Note: Descriptions are shown in the official language in which they were submitted.
3~6
sACKwASHING-TYPE FILTERING APPARATUS
Technical Field
This invention relates to a novel and imp
proved backwashing-type filtering apparatus that no-
moves solid particles from a liquid.
Background Art
Backwashing-type filters used in removing
particles in liquid flow systems generally involve plea-
in a filter in a large reservoir and allowing water to
rush through the filter, depositing the particles on
one face of the filter. ~ackwashing consists of a
valve-controlled reverse flow, flushing the particles
from the filter and carrying them to a drain. Refrig-
crating 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 back-
washing filters is that -the surface area through which
the liquid passes is usually long and generally tutu-
far in shape and of substantial extent and the solid
particles do not build up uniformly. Moreover, the
back washing 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 area of the lit-
ton medium. Hits U. S. Patent No. 3,169,109 discloses
a tapered displacement member within an elongated
cylindrical filter medium of uniform diameter throughout
its length to uniformly distribute the water pressure
over the entire area of the filter medium during a
back washing operation. A back washing filter currently
being manufactured by Ronnigen-Petter uses a backwash
I
diffuser in the center of the filter medium that has a
series of tapered sections that deflect the backwash flow
to eclualize fluid flow.
Summar~_of the I mention
According to one aspect of the present
inventiorl, there is provided in a filtering apparatus
for removing solid particles and the like from a liquid
adapted to be cleaned by backwashingl the combination
comprising: an outer housing and an inner filter
disposed within the outer housing defining there between
an anywhere outer flow passage, said filter having an
inner flow passage and having an outer face and an inner
face with liquid flow openings extending between said
outer and inner faces through which the liquid flows to
pass between said inner and outer flow passages 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 openings into and along said
inner flow passage and out an outlet in said inner flow
passage in the forward flow direction, and whereby a
backwash liquid is passed into and along said inner flow
passage, through said filter openings, and in-to said
outer flow passage to remove solid particles collected
on said filter in a hack flow direction, said outer
housirlg 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
surface that has said liquid flow openings 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 backfill
direction, said outer housing being tapered along its
-aye $
length to converge in a direction away from said inlet
toward said outlet in the forward liquid flow direction
and wherein said inner filter has a substantially
uniform external dimension substantially throughout its
lengthwise extent.
According to another aspect of the present
invention there is provided in a filtering apparatus
adapted for briny cleaned by back washing, the
combination comprising: a hollow filter with an inner
flow passage closed at an inlet end to flow in an axial
direction and open at an outlet end to flow in the axial
direction, said hollow filter having an outer face and
an inner face with a plurality of liquid flow openings
extending between said outer and inner faces; and a
filter medium forming said outer face, and an inner
support grid defining said inner face and supporting
said filter medium, said hollow filter being disposed in
an outer housing to define an outer annular flow passage
between said outer housing and said filter and having an
inlet, whereby a liquid with solid particles to be
filtered therefrom is passed through said inlet into
said outer annular wow passage and between said outer
and inner faces through said openings, the solid
particles collecting on the outer surface of said filter
medium and said liquid passing through said inner flow
passage and out said outlet in a forward flow direction,
and whereby a back washing liquid is passed back through
said outlet, into said inner passage, between said inner
and outer faces through said openings, through said
outer passage, and out said inlet in a backfill
direction to remove particles collected on said medium
in a back washing operation, said outer housing being
tapered along its length in relation to the external
dimension of said hollow filter along the filter face
that has said liquid flow openings so that said outer
it . 5
--2b~
flow passage between said outer housing and said inner
filter along the filter face that has said liquid flow
openings converges in the direction away from said inlet
to provide a decrease in liquid velocity and an increase
in liquid pressure in the direction away from said inlet
during a forward flow of liquid and, conversely, an
increase in liquid velocity and a decrease in liquid
pressure in the direction toward said inlet in said
outer flow passage during the backfill, said taper
providing substantially the same pressure drop between
said outer face and said inner face of said filter along
substantially the lengthwise extent of said filter face
that has said liquid flow openings during both said
forward flow operation and said backfill operation, said
outer housing being tapered along its length to converge
in a direction away from said inlet toward said outlet
in the forward liquid flow direction and wherein said
inner filter has a substantially uniform external
dimension substantially -throughout its lengthwise
extent.
