REFERENCE TO PROVISIONAL APPLICATION 
     This application is based on, claims priority to, and hereby refers to U.S. Provisional Patent Application Ser. No. 61/188,414, filed Aug. 8, 2008, having the same title as appears above, the entire contents of which are incorporated herein by this reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to fluid treatment devices and more particularly, although not necessarily exclusively, to chlorinators for circulating water used in swimming pools, spas, hot tubs, or other water-containing vessels. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 6,680,026 to Denkewicz, et al., discloses water-purification equipment useful especially in connection with swimming pools, spas, and hot tubs, where water recirculates. The equipment may provide “plug-in” forms of fluid-flow diverters “designed to penetrate, or fill, openings intermediate remote ends of conduits.” See Denkewitz, col. 2, ll. 3-4. As indicated in the Denkewicz patent:
         Embodiments of the invention contemplate diverting flowing fluid to purification equipment formed about or otherwise connected to such diverters, permitting diverted water to be purified before rejoining the flow. The . . . circulating nature of the water permits more of its volume ultimately to be diverted into the equipment for purification.
 
See id., ll. 13-15.
       

     Positioned within the equipment of the Denkewicz patent is water purification media such as “mineral-based pellets or other objects of silver-, zinc-, or copper-containing material.” However, other media alternatively may be used therein. According to the Denkewicz patent, “[c]hlorine or other chemicals which may be dissolved or contacted by the water being diverted are among suitable alternatives.” See id., ll. 57-59. 
     International (Patent) Publication No. WO 2006/110799 of Kennnedy, et al. [sic Kennedy, et al.] details additional equipment used to divert flowing fluid for purification. Diverted fluid may be treated by, for example, a salt water chlorinator (SWC) having an electrolytic cell. Treated water is then returned to the main flow stream via a series of fins, with the overall configuration of the equipment being designed to, among other things, cause the bulk of fluid experiencing pressure spikes to remain in the conduit. See, e.g., Kennedy, p. 12, ll. 4-10. Accordingly, housings detailed in the Kennedy publication may be “fabricated from less pressure-resistant materials, and need not be engineered in the same way as other pressure vessels.” See id., ll. 13-14. The contents of the Denkewicz patent and the Kennedy publication are hereby incorporated herein in their entireties by this reference. 
     SUMMARY OF THE INVENTION 
     The present invention provides additional equipment in the style of the diverters of the Denkewicz patent and the Kennedy publication. Intended mainly for use as chlorinators, devices of the invention may divert water flowing in conduits into the devices for treatment and subsequent return to the flow stream. Separate, spaced inlet and return tubes may be utilized within the conduits. The return tube of the device additionally may be designed to create vortex action, using a pressure differential to evacuate treated water from the device back into the conduit. 
     Additional features of the invention may include a housing, upper and lower sections of a clamp, and a threaded locking collar. The sections preferably are snap-fit together about a conduit, with the locking collar thereafter engaging the lower section to enhance a fluid seal. By permitting the sections to connect via snap-fitting, the invention avoids any need to utilize secondary fasteners. 
     Another optional feature of the invention is inclusion of an adaptor sleeve. The sleeve especially is useful when the main conduit to which the device is to be connected is smaller than a nominal diameter. In these instances, the sleeve may be positioned between the upper and lower housing sections to reduce the spacing between the two. Finally, gas removal from the housing also may occur. 
     It thus is an optional, non-exclusive object of the present invention to provide innovative fluid treatment devices. 
     It is, moreover, an optional, non-exclusive object of the present invention to provide “plug-in” types of equipment particular useful for treating circulating water. 
     It is a further optional, non-exclusive object of the present invention to provide fluid treatment devices in which a return tube creates vortex action to evacuate treated fluid from the devices and into conduits. 
     It is also optional, non-exclusive object of the present invention to provide fluid treatment devices in which conduit clamps do not require secondary fasteners. 
     It is another an optional, non-exclusive object of the present invention to provide fluid treatment devices in which a locking collar may be used to enhance the integrity of a fluid seal between the clamp and the conduit. 
     It is, furthermore, an optional, non-exclusive object of the present invention to provide fluid treatment devices in which an adaptor sleeve may facilitate accommodating smaller conduits when the devices are attached. 
