Abstract:
A method of creating perforations in wrapping film uses an apparatus that contains a plurality of needle points (or other piercing features) formed along a free-wheeling support bar. The bar is positioned to contact the film while it is being unrolled and is in a ‘tensioned ’ state (in some embodiments, immediately prior to contacting the element to be wrapped). In performing the method, the free-wheeling perforation apparatus contacts a mechanized film roller such that the exposed needle points rotate against the mechanized roller and make the perforations in the film as it travels over the film roller. As long as the film roller is formed of a pliable material, the needles will pierce the film and create the desired perforations. The size and placement of needles can be adjusted to provide the required pattern of perforations, as well as dictate the size of the actual perforations.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application No. 12/217,576, filed Jul. 7, 2008, which claims the benefit of U.S. Provisional Application No. 61/066,042, filed Feb. 14, 2008. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a method for creating perforations in a roll of film as it is being unwrapped and, more particularly, to the utilization of a rotating needle apparatus for creating perforations in a film as it is being unrolled. 
     BACKGROUND OF THE INVENTION 
     Stretch wrap films of the prior art are used in connection with a wide variety of overwrap packaging applications. In many applications, these films are required to be air and moisture vapor permeable materials. Techniques have been developed to introduce through-holes (i.e., perforations) into the film for such a purpose. In order to make a thin film with perforations, the prior art generally included a stretching apparatus to thin-out the film and a separate “punching” apparatus for introducing perforations into the stretched film. One exemplary method of producing such films is disclosed in U.S. Pat. No. 6,296,469 issued to M. Suzuki et al. on Oct. 2, 2001. In the Suzuki et al. apparatus, a pair of punching rollers is used which sandwich the film between the rollers. 
     U.S. Pat. No. 4,765,120, issued to T. E. Phillips on Aug. 23, 1988 discloses a device for perforating a film while wrapping a load. In particular, the Phillips arrangement includes electrodes positioned proximate to the film and an arrangement for generating an arc across the electrodes to form the perforations in the film. Such an arrangement is not considered to be well-suited for situations where the presence of constant arcing may damage the product being wrapped, the wrapping machine and/or other products/machines in the general area of the arcing equipment. 
     Another type of perforating apparatus is disclosed in U.S. Pat. No. 5,802,945, issued to F. Brinkimeier et al. on Sep. 8, 1998, which describes the use of a series of “needles” to introduce perforations into a roll of film. In order to be able to create a variety of perforation patterns and/or holes of varying diameter in the film, a needle roller arrangement is used that includes several separate needle rollers arranged in a freely rotatable manner in a rotary frame. One of the needle rollers interacts with a brush roller for perforating a film which passes between the brush roller and the needle roller. 
     U.S. Pat. No. 5,935,681 issued to H. K, Paulett on Aug. 10, 1999 discloses another arrangement for forming “air permeable” stretch film, where in this case the film comprises separate first and second layers of polymeric film (linear low density polyethylene) which is capable of stretching at least 150% beyond its original length. The layers will naturally cling together to form a laminate. Perforations are formed in the laminate by applying a “hot pin” to the laminate, whereby the polymeric film is melted. As the melt hardens, the perforations become defined by the welds, or reinforcements, which add strength to the film. 
     Laser-based systems have also been developed for creating perforations of a known, controlled sized along a roll of wrapping film (usually a plastic material, although other film materials may be used). See, for example, U.S. Pat. No. 6,730,874 issued to E. Varriano-Marston on May 4, 2004. In operation, a roll of plastic film is fed into a laser perforation apparatus, where the film is unrolled and perforated and thereafter taken up on an output reel. The laser-perforated roll is then ready for use at the food packaging machine. 
     One problem with many of these film perforation arrangements is that the perforating apparatus is generally not co-located with the items being wrapped; delays may occur in obtaining the perforated film at the plant where the wrapping is taking place. Further, the need to completely unroll and then re-roll the plastic film during the prior art perforation processes tends to create stress across and along the film, creating folds, offsets in the wrapped layers, and the like, which may lead to tears or other problems during the actual wrapping process. 
     Thus, a need remains in the art for an improved arrangement for creating perforations in the film used to wrap food products. 
