US2073718A - Fuel oil burner ignition - Google Patents

Description

March 16, 1937. c. E. VAWTER 2,

FUEL on, BURNER IGNITION Original Filed Nov. 20, 1930 INVENTOR C7zarksZVau/Zer: fieceas'ed @Germaniowrz Fun (07712012 xecuifir: 83 2a 4Q I ca'n/ W M IiRNEYS S '55 the igniting flame tame 16, 19st- FUEL on. Brianna IGNITION Charles E. Vawter, deceased, late of Philadelphia,

Pa, by Germantown Trust Company, executor,

' Philadelphia, Pa.-, assignor to Walter J. Laird,

Wilmington, Del.

Original application November 20, 1930. Serial No. 496,999, now Patent No. 1,955,520, dated April Divided and this application April 14, 1934, Serial No- 720,644

The present invention relates to improvements in the process of igniting fuel oil in oil burners, and the present application is a division of an application Ser. No. 496,999 filed November 20,

5 1930, now Patent 1,955,520, which in turn is a continuation in part of an application Ser. No. 443,730 filed April 12, 1930, now Patent-1,955,519.-

Two well-known forms of heat into which electricity can be translated are the spark and the 10 are. A spark is a disruptive discharge of sufficiently high voltage to break down the gas in the gap between two electrodes without previous ionization of the gas 'and consequent reduction of the resistance of the gap.

15 An arc discharge, on the other hand, takes place only after the resistance of the gap has been diminished by the ionization of the material between the electrodes. Thus, for example, it requires thousands of volts to produce a dis- 20 ruptive discharge between the spaced electrodes,

- but when the gap is once bridged by such a discharge, the resistance of the gap is so reduced by the ionization of the gas that it requires a relatively low voltage to maintain an are dis- 5 charge between the electrodes.

'Heretofore, in oil burner ignition, transformers have been used with. three amperes at 110 volts on the primary and twenty-five milliamperes at 10,000 voltsfor thespark ignition our- 30 rents from the secondary. Twenty-five milliamperes, however, does not provide sufficient heat to efliciently ignite the oil. It is, accordingly, necessary to increase the voltage across the secondary of the transformer to obtain the current 35 necessary to produce the desired heat. For example, to produce a minimum'current required,

1 such as a quarter of an ampere, would require Y 100,000 volts in the above described transformer system. Such a voltage would require insulation 40 entirely too bulky and expensive for practical use. By converting a disruptive spark discharge into an arc discharge, however, the low voltage current passing between the electrodes can be increased enormously.

Considerable dimculties have been experienced with the ignition systems used in oil burners. If an insufllciently hot igniting flame is obtained, unburnt -oil is permitted to accumulate, causing eventual failure of ignition and occasionally an 50 explosion with disastrous effects mayoccur. It

is well known that this difliculty in oil burners has seriously retarded their development.

The failure of oil to ignite is, as is well understood, due to the fact that the temperature of is below the flash point of the oil, or even that the electrodes between which ignition is obtained are short circuited due to electrodes.

Accordingly, the object of the invention is to provide an improved method or .process for igniting low grade oils having a high flash point.

Other objects of the invention are such as will the accumulations of carbon from the oil on the vention which is to follow, in which:

Fig. 1 is a schematic circuit diagram proved ignition system.

- Fig. 2 is a similar diagram containing certain modifications.

Fig. 3 is a diagrammatic illustration of the ini vention adapted for igniting oil, gas, or other combustible fluids. v

Referring first to Fig. 1, the source of electrical energy I may be either direct or alternating current and preferably of 110 volts, although as low as 60 volts may be used. I

The supply source mayconsist of either a-battery 2 or a generator 3. One terminal of the source of energy I is connected to the common return conductor 4 and the other terminal is connected by the lead 5 to the control switch 6, which is shunted by the condenser I. The condenser is connected across the make and break contact 6 to prevent arcing thereat. This circuit is completed over a variable resistance 8, contactor 9, winding of the relay l0, conductor H, the primary winding I! of the transformer l3, through the contacts l6 and the armature i5 controlled by the relay l0, conductor i5, and resistance l6, back to the common conductor 4. In this circuit, the resistance 8 is inserted in order to' control the amplitude of the current which flows thereover. The relay I is energized by current which flows in this circuit to attract its associated armature l which thereby disengages the contact M.

