Patent Publication Number: US-2021188491-A1

Title: Systems and methods for containers with locking lug and recess

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a divisional of U.S. patent application Ser. No. 15/851,486 filed Dec. 21, 2017, which claims priority to U.S. Provisional Application Ser. No. 62/437,649 filed Dec. 21, 2016, the contents of each of which are incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE APPLICATION 
     The disclosed subject matter relates to a thermoformed locking assembly, and articles, such as a container, having a thermoformed locking assembly. 
     DESCRIPTION OF THE RELATED ART 
     Articles, such as containers, are frequently made by thermoforming a web of material. Articles so produced can, for example, be used for shipping, storing, preparing and/or serving a wide range of food items, such as an egg carton for eggs or a cake container for cakes. It is beneficial, or perhaps necessary, for such thermoformed containers to be capable of being locked closed. 
     Although various locking assemblies are known, there remains a need for a thermoformed locking assembly and articles, such as a container, having a thermoformed locking assembly that can be securely locked closed, but readily opened when desired. 
     SUMMARY 
     The purpose and advantages of the disclosed subject matter will be set forth in and apparent from the description that follows, as well as will be learned by practice of the disclosed subject matter. Additional advantages of the disclosed subject matter will be realized and attained by the methods and systems particularly pointed out in the written description and claims hereof, as well as from the appended drawings. 
     To achieve these and other advantages, and in accordance with the purpose of the disclosed subject matter, as embodied and broadly described, the disclosed subject matter includes a thermoformed container including a base having a base flange and a lid having a lid flange. The lid is configured to be moved relative to the base between a closed position and an open position. The lid flange is adjacent to the base flange when in the closed position. At least one of the base flange or the lid flange is formed to include a locking lug having a lug undercut defining a cantilevered lug ledge having a lug engaging surface. The other of the base flange or lid flange is formed to include a locking recess having a recess undercut defining an opposing recess ledge having a recess engaging surface and a lug stop opposite the recess undercut. The locking recess is aligned to receive the locking lug and the lug stop is configured to position the locking lug in the locking recess such that the lug engaging surface is in engagement with the recess engaging surface to define a locking assembly when the base and lid are in the closed position. 
     Additionally, and as embodied herein, the lid can be hingedly connected to the base by a hinge. The hinge can be disposed on an opposite side of the container as the locking lug and locking recess. Alternatively, as further embodied herein, the base and the lid can be two separate members to allow removal of the lid when the lid is moved to the open position. 
     Furthermore, and as embodied herein, a minimum closing force can be applied to move the lid into the closed position with the lug engaging surface in engagement with the recess engaging surface, and a minimum opening force can be applied to move the lug engaging surface out of engagement with the recess engaging surface. The minimum opening force can be greater than the minimum closing force. The cantilevered lug ledge and the opposing recess ledge can each have an outer edge, and at least one outer edge can be chamfered or rounded to maintain the desired minimum closing force required to move the lid into the closed position with the lug engaging surface in engagement with the recess engaging surface. 
     In addition, and as embodied herein, the locking lug can include stiffening ribs along two sides of the locking lug. The locking recess likewise can include stiffening ribs along two sides of the locking recess. As additionally embodied herein, the locking lug can be generally L-shaped in cross section. Likewise, the locking lug can be provided with a single-sided configuration, wherein a lug undercut is provided only on one side of the locking lug. Similarly, the locking recess can be single-sided with the recess undercut on one side of the locking recess. In this manner, the locking lug and recess can be provided in a relatively small space, so as to be incorporated on containers of smaller size and reduced web thickness, without compromising the integrity of the minimum closing and opening forces as desired. As further embodied herein, the locking lug can include a ramp to reduce stack height. 
     In accordance with another aspect of the disclosed subject matter, a method of forming a thermoformed locking assembly, or an article, such as a container, having such locking assembly is provided. The thermoformed locking assembly includes a locking lug having an undercut defining a cantilevered lug ledge having a lug engaging surface and a locking recess having an undercut defining an opposing recess ledge having a recess engaging surface and a lug stop opposite the recess undercut. The method of forming the thermoformed locking assembly includes providing a mold having a mold surface with a moveable locking lug mold portion and a moveable locking recess mold portion. Each of the moveable locking lug mold portion and the moveable locking recess mold portion is moveable between a mold condition aligned with the mold surface and a retracted condition below the mold surface. The moveable locking lug mold portion has an upper surface with a cavity defined therein corresponding in shape to at least a portion of the locking lug. The moveable locking lug mold portion has a lug undercut mold member slidably mounted on an angled surface of the moveable locking lug mold portion with the lug undercut mold member having a flange corresponding to the lug undercut. The moveable locking recess mold portion has a protrusion extending above the mold surface when the moveable locking recess mold portion is in the mold condition. The protrusion corresponds in shape to at least a portion of the locking recess. The moveable locking recess mold portion has a recess undercut mold member slidably mounted on an angled surface of the moveable locking recess portion with the recess undercut mold member having a flange corresponding to the recess undercut. 
