WO2005094647A1

WO2005094647A1 - Conveyor oven apparatus and method

Info

Publication number: WO2005094647A1
Application number: PCT/US2005/009546
Authority: WO
Inventors: John Wiker; Mohan K. Panicker
Original assignee: Middleby Corporation
Priority date: 2004-03-23
Filing date: 2005-03-23
Publication date: 2005-10-13

Abstract

The conveyor (20) oven according to some embodiments includes one or more conveyors (22) passing through two or more tunnel segments of the oven, each of which has one or more temperature or position sensors coupled to a controller (42) for controlling the BTU output of a burner and/or the output of a fan associated with the corresponding tunnel segment (and in some case, another tunnel segment). If desired, the oven can utilize burner assemblies having two or more contiguous burners coupled as an integral unit, having a common air supply structure, coupled by an air supply conduit, and/or coupled by a conduit permitting ignition of one burner flame by another burner.

Description

CONVEYOR OVEN APPARATUS AND METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Priority is hereby claimed to United States provisional patent application number 60/555,474, filed on March 23, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] A conveyor oven is an oven with a conveyor that moves through a heated tunnel in the oven. Conveyor ovens are widely used for baking food products, especially pizzas, and the like. Examples of such ovens are shown, for example, in U.S. Pat. Nos. 5,277,105, 6,481,433 and 6,655,373.

[0003] Conveyor ovens are typically large metallic housings with a heated tunnel extending through them and a conveyor running through the tunnel. Usually such conveyor ovens are either 70 inches or 54 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 food products during their transit through the tunnel. The conveyor ovens include a heat delivery system including blowers which supply heat to the tunnel from a plenum through passageways leading to metal fingers 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. In modern conveyor ovens, 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.

[0004] The conveyor generally travels at a speed calculated to properly bake food products on the belt during the time period required for the conveyor to carry them through the entire length of the oven tunnel. Other food products requiring less time to bake may be placed on the conveyor at a point part way through the oven so that they travel only a portion of the length of the tunnel. A pizza is an example of a product which might require the full amount of baking time in order to be completely baked in the oven. A sandwich is an example of a product which might require only a portion of the full baking time.

[0005] Conveyor ovens are typically used in restaurant kitchens and commercial food manufacturing facilities. Typically they 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, this means that heat and noise are continuously escaping from the conveyor oven tunnel into the surrounding environment. This escape of heat wastes energy. It 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.

[0006] It is generally desirable to maintain uniform heating from one end of the heated tunnel of the oven to the other. Among the challenges to be overcome in achieving such uniform heating are the inherent variations in heating from oven to oven due to variations in the internal physical environment of otherwise identical ovens. A more significant challenge to maintaining uniform heating 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 by as much as 50-60° F from one end of the tunnel to the other.

[0007] Currently, the most common technique for balancing the heating through the length of the tunnel 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.

[0008] However, uniform heating through the length of the heated tunnel cannot be achieved 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 will reduce required baking times.

[0009] Additionally, in many applications it is necessary to be able to operate the 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.

BRIEF SUMMARY OF THE INVENTION [0010] Some embodiments of the present invention provide a conveyor oven for cooking food product, wherein the conveyor oven comprises a tunnel; a conveyor extending into and movable within the tunnel to convey food product within the tunnel; a heating element operable to generate heat to be provided to the tunnel; a fan having different states, including a first state in which the fan moves air in the tunnel and a second state in which the fan does not move air in the tunnel; a sensor positioned to detect at least one of a temperature within the oven and the presence of food product upon the conveyor; and a controller coupled to the fan, the controller responsive to the sensor by changing the state of the fan.

[0011] In some embodiments, a conveyor oven for cooking food product is provided, and comprises a tunnel having first and second tunnel segments at least partially defining different portions of the tunnel; at least one conveyor extending into and movable within the first and second tunnel segments; first and second heating elements operable to generate heat to be provided to the tunnel, each of the first and second heating elements having a respective heat output; at least one fan to move air in the tunnel; a first sensor positioned to detect at least one of a first temperature at a first location within the tunnel and the presence of food product upon the conveyor at a first location with respect to the tunnel; a second sensor positioned to detect at least one of a second temperature at a second location within the tunnel and the presence of food product upon the conveyor at a second location with respect to the tunnel; and a controller coupled to the first and second heating elements and the first and second sensors, the controller responsive to the first and second sensors by independently controlling the heat outputs of the first and second heating elements.

[0012] Some embodiments of the present invention provide a conveyor oven for cooking food product, wherein the conveyor oven comprises a tunnel having first and second tunnel segments at least partially defining different portions of the tunnel; at least one conveyor extending into and movable within the first and second tunnel segments; at least one heating element operable to generate heat to be provided to the tunnel, each of the at least one heating element having a respective heat output; first and second fans to move air in the tunnel, each of the first and second fans operable at a respective speed; a first sensor positioned to detect at least one of a first temperature at a first location within the tunnel and the presence of food product upon the conveyor at a first location with respect to the tunnel; a second sensor positioned to detect at least one of a second temperature at a second location within the tunnel and the presence of food product upon the conveyor at a second location with respect to the tunnel; and a controller coupled to at least one of the first and second fans and the first and second sensors, the controller responsive to the first and second sensors by independently controlling the speeds of at least one of the first and second fans.

[0013] In some embodiments, a burner assembly for an oven is provided, and comprises a first housing; a first tube located at least partially within the first housing and having an interior; a second housing coupled to the first housing; a second tube located at least partially within the second housing and having an interior; at least one gas inlet through which gas is supplied to the first and second tubes; at least one air inlet through which air is supplied to the first and second housings; and a conduit extending to and between the first and second housings and through which fluid communication is established between the interior of the first housing and the interior of the second housing, the conduit positioned to supply at least one of air from the first tube to the second tube to maintain a flame in the second tube, and heat from the first tube to the second tube to ignite a flame from the second tube.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] Preferred embodiments of the invention are shown in the attached drawings, in which:

[0015] FIGURE 1 is a perspective view of a conveyor oven in accordance with an embodiment of the present invention;

[0016] FIGURE 2 is a perspective view of a portion of the conveyor oven of Figure 1, in which a hinged oven access panel has been opened to reveal some of the internal workings of the oven;

[0017] FIGURE 3 is an enlarged elevation view of the controls of the oven of Figure 1;

[0018] FIGURE 4 is a diagrammatic representation of the tunnel of the oven of Figure 1 , apportioned into two segments with independent temperature sensing and independent heat delivery means;

[0019] FIGURES 5 A-5C include a diagrammatic representation of a pizza moving through the heated tunnel of the conveyor oven of Figure 1, with graphs showing changing BTU burner output and blower output as the pizza advances through the tunnel;

[0020] FIGURE 6 is a diagrammatic representation of a single burner of a contiguous multiple burner configuration in accordance with an embodiment of the present invention;

[0021] FIGURE 6A illustrates a venturi support disk of the burner of Figure 6;

[0022] FIGURE 6B illustrates a flame retention member of the venturi tube of the burner of Figure 6;

[0023] FIGURES 7 A and 7B are perspective views of a pair of contiguous burners in accordance with an embodiment of the present invention; [0024] FIGURE 8 shows the distal ends of the outer tubes of the burners of Figures 7 A - 7B;

[0025] FIGURES 9 - 9D illustrate crossover openings between the contiguous burners of Figures 7A - 7B;

[0026] FIGURE 10 illustrates an alternative dual contiguous burner configuration in accordance with an embodiment the present invention; and

[0027] FIGURE 11 is a top plan view of selected elements of the oven of Figure 1.

