Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
FILTER SYSTEM
FIELD OF THE INVENTION
This invention relates to fluid filter systems, and more particularly to
apparatus for
releasably sealing filter elements in a filter system and in particular, self
cleaning filter
systems.
BACKGROUND OF THE INVENTION
it has been recognized that the use of a plurality of filter elements
connected together
to accommodate a high flow of fluid is preferable to using a single large
filter. Previously,
such devices used compressible gaskets, O-rings, or the like in conjunction
with male-female
fittings or tangs to effect a liquid seal between the tubular filter elements;
see, for example,
U.S. patent number 5,141,637 to Reed et al. These sealing methods may be
suitable for
small, low flow filter units which can be coupled and uncoupled by hand. In a
large filter
unit (for example, one in which the tubular filter elements are too large to
be grasped and
rotated easily, each a sealing arrangement is unsatisfactory as it is very
difficult to break the
seal between filter elements when a filter element requires replacement or
when the unit is
undergoing routine maintenance. Even in the case of a filter unit having only
one filter
element, the use of compressible gaskets to provide a seal about the filter
element within the
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unit make removal of the filter element quite difficult if the filter element
weighs more than
one hundred pounds, is vertically oriented, or both.
Prior art filter systems are difficult to service and repair because it is
typically not
possible to observe the interior of the device without extensive disassembly
of it. For large
filter units, disassembly and reassembly require relatively long shutdown
periods, the efforts
of two or more workers and the assistance of additional machinery to lift and
move various
components. Because prior devices often do not have means to readily align
components
during assembly, expensive tubular filter elements can be damaged in the
course of
maintenance or repair of such devices.
For example, U.S. patent number 4,863,598 to Drori teaches a device for
holding a
stack of filter disks using externally located rod members which are secured
at either end to
annuli which secure the disks. However, stacked filter disks may induce a
pressure drop of
approximately 25 psi (1750 kg/cmz) or more from one side of the filter element
to the other,
and therefor are not suitable for many applications, such as the high volume
filters required
by power generating plants. Furthermore, this manner of filter assembly allows
material to
become trapped between the disks. Consequently, the only effective way to
clean these disks
is to release the filter elements, separate them, clean them and subsequently
reassemble them.
Known methods of self cleaning a filter element often involve scraping or
brushing
the filter element. U.S. patent number 5,569,383 to Vander Ark, 3r. et al, PCT
patent
application number W095/00230, U.S. patent number 4,156,647 to Nieuwenhuis and
U.S.
patent number 5,614,093 to Mueggenburg et al. all teach filters which use a
rotor with
cleaning blades or brushes to scrape clean the pre-filtration side of the
filter element. The use
of scrapers or brushes for cleaning can damage the filter element either
directly or by forcing
material through the filter elements.
Other methods of self cleaning a filter element involve backwashing, i.e.
reversing the
pressure differential between the pre- and post-filtration sides of the filter
element to expel
particular matter trapped in the filter element. Typically, such backwashing
requires closing
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the main inlet and outlet valves and opening backwashing valves to reverse the
pressure
differential (see, for example, U.S. patent number 5,312,544 to Kinney).
U.5. patent numbers 4,045,345 and 5,228,993 to Drori and U.S. patent number
5,108,592 to Wilkins et al: teach filters which use a series of valves and
other mechanical
devices to automate a backwashing procedure for cleaning the filter element.
Cleaning is
accomplished by reversing the flow of water through the filter element (ie.
exposing the post-
filtration side of the filter element to a high pressure) to expel particulate
matter caught in the
filter element. In U.S. patent number 4,045,345 Drori teaches the reverse flow
is induced by
pressure at the outlet of the filter, and particulate matter is expelled
through a slotted purging
chamber which rotates, along with the filter housing, around the filter
element. U.5. patent
number 5,228,993 to Drori and U.S. patent number 5,108,592 to Wilkins et al.
teach cleaning
using a reverse flow through the filter achieved by pressure from a supply
pipe. In all of
these teachings, particulate matter is expelled from the filter element by
spraying the post-
filtration side of the filter element through rotating nozzels. The use of
spray force for
cleaning can damage the filter element either directly or by forcing material
through the filter
elements. Furthermore, all of these methods of self cleaning require the
cessation and
reversal of normal filter flow.
