Note: Descriptions are shown in the official language in which they were submitted.
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1 filter Sector, Decal Stt-ip and Shower System for Disk filters
2
3 BACKGROUND OF THE INVENTION
4
FIELD OF THE INVENTION
6 [0001] The present invention relates to disk filters
7
8 DESCRIPTION OF THE PRIOR ART
9 [0002] Disk filters are well known, and are used, for example, in the pulp
and paper industry
and the ore processing industry. In the pulp and paper industry, disk filters
are frequently used to
11 dewater (i.e. remove water from) wood and paper fibres. Typically, a disk
filter comprises a
12 housing and a series of filter discs, each of which is made up of a
plurality of filter sectors. The
13 filter discs are mounted on and in fluid communication with a central
conduit adapted to rotate
14 within the housing. A slurry is introduced into the housing, and suction is
applied to the central
conduit, causing a layer of material to adhere to the filter discs. As the
disks rotate out of the
16 slurry, vacuum draws water from the slurry and the (now dewatered) material
can be peeled
17 away from the filter by means of a knock off shower system and collected
for further processing.
18 A further set of shower bars are typically disposed in the housing to
assist in cleaning material
19 accumulated on the disks. These are called cleaning showers and are
oscillating or fixed.
[0003] One problem associated with disk filters is that of "rewetting" of the
material
21 accumulated on the filter membranes. Water that remains in a filter sector
as it rotates out of the
22 slurry, or that has drawn out of the dewatered material, can pass back
through the filter
23 membrane as it drains and therefore pass back into the layer of material
that was just dewatered
24 This can sometimes prematurely cause the sheet to be peeled from the
sector.
[0004] Also, because filter discs are typically large and are therefore
subjected to significant
26 radial & axial forces, it is necessary to provide adequate structural
strength for the disc whilst
27 retaining the functionality of the disc.
28 (0005] A ftuther problem associated with disk filters is that the nozzles
of the shower bars
29 tend to become obstructed as small particles or pieces of material become
lodged therein. This
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1 necessitates frequent interruptions of the process so that the shower bars
can be cleaned, which is
2 costly and inefficient.
3
4 SLIwiMARY OF THE INVENTION
[0006] In one aspect, the present invention is directed to a filter sector for
a disk filter. The
6 filter sector has a root for securing the filter sector in fluid
communication with a central conduit
7 of a disk filter and a tip remote from the root. The filter sector includes
a pair of oppositely
8 directed filter support faces. The faces define a substantially open
interior volume. The faces
9 diverge from one another from the tip end to the root of the filter sector.
The sides of the sectors
are defined by radial flanges extending along the side edges between the tip
end and the root.
11 The radial flanges are defined by progressively overlapping flanges of
angle members secured to
12 one another.
13 [0007] In another aspect, the present invention is directed to a decal
strip arrangement for
14 securing filter sectors in a filter disk. The decal strip arrangement
includes a plurality of decal
strips, each of which includes an elongate channel dimensioned to fit over the
tips. The decal
16 strips are arranged as a hoop with each strip bridging a pair of adjacent
sectors.
17 [0008] In another aspect, the present invention is directed to a disk
filter. The disk filter
18 includes a housing, at least one filter disk mounted to rotate within the
housing, at least two
19 collection chutes disposed adjacent each at least one filter disk, and
generally two shower
systems for directing material that has accumulated on the at least one filter
disk toward a
21 collection chute and for cleaning the filter. The shower systems includes a
main shower header
22 connectable in fluid communication with a source of fluid and at least two
shower bars. Each of
23 the shower bars is connected in fluid communication with the main shower
header. Each shower
24 bar is movable between a first position in which it is disposed
substantially within the housing
and proximate to at least one filter disk for applying a spray of fluid to
that at least one filter
26 disk, and a second position wherein the shower bar is disposed
substantially outside the housing.
27 The housing can be substantially closed when any shower bar is in either
the first position or the
28 second position.
29
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1 BRIEF
DESCRIPTION
OF THE
DRAV~1NGS
2 [0009] An embodiment of the invention will now be described by
way of example only with
3 referenceto the appended drawings wherein:
4 [0010] Figure 1 is a side sectional view of a disk filter;
[0011] Figure 2 is a front sectional view of the disk filter of
Figure 1 one the line II-II;
6 [0012] Figure 3 is a front perspective view of a filter sector;
7 [0013] Figure 4 is a cross-sectional view of the filter sector
of Figure 3 taken along the line
8 IV-1V.
9 (0014] Figure 5 is a cross-sectional view of the filter sector
of Figure 3 taken along the line
V-V.
