US2434467A - Electric heating system for ovens - Google Patents

Electric heating system for ovens Download PDF

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US2434467A
US2434467A US319519A US31951940A US2434467A US 2434467 A US2434467 A US 2434467A US 319519 A US319519 A US 319519A US 31951940 A US31951940 A US 31951940A US 2434467 A US2434467 A US 2434467A
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Francis H Mccormick
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Motors Liquidation Co
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Motors Liquidation Co
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24COTHER DOMESTIC STOVES OR RANGES; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
    • F24C7/00Stoves or ranges heated by electrical energy
    • F24C7/08Arrangement or mounting of control or safety devices

Description

Jan. 13, 1948. F. H. MCCORMICK ELECTRIC HEATING SYSTEM Foa ovENs 17, 1940 4 Sheets-Sheet l Filed Feb.

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Jan. 13, 1948.

F. H. MCCORMICK ELECTRIC HEATING SYSTEM FOR OVENS Filed Feb. 17, 1940 4 Sheets-Sheet 2 Jan. 13, 1948. F. H. MccoRM|cK 2,434,467

ELECTRIC HEATING SYSTEM FOR OVENS Filed Feb. 17, 1940 4 Sheets-Sheet 3 mi; [g5 u N t I A I n 1 Q g s u N E N ,J N N Ii Q s' N C n i: w l z n A N l N f Illir asc C) dan Q fg; u

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7,1m/ OR 5 'f/3am ATTORNEYS Jan. 13, 1948. F H, MCCORMlCK 2,434,467

ELECTRIC HEATING SYSTEM FOR OVENS Filed Feb. 17, 1940 4 Sheets-Sheet 4 Patented Jan. 13, 1948 2,434,467 ELECTRIC HEATING SYSTEM FOR OVEN S Francis H. McCormick, Dayton, Motors Corporation, corporation of Delaware General Ohio, assgnor to Dayton, Ohio, a

Application February 17,1940, Serial No. 319,519

14 Claims.

This invention relates to a domestic appliance and more particularly to plural unit electric oven heating systems providing an automatic change from preheat to bake circuit arrangement.

It is an object of my invention to provide for a plural unit oven, improved oven heating circuits including an automatic control providing an automatic change from high heat in both the upper and lower portions of the oven to a low heat in the upper portion and ahigh heat in the lower portion of the oven, and to so design the circuit and to so place the thermostat control in the circuit that the disconnecting of only one conductor by the thermostate control will safely deenergize the entire heating circuit.

It is another object oi' my invention to provide a simplified control for a plural unit electric oven providing an automatic change from preheat to bake circuit arrangement.

It is still another objectof my invention to provide a plural unit oven circuit arrangement, in which an upper unit is fed from a tap on the lower unit for baking, when a Control providing an automatic change from preheat to bake circuit arrangement.

It is still another object of my invention to provide an electric oven heating system in which a simple electro-thermal control holds the preheat circuit closed and provides an automatic change to bake circuit arrangement under the control of the thermostat.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

in the drawings:

Fig. 1 is a view partly in section and partly diagrammatic of a two-unit electric oven heating system including an automatic control embodying one form of my invention; y

Fig. 2 is a top view of the control knob and dial as shown in Fig. 1,

Fig. 3 is a top view of the upper cam shown in Fig. l;

Fig. 4 is a top view of the lower cam shown in Fig. l;

Fig. 5 is a simple wiring diagram of the electrical circuits shown in Fig. 1;

Fig. 6 is a view partly in section and partly diagrammatic of a modied two-unit electric Oven heating system including a modified automatic mechanically interlocked control embodying another form of my invention;

(CI. B19-20) y Fig. 7 is a top view of the control knob and dial shown in Fig. 6;

Fig. 8 is a top view of the upper cam shown in Fig. 6;

5 Fig. 9 is a top Fig. 6;

Fig. 10 is a simple wiring diagram of the electric circuit shown in Fig. 6;

Fig. 11 is a modified simple wiring diagram 1o showing a modiilcation oi the electric circuits and supply conductors shown in Fig. 6;

Fig. 12 is a view partly in section and partly diagrammatic of another modified two-unit oven heating system including another modiiled au- 15 tomatic control embodied in my invention; and

Fig. 13 is a fragmentary view of the preheatu bake control similar to that shown in Fig. 12, but in the latched position assumed at the instant the control knob is turned to breil position.

Referring now to the drawings and more particularly to Fig. 1, there is shown an electric oven heating system for a two-unit oven designated by the reference character 20 provided with an upper heating unit 2i primarily for broiling, and a lower heating unit 25 primarily for baking. Both the upper and lower units 22 and 24 are connected by a single common con ductor 26 to a thermostat provided with a movable contact 28 and a stationary contact 30. The stationary contact 30 is connected by a conductor 32 to one conductor of a power source. The contacts 28 and 3D are opened and closed in accordance with the temperature oi a thermostat bulb 34 which is located within the oven 20. These contacts are also employed to deenergize the entire system when the oven is not used.

