Patent Publication Number: US-6670586-B2

Title: Infrared oven

Description:
FIELD OF THE INVENTION 
     The invention relates to the field of radiant energy ovens. More particularly, the invention relates to radiant energy ovens which employ heating elements for generation of infrared radiation. 
     BACKGROUND OF THE INVENTION 
     Most pizza restaurants use deck pizza ovens which must remain on 24 hours per day, 7 days per week. Some restaurants use convection conveyer belt pizza ovens which remain on only during the hours of operation of the restaurant. Convection conveyer belt pizza ovens, however, are more expensive to purchase than conduction deck ovens and consume more energy per hour of operation than conduction deck ovens. 
     Microwave ovens also have been employed to cook pizza. Microwave ovens, however, cannot be used to cook high quality pizza. Microwave ovens are employed to cook commercially available frozen pizzas. The resultant microwave cooked pizza is usually unsatisfactory. 
     Higher quality pizza can be baked in a conduction/convection oven. In this instance, the pizza is placed directly on the hot floor of the oven to crisp the bottom of the crust. Conduction/convection ovens, however, have “hot” spots and require constant operator attention to avoid over or under cooking of the pizza. Consistency therefore is a major problem. Moreover, conduction/convection ovens can require up to 20 minutes to cook a pizza. 
     In cooking and serving of pizza, energy and equipment costs have risen and have become an increasing economic burden on restaurants. In addition, productivity requirements for ovens continue to increase since restaurants desire to bake and serve pizza in the shortest possible time. 
     A need therefore exists for an oven which overcomes the time and energy disadvantages of the prior art ovens. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of an oven according to an embodiment of the present invention. 
     FIG. 1A is a cross sectional view taken along section AA of FIG.  1 . 
     FIG. 2 is a cross sectional view of support bracket. 
     FIG. 3 is an isometric view of a framework assembly having heating elements therein. 
     FIG. 4 is a rear view of an oven according to the present invention. 
     FIG. 5 is a front view of another embodiment of the oven of the invention. 
     FIG. 5A is a cross section of the oven of FIG. 5 taken on line A-A. 
     FIG. 6 is an isometric view of a box frame used in construction on an embodiment of the oven of the invention. 
     FIG. 6A is a cross section view of a frame member for use in construction of the oven. 
     FIGS. 7 and 7A are top and side views of an upper suffrage which includes electrical heating elements and a reflector. 
     FIGS. 8 and 8A are top and end views, respectively, of a lower suffrage which includes electrical heating elements. 
     FIG. 9 is an isometric view of a crumb tray with an integral reflector. 
     FIGS. 10 and 10A are front and side views, respectively, of an outer shell used in construction on an embodiment of the oven of the invention. 
     FIG. 11 is a schematic of the operation configure of timer, controller and heating elements. 
     SUMMARY OF THE INVENTION 
     The disclosed invention relates to an oven for cooking foodstuffs such as pizza by infrared radiation. The oven includes Nichrome-quartz heating elements which are governed by a pulse type controller. The pulse type controller cause the heating elements to generate infrared radiation over selected time periods to efficiently cook a foodstuff. 
     The oven of the invention enables pizza and other food products to be cooked consistently to a desired state regardless of the initial temperature of the oven or fluctuations in line voltage. 
