US2637393A - Automatic ignition and control mechanism for gaseous fuel burners - Google Patents

Description

y 1953 c, M. MAYER ET AL 2,637,393

AUTOMATIC IGNITION AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS Filed June 15, 1952 4 SheetsSheet l INVENTORS (has. MMQ yer Richard LPG/"l f/m @1' L. War/7e! M y 1953 c. M. MAYER ETAL AUTOMATIC IGNITION AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS 4 SheetsSheet 2 Filed June 13, 1952 r -mn 36 8 4! 20 W 6 h w i 5/ 5? 2/ 7s I v 53 A? 1 49 :Y 40 r 7 7 37 M w 36 w I! 3 A; J 1' INVENTORS Chas. f7- Mayer Pic/Yard A, P'c-w/ 9f/mer 1.. Warner By AQZwz IN VZA/TO/l? 4 Sheets-Sheet 3 M a J F e/ .L e P a M V/ M rr mm h Z 4 4% (Pg f fi 2T Q? M. MAYER ETAL AUTOMATIC IGNITION AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS May 5, 1953 Filed June 13, 1952 c. M. NkAYER ETI'AL AUTOMATIC IGNITIO AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS May 5 1953 4 Sheets-Sheet 4 Filed June 13, 1952 the main or pilot burner.

Patented May 5, 1953 AUTOMATIC IGNITION AND CONTROL MECHANISM FOR Gaseous FUEL BURNERS Charles Mayenlflansfield, Richard L. Perl, Galiomand Elmer L. Warner, 'Crestline ll hio, assignors to The Tappan Stove Oompany, Mansfield, Ohio, a corporation of Ohio Application June '13, 1952 Serial-No. 293,282

50 (ll-aims.

This invention relates to an automatic electric ignition and control mechanism'for cooking range burners using gaseous fuel and is a moclification of the control mechanisms showntin the patent to Charles M. Mayer and John M Hoff No. 2,577,787 issued December 11, 1951, the patout to Charles Mayer No. 2,578,? 18 issued December 18, 1951, the co-pending application of Richard L. Perl and John M. Hoff filed December 10, 1951, Serial No. 260,966, and in the copending application of Charles M. Mayer Serial No. 286,194, filed May 5, 1952. It isespecially designed and adapted for automatically igniting and controlling the operation of oven burners in cooking ranges, and may be used in conjunction with a time control mechanism or independently thereof as desired.

The mechanism is designed for use with a main gaseous fuel burner which is adapted to be ignited by a gaseous fuel pilot burner. As long as the pilot burner is ignited it is immaterial whether or not the main burner burns constantly. It may be ,extinguishedior some reason, but it will be promptly re-ignited by the pilot burner if fuel is supplied thereto. But if the pilotlburner is extinguished for any reason While the main control valve is still open to ,supply gas to the main burner a very dangerous situation sometimes arises. Let us assume that both the pilot burner and the main burner are extinguished during operation for some reason. Gas can then flow to the main burner but since the pilot burner is extinguished the main burner will not be ignited and unburned gas will accumulate in the oven which may violently explode when an attempt is made/to ignite either It has been found by experience that both the pilotburner and the main burner are frequently extinguished operation. This is sometimes due to a momentary failure of the gas supply Or the slamming of the oven door or to various other reasons,

In order to prevent any accumulation of unburned. gas and thus eliminate danger of an explosion therefrom in the event the pilotburner l is extinguished for any reason duringop eration, a safety control unit by which the supply of gas to both the main burner and the pilot burner is completely out. off, in the event that pilot burner is extinguished for any reason during op eration, is provided.

As shown herein the apparatus includes a. main gaseous fuel burner by which the oven in a cooking range is heated. The main burner is adapted to beignited by a gaseous fuel pilot burner whichiburns only during the timethe oven is in operation. .At other times the supply of gas to both the main burner and the pilot burner is out off by theesafety control unit which is interposed in a main conduit between the gas supply manifold and the main burner. During operations gas flows from the manifold into the safetycontrol unit. From the safety control unit gas flows through a small branch conduit'drrectly to the pilotburner; and through the main conduit, amanually operable normally closed main control valve, and a standard thermostat ically operated oven temperature control valve to the main burner. A normally open master control switch which is associated with themain control valve is provided to initiate operation of both the pilot burnerand the main burner. The master control switch ,is 'arranged to be closed by the opening of the main control valve and to he opened by the closing of the main control valve. 1 The closing of the master control switch energizes, through a normally closed thermostatically opened switch, a solenoid trans- "former whichv isoperatively connected to the safety control unit, and the solenoid transformer when energized energizes an electric resistance ignitionelement- The energization of the solehoid transformer also causeslit to set the safety control vunit to permit the now of gas from the safety control unit to. the pilot burner whilecutting off the supply of. gas irom the safety control unit to the main burner. pilot. burneris ignited by the electric ignition element and projects a flame against a thermostatic element which is operatively connected "to the normally closed switch. and'against a thermocouple which is operatively connected to an electromagnet in thesafety control unit. After the thermostatic element becomes heated it opens the normally closed switch Whichde-energizes the solenoid transformer and the electric ignition element. As soon as the solenoid transformer iszde-energized the safety control'uni't is automaticallyoperated byspring means to maintain the supplyof gas, to the pilotburnerthrough the branch conduit and to alsosupply gas tothe main burner through the main control valve and the oven temperature controlvalve. Themain burner is then ignited by the .pilot burner. The thermocouple, as long as it is heatedby the pilot burner, maintains the safety control unit through the elect-romagnet in,,ccndition to supply-gas .to both the main burner and the pilot burner. The oven temperature control valve then regulates the supply of gas to the main burner so as'to 3 maintain the desired oven temperature. As long as the pilot burner is ignited the main burner will burn normally under the control of the oven temperature control valve. But if during operation the pilot burner is extinguished for any reason the thermocouple will immediately cool and allow the safety control unit to automatically cut off the supply of gas to both the main burner and the pilot burner. As an example ,of the manner of operation of the apparatus, let us assume that during operation the pilot burner is suddenly extinguished, for instance, by a momentary failure of the gas supply from the manifold to the burners. The thermocouple immediately cools, allowing the safety control unit to cut off communication between the manifold and both the main burner and the pilot burner. Then after the thermostatic element has cooled, closing the normally closed switch, which is maintained open by the thermostatic element during normal operation of the oven, the solenoid transformer and the electric ignition element are again energized, since the master control switch is still closed. The energization of the solenoid transformer will cause it to operate the safety control unit to re-establish communication between the manifold and the pilot burner only. Then when gas is again available the pilot burner will be reignited and re-establish normal operation of the oven as previously described.

