US3649156A

US3649156A - Fluid fuel burner control system

Info

Publication number: US3649156A
Application number: US876472A
Authority: US
Inventors: Leonard E Conner
Original assignee: Eaton Yale and Towne Inc
Current assignee: Eaton Corp
Priority date: 1969-11-13
Filing date: 1969-11-13
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14

Abstract

Fluid fuel burner control system utilizing solid state components, and in which the several components, with their interconnecting circuitry, can be compactly mounted upon a panel or in a box, and installed in any desired location with a limited number of terminals for accommodating single conductors leading to the respective legs of an alternating current source of electrical energy, the fuel valve, an igniter and a flame sensor, which may be located remotely from the compact control panel or close to it, as desired. The circuitry of the system places the operation of the fuel valve under the control of an igniter circuit transformer and places the energization of the igniter circuit transformer under the control of a flame sensor, while the usual safety switch is responsive only to current which traverses the primary of the transformer which energizes the igniter, and the interruption of current flow through the transformer depends upon the electrical conductivity of flame at the burner.

Description

United States Patent Conner [54] FLUID FUEL BURNER CONTROL SYSTEM [72] Inventor: Leonard E. Conner, St. Louis, Mo.

[73] Assignee: Eaton Yale & Towne Inc., Cleveland, Ohio [22 Filed: Nov. 13, 1969 [21] App]. No.: 876,472

[52] US. Cl ..43l/78, 431/254 [51] Int. Cl ..F23n 5/00 [58] Field of Search ..43 1/6, 24, 66, 70, 78, 254

[56] References Cited UNITED STATES PATENTS 3,445,172 5/1969 Zielinski ..3 H78 X 3,446,565 5/1969 l-lantack ....431/70 3,520,645 7/1970 Cotton et al.. ....431/78 3,510,236 5/1970 Potts ...431/66 X Primary Examiner-Edward G. Favors Attorney-Teagno and Toddy ABSTRACT Fluid fuel burner control system utilizing solid state components, and in which the several components, with their interconnecting circuitry, can be compactly mounted upon a panel or in a box, and installed in any desired location with a limited number of terminals for accommodating single conductors leading to the respective legs of an alternating current source of electrical energy, the fuel valve, an igniter and a flame sensor, which may be located remotely from the compact control panel or close to it, as desired. The circuitry of the system places the operation of the fuel valve under the control of an igniter circuit transformer and places the energization of the igniter circuit transformer under the control of a flame sensor, while the usual safety switch is responsive only to current which traverses the primary of the transformer which energizes the igniter, and the interruption of current flow through the transformer depends upon the electrical conductivity of flame at the burner.

5 Claims, 1 Drawing Figure FLUID FUEL BURNER CONTROL SYSTEM The invention relates generally to the control of fluid fuel burners, such as those provided in domestic appliances, heating systems and the like, and is an improvement upon the system disclosed in US. Pat. No. 3,446,565.

Systems of the character referred to are usually provided with one or both of a manually adjustable timer switch and temperature switch," as well as a safety switch. Such switches usually take the form of a bimetallic or other thermostat connected in series with the source of electrical energy. In the case of the safety switch, a length of heater wire, or other electrical resistance adapted to generate heat, is usually provided adjacent the bimetallic element, so as to provide fine control over the time period during which the safety switch can remain in closed circuit position while the fuel valve is open, but without being ignited. In a typical situation, as illustrated in the aforesaid patent, the heater element of the safety switch is energized at full line voltage-with normally functioning ignition-until a heat-sensing switch adjacent the burner has been sufficiently heated to move from its normally closed position to the open position. Thus, whether or not there is a fault in the igniter circuit, the heater element of the safety switch must be energized at least for a period not only sufficient normally to ignite a flame at the burner, but for a period thereafter sufficient-with normally functioning ignitionfor that flame to have produced heat enough to actuate the burner-heat-sensing switch-before the safety switch can interrupt the circuit which is keeping the fuel valve open.

One object of the invention is to provide a control system for a fluid fuel fired device having an electrical igniter, and in which the fuel valve cannot open until the igniter circuit is energized, and cannot long remain open in the absence of flame at the burner.

Another object is to provide a compact prewired panel or box mounting the necessary control devices and circuitry for automatic control of a fluid fuel burning device, and which can be installed as a unit at any chosen location and connected to the device, near or far, in a simple and fool prooffashion.

