Field of the Invention The invention relates to a tear open system for a package, particularly a perforated tear open system for plastic film packages that combines a cardboard form and a plastic window.

More particularly, the tear open system relates to a system for providing easy access to the contents of a shrink film package.

BRIEF DESCRIPTION OF THE PRIOR ART The method and apparatus for forming shrink filmed display packages has been disclosed in a variety of patents and other publications. It is known to seal articles in pockets that are formed and sealed in plastic windows of paperboard blanks. These b lanks have one or more openings that are covered, on one surface, by a heat-deformable and heat-sealable plastic sheet.

The pockets are formed by heating the plastic material extending across the windows and deforming this plastic material to form a pocket. After the article is placed in the pocket, the pocket is closed, for example by folding the blank about a fold line and then heat sealing the plastic material. As the plastic sheet or film which is used is generally transparent, the article is provided in a decorative package in which it is sealed but nevertheless is fully visible. The teachings are best described, however, in U. S. 4,047,358, Method for Forming Article-Holding Display Packages, to Heffernan et al. The disclosures of this patents is i ncorporated herein by reference, as though recited in full.

As popular as these packages are, there have always been problems regarding the difficulty in opening the packages. The weight of cardboard required to maintain the integrity of the package makes opening the package by tearing the cardboard difficult. Separating the adhesive to pull open the package is also a problem as the adhesive is intended to maintain the two halves of the package adjacent one another.

The disclosed method and apparatus provides an easy opening mechanism in these popular paperboard packages.

SUMMARY OF THE INVENTION A perforating apparatus for use in the formation of shrink film packages is disclosed. The apparatus comprises a bottom seal tool with a plurality of penins ula regions forming a plurality of window areas. Each pair of window areas has a knife receiving area to receive a knife retaining block. The retaining block contains a perforation knife that extends beyond the surface of the sealing tool a sufficient distance to perforate the packages. At least one screw member extends through the peninsula, contacting the retaining block and securing the retaining block within the retaining channel. A change plate, having slots dimensioned and located to receive the knife blades is placed over the sealing tool surface. The packages are placed on the change plate and sealed by contacting the package with the upper platen. The upper platen is provided with a nonconductive material positioned to receive the knife blade. The resulting package has a perforation through the paperboard extending from one edge to the plastic window. The terms paperboard and press board are used herein to include any form of self-supporting paper that is used in packaging. This perforation enables the package to be easily opened.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a plan view, of a package in the open position, showing seal lines that would not be visible prior to forming the package; Figure 2, is a side view of a formed package; Figure 3, is a end view, partly in cross-section, of the package of Figure 2; Figure 4 is a cut away side view of the knife retaining block; Figure 5 is a plan view of the upper surface of the bottom sealing tool; Figure 6 is a plan view of the change plate of the package forming apparatus; Figure 7 is a plan view of the change plate and upper platen in an overlying relationship, but without a package in position between the change plate and seal tool Figure 8 is a cutaway side view of the bottom sealing tool, change plate, package and upper platen..

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION While the known packaging machines provide a satisfactory product, there has is a need for the ultimate user of the package to be able to readily open the package. Not only is this applicable to people with arthritis, are known to have particular problems with opening of sealed packages, but in instances where there a large number of packages to open. Places such as construction sites have a large number of packages to open and the ease of opening the disclosed package saves substantial time. Although the package is easy to open, it is impossible to hide any tampering of the package. Items that are easily damaged can be placed within the package without risk since the ease of opening prevents the contents from being damaged. Damage is also prevented to the user as the package does not require the use of scissors, knives or other sharp objects to puncture the plastic or cut the paperboard.

The disclosed package perforation apparatus and system enables the placement of the perforation on the package to be customized to suit the particular package design; the longer the perforation, the easier the opening. The packages manufactured in accordance with the disclosed system have the advantage of providing an easy open package while preserving the tamper protection of an unperforated product. This is especially advantageous when the packages are manufactured from heavy weight paperboard. The prior art openin g difficulties are in the paperboard since plastics typically tear easily once a tear has been started. The disclosed system is adaptable to existing tooling, and will work with stand up, frame view, one sided and other standard package forms. The blank and receiving pocket are formed by any means currently used by the manufacturer.

The full details of the manufacture of a shrink film package is fully disclosed in the prior art, as noted above, and made a part of the present invention. Generally, depend ing upon design, the package consists of two layers of cardboard material and one or two layers of plastic shrink film. It is noted that the paperboard used in the process can be of any thickness, as well known in the art, and can be recycled, virgin, or any of the materials commonly in use. The film can be Dupont brand Surlyn (P, PVC, and other flexible films.

The disclosed process involves indexing the package to a seal station, followed by folding the package loaded with an article. The lower seal stati on is then locked into the up position.

