US 3926565 A
Description (OCR text may contain errors)
United States Patent [1 1 Birtigh et a1.
[ Dec. 16, 1975 APPARATUS FOR CLEANING EXHAUST GASES  Inventors: Gerhard Birtigh, Frankfurt; Horst Parbel, Gelnhausen; Heinrich Sauer, Grossauheim, all of Germany  Filed: Mar. 12, 1974  Appl. No.1 450,518
 Foreign Application Priority Data Mar. 16, 1974 Germany 2313156  US. Cl. 23/288 FC  Int. Cl. 1301.] 8/02; B01J 35/04; FOlN 3/15  Field of Search 23/288 FC,288 F  References Cited UNITED STATES PATENTS 1,932,927 10/1933 Fischer 23/288 FC UX 3,124,930 3/1964 Powers 23/288 FC UX 3,211,534 10/1965 Ridgway 23/288 FC UX 3,248,188 4/1966 Chute 23/288 FC UX 3,362,783 1/1968 Leak 23/288 FC X 3,492,098 l/l970 DePalma et a1 23/288 FC UX 3,558,286 1/1971 Gourdine 23/288 F 3,692,497 9/1972 Keith et a1. 23/288 FC 3,773,894 11/1973 Bernstein et al 23/288 FC UX 3,798,006 3/1974 Balluff 23/288 FC Primary Examiner-Morris O. Wolk Assistant Examiner-Michael S. Marcus Attorney, Agent, or Firm-Browne, Beveridge, DeGrandi & Kline 57 ABSTRACT An apparatus for cleaning an exhaust gas comprising an elongated housing capable: of receiving a catalyst monolith, said housing provided at one end with an exhaust gas entry opening, and provided at the other end with an exhaust gas discharge opening, at least two bridges spaced apart within said housing and attached to said housing, at least one supporting rod for said monolith, said rod secured to one of said bridges and movably mounted on another of said bridges, a monolith catalyst having flow channels and at least one bore for receiving said at least one supporting rod, said bore being provided in the direction of said flow channels, andvari elastic intermediate layer surrounding said at least" one supporting rod, said catalyst held on said rods by said layer being under pressure. The apparatus is especially useful for cleaning exhaust gases from internal combustion engines.
U.S. Patent Dec. 16, 1975 3,926,565
I um I:
FIG. 2 FIG. 3
6 1 CAPILLARY 2 DIAMETER .FIG.5
APPARATUS FOR CLEANING EXHAUST GASES This invention relates to an apparatus for cleaning exhaust gases,-such as exhaust gases from an internal combustion engine.
When the apparatus includes a monolithmade of 1 ceramic material, it must be anchored in the metal housing. Constructions have been known in which the monolith is puttied in with cement. One disadvantage of this method of construction is that the cement is under aheavy load and can break as a result of mechanical shock or as a result of the combustion gases emerging from theengine cylinders in a sequence of high impluses. To these causes of failure must'be added the differing thermal expansion properties of the ceramic and metal. In the case of high temperatures, the metal housing can be lifted from the rigidly puttied ceramic core because of the differing thermal expansion properties.
In other known methods of construction, the monolith is forced into position by an elastic mass between the housing and body. This mass must be kept under a pressure sufficiently high to hold the monolith firmly in place, despite the considerably greater thermal expansion properties of the metal housing at high temperatures. With prolonged operating times, the steel jacket of the housing can expand to such an extent, that the prestressed ceramic monolith weakens. This results in the monolith no longer being firmly anchored in the housing.
Accordingly, there exists a need in the art for an apparatus for cleaning exhaust gases which will aid in overcoming the previous problems. The apparatus should be capable of withstanding mechanical shock and the sequence of high impluses of combustion gases which emerge from the cylinders of an internal combustion engine. Furthermore, the apparatus should be less susceptible to failure because of the different thermal expansion properties of the ceramic material comprising the catalyst and the metallic housing which holds the catalyst.
This invention aids in overcoming the disadvantages associated with prior art devices by providing an apparatus for cleaning an exhaust gas in which the apparatus comprises an elongated housing capable of receiving a catalyst monolith, and further in which the housing is provided at one end thereof with an exhaust gas entry opening and at the other end thereof with an exhaust gas discharge opening. At least two bridge means are spaced apart from each other within the housing, and each is attached to the housing. There is also provided at least one supporting rod for the monolith. The sup porting rod is secured to one of the bridge means and shiftably mounted on another of the bridge means. The apparatus includes a monolith catalyst positioned in the elongated housing. The monolith catalyst has flow 2 channels and at least one bore for receiving the supporting rod. The bore is provided in a direction substantially parallel to the direction of flow of gases through the flow channels. An elastic, intermediate layer surrounding each supporting rod is also provided. The catalyst is held inposition on the supporting rod by the layer being under pressure. Preferably, one bridge means is positioned near the gas entry opening and another of the bridge means is positioned near the gas discharge opening, and one end of at least one rod is attached to the bridge means near the gas entry opening while the other end of the rod is shiftably mounted on the bridge means near the gas discharge opening.
In a further embodiment, a space exists between the housing and the-monolith, and sealing means are provided in this space. Preferably,the sealing means comprises a gasket or a labyrinth packing. In a preferred embodiment, the space between the housing and the monolith is less than about one-half of the diameter of a flow channel in the monolith.
The elastic, intermediate layer between the supporting rod and the monolith is advantageous because it effectively dampens the sequence of shocks caused by the pulses of exhaust gases emanating from the engine.