DETAILED DESCRIPTION

[0028] 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 following 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. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms "connected," "coupled," and "mounted" and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings, and the terms "connected" and "coupled" and variations thereof are not restricted to physical or mechanical connections or couplings. Also, it is to be understood that phraseology and terminology used herein with reference to device or element orientation (such as, for example, terms like "front", "back", "up", "down", "top", "bottom", and the like) are only used to simplify description of the present invention, and do not alone indicate or imply that the device or element referred to must have a particular orientation. In addition, terms such as "first", "second", and "third" are used herein and in the appended claims for purposes of description and are not intended to indicate or imply relative importance or significance. Conveyors

[0029] FIG. 1 shows a 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 oven end 26 toward right oven end 28 or, alternatively in direction B, from right oven end 28 toward left oven end 26. Thus, oven ends 26 and 28 may serve respectively as the inlet and outlet of an oven with a rightwardly moving conveyor or as the outlet and inlet of an oven with a leftwardly moving conveyor.

[0030] The support, tracking and drive of conveyor 22 are achieved using conventional techniques such as those described in U.S. Patent Nos. 5,277,105 and 6,481,433 and 6,655,373, the contents of which are incorporated herein by reference insofar as they relate to conveyor support, tracking, and drive systems and related methods. In the illustrated embodiment, a chain link drive is housed within compartment 30 at the left end 26 of the oven. Thus, a food product, such as a raw pizza 32R, may be placed on the conveyor 22 of the ingoing left oven end 26 and removed from the conveyor 22 as fully baked pizza 32C (see FIG. 5C) at the outgoing right oven end 28. The speed at which the conveyor 22 moves is coordinated with the temperature in the heated tunnel 24 so that the emerging fully cooked pizza 32C is properly baked.

[0031] 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 left oven end 26 and travel at one speed to the center or other location of the oven 20, while a second conveyor beginning at such a location and ending at the right 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

[0032] 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 the conveyor 22 if less than a full bake cycle is required to produce a fully cooked product.

[0033] 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. 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

[0034] The oven controls, as shown in FIG. 3, can include a microprocessor-based controller 42 (such as a Honeywell UDC 3300 controller) which may be programmed to control and monitor the baking process by pressing appropriate set-up and display buttons 44a-44h while viewing alphanumeric display 46, which will display process variables and setpoints including oven temperature, hot air blower speed, etc. A "heat on" indicator can be illuminated when a minimum threshold heat output is generated by the oven 20 under control of the controller 42. The present temperature and/or the programmed setpoint temperature may be displayed. By simultaneously pressing selected keys in some embodiments, the value of the heat output with the heat on indicator in the "on" condition can be displayed. Also, the controller 42 can be configured to enable a user to cycle through actual temperature display indicators to reveal the actual temperatures, setpoint temperature, and the heat on condition. In the illustrated embodiment, the speed and direction of the conveyor 22 can be set using buttons 48a, 48b, 50a and 50b and their associated displays 48c and 50c. [0035] In some embodiments, the output display 46 can be automatically locked in a default display when a service person or operator places the controller 42 in a service mode by pressing appropriate key(s). Also, a failsafe condition can occur when any one of various tests fail, at which time a signal display (e.g., one or more flashing indicators) can be displayed, such as a signal display flashing alternately with a temperature display. For example, if the oven 20 has not reached 200° F within 15 minutes after an initial power-up of the oven 20, a message can be flashed on the display panel 46 indicating that controls need to be reset (e.g., power-cycled). As another example, if a temperature sensor fails to . operate properly, the display 46 can flash "open". Also, the display 46 can provide one or more prompts for servicing the oven 20. Each additional press of a service tool key can advance so that a service person can continually sequence through service prompts of a service mode. The service mode can be exited, for example, by either pressing an appropriate key or by pressing no key for a set period of time (e.g., sixty seconds). In either case, the system can be automatically returned to a normal state.

[0036] In the illustrated embodiment, a setpoint lock key 42d can automatically flash the temperature that has been selected for an operation of the oven 20. In some embodiments, this setpoint temperature can be increased or decreased by pressing either increment or decrement keys 42f, 42g. Also, in some embodiments the degrees (° F or ° C) used for the prompts can be changed by pressing either the increment or decrement keys 42f, 42g. While at a degrees ° F or ° C prompt, a selection of "F" or "C" can automatically change the units of all the display 46 to ° F or ° C. While a default display prompt is being displayed, an indicator can flash to indicate which display is chosen as the default display, which can be changed, for example, by pressing either the increment or decrement keys 42f, 42g.

[0037] In some embodiments, the oven 20 is operated by: (1) turning a blower control 52 to an "ON" position to start a blower (described in greater detail below), (2) setting the temperature to a desired level using the controller 42 as described above, (3) turning a heat control 54 to an "ON" position to supply gas and to trigger ignition of the oven burner(s) (described in greater detail below), (4) turning a conveyor control 56 to an "ON" position to drive the conveyor 22, and (5) after an appropriate pre-heat period, placing food products on the conveyor and beginning the baking process. Tunnel Segments

[0038] Heat delivery systems for supplying heat to the tunnel 24 are described in U.S. Patent Nos. 5,277,105, 6,481,433 and 6,655,373, the disclosures of which are incorporated herein by reference insofar as they relate to heat delivery systems for ovens. These systems typically include a heat source in the form of a single gas-fired burner (or other heat source) for heating a plenum. For example, the burner can be located at the front of the oven for heating a plenum located at the back of the oven. Blowers are typically provided to move heat in the plenum through passageways to metal fingers that open into the oven at appropriate spacings from the conveyor belt to deliver streams of hot air onto food products present on the conveyor, as discussed earlier. The heat source is cycled on and off as necessary by a controller responding to signals from temperature sensors (e.g., thermocouples) positioned, for example, at the inlet and outlet ends of the oven tunnel.

[0039] In some embodiments of the present invention, 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. This 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 20A and 20B of the oven 20. The heat in plenums 68 and 70 is blown into the two oven segments 20A, 20B 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, 20B.

[0040] The temperatures in each of the oven segments 20 A, 20B 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 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 the chamber through which the conveyor 22 moves. Either or both sensors 80, 82 can be positioned nearer the midpoints of the segments 20A, 20B or in other locations, if desired. 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 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).

[0041] 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 BTU output of the burners 60, 62 and the corresponding blower output as the pizza advances through the tunnel 24. Thus, a raw pizza 32R is shown in FIG. 5C resting on the conveyor 22 before the pizza enters the oven tunnel 24. In the illustrated embodiment of FIG. 5C, the oven 20 has been heated to a desired temperature.

[0042] The oven 20 according to some embodiments of the present invention can detect the presence of a raw pizza 32R on the conveyor 22 by a position sensor 79, 81. The position sensor 79, 81 can take a number of different forms, and need not necessarily comprise components on opposite sides of the conveyor 22 as illustrated in FIG. 4. By way of example only, the position sensor 79, 81 can be an optical sensor positioned to detect the interruption of a beam of light (e.g., by a raw pizza 32R) extending across the conveyor 22 at the entrance of the left tunnel segment 20 A, an infrared detector positioned to detect a raw pizza 32R having a reduced temperature on the conveyor 22, a motion sensor positioned to detect motion of a raw pizza 32R upon the conveyor 22, or any other sensor capable of detecting the presence of the raw pizza 32R on the conveyor 22. In the illustrated embodiment of FIG. 4, for example, the position sensor 79, 81 comprises a light source 79 emitting a laser or other beam of light across the conveyor 22 to a reflector 81, which reflects the beam of light back to a photocell 81 (which may or may not be associated with the light source 79). Alternatively, the light source 79 and the photocell 81 can be on opposite sides of the conveyor 22, in which case an interruption in the beam of light can still be detected by the photocell 81.

