US3569670A

US3569670A - Safety door latching system for self-cleaning oven having hydraulic thermostat with cam-actuated auxiliary switch

Info

Publication number: US3569670A
Application number: US847350A
Authority: US
Inventors: Christian A Eff
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1969-08-04
Filing date: 1969-08-04
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09

Abstract

A hydraulic oven thermostat for use with a baking oven having a high temperature self-cleaning oven cycle where the thermostat is furnished with an auxiliary switch and camming means interposed between the thermostat knob and the auxiliary switch for coordinating them in both the cooking position and an oven cleaning position as a function of the setting of the thermostat. The auxiliary switch is associated with an oven door latching mechanism, an automatic locking means for the latching mechanism as well as a release means for the locking means to insure that the oven door is locked before the heat-cleaning cycle is initiated as well as insuring that the oven door may not be unlocked until the oven temperature returns to the cooking temperature range.

Description

United States Patent [72] Inventor Christian A. Eff

Louisville, Ky. [21] Appl. No. 847,350 [22] Filed Aug. 4, 1969 [45] Patented Mar. 9, 1971 [73] Assignee General Electric Company [54] SAFETY DOOR LATCHING SYSTEM FOR SELF- CLEANING OVEN HAVING HYDRAULIC THERMOSTAT WITH CAM-ACTUATED AUXILIARY SWITCH 12 Claims, 7 Drawing Figs.

[52] U.S.Cl 219/413, 34/45, 219/397 [51] Int. Cl F27d 11/02 [50] Field ofSearch.. 219/395- [56] References Cited UNITED STATES PATENTS 2,470,043 5/1949 Monsarrat 34/45 3,121,158 2/1964 l-lurko 219/397 3,313,918 4/1967 Barber 219/412 3,317,708 5/1967 Bowling..... 219/412 3,301,999 1/1967 Chrisholm. 219/393 3,350,542 10/1967 Getman..... 219/412 3,462,584 8/1969 Guy 219/412 Primary Examiner Volodymyr Y. Mayewsky Attorneys-Richard L. Caslin, Harry F. Manbeck, Jr, Joseph B. Forman, Oscar B. Waddell and Frank L. Neuhauser ABSTRACT: A hydraulic oven thermostat for use with a baking oven having a high temperature self-cleaning oven cycle where the thermostat is furnished with an auxiliary switch and camming means interposed between the thermostat knob and the auxiliary switch for coordinating them in both the cooking PATENTEU MAR 9 1971 SHEET 1 BF 4 R WF f E v. WA N W T Isl R H c PEG? ms ATTORNEY PATENTEI] MR 9 ISII SHEEI' 2 OF 4 F'IG.3

INVENTOR- CHRST$AN A- EFF Hzs ATTORNEY PATENTEI] m 919m SHEET 3 OF 4 FIG INVENTOR. CHRISTIAN A. EFF

l-us ATTORNEY SAFETY DOOR LATCITWG $YSTEM FOR SELF- QLEANING OVEN HA /ENG HYDRAULIC THERMOSTAT WITH EAM-AQTIJATEID AUXUJIARY SWIITGKI BACKGROUND OF THE INVENTION in most standard baiting ovens a hydraulic thermostat is used for controlling the oven temperatures in the normal cooking temperature range between about 150 F and about 550 F. With the introduction of the high temperature pyrolytic process for self-cleaning ovens as is taught in the patent to Bohdan liurko U.S. Pat. No. 3,121,158, the ordinary hydraulic fluid was incapable of withstanding the high temperatures in the vicinity of 950 F. In recent times, high temperature fluids have been discovered for use in such hydraulic thermostats in competition with or as a substitute for existing electric thermostats or solid state control thermostats. It is desirable to preserve the resolution of a standard cooking thermostat while expanding the maximum temperature from about 550 F. to about 950 F. This may be done with the adoption of an auxiliary switch in-the thermostat housing and camming means interposed between the thermostat knob and the auxiliary switch for coordinating the auxiliary switch with the action of the thermostat. Special circuit arrangements are also provided to obtain the desired results.

' The principal object of the present invention is to provide a hydraulic oven thermostat with an expanded temperature scale that covers both normal cooking temperatures and high temperature heat-cleaning temperature.

A further object of the present invention is to provide a hydraulic thermostat of the class described with an auxiliary switch means operated by camming means interposed between the thermostat knob and the auxiliary switch for coordinating them in both a cooking position and a cleaning position whereby the thermostat may be calibrated independently for both its cooking temperatures as well as for its cleaning temperatures without affecting the calibration of the other.

A further object of the present invention is to provide a hydraulic thermostat of the class described with a circuit arrangement whereby the cooking circuits are cancelled and replaced by a cleaning circuit when the thermostat, oven timer and oven door latch are closed.

A further object of the present invention is to provide an oven thermostat and circuit arrangement of the class described whereby the oven door latch cannot be opened when the heat cleaning cycle is in operation until the oven thermostat is reset to a cooking position and the oven temperature drops into the cooking temperature range below about 550 F.

SUMMARY OF THE INVENTION The present invention, in accordance with one form thereof, relates to a hydraulic thermostat having a housing supporting an expansible member connected to a remote temperature sensor. The thermostat has a manually settable knob supporting the expansible member on its innermost end. The thermostat includes switching means adapted to be connected in the oven heating circuits, and a snap-acting switch mechanism connected to the switching means and acted upon by the expansible member. An auxiliary switch is combined in the thermostat housing and it is also adapted to be connected in the oven heating circuits. The auxiliary switch has a cooking position and a cleaning position, while the thermostat knob has a variable cooking range of nearly one revolution over a temperature scale between about l50 F. and about 550 F. The thermostat knob also has a clean position upon continued rotation thereof into the temperature range between about 750 F. and about 950 F. The thermostat knob is provided with camming means for governing the actuation of the auxiliary switch so that the cooking and cleaning positions of the auxiliary switch will coincide with the cooking and cleaning positions of the thermostat knob. The camming means in cludes a toggle mechanism for effecting snap-action of the auxiliary switch.

BRIEF DESCRIPTION OF THE DRAWINGS My invention will be better understood from the following description taken in conjunction with the accompanying drawings and its scope will be pointed out in the appended claims.

FIG. I is a left, side-elevational view, partly broken away and partly in section, of a household electric range embodyin the present invention.

FIG. 2 is a longitudinal cross-sectional elevational view on an enlarged scale of a hydraulic oven thermostat embodying the present invention taken through the center of the housing.

FIG. 3 is a top plane view of the thermostat of FIG. 2 with the left top cover removed and the right top cover partially broken away to show the interior construction of the thermostat with the thermostat set in the highest positions for the cooking circuits.

FIG. 4 is a diagrammatic showing of the relationship between the temperature dial of the thermostat and the position of the auxiliary switch mechanism on the interior of the thermostat, with the thermostat set in its lowest cooking position or warm position.

