Note: Descriptions are shown in the official language in which they were submitted.
CA 02377366 2001-12-13
Filter Device for Filtering Fluids
The present invention relates to a filter device for filtering fluids, the
device
comprising at least one filter element having an inner chamber defined by a
side wall
and a bottom for accommodating a filter cake, a feed line for feeding the
fluid to be
filtered, and a discharge line for discharging the filtered fluid.
Such filter devices are well known, e.g. from PCTIEP92/01436. They are e.g.
used
for a sterile filtration in the beverage industry.
For building up a filter tower, a plurality of filter elements (filter
carriers) are stacked
one upon the other such that a contact-pressure plate of an upper filter
element
which is formed on the bottom engages into the filter chamber of a filter
element
positioned thereunder so as to press the filter cake provided therein.
Although these known filter devices permit an exact and simple adjustment of
the
press force of the filter cake, it may turn out in some cases to be a
disadvantage due
to the vertical stacking of the individual filter elements that the weight of
the upper
filter elements acts on the lower ones, possibly resulting in slight
variations in the
press force in the lowermost element.
Furthermore, it is not easily possible in these known devices to adjust the
press
force in the individual stacked filter elements individually and, in
particular,
differently from one another, and it is also rather difficult to automate the
known
devices.
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It is therefore the object of the present invention to provide an improved
filter device
which can be used in many ways.
This object is achieved by a filter device comprising the features of claim 1.
Advantageous embodiments are the subject of subclaims
Since the filter element comprises a pressure plunger which is acting on the
inner
chamber and may e.g. serve to vary the volume, i.e. to press a filter cake
positioned
therein, the contact pressure desired for an individual filter element can be
selected
in an individual filter element, depending on the respective problems. The
pressure
plunger, however, need not necessarily be used for actually exerting pressure
on a
filter cake, or the like, but may just be used, depending on the respective
application,
for defining or adjusting the spatial volume positioned thereunder, which
might e.g.
be useful when a bioreactor is employed.
Thus this volume, or the contact pressure, is in particular selectable
independently
of the presence of filter elements positioned thereabove. Therefore, it is per
se also
possible to realize an operative filter system with only one single filter
element
according to the invention, such a system additionally offering the most
different
applications.
By contrast, in the known devices a plurality of filter elements must be
stacked one
upon the other because an upper filter element must engage into the filter
chamber
of a filter element positioned thereunder for pressing a filter cake.
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Furthermore, it is possible to adjust with a much higher accuracy the force
with which
the filter cakes are pressed in the individual filter elements because an
associated
pressure plunger is present in each individual filter element so that the
force of
compression can be adjusted in each individual filter element individually
and, in
particular, also differently with high accuracy.
A further special advantage of the filter devices according to the invention
is that
they can be automated easily by electronically or hydraulically controlling
the
individual processes such as precoating, if pre-pressed filter cakes are not
used at
any rate, filtration, purification and discharge.
The device according to the invention can be used in very different ways,
depending
on the problems, in the field of making beverages, but also in other fields in
the food
industry, and also in the chemical or pharmaceutical industry.
Hence, the term "filter device" does not only mean a filter as described above
with
respect to the prior art for the filtration of an unfiltered material, but
e.g. also means
a "reactor" used in the chemical industry, in which an unfiltered material is
not
filtered out, but in which a chemical substance (corresponding to the fluid to
be
filtered) flows into the inner chamber defined by the pressure plunger and
into a
mass supplied thereto (corresponding to the filter cake) and reacts therewith
chemically or biologically.
Use as a bioreactor, consisting e.g. of inlet layer, activated carbon layer,
outlet layer,
is also possible.
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Any desired filter aid may be used and the filter cake need also not be
precoated
specifically, but could be used in an already prefabricated manner. The use of
membranes is also possible.
The filter according to the invention can further be backwashed and
regenerated.
Since the filter cake is firmly enclosed, a backwashing is possible at a high
admissible throughput.
