Abstract:
A retainer pin is described for retaining, in one embodiment, a relatively thin blade against a transverse surface. The pin has a transition section which extends through an opening in the blade, a keeper section extending along one side of the blade, and a snap arm and snap end extending along an opposite side of the blade with a snap snapping over the edge of the blade.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to retainer pins such as a cotter pin. 
       PRIOR ART AND RELATED ART 
       [0002]    Retainer pins such as cotter pins are well known in the art. The present invention is an easier to install alternative to such pins suitable for certain applications. 
       SUMMARY OF THE INVENTION 
       [0003]    A retainer pin which may be used as a replacement for a cotter pin in some applications is disclosed. The retainer pin is particularly useful when used with a blade-like structure having an edge for receiving the snap end of the retainer pin. The pin has a linear retainer portion forming a transition between a snap arm and a keeper and when installed, the linear portion fits within, for instance, an aperture in a blade. The snap arm and keeper are generally parallel and extend in opposite directions from the retainer portion. The distal end of the snap arm defines an s-shaped snap generally parallel to the linear retainer portion, which snaps over the edge of the blade to keep the pin from moving in one direction as the pin contacts a surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a perspective view of the invented pin. 
           [0005]      FIG. 2  is an elevation view of the pin of  FIG. 1 . 
           [0006]      FIG. 3  is a side view of the pin of  FIGS. 1 and 2 . 
           [0007]      FIG. 4  is a cross-sectional view showing the pin of  FIG. 1  installed. 
           [0008]      FIG. 5  is cross-sectional elevation view of an installed pin used to describe the importance of the length L of the keeper section of the pin. 
           [0009]      FIG. 6  is an elevation view showing the pin installed in a blade where an edge is formed by a slot in the blade which slot receives the snap end of the retainer pin. 
           [0010]      FIG. 7  is a perspective view showing the pin about to be installed in the blade inserted into the base of an electrical power meter. 
           [0011]      FIG. 8  shows the arrangement of  FIG. 7  with the keeper section of the retainer pin installed within the blade. 
           [0012]      FIG. 9  shows the arrangement of  FIG. 8  where the retainer pin is about to be snapped onto the blade. 
           [0013]      FIG. 10  shows the arrangement of  FIG. 9  with the retainer pin installed on the blade. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    A retainer pin which may be used as a substitute for a cotter pin in some applications is disclosed. The retainer pin of the present invention is particularly useful where a relatively thin member such as a blade-like structure requires retention against a surface through which the member has been inserted. Specific details are set forth below such as specific dimensions to provide a thorough understanding of the present invention. It will be obvious to one skilled in the art that the present invention may be practiced without these specific details. 
         [0015]    An understanding of the retention pin described in this application is perhaps best understood from  FIGS. 7-10 . Referring then to  FIG. 7 , an electrical meter base  52  is shown having a surface  51 . The surface  51  has slots for receiving a plurality of blades  50  (typically four, only one of which is shown). The blades are part of an underlying assembly, which is hidden by surface  51  and which needs to be secured to the base  52 . The blades are bus bars, and after their installation into the base  52  a meter is secured onto the base  52 , making electrical contact with the blades. As shown in  FIG. 7 , the pin  10  is about to be installed within the aperture  55  of the blade  50 .  FIG. 8  shows the keeper end of the pin inserted into the aperture  55  and the transition section of the pin about to be installed into the aperture  55  as the pin is rotated. In  FIG. 9  the snap end is ready to be snapped onto the edge of the blade  50 . Finally, as shown in  FIG. 10  the snap end is engaging the blade  50 . 
         [0016]    The pin  10  now prevents the blade  50  from moving in the direction indicated by the arrow  56  because the pin is wedged against the surface  51  and extends through the aperture  55  of the blade  50 . In the prior art, the blade  50  and like blades is secured against the base  51  by placing a cotter pin through the aperture  55 . As will be appreciated the pin  10  of the present invention provides a much quicker installation. 
