US2693232A

US2693232A - Automatic ignition and control mechanism for gaseous fuel burners

Info

Publication number: US2693232A
Application number: US352636A
Authority: US
Inventors: John M Hoff; Elmer L Warner
Original assignee: TAPPAN STOVE CO
Current assignee: TAPPAN STOVE Co
Priority date: 1953-05-04
Filing date: 1953-05-04
Publication date: 1954-11-02
Anticipated expiration: 1971-11-02

Description

1954 J. M. HOFF ETAL AUTOMATIC IGNITION AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS Filed May 4, 1953 4 Sheets-Sheet 1 INVENTORS' J? h N. Hoff f/mer L. Warner Nbv.'2, 1954 J. M. .HOFF EI'AL AUTOMATIC IGNITION AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS Filed May 4, 1953 '4 Sheets-Sheet 2 v 5 70 35' 46' 77 4; 55 57 3a 39 av 46 I v 4 56 '1 "M 47 v 6 $2 $3 7 67 97 a 43 JNVENTORS N 544. H m

A TTOR NE 1 J. M. HOFF ET AL AUTOMATIC IGNITION Nov. 2, 1954 AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS Filed May 4. 1953 4 Sheeis-Sheet 3 INVENIORJ 10mm Hoff y 91/77:?!41. WOr/Yer Nov. 2, 1954 J. M. HOFF ETAL 2,693,232

AUTOMATIC IGNITION AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS Filed May 4, 1953 4 Sheets-Sheet 4 Q m m 1 g 4, Q 3 \l (MN 2 Rx W s V c I [Q x Q q g;

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. l I INVENTORS I E J b/Mi Hoff y //77 @l L. WQ/"l76l" A/Jm United States Patent Q AUTOMATIC IGNITION AND CONTROL MECHA- NISM FOR GASEOUS FUEL BURNERS rein M. Hoff, Mansfield, and Elmer L. Warner, Crestline, Ohio, assiguors toThe Tappan Stove Company, lldansfield, Ohio, a corporation of Ohio Application May 4, 1953, Serial No. 352,636

22 Claims. (Cl. 1619) This invention relates to an automatic electric ignition and control mechanism for cooking range burners using filed May 5, 1952, now Patent No. 2,637,392, and the co-pending application of Mayer et al. filed June 13, 1952, Serial No. 293,282, now Patent No. 2,637,393. It is especially 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 extinguished for some reason, but it will be promptly reignited by the pilot burner if fuel is supplied thereto. But if the pilot burner 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 the main or pilot burner. It has been found by experience that both the pilot burner and the main burner are frequently extinguished during 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. p

In order to prevent any accumulation of unburned gas and thus eliminate danger of an explosion therefrom in the event the pilot burner is extinguished for any reason during operation, 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 the pilot burner is extinguished for any reason duringoperation, 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 be ignited by a gaseous fuel pilot burner which burnsonly during the time the oven is in operation. At other times the supply of gas .to both the main burner and the pilot burner is cut oif by the safety control unit which is interposed in a main conduit between the gas supply manifold and the main burner. During operation gas flows from the manifold into the safety control unit. From the safety control unit gas flows through a small branch conduit directly to the pilot burner; and through the mam conduit, a manually operable normally closed main control valve, and a standard thermostatically operated oven temperature control valveto the main burner. A normally open master control switch which is associated with the main control valve is provided to initiate operation of both the p lot burner and the main burnerJ The master control switch is arranged to be closed by the opening of the ma n control valve and to be opened by the closing of the mam control valve. The closing of the master control switch ener- 'gizes, through a normally closed thermostatically opened 2,693,232 Patented Nov. 2, 1954 switch, .a solenoid transformer which is operatively connected to the safety control unit, and an electric resistance heating element which is operatively associated with a thermostatic element connected to the normally closed switch. The solenoid transformer when energized energizes an electric resistance ignition element and sets the safety control unit to permit the fiow of gas from the safety control unit to the pilot burner while cutting oil the supply of gas from the safety control unit to the main burner. The pilot burner is ignited by the electric ignition element and projects a flame against a thermocouple which is operatively connected to an electromagnet in the safety control unit. After the thermostatic element becomes heated by the electric resistance heating element it opens the normally closed switch which deenergizes the solenoid transformer and the electric ignition element. soon as the solenoid transformer is cleenergized the safety control unit is automatically operated by spring means to maintain the supply of gas to the pilot burner through the branch conduit and to also supply gas to the main burner through the main control valve and the oven temperature control valve. The main burner is then ignited by the pilot burner. The thermocouple, as long as it is heated by the pilot burner, maintains the safety control unit through the electromagnet in condition 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 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 oil 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, which deenergizes the electromagnet and causes the safety control unit to cut off communication between the manifold and both the main burner and the pilot burner. Then before the pilot burner and the main burner can be reignited the master control switch must be opened to deenergize the electric resistance heating element, and maintained open long enough for the thermostatic element to cool and close the normally closed switch, after which when the master control switch is again closed the apparatus will re-cycle as 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 it 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 setting of the time control mechanism opens the supplemental master switch which must be maintained closed during manual control of the apparatus. The main control valve is then manually opened and the master control switch is simultaneously closed, which has no effect since the supplemental master switch isv now open and the safety control unit is cutting off the supply of gas to both the main burner and the pilot burner. At the set time the control 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 by 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 can 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 controllled by the opening and closing of the main control va ve.

