Note: Descriptions are shown in the official language in which they were submitted.
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Disc filter and filter element for disc filter
The invention relates to a disc filter for fil-
tering water from a suspension, which filter has a
shaft and a plurality of sector-shaped filter plates
mounted discoidally around the shaft, each plate com-
prising a frame of a plate-shaped material provided
with recesses and elevations, the recesses and ele-
vations of which frame form between themselves fil-
trate channels for removing the filtered waterthrough one outlet or several outlets at the narrower
end of the filter plate inside the shaft, and filter
surfaces mounted on the frame on ~oth sides thereof,
through which surfaces the water to be filtered is
able to flow into the filtrate channels.
The invention relates further to a filter ele-
ment for a disc filter for the separation of water
from a suspension, which filter element has a sector-
shaped frame of a plate-shaped material provided with
recesses and elevations, the recesses and elevations
of which frame form between themselves filtrate chan-
nels for removing the filtered water through one out-
let or several outlets at the narrower end of the
filter plate, and a filter surface mounted on the
frame on both sides thereof, through which surface
the water is able to flow through the filtrate chan-
nels to the outlet end of the filter elPment.
Different kinds of disc filters are used in the
paper and mining industry for filtering water from a
pulp mixture or a suspension including metal and min-
eral particles either to separate the water from
these materials or to concentrate the suspension.
Such a filter comprises several filter elements, i.e.
filter plates, typically with a steady frame of met-
al, on which is fastened a separate filter surface,
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such as a filter bag or the like. The filter bag ismounted on the frame and fastened and tightened to it
in different ways, whereby the water is able to get
through ~he filter surface and flow through the chan-
nels of the frame to outlets on one side of the frameand further through the outlets out. The disc filters
comprise sector-shaped filter elements fastened
around the cylindrical shat to form an integral cir-
cumference, several such filter discs axially after
each other.
The filter bag and filter surfaces of prior art
filter elements wear and get damaged evPry now and
then so that they must be replaced by new ones. For
this, the filter element is detached from the filter
and the filter surface, such as a filter bag, mounted
thereon is removed, after which a new filter bag is
positioned on it and the element is mounted back to
its place. It is rather wearisome to detach the ele-
ment and to fasten and tighten it in place and if the
filters cGmprise several elements and several rows of
discs, a long time is needed for one replacement of
the filter elements. It also takes time to remove the
filter bags and to mount new ones, and therefore, a
replacement of the filter surfaces of the filter ele-
ments is rather expensive and time-consuming. In ad-
dition to this, costs are caused due to the fact that
the process stands still or because the production
during replacement is not as effective as at normal
operation.
Several different models of filter elements
have been manufactur~d, one of which is known from
Finnish Patent Application 883061. It describes a
filter element consisting of two perforated and
grooved plates mounted at a distance from each other,
between which plates remains a channel for a liquid
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to flow through the perforations. Ona edge of the
element has outlets for removing the liquid and the
filter surfaces of this filter element cGnsist of a
filter bag, which is mounted on the frame and shrunk
by means of heat treatment to lie tightly on it.
On the other hand, Finnish Patent 73141 and
U.S. Patent 3,948,779 disclose a solution in which
the frame of the filter element consists of a corru-
gated plate of metal or the llke. Also in this solu-
tion, the filter surfaces are formed by mounting afilter bag on the frame consisting o~ corrugated
plate and by tightening it in place by means of heat
treatment. A drawback of the prior art element struc-
tures is that the frame of the filter element must be
detached from the filter in order that the filter
surface, i.e. the filter bag, could be replaced, by
detaching at first the former and by mounting a new
one after that. Moreover, after the new filter bag
has been mounted the elements are fastened to the
disc filter by securing its frame by means of bolts
and nuts. This is difficult and time-consuming, and
such a filter element is also heavy and difficult to
handle.
