Patent Publication Number: US-2018038406-A1

Title: Blind Nut and Mounting Structure Thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation application of PCT application PCT/JP2016/055005 filed Feb. 22, 2016, which claims priority from Japanese Patent Application No. 2015-086518, filed Apr. 21, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a blind nut and a mounting structure thereof, and in particular to a blind nut wherein the post-fastening height is short as well as a mounting structure wherein the blind nut is mounted onto a mounted member thereof. 
     BACKGROUND OF THE INVENTION 
     A blind nut comprises a female screw member in which a female screw is formed, a hollow tubular member is provided adjacent to the female screw member and a tubular flange which has an opening on one end. When the tubular member of the blind nut is inserted into the mounting hole of the mounted member to cause the flange to be in contact with the surface of the mounted member, plastic deformation is carried out by using a fastening tool in order to enlarge the diameter of the tubular member, and the mounted member is sandwiched between the deformed tubular member and the flange. In this way, the blind nut is fixated onto the mounted member. When a male screw of a bolt engages with the female screw member of the blind nut fixated onto the mounted member, another mounted member can be further mounted. When a blind nut is utilized, work can be performed from one side of the mounted member, and thus it can be utilized to fasten a nut onto a mounted member which cannot be worked on from the rear side, exemplified as a panel, and the like. 
       FIG. 1  shows traditional blind nut  1 .  FIG. 1A  is a cross-sectional view showing traditional blind nut  1  set in mounting hole  43  of mounted member  41 . Blind nut  1  takes an overall cylindrical shape which is axially symmetrical around the central axis and has a female screw member  11  on one end. Female screw member  11  takes a cylindrical shape and has a female screw  15  formed therein. A male screw of a screw mandrel (not shown in the figures) of a fastening tool can be engaged with female screw  15 . Tubular member  12 , which extends from female screw member  11 , is thinner than female screw member  11  and is plastically deformed when mounted onto mounted member  41 . 
     Blind nut  1  has a flange  14  on the side opposite female screw member  11 . The outer diameter of flange  14  is larger than the inner diameter of mounting hole  43  of mounted member  41 . Pass-through hole  16  is formed from the edge of flange  14  to the edge of female screw member  11 . The inner diameter of pass-through hole  16  is constant from the edge of flange  14  to tubular member  12 ; it becomes smaller at female screw member  11 . 
       FIG. 1B  is a cross-sectional view showing a blind nut  1  that has been mounted onto mounted member  41 . When blind nut  1  is mounted by means of a fastening tool, tubular member  12 , which is thinner, is plastically deformed so that the diameter thereof expands to form enlarged-diameter member  12   a;  mounted member  41  is sandwiched between enlarged-diameter member  12   a  and flange  14 . In this way, blind nut  1  is mounted onto mounted member  41 . 
     A brief explanation of the method for fastening blind nut  1  onto mounted member  41  is provided below. When blind nut  1  is inserted into mounting hole  43  of mounted member  41 , the lower surface of flange  14  stops when it touches the upper surface of mounted member  41 . The screw mandrel of the exclusive-use fastening tool is caused to be engaged with female screw  15  of female screw member  11  of blind nut  1 , and the nose piece (not shown in the figures) of the fastening tool is in contact with the upper surface of flange  14 . Subsequently, flange  14  of blind nut  1  is forcefully pulled to female screw member  11  by utilizing the screw mandrel of the fastening tool; tubular member  12  is plastically deformed and is thin, so that its diameter is enlarged to form enlarged-diameter member  12   a.  Mounted member  41  is sandwiched between enlarged-diameter member  12   a  and flange  14  and thus fixated therein. 
     In a traditional blind nut, female screw member  11  is provided below thin tubular member  12 . As the diameter of tubular member  12  is enlarged by the blind nut, tubular member  12  is made of a material with a degree of hardness low enough to be plastically deformed. Due to the foregoing, in order to obtain enough strength to retain the screw, female screw member  11  must be of a certain length. Therefore, the entire length of the blind nut has been considerably long. Moreover, a process for increasing the strength of female screw member  11  by quenching it has been needed. 
