US2358432A - Burner control - Google Patents

Description

Sept. 19, 1944.

w, F. WOLFNER, 2D

BURNER CONTROL Filed Oct. 16, 1941 '2 Sheets-Sheet 1 has rasel 5 "Sept. 19, 1944. F. W LFNER, 2D 2,358,432

BURNER CONTROL Filed Oct. 16, 1941 2 Sheets-Sheet 2 Patented Sept. 19, 1944 UNITED STATES PATENT OFFICE 2,358,432 v BURNER coNi'aoL l William F. Wolfner, H, Methuen,Ma'ss., assignor to Photoswitch Incorporated, Cambridge, Man, a corporation of Massachusetts Application October 16, 1941, Serial No. 415,257 10 Claims. (Cl. 122-504) This invention relates to the control of burntype with an additional contact whose connection ers, especially of the type used with home heating will be described below. plants remotely controlled by a thermostat and The electric equipment. preferably mounted provided with automatic supervisory equipment y within a single housing together with the photowhich permits operation of the plant with a l tube P, as shownin Figs. 3 and 4, is supplied from absolute certainty and safety and independently l potentialsapp p l f e V ri s mpoof any apparatus mounted on boiler or flue. nents of the circuit.

Other objects are to provide a burner control An electronic tube T for example of the cold which reacts instantaneously to conditions which cathode type with cathode k, anode a and startit is to supervise, to provide a control suited for ing anode a is nne t d etw en transf m r direct cooperation in a simple and therefore reli- 1 terminal 0 and tap III; in series in the cathode able manner with other supervisory equipment connection are starting contacts ii and I2 of such as'a water level gauge; and to provide a comth rm tat S nd in e es n he anode nn cplete burner control which is an integral part of tion is tube relay ma net B controlling normally the heating system and can be installed nd open shunting switch BI and normally closed tested with a minimum of effort. ignition switch B2, which latter is inserted in These and other objects and aspects of the inseries to i only if intermittent ignition control is venticn will be apparent from the following dep d scription of a practical embodiment illustrating An actuating magnet A or other suitable relay its genus. The description refers to drawings, in means is connected to cathode is and controls two which normally open switches, namely, motor switch Al Fig. 1 is a schematical representation of an oil and heater holding or shunting switch A2. Magburner equipment according to the invention; net A is preferably so dimensioned that it will Fig. 2 is a simplified diagram of the circuit of operate its switches only if supplied with the Fig.1; proper line voltage. Switches A2 andLBI pro- Fig. 3 is a top elevation of the control apparavide a holding circuit for magnet A when contus according to Fig. 1; and tacts Cl and C2 are opened.

Fig. 4 is a side elevation of the apparatus ac- T0 tap I is connected 8 thermal Switch w cording to Fig, 3, with part; of t 1 burner and whose mechanical construction will be explained the apparatu housingm vert1ca1sect1 n in detail below and which has two bimetallic Th b n indicated at b of p 1 is equipped temperature responsive actuator elements 2|, 22, with an n burner h of the customary type and a which are associated with resistances constitutcombustion initiating and sustaining means such mg mam heater winding C providing 5 priming as the usual electric ignition device i and electro- 3:2; g zs ig g izgg i' g g ggg o A h t P gg g g is 5 3 3232 ggg s fgg ggg switches Cl, C2 and Di herein also referred to as priming and safety switches, respectively in detail in Figs. 3 and 4, in such a manner that The mam heater or priming switches CI and it receives radiation from the heating flame when The boiler may be equipped with a water level heats up faster than C.

Stri 22, which moves erpendicularl to 2i level is above the probe. p p y (normally to the drawing surface of Figs. 1 and The heater equipment further comprises a tem- 4) controls afety switch DL which Opens as perature detecting device such as thermostat S of soon as insulation lug :4 h passed spring 25 of usual d i cl0slng a circuit (Fig- 2) en s switch Di in its movement lateral to that spring.

mbient temperature reaches a certain value. The heater strip 22 is then retained in deflected even if tending to return to The thermostat may be of the so-called three wire position by spring 25,

keeping them apart, whereupon strip 22 is permitted to snap back into normal unheated position. "Release of button 30 then effects reclosure of switch Dlthrough contact of springs 25 and 26.