A further object is to provide such a system in which the several control operations are accomplished without radio interference, or other disquieting noises.

These and other objects of the invention are achieved by the use of static control components; making the opening of the fuel valve to depend upon the fact of current flow through the primary of an ignition transformer; making the opening of the usual safety switch to depend solely upon the duration and magnitude of current supplied to the primary of the ignition transformer; and making the flow of current through the primary of the ignition transformer to depend upon the non-existence of (as distinguished from the heat developed by existing) flame at the burner, which is to say that the electrical conductivity of flame is utilized to deactivate the ignition system, as well as to automatically reactivate the ignition system if the burner flame is blown out or is otherwise unintentionally extinguished without having to await the cooling-off period required by the usual heat-responsive switch at the burner.

One embodiment of the invention is diagrammatically illustrated in the accompanying drawing, which is a circuit diagram associated with diagrammatically represented appurtenances including a fluid fuel valve, its supply line, a burner, an igniter, and a flame sensor. In the accompanying drawing, the broken line M delineates the margins of a mounting panel or box which supports the various electrical control devices (except those which, for convenience, are preferably located remotely) and the interconnecting circuitry in the form util ized in one embodiment of the invention. In the form shown, the mounting panel M is provided with six binding posts T-l, T-Z, T-3, T4, T-S and T-6, which provide terminals for the circuitry mounted on mounting panel M, and at each of which a single electrical conductor, extending respectively to remote instrumentalities, may be readily connected. In the embodiment shown, the control system is intended to be energized by an alternating current source, such as a conventional 120 volt, 60 cycle domestic service, the opposite legs of which are designated L-l and L-2 in the drawing, which connect respectively with binding posts T-] and T-2 of the mounting panel M. Of course, if the supply has one leg grounded, it will be understood that terminal T-2 can be grounded.

As illustrated, line L-l is provided with a conventional series connected timer switch TM and a conventional temperature switch TR, which may be, and frequently are, located remotely from the mounting panel M.

Binding post T-3 is intended to be electrically connected with a flame sensor SS having an electrically conductive probe P which extends into a position to be enveloped by, or at least in contact with, any flame produced at burner B. Burner B is served with fluid fuel, such as gas, supplied through a conduit controlled by valve V, which may be any suitable electromagnetically operated valve having an inductive operator, such as solenoid S, the opposite terminals of which are connected to binding posts T-S and T-6. The valve V and the burner B may, or course, be located remotely from the panel M, as desired.

Binding post T-4 serves to connect a lead serving an igniter I having a spark gap located at the burner in a position such as to be adjacent, or enveloped by, the stream of fuel emerging from the burner when the valve V is in open position.

From binding post T4, line L-l extends to a junction 14, where it is divided into three branches, one extending through a resistance heater H (which forms a part of the conventional safety switch) and thence to diode D4. Another branch extends to diode D-2. The third branch extends from junction J- l to the switching element S-F of the aforesaid conventional safety switch, and from thence to diode D3. The diodes D-l, D-2 and D-3 are biased to pass current only in the direction indicated by their arrow-heads. By virtue of the presence of the diodes in the three circuit branches extending from junction 1- 1, it will be understood that the electrical energy supplied to the several components within, and served by, the instrumentalities mounted upon the mounting panel M is a half-waverectified alternating current, sometimes referred to as a pulsating current."

From diode D-l, the pulsating current is supplied to one end of the primary of transformer TF, as well as to one side of capacitor C-l, the other side of which is directly connected with binding post T-2, and from thence to line L-Z, which is the opposite leg of the alternating current source of which line L-l is a part. Thus, the primary of transformer TF and capacitor C-l receive charges of voltage, through diode D1, during the on-half-cycles at which L-l is positive to L-Z; and after about nine such on-half-cycles, the capacitor C-] will have become charged to line voltage and will begin to discharge into the primary of transformer TF during the off-half-cycles at which L-] is negative to L-2, but the direction in which the capacitors discharge is impressed upon the transformer is the same as that impressed through D-l during the on-half cycles. One end of said secondary being grounded as indicated by the forked symbol whose counterpart appears at the center of burner B, the induced voltage is transmitted through terminal T-4 to the spark gap at igniter I so that the igniter circuit is alive before any current actually flows through the primary of the transformer.