     JP Publication No. 2010-144901 to Kokai discloses a blind nut comprising a plastically deformable tubular member, a flange member formed on one edge of the tubular member, and a screw member formed on the other edge of the tubular member. The tubular member is thin; therefore, it can be bent to be mounted onto the mounted member and it screws a bolt onto the screw member formed therein. The screw member is thicker than the tubular member and is provided inside the tubular member. 
     With a traditional blind nut, the screw member is provided below the tubular member so that it has been necessary that there be some distance in the height direction. In Kokai (JP Pub. No. 2010-144901), the screw member is provided inside the tubular member in order to be closer to the location where the bolt is mounted, thus shortening the length of the blind nut. Moreover, uselessly utilizing a long bolt is no longer necessary. 
     However, in the blind nut disclosed in Kokai (JP Pub. No. 2010-144901), the screw member and the tubular member to be bent are formed as an integrated body by utilizing a soft material. The screw member is provided inside the tubular member; the screw member is formed to be thicker than the tubular member in order to assure the strength for retaining the screw, and the tubular member surrounds the outer perimeter of the screw member. Thus, the outer diameter of the blind nut has become larger. Moreover, in order to assure the screw-retaining strength, the screw member must have a certain length, and the screw member must be quenched. 
     JP Publication No. 2004-11876 to Kokai discloses a blind nut comprising a main body made of a plastically deformable material such as metal and the like, and a nut member constituted separately from the main body with a rigid material, such as metal, and the like. The main body has a hollow tubular member and a flange formed on one edge of the tubular member. The nut member has a female screw member and a coupling member. The nut member is provided inside the main body. The female screw member of the nut member is provided adjacent to the flange; the extended tubular member of the tubular member at a location separate from the flange is treated with a drawing process and coupled with the coupling member. 
     In the blind nut disclosed in Kokai (JP Pub. No. 2004-11876), since the nut member is not to be plastically deformed, it is formed using a material having a high degree of hardness in order to achieve a great fastening strength. Moreover, the edge of the female screw of the nut member provided inside the main body moves to a location adjacent to the flange to decrease useless space formed between the female screw of the nut and the mounted member. However, in Kokai (JP Pub. No. 2004-11876), since the extended tubular member of the tubular member is treated by a drawing process and coupled with the coupling member of the nut member, the drawn portion must have a certain height for coupling. Moreover, only the extended tubular member is drawn and coupled with the coupling member, and the female screw member provided above the coupling member is not drawn. In this way, the coupling member and the female screw member are aligned in the height direction, and the height of the nut member greatly increases. Moreover, it is possible that the lower portion of the female screw of the female screw member of the nut member become deformed. 
     JP Publication No. 2013-529768 to Kokai discloses a fastening tool comprising a tubular main body having a flange, a horizontal cylindrical surface and an annular lug extending inwardly adjacent to the rear end; a nut having a head member and a collar member extending from the head member through the lug; and a ring surrounding the middle portion of the collar. The peripheral portion of the nut is curved outwardly to form a retainer which prevents the ring from being separated from the collar member. 
     As the fastening tool disclosed in Kokai (JP Pub. No. 2013-529768) fixates the tubular main body and the nut, an annular lug is formed on the tubular main body. The annular lug is provided between the ring and the flange of the tubular main body, so that the height of the fastening tool increases. Moreover, the fastening tool disclosed in Kokai (JP Pub. No. 2013-529768) comprises three members; in other words, it is comprised of many parts. Furthermore, the process for curving the peripheral portion of the nut must be carried out, which increases the cost. 
