Abstract:
A lid and tray assembly includes at least two lift tabs and/or indentations at separated but not directly opposing locations about the lid periphery that can be actuated simultaneously or sequentially to provide two distinct locations from which initial disengagements can extend and merge to enable easy removal of the entire lid. Embodiments further include locations that can be pressed while corresponding tabs are lifted. Some embodiments include a peripheral skirt that is short enough to allow a user&#39;s fingers to pass beneath and support the tray sidewalls when lifting the tray-lid assembly from a horizontal surface, avoiding any need for the lid engagement to bear the weight of the tray and its contents. Lid-tray engagement can be by means of inserting a lid peripheral rim into a tray lip groove, or by engaging a lid rim undercut with a tray lip undercut.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation in part of co-pending application Ser. No. 14/242,972, filed on Apr. 2, 2014. Application Ser. No. 14/242,972 is a continuation of application Ser. No. 12/652,483, filed on Jan. 5, 2010 (now U.S. Pat. No. 8,701,930 issued Apr. 22, 2014), which claims the benefit of U.S. Provisional Application No. 61/142,423 filed Jan. 5, 2009. All of these applications are incorporated herein by reference in their entirety for all purposes 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to lids adapted for use with trays and containers, and more particularly to lids featuring ease of use and improved release from trays and containers. 
       BACKGROUND OF THE INVENTION 
       [0003]    Containers with detachable and re-attachable lids, including disposable food containers, trays and platters with compatible lids, are well known and are commonly employed in many industries, including food related industries such as restaurants, caterers, institutional food service establishments, cafeterias, and households. 
         [0004]    A tray, serving platter, or container base for use in catering and other food service applications frequently features a lid or cover that is cooperatively engageable therewith for presenting, handling, transporting, and/or protecting a variety of food items. The tray or base usually has an upwardly projecting sidewall terminating in a rim. The base or tray rim may simply feature a lip area, or may include sealing ridges, channels or other locking mechanisms that are adapted for cooperative engagement with corresponding grooves, inverted channels, or other cooperative features which are integrated with the lid. Note that the terms “tray” and “base” are used generically herein to refer to any type of tray, serving platter, container, or other support base which is attachable to a lid or cover. Note also that the term “lid” is used generically herein to refer to any type of lid or cover that is compatible with and attachable to a “tray” or a “base”. 
         [0005]    Disposable lids for use with food containers and platters are usually thermoformed from a sheet of Polyethylene Terephthalate (PET) or Oriented Polystyrene (OPS) although other plastic materials may be employed. The lid is configured to fit the base, and may include an elevated and/or dome-shaped central portion to allow for comfortably accommodating a certain quantity or height of foods or other contents, and will preserve the shape, form, decorative appearance and/or the general presentation of items such as certain food preparations, including desserts, cakes, sandwiches, or other foods. Or the lid may be substantially flat, and may be attachable to a container which has sufficient depth to surround food items or other contents to be contained therein. In some approaches, once a lid has been engaged with a tray to form a first tray-lid assembly, a second tray-lid assembly can be stacked on top of the first tray-lid assembly, and thus a plurality of tray-lid assemblies can be stacked on top of each other for compact storage and for ease of transportation and handling. 
         [0006]    In the case of food containment, it is paramount that food preparations be protected, and that inadvertent disengagement or removal of the lid from the tray be avoided. Therefore, in many cases one or more locking features and/or undercuts are provided at the periphery of the tray and/or the lid, resulting in a relatively tight interference fit between the lid and the tray. However, this tight interference fit can make it difficult for a user to disengage and/or remove the lid at the time of use, resulting in an inconvenience to the user at best, and spilling of the food at worst, as the user struggles to remove the lid from the tray. Depending on the material from which the lid is constructed, the lid may even tear or rip during removal, thereby rendering subsequent reengagement of the lid with tray or container ineffective or futile. 
         [0007]    A typical method for disengaging a generic container-lid assembly is by holding the container with one hand and pulling the lid off with the other hand. Sometimes a tab or an indent is provided in either the lid or the container so as to facilitate creating an initial separation or opening between the lid and the container at the location of the tab or indent, and then separating the lid from the container around the entire periphery of the container-lid assembly. However, this method of disengaging or separating a lid from a container can be difficult if the container is shallow, for example if the container is in the form of a tray or plate covered by a lid having a raised portion. In such cases, it can be difficult to grasp the shallow base so as to pull it away from the lid. 
         [0008]    A lid having a raised portion, herein referred to generically as a “dome” lid regardless of whether the lid is round, rectangular, or some other shape, may feature a downwardly projecting peripheral skirt that overhangs beyond the perimeter of the tray or container base. As will be appreciated by those skilled in the art, for a relatively shallow tray the overhang of the peripheral skirt of the lid can be almost as tall as the tray, making it even more difficult for a user to grasp the tray for lid removal, and making it difficult even to slide his or her fingers underneath the peripheral skirt of the lid for lifting and carrying of the tray-lid assembly. Instead, a user typically has to lift the tray-lid assembly by the peripheral edge of the lid without touching the tray. In this situation, the entire weight of the tray and its contents is thus borne by the locking or engagement mechanism between the tray and the lid, further necessitating that the tray and lid have a tight fit, which in turn makes it even more difficult to remove the lid from the tray. 
         [0009]    A particular difficulty for removing lids from tray-lid assemblies of the type described above is encountered due to the fact that in many cases the lid is flexible and the periphery of the tray-lid assembly is relatively large compared to the size of the tab or indent that is provided with the lid or the tray for initiating separation of the lid from the tray. Consequently, when a user exerts an upward or downward force on the tab or indent provided in the lid or tray for pulling the tray-lid assembly apart, the rim of the lid tends to press opposingly inwardly at other locations, causing the lid to grip even more tightly onto the tray at those locations, and thereby rendering removal of the dome from the tray base extremely difficult, or at least cumbersome. 
