CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/372,955 filed Apr. 16, 2002, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to water purification systems. More particularly, this invention relates to water purification systems incorporating a method for the exposure of water to ultraviolet light. 
     It is known to use ultraviolet (UV) radiation to disinfect drinking water. It is also known that ultraviolet radiation is a means for meeting the bacteriological requirements of the drinking water standards as enumerated in the Safe Drinking Water Act (SDWA), 42 U.S.C. §300(f) et seq. (1974). Studies have indicated that ultraviolet radiation at a level of 2,537 Angstrom units applied at a minimum dosage of 16,000 micro-watt-seconds per square centimeter at all points throughout a water disinfecting chamber is adequate to purify water for drinking. It is generally known to use 30,000 micro-watt seconds per square centimeter to obtain the desired effect. Using a higher standard helps account for any losses that may occur in the exposure chamber. If a UV lamp is used that maintains 80% power over 9,000 hours (approximately one year), then setting a standard of 38,000 micro-watt-seconds per square centimeter would insure that the lamp would require replacement no more than yearly, while adequately sterilizing the water flow that is exposed to the UV lamp. 
     In commonly configured ultraviolet light water purification systems, ultraviolet light serves the purpose of exposing a fluid to ultraviolet light radiation which either kills bacteria or renders bacteria unable to reproduce. A straight quartz fluid tube permits an ultraviolet light source to be inserted in the inside diameter of the tubing while water is passed over the outside diameter of the length of the lamp. 
     One commonly known means of exposing water to ultraviolet light is to place a light source in a straight quartz tube with water flowing through an outer chamber past the linear distance of the ultraviolet light source. Such a design generally requires a pressure cylinder to be built around the lamp-supporting construction. This also requires that the pressurized cylinder be at the same length or longer than the provided ultraviolet light source. It would, therefore, be advantageous to develop an apparatus that can more easily be used to purify water. 
     SUMMARY OF THE INVENTION 
     The invention relates to an apparatus for disinfecting a fluid. The apparatus includes a tube connected to a source of fluid. The tube allows the fluid to be transported from the source to a discharge. An ultraviolet lamp is positioned adjacent the tube, and is adapted to transmit light waves through the fluid. The tube can be a coiled tube having one or more coils thereby forming a helical tube. Each coil of the helical tube has an inner diameter and an outer diameter. The inner diameters of the coils define a space or opening. The ultraviolet lamp can be positioned within the opening. A fluid passing through the coils of the tube are exposed to the ultraviolet light. The tube can be made of germicidal glass or quartz. 
     The method of the invention includes moving water from a source to a discharge, through the tube while the lamp is activated. Water will become disinfected as it is exposed to the ultraviolet light of the lamp. Due to the shape of the tube, more water can be exposed to the ultraviolet light in a shorter distance than with linear tubes. 
     Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of a helical tube in accordance with the present invention. 
         FIG. 2  is a plan view of the helical tube shown in FIG.  1 . 
         FIG. 3  is an end view of the helical tube shown in  FIGS. 1 and 2 . 
         FIG. 4  is a sectional view of the helical tube through section line  4 — 4  with a lamp positioned within the helical tube. 
         FIG. 5  is an end view of the helical tube shown in  FIG. 4  with a lamp inserted within the helical tube. 
         FIG. 6  is a side elevational view of a water purification apparatus with the helical tube of the present invention connected to inlet and outlet ports. 
         FIG. 7  is an end view of the water purification apparatus shown in FIG.  6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, there is illustrated in  FIG. 1  a side elevational view of a helical tube indicated generally at  10 . The generally transparent tube  10  is adapted to allow a fluid, such as water, to pass through the inner surface of the tube  10 . Particularly, a fluid can enter from a source connecting tube  12 , pass through the coils of the helix (helical coils) generally shown at  14 , and exit from a discharge connecting tube  16 . Each coil  14   a ,  14   b ,  14   c ,  14   d , and  14   e  is generally hollow and interconnects to each adjacent coil. The coils on each end of the tube  10  are also connected to a source  12  and discharge  16  tube. The source connecting tube  12  and discharge connecting tube  16  can have any shape, such as the hollow, generally cylindrical shape shown in the Figures. The tubes  12  and  16  are preferably shaped so that the helical tube  10  can be connected to a source of fluid (not shown) and a discharge receptacle or an outlet pipe (not shown). The helical coils  14  are shown having an angled pitch, θ. However it is understood that the helix pitch angle, θ, can be larger or smaller as desired. Also, the helical coils  14  can be wound in the opposite direction. Additionally, as best seen in  FIG. 2 , the cross-sectional shape of the connecting tubes  12  and  16  is generally circular. Preferably the connecting tubes  12  and  16  are adapted to fit onto generally conventional piping. However, it should be understood that the cross-sectional shape of the connecting tubes  12  and  16  can have any desired shape such as generally oval or rectangular. 
