Abstract:
The disclosure relates to relates to the use of trim sensors, registration sensors or pressure sensors to sense the position of a zipper during the manufacture of reclosable packages, particularly manufacturing processes wherein the ends of the zipper need to line up at the fin seal to insure success of the closure. The output of the sensors is used to adjust belt or roller speeds, or similar operational parameters to bring the zipper profiles into alignment at the fin seal.

Description:
BACKGROUND OF THE DISCLOSURE 
       [0001]    This application claims priority under 35 U.S.C. §119(e) of provisional patent application Ser. No. 61/329,361, filed on Apr. 29, 2010, the disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates to the manufacture of reclosable packages or bags, particularly manufacturing processes wherein the ends of the zipper need to line up at the fin seal to insure success of the closure. This may be applied to wide mouth openings wherein a long unisex zipper is placed across the width of a film going through a machine, such as a vertical form fill seal machine, to make a pouch. The pouch could be of many styles, including a pillow, gusseted, or quad seal style. 
       DESCRIPTION OF THE PRIOR ART 
       [0003]    High speed manufacture of reclosable packages is well-developed and very satisfactory for its intended purposes. However, further increases in manufacturing speed and decreases in manufacturing costs are always sought. In particular, some manufacturing processes for reclosable packages including, but not limited to, form fill and seal processes, could benefit from improvements to bring fine adjustment to the alignment of zipper profiles at the fin seal to further decrease any registration tolerances or errors, and further consistently increase the aesthetic appeal of the resulting package. Typical tolerances or errors are on the order of one eighth to one quarter of an inch, and may be as low as one sixteenth of an inch for ease of closure. 
         [0004]    The possible misalignment of the zipper location at the fin seal can be induced by such factors as errors in the printing of the film registration marks; errors in the placement of the zipper on the film; errors created by the increased drag caused by the zipper at the fill tube and from the film distance travelled (drag) from the upstream sensor measuring the film registration marks; and errors created by the product flowing intermittently into the fill tube and hitting the pouch bottom creating a standing wave of varying tension around the fill tube. 
       SUMMARY AND OBJECTS OF THE DISCLOSURE 
       [0005]    It is therefore an object of the present disclosure to improve the fine adjustment in the alignment of zipper profiles at a fin seal in manufacturing processes for reclosable packages. This is particularly adaptable to, but not limited to, form fill seal manufacturing processes. 
         [0006]    This and other objects are attained by positioning a trim sensor (such as a vision system or similar apparatus or method) to sense the position of the zipper ends at the fin sealing location (such as the fill tube in a form fill seal apparatus). The output of the trim sensor is used to adjust belt or roller speeds, or similar operational parameters to bring the zipper profiles into alignment at the fin seal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Further objects and advantages of the disclosure will become apparent from the following description and from the accompanying drawing, wherein: 
           [0008]      FIG. 1  is a perspective view of a vertical form fill seal machine implementing an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0009]    Referring now to the drawings in detail wherein like numerals indicate like elements throughout the several views, one sees that  FIG. 1  is a perspective view of a vertical form fill seal machine  10  implementing an embodiment of the present disclosure. 
         [0010]    The vertical form fill seal machine  10  includes a roll  12 , from which a continuous sheet  14  of polymeric web or film is provided in a machine direction. Sheet  14  includes lateral edges  15 ,  17  oriented in the machine direction. Sheet  14  is typically guided by roller pairs such as those illustrated at  16 ,  18 ,  20 ,  22 . A zipper strip  24  is provided from zipper strip roll  26  (or other source, such as a cartridge-type supply of successive zipper strips  24  in the form of zipper segments). Zipper strip  24  may be colored, dosed or otherwise treated or marked in order to aid in the accuracy of the sensing thereof. The zipper strip  24  is applied and sealed across the sheet  14  of web or film in transverse direction, typically in the proximity of roller pair  18 . At least one sensor  30  is provided in the proximity of roller pair  22  for determining the presence and speed of sheet  14  of web or film. The output of sensor  30  is provided to control logic system  32  via first digital servo drive  34 . Control logic system  32  includes an operator terminal  38  which typically includes a keyboard and a display screen. Control logic system  32  is in communication with first and second digital servo drives  34 ,  36 . 
