US2021407A - Fuel control system - Google Patents

Description

Nov. 19, 1935. A. F. ERICKSON FUEL CONTROL SYSTEM 2 Sheets-Sheet 1 Filed Nov. 30, 1931 IDA U Hal [Tammi or ART/Me fife/cKJoN 6a 47- raz/vz Yr TF -l M Nov. 19, 1935. A E QN 2,021,407

FUEL CONTROL SYSTEM Filed Nov. 30, 19:51 2 Sheets-Sheet 2 Arrazh/sw Patented Nov. 19, 1935 UNITED STATES PATENT" OFl-lCE A A h mncom fi A i Arthur I. Erickson, San Francisco, Calif., as-

signor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application November 30, 1981, Serial No. 578,053

8 Claims. ((21. 158-28) This invention relates to improvements in syszicms for automatically controlling heat regula Objects of the invention are: to provide an 6 emcient system in which the starting circuit for the relay must pass through a contact of the stack switch which is normally closed when the stack is cold, and in which this circuit also passes througha safety switch and its heating coil; to

provide a circuit which shunts out the safety switch heater after flame is produced and which is also operated by stack temperature; to provide a stack temperature controlled switch in the ignition circuit which is normally closed when the stack is cold, and to control the stack switches by a common thermal element; and to so control of the system, shunting of the safety switch 86 after combustion is produced, and obtaining energization and de-energization of the igniter respectively before and after ignition: the overlap? ping control of starting and heater-shunt switches on temperature rise to assure maintenance of relay energization by establishment of a shunt holding circuit therefor. before the starting switch is opened as a result of rising temperature; and non-overlapping control of these switches on fall in temperature to obtain a standa 35 by period to delay a re-start after cessation of combustion; the use of a stack temperature controlled switch in the ignition circuit; the relay control of the ignition and motor circuits; the control of the stack switches by means of a common thermally controlled element; and the detailed arrangement of the circuits.

Objects, features and advantages of the invention will be set forth inthe description of the drawings forming a part of this application and in said drawings Figure 1 is a vertical longitudinal section through the thermostatically controlled stack switch structure on line i-l of Figure 2;

Figure 2 is a face view with the cover removed showing the switches; and Figure 3 is a diagrammatic view of the system in its cold-stack, warm-room condition.

The present embodiment of the invention in cludes, in addition to the control circuits: a room thermostat, a fuel controller, ana l ter,

a safety switch including a heater, a relay, and a plurality of thermostatically controlled switches, controlled by a common thermostatic element responsive to presence or absence of combustion, in this instance (though notalways) indi- 5 cated by stack temperature, the device being placed on the stack.

The thermostatically controlled device is illustrated'in detail in Figures land 2. This device is disclosed and'claimed in my copending application Serial Number 578,054. The device comrprises a suitable housing I having a tubular extension! to which one end of a helically coiled bimetallic element 8 is secured. The opposite end of this element is secured to a rod 4 which passes through the coil and is rotatably journaled in the extension 2, and which passes through the extension, through an insulating block it within the housing, and through a bushing i3 held by this insulating block. The end of this rod terminates within the housing'and is threaded as at 5. Arranged on this rod are toothed wheels respectively designated l-t and these wheels are secured by nuts 6 for rotation with the rod. Washers and disks 9 properly insulate the ratchet wheels from'the rod.

Mounted also within the casing and secured by one end to an extension of plate II, is a control arm it which has a freeend engageable with the toothed wheel I. The plate Ii is mounted on the insulating block l3, and has a suitable binding post. Also upon this plate is secured a contact arm it which carries contact pin it at its free end, which contact passes freely through an aperture It of the control arm It. A plate I! 35.

is also attached to the insulating block it and has a suitable binding post and has attached thereto spring arm I! which is provided with contact disk it cooperative with contact it. Pin I 5 and disk I! are viewed herein as constituting a switch, 40 otherwise designated the third or ignition switch, or contact. The manner of controlling element It by the toothed wheel 1 is substantially identical with the disclosure of Patent No. 1,768,892, issued to Benjamin Cyr, July 1, 1930, and in itself forms no part of the present invention. The switch l5,-l9 is normally closed, that is when the ribbon 3 is substantially cold.

