AU2002248767A1 - Automatic salt water monitor for a water softening device - Google Patents

Description

AUTOMATIC SALT LEVEL MONITOR FOR A WATER SOFTENING DEVICE

BACKGROUND

This invention relates to a monitor for the level of salt in a water

softener. More specifically, it relates to an automatic monitor that detects and

indicates when the salt level in the brine tank is insufficient to completely

regenerate the resin during subsequent regenerations.

While treating hard water, the ion exchange resin in a water

softener absorbs calcium and magnesium ions from the water and replaces

them with sodium ions. The resin becomes ineffective when the amount of

available sodium is depleted and the resin is saturated with calcium and

magnesium, and must be periodically regenerated. Water treatment is then

suspended while the resin is regenerated in a multi-step process to flush the

calcium and magnesium ions from the resin and restore the sodium level. The

resin is first backwashed, by reversing the flow of the incoming water, to

remove sediment. Next, the resin bed is contacted with a brine solution,

whereby the resin takes sodium ions from the high concentration solution and

displaces the calcium and magnesium ions into the brine. When an optimum

amount of ion exchange has taken place, the brine solution and the unwanted

hard water ions in it are discharged from the resin bed. After being rinsed to

remove residual brine, the restored resin bed is then returned to service treating

hard water. Preparation of the brine solution takes place in a brine tank that is

kept separate from the resin tank. The brine tank, which contains a supply of

salt, is filled with water to form a saturated salt solution. The salt supply must

be replaced periodically due to depletion of repeated regenerations. If the salt

level is too low to make a brine solution of a given strength, there will be an

insufficient sodium level to drive the exchange of calcium and magnesium ions

and the resin will not effectively treat the hard water when it is placed back in

service.

Generally, there is no automatic warning when the amount of salt

is insufficient to restore the resin bed to an optimum ion exchange capacity. It

has been left to the user to manually determine the salt level, usually by

visually inspecting and estimating the salt level in the tank. Any manual

determination of salt level is inconvenient for the user, who must frequently

look into the brine tank. An inexperienced user may not know how much salt

is required per regeneration, and create more work by adding salt too

frequently or having hard water when salt is not added frequently enough.

To avoid having to make frequent visual inspections, users often

prefer a softener unit with large salt capacity. Large units are more convenient,

but also take up large amounts of space that may be prohibitive in small living

spaces such as townhomes or condominiums. For areas where the softener unit

may be visible, the exterior of some models is styled with an attractive cabinet¬

like finish. However, since this type of exterior finish is more expensive and, because they are generally used where space is a premium, the size of such

units is usually small, requiring the user to frequently check the salt level.

The prior art provides an indicator stick, similar to a ruler, with

reference marks to aid in judging the depth of salt present. Visual inspection is

inaccurate even with reference marks, particularly when salt bridges are

formed. While the brine is being made, the salt continuously dissolves and

redeposits due to chemical equilibrium reactions. Salt bridges form when

pieces of salt "grow" together from salt deposition, and can make the volume

of salt appear to be greater than is actually present. The salt under the bridge

may be substantially dissolved, leaving only a small amount of salt in the tank

even when a visual inspection from the top of the tank looks as if the salt bed

has ample depth to complete additional regenerations.

Previous attempts to incorporate electronic monitors into water

softeners have not proven satisfactory. Monitors were designed that utilized a

weighted sensor on top of the salt to determine the salt level. However, if the

operator forgot to remove the sensor when salt was added, the sensor would

become buried, and falsely signal that the salt level was low.

A low salt level sensor utilizing a float is taught in U. S. Patent

No. 5,239,285, which is herein incorporated by reference. The salt level in this

invention was determined by displacement of water. A predetermined amount

of water was added to the brine tank, and if there was insufficient displacement

of the water to push a float to a given level, the low-salt alarm was activated. However, this method requires that a portion of the apparatus be submerged in

the brine, an environment that is corrosive and deposits salt on the equipment.

It is therefore an object of this invention to provide an improved

monitor for the salt level in a water treatment device.

It is another object of this invention to provide an improved

monitor for salt level that automatically checks the salt level without

intervention from the user.

It is still another object of this invention to provide an improved

salt monitor that provides an indication to the user when the amount of salt is

too low to provide effective regeneration.

It is yet another object of this invention to provide an improved

salt monitor that accurately indicates when salt should be added, even when

salt bridges are formed.