The object of this invention is to provide such
a disc filter and also such a filter element for the
filter by means of which the filter elements are
simply and easily mounted and the mounting can take
place quickly in such a way that a replacement of the
filter elements as a whole will be simpler and cheap-
er than according to prior art solutions. The discfilter of the invention is characterized in that
elongated fastening means provided with fluted
grooves facing each other are fastened ~o the shaft
for each filter plate and that each filter plate is
an integral filter element, in whi~h the filter sur-
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faces a~e fastened to the elevations of the frame insuch a way that they form a substantially undetach-
able whole and that the filter plates are mounted in
place by pushing them at the sector edges into the
grooves of two fastening means and by tightening them
against the shaft.
The filter alement of the invention is charac-
terized in that the frame consists of plate-shaped
plastic provided with corrugated recesses and eleva-
tions and that the filter surfaces are fastened tothe frame, to the corrugation ribs bearing against
the filter surfaces on both sides of the frame, sub-
stantially permanently in such a way that the filter
surfaces and the frame form an integral filter ele-
ment to be replaced as a whole.
The substantial idea of ~he invention is that afilter element to be replaced as a whole has been
formed by fastening the filter surfaces, i.e. a fil-
ter cloth or a filtering mesh, to the corrugation
ribs of a corrugated frame portion formed of a plas-
tic plate in such a way that they adhere to each
other permanently and thus form a stiff filter ele-
ment to be replaced as a whole. The narrow end of a
sector of the filter element has an opening for re-
~25 moving the water flowing through filtrate channels
; formed by the corrugations. The filter is provided
with fluted grooves, into which the filter element is
pushed so that its edges remain inside the grooves.
When tightening the element in the pushing direction
: 30 by means of a tightening means, a gasket around a
water outlet or outlets is pressed around the open-
!ings leading to the outlet channels of the filter
shaft and seals them. A filter element like this is
simple and easy and cheap to manufacture, because it
can be made by a simple compression-moulding press,
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and because no machining of metal and no expensive
metal are needed, as the case is at the manufacture :-
o~ prior art filter element frames. Further, the fil-
ter surfaces, such as a filter cloth or a filtering
mesh, of the filter elemen-t can be fastened simply to
the corrugated filter element, for instance by hot
welding, glueing or in some other suitable manner,
whereby the filtering mesh or the filter cloth stif-
fens the corrugated plate and prevents it from bend-
ing, because it is supported on both sides of theplate, respectively. When such a filter element is
used, a replacement can be carried out very quickly,
because it is sufficient to detach the tightening
means, to take away the used filter element and to
position a new filter element in its place immediate-
ly. The consequence is that detrimental breaks in the
process remain rather short and extra detaching and
mounting are avoided, because it is not necessary to
detach the frame of the filter element separately and
to fasten it to the filter. Even if the filter ele-
ment realized in this way is somewhat more expensive
than a filter bag or the like alone, the total costs
are considerably less than in the present solutions,
considering the savings of working time and a reduced
loss of process.
The invention is explained in greater detail in
the enclosed drawings, in which
Figure 1 shows a filter according to the in~en-
tion schematically and a junction between a throat
portion and the disc filter, partly in section,
Figure la shows a cross-section o~ a place de-
signated L-L in Figure 1,
Figure 2 shows a filter element according to
the invention schematically and partly in section,
and
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Figures 3a to 3d show cross-sections of the
filter element of Figure 2 designated A-A to ~-D.
Figure 1 shows a part of a disc filter, com-
prising a rotating cylindrical shaft 1 and a plurali-
ty of sector-shaped filter plates, filter elements 2,
mounted rotatably around the shaft. Between a filter
element 2 and the shaft 1 there is a throat portion 3
fastened to the shaft 1. Fluted fastening means 4 ex-
tend from the junction of two adjoining throat por-
tions 3 along an edge of the sector-shaped filter
element 2 and are on both sides provided with a flut-
ed groove for mounting the filter element 2 in place.
