Honeycomb body, especially a catalyst carrier body having sheet metal layers twisted in opposite directions and a method for producing the same

A honeycomb body and a method of producing the body including a stack of structured metal sheets disposed in layers at least partially spaced apart from each other defining a multiplicity of channels through which gases can flow, the stack having ends twisted in mutually opposite directions about at least two fixation points, and a jacket tube surrounding the sheets and being formed of at least one segment, the sheets having ends joined with the jacket tube.

The invention relates to a honeycomb body, especially a catalyst carrier 
body, preferably used in motor vehicles, including structured metal sheets 
disposed in layers forming a multiplicity of channels through which gases 
can flow, the sheets being surrounded by a jacket tube optionally being 
formed of a plurality of segments and the sheets being joined to the 
jacket tube by a joining technique. 
Honeycomb bodies of this kind which are used, for example, as catalyst 
carrier bodies and the problems of expansion and thermal stress arising 
with such a structure are described in European patent No. 0121174 and 
German Published, Non-Prosecuted Application DE-OS No. 33 12 944, for 
example. Various ways of overcoming the expansion problem are described 
for spirally wound layers of sheet metal brazed to one another. 
It is accordingly an object of the invention to provide a honeycomb body, 
especially a catalyst carrier body, having sheet metal layers twisted or 
entwined in opposite directions and a method for producing the same, which 
overcomes the hereinafore-mentioned disadvantages of the heretofore-known 
methods and devices of this general type and which particularly overcomes 
the problems of expansion and temperature distribution by means of a 
suitable structure, so that the service life of such catalyst carrier 
bodies can be increased, even under extreme loads. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, a honeycomb body, especially a catalyst 
carrier body, comprising a stack of structured metal sheets disposed in 
layers at least partially spaced apart from each other defining a 
multiplicity of channels through which gases can flow, the stack having 
ends twisted or entwined in mutually opposite directions about at least 
two fixation points, and a jacket tube surrounding the sheets and being 
formed of at least one segment, the sheets having ends joined with the 
jacket tube, such as by brazing or by a form-locking connection. A 
form-locking connection is one which is formed by the shape of the parts 
themselves, as opposed to a force-locking connection which requires force 
external to the parts being locked together. 
Due to the twisted or entwined shape of the metal sheets and because they 
can be connected to the jacket tube at their ends by joining techniques 
such as brazing, a very stable structure is obtained, which however is 
highly elastic in the event of expansion. 
In accordance with another feature of the invention, the jacket tube has a 
substantially round cross-section with a radius R, the fixation points are 
spaced apart, and the stack has a height h and a length L according to the 
following conditions: 
EQU (a) h=2R/n and 
EQU (b) L=n/2.multidot.R.multidot..pi. 
where n.gtoreq.2 and need not be an integer and preferably 
9.gtoreq.n.gtoreq.3. 
The stack that is twisted or entwined to form the honeycomb body must have 
the same cross sectional area as the honeycomb body being formed. As a 
result, there is always one specific length for round cross-sectional 
shapes, depending on the height of the stack which is selected. In order 
to obtain particularly elastic shapes, the stack should preferably have a 
height of one-third to one-fifth, or even one-ninth, of the diameter of 
the honeycomb body to be produced. However, other height ratios are also 
easily attainable. 
In accordance with a further feature of the invention, the jacket tube has 
an elongated cross section, and the fixation points are mutually offset 
with respect to the stack. Therefore, it is also possible to fill 
elongated round or polygonal cross sections of honeycomb bodies with 
structured metal sheets in a similar fashion. The difference in terms of 
production and in its later appearance is primarily in the disposition of 
the fixation points and possibly in the shape of the stack, as will be 
described in greater detail in conjunction with the drawings. 
In accordance with an added feature of the invention, the structured sheets 
have end surfaces being brazed to one another at least in portions 
thereof, preferably in a narrow peripheral zone thereof. Since it cannot 
be assured in all cases that each individual ply is touching the jacket 
tube at both ends, it may be helpful for the structured sheets to be 
brazed to one another in a narrow peripheral zone, to assure reliable 
retention. 
In accordance with an additional feature of the invention, the structured 
sheets are alternatingly disposed smooth and corrugated sheets. This is 
only one of many possible embodiments, since other known structures, such 
as double-corrugated structures or sheet metal plies having omega-shaped 
corrugations, may also be used. 
In accordance with yet another feature of the invention, the smooth sheets 
are slightly longer than the corrugated sheets and protrude at both sides 
beyond the corrugated sheets by a slight given length. Naturally, layering 
a stack having such sheets entails more effort than if the sheets were all 
the same length, but it is easily accomplished. In order to form such a 
structure, it is substantially easier to connect the ends of all of the 
corrugated and smooth sheets to the jacket tube by a joining technique 
such as brazing, because ends of corrugated plies of metal sheets can no 
longer slide in between the jacket tube and the ends of the smooth plies 
of metal sheets. 
