A molded plastic sliding panel used for covering an exterior building wall surface is made up of a body portion, an attachment portion provided above and adjacent to the body portion, a top locking portion extending horizontally across an upper portion of the sliding panel and a bottom locking portion provided at the bottom of the body portion. The top locking portion is adapted to engage with the bottom locking portion on an upper adjacent siding panel. The attachment portion can contain a plurality of apertures provided therein which sequentially become more elongated as they are positioned toward a side edge of the attachment portion in order to deal with thermal expansion and contraction of the panel.

FIELD OF THE INVENTION 
       [0001]    The present invention relates to molded plastic siding panels which are used to cover an exterior building wall surface and, in particular, to a molded plastic siding panel which has improved locking and attachment features. 
       BACKGROUND OF THE INVENTION 
       [0002]    Molded plastic siding panels used on exterior wall surfaces are well known in the prior art. These siding panels are typically made of synthetic thermoplastic polymers and are nailed to a wall support surface in horizontal rows partially overlapping each other for aesthetic purposes. The siding panels are typically installed on a wall surface starting with a bottom course and nailing several adjacent courses. Side marginal edge regions of each panel can mate with adjacent panels utilizing a male-female tongue-in-groove configuration. 
         [0003]    Various arrangements have been proposed for interlocking a siding panel with another siding panel provided directly above it. For example, U.S. Pat. No. 6,224,701 to Bryant et al discloses a molded plastic panel for covering an exterior building wall. The panel has a panel body which includes a locking lip for engaging a locking tab on an adjacent panel and a flexible hinge which connects the locking lip to the panel body. The panel also has an attachment hem or nail hem adjacent to a top wall having laterally elongated, laterally spaced nail slots  31  of the same size for locating nails. 
         [0004]    U.S. Pat. No. 6,955,019 to Donlin et al shows a wall covering comprising a plurality of plastic panels which are mounted on a support surface with a lower marginal edge region of one panel overlaying an upper marginal edge region of a previously mounted panel in a lower course and with a side marginal edge region of one panel overlying the side marginal edge region of the previously mounted adjacent panel in the same course. The marginal edge regions are provided with interlocks which engage and secure both the overlapping upper and lower marginal edge regions and the overlapping side marginal edge regions. For securing a panel to a support surface, the upper marginal edge region of each panel is formed with a row of elongated laterally spaced nailing apertures of the same size. 
         [0005]    In conventional panels which have intermittent locks, the siding installers may occasionally miss a lock and due to the line of sight during the installation, it may not be detected until the installer is finished with the installation and is reviewing the work. The missed lock would then be readily apparent and the correction of this would require the installer to reset the panel. 
         [0006]    Although U.S. Pat. No. 6,715,250 discloses a conventional siding panel which utilizes a continuous lock feature in which the panel is injection molded with a living hinge which is folded and welded to the panel to form the top lock, this panel requires additional steps to form the top lock. 
         [0007]    Additionally, conventional siding panels are provided with nail slots having a center nail hole that substantially anchors the location of the panel with all of the other nail holes being slots of the same size in which nails are inserted and left slightly raised so they do not anchor the panel to the wall and thereby allow the panel to expand and contract with a change in temperature and still remain flat on the wall. However, these conventional panels have a problem in that the center hole must be aligned with a stud in a non-nail based sheathing installation, i.e., a sheathing not capable of adequately supporting a fastener. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to provide a molded plastic siding panel having a continuous top interlocking mechanism that will easily allow the alignment of adjacent siding panels during installation. 
         [0009]    It is a further object of the present invention to provide a plastic siding panel having an attachment portion with nail slots provided therein which allow any slot provided on the panel to be used for the center location, such that the stud closest to the center of the panel to be the anchoring nail location. 
         [0010]    It is still a further object of the present invention to provide a plastic siding panel having an attachment portion with nail slots provided therein which allows any nail slot provided on the panel to be used as the centermost anchoring location regardless of the cut in the panel or location of intermediate framing members. 
         [0011]    These and other objects of the present invention are met by providing a monolithic molded plastic siding panel which is made in one molding process and comprises a continuous top interlocking mechanism which facilitates an easier installation by minimizing the chances of a non-continuous top interlocking mechanism not engaging with a bottom interlocking mechanism provided on an adjacent panel. 
         [0012]    These and other objects of the present invention are met by providing a plastic siding panel which has a continuous top interlocking mechanism formed by a separate member which engages with the attachment portion in a snap-fit connection. 
