US2761502A - Automatic ignition and control mechanism for gaseous fuel burners - Google Patents

Description

Sept. 4, 1956 J. M. HOFF ET AL AUTOMATIC IGNITION AND CONTROL MECHAN ISM FOR GASEOUS FUEL BURNERS 4 Sheets-Sheet 1 Filed April 1, 1954 Sept. 4, 1956 J. M. HOFF ET AL AUTOMATIC IGNITION AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS 4 Sheets-Sheet 3 Filed April 1, 1954 INVENTORS John M. Hoff p 1956 J. M. HOFF ET AL 2,761,502

AUTOMATIC IGNITION AND CONTROL MECHANISM FOR GASEOUS FUEL BURNERS Filed April 1, 1954 4 Sheets-Sheet 4 INVENTORS Jo /m M H off y fiC/far/es M Nay e1" gym ilnited States Patent AUTONATI IGNETEQN AND QONTROL MECH- ANZSM FOR GASEGUS FUEL BURNERS Eohn M. Hoff and (Charles M. Mayer, Mansfield, ()liio, assignors to The Tappan Stove Company, Mansfield, ()hio Application April 1, 1954, Serial No. 420,297

16 Claims. (Cl. 161-9) This invention relates to an automatic electric ignition and control mechanism for cooking range burners using gaseous fuel and is a modification of the control mechanism shown in the patent to Charles M. Mayer and John M. No. 2,577,787 issued December 11, 1951, the patent to Charles M. Mayer et al. No. 2,637,393 issued May 5, 1953, and the copending application of John M. Hoff and Elmer L. Warner filed May 4, 1953, Serial No. 352,636 now Patent No. 2,693,232. It is especially designed and adapted for automatically igniting and controlliru the operation of oven burners in cooking range 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 gaseon; fuel burner which is adapted to be ignited by a gaseous fuel pilot burner. As long as the pilot burner is i nited 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.

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 during operation, 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 burns only 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 off 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 main conduit, a manually operable normally closed main control valve, and a standard thermostatically operated oven temperature control valve to the main burner. A normally open master control switch which is. associated with. the main control valve is provided to initiate operation of both 2,761,502 Patented Sept. 4, 1956 the pilot burner and the main burner. The master control switch is arranged to be closed by the opening of the main control valve and to be opened by the closing of the main control valve. The closing of the master control switch energizes, through a normally closed thermally actuated switch and a normally closed gas pressure actuated switch, a solenoid transformer which is operatively connectedto the safety control unit. The solenoid transformer when energized energizes an electric resistance ignition element and an electric resistance heating element which is operatively associated with a thermostatic element connected to the normally closed thermally actuated switch, and sets the safety control unit to permit the flow of gas from the safety control unit to the pilot burner While cutting ofi 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. As soon as the solenoid transformer is deenergized 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. As soon as gas is admitted to the main burner the normally closed gas pressure actuated switch is opened by a sylphon bellows which is connected into the gas conduit for the main burner between the main control valve and the main burner. .By this time the thermostatic element has cooled and closed the thermally actuated switch but the circuit to the solenoid transformer remains broken since the pressure actuated switch which is in series with the thermally actuated switch is open and will be maintained open as long ,as gas is being supplied to the main 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 thepilot 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 other than a gas failure 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 theburners. Immediately upon the failure of the gas supply the gas pressure. actuated switch will close and make the circuit to the solenoid transformer since the thermally actuated switch is already closed. The solenoid transformer will then be energized which will energize the electric heating element associated with the'thermally actuated switch and the electric ignition element and will reset the safety control unit in condition to cut off communication between the manifold and the main burner while maintaining communication ,between the manifold and the pilot burner. If the gas failure is only momentary the apparatus will recycle as just described. But if the gas failure is prolonged, say for several minutes, the thermally actuated switch will be opened by the heating of the thermostatic element which willbreak the circuit to and deenergize the solenoid transformer, the heating element and the ignition element. The safety control unit will then be automatically set by spring means in condition to cut off communication between themanifold and both the main burner and the pilot burner. Then after the thermostatic element has cooled and again closed the thermally actuated switch the solenoid transformer will again set the safety control unit in condition to supply gas to the pilot burner while cutting off communication between the manifold and the main burner. This operation will be repeated until gas is again available at which time the apparatus will recycle to ignite the main burner as originally described. As another example of the manner of operation of the apparatus, let us assume that during operation the pilot burner is extinguished for some reason other than the failure of the gas supply. Upon the extinguishment of the pilot burner the thermocouple will quickly cool in a few seconds which will deenergize the electromagnet and allow the safety control unit to cut off the supply of gas to both the pilot burner and the main burner. The cutting off of the supply of gas to the main burner will cause the pressure actuated switch to close and make the circuit to the solenoid transformer. The apparatus will then automatically recycle to ignite the pilot burner and the main burner as originally 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 eifect since the supplemental master switch is 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 oif the supply of gas to both the main burner and the pilot burner, thus terminating operation.