Such a fastening means 4 is situated at each junction
of throat portions in such a way that a filter ele-
ment 2 can be mounted at each throat portion 3 sothat each of the transversally opposite edges of the
filter element 2 takes its place in the groove and
keeps the filter element 2 in place. The narrower end
of the sector of the fil~er element 2 further com-
prises a gasket 5 bearing against the edges of thethroat portion 3 and sealing an outlet of water chan-
nels or filtrate channels formed between the corruga-
tion ribs and valleys inside the filter element and
an outlet inside the throat portion 3 together. The
broader end of the filter element 2 comprises a fas-
tening iron 6 extending from edge to edge of the fil-
ter element and being at i~s ends fastened to the
fastening means 4 by a press plate 7 and a nut or a
bolt 8 in such a way that the fastening iron ~ pushes
the filter element 2 towards the shaft 1 and presses
the gasket 5 between the throat portion 3 and the
; filter element 2.
Figure la shows schematically a cross-section
of the fastening means 4 and how adjoining filter
elements 2 are positioned in the fastening means 4.
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From Figure la is seen how the fastening means 4 is
an H-shaped profile, for instance, provided with re-
spective grooves on both sides thereof. On the other
hand, filter elements 2a and 2b are at their edges
pushed into the ~rooves and then kept in place by the
edges of the groove and thus they sta~ motionless and
stable by the aid of the fastening means 4. The fas-
tening means 4 can be an H-shaped integral piece, but
it can also be manufactured of two U-shaped parts or
it can be some other part shaped and assembled
similarly, if it is only provided with a groove for
the edge of the filter element 2.
Figure 2 shows the filter element 2 according
to the invention. The filter element 2 is a corrugat-
ed plate forming a frame 9 provided with parallelcorrugations in the direction of a sector edge, which
plate is made of plastic, as polypropylene or some
other corresponding plastic material, typically by
pressing the straight plate exposed to heat between
mould pieces. A water guide groove 10 is mounted at
the other edge of the frame 9, in which the corruga-
tions end, into which groove the water flows from the
filtrate channels formed by the corrugations and
along which it flows forward into the lower part of
the filter element 2, i.e. through the openings of
the gasket 5 of the outlet end into the water outlet
channel of the throat portion shown in Figure 1 and
from there onwards. On the frame ~ and the water
guide groove 10 of the filter element 2 is mounted a
filter surface 11, which can consist of a filter
cloth manufactured of a plas~ic material or of a
me~allic filtering mesh. This filter surface is fas-
~tened to the frame 9 and to the water guide groove 10
;for instance by pressing it against the frame and the
~35 groove and by heating both the filter surface and the
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corrugation ribs of the frame in such a way that theyadhere to each other. The fastening can take place in
such a manner that the filter surface adheres to the
corrugation ribs situated on its side either over the
whole length of the ribs, or alternatively, only at
suitable distances defined in advance, but still in
such a way that it is fastened to the frame 9 perma-
nently and the rame 9 and the filter surfaces on
both sides thereof form an integral whole, i.e. an
integral whole filter element, the parts of which
cannot be separated from each other in practice. Ad-
ditionally, the filter element can comprise a rein-
forcement 12 mounted on the frame 9 to reduce a buck-
ling around its longitudinal shaft. There can be sev-
eral such reinforcements 12 or the filter element canbe made entirely without reinforcements. The reinfor-
cement 12 can either consist of the same material as
the frame or of a material di~ferent from that of the
frame and it can consist of plastic or metal, respec-
tively, according to the need of use and the forcesaffecting the filter element. Figur~s 3a to 3d show cross-sections along
lines A-A to D-D designated in Figure 2 as an example
of an embodiment of the invention. Figure 3a shows a
cross-section along line A-A in a situation in which
the filter surfaces 11 are normally in place. It
shows how the cross-section of the frame 9 is corru-
gated in such a way that the outermost corrugation in
the preferable embodiment turns subs~antially verti-
cally to the filter surfaces 11. The filter surfaces11 situated on both sides of the filter element 2 are
fastened to the corrugation ribs of the corrugated
frame 9 at points 13 by heating the filter surface 11
and the corruga-tion rib b~ pressing them simultane-
ously against each other, after which the junction
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formed is allowed to cool off.