FIG. 5 is a diagrammatic showing similar to that of FIG. 4 just after switching from the maximum cooking position or broil" into the clean position.

FIG. 6 is a diagrammatic showing, similar to that of FIGS. 4 and 5, with the then'nostat set in its full clean" position.

FIG. 7 is a schematic wiring diagram of the electrical circuits for the oven of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to a consideration of the drawings, and in particular to FIG. 1, there is shown for illustrative purposes a free-standing electric range 10 having a top cooking surface or cooktop 11 with a plurality of surface heating elements 12, an oven cavity 13 formed beneath the cooktop by a box-oven liner l4 and a front-opening drop door 15. The oven liner 14 is supplied with two standard resistance heating elements; namely, a lower baking element 16 and an upper broiling element 17. A third heating element has been added adjacent the oven door 15 to replenish the heat lost through and around the door during the heat-cleaning cycle, and thereby retain generally uniform oven wall temperatures. This third heater is identified as a mullion or perimeter heater 18 that is wrapped around the outside of the front of the oven liner; for example, in a manner that is taught by the Newell Patent [15. Pat. No. 3,017,488 which is assigned to the General Electric Company, the assignee of the present invention. The oven cavity is not shown with oven racks or oven rack supports, but of course they would be necessary in order to provide a means for supporting food to be cooked within the oven. They are not illustrated here for the sake of simplicity of illustration, because they do not form part of the present invention.

The variable control of the surface heating elements 12 is obtained by selector switches 20 which are illustrated as multiple pushbutton switches arranged in pairs along the opposite side arms of cooktop II to be oriented with the particular heating element that is being controlled thereby. In addition, the range is provided with a backsplash 21 that is vertically arranged along the back edge of the cooktop 11 and is provided with an instrument or control panel 22 in which are mounted the various control components of the range and especially of the oven, such as an oven thermostat 24 embodying the present invention. Other control components would be an oven selector switch 150, an oven timer 152, a remote-reading meat thermometer, oven indicator and pilot lights, convenience outlets and similar features. Some of these components are illustrated in FIG. 7 as elements in the circuit diagrams.

Other structural features of the range It) include the outer range body or cabinet 27 which has an appearance finish on the front, the two sides and the cooktop ill of the range, while a painted surface is applied on the back side. This cabinet serves as the superstructure that supports and encloses the various heating and control components of the range. Sandwiched between the oven liner 16 and the range body or cabinet 27 is an extra thick blanket of thermal insulating material 28 such as fiber glass or the like. The amount of insulation being used has been increased over the amount of insulation for standard ovens because of the high operating temperatures encountered during the heat-cleaning operation which will reach a maximum oven wall temperature somewhere between about 750 F. and about 950 F. Positioned around the blanket of insulation 28 are insulation panels or guards 29 which serve to support the insulation in place.

During the heat-cleaning operation water vapor, free carbon, soot, carbon monoxide gases and other products of combustion are formed and these are treated before they are returned to the kitchen atmosphere. A catalytic smoke eliminator 34 is positioned in an oven vent opening 35 in the top wall of the oven liner 14 to serve as an oxidation and exhaust means for the oven. For example, this catalytic smoke eliminator may be of the type that is taught in the Welch Patent U.S. Pat. No. 2,900,483 which is likewise assigned to the assignee of the present invention. Such a smoke, odor and vapor eliminating device generally includes a heating means in cooperation with a catalytic coating such as a platinum wire screen that becomes heated to a temperature of about 1300 F. and tends to consume the smoke, odors and vapors emanating from the oven cavity so that the oven exhaust air is treated by removing its objectionable constituents in a manner that is best described in the basic Hurko Patent U.S. Pat. No. 3,12 l ,l58 before it is returned to the kitchen atmosphere.

It is deemed necessary to provide a latching means for the oven door 15 to insure that the door is first closed and cannot be opened while the oven is being operated in a heat-cleaning cycle above normal cooking temperatures. A suitable door latching mechanism is identified generally as 37 in FIG. 1, although it is fully taught and claimed in the patent of Clarence Getman U.S. Pat. No. 3,189,375 that is also assigned to the assignee of the present invention. The door latching mechanism includes a manually operable handle lever 33 which extends through an elongated opening in the front edge of the cooktop 11 in a position just above and parallel to the top edge of the oven door 15. The handle lever 38 has two extreme positions, an open or unlocked position and a closed or locked position. There is a latching bolt 40 which is pivotally mounted within the range body and is adapted to extend from the front thereof for engagement with a slot or keeper (not shown) in the innerside of the door 15. The door latching mechanism 37 is provided with an extension rod 43 which is pivotally connected to the mechanism to move with a back and forth action depending upon the direction of movement of the handle lever 38. This rod 43 has two locking detents at the back of the range where the open position of the handle or latch is illustrated in FIG. 7 as a hole 45, and the closed or locking position is represented by the end 46 of the rod. Cooperating with the end of the extension rod 43 is an automatic locking means 48 in the form of a member pivoted about pin 49 and it is normally biased in a downward or locking position by means of a tension spring member 51. Notice that the locking means 48 has a finger 50 for engagement either with the hole 45 or the end 46 of the rod depending upon the position of the rod and hence the handle lever 38. A solenoid 41 serves as a release means for the automatic locking means 46. The purpose of locking the door latching mechanism 37 in its open position is to insure that it cannot be thrown into the closed position inadvertently, while it is locked in the closed position to insure that the door cannot be unlocked and the door opened while the oven temperature is above normal cooking temperatures during a high temperature heat-cleaning operation.

The main purpose for locating the automatic locking means 43 at a distance remote from the door latching mechanism 37 and the front of the oven is to remove the locking mechanism and particularly the release solenoid 41 from the high temperature areas of the range and to place it as far as possible away from the oven heat. The energization of the solenoid causes its armature to pick up and lift the locking means 48 so the handle lever 38 may be operated.

Turning now to a consideration of the oven thermostat 24 of FIG. 2, represents the hollow housing of the thermostat comprising a recessed base 56 and a two piece top cover 57 and 53 for closing the base. This hydraulic oven thermostat or temperature responsive control device comprises three main elements within the housing 55; namely, a fluid holding expansible member 60, a snap-action spring mechanism 61 and a double pole electrical switch mechanism 62.

