US2185317A

US2185317A - Control apparatus

Info

Publication number: US2185317A
Application number: US163054A
Authority: US
Inventors: Warren H F Schmieding
Original assignee: Ranco Inc
Current assignee: Robertshaw US Holding Corp
Priority date: 1937-09-09
Filing date: 1937-09-09
Publication date: 1940-01-02
Anticipated expiration: 1957-01-02

Description

1940- w. H. F. SCHMIEDING 2,135,317

CONTROL APPARATUS 7 Filed Sept. 9, 1937 2 Sheets-Sheet 1 1940; w. H. F. SCHMIEDING 1 common Arrm'rus v Filed Sept. 9, 19:57 '2 Sheets-Sheet 2 Patented Jan. 2, 1940 UNITED STATES CONTROL APPARATUS Warren H. F. Schmieding, Columbus, Ohio, as-

signor to Ranco Incorporated, Columbus, Ohio, a corporation of Ohio Application September 9, 1937, Serial No. 163,054

6 Claims.

The invention relates to control systems and more particularly to control systems and apparatus for controlling fluid fuel burners and the like.

a One of the objects of the present invention is to provide a control system which includes an electrically operated safety mechanism which is energized continuously during the operating period of the fuel burning device and which is capable of rendering the same inoperative after a predetermined period of operation, an ignition device and switch therefor being also provided, said switch being operated by the safety mechanism after a predetermined period of operation of the ignition device. A combustion responsive control is utilized to prevent the safety mechanism from rendering the system inoperative in the event that combustion is established and maintained.

It is a further object of the invention to prom vide a time delay switch for the system which causes a delay between successive energizations of the system, said time delay switch being operated to open circuit position by the electrically operated safety mechanism prior to the operation of the ignition switch and being maintained in such position during the normal operating perind of the system, the time delay switch being disposed so as to be closed by the safety mechanism subsequent to the closure of the ignition switch to assure that the ignition device is in readiness for operation before energization of the system.

In order to carry out the above object it is a further object to provide a holding switch and circuit therefor to shunt the time delay switch,

the holding switch and circuit maintaining the control system operative after the time delay switch has been opened by the electrically heat- M, ed safety mechanism. Upon deenergization of the system, the holding circuit is broken and the system cannot be reenergized until the safety mechanism closes the time delay switch to reestablish the starting circuit.

It is a still further object of my invention to provide means rendered effective upon deenergization of the system for preventing the electrically operated safety mechanism from operating, when the combustion responsive means is w ineffective."

Other and further objects and advantages will be apparent from the following description, reference being had to the accompanying drawings wherein preferred forms of embodiment of the 55 present invention are clearly shown.

In the drawings:

Fig. l is a schematic wiring diagram of one form of control system utilizing a two wire thermostat, the system being shown in operative position, and,

Fig. 2 is a schematic wiring diagram of an-- other form of control system utilizing a three Wire thermostat, and including an ambient temperature compensator in connection with the safety mechanism.

Referring to Fig. 1, one form of the present invention is shown wherein the system is utilized to control a fuel burning device, for example, an oil burner. A transformer relay is utilized to supply low voltage current to the secondary cirl5 cult of the system and also to function as a relay for actuating various control switches. A room thermostat 22 controls the normal operation of the system to cause the fuel burning device to be started and stopped when there is a demand for 20 heat and when that demand has been satisfied. The thermostat 22 is in series with a secondary coil 24 of the transformer relay 20. When there is a demand for heat, for example, when the temperature, of the enclosure to be heated, falls below a predetermined figure, room thermostat 22 closes to complete the secondary circuit, which includes secondary coil 24, wire 26, contacts 28 and 29 of the time delay switch 30, pigtail 32, heating coil 34, wire 36, thermostat 22 and wire 38. Completion of the secondary circuit causes the transformer relay 20 to draw armature 40 upwardly to close switches 42 and M. Closure of switch 42 completes the motor and ignition circuit to start the system in operation, 4

which circuit will be traced hereinafter. Closure of switch 44 causes a shunt secondary circuit to be established, around the time delay switch 30, including secondary coil 24, wire 26, wire 46, switch 44, wire 48, heating coil 34, wire 36, thermostat 22 and wire 38.

