Patent Publication Number: US-2021164650-A1

Title: Convection conveyor oven manifold and damper system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation of U.S. patent application Ser. No. 16/218,294, filed on Dec. 12, 2018, published as U.S. Publication No. 2019-0113229 A1 on Apr. 18, 2019, which is a continuation-in-part of International Patent Application No. PCT/US2017/037540, filed on Jun. 14, 2017, published as International Publication No. WO 2017/218695 on Dec. 21, 2017, which claims priority to U.S. provisional patent application No. 62/350,134 filed on Jun. 14, 2016, and to U.S. provisional patent application No. 62/445,141 filed on Jan. 11, 2017, the entire contents of each of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments of the present disclosure relate to gas and heat delivery systems, and particularly to gas manifolds for heat delivery systems suitable for use in convection conveyor ovens, and methods of controlling gas flow in such heat delivery systems. 
     BACKGROUND 
     A convection conveyor oven is a convection oven with a conveyor that moves through a heated tunnel in the oven. Convection conveyor ovens are widely used for baking food products, such as pizzas and baked sandwiches. Examples of such ovens are shown, for example, in U.S. Pat. Nos. 5,277,105, 6,481,433, 6,655,373, 8,087,407, and 8,839,714, the entire contents of each of which are hereby incorporated by reference. 
     Convection conveyor ovens typically have at least one large metallic housing with a heated tunnel extending through the housing and a conveyor running through the tunnel. Such convection conveyor ovens may be either 70 inches or 55 inches long, although they may be constructed in any suitable size. The conveyor transports food products through the heated oven tunnel at a speed which bakes the food during transit through the tunnel. Such convection conveyor ovens often include a heat delivery system including blowers which supply heated air to the cooking tunnel from a plenum through passageways leading to metal fingers or ducts opening into the oven tunnel at locations above and below the conveyor. The metal fingers act as airflow channels that deliver streams of hot air which impinge upon the surfaces of the food products passing through the tunnel on the conveyor. A microprocessor-driven control panel generally enables the user to regulate the heat, the speed of the conveyor, etc., to properly bake the food product being transported through the oven. 
     The conveyor can be set at a speed calculated to properly bake selected food products on the belt during the time period required for the conveyor to carry the food through the entire length of the oven tunnel during a full baking or cooking cycle. If less than the set full baking or cooking cycle is required for a particular type of food product and it is not desired to change the conveyor speed, the food products may be placed on the conveyor at a point partially through the oven so that they travel only a portion of the length of the tunnel, or can be placed on the conveyor moving at a faster speed through the tunnel. Alternatively, the conveyor speed can often be varied to accommodate the particular baking or cooking cycle for a selected food product. A sandwich is an example of a product which might require only a portion of the full baking time of a pizza. 
     Convection conveyor ovens are typically used in restaurant and other types of commercial and institutional kitchens and commercial food preparation and manufacturing facilities. Often such ovens are kept running for extended periods of time, including periods when products are not being baked. Since the inlet and outlet ends of the oven are open, heat and noise are continuously escaping from the conveyor oven tunnel into the surrounding environment. This escape of heat wastes energy, and also warms the surrounding environment —usually unnecessarily and often to uncomfortable levels. This is particularly the case where the conveyor oven is being used in relatively cramped restaurant kitchen environments. The escaping noise is also undesirable since it may interfere with interpersonal communication among those working near the oven. 
     Some convection conveyor ovens may also provide users with limited ability to reduce energy losses while running at less than full capacity. Users may only have the ability to turn such ovens on or off, which in many cases involves unacceptably long shut-down and/or start-up times. Therefore, it is necessary to leave such ovens on despite the waste of fuel or other energy supplied to the ovens when cooking food intermittently. It is not uncommon for a convection conveyor oven to be left running in a full production mode for substantially the entire period of time a restaurant or other cooking facility is open. 
     It is often desirable to maintain uniform heating from one end of the heated tunnel of the oven to the other. However, in other applications it is instead desirable to be able to control the delivery of heat at different points or sections along the conveyor, such as to control the temperature or quantity of heat delivered to an upstream portion of the tunnel independently of the temperature or quantity of heat delivered to a downstream portion of the tunnel. Among the challenges to be overcome in achieving uniform or localized heating control along the tunnel are the inherent variations in heating from oven to oven due to variations in the external environment of otherwise identical ovens. A more significant challenge to maintaining uniform or localized heating control through the length of the heated tunnel is the constantly changing physical and thermal configuration of the tunnel as food products being baked pass from one end of the tunnel to the other. For example, raw pizzas entering the inlet to the tunnel constantly change the physical and thermal configuration of the tunnel environment as they advance to the other end while drawing and emitting ever-varying amounts of heat. As a result, temperatures can vary significantly from one end of the tunnel to the other. 
     A very common technique for thermal control along the tunnel of conventional convection conveyor ovens involves monitoring temperatures near the inlet and outlet ends of the heated tunnel to maintain a predetermined average temperature over the length of the tunnel. Thus, for example, as a cold raw pizza enters the inlet to the tunnel causing a sudden drop in the tunnel temperature at the inlet, the drop in temperature is sensed and more heat is supplied to the tunnel to raise the temperature near the inlet heat sensor. Unfortunately, this also raises the temperature at the outlet of the oven, which causes the heat sensor at the outlet to trigger a heating reduction to prevent an excessive temperature at the oven outlet. In this way, temperature sensors near the inlet and outlet of the oven help to balance the heating of the tunnel to generally maintain a target average temperature. 
     However, uniform heating through the length of the heated tunnel may be difficult to achieve in this way. Thus, food products traveling through the oven do not see uniform heating which, it has been discovered, makes it necessary to slow the conveyor to a speed which completes the baking in more time than would be the case if uniform heating could be achieved throughout the length of the heated tunnel. In other words, improved heating uniformity from one end of the tunnel to the other may reduce required baking times. 
     Additionally, in many applications it is necessary to be able to operate the convection conveyor oven using either side as the inlet, by running the conveyor belt either from left-to-right for a left side inlet, or from right-to-left for a right side inlet. To be most successful in such interchangeable applications, it is particularly desirable to produce a uniform temperature from one end of the heated tunnel to the other. 
     Even in those convection conveyor ovens in which thermal control along different portions of the tunnel is possible, such control is limited by each individual burner&#39;s range of heat output. For example, relatively low or relatively high burner BTU output can generate problems associated with poor combustion. Low burner BTU output may generate incomplete combustion products such as carbon monoxide (CO) production and flame lift-off. To address these problems, when the oven is operating at a lower temperature, one or more of the burners may be turned off so that the remaining burners may function at a higher BTU output so that the remaining burners may burn more efficiently. The ability to independently control the gas supply to burners or sets of burners remains limited in many convection conveyor ovens. In addition, conventional gas supply systems needed for such control are often complex, expensive, and difficult to install, remove, and service. 
     In convection conveyor ovens, the burners that heat the tunnel or the multiple tunnel segments are typically positioned within a shared burner housing or burner box. Heat exchange tubes are in fluid communication with the burners in the burner housing to provide heated air to a plenum and to a cooking chamber. In convection conveyor ovens having multiple burners that may be controlled independently of each other, heat exchange tubes positioned near burners that are turned off may pull relatively cool external air through the heat exchange tubes and into the plenum, reducing the temperature of the air supplied to the plenum and reducing the effectiveness of the burners at supplying heated air to the plenum. 
     SUMMARY 
     Some embodiments of the present disclosure provide a gas manifold for a convection conveyor oven, wherein the manifold comprises an enclosed housing having at least one continuous wall defining an interior volume of the housing, wherein the interior volume comprises a first chamber and a second chamber, and wherein the first chamber is in selective fluid communication with the second chamber; and a gas inlet in fluid communication with the first chamber; wherein a plurality of gas outlets are disposed in the at least one continuous wall, with at least one of the gas outlets positioned to discharge gas from the first chamber, and at least another of the gas outlets positioned to discharge gas from the second chamber. 
     In some embodiments, a gas manifold for a convection conveyor oven is provided, and comprises a housing constructed of a single seamless integral body and defining a longitudinal axis, wherein the housing has a first end and a second opposite end spaced from the first end along the longitudinal axis; a first chamber and a second chamber defined by the housing, wherein the second chamber is in fluid communication with the first chamber and the first and second chambers are disposed between the first end and second end of the housing; a gas inlet in fluid communication with the first chamber, wherein the gas inlet is spaced from the second chamber along the longitudinal axis; and a first valve in fluid communication with the first chamber and the second chamber, wherein the first valve is operable to selectively control the flow of gas from the first chamber to the second chamber, wherein the housing defines a plurality of gas outlets spaced along the longitudinal axis, and wherein at least one of the gas outlets is positioned to discharge gas from the first chamber and at least another of the gas outlets is positioned to discharge gas from the second chamber. 
     Some embodiments of the present disclosure provide a gas manifold for a convection conveyer oven, wherein the manifold comprises a housing constructed of a single seamless integral body and defining an elongated interior space for receiving gas, wherein the elongated interior space has (i) a longitudinal axis, and (ii) a first end and a second opposite end spaced from the first end along the longitudinal axis; a gas inlet in fluid communication with the interior space, wherein the gas inlet is spaced from at least one of the first end and the second end of the interior space along the longitudinal axis; a plurality of gas outlets defined by the housing, wherein the plurality of gas outlets are positioned along the longitudinal axis between the first end and the second end of the interior space to discharge gas from the interior space; and a first valve in fluid communication with the inlet and at least one of the gas outlets, wherein the gas inlet and at least one of the gas outlets are positioned upstream of the first valve, and wherein the first valve has a first state in which gas received through the gas inlet is supplied to all of the gas outlets, and a second state in which gas received through the gas inlet is supplied to less than all of the gas outlets. 
     In some embodiments, a gas manifold for a convection conveyor oven is provided, and comprises a housing having a continuous wall defining an interior space of the housing; a gas inlet in communication with the interior space; a plurality of gas outlets spaced apart from one another along the continuous wall; and a first valve positioned downstream of the gas inlet and at least one of the gas outlets, the first valve having a first state in which gas received through the gas inlet is supplied to all of the gas outlets, and a second state in which gas received through the gas inlet is supplied to less than all of the gas outlets, wherein the housing and the first valve define a single integral unit. 
     Some embodiments of the present disclosure provide a gas manifold for a convection conveyor oven, wherein the manifold comprises a housing having a wall with a plurality of sides collectively defining an interior space of the housing; a gas inlet defined in one side of the plurality of sides and in communication with the interior space; a plurality of gas outlets spaced apart from one another along one continuous side of the plurality of sides; and a first valve positioned downstream of the gas inlet and at least one of the gas outlets, the first valve having a first state in which gas received through the gas inlet is supplied to all of the gas outlets, and a second state in which gas received through the gas inlet is supplied to less than all of the gas outlets, wherein the housing and the valve are configured to be mounted and installed in the oven as a single integral unit with the gas inlet. 
     In some embodiments, a gas manifold for a convection conveyor oven is provided, wherein the manifold is in fluid communication with a gas supply line, and wherein the manifold comprises an enclosed housing having a continuous wall defining an interior volume of the housing, wherein the interior volume comprises a first chamber and a second chamber and each chamber is in fluid communication with the gas supply line; a plurality of gas outlets disposed in the at least one continuous wall, with at least one of the gas outlets positioned to discharge gas from the first chamber, and at least another of the gas outlets positioned to discharge gas from the second chamber; a shut off valve in fluid communication with the gas supply line and the first chamber; and a variable flow valve in fluid communication with the gas supply line and the second chamber. 
     Some embodiments of the present disclosure provide a method of connecting a gas supply line to burners of a convection conveyor oven, wherein the method comprises orienting, as a single integral unit, a gas manifold assembly with respect to a gas supply line and a mounting location on the oven, the gas manifold assembly comprising a housing having a plurality of walls collectively defining an interior space of the housing, a gas inlet, a plurality of gas outlets, and a valve; mounting the gas manifold assembly at the mounting location as the single integral unit; connecting the gas inlet of the gas manifold assembly to the gas supply line; connecting each gas outlet of the manifold assembly to at least one of the burners of the oven via gas conduits; simultaneously supplying gas through the inlet and through all of the outlets of the gas manifold assembly to the burners of the oven; and reducing gas supply through the valve to at least one of the outlets of the gas manifold assembly while continuing to supply gas to another of the outlets. 
     In some embodiments, a gas manifold for a convection conveyor oven connectable to a gas supply is provided, and comprises a housing defining a longitudinal axis and a continuous wall extending along the longitudinal axis, wherein the housing has a first end and a second opposite end spaced from the first end along the longitudinal axis; a first chamber and a second chamber defined by the housing, wherein the first chamber and second chamber are disposed between the first end and second end of the housing; a first gas inlet in fluid communication with the gas supply and the first chamber; a first valve in fluid communication with the gas supply and the first gas inlet, wherein the first valve is operable to selectively control the flow of gas from the gas supply to the first chamber; and a second gas inlet in fluid communication with the gas supply and the second chamber, wherein the housing defines a plurality of gas outlets spaced along the continuous wall, and at least one of the gas outlets is positioned to discharge gas from the first chamber and at least one of the gas outlet is positioned to discharge gas from the second chamber, and wherein the valve has a first state in which gas is supplied to all of the gas outlets, and a second state in which gas is supplied to less than all of the gas outlets positioned. 
     Some embodiments of the present disclosure provide a gas manifold for a convection conveyer oven connectable to a gas supply, wherein the manifold comprises a housing defining an elongated interior space for receiving gas, wherein the elongated interior space has (i) a longitudinal axis, (ii) a continuous wall extending along the longitudinal axis, and (iii) a first end and a second opposite end spaced from the first end along the longitudinal axis; a first gas inlet in fluid communication with the interior space; a second gas inlet in fluid communication with the interior space, wherein the second gas inlet is spaced from the first gas inlet along the longitudinal axis; a plurality of gas outlets defined by the housing spaced along the continuous wall between the first end and the second end of the interior space to discharge gas from the interior space; and a first valve in fluid communication with the gas supply, the first gas inlet, and the gas outlets, wherein the first valve has a first state in which gas is supplied to all of the gas outlets, and a second state in which gas is supplied to less than all of the gas outlets. 
     In some embodiments, a gas manifold for a convection conveyor oven is provided, wherein the gas manifold is selectively in fluid communication with a gas supply, and wherein the gas manifold comprises an elongate housing including a longitudinal axis and a plurality of sidewalls that extend between a first end wall and a second end wall, the plurality of sidewalls, the first end wall, and the second end wall cooperatively defining an elongated interior volume extending along the longitudinal axis; a gas inlet in fluid communication with the interior volume, the gas inlet extending through one of the sidewalls; a plurality of gas outlets in fluid communication with the interior volume, the plurality gas outlets extending through one of the sidewalls and spaced apart along the longitudinal axis; and a valve at least partially positioned within the interior volume, the valve having a first position in which all of the gas outlets are in fluid communication with the inlet and a second position in which one of the gas outlets is not in fluid communication with the inlet. 
     Some embodiments of the present disclosure provide a convection conveyor oven comprising a plurality of gas burners configured to supply heated air to a cooking chamber, wherein the plurality of gas burners is in fluid communication with a gas manifold, the gas manifold extending along a longitudinal axis and including an elongate interior volume in fluid communication with a gas inlet and a plurality of gas outlets, the gas manifold including a valve to selectively block gas flow to at least one of the plurality of gas outlets; a plenum in fluid communication with the plurality of gas burners; a blower in fluid communication with the plenum and the cooking chamber; and wherein the air heated by the plurality of burners flows through the plenum and the blower to the cooking chamber. 