     The method includes positioning at least one web of thermoformable material on the mold surface with a first web portion proximate the moveable locking lug mold portion and a second web portion proximate the moveable locking recess mold portion and with both the moveable locking lug mold portion and moveable locking recess mold portion in the mold condition. For example, a single web can be positioned on both the moveable locking lug mold portion and the moveable locking recess mold portion if a single piece construction is desired. Alternatively, separate webs can be positioned on the moveable locking lug mold portion and moveable locking recess mold portion, respectively, if a two-piece construction is preferred. As disclosed in further detail, a web of less thickness can be used due to the mold of the disclosed subject matter. The method further includes thermoforming the at least one web to form an article including a locking lug and a locking recess. The locking lug has an undercut defining a cantilevered lug ledge having a lug engaging surface formed by the moveable locking lug mold portion. The locking recess has an undercut defining an opposing recess ledge having a recess engaging surface and a lug stop opposite the recess undercut formed by the moveable locking recess mold portion. The method further includes retracting the moveable locking lug mold portion and the moveable locking recess mold portion to the retracted condition. The lug undercut mold member slides along the angled surface of the moveable locking lug mold portion to release the lug undercut when the moveable locking lug mold portion is moved towards the retracted condition. The recess undercut mold member slides along the angled surface of the moveable locking recess mold portion to release the recess undercut when the moveable locking recess mold portion is moved towards the retracted condition. 
     Additionally, and as embodied herein, the lug undercut mold member can be biased towards an initial position. The lug undercut mold member can slide along the angled surface of the moveable locking lug mold portion against the bias until the lug undercut is released returning the lug undercut mold member to the initial position. 
     Furthermore, and as embodied herein, the recess undercut mold member can be biased towards an initial position. The recess undercut mold member can slide along the angled surface of the moveable locking recess mold portion against the bias until the recess undercut is released returning the recess undercut mold member to the initial position. 
     In accordance with another aspect of the disclosed subject matter, a thermoformed locking assembly is provided. The thermoformed locking assembly comprises a locking lug and a locking recess having one or more of the features set forth above, and as further described in detail herein. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the disclosed subject matter claimed. 
     The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the method and system of the disclosed subject matter. Together with the description, the drawings serve to explain the principles of the disclosed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The application file contains at least one drawing executed in color. Copies of this patent with color drawings will be provided by the Office upon request and payment of the necessary fee. 
         FIG. 1  is a plan view of an exemplary embodiment of a container in accordance with the disclosed subject matter in an open position. 
         FIG. 2  is a perspective view of another exemplary embodiment of a container in accordance with the disclosed subject matter in an open position. 
         FIG. 3A  is a bottom perspective view of an exemplary locking lug and recess of the container of  FIG. 2  in a closed position. 
         FIG. 3B  is a top perspective view of the locking lug and recess of the container of  FIG. 3A  in the closed position. 
         FIG. 4A  is a perspective view of another exemplary locking lug in accordance with the disclosed subject matter, a complementary locking recess (not shown) being a mirror image of the locking lug. 
         FIG. 4B  is a perspective view of another exemplary locking lug in accordance with the disclosed subject matter, a complementary locking recess (not shown) being a mirror image of the locking lug. 
         FIG. 5A  is a perspective view of the locking lug of  FIG. 4A , showing a finite element analysis to illustrate additional details of the locking lug in accordance with the disclosed subject matter. 
         FIG. 5B  is a perspective view of the locking lug of  FIG. 4B , showing a finite element analysis to illustrate additional details of the locking lug in accordance with the disclosed subject matter. 
         FIG. 6A  is a perspective view of the locking lug of  FIG. 4A , showing a finite element analysis to illustrate additional details of the locking lug in accordance with the disclosed subject matter. 
         FIG. 6B  is a perspective view of the locking lug of  FIG. 4B , showing a finite element analysis to illustrate additional details of the locking lug in accordance with the disclosed subject matter. 
