Patent Publication Number: US-8538249-B2

Title: Broiler for cooking appliances

Description:
BACKGROUND OF THE INVENTION 
     The present disclosure relates generally to cooking appliances and more particularly to broilers for cooking appliances. 
     Generally, heating elements in, for example, an oven cavity of a cooking appliance should efficiently and evenly direct heat towards food items being cooked. However, conventional heating elements such as, for example, sheath heaters, halogen lamps, and quartz lamps, transmit heat in all directions with much of the heat being absorbed by the oven cavity walls. This generally results in heat not being delivered efficiently and directly to the food, as well as extreme heat gradients where food is unevenly cooked across its exposed surface. Radiant ribbon heaters transmit heat more directional and can be more efficient in delivering heat directly to food, but they are generally sluggish since they require a backside insulative mat to support and position the ribbons and have a fair amount of heater mass to overcome. It is also the nature of the ribbons to be aligned width-wise in parallel with intended radiation path to the food rather than the more efficient perpendicular orientation. 
     Recently, there have been several advances in a variety of infrared quartz tubular heaters called carbon emitters that are produced by companies such as Panasonic and Heraeus Noblelight. These heaters, while encased and sealed in an inert gaseous environment, use a wide, yet flat carbon filament that heats up quickly and intensely when current is applied. The carbon filaments, which are generally made of carbon fibers and carbon dominated matrices, are very low in mass, and can heat up in less than 3 seconds and exhibit no adverse in-rush characteristics that tend to plague some of the more traditional heaters that principally use metallic filaments such as tungsten. For example, a standard quartz heater that uses a tungsten filament may have an in-rush current spike of 10 A compared to its eventually steady state current of 1 A. 
     Carbon emitters, while having no substantial in-rush surges, are also very directional in their ability to apply heat since the filaments are very thin and very wide. They are extremely efficient when the filaments within the tubes are placed in a perpendicular direction relative to the radiation path to the object being heated. There are industrial applications of carbon emitters. For example, carbon emitters have been used to dry coatings. However, they have not been used in either the commercial or residential appliance industry. With the need to limit demand peaks at the utilities and the difficulties to build new power plants in the US, the carbon emitter technology provides an opportunity to reduce the wattage required to adequate cook or broil food by more efficiently directing heat from the broiler above the food down onto the food. 
     It would be advantageous to be able direct heat efficiently and more evenly to the food being cooked within an oven cavity. 
     BRIEF DESCRIPTION OF THE INVENTION 
     As described herein, the exemplary embodiments overcome one or more of the above or other disadvantages known in the art. 
     One aspect of the exemplary embodiments relates to a broiler assembly for a cooking appliance. The cooking appliance has an oven cavity and the broiler assembly is disposed within the oven cavity. The broiler assembly includes a reflector having first and second sides, side retainers coupled to a respective one of the first and second sides, and at least one carbon emitter heating element mounted to the side retainers. 
     Another aspect of the exemplary embodiments relates to a cooking appliance. The cooking appliance includes a frame forming an oven cavity and a broiler assembly. The broiler assembly is disposed within the oven cavity. The broiler assembly includes a reflector having first and second sides, side retainers coupled to a respective one of the first and second sides, and at least one carbon emitter heating element mounted to the side retainers. 
     Still another aspect of the disclosed embodiments relates to a carbon emitter heating element for a broiler assembly. The broiler assembly includes a reflector having first and second sides, a first side retainer disposed on the first side of the reflector and a second side retainer disposed on the second side of the reflector. The first and second side retainers include apertures to allow mounting of the carbon emitter heating element laterally between the first and second sides. The carbon emitter heating element is a lamp having a first and second end, at least one carbon filament disposed within the lamp, a first insulator coupled to the first end of the lamp, and a second insulator coupled to the second end of the lamp. The first insulator is configured to engage an aperture of the first side retainer such that the first insulator is substantially laterally fixed within the aperture of the first side retainer. The second insulator is configured to engage an aperture of the second side retainer such that the second insulator is laterally movable within the aperture of the second side retainer. 
     These as other aspects and advantages of the exemplary embodiments will become more apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. Moreover, the drawings are not necessarily to scale and, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. In addition, any suitable size, shape or type of elements or materials could be used. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIGS. 1A and 1B  are schematic illustrations of an exemplary appliance incorporating features in accordance with the disclosed embodiments; 
         FIGS. 2A and 2B  are schematic illustrations of a portion of the appliance of  FIG. 1  in accordance with an exemplary embodiment; 
         FIGS. 3A-3C  are schematic illustrations of portions of a heating element in accordance with an exemplary embodiment; 
         FIGS. 4A and 4B  are exemplary illustrations of broil patterns using an appliance incorporating aspects of the disclosed embodiments; 
         FIG. 5A  is a heat flux pattern for a conventional sheath heater broiler; and 
         FIG. 5B  is an exemplary heat flux pattern for a heating element of the disclosed embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION 
     In one exemplary embodiment, referring to  FIG. 1A , a cooking appliance  100  is provided. Although the embodiments disclosed will be described with reference to the drawings, it should be understood that the embodiments disclosed can be embodied in many alternate forms. In addition, any suitable size, shape or type of elements or materials could be used. In the examples described herein, the cooking appliance  100  is configured as a free-standing range. However, it should be understood that the aspects of the exemplary embodiments may be applied to any suitable cooking appliance having any suitable oven cavity in a manner substantially similar to that described herein. 