In summary, a filter device according to the invention allows definite and
reproducible operating conditions at high throughputs, and a simple automation
as
well as a varied use are possible in different fields of application.
Advantageously, the filter element comprises a pressure pad for acting on the
pressure plunger and a feed line for feeding a driving means into the pressure
pad
to exert a force of pressure on the pressure plunger.
This makes it possible to exert a defined pressure on the pressure plunger
which is
displaceable in the filter element by feeding, for example, preferably water
as a
driving means under pressure into the pressure pad which is positioned above
the
pressure plunger and acts thereon. Hence, the pressure exerted by the pressure
plunger on the filter cake can be adjusted easily and accurately by simply
feeding
and discharging or sucking off the water. Alternatively, in particular with
smaller filter
devices, air may also be used as a driving means.
In an advantageous embodiment, at least one lateral wall of the pressure pad
is
substantially formed from an elastic material. Due to the elasticity of the
material, the
CA 02377366 2001-12-13
driving means to be filled into the pressure pad can be received in
differently large
quantities to be able to adjust the pressure to be produced within wide
ranges.
Preferably, the lateral wall of the pressure pad is clamped between the
pressure
plunger and a cover of the associated filter element. This can e.g. be
realized in that
at least one web of the wall material completely encloses an inner area
between
cover and pressure plunger in cylindrical or frustoconical fashion and is thus
secured to the pressure plunger and the cover, for instance on an upper
clamping
ring welded to the cover, or a leakage ring, in such a manner that the
pressure pad
is sealed relative to the pressure plunger positioned thereunder, so that no
driving
water can escape and mingle with the filtrate or the unfiltered material.
Hence, in this
instance, the pressure pad is defined by the side wall whose upper end has a
cover
connection member welded or detachably secured thereto, by the pressure plate
and
by the cover.
To make the pressure pad highly reliable from a functional point of view, the
lateral
wall of the pressure pad is advantageously double-walled, i.e. equipped with
an
inner and outer wall. In this instance, a large press path of the pressure pad
can be
realized; the strength and tightness of the pressure pad can here be ensured
in a
particularly efficient manner at the same time. In this instance the inner
wall can be
clamped to an upper clamping ring secured to the cover, or the outer wall of
the
lateral wall (30, 31 ) of the pressure pad (32) can be clamped on a leakage
ring.
The pressure plunger can be moved by negative pressure into an uppermost
position in which the pressure pad is completely retracted to permit, for
example, an
introduction of a filter aid into the inner chamber for producing the filter
cake. For
instance, when one of the two lateral walls of the pressure pad is elastically
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extensible, driving water can subsequently be filled into the pressure pad to
move
the pressure plunger into a filtration position in which the fluid to be
filtered
(unfiltered matter) is passed through the filter cake. Finally, in this
embodiment the
pressure pad can be moved back again in a defined way into an uppermost
position
by discharging or sucking off the driving water out of the pressure pad in a
particularly simple manner.
In particular when the outer wall is elastic and the inner wall is inflexible,
it is further
possible in an easy and reliable way to absorb the pressure, which rises at
the
beginning of the filtering process in the filter cake, by displacing the
pressure
plunger from the pressure pad without any change in the press force acting on
the
filter cake. Moreover, the inflexible side wall of the pressure pad can also
absorb
undesired pressure impacts, thereby ensuring clearly defined filtration
conditions.
This means that, although the outer wall is implemented in an elastically
deformable
way, the inflexible inner wall has the effect that the pressure plunger
behaves like a
hard, inflexible piston which is movable into different positions.
Elastic silicone, for example, is suited as a material for forming the outer
wall. The
inner wall can be made from a coated fabric or knitted fabric, such as for
example
polyester knit or kevlar knit, depending on the strength requirements.
