[0001]    This application claims priority to U.S. patent app&#39;n Ser. No. 60/990,974, filed 29 Nov. 2007, and Ser. No. 12/022,295, filed 30 Jan. 2008, the complete disclosures of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a backboard training device having high density polyethylene panels mounted so that buckling is avoided and unwanted sound is reduced. 
       BACKGROUND OF THE INVENTION 
       [0003]    A variety of sports utilize backboard training for practice and conditioning. Tennis players develop stroke technique, footwork and stamina. Soccer, Lacrosse, and basketball players likewise utilize the rebound of backboards to develop skills specific to their sports. The innate simplicity of a backboard belies its ability to provide both introductory through advanced level skill development in numerous sports. 
         [0004]    Backboard practice can take place against a garage door or any flat wall. Plywood and concrete block is often used to fashion backboards. However, both such products require constant maintenance. Wood requires painting, sealing and flashing to prevent rot and warping. Block is expensive to build and needs painting, caulking, parging and pointing. 
         [0005]    Backboard training is so popular that a number of companies have introduced panelized backboard products to the market place. These products are generally sold in custom paneled increments of 4 feet wide by 8 feet or 10 feet in height. The panels are normally attached to an existing fence structure or other support poles. The more panels you buy, the wider your backboard can be. 
         [0006]    Backboard kits are available with plywood panels, MDO panels, fiberglass panels, vacuum molded or otherwise molded plastic panels or painted-treated drywall panels. 
         [0007]    All of the above systems have limitations and problems. 
         [0008]    Fiberglass, vacuum molded and injection molded panels are subject to damage when used for Lacrosse or Soccer Practice. The balls used in these sports can puncture or crack the panels ruining the product. Fiberglass backboards utilize a thin, painted-on surface that is subject to U.V degradation and often develops dead spots. 
         [0009]    Plywood and MDO Board panels are subject to rotting, warping, delamination and require constant painting, sealing and flashing. 
         [0010]    HDPE panels are very difficult to mark, for example with lines, because paint and adhesives to do not stick to the surface. 
       SUMMARY OF THE INVENTION 
       [0011]    An objective of the invention is to provide a backboard training device that is low maintenance, such that it is not prone to rotting, warping, or delamination and does not require constant painting, sealing and flashing. 
         [0012]    Another objective of the invention is to solve the problem of buckling associated with HDPE panels. 
         [0013]    A further objective of the invention is to solve the problem of undesirable sound associated with use of HDPE panels. 
         [0014]    Another objective of the invention is to solve the problems associated with marking HDPE panels. 
         [0015]    The above objectives and other objectives are obtained by a backboard training device comprising:
       a. at least two panels mounted to a rigid support by a movable mount, the panels comprising high density polyethylene having a high coefficient of expansion;   b. the movable mount constructed and arranged to allow the panels to move in relation to each during ambient temperature changes to avoid buckling of the panels;   c. an anti-vibration strip disposed between the movable mount and the panels; and   d. an anti-friction strip disposed between the movable mount and the panels to allow the panels to move in relation to one another.       
 
