Heat retentive food server

Abstract

The present invention discloses a heat retentive food server for maintaining food at an elevated temperature, especially important in food service operations. The server is a container having an upper shell and lower shell and cavity defined therebetween containing a phase change material. The phase change material is preferably an ethylene acrylate copolymer, which absorbs energy upon heating, and then keeps freshly prepared hot foods placed in the server warm as the phase change material slowly cools and releases heat.

1 . A heat-retentive food server comprising: 
 (a) an upper shell;    (b) a lower shell;    said upper shell and said lower shell being joined together and having a cavity defined therebetween, said upper and lower shells being comprised of a thermoplastic material, and    (c) a heat storage material disposed in said cavity, said heat storage material comprising a phase change material substantially filling said cavity and being unrestrained therein, whereby said food server may be heated and placed adjacent to food for maintaining food at an elevated temperature,    wherein said phase change material comprises an ethylene acrylate copolymer.    
   
   
       2 . The server of  claim 1  wherein said phase change material comprises greater than about 12% by weight ethylene acrylate copolymer, based on the total weight of the phase change material.  
   
   
       3 . The server of  claim 1  wherein said phase change material is a solid at room temperature, said phase change material being formed to substantially match the shape of said cavity.  
   
   
       4 . The server of  claim 1  where said phase change material comprises an injection molding having a shape substantially matching the shape of said cavity.  
   
   
       5 . The server of  claim 1 , wherein said phase change material changes phase from a solid to a viscous, gelatinous state when heated to an elevated temperature.  
   
   
       6 . The server of  claim 5 , wherein said phase change material changes phase at a temperature of about 190° F. to about 230° F.  
   
   
       7 . The server of  claim 1  wherein said ethylene acrylate is selected from the group consisting of: ethylene methyl acrylate, ethylene ethyl acrylate and ethylene n-butyl acrylate.  
   
   
       8 . The server of  claim 1  wherein said heat storage material additionally comprises a microwave absorbing additive.  
   
   
       9 . The server of  claim 1  wherein said heat storage material additionally comprises up to 88% of one or more polymers selected from the group consisting of ethylene polymers and ethylene copolymers.  
   
   
       10 . The server of  claim 1  wherein said phase change material consists essentially of an ethylene acrylate copolymer.  
   
   
       11 . The server of  claim 1  wherein said server comprises a food cover for use with an underlying food holder, wherein said food cover may be heated and placed over said underlying food holder to maintain food placed upon said holder at an elevated temperature.  
   
   
       12 . The food server of  claim 11  wherein said food cover comprises said lower shell, and said lower shell comprises 
 (a) a top wall, and    (b) a side wall depending downwardly from said top wall, said upper shell being spaced apart from and surrounding said lower shell thereby defining said cavity.    
   
   
       13 . The food cover of  claim 12  further comprising an insulator positioned between said heat storage material and said upper shell so that heat is transferred from said heat storage material through said lower shell, and so that a minimum amount of heat is lost through said upper shell, thereby maintaining said food placed under said lower shell at an elevated temperature for an extended period of time.  
   
   
       14 . The server of  claim 1  wherein said upper shell comprises 
 (a) a substantially flat base portion for placing food thereon; and    (b) a side wall extending upwardly from said base portion thereby forming a trough for holding food, said lower shell comprising: 
 (i) a substantially flat support portion spaced downwardly from said upper shell base portion;  
 (ii) a side wall extending upwardly from said flat portion, said upper and lower shell side walls being joined at the upper ends thereof.  
   
   
   
       15 . The server of  claim 15  further comprising an insulator interposed between said phase change material and said lower shell, so that heat is transferred from said phase change material through said upper shell, and so that a minimum amount of heat is lost through said lower shell, thereby maintaining said food placed on said upper shell at an elevated temperature for an extended period of time.  
   
   
       16 . A method for repeatedly storing and releasing thermal energy comprising heating a phase change material so that it undergoes a phase transition and stores thermal energy, and allowing the phase change material to cool so that it undergoes a second phase change transition and releases thermal energy, wherein the improvement comprises the phase change material comprises an ethylene acrylate copolymer.  
   
   
       17 . The method of  claim 16  wherein the phase change material comprises greater than 12% by weight of ethylene acrylate copolymer.  
   
   
       18 . The method of  claim 16  wherein the phase change material is molded and shaped to fit into the space between the walls of a dual-walled serving container for food or beverages.  
   
   
       19 . A method for making a re-heatable food warming device comprising the steps of: 
 (a) forming a container from a thermoplastic material wherein said container has an upper shell and a lower shell;    (b) injection molding a phase change material comprising an ethylene acrylate copolymer into an internal cavity formed between the upper and lower shells such that the phase change material substantially fills the cavity; and    (c) sealing the upper and lower shells with a polymeric sealant at their periphery to contain the phase change material within the internal cavity.