To'adapt the apparatus for use in conjunction with any standard time control mechanism, we provide a normally closed supplemental control switch which is disposed in series with the master control switch. The supplemental control switch is adapted to be opened and closed at predetermined set times by the time control mechanism. When the time control mechanism is used the normally closed supplemental control switch is opened and the time control mechanism is set to initiate operation of the oven burner at a predetermined time by closing the supplemental control switch, and to terminate operation thereof at a predetermined set later time by opening the closed supplemental control switch. The main control valve is then manually opened and the master control switch is simultaneously closed. At the set time thecontrol mechanism will close the supplemental control switch which will effect the energization of the solenoid transformer and the electric ignition element. The apparatus will then operate as previously described in connection with manual control until the time control mechanism opens the supplemental control switch at the set later time to terminate operation. The opening of the supplemental control switch will cause the safety control unit to cut off the supply of gas to both the main burner and the pilot burner, thus terminating operation.

Prolonged power failures of many hours and sometimes of even several days duration frequently occur in various parts of the country. In order to eliminate the necessity of either keeping the main burner burning constantly during a prolonged power failure or manually actuating the safety control unit, as is normally done b3, the solenoid transformer, and then lighting the pilot burner with a match each time the oven is used, the mechanism is so constituted and arranged that the pilot burner will burn constantly during a power failure instead of being extinguished each time the supply of gas to the main burner'is cut off. The operation of the main burner is then controlled by the opening and closin of the main control valve.

The principal object of the invention is to provide an improved electrical ignition and automatic control system for cooking range oven burners using gaseous fuel.

Another object of the invention is to provide in an electrical ignition and control system of the character described means for completely shutting off the supply of gas to both the main burner and the pilot burner in the event the pilot burner becomes extinguished for any reason during operation.

Another object of the invention is to provide in an automatic ignition and control system for oven burners means by which the system may be easily converted from a fully automatic system to a constantly burning pilot burner system during power failures.

Still another object of the invention is to provide an improved electrical ignition and control system of the character described which may be used in conjunction with a time control mechanism or independently thereof as desired.

Another object of the invention is to provide an automatic ignition or control mechanism of the character described in which the safety control unit and the thermocouple circuit are utilized to initiate and terminate operation of the main burner by the time control mechanism.

Other and more limited objects of the invention will be apparent from the following specification and the accompanying drawings forming a part thereof, wherein:

Fig. 1 is a diagrammatic layout showing our improved electrical ignition and safety control mechanism applied to a cooking range oven burner using gaseous fuel;

Fig, 2 is an enlarged central vertical section through the safety control unit showing the various parts in position to cut off the supply of fuel to both the pilot burner and the main burner;

Fig. 3 is a view similar to Fig. 2 showing the various parts in the position they are automatically moved to when the master control switch is closed to initiate the operation of the main oven burner:

Fig. 4 is a wiring diagram of the apparatus; and

Fig. 5 is a view similar to Fig. 4 showing a slightly modified arrangement.

Referring now to the drawing by reference characters, the numeral l indicates a gaseous fuel burner which is mounted in or in heating relation to a cooking range oven 2. Gaseous fuel is supplied to the burner I from a manifold M through a conduit 3. Interposed in the conduit 3 are a safety control valve mechanism generally indicated by the numeral 4, a manually operable main control valve 5, and an oven temperature control valve 6. During operation gas flows from the manifold M through the conduit 3 to the safety control unit 4, to be described in detail hereinafter. From the safety control unit 4 the gas flows through the conduit 3, the main control valve 5, and the oven temperature control valve to the burner l. The oven temperature control valve 6 is operative to regulate the amount of gas flowing to the burner I during operation in order to maintain the oven 2 at any desired set temperature. The valve 6 is set to any desired temperat re by a handle I having a pointer 8 which cooperates with a graduated dial 9 carried by the valve The valve 6 is controlled according to the tem .erature setting by a thermostatic element It which ismounted in' the oven 2 andis connected to the valve 6 as shown at H. The main control'valve 5 isastandard shut off valve which is manually opened and closed by a handle 13 and a valve stem i2. The oven temperature control valve 5 is of standard well known construction. Consequently it is not shown in detail herein. There are many different constructions available any oneof which will work equally well herein. If desired theshut-off valve 5 and the oven temperature control valve 6 may be combined as a single unit and'both actuated by the same handle and stem. Many such combined valves are available. Gas is also supplied to a pilot burner 14 through abranch -conduitl5 which extends-between the safety control valve mounted in position to be heated bya flame from the pilot burner. The thermostatic'element I7 is operative to actuate a'double throw switch l9 which controls the'energization of the electrical ignition element I5 and a solenoid transformer 21! which when energized operates the safety control unit to supply gas to the pilot burner it only, as will be described in connection with the description of the safety control unit and the operation of the Whole apparatus. The switch! 5 also controls the energization of a signal light bulb L which when energized indicates'that the apparatus is functioning properly. The thermocouple 18, when heated, is operative "to hold the safety control unit in condition to maintain the supply of gas to both the pilot burner 14 and the main burner l, as will also bedeseribed in connection with the description of the satety control valve mechanism and the operation of the apparatus. An electric circuitbetween the thermocouple l8 and the safety control unit t is established by'a copper tube 2i andin insulated wire 22 within the tube 2 l.

A master control switch 23 is provided to control the operation of'the apparatus. The master control switch23 is associated'with-the main control valve 5 and is adapted to be opened and closedby a cam 25, carried by'the valve-stem I2, through a link 26 The arrangement is such that the'switch 23 is simultaneously closed with theopening of the main control 'valve 5, and isv simultaneouslyopened with the closing of the valve-'5.

The'construotion of the safety control unit 4 and its connection to the solenoid transformer 23 will now be described, reference being had to 3 Figs. 2 and 3, of'the drawings. This unit comprises a casing having-a chamber 36 in one end thereof and a chamber 3'! in the other end thereof. The chambers 35 and 31 are connected by a bore 33 of reduced diameter. A valve seat --39 is located at one end of the bore 38 and a similar valve seat 4015 located at the other end of the spring 66.

