Abstract:
A method for inspecting moving web material on a label application unit is provided. The web material includes repeated, pre-printed sections wherein each section corresponds to an individual package unit. The method includes detecting a position indicator located on the web material using a sensor where multiple sections of the moving web material includes a position indicator. A die section is moved in response to detection of the position indicator to re-position the die section for a cutting operation. It is determined whether movement of the die section is beyond a predetermined range using a processor. One or more of the method steps are repeated for more than one pre-printed section of the moving web material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority to provisional U.S. application Ser. No. 60/724,146, filed Oct. 6, 2005, the content of which is hereby incorporated by reference as if fully set forth herein. 
     
    
     TECHNICAL FIELD  
       [0002]     The present application relates to a quality control system and method for inspecting moving pre-printed web material.  
       BACKGROUND  
       [0003]     Many products are supplied in sealed bags, pouches or other packages formed from thin films or other flexible materials. For example, foodstuffs, tobacco products, small parts or loose items such as pharmaceuticals or other medical accessories are commonly provided in pouches or bags formed from flexible film material.  
         [0004]     The production of these products is carried out by forming such products as elongated webs which are thereafter segmented by cutting to yield lengths which are usable by the customer. While the character of the material along the length of the web may appear to be uniform, in many instances there are variations along the length of such webs. These variations may arise for example in the form of instantaneous or running defects within the material forming the web.  
         [0005]     Methods of inspecting web material following production have been developed to identify the location and nature of variations along the length of the web material. A continuous, non-stop inspection method is needed to reduce process downtime.  
       SUMMARY  
       [0006]     In an aspect, a method for inspecting moving web material on a label application unit is provided. The web material includes repeated, pre-printed sections wherein each section corresponds to an individual package unit. The method includes detecting a position indicator located on the web material using a sensor where multiple sections of the moving web material includes a position indicator. A die section is moved in response to detection of the position indicator to re-position the die section for a cutting operation. It is determined whether movement of the die section is beyond a predetermined range using a processor. One or more of the method steps are performed for more than one pre-printed section of the moving web material.  
         [0007]     In another aspect, a system for inspecting moving web material on a label application unit includes a first scanner arranged and configured to sense a position indicator carried by the moving web material. A second scanner is arranged and configured to sense a pre-printed mark. A sensor is arranged and configured to sense an edge of the moving web material. A detector is arranged and configured to detect an increase in web thickness as the moving web material passes thereby. A controller receives signals from at least one of the first scanner, second scanner, sensor and detector.  
         [0008]     Other advantages and features of the invention will be apparent from the following description of particular embodiments and from the claims. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0009]      FIG. 1  is a front view of an embodiment of a label application apparatus including quality assurance points;  
         [0010]      FIG. 2  is an embodiment of a method used to provide quality assurance and/or inspection of web material as the web material moves through the label application apparatus of  FIG. 1 ;  
         [0011]      FIG. 3  is a top view of section  3  of the label application apparatus of  FIG. 1 ;  
         [0012]      FIG. 4  is a top view of an embodiment of a label;  
         [0013]      FIG. 5  is a top view of section  5  of the label application apparatus of  FIG. 1 ; and  
         [0014]      FIG. 6  is a diagrammatic front view of an embodiment of a wrinkle detection assembly. 
     
    
     DESCRIPTION  
       [0015]     Referring to  FIG. 1 , a label application system and apparatus  10  is used, in the illustrated embodiment, to place label elements onto a web material  12 . The web material  12  includes multiple, pre-printed and repeated sections that may be used to form individual flexible pouches or bags (e.g., by separating the sections and forming the pouches or bags during a downstream forming process). As will be described in greater detail below, the apparatus  10  includes a quality control system, generally designated as  14 , having multiple quality assurance points A-E that are used to reduce the occurrence of and identify defects that may occur, for example, due to printing variations on the moving web material  12 . It should be noted that the label application unit  10  is exemplary only and should not be considered as unduly limiting as features described herein may have application in conjunction with other automated application processes.  