According to still a further 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 back washing, the
combination comprising: an outer housing and an inner
filter disposed within the outer housing defining
there between 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 flow
passage, through said filter, and into said outer flow
~2c-
passage to remove solid particles collected on said
filter in a backfill direction, 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
backfill directive, said outer housing being tapered
along its length to converge in a direction away from
said inlet toward said outlet in the forward liquid flow
direction and wherein said inner filter has a
substantially uniform external dimension substantially
throughout its lengthwise extent.
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 proton 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 l;
Figure 3 is an enlarged vertical sectional view
at the outlet end of the filtering apparatus chutney in
Figure l;
Figure 4 is an end elevation view showing one
half of a riny-like segment forming the support grid of
the filter with the opposite half not shown but being
identical in construction;
if
I D .
I ~22~-3~
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 lit-
toning 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 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 lit-
ton 13 arranged in inner spaced concentric arrangement
about a common central axis 15 to define there between
an annular outer flow passage I An inner flow past
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 passage 17
within jilter 13 is closed to flow in the axial direct
Tony at the inlet end and the outlet end 21 is open to
flow in the axial direction so that in general the
liquid passes via inlet 19, through the peripheral sun-
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 I
I
-4-
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 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 of openings 36 distributed substantially uniformly over
the entire peripheral surface area extending from an
outer surface to an inner surface thereof to pass a
liquid there through. 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 circumferential spaced ten-
soon rods 39 having external threads on both ends.
Rods 39 extend through aligned axial holes 41 in the
segments and through a hole in a front end plate 43 and
I 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 drawn tightly to-
getter between the front end plate 43 and rear end ring
44 as nuts 45 are tightened.
As best seen in Figures 4 and I each ring-
like segment 38 includes a ring portion 47 that is con-
tenuous for a full arc of 360 degrees and a plurality
of circumferential spaced pairs of axial portions 48
and 49 that project from opposite sides ox the ring
--5--
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 go 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 57 affixed to and extending
axially in front of the front end plate 43 and a tutu-
far support 56 affixed to and extending rearwardly from
the inside of deflector plate 55 and telescopes in
support 56. Four relatively thin, circumferential
spaced, radial plates 58 are affixed at 90-degree in-
tervals along an inner edge to the periphery of plate
55. on 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 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 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.
--6--
The outer housing 11 has an internal dime-
soon related in a particular way to the external dime-
soon 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-
vise a selected fluid velocity for the flow through theater annular passage, which in turn establishes a
selected pressure along the outer annular passage dun-
in a forward flow operating condition. Moreover, a
selected shell taper and thereby a selected width of
I the outer 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 so-
looted 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 pros-
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 along an x-y
coordinate system that has liquid pressure plotted
along the "y" axis and distance along the filter plot-
ted along the I 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 down sloping line. In turn, during a forward
I
--7--
fluid flow operation the pressure at the inlet of the
inner flow passage 17 gradually decreases toward the
outlet 21 along a down sloping 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
lo of uniform dimension, rather than taper for the outer
flow passage, would gradually increase from inlet to
outlet along an up sloping 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 gradually
increases toward the inlet 19 along an up sloping line
The taper of the shell 24 is selected with respect to
backfill liquid velocity so that the pressure at the
outlet in the outer passage 16 gradually increases
along an up sloping line to a pressure at the inlet, and
again the pressure lines for the inner and outer past
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 down slop-
in 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-
lying liquid flow in both the forward and bac]cflow opt
orations 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
-8- I
is coupled to an inlet pipe 74 defining an inlet champ
berm on automatic backfill valve 75 is connected to
the inlet pipe 74 and connects to a backfill manifold
76.
The downstream end portion of inlet pipe 74
has an external groove 78, 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 release
ably couple the control valves 73 and 75 to the inlet
end of the filtering apparatus 11. 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 port
lion 85 with an annular groove 86. A coupling ring 87
has end portions that fit in groove 32 of said groove
26 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 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 lit-
ton 13, and into inner flow passage 47 in the core of
the filter. This filtered liquid flows through outlet
valve 84 and into outlet manifold 93 for intended use.
In the back washing operation the valve 73
closes, shutting off forward flow through the filter.
9 ~2~3~L~
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 limp
station, 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
a-t 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 gym
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.
