Abstrict A water filtration system incorporating a fluid flow meter has
a modular turbine casing assembly in which a turbine is located
between upstream and downstream casing elements of identical shape
and formed to be stacked so as to trap the turbine in between. The
turbine is magnetized and rotation of the turbine is monitored electronically
with a reed switch having a lead wire which is positioned proximate
to the turbine to sense fluctuations in a magnetic field created
by the turbine on rotation of the turbine. The reed switch housing
itself is disposed at a location remote from the turbine. The system
further includes processor for calculating an adjusted accumulated
count data for low volumetric flow rates which are less than a predetermined
threshold value. Advantageously, the invention can be used to reliably
measure very low flow rates with very little power drawn.
Claims What is claimed is:
1. Modular turbine casing assembly having an upstream casing element,
a downstream casing element, and a turbine located between said
upstream and downstream casing elements, each said upstream and
downstream casing elements having a cylindrical wall defining an
internal shoulder at an upstream end, and a cooperating external
shoulder at a downstream end so that said upstream and downstream
casing elements may be stacked, each said upstream and downstream
casing elements having a turbine locator consisting of a central
hub and a number of radially extending ribs coupling the hub to
a circumferential rim adjacent to said cylindrical wall, each hub
having a spindle extending toward the upstream end of the casing
element and an opposing dimple exposed to the downstream end of
the casing element, the turbine having 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 respectively,
the turbine being adapted to be magnetized so that rotation of the
turbine can be monitored electronically, and the peripheral collar
having 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.
2. Modular turbine casing assembly according to claim 1 in which
the peripheral outer collar has a pair of oppositely disposed pockets
for receiving a pair of discrete magnets.
3. Modular turbine casing assembly according to claim 1 in which
the turbine locator is located at the downstream end of the associated
cylindrical wall.
4. Modular turbine casing assembly according to claim 1 in which
the circumferential rim of the turbine locator has a width which
is commensurate with the width of the peripheral collar of the turbine
so that turbulence of any fluid flowing through the assembly is
minimized.
5. Modular turbine casing assembly according to claim 1 in which
the radially extending ribs define openings therebetween which are
adapted to maximize fluid flow over the turbine blades.
6. A fluid flow conduit having a modular turbine casing assembly
according to claim 1 the fluid flow conduit having ends adapted
to be coupled to a fluid flow installation and the modular turbine
assembly being disposed in the said fluid flow conduct to allow
fluid to exit the turbine into a fluid stream, the fluid flow conduit
further having electronic sensing means for counting the revolutions
of the turbine.
7. A fluid flow conduit according to claim 6 in which the electronic
sensing means includes a reed switch mounted in a reed housing having
lead wires for conducting electricity into and out of the reed switch,
a selected one of said lead wires being positioned at a location
proximate to said turbine to sense fluctuations in a magnetic field
created by said turbine upon rotation thereof, said reed housing
being disposed at a location remote from the turbine.
8. A fluid flow conduit according to claim 6 having a fluid flow
meter, the fluid flow meter having electronic sensing means for
generating count data N corresponding to the revolutions of the
turbine, the electronic sensing means including a reed switch mounted
in a reed housing having lead wires for conducting electricity into
and out of the reed switch, a selected one of said lead wires being
positioned in a receiving groove formed in a head cover at a location
proximate to said turbine to sense fluctuations in a magnetic field
created by said turbine upon rotation thereof, said reed housing
being disposed in the head cover at a location remote from the turbine;
the fluid flow meter further having a lapsed 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, said factor F
being equal to 1 when a threshold count rate is exceeded and F being
greater than 1 when the count rate is below said threshold count
rate; and output means for alerting a user when an adjusted accumulated
count data .SIGMA.NF has exceeded a predetermined value selected
to indicate that a pre-determined volume of fluid has been filtered
or when the lapsed time data T has exceeded a predetermined period.
9. A water filtration system having a head cover removably coupled
to a sump container for receiving filtration media therein, the
head cover having a first passage defining a raw water inlet and
a second passage defining a clean water outlet, both said raw water
inlet and said clean water outlets being in fluid communication
with said sump container, and electronic sensing means for counting
the revolutions of a magnetized turbine adapted to determine volumetric
water flow through the water filtration system, the electronic sensing
means including a reed switch mounted in a reed housing having lead
wires for conducting electricity into and out of the reed switch,
a selected one of said lead wires being positioned in a receiving
groove formed in the head cover at a location proximate to said
turbine to sense fluctuations in a magnetic field created by said
turbine upon rotation thereof, said reed housing being disposed
in the head cover at a location remote from the turbine.
10. A water filtration system according to claim 9 in which the
reed switch is selected to have a small diameter lead wire of less
than 0.020 inches to minimize any counter rotating effect on the
magnetized turbine.
