Note: Descriptions are shown in the official language in which they were submitted.
CA 02483807 2011-12-09
FILTER DISC WITH PANEL SECTORS
Background of the Invention
This invention relates generally to filters for separation of liquids from
suspensions. More particularly, the present invention relates to disc filters
for separation of liquids from suspensions, in particular fiber stock
suspensions, having several filter elements which include a frame over
which a filter medium is mounted.
In one type of conventional disc filter, the filter includes a filter vat
containing the suspension to be filtered and a substantially tubular filter
core, or rotor. Sector-shaped filter elements are held by radially extending
holding devices and guides that are fixed to the filter core. The filter
elements could also be fixed to a disc filter with a rotor. The filter element
includes a frame having frame portions including a neck that could be flared
or straight, along the leading and trailing edges, and at the radially outer
side. The filter media is a porous bag that is shrunk onto the frame, thereby
defining the two outer filtration surfaces of the filter element. The bag is
fixed at the lower end by holding plates. The sector-shaped filter elements
are slid radially inward into the guides and the individual filter elements
are
connected to each other at the outer circumference by holding devices.
Accordingly, the filter elements are relatively cumbersome and heavy and
may only be replaced during relatively long machine shutdowns. In
addition, the entire filter media must be replaced if either of the filtration
surfaces is damaged.
Summary of the Invention
Briefly stated, the invention in a preferred form is a panel sector for a
disc filter for separation of liquids from a suspension. The disc filter is
rotatable about a filter axis, divided into multiple sectors, and includes a
substantially tubular filter core. The filter core has a core wall defining an
axially extending core channel, multiple core inlet fittings, and
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multiple core filtrate channels extending axially through the core wall from
the core inlet fittings to the core channel. Each panel sector comprises
front and back filter panel assemblies, a sector assembly for mounting the
front and back filter panel assemblies, and a top cap for retaining the filter
panel assemblies within the sector assembly. Each of the filter panel
assemblies includes a frame and a filter material clamped by the frame.
The sector assembly includes a radially outer, outer end plate, a radially
inner, core mounting plate subassembly for mounting the panel sector to
the disc filter core, first and second side channel subassemblies, at least
one structural member extending radially between the core mounting plate
subassembly and the outer end plate, and at least one support member
extending laterally between the first and second side channel
subassemblies. The core mounting plate subassembly has front and back
channels for receiving portions of the frames of the front and back filter
panel assemblies, respectively. Each of the side channel subassemblies
has front and back channels for receiving portions of the frames of the front
and back filter panel assemblies, respectively. The top cap includes
oppositely disposed first and second end portions and first and second
halve portions. The top cap first end portion is removably mountable to the
outer end plate of a one of the sector assemblies and the top cap second
end portion is removably mountable to the outer end plate of an adjacent
sector assembly. The first and second halve portions each have front and
back channels. The front and back channels of the first half portion receive
portions of the frames of the front and back filter panel assemblies,
respectively, mounted in the one of the sector assemblies and the front and
back channels of the first half portion receive portions of the frames of the
front and back filter panel assemblies, respectively, mounted in the adjacent
sector assembly.
The filter material may include a sheet of filter fabric and a sheet of
expanded material positioned on the downstream side of the filter fabric
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sheet to provide support to the filter fabric sheet. The expanded material
sheet is a web composed of a metal or a polymeric material forming
openings. Alternatively, the filter material may include only a stiffened
filter
fabric.
The top cap is U-shaped, having a base, a first leg and a second leg
defining a cavity. A second half portion of the outer end plate of the one of
the sector assemblies is received within the cavity of the end cap first half
portion, to form the front and back channels, respectively, of the end cap
first half portion; and a first half portion of the outer end plate of the
adjacent sector assembly is received within the cavity of the end cap
second half portion, to form the front and back channels, respectively, of the
end cap second half portion.
The sector assembly also includes first and second threaded studs
that extend radially outward from the outer end plate on either side of the
center of the outer end plate. Each panel sector further comprises first and
second nuts that are threadably mountable on the first and second
threaded studs, respectively. The base of the first and second end portions
of each top cap defines an opening for receiving a one of the threaded
studs.
