Patent Abstract:
A novel package wrapper is made of plastic film with a line of package-opening perforations through the film positioned in one face of the package and being overlaid by a piece of plastic tape which seals the perforations, the tape having a dry edge. The shrink wrap film and tear down tape exhibit the same shrink characteristics as those of the shrink wrap film, so that when the wrap film is shrunk during packaging the tape shrinks the same amount as the film and does not itself pucker or wrinkle the film. Package opening is accomplished by grasping the tape dry edge and pulling it toward the line of perforations. The tape peels from the wrapper film until it reaches the perforations, where continued pulling of the tape ruptures the film through the perforations and permits the film to be further torn to open the package.

Full Description:
This application is a continuation-in-part of prior application Ser. No. 10/918,389 filed Aug. 16, 2004, entitled EASY-OPEN PACKAGES abandoned. The invention relates to packages, and more particularly to easily openable packages, which in one application are air and moisture resistant shrink film wrapped for extending the shelf life of products adversely affected by bacterial action and oxidation. The invention is also useful for other products where ease of package opening is desirable. 

   BACKGROUND OF THE INVENTION 
   Conventionally, many products are packaged in plastic wrappers, some in shrink film. In the past, such wrappers have not been air and moisture proof, and during packaging, storage and display, over time, air and moisture can penetrate the wrapper and contact the product within, causing spoilage of spoilable products such as meat, fish and poultry due to oxidation and bacterial action. In some cases, such as packaging fresh meat, the package may be oxygen flushed to preserve color, and in other cases flushed with other gases such as nitrogen. 
   Such wrappers, however, despite being permeable, are physically strong and tough, and are time consuming to open, often requiring the use of cutting implements. Accordingly, two problems have existed with regard to such packages, first, the use of non-spoilage retarding air and moisture permeable wrapping materials, and second, consumer inconvenience because of the difficulty of opening such packages. 
   The first problem has been effectively solved by a new, non-permeable, shrink film, made by Sealed Air Inc. and marketed as Cryovac BDF film. Unfortunately, this improved film is even stronger and tougher than the previously used films, and has materially worsened the already bad package opening problem. Prior attempts to solve the opening problem for packages wrapped in this new film, as well as for the previously existing wrapper films, have not been successful, because such attempts have not been able to maintain the non-permeability barrier, thus negating the value of these packaging films. 
   SUMMARY OF THE INVENTION 
   One form of novel package wrapper according to the invention for use in packaging spoilable food products is made of a non-permeable food quality plastic shrink film, such as Cryovac BDF, utilizing a non-permeable tear-down tape sealed to one face of the package in overlying relation to a row of perforations in the wrapper film, thereby maintaining the non-permeability of the package wrapper. The wrapper perforations do not extend the full length of the package, and can be a row of slits ranging in size from 20 mils to 500 mils in length, and being spaced apart between 10 mils and 50 mils, and typically might be 125 mil slits spaced apart by 15 mils. The teardown tape extends beyond each end of the row of perforations a sufficient distance to insure non-exposure of the end slits, which may be by about ½″, but the tape ends stop short of the package ends to avoid being sealed into the package end seals, which would lock the tape ends and prevent the package opening teardown action. For effective package opening purposes the tape can extend substantially less than the package length, thereby using a relatively small amount of tape and reducing tape costs. The package is completely sealed but does not require the use of any tool to open it, the teardown tape providing the package opening function. 
   In this application the teardown tape is not made of shrink film because the application of a suitable adhesive to a shrink film tape requires heat curing to evaporate the adhesive solvent and render the tape usable. Unless the heat curing is done very slowly, which substantially increases the cost of tape production, the heating process would cause the tape to shrink, becoming a non-shrink tape, and rendering it unusable for its intended purpose, since it would pucker when the underlying shrink film were shrunk, disclosing the package wrapper perforations and unsealing the package. 
