Abstract:
A punch guide assembly includes a retaining clip for retaining the stripper plate inside the punch guide or allowing removal thereof without disassembly of any of the remaining components of the punch tool. The retaining clip is easily insertable into the punch guide and removable therefrom through an opening in the sidewall of the punch guide without the use of additional tools.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a punch guide assembly and, more particularly, a punch guide having an opening therein for insertion of a retaining clip for holding a stripper plate in place in the punch guide, the retaining clip being easily removable from the opening in the punch guide to release the stripper plate and allow removal thereof from the punch guide. 
     BACKGROUND OF THE INVENTION 
     A punch unit for use in a punch press generally includes a punch driver connected with a punch. The punch driver includes a punch head at its back end. A preloaded compression means, such as a compression spring, is provided between the punch head and the punch guide. A punch guide receives and guides the punch. A stripper plate is positioned in the bottom of the punch guide. The stripper plate is a hardened plate having an opening with the same shape as that of the punch tip. 
     During a stroke of the punch, a ram presses down on the punch head forcing the punch tip to enter a workpiece. The preloaded compression means then forces the punch and punch driver out of the workpiece and back to their normal position. As the punch tip exits the workpiece, the stripper plate prevents the edges of the cut hole from following the punch tip. 
     The punch and stripper plate are often replaced due to wear or because a different shaped punch tip is required. Because the opening in the stripper must closely match the shape of the punch tip, when the punch is changed, it is also typically necessary to change the stripper plate. 
     Accordingly, the need exists to provide a punch guide assembly, i.e., a combined punch guide and stripper plate, wherein the stripper plate is quickly and easily removed from or inserted into the punch guide without the need for complete disassembly of the punch tool. 
     SUMMARY OF THE INVENTION 
     Thus, it is a purpose of the present invention to overcome the drawbacks of the prior art and provide a punch guide assembly which permits a simpler and more rapid installation and removal of the stripper plate. 
     According to a preferred embodiment of the invention, a punch guide assembly for use in a punch tool includes a punch guide having an open end and at least one opening in a sidewall. A stripper plate is insertable into the open end. A retaining clip is insertable into the opening in the sidewall from the exterior of the punch guide. The retaining clip engages the stripper plate when inserted into the punch guide to retain the stripper plate therein. The retaining clip is readily accessible from the exterior of the punch guide to allow removal of the retaining clip, thereby releasing the stripper plate from the punch guide. In a preferred embodiment, the retaining clip includes two side arms connected at ends thereof by a bar to form a C-shape. These two side arms frictionally engage a groove in opposite sidewalls of the stripper plate when the retaining clip is inserted into the opening in the wall of the punch guide. 
     The punch guide may include a groove in the interior sidewall which corresponds to the groove in the stripper plate. This groove is engaged by protrusions extending outward from the retaining clip to hold the stripper plate more securely in place in the punch guide. 
     It is, therefore, an object of the invention to provide a punch guide assembly in which the stripper plate may be removed and replaced without disassembly of the remaining portion of the punch tool. 
     It is another object of the invention to provide a punch guide assembly in which the stripper plate is easily removed from or inserted into the punch guide without the use of additional tools. 
     These and other objects of the present invention will become apparent from the detail description to follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     There follows a detailed description of the preferred embodiments of the present invention which are to be taken together with the accompanying drawings, wherein: 
     FIG. 1 is a central longitudinal cross-sectional view of a punch unit in the completely assembled state; 
     FIG. 2 is a top perspective view of a stripper plate used in the punch guide assembly; 
     FIG. 3 is a central longitudinal cross-sectional view of a punch guide with the retaining clip removed; 
     FIG. 4 is a top plan view of a retaining clip; 
     FIG. 5 is a front elevational view of a punch guide in which the openings for insertion of a retaining clip are shown; 
     FIG. 6 is a cross-sectional view through the line A—A in FIG. 3; and 
     FIG. 7 is a cross-sectional view through the line A—A in FIG. 3 after insertion of a retaining clip. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures, like elements are represented by like numerals throughout the several views. 
