Water filter abstract
A low cost method and apparatus for indicating when to replace
a water filter in a water and ice delivery system for a refrigerator.
The invention uses a low cost microprocessor and senses the operational
condition of an ice maker water valve, a water dispenser valve to
monitor and track water usage. The microprocessor has a built-in
memory to retain water usage and other data during a power outage.
The invention also senses the status of a door switch to permit
user input of a reset message indicating that the filter has been
changed as well as an input indicating a different type of filter
has been installed. The microprocessor controls a tri-color light
emitting diode to display the status of the filter as "good",
"order" or "change" which is determined based
on the selection of the type of filter system, the amount of time
since the last filter change, and the amount of water usage since
the last filter change.
Water filter claims
What is claimed as novel is as follows:
1. A method for determining the need to replace a water filter
of a refrigerator having at least one water-using accessory that
is supplied water from the water filter in response to a demand
for filtered water by the at least one water-using accessory, the
method comprising: determining the elapsed time of the supply of
filtered water from the water filter to the at least one water-using
accessory; determining the volume of filtered water supplied for
the elapsed time by the step of calculating the product of the elapsed
time and a predetermined water flow rate of the at least one water-using
accessory; maintaining a total filtered-water volume by summing
the calculated filtered-water volume; and indicating to the user
when the total filtered-water volume reaches an amount that represents
a need to replace the filter.
2. The method according to claim 1 wherein the determination of
the elapsed time comprises sensing the initiation and cessation
of the flow of filtered water from the filter to the at least one
water-using accessory for each demand and determining the elapsed
time between the initiation and cessation.
3. The method according to claim 2 wherein the determination of
the elapsed time between the initiation and cessation comprises
monitoring a clock between the initiation and cessation and storing
a time value representative of the elapsed time in the memory of
a microprocessor.
4. The method according to claim 3 wherein the step of calculating
of product comprises storing the flow rate for the at least one
water-using accessory in the memory of the microprocessor and using
the microprocessor to multiply the stored time value by the stored
flow rate to obtain a filtered-water volume value.
5. The method according to claim 4 wherein maintaining of a total
filtered-water volume comprises adding the filtered-water volume
value to a filtered water total volume value stored in the memory
of the microprocessor.
6. The method according to claim 5 wherein the time value is determined
for each demand.
7. The method according to claim 6 wherein the filtered-water volume
value is determined for each demand.
8. The method according to claim 7 wherein the filtered water total
volume value is determined by summing the filtered-water volume
value at the end of each demand with the current filtered water
total volume value.
9. The method according to claim 8 and further comprising, when
the refrigerator has multiple water-using accessories with different
flow rates, selecting the flow rate for the one of the multiple
water-using accessories currently demanding water from multiple
flow rates stored in the microprocessor memory.
10. A method for determining the need to replace a water filter
in a water supply system of a refrigerator having at least one water-using
accessory, the water supply system includes an electrically actuated
valve that controls the flow of water from the filter to the at
least one water-using accessory and a controller operably coupled
to the at least one water-using accessory and electrically coupled
to the valve to open and close the valve in response to the demand
from the at least one water-using appliance, the method comprising:
determining the elapsed time that the valve is open; determining
the volume of filtered water supplied for the elapsed time by the
step of calculating the product of the elapsed time and a predetermined
water flow rate of the at least one water-using accessory; maintaining
a total filtered-water volume by summing the calculated filtered-water
volume; and indicating to the user when the total filtered-water
volume reaches an amount that represents a need to replace the filter.
11. The method according to claim 10 wherein the determination
of the elapsed time comprises the controller determining the time
that the valve is open.
12. The method according to claim 11 wherein the determination
of the elapsed time between the initiation and cessation comprises
monitoring a clock in the controller between the opening and closing
of the valve by the controller and storing a time value representative
of the elapsed time in the memory of a microprocessor of the controller.
13. The method according to claim 12 wherein the step of calculating
of product comprises storing the flow rate for the at least one
water-using accessory in the memory of the microprocessor and using
the microprocessor to multiply the stored time value by the stored
flow rate to obtain a filtered-water volume value.