     In some embodiments, a convection conveyor oven is provided, and comprises a plurality of gas burners configured to supply heated air to a cooking chamber, wherein the plurality of gas burners is in fluid communication with a gas manifold, the gas manifold including an elongate interior volume in fluid communication with a gas inlet and a plurality of gas outlets, the gas manifold including a valve positioned downstream of the inlet and at least one of the plurality of gas outlets and upstream of at least one of the plurality of gas outlets, the valve having a first position in which gas flows to all of the plurality of gas outlets and a second position in which gas does not flow through the at least one gas outlet positioned downstream of the valve; a plurality of heat exchange tubes, each of the plurality of heat exchange tubes in fluid communication with a respective outlet of each of the plurality of burners; a burner housing in fluid communication with the plurality of burners and the plurality of heat exchange tubes; and a damper positioned proximate an inlet of a heat exchange tube aligned with a burner in fluid communication with a gas outlet positioned downstream of the valve, the damper having a first position in which the heat exchange tube is in fluid communication with the housing and a second position in which the heat exchange tube is not in fluid communication with the housing. 
     In some embodiments, a gas manifold for a convection conveyor oven is provided, the gas manifold comprising an elongated housing defining a longitudinal axis and an interior volume extending along the longitudinal axis, the elongated housing having a wall that at least partially encloses the interior volume; a gas inlet in fluid communication with the interior volume, the gas inlet extending through the wall; a plurality of gas outlets in fluid communication with the interior volume, the plurality gas outlets extending through the wall and spaced apart along the longitudinal axis; a plurality of seat inserts, wherein each one of the plurality of seat inserts is removably coupled with one of the plurality of gas outlets; a plurality of valve openings formed in the wall and spaced along the longitudinal axis, wherein each one of the valve openings is aligned opposite one of the plurality of gas outlets; and at least one valve removably coupled to the wall and aligned with a first valve opening of the plurality of valve openings, wherein the at least one valve is aligned with a first gas outlet of the plurality of gas outlets, and wherein the at least one valve has a first position in which a first seat insert of the plurality of seat inserts is not in fluid communication with the gas inlet. 
     In some embodiments, a gas manifold for a convection conveyor oven is provided, the gas manifold comprising an elongated housing defining a longitudinal axis and an interior volume extending along the longitudinal axis, the elongated housing having a wall that at least partially encloses the interior volume; a gas inlet in fluid communication with the interior volume, the gas inlet extending through the wall; a plurality of gas outlets in fluid communication with the interior volume, the plurality gas outlets extending through the wall and spaced apart along the longitudinal axis; a seat insert removably coupled with a first gas outlet of the plurality of gas outlets and having a passageway to discharge gas from the interior volume; an injector coupled with the seat insert and in fluid communication with the passageway; and a plug removably coupled with a second gas outlet of the plurality of gas outlets, wherein the plug and the seat insert are configured to be interchangeably received in the first and second gas outlets. 
     In some embodiments, a gas manifold for a convection conveyor oven is provided, the gas manifold comprising an elongated housing defining a longitudinal axis and an interior volume extending along the longitudinal axis, the elongated housing having a wall that at least partially encloses the interior volume; a gas inlet in fluid communication with the interior volume, the gas inlet extending through the wall; a plurality of gas outlets in fluid communication with the interior volume, the plurality of gas outlets extending through the wall and spaced apart along the longitudinal axis; a seat insert removably coupled with a first gas outlet of the plurality of gas outlets and having a passageway to discharge gas from the interior volume; an injector coupled with the seat insert and in fluid communication with the passageway; a plug removably coupled with a second gas outlet of the plurality of gas outlets, wherein the plug and the seat insert are configured to be interchangeably received in the first and second gas outlets; a plurality of valve openings formed in the wall and spaced along the longitudinal axis, wherein each of the plurality of valve openings is aligned opposite one of the plurality of gas outlets; and a valve removably coupled to the wall and aligned with a first valve opening of the plurality of valve openings, wherein the valve has a first position in which the seat insert is not in fluid communication with the gas inlet. 
     Further aspects of the present disclosure, together with the organization and operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure are shown in the attached drawings, in which: 
         FIG. 1  is a perspective view of a conveyor oven in accordance with an embodiment of the present disclosure; 
         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 a compartment for housing internal workings (not shown) of the oven; 
         FIG. 3  is a schematic illustration of an embodiment of the control system of the conveyor oven of  FIG. 1 ; 
         FIG. 3A  is a schematic illustration of an embodiment of the control system of the oven of  FIG. 1 ; 
         FIG. 4  is a diagrammatic representation of the tunnel of the oven of  FIG. 1 , apportioned into two segments with independent temperature sensing and independent heat delivery systems; 
         FIGS. 5A-5C  include a diagrammatic representation of a pizza moving through the heated tunnel of the conveyor oven of  FIG. 1 , with graphs showing changing heat output and blower output as the pizza advances through the tunnel; 
         FIG. 6  is a flowchart illustrating an exemplary energy management mode for the conveyor oven of  FIG. 1 . 
         FIG. 7  is flowchart illustrating another exemplary energy management mode for the conveyor oven of  FIG. 1 . 
         FIG. 8  is a perspective view of an exemplary embodiment of a gas manifold with some parts depicted as translucent to reveal other parts. 
         FIG. 8A  is a front perspective view of the gas manifold of  FIG. 8 . 
         FIG. 8B  is a rear perspective view of the gas manifold of  FIG. 8 . 
         FIG. 9  is another perspective view of the gas manifold of  FIG. 8 , shown connected to a gas supply conduit and valves. 
         FIG. 10  is top view of the gas manifold of  FIG. 8  with some parts depicted as translucent to reveal other parts. 
         FIG. 11  is a side view of the gas manifold of  FIG. 8 , shown with the supply conduit and valves illustrated in  FIG. 9 . 
         FIG. 12  is a schematic diagram of one embodiment of a gas manifold shown connected to a gas supply conduit and valves. 
         FIG. 13  is a schematic diagram of another embodiment of a gas manifold shown connected to a gas supply conduit and valves. 
         FIG. 14  is a schematic diagram of yet another embodiment of a gas manifold shown connected to a gas supply conduit and valves. 
         FIG. 15  is a perspective view of yet another embodiment of a gas manifold. 
         FIG. 16  is a section view of the gas manifold of  FIG. 15  taken along line  16 - 16  with some parts depicted as translucent to reveal other parts. 
         FIG. 17  is a perspective view of another embodiment of a gas manifold. 
         FIG. 18  is a perspective section view of the gas manifold of  FIG. 17  taken along line  18 - 18  and showing the manifold valve in an open position. 
         FIG. 19  is a section view of the gas manifold of  FIG. 17  taken along line  18 - 18  and showing the manifold valve in an intermediate position. 
         FIG. 20  is a section view of the gas manifold of  FIG. 17  taken along line  18 - 18  and showing a manifold valve in a closed position. 
         FIG. 21  is a perspective view of the manifold of  FIG. 17  engaged with a plurality of burners. 
         FIG. 22  is a perspective view of a burner support housing engaged with a manifold, a plurality of burners, and a plurality of heat exchange tubes. 
         FIG. 23  is a perspective view of a slide mechanism engaged with the burner support housing of  FIG. 22  according to one embodiment. 
         FIG. 24 a    is a perspective view of the slide mechanism of  FIG. 23  in a closed position and engaged with the support burner housing of  FIG. 22 , with some parts made translucent to reveal other parts. 
         FIG. 24 b    is a perspective view of the slide mechanism of  FIG. 23  in an open position and engaged with the support burner housing of  FIG. 22 , with some parts made translucent to reveal other parts. 
         FIG. 25  is a section view of the slide mechanism engaged with the burner support housing of  FIG. 24 a   , taken along line  25 - 25 . 
         FIG. 26  is a perspective view of a slide mechanism engaged with the burner support housing of  FIG. 22 , shown in an open position according to an alternative embodiment. 
         FIG. 27  is a perspective view of the slide mechanism of  FIG. 26 , shown in the closed position. 
         FIG. 28  is a flowchart illustrating an exemplary slide mechanism control logic for the conveyor oven of  FIG. 22 . 
         FIG. 29  is a left perspective view of another embodiment of a gas manifold. 
         FIG. 30  is a right perspective view of the gas manifold of  FIG. 29 . 
         FIG. 31  is a bottom perspective view of the gas manifold of  FIG. 29 . 
         FIG. 32  is a partially exploded bottom perspective view of the gas manifold of  FIG. 29 . 
         FIG. 33  is a section view of the gas manifold of  FIG. 29  taken along line  18 - 18  and showing a plurality of manifold valve each in a closed position. 
         FIG. 34  is a side view of the gas manifold of  FIG. 29  engaged with a plurality of burners. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the 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 accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     Conveyors 
       FIG. 1  shows a convection conveyor oven  20  having a conveyor  22  which runs through a heated tunnel  24  of the oven. The 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 or first oven end  26  toward right or second oven end  28  or, alternatively in direction B, from second oven end  28  toward first oven end  26 . Thus, oven ends  26  and  28  may serve respectively as the inlet and outlet of an oven with a conveyor moving from the first to the second end or as the outlet and inlet of an oven with a conveyor moving from the second to the first end. 
     The support, tracking and drive of conveyor  22  are achieved using conventional techniques such as those described in U.S. Pat. Nos. 5,277,105 and 6,481,433 and 6,655,373, the entire contents of each of which are incorporated herein by reference, including for their teachings of conveyor support, tracking and drive elements and methods. In the illustrated embodiment, a chain link drive is housed within a compartment at the left end  26  of the oven. Thus, a food product, such as a raw pizza  32 R, may be placed on the conveyor  22  at the ingoing first oven end  26  and removed from the conveyor  22  as fully baked pizza  32 C (see  FIG. 5C ) at the outgoing second 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 fully cooked pizza  32 C is properly baked. 
     Normally only one conveyor is used, as shown. However, certain specialized applications may make two or more conveyors a preferable design. For example, a first conveyor may begin at first oven end  26  and travel at one speed to the center or other location of the oven  20 , while a second conveyor beginning at the center or other location and ending at the second oven end  28  may travel at a different speed. Alternatively, conveyors that are split longitudinally may be used, so that one conveyor carries a product in direction A while the other conveyor carries a product in direction B, or so that two side-by-side conveyors carry product in parallel paths and in the same direction (A or B) through the oven  20 . This enables one product to travel on the conveyor at one speed to bake one kind of product and the other conveyor to travel on the other conveyor at a different speed to bake another kind of product. In addition, three or more side-by-side conveyors can carry product in parallel paths through the oven  20 . 
     Access 
     With reference to  FIG. 1 , a hinged door  34  is provided on the front of the oven  20 , with a heat resistant glass panel  36  and a handle  35  so that a person operating the oven can view food product as it travels through the oven  20 . 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 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 an intermediate position on the conveyor  22  if less than a full bake cycle is required to produce a fully cooked product. 
     A hinged oven access panel  38  is also provided, open as shown in  FIG. 2 , to expose inner workings and controls of the oven  20 , including, for example, a gas manifold  100  as shown in  FIGS. 3A, 4, 8-12 and 15-16 , gas manifold  100 ′ as shown in  FIG. 13 , gas manifold  100 ″ as shown in  FIG. 14 , gas manifold  214  as shown in  FIGS. 17-21 , gas manifold  514  as shown in  FIGS. 29-34 , and described in greater detail below. As explained in more detail below, in some embodiments the hot air blowers and ducts, their associated components, and/or the temperature sensors of the oven  20  can be located within the area revealed by the opened access panel  38 . 
     Oven Controls 
       FIG. 3  shows a schematic illustration of the control system for the oven  20 . A microprocessor-based main controller  42  may include a central processing unit (“CPU”)  650 , and a user interface that can include one or more displays  655  and/or controls  660 . The CPU  650  can control a plurality of devices including one or more burners  60 ,  62  (including associated blower switches, ignition switches and blowers, fuel valves, and flame sensing elements), one or more fans  72 ,  74  (described in greater detail below), and one or more conveyors  22 . The CPU  650  may also receive input from a plurality of sensors including one or more temperature sensors  80 ,  82 ,  93 ,  95  and one or more photo sensors  79 ,  81  and/or  83 ,  85  (also described in greater detail below). 
     As shown in  FIG. 3A , in some embodiments the control system includes the main controller  42 , an ignition controller  44 , and a high-limit controller  46 . As will be discussed in greater detail below, the main controller  42  controls the oven temperature, the conveyor  22  speed, and one or more energy savings modes, and communicates with the ignition controller  44  to open a main control valve  48  in preparation for cooking, and to close the main control valve  48  when burner operations are no longer needed. The main control valve  48  is the gas valve that supplies gas to the oven  20  from an external source. 
     The ignition controller  44  operates a spark igniter to ignite the burners  60 ,  62  and is controlled by the main controller  42 . When the ignition controller  44  is turned on by the main controller  42 , the ignition controller  44  opens the main control valve  48  and signals the igniter to ignite the burners  60 ,  62 . Reference to burners  60 ,  62  should be understood to include all of the manifold embodiments described herein and their associated burners. A flame sensor  50  monitors burners  60 ,  62  to ensure that the burners  60 ,  62  remain lit. If the burners  60 ,  62  go out or cannot be ignited after a designated number of attempts (e.g., three attempts), the ignition controller  42  can enter a lockout mode in which the main control valve  48  is closed, and stops flow of gas to a manifold  100 . In some embodiments, once in the lockout mode, the ignition controller  44  cannot be restarted until the main controller  42  cuts power to the ignition controller  44  and then reapplies power to the ignition controller  44 . 
     The high-limit controller  46  monitors the temperature within the oven&#39;s heated tunnel or cooking chamber  24  through a high-limit thermocouple  49 , and in some embodiments is independent of the main controller  42 . If the temperature of the oven  20  exceeds a predetermined maximum temperature, in some embodiments the high-limit controller  46  opens a master power switch  51  of the oven  20  to cut off power supply to the entire oven  20 , turning off the burners  60 ,  62  and some or all of the oven components. 
     Tunnel Segments 
     Heat delivery systems for supplying heat to the tunnel  24  are described in U.S. Pat. Nos. 5,277,105, 6,481,433 6,655,373, 8,087,407, and 8,839,714, the entire disclosures of each of which are incorporated herein by reference, including for their teachings of heat delivery systems and methods. These systems typically include a heat source in the form of one or more gas-fired burners  60 ,  62  (or other heat source such as an electric heating element) for heating a plenum. For example, the burners  60 ,  62  can be located at the front of the oven for heating a plenum located at the back of the oven. Blowers  72 ,  74  are typically provided to move heated air in the plenum through passageways to metal fingers that open into the oven at appropriate spacing above, below and/or along the conveyor belt to deliver streams of hot air directly heated by the burners  60 ,  62  onto food products present on the conveyor, as discussed earlier. The heat source is cycled on and off or otherwise modulated or varied as necessary by the main controller  42 , which responds to signals from temperature sensors (e.g., thermocouples) positioned, for example, at the ends of the oven tunnel. 