SUMMARY OF THE INVENTION
The present invention addresses these and other problems associated with prior
devices by providing a liquid filtration device, comprising a housing having
an inlet, an outlet
and an inner surface, the housing containing:
(i) a removable filter element having an inner face, an outer face and first
and
second flanged ends, each flanged end having a sealing surface and a rod
aperture, and the
rod apertures of the first and second ends align in a lengthwise direction;
(ii) a housing flange on the housing inner surface, the housing flange being
. sealable with the first flanged end sealing surface of the filter element;
(iii) a sealing face on the housing inner surface, the sealing face being
sealable
with the second flanged end sealing surface of the filter element;
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(iv) a rod extending in a lengthwise direction through the rod apertures, the
rod having a first rod end for releasably securing the filter element and a
second rod end
secured to the housing; and
(v) fastening means for securing the first rod end, wherein, upon securing the
fastening means, sufficient force is applied to the sealing surfaces to define
a liquid flowpath
through the inlet, through the inner face of the filter element to the outer
face of the filter
element and out the outlet.
In another preferred embodiment, the filter has a plurality of filter elements
connected
in series, and each f lter element has a first sealing surface sealable with a
second sealing
surface of an adjacent filter element. The sealing surface may be chamfered.
In a further
preferred embodiment, the filter element is cylindrical.
The invention also teaches a door on the housing and the filter elements are
removable and replaceable through the door. The door may be hinged. In a
further preferred
embodiment, the filter has removable extensions for extending the length of
the rods to the
door.
In a preferred embodiment, the filter has a plurality of rod apertures at the
first and
second flanged ends and a plurality of rods extending therethrough.
Preferably, the flowpath through the filter surface is perpendicular to the
inner face.
Preferably, the filter element comprises a structural screen and a mesh
screen, the structural
screen consisting of a rigid or semi-rigid plate having multiple apertures,
and the mesh is
fixed to the structural screen by a sintering process. Preferably, the mesh
screen is the inner
face and the structural screen is the outer face. Preferably, the mesh screen
has a mesh size of
to 40 microns.
1n a preferred embodiment the invention also has a pre-screen positioned in
the
30 flowpath between the inlet and the filter element, and a pre-screen drain
positioned in the
flowpath between the pre-screen and the inlet.
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In another preferred embodiment, the filter has a housing having an inlet, an
outlet
and an inner surface, the housing containing:
(i) a removable filter element having an inner face, an outer face and first
and
second flanged ends, each flanged end having a sealing surface, the first
flanged end having a
guide receptacle and the second flanged end having a guide projection;
(ii) a sealing face on the housing inner surface, the sealing face being
sealable
with the second flanged end sealing surface of the filter element, and the
sealing face having
a guide receptacle which receives the guide projection;
(iii) a housing flange on the housing inner surface, the housing flange having
a sealing surface;
(iv) a frame releasably secured to the housing flange; and
(iv) jack means located on the frame for applying force to the filter element,
wherein, upon the application of force from the jack means, the sealing
surfaces are
sealed to define a liquid flowpath through the inlet, through the inner face
of the filter
element to the outer face of the filter element and out the outlet.
Preferably, this embodiment also has a guide rod extending from the first to
the
second flanged ends of the filter member. Preferably, the guide rod extends
outwardly from
the second flanged end to define the guide proj ection. In another embodiment,
the filter also
has a position pin and position pin receptacles located in both the first
flanged end and the
frame, the position pin receptacles for receiving the position pin. In a
further related
embodiment, the filter also has a support structure frame located between the
first flanged end
and the frame; a position pin; and position pin receptacles located in both
the first flanged
end and the support structure frame, the position pin receptacles for
receiving the position
pin; wherein the jack means applies force to the filter element through
applying force to the
support structure frame.