     In one aspect, the disclosed embodiments are directed to a cooking appliance  100  having a cooktop  110 , an oven  120  and a warming drawer/mini-oven  140 . In this example, the cooking appliance  100  is in the form of an electric operated free standing range. In alternate embodiments, the cooking appliance  100  may be any suitable cooking appliance, including but not limited to combination induction/electric and gas/electric cooking appliances having, for example, the electric heating elements described herein. The cooking appliance also includes any suitable controller  199  configured to control the appliance  100  as described herein. 
     The cooking appliance  100  includes a frame or housing  130 . The frame  130  forms a support for the cooktop  110  as well as internal cavities such as the oven cavity  125  of the oven  120  and/or the cavity for the warming drawer/mini-oven  140 . The cooktop  110  includes one or more cooking grates  105  for supporting cooking utensils on the cooktop  110 . Referring also to  FIG. 1B , the oven cavity  125  is defined by a top side  125 T, a bottom side  125 B, a front side  125 F, a rear side  125 R, and lateral sides  125 S 1 ,  125 S 2 . The oven cavity  125  may have any suitable dimensions and includes one or more rack supports  190  and a broiler assembly  160 . The rack supports  190  may be located at spaced apart positions A-F of the oven cavity  125 . In this example, position A is closest to the broiler assembly  160  (e.g. the top side  125 T of the oven cavity  125 ) and position F is the closest to the bottom side  125 B of the oven cavity  125 . One or more oven racks  170  may be placed in a respective one of the positions A-F on the rack supports  190  so that food items may be placed on the oven rack(s)  170  for cooking. 
     Referring to  FIGS. 2A and 2B , a broiler assembly  160  is shown in accordance with an exemplary embodiment. It should be understood that while the broiler assembly  160  is shown located at the top side  125 T ( FIG. 1B ) of the oven cavity  125  ( FIG. 1B ), the aspects of the exemplary embodiments can be equally applied to heating elements located at, for example, the bottom or sides of the oven cavity. In this example, the broiler assembly  160  includes a reflector  210 , one or more heating elements  220 A- 220 D and side retainers  230 A,  230 B. The heating elements  220 A- 220 D are arranged so that the heating elements  220 A- 220 D extend laterally (e.g. between lateral sides  125 S 1 ,  125 S 2 ) within the oven cavity  125  ( FIG. 1B ). While the heating elements  220 A- 220 D are arranged substantially parallel with each other, in other examples, the heating elements  220 A- 220 D may be configured in any suitable arrangement for providing a substantially uniform or even heat distribution within the oven cavity  125  ( FIG. 1B ), such as for example, with respect to a plane defined by an oven rack  170  located at one of oven cavity cooking positions A-F. 
     The reflector  210  may be constructed of any suitable heat reflective material including, but not limited to, aluminized steel. The reflector  210  may be configured to allow attachment of the broiler assembly  160  to, for example, the top  125 T of the oven cavity  125  ( FIG. 1B ). In alternate embodiments the reflector may be configured for attachment to one or more of the lateral sides  125 S 1 ,  125 S 2  and the rear side  125 R of the oven cavity  125  ( FIG. 1B ). The reflector  210  includes first and second ends  210 A,  210 B. 
     The side retainers  230 A,  230 B are coupled to a respective one of the first and second ends  210 A,  210 B in any suitable manner. For example, the side retainers may be coupled to the respective first and second ends  210 A,  210 B of the reflector  210  with mechanical fasteners, chemical fasteners, welds, etc. In other examples the side retainers may be integrally formed (e.g. unitary one-piece construction) with the reflector  210 . The side retainers  230 A,  230 B may be constructed of any suitable material including but not limited to aluminized steel (or any other heat reflective material). Each of the side retainers  230 A,  230 B include one or more apertures  240  configured to interface with the one or more heating elements  220 A- 220 D. 
