Abstract:
A rotary-type fastening structure for fixedly coupling an extension rod with a coupling plate, having a rotatable fastening device in the form of a main body with an off-center shaft hole. The rotatable fastening device can be rotated off-center so as to lean its lateral edge on the coupling plate and selectively secure the extension bar to the coupling plate.

Description:
FIELD OF THE INVENTION 
   The present invention is related to a rotary-type fastening structure for use in a slideway, and more particularly to an off-center rotary-type fastening structure with multi-stage locking devices. 
   BACKGROUND OF THE INVENTION 
   In the general server box, the aperture specification of the coupling plate coupled with the drawer slideway is fixed. The slideway is always coupled with the box or the lateral portion of the cabinet by a screwing method. As a result, the drawer or the tray can be coupled with the slideway for the push-pull purpose. However, different coupling plates are provided with different specifications. In order to be suitable for boxes of different specifications, the slideways of different specifications must be provided. Accordingly, the conventional structure is short of convenience and is not suitable for use in the industry. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing drawbacks of the conventional structure, the present invention discloses a rotary-type fastening structure for coupling an extension rod of a slideway with a coupling plate without the use of the screw. 
   It is a main object of the present invention to provide an off-center rotary-type fastening structure with multi-stage locking devices, wherein two rotatable fastening devices are off-center rotated so as to couple an extension rod with a coupling plate. As a result, a slideway of the present invention can be applied to different boxes for performing the push-pull operation. By contrast, in the general server box, the coupling plates of different specifications are applied to the slideway. Accordingly, in the present invention, the extension rod is coupled with the coupling plate by use of the rotary-type fastening structure. 
   It is another object of the present invention to couple the extension rod with the coupling plate by rotating the rotatable fastening devices, wherein the rotatable fastening devices are located to further lean on the elastic fastening sheet so as to fix the rotatable fastening devices. 
   Other objects and features of the present invention will become apparent from the following detailed description when taken in conjunction with the drawings in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevational view showing the structure of the present invention. 
       FIG. 2  is an exploded view showing the structure of the present invention. 
       FIG. 3  is a schematic view showing the utilization of the present invention. 
       FIG. 4  is an elevational view showing that the rotatable fastening devices are fastened. 
       FIG. 5  is a schematic view showing that the rotatable fastening devices of  FIG. 4  are released by rotation. 
       FIG. 6  is an elevational view showing another utilization of the present invention. 
       FIG. 7  is a schematic view showing that the rotatable fastening devices of  FIG. 6  are released by rotation. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The above-mentioned features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the drawings. 
   Referring to  FIG. 1  through  FIG. 3 , a rotary-type fastening structure of the present invention is a structure for coupling an extension rod  1  with a coupling plate  4 . In this preferred embodiment, two kinds of connection holes  41 ,  42  with different apertures are formed on the coupling plate  4  to adjust the method for locking the rotary-type fastening structure. 
   A lateral retaining plate  11  is mounted on each side of the extension rod  1 , wherein one of these two lateral retaining plates  11  has a locking hole  111  on the center region for further fixing the extension rod  1  to the coupling plate  4 . An elastic fastening sheet  12  is riveted on the extension rod  1  inside each of the lateral retaining plates  11 , and a through hole  14  is formed on the extension rod  1  between the elastic fastening sheet  12  and the lateral retaining plate  11  for the mounting of two rotatable fastening devices  3 . Besides, a retaining part  13  is mounted near the through hole  14 . 
   Each of the rotatable fastening devices  3  is axially positioned on the through hole  14  of the extension rod  1 . Each of the rotatable fastening devices  3  has a fan-shaped body  31 , wherein the fan-shaped body  31  has an off-center shaft hole  311 . A fingerboard  312  is mounted on one lateral edge of the fan-shaped body  31 . The rotatable fastening device  3  is axially positioned on the through hole  14  by penetrating a shaft  32  through the off-center shaft hole  311  such that the rotatable fastening device  3  is pivotally rotatable. 
   Referring to  FIG. 4  and  FIG. 5 , the extension rod  1  is fixedly coupled with the coupling plate  4 . The extension rod  1  is connected to the outside of the coupling plate  4  through the lateral retaining plate  11 . The lateral retaining plate  11  is mounted between the extension rod  1  and the coupling plate  4  by inserting two locking devices  2  into the connection holes  41 . In order to fix the extension rod  1  on the coupling plate  4 , the screwing locking method is adopted in the conventional structure. However, the improvement of the present invention consists in providing the multi-stage locking device without the use of the screw. In the present invention, the rotatable fastening device  3  is pivotally mounted on the through hole  14  of the lateral retaining plate  11  so that the locking devices  2  can be locked on the coupling plate  4  by use of different rims. In these diagrams, the aperture of the connection holes  41  is larger than the aperture of the connection holes  42 . As a result, if the extension rod  1  is coupled with the coupling plate  4  by inserting the locking devices  2  into the connection holes  41 , the first rims  21  of the locking devices  2  are utilized. Accordingly, the rotatable fastening devices  3  must be rotated in a larger rotation angle. If the rotatable fastening devices  3  are rotated, the fan-shaped bodies  31  of the rotatable fastening devices  3  are located to lean against the coupling plate  4  by use of the farther end so as to fixedly couple the extension rod  1  with the coupling plate  4 . If it is desired to separate the extension rod  1  from the coupling plate  4 , there is merely a need to pull the fingerboards  312  and to rotate the rotatable fastening devices  3  for positioning them by the retaining parts  13 . Thereafter, the rotatable fastening devices  3  are located to further lean on the elastic fastening sheet  12  so as to fix the rotatable fastening devices  3 . 
   Referring further to  FIG. 3 ,  FIG. 6 , and  FIG. 7 , if the locking devices  2  are inserted into the connection holes  42 , which have smaller aperture, the second rims  22  of the locking devices  2  are utilized. As a result, the rotatable fastening devices  3  must be rotated in a smaller rotation angle since the insertion depth of the locking devices  2  into the connection holes  42  is smaller than the insertion depth of the locking devices  2  into the connection holes  41 . 
   If there is a need to rotate the rotatable fastening devices  3  for tightly coupling the extension rod  1  with the coupling plate  4 , the rotatable fastening devices  3  are rotated off-center so as to fixedly mount the extension rod  1 . Besides, the extension rod  1  can be demounted easily by rotating the rotatable fastening devices  3 .