11. A water filtration system having a head cover removably coupled
to a sump container for receiving filtration media therein, the
head cover having a first passage defining a raw water inlet and
a second passage defining a clean water outlet, both said raw water
inlet and said clean water outlets being in fluid communication
with said sump container, a modular turbine casing assembly disposed
in said clean water outlet, the modular turbine casing assembly
having an upstream casing element, a downstream casing element,
and a turbine located between said upstream and downstream casing
elements, each said upstream and downstream casing elements having
a cylindrical wall defining an internal shoulder at an upstream
end, and a cooperating external shoulder at a downstream end so
that said upstream and downstream casing elements may be stacked,
each said upstream and downstream casing elements having a turbine
locator consisting of a central hub and a number of radially extending
ribs coupling the hub to a circumferential rim adjacent to said
cylindrical wall, each hub having a spindle extending toward the
upstream end of the casing element and an opposing dimple exposed
to the downstream end of the casing element, the turbine having
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 respectively, the turbine being adapted
to be magnetized so that rotation of the turbine can be monitored
electronically, and the peripheral collar having a height and diameter
adapted to locate inside the cylindrical wall of the down stream
casing element so that the turbine may rotate freely between the
upstream and downstream casing elements; and electronic sensing
means for counting the revolutions of the turbine, the electronic
sensing means including a reed switch mounted in a reed housing
having lead wires for conducting electricity into and out of the
reed switch, a selected one of said lead wires being positioned
in a receiving groove formed in the head cover at a location proximate
to said turbine to sense fluctuations in a magnetic field created
by said turbine upon rotation thereof, said reed housing being disposed
in the head cover at a location remote from the turbine.
12. A water filtration system according to claim 11 where the modular
turbine casing assembly is disposed in an elbow formed in said clean
water outlet so that clean water exits from the modular casing assembly
into a transverse passage for carrying clean water out of the system,
the transverse passage having an effective internal diameter commensurate
with the diameter of the turbine.
13. A fluid filtration system including a fluid flow meter characterized
by a substantially constant output having a predetermined variance
above a threshold volumetric flow rate and substantially linear
relationship between output and volumetric flow rate over a predetermined
range of volumetric flow rate below said threshold, the fluid flow
meter including a revolution counter commensurate with volumetric
flow for generating count data N; a lapsed 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, said factor F
being equal to 1 when a threshold count rate is exceeded and F being
greater than 1 when the count rate is below said threshold count
rate; and output means for alerting a user when an adjusted accumulated
count data .SIGMA.NF has exceeded a predetermined value selected
to indicate that a pre-determined volume of fluid has been filtered
or when the lapsed time data T has exceeded a predetermined period.
14. A water filtration system having a head cover removably coupled
to a sump container for receiving filtration media therein, the
head cover having a first passage defining a raw water inlet and
a second passage defining a clean water outlet, both said raw water
inlet and said clean water outlets being in fluid communication
with said sump container, a modular turbine casing assembly disposed
in said clean water outlet, the modular turbine casing assembly
having an upstream casing element, a downstream casing element,
and a turbine located between said upstream and downstream casing
elements, each said upstream and downstream casing elements having
a cylindrical wall defining an internal shoulder at an upstream
end, and a cooperating external shoulder at a downstream end so
that said upstream and downstream casing elements may be stacked,
each said upstream and downstream casing elements having a turbine
locator consisting of a central hub and a number of radially extending
ribs coupling the hub to a circumferential rim adjacent to said
cylindrical wall, each hub having a spindle extending toward the
upstream end of the casing element and an opposing dimple exposed
to the downstream end of the casing element, the turbine having
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 clement respectively, the turbine being adapted
to be magnetized so that rotation of the turbine can be monitored
electronically, and the peripheral collar having 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; and a fluid flow meter
having electronic sensing means for generating count data N corresponding
to the revolutions of the turbine, the electronic sensing means
including a reed switch mounted in a reed housing having lead wires
for conducting electricity into and out of the reed switch, a selected
one of said lead wires being positioned in a receiving groove formed
in the head cover at a location proximate to said turbine to sense
fluctuations in a magnetic field created by said turbine upon rotation
thereof, said reed housing being disposed in the head cover at a
location remote from the turbine; the fluid flow meter further having
a lapsed 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, said factor F being equal to 1 when a threshold count
rate is exceeded and F being greater than 1 when the count rate
is below said threshold count rate; and output means for alerting
a user when an adjusted accumulated count data .SIGMA.NF has exceeded
a predetermined value selected to indicate that a pre-determined
volume of fluid has been filtered or when the lapsed time data T
has exceeded a predetermined period.
Description 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 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 U.S. Pat. No. 3053087; U.S.
Pat. No. 3610039; U.S. Pat. No. 5372048; and U.S. Pat. No. 5876610.
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 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 .SIGMA.NF 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;
FIG. 9 is a schematic flow chart illustrating a process for adjusting
accumulated count data and user alert;
FIGS. 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 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.
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 arc 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 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
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 .SIGMA.NF 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 maybe 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 120 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.
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. |