US3514242A - Flame monitoring system - Google Patents

Description

y 6, 1970 R. L. COLLINS 3,514,242

FLAME MONITORING SYSTEM Filed Oct. 1, 1968 1 FIKM'EB EYEEFH SYSTEM TRIAL FOR IGNITION TIMER TFI is 0 42 22 a1 IGNITION FUEL VALVE cw b INVENTOR RAYMOND L. COLLINS. JR.

BY J

AGENT United States Patent 3,514,242 FLAME MONITORING SYSTEM Raymond L. Collins, Jr., Denville, NJ., assignor to McGraw-Edison Company, Elgin, IIL, a corporation of Delaware Filed Oct. 1, 1968, Ser. No. 764,286 Int. Cl. F23n 5/08 US. Cl. 431-79 5 Claims ABSTRACT OF THE DISCLOSURE A flame monitoring system is provided for detecting the flame of a fuel burner and for initiating the closing of the fuel valve if a flame failure occurs for any reason. A special feature of the system is that the burner will remain operative through limited periods of power interruption. If a flame failure occurs and the power is restored within the limited period the system will shut down the burner after power is restored. If no flame failure occurs and the power is interrupted for a longer duration than the limited period, the system leaves the burner running but without supervision of the flame monitoring system.

A standard flame monitoring system without the help of special equipment will shut down all burners imme diately when a power interruption occurs. An object of the present invention is to provide an improved flame monitoring system which with the use of only standard components will maintain the burner running through limited periods of power interruption, but which will shut down the burner if flame failure occurs during such limited period.

Other objects and features of the invention will be apparent from the following description and the appended claims.

In the description of my invention, reference is had to the accompanying schematic circuit diagram illustrating the invention.

In the drawing, power is supplied to the lines B and D from a standard 120 volt A.C. source indicated by the terminals 10. This power is led from the power line B through contacts 11a of a manual on-oif burner control switch 11 and lead line 12 to the closing winding 13 of a main fuel valve 14 of the burner and then from the valve 14 through a lead line 15 to the power line D. The valve 14, which has also an opening winding 16, is of a type which requires one winding to be deenergized while the other is energized to shift the valve to a position corresponding to the energized winding. Thus, an energization of the closing winding 13 of the main valve while the opening winding 16 is deenergized keeps the valve closed and the burner shut down. Vice versa, upon an energization of the opening winding 16 while the closing winding 13 is deenergized the valve will be opened.

Upon shifting the on-oif switch 11 to its operated position the switch 11a is opened to deenergize the closing winding of the main valve 14, and the switches 11b and 11c are closed to prepare the flame monitoring system for operation. The main valve :14 is not however yet open because the opening winding 16 is not yet energized.

.At the same time that the on-olf switch 11 is moved to its on position the burner system is purged to prepare it for safe starting by standard means not herein necessary to show. In connection with this purge operation a switch 17 in the flame monitoring system is closed.

3,514,242 Patented May 26, 1970 Upon pressing the button 18 of a start switch 19 a first timer relay 20 is energized from the line B via a start circuit through lead line 21, switch 110, lead line 22, switch :17, contacts a and b of the start switch 19, lead line 23, switch K and the timer relay 20 to the lead line D. The switch K is one of a group of switches of a relay K of an ultraviolet flame detector system 24 preferably incorporating a detector of the type disclosed in the Howling Pat. No. 3,047,761, dated July 31, 1962. This detector tube comprises symmetrical electrodes 25a in a special glass envelope 25 containing an ionizing gas such as hydrogen. Applied across the electrodes is a voltage of the order of 700 volts R.'M.S. received via a stepup transformer 26 the primary winding of which is connected by lead lines 27 across the power supply lines B and D. When a firing potential of 700 volts is applied across the electrodes and the electrodes are subjected to ultraviolet radiation the detector tube is fired to pass current. Once the tube is fired it continues to pass current until the applied potential falls below a sustaining value of around 330 volts. Thus, when the tube is operated from alternating current supply it is quenched automatically after each half cycle and the current flow through it occurs as discontinuous pulses. The detector tube is positioned so that it is exposed to the flame of the burner and will respond to the ultraviolet radiation from the flame. The relay K is operated after the first several current pulses and will stay operated as long as the detector tube is triggered by incident ultraviolet radiation.