Normally the primary coil 52 of transformer relay 20 is continuously energized. The circuit therefor is traced as follows: wire 50, coil 52, wire 66, safety switch 64 and wire 62. When the armature is attracted, due to the completion of the secondary circuit, the motor and ignition circuits are completed. The motor circuit includes, wires and 54, motor 55, wire 10, switch 42, wires 68 and 55, safety switch 64 and wire 62. The motor 56, in an oil burning system, is utilized for pumping in the oil and air for the burner, it being understood that this mixture is proportioned so that it will be ignited by the spark from spaced electrodes of the ignition device. The ignition circuit includes

wires

68, 64 and 58, ignition primary coil 68, wire I8, ignition switch I4, wires I2 and I8, switch 42,

wires

68 and 66, switch 64 and wire 62. It will be understood that the ignition system includes the usual high voltage secondary coil and electrodes. It'

will be apparent that current for the primary coil 52 of the transformer relay, the motor and the ignition must flow through the safety switch contact 64.

Thus when switch 42 is closed, by action of the transformer relay 28, both the motor 56 and the ignition primary 68 are energized, providing, of course, the safety switch 64 is in closed circuit position. It will be noted that the motor and ignition primary are preferably in parallel and, therefore, are energized substantially simultaneously.

Completion of the secondary circuit, due to closure of thermostat 22, causes current to flow continuously through heating coil 34 as long as the circuit is energized. Coil 34 is disposed in intimate heat transfer relation with a U shaped bimetallic strip or thermostat I8. Upon initial closure of the circuit, the thermostat I8 is in such position that the associated contacts 28 and 29 of time delay switch 38 are in closed circuit position. This allows the secondary circuit to be completed, through the time delay switch 38, which causes the relay 28 to pick up its armature 48. Subsequent and continued heating of bimetal I8 causes the same to deflect upwardly to open the time delay switch 38, however, the secondary circuit is now maintained operative due to the prior closure of the holding switch 44 which is closed by the attraction of armature 48.

The thermostat 18 carries a push rod 88 on the upper or free end thereof, which rod has a shouldered portion 82. The shoulder 82 is disposed to engage a pivotally mounted lever 84 which upon upward movement thereof actuates the ignition switch I4 to open circuit position. Thus after the bimetal 18 deflects upwardly, due to continued heating of coil 34, the ignition switch I4 is opened, to render the ignition device inoperative after a predetermined period of operation thereof and subsequent to the opening of the time delay switch 38. a

The thermostat I8 is also utilized to operate the safety switch 64. The free end of bimetal I8 abuts the upper end of an operating lever 86 of the safety switch 64, which lever is biased to open circuit position of the switch by suitable means, for example, a spring 88. As long as the end of bimetal I8 abuts the upper end of lever 86, the safety switch is maintained closed. It is apparent that if the fuel supply is previously ignited it is desirable to maintain the safety switch closed and thereby permit continued operation of the system. In order to maintain the safety switch closed during normal operation of the system, a combustion responsive control 98 is provided, of any conventional type, for example, a bimetallic thermostat. The control 98 is adapted to operate a latch lever 92 which is normally against the stop 94 when the combustion chamber is cold, and which lever 92 is displaced to a position against stop 96 after combustion has been established. The latch lever 92 is disposed to engage the moving end of a pivotally mounted lever 98 which is abutted by the upper end of push rod 88. Thus as thermostat I8 deflects upwardly, the push rod 88 causes lever 98 to move upwardly and, if combustion is established, to engage the latch lever 92, which action limits further I8.

Any suitable well known type of slip clutch is disposed between the bimetal, of combustion control 98, and latch 92 so that the latch 92 is moved in either direction in response to slight rise or lowering of the temperature of the combustion control.

Since under normal conditions the combustion control 98 acts more rapidly than does bimetal 18, the latch lever 92 is in position to limit upward movement of lever 98 prior to the time that the lever is displaced to engage the latch lever 92. A similar condition is present upon deupward movement of the bimetal 'energization of the system, the combustion control moving the lever 92 out of engagement with lever 98 before the bimetal I8 has cooled sufliciently to preclude the possibility of operation of the safety switch 64.

In order to prevent the bimetal I8 from opening the safety switch 64, under deenergization of the system, a rod I88 is provided on lever 98 which is disposed in the path of the armature 48. When the latter is released and drops downwardly, due to deenergization of the relay 28, the armature 48 engages rod I88 and thereby functions to prevent release of the safety switch upon deenergization of the system although the combustion control 98 has cooled sufliciently to release latch lever 92 from its engagement with lever 98.

Upon failure of combustion during an operating period of the system the control 98 moves latch lever 92 out of engagement with lever 98 to allow the thermostat I8 to move upwardly to release the safety switch 64. This action is substantially simultaneous with the release of lever 98, since the coil 34 is continuously energized during operating periods of the fuel burner and causes thermostat I8 to be heated above the temperature necessary to operate the safety device 64. Upon release of the safety switch, a manual resetting operation is necessary before the system can be reenergized.