The recessed base 56 of the housing 55 is a boxlike member of molded plastic such as phenolic resin or the like insulating material, while the two

cover members

57 and 58 are thin sheet metal parts. The shape of the base 56 is generally rectangular in plan view, as is best seen in FIG. 3. The base is first divided into two sections by a transverse, vertical partition 65. The first section at the right side of the partition 65 in FIGS. 2 and 3 is adapted to receive the switch mechanism 62, while the second section at the left side of the partition accommodates the expansible member 60 as well as the auxiliary switch 113, as is best seen in the assembly view of FIG. 2. Moreover, the first section is further divided into a first upper compartment 67 and a second lower compartment 68 by means of a horizontal partition 70. It is this first upper compartment 67 which encompasses the switch mechanism 62 and isolates these electrical parts from the remainder of the thermostat interior. Accordingly, the second section of the base for receiving the expansible member 60 and the auxiliary switch 113 may be considered as a third compartment 72. An opening 73 is formed in the lowerportion of the transverse partition 65 in the area between the second compartment 68 and the third compartment 72 for receiving a portion of the spring mechanism 61 therethrough, as is best seen in FIG. 2. Notice that the cover 58 shown in FIG. 2 is generally of U- shaped formation in side view in that it closes the top opening in the base 56 above the first compartment 67, and then it extends down the right side of the base in the vicinity of the second compartment 68. Some of the general elements of the thermostat of the present invention had been used before in a thermostat design taught in the patent of Paul R. staples U.S. Pat. No. 3,293,394 which is likewise assigned to the assignee of the present invention.

The third compartment 72 of the base 56 is open at the top, and it is adapted to be closed by the metal cc ver 57 which is fastened over the top opening thereof and held in place by fastening screws 75.

Attention will now be given to the expansible member 60. It is a hydraulic filled bellows or diaphragm assembly that converts volumetric expansion or contraction into rectilinear mo tion acting upon the underlying spring mechanism 61. Into the side of the diaphragm assembly 60 is connected a capillary tube 77 of, for example, 2 feet in length. This tube is adapted to extend out of the base 56 so that its free end may be positioned within the area whose temperature is to be controlled,

such as the oven cooking cavity 13. Provided on the free end of the tube would be a temperature sensing bulb or probe 78 which is shown located in the upper rear portion of the oven liner 14, as is best seen in FIG. 1.

It is necessary to be able to adjust the position of the expansible member 60 toward and away from the spring mechanism 61 for setting various desired temperature levels. The top of the diaphragm assembly is provided with a vertical pin 80 shown in FIG. 2 which is freely received within a mating hole 81 in a collar 82 that is fastened on the lower or innermost end of a threaded adjustment shaft 83. A thermostat knob $6 shown in FIGS. 4l-6 is adapted to slip onto the free end of the shaft 33. The shaft extends through the cover plate 57 and is adjustably held therein by a threaded bushing 84. This bushing has a barrel 85 which is adapted to fit through a close-fitting opening in the cover plate 57. A shoulder 87 is formed on the lower end of the barrel 35, and this shoulder together with a speed nut or retaining member 83 holds the barrel in place in the cover. As shown, the speed nut 88 may he slipped first over the shaft and then forced over the barrel 85 until its radial spring fingers 89 engage the bushing in the cover in a semipermanent manner. The shaft 83 being a threaded member, moves in or out of the housing as the shaft is turned. dince the diaphragm is confined between the shaft and the spring mechanism til, the diaphragm will stay in contact with the shaft and move therewith.

The diaphragm 151) is prevented from turning when the shaft $3 is turned by the presence of an inverted U-shaped clip 99 that has its base portion fixed to the diaphragm and its side portions overlying the spring mechanism 61 in close relationship, as is best seen in H6. 2.

Turning back to a consideration of the first compartment 67 of the thermostat base 56 and the electrical switch mechanism 62 assembled therein, there are four spaced switch contacts 92 fixed on the top surface of the horizontal partition 70. These four contacts are arranged in a transverse rectangular pattern as is best seen in FIG. 2, there being a pair of switch contacts located at each side of the first compartment 67. This switch mechanism 62 is a double pole, single throw switch for breaking both sides of the line of a power supply-circuit; as for example, the supply of energy to the heating elements of an electric oven;

elements

16, 17 and 18 of FIG. 1. Each fixed contact 92 is provided with a perpendicular terminal blade 93 that is adapted to extend down through a suitable slot in the partition 71). The blades 93 on the two opposite sides of the thermostat base 56 are then exposed to the exterior of the base. In other words the second compartment 68 of the base is of'narrow width as compared with the width of the first compartment 67, or in that matter the width of the third compartment 72. These terminal blades 93 serve as a means for fixing the fixed contacts 92 within the base as well as serve as means for making electrical connection thereto by use of mating electrical connectors (not shown).

In addition to the fixed contacts 92, the switch mechanism b2 includes a pair of movable contacts X, and X which are supported by an insulating carrier member 95 which is of generally T-shape having a vertical shank 96 and overhanging side arms 97. Each side arm 97 supports one of the movable contact members X, and X The lower end of the vertical shank is provided with a slot 101} so that a connection may be made with the pring mechanism 61.

Now that the expansible member 60 and the switch mechanism 62 has been described, attention is directed to the snap-acting spring mechanism 61 which is acted upon by the movement of the expansible member 60 for varying the position of the switch mechanism 62 according to the direction and extent of the temperature change experienced by the temperature sensor or bulb 78 on the end of the capillary tube. The spring mechanism 61 is in the form of a combined blade and amplitude spring which is best taught by the Staples patent mentioned above. The blade is formed upwardly to retain a natural upward bowed condition. The left end 102 may be identified as the supported end of the blade while the right end 1113. may be considered as the free or bistable end of the blade. Between the ends 102 and 103, the blade includes a center leg and right and left parallel side legs as shown in FIG. 3. The blade should be restrained from moving in a horizontal plane and this is accomplished by interlocking the supported end 162 with the base 56. Looking at FIG. 3, the end 1112 of the blade is provided with a pair of oppositely directed ears 165 which are each adapted to fit snugly into a vertical slot 1% formed in the base. Thus the ears 105 of the blade are dropped into the vertical slots 1% after the free end 103 of the blade is first inserted through the opening 73 in the transverse partition 65 and into the second compartment 68. For calibration purposes a vertical adjusting screw 1% is fitted up through the bottom wall of the base and is adapted to be in contact with the supported end N2 of the blade at a point on an imaginary line drawn between the supporting cars 1115, as is best seen in FiGS. 2 and 3.

At this stage in the description, the combined blade and amplitude spring 61 is unstable in that it is supported at only one point; namely, on the calibration screw 108. In addition there are two side supports 111) provided on the side legs of the blade, which are arranged opposite to each other in a generally expanded V-shape to provide a dull knife-edge each for bearing upon a support pad 111 of the bottom wall of the base 56. Each V-section or side support is arranged opposite each other or is a mirror image of the other so that the knife edges 110 are located in an imaginary transverse line with each other. Thus the blade 61 is provided with a three point system; namely, the calibration screw 108 at the supported end 102 of the blade and the two

knife edges

110, 110 at the two sides of the blade.

The center of the expansible member 60 is adapted to bear against the top portion of the center leg of the blade as at 112. In order to obtain accurate results, this bearing point is prevented from changing by creating a small raised embossment on the blade for engagement by the expansible member 60. Notice that this bearing point 112 is within the triangular area bounded by the three point support system of the calibration screw 108 and the two

knife edges

110, 110.

