US 3741710 A
Combination control apparatus including means for supplying air to a furnace, means for supplying gas to the furnace, means responsive to heat demand for varying the air flow and means responsive to the rate of air flow for adjusting the rate of gas flow to maintain a constant fuel/air ratio. Preferably, an air damper or valve is located in an air inlet pipe to a blower and a gas supply pipe is also connected to the inlet pipe adjacent the blower. The blower feeds the mixture into the furnace. A modulating-type pressure regulating valve controls the rate of gas flow and means responsive to air pressure, located between the air valve and the blower, adjusts the modulating valve to maintain an outlet pressure that provides a fuel/air ratio that is substantially constant.
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Description (OCR text may contain errors)
United States Patent Nelson A COMBUSTION CONTROL VALVE MEANS AND SYSTEM  Inventor: Lorne W. Nelson, 10118 Dupont I Avenue South, Bloomington, Minn.
 Filed: Dec. 20, 1971  Appl. No.: 209,793
[ 1 June 26, 1973 Primary Exa ir en-Edward G. Favors [5 7] ABSTRACT Combination control apparatus including means for supplying air to a furnace, means for supplying gas to the furnace, means responsive to heat demand for varying the air flow and means responsive to the rate of air flow for adjusting the rate of gas flow to maintain a constant fuel/air ratio. Preferably, an air damper or valveis located in an air inlet pipe to a blower and a gas supply pipe is also connected to the inlet pipe adjacent the blower. The blower feeds the mixture into the furnace. A modulating-type pressure regulating valve controls the rate of gas flow and means responsive to air pressure, located between the air valve and theblower, adjusts the modulating valve to maintain an outlet pressure that provides a fuel/air ratio that is substantially constant.
10 Claims, 1 DrawingFigure 1 WATER PAIENIEUmzsma 3.741.110
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2,052,375, 3,101,897. Such apparatus requires for satisfactory COMBUSTION CONTROL VALVE MEANS AND SYSTEM This invention relates to control apparatus for a gas burning furnace of the type which requires the use of 5 a premixed fuel-air supply for combustion purposes. This type of apparatus is used in small furnaces such as those located outside of buildings as well as small size furnaces used within buildings. Known prior arrangements of this type are illustrated in U..S. Pat. Nos. 1,834,130, 2,962,094, 2,502,345 and combustion purposes, control means that will provide a substantially constant fuel/air ratio, preferably with a minimum amount of excess air to assurecomplete and efficient combustion. This invention is directed to apparatus which requires a minimum number of elements to perform this desirable function as well as a minimum amount of installation time to assure as inexpensive as possible yet satisfactory heating system.
The single FIGURE of the drawing is a schematic illustration of the components of the apparatus or system in conjunction with a furnace of the hot water type.
The furnace is generally designated by the reference numeral 11 with an outlet conduit 11a leading to the space or spaces to be heated by the heating fluid (water) flowing in the conduit. A blower 13 is connected to the'furnace to'supply'a mixture of gasand air to a burner (notshown) for heating'water coils (not shown) connected to the conduit 11a. A return pipe for the water (not shown) is connected to the other end of the coils. I V
An-air inlet pipe 14, which may be a passageway in i a fuel-air mixing unit 12, is connected to the inlet of the able wall forms part of a pressure chamber or bellows' 19 which, in turn,- is connected by a capillary tube 20 to a bulb 21 located ina portion of the conduit 11a.
The bulb 21 is filled with an expandable fiuidso that as the temperature of the water in the conduit 11a lowers,
the volume of fluid in chamber 19 reduces to move the diaphragm 17 in a downward direction. This movement of the diaphragm operates the damper 15 through linkage 17, in an opening direction. In the portion ofthe inlet pipe between the damper and the blower inlet is a plate 22 having an orifice 23 to provide a pressure drop therethrough for a'purpose to be described below.