11 [0015] Figure 6 is a cross-sectional view of the filter sector
of Figure 3 taken along the line
12 VI- VI.
13 [0016] Figure 7 is a cross-sectional view of the filter sector
of Figure 3 taken along the line
14 VII-VII.
[0017] Figure 8 is a front view of twb adjacent filter sectors
of Figure 3 being assembled to
16 form a disc;
17 [0018] Figure 9 is a perspective view of a decal strip used in
the assembly of Figure 8;
18 [0019] Figure 10 is an enlarged view of the interconnection of
a pair of decal strips;
19 (0020] Figure 11 is a perspective view of a portion of the housing
of the disk filter showin in
Figure 1.
21 [0021] Figure 12 is a perspective view of a portion of a housing
for a disk filter with cleaning
22 shower bars in a first position;
23 [0022] Figure 13 is a perspective view on an enlarged scale of
the cleaning shower bar of
24 Figure 12;
[0023] Figure 14 is a perspective view of a portion of an alternative
embodiment of a shower
26 bar;
27 (0024] Figure 1 S is a view showing the shower bar of Figure 14
in a deployed position.
28 [0025] Figure 16 is a view similar to Figure 15 showing the shower
bar in a withdrawn
29 position.
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1 DESCRIPTION OF THE PREFERRED' EMBODIMENTS
2 [0026] With reference to Figures 1 and 2, a disk filter is indicated
generally at 1000. The
3 disk filter 1000 comprises a housing 10012 and a plurality of filter discs
1004 mounted co-axially
4 on a hollow central conduit 1006. As rain be seen in Figure 2, each filter
disk 1004 is made up
from a plurality of individual filter sectors 1008 mounted to the central
conduit 1006. The
6 interior of each sector 1008 is connected to the interior of the central
conduit 1006 by fluid
7 passages 1010. The front and rear surface of each filter sector 1008 carries
a filter membrane
8 1012 that allows fluid to flow to the interior but inhibits passage of
fibre. A motor 1014 rotates
9 conduit and thus the filter disc 1004 within the housing 1002. The conduit
1006 is connected to
a vacuum source that is selectively connected to the interior of each segment
as it rotates.
11 Collection chutes 1016 are aligned with each filter disk 1004 and extend
through the bottom of
12 the housing 1002 to a removal path 1017. Two sets of shower bars 1018, 1019
are disposed
13 above the filter disc 1004 to spray on to the disks and remove the fibre.
One set, 1018 is used to
14 remove product from the sector and the other set, 1018 is used to clean any
remaining product.
[0027] In operation, a volume of slurry 1020, for example a slurry of water
and wood or
16 paper fibres, is directed into the housing 1002. As can be seen in Figures
1 and 2, the collection
17 chutes 1016 extend well above the level ~of the slurry 1020. Suction is
applied to the central
18 conduit 1006 and as the filter discs 1004'rotate through the slurry 1020,
the suction draws the
19 slurry towards the submerged filter sectors 1008. This causes a layer of
material, in this case
fibres, to accumulate on the filter membrane 1012 as the water is drawn
through the filter
21 membrane 1012, in the filter sector 1008 and through the fluid passage 1010
into the central
22 conduit 1006.
23 [0028] As the filter discs 1004 continues to rotate, the filter sectors
1008 that were
24 submerged in the slurry 1020 emerge intb the atmosphere within the housing
1002, with the layer
of fibres still adhered to the filter membrane 1012. The suction applied
through the conduit 1006
26 draws liquid through the membrane 1012 to reduce the water content of the
fibres as they rotate.
27 As a sector rotates, the suction is removed from the interior of that
segment and when the filter
28 sectors 1008 rotate into alignment with the knock off shower 1018 and the
collection chutes
29 1016, fluid spray from the shower 1018 assists in peeling the fibre layers
away from the filter
membranes 1012 and fall into the collection chutes 1016. The (now dewatered)
fibres then fall
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1 by gravity down to the fibre removal path 1017, where the fibres are then
conveyed by an
2 appropriate mechanism, such as a screw knot shown) to another location for
further processing.
3 Continued rotation of the disc brings the', sector to the cleaning shower
1019 which removes any
4 remaining fibres from the filter membral~e 1012.
6 FILTER SECTOR
7 [0029] As best seen in figure 3, each of the filter sectors 1008 has a body
10 with an inner
8 end or root 12 located adjacent to the colriduit 1006 and a radially outer
tip 11. The body 10 has
9 oppositely directed front and rear faces 14, 15 that converge from the root
12 to the tip 11 and a
pair of side faces 24 that interconnect thd front and rear faces 14, 15.