         [0010]    Thus, there is a need for a lid that is securely engageable with a tray or a container and yet can be conveniently removed from the tray or container with relative ease and without disturbing the contents of the tray or container. These and other needs are met by the lid of the present invention. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    A lid is claimed for a tray that enables secure and reliable engagement between the lid and the tray while enabling easy removal of the lid from the tray without disturbing contents supported by the tray and without applying undue stress to the lid. In particular, the present invention enables removal of the lid from a tray-lid assembly in a reversible manner, i.e. without damaging the lid during removal. 
         [0012]    Note that except where the context requires a more specific definition, the term “tray” is used herein to refer generically to a tray, platter, dish, container, plate, or any other support base compatible with a lid or cover, and the term “lid” is used generically herein to refer to any sort of lid or cover compatible with a “tray,” including flat lids and “dome” lids that include raised portions and have cross sectional profiles that are rectangular, rounded, or any other raised shape. 
         [0013]    Note also that while the following discussion is presented in the context of describing feature(s) of a lid, whereby the feature(s) enable removal of the lid from a tray, the roles of the lid and the tray can be reversed without departing from the scope of the invention. In other words, a specific feature or features ascribed herein to the “lid” (or upper element) can be incorporated (in part or in total) into the “tray” (or lower element) of the tray-lid combination. For example, where embodiments are described as having two lift tabs and press areas in the lid, it will be understood that similar embodiments include one or both of the lift tabs and corresponding press areas in the base. Therefore, the invention applies generally to separable halves of a containing assembly comprising a first half and a second half, whereby terms used for convenience to describe one half of the containing assembly, such as “lid” and “cover,” can generally be exchanged herein with terms used to describe the other half of the containing assembly, such as “tray,” “container,” and “support base,” without departing from the meaning or scope of the invention. 
         [0014]    The claimed lid facilitates separation of the lid from the tray-lid assembly by providing at least two tabs at two locations on the outer periphery of the lid and/or two indentations in the outer periphery of the tray that are separated, but not directly opposite to each other. The two tabs or indentations thereby provide at least two distinct locations for initial disengagement of the lid from the tray. By disengaging the lid from the tray at two or more separated locations about the rim, the tendency of the elastic lid to responsively grip the tray is overcome, and the lid is released from the tray without the user applying undue effort, without subjecting the lid to undue stress, and without unduly disturbing the contents of the tray-lid assembly. 
         [0015]    An additional feature in embodiments of the present invention is to facilitate lifting of a tray-lid assembly securely from a flat surface by utilizing a lid construction that either does not have a peripheral skirt, or at most has only a peripheral skirt that is short enough to allow a user&#39;s fingers to reach underneath the skirt and support the sidewalls of the tray when lifting and/or carrying the tray-lid assembly, so that the entire weight of the tray-lid assembly, including any contents supported thereby, is not exclusively borne by the cooperative lid-tray engagement features. 
         [0016]    Still another feature in some embodiments of the present invention is to provide a lid having a peripheral flange, sometimes referred to herein as a “rim horizontal section,” wherein the peripheral flange has at least a first pressing area and a second pressing area that are cooperative with a first lifting tab and a second lifting tab. In some of these embodiments the lifting tabs are formed in a peripheral skirt of the lid, while in other embodiments they are outward extensions from the rim horizontal section, The first pressing area works cooperatively with the first lifting tab and the second pressing area works cooperatively with the second lifting tab such that during the process of removing the lid from the tray, a user presses the first pressing area and lifts the first lifting tab with one hand, while concurrently pressing the second pressing area and lifts the second lifting tab with the second hand. Once at least partial separations have been created at the first and second lifting tab locations, the separations propagate toward each other until they merge, such that the entire lid can be readily removed from the tray. 
         [0017]    One general aspect of the present invention is a method for using and opening a container assembly. The method includes engaging a lid with a container base by cooperatively locking a lid engagement feature provided in the lid proximal to a peripheral boundary of the lid, with a base engagement feature provided in the container base proximal to a peripheral boundary of the container base, said lid including a first graspable member and a second graspable member proximal to the peripheral boundary of the lid in locations that are not directly opposite to each other, each of said graspable members extending beyond the peripheral boundary of the container base, flexing the first graspable member manually via a user&#39;s first hand, thereby rotating the first graspable member upward and disengaging a first portion of the lid engagement feature from a corresponding first portion of the base engagement feature, creating a first region of disengagement therebetween, flexing the second graspable member manually via the user&#39;s second hand, thereby rotating the second graspable member upward and disengaging a second portion of the lid engagement feature from a corresponding second portion of the base engagement feature, creating a second region of disengagement therebetween, and removing the lid from the container base by lifting said lid away from said container base. 
         [0018]    In embodiments, the first and second regions of disengagement extend peripherally in both directions from the corresponding graspable members. In some embodiments, the first and second regions of disengagement merge to form a single region of disengagement that extends at least from the first graspable member to the second graspable member. 
         [0019]    In other embodiments, said lid and container base engagement features are substantially round. In various embodiments, the lid further includes a first press location cooperative with the first graspable member and a second press location cooperative with the second graspable member. 
         [0020]    In further embodiments, the lid includes visible indications associated with the first and second press locations suggesting that pressure be applied to the first and second press locations, and visible indications associated with the first and second graspable members suggesting that the first and second graspable members be lifted. And in some of these embodiments, the step of flexing the first graspable member manually via a user&#39;s first hand is accompanied by pressing on the first press location to facilitate disengagement at said first region, and the step of flexing the second graspable member manually via user&#39;s second hand is accompanied by pressing on the second press location to facilitate disengagement at said second region. 