     In some embodiments, a desired heating profile along the tunnel  24  (e.g., uniform heating from one end of the tunnel  24  to the other) is achieved by apportioning the tunnel  24  into two or more segments and by providing independent temperature sensing and independent delivery of heated air to each segment. One example of a multi-segment oven  20  is shown diagrammatically in  FIG. 4 , where the oven  20  has a pair of burners  60  and  62  with respective heating flames  64  and  66  supplying heat to respective independent plenums  68  and  70  associated with segments  20 A and  20 B of the oven  20 . The heated air in plenums  68  and  70  is blown into the two oven segments  20 A,  20 B by separate blower fans  72  and  74  through holes  75  and  77  in groupings of top fingers  76  and  78  (and through holes in corresponding groupings of bottom fingers, not shown) associated with the respective oven segments  20 A,  20 B. Accordingly, the oven  20  uses a single airflow that is heated directly by the gas burners  60 ,  62 , exhausted through heat exchange tubes (not shown) into the independent plenums  68 ,  70 , drawn in by the blower fans  72 ,  74 , and impinged onto the food product through holes  75 ,  77  in the groupings of top fingers  76 ,  78  (and through holes in corresponding groupings bottom fingers, not shown). In other embodiments, the gas burners may be used to heat the air in a single plenum for delivery of convection cooking airflow in tunnel  24 . 
     A number of different types of fans  72 ,  74  can be utilized for supplying heated air within the oven  20 , and can be driven by any type of motor. As will be described in greater detail below, it is desirable in some embodiments to control the speed of fans  72 ,  74  independently based at least in part upon one or more temperatures sensed within the oven  20 , one or more positions of food within, entering, or exiting the oven  20 , and/or the passage of one or more predetermined periods of time. To provide control over fan speed based upon any of these factors, the fans  72 ,  74  can be driven by motors  71 ,  73  coupled to and controlled by the main controller  42 . In some embodiments, the fans  72 ,  74  are driven by variable-speed motors  71 ,  73  coupled to and controlled by the main controller  42 . Power can be supplied to each variable-speed motor  71 ,  73  by, for example, respective inverters. In some embodiments, each inverter is a variable-speed inverter supplying power to the motor  71 ,  73  at a frequency that is adjustable to control the speed of the motor  71 ,  73  and, therefore, the speed of the fan  72 ,  74 . 
     The temperatures in each of the plenums  68 ,  70  or oven tunnel segments  20 A,  20 B can be monitored by temperature sensors (e.g., thermocouples or other temperature sensing elements)  80  and  82 , which are shown in  FIG. 4  as being mounted in the plenums near the inlet end  26  and the outlet end  28  of the oven  20 . Either or both temperature sensors  80 ,  82  can be located in respective plenums  68 ,  70  as shown in the figures. In some alternative embodiments, either or both temperature sensors  80 ,  82  are instead located within segments  20 A,  20 B of the tunnel chamber  24  through which the conveyor  22  moves. In addition to or in place of either or both temperature sensors  80 ,  82 , one or more position sensors  79 ,  81  and/or  83 ,  85  can be located to detect the position of a pizza or any other type of desired food product to be cooked on the conveyor  22 , and to thereby control one or more operations of the oven  20  as a result of such position detection (described in greater detail below). Furthermore, in those embodiments in which the oven  20  is heated by one or more gas burners  60 ,  62 , one or more gas output sensors (not shown) can be positioned to detect the amount of fuel supplied to the oven  20 . This information can be provided to the main controller  42  in order to control one or more operations of the oven  20 , such as to turn a conveyor  22  and/or one or both fans  72 ,  74  on or off, to adjust the speed of the conveyor  22  and/or one or both fans  72 ,  74 , and/or adjust or turn on or off one or both burners  60 ,  62 . 
     The operation of the oven proceeds as shown in  FIGS. 5A-5C , which includes a diagrammatic representation of a pizza moving through the oven tunnel  24  below graphs showing the changing heat output of the burners  60 ,  62  and the corresponding blower output as the pizza advances through the tunnel  24 . Thus, a raw pizza  32 R is shown in  FIG. 5C  resting on the conveyor  22  before the pizza enters the oven tunnel  24 . As the pizza  32  travels through the tunnel  24 , the main controller  42  can monitor conditions of the oven  20  to control the fans  72 ,  74 , gas burners  60 ,  62 , and conveyor  22  ( FIG. 3 ). It is to be understood that pizza is just one example of the type of food product that can be cooked or baked in the convection conveyor ovens disclosed herein, and the embodiments of the described invention are not limited to cooking pizza. 
     For example, the temperature sensor  80  (located in either or both the plenum  68  and cooking tunnel segment  20 A) can be used to detect the presence of a raw pizza  32 R on the conveyor  22 . To illustrate one embodiment of the oven,  FIGS. 5A-5C  follow a single pizza through cooking tunnel  24 . As the raw pizza  32 R enters the oven  20  and approaches position  32 ( 1 ), it draws heat causing sensor  80  ( FIG. 4 ) to call for the main controller  42  to supply additional gas to the burner  60  via the modulating gas valve  53  and/or to increase the speed of either or both fans  72 ,  74 . The main controller  42  can respond to detection of the raw pizza  32 R by increasing the heat output of the burner  60  of the left tunnel segment  20 A, and can also respond to the signal(s) from the position sensor  79 ,  81  by increasing the speed of either or both fans  72 ,  74 . Either response can occur immediately or after a lag time, and can occur relatively abruptly or gradually. 
     As a pizza advances to the right in this figure to position  32 ( 2 ), the pizza is now warmed. Therefore, less heat is drawn by the pizza, and the temperature in the first tunnel segment  20 A rises. In some embodiments, this temperature rise is detected by the temperature sensor  80  of the first plenum  68  or by a temperature sensor in the tunnel segment  20 A, which can signal the controller  42  to reduce the supply of gas to the left burner  60 , thereby producing a reduction in heat output as shown in  FIG. 5B . In these and other embodiments, the main controller  42  can also be triggered to reduce the supply of gas to the left burner  60  by a position sensor positioned in or adjacent the first tunnel segment  20 A to detect when the pizza has advanced to a location in the first tunnel segment  20 A. The position sensor can have any of the forms described above with reference to the position sensor  79 ,  81  at or adjacent the entrance to the left tunnel segment  20 A ( FIG. 4 ). The lowered heat output level can continue for any part or all of the remaining time that the pizza is in the first tunnel segment  20 A (e.g., all of such time as shown in the illustrated embodiment of  FIG. 5B ). 
     Next, the pizza reaches the position  32 ( 3 ) shown in  FIG. 5C , and then passes the midpoint of the tunnel  24  between the two segments  20 A,  20 B. Since the pizza has exited segment  20 A, and there is therefore no further significant perturbation to the heating environment in segment  20 A, the main controller  42  can lower the gas supply (and therefore the heat output) of the left burner  60  to a reduced steady state by controlling the selective control valve  55 . This reduction can be triggered by a threshold temperature change detected by the temperature sensor  80  in the first plenum  68  or tunnel segment  20 A and/or by the temperature sensor  82  in the second plenum  70  or tunnel segment  20 B. Alternatively or in addition, this reduction can be triggered by one or more signals from a position sensor positioned to detect when the pizza has advanced to a location between the first and second tunnel segments  20 A,  20 B (or near such a location). The position sensor can have any of the forms described above with reference to the position sensor  79 ,  81  at or adjacent the entrance to the left tunnel segment  20 A. 
     With continued reference to  FIGS. 5A-5C , the right burner  62  supplies heat to the second tunnel segment  20 B. The sensor  82  corresponding to the second tunnel plenum  70  or tunnel segment  20 B can initially detect a spillover of heat from the first tunnel segment  20 A (i.e., as the pizza enters and is in the first part of the baking process in the first tunnel segment  20 A). Upon detection of sufficient spillover heat (e.g., when the sensor  82  detects that a threshold temperature has been reached), the sensor  82  can trigger the main controller  42  to drop the initial heat output of the right burner  62  by controlling the modulating gas valve  53 . However, when the partially cooked pizza approaches the second tunnel segment  20 B, the pizza draws heat from the second tunnel segment environment. This heat draw can also be detected by the sensor  82  of the second tunnel segment  20 B, which can trigger the main controller  42  to supply additional gas to the burner  62  of the second tunnel segment  20 B by controlling the modulating gas valve  53 . As a result, the heat output of the right burner  62  can increase as the pizza moves to and through positions  32 ( 4 ),  32 ( 5 ), and  32 ( 6 ). Of course, when multiple food items are transported through cooking tunnel  20  in close succession, the heating and overall operating profile of oven  20  will vary from the example shown in  FIGS. 5A-5C . 
     In some embodiments, when the pizza leaves the position  32 ( 6 ) and begins exiting the tunnel  24  with no other food product following on conveyor  22 , the temperature sensor  82  of the second tunnel segment  20 B can detect a rise in the tunnel temperature, and can trigger the main controller  42  to reduce the output of the right burner  62  via the modulating gas valve  53  as shown in the heat output graph of  FIG. 5B . As described above, the speed of fans  72 ,  74  and/or the heat output of burners  60 ,  62  can be controlled as the heat load of the oven  20  varies during the cooking cycle for any number of different types of food products to maintain a steady state temperature (e.g., a cooking temperature) throughout the cooking tunnel  24  or in one of tunnel segments  20 A,  20 B. 
     The position sensors  83 ,  85  and the temperature sensors  80 ,  82  can be connected to the main controller  42  in parallel, thereby enabling the controller  42  to change the heat output of the burners  60 ,  62  and/or the speed of either or both fans  72 ,  74  based upon signals received by the position sensors  83 ,  85  and/or the temperature sensors  80 ,  82 . 
     The heat output of either or both burners  60 ,  62  can be controlled by the main controller  42  in any manner desired. For example, the gas supply to either or both burners  60 ,  62  can be lowered or raised or turned off by the main controller  42  relatively abruptly or gradually upon detection of threshold temperatures by either or both temperature sensors  80 ,  82 , after a set period of time, and/or after sufficient movement of the pizza is detected by a position sensor. 
     In some embodiments, the oven  20  can include one or more temperature sensors  93 ,  95  (e.g., thermocouples) coupled to the controller  42  and positioned to detect the heat output of either or both burners  60 ,  62 . Using such an arrangement of elements, a speed change of the fans  72 ,  74  can be delayed for a desired period of time in order to prevent undue cycling of the fans  72 ,  74  as temperatures rise and fall within the tunnel  24  and as the heat output of the burners  60 ,  62  rise and fall. In this regard, as the heat output detected by either or both temperature sensors  93 ,  95  decreases below a threshold level, power to either or both fans  72 ,  74  can remain unchanged for a set period of time, after which time power to the fans  72 ,  74  can be reduced to a standby speed of the fans  72 ,  74 . 
     In the embodiment illustrated in  FIG. 4 , for example, a relay  91  coupled to the temperature sensors  93 ,  95 , is also coupled to the main controller  42 , and cooperates with the main controller  42  ( FIG. 3 ) to control power to either or both fans  72 ,  74  in a manner as just described. In this embodiment, when the oven temperature or the output of either or both burners  60 ,  62  falls below a threshold value (e.g., 60% of maximum output in some embodiments), the relay  91  and the main controller  42  enter into a timed state. When the oven temperature or the output of either or both burners  60 ,  62  remains below the threshold value for a set period of time (e.g., five minutes in some embodiments), either or both burners  60 ,  62  can be shut off or otherwise varied (e.g., one burner  60 ,  62  being shut off while the heat output of the other burner  62 ,  60  is modulated). Either or both burners  60 ,  62  can be re-activated in some embodiments by detection of a sufficiently low threshold temperature by either of temperature sensors  80 ,  82 , by either of temperature sensors  93 ,  95 , by sufficient movement of a pizza detected by any of the position sensors described above, or after a set period of time has passed, and the like. Thus, as the oven temperature or heat output of either or both burners  60 ,  62  move above and below one or more threshold levels, the tendency of the fans  72 ,  74  to cycle (e.g., between high and low speed levels, and in some cases between on and off states) is reduced. Instead, the fans  72 ,  74  can remain at a full speed level until a lowered heat level is established for at least a set period of time, such as for five minutes in the illustrated embodiment. 
     Under some operating conditions, the heat output of the burners  60 ,  62  in some embodiments can be reduced to a relatively low level (e.g., as low as a 5:1 air to gas ratio, in some cases). Relatively low (and relatively high) per burner heat output can generate problems associated with poor combustion. For example, relatively low burner heat output can generate incomplete combustion and flame lift-off. To address these issues, the main controller  42  in some embodiments of the present invention is adapted to turn gas to either or both burners  60 ,  62  completely off in the event that either or both temperature sensors  80 ,  82  or either or both temperature sensors  93 ,  95  detect that a low threshold temperature has been reached. 
     In some of these embodiments, when either or both temperature sensors  80 ,  82  or either or both temperature sensors  93 ,  95  detect that a sufficiently low temperature has been reached, the controller  42  responds by turning off gas to one of the burners  60 ,  62  associated with that temperature sensor  80 ,  82 ,  93 ,  95  (either immediately or if a higher temperature is not detected after a set period of time), while the heat output of the other burner  60 ,  62  is modulated. The supply of gas to the burner  60 ,  62  that was turned off can be restored after a period of time and/or after one or more of the temperature sensors  80 ,  82 ,  93 ,  95  detects a temperature below a lower predetermined threshold temperature. In this manner, one of the burners  60 ,  62  can be cycled on and off in order to avoid operating both burners  60 ,  62  at a very low heat output. In some embodiments two or more burners  60 ,  62  will always be on or off together. In such cases, the controller  42  can respond to a low threshold temperature by turning off the supply of gas to one or both burners  60 ,  62 , and can restore the supply of gas to one or both burners  60 ,  62  after a period of time and/or after the temperature sensors  80 ,  82 ,  93 ,  95  detects that a lower threshold temperature has been reached. 
     Similarly, in some embodiments, when a temperature sensor  80 ,  82 ,  93 ,  95  detects that a sufficiently high temperature has been reached, the high-limit controller  46  responds by turning off gas to one of the burners  60 ,  62  associated with that temperature sensor  80 ,  82 ,  93 ,  95  (either immediately or if a lower temperature is not detected after a set period of time), while the heat output of the other burner  60 ,  62  is modulated. The supply of gas to the burner  60 ,  62  that was turned off can be restored after a period of time and/or after the temperature sensors  80 ,  82 ,  93 ,  95  detect a temperature below the low threshold temperature or a sufficient drop in temperature. In this manner, one of the burners  60 ,  62  can be cycled on and off in order to avoid operating both burners  60 ,  62  at a very high heat output for an extended duration. In some embodiments two or more burners  60 ,  62  will always be on or off together. In such cases, the high-limit controller  46  or main controller  42  can respond to a high threshold temperature by turning off the supply of gas to one or both burners  60 ,  62 , and can restore the supply of gas to one or both burners  60 ,  62  after a period of time and/or after the temperature sensor  80 ,  82 ,  93 ,  95  detects a temperature below the low threshold temperature or an otherwise sufficient drop in temperature. 
     Although only two tunnel segments  20 A,  20 B are used in the illustrated embodiment, more than two tunnel segments can be used in other alternative embodiments, each such alternative embodiment having one or more tunnel segments with any combination of the elements and features described above with reference to the illustrated embodiment. Finally, although gas burner(s) are preferred, other heating elements and devices can instead or also be used (e.g., one or more electric heating elements). As used herein and in the appended claims, unless otherwise required by the context, the term “heating elements” refers to gas burners, electric heating elements, microwave generating devices, and all alternative heating elements and devices. 