The thermostat includes a housing d3 provided with an opening which receives a bushing 49 which is rigidly secured to the edges of the opening. This bushing 49 is interiorly threaded in order to receive in threaded engagement, the threaded adjusting screw 41. The inner end of the screw 47 engages a stud 4|! which is attached to the expansible and contractible diaphragm di. The interior of the diaphragm il is in communicationA with a capillary tube l2 which in turn is in communication with the inferior ci the bulb 34. A contractible and expansible liquid is provided inthe bulb and the capillary tube 42 so that upon expansion of the liquid as a result of the heat to which the bulb is subjected, the liquid will be forced through the tube into the expansible and contractible diaphragm 55 means 4l.

view of the lower cam shown in A tip 39 is provided on the :face of N the diaphragm opposite the stud 48 to facilitate tact |89 as long as the heater remains ener the transmission of the expansive forces of the giZed. The heater is preferably placed suffidiaphragm to the operating levers. ciently close to the bimetal 96 and has sufllcient The tip 38 abuts a projection 44 upon the Opcapacity that it will rapidly heat the bimetal 96 erating lever 45. The operating lever 48 has a 5 and will almost instantaneously hold the contact knife edge which is seated in a notch of a bearing 98 against the stationary contact |89. If desired,

bracket 48 secured to the wall of the housing 43. an electromagnet may be substituted for the A light coil spring 45 is provided for keeping the heater Ill and the bimetal strip be replaced by projection 44 in engagement with the tip 38. an armature biased to close the contacts 98 and The other end of the operating lever 4B is provided 18 |8 I. with an aperture receiving the hooked end of a The other end of the heater is connected toggle tension spring 53. The other end of the directly to the conductor 88. This then connects toggle tension spring 53 is hooked through an the conductor 88 through the heater the conaperture in a contact arm 55 which has its one tacts |89 and 98 and through the bimetal 9G and end provided with a knife edge held by a station- 15 the conductor 94 with one terminal of the upper ary notched support 51. The other end of the unit 22 while the other terminal of the upper unit contact arm 55 carries the thermostat contact 28 22 is connected through the conductor 25, the

through a spring connection. The movement vof contacts 28 and 38 with the other supply conducthe contact arm 55 and the contact 28 away from tor 32. Thus, in the preheat circuit arrangethe contact 38 is limited by a stop 56. 20 ment, the upper unit 22 is directly connected The screw 41 is turned by an adjusting knob 48 across the supply conductors at full voltage, as is in order to set the thermostat to open and close the lower unit 24, which has its output reduced by at any desired temperature of the thermostat the change since no current is supplied from the bulb 34. The knob 48 is fastened by a set-screw tap to the upper unit 22. The contacts 98 and 68 to a sleeve 82 which in turn is provided with a 25 |88 will remain in engagement until the thermoplate 64 carrying a slot which receives the pin 88 stat bulb 34 reaches the temperature for which projecting from the screw 41. The plate 84 is the adjusting knob 48 of the thermostat is set. fastened to the sleeve 52 by screws 88 which ex- At this temperature, the expansion of the tend through adjusting slots in the plate 84. The diaphragm 4| will separate the contacts 28 and sleeve 62 rotates upon the outside of the bushing 30 38, thereby deenergizing all circuits. This will 49 and carries an indicating dial 18. This sleeve deenergize the heater and allow the bimetal 62 also carries an upper cam 12 and a lower cam strip 96 to cool. Upon cooling, the contact 98 14, each cf which is fixed to the sleeve 52. will return to its engagement with the stationary The upper cam 12 actuates a push rod 18 which contact |8|, thereby restoring the system to the is normally held against the cam by a spring 18. 35 bake circuit arrangement in which it will remain The other end of the push rod 15 is adapted to during succeeding cycles of the thermostat conengage a spring strip 88 which is anchored at its tacts 28 and 38. Thus, in this simple way, an opposite end to an anchorage 82. This spring automatic change from preheat to bake circuit strip 88 is normally tensioned to hold a movable arrangement is accomplished at the end oi' the contact 84 in engagement with a stationary con- 40 preheat cycle. This is performed without any tact 86. The closing of the contacts 84 and 88 load upon the thermostat so that the sensitivity connects the other conductor 88 of the supply of the thermostat is not affected. Also, the source through the conductor 98, the contacts 85 bimetal device is simple, noiseless and substanand 84 and through a conductor 92 to the other tially foolproof. terminal of the lower oven heating unit 24. 45 For broiling, the upper and lower cams 12 and For baking purposes, the other terminal of the 14 respectively, are used to separate the switch upper heating unit 22 is connected through the contacts 84 and 86 and to close the contacts 88 conductor 94, the bimetal strip 98, the double conand |89. For this purpose, the cam 12 is protact 98, stationary contact |8| and the conductor vided with a raised or hump portion |2|. When |83 with a tap |85 upon the lower unit 24. This 50 the knob 48 is rotated to set the broll legend tap |85 divides the lower unit into sections 23 opposite the indicator for the dial 18, the raised and 25 and is so located in the lower unit 24 that or hump portion |2| of the cam 12 will engage the voltage which is applied to the upper unit 22 and push outwardly the end of the rod 15 so that is just sufficient to provide substantially uniform the spring strip 88 will be deflected outwardly temperatures within the oven when the lower unit 55 to separate the contacts 84 and 85. At thesame 24 is energized at full voltage. Normally, this time, the lower cam 14 will be rotated to place point should be so located that about one-third a recessed portion |23 in registration with a lower the full voltage is applied to the upper unit 22. cam follower push rod |25 which extends through This, however, depends upon the resistance of the end of the bimetal strip 86 and is provided the upper unit 22. With this arrangement, the 50 with a collar |21 on the far side and a collar |29 upper unit 22 is placed in parallel with section 23 on the near side. The movement of the lower and in series with section 25. The bimetal strip cam push rod |25 into the recess |23 under the 98 is so selected and formed that when it is at influence of the follower spring |3| causes the any room temperature the contact 88 will be collar |21 to move the free end of the bimetal firmly held in engagement with the contact |8|. 65 strip 86 to the rlghtso that the contact 98 will For rapid1y bringing the oven to the desired be held in engagement with the Stationary Contemperature prior to baking, a more rapid pretact |89.

