Abstract:
An invention is afforded for a convection based cooking apparatus having enhanced heat retention. The convention based cooking apparatus includes a cooking chamber configured to holding food to be processed. An air inlet is situated in fluid communication with the cooking chamber for receiving air into the cooking chamber. In addition, a heating source is included that is configured to switch between an ON state and an OFF state, whereby a temperature of air located within the cooking chamber is regulated. Further, a drafting means is provided that is configured to circulate air present within the cooking chamber. Also included is an inlet control apparatus that regulates air flow into the cooking chamber via the air inlet. The inlet control apparatus allows air to flow into the cooking chamber via the air inlet when the heating source is in the ON state. The inlet control apparatus prevents air from flowing into the cooking chamber via the air inlet when the heating source is in the OFF state.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to ovens and more particularly to a convection based cooking apparatus having enhanced heat retention via an adjustable inlet shutter. 
         [0003]    2. Description of the Related Art 
         [0004]    Today, modern ovens are used throughout the world for heating, roasting, baking, and other food preparation purposes. Most conventional ovens typically use a gas burner or electrical heating element to heat air inside a thermally insulated chamber. The heated air then transfers heat to food product placed inside the chamber, resulting in the desired baking, roasting, or other desired cooking functionality. 
         [0005]    Conventional ovens are generally of two types: a standard oven and a convection oven. Standard ovens utilize a gas burner or electrical heating element to heat air inside the thermally insulated chamber. The heated air is then exhausted from the chamber via gravity. In this manner, heat is transferred to food product located within the chamber. 
         [0006]    To improve overall cooking efficiency and uniform heat transfer, convection ovens have been developed. Convection ovens circulate the heated air within the thermally insulated chamber to enhance overall cooking efficiency. More particularly, when using a gas burner as a heating element, a convection oven draws air into the oven via a vent and over the gas burner. The resulting products of combustion are then drawn into the thermally insulated chamber via a blower or fan, and circulated within the chamber. As more products of combustion are drawn into the cooking chamber, the pressure within the chamber increases. At a certain point, a portion of the hot air is released via an exhaust opening. 
         [0007]    When the temperature in the oven chamber is satisfied, the gas burner turns off, while the blower continues to run and circulate the air within the chamber. However, as the blower continues to run, it draws in colder air via the vent into the oven chamber since the gas burner is off and no longer heating the drawn in air. This cooler air mixes with the hotter air and drops the temperature in the oven chamber from the dilution of the heat. However, the pressure is still present within the oven chamber resulting in air escaping from the exhaust. Once the temperature drops to a predefined level, the thermostat senses the drop and turns the gas burner back on, resulting in hot air being pulled back into the oven chamber. 
         [0008]    Thus, convection ovens operate in cycles, turning on and off. That is, the oven heating elements are turned on to allow the heat within the oven chamber to increase to a predefined level. Then, once the predefined temperature is achieved, the heating elements are turned off, allowing the air within the oven chamber to cool until the temperature within the oven chamber drops below the predefined level, at which point the heating elements are turned on again. This cycle continues as the food product is cooked to maintain the oven temperature at approximately the desired cooking temperature. Unfortunately, the cooling of the oven temperature as a result of a combination of the heating elements being turned off and the chamber air being exhausted, causes undesirable energy consumption as the heating elements are frequently cycled on to increase the oven chamber temperature back to the desired level. 
         [0009]    In view of the forgoing, there is a need for an oven capable of reducing the amount of cycling required to maintain desired cooking temperatures within the oven chamber. The oven should be capable of maintaining heat levels within the oven chamber for increased time periods. In addition, the oven should be capable of achieving these increased heat maintenance levels for gas burner based heating elements, as well as when utilizing combi oven configurations. 
       SUMMARY OF THE INVENTION 
       [0010]    Broadly speaking, embodiments of the present invention address these needs by providing a convection based cooking apparatus having enhanced heat retention. In one embodiment, the convention based cooking apparatus includes a cooking chamber configured to holding food to be processed. An air inlet is situated in fluid communication with the cooking chamber for receiving air into the cooking chamber. In addition, a heating source is included that is configured to switch between an ON state and an OFF state, whereby a temperature of air located within the cooking chamber is regulated. Further, a drafting means is provided that is configured to circulate air present within the cooking chamber. In one aspect, the heating source can comprise at least one gas burner, and the drafting means can be a blower. Also included is an inlet control apparatus that regulates air flow into the cooking chamber via the air inlet. The inlet control apparatus allows air to flow into the cooking chamber via the air inlet when the heating source is in the ON state. In addition, the inlet control apparatus prevents air from flowing into the cooking chamber via the air inlet when the heating source is in the OFF state. In one aspect, the inlet control apparatus can comprise a shutter in communication with a linear solenoid. In this aspect, the shutter can prevent air from flowing into the cooking chamber via the air inlet when the heating source is in the OFF state, and allow air to flow into the cooking chamber via the air inlet when the heating source is in the ON state. 
