US2839649A - Control circuits for electronic ranges - Google Patents

Description

June 17, 1958 E. L. MAcolcz CONTROL CIRCUITS FOR ELECTRONIC RANGES Filed May i7, 195e moa/MM @WHQL/ff? 40 mz/ENTQR. Edward L. Maca/cz.

United States Patent O CONTROL CIRCUlT-S FOR ELECT RONC RANGE?,

Edward L. Macolcz, Chicago, Ill., assigner to General Electric Company, a corporation of New York Application May 17, 1956, Serial No. 585,456

11 Claims. (Cl. 21910.55)

The present invention relates to control circuits for f.

electronic ranges, and more particularly to Such a control circuit incorporating special facilities for effecting thawing of frozen foods, as well as standard facilities for effecting cooking of normal unfrozen foods.

An object of the invention is to provide a control cir- 1 cuit of the character noted, also incorporating improved facilities for preheating or preparing auxiliary equipment operatively associated with the oscillator of the electronic range and operative to condition the oscillator for operation.

Another object of the invention is to provide a control circuit of the character noted incorporating improved signalling facilities so that the operator may be informed at all times of the particular character of the operation that is proceeding in the electronic range.

A further object of the invention is to provide a con trol circuit of the character noted that is of simplified connection and arrangement and that may be controlled in a simple and ready manner.

Further features of the invention pertain to the particular arrangement of the elements of the control circuit, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic illustration of a control circuit for an electronic range and embodying the present invention; and

Fig. 2 is a time-schedule operation chart of the control switches and the operating positions of the program controller incorporated in the control circuit of Fig. l.

Referring now to Fig. l of the drawing, the control circuit there illustrated and embodying the features of the present invention is employed to govern the opera tions of an electronic range 11 that may be of any suitable type. As illustrated, the range 11 comprises a metallic enclosure, including a housing section 12 provided with an open front and a front door section 13, and defining an oven cavity or chamber 14, the front door section 13 being mounted adjacent to the lower edge thereof upon the housing section 12 for movements between a substantially vertical closed position and a substantially horizontal open position. The housing section 12 comprises a metal inner liner 15 and a metal outer shell 16 arranged generally in spaced-apart relation with ermal insulation 17 therebetween; and similarly, the door section 13 comprises a metal inner liner 18 and a metal outer shell 19 arranged generally in spaced-apart relation with thermal insulation 20 therebetween. Elec* tromagnetic wave energy is supplied to the oven chamber 14 via a transmission line 21 that may be of the coaxial conductor type, including an exterior tubular grounded metal sheath 22 and an interior rod-like ungrounded metal conductor 23, the extreme cuter end of the sheath 2,839,649 Patented June 17, 1958 ICC 22 being electrically connected to the shell 16 and to the liner 15 of the housing section 12 and the eXtreme outer end of the conductor 23 projecting through aligned openings provided in the shell 16 and in the liner 15 of the housing Section 12 and into the oven chamber 14 and serving as an antenna for radiating electromagnetic wave energy into the oven chamber 14.

The control circuit 10 comprises an ultra-high frequency generator or oscillator 24 including a magnetron 25 provided with a flamentary cathode 26, a plate 27 and a metal envelope 28, the plate 27 being electrically connected to the inner end of the inner conductor 23 of the transmission line 21 and the envelope 28 being electrically connected to the inner end of the sheath 22 of the transmission line 21. The magnetron tube 25 is capable of oscillating at an ultra-high frequency of 2450 megacycles, whereby microwave energy is radiated by the antenna 23 into the oven cavity 14. Also the generator 24 is provided with a magnet coil 29 arranged in an exciting circuit for the purpose of controlling the radio frequency power supplied by the magnetron 25 to the oven cavity 14, as well as a rectifier bridge 30. Further, the generator 24 comprises a pair of primary power supply conductors 31-32 and a pair of secondary power supply conductors 33-34. The primary power supply conductors 31-32 are connected to the primary winding of a coupling transformer 35, the secondary winding of which is connected to the input terminals of the rectifier bridge and the secondary power supply condoctors 33-34 are connected to the primary winding of a coupling transformer 36, the secondary winding of which is connected directly to certain auxiliary equipment, not shown, supplying the various filamentary cathodes 26, etc. The output terminals of the rectifier bridge 30 are connected between ground potential and the lamentary cathode 26 of the magnetron 25 via a power supply circuit, also including a resistor 37, so that about minus SOOO-volts is applied to the lamentary cathode 26; and a regulator 38, of any suitable type, is connected between the primary power supply conductors 31-32 for the purpose of maintaining a substantially constant voltage across the primary winding of the coupling transformer 35.

