Blind nut, a blind nut assembly and mounting structure thereof

Abstract

A blind nut assembly including a bush and nut. The bush includes a short cylindrical collar, which has a polygonal outer surface on the outer surface thereof, and a flange, the outer surface of which is polygonal. The nut consists of a female screw member, on which a female screw to be mated with a male screw on a bolt is formed; and a nut cylindrical member, which is formed adjacent to the female screw member, which has a polygonal inner surface on the inner surface thereof aligning with the polygonal outer surface of the collar, of which the outer surface is also a polygonal outer surface, and which has a wall thickness that is thinner than the female screw member. The nut head has an outer diameter which is larger than the maximum outer diameter of the nut cylindrical member, is formed above the nut cylindrical member.

Claims

1. Blind nut, comprising a bush consisting of a short cylindrical collar, which has a polygonal outer surface on the outer surface thereof, and a flange, which is formed on one end of the collar; and a nut body consisting of a cylindrical female screw member, on which a female screw to be mated with a male screw on a bolt is formed; and a nut cylindrical member, which is formed adjacent to the female screw member, which has a polygonal inner surface on the inner surface thereof aligning with the polygonal outer surface of the collar, and which has a wall thickness that is thinner than the female screw member.

2. The blind nut of claim 1, wherein a nut head member having an outer diameter larger than the outer diameter of the nut cylindrical member is formed on the end of the nut cylindrical member.

3. The blind nut of claim 1, wherein the outer surface of the flange of the bush is polygonal.

4. The blind nut of claim 1, wherein the outer surface of the nut cylindrical member is a polygonal outer surface having the same number of polygonal corners as the polygonal inner surface of the nut cylindrical member; and the plate thickness of the nut cylindrical member is constant in the circumferential direction.

5. The blind nut of claim 1, wherein the bush is formed with a material which is harder than the nut body.

6. The blind nut assembly of claim 1, which is an assembly of the blind nut and the bolt, wherein the lower surface of the bolt head of the bolt is in contact with the upper surface of the flange of the bush, the lower surface of the flange of the bush is in contact with the upper surface of the nut cylindrical portion of the nut body, the polygonal outer surface of the collar of the bush aligns with the polygonal inner surface of the nut cylindrical member of the nut, the collar of the bush is accommodated within the nut body so as not to be rotated, and the male screw of the bolt is mated with the female screw of the nut body.

7. The mounting structure of claim 6 for tightening the mounted member and the mounting member by means of the blind nut assembly, wherein the collar of the bush and a portion of the nut cylindrical member of the nut body are accommodated within the mounting hole of the mounting member, a portion of the inside of the nut cylindrical member is supported by the collar, and the area surrounding the mounting hole of the mounted member and the area surrounding the mounting hole of the mounting member are sandwiched between the lower surface of the flange of the bush and the expanded diameter member where the nut cylindrical member of the nut is expanded.

8. A blind nut comprising a bush consisting of a short cylindrical collar, which has a polygonal outer surface on the outer surface thereof; and a nut body, consisting of a cylindrical female screw member, on which a female screw to be mated with a male screw on the axial member of a bolt is formed, and a nut cylindrical member, which is formed adjacent to the female screw member, which has a polygonal inner surface on the inner surface thereof aligning with the polygonal outer surface of the collar, of which the outer surface is a polygonal outer surface thereof, having the same number of polygonal corners as the polygonal inner surface, and which has a wall thickness that is thinner than the female screw member.

9. The blind nut of claim 8, wherein a nut head member, of which the outer diameter is larger than the outer diameter of the nut cylindrical member, is formed on the end of the nut cylindrical member.

10. The blind nut assembly of claim 8, which is an assembly of the blind nut and the bolt; wherein the polygonal outer surface of the collar aligns with the polygonal inner surface of the nut cylindrical member of the nut body, the collar is accommodated within the nut so as not to be rotated, the lower surface of the bolt head member of the bolt is in contact with the upper surface of the nut cylindrical member of the nut body, and the male screw of the axis member of the bolt is engaged with the female screw of the nut body.

