Patent Publication Number: US-3875372-A

Title: Control circuit for a self-cleaning oven

Description:
United States Patent [191 Gilliom Apr. 1,1975  
 [ CONTROL CIRCUIT FOR A SELF-CLEANING OVEN John W. Gilliom, Mansfield. Ohio [22] Filed: Aug. 30, 1974 [21] Appl. No: 502,146  
  Related US. Application Data [62] Division of Scr. No. 433.523. Feb. I, 1974.  
 [75] Inventor:  
 3.757.084 9/1973 McLean et a1 219/493 X Primary [:Iraminer-Volodymyr Y. Mayewsky Attorney. Agem, or FirmDonnelly, Maky. Renner &amp;  
 Otto  
 [ ABSTRACT A locking mechanism for a self-cleaning oven includes an elongated latching rod having a latch lock portion for firm engagement with a slot in the oven door, and a spring bias coupling between the latching rod and drive motor therefor maintains the door under pressure when locked to deform the door seal preventing heat leaks during self-cleaning. The latching rod is supported within the oven frame in a channel, and a rivet connected to the former is positioned for movement within a cam slot in the latter to provide for pivoting of the latching rod during movement to and from engagement with the door. When the oven selector switch is in self-clean position. the door is closed and the timer is set. the control circuit for the selfcleaning oven automatically energizes the drive motor to lock the door; and at the expiration of the cleaning time set on the timer and the dropping of the oven temperature to a predetermined safe level. the control circuit again automatically energizes the drive motor to unlock the door.  
 5 Claims, 6 Drawing Figures CONTROL CIRCUIT FOR A SELF-CLEANING OVEN This is a division of application Ser. No. 438,523, filed Feb. 1, 1974.  
 BACKGROUND OF THE INVENTION This invention relates to a locking arrangement and automatic control for an oven door and more particularly to a spring-biased locking arrangement for maintaining pressure against the oven door seal of a selfcleaning oven when locked.  
  It is important from the standpoint of safety in the use of self-cleaning ovens, either of the free standing or built-in type, that the oven door be locked during the self-clean operation when oven temperature is increased, for example, to 950 F. at which pyrolysis occurs. In one prior art oven door latch illustrated in US. Pat. No. 3,462,585 a motor effects movement of the rod coupled to a rotatable latch member mounted on a pivot fixed relative to the oven, and such latch member is pivotally swung into and out of engagement with a protruding keeper mounted on the oven door. In such device as the latch member is rotated into engagement with the keeper to lock the door, a pressure is applied to the door seal at a level dependent on the amount of wear on the latter. In another door latching system illustrated in US. Pat. No. 3,757,084 a latch member pivotable about an axis fixed relative to the oven engages a keeper mounted on the oven door and is driven by a solenoid and snap-acting spring over-center arrangement. The latter device is relatively complicated and requires sufficient kinetic energy in the inertial movement of the latch member provided by the solenoid in order to move the spring pivot point beyond the center position to draw the latch member completely closed. Moreover, none of the prior art automatically locks and unlocks the oven door at the beginning and end of the self-clean operation.  
 SUMMARY OF THE INVENTION In the instant invention an elongated latching rod is supported above the oven cavity for movement by a motor to and from locking engagement with the oven door. A latch lock portion at one end of the latching rod is engageable with a slot in the oven door, and the latching rod is resiliently coupled to an eccentrically mounted cam driven by a motor so that when the door is locked a predetermined amount of pressure is applied to the oven door seal to prevent escape of hot air and gases during pyrolytic self-cleaning. Moreover, the latch lock portion of the latching rod is cut at an angle at its forward end so as to slide across the door liner with the spring connection operating as a universal joint to find the slot therein in the event of a slight door misalignment, and the spring also eliminates motor stalling. Fixed to the latching rod is a follower rivet, which is movable in a can slot in a latch support channel as the motor is operated, to provide for proper positioning of the latch lock portion relative to the door slot during locking and unlocking operation.  
  An automatic control circuit for operating the motor to lock and to unlock the door and to energize the oven for self-cleaning is timer operated, whereby upon adjusting the oven selector switch for self-clean operation, closing the oven door and setting the timer, the door will lock automatically and the oven will selfclean. Moreover, the door will unlock automatically at the expiration of the timer and the oven temperature has dropped to a predetermined safe level. The motor and control circuit are located relatively remote from the body of the oven cavity and the axis openings thereto in order to isolate the same from high oven temperatures to preclude any heat damage thereto.  