         [0011]    Sheet  14  of web or film is wrapped around fill tube  40  so that lateral edges  15 ,  17  are brought together and sealed in a fin seal by a machine direction sealing bar (not shown). Trim sensors (or registration sensors)  42 ,  43  are located near the junction of lateral edges  15 ,  17  around the fill tube  40  and senses the position of the transversely-oriented zipper strip  24  with respect to the fin seal formed in the sheet  14  of web or film. The trim sensors  42 ,  43  are positioned so as to monitor both ends of the zipper strip  24  and thereby provide information regarding the alignment thereof. The trim sensors  42 ,  43  may be electric eyes or comprise a vision system. Further alternatives include proximity sensors which may include inductive proximity sensors, capacity proximity sensors, ultrasonic proximity sensors and photoelectric sensors (with capacitive or photoelectric sensors being typically used for a plastic target and inductive proximity sensors typically being used for a metal target). Additionally, as described hereinafter, pressure switch  70  may be substituted for trim sensors  42 ,  43 . The output of trim sensors  42 ,  43 , similar to the output of sensor  30 , is supplied to control logic system  32  via first digital servo drive  34 . Control logic system  32  uses the information from trim sensors  42 ,  43  to adjust the web speed, including the side-to-side web speed, as induced by drive roller assembly  50  which includes first drive belt  51  on a first side of fill tube  40  and second drive belt  53  on a second side of fill tube  40 , opposite from the first side. First and second drive belts  51 ,  53  are driven by first and second drive roller servo motors  52 ,  55 , respectively, which are, in turn, controlled by control logic system  32  via first digital servo drive  34  thereby controlling the placement and alignment of the ends of zipper strip  24  with respect to the fin seal. In this context, the term “drive roller servo motor” is being used to describe a mechanical device that delivers torque to rollers, belts, gear boxes and similar devices. Additionally, a KAMBEROLLER® steering guide from Fife Corporation may be an acceptable alternative for this purpose. 
         [0012]    First digital servo drive  34  is illustrated as controlling both first and second drive belts  51 ,  53 , independently. This independent control is typically necessary in order to control the side-to-side web speed, and the alignment of zipper strip  24 . In some applications, first digital servo drive  34  may be replaced with two digital servo drives. 
         [0013]    The filled package  300  is formed by contents  200  being fed through fill tube  40  into the tube formed by sheet  14  with transverse sealing bar assembly  54  typically forming the upper seal of a lower completed package  300  and the lower seal of an upwardly adjacent package  300 ′ (or, if the packages are manufactured in an inverted configuration, the lower seal of a lower completed package  300  and the upper seal of an upwardly adjacent package  300 ′). Transverse sealing bar assembly  54  is driven by low inertia brushless servo motor  56 , which is controlled by control logic system  32  via second digital servo drive  36 . The calculated desired speed of transverse sealing bar assembly  54  may likewise be influenced by the reading from the trim sensors  42 ,  43 . 
         [0014]    In this way, trim sensors  42 ,  43  (or registration sensors) are added to the vertical form fill and seal machine  10  to correct the film position in order to maintain the correct position (such as, but not limited to, a print position) relative to the end of the package  300  (such as, but not limited to, a pouch). 
         [0015]    Further possible refinements to the disclosed embodiment include providing a sheet  14  of film with registration marks on either linear exterior and detecting these registration marks by registration sensors  42 ,  43  (typically electric eyes). The friction belts of drive roller assembly  50  which advance the sheet  14  of film are accelerated or decelerated as needed in order to line up the registration marks on either edge of the web or film as it descends the fill tube  40 . This is turn, aligns the edges of the zipper strip  24  with respect to the fin seal. A further refinement includes adding pressure switches (illustrated on  FIG. 1  as element  70 , and typically having the same line of communication as illustrated for trim sensors  42 ,  43 ) located on the forming tube  40  which may detect either side of the zipper strip  24 . 
         [0016]    Thus the several aforementioned objects and advantages are most effectively attained. Although preferred embodiments of the invention have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.