Patent Publication Number: US-2011048244-A1

Title: Apparatus and method for controlling a combustion blower in a gas-fueled conveyor oven

Description:
BACKGROUND 
     Conveyor ovens are commonly used for cooking a wide variety of food products, such as for cooking pizzas, baking and toasting bread, and the like. Examples of such ovens are shown, for example, in International Patent Application No. PCT/2009/030727, the entire contents of which are incorporated herein by reference. 
     Conveyor ovens typically have metallic housings with a heated tunnel extending therethrough, and one or more conveyors running through the tunnel. Each conveyor (in the form of a conveyor belt, for example) transports food items through the heated oven tunnel at a speed calculated to properly bake food on the conveyor belt during the time the conveyor carries the food through the oven. Conveyor ovens generally include a heat delivery system that may include one or more blowers supplying heated air to the tunnel, such as from a plenum to the tunnel. In some conveyor ovens, the hot air is supplied to the tunnel through passageways that lead to metal fingers discharging air into the tunnel at locations above and/or below the conveyor. The metal fingers act as airflow channels that deliver streams of hot air which impinge upon the surfaces of the food items passing through the tunnel on the conveyor. In modern conveyor ovens, a microprocessor-driven control can be employed to enable the user to regulate the heat provided to the tunnel, the speed of the conveyor, and other parameters to properly bake the food item being transported through the oven. 
     Some conveyor ovens include one or more gas burners positioned to heat air (e.g., in a plenum) before it is supplied to the tunnel to heat the food. In such ovens, the gas burner can include a modulating gas valve providing fuel to the burner, and a combustion blower providing enough air for efficient combustion of the fuel. An oven controller can monitor the temperature at one or more locations within the tunnel, and can adjust the modulating gas valve to provide more or less heat to the tunnel. If the measured temperature is lower than a set point temperature, the modulating gas valve is adjusted to supply more fuel. Conversely, if the measured temperature is higher than the set point temperature, the modulating gas valve is adjusted to supply less fuel. In some conventional ovens, the combustion blower and the modulating fuel valve are adjusted proportionally. For example, if the modulating fuel valve is adjusted to double the amount of fuel output, the speed of the combustion blower is also doubled. 
     SUMMARY 
     As described above, current conveyor oven systems generally adjust the speed of a combustion blower in proportion to the setting of a modulating gas valve. However, such systems typically do not account for other external influences that may affect the efficiency of the gas burner. In some cases, air flow generated by a main blower that circulates air in the conveyor oven (e.g., between the tunnel and a plenum of the conveyor oven) can affect the speed and amount of air provided by the gas burner, thereby affecting the quality of the flame of the gas burner. 
     Some embodiments of the present invention provide a conveyor oven comprising a main blower that circulates air within a cooking chamber; at least one gas burner; a valve having a setting that determines an amount of gas provided to the gas burner; at least one combustion blower that provides air to the at least one gas burner; and a controller that monitors an internal temperature of the oven, adjusts the setting of the valve based at least in part on the internal temperature of the oven, adjusts a speed of the main blower, wherein the speed of the main blower includes at least a high speed setting and a low speed setting, and adjusts a speed of the at least one combustion blower based at least in part on at least one of the internal temperature of the oven and the speed of the main blower. 
     In some embodiments, the controller lowers the speed of the combustion blower when the main blower transitions from the low speed setting to the high speed setting, and/or increases the speed of the combustion blower when the main blower transitions from the high speed setting to the low speed setting. Also, in some embodiments, the controller determines an appropriate speed setting for the combustion blower by accessing a look-up table stored on a computer-readable memory. The look-up table can identify a plurality of speed settings based on internal oven temperature and main blower speed. In some embodiments, the controller calculates an appropriate combustion blower speed setting based on internal oven temperature and main blower speed. 
     Some embodiments of the present invention provide a method of controlling a combustion blower in a conveyor oven, wherein the method comprises measuring an internal temperature of the conveyor oven as determined by a temperature sensor; determining the speed of a main blower circulating air within an internal chamber of the conveyor oven; providing fuel to a burner within the conveyor oven through an electronically-controlled modulating fuel valve; controlling the output of the modulating fuel valve to adjust the internal temperature of the conveyor oven toward a set-point temperature; determining a speed setting for a combustion blower based at least in part on at least one of the measured internal temperature of the oven and the speed of the main blower; and operating the combustion blower at the determined speed setting. 