1 her 36. burner l gas flows from the chamber 36 through and the secondary winding 11. is slidably mounted in the bore 19 of the spool trol valve 48 of suitable material is secured to one end of the valve stem 46 Within the chamber '36, and an armature 49 in the form of a'thin light iron disc, is securedto the othor'end of the stem within the sleeve 43. A very light relatively weak coiled compression spring disposedabout the valve stem 45 between the'control'valve 43'andthe end wall 45 of the sleeve 43 normally holds the control valve 48 against the valve seat 39; m1 electromagnet'fil is secured to one-endof' a hollow exteriorly threaded stud '52 which extends out through aligned apertures inzthe'end wall 44, of the sleeve 43; and'in the end of the cap 41; A nut 53 screwed onto theouter portion of the stud 52 securely holds the magnet 51 and the sleeve 43 in place. The-legsof the magnet 51 have a winding 54 thereon, one end of which is connected to the tube 21 andthe other end of which is connected to the'wire 22 in the tube 2|. The tube 21 s inserted into the hollow stud 52 and is held in place by a screw fitting- 5211'. A sleeve 55 is screwed into-a threaded recess in the end of the cap 42,,as indicated at 55,'and extends into the chamber 31 axslight distance. One end of the sleeve 55 is closed-by an-encl wall 5'1, and the other end, which is open, registers with a circular aperture 58' in-theend wall of the cap 42; A plunger" 59 is slidably mountedin the sleeve 55 and extends out through the aperture 58 in thecap 42. A stemt'Z, which issecured tothe inner end of the plunger 59, extends out through an aperture63 in the 'endwall 57 of the sleeve 55, and through the chamber 31 and into'the bore 38. The stem 62 has a collar 64 rigidly secured thereon between the end wall 51and theouter end of the stem. An interrupter valve 65 of-suitable material is slidably mounted upon the stem 62 between the end wall 51 ofthc sleeve 55 andthe collar 64. The interrupter "valve 55 is adapted to engage the valve seat 4Dtocut off the flow of gas into the chamber 31 during the initiation-of operation as will be hereinafter described. A compression spring 61 which is stronger than the spring 55 is disposed about the stem 62'within the sleeve 55 between the inner face of the end wall 51 and the'inner end of the plunger 59. The spring 61 isoperative to return the plunger 59, stem 62 and valve 65 from the position shown in Fig.- 3 back to their normal position as shown in Fig. 2, against the resistance A port 58 in the casing 35 provides communication between the chamber 36 and the conduit 3 to allow gas to flow from the manifold M through the conduit 3 into the cham- During normal operation of the'maln the reduced intermediate bore 38 and into the chamber 31. A port 59 which establishes communication between the branch conduit 15 and the bore 38 is provided to supply gas to the pilot valve 5 and the oven temperature control valve 6.

The solenoid transformer 20 comprises a spool 15 on which'are'wound the primary windinglfi An armature 18 15. The solenoid transformer 20 may be operatively associated with the safety control unit 4 in any suitable manner. As shown herein-it is secured to the cap 42 of the safety control unit 4, with the armature 18 thereof in axial aligns 7 ment with the plunger 59 of the safety control unit 4.

In order to accommodate the apparatus for automatic control whereby operation of the main oven burner I may be automatically initiated at a predetermined set time and automatically terminated at a predetermined set later time, we provide a normally closed supplemental master switch 85 which is adapted to be opened and closed by a standard time control mechanism 86, and interpose the secondary winding 80 of a transformer 8| in the thermocouple circuit 2 I22 in series with the winding 54 of the electro-magnet 5I.. The winding 80 is heavy wire having substantially no resistance.

The operation of the apparatus will now be described, particular reference being had to Fig. 4 of thedrawings. During manual control the supplemental master switch is maintained closed. To initiate operation under manual control it is only necessary to manually open the main control valve 5 and close the master switch 23, and then manually close the main control valve 5 and open the master switch 23 to terminate operation. When the switch 23 is closed current will flow. from one side 90 of the line through the lead 9|, switch 23, lead 92, switch I35 and lead 93 to the terminal 94 of the double throw switch I9. The current then fiows through the switch I9 to the. terminal 95 thereof and then through the lead 96 to the primary winding 16 of the solenoid transformer 20 and from there back to the other side 91 of the line through the lead 98. The solenoid transformer 20 and the electric ignition element I5 which is connected to the secondary winding 1! of the solenoid transformer 20 by the leads 99 and I are now energized. The solenoid transformer 20 being energized shifts the various, parts of the safety control unit 4 from the position shown in Fig. 2 to the position shown in Fig. 3, opening the control valve 48 and closing the interrupter valve 65. Gas can now flow to the pilot burner I4 where it is ignited by the ignition element I6, but gas cannot yet flow to the main burner I since the interrupter valve mechanism in the chamber 3'! of the safety control unit is maintaining the entrance thereto closed. The pilot burner being ignited heats the thermocouple I8 and the thermal element I I. The thermocouple being heated generates a minute current of the order of .015 volt which flows from the thermocouple through the tube 2I to the winding 54 of the electromagnet SI and from there through the wire 22 and secondary winding 80 of the transformer 8| back to the thermocouple I8. The thermocouple current energizes the electromagnet I sufiiciently for it to hold the control valve mechanism in the chamber 36 in the position shown in Fig. 3 against the slight resistance of the spring 50 after it has been moved to this position by the solenoid transformer 20, but not enough for the electromagnet to attract the mechanism from the position shown in Fig. 2 to the position shown in Fig. 3. The heating of the thermal element II causes it to actuate the switch I9 to break the circuit to and deenergize the solenoid transformer 20 and consequently the electric ignition element I6, and to make the circuit to the signal light bulb L through the terminal IQI and lead I02. As soon as the solenoid transformer 20 is de-energized the spring 6'1 returns the interrupter valve mechanism in the chamber 31. back from the position shown in Fig. 3 to the position shown in Fig. 2 while the electromagnet 5| holds the control valve mechanism in the chamber 36 in the position shown in Fig. 3. Gas can now flow through the main control valve 5 to the main burner I where it is ignited by the pilot burner I4. Under normal conditions the burner I will now operate under control of the oven temperature control valve 6 until its operation is terminated by the opening of the switch 23 and the simultaneous closing of the valve 5. The closing of 'themanually operable valve 5 cuts off the flow of gas from the control unit 4 to the main burner I, but it does not cut off the flow of gas to the pilot burner I4. This is effected by the opening of the master control switch 23 which effects the energization of the primary winding I03 of the transformer 8|. When the switch 23 is opened to terminate operation current flows from the side 90 of the line through leads 9| and I04 to the primary winding I03 of the transformer BI, and from the primary winding I03 through the leads I05 and 93 to the terminal 94 of the switch I9. From the terminal 94 the current flows through the switch I9 to the terminal IOI and from there back to the other side 91 of the line through the lead I02 and signal light bulb L. The energizing of the primary winding I03 of the transformer BI generates an alternating current of the order of .15 volt in the secondary winding thereof which is superimposed upon the minute direct current generated by the thermocouple in the thermocouple circuit. The superimposing of the higher voltage alternating current upon the much lower direct current in the thermocouple circuit momentarily de-energizes the electromagnet 5I after which the spring 50 returns the control valve mechanism in the chamber 36 back from the position shown in Fig. 3 to the position shown in Fig. 2, thus cutting off the flow of gas from the safety control unit 4 to both the main burner and the pilot burner.