In accordance with yet a further feature of the invention, the ends of the 
corrugated sheets have straight sections extending substantially centrally 
between adjacent smooth sheets. In this embodiment as well, the ends of 
all the sheet metal plies touch the jacket tube uniformly; in fact, they 
preferentially adapt to its contours, which facilitates making a firm 
connection. 
In accordance with yet an added feature of the invention, the structured 
sheets are alternatingly disposed corrugated sheets having corrugations 
forming a given small angle with one another, some of the channels formed 
by the corrugated sheets intersecting one another at the given angle, 
which is preferably substantially between 5 degrees and 30 degrees. A 
configuration of this kind is known in principle for filters from European 
patent No. 0 025 584. The use of alternating corrugated sheets with 
corrugations that form a small angle with one another, provides various 
advantages. For example, a certain crosswise mixing among the individual 
exhaust gas channels and a slightly irregular end surface, which 
distributes the pressure loss that occurs there over a short length, are 
provided. Until now it was virtually impossible to provide this kind of 
structure for spirally wound catalyst carrier bodies, because it is 
extremely difficult to make a slanting corrugation. Intermeshing crimping 
rollers with slanted teeth in fact generally deform a strip of sheet metal 
very severely, so that relatively long lengths with a fine, uniform 
slanting corrugation are almost impossible to produce. In the present 
invention, however, only relatively short lengths are needed, which can 
even be produced by a single pair of crimping rollers. To this end, metal 
sheets of predetermined length need merely be introduced alternatingly 
into a sufficiently wide pair of crimping rollers, in a position that is 
slanted slightly to one side or the other and the sheets are then united 
in a stack again following the pair of crimping rollers. Otherwise there 
are practically no changes in the method of production as compared with 
that for differently structured metal sheets, because the very small angle 
between the corrugations has virtually no other effect on the handling 
thereof. 
In accordance with yet an additional feature of the invention, the ends of 
the sheets are joined to the jacket tube by means of brazed seams 
extending substantially in circumferential direction, the brazed seams 
protruding inwardly and locking for increasing durability. The durability 
of these connections can be further increased by providing that the root 
of the weld is sunk inward somewhat, thereby additionally bringing about a 
form-locking connection between the jacket tube and the ends of the 
sheets. 
In accordance with still another feature of the invention, the jacket tube 
has an oval or irregular cross section which cannot be completely filled 
with an oppositely twisted stack of sheets, and including filler pieces 
are integrated into the stack, the filler pieces being wound or layered 
from structured sheets. Cross-sectional shapes that cannot be completely 
filled with a oppositely-twisted stack of metal sheets may be needed for 
specific applications. Irregular cross-sectional shapes and in particular 
oval cross-sectional shapes, which have more favorable stability at a 
relatively high internal pressure, can still be produced according to the 
invention. The filler pieces fill out the remaining cross-sectional area 
and can in turn be wound or layered from structured metal sheets. 
In accordance with still a further feature of the invention, the stack has 
a central region and end surfaces, and the sheets are pushed out toward 
one of the end surfaces in said central region, forming a 
quasi-round-conical end surface shape. Therefore, even a 
quasi-round-conical shape at the end surface (or a barrel or hemispherical 
shape) is attainable with the honeycomb bodies according to the invention. 
This kind of end surface shape is more favorable in some applications than 
a flat end surface, for reasons of fluidics. Although the shape resulting 
from telescopingly extending spirally wound catalyst carrier bodies cannot 
be attained exactly, still a similar effect can be attained, in fact all 
the more easily, as the height of the stack of sheets used to produce a 
honeycomb body of this kind becomes lower. 
With the objects of the invention in view, there is also provided a method 
for producing a honeycomb body, especially a catalyst carrier body, which 
comprises layering a given number of structured metal sheets with ends 
into a stack; grasping fixation points in the stack with at least one 
fork-type tool and twisting or entwining the stack in opposite directions 
with the at least one fork-type tool; providing the twisted stack with a 
jacket tube by inserting the twisted stack into the jacket tube or by 
wrapping the twisted stack with a jacket tube; and joining the ends of the 
structured sheets to the jacket tube, such as by brazing or using a 
form-locking connection. This is particularly useful for the production of 
a honeycomb body having a round cross section. 
In accordance with another mode of the invention, there is provided a 
method which comprises forming the stack with a substantially rectangular 
or parallelogram-shaped cross section, and placing the fixation points in 
a mutually offset position. This is particularly useful for a modified 
production method for elongated cross sections. 