         [0016]     Label application apparatus  10  includes an unwind unit  16  (e.g., commercially available from Kenne Technology, Inc. (KTI), Beloit, Ill.) where rolls  18  and  20  of pre-printed web material are continuously spliced in register (e.g., tolerance of +/−0.125 inch) followed by an edge reading ultrasonic web guide  22  (e.g., commercially available from AccuWeb, Inc., Madison, Wis.). After passing through a nipped infeed tensioning dancer  24 , the web material  12  wraps around two 12 inch drums  26  and  28 , where at one of either of the two 12 inch drums, a label head  30 ,  32  (e.g., commercially available from Quadrel Labeling Systems, Inc., Mentor, Ohio) using a printed eye mark (described below) will apply a label. The two label heads  30 ,  32  operate in tandem to provide a non-stop application. However, only one label head or more than two label heads may be used.  
         [0017]     After the label application, the web material  12  is die cut in register to the printed eye mark from the underside at a die cut station  34 . The web material  12  passes through a quality assurance section  36 , described below, a flagging label head  38 , an exit nipped pacing roll  40  and a turret rewind  42 . Finished product rolls  44 ,  46 ,  48  are spliced in register on a turret rewinder (e.g., commercially available from KTI), at a designated footage.  
         [0018]     Referring now to  FIG. 2 , a quality control method  50  is used to provide quality assurance or inspection of the web material  12  as the web material moves through the label application apparatus  10 . The quality control method  50  includes verifying die register in the web running direction at step  52 , verifying label placement in the web running direction at step  54 , verifying die cut across the web running direction at step  56 , verifying label placement across the web running direction at step  58  and/or detecting wrinkles in the web material at step  59 .  
         [0019]     A. Die Register In Web Running Direction  
         [0020]     Referring to  FIG. 3 , in one embodiment, each repeated section  60  of the web material  12  includes two pre-printed blocks or eye marks  62  located at opposite edges of the web material. In the illustrated example, the eye marks  62  are located directly across the web material  12  from each other. The eye marks  62  are a color (e.g., white) in contrast to the color of the web material  12  (e.g., red). As indicated above, each section  60  of web material  12  represents a bag or pouch.  
         [0021]     In operation, die section  64  (e.g., servo controlled die  66  and anvil  68 ; see FIG.  1 ) of die cut station  34  is verified to be held to a predetermined tolerance (e.g., +/−0.1875 inch) from a standard. An optical contrast scanner  70  (or die register sensor) reads one of the eye marks  62  in order to determine position of the web material  12 . The determined position is compared to a theoretical expectancy of the eye mark  62  that is related to the number of teeth (e.g., 160 teeth, ⅛ inch CP) of the die  66 . Depending on this comparison, the die section  64  may or may not be moved in the web running direction shown by arrow  65 . In one embodiment, the correction of the die section  64  is limited to a maximum tolerance (e.g., +/−0.1875 inch). Any correction of the die section  64  greater than the maximum tolerance will be marked as “out of process window” and a signal may be sent, for example, to a programmable logic controller (e.g., commercially available from Allen Bradley).  
         [0022]     B. Label Placement In Web Running Direction  
         [0023]     Referring also to  FIG. 4 , a label  72 , which may be clear, includes blocks  74 ,  76  and  78  of varnish with a given fluorescent level printed on the label  72 . The blocks  74 ,  76  and  78  are used to locate the label  72  at different locations (e.g., top  86 , bottom  88  and leading edge  90 ). The placement of the label  72  in the web running direction is toleranced a predetermined amount (e.g., +/−0.1875 inch) from a standard and is referenced to the eye marks  62  on either edge of the web material  12 .  
         [0024]     Optical contrast scanners  92  and  94  are offset from each other in the web running direction (e.g., 0.375 inch) to create a label sensor gate. A luminescence scanner  96  (e.g., such as a QL55 microprocessor-controlled luminescence sensor, commercially available from Banner Engineering Corp.) is located in the web running direction between the scanners  92  and  94  to detect the leading edge varnish block  76 .  
