Note: Descriptions are shown in the official language in which they were submitted.
CA 02587003 2007-05-16
TITLE OF THE INVENTION:
Fluid Filtration System With Fluid Flow Meter
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FIELD OF THE INVENTION
This invention relates to a fluid filtration system, in particular, to a water
filtration system for
domestic use and which includes a flow meter for alerting the user when
filtration media needs to
be replaced in the filtration system.
BACKGROUND OF THE INVENTION
While municipal water supplies are generally very good and provide acceptable
quality drinking
water, many home owners prefer to filter the main water supply in order to
provide a safer, better
tasting water in the home. Conveniently, such filtration equipment may be
installed at the point of
use under a sink near a faucet. The water supply is allowed to pass through a
selected number of
filter cartridges for removing sediment, dirt, rust and algae; to absorb
objectionable taste, odours,
colours and chlorine; and to reduce contaminants such as pesticides, and also
to trap and kill
harmful bacteria, cysts, and protozoa, as the case may be. Depending on the
nature of the filter
media used to treat the water, and the quality of the source water, it may
become necessary to
replace the filter on a periodic basis. In the case of a flow through water
filter system, a convenient
measure of when the filter media has reached its maximum capacity is to
monitor the time during
which the cartridge is in use. Alternatively, it is desirable to measure the
volume of water being
treated by the filter assembly.
For example, it is suggested by manufacturers that certain activated carbon
cartridges be replaced
typically every four months or six months depending on the cartridge and that
a ceramic cartridge
should be replaced every twelve months. It is however recognized that over a
period of for example
six months, different users will consume more or less water. It is therefore
preferable to determine
the volumetric throughput of the filter assembly and to change the filter
media accordingly. For
example, it is suggested that an activated carbon filter media should be
replaced before a period of
six months has expired if the throughput exceeds 600 gallons, failing which,
the quality of the water
may be adversely affected.
While water flow meters are generally well known, they are generally used by
utility supply
companies monitoring large volumetric flows. One of the problems which needs
to be addressed
in a domestic water supply environment is that the water volume throughput is
intermittent at the
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point of use and may also have a very small flow rate. It then becomes
challenging to provide
accurate measurements of volume flow rate at a reasonable cost. Flow meters
which incorporate
a magnetized turbine are described in US 3,053,087; US 3,610,039; US
5,372,048; and US
5,876,610.
An object of this invention is to provide a fluid flow meter which is
inexpensive to manufacture,
which can reedily be incorporated into a conduit of a standard water
filtration system and which will
operate satisfactorily at the anticipated low flow rate prevalent in domestic
water filtration units.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, there is provided a
modular turbine casing
assembly having an upstream casing element, a downstream casing element, and a
turbine located
between said upstream and downstream casing elements. The upstream and
downstream casing
elements each have a cylindrical wall that defines an internal shoulder at an
upstream end and a
cooperating external shoulder at a downstream end so that the upstream and
downstream casing
elements may be stacked. Each of the upstream and downstream casing elements
has a turbine
locator consisting of a central hub and a number of radially extending ribs
coupling the hub to a
circumferential rim adjacent to the cylindrical wall, each hub having a
spindle that extends toward
the upstream end of the casing element and an opposing dimple exposed to the
downstream end of
the casing element. The turbine has a central hub and a number of radially
extending turbine blades
coupling the hub to a peripheral collar of predetermined width, the central
hub having an axially
extending spindle on an upstream side and a recess on a downstream side
adapted to cooperate with
the dimple of the upstream casing element and the spindle of the downstream
casing element. The
turbine is adapted to be magnetized so that rotation of the turbine can be
monitored electronically
and the peripheral collar of the turbine has a height and diameter adapted to
locate inside the
cylindrical wall of the downstream casing element so that the turbine may
rotate freely between the
upstream and downstream casing elements.
In accordance with another aspect of the invention, a water filtration system
is provided which
includes electronic sensing means for counting the revolutions of a magnetized
turbine, the
electronic sensing means including a reed switch mounted in a reed housing
having lead wires for
conducting electricity in and out of the reed switch, a selected one of said
lead wires being
positioned in a receiving groove formed in the head cover for a water
filtration system which is
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removably coupled to a sump container for receiving filtration media. The
receiving groove is
proximate to the turbine to sense fluctuations in a magnetic field created by
the turbine upon
rotation of the turbine. Conveniently, the reed housing itself may be disposed
in the head cover at
a location which is remote from the turbine.
