Patent Publication Number: US-7713501-B2

Title: System for providing a chemical to a fluid

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of prior application Ser. No. 11/187,060, filed Jul. 22, 2005, now U.S. Pat. No. 7,595,022, which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention is directed to a system and a method for providing a chemical into a fluid stream and, in particular, to a system and a method for providing a low concentration of a chemical into a fluid stream from an elongate member, such as a monofilament line, strand, or the like, having the chemical therein. 
     BACKGROUND OF THE INVENTION 
     The beneficial effects of adding fluoride to drinking water are well known. 
     Fluoride at a concentration of about one part per million (ppm) is known to greatly reduce tooth decay, contribute to good bone health, and may also substantially reduce osteoporosis in post-menopausal women. It is also known, however, that high levels of fluorine can be toxic and a strong irritant to human tissue. Nevertheless, it is established that concentrations of fluoride at about 1 ppm, levels known to provide the health benefits, are well below the amounts resulting in adverse health effects. Consequently, it is important if fluoride is added to drinking water that the concentration be maintained and controlled near such levels. 
     Because of the beneficial health benefits of low levels of fluoride, many cities and municipalities have undertaken a fluoridation program adding a fluoride salt to public drinking water to achieve the about 1 ppm concentration of the fluoride. For instance, it is common for larger cities or municipalities to add a fluosilicic acid, sodium silicofluoride, or sodium fluoride to the city water supply as a part of the fluoridation program. In a large water system, such as a water processing facility that typically processes greater than about 30,000,000 gallons of water daily, it is feasible to achieve consistent, low-levels of fluoride in the drinking water using a variety of common chemical feed pumps, such as peristaltic or pulse-feed pumps at the water processing facility. Because the large water facility processes considerable volumes of water, such pumps are effective at providing, maintaining, and controlling the fluoride at the about 1 ppm concentration. 
     In smaller water systems, it is often not feasible to duplicate the fluoridation programs of the larger systems due to the difficulty of providing a consistent and low concentration of the fluoride in a smaller volume of water. Current peristaltic and pulse-feed pumps are not only expensive, but often are unable to provide the fluoride in small enough levels to consistently maintain about 1 ppm concentration in a low volume of water. Even utilizing very high-cost precision pumps, the metering of fluoride in low volumes of water at levels of 1 ppm consistently is often difficult to achieve and maintain. As a result, many small municipalities, such as cities that operate a water processing facility that typically processes less than about 60,000 gallons of water daily, usually do not undertake a fluoridation program because of the expense and difficulty in achieving and controlling the required low levels of fluoride in the water streams. 
     Likewise, individual homes in rural areas often do not fluoridate their water because such homes usually obtain water from individual wells, shared wells, or spring boxes. Efficiently fluoridating these individual water supplies is also very difficult for similar reasons. Moreover, in an individual home water system, such as the well, the volumes of water are substantially lower than the amounts processed by the small water processing facility; as such, even greater difficulties are encountered in supplying and maintaining a fluoride concentration of about 1 ppm in such home water systems. 
     In addition, other chemicals are often added to a variety of fluids in low levels for numerous reasons, such as disinfecting, maintaining proper pH, maintaining proper alkalinity levels, and the like. Often it is desired to achieve such characteristics in a continuous, low volume process. In such a process, similar difficulties arise when attempting to achieve consistent and low concentrations of chemicals in the fluid. 
     As a result, it is desired to obtain a system and method of supplying a consistent, low concentration of a chemical to a fluid that is cost effective and easy to maintain and control such low concentrations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a system embodying features of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is illustrated a system  10  for providing a chemical to a stream of a fluid embodying features of the present invention. In general, system  10  includes a fluid stream  12  having a downstream portion  14  and an upstream portion  16 , a chemical supply module  18 , and, preferably, a control mechanism  20 . Optionally, system  10  may also include a tank  22 , which may be downstream of the chemical supply module  18 , for collecting and testing fluid parameters. In a preferred embodiment, the system  10  provides a chemical to the fluid by measuring a fluid characteristic, such as the downstream chemical concentration and/or the fluid flow rate, and automatically adjusting the level of chemical release from the chemical supply module  18  accordingly so that a constant concentration of the chemical is obtained. Alternatively, the system  10  can be preset to provide a predetermined level of chemical to the fluid stream  12 , which can be manually adjusted as needed. 