         FIG. 7A  is a perspective view of the locking lug of  FIG. 4A , showing a finite element analysis to illustrate additional details of the locking lug in accordance with the disclosed subject matter. 
         FIG. 7B  is a perspective view of the locking lug of  FIG. 4B , showing a finite element analysis to illustrate additional details of the locking lug in accordance with the disclosed subject matter. 
         FIG. 8A  is a perspective view of the locking lug of  FIG. 4A , showing a finite element analysis to illustrate additional details of the locking lug in accordance with the disclosed subject matter. 
         FIG. 8B  is a perspective view of the locking lug of  FIG. 4B , showing a finite element analysis to illustrate additional details of the locking lug in accordance with the disclosed subject matter. 
         FIG. 9  is a schematic view of another exemplary embodiment of a locking lug and locking recess in accordance with the disclosed subject matter. 
         FIG. 10  is a schematic view of another exemplary embodiment of a locking lug and locking recess in accordance with the disclosed subject matter. 
         FIG. 11A  is a schematic view of another exemplary embodiment of a locking lug of a container in a stacking engagement with a locking lug of another container in accordance with the disclosed subject matter. 
         FIG. 11B  is a schematic view of another exemplary embodiment of a locking lug of a container in a stacking engagement with a locking lug of another container in accordance with the disclosed subject matter. 
         FIG. 12  is a perspective view of the container of  FIG. 1  in a closed position, with portions cut away to show an exemplary locking lug in engagement with an exemplary locking recess in accordance with the disclosed subject matter. 
         FIG. 13A  is a diagram illustrating additional details of exemplary locking lugs and locking recesses, including exemplary open/close lock force, average weight and material thickness. 
         FIG. 13B  is a diagram illustrating additional details of exemplary locking lugs and locking recesses, including exemplary open/close lock force, average weight and material thickness. 
         FIG. 13C  is a schematic illustrating additional exemplary configurations for locking lugs and locking recesses in accordance with the disclosed subject matter. 
         FIG. 14  is a perspective view of an exemplary mold for forming a container having a locking lug and a locking recess in accordance with the disclosed subject matter. 
         FIG. 15A  is an enlarged perspective view of the exemplary mold of  FIG. 14 , showing additional details of a locking lug mold portion and a locking recess mold portion in accordance with the disclosed subject matter. 
         FIG. 15B  is a cross-sectional view taken along line B-B of  FIG. 15A . 
         FIG. 15C  is an enlarged cross-sectional view of region C of  FIG. 15B . 
         FIG. 16  is a schematic view of an exemplary locking lug mold portion and locking recess mold portion of an exemplary mold in accordance with the disclosed subject matter. 
     
    
    
     DETAILED DESCRIPTION 
     The apparatus and methods presented herein may be used for storage, transportation, and display of various products, such as food items and other perishable and nonperishable products. The disclosed subject matter is particularly suited for storage, transportation, and display of food items, wherein the container lid and base provide a locking assembly to allow easy locking and release of the lid. 
     In accordance with the disclosed subject matter, as embodied and broadly described, the disclosed subject matter includes a thermoformed container including a base having a base flange and a lid having a lid flange. The lid is configured to be moved relative to the base between a closed position and an open position. For example, and as set forth in detail below, the lid can be hingedly connected to the base to form a container with one-piece construction, or the lid can be a separate member to form a container with two-piece construction if preferred. The lid flange is adjacent to the base flange when in the closed position. At least one of the base flange or the lid flange is formed to include a locking lug having a lug undercut defining a cantilevered lug ledge having a lug engaging surface. The other of the base flange or lid flange is formed to include a locking recess having a recess undercut defining an opposing recess ledge having a recess engaging surface and a lug stop opposite the recess undercut. The locking recess is aligned to receive the locking lug and the lug stop is configured to position the locking lug in the locking recess to define a locking assembly in accordance with the disclosed subject matter, such that the lug engaging surface is in engagement with the recess engaging surface when the base and lid are in the closed position. 
     Reference will now be made in detail to the various exemplary embodiments of the disclosed subject matter, exemplary embodiments of which are illustrated in the accompanying drawings. The structure and corresponding methods of operation of the disclosed subject matter will be described in conjunction with the detailed description of the systems. 