Flow of current through the primary of transformer TF is controlled by a silicon-controlled rectifier SCR-2, which, when triggered, permits the pulsating current to flow through the primary of transformer TF toward junction .l-2, through resistor R-3, and thence through terminal T-2 to line L-Z, thereby increasing the voltage induced in the secondary TFS of the transformer to a value sufficient to throw an arc across the spark gap of igniter I.

To trigger SCR-2, and thus permit the flow current therethrough toward L-2, a capacitor C-2 is charged via diode D-2 and resistor R-l through junction 1-3. The opposite side of condenser C-2 is connected directly to terminal T-2, as shown. After a number of half-cycles in which L-l is positive to L4, the capacitor C-2 will become charged to the breakover voltage of neon tube N (which, as shown, is connected through junction 1-3 to capacitor C-2) whereupon a triggering signal will be transmitted to the cathode of SCR-2, and cause it to become conductive in the direction toward .14.

Once SCR-2 is fired from condenser C-2, condenser C-] will discharge through the primary of the transformer. This is a pulse discharge, but when the magnetic field of the transformer primary collapses, it induces an EMF opposite that which existed by virtue of the discharge of condenser C-l thereby tending to recharge C-l. This creates an instantaneous reversal of current through SCR-2, which, once its current has passed through the zero value, the SCR is restored to blocking state and has to be retired to become conductive in the direction from L-! toward L-2.

The values of the resistance R-l, condenser C-2 and neon tube N-l are chosen so that SCR-2 will be reflred six times per second, but once there is flame at sensor P, the condenser C-2 will be short-circuited through J-3, R-2 and D-S to T-2, so that there is no longer the storage capacity at C-2 to retire SCR-2.

However, before there can be flame at sensor P, valve V must be opened to supply fuel to burner B. The series circuit from 1-1 through the normally closed safety switch S-F, diode D-3, terminal T-S, and solenoid S, is live at all times except when one or more of switches TM, TR and S-F is open, but no current can traverse the solenoid until SCR-l is triggered into a state of conductivity toward T-2, and, according to the invention, a condition precedent to such triggering of SCR-1 is that current be flowing through the primary of transformer TF and through SCR-2 toward R-3 and 1-4.

Current flowing through the primary of transformer TF and SCR-2 divides at junction J-Z, part passing through resistor R- 3, and another part passing through resistor R-6 to the cathode of SCR-1, and it is the latter which triggers SCR-l into a state of conductivity toward terminal T-2 and junction J-4. Resistor R-3 is designed to create, when energized, a voltage difference on the order of to volts between its opposite ends, and thereby becomes an ancillary source of electromotive force tending to drive current from junction 1-2 through R-6, to the cathode of SCR-1, and back toward R-3 through junction 1-4, thereby rendering SCR-l conductive, and thus initiating the energization ofsolenoid S to open valve V and admit fuel to the burner B, where sparking is already occurring at l.

During the time SCR-2 remained in a current blocking state, no current could flow from junction J-3 through resistor R-2 and diode D-S to terminal T-3 because no flame was existing at the burner B through which an electrical charge from probe P could be grounded or otherwise complete its circuit back to L-2. However, once flame has occurred at burner B, the electrical conductivity of that flame is utilized to ground probe P and its conductively connected components (diode D-5 and resistor R-Z) back to junction 1-3. This permits capacitor C-Z to discharge through the last-mentioned components and so reduces the voltage on neon tube N that it cannot transmit a triggering signal to the gate of SCR-2, while flame is bridging the gap between probe P and grounded burner B.

lf, despite the'sparking at l, ignition fails to occur, the heater H will, within a safe period of time, have actuated the safety switch SF into open circuit position, thereby effecting closure of valve V. Assuming, however, that ignition does occur before sufficient time has elapsed for heater H to actuate switch SF into its open circuit position, the valve V remains open as long as it is energized by current flowing through solenoid S. By virtue of the presence of diode D-3 in the circuit, the current which energized solenoid S is also a pulsating one which, during its on-half-cycle, also charges capacitor C-3, which in turn, during the off-half-cycle of the current flowing through D-3 discharges through solenoid S in the same direction as the current delivered in the on-half-cycle through D-3, thereby locking in the solenoid. in order to assure that SCR-l does not, at any time, resume its current-blocking state, a loop circuit, including diode D4 (biased to pass current toward terminal T-S), is provided to accommodate the current induced within the solenoid S by the collapsing flux which intervenes the peaks of successive half-cycles.