         [0021]    In certain embodiments, the lid includes visible indications associated with the first and second graspable members suggesting that the first and second graspable members be lifted. 
         [0022]    In embodiments, the graspable members are lift tabs. In some embodiments, said lid is dome shaped. In other embodiments, said graspable members are sequentially flexed by at least one of a user&#39;s hands. 
         [0023]    In certain embodiments, the first graspable member is flexed by a first hand of the user and the second graspable member is concurrently flexed by a second hand of the user. In further embodiments, the graspable members are located at an angular separation of between 20 degrees and 60 degrees. 
         [0024]    In exemplary embodiments, the graspable members are located at an angular separation of between 25 degrees and 50 degrees. In various embodiments, at least one of the graspable members is located at a vertex of the peripheral boundary of the lid. 
         [0025]    In embodiments, the first and second graspable members are located adjacent to either side of a vertex of the peripheral boundary of the lid. And in some embodiments, the material of construction of the lid is one of: polypropylene (PP), oriented polystyrene (OPS), polyethylene terephthalate (PET), styrene butadiene copolymer, and rubber modified styrene. 
         [0026]    Another general aspect of the present invention is a method for releasing a lid from engagement with a container base. The method includes providing a container assembly that includes said lid engaged with said container base, the lid including a lid engagement feature proximal to a peripheral boundary of the lid, said lid engagement feature being engaged in mutual cooperation with a base engagement feature provided in the container base, a first graspable member and a second graspable member being attached to the lid proximal to the peripheral boundary of the lid in locations that are not directly opposite to each other, each of said graspable members extending beyond the peripheral boundary of the container base, a first press location being cooperative with the first graspable member and a second press location being cooperative with the second graspable member, flexing the first graspable member while pressing on the first press location, said flexing and pressing being performed manually via a user&#39;s first hand, thereby rotating the first graspable member upward and disengaging a first portion of the lid engagement feature from a corresponding first portion of the base engagement feature, creating a first region of disengagement therebetween, flexing the second graspable member while pressing on the second press location, said flexing and pressing being performed manually via the user&#39;s second hand, thereby rotating the second graspable member upward and disengaging a second portion of the lid engagement feature from a corresponding second portion of the base engagement feature, creating a second region of disengagement therebetween, and removing the lid from the container base by lifting said lid away from said container base. 
         [0027]    In embodiments, the lid further includes a visible indication associated with the first press location suggesting that pressure be applied to the first press location, a visible indication associated with the first graspable member suggesting that the first graspable member be lifted a visible indication associated with the second press location suggesting that pressure be applied to the second press location, and a visible indication associated with the second graspable member suggesting that the second graspable member be lifted. 
         [0028]    In some of these embodiments, the steps of flexing the first graspable member and flexing the second graspable member are conducted concurrently. 
         [0029]    Yet another general aspect of the present invention is a method for using and opening a container assembly. The method includes engaging a lid with a container base by cooperatively locking a lid engagement feature provided in the lid proximal to a peripheral boundary of the lid, with a base engagement feature provided in the container base proximal to a peripheral boundary of the container base, a first graspable member and a second graspable member being attached to the lid proximal to the peripheral boundary of the lid in locations that are not directly opposite to each other, each of said graspable members extending beyond the peripheral boundary of the container base, flexing the first graspable member manually via a user&#39;s first hand, thereby rotating the first graspable member upward and disengaging a first portion of the lid engagement feature from a corresponding first portion of the base engagement feature, creating a first region of disengagement therebetween, flexing the second graspable member manually via the user&#39;s second hand, thereby rotating the second graspable member upward and disengaging a second portion of the lid engagement feature from a corresponding second portion of the base engagement feature, creating a second region of initial disengagement therebetween; the step of flexing the second graspable member being performed concurrently with the step of flexing first graspable member, and removing the lid from the container base by lifting the lid away from said container base. 
         [0030]    Some embodiments further include the steps of pressing on a first press area of the lid with said first hand while concurrently flexing said first graspable member, and pressing on a second press area of the lid with said second hand while concurrently flexing said second graspable member. And in some of these embodiments, said first and second press areas are located inwardly from said lid engagement feature proximal to said peripheral boundary of the lid. 
         [0031]    One general aspect of the present invention is a lid and container base, the lid being adapted for engagement with the container base and easy release therefrom. The lid and container base include a container base having a container bottom wall, a container sidewall that extends upward from said container bottom wall, and a peripheral container lip having a lip horizontal section that extends outward from said container sidewall and a lip undercut section that extends downward and inward from said lip horizontal section, a lid having a lid top, a lid side wall that extends downward from said lid top wall, and a lid engagement feature proximal to a peripheral lid boundary, said lid engagement feature comprising a rim horizontal section extending outward from said peripheral lid boundary and being substantially continuously about the peripheral lid boundary, and a rim undercut section that extends downward and inward from said rim horizontal section, said lid engagement feature being configured for mutual cooperation and engagement with the container lip whereby said rim horizontal section rests on said lip horizontal section and said rim undercut section extends downwardly and inwardly, overlying and adjacently parallel to said lip undercut section, thereby forming a base-lid assembly, and a pair of graspable members extending from said rim horizontal section in locations that are not directly opposite to each other, said graspable members being configured for grasping and flexing the rim undercut section outward and away from the lip undercut section, thereby disengaging the lid engagement feature from the container lip at two locations, from which said disengagement propagates around a portion of the peripheral boundary that is sufficient for allowing separation of the base-lid assembly and release of the lid from the container base. 