In another embodiment, the invention has a runner located on the inner surface
for
receiving the guide rod.
In another embodiment, the invention teaches a filter having self cleaning
apparatus.
1n this embodiment, the filter also has a cleaning member for cleaning the
inner face of the
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filter element, the cleaning member having: a cleaning head positioned
adjacent the inner
face; a discharge aperture extending through the housing; a conduit in flow
communication
from the cleaning head to the discharge aperture; and vacuum means for
providing suction to
the conduit and cleaning head to suction material from the inner face of the
filter element,
through the conduit and out the discharge aperture. In a preferred embodiment,
the filter
element is cylindrical and the cleaning member moves rotationally. In a
further preferred
embodiment, the filter cleaning member further comprises a plurality of
cleaning heads in
communication with the conduit, the cleaning heads positioned along the
cleaning member
such that substantially all of the inner face is subjected to vacuum from the
cleaning heads
when the motor is operated. Preferably, the cleaning head is a fm nozzle.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective partially broken away view of a preferred embodiment
of the
invention.
Figure 2 is a side cross sectional view of the device shown in Figure 1.
Figure 3 is an end plan view taken along line 3-3 of Figure 2.
Figure 4 is a cross sectional view taken along line 4-4 of Figure 2.
Figure 5 is a cross sectional view taken along line 5-5 of Figure 2.
Figure 6 is a cross sectional view taken along line 6-6 of Figure 2.
Figure 7 is a detailed view taken at station 7 of Figure 2.
Figure 8 is a detailed view taken at station 8 of Figure 2.
Figure 9 is a detailed view taken at station 9 of Figure 2.
Figure 10 is a cross sectional view of some features of an alternative
embodiment of
the device of Figure 1.
Figure 11 is a detailed view taken at station 11 of Figure 10.
Figure 12 is a detailed view taken at station 12 of Figure 10.
Figure 13 is a cross sectional view of some features taken along line 13-13 of
Figure
10.
Figure 14 is a detailed view taken at station 14 of Figure 13.
Figure 15 is a side view of an alternate embodiment of the cleaning member of
Figure
10.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
S The invention will be described as it applies to a large capacity, high flow
rate
continuous filter for water. The skilled person will appreciate that the
invention has broad
application to a variety of liquid filtration situations, and the scope of the
invention should
not be restricted because of the description of the preferred embodiment which
follows.
As shown in Figures 1 and 2, the liquid filtration device 10 of the invention
has a
housing 12 which is preferably cylindrical and which has a first end 14
provided with a
liquid-tight door 15, and a second end 17. The filtration device 10 may be
oriented vertically,
horizontally or otherwise. Fluid flow ports are preferably provided through
the housing wall
19 of the housing 12. Thus, an inlet 21 is provided near the first end 14 of
the housing 12, an
outlet 22 for filtered water is provided midway along the length of the
housing 12, and a
discharge aperture 23 is provided near the second end 17 of the housing 12.
A partition 25 is fixed within the housing 12 and spaced from the second end
17 to
thereby define a discharge chamber 28 between the partition 25 and the second
end 17. The
discharge aperture 23 has a valve 30 which is opened only during the vacuumed
cycle of
operation. Preferably, the operation of the valve 30 is governed by an
electronic controller.
One or more metal filter elements 33 are positionable within the housing 12. A
preferred embodiment will be described as shown in Figure 2 as having two
filter elements
33. One of the advantages of the invention is its capability to be sized with
the appropriate
number of filter elements 33 to meet the specifications of a particular
application. The
utilization of a plurality of relatively small filter elements 33 in the
device 10 of the invention
has a number of decided advantages which will be described.
