Abstract:
A sheathed electric resistive heating element support bracket constructed in accordance with the present invention includes first and second mounting portions interconnected through a transverse web portion. The web portion includes at least one heating element receiving journal and an edge portion along which is arranged a plurality of substantially circular lances. The substantially circular lances define a bore through which a mechanical fastener can pass to secure the bracket in a desired position. In this manner, the mechanical fastener and support bracket collectively serve as an electrical ground and an RF energy shield for the heating element. The heating element is secured into the journal through a snap-fit connection, while a crimping finger is also deformed over a portion of the heating element to fixedly maintain the heating element in the journal.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention pertains to the art of cooking appliances and, more particularly, to cooking appliances employing electric heating element support brackets adapted for microwave applications which, in addition to supporting a heating element within an oven, act as both a ground and an RF shield.  
         [0003]     2. Discussion of the Prior Art  
         [0004]     The art of cooking is currently undergoing substantial change. No longer is it the norm to have a family member home all day to prepare meals. Today, more and more consumers must rush home from work to prepare meals for themselves or their families. Time is of the essence, with the luxury of spending time preparing meals rapidly becoming a thing of the past. In light of these time constraints, consumers are demanding cooking appliances that will cook a meal in less time than conventional ovens, without sacrificing the quality of the prepared food. In order to meet these demands, manufacturers are combining conventional cooking systems with the rapid cook advantages of microwave cooking systems.  
         [0005]     Microwaves perform a cooking process by directing a microwave or RF energy field into an oven cavity. The RF energy field is in the form of a standing wave which reflects about the oven cavity and impinging upon a food item. As the RF energy fields impinge upon the food item, the energy fields are converted into heat through two mechanisms. The first or ionic is constituted by the linear acceleration of ions, generally in the form of salts, present within the food item. The second is the molecular excitation of polar molecules, primarily water, present within the food item.  
         [0006]     When introducing microwave systems into conventional ovens, there are several considerations which must be addressed. For instance, metal components within the oven cavity must be grounded in order to prevent damage to the microwave components. Metal located in the oven cavity may potentially reflect a portion of the RF energy field back into the magnetron. The reflected RF energy is dissipated as heat within the magnetron which causes distortions in the energy field, as well as ultimately leading to total failure of the component. In order to substantially eliminate this problem, an RF energy shield is needed to protect the magnetron. One effective method of establishing a shield is to properly ground all metal components. In this manner, the metal components will not act in a manner similar to that of an antenna transmitting the RF energy back into the magnetron. This is particularly true in connection with the mounting of metal components with screw or other mechanical fasteners which can act as antennae for microwaves, with arcing being a potential problem.  
         [0007]     In light of the above, a primary concern in conventional ovens having an electric heating element is the particular mounting and placement of the element within the oven. Placing the heating element in the oven cavity where it is exposed to microwave energy requires specific design considerations. Mechanical fasteners and support brackets used to secure the element to the oven can act as an antenna which focuses the RF energy and causes arcing within the oven. Continued arcing reduces the operational life of the magnetron, while also decreasing the overall efficiency of the appliance. Based on the above, there exists a need in the art of cooking for an electric heating element support bracket which can be arranged within the oven cavity. Particularly, there exists a need for a support bracket which serves as a ground for an electric heating element so as to provide an RF shield for preventing reflected microwave energy from damaging internal system components.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention is directed to a cooking appliance including both electric and microwave heat sources. More specifically, the invention is directed to a heating element support bracket suitable for use in RF applications. Specifically, the heating element support bracket includes first and second mounting surfaces interconnected through a transverse heating element support web. In one form of the invention, the heating element support web is constituted by an element support surface having at least one element receiving journal and an edge portion along which a plurality of substantially circular lances are arranged. More specifically, the substantially circular lances define a bore, through which a mechanical fastener can pass, for securing the bracket to an oven cavity surface. In this manner, the fastener serves as an electrical ground in order to establish an RF energy shield for the electric heating element.  
         [0009]     In accordance with a preferred form of the present invention, the element support web includes a second element receiving journal maintained in a spaced relationship from the first journal through an intermediate member. In this manner, a heating element having a plurality of heating coils may be supported by the bracket. In a preferred arrangement, a V-shape notch is arranged in at least one portion of the intermediate member such that the application of a force to the notch will cause a crimping effect to fix the element within the journal.  