The transformer I3 is a high frequency transformer and therefore preferably has. an air core. The primary winding l2 consists of relatively few 1 turns of heavy wire so that its resistance is prac-v tically negligible. A condenser I8 is connected between the interrupter I4 and the conductor Ii across the terf the im minals of the primary winding l2, forming therewith an oscillating circuit which is controlled by the interrupter II. -The capacity and inductive reactances are such that the natural frequency of be clear from the detailed description of the inv the circuit is extremely high, although preferably below the radio broadcasting range of frequencies,

'ber of turns. Such step-up in voltage in oscilso that the apparatus will not interfere with radio reception.

Between one endof the primary winding l2 and the secondary winding ll of the transformer I3, is connected an inductance 2| which excludes from the primary circuit all high voltage, high frequency currents from the secondary H which would otherwise pass directly across the common terminals of windings l1 and I2.

The lead 4 may be grounded when desired, as for instance for welding apparatus or if it appears to be safer to do so, both terminals may be left ungrounded, in which case the transmission of high frequency disturbance to the supply line is sometimes reduced. 5

It will be understood that the inductance 2 I, as well as the inductance of the relay ID, are wound with sufficiently heavy wire and are otherwise of appropriate construction for carrying the arc current from supply source I which will vary, depending upon the heating properties of the are discharge desired for any particular purpose. The ohmic resistance of inductance 2| and also of the relay winding ID are as low as possible so as to avoid overheating and to provide a more direct path for the arcing current over the arc gaps rather than through resistance .IB, as will be explained more fully hereinafter.

The secondary ll of the transformer I3 is connected in series with a condenser 23 which is connected over conductor 24 to one terminal of the arc discharge 25, the other terminal of which is connected to the opposite terminal of the secondary winding H of the transformer I3. Conductor 24 is also connected to the common return conductor 4.

In operation, the'switch 5 is a manually or automatically operated switch mechanically designed to remain closed as long as it is desired to produce an are at the electrodes 25. For operation, the contact 6 is closed, completing the circuit for the relay ill, described above. Relay H1 is energized and operates its armature 5' to disengage the contacts M.

The current flowing over this circuit also results in the storing of a considerable amount of electromagnetic and electrostatic energy in the primary circuit, including the primary winding l2 of the transformer l5 and condenser Hi.

When the interrupter contact M is opened as a result of the energization of relay Ill, a spark is produced thereacross due to the high inductance of windings l0 and I2 in the circuit. As a result, high frequency oscillations are produced in the circuit including the condenser l8 and the inductance |2, similar to the phenomena of a spark oscillator used in radio sets. Although this energy dissipates itself in a minutely short period of time, the oscillations are, while in operation, of a very high frequency, determined, oi course, by the constants of the oscillating circuit traced above and which, as stated hereinbefore, has a very high natural frequency.

During these oscillations, a high frequency voltage is generated in the secondary H, the voltage induced in the secondary being higher than in the primary, inasmuch as this is a step-up transformer. As this transformer is for the purpose of stepping up high frequency voltages, the step-up action is not necessarily due to the increased numlating circuits can always be secured by a proper choice of capacity and inductance constants in the primary and secondary circuit, and these should be arranged in combination with the ratio of turns of the windings. to give the'necessary step-up voltage relation for the range of inherent capacities of the parts connected to the spark gap. As the energy dies out in the primary circuit, it builds up in the secondary circuit until a voltage is built up in the secondary circuit sufficiently high to Jump the gap 25.

The passage of the disruptive discharge ionizes the gas between the electrodes of the gap, and this ionization reduces the electrical resistance of the gap to a sufficiently low value so that the potential from the supply source 2 is sufficient to cause the current from this source to flow through the primary circuit from relay II] by way of conductor I through the winding 2| and across the gap 25. The disruptive discharge which takes place first and bridges the gap 25 is thereby converted into an arc discharge.

The small current produced by the oscillatory spark discharge which bridges the gap 25 and which has a correspondingly small heating value is thus suddenly transformed into a current which may be or more times larger--say of the order of l ampere-and which is sufficient to produce an arc of intense heat. The intensity of this are is, moreover, sufficient for igniting low grade oils and other fuels. It will be understood that a current of the order of 60 volts and l ampere as set forth in this specification is in tended to indicate the characteristics of an are which will maintain the gap ionized without destructive effect on the oil burner electrodes, but that larger currents can be used in order to increase the heating effect of the are. When this system is employed for arc welding purposes, the operating current is, of course, larger than one ampere and such a current will be obtained in the circuit by the proper choice of the values of resistance 8 and the resistance of the winding ill and 2| through which this current will flow.