heating circuit arrangement is provided. For This movement of the knob 48 to the broil this purpose, the biinetal strip 96 is provided with position thus connects the upper unit 22 across an operating knob |81 by which the bimetal strip 70 full voltage and disconnects the lower unit 24 9E may be moved to place contact 98 in engageat the one terminal and also its tap |85. The ment with the stationary contact |89. The concircuit for broiling includes the source conductact |89 is connected to a heater which will tor 88, the heater the stationary contact heat the bimetal strip 88 and cause the contact |89, the movable contact 98, the bimetal strip 98 to remain in contact with the stationary con- 75 96, the conductor 94, the upper unit 22, the con- .y position for broiling purposes.

I heating cycle.

ductor 26, the movable contact 28, the stationary contact 30 and the source conductor 32. 'I'he knob 48 is turned sufilciently far to attain the broil position that the thermostat; is set at a temperature suiiciently high to maintain the thermostat contacts closed for a sufiicient length of time for broiling purposes. Ordinarily, the oven door is left open to prevent the oven temperatures from rising sufficiently high to open the thermostat contacts. kNo current ilows through the lower unit 24 because the conductor 92 at its one terminal is disconnected by the opening of the contacts 84 and 86 and the conductor |03 which is connected to the top |05 is disconnected by the movement of the contact 98 away from the contact |l.

When the knob 48 is turned substantially 360 degrees in the opposite direction to the "05 position, the upper cam 12 is turned so that a second raised portion |33 will engage the upper cam push rod 16 to again open the contacts 84 and 85. Likewise, the cam 14 will present a raised portion |35 to the lower cam push rod |25 so that the shoulder |29 will engage the bimetal Strip 90 to separate the contacts 98 and |00, if they should happen to be engaged. This movement of the knob 48 to the "oif position, will also open the thermostat contacts so that both sides of all circuits will be disconnected from the source conductors. This will provide positive assurance against any live conductors when the switch is turned to the off position.

However, this is not absolutely necessary, since the breaking of one side of the line is suilicient in this circuit, since only two source conductors are employed. If desired, the push rod and its cam may be eliminated and thefknob |01 be used to move the bimetal element 90 to preheat position when the knob 48 is turned to the broil With such a system, vthe bimetal 96 would naturally move when cooled to separate the contacts 98 and |09, since the thermostat contacts 28 and 30 would be open in the olf position. K

In Fig. 6 is shown a system in which the operation of the thermostat to open position mechanically changes a double throw switch from preheat to bake" position at the end of the first In this form, the control knob double throw switch as well as andv broil circuit arrangements. In Fig. 6, there is shown a two-unit oven designated by the reference character 220 including an upper heating unit 222, primarily for broiling, and a lower heating unit 224, primarily for baking. Both the-upper and lower units 222 and 224 are connected by a single common conductor 226 to a thermostat provided with a movable contact 228 and a stationary contact 230. The stationary contact 230 is connected by a conducsets the preheat provides the bake ltor 232 to one conductor of a power source. The

contacts 228 and 230 are opened and closed in accordance with the temperature of a thermostat bulb 234 which is located within the oven 22 0. 'Ihese contacts are also employed to deenergize the entire system'when the oven is not used.

The thermostat includes a housing 243 which rigidly supports the bushing 249 which threadedly receives the control knob mechanism, similai to that shown in Fig. 1. The rotation of the control knob 248/changes the position of the inner end of the screw 241 which engages a stud attached to the expansible and contractible 'diaphragm 24|.y The interior of thejdiaphragm 24| is in communication with a capillary tube 242 the upper heating unit 222 which in turn is in communication with the interior of the bulb 234, A contractible and expansible liquid is provided in the bulb and the capillary tube 242 so that upon expansion of the liquid as a result of the heat to which the bulb is subjected, the liquid will be forced through the tube into the expansible and contractible diaphragm means 24|.

A tip, provided upon the face of diaphragm 24| opposite the stud, abuts a projection upon operating lever 246. The operating lever 246 is pivoted at one end and is connected at the other end to a light toggle spring 245 which has its other end connected to a pivoted contact arm 255 carrying the movable contact 228. The contact cam by a spring 218. The other end of the pushl rod 210 is adapted'tofenga-ge'the spring 'strip 280 contacts 284 and 2st connects the other conductor 288 of the supply source to the other terminal of the lower oven heating unit 224 through the conductor 290, the contacts 286 and 284 and the conductor 292.