     The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the disclosed subject matter. For purpose of explanation and illustration, and not limitation, exemplary embodiments of the container, and of the locking assembly, in accordance with the disclosed subject matter are shown in  FIGS. 1-16 . The container is suitable for use with a wide variety of perishable and nonperishable products. For example, and without limitation, the container can be used for shipping, serving, storing, preparing and/or re-using food items, such as an egg carton for eggs or a cake container for cakes. 
     For purpose of illustration, and not limitation, reference is now made to  FIGS. 1 and 2  illustrating a thermoformed container  100 , according to an exemplary embodiment of the disclosed subject matter. As embodied herein, the thermoformed container  100  includes a base  101  having a base flange  111  and a lid  102  having a lid flange  112 . The base flange  111  and the lid flange  112  can extend outwardly from the base  101  and the lid  102 , respectively. At least one of the base flange  111  or lid flange  112  is formed to include a locking lug  121 . The locking lug  121  has a lug undercut  131  defining a cantilevered lug ledge having a lug engaging surface  141 . The other of the base flange  111  or the lid flange  112  is formed to include at least one locking recess  122 . The locking recess  122  has a recess undercut  132  defining an opposing recess ledge having a recess engaging surface  142  and a lug stop  192  opposite the recess under cut  132 . For purpose of explanation and illustration, and not limitation, as embodied herein, the thermoformed container  100  can have two locking lugs  121  each disposed proximate a corner of the base flange  111 , and two locking recesses  122  each disposed in a corresponding corner of the lid flange  112 . As described herein, locking recess  122  is aligned to receive locking lug  121  and lug stop  192  is configured to position the locking lug  121  with the lug engaging surface  141  in engagement with the recess engaging surface  142  when the lid is moved into the closed position. 
     The lid  102  is configured to be moved relative to the base  101  between a closed position and an open position. Reference is now made to  FIGS. 3A and 3B , the base  101  and lid  102  are shown in a closed position. The lid flange  112  is adjacent to the base flange  111  when the base  101  and the lid  102  are in the closed position. The locking recess  122  is aligned to receive the locking lug  121  such that the lug engaging surface  141  is in engagement with the recess engaging surface  142  when the base  101  and lid  102  are in the closed position. 
     Reference is now made to  FIG. 12 , showing lug stop  192  opposite the recess undercut  132 . Lug stop  192  can be configured to position the locking lug in the locking recess with the lug engaging surface in engagement with the recess engaging surface when the lid is moved into the closed position. The lug stop  192  can be configured such that little or no clearance is provided at the back of the locking lug  121  when the lid is moved into the closed position with the cantilevered lug ledge positioned under the undercut of the opposing locking recess ledge and the lug engaging surface in engagement with the recess engaging surface. As further embodied herein, the lug stop  192  can reduce or prevent movement and inadvertent release of the locking lug  121  from the lug recess  122  when in the closed position. For purpose of example and not limitation, lug stop  192  can be made vertical to facilitate molding of the locking recess. 
     Additionally, and as embodied herein, the lid  102  can be hingedly connected to the base  101  by a hinge  105 . The hinge  105  can be disposed on an opposite side of the container as the locking lug  121  and locking recess  122 . Alternatively, as further embodied herein, the base  101  and the lid  102  can be configured to allow removal of the lid  102  when the lid is moved to the open position, such as by providing a frangible hinge to tear off the lid  102  from the base  101 , or by forming the base  101  and lid  102  as separate members. Furthermore, a plurality of locking lugs  121  and a corresponding plurality of locking recesses  122  can be provided. For example, if the lid  102  is hingedly connected to the base  101  to form a one-piece construction, two locking lugs  121  and two locking recesses  122  can be provided, such as disposed on an opposite side of the container as the hinge  105 . Alternatively, if a two-piece construction is desired, a plurality of locking lugs  121  and corresponding locking recesses  122  can be provided, such as disposed at each corner of the container and/or along one or more edges. 
     Furthermore, and as embodied herein, a minimum closing force can be applied to move the lid  102  into the closed position with the lug engaging surface  141  in engagement with the recess engaging surface  142 , and a minimum opening force can be applied to move the lug engaging surface  141  out of engagement with the recess engaging surface  142 . The minimum opening force can be greater than the minimum closing force. 