The means for supplying gas to the furnace includes a manifold valve generally designated by the reference numeral 24. A slightly modified fonn of such avalve is disclosed in US. Pat. No. 3,354,901. This valve has an inlet passageway 25 and an outlet passageway 26 with a partition wall 27 therebetween. The partition wall has an opening in the form of avalve seat 28 therein which is normally closed by amain valve 29. This valve is connected by a valve stem 30 to a diaphragm 31 forming one wall of a pressure chamber 32. A coil spring 33 normally biases the valve 29 into engagement with the seat 28. A first control passageway 34, having a restric-.
. sure chamber 32. A third control passageway 38 leads from the three-way control valve to the outlet passageway 26 so that in one portion of the control valve, gas flows from the inlet 25 to the pressure chamber 32 and in a second position of the control valve, gas flows from the chamber 32 through passageway 37 to the outlet passageway 26. A fourth control passageway 39 leads from the pressure chamber 32 to a pressure chamber 40 of a pressure regulator valve generally designated by the reference numeral 41. A diaphragm 42 separates the pressure chamber 40 from'a pressure chamber 43 and has connected thereto a ball type of valve 44 that cooperates with a valve seat 39a at the end of passageway 39. The valve 44 is normally biased against the seat 39a by means of a coil spring 45. The chamber 40 is connected by a fifth control passageway 46 to the gas outlet 26. The chamber 43 is connected by a sixth control passageway 47 to the air intake conduit 14 at a position between the air valve 15 and the orifice member 22. The outlet passageway 26 of the gas valve is connected by a conduit 48 to the air intake conduit 14 at a position between air orifice member 22 and the blower 13. A restriction or orifice member 49 is 10- cated in this conduit. It is thus seen that both air and gasare supplied to the intake of the blower 13.
The above mentioned means for controlling air and gas flow are adapted to be placed in operation by means of a room thermostat 50 connected to one wire 51 of an electrical power supply and having a movable contact 52 that cooperates with fixed contact 53 to simultaneously energize the control valve, the blower and the igniter in the simplified arrangementshown in the drawing. The control valve is connected to the thermostat by wire 55 and to the ground by wire 56. The blower is connected to the thermostat through wires 57 and 58 and to the ground through wire 59. The igniter is connected to the thermostat by wires 60 and 58 and to the ground through wire 61. The other wire 62 of the power supply is grounded through wire 63.
Upon a call for heat in the space in which'the thermostat 50 is located, the movable contact '52 closes, against fixed contact 53 which starts the blower operating, the igniter operation and the control valve moving to'a position supplying gas from the inlet 25 to the pressure chamber 32. Upon the pressure in chamber 32 building up sufficiently to open the valve 29, gas will start to flow through the outlet passageway 26 to the air intake conduit 14 where it will be mixed with air flowing past the valve 15, under the influence of the blower 13, and delivered to the furnace. As the gas pressure in the outlet 26 builds up, the pressure will feed through passageway 46 to the chamber 40 and move the diaphragm 42 in the valve opening direction. The amount of opening. of valve 44 will depend upon the loading of spring 45 and the pressure Pa in the space between valve 15 and orifice member 22, as well as the pressure Pg in the outlet 26 The location of valve 44 determines how muchgas is bled from the chamber 32 past the valve to the outlet 26. Therefore, the outlet pressure Pg will be regulated by the pressure-Pa and by the proper selection of the size of the diaphragm 42 and the spring 45, it will be possible to maintain the pressure Pg the same as the pressure Pa. It is thus seen that should there be changes in the gas pressure supplied to the inlet 25 or should there be changes in the position of the valve the provision of the orifice member 22 in air conduit 14 and the provision of orifice member 49 in gas conduit 48, produces a pressure differential across each of these orifices which act back through the control passageways to opposide sides of the diaphragm 42, to provide control signals on the valve 44 that causes the valve 29 to adjust in the necessary manner.