Each filter element 33 has a panel with an inner face 31 and an outer face 32,
and first and second flanged ends 35 and 36 with sealing surfaces formed to
provide metal to
metal water seals about the filtration zone 40. Filtration zone 40 is defined
as the zone
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between the housing wall 19 and the outer face 32 of filter elements 33.
Filtration zone 40 is
in flow communication with outlet 22. Pre-filtration zone 85 is defined as the
zone between
the housing wall 19 and the inner face 31 of filter elements 33. Pre-
filtration zone 85 is in
flow communication with inlet 21.
As shown in a preferred embodiment in Figures 10 and 11, the invention can
also
comprise a pre-screen 94 located between inlet zone 60 and pre-filtration zone
85. The pre-
screen 94 is a filter means with a mesh size greater than that of filter
elements 33. Pre-screen
94 is secured to pre-screen frame 1 O 1 by means of pre-screen bolt 98. Pre-
screen 94
functions to prevent larger impurities, for example, seaweed, fish or shells
from entering the
filtration zone 40, where it might obstruct filter elements 33. Generally,
objects Filtered by
pre-screen 94 will be large enough that they will fall to the bottom of inlet
zone 60, where
they may be periodically purged from the filter housing 12 by opening pre-
screen drain 90 to
a lower pressure than the pressure in inlet zone 60. In other embodiments, pre-
screens may
be located in the flow path prior to inlet 21, or, depending on the operating
conditions, pre-
screens may not be required at all.
The filter elements 33 are preferably of metal wire mesh type wherein a fine
wire
mesh defining a desired pore size is applied to a structural screen made of
sheet metal (detail
not shown). The structural screen acts as a support for the finer mesh. In a
preferred
embodiment, the structural screen consists of a rigid or semi-rigid plate
having multiple
apertures, and the mesh is fixed to the structural screen by a sintering
process, such as the
proprietary process performed by Purolator Products Company (Tulsa, OK, USA).
By use of
this preferred embodiment, any damage to the fine mesh is restricted to the
mesh at a given
aperture of the structural screen, because the adjacent mesh is fixed to the
structural plate.
Isolated damage of this type may be easily repaired by simply soldering over a
given
structural screen aperture. Also, the use of this embodiment increases the
ease with which the
mesh may be cleaned, as cor!~pared to filter elements of the prior art. In a
preferred
embodiment, the mesh side of the filter element faces the pre-filtration zone.
Tn an alternative
embodiment the filter elements 33 are of a stainless steel wire mesh type in
which a fine wire
mesh defining a desired pore size is sandwiched between inner and outer
structural screens
also made of stainless steel. In another embodiment, the filter elements 33
comprise an outer
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structural screen, an inner filter mesh, and an intermediate structural screen
sandwiched
between the inner and outer layers.
By selecting the size of the openings in the filter element, the filter may be
used, for
example, to filter out zebra mussels, silt, algae, or other particulate
matter. In a preferred
embodiment, the mesh size is 40 microns or less. A mesh size of 40 microns
allows the filter
to remove zebra mussel larva. In the preferred embodiments described above,
the filters are
constructed with metal and stainless steel rings complete the flanged ends 35
and 36 of the
filter element. However, those skilled in the art will appreciate that for
other applications,
materials as diverse as ceramics or poly vinyl chlorides may be used.
Alternatively,
electrostatic or ionic filters may be used for other applications.
In the preferred embodiments shown, the filter elements are cyclindrical,
however, it
will be appreciated that other dimensions may be used for the filter elements,
so long as the
filter element has an inner and outer face and ends having sealing surfaces
capable of sealing
in the manner described below.
