JPH11294432A - Protection structure of nut for fastening and protection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent arbitrary removal of fastening structure consisting of a bolt and a nut. SOLUTION: A fastening structure 6 consists of a bolt 3 and a plurality of nuts 1 and 2, the nut comprises an inside nut 1 arranged on the inside for fastening; and an outside nut 2 arranged on the outside for fastening. The nuts 1 and 2 are contained in a protection member 10 consisting of a hollow body having an outer shape formed in a circular shape. The inside nut 1 is fixed at the inner wall 13a of the protection member 10, and the outside nut 2 is loosely fitted in the inner wall 14a of the protection member 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection structure and a protection method for a fastening nut fixed by a plurality of nuts and bolts, and more particularly, to a method for preventing a nut from being arbitrarily removed from a frame structure such as a steel tower. To a protection structure and a protection method.

[0002]

2. Description of the Related Art Conventionally, in a frame structure such as a steel tower, a nut is fixed with a resin, or a plurality of nuts are used (so-called double nuts) in order to prevent a nut from being loosened at a fastening portion. Fixed. However, since the fastening structure including the bolt and the nut is a screw-in structure, the fastening structure can be easily removed by using a spanner, a wrench, or the like. Even if double nuts are used to prevent loosening, arbitrarily removing these nuts can cause even large structures such as towers to collapse. This causes enormous damage and great social impact.

[0003]

As a security measure taking into account the arbitrary removal of the nut, the nut is fixed with resin so that the nut is hardened to turn. It is conceivable to cover the nut with a circular cap to make it difficult to turn with a normal spanner or wrench.

[0004] However, the former method of fixing with resin is poor in workability and expensive. On the other hand, the latter method using a circular cap can be removed by using a strong pipe wrench, and it is not possible to completely prevent arbitrary removal.

Accordingly, an object of the present invention is to provide a nut protection structure and a protection method that make it difficult to remove these nuts arbitrarily. In addition, an object of the present invention is to prevent an arbitrary removal of a fastening structure including the bolt and the nut.

[0006]

According to a first aspect of the present invention, there is provided a fastening structure comprising a bolt and a plurality of nuts, wherein the nut is disposed inside and fastened. An inner nut and an outer nut arranged outside and fastened to the outside. The nut is housed in a protective member formed of a hollow body having a circular outer shape. The outer nut is fixed to an inner wall, and the outer nut is loosely fitted to the inner wall of the protection member, wherein the tightening nut is protected.

According to a second aspect of the present invention, the protection member is configured such that the inner diameter of the protection member is smaller than the maximum outer size of the inner nut by expanding in the direction of the inner wall;
The protection structure according to claim 1, further comprising a press-fit fixing portion having a height equal to or less than the nut height of the inner nut, wherein the press-fit fixing portion is press-fitted and fixed to the inner nut.

According to a third aspect of the present invention, the nut includes an inner nut having a larger maximum outer dimension and an outer nut having a smaller maximum outer dimension than the inner nut. The protection according to claim 1, wherein the protection member is press-fitted and fixed to the inner nut by being smaller than a maximum outer size of the nut and equal to or greater than a maximum outer size of the outer nut. Structure.

According to a fourth aspect of the present invention, there is provided the protective structure according to any one of the first to third aspects, wherein the protective member is a cylinder.

According to a fifth aspect of the present invention, there is provided the protective structure according to the fourth aspect, wherein the cylinder has an open end that can be closed.

According to a sixth aspect of the present invention, the outer shape of the protection member is a circular shape whose diameter increases toward the object to be fastened. Protection structure.

The invention according to claim 7 is the protective structure according to any one of claims 1 to 5, wherein the inner nut is a square nut.

The invention according to claim 8 is a fastening structure comprising a bolt and a plurality of nuts, wherein the fastening is performed by an inner nut arranged and fastened inside and an outer nut arranged and fastened outside. The outer nut is press-fitted into the tightening structure from the opening side with a protective member formed of a hollow body having a circular outer shape and having an opening at one end with respect to the bolt tightening structure. Is a method of protecting a tightening nut, wherein the inner nut is loosely fitted and bites and fixes the inner nut to the inner wall of the protection member.

