Abstract:
A rotary die cut stacking system for use with a rotary die cutter having a rotary die configured to output die-cut sheets of material, the system including a stacker and a layboy for carrying die-cut sheets of material in a first direction from the die cutter to the stacker, wherein, the layboy has upper arms and lower arms defining a nip region therebetween for receiving the die-cut sheets, at least some of the upper arms and at least some of the lower arms being moveable transversely to the first direction, the layboy including at least one optical beam generator configured to direct an optical beam against a portion of the rotary die cutter so that a position of the arms relative to the rotary die can be determined based on the location of the optical beam on the portion of the rotary die cutter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application 60/911,226, filed Apr. 11, 2007, the entire contents of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention is directed towards a rotary die cut stacking system having an optical beam generator to assist with the positioning of layboy arms relative to a die cutter and to a method of mounting an optical beam generator in a rotary die cut stacking system, and, more specifically, towards a rotary die cut stacking system having a plurality of lasers mounted on layboy arms for assisting with the positioning of the layboy arms relative to a rotary die and to a method of mounting lasers on the layboy arms of a rotary die cut stacking system. 
         [0004]    2. Description of Related Art 
         [0005]    Devices for stacking sheets of material received from a rotary die cutter are well known. One example of such a device is the AGS2000 Rotary Die Cut Stacker made by the assignee of the present invention, A.G. Stacker, Inc., Weyers Cave, Va. Further examples of such devices are disclosed in U.S. Pat. Nos. 3,321,202 to Martin and 3,419,266 to Martin, each of which is expressly incorporated by reference in its entirety. 
         [0006]      FIGS. 1 and 2  illustrate a conventional rotary die cut stacking system. As illustrated therein, the system  100  typically comprises a layboy section  102  which receives blanks or sheets of material, such as those produced by a rotary die cutting machine having a top die  126  and a bottom drum  128 , and discharges the blanks onto a transfer conveyor  104 . The transfer conveyor  104  receives the blanks and transports them to a main conveyor  106 . The main conveyor  106  has an intake end  108  and a discharge end  110 . At its intake end  108 , the main conveyor  106  is mounted to a base  112  at a pivot point  114  so that the conveyor may be pivoted to raise the discharge end  110  of the conveyor  106 . At the discharge end  110  of the conveyor  106 , the blanks pass through an accumulator section  116  and form a stack at a stacking location  121 . 
         [0007]    The layboy section  102  has a first plurality of upper arms  130  and a second plurality of lower arms  132  which may be, but are not necessarily, equal in number. Typically, six to eight upper arms and six to eight lower arms are provided. Each of the upper and lower arms  130  and  132  is a moveable assembly rotatably supporting a driven belt  134 . The belts  134  on the upper and lower arms  130  and  132  form a nip region  136  where sheets or blanks from the rotary die cutter are drawn into the layboy section  102 . 
         [0008]    Conventional die cutting machines may output one, two, three of four rows of blanks simultaneously. As these rows of sheets enter the nip region  136  in rows of one, two, three or four and move along the layboy section  102 , the upper and lower arms  130 ,  132  steer the blanks and change the orientation and/or row spacing of the blanks in a predetermined manner so that the blanks are deposited onto the transfer conveyor  104  in a desired manner. When the layboy arms are used to space multiple rows of blanks, they will often not be parallel to each other, and they will not all be perpendicular to the surface of the die  126 . 
         [0009]    In conventional systems, an operator sets the positions of the layboy arms while standing on one side of the layboy section. Generally, a long rod is used to pull or push the individual arms back and forth in the width direction of the stacking machine to put the arms into appropriate positions. The layboy arms should be positioned so that they are not located between adjacent blanks and so that they contact parts of the blanks that can be readily driven. For example, on blanks having a plurality of openings or having flaps, it may be desirable for the bands of the layboy arms to contact the blanks at positions away from the flaps or openings. However, layboy  102  may be 80 to 200 inches wide, and the arms may each be angled differently with respect to the surface of the rotary die  126 . The distance from the edge of the layboy  102  to a given arm  130 ,  132  and the angle that a particular arm makes relative to the die  126  make it difficult to determine whether the layboy arms  130 ,  132  are positioned appropriately. Therefore, several adjustments may be necessary when a new run of blanks is started to determine the proper position of each of the six to eight layboy arms. Shutting down a production line while such adjustments are made reduces efficiency and can be costly. Because the relative positions of the arms and the die may not be readily determined, it may be necessary to stop the die cutter and reposition the layboy arms several times before a satisfactory placement is obtained. Accordingly, it would be desirable to provide an apparatus and method for helping a machine operator to place the arms of a layboy in a desired position relative to a die cutter in an efficient manner. 