The timer relay 20 has four sets of contacts 20a, 20b, 20c and 20d. All contacts are operated instantly when the timer relay is energized and the contacts 20b are returned instantly when the timer relay is deenergized; however, the contacts 20a, 20c and 20d have a delayed return set typically at two seconds. The contacts 20c, paralleling switch K are closed as the timer relay 20 is operated to become later effective in a hold circuit for the timer relay which includes a switch K of the relay K and contacts 11c of the on-otf switch 1 1. The contacts 20a which are closed as the timer relay 20 is operated energize a second timer relay 28 through the switch 110. Operation of the timer relay 28 closes contacts 28a in parallel with the timer contacts 20a to provide a hold circuit for the timer relay 28. The contacts 28a are closed instantly but are opened with a two second delay, the same as the contacts 20a, 2110 and 20d of the timer relay 20. The contacts 20b are closed as the timer relay 20 is operated to energize an ignition transformer 30 via the switch r11b, lead line 31, contacts c and d of the start switch '19, lead line 32, ignition transformer 30 and lead line 33 to power line D. Connected in parallel with the ignition transformer is a trialfor ignition timer TFI controlling a pair of instant closing-delayed opening switch contacts 34 in series with an ignition fuel valve 35 connected between the line 31 and the power line D. Thus, the timer T-FI is energized at the same time as the ignition transformer and by its energization it initiates opening of the ignition fuel valve 35 to ignite the burner. The timer TFI is set to delay opening of its contacts for approximately ten seconds to maintain power to the ignition fuel valve 35 for such duration after the timer TFI is deenergized. Detection of the igniter flame by the flame detector and the resultant energization of relay K causes the relay K to open contacts K and to close contacts K and K The closure of the contacts K and K provides a circuit from the power line B via switch 110, line 37, switches K and K line 38 and flame-on lamp 39 to line D and also from line 38 through flame-on lamp 40 in start switch 19 to line D. These lamps give an indication to the attendant that flame has been ignited. Upon receiving this indication the attendant will release the start button 18.

As the start switch is so released the contacts and d are opened to remove energizing current to the timer TFI but the switch contacts of this timer will stay closed for about ten seconds to hold the ignition fuel valve 35 open for that longer duration. When the start switch reaches its released position the contacts e and f are closed to complete a circuit from the line 31 via a line 42 to energize the opening winding '16 of the main fuel valve 14. This will cause the main fuel valve 14 to be opened since the closing winding 13 is already deenergized. This opening of the main fuel valve will permit igniting of the main flame by the ignition flame. When the igniter valve closes after the aforesaid ten seconds and the ignition flame is thereby extinguished, the flame detector in the presence of main flame continues to produce current pulses and the relay K remains energized. The burner is now in normal running condition with the timer relays 20 and 28 both standing operated to provide their function in the supervision of the burner flame.

If a flame failure should occur for any reason the flame detector relay K is dropped out to close the switch K and to open the switches K and K The opening of switch K turns off the flame-on lamps 40 and 41. The opening of switch K shuts off the timer relay 20. The contacts 20b of this timer relay are opened instantly to deenergize the opening winding of the main valve 14. However, the main valve does not then close because the closing winding 13 is standing still deenergized. In two seconds the switch contacts 20a and 20c are opened and the contacts 20d are closed. Power is now supplied from the power line B through switch lllc, switch contacts 28a and switch contacts 20d to activate a flame-out lamp 43 and an alarm relay 44. Operation of the alarm relay closes switch contacts 44a to energize the closing winding '13 of the main valve 14 and cause the main valve to be closed to shut down the burner. The attendant is apprised of this condition by the energization of the flame-out lamp 43 and, if desired, by any suitable sound alarm (not shown) controlled by the alarm relay 44.