         [0025]     In operation, optical contrast scanner  92  detects one of the eye marks  62  as the eye mark  62  passes thereunder, which opens the gate. The luminescence scanner  96  then reads the leading edge varnish block  76  in order to determine the position of the label. Then, the optical contrast scanner  94  reads the second eye mark  62 , which closes the gate. The information is fed to the PLC and is processed to track each repeat section of the web material  12 . If the gate closes before the luminescence scanner reads the leading edge of the varnish block, then the tolerance will be marked “out of process window” or the label is missing and a corresponding signal is sent to the PLC.  
         [0026]     C. Die Cut Across Web Running Direction  
         [0027]     Referring to  FIG. 5 , die section  64  is fixed in a frame such that it is moveable in the web running direction, but not moveable transverse to the web running direction. The web material  12  may, however, itself weave or at least temporarily shift in the cross web running direction, moving the die cut out of a specified tolerance (e.g., +/−0.125 inch from a standard). Sensors  98  and  100  (e.g., capacitance sensors, commercially available from Balluff, Inc., Florence, Ky.) are located to monitor the position of the web material  12  by looking for the web running direction edges  102 ,  104  of the web material. The sensors  98  and  100  are positioned to allow movement of the web material in the cross web running direction a specified tolerance (e.g., +/−0.125 inch from a standard). Movement of the web material  12  out of this tolerance will cause one of the sensors  98 ,  100  to provide a signal to the PLC and the corresponding section of the web material will be marked “out of process window.” 
         [0028]     In some embodiments, an imager, such as camera  106  (e.g., commercially available from Handy Scan) may be used to inspect the quality assurance functions at various repeat sections of web material  12 . In some embodiments, this inspection may not be continuous. For example, the web material  12  may be moving in the web running direction at approximately 250 feet per minute and every other section of web material monitored with the camera  106 . In one embodiment, the camera  106  takes still pictures every other repeat section and those pictures are monitored by an operator of the apparatus  10 .  
         [0029]     D. Label Placement Across Web Running Direction  
         [0030]     Referring briefly to  FIG. 4 , top varnish block  74  and bottom varnish block  78  are used to control the tolerance of label  72  placement in the cross web running direction. Referring again to  FIG. 5 , luminescence scanners  108  and  110  are mounted to gate a window in which the label must pass without detection of one of the varnish blocks  74  and  78 . If a scanner  108 ,  110  detects one of the varnish blocks  74 ,  78 , a signal is sent to the PLC and the label  72  is considered to be “out of process window.” 
         [0031]     E. Wrinkle Detection  
         [0032]     A wrinkle detection assembly  112  is used to detect regions of increased web material thickness. Referring to  FIG. 6 , wrinkle detection assembly  112  includes a plate  114  that is biased toward the web material  12  (e.g., by a spring). A sensor  116  (e.g., a laser scanner) monitors movement of a lever arm  118  that is connected to the plate  114 . The sensor  116  provides a signal to the PLC indicative of deflection of the lever arm  118 . The lever arm  118  is used to amplify movement of the plate  114 , which in turn amplifies the signal provided by the sensor  116 . In one embodiment, if the plate  114  deflects more than 0.002 inch, such as 0.004 inch or more, then a signal is sent to the PLC and the corresponding section of web material  12  is determined to have a wrinkle.  
         [0033]     In some embodiments, the PLC program runs a cascade ladder, which tracks each repeat of the web material  12  through the quality control method  50  to the flagging or defect label, label head  38  ( FIG. 1 ). If during the process a defect at any of the quality assurance points A-E occurs, that repeat section is flagged or marked with a defect label at label head  38 . In some embodiments, a green label is placed on each defective repeat section. In some implementations, information regarding the defect is displayed on an operator display for review by an operator. The quality assurance portion of the computer program has programmable gates to stop the apparatus  10  for both rate occurrence and total occurrence per roll. Further, the system is programmable so that, for example, if a certain number of defects or flags occur for a predetermined length of web material  12  (e.g., three defects within 20 feet of web material), then the label application apparatus  10  can be shut-down for correction.  
         [0034]     It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. Accordingly, other embodiments are contemplated and modifications and changes could be made without departing from the scope of this application as expressed by any claims now included or hereafter added.