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 auto matic 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 drawings by reference characters, the numeral 1 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 1 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 6 to the burner 1. The oven temperature control valve 6 is operative to regulate the amount of gas flowing to the burner 1 during operation in order to maintain the oven 2 at any desired set temperature. The valve 6 is set to any desired temperature by a handle 7 having a pointer 8 which cooperates with a graduated dial 9 carried by the valve 6. The valve 6 is controlled according to the temperature setting by a thermostatic element 10 which is mounted in the oven 2 and is connected to the valve 6 as shown at 11. The main control valve 5 is a standard shut off valve which is manually opened and closed by a handle 13 and a valve stem 12. The oven temperature control valve 6 is of standard well known construction. Consequently it is not shown in detail herein. There are many different constructions available any one of which will work equally well herein. If desired the shut 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 a branch conduit 15 which extends between the safety control valve mechanism 4 and the pilot burner 14. The pilot burner 14 is disposed adjacent the rear end of the main burner 1 in position to ignite the burner 1 when gas is supplied thereto. An electrical ignition element 16 is operatively associated with the pilot burner 14 in position to ignite the pilot burner 14 when gas is supplied thereto. A thermocouple 18 is mounted in position to be heated by a flame from the pilot burner, and a thermostatic element 17 is operatively connected to a double throw switch 19 which controls the energization of the electrical ignition element 16 and a solenoid transformer 29 which when energized sets the safety control unit 4 to supply gas to the pilot burner 14 only, as will be described in connection with the description of the safety control unit and the operation of the whole apparatus. The switch 19 also controls the energization of a signal light bulb L which when energized indicates that the apparatus is functioning properly. An electrical resistance heating element 17a which is associated with the thermostatic element 17 is provided to maintain the thermostatic element 17 heated during operation of the main burner 1. 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 1, as will also be described in connection with the description of the safety control valve mechanism and the operation of the apparatus. An electric ClICLllt between the thermocouple 18 and the safety control unit 4 is established by a copper tube 21 and an insulated wire 22 within the tube 21.

A master control switch 23 is provided to control the operation of the apparatus. The master control switch 3 is associated with the main control valve 5 and is adapted to be opened and closed by a cam 25, carried by the valve stem 12, through a link 26. The arrangement is such that the switch 23 is simultaneously closed with the opening of the main control valve 5, and is simultaneously opened with the closing of the valve 5.