   The teardown tape according to the invention for use in shrink film packaging is made of non-permeable ordinarily non-shrinkable plastic film, such as polypropylene, which is stretched on the packaging line just prior to application to the wrapper film to convert it into a shrinkable tape, and is provided with a dry edge for grasping to subsequently carry out the teardown function. The degree of stretch is calibrated to produce a tape having the same shrink characteristics as the wrapper film to which it is applied, so that the tape and film shrink together in the packaging machine heat tunnel with no puckering of the wrapper film at the perforation line. The tape can not be previously stretched and stored, because cold stretched tapes are perishable, in that somewhat after stretching tension is released they begin to contract. In non-shrink film applications the teardown tape is not stretched before application to the wrapper film. 
   In all applications, the attachment of the teardown tape to the wrapper film by the tape adhesive must be weak enough to allow the tape to be peeled off of the intact wrapper film without rupturing the unbroken film, but strong enough to hold to the wrapper film below the perforation line, rupturing the film through the perforations, and allowing teardown of the wrapper film. It is also required in food packaging applications that the adhesive not crystallize in a freezer, which would cause the tape to fall off of the package, and must be capable of being applied in cold and humid conditions. Rubber based and acrylic based adhesives satisfy these conditions. 
   The teardown package opening invention may also be utilized with non-shrink films for other packaging applications. In such cases, the teardown tape is not stretched, but is similarly applied to the film directly over the film perforations to effect package opening in the previously described way by grasping the tape dry edge and pulling it down across the perforations. 
   It is a primary object of the invention to provide a novel, easily openable and removable package wrapping. 
   It is another object of the invention to provide a novel, easily openable and removable package wrapping as aforesaid which utilizes a non-permeable shrink film wrapper film and a non-permeable teardown tape overlying and sealing a row of perforations in the wrapper. 
   It is an additional object of the invention to provide a novel package wrapping as aforesaid, which utilizes a non-permeable teardown tape structure completely overlying a row of perforations in the wrapper, wherein both the row of perforations and the tape length are shorter in extent than the length of the package face on which they are positioned, and the tape ends are not bound into any of the package seals. 
   It is a further object of the invention to provide a novel package wrapping as aforesaid that may be removed without causing injury to the package contents during package opening. 
   It is a still further object of the invention to provide novel methods of making the wrapped packages according to the invention as aforesaid. 
   It is yet another object of the invention to provide novel apparatus for making the wrapped packages according to the invention as aforesaid. 
   The foregoing and other objects of the invention will appear more fully hereinafter as disclosed by the following description and accompanying drawings, wherein: 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates in diagrammatic form, the novel packaging of products in a system incorporating the invention; 
       FIG. 2  illustrates a top plan view of the packaging operation as would be seen when viewed along the lines  2 — 2  on  FIG. 1 ; 
       FIG. 3  is an isometric view taken from above of a novel package made according to the invention; 
       FIG. 4  is a vertical cross section through the package of  FIG. 3  as would be seen when viewed along the lines  4 — 4  on  FIG. 3 ; 
       FIGS. 5 and 6  are plan views of alternative forms of package sealing tapes; 
       FIG. 7  is an isometric view similar to that of  FIG. 3 , but illustrating the use of the alternative forms of package sealing tapes shown in  FIGS. 5 and 6 ; 
       FIG. 8A  is similar to  FIG. 3  but shows the start of the package opening process for the package of  FIG. 3  by lifting and grasping of the dry edge of the package opener; 
       FIG. 8B  is an isometric view of the package of  FIGS. 3 and 8A  illustrating the package in a partially opened condition; 
       FIG. 9  is an isometric view taken from above of a shrink wrapped package illustrating the problem resulting from use of a non-shrink tape with a shrink film wrapper, rendering the package unsealed along the perforation line; 
       FIG. 10  is a vertical cross section through the package of  FIG. 9  as would be seen when viewed along the lines  10 — 10  on  FIG. 9 ; 
       FIG. 10A  is a vertical cross section through the package of  FIG. 9  as would be seen when viewed along the lines  10 A— 10 A on  FIG. 10 ; 
       FIG. 11  is a front elevational view of the novel apparatus according to the invention for creating the novel composite openable package wrapper, with the apparatus shown before start-up; 
       FIGS. 11A and 11B  are enlarged portions of the apparatus of  FIG. 11  enclosed by the phantom circle on  FIG. 11  illustrating sequential stages of the process; 
       FIG. 12  is an end elevational view of the novel apparatus according to the invention as seen from the side as would be viewed along the lines  12 — 12  on  FIG. 11 ; 
       FIG. 13  is a vertical sectional view through the novel apparatus according to the invention as would be seen when viewed along lines  13 — 13  on  FIG. 12 ; 
       FIG. 14  is a cross sectional detail view of the tape stretch controlling pulleys as would be seen when viewed along the lines  14 — 14  on  FIG. 13 ; 
       FIG. 15  is timing diagram showing the timing sequence of the apparatus as shown in  FIGS. 11 to 14 . 