For banking purposes, therother terminal of is connected through a conductor 294, to a contact arm 296 carrying a double contact 298, normally in contact with a stationary contact 30| connected by the conductor 303 with a tap 305 upon the lower unit 224. This tap 305 divides the lower unit into sections located in the lower unit 224 that the voltage applied to the upper unit 222 is just suflicient to provide substantially uniform heating and uniform temperatures within the oven when the lower unit 224,is energized at full voltage. In the normal oven, this point ordinarily falls so that the section 223 includes about one-third the total resistance of the lower unit 224. The contact arm 296 is pivoted at the end opposite the double contact 298. and is provided with a tension toggle spring 300 for keeping the double contact 208 either in engagement with the stationary contact 30| or a stationary contact 309.

For rapidly preheating the oven, theknob 243 is first turned to the broil position; This brings into operation the lower cam 214 which, like the upper cam 212, rotates with the knob 248. This lower cam 214' actuates a push rod 325 which is normally held against cam 214 by a follower spring 33|. Y

In order to provide an automatic preheat cycle prior to a normal baking cycle, the knob 248 is rst turned to the broil position and thereafter is immediately turned back to the baking temperature desired. When the knob 248 is turned to the broil position, the cam 214 will present a raised portion 323 to the adjacent end of the cam follower push rod 325. This will cause the cam surface 321 upon the push rod 325 to lift the vertical operating bar 329 until its hooked lower end raises the contact arm r296 across its dead center position so that the double contact 298 will then move into and be held in engagement with the stationary contact 309 by the toggle spring 300. This connects the one terminal of the upper unit 224 and the conductor 294 through the contact 298 and the contact 309 directly to the source conductor 288 instead of the tap 305. This, therefore, will connect the upper unit 222 across full voltage, thereby greatly increasing its output for rapid preheating purposes prior to baking.

The contact 298 will remain in contact with the stationary contact 309 until the thermostat bulb 234 reaches the baking temperature for which the adjusting knob 248 of the thermostat is set. At this time, the contacts 228 and 230 will be separated and the contact arm 255 will move downwardly carrying with it a pin 2 I 9 which will strike the contact arm 296 to separate the contact 298 from the contact 309 and to overcome the force of the toggle spring 300 to move the double contact 298 into engagement with the contact 30|. At this time, al1 the circuits of the system will be deenergized by the opening of the contacts 228 and 230. The contact 298 will remain in contact with the contact 30| throughout the succeeding cycles of the thermostat contacts 228 and 230 to maintain the proper baking circuit arrangement of the upper and lower units for baking purposes.

For broiling, the knob 248 is turned to the broil position and left in that position for the duration of the broiling operation. As mentioned before, this will throw the contact 298 into contact with the stationary contact 309 to connect the upper unit 222 directly across the supply conductors 288 and 232. At the same time, the upper cam 212 will present a raised portion 32| which will push the push rod 216 outwardly to separate the contacts 284 and 286 to deenergize the lower unit 224. In the broil position, the thermostat is adjusted to a sufiiciently high operating temperature to prevent cycling.

When the knob 248 is turned to the ofi position, the thermostat contacts 228 and 230 will be opened and the contact arm 255 will cause the pin 2 i 9 to engage the contact arm 296 to move the contact 298 again into contact with the stationary contact 30|. However, the cam 212 is provided with a second raised portion 333 which will push the push rod 216 outwardly in the orf position of the knob 248, to separate the contacts 286 and 284. This insures positive deenergization of the entire system.

The advantage of opening these contacts in the o position is illustrated in Fig. 11 in which the contact 30| is connected to a neutral (ground) conductor 302 instead of by the conductor 303 to the tap 805. Otherwise, the circuit shown in Fig. 11 is exactly like the circuit shown in Figs. 6 and l0 and all the other elements are identical. However, it will be seen that by opening the contacts 284 and 286 as well as moving contact 298 into Contact with the contact 30| and by opening the single thermostat contacts 228 and 230 in the ofi position, all parts of the system are safely deenergized and only a single set of simple contacts is required for the thermostat, even though the three-wire Edison circuit is used as a source.

In Figs. l2 and 13, there is shown another modied form which is substantially identical to the form shown in Figs. 1 to 5 excepting that the preheat is actuated as in Figs. 6 to 10 by first moving the regulating knob to the breil position and thence to the baking temperature desired, and excepting that a latch is also provided for instantaneously holding the bimetal in prehea position until the bimetal is suiiiciently heated to remain in the preheat position.

Referring now more particularly to Figs. 12 and 13, there is shown a control knob 448 provided with an upper cam 412 and a lower cam 414 which, through a primary lever 446 and a toggle spring 453, operates the pivoted contact arm 455 to open and close the thermostat contacts 428 and 430. The thermostat contacts 428 and 430 connect the conductor 432 with a conductor 426 which connects with one terminal of the heating unit 422 and one terminal oi the lower heating unit 424. These terminal are located within an oven indicated diagrammatically and designated by the reference character 420. The upper cam 412 operates a push rod 416 to open the contacts 484 and 486 in the broil and oil positions of the knob 448. The knob 448 is provided with legends upon its dial as shown in Fig. 2. The contacts 488 and 484 connect the source conductor 488 and the conductor 490 to the conductor 492 which connects to the other terminal of the lower unit 424.