~
In accordance with yet another aspect of the invention, the fluid filtration
system includes a fluid
flow meter that is characterized by a substantially constant output having a
predetermined variance
above a threshold volumetric flow rate and a substantially linear relationship
between output and
volumetric flow rate over a predetermined range of volumetric flow rate below
said threshold. The
fluid flow meter includes a revolution counter commensurate with volumetric
flow for generating
count data N; an elapsed time counter for generating a lapsed time data T;
processing means for
adjusting the count data N by multiplying N with a predetermined factor F. The
factor F is equal
to one above a threshold count rate and is greater than one below the
threshold count rate. Output
means are included for alerting a user when the adjusted accumulated count
data ENF has exceeded
a predetermined value selected to indicate that the predetermined volume of
fluid has been filtered
or when the lapsed time exceeds a predetermined period, whichever is reached
first.
BRIEF DESCRIPTION OF THE DRAWINGS
The above mentioned aspects of the invention and associated features will now
be described with
reference being made to the accompanying drawings in which:
Fig. 1 is a side elevation view of a water filtration housing and cartridge
assembly;
Fig. 2 is a cross-sectional view drawn through line 2-2 of Fig. 1;
Fig. 3 is a cross-sectional view through the water filtration housing and
cartridge assembly
of Fig. 1 drawn on a line orthogonal to 2-2;
Fig. 4 is an assembly drawing of a modular turbine casing assembly in
accordance with the
invention;
Fig. 5 is a cross-sectional drawn to a larger scale through the modular
turbine casing
assembly of Fig. 4;
Fig. 6 is a cross-sectional view of a portion of a head cover for the water
filtration housing
and housing and cartridge assembly of Fig. 1;
Fig. 7 is a top plan view of the head cover forming part of the water
filtration housing and
housing and cartridge assembly;
Fig. 8 is a calibration graph correlating flow rate with turbine count;
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Fig. 9 is a schematic flow chart illustrating a process for adjusting
accumulated count data
and user alert;
Fig. 10 and 11 are cross-sectional views showing the modular turbine casing
assembly
according to the invention disposed in alternative conduits.
DETAILED DESCRIPTION WITH REFERENCE To DRAWINGS
A typical water filtration housing and cartridge assembly is generally
indicated in the drawings by
reference numeral 20. The housing and cartridge assembly 20 has a head cover
22 which is
removably attached to a sump container 24. The head cover 22 has a raw water
inlet 26 formed
therein and a clean water outlet 28 (Fig. 3) is formed opposite from the raw
water inlet 26. The raw
water inlet 26 and clean water outlet 28 are disposed to be in fluid
communication with a cold water
supply line (not shown). Typically, the sump 24 is supported by means of a
bracket to a fixed
structure such as a cabinet (not shown). The sump container 24 is elongate and
has a closed bottom
end which is generally convex. The diameter of the sump container is designed
to accommodate,
in a close fitting manner, a cylindrical filter media 30 which, according to
the intended application,
may be a self, disinfecting, silver impregnated ceramic cartridge or a
disposable activated carbon
cartridge. In the embodiment described, the filter media will be assumed to be
an activated carbon
cartridge which requires replacement every six months or when a volumetric
throughput of 600
gallons has been filtered. It will be seen from Fig. 3 that the filter media
cartridge 30 has a bottom
cap 32 and an annular top cap 34 which seals the top and bottom ends thereof.
In addition, the head
cover 22 has a central well or spigot 38 which extends axially into the sump
container 24 and is
dimensioned to nest inside a central core 40 formed in the filter media
cartridge 30. Accordingly,
any water or fluid entering the water filtration housing and cartridge
assembly 20 through the raw
water inlet 26 as indicated by arrow 42 is forced to travel from the head
cover 22 into the sump
container 24 through an annular passage 44 defined between the sump container
24 and the filter
media cartridge 30, through the filter media cartridge 30 and into the central
core 40 before
emerging through the spigot 38 into the head cover 22 and out the clean water
outlet 28 as indicated
by arrow 46.
In accordance with a first aspect of the invention, there is provided a
modular turbine casing
assembly generally indicated in the drawings by reference numeral 48.. The
modular turbine casing
assembly 48 is conveniently disposed inside the spigot 38 in order to lie in
the path of clean water
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emerging through the central aperture 40 of the filter media cartridge 30 as
it enters the head cover
22 before emerging from the clean water outlet 28.