     Due to the foregoing, a blind nut low in height after being fastened has been in demand. Moreover, a blind nut with a small outer diameter and light in weight has been in demand. Moreover, a blind nut that does not require the process for quenching a screw member has been in demand. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide a blind nut with a short height after fastening. Another object of the present invention is to provide a blind nut with a small outer diameter that is lightweight. 
     In order to achieve the above stated objects, the blind nut of the present invention comprises a main body, which is formed with a plastically deformable soft material, and a nut member, which is formed with a hard material. The main body has a main body tubular member and a flange provided adjacent to the main body tubular member. The nut member has a nut base member which takes a short cylindrical shape, and a nut cylinder member which is provided adjacent to the nut base and which has an outer diameter smaller than that of the nut base. A pass-through hole on which a female screw is formed along its length is formed. On the inside of the main body tubular member of the main body, the nut cylinder members of the nut member are provided, and the lower edge of the main body tubular member is welded to be in contact with the step of the nut base. 
     A first mode of the present invention is a blind nut, which is to be mounted onto the mounting hole of a mounted member, comprising: 
     a main body, which is formed with a plastically deformable soft material, which has a main body tubular member, and a flange provided on an edge of the main body tubular member, onto which center holes are formed; and 
     a nut member, which is formed with a hard material, which has a short cylindrical nut base member having a circumferential step on its upper surface, and nut cylinder members provided adjacent to the step and having outer diameters smaller than that of the nut base, onto which a pass-through hole having a female screw is formed; 
     wherein the nut cylinder members of the nut member are provided inside the main body tubular member of the main body, and 
     the lower edge portion of the main body tubular member is in contact and coupled with the step of the nut base. 
     When the main body formed with a plastically deformable soft material and the nut member formed with a hard material are combined, the screw-fastening strength can be achieved in the nut member, which makes it possible to plastically deform the main body and fixate it. When the nut cylinder members of the nut member are provided inside the main body tubular member of the main body, the height of the blind rivet can be decreased. When the lower edge surface of the main body tubular member is in contact with the step of the nut base, the main body tubular member can easily be plastically deformed by lifting the nut member up. 
     As disclosed in Kokai (Pub. No. 2004-11876), if the main body tubular member of the main body is drawn and then coupled with the nut cylinder members of the nut member, the female screw of the nut member might be deformed. In the present invention, only the lower portion edge of the main body tubular member is coupled with the step of the nut base; thus, the female screw of the nut member will not be deformed. 
     Preferably, the nut member and the main body tubular member of the main body are inserted into the mounting hole of the mounted member, a part of the main body tubular member is plastically deformed to be enlarged, and the mounted member is sandwiched between the deformed enlarged-diameter member and the flange to mount the blind nut onto the mounted member. When a part of the main body tubular member is plastically deformed to be enlarged by the fastening tool, the blind nut can be easily mounted onto the mounted member. 
     The lower edge surface of the main body tubular member and the step of the nut base are preferably coupled by means of welding. When the lower edge surface of the main body tubular member and the step of the nut base are welded, plastic deformation can be conducted right above the lower edge surface of the main body tubular member to achieve enlargement, and, thus, the enlarged portion does not contain any wasted portion. 
     The main body tubular member preferably has a first tubular member, which is distant from the flange and takes a cylindrical shape; and a second tubular member, which is close to the flange and takes a cylindrical shape, having a hexagonal or square cross-sectional shape. When the second tubular member takes a hexagonal or square shape, and when the mounting hole of the mounted member also takes a hexagonal or square shape, it becomes possible to retain the blind nut so that it does not rotate. 
     A knurl is preferably formed on the outer peripheral surface of the main body tubular member adjacent to the flange. If the knurl is formed on the outer peripheral surface of the main body tubular member, when the diameter of the main body tubular member is enlarged, the knurl comes in contact with the mounted member to retain the blind nut so as not to rotate. 
     It is preferable that the pass-through hole of the nut member have an inner diameter that is constant across the entire nut member; the female screw is formed across the entire pass-through hole. The screw is retained across the entire nut member, which makes it possible to decrease the height of the nut member. 