     Energy Management 
     In some embodiments, it may be desirable to operate the oven  20  in one or more energy saving modes. Components of the oven  20  that can be controlled by the main controller  42  to provide energy savings may include either or both burners  60  and  62 , either or both fans  72  and  74 , and/or the conveyor  22 . Exemplary energy saving features and techniques that can be used with the disclosed embodiments and energy saving modes of operation that can be achieved with the disclosed embodiments are described in U.S. Pat. Nos. 8,087,407 and 8,839,714, the entire contents of each of which are hereby incorporated by reference. 
     Saving energy with the burners  60  and  62  may be achieved by lowering the temperature threshold in one or both of the plenums  68  and  70  and corresponding tunnel segments  20 A,  20 B heated by burners  60  and  62 . This lower temperature threshold can result in one or both of the burners  60  and  62  being on less often, or operating at a lower output, resulting in energy savings. For example, both of the burners  60  and  62  may be turned off completely, may be cycled on and off together, or one burner may be turned off while the other burner remains on and its heat output is modulated or adjusted toward a desired set-point temperature. Saving energy with the fans  72  and  74  may be achieved by reducing the speed or RPMs of one or both of the fans  72  and  74  which can require less power and, therefore, save energy. Additionally, one or both of the fans  72  and  74  may be turned off completely. Saving energy with the conveyor  22  may be achieved by slowing down or turning off the conveyor  22 . 
     Energy management strategies may include controlling any one or more of the burners  60 ,  62 , fans  72 ,  74 , and conveyor  22  of the oven  20  individually or in combination and/or controlling such components in the different tunnel segments of the oven  20  individually or in combination. In particular, the main controller  42  can execute instructions to adjust the fans  72 ,  74  and/or burners  60 ,  62  to carry out the energy saving procedures. 
       FIG. 6  illustrates a process for an energy management mode that can be utilized for a conveyor oven, such as the oven  20  of  FIG. 4  used, for example, to bake a pizza. At step  300 , the main controller  42  can check for the presence of a pizza on conveyor  22 . A pizza can be detected in any of the manners described herein, such as by one or more optical sensors  79  and  81 . If a pizza is detected, a timer can be reset, either or both of the fans  72  and  74  can be set to or maintained at a cooking (high) speed, and/or either or both of the burners  60 ,  62  can be set to or maintained at a cooking (high) output to set or maintain the temperature in one or both of the plenums  68 ,  70  at a cooking (high) temperature (steps  305 ,  310 , and  315 ). If no pizza is detected by the sensors  79  and  81  (step  300 ), the main controller  42  can check a timer to determine the period of time since the last pizza was put on the conveyor  22  (step  320 ). If the timer is less than a predetermined threshold, the operation of the oven  20  can remain unchanged (steps  305 ,  310 , and  315 ) and the main controller  42  can continue to check for the presence of a pizza (step  300 ). If the timer exceeds the predetermined threshold, the main controller  42  can go into an energy saving mode. In this energy saving mode, either or both fans  72  and  74  can be set to a low speed or one fan can be turned off and the temperature can be set to a low value (steps  325  and  330 ) by lowering the heat output of both burners  60 ,  62  or turning off one of the burners  60 ,  62  and adjusting the heat output of the other burner. Alternatively, in some embodiments, the fan speed is decreased and the temperature in the energy saving mode can be adjusted toward a set-point cooking temperature by adjusting the heat output of both burners  60 ,  62  or, alternatively, turning off one of the burners  60 ,  62  and adjusting the heat output of the other burner toward the set-point cooking temperature. In addition, in other embodiments, the oven temperature during an energy saving mode can be increased above the set-point cooking temperature while fan speed is decreased. The main controller  42  can then continue to check for the presence of a pizza on the conveyor  22  (step  300 ). The main controller  42  can remain in this energy saving mode until a pizza is detected on the conveyor  22  at step  300 . 
       FIG. 7  illustrates another embodiment of a process for an energy management mode that can be utilized for a conveyor oven, such as the oven  20  of  FIG. 4  used, for example, to bake a pizza. At step  335 , the main controller  42  can check for the presence of a pizza on conveyor  22 . A pizza can be detected in any of the manners described herein, such as by one or more optical sensors  79  and  81 . If a pizza is detected, a timer can be reset, either or both of the fans  72  and  74  can be set to a cooking (high) speed, and/or either or both of the burners  60 ,  62  can be set to or maintained at a cooking (high) output to set or maintain the temperature in one or both of the plenums  68 ,  70  at a cooking (high) temperature (steps  340 ,  345 , and  350 ). Since, as will be explained later, the oven temperature can be relatively low (e.g., if the oven  20  has been in an energy management mode), it may be necessary to wait until the temperatures in the plenums  68  and  70  reach levels that will result in temperatures satisfactory for baking when the pizza arrives in the respective plenums before allowing the pizza on conveyor  22  to enter the oven  20 . Therefore, at step  355 , the main controller  42  can wait until the temperatures of the oven  20  reach their thresholds. If in one of the alternative embodiments described above, the temperature of the oven  20  during the energy saving mode has been increased above the set-point cooking temperature, the temperature of the oven  20  can be reset to a set-point cooking temperature when pizza is again detected on the conveyor  22 . 
     Once the temperatures of the oven  20  reach their thresholds, the conveyor  22  can start (step  360 ) and the pizza can enter the oven  20  and bake. If no pizza is detected by the sensors  79  and  81  (step  335 ), the main controller  42  can check a timer to determine the period of time since the last pizza was put on the conveyor  22  (step  365 ). If the timer is less than a predetermined threshold, the operation of the oven  20  can remain unchanged (steps  340 ,  345 , and  350 ) and the main controller  42  can continue to check for the presence of a pizza (step  335 ). If the timer exceeds the predetermined threshold, the main controller  42  can enter an energy saving mode. In this energy saving mode, either or both fans  72  and  74  can be set to a low speed (step  370 ) or one fan can be turned off, burner  62  can be turned off independently of burner  60  and the heat output of burner  60  can be adjusted or set to a lower level (step  380 ). The conveyor  22  can also be turned off (step  385 ). The main controller  42  can then continue to check for the presence of a pizza on the conveyor  22  (step  335 ). The main controller  42  can remain in this energy saving mode until a pizza is detected on the conveyor  22  at step  335 . 
     Embodiments of two exemplary energy saving modes have been illustrated. Further embodiments can include, for example, other methods of controlling the components of the conveyor oven or adjusting or turning off operation of the fans, burners, and conveyor in other combinations or at different levels of operation during different time periods. 
     In preparation for turning off the entire oven  20  (e.g., when kitchen operations are shut down at the end of a business day or the oven  20  enters the energy saving mode), the main controller  42  may enter a cool-down mode. During the cool-down mode, the main controller  42  cuts the power to the ignition controller  44 , causing the ignition controller  44  to close the main control valve  48 . With the main control valve  48  closed, the gas supply to all three burners  60 ,  62  is shut off and each of the burners  60 ,  62  is extinguished. After the burners  60 ,  62  are extinguished, the main controller  42  continues to operate, controlling the fans  72 ,  74  and monitoring the oven temperature through temperature sensors  80 ,  82 ,  93 ,  95 . When the oven temperature drops below a predetermined threshold at which the oven  20  can safely be shut down completely, the main controller  42  will turn off other oven components, such as the fans  72 ,  74 . 
     As one skilled in the art will understand, numerous strategies and combinations of strategies exist for implementing energy management for an oven  20 . Considerations in deciding which strategies to implement include the time it will take to be ready for baking after entering an energy saving mode and the amount of energy required to reach baking temperature following an energy saving mode. As such it can be desirable to provide multiple energy management strategies and allow users to choose the strategy or combination of strategies that best meets their needs. 
     Gas Manifold 
     The main controller  42  ( FIG. 3 ) can control the operation of the burners such as burners  60 ,  62  of  FIG. 4  in several different ways to adjust the temperature of the oven  20  and/or engage in an energy saving mode as described above. For example, the main controller  42  can control operation of the burners  60 ,  62  in a continual or periodic effort to maintain a constant steady state temperature along the tunnel  24 , to maintain respective selected temperatures in two or more areas (e.g., segments) along the tunnel  24 , to maintain the temperature of the tunnel  24  or individual tunnel segments  20 A,  20 B within a selected temperature range or within a selected temperature deviation from a desired temperature, or to maintain respective temperatures in two or more areas or segments along the tunnel  24  within selected deviations or ranges from desired respective temperatures of the areas. In some embodiments, a gas manifold  100  is provided to selectively supply gas to a plurality of burners  110  for achieving any or all of these functions. The configuration of the gas manifold  100  can help the main controller  42  control some of the burners  110  independently of the other burners  110 . 
       FIGS. 8-16  illustrate exemplary embodiments of the gas manifold  100  for regulating the supply of gas to the plurality of gas burners  110 . The manifold includes an enclosed housing  114  defining an interior space  118  in which gas can flow. Housing  114  can comprise either a one-piece unit or multiple units connected together. In the illustrated embodiment of  FIGS. 8-16 , the housing  114  is constructed of a single integral unit produced by machining operations (e.g., drilling, milling, and the like) on a piece of metal to create the various features of the housing  114  described herein. In these and other manners, the housing  114  can be a single integral unit having no seams, and therefore fewer locations where leaks can form. A housing defined by a single, integral, and seamless body can also greatly simplify the manufacturing and assembly process of the gas supply components of the oven  20 , reduce part count, and reduce the opportunity for assembly error, and incorrect part interconnections (e.g., poor fit). The interior space  118  is at least partially enclosed by a wall  122  (which is shown clear in this figure to facilitate viewing of the interior space). The wall  122  may extend continuously between a first end  126  of the housing  114  and a second end  130  of the housing  114  spaced apart from the first end  126  with no gaps or openings, other than gas outlet ports, gas inlet ports, or valve openings, formed therein. In some embodiments, the wall  122  includes multiple sidewalls to enclose the interior space  118 . The housing  114  can be elongated as shown in  FIGS. 8-14 , and can thereby define a longitudinal axis  134  (see  FIGS. 10-11 and 15-16 ) extending through the first end  126  and the second end  130 . In the illustrated embodiment, the wall  122  of the housing  114  extends in a direction parallel to the longitudinal axis  134  for the entire length of the housing  114 . As shown in  FIGS. 8-8B , the wall  122  has a rectangular outer perimeter defined by a first sidewall  138 , a second sidewall  142  opposite the first sidewall  138 , a third sidewall  146 , and a fourth sidewall  150  opposite the third sidewall  146 , and includes an interior space  118  having a circular cross section defining a volume of the interior space  118 . The gas inlet  158  and gas outlets  162 A-C extend through the wall  122  of the housing  114  and into the interior space  118 . In other embodiments, the housing  114  can have any shape adapted to allow gas to flow through an interior space  118 , including without limitation other prismatic shapes having triangular, square, or other polygonal cross-sections, square manifolds, round or rotund manifolds, irregularly-shaped manifolds, and the like. 
     With continued reference to  FIGS. 8-16 , gas is supplied to the housing  114  through a gas inlet  154 . The gas inlet  154  is in fluid communication with the interior space  118  such that gas flowing through the gas inlet  154  is received within the interior space  118  of the housing  114 . In some of the illustrated embodiments, the gas inlet  154  extends through the fourth sidewall  150  of the housing  114  proximate the first end  126  of the housing  114 . A supply conduit  158  is coupled between a gas supply (not shown) and the gas inlet  154 . The gas inlet  154  may be disposed along any of the sidewalls  138 ,  142 ,  146 ,  150  of the housing. Also, some embodiments may include multiple gas inlets. In the case of housing  114  having multiple gas inlets, the gas inlets can be disposed along the housing  114  and spaced apart along the longitudinal axis  134  (see  FIG. 14 ). In other embodiments, a gas inlet  154  is disposed on the first end  126  or the second end  130  such that the longitudinal axis  134  extends through the gas inlet  154  (see  FIGS. 12-14 ). 
     Gas can exit the interior space  118  of the housing  114  through a plurality of gas outlets  162 A-C. The gas outlets  162 A-C are in fluid communication with the interior space  118  of the housing  114  and extend through the wall  122  of the housing  114  to discharge gas from the interior space  118 . In the illustrated embodiment, the gas outlets  162 A-C are spaced apart from the gas inlet  154  in respective positions downstream of the gas inlet  154 , and are also spaced apart from one another along the longitudinal axis  134  between the first end  126  and the second end  130  of the housing  114 . The size, shape, number, and position of gas outlets  162 A-C may vary. For example, in some embodiments, two gas outlets  162  are disposed on the third side  146  of the housing  114  and a third gas outlet  162  is disposed on the second end  130  of the housing  114  such that the longitudinal axis  134  extends through the third gas outlet  162 . Alternatively, the gas outlets  162  may be positioned on either or both sides of the gas inlet  154 . For example, a first gas outlet  162  may be disposed within the wall  122  in a position closer to the first end  126  of the housing  114  than the gas inlet  154 , and second and third gas outlets  162  may be disposed within the wall  122  in respective positions between the gas inlet  154  and the second end  130  of the housing  114 . In some embodiments, the gas outlets  162  may be evenly spaced along the longitudinal axis  134 , while in other embodiments, the spacing between the gas outlets  162  may vary. 
     The gas outlets  162 A-C are in fluid communication with the burners  110 A-C, respectively. Gas discharged from the interior space  118  of the housing  114  passes through the gas outlets  162 A-C and is received by the burners  110 A-C for combustion.  FIGS. 8-12  illustrate the gas manifold  100  with an exemplary arrangement of the housing  114  in fluid communication with three burners  110 . In the illustrated embodiment, each gas outlet  162 A-C communicates with one burner  110 A-C, although in other embodiments one or more of the gas outlets  162  may communicate with two or more burners  110 , such as by one or more Y, V, T, or other gas connections. The illustrated gas manifold  100  includes a first burner  110 A, a second burner  110 B, and a third burner  110 C. The burners  110 A-C are elongated and each have a proximal end  166  adjacent the housing  114  and a distal end  170  spaced from the housing  114 . The illustrated burners  110 A-C extend from the first side  138  of the housing  114 , and are oriented in a direction that is orthogonal to the longitudinal axis  134 . 
     In other embodiments, the number, position, and orientation of the burners  110 A-C may vary. In some embodiments the gas manifold  100  may include burners  110 A-C extending from multiple sides of the housing  114  and/or in different directions. By way of example only, a first burner  110 A may extend from a second end  130  of the housing  114  in a direction parallel to the longitudinal axis  134 , and second and third burners  110 B,  110 C may extend from the third side  146  of the housing  114  in a direction orthogonal to the first burner  110 A. The burners  110 A-C may also extend in a non-orthogonal direction relative to the longitudinal axis  134 . Again by way of example only, the burners  110  may extend from the fourth side  150  of the housing  114  at a 30 degree angle relative to the longitudinal axis  134 . Additionally, although the burners  110 A-C described and illustrated herein are of the same size and shape, in other embodiments, the burners  110 A-C can be different in size and shape. 