The construction of the safety control unit 4 and its connection to the solenoid transformer 20 will now be described, reference being had to Figs. 2 and 3, of the drawings. This unit comprises a casing 35 having a chamber 36 in one end thereof and a chamber 37 in the other end thereof. The

chambers

36 and 37 are connected by a bore 38 of reduced diameter. A valve seat 39 is located at one end of the bore 38 and a similar valve seat 40 is located at the other end of the bore 38. The chamber 36 is closed by a removable cap 41 and the chamber 37 is closed by a removable cap 42. A sleeve 43, havmg end walls 44 and 45, is carried by the cap 41 and extends into the chamber 36. A valve stem 46 which 1s sl1dably mounted in a bushing 47 carried by the end wall 45 of the sleeve 43, extends from the chamber 36 into the sleeve 43. A control 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 l ght iron disc is secured to the other end of the stem 46 w1th1n the sleeve 43. A very light relatively weak coiled compression spring 50 disposed about the valve stem 46 between the control valve 48 and the end wall 45 of the sleeve 43 normally holds the control valve 48 against the valve seat 39. An electromagnet 51 is secured to one end of a hollow exteriorly threaded stud 52 whlch extends out through aligned apertures in the end wall 44, of the sleeve 43, and in the end of the cap 41. A nut 53 screwed onto the outer portion of the stud 52 securely holds the magnet 51 and the sleeve 43 111 place. The legs of the magnet 51 have a winding 54 thereon, one endof which is connected to the wire 22 in the tube 21. The tube 21 is inserted into the hollow stud 52 and is held in place by a screw fitting 52a. A sleeve 55 is screwed into a threaded recess in the end of the cap 42, as indicated at 56, and extends into the chamber 37 a slight distance. One end of the sleeve 55 is closed by an end wall 57, and the other end, which is open, registers with a circular aperture 58 in the wall of the cap 42. A plunger 59 is slidably mounted in the sleeve 55 and extends out through the aperture 58 in the cap 42. A stem 62, which is secured to the inner end of the plunger 59,-extends out through an aperture 63 in the end Wall 57 of the sleeve 55, and through the chamber 37 and into the bore 38. The stem 62 has a collar rigidly secured thereon between the end wall 57 and the outer end of the stem. An interrupter valve 65 of suitable material is slida'bly mounted'upon the stem 62 between the end wall 57 of the sleeve '55 and the collar 64.. The interrupter valve 65 is adapted to engage the valve seat 40 to cut off the how of gas into-the chamber 37 during the initiation of operation as Wlll 116 11616111- after described. A compression spring 67 which 1s stronger than the spring 6'6 is disposed about the stem 62 within the sleeve 55 betweenthe inner face of the end wall-57 and the inner end of the plunger 59. The spring 67 is operative to return the plunger 59, stem 62 and valve 65 from the position shown in Fig. 3 back to their normal position asshown' in Fig. 2, against the resistance of the spring 66. A port 68 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 chamber 36. During normal operation of the main burner 1 gas flows from the chamber 36 through the reduced intermediate bore 38 and into the chamber 37. A port 69-which establishes communication between the branch conduit 15 and the bore 38 is provided to supply gas to the pilot burner 14; and :a port 70 establishescommunication between the chamber 37 and the conduit 3 to permit the flow of gas from the chamber 37 to the main burner 1 through the main control valve and the oven temperature control valve 6.

The solenoid transformer 20 comprises a spool 75 on which are wound the primary winding 76 and the secondary winding 77. An armature 78 is slidably mounted in the bore 79 of the spool 75. 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 78 thereof in axial alignment 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 1 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 81 in the thermocouple circuit 21-22 in series with the winding 54 of the electro-magnet 51. The winding 80 is heavy wire having substantially no resistance. 7

. The operation of the apparatus will now be described, particular reference being had to Fig. 4 of the drawings. 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 maizn'con trol 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 91, switch 23, lead 92, switch 85 and lead 93 to the terminal '94 of the double throw switch 19. The current then fiows through the switch 19'to the terminal 95 thereof and then through the lead 96 to the primary winding '76 of the solenoid transformer 20 and from there back to the other side 97 of the line through the lead 98. Current also flows from the lead 93 through the lead 115, the electrical resistance heating element 17a and back to the other side 97 of the line through the lead 116. The electric heating element 17a, the solenoid transformer 20 and the electric ignition element 16 which is connected to the secondary winding 77 of the solenoid transformer 20 by the