Serrated knives, protruding through the change plate slots in the lower seal, raise the package approximately 1/32 of an inch, depending upon the depth of cut required. The upper platen in the sealing tool presses the package down onto the knives, thereby causing the lower knives to penetrate the layers of material. Slots in the change plate are dimensioned to receive the knives and a non-conductive material in the upper platen enable the knives to completely penetr ate the paperboard, thereby perforating the package for easy opening. The perforation step is preferably performed at the seal station, simultaneous with the sealing step, enabling the front and backsides of the folded card to be cut simultaneously. Cuttin g prior to the folding operation necessitates extremely careful registration of the two sets of perforations, and would require a double set of knives. Additionally, perforation at the time of sealing also provides the additional function of facilitating the venting of air from the pocket during the shrinking step.

Figure 1 shows a package, indicated generally as 100, as it would appear if it were reopened after the complete process. Prior to sealing, the seal lines indicated for example as 108,106 112,114, and 104, would not be evident, nor would the perforations 120 and 122.

Opening 140 is provided for the hanging of the package from a display hook. Although the film 160 is typically of the same width as the paperboard 166, this is not critical. It is critical, however, that the film 160 fully covers the window 150 in the paperboard 166.

The seal lines are typically not continuous, as evidenced by the spaces such as 102, to enable the evacuation of trapped air. In addition to increasing the ease of opening the package, the perforations 120 and 122 greatly facilitate the venting step. The perforations 120 and 122 do not vent air to the outer edge of the frame 166, but rather through the surface of the paperboard.

Air is not, therefore, required to evacuate through the areas being compressed.

Figure 2 shows the package, indicated generally as 100, folded and in its final form. The film 160 has been shrunk to conform to the shape of the enclosed article. In Figure 3, the sealed package 100, housing a cylindrical object 110, is shown from the side view, illustrating the perforations 120 and 122. The perforations 120 and 122 have been simultaneously cut and provide for easy access to the article within the package.

Figures 4 illustrates the knife retaining block 420 with a knife blade 402 mounted in the receiving slot 412. To enable the set screws 406 to rigidly maintain the knife blade 402 in position without damage, a brace bar 404 is typically employed between the perforation knife blade 402 and set screws 406. As seen in this figure, a slot 412 within the striker plate 400 is dimensioned to receive the knife blade 402 and brace bar 404. The depth of the slot 412 is less than the height of the knife blade 402 to enable the blade 402 to perforate the paperboard 166.

The width of the notch 412 will be dependent upon the system being used and will be evident to those skilled in the art. It should be noted that the slot 412 can be placed at any position along the body of the retaining block 420, or that the block 420 can be reversed, to alter the cutting position of the knife blade 402 relative to the package.

The knife retaining block 420 is placed into a receiving area within the bottom seal tool 510. One or more channels 410 are drilled into t he seal tool 510, generally at right angles to the receiving area, to receive the screws that secure the retaining block 420 within the seal tool 510.

The receiving area within the bottom seal tool can be positioned appropriately to position the knife to the desired position and the manufacture of the receiving area with the tool will be known in the art. It should be noted that the knife blade 402 must extend beyond the surface of the bottom seal tool 510 a sufficient distance to enable the knife blade to 402 completely penetrate the package and come in contact with the receiving material 652 of the upper platen 650.

Figure 6 shows a change plate 600 for simultaneously forming four frame packages. The change plate 600 has a pair of slots 610, for re ceiving the knife blade 402 and enabling the perforation of the four packages. The slots 610 can be about. 125 inch wide by about and inch and one quarter long, in a typical installation. The exact dimensions are not narrowly critical and are dependent upon the size, shape and configuration of the knife blades 402. The exact location of the slots 610 must always properly align with the knife blades 402 to enable the perforating process to work effectively. Both the bottom seal tool and/or the change plat e can be readily interchanged on the sealing device to handle blanks of different shapes and with different dimensions of pockets, by simply removing the holding screws that hold the change plate and seal tool in place.

Figures 7 and 8 show the change plate 600 and the upper platen 650 sealing and perforating the packages. The upper platen 650 has a receiving area 654 containing a non- conductive material 652 to receive the knife blades 402. The receiving area 652 must align with the knife blades 402 to ensure that the knife blade 402 complete penetrates the packaging 660.

To enable a single platen to be used with different knife blade alignments, the receiving area can be enlarged. This also makes the alignment less critical during the machining and asse mbly process. As can be seen the slots 610 are aligned to enable the knife blade 402 to perforate the package, extending through the slots 610 into the upper platen receiving material 652. It should be understood that during the actual operation of the machinery the two elements would be separated by the material of the package 660, as illustrated in Figure 8. The package is not shown in Figure 7, for purposes of clarity only, and it not intended to depict the actual operation of the system.