Also, the circuit 10 comprises a program controller including a rotatably mounted operating shaft 41 carrying five insulating control cams C1 to C5, inclusive, that are operatively associated with five sets of switch springs S1 to S5, inclusive. The outer end of the operating shaft 41 carries a manually operable dial 42 that is provided with certain indicia cooperating with an index marker 43; and further a timer motor 44 of the synchronous type is provided that has an operating shaft 45. The operating shaft 45 is connected to escapement mechanism 46 that is provided with an operating shaft 47. The inner end of the operating shaft 41 and the outer end of the operating shaft 47 are interconnected by a slip clutch 48. In the arrangement, the program controller 40 comprises an off position, a thaw position, a preheat or O position, and a variable on position calibrated over a time scale extending up to thirty minutes; and corresponding indicia is carried by the dial 42 and cooperating with the index marker 43. In the arrangement: when the manual dial 42 is operated out of its off position into its thaw position or into its preheat position, operation of the timer motor 44 is not initiated; and when the manual dial 42 is operated out of its olf position or its preheat position into its variable on position, operation of the timer motor 44 is initiated, so that the operating shaft 41 and the manual dial 42 are returned back into their preheat or 0 position constituting a home position therefor, in order that further operation of the timer motor 44 is arrested.v More particularly, the operating timer motor 44 actuates the escapement mechanism' 46 so that the operating shaft 47 is rotated one step each minute; which step-by-step rotationis imparted to the operating shaft 41 through the friction clutch 48; and moreover, the friction clutch 48.accommodatesrotation of the operating shaftll under the control ofthe manual dial 42 independently of the operating shaft 47.

Further, the circuit lfcomprises a source of power supply of the three-wire Edison type f 236-volts, singlephase, A. C., including two outsideconductors 49 and `and a grounded neutral conductor 51. The outside conductors 49-and Stl'are connected by respective fuses 52 and 53 to two conductors 54 and 55. Also, the circuit 10 comprises a preheat timer 56, a thaw cycle switch 57, andl a thaw signalswitch 58. The preheat timer 56 is offthe thermal controltype including a. bimetallic element S9 provided with an associated electric heater. and a contact-spring61` cooperating with the bimetallic element S9; the thaw cycle switch 57 is also of the thermal controltype including abimetallic element62V providedwith an associated electric heater 63 and a contact spring 64 cooperating with the bimetallic element 62, the bimetallic element 62 also carrying a contact bridging member controlling an associated pair of contacts; and the thaw signal switch 5S is also of the thermal control typeincluding. a bimetallic element 66 provided with an associated electricrheater 67 and a Contact spring 68 cooperating with the bimetallic element 6^', the bimetallic element 66 also carrying a contact bridging member 69 controlling an associated pair of contacts.

Further, .the circuit 1t) comprises a relay 70 provided with two contact bridging members 71 and 72 controlling-two pairs of associated contacts, a visual signal or oven lamp 73, andan audible signal or bell 74.

ln ythe arrangement: the set of switch springs S1 com prises two individual switch springs respectively terminating the conductor54 .and a conductor 7S; the set of switch springs S2 comprises two individual switch springs respectivelyterminating the conductor S5 and a conductor76; the setof switch springs S3 comprises two individual switchsprings. respectively terminating two conductors 77 and 78; the set of`switchsprings S4 comprises two individual switch springs respectively terminating the conductor 77`and a conductor 79; and the set of switchsprings S5 comprisesthree individual switch springs,-the middleswitch spring terminating the conductor 77, the-right-hand switch spring terminating a conductor Strand the-left-hand switch spring terminating a conductor 81,

Finally, a doorswitch` 82 .isy incorporated in the electronicrange 11-andx provided with a contact bridging member 83 controlling an associated pair of contacts. In the arrangement, the door switch 82 is preferably of the micro-switch type; whereby the contact bridging member 83 is respectively operated into its closed and open positions, when the door section 13 is respectively operated into its closed and vopen positions with respect to the housing section12.