     Other aspects of the present invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a conveyor oven in accordance with an embodiment of the invention. 
         FIG. 2  is a perspective view of a portion of the conveyor oven of  FIG. 1 , in which a hinged oven access panel has been opened to reveal some of the internal components of the oven. 
         FIG. 3  is a schematic illustration of an embodiment of the control system of the conveyor oven of  FIGS. 1 and 2 . 
         FIG. 4  is a diagrammatic representation of the tunnel of the oven of  FIGS. 1-3 . 
         FIG. 5  is a cross-sectional illustration of the internal compartments of the conveyor oven of  FIGS. 1-4 . 
         FIG. 6  is a diagrammatic representation of a gas burner of the conveyor oven of  FIGS. 1-5 . 
         FIG. 7  is a flowchart illustrating an energy management mode for the conveyor oven of  FIGS. 1-6B . 
         FIG. 8  is a flowchart illustrating a method of controlling a combustion blower in the conveyor oven of  FIGS. 1-7 . 
         FIG. 9  is an example of a look-up table used to determine an appropriate speed of a combustion blower in the conveyor oven of  FIGS. 1-8 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the present invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  shows a conveyor oven  20  having a conveyor  22  which runs through a heated tunnel  24  of the oven. The illustrated conveyor  22  has a width generally corresponding to the width of the heated tunnel  24 , and is designed to travel in direction A from left oven end  26  toward right oven end  28  or, alternatively in direction B, from right oven end  28  toward left oven end  26 . Thus, oven ends  26  and  28  may serve respectively as the inlet and outlet of an oven with a rightwardly moving conveyor or as the outlet and inlet of an oven with a leftwardly moving conveyor. Although the conveyor oven  20  illustrated in  FIG. 1  has only a single conveyor  22 , any number of additional conveyors in any desired arrangement can be used in other embodiments. 
     In some embodiments, the oven  20  can have one or more sensors positioned to detect the presence of food product on the conveyor  20  at one or more locations along the length of the conveyor  20 . By way of example only, the oven  20  illustrated in  FIG. 1  has photosensors  79 ,  81  positioned at the entrance of the oven tunnel  24  to detect the presence of a food item on the conveyor  22 . In other embodiments, other types of sensors (e.g., other optical sensors, mechanical sensors, temperature sensors, and the like) can be positioned at the entrance of the oven tunnel  24 , at any other location upstream of the oven tunnel  24 , at the exit of the oven tunnel  24 , at any other location downstream of the oven tunnel  24 , and/or at any location within the tunnel  24 . Such sensor(s) can be connected to a controller  42  (described in greater detail below) to trigger a change in operation of the conveyor  22 , such as to start, stop, increase and/or decrease the output of one or more gas burners of the oven  20 , start, stop, speed up, or slow down one or more blower fans of the oven  20 , and/or start, stop, speed up or slow down the conveyor  22 . In these cases, such changes can be initiated immediately upon detection of the food product at one or more locations along the conveyor  20 , or can be initiated after a predetermined period of time (e.g., a programmed or otherwise set period of time) has passed. 
     The conveyor  22  can be implemented using conventional components and techniques such as those described in U.S. Pat. Nos. 5,277,105 and 6,481,433 and 6,655,373, the contents of which are incorporated herein by reference insofar as they relate to conveyor support, tracking, and drive systems and related methods. In the illustrated embodiment by way of example only, a chain link drive is housed within compartment  30  at the left end  26  of the oven. Thus, a food item  32 R, such as a raw pizza or a sandwich (to be toasted), may be placed on the conveyor  22  of the ingoing left oven end  26 , and removed from the conveyor  22  as a fully baked food item  32 B at the outgoing right oven end  28 . The speed at which the conveyor  22  moves is coordinated with the temperature in the heated tunnel  24  so that the emerging food item  32 B is properly baked, toasted, or otherwise cooked. 