     The nut cylinder members of the nut member preferably comprise a first cylinder member provided adjacent to the nut base and a second cylinder member adjacent to the first cylinder member and with an outer diameter smaller than that of the first cylinder member. 
     If the outer diameter of the second cylinder member is smaller than that of the first cylinder member, when the main body tubular member of the main body is plastically deformed and mounted onto the mounted member, the second cylinder member can be easily inserted therein. 
     A second mode of the present invention is a structure in which the blind nut is mounted onto the mounting hole of the mounted member, 
     wherein the blind nut comprises a main body, which is formed with a plastically deformable soft material, which has a main body tubular member and a flange provided on an edge of the main body tubular member, and onto which center holes are formed; and 
     a nut member, which is formed with a hard material, 
     which has a short cylindrical nut base member having a circumferential step on its upper surface, and nut cylinder members provided adjacent to the step and having an outer diameter smaller than that of the nut base, and 
     onto which a pass-through hole having a female screw is formed; 
     wherein the nut cylinder members of the nut member are provided inside the main body tubular member of the main body, and the lower edge surface of the main body tubular member is in contact and coupled with the step of the nut base, 
     the nut member and the main body tubular member of the main body are inserted into the mounting hole of the mounted member, and the mounted member is sandwiched between the enlarged-diameter member formed by enlarging a part of the main body tubular member and the flange for the blind nut to be mounted onto the mounted member. 
     The diameter-enlarged member of the main body tubular member is preferably enlarged right above the lower edge surface of the main body tubular member. When the diameter-enlarged member of the main body tubular member is enlarged right above the lower edge surface of the main body tubular member, the height of the main body can be decreased; thus, the height of the blind nut can be decreased as well. 
     It is preferred that the male screw on the shank of a bolt be engaged with the female screw of the nut member, and that the mounting member be sandwiched and mounted between the flange of the main body member and the head of the bolt. When the bolt is screwed onto the nut member, the mounting member can be easily mounted onto the mounted member. 
     According to the present invention, it is possible to obtain a blind nut short in height after it is fastened. Moreover, is possible to obtain a blind nut with a smaller outer diameter and lighter in weight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional view showing the state in which the traditional blind nut is set on the mounted member. 
         FIG. 1B  is a cross-sectional view showing the blind nut mounted on the mounted member. 
         FIG. 2  is an oblique view showing the main body of the blind nut of a working example of the present invention. 
         FIG. 3  is a top view of the main body shown in  FIG. 2 . 
         FIG. 4  is a front view of the main body shown in  FIG. 2 . 
         FIG. 5  is a bottom view of the main body shown in  FIG. 2 . 
         FIG. 6  is a cross-sectional view along the A-A line shown in  FIG. 4  of the main body shown in  FIG. 2 . 
         FIG. 7  is an oblique view showing the nut member of the blind nut of a working example of the present invention. 
         FIG. 8  is a top view of the nut member shown in  FIG. 7 . 
         FIG. 9  is a front view of the nut member shown in  FIG. 7 . 
         FIG. 10  is a cross-sectional view along the A-A line shown in  FIG. 9  of the nut member shown in  FIG. 7 . 
         FIG. 11  is an oblique view showing the state in which the nut member shown in  FIG. 7  is not yet inserted into the main body shown in the main body shown in  FIG. 2 . 
         FIG. 12  is an oblique view depicting the state in which the nut member shown in  FIG. 7  is inserted into the main body shown in the main body as illustrated in  FIG. 2 . 
         FIG. 13  is a top view of the blind nut shown in  FIG. 12 . 
         FIG. 14  is a front view of the blind nut shown in  FIG. 12 . 
         FIG. 15  is a cross-sectional view along the A-A line shown in  FIG. 14  of the blind nut shown in  FIG. 12 . 