11 [0030] The faces 14, 15, 24 define a hollow interior 19 and radial ribs 16
extend between the
12 front and rear faces 14, 15 to provide additional support. The ribs 16 and
side faces 24 are
13 interconnected by lateral supports 18 to define and open core for the body
10. The lateral
14 supports 18 are offset from one another can the faces 14, 15 to rrlinimise
impediment to follow
within the interior 19. The root 12 is provided with a gusset 20 to enhance
the structural rigidity
16 of the inner end. A flange 22 extends from the gusset 20 to provide a
mechanical connection to
17 the central conduit 1006.
18 [0031] The side faces 24 and ribs 16 are formed from a pair of overlapping
angle pieces 30,
19 32 each having a pair of flanges 34, 36. The flanges 36 overlap one another
in an axial plane
with the overlap increasing from the rood 12 to the tip 11 to define tapered
channels extending
21 from the tip to the root. The angle pieces 30, 32 are typically made of
stainless steel and are spot
22 welded to one another at spaced intervals along their length. The angle
pieces thus provide
23 tapering open channels extending from the tip 11 to the root 12.
24 [0032] The lateral supports 18 are also made of L-shaped stock oriented to
have one flange
21 lying in the plane of front or rear face 14, 15 and the other 23 projecting
axially into the
26 interior. The convergence of the faces 14, 15 causes the flange 23 to be
downwardly and
27 inwardly inclined to promote the flow ofwater into the cavity 19. At the
intersection of the ribs
28 16 and lateral supports 18, the flange 23 bf the stock is folded flat
through a piercing and coining
29 operation so that a generally planar suppprt grid is formed on each face
14, 15 to support the
membrane 1012. The membrane 1012 extends to the gusset 20 which is dimensioned
to extend
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1 radially beyond the collection chute 1016. This permits the membrane 1012 to
be terminated at a
2 position to avoid contact with the chute.
3 [0033] The tips 11 of the sectors 1008 are connected to one another by a
hoop structure
4 formed from interconnected decal strips '100 as best seen in figures 8, 9,
and 10. Bach of the
decal strips 100 is formed from a channel member 102 dimensioned to fit over
the tip 11 of the
6 sectors 1008. The channel member 102 is cranked at its mid point, as
indicated at 104, to
7 conform to the transition between adjacent sectors 1008. A slot 106 is
formed in the channel
8 member 102 at one end and a connector 108 extends from the opposite end. The
connector 108
9 is a channel member sized to fit over the channel member 102 and has a
transverse hole 110
extending through the side walls. The hole 110 is positioned to align with the
slot 106 of an
11 adjacent decal snip 102 to allow the members to be connected into a hoop.
In some
12 embodiment, the tips of the sectors 1008' are curved with a uniform radius,
in which case the
13 decal strips 100 are not cranked but are c~f complementary uniformly curved
formation to bridge
14 adjacent sectors.
[0034] When assembled on the filter wheel, each decal strip 100 is placed over
the tips of a
16 pair of adjacent sectors so as to bridge the sectors. The decal strips are
connected end to end
17 around the periphery of the wheel by a bolt 112 that passes through the
slot 106 and hole 108.
18 The bolt 112 also passes through a hole 113 in the tip 11 and is secured by
a nut 114 that is
19 preferably a single use aircraft nut that is suitable for use in corrosive
environments. With the
decal strips 100 secured, an outer hoop i$ provided that mechanically connects
the sectors 1008
21 and inhibits relative movement.
22 [0035] In the operation, as the filter disc rotates the bending stresses
imposed on individual
23 sectors is distributed through the decal strips into the adjacent sectors.
The converging faces 14,
24 15 also assist in preventing water from pissing back through the membrane
as it moves towards
the vacuum conduit 1006. The channel formed by the overlapping angle members
in the sides
26 and ribs in directing water to the outlet v~iithout contacting the membrane
and the lateral supports
27 18 similarly provide an open structure that does not impede the flow of
water with the vane.
28
29
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1 SHOWER SYSTEM
2 [0036] As noted above, a disk filter includes a housing and a plurality of
showers 1018, 1019
3 for assisting in the peeling of accumulated material away from the filter
membrane of a filter
4 disk so that the material falls into a collection chute and for cleaning the
fabric to begin another
cycle. Now referring to Figure 11, the housing 200 comprises a main housing
body 202 and an
6 access door 204.
7 (0037] Each of the showers 1018, 1019 includes a plurality of shower units
206 connected at
8 spaced intervals to a header 208 extendirng along the exterior of the
housing 202. Each of the
9 shower units 206 is similar in construction and therefore only one will be
described in detail.