     A hinged door  34  is provided on the front of the oven  20  shown in  FIG. 1 , with a handle  35  and a heat resistant glass panel  36  permitting a person operating the oven to view a food item as it travels through the oven  20 . In the illustrated embodiment, a stainless steel metal frame surrounds the oven opening, and provides a support for a gasket of suitable material (not shown), so that when the hinged door  34  is in its closed position, it fits against and compresses the gasket to retain heat in the oven  20 . Also, the operator may open the door  34  by pulling on handle  35  to place a different product on the conveyor  22  if less than a full cooking cycle is required to produce a fully cooked product. A hinged oven access panel  38 , open as shown in  FIG. 2 , provides access to internal components of the oven, such as gas burners  100 ,  150  and a combustion blower  155 . 
       FIG. 3  illustrates a schematic example of a control system for the oven  20  shown in  FIGS. 1 and 2 . In the illustrated control system, a controller  42  includes one or more displays  655 , and a control interface  660 . The illustrated controller  42  also includes a central processing unit (“CPU”)  650  for controlling operation of a plurality of devices, including the gas burners  100 ,  150 , two main blower fans  72 ,  74 , the conveyor  22 , and a combustion blower  155 . The CPU  650  can be in the form of a microcontroller or programmable logic controller (PLC) with an associated memory unit in which software or a set of instructions is stored, can instead be defined by a plurality of discreet logic elements, or can take any other form suitable for control of the gas burners  100 ,  150 , main blower fans  72 ,  74 , conveyor  22 , and combustion blower  155 . The illustrated CPU  650  receives input from a plurality of sensors including one or more temperature sensors  80 ,  82  positioned inside the oven, and one or more photosensors  79 ,  81  (described above). 
     Although the oven  20  illustrated in  FIGS. 1-3  includes two gas burners  100 ,  150  and two main blower fans  72 ,  74 , any number of gas burners  100 ,  150  and blower fans  72 ,  74  can be used in other embodiments. In those embodiments in which two or more gas burners  100 ,  150  and/or two or more blower fans  72 ,  74  are used, the CPU  650  can control operation of the gas burners  100 ,  150  independently with respect to one another and/or can control operation of the blower fans  72 ,  74  independently with respect to one another, or otherwise. 
     The controller  42  in the illustrated embodiment adjusts the internal temperature of the oven using a PID (proportional—integral—derivative) control module  55  (also described in greater detail below). The PID control module  55  calculates an amount of fuel needed by the gas burners  100 ,  150  to raise the actual temperature toward a setpoint temperature, and the CPU  650  generates a command or signal to an amplifier board or signal conditioner that controls a modulating fuel valve to regulate the amount of fuel provided to each of the gas burners  100 ,  150 . 
     Heat delivery systems for supplying heat to the tunnel  24  are described generally in U.S. Pat. Nos. 5,277,105, 6,481,433 and 6,655,373, the disclosures of which are incorporated herein by reference insofar as they relate to heat delivery systems for ovens. As shown diagrammatically in  FIG. 4  by way of example, the heat source for the conveyor oven  20  includes a pair of burners  100 ,  150  with respective heating flames  64 ,  66  supplying heat to respective independent plenums  68 ,  70  associated with segments  20 A and  20 B of the oven  20 . The heated air from the plenums  68 ,  70  is blown into the two oven segments  20 A,  20 B by separate blower fans  72 ,  74  through holes (e.g.,  75  and  77 ) in groupings of metal fingers  76 ,  78  associated with the respective oven segments  20 A,  20 B. The temperature in each tunnel segment  20 A,  20 B is monitored by a temperature sensor  80 ,  82 . The temperature sensors  80 ,  82  can include a thermocouple, a thermistor, or any other type of temperature sensing element. The temperature sensors  80 ,  82  can be positioned in either the tunnel  24  or within the plenums  68 ,  70 , and are connected to the controller  42 . 
     The configuration of the conveyor oven  20  illustrated in  FIG. 4  is presented by way of example only. In this regard, it will be appreciated that the conveyor oven  20  can have any number of tunnel segments  20 A,  20 B (including a single tunnel segment, or three or more tunnel segments), any number of temperature sensors  80 ,  82  located anywhere along the conveyor  22  (whether inside or outside the tunnel  24 ), any number of burners  100 ,  150 , and any number of fingers  76 ,  78 , sets of such fingers  76 ,  78 , or other elements and devices for distributing heated air to desired locations above and/or below the conveyor  22 . Also, although the illustrated conveyor oven  20  has two plenums  68 ,  70 , heated air can instead be produced and moved through the conveyor oven  20  through any other number of plenums, and through appropriate ducts and conduits that are not necessarily identifiable as plenums  68 ,  70 . 