leads

99 and 100 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 fiow to the pilot burner 14 where it is ignited by the ignition element 16, but gas cannot yet flow to the main burner 1 since the interrupter valve mechanism in the chamber 37 of the safety control unit is maintaining the entrance thereto closed. The pilot burner being ignited heats the thermocouple 18 and the heating element 17a being energized heats the thermal element 17. The thermocouple being heated generates a minute current of the order of .015 volt which flows from the thermocouple through the tube 21 to the-winding 54 of the electromagnet $1 and from there through the wire 22 and secondary wind ing 80 of the transformer 81 back to the thermocouple 18. Thethermocouple current energizes the electromagnet 51 sufficiently 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 17 causes it to actuate the switch 19 to break the circuit to and deenergize the solenoid transformer 20 and consequently the electric ignition element 16, and to make the circuit to the signal light bulb L through the terminal 101 and lead 102. The construction and arrangement of the thermal element 17- and the heating element 17a are such that the actuation of the switch 19 to' break the circuit to the solenoid transformer 20 and make the cir cuit to the signal light bulb L is delayed until after the pilot burner 14 has heated the thermocouple 1'8 sulficiently for it to generate current. As soon as the solenoid transformer 20 is deenergized the spring 67 returns the interrupter valve mechanism in the chamber 37 back from the position shown in Fig. 3 to the position shown in Fig. 2 while the electromagnet 51 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 1 where it is ignited by the pilot burner 14. Under normal conditions the burner 1 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 the manually operable valve 5 cuts off the flow of gas from the control unit 4 to the main burner 1, but it does not cut off the flow of gas to the pilot burner 14. This is elfected by the opening of the master control switch 23 which effects the energization of the primary winding 103 of the transformer '81. When the switch 23 is opened to terminate operation current flows from the side of the line through leads 91 and 104 to the primary winding 103 of the transformer 81, and from the primary winding 103 through. the. leads 105 and 93 to the terminal 94 of the switch '19. From the terminal 94 the current flows through the switch 19 to the terminal 101 and from there back to the other side 97 of the line through the lead 102 and signal light bulb L and lead 116. The energizing of the primary winding 103 of the transformer 81 generates an alternating current of the order of .15 volt in the secondary winding 80 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 deenergizes the electromagnet 51 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 18 and the alternating current generated by the transformer 81 are of such minute amplitude that neither one can energlze the electromagnet 51 sufiiciently for it to attract the armature 49 to it after the armature has once been released by the electromagnet 51 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 51 is so slight that it cannot overcome the holding force exerted upon the armature 49 by the electromagnet 51 when the armature is in contact therewith, but is suflicient to separate the armature 49 and electromagnet whenever the electromagnet is momentarily deenergized. When the electromagnet 51 is energized only by the direct current 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. Thus 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 1s equal to the positive value of the direct current. At the 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.

As long as outside current is available the mam control valve 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 1 is cut on and off before it reaches to valve 5 by the safety control unit 4 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 and the termination of the operation of the main burner 1. 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 14, but it is cut off from the burner 1 by the interrupter valve 65. After the thermostatic element 17 has been heated sufficiently to actuate the switch 19 the interrupter valve 65 is opened after which gas can flow from the safety control unit 4 through the open valve 5 to the main burner 1. The valve 5 is provided only to control the operation 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 18 will cool. The electromagnet 51 will then be deenergized 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 14 and the main burner 1. The master control switch 23 must then be opened to deenergize the heating element 17a and maintained open long enough for the thermal element 17 to cool and shift the switch 19 back into engagement with the contact 95 before the pilot burner 14 and main burner 1 can be reignited as described.

In order to adapt the mechanism for automatic operation of the burner 1, 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 86 which is operative to close and open the switch 85 at predetermined set times. Operating current is supplied to the time control mechanism through the leads 110 and 111. During manual control of the burner 1 the switch 85 is maintained closed. For automatic control the time control mechanism 87 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 87 automatically opens the switch 85. The valve 5 is then manually opened and the switch 23 closed. The opening of the valve 5 and the closing of the switch 23 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 4 to both the main burner 1 and the pilot burner 14. At the set time the 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 86 will open the switch 85 which will effect the energization of the primary winding 103 of the transformer 80 which in turn will effect the deenergization of the electromagnet 51, both exactly as described in connection 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 cut oil the flow of gas to both the main burner 1 and the pilot burner 14. At any time thereafter the apparatus may be reset for manual control by closing the valve 5 and switch 85 and opening the switch 23. If during automatic operation the pilot burner 14 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 lightbulb 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 acrossthe line -97 when the

switches

23, 85 and 94101 are all closed. If desired a condenser or inductance or otherresistance element can be substituted for the bulb L.

