US2171955A - Oil burner control-variable resistance with temperature type - Google Patents

Description

Sept. 5, 1939. R. H.`sU| LlvAN 2,171,955

OIL BURNER CONTROL-VARIABLE RESISTANCE WITH TEMPERATURE TYPE Filed June 17, 1936 Sme/whom Patented Sept. 5, 1939 PA'lENT OFFICE OIL BURNB CONTROL-VARIABLE RESIST- ANCE WITH TEIHPERATURE TYPE Raymond H. Sullivan, Rochester, N. Y.,

to General Motors Corporation, a corporation of Delaware Application June 17,

1 Claim.

This invention relates to control systems and more specically to control systems adapted to be utilized with Viluid fuel burners.

In a great many of the systems for controlling 5 uid fuel burners the use of contacts operated by the temperature within the combustion chamber or stack has resulted in a great deal of trouble due to the sticking contacts since the whole opwill become apparent as the speciilcation pro- Y ceeds, my invention resides in the construction and illustrated in the accompanying drawing, in which:

The figure shows a schematic diagram of a control circuit utilizing the principles of my in- 25 vention. Y

The main lines 2 and 4 may be attached to any source of electrical energy and have connectedv the other contact I 8 of said switch being con` nected by line 28 Vto one terminal of a Warp switch 22, the movable terminal of said switch being connected by line 24 to one end of a resistance 26. The resistance 26 is of the type whose resistivity changes appreciably, with the change in the temperature thereof and may be of nickel or nickel alloy.

Connected in seriesY with the resistance 26 is a second resistance coil 28 whose opposite terminal is connected by line 30 to one terminal of the room thermostat 32, the opposite terminal 34 of which is connected by line 36 to the other end of the secondary I0. 'The resistance means 28 is formed of advance wire or some other material which has a small resistance temperature coeilicient so that as the temperature changes-- there is a very small change in the resistivity of the means. Connected directly across 4the resistance means 28 is a relay coil 38 by wires48 and 42, said coil being-operated by the potential v drop across said resistance, p

From the contact 32 of the room thermostat runs a wire 44 which extends to a second relay as utilized in the following specication and claim assignor Detroit, Mich.,

1936, Serial No. 85,646 l coil 46, the opposite terminal of which is connected by wire 48 back to the wire 24.

Also extending from the wire 36 is agwire 58 which extends to one end of the resistance heating coil 52 of the warp switch 22, the other end of the heating coil being connected by -wire 54 to contact 56. A movable contact member 62 is adapted to cooperate with contact 56 to close a circuit between wirev 64 and wire 54, said wire 64 extending back and connected to line I2.

All of the circuits described thus far, ywith the exception of the incoming lines, have been low voltage circuits and include in the main the controlling apparatus. To the incoming line 2 is connected a wire 66 which extends to contact 68 and cooperates with a movable contact 10 which is' connected by wires 'I2 and I4 to one side of the motor 16. `'Ihe opposite side of the motor is connected by lines 18 and 80 totheother incoming line 4. Line 12 also extends down and is connected to a stationary contact 82 which `cooperates with the movable contact 84, the latter being connected by line 86 to one side of the primary 88 of the ignition transformer, the opposite sidev of the primary beingv connected to line. 8U which extends back to the incoming line 4. The secondary coil 90 of the ignition transformer has connected across it a spark gap 92.

From the foregoing it will be seen that tbe only portions oi the apparatus in the high voltage circuit are the motor for discharging the fuel into the combustion chamber and the ignition transformer, theremainder being all low voltage.

With respect to the high limit control mentioned above, this control embodies a magnetic member 94 -which is ,subjected to the heat of combustion in the stack and under normal temperatures will retain the contacts I4 and I8 in closed position. However, if the temperature becomes too high the magnetism of the device will be changed to such an extent that the circuit will open and cause the whole system to bedeenergized.

The operation of this circuit is as follows:

Under normal inoperative conditions the warp switch 22 is closed, the relays 38 and 46`are deenergized, the room thermostat is open and the motor is in rest position. If, now, 'the temperature of the space to be heated has fallen to such a degree that the'conta/cts of the room thermostat close, a circuit is completed from the transformer secondary IIJ, through line 3E, contact 34, contact'32, line 44, relay 4B, line 48, line 24, switch 22, line 28, contacts I4, I8 and line I2 back to the secondary. This energizes the relay lr6 which closes contact "lil against contact BI which starts the burner motor in operation through an obvious circuit. At the same time a circuit is completed through the two resistances 26 and 28 in series as follows: Secondary l0, line 36, contacts 34, 32, line 30, resistance 28, resistance 26, line 24, switch '22, line 20, contacts I8, I4 and line l2 back to the second I0. This causesga definite potential drop across he resistance 2l and gives sumcient voltage to operate relay 2l through an obvious circuit which closes contacts u, 22 and 62, I6. The closing of the first pair of contacts completes the circuit `i'r'om lines 12 and 80 to the primary 28 of the ignition transformer which causes sparks to jump through the gap 92 and ignition of the oil will normally follow. 'Ihe closing of the contacts 62, 56 places the heating coil 5 2 of the warp switch across the transformer secondary by the following circuit:` Secondaryl I0, line I2, wire il, contacts 62, 5S, line 54, coil 52, line 50 and line 36 back to the transformer secondary. Under normal conditions the combustion chamber will be heated and the resistivity of the resistance 26 will be increased to such an extent that the voltage drop across the resistance 28 will decrease and the relay 38 will have insuilicient strength to retain theb movable. contacts determined time and also the warp switch coil will be prevented from operating. 4If, however, the burner does not start 'and the relay 38 maintains an energized condition, the warp coil will, after a certain set predeterminedperiod, cause its contacts to open by the bending of` the bimetal -strip and the whole circuit will be deenergized. Also, if through some difficultyA or fault, the furnace is allowed to heat up to an abnormal temperature, the high limit control I6 lwill drop its contacts and cause the contacts Il, Il to open which also deenergizes the whole,

system. A

I claim: In a room heating system, a combustion chamber, a fluid fuel burner, means for propelling fuel .into said combustion. chamber, fuel igniting circuit, a permanent magnet, the magnetization RAYMOND H.

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