What has been described above'with relation to the oven thermostat illustrated in FIGS. 2 and 3 is generally of standard thermostat design as it is generally taught by the before mentioned Staples patent. The oven thermostat of the present invention has been modified as can be seen in FIGS. 2 and 3 by enlarging the third compartment 72 and installing an auxiliary switch 113 therein which is acted upon by a camming mechanism 114 that is interposed between the thermostat shaft 83 or knob 86 and the auxiliary switch. The auxiliary switch 113 is a single pole, double throw switch having a movable contact blade 116 mounted in cantilever fashion from a fixed terminal blade 117, and there being two fixed

contacts

118 and 119 that cooperate with the free end of the movable contact 116 depending upon the position of the cam ll 14.

The cam member 114 is a rather large member molded of electrical insulating material and having a pair of vertical trunnions 122 at the top and bottom thereof which are fitted into receiving openings in the bottom wall of the base 56 and the top cover 57 so as to be capable of limited movement about a vertical axis through an angle of about 45. The cam 114 has opposing

faces

124 and 125. Cam face 124 comprises a pair of circumferentially spaced

notches

126 and 127 for alternate engagement with a V-shaped cam follower 128 formed adjacent the center of the movable contact blade 116 of the auxiliary switch 113. The second face of the cam 114 includes an enlarged notch 130 adjacent the top of the cam for engagement by a rotating finger 131 that is fixed to the lower end of the shaft 83 of the thermostat so as to be movable therewith when the thermostat knob 86 is turned. There is a second rotating member supported by the shaft; namely, a freewheeling stop plate 133 which is capable of moving independently of the shaft 83. This stop plate has a raised abutment 134 which extends upwardly to lie within the same plane as the finger 131 such that the finger may engage the abutment 134 and thereby drive the stop plate ahead of it.

Turning to the diagrammatic showings of FIGS. 4-6, FIG. 4 shows the thermostat turned to its lowest cooking position or warm position, and you will notice that

switch contacts

116 and 118 of the auxiliary switch 113 are closed by the action of the cam member 114 and the interrelation between the cam follower 128 and the notch 126. Notice the rotating finger 131 had previously moved the abutment 134 of the stop plate up against the second face 125 of the cam member 114, thereby stopping further rotation in a counterclockwise direction.

The thermostat knob 86 has associated therewith a dial 136 with indicia printed around the periphery thereof and extending from a low setting or warm position of about F. to a maximum cooking temperature of about 550 F. Next it shows the highest cooking temperature or broil position. This indicia nearly covers the entire periphery of the dial 136. Hence,

to cover such a temperature range it is necessary to turn the knob on the thermostat through nearly a complete revolution or about 330, as can be seen by comparing the lowest extreme of the cooking scale of FIG. 4 with the highest extreme of the cooking scale of FIG. 5. The thermostat knob is turned clockwise by about 330 to completely cover the temperature scale from one end to the other. Further rotation of the knob in a clockwise direction first engages the rotating finger 131 in the slot 131! of the cam 114 and eventually the cam member 114 will shift counterclockwise by about 45 forcing the cam follower 128 out of the notch 126 and into the notch 127 thereby allowing the movable contact blade 116 to snap out of contact with fixed contact 118 and into contact with fixed contact 1111. in other words there is a type of toggle switch action here.

After the auxiliary switch 113 has been reset into its clean position of FIG. 5, the thermostat knob should be turned further to obtain the proper heat cleaning temperature within the oven. This is predetermined by the turning of the knob 86 in a clockwise direction forcing the rotating finger 131 to engage the abutment 13 of the stop plate 133 thereby driving it ahead until the abutment 134 engages a calibration screw 137 that is adjustably positioned in a sidewall of the base 56 of the thermostat housing at which point all further movement in the clockwise direction is halted.

Since the periphery of the dial 136 of the thermostat is substantially covered by cooking temperatures, one of the problems to be solved is how to indicate on the thermostat the clean" position. This has been solved by forming a slit 138 in the edge of the dial. The presence of this slit 138 permits the bending of the dial 136 into a flat spiral that has its lowest position at the lowest point of the temperature range and the dial Curves upwardly t the highest point of the temperature range thereby forming both a horizontal and a vertical slot of about one-eight of an inch. A generally J-shaped indicia strip 139 is fastened at one end 141) to the thermostat housing or mounting plate of the thermostat while the opposite end 141 of the indicia plate 139 is unsupported in the manner of a cantilever member. This indicia strip 139 is somewhat of a spring device in that it is normally biased against the underside of the dial 136 such that when the thermostat'knob is turned to the end of the cooking temperature range the tip 141 of the indicia plate will penetrate the slot 138 such that continued rotation of the thermostat knob will expose a major part of the indicia plate and thereby cover much of the indicia of the dial 136 and superimpose the indication clean to indicate to the housewife the oven thermostat is set to the clean" position.

The electric range 111 of the present invention is furnished with an electrical service of three-wire Edison source of power; nominally of 240 volts, single phase, 60 cycle, AC which is usually available in the average residence having adequate wiring. Looking at the schematic diagram of FIG. 7, this voltage source has a pair of line wires L and L with the voltage of 240 volts therebetween, and a grounded neutral conductor N with half voltage or 120 volts measured across any line wire L or L with the neutral conductor N for supplying the electrical load of the oven characterized by the three heating elements; the baking element 16, the broiling element 17 or the mullion heater 18. The power supply circuit to the load is furnished with the oven thermostat 24 of the present invention so as to govern the temperature within the oven cavity 13. The circuit is also supplied with an oven selector switch 151) which is a multiple position switch for setting up various heating circuits of the oven; namely, a bake circuit, a broil circuit or a time-baking circuit in conjunction with an oven timer 153. Associated with the oven thermostat 24 as mentioned previously, is an auxiliary switch 113 that is connected in line L Moreover, there is a latch interlock switch 154. The door latching mechanism 37 and particularly the extension rod 43 serves to operate a latch interlock switch 154 and a latch clean switch 155. Both of these switches have a normal position and a door latched position.

The oven selector switch 150 is provided with a series of line terminals L T, L, and N, and a series of three load terminals A, B, and C. The selector switch is provided with a plurality of switch contacts 156-1611. These switch contacts 156-160 are labeled with the particular cooking operation that is involved when the contacts are closed. For example,

.during a

baking operation contacts

156, 158 and 161) are closed. During a broiling operation,

contacts

156 and 159 are closed. During a time-baking operation,

contacts

156, 157 are closed. This oven selector switch is bypassed by the latch clean switch during the heat-cleaning cycle. This latch clean switch 155 has but two positions; a normal" position during cooking and a clean position when the oven door latch 37 is closed.