Especially since the wall comprises the inflexible knit, it can be ensured
that the wall
does not expand upon a counter-pressure, but can substantially be moved in one
direction only, so that pressure impacts can be absorbed without the pressure
pad
bounding back. In addition, the pressure is thereby distributed over the whole
filter
cake surface approximately evenly, resulting in a uniform pressure
distribution over
the whole filter cake surface.
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The use of silicone for the outer wall is particularly advantageous for the
reason that
silicone, as may be needed during operation and cleaning/maintenance of the
filter
device, is resistant to chemicals such as caustic soda solution, nitric acid,
H203, or
the like. At the same time, it is suited for foodstuff and also withstands hot
steam and
hot water at high temperatures.
Furthermore, said double-walled side wall makes it possible that a wide
pressure
range with a possible internal pressure of 20 bar (at an external pressure of
from 0
to 10 bar) can safely be provided due to a large displacement path of the
pressure
plunger of up to about 100 mm without any problems arising with respect to
strength
and tightness. Of course, these values can be increased in case of need.
In an advantageous embodiment, the bottom and the side wall of the filter
element
are detachably connected to one another. Since the bottom on which the filter
cake
rests in the inner chamber of the filter element can be detached from the
remaining
filter element after the filtering operation, for instance via corresponding
fastening
and releasing means, and thus also from the side wall defining the filter
cake, it is
possible to remove the filter cake in a particularly simple way and to discard
the
same in a dry state.
To this end, when bottom and side wall are detached from one another, the
pressure
pad can displace the pressure plunger - by further filling in driving means -
into a
discharge position in which the bottom is pressed open and the filter cake is
exposed, so that the cake can be discharged.
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To achieve high throughputs and to permit a simple and fast replacement of the
filter
cake in a filter element, the bottom and/or the side wall of the at least one
filter
element may be guidably arranged in a load frame. For instance, when both the
bottom and the side wall are each connected to the rods of the frame via a
laterally
projecting mounting or eyelet element, or the like, the bottom and the side
wall can
be easily guided separately along said rods, and the above-described process
of
opening the filter elements and of discharging the filter cake can be carried
out in a
particularly easy way.
To provide for high throughputs and a compact filter device in the case of
which the
installation height, the weight and the costs are kept small, a plurality of
filter
elements can easily be arranged in stacked fashion, for instance in the frame.
This
can e.g. be carried out by arranging the individual filter elements one upon
the other
(vertical filter) or side by side (horizontal filter) in a corresponding load
frame. A
horizontal arrangement has the advantage that the individual filter cakes can
be
disposed off very easily by gravitational force after the filtering process.
Advantageously, the pressure plunger comprises a pressure plate and, spaced
apart
therefrom, a perforated plate. To seal the pressure pad to be filled with
driving water
towards the filter cake, the pressure plate can be mounted as a tight plate at
the side
of the pressure plunger facing the pressure pad. The perforated plate serves,
inter
alia, to pass the fluid to be filtered therethrough into the filter cake. In
general, the
perforated plate is provided with a fine fabric to permit an encompassing of
the filter
cake and, nevertheless, to enable the unfiltered matter to flow therethrough
at the
same time.
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When a stainless steel grid is mounted in the cavity between pressure plate
and
perforated plate, a force can easily be transmitted from the pressure plate to
the
perforated plate and thus to the filter cake positioned thereunder without any
substantial deformation of the cavity that permits a uniform distribution of
the
unfiltered material over the whole surface of the filter cake.
To enable the driving water to flow in an evenly distributed manner into the
pressure
pad, the feed line for introducing the driving means comprises a driving-means
ring
channel surrounding the side wall of the filter element. A supply of the fluid
to be
filtered and a discharge of the filtrate can each take place via a ring
channel.
Generally, but not limited thereto, the inner chamber and in particular also
the filter
cake of the filter element are of a substantially rotationally symmetrical
construction
so that the driving means and the unfiltered material, respectively, can flow
in from
the side evenly via inlet lines which are evenly distributed over the
circumference of
the ring channels and are e.g. radially directed into the inner chamber of the
filter
element.