         [0032]    In embodiments, the graspable members are lift tabs. In some embodiments, the lid is dome shaped. In other embodiments, the graspable members are simultaneously operable with a user&#39;s left and right hands respectively. In various embodiments, the graspable members are sequentially operable with at least one of a user&#39;s hands. 
         [0033]    In certain embodiments, at least one of the graspable members further includes a press location cooperative therewith and located proximally thereto, the press location lying on or inward of said rim horizontal section, such that a user&#39;s thumb can press on the press location while at least one of the user&#39;s fingers simultaneously lifts said cooperative graspable member. And some of these embodiments further include a visible indication associated with each press location suggesting that pressure be applied to the press location, and a visible indication associated with each graspable member suggesting that the graspable member be lifted. 
         [0034]    In embodiments, the graspable members are located at an angular separation of between 20 degrees and 60 degrees. In some embodiments, the graspable members are located at an angular separation of between 25 degrees and 50 degrees. 
         [0035]    In various embodiments, the material of construction of the lid is one of: polypropylene (PP), oriented polystyrene (OPS), polyethylene terephthalate (PET), styrene butadiene copolymer, and rubber modified styrene. 
         [0036]    In embodiments, the peripheral lid boundary is substantially round. In other embodiments, the peripheral lid boundary is shaped substantially as a polygon. In some of these embodiments, at least one of the graspable members is located at a vertex of the peripheral boundary of the lid. In other of these embodiments, the pair of graspable members are located adjacent to either side of a vertex of the peripheral boundary of the lid. 
         [0037]    Another general aspect of the present invention is a lid adapted for engagement with a container base and easy release therefrom, the container base having a container bottom wall, at least one container sidewall extending upward from said container bottom wall, a lip horizontal section extending outward from said container sidewall, and a lip undercut section extending downward and inward from said lip horizontal section. The lid includes a lid top, a lid engagement feature comprising a rim horizontal section extending outward from said lid top and substantially continuously about a peripheral lid boundary, and a rim undercut section extending downward and inward from said rim horizontal section, said lid engagement feature being configured for mutual cooperation and engagement with the container lip whereby said rim horizontal section rests on said lip horizontal section and said rim undercut section extends downwardly and inwardly, overlying and adjacently parallel to said lip undercut section, thereby forming a base-lid assembly, a pair of graspable lift tabs extending from said rim horizontal section in locations that are not directly opposite to each other, said graspable members being configured for simultaneous grasping and flexing by left and right hands of a user, and first and second press locations cooperative with the lift tabs and located proximally thereto, each of the press locations lying on or inward of said rim horizontal section, such that the user&#39;s thumbs can press on the press locations while at least one finger of each of the user&#39;s hands simultaneously lifts each of said lift tabs, thereby flexing the rim undercut section outward and away from the lip undercut section and disengaging the lid engagement feature from the container lip at two locations, from which said disengagement propagates around a portion of the peripheral boundary that is sufficient for allowing separation of the base-lid assembly and release of the lid from the container base. 
         [0038]    In embodiments, the container base is a substantially flat tray. Some embodiments further include a visible indication associated with each press area suggesting that pressure be applied to the press area, and a visible indication associated with each lift tab suggesting that the lift tab be lifted. 
         [0039]    In various embodiments, the lid is made by a thermoforming process. In certain embodiments, the lid is made by an injection molding process. In some embodiments, the lid is made from polypropylene (PP) resin. And in other embodiments, the lid is made from polyethylene terephthalate (PET) resin. 
         [0040]    And in embodiments, the lid is thermoformed from an oriented polystyrene sheet. 
         [0041]    The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and examples of claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    The invention will be better understood upon reading the following Detailed Description in conjunction with the drawings in which: 
           [0043]      FIG. 1A  is a perspective view drawn to scale of a simple lid of the prior art having a single lift tab; 
           [0044]      FIG. 1B  is a perspective view drawn to scale of the simple lid of  FIG. 1A , illustrating lifting of a single lift tab and consequent opposing inward distortion of the lid that grips the tray and hinders release of the tray from the lid; 
           [0045]      FIG. 2  is a perspective view drawn to scale of a dome lid according to an embodiment of the present invention; 
           [0046]      FIG. 3  is a top view drawn to scale of the lid of  FIG. 2 ; 
           [0047]      FIG. 4  is a side view drawn to scale of the lid of  FIG. 2 ; 
           [0048]      FIG. 5  is an enlarged view drawn to scale of a press area and lift tab of the lid of  FIG. 2 ; 
           [0049]      FIG. 6  is a partial cutaway view drawn to scale of a tray-lid assembly according to an embodiment of the invention wherein the lid displays a short peripheral skirt; 
           [0050]      FIG. 7  is a partial cutaway view drawn to scale of a tray-lid assembly wherein the lid displays a relatively tall peripheral skirt as typically utilized in dome lids of the prior art; 
           [0051]      FIG. 8  is a perspective view drawn to scale of a user removing a dome lid from a tray with both hands according to an embodiment of the present invention; 
           [0052]      FIG. 9A  is a perspective view drawn to scale of the dome lid of  FIG. 8  having its lift tabs engaged with the tray and prepared for full engagement of the dome lid with the tray; 
           [0053]      FIG. 9B  is a perspective view drawn to scale of the dome lid and tray of  FIG. 9A  showing pressure being applied to the dome lid so as to attach the dome lid to the tray; 