     Illustrated in  FIG. 3  is an end view of the helical tube  10  of the present invention. The helical coils  14  are shown as having a generally circular shape. Thus, each coil  14   a ,  14   b ,  14   c ,  14   d , and  14   e , each have an outer diameter and inner diameter. It should be understood, however, that the helical coils  14  can also have any desired cross-sectional shape.  FIG. 3  illustrates an opening  18  defined by the inner diameters  20  of the helical coils  14  of the tube  10 . The opening  18  is illustrated as having a generally cylindrical shape, however, it should be understood that the opening  18  can have any shape or size, and have a non-uniform diameter. For example, the opening could be cylindrical with the coils  14  having a larger diameter at a first end and a relatively smaller diameter at a second end. For example, the inner diameter of coil  14   a  is larger than  14   b . Coil  14   b  has an inner diameter larger than coil  14   c , and so forth. Thus, the shape of the opening  18  could be generally conical. Also, although only six helical coils  14  are illustrated, it can be appreciated that any desired number of helical coils  14  can be used in the tube  10  as required with the invention. Generally, with a greater number of helical coils  14 , the overall length of the tube  10  could increase. However, a greater number of coils  14  could be formed in a similar or smaller area. This could be done by using smaller diameter coils, or using a smaller helix pitch angle, θ. Additionally, the spacing between coils  14  could be increased or decreased as desired to incorporate a greater or fewer number of coils  14  into the helical tube  10 . 
     Using a helical tube  10  reduces the linear flow requirements of a conventional straight tube fluid purification system. Fluid flow through a helical tube  10  allows there to be greater exposure of the fluid being carried within the tube  10  to a lamp  22  that is an ultraviolet light source over a shorter span length. Flow of a fluid through the helical tube  10  reduces the physical size of the purification unit versus a linear system since more flow can occur over the same linear distance. Additionally, since the helical tube  10  reduces the linear flow requirements when compared with straight tube systems, lower wattage lamps may be used. A shorter linear travel distance for a fluid with a helical tube  10  allows for the same micro-watts-seconds exposure of the fluid within a reduced space. 
     It is preferred that the helical tube  10  be formed from quartz or glass. It is further preferred that the type of glass used is of a germicidal type. Glass is typically a poor conductor of ultraviolet light but germicidal glass has improved conductive qualities. Quartz or glass tubing can also permit the flow of heated fluids through the tube  10  with a reduced possibility of malformation or deformation and, therefore, failure of the tube  10 . Another benefit of using helical quartz or glass tubing is that helical quartz or glass tubing can withstand the pressure requirements of a water purification system. This reduces space and costs because no outer pressure chamber is required to maintain a relatively higher system pressure. Also, it is know that quartz has a negligible expansion rate under the typical conditions of operating the present invention. Therefore, quartz is a preferred material from which the tube  10  and preferably at least the helical coils  14  can be made. It can be appreciated, however, that any suitable material can be used in accordance with the invention as described herein. The thickness of the quartz helical coils can vary according to the desired design specifications. The thickness of the quartz wall will typically not affect the disinfection process. The invention design also allows multiple ultraviolet lamps  22  to be inserted into the opening  18  of the helix thereby increasing the available ultraviolet wattage within the same physical structure of the entire water purification assembly, as is described in greater detail below. 
     Illustrated in  FIG. 4  is a cross-sectional view of the helical tube  10  illustrated in FIG.  1 . Again, it is shown that the preferred cross-sectional shape of the helical coils  14  is generally circular. However, the helical coils  14  can have any shape or size, as described above. Also shown in  FIG. 4  is a lamp  22  positioned within the opening  18  of the helical tube  10 . The lamp  22  is preferably an ultraviolet light, however, the lamp can be any type of lighting device that emits any type of radiation that can be used for the disinfecting of fluids. It is preferred that germicidal lamps be used since germicidal lamps have a sharply defined spectral output at 253.7 nanometers. Since this is very close to the wavelength most effective in inhibiting bacteria and molds, no wavelength correction is necessary. However, it can be appreciated that lamps can produce ultraviolet light having different wavelengths and be coated to adjust the wavelength for the optimal ultraviolet wavelength for inhibiting bacteria growth. 
     The lamp  22  preferably has electrical leads  24  that can are adapted to be connected to a source of electrical power (not shown). The source of electrical power, when activated, energizes the lamp  22  causing ultraviolet light to be emitted therefrom. In an alternate embodiment, the lamp  22  can have a power connection or electrical leads  24  at both ends, or at some other location along the length of the helical tube  10 . Alternatively, a single-ended ultraviolet lamp (a lamp having electrical connections at only one end) could also be used. 
     Illustrated in  FIG. 5  is an end view of the helical tube  10  with the lamp  22  positioned within the opening  18  of the tube  10 . The lamp  22  is preferably centrally positioned within the opening  18  such that a generally equal amount of radiation is applied in all directions. However it is understood that the lamp  22  can be positioned off-center and still apply radiation to the helical coils  14 . The lamp  22  illustrated is also shown as having a smaller diameter than that of the opening  18 . It should be appreciated that the lamp  22  can have a larger or smaller diameter than illustrated. However, the diameter of the lamp  22  is preferably such that the lamp  22  can be positioned within the opening  18  of the helical tube  10 . Alternatively, with a lamp  22  having a diameter that is smaller than the opening, a plurality of lamps  22  can be positioned within the opening  18  of the tube  10 . If a plurality of lamps  22  are positioned within the opening  18 , it is preferred that the lamps  22  be evenly spaced within the opening  18 . However, the lamps  22  can be positioned closer or farther apart or randomly positioned within the opening  18 . 