     In some embodiments, the speed of the main blowers  72 ,  74  may be varied at times to reduce the amount of energy used by the conveyor oven  20  during periods of non-activity. To provide control over fan speed in these and other cases, the main blowers  72 ,  74  can be driven by variable-speed electric motors (not shown) coupled to and controlled by the controller  42 . Power can be supplied to each variable-speed motor by, for example, respective inverters. In some embodiments, each inverter is a variable-speed inverter supplying power to the motor at a frequency that is adjustable to control the speed of the motor and, therefore, the speed of each of the main blowers  72 ,  74 . An example of such an inverter is inverter Model No. MD60 manufactured by Reliance Electric (Rockwell Automation, Inc.). By utilizing variable speed motors supplied by power through respective inverters as just described, a significant degree of control over fan speed and operation is available directly via the controller  42  connected to other components of the control system. A similar motor control arrangement can also be used to control the speed of the combustion blower  155  (described in greater detail below), which functions to provide an appropriate level of air to the burners  100 ,  150  for proper combustion of fuel supplied to the burners  100 ,  150 . 
     The main blowers  72 ,  74  described and illustrated herein can be located at any of a variety of locations with respect to the plenums  68 ,  70  of the oven  20 , and can be used to pull and/or push air with respect to the plenums  68 ,  70  and/or the tunnel  24 . For example, in some embodiments, the main blowers  72 ,  74  are positioned and oriented to draw air from the tunnel  24  into one of the plenums  68 ,  70 . The suction caused by the main blowers  72 ,  74  lowers the air pressure in the tunnel  24  and increases the air pressure in the plenums  68 ,  70 , thereby forcing heated air from the plenums  68 ,  70  into the tunnel  24  through the fingers  76 ,  78 . In other embodiments, the main blowers  72 ,  74  are oriented to draw heated air from each of the plenums  68 ,  70  into the tunnel  24  through the metal fingers  76 ,  78 . 
     An example of an orientation and layout of components in a conveyor oven  20  according to the present invention is shown in  FIG. 5 , which is a cross-sectional view of one of the oven segments  20 B shown in  FIG. 4 . With reference to  FIG. 5 , a main blower  74  draws air from the tunnel  24  into the plenum  70 . The air is heated in the plenum  70  and is forced back into the tunnel  24  through the metal fingers  78  due to the increased air pressure in the plenum caused by the main blower  74 . Upper and lower metal fingers  78  extend above and below the conveyor  22  in the tunnel  24 . Holes  77  on the upper and lower metal fingers  78  direct the heated air toward food items  32  that are located on the conveyor  22 , thereby cooking the food items. 
       FIG. 6  illustrates a burner  100  of the oven  20  illustrated in  FIGS. 1-5 . The illustrated burner  100  comprises a housing (e.g., an outer tube  102  as shown in the illustrated embodiment) attached to a mounting plate  104  which closes off the proximal end of the outer tube  102 . The outer tube  102  has a relatively elongated shape as shown in the illustrated embodiment. A smaller diameter venturi tube  106  is located within the outer tube  102 , and has open distal and proximal ends  107 ,  112 . The illustrated venturi tube  106  is generally centered with its longitudinal axis along the longitudinal axis of the outer tube  102 , and is secured in place near its distal end  107  by a venturi support  108  encircling the venturi tube  106  and secured within the inside diameter  109  of the outer tube  102 . 
     With continued reference to the illustrated embodiment of  FIG. 6 , a gas orifice  110  is located in the mounting plate  104 , and is spaced from the proximal open end  112  of the venturi tube  106 . Fuel is provided to the gas orifice  110  from a fuel source through an electronically-controlled modulating fuel valve (not shown). The open proximal end  112  of the venturi tube  106  receives pressurized gas from the gas orifice  110 , and also serves as a primary air inlet to admit a flow of air  115  into the venturi tube  106 . Powered air is supplied from the combustion blower  155  (see  FIG. 3 ) to the outer tube  102  below the venturi support  108 . The combustion blower  155  is coupled to the outer tube  102  in the illustrated embodiment via a conduit  113  leading to the outer tube  102 . 
