Abstract:
Provided is an apparatus for detecting a change in a specific gravity of a fluid surrounding the apparatus wherein the fluid moves upwardly and downwardly with respect to the apparatus. The apparatus includes a housing having a top and a plurality of openings for allowing the fluid to enter the housing. A first floatation device is provided having a first specific gravity and being located within the housing. The first floatation device includes a magnet. A second floatation device is provided having a second specific gravity and located within the housing adjacent said first floatation device. The said second floatation device includes a magnet aligned to have the same polarity as the magnet of the first floatation device. A switch fixedly attached to said top, the switch having an open state and a closed state where when one of said magnets is in proximity to the switch, the switch is in a closed state and wherein when both of said magnets are in proximity to said switch, the switch is in an open state. A signaling device is coupled to the switch wherein said signaling device is activated when the switch is in the closed state.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus for use in a fluid treatment system, and, more specifically, to an apparatus for detecting a change in the specific gravity of a brine solution within a brine tank as part of a fluid treatment system. 
       BACKGROUND 
       [0002]    A known water softening apparatus includes a brine tank. The brine tank includes salt upon which water is added to produce a brine (salt/water solution) which in turn is used to regenerate an exhausted treatment tank in a fluid treatment system. After the exhausted tank is regenerated, the brine solution is then purged from the regeneration tank, not to be used again. To produce more brine, water is added to the brine tank having the salt. The water dissolves a portion of the salt to create more brine. 
         [0003]    After each regeneration cycle, the amount of salt in the brine tank is reduced. Eventually, the salt in the brine tank will be depleted and the brine solution formed will not be saturated with salt. This unsaturated brine solution will not sufficiently regenerate an exhausted treatment tank. As a result, salt must be added to the brine tank so that proper regeneration of a treatment tank may take place. 
         [0004]    Most modern systems do not include a low salt level sensor. The operator must remember to periodically check the level of salt in the brine tank and add salt as needed. These systems are susceptible to operator forgetfulness and error and thus are not entirely satisfactory. As the salt is necessary for the proper functioning of the system and adding salt is the only regular maintenance most modern systems need. 
         [0005]    Previous attempts to incorporate a low salt level sensor were not satisfactory. A weight was used in an attempt to determine the level of solid salt in the brine tank. The weight was supposed to sit on top of the solid salt at the bottom of the tank. One of the problems with sensors of this type is that, when operators would add salt to the brine tank, salt would be poured over the weight and it would be buried and be unable to rise and sense the correct salt level. As a result, the sensing unit would falsely indicate that salt was needed. In addition, the salt level did not drop in a uniform manner and the salt would become unevenly distributed and the sensing device would falsely indicate that salt was needed when an adequate supply was present. 
         [0006]    In view of the foregoing, a salt level sensor is needed which can accurately relay when salt is actually needed without producing a frequent false alarm that salt levels are low or depleted in the brine tank. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    Disclosed is an apparatus for detecting change in the specific gravity of a fluid and signaling that a change has occurred in the specific gravity. In a preferred embodiment, the apparatus is used in conjunction with a water treatment system to detect a change in the specific gravity of the brine solution to signal when there is low or no salt in the brine tank. 
         [0008]    The apparatus is positioned in a brine tank and in a surrounding relationship with the fluid. The apparatus is adapted to detect a change in a specific gravity of a fluid surrounding the apparatus when the fluid moves upwardly and downwardly in the tank with respect to the apparatus. In the preferred embodiment, the apparatus includes a housing having a plurality of openings for allowing the fluid to enter the housing. The housing also includes a top. A first floatation device having a first specific gravity is positioned in the housing. The first floatation device can move freely within the housing in response to the rise and fall of fluid about the apparatus. A second floatation device having a second specific gravity is also positioned in the housing adjacent to the first floatation device. The second floatation device can move freely within the housing in response to the rise and fall of fluid about the apparatus. A sensing element is fixedly attached to the top. The sensing element is adapted to recognize the proximity of the floatation devices to the sensing element. A signaling device is coupled to the sensing element wherein the signaling device is activated by the state of the sensing element. 
