Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~IL~ERING APPARATUS
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Technical Field
This invention relates to a novel and improved
backwashing~type filtering apparatus that removes solid
particles from a liquid.
Back~round Art
BacXwashing-type filters used in removing
particles in liquid flow systems generally involve
placing a filter in a large reservoir and allowing water
to rush through the filter, depositing the particles on
one face of the filter. Backwashing consists of a
valve~controlled reverse flow, flushing the particles
from the filter and carrying them to a drain.
Refrigerating systems are one example of a liquid
systern wherein the liquid exposed to the atmosph~re
collects dirt, leaves, silt, ash, etc., as is dlscussed
in U. S. Patent No. 2~875~594. One p~roblem pre~alent in
back-washing filters is that the surface area through
which the liquid passes is usually long and generally
tubular in shape and of substantial extent and the solid
particles do not build up uniformly. Moreover, the
backwashing liquid flow is not uniformly applied to the
filter medium and difficulty is encountered in removing
the particles.
Attempts have been made to provide a uniform
liquid flow against the entire surface areas of the
filter medium. Hirs U. S. Patent No. 3,169,109
disclos0s a tapered displacement member within an
elon~ated cylindrical filter medium of uniform diameter
throughout its length to uniformly distribute the water
pressure over the entire area of the filter medium
durins a backwashing operation. A bacXwashing filter
currently being manufactured by Ronnigen-Petter uses a
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backwash diffuser in the ~enter of the f.ilter medium
that has a series of tapered sections that deflect the
backwash flow to equalize fluid flow.
Summary of the Invention
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According to one aspect of the present
invention, there is provided in filtering apparatus for
removing solid particles and the like from a liquid
including an outer housing and an inner filter having an
inner flow passage and disposed within the housing
defining therebetween an annular outer flow passage and
first mean~ including an inlet into said outer flow
passage providing a forward flow through said outer
passage, through said filter, and out an outlet in said
inner flow passage and second means including an inlet
into said inner flow passage providing a backflow
through said inner flow passage, said filter, and an
outlet in said outer flow passage, an improved inner
filter assembly comprising a generally cylindrical
support grid body having a plurality of liquid flow
openings extending between the outer and inner faces to
pass a liquid therethrough, said body being made up of a
plurality of ring-like segments stacked end to end and
having means to hold said segments together, each
segment having a centrally disposed continuous ring
portion, and a plurality of circumferentially spaced
pairs of axial portions of substantially equal length
projecting axially out from opposite sides of the ring
portion and having ends that abut an adjacent axial
portion of an adjacent ring-like segment for forming
said Iiquid flow openings; and a filter medium covering
the outer face of said grid body so that, in said forward
flow, the liquid passes through the filter medium and
then through said fluid flow openings and solid particles
are deposited on said filter medium and, in said
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backflow, the liquid passes through said flow openings
and then through said filter medium to remove said
deposited particles, each said ring portion and said
axial portions having a similar cross section, said
cross section being generally V-shaped, said cross
section with each said ring portion and said axial
portions being narrower in thickness and an outer
peripheral surface supporting said filter medium than at
an inner surface of said support grid body opposite
said outer peripheral surface, each ring portion
encompassing a central opening, said cen~ral opening
having a radial extent greater than the radial extent of
said ring portion to direct the backflow liquid first in
an axial direction and then in a radial direction
producing a liquid flow between adjacent ring portions
as well as the axial portions and at the filer medium
that enhances the removal of said solid particles
collected on said filter medium during said backflow of
liquidO
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The details of this invention will be
described in connection with the accompanying drawings,
in which:
Figure 1 is a side elevation view of filtering
apparatus embodying features of the present invention
with the outer housing and end support for the filter
shown in section and a portion of the filter medium
broken away to show the support grid,
Fi~ure 2 is an enlarged vertical sectional
view at the inlet end of the filtering apparatus shown
: in Figure 1;
Figure 3 is an enlarged vertical sectional
view at the outlet end of the filtering apparatus shown
in Figure l;
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Figure 4 is an end elevation ~iew showing one
half of a ring-like segment forming the support grid of
the filter with the opposite half not shown but being
identical in construction;
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Figure 5 is a sectional view taken along
lines 5-5 of Figure 4;
Figure 6 is a sectional view taken along
lines 6-6 of Figure 4;
Figure 7 is a vertical sectional view of a
suitable valve control for use at the inlet of the fil-
tering apparatus of F;.gure l; and
Figure 8 is a vertical sectional view of a
suitable valve control for use at the outlet of the
filtering apparatus of Figure 1.
Detailed Description
Referring now to the drawings, the filtering
apparatus shown, generally stated, includes an outer
housing 11 within which there is disposed an inner fil-
L5 ~er 13 arranged in inner spaced concentric arrangement- -
about a common central axis 15 to define therebetween
an annular outer flow passage 16. An inner flow pas-
sage 17 extends through the hollow core or inside of
filter 13.