         [0011]    In additional embodiment, a method is disclosed for providing enhanced heat retention in a convection based cooking apparatus. The method includes setting a heating source to an ON state and allowing air to flow into a cooking chamber via an air inlet. Next, a determination is made as to whether the temperature within the cooking chamber has reached a predetermined level. Then, when the temperature within the cooking chamber has reached the desired level, the heating source is set to an OFF state and air is prevented from flowing into the cooking chamber via the air inlet. During this process the air present within the cooking chamber is circulated. Similar to above, the drafting means can be a blower and the heating source can comprises at least one gas burner. An inlet control apparatus prevents air from flowing into the cooking chamber when the heating source is in the OFF state, and allows air to flow into the cooking chamber when the heating source is in the ON state. 
         [0012]    A further convection based cooking apparatus having enhanced heat retention is disclosed in an additional embodiment of the present invention. In this embodiment, a cooking chamber is included that is configured to holding food to be processed. In addition, an air inlet is in fluid communication with the cooking chamber for receiving air into the cooking chamber. Also, at least one gas burner is included that is configured to switch between an ON state that provides heat and an OFF state that does not provide heat, whereby a temperature of air located within the cooking chamber is regulated. Further, a drafting means is provided that is configured to circulate air present within the cooking chamber. Similar to above, an inlet control apparatus is included that is configured to regulate air flow into the cooking chamber via the air inlet. The inlet control apparatus allows air to flow into the cooking chamber via the air inlet when the gas burner is in the ON state, and prevents air from flowing into the cooking chamber via the air inlet when the gas burner is in the OFF state. In this aspect, the drafting means can be a blower. As above, the inlet control apparatus can comprise a shutter in communication with a linear solenoid. In this aspect, the shutter prevents air from flowing into the cooking chamber when the gas burner is in the OFF state, and allows air to flow into the cooking chamber when the gas burner is in the ON state. 
         [0013]    In this manner, embodiments of the present invention provide enhanced heat retention in the cooking chamber, allowing the heating source to remain cycled OFF for longer periods of time. This provides significant energy savings, both in terms of lower gas usage for the gas burner elements and in terms of overall heat output from the oven, resulting in lower kitchen air-conditioning requirements. Moreover, because of the reduced need for cycling the heating source, embodiments of the present invention provide increased cooking efficiency, and better finished food products, as well as increased production capability. Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
           [0015]      FIG. 1  is an illustration showing front view of an exemplary convection based cooking apparatus utilizing gas burner heating elements and having enhanced heat retention, in accordance with an embodiment of the present invention; 
           [0016]      FIG. 2A  is an illustration showing a side view of an exemplary convection based cooking apparatus having enhanced heat retention when the gas burning heating elements are in an ON state, in accordance with an embodiment of the present invention; 
           [0017]      FIG. 2B  is an illustration showing an isometric top view of an adjustable inlet shutter in an open position when the gas burner heating elements are in an ON state, in accordance with an embodiment of the present invention; 
           [0018]      FIG. 3A  is an illustration showing a side view of an exemplary convection based cooking apparatus having enhanced heat retention when the gas burning heating elements are in an OFF state, in accordance with an embodiment of the present invention; 
           [0019]      FIG. 3B  is an illustration showing an isometric top view of an adjustable inlet shutter in a closed position when the gas burner heating elements are in an OFF state, in accordance with an embodiment of the present invention; and 
           [0020]      FIG. 4  is a flowchart showing a method for providing enhanced heat retention in a convection based cooking apparatus, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    An invention is disclosed for a convection based cooking apparatus having enhanced heat retention using an adjustable inlet shutter. In general, embodiments of the present invention prevent the introduction of outside air into the oven cooking chamber when the heating elements are off and allow the introduction of cool outside air into the oven cooking chamber when the heating elements are on. By preventing the introduction of outside air into the oven cooking chamber when the heating elements are off, embodiments of the present invention maintain heat levels within the oven cooking chamber at desired levels much longer than is possible using conventional convection ovens. 
