US2275279A - Automatic lighter - Google Patents

Description

March 3, 1942. v. 0. BEAM AUTOMATIC LIGHTER Filed April 24. 1940 INVESTOR. l/m mv O. BERN Patented Mar. 3, 1942 AUTOMATIC LIGHTER vilynn 0. Beam, Cleveland Heights, Ohio, assignor to The Bryant Heater Company, Cleve land, Ohio, a corporation of Ohio Application April 24, 1940, Serial No. 331,451

Claims.

This invention relates to improvements in automatic lighters, that is to'say means for automatically igniting fluid fuel flowing from a bumer such as the burner of a heating system, and has to do more particularly with means for preventing contingent gas flow in the event of a sudden closing of the room thermostat contacts following closely after a no-call-i'or-heat signal from the thermostat. In some of its aspects the present invention is an improvement over that of my copending application Serial No. 232,816, filed October 1, 1938.

One of the objects of the invention is the simplification of the wiring system and the consequent simpliflcation of ,the installation of a burner control system of this character.

Another object of the invention is the provision of bimetal switch means operated by the heating coil with provision for impressing upon the coil alternately, voltages of relatively high and low value so that the said switch means requires no fine adjustment and is not appreciably aflected by changes in line voltageor ambien temperature.

Another object of the invention is the provision of means for causing the igniter coil of the system to function in connection with the heating coil in an improved manner for producing an intermittent or blnking action of the igniter coil.

Another object is the provision of a system in which the burning out of the igniter coil-will interrupt current to the valve motors-of both the main and pilot valves, whereby neither valve may be opened in the event that the gas flowing therefrom cannot be lighted.

Other objects and features of novelty will appear as I proceed with the description of that embodiment of the invention which, for the purposes of the present application,'1 have illustrated in the accompanying drawing, in which the single figure is a wiring diagram illustrating the invention.

In the drawing l0 represents a fuel pipe in which there is a valve ll controlling the flow of fuel to the main burner 9 of a heating system. A pilot tube l2 connected with the pipe is Drovided with a pilot valve l3 located in a valve casing It. The upper part l5 of the pilot tube extends from the top of this casing-to a position adjacent the man burner 9. Within the casing N there is a bi-metal strip l8 anchored at one end and carrying the valve piece I3 at its opposite end.

The main valve l l is adapted to close by gravity. It may be opened by an electric motor of iii conventional or known type which for the sake of simplicity I have shown in the drawing as a solenoid l'l surrounding a core l8 upon the lower I9 is a step-down transformer taking current 7 from a 110-volt line. From the two terminals of the transformer secondary flexible leads and 2| extend to the upper ends of a pair of conductors 22 and 23 which are adapted to move up and down with the armature of a relay coil 24. One end of this coil is connected at 23 to con-. ductor 23 and from the other end a conductor 25' extends to and is electrically connected with a conductor 28 which goes to one contact 21 of a room thermostat 28. Another contact 23 of the thermostat is connected through conductors 30 and 3| with movable conductor 22. It is apparent therefore that by virtue of these connections coil 24 will be energized and will raise conductors 22 and 23 from the position illustrated to a higher position whenever the conductors 25 and 3| are bridged, as by theroom thermostat 28 moving to engage the contacts 21 and 29.

Close to the pilot tube I5 where it may be affected by the flame from the pilot there is a thermally responsive member 32 pivotally mounted at 33 upon a suitable support and plvotally connected at 34 with a second member 35 which is mounted upon a pivot 36 and has a relatively long leg below that pivot. When the member 32 expands due to heat from the pilot the member 1 connected by a conductor 39 with the fixed end of the bi-metal element l6.

transformer.

to the room thermostat and thence through conductors 30, 3|, 22 and 20 back to the transformer.

In the present system the solenoid l1 and the igniter coil 31 are intended to be operative alternatively only, that is to say the igniter coil is never made incandescent while the solenoid I1 is energized to hold the valve open and the solenoid I1 is never energized while the coil 31 is hot. A two-way switch is utilized as a selector for one or the other of these two coils. While this switch may be of the type disclosed in my aforesaid copending application, I prefer to employ a snap-action switch, and a switch of that char-' acter is indicated herein diagrammatically as incorporating a switch blade 43 of spring metal anchored at 44, having a pivotal mounting 45 intermediate its ends and adapted to engage either one of two contacts 46 and 41. The extremity of the blade 43 beyond its pivot 45 is shown as loosely engaged by a pair of Jaws at the lower end of member 35. The movement of the member 35 in the anti-clockwise direction about its pivot 36 in response to an expansion of the thermal member 32 when heated will operate to snap the blade 43 toward the left away from contact 48 into engagement with contact 41. The mechanism just described is intended to represent merely any conventional means responsive to the pilot flame for effecting a snap-action switch movement from one of the two contacts 46 and 41 to the other.

