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[0001]    This application claims the benefit of the filing date of a provisional application Ser. No. 60/738,282 which was filed on Nov. 18, 2005. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to molded plastic panels for covering building surfaces. 
         [0004]    2. Description of the Related Art 
         [0005]    Molded plastic siding panels for exterior building walls are known in the prior art. These molded panels are made from synthetic thermoplastic polymers, including polypropylene, polyethylene, and various mixtures and copolymers thereof. 
         [0006]    Laterally elongated molded plastic panels are nailed to a wall support surface in horizontal rows partially overlapping each other in order to provide a pleasing appearance combined with a weather-resistant protective layer over the support surface. 
         [0007]    The molded plastic panels are typically installed by securing several adjacent courses to a wall support surface, starting with a bottom course. A lower marginal edge region of each panel in courses above the bottom course overlaps a panel in the course immediately below. Side marginal edge regions of each panel overlap side marginal regions of adjacent panels. 
         [0008]    Various mechanisms have been proposed for interlocking lower marginal edge regions of the plastic panels with panels in the course immediately below. Some of these methods include a locking tab extending forwardly and downwardly from the top of each panel, and a return leg extending upwardly and rearwardly from the bottom of each panel. As each panel is installed, the return leg of the panel being installed is interlocked with the locking tab of the panel below it, which has previously been installed. These interlocking components may require difficult and time consuming manufacturing processes. 
         [0009]    U.S. Pat. No. 6,224,701, issued to D. A. Bryant, et al. on May 1, 2001, and assigned to the assignee of the present invention, discloses a molded plastic siding panel. This panel is molded with the nail hem formed from two mating components connected by a living hinge, and the locking tab projecting upward from the top of the panel. After molding, the living hinge of the nail hem is folded, and the two opposing components are secured to each other initially by rivets on one half fitting with an openings on the other half. The two halves are then thermally or ultrasonically joined together. While this process has been found to produce a siding panel of high quality and which is easy to install, a simplified manufacturing process, having a reduced number of steps, is desired. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention provides a thermoplastic panel for covering building surfaces that is simpler to produce than conventional panels. The method of the present invention can be used to produce panels for a variety of applications including exterior walls, roofs, soffits and the like. In a preferred embodiment, the panel includes a body with an attachment hem and locking tab adjacent to the upper portion of the body, and a return leg attached to the bottom of the body. 
         [0011]    The panel is injection molded in a manner that permits it to be withdrawn from the mold in a shape that is very close to the final shape of the panel, with the attachment hem already completely formed, and the locking tab close to its final position. Pressure is applied to the locking tab as it cools, bringing it closer to the panel, so that when it is fully solidified, it is within its final, desired position. 
         [0012]    The use of this injection molding method eliminates the need to form a hinge within the nail hem, fold the nail hem, and then attach the opposing portions of the nail hem together, after injection molding the panel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]      FIG. 1  is a fragmentary front elevational view of a building wall covered with plastic panels made in accordance with the present invention. 
           [0014]      FIG. 2  is a front elevational view of a plastic siding panel according to the present invention. 
           [0015]      FIG. 3  is a left side elevational view of a plastic siding panel according to the present invention. 
           [0016]      FIG. 4  is a right side elevational view of a plastic siding panel according to the present invention. 
           [0017]      FIG. 5  is a side elevational view of Detail  5  in  FIG. 4 . 
           [0018]      FIG. 6  is a side elevational view of Detail  6  in  FIG. 3 . 
           [0019]      FIG. 7  is a side elevational view of Detail  7  in  FIG. 4 . 
       
    
    
       [0020]    Like reference characters denote like elements throughout the drawings. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    The present invention is directed toward an improved molded plastic panel for covering building surfaces. While the following description refers to an embodiment directed to a wall panel, the invention is applicable to other building surfaces such as walls roofs and soffits for example. 
         [0022]    Referring to  FIG. 1 , an exterior wall  10  is covered by several plastic panels  11 . The panels  11  each include three laterally extending, generally parallel rows of simulated wood shingles  12 , but the number of rows may vary. The shingles  12  preferably have irregular widths, and are separated from shingles in the same row by vertically extending gaps  15  of varying widths. The panels  11  may cover an entire exterior wall as shown in  FIG. 1 , or they may be combined with other exterior wall coverings. 
         [0023]    Referring to  FIGS. 2-4 , one of the panels  11  is shown in greater detail. The panel  11  includes a body  16  divided into a plurality of generally parallel, laterally extending rows, with three rows  18 ,  20 ,  22  present in the illustrated example. The gaps  15  between the shingles  12  have widths that vary randomly within predetermined limits in order to camouflage spacings between adjacent panels accompanying thermal contraction and expansion. 
