US2231986A - Ignition system for burners - Google Patents

Description

Feb. 1s, 1941. v o, BEAM 2231,986

IGNITION SYSTEM FOR BURNERS i f 75 2f Filed Jan. 14, 1938 32 2g -35 v INVENTOIL WL rfv/v 0 59M /7-. 2 BY A'ITORNEY in burners for domestic heaters or the like.

Patented Feb. 18, 1941 UNITED STATES PATENT OFFICE Application January 14, 1938, Serial No. 184,988

,This invention qrelates to improvements in ignition systems for burners, that is to say electrical systems for igniting gaseous or other fluid fuel It relates chiefly to the provision of simplied means for accomplishing automatic ignition while avoiding waste of fuel and guarding against the hazards of explosion in the event of temporary failure of the fuel supply or the like, and also `means for stopping the operation of the burner in the event of a failure in the electrical control system.

One of the objects of the invention is the provision of simple apparatus and wiring such that the electrical operation of the main fuel valve is subject to control by the flame from the pilot, whereby in the'V event of failure of fuel supply the absence of name from the pilot will cause closing of the main fuel valve.

' Another object is the provision of a double throw switch through which current for the ignition. and currentr for the main valve operator must pass alternatively and whenever those parts f the system are in operation, so that the ignition must be turned off before the main burner may be turned on, and the main burner must be turned off before the ignition may be turned on.

Other objects and features of novelty will appear as I proceed with ythe description of that embodiment of the invention which, for the purposes of the present application, I have illustrated in the accompanying drawing, in which Fig. 1 is a diagrammatic illustration of wiring and apparatus used in carrying out the invention.

Fig. 2 is a longitudinal section view of apparatus which may be employed in connection with the invention.

In the drawing I'have shown at I0 a. burner for the heater, the gaseous or other fuel supply for which is delivered to the burner by a'pipe II. In this pipe I locate at a suitable point a main valve i2 which may be operated electrically in any known manner. By way of example I have shown the valve attached to the lower end of the core I3 of a solenoid I4, the core I3 having a head I5 22-closes rst and a short time thereafter, when the temperature in the room has fallen a trie lower, contact 23 closes. Contact 22 is connected by means of a conductor 24 with the secondary of a transformer 25. This transformer is prefer- (Cl. 15S-117.1)

ably one of the constant current, high impedance type, although other transformers of the proper power rating function satisfactorily provided they are not of the constant voltage type. Contact 23 is connected by a conductor 26 with one end of solenoid I4, and also by a flexible lead 21 to the head I of core I3.

Fuel for the pilot I'I is taken from a pipe 28 which connects with the main fuel supply pipe 3 beyondl the valve I2. Pipe 28 extends into a housing 29 which also contains a bi-metal thermostat element 30 that may be warped from its natural state by the action of an electric heating coil 3| which is under control of the room thermostat. These parts are illustrated somewhat in detail in Fig. 2, wherein the housing 29 is shown as provided with a passage 32 for connecting pipe 28 with a valve chamber 33 that is closed on the side opposite the passage 32 by a flexible diaphragm 34. This diaphragm carries centrally a valve piece 35 having on its lower face a gasket 38 which is adapted to have a tight engagement with a circular seat 3l at the inner extremity of passage 32. A coil spring 38 tends Ato unseat the valve. An exit port 39 connects chamber 33 with the pilot I'I. During periods when the system is idle the valve 35 is held against its seat by a button 40 on the free'extremity of bi-metal element 30, which is so adjusted that under those conditions it exerts a rm pressure tending to seat the valve and cut off the flow of fuel to the pilot.

Bi-metal element 30 is contained in an elon- .gated cavity 4| in the housing 29, the housing being constituted partly of a molded cover member 42 of insulating material. The cavity 4I and the chamber 33 are of course effectively separated from each other by the diaphragm 34, which is sealed at its periphery and at the joint with valve piece 35.