11. The mounting structure of claim 10 for tightening the mounted member and the mounting member by means of the blind nut assembly, wherein the collar, and a portion of the nut cylindrical member of the nut body are accommodated within the mounting hole of the mounting member, a portion of the inside of the nut cylindrical member is supported by the collar, and the area surrounding the mounting hole of the mounted member and the area surrounding the mounting hole of the mounting member are sandwiched between the lower surface of the bolt head of the bolt and the expanded diameter member where the nut cylindrical member of the nut is expanded.

12. Blind nut assembly of claim 8 which is an assembly of the blind nut, bolt, and washer through which the bolt passes through, wherein the polygonal outer surface of the collar aligns with the polygonal inner surface of the nut cylindrical member of the nut body, the collar is accommodated within the nut so as not to be rotated, the lower surface of the bolt head member of the bolt is in contact with the upper surface of the washer, the lower surface of washer is in contact with the upper surface of the nut cylindrical member of the nut body, and the male screw of the axis member of the bolt is mated with the female screw of the nut body.

13. The mounting structure of claim 12 for tightening the mounted member and the mounting member by means of the blind nut assembly, wherein the collar and a portion of the nut cylindrical member of the nut body are accommodated within the mounting hole of the mounting member, a portion of the inside of the nut cylindrical member is supported by the collar, and the area surrounding the mounting hole of the mounted member and the area surrounding the mounting hole of the mounting member are sandwiched between the lower surface of the washer and the expanded diameter member where the nut cylindrical member of the nut is expanded.

14. The mounting structure of claim 11, wherein the mounting hole of the mounted member is polygonal, having the same number of polygonal corners as the polygonal outer surface of the collar and the polygonal inner surface of the nut cylindrical member.

15. The mounting structure of claim 14, wherein the mounting hole of the mounted member is square.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an exploded perspective view of a blind nut according to a first embodiment of the present invention.

(2) FIG. 2 is a top view of the bush of the blind nut of FIG. 1.

(3) FIG. 3 is a front view showing a portion of the bush of FIG. 2 as a cross section.

(4) FIG. 4 is a bottom view of the bush of FIG. 2.

(5) FIG. 5 is a top view of the nut body of the blind nut of FIG. 1.

(6) FIG. 6 is a front view showing a portion of the nut body of FIG. 5 as a cross section.

(7) FIG. 7 is a bottom view of the nut body of FIG. 5.

(8) FIG. 8 is a top view of a plain nut assembly with blind nut members assembled of FIG. 1.

(9) FIG. 9 is a front view showing a portion of the blind nut assembly of FIG. 8 as a cross section.

(10) FIG. 10 is a bottom view of the blind nut assembly of FIG. 8.

(11) FIG. 11 is a front view showing a portion of the state where the mounted member and the mounting member are fastened by the blind nut assembly of FIG. 8 as a cross section.

(12) FIG. 12 is a front view showing a portion of the state wherein the mounted member and the mounting member are fastened by the blind nut assembly of FIG. 8 as a cross section.

(13) FIG. 13 is a top view of a modification of the bushing.

(14) FIG. 14 is a front view showing a portion of a modification of the bush of FIG. 13 as a cross section.

(15) FIG. 15 is a bottom view of a modification of the bush of FIG. 13.

(16) FIG. 16 is an exploded perspective view of a blind nut according to a second embodiment of the present invention.

(17) FIG. 17 is a top view of the collar of the blind nut of FIG. 16.

(18) FIG. 18 is a front view showing a portion of the collar of FIG. 17 as a cross section.

(19) FIG. 19 is a top view of the nut body of the blind nut of FIG. 16.

(20) FIG. 20 is a front view of the nut body of FIG. 19.