As shown in Figure 8, the flanged end 35 of filter element 33 has a chamfered
surface
42 which abuts a mating surface 43 about the sealing surfaces of second
flanged end 36 to
provide a nesting engagement of two filter elements 33. The water seal between
the abutting
flanges 35 and 36 is assisted by the addition of a small cross sectional
diameter O-ring 44
carned in a groove 45 formed in the surface 43. Likewise, as shown in Figure
9, the partition
is provided with an chamfered partition seal surface 47 which aligns with and
provides a
sealing engagement with the mating surface 43 of a second flanged end 36. As
shown in
25 Figure 7, a water seal is provided for the filtration zone 40 about the
endmost first flanged
end 35 of the filter element 33 positioned nearest the first end 14 of the
housing 12 by a
housing flange 48. Housing flange 48 has a sealing surface 49 which aligns
with sealing
surface SO of endmost first flanged end 35. Housing flange 48 is fixed to the
wall 19. An O-
ring 52 is carried in a groove 53 formed in the surface 50 to provide a
sealing engagement of
the circumferential sealing surface 50 with the housing flange 48. These
sealing
arrangements thus are capable of forming a complete seal between filtration
zone 40 and pre-
filtration zone 85.
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The flanged ends 35 and 36 of the filter elements 33 have a plurality of holes
55
spaced around them for receiving filter guide rods 56. In most applications,
four filter guide
rods 56 are sufficient for the intended purpose. In the embodiments
illustrated, the rods are
cylindrical. However, it will be appreciated that the rods may be other
dimensions, so long as
they allow the filter elements to be installed or removed along the length of
the rod. The
filter guide rods 56 extend through and are fixed to the partition 25. The
filter guide rods 56
are sized to extend just beyond the endmost first flanged end 35, and the
filter guide rods 56
are threaded at their ends so that the filter elements 33 can be secured in
place by means of
nuts 57 (Figure 7). Preferably, a precision machined threadless fastening nut
is used.
However, it will be appreciated that any suitable releasable fastening means
known in the art
may be used, for example threaded bolts or latch mechanisms. When installing
and removing
the filter elements 33 from the housing 12, filter guide rod extensions 59 may
be added to the
ends of the filter guide rods 56 by a precision machined threadless fastening
coupling
arrangement as shown in Figure 7. These filter guide rods 56 provide a
significant advantage
over the prior art as they facilitate the proper positioning of the filter
elements 33 within the
housing 12, they ensure that the sealing surfaces of the filter elements 33
are aligned and
mated properly, and by virtue of the tightening of the nuts 57 at the end of
each filter guide
rod 56, the filter elements 33 are compressed together to provide the
necessary water seals to
separate filtered water in the filtration zone 40 from unfiltered water in the
pre-filtration zone
85. The extensions 59 when attached to the filter guide rods 56 assist with
the installation
and removal of filter screens. Preferably, these extensions are long enough to
exit the front of
the filter housing 12.
In a preferred embodiment shown in Figure 10, filter element guide rods 92 are
used
in place of filter guide rods 56. Filter element guide rod 92 extends between
annular flanged
ends 35 and 36 of filter element 33. Filter element guide rod 92 provides
structural support to
filter element 33, as well as a grip for manipulating filter element 33. As
seen in Figure 12,
filter element guide rods 92 are fixed to flanged ends 35 and 36 by means of
welds 117. A
guide projection 131 of filter element guide rod 92 projects outwardly from
flanged end 36.
When the filter elements 33 are assembled, guide projection 131 is received by
guide rod
receptacle 113, thus aligning one filter element 33 with the next during
assembly and
reassembly.
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In a preferred embodiment, the seals between the pre-filtration zone 85 and
the
filtration zone 40 can be tightened and secured by means of the structure
shown in Figure 11.
As in the first embodiment, housing flange 48 extends circumferentially along
the inner
surface of housing wall 19, and is attached thereto by means of, for example,
weld 133.
S When all filter elements 33 are installed, the endmost first flanged end 35
is proximal to
housing flange 48. Position pin 96 is held in position pin receptacle 114.