The lower side of cover 42 may be provided with a pocket to receive a metal block 43 which may be held in place by a screw 44, the latter serving also as a binding post. Bi-metal element 30 is secured to the lower surface of block 43 by screws 45 or the like.

The major part of heating coil 3l is separated from the bi-metal element 3|) by a wrapping 46 of insulating material. One end of the coil is electrically joined to the bi-metal element beyond the wrapping 46 in some suitable manner, as by a metal clamping band 41, while the other end is held in place and electrically joined to another clamping band 48. The latter band bears at all times against an abutment 49 which has a threaded shank that extends through a threaded hole in a metal plate 50 embedded in the bottom of cover 42. A nut 5| serves to hold abutment 49 in adjusted position. Abutment 49 acts as a conductor of electric current, and also by its ad- J'ustment regulates the normal deflection of the free end of the bi-metal member and accordingly the pressure exerted by the button 40 on the valve 35. 52 is a screw that takes into plate 50 assisting to hold that plate in place and serving also as a binding post. Another metal plate 53 embedded in the cover 42 is electrically con- .nected with a binding post 54 similar to binding post 52, and plate 53 carries an abutment screw 55 similar to abutment screw 49, which is adapted to be threadably adjusted and held in adjustment by a nut 56. Abutment screw 55 is contacted at times by a button 51 fastened to the upper surface of bi-metal element 39. Current may pass from binding post 54, plate 53, and abutment 55, through button 51, bi-metal element 3D, screws 45, and block 43 to binding post 44, or from binding post 52, plate 50 and abutment screw 49 through clamp 48, heating coil 3|, bi-metal element 30, screws 45, and block 43 to binding post 44. This combined switch and valve operating means, actuated by a heating coil, is disclosed in my prior application 136,847, filed April 14', 1937, and per se forms no part of the present invention.

When the pilot I1 is burning the flame issuing from port I9 envelops a metal link 58 which is formed of material having a high coefficient of expansion. This link is mounted at one end upon a xed pivot 59, while the other end is pivotally connected at 60 with the upper extremity of a lever 6| which is pivotally supported intermediate its ends upon a fixed pivot 62. When link 58 is heated by a pilot flame it lengthens, due to expansion, and this produces a small angular displacement of lever 6| in a clockwise direction around its pivot 62. Because of the considerable length of the lower arm of lever 6| as compared with that of its upper arm, a button 63 on the lower extremity partakes of a movement which may be twice or three times as great as the movement of pivot 60, and is therefore suiiicient to actuate a switch. Button 63 is caused to press against a hump 64 formed in a switch blade 65 that is fastened at one end by clamp 66 to an insulation support 61. 68 is a knife blade projection on the support 61, which engages blade 65 between hump 64 and clamp 66. The free end of blade 64 is adapted normally to make electrical connection with a fixed contact 69 carried by the support 61. When however the lower end of lever 6| swings clockwise under the influence of a llame from the pilot, blade 65 is forced to the left breaking engagement with contact 69 and engaging a contact 10 which is also carried by the support 61. Contact 69 is connected by a conductor 1| with an ignition coil 12 located op- DOsite pilot burner port I9. The opposite end of the coil is connected by a conductor 13 with conductor 24. Contact 10 is connected with the lower end of solenoid I4 by a conductor 14.

The remainder of the wiring consists of a conductor 15 which extends from the fixed part of thermostat 2| to plate I6, a conductor '|6 which extends from conductor 15 to binding post 52, a conductor 11 which runs from the clamp 66 at the fixed end of switch blade 65 to binding post 54, and a conductor 18 which runs from binding post 44 to the secondary of transformer 25.