[0043] In those embodiments of the present invention employing a position sensor 79, 81 at or adjacent the entrance of the left tunnel segment 20A as just described, the position sensor 79, 81 can be coupled to the controller 42, and can send one or more signals to the controller 42 responsive to the detection of a raw pizza 32R (or lack thereof) on the conveyor 22. The controller 42 can be responsive to the position sensor 79, 81 by increasing the BTU output of either or both burners 60, 62. In some embodiments, the controller 42 responds to the signal(s) from the position sensor 79, 81 by increasing the BTU output of the burner 60 of the left tunnel segment 20A, 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.

[0044] For example, the controller 42 can gradually increase the speed of both fans 72, 74 from a slow, relatively quiet standby level 71 to a full speed level 73, thereby supplying additional heat to both segments 20A and 20B of the tunnel (although an increase supply of heat can instead be provided to only one of the segments 20A, 20B in other embodiments). As another example, the controller 42 can respond to the signal(s) from the position sensor 79, 81 by quickly increasing the BTU output of the burner 60 of the left tunnel segment 20 A, by gradually increasing the BTU output of the burner 60 as the raw pizza 32R enters the left tunnel segment 20A, or by quickly or gradually increasing the BTU output of the burner 60 only after a set period of time permitting either or both fans 72, 74 to increase in speed. In these and other embodiments, the controller 42 can respond to the signal(s) from the position sensor 79, 81 by gradually increasing the BTU output of the burner 62 of the right tunnel segment 20, by gradually or quickly increasing the BTU output of the burner 62 following a lag time (e.g., a predetermined period of time that can be independent or dependent upon the speed of the conveyor 22), or by changing the BTU output of the burner 62 in any other manner.

[0045] If desired, the temperature sensor 80 can be used to detect the presence of a raw pizza 32R on the conveyor 22. For example, as the raw pizza 32R enters the oven 20 and approaches position 32(1), it draws heat causing sensor 80 (FIG. 4) to call for the controller 42 to supply additional gas to the burner 60 and/or to increase the speed of either or both fans 72, 74. The controller 42 can respond to detection of the raw pizza 32R by the temperature sensor 80 in any of the manners described above with reference to the position sensor 79, 81. The position sensor 79, 81 and the temperature sensor 80 can be connected to the controller 42 in parallel, thereby enabling the controller 42 to change the BTU output of the burner 60 and/or the speed of either or both fans 72, 74 based upon signals received by the position sensor 79, 81 or the temperature sensor 80.

[0046] Until air in the plenum(s) 68, 70 has been sufficiently heated, the above- described fan control generates a reduced amount of heat loss and fan noise from the oven tunnel 24 into the surrounding environment, and defines a load management setback of the oven 20. The establishment of a quiet and reduced airflow standby state of the fan(s) 72, 74 is an advantage of the load management setback. Also, while the fans 72, 74 in the illustrated embodiment are operated in tandem, in alternate embodiments they could be operated independently of one another (e.g., so that the fan speeds are increased from their slower steady state level on an independent "as-needed" basis). Finally, it is noted that the fans 72, 74 in the illustrated embodiment operate at about 2900 RPM at full speed and at a level of about 1400 RPM when in the standby mode. The full speed and standby speeds can vary depending at least in part upon design constraints of the oven 20, the food being cooked, etc. For example, the standby mode of either or both fans 72, 74 can be faster or slower as desired, such as a 2100 RPM standby speed for both fans 72, 74.

[0047] With continued reference to the illustrated embodiment of the present invention shown in FIGS. 5A-5C, as a pizza advances to the right 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 20A rises. In some embodiments, this temperature rise is detected by the temperature sensor 80 of the first tunnel segment 20A, which can signal the controller 42 to reduce the supply of gas to the left burner 60, thereby producing a reduction in BTU output as shown in FIG. 5B. In these and other embodiments, the controller 42 can 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 20A to detect when the pizza has advanced to a location in the first tunnel segment 20A. 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 20A. The lowered BTU output level can continue for any part or all of the remaining time that the pizza is in the first tunnel segment 20A (e.g., all of such time as shown in the illustrated embodiment of FIG. 5B). [0048] 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 20A, 20B. Since the pizza has exited, and there is therefore no further significant perturbation to the heating environment in segment 20A, the controller 42 can lower the gas supply (and therefore the BTU output) of the left burner 60 to a reduced steady state. This reduction can be triggered by a threshold temperature change detected by the temperature sensor 80 in the first tunnel segment 20A and/or by the temperature sensor 82 in the second tunnel segment 20B. 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 20A, 20B (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 20A.

[0049] With continued reference to FIGS. 5A-5C, the right burner 62 supplies heat to the second tunnel segment 20B. The sensor 82 corresponding to the second tunnel segment 20B can initially detect a spillover of heat from the first tunnel segment 20A (i.e., as the pizza enters and is in the first part of the baking process in the first tunnel segment 20A). 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 controller 42 to drop the initial BTU output of the right burner 62. However, when the partially cooked pizza approaches the right tunnel segment 20B, 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 20B, which can trigger the controller 42 to supply additional gas to the burner 62 of the second tunnel segment 20B. As a result, the BTU output of the right burner 62 can increase as the pizza moves to and through positions 32(4), 32(5), and 32(6). The reduction and increase of right burner BTU output just described can also or instead be triggered by one or more signals from one or more position sensors positioned in or adjacent the second tunnel segment 20B to detect when the pizza has advanced to one or more locations within the oven 20. The position sensor(s) 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 20A. [0050] In some embodiments, when the pizza leaves the position 32(6) and begins exiting the tunnel 24, the temperature sensor 82 of the second tunnel segment 20B can detect a rise in the tunnel temperature, and can trigger the controller 42 to reduce the output of the right burner 62 as shown in the BTU output graph of FIG. 5B. The resulting reduction in temperature in the second tunnel segment 20B can also be detected by the temperature sensor 80 of the first tunnel segment 20A due to heat spillover between the two tunnel segments 20A, 20B, and can trigger the controller 42 to increase the output of the left burner 60 to maintain the steady state temperature between the two oven segments 20A, 20B. Alternatively, the controller 42 can automatically increase the output of the left burner 60 when the output of the right burner 62 is reduced (or near in time to such reduction of the right burner 62). In some embodiments, the controller 42 can also respond by returning the speed of the fans 72, 74 to a standby state. This change in fan operation can take place relatively abruptly or gradually, and can take place immediately after a threshold temperature is detected by either or both sensors 80, 82 or after a predetermined period of time.

[0051] The increase of the left burner BTU output and the decrease in the right burner BTU output just described can also or instead be triggered by one or more signals from a position sensor positioned to detect when the pizza is exiting or has exited the right tunnel segment 20B. For example, the oven 20 illustrated in FIG. 4 has a position sensor 83, 85 (comprising a light source 83 and a photocell 85) that is substantially the same as the position sensor 79, 81 at the entrance to the left tunnel segment 20A described above. In other embodiments, the position sensor 83, 85 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 20A.

[0052] The position sensor 83, 85 and the temperature sensor 82 can be connected to the controller 42 in parallel, thereby enabling the controller 42 to change the BTU output of the burner 62 and/or the speed of either or both fans 72, 74 based upon signals received by the position sensor 83, 85 or the temperature sensor 82.

