Patent Grant
7575726
The devices and methods described herein are generally in the field of catalytic converter-type smoke eliminators, such as found in self-cleaning ovens.
Self-cleaning ovens clean by heating the oven above normal cooking temperatures to burn off and eliminate the residues created in the oven during normal cooking. The organic cooking residues oxidize and evolve as smoke and vapors, which comprise volatile organic compounds (VOCs) and particulate matter. Standard commercially available ovens include catalytic converters. These catalytic converters complete the oxidation process, converting the evolved smoke and vapors into carbon dioxide and water, thereby preventing smoke and odors from escaping into the kitchen during the self-cleaning cycle.
Standard catalytic converters for self-cleaning ovens normally include a catalyst coated ceramic honeycomb-shaped disk. These coated ceramic disks are positioned within the oven's exhaust conduit or vent, through which the hot smoke and VOCs pass. The disks, typically 1¼″ to 2″ in diameter and ½″ thick, are mounted in a flanged, cylindrical metal tube (or can), roughly 1″ to 5″ long, with impingement-crimped restraints on both sides of the disk. A metal sealing ring optionally is provided around the top circumference of the ceramic disk, forming a seal between the interior wall surface of the metal tube and the outer circumferential surface of the ceramic disk, to reduce gas bypass. The sealing ring also protects the ceramic disk from fracture during the crimping process, as the ring is interposed between the top surface of the ceramic disk and the notches of the impingement-crimped restraints. The flanged tube, which serves as at least a portion of the exhaust vent, is then mounted with screws into the kitchen range in communication with the self-cleaning oven. Another design of catalytic converter includes catalyst coated metal screens mounted in a metal tube, much like the ceramic substrate is.
A continuing trend in kitchen range design includes exhaust vents that have sharp bends and/or flat shapes, in which the standard cylindrical can and/or the ½ inch thick disk will not fit. In addition, catalyst installation with a separate metal can is labor-intensive and uneconomical. It would be advantageous to simplify the installation of a ceramic substrate catalyst or a catalyst coated metal screens into an exhaust vent that is narrow, flat, or has sharp bends, without the need for separate mounting components, such as screws. It therefore would be desirable to provide such catalyst devices that can be directly and easily installed into exhaust vents of any of a variety of self-cleaning oven applications.
Catalytic converter devices and exhaust vent installation systems are provided for use with an oven, particularly the self-cleaning ovens of kitchen ranges, and other devices or systems in which catalytic conversion of a flue gas is desirable.
In one aspect, a catalytic converter device is provided that includes: (a) a dish-shaped body formed of a mesh of metal strands, the body having a base member, sidewalls projecting from the base member, and a flange extending out from the sidewalls at a position distal from the base member, the mesh having a plurality of apertures therethrough; (b) a catalytic material on at least the surface of the mesh of metal strands; and (c) one or more (e.g., two, three, four, five, or six) locking tabs extending from the sidewall, the one or more locking tabs and the flange cooperating to secure the device within an orifice of the gas vent such that gases flowing into the vent will pass through the apertures. The base member can be in the shape of a round disk, which for example can have a diameter between about ½ inch and about 2 inches. The sidewall can have a height, for example, of between about 1/32 inch and about ½ inch or more.
The catalytic material may comprise a noble or precious metal, such as platinum, palladium, rhodium, ruthenium, iridium, osmium, silver, gold and mixtures thereof. The catalytic material may comprise a base metal, such as zinc, nickel, copper, manganese, iron, chromium, vanadium, molybdenum, and mixtures thereof.
In one embodiment, each locking tab is formed by punching a hole in the sidewall, such that a portion of each locking tab remains integral with the sidewall. In a preferred variation, the locking tab projects from an edge of the hole distal the flange and at an angle toward the flange.
In one embodiment, the mesh comprises woven metal strands. In an alternative embodiment, a collection of non-woven strands is bonded together, for example, by sintering them. In one embodiment, the mesh of metal strands is coated with the catalyst material. In another embodiment, the mesh of metal strands is formed of (e.g., consists essentially of) the catalyst material.
In another aspect, an oven is provided which comprises one of the foregoing catalytic converter devices. In one embodiment, the oven is a self-cleaning kitchen oven.