During periods of non-operation when either or both of the

switches

23 and 85 are open current will flow from the side 90 of the line through the

leads

91 and 104 to the primary winding 103 of the transformer 81, and from the primary winding 103 to the terminal 94 of the switch 19 through the

leads

105 and 93. From the terminal 94 current flows through the switch 19 to the terminal 95 and from there back to the other side 97 of the line through the lead 96, primary winding 76 of the solenoid 20, and lead 98. 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 circircuit whenever either of the

switches

23 or 85 is open. From this it will be apparent that the electromagnet 51 can only be energized by the thermocouple current when both of the

switches

23 and 85 are closed since current flowing from the side 90 of the line through the lead 91 will then follow the path of least resistance through the

switches

23 and 85 instead of through the primary winding 103 of the transformer 81.

The oven may be repeatedly used during a prolonged power failure without the necessity of manually lighting the pilot burner 14 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 pilotburner 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 103 secured to the armature 78, in which condition gas can flow to the pilot burner 14 and be ignited by a match. The control unit 4 must be held as shown in Fig. 3 until the pilot burner 14 has heated the thermocouple 18 sufiiciently for it to energize the electromagnet 51 after which the button 103 may be released. The electromagnet 51 will hold the control valve in the chamber 36 open as shown in Fig. 3 and the spring 67 will return the interrupter valve in the chamber 37 back to open position as shown in Fig. 2. Then the operation of the burner 1 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 electromagnet be deenergized by the transformer 81 during manual control.

In Fig. 5 we have shown a slightly modified form of the lnvention in which We place the secondary winding 80 of the transformer 81 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 21 by the lead 107 and the other side of the winding 80 is connected to the wire 22 by the lead 108. Also as shown in Fig. 5 we substitute an electrically actuated time delay mechanism 117 for the thermal element 17 and heating element 17a, and operatively connect it to the switch 19. The closing of the master control switch 23 Wlll energize the time delay mechanism 117 which will after a predetermined length of time actuate the sw1tch 19 to break the circuit to the solenoid transformer 20 and make the circuit to the signal light bulb L. The time delay mechanism 117 is of standard construction, consequently it is not shown in detail herein. Many different makes are available, any one of which Wlll work equally well herein. 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 beunderstood 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 ignitionand" control apparatus of the character described the combinationof a main burner, a pilot burner operative to ignite said main burner", an electric ignitionelement operative when energized to ignite said pilot burner, a gaseous fuel supply manifold, a main conduit through which fuel is sup plied tosaid 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 extendingv 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 sole 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 toset 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 betweensaid thermocouple and said electromagnetthrough which said magnet is energized by said thermocouple when said thermocouple is heated, a manually operable normally open master switch, anormally closedsupplemental 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, electrically energized means disposed in series with said master switch and saidsupplementalmaster switch and operative when energized to etfect the opening of said normally closed switch means after the elapse of a predetermined length of time after the closing of said master switch and said supplemental master switch, a transformer having a primary winding and a secondary winding, said secorrdary' 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 toblanket out the thermocouple current and thereby deenergize said electromagnet, said master switch and said supplemental master switch eachbeing 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.

7.. An automatic ignition and control apparatus as defined in claim 1 in which said electrically energized means comprises a thermostatic element connected to said normally closed switch means and an electric resistance heating element mounted in position to heat vsaid thermostatic element.

3. 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, electrically energized means disposed in series with said master switch and said supplemental master switch and operative when energized to effect the opening of said normally closed switch means and the closing of said normally open switch means after the elapse of a predetermined length of time after the closing of said master control switch and said supplemental master control switch, 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 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.

4. An automatic ignition and control apparatus. as defined in claim 3 in which said electrically energized means comprises a thermostatic element connected to said normally closed switch means and an electric resistance heating element mounted in position to heat said thermostatic element.