  Accordingly, a primary object of the invention is to prevent opening an oven door during self-cleaning operation.  
  Another object of the invention is to provide a predetermined and constant pressure on an oven door seal for a self-cleaning oven when the oven door is locked.  
  A further object of the invention is to provide an automatic control circuit for a self-cleaning oven, which locks the door, energizes the oven for self-cleaning operation and unlocks the door at the expiration of the cleaning time and the oven temperature has dropped to a predetermined safe level.  
  Still another object of the invention is to provide for locating the driving and control means for an oven door lock relatively remote from the oven cavity and heat thereof.  
  These and other objects and advantages of the present invention will become apparent as the following description proceeds.  
  To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described, the following description and the annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the invention may be employed.  
 BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings:  
  FIG. 1 is an elevational view, partially broken away and partially in section, of the upper portion of a selfcleaning range;  
  FIG. 2 is a side view, partially in section, of the driving portion of the oven door lock;  
  FIG. 3 is a bottom view of part of the driving portion of the oven door lock taken on the lines 33 of FIG.  
  FIG. 4 is an isometric view of the bottom of the driving portion of the oven door lock and switches coupled therein;  
 FIG. 5 is a top view of the oven door lock; and  
  FIG. 6 is a schematic electric circuit diagram of the control circuit for the oven and door lock of the selfcleaning range.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference numerals refer to like elements in the several figures, the upper portion of the self-cleaning range 10, which includes a self-cleaning oven 1 l and a door 12 for closing the same, a cook top 13 having burners l4, and a splash guard 15 including a control panel 16 at the front thereof is illustrated in FIG. 1. Within the splash guard are located clean and oven lock indicator lights l7, 18, a conventional oven clock timer l9 and a conventional oven selector switch 20, the latter being located on a control box 21 within which the oven control circuit is located, all being coupled to the range main electrical cable 22. A pigtail 23 provides electrical power to the range from an external supply, such as from an outlet receiving, for example, 220 volt power from the utility company, to energize the various electrical components therein.  
  The self-cleaning oven 11 is located below the cook top 13 and within the supportive framework 24 of the range and has upper and rear walls 25, 26 and additional side and bottom walls, not shown, forming the oven liner and defining the oven cavity 27. A space 28 surrounds the oven liner and may be provided with insulation to insulate the oven from the other parts of the range. The access opening 29 to the oven cavity is closed by the door 12, which is pivotable downward about a horizontal hinge, not shown, by manipulation of the handle 30 in conventional manner. A door seal 31, which preferably surrounds a major portion of the access opening 29, is shown at the abutting upward turned oven wall surface 32 and the door liner wall 33, and preferably comprises a resilient gasket member to prevent heat loss from the oven cavity, especially during self-cleaning operation. Although the self-cleaning oven shown and described in the drawings is located in a free standing range, with a door pivotable on a horizontal hinge, the invention may also be included in a built-in or other type of oven or in an oven with a door pivotable about a vertical hinge.  
  The broil heating element 34 is supported within the oven cavity 27 by a mounting bracket 35 and is provided with an electrical connection 36 to the main electrical cable 22 for energization by the control circuit in the control box 21. A bake heating element, not shown in FIG. 1, is also located in the oven cavity to heat the same for baking purposes, and, in a preferred embodiment, to raise the temperature of the oven cavity to approximately 950F. at which pyrolytic cleaning occurs. The broil and bake heating elements are preferably conventional electrical resistance heating elements rated, for example, at 3,000 and 2,400 watts, respectively.  
  A locking mechanism 40 located above the oven cavity 27 is operable to lock the oven door 12 in closed position whenever self-cleaning oven operation occurs. The locking mechanism includes a driving portion 41, having a motor 42 resiliently connected by a cam member 43, angle plate 44 and lock bias spring 45 to the rear end of the latching rod 46, and a latch lock portion 47 engageable with the door 12 through a slot 48 located therein and reinforced by a slotted channel reinforcement 49. The latching rod 46 is supported for movement within a latch channel 50 by support embossments 51, and movement thereof is limited by a follower rivet 52 extending into a cam slot 53 in such channel. A rod interlock 54 extends forward of the range supportive framework 24 for engagement with the door 12 when the latter is closed, and is coupled at its rear end to a door interlock switch, not shown in FIG. 1, which closes contact in the control circuit.  