(21) FIG. 21 is a bottom view of the nut body of FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

(22) Hereinafter, the blind nut 1 according to the first embodiment of the present invention shall be described with reference to the drawings. FIG. 1 is an exploded perspective view of a blind nut 1, a bolt 10, a mounted member 41, and a mounting member 42 according to the first embodiment. FIG. 1 is an exploded perspective view of a blind nut 1, a bolt 10, a mounted member 41 and a mounting member 42 according to the first embodiment. The blind nut 1 is provided with a bush 20 and a nut body 30. The bolt 10 has a shaft member 11 having a male screw 12 and a bolt head member 14 on the upper portion thereof. A bolt head hole 15 having a hexagonal cross section is formed in the bolt head member 14; a bolt head hole 15 of a hexagonal cross section shape is formed on the bolt head member 14, so that the bolt can be rotated by a tool such as a commercially-available hexagonal wrench.

(23) The bush 20 has a short tubular collar 21 and an upper flange 24 thereof. The nut body 30 has a female screw member 31 and a nut cylindrical member 33; a nut head member 35 is formed on the upper portion of the nut cylindrical member 33. An attachment hole 43 having a circular cross section is formed on the mounted member 41. A mounting hole 44 having a circular cross section is formed in the mounting member 42.

(24) The collar 21 of the bush 20 is inserted into the nut cylindrical member 33 of the nut body 30, the shaft member 11 of the bolt 10 is inserted into therein, the male screw 12 of the bolt 10 is screwably mounted into the female screw 32 of the female screw member 31 of the nut body 30 to form a blind nut assembly 1a.

(25) Next, the blind nut assembly 1a is inserted into the attachment holes 43, 44 of the mounted member 41 and the mounting member 42; when the male screw 12 of the bolt 10 is further screwed into the female screw 32 of the nut body 30, the nut cylindrical member 33 buckles to form an enlarged diameter member 33d, and between the flange 24 and the enlarged diameter member 33d, the mounted member 41 and the mounting member 42 are fastened.

(26) Each member of the blind nut 1 will now be described in detail. FIGS. 2-4 show the bush 20, and FIGS. 5-7 show the nut body 30. FIGS. 8-10 show the blind nut assembly 1a in which the bolt 10, the bush 20 and the nut body 30 are combined. FIGS. 11 and 12 are cross sectional views of the blind nut body 1a in a state where the mounted member 41 and the mounting member 42 are fastened. In the description of the present specification, the description will be done with the upper direction of FIG. 1 as the top.

(27) The bolt 10 is a commercially-available product and will now be described with reference to the exploded perspective view of FIG. 1. The bolt 10 is formed of a rigid material that is hard to deform, and has a shaft member 11 having a male screw 12 of an elongated columnar shape, and a bolt head member 14 of a diameter larger than that of the shaft member 11 on the upper portion.

(28) An outer peripheral portion of the bolt head member 14 is circular, and a bolt head hole 15 of a hexagonal cross section shape is formed in the upper central portion of the bolt head member 14. A tip portion of a commercially-available tool such as a hexagonal wrench wherein the cross section is of a hexagonal shape is inserted into the bolt head hole 15 so that the bolt 10 can be rotated. Alternatively, a hexagonal outer peripheral portion may be formed on the bolt head member 14, and this portion may be rotated by a wrench, or the like.

(29) With reference to FIGS. 2-4, the bush 20 of the blind nut 1 will now be described. FIG. 2 is a top view of the bush 20, FIG. 3 is a front view in which a portion is rendered as a cross section, and FIG. 4 is a bottom view. The bush 20 is a member for reinforcing the nut body 30 from the inside when a later-described nut body 30 buckles, and is made of a material harder than the nut body 30. The bush 20 is axially symmetrical about the central axis as a whole.

(30) The bush 20 has a collar 21 with a short tube at one end and a flange 24 at the other end. The collar outer surface 21b of the collar 21 is a polygonal outer surface having a substantially hexagonal cross section, and the vertex is chamfered. A collar hole 22 of a circular cross section shape is formed along the central axis of the collar 21.

