US2040620A - Electrical ignition device - Google Patents

Description

l. MccABE 2,040,620 ELECTRICAL IGNITIONVDEVICE I F'ii'ed June 15, 1951 4 Sheets-Sheet 1 May 12, 1936.

ATTORNEY May 12, 1936. E. MCCABI; 2,040,620

. ELECTRICAL IGNITION DEVICE Filed June 15, 1931 4 Sheets-Sheet 2 1E. 4- INVENTOR IRA- E MFCABE BY 'ITORNEY May 12, 1936. I. E; MCCABE 2,040,620

ELECTRICAL IGNITION DEVICE Filed June 15, 1951 4 Sheets-Sheet s I5 .INVEINTOR 1m E e/ass ATTORNEY May 12, 1936. I. M CABE ELECTRICAL IGNITION DEVICE Filed June 15, 1931 4 Sheets-Sheet 4 Patented May 12, 1936 UNITED STATES PATENT OFFICE 2 Claims.

This invention relates to improvements in ignition devices and more particularly to the socalled hot wire type particularly advantageous for use as means for igniting the flame of a fluid fuel burner.

It is an object of this invention to provide an igniter for an electrically operated and controlled fluid fuel burner of a resistance material which will be caused to become incandescent upon the passage of an electrical current therethrough and in which the 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 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 withstanding excessive high temperatures without deterioration, making it-especially advantageous for use as an ignition device, but also the additional property as its temperature rises of offering decreasing resistance to almost an unlimited degree, thereby making such resistance material by itself undesirable for ignition purposes, since it allows too much current to pass thru, produce the effect of a short circuit on the line. This invention further contemplates the provision of means in circuit with an ignition element of this resistance material which will allow sufficient current to pass therethrough when 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 incandescence without producing excessive temperature in the resistance element.

With these and other objects in view, reference is made to the accompanying sheets of drawings which illustrate preferred forms of this invention with the understanding that minor detail changes may be made without departing from the scope thereof.

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 55 the front of the casing removed.

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 partly in section and partly 5 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 constant current transformer. 10

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 with a wiring diagram showing its application to a fluid fuel burner 15- such as shown in Figure 4.

Figure 6 is a view similar to Figure l of another form of this invention showing an alternate means for limiting the amount of current possible to pass through a hot igniter element. 20

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 l is located within the combustion chamber 2 of a 25 commercial type of fluid fuel burner 3 in such relation that when brought to incandescence and the motor M discharges the fuel into the combustion chamber it will be ignited by the incandescent element l. The ignition element I is, 30

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 incandescence upon the passage of an electrical current 35 therethrough and the resistance of which decreases as the temperature thereof increases. It

is preferable to provide the ends of the element with caps 4 forming electrical connections with supports 5 of materials able to withstand high 40 temperatures, such as chrome nickel or chrome silicon alloys or steels inthe form of wires, which in turn are mounted upon a block 6 of insulating material, such as porcelain, provided with binding posts I for each support.

If such an igniter were connected directly to the commercial source of electricity after it became incandescent, through its increasing conductivity, it would either blow the fuses or consume an unlimited amount of current and acquire temperatures far in excess of that required to ignite the fuel.

To take advantage of the properties of this resistance material desirable to a hot wire ignition device, this applicant has provided means 5 for counteracting the undesirable properties, as hereinafter described.

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 sufiicient current is induced therein to bring the element I to incandescence, and thereafter limit the induced current to that sufiicient to cause and maintain incandescence. The coil 9 is preferably formed of windings of large size of great current carrying capacity, and is provided with binding posts l0, whereby it may be connected by similar wires H to the binding posts 1 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 Y element.

When forming a part of an electrically operated and controlled iiuid 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 therethrough to close a switch I 2, as disclosed in this applicants prior application Serial No. 465,882, filed July 7, 1930, to close a circuit to operate the burner motor M to supply fuel to be ignited andburned. 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 and as its temperature increases its conductivity increases, quickly becoming incandescent, whereupon the primary coil begins to be repelled or floats above the stationary secondary coil and thereafter the strength of the current is constantly limited to that required to maintain incandescency of the element 3. The upward movement of the primary coil ll frees a pivoted bracket I i, in the manner described in said prior application Ser. No. 465,882 which imparts, through connecting link it, rotation of a pivoted bell crank lever iii, the other arm of which supports a mercury tube switch lit to close a circuit from the commercial line it through. the burner motor M. Referring to Figures 1 and 4, it is seen that, while the motor switch ill is normally open, the incoming commercial current passes from binding post I i through the coil 8 and back by way of binding post Ill, but when the switch I2 is closed, it also passes from binding post ll through switch I2, through binding post 19, through the motor M and back through binding post it.