       SUMMARY OF THE INVENTION 
       [0010]    These and other problems are addressed by the present invention, a first aspect of which comprises a rotary die cut stacking system for use with a rotary die cutter having a rotary die configured to output die-cut sheets of material, the rotary die cut stacking system including a stacker with a conveyor for transporting die-cut sheets to a stacking location and a layboy for carrying the die-cut sheets of material in a first direction from the rotary die cutter to the stacker. The layboy comprises a first plurality of upper arms and a second plurality of lower arms defining a nip region therebetween for receiving the die-cut sheets, and at least some of the first plurality of upper arms and at least some of the second plurality of lower arms are moveable transversely to the first direction. The layboy also includes at least one optical beam generator associated with at least one of the first plurality of upper arms or second plurality of lower arms that is configured to direct an optical beam against a portion of the rotary die cutter. In this manner, a position of the at least one of the first plurality of upper arms or second plurality of lower arms relative to the rotary die can be determined based on the location of the optical beam on the rotary die cutter. 
         [0011]    Another aspect of the invention is a method performed with a rotary die cutting system that includes a rotary die cutter having a rotary die for outputting sheets of material in a first direction, a stacker for stacking sheets of material output from the rotary die cutter, and a layboy having a plurality of upper and lower arms for receiving sheets of material output from the rotary die cutter and transporting the sheets to the stacker. The plurality of upper and lower arms are slidable in a second direction transverse to the first direction. The method provides an indication of a position of at least one of the plurality of upper and lower arms relative to the rotary die cutter and includes steps of associating a first optical beam generator with at least one of the plurality of upper and lower arms, aligning the first optical beam generator with the first arm, and directing an optical beam produced by the first optical beam generator against the rotary die cutter. 
         [0012]    A further aspect of the invention comprises a rotary die cut stacking system for use with a rotary die cutter having a rotary die configured to output die-cut sheets of material. The stacking system comprises a stacker with a conveyor for transporting the output die-cut sheets to a stacking location and a layboy carrying the die-cut sheets of material in a first direction from the rotary die cutter to the stacker. The layboy comprises a plurality of upper arms and lower arms defining a nip region therebetween for receiving the die-cut sheets, and at least some of the plurality of upper arms are moveable transversely to the first direction. The layboy further includes a first plurality of lasers mounted on the first plurality of upper arms that are configured to direct a first plurality of laser beams against the rotary die. In this manner, a position of each of the first plurality of upper arms relative to the rotary die can be determined based on the location of the first plurality of laser beams on the rotary die. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    These and other aspects of certain embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
           [0014]      FIG. 1  is a top plan view of a conventional rotary die cut stacking system including a die cutter, a layboy section and a stacker; 
           [0015]      FIG. 2  is a side elevational view of the rotary die cut stacking system of  FIG. 1 ; 
           [0016]      FIG. 3  is side elevational view of the layboy section of the rotary die cut stacking system of an embodiment of the present invention in which one upper and one lower arm of the layboy section are visible; 
           [0017]      FIG. 4  is an isometric view of an upper arm of the layboy section of  FIG. 3  with an optical beam generating device mounted thereon; 
           [0018]      FIG. 5  is an isometric view of an upper arm of the layboy section of  FIG. 3 , with an optical beam generator mounted therein; 
           [0019]      FIG. 6  is a partial isometric view of the layboy section of  FIG. 3  taken in the direction of line VI-VI in  FIG. 3 ; and 
           [0020]      FIG. 7  is a partial isometric view of the layboy section of  FIG. 3  taken in the direction of line VII-VII in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Referring now to the drawings, wherein the showings are for purposes of illustrating preferred embodiments of the invention only, and not for the purpose of limiting same,  FIG. 3  illustrates a rotary die cutting system  200  that includes a stacker  202 , a layboy section  204 , and a rotary die cutter  206  having a rotary die  208  and an opposite drum  210 . Layboy section  204  comprises a first plurality of upper arms  212 , only one of which is illustrated in  FIG. 3 , and a second plurality of lower arms  214 , only one of which is illustrated in  FIG. 3 . The number of upper arms  212  may differ from the number of lower arms  214 , but it is often the same. 