     The burner  100  illustrated in  FIG. 6  also includes a target  124  with a surface  128  positioned opposite the distal end  107  of the venturi tube  106  and held in place by arms  126 . In some embodiments, the outer tube  102  of the burner  100  is coupled to a flame tube  130 , which can include a number of air openings  132 , thereby supplying further oxygen to the burning gas supporting the flame  134 . 
     The structure of the burner  100  illustrated in  FIG. 6  allows the combustion blower  155  to provide air to the burner flame, enabling a proper mix of fuel and air necessary to achieve an optimal flame. If insufficient air is provided to the burner flame, the flame will not be able to burn the fuel, and may extinguish itself. If too much air is provided, the flame will lift off of the burner, and may extinguish. Therefore, the speed of the combustion blower  155  can be modulated to optimize the flame. 
     However, the speed of the combustion blower  155  is not the only variable that can affect the efficiency of the flame. The flame can also be adversely (or positively) affected by the speed of the main blowers  72 ,  74 . For example, in some embodiments, the speed of the main blowers  72 ,  74  can be adjusted to save energy during operation of the oven—a change that can affect the efficiency of the flame. In the illustrated embodiment, the photosensor  79 ,  81  can be used to detect whether a food item has been placed on the conveyor  22  (see step  300  of  FIG. 7 ). If a food item is detected, a timer is reset (step  305 ), the speed of the main blower  72 ,  74  is increased (e.g., set to high in step  310 ), and the setpoint temperature of the oven is also increased (e.g., the output of the modulating fuel valve is set to high in step  315 ). If no food item is detected on the conveyor and the timer exceeds a predefined threshold (step  320 ), the speed of the main blower  72 ,  74  is set to a lower energy-savings mode (step  325 ), and the temperature of the oven can be either decreased to a lower “energy-savings” set-point temperature (step  330 ) or maintained at the original set-point temperature. Additional and more detailed conveyor oven operations associated with such energy-savings modes are described in International Patent Application No. PCT/2009/030727, the entire disclosure of which is incorporated herein by reference. 
     When the timer illustrated in  FIG. 7  expires, the amount of air provided to the burner  100 ,  150  can be automatically decreased as the speed of the main blower  72 ,  74  is decreased. Similarly, when a food item is later detected on the conveyor  22 , the amount of air provided to the burner  100 ,  150  can be automatically increased as the speed of the main blower  72 ,  74  is increased. Either transition can adversely affect the quality of the burner flame, absent other adjustment of airflow provided to the burner  100 ,  150 . 
     The temperature of the oven can also affect the rate at which air is circulated through the oven, independent or at least partially independent of the speed of the main blowers  72 ,  74 . As the air increases in temperature, the air becomes less dense. Therefore, suction from one oven chamber to another (e.g., suction from an oven plenum to the tunnel, or vice versa) can gradually reduce as air temperature at different locations within the oven  20  increases or decreases. For example, as air temperature within the tunnel  24  of the oven  20  increases in the illustrated embodiment, air pressure within the tunnel  24  increases, thereby reducing the ability of air to move from the burners  100 ,  150  into the tunnel  24 . Accordingly, increased air supply to the burners  100 ,  150  can be needed in order to maintain an optimal flame. 
     To address the changing needs of air supply to the burners  100 ,  150  based at least upon changes in main blower speed  72 ,  74 ,  FIG. 8  illustrates a method of controlling the conveyor oven  20  based upon the speed of the main blowers  72 ,  74 . The conveyor oven  20  described above in connection with  FIG. 4  is divided into two segments in which blower speed and burner output are controlled separately. As such, the method illustrated in  FIG. 8  is described by way of example only in reference to controlling the components associated with the first oven segment  20 A of the conveyor oven  20 . However, the method can also or instead be applied to any other segment of a conveyor oven, including in ovens that are not divided into separate oven segments. 
