Apparatus and method for controlling a damper in a gas-fired appliance

Abstract

A gas-fired appliance is provided having a burner which is configured to receive and burn pressurized gas, such as natural gas, during operation. A control comprises a pressure switch having an inlet exposed to pressure from the pressurized gas during operation of the burner, a battery, and a motor operatively connected to the battery and the pressure switch which is operated in response to the application of pressurized gas at the inlet. A damper assembly is connected to the motor. The damper assembly comprises a damper movable between an open position and a closed position in response to operation of the motor.

1 . A gas-fired appliance comprising:
 a burner, configured to receive and burn pressurized gas during operation;   a control comprising a pressure switch having an inlet exposed to pressure from the pressurized gas during operation of the burner, a battery, and a motor operatively connected to the battery and the pressure switch which is operated in response to the application of pressurized gas at the inlet; and   a damper assembly connected to the motor, the damper assembly comprising a damper movable between an open position and a closed position in response to operation of the motor.   
   
   
       2 . The gas-fired appliance of  claim 1 , further comprising:
 a pilot burner;   a thermoelectric device positioned near the pilot burner which generates electrical voltage when exposed to heat from the pilot burner;   a magnetic pilot valve having an electrical input, which valve is maintained in an open position in response to maintenance of the electrical voltage at the pilot valve electrical input; and   a switch circuit interposed into an electrical conduction path between the thermoelectric device and the magnetic pilot valve electrical input, the switch circuit being movable between an open state and a closed state in response to movement of the damper.   
   
   
       3 . The gas-fired appliance of  claim 2 , in which
 the motor operates a cam; and   the switch circuit is comprised of:   a first switch which is closed by the cam when the damper is in a first position; and   a second switch, connected electrically in parallel with the first switch, which is closed by the cam when the damper is in a second position.   
   
   
       4 . The gas-fired appliance of  claim 3 , further comprising:
 a resistor and a capacitor operably interconnected, the capacitor being connected between a signal path leading to the pilot valve electrical input and a ground reference voltage; and   whereby the capacitor charges when the switch circuit is in the closed state, and discharges when the switch circuit is in the open state.   
   
   
       5 . The gas-fired appliance of  claim 3 , in which the switch circuit further comprises a third switch connected in series with the pressure switch to stop the motor after the damper is moved from the first position to the second position or from the second position to the first position. 
   
   
       6 . The gas-fired appliance of  claim 5 , in which the motor and the battery are connected in series with the third switch and the pressure switch. 
   
   
       7 . The gas-fired appliance of  claim 1 , in which the battery comprises a 9V battery. 
   
   
       8 . The gas-fired appliance of  claim 1 , in which the battery comprises a AA battery. 
   
   
       9 . The gas-fired appliance of  claim 5 , in which the pressure switch and third switch comprise three way switches. 
   
   
       10 . A damper control mechanism for an appliance that operates through combustion of gas having a pressure that is greater than ambient pressure, the damper control mechanism comprising:
 a damper;   a motor operatively connected to the damper to control position of the damper;   a cam operatively connected to the damper; and   a control comprising a pressure switch having an inlet exposed to pressure from the pressurized gas during operation of the burner, a battery, and a switch operated by the cam, to selectively energize and de-energize the motor to control damper position responsive to change of the pressure at the inlet.   
   
   
       11 . The damper control mechanism of  claim 10 , in which in which the battery comprises a 9V battery. 
   
   
       12 . The damper control mechanism of  claim 10 , in which the battery comprises a AA battery. 
   
   
       13 . The damper control mechanism of  claim 10 , further comprising:
 a thermoelectric device having an output capable of generating an electrical voltage differential;   a circuit comprising one or more electrical switches, which circuit electrically connects the thermoelectric device and a magnet pilot valve; and   where the cam operates the one or more electrical switches to disconnect the thermoelectric device from the magnetic pilot valve when the movable diaphragm is not within either the first or the second position.   
   
   
       14 . The control mechanism of  claim 13 , in which the circuit further comprises a capacitor having a first terminal operably connected with the thermoelectric device and the magnetic pilot valve, and a second terminal connected to a ground reference voltage, whereby the capacitor can temporarily provide electrical energy to the magnetic pilot valve when the circuit opens the connection between the magnetic pilot valve and the thermoelectric device. 
   
   
       15 . The control mechanism of  claim 10 , in which the pressure switch and the cam operated switch comprise three way switches. 
   
   
       16 . A method for controlling a damper in a gas-fired appliance, comprising the steps of:
 applying pressurized gas to a first portion of the gas-fired appliance which includes a main burner; and   opening a damper by operatively connecting a battery to a motor connected to the damper using a pressure sensor sensing introduction of pressurized gas into the first portion of the gas-fired appliance.   
   
   
       17 . The method of  claim 16  in which:
 the step of applying pressurized gas to a first portion of the gas-fired appliance comprises the step of applying pressurized gas to a pressure switch; and   the step of opening a damper comprises the step of electrically connecting the battery to the motor via the pressure switch.   
   
   
       18 . The method of  claim 16 , in which the step of opening a damper comprises the steps of:
 providing a magnetic pilot valve which maintains an open position in response to the maintenance of an electrical signal at an input terminal;   applying the electrical signal to the magnetic pilot valve input terminal when the damper is in an open or closed position; and   removing the electrical signal from the magnetic pilot valve input terminal when the damper occupies a partially-opened position for at least a predetermined period of time.   
   
   
       19 . The method of  claim 18 , in which the predetermined period of time is at least about 2 seconds. 
   
   
       20 . The method of  claim 18 , in which the predetermined period of time is between about two seconds to about three seconds.