Abstract:
A punch press tool for stamping successive multicharacter impressions into a workpiece such as a piece of steel, sheet metal, or other workpiece, includes a guide body in which a stamp driver is slidably mounted for being driven downwardly toward the workpiece by a punch press ram which is a standard part of a high speed commercial punch press. A multicharacter marking stamp is supported at the lower end of the stamp driver for reciprocal movement therewith. The marking stamp includes multicharacter wheels that are rotated automatically during operation for advancing characters in sequence responsive to the movement of a character advancing arm. At least one character stamp operating lever is operatively associated with the punch press tool for articulation responsive to motion imparted to the tool by the ram. The lever has an operating element that is operatively associated with the character advancing arm of the multicharacter stamp for indexing the arm to enable successive characters thereof to be placed in an operating position responsive to a stroke of the punch press ram.

Description:
FIELD OF THE INVENTION 
     This invention relates to the punch and die art and more particularly to a punch press stamping tool for marking a workpiece with a stamped impression of numbers or letters in its surface. 
     BACKGROUND OF THE INVENTION 
     In the punch and die art and particularly in the field of high-speed automated forming and punching equipment for punching and forming sheet material, e.g., sheet metal and especially in the case of automated turret punch presses, the punch presses are operated by computer to rapidly perform a series of punching or forming operations. These punch presses which by themselves form no part of the present invention are typically provided with an upper turret and a lower turret that rotate and are indexed intermittently between punching operations. The turrets may, for example, hold as many as a dozen or more separate punches such as hole punches that are used one after another for performing given operations. When a punch is struck from above by the ram of the punch press, the punch element or punch insert is driven downwardly through the workpiece to perform the punching or forming operation. When released, the punch insert is retracted by a spring provided in the punch assembly. 
     While there have been several attempts to provide a satisfactory marking tool for punch presses, the prior tools are provided with characters that must be changed manually or in other equipment are able to make an impression of only one letter or number at a time. U.S. Pat. No. 5,993,090, for example, describes a marking punch provided with twelve letters, each of which is punched separately. So, for example, to punch the number 2007 would require four punch strokes and some mechanism for rotating the punch shaft between strokes but none is provided. U.S. Pat. No. 4,397,233 describes an automatic numbering assembly that instead of making an impression into the workpiece, transfers ink from an ink roller to a package as the drum rotates. Thus, the patented device is not suitable for making an impression in metal nor for being operated by the reciprocating ram of a punch press. A multicharacter punch numbering stamp has been made for a punch press by the Conic Company Ltd. of Okayama, Japan, but the digits of the numbering wheel must be individually set by hand between stamping operations. Thus each time the machine is run, it will continue to stamp the same number until the press is stopped and the wheels are rotated by hand to provide a new number. While numbering devices themselves are available commercially, there is no way to operate them using a high speed computer controlled punch press. Consequently, as far as the applicants were able to determine, no punch press tool for stamping successive multicharacter impressions into a workpiece has been developed that is able to be actuated by the rapidly reciprocating ram of an automated punch press and is capable of successively stamping numbers or other characters in sequence into a workpiece such as a sheet of metal. 
     In view of these and other deficiencies of the prior art, it is one object of the present invention to find a way to enable a high speed computer operated punch press to reliably impress alphanumeric characters or other indicia a selected depth into the surface of a workpiece and to advance the characters each cycle of the press ram. 
     Another object of the invention is to provide a device of the kind described in which the characters to be stamped are extended out below the unit but not far enough to strike objects unintentionally as the punch press operates and are preferably able to accommodate workpieces of various thicknesses. 
     These and other more detailed and specific objects and advantages of the present invention will be better understood by reference to the following figures and detailed description which illustrate by way of example but a few of the various forms of the invention within the scope of the appended claims. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention provides a punch press tool for stamping successive multicharacter impressions in a workpiece such as a piece of steel, sheet metal, or other workpiece, that includes a guide body in which a stamp driver is slidably mounted for being driven downwardly toward the workpiece by a punch press ram which is a standard part of a high speed commercial computer operated punch press. A multicharacter marking stamp is supported at the lower end on the stamp driver for reciprocal movement therewith. The marking stamp includes multicharacter wheels that are rotated automatically during operation for advancing characters in sequence responsive to the movement of a character advancing arm. At least one character stamp operating lever is operatively associated with the advancing arm of the stamp driver and is arranged for articulation responsive to the motion of the punch press tool. On the operating lever is a pressure element that is operatively associated with the character advancing arm of the multicharacter stamp for indexing the arm to sequentially position successive characters in an operative position responsive to a stroke of the punch press ram that drives the characters of the marking stamp into the workpiece. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a bottom perspective view of a punch press tool in accordance with the invention, showing its marking stamp in the operating (extended) position. 
         FIG. 2  is a fragmentary view of  FIG. 1  with the stamp in its raised (inoperative) position. 
         FIG. 3  is a top perspective view of the press tool of  FIG. 1 . 
