US2705045A - Combined gas and oil burner control system - Google Patents

Description

Mmmh 29, 1955 w. A. RAY 2,705,045

COMBINED GAS AND OIL BURNER CONTROL SYSTEM Filed Dec. 10. 1951 OIL-FLAME WEE.

on. 2 53 Bunwtof,

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attorney United States Patent COMBINED GAS AND OIL BURNER CONTROL SYSTEM William A. Ray, North Hollywood, Calif., assignor to General Controls Co., Glendale, Calif., a corporation of California Application December 10, 1951, Serial No. 260,893

4 Claims. (Cl. 158-11) The invention relates to heaters having means for burning either gas fuel or oil fuel as desired, or as may be necessitated because of shortage of either fuel; an object being to provide an electrical control system for such a heater whereby the change-over from one fuel to the other can be accomplished merely by manipulation of a selector switch.

Another object is the provision, in a control system of the character described in the preceding paragraph, of means for ensuring turn-off of the apparatus associated with the fuel previously in use before the apparatus associated with the other fuel can be put into operation, as well as for preventing operation of the other apparatus unless or until its particular safety requirements have been established.

For full understanding of the invention, and further 1 appreciation of its objects and advantages, reference is to be had to the following detailed description and accompanying drawing, and to the appended claims.

The single figure of the drawing is a schematic view of a burner control system embodying principles of the invention.

In the drawing, the letter B indicates a conventional thermostat comprising a bimetallic arm 11 fixed at one end and carrying at its other end an electrical contact 12 cooperable with a fixed contact 13.

The letter C indicates an electromagnetic relay comprising a core 14 and energizing coil 15; the relay being of the A. C. type and including a shading coil 16. Arranged for attraction toward the core when the same is energized is a series of five contact-forming armatures 17 which cooperate with fixed contacts, shown as arrow heads, to form switches C-1, C2, C3, C-4 and 0-5, the armatures 17 being gravity-biased to their inclined positions, as shown, wherein the relay-switches are open.

The letter D indicates a switching device of the manual-reset trip-free type. This device comprises a metallic bell-crank 18 pivotally mounted on an insulating base 19 and having at its upper end a contact 20 cooperable with another contact 21 carried on the crooked upper end of a resilient metallic arm 22 secured at its lower end to base 19, arm 22 being so flexed that contact 21 is in firm engagement with contact 20 when the bellcrank 18 is in the position shown. The bell-crank is biased by a compression spring 23 for clockwise rocking and, as shown, is latched, or restrained from such movement, by a bimetallic arm 24 fixed at its upper end and arranged so that its movable bottom end is engaged by the horizontal arm of the bell-crank near its tip. The bimetallic arm is so constructed that, when heated by current in an encircling heating-coil 25, it warps in the di rection of the arrow to release the bell-crank and thereby etfect opening of the contacts 20-21, the device D remaining in that condition (regardless of cooling of the bimetallic arm) until the device is reset by manual pressure on a button 26, fastened to arm 22, whose inner end engages the bell-crank (as arm 22 is flexed) and returns the bell-crank to its latched position, contacts 2021 reengaging when the button is released.

The letter E indicates a time-delay switching means comprising a bimetallic arm 27 fixed at its upper end and carrying on its lower end a pair of contact elements 28 and 29 separated by insulating material 30 and cooperable with fixed contacts, shown as arrow heads, to form switches E-l, E2 and E-S. The bimetallic arm 27 is arranged so that at room temperature the switches E-l and E-2 are closed and switch E-3 open, the arm warp- 2,705,045 Patented Mar. 29, 1955 ing in the direction of the arrow when heated by current in an encircling heating coil 31 to eifect opening of switches E-l and E2 and closing of switch E-3. The arrangement is such that during heating and during subsequent cooling the bimetallic arm moves slowly to elfect the time-delay switching.