14. The method according to claim 13 wherein maintaining of a total
filtered-water volume comprises adding the filtered-water volume
value to a filtered water total volume value stored in the memory
of the microprocessor.
15. The method according to claim 14 wherein the time value is
determined for each demand.
16. The method according to claim 15 wherein the filtered-water
volume value is determined for each demand.
17. The method according to claim 16 wherein the filtered water
total volume value is determined by summing the filtered-water volume
value at the end of each demand with the current filtered water
total volume value.
18. The method according to claim 17 and farther comprising, when
the refrigerator has multiple water-using accessories with different
flow rates, selecting the flow rate for the one of the multiple
water-using accessories currently demanding water from multiple
flow rates stored in the microprocessor memory.
Water filter description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a water filtration system for a refrigerator
and more particularly to an indicator for notifying a user when
to change the filter.
2. Description of the Related Art
Many refrigerators, and especially those using a side-by-side configuration
wherein the fresh food compartment is to the side of the frozen
food compartment, include integrated ice and water delivery systems.
Typically, such systems deliver water and ice through the door of
the frozen food compartment to a ice and water station recessed
in the door.
Examples of such systems can be seen in U.S. Pat. No. 5907958
issued Jun. 1 1999 to Coates, et al. and entitled "Refrigerator
water filter"; U.S. Pat. No. 5813245 issued Sep. 29 1998
to Coates, et al. and entitled "Pressure relief circuit for
refrigerator contained water filter"; U.S. Pat. No. 5715699
issued Feb. 10 1998 to Coates, et al. and entitled "Refrigerator
water filter"; U.S. Pat. No. 5707518 issued Jan. 13 1998
to Coates, et al. and entitled "Refrigerator water filter";
U.S. Pat. No. 5135645 issued Aug. 4 1992 to Sklenak, et al. and
entitled "Refrigerator water filter"; and U.S. Pat. No.
3982406 issued Sep. 28 1976 to Hanson, et al. and entitled "Refrigerator
water storage and dispensing system with water filter".
Increasingly such systems incorporate a filtration system with
a replaceable filter element or cartridge so as to improve the quality
of the ice and water delivered to the user of the refrigerator.
Since the filters must be periodically replaced to maintain the
quality of the water, various methods and apparatus could be used
to notify the user of the need to change the filter. However, such
many potential approaches would be costly, complex and inflexible
as to substitution of different types of filters having different
useful lives. Furthermore, in an effort to such reduce cost, many
such approaches fail to give the user advance warning that the filter
will soon need to replaced.
What is needed, therefore, is a filter monitoring and indicating
system that is flexible enough to permit its use with different
types of filters yet doesn't add the cost of requiring an additional
switch or sensor for detecting the type of filter being used.
What is further needed is an inexpensive filter monitoring and
indicating system that not only informs the user that the filter
needs to be replaced, but provides earlier warning that the filter
will need to be replaced soon and therefore a new filter needs to
purchased.
SUMMARY OF THE INVENTION
The present invention is directed to a low cost method and apparatus
for monitoring the operation of a water and ice delivery system
for a refrigerator and indicating when to replace a water filter
used in the water and ice delivery system.
The water filter monitoring and indicating method and apparatus
of the present invention relies on components existing in many conventional
water and ice delivery systems and refrigerators to reduce complexity
and number of components and senses the operational condition of
the fresh food compartment door and the valves regulating the water
flow into the ice maker and the water dispenser of the refrigerator.
The method and apparatus monitors and tracks the duration of valve
openings to estimate water consumption since the filter has been
changed as well as tracking the amount of time that has passed since
the last time the filter has been changed. The method and apparatus
further tracks user inputs to the fresh food compartment door switch
to determine when a filter has been replaced. The water filter monitoring
and indicating method and apparatus determines when the filter needs
to be changed by comparing the water usage and filter age data with
a first set of pre-selected standards for the type of filter being
used and further determines when a new filter should be ordered
by comparing the water usage and filter age data with a second set
of pre-selected standards for the type of filter being used, the
second set of pre-selected standards being more stringent than the
first set. The method and apparatus then uses a tri-color light
emitting diode to display one color when the filter should be replaced,
a second color when a filter should be ordered and a third when
the filter is good.
