Note: Descriptions are shown in the official language in which they were submitted.
CA 02278433 1999-06-22
TITLE OF THE INVENTION Canada
IMPROVED FILTER SYSTEM
FIELD OF THE INVENTION
This invention relates to improved self-cleaning filter systems.
BACKGROUND OF THE INVENTION
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, Jr. 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 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.S. 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 (i.e.
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
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CA 02278433 1999-06-22
slotted purging chamber which rotates, along with the filter housing, around
the filter
element. U.S. 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 nozzles. 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 filter element having an inner face, an outer face and first and second
ends, each end having a sealing face;
(ii) a first sealing face on the housing inner surface, the sealing face being
sealable with the first end sealing face of the filter element;
(iii) a second sealing face on the housing inner surface, the sealing face
being
sealable with the second end sealing face of the filter element, the sealing
faces sealable 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; and
(iv) a cleaning member for cleaning the inner face of the filter element, the
cleaning member having: a plurality of cleaning heads positioned adjacent the
inner face; a
discharge aperture extending through the housing; a plurality of conduits,
each the conduit in
flow communication respectively with one of the plurality of cleaning heads
from the
cleaning head to the discharge aperture; and vacuum means for providing
suction to the
conduits and cleaning heads to suction material from the inner face of the
filter element,
through the conduits and out the discharge aperture.
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In a preferred embodiment, the filter has four cleaning heads and four
conduits. In a
further preferred embodiment, each of the conduits is located in a quarter of
a hollow shaft
quartered lengthwise. The cleaning heads may be arranged as a first and second
pair each
with a first and second cleaning head, such that each first and second
cleaning head extend
from the shaft in parallel, and the first pair extends from the shaft in a
direction opposition
the second pair.
In a preferred embodiment, the filter further comprises a movement means
connected
to the cleaning member, and the movement means moves the cleaning head
parallel to the
inner face of the filter element.
In another embodiment, the filter has a plurality of cleaning heads arranged
in pairs,
each pair having a first and a second cleaning head, and the first cleaning
head is structurally
secured to the second cleaning head.
The invention also provides a filter for filtering liquids comprising a
housing having
an inlet, an outlet and an inner surface, the housing containing:
(i) a filter element having an inner face, an outer face and first and second
ends, each end having a sealing face;
(ii) a first sealing face on the housing inner surface, the sealing face being
sealable with the first end sealing face of the filter element;
(iii) a second sealing face on the housing inner surface, the sealing face
being
sealable with the second end sealing face of the filter element, the sealing
faces sealable 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; and
(iv) a deflector plate located between the outlet and the filter element.
The deflector plate preferably has a shape similar to a cross section of the
outlet
perpendicular to the flowpath through the outlet. The deflector plate
preferably has a surface
area similar to a cross section of the outlet perpendicular to the flowpath
through the outlet.
The deflector plate preferably has a surface area which is about 1.5 times an
area of a cross
section of the outlet perpendicular to the flowpath through the outlet.
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In one embodiment, the filter has a plurality of discharge apertures, each
discharge
aperture in flow communication respectively with one of the plurality of
conduits.
Preferably, the filter element is cylindrical and the cleaning member moves
rotationally. The
housing may also contain a partition to prevent the flow of fluid between a
discharge portion
of the filter which contains the discharge aperture and a filter portion of
the filter which
contains the filter element, and the conduit passes through the partition.
Preferably, the
cleaning member passes through the housing and the movement means is located
outside of
the housing.
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.
Figure 16 is a cross sectional view of some features taken along line 16-16 of
Figure
15.
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Figure 17 is a cross sectional view of some features taken along line 17-17 of
Figure
15.
Figure 18 is a cross sectional view of some features taken along line 18-18 of
Figure
15.
Figure 19 is a cross sectional view of some features taken along line 19-19 of
Figure
15.
Figure 20 is a cross sectional view of some features taken along line 20-20 of
Figure
15.
Figure 21 is a cross sectional view of some features taken along line 21-21 of
Figure
15.
Figure 22 is a cross sectional view of some features taken along line 22-22 of
Figure
15.
Figure 23 is a cross sectional view of some features taken along line 23-23 of
Figure
15.
Figure 24 is a cross sectional view of some features taken along line 24-24 of
Figure
15.
Figure 25 is a perspective partially broken away and cut away along line 24-24
view
of a preferred embodiment of hollow shaft 70 of Figure 15.
Figure 26 is a top perspective view of filter elements 33 of Figure 10.
Figure 27 is a top perspective view of an alternate embodiment of filter
elements 33
of Figure 10.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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
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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 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 101 by means of pre-screen bolt 98. Pre-
screen 94
functions to prevent larger impurities, for example, seaweed, fish or shells
from entering the
prefiltration zone 40, where it might obstruct filter elements 33. Generally,
objects filtered
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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.