As shown in Fig. 2, switch DI, CI, C2, heater D, heater C and magnet A are connected in series between tap I and cathode k, which may be grounded, whereas heater switch A2 is connected in parallel to switch Cl and shunting switch Bl in parallel to switch C2.

If a liquid level proble L is used, it is connected between cathode is and the thermal switch W through primary ll of a booster transformer 40, whose secondary 42 is connected to tap II of the main transformer. It will be noted that, due to this arrangement, it is possible to comply with the requirement that probes of this type carry only low voltage.

The phototube P is with its anode a connected to starting electrode g of tube T and with its cathode is to tap III or, if a level probe is used, the booster secondary 42. In the latter case, connection 45 is opened whereas, if the level probe is not used, connections 46 and 41 are opened, with 45 closed. A condenser 50 is connected between electrode 9 and cathode k.

Figs. 3 and 4 show the mechanical arrangement of the above-described circuit. The thermal switch W is shown in Fig. 4, which indicates that push button bar 30 has, two abutments 52 whose distance is greater than that of switch springs 25, 26 and which control switches Cl, C2 and heater strip 22, as above described. Figs. 3

and 4 further indicate that, according to the .dnvention, the phototube T is mounted within a hood 55 fastened with clips 56 to base plate 51. This construction permits removal of housing 58' from base plate 51 and ,bumer casting 59 with-' out exposing the phototube to light in case it is desired to inspect the installation in operative condition.

Figs. 3 and 4 further indicate terminal block Bil and bushings BI, 82 for the ignition leads, as well as oil ,supply tube 63. The wiring connec tions are arranged as far as possible below base plate 51, and it will be-apparent that the herein described preferred construction is especially compact and convenient, liminating a good deal of the wireconnec'tions and separately mounted circuit elements of conventional constructions.

The above-described arrangement operates as follows:

Under normal idling conditions with the burner cold, the controlling temperature above the critical value and the water level normal, the circuit elements are conditioned as indicated in Figs. 1 and 2.

If the thermostat contacts ll, l2 are now closed either by hand or due to the controlling temperature falling below the desired level, magnet A is energized through circuit Magnet A closes switches Al and A2, starting motor and ignition through circuit lAl-m2 and lAl-i-B22, and preparing a circuit directly including heater C and excluding heater D, through I--Dl--A2BlCA--S-0 Heaters C and D are now heating up, and D being, as above described, of higher resistance than C, heats up faster than C.

The ignition being efiective, the burner flame starts and the phototube receives light from the burner flame so that its impedance is considerably lowered, which causes -the potential at the electrode g to rise above the starting value; tube T becomes conductive and magnet B is energized.

Magnet B now closes switch BI, shunting out trol tube T conducting and magnet B energized,

and with magnet A and heater C energized in the direct circuit I-DIA2Bl--C--AS--O.

Itwill be observed that magnet A and hence motor 1n and ignition device 1. remain energized until switch C2 opens, regardless of the fact whether or not the flame starts and causes switch Bl to be closed, and whether switch Cl, at that time already shunted by A2,.has opened. This arrangement assures a proper cold priming period for starting when heaters C and D are cold.

If thermostat shut-oil? is effected by the rise' of room temperature during normal operation or the burner, the opening of contacts H, l2 'deenergizes magnet A and stops the motor, and darkening of the phototube restores the entire circuit to normal idling condition.

If a person should raise the thermostat setting immediately after normal thermostat shut-oft, the burner will not restart immediately but pause for a scavenging period, due to the fact that heater C has to cool down before switches C! and C2 are again closed in readiness for starting through energization of magnet A. Similarly, if the burner is normally running and a personshuts it off momentarily with the thermostat, immediately raising the thermostat setting again, the scavenging period will always be completed before starting is permitted, for the above reasons.

