" 1'5, 1-946. _’ = ' B, w. JONES f ' 7 . 2,409,492; f THERMAL TIllE SEQUENCING CONTROL SYSTEM I Filed ‘March 7, 1944 LI LZ } Inventor“: 'v. Benjamin W. Jones, byJv-WmW/M ' Has Attorney ~ ' 2,409,492 UNITED STATES PATENT OFFICE. Patented Oct. 15, 1946 2,409,492 THERMAL TIME SEQUENCING CONTROL SYSTEM Benjamin W. Jones, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application March 7, 1944, Serial No. 525,445 20 Claims. (Cl. 158-—28) 1 The invention relates to control systems, par ticularly sequencing control systems for operat ing ‘oil burners or other condition regulating de vices requiring a sequential time and condition responsive operation control. One of the objects is to provide an improved thermal time sequencing control system that is capable of providing repeated timed starting op 2 der the control of a thermal timer only for a lim ited initial period during the cooling time delay ‘thereof, and having the relay holding winding .then energized in response to the occurrence of a predetermined condition during the limited ef fective pickup energizing period of the pickup winding to supplement the partial energization of the pickup winding that is controlled by the mas‘ ter switch. Such improved sequential relay en ited cooling period under the automatic control 10 ergization control system is of particular advan erations of a burner or other device during a lim of a master controller responsive to a predeter mined condition, such as temperature, pressure or the like, and of automatically continuing op~ eration of the device only in case a resultant op erating condition, such as combustion or the like, is successfully established during one of the tage for operating a burner since it enables a thermal responsive control device that is heated upon the successful establishment of combustion by the burner, such, for example, as a thermo electric generator, to energize the holding Wind ing of the operation control relay and thereby continue operation of the burner under the joint limited cooling timed starting operations. control of the master switch and the thermo A particular object is to provide an improved electric generator after the operation control time and condition responsive sequencing control system utilizing only the initial part of the cool 20 relay has been temporarily picked up during the initial part of the cooling period of the thermal ing time delay of an electrically heated thermal timer to insure more accurate timing of each trial timer. operation interval since such cooling time is not only independent of variable voltage conditions Further objects and advantages of the present invention will appear in the following description of the accompanying drawing in which the single ?gure is a schematic circuit diagram of an auto matic oil burner sequential control system em bodying the improvements of the present inven but also is influenced the least by any'normal . ambient temperature variation. ‘Another object is to provide an improved sequencing control system wherein repeated pe riodic operations of a thermal timer alternately energize a timer heater and an electroresponsive operation control device in such a way as to maintain the control device energized only dur ing the initial part of the cooling period of the thermal timer and to maintain both the heater and the control device deenergized during the subsequent part of the cooling period, and where in a separate thermal lockout timer having a relatively long time delay produces a safety lock out only in case a predetermined condition is not established during a limited number of repeated timed energizations of, the operation control de tion in a preferred form. The oil burner It may be of any usual type having a driving motor, indicated schematically by the motor energizing winding l l, for operating a blower l2 and an oil pump I3. The blower l2 supplies air underpressure to the nozzle air tube 15 and the oil pump l3 supplies oil under pres sure, when the electromagnetic oil ?ow control valve I5 is energized, to the oil atomizing nozzle H. An ignition transformer It! produces an ig nition are between the electrodes H) to ignite the atomized oil projected from the nozzle l1 and thereby establish combustion in the combustion vice. chamber 2E1 of a furnace or other heating device. A further object is to provide an electrorespon sive control device having an incremental pick Operation of the oil burner 10 is always under up energization and an incremental holding en ergization with a thermal timer for limting the incremental pickup energization period thereof and with an improved condition responsive en the control of a master control switch 22 which may be responsive to a condition dependent upon the operation of the burner ll], such as room temperature or the like. . In accordance with the present invention, the ergizing means for providing the incremental room thermostat 22 operates ?rst to provide a holding energization therefor independently of I the thermal timer when a predetermined condi partial energization of the electroresponsive burner control relay 36 and then, through the tion is successfully established during the limited pickup period of energization of the device. agency of the periodic thermal timer 23, tem-' porarily provides an eiiective pickup energiza A more speci?c object is to provide an improved sequential control system having a unidirectional tion of relay 30 to start operation of the oil burn er iii. and continue such operation only for a lim current responsive operation control relay pro vided with magnetically interrelated pickup and holding windings and having the pickup winding ited initial period during the cooling of the ther mal timer 23 in case combustion is not estab lished. only partially energized under the control of a A shown, the thermal timer 23 is provided with master switch