Preferably, the line for supplying and/or discharging the driving means
extends
through recess channels in the cover of the filter element or holes in the
upper
clamping ring {knitted fabric).
To generate the necessary internal pressure of up to 20 bar, but also the
necessary
negative pressure for completely retracting the pressure pad into the precoat
position, the lateral wall of the pressure pad is sealingly secured to both
the
pressure plate and the cover. In this instance, the driving means can flow
over
CA 02377366 2001-12-13
recesses produced in the cover into the pressure pad or via holes in the upper
clamping ring (knitted fabric).
In a preferred embodiment at least one leakage line passes into the space
between
outer and inner wall of the lateral wall of the pressure pad. If, due to
material fatigue
or the like, the tightness of the pressure pad should nevertheless decrease in
an
undesired manner, the driving liquid passing into the intermediate space exits
through the leakage line. This liquid can e.g. be collected in a collecting
container so
that a leak is detected immediately and it can nevertheless be ensured that
the
driving means does not contaminate the filtrate or the unfiltered matter.
Furthermore,
a second leakage pipe might be mounted for flushing the space between the
walls.
The invention shall now be explained and described in more detail with
reference to
the embodiment shown in the drawing, in which:
Fig. 1 is a schematic illustration of a lateral view of a filter device
according to the
invention;
Fig. 2 is a schematic illustration of a vertical section through a portion of
the filter
device according to Fig. 1, the plane of section intersecting the longitudinal
axis of the leakage pipe 23;
Fig. 3 is a schematic illustration of a vertical section through a portion of
the filter
device according to Fig. 1, the leakage pipe being not positioned in the plane
of section;
Fig. 4 is a section through the portion of the inventive filter device as
illustrated in
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Fig. 2, the pressure plunger being positioned in a precoat position (Fig. 4a),
a
filtration position (Fig. 4b) and in a discharge position (Fig. 4c),
respectively.
In Fig. 1, a filter device according to the invention is altogether designated
by 1. The
filter device 1 comprises a load frame 2 which is substantially in axial
symmetry
around a center axis M'. In the frame 2, four filter elements 3 are stacked
one upon
the other and inserted in a vertically guidable manner in the load frame 2 via
guide
elements (not shown) on circumferentially distributed load frame tubes 49. In
the
state shown in Fig. 1, the four filter elements 3 are enclosed between an
upper and a
lower fixation plate 46a, 46b of the load frame 2 and are fixed by
compression.
The filter elements 3 are substantially disk-shaped and configured to be
substantially
in rotational symmetry around the vertical axis M. Without being limited to
such an
arrangement, the filter elements 3 are arranged in the load frame 2 such that
their
axis M coincides approximately with the center axis M' of the frame 2.
For the sake of better illustration, the left portion of the lowermost filter
element 3 is
exposed in Fig. 1 in a schematic sectional view so that the inner structure of
a filter
element 3, which is per se not visible from the outside, can be seen. The
inner
structure will be explained in more detail in the following when Figs. 2 and 3
are
described.
A plurality of approximately vertically extending pipes 4, 5, 47 which are
each
branched off to the individual filter elements 3 and connected thereto are
arranged in
spaced-apart relationship with one another on the circumference of the frame 2
in
which the filter elements 3 are stacked, each being rotated by about
45° with respect
to the center axis M of frame 2.
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In Fig. 1, a vertically extending feed pipe 4 for feeding the liquid to be
filtered
(unfiltered matter) into the individual filter elements 3 is shown at the left
side on the
circumference of the frame 2, and a discharge line 5 for discharging the
liquid
(filtrate), which has been filtered in the individual filter elements 3, into
a collecting
container (not shown) is illustrated at the right side. A vertical pipe 47
extends at the
front for feeding and discharging the driving water into and from the pressure
pads
32 (which will be described in more detail below) of the individual filter
elements 3.
Depending on the operative requirements, the number of the pipes 4, 5, 47 may
vary, but is restricted by the fact that at least one feed pipe and one
discharge pipe
for the filtrate/unfiltered matter and one line for the driving water should
be present.