As shown in a preferred embodiment in perspective views of the filter elements
33 in
Figure 26, the invention can also comprise a deflector plate 170. Deflector
plate 170 is
located between an interior mouth 175 of outlet 22 and the portion of filter
element 33 closest
to the interior mouth of interior mouth 175. Deflector plate 170 is a static
fluid directing
means arranged to cause the fluid coming into the interior mouth 175 of the
outlet 22 to be
drawn from a plurality of directions predominantly perpendicular to the outlet
22. Without
deflector plate 170, the fluid stream into the mouth of the outlet 22 may be
drawn
predominantly from fluid passing from pre-filtration zone 85 to filtration
zone 40 through the
portion of filter element 33 closest to the interior mouth 175 of outlet 22.
Deflector plate 170 is preferably the same shape as interior mouth 175 and as
large or
larger than the interior mouth 175. In the preferred embodiment shown,
deflector plate 170
is circular with a diameter about 1.5 times the diameter of mouth 175.
Deflector plate 170 is
secured to filter element 33 by any means known in the art, for example spot
welding to
flanged ends 35 and 36 or filter element guide rods 92. The dispersal and
redirection of the
incoming fluid stream, now drawn from a range of directions, rather than
directly from the
filter screen 33 inunediately adjacent mouth 175, facilitates efficient
generation of an
entrained fluid stream. This entrained fluid stream draws from filtration zone
40 in multiple
directions, and at an angle primarily perpendicular to the face of filter
element 33, thus one
does not generate a flow path which flows primarily through only one portion
of the filter
screen 33, namely that portion closest to mouth 175.
In another embodiment, shown in Figure 27, the deflector plate comprises two
plates
171 and 172. Deflector plate 171 is secured to a first filter means 33 while
deflector plate
171 is secured to a second filter means 33, such that deflector plates 171 and
172 align and
form a circular plate when the first and second filter means are placed
together in the liquid
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filtration device. This embodiment of deflector plate is used where the
location of mouth
175 and the size of filter elements 33 of the liquid filtration device are
such that, upon
assembly, the flanged ends 35 and 36 of two filter elements meet along a line
which
corresponds to a line bisecting mouth 175. Thus, upon assembly, the deflector
plates 171 and
172 join to form a deflector plate which is centered in relation to mouth 175.
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 compared to filter elements of the prior art. In a
preferred
embodiment, the mesh side of the filter element faces the pre-filtration zone.
In 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 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.
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In the preferred embodiments shown, the filter elements are cylindrical,
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 0-ring 44
carried in a groove 45 formed in the surface 43. Likewise, as shown in Figure
9, the partition
25 is provided with a 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
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 50 of endmost first flanged end 35. Housing flange 48 is fixed to the
wall 19. An 0-
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.
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
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CA 02278433 1999-06-22
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.
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.
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 0-ring 135
carried in a groove
CA 02278433 1999-06-22
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 0-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 0-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 regard to the above description, it will be appreciated that other
functional
equivalents of 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 frame 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
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.
The invention may further 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
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with guide rod receptacle 113, thus assisting the installation, removal, and
support of filter
elements 33.
Returning to Figures 1 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 0-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 from 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 1 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 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. Shaft 70 is closed at
first end 72. 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
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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.
In another alternative, rather than using a motor, the filter could be
designed to harness
the power of the flow of the water through the system for use in rotating the
shaft 70, for
example, by means of fins secured, directly or indirectly, to the shaft 70.
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
holes 81, 82, 83 and 84 (only 82 shown in Figure 2). 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 81, 82, 83, and 84 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 the filter elements 33 are returned to their former efficiency. While the
frequency and
duration of the vacuum cycle are adjustable to suit particular circumstances,
in a preferred
embodiment, the cycle is initiated when the pressure drops by about 5 psi at
the outlet 22, and
is maintained for 8-10 seconds. In other embodiments, the vacuum cycle could
run
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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 15, 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.
Structural strength is added to nozzle cleaning heads 123 by joining cleaning
heads
123 in pairs at two locations. First, cleaning heads 123 are joined in pairs
at their distal ends,
i.e., their intakes 120. Second, cleaning heads are joined in pairs by means
of a support bar
124, which connects to cleaning heads 123 at a position approximately half way
between their
intakes 120 and the connector tubes 141, 142, 143 and 144.
Also in the embodiment shown in Figure 15, the invention further comprises
connector
tubes 141, 142, 143 and 144 which are in flow communication between their
corresponding
cleaning heads 123 and the hollow of shaft 70. Connector tube 141 is the
closest of the four
connector tubes to first end 72 of shaft 70. Connector tube 142 is the second
closest of the
four connector tubes to first end 72 of shaft 70. Connector tube 143 is the
third closest of the
four connector tubes to first end 72 of shaft 70. Connector tube 144 is
closest of the four
connector tubes to second end 76 of shaft 70.
