Abstract:
A leak resistant paperboard tray formed from a blank having a scored surface that defines a base, panels and webbing flaps at the corners. When folded at the score lines of the scored surface in an appropriate manner, an leak resistant food tray forms and the webbing flaps are then adhered to neighboring walls to retain the shape in the folded condition. The adhesive is applied to exterior facing surfaces of the webbing flaps so that food contents of the container do not come into contact with the adhesive and thereby avoiding the risk of contamination.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Field of the Invention 
         [0002]    The invention relates to a robust food tray made of coated paperboard to be water and grease resistant and that adheres its webbing flaps to its upright panels retain its shape and also prevent the food contents from becoming contaminated by the glue or adhesive used in adhering the food tray in its assembled condition. The upright panels have upright edges that diverge as they extend further away from the base of the tray. 
         [0003]    Discussion of Prior Art 
         [0004]    100% Recycled Uncoated Paperboard 
         [0005]    100% recycled uncoated paperboard is made from a high percentage content of post-consumer waste content paper, which may contain mixed paper, retired books, old magazines, newspaper and old corrugated boxes. The phrase “post-consumer waste” means that the fibre has been reclaimed from materials that have already passed through the consumer&#39;s hands. The result is a paperboard that is not coated on either side and is highly susceptible to grease absorption and staining 
         [0006]    Conventional Manufacture of a Paperboard Box 
         [0007]    According to an article entitled FOLDING CARTONS, published online under the heading Packaging technology at http://packagingtech.net/56-folding-cartons.html?newsid=56: 
         [0008]    Paperboard Selection 
         [0009]    Successfully meeting the needs of a folding-carton user begins with choosing the paperboard best suited for the job. In general, this means selecting the grade with the lowest cost per unit area that is capable of satisfying the performance requirements of the specific application. Economics and performance dictate careful selection of paperboard grades for each use. 
         [0010]    Selection Criteria 
         [0011]    A variety of criteria are commonly used in the selection of paperboard grades. The Technical Association of the Pulp and Paper Industry (TAPPI) has published standardized test methods for many of these criteria (3) (see Testing, packaging materials). TAPPI Standard Methods are widely used and accepted by the industry. The most important and widely used criteria are shown below. 
         [0012]    FDA/USDA Compliance. 
         [0013]    This is a nondiscretionary criterion for food products and is dependent on the type of food and the type of contact anticipated between the food and the paperboard or coatings on the paperboard. 
         [0014]    Color. 
         [0015]    Color is typically chosen for marketing reasons. The side of the paperboard that becomes the outside of the carton is generally white, but the degree of whiteness varies among grades. Depending on the materials-selection and processing strategies of suppliers, outside board color can be blue-white or cream-white. These shades are noticeably different and can limit substitution of grades. Board color on the inside of cartons varies from white to gray to brown. 
         [0016]    Physical Characteristics. 
         [0017]    It is possible to establish minimum levels for each carton application that allow the package to satisfactorily withstand the rigors of packaging machinery, shipping, distribution, and use by the consumer. Physical properties commonly used to predict suitability of board for a given use include stiffness, tear strength, compressive strength, plybond strength, burst strength, tensile strength, elongation, and tensile energy absorption. Physical criteria normally define the basis weight and thickness of paperboard that is used to produce a carton. 
         [0018]    Printing Characteristics. 
         [0019]    Following the selection of a specific graphic design and printing method for the carton, a paperboard is selected based on these criteria: smoothness; coating strength; ink and varnish gloss; mottle resistance; and ink receptivity. Not all criteria are important for every printing technique. 
         [0020]    Barrier. 
         [0021]    The most common barrier requirements are for cartons to provide protection against moisture and grease. The choice of a barrier material and application method influences board choice. For example, if polyethylene (PE) is to be applied to the carton, a board with a treatment that holds the PE on the board surface can have economic and processing advantages over an untreated board. Materials and application methods are described below. 
         [0022]    Paperboard Types 
         [0023]    In the United States, the three most widely used types of paperboard are identified as follows: 
         [0024]    Coated Solid Bleached Sulfate (SBS). 100% virgin, bleached, chemical furnish, clay-coated for printability. 
         [0025]    Coated Solid Unbleached Sulfate (SUS). 100% virgin, unbleached, chemical furnish, clay-coated for printability. 
         [0026]    Coated Recycled. Multiple layers of recycled fibers from a variety of sources, clay-coated for printability. 
         [0027]    Coated recycled boards are the most widely used. Other types include folding box board (FBB) and white lined chipboard (WCC). 