In the preferred embodiment of the present invention, the water
filter monitoring and indicating system uses a low cost microprocessor
to compare the water usage and filter age data with the first and
second sets of pre-selected standards, to generate and track a conclusion
of a status of "good", "order" or "change"
(or alternatively, "used") for the filter based on such
comparison, and to illuminate the light emitting diode in pre-selected
color corresponding to that conclusion of status.
The microprocessor of the water filter monitoring and indicating
system of the present invention preferably includes a built-in memory
to retain water usage and other data during a power outage.
The light emitting diode of the water filter monitoring and indicating
system preferably is illuminated green for a filter status of "good",
yellow for a filter status of "order" and red for a filter
status of "change" or "used".
The water filter monitoring and indicating system preferably further
tracks user inputs to the fresh food compartment door switch to
determine what type of filter is being used and utilizes a different
first and second set of pre-selected standards for each type of
filter selectable by the user.
The light emitting diode of the water filter monitoring and indicating
system is preferably located within the fresh food compartment of
the refrigerator near the fresh food compartment door switch of
the refrigerator.
The present invention thereby provides a filter monitoring and
indicating system that is flexible enough to permit its use with
different types of filters yet doesn't add the cost of requiring
an additional switch or sensor for detecting the type of filter
being used by utilizing manual user input to the existing fresh
food compartment door switch at a rate which would be unlikely to
occur in normal door openings and closings.
What is further needed is an inexpensive filter monitoring and
indicating system that informs the user that filter needs to be
replaced, by illuminating red and further provides early warning
that the filter will need to be replaced soon and therefore a new
filter needs to purchased by illuminating yellow.
These and other advantages of the present invention will become
apparent to those skilled in the art when the following detailed
description of the preferred embodiment is read in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front perspective view of a refrigerator apparatus
having a water filtration and filter control and indicator system
embodying the present invention;
FIG. 2 is a schematic diagram of the ice and water assembly of
the refrigerator apparatus of FIG. 1;
FIG. 3 is a fragmentary enlarged front view of the refrigerator
control console of the refrigerator of FIG. 1;
FIG. 4 is a schematic electrical diagram illustrating the electrical
circuitry of the filter control and indicator system of FIG. 1;
FIG. 4b is a table indicating specifications of preferred components
of the filter control and indicator system of FIG. 4;
FIG. 5 is a flow chart illustrating the programming and logic of
the filter control and indicator system of FIGS. 1 and 4 and more
particularly illustrates the power-up and main subroutines of the
filter control and indicator system;
FIGS. 6 6A, 6B are flow charts illustrating the filter status
subroutine of the main subroutine of FIG. 5;
FIG. 7 is a flow chart illustrating the indicator subroutine of
the main subroutine of FIG. 5 including the indicator subroutine
and the diagnostics subroutine; and
FIG. 8 is a flow chart illustrating the reset subroutine of the
main subroutine of FIG. 5;
DESCRIPTION OF THE PREFERRED EMBODIMENT
The Refrigerator
In the illustrative embodiment of the invention as shown in FIG.
1 a refrigerator 10 comprising a side-by-side fresh food/freezer
configuration, is provided having a cabinet 12 forming fresh food
compartment 14 and freezer compartment 16.
The fresh food compartment 14 is provided with an access opening
18 and a fresh food door 20 hingedly mounted to the cabinet 12 for
selectively closing the access opening 18. The access opening 18
has a back wall 18a, side walls 18b and 18c, top wall 18d, and a
bottom wall 18e. The refrigerator 10 also has a partial front wall
22 disposed around the perimeter of the access opening 18 parallel
to and selectively engageable with the fresh food door 20 for sealing
the access opening 18.
The fresh food compartment 14 is further provided with a light
24 which is connected in series with a light switch 26. The light
switch 26 is a reciprocable switch actuated to selectively connect
the light 24 with a source of electrical power, not shown, when
the door 20 is in an open position and to disconnect the light 24
from the source of electrical power when the fresh food door 20
is in the closed position. In the preferred embodiment, the light
switch is located in portion of the partial front wall 22 above
the top wall 18d of the access opening.
