US2619287A - Apparatus for removing oil from the ignition electrodes of oil burners - Google Patents

Description

Nov. 25, 1952 LOGAN APPARATUS FOR REMOVING OIL FROM THE IGNITION ELECTRODES OF OIL BURNERS Filed April 18, 1951 INVENTOR M M Z m n w J Patented Nov. 25, 1952 APPARATUS FOR REMOVING OIL FROM THE IGNITION ELECTRODES OF OIL BURNERS Joseph A. Logan, Hadley, Mass., assignor to Gilbert & Barker Manufacturing Company, West Springfield, Mass, a corporation of Massachusetts Application April 18, 1951, Serial No. 221,547

1 Claim. 1

This invention relates to improvements in electrically-ignited oil burners, such for example as are adapted for house-heating service, and, more particularly, to the maintenance of the ignition electrodes clean and free from oil.

The ignition electrodes are usually mounted above the oil-atomizing nozzle with their tips close to but out of the direct path of the conelike spray which is emitted from the nozzle. The arc-like spark, produced between the tips of the electrodes, is distended by the blast of air from the fan of the burner and forced into the spray to vaporize and ignite the same. There is, however, an area adjacent the conical spray where very fine mist of oil or vapor exists and because of this, the electrodes may, at the end of a run of the burner, have a thin film of oil thereon. Also, after the oil cut-off valve has closed, there may be a few drops of oil emitted from the nozzle and these will vaporize and some of the vapor may lodge on the electrodes.

This invention has for its object the provision in an electrically-ignited oil burner, of means for prolonging the ignition spark, after the motor, which drives the air-supply fan and oil-supply pump, has stopped, for the purpose of removing from the electrodes any oil that may have been deposited thereon, such removal being effected by the heat of the spark and immediately following each run of the burner, so that the electrodes are left dry and less apt to accumulate dirt.

Illustrative examples of the invention are shown in the accompanying drawings, in which:

Fig. 1 is a sectional plan view of a gun-type oil burner with which the invention may be employed;

Fig. 2 is an electrical diagram showing a burner control system embodying the invention; and

Fig. 3 is a fragmentary diagrammatical view illustrative of a modification.

Referring to these drawings: there is shown in Fig. 1, by way of illustrative example, one type of oil burner with which the improvements of this invention may be used. This burner is of the familiar gun type, used largely for househeating service. It includes a fan I, mounted on a housing 2 and supplying the air for combustion through a tube 3, near the outlet end of which is mounted a nozzle 4, herein indicated as of the pressure or mechanical atomizing type. The fan I is driven by an electric motor 5, which also drives an oil pump 6 but preferably through a suitable speed-responsive clutch 1., such for example as shown in my Patent No. 1,985,934, granted January 1, 1935, whereby the starting of the pump is delayed until the motor and fan have acquired considerable speed. The pump 6 may, for example, be of the type shown in 'OsbornePatent No. 2,233,709, granted March 4, 1941, such pump being incorporated with the usual filter, cut-off and pressure-regulating 2 valves in one casing forming a fuel-feeding unit. The inlet to this unit is adapted to be connected by a pipe 1 to a supply tank or liquid fuel and the outlet of the unit is connected by .a pipe 8 to the atomizing nozzle 4. Ignition electrodes 9 are suitably mounted in tube 3 in igniting relation to the spray of oil emitted from the nozzle 4. The burner described represents one example of many burners with which the improvements of this invention may be used.

