Sealable snack container

[0001] This application claims priority to U.S. Provisional Patent Application No.

[0002] 61/378,229 filed Aug. 30, 2010, the disclosure of which is incorporated herein in its entirety by this reference.

[0003] The present invention relates to lidded thermoformed containers.

[0004] Containers for food storage are known. In many instances food storage containers are injection-molded which makes it possible to incorporate relatively complex molded-in features such as living hinges, freshness indicators and so forth. In this regard, see United States Patent Application Publication No. US 2004/0232026 of Goeking et al., entitled “Microwaveable Food Storage Container with Freshness Indicator and Steam Vent”.

[0005] A thermoformed food container is shown in U.S. Pat. No. 7,258,905 to Whitmore et al., entitled “Sealable Food Container With Improved Lidding and Stacking Features” which includes a base such as a plate or platter and a domed lid. While the lid and base include sealing features, it is apparent to one of skill in the art that a liquid-proof surface-to-surface, interference-fit seal is not readily achieved in connection with lidded thermoformed products because, in part, the base and lid are formed separately from different sheet stock in different forming tools. Gauge and mold variations as well as different forming parameters make tolerance control exceedingly difficult.

[0006] If a lid is too tight, the lid will either not easily fit the container base (if it fits at all), or when too much force is applied, crush the container; leading to extreme consumer frustration in either case. Accordingly, existing lidded thermoformed containers oftentimes have a base made of relatively heavy gauge material, while the lid is made of lighter sheet stock and the container is designed to have a relatively “light” capping force in order to avoid the foregoing problems as dimensional variation occurs during manufacturing. The seal thus has large tolerances and sealing of the container is severely compromised.

[0007] While liquid-proof and/or airtight seals are highly desirable, lightweight thermoformed containers are particularly difficult to lid tightly so that they are liquid-proof and/or airtight inasmuch as the capping force may crush the container unless heavyweight stock is used. See United States Patent Application Publication No. US 2007/0295721 of Van Handel et al., entitled “Sealable Portion Cups and Lids Therefor”.

[0008] Another desirable feature in single use and multi-use sealable container is a lid attached to the base or cup so that it is readily available and will not be misplaced. A problem with this arrangement is counter-top stability inasmuch as the weight of a lid tends to tip the container base. United States Patent Application Publication No. US 2003/0230582 of Whitmore et al., entitled “Separable Containers Arranged in Arrays With Integrally Formed Lids” shows thermoformed containers with hinged lids attached to cup portions. The hinge is a relatively stiff plastic hinge which lasts only a limited number of opening/closing cycles. Because of hinge stiffness, the hinge transmits torque due to the weight of the lid and makes a single container unstable on a counter-top as disclosed in the '582 publication. To ameliorate this problem, the product of the '582 publication is utilized in multi-container, separable arrays where the lids and cups are arranged so that the weight balances to make the arrays of containers counter-top stable; however, the arrangement is not adapted for using one container at a time as is frequently required.

[0009] There is provided a container that is a cup portion having a maximum gauge of less than 35 mils provided with a bottom panel, a sidewall and a sealing brim which defines an annular cup sealing surface; and a lid having a maximum gauge of less than 35 mils with a sealing rim defining an annular lid sealing surface; wherein the cup portion and lid portion are thermoformed such that the annular cup sealing surface and the annular lid sealing surface cooperate to form a seal extending around the assembled container and wherein the container does not leak when tested using the Leak Test Method 1.

[0033] The invention is described in detail below with reference to numerous embodiments for purposes of exemplification and illustration only. Modifications to particular embodiments within the spirit and scope of the present invention, set forth in the appended claims, will be readily apparent to those of skill in the art.

[0034] Unless more specifically defined below, terminology as used herein is given its ordinary meaning.

[0035] A “substantially elastic” hinge refers to a living hinge which is durable to at least 250 180° open/close operation; while a relatively pliant or relatively pliable hinge is incapable without an intervening external force of sustaining a hinge torque sufficient to support a lid in a horizontal position relative to the cup. A lid attached to a cup rotates “substantially downwardly” when it rotates downwardly as at least 15° from a horizontal position, in some embodiments the lid rotates at least 25° or at least 35° downwardly from a horizontal position. A “freely rotating hinge” is unable of sustaining a hinge torque sufficient to provide substantial resistance rotation.

[0036] The terminology “interference-fit seal” refers to a seal between sealing members which are configured such that they are urged into engagement by their geometries, typically involving a negative draft. One sealing member thus has a larger dimension or dimensions in the free state than the dimension or dimensions of the cooperating part with which it forms a seal. When the interference-fit seal is formed, the sealing members become the same size and develop a seal through elastic compression, plastic movement of material, or both, much like interference-fit class 5 threads. See Machinery's Handbook, R. Green, Ed., 24.sup.th edition, Industrial Press. In some embodiments, the lids and cups form substantially continuous seals between them so that the containers are Liquid-tight; it being understood that the seal, while highly effective, especially when viewed in light of the low cost nature of the articles, is of course less than perfect where the seal formed might allow a few drops of moisture to penetrate when a sealed container is partially filled with water and shaken; but compression, effort and/or agitation is required to remove more than a few drops of liquid. The containers are thus also suitable for liquid or semi-liquid sauces, condiments,

[0037] dressings, side dishes and so forth that are prepared and fresh-packaged shortly before consumption.

[0038] “Liquid-tight” means the container does not leak as determined by the Leak Test Method 1 described herein. “Air-tight” means the container is capable of expanding and holding an expanded shape for at least 5 minutes upon capping as described herein.

[0039] As used herein the terminology “polypropylene resin” or “polypropylene composition” or like terminology refers to a composition which is predominately (more than 50 mole %) made up of propylene repeat units and includes melt blends with other resins and additives. Likewise, polyethylene resins are mostly ethylene repeat units while polyethylene terephthalate resins are mostly ethylene terephthalate repeat units. An ethylene/propylene copolymer contains both ethylene and propylene repeat units in the resin and may be made up primarily of repeat units of either species.