         [0028]    Overall treatments or coatings are applied to webs of paperboard to provide specific functions. Clay-based coatings to provide high-quality printing surfaces are the most common treatment applied on the paperboard machine. Grease-resistant fluorochemicals are applied on board machines as well, either as furnish additives, surface treatments, additives to clay coatings, or in combination. Mold-inhibiting chemicals are also applied to boards designed for bar-soap packaging, to prevent moisture in the product from initiating mold growth. Surface treatments applied on other-than-board production equipment are discussed below under Carton Manufacturing Processes. 
         [0029]    Carton Manufacturing Processes 
         [0030]    After a paperboard grade has been selected for a specific carton style and use, a variety of manufacturing options are available for converting that board into cartons. Although it is a highly unusual carton that requires each one of the steps or stages described below, all are commonly employed to produce folding cartons in today&#39;s market. 
         [0031]    Extrusion Coating 
         [0032]    This technique involves the coating of one or both sides of the paperboard webbing with a relatively thin (generally less than 0.001-in. (25.4-mm)) layer of a thermoplastic polymer (see Extrusion coating). Low-density polyethylene (LDPE) is the most commonly used extrusion coating for folding cartons and provides a cost-effective means of obtaining excellent protection against water resistance as well as a fairly good water-vapor barrier. 
         [0033]    LDPE is also used as a heat sealant (see Sealing, heat), particularly when twoside coatings are employed. When the use temperature of the package exceeds 1501 F (651 C), HDPE or PP can be used to raise the acceptable use temperature to 2501 F (1211 C). These two polymers also provide improved grease resistance. Coating board with PET can raise the use temperature to over 4001 F (2041 C), suitable for most “dual-ovenable” applications. Coextrusion, in which back to-back layers of two plastics are laid onto paperboard, makes it possible to take advantage of the special properties of some exotic plastics, such as nylon, that by themselves will not adhere to paperboard. 
         [0034]    Laminating 
         [0035]    The earliest means of significantly enhancing the properties of paperboard was the combination with other materials through lamination (see Laminating). The most commonly used laminating adhesives are water-based glues (see Adhesives), or thermoplastic polymers. Materials laminated to paperboard include high-quality printing paper for enhanced graphics capabilities (see Paper), grease- or water-resistant paper for improved barrier, aluminum foil for barrier or aesthetics (see Foil, aluminum), and film (sometimes metallized) for barrier or aesthetics (see Metallizing). 
         [0036]    Printing 
         [0037]    Prior to the printing operation, paperboard is handled in webbing form. A decision must be made to continue in webbing form or convert the webbing to sheets before printing and die cutting. This choice is primarily dictated by the printing technique chosen (see Printing). Sheeting is most often done at the carton-producer&#39;s facility. A small segment of the industry purchases board sheeted at the paperboard mill. 
         [0038]    The main processes for carton printing today are offset lithography, flexography, and gravure. Letterpress and silk screen are used to a limited extent. The most recently introduced process, digital printing, can be used for short print runs and for customizing packaging in already premade bulk. Printing involves solid print, text, illustrations, and diagrammatic representatios. Brand positioning can have a major influence on the printing design. Functional needs have to be taken in to account. Products that retain ink odors require special attention in choice of inks and printing methods. Products that are packed hot may need rub-resistant print surfaces. 
         [0039]    Cutting and Creasing 
         [0040]    Following the printing operation, individual cartons are cut from webs or large sheets and creased or scored along desired folding lines. Reciprocating flat-bed or platen cutting is almost invariably used to cut and crease sheets printed by offset lithography. In this technique, an accurately positioned array of steel cutting knives and scoring rules is pressed against a printed sheet of paperboard. The knives penetrate through the paperboard to cut out the pattern of the carton. Rules force the board to deform into channels in the counter plate, producing controlled lines of weakness (scores) along which the board will later predictably bend or fold. Alternatively, scores can be produced by cutting partially through the paperboard or by alternating uncut segments with completely cut-through segments. 
         [0041]    Central Impression Flexographic Presses 
         [0042]    Central impression flexographic presses are conventional. According to the online encyclopedia Wikipedia at https://en.wikipedia.org/wiki/Flexography: 
         [0043]    Operational Overview 
         [0044]    1. Fountain Roller 
         [0045]    The fountain roller transfers the ink that is located in the ink pan to the second roller, which is the anilox roller. In Modern Flexo printing this is called a Meter or “metering” roller. 
         [0046]    2. Anilox Roller 
         [0047]    This is what makes flexography unique. The anilox roller meters the predetermined ink that is transferred for uniform thickness. It has engraved cells that carry a certain capacity of inks that can only be seen with a microscope. These rollers are responsible to transfer the inks to the flexible-plates that are already mounted on the Plate Cylinders. 