     In general, the system  10  provides a concentration of the chemical to the fluid stream  12  as it flows through the chemical supply module  18 . Preferably, the system provides a concentration of the chemical at approximately 1 ppm and, optionally, 1 ppm or lower. The fluid is preferably a water stream, but may also be air, oil, coolant, or other fluid requiring a concentration of a chemical therein. The chemical is preferably a metal halide and, most preferably, sodium fluoride. Accordingly, in one embodiment, the system  10  provides a fluoride, such as a sodium fluoride, to a water stream at a concentration of about 1 ppm or lower. In this manner, system  10  may be used as part of a fluoridation system. For purposes of this invention, fluoridation or fluoridate means providing a fluoride to a water stream at a concentration of generally 1 ppm; however, as further discussed below, the system  10  may also add other chemicals to the fluid stream  12 . 
     System  10 , however, is not limited to fluoridation. Other halides, such as other alkali metal halides or alkaline earth metal halides may also be provided to the fluid stream  12  in a similar manner. For instance, chemicals such as, but not limited to, sodium chloride, sodium bromide, potassium chloride, potassium bromide, magnesium chloride, magnesium bromide, calcium chloride, calcium bromide, or the like may also be used in system  10 , as appropriate, to disinfect, adjust fluid pH, maintain fluid alkalinity, or impart other characteristics to stream  12 . Likewise, silver nitrate may also be used as a disinfectant in a similar manner. The various chemicals to be added to the stream  12  may be utilized separately or in combination depending on the characteristics of the fluid stream  12  desired. 
     Preferably, system  10  fluoridates, disinfects, or provides other characteristics to a water-supply stream leading to an individual home or dwelling unit. In such use, the downstream portion  14  would lead to the individual home, or optionally as illustrated in  FIG. 1 , to the tank  22  for holding a small quantity of the water having the chemical therein for later use in the individual home. In this configuration, the upstream portion  16  would provide water from the home&#39;s water source, such as an individual well, a shared well, or a spring bank. Similarly, system  10  may also be used as part of a small water processing facility for a small city or municipality. In this form, system  10  would typically be installed in-line at the water processing facility. When used in this manner, system  10  preferably provides fluoridation to a city water system that processes less than about 60,000 gallons of water daily. 
     As previously discussed, one portion of the system  10  is the chemical supply module  18 . Preferably, the module  18  provides the chemical to the fluid stream  12  when the fluid flows through at least a portion  18   a  of the module  18 . Again referring to  FIG. 1 , the module  18  includes an elongate member  28  and, preferably, a first reel  24  and a second reel  26 , which is spaced a distance from the first reel  24 . The module  18  may also be contained within an optional cartridge or housing  30  such that the elongate member  28 , the first reel  24 , and the second reel  26  are enclosed by a protective cover or other barrier. 
     Again referring to  FIG. 1 , the module  18  is installable on a fluid conduit or pipeline  11  such that the fluid stream  12  flows through the portion  18   a  of the module  18 . When installed on conduit  11  in such a manner, a portion of the elongate member  28  contacts the fluid stream  12  and, preferably, as will be further described below, traverses through the fluid stream  12 . More specifically, in one embodiment, the conduit  11  generally includes apertures  36 , other openings, or the like sized so that the elongate member  28  extends into and through conduit  11  so as to contact the water stream  12 . If apertures  36  are used, such openings are preferably spaced on opposite sides of the conduit  11  and sealed with a seal member  44  suitable to seal the aperture  36  from water leakage but also sized to allow the elongate member  28  to pass therethrough. For instance, the seal member  44  may be any gland (Teflon or the like), packing material, or gasket known in the art to seal an opening but allow an elongate member, such as elongate member  28 , to extend therethrough. To install the module  18  on the conduit  11 , the system  10  preferably includes shut-off valves (not shown) upstream and downstream of the apertures  36  to facilitate installation of the module  18  without the water stream  12  flowing. However, the module  18  may be installed in any manner known in the art, with or without the fluid stream flowing, for coupling or mating a structure to a conduit or pipeline having a portion extending therethrough. 
