Abstract:
A vinyl siding panel which includes a top lock, a medial main body portion, a bottom lock, and a nailing hem adjacent the top lock comprises a channel with nail apertures in the channel base for receiving siding nails. The channel has an open end which has a dimension smaller than the nail head diameter so that the nail head bears against shoulders or bearing surfaces formed adjacent the channel. The channel can be of rectangular or tapered cross-section in order to space the nail head away from the nail apertures and thereby eliminate stress concentrations at the apertures. The lock structures are generally complementary in shape so that they interlock with other siding panels of like construction. The panel can be reinforced along its length for added rigidity. One area of reinforcement is the channel nailing hem which can be reinforced by extruding additional material to form the channel or by providing an elongated trough-like insert nested within the channel. The channel nailing hem provides improved wind resistance and enhances strength and rigidity of the panel.

Description:
FIELD OF THE INVENTION 
     The present invention pertains to interlocking panels with enhanced ruggedness and improved wind resistance, and in particular, to panels having channel nailing hems primarily intended for use as siding on houses and other structures. 
     BACKGROUND OF THE INVENTION 
     Siding composed of vinyl or other plastic material is a common medium for use as an external covering of a structure. Such siding is fabricated as elongate panels having connectors formed along the lengths of the upper and lower edges. In use, the siding panels are arranged in horizontal interlocking tiers. In general, siding panels include a top lock that is configured to interlock with a bottom lock of another panel. A nailing hem comprising a series of slots for receiving nails to attach the panel to an underlying structure is generally provided near the top lock of each panel. 
     A premium siding panel will frequently be formed by a pair of materials fused together. The outer layer or capstock is composed of a weather, wear and impact resistant material which also provides a good appearance. The underlayer or substrate is composed of a stiffer material to increase the strength of the panel. A focus of vinyl siding development has been improved resistance to winds. When a building is buffeted by winds, the stress concentration occurs at the nail slots in the nailing hem, and various configurations have been proposed to improve the attachment of the panel to the underlaying wall. 
     Conventional nailing hems can be classified into three general categories: single thickness, multiple thickness and rollover. Examples of single thickness nailing hems are illustrated in FIGS. 1A-2B. In FIGS. 1A-1B and  2 A- 2 B, conventional siding panel  10  includes a top lock  12 , a nailing hem  14 , a bottom lock  16 , and a medial body  18 . Body  18  ordinarily has a pair of faces  20 ,  22  separated by a center butt  24 . Top lock  12  is bent to form a dogleg protrusion  26  which extends downwardly over the upper face  20  of the siding panel to form a groove  28 . Bottom lock  16  has a channel-like shape. The distal wall  30  of the bottom lock is inclined back toward the lower face  22  of the body. The distal wall  30  of one panel is snugly fit within groove  28  of another panel to interlock the adjacent siding panels. Nailing hem  14  extends upward from top lock  12  and is provided with elongated slots  32  into which siding nails N or staples or screws are driven to attach the panel to an underlaying wall. 
     In general siding nails are not driven into the wall fully so that the nail head undersurface does not bear against the nailing hem. This clearance accommodates movement of the panels which occur due to fluctuations in temperature and other environmental conditions. In general, when nails N are driven through the nail slots, and the installed panels are exposed to winds, the panel will tend to move in the direction of arrow A in FIG.  1 B. This forces the panel against the nail head and the nail head exerts a load on a flat surface of the panel. The nail slot is thus the locus of a stress concentration, and eventually the slot can open further and ultimately can tear due to wind load. 
     The panel of FIGS. 1A-1B has a conventional lock geometry, and the panel of FIGS. 2A-2B has a more robust lock geometry in which the top lock occupies much more of the space in the channel-like bottom lock. 
     Examples of nailing hems configured of a double thickness of siding material are shown in FIGS. 3A-3B and  4 A- 4 B. Double thickness nailing hems are formed by providing additional panel material in a folded-over configuration. Siding panel  10  of FIGS. 3A-3B includes a variation on the top and bottom locks as well. Top lock  12  has an integrally formed double thickness nailing hem  14  above the lock structure, and a triangular cross-section lock with a free leg  34  opposite the upper face  20 . Bottom lock  16  has on its distal wall  30  an integrally formed hook  36  at its tip. When adjacent panels are interconnected, hook  36  of the bottom lock slides past free leg  34  of the adjacent lock and fits snugly against upper face  20  as shown in FIG.  3 B. Nailing hem  14  is provided with elongated nail slots to receive siding nails N or staples. Another embodiment of a double thickness nailing hem  14  is shown in FIGS. 4A-4B which shows a reinforced dog-leg type top lock  12 . The lock structure in this type of panel is configured so that the top lock occupies much of the space in the channel shape of the bottom lock so that the top lock abuts against lower face  22  of the adjacent panel. The top lock is also reinforced with an additional strip of material to enhance the rigidity of the panel, particularly in the lock area. Again, as with single thickness nailing hems, siding nails N are driven only to the extent that the undersurface of the nail head does not contact the nailing hem. While the double thickness nailing hem provides improved strength, the stress concentrations around the nail slot are still present and pose the same problems as the single thickness. That is, when subject to high winds, the nail head will tend to further open the slots and can ultimately lead to failure. 