     With continued reference to the illustrated embodiment, the proximal end  166  of each burner  110 A-C is coupled to the housing  114  at one of the gas outlets  162 A-C, respectively, to receive gas discharged from the gas manifold  100 . The burners  110 A-C can be coupled to the housing  114  in any suitable manner, such as by one or more clamps, braces, or other fixtures or structures adapted for this purpose. In the illustrated embodiment by way of example only, the burners  110 A-C are each directly coupled to the gas manifold  100 A-C by an injector  174 A-C, respectively. Each of the injectors  174 A-C may be coupled to the manifold  100  via a threaded connection (e.g., external threads of each of the injectors  174 A-C mating with internal threads of the housing  114 ). In some embodiments, each injector  174 A-C has one or more portions (e.g., wrench flat section  178 A-C in the illustrated embodiment) shaped to facilitate installation and removal of the injectors  174 A-C with a wrench. Each of the injectors  174 A-C in the illustrated embodiment has a hollow interior that allows gas to pass through from the interior space  118  to each individual burner  110 A-C. In some embodiments, an end of each of the injectors  174 A-C opposite the gas manifold  100  is slidingly received within the burner inlet. In other embodiments, supply tubes (not shown) of any length and construction (e.g., flexible or rigid) may be used with or without such injectors  174 A-C to direct the gas from each gas outlet  162 A-C to a corresponding burner  110 A-C. Alternatively, when multiple burners  110  are configured to receive gas from a shared gas outlet  162 , the burners  110  may be coupled to a common supply tube (not shown) leading to the shared gas outlet  162 . Gas is received by the burner  110  at a proximal end  166 , and is ignited as it passes through the burner  110 , thus producing a flame at a distal end  170  of the burners  110 . Each burner  110  may have its own independent igniter (not shown), or burners may share igniters. 
     The burners  110 A-C may be controlled and adjusted by the main controller  42  ( FIG. 3 ). As described above, the burners  110  are controlled by the main controller  42  to manage the heat load of the oven  20  or to operate the oven  20  in an energy saving mode. In doing so, the main controller  42  may execute instructions to increase or decrease the heat output of one or more burners  110 . The main controller  42  may turn off a burner  110  or execute instructions to modulate the heat output of a burner  110 . The exemplary arrangement of the gas manifold  100  illustrated in  FIGS. 8-12  and  FIGS. 15-20  enables the main controller  42  to operate at least one of the burners  110 A-C independently of the other burners  110 A-C. In other embodiments, the manifold  100  can be configured to operate sets of multiple burners independently of one another, as explained below. 
     In some of the illustrated embodiments, independent control of one or more burners  110 A-C with respect to one or more other burners  110 A-C is accomplished by creating two chambers  182 ,  186  within the housing  114  that may be in selective fluid communication with each other. In other words, the interior space  118  of the housing  114  is divided into a first chamber  182  and a second chamber  186  that are not in direct fluid communication. In the illustrated embodiments, the chambers  182 ,  186  are established by a plug  190 ,  190 ″ or valve  202 ′ located in the interior space  118  of the housing  114  and positioned to block the flow of gas from one chamber to the other ( FIGS. 8-16 ). Additional plugs  190  may be inserted into the interior space  118  of the housing  114  to create additional chambers. In other embodiments, the chambers  182 ,  186  are created by coupling two separate housings  114  together such that each housing  114  establishes a separate chamber  182 ,  186 . The chambers may be created in any appropriate manner as long as at least one chamber is not in direct fluid communication with at least one other chamber. 
     In some of the illustrated embodiments, the first chamber  182  extends between the first end  126  of the housing  114  and the plug  190 , and the second chamber  186  extends between the second end  130  of the housing  114  and the plug  190 . The plug  190  prevents direct fluid communication between the second chamber  186  and the first chamber  182  so that gas flowing through the first chamber  182  cannot flow directly into the second chamber  186  through the interior space  110  of the housing  114 . In the illustrated embodiment, the gas inlet  154  is configured to extend to and distribute gas to the first chamber  182 , and the second chamber  186  is positioned downstream (i.e., in series flow) of the first chamber  182  so that the gas outlets  162 A-B extending from the first chamber  182  are upstream with respect to the gas outlet  162 C extending from the second chamber  186 . 
     As shown in the illustrated embodiments, two gas outlets  162 A,  162 B extend from the first chamber  182 , and one gas outlet  162 C extends from the second chamber  186 . In other embodiments, however, any number (i.e., one or more) of gas outlets  162  can extend from each chamber  182 ,  186 . Each chamber  182 ,  186  therefore includes at least one gas outlet  162  that is in fluid communication with at least one burner  110 . For example, in the illustrated embodiments, the first burner  110 A and the second burner  110 B are in fluid communication with the first chamber  182  and the third burner  110 C is in fluid communication with the second chamber  186 . Accordingly, gas flowing through the gas inlet  154  can flow through the first chamber  182  and exit through the gas outlets  162 A,  162 B in communication with the first burner  110 A and the second burner  110 B, respectively, for combustion. However, based on this exemplary configuration, gas cannot flow along the interior space  118  of the housing  114  to reach the third burner  110 C because the plug  190 ,  190 ″ or valve  202 ′ blocks the gas from flowing through the housing  114  into the second chamber  186 . 
     Instead, in some exemplary embodiments, gas may be supplied to the second chamber  186  by selectively routing the gas externally to the housing  114  from the first chamber  182  to the second chamber  186 . More specifically, an outlet port  194  is defined through a wall  122  of the housing  114  and is in fluid communication with the first chamber  182 . An inlet port  198  is also defined in the wall  122  of the housing  114  and is in fluid communication with the second chamber  186 . A first valve  202  (either a shut off or modulating variable flow valve) is positioned downstream of the outlet port  194  and upstream of the inlet port  198 . In the illustrated embodiment, the first valve  202  is positioned external to the housing  114 . The first valve  202  is operable to selectively control the flow of gas from the first chamber  182  to the second chamber  186 . In other words, the first valve  202  can selectively open and close to allow gas to flow from the first chamber  182  to the second chamber  186  or otherwise modulate the flow of gas from the first chamber  182  to the second chamber  186 . When gas is allowed to flow into the second chamber  186 , the third burner  110 C can receive gas from the gas outlet  162 C that extends from the second chamber  186 . As such, the first valve  202  can be used to selectively provide gas to any burners  110  in fluid communication with the second chamber  186  for selective operation of such burners  110 . 
     As shown in  FIGS. 8-11 , one or more conduits  206  may extend between the outlet port  194  and the inlet port  198  to transfer gas from the first chamber  182  to the second chamber  186 . With reference to  FIGS. 8-11 , a first conduit  206 A is in fluid communication with the outlet port  194  of the first chamber  182  and a second conduit  206 B is in fluid communication with the inlet port  198  of the second chamber  186 . The first valve  202  is fluidly coupled between the first conduit  206 A and the second conduit  206 B. Alternatively, a single conduit  206  may be used to route gas from the first chamber  182  to the second chamber  186  with the first valve  202  directly coupled to the housing  114  at either the outlet port  194  or the inlet port  198 . 
       FIGS. 15-16  show an alternate embodiment of a gas manifold  100 ′″ for regulating the supply of gas to a set of gas burners  110   a - c . With the exception of structure and features described above and illustrated in  FIGS. 1-14  that are incompatible with the embodiment of  FIGS. 15-16 , reference is hereby made to the embodiments of  FIGS. 1-14  above for a more complete description of the features and elements of the embodiments of  FIGS. 15-16  (and possible alternatives thereto). With reference to  FIGS. 15-16 , in some embodiments, the first valve  202 ′″ can be directly coupled to the housing  114 ′″ at both the outlet and inlet ports  194 ′″,  198 ′″, thereby eliminating the need for the conduits  206 A′″,  206 B″. The outlet port  194 ′″ and the inlet port  198 ′″ may be positioned at different heights to accommodate the internal structure of the first valve  202 ′″. 
     In some embodiments, the first valve  202  can even be located partially or entirely within the housing  114  (e.g., within the interior space  118  of the housing  114 ), such as a first valve  202 ′ being received within a bore, counterbore, recess, receptacle, or other aperture defined by the housing  114  ( FIG. 13 ). In such embodiments, the first valve  202 ′ can be positioned to selectively establish fluid communication between the first and second chambers  182 ,  186  by opening or closing a passage within the housing  114  (e.g., within the interior space  118  of the housing  114 ) to selectively permit or otherwise modulate gas flow within and along the housing  114  between the first and second chambers  182 ,  186 . Also with respect to such embodiments, the first valve  202 ′ can be positioned so that at least a portion of the first valve  202 ′ is located between the first and second chambers  182 ,  186  to selectively open and close fluid communication between the first and second chambers  182 ,  186  ( FIG. 13 ). In such an embodiment, the valve  202 ′ may be used to separate the first and second chambers  182 ,  186 . Such embodiments can eliminate the need for the gas outlet  194  and the gas inlet  198 , the first and second conduits  206 A,  206 B, and the plug  190  as shown in the illustrated embodiment, thereby significantly simplifying the manifold  100 . 
     Although the outlet and inlet ports  194 ,  198  are both illustrated as being defined in the same wall  122  of the housing  114 , it will be appreciated that the outlet port  194  and inlet port  198  can be defined in any other wall and/or be defined in different walls of the housing  114  as long as they are in fluid communication with the first and second chambers  182 ,  186 , respectively. 
     Furthermore, additional valves may be used with the gas manifold  100  to further control the flow of gas. For example, in some embodiments, a second valve  210  (either a modulating variable flow or shut off valve) is in fluid communication with the supply conduit  158  upstream of the gas inlet  154 . With reference to  FIGS. 9 and 11 , the second valve  210  is positioned external to the housing  114 , and can be used to control the flow of gas to the first chamber  182 . The second valve  210  is operable to selectively control the flow of gas into the first chamber  182 . 
     In some embodiments, an existing single-chamber manifold may be retrofitted with the plug  190 ,  190 ″, the first valve  202 , and the conduits  206 A,  206 B to create a gas manifold substantially similar to the gas manifold  100  described above. For example, the plug  190 ,  190 ″ may be installed in the interior space  118  of an existing manifold to create separate chambers  182 ,  186 . In such embodiments, the plug  190 ,  190 ″ must be made of a thermostable deformable material, such as silicone, so that the plug  190 ,  190 ″ expands as it is secured within the interior space  118  so that the first chamber  182  is no longer in direct fluid communication with the second chamber  186 . The outlet port  194  may then be drilled through one of the sidewalls  122  of the housing  114  into the first chamber  182 . The inlet port  198  may be drilled through one of the sidewalls  122  of the housing  114  into the second chamber  186 . The first conduit  206 A is installed between the outlet port  194  and an inlet of the first valve  202 , whereas the second conduit  206 B is installed between an outlet of the first valve  202  and the inlet port  198 . Accordingly, a selective flowpath is established between the first chamber  182  and the second chamber  186 . For example, gas may flow from the gas inlet into the first chamber  182  and into the first conduit  206 A. When the first valve  202  is in the open position, gas may flow through the first valve  202  into the second chamber  186 . When the first valve  202  is in the closed position, gas may not flow into the second chamber  186 . 
     The gas manifold  100  can be installed in the oven as a single integral unit. More specifically, in some embodiments the housing  114  and the first valve  202  are permanently or releasably connected together (e.g., by threaded fittings as shown in the illustrated embodiment, or with clamps, brackets, fasteners, brazing, welding, or in any other suitable manner) as a single integral unit, and can therefore be mounted within the oven by an installer, service technician, or other user as a single integral unit. In other words, the housing  114  and first valve  202  can collectively define an assembly that can be moved into position, oriented, and secured in position with respect to the conveyor oven  20  while in an assembled and integrated state. Such modular installation of the assembly can greatly simplify installation, removal, and servicing, reduce parts count, and/or reduce manufacturing and setup time of the conveyor oven  20 . In other embodiments, the second valve  210  and/or the burners  110 A-C are also installed with the housing  114  and the first valve  202  as part of the same assembly (i.e., as part of the same single integral unit). 
     In operation, the main controller  42  can control the first valve  202  to regulate the flow of gas to the second chamber  186 , thereby controlling operation of the burner(s)  110  downstream from the first chamber  182  (i.e., those burners  110  supplied with gas through gas outlets  162  extending from the second chamber  186 ). In some embodiments, the main controller  42  can control the first valve  202  according to a set of predetermined instructions or programs. The main controller  42  may also communicate with the temperature sensors  80 ,  82 , position sensors  79 ,  81 ,  83 ,  85 , and thermocouples  93 ,  95  to control the first valve  202  as described above, for example, to adjust the oven toward a steady state temperature throughout the oven tunnel  24  or in a selected tunnel segment  20 A,  20 B, or to control operation of an energy saving mode. Additionally, the first valve  202  can control the flow of gas to the second chamber  186  in different ways depending at least in part upon the type of valve used or operation of the controller  42 . For example, the first valve  202  may be a shut-off valve that includes an open state and a closed state. In such embodiments, the first valve  202  fully blocks the flow of gas to the second chamber  186  when in a closed state, and allows gas to flow into the second chamber  186  when in an open state. Accordingly, when the first valve  202  is in the open state, gas is supplied to all of the gas outlets  162 , and thus, to all of the burners  110 . When the first valve  202  is in the closed state, gas is supplied to gas outlet(s)  162  extending from the first chamber  182 , but is shut off from gas outlet(s)  162  extending from the second chamber  186 . Therefore, when the first valve  202  is in the closed state, the burners  110  extending from outlets  162  corresponding to the first chamber  182  are turned on while the burners  110  extending from outlets  162  corresponding to the second chamber  186  are turned off. 
     Similarly, the first valve  202  can also be a modulating variable flow valve  202  that modulates the flow of gas to the second chamber  186 . The variable flow valve can be adjusted from a fully-opened state to a fully-closed state, as well as partially-opened states between the fully-open state and the fully-closed state. Likewise, the main controller  42  can control the second valve  210  to regulate the flow of gas to the first chamber  182 . The second valve  210  can be used to control operation of the burners  110  connected to both the first chamber  182  and the second chamber  186 . For example, when the second valve  210  blocks the flow of gas into the first chamber  182 , none of the burners  110  will receive gas, whereas when the second valve  210  and the first valve  202  are open, gas can be simultaneously supplied to both chambers  182 ,  186  and their corresponding outlets  162  and burners  110 . Similar to the first valve  202 , the second valve  210  can be used to control the flow of gas to the chambers  182 ,  186  in different ways depending at least in part upon the type of valve used. The second valve  210  may be a shut off valve or a modulating variable flow valve as described above with respect to the first valve  202 . 
       FIG. 12  provides an exemplary configuration of the gas manifold  100  with the burners  110 A-C and the first and second valves  202 ,  210 . In this configuration by way of example only, gas is supplied to the manifold  100  by a combination control valve  213  which functions as a shut-off valve for gas supply to the manifold  100  in addition to regulating and maintaining a constant gas pressure to components downstream of the combination control valve  213  (e.g., the manifold  100  and the first valve  202 ). Also in this configuration, the first valve  202  is a solenoid valve that can function as a shut off valve, and the second valve  210  is a modulating valve. A bypass loop  217  is provided around the second valve  210  in a manner as described and illustrated in U.S. Pat. No. 6,684,875, the contents of which are incorporated herein by reference, including those regarding modulating valves and valve bypass features, elements, and processes. In this regard, it will be appreciated that the bypass loop  217  can be external of the second valve  210 , or can be internal to the second valve  210  as described and illustrated in U.S. Pat. No. 6,684,875. 