In still another embodiment, a method is provided for reducing smoke and volatile organic compounds present in a gas flowing into a vent, which could be part of a kitchen range which comprises a self-cleaning oven. In one embodiment, the method comprises flowing the gas through apertures in a mesh of metal strands in a dish-shaped body of a catalytic converter device, at least the surface of the mesh of metal strands comprising a catalyst material, to oxidize smoke and volatile organic compounds present in the gas, wherein the body is secured within an orifice in the gas vent by the cooperation of one or more locking tabs and a flange which extend from sidewalls of the body.
In yet another aspect, an exhaust vent is provided for venting gases from an oven. In one embodiment, the exhaust vent comprises (a) a tube having an inlet orifice and an outlet orifice and having a gas passageway therebetween, the inlet orifice being defined in a planar body having an inner surface and an outer surface; and (b) a catalytic converter device secured within the inlet orifice, the device comprising (i) a dish-shaped body formed of a mesh of metal strands, the body having a base member, sidewalls projecting from the base member, and a flange extending out from the sidewalls at a position distal from the base member, the mesh having a plurality of apertures therethrough; (ii) a catalytic material on at least the surface of the mesh of metal strands; and (iii) one or more locking tabs extending from the sidewalls, wherein the locking tabs engage either the inner surface or the outer surface of the planer body of the vent, and the flange engages other of the inner surface or outer surface, the locking tabs and the flange cooperating to secure the device within the inlet orifice such that gases flowing into the vent will pass through the apertures.
The catalytic converter devices can be used in a variety of residential, commercial, or industrial ovens, as well as other devices or systems in which catalytic conversion of a flue gas is desirable. Self-cleaning kitchen ovens are preferred. The devices are used to reduce smoke and volatile organic compounds present in an exhaust gas flowing from an oven, such as in an exhaust gas vent.
Improved catalytic converter devices and exhaust vents have been developed for easier and more economical assembly and installation into a self-cleaning kitchen range or other self-cleaning oven. The present devices save space, installation time, and cost over commercially available catalytic converters.
The Catalytic Converter Device
The catalytic converter device includes a substrate, a catalyst material on the surface of the substrate (e.g., as a coating), and a means for securing the substrate into an orifice of a gas vent (e.g., an oven vent), such that exhaust gases flowing through the vent will pass through apertures in the device to oxidize smoke and volatile organic compounds present in the gas. The substrate can be in the form of a mesh of metal strands or it can in the form of a ceramic body. The means for securing the metal mesh substrate/catalyst can be an integral feature built into the substrate, or it can be a mounting ring. The means for securing the ceramic substrate generally includes a mounting ring.
Metal Mesh Device
One non-limiting example of a catalytic converter device which utilizes the mesh of metal strands is illustrated in
In one embodiment, an exhaust vent is provided which comprises a tube having an inlet orifice and an outlet orifice and having a gas passageway therebetween. The inlet orifice is defined in a planar body portion of the exhaust vent, wherein the body portion has an inner surface and an outer surface.
The size of the substrate can vary to accommodate a variety of oven sizes and gas flow rates, as well as operational and manufacturing considerations. The base member can be in the shape of a round disk, which may have a diameter, for example, between about ½ inch and about 2 inches. The sidewall may have a height, for example, of between about 1/32 inch and about ½ inch.
The metal mesh substrate generally is formed from a sheet of woven or non-woven metal strands, and it has regularly or irregularly sized and spaced apertures therethrough. The woven mesh is sometimes referred to in the art as a screen, given its visual similarity to a window screen. The metal strands can be formed from or coated with the catalyst material. In one embodiment, the mesh comprises woven metal strands. In an alternative embodiment, a collection of non-woven strands are bonded together, for example, by sintering them. In one embodiment, the mesh of metal strands is coated with the catalyst material. In another embodiment, the mesh of metal strands is formed of (e.g., consists essentially of) the catalyst material.
Ceramic Substrate
The ceramic substrate has a first surface, a second surface, a circumferential surface, and a plurality of apertures extending through the substrate from the first surface to the second surface. The first surface and second surface preferably are substantially flat or planar, and preferably are substantially parallel to one another. The circumferential surface preferably is circular, although essentially any other shape, such as square, oval, or triangular, can be used. The apertures preferably are circular or square, but can be other shapes as well. The apertures can extend through the substrate along axes that are perpendicular or angled with respect to the first surface, the second surface, or both surfaces. In a preferred embodiment, the apertures are patterned across the substrate in a honeycomb-like array. The particular dimensions can be readily selected based upon the specific design parameters of the vent, oven, or other device in which the catalytic converter device is to be installed and used.