         FIG. 16  is a cross-sectional view showing the state in which the blind nut is mounted onto the mounted member. 
         FIG. 17  is a cross-sectional view showing the state in which another mounting member is mounted by means of a bolt onto the blind nut which has been mounted onto the mounted member. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An explanation of blind nut  10  of a working example of the present invention shall be given below with reference to the drawings.  FIGS. 2 to 6  show main body  20  of blind nut  10 , and  FIGS. 7 to 10  show nut member  30  of blind nut  10 .  FIG. 11  shows the state in which main body  20  and nut member  30  are not yet coupled, and  FIGS. 12 to 15  show the state in which main body  20  and nut member  30  are coupled.  FIG. 16  shows the state in which blind nut  10  is mounted onto mounted member  41 , and  FIG. 17  shows the state in which mounting member  42  is mounted by means of bolt  45  onto blind nut  10  which has been mounted onto mounted member  41 . 
     Blind nut  10  of a working example of the present invention comprises main body  20 , which is formed with a plastically deformable material such as metal and the like; and nut member  30 , which is formed with a rigid material such as metal and the like. As shown in  FIG. 11 , nut member  30  is inserted from the lower side of main body  20 , and the lower edge surface of main body  20  and step  31   a  of nut base  31  of nut member  30  are welded by means of laser welding to form blind nut  10 . 
     Blind nut  10 , which has been formed in an integrated manner, is inserted into mounting hole  43  of mounted member  41 ; the diameters of first tubular member  21  and second tubular member  22  of main body  20  are enlarged by utilizing the fastening tool to mount blind nut  10  onto mounting hole  43 . Subsequently, bolt  45  is caused to be screwed onto female screw  37  of nut member  30  in order to mount mounting member  42  onto blind nut  10 . 
     An explanation regarding main body  20  of blind nut  10  shall be given below, with reference to  FIGS. 2 to 6 .  FIG. 2  is an oblique view showing main body  20  of blind nut  10 .  FIG. 3  is a top view,  FIG. 4  is a front view, and  FIG. 5  is a bottom view, respectively.  FIG. 6  is a cross-sectional view along the A-A line shown in  FIG. 4  of main body  20 . 
     Main body  20  is formed with a plastically deformable material such as metal, and the like. Main body  20  possesses first tubular member  21  on one edge thereof. First tubular member  21  takes a cylindrical shape, and first center hole  25  of which the cross-sectional surface takes a circular shape is formed thereon. The outer diameter of first tubular member  21  is smaller than the inner diameter of mounting hole  43  of mounted member  41 . The inner diameter of first tubular member  21  is either equivalent to or slightly larger than that the outer diameter of first cylinder member  32  of nut member  30  in order to receive first cylinder member  32 . Alternatively, the inner diameter of first tubular member  21  may be designed to be slightly smaller than the outer diameter of first cylinder member  32  of nut member  30  so that first cylinder member  32  of nut member  30  is pressed in. 
     Second tubular member  22  is provided adjacent to the upper portion of first tubular member  21 . The cross-sectional surface of second tubular member  22  takes a hexagonal shape, and second center hole  26  is provided thereon. The outer cross-sectional surface takes a hexagonal shape, and the apexes thereof are chamfered. The cross-sectional surface of second center hole  26  takes a hexagonal shape with rounded corners. The overall shape of second tubular member  22  is a hexagonal cylinder. The size of second tubular member  22  is small enough to be inserted in mounting hole  43  of mounted member  41 . First tubular member  21  and second tubular member  22  are parts that are to be plastically deformed in order to enlarge the diameters thereof when they are mounted onto mounted member  41 . 
     In this working example of the present invention, the cross-sectional surface of second tubular member  22  is hexagonal; however, it may be square or circular. If the cross-sectional surface of second tubular member  22  is designed to be circular, the surface may be knurled to prevent rotation. 
     Mounting hole  43  of mounted member  41  may be hexagonal to match the shape of second tubular member  22 ; it may also be square or circular. 
