Abstract:
A device for positioning stock within a metal forming machine has a body containing a pusher arm. The device may use interchangeable standard and reverse pusher arms . The pusher arms mount on pivot pins and have position restoring springs. The springs exert force on the pusher arms at a distance from the pivot pins, thereby inducing a moment in the pusher arm. The pusher arm translates this moment into a lateral force exerted by the pusher arm on a piece of stock metal. The body may be mounted in either a reverse or standard configuration resulting, in combination with the use of either the standard or reverse pusher arm, in the ability to exert a lateral force in different directions depending on the configuration used. The device may also have a single pusher arm which may be used in either configuration.

Description:
TECHNICAL FIELD 
     This invention relates generally to the metal forming industry and, more particularly, to devices for positioning stock within a metal forming machine, such as in a sheet metal punch. 
     BACKGROUND OF THE INVENTION 
     The applicant is aware of the following U.S. patents, the disclosures of which are incorporated by reference herein: 
     U.S. Pat. No. 2,369,551 
     U.S. Pat. No. 2,964,003 
     U.S. Pat. No. 3,400,838 
     U.S. Pat. No. 3,516,316 
     Stock pushers or crowders are known in the prior art. These devices are designed to assist in the metal forming process by assuring that stock pieces are properly positioned against a reference surface within a metal forming machine prior to the start of a machine cycle. This assures that the metal forming process, whether it be bending, punching or cutting, is performed in the same manner and at the same position on each piece of stock that is inserted into the machine. 
     For example, a design known from U.S. Pat. No. 3,400,838 discloses a device which has a lever, a compression spring, a cam, and a pivotal arm. The lever and compression spring are mounted to the moving die shoe of the metal forming machine. The cam is attached to the pivotal arm, which, in turn, is attached to a stripper plate located immediately above the stock piece. The compression spring urges the lever in a lateral direction towards the cam and pivotal arm. When the machine lowers the die shoe into its operating position, the lever comes into contact with the cam. The lever then forces the cam and the pivotal arm to move towards the stock until the pivotal arm makes contact with the stock and forces it against a reference surface. When the metal forming operation is complete, the lever is raised, allowing the cam and pivotal arm to move away from the stock. This design takes up considerable space within a metal forming machine and, due to its two-element design, requires realignment between the lever and cam/pivotal arm anytime the device is moved or the machine setup is adjusted. 
     Similarly, U.S. Pat. No. 2,369,551 also discloses a device which uses a depending lever to contact the stock. The lever is biased by an external spring. 
     U.S. Pat. No. 3,516,316 discloses a different design. An arm is pivotally attached to a moving stripper plate within a metal forming machine. A torsion spring urges the arm to pivot downward towards the workpiece holder so that one end of the arm extends below the bottom surface of the stripper plate. The stripper plate and pivoting arm are moved downward when the machine tool is moved downward for operation. The end of the arm comes into contact with the workpiece holder before the stripper plate and is forced to rotate against the force of the torsion spring and towards the stock. Prior to the stripper plate engaging the stock, the arm makes contact with the stock piece and forces it against a reference surface. When the operation is complete, the tool and stripper plate are raised, allowing the pivoting arm to rotate away from the stock and back to its starting position. 
     Another design is illustrated in U.S. Pat. No. 2,964,003. The design of this stock crowder has a unit that mounts directly to the moving die shoe which holds the machine tool. The unit has a mount; a pivoting, L-shaped lever; and a compression spring. The shorter leg of the L-shaped lever extends horizontally away from a pivot point. The longer leg of the lever extends vertically downward towards the stock piece. The compression spring, contained within the mount, acts on the shorter leg of the lever to create a moment in the lever about the pivot point. This moment urges the longer end of the lever into contact with the stock. The lever then forces the stock against a reference surface. In this design, the mount and lever occupy considerable space within a metal forming machine due in large part to the L-shaped design of the lever. When the user desires to change the direction of force applied by the device, a separate mount and lever must be used and the moving die shoe must be adapted to accommodate a seat for the compression spring. 
     SUMMARY OF THE INVENTION 
     The stock crowder of the present invention has a containing body with a pusher arm pivotably mounted in the body. The stock crowder may be mounted in a metal forming machine in either a standard or a reverse configuration. The pusher arm has a pivot pin adjacent to one end that forms a pivot point with the main body. The body contains a spring which is engaged with the pusher arm at a distance from the pivot point and provides a force necessary to create a moment about the pivot point. A standard pusher arm and a reverse pusher arm may be provided for use when the main body is mounted in the standard or reverse configuration, respectively. Alternatively, a single pusher arm may be adapted to both configurations, as described herein. In the invention&#39;s standard configuration, the spring, which may be a tension spring or a compression spring, exerts a force below the pivot point, thereby creating a moment and a resultant force in one direction. In the reverse configuration, the spring exerts a force above the pivot point, thereby creating a moment and a resultant force in the opposite direction as that obtained in the standard configuration. 
     An object of the present invention is to provide a more compact and rigid positioning device that will use less space within a metal forming machine. 
