US3530278A

US3530278A - Air inlet arrangement for heat-cleaning oven

Info

Publication number: US3530278A
Application number: US709123A
Authority: US
Inventors: Carl W Tilus
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1968-02-28
Filing date: 1968-02-28
Publication date: 1970-09-22
Anticipated expiration: 1987-09-22
Also published as: GB1201238A

Description

C. W. TILUS Sept. 22, 19170 AIR INLET ARRANGEMENT FOR HEAT-CLEANING OVEN Filed Feb. 28, 1968 INVENTOR Cor! W. Tilus BY ATTORNEY Carl W. Tilus, Manseld, Ohio,

United States Patent O 3,530,278 AIR INLET ARRANGEMENT FOR I-EAJI- CLEANING OVEN assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Feb. 28, 1968, Ser. No. 709,123 Int. Cl. F27d 1.7/02

U.S. Cl. 219-393 6 Claims ABSTRACT oF THE mscLosURE Heat-cleaning oven apparatus in which the air admitted during the cleaning cycle is admitted through ducts extending generally upwardly along one of the ixed vertical Walls of the oven for admission into the oven at a level well above the bottom wall of the oven, and with the oven door substantially sealing against admission of air therearound.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to domestic ovens of the heatcleaning type and to an arrangement for admitting the proper quantity of air to the oven during a heat-cleaning cycle.

Description of the prior art So far as I know, most of the currently marketed heacleaning ovens provide for the admission of air into the oven cavity through inlet means adjacent the lower edge of the oven door. The inlet is commonly formed by leaving a gap in the door gasket portion extending along the door lower edge so that when the door is closed, air can be admitted into the oven through the gap. In at least one arrangement of a slightly Varying nature, as exemplified by U.S. Pat. 3,348,023, the inlet means is formed in the lower portion of the door itself.

In another arrangement, as exemplified by U.S. Pat. 3,327,094, the door seals when locked, and air is admitted by leakage at various points around the oven liner such as where the bake and broil heating elements and oven lamp extend through the liner.

It has been customary, in construction of cooking ovens in which a heat-cleaning operation was not employed, to provide the air inlet near or at the lower edge of the oven door so that air admitted during normal baking and roasting operations would rise through the cavity by convection and exit through venting means at the top of the oven. Accordingly, since heat cleaning ovens are used for the same kind of cooking operations as non heatcleaning ovens, it was logical to provide the air inlet in the same location. However, upon analysis, I have concluded that a number of difficulties stem directly from this location and arrangement of air inlet. It is to be understood that there is a degree of criticality in the amount of air admitted during a heat-cleaning operation. Thus suflicient oxygen must be present at the smoke eliminator or catalytic oxidation unit to promote degradation of the gaseous products of combustion and prevent the emission of undue quantities of visible smoke. Further, the quantity of air suicient for a normal cleaning load may be quite inadequate for so-called demonstrator loads in which an inordinately large quantity of food substances are to be decomposed. This is especially critical in those heat-cleaning ovens of the type manufactured by the assignee of this application, in which the upper limit of the cleaning temperature may be as much as 150 F. above the upper limit of the cleaning temperature of most of the currently marketed heat-cleaning ovens. The higher heat and (consequently) shorter cleaning cycle of my 3,53%,278 Patented Sept. 22, 1970 assignees oven simply compounds enced with demonstrator loads.

Conicting with the demand for a greater quantity of air is the problem experienced by introducing the air at the lower front lip of the door area. This area is normally one of the coolest parts of the oven cavity due to the heat loss at the door seal junction. Acordingly this cooler area does not clean as Well as the remainder of the oven liner, and it will be appreciated that the admission of more air at this location would intensify the cool area problem. Also, the admission of air at the oor level promotes ignition and sustained aming combustion of quantities of food which have collected on the bottom wall of the oven.

Finally, it will be appreciated that diiculty is experienced in maintaining the proper size intake area at a door gasket gap with normal manufacturing tolerances due to differential thermal expansion of the oven liner and door during a cleaning cycle.