Four horizontally spaced-apart branch pipes 6 which via a valve element 7
extend
into the inlet ring channel 8 (to be described in more detail in the
following) of one of
the filter elements 3 are branched off from the approximately vertically
extending
feed pipe 4 which is connected to a source (not shown) for supplying the
unfiltered
matter. Like in the case of the feed pipe 4, individual branch pipes 6 also
extend
from the discharge pipe 5 and from the driving water pipe 47 into an outlet
ring
channel 10 and a driving-water ring channel 22, respectively, of a
corresponding
filter element 3. The flow through said branch pipes 6 can again be regulated
by a
valve element 7 mounted along the branch pipes 6.
As illustrated by lines 48 in Fig. 1, the pipes 4, 5, 47 may be composed in a
separable way of individual pipe sections, which makes it possible to displace
the
pipe sections respectively belonging to one of the filter elements 3 during
opening or
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closing of the filter elements for removing the filter cakes, namely
individually along
the guide rods 49 of the load frame 2.
With the help of Fig. 2, the inner structure of the filter elements 3 which
are stacked
one upon the other in the frame 2 according to Fig. 1 shall be described in
more
detail in the following.
A filter element 3 comprises an inner chamber 15 substantially defined by a
cover
plate 12, a bottom 13 and a cylindrical side wall 14. The bottom 13 is here
provided
with a disk-shaped base plate 16 of metal which is covered with a layer of a
coarse
fabric 17, a layer of a perforated plate 18 and a layer of a fine fabric 19.
Distributed
over the annular circumferential area of the bottom 13 and spaced-apart from
one
another, there are provided individual and radially extending outlet holes 20
which
laterally lead from the lower layer of coarse fabric (stainless steel grid) 17
of the
bottom 13 into the outlet ring channel 10 which surrounds the side of the
filter
element 3 and leads to the discharge pipe 5 shown in Fig. 1. The bottom 13 and
the
outlet ring channel 10 with the circumferentially distributed, radially
arranged outlet
holes 20 are here firmly connected to one another.
While in the embodiment illustrated in Figs. 1 to 4 the bottom 13 is sealingly
connected in a detachable way to the side wall 14 of the associated filter
element 3
by compression of all of the filter elements 3 between the fixation plates
46a, 46b in
the load frame 2, it would be possible as an alternative to detachably connect
the
bottom to the side wall 14 of the filter element 3 via a locking connection
element, or
the like, without the need for compressing all of the filter elements 3.
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In an upper portion of the filter element 3, the inlet ring channel 8
surrounds the side
wall 14. Like in the case of the outlet ring channel 10, a plurality of
circumferentially
distributed feed openings 21, of which one is shown in section in Fig. 2, lead
from
the inlet ring channel 8 radially into the inner chamber 15 of the filter
element 3. A
driving-water ring channel 22 which also surrounds the side wall 14 is
arranged
directly above the inlet ring channel 8. Openings, which are again distributed
over
the circumference, lead from said driving-water ring channel 22 into the inner
chamber 15, but said openings, without being limited to such an arrangement,
are
positioned in other sectional planes than the one shown in Fig. 2 for reasons
to be
described in more detail in the following.
Moreover, in a direction approximately perpendicular to the direction of
extension of
the driving-water ring channel 22 in the area of the section shown in Fig. 2,
a
leakage pipe 23 is passed through openings in two opposite and lateral driving-
water ring channel walls 24, 25, said passage areas of the leakage pipe 23
being
otherwise sealed to the outside.
The end of the leakage pipe 23, which is not shown in Fig. 2, leads outwards
to a
collecting container (not shown), and the other end, as shown in Fig. 2,
terminates in
the inner chamber 15 of the filter element in a hollow passage channel 26
which
passes through a cover connection member 50 projecting inwards from the side
wall.
