US 3474225 A
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Description (OCR text may contain errors)
Oct. 21, 1969 J, LE 3,474,225
FORCED AIR ELECTRIC OVEN Filed Aug. 24, 1967 2 Sheets-Sheet 1 ATTORNEYS Oct. 21, 1969 J. B. LEEDY 3,474,225
FORGED AIR ELECTRIC OVEN Filed Aug. 24, 1967 2 Sheets-Sheet 2 INVENTOR JAMES B. L EEO) @ZMMQMJM ATTORNEYS United States Patent 3,474,225 FORCED AIR ELECTRIC OVEN James B. Leedy, Mansfield, Ohio, assignor to The Tappan Company, Mansfield, Ohio, a corporation of Ohio Filed Aug. 24, 1967, Ser. No. 662,953 Int. Cl. F27d 11/00; A21b 1/22 US. Cl. 219-400 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates as indicated to electric ovens in which there is forced circulation of heated air and, more particularly, to an oven of this type having enhanced cleanability.
Range manufacturers have long been aware of the difficult job a housewife faces in cleaning the interior surfaces of her oven by the standard application of cleansing compounds, including the highly reactive chemical cleansers currently available, and this attention has led to two lines of development for improvement and simplification of the task. Automatic cleaning or self-cleaning by heating the surfaces of the cavity to a temperature much higher than that normally used for cooking is one approach that has led to the fairly recent commercial introduction of ovens capable of operating at temperatures in excess of 750 F. in a cleaning cycle to effect removal of accumulated food soils either by incineration, in gas ovens, or by degradation of the soils to gaseous products and catalytic conversion of the latter, with the second type of removal employed in electric ovens. These ovens must be of special design and construction in every respect in which the much higher than normal temperature operation is of significant effect and personal safety measures are recognized as necessary, for example, to protect the housewife who might inadvertently open the door of the oven during the cleaning cycle.
The other line of development has in contrast sought mechanically to make the cleaning job easier and more convenient by improving the surface characteristics of the cavity and has produced the removable liner type of oven. An early, but contemporary, oven employed separate panels removably placed over the two side and rear walls of the cavity to receive the food spatter and the like in cooking operations, with these panels of course extractable for cleaning when needed outside of the oven and, most conveniently, in the kitchen sink. These panels were, moreover, first coated with chrome to provide a surface which would be less pervious and hence more easily cleaned than the more common porcelain enamel coatings and, subsequently, non-stick organic finishes were applied to these removable panels or liners. Ovens of this second class are currently available with both chrome coated panels and panels which are coated with the polytetrafluoroethylene supplied under the trademark Teflon by E. I. du Pont de Nemours & Co. as the non-stick finish. An organic non-stick finish provides at this time the easiest surface to clean, but such finishes are definitely limited in respect of thermal stability. The commonly used Teflon should not, for example, be heated above about 550 F. to protect against decomposition and this limitation has in turn restricted mechanically the way in which the material can be used in the oven. The usual electric oven, as a more specific example, has an upper electric resistance heating element in sinuous sheathed form suitable for broiling in the cavity and a lower or bottom element which is supported at a fairly small spacing on the oven bottom and of course is used to perform baking and comparable operations. The proximity of the bake element to the bottom has precluded the use of Teflon on this surface and the so-called Teflon ovens today most commonly comprise chrome bottoms with the Teflon panels or surfaces only at the sides and rear wall.
As compared to the self-cleaning oven, however, the oven in which cleanability is materially enhanced by superior surface finishes has the advantage of less cost and maintenance potential, and it is a primary object of the present invention to provide an improved design for an oven of such second type.
A further object is the provision of an electric oven the bottom of which can safely carry an organic non-stick finish, as well as the side walls, whereby a very substantial degree of cleanability is added in view of the fact that the bottom ordinarily receives the majority of the food soils which accumulate in the normal use of the oven.
An additional object of the invention is to provide a novel form of air heating and circulating means in lieu of the conventional bottom or bake resistance heating element of an electric oven, whereby the bottom of the oven is not only unobstructed but free of the local heating effects of the same and accordingly coatable with a nonstick organic finish.
It is a still further object of the invention to provide such a heated forced air source in the oven as a detachable unit which can readily be extracted for servicing and the like.
Other objects and advantages of the present invention will become apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the 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 drawings:
FIG. 1 is a perspecitve view of a domestic range having an oven in accordance with the present invention;
FIG. 2. is a front elevation of the oven on an enlarged scale, with the door removed to enhance the illustration;
FIG. 3 is a fragmented sectional view the plane of which is indicated by the line 33 in FIG. 2; and
FIG. 4 is a further sectional view of the oven taken on the plane of the line 4-4 in FIG. 3.
With further reference to the drawings, the illustrated range is of free-standing electric type and conventional apart from the oven construction. Such range comprises the usual cabinet 10 in which the oven 11 is housed, behind a front door 12 for closure of the open front of the oven cavity, and the top 13 of the cabinet is formed as a cooking top comprising a plurality of surface resistance heating elements 14. Controls 15 for the oven and the surface elements are also located at the top and in a rear backguard 16.
