CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a Continuation application and claims the benefit of U.S. patent application Ser. No. 13/101,821, filed on May 5, 2011, currently pending, which in turn claimed the benefit of priority to U.S. Provisional Patent Application. No. 61/331,702 filed May 5, 2010, expired, both of which are incorporated by reference herein and made a part hereof.
BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention generally relates to an ignition system for a flame-emitting apparatus and more particularly to an ignition system for a cooking apparatus such as a rotisserie oven that confirms the presence of a flame.
2. Background of the Invention
Several types of apparatuses emit flames such as cooking apparatuses, heating lamps, gas lamps used for lighting and other decorative appliances. For operation of these apparatuses, a flame is ignited from a fuel source such as propane or natural gas. One type of cooking apparatus is a rotisserie oven. Rotisserie ovens are well known in the art. The ovens typically have a carousel mechanism or rotating member that rotates food items during cooking. The food items are supported by skewers that are removably connected to the rotating member. The rotisserie oven typically has a burner in communication with a fuel source. The ovens further have an ignition system used to initially ignite the burner. It is desirable for the system to confirm that the burner is properly ignited to avoid injecting fuel into the oven when a flame is not present in the burner to combust the fuel. It is also desirable to monitor if the burner flame is ever unexpectedly extinguished in order to interrupt the supply of fuel until the burner can again be properly ignited. Prior ignition systems experience difficulties in properly confirming that a flame is present when initially igniting the burner or confirming a flame continues to be present during operation of the oven. The flame-emitting apparatuses, including cooking ovens, may have a flame detecting system as part of an ignition system or a separate system that may use a flame sensor to detect the presence of a flame. The flame sensor can become fouled and rendered inoperable. Flame-emitting apparatuses may also use flame rectification systems that pass a current through a flame to detect a flame and other systems may employ optical methods in detecting a flame. Because of limitations in the structure and methods of such prior art systems, false readings can occur or the system can experience the inability to obtain a reading to confirm the presence of a flame.
Thus, while flame detecting systems according to the prior art provide a number of advantageous features, they nevertheless have certain limitations. The present invention seeks to overcome certain of these limitations and other drawbacks of the prior art, and to provide new features not heretofore available.
SUMMARY OF THE INVENTION The present invention provides a system for detecting a presence of a flame in a flame-emitting apparatus. The system may be part of an ignition system for the flame-emitting apparatus that confirms the presence of a flame. In one exemplary embodiment, the ignition system is used in a cooking apparatus.
According to one aspect of the invention, a system detects the presence of a flame in a flame-emitting apparatus. The flame-emitting apparatus has a burner and the burner is in communication with a fuel source. The burner emits a flame when the burner is fully ignited. The system has a temperature sensor configured to be positioned in the apparatus and is adjacent the burner wherein the sensor is configured to be positioned within the flame of the burner. A controller is operably connected to the temperature sensor and the burner wherein the controller receives temperature data from the temperature sensor. The controller determines whether a flame is present based on the temperature data received, and when determining that a flame is not present, the controller is configured to interrupt the supply of fuel to the burner.
According to another aspect of the invention, a rotisserie oven has a housing defining a cavity. A rotating member is positioned within the cavity and is configured to support and rotate a plurality of food items within the cavity. A burner is positioned within the housing and has an inlet configured to be in fluid communication with a fuel source. The burner further has an outlet allowing a flame member to extend therefrom into the cavity as a product of combusting fuel supplied to the burner. An ignition system is operably coupled to the housing and has an igniter positioned adjacent the burner. The system further has a temperature sensor positioned adjacent the burner wherein the sensor is positioned to be within an outer periphery of the flame. The system has an ignition controller operably coupled to the igniter and thermocouple and configured to control the delivery of fuel to the burner.
According to another aspect of the invention, the controller of the ignition system utilizes an algorithm to detect temperature changes within a predetermined range and controls the delivery of fuel in response thereto.
According to another aspect of the invention, a cooking apparatus has a housing defining an interior cavity configured for cooking a food item. A support member is configured for supporting the food item. A burner is configured to burn a fuel to emit a cooking flame to heat the food item. A temperature sensor has a portion positioned proximate the burner to detect a temperature of the cooking flame. A controller is in communication with the temperature sensor, and the controller is configured for analyzing output from the temperature sensor to determine if the cooking flame is present, based on a change in temperature detected by the temperature sensor.
According to another aspect of the invention, a cooking apparatus has a housing defining an interior cavity configured for cooking a food item. A support member is configured for supporting the food item. A burner has an aperture, and the burner is configured to burn a fuel to emit a cooking flame from the aperture to heat the food item when the burner is ignited. A temperature sensor has a portion positioned proximate the aperture to detect a temperature of the cooking flame, wherein the portion of the temperature sensor is configured to be positioned within the cooking flame when the burner is ignited. A control system is in communication with the temperature sensor, and the control system is configured for analyzing output from the temperature sensor to determine if the cooking flame is present.