         [0022]    In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present invention. 
         [0023]      FIG. 1  is an illustration showing a front view of an exemplary convection based cooking apparatus  100  utilizing gas burner heating elements and having enhanced heat retention, in accordance with an embodiment of the present invention. The convection based cooking apparatus  100  includes a cooking chamber  102  defined by a plurality of sidewalls  104 . A heating source  106  is disposed below the cooking chamber  102 . In the example of  FIG. 1  the heating source  106  is gas burner heating elements, which can switch between an ON state and an OFF state to regulate the temperature of air located within the cooking chamber  102 . 
         [0024]    In addition, a drafting means, such a blower  108  is disposed in a back wall of the cooking chamber  102 . Although the blower  108  is shown as being disposed in a back wall of the cooking chamber  102 , it should be noted that the blower  108  can be situated in any area from which it can operate as a drafting and/or circulating mechanism. As will be discussed in greater detail subsequently, the drafting means is configured to circulate air present within the cooking chamber  102  to provide enhancing cooking functionality. Situated near the blower  108  is a snorkel  110 , which operates to provide air to the cooking chamber  102  via an air inlet, as illustrated in  FIG. 2A . 
         [0025]      FIG. 2A  is an illustration showing a side view of an exemplary convection based cooking apparatus  100  when the gas burner heating elements are in an ON state, in accordance with an embodiment of the present invention. In operation, the blower  108  draws in air, via the air inlet  200 , across the heating source  106  (i.e., the gas burner heating elements), which heats the air. The resulting products of combustion are then drawn around the side walls  104  and into the cooking chamber  102  via the snorkel  110 , as illustrated in  FIG. 1 . It should be noted that in the present disclosure, the term air inlet  200  is defined as an opening or other means that allows air to flow into the oven, across the heating source  106 , and into the cooking chamber  102 . The air outlet  202 , on the other hand, is defined as an opening or other means that allows air to flow out of the oven cooking chamber  102 , without crossing the heating source  106 . 
         [0026]    Turning back to  FIG. 2A , the blower  108  continues to circulate the air present in the cooking chamber  102  to facilitate cooking the food product. As more products of combustion are drawn into the cooking chamber  102 , the pressure within the cooking chamber  102  increases. The pressure is alleviated by allowing the hot air to escape the cooking chamber  102  via an air outlet  202 . To enhance heat retention, embodiments of the present invention include an inlet control apparatus  204  that includes an adjustable inlet shutter  206 . An inlet control apparatus  204  is defined in the present application to mean a mechanism that allows air to flow into the cooking chamber  102  via the air inlet  200  when the heating source  106  (i.e., gas burners) is in the ON state, and prevents air flow into the cooking chamber  102  via the air inlet  200  when the heating source  106  is in the OFF state, and not providing heat to the cooking chamber  102 . At least a portion of the inlet control apparatus  204  is disposed between the air inlet  200  and the cooking chamber  102  when the heating source  106  is in the OFF state, thus prevents air flow into the cooking chamber  102  when the heating source  106  is in the OFF state. In one embodiment, at least a portion of the inlet control apparatus  204  is disposed in front of the air inlet  200  when the heating source  106  is in the OFF state, thus prevents air flow into the cooking chamber  102  when the heating source  106  is in the OFF state. In a further embodiment, at least a portion of the inlet control apparatus  204  is disposed just inside the cooking chamber  102  and covering the interface between the air inlet and the cooking chamber  102  when the heating source  106  is in the OFF state, thus prevents air flow into the cooking chamber  102  when the heating source  106  is in the OFF state. 
         [0027]    It should be borne in mind that the inlet control apparatus  204  is not associated with or used in conjunction with the air outlet  202 . 
         [0028]    For example, the adjustable inlet shutter  206  portion of the inlet control apparatus  204  of the embodiments of the present invention is configured to allow air to flow into the cooking chamber  102  via the air inlet  200  when the heating source  106  (i.e., gas burners) is in the ON state, providing heat to the cooking chamber  102 . However, when the heating source  106  is in the OFF state, and not providing heat to the cooking chamber  102 , the adjustable inlet shutter  206  is positioned between the air inlet  200  and the cooking chamber  102  to prevent air flow into the cooking chamber  102  via the air inlet  200 . In one embodiment, the adjustable inlet shutter  206  blocks the snorkel inlet portion  110   a  of the snorkel  110  when the heating source  106  is in the OFF state, thus blocking air flow from the air inlet  200  into the cooking chamber  102 . However, it should be noted that the inlet control apparatus  204  of the embodiments of the present invention can be located in any position that allows the inlet control apparatus  204  to prevent air flow into the cooking chamber  102  via the air inlet when the heating apparatus in the OFF state. For example, the inlet control apparatus  204  can be located outside and in front of the air inlet  200 . Alternatively, the inlet control apparatus  204  can be located just inside the air inlet  200 , either before or after the heating source  106 . 