     More specifically, in a preferred embodiment, the elongate member  28  is coupled both to the first reel  24  and the second reel  26 . That is, the elongate member  28  has a first end  32  coupled to the first reel  24  and also a sufficient length to have a portion  34  wound thereon. The elongate member  28  then extends outwardly from the first reel  24  and terminates in a second end  38 , which is coupled to the second reel  26 . The second reel  26  may also have a portion  35  of the elongate member  28  wound thereon. The elongate member  28  may be coupled to the reels  24  and  26 , for example, through a securing structure, such as a clamp, slot, or the like, or by being pinched under a few winds of the wound portions  34  or  35  around the reels  24  and  26 . However, the elongate member  28  may also be secured to reels  24  and  26  in any manner known in the art that secures an elongate member to a reel. In the configuration described above, the elongate member  28  also includes a supply portion  40 , which spans a gap  42  between the spaced first and second reels  24  and  26 . As is more further described below, the supply portion  40  incrementally changes as the elongate member  28  moves through the fluid  12  or, preferably, is unwound from the first reel  24  through the fluid stream  12  and wound on the second reel  26 . 
     When the module  18  is installed on the system  10 , the supply portion  40  contacts and moves through or traverses through the fluid stream  12 . In a preferred embodiment, the bulk of the elongate member  28  will initially be wound on the first reel  24  such that the elongate member  28  may then be unwound from the first reel  24 , contact the water stream  12  at the supply portion  40  in the gap  42 , and then be wound onto the second reel  26 . As a result, the supply portion  40  will incrementally change as the elongate member  28  is moved or unwound through the fluid  12 . 
     To supply the chemical to the fluid stream  12 , the elongate member  28  includes a chemical that is dispersible into the fluid stream  12  upon the fluid contacting the supply portion  40 . In order to supply the chemical to the fluid  12 , the elongate member  28  may be any material that includes a chemical therein and later allows the dispersal of such chemical into the fluid stream. For purposes of this invention, the “chemical therein” or the “chemical in” means the chemical in, on, imbedded, impregnated, or otherwise added to, introduced into or onto, or combined with the elongate member  28 . In one form, the elongate member  28  may be a line, cord, strand, filament, or the like that the chemical may be added therein and is also sufficiently flexible to be windable on the reels  24  and  26 . Preferably, the elongate member  28  is formed form a hydrophilic material, and most preferably, a monofilament line or an extruded polymer or monomer, such as a nylon strand. 
     The chemical may be added to the elongate member  28  through several mechanisms. For example, an aqueous solution of the chemical may be applied in a predetermined amount to a hydrophilic material, such as nylon. To apply the chemical to the elongate member  28 , the elongate member  28  is drawn through a supply reservoir containing an aqueous solution of the chemical. The concentration of the chemical in the supply reservoir may be varied depending on the concentration desired in the fluid stream  12 . That is, a higher concentration of the chemical in the aqueous solution within the supply reservoir will lead to higher concentrations in the fluid stream  12 . Alternatively, predetermined amounts of the chemical may be added to the polymer or monomer material prior to extrusion into the elongate member. That is, predetermined amounts of the chemical may be added to the raw plastic stock prior to the extrusion of the plastic into the elongate member  28 . Of course, the amounts of the chemical added to the plastic stock will vary depending on the desired concentration in the fluid stream  12 . 
     In use, the chemical is provided to the fluid stream  12  by introducing a portion of the elongate member  28 , such as the supply portion  40 , to the fluid stream  12 . While not wishing to be limited by theory, it is believed that the chemical is added to the fluid through a diffusion, leaching, or the general mass transfer of the chemical to the fluid as the fluid flows past the supply portion  40 . In one mechanism, the transfer of the chemical may be from a region of high concentration in the elongate member  28  to a region of lower concentration in the fluid stream  12 ; however, other transfer mechanisms are also possible. Eventually, after a sufficient duration or flow of water, the supply portion  40  will be generally depleted of the chemical; therefore, to constantly supply the chemical to stream  12 , a new supply portion  40   a  is provided to contact the fluid  12 . That is, the elongate member  28  is moved through the fluid  12  such that the new supply portion  40   a , which has yet to contact the fluid  12 , is moved to a position that contacts the fluid  12 . In a preferred operation, as previously described, the elongate member  28  is moved through the fluid by being unwound from the first reel  24  via the rotation of the second reel  26  to incrementally provide the new supply portion  40   a  at a predetermined rate. 