[0053] The BTU output of either or both burners 60, 62 can be controlled by the controller 42 in any manner desired. For example, the gas supply to either or both burners 60, 62 can be lowered or raised by the 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.

[0054] Accordingly, in some embodiments, the controller 42 can control either or both fans 72, 74 based at least in part upon the temperature detected by a temperature sensor 80, 82, an amount of time elapsed following a change in power supply to a burner 60, 62, and/or the detection of a position of pizza or other food on the conveyor 22 by a photo sensor 79, 81, 83, 85. For example, in some embodiments the speed of either or both fans 72, 74 is increased after air driven by the fan(s) 72, 74 has been sufficiently heated.

[0055] Similarly, in some embodiments the controller 42 can control the BTU output of either or both burners 60, 62 based at least in part upon the temperature detected by a temperature sensor 80, 82, an amount of time elapsed following a change in speed of a fan 72, 74, and/or the detection of a position of pizza or other food on the conveyor 22 by a photo sensor 79, 81, 83, 85. For example, in some embodiments the BTU output of either or both burners 60, 62 is increased only after either or both fans 72, 74 are brought up to a threshold speed.

[0056] 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 BTU 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 BTU output of the burners 60, 62 rise and fall. In this regard, as the BTU 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.

[0057] In the illustrated embodiment, for example, a relay 91 coupled to the temperature sensors 93, 95, is also coupled to the controller 42, and cooperates with the controller 42 to reduce power to either or both fans 72, 74 in a manner as just described. In this embodiment, when the output of either burner 60, 62 falls below a threshold value (e.g., 60% of maximum output in some embodiments), the relay 91 and controller 42 enter into a timed state. When the output of either burner 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 are shut off. Either or both burners 60, 62 can be re-activated in some embodiments by detection of a sufficiently low threshold temperature by either of the tunnel segment temperature sensors 80, 82, by sufficient movement of a pizza detected by any of the position sensors described above, after a set period of time has passed, and the like. Thus, as the BTU 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 BTU level is established for at least the set period of time, such as for five minutes in the illustrated embodiment.

[0058] Under some operating conditions, the BTU 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). A description of burner features enabling this low BTU burner output is provided below. Relatively low (and relatively high) burner BTU output can generate problems associated with poor combustion. For example, relatively low burner BTU output can generate incomplete combustion and flame lift-off. To address these issues, the 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 detect that a low threshold temperature has been reached.

[0059] In some of these embodiments, when either temperature sensor 80, 82 detects that a sufficiently low temperature has been reached, the controller 42 responds by turning off gas to the burner 60, 62 associated with that temperature sensor 80, 82 (either immediately or if a higher temperature is not detected after a set period of time). The supply of gas to the burner 60, 62 can be restored after a period of time and/or after the temperature sensor 80, 82 detects a temperature below a lower predetermined threshold temperature. In this manner, the burner 60, 62 can be cycled in order to avoid operating the burner 60, 62 at a very low BTU output. As will be described in greater detail below, 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 both burners 60, 62, and can restore the supply of gas to both burners 60, 62 after a period of time and/or after the temperature sensor 80, 82 detects that a lower threshold temperature has been reached.

[0060] Similarly, in some embodiments, when either temperature sensor 80, 82 detects that a sufficiently high temperature has been reached, the controller 42 responds by turning off gas to the burner 60, 62 associated with that temperature sensor 80, 82 (either immediately or if a lower temperature is not detected after a set period of time). The supply of gas to the burner 60, 62 can be restored after a period of time and/or after the temperature sensor 80, 82 detects a temperature below the low threshold temperature or a sufficient drop in temperature. In this manner, the burner 60, 62 can be cycled in order to avoid operating the burner 60, 62 at a very high BTU output. As will be described in greater detail below, 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 high threshold temperature by turning off the supply of gas to both burners 60, 62, and can restore the supply of gas to both burners 60, 62 after a period of time and/or after the temperature sensor 80, 82 detects a temperature below the low threshold temperature or an otherwise sufficient drop in temperature.

[0061] Although only two tunnel segments 20 A, 20B are used in the illustrated embodiment, more than two tunnel segments can be used in other 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. Also, as described above, the illustrated embodiment uses separate burners 60, 62 for each tunnel segment 20 A, 20B. In other embodiments, it is possible to achieve the desired segment- specific heating using a single burner and conventional structure and devices to direct heat to each segment independently in response to signals from temperature sensors associated with each of the segments. 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, the term "heating elements" refers to gas burners, electric heating elements, and all alternative heating elements and devices. Contiguous Burners

[0062] Many different heat sources can be used to independently supply heating to each of the oven segments 20A, 20B, including a number of different gas burner configurations. By way of example only, FIG. 6 illustrates a single burner of a contiguous multiple burner configuration which has been found to be particularly useful. This burner 100 comprises a housing (e.g., an outer tube 102 as shown in the illustrated embodiment) attached to a mounting plate 104 which closes off the proximal end of the outer tube 102. The outer tube 102 can have any shape desired, and in some embodiments has a relatively elongated shape as shown in the illustrated embodiment.

[0063] A smaller diameter venturi tube 106 is located within the outer tube 102 and has open distal and proximal ends 107, 112. The venturi tube 106 can be generally centered with its longitudinal axis along the longitudinal axis of the outer tube 102, although non- concentric relationships between the venturi tube 106 and the outer tube 102 can instead be employed. In some embodiments, the venturi tube 106 is secured in place near its distal end 107 by a venturi support 108 encircling the venturi tube 106 and secured within the inside diameter 109 of the outer tube 102. In some embodiments, a section 111 of the distal end 107 of the venturi tube 106 extends beyond the venturi support 108.

[0064] A gas orifice 110 can be located in the mounting plate 104, and can be spaced from the proximal open end 112 of the venturi tube 106. In some embodiments (see FIG. 6), the gas orifice 110 can be centered or substantially centered with respect to the open proximal end 112 of the venturi tube 106, although other non-centered relationships between the venturi tube 106 and the gas orifice 110 are possible. The open proximal end

112 of the venturi tube 106 receives pressurized gas from the gas orifice 110, and serves as a primary air inlet to admit a flow of air 115 into the venturi tube 106. In other embodiments, air can enter the proximal end 112 of the venturi tube 106 through apertures or gaps in the end of the venturi tube 106, through one or more conduits coupled to the venturi tube 106, or in any other manner. In some embodiments, powered air is supplied to that portion of the outer tube 102 below the venturi support 108. For example, a powered air supply can be coupled to the outer tube 102 in the illustrated embodiment via a conduit

113 leading to the outer tube 102. [0065] The venturi support 108 can have any shape adapted to support the venturi tube 106 and/or to at least partially separate an interior portion of the outer tube 102 from a burn region 116 opposite the proximal end 112 of the venturi tube 106. In some embodiments, the venturi support 108 is substantially disc shaped (e.g., see FIG. 6A). The venturi support 108 can have an opening 117 (e.g., a central circular opening 117 as shown in FIG. 6A) which fits about the circumference of the venturi tube 106. Also, one or more apertures can be defined within the venturi support 108, and in some cases can be defined between the venturi support 108 and the outer tube 102 and/or the venturi tube 106. For example, in the illustrated embodiment, the venturi support 108 has edges 119 and 121 that partially define open gaps 123 and 125 between the circumference of the venturi support 108 and the inside diameter 109 of the outer tube 102. These gaps 123, 125 can admit secondary air to the burn region 116 opposite the proximal end 112 of the venturi tube 106 in order to help support combustion as will be explained in greater detail below. In an alternate embodiment, one or more adjustable shutters (e.g., a rotatable overlapping flap, wall, or disk) can be provided to adjust the amount of secondary air admitted to the burn region 116.

