Patent Publication Number: US-2022235934-A1

Title: Gas Burner for Cooking Appliances

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the United States national phase of International Application No. PCT/AU2020/000043 filed May 27, 2020, and claims priority to Australian Provisional Patent Application No. 2019901832 filed May 28, 2019, the disclosures of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to gas burners for cooking appliances. 
     Description of Related Art 
     Gas cooking appliances generally have one or more burners in which gas is mixed with air and burned. In turn, the appliance (and hence the burner(s)) are connected to a gas supply such as a municipal gas supply network. In traditional gas cooking appliances the amount of gas supplied to the burner is regulated using a mechanical gas cock positioned between the gas supply and the burner. The gas cock is operated by a user who sets the gas cock at a desired level to obtain a desired flame height or heat output at the burner. 
     In use, it is difficult for users to accurately control the heat output of gas burners in gas cooking appliances using traditional gas cocks. One reason for this is the pressure of the gas supplied to the burner can vary over time. Accordingly, it would be desirable for a gas cooking appliance that allows a user to maintain control of the burner power output over time irrespective of fluctuations in gas pressures, temperatures, etc. 
     Gas cooking appliances that use electronic control systems to regulate the heat output of one or more burners in the cooking appliance have been proposed in the prior art. For example, U.S. Pat. No. 8,926,318 (Barritt, et al.) discloses a gas cooking appliance that has a pressure sensor operable to measure the pressure of gas supplied to a gas burner and generate an electrical output signal and an electronic controller electrically coupled to both the gas burner and the pressure sensor. The controller compares a measured gas pressure with a target pressure, and operates a gas valve to adjust the supply of gas to the gas burner based on the difference between the measured pressure and the target pressure. 
     There is a need for improved gas burner systems for gas cooking appliances that overcome one or more of the problems associated with the use of existing gas burner systems and/or provide a useful alternative to existing gas burner systems. 
     SUMMARY OF THE INVENTION 
     In a first aspect, there is provided a cooking appliance gas burner system comprising: 
     a gas burner adapted to receive gas flow from a gas feed line via a venturi; 
     a flow sensor comprising a gas flow input in fluid connection with the venturi and configured to measure pressure at the venturi, the flow sensor further comprising a differential pressure sensor configured to measure a pressure differential at the venturi between a maximum burner air/gas mixture flow rate and a user input burner air/gas mixture flow rate that is input by a user as a requested percentage of the maximum burner air/gas mixture flow rate; 
     a proportional valve configured to modulate the air/gas mixture flow rate into the gas burner; and 
     a controller configured to determine burner air/gas mixture flow rates from the flow sensor and regulate the burner air/gas mixture flow rate via the proportional valve based upon a user-defined input. 
     In a second aspect, there is provided a method of operating a cooking appliance, comprising: 
     receiving a user-defined input signal corresponding to a desired quantity of heat to be delivered by a gas burner to a cooking surface; 
     determining a maximum burner air/gas mixture flow rate; and 
     modulating the burner air/gas mixture flow rate to provide a target burner air/gas mixture flow rate based upon the user-defined input signal and the determined maximum burner air/gas mixture flow rate. 
     In a third aspect, there is provided a cooking appliance comprising the gas burner of the first aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Embodiments of the present invention will be discussed with reference to the accompanying figure wherein: 
         FIG. 1  is a schematic of a cooking appliance gas burner according to embodiments of the present disclosure. 
       In the following description, like reference characters designate like or corresponding parts throughout the figures. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , there is shown a cooking appliance gas burner system  10 . The gas burner system  10  comprises a gas burner  12  adapted to receive gas flow from a gas feed line  14  via a venturi  16 . The cooking appliance gas burner system  10  is suitable for use in gas cooking appliances to provide a variable burner rate to achieve a desired level of heating of a cooking surface. 
     The gas burner  12  can be any type of atmospheric natural gas or LPG burner that employs a venturi  16  method of inducing air flow into a burner. A wide range of gas burners  12  are commercially available and can be used for this purpose. Advantageously, the cooking appliance gas burner system  10  and methods disclosed herein can be used with any size gas burner  12 . 