           [0054]      FIG. 10  is a perspective view drawn to scale of a square dome lid with lift tabs at two corners according to an embodiment of the present invention; 
           [0055]      FIG. 11  is a perspective view drawn to scale of a square lid having two lift tabs located on either side of a corner and one additional lift tab located at an adjacent corner, according to an embodiment of the present invention; 
           [0056]      FIG. 12A  is a perspective view drawn to scale of a dome lid according to an embodiment of the present invention; 
           [0057]      FIG. 12B  is a perspective view drawn to scale of a tray that is compatible with the lid of  FIG. 12A ; 
           [0058]      FIG. 12C  is a top view drawn to scale of the lid of  FIG. 12A ; 
           [0059]      FIG. 12D  is a top view drawn to scale of the tray of  FIG. 12B ; 
           [0060]      FIG. 12E  is a side cross-sectional view drawn to scale of the lid of  FIG. 12A  positioned above the tray of  FIG. 12B ; 
           [0061]      FIG. 12F  is an enlarged side cross-sectional view drawn to scale of the rim of the lid of  FIG. 12A  positioned above the rim of the tray of  FIG. 12B , where the locations of the cross sections are shown in  FIGS. 12C and 12D ; 
           [0062]      FIG. 13A  is a perspective view drawn to scale of a dome lid according to an embodiment of the present invention for which the attachment mechanism includes a cleat; 
           [0063]      FIG. 13B  is a perspective view drawn to scale of a tray that is compatible with the lid of  FIG. 13A ; 
           [0064]      FIG. 13C  is a top view drawn to scale of the lid of  FIG. 13A ; 
           [0065]      FIG. 13D  is a top view drawn to scale of the tray of  FIG. 13B ; 
           [0066]      FIG. 13E  is a side cross-sectional view drawn to scale of the lid of  FIG. 13A  positioned above the tray of  FIG. 13B ; 
           [0067]      FIG. 13F  is an enlarged side cross-sectional view drawn to scale of the rim of the lid of  FIG. 13A  positioned above the rim of the tray of  FIG. 13B , where the locations of the cross sections are shown in  FIGS. 13C and 13D ; 
           [0068]      FIG. 14A  is a perspective view drawn to scale of a dome lid according to an embodiment of the present invention for which the attachment mechanism includes a cleat; 
           [0069]      FIG. 14B  is a perspective view drawn to scale of a tray that is compatible with the lid of  FIG. 14A ; 
           [0070]      FIG. 14C  is a top view drawn to scale of the lid of  FIG. 14A ; 
           [0071]      FIG. 14D  is a top view drawn to scale of the tray of  FIG. 14B ; 
           [0072]      FIG. 14E  is a side cross-sectional view drawn to scale of the lid of  FIG. 14A  positioned above the tray of  FIG. 14B ; and 
           [0073]      FIG. 14F  is an enlarged side cross-sectional view drawn to scale of the rim of the lid of  FIG. 14A  positioned above the rim of the tray of  FIG. 14B , where the locations of the cross sections are shown in  FIGS. 14C and 14D . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0074]    The present invention is generally directed towards a lid that can be securely engaged with a tray or container base and yet is readily removable without unduly disturbing the contents of the tray-lid assembly and without applying undue stress to the lid. The following description of one or more embodiments, in conjunction with the accompanying drawings, are offered by way of illustration only, and should not be regarded as restricting the scope of the invention. 
         [0075]    Note that except where the context requires a more specific definition, the term “tray” is used herein to refer generically to a tray, platter, dish, container, plate, or any other support base compatible with a lid or cover, and the term “lid” is used generically herein to refer to any sort of lid or cover compatible with a tray, including flat lids and “dome” lids that are round, rectangular, or any other shape. 
         [0076]    Note also that while the discussion that follows is presented in the context of describing features of a lid that enable removal of the lid from a tray, the roles of the lid and the tray can be reversed without departing from the scope of the invention, so that some or all of the features ascribed in embodiments herein to the “lid” (or upper element) can be incorporated into the “tray” (or lower element) of the tray-lid combination. Therefore, the invention applies generally to separable halves of a containing assembly, whereby terms used for convenience to describe one half of the containing assembly, such as “lid” and “cover,” can generally be exchanged herein with terms used to describe the other half of the containing assembly, such as “tray,” “container,” and “support base,” without departing from the meaning or scope of the invention. 
         [0077]    As will become readily apparent from the following description, a lid that is easy to use and can be readily removed without damaging the lid according to the present invention provides several advantages over prior art lids and tray-lid assemblies. In the case of a food-containing tray-lid assembly, the present invention enables a user to comfortably remove the lid from a tray or other container base with relative ease and without unduly disturbing any of the food items contained within the tray-lid assembly. In particular, the release features or mechanism of the present invention enables lid removal without use of excessive force, which could otherwise result in tearing or damaging of the lid during removal. Being undamaged, the lid can be reattached to the tray and reused as needed. 
         [0078]      FIG. 1A  illustrates a simple lid  100  of the prior art. Lid  100  includes a groove  102  into which a lip of a tray (not shown) can be inserted for secure engagement therewith. Lid  100  also includes a skirt  104  that extends downwardly from the groove  102 . A tab  106  is provided in an attempt to facilitate removal of lid  100  from a tray. As illustrated in  FIG. 1B , lifting of the tab  106  causes an initial separation between the groove  102  and the rim of the tray in a region  108  immediately proximal to the tab  106 . However, lifting the tab  106  also necessarily leads to an outwardly radial elongation  110  of the groove  102  toward the tab  106 , and consequently orthogonal, inwardly radial forces  112  on opposing sides of the groove  102 . These opposing, inwardly radial forces  112  cause the groove  102  to be tightly pressed toward the rim of the tray as the tab  106  is lifted, thereby causing removal of the lid  100  to be very difficult. In the resulting struggle to overcome this gripping force  112 , food or other contents of the tray-lid assembly can be disturbed, and in extreme cases the lid material can fail and the lid  100  can be damaged. 