         [0013]    These and other objects of the present invention are also met by providing a plastic siding panel having an attachment portion containing apertures which gradually become more horizontally elongated as they are positioned away from a center portion of the attachment portion, thereby enabling any of the apertures to serve as a center anchoring position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  illustrates the top and bottom locking mechanisms of a plastic siding panel according to an embodiment of the present invention. 
           [0015]      FIG. 2  illustrates a top interlocking mechanism of a plastic siding panel according to another embodiment of the present invention. 
           [0016]      FIG. 3  illustrates the apertures contained in an attachment portion of a plastic siding panel according to an embodiment of the present invention. 
           [0017]      FIG. 4  illustrates an embodiment of an attachment portion of a siding panel of the present invention where the nail slots progressively become wider as they extend from right to left. 
           [0018]      FIG. 5  illustrates an embodiment of an attachment portion of a siding panel of the present invention where the nail slots progressively become wider as they extend from left to right. 
           [0019]      FIG. 6  illustrates an embodiment of an attachment portion of a siding panel of the present invention where the nail slots have the same width for a portion of the right side of the siding attachment portion and then progressively become wider as they extend from right to left. 
           [0020]      FIG. 7  illustrates an embodiment of an attachment portion of a siding panel of the present invention where the nail slots have the same width for a portion of the left side of the siding attachment portion and then progressively become wider as they extend from left to right. 
           [0021]      FIG. 8  illustrates an embodiment of an attachment portion of a siding panel of the present invention where the nail slots have the same width at a center portion of the siding attachment portion and then progressively become wider as they extend outwardly from the siding center portion. 
           [0022]      FIG. 9  illustrates an embodiment of an attachment portion of a siding panel of the present invention where a conventional siding top interlocking mechanism is converted into a continuous top interlocking mechanism of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 1  illustrates an embodiment of a plastic siding panel  1  according to the present invention. The plastic siding panel  1  is monolithic and is prepared by molding a thermoplastic resin selected from the group consisting of a polyolefin, a polycarbonate, polyvinyl chloride, and mixtures and copolymers thereof. Preferably, the thermoplastic resin is a polyolefin, with polypropylene being especially preferred. Conventional additives used in siding panels can be present in the siding panel of the present invention and include fillers, pigments, UV inhibitors, anti-oxidants, etc. 
         [0024]    The thermoplastic resin can be formed into the monolithic plastic siding panel of the present invention by conventional molding processes such as injection molding, compression molding, transfer molding, extrusion molding, blow molding, etc., with injection molding being preferred. As illustrated in  FIG. 1 , the monolithic molded plastic siding panel  1  of the present invention comprises a rectangular shaped body portion  2  and a strip-shaped attachment portion  3  provided immediately above and adjacent to the body portion  2 . 
         [0025]    As illustrated in  FIGS. 1 and 3 , an embodiment of an attachment portion  3  of the present invention is provided with a plurality of apertures  15  which sequentially become more horizontally elongated as they are positioned away from a center position on the attachment portion  3 . The apertures  15  serve as nail slots for fastening the plastic siding panel  1  to a wall structure. The varying widths of the apertures  15  eliminate the need to initially fasten the panel through a center nail slot and will prevent the siding panel  1  from distorting in dramatic temperatures regardless of the width of the panel. It is only necessary that the fastener be placed at the center of the aperture or nail slot  15 . Markings can be provided on the attachment portion  3  to indicate the center of the nail slots  15  and/or the nail slots may be formed to guide the fasteners into the proper position. 
         [0026]    A continuous top interlocking mechanism  5  is provided on an upper portion of the siding panel  1 , preferably on the attachment portion  3  immediately below the apertures  15 . The top interlocking mechanism  5  is adapted to engage with a bottom interlocking mechanism  10  provided on an adjacent panel to align the panels on the wall structure during installation. As illustrated in  FIG. 1 , the top interlocking mechanism  5  comprises a plurality of spaced-apart ledge portions  6  which extend laterally from the attachment portion  3 . The spaced-apart ledge portions  6  are joined by a continuous side wall portion  7  which is joined to and extends downwardly from the ledge portions  6 . Alternatively, the continuous top interlocking mechanism  5  can be provided on the attachment portion  3  above the apertures  15  without departing from the scope of the present invention. 