     The oven includes a Nichrome-quartz heating element that operates at 220 V to 250V and which has a power rating of 1300 W, and a controller for supplying intermittent pulses of electrical energy to the heating element to cause the heating generate infrared energy of a wavelength of about 5.3 micron to about 9.1 micron. The controller supplies intermittent pulses of electrical energy which have a duration of about 0.5 to 2 sec., and at one sec. intervals between pulses. In another aspect, the oven includes a sensor for sensing a temperature of the heating element and for forwarding that temperature to the controller. The controller supplies intermittent pulses of electrical energy to the heating element to cause the heating element to operate at about 47° C. to about 271 ° C. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides an oven especially adapted for cooking foodstuffs such as pizza. The oven employs heating elements which generate infrared energy of a selected range of wavelengths of about 2.8 microns to about 9.1 microns, preferably about 5.0 microns to about 5.8 microns, to cook foodstuffs such as pizza as well as to kill pathogens such as E-coli and Salmonella. 
     In a first embodiment, oven  1 , as shown in FIGS. 1-4, includes inner chamber  9  positioned within outer body  5 . Inner chamber  9  can be maintained in spaced relationship to outer body  5  by supports  20 . Outer body  5  includes hinged door  22  to permit access to inner chamber  9 . Door  22  may be solid or have a glass section to enable viewing of pizza  32  in inner chamber  9  while it is being treated with infrared radiation. Outer body  5  has openings  7  on the front and rear surfaces thereof to permit ambient air to flow into inner chamber  9  as well as to permit hot air to flow from chamber  9  to leave oven  1 . Chamber  9 , as well as interior surface of door  22  may be formed of a reflective material such as aluminum or stainless steel, preferably aluminum. 
     Inner chamber  9  includes elongated support brackets  42  for receiving a plurality of support rods  11  thereon. Support brackets  42  can have a “L” shaped configuration as shown in FIG.  2 . Support rods  11  can be placed on support brackets  42  at a desired position within inner chamber  9  to support platter  30  that receives pizza  32  thereon. Platter  30  can be a standard wire mesh grid tray such as Pizza Screen from American Metal Craft. The rear wall of inner chamber  9  can have openings located along the bottom portion thereof to enable ambient air to flow into inner chamber  9 . 
     Support rods  11  can be positioned at a desired distance between heating elements  15 A, 15 B within inner chamber  9  to enable pizza  32  on platter  30  to be exposed to a desired intensity of infrared radiation. Typically, support rods  11  are located about 3-7 inches, preferably about 5 inches, from upper heating elements  15 A and about 3-7 inches, preferably about 5 inches, from lower heating elements  15 B. 
     Upper and lower heating elements  15 A, 15 B, as shown in FIG. 3, can be placed into an array and be maintained in a desired relationship to each other by framework  50 . Framework  50  can be constructed from metals such as aluminum. Framework  50  includes elongated members  52  and end members  54 . Elongated members  52  include lateral extending sections  52 A. For purposes of illustration, and without limitation, FIG. 3 shows a framework  50  which includes heating elements  15 B. It is to be understood, however, that framework  50  can be employed with heating elements  15 A. Framework  50  having heating elements  15 A, 15 B, can be secured to the interior of chamber  9  by conventional fasteners such as screws (not shown). 
     Heating elements  15 A, 15 B preferably are Nichrome-quartz heating elements which include a Nichrome wire housed in a sealed quartz tube. The Nichrome-quartz heating elements which may be employed have a power rating of about 400 watts to about 1600watts, and can generate infrared radiation at an intensity of about 10 KW/m 2  to about 20KW/m 2  over a wavelength range of about 5.3 microns to about 9.1 microns. Heating elements  15 A, 15 B receive power through leads connected to temperature controller  88 . Preferably, temperature controller  88  is a pulse type controller which varies the voltage and duration of electrical pulses to the heating elements. 