These and other objects and advantages will be made apparent from the following description of the drawings and detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which:
FIG. 1 is a perspective view of a flame-emitting apparatus in the form of a cooking apparatus such as a rotisserie oven utilizing an ignition system according to the present invention;
FIG. 2 is a front elevation view of the cooking apparatus utilizing the ignition system according to the present invention;
FIG. 3 is a side perspective view of the cooking apparatus showing additional control components associated with the apparatus;
FIG. 4 is a partial perspective view of a temperature sensor of the ignition system and a burner of the rotisserie oven;
FIG. 5 is a schematic view of a thermocouple used in the ignition system of the present invention including a partial enlarged portion;
FIG. 6 is a flow chart disclosing operational features of the ignition system according to the present invention;
FIG. 7 is a flow chart disclosing an exemplary embodiment of certain operational features of the ignition system according to the present invention;
FIGS. 8-10 are flow charts disclosing another exemplary embodiment of certain operational features of the ignition system according to the present invention;
FIGS. 11 and 12 are flow charts disclosing safety interlocks associated with the embodiment of the ignition system of FIGS. 8-10;
FIG. 13 is a flow chart of an igniter selection subroutine associated with the embodiment of the ignition system of FIGS. 8-10;
FIG. 14 is a perspective view of a gas lighting lamp utilizing the ignition system of the present invention;
FIG. 15 is a perspective view of a heating lamp utilizing the ignition system of the present invention; and
FIG. 16 is a schematic diagram illustrating various control components according to an embodiment of the present invention.
DETAILED DESCRIPTION While this invention is susceptible of embodiment in many different forms, there is shown in the drawings, and will herein be described in detail, preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.
The present invention relates generally to a variety of flame-emitting apparatuses including cooking apparatuses. A flame-emitting apparatus typically has some form of burner connected to a fuel source. The apparatus also may have an ignition system for initially igniting the fuel supplied to the burner. The present invention includes structures and methods that confirm the presence of a flame upon igniting the burner to assure proper operation. Such structures and methods may be an integral part of the ignition system or operably interact with the ignition system, and may be generally referred to as flame detecting systems, flame confirmation systems, flame proving systems, or flame rectification systems. Thus, the present invention applies to a wide variety of apparatuses including any type of cooking cavities as well as outdoor cooking devices, gas lamps used for lighting purposes, outdoor heat lamps, outdoor decorative appliances, hot water heaters, boilers or other devices connected to a fuel source wherein the device emits a flame. In a particular example disclosed herein, the device is a rotisserie oven and a detailed discussion is provided regarding the rotisserie oven. It is understood that the device could also be other types of cooking devices that have a burner positioned either in a cooking cavity or adjacent to the cooking cavity as an external heat source. It is further understood that the structures and methods described herein in detail apply to and can be utilized in any type of flame-emitting apparatus. The invention will now be described as utilized in one exemplary embodiment of a rotisserie oven.
Referring now in detail to the Figures, FIG. 1 discloses a rotisserie oven that can incorporate the present invention, the oven generally designated with the reference numeral 10. FIG. 1 illustrates the oven 10 that is configured to cook a plurality of food items. The food items may oftentimes be chickens or other types of birds although it is understood that various other food items can be cooked in the oven 10. The oven 10 generally includes a housing 14, a rotating or rotatable member 16, and a heating assembly 18. The housing 14 can be of any shape generally known in the art. The housing 14 has a plurality of walls defining an interior cavity 20. The interior cavity 20 is generally defined by a top wall, a bottom wall, a rear wall, a front wall and a pair of sidewalls. The housing 14 has an access door 22 in the front wall for placing the food item into the housing 14. The rotating member 16 may be in the form of a carousel mechanism and has a plate 24 rotatably mounted on each sidewall of the housing 14. It is understood the rotating member 16 has a drive mechanism for rotating the rotating member 16. The rotating member 16 includes a plurality of support members or skewers 26 and may be considered a movable skewer assembly. A respective end of each skewer 26 is removably mounted on the plates 24 of the rotating member 16. Thus, food items loaded onto the skewers 26 such that at least one skewer 26 extends at least partially through the food item and the skewers 26 are rotated within the housing 14 during cooking.
As shown in FIG. 2, the heating assembly 18 is operably associated with the housing 14 and provides a heat source for heating the interior cavity 20 and cooking the food item. The heating assembly 18 typically has a heating element that in one exemplary embodiment is a burner 28 that is in fluid communication with a fuel source such as propane or natural gas. As shown in FIG. 2, the burner 28 is generally positioned within the cavity 20 and generally at a bottom portion of the housing 14. It is understood that the burner 28 can be positioned in other areas of the housing 14. The burner 28 is a tubular structure having a proximate end 30 and a distal end 32. The burner 28 has a plurality of apertures 34 along a length of the burner 28. The burner 28 is in fluid communication with a gas supply 36 (FIG. 3) and a gas valve 38 (FIG. 3) is mounted between the proximate end 30 and the gas supply 36. As shown in FIGS. 2 and 4, when the burner 28 is in operation and combusting the fuel or gas supplied by the gas supply 36, a flame 40 is emitted and extends from the apertures 34 in the burner 28. The flame 40 has an outer zone 41 that defines an outer periphery 42 of the flame 40 and which generally may represent the hottest part of the flame 40. The flame 40 further has a middle zone 44 and an inner zone 46 that has little combustion due to lack of oxygen. It is understood that the rotisserie oven 10 has a master controller 48 (FIG. 2) that controls the heating assembly 16 as well as other operational features of the oven 10.