       FIG. 13  provides another exemplary configuration of the gas manifold, wherein like elements of  FIG. 12  are presented with like reference numbers each ending in a prime (′). Absent features and functionality that are incompatible with the embodiment of  FIG. 13  illustrated and described herein, the above description regarding the embodiment of  FIGS. 1-12  (and alternatives thereto) apply equally to the embodiment of  FIG. 13 . For further understanding of the features and functionality of the embodiment of  FIG. 13  (and alternatives thereto), reference is made to  FIGS. 1-12  and the description above in connection with  FIGS. 1-12 . In the configuration of  FIG. 13 , the plug  190  is not used, and is instead replaced with the first valve  202 ′, which can either be a shut off or modulating variable flow valve, in a manner as described above so that the valve  202 ′ is located at least partially within the manifold housing  114 , and selectively opens and closes fluid communication between the first and second chamber  182 ′,  186 ′. 
       FIG. 14  provides another exemplary configuration of the gas manifold wherein like elements of  FIGS. 12 and 13  are presented with like reference numbers each ending in a double prime (″). Absent features and functionality that are incompatible with the embodiment of  FIG. 14  illustrated and described herein, the above description regarding the embodiment of  FIGS. 1-12  (and alternatives thereto) apply equally to the embodiment of  FIG. 14 . For further understanding of the features and functionality of the embodiment of  FIG. 14  (and alternatives thereto), reference is made to  FIGS. 1-12  and the description above in connection with  FIGS. 1-12 . In the configuration of  FIG. 14 , the first valve  202 ″ is supplied with gas directly from the combination control valve  213 ″ rather than from the second valve  210 ″ and the first chamber  182 ″. In this illustrated embodiment, the gas manifold  100 ″ is provided with the plug  190 ″ that is positioned and functions in the same manner as the manifolds of  FIGS. 1-12 . However, gas enters the second chamber  186 ″ by way of a second gas inlet  155 ″ that can take any of the forms and be in any of the positions with respect to the second chamber  186 ″ as the first gas inlet  154 ″ described and illustrated herein can take with respect to the first chamber  182 ″. Reference is made to the description of the first gas inlet  154  above and accompanying  FIGS. 8-12  for more information regarding the second gas inlet  155 ″ and possible alternatives thereto. 
     With continued reference to the illustrated embodiment of  FIG. 14 , the first valve  202 ″ can be either a shut off or modulating variable flow valve positioned with respect to the manifold housing  114 ″ (not shown) in any of the manners described above with regard to the illustrated embodiment of  FIGS. 8-12 , such as by being mounted to one or more external surfaces of the housing  114 ″ and/or by mounting the first valve  202 ″ with respect to the housing  114 ″ so that both define a single integral unit as described above. Similarly, the first valve  202 ″ can be connected to the second gas inlet  155 ″ by one or more conduits or directly to an inlet port (not shown) of the housing  114 ″ as described in greater detail above with regard to the embodiment of  FIGS. 8-12 . In yet another embodiment (not shown), modulating valve  210 ″ shown in  FIG. 14  may be eliminated from the gas line between combination control valve  213 ″ and gas inlet  154 ″ to first chamber  182 ″, with only shut off or modulating valve  202 ″ provided in the gas line between combination control valve  213 ″ and gas inlet  155 ″ to second chamber  186 ″. 
       FIGS. 17-20  show an alternate embodiment of a gas manifold  214  for regulating the supply of gas to a set of gas burners  278   b - d  ( FIG. 21 ). With the exception of structure and features described above and illustrated in  FIGS. 1-14  that are incompatible with the embodiment of  FIGS. 17-20 , reference is hereby made to the embodiments of  FIGS. 1-14  above for a more complete description of the features and elements of the embodiments of  FIGS. 17-20  (and possible alternatives thereto), which above descriptions apply equally to the embodiments of  FIGS. 17-20 , with like elements being identified by like reference numbers in the 200-series of reference numbers. The gas manifold  214  includes a housing  218  with a longitudinal axis  222 . The housing  218  has a continuous sidewall  226  and first and second ends  234 ,  238  that defines an interior volume  230 . 
     As shown in  FIGS. 17-20 , the interior volume  230  extends between the first end  234  and the second end  238  of the housing  218  along the longitudinal axis  222 . The interior volume  230  is fitted with a gas valve  242 , which in the illustrated embodiment is proximate the second end  238 . In the illustrated embodiment, a portion of the interior volume  230  proximate the gas valve  242  has a substantially cylindrical cross-section having an axis  246 , although any other cross-sectional shape is possible. The axis  246  can be substantially perpendicular to the longitudinal axis  222  as shown in  FIGS. 18 and 19 , by way of example. The gas valve  242  includes a valve body  250  that is at least partially positioned within the interior volume  230  and is aligned with and movable along the axis  246 . Valve body  250  includes a valve disk  251  at one end that is movable with the valve body within volume  230 . An opening  254  connects the longitudinal and cylindrical portions of the interior volume  230  to form the single interior volume  230 . 
     The housing  218  includes a gas inlet  258 , and a plurality of gas outlets  262   a - d , and can also include a first opening  266  and/or a second opening  270  such as those shown in  FIGS. 17-20 . The gas inlet  258 , the plurality of gas outlets  262   a - d , the first opening  266 , and the second opening  270  of the illustrated embodiment are formed within the sidewall  226  of the housing  218 . In the illustrated embodiment, the gas inlet  258 , the first opening  266 , the second opening  270 , and the plurality of gas outlets  262   a - d  are threaded. The gas inlet  258  is sized to receive a gas conduit  274  ( FIGS. 22-23 ), although any other suitable type of connection to an upstream gas supply line can instead be used. The gas conduit  274  is coupled to a gas supply (not shown) and allows gas to enter the interior volume  230 . The gas outlets  262   a - d  of the illustrated embodiment are positioned along sidewall  226  of the housing  218 . In the illustrated embodiment, the gas outlets  262   a - d  are positioned along the axis  246 , and can be positioned on the same side of the housing  218 , such as in the manner shown in  FIGS. 17-20 . In alternate embodiments, different numbers and arrangements of gas outlets  262   a - d  are possible. 
     With reference to the illustrated embodiment of  FIGS. 17-21 , the fourth gas outlet  262   d  is an elongated gas outlet. A portion of the fourth gas outlet  262   d  extends into the interior volume  230 . The fourth gas outlet  262   d  is positioned along the axis  246  and is aligned with the valve body  250  and valve disk  251 . As shown in  FIGS. 18-20 , the valve body  250  is continuously repositionable from a fully open position ( FIG. 18 ) in which the valve disk  251  of valve body  250  is seated against the housing  218  opposite the inlet for the fourth gas outlet  262   d  or is otherwise in a retracted position, and a closed position ( FIG. 20 ) in which the valve disk  251  of valve body  250  is seated against the inlet of the fourth gas outlet  262   d.    
     As shown in  FIG. 21 , the gas outlets  262   b - d  are each in fluid communication with a burner  278   b - d , respectively, whereas the first gas outlet  262   a  is engaged with a plug  286 . For example, in the illustrated embodiment, the gas outlets  262   b ,  262   c , and  262   d  are in fluid communication with burners  278   b ,  278   c , and  278   d , respectively. The gas outlets  262   b - d  of the illustrated embodiment are each sized to receive an injector  282   b - d . The injectors  282   b - d  can be substantially the same as the injectors  174  described above, and can include a hollow passageway to allow gas to pass from the interior volume  230  of the housing  218  to the burners  278   b - d.    
     In the illustrated embodiment, the first opening  266  can be engaged with a plug (not shown), which prevents gas in the interior volume  230  from flowing out of the first opening  266 . Any other unused gas outlets  262   a - 262   d  can also be engaged with a plug (e.g., plug  286  described above and shown in  FIG. 21 ) based upon other configurations of the gas manifold  214 . In some embodiments, sensors may be installed through the openings  266 ,  270 , or the openings  266 ,  270  may function as additional gas inlets or additional gas outlets. For example, in the illustrated embodiment, the second opening  270  can be used as a manifold pressure monitoring port, and so can be sized to receive at least one sensor (not shown) for measuring a pressure within the manifold  214 . In such embodiments, the sensor can be in communication with the main controller  458  so that when the gas valve  242  and/or another gas control valve (e.g., main control valve  48  shown in  FIG. 3A ) are adjusted, the pressure within the manifold  214  can be monitored. 
     Additional valves may be used with the gas manifold  214  to further control the flow of gas. For example, in some embodiments a gas control valve (not shown, either a modulating variable flow and/or a shut off valve) is in fluid communication with the gas supply conduit  274  upstream of the gas inlet  258 . Any such valves can be positioned external to the housing  218 , and can be operable to selectively control the flow of gas to the interior volume  230  of the gas manifold  214 . Valves supplying gas to the gas manifold  214  can take any of the forms and can be connected and operated in any of the manners described above in connection with the embodiments of  FIGS. 1-14 . Reference is hereby made to these earlier embodiments for a more complete description of such valves and valve arrangements (and alternatives thereto) that can be utilized in the embodiments of  FIGS. 17-21 . 
     As discussed above, the gas manifold  214  can be installed in the oven  20  as a single integral unit. More specifically, in some embodiments the housing  218  and the gas valve  242  are permanently or releasably connected together (e.g., by threaded fittings as shown in the illustrated embodiment, or with clamps, brackets, fasteners, brazing, welding, or in any other suitable manner) as a single integral unit, and can therefore be mounted within the oven  20  by an installer, service technician, or other user as a single integral unit. In other embodiments, the gas control gas valve  242  and/or the burners  278   b - d  are also installed with the housing  218  and the gas valve  242  as part of the same assembly (i.e., as part of the same single integral unit). 
     In operation, and with reference to  FIG. 21 , a controller  458  controls the operation of the gas manifold  214 . The controller  458  is substantially similar to the main controller  42  discussed above, and will therefore not be described in detail. Reference is hereby made to the embodiments of  FIGS. 1-14  above for further description of the controller  458  and its operation (and alternatives thereto). The controller  458  in the embodiments of  FIGS. 15-28  controls the gas valve  242  to regulate the flow of gas to the fourth gas outlet  262   d  (see  FIGS. 17-20 ), thereby controlling operation of the burner  278   d  supplied with gas by the fourth gas outlet  262   d . In some embodiments, the controller  458  can control the gas valve  242  according to a set of predetermined instructions or programs. The controller  458  may also communicate with temperature sensors, position sensors, and thermocouples to control the gas valve  242  as described above, such as (by way of example only) to adjust the oven  20  toward a steady state temperature throughout the oven tunnel  24  or in a selected tunnel segment  20 A,  20 B, or to control operation of an energy savings mode. Additionally, the gas valve  242  can control the flow of gas to the fourth gas outlet  262   d  in different ways depending at least in part upon the type of valve used, and operation of the controller  458 . For example, the gas valve  242  may be a shut-off valve that includes an open state and a closed state. In such embodiments, the gas valve  242  fully blocks the flow of gas to the fourth gas outlet  262   d  when with valve disk  251  seated against the inlet of the fourth gas outlet  262   d  in a closed state, and allows gas to flow into the fourth gas outlet  262   d  with valve disk  251  retracted from the inlet of the fourth gas outlet  262   d  when in an open state. Accordingly, when the gas valve  242  is in the open state, gas is supplied to all of the gas outlets  262   b - d , and thus, to all of the burners  278   b - d . When the gas valve  242  is in the closed state, gas is supplied to the second and third gas outlets  262   b - c , but is shut off from the fourth gas outlet  262   d . Therefore, when the gas valve  242  is in the closed state, the burners  278   b - c  supplied by the second and third gas outlets  262   b - c  are turned on and can receive a modulated gas supply, while the burner  278   d  supplied by the fourth gas outlet  262   d  is turned off. 
     Similarly, the gas valve  242  can instead be a modulating variable flow valve that modulates the flow of gas to the fourth gas outlet  262   d . In such embodiments, the variable flow valve  242  can be adjusted from a fully-opened state to a fully-closed state, as well as partially-opened states between the fully-open state and the fully-closed state. Likewise, the controller  458  can control the gas supply valve (e.g., valve  48  in  FIG. 3A ) engaged with the gas conduit  274  upstream of the gas manifold  214  to regulate the flow of gas to the interior volume  230 . Such a gas supply valve  48  can be used to control operation of the burners  278   b - d  connected to all of the gas outlets  262   b - d . For example, when the gas supply valve  48  blocks the flow of gas into the interior volume  230 , none of the burners  278   b - d  will receive gas, whereas when the gas supply valve  48  and the gas valve  242  are open, gas can be simultaneously supplied and modulated to the interior volume  230 , the gas outlets  262   b - d , and the burners  278   b - d . Similar to the gas valve  242 , the gas supply valve  48  can be used to control the flow of gas to the interior volume  230  in different ways depending at least in part upon the type of valve used. The gas supply valve may be a shut off valve  48  or can instead be a modulating variable flow valve such as modulating gas valve  53  described above in connection with  FIG. 3A . 
       FIGS. 22 and 23  show a gas manifold  214  for installation in an oven  20  according to some embodiments. The gas manifold  214  may be mounted to a burner housing  290 . With reference to  FIGS. 24 a , 24 b   , and  25 , the burner housing  290  includes burner inlets  294   a - d  and heat exchange inlets  298   b - d . As described above in connection with  FIGS. 17-21 , the burners  278   b - d  are mounted to the gas outlets  262   b - d  (see  FIGS. 20 and 21 ), respectively, and are positioned within the burner housing  290 . The burners  278   b - d  are supported by a burner support  302  (see  FIG. 22 ). A first end  306   b - d  of each heat exchange tube  310   b - d  is connected to each of the heat exchange inlets  298   a - d  of the burner housing  290 . A second end  314   b - d  of each heat exchange tube  310   b - d  is in fluid communication with a plenum of the oven  20  (not shown). A target  318   b - d  is positioned proximate the second end  314   b - d  of each of the heat exchange tubes  310   b - d . The targets  318   b - d  are spaced from the second ends  314   b - d  of the heat exchange tubes  310   b - d  to restrict (slow) the flow of flue gasses from the heat exchange tubes  310   b - d  during operation of the oven  20  and to prevent flames from lifting off of the burners  278   b - d . Each of the burners  278   b - d  is aligned with a respective heat exchange tube  310   b - d  so that burners  278   b - d  are in fluid communication with the heat exchange tube inlets  298   b - d . In the illustrated embodiment, there are three burners  278   b - d  aligned with three heat exchange tubes  310   b - d . The illustrated embodiment shows a heat exchange tube  310   a  that is not in fluid communication with a burner (i.e. “dummy” tube). The heat exchange tube  310   a  is positioned adjacent one of the heat exchange tubes  310   b - d . A first end  306   a  of the heat exchange tube  310   a  is positioned adjacent the burner housing  290 , and a second end  314   a  of the heat exchange tube  310   a  is in fluid communication with a plenum of the oven  20  (not shown). A target  318   a  is positioned adjacent the heat exchange tube  310   a . The burner housing  290  does not include a heat exchange tube inlet aligned with the heat exchange tube  310   a , so that the heat exchange tube  310   a  that is not in fluid communication with one the burners  278   b - d  is not in fluid communication with the burner housing  290 . Such an arrangement prevents the heat exchange tube  310   a  from drawing relatively cool air into the plenum of the oven  20 . Alternate embodiments may include more or less burners, some or all of which are supported in other manners (e.g., with different structure for supporting each burner as an alternative to the illustrated burner support  302 , with no burner support, and the like). In some embodiments having four burners, the heat exchange tube  310   a  is in fluid communication with the housing  290  and one of the burners, as described above with respect to heat exchange tubes  310   b - c.    