     FIG. 1 shows a completely assembled punch tool with the stripper plate and retaining clip of the invention shown schematically therein. The punch tool includes a punch  1  which is guided linearly displaceably in a punch guide  2 . A punch driver  25  is connected with the punch  1 . The punch driver  25  includes a punch head  26  at its back end. A preloaded compression means, such as a compression spring  27 , is provided between the punch head  26  and the punch guide  2 . Rotation of the punch  1  in relation to the punch guide  2  is prevented by rotation preventing means such as a pin  3  fixed to the punch  1  which engages an interior longitudinal groove  4  in the punch guide  2 . An axial groove  5  is opened radially outwardly so that means on the punch press machine, not shown, can engage the groove  5  from the exterior and non-rotatingly maintain it on the punch press machine. A stripper plate  6  is inserted into the lower open end of the punch guide  2  and prevented from further movement into punch guide  2  by shoulder  24  which engages the top end  28  of the stripper plate  6 . Stripper plate  6  is then fastened on the lower end of the punch guide  2  by means of a retaining clip  7 . 
     As shown in FIGS. 2 and 3, the stripper plate  6  includes an aperture  11  through which the punch tip is guided. The size and shape of aperture  11  will of course vary depending upon the size and shape of the punch tip. The stripper plate  6  also includes a lug  12  which extends perpendicularly upwardly from the top end  28  and is designed to fit inside one or more longitudinal slots  13  in the interior of the punch guide  2 , as shown in FIG.  3 . This helps to retain the stripper plate  6  in the proper position in the punch guide  2  so that it does not rotate with respect to the punch guide  2 . 
     FIG. 4 shows a preferred embodiment of retaining clip  7 . In the preferred embodiment, the retaining clip includes two side arms  8 . Side arms  8  are connected at their ends by a bar  9 , forming a C-shape. The arms  8  resiliently engage the sidewalls of the stripper plate  6 . Thus, it is preferable that the stripper plate include a groove  10  in the sidewalls as shown in FIGS. 2 and 3 for receiving the side arms  8  of the retaining clip  7 . The groove  10  preferably extends around the entire circumference of the stripper plate  6  as the stripper plate  6  may be rotated to different positions, i.e., such that lug  12  may be received within different longitudinal slots  13  inside the punch guide  2 . 
     As shown in FIGS. 5 and 6, punch guide  2  includes openings  15  for receiving respective side arms  8  of the retaining clip  7 . These openings  15  are aligned with groove  10  when the stripper plate  6  is fully inserted into the punch guide  2 . Punch guide  2  may include slight indentations  23  in the exterior wall near opening  16  which allow retaining clip  7  to be more easily grasped when removed from the punch guide. Punch guide  2  may also include an opening  16  for receiving protrusion  17  on the retaining clip. Protrusion  17 , when positioned in opening  16 , helps to prevent the retaining clip  7  from rotating relative to the punch guide  2  and stripper plate  6 . Thus, when retaining clip  7  is inserted into punch guide  2  the edge  19  of protrusion  17  lies flat against the groove  10  as shown in FIG.  7 . 
     A groove  18 , as shown in FIG. 6, is also provided in the exterior of the punch guide  2  for receiving bar  9 . Thus, bar  9  lies flat against areas  29  of punch guide  2  as shown in FIG.  7 . Retaining clip  7  preferably includes a small notch  22  or other means by which the retaining clip  7  may be easily grasped for removal of the retaining ring. For example, a small wire ring may be located in notch  22  to allow retaining clip  7  to be easily pulled out of punch guide  2 . 
     In the preferred embodiment, the inner sidewalls of the punch guide  2  also include grooves  14  extending in a circumferential direction which align with the groove  10  in the stripper plate  6  when the stripper plate  6  is completely inserted into the lower open end of the punch guide  2 . In contrast to groove  10  in the stripper plate  6 , grooves  14  in the punch guide  2  need not extend around the full circumference of the punch guide  2 . Retaining clip  7  includes protrusions  20  at ends thereof which extend into the grooves  14  in the punch guide  2  to more securely hold the stripper plate  6  in place inside the punch guide  2 . Protrusions  21  extend inwardly to engage groove  10  of the stripper plate and also extend outwardly to engage groove  14  of the punch guide  2 . 
     Although the invention has been described in considerable detail with respect to preferred embodiments thereof, variations and modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention as set forth in the claims.