US3470354A - Catalytic smoke eliminator for high temperature self-cleaning ovens - Google Patents

Description

3,470,354 ERATURE 7 3 S W U I m mm I T N t w nc Lo C mum l 1 F Sept. 30, 1969 CATALYTIC smoxn ELIMINATOR FOR HIGH TEMP FIG.3.

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INVENTOR Carl W. Tilus W! ATTORNEY FIG.5.

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4 WITNESSES $2M $95M United States Patent 3,470,354 CATALYTIC SMOKE ELIMINATOR FOR HIGH TEMPERATURE SELF-CLEANING OVENS Carl W. Tilus, Mansfield, Ohio, assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 19, 1967, Ser. No. 676,446 Int. Cl. F27d 11/00; A21d 1/20 US. Cl. 219393 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention The invention relates to the art of catalytic oxidizing units for use in self-cleaning domestic ovens for eliminating smoke discharge during a cleaning operation of the oven.

Description of the prior art Of the self-cleaning (i.e., heat-cleaning) domestic ovens which are currently marketed so far as I know, one group operates with an average control temperature for the cleaning cycle in the order of about 880 F. for an extended period of time, While another group uses a substantially higher control temperature in the order of about 1050 F. for a substantially shorter period of time. The latter group of ovens, while in total producing no more (and perhaps less) smoke discharge for a single cleaning cycle, does produce, under heavy soil loads, the smoke and other combustion products at a high rate which gives visual evidence of the smoke issuing from the venting outlet. Accordingly, for the purpose of avoiding objections from some quarters having an influence on the marketing of such ovens, it is desirable that a catalytic oxidizing unit be provided which has a faster rate of oxidizing the combustion gases than those currently used in the noted latter group of ovens. It is further desirable that the catalytic oxidizing unit be compatible in structure with the oven structural arrangement of an even of the character adapted to carry out the cleaning operation at the high temperature, as disclosed in Kastovich US. patent application Ser. No. 552,663. Finally, the oxidizing unit should be of reasonable cost.

SUMMARY OF THE INVENTION The gist of the invention is the provision of a pair of closely spaced walls of extended area defining a catalytic oxidizing passage therebetween by the provision on at least one of the facing wall surfaces of a catalytic coating. The air flow pattern is radially in between the peripheral edges of the facing walls to a central outlet. The heating means for activating the catalyst during a self-cleaning operation is a heating element closely adjacent one of the Walls.

In modifications of the basic structural arrangement, means may be provided for enlarging the cross sectional area of the passage adjacent the outlet to accommodate the confluence of the exhausted gases passing to the outlet, I

and the provision of means on one or the other or both ice of the walls for partially disrupting a straight flow path of the exhaust gases between the spaced walls.

DRAWING DESCRIPTION FIGURE 1 is a partly broken side view of a range having a heat-cleaning oven provided with a catalytic oxidizing unit according to the invention;

FIG. 2 is a vertical sectional view corresponding to one taken along the line II-II of FIG. 3;

FIG. 3 is a partly broken top view of an oven liner having an underlying oxidizing unit according to the invention;

FIG. 4 is a vertical sectional view corresponding to one taken along the line IV-IV of FIG. 3 and enlarged relative to the FIG. 2 section;

FIG. 5 is a top view of a lower wall of an oxidizing unit provided with a modification;

FIG. 6 is a vertical sectional view corresponding to one taken along the line VIVI of FIG. 5; and

FIG. 7 is a vertical section taken through the center of the oxidizing unit adjacent the outlet vent and illustrating a modification adapted to accommodate the confluence of combustion gases adjacent the outlet vent.

PREFERRED EMBODIMENTS An oven provided with a smoke eliminator according to the invention may be embodied in a cooking range of the general character illustrated in FIGURE 1 for example. The oven cooking cavity 10 in which the cooking operations and the heating-cleaning operation takes place is defined on the top, bottom, sides and rear by an oven liner 12, and on the front by the oven door 14. Thermal insulation 16 is provided around the liner walls and in the oven door 14. The heating elements for the oven cavity include the lower element 18, normally energized for baking purposes, and the upper heating element 26 normally used for broiling purposes. These elements are connected through receptacles at the liner rear wall 22 to a source of electrical power of the character normally used for cooking ovens. In accordance with the noted Kastovich patent application, the broil element 20 also serves as the source of heat for the heat-cleaning operation of the oven.

The catalytic smoke eliminating unit generally designated 24 is preferably located in the top portion of the oven immediately below the top wall 26 of the oven liner. In essence it includes a pair of closely spaced, extended area, facing walls 28 and 30, at least one of the walls being provided with a catalytic coating on its surface facing the opposing wall. The combustion products to be exhausted from the oven during heat-cleaning flow into the space between the walls at the periphery of the walls and flow radially to the center of the space and through an outlet vent 32 into the room through an opening at one of the surface cooking units.

