Abstract:
A water treatment system includes a tank that contains a particle bed for removing minerals from water flowing through the tank. The regeneration of the particle bed is conducted in response to measuring its conductivity. A probe is provided for that measuring. That probe has a sleeve with a tubular portion for extending through and engaging a wall of the tank. A probe body is removably received within an aperture of the sleeve and includes a pair of electrodes that project inside the tank. A retainer that secures the probe body within the sleeve. Different mechanisms are provided for securing the sleeve to the tank depending upon the particular materials used to fabricate the tank.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates to apparatus for softening water; and particularly to systems for controlling regeneration of the resin in a water softening apparatus.  
         [0004]     It is quite common for water drawn from a well to be considered “hard” in that it contains di-positive and sometimes tri-positive ions which have leached from mineral deposits in the earth. Such ions form insoluble salts with common detergents and soaps producing precipitates that increase the quantity of detergent or soap required for cleaning purposes. When hard water is used in boilers, evaporation results in the precipitation of insoluble residues that tend to accumulate as scale.  
         [0005]     It is common practice to install a water softener in the plumbing system of a building that is supplied with hard water. The most common kind of water softener is an ion exchange apparatus that has a tank which holds a bed of resin through which the hard water flows to remove undesirable minerals and other impurities. Binding sites in the resin bed initially contain positive ions, commonly unipositive sodium or potassium ions. As hard water enters the resin, competition for the binding sites occurs. The di-positive and tri-positive ions in the hard water are favored due to their higher charge densities and displace the unipositive ions. Two or three unipositive ions are displaced for each di-positive or tri-positive ion, respectively.  
         [0006]     The capacity of the resin bed to absorb minerals and impurities is finite and eventually ceases to soften the water when a large percentage of the sites become occupied by the di-positive and tri-positive ions. When this occurs, it becomes necessary to recharge or regenerate the resin bed by flushing it with a regenerant, typically a solution of sodium chloride or potassium chloride. The concentration of unipositive ions in the regenerant is sufficiently high to offset the unfavorable electrostatic competition and the binding sites are recovered by unipositive ions. The interval of time between regeneration periods during which water softening takes place is referred to as a “service cycle.” 
         [0007]     Regeneration of early types of water softeners was affected manually only after it was discovered that the treatment capacity of the resin bed has been exceeded and the water flowing there through is no longer “soft.” In an effort to eliminate the need for manual regeneration, water softener control systems were provided with a mechanical clock which initiated water softener regeneration on a periodic basis. The frequency of such regeneration was set in accordance to the known capacity of the resin bed and the anticipated daily usage of soft water. Although mechanical clock-type water softener controllers alleviated the need for manually regenerating the resin bed, such controllers are subject to the disadvantage that regeneration at fixed intervals may occur too often or not often enough depending upon water usage. Regenerating the water softener resin bed when sufficient capacity to treat water still exists wastes the regenerant and the water used in regeneration. Conversely, failure to regenerate the water softener after the resin bed capacity has diminished to a point below that required to treat hard water may result in hard water leaving the water softener.  
         [0008]     In an effort to better regulate the frequency of water softener regeneration, demand-type water softener controls have been developed which determine the remaining capacity of the resin bed to soften water. One type of such an improved control system is disclosed in U.S. Pat. No. 4,426,294 in which a flow meter measures the volume of water being treated and regenerates the resin bed when a specified volume of water has flowed through the softener since the previous regeneration. While this type of system is adequate in many installations, municipal systems alternately may draw water from several wells which contain water having different degrees of hardness. In that case, the exhaustion of the resin bed is not a direct function of the volume of water which has been treated since the previous regeneration.  
         [0009]     Other types of control systems were developed which detect the exhaustion of the resin bed directly. For example, U.S. Pat. No. 5,234,601 utilizes electrodes to measure the electrical conductivity of the resin bed at two spaced apart locations. The ratio of the conductivity measurements, along with the minimum and maximum ratio values that occurred since the previous resin bed regeneration, are used to determine a probability of resin bed exhaustion and this trigger regeneration.  