         [0017]    Referring now to  FIGS. 1 ,  2  and  3 , the substantially coplanar pin has a keeper section  11 , transitional section  12  with a linear portion  13 , a snap arm  15  and a snap end  17 . The keeper section  11 , as will be described, has a length L which keeps the snap end in place, particularly in the presence of vibration or other movement. The transition section  12 , which is perpendicular to the keeper  11 , includes a linear portion  13  having a length approximately equal to the width of the blade, or the like structure. The snap arm  15  is generally perpendicular to the transition section  12  and extends in a direction generally opposite to, and parallel to, the keeper section  11 . The s-shaped snap end  17  is generally parallel to the transition section  12 . 
         [0018]    In the preferred embodiment, the retainer pin is a continuous member fabricated from either steel or an injection molded high-temperature plastic where high temperatures are to be encountered. As an example, a type  304  stainless steel or spring steel may be used. In an embodiment where the center of the aperture  55  of  FIG. 9  is approximately 10 mm from the edge of the blade  50  and the radius (r) of the retainer pin is approximately 0.8 mm, the diameter of the aperture  55  is slightly larger than 1.6 mm to allow the pin to pass through and be rotated into position. For this particular application, where the blade has a thickness of approximately 2.5 mm, the overall length of the pin measured from the end of the keeper section to the furthest extent of the snap end is 16.1 mm. The snap end measured from the top of the snap arm (as viewed in  FIG. 2 ) to the lowest point of the snap arm is 9.7 mm; the angle “a” of  FIG. 2  is 30°. The inside width of the pin (dimension “b” in  FIG. 2 ) is 7.32 mm. L, the length of the keeper, is approximately 4.2 mm long. 
         [0019]    The pin  10  is installed within an aperture  21  of a member  20  in  FIG. 4 . Note the width of member  20  is approximately equal to the length of the linear section of the pin. As can be seen in  FIG. 4 , retention of the snap end occurs at point  22  after the snapping action overcomes the corner of the member  20  at  22 . The aggressiveness of this snapping action is controlled particularly by the snapping arm&#39;s length and the tolerances used in manufacturing. It is necessary for the pin to be flexible enough to overcome the fulcrum at  22  and then spring back into its original shape. 
         [0020]    The length L of the keeper section is important, as demonstrated in  FIG. 5 , in preventing the angle α from exceeding more than a few degrees since otherwise the pin  10  may snap off its engaged position. In  FIG. 5  a blade  30  is shown having an aperture  31  with a radius R. The center of this aperture is a distance S from the surface  36 , which the member  30  is retained against and P is the distance from surface  36  to the center of the pin  11 ; the pin has a radius r. Note there is some distance, albeit small, between the bottom of the aperture  31  and the surface  36 . Assume: 
         [0000]        Q=P−r=S+R− 2 r    
         [0000]    α then is approximately equal to: 
         [0000]    
       
         
           
             α 
             = 
             
               
                 arcsin 
                  
                 
                   ( 
                   
                     Q 
                     / 
                     L 
                   
                   ) 
                 
               
               = 
               
                 arcsin 
                  
                 
                   ( 
                   
                     
                       S 
                       + 
                       R 
                       - 
                       
                         2 
                          
                         r 
                       
                     
                     L 
                   
                   ) 
                 
               
             
           
         
       
     
         [0000]    L should be long enough to prevent a from becoming more than a few degrees before the keeper section&#39;s end contacts the surface  36  as shown at point  35 . This contact prevents a from becoming larger, and the pin dislodging. 
         [0021]      FIG. 6  shows another installation where the pin  10  has a linear portion engaging the slot  41  of the blade  40 . The keeper section  11  is also shown. A slot  42  is formed in the blade  40  to allow the snap end to engage the slot edge  43 . This allows the pin to be used with a wider blade without the pin having to extend to the edge of the blade. 
         [0022]    Thus, a retainer pin has been disclosed which may substitute for a cotter pin in some applications and which is much easier to install.