     The gas burner  12  comprises an orifice and venturi  16  for the entrainment of air by mixing air with the gas required to generate the burner  12  power output. The gas is extracted from gas feed line  14  which, in turn, is connected to a gas supply network or similar The gas is supplied at a pressure of the gas supply source and, as will be appreciated, this can fluctuate over time. The gas passes through a gas jet  32  and into the venturi  16  where it is mixed with air which then provides the primary aeration of the gas burner  12 . 
     A flow sensor  18  comprises a gas flow input  20  in fluid connection with the venturi  16  and is configured to measure the pressure at the venturi  16  which, in turn, can be used to determine the rate of flow of a combined air/gas mixture in the burner  12 . Specifically, the flow sensor  18  comprises a differential pressure sensor  22  which is configured to measure a pressure differential at the venturi  16  between a maximum burner  12  air/gas mixture flow rate and a user input burner  12  air/gas mixture flow rate. The user input burner air/gas mixture flow rate is input by a user as a requested percentage of the maximum burner  12  air/gas mixture flow rate. 
     It will be appreciated that the differential pressure sensor  22  does not measure the pressure of the gas in the gas feed line  14  or elsewhere in the cooking appliance gas burner system  10 . Instead, the differential pressure sensor  22  measures the pressure at the venturi  16 . As the gas passes through the venturi  16 , it speeds up inducing the air flow but also creating a low pressure that is proportional to the air/gas mixture flow rate. The differential pressure sensor  22  and the flow sensor  18  therefore measure flow indirectly by measuring the pressure differential across the venturi  16 . As used herein the term “determining the gas flow rate” or similar terms means that the gas flow rate is determined based on some other measured parameter, such as pressure, and that value is then used to determine a flow rate. 
     In use, the flow sensor  18  determines the rate of flow of the combined air/gas mixture in the burner  12  based on a measured pressure at the venturi  16 . This positioning of the gas flow input  20  not only allows flow rates to be determined but also means that only air passes through the flow sensor  18 , obviating the need for a sensor rated for use with combustible gases. The pressure differential reading is also temperature compensated to provide a true measure of flow rate. 
     A range of differential pressure sensors  22  can be used in the gas flow sensor  18 . Differential pressure sensors  22  are commercially available and can be used for this purpose. For example, a commercially available digital differential pressure sensor  22 , range −125 to +125 Pa, can be used. 
     A proportional valve  24  is operable to control the supply of gas to the gas burner  12 . The proportional valve  24  is configured to modulate the air/gas mixture flow rate into the gas burner  12  in accordance with a voltage applied to it by a valve drive  28 . The proportional valve  24  includes an actuating device that moves a valve member between a closed valve position and a plurality of open valve positions. A range of gas proportional valves  24  are commercially available and can be used for this purpose, such as a −24V dc, 2 PSI, 0.2 cu m/hr gas proportional valve. 
     The gas feed line  14  is coupled to the proportional valve  24  at an inlet port  34 . An outlet port  36  of the proportional valve  24  is coupled to the gas burner  12  via the jet  32  and venturi  16  assemblies. As the valve member of the proportional valve  24  is opened, the amount of gas advanced through the proportional valve  24  increases proportionately. Although not shown in the figures, it is contemplated that a single gas burner  12  may have more than one proportional valve  24 . 
     In use, a maximum air/gas flow rate is determined by setting the proportional valve  24  to maximum voltage (i.e. fully open). This measurement provides a baseline from which lower flow rate/heat settings are calculated. For example, if the maximum air/gas flow rate is 1000 then a user can regulate to 200 for a gas burner  12  setting of 2 (or 20% of maximum). 
     A controller  26  is operably connected to the flow sensor  18 , the valve drive  28  and a user input interface  30 . The controller  26  is configured to receive electrical signals sent by the flow sensor  18  (and any other sensors), the user input interface  30 , and a flame sensor (if present). The controller  26  is also configured to activate electronically controlled components of the cooking appliance gas burner system  10  including the proportional valve  24  (e.g. via the valve drive  28 ) and/or an ignition device (if present). 