         [0022]    Each of the upper arms  212  and lower arms  214  includes a plurality of grooved wheels  216  for supporting a continuous band of material  218 . The bands  218  on the upper arms  212  and the bands  218  on the lower arms  216  approach each other in a nip region  220  into which sheets of material move when they enter the layboy section  204 . The bands  218  on the upper arms  212  are driven in a first direction by a drive (not illustrated), clockwise in  FIG. 3 , and the bands on the lower arms  214  are driven in a second direction, opposite to the first direction and counterclockwise in  FIG. 3 , so that sheets entering nip region  220  are pulled into and along layboy section  204  toward stacker  202 . The upper arms  212  and lower arms  214  can be individually positioned laterally with respect to rotary die  208  and angled with respect to the surface of the rotary die  208  and with respect to each other for reasons known to those of ordinary skill in the art. 
         [0023]    At least one, and in the preferred embodiment, each, of the upper arms  212  is provided with an optical beam generator for forming a dot or other image on a surface of rotary die cutter  206 . A presently preferred optical beam generator comprises a laser such as laser  230 ; however, other light sources capable of forming a discernable image on the die cutter  206  could alternately be used. Laser  230  may be mounted in a housing  232  on an upper surface  234  of upper arm  212 , as illustrated in  FIG. 4 , so that the beam  236  generated by the laser impinges on the surface of rotary die  208  as a dot  237  or other desired shape. An alternative placement of laser  230  is illustrated in  FIG. 5  which shows housing  232  mounted in the interior  242  of upper arm  212 . This provides additional protection for laser  230  while still allowing beam  236  to exit from the end of the upper arm  212  and impinge on the surface of the die  208 . Suitable wiring  244  may be connected to a switch or a controller (not illustrated) for controlling the lasers. The wiring  244  may, using either laser placement, be routed through the interiors  242  of the upper arms  212 . Low power lasers, such as the type used in conventional laser pointers, are known that can operate on battery power. In some systems, it may be desirable to use such battery powered lasers on the upper arms  212  to avoid the need for wiring. Such lasers could be controlled individually or by a suitable remote control (not illustrated). 
         [0024]    Optionally, additional lasers  240  can be mounted on lower arms  214  with their beams directed against the rotary die  208  to assist with the alignment of the lower arms  214 . However, it has generally been found adequate to provide only lasers  230  on the upper arms  212 ; once the upper arms are aligned as discussed hereinafter, the lower arms can be positioned relative to the upper arms with sufficient precision for most purposes. If lasers  240  are provided on the lower arms, it may be desirable to use lasers that produce a color of light different than the light emitted by the lasers  230  mounted on the upper arms to distinguish lasers  230  of the upper arms  212  from the lasers  240  of the lower arms  212 . Alternately, the lasers  230  of the upper arms could be aimed along a first portion of the die  208  while the lasers of the lower arms  214  could be aimed along a second portion of the die  208 . Only lasers  230  of upper arms  212  are discussed further herein; the placement and use of optional lasers  240  on lower arms  214  will be clear from the description of the lasers  230 . 
         [0025]    In some embodiments, lasers  230  may be illuminated continuously, while in others, the lasers  230  may be controlled by a switch or a controller to turn on only when upper arms  212  are being positioned. Optionally, as illustrated in  FIG. 3 , a limit switch  250  can be provided near a track on which transfer conveyor  104  is mounted. When transfer conveyor  104  moves away from die cutter  206 , which sometimes occurs during the setup of the system  200 , the limit switch  250  is opened so that lasers  230  cannot be operated. This reduces the risk of having the lasers  230  accidently shine directly into the eyes of a person in the gap. 