(31) The distance between the two opposing outer surfaces of the flange 24 is greater than the distance (maximum diameter) between the apexes of the collar 21. The cross section of the outer surfaces of the flange 24 is hexagonal and can be supported so as not to rotate with a tool, such as a spanner. On the upper surface of the flange 24, a flange recessed member 25 having a circular cross section shape is formed. The flange recess 25 is shallow, and the bottom face is flat. The inner diameter of the flange recessed member 25 is slightly larger than the outer diameter of the bolt head 14 of the bolt 10 so that the bolt head 14 can be accommodated. The central portion of the flange recessed member 25 is continuous with the lower collar hole 22.

(32) With reference to FIGS. 5-7, the nut body 30 of the blind nut 1 will now be described. FIG. 5 is a top view of the nut body 30, FIG. 6 is a front view in which a part is taken as a cross section, and FIG. 7 is a bottom view.

(33) The nut body 30 is a part that buckles to form a diameter-enlarged portion, and is made of a plastically deformable material such as mild steel, aluminum, or the like. The nut body 30 is axially symmetric around the central axis as a whole.

(34) The nut body 30 has a cylindrical female screw member 31 and a nut cylindrical member connected to the upper side of the female screw member 31; a nut head member 35 is formed on the upper side of the nut cylindrical portion 33.

(35) The internally screwed portion 31 is of a cylindrical shape, and a female screw 32 is formed on the inner surface. The female screw 32 can be screwed into the male screw 12 of the bolt 10.

(36) A nut cylindrical member 33 is formed on the upper side of the female screw member 31. The nut outer surface 33b of the nut cylindrical member 33 is a polygonal outer surface having a substantially hexagonal cross section shape, and the corner portion is chamfered. The nut cylindrical member 33 is a portion that buckles and expands in diameter, and the wall thickness of the nut cylindrical member 33 is thinner than the wall thickness of the female screw member 31 to facilitate buckling.

(37) The nut inner surface 33a of the nut cylindrical member 33 is a polygonal inner surface which is larger than the inner diameter of the female screw member 31 and whose cross section is substantially hexagonal; the corner portion thereof is chamfered. The nut inner surface 33a is matched with the collar outer surface 21b of the bush 20. The wall thickness of the nut cylindrical member 33 is substantially uniform in the circumferential direction and can be buckled uniformly.

(38) The distance between the opposing nut inner surfaces 33a is equal to or slightly larger than the distance between the opposing collar outer surfaces 22b of the collar 21, and the collar 21 of the bush 20 can be inserted into the nut cylindrical member 33. The lower surface of the flange 24 abuts against the upper surface of the nut head member 35 of the nut body 30, so that the bush 20 and the nut body 30 are held so as not to rotate relative to each other.

(39) On the upper side of the nut cylindrical member 33, a short nut head member 35 is formed. The cross section of the inner surface of the nut head member 35 is the same as that of the nut cylindrical member 33 and is a polygonal inner surface having a substantially hexagonal shape. The cross section of the outer surface of the nut head 35 is circular, and the outer diameter is substantially equal to or slightly larger than the distance (maximum outer diameter) between the apexes of the hexagon of the nut cylindrical member 33.

(40) The thickness of the nut head member 35 is thicker than the thickness of the nut cylindrical member 33. When the nut cylindrical member 33 buckles and expands its diameter, the nut head member 35 at the distal end portion is not deformed.

(41) The length of the collar 21 of the bush 20 is longer than the length of the nut head 35. Also, it may be short. In a state wherein the collar 21 of the bush 20 is inserted into the nut head 35 and the nut cylinder 33 of the nut body 30, the collar 21 protects the nut head 35 and the upper portion of the nut cylindrical member 33 from the inside.