When a power failure occurs, even if the same is momentary, armature 48 drops downwardly to open the motor switch 42 and also open the holding switch 44. Under this condition. the system cannot be reenergized until bimetal 18 cools sufiiciently to reengage contacts 28 and 29 of the time delay switch 38, to reestablish the secondary starting circuit. It should be noted that the ignition switch I4 is always closed prior to the closure of the time delay switch, which assures that the ignition device will be in readiness to function upon reenergization of the system.

If the fuel fails to ignite upon initial energization of the system, the bimetal I8 continues to move upwardly until the safety switch 64 is released to open. In this case the combustion control 98 is non-operative to displace the latch lever 92.

Referring to Fig. 2, a similar system is shown except that a three wire thermostat is utilized. Since the high voltage circuits, which include the motor and ignition devices, are similar to the high voltage circuit explained in Fig. l, a detailed explanation thereof will be omitted.

The starting secondary circuit may be traced as follows: secondary coil 24, wire I84, heating coil I86, which is connected to the bimetal I88, contacts I89 and- H8 of time delay switch II 2, wire II4, contacts I I6 and I I8 of thermostat I82 and wire I28. Upon closure of the secondary circuit, the transformer relay 28 is energized to Mil till

fih

draw armature 40 upwardly and close the high voltage circuit switch 42, and the holding switch 44. The closure of switch 44 completes the secondary holding circuit, which may be traced as follows: secondary 24, wire I04, heating coil I00, bimetal I08, wire I22, switch 44, wire I24, bimetal I26, contacts I20 and H8 of thermostat I02 and wire I20. After this secondary holding circuit is completed, due to the energization of the transformer relay 20, the time delay switch H2 may be opened without deenergizing the circuit, which is now maintained through switch 44.

The function and operation of the various switches included in the aforementioned secondary circuits of this system is similar to that described in connection with Fig. 1.

It will be noted that in order to start the system by energizing the secondary circuit, it is necessary to have all three contacts of thermostat I02 in engagement. However, upon closure of switch 44 it is only necessary to have contacts lit and I28 in engagement. This type of thermostat is well known and, therefore, further explanation of the same is unnecessary.

In the present embodiment an ambient temperature compensator is provided for the bimetal I00, which actuates the safety switch 64. The compensator consists of a U shaped bimetal I30, similar in shape to bimetal I08 and fixedly mounted at one end thereof as at I32. The other end of bimetal I30 is resiliently connected to bimetal IOB by a double headed rivet I34, which passes loosely through both bimetals, and a spring I36 which is disposed around the rivet I34, and compressed between the bimetals I08 and I30. When room temperature is increased, for example, bimetal I08 deflects upwardly while bimetal I30, which is formed in the opposite direction, deflects downwardly the same or a computed distance to translatably displace bimetal I08 so that the abutting end thereof is substantially unmoved with respect to its position relative to the end of the lever 86. In this manner the bimetal I08 is always maintained in substantially the same position regardless of variations in ambient temperature and thus, the operating times of the switches operated thereby are maintained substantially constant regardless of variations in ambient temperature.

In both embodiments the electrically heated thermostat operates the time delay switch, the ignition switch and the safety switch in the order named and upon cooling, reverses the aforementioned sequence for closing the ignition switch and the time delay switch.

From the foregoing it will be noted that the present invention provides a thermostatically operated safety switch that is in constant readiness to operate upon failure of combustion. The heating coil therefor is continuously energized during operating periods of the fuel burning device so that the thermostatic element is constantly heated and under a small amount of stress when latched by the combustion control. This stress factor permits substantially simultaneous release of the safety switch when the combustion control unlatches the thermostatic member due to failure of combustion. The present invention also provides latching means operative upon deenergization of the system to latch or hold the thermostatic member from releasing the safety switch. This, as previously explained, is necessary since the combustion control unlatches the thermostatic member before it has cooled to a temperature sufficiently low to assure that it will not release the safety switch.

It is well known, that at times during the starting of an oil burner, the fuel mixture does not burn steadily and at times the fire is extinguished, but if a spark is provided, the mixture will readily reignite and the burner would continue to function properly. In the present invention. the ignition circuit is maintained for a period of ninety to one hundred and twenty seconds, which period is sufficient to overlap the unsteady starting period of the burner. If the mixture does not stay ignited during the selected period of between ninety and one hundred and twenty seconds, some adjustment must be made and in that event the safety switch functions substantially immediately to deenergize all the circuits thus insuring safety.