In a preferred embodiment for use with self-cleaning kitchen ovens, the ceramic substrate is in the shape of a round disk. The disk may have a thickness of between about 1/32″ and about ½″, such as between about ⅛″ and about ¼″, and may have a diameter of between about ½″ and about 2″, such as between about 1″ and about 1⅝″. However, depending on design factors, such as the requirements of the oven manufacturer, other shapes and sizes of the ceramic substrate may be desired.
The ceramic material forming the ceramic substrate can be selected from a variety of ceramic materials known in the art. Representative examples of ceramic materials suitable for use as the ceramic substrate include cordierite, mullite, alumina, and silica. Cordierite often is a preferred substrate material, primarily for its low thermal expansion characteristics. A catalyst material coating typically is in a discontinuous form on the ceramic substrate.
The ceramic substrate can be made using ceramic molding, cutting, and firing techniques known in the art. See, for example, U.S. Pat. No. 3,790,654 to Bagley and U.S. Pat. No. 3,801,289 to Wiley.
The Catalyst Material
The substrate—e.g., ceramic, metal screen, etc.—has a surface that includes a catalyst. Suitable catalyst materials are selected from precious metals, base metals, or a combination thereof. Non-limiting examples of precious metals include palladium, platinum, rhodium, ruthenium, iridium, osmium, silver, and gold. The precious metal may also be a reduced precious metal, precious metal oxide, precious metal sulfide, precious metal with modifiers, or a combination thereof. Non-limiting examples of modifiers include potassium, calcium, magnesium, sodium hydrated oxides, and sodium hydroxides. Non-limiting examples of base metal include zinc, nickel, copper, manganese, iron, chromium, vanadium, molybdenum, and combinations thereof.
For coated substrates, the coating is applied using techniques known in the art to coat substantially all surfaces of the ceramic or metal substrate to maximize the area of contact between the catalyst and the gases flowing over and through the substrate. A substrate also preferably includes a high surface area wash coat, preferably a gamma alumina wash coat, applied before or with the catalyst coating, which serves to substantially increase the surface area of the substrate. Such wash coating processes are known in the art. Catalyst coatings may be applied, for example, by dip coating, by spray coating, or by chemical vapor deposition methods in the art.
The appropriate catalyst can be selected for each oven application. For self-cleaning kitchen ovens, the catalyst preferably should substantially effect complete oxidation of VOCs at about 600° F.
Mounting Ring
The optional mounting ring protects the ceramic substrate during installation and maintenance of the catalytic converter, and advantageously provides quick and easy installation of the device into an oven. In one embodiment, the mounting ring includes (i) a body in the shape of a ring; (ii) one or more retaining tabs extending from the body which secure the ceramic substrate within the ring about the circumferential surface of the ceramic substrate; and (iii) one or more locking tabs extending from the body. The one or more locking tabs are adapted to engage one or more surfaces of an exhaust vent of the oven to secure the catalytic converter within an orifice of the exhaust vent. Preferably the locking tabs secure the mounting ring by clipping, e.g., by snap-fit or slide-lock engagement, within the orifice, such that no screws are required and assembly is simplified.
By “shape of a ring” is meant that the body surrounds or forms a ring around the perimeter or circumferential surface of the ceramic substrate, whatever shape the circumference may be. Thus, while the ring shape preferably is circular, it can be elliptical, square, rectangular, or essentially any other shape in which the substrate periphery may be made.
In one embodiment, the mounting ring further includes a first lip extending inwardly from a first edge of the body. The first lip works in conjunction with the retaining tabs to secure the ceramic substrate within the ring. That is the substrate is trapped between the retaining tabs, which are bent in a position over an edge portion of the first surface of the ceramic substrate at a second edge of the body, and the first lip, which is positioned over an edge portion of the second surface of the ceramic substrate.
In another embodiment, the mounting ring further comprises a second lip extending outwardly from the second edge of the body. The second lip and locking tabs preferably are used to secure the mounting ring (and thus the catalytic converter device) within the orifice of the exhaust vent. This securing preferably is accomplished by snapping the mounting ring into the orifice such that a portion of one or more surfaces of the exhaust vent, such as those surfaces adjacent the orifice, are locked into place between the second lip and the locking tabs. In other words, the edge of the vent surrounding the orifice is captured between the second lip and the locking tabs.