The double throw bake and preheat switch includes a bimetal element 496 which carries a double contact 498. This bimetal element is so formed that at ordinary temperatures, it normally holds the contact 498 in engagement with a stationary contact 50|. This connects the upper heating unit 422 with the tap 505 on the lower unit. The circuit for the upper unit 422 in the bake circuit arrangement thus includes the source conductor 432. the contacts 430 and 428, the conductor 426, the upper heating unit 422, the conductor 494, the bimetal element 496, contacts 498 and 50|. the conductor 503, the tap 505, the section 425 of the lower unit 424, the conductor 492, the contacts 484 and 486, the conductor 490 and the source conductor 488.

For preheat purposes, the knob 448 is rst turned to the broil position and then turned to one of the bakingy temperature positions. The turning of the knob 448 to the broil position causes the cam follower 525 to engage the recess on the cam 414 corresponding to the recess |23 in the cam 14 to retract the follower 525 under the influence of the follower spring 53| in order to cause the cam shoulder 521 to engage the bimetal element 496 and to pull the bimetal element 496 into the position shown in Fie. 13 where the upper end of the bimetal 496 will ride over and be caught by the catch 55| on a second bimetal member 553 which is anchored to the support 555. This will close a circuit which in cludes the source conductor 488. the conductor 559, an electric heater 551 for heatingY the bimetal 553. a conductor 5|2, the electric heater 5| i, (corresponding to the heater of Fig. 1), the contact 509. the contact 498. the bimetal element 496, the conductor 494 which connects to one terminal of the upper heating unit 422 having its other terminal connected to the conductor 426, the contacts 428 and 430 and the source conductor 432.

The bimetal 553 assumes a lower position when at room temperature as shown in both Figs. l2 and 13, but when heated by the electric heater 551, it curls upwardly to the dotted position shown in Fig. 13, so that the bimetal 496 is unlatched. However, as long as the thermostat contacts 428 and 430 and contacts 498 and 509 remain closed, the heater 5| I will keep the bimetal 496 heated with the contact 498 in contact with the stationary contact 509. However, when the thermostat control bulb 434 connected to the di- `,the knob is turned to said upper heating means reaches the temperature for which the knob 488 is set, the thermostat contacts 428 and 430 will open, thus deenergizing the entire system including the electric heater H. This will allow the bimetal 496 to cool and to move the contact 498 into contact with the stationary contact without interference from the catch 55| which is so constructed that it will not cool as rapidly as the bimetal 496. For this purpose, the bimetal 553 may be made wider or of heavier metal or may have additional metal attached thereto in order to make it cool more slowly than the loimetal 496.

When the control knob 448 is turned to the off position, the upper cam 4'12 will separate the contacts 484 and 486, while the lower cam 414 will move the push rod 525 outwardly to cause the shoulder 529 to engage and move the bimetal element 496 so that the contact 498 will be positively held in engagement with the stationary contact 50|. Normally, after the first few seconds of the preheat cycle, the bimetal 553 will be bent upwardly by the heat applied to it by the heater 551 so that the bimetal 496 may be moved at any time thereafter without interference from the catch 55|. However, if the knob 448 should be returned to the oi position before the bimetal 553 is heated suiliciently when the knob has been in preheat or broil position, the shoulder 551 upon the push rod 525 will move outwardly and will engage a cam 56| provided upon the end of the bimetal member 553 so that the coaction of the cam surface upon the shoulder 52? with the cam 56! will raise the bimetal member 553, thereby releasing the catch from the end of the bimetal member 496 prior to the time the shoulder 525 engages the bimetal 595 to move it positively to its baking position. Thus, the system provides a, single knob control for all positions including the actuation oi a simple bimetal preheat balie switch which can be instantaneously latched in preheat position. Also, in this system, all contacts are opened when the 01T position so that complete safety is assured.

While the form of embodiment of the invention as herein disclosed, constitutes .a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l.. An electric oven heating system including an upper oven heating means, a lower oven heating means, a thermostat switch mechanism for connecting and disconnecting one terminalof-the upaphragm 441 v per and lower heating means to and from one conn ductor of an electrical power source, said lower heating means being provided with a tap at an intermediate point thereon, switch means for connecting and disconnecting the other terminal of to and from said tap, switch means for connecting and disconnecting said other terminal of said upper heating unit to and from a second conductor of said power source, means for connecting said other terminal of said lower heating means to said power source, and means controlled by said thermostat switch mechu anism for disconnecting said other conductor of said source from said other terminal of the upper heating means and connecting said other ter minal to said tap.