         [0079]    A lid designated by reference numeral  10 , according to an embodiment of the present invention, is shown in  FIGS. 2 through 6 , wherein like reference numerals represent like parts. Lid  10  is adapted for engaging with a tray or container base, and as particularly shown in  FIG. 6 , lid  10  is shown in a superjacent relationship with tray  30  and is engaged therewith. 
         [0080]    In  FIGS. 2 through 6 , lid  10  is shown with a plurality of ornamental design features, however, it will be apparent to those skilled in the art that the utilitarian structural features of the present invention can be readily utilized with or without a variety of aesthetic and/or ornamental lid designs, and that the features of the present invention are not limited to a particular lid style or design. Thus, variations in the lid sidewall and top wall are within the scope of the present invention, and do not affect the ease of use and release functionality described herein. Additionally, the height of the lid  10  is shorter or taller in certain embodiments, and/or the lid sidewall in some embodiments includes upright ribs and/or the lid top wall includes a combination of structural features, including a shape other than a flat top, such as a rounded shape. 
         [0081]    As shown in  FIG. 2 , the container lid  10  of the illustrated embodiment integrally comprises a generally planar central top wall  11 ; a raised shoulder portion  12  circumscribing or encircling top wall  11 ; a peripheral top portion  13  circumscribing raised shoulder portion  12 ; a sidewall  20  extending circumferentially downward from said peripheral top portion  13 ; a peripheral flange  23  extending outwardly from the bottom end of sidewall  20 ; a peripheral groove portion  24 ; and a downwardly projecting peripheral skirt  25 . 
         [0082]    In the embodiment shown in  FIGS. 2-6 , central top wall  11  is generally planar and substantially horizontal as shown, and is adapted to allow a user to view the contents of the tray-lid assembly. In other embodiments, the lid is opaque or translucent, and/or has a rounded or other non-planar shape or appearance. 
         [0083]    In the embodiment shown in  FIGS. 2-6 , the raised shoulder portion  12  of lid  10  is adapted for facilitating stacking of another tray-lid assembly on top of lid  10 , whereby nesting of the raised shoulder  12  into a recess provided in the bottom of a second tray stacked above the lid  10  serves to stabilize the stacked assembly (or assemblies) and prevent sliding thereof during transportation or while handling and carrying a plurality of stacked assemblies. 
         [0084]    As shown, peripheral top portion  13  may include a variety of ornamental features which also serve as structural stiffening members that strengthen the lid, so that the peripheral top portion  13  can retain its dimensional stability against a downward force typically applied thereto during assembly of lid  10  with a tray or container (see  FIG. 9 ), and when supporting the weight of another tray-lid assembly. In the exemplary embodiment illustrated herein in  FIGS. 2-6 , peripheral top portion  13  features a plurality of flutes  14  and a plurality of ribs  15 . In the illustrated embodiment, the flutes  14  and ribs  15  are organized in sections that form an alternately repeating pattern circumferentially arranged around raised shoulder portion  12 . As is best shown in  FIGS. 2 and 4 , the flutes  14  have an upwardly raised or convex geometry. However it will be appreciated by those skilled in the art that a variety of designs, geometries, patterns and/or other structural elements may be readily imparted to or included in embodiments of the lid of the present invention so as to provide aesthetic appeal and/or structural reinforcement. 
         [0085]    As is best shown in  FIG. 4 , sidewall  20  extends downwardly from peripheral top portion  13  and tapers radially outwardly so as to provide a gradual draft angle for ease of processing and so as to facilitate mold release during the thermoforming process or during any other processing method used for manufacturing lid  10 . Sidewall  20  includes a plurality of panels  21  and flutes  22  that are circumferentially arranged in an alternately repeating pattern therein. The bottom end of sidewall  20  is connected to peripheral flange  23  which is generally horizontal in the embodiment of  FIGS. 2-6 . 
         [0086]    Based on the views shown in various figures herein, it should be readily apparent that relative terms such as “horizontal” are used only for illustrative purposes in describing embodiments of the invention, and that more general terms such as “planar” can be substituted without departing from the scope of the invention. Furthermore modifiers such as ‘generally’ and ‘substantially’ are intended to be construed liberally. Thus, for example, ‘generally planar’ and ‘substantially planar’ are intended to allow for irregular deviations from perfectly flat surface and to reasonably broaden terms such as “planar” so as to encompass curved and other non-planar surfaces. 
         [0087]    As is best shown in  FIGS. 4 and 6 , peripheral flange  23  rolls downwardly to define a peripheral groove portion  24 . Peripheral groove portion  24  has a C-shaped or U-shaped cross section which is adapted for engaging with a tray by receiving a tray lip therein. Referring to  FIG. 6 , there is shown a cross-sectional view of a tray  30  attached to lid  10 . Tray  30  comprises a tray bottom wall  31  resting on a generally horizontal table surface  60 , a tray sidewall  32  which extends upwardly and outwardly from the tray bottom wall  31 , and a peripheral tray lip  33 . In the embodiment of  FIG. 6 , the peripheral tray lip  33  has a bead-like configuration. In other embodiments, the tray lip includes other features, such as a turned-down configuration (not shown). As shown in  FIG. 6 , peripheral tray lip  33  nests within the peripheral groove portion  24  of lid  10 , and the slight undercut in the groove portion  24  provides a reasonably secure interference fit between the lid  10  and the tray  30 . 
         [0088]    Lid  10  also features a peripheral skirt  25  which extends downwardly from the underside of the peripheral groove portion  24  and flares radially outwardly. Peripheral skirt  25  facilitates a good lid-fit by guiding the tray lip  33  within the peripheral groove portion  24 . 