and then effectively energized un 60 a thermal responsive operation control member 2,409,492 4 24 of the bimetal type which is normally bi sed when cool into attracted relation with the snap action permanent magnet 23 so as to maintain the timing heater circuit control contacts 25 ?rmly in engagement during the predetermined 33 when power is supplied to the former from the alternating current supply lines LI, L2, and to the latter from the thermoelectric generator A control lockout timing device 48 is provided, period of heating of the bimetal member so re and may be of the solder pot type, as shown, or other suitable type that provides a relatively quired to release the member 24 from the magnet and thermally bias member 24 to close the alter native circuit controlling contacts The ther long timing period compared to the heating and cooling time of the periodic thermal timer 23. As shown, the lookout timer 4-3 is provided with mal timing element 24 operates with a snap ac tion to open the contacts 28 and close the two contacts 21 after the electric heater 23 is ener~ gized to provide a limited period of heating of the a switch element 4| that is normally biased out 'of contact with the cooperating switch element 42 but is mechanically latched in contact there with by engagement of element Iii with the teeth of the ratchet wheel 43. The shaft M carrying the ratchet wheel 43 is normally held stationary by the solder 45 in the pot 45 as long as the solder is solid. The electric heater 4? is provided for heating the pct 35 to soften the solder sufficiently to permit the ratchet wheel 43 to rotate and 20 thereby permit switch member ‘33 to disengage the ratchet 43 in accordance with its bias and thereby move out of contact with. switch ele~ ment d2. thermal timing element 24. Since the thermal. timing element 24 effects the deenergization of the timer heater 28 by means of contacts 23, the two contacts 2? can be maintained closed only during a predetermined initial part of the cooling predetermined period, of the thermal by the snap responsive actionelement produced by magnet 25 in opening contacts and closing contacts 27. As a result, both contacts 23 and contacts 21 are maintained opened during the subsequent cooling of the thermal timing member‘ 24. When cool, member 24 then returns into at“ tractive relation with magnet 25 and recloscs con tacts 26. Thus the thermal timer 23 constitut " a periodic alternative circuit controllingr double throw switch having a snap action magnet for extending the heating period thereof and providing a unilateral thermal time delay movement after an‘ initial limited period of cooling. The electroresponsive control relay 3b is shown as of a special double Winding type, having,r a pickup both in winding magnetic3| attractive and a holding relation winding with the biased switch to operating operate plunger the movable 33. The switch plunger contact 33 3i‘! Operation When thermostat 22 closes its contacts, the re lay pickup winding 3! is partially energized through a circuit including conductor 53, contacts Fri, 42, conductor Ell, relay winding 3i, conductor 5i, heater 4?, recti?er 33, and current limiting resistor 39. But at the same time a periodic heater energizing circuit is established from the alternating current supply line L2 through the thermostat 22, conductor 50, the solder pot switch members 13!, 42, conductor 5|, relay contacts 34, 35, conductor 52, periodic heater 23, contacts 25, the periodic thermal timer operatin member 24, conductors and 53, to the other alternating current supply line Ll. In such periodic heater energizing circuit, the relay contacts and tacts 35. Only when the pickup Winding 3| is cl‘ ell) the thermal timer contacts 26 must both be closed fectively energized can plunger operate con to energize heater ‘28. thereby enabling the ther tact 34 into engagement with the upper contacts mal timer 23 to provide a partial cooling time de~ 36. But the holding winding 32 can thereupon lay interval subsequent to the cleenergization of become effective to attract the plunger with the relay 30 and prior to the energization of a. force tending to hold contact 33 in engagement heater 28 in the periodic time cycle. V‘Jith peri with contacts 36. As shown, the relay holding odic heater 2% thus energized, a limited heating winding 32 is connected to be energized directly period for the periodic timer operating element into engagement with the lower cooperating con from a suitable thermoelectric generator 31 lo~ cated in the combustion chamber 23 so as to be responsive to the establishment of combustion therein due to operation of the oil burner H}. The thermoelectric generator 31' inherently generates a relatively feeble unidirectional cur~ rent. Consequently, the energizati-on of relay 513 must be specially controlled so that the ' Yale unidirectional energlzation of holding winding 32 from generator 37 resulting from the establish ment of combustion in chamber ‘26 can be utilized effectively in maintaining the plunger wJ "3 at~ tracted to hold contact 34 in engagement with the contacts 36. To accomplish this in accord ance with the present invention, the pickup wind ing 3| is maintained partially energized with unidirectional current through the current lim-iting. resistor 39 when thermostat 22 closes its contacts so as to assist the holding winding 3“! in maintaining the plunger 33 in the attracted position after the establishment of combustion in the chamber 29 during the initial cooling pe~ riod of timing element Ell. The pickup windi 3| is energized with unidirectional cunent through the agency of the rectifier 3-3 in order that the cncrgizations provided by both the pick up Winding 3| and the holding winding 32 may jointly and cumulatively magnetize the plunger 24 is initiated. This timer heating period con tinues until the timing element 25 