Attached to the block l3 are a pair of bars II to which is attached, by one end, a resilient control arm 20. This arm carries two contact pins one at each opposite .side respectively indicated by numerals 12-23. The contact 22 cooperates with the contact diskil carried by spring arm 2! attached at itsopposite end to plate 26 also mounted on insulating block I3. Contact 23 cooperates with contact disk 21 carried by resilient arm 28, the opposite end of which is secured to plate 29 also mounted on the block l3. Upon an outward extension of plate 28 is attached a spring arm 30 which has at its free end, an angularly related portion II, the end of which is bevelled as at 32. The portion 3| is adapted to be frictionally engaged by the outer end of the arm 28 when this arm is forced against the extension 3| by means of the control arm 20. A frictional lock is thus provided which secures the spring arm 28 in the position mentioned, while the arm 20 moves away. In order that the arm 28 may be released to again assume the position shown in the drawings, the control arm 20 is provided with a hook 33 which engages an insulating plate 34 secured to the arm 28, this release taking place only after contacts 23 and 21 have been separated.

Pin 22 and disk 24 are viewed as constituting a first or starting switch or contact. Pin 23 and disk 21 constitute a second or heater shunt switch or contact. The character of the control means necessary for use with the type of switches herein used, differs radically from means used for the control of mercury tube switches. A feature of the invention is the control of the movable contact type of switch (as distinguished from the mercury tube switch) overlappingly on temperature rise and non-overlappingly on temperature fall, in the manner described.

It is one of the objects of this invention to so control the switches that the first and second are overlappingly controlled on rise in combustion temperature to open the first and close the second, and so that these switches are non-overlappingly controlled in reverse order on a fall in temperature, the second switch being opened before the first is closed.

Another feature of this invention is the control of all three switches by a common thermostatically controlled element. This is true because the toothed wheels I and I are fixed to a common thermally controlled element 4.

A specific feature of the invention is the latch arrangement by which the arm 28 is held latched while the control arm 20 travels away to open the second switch 23-21 before the first switch 22-24 closes. The operation of these switches is again referred to under the heading Operation".

Referring to Figure 3: The primary of the transformer is indicated at 55 and the secondary at 8B. The relay coil is indicated at 56. The fuel valve assembly may be a self-contained structure including any of the usual mechanisms. As herein shown, the valve 39 is operated by a rack bar 40 meshing with pinion M, in turn driven from the motor rotor through suitable reduction gearing diagrammatically indicated at 43. The rotor 42 is provided with a field coil 44 one end of which is connected by conductor 46 with the power line 45 and the other end of which is connected by conductor 41 through a movable switch element with contact 48 of the relay. The burner is indicated at 64 and is suitably arranged in furnace 65. The burner is connected with a suitable supply pipe 63 which is controlled by the valve. The smoke pipe or stack is indicated at 86 and it is on this stack that the casing having the three switches is mounted.

The ignition device includes a step-up transformer the primary of which is indicated at 14. One end of the primary is connected to line 41 and the opposite end is connected to one side of switch l5-l9. The secondary is connected to suitable electrodes 15 arranged adjacent the burner 64. The safety switch comprises the usual bimetallic elements 12 here indicated as a contact maker engageable with contact 10. The 5 Referring to Figure 3: The position of the parts corresponds to cold stack and warm room condition. Upon suflicient fall in room temperature, the room thermostat closes at R, B, W, and the relay 56 is energized through the following circuit: ll, 51, relay coil 56, 60, B, W, I, heater coil 1|, safety switch contacts 12-12, 1|, starting switch 24-22, 58, to II. It will be noted that this starting circuit is through stack switch 22-24, and the safety switch, and its heater.

0n closure of the relay, contact 59 establishes the usual holding circuit as follows: 88, 51, 54, holding contact 59, 62, R, W, 62, 1|, 12, 10, 12, 24-22, 58, to I0. On closure of the relay, the field coil 44 of the fuel controller or motor is energized to open the fuel valve. The circuit for the fleld coil is as follows: line 45, 46, coil 44, 41, 48,v 50 to line 49. The ignition circuit is as follows: 45, 46, 52, stack contact 16-, 12, a 14, 54, 41, 48, 50, line 49. The valve, when opened, stalls the motor, and is thus held open.

If combustion is successful, the stack thermostat is heated and 22 closes with 21, after which 22 breaks with 24. Making at 21 establishes a shunt circuit around the safety switch heater 1| as follows: 80, 51, relay coil 56, 59, 62, R, W, 68, 11, shunt switch 22-21, 52 to 80. When successfu combustion occurs, the contacts lS-IO open to de-energize the igniter, while the motor remains energized.