SUMMARY OF THE INVENTION

The present invention provides an automatic monitor for use with

a water conditioning apparatus. The improved monitor periodically checks the

level of salt in the brine tank without intervention by an operator and provides a

warning if the salt level is too low to effectively regenerate the ion exchange

resin during the next regeneration cycle. More specifically, the present invention provides an automatic

monitor for use in a tank with a water soluble softening agent. The monitor

includes a signal emitter that produces a signal capable of being detected by an

array of signal-detecting sensors. The sensors are displaced generally

vertically in the brine tank from the minimum depth of the softening agent to

the maximum depth of the softening agent. The sensor produces an output in

response to the signal.

The monitor also includes an electronic device for receiving and

interpreting the output and determining if a low softening agent condition is

present as the supply of the softening agent is depleted. An indicator warns

when a low softening agent condition is present. Preferably, the sensors are

linearly spaced within the tank.

The monitor of the present invention is advantageous to the user

because it continuously monitors the salt level in the brine tank and provides a

warning indicator when the salt level has dropped too low to successfully

complete another regeneration. Continuous real-time monitoring of the salt

level can also be achieved with the present monitor, if the electronics device

that interprets the sensor output is programmed to do so. There is no need for

the user to open up the softener cover on the brine tank to inspect the salt level.

Even inexperienced users know from the indicator exactly when to add salt

without having to guess if the amount of salt left is sufficient for the next

regeneration. The electronics of the present monitor are also optionally

programmable to anticipate the calculated salt level, so that problems can be

detected if the measured level differs significantly from the calculated level.

Such differences can be indicators of salt bridges, faulty sensors or emitters,

loss of eduction or overfilling of the brine tank. These features significantly

improve both the convenience to the user as well as the accuracy of the

reported salt level. Using a visual inspection of the brine tank, the user often

has no way to tell that problems, such as salt bridges, exist below the surface of

the salt bed. The present electronic monitoring system removes the

inconvenience of repeated checking and the guesswork from mamtaining an

appropriate salt level in the water softener.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a stylized diagram of a water softening system

constructed in accordance with the principles of the present invention;

FIG. 2 perspective view of a water softener with the present

automatic salt level monitor and with a portion of the cabinet removed to show

the sensors in the salt bed;

FIG. 3 is a circuit diagram of the circuit used to determine the

resistance of the photocells; FIG. 4 is a top plan view of the top cap attached to an interior

surface;

FIG. 5 is a perspective view of the sensor and shroud mounted on

an elongated member and inserted into the top cap;

FIG. 6 is a perspective view of a bottom cap;

FIG. 7 is a perspective view of a top cap;

FIG. 8 is an exploded perspective view of the sensors mounted on

an elongated member, showing how the elongated member fits inside the

protective device with the top and bottom caps;

FIG. 9 is a top plan view of the cover of a cabinet model with an

indicator array and display; and

FIG. 10 is a perspective view of the top of a cabinet model

softener with the cover removed.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGs. 1 and 2, the present softening agent

monitor, generally designated 10, is used in a water softener, generally

designated 12, to determine the amount of softening agent 14 in a chamber 16.

The monitor 10 is suitable for use in most water softeners 12 that use softening

agents 14 in solid form. Sodium salts, such as sodium chloride in pellets, a

solid block or in a granular form, are the most common softening agents 14, but use of any solid softening agent is contemplated for use with this invention.

Use of high purity salts is recommended to lengthen the time between salt

additions and to reduce the amount of impurities that accumulate in the bottom

of the water softener 12, but does not directly effect the operation of the

monitor 10 described herein.

Referring to FIG. 1, during softening, a unit controller 18

operates valves to allow fresh, hard water from a supply 20 to flow into a resin

tank 22 through an inlet 24, treated or soft water exits through an outlet 26.

Between the inlet 24 and the outlet 26, the hard water contacts a sodium rich

ion-exchange resin 28, where calcium and magnesium ions present in the hard

water are held by the resin 28 and sodium ions are released into the soft water.

Softened water is discharged from the softener through a treated water outlet

30.

When the resin 28 is saturated with hard water ions and the

sodium ions are depleted, the resin is regenerated. During regeneration, a brine

solution 31 is withdrawn from the salt chamber 16 through a brine valve and

enters the resin tank 22 through the inlet 24. Brine well 33 keeps said particles

of softening agent 14 from clogging the brine valve, while allowing the brine

solution to flow freely to the valve. Hard water ions are released from the resin

28 into the brine solution 32 as sodium ions from the brine are absorbed by the

resin. Spent brine 32 leaves the resin tank 22 through the outlet 26 and is

removed from the unit through a waste discharge 34. At the end of the regeneration cycle, water is added to the salt

chamber 16 so that the softening agent 14 dissolves, making a saturated brine

solution 32 to be used during the subsequent regeneration. The brine solution

32 is kept separate from the water supplies 20, 30 and resin 28 while softening

is taking place so that the brine 52 does not contaminate the fresh water

supplies and because ion exchange between the resin 28 and the hard water

would not occur efficiently in the presence of brine. Only during the

regeneration cycle is the brine solution 32 brought into contact with the ion

exchange resin 28.