         FIG. 4  is a central vertical sectional view of the tool of  FIGS. 1-3  with the stamp in the up or retracted position. 
         FIG. 5  is a view similar to  FIG. 4  with the stamp in the down or operating position. 
         FIG. 6  is a bottom exploded perspective view of the tool of  FIGS. 1-5 . 
         FIG. 7  is a bottom perspective view of stamp operating levers of  FIG. 6 . 
         FIG. 8  is a partial vertical sectional view similar to  FIG. 4  but with the character stamp removed. 
         FIG. 9  is a partial vertical sectional view similar to  FIGS. 5 and 8  showing. diagrammatically another embodiment of the invention with a single stamp operating lever. 
         FIG. 10  is a plan view of a stamping made with the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In  FIGS. 1-3  the punch press tool according to the invention, indicated generally by the numeral  10  comprises two major parts; a guide body  18  and a stamp driver  12  of cylindrical shape having a cylindrical boss  12   a  at its upper end that is bored at  12   b  to receive an adjustable striker head  12   c  of cylindrical shape which is screw threaded into the lower portion of the stamp driver by means of threads  12   d . The lower part of the stamp driver  12  is slidably mounted in a vertically disposed bore  16  in the guide body  18  which is provided on its outer surface with circumferentially spaced apart longitudinally extending keyways  18   a  for holding it at the proper angle about a vertical axis. 
       FIGS. 4 and 5  show how during use, the stamping tool  10  is mounted for operation on the upper turret  20  of a punch press by being placed within a circular tool holder  22  of conventional well known construction that is itself supported within an adapter ring  24 . The tool  10  is supported on the tool holder  22  by means of lifter springs  22   a . In operation, the upper punch press turret  20  rotates rapidly on a vertical axis (not shown) which is behind the tool  10  to place various tools in alignment with the punch ram  26  of the punch press as the ram reciprocates on a vertical axis indicated by an arrow  28  to strike whichever tool mounted on the turret is located in the punching station beneath the reciprocating ram  26 . One or more keys  30  in the tool holder  22  maintain the guide body  18  in the correct angular position about a vertical axis during operation. Between the stamp driver  12  and the guide body  18  are mounted several compression springs  5  for elevating the stamp driver between strokes. The stamp driver  12  has at its lower end a stamp driver end plate  12   e  which is held in place by bolts  13  and a lever bracket  12   f  which is secured in place by a bolt  15 . 
     Other punch assembly units of various designs suited for use in a high speed punch press are described in U.S. Pat. Nos. 5,054,347 and 6,895,787 as well as U.S. Pat. Nos. 7,658,134 and 7,726,554 which are all incorporated herein by reference. 
     Characters provided on a marking stamp  52  are advanced by an operating lever assembly that in  FIGS. 1-8  comprises a driving lever  42  and a driven lever  46 . Attached to the lower end of the lever bracket  12   f  of stamp driver  12  by a set screw or other fastener are horizontal pivot pins  40  upon which is pivotally mounted the generally U-shaped character stamp operating lever  42  (the driving lever) the outer end of which is pivotally secured to a horizontally disposed pivot pin  44  that is carried by the guide body  18 . As seen best in  FIGS. 6 and 7 , the inner free ends of the U-shaped lever  42  have upwardly facing convex working surfaces  42   a  that are engaged as shown in  FIG. 8  with the free end at the right of a second stamp operating lever  46  (a driven lever) which is mounted for pivotal movement on horizontal pins  48  also carried on bracket  12   f  ( FIG. 6 ) of the stamp driver  12 . Thus, as lever  42  pivots counterclockwise its working surface  42   a  allows lever  46  to pivot in the opposite direction but lever  42  is not physically connected to lever  46 . The lever  46  extends from pivots  48  toward the left at  46   a  and has on its lower surface an operating pad or other pressure applying element  46   c  that is engaged during use with the upper surface of a roller  50  which is secured to the free end of a character advancing arm  51  of the multicharacter marking stamp  52  (shown in dotted lines in  FIG. 5 ) which is itself affixed to the lower end of the stamp driver  12  by a draw bolt  54  so that during operation as the ram  26  of the punch press reciprocates, its engagement with the striker head  12   c  drives the stamp driver  12  downwardly through the guide body  18  thereby forcing the marking stamp  52  downwardly and into contact with a workpiece  60  which is supported on an anvil  62  so as to form an impression in its upper surface. 
     It can be seen that the invention allows the lengths of the lever arms of levers  42  and  46  to be chosen so as to move the operating pad  46   c  any desired distance as the ram and the stamp driver  12  reciprocate; whatever distance is correct for a particular actuator arm  51 . 