As further shown in FIGS. 2-13 and 16, the rotisserie oven 10 further has an ignition system 50. The ignition system 50 generally includes an igniter 52, a temperature sensor 54 and an ignition controller 56. It is understood that a power supply, breakers, switches etc. are in operable communication with the ignition controller 56. It is understood that the ignition controller 56 may be considered a part of the master controller 48 but is otherwise in operable communication with the master controller 48. As explained in greater detail below, the ignition system 50 may also be considered a flame proving system or flame confirmation system.
As shown in FIGS. 2 and 3, the igniter 52 is positioned generally at the proximate end 30 of the burner 28 and generally at a first aperture 34 of the burner 28. The igniter 52 may include a plurality of igniters 52. The temperature sensor 54 is a highly sensitive thermocouple 54 in an exemplary embodiment. The thermocouple 54 is a fast-acting thermal probe capable of reading temperatures in a very fast manner and at extreme temperatures. The thermocouple 54 is mounted to the housing 14 and is positioned proximate the distal end 32 of the burner 28. The thermocouple 54 is further positioned slightly above the apertures 34 of the burner 28. As can be appreciated from FIG. 4, the thermocouple 54 is positioned such that when the burner 28 is in operation and the flame 40 extends from the aperture 34, at least a portion of the thermocouple 54 is positioned directly within the flame 40 wherein the thermocouple 54 is positioned within the outer periphery 42 of the flame 40. The thermocouple 54 may extend through a plurality of the flames 40 extending from the burner 28. As further shown in FIGS. 2 and 3, the igniter 52 and the thermocouple 54 are each operably connected to the ignition controller 56.
FIG. 5 discloses the thermocouple 54 in greater detail. As discussed, the thermocouple 54 is designed to sense extreme temperatures as well as rapid temperature changes including increasing temperatures and decreasing temperatures. In one exemplary embodiment, the thermocouple 54 is considered a dual-probe unit having a first sensor 55 and a second sensor 57. The first sensor 55 and second sensor 57 both sense the temperature from the burner 28. The first sensor 55 may be considered to be the main sensor associated with the controller 56 for operation in the pre-ignition, ignition and operation phases. The second sensor 57 is a type of witness sensor that senses temperature. The multi-sensor design is used in a safety interlock as described below. The first sensor 55 and the second sensor 57 are housed within a sheath 59 of the thermocouple 54 and are insulated from one another. A powder may be compacted in the sheath 59 at a distal end of the sensors 55,57. The sheath 59 may have a cap fastened at the end of the sheath 59 enclosing the sensors.
In one general aspect of operation when the oven 10 is initially started up via the ignition controller 56, the gas valve 38 is opened to supply gas to the burner 28. The igniter 52 is activated to provide a spark, start-up flame or incandescence to light the fuel or gas supplied to the burner 28. If properly ignited, flames 40 should be present at the proximate end 30 and quickly migrate along the burner 28 to the distal end 32 and extend from each aperture 34 as shown in FIG. 2. The thermocouple 54 will be positioned directly within the flame 40, and the thermocouple 54 will sense a temperature change from an initial state prior to ignition. If the burner 28 is not fully ignited, for example, due to blockage in one or more of the apertures 34, the thermocouple 54 will not sense an appropriate temperature change as a flame will not be present at the burner 28. Temperature readings from the thermocouple 54 are communicated to the ignition controller 56 wherein the controller 56 recognizes a “flame not detected” condition and sends a signal to shut the gas valve 38 to prevent non-combusted fuel from continuing to be supplied into the oven 10. Supplying un-burnt fuel into the oven 10 can create a hazard. The ignition sequence can be then be re-initiated after a predetermined amount of time or after suitable troubleshooting is performed if necessary.
The ignition controller 56 also has software utilizing algorithms to further enhance the operation of the ignition system 50 and confirm the presence of the flame 40 during and after ignition. The algorithms are generally used by the system 50 to perform certain steps in sensing whether a rate of temperature change as sensed by the thermocouple 54 is sufficient. As explained in greater detail below, the system 50 may include a plurality of different starting temperature windows that have a rate of temperature change value assigned to the particular window to aid in properly determining the presence of a flame.
FIG. 16 illustrates an example embodiment of the master controller 48 and the ignition system 50. The master controller 48 in this example may be a general purpose or specialized computer device, and may include typical computer components, including a processor or processing system 110 (e.g., one or more microprocessors), a memory or memory system 112, which may include RAM, ROM, storage memory, etc., and an interface or interface system 114. The memory 112 may include software including computer executable instructions for use by the processor 110, such as an operating system, applications, databases, etc. The interface 114 may include various types of interfaces, including input/output interfaces for user input and user-readable output, as well as communication interfaces, such as a modem, LAN interface, cellular or other wireless interface, connection port (USB, Firewire, etc.), or other types of interfaces. The master controller 48 may include further components in some embodiments, such as a power supply (e.g., a battery or other power source).
In the embodiment illustrated in FIG. 16, the master controller 48 is in communication with the ignition controller 56 of the ignition system 50. The ignition controller 56 may include any of the components described above, including a processor 110, memory 112, interface 114, etc. Additionally, as indicated by the broken lines in FIG. 16, the ignition controller 56 may be considered part of the master controller 48 in one embodiment, and likewise, the master controller 48 may be considered part of the ignition system 50. The ignition controller 56 is in communication with the igniter 52, the sensor 54, and the burner 28 in this embodiment, and can transmit to and/or receive signals from the igniter 52, the sensor 54, and/or the burner 28. For example, the ignition controller 56 may transmit a signal to activate the igniter 52 or the burner 28 (e.g. the gas valve(s)). As another example, the ignition controller 56 may receive a signal indicative of the current in the igniter 52 or the temperature data from the sensor 54.