If a power interruption occurs of less than two seconds duration-the timing of the timer relays 20 and 28the timer relays do not drop out and the lack of any operating power to the main valve leaves it in open condition to keep the burner running. Upon return of power within the two second period the flame monitoring system reestablishes itself as though nothing happened. However, if a flame failure response occurs within a power interruption of less than two seconds the relay K drops out causing instantly the switch contact K to close and the switch contacts K and K to open. The deenergization of the timer relay 20 opens contacts 20b instantly so that power cannot be supplied to the opening winding 16 of the main valve 14 but power is not now available to the closing winding 13 with the result that the main valve 14 stays momentarily open. When power is restored the flame-on lamps do not light because switch K is open: However, the timer relay 28 is reenergized to stay on but the timer relay 20 drops out at the end of the two second delay period because the switch K is open. The delayed return of switch 20a to open position is without effect because the switch is shunted by the timer switch 28a standing still closed. The delayed return of switch 20d to closed position however energizes the alarm relay 44 and flame-out lamp 43 by way of the switch 110 and timer switch 28a. Operation of the alarm relay 44 closes the switch 44a causing power to be supplied to the closing winding '13 of the main valve to shut down the burner when power is restored.

If the power supply is interrupted for more than the two second timing duration of the timers 20 and 28, then the timers 20 and 28 both drop out with the result that when power is restored current is not supplied to the alarm relay 44 because switches 20a and 28a are open. The contacts 44a of the alarm relay therefore stay open to prevent the closing winding 13 of the main valve 14 from being energized. The main valve 14 therefore stays open and causes the burner to stay on but without supervision by the flame monitoring system. In order to reestablish the flame monitoring system it is therefore necessary for the attendant to shut down the burner and then press the start button 18 and release the same as hereinbefore described.

The embodiment of my invention herein particularly shown and described is intended to be illustrative and not necessarily limitative of my invention since the same is subject to changes and modifications without departure from the scope of my invention, which I endeavor to express according to the following claims.

I claim:

1. A flame monitoring system for a fuel burner including a power source, an electrically controlled fuel valve having opening and closing input circuits required to be deenergized at its opening circuit and energized concurrently at its closing circuit to close the valve and shut down the burner, a flame detecting means operated from said power source, a timer relay controlled by said flame detector to drop out responsive to a flame failure, an alarm relay controlled by said timer relay to close said fuel valve, said timer relay including means for causing said dropout to be delayed by a predetermined interval permitting, interruption in said power source within said interval without operating said alarm relay.

2. The flame monitoring system set forth in claim 1 wherein said timer relay has a hold circuit opened by said flame detector responsive to a flame failure and causing the timer relay to drop out at expiration of its set drop-out interval whereby upon a flame failure during a momentary power interruption within the drop-out interval of the timer relay said alarm relay is operated to shut down the burner when power is restored.

3. The flame monitoring system set forth in claim 1 wherein said timer relay has an initial activating circuit serially including a switch of said detector standing closed when the detector is not activated and has a hold circuit including in series a switch of the timer relay rendered closed as the timer relay is operated and a switch of said detector rendered closed when said detector is activated whereby the timer relay can be activated prior to flame ignition by its initial activating circuit and is held activated by its hold circuit until a flame failure occurs.

4. The flame monitoring system set forth in claim 1 including a hold circuit for said timer relay including a pair of contacts of said detector rendered closed when flame is detected and opened when flame failure occurs and also a pair of hold contacts of said timer relay rendered closed when the relay is activated and opened at the delayed drop out of the relay whereby upon elapse of said drop out interval and presence of power after a flame failure said timer relay is dropped out to activate said alarm relay to shut down the burner.

5. The flame monitoring system set forth in claim 4 including a manual start circuit for said first mentioned timer relay, a second timer relay having a drop-out interval equal to said first mentioned timer relay, said two timer relays including switch contacts in parallel standing open when said timer relays are not activated and respectively closed when said relays are operated of which the contacts associated with said first mentioned timer relay are activating contacts for said second timer relay and the contacts associated with said second timer relay are hold contacts for holding the second relay when once operated until a power interruption occurs, and an operating circuit for said alarm relay including in series switch contacts of said first mentioned timer relay rendered closed at the delayed drop out of said first mentioned timer relay and said parallel switch contacts of both timer relays whereby upon a power interruption of longer duration than said drop-out interval of said timer relays said timer relays are both dropped out to terminate the monitoring function of said system Without closing said fuel valve.

References Cited UNITED STATES PATENTS CARROLL B. DORITY, In, Primary Examiner US. Cl. X.R.

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