     The marking stamp  52  can be of any suitable commercially available construction such as a series 2000 automatic numbering head manufactured by the Pryor Company Ltd. of Sheffield England. Other suitable automatic sequential numbering stamps are manufactured by the Numberall Stamp &amp; Tool Company of Sangerville, Me., USA, and by Mecco Partners LLC of Ingomar, Pa., USA. These multicharacter marking stamps are each provided with multicharacter e.g. digital wheels  52   a  that are rotated incrementally during operation for sequentially advancing raised characters to place a series of letters or numbers located in an operating position at the bottom of the stamp so that the numbers or other characters increase or advance in a predetermined sequence responsive to the indexing of a character advancing arm  51  which swings up and down during operation through an arc so as to advance the number wheels one character at a time, each time the arm  51  is indexed upwardly by one or more return elements for biasing the arm  51  upwardly as pressure applied by the driven lever is released. The return element can be of any suitable construction such as a weight, compressed air, hydraulics, an electric solenoid, rubber or the like such as a pair of return springs  53  that are connected between the arm  51  and the top of stamp  52 . The return spring  53  serves to advance the character wheels  52   a  of the stamp  52 , whereas the stamp lever assembly forces the character advancing arm in the opposite direction (downwardly) to a retracted position against the tension of the return spring as the stamp driver  12  moves upwardly. Thus, in operation a downward stroke of the ram  26  drives the marking stamp and one or more of the raised characters that are in an operative position at the lower end of the stamp into the workpiece  60  to provide an impression of those characters in its upper surface typically with sequential numbers in successively stamped parts  80  ( FIG. 10 ). 
     Secured to the lower end of the guide body  18  by means of screws or other suitable fasteners is a stripper  18   b  having a rectangular opening  18   c  for the character wheels  52   a  of the stamp  52 . The stripper  18   b  serves to hold the workpiece  60  in place as the impression is made by the character wheels of the stamp  52 .  FIGS. 1 and 5  show how the character wheels  52   a  are extended downwardly and out through the opening  18   c  a short distance but not far enough to strike other objects as the press operates. 
     By manually retracting the height adjustment locking button  14 , then raising or lowering the striker head  12   c  by rotating it manually so as to screw it up or down on the threads  12   b  on the stamp driver  12 , the distance that the raised characters on the character wheels  52   a  protrudes through the opening  18   c  ( FIGS. 1 and 5 ) can be accurately set at any selected amount to thereby accommodate workpieces  60  of any thickness while also controlling the depth of the character impressions into the surface of the workpiece  60 . 
     To inactivate the stamp  52 , the draw bolt  54  is disconnected from the stamp  52  which is removed. The driven operating lever  46  is then rotated 180° about pivot  48  to separate actuator advancing arm  51  from the driven operating lever  46 . Stamp  52  is then replaced and the bolt  54  is connected. Operating lever  46  is then rotated to a position where it can rest on the stripper  18   b  i.e. on the opposite side of roller  50 . This enables the stamp  52  to repeatedly impress the same number or other character into the workpiece  60  whenever desirable or necessary. 
     Refer now to  FIG. 9  which illustrates diagrammatically another possible operating lever assembly employing a single operating lever  27  having a fulcrum pivot  27   a  that is supported on a flange  19  which is connected to the guide body  18  and a movable pivot  27   b  at its outer end that is in turn connected to a modified lever bracket  12   g  spaced outboard of the fulcrum pivot  27   a  so as to cause operating surface  27   c  of the lever  27  to be raised when the stamp driver  12  is lowered. The springs  53  are then able to advance the characters on wheels  52   a  sequentially to the next appropriate number or letter as pressure on arm  51  is removed. The use of two levers  42  and  46  rather than one does, however, provide unexpected benefits; lever  46  can swing through a greater arc than a single lever and can have the same radius as arm  51 . We also found that using two levers allows the stamp to be removed and the pressure pad  46   c  then placed in a position where it is inactive. Thus, the use of two levers rather than a single lever makes it possible to inactivate the stamp advancing mechanism when desired since it enables lever  46  to be moved to the opposite side of roller  50  i.e. below the roller where it cannot move the roller since in that position it is not in contact with working surface  42   a  of lever  42 . 
     The invention provides outstanding results and unique capabilities. It was found that it is able to actuate a stamp  52  with a relatively short stroke of the ram, typically about 7 mm., even though the actuator arm  51  for the multicharacter stamp  52  must move much further; about 21 mm. while at the same time providing a way to inactivate or disengage the character stamp advancing mechanism when desired so that the stamp is able, when necessary, to continue stamping the same number or other set of characters. It is also able if and when necessary to index the stamp to the next digit or letter between strokes and not during the punching operation, in other words, the character stamp can be advanced during the upward stroke of the punch. Furthermore, the character stamp when in the operating position does not extend too far from the lower end of the tool where it could create an obstruction, i.e., where it might strike other objects as the tool is moved rapidly from one position to another while the press operates. In addition, it is capable of moving the character stamp actuator arm in the upward direction while a machine component (a guide body sleeve surrounding the character stamp) moves the opposite direction, i.e., downwardly. It is also able to regulate the stamp depth and to accommodate workpieces of different thicknesses. 
     Many variations of the present invention within the scope of the appended claims will be apparent to those skilled in the art once the principles described herein are understood.