     SUMMARY OF THE INVENTION 
     The need remaining in the prior art is addressed by the present invention, which relates to a method for creating perforations in a roll of film as it is being unwrapped and, more particularly, to the utilization of a rotating needle apparatus for creating perforations in a film as it is being unrolled 
     In accordance with the present invention, a rotating perforation apparatus containing a plurality of needle points (or other piercing features) is positioned to contact the film while it is being unrolled and is in a ‘tensioned’ state (in some embodiments, immediately prior to contacting the element to be wrapped). In one embodiment, the rotating perforation apparatus is disposed along a bar which contacts a film roller and makes the perforations in the film as it travels across the film roller. As long as the film roller is formed of a pliable material, the needles will pierce the film and create the desired perforations. The size and placement of needles can be adjusted to provide the required pattern of perforations, as well as dictate the size of the actual perforations. 
     It is an advantage of the method of the present invention that a conventional film roller (which is a mechanically-driven apparatus) is used to effectuate the unrolling of the film from its stock “roll”. Therefore, in performing the perforation process of the present invention, the rotating perforation apparatus is “free-wheeling” (i.e., not driven) such that when it is placed against the driven film roller, the rotating perforation apparatus will naturally counter-rotate against the driven film roller and allow for the needle points to rotate against the film at essentially the same speed as the film is unrolling—eliminating the possibility of tears or jams occurring during the perforation step. 
     In one embodiment, the perforation method of the present invention may be used in an in-line fashion, applying perforations immediately prior to the film being placed over the item(s) being wrapped. Alternatively, the perforation method of the present invention may be used to form a large roll of perforated film which is thereafter used to wrap various items. Indeed, in one embodiment discussed in detail below, the needle points may be arranged along the perforation apparatus such that different sections of the film will receive different perforation patterns (including, perhaps, not forming perforations along selected widths of the film). The ability of the perforation method of the present invention to modify the perforation pattern is especially well-suited when used with the “large roll” of film, which may then be cut into smaller sections, each section have a different, pre-defined perforation pattern. 
     In a preferred embodiment, the perforation method utilizes a plurality of “rings”, each ring have a number of needle points disposed around the periphery thereof. The rings are inserted along a cylindrical support bar, which then forms the rotating perforation apparatus. The rings and support bar may further include a keying arrangement to ensure for alignment between the plurality of rings inserted along the bar (the alignment of the rings thus defining the perforation pattern that will be formed in the film). The rings may be re-configured in their placement to achieve different perforation patterns and, in one embodiment, may be interspersed with rings not including any needles, allowing for sections of a film to not be perforated as it passes between the driven film roller and the rotating perforation apparatus. 
     Other and further embodiments and advantages of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings, where like numerals represent like parts in several views, 
         FIG. 1  illustrates an exemplary film feed apparatus for providing in-line perforation of a wrapping film in accordance with the present invention; 
         FIG. 2  is another view of the apparatus of  FIG. 1 , with a covering element removed to expose the inventive in-line perforation apparatus; 
         FIG. 3  is a side view of this same arrangement of the present invention; 
         FIG. 4  is an isometric view of an exemplary needle-carrying ring of the perforation apparatus of the present invention; 
         FIG. 5  is a top view of the ring of  FIG. 4 ; 
         FIG. 6  illustrates an exemplary support bar for use in one embodiment of the present invention, in this view illustrating in particular a keying arrangement for use in fixing the needle-carrying rings (see  FIG. 5 ) in place therealong; 
         FIG. 7  is a view of the exemplary support bar of  FIG. 6 , with a plurality of needle-carrying rings disposed in position therealong; 
         FIG. 8  is an exploded view of an exemplary needle-carrying ring, showing in particular an arrangement for inserting removable needles into a ring structure; 
         FIG. 9  is an alternative embodiment of the present invention, modifying the placement of the perforation-creating needles along the perforation member; and 
         FIG. 10  is yet another embodiment of the present invention showing yet another pattern of needles across the perforation apparatus. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an exemplary film feed apparatus  10  for providing in-line perforation of a wrapping film in association with an in-line perforation apparatus  20  of with the present invention. Film feed apparatus  10  includes a stock, conventional roll  12  of wrapping film  14  (where this film may be any suitable type of plastic, foil, etc., used in a wrapping process). As film  14  is unwound, it is fed from underneath roll  12  and over the top of a driven roller  16 . As controlled by the speed of driven roller  16 , film  14  will exit apparatus  10  in the manner indicated by the arrows. In accordance with the present invention and described in detail below, in-line perforation apparatus  20  is positioned to create perforations  22  in film  14  as it exits apparatus  10 . 