is heated suf ?ciently to overcome the attraction of the per manent magnet 25 that holds contacts 25 in en~ gagement to extend the heating period and there- by predetermine the initial cooling period during which contacts 2? can be maintained closed by element 24. Thereupon the member 25 operates with a snap action to separate contact and close the two contacts 2?. The separation of contact 25 deenergizes the periodic heater 23 and thereby initiates the cooling of the thermal re sponsive operating element it. However. both contacts 2-? are maintained closed for only the initial limited period during the cooling of mem tion ber 24 of that magnet is predetermined 25 during the heating by the holding period. The closing of the left-hand. contact 27 short circuits the current limiting resistor 39 and there by establishes an effective energization 0;? the pickup winding 3| of the control relay 38, this pickup effective energizing circuit extending from line L2 'hrough the contacts of thermostat 22, conductor 59, the contacts 4|, 42 of the solder pot timer d9, conductor 53, pickup winding El, conductor 5'1’, the solder pot heater recti?er 38, periodic timer contacts 27, conductors and 54 to the other line Li. Upon the resulting ef~ 2,409,492 5 6 fective energization of pickup winding 3 I, plunger tion of the pickup winding 3| is removed. In each case, the energization of holding winding 32 by the thermoelectric generator 31 alone is insuffi cient to maintain the contact 34in engagement with contact 36 against the bias thereof to the 33 is picked up and moves contact 34 out of en gagement with. contact 35 and into engagement with contacts 36. The engagement of contact 3.4 with contacts 38 establishes an energizing cir- , cult for the operating winding I I of the oil burner operating motor. this burner operating circuit opposite position. Consequently, when thermo stat 22 opens its contacts, or the alternating cur rent voltage fails, relay 30 will disengage contact 34 from contact 36 and thereby deenergize the relay 4!), conductor EI, contacts 34, 35, conductor 10 burner operating motor I I to stop combustion. 60, the motor winding I I, and thence through When thermostat 22 again closes its contact, conductors 58 and 54 to the other supply line LI. the timer 23 again operates after a heating pe- ' The oil valve I6 is simultaneously energized in riod to close its contacts 21, thereby short circuit parallel circuit with the motor winding II. ing the current limiting resistor 39 to effectively Likewise, the primary winding of the ignition 15 energize the pickup winding 3I of relay 39 and transformer I8 is energized in parallel circuit start operation of the burner In. Now let us as with the motor winding I I through the right sume that for some unknown reason combustion hand contact 21 of the periodic thermal timer is not successfully established within the ensuing 23 during the initial limited cooling period of the initial part of the cooling period of the thermal timing element 24. 20 timer 23. In this case, the periodic timing mem Thus the motor II starts operation of both the ber 24 will, after the initial cooling period, dis extending from line L2 through the contacts of the thermostat 22, the contacts of the solder pot blower I2 and the oil pump I3 to discharge a com bustible oil and air mixture from the burner noz engage contact 21 and thus terminate the effec tive energization of the relay pickup winding 3|. zle I5. At the same time, transformer I8 estab Relay 30 at once responds in accordance with it's lishes an are between the electrodes I9 to ignite 25 bias to reclose contacts 35, and at the end of the the mixture. Under these conditions, combus tion should normally be established in the cham ber 20 within the limited period provided by the cooling of the thermal timing element 24 prior to the opening of contacts 21. subsequent cooling period of the timer 33 con tacts 26 will be reclosed to again establish the winding 32. ber 24. During this initial cooling period burner energizing circuit for the timer heater 28; There upon heater 28 again heats the periodic timing element 24 for the heating period required to ef Assuming that combustion is successfully es fect snap action thereof to disengage contacts 26 tablished, thermoelectric generator 31 will be and re-engage contacts 21. Again the pickup come heated in responseto the establishment of winding 3I of relay 30 becomes effectively ener combustion, and thereupon supply a unidirec gized while heater 28 is deenergized to provide tional energizing current to the relay holding 35 another limited initial cooling period of the mem Consequently, before the timing member 24 has cooled su?iciently to begin the re turn movement to its biased position in which it is shown and thereby open both contacts 2?, the unidirectional energization of holding winding 32 I0 is again operated to attempt to establish com bustion. In case combustion still is not success fully established, the periodic timer 23, after the 40 subsequent cooling period is completed, may re normally becomes effective to assist the continued peat the alternate energization of heater 28 dur partial unidirectional ‘energization of the pickup ing the heating time of element 24 and the ef winding 3I provided under the control of thermo fective energization of pickup winding 3| during stat 22 by means of the energization limiting re the initial cooling time of element 24. During sistor 39. The joint magnetizing action of hold~ "A Li each subsequent cooling time delay period both ing winding 32 and the partial energization of heater 28 and winding 3| are maintained deen pickup winding 3I is required to hold plunger ergized by the timing element 24. This enables 33 in its attracted position and thereby maintain the subsequent part of the cooling period, as well contact 34 in engagement with contact 