Gas burner for cooking appliances

A cooking appliance gas burner system includes a gas burner adapted to receive gas flow from a gas feed line via a venturi. A flow sensor includes a gas flow input in fluid connection with the venturi and configured to measure pressure at the venturi. The flow sensor further includes 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 is configured to modulate the air/gas mixture flow rate into the gas burner. A controller is configured to read 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.

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; anda 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; andmodulating 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.

In the following description, like reference characters designate like or corresponding parts throughout the figures.

DESCRIPTION OF THE INVENTION

Referring now toFIG.1, there is shown a cooking appliance gas burner system10. The gas burner system10comprises a gas burner12adapted to receive gas flow from a gas feed line14via a venturi16. The cooking appliance gas burner system10is 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 burner12can be any type of atmospheric natural gas or LPG burner that employs a venturi16method of inducing air flow into a burner. A wide range of gas burners12are commercially available and can be used for this purpose. Advantageously, the cooking appliance gas burner system10and methods disclosed herein can be used with any size gas burner12.

The gas burner12comprises an orifice and venturi16for the entrainment of air by mixing air with the gas required to generate the burner12power output. The gas is extracted from gas feed line14which, 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 jet32and into the venturi16where it is mixed with air which then provides the primary aeration of the gas burner12.

A flow sensor18comprises a gas flow input20in fluid connection with the venturi16and is configured to measure the pressure at the venturi16which, in turn, can be used to determine the rate of flow of a combined air/gas mixture in the burner12. Specifically, the flow sensor18comprises a differential pressure sensor22which is configured to measure a pressure differential at the venturi16between a maximum burner12air/gas mixture flow rate and a user input burner12air/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 burner12air/gas mixture flow rate.

It will be appreciated that the differential pressure sensor22does not measure the pressure of the gas in the gas feed line14or elsewhere in the cooking appliance gas burner system10. Instead, the differential pressure sensor22measures the pressure at the venturi16. As the gas passes through the venturi16, 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 sensor22and the flow sensor18therefore measure flow indirectly by measuring the pressure differential across the venturi16. 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 sensor18determines the rate of flow of the combined air/gas mixture in the burner12based on a measured pressure at the venturi16. This positioning of the gas flow input20not only allows flow rates to be determined but also means that only air passes through the flow sensor18, 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 sensors22can be used in the gas flow sensor18. Differential pressure sensors22are commercially available and can be used for this purpose. For example, a commercially available digital differential pressure sensor22, range −125 to +125 Pa, can be used.

A proportional valve24is operable to control the supply of gas to the gas burner12. The proportional valve24is configured to modulate the air/gas mixture flow rate into the gas burner12in accordance with a voltage applied to it by a valve drive28. The proportional valve24includes 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 valves24are 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 line14is coupled to the proportional valve24at an inlet port34. An outlet port36of the proportional valve24is coupled to the gas burner12via the jet32and venturi16assemblies. As the valve member of the proportional valve24is opened, the amount of gas advanced through the proportional valve24increases proportionately. Although not shown in the figures, it is contemplated that a single gas burner12may have more than one proportional valve24.

In use, a maximum air/gas flow rate is determined by setting the proportional valve24to 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 burner12setting of 2 (or 20% of maximum).

A controller26is operably connected to the flow sensor18, the valve drive28and a user input interface30. The controller26is configured to receive electrical signals sent by the flow sensor18(and any other sensors), the user input interface30, and a flame sensor (if present). The controller26is also configured to activate electronically controlled components of the cooking appliance gas burner system10including the proportional valve24(e.g. via the valve drive28) and/or an ignition device (if present).

The controller26includes a number of electronic components commonly associated with electronic units utilised in the control of electromechanical systems. For example, the controller26may 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 controller26to control operation of the cooking appliance gas burner system10.

The cooking appliance gas burner system10may have an ignition device (not shown) that is operable to ignite gas exiting from the gas burner12and produce a controlled flame in response to control signals received from the controller26.

Optionally, the cooking appliance gas burner system10may have a flame sensor positioned adjacent to the gas burner12to sense or detect whether a flame is produced in the gas burner12. The flame sensor may be operably connected to the controller26which, in turn, may operate the valve drive28to close the proportional valve24if no flame is detected at the gas burner12.

The cooking appliance gas burner system10disclosed herein provides a novel means of electronically regulating the flow of the gas/air mixture to a gas burner12. The system obviates the need for a gas cock allowing full electronic control of the gas burner12heating level Unlike other known systems, the cooking appliance gas burner system10disclosed herein measures the flow of the air/gas mixture into the burner12and uses this information to regulate the burner12heating level.

In use, heating is initiated when the user sets a non-zero heating level using the controller26. The heating level is converted into a percentage of the maximum gas burner12output. The controller26initially sets the proportional valve24level to maximum and measures the flow rate of the air/gas mixture. The resulting flow measurement determines the maximum flow level for the gas burner12. The controller26then adjusts the valve drive28to achieve the requested percentage of the maximum flow based on continuous flow measurements.

The cooking appliance gas burner system10differs from existing systems in the following ways:The burner12heat rate is accurately controlled by measuring the air/gas flow rate at the gas burner12and using this as the basis for regulating the flow rather than just the gas flow or gas line14pressure;The gas flow rate can be varied using a low cost, simple proportional valve24rather than an electromechanical gas cock or precision proportional valve;The air/gas flow rate is measured giving a much better indication of gas burner12output level;The flow rate measurement is not dependent on gas line14pressure and is compensated for temperature;Flow is measured at the venturi16of the gas burner12at a low pressure point. This means that only cool air is passing through the flow sensor18;The cooking appliance gas burner system10can be retro-fitted to existing gas burners12requiring only a small hole to be drilled in the venturi16;The cooking appliance gas burner system10does not require use of a sensor that is safe to use with flammable materials; andThe cooking appliance gas burner system10is 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.

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.