Referring to FIG. 1, where it is necessary to have an

uninterrupted soft water supply, multiple resin tanks 22 may be used so that

one unit is softening while one or more others are regenerating. For home use,

the entire water softener is often contained in a cabinet 35, shown in FIG. 2.

Some water softener designs utilize the cabinet 35 as the salt chamber 16,

allowing the softening agent 14 to be placed into the cabinet and occupy space

around and between other elements of the softener 12. As shown in FIG. 10,

models that utilize a single cabinet 35 often have a deck 36 that covers a large

portion of the top of the cabinet. An opening 37 is provided in the deck for

addition of the softening agent 14.

The resin tank 22 separates the ion exchange resin from the

softening agent 14. Preferably, the resin tank 22 is a smaller tank that is

housed inside the cabinet 35 of the water softener 12. However, the salt chamber 16 and the resin tank 22 may both be portions of the cabinet 35 that

are separated from each other by dividers or partitions inside the cabinet, or,

the salt chamber 16 and resin tank 22 may be entirely separate tanks. Any

arrangement may be used for the salt chamber 16 and resin tank 22 that keeps

the water being softened from contact with the softening agent 14.

The monitor 10 includes at least one signal emitter 38, an array of

signal receivers or sensors 40, a controller 42 and an indicator 44 (FIG. 1). The

signal emitter 38 produces a signal inside the salt chamber 16 in response to a

request from the controller 42 at an appropriate time, as will be discussed

below. Emission of the signal is sufficiently long in duration that each of the

sensors 40 has an opportunity to respond to it and the response transferred to

the controller 42. For most signals, such as light or sound, duration in excess

of one minute is rarely needed, and duration is often considerably shorter. The

preferred signal is light, due to its reasonable cost, ease of use and reliability,

making a light bulb or light source 46 the preferred signal-emitter 38, and

shown in FIG. 2. Other types of signals, such as sound, are also suitable as

long as some detectable characteristic of the signal is changed if it passes

through the softening agent 14 to the sensor 40 compared to receipt of the

signal when the level of softening agent has fallen below the sensor.

Positions of the one or more emitters 38 are limited to areas that

allow every sensor 40 to receive a signal from at least one emitter. The

emitters 38 are also placed above the highest brine 32 level to eliminate reflection and refraction of the signal as it passes through the brine and the air-

liquid interface. Preferably, the emitter 38 is placed so that signals reaching the

sensor 40 from the emitter are from a different direction than background

signals that do not originate at the emitter 38. For example, when a light 46 is

used, room light is a background signal source that can cause an output change

in a photocell 40, even when the sensor 40 in the softening agent 14 does not

receive the signal from the emitter 38. When the emitter signal and

background signal come from differing directions, it is easier to use direction to

shield the sensor 40 from background signals.

The emitted signal is detected by an array of signal-detecting

sensors 40 designed to detect the type of signal being emitted and produce a

measurable output in response to the signal. When the signal emitter 38 is a

light, the preferred sensors 40 are photocells. In response to light, the photocell

40 decreases its resistively by more than a factor of 10. This change is

resistivity is a measurable from the photocell 40, and is preferably used to

detect whether or not the signal is being blocked from reception at the

photocell 40 by the salt bed 14. When placed inside the salt chamber 16, the

photocell 40 will normally register high resistance on the order of 1 MΩ, when

the light signal is not present, compared to a low resistance of about 10 kΩ

to 100 kΩ when the light signal is being received. If the softening agent 14 is

covering the photocell 40, the circuit containing the photocell responds a high

resistance signal. However, when the softening agent 14 is depleted to a level below the photocell 40, it is exposed to the light from the emitter 28 and the

resistance of the photocell drops.

FIG. 3 is a control circuit, generally 50, that shows how the

photocells are wired in a 4 x 2 matrix. As the resistance of the photocell 40

changes, a control circuit, generally 50, produces changes in the voltage or

current, either of which is measurable by the controller 42. The photocell 40

acts as a variable resistor. According to Ohms' s Law:

V = I * R

at constant current (I), voltage (V) and resistance (R) are

proportional. When the controller 42, seen in FIG. 2, measures voltage, it

sends a small, but constant current through the photocell 40. If the resistance

through the photocell 40 is high, the voltage returned to the controller 42 will

also be high. If the resistance through the photocell 40 drops, the voltage will

also decrease. Thus, the voltage provides the output from the photocell 40 that

informs the controller 42 as to whether a particular sensor 40 is covered by the

salt 14. Optionally, the controller 42 could detect change in resistance of the

photocell 40 by measuring the current in the circuit at a constant voltage.