The core mounting plate subassembly includes a core mounting
plate having a central opening. The core mounting plate is mounted to the
disc filter core such that the central opening provides fluid communication
with a one of the core inlet fittings. The core mounting plate subassembly
also includes front and back shrouds that extend radially outward from an
inner end, mounted to the core mounting plate, to an outer portion. The
outer portions of the front and back shrouds each have inner and outer
segments forming a shoulder on each of the shrouds. The radially inner
portion of the structural member extend between the outer segments and
are mounted to the inner segments. The structural member and the
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shoulders and outer segments of the front and, back shrouds define the
front and back channels.
The sector assembly includes multiple structural members and a
front pair of support members and a back pair of support members. Each
of the support members may have a zig-zag shape forming inner and outer
bend portions. Each of the support members extends radially between the
core mounting plate subassembly and the outer end plate and extends
laterally from a one of the side channel subassemblies to a position
substantially equidistant from both side channel subassemblies.
The support members are received in notches in the front surfaces
of the back pair of structural members and notches in the back surfaces of
the front pair of structural members. Preferably, the front surfaces of the
structural members and the front surfaces of the front pair of support
members are substantially co-planar and the back surfaces of the structural
members and the back surfaces of the back pair of support members are
substantially co-planar. Each of the structural members and each of the
support members has a radially outer end mounted to the outer end plate
and a radially inner portion mounted to the core mounting plate
subassembly.
Each of the side channel subassemblies includes U-shaped inside
and outside channel members, with the inside channel member mounted
within the outside channel member. The front legs of the inside and outside
channel members defining the front channel and the back legs of the inside
and outside channel members defining the back channel. Inner and outer
end portions of the inside channel member extend radially beyond the
outside channel member. The inner end portion of the inside channel
member of each side channel subassembly is mounted to the core
mounting plate subassembly and the outer end portion of the inside channel
member of each side channel subassembly is mounted to the outer end
plate.
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Brief Description of the Drawings
The present invention may be better understood and its numerous
objects and advantages will become apparent to those skilled in the art by
reference to the accompanying drawings in which:
5 Figure us an exploded view of a portion of a filter having sector
assemblies, filter panel assemblies, and top caps in accordance with the
subject invention;
Figure 2 is an enlarged front view of one of the sector assemblies of
Figure 1;
Figure 3 is a side view of the sector assembly of Figure 2;
Figure 4 is an enlarged end view, taken along line 4-4 of Figure 2;
Figure 5 is an enlarged sectional view, taken along line 5-5 of Figure
2;
Figure 6 is an enlarged end view, taken along line 6-6 of Figure 2;
Figure 7 is an enlarged sectional view, taken along line 7-7 of Figure
2;
Figure 8 is an enlarged side view of area 8 of Figure 2;
Figure 9 is an enlarged sectional view, taken along line 9-9 of Figure
8;
Figure 10 is an enlarged front view of the top cap of Figure 1;
Figure 11 is an enlarged end view, taken along line 11-11 of Figure
10;
Figure 12 is an enlarged front view of the outer end plate of Figure
2;
Figure 13 is an enlarged front view of one of the filter panel
assemblies of Figure 1;
Figure 14 is an enlarged sectional view, taken along line 14-14 of
Figure 13, illustrating a first embodiment of the frame;
Figure 15 is front view of a conventional disc filter;
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Figure 16 is an enlarged front view of the filter element of Figure 15;
and
Figure 17 is an enlarged sectional view, taken along line 14-14 of
Figure 13, illustrating a second embodiment of the frame.
Detailed Description of the Preferred Embodiment
In one type of conventional disc filter 10 (Figures 15 and 16), the
filter 10 includes a filter vat 12 containing the suspension to be filtered, a
substantially tubular filter core 14, and optionally a hood 16. Sector-shaped
filter elements 18 are held by radially extending holding devices and guides
20 that are fixed to the filter core 14. The filter core 14 has core inlet
fittings
22 which are integral with or affixed to the core and lead radially to the
core
filtrate channels 24, which extend axially through the core. Discharge
fittings 26 of the filter elements are slid into these inlet fitting(s). The
filter
rotates about the core axis in the direction of the arrow 28, whereby the
discharge fitting 26 of the filter element 18 is the last part of the filter
element to emerge from the suspension, preventing the filtrate from flowing
backward, away from core 14.
