Note: Descriptions are shown in the official language in which they were submitted.
1(~8~769
The present invention relates to a housing for a monolithic
automobile exhaust catalyst.
A monolithic catalyst comprises a fragile ceramic catalyst
body having a plurality of openings extending axially through it,
and a coating of a precious metal catalyst on the walls around
those openings. One kind of housing for such bodies is disclosed
in German Patent 2,213,539. In that kind of housing, there is
a layer of mineral fibers between the body of the catalyst and
the housing, which envelops the body of the catalyst. Parts of
the layer of mineral fibers are in the shape of rings which are
positioned between the facing ends of the catalyst and the
housing. Therefore, shocks transverse to the direction of flow,
and also shocks in the direction of flow may be absorbed by the
layer of mineral fibers. In addition, the space between the
catalyst body and the housing is sealed. The layer of mineral
fibers is compressed only radially in the area of the periphery
' of the catalyst body and only axially in the areas between the
facing ends of the catalyst body and the housing. Because of
the limited elasticity of the fiber material layer, it cannot
cope with greater strains of shock, it may develop a permanent
compression and thus result in a loosening of the support of the
catalyst body.
Another mechanism is disclosed in German Patent 1,467,507.
in which the catalyst body is mounted in the housing by an
elastic, corrugated part made of a wire mesh, which surrounds
its peripheral surface. The wire mesh is positioned only to
` absorb shocks in a radial direction. Fixed metal rings are
positioned to hold the catalyst against axial movement, i.e.,
without resilience.
The object of the present invention is to improve the
first mentioned known mechanism in regard to its useful life and
shock resistance, and to obtain for axial shocks the damping
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characteristics which are achieved in regard to radial shocks in
the devices of the second mentioned known mechanism.
Briefly, the present invention accomplishes these
objectives by providing an insert. consisting of a mesh or
texture or some other combination of loops made of metal wire,
- between the circumference of the catalyst body and the housing,
and extending over the end of the catalyst body to form a ring
to absorb axial shocks. The housing is further characterized
in that the vertical distance of the front edge (leading edge) ;
of the catalyst body from the housing wall is smaller than the
~;~ thickness of the insert in the area between the peripheral
surface of the body of the catalyst and the housing. In
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's addition, the insert is folded at both terminal edges, that is,
the insert is doubled against itself in the area between each -
facing end of the catalyst body and the housing 1.
,4.~ By the doubling up of the terminal edges of the insert,
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~' a particularly high degree of sealing of the insert around the
front edge of the body of the catalyst is achieved. At the
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same time, this results in durably firm seating of the catalyst
body, whereby the front edges at both ends of the catalyst body
are safely supported, so that they cannot fracture.
i~ Hitherto, a prejudice has existed among experts
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`,; against direct support of the front edge of the catalyst body
~-~ by an insert made of metal wire. Experiments with such an
insert drawn, without constriction, over the front edge of the
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~ catalyst body have confirmed this concern. ~owever, it has
-', been found, contrary to the expectations of the experts, that
~, a useful life of the catalyst body, sufficient for present
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f''. requirements, can be achieved according to the present invention.
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This is accomplished because of the sealing of the insert in
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; the area of the front edges, i.e., because of the localized
compression of the front of the insert by the edge of the
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catalyst body. As a result of the fact that the front edge
is subjected to simultaneous radial and axial compression,
which eliminates free play, cracking of the catalyst body in
the area of its edges may largely be avoided. This state may
be maintained for a very long time without any loosening of
the seating of the catalyst body occurring thereby. As a
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result of the strong compression of the insert in the area of
the front edges, the mounting compensates for the slowly
- continuing rounding of the front edge of the body of the catalyst
by a corresponding relaxation of the initial stress created by
- the pressing of the front edge of the catalyst body into the
insert. The firm seating of the catalyst body thereby is
' maintained constantly, which prevents premature crumbling of ,,,;
~i its edges.
In accordance with a further feature of the present
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~ invention, the embedding of the catalyst body in the insert
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compacts the insert, in the area of the front edge of the
- catalyst body, to cause a biaxial state of stress. At the same
time it is irrelevant whether the housing is round in the area
of the front edge of the catalyst body or is conical, the
incEeased compression of the insert between the front edge of
the catalyst body and the housing controlling the stresses.