The cover connection member 50 is welded to the upper side of the annular side
wall 14 and receives the cover 12 via a recess 51 with associated sealing ring
52 on
the upper side. The clamping element 27 surrounds the center axis M of the
filter
element 3 in ring-like configuration. The upper clamping ring 60 of the
surrounding
clamping element 27 is welded at several places to the cover 12 of the filter
element
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3. The screws of the screw connection 28 with which the leakage ring 61 is
screwed
on extend through the clamping ring 60. Although the screw connections are
preferably located in a plane different from that of the through hole 26, such
a screw
connection 28 is shown in the section of Fig. 2 for better illustration.
The bottom side of the cover connection member 50 and of the clamping element
27,
respectively, is formed by the stop surtace 29 extending in a direction
approximately
perpendicular to the side wall 14. Though not being limited to this
embodiment, the
filter element 3 is provided on the circumference of the driving-water ring
channel 22
with only one single leakage pipe 23, so that the clamping element 27 is only
provided in the area of the opening of said leakage pipe 23 with a single
passage
channel 26 (i.e. the one shown in Fig. 2) of the leakage ring 61 for a leakage
pipe. A
possible alternative would be, as already described above, the mounting of
further
leakage pipes for cleaning the space between the walls.
Furthermore, the clamping ring has secured thereto an inner and, the leakage
ring,
an outer elastic side wall 30, 31 of a double-walled pressure pad 32. The
clamping
element 27 is constructed such that the leakage ring 61 is arranged on the
upper
side of the stop surface 29 of the cover connection member 50 and the outer
side
wall 31 is clamped thereinbetween, and the inner side wall 30 is further
clamped
between leakage ring 61 and the clamping ring 60 secured to the cover 12.
The inner side wall 30 is here made from a watertight and coated knitted
fabric of
polyester which is inflexible and forms the inner wall of the pressure pad 32.
The
side wall 31 is the outer wall of the pressure pad 32 and is made from elastic
silicone.
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The two walls 30 and 31 of the pressure pad 32 are secured over the whole
circumferential portion of the annular clamping element 27 to said element 27,
thereby enclosing an inner portion of the inner chamber 15 entirely. The
passage
channel 26 of the leakage ring 61 which is connected to the leakage pipe 23
terminates in the area between the two side walls 30, 31.
The end portion of said two side walls 30, 31 which is opposite to the end
secured to
the clamping element 27 is clamped between the upper side of a planar pressure
plate 34 and a clamping ring 35 secured to said plate. The two clamping rings
35 are
of an annular shape and extend on the surface of the pressure plate 34 around
the
center axis M of the filter element 23, the rings being connected at various
places of
the ring extension by screw connections in a sealing way to the pressure plate
34.
The clamping ring 35 on which the outer wall 31 of the pressure pad 32 is
clamped is
here situated radially further to the outside than the clamping ring 35 of the
inner
wall 30 of the pressure pad 32.
Thus, an approximately frustoconical inner area of the inner chamber 15 is
created
by the extension of the inner and outer walls 30, 31 between cover plate 12
and
pressure plate 34, the inner area substantially forming the pressure pad 32.
The pressure plate 34 is here part of the pressure plunger 36 which further
comprises a perforated plate with a fine fabric coating 38 positioned
thereunder, said
perforated plate being spaced apart by a stainless steel grid 40 from the
planar
pressure plate 34. The stainless steel grid 40 is here shaped such that the
fluid filled
in through the f~ed line openings can flow through cavities provided between
the
perforated plate 37 and the pressure plate 34 over the sieve-like surface of
the
CA 02377366 2001-12-13
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pressure plunger 36 in evenly distributed fashion also into a central area of
the filter
element, and into the area located thereunder.