Referring to FIGURES 2-4 which illustrate in some what more detail the structural arrangement of the smoke eliminating unit, as there shown the upper plate 28 is generally rectangular and is provided with a central opening 34 coincident with a central opening 36 in the top wall 26 of the oven liner. The outlet vent 32 is in the form of an upright tube with a flanged lower end 38 secured in the liner wall opening 36.

The lower wall 30 of the eliminating unit is generally coextensive in area with the upper Wall 28. The spacing between the upper and lower walls is provided by spacers 42 distributed throughout the passage 40 at sufficiently close intervals to hold the spacing during differential expafiision and contraction of the walls relative to each ot er.

The upper heater 20 is of serpentine character as best seen in FIG. 3. As viewed in plan, it is of open work character and has a peripheral outline, as defined by its extremities, which bounds an area of the lower wall 30 coextensive with at least the major portion of the area of the lower wall. The heat energy produced by the heater activates the catalytic coating 44 (FIG. 4) provided on one or both of the inner faces of the passage. The heater is hungfrom the lower wall 30 by means of Z-shaped clips 46 supporting the front-to-rear runs of the heater. The clips are preferably oriented to face one side so that the heater may be pulled forwardly out of its receptacle and then moved slightly to that side to be removed from the oven.

It is noted while the catalytic coating is shown on both the upper and lower walls defining the passage 40, it may be desirable for reasons of economy to coat only the one wall; preferably the lower wall 30 subject to the greatest heating. Also, while a separate upper wall 28 is illustrated as defining the upper surface of the passage 40, in some cases the top wall 26 of the oven liner may be used as the upper wall of the passage.

The general pattern of air flow (illustrated by the broken line arrows of FIGS. 1-4) from the oven cavity into the passage 40 is through the peripheral space at the edges of the two walls and then radially to the center of the passage and out through the outlet vent 32.

Modifications of the arrangement for the purpose of promoting smoke elimination through variations in the basic structure are illustrated in FIGS. 5-7. In FIG. 7, the lower wall 30 is shown with a depressed area portion 48 opposite the outlet 32 for the purpose of accommodating the confluence of the combustion products at the center of the passage.

FIGS. 5 and 6 illustrate an arrangement for varying the passage spacing transverse to the direction of air flow at selected locations in the passage. This provides a tortuous flow path for a part of the air flowing generally radially into the central outlet vent-32. The means illustrated comprise upwardly directed embossments 50 in the lower wall 30 in a pattern as shown in FIG. 5 for example. Thus a part of the air is constrained to follow the circuitous path illustrated by the broken line arrows of FIG. 5 in passing from the peripheral edges of the walls to the central outlet 32.

The catalytic coating 44 may be any of the catalytic materials conventionally used for such purposes, such as a platinum material. A spacing between the wall facing surfaces of the coatings, or coating and forming the passage in the order of .060 to .080 will give satisfactory operation.

It is noted that the system according to the invention has the characteristics of a high capacity fume abatement system because the air flow permitted is of substantial volume due to the use of a wide surface area of catalyst. It will also be appreciated that the structural arrangement disclosed lends itself very well to the type of heat-cleaning operation in which the upper heating element 20 of the oven is alone energized to provide the heat energy for the heat-cleaning operation since the catalytic unit is located close to the heater for rapid temperature rise and has a passageway area generally coextensive with the area bounded by the extremities of the upper heating element 20.

I claim as my invention:

1. In a heat-claiming domestic oven of the type in which oven temperatures are elevated well above cooking range temperatures for effecting the heat cleaning:

means defining an oven cavity in which gases are produced during a heat-cleaning operation;

an outlet vent for exhausting said gases from said oven cavity;

a catalytic oxidizing passage through which said gases are constrained to flow in passing from said cavity to said outlet vent during said cleaning operation, said passage being defined by horizontally disposed upper and lower, slightly spaced apart, extended surface area walls in the extreme top portion of said cavity, at least one of the facing surfaces thereof being coated with an oxidizing catalyst, the outlet from said passage being generally centrally located relative to the area of said walls and in communication with said outlet vent, the inlet for said oxidizing passage being generally coextensixe with the peripheral edges of said walls, so that the flow of said gases is generally radially through said passage and then to said outlet vent, and;

means in the form of an electrical resistance heating element closely attached to the bottom surface of said lower wall for heating said walls during said cleaning operation to a temperature providing etfective oxidization of said gases in said passage.

2. In an oven according to claim 1.

said heating means comprises an openwork heating element with a peripheral outline defined by its extremities bounding an area coextensive with at least the major portion of the area of said passage.

3. In an oven according to claim 1:

at least one of said walls includes an area adjacent said outlet and spaced further from the facing area of said other wall, than the spacing between said walls throughout the remainder of said passage, to accommodate the confluence of said gases in said area adjacent said outlet vent.

4. In an oven according to claim 1:

including means in said passage varying the passage spacing transverse to the direction of air flow at selected locations therein.

5. In an oven according to claim 4:

said means comprises portions embossed in at least one of said walls and projecting toward the other of said walls.

References Cited 3,290,483 12/1966 Hurko 219-293 VOLODYMYR Y. MAYEWSKY, Primary Examiner U.S. Cl. X.R.

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