36 inde as the entire heating period of the thermal timer, pendently of the control of timer 23 during and 50 to be utilized for timing the interval between the after the subsequent part of the cooling period successive attempts to establish combustion. thereof. In this way, the oil burner operating However, during each alternate eifective ener motor II is maintained in operation to continue gization of the pickup winding 3|, the lockout combustion in the furnace chamber 20 under the heater 4‘! also is effectively energized to supply joint control of both the thermal electric gen - heat to the solder pot 46. After a limited number erator 3'! and the master thermostat 22 and also of repeated energizations of the lookout heater responsive to voltage failure of the supply lines 41, sufficient heat will be accumulated by the sol LI,L2. der pot 46 to soften the solder therein and per In case for any reason combustion should fail, mit the ratchet wheel 43 to turn and thereby dis the output of thermoelectric generator 31 will 60 engage the lockout switch member 4| from the quickly decrease so that holding winding 32 is stationary contact 42. This serves to stop all no longer effectively energized. Under this con further operation of the burner control system dition the partial energization of pickup wind" until the solder pot has cooled and switch mem_ ing 3I alone is not sufficient to magnetically hold ber M has been manually reset. In this way the 65 the plunger 33 in the attracted position. Hence improved control system of the present invention the control relay 38 will respond to open the en provides repeated attempts to establish combus ergizing circuit of the burner operating motor I I tion by operation of the periodic thermal timer and thereby prevent continued supply of the com~ 23 before the lookout thermal timer 4!] will re bustible vmixture to the combustion chamber spond to lock out the control. when combustion fails 'while the thermostat 22 is What I claim as new and desire to secure by calling for operation of the burner. Letters Patent of the United States is:v If at any time during successful operation of 1. In combination, a pair of heaters, energizing the burner either the thermostat 22 becomes sat circuit means including a selective electrorespon is?ed and opens its contacts or the alternating sive control device therefor having means ‘biased current voltage fails, then the partial energiza 75 for energizing one of said heaters while said de 2,409,492 7 8 vice is energized below a predetermined value and operable to energize the other of said heaters while said device is energized above said value, a snap action thermal time switching element heated by said one heater and connected for de~ energizing said one heater after a heating time delay and temporarily energizing said device ther energization of said heaters and said device control device, energizing control means therefor including a thermal time delay control element having a heater under the joint control of said above said value during the initial part of the device and said element for operating said ele under control of said master switch in the con tinued absence of said condition, 5. In a control system, an electroresponsive ensuing cooling time delay, and means responsive ment to deenergize said heater and thereupon to an operating condition of the other of said 10 temporarily energize said device only during an heaters for maintaining said device energized initial part of the cooling period of said time above said value independently of said time delay element, and automatic means including a switching element during and alter the subse~ burner having a ?ame responsive means rendered quent part of said cooling time delay to maintain effective under the control of said device during said other heater energized. said temporary energization thereof for main 2. In combination, an electric heater, a com taining said control device energized during and after the subsequent part of said cooling period. bustion heater, energizing circuit means for alter nately operating said heaters including a snap action thermal time delay switching element 6.121 a control system, an clectroresponsive control device having energizing circuit means, energization control means therefor including means for limiting the energization of said device, a heating and cooling time control element hav heated by said electric heater and connected for ‘ deenergizing said electric heater after a heating time delay and having electrical means tern porarily controlled thereby during the initial part of the ensuing cooling time delay period for oper ing a heate ' under the joint control of said device and said element for operating said element to temporarily energize said heater to heat said ele ment only while said energization limiting means is effective and to temporarily render said en ergization limiting means ineffective only during the ensuing cooling period of said element, and separate energizing means rendered effective under the control of said device during said cool ing period for supplementing the limited ener gization of said control device after said cooling period and thereby maintaining said device en ergized under the joint control of said energiza tion control means and said separate energizing ating said combustion heater, and means respon sive to an operating condition of said combustion heater for controlling said electrical means to continue operation of said combustion heater dur~ ing the subsequent part of said cooling time delay period and after said cooling period. 3. In combination, an electrically operated com~ bustion heater and a pair of electric heaters hav— ing energizing circuit means, sequential energiza tion control means therefor including a snap action thermal time delay switching element heated by one of said electric heaters and having electrical means controlled thereby for alternately deenergizing said one heater after a heating time means. 