The inductance of the relay II), in addition to controlling the armature l5, functions also by means of its inductance to prevent the high frequency currents of the primary circuit from entering the supply source I. The value of this inductance is'made as low as possible, however, so as to reduce to the lowest possible extent its retarding action on the building up of the arc current across gap 25. By making resistance l6 non-inductive the time required for the current to build up in the primary circuit is as short as possible.

It is also to be noted that an ionizing arc is drawn between the interrupter contacts |4 whenever discharge takes place across the gap 25. The interrupter contacts l4 and the electrodes of gap 25 are connected in parallel with the source Hence, normally, if an arc is established across the gap 25, it will not be maintained across the contacts I4, and if an arc is maintained across the contacts i l, it will not be established across the gap 25.

By placing the resistance I6 in series with the interrupter contacts l4, however, and choosing a value of this resistance which is large in comparison with the resistance of the winding 2|, the current from the source 2, which chooses the path of least resistance flows through the coil 2| and the ionized gap 25, so that the arc is prevented from being maintained across interrupter I4 and will be established across the gap.

If for any reason, the are, after it has been established, is extinguished while switch 6 is closed, the circuit for electromagnet I0 is opened at both its own armature i5, which is then in aorsma' its energized position disengaging contact i4 and also at gap 25.* The electromagnet will therefore nected between the secondary ii and the common return conductor 4, and which functions in the manner described in connection with condenser 23 in Figure l to produce-an oscillatory circuit with the secondary winding I! and the arc electrodes 25. With this'arrangement, however, the arcing current flows through winding I1 and, ac-

cordingly the resistance of winding I! must be made relatively small. Also to prevent arcing at contacts M, the resistance of i6 must be made large with respect to the ohmic resistance of thesecondary H, in order to provide a path of least resistance through the secondary H to gap 25 for the arcing currents. a

The apparatus for producing an arc discharge for ignition of oil burners is shown in Fig. 3 in which the walls of the furnace, are diagrammati cally illustrated at 8|. A burner 80 projects through the walls 8| into the furnace, and it will be understood. that from this burner an appropriate mixture of fluid fuel and air is discharged under suitable pressure into the combustion chamber within the furnace. Projecting through an opening in the wall there is a unit 82 comprising any desired form of arcing device, such as illustrated. In the device, shown for illustration, the high voltage terminal of the arcing electrodes 25 of either Figs. 1 or 2', is connected through the screw 83 to the electrode 84 which is secured to the body 01' insulating material 85. Gonnection to the other branch of the circuit is made by means of the fastening of the main portion of the unit to the grounded side of the system through the screw threaded collar 86 on which is mounted the secoi. electrode 01. Electrode 8? is usually permanently adjusted and shaped relative to electrode 84, so that for a short distance the electrodes are nearly parallel in order to increase their life. r I

This arcing apparatus has especial advantages in connection with oilburnersa Thus, for example, it will ignite low grade oils that have a high flash point. Furthermore, inste'ad of short circuiting the gap as in other systems, any carbon which accumulates on the terminals in this system actually aids operation, as it is burnt up by the arc. Also, any moisture which may collect does not have the effect on the high frequency current to the same extent as such moisture does on the low frequency currents. It will iinally be noted that these systems work equally efljectively on director alternating currents.

Although there is ilustrated a formof the'invention for igniting oil burners, it willbe understood that this showing is diagrammatic and any I other form may be used. Furthermore, any well known form of temperature control may be used in conjunction with the system.

It is not desired to limit the invention to the specific illustrations thereof herein given, except in so far as set forth in the following claims.

What is claimed is: v

1. The improvements in the process of fluid fuel burner ignition which comprise maintaining ajump spark electric current of at least'10,000 volts and a few milliamperes, and then decreasing the voltage to about and increasing the current i sufllciently to prevent the cessation. of current flow by the air and fuel blast from the burner.

2. The improvements in the process 01' fluid fuel burner ignition which comprise producing a jump spark electric current of at least 10,000 volts and a few milliamperes, converting the spark into an are having a current of not less than about 1 ampere, and continuously maintaining either the are or the spark.

GERMANTOWN 'raus'r COMPANY,

Executor of the Estate of Charles E.-Vawter,

Deceased.

By C. S. SMYTH,

Vice President.

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