Abstract:
A door and frame assembly useful for commercial coolers and heaters comprises a door frame having an upper horizontal member and opposing side members with an insulated door fitted in the door opening between the sides and with a discontinuous heating element extending at least along one, and preferably both, of the sides.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application incorporates by reference and claims priority to Provisional Application Ser. No. 60/482,499 for “Door and Frame System for Commercial Coolers and Freezers,” having a filing date of Jun. 25, 2003, and commonly owned with this application. 

   BACKGROUND OF THE INVENTION 
   The present invention is directed to door and frame assemblies, systems and methods which are designed specifically for installation with commercial freezers and coolers, such as those used in supermarkets and similar facilities. 
   DESCRIPTION OF THE PRIOR ART 
   A number of door and frame assemblies have been devised in the past for use with commercial freezers and coolers. By way of example, U.S. Pat. Nos. 5,161,329 and 6,240,703, both to Brown, disclose constructions useful for these purposes. 
   While the constructions shown in the aforementioned Brown patents solve many of the needs of such door and frame assemblies, there is a need for a more facile, low cost assembly, system and method; there is also especially a need for door and frame systems that provide heating to avoid freezing of the door to the frame, but in a dependable manner which is not damaged while the freezer or cooler is in use. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a door and frame assembly useful for commercial coolers and heaters. The frame assembly comprises a door frame having an upper horizontal member and opposing side members each of which extends from an end of the horizontal member. The upper and side members define a door opening, and the assembly includes an insulated door fitted into the door opening and pivotally mounted to one of the members so as to rotate between open and closed positions. 
   In accordance with the present invention, the assembly is provided with heating means along at least one of the side members, the heating means comprising an electrical heating element which is free of a continuous electrical circuit with heating means along the opposing side. 
   In a preferred embodiment, the assembly further includes another heating means along the opposing side, the another heating means comprising an electrical heating element which is free of a continuous electrical circuit with the heating means along the first, opposing side. 
   The insulating door of the present invention preferably comprises opposing molded sheets of thermoplastic material forming a void therebetween with a foam insulation in the void. 
   The method of the present invention contemplates the fabrication of a door frame assembly useful for commercial coolers and heaters. The method utilizes the step of providing a door frame having an upper horizontal member and opposing side members each of which extend from an end of the horizontal member, with the upper and side members defining a door opening. The method further comprises the step of fitting an insulated door pivotally mounted to one of the members so as to rotate between open and closed positions, and installing heating means along at least one of the side members, the heating means comprising an electrical heating element which is free of a continuous electrical circuit with heating means along the opposing side. 

   
     THE DRAWING 
     The present invention is directed to a door and frame construction, system and method which is designed to provide the benefits of prior art door and frame structures, and to also meet the further needs discussed above. The features and benefits of the door and frame construction, system and method of the present invention will be described in detail with reference to the drawing figures, in which: 
       FIG. 1  is a front elevation of a door and frame construction and system in accordance with the present invention. 
       FIG. 2  is an exploded view of the shell portions of the door portion of the assembly shown in  FIG. 1 . 
       FIG. 3  is a side view, partially cut away, of the construction of the door in the assembly of  FIG. 1 . 
       FIG. 4  is a partially cut away view along the line  4 - 4  of the construction of  FIG. 1 , illustrating a first embodiment of a heating element along an inside facing surface of the frame in  FIG. 1 . 
       FIG. 5  is a partially cut away cross section of a second embodiment of a heating element along the inside face of the frame in  FIG. 1 . 
       FIG. 6  is a schematic illustration of the electrical circuit providing power to the heating elements in the alternate constructions of  FIGS. 4 and 5 . 
   

