Abstract:
Filters and methods of filtering debris from fluid are detailed. A vortex of debris-laden fluid may be created within a filter, causing certain debris (including, for example, leaves) to settle therein. Some versions of the filters may include two stages, one having a perforated tube and a second having a generally frustoconically-shaped tube, which may or may not be perforated.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to both U.S. Provisional Patent Application Ser. No. 61/406,630, filed Oct. 26, 2010, and French Patent Application No. 10/04604, filed Nov. 26, 2010, the entire contents of both of which are hereby incorporated by this reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to particulate filters and more particularly, although not exclusively, to filters of leaves and other debris frequently encountered during cleaning of swimming pools and spas. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 5,269,913 to Atkins details exemplary debris traps for use with automatic swimming pool cleaners (“APCs”). Depicted in the Atkins patent is a generally cylindrical filter suspended within a housing. Attached to the housing may be a lid having a conduit with an inlet and an outlet and, at its midpoint, a downspout extending perpendicularly therefrom. The downspout prevents direct fluid flow through the conduit but is open to the inlet, penetrates the filter, and terminates in an open end within the filter. As noted in the Atkins patent:
         Water and debris entering the inlet are directed downward into the interior of the filter by the perpendicular tube. The water then filters outward through the filter and migrates to the outlet along the open space between the filter and the housing, trapping the debris within the filter where the heavier debris settles to the bottom of the housing rather than collecting on the filter.
 
See Atkins, col. 2, 11. 32-39.
       

     U.S. Patent Application Publication No. 2010/0213118 of Tandon describes a sediment filter intended to eliminate “need for frequent back flushing of swimming pool sand filters.” See Tandon, p. 2, ¶ 0023. According to the Tandon application, the filter includes multiple cyclones as well as
         a sediment bowl with a hemispherical bottom and a sump therein for collecting sediment, a cylindrical cyclone housing disposed above and sealingly connected to the sediment bowl, a removable and replaceable cyclone cartridge inserted into the cyclone housing, a diffuser plate sealingly connected to the cyclone cartridge and cyclone housing, a fluid inlet for introducing fluid into the cyclone housing, and a fluid outlet for discharging fluid from the cyclone housing.
 
See Tandon, p. 2, ¶ 0018. “As sediment is removed from the fluid in each cyclone, it is separated out and delivered down into the sediment bowl sump, while the fluid is directed upwardly and out to the fluid outlet.” See id., Abstract.
       

     Filters of the Tandon application are designed to connect to outlets of fluid pumps and remove (i.e. pre-filter) fine particulates from water exiting a pump before the water enters a standard pool filter. As configured, the filters would not operate to separate leaves or other large debris from the water. Such would be true even if the (small) cyclones were scaled, although no suggestion of such scaling exists in the Tandon application. 
     SUMMARY OF THE INVENTION 
     The present invention provides alternate filters and methods of filtering debris from fluid. Designed principally (although not necessarily exclusively) to be connected to an inlet of a fluid pump, the invention allows separation of debris from fluid flowing to the pump. Further, debris separation may occur outside the primary fluid flow path. 
     The invention is especially useful as part of a system for cleaning circulating water of a swimming pool or spa. Leaves, in particular, present significant problems for existing cleaning systems, as their relatively large surface areas, relatively light dry weights, and saturated specific gravities similar to that of water make them difficult to separate from the water without degrading performance of the system. Indeed, conventional cyclonic filters would perform poorly in filtering leaves entrained in water, as the attraction force to the primary flow due to their large surface areas will exceed that of the centrifugal force generated, precluding their separation from the water. 
     Unlike conventional such filters, that of the present invention successfully separates leaves (and other debris) from water or other fluid. Certain versions may include a first stage adjacent an inlet and outlet and a second stage remote from the inlet and outlet. A disc or other object preferably (although not necessarily) separates an inner core comprising the first and second stages, with the disc (when present) functioning to inhibit debris from migrating from the second stage back toward the inlet or outlet. 
     Beneficially included in the first stage is a perforated first tube of generally cylindrical shape. Although the first tube preferably is generally cylindrical, use of the term “tube” herein is not necessarily intended to imply any cylindrical structure. Indeed, by contrast, a second tube of generally frustoconical shape may be included in the second stage. The second tube may, but need not necessarily, also be perforated. Because the first tube is perforated, its interior region may continue to form part of the primary fluid flow path and thus may be directly connected to the outlet. 
     Filters consistent with the present invention also may include housings and position the inlet and outlet in lids attachable to (and desirably decouplable from) the housings. Surrounding at least part of the first tube within a housing may be a director advantageously being generally cylindrical in shape. At least some fluid entering the housing via the inlet initially may be restricted to an annular region between the interior of the director and the exterior of the first tube. Preferably, however, the director terminates a distance from the disc, allowing that fluid to pass by the disc into the second stage. 