The conductors 7S and 76 are respectively connected directly to the secondary power supply conductors 33 and 34 and to theleft-hand .contacts governed by the respectivecontact bridging members 71' and 72; while the right-hand contactsA governed by the respective contact bridgingmembers 71 and72vv are respectively connectedY to the primary power supply-conductors 31 and 32. The electric heater 6tl-is connected between the conductor -76 .and the neutralconductoriSl; the bimetallic element 59. isconnected to the: conductor76; and the contact` spring 61:is connected to a .conductor 84. The electric heater 63 isconnected between the conductor 76 and the bimetallic element 62;.the contact spring.64 Y

is connected to the neutral conductor 51; the left-hand contact of the pairassociated with the Contact bridging member 65 is connected to the conductor 78; and

the righthand contact of this pair is connected' toa conductor 85. The heater 67 is connected between the conductor 79 and the bimetallic element 66; the contact spring 63 is connected to the neutral conductor 51; the right-hand contact of the pair associated with the contact bridging member 69 is connected to the neutral conductor 5l; and the left-hand contact of this pair is connected to a conductor 86. rl`he winding of the relay. 7@ is connected between the conductor 85 and the neutral conductor Si; the oven lamp 73 is connected between the conductors 34 and 86; the bell 745 is connected between the conductor 8l and the neutral conductor 51; the timer motor 44 is connected between the conductor 817 and the neutral conductor 51; and the pair of contacts associated with the contact bridging member 83 respectively terminate the conductors 77 and 84.

ln the preheat timer 56 the bimetallic element 59 normally disengages the contact spring 61; and when the electric heater 60 is energized throughout a time interval of seconds, the bimetallic element 59 is dellected` into engagement with the contact spring 61. Upon subsequent cooling of the electric heater 60, the 'bimetallic element 59 is deflected back into its normal position disengaging the contact spring 61. In the thaw cycle switch 57, the bimetallic element 62 'normally engages the contact springd'moving the contact bridging member 65 into its closed position. When a potential is impressed between the conductor 79 and the neutral conductor 51, the electric heater 63 is energized deflecting the bimetallic element 62 into its open position with respect to the contact Vspring 64 and moving. the contact bridging member 65 intoits open position; whereby the disengagement between the bimetallic element 62`and the contact spring 64 interrupts the circuit for energizing the electric heater 63, so that the bimetallic element`62'cools and deliects back into its normal position engaging the contact spring 64 and moving the contact bridging member 65 back into its closed position. The thaw cycle switch 57 occupiesl its close-d positionV for twenty-seconds and lits open position'for forty-seconds, moving therebetween cyclically, as long as the potential is impressed between the conductor 79 and the neutral conductor 51. In the thaw signal switch 5S, the bimetallic element 66 normally engages the contact spring 68 moving the contact'bridging member 69 into its closed position. When a potential is impressed between. the conductor 79 and the neutral conductor 51, the electric heater 67 is energized deflecting the bimetallic element 66 into its open position with respect to the contact spring 68 and moving the contact bridging member 69 into'its open position; whereby the disengagement between the bimetallic element 66 and the contact spring 68 vinterrupts the circuit for energizing the electric heater 67, so that the bimetallic element 66 cools and detlccts back into its normal position engaging the contact spring 68'and moving the contact bridging member 69 'back into its closed position. The thaw sig nal section' 58 occupies its closed position for twoseconds and its open position for two seconds, moving therebetween cyclically, as long as the potential is impressed between the conductor 79 and the neutral conductor 51.

As illustrated in the chart of Fig. 2, when the program controller 40 occupies its off position, the control camsA C1 to C4, inclusive, operate the sets of switch springs S1 to S4, inclusive, into their open positions andthe control cam C5 operates the set of switch springs S5 to open both the l and-2 contacts thereof. When the program controller 40 occupies its preheat or 0 position, the control cams C1 and C2 operate the sets of switch springs S1 and S2 into their closed positions and the control cam C5 operates therset of switch springs S5 to close the 2 contacts thereof. When the program controller 40 occupies its variable on position, thecontrol cams C1,

C2 yand C3 operate the sets of switch springs S1, S2 and S3 into their closed positions, and the control cam-C5011# erates the set of switch springs S5 to close the "1 contacts thereof. When the program controller 40 occupies its thaw position, the control cams C1 to C4, inclusive, operate the sets of switch springs S1 to S4, inclusive, into their closed positions.