[0066] In some embodiments, the venturi tube 106 can have a flame retention member 118 which can help prevent lift-off of the flame from the distal end 107 of the venturi tube 106. As seen in FIG. 6B, in some embodiments the flame retention member 118 comprises a ring 120 spaced from the inside diameter of the distal end 107 of the venturi tube 106, thereby defining an annular space 122 between the ring 120 and the inside diameter of the venturi tube 106. The ring 120 can be permanently or releasably retained in place with respect to the venturi tube 106 in a number of different manners, such as by one or more fingers, pins, clips, or other fasteners, by an apertured disc, and the like. In the illustrated embodiment, the ring 120 is retained in place by a corrugated member 128 located within the annular space 122. The corrugated member 128 abuts the inside diameter of venturi tube 106 and the outside diameter of the ring 120, and can be permanently attached to the venturi tube 106 and/or the ring 120. Also, the corrugated member 128 can hold the ring 120 in place with respect to the venturi tube 106 by friction (e.g., between the corrugated member 128 and the venturi tube 106 and/or between the corrugated member 128 and the [0067] In some embodiments, a target 124 is positioned opposite (and can be spaced from) the distal end 107 of the venturi tube 106. This target 124 can be retained in this position with respect to the venturi tube 106 in any manner, including those described above with reference to the retention of the ring 120 within the venturi tube 106. In the illustrated embodiment, for example, the target 124 is held in place by arms 126 extending from the target 124 to the outer tube 102, although the arms 126 could instead extend to the venturi tube 106 or other adjacent structure of the burner 100. The arms 126 can be permanently or releasably attached to the outer tube 102 and/or to the target 124 in any suitable manner, such as by welding, brazing, or riveting, by one or more snap-fits or other inter-engaging element connections, by clips, clamps, screws, or other fasteners, and the like. In the illustrated embodiment, the arms 126 are attached to the outer tube 102 by frictionally engaging the inside diameter 109 of the outer tube 102.

[0068] The target 124 can have a convex shape, with an apex extending generally toward the distal end 107 of the venturi tube 106. This target 124 can act to spread a portion 135 of the flame 134 emitted from the distal end 107 of the venturi tube 106, facilitating mixing of gas escaping from the venturi tube 106 with primary air and secondary air being supplied to this region through the venturi tube 106 and the gaps 123, 125, respectively. In other embodiments, the target 124 can be substantially flat, can present a concave surface to the distal end 107 of the venturi tube 106, can have any other shape suitable for spreading the flame 134 as described above, and can have an apex directed toward or away from the distal end 107 of the venturi tube 106.

[0069] With continued reference to FIG. 6, in some embodiments the outer tube 102 of the burner 100 is coupled to a flame tube 130, such as by being received within an end of the flame tube 130. The flame tube 130 can include a number of air openings 132 in any arrangement or pattern, thereby supplying further oxygen to the burning gas supporting the flame 134, which can extend into the flame tube 130 when the burner 100 is turned on.

[0070] In some embodiments of the present invention, the oven 20 has at least one pair of contiguous burners 100 and 150 of the design illustrated in FIGS. 6-6B. A pair of such burners 100, 150 is illustrated in FIGS. 7A and 7B. The outer tubes 102, 102' of the respective burners 100, 150 can be mounted to a common base plate 104, and can each be fitted with a target 124, 124' as described above. Powered air for combustion can be supplied to a venturi enclosure 152 (e.g., a venturi box having a rectangular shape or any other shape desired) by way of an inlet 154 connected to a source of powered air, as described in more detail below.

[0071] In FIG. 7B, the cover of the venturi enclosure 152 has been removed to expose a base 156 of the venturi enclosure 152. The venturi enclosure 152 can have a respective base for each burner 100, 150, or can have a common base 156 (such as that shown in FIG. 7B). The base 156 illustrated in FIG. 7B has a pair of openings 158 and 160 associated respectively with each of the two burners 100, 150. Air supply tubes 162 and 164 can extend from openings 158 and 160 to the outer surface of each respective outer tube 102 and 102', with the distal edge of each air supply tube 162, 164 shaped to follow and to sealingly engage the contour of the outer tubes 102, 102'. Outer tubes 102 and 102' can each have a respective inlet 166 and 168 in communication with the air supply tubes 162, 164. Thus, powered air from a blower 155 (see FIG. 2) entering the venturi enclosure 152 through the inlet 154 can pass through air supply tubes 162 and 164 and through air inlets 166 and 168 in the outer tubes 102, 102' of the burners 100, 150. In the illustrated embodiment, this powered air enters the venturi tubes 106 of the burners 100, 150 through the proximal ends 107 of the venturi tubes 106, and also passes through gaps 123 and 125 in the venturi support disks 108.

[0072] Gas can be supplied to the burners 100, 150 at their proximal ends 112 in any suitable manner, such as through a shared supply tube or through respective supply tubes 170 and 172 as shown in FIGS. 7 A and 7B. The supply tubes 170, 172 shown in FIGS. 7 A and 7B have been cut away to facilitate viewing the rest of the burners 100, 150. The supply tube(s) can be mounted to the burners 100, 150 in any manner, such as by one or more clamps, braces, or other fixtures, and can be mounted to one or more mounting frames, plates, or other structures adapted for this purpose. By way of example only, the supply tubes 170, 172 in the illustrated embodiment are mounted on brackets 174 and 176 attached to a common plate 178, which in turn is attached to the base plate 104 of the burners 100, 150. Either or both gas supply tubes 170, 172 can have any type of common valve or respective valves in order to control the supply of gas to the burners 100, 150. In the illustrated embodiment, for example, a threaded valve pin 180, 182 on each supply tube 170, 172 can be advanced and retracted for fine adjustment of gas supplied to the burners 100, 150 through orifices (not shown) in the gas supply tubes 170, 172 adjacent the gas orifices 110 (see FIG. 6). The present design makes it possible to use a single main gas valve with any number of contiguous burners, and in some embodiments to also adjust each burner 100, 150 independently of the others.

[0073] The distal ends of the outer tubes 102 and 102' in the illustrated embodiment are shown in FIG. 8 (in which the target 124' has been removed from the second burner 102'). In this figure, the outer tubes 102, 102' are spot welded in place in a support plate 184. In other embodiments, the support plate 184 is not required, in which case a common mounting plate 104 (or respective mounting plates 104 coupled together in any manner) can secure the outer tubes 102, 102' with respect to one another. In those embodiments in which a support plate 184 is utilized, the support plate 184 can be attached to the outer tubes 102, 102' in any manner, such as in any of the manners of attachment described above with reference to the attachment of the arms 126 to the outer tube 102. Also, in some embodiments, the outer tubes 102, 102' and the burners 100, 150 can be secured in place with respect to one another by a common support plate 184 (or by respective support plates coupled together in any manner) without this function being performed by one or more mounting plates 104 as described above.

