Method and Apparatus for Forming Composite Container Including a Tab-Cut Label Layer

The use of composite containers for packaging products such as biscuit dough and the like are well known in the patented prior art, as evidenced, for example, by the U.S. Pat. Nos. to Fienup et al 2,793,126 and Geist et al 2,793,127 and 3,144,193. As shown in the Geist et al U.S. Pat. No. 3,144,193, it is conventional in the art to provide in the outer surface of the tubular composite body wall adjacent one metal end closure member a continuous circumferential "collar" cut that extends completely through the label layer to define at one edge portion thereof a triangular-shaped pull tab portion. By means of this pull tab portion, the outer label layer may be removed from the container, whereupon the container is struck laterally against a sharp edge surface (of a kitchen counter or table, for example) to effect bursting of the body wall along the helical butt joint contained therein.

It is also known in the art, as evidenced, for example, by the Vallas U.S. Pat. Nos. 2,891,714 and 2,901,162, to provide a slit or cut in the edge portion of a label layer to define a pull tab portion for removing the label layer from the container, which slit extends parallel with the plane of the metal end closure member. Following removal of the label layer, printed instructions on the body wall become visible for instructing the user how to strike the container against a sharp edge to open the same along a perforated line of weakness.

Finally, in the recently issued Thornhill et al U.S. Pat. No. 3,981,433, a one-step easy-open container for refrigerated dough products and the like is disclosed, in which the container automatically opens (owing to the pressure of the dough product packaged therein) when the label layer is partially removed from the container by pulling on a tab portion defined in the label layer by a circumferential collar cut provided in the outer surface of the container. To this end, the unbounded helical butt joint of the body wall layer is straddled on its inner surface by a helically extending expansible fold portion of the impervious liner layer.

These known composite containers possess certain inherent structural and/or functional drawbacks. In the case of composite containers of the collar cut type, the circumferential cut extends completely around the container, thereby intersecting the abutted edges of the helical seam of the fibrous body wall layer to produce a critically weak area adjacent the point of intersection. Thus, the inner liner layer is the only material holding the pressurized product in at that point. Furthermore, when the collar cut is formed in the composite container wall, generally the collar cutting means extends not only through the label layer, but also partially into the fibrous body wall layer (up to a depth of 0.010 inches or more) thereby weakening the body wall of the container circumferentially. Furthermore, in a collar cut container, the moisture formed by condensation on the outer surface of the container penetrates the collar cut and into the fibrous body wall layer, thereby weakening the container strength and, in some cases, causing the container to burst open at the helical seam. Moreover, the cutting of a circumferential collar cut on a container, or a partial collar cut (as shown by the aforementioned Vallas patents) on a completed container, requires additional handling and supporting of the container during manufacture, thereby increasing tooling costs and unit manufacturing time.

The present invention was developed to avoid the above and other drawbacks of the known composite containers.

Accordingly, a primary object of the present invention is to provide an improved one-step easy-open composite container for dough products and the like in which the label layer is provided-- prior to the winding thereof onto the body wall layer--with a plurality of longitudinally spaced tab cuts that are each arranged at an acute angle relative to the line of end cut of the label layer, whereby the corresponding angle between the tab cut and the overlapping edge of the label layer defines a pull tab portion for initiating tearing the label layer from the container. More particularly, after the label layer containing the tear cuts is wound upon the tubular body wall layer, the tear cut extends generally in the direction of the metal end, thereby all but eliminating the area of the body wall layer that may be exposed to moisture. In addition, the label tear cut on the bias completely seals off the critical point of the helical but joint in the body wall from any direct moisture penetration, thereby reducing market potential failure. Furthermore, the label tear cut on the bias completely eliminates cutting into the fibrous body wall layer, thereby eliminating the weakening of the body wall of the container circumferentially. In accordance with an important advantage of the invention, by eliminating these critically weak areas, the manufacturer can use lighter materials without sacrificing container strength or market integrity. Consequently, material cost savings to the manufacturer has the advantage of eliminating the scoring knives at the tube cutting station and related tooling and maintenance of this tooling. Overall, tooling cost, spoilage and maintenance downtime are greatly reduced.

In accordance with a more specific object of the invention, the novel label containing the bias cut tab portion is used in connection with a fibrous body wall layer having an unbonded helical butt joint across which is mounted an impervious inner liner layer which is folded to define an expansible portion that extends helically of the container opposite the body wall butt joint. When the pull tab is pulled to partially tear the label layer from the container circumferentially adjacent the metal end, it will tear for a distance sufficient to expose the butt joint which expands (owing to the pressurized dough product) to separate the edges thereof and, consequently, to expand the folded inner liner portion to automatically open the same, thereby to permit removal of the packaged dough product from the container.