If ignition failure should occur, that is, if the burner flame should fail to start although the ignition device is effective, the photocell will fail to render tube T conductive and magnet B will not be energized, so that Bl fails to shunt out heater D. Heater strip 22, after a predeterm ned time, will permit switch DI to open, which deenergizes the circuit of magnet A and opens switch AI, stopping motor and ignition. Both heater coils C and D will now cool oil, since their circuits are interrupted at Dl; switches Ci and C2 will stay closed, but switch D! will remain open due to the above-described mechanical correlation of heater strip 22 and switch spring 25. Therefore all elements excepting Di are in position for starting, so that the burner can now be restarted by releasing starter button 38 after it has been depressed. It will be noted that the burner cannot be started or kept running by keeping button 30 in depressed position; only release of the button 30 initiates the starting cycle.

If flame failure should occur, that is, if the flame should become extinguished after having been properly ignited, phototube P becomes dark, magnet B is deenergized and switch Bi opens. Switch B2, if provided, closes. Switch Bl opens the energizing circuit of magnet A and 5 coil C under "normal operating conditions. namely, IDl-A2BlCAS-O and magnet A releases switches Al and A2; switch Al stops the motor. Heater coil C cools and, after a predetermined time, closes first switch C2 and then switch Ci, due to, the above-described construction of these switches. During a scavenging period which terminates when switch ql closes, starting is impossible since, although C2 is closed, A2 has opened with magnet A becoming deenergized. Switch DI being still closed since -D was cool because C2 was open, and assuming that H and I! remain closed, magnet A becomes aga n energized and starts ignition and motor so that normal operation may begin, provided proper combustion is possible; if the fuel should fail to ignite, the condition explained above under "ignition failure prevails and the circuit will perform the operations described under that heading/ It will be observed that in this case also a priming period is provided, which lasts from the end of the scavenging period or the energization of A until C2 opens.

If power supply failure should occur, relay A becomes deenergized for lack of potential supplied thereto vand the motor will stop. Heater coil C becomes likewise deenergized and switches Cl and C2 will close after a predetermined time corresponding to the cooling period of strip C. Closing of switches C l and C2 reenergizes coils D and C and magnet A and normal operation will begin provided that power supply-has been resumed during the cooling of strip C.

In case of oil failure/extinction of the flame causes magnet B to become deenergized, whereupon magnet A also becomes deenergized, A1 and A2 open, C cools, C2 closes, and Cl closes, terminating the scavenging period. With the closing of Cl, heater D begins to deflect and in due time permits safety switch Di to open, with all other elements in position for starting as described above with reference to ignition failure.

'In case of parts failure, that is, if any one of the electrc current elementsof the apparatus should become defective, the circuit energizing magnet A becomes necessarily deenergized and the burner is shut down or prevented from starting; it will now be apparent that this response is inherent in the circuit according to theinventlon, since the elements sustaining normal operation, namely, magnets A and B and heater coils C and D, are energized during, and have to be in good condition for such operation, so that any failure affecting these essential elements will stop operation. I

If water failure should occur, that is, if contacts 43 44 (Fig. 2) should be interrupted due to the water level falling below probe L, the circuit a groundIDi-4l-L-ground-O is inter- 65 rupted and the potential difference supplied by secondary 42, retaining electrode 9 at starting/ level, is eliminated. The windings of trans former 40 are so arranged that the voltage across secondary 42 lifts the potential of electrode g 7 above the starting value if phototube P is illuminated and the water level above probe 1, but that electrode 9 goes below the starting poten- Cir ' 'tial level if either phototube P becomes dark or the water level falls below the probe. There- 75 fore tube T becomes non-conductive and magnet B deenergized if water. failure occurs, switch Bl opens, and the circuit operates as described above under the heading "flame failure."