A burner of this type is usually controlled by a thermostat switch, which responds to room temperature and closes on a demand for heat from the burner and opens when the demand is satisfied. A typical control system for the burner is shown in Fig. 2. The room thermostat switch consists of a bi-metallic blade [0 and two stationary contacts H and I2, which are adapted to be successively engaged in the order named on a demand for heat from the burner. The thermostat may also include an electric heating coil l3, which is brought into play near the end of each run of the burner to accelerate the opening of the thermostat switch, when the demand for heat is satisfied. This switch controls a relay which in turn controls the motor '5 and the ignition means. The coil M of this relay is arranged in series with a time switch l5, an electric heating coil l6 associated with the time switch and two pairs of engaged contacts I! and IS, in a low voltage starting circuit which is supplied from the secondary IQ of a step down transformer 20. The primary 2] of this transformer is connected by wires 22 and 23 to terminals 24 and 25, respectively, which are adapted for connection to a suitable source of electricity exemplified by the line wires 26 and 21 of a volt, 60 cycle, alternating current supply. The secondary 19 may, for example, supply current at 24 volts. The starting circuit may be traced as follows: from the right hand terminal of secondary [9 by a wire 28, terminal 29 and wire 30 to contact H, thence by blade ill, contact l2, wire 3|, terminal 32, wires 33 and 34, engaged contacts I8 and I1, wire 35, heating coil l6, closed switch [5 and wire 36 to coil l4 and thence by a wire 31 to the other terminal of secondary I9. On closure of this starting circuit, the coil 14 will be energized and a series of switches 38, 39, 40, 4| and 42 will be simultaneously closed. Closure of switch 38 will close a circuit to motor 5 which circuit may be traced as follows: from wire 26 by terminal 24, wire 43, closed switch 38, wire 44, terminal 45 and wire 46 to one terminal of motor 5 and thence from the other terminal of the latter by wire 41 and terminal 25 to the other line wire 21. Ordinarily, the ignition circuit would also be closed by the same switch used to start the motor 5 but, for reasons later to appear, a separate switch 39 is used for the purpose. The ignition means consists of a step-up transformer 48 and electrodes 3 9 which are connected to the secondary 49 of this transformer by wires 50. The primary 5| of this transformer is connected in series with switch 39 in a circuit which may be traced as follows: from line wire 26, by terminal 24, wires 43 and 52, closed switch 39, wire 53, terminal 54, wire 55, primary 5|, wire 56, terminal 51, wire 58 and terminal 25 to line wire 21.

The starting circuit described includes the time switch I5, which usually consists of a bi-metallic member heated by coil I6 and caused to open in a predetermined time, say for example, 90 seconds. simultaneously energized, combustion occurs within the predetermined time, the heating coil l6 of the safety switch will be shunted out to prevent the latter from opening. A suitable thermostat, indicated conventionally at 59 and responsive to burner temperature, actuates' the described pairs of contacts I1 and I8, which are initially engaged, as well as a pair of contacts 60, which are initially open. On occurrence of combustion, thermostat 59 first causes contacts 53 to engage, then causes contacts I8 to separate and finally causes contacts IT t separate. The closure of contacts 60 closes a holding circuit to relay coil I4, which excludes the heatin coil I6. This holding circuit may be traced as follows: from the right hand terminal of secondary I 9, by wire 28, terminal 29, wire 30, contact I I, blade I0, contact I2, wire 3|, terminal 32, wires 33 and 6|, closed switch 4|, wire 62, closed switch 42, wire 63, engaged contacts 60, wire 64, closed switch I 5, wire 35, relay coil I4 and wire 31 to the left hand terminal of secondary I9, first shunted out by the low resistance circuit which includes wire 35, engaged contacts I1, a wire 65, engaged contacts 60 and wire 64, and then cut out of circuit by the subsequent opening of contacts I1. The burner will now operate on a circuit which includes the contacts 50 and which will be quickly broken in the event of failure of combustion by the opening of these contacts.

The closure of switch 40 prepares a circuit, which will cause the heating coil l3 of the accel-' crating thermostat switch to operate at the proper time, namely, shortly before the end of each run of the burner. This circuit usually includes wires 62 and 65, closed switch 40, wires 61 and 68, terminal 69, wire 10, coil l3 and the blade ID of the room thermostat switch. However, for the purposes of this invention, such circuit also includes the heating coil 1| of a suitable time switch 12. The described circuit is shunted out, as long as blade Iii engages both contacts II and I2 by the following low-resistance path, namely, contact I2, wire 3|, terminal 32, wires 33 and BI and closed switch 4|. However, as the demand for heat is nearly satisfied, the blade If] disengages from contact I2, while maintaining engagement with contact II, so that the burner now operates on a circuit which includes the heating coils I3 and 1|, This latter circuit may be traced as follows: from the right hand terminal of secondary I9, by wire 28, terminal 29, wire 30, contact II, blade l0, coil I3, wire 18, terminal 39, wire 68, coil 1 I, wire 61, closed switch 40, wires 66 and 52, closed switch .2, wire 63, engaged contacts 60, wires 64, closed switch I5, wire 36, coil I4 and wire 31 to the left hand terminal of secondary I 9. This last-named circuit will come into play in about two minutes before the end of the burner run and the coil I3 will heat blade I and cause If when motor and transformer 48 are- The heating coil is 4 it to disengage from contact II sooner than it otherwise would.