(42) Again referring to FIG. 1, a mounting hole 43 having a circular cross section is formed in the mounted member 41. A mounting hole 44 having a circular cross section is formed in the mounting member 42. In this specification, the plate material on the opposite side (blind side) from the side where the blind nut is inserted is referred to as a mounted member 41, and the plate material on the side of insertion (work side) is referred to as a mounting member 42.

(43) The inner diameter of the mounting hole 44 of the mounting member 42 is slightly larger than the outer diameter of the nut head member 35. The axial length of the nut head 35 is substantially equal to the plate thickness of the mounting member 42. The inner diameter of the mounted hole 43 of the mounted member 41 is slightly larger than the outer diameter of the nut cylindrical member 33, and slightly larger or slightly smaller than the outer diameter of the nut head member 35.

(44) The outer diameter of the flange 24 of the bush 20 is larger than the inner diameter of the mounting hole 44 of the mounting member 42. Although the mounting hole 43 of the mounted member 41 has a circular cross section, the mounting hole 43 may have a substantially hexagonal shape according to the outer shape of the nut cylindrical member of the nut body 30. Even the mounting hole 44 of the mounting member 42 can be formed into a substantially hexagonal shape.

(45) With reference to FIGS. 8-10, a blind nut assembly 1a wherein the bolt 10, the bush 20 and the nut body 30 are combined will now be described. FIG. 8 is a top view of the blind nut assembly 1a, FIG. 9 is a front view in which a part is rendered as a cross section, and FIG. 10 is a bottom view.

(46) To assemble the blind nut assembly 1a, the hexagonal direction around the center axis of the collar 21 of the bush 20 is matched with the hexagonal direction around the central axis of the nut cylindrical member 33 of the nut body 30. When the collar 21 of the bush 20 is inserted from the side of the nut head 35 of the nut body 30, the lower surface of the flange 24 of the bush 20 abuts the upper surface of the nut head 35 and stops. In this state, the nut body 30 and the bush 20 are held so as not to rotate relative to each other.

(47) Next, the bolt 10 is inserted into the collar 21 from the flange 24 side of the bush 20, from [sic] the shaft member 11. The bolt 10 is rotated by a tool such as a hexagonal wrench, and the male screw 12 of the bolt 10 is mated into the female screw 32 of the female screw member 31 of the nut body 30. When the lower surface of the bolt head member 14 of the bolt 10 comes in contact with the upper surface of the flange recess portion 25 of the bush 20, it becomes impossible to further screw the bolt 10. In this way, the assembly of the bolt 10, the bush 20 and the nut body 30 is referred to as blind nut assembly 1a.

(48) FIG. 11 is a front view showing a portion of a state in which the mounted member 41 and the mounting member 42 are fastened by the blind nut assembly 1a as a cross section. In FIG. 11, the outer diameter of the nut head member 35 is larger than the inner diameter of the mounting hole 43 of the mounted member 41.

(49) In order to fasten the mounted member 41 and the mounting member 42 by the blind nut assembly 1a, the mounting hole 43 of the mounted member 41 and the mounting hole 44 of the mounting member 42 are aligned, and the blind nut assembly 1a is inserted into the mounting holes 43, 44 with the female screw member 31 of the nut body 30 as the head. The lower surface of the flange 24 contacts the outer peripheral portion of the mounting hole 44 of the mounting member 42.

(50) The hexagonal portion of the flange 24 of the bush 20 is pressed with a tool such as a spanner so as not to be rotated, the tip end of a tool (not shown in the figure), such as a hexagonal wrench, is engaged with the bolt head hole 15 of the bolt 10, and the male screw 12 of the bolt 10 is further mated with the female screw 32 of the nut body 30 when rotated. Since the female screw 32 is pulled upward, the nut cylindrical member 33 is compressed in the vertical direction and buckled, and the enlarged diameter member 33 d is formed.

(51) At this time, since the nut cylindrical member 33 is supported from the inside by the collar 21 of the bush 20, the nut cylindrical member 33 does not deform inward does not abnormally deform in the circumferential direction, normally expands to the outside, and the enlarged diameter member 33d is formed.