         [0020]    In a preferred embodiment, the movable mount comprises a plurality of wheels attached to the panels, and at least one track mounted to the rigid support, the wheels contacting the at least one track so that the panels can slide in relation to one another in a horizontal direction. 
         [0021]    In another preferred embodiment, the movable mount comprises a plurality of slots substantially aligned in a horizontal direction, the panels being movably secured to the movable mount using bolts that pass through the panels and the slots, the slots having a width greater than the diameter of the bolts to allow movement in a vertical direction and the slots having a length to accommodate expansion and contraction of the panels. 
         [0022]    The objectives associated with marking and other objectives are obtained by an HDPE panel comprising a surface layer and at least one other layer bonded to the surface layer, the surface layer and the at least one other layer having different colors, and at least one marking formed by removing the surface layer in the shape of the marking to expose the color of the at least one other layer. 
         [0023]    The above objectives are also obtained by a backboard training device comprising a plurality of HDPE panels, each HDPE panel comprising a surface layer and at least one other layer bonded to the surface layer, the surface layer and the at least one other layer having different colors, and at least one marking formed by removing the surface layer in the shape of the marking to expose the color of the at least one other layer, wherein the other layer and surface layer are coextruded. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  illustrates a top view of buckled HDPE panels which are mounted to rigid support posts using a non-movable mount; 
           [0025]      FIG. 2  illustrates a front view of HDPE panels mounted to rigid support posts using a non-movable mount; 
           [0026]      FIG. 3 . illustrates a non-movable mount; 
           [0027]      FIG. 4 . illustrates a movable mount having slots; 
           [0028]      FIG. 5  illustrates a side view of HDPE panels mounted to a movable mount having slots; 
           [0029]      FIG. 6  illustrates a side view of a movable mount having wheels; 
           [0030]      FIG. 7  illustrates a front view of HDPE panels mounted to a movable mount having wheels; 
           [0031]      FIG. 8  illustrates a side view of a movable mount having wheels; 
           [0032]      FIG. 9  illustrates a side view of a movable mount having wheels; 
           [0033]      FIG. 10  illustrates a front view of HDPE panels mounted to a movable mount having wheels; 
           [0034]      FIG. 11  illustrates a frontal view of an HDPE panel; 
           [0035]      FIG. 12  illustrates a side view of an HDPE panel; and 
           [0036]      FIG. 13  illustrates a backboard training device comprising a plurality of HDPE panels. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    The invention will now be explained with reference to the attached Figs., without being limited thereto. The backboard training device comprises at least two HDPE panels mounted to a rigid support by a movable mount. The HDPE panels are highly flexible, resist puncture, cracking and weathering. However, the HDPE panels have a high coefficient of expansion, which results in severe buckling of the panels if they are not movably mounted to the rigid support. The HDPE panels have a high coefficient of expansion, for example greater than 0.00005 in/in ° F. The HDPE panels are usually about 4 feet by 8 feet or 4 feet by 10 feet, but can be sized as desired. The panels are usually at least about 0.5 inches in thickness to provide sufficient rigidity to avoid deforming during use, but can be any thickness as desired. Usually, the multiple panels are aligned in a horizontal direction with the length facing upward, as shown in the accompanying Figs. The movable mount is constructed and arranged to allow the panels to move in relation to each other during ambient temperature changes to avoid buckling of the panels. 
         [0038]    The movable mount disclosed herein allows the HDPE panels to expand and contract with ambient temperature variations without developing undesirable warping or buckling that will render the backboard unplayable, damage the hardware of the mounting system, and damage the panels. 
         [0039]    When an HDPE panel is bolted directly to a solid support without a means for it to freely expand and contract, the panels will buckle. As shown in  FIGS. 1-3 , the panels  2  are mounted to the rigid support posts  4  using a non-movable mount  6  and bolts  8 , such that the panels  2  cannot move in relation to one another. When the HDPE panels expand due to increased ambient temperature, they buckle as shown in  FIG. 1 , rendering them unplayable. Furthermore, the buckling can sheer off the mounting bolts  8 . 
         [0040]    Friction-Reducing, Vibration-Dampening Strip 
         [0041]    A friction-reducing, vibration dampening strip  16  is disposed between the movable mount and the panels. The friction-reducing, vibration dampening strip  16  serves two important purposes unique to the present invention:
       a. It allows the panels to expand and contract smoothly along the face of the mounting bracket; and   b. It reduces undesirable noise-causing vibration between the HDPE backboard panel and the steel mounting components during use.       
 