According to this invention, the disengagement of blade ID from contact I2 is utilized to set in action a time switch such as 12, regardless of whether or not the heating coil I3 is employed. This time switch may be any commercial form of thermostat-operated switch which will close in a predetermined time, say 90 seconds, after the coil 1| is energized and will open in a like time after coil 1| is deenergized. This time switch controls a circuit to the coil 13 of a second relay, which circuit may be traced as follows: from the right hand terminal of secondary |9 by wire 28 to wire 14, coil 13, wire 15, closed switch 12, wire 16 to wire 31, and up wire 31 to the left hand terminal of the secondary. Relay coil 13, when energized, will close a switch 11, the terminals of which are respectively connected by wires 18 and 19 to wires 52 and 53, whereby an alternate circuit to the primary 5| of the ignition transformer is closed. This alternate circuit will serve to maintain the ignition after the switch 35 opens because of the dropping out of the first relay, when the room thermostat switch opens by the disengagement of its blade I0 from contact II. When blade l0 leaves contact II, the circuit to the heating coil 1| of time switch 12 will be broken. However, the circuit to relay coil 13 is not broken by the opening of the room thermo-' stat switch and the dropping out of the relay, which it controls, so that the coil 13 remains energized until switch 12 opens. This occurs in a predetermined time interval, which as described is 90 seconds but which may obviously be varied as desired.

In the event of failure of combustion, the contacts disengage almost immediately and, somewhat later, the contacts I8 re-engage, followed by the re-engagement of the contacts I1. The time between the opening of contacts 60 and the engagement of contacts I1, usually about 60 seconds, affords a scavenging period, afterwhich the burner will start up on the starting circuit previously described. occur Within seconds, switch |5 will open to stop the burner and this switch will lock out so that-the burner cannot again be started until this switch is manually reset. The stopping ofthe burner, due to a combustion failure, cannotv adversely affect the provisions of this invention for prolongation of the ignition period. Should the burner stop, due to combustion failure, the circuit to heating coil 1| will be broken by the separation of cont-acts 63 and the subsequent opening of switch 40. occurs after blade ID has left contact I2 and thus while coil 1| is energized, the circuit to the coil will be broken and heating of the thermostat of the time switch will be stopped. 'If the heating has progressed far enough to close switch 12, the ignition will be kept on for a while after the motor 5 stops, which is what the invention provides for from the back wall of the control box into the stack of the heating apparatus, fired by the oil burner.

The operation will be clear from the foregoingdescription. The burner motor and the ignition If combustion does not,

If the combustion'failure' means are simultaneously started by the relay I4, when actuated by the room thermostat switch, but the opening of the ignition switch by the dropping out of this relay is inefiective to stop the ignition because of the alternate circuit, established by the pulling in of relay '68. This occurs just before the end of each run of the burner by the closing of switch I2. The latter is a time switch which will remain closed until after the burner motor has been stopped. After the lapse of the selected predetermined time, switch l2 will open and cannot again be closed until near the end of the next run of the burner. With the described arrangement the switch 12 must be arranged to close in an interval slightly less than that during which blade i5 is disengaged from contact I2 while still engaged with contact II, so that the switch will surely close before the blade I5 leaves contact I I to stop the burner and the first-named interval must be long enough to keep the switch i2 closed until after the burner has stopped.