The modular turbine casing assembly 48 is shown in more detail in Fig. 4 and
comprises an
upstream casing element 50, a downstream casing element 52 and a turbine 54
located between the
upstream and downstream casing elements. The modular turbine casing assembly
48 is shown in
cross section and in an assembled configuration in Fig. 5 of the drawings. The
upstream casing
element 50 and the downstream casing element 52 are identical in shape and may
therefore be
molded using a single cavity or multiple identical cavities. Like parts of the
upstream and
downstream casing elements 50, 52 will therefore be identified by like
numerals. Acetal is a
suitable material for fabricating the turbine casing.
Each of the upstream and downstream casing elements 50, 52 has a cylindrical
wall 56 which can
be made to a thickness of 0.075 in and which defines an internal shoulder 58
at an upstream end and
a cooperating external shoulder 60 at a downstream end so that said upstream
and downstream
casing elements may be stacked.
Each said upstream and downstream casing elements 50, 52 has a turbine locator
62 consisting of
a central hub 64 and a number of radially extending ribs 66 coupling the hub
to a circumferential
rim 68 adjacent to the cylindrical wall 56. Each hub 64 has a spindle 70
extending toward the
upstream end of the casing element and an opposing dimple 72 exposed to the
downstream end of
the casing element.
The purpose of the turbine locator 62 is to locate the turbine 54 between the
upstream casing
element 50 and the downstream casing element 52 as will be explained. The
turbine 54 has a central
hub 74 and a number of radially extending turbine blades 76 coupling the hub
74 to a peripheral
collar 78. The turbine blades 76 are oriented transversely with respect to the
collar 78 so that any
fluid flow impinging on the blades will cause the turbine 54 to rotate. The
central turbine hub 74
has an axially extending spindle 80 on an upstream side and a recess 82 on a
downstream side
adapted to cooperate with the dimple 72 of the upstream casing element and the
spindle 70 of the
downstream casing element respectively.
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The turbine 54 has a pair of oppositely disposed pockets.84 formed in the
collar 78 for receiving
a pair of magnets 86. The turbine 54 is thereby adapted to be magnetized so
that rotation of the
turbine can be monitored electronically. The peripheral collar 78 is
dimensioned to locate inside
the cylindrical wall 56 of the downstream casing element 52 so that the
turbine 54 may rotate freely
between the upstream and downstream casing elements 50, 52. Conveniently, the
turbine locator
62 is located at the downstream end of the associated cylindrical wall 56.
It will be noted that dimples 72 and recess 82 are all oriented so as to be
exposed to the downstream
end of the modular turbine casing assembly 48 and this feature conveniently
minimizes entrapment
of any loose filter particles which might otherwise interfere with the
rotational motion of the turbine
54 where the spindles 70, 80 bear on the adjacent recess 82 and dimple 72.
The circumferential rim 68 of the turbine locator 62 has a width which is
commensurate with the
width of the peripheral collar 78 of the turbine 54 so that turbulence of any
fluid flowing through
the assembly 48 is minimized. Further, the radially extending ribs 66 define
openings 88
therebetween which are adapted to maximize fluid flow over the turbine blades
76.
It will therefore be appreciated that the modular turbine casing assembly 48
can be assembled into
a neat capsule which may conveniently be inserted into a fluid outlet of
commensurate diameter.
In the example given, the modular turbine casing assembly 48 locates in the
spigot 38. Because
there are so few parts requiring assembly, there is very little structural
interference with water
flowing through the modular turbine casing assembly 48 and this allows the
assembly to be
responsive to very low flow rates. Appropriate location of the modular turbine
casing assembly 48
in a water filtration housing and housing and cartridge assembly 20 will
minimize any inaccuracies
resulting from turbulence in the water flow. For example, it will be seen from
Fig. 3 of the
accompanying drawings that the modular turbine casing assembly is downwardly
spaced from the
clean water outlet passage which terminates in the clean water outlet 28.
In accordance with a second aspect of the invention, electronic sensing means
are provided for
counting the revolutions of the magnetized turbine 54 in order to determine
volumetric water flow
through the water filtration housing and housing and cartridge assembly. Most
preferably, the
electronic sensing means will include a reed switch mounted in a reed switch
housing 90
electronically coupled to an electronic circuit board 92 which is mounted to
the head cover 22 as
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shown in Fig. 6. The reed switch housing 90 has lead wires for conducting
electricity into and out
of the reed switch and one of the lead wires 94 is positioned in a receiving
groove 96 formed in the
head cover 22 at a location proximate to the turbine 54 to sense fluctuations
in a magnetic field
created by the turbine 54 on rotation of the turbine. This allows the reed
switch housing 90 to be
disposed in the head cover 22 at a location which is remote from the turbine
54. In order to have
sensitivity to changes in magnetic fields at very low fluid flow rates, the
reed switch is selected to
have a small diameter lead wire of less than 0.020 inches. A preferred reed
switch will have a
miniature single pole, single throw, double-ended reed switch with normally
open contacts and
containing two magnetically actuated reeds. The fine diameter wire is critical
to allow operation
at low flow rates as otherwise the attractive force with the magnetic field is
so high that the turbine
54 could slow down or otherwise interfere with the motion of the turbine and
the readings would
be inaccurate. Conveniently, by locating the lead wire 94 close to the turbine
54, the reed switch
itself may be spaced as far as 0.250 inches away from the magnetic source. The
electronic circuit
board 92 is shielded by a translucent cover 98 through which a user may
observe indicator lights 100
and have access to a reset button 102 for initializing the electronic circuit
board. A capacitor 101
powered by a watch size battery 103 is electrically coupled to the reed
switch.