If the ignition controller 56 is separate from the master controller 48, the ignition controller 56 may transmit at least some signals received from the igniter 52, the sensor 54, and/or the burner 28 to the master controller. Likewise, in this configuration, some of the signals transmitted by the ignition controller 56 to the igniter 52, the sensor 54, and/or the burner 28 may be transmitted in response to a signal from the master controller 48. Further, if the ignition controller 56 is separate from the master controller 48, the igniter 52, the sensor 54, and/or the burner 28 may additionally or alternately be in communication with the master controller 48, as indicated by the broken-line connectors in FIG. 16.
It is understood that if the ignition system 50 includes multiple igniters 52, sensors 54, and/or burners 28, the ignition controller 56 may be in communication with each of the multiple igniters 52, sensors 54, and/or burners 28.
Aspects of the processes, communications, algorithms/routines, calculations, analysis, etc. described herein may take the form of a computer program product stored by one or more computer-readable storage media having computer-readable program code, or instructions, embodied in or on the storage media (e.g., in the memory 112). The computer-readable storage media may be tangible and/or non-transitory. Any suitable computer readable storage media may be utilized, including hard disks, CD-ROMs, optical storage devices, magnetic storage devices, microchips, and/or any combination thereof. Additionally, signals transmitted as described herein may be transmitted wirelessly or through a wire or other tangible conducting medium.
FIG. 6 discloses the general operation of one exemplary embodiment of the ignition system 50 utilizing certain algorithms in greater detail for detecting the presence of a flame. FIG. 7 discloses more specific examples of the operation of the ignition system 50. At the initiation of the ignition phase, the gas valve 38 is opened and gas is supplied to the burner 28. The ignition controller 56 activates the igniter 52 to provide a spark, start-up flame or incandescence to ignite the burner 28. The thermocouple 54 senses an initial temperature immediately following ignition and communicates such reading to the ignition controller 56. The ignition controller 56 determines an initial rate of temperature change from the initial temperature and the temperature sensed immediately following ignition (such temperature will be considered the maximum value the temperature rose to upon this initial temperature change determination, and designated as sensed temperature TS) to determine if such change is sufficient. If a sufficient rate of temperature change is not detected, the system 50 determines that a “flame not detected” condition exists and the burner 28 has failed to ignite. The ignition controller 56 shuts off the gas valve 38 and the ignition process is stopped. After a purge time is completed to allow gas to sufficiently diffuse, the process can be re-initiated a predetermined number of times. If the trials exceed the predetermined number of times, the ignition process terminates and transmits a signal to the alarm output identifying there has been a safety lock.
As further shown in FIG. 6, if the thermocouple 54 senses temperatures resulting in a rate of temperature change that the ignition controller 56 recognizes as being sufficient, the ignition controller 56 recognizes that the flame 40 is detected from the burner 28. The ignition controller 56 also has a plurality of different temperature windows covering certain operating temperature ranges of the oven 10. For example, a first window W1 may be designated for a temperature range equal to or lower than a lowest oven temperature. A second window W2 may be designated for a second temperature range covering an intermediate range. Other windows W having other temperature ranges can also be designated including a final window Wn that represents the highest temperature range for the oven 10. The ignition controller 56 recognizes the sensed temperature TS corresponding to the highest temperature sensed at the initial inquiry as described above. As the system 50 continues through its operational steps, the ignition controller 56 uses this initial highest sensed temperature TS and determines the corresponding window W to be used to further confirm the presence of a flame. As discussed, each window W corresponds to a temperature range of the oven 10. Each window W has a predetermined acceptable rate of temperature change (or threshold amount) that would indicate a flame is present. Initially, the ignition controller takes the first sensed temperature TS as discussed above and determines which window W the sensed temperature TS falls into. The thermocouple 54 continues to sense temperature values that are communicated to the ignition controller 56. The ignition controller 56 determines the rate of temperature change from the temperatures sensed by the thermocouple 54 and then determines if the rate of temperature change is sufficient for the given temperature window W. If the temperature change is sufficient for the given window W, it is determined that the flame is present and the burner is functioning correctly, and wherein that gas can still be supplied to the burner 28. As such, the system 50 continues to loop through these inquiries wherein the thermocouple 54 continues to sense temperature TS wherein the appropriate window W is determined as well as the rate of temperature change which is compared to the acceptable rate of temperature change for that window W. If the ignition controller 56 does not sense a rate of temperature change that is sufficient for the particular window W, then a flame failure condition is detected by the ignition controller 56 and the controller 56 shuts off the gas valve 38. It is understood that each window can be programmed for different rates of change.
Once the ignition system 50 determines that the burner 28 has been properly ignited, the oven 10 continues to operate in normal fashion. It is understood that the ignition system 50 continues to monitor the oven temperature continuously during operation. If, for example, the flame 40 from the burner 28 was unexpectedly extinguished during operation, the thermocouple 54 senses falling temperatures that are communicated to the ignition controller 56. In response, the ignition controller 56 shuts off the gas valve 38 to interrupt fuel supply to the burner 28. It is further understood that the master oven controller 48 has a thermostat associated therewith. The master oven controller 48 may also shut-off the burner 28 based on cavity temperature readings associated with the thermostat and according to desired cooking parameters for the particular food items being cooked. For example, after the temperature reaches a certain level, the burner may be shut-off and then when the cavity temperature falls to a certain level, the master controller 48 sends a signal for the burner 28 to again be ignited. The ignition system 50 is used to ignite the burner 28 according the description above.