The pivot 45 is electrically connected by a conductor to a contact 52 within the casing |4, so positioned that when heat from coil 40 warps bi-metal element It the latter first moves valve 3 into open position and then after further movement in the same direction makes engagement with contact 52.

Contact 48 is connected by a conductor 53 with conductor 30, while contact 41 is connected by ingly after the core is raised by current flowing through the thermostat contacts 29 and 21 and conductor 23 to solenoid H a supplemental path is set up through contact 23, the thermostat, conductor 53, contact 55, core l8, conductor 53 and conductor 28 to the solenoid.

When the two relay conductors 22 and 23 are in their lowered position, as they are when the system is idle, they engage two contacts 80 and ll, 80 being connected by a conductor 62 with conductor 5| and- 6| being connected by a conductor t3 with'conductor 54.

Operation.When the room thermostat calls for heat a circuit is set up from the transformer through conductors2| and 23 to relay coil 24, through conductors 25' and 26 to contact 21, through the thermostat to contact 29 and back by way of conductors 30, 3|, 22 and 20 to the The conductors 22 and 23 are thereby raised away from engagement with contacts 80 and SI. Simultaneously a circuit is set up 'from the transformer through conductors 2|,

23 and 30 to ignition coil 31, thence through conductor 39 to bi-metal element It and coil 40 and then through conductors 42, 25' and 26 to contact 21, the room thermostat and contact 23 and back through conductors 30, 3|, 22 and 20 to the transformer. As soon as this occurs the coil 43 begins to heat, thereby causing bi-metal element It to deflect upwardly. Gradually the pilot valve l3 opens, admitting gas to the pilot tube It. After this flow has been well established the bi-metal element engages contact '2, whereupon a supplemental current path is set up by-passing coil 40, this path proceeding as before from the right side of the transformer through the coil 31 to the bi-metal element It and then through contact 52 and conductor 5| to pivot 4| and through switch blade 43 and contact 4! and then through conductors 53, 30, 3|, 22 and 20 back to the transformer.

The transformer II is preferably one of the constant current, high impedance type, although other transformers of the proper power rating may be employed, provided they are not of the constant voltage type. As soon as this latter current path is established the current through coil 31 is sharply increased and the coil becomes incandescent and tends to light the gas emerging from the pilot. The reduced current through the coil 40 then permits that coil to cool somewhat so that the bi-metal element It pulls away from the contact 52, again forcing the, lighter coil current to flow through the heating coil. This reduces the current flow through coil 31 well below that necessary tobring it to the igniting temperature.

Coil 40 then heats up again and the bi-metal element engages contact 52 again causing the current through coil 31 to jump to a high value. The resistance of coil 40 is vry much greater than that of coil 31. The ratio maybe of the order of thirty to one. In thismanner current through coil 31 is made to alternate from high to low, and-the coil blinks. This blinking action is effective and important. While the coil is cool gas may enter it. When the coil heats up the maximum temperature is along the axis of the coil and accordingly that is where the igniting of the gas takes place most readily. If the coil were maintained hot continuously the high temperature within the coil would tend to produce flow out of the coil instead of into it and iamtion of the gas would be dimcult. With a blinking coil however the gas has an opportunity to enter the coil at each low current period. In the blinking action the voltage of coil 40 may be caused to vary between less than one volt to seventeen volts or more, due to the voltage drop across coil 31. The adjustment of point 52 is therefore not delicate, and in fact this point may be set permanently at the factory.

When the pilot gas has been ignited thermal member 32 becomes heated after a short interval,

- causing the lower end of member 35 to move toward the right or anti-clockwise. The upper end of blade 43 is thereby forced toward the right and the main portion of the blade is snapped from the position illustrated to a position where it is bowed in the opposite direction and is in engagement with the contact 41. When this occurs a circuit is set up through the main valve motor H as follows: From the right side of the transformer through conductors 2|, 23 and 33, coil 31, conductor 39, bi-metal element ll, contact 52, conductor 5|, pivot 45, blade 43, contact 41, conductor 54, solenoid |1, conductor 26, contact 21, the room thermostat, contact 23 and conductors 30, 3|, 22 and 20 back to the transformer. A. supplemental path is also set up through conductor 58. Two paths for current through coil 31 are now open, one through heating coil 40 and the other through solenoid l1. This provides a balanced condition, that is to say heating coil 40 remains energized sufllciently to hold bi-metal element It against contact 62 and solenoid ll remains energized suflicient-ly to hold up the valve piece II. The coil 31 remains relatively cool.

