US2649524A

US2649524A - Thermally responsive oven burner control unit

Info

Publication number: US2649524A
Application number: US227836A
Authority: US
Inventors: Richard L Perl
Original assignee: TAPPAN STOVE CO
Current assignee: TAPPAN STOVE Co
Priority date: 1951-05-23
Filing date: 1951-05-23
Publication date: 1953-08-18
Anticipated expiration: 1970-08-18

Description

Aug. 18, 1953 R. PERI. 2,649,524

THERMALLY RESPONSIVE OVEN BURNER CONTROL UNIT Filed May 25, 1951 4 Sheets-Sheet 1 i INVENTOR. H10/farai. Pe/d/ fty Aug. 18, 1953 R. L. PERI. 2,649,524

THERNALLY RESPONSIVE OVEN BURNER CONTROL UNIT Filed May 23, 1951 4 Sheets-Sheet 2 INVENTOR. f. 3 Flc/'fara' Per/ Aug. 18, 1953 R. L.. PERL 2,649,524

TRERMALLY RESPONSIVE OVEN BURNER CONTROL UNIT Filed May 23. 1951 4 Sheets-Sheet 5 INVENTOR. Ruba/d4. 236/4/ Aug. 18, 1953 R. L. PERI. 2,649,524

THERMALLY RESPONSIVE OVEN BURNER CONTROL UNIT Filed May 2s, 1951 4 sheets-sheet 4 34 l' @i423 *#22 JNVENTOR.

, l RzCha/dLPe/V Patented ug. 18, 1953 THERMALLY RESPONSIVE OVEN BURNER GONTROLUNIT Richard L. Perl, Galion, Ohio, assignor to The Tappan Stove Company, Mansfield, Ohio, a corporationof Ohio Application May 23, 195 1, Serial No. 227,836 23 Claims. @L200-137) This invention relates to a thermally responsive control unit for use in automatic ignition and control systems for the oven burners "of cooking ranges using .gaseous fuel, and is an improvement of the control unit disclosed in the co-pending application .of Charles M. Mayer, Serial No. 196,659, filed November -20, 1950, and now abandoned. It .is especially adapted for use in automatic ignition and control systems in which the main burner is ignited by an associated pilot burner which must burn constantly all of the time the main 'burner is turned on. The pilot burner is ignited by an electrical resistance ignition element which is automatically de-energized after the pilot burner has been ignited. l

In most cooking ranges in use today it is immaterial whether or not the ovjen burner burns constantly as long as the pilot burnerassociated therewith is ignited. 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 vis extinguished for any reason while the maincontrol valve is still open to supply gas to the main burner a very dangerous situation sometimesarises. 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 .ignitedand unburned gas will accumulate in the oven which may violently explode when an attempt ismade to ignite either the main or pilot burner. Ithas been found by experience that both the pilot burner and the main burner are frequently extinguished during use while the main control valvejis open to supply gas to the main burner. This issometimes due to a momentary failureof thegas supply or the slamming of the oven door or to various other reasons. y

In order to prevent-an accumulation of unburned gas and thus eliminate danger of an eX- plosion therefrom in the event themppilot burner is extinguished for .anyreason while the.'con trol valve is still open to supply gas to the main burner, a safety control valve mechanism by which the supply of gas tothe main burner is cut oi independently of themain controlvalve, in the event the pilot burner is'extinguished Vfor any reason while the main gas.'- control valye is open, is provided.