[0040] In some embodiments, a wide variety of thermoformable, microwavable materials may be used to make the containers described herein. When a material is described herein as being “a component”, it is understood to contemplate being 100%, at least 90%, at least 75%, at least 50%, at least 25%, at least 10%, at least 5%, or at least 1% by weight of all the compositions used to make the containers described herein. In some embodiments, nucleated polypropylene is used as a component of the containers described herein. In some embodiments, polypropylenes used as a component of the container described herein are selected from the group consisting of isotactic polypropylene, and copolymers of propylene and ethylene, for example, wherein the ethylene moiety is less than about 10% of the units making up the polymer, and mixtures thereof. In some embodiments, polymers used are isotactic polypropylenes with melt-flow indices of from about 20 to about 100, in some embodiments between about 30 and 60. In some embodiments, the resin from which the containers are made includes polypropylene melt blended with a polyethylene component. In some embodiments, polyethylene component may be any suitable polyethylene such as HDPE, LDPE, MDPE, LLDPE or mixtures thereof.

[0041] In some embodiments, various polyethylene polymers which may be used with or without polypropylene and are described at length in the Encyclopedia of Polymer Science & Engineering (2nd Ed.), Vol. 6; pp: 383-522, Wiley, 1986; the disclosure of which is incorporated herein by reference. HDPE refers to high density polyethylene which is substantially linear and has a density of generally greater than 0.94 up to about 0.97 g/cc. LDPE refers to low density polyethylene which is characterized by relatively long chain branching and a density of about 0.912 to about 0.925 g/cc. LLDPE or linear low density polyethylene is characterized by short chain branching and a density of from about 0.92 to about 0.94 g/cc. Finally, intermediate density polyethylene (MDPE) is characterized by relatively low branching and a density of from about 0.925 to about 0.94 g/cc. In some embodiments, any of the above mentioned polymers may be used as a component in the herein described containers.

[0042] In some embodiments, polypropylene/polyethylene copolymers with higher polyethylene content or a polyethylene based composition are used. In some embodiments, polyethylene terephthalate based compositions is used. In still further embodiments, any other suitable polymeric composition is used so long as the composition is sufficiently resilient and is preferably microwaveable.

[0043] “Thermoforming”, “thermoformed” and like terminology refers generally to a forming process involving draping of a softened sheet over a shaping mold. In the more advanced form, thermoforming is the automatic high speed positioning of a sheet having an accurately controlled temperature into a pneumatically actuated forming station whereby the article's shape is defined by the mold, followed by trimming and regrind collection as is well known in the art. Still other alternative arrangements include the use of drape, vacuum, pressure, free blowing, matched die, billow drape, vacuum snap-back, billow vacuum, plug assist vacuum, reverse draw with plug assist, pressure bubble immersion, trapped sheet, slip, diaphragm, twin-sheet cut sheet, twin-sheet roll-fed forming or any suitable combinations of the above. Details are provided in J. L. Throne's book, Thermoforming, published in 1987 by Coulthard. In some embodiments, the containers described herein are thermoformed by any means described herein or by any thermoforming means that are otherwise well known in the art.

[0044] Pages 21 through 29 of that book are incorporated herein by reference. Suitable alternate arrangements also include a pillow forming technique which creates a positive air pressure between two heat softened sheets to inflate them against a clamped male/female mold system to produce a hollow product. Suitable formed articles are trimmed in line with a cutting die and regrind is optionally reused since the material is thermoplastic in nature. Other arrangements for productivity enhancements include the simultaneous forming of multiple articles with multiple dies in order to maximize throughput and minimize scrap. Articles that are thermoformed should be designed so as to permit the die section to be parted free of the molded articles without undue interference with the surfaces of the articles. The surfaces of such articles generally include a so-called positive “draft” with respect to the direction in which the die sections are moved during parting to insure that there is little or no interference between the molded article and the interior surfaces of the die sections during parting. Interference between the articles and the dies is commonly known as “negative draft”. The draft may be thought of as the difference between the upper lateral span of a mold cavity and that span below it. A positive draft allows the pattern to be pulled cleanly from the mold, however, undercuts inherently have a negative draft.

[0045] In some embodiments, container 10 has a cup portion 12 provided with a bottom panel 14, a sidewall 16 as well as a sealing brim 20 which defines an annular cup sealing surface 22. Container 10 is also provided with a lid 24 which in some embodiments has a generally planar top panel 26 as well as a sealing rim 28 defining an annular lid sealing surface 30.

[0046] In some embodiments, lid 24 of container 10 is attached to cup portion 12 by way of a hinge portion 32 which defines a hinge 34 therebetween. In some embodiments, hinge 34 is a substantially elastic hinge. In some embodiments, this includes an arched profile 36 which is in some embodiments shaped and coined during thermoforming. In some embodiments, hinge 34 is coined in the mold while the material is hot, that is, two pieces of metal meet at a specified gap to thin the material creating an arched profile and hinge. In some embodiments, a slug of material is cut from the center of hinge portion 32 to remove memory and create a cutaway portion 35, giving the hinge a “dead” or “floppier” performance. In some embodiments, the potion of material cut from the center of the hinge potion is at least 0.5 inches long (direction parallel to axis of rotation of the hinge shown generally at 35b), at least 1 inch long, at least 1.5 inches long, at least 2 inches long, at least 3 inches long, or at least 4 inches long. In some embodiments, the potion of material cut from the center of the hinge potion is at least 0.05 inches wide (direction perpendicular to axis of rotation of the hinge), at least 0.1 inches wide, at least 0.25 inches wide, at least 0.5 inches wide, or at least 1 inches wide. In some embodiments, the portions 38, 40 of hinge 34 that are kept intact are 0.05 inches to 1 inch long (direction parallel to the axis of rotation), 0.1 to 0.5 inches long, or 0.1 to 0.25 inches long. In some embodiments it is believed that keeping the two outside portions 38, 40 of the hinge, closing alignment is maintained between cup portion 12 and lid 24 as the container is closed/reopened/reclosed. In some embodiments where the thermoformed container is trimmed with a die, the width 35a of cutaway 35 is at least 0.15 inches. In some embodiments, steel rule trimming or machined metal pinch trimming is used. In some embodiments, a land at 42 is provided for a cutaway receiver or die. The axis of rotation of hinge 34 is shown in FIG. 2 generally at 35b.