The filter element 18 comprises a frame 30 to which spaced apart
plates 32 are mounted. Each element 18 has frame portions along the
leading and trailing edges, and at the radially outer side. The filter media
in the form of a porous bag or the like, is shrunk onto the frame 30 and
defines the two outer filtration surfaces of the filter element. The bag is
fixed at the lower end which faces the filtrate discharge, using holding
plates. These holding plates serve at the same time as covers for the core
filtrate channels required for filtrate discharge. The sector-shaped filter
elements 18 are slid radially inward into the guides 20 and the individual
filter elements are connected to each other at the outer circumference by
holding devices 34.
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With reference to Figures 1-14 wherein like numerals represent like
parts throughout the figures, a panel sector in accordance with the present
invention is generally designated by the numeral 40. The sector assembly
42, filter panel assemblies 44 and top cap 46 comprising the panel sector
5 40 may be back-fitted into conventional disc filters 10 or utilized in
new
construction disc filters.
Each panel sector 40 includes a sector assembly 42, two filter panel
assemblies 44, and a top cap 46. The sector assembly 42 is a sturdy open
deck framework having a periphery formed by a radially inner, core
10 mounting plate 48, a radially outer, outer end plate 50, and first and
second
side channel subassemblies 52, 52' . The peripheral components of the
sector assembly 42 provide channels for mounting the filter panel
assemblies. The outer end plate 50 (Figure 12) of each sector assembly
42 is bent at the center 54, forming an angle a such that the outer perimeter
15 of the sector assemblies 42 in an assembled filter approximates a
circle.
A threaded stud 56 extends radially outward from the outer face 58 of the
outer end plate 50 on either side of the center 54.
The core mounting plate 48 (Figure 5 and 6) has multiple openings
60 for attaching the sector assembly 42 to the core and a central opening
20 62 to provide a passage for the flow of filtrate/suspension. Front and
back
shrouds 64, 64' extending radially outward from an inner end 66, mounted
to the outer surface 68 of the core mounting plate 48, to an outer portion 70
having inner and outer segments 72, 74. The front and back shrouds 64,
64' form a space 76 therebetween, where the distance DouT between the
25 shroud 64, 64's in the outer segment 74 is greater than the distance DIN
between the shrouds 64, 64' in the inner segment 72, forming a shoulder
78 on each of the shrouds 64, 64'.
The interior components of the sector assembly 42 include multiple
structural members 80 that extend radially between the outer portions 70
30 of the front and back shrouds 64, 64' and the outer end plate 50. The
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structural members 80 are sandwiched between a front pair of support
members 82 and a back pair of support members 84. Notches 86 in the
front and back surfaces 88, 90 of the structural members 80 receive the
support members 82, 84 such that the front surfaces 88 of the structural
members 80 and the front surface 92 at the front pair of support members
82 are substantially co-planar and the back surfaces 90 of the structural
members 80 and the back surface 94 of the back pair of support members
84 are substantially co-planar. Each of the support members 82, 84 has a
zig-zag shape, extending radially between the outer portions 70 of the front
and back shrouds 64,64' and the outer end plate 50 and extending laterally
across a half 96, 96' of the sector assembly 42, having inner and outer
bend portions 98, 100. Each of the structural members 80 and the support
members 82,84 has a radially outer end 102, 104 mounted to the outer end
plate 50 and a radially inner portion 106, 108 disposed within space 76 and
mounted to the inner segments 72 of the front and back shrouds 64, 64'.
With reference to Figure 7, each of the side channel subassemblies
52 includes U-shaped inside and outside channel members 110, 112. The
inside channel member 110 is mounted within the outside channel member
112, with the outer surface 114 of the base of the inside channel member
110 contacting the inner surface 116 of the base of the outside channel
member 112. The inside and outside channel members are substantially
coaxial, the inner surfaces 116 of the legs 118 of the outside channel
member 112 and the outer surfaces 114 of the legs 120 of the inside
channel member 110 forming front and back channels 122, 124. The radial
length of the inside channel member 110 is greater than the radial length
of the outside channel member 112, such that an outer end portion 126 of
the inside channel member 110 extends radially outward beyond the
radially outer end of the outside channel member 112 and an inner end
portion 128 of the inside channel member 110 extends radially inward
beyond the radially inner end of the outside channel member 112. The
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inner end portion 128 of each side channel subassembly 52 is disposed
within space 76 and mounted to the inner segments 72 the front and back
shrouds 64, 64'. The outer end portion 126 of each side channel
subassembly 52 is mounted to the outer end plate 50. In addition, the
radially outer ends 104, the radially inner portions 108, and the outer bend
portions 100 of the support members 82, 84 are mounted to the inner ends
130 of the legs 120 of the associated inside channel member 110.