Both the direct current generated by the thermocouple I8 and the alternating current generated by the transformer 8I are of such minute amplitude that neither one can energize the electromagnet 5I sufficiently for it to attract the armature 49 to it after the armature has once been released by the electromagnet 5I and moved away therefrom by the spring 50, no matter how minute the separation between the magnet and armature may be. The force exerted by the spring 50 tending to move the armature 49 away from the electromagnet 5I is so slight that it cannot overcome the holding force exerted upon the armature 49 by the electromagnet 5| when the armature is in contact therewith, but is sufficient to separate the armature and electromagnet whenever the electromagnet is momentarily deenergized. When the electromagnet 5I is energized only by the directcurrent generated by the thermocouple the polarity of the electromagnet remains constant, but when the alternating current generated by the transformer is applied to the electromagnet the polarity thereof is constantly reversed. The superimposing of the higher voltage alternating current upon the lower voltage direct current momentarily renders the holding force of the electromagnet zero each time the polarity thereof reverses, which occurs when the negative value of the alternating current is equal to the positive value of the direct current. At this moment the holding force of the electromagnet is zero the spring 50 will separate the armature and magnet after which the electromagnet cannot attract the armature back to it.

accuses control valve 5 performs no useful function in either initiating or terminating operation of the apparatus, as the flow of gas from the manifold M to the main burner I is cut on and off before it reaches to valve 5 by the safety control unit which is interposed in the conduit 3 between the manifold M and the valve 5. The master control switch 23 through the safety control unit 4 controls both the initiation of and the termination of the operation of the main burner I. The closing of the normally open master control switch 23 effects the opening of the control valve 48 and the closing of the interrupter valve 65 in the control unit 4. Gas then flows to the pilot burner l4, but it is cut off from the burner l by the interrupter valve 65. After the pilot burner has been ignited and heats the thermostatic element 11 the interrupter valve 65 is opened after wh ch gas can flow from the safety control unit t through the open valve 5 to the main burner l. The valve 5 is provided only to control the oper ation of the main burner 1 during prolonged power failure after the apparatus has been converted from a fully automatic ignition and control system to a constantly burning pilot burner system.

If the pilot burner is extinguished for any reason during operation, then the thermocouple l8 and the thermal element l'l will cool. The electromagnet 5| will then be de-energized and release the control valve mechanism in the chamber 36 which will then be returned by the spring 50 to the position shown in Fig. 2 cutting off the supply of gas to both the pilot burner l4 and the main burner l. cools, which is after the thermocouple 18 has cooled, it will actuate the switch 19 to again make the circuit to the solenoid transformer 20 and break the circuit to the signal light bulb L. The apparatus will then re-cycle as described as soon as gas is available.

In order to adapt the mechanism for automatic operation of the burner I, we interpose the normally closed supplemental control switch 85 in series with the main control switch 23 and provide the standard electrically operated time control mechanism tit-which is operative to close and open the switch 85 at predetermined set times. Operating current is supplied to the time control mech anism through the leads H and Ill. During manual control of the burner l the switch 85' is maintained closed. For automatic control the time control mechanism 8? is first set to initiate operation at a predetermined time and to terminate operation at a predetermined later time.

The setting of the time control 8'! automatically opens the switch 85. The valve is then man ually opened and the switch 23 closed. The open ing of the valve 5 and the closing of the switch 223 will have no effect as long as the switch 85 is open since the safety control unit 4 is in the condition shown in Fig. 2 with the valve 48 in the chamber 36 cutting off the flow of gas from the safety control unit ito both the main burner i and the pilot burner M. time control mechanism will close the switch 85 after which the mechanism will function exactly as described in connection with manual control until time to terminate operation. At the predetermined set time for terminating operation the time control mechanism 85 will open the switch 55 which will effect the energization of the primary winding Hit of the transformer 80 which in turn will shoot the de-energization of the electromasnet 5!, both exactly as described in con When the thermal element l1 At the set time the y nection with manual operation. The electromagnet will then release the control valve 48 in the safety control unit 4 and the spring 50 will then close the valve 48 and out off the flow of gas to both the main burner I and the pilot burner [4. At any time thereafter the apparatus may be reset for manual control by closing the valve 5 and switch and opening the switch 23. If during automatic operation the pilot burner M is extinguished for any reason the apparatus will function to cut off the supply of gas as described in connection with manual operation.

The signal light bulb L performs two separate and distinct functions. First, when energized it shows that the apparatus is functioning properly, and second it supplies the necessary impedance to prevent shorting across the line %91 when ,the switches 23, 85 and. fi l-[ill are all closed. If desired a condenser or inductance or other cesisstance element can be substituted for the During periods of non-operation when either Or both of the switches 23 and 85 are open current will flow from the side so of the line through the leads 9! and HM to the primary winding I03 of the transformer SI, and from the primary winding I33 to the terminal 9 of the switch 19 through the leads Hi5 and 93. From the terminal as current flows through the switch [9 to the terminal 95 and from there back to the other side ii! of the line through the lead as, primary winding it of the solenoid 25, and lead 93. A blanking out alternating current of higher voltage is thus always superimposed upon the direct much lower voltage current generated by the thermocouple in the thermocouple circuit whenever either of the switches 23 or 85 are open. From this it will be apparent that the electromagnet 5! can only be energized by the thermocouple current when both of the switches 23 and 85 are closed since current flowing from the side 99 of the line through the lead 9! will then follow the path of least resistance through the switches 23 and 85 instead of through the primary winding 1% of the transformer 8|.

The oven may be repeatedly used during a prolonged power failure without the necessity of manually lighting the pilot burner M with a match each time it is used, as the construction and arrangement of the apparatus is such that it can be quickly and easily converted from a fully automatic electric ignition system to a constantly burning pilot burner system. In order to convert the apparatus to a constantly burning pilot burner system the safety control unit 4 is manually set and held in the condition shown in Fig. 3, by depressing the button 1% secured to the armature 18, in which condition gas can flow to the pilot burner [i1 and be ignited by a match. The control unit t must be held as shown in Fig. until the pilot burner M has heated the thermocouple l8 sufficiently for it to energize the electrornagnet 5i after which the button Hi3 may be released. The electromagnet 5! will hold the control valve in the chamber 35 open as shown in Fig. 3 and the spring fil will return the interrupter valve in the chamber 3"! back to open position as shown in Fig. 2. Then the operation of the burner i is manually controlled by the opening and closing of the valve 5. Obviously the apparatus cannot be automatically controlled by the time control mechanism 86 during a power failure, nor can the electroinagnet be de-energized by the transformer 6| during manual control.

In Fig. we have shown a slightly modified form of the invention in which we place the secondary winding 88 of the transformerv Bl in parallel with the electromagnet winding 54 instead of in series therewith. As shown one side of the winding 80 is connected to the tube 2| by the lead I 0! and the other side of the winding 80 is connected to the wire 22 by the lead I08. Otherwise the construction and operation of this form of the invention is the same as that shown in Figs. 1 to 4 and the same reference characters have been applied to similar parts.

From the foregoing it will be apparent to those skilled in this art that we have provided a very simple and efficient mechanism for accomplishing the objects of the invention.

It is to be understood that we are not limited to the specific constructions shown and described herein as various modifications may be made therein within the scope of the appended claims.