2. An electric oven heating system including an upper oven heating means, a lower oven heating means, a thermostat switch mechanism for connecting and disconnecting one terminal of the upper and lower heating means to and from one conductor of an electrical power source, said lower heating means being an intermediate point thereon, switch means for connecting and disconnecting the other terminal of said upper heating means to and from said tap, switch means for connecting and disconnecting said other terminal of said upper heating unit to and from a second conductor of said power source, means for connecting said other terminal of said lower heating means to said power source, and means controlled by said thermostat switch mechanism for disconnecting said other conductor of said source from said other terminal of the upper heating means and connecting said other terminal to said tap, means for closing one of said switch means and opening the other to disnect said other terminal of said upper heating means from said tap and connecting said other terminal to said second conductor of said power source, and means for disconnecting said other terminal of said lower heating means from said second conductor of said power source for broiling purposes.

3. An electric oven heating system including an upper oven heating means, a lower oven heating means, a thermostat switch mechanism for conv for connecting and disconnecting necting and disconnecting one terminal of the upper and lower heating means to and from one conductor of an electrical power source, said lower heating means being provided with a tap at an intermediate point thereon, switch means the other terminal of said upper heating means to and from said tap, switch means for connecting and disconnecting said other terminal of said upper heating unit to and from a second conductor of said power source, means for connecting said other terminal of said lower heating means to said power source, means controlled by said thermostat switch mechanism for disconnecting said other conductor of said source from said other terminal of the upper heating means and connecting said other terminal to said tap, means for closing one of said switch means and opening the other to disconnect said other terminal of said upper heating means from said tap and connecting said other terminal to said second conductor of said power source, and means for simultaneously disconnecting said other terminal of said lower heating means from said second conductor of said power source for broiling purposes.

4. An electric oven heating system including an upper oven heating means, a lower oven heating means, a thermostat switch mechanism for connecting and disconnecting one terminal of the upper and lower heating means to and from one conductor of an electrical power source, said lower heating means being provided with a tap at an intermediate point thereon; a double throw switch having one contact connected to said tap, another contact connected to a second conductor of said source, and the double contact to said other terminal of said upper heating means, means for connecting the other terminal of said lower heating means to said second conductor of said power source, and means controlled by said thermostat switch mechanism lor operating said double throw switch.

5. An electric oven heating system including an upper oven heating means, a lower oven heating means, a thermostat switch mechanism for connecting and disconnecting one terminal of the provided with a tap at upper and lower heating means to and from one conductor of an electrical power source, said lower heating means being provided with a tap at an intermediate point thereon; a double throw switch having one contact connected to said tap, another contact connected to a second conductor of said source, and the double contact to said other terminal of said upper heating means, means for connecting the other terminal of said lower heating means to said second conductor of said power source, means for said double throw switch for normally holding it in one position providing a connection between said other terminal of said upper heating means and said tap, and electrically operated means for holding said double throw switch in a second position connecting said other terminal and said second conductor.

6. An electric oven heating system including an upper oven heating means, a lower oven heating means, a thermostat switch mechanism for connecting and disconnecting one terminal of the upper and lower heating means to and from one conductor of an electrical power source, said lower heating means being provided with a tap at an intermediate point thereon; a double throw switch having one contact connected to said tap, another contact connected to a second conductor of said source, and the double contact to said other terminai of said upper heating means, means for connecting the other terminal of said lower heatingr means to said second conductor of said power souice, means lor said double throw switch for normally holding it in one position, providing a connection between said other terminal of said upper heating means and said tap, and electricaliy operated means connected in series with said another contact for holding said double throw switch in a second position connecting said other terminal and said second conductor.

rI. An electixc oven heating system including upper and lower oven heating means, control means having oiif preheat," "bake and broil positions, said control means including means for disconnecting one terminal of said lower heating means in oit and broil positions and connecting said terminal to a source conductor in preheat" and bake positions, said control means including a control device connected to one tei'- minal of the upper heating means and having a normal ake position normally providing a bake circ 'f arrangement energizing both heating mea with the lower heating means energiZed at a higher voltage than the upper heating means, said control device also having a selective preheat position providing a preheat circuit arrangement in which the upper and lower heating means are energized at substantially the same voltage, said control means including a thermostatic device for changing said control device from preheat to bake position, said thermostatic device also including contacts connected to other terminals of said upper and lower heating means.

8. An electric oven heating system including upper and lower oven heating means, control means having ofi, preheat, bake and broil positions providing preheat, bake and broil circuit arrangements oi the oven heating means in the respective positions and completely deenergizing said heating means in the ofi position, said upper and lower heating means being both energized at full wattage in said preheat position, said upper heating means being energized at reduced wattage with said lower heating means at full wattage in bake position,

and said upper heating means alone being energized in broil position, said control means including a selective double throw switch mechanism for changing the circuit arrangement from the preheat to bake arrangement and for selecting the preheat arrangement, said double throw switch being connected to one terminal of said upper heating means and to one source conductor, said control means including another switch means connected to one terminal of said lower heating means and to said one source conductor together with means for closing said an.. other switch in the bake and preheat positions and opening said another switch in the off and broil positions, said control means also including a thermostatic switch for controlling the movement of the,double throw switch to change the circuit arrangement from preheat to bake circuit arrangement, said thermostat switch having contacts connected to other terminals of said upper and lower heating means and to another conductor of said source, said thermostat being movable to separate its contacts in the olf position.