     Other objects, features, and advantages of the present invention will be apparent to those skilled in the relevant fields with reference to the remaining text and the drawings of this application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1B  are elevational views of exemplary equipment of the present invention. 
         FIG. 2  is a cross-sectional view of the equipment of  FIGS. 1A-1B . 
         FIG. 3  is an exploded view of portions of the equipment of  FIGS. 1A-1B  shown in connection with a fluid conduit to which the equipment may attach. 
         FIG. 4  is another exploded view of portions of the equipment of  FIGS. 1A-1B  shown in connection with the fluid conduit of  FIG. 3 . 
         FIG. 5A  is an isometric, bird&#39;s-eye view of an upper housing section of the equipment of  FIGS. 1A-1B . 
         FIG. 5B  is an isometric, worm&#39;s-eye view of an upper housing section of the equipment of  FIGS. 1A-1B . 
     
    
    
     DETAILED DESCRIPTION 
     Depicted in  FIGS. 1A-2  is exemplary equipment  10  of the present invention. Equipment  10  preferably constitutes a fluid treatment device. Also illustrated in  FIGS. 3-4  is conduit C to which equipment  10  may attach. Conduit C preferably conveys liquid from one location to another. Even more preferably, conduit C conveys water circulating to or from a swimming pool, spa, hot tub, or similar vessel. 
     Illustrated in  FIGS. 1A-1B  and various of  FIGS. 3-5B  are components of equipment  10  including housing  14 , locking object in the exemplary form of collar  18 , and clamp  22 . Clamp  22  may comprise upper section  26  and lower section  30  and is designed to encircle, or otherwise surround, a portion of conduit C. Further, upper section  26  is configured to communicate with (i.e. plug-into) conduit C to permit fluid to flow thereto and therefrom.  FIG. 1B  depicts inlet  34  through which fluid may flow from conduit C into housing  14  via upper section  26 . 
     Additionally shown in  FIGS. 3-4  is optional sleeve adaptor  38  as well as seal  42 , o-ring  46 , and outlet  50 . Sleeve adaptor  38 , if present, may be generally semi-cylindrically shaped and configured to nest in a similarly-shaped portion of lower section  30 . Adaptor  38  is, in essence, a spacer, intended to fill any gap between conduit C and lower section  30  when the two are attached. Use of adaptor  38  renders equipment  10  more versatile, as it may accommodate conduit C of different diameters. 
     Seal  42  and o-ring  46  prevent, or at least reduce, fluid leakage between and from conduit C and equipment  10 . Seal  42  preferably is an elongated object with concave lower surface  54  contacting outer surface  58  of conduit C. Seal  42  additionally may include two spaced openings  62  and  66 , the former receiving inlet  34  and the latter receiving outlet  50 . O-ring  46 , by contrast, beneficially fits between locking collar  18  and upper section  26 . 
     As depicted especially in  FIG. 5B , spaced inlet  34  and outlet  50  preferably are generally tubular in shape and integral with upper section  26 . They need not necessarily be so shaped or integrally formed with upper section  26 , however. Instead, for example, inlet  34  and outlet  50  could engage or otherwise connect to corresponding portions of section  26 . 
     To employ equipment  10 , conduit C must include an opening in its upper wall. Such opening may be drilled or created in any other appropriate way. Advantageously, conduit C will include two openings, with the openings spaced and sized similar to spacing and sizing of inlet  34  and outlet  50  as well as spacing and sizing of openings  62  and  66  of seal  42 . Although not presently preferred, conduit C could, for example, include only one opening shaped and sized similar to seal  42 . 
     Lower section  30  may then be placed underneath conduit C with its saddle portion  70  opposite the upper wall openings of conduit C. (As noted earlier, adaptor  38  optionally may be employed as a spacer between conduit C and lower section  30 .) Seal  42 , by contrast, may be positioned in contact with the upper wall of conduit C so that fluid may communicate between the conduit C and openings  62  and  66 . Upper section  26  may be positioned atop seal  42  so that inlet  34  extends into conduit C through opening  62  and outlet  50  extends into conduit C through opening  66 . Upper section  26  beneficially includes one or more tabs  74  designed to engage apertures  78  of lower section  30  so as to connect (e.g. snap-fit) upper section  26  to lower section  30  about conduit C. Doing so forms clamp  22  and helps compress seal  42  against conduit C. 
