Patent Publication Number: US-6905269-B2

Title: System and method for continuous label printing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/393,609 filed Jul. 3, 2002, entitled Continuous Label Printing Apparatus, System and Method, which is hereby incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to a printing system and, more particularly, to a continuous label printing system utilizing a sheet printer. 
   Generally, labels are printed by a continuous printing process utilizing a roll label print media. Generally the continuous process for printing labels has been reserved to the flexographic, gravure and thermal printing processes. 
   Flexographic printing, also known as aniline printing, is a form of relief printing in which a slightly raised image of the label is formed on a printing plate by engraving. In flexographic printing, the raised image is inked and the ink is transferred directly to the print media, typically by a large rotary press. Color labels are printed by passing the print media through the system multiple times. In a four color printing process, the print media is passed through the system four times, once for each of black, cyan, magenta and yellow. Each plate has a high initial cost and has a limited life, requiring periodic replacement. While flexographic systems are efficient at printing very high volumes of labels and/or other documents, flexographic systems also require extensive set-up time (i.e. engraving and replacing the plates) making it cost prohibitive for small runs. Further, flexographic systems are also very large and expensive to purchase. Generally, a print run must be on the order of millions of labels in order for the print run to be cost effective. 
   Another process for printing labels is known as gravure or rotogravure printing. In gravure printing, the printing area is etched into a surface of a plate or a metal cylinder. In contrast to flexographic printing, the etched out sections are filled with ink and the excess ink on the non-image area is removed by a thin stainless steel blade referred to as a doctor blade. The size and depth of the etched out areas determine how much ink is deposited on the print media. Gravure etched cylinders can cost thousands of dollars. Generally, a print run for a gravure system is on the order of millions of copies in order to be cost effective. Thus, gravure systems suffer from the same drawbacks for a short print run as do flexographic systems. 
   Thermal printing is a non-impact printing process that uses heat to register an impression on paper. A typical thermal transfer printer has a print head containing many small resistive heating pins that on contact, either melt wax-based ink onto ordinary media or burn dots onto specially coated media. Similar to flexographic printing, thermal printing is usually accomplished through a multi-pass process wherein each color is applied separately. However, thermal-transfer printing systems are not bound by the limits of a printing plate and can rapidly change the image being printed. The major drawback to thermal printing compared to flexographic and gravure printing, is the relatively low quality of the printed image, especially on print media that is not specialty paper. Further, thermal printing equipment is also very expensive to purchase and to maintain as the print heads must be cleaned frequently to remove melted wax or burned-on ink. 
   What is needed but not provided by the prior art, is a continuous label printing system that allows for just-in-time printing of variable information color images, text and bar codes in small batches without the need for engraved printing plates such as used on flexographic and gravure printing, and which provides a quality equivalent to flexographic and gravure printing. Further, the continuous label printing system should be capable of utilizing print media from a roll and provide the printed-on media in a roll. 
   BRIEF SUMMARY OF THE INVENTION 
   Briefly states, the present invention provides a system for continuous printing. The system comprises: an unwind storing a roll of print media; a cutter which receives the print media from said unwind and which cuts the print media into sheets of variable length; a sheet printer which receives the sheets of print media from said cutter, prints a design on each of the sheets and outputs printed-on sheets; an edge sensor which detects a leading edge of each of the printed-on sheets when output from said sheet printer; a rewind which receives the printed-on sheets output from said sheet printer; and a controller which receives an output signal from said edge sensor indicating the detection of the leading edge and, based upon the output signal, synchronizes said rewind and the received printed-on sheets to cause a trailing edge and the leading edge of each successive printed-on sheet received by said rewind to be butted one to the other on the rewind. 
   The present invention further provides a system for continuous printing. The system comprises: an unwind storing a roll of print media; a cutter which receives the print media from said unwind and which cuts the print media into sheets; a sheet printer which receives the sheets of print media from said cutter, prints a design on each of the sheets and outputs printed-on sheets; and a controller which receives an output signal from said printer and, based upon the output signal, synchronizes said unwind, said cutter and said sheet printer to provide a substantially continuous flow of print media from said unwind to said sheet printer. 
   The present invention also provides a system for continuous printing. The system comprises: sheet printer which receives sheets of print media and outputs printed-on sheets of the print media; an edge sensor which senses a leading edge of each of the printed-on sheets when output from said printer; a rewind which receives the printed-on sheets output from said printer; and a controller which receives an output signal from said edge sensor indicating the detection of the leading edge and synchronizes, based upon the output signal, said sheet printer and said rewind to cause a trailing edge and the leading edge of each successive printed-on sheet received by said rewind to be butted one to the other on the rewind. 