     Main body  20  possesses flange  24 , which is provided adjacent to the upper portion of second tubular member  22 . The cross-sectional surface of flange  24  is circular on its outer surface; and second center hole  26  on its inner surface is hexagonal. In other words, second center hole  26  with a hexagonal cross-sectional surface is formed in the area extending from flange  24  to second tubular member  22 . The outer diameter of flange  24  is larger than the outer diameter of second tubular member  22  and larger than the inner diameter of mounting hole  43  of mounted member  41 . Main body  20  is overall axially symmetrical around the center axis. 
     An explanation concerning nut member  30  of blind nut  10  is provided below with reference to  FIGS. 7 to 10 .  FIG. 7  is an oblique view showing nut member  30 ,  FIG. 8  is a top view and  FIG. 9  is a front view, respectively.  FIG. 10  is a cross-sectional view along the A-A line shown in  FIG. 9  of nut member  30 . 
     Nut member  30  is formed using a rigid material such as metal, and the like. Nut member  30  comprises circular nut base member  31 , and nut cylinder members, which are provided adjacent to the upper portion of nut base member  31 . Nut cylinder members are separated into first cylinder member  32  and second cylinder member  33 , which is provided adjacent to the upper portion of first cylinder member  32 . 
     Nut base member  31  of nut member  30  takes a cylindrical shape. The outer diameter of nut base member  31  is approximately equal to the outer diameter of first tubular member  21  of main body  20 . 
     The outer diameter of first cylinder member  32  is smaller than the outer diameter of nut base member  31 . The outer diameter of first cylinder member  32  is either approx.-imately equal to or slightly smaller than the inner diameter of first tubular member  21  of main body  20 ; alternatively, it is slightly larger in a manner so as to be pressed in. First tubular member  21  of main body  20  is primarily provided in the area surrounding first cylinder member  32 . Circumferential step  31   a  of nut base member  31  receives the lower edge of first tubular member  21  of main body  20 . The length of first cylinder member  32  is approximately the same as the length of first tubular member  21  of main body  20 . 
     Second cylinder member  33  takes a circular shape approximately the same as the shape of first cylinder member  32 . The outer diameter of second cylinder member  33  is slightly smaller than the outer diameter of first cylinder member  32 . Nut base member  31 , first cylinder member  32  and second cylinder member  33  share the same central axis. 
     When nut member  30  is combined with main body  20 , second tubular member  22  of main body  20  is primarily provided in the area surrounding second cylinder member  33 . The outer surface of second cylinder member  33  and hexagonally-shaped second center hole  26  of second tubular member  22  are provided so as to be slightly spaced from one another. 
     The length of second cylinder member  33  is less than the length of second tubular member  22  of main body  20 . When main body  20  and nut member  30  are combined as shown in  FIG. 15 , the upper edge of second cylinder member  33  is located at the middle height in the height direction of second tubular member  22 . 
     In this working example of the present invention, the cylinder members of nut member  30  are separated into first cylinder member  32  and second cylinder member  33 . However, first cylinder member  32  and second cylinder member  33  may have the same outer diameter and be constituted as one integrated nut cylinder member. 
     Pass-through hole  35  is formed in the area extending from the lower surface of nut base member  31  to the upper surface of second cylinder member  33 . The inner diameter of pass-through hole  35  is constant all the way across nut base member  31 , first cylinder member  32  and second cylinder member  33 . Female screw  37  is formed in the area extending from the upper edge to the lower edge of pass-through hole  35 . As stated below, main body  20  and nut member  30  are coupled by means of laser welding, so that the thread of female screw  37  of nut member  30  is not deformed. Due to the foregoing, female screw  37  can be formed all along nut member  30 . 