FIG. 7 discloses a set of operational parameters for the ignition system 50 in accordance with another exemplary embodiment of the invention. As discussed, the system 50 determines several temperature differences during operation represented by the reference numeral DT4, wherein DT4 represents a temperature difference in any four seconds. Via the operator or automatic controls, the gas valve 38 is opened and gas is supplied to the burner 28. The ignition controller 56 activates the igniter 52 to provide a start-up spark, start-up flame or incandescence to the burner 28 and ignite the burner 28. The thermocouple 54 senses temperature and communicates such temperature values to the ignition controller 56. The ignition controller 56 determines whether a temperature difference exists that is greater than or equal to 30° C. as shown in FIG. 7. If the determined temperature change does not meet this value, a “flame not detected” condition is recognized and the ignition controller 56 concludes that the burner 28 failed to ignite. In response, the ignition controller 56 shuts off the gas valve 38. After a preprogrammed purge time to allow the gas in the oven 10 to sufficiently diffuse, the ignition process can again be initiated as described above. The ignition system 50 may also be pre-programmed allowing re-initiation of the ignition process a set number of times. For example, the system 50 can be programmed to allow 5 ignition trials. If the burner 28 is not properly ignited after the fifth try, the operator must perform more detailed troubleshooting prior to re-initiating the ignition process.
As further shown in FIG. 7, if the ignition controller 56 receives sensed temperature data from the thermocouple 54 and determines a temperature difference exists and is greater than or equal to 30° C., a “flame detected” condition is recognized. The upper limit of the initial sensed temperature is designated as TS. In this condition, the oven 10 continues to a normal operation condition. As discussed, a plurality of windows W are designated in the ignition controller 56. In this exemplary embodiment, the system 50 has a first window W1, a second window W2 and a third window W3. The first window W1 is set for a temperature range of temperatures equal to or less than 600° C. The designated rate of temperature change for the first window W1 is a change of less than or equal to 5° C. The second window W2 is set for an initial temperature range between 600° C. to 900° C. The designated rate of temperature change for the second window W2 is a change of less than −25° C., e.g. a temperature drop of 25° C. A third window W3 is set for an initial temperature range of 900° C. or greater. The designated rate of temperature change for the third window W3 is a change of less than −35° C., e.g. a temperature drop of 35° C. The ignition controller 56 recognizes the initial sensed temperature value TS corresponding to the highest value sensed at the initial inquiry and determines which window W the temperature TS is assigned. For example, if the initial sensed temperature TS is 550° C., the first window W1 is designated and the ignition controller 56 continues to receive sensed temperature values from the thermocouple 54. The ignition controller 56 determines if a temperature difference exists that is less than or equal to 5° C. If the determined temperature difference is less than or equal to 5° C., a “flame failure” condition is detected wherein the ignition controller 56 shuts off the gas valve. The condition can then be troubleshot and the ignition sequence re-initiated when appropriate. If the determined temperature difference is not less than or equal to 5° C., a normal operation condition is detected wherein ignition controller 56 continues to loop through sensed temperature values received from the thermocouple 54. As the temperature sensed by the thermocouple 54 continues to rise due the normal operation of the oven 10, the ignition controller 56 again determines which window is designated. For example, as temperature rises, the TS value may rise to a value between 600° C. and 900° C. wherein the second window W2 is designated. The ignition controller 56 then determines if a temperature difference exists that is less than −25° C., e.g., whether a temperature drop of 25° C. exists. If this condition does exist, a “flame failure” is detected and the ignition controller 56 shuts off the gas valve. If the determined temperature difference is not less than −25° C., e.g., a temperature drop of 25° C. does not exist, a normal operation condition continues to be detected wherein the ignition controller 56 continues to loop through sensed temperature values received from the thermocouple 54. As the sensed temperature TS continues to rise due to the normal operation of the oven 10, the ignition controller 56 again determines which window is designated. For example, as temperature rises, the TS value may rise to a value greater than 900° C. wherein the third window W3 is designated. The ignition controller 56 then determines if a temperature difference exists that is less than −35° C., e.g., whether a temperature drop of 35° C. exists. If this condition does exist, a “flame failure” is detected and the ignition controller 56 shuts off the fuel valve. If the determined temperature difference is not less than −35° C., e.g., a temperature drop of 35° C. does not exist, a normal operation condition continues to be detected wherein the ignition controller 56 continues to loop through sensed temperature values received from the thermocouple 54. Thus, the hardware and software/algorithms cooperate to provide a more reliable system to detect a flame appropriately and determine the burner 28 is operating properly.
It is understood that depending on initial oven temperature, the sensed temperature TS may be at a value wherein the certain windows may be skipped in the above described process. For example, the oven 10 may have been operating and warm and is then re-ignited after a short period of down time. The sensed temperature TS may initially be at a level of over 600° C. wherein the ignition controller 56 proceeds directly to the second window W2 in the process. The process can also start directly in the third window W3 depending on the value of the sensed temperature TS.