In accordance with a further object of the invention, in one embodiment, the circumferential end cut is slightly spaced from the tab cut, and in another embodiment, the cuts are contiguous. In order to assist in the tearing away of the label from the body wall along a circumferential tear line adjacent the metal end closure member a layer of conventional adhesive-resistant material (such as lecithin [a soybean-type produce with fatty acid base], silicone or microcystalline wax) or a conventional release adhesive (such as polyvinyl alcohol and polyvinyl acetate formulation using clay and water, or various groups of hot melts) may be provided on those portions of the surface of one of the body wall and label layers facing the other of these layers which contain the circumferential cuts, the remaining portions of the surface being coated with a conventional liquid adhesive (such as a polyvinyl alcohol adhesive) for bonding the label layer to the body wall layer. To further assist in the tearing of the label layer from the body wall layer, the surface portion of the body wall layer may consist of reprocessed news lining, the remaining portion of the body wall layer consisting of reprocessed kraft stock. The impervious liner layer normally comprises a metal foil (such as aluminum foil) faced with kraft paper, and the label layer may similarly be formed of a metal foil faced with kraft paper, the paper layers of these laminates facing the fibrous body wall layer.

Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawing, in which:

FIG. 1 is a perspective view of the composite container of the present invention;

FIG. 2 is a perspective view of the container of FIG. 1 with the label layer partially torn away to permit automatic bursting of the inner liner layer along the helical body wall butt joint;

FIGS. 3 and 4 are sectional views taken along lines 3--3 and 4--4, respectively, of FIG. 1;

FIGS. 5 and 6 are transverse sectional views of the container illustrating the one-step opening operation of the container;

FIG. 7 is a somewhat diagrammatic top view of a first method and apparatus for producing the composite container of FIG. 1;

FIG. 8 is a detailed view taken along line 8--8 of FIG. 7;

FIG. 9 is a diagrammatic illustration (with certain parts removed) of a modification of the apparatus of FIG. 7; and

FIG. 10 is a detailed sectional view taken along line 10--10 of FIG. 9.

The composite container of the present invention includes a tubular composite body wall 2 the upper and lower ends of which are closed by conventional metal end closure members 4. The composite body wall layer includes an impervious inner layer 6, a fibrous body wall layer 8, and an outer label layer 10, which layers are helically wound in the same sense upon a mandrel and are adhesively bonded together by a conventional liquid adhesive (for example, a polyvinyl alcohol adhesive). More particularly, the impervious inner layer 6 is formed from a metal foil-kraft paper laminate, the paper layer of which is bonded to the fibrous body layer 8. Similarly, the outer label layer 10 may comprise a metal foil-kraft paper laminate, the paper layer 10a of which is bonded to the fibrous body wall layer 8, and the metal foil layer 10b of which is exposed and carries the printed advertising indicia. In order to assist tearing of the label layer from the fibrous body wall layer, the fibrous body wall layer 8 may include a surface portion 8a that is formed from reprocessed newspaper stock, the remaining portion 8b of the fibrous body wall layer 8 being formed of reprocessed kraft paper.

As in the invention disclosed in the aforementioned Thornhill et al U.S. Pat. No. 3,981,433, the adjacent edges of the helical butt joint 12 contained in the fibrous body wall layer 8 are unbonded, one edge portion 6a of the inner liner layer 6 terminating short of the butt joint. The other longitudinal edge portion of 6b of the inner liner layer 6 extends in straddling relationship across the butt joint and above the first edge portion 6a, said second edge portion being reversely folded back upon itself to define a third inner liner portion 6c that extends between the first and second liner portions 6a and 6b. The third liner portion 6c terminates short of the butt joint 12 and at least the free extremity thereof is bonded to the adjacent edge of the first edge portion 6a. Thus, the inner liner portion 6a, 6b and 6c define an expansible folded seam that straddles the unbonded butt joint 12 and isolates the same from the moisture of a product, such as leavened dough 14 in the form of biscuits.