Figure 3b shows a cross-section of the other
edge of the filter element along line B-B presented
in Figure 2, and from Figure 3b is seen how the flow
guide 10 is mounted at the edge of the frame 9 in
suoh a way that a channel lOa is formed inside it.
Correspondingly, the filter surfaces 11 are fastened
to the corrugation ribs 13 of the frame 9 and also,
if necessary, to the flow guide 10 at point 13a. The
flow guide 10 again is fastened to the corrugated
frame 9 consisting of a plate in such a way that the
distance betweén the corrugation ribs of the frame 9
and the outermost surfaces of the U-shaped flow guide
10 is substantially the same.
Figure 3c shows a cross-section along line C-C
designated in Figure 2 in the longitudinal direct~on
of the filter element parallelly with the corruga-
tions thereof. It shows how the filter surfaces 11
are fastened to the corru~ation ribs at fixed dis-
tances at the same time as they are turned over the
upper edge of the filter element preferably to sur-
round it so that a closed filter surface is formed
without a necessity of securing the filter surface 11
at the edges along the whole length of the edge por-
tion by means o continuous fastening.
A cross-section along line D-D designated in
Figure 2 is seen from Figure 3d showing how the rein-
forcements 12 are mounted to the frame 9 o the fil-
; ter element 2. The reinforcements 12 have such a
thickness that they can be fastened to the frame 9,
if necessary, for instance by hot welding or in an-
other similar manner in such a way that they sink
substantially to the level of the corrugation ribs of
the frame 9 and do not substantially project from tha
rest of the surface. It is then easy to fasten the
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filter surfaces 11 to the frame 9 of the filter ele-
ment in the manners presented.
The invention has been described above and in
the drawings only by way of example and it is in no
way restricted to it. Instead with continuous paral-
lel corrugations, the frame can be manufactured in
such a way that the corrugations run for instance
radially and continuously from the broader end of the
filter element to its narrower end. Excluding the
narrower outlet end, the edges of the filter element
can be formed at the same time as the filter element
is formed anyway, by pi-essing it in a heated state
between the moulds, and then, separate flow guides as
shown in the figure are not necessarily needed. At
the other edges of the element, except for its nar-
rower outlet end, it is possible to mount flow guides
serving as support in such a way that they circle
from the other edge of the outlet end of the element
around its broader end and back again to the other
edge of the outlet end. Instead of continuous corru-
gations, various interrupted perforated and united
corrugations can be used to facilitate and simplify
the water flow. The filter surfaces 11 can consist of
a metallic filtering mesh, which is pressed and fas-
tened by heating to the outermost parts of the sur-
face of the frame portion ei~her over the whole
length thereof or only over a par~ of their length,
for instance a~ points defined at fixed distances.
Metallic filtering meshes can as well be fastened by
glueiny along the continuous surface portions of the
whole frame portion and the metallic mesh or at suit-
able distances by means of a small amount of glue.
Moreover, the filter surface 11 can consist of a fil-
ter cloth, which is similarly fastened to the frame
portion along the surfaces being in continuous con-
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tact with the corrugation ribs either over the whole
length of the corrugation ribs bearing against the
filter cloth or at suitable distances only. If made
of a filter cloth, the filter surface can be caused
to turn around one edge of the filter element, in
which case it forms a continuous filter surface and
due to this, mesh is not needed for the whole length
of the surface. Respectively, the edges of the filter
cloth can in this case be turned on each other at one
end of the filter element and fastened to the edge,
as can be done also at the broader sector-shaped end
of the filter element. The gasket of the filter ele-
ment can in both cases be fastened to the outlet end
of the filter element by glueing, hot welding etc.
Instead of glueing and hot welding, ultrasonia weld-
ing or some other suitable method can be used for
fastening the filter surface as well as the gasket.
The gasket can, of course, be ~ounted as loose and it
can, in principle, also be fastened to the edge of
the outlet channel facing the outlets of the filter
element, but it is more reliable and secure in prac-
tice to replace the gasket at the same time as the
filter element is replaced.
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