I have shown my .improyedcontrol unit vincorporated in an automatic ignition` andcontrol system which includes 'a main gaseous fuel :main control valve. control switch, as the main control valve is 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 lout off b y a main control valve which is interposed in a conduit between the gas supply mani- '.fold and the burners. When the main control valve is open gas will ilow from the manifold through the main control valve and into a safety control valve mechanism. From the safety control valve mechanism gas will flow through a small branch conduit directly to the pilot burner; and through the main conduit and a standard V'thermostatically operated oven temperature control valve to the main burner. A normally open master control switch which is operatively associatedwith the main control valve is arranged to be closed bythe opening of the main control ,valve and `to be opened by the closing of the The closing of the master opened to supply gas to the burners, makes a ycircuit which through a normally closed switch in the control unit energizes an electric resistance ignition element and a solenoid which is operatively connected to the safety control valve mechanism. The energization of the solenoid causes, it to operate the safety control valve mechanism to permit the ilow of gas to the pilot burner while cutting off the supply of gas to the main burner. The pilot burner is then ignited by the electric ignition element and projects a ilame against a thermostatic element, in the control unit, which controls the operation of the normally closed switch, and against a thermo- Mcouplewhich is in circuit with an electromagnet in the safety' control valve mechanism. After the thermostatic element becomes heated it opens the normally closed switch which de-en- Y ergizes theelectric ignition element and the solenoid. As soon as the solenoid'is Vcie-energized the safety `control vmechanism is automatically Yoperated by spring means to supply gas to the main burner through the oven temperature con- .safety control valve mechanism through the lectromagnet in condition to supply gas to both the main burnerand the pilot burner. The'oven ytemperature control valve then regulates the supply ofgas to the main burner so as tomam-y tainV the desired oven temperature. MAs long as 3 the pilot burner is ignited the main burner will burn normally under the control of the oven temperature control valve until the main control valve is manually turned off. But if during operation the pilot burner is extinguished for any reason the thermocouple will immediately cool and de-energize the electromagnet which will allow the safety control valve mechanism to cut off automatically 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, causing the safety control valve mechanism to cut oiT communica-v tion between the manifold and both the main burner and the pilot burner. The main control Valve is still open and the master switch closed. Then after the thermostatic element has cooled, closing the normally closed switch, which is maintained open by the thermostatic element during normal operation of the oven, the electric ignition element and the solenoid are again energized. The energization of the solenoid will cause it to operate the safety control valve mechanism to re-establish communication between the manifold and the pilot burner only.

Then when gas is again available the pilot burner f will be ignited and 1re-establish normal operation of the oven as previously described. In the event of a power failure during normal operation of the oven, the main burner will continue to operate normally under the control of the oven temperature regulator valve until the burner is turned oif by the main control Valve, assuming of course that the pilot burner continues to burn. In the event of a power failure before gas is turned on by the main control valve, the pilot burner can be manually ignited, and the supply of gas to both the main burner and the pilot burner will then be controlled by the pilot burner through the thermocouple and safety control Valve mechanism as previously described.

The principal object of the invention is to provide a very simple, efcient and inexpensive thermally responsive unit for use in automatic ignition and control systems for the oven burners of cooking ranges which is not affected by prolonged high ambient temperatures in the oven.

`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 my improved control unit incorporated in an automatic ignition and safety control system for an oven burner using gaseous fuel;

Fig. 2 is an enlarged plan View of the control unit;

Fig. 3 is a view in sectional elevation taken on the line 3-3 of Fig. 2;

Fig. 4 is a vertical sectional view taken on the line 4 4 of Fig. 2;

Fig. 5 is a sectional View taken on the line 5-5 of Fig. 2

Fig. 6 is a view similar to Fig. 2 showing a modified form of the control unit;

Fig. 7 is a sectional elevation taken on the line 'I-I of Fig. 6;

Fig. 8 is a view similar to Figs. 2 and 6 of still another form of the control unit, and

Fig. 9 is a sectional elevation taken on the line 9-9 of Fig. 8.