Prolonged power failure of many hours and sometimes of even several days duration frequently occurs 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 controlled by the opening and closing 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 an apparatus of the aforesaid character which will automatically recycle to relight the pilot burner and the main burner after each accidental extinguishment of the pilot burner during operation.

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

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. l 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 unit 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 unit 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 17 is mounted in position to be heated by a flame from the pilot burner and 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 unit and the operation of the apparatus. An electric circuit between the thermocouple 17 and the safety control unit 4 is established by a copper tube 31 and an insulated wire 3?. within the tube 31.

A solenoid transformer 18 is carried by the safety control unit 4 and is operative when energized to set the safety control unit 4 in condition to supply gas to the pilot burner 14 while cutting off the supply of gas to the main burner i. The solenoid transformer 18 is also operative when energized to energize the electric ignition element 16 and a heating element 19 which are disposed in parallel circuits both of which include the secondary winding of the solenoid transformer. The energization of solenoid transformer 13 is controlled by a double throw gas pressure actuated switch 20 and a single throw thermally actuated switch 21 disposed in series with each other and with the primary winding of the solenoid transformer is. The pressure actuated switch 20 also controls the energization of a signal light bulb L which when energized indicates that the apparatus is functioning properly.

The pressure switch 20 is actuated by a sylphon bellows 22 which is connected into the gas supply conduit 3 between the main control valve 5 and the main burner 1 by a small diameter conduit 23; and the thermally actuated switch 21, which is normally closed, is actuated by a thermostatic element 24 which is adapted to be heated by the heating element 19.

A master control switch 25 is provided to control the operation of the apparatus. The master control switch 25 is associated with the main control valve 5 and is adapted to be opened and closed by a cam 26, carried by the valve stem 12, through a link 27. The arrangement is such that the switch 25 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 18 will now be described, reference being had to Figs. 2 and 3, of the rawings. This unit comprises a casing 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, having end walls 44 and 45, is carried by the cap 41 and extends into the chamber 36. A valve stem 46 which is slidably mounted in a bushing 47 carried by the end wall 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 4-6 within the chamber 36, and an armature 59 in the form of a thin light iron disc is secured to the other end of the stem 46 within the sleeve 43. A very light relatively weak coiled compression spring 51 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 which 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 in place. The legs of the magnet 51 have a winding 54 thereon, one end of which is connected to the tube 31 and the other end of which is connected to the wire 32 in the tube 31. The tube 31 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 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 64 rigidly secured thereon between the end wall 57 and the outer end of the stem. An interrupter valve 65 of suitable material is slidably 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 flow of gas into the chamber 37 during the initiation of operation as will be hereinafter described. A compression spring 67 which is stronger than the spring 66 is disposed about the stem 62 within the sleeve 55 between the 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 Pig. 3 back to their normal position as shown in Fig. 2, against the resistance of the spring 66. A port 62; 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 7% establishes communication 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 5 and the oven temperature control valve 6.