     Heating elements which may be used include Nichrome-quartz heating elements such as models QIM 165 and QIM 166 from Thermo Innovations Corp, Manasquan, N.J. 08736. Model QIM 165 heating element operates at 220 V and has a power rating of 1300 W. Model QIM 166 heating element operates at 250 V and has a power rating of 1300W. These heating elements can be operated at about 47° C. to about 271° C. and generate infrared radiation over a wavelength range of about 5.3 to about 9.1 microns. 
     In a first aspect of the first embodiment of oven  1 , as shown in FIG. 1A an upper array  79 A of heating elements  15 A and a lower array  79 B of heating elements  15 B are employed. The number of heating elements may vary in each of the upper and lower arrays. Typically, an array includes two to ten, preferably three heating elements. 
     Heating elements  15 A, 15 B in each array can be placed in a symmetrical or asymmetrical arrangement with respect to the axis of symmetry of that array. By selecting a lateral spacing between adjacent heating elements  15 A, 15 B as well as the distance between elements  15 A, 15 B from pizza  32 , an evenly distributed infrared energy field is created to cook uniformly and quickly foodstuffs such as pizza  32 . 
     In a second embodiment of the invention, oven  1 A, as shown in FIGS. 5-10, includes hollow frame members  60  assembled to form box frame  62  as shown in FIG.  6 . Frame members  60  preferably have a cross section as shown in FIG.  6 A. Highly reflective metal sheets such as aluminum are attached to box frame  62  to yield a chamber that has rear, bottom and side walls. Heating elements  15 A together with concave reflectors  95  are assembled onto upper subframe  75  as shown in FIGS. 7 and 7A. Upper subframe  75  is assembled from frame members  60  such as those used to form box frame  62 . Heating elements  15 A are secured to upper subframe  75 , and concave reflectors  95  are secured to upper subframe  75  over heating elements  15 A. Electrical leads are passed through frame members  60  of upper subframe  75  for attachment to heating elements  15 A. Concave reflectors  95  extend along a desired length of the heating element, preferably the entire length of the heating element. Lower subframe  85 , as shown in FIGS. 8 and 8A, is made similarly to upper subframe  75  except that no reflectors are attached to lower subframe  85 . 
     The upper and lower subframes having the heating elements therein are attached to the side walls of chamber  9  by fasteners (not shown). Useful fasteners include screws, pins and the like. 
     Crumb tray  90 , preferably having reflectors  95  which have a concave curvature, as shown in FIG. 9, is positioned below lower subframe  85  so that tray  90  and reflectors  95  are below heating elements  15 B. Crumb tray  90  can slide into an opening provided below the bottom surface of lower subframe  85  as shown in FIG.  5 . An outer shell  100  of reflective metal as shown in FIG. 10 then is attached over box frame  62  by fasteners  118 . Useful fasteners include screws, pins and the like. A layer of insulation  105  such as fiberglass is secured to the interior surface of outer shell  100  in insulation shelf  102  of outer shell  100  as shown in FIGS. 10 and 10A. 
     As in the first embodiment, in this second embodiment of the oven of the invention, inner chamber  9 A includes elongated support brackets  42  for receiving a plurality of support rods  11  thereon. The rear wall  13  of inner chamber  9 A can have holes located along the bottom portion thereof to enable air to flow into chamber  9 A. Support brackets  42  can have a “L” shaped configuration as shown in FIG.  2 . Support rods  11  can be placed on support brackets  42  at a desired position within chamber  9 . Support rods  11  function to support platter  30  that has a foodstuff such as a pizza thereon. Support rods  11  can be positioned at a desired distance between heating elements  15 A,  15 B within chamber  9 A to enable the pizza to be exposed to a desired intensity of infrared radiation. Typically, support rods  11  are located about 3-7 inches, preferably about 5 inches, from the upper heating elements and about 3-7 inches, preferably about 5 inches, from the lower heating elements. 