         [0010]     In this conductivity based system, wires extend from the controller through the opening at the top of the resin tank through which the water also entered and exited the tank. Thus the wires and their connection to the sensing electrodes were exposed to the water and to the brine solution used during regeneration. That exposure often had a deleterious effect on the wires and the electrode connection.  
         [0011]     The present inventors proposed solving this problem by extending the electrodes through the sidewall of the resin tank, however this approach was complicated by the curved sidewall of the tank. In addition, some resin tanks have a polyethylene liner within a fiberglass outer shell and the liner is not adhered to the shell which makes a water tight connection between the electrode and the tank very difficult.  
         [0012]     Therefore, it is desirable to provide a water tight assembly for inserting the conductivity sensing electrodes through the sidewall of the resin tank in a water tight manner.  
       SUMMARY OF THE INVENTION  
       [0013]     A water treatment system includes a tank that contains a particle bed which removes minerals from water that flows through the tank. A probe is provided to measure conductivity of the resin bed to provide a signal that is used to determine when the particle bed requires regeneration.  
         [0014]     The probe comprises a sleeve with a tubular portion for extending through and engaging a wall of the tank. An aperture extends through the sleeve. The sleeve may have one of several forms so as to be securable to tanks of different construction. One embodiment of the sleeve is designed for tanks with a liner made of a non-bondable material that can not be attached to the inner surface of a rigid outer shell of the tank. This particular sleeve has an outwardly projecting flange at an interior end of a tubular portion that extends through an opening in the tank wall. The tubular portion has external screw threads that are engage by a nut outside the tank to secure the sleeve in the opening. Another embodiment of the sleeve is designed for use on tanks where the liner is made of a material that is bonded to the inner surface of the rigid outer shell. Here, external screw threads on the tubular portion engage threads on an opening through a wall of the rigid outer shell to secure the sleeve on the tank.  
         [0015]     A probe body is removably received within the aperture of the sleeve and has at least one electrode projecting into contact material inside the tank. A retainer that secures the probe body within the sleeve. 
     
    
     DESCRIPTION OF THE OF THE DRAWINGS  
       [0016]      FIG. 1  is a schematic view of a system for regenerating a water softener according to the present invention;  
         [0017]      FIG. 2  is a schematic block diagram of the controller in  FIG. 1 ;  
         [0018]      FIG. 3  is an isometric view of a conductivity probe that is used with the controller in  FIG. 2 ;  
         [0019]      FIG. 4  is a cross section view through the conductivity probe of  FIG. 3 ;  
         [0020]      FIG. 5  is a cross section view along line  5 - 5  in  FIG. 4 ; and  
         [0021]      FIG. 6  is an cross sectional view of a second embodiment of a conductivity probe. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     Referring initially to  FIG. 1 , a water softener  10  includes a softening tank  12  which contains a bed  14  of ion exchange resin particles. An outlet conduit  16  extends through the bed  14  from a point adjacent the bottom of the bed. An inlet conduit  18  extends into the water softener tank  12  and has a discharge opening above the level of the resin bed  14 . Hard water is delivered through an inlet line  20  and treated water is delivered through a service line  22 . The inlet line  20  and the service line  22  are connected through a normally closed first service valve  24 . A normally open second service valve  26  is interposed between the outlet conduit  16  and the service line  22 . A drain line  28  containing a normally closed first drain valve  30  also extends from the outlet conduit  16 .  
         [0023]     Hard water ordinarily is delivered to the inlet conduit  18  through a normally open service inlet valve  32 . Alternatively, hard water entering the inlet line  20  can pass through an injector  34  to draw a regenerant solution from a brine tank  36  when a brine inlet valve  38  is opened and when the service inlet valve  32  is closed. The brine tank  36  contains a common salt  33 , such as a sodium chloride or potassium chloride. The withdrawn brine is delivered through line  35  to the inlet conduit  18  of the softener. The inlet conduit  18  also is connectable to a drain through a normally closed second drain valve  39 .  
