US2089394A - Electrical ignition device - Google Patents

Description

4 Sheets-Sheet l INVENTOR. /KA- 5 1 0455 ATTORNEY.

Aug. 10, 1937. I. E. M CABE ELECTRICAL IGNITION .DEVICE Original Filed June 15. 1931 Aug. 10, 1937. 1. 'E. M CABE 2,089,394

ELECTRICAL IGNITION DEVICE Original Filed June 15, 1931 4 Sheets-Sheet 2 INVENTOR.

//M 6. C455 BYWM ATTORNEY.

Aug. 10, 1937. Y I. E. MQCABE 2,089,394

ELECTRICAL IGNITION DEVICE Original Filed June 15. 1931 4 Sheets-Sheet 5 INVENTOR. /AA E. [WC/15E.

ATTORNEY.

Aug. 10, 1937. E. MCCABE 2,089,394

ELECTRICAL IGNIT'ION DEVICE Original Filed June 15, 1931 4 Sheets-Sheet 4- ATTORNEY.

- Patented Aug. 10, 1937 UNITED STATES PATENT OFFICE ELECTRICAL IGNITION DEVICE Ira E. McCabe, Chicago, 111. Original application June 15, 1931, Serial No.

544,516. Divided and this application January 19, 1935, Serial No. 2,511

It is an object of this invention to provide an m igniter for an electrically operated and controlled will be caused to become incandescent upon the passage of an electrical current therethrough and in whichthe resistance to the flow of current decreases as the'temperature of the resistance material increases without deterioration of the igniting element. Heretofore, igniters of the hot wire type deteriorate upon continued passage of current, the passage of too great a. current, or by being subjected to the excessive heat of the 2 fluid fuel flame.

This invention. contemplates the utilization of a commercial electrical resistance, known to the trade as Durhy, one of the carborundums, which possesses the property of being quickly brought to incandescence upon the passage of an electrical current therethrough when cold and thereafter 1 withstanding excessive high temperatures without deterioration, making, it especially advantageous for use as an ignition device, but also the additionalproperty as its temperature rises of offering decreasing resistance to almost an unlimited degree, thereby making such resistance, s'ince'it allows too-much current to pass through, produce the effect of a short circuit on the line. The invention therefore contemplates the provision of means in circuit with an ignition element of this resistance material which will allow suflicient current to pass therethrough when 11 cold .to, bring it to'incandescence and then prevent,.the decreasing resistance thereof from blowing out the fuses to the commercial line or the consuming of -more current than necessary to maintain incandes'cence without producing excessive temperature in the resistance element, and also, to delay the-admittanceof fuel to a fluid fuel burner until the igniter becomes incandescent.

With these and other objects in view, reference is made to the accompanying sheets of drawing which illustrate preferred forms of this invenmay be made without departing from the scope thereof.

fluid fuel burner of a resistance material which constant current transformer.

tion with the understanding that minor changes In the drawings Figure 1 is a view in front elevation of a constant current transformer employed in a preferred form of carrying out this invention, with the front of the casing removed. 5

Figure 2 is a view in side elevation of Figure 1, with the casing shown in section.

. Figure 3.is a view in side elevation of an ignition element, with parts broken away.

Figure 4 is a view partlyin-section and partly in elevation of an application of this form of this invention to a commercial type of electrically operated and controlled fluid fuel burner, illustrating a wiring diagram with connections to a Figure 5 illustrates in perspective a commercial type of ignition and motor control showing another form that may be employed in carrying out this invention together wtih a wiring diagram showing its application to a fluid fuel burner such as shown in Figure 4.

Figure 6 is a view similar to Figure 1 of another form of this invention showing an alternate means ior limiting the amount of current possible to pass through a hot igniter element.

Figure 7 is a schematic wiring diagram of an application of the means illustrated in Figure 6.

In the embodiment of this invention illustrated in Figures 1 to 4, inclusive, an ignition element I is located within the combustion chamber 2 .of a commercial type of fluid fuel burner 3 in such relation that when brought to incandescen'cy and the motor M discharges the fuel into the combustion chamber it will be ignited by the incandescent element I. The ignition element l is, preferably, a short length in cylindrical form, of much greater diameter than the usual hot wire heretofore employed, of the above described Durhy material which readily heats to incandescency upon the passage of an electrical current therethrough and the resistance of ,which decreases as the temperature thereof increases.

. It ispreferable to provide the ends of the element silicon alloys 0rsteels in the form of wires, which in turn are mounted upon a block 6 of insulating material, such as porcelain, provided with-bind-' ing posts I for each support.

