Discs having recessed areas, or pockets, in their undersides are detailed. The pockets allow provision of increased suction in localized regions, especially useful when the body of an associated cleaner pivots from side to side. Downwardly-extending wear surfaces may be present as well within the pockets.

REFERENCE TO PROVISIONAL APPLICATION 
       [0001]    This application is based on and hereby refers to U.S. Provisional Patent Application Ser. No. 60/925,764, filed Apr. 23, 2007, and having the same title as appears above, the entire contents of which provisional patent application are incorporated herein by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to discs and associated components of cleaners of liquid containing vessels and more particularly, although not necessarily exclusively, to automatic swimming pool cleaners having discs with pocketed undersides for enhanced localized suction. 
       BACKGROUND OF THE INVENTION 
       [0003]    Commonly-owned U.S. Pat. No. 5,465,443 to Rice, et al., whose contents are incorporated herein in their entirety by this reference, describes various discs for, principally, automatic swimming pool cleaners. Extending upward from the upper surfaces of the discs are multiple fins. By contrast, except for a downwardly-projecting ramp positioned about a central aperture of the disc, its lower surface is generally planar. 
         [0004]    U.S. Pat. No. 5,617,606 to Scott, II, et al., also commonly owned with this application, details other discs for automatic swimming pool cleaners. Projecting above the majority of the upper surfaces are one or more flutes, whose edges may be curved or straight as desired. Similarly projecting upward at the outer peripheries of the discs may be a raised, or upturned, lip. 
         [0005]    Like the discs of the Rice patent, those of the Scott, II patent may include annular ramps projecting downwardly from their lower surfaces. Otherwise, however, the lower surfaces of the discs are generally flat, again similar to those of the discs of the Rice patent. The contents of the Scott, II patent are incorporated herein in their entirety by this reference. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides alternatives to conventional discs, including those of the Rice and Scott, II patents. Unlike the generally flat lower surfaces of the discs of those patents, lower surfaces of the present discs contain one or more recessed areas intermediate their inner and outer peripheries. Such recessed areas, or pockets, are configured to provide increased suction in localized regions. They are especially (although not exclusively) useful with cleaners whose bodies pivot. See, e.g., U.S. patent application Ser. No. 11/708,925 of Moore, et al. (the “Moore Application”). The contents of the Moore Application are incorporated herein in their entirety by this reference. 
         [0007]    Optionally included within any of the pockets may be one or more downwardly-extending elements or projections. These projections may, in effect, be unrecessed portions of the lower surface; alternatively, they may be recessed but to a lesser extent than the remainder of the pockets. In use, the projections function as contact, or wear, surfaces as the cleaners to which the discs are attached move throughout pools (or spas or other liquid-containing vessels). 
         [0008]    Discs of the present invention may be similar to those of the Moore Application. In particular, the discs may comprise multiple parts. Alternatively, they may be molded as unitary structures, as are commercial versions of the discs of the Rice and Scott, II patents. 
         [0009]    It thus is an optional, non-exclusive object of the present invention to provide novel discs for, principally, automatic swimming pool cleaners. 
         [0010]    It is also an optional, non-exclusive object of the present invention to provide discs whose lower surfaces include means for locally increasing suction force. 
         [0011]    It is a further optional, non-exclusive object of the present invention to provide discs having recessed areas of their lower surfaces for supplying localized increased suction. 
         [0012]    It is another optional, non-exclusive object of the present invention to provide discs with wear members present within the recessed areas. 
         [0013]    Other objects, features, and advantages of the present invention will be apparent to those skilled in the relevant art with reference to the remaining text and the drawings of this application. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a generally bird's-eye view of an automatic swimming pool cleaner incorporating a disc consistent with the present invention. 
           [0015]      FIG. 2  is a perspective view of the automatic swimming pool cleaner of  FIG. 1  illustrating the act of transitioning from a horizontal surface to a vertical surface of movement. 
           [0016]      FIG. 3  illustrates, somewhat schematically, barbed gripping material attached to the underside of portions of a disc consistent with the present invention. 