     Examples of nailing hems with a rollover shape are shown in FIGS. 5A-5B and  6 A- 6 B. Panel  10  illustrated in FIGS. 5A-5B has a conventional lock structure with nailing hem  14  extending above top lock  12 . Nailing hem  14  has an open roll  40  formed at its top end. Siding nails N or staples or screws are driven to secure panel  10  to the extent that the undersurface of the nail head bears against roll  40 . The panel illustrated in FIGS. 6A-6B also has a conventional lock structure with nailing hem  14  extending above the top lock. Nailing hem  14  has a closed roll  42  formed at its top end. Siding nails N are driven to secure panel  10  to the extent that the undersurface of the nail head bears against roll  42 . In both of these types of nailing hems, elongate slots are provided for siding nails N. In these rollover nailing hems, much of the force that the nails exert on the nailing hems are borne by the roll portions to alleviate the stress concentrations on the nail slots. However, rollover nailing hems are an imperfect solution because upon wind loading, the panels tend to move and the nail head tends to exert a load on the flat surfaces around the nail slots making tearing and failure more likely. 
     SUMMARY OF THE INVENTION 
     The present invention pertains to interlocking panels having a channel nailing hem above the top lock. A channel nailing hem provides improved nail holding capacity which translates to increased wind resistance, and more rigidity to the panel. The panel has a top lock, a medial body portion, and a bottom lock. The locks are complementary in shape so that they interlock with other panels of like construction. 
     The rigidity of the panel can be further enhanced by forming the panel with areas of increased substrate thickness along selected portions of the panel. Another way is to affix an additional strip of material to at least one of the lock portions or other panel portion for rigidifying the panel. The strip can be of the same material as the panel or a higher strength material, and can be co-extruded with the panel. Greater rigidity enables easier installation of the panels in an interlocked manner. The panels of the present invention can even be installed by one person. Moreover, the present invention provides a stronger overall construction which permits the use of the panels as siding in coastal areas and other environments which have wind load requirements. In those situations, vinyl siding must exhibit increased nail holding capability. 
     In one aspect of the invention, the channel in the nailing hem has an open rectangular cross-section above the top lock with elongated slots in the base of the channel. When siding nails, staples or screws are driven into the nail slots, the undersurface of the nail or screw head bears against the surfaces formed by the sides of the channel to eliminate stress concentrations around the slots and improve wind resistance. When staples are used, one leg of the staple is driven into the nail slot and the other leg is driven above the top edge of the panel with the crossbar of the staple overlaying one wall of the channel. 
     In another aspect of the invention, the channel has an open trapezoidal cross-section with the wider side forming the base with elongated slots provided, and the narrower side forming the opening. When siding nails are driven into the nail slots, the undersurface of the nail head bears against the surfaces formed by the sides of the channel. This eliminates stress concentrations around the slots and the narrower opening ensures that the nail heads will remain above the channel. 
     In yet another aspect of the invention, the channel of the nailing hem itself is reinforced either by forming the substrate with increased thickness, co-extruding a strip of material or by providing a separate trough that fits within the channel. This reinforcement to the nailing hem channel provides more protection against failure around the nail slots and also rigidifies the panel. 
     In still another aspect of the invention, the panel is reinforced by increasing the thickness of the substrate or by a strip of additional material co-extruded along its length. This reinforcement can be provided anywhere along the panel, most preferably in one or both of the lock elements. 
     These and other features and advantages of the invention may be more completely understood from the following detailed description of the preferred embodiment of the invention with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a side view of a siding panel of a conventional lock structure with a conventional single thickness nailing hem. 
     FIG. 1B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 1A shown interconnected. 
     FIG. 2A is a side view of a siding panel of an enhanced lock structure with a conventional single thickness nailing hem. 
     FIG. 2B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 2A shown interconnected. 
     FIG. 3A is a side view of a siding panel of a conventional lock structure with a conventional double thickness nailing hem. 
     FIG. 3B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 3A shown interconnected. 
     FIG. 4A is a side view of a siding panel of a reinforced lock structure with a conventional double thickness nailing hem. 
     FIG. 4B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 4 shown interconnected. 
     FIG. 5A is a side view of a siding panel of a conventional lock structure with a conventional open roll nailing hem. 