What is claimed is:

1. In an automatic ignition and control apparatus of the character described the combination of a main burner, a pilot burner operative to ignite said main burner, an electric ignition element operative when energized to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to cut off the supply of fuel to said main burner and said pilot burner interposed in said conduit between said main burner and said manifold, a manually operable shut off valve interposed in said conduit between said safety control unit and said main burner, a branch conduit extending between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoid being operative upon energization to first set said safety control unit in condition to supply fuel to said pilot burner while cutting off the supply of fuel to said main burner and upon subsequent deenergization to set said safety control unit in condition to also supp y fuel to said main burner, an electromagnet associated with said safety control unit and operative when energized to maintain said safety control unit in said last set condition, a thermocouple adapted to be heated by said pilot burner, an

electric circuit between said thermocouple and said electromagnet through which said magnet is energized by said thermocouple when said thermocouple is heated, a manually operable normally open master switch, a normally closed supplemental master switch disposed in series with said master switch, said master switch and said supplemental master switch being operative when both are closed to effect the energization of said solenoid and said electric ignition element, a normally closed switch means disposed in series with said master switch which is operative when opened to effect deenergization of said solenoid and said electric ignition element, and a thermostatic element adapted to be heated by said pilot burner and operative when heated to maintain said normally closed switch means open and when cool to maintain said normally closed switch means closed, a transformer having a primary winding and a secondary winding, said secondary winding being connected into said thermocouple circuit, said transformer being operative when energized to superimpose an alternating current upon the thermocouple current of sufficient voltage to blanket out the thermocouple current and thereby de-energize said electromagnet, said master switch and said supplemental master switch each being operative when open to effect the energization of said transformer, and a time control mechanism operat1ve to open and close said supplemental master switch at predetermined set times.

2. An automatic ignition and control apparatus as defined in claim 1 in which said secondary winding is connected into said thermocouple circuit in series with said electromagnet.

3. An automatic ignition and control apparatus as defined in claim 1 in which said secondary winding is connected into said thermocouple circuit in parallel with said electromagnet.

4. In an automatic ignition and control apparatus of the character described the combination of a main burner, a pilot burner operative to ignite said main burner, an electric ignition element operative when energized to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to cut off the supply of fuel to said main burner and said pilot burner interposed in said conduit between said main burner and said manifold, a manually operable shut off valve interposed in said conduit between said safety control unit and said main burner, a branch conduit extending between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoid being operative upon energization to first set said safety control unit in condition to supply fuel to said pilot burner while cutting off the supply of fuel to said main burner and upon subsequent de-energization to set said safety control unit in condition to also supply fuel to said main burner, an electromagnet associated with said safety control unit and operative when energized to maintain said safety control unit in said last set condition, a thermocouple adapted to be heated by said pilot burner, an electric circuit between said thermocouple and said electromagnet through which said magnet is energized by said thermocouple when said thermocouple is heated, a manually operable normally open master switch, a normally closed supplemental master switch disposed in series with said master switch, said master switch and said supplemental master switch being operative when both are closed to effect the energization of said solenoid and said electric ignition element, a normally closed switch means disposed in series with said master switch, a normally open switch means, a thermostatic element adapted to be heated by said pilot burner and operative when heated to maintain said normally closed switch means open and said normally open switch means closed, a transformer having a primary winding and a secondary winding, said secondary winding being connected into said thermocouple circuit, an impedance adapted to be connected in series with said master switches, said transformer being operative when energized to superimpose an alternating current upon the thermocouple current of suflicient voltage to blanket out the thermocouple current and thereby de-energize said electromagnet, said normally closed switch means being operative when closed to connect said primary winding in series with said solenoid and when open to effect the de-energization of said solenoid and said electric ignition element, said normally open switch means being operative when age to blanket out the thermocouple current and thereby deenergize said electromagnet, said normally closed switch means being operative when closed to connect said primary winding in series with said solenoid and when open to effect the deenergization of said solenoid and said electric ignition element, said normally open switch means being operative when closed to connect said impedance in. series with said master switches, said master switch and said supplemental master switch each being operative when open to effect the energization of said transformer, and a time control mechanism operative to open and close said supplemental master switch at predetermined set times.

14. An automatic ignition and control apparatus as defined in claim 13 in which said secondary winding is connected into said thermocouple circuit in series with said electromagnet.

15. An automatic ignition and control apparatus as defined in claim 13 in which said secondary winding is connected into said thermocouple circuit in parallel with said electromagnet. 16. An automatic ignition and control apparatus as defined in claim 13 in which said master switch and said supplemental master switch are also operative when both are closed to maintain said transformer de-energized.

' 17. In an automatic ignition and control apparatus of the character described the combina tion of a main burner, a pilot burner operative to ignite said main burner, an electric ignition element operative when energized to ignite said pilot burnerfa gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to cut off the supply of fuel to said main burner and said pilot burner interposed "in said conduit between said main burner and said manifold, a branch conduit extending between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoid being operative upon energization to first set said safety control unit in condition to supply fuel to said pilot burner while cutting off the supply of fuel to said main burner and upon subsequent deenergization to set said safety control unit in condition to also supply fuel to said main burner,

an electromagnet associated with said safety control unit and operative when energized to maintain said safety control unit in said last set condition, a thermocouple adapted to be heated by said pilot burner, an electric circuit between said thermocouple and said electromagnet through which said magnet is energized by said thermocouple when said thermocouple is heated, a manually operable normally open master switch, said master switch being operative when closed to effect the energization of said solenoid and said electric ignition element, a normally closed switch means disposed in series with said master switch which is operative when opened to effect deenergization of said solenoid and said electric ignition element, and a thermostatic element adapted to be heated by said pilot burner and operative when heated to maintain said normally closed switch means open and when cool to maintain said normally closed switch means closed, a transformer having a primary winding and a secondary winding, said secondary winding being connected into said thermocouple circuit, said transformer being operative when energized to superimpose an alternating current upon the 16 thermocouple current of sufficient voltage to blanket out the thermocouple current and thereby deenergize said electromagnet, said master switch being operative when open to effect the energization of said transformer.

18. An automatic ignition and control apparatus as defined in claim 17 in which said secondary winding is connected into said thermocouple circuit in series with said electromagnet.

19. An automatic ignition and control apparatus as defined in claim 17 in which said secondary winding is connected into said thermocouple circuit in parallel with said electromagnet.

20. An automatic ignition and control mechanism as defined in claim 17 in which said master switch is also operative when closed to maintain said transformer deenergized.

21. In an automatic ignition and control apparatus of the character described the combination of a main burner, a pilot burner operative to ignite said main burner, an electric ignition element operative when energized to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to cut off the supply of fuel to said main burner and said pilot burner interposed in said conduit between said main burner and said manifold, a branch conduit extending between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoid being operative upon energization to first set said safety control unit in condition to supply fuel to said pilot burner while cutting off the supply of fuel to said main burner and upon subsequent deenergization to set said safety control unit in condition to also supply fuel to said main burner, an electromagnet associated with said safety control unit and operative when energized to maintain said safety control unit in said last set condition, a thermocouple adapted to be heated by said pilot burner, an electric circuit between said thermocouple and said electromagnet through which said magnet i energized by said thermocouple when said thermocouple is heated, a manually operable normally open master switch, said master switch being operative when closed to effect the energization of said solenoid and said electric ignition element, a normally closed switch means disposed in series with said master switch, a normally open switch means, a thermostatic element adapted to be heated by said pilot burner and operative when heated to maintain said normally closed switch means open and said normally open switch means closed, a transformer having a primary winding and a secondary winding, said secondary winding being connected into said thermocouple circuit, an impedance adapted to be connected in series with said master switch, said transformer being operative when energized to superimpose an alternating current upon the thermocouple current of suflicient voltage to blanket out the thermocouple current and there by deenergize said electromagnet, said normally closed switch means being operative when closed to connect said primary winding in series with said solenoid and when open to effect the dc energization of said solenoid and said electric ignition element, said normally open switch means being operative when closed to connect said impedance in series with said master switch, and said master switch being operative when open to effect the energization of said transformer.