     In the view of  FIG. 1 , the actual working parts of in-line perforation apparatus  20  are hidden by a protective cover  24 .  FIG. 2  is another view of apparatus  10  of  FIG. 1 , in this case with film roll  12  taken away, and protective cover  24  removed to expose the various components of in-line perforation apparatus  20 . As shown, apparatus  20  includes a perforation member  26  which is formed to include a plurality of needle points  28  (or other sharp elements capable of forming perforations in films). Perforation member  26  is located along a central region of a free-wheeling support bar  30 . As shown in  FIG. 2 , support bar  30  is positioned against driven roller  16 . Therefore, as driven roller  16  rotates clockwise (as shown by the arrows in  FIG. 2 ), free-wheeling support bar  30  will naturally rotate counter-clockwise at the same rate of rotation as driven roller  16 . It is an advantage of the present invention, therefore, that the in-line perforation apparatus does not itself need to be motorized; rather, it will utilize the rotational motion of the film roller apparatus itself to rotate the needles against the film. 
     The rotation of support bar  30  against driven roller  16  will therefore bring needle points  28  into contact with film  14  as it passes over roller  16  (see  FIG. 1 ), creating perforations  22  in film  14 . Advantageously and as described in detail below, the size and location of the perforations is easily controlled by properly configuring the arrangement of perforation member  26 , as well as the diameter of the needles used for needle points  28 . 
     In the particular embodiment of the present invention shown in  FIG. 2 , a pair of guides  32 ,  34  are attached to apparatus  10  and used to hold support bar  30  in place against driven roller  16 . As shown, each guide includes an associated channel (guide  32  including a channel  36 , and guide  34  including a channel  38 ) for controlling the movement and placement of support bar  30 . In a preferred embodiment, guides  32  and  34  are formed to allow for roller  30  to be retracted to allow for visual inspection of perforation member  26  and needle points  28 . 
     It is to be understood that there exist many other arrangements for attaching rotating perforation apparatus  20  to a film unrolling apparatus (such as apparatus  10 ), where these attachment arrangements may be either permanent or removable. As long as perforation apparatus  20  is free to rotate against a driven film roller with a pliable surface, the action of creating perforations in an unrolling film will take place in accordance with the teachings of the present invention. 
       FIG. 3  is a side view of this same arrangement of the present invention, in this view showing the placement of perforation member  26  against a portion of driven roller  16  as film  14  is fed between the two components. Also shown in this view (in phantom) is channel  36  formed within guide  32 . Film  14  is exaggerated in thickness in the view of  FIG. 3  in order to clearly show how the film exits roll  12  and passes between driven roller  16  and perforation member  26 . Location A illustrates the position where needle points  28  on perforation member  26  come into contact with film  14 , piercing the film and coming to rest against the pliable surface of roller  16 . The interaction between needle points  28  and driven roller  16  will result in perforation member  26  rotating counterclockwise as driven roller  16  rotates in a clockwise fashion, allowing perforations to continue to be made in film  14  as it passes along. 
     While needle points  28  may be directly formed on the support bar, a preferred embodiment of the present invention utilizes a perforation member  26  consisting of a plurality of separate rings  40  which may be placed alongside one another to form member  26 .  FIG. 4  is an isometric view of an exemplary ring  40 , including a central aperture  42  for positioning over support bar  30  (see  FIG. 2 ). A number of needle points  28  are shown as disposed around the circumference of ring  40  in predetermined locations. The length of points  28  is exaggerated in this view so as to show their placement around the periphery of ring  40 . In order to provide alignment between needle points  28  from one ring to the next, each ring  40  is formed to include a keying feature  44 , which will mate with a key  46  on support bar  30  (see  FIG. 2 ). Keying feature  44  is best shown in  FIG. 5 , which is a top view of ring  40 . 