[0047] In some embodiments, the container has a maximum gauge of less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments at least 90% of the container has a maximum gauge of less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments the container has a maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils. In some embodiments at least 90% of the container has a maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils.

[0048] In some embodiments, the cup portion of the container has a maximum local gauge of less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments at least 90% of the cup portion of the container has a maximum gauge of less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments the cup portion of the container has a maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils. In some embodiments at least 90% of the cup portion of the container has a maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils.

[0049] In some embodiments, the lid portion of the container has a maximum local gauge of less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments at least 90% of the lid portion of the container has a maximum gauge of less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments the lid portion of the container has a maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils. In some embodiments at least 90% of the lid portion of the container has a maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils.

[0050] In some embodiments, the container is thermoformed from a sheet stock having a starting maximum gauge of less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments the container is thermoformed from a sheet stock having a starting maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils.

[0051] In some embodiments, the cup portion of the container is thermoformed from a sheet stock having a starting maximum gauge less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments the cup portion of the container is thermoformed from a sheet stock having a starting maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils.

[0052] In some embodiments, the lid portion of the container is thermoformed from a sheet stock having a starting maximum gauge less than 50 mils, less than 45 mils, less than 40 mils, less than 35 mils, less than 30 mils, less than 25 mils, less than 20 mils, less than 15 mils, or less than 10 mils. In some embodiments the lid portion of the container is thermoformed from a sheet stock having a starting maximum gauge between 10 mils and 50 mils, between 10 mils and 35 mils, between 10 mils and 25 mils, between 15 mils and 50 mils, between 15 mils and 35 mils, between 15 mils and 25 mils, between 20 mils and 50 mils, between 20 mils and 35 mils, or between 20 mils and 25 mils.

[0053] In some embodiments, the cup portion of the container has an interior volume less than 50 ounces, less than 40 ounces, less than 30 ounces, less than 25 ounces, less than 20ounces, less than 15 ounces, less than 10 ounces, less than 5 ounces, or less than 2 ounces. In some embodiments, the cup portion of the container has an interior volume between 2 ounces and 50 ounces, between 2 ounces and 30 ounces, between 2 ounces and 25 ounces, between 2 ounces and 15 ounces, between 4 ounces and 50 ounces, between 4 ounces and 35 ounces, between 4 ounces and 25 ounces, between 4 ounces and 15 ounces, between 10 ounces and 50 ounces, between 10 ounces and 40 ounces, between 10 ounces and 30 ounces, or between 10 ounces and 20 ounces.

[0054] In some embodiments, the container has a capping force (measured using the Capping Force Method 1 described herein in lbs/lineal inch) of at least 0.1, 0.2, 0.3, 0.35, 0.4, 0.45, 0.48, 0.5, 0.6, or 0.7. In some embodiments, the container has a capping force (measured using the Capping Force Method 1 described herein in lbs/lineal inch) less than 1.0, 0.9, 0.8, 0.7, 0.6, 0.55, 0.5, 0.45, 0.4, or 0.3. In some embodiments, the container has a capping force (measured using the Capping Force Method 1 described herein in lbs/lineal inch) between any of the upper and lower limits previously described. In some embodiments, the container has a capping force (measured using the Capping Force Method 1 described herein in lbs/lineal inch) between 0.1 and 1, 0.3 and 1, 0.3 and 0.9, 0.35 and 1, 0.35 and 0.9, 0.35 and 0.8, 0.35 and 0.7, 0.4 and 1, 0.4 and 0.9, 0.4 and 0.8, 0.4 and 0.7, 0.45 and 1, 0.45 and 0.9, 0.45 and 0.8, 0.45 and 0.7, 0.5 and 1, 0.5 and 0.9, 0.5 and 0.8, or 0.5 and 0.7.

[0055] In some embodiments, the container has a leak capping force (measured using the Leak Capping Force Method 1 described herein in lbs/lineal inch) of at least 0.1, 0.2, 0.3, 0.35, 0.4, 0.45, 0.48, 0.5, 0.6, or 0.7. In some embodiments, the container has a leak capping force (measured using the Leak Capping Force Method 1 described herein in lbs/lineal inch) less than 1.0, 0.9, 0.8, 0.7, 0.6, 0.55, 0.5, 0.45, 0.4, or 0.3. In some embodiments, the container has a leak capping force (measured using the Leak Capping Force Method 1 described herein in lbs/lineal inch) between any of the upper and lower limits previously described. In some embodiments, the container has a leak capping force (measured using the Leak Capping Force Method 1 described herein in lbs/lineal inch) between 0.1 and 1, 0.3 and 1, 0.3 and 0.9, 0.35 and 1, 0.35 and 0.9, 0.35 and 0.8, 0.35 and 0.7, 0.4 and 1, 0.4 and 0.9, 0.4 and 0.8, 0.4 and 0.7, 0.45 and 1, 0.45 and 0.9, 0.45 and 0.8, 0.45 and 0.7, 0.5 and 1, 0.5 and 0.9, 0.5 and 0.8, or 0.5 and 0.7.

[0056] In some embodiments, the container has a crush force (measured using Crush Force Test Method 1 described herein in lbs of force) of at least 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 or 65. In some embodiments, the container has a crush force (measured using Crush Force Test Method 1 described herein in lbs of force)) less than 100, 90, 80, 70, 60, 50, 40, 35, 30, 25, 20, 15. In some embodiments, the container has a crush force (measured using Crush Force Test Method 1 described herein in lbs of force) between any of the upper and lower limits previously described. In some embodiments, the container has a crush force (measured using Crush Force Test Method 1 described herein in lbs of force) between 10 and 100, 10 and 70, 10 and 50, 10 and 40, 10 and 35, 10 and 30, 15 and 100, 15 and 70, 15 and 50, 15 and 40, 15 and 35, 15 and 30, 20 and 100, 20 and 70, 20 and 50, 20 and 40, 20 and 35, or 20 and 30.

