Patent Publication Number: US-2010117261-A1

Title: Method of making a plastic bench top

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to plastic manufacturing processes, and particularly to a method of making a plastic bench top that uses less material while preserving strength and rigidity. 
     2. Description of the Related Art 
     Elongated plastic benches, which are typically formed from high density polyethylene and other plastics, are commonly found in locker rooms and the like. The bench tops for such benches are typically formed from elongated plastic members having thicknesses of between approximately 1⅜ inches and 1½ inches by extrusion or molding processes. This thickness provides a bench top having sufficient rigidity and structural stability for usage in a high volume area, such as a locker room. 
     Benches formed from plastic having such thicknesses, however, are difficult and costly to manufacture and, due to their volumes, costly to ship. It would be desirable to provide a plastic bench top having the same high level of rigidity and structural stability, but being formed from a plastic having a thickness of less than one inch, allowing for ease of manufacturing, in terms of labor and cost, and ease in shipping. 
     Thus, a method of making a plastic bench top solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The method of making a plastic bench top is a method for manufacturing bench tops having a U-shaped channel formed by flanges depending from opposite sides of an elongated planar member. The bench top is mounted on pedestals, legs or the like. In general, the method includes forming a fold line by machining or by heating along the lateral edges of the elongated planar member to define flanges, folding the flanges so that the flanges are orthogonal to the planar member, and welding or fusing the joint, if necessary. Alternatively, discrete flange members may be heated simultaneously with the elongated lateral edges of the planar member, the heating element is withdrawn from between the flange and the planar member, and the flange is butted against the longitudinal edge to form a butt weld. 
     Three different methods may be used to form the fold line. In one method, V-shaped grooves are machined in the planar member. The flanges are folded to mate the diagonal sides of the groove, the joint being made permanent by a fillet weld. In a second method, arcuate or cylindrical heating elements are placed on opposite sides of the planar member to soften the plastic, which is then folded in radius bends to form the channel. In a third method, V-shaped heating elements are used to form V-shaped grooves in the planar member on opposite elongated sides to form the flanges, which are than folded orthogonal to the planar member and fused together to form the channel. 
     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a bench including a bench top formed from the method of making a plastic bench top according to the present invention. 
         FIGS. 2A and 2B  are perspective views illustrating a first embodiment of the method of making a plastic bench top according to the present invention. 
         FIGS. 3A and 3B  are end views illustrating the method of  FIGS. 2A and 2B . 
         FIGS. 4A and 4B  are end views illustrating an alternative embodiment of the method of making a plastic bench top according to the present invention. 
         FIGS. 5A and 5B  are side views illustrating another alternative embodiment of the method of making a plastic bench top according to the present invention. 
         FIGS. 6A and 6B  are side views illustrating yet another alternative embodiment of the method of making a plastic bench top according to the present invention. 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention provides a method for making plastic bench tops for benches, such as the exemplary bench illustrated in  FIG. 1 . As shown, the exemplary bench includes a plastic bench top  10  having a U-shaped channel  24 . The bench top  10  may be mounted on pedestals  12 , legs or the like. It should be understood that the bench top  10  is shown for exemplary purposes only, and may have any desired dimensions, color, etc. Such elongated, plastic bench tops  10  are often used in locker rooms and the like, where durable and water-resistant benches are desired. 
     As best shown in  FIGS. 2A and 3A , the method involves forming the bench top  10  from an elongated, planar plastic member  14  having a pair of laterally opposed, longitudinally extending side edges  18 , a top surface  21  and a bottom surface  23 . A pair of longitudinally extending V-shaped grooves  16  are then formed in the bottom surface  23  thereof, e.g., by machining the plastic with a cutting tool. The pair of longitudinally extending V-shaped grooves  16  divide the elongated plastic member  14  into a central portion  20  and a pair of laterally opposed flanges  22 . The pair of longitudinally extending V-shaped grooves  16  may be cut, drilled or otherwise machine formed or removed from the bottom surface of the elongated plastic member  14 . Alternatively, the V-shaped grooves  16  may be formed during the molding process of forming the elongated plastic member  14 . Exemplary dimensions include a thickness of between approximately ½ inches and one inch. Elongated plastic member  14  may be formed from any suitable type of plastic, such as, for example, high density polyethylene (HDPE). 