The perforated plate 37 with the associated fine fabric 38 tightly acts as a
circular
disk via a fixation and strip-off ring 39 of plastics, such as lauramide, on
the inside of
the side wall 14 of the filter element 3. Thus the pressure plunger 36 extends
over
the whole cross-section of the inner chamber 15. The area of the perforated
plate
with the associated fixation and strip-off ring 39, which area is the outer
one when
viewed in radial direction, is here shaped such that, when the pressure pad is
completely retracted into the uppermost position, the upper side thereof
tightly acts
on the bottom side of the cover connection member 50 which is formed by the
stop
surface 29.
For a safe fixation of the pressure plunger in the uppermost position, spacer
blocks
or the like (not shown) might additionally be secured to the upper side of the
pressure plate, said spacer blocks acting on the cover when the pressure pad
is fully
retracted into the uppermost position. Said spacer blocks have, in particular,
the
function to prevent a bending of the pressure plunger in the completely
retracted
state of the pressure pad.
The pressure plunger 36 has positioned thereunder a filter cake 41 which is
firmly
and tightly enclosed between the fine fabric 19 of the bottom 13, the fine
fabric 38 of
the pressure plunger 36 and the surrounding side wall 14. The filter cake 41
may
here have been introduced either in an already preshaped condition into the
inner
chamber 15 of the filter element 3 or, prior to the filtering process, may be
produced
by precoating filter aids, such as kieselguhr or the like, through the inlet
ring channel
8 into the inner chamber 15 of the filter element 3 only at said place.
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Fig. 3 shows a further section through the filter element 3 illustrated in
Fig. 2. The
section is positioned outside the area of the leakage pipe 23 and illustrates,
in
particular, that a plurality of circumferentially distributed driving-water
feed and
discharge passages 42 lead from the driving-water ring line 22, which
surrounds the
cover connection member 50, into the interior 15 of the filter element 3.
Specifically,
such a driving-water line passage 42 illustrated in Fig. 3 leads through a
recess or
through hole 43 in the cover 12. The driving-water line passage 42 extending
through the hole 43 terminates in the area of the pressure pad 32.
Thus, water as a driving means can be filled at a high overpressure via the
driving-
water ring channel 22 by means of a pump source (not shown) via the individual
driving-water line passages 42 into the pressure pad 32, with the water
collecting in
the area defined by the lateral inner wall 30 and being approximately evenly
distributed above the pressure plate 34. The weight, but in particular the
overpressure exerted by the amount of water filled into the pressure pad 32,
has the
effect that the filter cake 41 positioned thereunder can be pressed with a
defined
force by the pressure plunger 36. Furthermore, the water accumulating in the
otherwise completely sealed pressure pad 32 can also be sucked off again
through
the driving-water lines 47, 22, 42 by the generation of a negative pressure.
The operation of a filter device 1 according to the invention will now be
explained in
more detail with the help of Figs. 4a to 4c. Each of Figs. 4a to 4c shows a
section
through a filter element 3 according to the invention, the section showing
approximately the area illustrated in Fig. 2.
r
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At the beginning of a filtering operation, the filter element 3 is in the
precoat position
shown in Fig. 4a, in which the pressure pad 32 is fully retracted and located
in its
uppermost position. Such a complete retraction of the pressure pad 32 is
achieved
by a negative pressure by means of a pump source, not shown in the drawings,
such
as for example a water hydraulics unit which e.g. generates a negative
pressure
through the above-described driving-water lines 47, 22, 42 in the otherwise
completely sealed pressure pad 32. Since the pressure pad 32 acts on the stop
surface 29 of the cover connection member 50 in said position, the filter aid
can then
be introduced in said precoat position through the feed pipes 4, 8, 21 for
producing
the filter cake 41 in the inner chamber 15.
Subsequently, driving water is admitted into the pressure pad 32 through the
driving-
water ring channel 22. Due to the pressure at which the water is filled in,
the
pressure plunger 36 moves downwards, thereby pressing the filter cake 41 with
a
defined force.