Referring now to the drawings by reference characters, the numeral I indicates a gaseous fuel burner which is mounted in or in heating relation to a cooking range oven 2. Gaseous fuel is supplied to the burner I from a manifold M through a conduit 3. Interposed in the conduit 3 are a main control valve Il, a safety control valve mechanism generally indicated by the numeral 5, and an oven temperature control Valve 5. The main control valve 4 is a cut-olf valve of standard construction which when in open or on position permits the iiow of gas through the conduit `3 from the manifold M to the burner I, and in closed or ofi position cuts off the flow -of gas to the burner I. This valve is manually opened and closed by a handle 'I and a valve stem 8; and directly controls the operation of the entire system in that it initiates the operation of the entire system when it is turned to the on position and terminates the operation when it is turned to the off position. From the main control valve 4 gas flows through a connector `9 to the safety control valve mechanism 5. From the safety control Valve mechanism 5 the gas flows through a connector I9, a standard oven temperature control valve 6 and the conduit 3 to the burner I. The oven temperature control valve 6 is operative to regulate the amount of gas flowing to the burner I in order to maintain the oven at any desired set temperature. The valve 6 which is set to any desired temperature by a handle II having a pointer l2 which cooperates with a graduated dial I3 carried by the valve 5 is controlled according to the temperature setting by a thermostatic element I4 which is mounted in the oven 2 and is connected to the Valve G as shown at I5. Gas is also supplied to a pilot burner I5 through a branch conduit I1 which extends between the safety control valve mechanism `5 and the pilot burner I6. The pilot burner I6 is disposed adjacent one end of the main burner I in position to ignite the burner I when gas is supplied thereto. An electrical ignition element I8 is operatively associated with the pilot burner I6 in position to ignite the pilot burner I6 when gas is supplied thereto. The pilot burner I6 is mounted upon the control unit I9 in position to heat a thermostatic element 2U incorporated therein and forming a part thereof. A thermocouple 2i is mounted upon the control unit I9 adjacent the pilot burner I6 in position to be heated thereby. The thermostatic element 20 is operative to open and close a switch 22 which controls the energization of the electrical ignition element I8 and a solenoid 23 which when energized operates the safety control valve mechanism 45 through linkage 2d to supply gas to the pilot burner If. The thermocouple 2| when heated is operative to hold the safety control valve mechanism in condition to maintain the supply of gas to both the pilot burner I6 and the main burner I. A master switch 25 which is associated with the main control valve l is adapted to be opened and closed simultaneously with the closing and opening of the main control valve Il. As the control valve 4 is turned from the off or closed position to the on or opened position the switch 25 is moved from the open position to the closed position by an operating lever 26 which cooperates with a cam section 2'I on the main control valve stem 8. Conversely, when the main control valve 4 is turned from the open or on position to the closed or oif position the switch 25 is moved from the rwardly extending iinger 59.

" "aerem A v closed position to the open position. An electric circuit between the 'thermocouple 2| andthe safety control valve mechanism Vis established by a copper tube 28 and an enclosed 'insulated wire. The ignition and control system just described per se constitutes no Vpart of the subject matter of this application ibut is shown and claimed in the co-pe'nding applications, Serial Nos. 153,664 now Patent No. '2,577,787 and 163,764 now Patent No. 2,578,717, l'ed April 3, 195o, and May 23, 1950, respectively, by Charles M. Mayer and John M. Hoff.

The control unit I9 which constitutes the subject matter of this application comprises a base 3D having upper and lower horizontal sections A3| and 32 which are connected together by a vertical web 33. The 4free edge-of the lower section 32 is turned downwardly as shown at'34 for stiiening purposes. The base has integral therewith a pair of tabs 35 which are welded to a transverse plate 435 which is secured to an inner wall 37 of the oven '2 by bolts '38. The base 35 extends inwardly from the wall 31 along one side of the burner I as shown in Figs. 1 and 2. The normally closed switch 22 comprises ai f' block 3S of insulating material, a stationary contact 4B, and a movable contact II. The stationary contact lill is held in position in the block 39 by a terminal'bolt 42, and the movable contact 4I is carried by the free end of a spring arm 43 which is biased toward the stationary contact 49 and is held in position in the block 33 by a terminal bolt '44. The block 39 is secured by bolts 45 tothe under side of a downwardly inclined sheet metal plate 46 which has one end thereof welded to the underside of the lower section 32 of the base yas indicated at d?. The free end of the `plate "45 is urged downwardly by the inherent resiliency of the plate itself. A rotatable screw 43 which extends downwardly through a vertical bore inthe lower section 32 -is threaded through an aperture adjacent `the free end of the plate '45 and is operative when rotated to adjust the free endof the plate 46 upwardly and downwardly, and withit the switch 22 carried thereby.