The outer flow passage 16 has an inlet 19 for
flow in the axial direction into one end and the oppo-
site end of the outer annular passage is closed to flow
in the axial direction. The inner flow passa~e 17
within filter 13 is closed to flow in the axial direc-
2S tion at the inlet end and the outlet end 21 is open to
~low in the axial direction so that in general the
liquid passes via inlet 19, through the peripheral sur-
face of the filter 13, through the hollow core or inner
~ flow passage 17, and out outlet 21 in the forward flow
direction, as is indicated by arrows.
; The outer housing 11 shown is constructed
with a shell 24 that is tapered throughout its length-
wise extent and has a tubular inlet pipe end 25 affixed
to the inlet end of shell 24. The inlet pipe end 25
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has an external groove 26 and an internal groove 27.
tubular pipe reducer 28 is affixed to the outlet end of
the shell 24 and has a converging inner surface 29 and
a straight inner surface 30. A tubular outlet pipe end
31 is affixed to the outlet end of reducer 28 and pipe
end 31 has an external groove 32.
The filter 13 has an inner support grid 35.
Filter 13 is of a generally cylindrical shape and has a
substantially uniform diameter throughout its length-
wise extent. The support grid 35 has a plurality ofopenings 36 distributed substantially uniformly over
the entire peripheral surface area extending from an
outer surface to an inner surface thereof to pass a
liquid therethrough. A filter medium 37 covers the
entire peripheral surface of the support grid 35. The
filter medium is a fabric or wire mesh or the like of
a mesh size that will collect the solid particles on
the external surface thereof.
The support grid 35 is made up of a plurality
of identical ring-like segments 38 stacked end to end
and held together by four circumferentially spaced ten-
sion rods 39 having external threads on both ends.
Rods 39 extend through alined axial holes 41 in the
segments and through a hole in a fron-t end plate 43 and
thread into internal threads in a hole in a rear end
ring 44. A nut 45 threads over the externally threaded
end portion of the tension rods beyond the front end
plate so that the segments 38 are d.-awn tightly to-
gether between the front end plate 43 and rear end ring
44 as nuts 45 are tightened.
As best seen in Figul-es 4 and 5, each ring-
llke segment 38 includes a ring portion 47 that is con-
tinuous for a full arc of 360 degrees and a plurality
of circumferentially spaced pairs of axial portions 48
and 49 that project from opposite sides of the ring
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portion 47. The cross section of both the ring portion
47 and the axial portions 48 and 49 is the same and
somewhat V-shaped, being narrower at the outer surface
and wider at the inner surface, with r.ounded corners to
facilitate or enhance fluid flow.
As shown in Figures 4 and 6, the holes 41
that receive the tension bolt 39 are located at 90-
degree intervals in the arc and are construc-ted as
cylindrical body portions 51 and 52 that extend as a
pair of axial portions projecting out from opposite
sides of ring portion 47 in the same manner and to the
same extent as axial portions 48 and 49.
A dome-shaped deflector plate 55 is mounted
at -the front end of the filter 13. Plate 55 has a
tubular support section S7 affixed to and extending
axially in front of the front end plate 43 and a tubu-
lar support 56 affixed to and extending rearwardly from
the inside of deflector plate 55 and telescopes in
support 56. Four relatively -thin, circumferentially
spaced, radial plates 58 are affixed at 93-degree in-
tervals along an inner edge to the periphery of plate
55. An annular retainer 59 at the outer end telescopes
in memher 25 in a close-fitting relationship and is
held against axial movement by a retaining ring 61 in
groove 27.
The front end of che filter medium 37 is shown
wedged between the inside of deflector plate 55 and the
outside of end plate 43 to hold it to the support grid
35. The rear end of the filter medium 37 is held to
the support grid by an external annular clamp 62 that
forces it down against rear end ring 44. The rear end
of the ou-ter annular passage is sealed closed by an
O-ring 65 that fits in an annular external groove 66
in rear end ring 44 and abuts against surface 30 o
ring 28.
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The outer housing 11 has an internal dimen-
sion related in a particular way to the external dimen-
sion of the filter 13 so that the outer flow passage
16 changes in dimension along the filter 13 to provide
a substantially uniform liquid velocity at all points
along the filter during either the forward or the back-
flow operating conditions.
In particular, the shell 24 is tapered a
selected angle to converge from inlet to outlet to pro-
vide a selected fluid velocity for the flow through theouter annular passage, which in turn establishes a
selected pressure along the outer annular passage dur-
ing a forward flow operating condition. Moreover, a
selected shell taper and thereby a selectecl width of
the outer flow passage also provides a selected fluid
veloci-ty for the flow through the outer flow passage in
the reverse direction, This in turn establishes a se-
lected pressure alon~ the inner flow passage 17 and
these inner and outer fluid velocities and pressures
are selected and established by the extent or size of
the taper, so that the pressure differentials or pres-
sure drops across the filter medium and thereby the
liquld flow throuyh the filter medium are the same
throughout the lengthwise extent of the filter 13.