     The controller  26  includes a number of electronic components commonly associated with electronic units utilised in the control of electromechanical systems. For example, the controller  26  may include a processor and a memory device. The memory device can be used to store instructions in the form of, for example, a software routine (or routines) which, when executed by the processor, allows the controller  26  to control operation of the cooking appliance gas burner system  10 . 
     The user input interface  30  can be any form and may, for example, comprise an LED display, an on button, an off button, and up and down controller buttons to allow a user to input a desired heating level. The desired heating level may be a percentage of the maximum heating level (and hence the maximum gas flow rate) and may, for example, be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% of the maximum flow rate. The controller  26  is configured to read gas burner  12  air/gas mixture flow rates from the flow sensor  18  and regulate the gas burner  12  air/gas mixture flow rate based upon the user-defined input via the proportional valve  24  and the valve drive  28 . The controller  26  is also operable to generate a control signal indicative of the maximum air/gas mixture flow rate. 
     The cooking appliance gas burner system  10  may have an ignition device (not shown) that is operable to ignite gas exiting from the gas burner  12  and produce a controlled flame in response to control signals received from the controller  26 . 
     Optionally, the cooking appliance gas burner system  10  may have a flame sensor positioned adjacent to the gas burner  12  to sense or detect whether a flame is produced in the gas burner  12 . The flame sensor may be operably connected to the controller  26  which, in turn, may operate the valve drive  28  to close the proportional valve  24  if no flame is detected at the gas burner  12 . 
     The cooking appliance gas burner system  10  disclosed herein provides a novel means of electronically regulating the flow of the gas/air mixture to a gas burner  12 . The system obviates the need for a gas cock allowing full electronic control of the gas burner  12  heating level Unlike other known systems, the cooking appliance gas burner system  10  disclosed herein measures the flow of the air/gas mixture into the burner  12  and uses this information to regulate the burner  12  heating level. 
     In use, heating is initiated when the user sets a non-zero heating level using the controller  26 . The heating level is converted into a percentage of the maximum gas burner  12  output. The controller  26  initially sets the proportional valve  24  level to maximum and measures the flow rate of the air/gas mixture. The resulting flow measurement determines the maximum flow level for the gas burner  12 . The controller  26  then adjusts the valve drive  28  to achieve the requested percentage of the maximum flow based on continuous flow measurements. 
     The cooking appliance gas burner system  10  differs from existing systems in the following ways:
         The burner  12  heat rate is accurately controlled by measuring the air/gas flow rate at the gas burner  12  and using this as the basis for regulating the flow rather than just the gas flow or gas line  14  pressure;   The gas flow rate can be varied using a low cost, simple proportional valve  24  rather than an electromechanical gas cock or precision proportional valve;   The air/gas flow rate is measured giving a much better indication of gas burner  12  output level;   The flow rate measurement is not dependent on gas line  14  pressure and is compensated for temperature;   Flow is measured at the venturi  16  of the gas burner  12  at a low pressure point. This means that only cool air is passing through the flow sensor  18 ;   The cooking appliance gas burner system  10  can be retro-fitted to existing gas burners  12  requiring only a small hole to be drilled in the venturi  16 ;   The cooking appliance gas burner system  10  does not require use of a sensor that is safe to use with flammable materials; and   The cooking appliance gas burner system  10  is self-calibrating.       

     Also disclosed herein is a method of operating a cooking appliance. The method comprises receiving a user-defined input signal corresponding to a desired quantity of heat to be delivered by a gas burner to a cooking surface; determining a maximum burner air/gas mixture flow rate; and modulating the burner air/gas mixture flow rate to provide a target burner air/gas mixture flow rate based upon the user-defined input signal and the determined maximum burner air/gas mixture flow rate. 
     Also provided herein is a cooking appliance comprising the gas burner system. 
     Throughout the specification and the claims that follow, unless the context requires otherwise, the words “comprise” and “include” and variations such as “comprising” and “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. 
     The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge. 
     It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.