         [0024]     During service operation, the drain valves  30  and  39 , the first service valve  24  and the brine inlet valve  38  are all closed. In this mode of operation, the second service valve  26  and the service inlet valve  32  are open allowing hard water to flow from the inlet line  20  through the inlet conduit  18  onto the top of the resin bed  14 . The water passes through the bed  14  and treated water is withdrawn from the bottom of the bed  14  through outlet conduit  16  and into the service line  22 .  
         [0025]     The resin bed  14  eventually becomes exhausted and no longer is capable of softening the water. A typical resin bed regeneration process commences with a backwash step. In this step, a controller  40  closes the service inlet valve  32  and the brine inlet valve  38 , while opening the first service valve  24  and the second drain valve  39 . Hard water from the inlet line  20  feeds through the outlet conduit  16  and upwards through the resin bed  14  finally exiting through the inlet conduit  18  and the now open second drain valve  39 . Water continues to be supplied to the service line  22  at this time even though it is not being treated.  
         [0026]     The backwash step is followed by a brining and rinsing. For this operation, the second service valve  26  and the second drain valve  39  are closed while the brine inlet valve  38  and the first drain valve  30  are opened. In this state, hard water is forced through the injector  34  and brine is withdrawn from the tank  36  through a brine line  35 . The withdrawn brine is discharged into the softener tank  12  through inlet conduit  18 . The brine passes through the resin bed  14  and drains through the outlet conduit  16  and the now open first drain valve  30 . The concentrated brine solution replaces the di-positive and tri-positive ions in the resin with unipositive ions recharging the bed. When the contents of the brine tank  12  have been exhausted, an air check valve  37  closes to prevent air from being injected into the system and water will continue to flow through the injector  34  free of brine. This water propels the brine solution from the tank and then rinses the bed  14  to remove residual brine. Untreated water will be supplied to the service line  22  through the open first service valve  24  during this stage of operation.  
         [0027]     During the next stage of operation, the brine tank  36  is refilled and the softener resin bed  14  is purged. This is accomplished by opening the service inlet valve  32  and the second service valve  26 . Hard water then can enter the brine tank  36  through the open brine valve  38  and can enter the tank  12  through the inlet conduit  18 . Water passing through the resin bed  14  exits via the open drain valve  30 . The apparatus is returned to a service condition by closing the first service valve  24 , the first drain valve  30  and the brine inlet valve  38 .  
         [0028]     Referring to  FIG. 2 , the controller  40  which operates the various valves illustrated in  FIG. 1  is built around a microcomputer  42  which has internal analog-to-digital converters, memory, and clock circuits. An electrically erasable programmable read only memory (EEPROM)  44  is connected to the microcomputer  42  for the storage and retrieval of data. Outputs of the microcomputer  42  are connected to a Walsh sine wave summer  46  as described in an article entitled “Walsh Functions: A Digital Fourier Series” which appeared in Byte Magazine September 1977, pages 190-198, which is incorporated by reference herein. The output of the Walsh sine wave summer  46  is low pass filtered to remove high order harmonics leaving an essentially pure sine wave at a frequency of approximately 1,000 Hz. with an amplitude of approximately 100 mv-pk. The low excitation voltage is selected to prevent chemical reduction or oxidation from occurring at electrodes in the resin bed. A relatively high excitation frequency was selected to reduce the electrode double layer capacitance.  
         [0029]     The output signal from the Walsh sine wave summer  46  is applied to common electrodes of two conductivity probes  47  and  48  that extend into the resin bed  14 . The lower conductivity probe  48  is located at approximately thirty-eight percent of the effective height (X) of the bed which is the distance between the uppermost inlet opening at the bottom of outlet conduit  16  and the top of the resin bed. The position was chosen so that the lower conductivity probe  48  produces a indication of a conductivity change when approximately twenty percent of the capacity of the resin bed remains to treat water. The upper conductivity probe  47  is positioned in the resin bed approximately six inches above the lower conductivity probe  48 .  