While the forms of embodiment of the present invention as herein disclosed constitutes preferred forms, it is to be understood that other forms might be adapted, all coming within the scope of the claims which follow:

I claim:

1. A control system for a fuel burning device comprising in combination, electrically operated means for controlling the fuel burning device; a safety switch operable to render the fuel burning device inoperative; electrically heated thermal means operable after a predetermined period of heating to operate the safety switch, said thermal means being heated continuously during the operating period of the fuel burning device, means for preventing operation of the safety switch by the thermal means, said last means being rendered efiective upon the establishment of combustion and prior to the operation of the safety switch by the thermal means; and means rendered effective upon deenergization of the electrically operated means for preventing operation of the safety switch by the thermal means when said combustion responsive means is ineffective.

2. A control system for a fuel burning device comprising in combination, electrically operated means for controlling the fuel burning device; a safety switch operable to render the fuel burning device inoperative; an ignition device for igniting the fuel; an ignition switch for controlling the operation of said ignition device; electrically heated thermal means operable after a predetermined period of heating to operate first the ignition switch and then the safety switch, said thermal means being heated continuously during the operating period of the fuel burning device; means for preventing operation of the safety switch by the thermal means, said last means being rendered effective upon the establishment of combustion and prior to the operation of the safety switch by the thermal means; and means rendered effective upon deenergization of the electrically operated means for preventing operation of the safety switch by the thermal means when said combustion responsive means is ineffective. 5

3. A control system for a fuel burning device comprising in combination, electrically operated means for controlling the fuel burning device; a circuit for said means; a time delay switch operable to deenergize the circuit for the electrically operated means; an ignition device for igniting the fuel; an ignition switch for controlling operation of the ignition device; a safety switch operable to render the fuel burning device inoperable; electrically heated thermal means operable after predetermined periods of heating to operate the time delay switch, the ignition switch, and the safety switch, said last means being heated continuously during the operating period of the fuel burning device; means rendered effective upon energization of the electrically operated means for nullifying the effect of the time delay switch on said circuit, whereby the electrically operated means are maintained operative; means rendered effective upon the establishment of combustion, and prior to the operation of the safety switch, for preventing operation of the safety switch by the thermal means; and means rendered effective upon deenergization of the electrically operated means for preventing operation of the safety switch by the thermal means when said combustion responsive means is ineffective.

4. A control system for a fuel burning device comprising in combination, electrically operated means for starting and stopping the fuel burning device; a safety switch operable to render the fuel burning device inoperative; means operable to actuate the safety switch after the electrically operated means is operated to start the device, and operable to actuate the safety switch for a predetermined period after the electrically operated means is operated to stop the device; means for preventing operation of the safety switch by the second mentioned means, the last mentioned means being effective upon the establishment of combustion and prior to operation of the safety switch by the second mentioned means; and means rendered effective upon stopping of the device for preventing operation of the safety switch by the second mentioned means when said combustion means is ineffective.

5. A control system for a fuel burning device comprising in combination, electrically operated means for controlling the fuel burning device; a safety switch operable to render the fuel burning device inoperative; electrically heated thermal means operable after a predetermined period of heating to operate the safety switch, said thermal means being heated during the operating period of the fuel burning device; means for preventing operation of the safety switch by the thermal means, said last means being rendered effective upon the establishment of combustion and prior to the operation of the safety switch by the thermal means; and means rendered effective upon deenergization of the electrically operated means for preventing operation of the safety switch by the thermal means when said combustion responsive means is inefiective.

6. A control system for a fuel burning device comprising in combination, electrically operated means for controlling the operation of the de-v vice; a control circuit for the electrically operated means, said circuit including a delay switch and a control switch; a circuit forming a shunt around the delay switch, said shunt circuit including switching means operated in response to energization of the control circuit for completing the shunt circuit when the electrically operated means is energized and for opening the shunt circuit when the electrically operated means is deenergized; an ignition device for igniting the fuel; an ignition switch for controlling operationof the ignition device; a safety switch operable to render the fuel burning device inoperable; a third means, operable after predetermined periods after energization of the elec trically operated means for opening the delay switch, the ignition switch and the safety switch and operable upon deenergization of the burner device to first close the ignition switch and then the delay switch; means responsive to combustion for preventing operation of the safety switch; said third means being operable to actuate the safety switch for a predetermined period after the electrically operated means is operated to stop the device; and means rendered effective upon stopping of the device by the electrically operated means for preventing operation of the safety switch by the third mentioned means.

WARREN H. F. SCHMIEDING.