     In this second embodiment, the heating elements also are Nichrome-quartz heating elements which include a Nichrome wire housed in a sealed quartz tube. The heating elements typically have a power rating of about 400 watts to about 1600 watts and generate infrared radiation at an intensity of about 7 KW/m 2  to about 31 KW/m 2 . Preferably, the heating elements are QIM-166 heating elements from Thermo Innovations Corp. Heating elements  15 A,  15 B receive power through leads connected to temperature controller  88 . 
     Temperature controller  88  enables regulation of the temperature of the heating elements and the consequent wavelength and intensity of infrared radiation received by the pizza. Controller  88  preferably enables upper heating elements  15 A to operate at the same or different temperature from lower heating elements  15 B. Controller  88  can manually be set to a desired pulse mode setting to control the electrical power to the heating elements. 
     Useful temperature-process controllers include Model CN 4321TR-D1 From Omega Corp., as well as Infinite Control Mechanism models CH-152 or CH-252 from Omega Engineering Corp., Stamford, Conn. 
     Controller  88  is activated for a desired cooking cycle by a digital or analog timer  120  that is electrically connected to the controller  88 . Useful timers include Handset Interval Timer INM from Precision Timer Co, Inc., Westbrook, Conn. and PTC-21 Series 1/16 DIN Multi-Programmable Dual Display Timers from OMEGA Engineering Corp, Stamford, Connecticut. When the cooking cycle is complete, the timer shuts off to deactivate the controller. 
     Operation 
     During operation of each embodiment of oven  1  to cook a foodstuff such as pizza  32 , platter  30  having pizza  32  thereon is first placed on support rods  11  at a desired distance from each of heating elements  15 A, 15 B within inner chamber  9 . Platter  30  can be a standard grid tray such as Pizza Screen from American Metal Craft. Heating elements  15 A, 15 B are placed both above and below pizza  32  to expose pizza  32  to the infrared radiation generated by the heating elements. Upper heating elements  15 A may be operated at the same or different power levels from lower heating elements  15 B. 
     In a first aspect of this second embodiment, a sensor and a temperature-process controller are used to control electrical energy supplied to the heating elements. A useful sensor is Model no. TJ 36-CASS-14U-12 from Omega Corp., Stamford, Conn. The sensor is placed in contact with the glass tube component of a heating element. The sensor senses the temperature of the glass tube and forwards it to the controller. A useful controller is a maintenance pulse type controller such as Model CN 4321 TR-D1 from Omega Corp. The controller is preset to a desired value to control the electrical energy sent to the heating elements. The controller preferably enables each of the heating elements to receive about equal amounts of electrical energy so that all of the heating elements can operate at about the same temperature. When the temperature of the heating elements is about equal to the preset temperature of the controller, the controller adjusts the electrical energy supplied to the heating elements from continuous to pulsating. The electrical pulsations from the controller enables control of the temperature of the heating elements and the consequent wavelength and intensity of the infrared radiation received by the pizza. 
     The time-temperature behavior of a QIM-165 heating element when energized by Model CN 4321 TR-D1 controller that is preset to achieve an operating temperature of 260° C. in the heating element is shown in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Time to Temperature at Controller Preset Temperature of 260° C. 
               