The entire system is powered with very little energy. Conveniently, a three
volt coin type battery
(CR2032) is sufficient to operate the fluid flow meter in accordance with the
invention. It is
expected that the battery life will be approximately two years and the unit
may have a respective
visual alarm to indicate whether the battery is still operating.
Operational tests conducted on a fluid filtration system incorporating the
water filtration housing
and housing and cartridge assembly 20 and modular turbine casing assembly 48
in accordance with
the invention and coupled to the electronic circuit board 92 with reed switch
circuitry to define a
fluid flow meter show that the turbine counts per gallon are relatively
constant above threshold
volumetric flow rates of 0.5 gallons per minute while there is a substantially
linear relationship
between output and volumetric flow rates below 0.5 gallons per minute and
exceeding 0.25 gallons
per minute. A graphical output illustrating the observations is shown in Fig.
8 of the accompanying
drawings.
A schematic flow chart of a fluid flow meter made in accordance with the
invention is illustrated
in Fig. 9. The fluid flow meter includes a fluid revolution counter 104 to
generate an accumulated
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count data N (106) generated from the reed switch pulses on each rotation of
the turbine 54. In
addition, the fluid flow meter has an elapsed time counter 108 for generating
lapsed time data T.
Processing means 109 then compares a count rate R to a threshold value of the
count rate in order
to select a predetermined multiplying factor F for adjusting the accumulated
count data N. If the
count rate is less than 0.08 sec/count (110) in the sample given, the
adjustment factor is 1 and
therefore there is no change to the count data N. However, if the count rate R
is calculated to be
more than 0.08 sec/count a further test is applied to ascertain whether the
adjustment factor should
be F=1.1 at a count rate less than 0.10 sec/count (112) or F=1.2 for a count
rate R greater than 0.10
sec/count (114). The adjustment factor F is then multiplied by the count data
N (116) and added
to a cumulative total YNF and compared to a predetermined value in order to
determine-whether
an alarm must be activated. Activation of the alarm is indicated in Box 118.
In the embodiment
shown, the alarm is a visual alarm in which the indicator light 100 will flash
periodically at a preset
volume of 600 gallons or lapsed time of six months (120) whichever is reached
first.
After replacement of an activated carbon filter media, the reset button 102
may be depressed to
initialize the count data N and lapsed time data T. Additional alarms may be
incorporated into the
fluid flow meter which are activated, for example, in the case of a ceramic
filter media, only when
a predetermined time limit of twelve months has elapsed. The visual alarm
could be a different
colour so that where the water filtration system includes a tandem unit
comprising an activated
carbon filter and a ceramic filter disposed side by side, the appropriate
filter media is serviced.
It will be understood that several variations may be made to the above
described embodiment of the
invention within the scope of the appended claims. In particular, the modular
tubular casing
assembly may be located in any suitable conduit through which a fluid flows in
order to measure
the volumetric flow of the fluid through the conduit.
In Fig. 10, the modular turbine casing assembly 48 is shown incorporated into
an S-shaped elbow
conduit 122 consisting of two components 124 and 126 joined together.
Electronic sensing means
128 are disposed outside the elbow to sense the rotations of the turbine in
the modular turbine
casing assembly 48. Note that the modular turbine casing assembly 48 is
downwardly spaced in the
exit component 124 so that fluid may exit the turbine into a transverse fluid
stream.
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In Fig. 11, the modular turbine casing assembly 48 is shown incorporated into
a straight conduit 130
having oppositely disposed bell-shaped ends 132, 134 so that it may be
retrofitted into existing
water conduct installations.
It will also be understood that the processing means incorporated into the
fluid flow meter according
to the invention may be modified to provide a number of different alarms
according to the nature
of the filter media being used. Other such variations will be apparent to
those skilled in the art.
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