   

   In the several figures, like elements are denoted by like reference characters. 
   DETAILED DESCRIPTION 
   Considering first  FIGS. 1 and 2 , there is seen a horizontal packaging machine  20  into which flow a series of containers  21  holding a product to be packaged, the containers being moved into the packaging machine  20  on a conveyor  22 , and emerging from the packager  20  as the finished wrapped packages  23 . The packaging machine  20  could be, for example, a Linium Model 305 horizontal packaging machine made by Doboy Inc. The containers  21  are packaged in the composite wrapper film  24  shown disposed above the containers  21  and as emerging from the wrapper former  25  to be subsequently described in detail. The composite wrapper  24  is formed by the wrapper former  25  from the supply roll of packaging wrapper film  26  and precisely cut tape strip lengths  28  from the supply roll of wrapper film sealing tape  27 . 
   As seen in  FIG. 3 , the wrapper film  26  is provided by the wrapper former  25  with a row of perforations  29  overlaid and sealed by the adhesive coated portion  30  of the tape strip  28 , the end portions of the tape strip  28  extending beyond the ends of the row of perforations a sufficient distance to insure that the package is sealed. The wrapper perforations may be slits ranging from 20 mils to 500 mils in length spaced apart from 10′ mils to 50 mils, and typically, in a food package wrapped in a tough film such as 1 mil thick Cryovac BDF non-permeable shrink film, might be: slits of 125 mils in length spaced apart by 15 mils. Other permeable shrink films may vary in thickness between 0.5 mils and 1.25 mils. The general rule to be followed is that, in a package containing a food product the slits are made sufficiently small that the tape adhesive does not contact the food product. 
   The tape strip  28 , which may preferably be made of 2 mils thick polypropylene or polyester about 1.25″ wide, or alternatively of 3 mils thick PVC or polyethylene, is provided with an approximately ¼″ wide dry edge  31  by the wrapper former  25 , as seen in  FIG. 3 , by turning one edge of the tape back upon itself. As seen in  FIGS. 5 and 6 , the tape dry edge may be formed in other ways known in the art, as for example by deadening the marginal portions  231  and  231 A of the tape adhesive coating  230  with a non-tacky substance such as ink. The marginal portions  231  and  231 A can alternatively also be an overlying narrow strip of material adhered onto the marginal portion of the adhesive coated tape, or can be formed by zone coating the adhesive  230  onto the tape substrate to leave the areas  231  and  231 A uncoated. In the alternative tape forms shown in  FIG. 6 , the adhesive coated marginal areas  230 A provide tape ends hold downs, as shown in  FIG. 7 . These hold downs  230 A prevent the tape ends from becoming caught by packages that may be stacked on one another and undesirably tear off a tape on an underlying package. The tape  228  is severed, as at  232 , substantially centrally through the adhesive area  230 A, to form the discrete pieces of tape adhered to successive packages. 
   To open the package  23 , as seen in  FIGS. 3 ,  8 A and  8 B, the tape dry wrapper film  26  until the perforation line  29  is passed, at which point the hold of the adhesive  30  to the wrapper film  26  below the perforation line  29  is strong enough to rupture the wrapper film through the perforation line and tear the film away from the package, as seen in  FIG. 8B , the perforation line being split in two, as at  32  and  33 . In general, the wrapper film  26  can be completely torn around the package to open it. Or, the now torn open package film can be pulled open in other directions as desired from any of the sides of the opening. As seen in  FIGS. 3 and 4 , prior to package opening, the perforation line  29  is completely sealed by the overlying tape  28 . 