(52) When the bolt 10 is tightened until a predetermined fastening torque is reached, the mounted member 41 and the mounting member 42 are sandwiched between the lower surface of the flange 24 and the enlarged diameter member 33d, and the fastening is completed. In this way, the mounted member 41 and the mounting member 42 are fastened by the blind nut assembly 1a.

(53) A method of removing the blind nut assembly 1a from the mounted member 41 and the mounting member 42 will now be described. The hexagonal portion of the flange 24 of the bush 20 is pressed with a tool such as a spanner, and the tip of a tool such as a hexagonal wrench is engaged with the bolt head hole 15 of the bolt 10 and is rotated in the reverse direction. When this happens, the male screw 12 of the bolt 10 is unscrewed from the female screw 32 of the nut body 30, and the bolt 10 can be withdrawn upward.

(54) Since the engagement between the bush 20 and the nut body 30 is released, the bush 20 can also be pulled upward. The mounting member 42 can be removed from the nut body 30 and the bush 20. The outer diameter of the nut head member 35 is larger than the inner diameter of the mounting hole 43 of the mounted member 41, and the mounted member 41 is sandwiched between the nut head member 35 and the enlarged diameter member 33d. Therefore, the mounted member 41 cannot be removed from the nut body 30.

(55) FIG. 12 is a front view showing a portion of a state in which the mounted member 41 and the mounting member 42 are fastened by a blind nut assembly 1a, similar to FIG. 11. In FIG. 12, the outer diameter of the nut head 35 is smaller than the inner diameter of the mounting hole 43 of the mounted member 41. As in FIG. 11, when the blind nut assembly 1a is removed, the mounting member 42 can be removed. In FIG. 12, the mounted member 41 can also be removed from the nut body 30.

(56) FIGS. 11 and 12 will now be compared. As shown in FIG. 11, if the outer diameter of the nut head member 35 is larger than the inner diameter of the attachment hole 43 of the mounted member 41, although the mounting member 42 can be removed, the mounted member 41 cannot be removed from the nut body 30. As shown in FIG. 12, if the outer diameter of the nut head 35 is smaller than the inner diameter of the mounting hole 43 of the mounted member 41, the mounting member 42 and the mounted member 41 can be removed from the nut body 30.

(57) In the first embodiment, the nut head 35 of the nut body 30 and the polygonal inner surface of the nut cylindrical member 33 engage with the polygonal outer surface of the collar 21 of the bush 20. The nut cylindrical member 33 is supported by the collar 21 so as not to deform inwardly and not to rotate. Therefore, when the nut cylindrical member 33 is buckled to form the enlarged diameter member 33d, the nut cylindrical member 33 is not deformed inward, it does not deform in the circumferential direction, and the expanded diameter portion 33d of a certain shape can be molded.

(58) When the bush 20 is made of a hard material that is difficult to deform, the nut cylindrical member 33 is stably supported by the bush 20 when buckling, and the enlarged diameter member 33d can be more reliably formed. Without the portion of the collar 21 of the bush 20, when the nut cylindrical member 33 is buckled, the nut cylindrical member 33 may be deformed inward or in the circumferential direction, and the enlarged diameter member 33d cannot be normally molded.

(59) An example of a modification to the bush will now be described with reference to FIGS. 13-15. For an example of a modification to the bushing, e is added to the reference number representing the parts of the bush 20. FIG. 13 is a top view of the bush 20e, FIG. 14 is a front view in which a part is cross-sectioned, and FIG. 15 is a bottom view. With the bush 20e, the plate thickness of the flange 24e is thinner than the bush 20, and the upper surface and the lower surface of the flange 24e are inclined downward in the radial direction outward. No flange recess is formed on the upper surface of the flange 24e. The collar 21e is the same as the collar 21.