The solenoid transformer 18 comprises a spool 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 18 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 73 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 burnerl 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 3132 in series with the winding 54 of the electromagnet 51. 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 the drawings. During manual control the supplemental master switch 85 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 25, and then manually close the main control valve 5 and open the master switch 25 to terminate operation. When the switch 25 is closed current will flow from one side of the line through the lead '91, switch 25, lead 92, switch 85 and lead 93 to the double throw pressure switch 20. The current then flows through the switch 20 to the ter- 7 minal 94 thereof and then through the lead 95 to the terminal 96 of the time delay switch 21 and from there back to the other side 97 of the line through the lead 98, the primary winding 75 of the solenoid transformer 18 and the lead 99. The solenoid transformer 18 is now energized. The energizing of the solenoid transformer 18 effects the energization of the electric ignition element 16 which is connected to the secondary winding 77 of the solenoid transformer 13 by the leads 100 and 101, and the heating element 19 which is connected to the secondary winding 77 in parallel with the electric ignition element 16 by the leads 102 and 103. The solenoid transformer 18 being energized shifts the various parts of the safety control unit 4 from the position shown in Fig. 2 to the position shown in Figure 3, opening the control valve 48 and closing the interrupter valve 65. Gas can now flow 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 17 and the heating element 19 being energized heats the thermal element 24. The thermocouple being heated generates a minute current of the order of .015 volt which flows from the thermocouple through the tube 31 to the winding 54 of the electromagnet 51 and from there through the wire 32 and secondary winding 80 of the transformer 81 back to the thermocouple 17. The thermocouple current energizes the electromagnet 51 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 18, 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 24 causes it to actuate the time delay switch 21 to break the circuit to and deenergize the solenoid transformer 18 and consequently the electric ignition elemeat 16 and the heating element 19. The construction and arrangement of the thermal element 24 and the heating element 19 are such that the actuation of the switch 21 to break the circuit to the solenoid transformer 18 is delayed until after the pilot burner 14 has heated the thermocouple 17 sufficiently for it to generate current. As soon as the solenoid transformer 18 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 to the main burner 1 where it is ignited by the pilot burner 14. The gas now flowing from the control unit 4 through the control valve 5 to the main burner 1 expands the sylphon bellows 22 which shifts the contact arm 104 of the switch 20 from the terminal 94 into engagement with the terminal 105, which makes a second break in the solenoid transformer circuit and energizes the signal light bulb L through the lead 106. vAfter the pressure switch 20 has been actuated to make the second break in the solenoid transformer circuit the thermally actuated switch 21 will close due to the cooling of the thermal element 24 after the heating element 19 therefor has been deenergized. The pressure switch 20 will then maintain the solenoid transformer circuit broken as long as gas is being supplied to the main burner 1. Under normal conditions the burner 1 will now operate under the control of the oven temperature control valve 6 until its operation is terminated by the opening of the switch 25 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, which causes the bellows 22 to shift the switch 20 to make the solenoid circuit, but it does not cut off the flow of gas to the pilot burner 14.

This is effected by the opening of the master control switch 23 which etfects the energization of the primary winding 107 of the transformer 81. When the switch 25 is opened to terminate operation current flows from the side of the line through leads 91 and 108 to the primary Winding 107 of the transformer 81, and from the primary winding 107 through the leads 109 and 93 to the terminal of the switch 20. From the terminal 105 the current flows back to the other side 97 of the line through the lead 106 and signal light bulb L. The energizing of the primary winding 107 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 59 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 17 and the alternating current generated by the transformer 81 are of such minute amplitude that neither one can energize 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 sufficient to separate the armature 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. This 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.

As long as outside current is available the main 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 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 25 through the safety control unit 4 controls both the initiation and the termination of the operation of the main burner l. The closing of the normally open master control switch 25 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 24 has been heated sufficiently to actuate the switch 21 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.