It is preferable to provide some means to brealr the circuit to the ignition device within a pre determined 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 re sponsive to combustion to open.

In such case it is 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.

One form of accomplishing this is 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 position shown in the drawings; The binding post 2| 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 12 to binding post 29. The ignition. switch 22 is also connected by lead 36 through binding post 3i and through the primary coil E2 of the constant current transformer back to the The binding post I:

turn of the commercial line it. 2i is connected by lead 32 through the shunt switch 23 to binding post 29. Binding post also connected by lead 33 through the holding magnet H, through binding post 3a, and throu the burner motor back to the commercial line When the room thermostat l8 closes the incorning current passes through lead it, binding post 2!] and through the normally closed safety switch 2i] to the binding post through the thermally actuated safety device to binding post mally closed and the shunt switch fit is norma open when the burner is cold. The current th passes from binding post 25 through lead fl'l, through closed ignition switch through lead 353, binding post and continuing on througltv. lead 3d through the primary coil of the co stant current transformer and thence has i the return lead of the commercial line try, indicated by the arrows. The energizing oi the primary coil i3 will induce a flow of current tln'ough the secondary coil 9 which will heat the ignition element l and when it has been brought to incandescence the coil ll will begin to float and in floating will cause the switch ill to close and thereafter the incoming current will branch at the binding post so that part of it passes through lead All through switch ill to binding post 29 and from thence through holding mag net H and binding post 3t by the way of lead 33 through the burner motor M bacit to the commercial line it, whereby fuel is supplied to burner to be ignited by the element i. Upon ignition of the fuel the thermal element fi l in the stack will cause first the shunt switch 23 to close and then the ignition switch 22 to open, so that thereafter the incoming current will pass from binding post 25 through the shunt switch Zi and from thence The ignition switch Eli is nor closed when the magnet 23, binding post 29, 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 is de-energized after ignition occurs.

Figures 6 and 7 illustrate another manner for limiting the amount of current passing through the ignition element I. 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 i is de-energized. As seen from the diagram in Figure 7, when the line circuit is closed, as through a room thermostat, the incoming current passes through binding post 40 through magnet 35, switch 38, binding post 4!, through ignition element 1, binding post 42 back to the commercial line l3. The initial resistance of the ignition element l is suflicient 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 its armature and switch 38 is opened and switch 31 is closed. The coils of the magnet 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 39 to the ignition element I. 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 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 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 temperaas its temperature increases post 40,

ture 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 self-checking and safe method of attaining combustion in automatic fuel burning apparatus.

What I claim is: l

1. An electrical incandescent resistance igniter for fluid fuels, the resistance of which decreases to produce a temperature therein far in excess of that required for ignition purposes under any constant external temperature, in combination in an electric circuit with means introducing additional resistance in the circuit to prevent short circuiting or destruction of the circuit, said means actuated bythe increase in current flow as the resistance in the igniter decreases for automatically regulating and limiting the passage of current through the igniter to that sumcient to bring the igniter to operative condition and to maintain it operative irrespective of external temperature changes, said means including a resistance element, a normally closed switch in said circuit for shunting said element, and an electro-magnet in said circuit for opening said switch energized by the increase of current flow when the igniter becomes operative.

2. The ,combination of an electrical incandescent resistance igniter for fluid fuels, increasing in conductivity as its temperature increases, in an electric circuit with a resistance element in said circuit for limiting the how of current to that sufllcient to maintain theigniter operative, a normally closed electrically operated switch normally shunting the said element, and an electromagnet for opening said switch in said circuit constructed to be energized upon a flow of current therethrough sufficient to operate the igniter to open said switch establishing the resistance element in said circuit to prevent unnecessary flow of current or the destruction of safety fuses in said circuit.

IRA E. MCCABE.

Images