            
           
           
               
               
               
            
               
                 Time 
                 Temperature ° C. of 
                 Wavelength 
               
               
                 (sec) 
                 Heating Element 
                 (microns) 1   
               
               
                   
               
            
           
           
               
               
               
            
               
                  0 
                  47 
                 9.1 
               
               
                  30 
                  59 
                 8.7 
               
               
                  60 
                 115 
                 7.5 
               
               
                  90 
                 162 
                 6.7 
               
               
                 120 
                 197 
                 6.2 
               
               
                 150 
                 220 
                 5.9 
               
               
                 180 
                 240 
                 5.6 
               
               
                 210 
                 252 
                 5.5 
               
               
                 240 
                 262 
                 5.4 
               
               
                 270 
                 268 
                 5.4 
               
               
                 294 
                 271 
                 5.3 
               
               
                   
               
               
                   1 Wavelength of infrared radiation calculated from Wien&#39;s law  
               
            
           
         
       
     
     Table 2 shows the time-temperature behavior of a QIM-165heating element when energized by Model CN 4321 TR-D1 controller is preset to achieve an operating temperature of 275° C. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Time to Temperature at Controller Preset Temperature of 275° C. 
               
            
           
           
               
               
               
            
               
                 Time 
                 Temperature ° C. of 
                 Wavelength 
               
               
                 (sec) 
                 Heating Element 
                 (microns) 1   
               
               
                   
               
            
           
           
               
               
               
            
               
                  0 
                  41 
                 9.2 
               
               
                  30 
                  62 
                 8.7 
               
               
                  60 
                 112 
                 7.5 
               
               
                  90 
                 167 
                 6.6 
               
               
                 120 
                 205 
                 6.1 
               
               
                 150 
                 233 
                 5.7 
               
               
                 180 
                 254 
                 5.5 
               
               
                 210 
                 268 
                 5.4 
               
               
                   
               
               
                   1 Wavelength of infrared radiation calculated from Wien&#39;s law  
               
            
           
         
       
     
     In a second aspect of the operation of this second embodiment of the oven, each of the upper and lower heating elements  15 A, 15 B is a QIM-166 heating element from Thermo Innovations Corp. Each of the heating elements has a concave reflector  95  associated therewith. The heating elements are energized by a pulse type temperature-process controller such as any of Infinite Control Mechanism models CH-152 or CH-252 from Omega Corp. The controller is set to a desired value to control electrical power to the heating elements. The controller enables upper heating elements  15 A to operate at the same or different temperature from lower heating elements  15 B. This aspect of the opertion of the oven further is illustrated below in non-limiting Examples 1-14. 
     Examples 1-14: 
     In examples 1-14 below, an upper array of three heating elements and a lower array of three heating elements are employed. The heating elements in each array are the Thermo Innovations Corp. QIM-166 heating elements described above. A concave reflector is employed with each of the heating elements in both the upper and lower arrays. The controller employed for providing electrical power to the heating elements is a CH-252 controller from Omega Engineering Corp. The CH-252 controller has a maximum power rating of 3600 watts and operates at 240 Volts. The pizza is located 5 inches from each of the upper and lower arrays of heating elements. 
     The CH-252 controller is activated by a timer to provide pulses of electrical energy at 240 V to each of the heating elements. The length of the pulses and the time periods between pulses depends on the preset mode values which can be manually applied to the controller dials. The preset mode values, together with duration of the pulses and the time periods between pulses for the mode values, is given in Table 3. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Preset 
                 Duration of 
                 Time between 
               
               
                   
                 Mode Value 
                 Electrical Pulse 
                 Electrical pulses 
               
               
                   
                   
               
             
            
               
                   
                 2 
                 1 sec 
                 2 sec 
               
               
                   
                 3 
                 1 
                 1.5 
               
               
                   
                 4 
                 1 
                 1.0 
               
               
                   
                 5 
                 1 
                 0.75 
               
               
                   
                 6 
                 1 
                 0.5 
               
               
                   
                   
               
            
           
         
       
     
     In examples 1-14 below, a pizza is located 5 inches from each of the upper and lower arrays of heating elements. The time periods for cooking of the pizzas are shown in Table 4. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                 Weight 
                 Controller Mode 
                   
               
               
                   
                   
                 of 
                 Settings For Upper 
                 Time to 
               
               
                   
                   
                 Pizza 
                 and Lower Arrays of 
                 Complete 
               
               
                 Ex. 
                 Pizza 
                 (Oz) 
                 Heating Elements 
                 Cooking 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                  2 
                 Di Giorno 
                 12 
                 Upper Array: 3 mode 
                 8 minutes 
               
               
                   
                 Rising Crust 
                   
                 Lower Array: 6 mode 
                 from solid 
               
               
                   
                 Pizza Four 
                   
                   
                 frozen to 
               
               
                   
                 Cheese-Frozen 
                   
                   
                 cooked 
               
               
                  3 
                 Freshetta 
                 14 
                 Upper Array: 3 mode 
                 7-8 minutes 
               
               
                   
                 Rising Crust 
                   
                 Lower Array: 6 mode 
                 from solid 
               
               
                   
                 Pizza Four 
                   
                   
                 frozen to 
               
               
                   
                 Cheese-Frozen 
                   
                   
                 cooked 
               
               
                  4 
                 Di Giorno 
                 12 
                 Upper Array: 2 mode 
                 11 minutes 
               
               
                   