         [0089]    As mentioned above, the present invention provides ease of use and release functionality. The release functionality is accomplished by means of at least two lift tabs. Accordingly, in the embodiment of  FIGS. 2-6 , lift tabs  27  and  29  are provided in the tray skirt  25 . Lift tab  27  is adapted to work cooperatively with press area  26 . Lift tab  29  is adapted to work cooperatively with press area  28 . Press areas  27  and  28  lie in the peripheral flange  23  proximate to panels  21 . 
         [0090]    A typical method of removing the lid  10  of the embodiment of  FIG. 6  from the tray  30  will now be described. With reference to  FIG. 8 , during removal of the lid from the tray, a user presses on press area  26  and lifts lift tab  27  with one hand, and concurrently presses on press area  28  and lifts lift tab  29  with the second hand. The lifting action with both hands serves to rotate the tabs upwardly thereby disengaging a sufficient peripheral portion of lid  10  from the peripheral tray lip of the cooperatively engaged tray or container base to allow removal of the entire lid from the tray. The region of initial disengagement extends peripherally away from each point of lifting action in both directions, and may or may not extend continuously between the two points of lifting action. The removal of the lid of the present invention from a tray by a user is graphically shown in  FIG. 9 . As is best shown in  FIGS. 2, 3, 5, and 8 , press areas may be indicated by integrally forming or molding the word “PRESS” therein, and lift tabs may be indicated by integrally forming or molding the word “LIFT” therein for the purposes of providing simple lid removal instructions to a user. 
         [0091]    Since lift tabs  27  and  29  lie along the peripheral skirt  25 , the arcuate distance between lift tab  27  and  29  can be optimized for allowing a user to comfortably grip the respective tabs with both hands and for providing a convenient release from the tray. According to some embodiments of the invention, the arc angle between lift tabs  27  and  29  varies from 20 to 60 degrees, and according to some embodiments of the invention the arc angle between the lift tabs is between 25 to 50 degrees. Polygon-shaped trays and lids can have lift tabs located at two or more adjacent corners, as illustrated in  FIG. 10 . In other embodiments, two lift tabs are located on either side of one corner, as shown in  FIG. 11 . Various embodiments that include more than two lift tabs, for example on larger trays and lids, may require sequentially applied lifting actions by which suitable peripheral portions of the lid are disengaged from the tray. It will be appreciated by those of ordinary skill that removing the lid of the present invention with one hand by using a single lift tab is significantly more cumbersome compared to utilizing two of the lift tabs concurrently, or more than two sequentially, for removing the lid from the tray. 
         [0092]      FIG. 5  shows an enlarged view of one of the lift tabs, particularly lift tab  27 . Lift tab  27  features a front wall  27   a , an arcuate front end  27   b , and a pair of wedge-shaped side ends  27   c  and  27   d . Front wall  27   a  may be curved outwardly to allow lifting or flexibly turning or rotating of the tab  27  upward, and thereby locally disengaging the peripheral groove portion  24  from tray  30 . Local disengagement of peripheral groove portion  24  from tray  30  at both tab locations  27  and  29  sufficiently disturbs the lid engagement to allow an easy removal of the lid from the tray or container base. It will be realized that tabs  27  and  29  can feature a variety of shape configurations which are all deemed within the scope of the invention, including rectangular, button-shaped, or other structural shapes and appearances. 
         [0093]    According to an embodiment of the invention, the peripheral groove portion  24  and lift tabs  27  and  29  are adapted for detachably engaging and fitting lid  10  with a tray or container base  30 . Accordingly lid  10  is constructed of suitable materials to allow engagement and subsequent reengagement if desired by the user. 
         [0094]    It will be apparent to those skilled in the art that the lids of the present invention can be made of a suitable thermoplastic material which can be processed by common polymer processing methods known in the art, such as thermoforming or injection molding. The choice of a thermoplastic resin is typically governed by a variety of factors, including cost, resin processability, and other functional requirements of the lid. Accordingly, lids of the present invention can be manufactured by thermoforming and/or injection molding. In some embodiments of the present invention, the lid is thermoformed from a polyethylene terephthalate (PET) sheet material. According to other embodiments of the present invention, the lid is injection molded from a suitable grade of polypropylene resin. 
         [0095]    Certain embodiments of the present invention also include a low profile or short peripheral skirt. As shown in  FIG. 6 , arrow segment  40  indicates the vertical spacing between the bottom of peripheral skirt  25  and the table surface  60 , and arrow segment  50  indicates the horizontal spacing between the outer edge of peripheral skirt  25  and tray sidewall  32 . The advantages will be better understood by contrasting the peripheral skirt  25  according to the embodiment of  FIG. 6  with the construction of a prior art lid.  FIG. 7  illustrates a lid  210  according to the prior art fitted onto tray  230 . The peripheral skirt  225  of lid  210  is appreciably longer than peripheral skirt  25  of lid  10 . The longer length of peripheral skirt  225  results in a much reduced spacing, indicated by arrow segment  240 , between the table surface  260  and peripheral skirt  225 . This poses an inconvenience to the user when lifting the tray-lid assembly represented by tray  230  and lid  210 . Furthermore, the horizontal distance between the outer edge of peripheral skirt  225  and the tray sidewall  232  represented by arrow segment  250  is also too large for a user to conveniently reach the tray with his or her fingers when lifting the tray-lid assembly, thus requiring the fit between the tray and lid to be sufficiently tight for the tray-lid engagement feature to support the entire weight of the assembly and of any items contained therein. However, in some embodiments of the present invention, the distance between the tray sidewall  32  and the outer peripheral skirt  25  represented by arrow segment  50  is sufficiently short to conveniently allow a user to lift the tray-lid assembly while touching and supporting the tray, thereby reducing the stress or weight felt by the tray-lid engagement features. In addition, allowing a user to hold the tray-lid assembly more securely without relying on just the tray-lid engagement and/or interlocking features also provides ease of use and safety. 