Position pin 96
projects outwardly from endmost first flanged end 35 and is received by a
support structure
frame 105. A seal between endmost first flanged end 35 and support structure
frame 105 is
assisted by the addition of a small cross sectional diameter O-ring 135 carned
in a groove 137
formed in the surface 139 of support structure frame 105. Pre-screen frame 101
is placed
over support structure frame 105 and secured to housing flange 48 by means of
pre-screen
frame bolt 98. An O-ring 111 is carried in a groove 112 formed in the pre-
screen frame 101
to provide a sealing engagement of the circumferential sealing surface 109
with the
circumferential housing flange 48. An O-ring 52 is carried in a groove 53
formed in the
support structure frame 105 to provide a sealing engagement of the support
structure frame
105 with the pre-screen frame 101. These sealing arrangements thus form a seal
between
filtration zone 40 and pre-filtration zone 85 when frame bolt 103 is
tightened. To ensure a
tight and secure seal between flanged ends 35 and 36 seen in Figures 12 and
10, a jack screw
107 is received through pre-screen frame 101. When tightened, jack screw 107
applies force
to support structure frame 105, and this force is transmitted to the flanged
ends of each filter
element 33 in the series.
Having regarding to the above description, it will be appreciated that other
functional
equivalents of the the sealing structure of Figure 11 can be used. For
example, the structure
could be designed such that sealing surface 106 sealed with housing flange 48
rather than pre-
screen fi~ame 101. As another example, support structure frame 105 could be
removed,
support structure 75 could be incorporated into pre-screen frame 101, and
flanged end 35
could align directly with pre-screen frame 101. In this embodiment, jack screw
107 could be
received by position pin receptacle 114 to ensure alignment, or another
position pin
receptacle (not shown) on pre-screen frame 101 could be used to ensure
alignment between
pre-screen frame 101 and flanged end 35. However, it will be appreciated that
use of the
preferred embodiment, described above and shown in Figure 11, accommodates a
water tight
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seal even if circumferential housing flange 48 is not perfectly circular. The
present inventors
have found that, because housing flange 48 is welded to housing wall 19,
flange 48 will not
form a true circle if housing wall 19 is not perfectly cylindrical, if the
welding process
induces any distortion, or if the water loads during operation induce any
distortion.
S
The invention may fiuther comprise a runner 119, shown in Figure 13. Runner
119
preferably has a runner groove 121, which is suitable for receiving guide rod
92 of Figure 10.
Runner 119 facilitates the installation and removal of filter elements 33 by
bearing some of
the weight of the filter elements and by acting as a guide for aligning guide
projection 131
with guide rod receptacle 113, thus assisting the installation, removal, and
support of filter
elements 33.
Returning to Figures l and 2, an inlet zone 60 is defined within the housing
12 from
the first end 14 to the first filter element 33. The inlet 21 extends through
the wall 19 of the
housing 12 into the inlet zone 60. The first end 14 has a flange 62 to which
the door 15 seals
with the aid of an O-ring and a plurality of swing bolts 64 spaced around the
circumference of
the flange 62. The door 15 has hinges 65 (best shown in Figure 3) to swing
completely away
fi-om the opening of the first end 14, thus allowing for ready access to the
interior of the
housing 12.
Thus, in use, as shown by the arrows in Figures l and 2, unfiltered water
enters the
filter housing 12 through the inlet 21, into the pre-filtration zone 85 where
the pressure of the
system forces a flow through the filter mesh of the filter elements 33 to
provide a flow of
filtered water into the filtration zone 40. The water passes perpendicularly
through the filter
element 33 and into filtration zone. From here filtered water passes from the
filtration zone
40 through the outlet 22 and on to its intended purpose. After a period of
use, the filter
elements 33 will become partially clogged with particulate matter, and a
pressure drop will
occur at the outlet 22. In response to this problem, the invention can include
a vacuum filter
cleaning system.