[0057] In some embodiments, the container has a crush force/capping force ratio (measured using the Crush Force Method 1 and Capping Force Method 1 described herein) of at least 1, 2, 3, 4, 5, 10, or 15. In some embodiments, the container has a crush force/capping force ratio (measured using the Crush Force Method 1 and Capping Force Method 1 described herein) of less than 20, 15, 10, 5, 4, or 3. In some embodiments, the container has a crush force/capping force ratio (measured using the Crush Force Method 1 and Capping Force Method 1 described herein) between any of the upper and lower limits previously described. In some embodiments, the container has a crush force/capping force ratio (measured using the Crush Force Method 1 and Capping Force Method 1 described herein) between 1 and 20, 1 and 15, 1 and 10, 1 and 5, 1 and 4, 1 and 3, 2 and 20, 2 and 10, 2 and 5, or 2 and 4.

[0058] In some embodiments, it is contemplated to manufacture at least 1, 2, 3, or 4 consecutive packages of at least 2, 3, 4, 5, 6, 7, or 8 containers contain containers where all of the containers in the package have a capping force or leak capping force (measured using the Capping Force Method 1 or Leak Capping Force Method 1 described herein in lbs/lineal inch) of at least 0.1, 0.2, 0.3, 0.35, 0.4, 0.45, 0.48, 0.5, 0.6, or 0.7. In some embodiments, less than 20%, less than 10%, less than 5%, less than 1%, or 0% of the containers in the aforementioned packages leak as tested by Leak Test Method 1 described herein. In some embodiments, it is contemplated to manufacture at least 1, 2, 3, or 4 consecutive packages of at least 2, 3, 4, 5, 6, 7, or 8 containers contain containers where all of the containers in the package have a capping force or leak capping force (measured using the Capping Force Method 1 or Leak Capping Force Method 1 described herein in lbs/lineal inch) less than 1.0, 0.9, 0.8, 0.7, 0.6, 0.55, 0.5, 0.45, 0.4, or 0.3. In some embodiments, less than 20%, less than 10%, less than 5%, less than 1%, or 0% of the containers in the aforementioned packages leak as tested by Leak Test Method 1 described herein. In some embodiments, it is contemplated to manufacture at least 1, 2, 3, or 4 consecutive packages of at least 2, 3, 4, 5, 6, 7, or 8 containers contain containers where all of the containers in the package have a capping force or leak capping force (measured using the Capping Force Method 1 or Leak Capping Force Method 1 described herein in lbs/lineal inch) between any of the upper and lower limits previously described. In some embodiments, less than 20%, less than 10%, less than 5%, less than 1%, or 0% of the containers in the aforementioned packages leak as tested by Leak Test Method 1 described herein. In some embodiments it is contemplated to manufacture at least 1, 2, 3, or 4 consecutive packages of at least 2, 3, 4, 5, 6, 7, or 8 containers contain containers where all of the containers in the package have a capping force (measured using the Capping Force Method 1 or Leak Capping Force Method described herein in lbs/lineal inch) between 0.1 and 1, 0.3 and 1, 0.3 and 0.9, 0.35 and 1, 0.35 and 0.9, 0.35 and 0.8, 0.35 and 0.7, 0.4 and 1, 0.4 and 0.9, 0.4 and 0.8, 0.4 and 0.7, 0.45 and 1, 0.45 and 0.9, 0.45 and 0.8, 0.45 and 0.7, 0.5 and 1, 0.5 and 0.9, 0.5 and 0.8, or 0.5 and 0.7. In some embodiments, less than 20%, less than 10%, less than 5%, less than 1%, or 0% of the containers in the aforementioned packages leak as tested by Leak Test Method 1 described herein.

[0059] In some embodiments shown in FIGS. 1 through 5, a plurality of chamfered surfaces 44, 46, 48, 50 are provided at the corners of cup 12. In some embodiments, these surfaces are chamfered at an external angle 52 between 35° and 50° (in some embodiments this angle is 45°) from a plane defined by bottom panel 14 and chamfered at an external angle between 35° and 50° (in some embodiments, this angle is 45°) from the adjacent surfaces (i.e. the chamfered panels 44, 46, 48 and 50 form an internal angle at 54 between 130° and 145° (in some embodiments, this angle is 135°) with adjacent surfaces of cup 12. In some embodiments, angles 52, 54 are consistent about the peripheries of the chamfered corner panels. In some thermoformed embodiments, the material does not thin as much in the corners because the reduced draw-down; that is in some embodiments, panels 44, 46, 48 and 50 are thicker than adjacent areas of cup 12. In some embodiments, the panel structure flat surface is perpendicular to a typical impact.

[0060] In some embodiments, Cup portion 12 and lid 24 are formed from adjacent areas of one piece of sheet stock in the same tool at the same time. In some embodiments, a span 55 (FIG. 6 and following) of lid sealing rim 28 must be at least 0.1 inches, at least 0.25, or at least 0.5 inches wide. In some embodiments, span 55 is between 0.1 inches and 1 inch wide, or between 0.1 and 0.5 inches wide. In some embodiments, a benefit of being a significant span at 55 is that there is an area to grasp when the contents are hot. In some embodiments a Lip 57 extends horizontally around cup 12 and lid 24. In some embodiments, lip 57 has a distance 56 of least 0.05 inches, at least 0.1 inches or at least 0.25 inches. In some embodiments, lip 57 has a distance 56 between 0.05 and 0.5 inches, between 0.05 and 0.25 inches, between 0.1 and 0.5 inches, or between 0.1 and 0.25 inches. In some embodiments, lip 57 is trimmed.

[0061] In some embodiments to further stability of the container, the depth to draw ratio of container 10, that is height 58/width 60 (FIG. 5), is less than 1, less 0.85, 0.75, or 0.6. In some embodiments, a recessed area 62 or “kick” is molded into the bottom panel 14 and provides a ridge 64 an example of which is seen in FIG. 9. If panel 14 is warped from the forming process or from trapped air, ridge 64 helps to reduce rolling of the container. In some embodiments, recessed area 62 has a surface area of between 1 and 10 inches², between 1 and 8 inches², between 1 and 4 inches², between 2 and 10 inches², or between 2 and 5 inches². In some embodiments, recessed area 62 has a surface area of at least 0.5 inches², at least 1.0 inches², at least 2 inches², or at least 4 inches².