An additional advantage of this state of stress may
be achieved, according to another feature of the invention, by
supporting the front end of the insert radially inwardly by a
fixed support. The support preferably is a ring attached to the
inside of the housing.
The insert itself may be constructed in one piece,
i.e., it may envelop the catalyst body over its entire peripheral
- 30 surface, inclusive of the areas of both front edges. However,
it is within the scope of the invention, to divide the insert
into individual rings, whereby the invention would merely
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provide rings which envelop the front edges of the body of the
; catalyst, i.e., which follow partly along the peripheral surface
and partly between the facing end of the catalyst body of the
` catalyst and the housing, i.e., on both sides of the front edge.
The mounting of the catalyst body is facilitated by
the use of a housing bisected along a plane parallel to the
direction of flow. However, the use of a cylindrical housing
is also possible within the scope of the invention. In this
latter construction, at least one front side wall of the
terminal chamber is connected with the housing under axial
pressure only after the insertion of the body of the catalyst -
into said housing.
, The apparatus according to the invention will be
,i understood further from the following description, in which
reference will be made to the drawings in which: -
FIGURE 1 shows a cross-section through one-half
; of the housing and the catalyst body, the
mirror-image second half of the unit being
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omitted
FIGURE 2 shows the geometry of the annular gap between
the catalyst body and the housing,
FIGURES 3 and 4 are enlarged cross-sections of
portions of the unit showing details of the
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, corner structure.
The sectional view of FIGURE 1 illustrates two
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embodiments. The upper half, more fully illustrated in FIGURE 3,
does not include a support attached to the housing, whereas
the lower half, more fully illustrated in FIGURE A, provides
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a support member attached to the housing which abuts the insert
adjacent to the facing end of the catalyst body. In FIGURE 1,
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the housing is indicated by 1, the insert by 2, the catalyst body
~ by 3 and a support member attached to the housing by 4. The
'; flow of exhaust gas through the catalyst body takes place along
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~- the direction indicated by arrows in FIGURE 1. The catalyst
body may be circular orelliptical cross-section and the housing
` has the same shape. There is a clearance between the periphery
of the catalyst body and the housing which is of substantially
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uniform dimension, along the length of the catalyst body, except
in the regions of the corners as described below.
The raw material of the housing 1 preferably consists
of a nickel-chrome-alloyed steel with ferritic or austenitic
texture which is heat or scale resistant up to 1150C.
.
The body of the catalyst consists e.g. of the fire-
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,~ resistant, ceramic material such as magnesium silicate, aluminum
~- oxide or similar materials.
The wire used ~or the production of the insert consists
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.` preferably of a steel alloy with chromium, aluminium and/or
,~ cobalt.
The detailed illustrations in FIGURES 3 and 4 clearly
show the grooving in of the front edge 5 of the catalyst body 3
into the area of the front edge of the insert 2.
According to FIGURE 4, the end of the insert 2 adjacent
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the end of the catalyst body is supported radially by a ring 4
which extends around the inside of the housing, and which is
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~ connected with the housing wall at 7 by spot welding.
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As seen in FIGURE 3, the terminal edge of the insert 2
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- is bent back to the outside. The bent back end 8 of the insert
~ extends partly in an axial direction along the periphery of the
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catalyst body so that unintended slipping of the end of the
- insert of the outside is prevented, even without attachment of
- a supporting ring 4 as shown in FIGURE 4.
FIGURE 2 shows the geometric relationships of the
parts of the housing in relationship to the catalyst body.
The dimension ~'a" is less than the dimension "b" so that the
catalyst body compresses the insert 2 locally, forming a gronve.
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The dimension "al' is obtained by measuring the vertical (radial)
~i~; distance between the front edge 5 of the catalyst body and the
nearest place on the wall of housing 1.
A typical dimension "b" is about 4,5 mm and a typical
dimension "a" is 3,5 mm. The dimension "a" should be at most
;;; 80 % of the dimension "b". This reduction of the clearance
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~; between the housing and the catalyst body causes a localized
compression of the insert 1 in the vicinity of the corner of
the catalyst body. At the same time, the insert is compressed
to a lesser extent in the axial direction between the facing
end of the catalyst body and the housing and also in a radial
direction between the periphery of the catalyst body and the
housing. As a result of this compression, the insert is
subject to biaxial tension at the corner of the catalyst body.
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