In further explanation of the action of the stack controlled switches: Referring to Figure 2, the rotation of the toothed wheels as the temperature rises is in anti-clockwise direction, as '0 indicated by the arrow. The parts are shown in the cold position. On temperature rise, the disks 1 and I move the arms II and 20, the first to the right and the second downwardly, and after a suflicient movement, It engages l4 and moves it away from l9, and 22 engages 21, and finally moves arm 28 to latched position. Continued motion of the disks in the same direction merely results in idling action while an open circuit relation is maintained the idling action is due to the relations of the tip of the arm 2| to the teeth of the disk I, which are such that the disk can continue to rotate while the control arm 20 remains in the same circuit control position. The same action occurs between arm Ill and toothed disk 9. See the Cyr patent previously referred to. Switch 22-24 remains closed until switch 23-21 closes, and thereafter the latching of arm 28 is accomplished. After latching, idling takes place without open- 7 ing switch 23-21. Arm 25 is biased to follow control arm 20 for a short distance, as arm 2| moves from its position in Figure 2.

Upon temperature fall, the rod and disks with it rotate in clockwise direction, resulting in subi switch 22-21. As-nr'm' movement continues,

tacts is as follows: Ontemperature rise in the hook 22 engager'arm 20 and moves it from frictional engagement with the extension it. This control of the contacts overlappingly on'temperature rise and non-overlappingly on temperature fall is an important feature of. the invention.

During the first part of temperature rise, switch 22-22 remains closed until switch 23-21 closes after which 22, 24 opens and then the arm 28 m moved to frictionally locked position. On temperature fall, 22-21 is immediately opened and at some predetermined time thereafter, the starting switch 22-24 is closed, and thereafter the hook restores 22' to its initial unlatched position.v

The sequence of operation of the various constack, contacts 22-21 (for maintaining fuel supply) are first to close after which contacts 22-24v (starting contacts) open. On further continued rise in the stack temperature, contacts (ignition contacts) open. When the stack tem-a pemture falls, contacts 22-21 are first to open.

On continued fall in stock temperature, contacts ll-ll (ignition contacts) close, and'on further fall in' stack temperature. contacts 22 4 close,

By having the contacts 22-21 close first'pn tem-" perature rise, and by having contacts 22-24 open before the there is given a slightly longer ignition period which tends to insure the establishment of proper ignition. On cooling of the stack, it is quite necessary that the hot contacts or contacts 22-21 open before the ignition contacts close. This is evident if flame failure is assumed. Under such conditions, fuel will continue to be supplied to the combustion chamber until the hot contacts or contacts 22-21 open. If ignition is returned by closure of contacts lB-IO before the supply gas is discontinued (by opening contacts 22-21) an explosion would result. It is one of the objects of this invention to delay starting for a predetermined time after combustion failure to prevent explosion. On the other hand, when contacts 22-21 open first, the supply of the gas is discontinued, and the relay is de-energized (fuel supply stopped) and thus a subsequent closure of the ignition contacts li-ll has no result insofar as combustion is concerned, until the relay or fuel controlling device is again energised by reclosure of contacts 22-24, which reclosure is delayed. Contacts ll-ll should close before the contacts 22-24 so that the ignition will be ready to operate as soon as the relay is reenergized.

An important feature of this invention is the control of a system of the nature described by the use of only a single relay, operating in con- Junction with the switches, all of which are controlled by a common thermostatic element. 1 Another feature is the control of, these switches by stack temperature.

I claim as my invention:

1. A device of the class described including a fuel controller, an igniter, a timed safety switch and an actuator therefor, and combustion responsive means and circuits operable thereby, on a call for heat to close fuel controller and igniter and actuator starting circuits, and after combustion to close a fuel controller holding circuit which is in shunt circuit around the actuator before the fuel controller starting circuit is broken, and after combustion failure to open d r, 2,021,407 'stantially immediately moving 22, opening ignition contacts ll-ll open,

the shunt circuit and close the starting circuit for the controller only after a timed period.

2. A device of theclass described including a fuel controller, an igniter, a timed safety switch and an actuatortherefor, and commoncombus- 5 tion responsive, means and circuits controlled thereby on a call forheat to close. fuel controller and igniter and actuator starting circuits,

and after combustion to, close a fuel controller holding'circuit which is in shunt circuit around the actuator before the fuel controller starting circuit is broken, and after combustion failure to open the shunt circuit and close thestartlng circuit. for the controller only after a timed period.