  Turning now more particularly to FIGS. 2 and 3, the driving portion 41 in the locking mechanism 40 is shown in more detail to illustrate the features of the invention. The rod interlock 54 passes through an opening 55 in the latch channel end plate 56 and has stops 57 formed thereon to prevent withdrawal in a forward direction. The rear end of the rod interlock 54 is located in abutment with the switch plunger 58, which is part of the door interlock switch arrangement to be described in more detail below, to operate the same when the oven door is closed to drive the rod interlock to the right or rear of the oven.  
  The motor 42 in the driving portion preferably has an internal reduction drive to provide relatively slow output rotational speed, for example at 1 rpm, on the drive shaft 59 with sufficient torque to operate the locking mechanism. A cam member 60 made of nylon, for example, is attached to the drive shaft and includes a cam surface 61 for operating control switches, not shown in FIGS. 2 and 3, and an eccentric mount 62 to which the horizontal surface 63 of the angle plate 44 is connected by a cup washer 64 and cotter pin 65.  
  A slot 66 in the vertical surface 67 of the angle plate 44 receives the latching rod mounting arm 68, which has a reduced cross-section relative to the major extent of the latching rod 46, and the slot also has a crosssection smaller than that of the major extent of the latching rod. The lock bias spring 45 has one end secured in a cut-out 69 formed in the mounting arm 68 and another end in abutment with the vertical surface 67 of the angle plate normally tending to draw the larger cross-sectional area portion of the latching rod into abutment with such vertical surface.  
  The support embossments 51 of the latch channel 50 provides minimum friction sliding points for the latching rod as it is moved forward and rearward by the motor, angle plate, and lock bias spring arrangement, and the follower rivet 52, which is fixed to the latching rod, has a roller follower 70 formed, for example, of brass to guide the latching rod within the cam slot 53. In FIGS. 2 and 3 the locking mechanism illustrated in solid lines is in locked position, whereby the latching rod has been drawn from a neutral or unlocked forward position to the right or rear of the range by a clockwise rotation of the motor drive shaft 59 as indicated by the arrow 71 in FIG. 3, and the unlocked position of the angle plate 44 and follower rivet 52 is illustrated in phantom in FIG. 2 where the latching rod is moved to the left or forward relative to the range body by further drive shaft clockwise rotation.  
  Referring now to FIG. 4, the door interlock switch 72, clean switch 73, and motor control switch 74 are located on a switch mounting plate 75 for actuation, respectively, by the rod interlock 54 and the cam surface 61. Each of such switches is preferably a single pole double throw switch, which makes a first circuit connection when the respective plunger 58, 76, 77 thereof is released or makes a second circuit connection when the respective plunger is depressed relative to the switch body.  
  The eccentric mount 62, angle plate 44 and latching rod 46 are illustrated in FIG. 4 in the locked position, whereby such elements are withdrawn furthest to the right or rear of the range by the clockwise direction rotation of the motor drive shaft indicated by the arrow 7 1. When the latching rod is in locked position, the follower rivet 52 is located proximate the right hand portion of the cam slot 53, and the switch plungers 76, 77 are depressed by the cam surface 61 to throw the respective switches 73, 74 to their second or locked positions. Moreover, the rod interlock 54 is in its right hand position, since the oven door is closed when it is locked, to urge the plunger 58 of the door interlock switch 72 to the right throwing the same in its second or door closed position.  
  The cam slot 53 is slightly over-sized to allow for wear of the door seal 31, shown in FIG. 1, so that the lock bias spring 45 assures that the predetermined amount of pressure, such as fourteen pounds, is always applied to the door seal when the door is locked in closed position. The convex surface 78 and sloped surface 79 of the cam slot 53 cooperate with the follower rivet 52 when the latching rod 46 is driven by the motor to locked and unlocked positions, respectively, relative to be reinforced slot 48 in the oven door.  
  A top view of the locking mechanism 40 is illustrated in FIG. 5. The motor 42 is located on the switch mounting plate 75, and the motor leads 80, 81 are adapted for coupling to the control circuit to provide energy to the motor to drive the locking mechanism. The drive shaft 59 extends downwardly through an opening in the switch mounting plate 75 from the reduction drive portion 82 of the motor to drive the latching rod 46 within the latch channel 50. The latch lock portion 47 of the latching rod has a cut-out 83 therein with the forward transverse end surface 84 of such cut-out being obtuse relative to the longitudinal axis of the latching rod to provide for smooth engagement with and, particularly, releasing from the reinforced slot in the oven door during latching operation. Moreover, the forward transverse end surface 85 of the latching rod 46 is cut at an obtuse angle relative to such longitudinal axis to facilitate sliding of the rod across an end wall of the door slot 48 and into the same in the event of a slight door misalignment.  
