Note: Descriptions are shown in the official language in which they were submitted.
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BACKWASHING-TYPE FILTER~NG APPARATUS
WITH FILTER SUPPORT GRID OF RING-LIKE SEGMENTS
Technical Field
This invention relates to a novel and im-
proved backwashing-type filtering apparatus that re-
moves solid particles from a liquid.
Background Art
Backwashing-type filters used in removing
particles in liquid flow systems generally involve plac-
ing 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. Refrig-
erating systems are one example of a liquid system
wherein the liquid exposed to the atmosphere collects
dirt, leaves, silt, ash, etc., as is discussed in U. S.
Patent No. 2,875,594. One problem prevalent in bac~-
washing filters is that the surface area through which
the liquid passes is usually long and generally tubu-
lar in shape and of substantial ex-tent and the solid
particles do not build up uniformly. Moreover, the
backwashing li~uid 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 area of the fil-
ter medium. Hirs U. S. Patent No. 3,169,109 discloses
a tapered displacement member within an elongated
cylindrical filter medium of uniform diameter throughout
3U its length to uniformly distribute the water pressure
over the entire area of the filter medium during a
backwashing operation. A backwashing filter currently
being manufactured by Ronnigen-Petter uses a backwash
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48
diffuser in the center of the filter medium that has a
series of tapered sections that deflect the backwash flow
to equalize fluid flow.
Summary of t e Invention
According to one aspect of the present
invention, there is provided in a filtering apparatus for
removing solid particles and the like from a liquid
adapted to be cleaned by backwashing, the combination
comprising: an outer housing and an inner filter disposed
~ithin the outer housing defining therebetween an
annular outer flow passage, said filter having an inner
flow passage whereby a forward flow liquid with solid
particles is passed through an inlet into said outer flow
passage, the solid particles being deposited on said
filter and the liquid passing through the filter into and
along and out an outlet in said inner flow passage in the
forward flow direction, and whereby a backwash liquid is
passed into said inner ~low passage, through said filter,
and into said outer flow passage to remove solid
; 20 particles collected on said filter in a back~low
direction, said filter including an inner support grid
having a plurality of liquid flow openings extending
between the outer and inner faces to pass a liquid
therethrough and a filter medium mounted on said support
; 25 grid between said inner and outer flow passages, said
support grid being made up of a plurality of ring-like
segments, each segment having a centrally d.isposed ring
portion that i5 continuous for a ~ull arc of 360 degrees,
and a plurality of circumferentially spaced pairs of
axial portions projecting axially out from opposite sides
: of the ring portion and having 1at ends that abut an
adjacent axial portion of ~n adjacent ring for forming
said liquid flow openings, said outer housing having an
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internal dimension related to the external dimension of
said inner filter so that said outer flow passage changes
in dimension along the filter in such a way as to provide
substantially a uniform liquid velocity through said
5 filter at all points along said filter in both said
forward flow direction and said backflow direction.
According to another aspect of the present
invention, there is provided in a filtering apparatus for
removing solid particles and the like from a liquid
10 adapted to be cleaned by backwashing, the combination
comprising: an outer housing and an inner filter
disposed within the outer housing defining therebetween
an annular outer flow passage, said filter having an
inner flow passage whereby a forward flow liquid with
15 solid particles is passed through an inlet into said
outer flow passage, the solid particles being deposited
on said filter and the liquid passing through the filter
into and along and out an outlet in said inner flow
passage in the forward flow direction, and whereby a
20 backwash liquid is passed into said inner ~low passage,
through said filter, and into said outer flow passage to
remove solid particles collected on said filter in a
backflow direction, said filter including an inner,
generally cylindrical/ support grid body having a
: 25 plurality of liquid flow openings extending between the
outer and inner faces to pass a liquid therethrough and a
filter medium mounted on said support grid between said
inner and outer flow passages, said support grid being
made up of a plurality of ring-like segments stacked end
30 to end, each segment having a centrally disposed ring
portion that is continuous ~or a full arc of 360 degrees,
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
35 having ends that abut an adjacent axial portion of an
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adjacent ring for forming said liquid flow openings, said
outer housing having an internal dimension related to the
external dimension of said inner filter so that said
outer flow passage changes in dimension along the filter
in such a way as to provide substantially a uniform
liquid velocity through said filter at all points along
said filter in both said forward flow direction and said
backflow direction; and means to hold said segments
together.