Operation.-Assuming that the burner has been quiescent for a time, and that the temperature of the premises has fallen suiciently to cause room thermostat 2| to engage contact 22, plate I6 will then be made alive because of the current path through conductor 24, contact 22, thermostat 2|, andl conductor 15. Also, current will flow from conductor 15 through conductor 16 to binding post 52, through heating coil 3|, energizing that coil, through bi-metal element 30 to binding post 44, and back through conductor 18 to the transformer. The heat from coil 3| will, after a predetermined time has elapsed, produce a ilexure in bi-metal element 30, relieving the pressure of its free end against the valve 35. Spring 38 will then lift the valve from its seat and fuel will flow to the pilot. This flexure of the bi-metal element 30 will proceed far enough also to bring button 51 into contact with abutment screw 55. As soon as this contact is made current will flow from the transformer through conductors 24 and 13 to the ignition coil 12, energizing that coil, and by way of conductor 1|, contact 69, and switch blade 65 to clamp 66, and thence through conductor 11 to binding post 5 4, through bi-metal element 30 to binding post 44, and back through conductor 13 to the transformer. Fuel emerging from the port I9 of pilot I 1 may under favorable circumstances ignite immediately. If it does not the additional load of coil 12 will reduce the voltage across the secondary coil of the transformer, which in turn will reduce the heating eiect of coil 3|, permitting bimetal element 30 to bend away from abutment screw 55, thereby breaking the circuit through ignition coil 12. This movement of bi-metal element 30 will not however be sufilcient to close the pilot fuel valve. 'I'he load of the ignition coil then being taken off the line, the voltage will again increase and more energy will be available for the heating coil 3|, which presently will again cause engagement between button 51 and abutment screw 55, thereby bringing the ignition coil again into action. The intermittent action of theV ignition coil in this manner will continue until the pilot is ignited. When this occurs the heatresponsive link 58 will lengthen and swing lever 6| clockwise upon its pivot 62. The lever will then act through button 63 to force the lower end of switch blade 65 to the left, thereby breaking the ignition coil circuit. Within a short time interval however blade 65 will come into engagement with contact 10. The pilot will continue to burn and the lever 6| will continue to hold the switch plate against contact 10. 'I'he pilot flame will also travel upwardly along slot 20 to port I8, and flame will extend from that port into position to .ignite fuel emerging from main burner Ill.

Now, as soon as the room thermostat completes its action under the call for heat, that is when it engages contact 23, the valve I2 for the main burner will be opened by solenoid I4, the energization of that solenoid taking place through the ilow of current from the transformer through conductor 24, contact 22, thermostat 2|, contact 23, conductor 26, solenoid I4, 'conductor 14, contact 10, switch blade 65, clamp 66, conductor 11, binding post 54, bi-metal element 30, binding post 44, and conductor 18 back to the transformer. The movement of switch blade'65 away from contact 69 oi' course breaks the circuit through igniter coil 12, and the intermittent energization of that coil stops. As soon as the head I5 of core I3 rises into contact with plate I6, valve I2 is latched in open position independently of thermostat contact 23, that is current flows from the transformer through conductor 24, contact 22, theormostat 2|, con'ductor15, plate I6, core head |5, flexible conductor 21, solenoid I4, conductor 14, contact 1|), switch blade 65, clamp 66, conductor 11, binding post 54, bi-metal element 30, binding post 44 and conductor 18 back to the transformer.

Now, when the temperature of the premises rises sufficiently to cause'the room 'thermostat to break contact 23 nothing happens, for the path of current to the solenoid through con-- ductor 26 is short-circuited by conductor 15. It is not until the temperature rises far enough to open contact 22 that the circuit through the solenoid is broken and the main valve l2 closes.

When this occurs the circuit through heating coil 3l is also broken, since that circuit passes through the thermostat contact 22 also. The bimetal element 30 then cools and moves back to its normal position, illustrated in Fig. 2, breaking electric connection with binding post 54 and closing pilot valve 35. The pilot then goes out,

. the link 58 cools and shortens, and the lever 6i swings anti-clockwise, withdrawing button 63 and permitting switch plate 65 to move by its own resilience away from contact lll and into engagement with contact 69. The system will then `be set to resume starting operation the next time the room thermostat calls for heat.