     To maintain a generally constant amount of the chemical in the fluid  12 , the concentration of the chemical can be adjusted by changing various system parameters. For instance, altering the amount of the chemical added in the elongate member  28 , as described above, is one factor that affects the amount of the chemical available to transfer to the fluid  12 . Likewise, altering either the rate at which the elongate member  28  is moved through the fluid or the flow rate of the fluid past the elongate member  28  are other factors that affect the amount of the chemical transferred to the fluid  12 . In addition, varying the diameter or width of the elongate member  28  or altering the length of the supply portion  40  may also be used to control the concentration of the chemical in the fluid  12 . That is, a larger diameter or larger supply portion  40  provides more of the elongate member  28  to supply the chemical and, therefore, higher concentrations. Consequently, the amount of the chemical that is available to transfer to the fluid  12  is generally dependent on the amount of the chemical in the elongate member  28 , the diameter or size of the elongate member  28 , the length of the supply portion  40 , and/or the duration that each incremental supply portion  40  contacts the fluid  12  as determined by an unwind rate or fluid flow rate. 
     While not wishing to be limited by theory, in a preferred embodiment, the rate of the elongate member  28  moving through the fluid  12  and the flow rate of the fluid  12  each have a generally inverse relationship with the amount of chemical provided to the fluid. For instance, given a generally constant flow rate, if the elongate member  28  moves through the fluid  12  as a fast rate of speed, such as by rotating the second reel  26  at a fast revolution, then each incremental supply portion  40  will only contact the fluid  12  for a first duration providing a first concentration of the chemical in the fluid  12 . On the other hand, if the elongate member  28  moves through the fluid  12  at a slower rate of speed, such as by rotating the second reel  26  at a slower revolution, then each incremental supply portion  40  will contact the fluid  12  for a longer, second duration to provide a higher, second concentration of the chemical in the fluid  12 . Likewise, given a generally constant rate of movement of the elongate member  28 , then increasing or decreasing the fluid  12  flow rate will also affect the chemical concentration in a similar manner. In one instance, to achieve a concentration of about 1 ppm of sodium fluoride in water, the system  10  will include the elongate member  28  having about 11 weight percent of sodium fluoride therein, which is unwound at a speed of about one inch per hour through a water stream flowing at 11 gallons per minute. Of course, other combinations of such parameters will also achieve the about 1 ppm. 
     Again referring to  FIG. 1 , the system  10  also preferably includes the control mechanism  20 , which monitors and controls the system  10 . In general, control mechanism  20  preferably includes a control unit  46 , at least one sensing device  48 , a motor device  50 , and a resistance mechanism  52 . While illustrated with the control mechanism  20 , the system  10  may also operate without the control mechanism  20  at preset conditions requiring each condition to be manually adjusted if needed. 
     The control unit  46  is preferably a digital or analog microprocessor or a combination of microprocessors. For example, the control unit  46  may be a typical adjustable or variable speed drive; however, any type of controller known in the art is suitable for control unit  46 . The control unit  46  generally monitors or receives information from various sources and generally controls or provides appropriate outputs, such as system adjustments, to ensure the system  10  provides the desired concentration of the chemical to the fluid  12 . For instance, the control unit  46  may receive, by way of non-limiting example, information on the fluid  12 , information on the module  18 , or information on overall system  10  parameters. Based on such information, the control unit  46  will initiate, for example, appropriate outputs or controls on the system  10  such as increasing or decreasing the fluid  12  flow rate; increasing, decreasing, or stopping the movement of the elongate member  28 ; signaling an appropriate alarm condition; or other appropriate controls or outputs. 
     As discussed above, the control unit  46  may receive information on the fluid  12 . Such information may include the flow rate or the concentration of the chemical in the fluid  12  from an appropriate sensing device, which may be either upstream  16  or downstream  14  of the module  18 . In addition, if optional tank  22  is utilized, a concentration of the chemical in tank  22  may also be provided to the control unit  46 . 
     The control unit  46  may also receive information on the module  18 . Such information may include the status of the first and second reels  24  and  26 . For instance, the unit  46  may receive data on an amount, length, or weight of the elongate member  28  on the first reel  24  and may provide an indication of such information so as to prevent runout of the elongate member  28 . Likewise, the unit  46  may also receive an indication that the second reel  26  has a predetermined amount, weight, or length of the elongate member  28  wound thereon. Based on such information, control unit  46  may provide an indication of when the reels need to be changed because a large portion of the elongate member  28  has been unwound from the first reel  24  and is now wound on the second reel  26 . The unit  46  may also receive information indicating that the elongate member  28  is broken, the first reel  24  is unwinding at an incorrect rate (i.e. too fast, too slow, or stopped), the second reel  26  is unwinding at an incorrect rate (i.e. too fast, too slow, or stopped), or other trouble conditions with respect to the module  18 . 