  In operation of the mechanical portion of the locking mechanism 40 described above with reference to FIGS. 1 through 5, whenever the oven selector switch 20 is adjusted for self-cleaning, the oven timer 19 is set for a predetermined cleaning time, and the door 12 is closed to move the rod interlock 54 to throw the door interlock switch 72 to the door closed position, the motor 42 will be energized by the control circuit to rotate approximately l80 in the clockwise direction. Moreover, if the door and slot 48 are misaligned relative to the latching rod 46, the transverse surface 85 will slide across the slot end wall as permitted by the universal joint action of the lock bias spring 45. During such motor rotation the eccentric mount 62 is moved from a left or forward position relative to the range as viewed, for example, in FIG. I, to a right or rearward most position to lock the oven door. When the eccentric mount 62 is rotated and the latching rod 46 is drawn to the rear of the range, the follower rivet 52 is drawn along the convex surface 78 of the cam slot 53, and the latching lock portion 47 engages the door 12 within the slot 48 thereof.  
  Moreover, as the eccentric mount 62 rotates clockwise, as viewed, for example in FIG. 3, from unlocked to locked position, the door 12 is drawn tightly closed and the door seal 31 is deformed under a pressure determined by the force of the lock bias spring 45 bearing against the vertical surface 67 of the angle plate 44. The lock bias spring 45 connection between the latching rod 46 and motor prevents the latter from stalling in case the door and oven frame tolerances are not exact or, for example, a foreign object lodges between the same, and thus precludes destruction of the motor and/or the gears that might otherwise occur. After the cam member 60 has rotated approximately 75 from the unlocked position thereof locking is virtually complete and the further rotation to approximately 180 from the unlocked position draws the angle plate 44 against the lock bias spring 45. The plunger 76 of the clean control switch 73 is depressed at about 50 rotation of the cam surface 61 to throw such switch from its normally unlocked position to its locked position to energize the oven for self-cleaning operation, and as such cam surface rotates to its fully locked position, the plunger 77 of the motor control switch 74 is released from its depressed position to throw the same to its door locked position de-energizing the motor and conditioning an unlock circuit for re-energization thereof upon termination of the cleaning operation.  
  After the cleaning operation has been completed, whereby the time set on the oven timer 19 has expired and the oven temperature has dropped to a predetermined safe level, the motor 42 is re-energized through the unlock circuit to rotate further in the clockwise direction to unlock the door. As the motor rotates to the unlocked or neutral position, the respective plungers of the switches 73, 74 are released, with that of the latter being released at the completion of the motor 360 rotation to de-energize the same and to condition the lock circuit for motor energization to lock the oven door upon initiation of a further oven cleaning operation.  
  The control circuit for the oven portion of the self-cleaning range 10 is illustrated in FIG. 6 receiving electrical power on first and second power lines 101 and 102 and neutral power line 103. The oven selector switch 20 in the control circuit is a conventional cam operated multiple pole switch including a number of single pole double throw switches 104a through 104e, each including a movable switch arm 105 adjustable to connection with either of first or second fixed contacts 106, 107; and the connections shown for the selector switch in FIG. 6 set the control circuit 100 for selfcleaning operation. The selector switch 20 also can be adjusted for pre-heat, bake, time bake or broil operation.  
  The broil and bake heating elements 34, 108 are connected, respectively, by the lines 109, 110 to the switches 104b, c for selective connection to the first power line 101, and such heating elements are also connected by the high temperature thermostat 111 to the clean control switch 73, which includes a switch arm 112 movable between first and second fixed contacts 113, 114. The high temperature thermostat 111 is preferably set to open circuit whenever the temperature within the oven cavity 27 exceeds a predetermined maximum level, for example, 950F., which normally is attained only during self-cleaning operation.  
  The first fixed contact 1 13 of the clean control switch is connected via a low temperature oven operation circuit 115, which includes a line 116 and a conventional adjustable thermostat 117 that controls oven temperature during pre-heating, baking and broiling, to the second power line 102; and the second fixed contact 114 of the clean control switch is connected by the line 118, switch 1040 when closed for self-cleaning operation, and line 119 to the second power line 102, bypassing the adjustable thermostat 117. An oven indicator lamp 120, preferably located in the control panel 16, is connectable for energization to indicate oven operation in pre-heat, bake or broil modes by connections via the switch 104e to the first power line 101 and via the movable switch arm 112 and first fixed contact 113 in the clean control switch 73 to the second power line 102.  
