Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Process for the Manufacture of a Filter
and the Filter then Manufactured
Technical Field
The invention relates to a process for the manufacture of
a filter for liquid or gaseous media, especially for
exhaust gases of combustion engines, which consists of
one or several layers or plies or plates made out of a
mesh or network or reticulation or fabric of metal wires,
and a filter thereafter manufactured.
Back~round of the Invention
Filters are already known which consist of a plurality of
layers or plies of metal fibers which; are sintered
together. Sintering is generally done in a furnace or
oven under pressure and at a suitably high temperature,
care having to be taken at the same time that a vaccum is
present.
A disadvantage is, however, that this method or process
is relatively expensive and frequently - depending on the
medium to be filtered - there also exists the problem
that the filter plugs or clogs up. Then the filter must
either be replaced or cleaned in a costly and/or time-
consuming way.
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ummarv of the Inv ntion
The object of the present invention is therefore to
create a process or method for the manufacture or
production of a filter and a filter which is easy to
manufacture or produce and which has a good filtering
performance or capacity.
According to the invention this problem is solved in that
a filter plate consisting of a plurality of plies or
layers of wires is brought or placed between the
electrodes of a resistance welding device or unit, the
wires are pressed against one another and subsequently a
resistance welding is performed for partial joining or
connection of the wires to one another.
A filter manufactured or produced in this way can be made
in a much simpler and less expensive way than known
filters. In the process the manufacture or production can
take place in a single operation, and namely with
resistance welding devices or units of, as the case may
be, a known type. During resistance welding the
individual or single wires are welded together
essentially solely in lumps or punctiform. Due to this
they do on the one hand form a compact unit, but on the
other a high flow-through capacity is ensured, for a
multiplicity of pores or openings are available for the
filtering operation.
In a simple way, following resistance welding, the filter
body can be brought into the desired filter form or shape
and, as the case may be, be connected to several into a
filter unit.
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In an improvement of the invention provision is made for
the individual layers or plies to consist of wires having
different thicknesses. By this measure, which can be
implemented without any problems in the Production
process according to the invention, the f~lters can each
be optimally matched to the demands made upon them and to
the fields of application. They can, for example, be used
in the area of the inlet s;de of thinner and/or finer
wires, whereby in particular in the case of a gaseous
medium particles can already be held back or retained on
the surface and only a very small portion or percentage
of the -particles penetrated into the filter medium at
all.
This measure has the advantage that a reduction of the
filter performance or capacity is thereby avoided, as is
the case in the state of the art due to plugging,
clogging or fouling of the filter with corresponding
particles. On the other hand, coarser and thicker or
stronger wires in the central area and/or in the area of
the outlet side produce a corresponding strength for the
filter body. ,
It goes without saying that also any other combination
of wire thicknesses or strengths can, however, be used
where required.
In a simple way, with the process according to the
invention, wires with differing material compositions
and/or differing coatings can also be welded to one
another, which further extends or expands the range of
application of the filter according to the invention.
In particular different effects can thereby be exercised
on the medium to be filtered. For example, catalytic
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effects can be achieved, which is of great advantage
particularly for the cleaning of exhaus~ gases of
combustion engines. In this way, other environment-
polluting substances such as carbon monoxide,
hydrocarbons and nitrogen oxides can also-be removed from
the exhaust gas, for example in addition to soot
particles from a diesel engine. For this purpose i~ is
solely necessary to provide at least single plies or
layers of the filter body with coatings of platinum,
rhodium, vanadium or another material or substance with
a catalytic effect.
In a further very advantageous improvement of the
invention provision can be made for powdery, grainy or
chip-like particles to be applied to the individual
layers or plies or their wires, preferably by a sintering
operation.
Through the additionally applied particles the separating
effect is significantly increased. Due to the particles,
a distinct enlargement of the surface is achieved, with
which a many times larger adsorption area and thus a
significantly larger separating area is made available.
At the same sintering capacity the thickness of the
individual filter plies or layers can, for example, in
this way be significantly reduced.
A further advantage through the application of the
particles lies in the fact that where required, depending
upon the planned application, the particles to be applied
can also be correspondingly selected. These may, for
example, consist of metal, of plastic or of ceramic
materials or even of mixtures thereof.
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In an application as a catalytic converter body,
particles are used, for example, which have catalytic
properties, such as platinum, rhodium or vanadium.