The latch clean switch 155 is a multiple circuit switch having two positions, a normal cooking position and a heat cleaning position. It is normally biased into the cooking position, and it only switches to its clean position when the door latching mechanism 37 has been closed. This latch clean switch 155 includes switch contacts 162-168.

Switch contacts

162, 165 and 163 are closed during normal cooking operations while the remaining

switch contacts

163, 164, 166 and 167 are closed once the door latching mechanism 37 is closed. One side of the latch clean switch 155 is provided with five switch terminals DH, while the other side is provided with four switch terminals J M.

The baking circuit has the bake element 16 operated at full wattage across lines L and L at 240 volts, while at the same time the broil element 17 is operated at quarter wattage across lines L and neutral conductor N at 120 volts. The baking circuit may be traced from line L through the auxiliary switch 113 and its

contacts

116 and 118, and by lead 260 to thermostat switch contacts X and by lead 201 to line terminal 1.: of the oven selector switch 150. Then through switch contacts 156 to load terminal A, then through lead 202 to switch terminal D, and through switch contacts 162 to both the bake element 16 and the broil element 17. From the bake element 16, the circuit returns to line L, through lead 2114, through the latch clean switch by way of terminal L, switch contacts 165, terminal F and lead 205, and then through the oven selector switch 150 by way of terminal B, switch contact 155, terminal L and then by lead 206 through thermostat contact X, to line L Then coming 'from the broil element 17, the circuit is through lead 207, through the latch 'clean switch 155 by way of terminal M, switch contacts'168, terminal F1, and then by lead 208 through the oven selector switch 150 by way of terminal C, switch contacts 161), terminal N, then by way of lead 209 through neutral conductor N. An oven cycle lamp 1711 is connected in the heating circuits across line L and neutral conductor N by way of

leads

211 and 212 where lead 211 is connected in lead 207 to the broil element 17 while lead 212 is connected from the lamp 170 back to neutral conductor N. Thus, whenever the thermostat switch contact X and X cycle the oven heating elements OFF and ON, the oven cycle lamp 170 will do likewise.

The time-baking" circuit is somewhat the same as the baking circuit except the broil unit 17 is not energized and the oven selector switch contacts 158 are opened and switch contacts 157 are closed whereby this portion of the circuit is through terminal T, and then by way of lead 214; to the timer switch contacts 152, to thermostat switch contacts X to line L,.

The broil circuit is a simple circuit where only the broil element 17 is energized at full wattage across full voltage of 240 volts across lines ll. and L This broil circuit may be traced as follows: the circuit is from line L through the

auxiliary switch contacts

116 and 118, through the thermostat contacts X and through oven selector switch contacts 156, and through latch clean switch contacts 162 to the broil element 1'7, and back through latch clean switch contacts 161%, selector switch contacts 159, and through oven thermostat contacts X to line L,.

Next is the clean circuit where all three

heating elements

16, 17 and 18 are energized at l20 volts across line L and neutral conductor N. in order to set up the heat-cleaning circuit there are several preliminary operations that must be performed first. As was mentioned previously it is imperative that the oven door be closed beforethe heat-cleaning cycle is initiated, and also that the door remain closed and incapable of being opened while the oven temperatures are above normal cooking temperatures. There is'a door latch control circuit that is associated with the auxiliary switch 113, the latch interlock switch 154 and the solenoid 41. Remember the door latching mechanism 37 is provided with an automatic locking means 418 which locks the door latching mechanism in both its open and its closed positions. Thus, this locking means 48 must be unlocked before the handle lever 38 of the door latching mechanism 37 may be shifted. included in series circuit with the solenoid dl is a normally open door switch 175 which is closed when the oven door 15 is closed.

Thus, in order to shift the handle lever 38 from its open to its closed position it is necessary to set the thermostat 2M0 its clean position, and to close the oven door 15 thereby closing the door switch 175. This completes a circuit through the solenoid 41 from line 1. through the auxiliary switch 113 and its

switch contacts

116 and 119, throughlead 216 and2l7 to the latch interlock switch 154 and its switch contacts 17-7, and then by lead 218 through the solenoid 41, and lead 219 through. the door switch 175 and then lead 220 backto neutral. Once the solenoid 41 is energized itpicks up the locking means 48 thereby rendering the latching mechanism free to be moved to i ts closedfposition. Once the latching means 37 reaches its closed position, it actuates the latch interlock switch 154 and closes a setof switch contacts 179 open in this door latch circuit. The latching means 37 also clean position that there is a circuit through a cooling fan motor 181 and a clean pilot lamp 182. The purpose of the cooling fan is to blow airaround the outside of the insulated of the outside of the range body 27.

Modifications of this'invention will occur to those skilled in this art, therefore it is to be understood that this invention is not limited to the particular embodiments disclosed, but that it is intended to cover all modifications which are within the true spirit and scope of this invention as claimed.

Iclaimr I 1. In a high temperatureself-cleaning oven, a temperature responsive control device, said device comprising a housing, an expansible member adjustably mounted through one wall of the housing and furnished with a remote temperature sensor, said expansible member expanding and contracting according to the direction and extent of temperature change of the said temperature sensor, and manual settable means combined with the expansiblemember for selecting a predetermined control temperature, electrical switching means including a switch actuator in the form of a snap-acting spring mechanism governed by the expansionand contraction of the expansible member, said switching means being adapted to be connected in a power circuit that governs the heating means for a self-cleaning oven, and an auxiliary switch means asshifts the latch clean switch 155 intoits clean position closing

switch contacts

163, 164, 166 and 167. The oven timer 152. is set for a variable cleaning cycle from about 1 hourto 3 hours depending upon the amount of oven soil to be removed. The solenoid circuit remains open until the oven completesits heat-cleaning cycle and the timer switch 152 is opened 'causing the heat to drop toward the normal oven cooking'temperature range. Then the housewife will reset the oven thermostat 24 and set it to one of the cooking positions thereby closing

auxiliary switch contacts

116, 118 such that the door latch circuit is controlled by the oven thermostat contacts X Then, when the oven temperature reaches the temperature set by the oven thermostat the thermostat contacts X 2 will closethereb'y completing the.door latch circuit and again energizing the solenoid and permitting the latch leverS to be shiftedfrom its closed to its open position which in turn will operatethe latch interlock switch 154 and deenergize the solenoid 41.

