
It's also getting thinner.

The outer diameter of the cylindrical portion of the blind nut 10 is slightly smaller than the inner diameter of the mounting hole 22 of the member to be fastened, so that the blind nut 10 can be inserted into the mounting hole. 6th
As shown in the figure, the blind nut 10 fitted to the member to be fastened 16 is compressed in the axial direction, and the thin wall portion 36 bulges out in the radial direction as shown in FIG. As shown in the figure, this bulging portion 38 has a substantially U-shaped cross section, and the flange portion 14 and the U-shaped bulging portion 38
The member to be fastened 16 is crimped and clamped between. In this way, the blind nut 10 is fixed to the member to be fastened 16, but the thin wall portion 36 that has been plastically deformed
A portion of the blind nut 10 bites into the groove 24 of the mounting hole 22, so even if a large torque is applied to the blind nut 10, the portion biting into the groove 24 prevents the blind nut 10 from slipping.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing an application example of a blind nut, Figure 2 is a sectional view showing a fastening method using a blind nut and bolt, and Figure 3 is a side view showing a tool for forming a modified mounting hole. Figure 4 is the third
The front view of the tool shown in the figure is seen from the axial direction.
A plan view showing the blind nut inserted into the mounting hole formed by the tool shown in the figure, Figure 6 is a sectional view taken along the line - in Figure 5, and Figure 7 shows the blind nut after caulking. FIG. 8...Bolt, 10...Blind nut, 1
2... Threaded portion, 16... Member to be fastened, 20... Tool, 22... Mounting hole, 24... Concave groove.

Claims (1)

[Claims] 1. A blind nut rotation prevention mechanism using a blind nut that is made of a hollow cylindrical body made of a plastically deformable material, has a female thread at the front inner diameter part, and has a flange part expanding radially outward at the rear end. A groove cut out radially outward from the circumferential surface of the mounting hole of the fastened member is provided in the fastened member, and the intermediate wall of the blind nut bulges radially outward including the inside of the mounting hole groove. A blind nut rotation prevention mechanism that prevents the blind nut from idling by fitting the formed bulge into the groove.