The thermostatic element V2|) is formed from a single piece of thin sheet metaland comprises a relatively long narrow :horizontal .section 55.

having an upturned section L5| 'along one edge thereof and a pair of spaced -

legs

52 and 53, extending downwardly lfrom the "other 'edge thereof. The leg'52 is disposed'a't oneend ofthe element and the leg 53 is 'disposed "substantially midway between the ends thereof. The

legs

52 and 53 terminate in horizontally extending feet '54 and 55 which are spot -welded to the top of the lower section 32 ofthe base 30, asindicated at 55 and 57. An arm l58 'extends outwardly from the leg 63 and downwardly-from the-edge of the horizontal section v50 opposite the 4upturned section 5|, in substantially the plane of the

legs

52 and 53, andterminatesin a down- The nger 59 extends down through an-aperture 6I) in thelower `section 32 of the base 30 and isfadapted to engage an insulating button 6| 4secured to the spring arm 3 of the switch`22.

The horizontal arm `62 of an angular bracket 53 is welded to the upper section3| of the base Yand extends outwardly therefrom. vrThe'thermocouple 2| and the pilot burner "I6 are rigidly secured to the vertical arm "'54 of `the bracket 83 by a clamp' and bolt'56. YThethermocouple 2| is disposed directly above'thepiltburner I6 with Vthe ends of vboth the thermocouple and the .pilot burner closely adjacent the upturned section 5I of the thermostatic element. The electric ignition element yI8 is mounted at `one side of the pilot burner VII adjacent the end thereof in an insulating block VIil which is 'fastened to the vertical arm -64 of the bracket 63 by a screw 68. When gas is supplied to the pilot burner I6 it will be ignited by the electric vignition element I8, after which the name from the pilot burner will impinge upon the section 5I of the thermostatic element 20 and fan out as shown by the line F in Fig. 3, and heat both `the thermostatic element 20 land the thermocouple 2|. vIt will also ignite the main burner when gas is supplied thereto.

The localized heating of the thermostatic Velement between the legs 52 land 53 will cause the element to elongate and rock the arm 58 downwardly about the foot 55 as a pivot. The downward movement of the end of lthe arm -58 will through the nger 59 depress the spring switch arm i3 and separate the contacts im and 4I ,thus opening the normally closed switch 22. 'The adjusting screw 48 is provided in order to adjust the relative positions of the lower end of the finger 59 and the spring arm 43 with respect to each other.

In operation it is only necessary to open the main control valve 4 manually which simultaneously closes the normally open Ymaster switch 25. The closing of the master switch `25 will through the normally closed switch 22 complete a circuit through and energize the solenoid .23 and the electric ignition element I8. Theenergizing of the solenoid 23 causes it to set the safety control valve 5 in condition to vsupplygas to the pilot burner I6 only, which is then ignited by the ignition element I8. After the pilot burner I6 has been ignited it projects a flame against and heats the thermostatic element 20 and the thermocouple 2|. The heating of the thermostatic element 25 causes it to open the normally closed switch 22 and break-the circuit to and de-energize the solenoid 23 and the ignition element I8; and the heating of the thermocouple v2| renders it operative to maintain the safety control valve mechanism 5 in position to supply gas to the pilot burner, Vand to the main burner I after the solenoid 23 has been de-energized. The de-energizing of the solenoid 23 renders the safety control valve 5 operative also to supply gas to the main burner I which is then ignited by the pilot burner I5. After this, under normal conditions, the main burner I will operate under control of the oven temperature control valve E until operation is terminatedby the manual closing of the main control valve 24.