The diferellce between a -tapered housing and
an outer housing of uniform diameter throughout its
length may be graphically illustrated along an x-y
coordinate system that has liquid pressure plotted
along the "y" axis and distance along the filter plot-
: 30 ted along the "x" axis.
During a forward fluid flow operation -the
liquid pressure at -the inlet of the outer flow passage
16 is at a certain pressure level and gradually de-
creases toward the outlet of the outer flow passage
along a downsloping line. In turn, during a forward
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fluid flow operation tne pressure at the inlet of the
inner flow passage 17 gradually decreases toward the
outlet 21 along a clownsloping line, the -taper of tne
housing being selected so that the plotted lines rep-
resenting liquid pressure for the inner flow passageand outer flow passage are parallel, indicating the
same differential pressure across the filter medium at
all points along the filter medium.
A plot of liquid pressure for an outer shell
of uniform dimension, rather than taper for the outer
flo~J passage, would gradually increase from inlet to
outlet along an upsloping line and would not result in
a uniform pressure drop or differential along the
filter.
The same factors are considered in selecting
the taper of -the outer housing during a backwash flow
operation. In the inner passage the liquid pressure
at the outle-t 21 proceeding toward inlet 19 gradually
increases toward the inlet 19 along an upsloping line.
The taper of the shell 24 is selected with respect to
backflow liquid velocity so that the pressure at the
~ outlet in the outer passage 16 gradually increases
; along an upsloping line to a pressure at the inlet, and
again the pressure lines for the inner and outer pas-
sages are parallel to indicate a uniform pressure drop
along the filter. The pressure curve for an outer
housing of uniform dimension would be along a downslop-
ing curve from the outlet to the inlet of the outer
passage and would not result in a uniform pressure drop
along the filter.
A valving arrangement suitable for control-
ling liquid flow in both the forward and backflow op-
erations for the above described filtering apparatus is
illustrated in Figures 7 and 3. An inlet manifold 72
is coupled to an automatic inlet valve 73 which in turn
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is coupled to an inlet pipe 74 defining an inlet cham-
ber. An automatic backflow valve 75 is connected to
the inlet pipe 74 and connects to a backflow manifold
76.
The downstream end portion of inlet pipe 74
has an external groove 78, as seen in Figure 1. A
coupling ring 7g has an end portion that fits in yroove
78 and groove 26 in the filtering apparatus to releas-
ably couple the control valves 73 and 75 to the inlet
end of the filtering apparatus 11. A joint sealant 81
is provided inside ring 79 to seal the joint between
inlet pipe 74 and tubular pipe end 25 in a conventional
manner .
At the outlet end o the filtering apparatus
there i5 provided an outlet valve 84 having a pipe por-
-t.ion 85 with an annular groove 86. A coupling ring 87
has end portions that fit in groove 32 of said groove
86 to couple the outlet valve to the outlet end OL the
filtering apparatus. A handle 88 is used to turn valve
84 to open or closed positions as required. Again a
sealant 91 is provided inside ring 87 to seal the joint
between pipe end 31 and valve 84. The outlet valve 84
is then coupled to an outlet manifold 93 via a coupling
ring 94 in a conventional manner.
Operation
During the forward flow filtering operation,
liquid from the inlet manifold 72 flows through the
normally open inlet valve 73 into inlet pipe 74 and
then flows into outer annular passage 16 through fil-
ter 13, and into inner flow passage 47 in the core of
the filter. This Eiltered liquid flows through outlet
valve 34 and into outlet manifold 93 for intended use.
In the backwashing operation the valve 73
closes, shutting off forward flow through the filter.
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The backwash valve 75 opens to atmosphere, allo~ing
water from the outlet manifold 93 to rush backwards
through the filtering apparatus, washi.ng debris off of
the filter 13 and out through backwash valve 75, thus
cleaning -the filter~
3y way of il].ustration and not by way of lim-
itation, below is a table listing an example for the
above described filtering apparatus for filtering out
solid partiGles in a refrigeration system using ~ater
exposed to the atmosphere.
Length of outer passage 1636 irlches
Internal diameter of outer passage
at inlet 19 6 inches
Internal diameter of outer passage
at inlet 21 4-1/2 inches
Outer diameter of filter 133-1/4 inches
Fluid flow inlet 19 and outlet 21 300 gpm
Although the present invention has been de-
scribed with a certain degree of particularity, it is
understood that the present disclosure has been made by
way o example and that changes in details of structure
may be made without departing from the spirit thereof.