   DETAILED DESCRIPTION 
   With continuing reference to the drawings, the door and frame assembly  10  of the present invention is designed for installation in an opening of a freezer or cooler having an outer wall  12  with the assembly  10  fitted in the opening. 
   In accordance with the present invention, the door and frame assembly  10  comprises a door frame  14  having left and right vertical sides  16 ,  18  and a horizontal member  20  between the sides  16 ,  18 . The frame  14  is preferably molded from a suitable plastic material such as fiberglass, ABS plastic or polycarbonate, for example. 
   The frame  14  further comprises an inner surface  22  extending parallel with but recessed from the sides and horizontal members  16 ,  18  and  20  by the dimension of an indented surface  24  (note  FIGS. 4 and 5 ). A heater element, described in greater detail below in  FIGS. 4 and 5 , is carried along the inner surface  22  along the horizontal member  20  and the vertical sides  16 ,  18 . 
   As shown in  FIG. 1 , the frame  14  defines a door opening  26  into which a door  28  is fitted. The door is attached to one of the vertical sides  16 ,  18  with hinges  34 , and includes an opener handle  36  and a latch  38  mounted along one of the vertical sides opposing the hinges  34 . Preferably, the door  28  is provided with plural molded bumper ribs  40  along the bottom thereof, to absorb the impact of wheeled carts or other equipment that may be inadvertently banged against the door. As shown in  FIG. 1  and described in greater detail below with reference to  FIG. 6 , the door and frame assembly  10  also includes a switch plate  42  along one of the vertical sides  16 ,  18  and an electrical switch  44  extending through the switch plate  42  to permit the turning off and on of lights  43  within the cooler. Further, there is provided a cover plate  46 , preferably along the horizontal member  20 , and an in-line fuse  48 , both associated with the electrical heating circuit. 
   The construction details of the door  28  will now be described with reference to  FIGS. 2 and 3 . 
   As shown in  FIG. 2 , the door  28  is fabricated with a rear molded shell  30  and a front molded shell  32 . Each of the molded shells is provided with mating extremities  31  and  33 , respectively, which permit the two shells to be bonded together by conventional means. The two shells may be molded from fiberglass, ABS plastic or polycarbonate. 
   Noting  FIG. 3 , once the rear and front shells  30 ,  32  are bonded together, an insulating foam  29  is injected into the space between the two shells, using a conventional delivery technique through an appropriate portal in one of the shells. 
   Alternate forms of the installation for heating strips are depicted in  FIGS. 4 and 5 . In both arrangements, the heating element is placed along the indented inner surface  22 , which as shown in  FIG. 4  is spaced from one of the vertical sides  16 ,  18  by indent surface  24 . In the arrangement of  FIG. 4 , the frame  14  has a molded slot  42  which extends the vertical length of both sides  16 ,  18  and across the horizontal member  20 , so that the heating element may be placed in the slot  42  as shown in  FIG. 4 . In this arrangement, a metal, heat conductive bracket is installed along both the vertical and horizontal dimensions of the inside detented surface  22 , the bracket having a first arm  54  extending parallel with the surface  22  and a second arm  56  extending laterally from the first arm, either arm being attached to the frame  14  with fasteners  58 . 
   The second form of the heating element is shown in  FIG. 5 , and utilizes a flat bracket  62  attached along the indented inside surface  22  with fasteners  66 , the bracket having means for holding an outside cover  60  into engagement with the bracket; in the example of  FIG. 5 , the holding means comprises curled ends  64  of the bracket  62  adapted to be snapped through an opening  61  in the cover  60 . 
   In accordance with one aspect of the present invention, the heater element used in the constructions of  FIGS. 4 and 5  is a special purpose heating cable manufactured by the Raychem Corporation of Menlo Park, Calif. under the trademark FROSTEX as a pipe heating system for preventing freezing of outdoor piping. As shown in  FIG. 4 , a FROSTEX strip is installed into the slot  42 , the strip comprising an inner heating element  50  and an outer, thermally conductive and electrically insulative shield  52 . A similar arrangement is used in the construction of  FIG. 5 , except the FROSTEX heating system may be of a thinner configuration, including inner heating element  68  and outer, electrically insulative shell  70 . 
   A principal benefit of a heating element like that provided by the FROSTEX product is illustrated in  FIG. 6 . In prior art heating arrangements for freezer door and frame assemblies, it was necessary to extend a wiring underneath a threshold below the door, in order to complete an electrical circuit. However, the threshold constructions are frequently damaged from heavy carts and other equipment that are banged against and dragged across the threshold, and as a result the return circuit underneath the threshold is often damaged, rendering the heater unworkable. In contrast, the utilization of the FROSTEX product in the door and frame assembly  10  of the present invention avoids the need for a return circuit underneath the threshold, because the FROSTEX product achieves heating along its length without a return circuit. Thus, turning to  FIG. 6 , the heating elements  52  (from  FIG. 4 ) may extend downwardly along the indented surface  22  of the vertical side  16 ,  18  to a termination  53 , without completing a circuit underneath a threshold of the door  28 . Electrical power is received through power line  51 , subject to any fault detection at fuse  48 , and services both the heating circuits  52  and lights  43 . It will of course be appreciated by those skilled in the art that if it is desired to heat the bottom of the door to further reduce the likelihood that the door will be stuck because of freezing, then the heating element  52  along either side  16 ,  18  may be extended across the threshold as shown by the dotted extension  54  in  FIG. 6 , without the possible interference with the remainder of the heater. 
   It will be appreciated by those skilled in the art that numerous modifications and improvements may be made in the door and frame assembly, system and method of the present invention without departing from the spirit and scope of this invention. For example, the heating system shown in  FIGS. 4-6  and described above may be retrofitted onto existing freezer door installations.