         [0010]     In accordance with a more preferred form of the invention, a shoulder portion is formed in each journal to establish a snap-fit for the heating element. In any event, additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of a preferred embodiment when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of a wall oven including a microwave and convection cooking system constructed in accordance with the present invention;  
         [0012]      FIG. 2  is a top view of the convection cooking system including a plurality of heating element support bracket arranged in accordance with the present invention;  
         [0013]      FIG. 3  is a cross-sectional view of the convection cooking system of  FIG. 2 ;  
         [0014]      FIG. 4  is a plan view of the heating element support bracket of  FIG. 2 ; and  
         [0015]      FIG. 5  is a perspective view of the heating element support bracket of  FIG. 4  secured to a heating element in accordance with a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     With initial reference to  FIG. 1 , a cooking appliance constructed in accordance with the present invention is generally shown at  2 . Although cooking appliance  2  is depicted as a dual wall oven, it should be understood that the present invention is not limited to this model type and can be incorporated into various types of oven configurations, e.g., cabinet mounted ovens, free standing ranges and slide-in ranges. In the embodiment shown, cooking appliance  2  includes an upper oven  4  having an upper oven cavity  6  and a lower oven  8  having a lower oven cavity  10 . In the embodiment shown, upper oven  4  is provided to perform a combination microwave/convection cooking process, and lower oven  8  is provided to perform a standard cooking operation. As shown, cooking appliance  2  includes an outer frame  12  for supporting both upper oven cavity  6  and a lower oven cavity  10 .  
         [0017]     In a manner known in the art, a door assembly  14  is provided to selectively provide access to upper oven cavity  6 . As illustrated, door assembly  14  includes a handle  15  arranged at an upper portion  16  thereof. Door assembly  14  is adapted to pivot at a lower portion  18  to enable selective access to within oven cavity  6 . In a manner also known in the art, door  14  is provided with a transparent zone  22  for viewing the contents of oven cavity  6  while door  14  is closed. In addition, a seal (not shown) is provided about a peripheral edge of door assembly  14  to prevent oven gases from escaping from within oven cavity  6  during a cooking operation. In a similar manner to that described above with respect to door assembly  14 , a second door assembly  24  is provided for lower oven  8 .  
         [0018]     As best seen in  FIG. 1 , oven cavity  6  is preferably defined by a bottom portion  27 , an upper portion  28 , opposing side portions  30  and  31  and a rear portion  33 . In the preferred embodiment, arranged above upper oven  4  is a microwave cooking system generally indicated at  37 . As shown, microwave cooking system  37  includes a waveguide  39  having arranged thereon a microwave emitter or magnetron  40 . As further shown in  FIG. 1 , cooking appliance  2  includes an upper control panel  50  arranged above upper oven  4  and carried at least partially by frame  12 . In the embodiment shown, control panel  50  includes first and second rows of oven control buttons  52  and  53  for programming, in combination with a numeric pad  55  and a display  57 , particular cooking operations for upper and lower ovens  4  and  8  respectively. Since the general programming and operation of cooking appliance  2  is known in the art and does not form part of the present invention, these features will not be discussed further here.  
         [0019]     In general, the structure described above with respect to cooking appliance  2  is already known in the art and does not constitute part of the present invention. Therefore, this structure has only been described for the sake of completeness. Instead, the present invention is particularly directed to a convection cooking system and, more particularly, to a heating element support bracket adapted to position a heating element within the convection cooking system, while providing a ground for the heating element. In this manner, the heating element can be exposed to an RF energy field without causing damage to magnetron  40 .  
         [0020]     In accordance with a preferred embodiment of the present invention, cooking appliance  2  further includes a convection cooking system generally indicated at  70  in  FIGS. 1-3 . As shown in  FIGS. 2 and 3 , convection cooking system  70  includes a convection fan housing  75  having an outer peripheral portion  77 . Arranged at diametrically opposing positions along outer peripheral portion  77  are a pair of mounting flanges  79  and  80  each of which includes a respective plurality of apertures, two of which are indicated at  83 , for securing convection fan housing  75  to oven cavity  6 .  