The letter F indicates an electromagnetic switching system comprising a core 32, energizing coil 33, and cooperating armature 34. The armature forms a contact arm and cooperates with fixed contacts, indicated by arrow heads, to form switches F-l and F-2. Armature 34 is biased by a tension spring 35 so that switch F-l, only, is normally closed, and is attractable toward core 32 to effect opening of switch F-l and closing of switch F-Z when the core is energized by current. in coil 33. This coil is connected by wires 36 to the output of an electronic or magnetic amplifier, indicated by the legend, which, it is to be assumed, includes its own source of electrical operating energy.

Operation of the device or system F is controlled by one or the other of a pair of combustion responsive devices 37 and 38 which are connected to the input of the amplifier by wires 39 and 40 respectively, and by a common wire 41 through switching means to be described. The device 37 may be of the type shown in my copending application Serial No. 247,811, filed September 22, 1951, now Patent No. 2,677,711, and is adapted to be subjected to radiation produced by the flame of an oil burner. The other device 38 may be of the type shown in my copending application Serial No. 111,197, filed August 19, 1949, now Patent No. 2,675,416, and is adapted to be immersed in a pilot-burner gas flame. These devices are of the thermo-electric generating type and each is constructed so that it responds rapidly to eifect, through the amplifier, pull-in of armature 34 in less than 5 seconds after establishment of combustion, and drop-out of the armature in less than 10 seconds after cessation of the combustion. The particular combustion responsive devices described are not essential to the present invention and other means, such as of the photoelectric type, may be substituted; furthermore, a single combustion responsive device could be employed in place of the sepa rate devices if its response to the combustion produced both by oil and by gas were satisfactory.

The combustion-responsive devices: 37-38, while shown for the sake of clarity adjacent the combustionsafety device or system F, are to be assumed to be associated with the heating apparatus shown schematically at the lower left of the drawing. This apparatus comprises a main burner 42 to which fuel gas is supplied from a conduit 43 through an electrically operated valve 44, a pilot burner 45 for igniting the main burner (and to the flame of which pilot burner the device 38 responds) being connected to the supply conduit through a supplemental electrically-operated valve 46. For igniting the pilot burner there is an electrical device 47 of the hotwire type shown connected to a step-down transformer 48. The heating apparatus also comprises an oil burner 49 of conventional construction and including an electrically-driven blower. For igniting the oil there are sparking electrodes 50 connected to a high-voltage transformer 51, and for controlling supply of oil to this burner there is an electrically operated valve 52. This valve is shown electrically connected, by a link 53, in common with the oil burner; however, in the event that the oil burner is also adapted for burning gas, the link 53 is opened and the valve 52 connected for independent operation. Each of the valves 44, 46 and 52 is of the normally-closed type. While, for the sake of clarity, the gas and oil burners are shown as being separate, they could be combined as a single unit for the purpose of the present invention.

Shown at the lower right of the drawng is a manuallyoperable selector switch generally indicated by the numeral and comprising a shaft 61 which carries a plurality of cams 62, 63, 64 and 65 cooperable with vertical contact arms. At the top of the individual ones of these contact arms are characters S1, 8-2, 8-3, 8-4, 8-5, 8-6, 8-7 and 8-8 which indicate the switches formed by the arms and the respective adjacent fixed contacts. For rotating the cam-shaft 61 there is a handle 66 whose pointed upper end cooperates with indicia Oil, Off, and Gas to indicate the selected fuel-burning condition of the system. This handle is connected to shaft 61 through a retarding mechanism 67 whose purpose is to prevent very rapid actuation of the cam-shaft from one controlling position to the other regardless of how rapidly the handle 66 is turned, the retarding mechanism 67 being of conventional construction and comprising, for example, lost-motion and dash-pot means to effect the desired delay of a few seconds. It is to be observed that cam 62 is doublelobed so that switch Sl is closed when the handle is turned to either Oil or Gas; while the other cams 63, 64 and 65 are single-lobed so that switches S3, S7 and S-4 (as well as Sl) are closed for burning oil, and S2, S8, S6 and S (and Sl) closed for gas. The arms of switches S-5 and S-6 are interconnected for concurrent actuation by an insulator 68. All of the selector switches are open when the handle is in its Off position as shown.