In the event the pilot burner Iis extinguished for any reason during operation the thermocouple 2| will cool in a few seconds which will cause the safety control valve 5 to cut off the supply of fuel to both the main burner andthe pilot burner. The main burner will then'be extinguished along with the'pilot burner. As soon as the thermostatic element 20 cools it will close the switch -II which will energize both'the ignition element I8 and the solenoid 23 as previously described, since the main control -valve isrstill open and the switch 25 is closed. The pilot burner I6 will then be reignited and the rest of the apparatus will again function as described, provided there 'is gas available. If no gas is available everything will remain in condition to ignite the pilot lburner Hand reinitiate operation as soon as gas is again available. In the event of either a momentary or prolonged power failure during operation, the apparatus will continue to operate normally until terminated by the manual closing of the main control valve, provided of course that all other conditions are normal. In order to operate the apparatus during a prolonged power failure which occurred prior to operation, it is only necessary to hold a match to the pilot burner I6 and manually hold the safety control valve in position to supply gas to the pilot burner a sufiicient time for the thermocouple 2li to become heated. The apparatus will then continue to function normally as described under the control of the pilot burner I6 and the oven temperature control valve 5.

Since the control unit i9 is mounted in the oven 2 adjacent the burner I, it is subjected to the ambient temperature of the oven which sometimes exceeds 600" Fahrenheit. It has been found by experience that when the unit i9 is subjected to high ambient temperatures for prolonged periods of time, the base 3Q of the unit i9 elongates, bends, twists and otherwise distorts; and that this distortion sometimes counteracts the downward movement of the end of the arm 58 and finger 59 effected by the localized heating of the thermostatic element 20 by the pilot burner it. This counter movement of the arm 53 is principally due to the elongation of the section (-32, of the base 39, between the

legs

52 and 53 of the thermostatic element. When this condition occurs the switch 22 closes which re-energizes the solenoid 23 and the electric ignition unit it. The re-energization of the solenoid 23 causes it to operate the safety control valve mechanism to cut off the supply of gas to and extinguish the main burner while continuing the supply of gas 4to the pilot burner. The solenoid 23 will remain energized, cutting on the supply of gas to the main burner l until the temperature in the oven 2 drops and the base 3i) of the unit i9 cools suiiiciently for the thermostatic element 20, under the influence oi the pilot burner I6, to again open the switch 22. The device will then operate as described until the base 3i? is again distorted by the ambient temperature sufliciently to counteract the action of the thermostatic element 2. From this it will be seen that under certain conditions it is impossible to maintain a constant temperature in the oven 2. Sometimes the distortion of the base is such that it amplies the downward'movement of the end of the arm 58 and the nger 59 in which case the switch 22 will not close upon the extinguishment of the pilot burner i6 and the cooling of the thermostatic element down to the ambient temperature of the oven, but will remain open until the base B cools considerably, which objectionally delays the recycling of the apparatus.

In order to overcome this objectionable condition, I provide means on the control unit I9 by which the distortion of the base 3Q of the control unit I9 is counteracted and the relative positions of the end of the nger 5i! and the switch arm 43 with respect to each other are maintained fixed during all conditions oi operation. This means consists of a iiat bi-metallic disc 'l0 which is placed upon the lower section 32 of the base 30, and has the adjusting screw i8 inserted through a medial aperture therein. As the bi-metallic disc 'iii is heated by the ambient temperature in the oven 2, the midscction through which the adjusting screw 48 extends will bow upwardly and raise the switch 22 accordingly. The upward bowing of the bi-metallc disc 'I0 is concurrent with the distortion of the base 3U. Consequently as the arm 58 and finger 59 are moved upwardly by the distortion of the base 36 the switch 22 is likewise moved upwardly by the bowing of the disc it. Thus after the switch 22 has been openedby the heating of the thermostatic element 2i) by the pilot burner I6, the relation between the nger 59 and the spring arm `lili will be maintained iixed and the switch 22 open all during operation, regardless of the ambient temperature within the oven, provided of course that the pilot burner it remains ignited.

In Figs. 6 and 7, I have shown a slightly modied form of the control unit i9. In this form of the invention I 'place a bi-metallic disc ll, similar to the disc lil, under the foot 54 of the leg 52 and weld the foot 54 to the midseotion or" the disc "ii, as indicated at l2. I then weld one edge of the disc 'ii to the base 30, as indicated at lf3. Otherwise the construction and operation of this form of the invention are the same as those shown in Figs. 1 to 5 and the same reference characters are applied to like parts.