FIGS. 8-13 disclose further exemplary embodiments regarding the ignition system and additional various algorithms used by the master controller to ignite and monitor operation of the apparatus. Similar elements of prior exemplary embodiments of the ignition system will be designated with like reference numerals. In this particular exemplary embodiment, the ignition system 50 includes various stages including a pre-ignition phase, an ignition phase and an operating phase. The system further includes safety interlocks and an igniter selection subroutine to be described. It is understood that specific temperatures, temperature ranges and temperature changes are designated for the exemplary embodiment described and can be altered without departing from the invention. As described in greater detail below, it is understood that the controller associated with the ignition system 50 analyzes output from the temperature sensor to determine if the cooking flame is present. In one exemplary embodiment, the analysis is based on a change in temperature detected by the temperature sensor.
As previously discussed, the ignition system 50 may be employed in a rotisserie oven 10 in an exemplary embodiment, but can also be used in other cooking apparatuses or other types of flame-emitting apparatuses. As shown in FIG. 8, a pre-ignition phase is set in the apparatus 10 prior to the ignition phase. In the pre-ignition phase, certain settings associated with the controller 56 are initiated including a timer associated with the controller 56 being initiated to be set at “zero.” The timer is relied upon throughout the different phases of operation of the ignition system 50 and apparatus 10. The ignition system 50 further has lockout cycles C and start cycles S. The lockout cycles C are set to a predetermined value (such as 5 in an exemplary embodiment), and the start cycles S are set to a predetermined value (such as 5 in an exemplary embodiment). A start temperature is initiated, which is the initial temperature reading of the thermocouple 54 in the apparatus 10. The system 50 provides a pre-purge period set at a predetermined time T1 such as 30 seconds in an exemplary embodiment. During a purge period it is understood that no gas is being supplied to the burner 28 and there should be no temperature readings showing a positive temperature change.
After pre-purge period T1 elapses and the timer reads a time of greater than or equal to 30 seconds, the controller 56 reads the instant temperature sensed from the thermocouple 54. As shown in FIG. 8, if the instant temperature sensed is greater than a set flame presence at start temperature limit F4, e.g., 650 degrees C. in an exemplary embodiment, a “flame detected at start” condition is determined. This can be an indication that a flame is already present in the apparatus 10, the apparatus 10 is too hot to be ignited, or a possible electrical short is present in the apparatus. It is understood that the flame presence at start temperature limit F4 could be set at other values. If the controller 56 determines a flame detected at start condition, the gas valve is shut off and the igniter is shut off. Thus, the controller 56 is configured to transmit a signal to shut down the burner. It is understood that shutting off the gas valve to interrupt the gas/fuel supply shuts down the burner. It is further understood that the gas valve 38 is associated with a pair of gas valve output relays K3, K4. The two relays are in serial activating the gas valve 38. An alarm (e.g., visual, audible, sensory perceptible etc.) may also be signaled at the flame detected at start condition. The start cycles S value previously initiated is also reduced by a value of 1. In such case, an ignition retry can be prepared (FIG. 10.) as explained below. As further shown in FIG. 8, if the controller 56 senses the flame presence at start temperature limit F4 from the thermocouple 54 to be less than 650° C., the controller 56 then determines if an increasing temperature condition is present. In particular, the controller 56 determines if the temperature sensed from the thermocouple 54 is greater than the initiated start temperature by a predetermined threshold value designated as Delta 5, e.g. 16° C. in an exemplary embodiment. If the temperature sensed is more than 16 degrees greater than the start temperature determined at initiation, a “flame detected at start” condition is determined. If the controller 56 determines a flame detected at start condition, the gas valve is shut off and the igniter is shut off. An alarm may also be signaled. The start cycles S value previously initiated is also reduced by a value of 1. In such case, an ignition retry can be prepared (FIG. 10.) as explained below.
If a “flame detected at start” condition is not present, (e.g., the sensed temperature is not greater than 650° C. or the temperature is not increasing greater than 16° C. from the initiation start temperature), then the system 50 proceeds to the ignition phase. As further shown in FIG. 8, at this phase, the igniter 52 is energized and the timer is again initiated. The alarm is not energized. The system 50 provides an igniter preheat, or warm-up period for a predetermined period of time T2, such as for 8 seconds. This allows the igniter 52 to attain an appropriate temperature condition to light the burner 28. After the igniter warm-up period T2 has elapsed and the timer reads a time greater than or equal to T2, the gas valve 38 is opened and the timer is again initiated. The igniter 52 provides the necessary spark/energy to light the burner 28 and establish a flame. The controller 56 is now in a condition to determine if the igniter 52 has properly lit the burner 28 wherein a flame has been established. The controller 56 determines whether a threshold temperature difference exists from temperatures sensed by the thermocouple 54. In particular, the controller 56 determines from the sensed temperatures if there is a temperature difference TPD2 of greater than or equal to 5° C. over any consecutive predetermined time period, such as 2 seconds. The timer is set for a trial for ignition period T3 for a predetermined time such as 14 seconds. Thus, the controller 56 operates in a loop to determine if the sensed temperature has increased by 5° C. over any 2 seconds of the 14 second trial for ignition period T3. If the timer reads a time that is greater than or equal to the trial for ignition period T3 and the controller 56 has determined that the required temperature increase TPD2 is not present, a sensing failure condition is determined by the controller 56. In response to this condition, the gas valve 38 is shut off and the igniter 52 is shut off. This condition is also considered a lockout cycle occurrence wherein the initiated lockout cycle value C is reduced by 1. In such case, an ignition retry can be prepared (FIG. 10) as explained below.
