US3036189A - Electric cooking range - Google Patents

Description

y 1962 E. L. WARNER 3,036,189

ELECTRIC COOKING RANGE Filed May 21, 1959 INVENTOR.

ELMER L. WARNER BY 0m, ma #pmdgw ATTORNEYS 3 ,036,189 Patented May 22, 1962 3,036,189 ELEQTRHC CGGKING RANGE Elmer L. Warner, tirestiine, Ohio, assignor to The Tap pan Company, Mansfield, Ohio, a corporation of Ohio Filed May 21, 1959, Ser. No. 814,829 2 Claims. (Cl. 219-20) This invention relates as indicated to electric ovens designed for cooking food and, more particularly, to the circuit means which establish and control the various conditions of use of such an oven.

A typical oven of the type to which the invention relates will comprise a top heating element, a bottom heating element of less capacity, and some form of thermostatic controller including manually operated switches for connecting such elements to an avail-able source of electric energy in accordance with adjustable settings of the controller. A three-wire, two-voltage supply is most generally employed, with a neutral conductor, and the controller switches are operative variously to connect the top and bottom elements to such supply and thereby provide at least broil and bake conditions of operation.

When this oven is to be used for broiling, the controller is set at its broil position in which the top element of high capacity is connected across the two line conductors of the supply to receive the full voltage available, and the bottom element is completely disconnected or de-encrgized. The bottom element is used for baking, butysome heat from the top or broil element is desired in this use to provide uniform browning of the food. It is accordingly common to connect, through the controller, the bottom element across the full voltage circuit and the top element etween one line and neutral to receive energy at half voltage.

It has been found, however, that even with the reduced level of energization of the broil element in such baking condition of the oven, the amount of heat produced thereby is excessive in many cases. The conventional solution to this problem has been to connect an external resistance in series with the top element when thus connected to receive half voltage, but this arrangement'obviously adds to the circuits and the switching required and also means that the unneeded heat is still being generated; the heat produced in the external resistance is wasted and must be dissipated.

It is therefore a primary object of my invention to provide an electric oven characterized by an improved top heat control. Another important object is to provide efficient Wattage control of an electric oven broil element for the purpose above mentioned by simple and economical means.

It is also an object of the invention to provide such improved control without adding to the number of circuits or physical components found in a conventional oven of the type concerned.

claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

FIG. 1 illustrates schematically an oven in accordance with the present invention;

FIG. 2 is a wiring diagram of the oven in one condition of energization thereof;

FIG. 3 is asimilar wiring diagram, but with the control p fist switches in different adjusted positions of the same; and

'FIG. 4 shows the same diagram with the switches in still further positions of adjustment.

Referring now to the drawing in detail, reference numeral 10 designates an oven having a top heating element, shown as a resistance 11, and a bottom heating element, shown as resistance 12. An oven controller is indicated generally by reference numeral 13, while "a three-wire electrical distribution system for operating the oven is represented by the conductors marked respectively L N and L The full voltage in such system would ordinarily be within the range of 230240 and the half-voltage between each line L and L and the neutral N therefore on the order of -120 volts.

With a very significant exception to be discussed herein after, this controller is conventional and comprises a dou-t ble pole contactor 14 and an actuating diaphragm 15 therefor, with the latter connected to a bulb 16 in the oven and containing an appropriate thermostatic liquid. Expansion of such liquid of course causes the contactor 14 to open at a given oven temperature, and the temperature setting for such action is adjustable by manipulation of the controller knob 17. As is well-known, the controller includes a plurality of switches to establish diiferent connections of the oven heating elements in accordance with the manual setting of the controller.

In the illustrated wiring of the oven, the line conductors L and L are connected by wires 18 and 19, respectively, to the first and second sides of the thermostatically controlled contactor 14. The conductor L is connected through the wire 18, one side of the contactor 14; and a wire 20 to a movable switch contact 21; the latter has been shown and will be referred to for convenience as a switch arm. schematically, this switch arm is adapted "to cooperate with one or the other of two stationary contacts 22 and 23 both having connections to one endof the bottom oven element 12.