         [0029]    In one embodiment, the inlet control apparatus  204  comprises an adjustable inlet shutter  206  coupled to a linear solenoid  208 . For example, the linear solenoid can be an electrical coil wound around a cylindrical tube with a ferro-magnetic actuator that is free to move in and out of the coils body.  FIG. 2B  is an illustration showing an isometric top view of an adjustable inlet shutter  206  in an open position when the gas burner heating elements are in an ON state, in accordance with an embodiment of the present invention. The linear solenoid  208  can be actuated to control when the adjustable inlet shutter  206  closes the interface (i.e., the snorkel inlet portion  110   a ) between the air inlet  200  and the snorkel  110 , thus preventing outside air from flowing into the cooking chamber  102 . Similarly, the linear solenoid  208  can be actuated to control when the adjustable inlet shutter  206  opens the interface between the air inlet  200  and the snorkel  110 , thus allowing outside air into the cooking chamber  102 . Although  FIG. 2A  illustrates the usage of a linear solenoid as an element of the inlet control apparatus  204 , it should be noted that any apparatus, for example a rotary solenoid, capable of operating the adjustable inlet shutter  206  and/or blocking or allowing outside air to flow from the air inlet  200  into the cooking chamber  102  can be utilized in the embodiments of the present invention as an inlet control apparatus  204  or part thereof. 
         [0030]      FIG. 3A  is an illustration showing a side view of an exemplary convection based cooking apparatus  100  having enhanced heat retention when the gas burning heating elements are in an OFF state, in accordance with an embodiment of the present invention. When the gas burner heating elements  106  are in the OFF state, the blower  108  continues to circulate the air within the cooking chamber  102 . However, as described previously, when the heating source  106  is in the OFF state, and not providing heat to the cooking chamber  102 , the inlet control apparatus  204  prevents outside air from entering the cooking chamber  102  via the air inlet  200 . For example, in  FIG. 3A  the adjustable inlet shutter  206  is pushed forward via the linear solenoid  208 , which closes the interface  110   a  between the air inlet  200  and the snorkel  110 . This is also illustrated in  FIG. 3B , which shows an isometric top view of an adjustable inlet shutter  206  in a closed position when the gas burner heating elements are in an OFF state, in accordance with an embodiment of the present invention. As a result, outside air is prevented from flowing into the cooking chamber  102 . Moreover, the pressure within the cooking chamber  102  enhances the seal between the adjustable inlet shutter  206  and the interface  110   a  of the snorkel  110 , thus substantially reducing air leakage. 
         [0031]    As can be appreciated, in order for air to escape the cooking chamber  102  via the air outlet  202 , air flow must come from the air inlet  200  via the snorkel  110 . Thus, closing the interface  110   a  between the air inlet  200  and the snorkel  110  also substantially restricts air from escaping the cooking chamber via the air outlet  202 . Hence, embodiments of the present invention eliminate heat dilution caused by cooler air being drawn into the cooking chamber  102  via the air inlet  200  when the heating source  106  is in the OFF state. In this manner, embodiments of the present invention provide enhanced heat retention in the cooking chamber  102 , allowing the heating source  106  to remain cycled OFF for longer periods of time. This provides significant energy savings, both in terms of lower gas usage for the gas burner elements and in terms of overall heat output from the oven, resulting in lower kitchen air-conditioning requirements. Moreover, because of the reduced need for cycling the heating source, embodiments of the present invention provide increased cooking efficiency, and better finished food products, as well as increased production capability. 
         [0032]    Eventually, the temperature of the air present within the cooking chamber  102  may fall below a desired level, at which point the heating source  106  is set back to the ON state. In addition to setting the heating source  106  back to the ON state, embodiments of the present invention also open the interface  110   a  between the air inlet  200  and the snorkel  110 , thus allowing air to enter the cooking chamber  102 . Opening the interface  110   a  between the air inlet  200  and the snorkel  110  also allows air to vent and escape from the cooking chamber  102  as the pressure within the cooking chamber  102  rises due to the rising temperature within the chamber. This cycling process is further illustrated next with reference to  FIG. 4 . 