     Referring also to  FIGS. 3A and 3B , the one or more heating elements  220 A- 220 D are carbon emitter infrared heaters or heating elements. The carbon emitter heating elements  220 A- 220 D of the disclosed embodiments have a carbon filament design that combines the versatile medium-wave spectral emission with very short reaction times of just seconds. In one embodiment, the carbon emitter heating elements  220 A- 220 D are made with fused silica or quartz tubes  325 . The tubes  325  are filled with an inert gas, such as for example, argon. A carbon filament  320 , generally in the form of substantially flat or thin carbon sheets, is disposed within the tube  325 . In one embodiment, a substantially flat, wide carbon filament  320  is disposed within a quartz or fused silica transparent lamp  325  (e.g. a carbon emitter lamp). 
     The carbon filament  320  includes an insulator  310 ,  315  on each end that allows the heating element  220 A to be easily placed in the oven in the proper orientation. In the embodiments, described herein, the proper orientation is generally with the flat carbon filament  320  facing the bottom of the oven. In alternate embodiment, the orientation of the heating elements  220 A- 220 D is any suitable orientation that directs the heat evenly and efficiently to the food being cooked. The carbon filament  320  of the disclosed embodiments provides the highly directional characteristic to the way the heating element  220 A delivers heat flux. 
     It should be understood that while multiple individual heating elements  220 A- 220 D are shown and described herein, in other examples the one or more heating elements  220 A- 220 D may include a substantially flat lamp assembly configured to house multiple carbon filaments  320  to form a multi-filament lamp. Each of the multiple carbon filaments  320  in the multi-filament lamp may be operable in substantially the same manner as the individual heating elements  220 A- 220 D as described herein. 
     The carbon filament  320  may have a surface  320 S that is substantially flat and has a suitable width W. The carbon filament  320  is configured to radiate substantially all of its energy in a direction X (see also  FIG. 1B ). The direction X is substantially perpendicular to the surface  320 S. In this fashion, substantially all of the energy from the carbon filament  320  is transmitted directly to food items placed beneath the broiler assembly  160  on the oven racks  170 . In one example, the width W of the of the carbon filament may be up to approximately 0.5 inches and the surface  320 S may be configured to achieve an operating temperature of about 2,800° C. In other examples, the width W may be more or less than about 0.5 inches and the surface  320 S may be configured to achieve an operating temperature of more or less than about 2,800° C. In one embodiment, the length of the tubes  325  is approximately 19″ with a diameter of approximately 0.5″. Each of the heating elements  220 A- 220 D has a heating output of approximately 700 W. In one example, the heating elements  220 A- 220 D are products of Panasonic Corp. The carbon filaments, which are approximately 16-inches in length, can be made various ways. They are generally carbon fibers with an inorganic binder used to give them some structural capabilities. A metallic conductive spring clip (not shown) is used to electrically and structurally connect each end of the carbon filament to current going in and out of each heating element. This clip acts not only as a conductive path, but also isolates substantially from thermal expansion during heating and large structural loads during shipping and handling. In one embodiment, the one or more heating elements  220 A- 220 D of the broiler assembly  160  are generally configured to achieve the operating temperature within about 3 seconds of activating the broiling elements. In alternate embodiments the operating temperature may be reached in a time period faster or slower than about 3 seconds. 
     Each of the one or more heating elements  220 A- 220 D includes thermal insulators  310 ,  315  disposed on respective ends  225 ,  226  of the one or more heating elements  220 . In one example, the insulators  310 ,  315  may be constructed of any suitable insulating material such as ceramic. A first insulator  310  may be disposed on end  225  of a respective heating element, such as heating element  220 A. It should be understood that the other heating elements  220 B-D are configured similarly to heating element  220 A. The first insulator  310  includes an insulator body  310 B. In this example, the insulator body  310 B is substantially cylindrical in shape but in alternate embodiments, the insulator body  310 B may have any suitable shape and/or cross-section. The insulator body  310 B includes an interface slot  310 C configured to receive at least a portion of the heating element  220 A for coupling the insulator  310  with the heating element  220 A. In other examples, the insulator body  310 B may have any suitable recess or other opening for receiving at least a portion of a heating element  220 A for coupling the insulator  310  with the heating element  220 A. The insulator body  310 B also includes a retaining slot  310 R that is configured to engage an edge of a respective aperture  240  in one of the side retainers  230 A,  203 B for stationarily locating the heating element  220 A within the broiler assembly  160 . 