If such an igniter were connected directly to the ommercial source of electricity after it became incandescent, through its increasing conductivity, it would either blowthe fuses or consume an unlimited amount of current and acquire tempera- 55 One of such means is illustrated in Figures 1,

2 and 4 which employs a constant current transformer similar to that disclosed in the applicant's prior pending application. Serial No. 331,542, filed January 10, 1929, in which the primary coil 8 is adapted to be connected to the commercial line and is arranged to float above the. stationary secondary coil 9 when suiiicient current is induced therein to bring the element to incandescence,

and thereafter limit the induced current to that suflicient-to cause and maintain incandescence. F The coil 9 is preferably formed of windings of large size of great current carrying capacity, and is provided with binding posts I 0, whereby it may be connected by similar wires II to the binding posts I of the ignition element. It might be stated here that if the temperature of the ignition element be reduced, such as by the passage of cool air thereover from the draft pipe of a forced draft fluid fuel burner, its resistance would be increased which would be compensated immediately by an increase in the flow of current from the constant current transformer which increase in wattage tends to maintain it incandescent irrespective of variations of temperature of the atmosphere surrounding the element.

When forming a part of an electrically operated and controlled fiuid fuel burner mechanism, it is preferable to employ the movement of the primary coil 8 as it is repelled or floats upon the closing of the circuit threthrough to close a switch l2, as disclosed in this applicants prior application 0 Serial No. 465,882, flied July 7, 1930, to close a circuit to operate the burner motor M to supply fuel to be ignited and burned. The windings of the coils 8 and 9 bear such relation to each other that as soon as the primary coil is connected in the commercial line, as by the closing of a room thermostat, current will be immediately induced in the secondary and begin to pass through the ignition element l raising its temperature andas 50. its temperature. increases its conductivity increases, quickly becoming incandescent. where-- upon the primary coil begins to be repelled or floats above the stationary secondary coil and thereafter thestrength of the current is constantly limited to that required to maintain incandescency of the element The upward movement of the primary coil8 frees a pivoted bracket H, in the manner described in said prior application Serial No. 465,882, which allows through connecting link l5, rotation 01' a pivoted bell crank lever IS, the other arm of which. supports a mercury tube switch |2, to close a circuit from the commercial line l3 through the burner motor M. Referring to Figures 1 and 4, it is seen that, while the motor switch I2 is normally open, the

incoming commercial current passes from binding post l1 through the coil 8' and back by way of binding post l8, butwhentheswitch I2 is closed,

it also passes from binding post through switch I2, through binding post l9, through the motor M and back through binding post l8.

It is preferable to provide some means to break .the circuit to the ignition, device within apredete'rmined time after ignition for the sake of economy, there being no necessity to consume current for the ignition element thereafter; Any

commercial device may be employed for this purpose such as a normally closed stack switch in the commercial line to the ignition device responsive to combustion to open.

In such-case itis necessary to provide some means to maintain the motor circuit closed after the breaking of the ignition circuit, such as by providing an additional switch in the stack safety in' circuit with the commercial line and motor normally open and adapted to be closed before the ignition circuit opens. I

One form of accomplishing thisis shown in Figure 5 which illustrates the employment of a commercial control device as disclosed in the applicants prior application Serial No. 418,684, filed January 6, 1930, to this particular ignition device. The control device shown in Figure 5 includes a normally closed safety switch 20- connected to the incoming current of the commercial line I3 through binding post 2| and to a binding post 2| a normally closed ignition switch 22 and a normally open shunt'switch 23 both actuated by the thermal element 24 located in the stack of the furnace and responsive to heat from the burner flame to tilt the ignition switch 22 to open position and the shunt switch 23 to closed position. The binding post 2 I is connected through a thermal safety operating device to binding post 25..

Binding post .25 is connected by lead 21 to the ignition switch 22 and by leads 28 through the normally open transformer operated switch |2 to binding post 29. The ignition switch 22 is also connected by lead 30 through binding post 3| and 28. to the binding post. 2| and from thence I through the thermally actuated safety device to binding post 25. The ignition switch 22 is normally closed and the shunt switch 23 is normally open when the burner is cold. ,Thecurrent then passes from binding post 25 through lead 21, through closed ignition switch 22, through lead 30, binding post 3| and continuing on through lead 38 through the primary coil 8 of the constant current transformer and thence back to the return lead of the commercial line l3, as indicated by the arrows. The energizing of the primary coil 8 will induce a flowof current through the secondary coil 9 which will heat the ignition element and when it has been brought to incandescence the coil 8 will begin tov float and in floating will cause the switch l2 to close and thereafter the incoming current will branch at the binding post 25 so that part of itpasses through lead 28 through switch |2 to binding post 29 and from thence through holding magnet H and binding post 34 by way of lead 33 through the burner motor M back to-the commercial line l3,-

whereby fuel is supplied to the burner 'to be ignited by the element Upon ignition of the fuel the thermal element 24 in the stack ,wiil cause incoming current will pass from binding post 2|",

through the shunt switch; binding Post,

holding magnet H, binding post 34 and through the lead 33 to maintain the motor operative. By

this means the motor circuit is maintained and the primary of the constant current transformer 5 is de-energized after ignition occurs.