     An explanation regarding blind nut  10 , in which main body  20  and nut member  30  are combined, is provided below with reference to  FIGS. 11 to 15 .  FIG. 11  is an oblique view showing the state in which nut member  30  is not yet inserted into main body  20 .  FIG. 12  is an oblique view showing the state in which nut member  30  is inserted into main body  20 ;  FIG. 13  is a top view, and  FIG. 14  is a front view thereof, respectively.  FIG. 15  is a cross-sectional view along the A-A line shown in  FIG. 14  of blind nut  10 . 
     As shown in  FIG. 11 , nut member  30  is inserted with the second cylinder member first from first tubular member  21  of main body  20 . As shown in  FIG. 15 , the lower edge of first tubular member  21  is in contact with step  31   a  of nut base member  31 . The inner surface of first tubular member  21  of main body  20  is in contact with the outer peripheral surface of first cylinder member  32  of nut base member  31 . Second cylinder  33  of nut base member  31  is provided inside second center hole  26  of main body  20 . The cross-sectional surface of second center hole  26  takes a hexagonal shape, and the inner surface of second tubular member  22  is adjacent to second cylinder member  33  of nut member  30  in the central portion of each side of the cross-sectional hexagon. The upper surface of second cylinder  33  is positioned in the middle of the lengthwise direction of second tubular member  22 . 
     In this state, the lower edge surface of first tubular member  21  of main body  20  and step  31   a  of nut base member  31  are laser-welded to integrate main body  20  and nut member  30 . Only the lower edge surface of first tubular member  21  and step  31   a  of nut base member  31  are welded. Due to the foregoing, when blind nut  10  is mounted onto mounted member  41 , the portion right above the lower edge surface of first tubular member  21  can be plastically deformed, and thus the height of blind nut  10  can be decreased. 
     First tubular member  21  and nut base member  31  may be welded by means of welding methods other than laser-welding. Moreover, these members may be coupled by methods other than welding. 
       FIG. 16  is a cross-sectional view showing blind nut  10  mounted onto mounted member  41 . Mounting hole  43  is formed on mounted member  41 . The shape of mounting hole  43  is hexagonal so that second tubular member  22  having the hexagonal cross-sectional surface fits therein. 
     Alternatively, if the cross-sectional surface of second tubular member  22  is square or circular, the shape of mounting hole  43  may be matched up with the shape of second tubular member  22  to be square or circular. When blind nut  10  is mounted onto mounted member  41 , blind nut  10  is inserted into mounting hole  43  of mounted member  41  with nut base member  31  first. The lower surface of flange  24  is in contact with the outer periphery of mounting hole  43  of mounted member  41 . 
     The male screw of the screw mandrel of the fastening tool (not shown in the figures) is caused to rotate so as to be engaged with female screw  37  of nut member  30 . When the nose piece (not shown in the figures) of the fastening tool comes in contact with the upper surface of flange  24 , rotations of the screw mandrel are stopped. [The nose piece is] pulled strongly to the fastening tool without rotating the screw mandrel. 
     Nut base member  31  of nut member  30  pushes up first tubular member  21  and second tubular member  22  of main body  20  in an upward direction. First tubular member  21  and second tubular member  22  are plastically deformed to form enlarged-diameter member  22   a.  Mounted member  41  is sandwiched between the lower surface of flange  24  and enlarged-diameter member  22   a.  The upper edge surface of second cylinder member  33  of nut member  30  has moved to a height that is approximately the same height as the lower surface of flange  24 . 
     The outer diameter of second cylinder member  33  is slightly smaller than the outer diameter of first cylinder member  32 , and there is a small space between second cylinder member  33  and second center hole  26  of main body  20 . Therefore, even when the destination position of the upward movement of second cylinder member  33  is slightly varied, upward movement is possible. 
     When the fastening operation by the fastening tool is completed, the screw mandrel is reversely rotated to cancel engagement with female screw  37  of nut member  30 . In this way, blind nut  10  is mounted onto mounted member  41 . 