In the filtration position shown in Fig. 4b, the fluid to be filtered can now
be filled via
the inlet ring channel 8 into the inner chamber 15 of the filter. The
unfiltered matter
which has radially been filled from various sides via the feed openings 21
into the
inner chamber 15 is distributed approximately evenly over the whole surface of
the
cavities existing between pressure plate 34 and perforated plate 37 and fine
fabric
38, respectively, thereby penetrating through the sieve-like fabric into the
filter cake
41 enclosed thereunder, passing through the filter cake and exiting in a
filtered state
in the area of the bottom 13 out of the filter cake 41. The filtered liquid is
discharged
via the outlet hole 20, the outlet ring channel 10 and the discharge pipe 5
into a
collecting container.
CA 02377366 2001-12-13
If, for example due to material fatigue, liquid passes into the space between
outer
wall 31 and inner wall 30 of the pressure pad 32, said liquid can be
discharged
through the leakage line 23 and collected in a collecting container, so that
the
imperative separation of driving water and filtrate or unfiltered matter
remains
ensured and a leak can immediately be recognized at the same time.
After the filtering operation has been terminated, the bottom is moved into
the
operative position shown in Fig. 4c. In this discharge position, the bottom 13
with the
associated discharge ring channel 10 is separated from the side wall 14 of the
filter
element 3. To achieve such a separation, the connection between bottom 13 and
side wall 14 is severed after filtration by moving the fixation plates 46a,
46b apart,
and the bottom 13 of the filter element 3 is pressed open by further
increasing the
pressure. As soon as the filter cake 41 has been exposed entirely, it can be
discharged through the now existing opening 45 between bottom 13 and bottom
side
of the side wall 14.
If a plurality of filter elements 3 are arranged in stacked fashion in a frame
2 and if
both the bottom 13 with the outlet ring channel 10 and the side wall 14 of
each
individual filter element 3 are each vertically displaceably connected to the
frame,
e.g. by mounting means, the procedure may be as follows:
First of all, as described above with reference to Fig. 4c, the bottom 13 of
the
lowermost filter element 3 is pressed open and the filter cake 41 thereof is
pushed
out. Subsequently, the rest of said lowermost element 3 may again be pushed
downwards to such an extent that it is connected to the bottom 13, for
instance by
locking. This is accomplished via the pressure plunger which, like with the
lowermost
element, now displaces the bottom in the second lowermost element via the
filter
CA 02377366 2001-12-13
21
cake thereof and thus the remainder of the lower element. Of the lowermost
element,
cover and side wall and, of the second lowermost element, the bottom and the
filter
cake move jointly downwards. Thus the filter cake of said second lowermost
element
can also be pushed out and may possibly be replaced. Finally, the process is
repeated with the filter elements positioned thereabove. Since, as described
with
reference to Fig. 1, the individual sections of the pipes 4, 5, 47 pertaining
to one
respective filter element can be separated from one another, the previously
described process can be carried out without any problems.
Thus the advantage consists in that just a free intermediate space having
approximately the thickness of a single filter cake 41 must be provided for
replacing
the filter cakes in the individual stacked filter elements 3 owing to the
filter element
components displaceably secured along a vertical axis. This means that the
installation height of the filter device according to the invention can be
kept small.
When the individual filter elements are stacked not, as has been shown, as
vertical
filters but as horizontal filters, this yields the particular advantage that a
disposal of
the filter cakes is particularly easy.
As has already been mentioned, the device according to the invention can be
used
in many different ways. It can be used not only for filtering material to be
filtered in
the food industry, but also in the chemical industry, for instance for
reaction filtration
or as a bioreactor. For instance, it is not imperative that the individual
filter elements
are exclusively interconnected, as in the described embodiment, in parallel
with one
another. In addition or as an alternative, at least some filter elements could
also be
connected in series, so that the outlet of the one filter element is connected
to the
inlet of another filter element. It is also possible - in a way different to
the one
o
CA 02377366 2001-12-13
22
described above - to supply the matter to be filtered via the ring channel 10,
which
then becomes the Ninlet ring channel", and to discharge said matter via the
ring
channel 8.