  The conventional oven timer 19 is connected between the first and neutral power lines 101, 103&#39;, and  
 when set or energized for a duration to control oven operation for time baking or self-cleaning, closes the normally open first timer switch 121 and throws the movable switch arm 122 in a second timer switch 123 from its normal connection with a first fixed contact 124 to connection with a second fixed contact 125. The movable switch arm 122 of the second timer switch is coupled to the first fixed contact 126 of a single pole double throw lock thermostat 127, which also has a movable switch arm 128 and second fixed contact 129, the former being connected to the line 118 and the latter being connected to one side of the lock indicator lamp 18. The lock thermostat 127 is preferably set to operate or to switch at approximately 550F., which is the normal maximum operating temperature for baking or broiling, whereby below such temperature a connection is made by the switch arm 128 to the first fixed contact 126 and above such temperature a connection is made to the second fixed contact 129. Moreover, a conventional catalyst heating element 130 is coupled to the first fixed contact 126 of the lock thermostat 127 to heat the oven catalytic exhaust before the oven tem perature has exceeded 550 during self-clean operation.  
  The clean indicator lamp 17 is connected by the line 131 to the first power line 101 and by the line 132, switch 1040 when closed as shown, and line 119 to the second power line 102 to indicate when energized that the oven is operating in self-cleaning mode; and an oven lamp 133 is energized by a connection between the movable switch arm 134 and the first fixed contact 135 of the door interlock switch 72 when the oven door is open and is de-energized when such movable switch arm is in connection with the second fixed contact 136 of the door interlock switch when the door is closed.  
  The neutral lead 80 of the motor 42 is connected to the second fixed contact 136 of the door interlock switch 72, and the motor power lead 81 is connected to the movable switch arm 137 of the motor control switch 74. Such movable switch arm is normally in connection with the first fixed contact 138 in the motor control switch, when the oven is operated in preheat, bake, time bake or broil modes, and is thrown into connection with the second fixed contact 139 by the cam surface 61 when the oven door is locked. The motor lock circuit 140 is defined by the first fixed contact 138 of the motor control switch, line 141, switch 105d in the oven selector switch 20 when in position as shown, line 142, second timer switch 123, line 143, lock thermostat 127, line 118, switch 104a in the oven selector switch when in position as shown, and line 119 to the second power line 102. Moreover, the motor unlock circuit 144 is defined by the second fixed contact 139 in the motor control switch line 145, second timer switch 123, line 143, lock thermostat 127, line 118, switch 104a in the selector switch when in position as shown, and line 119 to the second power line 102.  
  Exemplary oven 11 and control circuit 100 operation is described below. When the oven selector switch 20 is in the off position, the movable switch arms 105 are centered between respective first and second fixed contacts 106 and 107, and no connections are made to energize the broil or bake heating elements 34, 108. For pre-heating, both the broil and bake heating elements are used for efficiency, and the movable contacts 1050, b, c and e in the selector switch 20 are adjusted to connection, respectively, with the second fixed contact 107a and the first fixed contacts 106b, c and e in order to energize such heating elements as well as the oven on indicator lamp 120. For baking the movable contacts C and e are adjusted in connection, respectively, with the first fixed contacts 106( and e to energize the bake heating element and the oven indicator lamp; and for timed baking the movable contacts 105C and e are adjusted to connection, respectively, with the second fixed contacts 107C and e to provide for energization of the bake heating element and oven indicator lamp only when the timer 19 is energized to close the first timer switch 121, such energization being terminated at the expiration of the duration set on the timer. Moreover, for broiling the movable contacts 105]) and e are adjusted to connection, respectively, with the first fixed contacts 106b and e to energize the broil element and the oven indicator lamp.  
  For self-cleaning oven operation, which uses only the bake heating element although the broil or other heating element may alternatively or additionally be used, the oven door 12 is closed throwing the switch arm 134 into connection with the second fixed contact 136 in the door interlock switch 72 to provide a connection for the motor 42 to the neutral power line 103, and the selector switch 20 is adjusted to the self-clean position to make the connection at switches 104a, c and d as illustrated in FIG. 6. Setting and energizing the timer 19 for a desired duration of self-cleaning operation closes the first timer switch 121 to energize the bake heating element 108 after the motor has begun. Moreover, the energized timer 19 moves the switch arm 122 in the second timer switch 123 in connection with the second fixed contact 125, to energize the motor lock circuit to provide power to the motor 42.  