Each filter panel assembly 44 may include a sheet 132 of filter fabric
and a sheet 134 of expanded material clamped within a frame 135 (Figure
13). The expanded material sheet 134 is a web 140 composed of an
appropriate metal or polymeric material forming diamond-shaped openings
142. The expanded material sheet 134 is positioned on the downstream
side of the filter fabric sheet 132 to provide support to the filter fabric
sheet
132. Alternatively, a sheet 132' of stiffened filter fabric may be used
without
1 5 an expanded material backer.
In a first embodiment (Figure 14), the frame 135 includes
substantially identical front and back frames 136, 138, which are mounted
together by a number of spot welds 152 along the periphery of the frame
135. The expanded material sheet 134 and the filter fabric sheet 132 are
clamped between the front and back frames 136, 138. In a second
embodiment (Figure 17), the frame 135 is a unitary U-shaped clamping
member 137 having a pair of legs 139, 139' that are crimped to clamp
together the expanded material sheet 134 and the filter fabric sheet 132.
The frame 135 includes a radially inner frame segment 144, a radially outer
frame segment 146, and first and second side frame segments 148, 148'.
The outer frame segment 146 is bent at the center 150, forming an angle
13, where 13 is substantially equal to angle a of the sector assembly outer
end plate 50.
With reference to Figures 10 and 11, the U-shaped top cap 46
includes a base 154 and a pair of legs 156. An opening 158 extends
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through each of the two end portions 160 of the base 154. The top cap 46
is bent at the center 162, forming an angle y, where y is substantially equal
to angle a of the sector assembly outer end plate 50.
A new filter is constructed by mounting all of the sector assemblies
5 42 to the core and then installing the filter panel assemblies 44. The
two
filter panel assemblies 44 are installed in the uppermost sector assembly
42' by inserting the first and second side frame segments 148, 148' of one
of the filter panel assemblies 44 into one of the front or back channels 122,
124 until the inner frame segment 144 of the frame 135 is received within
10 space 76 and the radially inner end of the filter panel assembly 44
contacts
shoulder 78. The second filter panel assembly 44 is installed into the other
of the front or back channels 122, 124 in the same way. The core is then
rotated until the adjacent sector assembly 42" is the uppermost sector
assembly and two filter panel assemblies 44 are installed in the subsequent
1 5 sector assembly 42" in the same manner. The filter panel assemblies 44
of the prior and subsequent sector assemblies 42', 42" are then fixed in
place by positioning a top cap 46 over the adjacent sector halves 96, 96',
with the threaded stud 56 of the prior sector assembly 42' extending
through one of the openings 158 in the top cap 46 and the threaded stud
20 56' of the subsequent sector assembly 42" extending through the other
opening 158 of the top cap 46. A nut 164 is torqued onto the two threaded
studs 56, 56' to lock the top cap 46 in place. It should be appreciated that
the outer frame segments 146 of the filter panel assemblies 44 installed on
the prior and subsequent sector assemblies 42', 42" are received within the
25 channel 166 formed by the legs 156 of the top cap 46. This process is
repeated until all of the filter panel assemblies 44 are installed.
A damaged filter panel assembly 44 may be replaced by rotating the
core until the sector assembly having the damaged filter panel assembly 44
is the uppermost sector assembly 42'. The four nuts 164, 164', 164",
30 164" locking the two top caps 46, 46' fixing the damaged filter panel
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assembly 44 to the uppermost sector assembly 42' are removed and the
two top caps 46, 46' are removed. The outer frame members 146 of the
damaged filter panel assembly 44 may then be grasped and the damaged
filter panel assembly 44 withdrawn from the associated front or back
channels 122, 124. A replacement filter panel assembly 44 is installed by
inserting the first and second side frame members 148, 148' of the
replacement filter panel assembly 44 into the associated front or back
channels 122, 124 until the inner frame segment 144 is received within
space 76 and the radially inner end of the replacement filter panel assembly
contacts shoulder 78. The two top caps 46, 46' and four nuts 164, 164',
164", 164" are then replaced, completing the repair.