SUMMARY OF THE INVENTION In accordance with my invention, the means for admitting the air into the cavity during a heat-cleaning cycle is provided apart from the front of the oven cavity and comprise duct means extending generally upwardly along one of the upright walls of the oven with the lower end inlet means of the duct means being in communication with a room-air-region adjacent the lower part of the oven, and the upper end of the duct means comprising outlet means in communication with the oven cavity at a level well above the bottom Wall of the oven. With this arangement the door substantially seals the front face of the oven so that cooler areas around the door are not aggravated by the liow of additional cool air. By introduction of the air at a high level in the oven, ignition and sustained burning of the fats and greases on the oven bottom wall is materially reduced, while the fully adequate supply of air is provided for the smoke eliminator or catalytic oxidizer at the top of the oven with all cleaning loads. By providing duct means which extend generally upwardly and closely adjacent the vertical walls, preheating of the air being admitted to the oven is provided, as well as the stack elIect of the duct means reduces the chance of a backfire reaching out through the ducts in a reverse direction. Finally, problems of close manufacturing tolerances relative to the door and liner are substantially eliminated by this arrangement.

DRAWING DESCRIPTION FIG. l is a partly diagrammatic front elevational view of a cooking range provided with a heat-cleaning oven, the oven door being omitted;

FIG. 2 is a partly diagrammatic and partly-broken elevational View of the right side of the range of FIG. l; and

FIG. 3 is a horizontal section corresponding to one taken along the line 3 3 of FIG. 2.

PREFERRED EMBODIMENT In the cooking range illustrated, the forwardly-open oven cavity 10 is dened by opposite side walls 12V and 14, bottom Wall 16, rear wall 18, and top Wall and smoke eliminator section 20. The open front face of the oven cavity is closed during normal cooking operation and during a heat-cleaning operation by the swing down door 22 (FIG. 2) which carries gasket means for substantially sealing the front of the oven cavity against the ingress of room air.

The heating means in the cavity 10 includes the exemplary electrically energizable upper element 24 and a lower element 26. In the illustrated range, the upper element is associated with the smoke eliminator section 20 the problems experiwhich includes a series of vent openings in the plenum 28 arrayed to follow the shape of the element 24 as taught in Kastovich U.S. Pat. application 552,663. The exit of the degraded gases from the plenum is by way of vent outlet 30 to the room.

The admission of air to the oven cavity 10 according to the illustrated form of the invention is through vertically extending duct means comprising a pair of

ducts

32 and 34 adjacent the rear wall 18. Both ducts have a substantial vertical dimension and may conveniently be of generally channel shape in transverse section with the edges of the legs of the channel having outwardlydirected flanges 36 (FIG. 3) which abut and are secured to the exterior face of the rear wall 18 of the oven cavity. The lower open ends 38 of the ducts are in communication with the region 40 in which the storage drawer 42 is located, while the open upper ends 44 of the ducts are in communication with the over cavity at a level about two-thirds of the lway up from the bottom wall 16.

The thermal insulation 46 (FIGS. 2 and 3) about the oven also encompasses the sides and back of the

ducts

32 and 34 so that the air therein is heated and rises therethrough by convection. The convection iiow is of course promoted by the substantial height of the ducts, which also resist reverse flow resulting from combustion backring.

The arrangement according to the invention also results in an apparent reduction in backring. This is probably explainable as resulting from a reduction in the likelihood of flaming combustion occurring in the oven since the air ow, as generally indicated by the broken line arrows, does not sweep over the bottom wall 16 but is rather directed generally toward the upper part of the oven cavity and the smoke eliminator section 20. It is to be normally expected that the soil which lends itself to ilaming combustion will be gathered on the bottom wall which, in an arrangement according to the invention, may be considered to be somewhat starved of air to support aming combustion. Thus the pyrolytic decomposition of these materials on the bottom wall may be likened to a smoldering type of burning which, while producing substantial smoke, does not result in a great deal of flaming combustion. However the ample supply of air admitted by the arrangement according to the invention is available at the smoke eliminator section to permit the further degradation of the smoke.

It will be appreciated that while two

separate ducts

32 and 34 are shown (because of the central heating element terminals), a single duct, or more than two, may ibe used so long as adequate distribution of air is achieved. Further, the duct means may be located along one of the side walls instead ofthe rear wall, although it is preferable to keep the outlet of the duct means spaced apart from the front opening of the oven cavity which normally has somewhat lower liner temperatures. In other words, it is considered inadvisable to aggravate the condition of cold areas usually found near the front of the cavity.