In accordance with the present invention, overlapping edge of the label layer 10 is provided with a tab cut 16 which extends generally toward the adjacent upper metal end portion 4, thereby defining a pull tab portion 18 on the label layer. As shown in FIGS. 2, 5, and 6, when the user pulls on the pull tab portion 18, the label layer 10 is progressively torn from the body layer 8 to expose the unbonded butt joint, one edge 16a of the tab cut being carried by the pull tab portion 18 and the other edge 16b being spaced from the butt joint 12, whereupon the pressure of the packaged dough product causes the mating edges of the butt joint to separate to permit progressive expansion of the inner layer 6. As shown in FIGS. 5 and 6, the inner liner 6 is caused to rupture either at a line of weakness defined by a creased fold line 6d, or by pulling the reversely folded third portion 6c progressively away from the inner liner first edge portion 6a. During this partial removal of the outer label layer 10, it is torn at its upper end along a circumferential tear line 20 adjacent the upper metal end closure member 4 as shown in FIG. 2. The label layer 10 is progressively removed until a sufficient portion of the butt joint 12 is exposed to permit the expansion thereof by twisting the metal end members 4 in opposite directions to further open the butt joint to permit the removal of the packaged products from the container.

Referring now to FIG. 7, it will be seen that the inner liner layer 6 is initially helically wound upon a stationary mandrel 30, and the fibrous body wall layer 8 has a layer of liquid adhesive applied to the upper surface thereof by an adhesive-applying roller 32 prior to the helical winding thereof upon the outer surface of the liner layer 6. The body wall-inner liner layer laminate is longitudinally displaced to the left on the mandrel 30 by means of conventional belt conveying means 34.

The outer label layer 10 is fed longitudinally in edge-overlapping relation to the mandrel 30 and is coated on its lower surface with a layer of liquid adhesive by the adhesive supply means 36. In accordance with the present invention, the label layer 10 passes through a cutting station 38 which includes vertically arranged reciprocatory knife means 41 (FIG. 8) that reciprocate vertically relative to a stationary shear member 42, thereby to form in the label layer 10 a plurality of successive parallel longitudinally-spaced tab cuts 16. Each of the tab cuts 16 is arranged at an acute angle (.alpha.) relative to the associate line of end cut 40 (which will be discussed below), said tab cut being angularly arranged to the label edge to define the tab portion 18. The length of each tab cut 16 is about three-fourth of an inch, said tab cut terminating either immediately adjacent or slightly spaced from the end cut severing lines 40 (which may or may not be printed on the label layer). The pre-tab cut label layer 10 is then wound helically in edge-overlapping adhesively bonded relation upon the outer surface of the body wall layer 8, whereupon the resulting laminate is conveyed by the belt conveyor means 34 toward a cutting station 44 including a rotatably mounted knife 46 that circumferentially cuts the tubular laminate into cylindrical sections along circumferential cuts defined by the dividing lines 40. Alternatively, the laminate could be severed in desired longer lengths (for example, an eight can length), and be removed from the mandrel 30 for severing into sections at another cutting station, as desired. In any event, the severed sections are transported to an end applying station 47 at which a metal end 4 is connected with the composite tubular body wall 2 in any conventional manner (for example, by the rolled seam illustrated in FIG. 4). In accordance with the specific feature of the invention, it may be desirable to apply to the mating surfaces of either of the body layer 8 or the label layer 10 opposite the line of circumferential end cut 40 a layer 49 (FIG. 2) of either an adhesive resistant material (such as lecithin, silicone, or a microcrystalline wax) or a release adhesive (such as polyvinylchloride and polyvinylacetate formulation using clay and water, or various hot melts) whereby the label layer may be torn more readily from the fibrous body wall layer. Thus, prior to passage of the label layer 10 to the adhesive supply means 36, the label layer passes through a preliminary station 50 at which an adhesive resistant material or a release adhesive is coated on the under surface of the label layer opposite the line of circumferential cut 40. Alternatively, the adhesive resistant material or the release adhesive could be applied to the under surface of the body wall layer strip 8 by similar rotary applicator means 52 having a helical rib of suitable configuration.

Referring now to the modification of FIG. 9, the reciprocatory cutter means of the embodiment of FIG. 7 are replaced with rotary cutter means 60 having a relatively short helical blade 62 for forming the tab cuts 16 in the edge portion of the label layer 10. In this embodiment, a backup roll 64 containing a slot 66 for receiving the knife blade 62 is arranged opposite the rotary cutting drum 60. As in the embodiment of FIG. 7, the tab cut 16 is arranged at an acute angle (.alpha.) relative to the end dividing circumferential line of cut 40, whereby the angle (.beta.) that is contained between the tab cut and the label layer edge defines the pull tab portion 18 on the label layer 10. Thus, in both embodiments of the invention, the tab cuts 16 are formed in the label layer prior to the winding thereof on the mandrel upon the outer surface of the fibrous body wall layer 8.