22. An automatic ignition andocontrol appdra s tus as set forth in claim 21 in which said .sed: ondary winding is conneoted into. said .t1'l ."mQ=- couple circuit in series with saidelectmmagnet,

23. An automatic ignition and control apparw tus as definediin claim 21 inwhich said secondary winding is connected into. said thermocoup e i1r= 01111; in parallel with said eleotremagnet.

24. An automaiioiisnii-im and ddnt dl pp ratus as defined. in olaim 21 in wliioh said, master switch and said s pplemental master swit h are also. operative when oth v are closed into aid transform r de-enezr ized.

25 dn-s utdmatis nition and control 311- pdraius of ihs Qhdr dter d ssribsd heoombins onvoi a main burner, a nildt bu r d etive. o i nit sa d main burdens-ands i A ni on elemen dnsrs ivdi hen energized to .ienite'sdid pilot; burner, egasssmsfllel su ply mdl' ifDli a mai odnd ii n which nu l is supplied to burner 111 said mdnii ld, a sa ety dnti' ldnii opera iv tds i t e surel f o said indi bumd dri s d pil ts ner inter- 1 sa d n-bii ner v v h duitexten etween said sdfetyod 'QIFQLWZHQ and said 19 mrne thr u h hicl 7. did is. us lisd. to said .p dt uri srz rd s lsn i dd rsti 1y sssd iste ith id-ssfetys tr said .pl ns d bsins 99$ i d 11pm nersizdt on to first sets dlsd ety coni rolsnit in condition to supply m to d 1 3951 1 3 4 Whils wining off the s pplypi fue o sa d-main burner-and upon iibssdusni detion to sdtfsdi afety con r l ,unit i condi isntdd sd supply i iel to s ma n burner, n lssir msss s dis d W hss si s d Ql' QiBM fi e sti ewhsn nergi ed to mai tai said sa ety c ntrol un t in d id asi set condi= @1011; s t erm dsup-lel ddp ed t h h dtsd bysdid pilot homer, an 31 81 11? dir uit be ween i 1,

hermocouple and sa d lsctr m gn t h ough hich s d magn t snerg'i ed y said ermor uple wh n said th rm wimle s he ted, a man,- s ly spe db e normall own masterswit h is ormally clos d up lem ta master swi h dis posed i ser es with said master switch sa d aster i h and id sup lem ntal master witch-b in pe a ve n both are dlosed is ffe t. th en siz ion of said s e oid nd said elegtrig ignition element, a n mall ldss a wit h mea disposed i ser es w th aid m ster wi sh, a no mally open swit h means, a thermos tatic element adap d t bs estsd .by said p l t urner and operative Whs 'hed edio mai ta n aid norma1'1yc10sed s tch m ns open and id w ll 1. 6 switch m ans ,cl s d, a rsnsiorm r havin spr marywindms nd se ndsry wind mg, said secondary Winding being connected into sa d the mocouple d r s trdnsidrmer being operative when energized to superimpose vdin alternating current upon the therm c up ent, of ssii ien vo age to blan out the thermdcs ple current and th r by deeen nrsi e said l s m sn d s ms sl di sii llifl ins W0 branches; said primary winding being interposed n one of said ranches and said mast switch nd-said: upplementa m ster w tch b n in terposod n e ss i the other of d dbr nches an impedance, said normally closed. witch means eing operat ve when ,closed t oonnsci aid primary w n ng in se ies With sa sole id nd hn open to sf ee the d snsrsizdtipn isdid lenoid an sdidle ssi i gnition elsmestv said no mally pen swi ch eans bein psraiiwe when c osed i do m t s dparausfl 'si t in.

, p116? idder determined set series with ssidimssd d e, ssid mssis switch nd sdid iisnlem nial swim ed h bein when 919%; fi v e ddsrs z i n of siqs sr @Q m% sdn d mss s ism ns siwe to. o en nd los sa u p ment master w tch at srsdet xmins s tw'h'e di s1 au omatic gn tion a qs t l an arsius Q1". igb cha act d s r bedihs c m n on o a main bum n a piiot I sr'nsr dp' a v 1 i s aid b ms c i isn sn lsmnwper-stiv i en snerjs zsd 'w ignite d il thu is ga eous Iss1 s p l mani sh Whidhfiu is su p i 'to aid. m m'bumi irdin said md ii ldfd s ty ncdnirol nsi di e 20cm th supp y f fuel is. s nd main bu ner nd s id pildt bu n r inte'n ds sa d c nduit, se ssn did ma bu ne nd fil f ailimlfld so al yerable s ut Q 1 alv l stsrpdssd in s id ddn ui betwee said die con rol. n t and id ma n bu n s branch ondidi xt nding iis esn said sa ety son rql 9 1; a? dd dpild urn 3191 22 w c fuel supp d o s id ils humsr; sol noid 9 iivs y @fiQQififli-ilifi? said s fet dnt l uni id sdl nsid bsni o di vs r ms isn rslz n, 90

rst sst s -saietye ntml uhit i dndi id 29 pp y dlidsaidpi fit bur-1 h h le u in hdsup lysi iddldsd d ginhu nsr a d lin n dbssqusni de-ensrsi a iQIi-w et s id dl i (i011- ol, unit in d idi ibn ids d su ply u l T -sa d ma n burn r, dnls r mssns ds Qdiawd wi h aid SQIQWQQQEIDIHIQIH? and dd sti e w neridb sizedi m imain d dsdis s r9 u n sa Ms: se sdndiiidn, a ihsr sdd saddp sd 19 1 9 eated by said ilot-burne dn e e io ,ci c t i sss said id lrm ddnple dhdsd s s rd es ei thross w l chsdild was?? is s rsiz d by aid il srns sd ple when said thsrinos buni i eated, 11y Qper 'hle norma bnei ast r swii h sdrma ly dissed sdnp ms s missisr wiisli dispdssd n ,se iss'w th id mssis wims; mdsisr witch and sai sup i msmsl mssisr s ims b in 'opsrdi vs whe t a e 195?.1 t9 fifisstrihdsnergization of aid solsnoid v and said s sstri ignition el e t s n m l losed swiis m d dis dsed-in s ries wi h d aster 9h w ish, is o erative when opened to ds t defin siz n d i sid solen ddn s i o means r pod o s dd 9p v.idtivs t9 md i a d i165- mdll d wiic'hmi sns 1 9 w ils sd si'lb urner is i o is I fip lild 'r i i a p mary wl dms and sssdddar wi d n sa enddiiy W ndin no s nneoiddi fidssi il -drmdcou ils 9 mm "d d imssie msr b in wer i e when @1 sd fiOfil il im qse vam a i in ,cdr e idqn'i s ihd mqcddbls sl r ni f dffidisni ydlidss to his 944 t e i l rmoc .3mm? and ili isby sldsne siz said le t o a net, said mas r sw h dd sd d su bl master swim: o dps diivs w ii s t6 M m d-t ansi rm f-d ime 99 1 9190 has rsd iid 11 s n'dn ldserss dsupp msni l ma te iisds di iii ns ddddimla paras id de ned-1n shim din TWhiQlo aid t}.-