         [0048]    3. Doctor Blade (Optional) 
         [0049]    The doctor blade scrapes the anilox roll to ensure that the predetermined ink amount delivered is only what is contained within the engraved cells. Doctor blades have predominantly been made of steel but advanced doctor blades are now made of polymer materials, with several different types of beveled edges. 
         [0050]    4. Plate Cylinder 
         [0051]    The plate cylinder holds the printing plate, which is soft flexible rubber-like material. Tape, magnets, tension straps and/or ratchets hold the printing plate against the cylinder. 
         [0052]    5. Impression Cylinder 
         [0053]    The impression cylinder applies pressure to the plate cylinder, where the image is transferred to the substrate. This impression cylinder or “print Anvil” is required to apply pressure to the Plate Cylinder. 
         [0054]    Presses 
         [0055]    Stack Press 
         [0056]    Color stations stack up vertically, which makes it easy to access. This press is able to print on both sides of the substrate. 
         [0057]    Central Impression Press 
         [0058]    All color stations are located in a circle around the impression cylinder. This press can only print on one side. Advantage: excellent registry 
         [0059]    In-Line Press 
         [0060]    Color stations are placed horizontally. This press prints on both sides, via a turnbar. Advantage: can print on heavier substrates, such as corrugated boards. 
         [0061]    For maximum efficiency, the flexo presses produce large rolls of material that are then slit down to their finished size on slitting machines. 
         [0062]    While a central impression flexographic press may be used to configure paperboard into a tray, other kinds of units of any form may be used instead, such as: stack, tandem or in-line type units either tied into die cutters or roll to roll flexographics, the product of which is brought to die cutters to be cut. Conventionally, they may have 4 to 10 print units/decks and the print format is adjusted by changing a format cylinder. 
         [0063]    The paperboard tray can be formed out of multiple substrates, with or without ant-fingerprint coating. All the substrates can or not have poly coating inside as desired. All three types of configurations of print decks are preferably flexographic and formed into a flexographic press as is conventional. The flexographic press can be used in a roll-to-roll configuration and the rolls brought to a die cutter for cutting into blanks. 
         [0064]    Conventional paperboard food trays—flimsy because of their inability to carry heavy food loads without compromising their integrity and they leak soon after liquid based foods and condiments such as salsa or sauces are placed in them. According to U.S. Pat. No. 6,543,679, which discloses a stackable food tray with condiment compartment: 
         [0065]    Finger foods, such as chicken nuggets, popcorn shrimp, french fries, and onion rings, are often served in paperboard trays. These trays have flat bottom panels and side panels that extend upwardly therefrom at an angle to define a top opening larger than the bottom panel. In the interest of space efficiency, these trays are preferably stackable or nestable so that one tray fits inside another tray. This allows large stacks of trays to be shipped and stored in a relatively small space until needed. 
         [0066]    Many of the above foods are frequently eaten with condiments such as ketchup, cocktail sauce, and barbeque sauce. Since these foods are often eaten with one&#39;s fingers, a person typically holds a food item in his fingers and dips it into a condiment. When eating in a sit-down restaurant, the condiment may be dispensed directly into the paperboard tray next to or on top of the food product, or a tub of the condiment can be placed on a table next to the consumer. 
         [0067]    It would be preferable to construct a leak resistant paperboard tray that is more robust than conventional finger food paperboard trays so as to handle heavier food beyond finger food such as hot entrés, salads, barbeque dinners and heavy sides such as potato salad, coleslaw, mac and cheese etc. That is, being more robust in the sense of being less susceptible to collapse or otherwise comprising its integrity when filled to the brim or more with heavier food than finger foods. Preferably, the more robust tray is also less susceptible to tipping over when food accumulates more on one side of the paperboard tray than on the opposite side. Such accumulate food is apt to press more against one upright side panel that against an opposite upright side and thus render the tray unbalanced. 
       SUMMARY OF THE INVENTION 
       [0068]    One aspect of the invention resides in a leak resistant food tray that has a scored surface with score lines that define a base, a plurality of panels, and a plurality of webbing flaps. The base is separated from the panels by two pairs of the score lines that are transverse to each other, which the score lines of the respective pairs being substantially parallel to each other. The plurality of webbing flaps are separated from neighboring ones of the panels by further ones of the score lines that are obliquely angled in a manner symmetric to each other. Each of the webbing flaps is divided into symmetric halves by another of the score lines. The scored surface is foldable at the score lines in a manner that bends the plurality of panels into an upright orientation from the base and folds the webbing flaps so that one of the halves of the webbing flaps faces a neighboring one of the panels. 