[0074] With reference again to FIG. 8, one burner 150 is provided with an igniter 186, which produces a spark to ignite gas escaping from the distal end 107 of venturi tube 106 (see FIG. 6). The flame produced crosses over to the other burner 150 by way of a crossover structure which will discussed below. The burner 150 can be provided with a flame sensor 188 as a fail-safe measure to shut off the gas supply to both burners 100, 150 should the flame produced in burner 150 fail to cross over to the adjacent contiguous burner 100. In some embodiments, each burner 100, 150 can be provided with a respective flame sensor 188 that can trigger gas shut-off when no flame is detected from the corresponding burner 100, 150 after a sufficient period of gas supply time has elapsed. Also, in some embodiments (e.g., where independent burners 100, 150 are used to deliver heat to each of the oven segments), each burner 100, 150 can have its own independent igniter 186. [0075] In some embodiments of the present invention, the outer tubes 102 and 102' of the burners 100, 150 are each provided with at least one aperture 200, 202 (see FIGS. 9A and 9C) through which fluid communication is established between the burn regions 116 of the burners 100, 150. By such fluid communication, heat from a flame 134 ignited in one of the burners 100, 150 can raise the temperature in the other burner 150, 100 sufficiently to ignite the other burner 150, 100.

[0076] The aperture(s) 200, 202 in each of the outer tubes 102, 102' can be rectangular, round, oval, irregular, or can have any other shape desired. Also, the apertures 200, 202 can be open to or located a distance from the ends of the outer tubes 102, 102' adjacent the burn regions 116 (e.g., see FIGS. 6 and 9A), and can extend in a direction away from the respective venturi tubes 106 to locations past the targets 124, 124'. In the illustrated embodiment, for example, each of the outer tubes 102, 102' has a substantially rectangular aperture 200, 202 located a distance from the end of the respective outer tube 102, 102' adjacent the region 116.

[0077] The apertures 200, 202 in the outer tubes 102, 102' can, in some embodiments, be joined by a conduit 212 extending between the apertures 200, 202. Such a conduit 210 can help direct heat to an unlit burner 100, 150 to a lit burner 150, 100 in order to light the unlit burner 100, 150. The conduit 210 can have any shape desired, such as a substantially rectangular or round cross-sectional shape, an irregular shape, and the like. The conduit 210 can be enclosed or partially enclosed, and in the illustrated embodiment of FIGS. 9A-9D is enclosed on all sides by top, bottom, front, and back plates 204, 206, 208, and 210, respectively. The plates 204, 206, 208, 210 or other elements used to define the conduit 212 can be sealed to one another and to the outer tubes 102, 102', such as by fluid-tight welds, brazing, and the like. Such seals can protect the interior of the conduit 212 from the surrounding environment.

[0078] Thus, when gas passing through a first burner 100 is ignited, the flame produced at the distal end 107 of the venturi tube 106 in the first burner 100 can cross over through the conduit 212 to the distal end 107 of the venturi tube 106' in the second burner 150, thereby igniting the contiguous second burner 150. In such embodiments, the two burners 100, 150 are therefore either always on or always off together. Furthermore, should the flame 134 in the first burner 100 fail to cross over or be lost in the second burner 150, the sensor 188 (if employed) can signal the controller 42, which can respond by cutting off gas to both burners 100, 150. This arrangement thus makes it possible to avoid situations in which only one of two burners 100, 150 is lit and operating.

[0079] As described above, powered air can be supplied to both burners 100, 150 by a common venturi enclosure 152 (see Fig. 7 A). In some alternative embodiments, one of the burners can be coupled to a powered source of air, and can be coupled to the other burner through an air supply conduit in order to feed air to the other burner. An example of such an alternative embodiment is illustrated in FIG. 10. In the illustrated embodiment of FIG. 10, powered air is supplied to the interior of the first burner 250 through a port 252, an air supply conduit 254, and a side of the outer tube 256 of the first burner 250. Air is supplied to the second burner 262 through another port (not shown) in the outer tube 256 of the first burner 250, through another air supply conduit 258, and through the side of the outer tube 260 of the second burner 262.

[0080] While the illustrated embodiments of FIGS. 7 A- 10 each have a pair of burners 100, 150, 250, 262, other embodiments can utilize more than two burners by interconnecting additional contiguous burners (e.g., through any combination of common or connected mounting plates 104, common or connected support plates 184, venturi enclosure(s) 152 shared by burners, flame ignition conduits 212 extending between burners, and/or air supply conduits 258 extending between burners as described above and illustrated in the figures). Furthermore, although a common source of powered air can be used to supply air to two or more burners 110, 150, 250, 262 (as shown in the illustrated embodiments), air can be supplied to the individual burners 100, 150, 250, 262 on an individual basis. Additionally, the burners 100, 150 and 250, 262 of the burner assemblies described and illustrated herein are of the same size. However, in other embodiments, the burners 100, 150 and 250, 262 can be different in size (e.g., the second burner 150, 262 can be smaller than the first burner 100, 250 in applications in which the first burner 100, 250 supplies an inlet tunnel segment 20A, 20B of the oven 20 and the second burner 150, 262 supplies the outlet tunnel segment 20B, 20A of the oven 20). [0081] Returning now to the design of burner 100 illustrated in FIG. 6, it is noted that the burner 100 has the ability to produce heat in an unusually wide BTU range. In this regard, it should be noted that burners of this general type typically operate at a 3:1 ratio of air to gas. However, the relatively low BTU draw required of burners in some applications according to the present invention (e.g., in more efficient ovens 20 employing one or more features of the present invention described earlier) can call for an air to gas ratio as low as 5:1. Such a lean fuel mixture can result in flame lift-off from conventional burners. This result can be avoided by the use of burner features described above, including a reduced primary air input at the proximal end 112 of the venturi tube 106, a secondary air supply (e.g., via gaps 123, 125 in the illustrated embodiments), and/or the air openings 132 in the flame tube 130. It has been found that reduced primary air, combined with the addition of the secondary air supply and the flame tube air openings 132 supports a reduced gas supply level, and hence a reduced BTU production without flame lift off or dirty burning (encountered when there is insufficient oxygen to support the flame 134).

[0082] FIG. 11 is a top plan view of selected elements of the oven 20 illustrated in FIGS. 1-4. Gas inlets 251, 253 are coupled to and supply gas to the gas supply tubes 170, 172, respectively (all of which are shown on the outside of the front wall 254 of the oven 20), which lead to the burners 102, 102' (see FIGS. 7A and 7B). Also, the blower 155 supplies air to the venturi enclosure 152 via the air inlet 154 as described above. Extending from the other side of the front wall 254 are the flame tubes 130 and 130'. A barrier 258 is located at the distal ends 256 and 256' of the flame tubes 130, 130' and is positioned between the two flame tubes 130, 130'. The barrier 258 can be a plate or any other structure separating the flames 134 of the two tube flame tubes 130, 130' from each other. Alternatively or in addition, the barrier 258 can be positioned to separate the heater plenums 68, 70 from each other (e.g., can extend downwardly between the heater plenums 68, 70 in the illustrated embodiment of FIG. 11), so that heat produced by the first burner 100 associated with one flame tube 130 is directed into one heater plenum 70, and heat produced by the second burner 150 associated with the other flame tube 130' is directed into the other heater plenum 68.

[0083] The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims. For example, the oven controller 42 in a number of the embodiments described above is responsive to one or more temperature sensors 80, 82 and/or position sensors 79, 81, 83, 85 by changing the BTU output of one or more burners 60, 62 and/or by changing the speed of one or more fans 72, 74. In these and other embodiments, the controller 42 can be responsive to an amount of conveyor movement detected by one or more suitable sensors (e.g., rotary encoder(s), other optical or mechanical sensors positioned to detect the amount of movement of the conveyor, and the like). In this manner, such sensor(s) can send signals to the controller 42 to change the BTU output of one or more burners 60, 62 and/or to change the speed of one or more fans 72, 74 based upon the amount of movement of the conveyor 22 - and therefore the amount of movement of a pizza or other food on the conveyor 22.