     Now referring to  FIG. 6 , a water purification apparatus  30  including the helical tube  10  described above is illustrated. In commonly configured ultraviolet light water purification systems, ultraviolet light serves the purpose of exposing a fluid, preferably water, to ultraviolet light radiation which either kills bacteria or renders bacteria unable to reproduce. A straight quartz tube permits an ultraviolet light source to be inserted in the inside diameter of the tubing while water is passed over the outside diameter of the length of the lamp. Such flow is typically understood to be laminar flow. Laminar flow is classically defined as a well ordered pattern of flow whereby fluid layers are assumed to slide over one another. Utilizing tubing formed into a helical shape induces turbulence in the flow of the water. Turbulent flow is irregular or unstable flow. Because the flow is turbulent, more of the water is exposed to the ultraviolet light source. Additionally, more water is exposed to the light source without reducing the conductivity of the light waveforms. 
     The illustrated helical tube apparatus  30  has a plurality of ultraviolet lamps  22  positioned within the opening  18  of the tube  10 . A portion of the helical coils  14  are shown with a section of the coils  14  removed so as to illustrate the general position of the lamps  22  within the opening  18 . As best shown in  FIG. 7 , three lamps  22  are illustrated as being positioned within the opening  18 . However, it should be understood that a greater or fewer number of lamps  22  can be used. Additionally, the positions of the lamps  22  can be different than those shown in the Figures. Each lamp  22  is positioned so that the electrical leads  24  are positioned on the same side of the opening  18  within the tube  10 . However, the leads  24  can be positioned in any manner so that the leads  24  of the lamps  22  can be connected to a source of electricity. 
     Illustrated in  FIG. 7  is the water purification apparatus  30  of the present invention. The source connecting tube  12  of the apparatus  30  is received within an adapter  34  so that a fluid source (not shown) can be connected to the helical tube  10 . The adapter  34  can include conventional pipe threads at a second end and a compression ring and cap assembly  32  at a first end. The source connecting tube  12  can be received within the first end of the adapter  32 . When the cap  32  is tightened, the compression ring (inside the cap  32 ) forms a seal with the source connecting tube  12 . At the other end of the adapter  34 , a conventional pipe, tube, or hose (not shown) can be connected by threading it onto the pipe threads. The discharge connecting tube  16  is similarly connected via an adapter  36  to a discharge chamber (not shown). It should be understood that the helical tube  10  can be adapted to connect to a source and discharge by any means. However, with the compression ring apparatus  34  and  36 , it is preferred that the source connecting tube  12  and discharge connecting tube  16  are circular in cross-sectional shape. The discharged fluid can be collected from the chamber or transferred to another collection area. For example, the fluid can be piped for further processing, be bottled, or stored for any other use where purified water is desired. 
     Although a helical tube has been illustrated as the preferred embodiment, it can be appreciated that a transparent, linear tube could also be used without departing from the scope of the invention. Particularly, a light source could be positioned adjacent a tube that transports a fluid. Activation of the lamp while fluid is flowing through the pipe causes ultraviolet light to disinfect the fluid. In accordance with the present invention, wherein increased flow using the same or less amount of space and energy is desired, a plurality of transparent, linear tubes could be positioned adjacent the same lamp. Thus, a single lamp surrounded by a plurality of fluid tubes causes the fluid passing through each of the tubes to be acted upon by the light emitted. Alternatively, a lamp could be positioned adjacent a tube, wherein the tube is curved, but only extends in a single plane, similar to a radiator. When the fluid passes through the tube, the lamp acts on the fluid throughout the length of the tube. The lamp could be a “flat panel” lamp, or could be multiple linear lamps positioned in a row. 
     Although the illustrated water purification apparatus is horizontally oriented, it can be appreciated that the apparatus can also be mounted vertically, or at any desired angle, with the input and output ends adjusted accordingly. Additionally, although the invention has been described as using ultraviolet light to disinfect a fluid, it can be appreciated that any source of electromagnetic radiation could also be used in accordance with the invention. 
     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.
An apparatus for disinfecting a fluid includes a tube connected with a source of the fluid. The tube allows the fluid to be transported from the source to a discharge. An ultraviolet lamp is positioned adjacent the tube, and is adapted to transmit light waves through the fluid. The tube can be a coiled tube having one or more coils thereby forming a helical tube. Each coil of the helical tube has an inner diameter and an outer diameter. The inner diameters of the coils define a space or opening. The ultraviolet lamp is positioned within the opening. A fluid passing through the coils of the tube are exposed to the ultraviolet light. The method of the invention includes moving water from a source to a discharge, through the tube while the lamp is activated. Water will become disinfected as it is exposed to the ultraviolet light of the lamp.