Apparatus for purification of waste from combustion engines

A monolithic type of catalyst carrier for the exhaust system of a combustion engine is securely held in a tubular metal housing under the variations in temperature of operation by surrounding the monolith with a jacket, which extends between the monolith and the casing, and which has a thermal expansion coefficient that is equal to or greater than the difference between the thermal expansion coefficient of the monolith and that of the metal of the casing. The tubular casing also has tubular conduits on both ends with gradually decreasing diameters as the distance from the casing increases. Packing rings are provided between the peripheral edges of the monolith and the ends of the connected tubular conduits. Preferably, also, the end peripheral edges of the monolith are further protected by a flanged metal ring of which the flanged portions extend over a portion of the periphery at the ends of the monolith.

The invention concerns an apparatus for purification of waste or exhaust 
gases of combustion engines with at least one catalyzer carrying block 
(monolith) held in a metal housing through which the waste gas passes. 
With this arrangement, the main thing is that the monolith or monoliths be 
suppported perfectly in the radial as well as in the axial direction. 
Therefore, above all, the temperature fluctuation to which the apparatus 
is subjected must be taken into consideration, whereby the exceptionally 
large difference in the thermal expansion coefficients of the different 
parts must be considered. Besides, there occurs, when the apparatus is 
built into an automobile, not insignificant stress of a mechanical kind 
from that which originates from the shaking occurring in driving to others 
which are caused by the high frequency pulsating gas flow. 
Accordingly, a series of proposed solutions have already been made in order 
to deal with the occurring problem of seating the monolith in the metal 
housing. Thus, i.e., in the proposal of German Pat. No. 1,476,507, the 
monolith is surrounded with a sheaf of corrugated material, either of 
corrugated sheet metal or of corrugated wire mesh and the monolith, as 
also the sheet of corrugated material, is reinforced on both sides of a 
front-sided flange inwardly directed from the metal housing. 
According to German Offen, No. 2,213,539, it is known to provide for 
depositing the monolith through a yieldable elastic gastight layer of fire 
resistant mineral fiber which surrounds the entire surface of the monolith 
and which, for the installation, is curved over the front sides towards 
the interior. Thereby, between the said layer and the monolith, protective 
sheath of cement or a putty mass of suitable composition is provided. 
The German Offen. No. 2,243,251, a support can be derived in which a 
ring-form part of metal strip and a sheet metal ring are provided in the 
front edge regions of the monolith. These ring-form parts are formed as 
stampings from steel, expecially stainless steel wire, which satisfies the 
requirements for satisfactorily supporting the monolith in the radial 
direction, as well as in the axial direction. 
Finally, it is known from German Offen. No. 2,245,535 to provide an elastic 
sheath for the monolith in the shape of a body formed from metal strip 
which surrounds the sheath as well as the front edge area of the monolith, 
if necessary, under residual stress, and can undergo different 
partitioning and supplements. 
While the first name state of technique is unsatisfactory because there, no 
elastic positioning in the axial direction is possible, in this direction 
the mechanical stress transferred directly from the gas current occurs; 
the other inventions mentioned offer an elastic mounting in the axial 
direction. The prior provided means are certainly susceptible to essential 
improvement; the problem to come under consideration first of all is to 
improve and simplify the proportions of the support of the monolith or 
monoliths. 
The invention solves the problem by an arrangement for purifying waste 
gases of combustion engines with at least one catalyst carrier block 
(monolith) through which the waste gas is passed and which is supported in 
a metal housing by a surrounding jacket extending between the outer 
surface of the monolith and the housing, and that this jacket consists of 
a material with a thermal expansion coefficient and/or a deflection rate 
which is greater than the difference between the thermal expansion 
coefficient of the monolith on the one hand and the metal housing on the 
other hand. 
This jacket can, e.g., consist of a so-called spring matting, which 
satisfies the aforementioned requirements as to thermal expansion 
coefficients. Felt-like products of this type, from plastics of 
essentially ceramic materials, are known, which have this type of large 
thermal expansion coefficients. 
Another possibility consists in making a jacket from a prestressed mineral 
wool body which has the necessary springiness. It is possible, e.g. to 
compress a conventional mineral wool matt having a weight of about 200 
g/dm.sup.3 several times, e.g. to a weight of 7-800 g/dm.sup.3. A jacket 
for the monolith formed from this mineral wool compressed body has the 
required properties. 
This jacket suffices to give around the monolith, as well in the radial 
direction as in the axial direction, the necessary lasting solid set at 
all temperatures. Nevertheless, in the front edge area of the monolith, 
additional thrust protection in the form of packing rings from temperature 
resistant materials, e.g. metal-asbestos, can be provided, which monoliths 
are surrounded by a split supporting and protecting ring of sheet metal, 
which is arranged essentially between the packing ring and the surface of 
the monolith. 
By a preferred embodiment, this supporting and protecting ring can largely 
span the packing ring and be provided with the flange for fitting over the 
surface of the monolith. 
In place of the packing rings of e.g. metal-asbestos, a ring formed of 
stamped tangled wire can be used which just as simply takes over the 
problem of axial thrust protection and the protection of the jacket 
against exhaust discharge.