5. An automatic ignition and control apparatus as defined in claim 1 in which said master switch and said supplemental master switch are also operative when both are closed to maintain said transformer deenergized.

6. An automatic ignition and control apparatus as defined in claim 3 in which said master switch and said supplemental master switch are also operative when bothd are closed to maintain said transformer deenerg1ze 7. 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 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, electrically energized means disposed in series with said master switch and said supplemental master switch and operative when energized to effect the opening of said normally closed switch means after the elapse of a predetermined length of time after the closing of said master switch and said supplemental master switch, 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 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.

8. An automatic ignition and. control apparatus as defined in claim 7 in which said electrically energized means comprises a thermostatic element connected to said normally closed switch means and an electric resistance heating element mounted in position to heat said thermostatic element.

9. An automatic ignition and control apparatus as defined in claim 7 in which said master switch and said supplemental master switch are also operative when both are closed to maintain said transformer deenergized.

10. 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, 21 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 sole noid 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, 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, electrically energized means disposed in series with said master switch and said supplemental master switch and operative when energized to effect the opening of said normally closed. switch means and the closing of said normally open switch means after the elapse of a predetermined length of time after the closing of said master control switch and said supplemental master control switch, 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 sufiicient 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 times.

11. An automatic ignition and control apparatus as defined in claim 10 in which said electrically energized means comprises a thermostatic element connected to said normally closed switch means and an electric resistance heating element mounted in position to heat said thermostatic element.

12. An automatic ignition and control apparatus as defined in claim 10 in which said master switch and said supplemental master switch are also operative when both are closed to maintain said transformer deenergized.

13. 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 mainburner, 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, electrically energized means disposed in series with said master switch and operative when energized to effect the opening of said normally closed switch means after the elapse of a predetermined length of time after the closing of said master switch, 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 deenergize said electromagnet, said master switch being operative when open to effect the energization of said transformer.

14. An automatic ignition and control apparatus as defined in claim 13 in which said electrically energized means comprises a thermostatic element connected to said normally closed switch means and an electric resistance heating element mounted in position to heat said thermostatic element.

15. An automatic ignition and control mechanism as defined in claim 13 in which said master switch is also operative when closed to maintain said transformer deenergized.

16. 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 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, a

normally open switch means, electrically energized means disposed in series with said master switch and operative when energized to effect the opening of said normally closed switch means and the closing of said normally open switch means after the elapse of a predetermined length of time after the closing of said master switch, 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 sufiicient 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 switch, and said master switch being operative when open to effect the energization of said transformer.

17. An automatic ignition and control apparatus as defined in claim 16 in which said electrically energized means comprises a thermostatic element connected to said normally closed switch means and an electric resistance heating element mounted in position to heat said thermostatic element.

18. An automatic ignition and control apparatus as defined in claim 16 in which said master switch is also operative when closed to maintain said transformer deenergized.

19. 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 electroma net 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 throu h 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, electrically energized means disposed in series with said master switch and said supplemental master switch and operative when energized to effect the opening of said normally closed switch means and the closing of said normally open switch means after the elapse of a predetermined length of time after the closing of said master control switch and said supplemental master control switch, 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 suflicient voltage to blanket out the thermocouple current and thereby deenergize 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 pri mary 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 parallel circuit in series with said impedance, said master switch and said supplemental master switch each being operative when open to etfect the energization of said transformer, and a time control mechanism operative to open and close said supplemental master switch at predetermined set times.

20. An automatic ignition and control apparatus as defined in claim 19 in which said electrically energized means comprises a thermostatic element connected to said normally closed switch means and an electric resistance heating element mounted in position to heat said thermostatic element.

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 circuitbetween 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 s id solenoid and said e ectric ignition element. electrically energized means disposed in series with said master switch and operative when energized to effect the opening of said normally closed switch means after the elapse of a predetermined len th of time after the cl sing of said master switch.

22. An automatic ignition and control apparatus as defined in claim 21 in which said electrically energized means comprises a thermostatic element connected to said normally closed switch means and an electric resistance heating element mounted in position to heat said thermostatic element.

References Cited in the file of this patent UNITED STATES PATENTS