How the apparatus operates to provide a constant fuel/air ratio is explained by the following equations wherein:
Wg is the mass flow rate of gas,
K is a selected gas density constant,
Ag is the area of the gas orifice 49,
Pg is the gas pressure at the gas valve outlet,
Wa is the mass flow rate of air,
K is the air density constant,
Aa is the area of air orifice 23,
Pa is the air pressure upstream of the air orifice,
Ps is the pressure of the gas-air mixture, and
K is the fuel/air ratio constant desired. Therefore,
Wg=K Ag \IPg-Ps By making the gas valve so that Pg always equals Pa and the quantity K Ag/K, Aa K Fuel/Air K V (Pa Ps)/(Pa Ps K' (constant) It is thus seen that regardless of variations in heat demand or fluctuations in gas supply pressure, the apparatus will function to maintain a constant fuel/air ratio for proper combustion.
It is to be noted that as the water temperature in the discharge conduit 11a of the furnace decreases in temperature, the diaphragm 18 moves to increase the air flow. With increase in air flow a greater pressure develops in chamber 43 causing the valve 44 to move closer to seat 391;, which causes increased pressure in chamber 32 and wider opening of gas valve 29. Upon an increase in watertemperature in conduit 11a, the reverse takes place. It is thusseen that the sensor 21 will adjust the amount of air flow in accordance with water temperature to maintain the water temperature necessary to provide proper heating of the space in which the thermostat 50 is located.
lnstead of having the water temperature sensor 21 operate the air damper 15, the pipe 14 could be so shaped as to serve as a restriction to air flow in place of the damper, and a suitable sensor and motor control means could be used to vary the speed of blower 13 to vary the air flow.
Obviously, additional controls can be used including those to limit the range of the water temperatures above which and below which the water in the conduit 110 should not reach. However, these controls are old and well known in the art and are unnecessary for an understanding of the operation of the apparatus described above.
The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:
1. Combustion control apparatus comprising conduit means for delivering air to a furnace, air flow control means in said conduit means for regulating the rate of air flow according to heat demand, air flow restricting means in said conduit means, gas pressure actuated valve means for delivering gas to said conduit means downstream of said air flow restricting means, said valve means including pressure regulating means and a gas flow restricting means downstream of said pressure regulating means, temperature responsive means arranged to supply gas to saidvalve means to, open said valve means, and means responsive to air pressure upstream of said air flow restricting means to adjust the gas pressure on said pressure regulating means by bleeding valve actuating gas therefrom to maintain the outlet gas pressure from said pressure regulating means substantially equal to said air pressure.
2. Combustion control apparatus as defined in claim 1 wherein said air flow control means includes a sensor adapted to sense the temperature of heating fluid heated by the burning of said gas and air. I
3. Combustion control apparatus as defined in claim 1 wherein said conduit means for delivering air in cludes a blower downstream from said air flow restricting means.
4. Combustion control apparatus as defined in claim 1 wherein said pressure regulating means includes a movable wall operably connected to a main valve, a pressure chamber on ohe side of said movable wall and means normally biasing said main valve closed and said wall into said chamber, said temperature responsive means includes a three-way control valve selectively operable to establish communication between the inlet side of said main valve and said pressure chamber or between said chamber and the outlet side of said main valve, said air pressure responsive means includes a pressure regulator valve located between said pressure chamber and the outlet side of said main valve and a diaphragm actuator for said pressure regulator valve being exposed on the valve side thereof to said main valves outlet gas pressure and on the other side thereof to air pressure upstream of said air flow restricting means. v V
5. The combination defined in claim 4 wherein gas flow to the control valve is restricted.
6. The combination defined in claim '5 wherein said temperature responsive means includes a remote sensor located in a space the temperature of which is to be controlled by said apparatus.
7. The combination defined in claim 6 in combination with an igniter controlled by said'remote sensor.
8. The combination of claim 5 in combination with thermostatic means electrically connected to said blower and three-way valve and an igniter also electrically, connected to said thermostatic means.
9. Combustion control apparatus as defined in claim 1 wherein said means for regulating the rate of air flow is valve means located upstream of said air flow restricting means.
l0. Combustion control apparatus as defined in claim 9 wherein said air flow-valve means is controlled by a sensor responsive to heat demand. I8 4 I l 4