       FIG. 6  illustrates an exemplary support bar  30  of the perforation apparatus of the present invention, with perforation member  26  removed to clearly show the placement and extent of key  46 . Again, such a keying arrangement is considered to be exemplary only. Various other arrangements for fixing/aligning rings  40  (or any other embodiment of perforation member  26 ) may be contemplated and are considered to fall within the scope of the present invention. Indeed, for embodiments where the needle points are directly formed on the exterior surface of support bar  30 , there is no need to form such a keying element. 
       FIG. 7  illustrates the same exemplary support bar  30  as shown in  FIG. 6 , in this illustration with a plurality of rings  40  disposed along bar  30  and “locked” in place by inserting the individual keying features  44  of rings  40  into key  46  of bar  30 . Advantageously, the use of the keying arrangement provides both physical attachment of rings  40  to support bar  30  and alignment of needle points  28  from one ring to the next. 
       FIG. 8  is an exploded view of an exemplary ring  40 . As shown, ring  40  comprises a bottom element  50  and a top element  52 , with a plurality of needles  54  disposed therebetween such that needle points  28  will be exposed when elements  50  and  52  are joined together. For the sake of clarity, only one needle  54  is illustrated in  FIG. 8 . In this particular arrangement, needle  54  is L-shaped, with short leg  56  placed within a mating aperture  58  in bottom element  50 . Side leg  60  of needle  54  rests within a groove  62  formed in the top surface of bottom element  50 , with the end tip remaining exposed as needle point  28 . The length of the exposed point  28  is determined by the position of aperture  58  relative to the length of needle  54  and the diameter of bottom element  50 . A locking element  64  (in this embodiment, a screw) is used to hold needle  54  motionless in place along groove  62 . Once the plurality of needles  54  are in place, top element  52  is positioned over bottom element  50  (with keying features  44  aligned) and attached thereto to form ring  40 . 
     It is to be understood that various other arrangements may be used to hold the needle points in position. Indeed, while the preferred embodiments may utilize removable needles, it is possible to utilize a perforation element with permanently-fixed needle points, where the entire element is then replaced when necessary. 
     As mentioned above, the arrangement of the present invention is capable of providing “in-line” perforation of wrapping film—that is, creating perforations in the film as it is being unrolled and presented to the product-to-be-wrapped. Alternatively, the arrangement of the present invention may be used to create rolls of perforated film which are then inventoried and used at a later date/location to wrap product. In the latter case, an extended width stock roll may be perforated, and then “sliced” into smaller widths which are used for various products. Advantageously, the perforation apparatus of the present invention may be configured to modify the perforation pattern across the width of the film, thus creating the ability to apply a number of different perforation patterns, each pattern associated with a different “slice” when the extended width stock roll is separated into its separate components. 
       FIG. 9  contains an exemplary arrangement of rotating perforation apparatus  20  which provides for a modified perforation pattern, as discussed above. In this case, a first set of rings  40 - 1  is disposed at a first end  26 - 1  of perforation member  26 . A spacer element  43  is disposed adjacent to rings  40 - 1 , where spacer element  43  does not include any needle points. A second set of rings  40 - 2  is disposed at a second, opposing end  26 - 2  of perforation member  26 . In accordance with this embodiment of the present invention, the number and placement of needle points  28  within second set of rings  40 - 2  may differ from the needle point placement within first ring  40 - 1 . With this particular arrangement, therefore, an unrolling film will be processed to contain perforations along its two outer sections, the central portion remaining untouched. Thereafter, the film stock may be “sliced” into three different sections, each having been processed in accordance with its individual requirements. 
     It is to be understood that various other combinations of needle point patterns and blank spacings may be used in creating any desired perforation pattern along the perforation apparatus of the present invention. For example,  FIG. 10  illustrates an embodiment where the needle point pattern is modified by alternating “blank” rings  41  with rings  40  including needle points  28 . Many other arrangements are possible and all are considered to fall within the spirit and scope of the present invention. 
     Indeed, the scope of the present invention is seen to include any type of in-line arrangement disposed adjacent to a driven roller associated with unrolling a wrapping film, allowing for perforations to be made in the film as it is passing over the driven roller, eliminating the need for a separate “perforating” process to be employed. While various ones of the preferred embodiments of the present invention have been described above, it is to be understood that the spirit and scope of the present invention is only to be limited by the claims appended hereto.