[0014]

According to the protection structure of the first aspect, the structure is tightened by a plurality of nuts, that is, a so-called double nut. The nut of this fastening structure is housed by a hollow protective member having a circular outer shape. The inner wall of the protection member is fixed to the inner nut, but is loosely fitted to the outer nut.

According to this structure, since the protective member has a circular outer shape, it is difficult to bite a wrench or a wrench. Also, even if the protective cap is forcibly rotated in the nut removing direction, the protective member is fixed to the inner nut and not fixed to the outer nut, so the nut does not loosen due to the effect of the double nut. .

Further, since this protection member is fixed to the inner nut, it cannot be easily removed. This eliminates the desire to easily remove the nut, and prevents arbitrary removal of the nut in the fastening structure, which is effective in crime prevention.

According to the second aspect of the present invention, since the inner diameter is smaller than the maximum outer dimension of the inner nut, and the inner nut is provided with a press-fit fixing portion having a height equal to or less than the nut height, The press-fit fixing portion is press-fitted into the inner nut and fixed.

According to this structure, since the mounting of the protective member can be performed by press-fitting, it is extremely easy and the operability is improved. Further, this protection structure has an advantage that it can be applied as it is to an existing double nut fastening structure such as a steel tower.

In the protective structure according to the third aspect, the bolt is fastened by a double nut composed of an inner nut having a large outer dimension and an outer nut having a small outer dimension.
The protective structure according to claim 1 is obtained by press-fitting a protective member having a constant inner diameter into such a fastening structure.

According to this structure, since the inner diameter of the protective member used may be constant, it is easy to form and obtain the protective member, and the unit cost of the protective structure is reduced.

According to the fourth aspect of the present invention, since the protection member is a cylinder, it is possible to use a protection member having a simple structure which can only cut an existing thick pipe. This reduces the cost of the protection structure.

In the protective structure according to the fifth aspect, since the cylinder can be closed at the open end, the appearance is beautiful. In addition, an effect of preventing dirt and corrosion of the fastening structure is expected.

According to the protection structure of the sixth aspect, since the outer shape of the protection member is a circle whose diameter increases toward the object to be fastened, not only is it more difficult to bite a wrench or the like,
Since the fixing part with the inner nut is made thick and reinforced,
Removal becomes even more difficult.

Although the shape of the nut according to the present invention is not limited, a square nut is used as the inner nut in the present invention. The corners of the square nut can be used for fixing to the protection member, thereby easily or reliably fixing the inner nut and the protection member.

[0025]

[Embodiment 1] Hereinafter, a specific embodiment of the present invention will be described with reference to the drawings using a hexagonal nut, but it is similarly used for other polygonal nuts such as a quad nut.

FIGS. 1 to 7 are views for explaining a protection structure for a tightening nut according to Embodiment 1 of the present invention.

FIG. 1 shows an example to which the present invention is applied, in which two nuts 1 and 2 and one bolt 3 of the same size are used.
Shows a fixing structure 6 in which steel members 4 and 5 as members to be fastened are fastened. Two steel members 4, 5
In the through hole 7, a bolt 3 penetrates from one side 5a side, and a screw portion 8 protrudes to the other side 4a side. Two nuts 1 and 2 are screwed into the screw portion 8 via a washer 9, so that a so-called double nut is fixed by the two nuts 1 and 2.

The nuts 1 and 2 and the bolts 3 conform to, for example, JIS standards. The dimensions of each part of the nut (nut height H, width across flats B, diagonal dimension C) are shown in FIG.
In the following description, reference numerals 1 and 2 indicating nuts are attached to these dimensions as subscripts. The nut height H1 of this nut 1 is 17
mm, the width (two-plane width) B1 between the opposing surfaces 1a and 1a
Is 32 mm, and the width (diagonal dimension) C1 between the opposing vertices 1b and 1b is 37 mm. In the first embodiment, nuts 1 and 2 have the same standard.

Here, the double nut fixing means the nut 1
Is screwed, and then the nut 2 is screwed and fixed, and the nut 1 and the nut 2 are urged in opposite directions (x and y directions in the figure). Thereby, the nut 1
Are pressed against the thread 8a above the bolt 8, and the thread of the nut 2 is pressed against the thread 8b below the bolt 8. This prevents the nuts 1 and 2 from rotating and loosening.