         [0009]    In a preferred embodiment, the apparatus includes a cage that houses the two floatation devices where each floatation device includes a magnet positioned at its upper end being oriented to have the same polarity or orientation. The housing includes a cap that houses a magnetic reed switch. 
         [0010]    In a preferred embodiment, the reed switch includes a pair of contacts, each contact being in communication with a post that extends out of the reed switch encapsulation. Further, these posts are connected to a wire that is in communication with a signaling device. A signaling device can be any device known in the art in view of this disclosure. Examples of such a signaling device include a visual signaling device such as an light emitting diode (LED) or an audible signal such as an alarm. 
         [0011]    The floatation devices are of the same construction but are made from different materials thereby having different specific gravities. The floatation devices are, preferably, injection molded. In a preferred embodiment, the floatation devices include a protrusion at either end which aids in minimizing water tension during operation of the apparatus. 
         [0012]    In a preferred embodiment, normal operation of a brine drum used in fluid treatment, i.e., water softening systems, brine solution is drawn out of the brine tank by the valve control through conduit and used for regeneration of the fluid treatment tanks. Once the exhausted tank is regenerated, water is pumped back into the brine tank by the valve control through conduit in order to produce more brine for future tank regeneration. As water is added to the brine tank, the salt in the tank dissolves in the water thus producing saturated brine. Through continuous cycles, the salt is depleted and more salt must be added to the brine tank to ensure that the brine is of sufficient concentration to regenerate an exhausted tank. When the salt level is full or adequate, the brine takes on a certain specific gravity. As the salt is depleted, the specific gravity of the brine will change. In a preferred embodiment, one of the floatation devices has a lower specific gravity than the other floatation device. 
         [0013]    In the preferred operation, when the brine is in a saturated state or a state having sufficient dissolved salt to regenerate a treatment tank, both floatation devices rise to the top of the apparatus housing as the brine moves upwardly and downwardly during a regeneration cycle. This upwardly and downwardly movement is a direct result of the specific gravities of the flotation devices with respect to the specific gravity of the fluid. It must also be noted that the two-floatation device may be employed to detect a change is specific gravity of a fluid that does not rise and fall in a tank. In this case, the floatation devices will float or sink when there is a change in the specific gravity of the fluid. When used in a treatment system including a brine tank where the level of the water changes during use of the brine, the floatation devices respond to the rise and fall of the water in relation to the specific gravity of the fluid. In this type of system, when the fluid reaches a specific gravity that is between the specific gravities of the floatation devices, it can trigger an alarm signally a change in the specific gravity. Since the alarm can only be triggered by a change is specific gravity of the fluid, a false alarm due to the rise and fall of the fluid in a tank is prevented. 
         [0014]    In the preferred operation, the magnets in each floatation device provide an equal influence on the magnetic reed switch thus keeping the contacts in an open state. When the salt in the tank becomes depleted, the specific gravity of the brine becomes less creating a less saturated condition. In this condition, the floatation device having the higher specific gravity will remain at the bottom of the apparatus while the floatation device having the specific gravity closer to water will rise to the top of the apparatus. The magnet in the floatation device that has risen to the top of the apparatus interacts with the contacts in the reed switch causing the contacts to contact each other. The switch closes completing a circuit which activates the signaling device. 
         [0015]    In a preferred embodiment, when the two floatation devices are at the top of the apparatus, each magnet interacts with the contacts in the switch causing the contacts to repel one another. In this way, the hysteresis tendency of the contacts to remain closed is reduced. Thus, on the successive brine fill upon addition of salt, the contacts will be forced apart due to the interaction of both magnets on the contacts. 
         [0016]    The present invention is also directed to a method for detecting a change in a specific gravity of a fluid. The preferred method includes first providing a supply tank including a fluid that is used in the regeneration of a treatment tank in a fluid treatment system wherein the fluid moves upwardly and downwardly within the tank during a regeneration cycle. Next an apparatus is provided and is fixedly disposed in the supply tank. The apparatus is in a surrounding relationship with said fluid and is adapted to detect a change in the specific gravity of the fluid as the fluid moves upwardly and downwardly within the tank. A signaling device is further provided which is activated by said apparatus when the apparatus detects a change in the specific gravity of the fluid. 