The difference in output from a sensor 40 that is covered with

softening agent 14 and one that is above the agent is most easily determined

when the change in output between these two conditions is maximized.

Preferably, background signal is eliminated to maximize the difference in

output from the sensor 40 that is attributable to the signal emitter 38. When photocells 40 are used, for example, the monitor optionally includes an

interlock requiring the cover 54 (FIG. 9) to be in place on the water softener 12

during evaluation of the depth of the softening agent 14 to eliminate room light

from producing a response from the photocell 40. This ensures that light

perceived by the photocells 40 was produced by the emitter 38.

Turning now to FIG. 5, background signals are also reduceable

by shielding the sensor 40 with a device, such a shroud 56, that blocks signals

not originating from the direction of the emitter 38. The shroud 56 has at least

one wall 58 that is made of a material opaque to the type of signal produced by

the emitter 38. Preferably, positioning of the wall 58 should maximize

blockage of background signals, while allowing signals from one or more

emitter 38 to reach the sensor 40. More than one wall 58 is optionally used

where background signals are likely to come from a plurality of sources, as

long as the emitter 38 signals reach the sensor 40. As the length of the shroud

wall 58 increases, the range of angles diminishes from which the signal will

contact the sensor 40. Preferably, the shroud 58 includes a supporting

structure, such as a clip 62 or other known fastener for attaching it to the sensor

40.

Now referring to FIG. 2, continuous monitoring of the softening

agent 14 level is achieved by using an array of two or more sensors 40 that are

displaced generally vertically in the salt chamber 16. A single sensor 40 can

only indicate whether or not the softening agent 14 is present at the depth at which that sensor 40 is located. Multiple sensors 40 arranged generally

vertically within the salt chamber 16 will each give an output as to the presence

or absence of softening agent 14 at that depth. Location of sensors 40

vertically displaced from the minimum depth of the softening agent 14 to the

maximum bed depth, provides for sensing of the bed depth at any sensor level.

As the softening agent 14 is depleted, successive sensors 40

decrease in resistance as they are exposed to the emitter 38. Addition of an

optional reference sensor 64 above the maximum depth of the softening agent

14 is useful in distinguishing when the emitter 38 is malfunctioning compared

to when the bed is full, and all sensors 40 are covered with softening agent.

Preferably, four or more sensors 40 located within the bed of the softening

agent 14 and the optional reference sensor 64 are used.

It is to be understood that the sensors 40 are not necessarily

placed in a straight line, nor that the generally vertical displacement between

sensors is constant. Preferably the sensors 40 are linearly spaced vertically

throughout the bed depth, however, any useful spacing arrangement is suitable

for use with this invention, including, but not limited to staggered placement.

In some applications, it may be preferable to have the sensors 40 more closely

spaced at the bottom of the bed of the salt or softening agent 14, providing

additional accuracy near the bottom of the salt. It may also be advantageous, in

some cases, to have the sensors 40 horizontally displaced as well as vertically

displaced. Where the sensors 40 are horizontally displaced, multiple emitters 38 may be required to reach all sensors 40 with the signal. Horizontal

displacement of some sensors 40 with respect to other sensors may allow the

monitor 10 to continue to function properly even when sensors in one portion

of the bed are inoperative because they are somehow blocked from receiving a

signal from the emitter 38.

The specific number of sensors 40 is not important, however,

increasing the number of sensors improves the accuracy of measurement of the

softening agent 14 by decreasing the vertical distance between sensors. At

least one critical sensor 66 is preferably located in a position at or slightly

below a level where there is insufficient salt or softening agent 14 to

completely restore the resin 28 on the next regeneration. When the output from

the critical sensor 66 indicates that the level of softening agent 14 has dropped

below this sensor, a low softening agent condition is present and a warning is

communicated to the operator, preferably by the indicator 44.

Periodically, the salt chamber 16 is resupplied with 50-100

pounds or more of the softening agent 14. This process results in forces being

exerted on walls 68 and a floor 70 of the chamber 16 due to the weight of the

softening agent 14 as the pieces of softening agent bounce off the walls and fall

to the floor. Preferably, the sensors 40 are enclosed in a protective device 72

(best seen in FIG. 8) that shields them from forces generated during

resupplying of the softening agent 14 or pressure from the weight of the bed

above the sensors. The protective device 72 may be any device that is shaped and configured to be transparent to the signal from the emitter 38, but will

prevent damage or dislodging of the sensors 40 by falling pieces or the weight

of softening agent 14.