     In use of the filters, fluid (such as debris-laden water) may enter via an inlet, with the inlet imparting a spinning, spiral motion to the fluid (i.e. creating a vortex) in the annular region between the director and the first tube. Some fluid will enter the interior region of the first tube through its perforations and transit to the outlet, while the remainder of the fluid, laden with debris, will continue to spin in the annular region. Angling perforations of the first tube in a direction opposite the spiral flow therearound will assist in preventing debris from entering its interior region. 
     When the debris-laden fluid reaches a terminating edge of the director, it travels (under centrifugal force, applicants currently believe) outward to (or toward) the interior surface of the housing, traveling beyond the disc into the second stage. In this second stage, the fluid spins more slowly, allowing debris to settle therein. Assuming the filter is oriented vertically, gravity as well may assist in settling debris in the second stage, as the second stage will be below the first stage. 
     Alternatively, the second stage may contain a second tube of non-frustoconical (e.g. cylindrical) shape or omit any second tube entirety. Indeed, in some versions of the invention, the second stage may simply comprise a sump or other area capable of receiving debris. As well, the second stage may be detachable from the first stage. 
     Because perforations comprise a substantial amount of the overall surface area of the first tube, the primary fluid flow provides relatively low attractive force to leaves present in the annular region. Accordingly, forces associated with the spinning motion are able to overcome the attractive forces and cause leaves to continue (or resume) their spiral motion through the first stage toward the second stage. Forming the first tube of low-friction material may also be beneficial in overcoming the attractive forces. 
     It thus is an optional, non-exclusive object of the present invention to provide filters and methods of filtering fluids. 
     It is also an optional, non-exclusive object of the present invention to provide filters principally for use in separating debris from water of swimming pools and spas. 
     It is another optional, non-exclusive object of the present invention to provide filters in fluid communication with inlets of pumps. 
     It is a further optional, non-exclusive object of the present invention to provide filters in which debris may be separated from fluid in a region outside the primary fluid flow path. 
     It is an additional optional, non-exclusive object of the present invention to provide two-stage debris filters, with a first stage including a perforated tube and a second stage including a frustoconically-shaped tube. 
     It is, moreover, an optional, non-exclusive object of the present invention to provide a filter whose perforated tube defines an interior region forming part of the primary fluid flow path and that is in fluid communication with an outlet. 
     It is yet another optional, non-exclusive object of the present invention to provide filters configured to impart spinning, spiral motion to entering fluid, with such motion (together with gravity in certain circumstances) overcoming, at least for some leaves, forces tending to attract the leaves to the perforated tube. 
     Other objects, features, and advantages of the present invention will be apparent to those skilled in appropriate fields with reference to the remaining text and drawings of this application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary filter of the present invention. 
         FIG. 2  is a cut-away view of the filter of  FIG. 1 . 
         FIG. 3  is a perspective view of an exemplary inner core of the filter of  FIG. 1 . 
         FIG. 4  is a cut-away, generally top or bottom view of a portion of a first tube of the inner core of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Depicted in  FIGS. 1-2  is an example of a filter  10  consistent with the present invention. Filter  10  may include housing  14  to which lid  18  may be attached. Such attachment may be permanent; alternatively (and preferably), lid  18  may be removable from housing  14 . However, when housing  14  and lid  18  are attached, the attachment should be fluid-tight (or nearly so) to avoid creating a leakage path into or from the housing  14 . Housing  14  may include floor  20  and may be generally cylindrical in shape, although other shapes may be utilized instead. 
     Lid  18  may comprise inlet  22 , outlet  26 , and director  30 . (Alternatively, director  30  may be part of housing  14  or otherwise not be part of lid  18 .) Inlet  22  is defined by termination of inlet conduit  34 , whereas outlet  26  is defined by termination of outlet conduit  38 . Inlet conduit  34  is configured to impart spinning, spiral motion (downward as filter  10  is oriented in  FIGS. 1-2 ) to fluid entering filter  10  via inlet  22 . 
     Positioned within housing  14  may be central, inner core  42  of filter  10 . As illustrated in  FIGS. 1-3 , core  42  comprises first tube  46 , second tube  50 , disc  54 , and base  58 . These components may be integrally formed (as is shown in  FIG. 3 ); alternatively, they may be connected in any suitable manner. Because filter  10  preferably is oriented upright when in use, first tube  46  typically will be above second tube  50 . Filter  10  conceivably may be oriented otherwise than upright at times, however. Core  42  preferably is removable from within housing  14  to facilitate, among other things, removal of accumulated debris. Indeed, at least some versions of inner core  42  may include a pliable wiper or similar component attached to the periphery of base  58  so as to wipe (“squeegee”) debris from the interior of the wall of housing  14  as the core  42  is removed. 
     As depicted, first tube  46  is generally cylindrical, whereas second tube  50  is generally conical (or, preferably, frustoconical) in shape. First tube  46  additionally includes multiple perforations in the form of openings  60 , allowing fluid to flow from its exterior  62  to its interior region  66 . Interior region  66  additionally is connected to outlet conduit  38  at a nominally upper end  68  of first tube  46  so as to allow fluid within region  66  to travel via the conduit  38  to outlet  26 . Inlet conduit  34 , interior region  66 , and outlet conduit  38  thus may form most or all of a primary fluid flow path through filter  10 . 