7. In a control system, an electroresponsive device having a control member biased to one delay and temporarily energizing said combustion heater and the other of said electric heaters dur ing the initial part of the ensuing cooling time delay and maintaining said pair of electric heaters deenergized during the subsequent part of said cooling time delay, means responsive to an oper ating condition of said combustion heater for con trolling said electrical means to maintain said combustion heater energized independently of said time delay element, and thermal means 40 control position and operable to another control position upon a predetermined energization of said device, energizing circuit means for par g: tially energizing said device, a snap action ther mal time delay switching element connected for temporarily effecting said predetermined ener gization of said device during the cooling of said element, an electric heater for said element hav ing an energizing circuit controlled jointly by cumulatively responsive _to predetermined re said control member and said switching element peated energizations of said third heater for ter 50 to energize said heater to heat said element only minating the repeated sequential cnergization of while said control device is partially energized, said three heaters in the continued absence of said element having means for deenergizing said said condition. heater upon a predetermined heating of said ele 4. In combination, three heaters having ener ment, and automatic energizing means rendered gizing circuit means, a master control switch 55 effective during said temporary predetermined therefor having an electroresponsive control energization of said control device for supple transfer device interconnected therewith for al menting said partial energization of said device ternately energizing a pair of said heaters, a snap to maintain said control member in said other action thermal time delay switching element control position under the joint control of said heated by one of said pair of heaters and inter~ connected for alternately deenergizing said one heater after a heating time delay and temporarily e?’ectively energizing said device and the third one of said heaters only during the initial part of partial energizing means and said automatic en ergizing means. 8. In a control system, an electroresponsive control device having two complementary ener gizing windings provided with energizing circuits, the ensuing cooling time delay and maintaining 65 energizing control means therefor responsive to said first and third heaters effectively deenergized one condition and including means for limiting during the subsequent part of said cooling time the energization of one of said windings, a snap delay, means responsive to an operating condition action thermal time delay switching element cOn~ of the other of said pair of heaters for maintain nected for temporarily rendering said limiting ing said control transfer device effectively en 70 means ineffective during the cooling of said ele ergized independently of said time delay switch ment, an electric heater for said element hav ing element, and control lockout means respon— ing an energizing circuit controlled jointly by sive to a predetermined repeated energization of said control device and said element to energize said third heater during the initial part of suc said heater only While said limiting means is cessive cooling time delays for terminating fur 75 e?ective, said element having means for cleaner- 2,409,492 . 10 9 gizlng said heater upona predetermined heating ofv said element, and means responsive to the occurrence of a second predetermined condition during said cooling period for energizing the other of said windings to maintain said device eluding a recti?er and an energization limiting means, ‘a thermal time delay switching element having an electric heater energized under the control of said element for operating said ele ment to render said limiting means ineffective energized under the joint control of both said only during the initial part of the cooling period condition responsive means. of said element, said element having means for deenergizing said heater upon a predetermined heating of said element, and a thermoelectric 7 9. In a control system, energizing circuit means including an electroresponsive control device hav ing complementary energizing windings, energize ing control means for one of said windings in cluding a unidirectional current supply means having means for limiting the current supplied thereby, a thermal timing element having a heat er energized under the control of said element for operating said element to deenergize said heater upon a predetermined heating of said ele~ generator having a, combustion heater operated under the control of said switching device during said initial part of said cooling period for main taining the other winding of said electromagnet energized with unidirectional current to continue operation of said combustion heater during the subsequent part of said cooling period and after said period. 13. In combination with energizing circuit ment and temporarily render said current limit means, a combustion heater having an alternat ing means ineffective only during the initial part of the cooling period of said timing element, and 20 ing current driving motor and igniter, a pair of temperature responsive unidirectional energizing electric heaters, a master switch having an elec means normally rendered effective during said temporary energization of said device for main taining the other of said complementary windings troresponsive relay controlled thereby and con nected for alternately energizing said combustion heater driving motor and one of said pair of elec energized during and after the subsequent part 25 tric heaters, a snap action time delay switching element heated by said one electric heater and of said cooling period. 