As best seen in FIG. 8, most preferably, the protective device 72

is a tube that is transparent to the type of signal sent by the emitter 38. A single

protective device 72 is preferably used to enclose all of the sensors 40, but use

of a plurality of devices, each enclosing one or more sensors is also considered

to be part of this invention. When light is used, a clear plastic tube 72, having a

diameter slightly larger than the largest dimension of the sensor 40, is

preferred. Many types of protective devices 72 are possible, such as a wire

mesh cage, a small box for each sensor mounted to the tank wall 68 salt

chamber 16 and the like.

To provide consistent information as to the level of the softening

agent 14, the sensors 40 are each to be held at a constant depth within the bed.

Preferably the sensors 40 are mounted to a fixed object, such as the cabinet

wall 68, the salt chamber 16 or the resin tank 22, as shown in FIG. 4. Another

preferred arrangement is where the protective device 72 is held in place, and

the sensors 40 are held at consistent positions within the device.

Referring to FIGs. 6, 7 and 8, a top cap 76 and a bottom cap 77

are suitable to seal the tube 72, while allowing access to the tube contents for

maintenance purposes, if desired. Both caps 76, 77 are preferably friction fit

onto the plastic tube 72 with the assistance of optional radially projecting ribs 78 to hold them in place in the tube. Adhesives are also suitable for fixing the

caps 76, 77 to the plastic tube 72, as are any other ways known in the art of

affixing a cap to a tube, such as using 0-rings 79. The preferred top cap 76 and

bottom cap 77 are described below, however, many such caps can be designed

to perform the same functions.

Both preferred caps 76, 77, best seen in FIGs. 6 and 7, include

three concentric, cylindrical cross-section portions 80, 81 and 82. A first

cylindrical portion 80 is the most narrow, and fits farthest into the plastic tube

72. Next, a second cylindrical portion 81 is sized to fit tightly into one end of

the plastic tube 72. The ribs 78 preferably are located on the second cylindrical

portion 81 and radially project outward to assure a good friction fit between

plastic tube 72 and the bottom cap 77. A third cylindrical portion 82, generally

the widest portion, remains on the outside of the plastic tube 72. When an O-

ring 79 is used to seal the tube 72, it is suitably placed around the first

cylindrical portion 80 and rests against a ledge 85 that connects the first portion

with the second portion 81. Although a cylindrical shape is preferred, the

shape of the third portion 82 is variable depending on the method of attaching

the plastic tube 72 to the water softener 12. Preferably, the bottom cap 77 rests

on the floor 70 of the softener 12 in an optional tray 83. The bottom cap 77

will most commonly rest in a depression 84 to prevent it from sliding from one

side to another. As best seen in Figure 7, the preferred top cap 76 is also

generally cylindrically shaped. A flange portion 86 rests over the top of the

plastic tube 72. When the softener 12 is mounted in a cabinet 35, the top cap

76 preferably attaches through the deck 36, and secures to the deck with a twist

lock 87. A salt sensor access hole 88 in the deck 36 is sized and configured to

receive the top cap 76 so that the flange 86 rests on the top surface of the deck.

The top cap 76 also has finger grips 89 and a lower lip 90 that is spaced

downwardly toward the floor 70 of the cabinet 35 at least the thickness of the

deck 36 from the flange 86. When the top cap 76 is twisted by exerting a

rotational force on the finger grips 89, the deck 36 is wedged between the

flange 85 and the lower lip 90, holding the cap in place.

The top cap 76 also features one or more openings 91 through

which wires pass between the sensors 40 and the controller 42.

Communication between these elements is most easily accomplished through

the use of conventional wiring 92 (best seen in FIG. 2), however, information

or instructions are optionally transferred by other means, such as an infra red

beam, fiber optics and other techniques as will be apparent to those skilled in

the art.

Referring again to FIGs. 2 and 3, the controller 42 initiates the

production of a signal from the emitter 38, receives and interprets the output

from the sensors 40, and activates one or more of the indicators 44. Most

modern water softening systems include a microprocessor 94 in the electronic unit controller 18. Some duties of the unit controller 18 include timing of the

softening and regeneration cycles, and the opening and closing of valves as

appropriate. It should be appreciated that the microprocessor 94 functions,

except those specifically described in this application, are not a part of this

invention and are not to be confused with the controller 42 functions, even

when carried out by the same or similar equipment. Nor is it anticipated that

the controller 42 be a physically separate unit from the unit controller 18 if the

functions described here are present and available to monitor the sensors 40

and indicate when a low-salt condition is present. Although the monitor 10 of

the present invention, as described, is most advantageously designed to be used

with such modern water treatment systems, the monitor and process of this

invention may also be used with less complex systems or retrofit into older

water softener units 12.