[0062] In some embodiments, lid 24 and cup 12 are tabbed to facilitate easy opening. In some embodiments, tab 66 on cup 12 acts as a hold point, while tab 68 on lid 24 acts as a lift point and is wider than tab 66. In some embodiments, tab 68 is pulled from the outside corner to create the most available leverage. In some embodiments, texture is provided to tab 66 and/or a “lift” label to tab 68. In some embodiments, no tab is used.

[0063] In some embodiments, the containers are thus formed so that they are stackable, but will resist tight nesting so as to be inseparable. In some embodiments, the containers have stacking ridges 69a, 69b, 69c and 69d. Referring to FIG. 6, there is shown substantially two nested containers 10 and 10′ stacked such that their lids 24, 24′ and cups 12, 12′ are partially nested. In some embodiments, the sealing areas of the cups and lids are undercut slightly so that they do not easily nest in complete surface-to-surface contact as is shown in FIG. 6, and provide an interference seal as shown in FIG. 10. In some embodiments, raised areas 70, 70′ to assist in sealing the container as hereinafter described in more detail in connection with FIGS. 8-10.

[0064] In some embodiments, the containers are conveniently packaged or stored as shown in FIG. 7. In some embodiments, a packaged ensemble 71 of containers includes first stack 72 of containers (in some embodiments at least 2, at least 4, at least 5, at least 8, or at least 10) is oriented with the cup portion openings directed towards 74, while a second stack 76 (in some embodiments at least 2, at least 4, at least 5, at least 8, or at least 10) is placed on stack 72 with the cup openings toward 78. In this way 20 cups form a compact “cube” which is convenient for shipping, storage and distribution.

[0065] Referring now to FIGS. 8, 9, 10 and 11, the various features of some embodiments, including sealing features of some embodiments of the container 10 are illustrated further. FIG. 8 is a top view showing container 10 in a closed position wherein lid 24 is sealed to cup portion 12. In some embodiments, the container has a raised portion 70 on the lid. In some embodiments, raised portion 70 is a “push button” closure when pressed by one finger to close the container. In some embodiments, the raised portion helps expel air in the closure process and/or helps keep packaged food fresher longer.

[0066] FIG. 9 is an elevation section along plane 9-9 of FIG. 8 showing the cooperation of the various parts in a closed position of some embodiments of the present invention. FIG. 10 is an enlarged view at the brim of FIG. 9 as indicated which shows the interference-fit seal of some embodiments of container 10. In some embodiments, seal 80 is an interference-fit seal between sealing surface 22 of sealing brim 20 of cup portion and sealing surface 30 of lid 24. In some embodiments, surfaces 22 and 30 are in surface-to-surface interfacing contact entirely around the container over a contact distance or band width 82. In some embodiments, Seal width 82 is less than 100 mils, less than 80 mils, less than 60 mils, less than 50 mils, less than 40 mils or less than 30 mils. In some embodiments, the interference distance between the two parts is indicated at 84 and is less than 50 mils, less than 40 mils, or less than 30 mils and/or less than 25 mils per part, less than 20 mils per part or less than 15 mils per part, that is, the amount each part is compressed. Note that in some embodiments, interference occurs only at the seal, and that the sealing brim is otherwise non-interfering with the sealing rim of the lid as shown in FIG. 10. In some embodiments, the parts have clearance at the outer portions of the lid and base upon assembly of the container as indicated at 86.

[0067] In some embodiments, any type of seals may be used that is well known to one skilled in the art, including but not limited to, screw seals.

[0068] In some embodiments, lid 24 has chamfered corners at 88, 90 to facilitate closing of the container inasmuch as brim 20 of cup 12 and sealing rim 28 of lid 24 are undercut at 92, 94. In some embodiments, the chamfered corners have a chamfer length 96 of at least 5 mils or more. In some embodiments, the chamfered lip of lid 24 has a chamfer angle 98 with a horizontal line 100 of between 35° and 55° (in some embodiments the angle is 45°.

[0069] It will be appreciated by one of skill in the art that the sealable container of this invention may be fabricated in a variety of overall shapes; for instance, container 10 of FIGS. 1 though 11 has a generally rectangular (horizontal) cross section when viewed through the opening of the cup (plan view) as well as tapered sidewalls so that the cup has a frusto-pyramidal shape. In some embodiments, the cup can be shaped as shown below in FIGS. 12 through 14 such that the cup has a generally circular (horizontal) cross section when viewed through the opening of the cup (plan view) and in some embodiments has tapered sidewalls such that the cup has a generally frusto-conical shape.

[0070] Referring to FIGS. 12, 13 and 14, another embodiment showing a container 110 with a cup portion 112 attached by way of a hinge portion 132 to a lid 124. In some embodiments, cup 112 includes a bottom panel 114 as well as a sidewall 116 and a U-shaped sealing brim at 120. In some embodiments, lid 124 includes a generally planar top panel 126 with a sealing rim 128.

[0071] In some embodiments, hinge portion included a circular cutaway to increase flexibility and likewise has an arched profile as discussed in connection with container 10. In some embodiments, the circular cutaway has a diameter of at least 0.05 inches, at least 0.1 inches, at least 0.25 inches, at least 0.5 inches, at least 0.75 inches, or at least 1 inch. In some embodiments, the portions of hinge that are kept intact are 0.05 inches to 1 inch long (direction parallel to the axis of rotation), 0.1 to 0.5 inches long, or 0.1 to 0.25 inches long. In some embodiments it is believed that keeping the two outside portions of the hinge, closing alignment is maintained between cup portion and lid as the container is closed/reopened/reclosed. In some embodiments, lid 124 includes an opening tab 168, while cup 112 includes a corresponding tab 166.

[0072] Products of the invention and various available thermoformed products were tested for Capping Force, Lid Open Force, Container Crush Force, and Corner Crush Force using a universal Instron® tensile/compression tester. All of the values reported in this application are tested according to the following specifications.

