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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a swimming pool brush. More particularly, it relates to a swimming pool brush that includes a hydrofoil to enhance the pressure of the brush against the sidewalls of a swimming pool. 
     2. Description of the Prior Art 
     Manual tools for brushing the sidewalls of a swimming pool include an elongate pole having a brush releasably secured to a leading end of the pole. The tool is used by grasping the elongate pole away from the leading end and moving the pole up and down so that the brush bears against the sidewall. It is important to apply pressure to the brush to enhance its cleaning effect. The pressure is applied by pushing out on the upper or trailing end of the pole with a first hand while pulling the pole in towards the sidewall with a second hand at a location between the leading and trailing ends. The second hand thus defines a fulcrum where leverage is applied to the brush. 
     There are several patents disclosing plates attached to a swimming pool brush that increase the pressure of the brush against a swimming pool sidewall so that a user need not exert extra energy to increase such pressure. In some of the prior art patents, the plate is fixedly secured to the brush head and has utility in causing water to push the brush in the direction of the sidewall during a down stroke, thereby increasing the pressure on the brush as desired. 
     A major drawback of such plates is a vacuum created on the trailing side of the plate as the brush is pushed downwardly. Water flowing upwardly around the edge of the plate creates a venturi effect low pressure area on the trailing side of the plate, thereby lifting the plate away from the sidewall and thus reducing the pressure of the brush against the sidewall. There are no known disclosures of a brush head that minimizes the venturi effect. 
     Prior art brushes must be discarded when worn down. Thus there is a need for a brush that can still be used even after it would be considered worn out by conventional standards. 
     The prior art, however, does not disclose brushes that can be re-used even when apparently worn down. 
     There is a need for an improved swimming pool brush having a hydrofoil that increases the pressure of a brush head against a swimming pool sidewall during a downstroke while simultaneously minimizing the pressure-reducing effects created on the trailing side of the hydrofoil. 
     A need exists as well for a brush head that wears out on a first side thereof and which is reversibly mounted so that a second side thereof can be used when the first side is worn down. 
     However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in this art how the needed brush assembly could be provided. 
     SUMMARY OF INVENTION 
     The long-standing but heretofore unfulfilled need for an improved swimming pool brush is now met by a new, useful, and nonobvious invention. The novel swimming pool brush includes a brush head having a top wall and a bottom wall. At least one aperture is formed in the brush head and a plurality of bristles is secured to the bottom wall in depending relation thereto, in surrounding relation to the at least one aperture. 
     A first plurality of clips is formed integrally with the top wall on a first side of the at least one aperture. A hydrofoil plate having a first longitudinally-extending edge is adapted to be hingedly engaged by the first plurality of clips. The hydrofoil plate has a first, extended position when the brush head is immersed in water and pushed downwardly against a substantially vertical swimming pool sidewall. The first position is a position of rotational adjustment where the plate is positioned a few degrees above a plane that is substantially perpendicular to the swimming pool side wall. 
     The hydrofoil plate has a second, retracted position when the brush head is pulled upwardly against a swimming pool sidewall. The second position is a position of rotational adjustment where the plate is positioned in a plane that is substantially parallel to the swimming pool sidewall. 
     When the plate is in its first position, it is pushed by water in the swimming pool towards the swimming pool sidewall, thereby increasing pressure of the bristles against the sidewall. 
     The at least one aperture formed in the brush head is operative to reduce a venturi effect created by water flowing over the hydrofoil plate when the hydrofoil plate is in the first position. 
     The at least one aperture creates a venturi effect that advantageously pushes the bristles away from the swimming pool sidewall when the hydrofoil plate is in the second position. 
     A semicircular recess is formed in the top wall of the brush head, mid-length thereof. A connector member has a semicircular first end adapted to fit within the semicircular recess. The connector member has a tubular second end adapted to releasably engage an elongate pole. The semicircular first end is mounted for rotation within the semicircular recess so that the connector and hence the elongate pole are attachable to the brush head in an infinite plurality of functional positions of angular adjustment. 