         [0033]      FIG. 4  is a flowchart showing a method  400  for providing enhanced heat retention in a convection based cooking apparatus, in accordance with an embodiment of the present invention. In an initial operation  402 , preprocess operations are performed. Preprocess operations can include, for example, setting a thermostat to a desired temperature, placing food product within the cooking chamber of the oven, and other preprocess operations that will be apparent to those skilled in the art in view of the hindsight provided by a careful examination of the present disclosure. 
         [0034]    In a heating operation  404 , the heating source is set to an ON state that provides heat and the interface between the air inlet and the cooking chamber is opened, allowing outside air to flow into the cooking chamber via the air inlet. For example, during operation, the blower draws in air via the air inlet and across the heating source, which heats the air. The resulting products of combustion are then drawn around the side walls and into the cooking chamber via the snorkel. The blower also circulates the air present in the cooking chamber to facilitate cooking the food product. As more products of combustion are drawn into the cooking chamber, the pressure within the cooking chamber increases. The pressure is alleviated by the air outlet, which allows the hot air to escape the cooking chamber when the heating source is set to the ON state. 
         [0035]    A decision is then made as to whether the temperature within the cooking chamber is equal to or greater than a desired cooking temperature, in operation  406 . If the temperature within the cooking chamber is equal to or greater than the desired cooking temperature, the method continues to an OFF cycle operation  410 . Otherwise, the method branches to operation  408 . 
         [0036]    In operation  408 , the heating source continues to heat the air drawn into the cooking chamber. For example, in one embodiment a thermostat is used to set and detect a desired temperature within the cooking chamber of the oven. When the thermostat determines that the temperature in the cooking chamber has not yet reached the desired temperature, the heating source continues to provide heat to the oven. However, when the thermostat determines that the temperature in the cooking chamber has reached the desired temperature, the heating source cycles to an OFF state in operation  410 . 
         [0037]    In operation  410 , the heating source is set to an OFF state and the interface between the air inlet and the cooking chamber is closed, preventing outside air to flow into the cooking chamber via the air inlet. When the gas burner heating elements are in the OFF state, the blower continues to circulate the air within the cooking chamber. However, the inlet control apparatus prevents outside air from entering the cooking chamber via the air inlet when the heating source is set to the OFF state and no longer provides heat. 
         [0038]    A decision is then made as to whether the temperature within the cooking chamber is less than the desired cooking temperature, in operation  412 . If the temperature within the cooking chamber is equal to or greater than a desired cooking temperature, the method branches to circulation operation  414 . Otherwise, the method returns to heating operation  404 . 
         [0039]    In circulation operation  414 , the blower continues to circulate the air present in cooking chamber. For example, when the thermostat determines that the temperature in the cooking chamber has reached the desired temperature, the heat source is set to the OFF state, the interface between the air inlet and the cooking chamber is closed, and the blower continues to circulate the air present in the cooking chamber. As described previously, closing the interface between the air inlet and the cooking chamber prevents air from being drawn into the cooking chamber and thus reduces or eliminates heat dilution caused by cooler air being drawn into the cooking chamber when the heating source is in the OFF state. Also, closing the interface between the air inlet and the cooking chamber also substantially restricts air from escaping the cooking chamber via the air outlet. Eventually, the temperature of the air present within the cooking chamber may fall below a desired level. At that point the heating source is set back to the ON state and the interface between the air inlet and the cooking chamber is opened again, thus allowing air to flow into the cooking chamber and escape from the cooking chamber via the air outlet as the pressure rises due to the rising temperature, in heating operation  404 . 
         [0040]    In this manner, embodiments of the present invention provide enhanced heat retention in the cooking chamber, allowing the heating source to remain cycled OFF for longer periods of time. This provides significant energy savings, both in terms of lower gas usage for the gas burner elements and in terms of overall heat output from the oven, resulting in lower kitchen air-conditioning requirements. 
         [0041]    It should be noted that the described embodiments of the present invention also apply to combi ovens. A combi oven combines the abilities of a convection oven and a steam cooker, thus allowing the user to regulate the humidity within the cooking chamber as well as the temperature. In such embodiments, similar to above, the cooking chamber is allowed to enter the cooking chamber via the air inlet when the heating source is in the ON state, heating the air within the cooking chamber. When the heating source is cycled to the OFF state, the inlet control apparatus prevents outside air from entering the cooking chamber via the air inlet. 
         [0042]    Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.