During the period preceding actual ignition of fuel at the burner B, the elements between 1-3 and probe P of the sensor have been charged, but no current has been able to flow therethrough because there was nothing to conduct electrical current from probe P to the grounded burner B. Once flame occurs, however, the conductivity of the flame is utilized to conduct current from probe P to the grounded burner, thereby completing a circuit which prevents further charging of capacitor C-2, and further discharging thereof through neon tube N to trigger SCR-2. At this time, SCR Z will suffer a reversal of current direction at the end of the next on-half-cycle. Such reversal of current causes the flow through SCR-2 to pass through zero which restores SCR-2 to its blocking state, unless and until it is triggered again, but since the triggering instrumentalities are now grounded through .l-3, R-2, D-5 and sensor SS through flame to burner B, SCR-2 cannot be retriggered as long as flame persists at the burner.

For optimum performance on 115 volt, 60 cycle alternating current-source, it is preferred that the several components of the embodiment illustrated in the drawing have the following magnitudes and characteristics:

Heater H: 1,000 ohms Diodes: l ampere, 200 volt Transformer: l0 kv, output pulse transformer Resistor R-I: 5.0 megohms Resistor R-21 0.] megohms Resistor R-J: 0.47 ohms Resistor R-4: 0.75 megohms Resistor R5: 0.75 megohms Resistor 11-6: 5 l0 ohms Capacitor C- l: 20 micro-farads Capacitor (-21 0.22 micro-farads Capacitor C-3: 2.0 microfaruds Solenoid S: 500 ohms (DC); 2,000 ohms impedance at 60 eyc.

Neon Bulb N: Brealtover voltage Maintaining voltage 60 SCR's: 7 ampere, 300 volt Flame: 8 megohrns between probe and burner From the foregoing description, those skilled in the art will understand that under normal operating conditions, the system provides a sequence of operations which may be subdivided into several steps as follows:

With current available, a high voltage pulse spark occurs and is proven before the automatic main burner gas valve becomes energized.

Proof of spark signals the automatic gas valve circuit to be energized,

A safety lockout circuit turns off the gas valve circuit within a predetermined time interval if no proof of flame exists.

If flame is present, the sensor probe circuit responds to deenergize both the igniter circuit and the safety lockout circuits.

if current interruption occurs by means of a switch, thermostat switch or power loss, the gas valve circuit is deenergized and remains off until the current returns and a normal ignition cycle ensues.

Under abnormal conditions, the system reacts as follows:

If spark gap at l is shorted, excessive current will flow through heater H and switch SF will open within seconds to deenergize the gas valve circuit.

If the sensor SS is shorted from a cold start, the gas valve circuit remains deenergized because SCR-1 cannot be triggered.

if, for some reason, the gas valve is energized, and gas is being discharged at the burner without ignition, the heater H will, within a short time interval, actuate switch SF to close the valve, but the igniter circuit remains on and only turns off through actuation of a conventional timer such as TM.

A particular advantage of the system disclosed is that the prewired panel M operates to accomplish the same results regardless of polarity of lines L-l and L-2, and regardless of which, if either, of the source legs is grounded. For example, when line L-2 is grounded at the power source, the flame senlOlOTI sor circuit extends from junction 1-3 through resistor R-2, diode Du5, sensor probe P (which may be a stainless steel bar) through the flame to the burner which is grounded. On the other hand, ifline L-Z is not grounded at the power source, the flame sensing circuit extends from junction 1-3 through R-Z, D-2, the sensor probe and the flame to the grounded burner as before, but from the grounded burner, the circuit is completed through ground to the ground (forked symbol) at the lower end of transformer secondary TFS, and from there through resistors R-5 and R-4 and terminal T-2 to line L-2. The third alternative is that L-l be grounded at the supply source, in which case an infinitive impedance will exist between terminal T-3 and terminal T-l during the half-cycle of the supply source when L1 is positive with reference to L-2, the flame sensor circuit will be made from 1-3 through R-2, D-S, T-3, probe P and flame to ground at burner B. Hence, the prewired panel M can be installed without regard to which, if either, leg of the supply source is grounded. It is, however, sometimes desirable to provide the burner with two grounds, one always being a part of the igniter circuit and having its counterpart at the lower end of transformer secondary TFS, and the other serving optionally to complete the flame sensor circuit when L-2 is grounded.