It is considered that the air inlet means according to the invention is particularly adaptable for use in that type of heat-cleaning oven disclosed in the noted Kastovich U.S. patent application in which substantially all of the heat for the heat-cleaning operation is derived from the top heating element 24 and in which this element is used as a smoke eliminator in accordance with the same noted patent application. However the principles of this invention may also be applied to other types of heat cleaning ovens in which heat is contributed for the cleaning operation from both of the heating elements, and in which an independent catalytic oxidation unit is used for the smoke elimination.

I have found that with the arrangement according to the present invention, the cross sectional open areas of the ducts may be in the order of 3 times the open area of a gasket gap normally provided in the arrangement of applicants assignees prior art units, with quite satisfactory results obtained. It will be appreciated, that with oven cavities of varying sizes, the extent of the opening into the oven may desirably be arranged to be adjusted by damper means to limit the amount of air admitted during baking operations. The amount of air to be admitted would depend of course upon the overall oven system and would normally be determined empirically.

I claim: 1. In a heat-cleaning oven in which food products to be removed are pyrolytically decomposed:

housing means dening an oven cavity having vertical side walls, top, bottom, and vertical rear walls, and an open front face; a door for substantially sealing said front face; electrical resistance heating means for supplying heat to said cavity to etect the pyrolytic decomposition of said food products; passage means deiining a venting exit for combustion gases produced in said oven during a heatcleaning operation; and duct means for admitting air by convection ow into said cavity during said heat-cleaning operation to supply oxygen for promoting the pyrolytic decomposition, said duct means being located apart from said front face of said oven, and extending generally upwardly along at least one of said vertical walls with lower inlet end means in communication with a room air region adjacent a lower part of said oven, and upper end outlet means in communication with said oven cavity at a level well above said bottom lwall of said oven. 2. In a heat-cleaning oven according to claim 1: said duct means is located closely against the exterior face of said rear wall. 3. In a heat-cleaning oven according to claim 2: said duct means comprises at least a pair of vertically extending ducts. 4. In a heat-cleaning oven according to claim 1: said upper end outlet means of said duct means is spaced about two-thirds of the way up from the bottom wall of said oven. 5. In a heat-cleaning oven according to claim 1: said electrical resistance heating means for supplying heat to said cavity comprises a heating element l0- cated closely below said top wall of said oven cavity, said upper heating element supplying substantially all of the heat to said cavity during a heat-cleaning operation and serving as the source of energy for smoke elimination. 6. In a heat-cleaning oven in which food products to be removed are pyrolytically decomposed:

housing means defining an oven cavity having vertical side walls, top, bottom, and vertical rear walls, and an open front face; a door for substantially sealing said front face during a heat-cleaning operation; top and bottom electrical resistance heating elements in said cavity; electrical means for energizing only said top heating element to provide the heat to effect the pyrolytic decomposition of said food products; passage means dening a venting exit for combustion gases produced in said oven during said heat-cleaning operation; and duct means for admitting air by convection flow into said cavity during said heat-cleaning operation to supply oxygen for promoting the pyrolytic decomposition, said duct means comprising at least one vertically extending duct located along one of said vertical walls and having a lower inlet in communication with a region adjacent the lower part of said oven, and having an outlet at the upper end of said duct in communication -with said oven cavity at a level closer to said topl wall of said oven than to said bottom wall of said oven so that the air admitted into said oven cavity tends to be directed into the upper part thereof adjacent said upper heating element.

References Cited UNITED STATES PATENTS Cline 219-400 Perl 219-400 Beasley et a1. 126-21 Lewis et a1. 219-391 Keppler 219-400` X Weeks 219-413 6 3,053,963 9/1962 Dills 219-413 3,081,763 3/1963 Newell et al. 126-21 3,333,531 8/1967 Reuther 99-339 FOREIGN PATENTS 513,684 10/1939 Great Britain. 533,223 2/1941 Great Britain.

VOLODYMYR Y. MAYEWSKY, Primary Examiner 10 Us. c1. XR.