The system is assumed to be connected to the A. C. service indicated by the symbol at the extreme upper left of 'the drawing, and from which supply wires 69 lead to the now-open relay switches C-1 and C-2. Connected directly to the supply wires 69 is the primary of a stepdown transformer 70 for energizing circuit means normally controlled by the thermostat B. This circuit means can be traced as follows: wire 71 connecting the lower terminal of the secondary 72 of transformer 70 to the coil of relay C, wire 73 connecting the relay coil to selector switch Sl, wire 74 connecting switch Sl through bell-crank 18 to contact of the trip-free device D, wire 75 connecting contact 21 of device D through arm 22 to the contact arm 34 of switching device F, wire 76 connecting contact F1 to the heating coil of device D, wire 77 connecting coil 25 to contact element 28 of timer E, wire 78 connecting timer switch 15-1 to the fixed contact 13 of thermostat B, and wire 79 connecting contact 12 of the thermostat through the bimetallic arm to the top terminal of transformer secondary 72.

Assuming, in connection with the circuit just traced, that the selector switch has been turned to either one of its fuel-burning positions so that switch S-1 is closed, and that switches 2021, F-1 and E1 also are closed as shown, current will flow in the circuit upon closing of the thermostat in response to demand for operation of the heating apparatus shown at the lower left of the drawing. The resultant energization of relay C effects closing of its various switches so that one of the supply wires 69 is connected through switch 0-1 to a wire 80 to which is permanently connected, as shown, one lead of each of the electric devices associated with the gas and oil burners, namely, oil burner 49, fuel- supply valves 44, 46 and 52, and ignition transformers 48 and 51. The other of the supply wires 69 is conneceted through switch C-2 to a wire 81 which leads to selector switches S4 and SS in common, as well as to a wire 82 which leads through timer switch E-2 (closed) and another wire 83 to the selector switches S-7 and S8 in common.

Switches S4 and S-7, closed when the selector switch is in oil-burning position, lead respectively through wires 84 and 85 to the oil burner 49 and its fuel-supply valve 52 in common, and to the ignition transformer 51, so that upon closing of relay C operation of the oil burner is initiated if the selector switch is in a corresponding position.

Switches S5 and S-8, closed when the selector switch is in gas-burning position, lead respectively through wires 86 and 87 to the pilot-burner (or supplemental) gassupply valve 46, and to the ignition transformer 48, so that upon closing of relay C operation of the pilot gas burner is initiated if the selector switch is in a corresponding position.

Energization of relay C also effects closing of switch 05, one side of which is connected by a wire 88 to the wire 78; the other side of switch C-5 being connected through a wire 89, timer heating-coil 31, and wire 90 to the switch F-2. However, when, and for at least a brief period after, relay C closes, the combustion safety device F is unenergized so that the switch F2 is open and timer heating-coil 31 remains unenergized upon closing of relay C.

The combustion responsive devices 37 and 38 are connected respectively by wires 91 and 92 to one side of the selector switches S3 and S-6, the other sides of these switches being connected in common by a wire 93 to the common wire 41 of the amplifier. The devices 37 and 38 are responsive, respectively, to flame produced by the oil burner 49 and to flame produced by the gas pilotburner 45, so that if either kind of combustion is initiated, as described above, the device F is energized and its armature 34 attracted to effect opening of switch F-l and closing of switch P4.

In the event that, due to some defect, combustion were not established within a brief period after closing of thermostat B and relay C, the current passing by way of switch F1 through the heating coil 25 of device D would effect warping of the bimetallic arm 24 and tripping of the device so that the basic control circuit means would be opened at contacts 2021, the system remaining inoperable until, after the cause of the combustion failure had been corrected, the trip-free device D were reset manually as described hereinbefore. The device D is designed to trip in, say, 15 seconds when, as described, pull-in of the combustion safety device F occurs normally in about 5 seconds.

When, in response to establishment of combustion, switch F1 is opened and switch F-2 closed, the heating coil 25 of device D is removed from the basic control circuit and is replaced therein by the heating coil 31 of timer E, the control circuit means then being traceable as follows: from the lower terminal of the transformer secondary 72 through wire 71, relay coil 15, wire 73, switch Sl, wire 74, contacts 20-21, wire 75, switch F2, wire 90, heating coil 31, wire 89, relay switch C5, wire 88, wire 78, thermostat B, and wire 79 back to the transformer.