         [0027]    At a lower portion of the body portion  2 , a bottom interlocking mechanism  11  is provided. The bottom interlocking mechanism  10  comprises a continuous ledge portion  11  which extends laterally along the length of the body portion  2  in a direction opposite to the ledge portions  6  and a continuous lip portion  12  which extends upwardly from the continuous ledge portion  11 . The bottom interlocking mechanism  10  is adapted to resiliently engage with the top interlocking mechanism  5  through the resilient engagement between the continuous side wall  7  and the continuous lip portion  12 . As with conventional siding panels, a longitudinally extending groove can be provided in one of the side surfaces of the body portion  2  and a longitudinally extending ridge can be provided in the opposite side surface which is adapted to engage with a longitudinally extending groove provided in an adjacent siding panel. 
         [0028]    Another embodiment of the top interlocking mechanism  5  of the present invention is illustrated in  FIG. 2 . In this embodiment, the attachment portion  3  is molded to form a first connection member  16  containing a space  17  defined by a bottom wall  18  and inwardly extending lips  19  which is adapted to receive a plug portion  21  of a second connection member  20 . The second connection member  20  is an extruded part which extends laterally continuously along the width of the attachment portion  3  and together forms the top interlocking mechanism  5  with the first connection member  16  when the plug portion  21  is engaged in the space  17 . The plug portion  21  has a bottom wall  24  which flush engages with the bottom wall  18  of the space  17  and outwardly extending lips  25  having a top surface which sealingly engages with the bottom surface of lips  19  to firmly attach the second connection member  20  to the first connection member  16  and form another embodiment of the continuous top interlocking mechanism  5  of the present invention. 
         [0029]      FIG. 9  illustrates another embodiment of the top interlocking mechanism  5  of the present invention wherein a conventional top interlocking mechanism  30  made up of a plurality of “L-shaped” spaced-apart locking members  31  is converted to a continuous top interlocking mechanism of the present invention by inserting a continuous “U-shaped” member  32  by inserting U-shaped member  32  under the L-shaped member  31  along the entire width of the attachment portion  3 . 
         [0030]      FIGS. 4-8  all illustrated different embodiments of the nail slots  15  provided on an attachment portion  3  of the present invention. In  FIG. 4 , the nail slots  15  progressively become wider as they are provided in the leftward direction on the attachment portion  3 .  FIG. 5  illustrates an embodiment of an attachment portion  3  of the present invention in which the nail slots  15  progressively become wider as they are provided in the rightward direction along the attachment portion  3 .  FIG. 6  illustrates an attachment portion  3  according to an embodiment of the present invention where the nail slots  15  have a constant size at the right side of the attachment portion  3  and then become progressively wider as they are provided in the leftward direction along the attachment portion  3 .  FIG. 7  illustrates another embodiment of an attachment portion  3  of the present invention where the nail slots  15  have a constant size at the left side of the attachment portion  3  and then become progressively wider as they are provided in the rightward direction along the attachment portion  3 .  FIG. 8  illustrates an attachment portion  3  according to another embodiment of the present invention wherein the nail slots  15  have a constant size at a central portion of the attachment portion  3  and become progressively wider as they are provided outwardly from the central portion of the attachment portion  3 . 
         [0031]    By providing the attachment portion  3  with nail slots  15  having a different width, it is not necessary for a center nail slot of an attachment portion to be centered on a nail stud during installation of the plastic siding as the varying widths of at least some of the nail slots  15  allow them to be used as the center nail slot and still give the siding panel the ability to compensate for thermal expansion and reduction. Additionally, the attachment portion of the present invention having nail slots of varying widths are especially suitable for use in non-nail based sheathing applications using rigid foam, gypsum, etc. where the varying widths of the nail slots allow the nails slots to be easily located over a framing member without the need for a center nail hole to be provided over a framing member, or in installations where a sheathing member is not used. 
         [0032]    The body  2  of the siding panels of the present invention can be provided with a decorative pattern characteristic of conventional roofing and siding materials such as shake shingles, tile, brick or the like and the color of the siding panel can be evenly distributed throughout the resin, painted on the siding panel or achieved by a combination thereof. Moreover, since the monolithic plastic siding panels of the present invention are molded in one molding process step, there is no need for hinges or other attached components as is typically required with the prior art plastic siding panels. 
         [0033]    Although the present invention has been described in connection with specific embodiments, it is not limited to the particular constructions herein disclosed and shown in the drawings and also comprises any modifications or equivalents within the scope of the appended claims.