It will now be understood that operation without water level supervision can be provided by connecting the phototube P directly to tap HI through jumper 45, the booster arrangement being rendered inefiective by opening jumpers 40 and 41.. The booster voltage will be so chosen that the potential level of electrode g is the same whether supplied through transformer 40 or directly from tap III; in other words, the potential difierence at secondary 42 corresponds to that between taps II and III, provided of course that, as indicated above, these values are so chosen that either darkening of the phototube or elimination of the effect .of primary 4! brings the potential of the auxiliary anode 9 below the value which renders the tube conductive.

It will be evident that hot cathode electron tubes can be used analogously if operating conditions similar to those above described are provided. The term triode" as herein used in cludes high vacuum as well as gas tubes with at least three electrodes including a control electrode.

If a so-called three-wire thermostat is used,

that is, a thermostat which has an auxiliary resistor which heats the thermostat proper independently of the room temperature, the third wire containing this resistor is provided with a normally open switch A3 controlled by magnet l A similarly to motor switch Al, as indicated in Figs. 1 and 2.

It should be understood that the present dis-l closure is for the purpose of illustration only and that this invention includes all modifications and equivalents which of the appended claims.

I claim,

1. In heating plant control apparatus of the type described, the combination of a current source. a combustion burner, means for initiating and sustaining periods of heating by said burner, and detecting means distinguishing between heating and nonheating periods of said plant, with an actuating circuit including in .direct series connection a, priming timer. a safety timer, normally closed priming switch means, said priming switch means being arranged to be opened and reclosed by said priming timer after a first predetermined period from energization and deenergization of said circuit, respectively, and a normally closed safety switch arranged to be opened-by said safety timer after a second predetermined period from said energization;

relay means for actuating said sustaining means upon 'energization of said circuit; and shunting switch means in parallel to said safety timer and said priming switch means and arranged to be closed by said detecting means upon beginning and opened upon termination of a heating period; said safety timerdeenergizing said actuating circuit by opening 'said safety switch after said second period upon failure of said dotecting means to close said s untin'g switch means, and sa d priming timer establishing said actuating circuit 'solely through said shunting switch means by opening said primin switch means and reestablishing normal condition by closing said priming switch means, after said first periods.

2. In heating plant control apparatus of the fall within the scope E type described, the combination of a current source, a combination burner, means for initiating and sustaining periods of heating by said burner, and detecting means distinguishing between heating and nonheating periods of said plant, with an actuating circuit including in direct series connection a priming timer a safety timer a normally closed priming switch a normally closed second priming switch, said priming switches being arranged to be opened and re closed by said priming timer after a first predetermined period from energization and deenergization of said circuit, respectively, with said second priming switch opening somewhat prior to and closing somewhat after said first priming switch, and a normally closed safety switch arranged to be opened by said safety timer after a, second predetermined period from said energization; relay means for actuating said sustaining means upon energization of said circuit; and shunting switch means in parallel to said safety timer and said priming switches and arranged to be closed by said detecting means upon beginning and opened upon termination of a heating period; 'said safety timer deenergizing said actuating circuit by opening said safety switch after said second period upon failure of said detecting means to close said shunting switch means, said priming timer establishing said actuating circuit solely through said shunting switch means by opening said priming switches and reestablishing normal condition by closing said priming switches after said first periods, and said delayed closing of said second priming switch securing a scavenging period upon initiation of a heating period while said priming timer is in switch opening condition.