     In a preferred embodiment, the at least one aperture is a pair of longitudinally-extending apertures disposed on opposite sides of the semicircular recess. The longitudinal axis of the apertures is coincident with a longitudinal axis of the brush head. 
     A bead is formed along a first longitudinally-extending edge of the hydrofoil plate and a plurality of apertures is formed in the hydrofoil plate adjacent the bead in longitudinally spaced apart relation to one another. 
     A first plurality of clips is formed in the top wall of the brush head, adjacent a first longitudinal edge thereof, in longitudinally spaced apart relation to one another. A second plurality of clips is also formed in the top wall of the brush head, adjacent a second longitudinal edge thereof, in longitudinally spaced apart relation to one another. 
     The plurality of apertures formed in the hydrofoil plate includes individual apertures spaced apart from one another to coincide with the spacing between the clips so that the clips releasably engage the bead at longitudinally spaced intervals along its extent. The hydrofoil plate may therefore be hingedly mounted to the brush head along the first or second longitudinal edge thereof. In use, the hydrofoil plate is hingedly attached to the first plurality of clips until the bristles that contact the pool side walls are worn down. The hydrofoil plate is then detached from the first plurality of clips and attached to the second plurality of clips so that unworn bristles will contact the pool side walls. 
     When the hydrofoil plate is moved from one longitudinal edge of the brush head to the other, the angle of the connector is also reversed so that the elongate pole does not interfere with the hydrofoil plate. More particularly, the brush head has a first position when the hydrofoil plate is secured to the first plurality of clips and has a second position when the hydrofoil plate is secured to the second plurality of clips. The second position is rotated one hundred eighty degrees relative to the first position so that a first edge of the brush bears against swimming pool sidewall when the brush head is in the first position and so that a second edge of the brush bears against a swimming pool sidewall when the brush head is in the second position. 
     The hydrofoil plate has a first position of rotational adjustment when the brush head is immersed in water and displaced in a downwardly direction in sliding relation to a swimming pool sidewall. The plate, when in said first position, is disposed a few degrees above an imaginary plane that is perpendicular to the swimming pool sidewall. The plate has a second position of rotational adjustment when the brush head is immersed in water and displaced in an upwardly direction in sliding relation to the swimming pool sidewall. The plate, when in said second position, is substantially parallel to the swimming pool sidewall. 
     Water, when flowing past the plate when the plate is in said first position, pushes the brush head towards the swimming pool sidewall. When flowing past the plate when the plate is in its second position, the water creates a venturi effect that pulls the brush head away from the swimming pool sidewall. 
     In a second embodiment, a ball and socket joint interconnects the elongate handle and the brush head. The ball and socket joint includes a ball secured to a leading end of the elongate handle and a socket formed integrally with a top wall of the brush head. 
     The socket has four upstanding arcuate walls adapted to rotatably engage spherical walls of the ball. Each arcuate wall is circumferentially spaced apart from its contiguous walls by a distance substantially equal to a width of the elongate handle so that the elongate handle slideably fits therebetween. A concavity is formed in each wall of said the upstanding arcuate walls of the socket. 