     FIG. 5B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 5A shown interconnected. 
     FIG. 6A is a side view of a siding panel of a conventional lock structure with a conventional closed roll nailing hem. 
     FIG. 6B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 6A shown interconnected. 
     FIG. 7A is a side view of a siding panel with a channel nailing hem in accordance with a first preferred embodiment of the invention. 
     FIG. 7B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 7A shown interconnected. 
     FIG. 7C is a detailed view similar to FIG. 7B but showing the panel attached with a staple. 
     FIG. 8A is a side view of a siding panel with a channel nailing hem in accordance with a second preferred embodiment of the invention. 
     FIG. 8B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 8A shown interconnected. 
     FIG. 8C is a detailed view similar to FIG. 8B but showing the panel attached with a staple. 
     FIG. 9 is a detailed side view of adjacent siding panels with a reinforced channel nailing hem in accordance with a third preferred embodiment of the invention. 
     FIG. 10A is a side view of a siding panel with a channel nailing hem in accordance with another preferred embodiment of the invention. 
     FIG. 10B is a detailed side view of adjacent siding panels of the construction of the panel shown in FIG. 10A shown interconnected. 
     FIG. 11 is a schematic illustration of the panel of FIG. 10A shown with a reinforcement option. 
     FIG. 12 is a schematic illustration of the panel of FIG. 10A shown with a reinforcement option. 
     FIG. 13 is a schematic view of a panel in accordance with another preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention pertains to interlocking panels composed of vinyl or other plastic materials. The panels are primarily intended for use as siding installed on buildings and other structures. The panels have a novel construction which enhances the strength of the siding structure, most particularly by providing improved wind resistance. In general the channel nailing provides increased rigidity to the panel, and rigidity can be further enhanced along any portion of a panel by increasing the thickness of the panel or co-extruding a strip of material with the panel. 
     In the preferred embodiments, like reference numerals are used to refer to like parts. The following description refers to specific attachment hardware such as nails, screws and staples. It will be understood that the term “nail” is used in a broad sense and includes screws and other hardware as well. In one preferred embodiment, a siding panel  50 , FIGS. 7A-7C, in accordance with the present invention includes a top lock  52 , a bottom lock  54  and a medial body portion  56 . Body portion  56  can have a wide variety of configurations, but preferably includes a pair of vertical face sections  58 ,  60  separated by a center butt or ledge  62 . The top and bottom locks can also have a wide range of shapes. Locks  52  and  54  have complimentary shapes so that siding panels can be interlocked together, FIG. 7B, that is, top lock  52  interlocks with bottom lock  54  of an adjacent siding panel. Panel  50  includes a nailing hem  64  provided above the top lock. Nailing hem  64  includes a channel  66  defined by a channel base  68  and channel sides  70  and  72 . Elongated nail slots  74  are provided in channel base  68  for receiving siding nails N which secure panel  50  to an underlaying wall or wall studs. Nail N is driven into the channel  66  and through slot  74  to the extent that nail head  76  is positioned to the outside of channel  66 . Channel sides  70  and  72  are generally parallel and is open to one end opposite the base. Adjacent to sides  70  and  72  are perpendicularly arranged bearing surfaces  78  of the nailing hem. 
     The arrangement of the channel and nail when the panel is installed is such that undersurfaces  80  of nail head  76  will bear against bearing surfaces  78  of the nailing hem. In this manner, channel  66  and the bearing surfaces  78  take the load imposed by nail head  76  when the installed siding panel is exposed to winds. Wind loading on installed siding panels will tend to move the panel in the direction of arrow A in FIG. 7B, so that nail head  76  imposes a load on bearing surfaces  78  of the nailing hem. Because the bearing surfaces  78  are designed to take the load, and because the nail slot is formed in the base and away from the bearing surfaces, this nailing hem eliminates the stress concentrations at the slot so prevalent in prior art siding panels. 
     When the same panel is attached to an underlaying wall or studs with staples S, FIG. 7C, the same principles for eliminating stress concentrations apply. One leg of the staple is driven through the nail slot and the other leg is driven above the top edge of the panel. Crossbar  81  of the staple overlays bearing surface  78  on the top end of the nailing hem. In this manner, the undersurface of crossbar  81  bears against bearing surface  78  so that when the panel is subject to winds, the crossbar of the staple is loaded by the panel. The spacing of the crossbar away from the nail slot in this manner eliminates the stress concentrations around the slot which occur when conventional siding panels are stapled to studs. 