Considering now the operation of the control circuit 10, in conjunction with the electronic range 11, in order to bring about a preheating of the auxiliary equipment operatively associated with the oscillator 24, so as to condition the same for operation, the program controller 40 is operated from its off position into its preheat or t) position, so that the sets of switch springs S1 and S2 are closed and the contacts 2 of the set of switch springs S5 are closed. Closure of the sets of switch springs S1 and S2 connects the conductors 54 and 55 to the conductors 75 and 76 that are directly connected to the secondary power supply conductors 33 and 34; whereby the primary winding of the coupling transformer 36 is ener gized bringing about initiation of operation of the auxiliary equipment mentioned. For example, the iilav mentary cathode 26 of the magnetron 25 is heated so as to render the same electron-emissive, thereby to condition the magnetron for operation. Also, a circuit is completed for energizing the electric heater 60 of the preheat timer 56, whereby the bimetallic element 59 is deflected to engage the contact spring 61, after a time interval of seventy-tive seconds, as previously noted; whereby the conductor 76 is connected to the conductor 84. Assuming that in the electronic range 11, the door section 13 occupies its closed position with respect to the housing section 12, the door switch 82 occupies its closed position connecting the conductor 84 to the conductor 77, the conductor 77 being connected to the conductor 81 at the closed "2 contacts of the set of switch springs S5; whereby the bell 74 is operated to produce an audible signal indicating that the auxiliary equipment operatively associated with the oscillator 24 is preheated. Also, the connection of the conductor 76 to the conductor 84 completes a parallel circuit for continuously illuminating the oven lamp 73, the last-mentioned circuit including the conductor 86 and the closed contact bridging member 69. The continuous illumination of the oven lamp 73 serves to render a visual signal to the operator that the auxiliary equipment has been preheated.

At this time, the operator may place the food into the oven chamber 14 after rst moving the front door section 13 into its open position with respect to the housing section 12; whereby the door switch 82 is operated into its open position disconnecting at the contact bridging member 83, the conductor 84 from the conductor 77. When the conductor 77 is thus opened, the circuit for operating the bell 74 is interrupted indicating to the operator that the front door section 13 occupies its open position. After the operator places the food mentioned into the oven chamber 14, the front door section 13 is returned into its closed position thereby again operating the door switch 32 into its closed position; whereby the contact bridging member 83 in its closed position reconnects the conductor 84 to the conductor 77, so that the bell 74 is again operated.

At this time, it may be assumed that a thawing operation is to be carried ort and that food in a frozen condition is placed in the oven cavity 14; whereby the program controller 40 is operated from its preheat or l) position into its thaw position, so that the sets of switch springs S1 to S4, inclusive, are closed. Closure of the sets of switch springs S1 and S2 effects energization ot' the auxiliary equipment operatively associated with the oscillator 2li, as previously explained. Closure of the set .of switch springs S3 completes a circuit for operating the relay 70, this circuit including the conductor SS, the contact bridging member 65, the conductor 73, the closed set of switch springs S3 and the conductor 77; whereby the relay 70 is operated, so as to operate the contact bridging members 71 conductors 31 and 32.

Closure of the contact bridging members 71 and 72 conects the conductors 7S and 76 to the primary power supply c-onductors 31 and 32; whereby the primary winding of the coupling transformer 35 is energized effecting energization of the rectier bridge 3f) and the consequent operation of the'magnetron 25; whereby the microwaves are radiated by the antenna B3 into the oven cavity 14.

Closure of the set of switch springs S4 connects the conductor 77 to the conductor 79, thereby energizing in parallel relationship the electric heaters 63 and 67 of the respective thaw ycle switch 57 and the thaw signal switch 58. Accordingly, cyclic operation of the thaw cycle switch 57 and cyclic operation of the thaw signal switch 58 are brought about. Each time the thaw cycle switch 57 operates into its open position, it interrupts, at the 't l 'itlging member 65, the circuit for operating the rel so as to cause the latter relay to restore and disconnect, at the contact bridging members 71 and 72, the conductors 75 and 76 from the primary power supply Each time the thaw cycle switch 57 operates into its closed position, it recornpletes, at the contact bridging member 6.5, the circuit for Operating the relay 70, so as to cause the contact bridging members 71 and 72 to reconnect the conductors 75 and 76 to the primary power supply conductors 31 and 32. Accord- Y ingly, the cyclic operation of the thaw cycle switch 57 effects cyclic operation of the relay 70 and consequent cyclic operation of the magnetron 25; whereby in each cycle of operation of the thaw cycle switch 57, the magnetron 25 is operated for twenty seconds and restored for forty seconds, so that the microwave power is supplied to the oven cavity for twenty seconds and is cut off for forty seconds.