As seen in Figure 2, a hollow shaft 70 extends from the second end 17 of the
housing
12 longitudinally through the center of the partition 25 and the filter
elements 33. The shaft 70
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has a first end 72 which is supported by a bearing 73 in a cross-shaped
support structure 75
attached to the filter guide rods 56 by the nuts 57. The second end 76 of the
shaft 70 is
attached to rotation means, such as a gear box 79, shown in Figure 1. Gear box
79 is actuated
by motor 77, both of which are located at the second end 17 of the housing 12.
Gear box 79
may contain a means for selecting various gears relating to various rotational
velocities of
shaft 70. Alternately, gear box 79 can be designed with a pre-selected optimal
gear ratio to
achieve an optimal rotational velocity for shaft 70. The optimal velocity will
depend on
operating conditions of the system for which the filter is designed, for
example, the flow rate
required, the pressure differential between the prefiltration zone 85 and the
discharge chamber
28, and the size and quantity of impurities flowing into the filter.
The shaft 70 has a plurality of hollow filter cleaning heads 80 which extend
radially
outward from the shaft 70 to a position proximal to the inner surface of each
filter element 33.
A portion of the shaft 70 near its second end 76 in the discharge chamber 28
has a plurality of
1 S holes 82 through it. Thus there is provided flow communication from the
inner surfaces of the
filter elements 33, through the cleaning heads 80, through the hollow shaft 70
to the discharge
chamber 28.
Once the filtrate trapped on the filter element becomes dense enough to cause
a
predetermined drop in pressure, for example, 5 psi (350 kg/cm2), the vacuum
cycle may be
initiated to remove the filtrate. When the vacuum cycle commences, the motor
77 starts to
rotate the gears inside of gear box 79, and the gears rotate the shaft 70
inside of the filter
elements 33. Motor 77 may be powered by any means known in the art, for
example,
electricity or water turbine.
The cleaning heads 80 on the shaft are located with apertures close to the
inner face 31
of the filter elements. Since there is water pressure inside the filter body
during normal
operation, a suction pressure is created once the valve 30 is opened to the
atmosphere. As
seen by the arrows in Figures 1, 2, 5 and 6, the opening of the valve 30 to
the atmosphere
creates a suction which draws water through the holes 82 in the shaft 70 which
in turn
provides a suction at the ends of the cleaning heads 80. By rotating the shaft
70 during the
vacuum cycle, the cleaning heads 80 are able to remove entrapped particulate
matter so that
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the filter elements 33 are returned to their former efficiency. While the
frequency and duration
of the vacuum cycle is adjustable to suit particular circumstances, in a
preferred embodiment,
the cycle is initiated when the pressure drops by about S psi at the outlet
22, and is maintained
for 8-10 seconds. In other embodiments, the vacuum cycle could run
continuously during
filtration, so long as the rate of water flowing through the shaft 70 is less
than the rate of water
flowing through the inlet 21. In another embodiment, during the cleaning cycle
the flow rate
through the filter can be reduced or even eliminated, for example, by use of a
valve (not
shown) at inlet 21.
In the embodiment shown in Figure 1 S, the cleaning heads are fin nozzle
cleaning
heads 123. The fin nozzle design increases the efficiency and effective force
of the vacuum to
better clean the filter elements. The fin nozzle design also decreases the
outer surface area of
the cleaning heads, thus decreasing the resistance to rotation encountered by
the cleaning
heads during rotation, thus requiring less energy to rotate the cleaning
heads. Also in the
embodiment shown in Figure 15, the cleaning heads are offset such that the
distribution of
weight of the cleaning heads is distributed more evenly from the centerline of
shaft 70.
Also in the embodiment shown in Figure 15, the invention fiurther comprises
connector
tubes 125 which are in flow communication between the cleaning heads 123 and
the hollow of
shaft 70. Stem 129 of cleaning head 123 adjustably inserts into connector
tubes 125 to form a
substantially water tight seal. Adjuster screw 127 provides a means for
adjusting the outward
projection of cleaning head 123 from shaft 70. By adjusting adjuster screw
127, the intake of
cleaning head 123 can be positioned a preferred distance from inner face 31.