9. An electric over system adapted to be connected to two lines of a source of electric power comprising a unitary upper heating resistance, a series sectional lower heating resistance, thermostatic switch mechanism having knob means adapted to be placed in oil temperature adjustable bake, broil and preheat" positions and having two single throw single contact arms and a double throw single contact arm so actuated by said knob means that said resistances are disconnected irom said two lines in the off position, are placed in parallel across said lines in "preheat position, are placed with the lower resistance across said lines and with the upper resistance across one of said lines and at the junction of the sections of said lower heating resistance in the bake" position, and are placed with the upper heating resistance only across the lilies in the broil position, the thermostatic switch mechanism automatically changing the setting from preheat, to bake at the end of the preheating cycle.

10. An electric oven system adapted to be connected to two lines of a source of electric power comprising a unitary upper heating resistance, a series sectional lower heating resistance, thermostatic switch mechanism having knob means adapted to be placed in oil temperature adjustable bake, broil and preheat positions and having two single throw single contact arms and a double throw single contact arm so actuated by said knob means that said resistances are disconnected fi'om said two lines in the oi position, are placed in parallel across said lines in preheat position, are placed with the lower resistance across said lines and with the upper resistance across one of said lines and at the junction of the sections of said lower heating resistance in the bake position, and are placed with the upper heating resistance only across the lines in the broil position, the thermostatic switch mechanism automatically changing the setting from "preheat" to bake at the end of the preheating cycle by means oi a heating device acting on one of said arms.

l1. An electric oven system adapted to be connected to two lines of a source oi electric power comprising a unitary upper heating resistance, a series sectional lower heating resistance, thermostatic switch mechanism having knob means adapted to be placed in off" temperature adjustable bake, broil and preheat positions and having two single throwsingle contact arms and a double throw single contact arm so actuated by said knob means that said resistances are disconnected from said two lines in the off position, are placed in parallel across said lines in preheat position, are placed with the lower resistance across said lines and with the upper resistance across one of said lines and at the Junction of the sections of said lower heating resistance in the bake position, and are placed with the upper heating resistance only across the lines in the broil position, the thermostatic switch mechanism automatically changing the setting from preheat to bake at the end of the preheating cycle by means of a snap action spring on one of said arms actuated by another of said arms.

12. An electric oven system adapted to be connected to three lines of a source of electric power comprising a unitary upper heating resistance, a unitary lower heating resistance, thermostatic switch mechanism having knob means adapted to be placed in oif, temperature adjustable bake and broil positions and having two single throw single contact arms and a double throw single contact arm so actuated by said knob means that said resistances are disconnected from at least two of said lines in the off position, are placed in parallel across two of said lines at relatively high voltage upon manipulation from broil to bake positions, are placed with the lower resistance across two of said lines at relatively high voltage an-d with the upper resistance across one of said lines and the other of said lines at a relatively low volta-ge in the bake position, and with the upper resistance across two of said lines at relatively high voltage in the brcil position, the thermostatic switch mechanism automatically changing the setting of the two resistances in parallel at relatively high voltage to the bake setting at the end of a preheating cycle.

13. An electric oven system adapted to be connected to three lines of a source of electric power comprising a unitary upper heating resistance, a unitary lower heating resistance, thermostatic switch mechanism having knob means adapted to be placed in off temperature adjustable bake, and broil" positions and having two single throw single contact arms and a double throw single contact arm so actuated by said knob means that said resistances are disconnected from at least two of said lines in the off position, are placed in parallel across two of said lines at relatively high voltage upon manipulation from broil to bake positions, are placed with the lower resistance across two of said lines at relatively high voltage and with the upper resistance across one of said lines and the other of said lines at a relatively low voltage in the bake position, and with the upper resistance across two of said lines at relatively high voltage in the broil position, the thermostatic switch mechanism automatically changing the setting of the two resistances in parallel at relatively high voltage to the bake setting at the end of a preheating cycle by means of a snap action spring on one of said arms actuated by another of said arms.

14. An electric heating means for heating a zone to be heated, single pole thermostatic switch means for controlling the connection of the heating means to one live supply line of a power source to regulate the temperatures of said zone, connecting means for Aconnecting said heating means selectively into a baking circuit arrangement and into a preheat circuit arrangement and including switch means controlling the connection to another live supply line of said power source, manually operable means having off and on positions for operating said connecting means to change from the baking circuit arrangement to the preheat circuit arrangement in the on position and disconnecting said live supplylines in the oi position, and electrically operated means energized in response to the opening of said thermostatic switch means for controlling the operation or" said connecting means to change from the preheat circuit arrangement to the baking circuit arrangement.

FRANCIS H. MCCORMICK.