Stem 129 of cleaning head 123 adjustably inserts into connector tubes 141,
142, 143
and 144 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 120 of cleaning head 123 can be positioned a preferred
distance from
inner face 31. The preferred clearance between inner face 31 and the intake
120 of cleaning
14
CA 02278433 1999-06-22
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 1/16th of an
inch (1.59 mm to
3.17 mm).
In the preferred embodiment, shown in Figures 15-25, shaft 70 comprises four
vacuum
chambers 161, 162, 163, 164 within the shaft. Each of the four vacuum chambers
is of a
different length. Shaft 70 has a first vacuum chamber 161 which extends
between and is in
flow communication with connector tube 141 and hole 81. Second vacuum chamber
162
extends between and is in flow communication with connector tube 142 and hole
82. Third
vacuum chamber 163 extends between and is in flow communication with connector
tube 143
and hole 83 (not shown). Fourth vacuum chamber 164 extends between and is in
flow
communication with connector tube 144 and hole 84. By use of the separate
vacuum
chambers, the vacuum at holes 81, 82, 83 and 84 are more evenly distributed to
each
connector tube 141, 142, 143 and 144, and hence more evenly distributed to
each stem 129
and cleaning head 123. Without separate vacuum chambers, vacuum in shaft 70
might be
primarily draw from the closest cleaning heads - e.g. those extending from
connector tubes
143 and 144 - at the expense of decreased vacuum available to the cleaning
heads extending
from connector tubes 141 and 142.
Vacuum chambers 161, 162, 163 and 164 may be created by securing various
plates
and end walls within shaft 70, as follows.
As shown in Figures 15 and 17 to 25, a bisecting plate 151 extends lengthwise
along
the interior of shaft 70, from connector tube 141 to second end 76 of shaft
70, bisecting the
interior of the shaft. As shown in Figure 17, a first end wall 181 seals the
end of vacuum
chamber 161 which is proximal to first end 72 of shaft 70 such that a portion
of the interior of
the bisected shaft 70 is in flow communication with connector tube 141 and
hole 81 to form
first vacuum chamber 161.
As shown in Figures 15 and 19 to 25, a first quartering plate 153 extends
lengthwise
within shaft 70, from connector tube 142 to second end 76 of shaft 70,
bisecting the interior of
vacuum chamber 161 along that length, to divide out second vacuum chamber 162
from first
CA 02278433 1999-06-22
vacuum chamber 161 which continues along the interior of shaft 70, reduced in
cross-
sectional area by half. As shown in Figure 19, a second end wall 182 seals the
end of vacuum
chamber 162 which is proximal to first end 72 of shaft 70 such that a
dedicated portion of the
interior of the shaft 70 is in flow communication with connector tube 142 and
hole 82 to form
second vacuum chamber 162.
As shown in Figures 15 and 21 to 25, a third end wall 183 seals the end of
vacuum
chamber 163 at connector tube 143 such that the interior of the shaft 70 is in
flow
communication with connector tube 143 and hole 83 (not shown) to form third
vacuum
chamber 163.
As shown in Figures 15 and 23 to 25, a second quartering plate 154 extends
lengthwise
within shaft 70, from connector tube 144 to second end 76 of shaft 70,
bisecting the interior of
vacuum chamber 163 along that length, to divide out fourth vacuum chamber 164
such that
third vacuum chamber 163 continues along the interior of shaft 70, reduced in
cross-sectional
area by half. As shown in Figures 23 and 25, a fourth end wall 184 seals the
end of vacuum
chamber 164 which is proximal to first end 72 of shaft 70. The interior of the
shaft 70 is thus
in flow communication with connector tube 144 and hole 84 to form fourth
vacuum chamber
164.
Because shaft 70 is closed at first end 72, the interior of shaft 70 which
does not
comprise one of vacuum chambers 161, 162, 163 or 164 remains essentially water-
tight and
free from water. This avoids the creation of a "dead zone" within the shaft 70
which contains
water not subjected to flow. By avoiding such a "dead zone" the likelihood of
buildup of
debris or organic growth, such as zebra mussels, is decreased.
As shown in Figure 15, holes 81, 82, 83 and 84 (83 not shown; located opposite
hole
81 on shaft 70) are positioned such that the holes collectively do not
significantly compromise
the structural strength of end 76 of shaft 70. In order to maximize the
distance between the
four holes, and hence maximize the area of structural shaft 70 between each
hole, each of the
holes 81, 82, 83 and 84 are stagged 90 degrees rotationally around shaft 70,
and holes 81 and
83 are staggered lengthwise on shaft 70 in relation to holes 82 and 84.
16
CA 02278433 1999-06-22
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
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 function 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 0-ring in conjunction with a locking slit, the use of the
sealing surfaces
17
CA 02278433 1999-06-22
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.
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 5 psi
(350 kg/cmZ), 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 movement
means,
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.
18