         [0017]    Additional features of the invention will become apparent and a fuller understanding obtained by reading the following detailed description made in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a perspective view of a water treatment system employing a signaling device according to the present invention, 
           [0019]      FIG. 2  is a perspective view of a signaling device according to the present invention; 
           [0020]      FIG. 2   a  is a top plan view of the signaling device of  FIG. 2  shown from line  2   a - 2   a  of  FIG. 2 ; 
           [0021]      FIG. 3  is a cross-sectional view of a floatation device for use in the signaling device of  FIG. 2 ; 
           [0022]      FIG. 4  is a cross-sectional view of a floatation device for use in the signaling device of  FIG. 2 ; 
           [0023]      FIG. 5  is an exploded perspective view of the signaling device of  FIG. 2 ; 
           [0024]      FIG. 6  is a cross-sectional view of the signaling device of  FIG. 2 ; 
           [0025]      FIG. 7  is a top view of the signaling device of  FIG. 2 ; and 
           [0026]      FIG. 8  is a front elevational view of a reed switch for use in the signaling device of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  illustrates the overall construction of a water softener system that incorporates the present invention. Although a water treatment system is described, the present invention can be employed in any system where fluid treatment is desired. The system shown includes a pair of fluid treatment tanks  10 ,  12 , an upstanding brine tank  14  and a valve assembly  16  fastened to the tanks  10 ,  12 . The valve  16  controls the usage and regeneration of the tanks  10 ,  12  and is operative to connect one of the tanks  10 ,  12  to a water supply or other supply where fluid treatment is required and further controls the regeneration of an exhausted tank. A drain conduit  17  connected to the valve  16  discharges brine solution and “backwash” fluid during a regeneration cycle. 
         [0028]    The brine tank  14  is of known configuration and comprises a cylindrical, upstanding container capped by a removable cover  18 . A salt grid  20  is disposed horizontally across the container a predetermined distance above the bottom. A granular salt supply, indicated generally by the reference character  22 , is supported by the horizontal grid  20 . A brine solution reservoir  24  is then defined below the grid  20 . The reservoir  24  communicates with the valve assembly  16  through a conduit  26 , the fluid communication being controlled by a brine valve  28  (shown schematically). The brine valve is disposed within a brine well  30  that comprises a downwardly extending tube having apertures  32  at its lower end through which the brine solution is admitted. The brine valve  28  serves a dual function in that it controls both the outflow of brine solution from the reservoir  24  to the valve assembly  16  and the inflow of water to replenish the brine solution used during regeneration. 
         [0029]    In the illustrated embodiment, a sensing device  40  is affixed to the salt grid  20 . The sensing device  40  is configured to sense when the brine solution in the brine tank  14  is approaching a specific gravity of that of water, indicating that the brine tank  14  is low in salt. The sensing device is typically held in place through mechanical means such as being bolted to the grid, however, other attachments means are also contemplated such as, adhesives or other bonding techniques. Turning to  FIGS. 2-8 , the brine sensing device  40  is shown in more detail. The sensing device includes a cage structure  42  having an I-shaped base  44 , four outer retaining elements  46   a - d  and a central retaining element  48  each of which extend generally perpendicularly away from the base  44  to an opposing cage top  49 . The retaining elements  46   a  and  46   b  along with the central retaining element  48  define one portion of the cage structure  42  that houses a first floatation device  50 . Likewise, retaining elements  46   c  and  46   d  along with the central retaining element  48  define a second portion to the cage structure  42  that houses a second flotation device  52 .  FIG. 2   a  illustrates the preferred configuration for housing the floatation device  50  within the cage structure  42 . The retaining element  46   a  is spaced a distance from the retaining element  46   b  by a distance less than the diameter of the floatation device  50 . Furthermore, the retaining elements  46   a  and  46   b  are spaced a distance from the central retaining element  48  by a distance less than the diameter of the floatation device  50 . In this configuration, the flotation device  50  is confined by the retaining elements  46   a  and  46   b  and the central retaining element  48  at three points and is permitted to freely flow for the length of the retaining elements  46   a  and  46   b  and central retaining element  48 . This limits friction so that the floatation device  50  can easily move with respect to the level of solution within the brine tank  14  where the specific gravity of the fluid is higher than that of the floatation device  50 .  FIG. 2   a  shows the configuration with respect to floatation device  50 , however, this same configuration is employed with respect to floatation device  52 . In this regard, floatation device  52  is confined by retaining elements  46   c  and  46   d  along with the central retaining element  48 . This configuration secures the first floatation device  50  and the second floatation device  52  such that they are positioned directly over the top  49  being a predetermined horizontal distance from each other. This configuration also provides a known travel path of the floatation devices  50  and  52  within the cage  42  in response to the rise and fall of water/brine within the tank  14 . 