REFERENCES CITED The following references are of recordin the le of this patent:

US319519A 1940-02-17 1940-02-17 Electric heating system for ovens Expired - Lifetime US2434467A (en)

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Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2541314A (en) * 1948-10-27 1951-02-13 Robertshaw Fulton Controls Co Temperature regulating device
US2607870A (en) * 1950-12-11 1952-08-19 Tappan Stove Co Indicating and control mechanism for electric heating units
US2666124A (en) * 1950-04-25 1954-01-12 Proctor Electric Co Control apparatus for electrical heating units
US2668221A (en) * 1949-07-16 1954-02-02 Gen Motors Corp Domestic appliance
US2732476A (en) * 1956-01-24 Smith
US2748244A (en) * 1951-05-16 1956-05-29 Gen Motors Corp Domestic appliance
US2758190A (en) * 1951-07-21 1956-08-07 Ranco Inc Control apparatus
US2782291A (en) * 1953-01-19 1957-02-19 Procedes Sauter Thermostatic heating control systems
US2804531A (en) * 1952-10-30 1957-08-27 Nash Kelvinator Corp Range
US2806119A (en) * 1954-12-15 1957-09-10 Gen Electric Oven heating system
US2810811A (en) * 1954-10-26 1957-10-22 Market Forge Company Time controlled apparatus with electromechanical relay
US2811627A (en) * 1954-11-01 1957-10-29 Gen Motors Corp Domestic appliance
US2815428A (en) * 1954-11-01 1957-12-03 Gen Motors Corp Domestic appliances
US2816998A (en) * 1954-02-02 1957-12-17 Gen Motors Corp Domestic appliance
US2820130A (en) * 1955-04-08 1958-01-14 American Motors Corp Range
US2845517A (en) * 1956-07-12 1958-07-29 American Motors Corp Range
US2846556A (en) * 1956-11-07 1958-08-05 King Seeley Corp Temperature controlling apparatus
US2863976A (en) * 1956-07-10 1958-12-09 American Motors Corp Range
US2883508A (en) * 1958-01-15 1959-04-21 American Motors Corp Range
US2913562A (en) * 1954-09-08 1959-11-17 Robertshaw Fulton Controls Co Temperature responsive control
US3073938A (en) * 1957-04-30 1963-01-15 Proctor Silex Corp Apparatus for regulating oven temperatures

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Publication number Priority date Publication date Assignee Title
US1816866A (en) * 1929-07-10 1931-08-04 Walker & Pratt Mfg Co Electric range
US1849922A (en) * 1929-03-26 1932-03-15 Arrowhart & Hegeman Electric C Electric switch
US2203236A (en) * 1938-04-26 1940-06-04 E C Randolph Electric switch
US2218778A (en) * 1939-09-13 1940-10-22 Leland S Weimer Control system for electric cooking ovens
US2260840A (en) * 1939-08-19 1941-10-28 Gen Electric Temperature control system

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Publication number Priority date Publication date Assignee Title
US1849922A (en) * 1929-03-26 1932-03-15 Arrowhart & Hegeman Electric C Electric switch
US1816866A (en) * 1929-07-10 1931-08-04 Walker & Pratt Mfg Co Electric range
US2203236A (en) * 1938-04-26 1940-06-04 E C Randolph Electric switch
US2260840A (en) * 1939-08-19 1941-10-28 Gen Electric Temperature control system
US2218778A (en) * 1939-09-13 1940-10-22 Leland S Weimer Control system for electric cooking ovens

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2732476A (en) * 1956-01-24 Smith
US2541314A (en) * 1948-10-27 1951-02-13 Robertshaw Fulton Controls Co Temperature regulating device
US2668221A (en) * 1949-07-16 1954-02-02 Gen Motors Corp Domestic appliance
US2666124A (en) * 1950-04-25 1954-01-12 Proctor Electric Co Control apparatus for electrical heating units
US2607870A (en) * 1950-12-11 1952-08-19 Tappan Stove Co Indicating and control mechanism for electric heating units
US2748244A (en) * 1951-05-16 1956-05-29 Gen Motors Corp Domestic appliance
US2758190A (en) * 1951-07-21 1956-08-07 Ranco Inc Control apparatus
US2804531A (en) * 1952-10-30 1957-08-27 Nash Kelvinator Corp Range
US2782291A (en) * 1953-01-19 1957-02-19 Procedes Sauter Thermostatic heating control systems
US2816998A (en) * 1954-02-02 1957-12-17 Gen Motors Corp Domestic appliance
US2913562A (en) * 1954-09-08 1959-11-17 Robertshaw Fulton Controls Co Temperature responsive control
US2810811A (en) * 1954-10-26 1957-10-22 Market Forge Company Time controlled apparatus with electromechanical relay
US2815428A (en) * 1954-11-01 1957-12-03 Gen Motors Corp Domestic appliances
US2811627A (en) * 1954-11-01 1957-10-29 Gen Motors Corp Domestic appliance
US2806119A (en) * 1954-12-15 1957-09-10 Gen Electric Oven heating system
US2820130A (en) * 1955-04-08 1958-01-14 American Motors Corp Range
US2863976A (en) * 1956-07-10 1958-12-09 American Motors Corp Range
US2845517A (en) * 1956-07-12 1958-07-29 American Motors Corp Range
US2846556A (en) * 1956-11-07 1958-08-05 King Seeley Corp Temperature controlling apparatus
US3073938A (en) * 1957-04-30 1963-01-15 Proctor Silex Corp Apparatus for regulating oven temperatures
US2883508A (en) * 1958-01-15 1959-04-21 American Motors Corp Range

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