     The ball is centrally bored and internally threaded. An externally threaded screw is secured to the distal end of the elongate handle and a detent is secured to a distal end of the externally threaded screw. The elongate handle is locked into a preselected position when the detent is seated within a preselected concavity. The detent is seated within a preselected concavity by rotating the handle in a first direction about a longitudinal axis of symmetry of the elongate handle when the elongate handle is positioned in a preselected space between two contiguous arcuate walls. The elongate handle is unlocked by rotating the handle in a second direction opposite to the first direction about the longitudinal axis of symmetry of the elongate handle so that the detent is unseated from the preselected concavity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of the novel brush head as it is being pushed downwardly relative to a swimming pool side wall; 
         FIG. 2  is a perspective view of the novel brush head as it is being pulled upwardly relative to a swimming pool side wall; 
         FIG. 3  is a front elevational view of the novel brush; 
         FIG. 4  is an end view of the novel brush head when the novel hydrofoil plate is attached to the first plurality of clips; 
         FIG. 5  is an end view of the novel brush head when the novel hydrofoil plate is attached to the second plurality of clips; 
         FIG. 6  is a transverse sectional view taken along line  2 - 2  in  FIG. 3 ; 
         FIG. 7  is a bottom plan view of the novel brush head; 
         FIG. 8  is a perspective view of a second embodiment of the novel brush head having a ball and socket connection between the handle and the brush head and depicting the handle in a first position of four possible positions provided by said ball and socket connection; 
         FIG. 9A  is an exploded view of the ball and socket assembly; 
         FIG. 9B  is a top plan view of the novel socket; 
         FIG. 10  is a top plan view of the structure depicted in  FIG. 8 ; and depicting the handle in a second position of said four possible positions; and 
         FIG. 11  is a front elevational view of the structure depicted in  FIG. 8 , depicting the handle in a second position of said four possible positions; 
         FIG. 12  is an end elevational view of the novel brush head when in its  FIG. 8  configuration; and 
         FIG. 13  is a sectional view depicting the detent of the ball positioned within a concavity formed in the socket. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to  FIGS. 1-7 , it will there be seen that an illustrative embodiment of the invention is denoted as a whole by the reference numeral  10 . 
     Brush  10  includes brush head  12  within which is formed longitudinally-extending apertures  14  and  16  positioned on opposite ends of semicircular recess  11  (said recess being depicted in  FIG. 6 ). The longitudinal axis of symmetry of apertures  14  and  16  is coincident with a longitudinal axis of symmetry of brush head  12  and recess  11  is positioned mid-length of brush head  12 . 
     Bristles  18  are secured to and depend from bottom wall  20  of brush head  12  in surrounding relation to said apertures as best understood in connection with  FIG. 7 . This allows water to flow unobstructed through said apertures when brush head  12  is moving up and down along a swimming pool sidewall. As depicted in  FIG. 1 , bristles  18   a  are worn down before bristles  18   b  when the novel apparatus is in the  FIG. 1  configuration. 
     Bristles  18  collectively define end flairs  18   c ,  18   d  ( FIGS. 4 and 5 ) that are circumferentially spaced from one another. 
     Connector  13  has a semicircular leading end  15  that fits within semicircular recess  11  as best understood in connection with  FIG. 6  and a tubular trailing end  17  that releasably engages elongate pole  19  ( FIG. 1 ), i.e., said tubular trailing end ensleeves the leading end of handle  19 . A well-known flexible “V” shaped locking device  17   a  is positioned in the hollow interior of handle  19  and has a bulbous protrusion  17   b  formed in each of its free ends and said protrusions extend through diametrically opposed openings formed in trailing end  17  as depicted in  FIG. 3  and through diametrically opposed openings  19   a  formed in the leading end of pole  19  as depicted in  FIG. 1  when the locking device is in repose. A user disconnects pole  19  from tubular trailing end  17  by manually pressing on protrusions  17   b  to drive them radially inwardly out of openings  19   a  so that pole  19  may slidingly disengage from tubular trailing end  17 . 
     The mating of semicircular leading end  15  and semicircular recess  11  enables connector  13  to be positioned in an infinite plurality of functional positions of angular adjustment as indicated in  FIG. 6 . Nut  21  is housed in a confined recess built into brush head  12  and therefore is held against rotation. A blind bore formed in leading end  15  receives screw  23 . A semicircular slot  25  ( FIG. 7 ) formed in a bottom side of brush head  12  receives screw  23  so that said screw may be aligned with the blind bore formed in said leading end  15  for any angular position of connector  13 . Accordingly, screw  23  engages nut  21  to secure connector  13  to brush head  12  and the angular relation between said connector and brush head may be adjusted to any angle. 
     A first plurality of clips, collectively denoted  22 , is formed integrally with top wall  23  of brush head  12  on a first side of apertures  14  and  16  and a second plurality of clips, collectively denoted  24 , is formed integrally with said top wall  23  on a second side of apertures  14  and  16 . 