[0073] All capping or closing forces that are reported in this specification are measured by the following method. Testing was performed using an Instron 4502 with Merlin software. Acrylic stands were made for each size of container so it was supported by its upper rim. ¼ inch diameter stainless steel ball bearings were added to the container to obtain a weight in ounces that was ⅔ of its capacity in ounces (i.e. 16 ounces of ball bearings were added to a container that has a volume of 24 ounces). Should it not be possible to reach the exact weight given that it is impossible to add a portion of a ball bearing, the number of ball bearings that gives you a weight closest to that required will be added. The cover was set on top of the container and the container, cover and stand was placed into and centered on the tensile tester platform below the compression probe (FIG. 1).). The probe has a round contact surface with a surface area of 1.0 in². The probe was brought down onto the lid and a preload less than 0.1 lbf was applied. The test is initiated and the probe compressed the lid at a 10 in/min. speed for a 0.5 inch or until the crush force of the container is reached. The capping force is defined as the final plateau or dip in the load/elongation curve. The plateau is caused by the lid corners clicking into place on the container. The highest load in pounds of force on the plateau or dip is taken as the lid close force. There is provided in FIG. 15 a typical capping force plot for a container of the invention.

[0074] All leak capping forces that are reported in this specification are measured by the following method. Testing was performed using an Instron 4502 with Merlin software. Acrylic stands were made for each size of container so it was supported by its upper rim. The container is filled ⅔ full with tap water. The cover was set on top of the container and the container, cover and stand was placed into and centered on the tensile tester platform below the compression probe (FIG. 16). The probe has a round contact surface with a surface area of 1.0 in². The probe was brought down onto the lid and a preload less than 0.1 lbf was applied. The test is initiated and the probe compressed the lid at a 10 in/min. speed for a 0.5 inch or until the crush force of the container is reached. The container was removed from the tester after every 0.005 inches that probe compressed the lid and the container is tested for leaks using Leak Test Method 1. The leak capping force is defined as the force measured by the Instron at the minimum extension of the Instron where the container does not leak as defined by Leak Test Method 1. To shorten the procedure, one skilled in the art can use the capping force plot for a container to pick a starting point to begin the measurements. The only criterion for the starting point that is picked is that the container leaks at the initial Instron extension. It is understood that some containers will always leak and those containers that do not produce a leak-proof seal will not have a leak capping force and will be outside the scope of any embodiments that require a measured leak capping force.

[0075] Testing was performed using an Instron 4502 with Merlin software. An Acrylic stands with two 1″, “C”-clamps was fabricated to hold the two tabs of the container. One clamp was stationary and held to the base and the other was connected to the moving upper platen and the load cell. The tab that was closest to the center of the container was secured by the stationary clamp and the tab in the corner was secured by the clamp that was connected to the load cell (FIG. 17). If the container only had one tab it was secured by the clamp that was connected to the load cell and the base of the container was held by hand during the test. Metal balls were added to the container before the lid close force test to obtain a weight that was ⅔ of its capacity. Once the container was secured by both clamps the test was initiated and the cover was pulled off at a speed of 20 in/min. The lid open force is defined as the maximum load in lbf to remove the lid. FIG. 18 is a typical plot seen when measuring Lid Open Force.

[0076] Testing was performed using an Instron 4502 with Merlin software. Two parallel platens were used. A large solid base and an upper movable upper platen that was larger than the container being crushed. The lid was placed on the container and closed. It was placed between the upper and base platen. The upper moveable platen was brought down to contact the container with a preload less than 0.1 lbf (FIG. 19). The test was initiated and the container was crushed at 10 in/min until the sidewall buckled. The crush force is defined as the load in pounds of force at which the sidewall buckles. A typical plot showing crush-force measurement appears in FIG. 20.

[0077] Testing was performed using an Instron 4502 with Merlin software. A large solid base and an upper movable probe were used for the corner crush test. The probe is a 1 in^t with a diameter of 1.082 inches. The lid was placed on the container and closed. It was placed on the solid base positioning the corner opposite the tab under the probe. The upper moveable probe was brought down to contact the container with a preload less than 0.1 lbf (FIG. 21). The test was initiated and the container was crushed at 10 in/min until the sidewall buckled. The corner crush force is defined as the load in lbf at which the sidewall buckles. A typical plot showing Corner Crush Force appears in FIG. 22.

[0078] Leak testing was performed by filling the container ⅔ full with tap water, lidding the container and placing the container on its side on blotter paper. After 10 minutes, the amount of water collected on the blotter was measured by weighing the blotter paper before and after the test. A container is considered to have leaked if more than 0.1 mL of water is collected on the blotter paper.

[0079] Container thickness can be measured by a Magna-Mike 8500. In applications such as plastic containers, the operator simply drops the small target ball inside the container. The magnetic probe held on the outsider of the container attracts the target ball. When the operator scans the probe along the surface or critical corners, the small steel target ball will follow. Should an area not be accessible to either the small target ball or the probe, the portion of the container that the operator desires to measure may be cut out to allow access to that point.

[0080] All testing was performed under ambient conditions. Results appear in Tables 1-3 below.