Similarly, the freezer compartment 16 is provided with an access
opening 28 and a freezer door 30 hingedly mounted to the cabinet
12 for selectively closing the access opening 28. The access opening
28 has a back wall 28a, side walls 28b and 28c, top wall 28d, and
a bottom wall 28e. The refrigerator 10 also has a partial front
wall 32 disposed around the perimeter of the access opening 28 parallel
to and selectively engageable with the freezer door 30 for sealing
the access opening 28. The freezer compartment 14 is further provided
with a rocker-type light 34 which is connected in series with a
light switch 36 functionally similar to the light 24 and light switch
36 in the fresh food compartment 14.
As is further well known in the art, the refrigerator 10 is provided
with a water and ice supply system 40 shown schematically in FIG.
2 for delivering water from an external source 42 through a filter
44 to an ice and water delivery system 46.
The filter 44 may be mounted to the refrigerator below the bottom
wall 28e of the access opening 28 and accessed for servicing by
selective removal through an opening through the lowermost portion
of the partial front wall 32 as shown in FIG. 1.
The ice and water delivery system 46 includes an ice making assembly
48 mounted within the freezer compartment 16 and an ice and water
dispensing system 50 mounted in the freezer door 30.
The ice making assembly 48 is mounted to the inside surface of
the back wall 28a of the freezer compartment 16. The ice and water
dispensing system 50 is provided below the ice making assembly 48
for receiving ice pieces therefrom as well as for receiving cool
water from a water supply system 40. As shown in FIG. 2 the water
and ice supply system 40 includes electrically operable water valves
52 and 54 for supplying water, respectively, to the ice making assembly
48 and the ice and water dispensing system 50.
The ice and water dispensing system 50 includes an ice storage
receptacle or bin 56. When operated, the ice and water dispensing
system 50 transfers ice pieces from the ice storage receptacle or
bin 56 through the freezer door 30 whereby ice pieces may be dispensed
through a conventional, forwardly exposed ice dispenser station
or external ice service area 58.
In the preferred embodiment of the present invention, a refrigerator
control console 60 is defined on an upper portion of the partial
front wall 22 of the fresh food compartment 16 in the vicinity of
the light switch 26. The refrigerator control console 60 which
is shown integral with the front wall 22 includes a fresh food
compartment temperature control switch 62 a freezer compartment
temperature control switch 64 the light switch 26. In the vicinity
of the light switch 26 the refrigerator control console also includes
a filtration system status indicator 66 described later in detail.
The refrigerator control console 60 further incorporates a consumer
label 67 surrounding the switch 26 and the indicator 66 on which
is printed the following written matter describing the operation
of the filter 44 and the meaning of the status indicator 66:
"EZ-CHANGE SIGNAL FILTER INDICATOR RESET Green = Good Filter
Push the light switch Yellow = Order Filter 5 times in 10 seconds
to reset Red = Change Filter filter indicator to green."
Components of the Water Filter Status Monitoring and Indicating
System
Referring now to the FIG. 4 the Refrigerator 10 includes a water
filter status monitoring and indicating system 70. The water filter
status monitoring and indicating system 70 includes a power supply
72 comprising resistor 74 capacitors 76 78 and 80 and diodes 82
84 and 86 in a conventional capacitive drop design with capacitor
76 as the charge pump device, diode 82 as the rectifier. Diode 84
provides noise suppression and functions as a clamping diode. Diode
86 (5.1V, 500 mW) is a zener diode used as a simple voltage regulator.
Capacitor 80 functions as the reservoir capacitor and capacitor
78 provides high frequency bypass. Resistor 74 is critical to line
surge performance of the overall circuit since it absorbs most of
the pulse energy.
The water filter status monitoring and indicating system 70 has
an input connector 90 with three identical discrete digital inputs
94 96 and 98 respectively, for monitoring the light switch 26
and the water valve electrical input of water valve 54 associated
with the water dispenser of the ice and water dispensing system
50 and the water valve electrical input of water valve 52 associated
with the ice making apparatus 48. These inputs are designed for
120V (RMS) signals directly from the monitored loads. Each of these
inputs has an identical input resistive divider network respectively
comprised of pairs of resistors 114a, 114b, 116a, 116b, 118a and
118b. Each resistor pair, 107 108 and 109 can also be viewed as
a series device to limit current into the microprocessor input pin,
respectively, to the microprocessor device 140 described later,
and a shunt device to provide input pull-down to a known state when
the associated load is not activated.