However, the nuts 1 and 2 are both exposed, and can be removed by removing the nuts 1 and 2 with a wrench or the like while sandwiching and rotating the respective surfaces 1a and 2a.

FIG. 3 is a view for explaining a sleeve 10 as a protective member used in the present invention.
Reference numeral 0 denotes a cylindrical hollow body having a circular outer shape 11 and having a space 12 therein. The sleeve 10 is formed of a material which is softer than the steel bars forming the nuts 1 and 2, for example, is formed by processing an aluminum pipe or the like. It may be formed from other materials such as iron and resin.

The outer diameter D10 of the sleeve 10 is sufficiently larger than the diagonal dimensions C1 and C2 of any of the nuts 1 and 2 (D10> C1 and C2), for example, about 44 mm.
A step is provided on the inner wall. A thick portion having a thickness of about 4 mm is a press-fit fixing portion 13, and a thin portion having a thickness of 3 mm is a loose fitting portion 14. Height H1 of sleeve 10
0 is about 50 mm, which is slightly longer than twice the nut height H1. The height H13 of the press-fit fixing portion 13 measured from the lower end 10a is about 17 mm, which is almost equal to the nut height H1, but does not become higher than the nut height H1 (H13 = or <H1).

The inner diameter d13 of the press-fit fixing portion 13 is set to about 36 mm, which is larger than the two-sided width B1 and is always smaller than the diagonal dimension C1 (C1> d13).
> B1). On the other hand, the inner diameter d14 of the loose fitting portion 14 is about 38 mm
And is set to be larger than the diagonal dimension C2 (d
14> C2).

As shown in FIG. 4, the sleeve 10 is press-fitted with the opening end 10a of the sleeve 10 on the press-fitting fixing portion 13 side facing the fixing structure 6. Since the inner diameter d13 is smaller than the diagonal dimension C2, the inner wall 13a of the press-fit fixing portion 13 has the vertex 2
The inner wall 13a is deformed by the apex 2b by forcibly pressing the sleeve 10 in with a silencing hammer or the like. As a result, the sleeve 10 can be press-fitted, and the lower end 10a of the sleeve 10 is press-fitted until it comes into contact with the washer 9, thereby obtaining the protective structure 15 as shown in FIG.

In the protection structure 15, the nuts 1 and 2 fixed with double nuts are housed in the hollow 12 of the sleeve 10. As shown in FIG. 6, the inner nut 1 has a vertex 1b biting into the inner wall 13a and is fixed. This biting depth is about 1 mm. Also, surface 1a
And an inner wall 13a is formed with a gap.

On the other hand, as shown in FIG. 7, the outer nut 2 is loosely fitted with a slight gap formed between the apex 2b and the inner wall 14a of the sleeve 10 at both apexes 2b.

With this configuration, the two nuts 1 and 1
Since both 2 are housed in the sleeve 10, a wrench or the like cannot be directly operated. Further, since the outer shape 11 of the sleeve 10 is circular, it is difficult to bite a wrench or a wrench. Even if the user forcibly bites the sleeve 10 with a wrench or wrench, and tries to forcibly rotate the nut in the direction of removing the nut with the force of two adults, the nut cannot be removed. This is because the sleeve 10 is fixed to the inner nut 1 but is not fixed to the outer nut 2, so that the nuts 1, 2
Is not loosened.

The sleeve 10 is provided with the inner nut 1
, So it cannot be easily removed. Thus, it is difficult to easily remove the nuts 1 and 2 and the desire to remove the nuts 1 and 2 is lost. If it is forcible, arbitrary removal of the nut can be prevented, which is effective in crime prevention.

In the first embodiment, an example is shown in which the position of the vertex 1a and the position of the vertex 2a coincide with each other. However, even if the position is shifted, the deformation trajectory due to the vertex 1a remains on the inner wall 13a. It is only formed and the other effects are exactly the same.

Hereinafter, modified examples of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. Note that the same or equivalent parts as those in the first embodiment will be described with the same reference numerals.

[0041]

[Modification 1] In the first embodiment, the sleeve 10 is press-fitted into the fixing structure 6 fastened by the double nut. However, as shown in FIG. 8, the single nut 1 without the washer 9 is used. The present invention is also applicable to a directly fixed fastening structure 6 '.