   Similarly, to open the package  223 , as seen in  FIG. 7 , the tape dry edge  231 A is grasped and pulled toward the line of perforations  229  against the hold of the adhesive  230 . The tape  228  first peels from the wrapper film  226  at the end tacks  230 A, and downward until the perforation line  229  is passed, at which point the hold of the adhesive  230  to the wrapper film  226  below the perforation line  229  is strong enough to rupture the wrapper film through the perforation line and tear the film away from the package, as previously seen in  FIG. 8B . 
   It should be noted in  FIG. 2  that the package trays  21  are offset asymmetrically with respect to the longitudinally extending side edges of the wrapper film  26 , so that the resulting longitudinal package seal  26 A shown in  FIGS. 3 ,  4 ,  8 A and  8 B, and package seal  226 A shown in  FIG. 7  are positioned on the package side proximate to the tear down tape strip  28 . The orientation of the tear down tape strip  28  is such that the dry edges  31  and  231 A pull in a direction away from the package seals, as seen in  FIGS. 8A and 8B , permitting the major part of the package wrapper to be torn open before encountering the longitudinal package seals  26 A and  226 A, which would prevent further wrapper tearing. 
   Considering now the package shown in  FIGS. 9 ,  10  and  10 A,  FIG. 9  illustrates the problem resulting from use of a non-shrink tape  128  with a shrink film wrapper  126 , rendering the package  123  unsealed along the perforation line  129 , best seen in  FIG. 10A .  FIGS. 9 and 10A  show how the tape  128  does not shrink with the wrapper film  126 , creating the convoluted or rippled tape configuration resulting in tunnels  200  allowing the movement of air through the now open perforations  129 . Accordingly, it is seen that this is an unsealed package, which is unacceptable. This problem has been solved by the package structure according to the invention. 
   Referring now to  FIGS. 11 through 15 , but first to  FIGS. 11 to 14 , there is seen the apparatus for making the composite package wrapper  24  consisting of the shrink film  26  and the discrete strips of stretched shrinkable sealing tape  28  adhered thereto at the proper locations to precisely overlie and close the perforation line  29  in the film  26 . The form of dry edge tape shown is the turned edge form designated as  31  in  FIG. 3 , but is only shown as illustratively, any of the other described forms being equally suitable. 
   During packaging, the film  26  is being pulled by the packaging machine  20  and feeds off of its supply roll around guide roller  34 , around and between pinch roller  35  and drum  36  where the tape strips  28  are at proper intervals pressed onto the film between the pinch roller  35  and drum  36  overlying the line of perforations cut through the film by the perforator disc  37  when the latter is moved against the film passing over the pinch roller  35  by actuation of air cylinder  38  by air from the Air Supply under the control of solenoid actuated air valve S 3 . The composite film  24  exiting from between the pinch roller  35  and drum  36  passes around a series of guide rollers  39  and  39 A and out of the wrapper former  25  properly positioned over the products on conveyor  22 , and on to the packaging machine  20 . Consequently, when film is being pulled, roller  35  and drum  36  are continuously rotating and function to time the other events in the cycle. However, as previously noted and as will be subsequently seen, the tape  27  is not being fed constantly, but is fed intermittently, its non-adhesive surface sliding on the rotating surface of drum  36  when not being fed. As best seen in  FIGS. 11 and 14 , the roller  39 A is shiftable toward and away from the rollers  39  by means of a rack and pinion drive  39 B to adjust the position of tape strip  28  relative to the package. 
   The tape  27  from which the perforations sealing tape strips  28  are formed feeds off of its supply roll  27 A and passes around an edge turner  40  which turns one marginal side edge portion of the tape upon itself, adhesive face to adhesive face, so that the turned marginal edge is adhered to the main portion of the tape and forms the previously described dry edge  31 . The dry edge tape then passes around a guide roller  41 , between tape differential stretcher entrance rollers set  42 , past tape heater  44 , between tape differential stretcher exit rollers set  43 , around guide roller  45 , around dancer roller  46 , and onward to tape pinch roller set  47  and  48 , roller  48  being only unidirectionally rotatable. 