         [0030]      FIGS. 3 and 4  illustrate the detail of the first flotation devices  50  and second floatation device  52 . The first floatation device  50  and the second floatation device  52  are of identical construction, however, they differ with respect to their overall specific gravities. Turning to  FIG. 3 , the first floatation devices  50  includes a substantially cylindrical base  60  having somewhat cone-shaped bottom surface  62  and an opposing open top end  63 . The cylindrical base  60  includes a slot or cavity  64  that extends from the open end  63  into the cylindrical base  60  providing a hollow center to the floatation device  50 . A series of prongs  66  (shown best in  FIG. 3  with respect to the second floatation device  52 , prongs labeled as  66 ′) extend from the bottom of the slot  64  upward toward the open end  63 . A cap  68  is positioned over the open end  63  of the cylindrical base  60  is welded in place via ultrasonic welding. Other methods of adhering the cap to the base are likewise contemplated such as the use of an adhesive or through a series of mechanical fixtures. Regardless of the method use to secure the cap  68  to the cylindrical base  60 , a fluid-tight seal must be attained so that no water or brine is permitted to enter the flotation device  50 . The cap  68  includes a slight arch of the top. This arch along with the cone shape on the bottom of the base  60  acts to minimize water tension on the top and bottom of the floatation device, respectfully. Further, a magnet  70  is seated in the cap  68  prior to securing the cap  63  to the base  60 . The magnet  70  is centrally positioned in the cap  68  and is located and held in the cap  63  by the prongs  66 . The magnet in the first floatation device  50  is positioned to have the same polarity as the magnet  70 ′ of the second floatation device  52  (i.e., the north and south end of each magnet point in the same direction). 
         [0031]    The first floatation device  50  has a specific gravity of about that of a saturated solution. In the illustrated embodiment, the specific gravity is greater than that of water or greater than 1.0 g/cm 3 . To obtain such a specific gravity, the cap  68  and base  60  of the first floatation device  50  are constructed from a plastic material that has a specific gravity greater than that of water. Such plastic material may be filled, if necessary, with a filler material such as glass or other materials as known to those of ordinary skill in the art. One such plastic material that provides a useable specific gravity greater than water for the first floatation device  50  is a polyphenylene ether/PPO, polystyrene plastic commonly referred to as Noryl GFN3 and is commercially available from General Electric Company. Typically, this construction produces a first floatation device  50  (including the base  60 , cap  68  and encapsulated magnet  70 ) having a specific gravity greater then 1.0 g/cm 3 . Yet, depending on the amount of fill in the plastic material, a specific gravity in the range from greater than 1.0 g/cm 3  to about 1.21 g/cm 3  can be obtained. In the case of a water softening system employing a brine tank, a first floatation device  50  having a specific gravity of about 1.21 g/cm 3  is desired. 
         [0032]    As discussed, the first flotation device  50  has the same overall construction as the second floatation device  52 . However, the floatation devices are each of a different specific gravity. Referring to  FIG. 4 , the second floatation device  52  illustrated. The second floatation device  52  is constructed from a plastic material and is formed via injection molding of the base  60 ′ and cap  68 ′. The base  60 ′ and cap  68 ′ are then welded together by an ultra-sonic weld. The cap  68 ′ and base  60 ′ of the second floatation device  52  is constructed of a plastic material which should have a specific gravity close to that of water (1.0 g/cm 3 ). One such material is an acrylonitrile-butadiene-styrene copolymer and is commonly known. Use of this material produces a water floatation device having an overall specific gravity in the range from less than 1.0 g/cm 3  to about less than 1.21 g/cm 3 . However, the specific gravity to be employed is dependent on the fluid the floatation device is be used in and the specific gravity must be less than that of a first floatation device  50 . In the case of a water treatment system employing a brine tank, a second floatation device  52  having a specific gravity of about 0.98 g/cm 3  is desired. 