In accordance with a further mode of the invention, there is provided a 
method which comprises placing the at least one filler piece into the 
stack and preferably into a middle region of the stack. This is 
particularly useful for producing honeycomb bodies having an oval or 
irregular cross-sectional area. Except for the introduction of suitably 
shaped filler pieces into the stack of sheets serving as a starting 
material, the method is no different from those described above. In 
principle, it would also be possible to place the filler pieces into the 
jacket tube by using a suitable introducing device after the sheet metal 
stack has been twisted or entwined in opposite directions. 
In accordance with an added mode of the invention, there is provided a 
method which comprises performing the step of joining the ends of the 
structured sheets to the jacket tube substantially in the middle of the 
jacket tube in the circumferential direction, in the event that the 
frictional forces that are already available are not adequate for the 
ensuing steps, pushing out a central region of the stack toward one end 
surface with a punch-type tool, and additionally joining the sheets with 
the jacket tube. The step of joining the ends of the structured sheets to 
the jacket tube may be performed with a brazed seam extending in the 
circumferential direction around the jacket tube. The step of additionally 
joining the sheets to the jacket tube may be performed by brazing. In this 
process although the individual sheets do turn about the sole fastening 
seam in the middle thereof if one is provided, they do not tear loose, so 
that considerable force can be exerted to attain the deformation. The 
result is an approximately round-conical, hemispherical or barrel-shaped 
end surface, and the individual channels no longer extend quite exactly in 
the axial direction of the catalyst carrier body, but this does not entail 
any disadvantages. The thus-deformed honeycomb body is secured to the 
jacket tube by a (further) joining technique such as brazing and/or 
form-locking connections of the sheets. 
It should also be emphasized that in all of the catalyst carrier bodies 
produced according to the invention, both ends of each sheet metal ply in 
principle touch the jacket tube, thereby making it possible to connect 
each sheet metal ply to the jacket tube by welding or brazing at both 
ends. 
The sheet metal plies no longer need necessarily be joined to one another, 
because as a result of the opposite winding thereof it is almost 
impossible to dislodge them from their position as long as they are firmly 
joined by brazing or welding over the entire length thereof, or at a 
plurality of points along their line of contact with the jacket. 
In accordance with a concomitant mode of the invention, there is provided a 
method which comprises performing the step of joining the ends of the 
structured sheets to the jacket tube by providing the inside of the jacket 
tube with brazing material, and heating the jacket tube from the outside 
after providing the structured sheets with the jacket tube, such as by 
means of induction coils or infrared radiation. This provides further 
advantages in terms of production. For instance, only the inside of the 
jacket tube need be provided with brazing metal, for instance in the form 
of brazing powder, paste or foil, and in the brazing operation only the 
jacket tube need be heated up to the brazing temperature. While entire 
honeycomb structures are very difficult to heat, the jacket tube itself 
can be brought to brazing temperature much more easily, for example by 
induction coils or thermal radiation. This is another substantial 
advantage in terms of production, in addition to that of the greater 
elasticity of the honeycomb body according to the invention. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
honeycomb body, especially a catalyst carrier body, having sheet metal 
layers twisted or entwined in opposite directions and a method for 
producing the same, it is nevertheless not intended to be limited to the 
details shown, since various modifications and structural changes may be 
made therein without departing from the spirit of the invention and within 
the scope and range of equivalents of the claims. 
The construction and method of operation of the invention, however, 
together with additional objects and advantages thereof will be best 
understood from the following description of specific embodiments when 
read in connection with the accompanying drawings.

Referring now to the figures of the drawings in detail and first, 
particularly, to FIG. 1 thereof, there is seen a stack 3 having a height h 
and a length L, which is formed by layering alternating plies of smooth 
metal sheets 1 and corrugated or wavy metal sheets 2. Depending on the 
manufacturing method and on the desired cross section produced, the stack 
need not necessarily be layered at the outset into a cuboid with flat 
lateral surfaces 4. Other shapes, such as parallelograms or the like, may 
be more advantageous in the production process. Such a stack 3 is grasped 
at fixation points 5, 6 by a fork or similar fixation device and twisted 
or entwined in opposite directions by rotating the fork or bending over 
the ends of the stack. In this manner a shape like that diagrammatically 
shown in FIG. 2 is produced. Sheets twisted or entwined in this way can be 
secured by a joining technique such as brazing in a jacket tube or shell 
7, producing an elastic yet stable catalyst carrier body. In principle, 
the jacket tube may also be formed of a plurality of segments, by way of 
example. In order to improve stability, the individual sheets 1, 2 may be 
brazed to one another at the end surfaces, preferably in an annular 
peripheral zone 8. In this manner, a stable structure is created even if 
individual plies should happen to not touch the jacket tube because of 
variations in length. 