     Reference is now made to  FIGS. 4A and 4B , the locking lug  121  can include stiffening ribs  151  along two sides of the locking lug  121  to provide additional support to the undercut  131 , according to an aspect of the disclosed subject matter. Similarly, locking recess  122  likewise can include stiffening ribs along two sides of the locking recess. As embodied herein, both the lug and recess are provided with stiffening ribs, such that the desired minimum opening and closing forces are less sensitive to material thickness of the web since the ribs minimize deflection of the lug and recess. As additionally embodied herein, the locking lug  121  can be generally L-shaped in cross section. Furthermore, and as evident from the figures, the locking lug can be provided with a single-sided configuration, wherein a lug undercut is provided only on one side of the locking lug (e.g., on a front side of the lug). Similarly, the locking recess can be single-sided with the recess undercut on one side of the locking recess. In this manner, the locking lug and recess can be provided in a relatively small space, so as to be incorporated on containers of smaller size and reduced web thickness, without compromising the integrity of the minimum closing and opening forces as desired. 
     Reference is now made to  FIGS. 5A-6B , a finite element test, applying a downward force to the exemplary locking lugs of  FIGS. 4A and 4B , is shown for purpose of illustration and comparison, showing a locking lug  121  without stiffening ribs ( FIGS. 5A and 6A ) and with stiffening ribs  151  ( FIGS. 5B and 6B ), in accordance with the disclosed subject matter. 
     Reference is now made to  FIGS. 7A-8B , a finite element test, applying an upward (pry-up) force to the exemplary locking lugs of  FIGS. 4A and 4B , is shown for purpose of illustration and comparison, showing a locking lug  121  without stiffening ribs ( FIGS. 7A and 8A ) and with stiffening ribs  151  ( FIGS. 7B and 8B ), in accordance with the disclosed subject matter. 
     Reference is now made to  FIGS. 9-11B , the lug undercut  131  and recess undercut  132  can define a cantilevered lug ledge and an opposing recess ledge, respectively, and each of the cantilevered lug ledge and opposing recess ledge can have an outer edge  133 ,  134 , respectively, according to an aspect of the disclosed subject matter. As further embodied herein, outer edges  133  or  134  can be configured to reduce or maintain the minimum closing force required to move the lid into the closed position as desired. For purpose of example and not limitation, outer edges  133  or  134  can be rounded, chamfered, or chord shaped. Furthermore, and as embodied herein, locking lug  121  can include ramps  161 ,  162 , which can allow for more efficient stacking of containers  100  when in the open position. Further referencing  FIGS. 11A and 11B , Stack Height A  302  of containers  100  without ramps  161  and  162  and Stack Height B  303  of containers with ramps  161  and  162  are shown. For purpose of example and not limitation, Stack Height B  303  can be less than Stack Height A  302 . As further embodied herein, ramps  161  and  162  can be formed at angle  301 . For purposes of example and not limitation, containers  100  can be formed such that angle  301  is approximately 30 degrees and Stack Height B  303  is approximately 0.124 inches or less. 
     Reference is now made to  FIGS. 13A and 13B , diagrams illustrating opening and closing forces to move the lid  102  and the base  101  between an open and closed position are provided for different material thicknesses. As shown in  FIGS. 13A and 13B , a lower closing force than opening force can be achieved using the locking lugs and locking members of the disclosed subject matter, which can allow for easy filed packing, maintaining a closed container during shipping and a secure yet easy container to open when consuming the food product.  FIGS. 13A and 13B  further show a range of PET sheet gauges for purpose of illustration and confirmation of the disclosed subject matter. As shown, sheet gauges can be used from 18-mil down to 15.5-mil, and the containers were formed without any container stripping issues experienced with previous down gauge trials with button, bar and bone button lock geometries. The containers formed according to the disclosed subject matter can thus close easily with less than 1-lb. force, provide an audible click when the lock engages and stay securely locked with greater than 2.5 lbs. force to open. 
     As shown in  FIG. 13A , for purpose of illustration and not limitation, opening and closing forces for exemplary containers in accordance with the disclosed subject matter are illustrated. Container B formed having a material thickness of 15.5 mil provided a closing force of about 0.871 lbs. and an opening force of about 1.666 lbs. Container B formed having a material thickness of 16.0 mil provided a closing force of about 0.928 lbs. and an opening force of about 1.713 lbs. Container B formed having a material thickness of 16.5 mil provided a closing force of about 1.346 lbs. and an opening force of about 1.687 lbs. Container B formed having a material thickness of 17.0 mil provided a closing force of about 0.972 lbs. and an opening force of about 1.944 lbs. Container B formed having a material thickness of 17.5 mil provided a closing force of about 0.585 lbs. and an opening force of about 2.090 lbs. For purpose of illustration and not limitation, an exemplary container (“container C”) having a locking lug and locking recess in accordance with the disclosed subject matter. Container C formed having a material thickness of 15.5 mil provided a closing force of about 0.6 lbs. and an opening force of about 1.45 lbs. Container C formed having a material thickness of 16.0 mil provided a closing force of about 0.55 lbs. and an opening force of about 1.55 lbs. Container C formed having a material thickness of 16.5 mil provided a closing force of about 1 lb. and an opening force of about 1.55 lbs. Container C formed having a material thickness of 17.0 mil provided a closing force of about 1.1 lbs. and an opening force of about 1.9 lbs. Container C formed having a material thickness of 17.5 mil provided a closing force of about 1.15 lbs. and an opening force of about 1.8 lbs. 