         [0044]    The noise associated with backboard practice has long been considered a nuisance. 
         [0045]    I have found that if the HDPE panels are bolted directly to the support posts, a very loud undesirable sound is produced by the impact of balls on the HDPE panels. For example, through the use of the strip  16 , I have been able to reduce the sound of a tennis ball hitting the backboard to a decibel level less than a tennis ball hitting a tennis racket, making the backboard far more attractive to potential customers. 
         [0046]    Furthermore, I have also found that the movement of the panels  2  during contraction and expansion can be made uniform by using the strip  16 . The strip  16  can comprise open or closed cell foam, polystyrene, felt, rubber or synthetic material so long as it is weather proof. The surface of the strip  16  constructed to face the HDPE panels  2  should be formed of a low friction material, such as closed cell polystyrene. If desired, the strip  16  can be in multiple layers or separate strips that are placed upon one another, so long as the anti-friction surface faces the HDPE panels  2 . 
         [0047]    Slotted Movable Mount 
         [0048]    It has been found that the use of a movable mount  12 , as shown in  FIGS. 4 and 5 , having elongated slots  14  allows the HDPE panels  2  to expand and contract in a horizontal direction along the movable mount  12 . The movable mount  12  directly replaces the non-movable mount  6  shown in  FIG. 2 . The HDPE panel  2  is bolted directly to the movable bracket  12  using bolts  8  and nuts  9 , utilizing minimal torque on the mounting bolts. Preferably, the bolts  8  and nuts  9  are corrosion resistant. Preferably, the head of the bolt  8  is recessed in the HDPE panel  2 , as shown in  FIG. 5 . The bolts  8  and slot  14  are sized such that the diameter of the bolt  8  is smaller than the width of the slot  14  so that the bolt  8  can slide in the slot  14 . A friction-reducing and vibration-dampening strip  16  is placed between the panel  2  and a surface of the movable mount  12 . The HDPE panel  2  can expand and contract horizontally by the bolts  8  sliding in the slot  14  and the panel  2  sliding along the friction-reducing and vibration dampening strip  16 . 
         [0049]    The movable mount  12  is secured to the support posts  4  using clamps or other securing structure as desired. 
         [0050]    The length of the slot  14  should be sufficient to account for the total horizontal expansion and contraction of all the HDPE panels  2  added together. 
         [0051]    The width of the slot  14  can also be made sufficiently greater than the diameter of the bolt  8  to account for vertical expansion of one panel. The vertical expansion will typically be less than the horizontal expansion since usually one panel is used in the vertical direction and multiple panels are used in the horizontal direction. 
         [0052]    Upward Facing Track and Wheel Movable Mount 
         [0053]    It has been found that the use of a movable mount  20 , as shown in  FIGS. 6 and 7 , having a track  21  and wheels  22  allows the HDPE panels  2  to expand and contract in a horizontal direction along the movable mount  20 . The rotating wheels  22  are attached to the HDPE panels  2  using bolts  8  and nuts  9 . The wheels  22  are then introduced to the track  21 . Preferably, the track  21  is in the form of an upward-facing “U” shaped channel, as shown in  FIG. 6 . Once the wheels  22  are positioned on the track  21 , the nuts  9  are tightened on the backside of the wheels  22 . A friction-reducing and vibration dampening strip  16  is present between the movable mount  20  and the HDPE panels  2 . The nuts  9  should only be tightened sufficiently to hold the HDPE panels  2  against the strip  16  but not so tight that the HDPE panels  2  cannot move in a horizontal direction due to contraction and expansion. This provides a clamping force that secures the HDPE panels  2  to the movable mount  20 . 
         [0054]    The HDPE panels  2  can also be secured to the movable mount  20  using optional anti-lift clamps  23  as shown in  FIG. 9 . The anti-lift clamps  23  are secured to the wheels  22  using the bolt  8  and nut  9 . A part of the anti-lift clamp  23  travels below the track  21 , preventing the wheel  22  from lifting off of the track  21 . 
         [0055]    The movable mount  20  is secured to the support posts  4  using a clamp  24  or other securing structure as desired. 
         [0056]    If desired, the track be angled away from the HDPE panels  2  so that as the HDPE panels  22  expand in the vertical direction the wheels  22  can ride higher on the angled track on the upper tracks compared to the wheels  22  on the bottom most track. 
         [0057]    Forward-Facing Track and Wheel Movable Mount 
         [0058]    It has been found that the use of a movable mount  30 , as shown in  FIGS. 9 and 10 , having a track  32  and wheels  34  allows the HDPE panels  2  to expand and contract in a horizontal direction along the movable mount  30 . 
         [0059]    The rotating wheels  34  are attached to the HDPE panels using bolts  8  and nuts  9 . The wheels  34  and HDPE panels  2  are then introduced to the track  32 . Preferably, the track  32  is in the form of a forward-facing “U” shaped channel as shown in  FIG. 8 . 
         [0060]    Friction-reducing and vibration dampening strips  16  are present between the movable mount  30  and the HDPE panels  2 . The nuts  9  should only be tightened sufficiently to hold the HDPE panels  2  against the strips  16  but not so tight that the HDPE panels  2  cannot move in a horizontal direction due to contraction and expansion. 
         [0061]    The movable mount  30  can be secured to the support posts  4  using curved clamps  38 , bolts  36  and nuts  40 . 
         [0062]    Example of HDPE Panels 
         [0063]    A non-limiting example of a HDPE panel has a width of about 4 feet, a height of about 8 or 10 feet, and a thickness of about ¾ inch. The HDPE panel has a coefficient of expansion of about 0.000067 in/in ° F. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Preferred Thermal Expansion &amp;Contraction Coefficiants for: 
               
               
                 48″ Wide HDPE Backboard Panels 
               
               
                 Note: Provides maximum strength and durability in all tested U.S. 
               
               
                 Climates when mounted in accordance with the enclosed, 
               
               
                 specified mounting systems. 
               
               
                 Thermal expansion or contraction coefficient 0.000067 in/in F. 
               
             
          
           
               
                 Sheet Length (inches) and 
                   
               
               
                 contraction/expansion (inches) 
                 All for 48″ wide panelled increments 
               
             
          
           
               
                 Temperature Differential (F.) 
                 96 
                 120 
                 144 
               
               
                   
               
             
          
           
