Abstract:
A stripper plate supporting assembly has a stripper spool unit including a stripper spool and retaining screw for supporting the stripper plate in a die press in a manner that the stripper plate may be removed from a die set without removing the die set from the press. The stripper spool has a shank with at least one spring biased pin in its flat end. At least one opening or socket is provided in the stripper plate for receiving the pin and preventing the stripper spool from turning with the retaining screw.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an assembly for supporting a stripper plate in a die set such that the stripper plate can be easily assembled and removed.  
           [0003]    2. Brief Description of the Prior Art  
           [0004]    Die assemblies include upper and lower die shoes. The lower shoe is adapted to be mounted on the bed of a punch press and the upper shoe is adapted to be mounted to a power ram for reciprocating the upper die shoe toward and away from the lower die shoe. Stamping a work piece is performed by suitable dies and punches mounted on the die shoes. One or more stripper plates complete the die set into a die assembly.  
           [0005]    Stripper plates have long been used in die assemblies to strip the material being worked from the punches but stripper plates may perform other functions in addition to traditional stripping operations. These additional functions include retaining forming inserts, functioning as pressure devices, serving as guides for weak or thin punches, flattening parts, and so forth.  
           [0006]    In the past, it has been customary, to mount the stripper plate on the die set by means of shoulder bolts extending through the upper or lower die shoe and screwing in to the stripper plate. The stripper plate is spring biased on the stripper bolts with springs that surround the shoulder bolts or are otherwise spaced between the stripper plate and the respective die shoe. During the operation of the press, breakdowns, the need to change punches, and the like, and other difficulties often require removal of the stripper plate. Stripper bolts that screw into the stripper plate are inconvenient as they require removing the die set from the press in order to remove the stripper plate.  
           [0007]    Various means have been proposed to facilitate the removal of the stripper plate without removing the die set from the press. One such system makes use of a retaining screw which is threaded from the face of the stripper plate into a stripper spool, but with this system the stripper spool tends to spin with the retaining screw making installation and removal of the stripper plate difficult.  
           [0008]    Flats have been provided on the stripper spool for the purpose of holding the spool while the retaining screw is threaded into the spool; however, lack of space in the die set makes access to the wrench flats very difficult or impossible. Spikes have been provided on the spool for digging into the rear face of the stripper plate to keep the spool from spinning with the retaining screw. When the stripper plate is reinstalled, the holes in the rear face of the stripper plate may not line up with the spikes. In time the spikes form a groove in which the spikes spin along with the spool. Another solution provides a projection on the head of the stripper spool which prevents the spool from rotating with the retaining screw but this requires the die shoe to be machined with an odd-shaped counterbore for receipt of the projection.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    In view of the above, it is an object of the present invention to provide a stripper spool unit for supporting a stripper plate in a manner that the stripper plate can be removed for servicing the die without removing the die from the press. Other objects and features of the invention will be in part apparent and in part pointed out hereinafter.  
           [0010]    In accordance with the present invention, a stripper plate supporting assembly has a stripper spool with a shank, a head and a flat end remote from the head, with a drilled and tapped longitudinal hole extending inwardly from the flat end. A bore is provided in the flat end spaced from the drilled and tapped hole for receipt of a pin which is spring biased to normally project a free end of the pin beyond the flat end of the stripper spool. It will be understood that the terms “a bore” and “a pin” as used herein includes the plural (i.e., one or more bores and/or one or more pins).  
           [0011]    The assembly further includes a die set with a bore having a diameter for close sliding fit with the stripper spool shank and a shoulder for limiting the length of relative travel between the stripper plate and the die set. A stripper plate is provided with a bore in axial alignment with the drilled and tapped hole in the stripper spool. The stripper plate additionally has an opening or socket spaced from the bore for receipt of the free end of the pin. It will be understood that the term “an opening” includes the plural (i.e., one or more openings).  
           [0012]    A retaining screw extends through the stripper plate bore and threads into the drilled and tapped hole. The retaining screw coacts with the stripper spool to hold and support the stripper plate in position against the flat end of the stripper spool, with the free end of the pin received in the opening or socket in the stripper plate preventing the stripper spool from turning with the retaining screw, allowing the stripper plate to be easily and quickly positioned on and removed from the die set without removing the die set from the press.  
           [0013]    The invention summarized above comprises the constructions hereinafter described, the scope of the invention being indicated by the subjoined claims. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0014]    In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated, corresponding reference characters refer to corresponding parts throughout the several views of the drawings in which:  
         [0015]    [0015]FIG. 1 is an exploded perspective view of a stripper spool and retaining screw unit in accordance with the present invention;  
         [0016]    [0016]FIG. 2 is a side elevation in section of a stripper plate supporting assembly in accordance with the present invention;  
         [0017]    [0017]FIG. 3 is a side elevation in section showing the retaining screw being threaded into the stripper spool for supporting a stripper plate;  
         [0018]    [0018]FIG. 4 is a section taken along line  4 - 4  in FIG. 3;  
         [0019]    [0019]FIG. 5 is a side elevation in section showing the retaining screw tightened in the stripper spool for supporting the stripper plate; and,  
         [0020]    [0020]FIG. 6 is a section taken along line  6 - 6  in FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    Referring to FIG. 2 more particularly by reference character, reference number  10  refers to a stripper plate supporting assembly in accordance with the present invention. Assembly  10  includes an upper die shoe  12  and a lower die shoe  14 . Lower die shoe  14  is adapted to be mounted to the bed of a punch press (not shown) and upper die shoe  12  is adapted to be mounted to a power ram (not shown). Attached to upper and lower die shoes  12 ,  14  are one or more punches  16  or other forming tools held by punch plates  18  which cooperate with one or more corresponding dies  20  held by die plates  22  associated with the opposite die shoe. In some instances, die plates  22  may be integral with dies  20 . Clearance holes  24  may be provided in the die shoe bearing die  20  for slugs to drop after they are punched out of a work piece.  