     Another object of the invention is to provide a stock pusher which fits in a wider range of metal forming machines and requires fewer mounting or adapting pieces. 
     Another object of the present invention is to provide a positioning device that is capable of operating in several modes, providing flexibility in use while reducing the number of parts required for this feature. 
     These and other objects, aspects, features and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the reference drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a stock pusher, according to the invention, in a standard configuration. 
     FIG. 2 is an exploded perspective view of an alternate embodiment of the stock pusher. 
     FIG. 3 is a series of side views of the standard and reverse pusher arms. 
     FIGS. 3A and 3B are side views of a standard pusher arm. 
     FIGS. 3C and 3D are side views of a reverse pusher arm. 
     FIG. 4 is a bottom view with hidden lines shown of a stock pusher in a standard configuration. 
     FIG. 5 is a cross-sectional view of the stock pusher from section line A—A of FIG.  4 . 
     FIG. 6 is a bottom view of a stock pusher in a reverse configuration. 
     FIG. 7 is a cross-sectional view of the stock pusher from section line B—B of FIG.  6 . 
     FIG. 8A is an elevation view of a stock pusher in a standard configuration. 
     FIG. 8B is an elevation view of a stock pusher in a reverse configuration. 
     FIG. 9 is a partial schematic view of a stock in a standard configuration as installed in a metal forming machine. 
     FIG. 10 is an exploded perspective view of a stock pusher, according to an alternate embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is now made to the drawings which illustrate the best known mode of carrying out the invention and wherein the same reference numerals indicate the same or similar parts throughout the several views. 
     A stock pusher  2  according to the present invention is shown in FIG.  1 . The stock pusher  2 , of FIG. 1, has a two piece body  3  made with a base  4  and a cap  6 . The base  4  contains a semicircular channel  8  and a substantially rectangular channel  10  along a cap face  12 . The cap  6  contains a semi-circular channel  14  and a substantially rectangular channel  16  along a base face  18  which match the semi-circular channel  8  and substantially rectangular channel  10  of the base  4  to form channels  9  and  11 , as shown in FIGS. 5 and 6. It will be appreciated that the channels  9  and  11  may be of cross sections other than those shown and still provide the required function, as described herein. A standard pusher arm  20  of linear design has spring pocket  21 , as shown, and has a cylindrical pivot pin  22  adjacent to one end and an angled surface  23  at the opposite end. The stock pusher, including pusher arm  20 , is preferably made of a strong durable material, such as 4140 pre-hardened aluminum or an equivalent sturdy structural material, as is known in the art. The base  4  and cap  6  especially may be made of such material. The pivot pin  22  may be either integrated with the pusher arm  20  or a separate piece, or pieces which slides into an aperture contained in the pusher arm  20 . When the base  4  and cap  6  are joined, the channel  9  receives and hold in place the pivot pin  22  on either side of the pusher arm  20 , forming two pivot points  25 , while the channel  11  restricts movement of the pusher arm  20  to a single plane. It will be appreciated that other shapes may be used for channel  11 ; it may be circular in cross-section, for example. In that configuration, a slotted disc or guide bars, not shown, may be used to guide pusher arm  20 . The joined base  4  and cap  6  allow the pusher arm  20  to move about the pivot points. The base  4  and cap  6  may be held together by any standard, removable joining means  26 , such as screws or bolts. It will be appreciated that other shapes may also be used for pivot pin  22  and pivot points  23 , as is known in the art. For example, pivot pin  22  may be of compound shape such as a rectangle with curved ends which cooperate with the curvature of channel  9 , or a bolt or other fastener as shown in FIGS. 2 and 10. 
     The pusher  2  applies a force to the pusher arm  20  at a distance from the cylindrical pivot pin  22  to create a moment about the pivot points  25 , for example, at a distance X, as shown. This force may be supplied by a compression spring  32  contained in a bore  34  within the base  4 . The compression spring  32  may be held within the bore  34  by a threaded plug  36 , as shown. Any suitable compression spring  32  , such as a conventional steel spring for example, may be used. The pusher arm  20  may be provided with a recessed area, or pocket  21  to receive an end of the compression spring  32 . The amount of force applied to the pusher arm  20  may be adjusted both by adjusting the plug  36  to control the level of preset compression placed on the spring  32  and by using springs of varying stiffness and length. It will be appreciated that a tension spring, not shown, may also be used instead of compression spring  32 , for example by reversing the location of bore  34 . Bore  34  may also be of other cross-sections, for example, of square cross-section. Further, spring  32  may be held in bore  34  by other keepers and fasteners, such as by a snap-ring. 
     The compression spring  32  tends to force the pusher arm  20  to rotate about the pivot points  25 , away from the base  4 . When the device is used in a metal forming machine as shown in FIG. 9, this movement will bring the pusher arm  20  into contact with whatever stock or workpiece is placed in the machine and force the stock into position against a reference surface. The force of the pusher arm  20  will be applied to the stock throughout the operation of the machine, insuring that the workpiece is in the proper position for whatever metal forming operation is performed. 