     Openings  60  may be formed in first tube  46  in any appropriate way. The openings  60  additionally may be of any number, size, or shape adequate to achieve any object of the invention. Preferably, though, openings  60  comprise a significant portion of the surface area of exterior  62  so as to not provide too great a resistance to fluid flow. Further, as shown in  FIG. 4 , openings  60  may be angled such that spinning, debris-laden fluid must transit an acute angle A from exterior  62  to interior region  66 , discouraging debris from passing through the openings  60 . 
     Second tube  50  preferably, but not necessarily, is perforated. Regardless, it defines an exterior  70  whose diameter decreases from its nominally upper end  74  to its nominally lower end  78 . Upper end  74  may be adjacent lower end  82  of first tube  46 , whereas lower end  78  may be adjacent base  58 , which in turn may be adjacent floor  20  in use. The maximum diameter of second tube  50 , furthermore, preferably is approximately the same as, or less than, the diameter of first tube  46 . 
     Positioned between or adjacent upper end  74  and lower end  82  may be disc  54 . Disc  54  thus effectively divides filter  10  into two stages, a first stage above the disc  54  and a second stage below the disc  54  (in the orientation of  FIGS. 1-3 ). Disc  54  preferably has—but need not necessarily have—cross-sectional shape similar to that of housing  14 . If disc  54  is annular or circular, however, it should have smaller diameter than the diameter of housing  14  so that fluid may flow from the first stage to the second stage through an (annular) gap G. 
     At least some versions of filter  10  may be connected, through suitable hoses or conduits, between a pump and a “suction-side” APC. When the APC is placed within a swimming pool and the pump is activated, both filter  10  and the APC are at least partially evacuated. This action in turn causes debris-laden water to flow into and through the APC and then through a hose or conduit to inlet  22 . Some of the water will travel through filter  10  in the primary flow path described above and exit via outlet  26  for continued travel toward the pump. 
     The remainder of the debris-laden water entering inlet  22  will continue to spin downward between director  30  and exterior  62  of the first stage of filter  10 , with centrifugal force (and, if applicable, gravity) eventually forcing the water through gap G to the second stage. Because these forces are intended to be larger than the force attracting larger debris (e.g. leaves) onto openings  60 , the larger debris effectively may be “torn” or “ripped” from the openings  60  for conveyance through gap G. Continuous in-flow of water into inlet  22  aids in creating the vortex, moving the debris around second tube  50  toward base  58 . However, because of the decreasing diameter of second tube  50  and its increasing distance from the suction force applied by the pump to outlet  26 , the water in the second stage spins more slowly, operating to “wind” debris around exterior  70  of second tube  50 , compressing the volume of debris and thus allowing longer use of filter  10  prior to removing accumulated debris therefrom. The arrangement of forces and size of disc  54  additionally inhibit debris from returning through gap G back into the first stage. 
     In a general sense, therefore, filter  10  strains leaves in water rather than, for example, particles in air. Filter  10  does not necessarily centrifugally “spin out” particles for collection in a sheltered part of housing  14 , unlike analogous structures of cyclonic air vacuum cleaners. Instead in filter  10  a high-velocity rush of water is created past a portion of a strainer (e.g. first tube  46 ), an aim of which is to “tear off” leaves from the water, keeping the water void of leafy debris so it may pass through openings  60  generally unrestricted. 
     Leafy debris, and most other light-weight pool debris, is naturally attracted to exterior  62  of first tube  46 , even though some centrifugal force is present. Centrifugal force of this nature does not separate light debris in water, however, nor does it keep leafy debris away from the strainer. Indeed, applicants submit that one is not able to separate this type of debris from water centrifugally. 
     Rather, in filter  10  the debris is not afforded the chance to adhere to the upper portion of the strainer (e.g. to first tube  46 ), as in that narrow portion the cyclone maintains a speed of water, the force of which is greater than the force of the draw through the strainer. The high speed water therefore “cleans” the narrow upper portion of the strainer. The wider, lower portion of the strainer (e.g. second tube  50 ), in contrast to the former, is designed to slow this cyclone in this area. This slowing in turn encourages the light, leafy debris to attach and wrap around the lower portion of the strainer. In this region the force of the draw through the strainer is greater than the force of the cyclonic water and the reverse happens—the leafy debris is collected away from the upper portion of strainer, an area desirably kept “clean.” 
     An aim of filter  10 , therefore, is to create a high-speed velocity stream of water past a portion of strainer and then a low-speed velocity stream of water for collection. This approach also may work linearly, but for convenience and compactness using a generally cylindrical housing  14  is presently preferred. Both first tube  42  and second tube  46  strain water thence flowing to outlet  26 , resulting in more efficient straining (as opposed to more efficient cyclonic action, as desired in conventional air cyclone vacuum cleaners). Further unlike air cyclone vacuums, filter  10  preferably contains no “dead zone” or low-flow sump within housing  14 . 
     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. Additionally, the contents of the Atkins patent and Tandon application are incorporated herein in their entireties by this reference.