Now, in the event that there should be a fail- .ure of fuel during operation of the burner the present system will cause the closing of the main valve and the avoidance of any explosion hazard. As the lack of fuel causes the pilot burner to go out, link 58 cools, lever 6I swings away from switch blade 65and that blade breaks the solenoid circuit at the contact 10. The valve I2 then falls to its closed position, and it cannot be raised again until after the pilot name Lis resumed. When the fuel supply fails while the room thermostat is still calling for heat, the heating coil 3| remains energized and the pilot fuel valve remains open. Also, within a very short time the intermittent energization of ignition coil 12 is resumed, so that as soon as the,

failure of fuelis overcome the pilot again ignites and the cycle of ignition of the main burner occurs in the regular way.

The system herein disclosed incorporates features that will cause automatic recycling in the event of an electric power failure of appreciable duration, that is a power failure long enough to cause the bi-metal element 30 to cool and close the pilot valve. The main valve will of courseclose immediately upon a power failure because the solenoid I4 will then be deenergized. Also. the various components of the entire valve assembly are so arranged and connected that a failure of any part of the assembly will prevent the main gas valve from opening or will close that valve if it is open at the time the failure occurs.

Having thus described my invention, I claim:

l. In fluid fuel-burning equipment, a main burner, a valve for the fuel supply thereto, a pilot, a valve for the fuel supply to the pilot, an electric igniter for the pilot, a room thermostat, an electric circuit for operating the main valve, a circuit for the igniter, a double throw switch adapted when in one position to ,make contact-s in said main valve operating circuit and when in another position' to make contacts in said igniter circuit, means embodying a heating coil undervthe control of the room thermostat for Opening saidv pilot valve and complet'- ing either of said circuits through said double throw switch, and means responsive to the presence or absence of a pilot lflame for moving said double throw switch from one operative position4 stat, a circuit controlling the valve for said,y

main burner, said circuit including a first switch and a second switch, a heating coil working under the control of the room thermostat for opening said pilot valve, closing said first switch and energizing said igniter, and means under the control of the flame from said pilot for closing said second switch and deenergizlng said igniter.

' 3. In fluid fuel burning equipment, a main burner, a valve for the fuel supply thereto, a pilot, a valve for the fuel supply to the pilot, a room thermostat, a circuit controlling at all times the valve for said main burner, said circuit including a first switch and a second switch, delayed action means working under the control of the room thermostat for opening said pilot valve and closing said first switch when the thermostat calls for heat and for closing said pilot valve and opening said first switch when the heat requirement of the thermostat is satisfled, and means under the control of the flame from said pilot for closing said second switch and for opening the same upon the cessation of flame from said pilot.

4. In fluid fuel burning equipment, a main burner, a valve for the fuel supply thereto, a pilot, a valve for the fuel supply to the pilot, an electric igniter for the pilot, a room thermostat, a circuit controlling at all times the valve for said main burner, said circuit including a first switch and a second switch, delayed action means working under control of the room thermostat for opening said pilotvalve, closing said first switch, and energizing said igniter when the thermostat calls for heat, and means under control of the flame from said pilot for deenergizing said igniter and closing said second switch, and upon the cessation of fiame from the pilot for opening said second switch.

5. In fluid fuel burning equipment, a main burner, a valve for the fuel supply thereto, a pilot, a valve for the fuel supply to the pilot, an electric igniter for the pilot, an electric circuit for operating the main valve, a circuit for the igniter, a double throw switch adapted when in one position to make contacts in` saidmain valve operating circuit and when in another position to make contacts in said igniter circuit, electrical means functioning a predetermined time after energizatin to open saidpilot valve and said double throw switch from ne operative position to the other, whereby the presence or ab-v sence of a pilot flame determineswhich ofthe said circuits shall be completed subject always to the control of said electrical means. VILYNN O. BEAM.l

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