               
                 5 
                 0.0322 
                 0.0402 
                 0.0482 
               
               
                 10 
                 0.0643 
                 0.0804 
                 0.0965 
               
               
                 15 
                 0.0965 
                 0.1206 
                 0.1447 
               
               
                 20 
                 0.1286 
                 0.1608 
                 0.1930 
               
               
                 25 
                 0.1608 
                 0.2010 
                 0.2412 
               
               
                 30 
                 0.1930 
                 0.2412 
                 0.2894 
               
               
                 35 
                 0.2251 
                 0.2814 
                 0.3377 
               
               
                 40 
                 0.2573 
                 0.3216 
                 0.3859 
               
               
                 45 
                 0.2894 
                 0.3618 
                 0.4342 
               
               
                 50 
                 0.3216 
                 0.4020 
                 0.4824 
               
               
                 55 
                 0.3538 
                 0.4422 
                 0.5306 
               
               
                 60 
                 0.3859 
                 0.4824 
                 0.5789 
               
               
                 65 
                 0.4181 
                 0.5226 
                 0.6271 
               
               
                 70 
                 0.4502 
                 0.5628 
                 0.6754 
               
               
                 75 
                 0.4824 
                 0.6030 
                 0.7236 
               
               
                 80 
                 0.5146 
                 0.6432 
                 0.7718 
               
               
                 85 
                 0.5467 
                 0.6834 
                 0.8201 
               
               
                 90 
                 0.5789 
                 0.7236 
                 0.8683 
               
               
                 95 
                 0.6110 
                 0.7638 
                 0.9166 
               
               
                 100 
                 0.6432 
                 0.8040 
                 0.9648 
               
               
                 105 
                 0.6754 
                 0.8442 
                 1.0130 
               
               
                 110 
                 0.7075 
                 0.8844 
                 1.0613 
               
               
                 115 
                 0.7397 
                 0.9246 
                 1.1095 
               
               
                 120 
                 0.7718 
                 0.9648 
                 1.1578 
               
               
                 125 
                 0.8040 
                 1.0050 
                 1.2060 
               
               
                   
               
             
          
         
       
     
         [0064]    Another example of a suitable HDPE panel is disclosed in my U.S. patent application Ser. No. 12/022,295.  FIG. 11  shows a front view of an exemplary HDPE panel  42  having a surface layer  43  in one color and an other layer  38  having a second color. The HDPE panel  32  has marking  36  in the shape of a line engraved in the surface  44  so the second color of the other layer  8  is exposed.  FIG. 12  is a side view of the HDPE panel  42  having a surface  44  in one color and a marking  46  in the shape of a line engraved in the surface layer  44  so the second color of the other layer  48  is exposed.  FIG. 12  also shows an optional third layer  50 . 
         [0065]    The thickness of the surface layer  44  can be as desired. The surface layer  44  should be sufficiently thick so that any wear marks from use do not show the color of the other layer  48 . Preferably the thickness of the surface layer  44  is about ¼ inch or less, most preferably about ⅛ inch or less. 
         [0066]    The HDPE panels are typically sized at about 4 feet by 8 feet or 4 feet by 10 feet. However, any desired size can be produced. The thickness of the HDPE panels should be selected to provide a desired level of rigidity during use. Typically, a thickness from about 0.5 inch to about 2 inches, preferably about 0.7 to about 1.5 inches, is sufficient. If the panels are too thick, then weight and higher cost may become a problem. If the panels are too thin, they may undesirably flex during use. 
         [0067]    The HDPE panels can withstand the impact of lacrosse balls, soccer balls, baseballs and soccer balls without being punctured, split or otherwise damaged. The HDPE panels are highly immune to degradation or damage due to drastic temperature variations, weather or air pollution conditions. 
         [0068]    The HDPE materials are now well known. Thus, the HDPE material can be selected as desired. Formation of panels using extrusion methods are also now well known. Those skilled in the art will easily be able to use known manufacturing methods to form the novel HDPE panels described herein. While the different layers of the HDPE panels can be bonded using any desired method, preferably the layers are coextruded. 
         [0069]    Coloration of HDPE materials by addition of pigments is also well known. Using the description provided herein, one skilled in the art will be able to use known methods to coextrude the novel HDPE panels having different colored layers. 
         [0070]    Preferably, the HDPE material includes ultra-violet inhibitors to reduce damage caused by sunlight. 
         [0071]    The markings  46  can be in any shape as desired. Non-limiting examples a markings  46  are tennis net lines and target markings, such as a Lacrosse Goal or Soccer Goal, engraved into the panel, thus, providing a permanent, no-maintenance feature. 
         [0072]    The HDPE panels can be used in a backboard training device by mounting a plurality of them to a rigid support. Preferably, a movable mount is utilized to avoid buckling due to expansion and contraction. An example of a backboard training  52  device utilizing multiple HDPE panels  42  is shown in  FIG. 3 , having the markings  46  lined up to form a tennis net line. 
         [0073]    If the panels are to be used as a tennis training backboard, preferably, the surface layer  44  is colored green and the other layer  48  is colored white, so that white lines representing the net and/or out of bounds are clearly defined. 
         [0074]    While the claimed invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one of ordinary skill in the art that various changes and modifications can be made to the claimed invention without departing from the spirit and scope thereof.
A backboard training device having high density polyethylene panels mounted so that buckling is avoided and unwanted sound is reduced.