   As best seen in  FIGS. 11 and 13 , the dancer roller  46  carried on dancer arm  49  is rotatable on a shaft  50  which controls the voltage output of potentiometer  51  through engagement of gears  50 A and  50 B that in turn controls on and off operation of the motor  61 . The motor  61 , when turned on, drives split pulley  62  through a speed reducing gear box  63  and pulley drive coupling  64  to drive the stretch rollers set  42 . The pulley  62  drives smaller diameter split pulley  65  through the belt  66  to drive the second set of stretch rollers  43  at a faster rate than the rollers  42 , the differential rotations of the stretcher rollers sets  42  and  43  producing the stretched tape. 
   As seen in  FIG. 14 , the pulleys  62  and  65  are both adjustable diameter pulleys, so that the differential rotation rates of the pulleys may be controlled through a continuous range by relative diameter adjustment between the pulleys to produce different degrees of tape  27  stretch as required. The diameter of pulley  62  is changed by loosening locking screw  68  and rotating pulley half  62 A on threaded shaft  67 A, and retightening the locking screw  68 . Rotating pulley half  62 A away from pulley half  62 B effectively reduces the pulley diameter to allow belt  66  to ride downward in the pulley vee and reduce the drive ratio to pulley  65 . Rotating pulley half  62 A toward pulley half  62 B has the opposite effect. The effective diameter of pulley  65  is similarly adjusted by loosening locking screw  69 , shifting pulley half  65 A on shaft  67 B, and retightening locking screw  69 . 
   The to-and-fro motion of the dancer roller  46  relative to the tape pinch rollers  47  and  48  controls the rotation of the differential stretcher rollers  42  and  43  to adjust the variable length tape loop extending between rollers  45 ,  46 , and  47 / 48  needed to synchronize the feeds of the wrapper film  26  and the tape strips  28 . The tape pinch roller  47  is spring loaded toward unidirectionally rotatable roller  48  and maintains a constant holding pressure on the tape  27  against roller  48  to prevent it from being back-pulled when the dancer roller  46  rotates away to increase the size of the tape loop. 
   As best seen in  FIGS. 11A and 11B , tape pinch roller  47  is mounted on an arm  52 A carried on a fixed pivot  53 , and arm  52  also carried on fixed pivot  53  carries a tape drive pressure roller  54  controllable to, when required, press the tape  27  against the constantly rotating drum  36  to advance the tape. Movement of the arm  52  about its pivot  53  is controlled by air cylinder  55  to which it is rotatably connected by pivot  56 , air cylinder  55  being selectively actuatable by air from the Air Supply under the control of solenoid actuated air valve S 1 . The means for severing the continuous tape  27  into the tape strips  28  is provided by a hot knife tape cutter  57  carried and selectively actuated by air cylinder  58  by air from the Air Supply under the control of solenoid actuated air valve S 2 . 
   The actuation of the solenoid actuated air valves S 1 , S 2  and S 3  is controlled by signals generated by Controller  59  in response to signals received on signal input line  71  from the packaging machine  20  and signals received on signal input lines  79  and  84  from Encoder disc  60 , driven by the film feed pinch roller  35 , as best seen in  FIGS. 11 and 13 . The timing diagram of  FIG. 15  shows the sequence of the initial triggering pulse  70  received from the packaging machine  20  by the Controller  59  on signal line  71  during each cycle of operation, and the timed signals generated by the Controller  59  in response to that signal and those generated by the Encoder  60 . The Controller  59  may suitably be an Allen-Bradley MicroLogic 1000 and the Encoder  60  may be a Dynapar Model HS 20. 
   The tape stretching operation to produce the stretched tape disposed in the tape loop controlled by the oscillatory motion of dancer arm  49  is carried out by the differentially rotating stretcher rollers sets  42  and  43 , tape drive rollers  43  rotating more rapidly than drive rollers  42 , as previously described, thereby stretching the tape between the two sets of rollers. The tape is stretched the amount required to produce a subsequent contraction that matches the shrink characteristics of the packaging film  26 , so that in a finished package the tape and film shrink at the same rate to produce a package as shown in  FIGS. 3 and 7 , and not one as shown in  FIG. 9 . 