.Thus it will be understood that the thermostat 24 controls the energization of thesolenoid 41 which in turn controls the housewifes ability to close or open the door latching mechanism 37. A modification would be to have the locking means 18 only lock the door latching means 37 in the closed position of the door latch which is the high temperature, heatcleaning position. v

The power to the heating elements during the clean cycle may be traced as follows whereby the latch clean switch 155 bypasses the oven selector switch 150 completely. The heating circuit is across line L, and neutral conductor N through thermostat switch contacts X and through the timer switch 152, and'then by lead 222 to the latch clean switch terminal G, and then branching through both switch

contacts

166 and 167 to carry the circuit through both the bake element 16 and the broil element 17 and then by way of lead 203 to latch clean switch contacts 16?. In addition, the mullion heater 18 is connected by lead 227 to lead 204 of the bake element 16, and then on its other side by lead 223 to latch clean switch contacts 16d and then through switch terminal E, and back sociated with the said thermostat housing and adapted to be connected in either a' cookinig circuit or an oven door locking control circuit, whereby the temperature responsivecontrol device has a variable"bake"'position between about 150 F. and about 550 F. and a fixed clean position somewhere between about 750 F. and about 950 F., the variable bake" position being for. substantially a complete revolution of the manual'settable means with the auxiliary switch being set in a cooking circuit,-while the fixed clean. position of the control device actuates the auxiliary switch into its second oven door locking control circuit, the said manual settable-means including camming means for governing the position of the auxiliary switch as a function of the position of the manual settable means.

2. In a high temperature self-cleaning oven, a hydraulic thermostat comprising a housing supporting an expansible member with a remote temperature sensor, a manual settable shaft extending through onewall of the housing and engaging the expansible member on its innermost end, thermostat switching means adapted to be connected in the oven heating circuits, a snap-acting switching mechanism connected to the switching means and acted upon by .the expansible member, and auxiliary switch means combined with the thermostat housing and adapted to be connected in the-oven heating circuits saidauxiliary switch means having a cooking position through the smoke eliminator 34 by means of leads 224 and and a cleaning position, the thermostat shaft having-a variable cooking range of about one revolution over a temperature scale between about F. and about 550 F., the thermostat shaft also having a clean position upon continued rotation thereof within the temperature scale above about 750 F., the thermostat shaft having camming means for governing the actuation of the auxiliary switch means so that the cooking and clean positions of the auxiliary switch means will coincide with the cooking and clean positions of the thermostat shaft, said camming means including a mechanism for effecting snap-action of the auxiliary switch means.

3. In a high temperature self-cleaning oven, a hydraulic thermostat as recited in claim 2 wherein the said camming means includes a rotatable finger mounted on the thermostat shaft and a rotatable cam supported by the housing and engageable by the said finger to actuate said auxiliary switch in the transition of both the thermostat and the auxiliary switch between the cooking and the clean" positions, the auxiliary switch including a movable spring contact member biased against the said cam and movable thereby.

4. In a high temperature self-cleaning oven, a hydraulic thermostat as recited inclaim 3 wherein the thermostat knob is furnished with a dial that includes the cooking temperatures marked thereon, the dial including an opening at the top of the cooking temperature scale, the thermostat housing supporting an arcuate cantilever, clean" indicia blade which underlies the dial and is adapted to protrude through the said opening and overlie a portion of the dial when the thermostat knob is turned to its clean" position.

5. In a self-cleaning oven comprising an insulated cabinet supplied with an oven liner and an access door to form an oven cooking cavity, electrical heating means for saidoven cavity, a circuit network adapted to connect the heating means to an electrical power supply, a manual selector switch means for the circuit network to effect cooking operations having normal cooking temperatures between about 150 F. and about 550 F and door latching means movable between open and closed positions for holding the door closed during a heat-cleaning cycle when the oven temperatures are above the normal cooking temperatures for removing food soils lodged on the walls of the oven cavity, and locking means and a latch interlock switch means operated when the door latching means is closed for deactivating the release means whenever the heat-cleaning cycle is initiated, the invention comprising a door latch clean switch for bypassing the manual selector switch when the latch is closed,'a manually settable oven thermostat having switch contact means in the circuit network which are closed when the oven temperature is below the temperature preset on the thermostat and which contact means are opened when the oven temperature reaches the said preset temperature, said thermostat having a temperature scale which covers the full range of coking and heat-cleaning temperatures, and an auxiliary switch combined with the thermostat and connected in the circuit network to have a cooking position and a clean" position, and camming means interposed between the thermostat and the auxiliary switch for coordinating them in the cooking position and in the clean position, whereby the thermostat must be reset to a cooking position and the oven temperature must drop into the cooking temperature range before the said electroresponsive release means is energized to unlock the door latching means.

6. In a self-cleaning oven as recited in claim wherein the said manually settable thermostat has a knob with a variable cooking range of about one revolution over a temperature scale between about 150 F. and about 550 F., the thermostat knob also having a clean position upon continued rotation thereof to reach a maximum temperature setting of about 950 F., the said camming means being associated with the thermostat knob and including a toggle mechanism for effecting snapaction of the auxiliary switch means.

7. In a self-cleaning oven as recited in claim 6 wherein the said camming means includes a rotatable finger mounted to the thermostat knob and a rotatable cam that is engageable by the said finger in the transition of both the thermostat and the auxiliary switch between the cooking and the clean" positions, the auxiliary switch including a movable spring contact member pressed against the said tumbler and movable thereby.

8. In a self-cleaning oven as recited in claim 7 wherein the thermostat knob is furnished with a dial that indicates the range of cooking temperatures, the dial including an opening at the top of the cooking temperature scale, the thermostat including a housing that supports an arcuate cantilever clean indicia indicator which underlies the dial and is adapted to protrude through the said opening and overlie a portion of the dial when the thermostat knob is turned to its clean" position.

9. A self-cleaning oven comprising walls defining an oven cavity, one wall of the cavity including a door for gaining access thereto, a source of electric power supply, a first baking circuit adapted to be completed to said power source, a second broiling circuit adapted to be completed to said power source, and a third clean" circuit adapted to be completed to said power source, a manual selector switch having an OFF position, a bake position and a broil position, said manual selector switch in its OFF position interrupting both of said positions, said selector switch in its bake position preparing said first bakig" circuit, said selector switch in its broil position preparing aid second broiling circuit, an adjustable oven thermostat having a variable bake" position, a fixed broil" position and a "clean" position, said thermostat in its variable bake" position correspondingly presetting a variable bake temperature for said cooking cavity in the normal cooking temperature range extending from about F. to about 550 F., said thermostat in its broil position correspondingly presetting a broil temperature substantially near 550 F said thermostat in its clean position presetting a givenheat-cleaning temperature for said cooking cavity in the temperature range above about 750 F., door latching means movable between open and closed positions for holding the door closed during the heatcleaning operation, locking means for locking the door lathing means, an electroresponsive means for releasing the locking means, and a latch interlock switch means having a first open latch position and a second closed latch position, the thermostat including an auxiliary switch means having a first cooking switch position in series with the thermostat and selector switch means and a second cleaning" switch position to be in circuit with the first open latch position of the latch interlock switch means and the electroresponsive means when the door latching means is in an open position, said electroresponsive means being in circuit with the second closed position of the latch interlock switch and the thermostat and first cooking position of the auxiliary switch means.