For example, in the first modification, the nut height H
1 are fastened by a single nut 1 of 22 mm. Prior to press-fitting the sleeve 10, as shown by a two-dot chain line in FIG. 8, the same nut 2 used in the first embodiment having a nut height H2 of 17 mm is screwed into the screw head 8 as a stop nut. This results in a double nut fastening structure.
At this time, the height H2 of the nut 2 may be equal to H1, but particularly in the double nut structure, H2 is sufficiently effective even if it is lower than H1. If the nut 2 having a small play, that is, a so-called high screw precision is selected as the nut 2, the fixing effect becomes remarkable, so that it is good.

Thereafter, the protective structure is obtained by press-fitting the sleeve 10 exactly in the same manner as in the first embodiment.
Other configurations and operations are substantially the same as those in the first embodiment, and therefore, description thereof is omitted.

[0044]

[Modification 2] In this modification 2, as shown in FIG. 9, a member for reducing the sliding frictional resistance between the nut 1 and the nut 2,
For example, a double nut fastening structure 6 in which a washer 9 ′ having a small outer diameter is provided between the nut 1 and the nut 2 is used. Here, the outer diameter of the washer 9 'is equal to or less than the diagonal dimension C1. The protective structure of the present invention can be formed by press-fitting the sleeve 10 into such a fastening structure as in the first embodiment.

In the first embodiment, when the sleeve 10 is rotated and the nut 1 is urged to rotate in the loosening direction, if the nut 1 and the nut 2 rotate together, the fastening structure may be loosened even with the double nut. However, in the second modification, since a member for reducing the sliding frictional resistance is inserted between the nut 1 and the nut 2, even if the sleeve 10 is rotated, the nut 2 is rotated with respect to the rotation of the nut 1. It doesn't follow, so it doesn't come loose.

Other functions and effects are the same as those of the first embodiment, and therefore, detailed description is omitted.

[0047]

[Modification 3] In this modification 2, as shown in FIG.
The height H10 of the sleeve 10 is increased, and its inner wall 14a
A step 14b is provided slightly near the upper end 10b. The periphery 16a of a disk-shaped aluminum cap 16 having a thickness of 3 mm is brought into contact with the step 14b and press-fitted.
As a result, the upper end 10b is closed, so that the appearance becomes beautiful. Further, an effect of preventing the fastening structure 15 from being stained and corroded is also expected.

In the aluminum cap 16, the periphery 16a and the step 14b may be fixed with an adhesive, or both may be screwed and fixed.

[0049]

[Modification 4] The sleeve 10 shown in FIG. 3 may have a slope near the lower end 10a. As shown in FIG. 11A, if the inclined wall 13 b is provided on the inner wall 13 a, the press-fitting of the sleeve 10 becomes easy. Also, as shown in FIG.
If the slope 13c is provided outward, even if there is a gap between the lower end 10a and the surface 5a, it becomes difficult to remove the gap by a driver or the like.

[0050]

[Modification 4] As shown in FIG. 12, a sleeve 10 provided with a step 13d for accommodating the washer 9 by increasing the inner diameter d13 near the lower end 10a may be used. With this configuration, the space up to the washer 9 is housed in the hollow space 12, and there is no gap between the lower end 10a and the surface 4a.
Even without providing the inclination 13c as shown in FIG.

[0051]

[Modification 5] When the opening end 10b faces upward in the vertical direction,
If the lower end 10a and the washer 9 or the fastened body 4a are in close contact, rainwater may stay in the sleeve 10. In such a place, the sleeve 10 has a notch 13e near the lower end 10a, as shown in FIG.
May be provided. Even if rainwater enters inside, the rainwater is discharged from the cut 13e. In this figure,
There are two cuts, but the number of cuts is not limited. For example, four cuts may be made evenly around the entire circumference.
In some cases, it may be provided innumerably.

Although the first embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to the first embodiment, and there are design changes and the like within a range not departing from the gist of the present invention. Is also included in the present invention. For example, in the embodiment, detailed dimensions of each member are shown, but the dimensions are not limited within the scope of the present invention.