The main burner being then lighted, the furnace continues to operate until the thermostat ceases to call for heat, whereupon the circuit through -the solenoid ll opens and the main valve closes. Simultaneously the circuit through relay coil 24 opens and the conductors 22 and 23 drop into engagement with contacts 60 and 8!.

Thereupon a shunt circuit is set up from the right side of the transformer through contact 6!, conductors $3 and 54, contact All, blade 43, pivot 45, conductors 5| and 62, contact 60 and conductors 22 and back to the transformer.

The opening of the room thermostat contacts of course breaks the circuit through coils 31 and 40 and the bi-metal element It gradually cools and swings downward. Its engagement with contact 52 is broken first and then after a predetermined time interval pilot valve I3 is closed, terminating the flame from the pilot. member 32 then cools causing spring blade 43 to snap away from engagement with contact 41 into engagement with contact 48, whereupon the system is in readiness for the next lighting cycle whenever the room thermostat again calls for heat.

Now if, during the short interval following the extinguishment of the pilot flame prior to the snapping of the switch blade 43 from engagement with contact 41 into engagement with contact 46, the contacts of the room thermostat should be closed manually or otherwise no harm could result, that is to say the main valve could not open and admit a quantity of raw gas to the combustion chamber, because the establishment of the shunt circuit previously referred to prevents sufficient electrical energy from becoming available to operate either the solenoid H or the to its other position in engagement with contact 68. This will break the shunt circuit and put the system into condition for a new lighting cycle, the first eifect of which will be to energize relay coil 24 and lift conductors 22 and 23 out of engagement with contacts 80 and 6| thereby opening the shunt circuit at another point so. as to prevent its becoming effective when switch blade 43 engages contact 41 during the lighting cycle.

Should there be a failure of igniting coil 31 at any time, as by burning out, the whole system would be thrown out of operation because the current for operating both the pilot valve and the main valve must pass through the igniter coil. Hence no raw gas can enter the combustion chamber until a new coil is installed.

Having thus described my invention, I claim:

1. In a control system for fluid fuel burners, an igniter coil, and means for energizing said igniter coil intermittently comprising a heating coil arranged in series with the igniter coil, a supplemental circuit around said heatingcoil, a switch in said supplemental circuit, and means actuated by heat from said heating coil for closing said switch, thereby establishing a current path for said igniter coil around saidheating coil and bringing the igniter coil to igniting temperature and maintaning it there until the switch opens because of the cooled heating coil, after which the cycle is repeated.

Thermal 2. In a control system for fluid fuel burners, an igniter coil, means for energizing said igniter coil intermittently comprising a heating coil in series with the igniter coil, a supplemental circuit around said heating coil, said supplemental circuit comprising two parallel branches, a switch controlling said supplemental circuit, means actuated by heat from the heating coil for closing said switch, a main valve motor in one of said branches, and means for selecting one or the other of said branches, whereby when the branch containing the main valve motor is in the supplemental circuit current through the valve motor and the heating .0011 will be balanced sufliciently to maintain said switch closed and when the other branch is selected a low resistance path will be set up through the supplemental circuit causing current through the heating coil to fall below a value sumcient to maintain the switch closed.

3. In a control system for fluid fuel burners, an igniter coil, means for energizing said igniter coil intermittently comprising a heating coil in series with the igniter coil and a supplemental circuit around said heating coil, said supplemental circuit comprising two parallel branches, a switch controlling said supplemental circuit, means actuated by heat from the heating coil for closing said switch, a main valve motor in one of said branches, a pilot, and thermally responsive means controlled by the pilot flame for selecting one or ithe other of said branches, whereby. when the branch containing the main valve motor is in the supplemental circuit current through the valve motor and the heating coil will be balanced sufliciently to maintain said switch closed and when the other branch is selected a low resistance a path will be set up through the supplemental cirboth of said valves.

cuit causing current through the heating coil to fall below a value sumcient to maintain the switch closed.

4. In a control system for fluid fuel burners, a

current source, a room thermostat, an igniter coil,

means in circuit with said current source and a heating coil in series with the igniter coil, a

supplemental circuit around said heating coil,

said supplemental circuit comprising two parallel branches, a switch controlling said supplemental circuit, means actuated by the heat from the heating coil for closing said switch, a main valve motor in one of said branches under control of the room thermostat, a two-way switch for selecting one or the other of said branches, a safety shunt circuit including said current source and said two-way switch when the latter is in valve motor energizing position, and means tend ing to break said shunt circuit when the room thermostat is calling for heat, said shunt circuit VILYNN O. BEAM.

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