Abstract: An apparatus and method for rotating a part includes a sequence of relays to rotate the part given number of degrees. The apparatus does not require software or complex mechanical gearing.

Abstract: Example dual-burner assemblies for cookboxes of gas grills are disclosed. An example dual-burner assembly includes a first burner tube and a second burner tube. The first burner tube has a first maximum heat output. The second burner tube has a second maximum heat output. The second burner tube is spaced apart from the first burner tube by a distance of no more than 0.750 inches. The second maximum heat output is less than the first maximum heat output.

Abstract: A water heater may include a water tank, a burner, a pilot for igniting the burner, an ignitor for igniting the pilot, a thermoelectric device in thermal communication with a flame of the pilot, a controller for controlling an ignition sequence of the pilot using the ignitor, and a rechargeable power storage device for supplying power to the ignitor and the controller. The rechargeable power storage device may be rechargeable using the energy produced by the thermoelectric device. The controller is configured to selectively ran only the pilot for at least pan of a heating cycle to increase the recharge lime of the rechargeable power storage device while still healing the water in the water heater.

Abstract: A gas powered water heater includes a storage tank, a main burner, a flame sensor assembly, and a controller communicatively coupled to the flame sensor assembly. The flame sensor assembly includes a probe positioned proximate the main burner to couple an electric current to the main burner through a flame on the main burner and not to couple an electric current to the main burner when the flame is not present on the main burner, and a detector that provides signals representative of the electric current provided through the probe. The controller is programmed to determine a length of time taken for a transition between a signal representative of no electric current and a signal representative of a steady state electric current, and determine, based at least in part on the determined length of time, a strength of the flame on the main burner.

Abstract: A method of controlling water heater pilot flame ignition includes receiving, by a controller of a water heater, a user input and controlling a pilot gas valve to start a gas flow to a pilot burner in response to the user input. The method further includes, in response to the user input, controlling, by the controller, an igniter to generate an ignition spark for lighting a pilot flame. The method also includes controlling, by the controller, the pilot gas valve to maintain the gas flow to the pilot burner if the pilot flame is lit.

Abstract: A method of operating a multi-ring gas burner includes sending a spark to a first ring of the multi-ring burner. After sending the spark to the first ring, the method determines a flame status of the first ring and adjusts a position of an electronic gas valve connected to a second ring of the multi-ring gas burner based on the determined flame status of the first ring.

Abstract: A fuel-fired heating appliance has two fuel flow paths to a burner, each actuatable to a closed state and to an open state. A heat exchanger is in fluid communication with an area proximate the burner. A controller executes the steps: (a) while the first fuel flow path is closed, opening the second flow path; (b) following ignition of fuel flowing from the second flow path, opening the first fuel flow path; and (c) following step (b), closing the second fuel flow path while opening the first fuel flow path.

Abstract: A remote burner monitoring system including one or more burners each including integrated sensors, a data collector corresponding to each of the burners for receiving and aggregating data from the sensors of the corresponding burner, and a local transmitter corresponding to each of the data collectors for transmitting the data, a data center configured and programmed to receive the data from the local transmitters corresponding to the one or more burners, and a server configured and programmed to store at least a portion of the data, to convert the data into a display format, and to provide connectivity to enable receipt and transmission of data and the display format via a network including at least one of a wired network, a cellular network, and a Wi-Fi network.

Abstract: A method includes identifying a first steady-state gain associated with a relationship between a characteristic of a furnace and a setpoint used by a controller that is configured to control the characteristic of the furnace, The first steady-state gain is identified using data collected when the furnace is not suffering from flooding. The method also includes identifying a second steady-state gain associated with the relationship during operation of the furnace. The method further includes comparing the first and second steady-state gains and identifying actual or potential flooding of the furnace based on the comparison.

Abstract: A gas regulating fitting that ensures simple manual operation is to be created. In particular, the device is to be capable of being switched both on and off in one operation. To that end, a microswitch (12) connected to an electronic control unit is arranged on the housing (1). The microswitch is operated when a tappet (10) arranged axially to the safety pilot valve (26) and the main valve (19) is manually operated. The electronic control unit thereby receives an electrical signal whereby the gas regulating fitting is activated in its switched-off state, and the gas flow flowing through the open safety pilot valve (26) is therefore ignited, whereas the holding current flowing to the thermoelectric safety pilot valve (26) is interrupted in the switched-on state of the gas regulating fitting, and the gas regulating fitting is therefore deactivated. The gas regulating fitting can be used to ignite and regulate a gas flow flowing to a burner.