     As shown in  FIG. 13B , for purpose of illustration and not limitation, opening and closing forces for an exemplary container (“container B”) in accordance with the disclosed subject matter are illustrated. Container B formed having a material thickness of 16.0 mil provided a closing force of about 1.32 lbs. and an opening force of about 1.93 lbs. Container B formed having a material thickness of 16.5 mil provided a closing force of about 1.29 lbs. and an opening force of about 2.46 lbs. Container B formed having a material thickness of 17.0 mil provided a closing force of about 1.10 lbs. and an opening force of about 2.05 lbs. Container B formed having a material thickness of 17.5 mil provided a closing force of about 1.42 lbs. and an opening force of about 2.48 lbs. Container B formed having a material thickness of 18.0 mil provided a closing force of about 1.39 lbs. and an opening force of about 2.51 lbs. 
     As shown in  FIG. 13C , for purpose of illustration and not limitation, exemplary locking members in accordance with the disclosed subject matter are illustrated. For example and not limitation, an exemplary locking member (“Latch A”) can have an engaging surface with a dimension w 1  within a range of about 0.053 in to about 0.062 in. As embodied herein, Latch A can have a locking lug dimension h 1  of about 0.170 in and a locking lug dimension h 2  of about 0.180 in. For example and not limitation, an exemplary locking member (“Latch B”) can have an engaging surface with a dimension w 1  within a range of about 0.048 in to about 0.057 in. As embodied herein, Latch B can have a locking lug dimension h 1  of about 1.170 in and a locking lug dimension h 2  of about 0.180 in. For example and not limitation, an exemplary locking member (“Latch C”) can have an engaging surface with a dimension w 1  within a range of about 0.043 in to about 0.052 in. As embodied herein, Latch C can have a locking lug dimension h 1  of about 0.170 in and a locking lug dimension h 2  of about 0.180 in. 
     Hence, as evident from the above, a container having the locking lug and recess arrangement of the disclosed subject matter can be provided with reduced material web thickness and reduced flange size without compromising the integrity of the desired minimum closing and opening forces. 
     In accordance with another aspect of the disclosed subject matter, a method of forming a thermoformed locking assembly, or article, such as a container, having such locking assembly, is provided. The thermoformed locking assembly includes a locking lug having an undercut defining a cantilevered lug ledge having a lug engaging surface and a locking recess having an undercut defining an opposing recess ledge having a recess engaging surface and a lug stop opposite the recess undercut. The method of forming the thermoformed locking assembly includes providing a mold having a mold surface with a moveable locking lug mold portion and a moveable locking recess mold portion. The mold surface can be a single assembly with both the moveable locking lug mold portion and the moveable locking recess mold portion, or the mold surface can include separate assemblies for each of the locking lug mold portion and locking recess mold portion respectively, such as if a two-piece construction is desired. Each of the moveable locking lug mold portion and the moveable locking recess mold portion are moveable between a mold condition aligned with the mold surface and a retracted condition below the mold surface. The moveable locking lug mold portion has an upper surface with a cavity defined therein corresponding in shape to at least a portion of the locking lug. The moveable locking lug mold portion has a lug undercut mold member slidably mounted on an angled surface of the moveable locking lug mold portion with the lug undercut mold member having a flange corresponding to the lug undercut. The moveable locking recess mold portion has a protrusion extending above the mold surface when the moveable locking recess mold portion is in the mold condition. The protrusion corresponds in shape to at least a portion of the locking recess. The moveable locking recess mold portion has a recess undercut mold member slidably mounted on an angled surface of the moveable locking recess portion with the recess undercut mold member having a flange corresponding to the recess undercut. 