A wire 24 is shown connected between the wire 20 and a second movable switch con-tact or arm 25. Such arm 25 is adapted to cooperate with stationary contacts 26 and 27, there being a common connection, indicated by the wire 28, between these two last contacts and one end of the top oven element 11.

The controller here has a third switch arm 29, which is bi-metallic and is connected by a wire 30 to the neutral conductor N in the supply. Such arm 29 is adapted to be moved into and out of engagement with a stationary contact 31 connected by wire 32 to the same end of the top element 11 which is connected with the aforementioned other switch contacts 26 and 27. The remaining ends of the two oven elements 11 and 12 are commonly connected by a wire 33 to the other side of the thermostatic contactor. 14 and thus through the same and the wire 19 to the supply conductor L There is also illustrated in FIG. 1 a further external circuit between the oven controller 13 and the neutral conductor N which includes a signal lamp 34, and it will be understood that the internal connection of this circuitwill be such that the lamp is illuminated when the oven is operative.

The movable switch contacts 21, 25 and 29 are interconnected mechanically, as indicated in the drawing, for actuation by means of the control knob 17, and the relative positioning of the stationary contacts of the three manual control switches thus formed provides three conditions of operation or energization of the oven in the illustrated embodiment. Such conditions are respectively shown in FIGS. 2, 3 and 4, and the controller 13 will of course be provided with suitable indicia to indicate the different settings.

As stated at the outset, the invention is particularly concerned with the bake setting or, more exactly, the

conditions for baking which will obtain within the usual range of temperatures provided by adjustment of the thermostatic contactor. This arrangement is shown in FIG. 2, and it will be seen therefrom that the bottom oven element 12 is connected across the conductors L and L in a circuit comprised of the wire 18, one side of the thermostatic contactor 14, wire 20, movable contact arm 21, stationary contact 22, the element 12, the other side of contactor 14, and the wire 19. The bottom heating element 12 thus receives the full voltage of the supply, indicated earlier to be within the range of 230-240 volts. At the same time, a circuit is established connecting the top element 11 to the neutral conductor N, through the wire 32, stationary contact 31, the bi-metallic arm 29, and the wire 30.

As long as the arm 29 engages such stationary contact 31, the top element will therefore be energized at half voltage. Such arm, however, is itself in the circuit, so that current flows through and produces heating of the same. The arm being bi-metallic, heating thereof to a predetermined degree, determinable by its composition and resistance, causes the arm to warp, in this case in a direction to move away from the stationary contact 31 and thus open automatically the energization circuit for the top oven element. Cooling of the arm, upon cessation of current flow through the same, causes the arm to relax or return to its position of engagement with the stationary contact 31, this being the position to which it has been adjusted by setting of the oven controller as above described.

The switch formed by the bi-metallic arm 29 and cooperable contact 31 is therefore a cycling switch effective to reduce the wattage of the top oven element 11 for the duration of the bake period of operation of the oven. The reduction in wattage thus effected will depend upon the operating characteristics of the particular bi-metal employed and these will by selection be such to provide the desired top heat level. In each case, it will accordingly be seen that the heat output at the top of the oven during baking is below that obtained by energizing the top element at only half voltage, with this objective realized in efiicient and economical manner. mostatic contactor of course operates to turn the oven off and on in accordance with the temperature setting thereof as usual.

The broil condition of the oven is shown in the diagram of FIG. 3, with the bi-metallic blade 29 here moved manually and held away from its cooperable stationary contact 31. The movable switch contact 25, which was open in the bake condition illustrated in FIG. 2, is engaged with the stationary contact 26, while the movable switch contact 21 is moved out of engagement with the stationary contact 22 to an open position. Only the top element 11 is here energized, and this element is connected across the line conductors L and L to receive full voltage, thereby providing the high capacity top heat suitable for broiling.

A pre-heat condition has been shown in FIG. 4, in which the bi-metal 29 is open, the movable contact 25 is engaged with stationary contact 27, and the movable contact 21 is engaged with its cooperable stationary contact 23. This arrangement of the switches connects both the top and bottom elements of the oven in obvious manner across the line conductors L and L whereby both receive the full voltage for quick preheating of a cold oven.