In the can manufacturing process, a spirally wound tube is formed by laminating a layer of paper board (97# basis weight) in combination with an aluminum foil inner liner around a stationary cylindrical mandrel. The inner liner (0.00035 inch aluminum and 30# basis kraft paper) is simultaneously heat sealed in a continuous spiral bond which provides the internal integrity of the final can, preventing or at least arresting the entrance/exit of moisture through this barrier. The last layer is generally a preprinted label (0.0003 inch aluminum foil and 40# basis kraft paper) which becomes the final outer wrap of the can. In the prior "collar cut" containers, this outer wrap is circumferentially cut with the cut extending not only through the label but also partially cutting into the fibrous body wall layer up to a depth of 0.010 inches or more. According to the present invention, by precutting the label layer with the tab cuts, the use of collar cutting means is eliminated. In any event 55 or 60# 2CR metal ends are attached to the can body. Within this construction, the internal contents of a leavened dough is contained as long as the dough remains chemically stable and there is no degradation in the structure of the can itself.

This multiple layered can makes it possible to use extremely thin, high cost materials only where they are strategically required in the construction, thereby allowing the paperboard to be sandwiched in between these materials to build strength and rigidity into the can body wall. Reiterating, a composite can of this construction is designed to withstand market conditions in relation to the chemical limitations of the internal dough product it must contain and the market environment in the retail dairy case.

The common term "shelf life" as it refers to the product is the time in which the dough product must be used before it chemically deteriorates. The can is so designed that it will last longer than the shelf-life of its contents. Thus, it is around a prescribed set of conditions that any changes or alterations are made in the can construction since preservation of the product is of prime consideration. Since changes in materials and technology are always present and under consideration, a planned design to examine can integrity was established over the years and is accepted as an industry standard and referred to as a Condition III High Humidity test. The Condition III procedure outlined as follows is the path which most closely associates itself to an accelerated internal and external aging test of manageable proportions that may be considered representative of the market environment before usage:

(a) cans are packed with leavened dough to greater than normal manufacturing dough weights, designed to deliberately stress the can materials from the inside;

(b) the packed cans are then submitted to a (1) hour proofing period at 90.degree. F to activate the leavening agent in the dough; and

(c) the packed cans are then subjected to an abusive exterior environment of high humidity in temperature cycling as defined--4 hours at 40.degree. F, 2 hours at 40.degree.-60.degree. F, 4 hours at 60.degree. f, 2 hours at 60.degree.-40.degree. F, etc.

Under the high humidity conditions, the dew point is passed from 60.degree.-40.degree. F thus causing condensation to form around and on the exterior of the can. This condition will cause premature failure of weaker can constructions and in those cans with critical defects.

Thus, a specific test may be conducted to purposefully measure a particular manufacturing alteration; as in this case, the opening characteristics of cans with various label cuts and basis weight body stock papers. As always these "experimental cans" with the particular design or material change are tested under these conditions and compared simultaneously to the conventional collar-cut cans, known as "controls".

To illustrate the cost savings potential of the tab cut label over the conventional collar-cut label, label tests were conducted under the procedure previously described.

Table I is specific as to the actual material construction of each of the experimental and control cans.

Table II illustrates the design and test results used for comparison to gain factual data on (a) reduced basis weight paper board with the new tab-cut label (b) reduced basis weight paper with a controlled conventional label cut depth (c) the conventional label cut using 97 lb. basis weight paper.

From the above test we can draw the following statistically based conclusion to determine the average can life. This is done on a computer evaluation using the null and alternate hypothesis along with standard "T" tests. All were observed at the 97.5% confidence level for the can treatments as set up in this experimental design.

In summary, the cans in experimental #1 (tab-cut label/80# basis wt. paper) are equal to or better than cans in experimental #2 (controlled label cut depth/80# basis wt. paper) and the control cans (conventional collar-cut/97# basis wt. paper). These results indicate a manufacturing cost savings can be achieved by using the tab-cut label/80# basis wt. paper can construction over the conventional collar-cut label using 97# basis wt. paper without reducing can integrity. At today's paper market pricing the savings could be between 15 and 20%.

While in accordance with the provisions of the Patent Statutes the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made without deviating from the inventive concepts set forth above.