While one complete embodiment of the invention has been disclosed in detail, the invention is not limited to the details of that embodiment.

What is claimed is:

l. A fluid fuel burner control system comprising a burner, an electromechanical valve for controlling the flow of fuel to said burner, said valve having a deenergized condition preventing the flow of fuel to said burner and an energized condition providing for the flow of fuel to said burner, an igniter for igniting fuel flowing from said burner, a flame sensor for sensing the presence of a flame at said burner, first circuit means for activating said igniter, second circuit means having a first nonconductive condition in which said valve is deenergized and a second conductive condition for energizing said valve to enable fluid to flow to said burner, and third circuit means connected to said flame sensor for rendering said first circuit means ineffective to activate said igniter by establishing a ground potential between said first circuit means and said flame sensor when said flame sensor senses the presence of a flame at said burner, said first circuit means being connected to said second circuit means for biasing said second circuit means to said second conductive condition to energize said valve in response to the flow of current through said first circuit means which efi'ects activation of said igniter by said current flow in said first circuit means.

2. A fluid fuel burner control as defined in claim 1 wherein said second circuit means includes a first SCR having a conductive condition for energizing said valve and a nonconductive condition for deenergizing said valve, said first SCR including a gate connected to said first circuit means for rendering said first SCR conductive upon the application ofa positive gating potential thereto by said first circuit means to effect energization of said valve, said first circuit means effecting the application of said positive gating potential to said gate of said first SCR in response to activation of said igniter by said first circuit means.

3. A fluid fuel control as defined in claim 2 wherein said first circuit means includes a transformer having a primary winding and a secondary winding, a second SCR having a conductive and a nonconductive condition for controlling the energization of said primary winding of said transformer, said second winding of said transformer being connected to said igniter and having a current induced therein when said primary winding is energized and said second SCR is conductive, said second SCR including a cathode connected to said gate of said first SCR to provide said positive gating potential thereto upon conducting of said second SCR, energization of said primary winding and activation of said igniter by current induced in said secondary winding.

4. A fluid fuel control as defined in claim 3 wherein said first circuit means further includes a capacitor for effecting the application of a positive gating potential to the gate of said second SCR and wherein said third circuit means is connected to said capacitor and prevents said capacitor from charging to apply said positive gating potential to said gate of said second SCR when said flame sensor senses the presence of a flame at said burner.

5. A fluid fuel control as defined in claim 4 further including a safety switch having a heating element and a switching element movable from a normally conductive condition to a nonconductive condition in response to said heating element reaching a predetermined temperature for a predetermined amount of time, said heating element being series connected with said primary winding of said transformer and being energized when said primary winding is energized to effect actuation of said igniter, said switching element being series connected with said first SCR for rendering said first SCR nonconductive when said switching element moves to said nonconductive condition to deenergize said valve.

Claims

1. A fluid fuel burner control system comprising a burner, an electromechanical valve for controlling the flow of fuel to said burner, said valve having a deenergized condition preventing the flow of fuel to said burner and an energized condition providing for the flow of fuel to said burner, an igniter for igniting fuel flowing from said burner, a flame sensor for sensing the presence of a flame at said burner, first circuit means for activating said igniter, second circuit means having a first nonconductive condition in which said valve is deenergized and a second conductive condition for energizing said valve to enable fluid to flow to said burner, and third circuit means connected to said flame sensor for rendering said first circuit means ineffective to activate said igniter by establishing a ground potential between said first circuit means and said flame sensor when said flame sensor senses the presence of a flame at said burner, said first circuit means being connected to said second circuit means for biasing said second circuit means to said second conductive condition to energize said valve in response to the flow of current through said first circuit means which effects activation of said igniter by said current flow in said first circuit means.

2. A fluid fuel burner control as defined in claim 1 wherein said second circuit means includes a first SCR having a conductive condition for energizing said valve and a nonconductive condition for deenergizing said valve, said first SCR including a gate connected to said first circuit means for rendering said first SCR conductive upon the application of a positive gating potential thereto by said first circuit means to effect energization of said valve, said first circuit means effecting the application of said positive gating potential to said gate of said first SCR in response to activation of said igniter by said first circuit means.