Abstract: A heating apparatus may include a control valve assembly. A control valve assembly can have a housing and a valve body positioned within the housing. The housing can define an inlet and first and second outlets. The control valve assembly can also include an igniter having a sensor for firing an electrode. An extension can be used to activate the sensor and to thereby activate the igniter.

Abstract: An ignition control system for an appliance is disclosed. The appliance includes a gas burner, a user actuable valve for controlling a flow of fuel to the burner and an electrical resistance igniter for igniting fuel at the burner. The system includes a user actuable control interface having an off state and an on state, coupled to the valve operative to control the valve and provide a control signal indicative of the state of the control interface. The system also includes a controller having a timer circuit responsive to the control signal and a boost circuit coupled to the timer circuit. The timer circuit selectively activates the boost circuit for a predetermined period of time. A first DC power supply is selectively coupled to the igniter to provide power to the igniter through the boost circuit. A second DC power supply is coupled to the igniter and control interface.

Abstract: A large-scale combustion system has a fuel line having a burner end, a burner at the burner end of the fuel line, a source of fuel flowing through the fuel line to the burner, a hot surface igniter adjacent to the fuel line, a flame holder disposed adjacent to the hot surface igniter, and a source of igniter combustion air. The hot surface igniter is activated to ignite the source of fuel, the ignited fuel leaving the burner, and the hot surface igniter is protected from a heat caused by the ignited fuel. A flame detector detects ignition of the source of fuel and in response to detection of ignition the hot surface igniter is deactivated.

Abstract: A system or apparatus that in one implementation includes an electromagnetic valve having an actuator rod with a first coil and a second coil positioned at different longitudinal locations on the actuator rod and being situated electrically parallel to one another in an electrical circuit. The electromagnetic valve is constructed to induce a first voltage in the second coil when the electromagnetic valve is in the open position and to induce in the second coil a second voltage lower than the first voltage when the electromagnetic valve is in the closed position. A switch changeable between a first position and a second position is located in the electrical circuit. When the switch is in the first position the electrical circuit is configured to allow current from a power source to be delivered to the second coil. When the switch is in the second position the electrical circuit is configured to not allow current from a power source to be delivered to the second coil.

Abstract: Disclosed herein is a method of controlling a gas type clothes dryer. The method control the dryer to continuously detect condition of a flame sensor even after ignition of the dryer, thereby preventing a drying operation from being performed when a flame has been extinguished due to insufficient gas supply caused by failure of a gas valve.

Abstract: The aim of the invention is to create a gas regulating fitting which, once a gas stove has been successfully started up, can switch the pilot burner into the off position when the main burner is in the off position, in order to maintain the power consumption of the gas stove as low as possible. The aim of the invention is also to provide the gas regulating fitting with as simple a structure as possible. To this end, the gas regulating fitting comprises a sensor (34) by which means the operating state of the main burner (33) can be detected. The sensor (34) is connected to a thermoelectric safety pilot valve (17) in such a way that, when the operating state of the main burner (33) is switched from the on position into the off position by a signal emitted from the sensor (34), the thermoelectric safety pilot valve (17) assumes the closed position thereof. The gas regulating fitting can be used to ignite and to regulate a gas flow flowing to a burner.

Abstract: This invention relates to a solid oxide fuel cell system comprising at least one longitudinally extending tubular solid oxide fuel cell and a longitudinally extending heater mounted in thermal proximity to the fuel cell to provide heat to the fuel cell during start up and during operation as needed. The heater and fuel cell can be encased within a tubular thermal casing; the inside of the casing defines a first reactant chamber for containing a first reactant, such as oxidant. The fuel cell comprises a ceramic solid state electrolyte layer and inner and outer electrode layers concentrically arranged around and sandwiching the electrolyte layer. The outer electrode layer is fluidly communicable with the first reactant, and the inner electrode layer is fluidly isolated from the first reactant and fluidly communicable with a second reactant, such as fuel.