In the first embodiment, the sleeve 10 having a substantially cylindrical outer shape is used. However, by making the outer shape a hemispherical or conical shape, it becomes more difficult to bite a wrench or the like. In addition, with such a configuration, the thicker portion is more easily obtained closer to the object to be fastened, whereby the fixing of the fixing portion is also ensured.

[0054]

Embodiment 2 Hereinafter, Embodiment 2 of the present invention will be described.
Will be described with reference to FIG. 14 and FIG. Note that the same or equivalent parts as those in the first embodiment will be described with the same reference numerals.

In the second embodiment, as shown in FIG. 14, the outer diameter D20 is about 44 mm and the inner diameter d2 is a protective member.
A sleeve 20 made of an aluminum pipe having a uniform diameter of about 36 mm is used. The nut 2 has a small diagonal dimension C2 of less than 35 mm.

Fixing the open end 20a of the sleeve 20 to the fixing structure 6
And press-fit this sleeve 20. Since the inner diameter d20 is smaller than the diagonal dimension C1, the inner wall 20c has the vertex 1b.
The inner wall 20c is deformed by the apex 1b by forcibly press-fitting, as in the first embodiment, and the sleeve 20 can be press-fitted. As a result, the lower end 20a of the sleeve 20 is press-fitted until it comes into contact with the washer 9, thereby obtaining the protective structure 15 as shown in FIG.

In the protection structure 15, the nuts 1 and 2 fixed to the double nuts are housed in the sleeve 20. The inner nut 1 has a vertex 1b biting into the inner wall 20a and is fixed to form a press-fit fixing portion. In addition, a gap is formed between the surface 1a and the inner wall 20a.

On the other hand, the outer nut 2
A gap is formed with the inner wall 20a, and the inner wall 20a is loosely fitted.

With this configuration, two nuts 1 and 1
Since both 2 are housed in the sleeve 20, a wrench or the like cannot be directly operated. Further, since the outer shape of the sleeve 20 is circular, it is difficult to bite a wrench or a wrench. Even if the sleeve 20 is forcibly bitten with a wrench or the like and rotated in the nut removal direction, the sleeve 20 is fixed to the inner nut 1 and not fixed to the outer nut 2, so that the effect of the double nut is The nuts 1 and 2 do not come loose.

The sleeve 20 is provided with the inner nut 1
, So it cannot be easily removed. Thus, it is difficult to easily remove the nuts 1 and 2 and the desire to remove the nuts 1 and 2 is lost. If it is forcible, arbitrary removal of the nut can be prevented, which is effective in crime prevention.

In the second embodiment, an example is shown in which the position of the vertex 1a and the position of the vertex 2a coincide with each other.
Is smaller than the inner diameter d13 of the press-fit fixing portion 13, so that the deformation trajectory generated in the first embodiment is not formed on the inner wall 20c.

In the case of the second embodiment as well, the first embodiment
Similar effects can be obtained even if various modifications are made in the same manner as described above.

[0063]

Embodiment 3 Hereinafter, Embodiment 3 of the present invention will be described.
Will be described with reference to FIG. Note that the same or equivalent parts as those in the first embodiment will be described with the same reference numerals.

In the third embodiment, a sleeve 30 made of an aluminum pipe having an outer diameter D30 of 46 mm and an inner diameter d30 of 39 mm is used as a protective member.

Fixing the open end 30a of the sleeve 30 to the fixing structure 6
The sleeve 30 is mounted. Since the inner diameter d30 is larger than the diagonal dimensions C1 and C2, the sleeve 30 can be mounted without press-fitting. Thereby, the sleeve 30 is mounted until the lower end 30a comes into contact with the surface 4a. Then, the adhesive 17 is applied around the nut 1 (1a,
If it is injected only into 1b), a protective structure 15 is obtained as shown in FIG.

In the protection structure 15, the nuts 1 and 2 fixed to the double nuts are housed in the sleeve 30. This inner nut 1 is provided around the nut 1 (1a, 1a).
b) is adhesively fixed to the inner wall 30c to form an adhesive fixing portion. On the other hand, the outer nut 2 is loosely fitted with a gap formed between the apex 2b and the inner wall 30a to form a loose fitting portion.

According to this structure, the same operation and effect as those of the first embodiment are exhibited except that the fixing is not press-fitting but fixing with an adhesive, and therefore detailed description is omitted.