         [0033]    In some cases, when the first floatation device  50  and second floatation device  52  are constructed the desired specific gravity is not obtained. When this happens, weights such as small brass balls may be added to the floatation device  50 ,  52  to modify the specific gravity. The brass balls (not shown) are of known weight and are placed in the slot or cavity  64  or  64 ′. Once the correct specific gravity is obtained with the addition of the brass balls the cap  68  or  68 ′ can be welded to the base  60  or  60 ′ to prevent any further changes to the floatation devices specific gravity by a fluid leaking into the first floatation device  50  or second floatation device  52 . 
         [0034]    The cage top  49  is a generally circular in nature and adapted to support or retaining element  46   a - d  of the cage  42 . The cage top  49  includes a generally horizontal passage  54  that extends across the cage top  49  from a passage inlet  71  to a passage outlet  74 . The passage  54  further includes an overflow bore  75 . This passage  54  houses a magnetic reed switch  56 . 
         [0035]    The reed switch  56  is a standard reed switch and is commercially available. The reed switch  56  (referring to  FIG. 8 ) includes two wire posts  76 ,  78  that extend out of the glass encapsulated reed contact or reed switch  56 . During operation, the wire posts  76 ,  78  act as an antenna to interact with the magnetic flux of the magnet  70  or  70 ′ in the first floatation device  50  and the second floatation device  52 . A jacketed cable  80  is affixed to the wire post  76 ,  78  to carry an electronic signal from the reed switch  56  to an alarm or signaling device  82 . The signaling device  82  ( FIG. 1 ) can be a variety of different signaling devices such an LED, an audible alarm and/or an input to an electronic device. The jacketed cable  80  has two insulated wires  84  and  86  which contact the wire posts  76  and  78 , respectively. Typical wire as used for the wires  84  and  86  have an insulating coating which is removed to expose the metal wire for making an electrical connection. In this case, a portion of the insulated wire  84  is stripped away exposing the metal core  84   a . The metal post  76  and the metal core  84   a  are both inserted into a wire ferrule  88  and the ferrule is crimped to make a secure connection between the metal core  84   a  and the metal post  76 . Likewise, the second insulated wire  86  is stripped to expose the metal core  86   a . The metal post  78  and metal core  86   a  are inserted into a ferrule  88  and the ferrule  88  is crimped to make a secure connection between the metal core  86   a  and the metal post  78 . Although a crimped ferrule is use to connect the metal posts  76  and  78  to the wire cores  84   a ,  86   a , other techniques may be employed to provide an electrical connection. One other such technique is soldering. Encapsulated in the reed switch  56  are a first contact  92  and an opposing second contact  94 . The first contact  92  is coupled to the metal post  76  and the second contact  94  is coupled to metal post  78 . In their normal position, the first contact  92  is separated from the second contact  94 , thus, producing an open switch. As explained below, the contacts  92  and  94  can contact each other to close the circuit thereby activating the signal device  82 . 
         [0036]    Once the reed switch  56  is connected to the jacketed cable  80 , it is inserted into the passage  54  through the passage inlet  71  far enough so that at least a portion of the jacketed cable  80  enters the passage  54 . To secure and protect the reed switch  56  within the passage  54 , a potting compound is injected into the passage outlet  74 . The potting compound fills the passage  54  housing the reed switch  56  and associated components thereby encapsulating the reed switch  56 . The potting compound is continuously injected into the passage outlet  74  until there is an overflow of potting compound exiting the overflow bore  75 . At this point, injection of the potting complete is complete encapsulating the reed switch  56  in the passage  54  and protecting the reed switch  56  from the water/brine solution and physically protecting the reed switch  56  from damage. Potting compounds suitable for use in potting the passage  54  are commonly known and within one of ordinary skill in the art to develop. The passage inlet  71  includes ribs  73  on its outer peripheral upon which wire shrink wrap is utilized to make a seal between the cap  49  and jacketed cable  80  as well as provide mechanical strain relief on the cable connection to the passage  54 . 