In Figs. 8 and 9, I have shown another modification of the control unit i9. In this form of the invention I place a lui-metallic disc "i5, similar to thev discs it and li, under the foot 55 oi the leg 53 and weld the foot 55 to the disc l5, as indicated at l5, and weld one edge of the disc l5 to the frame til, as indicated at Il. Otherwise the construction and operation of this form of the invention are the same as those shown in Figs. l to 5, and in Figs. 6 and 7, and the same reference characters are applied to like parts.

In order to counteract the amplified opening of the switch 22 due to the distortion of the base 30, I construct the bi-metallic discs l0, 'Il and l5 so that they are arcuate when cool and flat when heated.

From the foregoing it will be apparent to those skilled in this art that I have provided a very simple and enicient means for accomplishing the objects of my invention; and it is to be understood that I am not limited to the specific constructions shown and described herein as various modifications may be made thereto within the scope of the appended claims.

What is claimed is:

1. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, a downwardly inclined resilient plate having the upper end thereof rigidly secured to the under side of said base, an electric switch having an open anda closed position carried by said plate, a thermostatic element secured to the upper side of said base and operative when heated by a pilot burner iiame impinging thereon to shift said switch from one position to the other position, and means to raise and lower the free end of said plate and thereby adjust the position of said switch relative to said thermostatic element.

2. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, an electric switch having an open and a closed position, a thermostatic element mounted upon said base, interengageable means between said switch and said thermostatic element, said thermostatic element when heated by a pilot burner flame impinging thereon flexing sufficiently to shift said switch through said interengageable means from one, position to the other, said base being. distortable by the ambient temperature in the oven in. a direction to counteract the flexing action of said thermostatic element, and thermally responsive means incorporated in said control unit and operative to counteract the distortion of said base.

3, A thermally responsive control unit as defined in claim 2 in which said thermally responsive means comprises a bi-metallic disc and D- erative connections between said bi-metallic disc and said switch through which said bi-metallic disc moves said switch in accordance with the distortion of said base to maintain the relative positions of said switch and said thermostatic element with respect to each other fixed during operation of the oven burner.

4. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cookingT range ovensubject to the ambient temperature therein, a downwardly inclined resilient plate having the upper end thereof rigidly secured to the under side of said base, an electric switch having an open and a closed position carried by said plate, a thermostatic element secured to the upper side of said base, interengageable means between said switch and said thermostatic element, said thermostatic element when heated by a pilot burner flame impiriging thereon flexing sufhciently to shiftv said switch through said' interengageable means from one position to the other, adjusting means by which the free end of said plate is raised and lowered toV adjust the position of said switch relative to said thermostatic element, said base being distortable by the ambient temperature in said oven in a direction to counteract the ilexing action of said thermostatic element', and thermally responsive means incorporated in said control unit and operative to counteract the distorting movement of said base.

5. A thermallyl responsive control unit as dened in claim 4 in which said thermallyl responsive means comprises a bi-metallic disc and operative connections between said bi-metallic disc and said adjusting means through which said bimetallic disc raises the free end oiV said plate in accordance with the distortion of said base to maintain the relative positions of said vswitch and said thermostaticelement with respect to each other Xed during operation of the oven burner.

6. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range` oven subject to the ambient temperature therein, a downwardly inclined resilient plate havingr the upper end thereof rigidly secured to the under side of said base, an electric switch having an open and a closed position carried by said plate, a thermostatic element secured to the upper side of said base, interengageable means between said switch and said thermostatic element, said thermostatic element when heated by a pilot burner flame impinging thereon flexing sufficiently to shift said switch through said interengageable means from one position to the other, a screw rotatably mounted in an aperture in said base and extending downwardly through a threaded aperture in said plate and having a head on the upper end thereof, said screwA being operative to raise and lower the free end of said plate to adjust the position of said switch relative to said thermostatic element, said base being distortable by the ambient temperature in said oven in a direction to counteract the flexing action of said thermostatic element, and thermally responsive means incorporated in said control unit and operative to counteract the distorting movement of said base.