`Each time the thaw signal switch 5S operates into its open position, it interrupts, at the contact bridging member 6?, the circuit for illuminating the oven lamp 73; and each `time the thaw signal switch 58 operates into its closed position, it recompletes, at the contact bridging member 69, the circuit for illuminating the oven lamp 73. Accordingh, the oven lamp 73 is flashed alternately on and otr two seconds each, so as to give the operator a visual signal that the circuit 10 is operating in a thaw cycle at this time.

ln passing, it is mentioned that the cyclic operation of the magnetron 25 in the thaw position of the program controller 46 is adequate to effect enough heating of a dielectric material (a frozen food) in the oven cavity 14 to thawing thereof, but is inadequate to effect any substantial cooking of the food in the oven cavity 14.

After an appropriate time interval adequate to eftect thawing ot the frozen food in the oven cavity 14, the program controller is operated into its variable on position, setting a corresponding variable time interval;l whereby the sets of switch springs S1 t-o S3, inclusive, are closed and the contacts l of the sets of switch springs S5 is closed, as previously noted. Closure of the sets of switch springs S1 and S2 connects the conductors 54 and to the conductors 75 and 76, as previously noted; while closure of the set of switch springs S3 connects the conductor 77 to the conductor 7S, so as to bring about operation of the relay and the consequent operation of the magnetron 25, in the manner previously explained. In this case, the set of switch springs S4 occupies its open position, so that the thaw cycle switch 57 and the thaw signal switch 58 are not operated. Accordingly, the circuit for operating the relay 7) is continuously completed, so that the operation of the magnetron 25 is continuous; and likewise, the thaw signal switch 58 is not operated, so that the illumination of the oven lamp 73 is continuous.

losure of the contacts l of the set of switch springs S5 connects the conductor 77 to the conductor 80; whereby the timer motor 44 is operated. The continuous illumination of the oven lamp 73, without the concurrent operaand .72 int-o their closed positions. 75 tion of the bel 74, indicates to the operator that the elec- J tronic oven 11 is undergoing a continuous timedcycle ofoperatio11 ina' normal cooking operation.

The" operatingv timer motor 44 governs the escapement mechanism 46, so that the operating shaft il is operated step-by-step and ultimately returned from its variable on position into its preheat or G position, after a corresponding time interval.; whereby the set of switch springs S3 iso'pened, and the set of switch springs S5 is operated to openfthe contacts l thereof and to close the contacts 2 thereof. Opening of the set of switch springs S3 disconnects =the conductor 77 from the conductor 73, thereby to interrupt the circuit for operating the relay 7 i?, so that the'contact bridging members 71 and 72 disconnect the conductors 75 and 76 from the primary power supply conductors 31 and 32 to bring about the restoration of the magnetron 25, and consequently the termination of the normal cooking operation in the oven cavity 3.4. Opening ofthecontacts l ot' the set of switch springs S5 interrupts theA circuit for operating the timer motor 44, while `the manual dial t2 occupies its preheat or position; while closure of the contacts 2 of the set of switch springs S5 recompletes the previously traced circuit for operating the bell '74. The continuous illumination of the oven lamp 73 with the concurrent operation oi the bell 74 indicates to the operator that the continuous heating operation of the electronic range 1i has been completed and that the -circuit itl has been automatically restored into its preheat or 0 position retaining operated the auxiliary equipment operatively associated with the magnetron 25.

Of course, during the variable time interval of operation of the magnetron 25 corresponding to the variable on position of the program controller 40, the food in the oven cavity ldcontinuously absorbs the microwave energy radiated from the antenna 23, so as to effect continuous cooking thereof in a well-known manner.

Recapitulating: in the thaw position of the program controller 4t), the relay itl is intermittently operated; and in the variable on position of the program controller 40, the relay 70 is continuously operated; while in the olf position and in the preheat or 0 position of the program controller di), the relay 7i) is restored. Accordingly, the magnetron 25 is operated only in the thaw position and in the variable on position of the program controller 40; however, the operating circuit therefor includes the door switch 82, whereby at any time, opening of the front door section 13 with respect to the housing section 11 operates the door switch 32 into its open position interruptingthe circuit for operating the relay 76 in order to bringiaboutY termination of operation of the magnetron 25. Accordingly, when the program controller 40 occupies either its thaw position or its variable on position, the heating effect in the oven cavity it may be terminated by opening the front door section 13 with respect to the housing section l2; which arrangement constitutes a safety interlock preventing operation of the magnetron 25, when the front door section 13 occupies its open position. This precaution is necessary as it is highly undesirable for the microwave energy to be radiated from the oven cavity 14 to the exterior, since the same might produce effects injurious to the operator.