Claims

What is claimed is: 1. A conveyor oven for cooking food product, the conveyor oven comprising: a tunnel; a conveyor extending into and movable within the tunnel to convey food product within the tunnel; a heating element operable to generate heat to be provided to the tunnel; a fan having different states, including a first state in which the fan moves air in the tunnel and a second state in which the fan does not move air in the tunnel; a sensor positioned to detect at least one of a temperature within the oven and the presence of food product upon the conveyor; and a controller coupled to the fan, the controller responsive to the sensor by changing the state of the fan.

2. The conveyor oven as claimed in claim 1, wherein the sensor is positioned within at least one of the tunnel and a plenum of the oven.

3. The conveyor oven as claimed in claim 1, wherein: the fan has a third state in which the fan moves air at a rate different from that of the fan in the first state; and the controller is responsive to the sensor by changing the state of the fan between the first and third states.

4. The conveyor oven as claimed in claim 1, wherein the sensor is a position sensor positioned to detect a location of food product with respect to the tunnel.

5. The conveyor oven as claimed in claim 4, wherein the sensor comprises a photocell.

6. The conveyor oven as claimed in claim 1, wherein: the sensor is a temperature sensor; and the controller is adapted to change a speed of the fan responsive to detection by the temperature sensor of at least one of a predetermined temperature change and a threshold temperature.

7. The conveyor oven as claimed in claim 1, wherein: the sensor is a temperature sensor; and the controller is adapted to increase a heat output of the heating element responsive to detection by the temperature sensor of at least one of a predetermined temperature drop and a threshold temperature.

8. The conveyor oven as claimed in claim 1, wherein: the tunnel comprises an entrance and an exit; and the sensor is located adjacent the tunnel entrance, and is adapted to detect at least one of food product approaching the tunnel entrance and food product entering the tunnel entrance.

9. The conveyor oven as claimed in claim 1, wherein: the tunnel comprises an entrance and an exit; and the sensor is located adjacent the tunnel exit, and is adapted to detect at least one of food product approaching the tunnel exit and food product exiting the tunnel exit.

10. The conveyor oven as claimed in claim 1, wherein: the sensor is a temperature sensor; and the controller is adapted to turn off the heating element responsive to detection by the temperature sensor of at least one of a predetermined temperature change and a threshold temperature.

11. The conveyor oven as claimed in claim 10, wherein the controller is adapted to turn off the heating element following a predetermined period of time during which a threshold temperature detected by the sensor is reached or passed.

12. The conveyor oven as claimed in claim 1, wherein: the sensor is a temperature sensor; and the controller is adapted to turn off the heating element responsive to detection by the temperature sensor of at least one of a predetermined temperature increase and a first threshold temperature, and to turn on the heating element responsive to detection by the temperature sensor of a predetermined temperature decrease and a second threshold temperature.

13. A conveyor oven for cooking food product, the conveyor oven comprising: a tunnel having first and second tunnel segments at least partially defining different portions of the tunnel; at least one conveyor extending into and movable within the first and second tunnel segments; first and second heating elements operable to generate heat to be provided to the tunnel, each of the first and second heating elements having a respective heat output; at least one fan to move air in the tunnel; a first sensor positioned to detect at least one of a first temperature at a first location within the tunnel and the presence of food product upon the conveyor at a first location with respect to the tunnel; a second sensor positioned to detect at least one of a second temperature at a second location within the tunnel and the presence of food product upon the conveyor at a second location with respect to the tunnel; and a controller coupled to the first and second heating elements and the first and second sensors, the controller responsive to the first and second sensors by independently controlling the heat outputs of the first and second heating elements.

14. The conveyor oven as claimed in claim 13, wherein the first and second heating elements heat air supplied directly to the first and second tunnel segments, respectively.

15. The conveyor oven as claimed in claim 13, wherein: first and second fans move air in the tunnel; and the first and second heating elements heat air supplied directly to the first and second tunnel segments via the first and second fans, respectively.

16. The conveyor oven as claimed in claim 13, wherein the first and second sensors detect temperatures of the first and second tunnel segments, respectively.

17. The conveyor oven as claimed in claim 16, wherein: the first sensor is positioned in at least one of a first position and a second position; the second sensor is positioned in at least one of a third position and a fourth position; the first and third positions are within the tunnel; and the second and fourth positions are within different plenums of the oven.

18. The conveyor oven as claimed in claim 13, wherein the controller is responsive to at least one of the first and second sensors by controlling a speed of the at least one fan.

19. The conveyor oven as claimed in claim 13, wherein: the at least one fan has a first state in which the at least one fan does not move air, a second state in which the at least one fan moves air at a first rate, and a third state in which the at least one fan moves air at a second rate faster than the first rate; and the controller is responsive to at least one of the first and second sensors by changing the fan between at least the first, second, and third states.

20. The conveyor oven as claimed in claim 13, wherein the controller is responsive to both of the first and second sensors by controlling a speed of the at least one fan.

21. The conveyor oven as claimed in claim 13, wherein: first and second fans move air in the tunnel; the first and second heating elements heat air supplied directly to the first and second tunnel segments via the first and second fans, respectively; and the controller is responsive to at least one of the first and second sensors by controlling speeds of the first and second fans.

22. The conveyor oven as claims in claim 21, wherein the controller is responsive to at least one of the first and second sensors by independently controlling speeds of the first and second fans.

23. The conveyor oven as claimed in claim 13, wherein at least one of the first and second sensors is a position sensor to detect a location of food product with respect to the tunnel.

24. The conveyor oven as claimed in claim 23, wherein at least one of the first and second sensors comprises a photocell.

25. The conveyor oven as claimed in claim 13, wherein: at least one of the first and second sensors is a temperature sensor; and the controller is adapted to increase a speed of the at least one fan responsive to detection by the temperature sensor of at least one of a predetermined temperature increase and a threshold temperature.

26. The conveyor oven as claimed in claim 13, wherein: at least one of the first and second sensors is a temperature sensor; and the controller is adapted to increase the heat output of at least one of the first and second heating elements responsive to detection by the temperature sensor of at least one of a predetermined temperature decrease and a threshold temperature.

27. The conveyor oven as claimed in claim 13, wherein: the tunnel comprises an entrance and an exit; and the first sensor is located adjacent the tunnel entrance, and is adapted to detect at least one of food product approaching the tunnel entrance and food product entering the tunnel entrance.

28. The conveyor oven as claimed in claim 13, wherein: the tunnel comprises an entrance and an exit; and the second sensor is located adjacent the tunnel exit, and is adapted to detect at least one of food product approaching the tunnel exit and food product exiting the tunnel exit.

29. The conveyor oven as claimed in claim 27, wherein the second sensor is located adjacent the tunnel exit, and is adapted to detect at least one of food product approaching the tunnel exit and food product exiting the tunnel exit.

30. The conveyor oven as claimed in claim 13, wherein: the first sensor is a temperature sensor; and the controller is adapted to turn off at least one of the first and second heating elements responsive to detection by the first sensor at least one of a predetermined temperature change and a threshold temperature.

31. The conveyor oven as claimed in claim 30, wherein the controller is adapted to turn off the at least one of the first and second heating elements following a predetermined period of time during which a threshold temperature detected by the first sensor reached or passed.

