Abstract:
A pressure proving gas valve insures safe and efficient operation of a fuel-burning appliance by monitoring combustion air pressure and appropriately controlling the valve based upon this air pressure. An air pressure sensor is incorporated into a pressure proving valve housing itself thus providing integrated solution for the control of the combustion process. Consequently, when heat is called for, no fuel is provided to the combustion chamber unless appropriate combustion air pressure is sensed. Further, by monitoring the actual air pressure, additional control capability is provided. That is, a variable speed blower associated with the combustion apparatus can be controlled to provide very precise fuel to air mixtures.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to gas valves used in fuel burning appliances. More specifically, the present invention relates to a gas valve which safely operates by insuring that combustion air is present before gas is provided to the combustion chamber. 
     In fuel burning heating systems, gas valves are typically used to control the flow of fuel into a combustion chamber. Several different control methods have been used for operating this gas valve. Generally speaking, the gas valve is operationally attached to a thermostat. When the thermostat calls for heat, the gas valve is then actuated, providing gas to the combustion chamber. Other components of the heating system (blowers, vents, etc.) are also operated to cause the heating of air, which is thus provided at a furnace output. 
     As can be appreciated, it is essential that combustion air be present in order to allow burning of the combustion fuel. If combustion air is not present, and the gas valve is opened, a potentially dangerous situation is created. 
     One method for insuring that combustion air is present in the combustion chamber includes the use of a pressure switch which is operationally coupled to the combustion chamber. More specifically, a pressure switch is attached such that its input is connected to the combustion chamber. Thus, when the pressure is above a predetermined level, this pressure switch is closed. This switch can then be used as a safety system for the furnace. More specifically, the furnace will not be allowed to operate unless this pressure switch is closed. 
     Unfortunately, typical pressure switches utilized in this fashion are large and cumbersome. These pressure switches are typically a pancake type pressure switch which is typically configured in a disk shaped format, about three inches in diameter. These pressure switches take up space and are not easily integrated into heating systems. Also, this switch provides only an on/off type output. Thus, the switches do not provide any additional information which may prove useful in the operation of the furnace. Additionally, the pressure level at which the switch closes cannot be adjusted after the switch has been installed. Consequently, this type of pressure sensor has many drawbacks and is not the most beneficial device to use. 
     SUMMARY OF THE INVENTION 
     The present invention provides an integrated solution which safely and efficiently operates a gas valve for a combustion furnace. In addition to the typical functions of a gas valve (i.e., control of fuel to a combustion chamber), the valve includes an integrated combustion air sensor for monitoring combustion air. The output from the sensor is provided to a controller which will not allow the valve and/or furnace to operate when combustion air is not present. 
     All components of the pressure proving gas valve are contained in a single housing. These components include the valve element, the controller, and combustion air sensor, and all necessary inlet and outlet ports. More specifically, the housing includes a fuel inlet port, a fuel outlet port and an air flow inlet port. The fuel inlet port and the fuel outlet port are on opposite sides of the valve element, thus controlling the flow of combustion fuel therethrough. Similarly, the airflow inlet port is in communication with the combustion air sensor, to allow its efficient operation. In addition to these inlets, all necessary electrical connections are provided through openings in the housing. These electrical connections include those necessary to communicate with the controller. Further, connections to an external thermostat are provided, thus allowing the basic function of the valve. 
     By including the combustion air sensor within the valve housing itself, additional functionality and wiring simplicity is also provided. Typically, a fan or blower of some type is associated with the furnace. This fan could thus be connected to the controller to regulate airflow as necessary. Thus, in addition to sensing the presence of airflow, the airflow itself could be specifically controlled. Specific air to gas ratios can then be achieved in the combustion process. Without the airflow sensor within the gas valve, this overall functionality is difficult and costly to achieve. 
     It is an object of the present invention to provide additional safety functions to a gas valve by insuring airflow is present. Thus, gas will not be provided to the combustion chamber without airflow also being present, thus avoiding potentially dangerous situations. 