[0038] Each of the shower unit 206 teas a U-shaped stand pipe 210 including a
shut off valve
11 212. A quick connect coupling 214 is disposed a the end of the stand pipe
for connection to a
12 shower bar 216. The coupling 214 may be of any convenient known
construction such as a cap
13 and groove or a ball and groove connectpr.
14 [0039] The shower bar 216 projects through an aperture 218 provided in the
door 204. In the
case of the shower 1018, the shower bar '216 terminates in a nozzle 218
positioned adjacent one
16 of the filter disks to assist in peeling awaly the fibre mat. In the case
of the shower 1019, the
17 shower bar has a plurality of nozzles 218 disposed along its length and
projeting in opposite
18 directions onto adjacent filter disks.
19 [0040] If a nozzle 218 becomes blocked and requires routine maintenance,
the shut off valve
212 may be closed to isolate the shower bar 216 which may then be released
from the coupling
21 214. The shower bar may then be pulled from the housing 202 through the
aperture and
22 appropriate repairs or maintenance perfo~ned. During this time, the filter
disk may continue to
23 rotate and thereby avoid costly shut down of the production line. In order
to replace the shower
24 bar 216 it is simply necessary to insert it through the aperture and again
engage the quick release
coupling 214. The supply can then be reconnected with the valve 212.
26 [0041] A further embodiment is shown in Figures 14 through 16 in which like
reference
27 numerals will be used with a suffix 'a' far clarity. In the particular
embodiment shown in
28 Figures 14 to 16, the shower bars 210a axe connected to the main shower
header 208a so as to be
29 pivotable relative thereto. As can best b~ seen in Figure 14, at each
location on the main shower
header 208a where a shower bar 210a is !to be attached, a stand pipe 210a
protrudes from the
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1 main shower header 208 and terminates ~t a 90° elbow 220. A
compression tee 222 or similar
2 mechanical disconnect device is secured I,to the elbow 220 by way of a nut
224, which
3 arrangement permits the compression tee 222 to pivot relative to the elbow
220. A handle 226 is
4 secured in one opening in the compressi4n tee 222, and a shower bar 210a
having a plurality of
nozzles 218a is secured in the other branich of the compression tee 222. The
elbow 220 includes
6 a shut off valve (not shown) to isolate eaich shower bar, and the nut 224
can be loosened to allow
7 the shower bar 210a to be pivoted, and tiightened to secure the shower bar
210a in the desired
8 position.
9 [0042] The door 204 can be opened end closed when the shower bars 21 Oa are
in the first
position as shown in Figure 15. When the door 204 is open, the shower bar 210a
can be pivoted
11 from the first position shown in Figure 15 to the second position shown in
Figure 16. As can be
12 seen clearly in Figure 16, the door 204 c~.n be closed when the shower bars
210a are in the
13 second position inside the housing 200. Thus, the housing 200 can be
substantially closed when
14 any shower bar 210a is in either the first position or the second position.
The door 204 includes
cut outs 226 to accommodate the connedtions between the shower bars 210a and
the externally
16 mounted main shower header 208. Despite these recesses 226, the housing
remains substantially
17 closed in the sense that the filtration process can continue.
18 [0043] When a disk filter is in operation, all of the shower bars 210a will
ordinarily be in the
19 first position, that is, disposed substantially within the housing 200, and
the disk filter will
operate as described above. When the npzzles of one or more of the shower bars
210 become
21 obstructed, the disk filter does not have to be stopped. The relevant door
or doors 204 can be
22 opened and the affected shower bar or b~.rs 210 can be moved into their
second position outside
23 of the housing 200. The door or doors 204 are then closed. The affected
shower bar or bars 210
24 are then isolated using the shut off valve in the elbow 220. The remaining
shower bars 210 will
continue to function while the affected shower bars 210 are cleaned or
replaced. The clogging
26 of any shower bar will thus require no interruption to move that shower bar
into its second
27 position outside the housing, where it cats be cleaned without affecting
operation of the other
28 shower bars.
29 [0044] The pivotal arrangement of t)~e shower system described above is
exemplary only, as
there are many arrangements by which tie shower bars can be connected in fluid
communication
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1 with the main shower header so as to be provable between a first position
wherein the respective
2 shower bar is disposed substantially within the housing, and a second
position in which the
3 shower bar is disposed outside the housing.
4 [0045] Although the invention has been described with reference to certain
specific
embodiments, various modifications thereof will be apparent to those skilled
in the art without
6 departing from the spirit and scope of the invention as outlined in the
claims appended hereto.
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