In view of the foregoing, vit is apparent that there has been provided an improved control and signalling circuit arrangement for an electronic range incorporating facilities forv carrying out preheating, thawing and regular cooking operations, together with facilities for signalling and indicating the particular operations that are being carried out, all in a simple and positive manner.

While there has been described what is at present considered lto be the preferred embodiment of the invention, it will'be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modications as fall within the true spirit and scope of the invention.

What isclaimed is: K l: In heatingl apparatus including a metallic enclosure adapted to`serve as an oven, and anoscillatoroperative to'supply electromagnetic wave energy to-'the` interior of said enclosure in order to heat a dielectric body posi-A tionedtherein; the lcontrol circuit'combination comprising a source of electric power, auxiliary equipment operatively associatedwith said oscillator and operative to condition saidoscillator` for operation, a relay operative to connect` said power source to saidoscillatorin'order to ei'iect operation of tsaid conditioned oscillator, a'signal device operative toindicate a given condition of said oven, a: program controller having an off position and a signal-position. and a variable on position, said programl coni relier in :its variable on and signal positions eifecting` operation oi" said auxiliary equipment and in its-oi position effecting-.restoration lof said auxiliary equipment, said program' controller in its variable' on position eiiectingoperationof saidfrelay and in its' oifand'sign'al positions effecting restoration of said relay, said program controller' in itssignal position effecting operation of said signal and in its ofi and variable on positions effecting restoration of said signal, a manually operable'device'forl selectively operating said program controller into any of its positions, and timing means responsive to operation of said program controller into its variable on position for returning the same bacl; into its signal4 position-in a corresponding variable time interval.

2. in heating apparatus including a metallic enclosure adapted to serve as an oven, and an oscillator operative? to supply electromagnetic wave energy to the interior of said enclosure inorder to heat a dielectric body positioned therein; the control circuit combination comprising a source of electric power, auxiliary equipment operatively associated with said oscillator and operative to condition said oscillator for operation, a relay operative to connect said power source to said oscillator in order to effect operation of said conditioned oscillator, aV preliminary timer operative after a given time interval into a control condition, means responsive to operation of' said preliminary timer into its control condition ioripreparing said relay for operation, a signal device operative` to indicate a given condition of said oven, a program controller having an off position and a signal position and a variable on position, said program controller in'its variable on and signal positions effecting operation of both said auxiliary equipment and said preliminary timer and in its off position effecting restoration of both said auxiliary equipment and said preliminary timer, said program controller in its variable on position efecting-operation of said prepared relay and in its off and signal positions eecting restoration of said relay, said programv controller in its signal position effecting operation of said signal and in its oif and variable on positions effecting restoration of said signal, a manually operable device for selectively operating said program controller into any one of its positions, and timing means responsive to operation of said program controller into its variable'on position for returning the same back into its signal position in a corresponding variable time interval.

3. ln heating apparatus including a metallic enclosure adapted to serve as an oven and provided with a housing section and a cooperating door section, and an oscillator' operative to supply electro-magnetic wave energy to the interior of said enclosure in order to heat a dielectric body positioned therein; the control circuit combination comprising a source of electric power, a relay operativeY to' connect said power source to said oscillator in order to effect operation thereof, a circuit for operating said* relay, a door switch included' in said relay circuit and operated into respective 'open and closed positions yin re-V sponse to movements of said door section into respective openand closed positions with respect to said housing section; a signal device operative to indicate a` given" condition of said oven, a control switch included in said relay circuit, a program controller having an olf position and a signal position and a variable on position, said program controller in its vai fiable on position operating said control switch into its closed position and in its off and signal positions operating said control switch into its open position, said program controller in its `signal position eecting operation of said signal and in its off and variable on positions effecting restoration of said signal, said relay circuit being closed to effect operation of said relay in response to concurrent operations of said door switch and said control switch into their closed positions, a manually operable device for selectively operating said program controller into any one of its positions, and timing means responsive to operation of said program controller into its variable on position for returning the same back into its signal position in a corresponding variable time interval.