10. In a high temperature oven comprising walls defining an oven cavity, one wall of the cavity including a door for gaining access thereto, heating means for supplying heat to the oven cavity for normal cooking temperatures between about 150 F. and 550 F and a self-cleaning oven cycle with a maximum temperature above about 750 F., door latching means movable between an open and a closed position for holding the door closed during a high temperature operation above normal cooking temperatures, locking means for locking the door latching means in its closed position, and electroresponsive means for releasing the said locking means; the improvement comprising a manual control thermostat having thermally controlled switch contact means for governing power delivered to the heating means and auxiliary switch contact means settable into a cooking or a high temperature position as a function of the setting of the thermostat into a cooking or a high temperature position respectively, a latch interlock switch means having an unlatched and a latched position governed by the position of the door latching means, and circuit means including said thermostat and said latch interlock switch for controlling the energization of said electroresponsive means thereby to allow latching and unlatching of said door, said circuit means having a first circuit actuated through said auxiliary switch contact means when said thermostat is set to the high temperature position to allow latching of the door, and a second circuit actuated through said auxiliary switch contact means and said thermally controlled switch contact means to allow unlatching of the door, said second circuit being closed only when said thermostat is reset into a cooking temperature position and the temperature in the oven cavity returns to the cooking temperature setting of the thermostat thereby to prevent opening of the door during high temperature operations.

11. In a high temperature oven comprising walls defining an oven cavity, one wall of the cavity including a door for gaining access thereto, heating means for supplying heat to the oven cavity for normal cooking temperatures between about 150 F. and 550 F. and a self-cleaning oven cycle with a maximum temperature above about 750 F., door latching means movable between an open and a closed position for holding the door closed during a high temperature operation above normal cooking temperatures, locking means for locking the door latching means in its closed position, and electroresponsive means for releasing the said locking means; the improvement comprising a manual control thermostat having thermally controlled switch contact means for governing power delivered to the heating means and auxiliary switch contact means settable into a cooking or a high temperature position as a function of the setting of the thermostat into a cooking or a high tempera ture position respectively, a latch interlock switch means having an unlatched and a latched position governed by the position of the door latching means, and circuit means including said thermostat and said latch interlock switch for controlling the energization of said electroresponsive means to prevent opening of the door when the oven cavity is in a high temperature mode, said circuit means incorporating both the auxiliary switch contact means and the thermally controlled switch contact means of said thermostat and being arranged to disable .for governing variable heating rates of the said heating means during cooking, and a latch clean switch having a first normal cooking position in series with the oven selector switch and a second clean position that is set when the door latching means is closed for bypassing the said oven selector switch and setting up a high temperature heating circuit.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 569,670 Dated March 9, 1971 It is certified that error appears in the above-identified pater and that said Letters Patent are hereby corrected as shown below:

Column 10, line 51, cancel "cuits" and insert cuit (Please note that the designation of the line numbers located in the space between Columns 9 and 10 do not correspond to the actual lines beside which they are positioned. Column 11, line 19, after "means" insert for locking the door latching means in its closed posi tion, electroresponsive release means for the said lockin means, Column 12, line 3, cancel "bakig" and insert baking Column 12, line 4, cancel 'aid" and insert said Column 12, line 17, cancel "lathing" and inse latching Signed and sealed this 1 Tth day of August 1 971 (SEAL) Attest:

EDWARD I LFLETCHELJR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents FORM PO-1050 (IO-69)

Claims

1. In a high temperature self-cleaning oven, a temperature responsive control device, said device comprising a housing, an expansible member adjustably mounted through one wall of the housing and furnished with a remote temperature sensor, said expansible member expanding and contracting according to the direction and extent of temperature change of the said temperature sensor, and manual settable means combined with the expansible member for selecting a predetermined control temperature, electrical switching means including a switch actuator in the form of a snap-acting spring mechanism governed by the expansion and contraction of the expansible member, said switching means being adapted to be connected in a power circuit that governs the heating means for a self-cleaning oven, and an auxiliary switch means associated with the said thermostat housing and adapted to be connected in either a cooking circuit or an oven door locking control circuit, whereby the temperature responsive control device has a variable ''''bake'''' position between about 150* F. and about 550* F. and a fixed ''''clean'''' position somewhere between about 750* F. and about 950* F., the variable ''''bake'''' position being for substantially a complete revolution of the manual settable means with the auxiliary switch being set in a cooking circuit, while the fixed ''''clean'''' position of the control device actuates the auxiliary switch into its second oven door locking control circuit, the said manual settable means including camming means for governing the position of the auxiliary switch as a function of the position of the manual settable means.

2. In a high temperature self-cleaning oven, a hydraulic thermostat comprising a housing supporting an expansible member with a remote temperature sensor, a manual settable shaft extending through one wall of the housing and engaging the expansible member on its innermost end, thermostat switching means adapted to be connected in the oven heating circuits, a snap-acting switching mechanism connected to the switching means and acted upon by the expansible member, and auxiliary switch means combined with the thermostat housing and adapted to be connected in the oven heating circuits, said auxiliary switch means having a cooking position and a cleaning position, the thermostat shaft having a variable cooking range of about one revolution over a temperature scale between about 150* F. and about 550* F., the thermostat shaft also having a ''''clean'''' position upon continued rotation thereof within the temperature scale above about 750* F., the thermostat shaft having camming means for governing the actuation of the auxiliary switch means so that the cooking and ''''clean'''' positions of the auxiliary switch means will coincide with the cooking and ''''clean'''' positions of the thermostat shaft, said camming means including a mechanism for effecting snap-action of the auxiliary switch means.

3. In a High temperature self-cleaning oven, a hydraulic thermostat as recited in claim 2 wherein the said camming means includes a rotatable finger mounted on the thermostat shaft and a rotatable cam supported by the housing and engageable by the said finger to actuate said auxiliary switch in the transition of both the thermostat and the auxiliary switch between the cooking and the ''''clean'''' positions, the auxiliary switch including a movable spring contact member biased against the said cam and movable thereby.

4. In a high temperature self-cleaning oven, a hydraulic thermostat as recited in claim 3 wherein the thermostat knob is furnished with a dial that includes the cooking temperatures marked thereon, the dial including an opening at the top of the cooking temperature scale, the thermostat housing supporting an arcuate cantilever, ''''clean'''' indicia blade which underlies the dial and is adapted to protrude through the said opening and overlie a portion of the dial when the thermostat knob is turned to its ''''clean'''' position.

