US2129094A - System of control for burners - Google Patents

Description

Sept. 6, 1938.

H. E. LAKE 2,129,094

SYSTEM OF CONTROL FOR BURNERS Filed Dec. 9. 1935 e L i as i ATTORNEYS Harr 5 burn Patented Sept.

UNITED STATES PATENT OFFICE 2,129,094 SYSTEM OF CONTROL FOR BURNERS Harry E. Lake, Flushing, N. Y., assignor to Barburners of the so-ca her-Colma Company, ration oi Illinois Rockford, 111., a. com- Applicatlon December 9, 1935, Serial No. 53,539 2 Claims. (Cl. l58--28) This invention relates generally to control equipment for governing the cyclic operation of lled intermittent type.

The general object is to provide a novel oil essary for safe operation of the burner under all abnormal conditions ordinarily occurring in service use, and which effects automatic recycling of the burner at the ti me and under the conditions when such recycling may safely occur.

The invention also resides in the novel character of the construction employed for carrying Other objects an out the foregoing object.

d advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing which shows the improved control system as applied to the control of the liquid fuel burner l of upon operation of a conventional type adapted an electric motor 2 to discharge atomized fuel into the combustion chamber within a boiler and having an outl 3 indicated in dotted outline et flue 4 through which the products of combustion are discharged. While any preferred form played, a spark igniter of ignition means may be em- 5 is illustrated and arranged to be rendered operative upon energize.-

@ tion of the former The motor 2 is through a circuit primary winding of a step-up transarranged to he energized which extends from a high voltage power source 7 through a conductor ii,

the motor a normally open switch 9 of an electromagnetic relay to, and a conductor it having interposed therein a normally closed safety switch it? and a normally closed switch it arranged to be opened in response to an abhor really high pressure fluid. Thus, with t as they normally are, the motor will and stopped and th or temperature or the boiler he switches l2 and it closed he started e supply of fuel to the comhnstion chamber will he initiated and interrupted of the magnet iii.

response to energization and deenergia'ationthe safety switch it is maintained closed onder normal operating conditions and is arranged to he opened after the lapse of mined by the period during slow acting device r After losing opened,

position until reset device comprises a 5m rial normally acting an interval deterwhich a suitable emains electrically energized. the switch remains in this manually. The slow-acting strip 6 of bimetallic mate as a latch to hold a movable contact ill of the safety switch in'closed position and arranged to warp, when heated by a resistance element H, in a direction to release the contact and permit movement thereof away from the fixed contact l8. switch, the motor circuit remains broken until the :atch is reset by manual operation of a lever 9.

The primary winding of the ignition transformer 9 and. 20 are closed, but may be rendered ineffective by opening of the switch 20 alone. The latter is arranged to a second relay 2|. Preferably the switches 9 and 20 are formed by a common stationary contact 22 cooperating with movable contacts 23 and 24 carried respectively by the armatures 25 and 26 of the magnets it and M.

The energizing circuits for the relays are preferably operated at low voltage under the control of a room thermostat having or well known equivalent mechanism not shown) to an arm 3t carrying a contact which cooperates with two switches 33. and 3t. Stack switches or this character operate to detect predetermined rises and falls in the stack tempera ture, so that upon heating of the element 29 as the burner is started, the closed-when-cold switch will he opened, and after the lapse of closed, clutch occurring as the stack temperature continues to rise. divhen the stacle temperature falls After opening of the.

be opened upon energization of .lner as-lwhen switch 39 operated by will be closed.

. 34, a conductor 3'4 during starting of the burner is shorter than the'interval during which the resistance l1 must be energized and the thermostatic element It heated in order to effect opening of the safety switch l2.

The circuit for the relay l extends from the source of low voltage current such as the secondary ofa transformer 35 through a conductor 36, the room thermostat switch 21, a conductor 31, the closedwhen-cold stack switch 33, a. conductor 38, a

the armature 25 and normally closed when the relay 2| is deenergized, a conductor 40 in which the resistance U is interposed, the winding of the relay ID, and a conductor 4|. When the relay I0 is thus energized, the'switch 9' is closed thereby completing the high voltage circuits for the burner motor 2 and the circuit through the then closed ,switch 20 and the ignition transformer. The igniter is thus rendered operative, and fuel is sprayed into the combustion chamber. Energization of the relay-l0 alsocloses a normally open switch 42 interposed in a conductor 43 in parallel with the closed-when-cold stack switch 33 so that continued energization of the heater l1 and the relay ID is maintained under the control of the room thermostat switch independently of the combustion switch.