Abstract: An automated ignition assembly for a gas-fueled appliance includes a pressure plate positioned between an upper bellows and a lower bellows, each of which is in selective communication with a fuel gas source. If fuel gas is directed to the lower bellows, gas within the upper bellows is diverted to an ignition site; as the lower bellows inflates, it lifts the pressure plate and an associated linkage assembly to engage a piezo igniter, which creates a spark at the ignition site. The lower bellows is then deflated and the upper bellows is inflated to again engage the piezo igniter. Once a flame has been generated, or if a flame has not been generated within a predetermined time period, an automated valve disables fuel gas flow to the bellows.

Abstract: A gas burner includes a gas valve block having a gas input control part connected to a fuel gas source and a gas output control part connected to a flame tube and gas nozzle for producing an igniting flame for burning fuel gas outputted through the flame tube, a differential pressure device adapted to control the fuel gas passage between the gas input control part and the gas output control part through a normal-close valve and a normal-open valve, an electronic igniter controlled by a cock in the gas valve block through a micro-switch to discharge sparks through discharging electrode means for burning fuel gas outputted through the gas nozzle, and a temperature switch for controlling the operation of the normal-open valve and the electronic igniter subject to a predetermined temperature range.

Abstract: A temperature control system for a gas-fired appliance which uses a thermoelectric device to develop power for recharging a primary energy source, such as a rechargeable battery. The present invention provides a reliable and efficient system for controlling and powering a temperature control system.

Abstract: An apparatus for controlling gas supply includes a battery supply, a pilot seat on which are mounted a thermopile, a pilot burner, a spark generator and a detector, a pilot valve, a main burner valve, an auxiliary burner valve, and a control board including a pilot timer control for controlling electric power to the control board from the battery supply, a pilot control circuit controlled by the pilot timer control for controlling electric current supplied to the pilot valve, a main valve control circuit for controlling the main burner valve, an ignitor control circuit connected to the main valve control circuit for controlling the spark generator, a pilot and main valve transfer control connected to the battery supply for switching the battery supply to the thermopile, an auxiliary valve transfer control for controlling the auxiliary burner valve, an auxiliary valve control circuit for controlling the auxiliary valve transfer control, an auxiliary timer connected to the battery supply for controlling electri

Abstract: In this combustion gas control device, an electromechanical control is provided for automatically controlling the supply of the gas to the pilot burner when it is being ignited and subsequently to the main burner. The device has a main chamber, a pilot chamber and an outlet chamber. A spring-biassed valve is provided between the main chamber and the pilot chamber to close communication between the main chamber and pilot and outlet chambers. The spring-biassed valve is opened when a solenoid is actuated to allow gas from the main chamber to flow into the pilot chamber to the pilot outlet for lighting the pilot light. A diaphragm cover is provided between the pilot chamber and outlet chamber while the pilot is lighted to prevent gas from entering the outlet chamber.

Abstract: A device for automatically controlling the operation of a burner comprises an electric control unit which controls the ignition and the flame of the burner and which opens a normally-closed solenoid valve disposed in a first fuel-supply line to the burner, and a pilot burner for the burner supplied by manually-operable second regulation and safety valve means operatively associated with the control unit and disposed in a second fuel-supply line to the burner, the second valve means being openable manually and being kept open by a current I generated by a thermocouple in the presence of a flame of the pilot burner when the control unit is de-activated and advantageously being closable by the control unit against the action of the current I when the control unit is activated.

Abstract: A fuel control system, parts therefor and methods of making and operating the same are provided, the fuel control system comprising an ignition unit for igniting fuel issuing from a burner, and a flame detecting unit for detecting flame at the burner, the flame detecting unit comprising a sensing device for receiving an electrical signal caused by flame rectification at the burner, and an output device for cycling the signal to the sensing device in an on and off manner in each cycle of operation of the output device, the control system having a modulating unit for modulating the on time and the off time of the output device in each cycle of operation thereof.

Abstract: A controller for a gas burner system compensates for the tendency of a flame rod sensor in the burner system to on occasion provide a spike in its signal on first lightoff of a pilot flame, by delaying the signal which causes opening of the burner system's main burner valve until the sensor signal has had a chance to reach to its normal level indicative of the presence of the pilot flame. This time varies from about 5 to 30 seconds.