It the pilot burner is extinguished for any reason other than gas failure during operation, the thermocouple 17 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 cutting 01f of the supply of gas from the control unit 4 to the main burner 1 will reduce the pressure in the bellows 22 which will cause it to close the pressure actuated switch 26 and make the circuit to the solenoid transformer 18. The apparatus will then automatically recycle to ignite the pilot burner 14 and the main burner 1 as previously described. But if the pilot burner 14, and with it the main burner 1, are extinguished during operation by reason of gas supply failure, the gas pressure actuated switch 2% will immediately close and make the circuit to the solenoid transformer 18 since the thermally actuated switch 21 is already closed. The solenoid transformer will then be energized which will energize the heating element 19, associated with the thermally actuated switch 21, and the electric ignition element 16, and will reset the safety control unit 4 in condition to cut off communication between the manifold M and the main burner 1 while maintaining communication between the manifold M and the pilot burner 14. If the gas failure is only momentary the apparatus will recycle as previously de-- scribed in connection with the initiating of operation. But if gas failure is prolonged, for say several minutes or more, the thermally actuated switch 21 will be opened upon the heating of the thermostatic element 24, by the heating element 19, which will break the circuit to and deenergize the solenoid transformer 18 which in turn will deenergize the heating element 19 and the ignition element 16.v The safety control unit 4 will then be automatically set by the spring 50 in condition to cut 011 communication between the manifold M and both the main burner 1 and the pilot burner 14 as shown in Fig. 2. Then after the thermostatic element 24 has cooled and again closed the thermally actuated switch 20 the solenoid transformer being again energized will again set the safety control unit 4 in condition to supply gas to the pilot burner 14 While cutting ofi the supply of gas to the main burner 1. This operation will be successively repeated until gas is again available at which time the apparatus will ignite the pilot burner 14 and main burner 1 as previously 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 25 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 86 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'86 automatically opens the switch 85. The valve is then manually opened and the switch 25 closed. The opening of the valve 5 and the closing of the switch 25 will have no efiect 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 43 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 efiect the energization of the primary Winding 107 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 cutoff 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 25. 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 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 9097 when the switches 25, and 20105 are all closed. if desired a condenser or inductance or other resistance element can be substituted for the bulb L.

During periods of non-operation when either or both of the switches 25 and 85 are open current will flow from the side of the line through the leads 91 and 108 to the primary winding 167 of the transformer 81, and from the primary winding 107 to the switch 26 through the leads 109 and 93. From the switch 20 the current Will flow back to the other side 97 of the line through the lead 95, switch 21, lead 98, primary winding '76 of the solenoid 13 and lead 9. 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 25 or 85 are open. From this it will be apparent that the electromagnet 51 can only be energized by the thermocouple current when both of the switches 25 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 25 and 85 instead of through the primary winding 107 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 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 112 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 sufficiently for it to energize the electromagnet 51 after which the button 112 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.

If the power failure occurs during operation of the main burner 1 the apparatus will automatically convert to a constantly burning pilot burner system since thereis no current available to effect the deenergization of the electromagnet 51 and the extinguishment of the pilot burner 14 when the valve 5 is closed to extinguish the main burner 1. Obviously the apparatus cannot be automatically controlled by the time control mechanism 86 during a power failure.

In Fig. 5 we have shown a slightly modified form of the invention in which we place the secondary winding 80 ofthe transformer 81 in parallel with the electromagnet winding 54 instead of in series therewith. As shown one side of the winding80 is connected to the tube 31 by the lead 113 and the other side of the winding 80'is connected to the Wire 32 by the lead 114. Also as shown in Fig. we substitute an electrically actuated time delay mechanism 115 for the thermostatic element 24 and heading element 19, and operatively connect it to the switch 21. The closing of the master control switch 25 will energize the time delay mechanism 115 which will after a predetermined length of time actuate the switch 21 to break the circuit to the solenoid transformer 18. The time delay mechanism 115 is of standard construction, consequently it is not shown in detail herein. Many different makes are available, any one of which will 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 efiicient mechanism for accomplishing the objects of the invention.

It is to be understood that we are not limited to the specific construction 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 ofi 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 first normally closed switch means, a second normally closed switch means disposed in series with said first normally closed switch means, each of said normally closed switch means being operative when open to effect the deenergization of said solenoid and said electric ignition element, electrically energized means operative when energized to effect the opening of said first 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, gas pressure actuated means connected into said main conduit between said safety control unit and said main burner and operative after the opening of said first normally closed switch means to open said second normally closed switch means, 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 analternating 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.