         [0069]    Glue or adhesive serve as a means for adhering the one of the halves of the webbing flaps to the neighboring one of the panels to maintain the scored surface in the upright orientation when the scored surface is folded at all of its score lines. The adhesive adheres only exterior facing sides to each other of the webbing flaps and neighboring ones of the panels. 
         [0070]    The plurality of panels may include a pair of opposite side panels and a pair of opposite end panels, with the side panels being larger lengthwise than the end panels. Pairs of webbing flaps may be adhered to just the side panels or to just the end panels. Alternatively, a pair of the webbing flaps may be adhered to different ones of the side panels and the remaining pair adhered to different ones of the end panels. Another possibility is to adhere three of the webbing flaps to the side panels and the remaining one to an end panel or adhere three of the webbing flaps to the end panels and the remaining one to a side panel. 
         [0071]    The leak resistant food tray of the present invention conserves paperboard in that each is folded from a square blank as the scored surface with no need to trim away wastage. Further, webbing flaps are on the outside of the tray rather than the inside so that the food contents (which may include liquids) of the leak resistant food tray won&#39;t come into contact with residual glue that was applied to adhere the webbing flaps to the side panels. 
         [0072]    The leak resistant food tray is substantially straight paneled with a slight taper. The leak resistant food tray may be shipped with smaller such leak resistant food trays in a nested configuration or else may be shipped with same size leak resistant food trays in a stable, stacked configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0073]    For a better understanding of the present invention, reference is made to the following description and accompanying drawings, while the scope of the invention is set forth in the appended claims. 
           [0074]      FIG. 1  is an isometric top view of a leak resistant food tray in accordance with the invention. 
           [0075]      FIG. 2  is an isometric view of stacking multiple leak resistant containers of the same dimension. 
           [0076]      FIG. 3  is a top view of nesting multiple leak resistant containers of different length and width dimensions, although the height is substantially the same for each. 
           [0077]      FIG. 4  is a top view of a blank that is scored for folding into the shape of the lead resistant food tray of  FIG. 1 . 
           [0078]      FIG. 5  is an isometric bottom view of the leak resistant food tray of  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0079]    Turning to the drawings,  FIGS. 1-5  show a leak resistant food tray  10  with webbing flaps  12  at the edge corners that render the tray leak resistant. The leak resistant food tray  10  has slightly tapered panels—side panels  14  and end panels  16  that taper to a base  30 . 
         [0080]    In the case of  FIGS. 1 and 5 , the side panels  14  are longer lengthwise than the end panels  16 . However, the side panels  14  and the end panels  16  could instead be the same length. Further, the side panels  14  are symmetric to each other and the end panels  16  are symmetric to each other. 
         [0081]    For purposes of illustration, one of the webbing flaps  12  is shown before its attachment to the side panel  14  with eight adhesive dots  18  applied to one exterior facing surface that faces the outward facing side of a side panel  14  and is to be pressed against it. That exterior facing surface is part of one half  22 A of two symmetric halves  22 A,  22 B of one of the webbing flaps  12 . The two halves  22 A,  22 B arise because of a fold line  24  formed by additional score lines along a symmetric centerline of the webbing flap  12 . Such Is typical for all the webbing flaps  12  to make attachment to neighboring side walls  14  or end walls  16  as the case may be. 
         [0082]    The base  30  is separated from the side panels  14  and the end panels  16  by pairs of score lines that are transverse to each other, with the score lines of each pair being substantially parallel to each other. Each webbing flap  12  is connected to a neighboring side panel  14  along a fold line  26  formed by further score lines and connected to a neighboring end panel  16  along a further fold line  28  formed by further score lines. The adhesive dots  18  are arranged in line to be closer to the additional score lines than to the further score lines over a majority of the length of the fold line  24 , because the fold line  24  eventually reaches a corner with the fold line  26  or  28  as the case may be. 
         [0083]    The side panels  14  and the end panels  16  extend upright from the periphery of a base  30 . The topside of the base  30  is shown in  FIGS. 1-4  and the underside of the base  30  is shown in  FIG. 5 . 
         [0084]    The interior facing side of the webbing flaps  12  that has no adhesive applied and is free of any gluing areas. Preferably, the exterior facing sides of the one half  22 A of the webbing flaps  12  are double-glued at the adhesive dots  18  to hold the corners securely and thus two hits of adhesive dots are applied to each webbing flap  12 . The adhesive  18  is conventional and preferably resistant to withstand exposure to microwaves in a conventional microwave oven (such as 800 Watt delivery) without losing adhesion integrity so the adhesive won&#39;t release itself when so exposed within confines of a conventional microwave oven powered to deliver the 800 Watt microwave radiation energy and US Food and Drug Administration approved for use with foods. 