     It is an additional object of the present invention to provide an integrated solution and additional functionality to the gas valve by coordinating multiple operations. As is well understood, a valve can be controlled to efficiently run the gas-burning portion of the furnace itself. However, by being able to monitor and control airflow through the furnace, in addition to gas flow, multiple operating conditions can be achieved. For example, very specific fuel air ratios can be maintained in the combustion chamber for whatever purpose is necessary. 
     The present invention further provides an additional safety feature by sensing and indicating that the combustion path is blocked or someway restricted. For example, should the exhaust pathway be blocked somehow, the valve of the present invention would recognize that and shut off. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects and advantages of the present invention can be seen by reviewing the following detailed description in conjunction with the drawings in which: 
     FIG. 1 is a schematic drawing of one version of the present invention; 
     FIG. 2 illustrates one embodiment of gas valve itself; 
     FIG. 3 is a flow chart illustrating one method of operation for the present invention; and 
     FIG. 4 illustrates a schematic diagram of an alternative embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, there is shown a schematic drawing of the pressure proving valve  10  of the present invention. As expected, the pressure proving valve  10  is located in close proximity to a combustion chamber  12  which has an exit air chamber  14  located down stream from combustion chamber  12 . Associated with pressure proving valve  10  is a gas inlet  16  and a gas outlet  18 . Within the housing  20  of pressure proving gas valve  10 , there exists a valve assembly  22  which performs a typical gas valve function including regulating the flow of gas and appropriately turning it on or off. This also may include the regulation of a variable level of gas flow, as is appropriate for the heating system. 
     The pressure proving valve  10  further has an airflow connection  24  attached thereto. In the preferred embodiment, this is a pressure sensor inlet. As the flow of air can be determined by measuring pressure at various points, a pressure sensor is appropriately used for providing combustion air information to other components. Alternatively, a mass airflow sensor or a microbridge airflow sensor may be used. Cooperating with airflow connection  24  is a combustion air sensor or transducer  26  (of one of the preceding types of sensors) which is located within housing  20 . Also located within housing  20  is a controller  30  which is in operational connection with the sensors and receives information and coordinates the operation of the gas valve. This controller can typically be a microcontroller or microprocessor of some type. In order to provide power, a power connection  32  is provided to pressure proving valve  10 . Furthermore, a thermostat  34  is typically associated with the valve and provides control signals thereto. As is well known, the thermostat generally provides a signal calling for heat which subsequently causes the gas valve to open, thus creating appropriate conditions for combustion to occur within the combustion chamber. 
     Referring now to FIG. 2, there is shown a cross sectional view of the pressure proving valve  10  of the present invention. As previously mentioned, pressure proving valve  10  is primarily constructed of a single housing  20  which accommodates many other parts. Housing  20  has an inlet channel  42  and an outlet channel  44  situated on opposite sides of the valve. Shown here in schematic format again is valve  22  which separates inlet channel  42  from outlet channel  44 . 
     Also located in housing  20  is airflow sensor inlet  46 . Airflow sensor inlet  46  is configured to have air flow sensor tube  24  attached thereto and also to house an appropriate combustion air sensor. As previously mentioned, one method of sensing airflow is simply to provide a pressure sensor which is capable of measuring pressures at various points. From these measurements, several different values and characteristics can be calculated. 
     Although not shown in FIG. 2, appropriate connection channels are provided within housing  20  so that electrical signals can be communicated from the air flow sensor to other devices. 
     Also situated within housing  20  is a controller housing  48  which will house the controller and all necessary connections thereto. As previously mentioned, controller  30  provides many control and operational functions for the present invention. Consequently, various connections are necessary including thermostat connections, power connections, etc. Also shown within housing  20 , and associated with valve  22 , is a valve mechanism housing  52  which houses and maintains all controls for valve  22 . A connection channel  54  is provided to allow connection between controller  30  and valve  22 . 
     Referring now to FIG. 3, there is shown a flow chart illustrating the control methodology of the pressure proving gas valve. In summary, the pressure proving valve allows the ability for the valve to determine whether appropriate conditions exist within the combustion chamber prior to providing combustion fuel. Thus, in situations where the combustion air path is blocked, gas is not allowed to dangerously accumulate within that area. As can be expected, there is typically a set up and system configuration process which must precede any functional operation. This set up and initiation typically involves verifying the presence and operation of all sensors, as well as verifying the operational status of the valve. The process may be used by controller  30 . 
