US2113858A - Control unit - Google Patents

Description

April 12, 1938. w. A. RAY

CONTROL UNIT Filed Sept. 28, 1956 Thermaslal zNvzsNfoR. M70290? ,4 255/ ATTORNEY.

Patented Apr. 12, 1938 I UNITED STATES CONTROL UNIT William A. Bay, San Francisco, Calif., assignor-v to General Controls Company, a corporation of California Application September 28, 1936, Serial No. 102,956

3 Claims.

This invention relates to a control unit, particularly one useful in conjunction with a conditioning .means giving oflf heat by conduction and convection and radiant heat. The invention 5 is particularly concerned with the control and operation of an oil burner, and will therefore .be-

particularly described in conjunction therewith. It is in general the broad objectof the present invention to provide-a novel, simple and inex- 1 pensive control unit.

Referring to the drawing, I have shown in the single diagrammatic figure an oil burner 6 as dis- 20 charging into a fire box 1. Positioned above the burner so as to be out of the direct contact with the flame, is a thermopile structure indicated generally at 8. 'The thermopile I have found should be exposed to radiant heat from 25 the burner on only one side thereof, while subject substantially equally, throughout its extent to heating by conduction and convection. By observing this, the effective current generated is sufiicient to operate a relay or other control unit.

' This thermopile is made up of pipe 9 inserted through the wall of the firebox and having a pluralityv of thermocouples ll connected together in a cumulative relationship. It is to be noted that the thermopile is made up of a plurality of elements, usually. dissimilar materials such as a heavy iron and constantan wire (0.0625 inch) threaded back and forth-through opaque insulating washers l0 about four times with dissimilar ends joined. The elements constituting the'se'veral thermocouples are relatively short, so that they are subject to relatively the same degree of'heat by conduction and convection throughout their length. A. thermopile made up with a number of thermocouples suffices to generate suflicient current, I have if the thermopile is made up of two rather large and heavy pieces of the dissimilar materials, this 55 will sufiice, and the invention is not limited to A further object of the invention is to provide any number, size or length of the elements of dissimilar materials so long as a sufficient current is generated thereby, and so long as the thermopile is subject throughout its extent to substantially the same degree of conduction and 5 convection heat from the furnace. In the drawing the length of thethermopile has been exaggerated to enable a clear showing of its relation to the other elements. In practice, the elements -of the thermopile are made about one 10 inch in length.

When the burner is operating, the thermopile throughout its entirety will be subject to the same degree of heat by conduction and convection, but the exposed ends l8 of the ther- 5 mopile will be subject to the radiant heat from the furnace, thus making the thermopile unequally thermally energized so that a current is generated. This makes the thermopile independent of the ambient furnace temperature and responsive only to burner operation. Thus the thermopile is equally effective upon burner op.- eration even though the furnace temperature varies between 0 F. and 2000 F.

In the attached drawing I have shown the thermopile as utilized with a novel control circuit. Of course the thermopile can be used with other circuits, but the present circuit, being simple, accurate and quite responsive, utilizing a minimum of equipment, is one which I prefer. so

The control circuit and the operation of the thermopile will probably be best understood by considering the actual operation. Let us assume that the burner 6 is not operating and that control device 23, such as a thermostat, calls for operation of the burner 6. Closing of the control device as thermostat 23 results in a circuit being closed through line 42 connected to the secondary of the transformer ll. Current then flows through line and through relay coil 39 of re- 40 lay 36, through line 63 and heating coil 62 of closed safety trip switch 21. The heating coil 62 is connected by line6l to contact 60, which, when the furnace is 'cold, is engaged by arm 2| of the relay operatedby thermopile 8. Arm 2| is connected byline 29 to arm 43 of control device 30. Arm 43 cooperates with a contact 46, which is in turn connected by line 41 to arm 26 of the closed safety trip switch 21. Arm 26 engages contact 25, this contact being connected by line 24 to the control device as thermostat 23. When current flows through the relay coil 39 of the relay 36, the contact arms and GI are moved into engagement with their respective contacts 31 and 61, to complete other circuits presently disclosed. 1

If the relay does not operate, full current 'will continue to flow through the coil 62 which heats the bimetal arm 26 and causes it to move and disengage the contact 25, thus interrupting the primary control circuit. I

When the contact 61 is engaged by thearm 6|, a circuit through lines 53 and 54 to the oil burner motor is completed and the oil burner starts into operation. At the same time, a circuit through lines 53 and transformer primary 50 is completed so that a high tension current is furnished to spark gap to ignite the burner. This circuit is completed through contact 48 and arm 44 connected by line 55 to line 54. We thus have the blower motor operating and a high.