To initiate the signal from the emitter 38 when there is no liquid

in the salt chamber 16, the controller 42 is designed to generate the signal once

an appropriate time is reached during the regeneration cycle. A modem unit

controller 18 is programmed to initiate signal from the emitter 38 at any desired

time. In less sophisticated softening units 12, information as to the timing of

the regeneration cycle can be determined from, for example, the position of a

cam wheel (not shown) that opens and closes valves during regeneration.

Whatever control mechanism is used to control regeneration is tapped to

provide the controller 42 with timing information. After initiating a signal from the emitter 38, the duration and

cessation of the signal is preferably determined by the controller 42. However,

in simple units, a separate timer or other means is suitable to produce signal for

a predetermined time period, then turn it off.

The preferred controller 42 includes a circuit board 96 that

performs mathematical calculations as well as detects output from the sensors

40, allowing more sophisticated output analysis. The circuit board 96 is

designed and built using any technique that is known to those skilled in such

arts. Circuitry for this controller 42 includes simple arithmetic functions,

comparison of values and activation of one or more indicators 44 (FIGs. 1 and

9).

Preferably, the controller 42 also includes optional functions that

take advantage of modern electronics. For example, the board 96 optionally

includes stored data as to approximately how much softening agent 14 is used

per regeneration. The board then calculates the expected bed level based on the

previous bed level and compares them. Extreme discrepancies between the

calculated bed level and the measured bed level signal a problem in bed level

measurement, such as for formation of salt bridges, a malfunctioning or

inoperative sensor 40, loss of eduction or overfilling of the salt chamber 16.

Salt bridges are also discoverable if the sensor 40 outputs indicate that it is

clear of the softening agent bed, but the sensor above it is still covered by

softening agent 14. When the controller 42 determines that the softener 12 requires

attention, it activates one or more indicators 44 for warning the operator. This

occurs periodically when a low softening agent 14 condition is present as

determined by the critical sensor 66 or when the controller 42 calculates that

the softening agent 14 is depleted. If the optional reference sensor 64 is present

and is not activated by the signal from the emitter 38, the controller should also

warn of that condition. Referring to FIG. 9, any indicator 44 is suitable that

informs the operator of a condition requiring attention, such as a displayed

message, an indicator light 44 or series of lights 98, a warning sound and the

like. Preferably, if the indicator 44 is used for a plurality of warning

conditions, some provision is made to distinguish between them.

When a circuit board 96 is used, the indicator 44 optionally takes

the form of a display device 100 such as an LCD to deliver additional

information compared to a simple on/off indicator 44. The display 100 could

show the bed level by calculating the bed level as determined by the sensor 40

output. For example, if the sensors 40 change from a signal-detecting

condition to a no-signal-detecting condition between 50% and 60% of the bed

depth, this information could be communicated to the operator by the display

100, providing a real-time indicator of the level of softening agent 14. If no

output at all is detected from a sensor 40, the display 100 could show a

message requesting that the particular sensor be checked for malfunction. The

display 100 is also useful for a number of other messages and indications that will be obvious to those skilled in the art. Preferably, the display 100 is located

on the outside of the cabinet 35, so that it is visible to the operator without

having to open the tank cover 54. A suitable location for the display 100 is on

or near the control valve 102 on the top of the softener 12.

The display 100 takes the form of any type of display device

known in the art. A preferred display 100 is a series of light emitting diodes

(LED) as the lights 98 could be used to indicate the salt level. Such an array of

LED's 98 optionally has a scale or reference marks so that the diode or diodes

that are activated can be easily related to the amount of salt in the salt chamber

16. The number of LEDs 98 is not important, as the controller 42 is capable of

performing the arithmetic calculation to translate the information when the

number of LEDs does not match the number of sensors 40. Another suitable

display 100 includes a digital display, capable of showing multiple error codes

or messages to distinguish between a plurality of conditions for which

intervention by the user is desirable.

Now referring to FIGs. 1, 5, and 8, the controller 42 receives the

output from the sensors 40 by any means known in the art. Preferably,

information is transferred by an elongated bar-like member 104 that fits inside

the plastic tube 72, into which the sensors 40 are plugged. This arrangement

has many advantages. The wiring 92 and sensors 40 are protected from the

water and salt in the salt chamber 16. The elongated member 104 is preferably

a sensor circuit board that allows sensors to plug directly into the circuit controller board 96, particularly where the sensors 40 are mounted within the

plastic tube 72. Many other ways are available to communicate the output to

the controller 42, including but not limited to running wires down the tube 72,

beaming an infrared signal along the length of the tube, and other techniques as

will be apparent to those skilled in the art.

Friction-fitting of the elongated member 104 into an optional slot

or guides 108 in the bottom cap 77 aligns the elongated member 104 so that the

sensors 40 are in a consistent position to receive the signal from the emitter 38.