           [0017]      FIG. 4  shows aspects of an alternate automatic swimming pool cleaner of the present invention. 
           [0018]      FIG. 5  illustrates portions of upper surfaces of a disc similar to that of  FIG. 1 . 
           [0019]      FIG. 6  illustrates portions of lower surfaces of the disc of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Depicted in  FIGS. 1-2  is an exemplary automatic swimming pool cleaner  10  of the present invention. Cleaner  10  is designed primary for attachment to the inlet, or suction side, of a pump of a swimming pool filtration system. Some or all aspects of the present invention are not necessarily limited to use with suction-side automatic swimming pool cleaners, however, and conceivably could be employed as part of other devices as well. 
         [0021]    Shown in  FIGS. 1-2  as part of cleaner  10  are body  14 , inner pipe  18 , and outer pipe  22 . Similar to those of the cleaner described in U.S. Pat. No. 4,742,593 to Kallenbach, inner and outer pipes  18  and  22  of cleaner  10  may be concentric, with outer pipe  22  adapted to be connected to a flexible hose leading, ultimately, to the inlet of a pump. Extending from body  14  may be arm  26 , whose end  30  may contain a weight (not shown) functioning, in part, to balance a float (also not shown) typically positioned within body  14 . However any weight need not necessarily be placed within end  30 , and indeed need not necessarily be positioned at any point within arm  26 . In use, aim  26  also may function as a bumper or bearing surface in certain situations. 
         [0022]    Also illustrated in  FIGS. 1-2  as part of cleaner  10  are apron  34  and disc  38 . Apron  34  may be connected directly or indirectly to footpads  68 , each of which may provide a bearing surface as cleaner  10  traverses a vessel; apron  34  may also serve as an interface connecting disc  38  to body  14 . Although disc  38  too functions, to modest extent, as a bearing surface, it also operates to effect sealing of certain surfaces as body  10  is evacuated by the pump. 
         [0023]      FIGS. 1-6  detail aspects of (nominal) underside  42  of body  14 . Visible in underside  42  is inlet  46 , through which debris-laden water or other fluid may flow into cleaner  10 . In normal use, inlet  46  is adjacent a to-be-cleaned pool surface. Also illustrated in  FIG. 6  within inlet  46  is inlet end  50  of valve  54 , through which the debris-laded fluid passes before travelling through inner pipe  18  to the flexible hose and, from there, to some type of filter. 
         [0024]    Valve  54  accordingly is “in-line,” in that it forms part of this main fluid-flow path through body  14 . Any suitable valving mechanism may be employed as valve  54 . Preferably, however, valve  54  is of the diaphragm type, as depicted in the Kallenbach patent. Other aspects of disc  38  also are detailed in  FIGS. 1-6 . Disc  38  may be formed of moldable plastic or other material. Preferably, however, disc  38  lacks uniform flexibility. Instead, disc  38  has lesser flexibility forward of body  14  of automatic swimming pool cleaner  10  and greater flexibility elsewhere. 
         [0025]    As depicted in  FIGS. 1-6 , forward section  78  of disc  38  may, but need not necessarily, constitute an arc-shaped segment of material similar to that described in U.S. Pat. No. 5,421,054 to Dawson, et al., whose contents also are incorporated herein in their entirety by this reference. As initially noted therein, fins  82  may extend radially upward from and outward of a serpentine periphery, with the fins  82  providing sufficient rigidity to disc  38  to enable it to ride over various objects, including many drains, lights, valves, and other nozzles, projecting from internal surfaces of pools. Enhanced rigidity of forward section  78  additionally inhibits its assuming the shape or a corner or other transition within a pool (and thereby sticking in the corner or at the transition) and prevents forward section  78  from folding under itself when departing from vertical surfaces such as walls. 
         [0026]    Connected to any, some, or all of forward section  78 , apron  34 , footpad  68 , or body  14  are mid-section  86  and rear section  90  of disc  38 . Contrasted with forward section  78 , mid-section  86  and rear section  90  are more flexible, as they rarely function as the leading edge of cleaner  10 . This greater flexibility provides improved sealing of disc  38  to the surface to be cleaned. Flexibility of rear section  90  additionally may improve the ability of cleaner  10  to climb pool walls by permitting body  14  to rotate rearward some as generally illustrated in  FIG. 2 . 