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

3. An automatic ignition and control mechanism as defined in claim 1 in which the secondary winding of said transformer is connected into said thermocouple circuit in series with said electromagnet and said thermocouple.

4. An automatic ignition and control mechanism as defined in claim 1 in which the secondary winding of said transformer is connected into said thermocouple circuit in series with said electromagnet and in parallel with said thermocouple.

5. 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 bumer 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 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 eifect the energization of said solenoid and said electric ignition element, a first normally closed switch means, a second normally closed switch means disposed in series with said first normally closed switch means, a normally open switch means, electrically energized means operative when energized to effect the opening of said first 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, gas pressure actuated means connected into said main conduit between said safety control unit and said main burner operative after the opening of said first normally closed switch means to open said second normally closed switch means and to close said normally open switch means, 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 super-impose an alternating current upon the thermocouple current of suificient voltage to blanket out the thermocouple current and thereby deenergize said electromagnet, said first and second normally closed switch means being operative when both are closed to connect said primary winding in series with said solenoid and when either is 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.

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

7. An automatic ignition and control mechanism as defined in claim 5 in which the secondary winding of said transformer is connected into said thermocouple circuit in series with said electromagnet and said thermocouple.

8. An automatic ignition and control mechanism as defined in claim 5 in which the secondary winding of said transformer is connected into said thermocouple circuit in series with said electromagnet and in parallel with said thermocouple.

9. 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 transformer having a primary winding and a secondary winding operatively associated with said safety control unit, said solenoid transformer 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 transformer and said electric ignition element, said ignition element being disposed in series with the secondary winding of said solenoid transformer, a first normally closed switch means, a second normally closed switch means, said first normally closed switch means and said second normally closed switch means being disposed in series with each other and the primary winding of said solenoid transformer, said first normally closed switch means and said second normally closed switch means each being operative when opened to deenergize said solenoid transformer, electrically energized means disposed in series with the secondary winding of said solenoid transformer in parallel with said electric ignition element, said electrically energized means being operative when energized to effect the opening of said first 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, gas pressure actuated means connected into said main conduit between said safety control unit and said main burner and operative after the opening of said first normally closed switch means to open said second normally closed switch means, 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.

10. An automatic ignition and control apparatus as defined in claim 9 in which said electrically energized means comprises a thermostatic element connected to said first normally closed switch means and an electric resistance heating element mounted in position to heat said thermostatic element.

11. An automatic ignition and control mechanismas defined in claim 9 in which the secondary winding of said transformer is connected into said thermocouple circuit in series with said electromagnet and said thermocouple.

12. An automatic ignition and control mechanism as defined in claim 9 in which the secondary winding of said transformer is connected into said thermocouple circuit in series with said electromagnet and in parallel with said thermocouple.

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 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 transformer having a primary winding and a secondary winding operatively associated with said safety control unit, said solenoid transformer 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 transformer and said electric ignition element, said ignition element being disposed in series with the secondary winding of said solenoid transformer, a first normally closed switch means, a second normally closed switch means, a normally open switch means, said first normally closed switch means and said second normally closed switch means being disposed in series with each other and with the primary winding of said solenoid transformer, electrically energized means disposed in series with the secondary winding of said solenoid transformer in parallel with said electric ignition element, said electrically energized means being operative when energized to effect the opening of said first 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, gas pressure actuated means connected into said main conduit between said safety control unit and said main burner and operative after the opening of said first normally closed switch means to open said second normally closed switch means and to close said normally open switch means, 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 deenergize said electromagnet, said first and second normally closed switch means being operative when both are closed to connect said primary winding in series with said solenoid transformer and when either is open to efiect the deenergization of said solenoid transformer and said electric ignition element and said electrically energized means,

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.

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 first 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 the secondary winding of said transformer is connected into said thermocouple circuit in series with said electromagnet and said thermocouple.

16. An automatic ignition and control mechanism as defined in claim 13 in which the secondary winding of said transformer is connected into said thermocouple circuit in series with said electromagnet and in parallel with said thermocouple.

References Cited in the file of this patent UNITED STATES PATENTS

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