         [0022]    One or more spring biased stripper plates  26  supported on stripper spools  28 , more particularly described below, complete assembly  10 . The term “stripper plate” as used herein includes floating members that strip the material being worked from the forming tools as well as floating members that retain forming inserts, function as pressure devices, serve as guides, flatten the parts and so forth. Stripper plate  26  overlies a sheet of stock (not shown) to be worked. It is understood that the stock is fed and indexed into the press, and the usual provisions are made for maintaining alignment of the stripper plates  26 , punches or other forming tools  16 , dies  20  and the stock.  
         [0023]    With reference to FIGS.  1 - 3  and  5 , each stripper spool  28 , a pair of which are shown in FIG. 2, has a shank  30 , a head  32  and a flat end  34  remote from the head. A drilled and tapped longitudinal hole  36  extends inwardly from flat end  34 . A closed-ended longitudinal bore  38 , spaced from drilled and tapped hole  36 , is provided in flat end  34 . A pin  40  is received in bore  38  and held by a spring  42  to normally project a free end  44  of pin  40  beyond flat end  34 . While only one bore  38  and one pin  40  is shown in the drawings, it will be apparent that more than one of each may be used.  
         [0024]    Stripper spools  28  are supported by one of die shoes  12 ,  14 . In some die sets, stripper plates  26  are provided on upper die shoe  12  only. In other die sets, stripper plates  26  are provided on lower die shoe  14 , while in more complex die sets, stripper plates  26  may be provided on both shoes. As seen in FIGS. 3 and 5, a bore  46  with a diameter having a close sliding fit with shank  30  is formed in upper die shoe  12  and is counterbored, as at  48 , at a side of upper die shoe  12  remote from stripper plate  26 , to a depth above head  32  equal to the travel which stripper plate  26  is to have relative to the die set during the die press cycle. Counterbore  48  has a diameter such as to provide a smooth sliding fit with head  32  of stripper spool  28  with the bottom of counterbore  48  forming a shoulder  50  stopping movement.  
         [0025]    Stripper plates  26  have a bore  52  in axial alignment with each drilled and tapped hole  36  in stripper spool  28  for receipt of a retaining screw  54 . An opening or socket  56 , spaced from bore  52 , is provided on the back face of stripper plate  26  for receipt of spring biased pin  40 . While only one opening or socket  56  is shown in the drawings, it will be apparent that more than one may be provided. Retaining screw  54  may be of the ordinary Allen or similar type or flat-headed if stripper plate  26  is thin. A counterbore  60  may be provided in the face of stripper plate  26  for receipt of a head  62  of retaining screw  54 . Retaining screw  54  is inserted through bore  52  and into engagement with the threads in drilled and tapped hole  36  and tightened to hold stripper plate  26  tightly and firmly against flat end  34  of stripper spool  28 , with head  62  of retaining screw  54  within counterbore  60 .  
         [0026]    As illustrated in FIGS.  3 - 4 , initially spring biased pin  40  is not in opening or socket  56  and stripper spool  28  tends to rotate with retaining screw  54  when it is threaded into stripper spool  28 . As stripper spool  28  rotates, pin  40  slides over the back side of stripper plate  26  until it is caught in opening or socket  56  as shown in FIGS.  5 - 6  stopping stripper spool  26  from further rotation, thereby ensuring that retaining screw  54  may be easily tightened and loosened within and relative to stripper spool  28  and allowing stripper plate  26  to be easily and quickly positioned on and removed from the die set without removing the die set from the press. This is convenient, for example, if a punch should break and require replacement, sharpening, removal or altering in position. When this happens, all that is necessary to change or dress the punch is to remove the several retaining screws  48  which secure stripper plate  26  to stripper spools  28 . When this is done, stripper plate  26  can be removed to expose the punches so that they can be replaced, sharpened or removed as may be required.  
         [0027]    Stripper plate  26  is resiliently biased from the associated die shoe  12 ,  14  on springs  64 . Springs  64  may be held against lateral deflection in a number of ways which are unrelated to the present invention. For example, springs  64  may surround stripper spools  28  as shown in FIGS. 2, 3 and  5 . In other embodiments, one end of springs  64  may be received in sockets provided in the die with the other end seated on trunnions rising from the stripper plate and so forth. Springs  64  urge stripper spools  28  into engagement with shoulders  50  when upper and lower die shoes  12 ,  14  are at their greatest point of separation at the beginning of a stamping operation. Heads  32  of stripper spools  28  slide in counterbores  48  during the final portion of the stamping operation.  
         [0028]    Upon completion of the punching operation, the ram, together with upper shoe  12  rises. In the die set shown in FIG. 2, stripper plate  26  and punch  16  are mounted on upper die shoe  12  and the work piece tends to cling to rising punch  16  but upward movement of the work piece is prevented by stripper plate  26 . Springs  64 , through heads  32 , hold stripper plate  26  down in engagement with the work piece until the punches leave the work piece and until heads  32  seat on shoulders  50 . Thereafter, further upward movement of the ram and upper die shoe  12  elevates stripper plate  26 , punches  16  and the parts of the stripper spring unit in unison, thereby freeing the work piece for removal and replacement. It will be understood that stripper plate  26  functions in mirror image to that described above when it is mounted on lower die shoe  14 .  
         [0029]    In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.