4. The heating apparatus control circuit combination set forth in claim l, wherein said signal is of the audible type.

5. in heating apparatus including a metallic enclosure adapted to serve as an oven, and an oscillator operative to supply electromagnetic wave energy to the interior of said enclosure in order to heat a dielectric body positioned therein; the control circuit combination comprising a source of electric power, auxiliary equipment operatively associated with said oscillator and operative to condition said oscillator for operation, a relay operative to connect said power source to said oscillator in order to effect operation of said conditioned oscillator, a cycle device operative in each cycle thereof to effect operation and then restoration of said relay, a program controller having a home position and a variable on position and a thaw position, said program controller in its variable and on thaw positions eecting operation of said auxiliary equipment and in its off position effecting restoration of said auxiliary equipment, said program controller in its variable on position effecting operation of said relay and in its home position effecting restoration of said relay, said program controller in its thaw position eiecting cyclic operation of said cycle device and in its home and variable on positions effecting restoration of said cycle device, a manually operable device for selectively operating said program controller into any one of its positions, and timing means responsive to operation of said program controller into its variable on position for returningr the same back into its home position in a corresponding variable time interval.

6. ln heating apparatus including a metallic enclosure adapted to serve as an oven, and an oscillator operative to supply electromagnetic wave energy to the interior of said enclosure in order to heat a dielectric body positioned therein; the control circuit combination comprising a source of electric power, auxiliary equipment operatively associated with said oscillator and operative to condition said oscillator for operation, a relay operative to connect said power source to said oscillator in order to effect operation of said conditioned oscillator, a preliminary timer operative after a given time interval into a control condition, means responsive to operation of said preliminary timer into its control condition `for preparing said relay for operation, a program controller having an oits position and a preheat position and a variable on position and a thaw position, said program controller in its variable on and preheat and thaw positions effecting operation of both said auxiliary equipment and said preliminary timer and in its off position effecting restoration of both said auxiliary equipment and said preliminary timer, said program controller in its variable on position effecting operation of said prepared relay and in its off and preheat positions effecting restoration of said relay, a cycle device operative in each cycle thereof to effect operation and then restoration of said prepared relay, said program controller in its thaw position effecting cyclic operation of said cycle '10` device and in its olf and preheat and variable on positions effecting restoration of said cycle device, a manually operable device for selectively operating said program controller into any one of its positions, and timing means responsive to operation of said program controller into its variable on position for returning the same back into its preheat position in a corresponding variable time interval.

7. In heating apparatus including a metallic enclosure adapted to serve as an oven and provided with a housing section and a cooperating door section, and an oscillator operative to supply electro-magnetic wave energy to the interior of said enclosure in order to heat a dielectric body positioned therein; the control circuit combination comprising a source of electric power, a relay operative to connect said power source to said oscillator in order to effect operation thereof, a circuit for operating said relay, a door switch included in said relay circuit and operated into respective open and closed positions in response to movements of said door section into respective open and closed positions with respect to said housing section, a first control switch included in said relay circuit and having a normally closed position, a cycle device operative in each cycle thereof to open and then to reclose said first control switch, a second control switch included in said relay circuit, a program controller having a home position and a variable on position and a thaw position, said program controller in its variable on and thaw positions operating said second control switch into its closed position and in its home position operating said second control switch into its open position, said program controller in its thaw position effecting cyclic operation of said cycle device and in its home and variable on positions effecting restoration of said cycle device, said relay circuit being closed to effect operation of said relay in response to concurrent operations of said door switch and said first control switch and said second controi switch into their closed positions, a manually operable device for selectively operating said program controller into any one of its positions, and timing means responsive to operation of said program controller into its variable on position for returning the same back into its home position in a corresponding variable time interval.

8. In heating apparatus including a metallic enclosure adapted to serve as an oven, and an oscillator operative to supply electromagnetic wave energy to the interior of said enclosure in order to heat a dielectric body positioned therein; the control circuit combination comprising a source of electric power, a relay operative to connect said power source to said oscillator in order to effect operation thereof, a signal device operative to indicate a given condition of said oven, a program controller having a variable on position and a signal position and a thaw position, said program controller in its variable on position effecting operation of said relay and in its signal position effecting restoration of said relay, said program controller in its signal position effecting operation of said signal and in its variable on and thaw positions efecting restoration of said signal, a cycle device operative in each cycle thereof to effect operation and then restoration of said relay, said program controller in its thaw position effecting cyclic operation of said cycle device and in its signal and variable on positions eri'ectiug restoration of said cycle device, a manually operable device for selectively operating said program controller into any one of its positions, and timing means responsive operation of said program controller into its variable on position for returning the same back into its signal position in a corresponding variable time interval.