   Referring now to  FIGS. 11 ,  11 A,  11 B and  15 , the sequence of operation is as follows. The packaging machine  20 , at the proper time in each packaging cycle, designated on  FIG. 15  as t 0 , generates a signal  70 , which is sent to Controller  59  over signal input line  71 . In response to input signal  70 , the Controller generates tape drive output signal  72  on signal output line  73 , activating solenoid actuated air valve S 1  to send air from the Air Supply to air cylinder  55 , causing the latter to extend its piston, pivoting arm  52  about pivot  53  to move tape drive pressure roller  54  downward to press the tape  27  against the rotating drum  36  while spring loaded tape pinch roller  47  remains down to continue pressing the tape  27  against unidirectionally rotatable pinch roller  48 . Also at the same time, Controller  59  generates film perforator start signal  74  on signal output line  75 , actuating solenoid actuated air valve S 3  to send air from the Air Supply to air cylinder  38 , causing the latter to extend its piston to move perforator disc  37  into engagement with the film  26  and commence perforating the film. 
   The advance of the tape  27  pivots the dancer arm  49  up to allow tape to be drawn from the dancer tape loop as shown by the dancer position waveform  76 , which causes the potentiometer  51  to generate a signal  77  starting motor  61  and activating the tape stretcher drive rollers  42  and  43 . As best seen in  FIGS. 12 and 13 , the Encoder  60  rotates synchronously with the pinch roller  35 , and when it has measured the proper length of the perforation row being made by perforator disc  37  it generates a signal  78  to the Controller  59  on line  79 , in response to which the Controller terminates the signal  74  on signal line  75 , thereby deactivating solenoid air valve S 3  and air cylinder  38  and retracting the perforator disc  37  from engagement with the film  26  at time t 1 . 
   As best seen in  FIGS. 11A and 11B , shortly thereafter, at time t 2 , the Encoder  60  generates a signal  80  on signal output line  81  actuating solenoid actuated air valve S 2  to send air from the Air Supply to air cylinder  58 , causing the latter to extend its piston and press hot knife tape cutter  57  down against the tape  27  to cut the tape. However, tape cutting is not instantaneous and the hot cutter  57  remains in contact with the tape for the necessary interval to insure severing, the interval being shown on  FIG. 14  as the interval t 3 −t 2 =about 5% t 2 −t 0 , during which interval the cutter  57  rotates about pivot  82  and remains engaged with the tape  27  against drum  36 . At the end of the tape cutting interval the Encoder  60  generates a signal  83  on signal line  84  to the Controller  59  which causes the latter to terminate the signal on line  81 , thereby deactivating air valve solenoid S 2  and deactuating air cylinder  58  and retracting the hot knife tape cutter  57  out of engagement with the tape  27 . The timing of Encoder  60  signal  80  at t 2  determines the length of the tape strip  28 , which is in turn determined by the length of the row of perforations  29 . 
   At the start of tape severing at t 2 , the Controller  59  terminates the tape drive signal  72  on signal line  73 , thereby deactivating air valve solenoid S 1  and deactuating air cylinder  55  to raise pressure roller  54  and terminate the tape advance. Because the tape rollers are still feeding tape, the dancer arm  49  moves down rapidly, quickly increasing the tape loop and rotating the potentiometer  51  to rapidly decrease the voltage to the motor driving the stretcher rollers  42  and  43  and terminating their movement. At this point, the cycle is complete, and a new cycle is initiated when the packaging machine generates its next pulse  70 , as shown on  FIG. 14 . 
   If packaging is to be carried out with non-shrink-wrap film, the perforations sealing tape will also be non-shrink, the tape stretcher rollers sets  42  and  43  would be replaced with only a single set of tape feed rollers, and the tape heater would be turned off. The packaging machine  20  could be a Linium Model 301 horizontal packager made by Sig Doboy Inc. In all other particulars the apparatus and operation would remain the same. Because of the contraction with time of the stretched tape according to the invention, the manufacture for storage and subsequent use of pre-formed rolls of shrink film with applied stretched tape strips is not practical. However, with the use of non-shrink film and non-stretched tape strips, the manufacture for storage and subsequent use of pre-formed rolls of packaging film with pre-applied tape strips is practical. 
   Having now described our invention, it will be understood that modifications and variations thereof may now naturally occur from time to time to those normally skilled in the art without departing from the essential scope or spirit of the invention, and accordingly it is intended to claim the invention both broadly and specifically as indicated in the appended claims.

Technology Classification (CPC): 1