In FIG. 1, a monolith 2 is provided in the housing 1. In place of this 
single monolith, several monoliths can be inserted in succession. The 
housing 1 is completed by two end conduits 3 and 4, which equilaterally 
diminish in cross-section to provide a connection for the tubes of the 
engine in which the apparatus is installed. 
On the radial as well as in the axial supporting of the monolith 2 in 
housing 1, a jacket 5 is provided which fills the ring space between 
housing 1 and monolith 2. This jacket consists here of a material which 
has either a high heat expansion coefficient or a springiness or 
deflection rate that secures a satisfactory seating and mounting of the 
monolith in the housing at all occurring temperatures. For this purpose, 
the jacket can consist either of a so-called spring matt which has a 
higher heat expansion coefficient than that of the steel of the housing. 
This results in that, under the heat effect, the radial bedding pressure 
on the monolith, notwithstanding the sheet metal housing has a heat 
expansion coefficient significantly higher than the monolith, is at least 
maintained and if necessary, even strengthened. 
There are known materials of ceramic or synthetic fibers which have this 
kind of properties. 
One such possibility consists of a jacket 5 of a shaped body of 
pretensioned mineral wool which has a large padding weight, such that it 
is equipped with a springiness that likewise suffices to equalize the 
expansion difference between the monolith and the sheet metal housing due 
to the different heat expansion coefficients. For this, for example, long 
fibrous basalt wool can be provided which has a density greater than 500 
g/dm.sup.3, such as sold in Germany under the trademarks "Mevo 
Steinwolle", "Basalan", "Silan", or "Kerlan". 
With the described jacketing, it is possible to support the monolith 
radially as well as in the axial direction. An additional seating in the 
axial direction is no longer required. 
Nevertheless, it is advantageous to provide packing rings 6, which are 
arranged in the end edge regions of the monolith between the monolith and 
the adjacent opposing area of the end housing conduits 3. These sealing 
rings can be made of a special material which is heat resistant to over 
1100.degree. C, e.g. a fabric or rope formed of asbestos and fine metal 
wire or also a high heat resultant metal wire knit. These packing rings 
serve essentially to reduce the exhaust on the jacket and to operate as 
protection against axial thrust. 
Between monolith 2 and the packing ring 6, a sheet metal ring 7 can be 
provided with advantageously, as shown in the drawing, largely span the 
packing rings 6 and extend, with flange 8, over a certain area of the 
surface of the monolith 2. This split, sheet-metal ring, serves to improve 
the combining of the different parts, furthermore, it centers the packing 
ring in relation to the monolith. 
With such structure, it is also possible to accomplish the seating of the 
monolith in the housing and the production of all parts independently in 
one operation and test the whole system through a definite squeezing 
pressure and then in a further independent operation, to put on the 
housing ends 3 without the possibility that any part thereof could fall 
out. 
The zone of each end 3 which cooperates with the packing ring 6 can either 
be built to connect with the housing 1 as shown in FIG. 2 or it can also 
be connected to the housing 1 as shown in FIG. 3.