         [0030]      FIGS. 3 and 4  illustrate a first embodiment of a sensor probe  60  that can be used as the upper and lower conductivity probes  47  and  48  in  FIG. 1 . The sensor probe  60  has a sleeve  61  comprising a tubular section  62  with exterior thread and an outwardly projecting flange  64  at one end of the tubular section. The sleeve  61  extends through an aperture in the sidewall of the water softener tank  12  with the flange  64  compressing an annular rubber seal  66  against the inner surface of the tank  12  to provide a water tight seal. This sensor probe  60  is intended for use with a tank  12  having a fiberglass or steel outer body  67  with an polyethylene inner liner  69 . Polyethylene and similar non-bondable materials form an inner liner  69  that is not bonded to the rigid outer body  67 , nor can the probe sleeve  61  be adhered or otherwise bonded to these inner liners. As a result, the probe  60  has a flange  64  and the annular rubber seal  66  that provides a water tight abutment between the probe components and the inside surface of the tank  12 . The probe  60  is held in place by a hexagonal nut  68  which is threaded onto the exterior of the tubular section  62  until it abuts the outer surface of the tank  12 .  
         [0031]     A sensor body  70  is inserted from outside the tank into a central aperture  72  in the sleeve&#39;s tubular section  62 . An annular exterior groove near an interior end  74  of the sensor body  70  contains an O-ring  78  to establish a water tight seal between the sensor body  70  and the sleeve  61 . The sensor body  70  is held within the sleeve  61  by a U-shaped retaining clip  80  which slides within grooves  82  on opposite sides of the tubular section  62  of the sleeve, as also shown in  FIG. 5 . The side legs of the retaining clip  80  extend through the sleeve grooves  82  and enter an annular notch  84  around the outside of the sensor body  70 . The engagement of the retaining clip  80  with the sleeve  61  and the groove  82  of the sensor body  70  holds the sensor body against the interior rib  76  of the sleeve.  
         [0032]     A pair of walls  88  and  89  project outwardly from the interior end  74  of the sensor body  70  into the resin bed  14  inside the water softener tank  12 . A pair of electrodes  90  and  91  project through the wall at the interior end  74  of the sensor body  70 . When the sensor body  70  in inserted into the sleeve  61 , each electrode  90  and  91  extends through a separate small aperture in the interior end wall  76  of the sleeve&#39;s central aperture  72 . Those small apertures permit the sensor body  70  to be replaced with minimal loss of water from the tank  12 . The electrodes  91  and  92  are fabricated of gold plated, stainless steel, for example. The stainless steel of the electrode structure resists corrosion, while the gold plating makes the surface chemically inert. However, the gold resists wetting by the water within the tank  12 . In order to improve the wetting, a sleeve of an ion exchange material, such as Nafion (trademark of E.I. du Pont de Neumours &amp; Co., Inc.) is inserted over each electrode  91  and  92 . The sleeve “wets” the hydrophobic gold surface and keeps macro-molecules away from the electrode surface, thereby further stabilizing and preventing electrode contamination. The sleeve also protects the relatively soft gold surface from abrasion. Alternatively, graphite rods may be used as the electrodes and would not require gold plating.  
         [0033]     The two electrodes  90  and  91  project into a cavity  86  in the sensor body. The cavity  86  is designed to receive a mating electrical connector (not shown) on the end of the cable that connects the sensor probe to the controller  40 . That connector electrically engages ends of the electrodes  90  and  91 .  