     In traditional blind nut  1  shown in  FIG. 1( b ) , female screw  15  is provided below enlarged-diameter member  12   a,  which increases the overall height of blind nut  1 . In the blind nut of the working example of the present invention shown in  FIG. 16 , female screw  37  of nut member  30  enters the inside of enlarged-diameter member  22   a.  Although the length of female screw  37  is sufficiently secured, the overall height of blind nut  10  is decreased. 
     In a traditional blind nut formed in an integrated manner, the portion to be enlarged and the female screw member to be engaged with a bolt were formed in an integrated manner. Because the portion to be engaged with the female screw was formed with a soft material that would easily be plastically deformed, the portion had to be thick and the outer diameter large. 
     In the blind rivet of the working example of the present invention, the portion to be enlarged and the female screw member are separate members; thus, the portion to be enlarged can be formed with a soft material, and the female screw member can be formed with a hard material. Due to the foregoing, the female screw member can be thinner. And also due to the foregoing, the outer diameter of the blind rivet can be decreased. 
     Moreover, in the blind nut formed in an integrated manner, the female screw member needed to be quenched. In the blind rivet of the working example of the present invention, the female screw member is formed with a hard material, and, thus, no quenching process is necessary. 
     Moreover, as regards a traditional blind rivet consisting of two parts in which the main body is drawn to be coupled with the nut member, it has been possible for the thread of the female screw member of the nut member to become deformed in the drawing process. Because of this, the female screw could not be formed on the portion of the nut member to be coupled with the main body; thus, it has been necessary to separate the coupling portion from the female screw portion, which increased the height. 
     In the blind rivet of the working example of the present invention, the main body and the nut member are coupled by means of laser-welding, and, thus, it is not likely that the thread of the female screw of the nut member will be deformed. Wherefore, it is possible for the female screw to be formed along the entire length of the nut member. 
       FIG. 16  shows enlarged-diameter member  22   a  being gradually enlarged. However, as shown in enlarged-diameter member  12   a  in  FIG. 1( b )  showing the prior art, enlarged-diameter member  22   a  may be enlarged to exhibit plastic deformation so as to be crushed in both upward and downward directions. 
       FIG. 17  is a cross-sectional view showing the state in which mounting member  42  is mounted by means of bolt  45  onto blind nut  10  which has been mounted onto mounted member  41  shown in  FIG. 16 . Bolt  45  having head  46  and shank  47  is prepared. The male screw of shank  47  can be engaged with female screw  37  of nut member  30 . The position of pass-through hole  36  of nut member  30  and the position of mounting hole  44  of mounting member  42  are aligned to position mounting member  42  on flange  24  of blind nut  10 . Shank  47  of bolt  45  is inserted through mounting hole  44  of mounting member  42  into pass-through hole  35  of nut member  30 . The male screw provided on shank  47  of bolt  45  is caused to be engaged with female screw  37  of nut member  30  to mount mounting member  42  onto blind nut  10 . If mounting hole  43  of mounted member  41  takes a hexagonal shape, when bolt  45  is caused to be engaged, blind nut  10  is supported so as not to rotate within mounting hole  43 . 
     In  FIG. 17 , mounting member  42  is mounted on the side of flange  24  of blind nut  10 ; however, mounting member  42  may also be mounted on the side of nut base member  31  (the lower side in  FIG. 17 ) of blind nut  10 , which is the opposite side of the side shown in  FIG. 17 . 
     In the working example of the present invention, the cross-sectional surface of second tubular member  22  is hexagonal. The cross-sectional surface of second tubular member  22  may take other polygonal shapes having other angular numbers. For example, the cross-sectional surface of second tubular member  22  may be square, or the cross-sectional surface of second tubular member  22  may be circular. 
     According to the working example of the present invention, it becomes possible to obtain a blind nut with a lower height after it is fastened. It also is possible to obtain a blind nut with a smaller outer diameter and lighter weight. It also is possible to obtain a blind nut that does not require quenching the screw member.