Abstract: A fuel valve and ignitor control system in which pull-in current for a fuel valve operating on rectified alternating current is supplied through a first normally open relay whose coil is connected in series with normally open contacts of a second relay and an intermittently operating hot surface ignitor. Normally closed contacts of the second relay are connected in series with the ignitor and the fuel valve through a holding resistor, whereby actuation of the second relay provides unrectified alternating current to the ignitor and actuates the first relay to provide pull-in current to the fuel valve, and whereby deactivation of the second relay provides holding current to the fuel valve through the ignitor.

Abstract: A heat exchanger system, a fuel control system therefor and methods of making the same are provided, the fuel control system having an electrical circuit means that comprises an ignition trial portion, a flame sensing control portion and a timer portion that comprises a counter having a plurality of outputs and a timer that clocks the output of the counter on each discharge of the timer, the timer portion also comprising a capacitor, a trial time resistor and a wait time resistor that are selectively placed in series with the capacitor by the counter when clocked to certain outputs by the timer to determine an ignition trial time period and a wait time period, and a transistor operatively interconnected to the capacitor to discharge the capacitor when flame is sensed by the flame sense portion.

Abstract: This invention relates to an ignition device for water heaters and in particular to one including a body portion, a water container including a diaphragm fixedly mounted on the bottom of the body portion and having a lift rod extending into the body portion, a valve mounted within the body portion and located above the lift rod of the water container, a linking rod attached on the top of the housing of the valve and extending upwardly through a valve gasket to connect with a gas valve, and a solenoid mounted on a top of said body portion and connected with a leak-proof gasket via a rod, whereby the gas valve will be automatically closed when the fire is blown out thereby preventing gas from leaking outside and therefore ensuring safety.

Abstract: A heat exchanger system, a fuel control system therefor and methods of making the same are provided, the fuel control system having an electrical circuit means that comprises an ignition trial portion, a flame sensing control portion and a timer portion that comprises a counter having a plurality of outputs and a timer that clocks the output of the counter on each discharge of the timer, the timer portion also comprising a capacitor, a trial time resistor and a wait time resistor that are selectively placed in series with the capacitor by the counter when clocked to certain outputs by the timer to determine an ignition trial time period and a wait time period.

Abstract: A primary gas furnace control including a thermostatically controlled intermittent ignition system, the control being effective to monitor and control main gas valve action through use of flame rectification. The control features a slight delay on main valve dropout with flame failure and an extension of the ignition source into the main burner cycle to prevent nuisance recycling. If desired, the control may also include timed pilot valve, thermostat resettable, lockout as well as prepurge capability for use in applications requiring a furnace combustion chamber purge prior to an ignition cycle.

Abstract: A heat exchanger system, a fuel control system therefor and methods of making the same are provided, the fuel control system having an electrical circuit means that comprises an ignition trial portion, a flame sensing control portion and a timer portion that comprises a counter having a plurality of outputs and a timer that clocks the output of the counter on each discharge of the timer, the timer portion also comprising a capacitor, a trial time resistor and a wait time resistor that are selectively placed in series with the capacitor by the counter when clocked to certain outputs by the timer to determine an ignition trial time period and a wait time period.

Abstract: A control system for a gas furnace, control device therefor and methods of making the same are provided, the system comprising an electrical circuit that has a metal oxide varistor therein that is adapted to interconnect one end of a secondary winding of a transformer to frame ground only after the potential for sparking is reached at an igniter that is interconnected to the other end of the secondary winding and causes the varistor to break over and cause the igniter to spark.

Abstract: A fuel burner includes an electrical igniter which lights a pilot burner which then lights the main burner. Operation of each of these steps is monitored, and if any are improper, the control device reverts to lighting the pilot burner with the main burner valve shut. If the igniter is sensed as incapable of lighting the pilot burner, the pilot burner valve is shut, and an error is indicated to the operator.

Abstract: A burner control system for an intermittent pilot burner system uses a single pole double throw relay to control first and second electromagnetic valves respectively supplying fuel for both burners and for the main burner only. The normally open contact pair supplies the current for the first and the normally closed contact pair supplies the current for the second valve. By selecting the valve supplying fuel for both burners to be of the type which has an appreciably higher pull-in current than drop-out current, and by shunting the relay's normally open contacts with a properly selected resistor, only a single relay is necessary. This resistor is selected to supply current sufficient to hold the valve open (current greater than the drop-out value) after the valve has received pull-in current through the closing of these normally open contacts, but insufficient to open the valve. Use of a single relay reduces cost, size, and power, and increases safety of the control system.