The oven has a top wall 17, opposed side walls 18, and a bottom wall 19, with these several walls preferably sections of a continuous liner as shown, and the cavity is completed by a fixed rear wall 20. A separate and removable rear panel 21 is disposed within the cavity in spaced relation to the rear wall 20, for example, against tapped projections 22 respectively in the corner regions which receive screws 23 passed through registering corner holes in the panel 21. For a purpose which will become apparent, it is preferred that these screws, or equivalent fasteners, be readily actuatabl-e to free and remove the panel 21 from the interior of the oven.
The upper central portion of the panel is provided with a louvered intake opening 24, and a recirculating fan 25 is mounted at the rear of the panel with its inlet behind such opening. The outlet of the fan is directed into ducting also attached to the rear of the panel 21 and forming therewith a first discharge section 27 leading from the fan outlet to a horizontal section 28 having vertical continuations 29 at its ends which lead respectively to two louvered outlets 30 in the lower corner regions of the panel 21. This panel is approximately coextensive in area with the rear wall of the oven, and it will be appreciated that the fan when operating will draw in air from the upper portion of the cavity and return it at the lower corner regions.
An electric resistance coil heater 31 is supported within the horizontal duct section 28 to heat the air thus circulated therethrough, and a limiting thermostatic device 32 is shown at this section to respond to the temperature therein. The oven will be provided with a conventional variable thermostatic control device, not shown, for the heater, with the thermostat 32 serving as a safety operative for example to open the circuit at a temperature of about 550 F. The fan 25 and the heater 31 should preferably be interlocked appropriately in control to insure that the heater cannot be energized unless the fan is operative.
The oven is further equipped with an upper or broil element 32 of standard sheathed type, with the upper edge 33 of the removable panel 21 relieved to accommodate the connection of the broil element and, as earlier noted, this oven does not include the ordinary bottom or bake element. The forced air assembly carried by the panel 21 is utilized for the operations which would normally be fully or partially carried out by the usual sheathed bake element. It will also be apparent that the rear panel assembly constitutes a self-contained source of heated air which can very easily be withdrawn from the oven for servicing and the like.
It is preferred that the oven sides 18, the bottom 19 and the interior surface of the removable rear panel 21 be coated with a non-stick organic finish, such as the polytetrafiuoroethylene previously mentioned, silicone resin, etc. The top wall of the oven will not carry such a coating in view of the proximity of the broil element, but a removable metal shield can if desired be supported between the element and the top wall as is known in other oven constructions. The inner surfaces of the oven door 12 can also in this design carry such a non-stick finish, so that all of the interior surfaces of the cavity except the top can be coated with this easily cleaned material.
The oven is also shown as containing rack supports 34 respectively removably mounted on the side walls 18 and a plurality of wire racks 35 supported thereby. Both these supports and racks can also be coated with a non-stick finish to enhance the cleanability of such components as well. The temperature limit established by the thermostat 32 will of course be selected at the value recommended as the working maximum for the particular finish used.
The lack of the usual obstruction of the oven bottom by the conventional bake element is obviously quite advantageous and the added benefit of the non-stick coating on this smooth bottom provides a major improvement in respect of the desired ease of cleaning. Other means of mounting the rear panel heating assembly might of course be employed and, if desired, the non-stick surfaces at the sides and bottom could be wholly or partially realized with separable panels or liners carrying the same and removably held adjacent corresponding fixed walls of the oven.
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 employed.
I, therefore, particularly point out and distinctly claim as my invention:
1. In a domestic oven having top, bottom, rear, and side walls forming an open front cooking cavity, and a front door for closing the cavity, a first electric heating element in the upper portion of the cavity operative for broiling therein, a second electric heating element, a fan, a panel support on which the second element and fan are mounted on the same side and with the fan arranged to produce a flow of air over the thus associated element, said panel support being readily removable from the cavity for access to said second heating element and said fan, means for installing said support vertically within the cavity with said side thereof at the back relative to the interior of the cavity, air intake and outlet means in the upper and lower portions, respectively of said panel support for providing communication between the cavity interior and the back of the support to establish by conjoint operation of the second element and fan a circulation of heated air through the cavity for baking operations thereon, said exposed bottom and side walls of said cavity having nonsticking surfaces and said bottom Wall being smooth and unobstructed for ease of cleaning.
2. The combination set forth in claim 1, wherein said bottom and side walls of said cavity carry an organic nonstick coating.
3. The combination as set forth in claim 2, wherein said organic coating comprises polytetrafluoroethylene.
References Cited UNITED STATES PATENTS 2,214,630 9/1940 Wheeler 219-400 2,822,458 2/1958 Hatch 2l9-400 3,063,441 11/1962 Stoligrosz 12621 3,111,573 11/1963 Crowe et al 219-474 X 3,145,289 8/1964 Swetlitz 219395 3,241,545 3/1966 Reinert et al 1 2619 3,246,690 4/1966 Fry 64 VOLODYMYR Y. MAYEWSKY, Primary Examiner U.S. Cl. X.R.