  The energized motor 42 then rotates from its initial unlocked position mechanically operating the locking mechanism 40 as described above with reference to FIGS. 1 through 5. When the motor has rotated approximately 50 from its starting unlocked position, the cam surface 61 actuates the clean control switch 73 throwing the movable switch arm 112 into engagement with the second fixed contact 114 to energize the bake heating element via the line 118, switch 104a in the oven selector switch 20 and line 119, bypassing the adjustable thermostat for self-cleaning operation. At the completion of the motor lock cycle whereby the drive shaft 59 is rotated approximately from its starting unlocked position, the cam surface 61 throws the movable switch arm 137 of the motor control switch 74 into connection with the second fixed contact 139 thereof to de-energize the motor and to condition the motor unlock circuit 144 for unlocking motor energization. The lock thermostat 127 switches when the oven temperature exceeds 550F. to prevent motor 42 energization during self-cleaning and to energize the lock indicator lamp 18.  
  At the expiration of the duration set on the timer 19 ending the self-cleaning oven operation, the first timer switch 121 is opened to de-energize the bake heating element 108, and the movable switch arm 122 of the second timer switch 123 is thrown into connection with the first fixed contact 124 thereof to further condition the motor unlock circuit 144 for motor 42 reenergization when the oven temperature has dropped below that set on the lock thermostat 127 which closes the unlock circuit. Such re-energization of the motor 42 to complete its 360 operation from the original starting position, unlocks the oven door 12 and throws the movable switch arms 112, 137 in the clean control and motor control switches 73, 74 into connection with the respective first fixed contacts 113, 138 thereof, resetting the low temperature oven operation circuit 115 for normal pre-heating, baking and broiling and connecting the motor lock circuit 140 for further energization of the motor upon the initiation of the next cleaning operation.  
  It should now be understood that the instant invention provides both a novel locking mechanism for the door of a self-cleaning or other oven and also provides for completely automatic locking and unlocking control functions whereby the oven door is automatically unlocked at the expiration of the self-cleaning operation and the oven temperature is dropped to a predetermined safe level.  
  The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:  
  1. in a control circuit for a self-cleaning oven including a selector switch for multiple mode oven operation using broil and bake electrical heating elements selectively coupled for energization with at least one of said heating elements being energizable during self-cleaning operation, a timer for controlling the duration of selfcleaning operation, and an oven door lock and electrical drive therefor energizable to lock and to unlock the oven door, the improvement comprising:  
 lock and unlock circuits for energizing said electrical drive respectively to lock and to unlock the oven door, the selector switch providing a connection for potential energization of said lock and unlock circuits when in the self-cleaning position; electrical drive control means actuated by the electrical drive for alternately connecting the latter to one of said lock and unlock circuits; timer operated switch means for coupling said lock and unlock circuits to a source of electrical energy to energize the electrical drive to lock and to unlock the oven door; whereby for commencing self-cleaning oven operation said electrical drive control means connects the electrical drive to said lock circuit and energization of the timer controls said timer operated switch to provide electrical power to said lock circuit to operate the electrical drive to lock the oven door, and at the completion of the selfcleaning oven operation said electrical drive con trol means connects the electrical drive to said unlock circuit and after the expiration of the timer the timer operated switch provides power to said unlock circuit to operate said electrical drive to unlock the oven door.  
  2. A control circuit as set forth in claim I, further comprising thermostat switch means coupled in said lock and unlock circuits for preventing energization of said electrical drive when the oven temperature exceeds a predetermined level.  
  3. A control circuit as set forth in claim 1, wherein said electrical drive control means comprises a single pole double throw switch having a movable contact movable between first and second fixed contacts coupled, respectively, to said lock and unlock circuits, said movable contact being coupled to said electrical drive.  
  4. A control circuit as set forth in claim 1, wherein said timer operated switch means comprises a single pole double throw switch having first and second fixed contacts coupled, respectively, to said lock and unlock circuits and a further contact movable to connection with either of said first and second fixed contacts under control of the timer.  
  5. A control circuit as set forth in claim 1, further comprising door interlock switch means responsive to closure of the oven door for completing said lock and unlock circuits for energization of said electrical drive. i i i