In preferred embodiments, the mounting ring comprises two, three, or more preferably four, retaining tabs, and two, three, or more preferably four locking tabs. In another preferred embodiment, the locking tabs extend from the retaining tabs. The retaining tabs should be spaced about the ring. For example, four folding tabs preferably are spaced 90° from one another on a circular ring-shaped body.
In a preferred embodiment, the body is in the shape of a circular ring having an internal diameter of between about 1″ and 1⅝″.
In yet another embodiment, retaining tabs are bent over both the first surface and the second surface of the ceramic substrate, and the mounting ring is integrally formed into the exhaust vent, eliminating the need for locking tabs.
The mounting ring preferably is formed from a metal, although other non-metal, heat resistant materials can be used. Such materials should be substantially rigid and durable. Preferred metal materials include steels, stainless steels, aluminum, aluminized steels, and mixture or combinations thereof.
The mounting ring embodiment of the catalytic converter device can be farther understood with reference to the non-limiting examples illustrated in
The mounting ring is stamped from a sheet of metal, preferably about 0.021 inches thick, to yield a cutout preform, as shown in
Preferably, the ring-shaped body first is readied to receive the substrate, either by being provided with a first lip or by bending one or more retaining tabs along the first edge, while the retaining tabs for the upper side are in their unbent position. Next, the substrate is placed within the ring via the open second edge. Then, the retaining tabs are bent over the first surface of the substrate along the second edge of the body, thereby trapping the substrate in the ring. The mounting ring then is clipped into place in a vent, such as at an inlet orifice of an oven exhaust vent. In one embodiment, the mounting ring is pushed straight into an orifice in a flat tube shape exhaust vent, wherein the orifice has a diameter slightly larger than that of the body of the mounting ring. Once inserted, the mounting ring is rotated, typically between 10 and 45°, to secure the mounting ring in place. See
Use of the Catalytic Converter Devices
The catalytic converter device is used in substantially the same manner as current commercially available catalytic converters. The catalytic converter devices can be adapted to remove smoke and VOCs from small quantities of air or other gases from a variety of sources. The converted air can be released wherever appropriate, but the catalytic converter devices are particularly useful where the air is returned indoors instead of being vented outdoors.
In a preferred embodiment, the catalytic converter device is employed in a self-cleaning kitchen oven. The catalytic converter device must be mounted in sufficient thermal proximity to the heat source of the oven so that the catalyst can reach its light-off temperature, that is, the temperature required to trigger the catalytic oxidation reaction. The oven is operated in the self-cleaning mode as directed by the oven manufacturer, which typically involves heating the oven above normal cooking temperatures to partially burn and volatilize the organic cooking residues. Convective forces cause the resulting smoke and vapors comprising VOCs and particulate matter to pass into an exhaust vent and contact the catalyst of the catalytic converter device. The catalytic converter complete the oxidation process, converting the evolved smoke and vapors into carbon dioxide and water, which then flow from the exhaust vent. Thus, smoke, VOCs, and unpleasant odors are prevented from escaping the oven and into the kitchen.
A non-limiting example of a self-cleaning kitchen oven using the catalytic converter device described herein is shown in
The catalytic converter device may also be used in other types of ovens, such as commercial and laboratory ovens. For example, the catalytic converter device can he used with the dental mold ovens used to thermally remove wax from various dental prosthetics made by wax molds. The process of burning off the wax results in VOCs being evolved. These VOCs can be oxidized and eliminated using the present catalytic converter device, preventing their release into dentists' laboratories and offices.
Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein.
This is a continuation-in-part of U.S. application Ser. No. 09/827,473, filed Apr. 6, 2001, now pending. That application is incorporated herein by reference.
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| 3785778 | Burstein et al. | Jan 1974 | A |
| 4437451 | Wysong | Mar 1984 | A |
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| 5934268 | Onocki | Aug 1999 | A |
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|---|---|---|
| 199 12 453 | Sep 2000 | DE |
| 19912453 | Sep 2000 | DE |
| 0 831 277 | Mar 1998 | EP |
| 2 739 791 | Apr 1997 | FR |
| 1 204 423 | Sep 1970 | GB |
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| Number | Date | Country | |
|---|---|---|---|
| 20070048197 A1 | Mar 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09827473 | Apr 2001 | US |
| Child | 11552762 | US |