As discussed above, if the controller 56 determines a flame detected at start condition, or an ignition sensing failure, the controller 56 enters a prepare for ignition retry condition. In such condition as shown in FIG. 10, the controller 56 first determines the countdown values of start cycles S and lockout cycles C. As discussed above, at initiation, the start cycle S and lockout cycles C were initiated to an initial value, such as 5. If the controller 56 determines that the start cycle S value is less than or equal to zero, an alarm is activated. The start cycle S value reading 0 may indicate a determination that the flame is present prior to commencement of the ignition phase where the igniter 52 is energized as shown in FIG. 8. An operator can then troubleshoot the alarm, solve the problem and prepare the apparatus 10 and ignition system 50 to be re-initiated. Similarly, if the controller 56 determines that the lockout cycle C value is less than or equal to zero, an alarm is activated. The lockout value C value reading 0 may indicate that the flame is not present subsequent to a specified number of ignition attempts. The alarm may be perceptively different from the alarm generated regarding the start cycle S value. An operator can troubleshoot the alarm, solve the problem, and then prepare the apparatus 10 and ignition system 50 to be re-initiated. If the start cycle S value or the lockout cycle C value is greater than zero, the controller 56 proceeds to prepare for an ignition retry. The timer is initiated and an inter-purge period T4 is set, such as for 15 seconds. After the inter-purge period T4 has elapsed, the timer is again initiated and the start temperature is again initiated at the current sensed temperature. The controller 56 then proceeds to the pre-purge period T1 wherein the timer is set for 30 seconds. As such, the actual inter-purge period may be considered to be the combination of T1+T4. The controller 56 then again proceeds through the steps in FIG. 8 to ignite the burner 28 as described above.
Referring back to FIG. 8, if during the trial for ignition period T3, the controller 56 determines from the sensed temperatures that the temperature difference in any 2 consecutive seconds TPD2 meets the condition of being greater than or equal to the threshold temperature change of 5° C. (Delta 2), a flame detected condition is determined wherein the controller 56 concludes that the burner 28 has been properly lit and a flame exists at the burner 28. Thus, a cooking flame is determined to be present based on the change in temperature detected by the temperature sensor is greater than the designated threshold temperature change and over a predetermined time period (e.g., in this instance Delta 2 and TPD2). In such case, the apparatus 10 is considered to be in a normal operation condition representing the operation phase, and the igniter is shut off. The timer is again initiated.
In the operation phase once the timer is initiated (FIG. 9), a flame failure period T5 is set at a predetermined period, such as 14 seconds in an exemplary embodiment. During the flame failure period, the controller 56 monitors sensed temperatures to determine if there is a threshold temperature decrease TPD1 of 1° C. in any predetermined time period, such as 1 second. If such condition is not sensed, the timer is re-initiated. If the controller 56 determines from the sensed temperatures that there has been a temperature decrease of 1° C. but operation is still within the flame failure period T5, the controller 56 continues to monitor the temperature difference in any one second TPD 1. If the controller 56 determines from the sensed temperatures that there has been a temperature decrease of 1° C. and the time period is greater than or equal to the flame failure period T5 (14 seconds), a flame failure condition is determined wherein the gas valve 38 is shut off and a visible alarm may be indicated. In such case, the apparatus can be re-initiated at Step 1. In other words, the flame failure is determined if the temperature decreases more than 1° C. over a 1 second time period and the condition has not been rectified in 14 seconds. This determination operates in a continuous loop through normal operation.
During normal operation of the apparatus 10, the controller 56 also determines if the sensed (instant) temperature is less than or equal to a minimum stage 1 temperature F2, such as 500° C. in an exemplary embodiment. If the minimum stage 1 temperature F2 is less than or equal to 500° C., the controller 56 determines if there is any negative temperature difference in any 2 consecutive seconds TPD2, unless or until the temperature returns to 500° C. or greater. Accordingly, the controller 56 continuously monitors if there is any drop in temperature in any 2 second period. If there is not such a temperature drop, the controller 56 operates in this loop and continuously monitors for a negative temperature difference in any 2 consecutive seconds TPD2, unless or until the temperature returns to 500° C. or greater. If the controller 56 does determine that the sensed temperature has dropped in any 2 consecutive seconds, a flame failure condition is determined wherein the gas valve 38 is shut off and a visible alarm may be indicated. In such case, the apparatus can be re-initiated at Step 1.
As further shown in FIG. 9, if the controller 56 determines that the sensed temperature is greater than the minimum stage 1 temperature F2, e.g. 500° C., the controller 56 then determines if an additional predetermined temperature difference condition is present. In particular, the controller 56 monitors the sensed temperatures and determines whether there is a threshold negative temperature difference of 16° C. in any predetermined time period, such as 4 consecutive seconds TPD4. If the controller 56 determines that there has been a temperature drop of more than 16° C., a flame failure condition is determined wherein the gas valve 38 is shut off and a visible alarm may be indicated. In such case, the apparatus 10 can be re-initiated at Step 1. If the controller 56 determines that there has not been a temperature drop of more than 16° C., the controller 56 operates in a loop and continues to monitor temperature in the above fashion, which indicates that the apparatus 10 continues in the operation phase and operating normally.