(60) The bush 20e is used in place of the bush 20 of the first embodiment. That is, the bush 20e, the bolt 10 of the first embodiment and the nut body 30 are combined, and the male screw 12 of the bolt 10 is mated into the female screw 32 of the nut body 30 to form the blind nut assembly 1e. The mounted member 41 and the mounting member 42 are fastened by the blind nut assembly 1e using the modified bush 20e. When the blind nut assembly 1e is inserted into the mounting holes 43, 44 of the mounted member 41 and the mounting member 42, the outer peripheral portion of the flange 24e abuts the upper surface of the mounting member 42. As the bolt 10 is screwed in, the nut cylindrical member 33 buckles to form the enlarged diameter member 33d. At this time, the flange 24e is deflected, and the entire lower surface of the flange 24e comes into contact with the upper surface of the mounting member 42. By using the bush 20e, a stable axial force can be obtained even after fastening by the spring action of the flange 24e.

Second Embodiment

(61) Next, a blind nut 2 according to a second embodiment of the present invention will be described. Regarding the blind nut 2, mainly the aspects that are different from the blind nut 1 will be described. The same portions as those of the first embodiment are denoted by the same reference numerals. These correspond to the reference numerals of the first embodiment; however, for parts that are different, the reference numerals of the first embodiment will be described with () [prime] added. FIG. 16 is an exploded perspective view of the blind nut 2, the commercially-available bolt 11, the commercially-available washer 17, the mounted member 41, and the mounting member 42 according to the second embodiment. The blind nut 2 includes a bush 20 and a nut body 30.

(62) Referring to FIG. 16, the bolt 10 has a shank 11 having a male screw 12 and a bolt head 14 on the top thereof. The bolt head 14 has a hexagonal cross section shape and can be rotated by a tool, such as a commercially-available spanner. As in the first embodiment, the bolt head 14 may form a hexagonal bolt head hole, and it can rotate by inserting a tool such as a hexagonal wrench into the bolt head hole.

(63) The washer 17 is a commercially-available product with a short cylindrical shape; its upper and lower surfaces are flat, and a through hole is formed in the center. The inner diameter of the center hole of the washer 17 is larger than the outer diameter of the shaft member 11 of the bolt 10 and smaller than the distance between the hexagonal opposing sides of the bolt head member 14. When the bolt head 14 has the same function as the washer 17, the washer 17 may be omitted.

(64) FIG. 17 is a top view of the collar 21 of the blind nut 2, and FIG. 18 is a front view showing a portion of the collar 21 as a cross section. The bush 20 is a short cylindrical collar 21. Although there is no flange portion, it is referred to as a bush 20 for matching with the part name of the first embodiment. In other words, the bush 20 consists of only the collar 21. The outer surface of the collar 21 is a polygonal outer surface having a substantially rectangular cross section, and the corner portion is chamfered. A collar hole 22 having a circular cross section is formed on the collar 21. The collar 21 and the nut cylindrical member 33 do not rotate relative to each other.

(65) FIG. 19 is a top view of the nut body 30, FIG. 20 is a front view of the nut body 30, and FIG. 21 is a bottom view of the nut body 30. The nut body 30 has a female screw member 31 and a nut cylindrical member 33 above that; a nut head member 35 is formed on the upper end portion of the nut cylindrical member 33. The female screwed portion 31 is cylindrical, and a female screw 32 is formed on the inner surface. The female screw 32 can be mated into the male screw 12 of the bolt 10.

(66) A nut cylindrical member 33 is formed on the upper side of the female screw 32. The nut outer surface 33b of the nut cylindrical member 33 is a polygonal outer surface having a substantially quadrangular cross section, and the corner portion is chamfered. A portion of the nut cylindrical member 33 buckles and expands in diameter.