Figures 6 and 7 illustrate another manner for limiting the amount of current passing through the ignition element This device includes an electromagnet 35 having a pivoted armature 36 which mounts mercury tube switches 31 and 38 so that when one is open the other is closed and a resistance unit 39. The switch 38 is normally.

closed when the magnet I is de-energized. As seen from the diagram in Figure 7, when the line 15 circuit is closed, as through a room thermostat,

' the incoming current passes through binding post, 40 through magnet 35, switch 38, binding post 4l, through ignition element I, binding post 42 back to the commercial line l3. The initial resistance 20 of the ignition element I is sufflcient to allow current to pass through the coils of the magnet 35 without energizing it, but as the igniter l heats up, its resistance decreases, so that by the time it is incandescent the magnet is energized, attracts 35 its armature and switch 38 is opened and switch 31 is closed. The coils of themagnet 35 are also connected to the resistance unit 39, so that when switch 38 is opened the current passing through the magnet then passes through the resistance unit as to the ignition element a. The resistance unit 39 is so constructed as to allow sufiicient current to pass therethrough to maintain the magnet energized while the igniter remains incandescent.

The closing of the switch 31 completes a circuit from the commercial line l3 through binding post 40, switch 31, binding post 43, motor M and binding post 42 back to the commercial line. The use of this material as an ignition element in conjunction with the devices described herein insures lo that fuel cannot enter the combustion chamber until the igniter is in circuit and incandescent. In other words if the igniter itself were broken or failed to reach the required temperature where its resistance would be decreased to the correct amount, the circuit to the fuel supplying means would not be made. This device supplies a selfchecking and safe method of attaining combustion in automatic fuel burning apparatus;

What I claim is:

F0 1. An ignition device for fluid fuel burners including an electrical incandescent resistance igniter, the resistance of which decreases as its temperature increases, in combination with an e electric circuit including means for'supplying fuel 55 to the igniter and a control for the said-circuit provided with means for limiting the passage of current through the igniter after the igniter becomes operative and preventing the supplying of fuel prior thereto.

i0 2. An ignition device for fluid fuel burners including an electrical incandescent resistance igniter, the resistance of which decreases as its temperature increases to produce a temperature therein far in excess of that required for ignition purposes under any constant external temperature, in combination with an electric circuit including means for supplying fuel to the igniter and a control for the said circuit provided with means for automatically regulating and limiting 0 the passage of current through the igniter to that sufiicient to bring the igniter to operative condition and to maintain it operative irrespective of external temperature changes. said means while the igniter remains operative permitting the supplying of fuel.

3. An ignition device for fluid fuel burners including an electrical incandescent resistance igniter, the resistance of which decreases as its temperature increases, in combination with an electric circuit including means for supplying fuel to the igniter and a control for the said circuit provided with means actuated by the increase in current flow as the resistance of the igniter decreases for limiting the passage of current through the igniter to a predetermined flow after the igniter becomes operative, said means including a constant current transformer of the floating coil type whereby one coil is repelled as the igniter becomes operative, and means coacting with the floating coil controlling the supply of fuel.

4. An incandescent ignition system for an electrically operated and controlled fluid fuel burner mechanism,-a main electric circuit, a motor for supplying fuel to the burner, an electrical resistance igniter for igniting the fuel, the resistance of which decreases as its temperature increases, a constant current transformer, means connecting the primary coil of said transformer in said main circuit, means connecting the resistance igniter in circuit with the secondary coil of said transformer, and a normally open switch in said main circuit adapted to connect said motor in said main circuit actuated by the repulsion of the primary coil when the resistance igniter becomes operative to close and operate the motor supply fuel to the igniter. 5. In an incandescent ignition system for an electrically operated and controlled fluid fuel burner mechanism, a main electric circuit, a motor for supplying fuel to the burner, an electrical resistance igniter for igniting the fuel, the resistance of which decreases as its temperature increases, a constant current transformer, means connecting the primary coil of said transformer in said main circuit, means connecting the resistance igniter in circuit with the secondary coil of said transformer, a normally open switch in said main circuit operative to connect said motor in said main circuit actuated by the repulsion of the primary coil when the resistance igniter becomes operative to close and operate the motor to supply fuel to the igniter, and a thermally actuated switch mechanism including when cold a normally closed switch connecting the primary coil of said transformer in said main circuit and a normally open switch operative to connect said motor directly in said main circuit responsive upon combustion of the fuel to first close said normally open switch to the motor to continue to supply fuel to the burner and then open the switch to the primary coil of the transformer to discontinue the operation of the igniter.

6. In combination with a burner and its fuel feeding means, a control system therefor including a resistance igniter operatively associated with said burner and having a negative temperature coemcient of resistance. and means effectuatwith the desired ignition temperature.

IRA E. MCCABE.

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