         [0024]    Referring to  FIGS. 3-5 , an attachment hem  24  extends upward from the top of the body  16 . The attachment hem  24  includes an attachment body  36  having a positioning rib  28  extending rearwardly therefrom. A plurality of nail holes  30 , surrounded by rearwardly projecting reinforcing ribs  32 , are defined within the attachment hem  24 . The positioning rib  28 , and nail hole reinforcing ribs  32 , are dimensioned to permit the entire panel  11  to fit flat against the side of a wall  10 . 
         [0025]    A locking tab  34  extends downward and slightly outward from the attachment body  16 , defining a channel  36  between itself and the body  16 . The locking tab  34  extends substantially across the entire top of the panel  11 . The locking tab  34  includes a tapered nose  38  and the locking rib  40  projecting into the channel  36 . 
         [0026]    Referring to  FIGS. 3 and 6 , a locating ridge  42  projects rearwardly from the intersection of the upper and middle rows  18  and  20 , respectively. 
         [0027]    Referring to  FIGS. 4 and 7 , the bottom of the body  16  includes a return leg  44  extending upward and rearward therefrom. The return leg  44  defines a channel  46  between itself and the body  20 . The return leg  44  includes a base portion  48  and a tip portion  50 , with an obtusely angled corner  52  defined therebetween. 
         [0028]    The panel  11  is preferably made from a thermoplastic polymer selected from the group consisting of polyolefin, polycarbonate, polyvinyl chloride, and mixtures and copolymers thereof Polyolefins, especially polypropylene and mixtures and copolymers with polyethylene, are particularly preferred. 
         [0029]    The panel  11  is manufactured by injection molding. The mold includes an elongated member structured to fit under that portion of the plastic that will become the locking tab  34 , and which takes up the space of the channel  36 . As the opposing molds portions are withdrawn from a panel  11 , the piece taking up the space of the channel  36  will be moved downward with respect to the panel  11 , out of the channel  36 , prior to or during removal of the mold portion from the panel  11 . At this point, the panel  36  is wider than desired, but the plastic will still be warm and flexible. Downward and inward pressure applied to the locking tab  34  will cause it to cool and solidify in the desired position. 
         [0030]    Referring to  FIG. 2 , the left side of the panel  11  includes an outwardly extending fin  54 , extending from the middle row  20 . Similarly, the right side of the panel  11  includes a pair of outwardly extending fins  56 ,  58 , extending from the upper row  18  and lower row  22 , respectively. The fins  54 ,  56 ,  58  extend slightly rearwardly, so that they will nestle underneath adjacent panels. 
         [0031]    To install the panels  11  on a wall  10 , a starter strip is first attached to the wall along its lower edge, in a manner well known in the art of siding installation, as described in U.S. Pat. No. 6,224,701, owned by the assignee of this invention, and expressly incorporated herewith. The starter strips include a downwardly opening groove structured to receive the return leg  44  of the lowermost row of panels  11 . With the return leg  44  secured within the starter strip, a panel is secured in place. The engagement of the return leg  44  and starter strip is structured to permit horizontal expansion and contraction of the panel. The upper portion of each panel  11  is secured by driving fasteners through the nail holes  30  and into the wall  10 . The holes  30  are preferably elongated to permit expansion and contraction of the panel  11  without buckling. Horizontally adjacent panels  11  are installed with the flange  54  of one panel inserted between the adjacent flanges  56 ,  58  of the adjacent panel, thereby resisting vertical movement of one horizontally adjacent panel with respect to another, while permitting horizontal movement due to thermal expansion and contraction. The varying widths of the gaps  15  make it more difficult to determine the locations of the joints between adjacent panels, regardless of thermal expansion and contraction. 
         [0032]    Once the lowermost row of panels  11  is installed, the next row of panels is installed by inserting the return legs  44  underneath the locking tabs  34 , thereby securing the next row of panels to the row of panels below it. Horizontally adjacent panels are joined in the same manner as horizontally adjacent panels in the previous row. Fasteners are again driven through the holes  30  within the attachment hem  24  to secure the upper edge of the panel to the wall  10 . The process continues until a desired portion of the wall  10  is covered with panels  11 . 
         [0033]    The present invention therefore provides a molded panel having a continuous locking tab along its top edge, extending between the sides of the panel without any openings or spaces therein. Such a continuous tab facilitates connecting the panel with a vertically adjacent panel. The panel may be made by a simplified manufacturing procedure, having fewer steps. 
         [0034]    While specific embodiments of the invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. For example, panels produced in accordance with the method of the present invention can be used as roofing panels and in soffits. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Summary:
A molded panel for buildings is manufactured in a manner that permits the blocking tab along the upper edge of the panel to be molded in a position that is close to its final desired position. Pressure is applied to the locking tab as it cools, thereby bringing the locking tab into its final position.