     Starting at step  300 , the control process begins. Next, in step  302 , the system determines whether the thermostat has called for heat. If not, the valve need do nothing, and it simply waits until an appropriate call for heat is made by the thermostat. If the call for heat is made, the system then moves on to step  304  wherein it determines if air flow is present through the combustion chamber. As previously described, a heating system typically includes an inducer mechanism which draws air into the combustion chamber which can then provide appropriate conditions for the burning of heating fuel. In most situations, this heating fuel is natural gas, however, other fuels may be used. By measuring for air flow at this point in time, the system can then determine the necessary combustion air is being provided. Next, at step  306  the system determines if air flow is at an appropriate level. As can be expected, the air flow must be above some minimum level in order to provide enough air for combustion to occur. At the same time, too much air flow can pass through the combustion chamber which also provides conditions which are not conducive to the efficient burning of fuel. If the air flow is not within this predetermined range, the system moves to step  308  wherein a warning signal is created and the heating system is shut down. Most importantly, no fuel is provided to the combustion chamber at this point. This is done by simply turning off the valve portion of the pressure proving valve and not allowing any fuel to pass from inlet channel  42  to outlet channel  44 . 
     Alternatively, if the pressure is within the predetermined range, the system moves to step.  310  wherein the valve is operated according to predetermined criteria. This criteria typically includes responding to signals provided by the thermostat, and appropriately providing fuel to the combustion chamber for its heating operation. Additionally, air flow is continually monitored during this step to insure an operational flow of combustion air through the system. This insures safe and accurate operation of the heating system, and avoids the creation of dangerous situations. In step  312 , the system analyzes this air flow reading, or pressure signal, and determines whether the air flow is within the necessary range. If the air flow is within the necessary range, the system continues to operate. This is shown in FIG. 3 as a perpetual loop from steps  312  back through steps  316 ,  310  and  312 . Alternatively, should the air flow fall outside the desired range, the system is again shut down and a warning signal is created. This is shown in step  314 . Once step  314  is reached, no further action is taken by the system until the dangerous condition is attended to. Typically, this involves operator interaction, but may include other software test functions which could be carried out by other systems. 
     Referring now to FIG. 4, there is shown an alternative embodiment of the present invention in which additional features are added. These features are made possible by the inclusion of the pressure proving characteristic previously discussed. As can be seen, the system shown in FIG. 4 is very similar to that shown in FIG. 1, however, a variable speed blower  60  has now been added. Additionally, a blower connection  62  is provided which connects controller  30  to variable speed blower  60 . Another variation is the addition of a second airflow connection  64  and a second combustion air sensor  68 . When installed, the first airflow connection  24  is positioned on one side of an orifice  66  while second airflow connection  64  is positioned on a second side of orifice  66 . In this case, the two airflow sensors  26 ,  68  are pressure sensors. By knowing the pressure on either side of this orifice, the amount of air flow is easily calculated. Once this air flow is determined, many different features are enabled in the system. As previously mentioned, controller  30  provides overall control and operational features to pressure proving valve  10 . Allowing controller  30  to calculate the actual air flow, and by having an output connected to variable speed blower  60 , very precise control of the combustion operations is achieved. That is, variable speed blower  60  could be controlled such that very precise fuel to air mixtures are achieved. The process of choosing a particular design fuel to air ratio is well known in the art. 
     As can be appreciated, there are several modifications that could be made which would provide similar functionality. For example, while FIG. 4 shows a forced draft system, an induced draft system could be used. An induced draft system can be easily achieved by simply moving the variable speed blower  60  to the down stream side of the combustion chamber. Also, as outlined in relation to the system shown in FIG. 1, a single sensor could be used to determine air flow. 
     Those skilled in the art will further appreciate that the present invention may be embodied in other specific forms without departing from the spirit or central attributes thereof. In that the foregoing description of the present invention discloses only exemplary embodiments thereof, it is to be understood that other variations are contemplated as being within the scope of the present invention. Accordingly, the present invention is not limited in the particular embodiments which have been described in detail therein. Rather, reference should be made to the appended claims as indicative of the scope and content of the present invention.