3. In heating plant control apparatus of the type described, the combination of a current source, a combustion burner, means for initiating and sustaining periods of heating by said burner, and detecting means distinguishing between heating and nonheating periods of said plant, with an actuating circuit including in direct series connection a priming timer, a safety timer, normally closed priming switch means, said priming switch means being arranged to be opened and reclosed by said priming timer after a first predetermined period from energization and deenergization of said circuit, respectively, and a normally v,closed safety switch arranged to be opened by said safety timer after a second predetermined period from said energization; relay means for actuating said sustaining means upon energization of said circuit; and shunting switch means in parallel to said safety timer-and said priming switch means and arranged to be closed by said detecting m'eans upon beginning and opened upon termination of a heating period, said timers being so arranged that said second period is shorter than said first period when said shunting switch is open wherea closing of said source, a combustion burner, means for initiating and sustaining periods of heating by said burner, and detecting means distinguishing between heating and nonheating periods of said plant, with an actuating circuit including in direct series connection a priming timer, a safety timer, a normally closed priming switch, a normally closed second priming switch, said priming switches being arranged to be opened and reclosed by said priming timer after a first predetermined period from energization and deenergization of said circuit, respectively, with said second priming switch opening somewhat prior to and closing somewhat after said first priming switch, and a normally closed safety switch arranged to be opened by said safety timer after a second predetermined period from said energization; relay means for actuating said sustaining means upon energization of said circuit; a normally open presetting switch in parallel to said second priming switch and arranged to be closed upon said energization of the actuating circuit; and a shunting switch in parallel to said safety timer and said first priming switch and arranged to be closed by said detecting means upon beginning and opened upon termination of a heating period, the closing of said shunting switch causing deenergization of said safety timer and hence increased current supply and more rapid operation of said priming timer with shortening of said first period to less than said second period prior to the opening of said priming switches; said safety timer deenergizing said actuating circuit by opening said safety switch after said second period upon failure of said detecting means to close said shunting switch, said priming timer establishing said actuating circuit solely through said holding and shunting switches by opening said priming switches and reestablishing normal condition by closing said priming switches after said first periods, and said delayed closing of said second priming switch securing a scavenging period upon initiation of a heating period while said priming timer is in switch opening condition.

5. In heating plant control apparatus of the type described, the combination of a current source, a combustion burner, means for initiating and sustaining periods of heating by said burner, and detecting means distinguishing between heating and nonheatin periods of said plant, with an actuating circuit including in direct series connection relay means for actuating said sustaining means upon energization of said circuit, a priming timer, a safety timer, a normally closed priming switch, a normally closed second priming switch, said priming switches being arranged to be opened and reclosed by said primin timer after a first predetermined period from energization and deenergization of said circuit, respectively, with said second priming switch opening somewhat prior to and closingsomewhat after said first primin switch, and a normally closed safety switch arranged to be opened by said safety timer after a second predetermined period from said energization; a normally open holding switch in parallel to said second priming switch and arranged to be closed upon said energization; and a shunting switch in parallel to said safety timer and said first priming switch and arranged to be closed by said detecting means upon beginning and opened upon termination of a heating period, said timers being so arranged that said second period is shorter than said first period when said shunting switch is open wherea closing of said shunting switch renders said second period longer than said first period; said safety timer deenergizing said actuating circuit by opening said safety switch after said second period upon failure of said detecting means to close said shunting switch, said priming timer establishing said actuating circuit solely through said holding and shunting switches by opening said priming switches and reestablishing normal condition by closing said priming switches after said first periods, and said delayed closing of said second priming switch securing a scavenging period upon initiation of a heating period while said priming timer is in switch opening condition.

6. In heating plant control apparatus of the type described, the combination of a current source, a combustion burner, means for initiating and sustaining periods of heating by said burner, and detecting means distinguishing between heating and nonheating periods of said plant, with a priming unit including a thermo-responsive actuator, a resistance in heat conductive relation with said actuator, a first and second priming switch which primin switches ar normally retained closed by said actuator which, after a predetermined period from energization and hence heating of said resistance open said second and shortly thereafter said first priming switch and which actuator after a predetermined period from deenergization and hence cooling of said resistance closes said first and shortly thereafter said second priming switch; a safety timer; a normally closed safety switch arranged to be opened by saidsafety timer after a second predetermined period from said energization; said resistance, said safety timer, said priming switches and said safety switch being connected directly in series and constituting an actuating circuit; relay means for actuating said sustaining means upon energization of said circuit; and shunting switch means in parallel to said safety timer and said priming switches and arranged to be closed by said detecting means upon beginning and opened upon termination of a heating period; said safety timer deenergizing said actuating circuit by opening said safety switch after said second period upon failure of said detecting means to close said shunting switch means, said priming unit establishing said actuating circuit solely through said shunting switch means by opening said priming switches and reestablishing normal condition by closing said priming switches after said first periods, and said delayed closing of said second priming switch securin a scavenging period upon initiation of a heating period while said actuator is in switch opening condition.