The device F is designed so that movement of its armature 34 from one switching position to the other is through a very short distance, and occurs very quickly, so that relay C cannot become deenergized and drop-out during this switching, the fixed contact of switch C-S being resiliently mounted, as indicated at 94, so that opening of switch C5 is delayed to further ensure against the possibility of interruption of the basic control circuit when the device F is operated.

With passage of current through coil 31 the bimetallic arm of timer E warps in the direction of the arrow, the first effect of this being the opening of switch E-l which,

' however, is at present unimportant since the portion of the circuit previously controlled by switch E1 (and which included the heating coil of device D) is already open at F-l. With continued warping of the timer arm the switch 15-2 is opened to effect interruption of igniter 47 or 50. If the particular fuel being consumed is oil, the starting operation of the burner is then complete.

However, with continued heating of timer arm 27 it warps until closing of switch E3 is effected, whereupon, if the selector switch 60 is in gas-burning position, the

- electric supply wire 82 is connected through switch E-3,

wire 95, switch S2, and wire 96 to the main-burner supply valve 44 so that gas is then supplied to the main burner 42 and ignited by the flame of pilot burner 45. An important function of the timer E is to delay supply of gas to the main gas-burner until the pilot-burner flame has become stabilized with heating of the pilot-burner structure so that the possibility of the pilot flame being extinguished by rush of gas from the main burner is minimized, the arrangement being such that this delay is of the order of 3060 seconds.

Under normal circumstances, while thermostat B is closed current continues to flow through the heating coil of timer E and the energizing coil of relay C, in series, so that when the space-heating requirements are satisfied and thermostat B accordingly opens, the relay C is deenergized and drops-out to effect opening of its various switches, timer B being in warped condition so that switches E-l and 13-2 are open. Operation of the heating system cannot now be reinitiated by closing of the thermostat until the timer arm has cooled and returned to its normal position wherein switches 13-1 and E-2 are closed. The main advantage of this delay, which preferably is of the order of 60l20 seconds, is to permit escape of any unburned gases which, especially immediately after the oil burner had been in operation, might be present. It is important that electric ignition be established immediately upon supply of fuel, switch E-2, which controls energization of the igniters, therefore being shown as including a resilient portion 97 which is flexed so that this switch closes before switch E-l as the timer arm returns to normal position.

After combustion has been established and the safety device F has responsively switched the heating coil of timer E into the control circuit, if the combustion of fuel oil, or of gas at the pilot burner, were to fail or become substantially weakened (as due to incomplete combustion of fuel oil) the resultant opening of the control circuit means by switch F-2 would effect drop-out of relay C and shut-down of the system. In practice, additional safety devices, responsive to conditions such as, for example, boiler pressure, may be operatively connected in the basic control circuit.

It is to be observed that, in normal operation, current in the coil of relay C is controlled by relay switch C5 so that when this relay drops-out it cannot be reenergized until a path, independent of switch C-S, is formed for initiating current in the relay coil. Such a path is completed by the switch E-l upon return of timer E to normal position and comprises, initially, the coil of tripfree device D, this coil being replaced in the path by the coil 31 of timer B when the combustion-safety device F pulls-in, as has been described.

To obtain, through timer E, a delay period during which operation of the system cannot be reinitiated following each interruption of the basic control circuit by opening of the thermostat (or by opening of switch S1 in the movement of switch 60 away from either one of its fuel-selecting positions), the trip-free device D and the combustion-safety device F (while obviously desirable in the system as a whole) are not essential and could be eliminated, the top connection of selector switch S1 then going directly to the upper end of the timer heating-coil 31, and also to the timer contact-element 28 through a re sistor having a value approximately equal to that of coil When, to change-over the heating system for use of the alternate fuel, the selector switch 60 is moved away from the position corresponding to the fuel previously in use, the basic control circuit means is immediately interrupted by switch S-1 and relay C drops-out so that, in the event that the system had been in operation when the selector switch was moved, the supply of one fuel is stopped and the supply of the other fuel prevented until switch E-l closes at the completion of the delay period provided by timer E. And, with the thermostat closed, unless proper combustion of the other fuel is promptly established (as might be prevented by some defect in the fuel-supplying or igniting means) the system is rendered inoperative and safe by tripping of the device D after the combustion-safety device F fails to pull-in within the predetermined period. The retarding means 67, previously described, serves to prevent the possibility of operating the selector switch so quickly from one fuel-selecting position to the other that the relay C might fail to dropout.