     The method further includes positioning at least one web of thermoformable material on the mold surface with the moveable locking lug mold portion and the moveable locking recess mold portion each in the mold condition, such that a first web portion is proximate the moveable locking lug mold portion and a second web portion is proximate the moveable locking recess mold portion. For example, a single web can be positioned on both the moveable locking lug mold portion and the moveable locking recess mold portion if a single piece construction is desired. Alternatively, separate webs can be positioned on the moveable locking lug mold portion and moveable locking recess mold portion respectively if a two-piece construction is preferred. As noted above, a web of reduced thickness can be used due to the mold of the disclosed subject matter. The method further includes thermoforming the at least one web to form an article including a locking lug and a locking recess. The locking lug has an undercut defining a cantilevered lug ledge having a lug engaging surface formed by the moveable locking lug mold portion. The locking recess has an undercut defining an opposing recess ledge having a recess engaging surface and a lug stop opposite the recess undercut formed by the moveable locking recess mold portion. The method further includes retracting the moveable locking lug mold portion and the moveable locking recess mold portion to the retracted condition. The lug undercut mold member slides along the angled surface of the moveable locking lug mold portion to release the lug undercut when the moveable locking lug mold portion is moved towards the retracted condition. The recess undercut mold member slides along the angled surface of the moveable locking recess mold portion to release the recess undercut when the moveable locking recess mold portion is moved towards the retracted condition. 
     Reference is now made to  FIGS. 14-15C  illustrating a mold  200  for forming the thermoformed container  100 , according to an aspect of the disclosed subject matter. The mold  200  has a mold surface  201  with a moveable locking lug mold portion  211  and a moveable locking recess mold portion  212 . Each of the moveable locking lug mold portion  211  and moveable locking recess mold portion  212  is moveable between a mold condition aligned with the mold surface  201  and a retracted condition below the mold surface  201 . The moveable locking lug mold portion  211  has an upper surface with a cavity  231  defined therein corresponding in shape to at least a portion of the locking lug  121 . The moveable locking lug mold portion  211  has a lug undercut mold member  221  slidably mounted on an angled surface  251  of the moveable locking lug mold portion  211  with the lug undercut mold member  221  having a flange  261  corresponding to the lug undercut  131 . 
     The moveable locking recess mold portion  212  has a protrusion  232  extending above the mold surface  201  when the moveable locking recess mold portion  212  is in the mold condition. The protrusion  232  corresponds in shape to at least a portion of the locking recess  122 . The moveable locking recess mold portion  212  has a recess undercut mold member  222  slidably mounted on an angled surface  252  of the moveable locking recess portion  212  with the recess undercut mold member  222  having a flange  262  corresponding to the recess undercut  132 . 
     For purpose of illustration and not limitation, as embodied herein, a method of forming container  100  includes positioning at least one web of thermoformable material on the mold surface  201  with the moveable locking lug mold portion  211  and the moveable locking recess mold portion  212  each in the mold condition. The method includes thermoforming the at least one web to form an article including a locking lug  121  and a locking recess  122 . The locking lug  121  has a lug undercut  131  defining a cantilevered lug ledge having a lug engaging surface  141  formed by the moveable locking lug mold portion  211 . The locking recess  122  has a recess undercut  132  defining an opposing recess ledge having a recess engaging surface  142  and a lug stop  192  opposite the recess undercut formed by the moveable locking recess mold portion  212 . The method includes retracting the moveable locking lug mold portion  211  and the moveable locking recess mold portion  212  to the retracted condition. The lug undercut mold member  221  slides along the angled surface  251  of the moveable locking lug mold portion  211  to release the lug undercut  131  when the moveable locking lug mold portion  211  is moved towards the retracted condition. The recess undercut mold member  222  slides along the angled surface  252  of the moveable locking recess mold portion  212  to release the recess undercut  132  when the moveable locking recess mold portion  212  is moved towards the retracted condition. Additional features of the locking lug and locking recess as set forth above can be incorporated with the method as desired. 
     Additionally, and as embodied herein, the lug undercut mold member  221  can be biased towards an initial position, and the lug undercut mold member  221  can slide along the angled surface  251  of the moveable locking lug mold portion  211  against the bias until the lug undercut  131  is released returning the lug undercut mold member  221  to the initial position. Additionally or alternatively, as embodied herein, the recess undercut mold member  222  can be biased towards an initial position, and the recess undercut mold member  222  can slide along the angled surface  252  of the moveable locking recess mold portion  212  against the bias until the recess undercut  132  is released returning the recess undercut mold member  222  to the initial position. 