' n rsw of idle sd.iierdoier'q sc p, q pn o tion of a main burner, a pilot burner operative to ignite said main burner, an electric ignition element operative when energized to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to out off the supply of fuel to said main burner and said pilot burner interposed in said conduit between said main burner and said manifold, a manually operable shut off valve interposed in said conduit between said safety control unit and said main burner, a branch conduit extending between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoid being operative upon energization to first set said safety control unit in condition to supply fuel to said pilot burner while cut-- ting off the supply of fuel to said main burner and upon subsequent deenergization to set said safety control unit in condition to also supply fuel to said main burner, an electromagnet associated with said safety control unit and operative when energized to maintain said safety control unit in said last set condition, a thermocouple adapted to be heated by said pilot burner, an electric circuit between said thermocouple and said electromagnet through which said magnet is energized by said thermocouple when said thermocouple is heated, a manually operative normally open master switch, a normally closed supplemental master switch disposed in series with said master switch, said master switch and said supplemental master switch being operative when both are closed to effect the energization of said solenoid and said electric ignition element, a normally closed switch means disposed in series with said master switch, a normally open switch means, means responsive to said pilot burner and operative to maintain said normally closed switch means open and said normally open switch means closed while said pilot burner is ignited, a transformer having a primary winding and a secondary winding, said secondary winding being connected into said thermocouple circuit, an impedance adapted to be connected in series with said mas ter switches, said transformer being'operative when energized to superimpose an alternating current upon the thermocouple current of suf ficient voltage to blanket out the thermocouple current and thereby deenergize said electromagnet, said normally closed switch means being operative when closed to connect said primary winding in series with said solenoid and when open to effect the deenergization of said solenoid and said electric ignition element, said normally open switch means being operative when closed to connect said impedance in series with said master switches, said master switch and said supplemental master switch each being operative when open to effect the energization of said transformer, and a time control mechanism operative to open and close said supplemental master switch at predetermined set times.

30. An automatic ignition and control apparatus as defined in claim 29 in which said secondary winding is connected into said thermocouple circuit in series with said electromagnet.

31. An automatic ignition and control apparatus as defined in claim 29 in which said secondary winding is connected into said thermocouple circuit in parallel with said electromagnet.

32. An automatic ignition and control apparatus as defined in claim 26 in which said master switch and said supplemental master switch are also operative when both are closed to maintain said transformer deenergized.

33. An automatic ignition and control appa ratus as defined in claim 29 in which said master switch and said supplemental master switch are also operative when both are closed to maintain said transformer deenergized.

34. In an automatic ignition and control apparatus of the character described the combination of a main burner, a pilot burner operative to ignite said main burner, an electric ignition element operative when energized to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to cut off the supply of fuel to said main burner and said pilot burner interposed in said conduit between said main burner and said manifold, a branch conduit extending between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoid being operative upon energization to first set said safety control unit in condition to supply fuel to said pilot burner while cutting oil the supply of fuel to said main burner and upon subsequent deenergization to set said safety control unit in condition to also supply fuel to said main burner, an electromagnet associated with said safety control unit and operative when energized to maintain said safety control unit in said last set condition, a thermocouple adapted to be heated by said pilot burner, an electric circuit between said thermocouple and said electromagnet through which said magnet is energized by said thermocouple when said thermocouple is heated, a manually operable normally open master switch, a normally closed supplemental master switch disposed in series with said master switch, said master switch and said supplemental master switch being operative when both are closed to effect the energization of said solenoid and said electric ignition element, a normally closed switch means disposed in series with said master switch which is operative when opened to eii'ect deenergization of said solenoid and said electric ignition element, means responsive to said pilot burner and operative to maintain said normally closed switch means open while said pilot burner is ignited, a transformer having a primary winding and a secondary winding, said secondary winding being connected into said thermocouple circuit, said transformer being operative when energized to superimpose an alternating current upon the thermocouple current of sufiicient voltage to blanket out the thermocouple current and thereby deenergize said electromagnet, said master switch and said supplemental master switch each being operative when open to effect the energization of said transformer, and a time control mechanism operative to open and close said supplemental master switch at predetermined set times.

35. An automatic ignition and control apparatus as defined in claim 34 in which said secondary winding is connected into said thermocouple circuit in series with said electromagnet.

36. An automatic ignition and control apparatus as defined in claim 34 in which said secondary Winding is connected into said thermocouple circuit in parallel with said electromagnet.

37. An automatic ignition and control apparatus as defined in claim 34 in which said master switch and said supplemental master swltchare' also operative when both are closed to maintain said transformer deenergized.

38. In an automatic i nition and control apparatus of the character described the combination a main burner, pilot burner operative to i nite said main burner, an electric ignition e1 entoperative when energized to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to main burner from said manifold, a safety control unit operative to cut off the supply of 4 to said main burner and said pilot burner interposed. in said conduit between said main burner and said manifold, a branch conduit extending between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoid being operative upon energization to first set said safety control unit in condition to supply fuel to said pilot burner while cutting off the supplyof fuel to said main burner and upon subsequent deenergization to set said safety control unitin condition to also supply fuel to said main burner, an electromagnet associated with said safety control unit and operative when energizedto maintain safety control unit in said last set condition, a thermocouple adapted to be heated'by said pilot burner, an electric circuit between vsaid thermocouple and said electromagnet through ich said magnet is energized by saidthermocouple when said thermocouple is ,heated, av

manually operable normally open master. switch,

a normally closed supplemental master switch,

disposed in series with said master switch, said master switch and said supplemental master switch being operative when both-are closed to effect the energization of said solenoid and said electric ignition element, a normally closed switch leans disposed in series with said master switch, a normally open switch means, means responsive to said pilot burner and operative to maintain said normally closed switch means open while said pilot burner is ignited, a transformer having a primary winding and a secondary winding, said secondary winding being connected into said thermocouple circuit, an impedance adapted to be connected in series with said master switches,

said transformer being operative when energized to superimpose an alternating current upon the thermocouple current of sufficient voltage to blanket out the thermocouple current and thereby deenergize said electromagnet, said normally closed switch means being operative when closed l to connect said primary winding in series with said solenoid and when open to effect the deenergization of said solenoid and said electric ig nition element, said normally open switch means being operative when closed to connect said impedance in series with said masterswitches, said master switch and said supplemental master switch each being operative when open to effect the energization of said transformer, and a time control mechanism operative to open and close said supplemental master switch at predetermined set times.