         [0027]    Because of float placement within some versions of cleaners  10 , the center of gravity of such cleaners  10  is forward of fins  82 . Consequently, when a swimming pool pump is inactive, inner and outer pipes  18  and  22  tend to rest at a low angle to the horizontal, effectively causing cleaner  10  to “lie down.” When the pump is activated, cleaner  10  may attempt to travel backward, undesirably, rather than forward. Accordingly, undersides  94  of tongues  98  from which fins  82  protrude may include barbed gripping material  102  as shown in  FIG. 3 . Such material is configured to inhibit backward movement of cleaner  10  in these circumstances, thereby encouraging desired forward movement thereof. 
         [0028]    Alternatively or additionally, one or more tabs  106  may be attached to or integrally formed with forward section  78  of disc  38 . Shown in  FIG. 4 , an exemplary tab  106  is adapted to lie flat when cleaner  10  is moving forward so as not to impede such movement. However, should cleaner  10  attempt to travel backward in use, tab  106  will contact (catch) the floor of the pool, in turn forcing forward section  78  upward. As forward section  78  moves upward, rear section  90  will be forced downward, allowing it to adhere to the pool surface temporarily and cease the backward movement. One tab  106  preferably is positioned at rear edge  110  of forward section  78  (opposite fins  82 ), although more tabs  106  may be used and positioned otherwise as needed. 
         [0029]    Detailed in  FIGS. 5-6  is an improved version of disc  38 . Disc  38 A, like disc  38 , may include forward section  78 A, mid-section  86 A, and rear section  90 A. Again similar to the manner in which disc  38  is assembled, mid-section  86 A and rear section  90 A may be connected to any or all of forward section  78 A, apron  34 , footpad  68 , or body  14 . 
         [0030]    Defined by at least mid-section  86 A are upper surface  110  and lower surface  114 . As illustrated in  FIG. 6 , formed in lower surface  114  generally between inner periphery  118  and outer periphery  122  is recessed area  126 . Such recessed area  126  thus is configured substantially as a pocket, with the area  126  capable of being (at least partially) evacuated during operation of cleaner  10 . Recessed area  126  may beneficially extend to outer periphery  122  in some embodiments of disc  38 A, with such extension shown in  FIG. 6  where mid-section  86 A overlaps forward section  78 A. Likewise, in certain circumstances, recessed area  126  may extend to or near inner periphery  118 . 
         [0031]    Projecting (nominally downwardly when cleaner  10  is upright) from roof  130  of recessed area  126  may be one or more elements  134 . Elements  134 , if present, may span the depth of recessed area  126 . Elements  134  thus are configured to contact a to-be-cleaned surface when unrecessed portion  138  of lower surface  114  does, providing wear surfaces for recessed area  126 . Should such elements  134  not be present, risk of frictional wear of roof  130  exists. 
         [0032]    Presently-preferred versions of elements  134  are shaped as cylinders, with multiple such elements  134  molded as part of disc  38 A and spaced within recessed area  126 . Elements  134  need not be shaped as cylinders, however. Indeed, elements  134  are optional and need not be shaped in any particular way or necessarily present. 
         [0033]      FIG. 6  illustrates two recessed areas  126 , one to each side of valve  54 . If valve  54  is designed to move periodically, valve assembly  58  may reposition inlet end  50  from side to side, periodically reorienting inlet end  50  toward one or the other of the recessed areas  126 . Providing the recessed area  126  as suction force is applied via valve  54  facilitates the corresponding mid-section  86 A adhering to the to-be-cleaned surface, supplying a region adapted for evacuation. However, recessed areas  126  may be useful regardless of whether valve  54  is fixed or moveable and with valves other than valve  54 .  FIG. 5 , finally, shows raised area  138  of upper surface  110  corresponding to recessed area  126 . 
         [0034]    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.