The particles themselves can be introduced into the
filter body in any way desired. For example, they can be
introduced through a viscous carrier liquid; likewise
shaking-in is possible or an introduction by means of an
electrical and/or magnetic charging of the layers or
plies and a subsequent doping with the particles.
In case-of need the sintering operation can be selected
so that in addition to a sintering-on of the individual
particles onto the layers or plies or wires, the wires
are also sintered at points or spots to one another and
in this way form a more stable unit or whole.
Resistance welding of the wires to one another can take
place in different ways.
If plates or bodies of a well-defined or definite size
are manufactured, for production in one single operation
electrodes can be provided, which are at least as large
as the filter plate to be formed. If then the filter
plate or body to be welded is brought between the two
electrodes, nears the electrodes to each other and
presses the individual or single layers or plies, a
filter plate or body of a well-defined or definite size
can be produced in one single operation.
In the same way, the manufacture of a plurality of plates
or bodies from one band or strip is possible, which is
then pushed through stepwise or cyclewise between the
electrodes. In this way any desired size of filter plate
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can be obtained by an appropriate separation of
individual plates or units.
If the electrodes are formed as rotating rolls, a band or
strip of any desired length can be formed in a continuous
operation, with this having to be pulled through between
the two oppos,ng rolls solely under pressure.
A very advantageous and not obvious improvement of the
invention consists in that the wires are pressed, prior
to resistance welding, out of their in general round or
circular cross-sectional shape into a flat shape and
namely preferably into an at least approximately
rectangular form or shape. In this way one obtains a
considerable surface enlargement and thus a larger
filtering area and from this in turn there results a high
filtering capacity or performance. This can be achieved
with little effort or expense.
A further increase in the filtering capacity or
performance is produced if provision is made for the
flat-pressed surfaces also to be profiled~ In this way,
for example, a wave-shaped can be pressed in, with which
the surface becomes even larger.
Detailed Descri~tion of the Invention:
The following Figures show:
Fig. 1: A filter plate in a resistance welding unit
Fig. 2: The manufacture of filter plates or bodies in
a continuous production operation
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ig. 3: An enlarged representation of a deformed wire
in cross-section.
Fig. 1 shows schematically the manufacture of an
individual or single filter plate or body in a resistance
welding unit 1 with a positive electrode 2 and a negative
electrode 2, each in plate,form. The two plates or bodies
2 and 3 possess a size which corresponds to the size of
the filter plate or body 4 to be manufactured and which
lies between the two electrodes. The filter plate 4
consists of a plurality of layers or plies 6 of single or
individual wires 5, each of which are connected to the
other in every position by longitudinal and transverse
wires to form a mesh or network or reticulation or
fabric.
If the two electrode plates 2 and 3 are now brought
closer together, and a pressure is exerted on the inter-
posed filter plate or body by the electrode plates 2 and
3, with the resistance welding taking place simultaneous-
ly, the individual or single wires 5 join together in the
layers or plies. Also the individual layers 6 join
together during the welding. Thus a firm or solid and
uniform filter plate or body 4 is formed. This filter
plate 4 can subsequently be brought into the desired
filter form or shape.
Fig. 2 shows a manufacturing or production process of
plates or bodies 4 out of a continuous band or strip 40
pushed through continuously between two electrode rolls
20 and 30 under pressure in the direction of the arrow.
The band or strip is likewise built up from a plurality
of layers or plies 6 with longitudinal and transverse
wires, the only difference to the manufacturing or
production process shown in Fig. 1 being that filter
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plates or bodies can be subsequently separated from the
band or strip in the desired size and shape or form.
Fig. 3 shows the shape or form of an individual or single
wire 5, which is brought out of a wire with a round or
circular cross-section (shown in broken lines) into an
essentially rectangular form or shape prior to resistance
welding. This can be done in any desired way. As can be
further seen from Fig. 3, the effective filter surfaces
7 and 8 are also profiled in the shape of waves as inflow
and, as the case may be, outflow sides (see direction of
arrow),-resulting in a further surface enlargement.
Also shown in Fig. 3 by means of points or dots is a
doping of the layers or plies 6 or their single or
individual wires 5 with small particles 9, which are
applied to the filter surfaces 7 and 8, for example by a
"flooding-in" by means of a viscous liquid. The
connection of the particles 9 to the individual or single
wires 5 can be accomplished by a sintering operation in
a way known per se.
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