     As depicted in the transverse sectional view of  FIG. 6 , brush head  12  has a foam interior  12   a  and a hard polypropylene exterior  12   b.    
     Elongate bead  29  ( FIG. 3 ) is formed in hydrofoil plate  28  along a first or inner edge thereof, said bead having a cross-sectional diameter greater than a thickness of plate  28 . A plurality of apertures, collectively denoted  30 , is formed near said first, inner edge in plate  28  adjacent said bead  29 . The individual apertures are spaced apart from one another to coincide with the spacing between clips  22  so that clips  22  may releasably engage bead  29  at spaced intervals along its extent. Clips  22  and  24  and apertures  30  are equidistantly spaced apart in the preferred embodiment, but such equidistant spacing is not critical. The clipped connection is a pivotal or hinged connection because plate  28  is free to swing between its depicted  FIG. 1  and  FIG. 2  positions as a user oscillates brush head  12  up and down pool sidewall  11 . 
     When a user displaces brush head  12  in a downwardly direction, as illustrated in  FIG. 1 , the resistance of the water pushes plate  28  into its  FIG. 1  position. Plate  28  is positioned in a plane that is substantially perpendicular to vertical sidewall  31  of the swimming pool. More particularly, plate  28  is positioned a few degrees above a plane that is perpendicular to said vertical sidewall. The relative motion of water with respect to plate  28  is denoted by directional arrow  32 . Water on the lower side  28   a  of plate  28  thus pushes said plate and said brush head towards pool sidewall  31 . Water flowing around plate  28  creates a venturi effect, i.e., a low pressure area above top surface  28   b  of plate  28 , i.e., on the trailing side of said plate as it is pushed downwardly. In the absence of longitudinal apertures  14  and  16 , this venturi effect would reduce the force directed towards pool sidewall  31 . However, apertures  14  and  16  allow water flowing around plate  28  to flow through said apertures  14 ,  16 , thereby reducing the venturi effect and maximizing the pressure applied to the bristles as they are pushed downwardly. 
     When the user displaces brush head  12  in an upwardly direction, as illustrated in  FIG. 2 , the resistance of the water causes plate  28  to pivot about its hinged connection to brush head  12  until it lies in a plane that is substantially parallel to sidewall  31 . When so positioned, plate  28  causes almost no resistance as the user pulls upwardly on pole  19  to which brush head  12  is secured. Water flowing in the relative direction indicated by directional arrow  38  creates a venturi effect as it flows past each aperture  14 ,  16 , thereby creating a low pressure area that lifts the brush head away from sidewall  31  to further reduce the energy expended by the user in performing the upward, non-cleaning stroke. 
     In this way, apertures  14  and  16  in brush head  12  offset a first venturi effect during its downward cleaning stroke that enhances the pressure of the bristles against sidewall  31  and a second venturi effect that reduces the pressure of the bristles against sidewall  31  during its upward, non-cleaning stroke. 
     It will be noted from an inspection of  FIGS. 1 and 2  that brush  12  will wear primarily along upper edge  18   a  because said upper edge will bear hardest against sidewall  31  when the brush is in use. To reverse the brush, plate  28  is unclipped from clips  22  and re-positioned to the opposite side of the brush head so that it can be clipped to clips  24  as indicated in  FIGS. 4 and 5 . This requires loosening and re-tightening of connector  13 . Screw  23  is loosened, hydrofoil plate  28  is re-positioned from its  FIG. 4  to its  FIG. 5  position, connector  13  is re-positioned from its  FIG. 4  to its  FIG. 5  position, and screw  23  is re-tightened to nut  21  to secure connector  13  into its new position. The brush is then used as before but a new side  18   b  now bears against pool sidewall  31 . 
       FIGS. 8-13  depict a second embodiment where handle  19  is connected to brush head  12  in four (4) distinct and locked positions by a ball and socket joint. In the depicted embodiment, tubular housing  17  is an adaptor that ensleeves the leading end of handle  19  and said adaptor directly engages the ball. However, in an undepicted embodiment, tubular housing  17  could be eliminated and the leading end of handle  19  could directly engage the ball. 