     In some embodiments, it is desirable to prevent air passage through the heat exchanger tube  310   d  corresponding to the burner  278   d  when the burner  278   d  is off. Such air passage can result in heating inefficiencies during operation of the other burners  278   b  and  278   c . For this purpose, and as shown in  FIG. 23 , the heat exchange tube  310   d  that corresponds to (e.g., is aligned with) the burner  278   d  is selectively covered by a damper assembly  322 . The burner  278   d  is connected to the outlet  262   d , which is better shown in  FIGS. 17-20 . As will be described in greater detail below, the damper assembly  322  is configured to block access to the heat exchange tube  310   d  when the gas valve  242  is in the closed position and prevents gas flow to the third burner  278   d.    
     As shown in  FIGS. 23-25 , the damper system  322  includes a damper support  326 , a damper  332 , and a damper actuator  334 . In the illustrated embodiment, the damper support  326  includes a first side bracket  338 , a second side bracket  342 , and a connecting bracket  346 . With reference to  FIGS. 23, 24   a , and  24   b , the first side bracket  338  and the second side bracket  342  of the illustrated embodiment are positioned within a slot  350  formed in a bottom  354  of the burner housing  290 , whereas the connecting bracket  346  is positioned above the first side bracket  338  and the second side bracket  342 . The first side bracket  338  and the second side bracket  342  are substantially L-shaped, and are positioned on either side of the heat exchange tube inlet  298   d . The first side bracket  338  is substantially similar to the second side bracket  342 . Accordingly, only the second side bracket  342  will be described in detail below. 
     With reference to  FIG. 25 , a first portion  358  of the second side bracket  342  is engaged with a side  262  of the burner housing  290 , and a second portion  366  of the second side bracket  342  is positioned along the bottom  354  of the burner housing  290 . The second portion  366  includes a protrusion  370  that extends through a slot  350  formed in the bottom  354  of the burner housing  290 . The second side bracket  342  also includes a track  374  that extends along the first portion  358  and along the protrusion  370  of the second portion  366  so that the track  374  extends through the slot  350  from one side of the bottom  354  of the burner housing  290  to an opposite side thereof. 
     The damper  332  is made from a flexible, thermostable material such as aluminum or polyterafluroethylene (PTFE). The damper  332  is positioned along the tracks  374 ,  378  in the first side bracket  338  and the second side bracket  342 , respectively. The damper  332  is movable between a first position ( FIG. 24 a   ) in which the inlet  298   d  to the heat exchange tube  310   d  is blocked, and a second position ( FIG. 24 b   ), in which the inlet  298   d  to the heat exchange tube  310   d  is open. In some embodiments, the damper  332  is continuously positionable (i.e., capable of being moved and stopped to any position in a range of positions) along the tracks  374 ,  378 . 
     Although the damper support  326  in the illustrated embodiment includes the side brackets  338 ,  342 , connecting bracket  346 , and tracks  374  along which the damper  332  is moved, it should be noted that any other structure performing the same function (i.e., guiding and supporting the damper  332  in movement between opened and closed positions as described above) can instead be used, such as any other suitable frame or bracket at least partially surrounding the first heat exchange inlet  298   d . Also, although the damper support  326  is shown secured to the burner housing  290  by protrusions  370  extending through slots  350  in the bottom  354  of the burner housing  290 , it should be noted that the damper support  290  can be secured to and/or with respect to the bottom  354  or any other wall or structure of the burner housing  290  in any manner desired, such as by adhesive or cohesive bonding material, fasteners, snap-fit connections, inter-engaging elements, and the like. 
     With continued reference to the embodiment of  FIGS. 22-25 , a number of other dampers and damper materials can be used to perform the same function as the damper  332  described above. For example, rather than utilizing a flexible, thermostable material such as aluminum or polyterafluroethylene (PTFE), more rigid and inflexible materials can still be used for the damper  332 . For example, the damper  332  can be constructed of rigid bars of material hinged together (whether via hinge elements pivotably connected to like the roll top of a roll-top desk) to flex while running along the tracks  374  of the damper support  326  described above. 
     The damper actuator  334  of the illustrated embodiment is mounted to the bottom  354  of the burner housing  290  and includes an arm  382 , a damper guide  386 , a pin  390 , and a motor  394 . As shown in  FIGS. 24 a  and 24 b   , the arm  382  has a first end  398  and a second end  402 . A slot  406  extends from the first end  398  along a length of the arm  382 . The second end  402  of the arm  382  includes an opening  410  sized to engage an output shaft  414  of the motor  394 . The damper guide  386  is secured to the bottom  354  of the burner housing  290 , and can extend substantially parallel to the burners  278   b - d  as shown. The illustrated damper guide  386  includes a longitudinally extending slot  418 . The pin  390  is engaged with the damper  332  and is positioned within the slot  406  of the arm  382  and the slot  418  of the damper guide  386 . The pin  390  is movable from a first position proximate a first end  422  of the damper guide  386  ( FIGS. 24 a  and 24 b   ) and a second position proximate a second end  426  of the damper guide  386 . In the illustrated embodiment, the motor  394  is a non-spring return motor capable of at a least a 0° and 90° range of motion, and is secured to the bottom  354  of the burner housing  290  by a motor mounting block  430 , although other suitable motor mounts can instead be used as desired. In other embodiments, however, any other type of prime mover (e.g., solenoid, hydraulic or pneumatic actuator, rotary magnetic system, and the like) can instead be used to move the arm  382 , or to otherwise directly or indirectly move the damper  332  between its opened and closed positions. 
     In the illustrated embodiment, one of the heat exchange inlets  298   d  of the burner housing  290  is provided with a damper system  322 . However, in other embodiments two or more damper systems  322  can be provided on the burner housing  290  to perform similar functions (i.e., on other heat exchange inlets  298   b ,  298   c ) as the damper system  322  described above for heat exchange inlet  298   d . In this regard, each such damper system  322  can be individually controllable and actuatable with its own damper support, damper, and damper actuator in the manner described above with regard to the damper system  322  for heat exchange inlet  298   d . Any number of the same or different damper systems  322  can be installed and used on the burner housing  290  as desired. 
     Also, although the damper  332  of the illustrated damper system  322  slides along tracks  374  of the damper support  326 , and in so doing flexes as it turns a corner between opened and closed positions, the damper  332  can be installed and actuated in a number of other ways to selectively cover and close the heat exchange inlet  298   d . By way of example only, the damper  332  can slide along straight tracks in a damper support  290  in which the damper  332  only translates to and from a position closing the heat exchange inlet  298   d , can rotate or pivot toward and away from such a position, or can move toward and away from such a position in any other manner. Depending at least in part upon the shape and orientation of the damper support  326  with respect to the burner housing  290 , such damper movement can be established by flexible or inflexible dampers  332  driven by any of the actuators described herein. 
       FIGS. 26 and 27  show an alternate embodiment of a damper system  322 ′. The damper system  332 ′ includes a damper support  326 ′, a damper  332 ′, and a damper actuator  334 ′. The damper support  326 ′ and the damper  332 ′ are substantially the same as described above in connection with  FIGS. 22-25 , and will not be described in detail below. Reference is hereby made to  FIGS. 22-25  and the accompanying text for further description of the elements and features of the damper support  326 ′ and damper  332 ′ (and alternatives thereto). Like parts in  FIGS. 26 and 27  are referred to with like numbering, wherein parts of the damper system  322 ′ will be indicated with the prime symbol “′”. 
     As shown in  FIGS. 26-27 , the damper actuator  334 ′ is mounted to a bottom  354 ′ of a burner housing  290 ′ and includes an arm  434 ′, a damper guide  386 ′, a pin  390 ′, and a solenoid  394 ′. With continued reference to  FIGS. 26-27 , the illustrated arm  434 ′ is substantially “L”-shaped, and has a first end  438 ′, a central portion  442 ′, and a second end  446 ′. The first end  438 ′ is engaged with the damper  332 ′ and includes the downwardly extending pin  390 ′. The pin  390 ′ is received in a slot  406 ′ of the damper guide  386 ′. The central portion  442 ′ is pivotally mounted to the burner support housing  290 ′. The second end  446 ′ of the illustrated arm  434 ′ is engaged with an output shaft  414 ′ of the solenoid  394 ′. The second end  446 ′ of the arm  434 ′ may be secured to the solenoid  394 ′ using a clip  450 ′ as shown in  FIGS. 26-27 , or may be connected to the output shaft  414 ′ of the solenoid  394 ′ using other fastening devices. In the illustrated embodiment of  FIGS. 26 and 27 , the solenoid  394 ′ may be a linear actuator, and is secured to the bottom  354 ′ of the burner housing  290 ′ by a support bracket  454 ′. 
     The damper guide  386 ′ of the illustrated embodiment of  FIGS. 26 and 27  is secured to the bottom of the burner housing  290 ′ and can extend substantially parallel to the burners  278   b - d  as shown. The damper guide  386 ′ includes a longitudinally extending slot  418 ′. The pin  390 ′ engaged with the first end  422 ′ of the arm  434 ′ is positioned within the slot  418 ′ of the damper guide  386 ′, and is movable from a first position proximate a first end  422 ′ of the damper guide  386 ′ ( FIG. 27 ) and a second position proximate a second end  426 ′ of the damper guide  386 ′ ( FIG. 26 ). 
     In the illustrated embodiment of  FIGS. 26 and 27 , the solenoid  394 ′ is a two-position linear actuator, for example, a spring-returned solenoid, and is secured to the bottom  354 ′ of the burner housing  290 ′ by a support bracket  454 ′. With reference to  FIGS. 23-28 , in operation, the controller  458  determines whether controllable burner  278   d  is off. When the controllable burner  278   d  is off, the controller  458  actuates the motor  394  or solenoid  394 ′ to close the damper  332 ,  332 ′. To close the damper  332 ,  322 ′, the controller  458  commands the motor  394  or solenoid  394 ′ to rotate the output shaft  414 ,  414 ′ a calculated degree. The rotation of the output shaft  414 ,  414 ′ rotates the arm  382 ,  434 ′. As a result, the pin  390 ,  390 ′ moves along the slot  418 ,  418 ′ of the damper guide  386 ,  386 ′ to move the damper  332 ,  322 ′ in a direction shown by arrow  438 ,  438 ′ along the bottom  354 ,  354 ′ of the burner housing  218 ,  218 ′ and in a direction shown by arrow  442 ,  442 ′ along the tracks  374 ,  378 ,  374 ′,  378 ′, of the first side bracket  338 ,  338 ′ and the second side bracket  342 ,  342 ′ into the closed position. In some embodiments, the controllable burner  278   d  is always off when the oven  20  is operating in the idle mode. In such embodiments, the controller  458  determines whether the oven is operating in the idle mode. When the oven  20  is entering into or operating in the idle mode, the controllable burner  278   d  is off, so the controller  434  actuates the motor  394  to close the damper  332 . 
     When the oven  20  is not operating in the idle mode or is exiting the idle mode, in some embodiments the controller  458  senses a temperature of the cooking chamber of the oven  20 . In the illustrated embodiment, when the sensed temperature is below a threshold temperature (e.g., 360° F.), the controller  458  turns the controllable burner  278   d  off and actuates the motor  394  or solenoid  394 ′ to move the damper  332 ,  332 ′ to the closed position as described above. If the controller  458  senses that the temperature is above a threshold temperature (which can be the same or different from the threshold temperature just described), the controller  458  turns the controllable burner  278   d  off and actuates the motor  394  or solenoid  394 ′ to move the damper  332 ,  332 ′ to the closed position as described above. 
     When the controller  458  determines a need to activate the controllable burner  278 , the controller  458  determines whether the damper  332  is in an open or a closed position. To open the damper  332 ,  332 ′, the controller  458  commands the motor  394  or solenoid  394 ′ to rotate the output shaft  414 ,  414 ′ a calculated degree. The rotation of the output shaft  414 ,  414 ′ rotates the arm  382 ,  434 ′. As a result, the pin  390 ,  390 ′ moves along the slot  418 ,  418 ′ of the damper guide  386 ,  386 ′ to move the damper  332 ,  322 ′ in a direction opposite to that shown by arrow  438 ,  438 ′ along the bottom  354 ,  354 ′ of the burner housing  218 ,  218 ′ and in a direction opposite to that shown by arrow  442 ,  442 ′ along the tracks  374 ,  378 ,  374 ′,  378 ′, of the first side bracket  338 ,  338 ′ and the second side bracket  342 ,  342 ′ into the open position. In some embodiments, when the controller  458  senses that the damper  332 ,  332 ′ is in the open position, the controller  458  energizes the gas valve  242  to bring the controllable gas outlet  262   d  into communication with the interior volume  230  of the gas manifold  214 , and ignites the controllable burner  278   d . The controller  458  can be programed so that the controllable burner  278   d  is never ignited when the damper  332 ,  332 ′ is closed. 
       FIGS. 29-34  show an alternate embodiment of a gas manifold  514  for regulating the supply of gas to a set of gas burners  578  ( FIG. 34 ). With the exception of structure and features described above and illustrated in  FIGS. 1-21  that are incompatible with the embodiment of  FIGS. 29-34 , reference is hereby made to the embodiments of  FIGS. 1-21  described above for a more complete description of the features and elements of the embodiments of  FIGS. 29-34  (and possible alternatives thereto), which above descriptions apply equally to the embodiments of  FIGS. 29-34 , with like elements being identified by like reference numbers in the 500-series of reference numbers. The gas manifold  514  is modular and can be reconfigured to operate a different number of burners  578  independently of each other as explained below. 
     As shown in  FIGS. 29-34 , the gas manifold  514  includes an elongated housing  518  that defines a longitudinal axis  522  extending through a first end  534  of the housing  518  and a second end  538  of the housing  518  spaced apart from the first end  534 . The housing  518  can comprise either a one-piece unit or multiple units connected together, as described above in connection with the housing  114  of the embodiments of  FIGS. 8-16 . In the illustrated embodiment of  FIGS. 29-34 , the housing  518  is constructed of a single integral unit and may produced by machining operations (e.g., drilling, milling, and the like) on a piece of metal to create the various features of the housing  518  described herein. The housing  518  defines an interior volume  530  that is at least partially enclosed by a wall  526 . In the exemplary embodiments of  FIGS. 29-34 , the wall  526  extends continuously between the first end  534  and the second end  538  in a direction parallel to the longitudinal axis  522  for the entire length of the housing  518  and has a rectangular outer perimeter defined by a first sidewall  526   a , a second sidewall  526   b  opposite the first sidewall  526   a , a third sidewall  526   c , and a fourth sidewall  526   d  opposite the third sidewall  526   c . In the illustrated embodiment, the interior volume  530  has a circular cross section along the longitudinal axis  522  extending between the first end  534  and the second end  538  of the housing  518 , although other cross-sectional shapes are possible, including without limitation other rounded or polygonal cross-sections. In other embodiments, the housing  518  may be an extruded part having a through opening that extends along the longitudinal axis  522  between the first end  534  and the second end  538  of the housing  518  to define at least a portion of the interior volume  530 , wherein each end of the through opening can be engaged with a plug (not shown) to prevent gas in the interior volume  530  from flowing out of the ends of the through opening. 