         [0034]     With reference to  FIG. 6 , some types of water softener tanks have a acrylonitrile butadiene styrene (ABS) liner  100  that is enclosed by and bonded to a fiberglass or steel outer body  102 . The ABS liner  100  provides a water tight enclosure for the resin bed  14  and water being treated by the softener, while the outer body  102  provides a rigid structure for the softener tank  12 . Because with this type of tank construction, the liner is bonded to the outer body to form an integrated structure, a sleeve  104  of the sensor  106  can be secured in a threaded aperture in the sidewall of the tank  12 . Thus, the sleeve  104  has a cylindrical tubular portion  108  with external threads that engage threads cut in the outer body  102  of the tank  12 . Upon inserting the sleeve  104  the threads are coated with an adhesive sealant which bonds the sleeve to the tank to form a water tight fitting. Alternatively, or in addition, a rubber sealing ring  110  can be provided between the outer surface of the tank  12  and a flange  112  at the outer end of the tubular portion  108  of the sleeve  104 .  
         [0035]     The sleeve  104  has an aperture there through for receiving the sensor body  114  which is structurally similar to the sensor body  70  in  FIG. 4 . Specifically, the sensor body  114  has an open end  116  adjacent the outer end of the sleeve  104  and a closed end  118  adjacent the sleeve&#39;s inner end. A pair of walls, only one of which, wall  120 , is visible in the drawing, project from that end into the resin bed of the tank  12 . A pair of electrodes  121  and  122  extend through the eludes end of the sensor body  114  between the two walls similar to that of the first sensor embodiment. The electrodes  121  and  122  extend into the cavity of the sensor body  124  for the purpose of making electrical connection to the cable from the controller  40 . An annular groove  126  extends around the sensor body  124  to receive the legs of a U-shaped retaining clip  128  that is placed within notches in the sleeve  104 . The engagement of the retaining clip  128  with the sensor body  114  held in abutment against the interior end  130  of the sleeve with the walls and the electrodes  121  and  122  extending through an aperture in that sleeve end  130 . An O-ring  132  provides a seal between the exterior of the sensor body  114  and the interior surface of the sleeve  104 .  
         [0036]     Referring once again to  FIGS. 1 and 2 , the non-common electrode of each of the conductivity probes  47  and  48  is connected to a separate current-to-voltage converter  50  and  51 , respectively. Each of these converters  50  and  51  transforms the magnitude of the current flowing through the associated probe  47  or  48  into a corresponding voltage level. The voltage outputs from the current to voltage converters  50  and  51  are applied to inputs of the microcomputer  42  which are connected to internal analog-to-digital (A/D) converters. The microcomputer  42  periodically enables each A/D converter in order to read the magnitude of the voltage produced by the associated current-to-voltage converter  50  and  51 .  
         [0037]     Another input line to the microcomputer  42  is connected to a service switch  52  which is closed whenever a regeneration of the water softener  10  is occurring. A set of indicator lamps  59  are activated by the microcomputer  42  as will be described, to provide indications to the user of events such as depletion of the salt in the brine tank  36  and probe failure. Other types of signaling devices, such as audible alarms, can be used.  
         [0038]     The microcomputer  42  executes a control program which detects the currents flowing through the conductivity probes to determine when the resin bed  14  requires regeneration. The algorithm that the controller employs to determine when to regenerate the resin bed based on the conductivities is described in detail in U.S. Pat. No. 5,234,601. Whenever the control program from the microcomputer  42  determines that regeneration is required, a control signal is sent via line  54  to a conventional valve control clock and timer  56  as used in previous water softeners which regenerated the resin bed at a periodic interval and at a time of day (e.g. 2 a.m.) when water use is minimal. However, the valve control clock and timer  56  initiates regeneration of the resin bed  14  at that time of day only when a control signal is being received over line  54 . If these conditions are met, the valve control clock and timer  56  rotates a cam shaft  58  which opens and closes the different valves illustrated in  FIG. 1  in the sequence previously described to regenerate the resin bed.  
         [0039]     The foregoing description was primarily directed to a preferred embodiment of the invention. Although some attention was given to various alternatives within the scope of the invention, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from disclosure of embodiments of the invention. Accordingly, the scope of the invention should be determined from the following claims and not limited by the above disclosure.