         [0037]    The brine sensing device  40  is positioned in the brine tank in the salt grid  20 . The cage top  49  includes a pair of spin/push clips  90  that secure into a receptacle (not shown) on the salt grid  20  such that the cage top rest in contact with the salt grid  20  and the cage portion extends below the salt grid  20 . In this configuration, the sensing device  40  remains in place as the fluid rises and falls with respect to the sensing device  40 . In turn, the floatation devices  50  and  52  are permitted to move with the fluid provided that the specific gravity of the first floatation device  50  and second floatation device  52  is less than the specific gravity of the fluid. 
       Operation: 
       [0038]    During the normal operation of a brine drum used in fluid treatment, i.e., water softening systems, brine solution is drawn out of the brine tank  14  by the valve control  16  through conduit  26  and used for regeneration of the fluid treatment tanks  10 ,  12 . Once the exhausted tank, either  10  or  12 , is regenerated, water is pumped back into the brine tank by the valve control  16  through conduit  26  in order to produce more brine for future tank regeneration. This use and replenishing causes the level of brine in the brine tank  14  fluctuate. The brine sensing device  40  is typically positioned on the salt grid  20  where the lower level, indicated by the arrow  100  in  FIG. 1 , of the brine after the brine is drawn from the tank is at least 0.5″ below the salt grid  20  and the upper level, indicated by the arrow  102  in  FIG. 1 , of the brine after water is added for replenishing brine must be above the salt grid  20  for normal operation of the sensing device  40 . This placement of the sensing device ensures that the sensing device  40  is not located in a brine layer which commonly forms at the bottom of a brine tank. 
         [0039]    Prior to brine being supplied to a tank  10 ,  12  for regeneration, the brine level is at the upper level  102  within the brine tank  14 . Due to the presence of salt within the tank  14 , the solution is saturated. At this point, the saturated solution has a specific gravity that is much greater than that of water and is near or about 1.21 g/cm 3 . As stated, the first floatation device  50  has a specific gravity of about 1.20 g/cm 3  and second floatation device  52  has a specific gravity of about 0.98 g/cm 3 . Therefore, both of the floatation devices  50  and  52  will be at the top of the cage  42  since each floatation device has a specific gravity less than the of the saturated solution. 
         [0040]    In this position, the magnetic flux of the magnet  70  in the first floatation device  50  interacts with the metal post  76  of the reed switch  56 . Similarly, the magnetic flux of the magnet  70 ′ in the second floatation device  52  interacts with the metal post  78  of the reed switch  56 . The magnetic flux of the magnet  70  in the first floatation device  50  is received by the antenna-acting metal post  76  and is transferred to the first contact  92 . Likewise, the magnetic flux of the magnet  70 ′ in the second floatation device  52  is received by the antenna-acting metal post  78  and is transferred to the second contact  94 . The magnets  70  and  70 ′ are of the same polarity and this polarity is reflected by the first contact  92  and second contact  94  thus causing the first contact  92  to repel the second contact  94  thus keeping the switch in the open position. Imparting the same magnetic field on the opposite ends of the reed switch  56  ensures that the first contact  92  will repel the second contact  94  reducing the hysteresis tendency of the contacts  92 ,  94  to remain closed once they have come into contact with each other. 