As shown in FIG. 11, the ignition system 50 also has certain safety interlocks to shut down the apparatus 10 under certain conditions. The system has a high limit (maximum) temperature F MAX. In an exemplary embodiment, F MAX is set at a threshold level or amount of 1023° C. If the controller 56 receives a sensed temperature greater than or equal to F MAX, the igniter 52 is shut off, the gas valve 38 is shut off and an alarm is activated. The system 50 has a low limit (minimum) temperature F MIN. In an exemplary embodiment, F MIN is set at a threshold level or amount of 0° C. If the controller 56 receives a sensed temperature less than or equal to F MIN, the igniter 52 is shut off, the gas valve 38 is shut off and an alarm is activated. The system 50 also has a maximum accepted delta temperature D MAX. In an exemplary embodiment, D MAX is set at a threshold level or amount of 75° C. If the controller 56 receives sensed temperature readings of a threshold temperature difference greater than or equal to 75° C. in any 1 second TPD1 (e.g., a temperature rise), the igniter 52 is shut off, the gas valve 38 is shut off and an alarm is activated. Similarly, if the controller 56 receives sensed temperature readings of a threshold negative temperature difference greater than or equal to 75° C. in any 1 second TPD1 (e.g., a temperature drop), the igniter 52 is shut off, the gas valve 38 is shut off and an alarm is activated. It is understood that all of the safety interlocks described herein can be analyzed over a predetermined period of time.
As shown in FIG. 12, the ignition system 50 also has thermocouple failure safety interlock. As discussed above, in an exemplary embodiment, the thermocouple 52 utilizes the first sensor 55 and the second sensor 57, which may also be considered two thermocouples in the sheath 59. Each sensor 55,57 senses temperature in the apparatus. Under typical operation, the first sensor 55 and the second sensor 57 should have similar temperature readings. If the controller 56 determines that the sensed temperature readings between the first sensor 55 and the second sensor 57 are greater than or equal to a threshold amount, such as 100° C., the igniter 52 is shut off, the gas valve 38 is shut off and an alarm is activated.
As shown in FIG. 13, the ignition system 50 has an igniter selection subroutine. In an exemplary embodiment, the ignition system 50 utilizes a first igniter 52 and a second igniter 52. The system 50 reads whether an acceptable minimum current is present in the first igniter 52. If present, the system 50 operates in a loop wherein the first igniter 52 remains activated. If the first igniter 52 has a current that is less than the acceptable minimum current, a first igniter failure condition is determined and the system 50 switches to the second igniter 52. A visible or audible alarm may be energized to indicate that the second igniter 52 is energized. An igniter timer delay is provided at a set time (e.g., 1300 milliseconds) wherein the system 50 also indicates that the first igniter is off. This igniter time delay provides an operator a short signal that the system 50 has changed from the first igniter 52 to the second igniter 52. This provides an indication to the operator that the igniters 52 are in need of service.
It is understood that the thermocouple 54 can be located at various locations. It has been determined that locating the thermocouple within the periphery of the flame 40 provides accurate data for use by the system 50. It is further understood that the thermocouple 54 is positioned at the distal end 32 of the burner 28 in an exemplary embodiment. The thermocouple 54 could also be placed at other locations along the burner 28.
The ignition system 50 is used in a rotisserie oven 10 in one exemplary embodiment of the invention. The system is particularly suited for applications where fouling of a flame sensor from grease, surface contaminants or humidity is prevalent. It is understood that the ignition system or portions of the system used to confirm the presence of a flame, can be used in other types of flame-emitting apparatuses. For example, FIG. 14 discloses a lighting application wherein a street lamp is connected to a fuel source to provide light. FIG. 15 discloses an outdoor heating lamp. The above discussion regarding the ignition system and detecting the presence of a flame applies to such apparatuses. Other apparatuses where the invention can be utilized include other types of cooking apparatuses. Such cooking apparatuses include, but are not limited to, barbeque grills, boosters for heating water, fryers/donut fryers, salamander/cheesemelter, conventional ovens, accelerated cooking ovens, convection ovens, combi ovens, deck ovens, proofers, full size bakery ovens, char broilers (standard or upright), griddles, stove top/hot plates, rotisseries, pizza ovens (conveyor, deck, wood-gas combination), hot food tables (buffet style)/steam tables, ranges (multiple burners), waffle/crepe machines, stock pots, skillets/braising pans, pasta cookers, hot dog steamers, pannini machines, toasters, coffee roasters, wok ranges, Chinese pork roasters, vertical broilers, Mongolian barbeque grills, rethermalisers, rice cookers and soup kettles.
The system can also include other non-cooking apparatuses including, but not limited to, gas lamps used for lighting purposes, outdoor heat lamps, outdoor decorative appliances, hot water heaters, boilers, dishwashers, commercial water heaters, commercial patio heaters, or other devices connected to a fuel source wherein the device emits a flame.
The ignition system 50 of the present invention provides benefits over prior art flame proving systems. The temperature sensor is positioned directly in the flame wherein more reliable temperature data can be obtained. The use of the algorithms further enhances operation in providing a more reliable system for proving that a flame exists after igniting the burner.
While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention and the scope of protection is only limited by the scope of the accompanying Claims.