Another means of securing the prolongation of the ignition is shown in Fig. 3. This is a fragmentary diagram showing only the changes necessary to make in the diagram of Fig. 2. The heating coil H, time switch 72, coil I3, switch TI and wires 68, I l and 16 have been omitted. The heating coil I3 may also be omitted as shown and wire Til connected directly to blade Ill. The switch I! is replaced by a time switch which includes a brush BI and a long contact over which the brush may be moved against the force of a spring 83. Brush BI is fixed to the plunger 8% of a solenoid 85. This plunger carries a piston 85 movable in a dashpot 87 having a large opening 88 covered by a valve 95! which has a very small opening 89. The contact 82 is connected to wire I8 and the brush 8| is connected through the intermediary of plunger 84 and dashpot 87, to wire 19. The solenoid 85 is respectively connected by wires 9| and 92 to wire 31 and terminal 69. The wire El from switch ie is connected to wire 9!. On starting, after blade Ill has engaged both contacts I! and I2 to energize relay coil id and cause the closing of switches 38, 39, 45, i! and 42, the solenoid will be shunted out, the shunt comprising contact I2, wire 3!, terminal 32, wires 33 and GI, closed switch 4|, wire 66, closed switch ill, and wire 6'1. When blade Ill leaves contact I2 near the end of the run of the burner, a circuit will be closed to solenoid 85 as follows: from the right hand terminal of secondary I9 by wire 28, terminal 29, wire 35, contact I I, blade I0, wire It, terminal 59, wire 92, coil 85, wire 9| to wire 31 and up wire 31 to the left hand terminal of the secondary. The solenoid 85 will thus be energized to move plunger 34 and carry brush 81 into engagement with contact 82 and thus, as before, close an alternate circuit to the primary 5| of the ignition transformer. The piston 86 will move freely because valve 90 will open to allow free flow of air through the large hole 88 into the dashpot. The solenoid 85 remains energized and holds the brush 8| engaged near the left hand end of contact 82 until blade [0 leaves contact II. Then, the previously stressed spring 83 expands and moves the brush 8i to the right along contact 82 but this movement is slowed because valve 89 closes and the only outlet for air is the small hole 89. Thus, the brush ill will not move off the contact 82 until the lapse of a predetermined time after the circuit to the burner motor is open and the oil-supply pump stops, whereby any oil on the spark electrodes will be removed by the heat of the spark and the electrodes left dry and clean.

The control system disclosed is of the type which maintains ignition continuously during each run of the burner. This type is generally preferable because of the safety afforded by having ignition always available for re-igniting the oil after a momentary interruption, should one occur. However, the invention is not limited to use with burners having continuous ignition, because if the circuit to the ignition transformer is cut off shortly after ignition occurs, the switch 'I'I of Fig. 2 or the switch iii, 82 of Fig. 3 will close another circuit to the ignition transformer shortly before the burner stops and maintain such circuit closed for a time after the burner stops. In other words, the operation of the invention in providing for ignition after cessation of the oil supply to the burner nozzle would not be affected by an earlier opening of the ignition switch 39 because of the establishment of an ignition circuit which is entirely independent of this switch.

What is claimed is:

In an oil burner, having an atomizing nozzle, electrically-operated means for supplying oil to said nozzle, an electric igniter adjacent said nozzle, energizing circuits one for said means and one for said igniter, and means controlling the opening and closing of both said circuits and including a switch having first and second contacts and a blade movable relatively thereto, a bi-metallic member for moving the said blade in response to variations in temperature in the space to be heated by the burner, said member being operable on falling temperature to move said blade successively into engagement with the first and second contacts in the order named and said blade when engaging both contacts causing both said circuits to close to start the burner, said member on rising temperature being operable to successively move the blade out of engagement with the second and first contacts in the order named and the blade when disengaged from both contacts causing both said circuits to open to stop the burner, an alternate energizing circuit for said igniter, a time-controlled switch in the last-named energizing circuit operable after it has been closed to open in a predetermined time, electrically-operated means for closing said time switch, an energizing circuit for the last-named means including said blade and first contact, and a low resistance circuit including said blade and second contact for shunting out the last-named energizing circuit when the blade engages both said contacts, said blade on rising temperature disengaging first from the second contact to open the shunt circuit and enable the last-named energizing circuit to close the time switch.

JOSEPH A. LOGAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re.15 .281 Jacobsen Feb. 7, 1922 1,671,910 Sweatt et a1. May 29, 1928 2,364,132 De Lancey Dec. 5, 1944 2,569,089 Aubert Sept. 25, 1951

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