In FIG. 3, a correspondingly produced catalyst carrier body can be made 
from a correspondingly longer stack of sheets 1, 2. It is only necessary 
for the fixation points 35, 36 to be offset from one another, which 
directly results in the desired cross sectional shape that fits into a 
corresponding jacket tube 37. Once again, the end surfaces may be brazed 
completely or in part, particularly in a peripheral zone 38. 
Another configuration of the sheet plies 1, 2, which is even more favorable 
from the standpoint of elasticity and stability in an elongated cross 
section, is shown in FIG. 4. Once again this configuration can be produced 
from a stack of metal sheets analogously to the above-described methods by 
grasping them at fixation points 45, 46 offset from one another. The stack 
may optionally also have an approximately parallelogram-shaped cross 
section. In the embodiment shown in FIG. 4 as well, the individual plies 
need merely be connected at their ends by a joining technique such as 
brazing in the jacket tube 47. However, joining them at the end surface, 
in particular in a peripheral zone 48, is also possible. 
It should be noted that in the illustrated embodiments of FIGS. 2, 3 and 4, 
in general smooth outer sheet plies 9, 39 or 49 of the initial stack are 
folded over against one another, so that this layer is formed of a double 
corrugated ply of sheet metal. Naturally, this can be avoided in principle 
by providing that the uppermost or lowermost sheet ply of the stack be cut 
off directly next to the fixation points. Such a provision is not highly 
significant, however, because the metal sheets are very thin in any case. 
In FIG. 5, the portion V from the peripheral region of FIG. 4 is shown on a 
larger scale. In this illustrated embodiment, the corrugated sheets 2 have 
straight sections 52 at the ends thereof, which extend approximately 
centrally between the adjoining smooth sheets 1. As a result of this 
embodiment, the ends of all of the sheets have the same play available for 
touching the jacket tube, so that they adapt to it and a firm connection 
with the jacket tube in the presence of various angles of contact can be 
more easily accomplished. 
The same result can be attained with an embodiment according to FIG. 6, 
which shows the portion VI from the peripheral region of FIG. 1. By 
shortening the corrugated sheet plies 2 relative to the smooth sheet plies 
1 by a distance d, all of the ends of the sheet plies can again touch the 
jacket tube and adapt to it. In order to permit the production of a 
uniform stack from longer smooth sheets 1 and shorter corrugated sheets 2, 
it may be advantageous to provide the ends of the smooth sheets with 
grooves having a depth d, into which crosswise rods are inserted during 
stacking, so that the corrugated sheets 2 can assume their precise 
position between the crosswise rods. 
FIG. 7 shows an alternative structure for the sheet plies of the catalyst 
carrier body according to the invention. In the FIG. 7 embodiment, both 
sheet plies 71, 72 may have corrugations, which form a small angle .alpha. 
with one another. This embodiment has the advantage of requiring no smooth 
sheet plies as intermediate plies and additionally of causing the channels 
formed by the corrugations to intersect one another and communicate with 
one another, which makes the gases turbulent and thus leads to better 
contact with the surfaces. 
FIG. 8 shows another embodiment of the invention, from which it is clear 
that oval or complicated cross sections can also be filled with sheet 
plies by using .the method according to the invention. Once again the 
catalyst carrier body basically is formed of an oppositely or contrarily 
twisted or entwined stack of smooth sheets 1 and corrugated sheets 2. The 
sheets are twisted or entwined about the fixation points 85, 86, 
analogously to the embodiment illustrated in FIG. 4. However, in order to 
enable the entire cross section to be filled up, a filler piece 81 which 
is additionally required, is inserted into the stack before or after the 
stack is twisted or entwined. Such a filler piece 81 must be pre-shaped in 
accordance with the cross-sectional area still to be filled and it can 
also be formed of structured sheets. In this manner, almost any cross 
section inside a jacket tube 87 can be filled. 
In FIGS. 9, 10, 11 and 12, suitable filler pieces are shown. The filler 
piece 81 is formed of layered smooth sheet metal strips 1 and corrugated 
sheet metal strips 2 which differ in length. In FIG. 10, the filler piece 
is produced from smooth sheet metal strips 1 and corrugated sheet metal 
strips 2 wound over one another in spiral fashion. FIGS. 11 and 12 show 
further variations that are suitable as filler pieces. 
In FIG. 13 an end view of a honeycomb body of rectangular cross section is 
shown, as an example of the numerous cross sections that can be filled 
according to the present invention. Fixation points 135, 136 are again 
offset relative to the stack and have the same spacing h from their 
respective narrow ends as well as from both long or longitudinal sides. 
However, in order to produce such a cross section, a plurality of steps 
for deforming the stack are necessary before insertion into a jacket tube 
137. 
Catalyst carrier bodies constructed according to the invention are not 
vulnerable to alternating thermal stresses and therefore can have an 
increased service life even when installed near the engine.