Abstract: A remote-controlled system for igniting a gas barbeque unit and the like is shown. The system controls the gas flow to the pilot lighter and the burner of the barbeque unit, and generates a spark to ignite the pilot lighter and in turn the burner. The system will automatically shut off when the pilot lighter is accidentally extinguished so as to prevent gas leakage to cause any explosion. The system may be operated by a low voltage 9-volt battery.

Abstract: A control unit for a gas furnace that has an electrically operable pilot gas valve and an electrically operable main gas valve and a method of making the control unit are provided, the control unit comprising an electrical circuit having a gas valve section that comprises a silicon controlled rectifier and a first capacitor and a second capacitor so electrically interconnected together that the capacitors are adapted to be charged on each half wave cycle of a certain polarity of an alternative current source that is imposed on the circuit and that second capacitor is adapted to discharge through a relay coil that controls the gas valve to energize that relay coil only when the silicon controlled rectifier conducts, the silicon controlled rectifier being adapted to conduct only when the first capacitor is discharged, another section of the electrical circuit being adapted to discharge the first capacitor only on each half wave cycle of the other polarity of the alternative current source.

Abstract: A primary gas furnace control including a thermostatically controlled intermittent ignition system, the control being effective to monitor and control main gas valve action through use of flame rectification. The control features a slight delay on main valve dropout with flame failure and an extension of the ignition source into the main burner cycle to prevent nuisance recycling. If desired, the control may also include time pilot valve, thermostat resettable, lockout as well as prepurge capability for use in applications requiring a furnace combustion chamber purge prior to an ignition cycle.

Abstract: Electronic control system for an oil burner has a primary direct current power source controlled by a thermostat and a secondary direct current power source independent of the thermostat. A first relay is in circuit with the oil burner motor to energize the same and a second relay is in series with the first and with an alternating voltage source for energizing the ignitor of the furnace. An electronic circuit controls the first relay switch and includes a pair of silicon controlled rectifiers (SCR's) connected in series for energizing the first relay. A second electronic circuit includes a pair of interconnected NPN transistors for controlling the operation of the second relay switch. The first NPN transistor is conductive when the second relay switch is energized and the second NPN transistor is connected to the first to turn "OFF" the same in response to flame being sensed in the furnace.

Abstract: A furnace employing a plurality of spaced burners, a carryover tube passing adjacent the burners, a hot surface igniter at one end of the carryover tube, a flame sensor at the other end of the carryover tube and an ignition control for controlling actuation of the hot surface igniter and the flow of combustible gas to the carryover tube and main burners, the ignition control being responsive to the flame sensor.

Abstract: A control unit for a gas furnace that has an electrically operable pilot gas valve and an electrically operable main gas valve and a method of making the control unit are provided, the control unit comprising an electrical circuit having a gas valve section that comprises a silicon controlled rectifier and a first capacitor and a second capacitor so electrically interconnected together that the capacitors are adapted to be charged on each half wave cycle of a certain polarity of an alternative current source that is imposed on the circuit and that the second capacitor is adapted to discharge through a relay coil that controls the gas valve to energize that relay coil only when the silicon controlled rectifier conducts, the silicon controlled rectifier being adapted to conduct only when the first capacitor is discharged, another section of the electrical circuit being adapted to discharge the first capacitor only on each half wave cycle of the other polarity of the alternative current source.

Abstract: A primary gas furnace control including a thermostatically controlled intermittent ignition system, the control being effective to monitor and control main gas valve action through use of flame rectification. The control features a slight delay on main valve dropout with flame failure and an extension of the ignition source into the main burner cycle to prevent nuisance recycling. If desired, the control may also include timed pilot valve, thermostat resettable, lockout as well as prepurge capability for use in applications requiring a furnace combustion chamber purge prior to an ignition cycle.

Abstract: A fail safe gas shut off system is provided for a gas appliance. Two normally closed valve stages are provided in series, with each stage operated by a bidirectional solenoid armature. When the armature moves in one direction, the first stage of the valve is opened to supply gas to a pilot burner and to the second stage of the valve. When the pilot flame heats an emissive element to produce sufficient radiation, a photovoltaic device illuminated by the emissive element produces current for an electromagnet which latches the first stage of the valve in its open position. The armature can then move in the opposite direction and open the second stage of the valve to supply gas to the main burner. In the event of pilot flame failure, the emissive element darkens, and current from the photovoltaic device ends. The electromagnet releases the first stage of the valve which is biased closed and cuts off gas flow to both the pilot and main burners.