As pointed out in the above, the oven controller 13 is basically of known type, and a more particular example of such a device is a double-pole, three-position range thermostat now being made by The Hart Manufacturing Company of Hartford, Connecticut. This thermostat, and others on the same general order, includes plural control switches functionally effective to connect the top and bottom oven elements to the three wire supply in at least the bake and broil circuit arrangements shown The therrespectively herein in FIGS. 2 and 3, i.e., with each such switch having a movable contact actuated solely by the mechanical operating mechanism in entirely ordinary manner.

The present invention differs from such usual construction by the described use of a bi-metallic blade in place of the movable contact relied on to establish the half-voltage energization circuit for the top heating element in the bake condition of oven operation. Such bimetal is manually actuated for its such adjustment, but is additionally automatic by reason of its responsiveness to current flow through the same, whereby this control switch now also serves the entirely new and different function of a wattage limiter in such an assembly. The improved top heat control of the invention can therefore be realized without adding to or complicating the control system and, in fact, with utilization of the same number of elements.

It will of course be understood that the specific mechanical details of the components are not limiting on the invention, but the immediately foregoing discussion demonstrates the very substantial advantage of maximum utilization of existing components in adapting previously known systems for the improved operation provided by the present invention.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be em ployed.

I, therefore, particularly point out and distinctly claim as my invention:

1. In combination with an oven having top and bottom electric heating elements, a first source of electric energy at a predetermined voltage, and a second such energ source of relatively reduced voltage; manually actuated and adjustable controller means for variously connecting the oven elements to such sources of supply to establish different conditions of energization thereof and hence heating of the oven, said controller means comprising switch means having first and second conditions of manual adjustment, circuit means extending from such sources of supply to said switch means and from said switch means to said oven heating elements, a thermal interrupter included in said circuit means, said switch means in the first condition of adjustment thereof being operative through said circuit means to connect said bottom heating element across said first source of energy and simultaneously to connect said top heating element and said thermal interrupter in series across said second energy source, said thermal interrupter including a bimetallic switch arm and cooperable contact, with the two brought into engagement by the manual adjustment of the switch means to said first condition of adjustment of the same to complete therethrough the connection of the top element to the second source, and current flow in such connection of the top element causing the bimetallic switch arm to be heated and move out of engagement with said contact to open such connection, whereby in said one condition of adjustment of the switch means the bottom element is energized by the first source at relatively high voltage and the top element is intermittently energized by the second source of relatively low voltage, the switch means in the second condition of manual adjustment thereof maintaining the bottom element de-energized and connecting the top element across the first source to receive the relatively high voltage energy of the same, the connection of the top element to the relatively high voltage energy source in such second adjusted condition of the switch means being independent of said thermal interrupter for continuous energization of the top element.

2. In combination with an oven having top and bottom electric heating elements, and a source of electric energy comprising first, second and neutral line conductors; first circuit means for connecting one side of said bottom heating element to said first line conductor and including first switch means therein, second circuit means for connecting one side of said top heating element to said first line conductor and including second switch means therein, third circuit means for connecting said one side of said top heating element to said neutral line conductor, said third circuit means including third switch means having a control arm which is bi-metallic and a contact cooperable therewith, fourth circuit means for connecting the respective other sides of the top and bottom heating elements to said second line conductor, and manually operated control means for commonly controlling the settings of the first, second and third switch means, said manually operated control means having one first position of adjustment in which the first and third switch means are closed, whereby the bottom heating element is connected across the first and second line conductors by the first and fourth circuit means and the top heating element is connected through said bi-metallic control arm and the second and fourth circuit means across the first and neutral line conductors, the bottom heating element being thus energized at full source voltage and the top element intermittently energized at reduced voltage, the manually operated control means having another position of adjustment in which the second switch means closes to connect the top heating element between the first and second line conductors through the second and fourth circuit means, with the first and third switch means open in such other position of adjustment, whereby the top element by such other adjustment receives full source voltage from the first and second line conductors.

References Cited in the file of this patent UNITED STATES PATENTS 2,648,756 Vogelsberg Aug. 11, 1953 2,790,056 Fry Apr. 23, 1957 2,817,741 Turner Dec. 24, 1957 2,828,399 Fry Mar. 25, 1958 2,830,164 Weber et a1. Apr. 18, 1958 2,906,845 Turner Sept. 29, 1959

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