TABLE 1
Container Properties
	Container		Lid	Close	Tip Container
	Capacity	Lid Close	lineal	Force per/	on Side
ID	ounces	lbs force	inch	lineal in	Leak Y/N
Gladware	24	0.9	19.0	0.05	y
Gladware	24	1.6	19.0	0.08	y
Gladware	24	1.9	19.0	0.10	y
Gladware	24	2.3	19.0	0.12	y
Gladware	24	2.3	19.0	0.12	y
Gladware	24	2.5	19.0	0.13	y
Gladware	24	2.7	19.0	0.14	y
Gladware	24	3.4	19.0	0.18	y
Gladware	24	3.5	19.0	0.18	y
6.d	6	3.0	11.1	0.27	y
Gladware	24	5.8	19.0	0.31	y
6.c	6	3.7	11.1	0.33	y
Gladware	24	7.1	19.0	0.37	y
Ziploc	20	7.7	19.5	0.39	y
Ziploc	20	8.6	19.5	0.44	n
Ziploc	20	8.8	19.5	0.45	y
Gladware	24	9.1	19.0	0.48	n
24.a	24	9.1	18.5	0.49	n
Ziploc	20	9.7	19.5	0.50	n
Ziploc	20	9.9	19.5	0.51	n
Ziploc	20	10.0	19.5	0.51	y
Gladware	24	10.1	19.0	0.53	n
Ziploc	20	10.6	19.5	0.54	n
24.b	24	10.1	18.5	0.55	n
Ziploc	20	10.7	19.5	0.55	n
Ziploc	20	10.8	19.5	0.55	n
Ziploc	20	10.8	19.5	0.55	n
Ziploc	20	11.1	19.5	0.57	n
Ziploc	20	11.2	19.5	0.57	n
Ziploc	20	11.4	19.5	0.58	n
Gladware	24	11.3	19.0	0.59	n
18.a	18	11.1	18.5	0.60	n
Ziploc	20	11.8	19.5	0.61	n
Gladware	24	11.6	19.0	0.61	n
Ziploc	20	12.1	19.5	0.62	n
8.c	8	8.0	12.4	0.65	n
Ziploc	20	12.6	19.5	0.65	n
Target	24	12.7	18.5	0.69	n
6.b	6	7.7	11.1	0.69	n
Liddles	8	8.6	12.4	0.69	n
Target	24	13	18.5	0.70	n
Target	24	13	18.5	0.70	n
Target	24	13.4	18.5	0.72	y
8.a	8	9.0	12.4	0.73	n
8.d	8	9.0	12.4	0.73	n
Gladware	24	14.6	19.0	0.77	n
Target	24	14.4	18.5	0.78	n
Target	24	15.4	18.5	0.83	n
Target	24	15.9	18.5	0.86	y
8.e	8	10.7	12.4	0.86	n
6.a	6	9.7	11.1	0.87	n
Target	24	16.9	18.5	0.91	n
Target	24	18.5	18.5	1.00	n
Target	24	19.3	18.5	1.04	n
Target	24	19.5	18.5	1.05	n
2.a	2	9.8	8.0	1.23	n

TABLE 2
Container Dimensions and Properties
				Seal	Side			Lid	Crush		Close	Tip
	Container		Lid Rim	Area	Wall		Crush	Close	to	Lid	Force	Container	Lid
	Capacity	Thickness	Chamfer	Length	Height		Force	lbs	Close	lineal	per/	on Side	Open
ID	ounces	mils	Angle	mils	inches		lbs	force	Ratio	inch	lineal in	Leak Y/N	lbs force
2.a	2	20	45	60	1		41	9.8	4.2	8.0	1.23	n	6.4
4.a	4	20	45	60	1.5					9.6	0.00
6.a	6	20	45	60	1.5		17	9.7	1.8	11.1	0.87	n	2.5
6.b	6	22.5	45	60	1.5		18	7.7	2.3	11.1	0.69	n	1.8
6.c	6	25	45	60	1.5	loose	27	3.7	7.3	11.1	0.33	y	2
						fit
6.d	6	28	45	60	1.5	loose	30	3.0	10.0	11.1	0.27	y	3.2
						fit
8.a	8	20	45	60	1.75		17	9.0	1.9	12.4	0.73	n	2.5
8.b	8	20	45	40	1.75		38	8.6	4.4	12.4	0.69	n	2.9
8.c	8	20	45	30	1.75		31	8.0	3.9	12.4	0.65	n	2.4
8.d	8	20	45	60	1.75		17	9.0	1.9	12.4	0.73	n	3.8
8.e	8	22.5	45	60	1.75		19	10.7	1.8	12.4	0.86	n	4.4
18.a	18	20	45	60	1.5		37	11.1	3.3	18.5	0.60	n	2.8
24.a	24	20	45	60			24	9.1	2.6	18.5	0.49	n	3.9
24.b	24	22.5	45	60			20	10.1	2.0	18.5	0.55	n	4.2
Gladware	24						105	7.1	14.8	19.0	0.37	y	2.4
Gladware	24							1.6		19.0	0.08	y
Gladware	24							2.3		19.0	0.12	y
Gladware	24							5.8		19.0	0.31	y
Gladware	24							1.9		19.0	0.10	y
Gladware	24							0.9		19.0	0.05	y
Gladware	24							2.3		19.0	0.12	y
Gladware	24							2.5		19.0	0.13	y
Gladware	24							2.7		19.0	0.14	y
Gladware	24							3.4		19.0	0.18	y
Gladware	24							3.5		19.0	0.18	y
Gladware	24							11.3		19.0	0.59	n
Gladware	24							11.6		19.0	0.61	n
Gladware	24							9.1		19.0	0.48	n
Gladware	24							10.1		19.0	0.53	n
Gladware	24							14.6		19.0	0.77	n
Ziploc	20						74	7.7	9.6	19.5	0.39	y	5
Ziploc	20							8.8		19.5	0.45	y
Ziploc	20							10.0		19.5	0.51	y
Ziploc	20							8.6		19.5	0.44	n
Ziploc	20							10.8		19.5	0.55	n
Ziploc	20							9.9		19.5	0.51	n
Ziploc	20							11.2		19.5	0.57	n
Ziploc	20							12.6		19.5	0.65	n
Ziploc	20							9.7		19.5	0.50	n
Ziploc	20							10.7		19.5	0.55	n
Ziploc	20							11.1		19.5	0.57	n
Ziploc	20							10.8		19.5	0.55	n
Ziploc	20							11.8		19.5	0.61	n
Ziploc	20							10.6		19.5	0.54	n
Ziploc	20							11.4		19.5	0.58	n
Ziploc	20							12.1		19.5	0.62	n
Target	24						82	12.7	6.5	18.5	0.69	n	4.8
Target	24							18.5		18.5	1.00	n
Target	24							13		18.5	0.70	n
Target	24							16.9		18.5	0.91	n
Target	24							14.4		18.5	0.78	n
Target	24							19.3		18.5	1.04	n
Target	24							19.5		18.5	1.05	n
Target	24							13		18.5	0.70	n
Target	24							15.4		18.5	0.83	n
Target	24							13.4		18.5	0.72	y
Target	24							15.9		18.5	0.86	y