     When the work piece is removed from the machine, the force of the compression spring  32  will rotate the pusher arm  20  until it encounters the wall of the channel  11 . A stop for restricting this movement may be provided in the device, for example, by stop screw  40  inserted into a threaded hole  42  contained in the cap  6 , as shown in FIG.  5 . The distance which the stop screw  40  extends into the pusher arm&#39;s movement may be adjusted simply by turning the screw  40  one way or another. The position of stop screw  40  may be fixed by a set screw  41 , as shown. 
     Because proper operation of the device requires that the pusher arm  20  be able to freely pivot within the pivot points, lubrication of the pivot pin  22  and channel  9  may be provided. For example, one or more bores  44  through the base  4  leading to the channel  9  may be provided, as shown. Grease fittings  46  may be inserted into the bores  44  to aid in the delivery and retention of lubricant. Alternatively, pivot pin  22  and channel  9  may be provided with a self lubricating coating, as known in the art. 
     Pusher  2  will generally be mounted to an upper, moveable portion of the metal forming machine  80 , as seen in FIG.  9 . This mounting may be accomplished by a plurality of bores  48  through the body  2 . Screws  50  and/or dowels  52  may be inserted through the bores  48  and into the upper portion of the metal forming machine  80 . This mounting system allows the cap  6  and pusher arm  20  to be removed from the device while leaving the base  4  mounted to the metal forming machine. In addition, this system allows the pusher  2  to be installed in either a standard configuration or a reverse configuration simply by rotating the base  4  and cap  6  180° about the horizontal and vertical axes, as illustrated in FIG. 8A and 8B. It will also be appreciated that a plurality of bores  48  may be placed on pusher  2 , including on cap  6 , not shown. The placing of the bores  48  may permit a single pusher design to be used in a variety of installations. 
     The capability of installing the pusher  2  in two positions makes the entire device capable of exerting a force in two different directions with only a minimal need for interchanging parts. In order to reverse the direction of force, only the pusher arm  20  must be replaced. A reverse pusher arm  54 , as shown in FIGS. 1,  3 C and  3 D, may be used in place of the standard pusher arm  20 . As opposed to the standard pusher arm  20 , wherein the pivot pin  22  is positioned substantially at one end of the arm  20 , the reverse pusher arm  54  possesses a cylindrical pivot pin  56  that is spaced a distance, Y, from the end of the arm  54 , as shown in FIG.  3 D. This change of position of the pivot pin in combination with the rotation of the base  4  and cap  6  by 180° about the horizontal axis places the spring  32  in contact with the reverse pusher arm  54  at a distance, Z, above the pivot pin  56 , as shown in FIG.  7 . This is in contrast to the standard configuration in which the spring  32  contacts the pusher arm  20  below the pivot pin  22 . Other than the position  20  of the pivot pin  56  the design and usage of the reverse pusher arm  54  is similar to that of the standard pusher arm  20 . 
     The reverse configuration results in a moment being imparted to the reverse pusher arm  54  in the opposite direction of the moment induced in the standard pusher arm  20 . In turn, the direction of force applied by the reverse pusher arm  54  is opposite that imposed by the standard pusher arm  20 . Only one new part is required to accomplish this change in direction. If desired, a single pusher arm  20  may be modified to perform the duties of both the standard  20  and reverse pusher arms  54 , as shown in FIG. 10, by simply providing a pusher arm  20  with two pivot holes  60 ,  62 . The pivot holes  60 ,  62  permit the pusher arm  22 , shown in FIG. 10, to be reversed as described herein with reference to FIGS. 8A and 8B. In the alternate embodiment as shown in FIG.  2  and FIG. 10, the body  3  of pusher  2  may be a single piece. 
     OPERATION OF THE DEVICE 
     During operation, the pusher  2  may be mounted to the die shoe  82  of a metal forming machine  80 , as shown in FIG.  9 . The spring  32  exerts a force on either the standard pusher arm  20 , as shown or the reverse pusher arm  54 , at a distance from the pivot points  25  and pivot pins  22 . This creates a moment about the pivot points  25  and makes the pusher arm  20  or  54 , rotate about the pivot points  25 , as described herein. When the die shoe  82  of stamping machine  80  advances toward workpiece  84 , pusher arm  20  contacts the edge  86  of workpiece  84 , as shown. The force supplied to pusher arm  20  by spring  32  is translated to workpiece  84  and forces workpiece  84  firmly against positioning stop  88 , as shown. The workpiece  84  is held against positioning stop  88 , to maintain the accuracy of the performed operation, until the operation of the stamping machine completes the desired work on the workpiece  84 . The stamping machine  80 , with pusher  2 , can then return to its initial position in preparation for another cyle. 
     Other objects, features and advantages of the present invention will be apparent to those skilled in the art. While preferred embodiments of the present invention have been illustrated and described, this has been by way of illustration and the invention should not be limited except as required by the scope of the appended claims and their equivalents.