         [0085]    A benefit derived from applying the adhesive dots  18  just to the exterior facing side, rather than to the interior facing side, of one half  22 A of the webbing flaps  12  is that doing so prevents the interior of the tray from having residual glue contamination of food and avoids the so called “angle hair” glue filaments from being found in the interior of the tray that might be mistaken for human hair by persons who are served with the trays containing food. The adhered webbing flaps  12  also help retain the side panels  14  and the end panels  16  in their inclined orientations so that the open top has the wider periphery than that of the base  30 . 
         [0086]    The slight taper of the side panels  14  and end panels  16  to the base  30  allows for stacking of the leak resistant food trays of the same dimension in the manner of  FIG. 2  or for nesting of the leak resistant food trays of different dimensions in the manner of  FIG. 3 . Either way, the slight taper gives each tray&#39;s side panels  14  and end panels  16  that are rigid for giving dimensional stability so as to help avoid tipping over, e.g., when stacked upon each other. Further, the leak resistant food trays  10  can accommodate more food contents than they would otherwise without the taper. Indeed, heavier loads can be accommodated that would otherwise be the case without the taper. It should be appreciated from  FIG. 3  that the webbing flaps  12  could be adhered to the end panels  16  as opposed to the side panels  14  or vice versa or to some mixture or side and end panels. 
         [0087]    The interior facing side of the leak resistant food tray  10  is coated with a coating that resists grease staining and resists water staining so that the tray may accommodate greasy foods and foods with thick, viscous gravies that traditional uncoated paperboard food trays cannot accommodate without compromising their integrity. However, there is no need to coat the webbing flaps  12  with such a coating and thus the webbing flaps  12  may lack such a coating altogether. 
         [0088]    Turning to  FIG. 4 , a paperboard blank  40  is shown scored with score lines on one face and thus has a scored surface. The score lines are folded appropriately to form the configuration of the leak resistant food tray  10  of  FIG. 1 , which will retain its shape after the webbing flaps  12  are adhered to the side panels  14  or end panels  16  as the case may be. The paperboard blank  40  is coated at least on one side, but the coating only needs to be over the interior facing surfaces of the base and panels. No coating needs to be applied to the webbing flaps  12 . 
         [0089]    The blank  40  (in the shape shown) uses up to ninety percent less inter-sheet waste than conventional blanks in forming a food tray, because blanks for conventional food trays are not perfect squares or rectangles. The blank  40  of  FIG. 4  allows for a maximum paperboard optimization with minimal waste due to it being essentially a perfect square or rectangle (albeit with chamfered corners). As can be appreciated, the blank  40  in its flattened condition fits within confines of a square or rectangular area (as the case may be) defined by lines (not shown) aligned with the edges of the panels that intersect each other at respective corners. 
         [0090]    Further, the fold lines  42  of  FIGS. 4 and 5  define the perimeter of the base  30 . Such a base periphery is smaller than the periphery of the open top of the leak resistant food tray  10  of  FIG. 1  because of the slight taper of the side panels  14  and end panels  16 . This slight taper arises in part due to the both the fold lines  26  and the further fold lines  28  being angled (see  FIG. 4 ) so that the side panels  14  and the 3nd panels  16  diverge as they extend away from the base  30 . That is, fold lines  26  and further fold lines  28  are not parallel and not collinear with the fold lines  42  because they obliquely angle from the perimeter of the base outward are symmetric with respect to each other (that is, they define equivalent oblique angles). Also, as can be seen in  FIG. 5 , the underside of the base  30  is flat. 
         [0091]    The manufacture of the leak resistant food trays  10  may follow the same procedure as the conventional manufacture of a paperboard box that is mentioned in the Background of the Invention of this application. While it is preferred that the leak resistant food trays  10  be formed without lids, one might appreciate from  FIG. 3  that should a lid be needed, providing open trop trays  10  of different dimensions would mean that a larger dimension tray could be flipped upside down to serve as a lid for a smaller dimension tray, depending upon the height of the food, if any, that extends above the panel height of the smaller dimension tray. 
         [0092]    The paperboard leak resistant food tray  10  of the present invention is more robust (as a result of its sturdy construction) than conventional finger food paperboard trays so as to handle food beyond finger food such as hot entrés, salads, barbeque dinners and heavy sides such as potato salad, coleslaw, macaroni and cheese etc. 
         [0093]    While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be understood that various changes and modifications may be made without departing from the scope of the present invention.