TABLE 3
Selected Force Values For Containers
Lid Close Force, Lid Open Force, Crush Force and Corner Crush Force Testing
24-Apr-09
						Corner
						Crush
Sample	Sample		Lid Close Force	Lid Open Force	Crush Force	w/ probe
Number	ID	Repeat	(lbf)	(lbf)	(lbf)	(lbf)
1-1	Gladware, 24 oz	Average:	7.062	2.444	105.4	38.5
2-1	Ziploc, 20 oz	Average:	7.743	5.016	74.4	16.2
3-1	Target, 24 oz	Average:	16.648	4.770	81.615
4-1	Target, 25 oz	Average:	9.370	4.075	91.4
5-1	2 oz, 20 mil	Average:	9.822	6.362	40.6	22.2
6-1	8 oz, 22.5 mil	Average:	10.700	4.418	18.8	8.45
7-1	8 oz, 20 mil	Average:	9.040	3.794	16.7	3.26
8-1	18 oz, 20 mil	Average:	11.214	2.845	36.6	12.1
9-1	6 oz, 28 mil	Average:	12.161	3.225	27.7	11.7
10-1	6 oz, 25 mil	Average:	5.170	1.955	26.8	16.4
11-1	6 oz, 20 mil	Average:	9.699	2.536	20.0	10.7
12-1	6 oz, 22.5 mil	Average:	7.683	1.826	18.2	7.9
NOTE:
Data repeats can be compared because testing was done the same container. Test order was Lid close, Lid Open and then Crush. The Corner Crush tests were performend on separate containers.

[0081] In some embodiments, the geometry of the container and the hinge characteristics are selected to promote countertop stability of the container, particularly, in some embodiments, hinge is not capable of sustaining a force sufficient to upset an empty and/or a nearly empty container and cause spills.

[0082] In some embodiments, the height of the cup is no greater than its width. In some embodiments, the weight of the lid will be within 25%, 15%, 10%, 5%, or 1% of the weight of the cup. In some embodiments, the lid and cup are thermoformed from about the same area of polymer as the other. Similarly, in some embodiments, the base of the cup will be narrower than its mouth.

[0083] If the moment required to hold the lid in a downwardly deflected position increases monotonically (not necessarily linearly, just increasing as the angle increases) with its deflection from neutral, the maximum moment exerted on the hinge by the lid will be when the lid is about to touch the table the cup is resting on. At that point, the weight of the lid exerts a moment equal to the mass of the lid times its effective moment arm which is:

m_lr_lcos θ

[0084] where

• [0085] m_l is the mass of the lid portion
• [0086] r_l is the radius to the center of mass of the lid from the hinge line and
• [0087] θ is the angle by which the lid droops from horizontal.

[0088] But cos θ when the lid is about to touch the table is equal to

$\begin{array}{cc}\frac{\sqrt{w_l^2-h_c^2}}{w_l}& \end{array}$

[0089] where

• [0090] w_l is the length of the lid, r_l is w_l/2; and H_c is the height of the hinge above the table.

[0091] Thus unless the hinge is able to exert a moment exceeding

$\begin{array}{cc}{m}_lr_l\cos \theta =m_l\left(\frac{w_l}{2}\right)\cos \theta =\frac{m_l\left(w_l\right)}{2}\frac{\sqrt{w_l^2-h_c^2}}{w_l}=\frac{m_l\sqrt{w_l^2-h_c^2}}{2}& \end{array}$

The lid will rest upon the table.

[0092] Similarly for the cup to rise off of the table the hinge must be capable of sustaining a moment of greater than

m_cr_c

where m_c is the mass of the cup portion and rc is the horizontal distance to the center of mass of the cup portion from the hinge.

[0093] So unless the hinge is capable of sustaining a moment which more than the greater of:

$\begin{array}{cc}{m}_cr_c\mathrm{and}\frac{m_l\sqrt{w_l^2-h_c^2}}{2}& \end{array}$

the lid will flop to the table without tilting the cup.

[0094] Accordingly, in some embodiments, the maximum moment the hinge is capable of sustaining is either:

less than m_cr_c or
less than

$\frac{m_l\sqrt{w_l^2-h_c^2}}{2}$

In some embodiments, the lid will flop toward the table or countertop without tilting the cup.

[0095] In some embodiments, an elastic hinge is designed so the hinge will not break, that is, not exceed the yield strength of the material in normal use. In some embodiments, the required hinge length L for a material of thickness t may be calculated as:

$L=\frac{t\pi E_{\mathrm{secant},\mathrm{yield}}}{{\sigma }_{\mathrm{yield}}}$

[0096] where E_secant,yield is the secant modulus at yield and σ_yield is stress at yield. On the other hand, for a plastic hinge the ultimate modulus and stress at break are used:

$L=\frac{t\pi E_{\mathrm{secant},\mathrm{ultimate}\mathrm{strength}}}{{\sigma }_{\mathrm{ultimate}}}$

where E_{secant,ultimate strength} is the secant modulus at break and σ_ultimate the stress at break. Plastic hinges are typically relatively stiff and last for only a limited number of open/close operations.

[0097] It has been unexpectedly found in accordance with the present invention that the coined hinge of some embodiments of the present invention behaves substantially as an elastic hinge as opposed to plastic hinge behavior as is typical in thermoformed products. In some embodiments of the present invention, the container has a coined hinge. In some embodiments of the present invention, a hinge is concurrently thermoformed with the rest of the container over an arched rule to provide an arched profile to the hinge as is seen in the various Figures. In some embodiments, while the hinge is still warm, in some embodiments immediately after the part is thermoformed, the arched hinge is struck with a suitably shaped anvil under pressure to thin the material in the hinge and provide a living hinge type of profile wherein there is provided a thinned region extending over the length of the hinge on the compression side of the hinge and an opposite large radius on the extending part of the hinge. Without being bound by any theory, it is believed the coining step at least partially orients the polymer in a direction transverse to the hinge axis of rotation to provide the remarkable elasticity observed in the product.

[0098] While the invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those of skill in the art. In view of the foregoing discussion, relevant knowledge in the art and references discussed above in connection with the Background and Detailed Description, the disclosures of which are all incorporated herein by reference, further description is deemed unnecessary. In addition, it should be understood that aspects of the invention and portions of various embodiments may be combined or interchanged either in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.