         [0041]    As brine is drawn out of the brine tank  14  during a tank regeneration cycle, the first floatation device  50  and second floatation device  52  begin to drop away from the cap  49  in the cage  42 . As the first floatation device  50  and the second floatation device  52  drop away from the cap  49  the magnet  70  in the first floatation device  50  and the magnet  70 ′ in the second floatation device  52  exert less influence on the metal posts  76 ,  78  thereby reducing the induced magnetic field exerted on the first contact  92  and second contact  94 . In some instances, the first floatation device  50  may drop at a faster rate then the second floatation device  52  or vice versa. When this situation occurs, a false signal could result indicating the tank  14  is out of salt. However, there is a maximum distance that the magnet  70  of first floatation device  50  or the magnet  70 ′ of the second floatation device  52  must be within for the contacts  92 ,  94  to close and over come the mechanical movement of the contacts  92 ,  94 . Because the distance between the magnets  70 ,  70 ′ and the metal posts  76 ,  78  is so small, one of the first floatation device  50  or the second floatation device  52  must be very close to the metal posts  76 ,  78  while the other floatation device must be a considerable minimum distance away before the magnet of the closer floatation device can assert enough magnetic flux on the metal post, which is translated to one of the contacts, to overcome the mechanical movement and minimal influence of the opposing magnet to cause the contact  92 ,  94  to come into contact, thereby closing the switch. This essentially creates a “deadband” where one of the first floatation device  50  or second floatation device  52  can travel away from the reed switch  56  without causing the contacts  92 ,  94  to come into contact with each other. Thus, one floatation device can move in the cage  42  prior to the other floatation device without causing a false signal to occur. 
         [0042]    When the brine in the tank  14  is drawn to a lower level  100 , both floatation devices  50  and  52  move away from the top of the cage  42  at slightly different rates. As long as the floatation device that moves first is within the deadband described above before the other floatation device moves, the contacts  92 ,  94  will not falsely close. At the brine continues to drop in the tank  14 , the floatation devices  50  and  52  drop in the cage  42  as the brine drops to the lower level  100  in the tank  14  without any influence on the reed switch  56 . 
         [0043]    When the brine is at a lower level  100  within the brine tank  14 , the valve  16  permits water to flow into the tank through conduit  26 . Some of the saturated brine mixes with the incoming water to create a layer of less concentrated brine solution between the lower brine level and the rising brine/water mixture. This less saturated solution has a specific gravity greater than the of either the first floatation device  50  or the second floatation device  52 , thus, the floatation devices  50  and  52  both rise to the top of the cage as the water/brine level increases. As the less saturated solution rises above the salt grid  20 , the less saturated solution comes into contact with the salt and begins to further saturate the solution back to a more saturated brine condition. At this time, both floatation devices  50  and  52  stay at the top of the cage  42  and again influence the reed switch  56  equally so that the first contact  92  does not come into contact with the second contact  94 . 
         [0044]    The described cycle takes place each time one of the tanks  10  or  12  require regeneration. As long as there is salt on the salt grid  20  there will be no significant changes to the specific gravity of the brine solution within the tank  14 . However, when a cycle repeats and there is little or no salt on the grid  20 , the solution between the lower level  100  and the upper level  102 , does not increase in saturation and thus the specific gravity of the solution begins to drop. At this point, the solution may still have a specific gravity greater than that of either the first floatation device  50  or the second floatation device  52  and the floatation devices  50  and  52  are again lowered again on the drawn down cycle of the brine. On the successive water fill, water is injected into a slightly reduced concentration brine solution and the brine concentration is even further reduced. At this point, the specific gravity of the reduced brine is less than that of the of the first floatation device  50  but greater than the of the second floatation device  52 . When the refill is occurring, the first floatation device  50  will not rise back to the top of the cage  42 . The second floatation device  52 , on the other hand, having a specific gravity less than the reduced brine solution will rise to the top of the cage  42 . Upon completion of the water refill, the level of the brine in the brine drum  14  is back to the upper level  102  and the first floatation device  50  is at the bottom of the cage  42  and the second floatation device  52  is at the top of the cage  42 . Thus the magnet  70 ′ in the second floatation device  52  exerts a magnetic influence on the metal post  78  which is translated to the contact  94 . The contact  94  attracts the opposing contact  92  since there is no opposing magnetic influence on the contact  94  from the magnet  70  of the first floatation device  50 . As such, the contact  94  attracts the contact  92  closing the switch. The closed switch completes a circuit which sends a current to the signaling device  82  outside of the brine tank  14  signaling that the salt within the tank is low or completely exhausted. This signaling occurs within one to two cycles of a low or depleted salt condition. 
         [0045]    Although the invention has been described with a certain degree of particularity, it should be understood that various changes can be made to those skilled in the art without departing from the spirit or scope of the invention as hereinafter claimed