     The second insulator  315  may be disposed at the opposite end  226  of the heating element  220 A. The second insulator  315  includes an insulator body  315 B. In this example, the insulator body  315 B is substantially cylindrical in shape but in other examples the insulator body  315 E may have any suitable shape and cross-section. The insulator body  315 B includes an interface slot  315 C that is substantially similar to the interface slot  310 C described above for coupling the insulator  315  to the heating element  220 A. In other examples, the insulator body  315 B may have any suitable recess or other opening for receiving at least a portion of a heating element  220 A for coupling the insulator  310  with the heating element  220 A. The insulator body  315 B also includes a retaining surface  315 S. The retaining surface  315 S is configured to engage an edge of a corresponding aperture  240  in another one of the side retainers  230 A,  203 B for supporting the heating element  220 A in the broiler assembly  160 . The retaining surface  315 S is a substantially flat surface that allows the heating element  220 A and insulator  315  to float or move around within the corresponding aperture  240  of the other side retainer  230 A,  230 B. In other examples, the insulators  310 ,  315  may have any suitable shapes and configurations for locking a respective one of the one or more heating elements  220 A- 220 D to one of the side retainers  230 A,  230 B while allowing the one of the one or more heating elements  220 A- 220 D to move within another one of the side retainers  230 A,  230 B. 
     Referring again to  FIG. 2A  and also to  FIGS. 4A and 4B , compared with conventional heaters, the broiler assembly  160  described herein provides a relatively uniform heat distribution within the oven cavity  125  ( FIG. 1B ). As can be seen in  FIG. 4A , a toast pattern  400  is illustrated with respect to slices of bread placed on an oven rack  170  located at, for example, oven cavity cooking position D. As can be seen in  FIG. 4A , the toast pattern  400  is relatively even from front  170 F to back  170 R as well as side to side  170 S 1 ,  170 S 2  (corresponding to the front  125 F, back  125 R and lateral sides  125 S 1 ,  12 S 2  of the oven cavity,  FIGS. 1A and 1B ) along the oven rack  170 .  FIG. 4B  illustrates another toast pattern  410  illustrated with respect to slices of bread placed on the oven rack  170  located at oven cavity cooking position C. As can be seen in  FIG. 4B , the toast pattern  410  is relatively even from front  170 F to back  170 R and side to side  170 S 1 ,  170 S 2  along the oven rack  170 . Compared with conventional heaters such as sheath heaters, halogen lamps, etc, the broiler assembly  160  of the present disclosure reduces the energy usage by about ⅔ while still being able to provide a comparable heating or browning performance and a relatively even heat distribution. 
     Referring to  FIGS. 5A and 5B , examples of heat flux patterns for both a conventional sheath heater broil element and a carbon emitter heating element of the disclosed embodiments are illustrated. The plot shown in  FIG. 5A  illustrates how the heat flux emitted by a conventional sheath heater broil element varies as a function of both vertical spacing from the food and lateral position within the oven cavity. Curve  502  represents a vertical distance of approximately 2 inches from the broil element. Curves  504 ,  506  and  508  represent vertical distances of approximately 4, 6 and 8 inches, respectively, from the broil element. As shown by curve  502 , the gradients, such as points  510  and  512 , become excessively large as the food is pushed closer to broil element, resulting in uneven browning and cooking. As the food is lowered away from the broil element, the gradients become less severe, but the flux intensity drops off significantly, resulting in longer cooking times. 
     In  FIG. 5B , the heat flux intensity is again shown as a function of vertical spacing from the heating element and lateral spacing within oven cavity, where the heating element is the carbon emitter heating element, such as element  220 A, of the disclosed embodiments. Here, curve  520  represents a vertical distance of approximately 2 inches from the heating element, while curves  522 ,  524  and  528  represent vertical distances of approximately 4, 6 and 8 inches, respectively, from the heating element As shown in  FIG. 5B , the gradients, such as gradients  528  and  530 , are much lower for this broiler. In particular, the flux intensity stays relatively constant, which means food can be ensured of cooking evenly and quickly regardless of its placement in the oven. 
     In one aspect of the exemplary embodiments, the controller  199  ( FIG. 1A ) may be configured to individually cycle (e.g. turn on and off) each of the one or more heating elements  220 A- 220 D. Individually cycling the one or more heating elements  220 A- 220 D may allow for a more even heat distribution (e.g. front to back and side to side with respect to a plane of a given oven cavity cooking position A-F) than if all of the one or more heating elements are continuously active. The cycling of the heating elements  220 A- 220 D may also allow for the placement of food on oven racks at closer distances to the one or more heating elements  220 A- 220 D. 
     The exemplary embodiments described herein provide a broiler assembly  160  ( FIG. 1B ) that directs substantially all of its energy towards food placed within the oven cavity  125  ( FIGS. 1A and 1B ) adjacent the broiler assembly  160 . This provides for increased efficiency (e.g. energy into the food versus energy supplied in the oven cavity) by about 25% compared to conventional broilers, as well as a more even application of heat across the food tray and the food being cooked. The increased efficiency may translate into less energy needed to cook food, less preheat needed to reach a desired operating temperature, potentially faster cooking times and more even cooking. 
     Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to the exemplary embodiments thereof, it will be understood that various omission and substitutions and changes in the form and details of devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps, which perform substantially the same way to achieve the same results, are with the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.