System for controlling the delivery of a fuel gas to a burner apparatus

Abstract

A system for controlling the delivery of a fuel gas to a burner apparatus includes a gas-delivery duct extending between an inlet opening and an outlet opening, a pressure-regulator device including a servo-valve in the duct, having a closure member with diaphragm control, the diaphragm being subjected, on one side, to the pressure regulated by the pressure-regulator device and, on the other side, to a calibration pressure established in a calibration chamber of the regulator device, as well as a calibration spring provided in the calibration chamber and acting on the diaphragm. The system also includes a delivery-pressure modulator unit including a modulation valve with a valve seat disposed in the duct downstream of the pressure-regulator device and cooperating with a respective closure member operatively connected to an actuator device arranged for the modulation control of the delivery pressure, as well as a flow communication device between the calibration chamber of the pressure-regulator device and the modulator unit, for bringing into the calibration chamber a pressure signal that is correlated proportionally with the gas-delivery pressure so that the pressure regulated by the pressure-regulator device is in turn correlated with the pressure signal.

1 . A system for controlling the delivery of a fuel gas to a burner apparatus comprising: 
 a gas-delivery duct extending between an inlet opening and an outlet opening,    a pressure-regulator device including a servo-valve in the duct, having a closure member with diaphragm control, the diaphragm being subjected, on one side, to the pressure regulated by the pressure-regulator device and, on the other side, to a calibration pressure established in a calibration chamber of the pressure-regulator device, a calibration spring being provided in the calibration chamber and acting on the diaphragms,    a delivery-pressure modulator unit including a modulation valve with a valve seat disposed in the duct downstream of the pressure-regulator device and cooperating with a respective closure member operatively connected to actuator means arranged for the modulation control of the delivery pressure, and a flow communication means between the calibration chamber of the pressure-regulator device and the modulator unit, for bringing into the calibration chamber a pressure signal that is correlated proportionally with the gas-delivery pressure so that the pressure regulated by the pressure-regulator device is in turn correlated with the said pressure signal.    
   
   
       2 . The system according to  claim 1  in which the calibration chamber is in flow communication with the delivery duct downstream of the modulator unit by means of a connecting duct, and the pressure signal corresponds to the gas-delivery pressure obtained by means of the modulation valve.  
   
   
       3 . The system according to  claim 1  in which the pressure signal brought to the calibration chamber of the pressure-regulator device is indicative of the air-output pressure of a fan associated with an air-gas mixer in which the output air-flow of the fan is mixed with the gas-flow delivered by means of the modulation unit at the delivery pressure.  
   
   
       4 . The system according to  claim 1  in which the modulation valve is of a proportional type with a finite number of modulation levels.  
   
   
       5 . The system according to  claim 4  in which the actuator means associated with the closure member of the modulation valve comprise a control rod the axial movement of which relative to the corresponding valve seat is controlled by drive means of the stepping type.  
   
   
       6 . The system according to  claim 5  in which the modulator unit comprises drive transmission means suitable for converting the rotary movement of the drive means into a translational movement of the operating rod of the closure member of the modulation valve.  
   
   
       7 . A system according to  claim 3  in which the flow communication means comprise a connecting duct between the calibration chamber of the pressure-regulator device and a casing portion of the fan which casing portion is defined in the region of the outlet of the fan, upstream of the air-gas mixing region of the air-gas mixer.  
   
   
       8 . The system according to  claim 3  in which the fan is of a modulating type and its output pressure can be modulated selectively between a minimum and a maximum pressure value.  
   
   
       9 . The system according to  claim 7  comprising a differential pressure sensor provided with detection terminals which are arranged, respectively, in said connecting duct and in a section of the gas-delivery duct upstream of the air-gas mixing region of the air-gas mixer.  
   
   
       10 . The system according to  claim 9  comprising electronic board control means arranged to process, in dependence on the pressure signal detected by said differential pressure sensory, a control signal for controlling said actuator means so that the delivery pressure is modulated in order to keep the pressure differential at a suitable value such as to ensure that the ratio between the air flow-rate and the gas flow-rate remains constant.  
   
   
       11 . The system according to  claim 2  in which the modulation valve is of a proportional type with a finite number of modulation levels.  
   
   
       12 . The system according to  claim 3  in which the modulation valve is of a proportional type with a finite number of modulation levels.  
   
   
       13 . The system according to  claim 7  in which the fan is of the modulating type and its output pressure can be modulated selectively between a minimum and a maximum pressure valve.