         [0026]    Whether the lasers  230  are mounted on upper surface  234  of upper arm  212  or in the interior  242  of upper arm  212 , the lasers  230  are aligned with the longitudinal centerline of each of the upper arms  212  and with the centerlines of grooved wheels  216  and the bands  218  supported thereon. When the upper arms  212  are perpendicular to the surface of die  208 , the location of the laser beam  236  on the surface of the die  208  provides an indication as to which portion of a blank exiting the die cutter  206  will contact bands  218 . For example, if a given laser beam  236  impinges on an area between die blades  260 , for cutting the outer edges of adjacent blanks, the operator will know that the band  218  on the upper arm  212  supporting that laser will not contact any blank reaching the layboy section  204 . Therefore, that particular layboy upper arm  212  will have to be moved. Similarly, if a given laser beam  236  impinges on a portion of the die  208  that form flaps in a die-cut sheet, the band  218  on that upper arm  212  will contact the flap of a die-cut sheet reaching that layboy arm. This is also often not desirable, and the upper arm  212  can be repositioned to impinge against a portion of the die-cutter representing the portion of the blank that should contact the band  218 . 
         [0027]    When the upper arms  212  are angled slightly with respect to the surface of die  208  there will be a difference between the location on the die illuminated by the laser beam  236  and the corresponding portion of the die-cut sheet reaching the layboy section  204 . However, those skilled in the art already appreciate the need to align arms angled with respect to the surface of die  208  in a different manner than arms perpendicular to the surface of die  208 , and laser beam  236  impinging on the surface of die  208  provides a nearly instantaneous way of appreciating the relationship between each of the arms  212  and the die  208 . It is also possible to align the laser beam  236  with a portion of rotary die cutter  206  other than die  208 , such as a portion of a housing, for example. However, when it is possible to align the laser beam  236  with the surface of the die  208 , it is a relatively simple matter for the machine operator to understand the relationship between the upper arms  212  and the die  208 . 
         [0028]    In operation, layboy section  204  is moved away from die cutter  206  to create a gap large enough for an operator to enter, and a suitable die  208  is installed on die cutter  206 . Lasers  230  should be deactivated at this time to protect the eyes of the operator standing between the layboy  204  and the die cutter  206 ; safety sensor  250  provides additional protection against accidental activation. At this time the relative angles between the upper arms  212  of the layboy section  202  are set in a manner known in the art and based in part on the number of blanks (two, three or four, for example) that will be output from the die  208 . The die cutter  206  is then moved back to a position close to the layboy  202 , and lasers  230  are actuated in a suitable manner to form points of light  237  on the surface of die  208 . An operator uses a long rod, possibly having an angled hook on one end (not illustrated) to slide each of the upper layboy arms  212  to a predetermined position relative to the upper die based in part on the location of the point of laser light on the die  208 . The lower arms  214  of the layboy are then positioned relative to the upper arms in a conventional manner, slightly offset from each of the upper arms, for example, to reduce the pinching of die-cut blanks traversing the layboy section  202 . The lasers may then be extinguished, and the operation of the die-cutting system commenced. Using lasers  230 , the set up of a new die can be done quickly and accurately with less need for slow test runs to determine where a die-cut sheet will contact one of the bands  218  and less need for the multiple adjustments of the layboy arms that were often required with conventional systems. 
         [0029]    Two possible mounting locations for lasers  230  have been described. However, the mounting of the lasers  230  is not particularly limited as long as a relationship between the laser  230  and the layboy arm  212  on which it is mounted is known. The present system, therefore can be provided as original equipment with new die cut stacking systems and also retrofitted onto existing systems without affecting the operation of those legacy systems. Because the lasers  230  do not need to be controlled by a system controller, retrofits may sometimes use separate on-off switches for the lasers  230  that are mounted in a convenient location for operators. 
         [0030]    The present invention has been described herein in terms of several presently preferred embodiments. However, various modifications and additions to these embodiments will become apparent to those skilled in the relevant arts upon a reading of the foregoing disclosure. It is intended that all such modifications and additions comprise a part of the present invention to the extent they fall within the scope of the several claims appended hereto.