The input connector 90 further has inputs 100 and 106 respectively
connected to the neutral and the hot lines of the AC power supplied
to the refrigerator 10. Inputs 92 102 and 104 of the input connector
90 are not used.
The water filter status monitoring and indicating system 70 also
has a power-on reset circuit 120 comprised of resistors 122 124
and 126 transistor 128 and capacitor 130.
Resistors 122 and 126 set the reset threshold voltage and provide
base drive for the transistor 128 and, in turn provides a pull-up
voltage to master clear input 147. Resistor 124 is a passive pull-down
to the master clear input 147 of the microprocessor device 140 when
VDD is low which establishes a valid logic low when VDD is below
the threshold. Capacitor 130 provides filtering for high frequency
noise and transients.
The water filter status monitoring and indicating system 70 further
includes the filtration system status indicator 66 which in the
preferred embodiment consists of a bi-color device 110 containing
a red LED die 132 and a green LED die 134.
The microprocessor device 140 provides all logic functionality
and memory. In addition to red and green, the color amber can be
achieved by alternating resistors 136 and 138 by providing alternating
signals from microprocessor output pins 144 and 146.
Microprocessor device 140 is preferably a Microchip PIC12CE518
device, which contains 512 words of program ROM (implemented as
OTP EPROM) and includes a 16 by 16 EEPROM.
The specifications of the preferred components of the water filter
status monitoring and indicating system are shown in Table 1 of
FIG. 4b.
Programming Logic of the Water Filter Status Monitoring and Indicating
System
FIG. 5 through FIG. 8 illustrate the programming and logic of the
water filter status monitoring and indicating system 70 which is
programmed into the microprocessor device 140. The Logic is intended
to provide programming for alternative models, such as an A model
refrigerator a B model refrigerator or a C model refrigerator, each
having different functionality. The various models may have different
replacement criteria for the filters depending on the gallon rating
and the useful life of the filter.
Referring to FIG. 5 when the power is first supplied to the microprocessor
device 140 a Power-up Subroutine 200 is initiated. At step 202
the microprocessor device reads the stored memory. At Step 204
the microprocessor device 140 sends a signal to the indicator 66
to flash red if the refrigerator is a Model A and green if it is
a model B.
The microprocessor device 140 then enters a continuously repeated
main subroutine 206. Within each repetition of main subroutine 206
microprocessor device 140 updates its clock at step 208 and, once
every 18 hours, stores the time and water used in the non-volatile
memory at step 210. At steps 214 and 216 respectively, the amount
of water used is incremented if the ice valve 52 is open or if the
fresh water valve 54 is open. The open time for each valve 52 and
54 is weighted for the normal water flow rate associated with the
valve. At steps 216 218 and 220 respectively, the microprocessor
calls the filter status subroutine 250 the control subroutine 300
and the reset subroutine 350 after which the main subroutine 206
repeats.
Referring to FIG. 6 the filter status subroutine 250 determines
at steps 252 and 254 whether refrigerator 10 is a model A, B or
C and directs the program to one of water usage comparison subroutines
256a, 256b and 256c, respectively for the appropriate model. In
each respective water usage comparison subroutine 256a, 256b, and
256c, at respective steps 258a, 258b and 258c, the status of the
filter is designated as "good" if less than a first predetermined
time period has passed and less than a first predetermined quantity
of water has been consumed, as indicated by the information stored
in memory since the last reset. In each respective water usage comparison
subroutine 256a, 256b, and 256c, at respective steps 260a, 260b
and 260c, the status of the filter is designated as "used"
if more than a second predetermined time period of usage or more
than a second predetermined quantity of water has been consumed
since the last reset. In each respective water usage comparison
subroutine 256a, 256b, and 256c, at respective steps 262a, 262b
and 262c, the status of the filter is designated as "warn"
if the status has been set as neither "good" or "used".