10. In a control system, energizing circuit means including an electroresponsive device hav ing complementary energizing windings, energiz ing control means for one of said‘ windings in cluding unidirectional current supply means hav ing means for limiting the current supplied there by, a thermal time delay switching element hav ing an electric heater energized under the joint control of said device and said element for oP- ' having a normally closed movable contact for deenergizing said one electric heater after a heat ing time delay and a pair of normally open mov able contacts, one having a recti?er intercon nected therewith for jointly energizing said'relay and the other of said electric heaters with unidi rectional current and the other for energizing said igniter to start operation of said combustion > heater during the initial part of the ensuing cool- ‘ ing time delay period of said switching element, a thermoelectric generator heated upon establish ment of combustion by said combustion heater of the cooling period of said element, said elee during said initial part of said period for main ment having means for deenergizing said heater upon a predetermined heating of said element, 40 taining said relay energized during the subse quent part of said period and after said period and thermoelectric generating means having a _ and automatic lockout means cumulatively re combustion heater started into operation under sponsive to a predetermined repeated energiza the control of said device during said temporary tion of said other electric heater for preventing energization of said one winding for maintaining the other of said complementary windings ener 45 further energization of said heaters and said re lay under control of said master switch in the gized to continue operation of said combustion continued absence of combustion by said com heater during the subsequent part of said cooling bustion heater. ' period and after said cooling period. 14. A control system having, in combination, ll. In a control system, energizing circuit crating said element to render said current limit ingjmeans ineffective only during the initial part means including an electroresponsive control de vice having'complementary energizing windings, energizing means for one of said windings‘ in cluding a recti?er having means for limiting the 50 an electroresponsive control device having ener gization limiting means and cumulative energiz ing means. for separately controlling operation thereof, an electric heater having energizing cir cuit means under the control of said device, cir current recti?ed thereby, a thermal timing ele ment having an electric heater provided with an 65 cuit means including a thermal timing control element heated by said heater and having snap energizing circuit under the control of said ele action means for holding said element in one po ment for periodically operating said element to sition to produce snap action movement of said render said current limiting means ineffective element from said one position to deenergize said temporarily during the initial part of each cool ing period of said element, said element having 60 heater and to another position for rendering said energization limiting means ineffective and means for deenergizing said heater upon a pre thereby effect atemporary operation of said de determined heating of said element, and a ther vice only during. the initial cooling of said ele moelectric generator having a combustion heater ment, condition producing means normally ren operated under control of said device during each deredeflective upon operation of said device, and temporary energization thereof by said recti?er condition responsive means for rendering said for maintaining the other of said complementary cumulative energizing means effective to operate windings energized to continue operation of said said device to maintain said condition producing combustion heater when combustion is established means effective during and after the subsequent during the initial part of one of said cooling pe 70 cooling of said element. 15. A control system having in combination a 12. In a control system, energizing circuit movable control member, means biasing said means including a switching device having an op member to move from one control position to erating electromagnet provided with complemen another control position, a pair of electromag tary energizing windings, unidirectional energiz~ ing control means for one of said windings in 75 netic means for jointly holding said member in riods. v - ' 11 2,409,492 said one position upon a predetermined energiza tion of each of said means, circuit means includ ing a condition responsive device for providing said predetermined energization of one of said electromagnetic means, circuit means including a condition responsive device normally rendered ef fective upon operation of said control member to said one position for providing said predeter mined energizaticn of the other of said electro 12 means for holding said element in said one posi tion until after a predetermined heating of said element, an electric heater having a circuit en ergized under the joint control of said device when ineffectively energized and said element in said one position for biasing said control element for snap action movement from said one position to deenergize said heater and to said other posi tion for temporarily effectively energizing said magnetic means, and circuit means including a IS device during the initial part of the cooling time snap action thermal timing device having an in ,rval of said element predetermined by said electric heater