     The first of said four (4) locked positions is depicted in  FIGS. 8 and 10 . Handle  19  is perpendicular to the longitudinal axis of symmetry of brush head  12 . The second of said four (4) locked positions is not depicted but it also positions handle  19  perpendicular to said longitudinal axis of symmetry in diametrically opposed relation to the position depicted in  FIGS. 8 and 10 . In other words, handle  19  extends downwardly from brush head  12  as drawn in  FIG. 8  and it would extend upwardly in said second position.  FIG. 11  depicts the third of said four locked (4) positions. Handle  19  extends to the left as drawn in parallel relation to the longitudinal axis of symmetry of brush head  12 . The fourth locked position would look like  FIG. 11  except that handle  19  would extend to the right as drawn. 
     In the depicted embodiment, tubular housing  17  has a boss  17   a  secured to its leading end and said boss supports externally threaded screw  34  having a rounded detent  36  ( FIG. 9A ) formed in the leading end of said screw  34 . Internally threaded bore  38  is formed in and extends diametrically through ball  40 . Rotation of handle  19  in a clockwise direction causes rotation of tubular housing  17  and thus of screw  34  so that said screw is advanced into bore  38 . Counter rotation of said handle effects retraction of screw  34  from said bore. 
     Ball  40  is rotatably captured within socket  42  that is formed integrally with a recess formed in top wall  23  of brush head  12 . Socket  42  includes four (4) arcuate walls, collectively denoted  42 , that extend above the plane of top wall  23 . The four (4) arcuate walls are circumferentially spaced apart from one another to provide four (4) slots, each of which accommodates tubular housing  17  when handle  19  is in one of its four (4) locked positions. A detent-receiving concavity is formed in each of the four (4) arcuate walls, on an interior surface thereof, and each concavity receives detent  36  when handle  19  is positioned in one of its four locked positions. The concavities are denoted  36   a ,  36   b ,  36   c , and  36   d  in  FIG. 9B . 
     A user positions handle  19  in one of its four (4) positions to align detent  42  with an associated concavity and then rotates handle  19  clockwise (assuming that threads  34  are right-handed) to advance detent  42  fully into its associated concavity so that the detent is locked in said concavity when handle  19  can no longer be rotated in said clockwise direction under manual power. This assures that handle  19  remains in its selected locked position as the pool is scrubbed. When the user desires to re-position handle  19  into another one of its four locked positions, handle  19  is rotated counterclockwise until detent  36  withdraws from its concavity, thereby freeing rotational movement of ball  40  so that handle  19  can be placed into another one of the four (4) slots defined by the four arcuate walls  42  of the ball-capturing socket. It is then re-tightened by rotating the handle in the clockwise direction, with detent  36  advancing into a different one of the concavities to perform the locking function. 
     A ball and socket similar to the novel ball and socket is disclosed in U.S. Pat. No. 5,551,115 to the present inventor. That earlier structure did not include detent  36  or detent-receiving concavities. 
     It should be understood from  FIG. 9A  that if it were desired to eliminate tubular housing  17 , screw  34  would be secured to the leading end of handle  19  so that said screw  34  could directly engage internally threaded bore  38  formed in ball  40 . The depicted embodiment including adaptor  17  is preferred so that pool owners may purchase the novel brush head and use it with their existing conventional handle  19 . 
     It will be thus seen that the advantages set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.

Summary:
A swimming pool brush includes a brush head having a pair of apertures formed in the brush head and a plurality of bristles secured in depending relation to the brush head in surrounding relation to each aperture. A first plurality of clips is formed in a top wall of the brush head on a first side of the apertures. A hydrofoil plate has a first edge adapted to be hingedly engaged by the first plurality of clips, an extended position when the brush head is immersed and pushed downwardly against a swimming pool sidewall and a retracted position when the brush head is pulled upwardly against the sidewall. A venturi effect is created by the plate when in its extended position but the apertures minimize the venturi effect. The plate may be mounted to a second plurality of clips so that the brush head can be reversed and re-used.