Finally, at step 270 the time and water used is stored in non-volatile
memory if the status of the filter has not been changed by the water
usage comparison subroutine 256a, 256b or 256c. The status is not
restored if it hasn't changed so as to maximize the useful life
of the EEPROM non-volatile memory.
Referring to FIG. 7 the control subroutine 300 determines at step
302 if the fresh food door 20 is open by monitoring the voltage
across the fresh food light 24.
If the fresh food door 20 is detected as open, then indicator subroutine
310 is run. At step 312 the green LED die 134 is illuminated if
the status of the filter has been saved as "warn" or as
"good". At step 314 the red LED die 132 is illuminated
if the status of the filter has been saved as "warn" or
as "used". Thus, if the status has been saved as "warn",
both LED die are alternatingly illuminated and the status indicator
66 appears amber in color.
The alternating signal of red and green is created by step 312
always turning off the green die, off if it is on, and, after a
built-in time delay by having step 314 always turn off the red die,
if it is on. After a subsequent time delay, the programming again
returns to step 312 turning off the red LED and turning on the
green LED.
If the fresh food door 20 is detected as closed, then diagnostic
subroutine 320 is run. At step 312 the green LED die is illuminated
if the water dispenser valve 54 is open. At step 324 the red LED
die is illuminated if the water valve 52 to the ice making apparatus
48 is open. If both valves 52 and 54 are open, both LED die are
illuminated and the status indicator 66 appears amber. The diagnostic
subroutine 320 permits detection of malfunctions of the water valves
52 and 54 or the water filter status monitoring and indicating system
70 by a service technician manually by depressing the light switch
26 and selectively operating the valves 52 or 54 the service technician
can isolate faults in the system.
Referring to FIG. 8 the reset subroutine 350 determines at step
352 if the light switch 26 has been depressed 5 times in less than
ten seconds, indicating the user is sending a reset instruction
to the microprocessor device 140. The user should do this when the
filter is replaced. If a reset instruction has been detected at
step 352 then the time and water usage counters are reset to zero
at step 356 and stored to non-volatile memory at step 358. However,
if the system has already been reset, within the last 10 seconds,
that is, a reset instruction has been sent twice, then, at step
354 the microprocessor device reads the input as an instruction
that a different type of filter is being used and changes the model
setting from a model A to a model B. Finally, at step 360 the indicator
is illuminated red or green to indicate the model setting.
Operation of the Water Filter Status Monitoring and Indicating
System Components
The purpose of the water filter indicator is to provide the consumer
with a reliable measure of the filter cartridge end of life condition.
There are two criteria for end of life, namely a prescribed number
of gallons and a fixed period of real time. In order to monitor
the water flow, the electrical inputs to both the ice maker valve
and the dispenser valve are monitored by the WFI. Since the processor
"knows" that the valves have flow rates of 0.3 and 0.5
gallons per minute, the flow can be computed from the amount of
time which each is energized. It is in this fashion that the usage
in gallons is accumulated.
Real time is simply accumulated by a divider from the processors
clock. Since the clock used in this case is the internal RC oscillator,
it is subject to more inaccuracy than would be experienced with
a crystal controlled or 60 Hz based time keeping scheme. The Microchip
literature guarantees this tolerance to be about 7.0% over voltage
and temperature 4variations. Also included in the microprocessor
is an EEPROM device, which provides non-volatile retention of flow
as well as real time.
The state of the water filter is indicated on a bi-color LED incorporating
a red and a green die in the same package. By activating both die
at a 50% duty cycle an amber color is obtained. Up to 90% life the
indicator is green, from 90% to just less than 100% it is amber,
and at end of life it shows red. User reset of the accumulated flow
and time variables is effected by activating the door switch five
times within 5 seconds.
In order to facilitate factory test as well as servicing in the
field, the LED displays usage status only when the door is open.
When the door is closed, the LED is off unless one or both of the
valve inputs is active. The LED indicates red for the ice maker
valve, green for the dispenser valve and amber if both valves are
active.
The above constitutes a detailed description of the best mode of
the present invention as contemplated by the inventors at the time
of filing. It is further contemplated that changes and modifications
may be made from the best mode described herein within without departing
from the spirit of the present invention or the intended scope of
the claims below. |