The slot 108 also holds the elongated member 104, and thus the sensors 40, at a

consistent depth in the bed.

There is space on the elongated member 104 between the sensors

40 to hold optional electronic components, such as diodes 110 (shown in FIG.

3), that may be part of the controller 42 circuit. As shown, diodes 110 between

each of the sensors 40 allows current flow in only one direction. By measuring

the current of voltage between electrical leads 112 at each sensor 40, current

flow in a single direction enables the controller 42 to determine the output of

each individual sensor, and therefore determining the two sensors that are

immediately above and below the top of the salt bed.

Preferably, a sensor assembly 114 comprising the plastic tube 72,

the elongated member 104 upon which the sensors 40, diodes 110 and other

components are mounted, the top cap 76 and the bottom cap 77 are

manufactured as a sealed unit. Sealing of the caps 76, 77 to the tube 72 assures the integrity of the assembly 114 and minimizes the possibility that the highly

corrosive brine solution will leak into the protective tube. Most preferably, the

O-rings 79 seal each of the caps 76, 79 to the tube. Adhesives may be used in

addition to the O-rings 79 or other sealing device. Sealing protects the sensors

40 from damage due to the presence of the corrosive brine 32, or covering of

the sensor with salt deposits. If the assembly becomes inoperable, the entire

assembly 114 is preferably removed from the cabinet 35 and replaced.

Use of the plastic tube 72 as the protective device may optionally

provide maintenance access to the sensors 40 even when those sensors are

located below the level of the softening agent. If, for example, a sensor 40

malfunctions, is disconnected, needs to be reset or otherwise becomes

inoperative, it can be withdrawn from the chamber 16 through the protective

tube 72, instead of being required to empty the entire bed of softening agent 14

to access the bad sensor. However, when the caps 76, 79 are removed, there is

potential for the seals, such as O-rings 79, to be damaged, incorrectly installed,

or not installed at all. If this occurs leakage of brine into the tube 72 could

damage any of the electrical components.

Again referring to FIG. 2, timing of when the monitor 10 takes

readings of the bed level is also important. Certain signals, such as light or

sound, are reflected or altered as they pass through water. Throughout the

softening cycle, during a portion of the time water is present in the salt

chamber 16, permitting a saturated solution 32 to form as the softening agent 14 is exposed to water. After the brine solution 32 has been pumped into the

resin tank 22 for regeneration, water is absent from the salt chamber 16 until

the last step when the tank is refilled with water. Optimally, determination of

the bed level takes place during resin regeneration, when there is no water in

the salt chamber 16 to interfere with the signal. The controller 42 is preferably

programmable to check the bed level only at the appropriate time in the

regeneration cycle and if the cover 54 is in place, and to display an appropriate

message if both of these criteria are not met.

During use, the controller initiates the bed level check at time

when there is no liquid in the salt chamber 16 by requesting the emitter 38 to

produce a signal. The emitter 38 then generates the signal for a sufficient

period of time for the signal to be received by each of the sensors 40.

While the signal is being emitted, the sensors 40 receive it. All

sensors 40 should receive the signal unchanged unless they are covered by the

bed of softening agent 14. If those of the sensors 40 that are below the surface

of the bed receive the signal, the signal is changed in some was, as by a change

in frequency or intensity. Where photocells 40 are used, the intensity of the

light is so reduced that the photocells remain in a state of high resistance. If a

reference sensor 64 is present and fails to receive the signal, the controller

preferably activates an error light or sound to warn the operator that some

portion of the monitor 10 is not functioning properly. Output from the sensors 40 are evaluated by the controller 42 to

ascertain whether or not they are receiving the signal, and whether that signal is

modified by the presence of the bed of softening agent 14. In the case of

photocells 40, the controller 42 measures either the voltage or amperage of the

circuit to determine the resistance of the photocell. In evaluating the sensor 40

outputs, the controller 42 determines which of the sensors 40 is above the

surface of the bed of the softening agent 14 and which sensors are below the

surface. If the critical sensor 66 indicates that it is exposed to the signal, or by

calculation the controller 42 determines that there is insufficient softening

agent 14 to complete the next regeneration, the controller activates an indicator

44 that warns the operator of a low softening agent 14 condition. Where the

softener 12 continuously displays the bed depth, the controller 42 sends an

appropriate message to the indicator 44.

Although the salt level monitor 10 of the present invention has

been shown and described as an array of sensors 40 that respond to a single

emitter 38, those skilled in the art will also recognize that a similar result is

obtainable using a single sensor 40 and an array of emitters 38. An array of

lights, for example, could be lit in sequence along the length of the array and

the output of the photocell 40 evaluated between energizing of one light and

activation of the next light in the sequence. Although the preferred monitor 10

is described as part of a modern electronically controlled softener 12, a basic

version of the monitor is adaptable for retrofit into older model softeners. While a particular embodiment of the present invention has been shown and

described, it will be appreciated by those skilled in the art that changes and

modifications may be made thereto without departing from the invention in its

broader aspects and as set forth in the following claims.