3. A device of the class described, comprising 16 a room thermostat, a fuel controller, an igniter, first, second and third switches which are controlled in response to combustionconditions, a timedsafety switch'including an actuator, a relay and circuits by which it controls the fuel controller 20 and igniter, the igniter circuit including therein the third combustion responsive switch, a circuit for initially energizing the relay which includes therein the thermostat, the first combustion responsive switch, and the safety switch and actuator, a holding circuit in shunt around the safety .switch actuator which-includes thereinsaid relay,

room thermostat and second combustion responsive switch, means by which the switches are controlled, the first and second switches overlappingly to close the second and open the first on temperature rise, and non-overlappingly controlled to open .-the second and after a time period close the first on fall in temperature.

4. In combination, an electrically operated fuel controller, an electro-magnetic coil, a normally open switch movable to closed position by said electro-magnetic coil when energized, an energizing circuit for the fuel controller including said switch, an actuator responsive to the presence or 40 absence of combustion, switching mechanism controlled thereby, a main switch, a first circuit including the main switch and combustion responsive switching mechanism for initially energizing the electro-magnetic coil when combustion is absent, and a second circuit including the main switch and combustion responsive switching mechanism, which circuit is closed prior to opening of the first circuit when combustion is established, for maintaining energization of the electromagnetic coil, said switching mechanism operating first to open the second circuit and subsequently to close the first circuit upon cessation of combustion, whereby, in the event of flame failure during operation of the system, the feeding of fuel is interrupted for a period of time after which the supply of fuel is resumed.

5. In combination, an electrically operated fuel controller, an electro-magnetic coil, a timed safety switch and an electrical actuator therefor, a main switch, a first circuit, a second circuit, a device responsive to the presence or absence of combustion, switching mechanism controlled thereby for closing the second circuit prior to opening of the first circuit on the establishment of combustion and for delaying closing of the first circuit for a time period after opening of the second circuit upon the cessation of combustion, said first circuit including the main switch, the safety switch and its actuator, and the electromagnetic coll, said second circuit including the main switch and the electro-magnetic coil, a normally open switch adapted to be closed by said electro-magnetic coll when energized, and a fuel 76 controller circuit including said last named switch.

8. In combination, an electrically operated fuel controller, a relay coil, a thermal safety switch and an electrical heating element therefor, a main switch, a first circuit, a second circuit, a device responsive to the presence or absence of combustion, switching mechanism controlled thereby for closing the second circuit prior to opening of the first circuit on the establishment of combustion and for delaying closing of the first circuit for a time period after opening of the second circuit on the cessation of combustion, said first circuit including the main switch, the safety switch and its electrical heating element, and the relay coil in series, said second circuit including the main switch and relay coil in series and operating to shunt the electrical heating element during that period in which both circuits are closed. a normally open switch adapted to be moved to closed position by the relay coil when energized, and a fuel controller circuit including said switch.

7. In combination, a fuel controller, a timed safety switch and electrical actuator therefor, first and second combustion responsive switches, a main switch, a circuit including the main switch, safety switch and its actuator and the first combustion responsive switch, a shunt circuit for said actuator and first combustion responsive switch controlled by the second combustion responsive switch, means controlled by said circuits for causing the fuel controller to supply fuel to a combustion chamber when said circuits are energized in their normal sequence, and means by which said first and second combustion controlled switches are overlappingly controlled to close the second and then open the first upon the establishment of combustion, and non-overlappingly controlled to open the second and after a time period to close the first upon cessation of com- 5 bustion, whereby the safety switch actuator is operatively de-energized upon closure of the second combustion responsive switch, and whereby the circuit thereto is opened upon the opening of the first combustion responsive switch. 8. In combination a fuel controller, a timed thermal safety switch and electrical heating element therefor, first and second combustion responsive switches, a room thermostat. a circuit including the thermostat, safety switch and its 16 electrical heating element and the first combustion responsive switch, a shunt circuit for said electrical heating element and first combustion responsive switch controlled by the second combustion responsive switch, means controlled 20 by said circuits for causing the fuel controller to supply fuel to a combustion chamber when said circuits are energized in their normal sequence, and means by which the first and second combustion controlled switch are overlappingly controlled to close the second and then open the first upon establishment of combustion, and nonoverlappingly controlled to open the second and after a timed period to close the first upon cessation of combustion, whereby the electrical heating element is operatively de-energized upon closure of the second combustion responsive switch and whereby the circuit thereto is opened upon opening of the first combustion responsive switch.

ARTHUR F. ERICKSON.

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