   The present invention also comprises a method of continuous printing. The method comprises: feeding sheets of print media to a sheet printer; printing a design on each of the sheets and outputting printed-on sheets; and feeding each of the printed-on sheets to a rewind for storage thereon, wherein said sheet printer and said rewind are synchronized such that leading and trailing edges of successive printed-on sheets received by said rewind are butted one to the other so as to form a roll of print media on the rewind. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
     In the drawings: 
       FIG. 1  is a diagram of a continuous label printing system in accordance with a preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Certain terminology is used in the following description for convenience only and is not limiting. The words, “right”, “left”, “lower”, and “upper” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the object discussed and designated parts thereof. The terminology includes the words above specifically mentioned, derivatives thereof and words of similar import. Additionally, the word, “a” as used in the claims, means “one or more than one.” 
   In the drawings, wherein like numerals are used indicate like elements throughout, there is shown in  FIG. 1  a diagram of a continuous printing system  10  in accordance with a preferred embodiment of the present invention. 
   In the preferred embodiment, print media  21  on which labels are to be printed is stored as a roll  20  on an unwind  14 . Preferably, the print media  21  comprises blank label stock comprising a paper tape having a dielectric layer on one side and an adhesive layer and a releasable backing layer on the other side. However, the print media  21  may be formed of other materials such as, for example, vinyl or polyester and still be within the spirit and scope of the invention. The label unwind  14  includes all the necessary drives, rollers, motors, gears, pulleys, guides and mounting brackets to unwind the roll  20 . Unwinds  14  are well known in the printing art and therefore are not described further, for the sake of brevity. 
   In the preferred embodiment, the print media  21  is fed from the unwind  14  to a sheet cutter  16 . The sheet cutter  16  cuts the print media  21  into separate sheets  22  of variable length depending upon a synchronizing signal from a controller  18  (described below). Cutters  16  for cutting label stock are well known in the printing art and therefore are not described further, for the sake of brevity. 
   Preferably, the sheets  22  formed by the cutter  16  are dispensed to a sheet printer  12  containing a sheet feeder  19 . The sheet feeder  19  provides for temporary storage of the sheets  22 . Sheets stored in the sheet feeder  19  are dispensed, one at a time to a print engine in the sheet printer  12  for printing on by the sheet printer  12 . While it is preferred that the sheet feeder  19  is integral with the sheet printer  12 , a separate sheet feeder is within the spirit and scope of the invention. 
   Preferably, the sheet printer  12  is capable of receiving and printing on sheets  22  of variable lengths, of printing a unique design on each single sheet  22  and outputting printed-on sheets  23 . In the preferred embodiment, the sheet printer  12  is a single-pass color electrophotographic printer, i.e. a printer using the electrophotographic process, capable of printing on sheets  22  of different lengths at least as long as 47.24 inches. Printers having the aforementioned characteristics are manufactured by Okidata Corporation as the series C9300/9500, C7300/C7500 and C5100/C5300 printers. However, as would be clear to those skilled in the art, it is not necessary for the sheet printer  12  to be able to print on sheets of different lengths or on lengths greater than standard letter size. Further, the present invention is not limited to using a color electrophotographic printer. The printer  12  could be, for instance, an ink jet printer, a bubble-jet printer, or an impact printer such as a dot matrix printer, and could be a black and white printer, and still be within the spirit and scope of the invention. 
   The preferred embodiment further includes a sensor  30  for detecting a leading edge of each of the printed-on sheets  23  when output from the sheet printer  12 . The sensor  30  may be an opto-electric device such as a photo-diode, a mechanical device, an electromechanical device or a combination thereof capable of edge detection. In the preferred embodiment, the sensor  30  is a photo diode and accompanying electronic circuitry. The sensor  30  provides an output signal to the controller  18  which indicates a time signifying detection of the leading edge of each printed-on sheet  23  by the sensor  30 . 
   The preferred embodiment of the printing system  10  also includes a rewind  26  which receives the printed-on sheets  23  output from the sheet printer  12  and stores the printed-on sheets  23  as a roll  25  such that the leading and trailing edges of each successive printed-on sheet  23  received by the rewind  26  are butted one to the other. The rewind  26  includes all the necessary drives, rollers, motors, gears, pulleys, guides and mounting brackets to form the roll  25  of the printed-on sheets  23  on the rewind  26 . Rewinds  26  are well known in the printing art and therefore are not described further, for the sake of brevity. 
   In the printing system  10 , the time for printing an image on each individual sheet  22  in the sheet printer  12  may vary from sheet  22  to sheet  22 . In the preferred embodiment, in order that the sheet feeder  19  not be over or under run by the sheets  21  received from the cutter  16 , and for the printing system  10  to abut the printed-on sheets  23  in roll form  25  on the rewind  26 , operation of the unwind  14 , the cutter  16 , the printer  12 , and the rewind  26  are synchronized. In the preferred embodiment, the output signal from the sensor  30  is provided to the controller  18  for synchronizing the unwind  14 , the cutter  16 , the printer  12  and the rewind  26 . 