Claims (23)

What is claimed is:

1. An automatic monitor (10) for use in a tank (16) with a

water soluble softening agent, (14) comprising:

a signal emitter (38) that produces a signal in response to a

request;

an array of signal-detecting sensors (40) displaced in the tank

(16) from the minimum depth of the softening agent (14) to the maximum

depth of the softening agent, (14) each of said sensors (40) producing an output

in response to said signal that varies depending on whether or not said sensor is

covered by the softening agent;

a controller (42) configured for issuing said request, receiving

and interpreting said output and determining a low softening agent condition

when the level of the softening agent (14) is depleted to a predetermined level;

and

an indicator (44) configured for warning when said low softening

agent condition is present.

2. The monitor (10) of claim 1, wherein said softening agent

(14) is salt.

3. The monitor (10) of claim 1, wherein said sensors (40) are

linearly spaced vertically in the tank. (16)

4. The monitor (10) of claim 1, wherein said sensors (40) are

photocells and said emitter (38) is a light.

5. The monitor (10) of claim 4, wherein said photocells (40)

are secured to an elongate circuit (104) board which is electronically connected

to said controller. (42)

6. The monitor (10) of claim 1, further comprising a

protective device (72) that houses said sensors. (40)

7. The monitor (10) of claim 6, wherein said protective

device (72) is a transparent tube.

8. The monitor (10) of claim 6, further including upper (76)

and lower caps (72) for enclosing said tube (72) and securing same in

operational position in the tank. (16)

9. The monitor of claim 8, wherein said top cap (76) further

comprises: a lock (87) that engages a mounting surface (36) when said top cap

(76) is positioned in an opening in said mounting surface (36) and rotated.

10. The monitor (10) of claim 1, wherein said indicator

includes a display (100) for communicating a real-time indication of the

softening agent (14) level.

11. The monitor (10) of claim 1, wherein said controller (42)

is configured to determine a no-output condition.

12. The monitor (10) of claim 1, wherein said controller (42)

sends a signal only when no brine (31) is present in said tank. (16)

13. A water softener (12) comprising:

a main tank (22) housing an ion exchange resin; (28)

a salt chamber (16) housing a softening agent (14) that forms a

brine solution (31) when said softening agent (14) is dissolved in water, said

resin (28) being regenerated by said brine (31) at periodic intervals;

a signal emitter (38) that produces a signal in response to a

request;

an array of signal-detecting sensors (40) displaced generally

vertically in the tank (16) from the minimum depth of said softening agent (14)

to the maximum depth of the softening agent (14), said sensor producing an

output in response to said signal; a controller (42) for issuing said request, receiving and

inteφreting said output and determining a low softening agent (14) condition

when the level of said softening agent (14) is depleted to a predetermined level;

and

an indicator (44) warning when said low softening agent (14)

condition is present.

14. The water softener (12) of claim 13, wherein said emitter

(38) produces a signal only when said brine solution (31) is absent from said

brine tank. (16)

15. The water softener (12) of claim 13, wherein said emitter

(38) is a light.

16. The water softener (12) of claim 13, further comprising a

plastic tube. (72)

17. The water softener (12) of claim 16, wherein said array of

signal-detecting sensors (40) is sealed within said plastic tube (72) and said

plastic tube (72) is removably mounted to said salt chamber. (16)

18. A process for monitoring the level of a softening agent

(14) in a water softener (12), comprising: a controller (42) requesting an emitter (38) to send a signal;

said emitter (38) sending said signal an array of sensors (40);

changing at least one property of said signal as it passes through

said softening agent (14) bed;

each of said sensors (40) varying an output in response to said

signal, said output varying in response to said property of said signal that is

changed if it passes through said softening bed (14);

said controller (42) inteφreting said outputs and determining if a

low softening agent condition is present; and

said controller (42) generating an indication when the low

softening agent condition is present.

19. The process of claim 18, wherein said indicating step

comprises activating at least one light emitting diode (38).

20. The process of claim 18, wherein said controller (42)

inteφrets changes in circuit voltage due to varying resistance from a photocell

(40).

21. The process of claim 18, wherein said requesting step

comprises supplying power to said emitter (38).

22. The process of claim 18, wherein said emitting step

comprises iUuminating a light (38).

23. The process of claim 22, wherein said sensor (40)

comprises a photocell that varies in resistance in response to light (38).