7. In a heating plant, comprising a boiler, a burner device for heating said boiler that is served by a combustion sustaining motor and supervised by a water probe on said boiler and a control thermostat; a current source; a phototube adapted to receive radiation from the flame of said burner; an electron discharge device having at least a control electrode and an anode and cathode connected to said source; means for connecting said phototube between said control electrode and said source for applying to said electrode through the phototube, while its conductivity is increased through radiation from said flame, a potential rendering the discharge device conductive; means controlled by said probe for lowering said potential sufficiently to render said discharge device non-conductive; relay means in the anode circuit of said discharge device; and an actuating circuit adapted to be energized from said source by said thermostat and including means for starting said motor upon energization of the actuating circuit, an actuator responsive to temperature increase, switching means controlled by said relay means fOr heating said actuator when the discharge device is nonconductive and the actuating circuit energized, and a normally closed circuit breaker controlled by said actuator to deenergize said actuatin circuit upon heating of said actuator.

8. In a heating plant, comprising a boiler, a burner device for heating said boiler that is served by a combustion sustaining motor and an electric ignition device and supervised by a water probe on said boiler and a control thermostat; a current source; an electron discharge device having at least a control electrode and an anode and cathode connected to said source, a relay magnet in the anode circuit of said discharge device; a potential divider connected to said source; a phototube adapted to receive radiation from the flame of said burner; a connection from a point of intermediate potential of said divider through said phototube to said control electrode and containing a transformer secondary for applying to said electrode through the phototube and the secondary a potential controlled by the impedances of said phototube and said secondary; a condenser between said control electrode and said cathode; a switch adapted to be closed by said relay magnet for energizing said ignition device upon said discharge devic becoming conductive; an actuating circuit including in series a manually controllable resetting switch connecting to a point of lower potential of said divider, two safety switches, a temperature responsive resetting switch actuator normally holding said resettin switch closed, a temperature responsive safety switch actuator normally retaining said safety switche closed and a, magnet for starting said motor connecting to said cathode, and in parallel to one of said safety switches a holding switch controlled by said starting magnet and in parallel to the second safety switch a shunting switch controlled by said relay magnet; a connection between a point of lowest potential of said divider and said cathode and containing said control thermostat; and a connection between said resetting switch and said cathode containing said probe and a transformer primary coupled to said transformer secondary.

9. Electronic control apparatus providing response of a single electron discharge device to two irregularly varying conditions supervised by two independent detecting elements, comprising an alternating current source; an electron discharge device having an input circuit and an output circuit supplied from said source; means responsive to conductivity changes of said discharge device; a first control circuit adapted to apply between said input and outut circuits 9. control potential and including a. first detecting element having an impedance varying with said first condition and an inductance; and a second control circuit including a second inductance which is coupled to said first inductance, and a second detecting element adapted to vary the current in said second inductance in accordance with said second condition; the conductivity of said discharge device changing with the change of control potential due to variation of the impedance of said first detecting element as well as with the ence from saidmsource and including a transformer primary coupled to said secondary and current control means constituting a second detecting element adapted to varythe current flow in said primary and hence tge potential drop in said secondary; the control potential applied to said electrode and hence the conductivity of said discharge device being controllable by the light flux on said phototube as well as by the potential drop across said secondary as affected by said second detecting element.

WILLIAM F. WOLFNER, II.

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