     The housing  518  includes a gas inlet  558 , a plurality of gas outlets  562  ( FIG. 32 ), and a plurality of valve openings  564  ( FIG. 33 ), and can also include a first opening  566  and/or a second opening  570  such as those shown in  FIGS. 29-33 . The gas inlet  558 , the plurality of gas outlets  562 , the plurality of valve openings  564 , the first opening  566 , and the second opening  570  of the illustrated embodiment are formed within the wall  526  of the housing  518 . The gas inlet  558  is in fluid communication with the interior volume  530  of the housing  518  such that gas flowing through the gas inlet  558  is received within the interior volume  530 . The gas inlet  558  of the illustrated embodiment is formed in the first sidewall  526   a . However, the gas inlet  558  can be formed in any of the sidewalls  526   a - 526   d  of the housing  518  based upon other configurations of the gas manifold  514 . The gas inlet  558  may be threaded and sized to receive a gas conduit (e.g., gas conduit  274  shown in  FIGS. 22-23 ), although any other suitable type of connection to an upstream gas supply line can instead be used. The gas conduit is coupled to a gas supply (not shown) and allows gas to enter the interior volume  530 . 
     As shown in  FIGS. 31-32 , each gas outlet  562  is in fluid communication with the interior volume  530  and extends through the wall  526  of the housing  518 . In the illustrated embodiment, the plurality of gas outlets  562  includes four gas outlets  562   a - d . The gas outlets  562   a - d  are positioned along the wall  526  of the housing  518  and are spaced apart from the gas inlet  558  in respective positions downstream of the gas inlet  558 . For example, the gas outlets  562   a - d  of the illustrated embodiment are spaced apart from one another along the axis  522  between the first end  534  and the second end  538  of the housing  518 , and can be positioned on the same side of the housing  518 , such as in the manner shown in  FIGS. 29-34 . Alternatively, different numbers and arrangements of gas outlets  562  are possible. For example, at least two gas outlets  562  may be positioned above one another in a direction perpendicular to the axis  522  on the same side of the housing  518 , or at least two gas outlets  562  may be spaced apart from one another along the axis  522  and positioned on different sides of the housing  518 . 
     Each gas outlet  562  may be sized to interchangeably receive a seat insert  584  or a plug  586 . In some embodiments, each gas outlet  562  may be removably coupled with a seat insert  584  or a plug  586 . In the illustrated embodiment, for example, each gas outlet  562  may be threadedly engaged with a seat insert  584  or a plug  586 , for example, internal threads of each gas outlet  562  mating with external threads of a seat insert  584  or a plug  586 . In particular, the first three gas outlets  562   a - c  of the illustrated embodiment are threadedly engaged with seat inserts  584   a - c , respectively, and the fourth gas outlet  562   d  is threadedly engaged with a plug  586   d . Each of the seat inserts  584   a - c  received in one of the gas outlets  562   a - c  is removable and can be replaced with an additional plug  586 . Likewise, the plug  586   d  received in the gas outlet  562   d  is removable and can be replaced with an additional seat insert  584 . In other embodiments, the gas outlets  562  may be coupled to the seat inserts  584  or the plugs  586  by a fastener, a press fit, a snap fit, a weld, a braze, or by any other suitable method of attachment. 
     Each of the seat inserts  584   a - c  has a hollow passageway to discharge gas from the interior volume  530  as shown in  FIG. 33 . In the illustrated embodiment, each of the seat inserts  584   a - c  is an elongated seat insert that defines a longitudinal axis between opposite open ends of the seat insert. The hollow passageway of each of the seat inserts  584   a - c  of the illustrated embodiment extends between the open ends of the seat insert along its longitudinal axis  585   a - c . A portion of each of the seat inserts  584   a - c  extends into the interior volume  530 . The longitudinal axis of each of the seat inserts  584   a - c  can be substantially perpendicular to the longitudinal axis  522  of the housing  518  when the seat insert is received in one of the gas outlets  562   a - c , by way of example. 
     As shown in  FIG. 34 , the seat inserts  584   a - c  are each in fluid communication with a burner  578   a - c , respectively. For example, in the illustrated embodiment, the seat inserts  584   a ,  584   b , and  584   c  are in fluid communication with burners  578   a ,  578   b , and  578   c , respectively. As a result, the gas outlets  562   a - c  corresponding to the seat inserts  584   a - c  also are each in fluid communication with the burners  578   a - c , respectively. The burners  578   a - c  may be in-shot burners, as shown in  FIG. 34 , or any other suitable type of burner, including, for example, gas jet burners. As shown in  FIGS. 31-34 , the seat inserts  584   a - c  of the illustrated embodiment are coupled to the burners  578   a - c  by an injector  582   a - c , respectively. In particular, the seat inserts  584   a - c  are each sized to receive an injector  582   a - c . The injectors  582   a - c  can be substantially the same as the injectors  174  described above, and can include a hollow passageway to allow gas to pass from the interior volume  530  of the housing  518  to the burners  578   a - c.    
     In the illustrated embodiment, each of the injectors  582   a - c  may be coupled to one of the seat inserts  584   a - c  via a threaded connection, for example, external threads of each of the injectors  582   a - c  mating with internal threads of the seat inserts  584   a - c . With this configuration, each injector  582  is removable from a corresponding seat insert  584  and is interchangeable with another injector, for example an injector having the same or different gas flow properties. In other embodiments, each injector  582  and corresponding seat insert  584  may be permanently connected together as a single integral unit. Additionally, in some embodiments, an end of each of the injectors  582   a - c  opposite the gas manifold  514  is slidingly received within an inlet of a burner  578   a - c . In other embodiments, supply tubes (not shown) of any length and construction (e.g., flexible or rigid) may be used with or without such injectors  582   a - c  to direct the gas from each seat inserts  584   a - c  to a corresponding burner  578   a - c . Alternatively, when multiple burners  578  are configured to receive gas from a shared seat insert  584 , the burners  578  may be coupled to a common supply tube (not shown) leading to the shared seat insert  584 . Gas is received by the burner  578  at a proximal end, and is ignited as it passes through the burner  578 , thus producing a flame at a distal end of the burner  578 . Each burner  578  may have its own independent igniter (not shown), or burners may share igniters. Further, the burners  578  may include a carryover tube for carrying the ignition flame from one burner to the next that is integral to each burner or is separate from and is connected to the burners. 
     With continued reference to the illustrated embodiment of  FIGS. 29-34 , the plurality of valve openings  564  are each in fluid communication with the interior volume  530  and extend through the wall  526  of the housing  518  ( FIG. 33 ). Each valve opening  564  is positioned along the wall  526  opposite a corresponding gas outlet  562 . In the illustrated embodiment, the plurality of valve openings  564  includes four valve openings  564   a - d  positioned along the wall  526  at locations opposite the gas outlets  562   a - d , respectively. 
     The gas manifold  514  may include one or more gas valves  542  that are each aligned with a corresponding valve opening  564 . In the illustrated embodiment, a first gas valve  542   a  is aligned with the first valve opening  564   a  and a second gas valve  542   b  is aligned with the second valve opening  564   b . The gas valves  542   a - b  can be removably coupled to the wall  526  of the housing  518  (e.g., by threaded fittings as shown in the illustrated embodiment). With this configuration, the gas valves  542   a - b  of the illustrated embodiment are removably installed opposite gas outlets  562   a - b , respectively, and are each aligned with a corresponding seat insert  584   a - b  received in one of the gas outlets  562   a - b . Alternatively, different numbers and arrangements of valve openings  564  and gas valves  542  are possible. For example, at least two valve openings  564  may be formed above one another in a direction perpendicular to the axis  522  on the same side of the housing  518 , or at least two valve openings  564  may be spaced apart from one another along the axis  522  and formed on different sides of the housing  518 . 
     As shown in  FIG. 33 , in the illustrated embodiment, each of the gas valves  542   a - b  is received in a corresponding valve opening  564  and includes a valve body  550   a - b . Each valve body  50   a - b  is at least partially positioned within the interior volume  530  and is aligned with and movable along the longitudinal axis of the corresponding seat insert  584   a - b . In particular, each of the valve bodies  550   a - b  has a valve disk  551   a - b  at one end that is movable with the respective valve body within volume  530 . In operation, each of the valve bodies  550   a - b  is continuously repositionable from a closed position ( FIG. 33 ) in which the valve disk  551   a - b  of valve body is seated against the corresponding seat insert  584   a - b  and a retracted position, including a fully open position (not shown) in which the valve disk  551   a - b  of valve body is seated against the housing  518 . In other embodiments, the valve bodies  550   a - b  may initially be positioned entirely outside the interior volume  530 , including, for example, in the valve opening  564 . 
     Any valve opening  564  that does not receive a gas valve  542  can be sealed to prevent gas in the interior volume  530  from flowing out of the unused valve opening  564 . In the illustrated embodiment, cover plates  568   c - d  are mounted over the third and fourth valve openings  564   c - d , respectively, in sealing engagement with the housing  518 , and can be removably coupled to the housing  518  (e.g., by threaded fittings as shown in the illustrated embodiment) to selectively cover and close the valve openings  564   c - d . Each of the cover plates  568   c - d  covering one of the third and fourth valve openings  564   c - d  is removable and can be replaced with an additional gas valve  542 . Likewise, each of the gas valves  542   a - b  installed in one of the first and second valve openings  564   a - b  is removable and can be replaced with an additional cover plate  568 . In some embodiments, other suitable structure can instead be used to selectively seal the valve openings  564 , such as any suitable plug removably and sealingly engaging with the valve openings  564 , for example a plug having external threads mating with internal threads of each valve opening  564 . 
     With reference to  FIGS. 29-33 , the first opening  566  can be engaged with a plug (not shown), which prevents gas in the interior volume  530  from flowing out of the first opening  566 . For example, the first opening  566  may be threadedly engaged with a plug, for example, external threads of the plug mating with internal threads of the first opening  566 . Any unused gas outlets  562   a - d  can also be engaged with a plug (e.g., plug  586  described above) based upon other configurations of the gas manifold  514 , for example, via a threaded connection. In some embodiments, sensors may be installed through the openings  566 ,  570 , or the openings  566 ,  570  may function as additional gas inlets or additional gas outlets. For example, in the illustrated embodiment, the second opening  570  can be used as a manifold pressure monitoring port, and so can be sized to receive via a threaded connection at least one sensor (not shown) for measuring a pressure within the manifold  514 . In such embodiments, the sensor can be in communication with a main controller  560  (described in greater detail below) so that when the gas valve  542  and/or another gas control valve (e.g., main control valve  48  shown in  FIG. 3A ) are adjusted, the pressure within the manifold  514  can be monitored. 
     Additional valves may be used with the gas manifold  514  to further control the flow of gas. For example, in some embodiments, one or more gas control valves as described above in the embodiments of  FIGS. 1-21 , such as a modulating variable flow and/or a shut off valve (not shown), may be in fluid communication with the gas supply conduit (e.g., gas conduit  274  shown in  FIGS. 22-23 ) upstream of the gas inlet  558 . Any such valves can be positioned external to the housing  518 , and can be operable to selectively control the flow of gas to the interior volume  530  of the gas manifold  514 . Valves supplying gas to the gas manifold  514  can take any of the forms and can be connected and operated in any of the manners described above in connection with the embodiments of  FIGS. 1-21 . Reference is hereby made to these earlier embodiments for a more complete description of such valves and valve arrangements (and alternatives thereto) that can be utilized in the embodiments of  FIGS. 29-34 . 
     The gas manifold  514  can be installed in the oven  20  as a single integral unit. More specifically, in some embodiments the housing  518  and the gas valves  542  are permanently or releasably connected together (e.g., by threaded fittings as shown in the illustrated embodiment, or with clamps, brackets, fasteners, brazing, welding, or in any other suitable manner) as a single integral unit, and can therefore be mounted within the oven  20  by an installer, service technician, or other user as a single integral unit. In other embodiments, the gas control valve and/or the burners  578  are also installed with the housing  518  and the gas valves  542  as part of the same assembly (i.e., as part of the same single integral unit). 
     In operation, and with reference to  FIG. 34 , a controller  560  controls the operation of the gas manifold  514 , including gas valves  542   a - b  and any additional valves that control the gas supply to the manifold  514 . The controller  560  is substantially similar to the main controller  42  discussed above, and will therefore not be described in detail. Reference is hereby made to the embodiments of  FIGS. 1-21  above for further description of the controller  560  and its operation (and alternatives thereto). The controller  560  in the embodiments of  FIGS. 29-34  controls the gas valves  542   a - b  to regulate the flow of gas to the gas outlets  562   a - b , thereby controlling operation of the burners  578   a - b  supplied with gas by the gas outlet  562   a - b  through the seat inserts  584   a - b  and the injectors  582   a - b . In some embodiments, the controller  560  can control the gas valves  542   a - b  according to a set of predetermined instructions or programs. The controller  560  may also communicate with temperature sensors, position sensors, and thermocouples to control the gas valves  542   a - b  as described above, such as (by way of example only) to adjust the oven  20  toward a steady state temperature throughout the oven tunnel  24  or in a selected tunnel segment  20 A,  20 B, or to control operation of an energy savings mode as described above and in in U.S. Pat. Nos. 8,087,407 and 8,839,714, the entire contents of each of which are hereby incorporated by reference. 
     Additionally, the gas valves  542   a - b  can control the flow of gas to the gas outlets  562   a - b  in different ways depending at least in part upon the type of valve used, and operation of the controller  560 . For example, a gas valve  542  may be a shut-off valve that includes an open state and a closed state. In such embodiments, the gas valve  542  fully blocks the flow of gas to a corresponding gas outlet  562  with the valve disk  551  seated against the inlet of the gas outlet  562  in a closed state and allows gas to flow into the gas outlet  562  with valve disk  551  retracted from the inlet of the gas outlet  562  when in an open state. Accordingly, when each of the gas valves  542   a - b  is in the open state, gas is supplied to all of the gas outlets  562   a - c , and thus, to all of the burners  578   a - c . When, for example, the first gas valve  242   a  is in the closed state, gas is supplied to the second and third gas outlets  562   b - c , but is shut off from the first gas outlet  562   a . Therefore, when the first gas valve  242   a  is in the closed state, the second and third burners  578   b - c  supplied by the second and third gas outlets  562   b - c  are turned on and can receive a modulated gas supply, while the first burner  578   a  supplied by the first gas outlet  562   a  is turned off. 
     Similarly, a gas valve  542  can instead be a modulating variable flow valve that modulates the flow of gas to a corresponding gas outlet  562 . In such embodiments, the variable flow valve  542  can be adjusted from a fully-opened state to a fully-closed state, as well as partially-opened states between the fully-open state and the fully-closed state. Likewise, the controller  560  can control the gas supply valve (e.g., valve  48  in  FIG. 3A ) engaged with the gas conduit upstream of the gas manifold  514  to regulate the flow of gas to the interior volume  530 . Such a gas supply valve  48  can be used to control operation of all of the burners  578   a - c  connected to the gas outlets  562   a - c . For example, when the gas supply valve  48  blocks the flow of gas into the interior volume  530 , none of the burners  578   a - c  will receive gas, whereas when the gas supply valve  48  and the gas supply valves  542   a - b  are open, gas can be simultaneously supplied and modulated to the interior volume  530 , the gas outlets  562   a - c , and the burners  578   a - c . Similar to the gas valve  542 , the gas supply valve  48  can be used to control the flow of gas to the interior volume  530  in different ways depending at least in part upon the type of valve used. The gas supply valve may be a shut off valve  48  or can instead be a modulating variable flow valve such as modulating gas valve  53  described above in connection with  FIG. 3A . 
     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.