energized upon said predetermined holding means, said element having circuit con energization of said one electromagnetic means trolling means for maintaining both said heater under the joint control of said timing device and deenergized and said device ineffectively ener said control member in said other position for gized during the subsequent part of said cooling operating said timing device to deenergize said heater and provide a temporarily increased en ergization of said one electromagnetic means to operate said control member from said one con time interval of said element, condition produc ‘ng means for normally establishing a second con dition under the control of said device upon ef fective energization thereof, and circuit means trol position to said other control position during 20 including a second condition responsive means the cooling of said timing device. ior maintaining said device effectively energized 16. A control system having in combination an jointly with said ?rst condition responsive ener electroresponsive control device having a con gization control means upon the continuance of trol member biased to move to a predetermined said second condition during and after said sub position upon only a partial energization of said 25 sequent part of said cooling time interval of said device and having energizing circuit means in element. cluding control means for partially energizing 19. A sequential condition timing control sys said device, circuit means including a thermal em having, in combination, an electroresponsive timing element for temporarily providing addi control device having energizing circuit means tional energization of said device to move said 30 including a ?rst condition responsive energiza control member to another position while said tic-n control means for inei‘r‘ectively energizing element is cooling, a heater for element hav said device and energization control element for ing energizing circuit means energized only when temporarily eff ictively energizing said device dur~ saiddevice is partially energized and said element ing the initial. cooling of said element and pro a Cl is cool, said element having means for deener g a subsequent cooling time delay there gizing said heater after said element is heated to , a heater for said element having a circuit a predetermined temperature, and means includ energized under the joint control of said device ing condition responsive means normally ren and said timing control element only When said dered effective during said temporary additional device is inefiectively energized and said element cnergization of said device for maintaining a sub 40 is cool whereby said heater is maintained deen sequent additional energization of said device to ergized during said subsequent cooling time de maintain said member in said other position un lay of said element independently of the con der the joint control of said control means and trol of said control device, condition producing said condition responsive means. means for normally establishing a second condi— 17. A control system having in combination 45 tion upon eiiective energization of said device, alternating current circuit means including an and circuit means including a second condition electroresponsive switching device biased to a responsive means for maintaining said device ef predetermined position, circuit means including a recti?er and a snap action thermal responsive fectively energized jointly with said ?rst condi tion responsive means during said subsequent cooling time delay and thereafter to maintain said condition producing means effective and said heater deenergized independently of the control of said timing element. switching element movable upon a predetermined heating thereof for temporarily providing a pre determined direct current energization of said de vice to effect operation thereof to another posi tion only during the initial part of the interval 20. In combination, an electric control device said element iscooling, a heater for said element an electric heater having interconnected se having energizing circuit means energized under lective energizing circuit means including a ther the control of said device in said predetermined mal time delay double throw switch heated by position and deenergized upon said predeter electric heater under the joint control of said mined heating of said element, and means in device and switch and having a snap action cluding thermoelectric generating means normal 60 means for holding said switch to extend the heat 13/ rendered effective upon said temporary pre ing period thereof and thereby thermally bias determined direct current energization of said said switch to deenergize said heater and tem device for providing a cumulative direct current porarily effectively energize said control device energizaticn of said device to maintain said de during the initial part of the cooling time delay vice in said other position during and after the interval of said switch, condition producing subsequent part of said interval. ~ means normally rendered effective under control 18. A- sequential condition timing control sys of said device upon said effective energization tem having, in combination, an electroresponsive control device having energizing circuit means including a ?rst condition responsive energize tion control means for ineffectively energizing said device and a thermal timing,r energization control element biased when heated to move from one control position to another control position for effectively energizing said device. snap action thereof, and condition responsive means having connections for maintaining said device effective ly energized upon continued effective operation of said condition producing means during and after the subsequent part of said cooling time delay intervals. BENJANIIN W. JONES.