     As shown in  FIG. 5A , upper section  26  may include channel  82  in which o-ring  46  may be placed. Thereafter, internally-threaded collar  18  may engage threads  86  of saddle portion  70  of lower section  30  so as to draw it toward upper section  26  as collar  18  rotates, further facilitating sealing of equipment  10  about conduit C. Collar  18  also connects housing  14  to upper section  26  as detailed in  FIGS. 2 and 4 . Persons skilled in the art will recognize that collar  18  may engage lower section  30  other than via threads, and that collar  18  need not necessarily be an object distinct from, for example, housing  14 . 
     Upper section  26  further may include baffle  90  positioned between inlet  34  and outlet  50 . Baffle  90  assists in preventing fluid entering housing  14  via inlet  34  from immediately exiting the housing  14  via outlet  50 . Although baffle  90  need not necessarily be present as part of upper section  26 , its presence currently is preferred. 
     Once connected about conduit C, equipment  10  may function to sanitize, purify, or otherwise treat fluid (such as water) travelling through the conduit C. In use, pressurized fluid flows though conduit C in the direction of arrows A. As it does so, the fluid encounters inlet  34 , with the pressure driving some of the fluid into the inlet  34  (while the remaining fluid continues to travel within conduit C). As depicted especially in  FIGS. 1B ,  2 - 3 , and  5 B, inlet  34  may include tapered end  92  whose trailing edge  93  extends farthest into conduit C. End  92  thus presents an open face to the flowing fluid, facilitating its entry into inlet  34 . From inlet  34 , fluid may then enter housing  14  in which treatment may occur. 
     Indeed, housing  14  may perform any desired type of fluid treatment. Preferably, however, housing  14  includes therein chlorinator  94 , which more preferably is an SWC. Through operation of chlorinator  94 , chlorine is added to water entering housing  14  via inlet  34  (i.e. hypochlorous acid is formed) before the water exits the housing  14  via outlet  50  to return to conduit C. 
     Illustrated in  FIG. 2  using arrows B, D, and E is the major flow path of fluid within housing  14 . As depicted, fluid flows initially upward, in the direction of arrows B (which is generally perpendicular to arrows A), through plates  98  of chlorinator  94 . Under force of gravity, the fluid then travels generally in the direction of arrow D before flowing downward in the direction of arrows E. Note that some fluid flowing in the direction of arrows C is likely to travel again through plates  98 , whereas other fluid is not. Regardless, however, all fluid flowing in the direction of arrows E may be received by outlet  50  for return to conduit C. 
     Produced additionally by salt-water chlorination is hydrogen (and other) gas, which beneficially may be introduced into the circulating water to avoid its undesired build-up within housing  14 . Chlorinator  94  thus may include gas tube  102  extending from within housing  14  into outlet  50 . Via tube  102  and outlet  50 , gas such as hydrogen may be entrained with treated water exiting housing  14  and re-entering conduit C. Tube  102  additionally may function to bleed air from housing  14  and, if desired, may be conjoined with outlet  50  in a single part. 
     Similar to inlet  34 , outlet  50  may include a tapered end  106  extending into conduit C. Unlike end  92  of inlet  34 , however, end  106  opens opposite to the direction of fluid flow within the conduit C so as to present a closed face thereto. Stated differently, end  106  opens opposite the direction indicated by arrows A, with its leading edge  110  extending farthest into conduit C. This configuration of end  106  allows the flowing fluid to create a lower-pressure area within outlet  50 , creating vortex action facilitating removal of treated water from housing  14 . Selecting a lesser diameter for tube  102  than for outlet  50  enhances ability of the lower-pressure region to remove gas from housing  14  too. 
     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention.
Treatment devices for fluid such as water are described. Principally (although not necessarily exclusively) designed for use as chlorinators, the devices may divert water flowing in conduits into the devices for treatment and subsequent return to the flow stream. A return tube of the device may be designed to create vortex action, using a pressure differential to evacuate treated water from the device back into the conduit.