5. In a self-cleaning oven comprising an insulated cabinet supplied with an oven liner and an access door to form an oven cooking cavity, electrical heating means for said oven cavity, a circuit network adapted to connect the heating means to an electrical power supply, a manual selector switch means for the circuit network to effect cooking operations having normal cooking temperatures between about 150* F. and about 550* F., and door latching means movable between open and closed positions for holding the door closed during a heat-cleaning cycle when the oven temperatures are above the normal cooking temperatures for removing food soils lodged on the walls of the oven cavity, and locking means and a latch interlock switch means operated when the door latching means is closed for deactivating the release means whenever the heat-cleaning cycle is initiated, the invention comprising a door latch ''''clean'''' switch for bypassing the manual selector switch when the latch is closed, a manually settable oven thermostat having switch contact means in the circuit network which are closed when the oven temperature is below the temperature preset on the thermostat and which contact means are opened when the oven temperature reaches the said preset temperature, said thermostat having a temperature scale which covers the full range of coking and heat-cleaning temperatures, and an auxiliary switch combined with the thermostat and connected in the circuit network to have a cooking position and a ''''clean'''' position, and camming means interposed between the thermostat and the auxiliary switch for coordinating them in the cooking position and in the ''''clean'''' position, whereby the thermostat must be reset to a cooking position and the oven temperature must drop into the cooking temperature range before the said electroresponsive release means is energized to unlock the door latching means.

6. In a self-cleaning oven as recited in claim 5 wherein the said manually settable thermostat has a knob with a variable cooking range of about one revolution over a temperature scale between about 150* F. and about 550* F., the thermostat knob also having a ''''clean'''' position upon continued rotation thereof to reach a maximum temperature setting of about 950* F., the said camming means being associated with the thermostat knob and including a toggle mechanism for effecting snap-action of the auxiliary switch means.

7. In a self-cleaning oven as recited in claim 6 wherein the said camming means includes a rotatable finger mounted to the thermostat knob and a rotatable cam that is engageable by the said finger in the transition of both the thermostat and the auxiliary switch between the cooking and the ''''clean'''' positions, the auxiliary switch including a movable spring contact member pressed against the said tumbler and movable thereby.

8. In a self-cleaning oveN as recited in claim 7 wherein the thermostat knob is furnished with a dial that indicates the range of cooking temperatures, the dial including an opening at the top of the cooking temperature scale, the thermostat including a housing that supports an arcuate cantilever ''''clean'''' indicia indicator which underlies the dial and is adapted to protrude through the said opening and overlie a portion of the dial when the thermostat knob is turned to its ''''clean'''' position.

9. A self-cleaning oven comprising walls defining an oven cavity, one wall of the cavity including a door for gaining access thereto, a source of electric power supply, a first ''''baking'''' circuit adapted to be completed to said power source, a second ''''broiling'''' circuit adapted to be completed to said power source, and a third ''''clean'''' circuit adapted to be completed to said power source, a manual selector switch having an ''''OFF'''' position, a ''''bake'''' position and a ''''broil'''' position, said manual selector switch in its ''''OFF'''' position interrupting both of said positions, said selector switch in its ''''bake'''' position preparing said first ''''bakig'''' circuit, said selector switch in its ''''broil'''' position preparing aid second ''''broiling'''' circuit, an adjustable oven thermostat having a variable ''''bake'''' position, a fixed ''''broil'''' position and a ''''clean'''' position, said thermostat in its variable ''''bake'''' position correspondingly presetting a variable ''''bake'''' temperature for said cooking cavity in the normal cooking temperature range extending from about 150* F. to about 550* F., said thermostat in its ''''broil'''' position correspondingly presetting a broil temperature substantially near 550* F., said thermostat in its ''''clean'''' position presetting a given heat-cleaning temperature for said cooking cavity in the temperature range above about 750* F., door latching means movable between open and closed positions for holding the door closed during the heat-cleaning operation, locking means for locking the door lathing means, an electroresponsive means for releasing the locking means, and a latch interlock switch means having a first open latch position and a second closed latch position, the thermostat including an auxiliary switch means having a first cooking switch position in series with the thermostat and selector switch means and a second ''''cleaning'''' switch position to be in circuit with the first open latch position of the latch interlock switch means and the electroresponsive means when the door latching means is in an open position, said electroresponsive means being in circuit with the second closed position of the latch interlock switch and the thermostat and first cooking position of the auxiliary switch means.

10. In a high temperature oven comprising walls defining an oven cavity, one wall of the cavity including a door for gaining access thereto, heating means for supplying heat to the oven cavity for normal cooking temperatures between about 150* F. and 550* F. and a self-cleaning oven cycle with a maximum temperature above about 750* F., door latching means movable between an open and a closed position for holding the door closed during a high temperature operation above normal cooking temperatures, locking means for locking the door latching means in its closed position, and electroresponsive means for releasing the said locking means; the improvement comprising a manual control thermostat having thermally controlled switch contact means for governing power delivered to the heating means and auxiliary switch contact means settable into a cooking or a high temperature position as a function of the setting of the thermostat into a cooking or a high temperature position respectively, a latch interlock switch means having an unlatched and a latched position governed by the position oF the door latching means, and circuit means including said thermostat and said latch interlock switch for controlling the energization of said electroresponsive means thereby to allow latching and unlatching of said door, said circuit means having a first circuit actuated through said auxiliary switch contact means when said thermostat is set to the high temperature position to allow latching of the door, and a second circuit actuated through said auxiliary switch contact means and said thermally controlled switch contact means to allow unlatching of the door, said second circuit being closed only when said thermostat is reset into a cooking temperature position and the temperature in the oven cavity returns to the cooking temperature setting of the thermostat thereby to prevent opening of the door during high temperature operations.

11. In a high temperature oven comprising walls defining an oven cavity, one wall of the cavity including a door for gaining access thereto, heating means for supplying heat to the oven cavity for normal cooking temperatures between about 150* F. and 550* F. and a self-cleaning oven cycle with a maximum temperature above about 750* F., door latching means movable between an open and a closed position for holding the door closed during a high temperature operation above normal cooking temperatures, locking means for locking the door latching means in its closed position, and electroresponsive means for releasing the said locking means; the improvement comprising a manual control thermostat having thermally controlled switch contact means for governing power delivered to the heating means and auxiliary switch contact means settable into a cooking or a high temperature position as a function of the setting of the thermostat into a cooking or a high temperature position respectively, a latch interlock switch means having an unlatched and a latched position governed by the position of the door latching means, and circuit means including said thermostat and said latch interlock switch for controlling the energization of said electroresponsive means to prevent opening of the door when the oven cavity is in a high temperature mode, said circuit means incorporating both the auxiliary switch contact means and the thermally controlled switch contact means of said thermostat and being arranged to disable the electroresponsive means after latching of the door unless the thermostat is set in its cooking position and the temperature of the oven cavity returns to the cooking temperature setting of the thermostat.

12. In a high temperature oven as recited in claim 10 with the addition of circuit means including an oven selector switch for governing variable heating rates of the said heating means during cooking, and a latch clean switch having a first normal cooking position in series with the oven selector switch and a second clean position that is set when the door latching means is closed for bypassing the said oven selector switch and setting up a high temperature heating circuit.