9. In heating apparatus including a metallic enclosure adapted to serve as an oven, and an oscillator operative to supply electromagnetic wave energy to the interior of said enclosure in order to heat a dielectric body positioned therein; the control circuit combination comprising a source of electric power, auxiliary equipment operatively associated with said oscillator' and operative to condition "l said oscillator for operation, a circuit for operating said auxiliary equipment and including a first switch, a relay operative to connect said power source to said osciliator in order to eilect operation of said conditioned oscillator, a circuit for operating said relay and also including said first switch and a normally open second switch a third switch and a normally closed fourth switch, a signal, a circuit for operating said signal and also including said rst and second switches and a normai'ly closed 'fth switch, preheat timer operative after a o time intervai into Cre-l condition, ,i cans responsive to operation of said preheat timer into its control condition for operating said second switch into its closed position, a

o' Aating said preheat timer and aiso iniirst switch, a tiret cycle device opM buck into tion, a second cycle device operative in cach cycle thereof operate said fifth switch from itscicsed positn into its onen Z ition and into its closed position, a circuit for cyclic-ally operating said first and ,s and including a sixth switch, a program contro ng an oit position and a preheat position and a vr more on position and a thaw position, said program con. .er in its ofi position operating said lirst and third and sixth switches into their open positions, said program c xtroilcr in its preheat position operating said rst switch into its closed position and operating said thir and sixth switches into their open posit-ions, said program controller in its variable on position operating said irst and 'third switches into their closed positions and said sixth switch into its open position, said controller in its thaw position operating said third and sinh switches into their closed posia nanuaily operable device for selectively operating said program controller into any one of its positions, and timing means responsive to operation of said program controller into its variable on positionor reng the same back into its preheat position in a corsnding variable time interval.

lG. In heating apparatus including a metallic enclosure adapted to serve as an oven, and an oscillator operative to supply electromagnetic wave energy to the interior of said enclosure in order to heat a dielectricbody positioned therein; the control circuit combination comprisiA g a source of electric power, auxiliary equipment operatively associated with said oscillator and operative to condition said oscillator for operation, a visual signal, an audible signal, timer, a cycle device, a program controller having an oli position and a preheat position and a variable on position and a thaw position, said program contro-ller in its preheat and variable on and thaw positions connecting said power source to said auxiliary equipment and initiating operation of said timer and in its o position disconnecting said power source from said auxiliary equipment and arresting operation of said timer, said timer being operated into a control condition in re- Cil spouse to a predetermined timing operation thereof, means responsive to operation of said timer into its control condition for operating said visual signal, means governed by said program controller in its variable on and thaw positions and responsive to operation of said timer into its control condition for connecting said power source to said oscillator, said program controller in its thaw position initiating cyclic operation of said cycle device and in its ot and preheat and variable on positions arresting cyclic operation of said cycle device, means governed by said program controller in its thaw position and responsive to cyclic operation of said cycle device for cyclically disconnecting and reconnecting said power source with respect to said oscillator, said program controller' in its preheat position operating said audible signal, a manually operable device for selectively operating said program controller into any one of its positions, and timing means responsive to operation of said program controller into its variable on position for returning the same back into its preheat position in a corresponding variable time interval.

1l. In heating apparatus including a metallic enclosure adapted to serve as an oven, and an oscillator operative to supply electromagnetic wave energy to the interior of said enclosure in order to heat a dielectric body positioned therein; the control circuit combination comprising a source of electric power, a visual signal, an audible signal, a program controller having an off position and a signal position and a variable on position and a thaw position, said program controller in its variable on position effecting continuous connection of said power source to said oscillator and in its thaw position efecting intermittent connection and disconnection of said power source with respect to said oscillator and in its olf and signal positions effecting continuous disconnection of said power source from said oscillator, said oscillator being operated in response to the connection of said power source thereto, said program controller in its variable on and signal positions continuously operating said visual signal and in its thaw position intermittently operating said visual signal and in its ot position continuously restoring said visual signal, said program controller in its signal position operating said audible signal and in its off and thaw and variable on positions restoring said audible signal, a manually operable device for selectively operating said program controller into any one of its positions, and timing means responsive to operation of said program controller into its variable on position for returning the same back into its signal position in a corresponding variable time interval.

References Cited in the tile of this patent UNITED STATES PATENTS

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