39. An automatic ignition and control apparatus as defined in claim 38 in which said secondary winding is connected into said therrnocouple circuit in series with said electromagnet.

40. An automatic ignition and control apparatus as defined in claim 38 in which said secondary winding is connected into said thermocircuit 22 couple circuitin'parallel with said electromag net.

41.. An automatic ignition and. control apparatus as defined in claim 38 in which said master switch and said supplemental master switch are also operative when both are closed to maintain said transformer deenergized.

a2. In an automatic ignition and control apparatus-of the character. described the combina ion of a main burner, a pilotburner operative to ignite said main burner, an electric ignition element operative when energised to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to out off the supply of fuelto said main burner and said pilot burner interposed in said conduit ioetween said main burner and said manifold, a branch conduit extending between said safety control unit and'said ilot burner'through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said so1e noid being operative upon energization to first set said safety control unit in condition to supply fuel to said pilot burner while cutting off the supply of fuel to said main burner and upon subsequent deenergization to set said safety control unit in condition to also supply fuel to said main burner, an electromagnet associated with said safety control unit and'operative when energized to maintain said safety control unit in saidlast set condition, a thermocouple adapted to be heated by said pilot burner, an electric between said thermocouple and said electromagnet through which said magnet is energized. by said thermocouple when said thermocouple is'heated, a manually operable normally open master switch, said master switch being operative when closed to effect the en ergiaation of said solenoid and said electric ignition element, a normally closed switch means disposed in series with said master switch which is operative when opened cleaner-giration of said solenoid and said electric ignition element, means responsive to said pilot burner and operative to maintain said normally closed switch means open while said pilot burner is ignited, a transformer having a primary winding and a secondary winding, said secondary winding be ing connected into said thermocouple circuit, said transformer being operative when one. to superimpose an alternating current upon the thermocouple current of sufficient voltageto blanket out the thermocouple current and thereby deenergize said electromagnet, said master switch being operative when open to eff ct the energization of said transformer.

43. An automatic ignition and control apparatus as defined in claim 42 in which said secondary winding is connected into said thermocouple circuit in series with said elcctromagnet;

44. An automatic ignition and control apparatus as defined in claim d2 in which said secondary winding is connected into said thern1ocouple circuit in parallel with said electron-lagnet.

45. An automatic ignition-and control mechanism as defined in claim 42 in which said master switch is also operative when closed to maintain said transformer deenergized.

46. In an automatic ignition and control apparatus .of the character described the combination of a main burner, a pilot burner operative to ignite said main burner, an electric ignition element operative when energized to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to out off the supply of fuel to said main burner and said pilot burner interposed in sale conduit between said burner and said manifold, a branch conduit extending between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoi-d being operative upon energization to first set said safety control unit in condition to sup" ply fuel to said pilot burner while cutting off the supply of fuel to said main burner and upon subsequent deenergization to set said safety con-- trol unit in condition to also supply fuel to aid main burner, an electromagnet associated wi 1 said safety control unit and o erative when energized to maintain said safety control unit in said last set condition, a thermocouple apted to be heated by said pilot burner, electric circuit between said thermocouple and said electromagnet through. which said magnet is energized by said thermocouple when said thermocouple is heated, a manually operable normally open master switch, said master switch being operative when closed to chest the energization of said solenoid and said electric i nition element, a normally closed switch means isposed in series with said master swi ch, normally open switch means reopen to said pilot burner and operative to maintain said normally closed switch means and said normally open switch means closed Willis said pilot burner is ignited, a transformer hay-- ing a primary winding and a secondary winding, said secondary winding being connected into said thermocouple circuit, an impedance a ted to be connected in series with switch, said transformer being ope tive ween energized so superimpose alternati it current upon the thermocouple current of sufficient voltage to blanket out the thermocouple current thereby deenergise said electromagnet, said normally closed switch means being operative i closed to connect said primary winding in s was with said solenoid and when open to e sect the deenergization of said solenoid and said electric ignition element, said normally open switch means being operativewhen closed to connect said impedance in series with said master switch, and said master switch being operative when open to effect the energization of said transformer.

t7. An automatic ignition control apparatus as set forth in claim 46 in which said secondary winding is connected into said thermocouple circuit in series with said electromagnet.

48. An automatic ignition and control apparatus as defined in claim id in which said secondary winding is connected into said thermocouple circuit in parallel with said electromagnet.

49. An automatic ignition and control apparatus as defined in claim l6 in which said master switch and said supplemental master switch are also operative when both are closed to maintain said transformer deenergized.

50. In an automatic ignition and control apparatus of the character described the combination of a main burner, a pilot burner operative to ignite said main burner, an electric ignition element operative when energized to ignite said n OK pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is supplied to said main burner from said manifold, a safety control unit operative to cut off the supply of fuel to said main burner and said pilot burner interposed in said conduit between said main burner and said manifold, a branch conduit extending'between said safety control unit and said pilot burner through which fuel is supplied to said pilot burner, a solenoid operatively associated with said safety control unit, said solenoid being operative upon energization to first set said safety control unit in condition to sup ply fuel to said pilot burner while cutting off the supply of fuel to said main burner and upon subsequent deenergization to set said safety control unit in condition to also supply fuel to said main burner, an electromagnet associated with said safety control unit and operative when energized to maintain said safety control unit in said last set condition, a thermocouple adapted to be heated by said pilot burner, an electric circuit between said thermocouple and said electrornagnet through which said magnet is energized by said thermocouple when said thermocouple is heated, a manually operable normally open master switch, a normally closed supplemental master switch disposed in series with said master switch, said master switch and said supplemental master switch being operative when both are closed to effect the energization of said solenoid and said electric ignition element, a normally closed switch means disposed series with said master switch, a normally open switch means, means responsive to said pilot burner and operative to maintain said normally closed switch means open and said nor mally open switch means closed while said pilot burner is ignited, a transformer having a primary winding and secondary winding, said secondary winding being connected into said thermocouple circuit, said transformer being operative when energized to superimpose an alternating current upon the thermocouple current of suiiicient voltage to blanket out the thermocouple current and thereby denergise said electromagnet, a parallel circuit having two branches, said primary Winding being interposed in one of said branches and said master switch and said supplemental master switch being interposed in series in the other of said branches, an impedance, said normally closed switch means being operative when closed to connect said primary winding in series with said solenoid and when open to effect the deenergization of said solenoid and said electric ignition element, normally open switch means being operative when closed to connect said parallel circuit in series with said impedance, said master switch and said supplemental master switch each being operative when open to effect the ener 'ization of said transformer, and a time control mechanism operative to open and close said supplemental master switch at predetermined set times.

CHARLES M. MAYER. RICHARD L. PERL. ELIVIER L. WARNER.

Name Date Hildebrecht July 14, 1942 Number

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