In the case of the third embodiment, the first embodiment
Similar effects can be obtained even if various modifications are made in the same manner as described above.

[0069]

As described above, according to the present invention, there is provided a nut protection structure and a protection method which make it difficult to arbitrarily remove a nut. As a result, it is possible to prevent arbitrary removal of the fastening structure including the bolt and the nut.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a fixing structure using a double nut applied to a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams illustrating dimensions of a nut according to the first embodiment. FIG. 2A is a side view, and FIG. 2B is a plan view.

3A and 3B are diagrams illustrating a protection member used in the first embodiment of the present invention, wherein FIG. 3A is a cross-sectional view and FIG. 3B is a plan view.

FIG. 4 is an assembly view showing a state in which the protection structure of the first embodiment is formed.

FIG. 5 is a sectional view showing a protection structure according to the first embodiment.

FIG. 6 is an end view taken along line AA of the protection structure of FIG. 5;

FIG. 7 is an end view taken along the line BB of the protection structure of FIG. 5;

FIG. 8 is a cross-sectional view illustrating a protection structure according to a first modification.

FIG. 9 is a cross-sectional view illustrating a protection structure according to a second modification.

FIG. 10 is a cross-sectional view illustrating a protection structure according to a third modification.

FIGS. 11A and 11B are cross-sectional views of a protection member used in Modification Example 4. FIGS.

FIG. 12 is a perspective view showing a sleeve according to a fourth modification.

FIG. 13 is a sectional view showing a protection structure according to a fifth modification.

FIG. 14 is an assembly view showing a state in which a protection structure according to the second embodiment is formed.

FIG. 15 is a sectional view showing a protection structure according to the second embodiment.

FIG. 16 is a sectional view showing a protection structure according to a third embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inner nut 2 outer nut 3 bolt 10, 2030 protective member (sleeve) 13 press-fit fixing portion 13a inner wall of press-fit fixing portion 14 loose fitting portion 14a inner wall of loose fitting portion

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Endo 2109-8 Yashima Nishimachi, Takamatsu City, Kagawa Prefecture Inside Techno Success Co., Ltd. (72) Inventor Kazuhide 2109-8 Yashima Nishimachi, Takamatsu City, Kagawa Prefecture Techno Success Stock In company

Claims (8)

[Claims] 1. A fastening structure for a body to be fastened by a bolt and a plurality of nuts, wherein the nut includes an inner nut arranged and fastened inside, and an outer nut arranged and fastened outside. Wherein the nut is housed in a protective member composed of a hollow body having a circular outer shape, the inner nut is fixed to an inner wall of the protective member, and the outer nut is an inner wall of the protective member. Is a protective structure for a tightening nut, which is loosely fitted. 2. The protection member according to claim 1, wherein an inner diameter of the protection member is smaller than a maximum outer size of the inner nut by expanding in an inner wall direction, and the protection member has a height equal to or less than a nut height of the inner nut. The protection structure according to claim 1, further comprising a press-fit fixing portion configured, wherein the press-fit fixing portion is press-fitted and fixed to the inner nut. 3. The nut comprises an inner nut having a larger maximum outer dimension and an outer nut having a smaller maximum outer dimension than the inner nut, and the inner diameter of the protective member is the maximum outer dimension of the inner nut. 2. The protection structure according to claim 1, wherein the protection member is press-fitted and fixed to the inner nut by being smaller than the maximum outer dimension of the outer nut. 4. The protection structure according to claim 1, wherein the protection member is a cylinder. 5. The protection structure according to claim 4, wherein the cylinder has an open end that can be closed. 6. The protection structure according to claim 1, wherein the outer shape of the protection member is a circle whose diameter increases toward the object to be fastened. 7. The protection structure according to claim 1, wherein the nut is a square nut. 8. A tightening structure of a bolt and a plurality of nuts, wherein the bolt is tightened by an inner nut which is arranged and fastened inside and an outer nut which is arranged and fastened outside. On the other hand, by pressing a protection member composed of a hollow body having a circular outer shape and having an opening at one end into the tightening structure from the opening side, the outer nut can play with the inner wall of the protection member. A method of protecting a tightening nut, wherein the nut is fitted and bitten into the inner wall of the protection member.