If the fuel is ignited properly, the resulting rise in the stack temperature will cause the switch 33 to be opened, and after the lapse of the allotted interval;-the closed-when-hot switch 34 During this interval, energization of the relay I0 is continued under the control of the switch 42. Closure of the switch 34 results in energization of the second relay 2| in series"with the first relay in through a circuit which extends from the current source 35 through'the conductor 36, the room thermostat switch -21, the conductors 31 and 43, the switch 42, the lconductor 38, the closed-when-hot switch 44, the winding of the relay 2!, a conductor 45, the winding of the relay Ill, and the conductor 4|. Attraction of the relay armature-26-opens the switch 20 thereby interrupting the operation of the igniter 5 and also opens the switchi33-which opens the circuit through the resistance, this occurring under normal conditions. before the thermostatic element l6 has warpadto a position permitting the safety switch H to open. Thus, if ignition is successful, operationof-the burner motor, after the trial period, is continued under the control of the room thermostat switch 21, the closed-when-hot switch 34, and the switch 42.

When the room thermostat ceases to call for heat as evidenced by opening of the switch 21, the holding circuit through the windings of the relays l0 and 2| will be interrupted thereby stopping the motor. Reclosure of this circuit by the action of the thermostat and starting of the motor may again occur after the stack has cooled to a degree sufiicient to permit closure of the closedwhen-cold switch 33'.

Failure of the voltage supply when the burner is operating will be accompanied by opening of the switch 42 as the relay l0 becomes deenergized. This results in opening of the holding circuit and stopping of theburner in the same manthe room thermostat switch is opened. Thus, in the eventof amomentary voltage failure, the control system will effect recycling of the burner but only after the stack has 7 cooled sufficiently to permit closure of the closedeffecting initial energization of burner motor.

when-cold switch 33 which requires an interval or time sufficient toenable the combustion chamber to be purged of combustible gases vby natural circulation.

In the event of flame failure while the burner is operating, as might be occasioned by the presenceof air or water in the fuel supply line, the stachtemperaturewill fall, resulting in opening of the closed when hot switch 34 and therefore of the holding circuit causing the relay ID to be deenergized and the, burner motor to be stopped. Then, when the closed-When-cold switch 33 becomes closed as it will after the lapse of the purging interval, the starting circuit will, if the room thermostat -,is,,still calling for heat, again be completed and recycling of the control mechanism will occur. I y 1 With the arrangement above described, the room thermostat switch, cannot be manipulated accidentally in a manner such as to effect momentary operation of the burner or momentary 1nterruption of its operation without the desired purging interval being interposed between any two successive periods of motor operation.' Thus, the present controleffects recycling of the burner automatically in response to the occurrence of any abnormal condition where such recycling is permissible but only after the proper time for purging the combustion chamber has been allowed. Similarly, the control provides for locking the system against recycling in the event of initial failure of ignition .upon starting of the Such failure is evidenced by failure of the closed-when-cold switch 33 to open which continues the energization of the heater I1 until the latch l6 has warped to a position to allow the safety switch H to open.

Advantage is taken of the circuits above described to incorporate in the control system a simple and reliable mechanism for rendering the burner inoperative in the case of hot water or steam heating systems when the water in the boiler 3 falls below a predetermined safe level. For this purpose, the primary winding 46 of a transformer 41 is interposed in the low voltage circuits in series with the winding of the motor relay l0. One terminal of the secondary winding 48 is connected to an electrode 49 which may be a pipe communicating with the boiler at the proper level. The other winding terminal is connected to an electrode 50 which is: insulated and spaced from the electrode 49 and positioned at the minimum water level to be maintained. The transformer is so constructed that the primary winding 46 will act as a choke in the low voltage supply to the motor relay l0, so that when the electrode 50 is immersed in the boiler water, the impedance of the primary winding will be relatively low. But when the water level falls below the electrode when the burner is operating, impedance of the primary will be increased to suchan extent that the resulting reduction in the voltage applied to the winding of the motor relay will cause this relay to release its armature and permit the switches 9 and 42 to open. In the event that the room thermostat calls for heat following a fall in the water level below the desired point, the relay l0 cannot be energized to the degree necessary to close the motor switch. With this arrangement, electrodes of very small size may be used and the necessity of switches or other moving parts subject to deterioration is avoided.

I claim as my invention:

the

tion circuit, a first switch constituting a main conmotor and ignition circuit a sec nd lay p trol, a combustion responsive thermostat having 60! When energized to Open Said gn on c u t, a closed-when-hot and closed-when-cold switches, ma c nt ol w a Combustion responsive 1 render the control system inoperative upon prowhen-cold switches, an electrically heated safety up first switch, said closed-when-cold switch, a norand closed-when-cold combustion switch for mally closed switch which is opened when said eirecting initial energization of said first relay and second relay is energized, said operating element said resistance element and maintaining such and the winding of said first relay, a circuit for energization during a burner starting period, and maintaining initial energization of said first relay a low voltage circuit including said control switch independently of said closed-when-cold switch and said closed-when-hot switch and operating 20 including the winding of the relay, said operating to energize said first and second relays in series 20) element, said normally closed switch, and a norrelation independent]

Images