Brief Description of Drawings
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;
Figure 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;
Figure 4 is an end elevation view 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 Figure l; and
Figure 8 is a vertical sectional view of a
suitable valve control for use at the outlet of the
filtering apparatus of ~igure 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-
ter 13 arranged in i.nner 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 1~ for
flow in the axial direction into one end and the oppo-
site end of the outer annular passage i5 closed to flow
in the axial direction. The inner flow passage 17
within filter 13 is closed to flow in the axial direc-
tion at the inlet end and the outlet end 21 is open to
flow in the axial di.rection 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
3~ direction, as is indicated by arrows.
The outer housing.ll shown is constructed
with a shell 2~ that is tapered throughout its length-
wise extent and has a tubular inlet pipe end 25 affixed
to the inlet end of shell 24, T~e inlet pipe end 25
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has an external groove 26 and an internal groove 27. A
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 affi~ed 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 e~ternal 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 bo-th ends.
Rods 39 extend through alined axial holes 41 in the
segments and through a hole in a front 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 a e drawn tightly to-
gether between the front end plate 43 and rear end ring
44 as nuts 45 are tightened.
As best seen in Figures 4 and 5, each ring-
like 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 a~ial 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 rounded 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 constructed 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 rnanner 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 57 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 90-degree in-
tervals along an inner edge to the periphery of plate
55. An annular retainer 59 at the outer end telescopes
in member 25 in a close-fitting relationship and is
held against axial movement by a retaining ring 61 in
groove 27.
The front end of the filter medium 37 is shown
wedged between the inside of deflector plàte 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 a~ external annular clamp 62 that
forces it down against rear end rin~ 44. The rear end
of the outer 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 of
ring 23.
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The outer housing 11 has an internal dimen-
sion related in a particular way to the external dimen-
sion o-E 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 selected width of
the GUter flow passage also provides a selected fluid
velocity for the flow through the outer flow passage in
the reverse direction. This in turn establishes a se-
lected pressure along 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
liquid flow through the filter medium are the same
throughout the lengthwise extent of the filter 13.
The difference between a tapered housing and
an outer housing of uniform diameter throughout its
length may be graphically illustrated alony an x-y
coordinate system that has li~uid pressure plotted
along the "y" axis and distance along the filter plot-
ted along the "x" axis.
During a forward fluid flow operation the
li~uid pressure at the inlet of the ou~er 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 the pressure at the inlet of the
inner flow passage 17 gradually decreases toward the
outlet 21 along a downsloping line, the taper of the
housing being selected so that the plotted lines rep-
resenting liquid pressure for the inner -flow passage
and 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
flow 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 outlet 21 proceeding toward inlet 19 yradually
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 dropalong 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 uni-form pressure drop
along the ~ilter.
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 8. 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 7
has an external groove 7g, as seen in Figure 1. A
coupling ring 79 has an end portion that fits in groove
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 of the filtering apparatus
there is provided an outlet valve 84 having a pipe por-
tion 85 with an annular groove 86. A coupling ring 87
has end portions that fit in groove 32 of said groove
36 to couple the outlet valve to the outlet end of 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 g3 via a coupling
ring 94 in a conventional manner.
Operation
During the forward flow filtering operation,
liquid from the inlet manifold 72 flow~ through the
normally open inlet valve 73 into inlet pipe 74 and
3~ then flows into outer annular passage 16 through fil-
ter 13, and into inner flow passage 47 in the core of
the filter. This filtered liquid flows through outlet
valve ~4 and into outlet manifold 93 for intended use.
In the bac~washin~ operation the valve 73
closes, shutting off forward flow through the fil-ter.
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The backwash valve 75 opens to atmosphere, allowing
water from the outlet manifold 93 to rush backwards
through the filtering apparatus, washing debris off of
the filter 13 and out through backwash valve 75, thus
cleaning the filter.
By way of illustration and not by way of lim-
itation, below is a table listing an example for the
above described filtering apparatus for filtering out
solid particles in a refrigeration system using water
exposed to the atmosphere.
Length of outer passage 1636 inches
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 21300 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 of example and that changes in details of structure
may be made without departing from the spirit thereof.