         [0021]     As best seen in  FIG. 3 , housing  75  includes a heating or combustion chamber  90  within which are arranged parts of a fan assembly  95 . In the embodiment shown, fan assembly  95  includes a motor  98  operatively connected to a fan or impeller  99  through a drive shaft  100 . As illustrated, motor  98  is secured to a surface portion  101  of fan housing  75  through a plurality of mounting studs  103 . Further arranged within heating chamber  90  is a heating element  110  which extends about an outer periphery of fan  99 . In a preferred form of the invention, heating element  110  includes first and second coils  112  and  113  that are supported within heating chamber  90  by a plurality of heating element support brackets  120 - 122  (also see  FIG. 5 ). In a preferred form of the invention, support brackets  120 - 122  are secured to a bottom portion of heating chamber  90  through a mechanical fastener  125 , preferably a screw. In accordance with the most preferred embodiment, mechanical fastener  125  establishes a ground that effectively shields heating element  110  from the effects of microwave energy generated by magnetron  40 . With this arrangement, the possibility of heating element  110  reflecting a portion of the RF energy field back into magnetron  40  is substantially eliminated. Finally, housing  70  includes an inlet portion  130  adapted to provide access for an incoming air flow which transforms to a convective heating air stream as the airflow passes over heating element  110 . After the convection air flow passes over heating element  110 , the airflow is directed into oven cavity  6  through a cover portion  140  secured to housing  75  as shown best in  FIGS. 1 and 3 .  
         [0022]     Reference will now be made to  FIGS. 4 and 5  in describing the specific structure of each heating element support bracket  120 - 122 . Since the structure of each support bracket  120 - 122  is identical, a detailed description of support bracket  120  will be made and it is to be understood that support brackets  121  and  122  have commensurate structure. In accordance with the preferred embodiment of the present invention, heating element support bracket  120  includes a first mounting surface  155  and a second mounting or cover supporting surface  158  separated through a transverse web portion  160 . As shown, transverse web portion  160  includes first and second heating element receiving journals  165  and  166  adapted to receive a respective one of coils  112  and  113  of heating element  110 . Web portion  160  further includes an edge portion  170  defined by a plurality of substantially circular lances, one of which is indicated at  173 . In accordance with this preferred embodiment, lances  173  define a central bore  175  adapted to receive one of mechanical fasteners  125  for securing bracket  120  within fan housing  75 . More specifically, in accordance with one preferred embodiment of the invention, central bore  175  has a first end  176  which is open, and a second end  177  which is closed by a terminal wall portion  177  of second mounting surface  156 . Preferably, bracket  120  is formed from a single, stamped sheet of metal which is folded about an axis defined by central bore  175 , thereby resulting in the formation of a first half  180  and a second half  182 .  
         [0023]     In the embodiment shown, heating element receiving journals  165  and  166  are separated by an intermediate member  190  having a first portion  192  associated with first half  180 , and a second portion  193  associated with second half  182 . Second portion  193  includes a V-shaped notch  200  having a first crimp finger  203  and second crimp finger  204 . With this arrangement, once coils  112  and  113  of heating element  110  are positioned into receiving journals  165  and  166 , a force applied to V-shaped notch  200  will outwardly deform first and second crimping fingers  203  and  204 , thereby fixing coils  112  and  113  into journals  165  and  166 . In addition to crimping fingers  203  and  204 , each outside edge portion of element receiving journals  165  and  166  includes a respective shoulder portion, one of which is shown at  210 . With this arrangement, each shoulder portion  210  provides a snap-fit for a respective coil  112 ,  113 . With this arrangement, coils  112  and  113  are maintained in position within support bracket  120  prior to deforming first and second crimp fingers  203  and  204 .  
         [0024]     As set forth above, brackets  120 - 122  establish a ground between heating element  110  and oven  2 . In this manner, microwave cooking system  37  can be operated in conjunction with electric heating element  110  of convection cooking system  70  without requiring additional shielding for magnetron  40 . Also, given the arrangement of fastener  125  within lances, with a tip thereof (not shown) terminating adjacent second end  177  of mounting surface  156 , fastener  125  will not act as an antenna for the microwave energy. In any case, although described with reference to a preferred embodiment of the invention, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. For instance, while the microwave cooking system is shown mounted on an upper surface of the oven cavity and the convection cooking system mounted to a rear portion, the particular positioning of these systems could be altered depending on the particular model and structure of the cooking appliance. In general, the invention is only intended to be limited by the scope of the following claims.