The preferred
clearance between inner face 31 and the intake of cleaning head 123 will
depend on the size of
the impurities which are to be suctioned from filter element 33. This
preferred clearance is
often between 1/8th to 1/l6th of an inch (1.59 mm to 3.17 mm).
From the foregoing it will be appreciated that the present invention provides
a number
of advantages over prior devices. Stainless steel wire mesh filter units are
expensive
components, particularly those large units required for high throughput
devices. Previously,
filter units have been designed to serve a particular purpose, and thus, one
design has usually
been found not to be suitable for either scaled up or scaled down
applications. In contrast, the
14
CA 02355723 2001-06-18
WO 99/33542 PCT/CA98/01200
present invention provides a combination of components which can readily be
sized and
configured to serve a wide variety of applications. The present invention is a
modular system
which allows the use of a plurality of smaller filter units which are nested
together using metal
to metal water seals. The releasable securing mechanism for the filter
elements of the present
invention is particularly useful in that it allows for a plurality of filter
elements of a smaller
size, as opposed to a single filter element of a larger size to be used. This
facilitates
construction, maintenance, removal and replacement of the filter elements.
These filter units
are lighter and easier to manufacture, hence, cheaper than larger units.
Because they are
smaller and lighter, the filter units of the invention are easy to install and
remove.
The guide rods of the present device ensure an accurate alignment of the
filter units
and provide means for ensuring that the filter elements and their respective
seals are aligned
and centered properly, and to generally assist in securing them in place.
These rods allow the
design of the invention to be scaled up to handle very large flows. The rods,
together with the
use of the sealing surfaces and the support structure enable one to compress
the filter elements
together to form the proper sealing required for the fimction of the filter.
Also, the use of the
cross shaped support structure 75 allows the shaft 70 to be centered and
solidly supported.
The large water-tight door at one end of the present device allows a worker to
more
readily observe the filter operation, including the rotation of the shaft,
while the device is
empty of water, thus enabling a quicker determination of a malfunction than is
possible with
prior devices. Removal and replacement of the filter elements is likewise
facilitated by the use
of the door.
Removal and replacement of the filter elements are further facilitated by the
sealing
mechanism of the present invention. Whereas the prior art teaches methods of
sealing using,
for example, a lower O-ring in conjunction with a locking slit, the use of the
sealing surfaces
of the present invention, in conjunction with the compression from the rods
allows for removal
and replacement of filter elements without rotating or otherwise unlocking the
filter elements.
This allows for the handling of larger filter elements than would be practical
with conventional
methods of sealing in the art.
CA 02355723 2001-06-18
WO 99/33542 PCT/CA98/01200
Thus there are several aspects of the present invention that counter size and
mass
concerns of industrial filters. The present invention is particularly suited
to industrial uses
requiring high throughput, large volume filters. The sealing mechanism of the
present
invention has been found to be useful for filters where the pressure
differential from one side
of the filter element must be kept at a low level, for example, less than
approximately S psi
(350 kg/cm2), in order to maintain the required flow of water.
The present invention also provides a low maintenance filter system, thus
increasing
cost efficiency. By employing a minimum of moving parts, and by providing for
a self
cleaning system, the filters of the invention can operate for months, and
possibly years without
requiring maintenance apart from standard maintenance for the motor, which is
conveniently
located outside the filter housing. Unlike self cleaning filters of the prior
art, motor or
gearbox maintenance may be readily performed without opening or draining the
filter housing.
The filter of the present invention may be particularly suited for water
intake ports,
such as those found at power plants. The filter of the present invention is
also useful for other
applications, for example, in the food industry, pulp and paper industry, and
for fish
hatcheries. The filter is also useful for non-water applications, for example,
for filtering
machine cuttings out of an oil emulsion.
Although preferred embodiments of the invention have been disclosed for
illustrative
purposes, it will be appreciated that variations or modifications of the
disclosed apparatus lie
within the scope of the present embodiments.
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