   The controller  18  synchronizes the unwind  14 , the cutter  16  and the printer  12  such that the print media  21  is drawn from the unwind  14  at a rate which can be cut and processed by the cutter  16 , the printer  12  and the rewind  26  to provide a substantially continuous flow of print media from the unwind  14  to the printer  12  without an excessive over or under run of the sheets  22  in the sheet feeder  19 . Preferably, the controller  18  synchronizes the unwind  14 , the cutter  16 , and the printer  12  by commanding the unwind  14  to feed a desired length of print media  21  to the printer  12 . At the moment the desired length of print media  21  passes a blade of the cutter  16 , the controller  18  commands the cutter  16  to cut the print media  21  to form a sheet  22  of the desired length, which sheet  22  is then deposited in the sheet feeder  19 . The controller  18  then commands the printer  12  draw the sheet  22  from the sheet feeder  19  and to print an image on the sheet  22 . If a successive sheet is to be printed upon, the controller  18  commands the unwind  14  to feed another desired length of print media to the printer  12  based upon the receipt of the output signal from the sensor  30 , and so on. 
   The controller  18  also controls the rewind  26  to cause the trailing edge and leading edge of each successive printed-on sheet  23  output from the printer  12  and received by the rewind  26  to be butted one to the other on the rewind to form a roll  25  of virtually continuous printed-on media  21 ′ on the rewind  26 . The output of the sensor  30  synchronizes the revolution of the rewind  26  with the leading edge of each printed-on sheet  23  by utilizing the outputs signal from the sensor  30  which indicates that the leading edge of the printed-on sheet  23  is concurrent with the sensor  30 . In the preferred embodiment, the revolution of the rewind  26  is made discontinuous, i.e., the instantaneous position of the rewind  26  is adapted to cause the leading and trailing edges of each successive printed-on sheet  23  to abut as the printed-on sheets are wound on the rewind  26 . Alternatively, the rewind  26  could operate at a generally fixed revolution rate, and the timing of the feed of the printed-on media  23  to the rewind  26  could be adjusted. 
   In addition, to receiving the edge detecting signal from the edge detector  30 , the controller  18  accepts signals from the unwind  14 , the cutter  16 , the printer  12  and the rewind  26 . Such signals are, for example, indicative of the positions of the unwind  14 , rewind  26  and the print media  21  and the operability status of the unwind  14 , the cutter  16 , the printer  12  and the rewind  26 . 
   The controller  18  is based upon a computer of conventional design. In the preferred embodiment the controller  18  and a corresponding computer program are incorporated into an existing computer within the printer  12 . Alternatively, the controller  18  may be a separate computer within the printer  12 ; or incorporated into the unwind  14 , the cutter  16 , or the rewind  26 ; or be a separate computer such as a personal computer (PC) or an industrial controller. 
   In addition to synchronizing the unwind  14 , the cutter  16 , the printer  12  and the rewind  26 , the controller  18  also receives the images to be printed on the print media  21  from an external equipment  32  such as a computer and forwards the print images to the print engine of the sheet printer  12 . The electrical interface for interfacing the controller  18  to the external equipment could utilize any one of a number of communication means such as, for example, Ethernet, IEEE-1284, and universal serial bus (USB). In addition to receiving images from the external equipment  32 , the controller  18  also interchanges control and status data with the external equipment  32 . 
   Optionally, the label printing system  10  also includes a sheet binder  24  interposed between the sheet printer  12  and the rewind  26 . The sheet binder  24  binds or attaches successive printed-on sheets  23  into a continuous roll  25  on the rewind. In the preferred embodiment, the sheet binder  24  attaches the successive sheets with an adhesive. However, the sheet binder  24  could also attach the sheets  23  by other means, such as welding, stitching, taping within the spirit and scope of the invention. 
   Optionally, the printing system also includes a coating system  34  for coating the fronts or the backs of the printed-on sheets  23  with glue, polymeric material, clear coat film and the like for attachment of the print media  21  onto packages or for protection of the ink deposited on the print media  21 . 
   In a second preferred embodiment, the printing system is configured to directly utilize the print media  21  in the form of sheets  22  of variable length. The sheets  22  may be received by the sheet feeder  19 , or may be received from one or more trays within the printer  12  after being manually loaded into the trays. 
   In a third preferred embodiment, the printing system  10  is configured for feeding the print-on sheets  23  directly to a labeling system (not shown) instead of to the rewind  26 . When configured for feeding the printed-on sheets  23  to the labeling system, the printed-on sheets  23  are supplied directly to the labeling system after passing the sheet binder  24 . Desirably, the labeling system may include rollers, cutters, joiners, applicators and the like for directly placing the labels onto product packages such as bottles, cans, boxes, cases and the like. 
   From the foregoing it can be seen that the present invention comprises a system and method for continuous, just-in-time, short run printing of variable image labels, on print media from a roll, utilizing a sheet printer. However, as would be appreciated by those skilled in the art, the present invention is not limited to printing labels from roll media. The present invention can also be used for printing signs, banners, tags etc. and can utilize print media other than roll media, such as card stock, waterproof and UV resistant synthetics, fan-fold continuous forms etc. 
   It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.