     The control unit  46  may also receive other information on the system  10 , such as the status of various components, devices, or system conditions. For instance, the unit  46  may receive information on the status of the at the least one sensing device  48 , the status on the motor device  40 , the status on the resistance mechanism  52 , or the status of other components. With such information, the control unit may make appropriate adjustments or controls to the system  10 , such as indicating an alarm condition, stopping the system operation all together, or other appropriate controls. 
     Again referring to  FIG. 1 , the embodiment is shown with at least one sensor  48 , which may be at a down stream  14  location, an upstream location  12 , at the tank  22 , or other suitable location. Preferably, the system  10  includes two sensors  48   a  and  48   b . For example, the sensor  48   a  is preferably a volume or flow rate sensor to measure fluid flow and the sensor  48   b  is preferably a concentration sensor to measure the concentration of the chemical in the fluid  12 . 
     More specifically, sensor  48   a  may be any type of sensor that measures volume, flow rate, or rate of the fluid  12  in the conduit  11 . The sensor  48   a  may be a paddle, turbine, ultrasonic, or the like sensor that determines the rate of flow of the fluid  12  and, preferably, provides such information to the control unit  46 . As illustrated in  FIG. 1 , the sensor  48   a  is shown in an upstream  16  location; however, any location within system  10  is suitable for sensor  48   a.    
     As a flow rate sensor, the sensor  48   a  preferably measures the flow, rate, or volume per unit time of the fluid  12  within the conduit  11  and, preferably, provides such information to control unit  46 . Based on such information, control unit  46  may then adjust various parameters of the system  10 , such as the rate at which the elongate member  28  moves through the fluid. As previously discussed, adjusting the rate at which the reels are rotated is one method that the control unit  46  may alter the duration that each incremental supply portion  40  remains in contact with the fluid  12 ; as such, adjusting the amount of chemical that is provided to the fluid  12 . For instance, in order to maintain a generally constant concentration of the chemical in the fluid  12 , if the flow rate sensor  48   a  determines that the fluid flow rate is increasing, then the control unit  46  may also increase the rate of unwind of the elongate member  28  from the first reel  24  a corresponding amount by increasing the rate at which the second reel  26  rotates. If the flow sensor  48   a  determines that the fluid flow rate is decreasing, then the control unit  46  may then decrease the rate at which the elongate member  28  is unwound from the first reel  24  a corresponding amount by decreasing the rate at which the second reel  26  rotates. Optionally, the flow rate sensor  48  may also be a manual sensor that provides a measurement of flow rate that requires a manual adjustment to the module  18  to maintain the desired concentration of the chemical. 
     The sensor  48   b  preferably is a device that measures the concentration of the chemical in the fluid  12 . As such, the sensor  48   b  may be any type of sensor that measures a concentration of the chemical in a fluid that is known in the art. It should also be apparent to one skilled in the art that the sensor  48   b  will preferably vary depending on the chemical selected. Preferably, sensor  48   b  measures the chemical concentration and also provides such information to the control unit  46 . As with sensor  48   a , the control unit may adjust the system  10  in a similar manner based on the information received from the sensor  48   b . Additionally, sensor  48   b  may also be a manual test kit or other device that validates the proper concentration of the chemical upon a manual test initiated by the user of the system. In this manner, the system  10  may also operate at predetermined conditions, which may be manually adjusted based on the results of the manual testing. 
     Again referring to  FIG. 1 , the motor device  50  is any device that provides a rotary motion to the second reel  26 . Preferably, motor device  50  is a stepper motor or equivalent. In one form, the motor device  50  is controlled by the control unit  46  and adjusts the rotation speed or revolution rate of the second reel  26  based on the flow sensor  48   a , the concentration sensor  48   b , or other input. As illustrated, the motor device  50  is coupled to the second reel  26  via a belt  54  that transfers the rotary motion to the second reel  26 ; however, the motor device  50  may be coupled to the second reel  26  by any method known in the art. 
     The resistance mechanism  52  is any device that impedes the rotary motion of the first reel  24 , such as a braking device. In this manner, the resistance mechanism  52  generates a resistance force to the rotation of the first reel  24 . That is, the resistance mechanism  52  impedes the unwinding of the elongate member  28  as the second reel  26  rotates and unwinds or pulls the elongate member  28  off the first reel  24 . Accordingly, an appropriate amount of tension is maintained on the supply portion  40  within the gap  42 . However, the brake force and tension may vary depending on the type of material used for the elongate member  28 , the unwind rate, the flow conditions, or other system parameters. 
     It will be understood that various changes in the details, materials, and arrangements of parts and components which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.