The selector switches should be arranged so that switches S-3 and 5-6 (which control the flame responsive devices 37 and 38) open before switch S-l opens, and close before switch S-1 closes, so that in the remote event of existence of combustion when the selector switch is actuated, the device F would pull-in upon closing of switch S3 or 8-6 so that when switch S-1 subsequently closed the control circuit would be open at switch F-l and initiation of operation of the system prevented.

If a continuously burning pilot burner is employed in the system, wire 92 of the pilot-flame-responsive device 38 must be opened and reconnected through wires 98 (shown in broken lines) and the relay switches C-3 and C-4 interconnected by jumper 99. If this change were not made the device F would be energized continuously while gas fuel were in use and switch F-1 therefore continuously open, so that completion of the initial control circuit by the thermostat would be prevented. With the change described, switch F-l would be closed until relay C pulledin.

The specific embodiment of my invention herein shown and described is obviously susceptible of modification to a still further degree without departing from the spirit of the invention, and I intend therefore to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a control system for a combined gas and oil burning heater: a first and a second electrically operable means for controlling, respectively, supply of gas fuel and of oil fuel to said heater, and capable: of effecting the supply of fuel only when energized; a source of electrical energy for said fuel supplying means; a manually operable switching means including a selector switch movable into connecting relation to the individual ones of said fuel supplying means; electrically operable switching means comprising a coil and a pair of normally-open switches both actuated to closed position when said coil is energized, one of said pair of switches when closed being arranged to connect, through said selector switch, the selected one of said fuel supplying means to said source; circuit means for controlling the operation of said electrically operable switching means in accordance with the requirements for heating, said circuit means comprising, in series, said coil, the other of said pair of normallyopen switches, a thermostat responsive to heat produced by said heater, and a source of electrical energy; a circuit for temporarily shunting said other of said pair of normally-open switches so as to permit completion of said circuit means by said thermostat and thereby operation of the selected one of the fuel supplying means; and electrically operable time-delay means operatively connected to said circuit means and so controlling said shunting circuit as to render the same effective, and thereby permit said completion of said circuit means, only after a predetermined delay period following interruption of said circuit means; said manually operable switching means including means forming part of said circuit means and arranged to momentarily interrupt the circuit means upon movement of said selector switch away from either one of its connecting positions.

2. A control system as defined in claim 1 and including 1 mechanical means for retarding movement of said manually operable switching means from either one to the other of its controlling positions.

3. A control system as defined in claim 1 and wherein said electrically operable time-delay means is connected in series with the other components of said circuit means when the circuit means is energized.

4. A control system as defined in claim 1 and wherein said electrically operable time-delay means is of the thermally operable type and comprises an electric heater connected in series with the other components of said circuit means when the circuit means is energized.

References Cited in the file of this patent UNITED STATES PATENTS 1,786,901 Doherty Dec. 30, 1930 1,793,011 Ray Feb. 17, 1931 1,840,744 Scott Jan. 12, 1932 1,885,478 Powers Nov. 1, 1932 2,062,605 Peters Dec. 1, 1936 2,168,680 Nordgren Aug. 8, 1939 2,170,497 Gille Aug. 22, 1939 2,282,197 Maynard May 5, 1942 2,369,530 Bulger Feb. 13, 1945 2,486,612 Pratt Nov. 1, 1949 2,538,222 Wilson Jan. 16, 1951 2,552,302 Young May 8, 1951 2,655,208 Outterson Oct. 13, 1953

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