                 Rising Crust 
                   
                 Lower Array: 5 mode 
                 from solid 
               
               
                   
                 Pizza 
                   
                   
                 frozen to 
               
               
                   
                 Pepperoni- 
                   
                   
                 cooked 
               
               
                   
                 Frozen 
               
               
                  5 
                 Di Giorno 
                 12 
                 Upper Array: 2 mode 
                 10 minutes 
               
               
                   
                 Rising Crust 
                   
                 Lower Array: 6 mode 
                 from solid 
               
               
                   
                 Pizza Four 
                   
                   
                 frozen to 
               
               
                   
                 Cheese-Frozen 
                   
                   
                 cooked 
               
               
                  6 
                 Di Giorno 
                 13.8 
                 Upper Array: 2 mode 
                 10 minutes 
               
               
                   
                 Rising Crust 
                   
                 Lower Array: 5 mode 
                 from solid 
               
               
                   
                 Pizza 
                   
                   
                 frozen to 
               
               
                   
                 3 Meat-Frozen 
                   
                   
                 cooked 
               
               
                  7 
                 Di Giorno 
                 13.8 
                 Upper Array: 4 mode 
                 7 minutes 
               
               
                   
                 Rising Crust 
                   
                 Lower Array: 6 mode 
                 from solid 
               
               
                   
                 Pizza 
                   
                   
                 frozen to 
               
               
                   
                 Supreme- 
                   
                   
                 cooked 
               
               
                   
                 Frozen 
               
               
                  8 
                 Di Giorno 
                 12 
                 Upper Array: 3 mode 
                 11 minutes 
               
               
                   
                 Rising Crust 
                   
                 Lower Array: 5 mode 
                 from solid 
               
               
                   
                 Pizza Four 
                   
                   
                 frozen to 
               
               
                   
                 Cheese-Frozen 
                   
                   
                 cooked 
               
               
                  9 
                 Di Giorno 
                 13.8 
                 Upper Array: 4 mode 
                 8 minutes 
               
               
                   
                 Rising Crust 
                   
                 Lower Array: 6 mode 
                 from solid 
               
               
                   
                 Pizza 
                   
                   
                 frozen to 
               
               
                   
                 3 Meat-Frozen 
                   
                   
                 cooked 
               
               
                 10 
                 Subway 3 
                 12 
                 Upper Array: 5 mode 
                 7 minutes 
               
               
                   
                 frozen 
                   
                 Lower Array: 6 mode 
                 from solid 
               
               
                   
                   
                   
                   
                 frozen to 
               
               
                   
                   
                   
                   
                 cooked 
               
               
                 11 
                 Subway 1 
                 4 
                 Upper Array: 4 mode 
                 4 minutes from 
               
               
                   
                 frozen 
                   
                 Lower Array: 6 mode 
                 cold to cooked 
               
               
                 12 
                 Subway 1 fresh 
                 4 
                 Upper Array: 3.5 mode 
                 3.5 minutes 
               
               
                   
                   
                   
                 Lower Array: 6 mode 
                 from cold 
               
               
                   
                   
                   
                   
                 to pre-cooked 
               
               
                 13 
                 Subway 1 fresh 
                 4 
                 Upper Array: 3.5 mode 
                 4 minutes 
               
               
                   
                   
                   
                 Lower Array: 6 mode 
                 from cold 
               
               
                   
                   
                   
                   
                 to pre-cooked 
               
               
                 14 
                 Subway 1 fresh 
                 4 
                 Upper Array: 3 mode 
                 4.5 minutes 
               
               
                   
                   
                   
                 Lower Array: 6 mode 
                 from cold 
               
               
                   
                   
                   
                   
                 to pre-cooked 
               
               
                 15 
                 Subway 1 fresh 
                 4 
                 Upper Array: 3 mode 
                 4 minutes 
               
               
                   
                   
                   
                 Lower Array: 6 mode 
                 from cold 
               
               
                   
                   
                   
                   
                 to pre-cooked