(67) The nut inner surface 33a of the nut cylindrical member 33 is a polygonal inner surface which is larger than the inner diameter of the female screw member 31; it has a substantially quadrangular section, and the corner portion is chamfered. The nut inner surface 33a is matched with the collar outer surface 21b of the bush 20. The nut inner surface 33a is slightly smaller than the collar outer surface 21b so that the collar 21 can be inserted into the nut cylindrical member 33 of the nut body 30 by pushing it. When the collar 21 is pushed into the nut cylindrical member 33, the upper surface of the collar 21 is almost flush with the upper surface of the nut head member 35. The nut cylindrical member 33 is supported from the inside by the collar 21.

(68) A short nut head member 35 is formed on the upper side of the nut cylindrical member 33. The cross section of the inner surface of the nut head member 35 is the same as the nut cylindrical member 33 and is substantially square. The cross section of the outer surface of the nut head member 35 is circular and is equal to the maximum diameter (the distance between the apexes of the quadrangle) of the nut cylindrical member 33.

(69) The thickness of the nut head member 35 is thicker than the thickness of the nut cylindrical member 33. Even when the nut cylindrical member 33 buckles and expands its diameter, the nut head member 35 at the distal end portion will not be deformed. The collar 21 protects the upper portion of the nut cylindrical member 33 from the inside when the nut cylindrical member 33 buckles and expands its diameter.

(70) A rectangular mounting hole 43 is formed in the mounted member 41. A circular mounting hole 44 is formed in the mounting member 42. Alternatively, the mounting hole 44 of the mounting member 42 may also be formed in a square shape. When the nut cylindrical member 33 having a substantially rectangular cross section is inserted into the rectangular mounting hole 43, the nut cylindrical member 33 is held so as not to rotate with respect to the mounting hole 43. Therefore, when buckling the nut cylindrical member 33, there is no need to stop the rotation with the bush 20. Since it is not necessary to hold the bush 20 against rotation, the bush 20 is not provided with a polygonal flange on the outer surface.

(71) The bolt 10, the washer 17, the bush 20 and the nut body 30 are combined to form a blind nut assembly 2a. The bush 20 is inserted into the nut body 30. The collar hole 22 and the hole of the washer 17 are aligned thereon, and the washer 17 is placed. The bolt 10 is inserted from the hole of the washer 17, and the male screw 12 of the bolt 10 is engaged with the female screw 32 of the nut body 30 to form the blind nut assembly 2a.

(72) The blind nut assembly 2a is used to tighten the mounted member 41 and the mounting member 42. The position of the mounting hole 44 of the mounting member 42 is aligned with the position of the mounting hole 43 of the mounted member 41, and the blind nut assembly 2a is inserted. The blind nut assembly 2a is rotationally stopped by a rectangular mounting hole 43. When the bolt 10 is tightened using a tool such as a spanner, the nut cylindrical member 33 buckles and expands in diameter to form an enlarged diameter member 33d, and the mounted member 41 and the mounting member 42 are tightened between the lower surface of the washer 17 and the enlarged diameter member 33d.

(73) In order to remove the blind nut assembly 2a from the mounted member 41 and the mounting member 42, by rotation of the bolt 10 in the reverse direction with a tool, the screwing between the male screw 12 of the bolt 10 and the female screw 32 of the nut body 30 is released.

(74) In the second embodiment, the shape of the mounting hole 43 of the mounted member 41 is a polygon conforming to the shape of the nut cylindrical member 33 of the nut body 30. Since the nut body 30 is rotationally stopped by the mounting hole 43, there is no need to stop the rotation by the bush 20. Therefore, the bush 20 has a simple shape of only the collar 21. Since the lower surface of the bolt head 14 directly contacts the upper surface of the nut head member 35 of the nut body 30, it is better to use the washer 17.

(75) Also in the second embodiment, the nut head member 35 and the nut cylindrical member 33 of the nut body 30 are reinforced by the collar 21 from the inside. Therefore, when the nut cylindrical member 33 is buckled to form the enlarged diameter member 33d, abnormal deformation does not occur, and the enlarged diameter member 33d can form a certain shape.