     With continued reference to  FIG. 8 , the controller  42  begins by monitoring the temperature sensor  80  (see  FIG. 4 ) and measuring the oven temperature (step  801 ). If the actual temperature in the oven  20  is greater than the set-point temperature (step  803 ), the controller  42  decreases the flow rate of the modulating fuel valve (step  805 ) thereby decreasing the amount of fuel provided to the burner and decreasing the strength of the burner flame. Conversely, if the actual temperature in the oven  20  is less than the set-point temperature, the controller  42  increases the flow rate of the modulating fuel valve (step  807 ) thereby increasing the amount of fuel provided to the burner and increasing the strength of the burner flame. 
     As described above in reference to  FIG. 7 , the controller  42  can operate the main blower  72  to run the main blower  72  at a high-speed or lower-speed setting (and in some embodiments, at a number of other speeds or in any of a range of speeds). Therefore, in this embodiment, the controller  42  acts as a “feed-forward” system, and is able to determine the speed of the main blower  72  (step  809 ) without necessitating any additional sensor equipment. In other embodiments, a pressure sensor can be positioned adjacent or otherwise with respect to the main blower  72 , or a motor speed sensor can be used to directly measure the speed of the main blower  72  (i.e., a “feedback” system). 
     At this point, the controller  42  in the illustrated embodiment has already determined the internal temperature in the oven  20 , the flow rate of the modulating fuel valve, and the speed of the main blower  72  (or these values are otherwise known or set). The controller  42  then uses this information to determine an appropriate speed for the combustion blower  155  (step  811 ). This determination can be reached in a number of different manners. In some embodiments, the controller  42  accesses a computer readable memory which stores a look-up table. As illustrated in  FIG. 9 , the look-up table identifies a series of combustion blower speeds based upon oven temperature and main blower speed. For example, if the oven temperature is measured as 290 degrees and the controller  42  is operating the main blower  72  at a high-speed setting, the look-up table defines Y 5  as the appropriate combustion blower speed. Similarly, if the oven temperature is measured as  260  degrees and the controller  42  is operating the main blower  72  at the low-speed setting, the look-up table identifies X 2  as the appropriate combustion blower speed. 
     The values of variables X 1  through X 11  and Y 1  through Y 11  will vary depending upon the size, shape, and configuration of the conveyor oven  20  and, therefore, can be specific to each conveyor oven model utilizing such a look-up table. Furthermore, some embodiments of the look-up table can include additional variables that affect the identified combustion blower speed. For example, in some look-up tables, the combustion blower speed setting can be based upon oven temperature, main blower speed, and the flow rate of the modulating fuel valve associated with the burner. 
     In other embodiments, the controller  42  determines the appropriate combustion blower speed by calculating a value. By way of example only, the value can be calculated by the controller based at least in part upon the following formula: 
       Combustion Blower Speed=( A ×Gas Flow Rate)−( B ×Main Blower Speed)+( C ×Oven Temperature)
 
     or by the following alternate formula: 
       Combustion Blower Speed=( A ×Gas Flow Rate)−( B ×Main Blower Speed)
 
     or by the following alternate formula: 
       Combustion Blower Speed=( A ×Gas Flow Rate)+( C ×Oven Temperature)
 
     wherein A, B, and C are coefficients determined at least in part upon the size, shape, and configuration of the conveyor oven  20  and components of the conveyor oven  20 , such as the size and/or shape of the plenum  68 ,  70 , the position of the combustion blower  155  with respect to the fingers  76 ,  78  and the plenum  68 ,  70 , and the like. 
     With continued reference to  FIG. 8 , after the controller  42  has determined an appropriate speed for the combustion blower  155  (step  811 ), the controller  42  proceeds to operate the combustion blower  155  at that speed (step  813 ). The controller  42  can repeat the method illustrated in  FIG. 8  periodically to continue to adjust the internal temperature of the conveyor oven  20  toward a set-point temperature while maintaining optimal flame conditions. 
     The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims. For example, although a specific type of burner is described above in connection with ovens according to the present invention, the invention can be applied to any type of gas burner system having other types of burners. As another example, the conveyor oven  20  can have any number of combustion blowers  155  corresponding to any number of burners  100 ,  150 , and can have any number of main blower fans  72 ,  74 , all of which can be located anywhere in the oven  20 . In such embodiments, the CPU  650  can control operation of the gas burners  100 ,  150 , the combustion blowers  155 , and/or the blower fans  72 ,  74  independently with respect to one another or with respect to other components of the conveyor oven  20 , or otherwise.