Abstract: A control circuit for a fuel valve in a gas fired furnace controlled by an electronic thermostat is disclosed. The thermostat requires a load current to properly operate, and a pickup and hold circuit along with a time delay circuit are integrated to control a load current circuit to provide the correct load current for the thermostat.

Abstract: A self-powered control system for a gas-fired appliance having a pilot burner and a main burner includes an emissive surface in the flame of the pilot burner and a photovoltaic device for irradiation from the emissive surface for providing electrical power for the control system. Two normally closed electromagnetic latching valves are arranged in series between a source of fuel gas and the main burner with a connection to the pilot burner between the two valves. The first valve is latched open when the photovoltaic device is irradiated by the emissive surface and is unlatched to close when the device is not so irradiated. The second valve is unlatched to close when the main burner is not burning. A double acting solenoid or the like is used for sequentially opening the first and second valves for lighting the pilot and main burners. A safe, reliable control system is thereby provided without external electrical power. Similar principles are used for powering a safety flue damper and air flow fan.

Abstract: A liquid-fueled thermoelectric field burner operable in two modes, a start-up mode and a steady-state mode. A rechargeable battery backed up by a manually operated generator permits cold start-up of a preheat burner followed by operation of a main burner which provides heat to thermoelectric converters which operate to provide necessary power for steady-state operation. Cold start-up is facilitated by atomizing the liquid fuel for combustion in the preheat burner, and steady-state blue flame operation is enhanced by mixing vaporized fuel and preheated air for combustion in a main burner. The thermoelectric converters are cooled by air from a cooling blower.

Abstract: A primary gas furnace control including a thermostatically controlled intermittent ignition system, the control being effective to monitor and control main gas valve action through use of flame rectification. The control features a slight delay on main valve dropout with flame failure and an extension of the ignition source into the main burner cycle to prevent nuisance recycling. If desired, the control may also include timed pilot valve, thermostat resettable, lockout as well as prepurge capability for use in applications requiring a furnace combustion chamber purge prior to an ignition cycle.

Abstract: A spark ignition system for a pilot flame uses a flame sensing rod to switch ac voltage from a spark generator to a main valve, thereby providing positive suppression of spark generation once the pilot flame is sensed. A main oscillator activated by a flame sensing signal is provided to operate a switch for this purpose. Should the pilot flame be extinguished, the switch automatically reverts to its first state, thereby closing the main valve and reactivating the spark generator. The entire system is operative only when ac voltage is present from a thermostat demanding heat. The pilot valve connected directly to the thermostat is open to emit gas whenever there is a demand for heat.

Abstract: A primary gas furnace control including a thermostatically controlled intermittent ignition system, the control being effective to monitor and control main gas valve action through use of flame rectification. The control features a slight delay on main valve dropout with flame failure and an extension of the ignition source into the main burner cycle to prevent nuisance recycling. If desired, the control may also include timed pilot valve, thermostat resettable, lockout as well as prepurge capability for use in applications requiring a furnace combustion chamber purge prior to an ignition cycle.

Abstract: An improved electrical circuit for controlling the operation of a gas solenoid valve which regulates the flow of gas to a burner. Field effect transistors, whose operation is controlled by a flame rectification circuit and/or a timing circuit, directly control the operation of a relay which, in turn, operates the gas solenoid valve, thus eliminating the need for much more complicated circuitry to effect actuation of the gas solenoid valve.

Abstract: The invention relates to a hot-gas generating burner comprising a nozzle charging a fuel jet which then enters a mixing tube, and an orifice plate surrounding the outlet of the nozzle. The casing of the burner is divided by the orifice plate into an upstream-disposed precombustion chamber which includes the nozzle, and a downstream combustion chamber which contains the mixing tube. The orifice has a central passage for the fuel jet which is discharged from the nozzle and a number of openings surrounding the passage. In order to reduce the noise concomitant with the operation of the burner, the spacing between the peripheries of the neighboring openings equals at least 50% of the diameter of the openings, and/or the openings in the orifice plate are associated with at least one air duct in the direction of flow.