The intermediate layer can consist of any kind of temperature resistant, resilient material. Preferably, the elastic, intermediate layer is a web of wire, rock wool, asbestos wool, spun glass or silica-alumina (e.g. fiberfrax). The housing can be provided with a heat insulating jacket or with cooling ribs or cooling vanes. Generally, the cooling ribs or vanes will be on the outside of the housing.
This invention will be explained in greaterdetail with reference to the drawing in which:
FIG. 1 is a cross-section of an exhaust gas cleaning apparatus according to this invention, and l I FIGS. 2, 3 and 4 depict preferred embodiments involving thespace between the housing and the catalyst monolith.
FIG. 5 depicts a housing having a circular cross-section taken along 5- 5 of FIG. 1
FIG. 6 depicts an embodiment alternative to FIG. 5.
The holding arrangement depicted in FIG. 1 avoids the disadvantages of known exhaust gas cleaning de vices, while retaining the advantages associated with an elastic, intermediate layer between metal parts and a monolith ceramic. Referring to FIG. 1, a monolith l is held in position by a metal rod 2. Between the monolith 1 and rod 2 is an elastic mass 3 (e.g. fiberfrax fibers) under pressure. Elastic mass 3 is held in position by the frictional forces on the metal rod and on the monolith. The metal rod 2 is securely attached to housing 6, which is of substantially cylindrical shape, by means of bridges 4 and 5. Housing 6 is provided with an exhaust gas inlet opening 7 and an exhaust gas discharge opening 8. The rod 2 is fixedly secured to bridge 4. It is shiftably mounted in bridge 5. The pressure thrust of the exhaust gases are absorbed by not only the elastic, intermediate layer 3, but also by the elasticity of the metal rod 2 and flexibility of the bridge. Since the ceramic monolith exhibits only slight thermal expansion, the contact pressure between the rod and monolith does not decrease even in the case of high operating temperatures. Furthermore, loosening of the connection between metal and ceramic which occurs in prior art devices, cannot occur in the device of this invention.
Since the metal housing 6 does not perform any holding functions, the cross-section thereof can be arbitrarily selected. For example, in FIG. 5, a housing having a substantially round cross-section is shown. When housings having round crosssections are employed, a single supporting rod is generally sufficient. In FIG. 6, a housing 6 having an elongated cross-section is depicted, and two supporting rods 2 are shown. In the foregoing Figs, like numerals have like meanings.
The sealing means between the housing 6 and the monolith 1 can be freely selected. A labyrinth, such as that depicted in FIG. 2, as well as a gasket, such as that depicted in FIG. 3, can be employed. The sealing means can be continuous or discontinuous (i.e. having openings therein for the passage of gases). The arrangement for holding the sealing means in position will be apparent to persons skilled in the art.
It is particularly advantageous to fit the monolith in the housing with little clearance between these two elements since the entire catalyst volume can be effectively utilized. An adequate seal can be achieved when the distance between the catalyst and housing is less than about one-half the diameter of the flow channels in the monolith. This is depicted in FIG. 4.
The outside surface of the monolith can still serve as an effective catalytic surface. During operation, good heat transmission can be provided in order to avoid overheating of the catalyst. In the present invention, in which the monolith is positioned in the metal housing without insulation, a large portion of the reaction heat can be transmittedthrough the wall of the housing. Cooling effects can be enhanced by providing cooling vanes or ribs on the housing.
This invention has several advantageous features. First of all, the adverse effects of mechanical shock are minimized because of the method of construction of the apparatus of this invention. Furthermore, the sequence of rapid impulses of exhaust gases from an internal combustion engine can be absorbed by the device of this invention without damage to the monolith or apparatus. Additionally, since the ceramic monolith is not in direct contact with a metallic surface, the differences in thermal expansion properties for the ceramics and metals is not troublesome.
What is claimed is:
1. An apparatus for cleaning an exhaust gas comprising an elongated metal housing capable of receiving a catalyst ceramic monolith, said housing provided at one end with an exhaust gas entry opening, and provided at the other end with an exhaust gas discharge opening, at least two bridge means spaced apart within said housing and attached to said housing, at least one supporting rod for said monolith, said rod secured to one of said bridge means and movably mounted on another of said bridge means, a ceramic monolith catalyst element having flow channels for conveying the exhaust gas from the entry opening to the discharge opening and at least one bore for receiving said at least one support rod and the largest cross-sectional dimension of said ceramic being smaller than the adjacent respective internal cross-sectional dimension of said housing to form a space therebetween, said bore being provided in the direction of said flow channels, and an elastic, intermediate layer surrounding said at least one supporting rod and held thereon by said layer being under pressure.
2. An apparatus according to claim 1 in which one of said bridge means is positioned near said gas entry opening and one of said bridge means is positioned near said gas discharge opening.
3. An apparatus according to claim 1 in which said elastic, intermediate layer is a web of wire, spun glass, alumina-silica fibers, rock wool or asbestos wool.
4. An apparatus according to claim 1 in which sealing means are provided in said space between said housing and said monolith.
5. An apparatus according to claim 4 in which said sealing means comprises a gasket or a labyrinth.
6. An apparatus according to claim 4 in which the flow channels of the monolith are of substantially equal diameter and said space is less than about one-half of the diameter of a flow channel.
7. An apparatus according to claim 1 in which one of said bridge means is positioned near said gas entry opening and another of said bridge means is positioned near said gas discharge opening, and one end of at least one of said rods is attached to the bridge means near said gas entry opening and the other end of said rod is movably mounted on the bridge means near said gas discharge opening.
8. apparatus according to claim 7 in which sealing means comprising a gasket or a labyrinth are provided in said space.
9. An apparatus according to claim 8 in which said elastic, intermediate layer is a web of wire, rock wool,
asbestos wool, spun glass or alumina-silica fibers.