32. The conveyor oven as claimed in claim 13, wherein: the first sensor is a temperature sensor; and the controller is adapted to turn off at least one of the first and second heating elements responsive to detection by the first sensor of at least one of a predetermined temperature increase and a first threshold temperature, and to turn on at least one of the first and second heating elements responsive to detection by the first sensor at least one of a predetermined temperature decrease and a second threshold temperature.

33. A conveyor oven for cooking food product, the conveyor oven comprising: a tunnel having first and second tunnel segments at least partially defining different portions of the tunnel; at least one conveyor extending into and movable within the first and second tunnel segments; at least one heating element operable to generate heat to be provided to the tunnel, each of the at least one heating element having a respective heat output; first and second fans to move air in the tunnel, each of the first and second fans operable at a respective speed; a first sensor positioned to detect at least one of a first temperature at a first location within the tunnel and the presence of food product upon the conveyor at a first location with respect to the tunnel; a second sensor positioned to detect at least one of a second temperature at a second location within the tunnel and the presence of food product upon the conveyor at a second location with respect to the tunnel; and a controller coupled to at least one of the first and second fans and the first and second sensors, the controller responsive to the first and second sensors by independently controlling the speeds of at least one of the first and second fans.

34. The conveyor oven as claimed in claim 33, wherein first and second heating elements heat air supplied directly to the first and second tunnel segments, respectively.

35. The conveyor oven as claimed in claim 34, wherein the first and second heating elements heat air supplied directly to the first and second tunnel segments via the first and second fans, respectively.

36. The conveyor oven as claimed in claim 33, wherein the first and second sensors detect temperatures of the first and second tunnel segments, respectively.

37. The conveyor oven as claimed in claim 36, wherein: the first sensor is positioned in at least one of a first position and a second position; the second sensor is positioned in at least one of a third position and a fourth position; the first and third positions are within the tunnel; and the second and fourth positions are within different plenums of the oven.

38. The conveyor oven as claimed in claim 33, wherein the controller is responsive to at least one of the first and second sensors by controlling a speed of at least one of the first and second fans.

39. The conveyor oven as claimed in claim 33, wherein: each of the first and second fans have a first state in which the fan does not move air, a second state in which the fan moves air at a first rate, and a third state in which the fan moves air at a second rate faster than the first rate; and the controller is responsive to at least one of the first and second sensors by changing at least one of the first and second fans between at least the first, second, and third states.

40. The conveyor oven as claimed in claim 33, wherein the controller is responsive to both of the first and second sensors by controlling a speed of each of the first and second fans.

41. The conveyor oven as claimed in claim 33, wherein: first and second heating elements heat air supplied directly to the first and second tunnel segments via the first and second fans, respectively; and the controller is responsive to at least one of the first and second sensors by controlling speeds of the first and second fans.

42. The conveyor oven as claims in claim 41 , wherein the controller is responsive to at least one of the first and second sensors by independently controlling speeds of the first and second fans.

43. The conveyor oven as claimed in claim 33, wherein at least one of the first and second sensors is a position sensor to detect a location of food product with respect to the tunnel.

44. The conveyor oven as claimed in claim 43, wherein at least one of the first and second sensors comprises a photocell.

45. The conveyor oven as claimed in claim 33, wherein: at least one of the first and second sensors is a temperature sensor; and the controller is adapted to increase a speed of at least one of the first and second fans responsive to detection by the temperature sensor of at least one of a predetermined temperature increase and a threshold temperature.

46. The conveyor oven as claimed in claim 33, wherein: at least one of the first and second sensors is a temperature sensor; and the controller is adapted to increase the heat output of at least one heating element responsive to detection by the temperature sensor of at least one of a predetermined temperature decrease and a threshold temperature.

47. The conveyor oven as claimed in claim 33, wherein: the tunnel comprises an entrance and an exit; and the first sensor is located adjacent the tunnel entrance, and is adapted to detect at least one of food product approaching the tunnel entrance and food product entering the tunnel entrance.

48. The conveyor oven as claimed in claim 33, wherein: the tunnel comprises an entrance and an exit; and the second sensor is located adjacent the tunnel exit, and is adapted to detect at least one of food product approaching the tunnel exit and food product exiting the tunnel exit.

49. The conveyor oven as claimed in claim 47, wherein the second sensor is located adjacent the tunnel exit, and is adapted to detect at least one of food product approaching the tunnel exit and food product exiting the tunnel exit.

50. The conveyor oven as claimed in claim 33, wherein: the first sensor is a temperature sensor; and the controller is adapted to turn off at least one heating element responsive to detection by the first sensor of at least one of a predetermined temperature change and a threshold temperature.

51. The conveyor oven as claimed in claim 50, wherein the controller is adapted to turn off the at least one heating element following a predetermined period of time during which a threshold temperature detected by the first sensor is reached or passed.

52. The conveyor oven as claimed in claim 33, wherein: the first sensor is a temperature sensor; and the controller is adapted to turn off a heating element of the at least one heating element responsive to detection by the first sensor of at least one of a predetermined temperature increase and a first threshold temperature, and to turn on the heating element of the at least one heating element responsive to detection by the first sensor of a predetermined temperature decrease and a second threshold temperature.

53. A burner assembly for an oven, the burner assembly comprising: a first housing; a first tube located at least partially within the first housing and having an interior; a second housing coupled to the first housing; a second tube located at least partially within the second housing and having an interior; at least one gas inlet through which gas is supplied to the first and second tubes; at least one air inlet through which air is supplied to the first and second housings; and a conduit extending to and between the first and second housings and through which fluid communication is established between the interior of the first housing and the interior of the second housing, the conduit positioned to supply at least one of air from the first tube to the second tube to maintain a flame in the second tube, and heat from the first tube to the second tube to ignite a flame from the second tube.

54. The burner assembly as claimed in claim 53, wherein the first and second housings are coupled by at least one base.

55. The burner assembly as claimed in claim 54, wherein the base at least partially defines an enclosure through which air is supplied to the burner assembly.

56. The burner assembly as claimed in claim 54, wherein the base at least partially supports the first and second housings in position with respect to one another.

57. The burner assembly as claimed in claim 53, further comprising a flame target coupled to an end of the first housing.

58. The burner assembly as claimed in claim 53, further comprising a sensor positioned to detect a presence of flame from at least one of the first and second tubes.

59. The burner assembly as claimed in claim 58, further comprising a controller coupled to the sensor, the controller adapted to turn off a supply of gas to at least one of the first and second tubes responsive to a signal from the sensor.

60. The burner assembly as claimed in claim 59, wherein the controller is adapted to turn off the supply of gas after a predetermined period of time in which no flame is detected by the sensor.

61. The burner assembly as claimed in claim 59, wherein the controller is adapted to turn off gas to both of the first and second tubes responsive to a signal from the sensor.

62. The burner assembly as claimed in claim 53, further comprising a ring located at and within an end of the first tube, the ring having a cross-sectional size smaller than a cross-sectional size of the first tube to define a space extending around the ring between the ring and the first tube.

63. The burner assembly as claimed in claim 53, wherein the conduit supplies air from the first housing to the second housing, and is located between opposite ends of the first housing and between opposite ends of the second housing.

64. The burner assembly as claimed in claim 53, wherein the conduit supplies gas from the first housing to the second housing, and is located at an end of the first housing and at an end of the second housing.

65. The burner assembly as claimed in claim 53, wherein the conduit is a first conduit, and supplies air from the first housing to the second housing, the burner assembly further comprising a second conduit extending to and between the first and second housings and through which fluid communication is established between the interior of the first housing and the interior of the second housing, the second conduit positioned to supply heat from the first tube to the second tube to ignite a flame from the second tube.