     Alternatively, as illustrated in  FIG. 4A , the pair of longitudinally extending V-shaped grooves  16  may be formed by melting the bottom surface  23  of the elongated plastic member  14  through the application of heat thereto by an external heat source, such as a pair of longitudinally extending V-shaped heating elements H 1 . It should be understood that V-shaped grooves  16  may be formed via any suitable method. 
     The flanges  22  are then folded about the pair of longitudinally extending V-shaped grooves  16  so that opposing faces of the V-shaped groove  16  bear against each other and the pair of laterally opposed flanges extend substantially orthogonal to the central portion  20 , forming the U-shaped channel  24  on the bottom side of the plastic bench top  10 . When the pair of longitudinally extending V-shaped grooves  16  are cut, drilled or otherwise machine formed or removed from the bottom surface  23  of the elongated plastic member  14 , as in  FIGS. 2A ,  2 B,  3 A and  3 B, the pair of side portions  22  may be fillet welded or fused to the central portion  20  to secure the flanges  22  in place. The fillet welds from this welding process are designated generally as  30  in  FIG. 3B . 
     When the pair of longitudinally extending V-shaped grooves  16  are melted into the bottom surface  23  of the elongated plastic member  14 , as in  FIG. 4A , the initial melting removes the need for additional welding to secure the flanges  22  in place, as opposing faces of the V-shaped groove  16  fuse together. Once cooled, the flanges  22  are fixed in place with respect to the central portion  20 . The seams from the fused joint are designated generally as  32  in  FIG. 4B . 
     In the alternative embodiment of  FIGS. 5A and 5B , the method includes, as in the previous embodiment, first providing an elongated planar plastic member  14  having a pair of laterally opposed, longitudinally extending side edges  18 , a top surface  21  and a bottom surface  23 . As shown in  FIG. 5A , a work surface W is further provided, with top surface  21  resting on the work surface W. Heat is next applied to at least the bottom surface  23  of the elongated plastic member  14  to form a pair of longitudinally extending melted regions  31 , which divide the elongated plastic member  14  into the central portion  20  and the pair of flanges  22 . As shown in  FIG. 5A , the work surface W may include recesses to hold additional heating elements H 2 , so that heat is applied by heating elements H 2  to the bottom surface  23  and well as the top surface  21 . The flanges  22  are then folded about the pair of longitudinally extending melted regions  31  so that the flanges extend substantially orthogonal to the central portion  20  to form the bench top  10 . The heating elements are arcuate or cylindrical in order to form radius bends defining the flanges  22 . 
     As a further alternative embodiment, illustrated in  FIGS. 6A and 6B , an elongated planar plastic member  120  having a pair of laterally opposed, longitudinally extending side edges  119 , a top surface  121  and a bottom surface  123  is provided, as in the previous embodiments, as well as a pair of longitudinally extending leg members  122 , each having opposed top and bottom surfaces  127 ,  125 , respectively. Heat is then applied from an external heat source, such as the pair of heating elements H 3 , to the bottom surface  123  of the elongated plastic member  120  adjacent the laterally opposed, longitudinally extending side edges  119  thereof, and the heat is further simultaneously applied to the top surfaces  127  of the pair of longitudinally extending leg members  122  by placing heating elements H 3  between the planar member  120  and the leg members  122 . The heating elements H 3  are then removed, and the heated top surfaces  127  of the pair of longitudinally extending leg members  122  are butt welded to the heated bottom surface  123  of the elongated plastic member  120  to form the plastic bench top  100 , the leg members  122  defining the channel flanges. The seams from this butt welding process are designated generally as  124  in  FIG. 6B . Preferably, as shown in  FIG. 6A , the heating elements H 3  are movably mounted with respect to work surface W. Thus, after melting, the heating elements H 3  may be slid to the sides, allowing the leg members  122  to drop and be positioned on the melted bottom surface  123 . 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.