     Furthermore, and as embodied herein, the mold  200  can include a male lock assembly pocket  282  and a female lock assembly pocket  281 , which can be configured to secure the web of thermoplastic material to the mold  200 . 
     With reference to  FIG. 15C , for purpose of illustration and not limitation, the moveable locking recess mold portion  212  has a longitudinal dimension of “B” and the flange  262  of recess undercut mold member  222  has a longitudinal dimension of “A,” and as embodied herein, B is greater than A. 
     Reference is now made to  FIG. 16  illustrating the moveable locking recess mold portion  212  and the moveable locking lug mold portion  211  in an engaged position, which can be used to determine tolerances for the mold  200 . 
     For example, compact locking lugs (e.g., male locks) and locking recesses (e.g., female locks) were formed into the base and lid of a container and sized to minimally impinge on internal volume of the clamshell with sufficient engagement of the locking lug and locking recess engagement surfaces, created by undercuts in the locking lug and locking recess features, to secure the container closed after the container is filled, thus creating sufficient lock engagement to keep the container closed during handling and transportation, while still allowing the container to be opened easily. As such, a container can be formed having a minimum opening force and minimum closing force such that the minimum opening force is greater than the minimum closing force. For purposes of example and not limitation, a container so configured can allow the container to stay closed while handled and shipped to an end-user location. 
     Molds according to the disclosed subject matter, including the moveable locking lug mold portion and moveable locking recess mold portion, can allow the formation of a sufficient undercut in the locking lug and the locking recess while still allowing the web of thermoformed material to strip easily from the mold surface. It can be desirable to use thinner webs of thermoformable material for cost-saving purposes, however, when thinner webs are used, the locking lug and locking recess can require larger undercuts to provide more engagement between the engagement surfaces of the locking lug and locking recess to keep the container closed. This added engagement can make it difficult to remove the locking lug and locking recess from the mold at the undercuts without damaging the locks. 
     With the movable retracting mold geometry and mechanism as disclosed and embodied herein, the locking lug and locking recess undercuts can be removed from the mold when thinner webs are used. For example, the movable locking lug mold portion can include a lug undercut mold member that can be biased towards an initial position and that can slide along an angled surface of the moveable locking lug mold portion, which can allow the lug undercut mold member to release the web from the mold without damaging or deforming the thermoformed web. Similarly, the movable locking recess mold portion can include a recess undercut mold member that can be biased towards an initial position and that can slide along an angled surface of the moveable locking recess mold portion, which can allow the recess undercut mold member to release the web from the mold without damaging or deforming the thermoformed web. 
     As the geometry of the locking lug and locking recess gets smaller, it can be more difficult to form the undercut geometry, and the smaller locking lug and locking recess undercut geometry can have less engagement. As such, and as embodied herein, a stiffening rib can make thermoforming the locking lug and locking recess easier and more controllable and can provide stronger engagement as thinner webs are used for material savings purposes. 
     Additionally, and as embodied herein, a mold with a moveable locking lug mold portion and a moveable locking recess mold portion as described further herein can allow thermoformed locking lugs and locking recesses to be released from the mold as the moveable locking lug mold portion and moveable locking recess mold portion can retract during part ejection. For example, locking assemblies made according to the methods disclosed herein can have small geometry that can fit into a corner of a hinged container and can be easily manufactured. As further embodied herein, the moveable locking lug mold portion and moveable locking recess mold portion can release the undercuts after molding. 
     As embodied herein, low stack height geometry can provide high packaging cube efficiency. Additionally, and as described further herein, the locking lug and locking recess geometry can provide a differential in closing and opening force of a container such that the container can be easier to close and slightly harder to open. This can make it easier to field pack containers and close the containers under low close force. The containers can stay closed and not open during shipment, and can require additional force to open during use of the container contents. 
     While the disclosed subject matter is described herein in terms of certain preferred embodiments, those skilled in the art will recognize that various modifications and improvements can be made to the disclosed subject matter without departing from the scope thereof. Moreover, although individual features of one embodiment of the disclosed subject matter can be discussed herein or shown in the drawings of the one embodiment and not in other embodiments, it should be apparent that individual features of one embodiment can be combined with one or more features of another embodiment or features from a plurality of embodiments. 
     In addition to the specific embodiments claimed below, the disclosed subject matter is also directed to other embodiments having any other possible combination of the dependent features claimed below and those disclosed above. As such, the particular features presented in the dependent claims and disclosed above can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter should be recognized as also specifically directed to other embodiments having any other possible combinations. Thus, the foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the method and system of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.