tension spark being supplied so that the furnace is started into operation and heat is supplied thereto. I

Engagement of relay arm 34 with contact 31 results in heating coil 62 being placed in parallel ,virith heating 'coil' 32 for'bimetal arm 3|, so that the rate of heating of heating coil 62 is reduced and the safety trip switchremains closed for a longer period than otherwise. Relay coil 39 is connected by line 40 to-one side of the secondary of the transformer 4|. The other side of the relay coil 39 is connected by line 38 to contact 31, while arm 34 is connected by line 33 to the heating coil 32 in the control device 30. Heating coil 32 is effective to heat the bimetal strip 3| and move contact arms 43 and 44, there being an intermediate insulating strip between the two arms so that arm 43. can move arm 44.

The other end of theheating coil 32 is con-- nected by line 29 to the relay arm 2| and thus to contact 60 and line 6|, which extends to the heating coil 62, thus placing the two heating coils 62 and 32 in parallel. Heating of the coil 32 is effective to operate the bimetal strip 3| and move arms 43 and 44 so that the circuits they respectively control are opened. Thus the spark ignition of the burner is discontinued after a few minutes upon the opening of the circuit by arm 44 passing out of engagementwith contact 48. This condition is of course maintained so long as arm 2| is in engagement with contact -because heaters 62 and 32 are in parallel. condition the burner motor 6 continues to operate, and heat is s pplied .to the furnace.

When the thermocouple structure indicated generally at 8 becomes heated by the radiant heat so that it generates sumcient current, relay coil I4 is energized and pulls arm 2| insa counterclockwise direction to engage contact 22, the-arm 2| being preferably supported for a snap action. This results in cutting out .the heatingcoil 62 and establishing a direct circuit through heating coil 32, maintaining the contact in engagement with the contact 31 and the arm 6| in enagement with the contact 6'| ""Tl}15 is an indication of satisfactory operation If'the relay coil I4 is not energizecLsafety trip switch 21 remains in control and thermostat or control device 23 does not come into sole control. The. burner 6 continues to o erate so long as control device 23 determines. hen it opens thecircuit the humor" 6 stops.

The control circuit quickly reconditions itself,

Inthis coil 32 cooling off to permit arms 43 and 44 to engage contacts 46 and 48. The thermopile ceases to generate current as soon as the radiant heat fromv the flame from the burner 6 ceases, and this is so even though the furnace including the wall and pipe 9 are veryhot since this heat affects the thermopile equally. It is a feature of .this invention that the thermopile is so placed that it is responsive very quickly to the burner operation while it is out of the direct flame; it is exposed to the fire but is not in it.

With the thermopile positioned in accordance with this invention, residual heat does not affect the effective available current since what' causes heat generation by a thermopile is the difference in heat between the metal junctions. Thus, the thermopile will not generate any substantial current even though it be at a high temperature (say 400 F.) so long as it is uniform, but subject ends l8 to a temperature of 1800" F. and the remainder of the pile to a temperature of only say 550 F. and the pile generates sufllcient current to operate relay I5. The term ambient temperature." refers to the varying space temperature of the furnace and tothe varying temperature of the furnace walls to which the thermocouple unit is subject as a whole substantially uniformly at all times. Thus, when the burner is not working, the space furnace temperature and-the wall temperature drops, approaching atmospheric. When the burner operates, the space furnace temperature and the wall temperature, the fundamental temperatures affecting'the entire thermocouple unit as a whole can vary between wide limits. However, because of the arrangement of the thermocouple in accordance with this invention, this ambient temperature does not cause current generation.

I claim: a

1. In combination, a furnace wall, a burner for said furnace, and control means for controlling f saidburner including a thermocouple unit including a conduit in the furnace wall and open at a plurality of thermocouples threaded between 4 said pair of members with opposite ends thereof extending toward the ends of said tubular mem- '-ber..

3. In combination, a furnace having walls de-.-

fining a fire space, a fuel burner for burning a fuel and providing 'a fire in said .space, control .means for controlling said burner including a thermocouple unit having a hot and a cold junction, and means positioning said unit-- in said furnace with said junctions subject to a substantially qual extent to heat by conduction and convection from said fire space and by conduc tion, convection and radiation by said walls and with only the hot junction exposed to radiant heat from the burner flame but not to heat by said flame.

- A. RAY.

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