         [0096]    As shown in  FIGS. 2A-9B , the side wall  20  and top portion  11  of the lid  10  may include a variety of ornamental features which also serve as structural stiffening members that strengthen the lid  10 , so that the lid  10  can retain its dimensional stability against a downward force typically applied thereto during assembly of lid  10  with a tray or container  30 , and when supporting the weight of another tray-lid assembly. It will be appreciated by those skilled in the art that a variety of designs, geometries, patterns and/or other structural elements may be readily imparted to or included in embodiments of the lid  10  of the present invention so as to provide aesthetic appeal and/or structural reinforcement. 
         [0097]    The dual tab feature described above is not limited to round lids, but can be implemented on lids of any shape, including rectangular and square lids. A square lid  10  with two corner tabs  27 ,  29  according to an embodiment of the present invention is shown in  FIG. 10 . It will be realized that the positions of the two or more tabs can be optimized to provide ease of release on square and rectangular lids. According to another exemplary embodiment of the invention illustrated in  FIG. 11 , the two tabs  27 A,  27 B are located in a proximate relationship about a bottom corner of a square or rectangular lid  10  and are disposed in a slightly offset position from that corner on both sides thereof. In addition,  FIG. 11  shows a third lift tab  29  at an adjacent corner. Dual or multiple tabs can thus also be implemented on lids having a general shape such as a polygonal shape. Thus, the exemplary embodiments shown in  FIG. 10  and  FIG. 11  are illustrative of embodiments of the invention for non-round containers and do not limit the scope of the invention with regards to lid shape and locations of tabs. 
         [0098]    As shown in  FIGS. 12A-12F , in embodiments of the present invention the container lid  10  integrally comprises a generally planar top portion  11 , a sidewall  20  extending circumferentially downward from said top portion  11 , a rim horizontal section  23  extending outwardly from the bottom end of sidewall  20 , and a rim undercut section  54  extending downward and inward from a peripheral edge of the rim horizontal section  23 . 
         [0099]    In the illustrated embodiment, tray  30  comprises a tray bottom  31 , a tray sidewall  32  which extends upwardly and outwardly from the tray bottom  31 , a lip horizontal section  33 , and a lip undercut section  34  extending downward and inward from a peripheral edge of the lip horizontal section  33 . As shown in  FIG. 12F , when the lid  10  is engaged with the tray  30 , the rim horizontal section  23  of the lid  10  rests on top of the lip horizontal section  33  of the tray  30 , and the rim undercut section  54  of the lid  10  extends downward and inward from a peripheral edge of the rim horizontal section  23 , overlying and adjacently parallel to the lip undercut section  34  of the tray  30 , thereby forming a securely engaged tray-lid assembly. 
         [0100]    As mentioned above, the present invention provides ease of use and release functionality. The release functionality is accomplished by means of at least two lift tabs  27 ,  29 . In the embodiment of  FIGS. 12A-12F , press areas  26 ,  28  are also provided in the horizontal rim section  23 , such that lift tab  27  is adapted to work cooperatively with press area  26 , and lift tab  29  is adapted to work cooperatively with press area  28 . 
         [0101]      FIGS. 13A-14F  illustrate two additional embodiments that include press locations but do not include visible indications that label the press locations. As can be seen in  FIGS. 13B and 14B , the attachment mechanisms of the trays in these embodiments include receiving regions of enhanced engagement or recessions  56  that cooperate with the protruding regions of enhanced engagement or cleats  55  in the attachment mechanisms of the lids respectively, as can be seen in  FIGS. 13A and 14A . The regions of enhanced engagement strengthen the attachment of the lid  11  to the container base  31  along the sides of the lid  11 , so that the overall attachment of the lid  11  to the container base  31  is not as strongly dependent on the attachment at the vertices. As a result, the attachment at the vertices can be made weaker without reducing the overall lid-tray attachment to an unacceptable degree. This renders inadvertent detachment of the lid  11  unlikely, while allowing the lid  11  to be intentionally released from the container base  31  without requiring the user to apply undue effort, without subjecting the lid  11  to undue stress, and without unduly disturbing the contents of the base-lid assembly. These features are explained in more detail in co-pending U.S. patent application Ser. No. 14/877,001, which is incorporated herein by reference for all purposes. 
         [0102]    In all of the illustrated embodiments of the present invention, central top wall  11  is generally planar and substantially horizontal as shown, and is adapted to allow a user to view the contents of the tray-lid assembly. In other embodiments, the lid is opaque or translucent, and/or has a rounded or other non-planar shape or appearance. 
         [0103]    The embodiments discussed above all include lids that incorporate lift tab features of the present invention for facilitating separation of a lid from a tray. However, it will be understood by anyone skilled in the art that the same purpose can be accomplished by providing indentation features or recessed locations in the tray for allowing access to a user&#39;s hands for grasping and manipulating the lid periphery. Therefore, the graspable tabs can be created by indentations provided in either the tray or the lid. Furthermore, graspable members for manipulating separation of a tray-lid assembly may be configured in the form of lift tabs, push tabs, indentations, or combinations thereof. In addition, it will be understood by those skilled in the art that the features of the present invention can be included in the lower, or “tray” portion of a tray-lid assembly, rather than in the lid. 
         [0104]    The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as restrictive. Many modifications and variations are possible in light of this disclosure. The advantages of the invention may be further realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.