'7. A thermally responsive control unit as deiined in claim 6 in which said thermally responsive means comprises a bi-metallic disc interposed between said screw head and the top of said lbase and operative to raise said screw and said plato in accordance with the distortion of said base to maintain the relative position of said switch and said thermostatio element with respect to each other xed during operation of the oven burner.

8. A thermally responsive control unit; for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, a downwardly inclined resilient plate having the upper end thereof rigidly secured tok the under side of said base, an electric switch having an open and a closed position carried by said plate, a thermostatic element having two spaced downwardly extending legs the lower ends of which are rigidly secured to the upper side of saidbase, interengagable means between said switch and said thermostatic element, said thermostatic element when heated by a pil-ot burner name impinging thereon flexing sufficiently to shift said switch through said interengageable means from one position to the other, a screw rotatably mounted in an aperture in said base and extending downwardly through a threaded aperture in said plate and having a head on the upper end thereof, said screw being operative tov raise and lower the free end of said plate to adjust; the position of said switch relative to said thermostatic element, said base being distortable by the ambient temperature in said oven in a direction to counteract the flexing action of said thermostatic element, and thermally responsive means incorporated in said control unit and operative to counteract the distorting movement of said base.

9. A thermally responsive control unit as defined in claim 8 in which said thermally responsive means comprises a bi-metallic disc interposed between said screw head and the topfoi said base and operative to raise said screw and said plate in accordance with the distortion of said base to maintain the relative positions of said switch and said thermostatic element with respect to each other nxed duringA operation of the oven burner.

l0. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, an electric switch having an open and a closed position, a thermostatic element having two spaced downwardly extending legs the lower end of at least one of which is rigidly secured directly to said base, interengageable means between said thermostatic element and said switch, said thermostatic element when heated `by' a pilot burner flame impinging thereon eXing suiliciently to shift said switch through said interengageable means from one position to the other, said base being distortable by the ambient temperature in said oven in a direction to counteract the flexing action of said thermostatic element, and thermally responsive means incorporated in said control unit and operative to. counteract the distorting movement of said base,

1l. A thermally responsive control unit as dei'lned in claim l0 in which said thermally responsive means comprises a bi-metallic disc interposed between one of said legs and said base, said bi-metallic disc being rigidly secured to said base and to said one o said legs and operative to move said switch in accordance with the distortion of said :base to maintain the positions of said switch and said thermostatic element with respect to each other iixed during operation of said oven burner.

12. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, an electric switch having an open and a closed position, a thermostatic element having a downwardly extending medial leg and a spaced downwardly extending end leg the lower end of which is rigidly secured to said base, interengageable means between said thermostatic element and said switch, said thermostatic element when heated by a pilot burner ame impinging thereon ilexing sufficiently to shift said switch through said interengageable means from one position to the other, said base being distortable by the ambient temperature in said oven in a direction to counteract the ilexing action of said thermostatic element, and thermally responsive means incorpoated in said control unit and operative to counteract the distorting movement of said base.

13. A thermally responsive control unit as defined in claim l2 in which said thermally responsive means comprises a bi-metallic disc interposed lbetween said medial leg and said base, said bi-metallic disc being rigidly secured to said base and said medial leg and operative to move said switch in accordance with the distortion of said base to maintain the positions of said switch and said thermostatic element with respect to each other fixed during operation of said oven burner.

14. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, an electric switch having an open and a closed position, a thermostatic element having a downwardly extending end leg and a spaced downwardly extending medial leg the lower end of which is rigidly secured to said base, interengageable means between said thermostatic element and said switch, said thermostatic element when heated by a pilot burner flame impinging thereon flexing suiliciently to shift said switch through said interengageable means from one position to the other, said base being distortable `by the ambient temperature in said oven in a direction to counteract the iiexing action of said thermostatic element, and thermally responsive means incorporated in said control unit and operative to counteract the distorting movement of said base.

l5. A thermally responsive control unit as defined in claim 14 in which said thermally responsive means comprises a bi-metallic disc interposed between said end leg and said base, said bimetallic disc being rigidly secured to said base and said end leg and operative to move said switch in accordance with the distortion of said base to maintain the positions of said switch and said thermostatic element with respect to each other fixed during operation of said oven burner.

16. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, @Il

electric switch carried by said base, a thermostatic element mounted upon said base, interengageable means between said switch and said thermostatic element, said thermostatic element when heated by a pilot burner iiame impinging thereon flexing sufciently to actuate said switch through said interengageable means, said base being distortable by the ambient temperature in the oven in a direction to change the actuating eiTect of said thermostatic element on said switch, and thermally responsive means incorporated in said control unit and operative to counteract the distorting movement of said base.

17. A thermally responsive control unit as deiined in claim 16 in which said thermally responsive means comprises a bi-metallic disc and operative connections between said bi-metallic disc and said switch through which said bi-metallic disc moves said switch in accordance with the distortion of said base to maintain the relative positions of said switch and said thermostatic element with respect to each other xed during operation of the oven burner.

18. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, a downwardly inclined resilient plate having the upper end thereof rigidly secured to the under side of said base, an electric switch carried by said plate, a thermostatic element secured to the upper side of said base, interengageable means between said switch and said thermostatic element, said thermostatic element when heated by a pilot burner llame impinging thereon iiexing sufficiently to actuate said switch through said interengageable means, adjusting means by which the free end of said plate is raised and lowered to adjust the position of said switch relative to said thermostatic element, said base being distortable by the ambient temperature in said oven in a direction to change the actuating eiect of said thermostatic element on said switch, and thermally responsive means incorporated in said control unit and operative to counteract the distorting movement of said base.

19. A thermally responsive control unit as defined in claim 18 in which said thermally responsive means comprises a bi-metallic disc and operative connections between said bi-metallic disc and said adjusting means through which said loi-metallic disc moves the free end of said plate in accordance with the distortion of said base to maintain the relative positions of said switch and said thermostatic element with respect to each other xed during operation of the oven burner.

20. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, an electric switch carried by said base, a thermostatic element mounted upon said base, interengageable means between said switch and said thermostatic element, said thermostatic element when heated by a pilot burner flame impinging thereon exing sufficiently to open said switch through said interengageable means, said base being distortable by the ambient temperature in the oven in a direction to amplify the opening of said switch, and thermally responsive means incorporated in said control unit and operative to counteract the distorting action of said base.

21. A thermally responsive control unit as defined in claim 20 in which Said thermally responsive means comprises a bi-metallic disc and operative connections between said bi-metallic disc and said switch through which said 1oi-metallic disc moves said switch in accordance with the distortion of said base to maintain the relative positions of said switch and said thermostatc element with respect to each other iixed during operation of the oven burner.

22. A thermally responsive control unit for a gaseous fuel oven burner comprising a base adapted to be mounted in a cooking range oven subject to the ambient temperature therein, a downwardly inclined resilient plate having the upper end thereof rigidly secured to the under side of said base, an electric switch carried by said plate, a thermostatic element secured to the upper side of said base, interengageable means between said switch and said thermostatic element, said thermostatic element when heated by a pilot burner flame impinging thereon flexing suiciently to open said switch through said interengageable means, adrusting means by which the free end of said plate is raised and lowered to adjust the position of said switch relative to said thermostatic element, said base being distortable by the ambient temperature in said oven in a direction to amplify the opening of said switch, and thermally responsive means incorporated in said control unit and operative to counteract the distorting movement oi said base.

, 23. A thermally responsive control unit as defined in claim 22 in which said thermally responsive means comprises a loi-metallic disc and operative connections between said loi-metallic disc and said adjusting means through which said bimetallic disc moves the free end of said plate in accordance with the distortion of said base to maintain the relative positions of said switch and said thermostatic element with respect to each other fixed during operation of the oven burner.

RICHARD L. PERL.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 2,159,658 Hall May 23, 1939 2,275,657 Wetzel Mar. 10, 1942 2,291,805 Denison Aug. 4, 1942 2,476,118 Short July 12, 1949 2,553,062 Riehl May 15, 1951