     Another embodiment of a channeled nailing hem is illustrated in FIGS. 8A and 8B in which channel  66 ′ has a trapezoidal cross-section comprising a base  68  forming the wide base of the trapezoid, sides  70 ′ and  72 ′ which are angled to form the converging sides of the trapezoid. The narrower end of the trapezoid shape is the channel opening. In this configuration bearing surfaces  78  of the nailing hem are closer together. As seen in FIG. 8B, when a siding nail N is driven into the channel and through slot  74  in the base  68 , the undersurface of the nail head  76  bears against bearing surfaces  78  such that angled sides  70 ′ and  72 ′ of the channel provide structural support for the load imposed by the nail head. Of course the nail slot is spaced away from the point of load so as to eliminate any stress concentrations around the slot. 
     Again, when this type of panel is attached with staples S, FIG. 8C, crossbar  81  of the staple is loaded by the panel as in the embodiment of FIG.  7 C. 
     A channeled nailing hem also provides for improved rigidity and ruggedness to the siding panel as a whole due to the channel convolutions, which is especially advantageous during installation. While the embodiments of the channel nailing hem discussed herein include the rectangular and trapezoidal cross-section, other shapes that would provide bearing surfaces for the nail head, such as a circular arc, are contemplated to be within the scope of the present invention. 
     Another embodiment of the present invention provides a reinforced channel in the nailing hem. FIG. 9 illustrates one manner of providing the reinforcement in the way of an insert or trough piece  82  which fits into channel  66 . Insert  82  is provided with elongated slots which are arranged in corresponding relation to nail slots  74  at the base  68  of the channel. The insert may be a metal or thermoplastic piece, and may be secured in the channel by an interference fit or possibly with an adhesive. 
     The channel could also be reinforced during the extruding process by making the channel area of a thicker cross-section or coextruding a strip of additional material to strengthen the channel walls. The reinforcement to the channel will further enhance the strength of the panel attachment to the underlaying wall or wall stud. 
     All of the channel nailing hems described heretofore can be integrated to a panel having the improved lock structure geometry of shown in FIGS. 4A-4B. Specifically, even without the reinforcing strip, the geometry of the locking structure in which the top lock  12  has a generally horizontally projecting wall and an elongate inclined wall extending up from the projecting wall, and the bottom lock has an L-shaped projection complimentary in shape to the top lock. When the top lock is interconnected with a bottom lock, at least a portion of the projecting wall of the top lock abuts against the horizontal arm of the bottom lock so that a portion of the inclined wall abuts against the body face  22 . In this manner, the top lock occupies most of the space defined by the bottom lock, and the installed panels are sturdier. This lock structure may be used with a reinforcement such as shown in FIG. 4A, or without such reinforcement. 
     In yet another embodiment of the invention, FIGS. 10A-10B, siding panel  50  is provided with a larger dog-leg type top lock  52 ′ which is configured so that the top lock occupies much of the space in the channel shape of bottom lock  54 . Top lock  52 ′ has a projecting wall and an elongate inclined wall extending upward from the projecting wall which, when interlocked with a bottom lock of another panel can be configured to abut against the body portion of the adjacent panel. Nailing hem  64  includes a trapezoidal channel  66 ′ defined by a channel base  68  and channel sides  70 ′ and  72 ′. Elongated nail slots are provided in channel base  68  for receiving siding nails N or staples S which secure panel  50  to an underlaying wall or wall studs. As with previous embodiments, when attachment hardware is used to secure panel  50  to an underlaying wall, it can be seen that the undersurface of a nail head or a staple cross bar would be supported and bear against bearing surfaces  78  formed by channel sides  70 ′ and  72 ′. 
     Two possibilities for reinforcing the panel are illustrated schematically in FIGS. 11 and 12 using panels identical to the one shown in FIGS. 10A-10B. The area reinforced is indicated by the letter R. In FIG. 11 the top lock portion is reinforced, and in FIG. 12 a portion of the panel that provides a bearing surface is reinforced. The reinforcement can be accomplished by forming the desired areas of thicker substrate material or by co-extruding another material in that area. While these two possibilities for reinforcement are shown, it will be understood that such thickening or co-extrusion can be done anywhere along the panel. 
     An alternative lock structure is shown schematically in FIG. 13 in which the top lock and channel structure formed by the edge of the panel being folded over. Top lock  52 ′ has a dog-leg configuration with a free edge of the panel material being disposed so as to hook onto a bottom lock upward leg. A nail channel  66 ′ is formed above the top lock with the upper face  58  in opposition to the channel base  68 . In this manner, corresponding nail slots are punched in the channel base  68  and upper face  58 , through both thicknesses of material. Contrary to the prior art double-thickness nail hems, the configuration shown in FIG. 13 would have increased nail holding capability since the nail head or staple crossbar would be spaced away from the nail slots to eliminate stress concentrations. 
     While the embodiments described herein are siding panels with a top lock and a bottom lock which extend horizontally along a wall, it is contemplated to be within the scope of the invention to apply the improved nailing channel to any attachment area of building panels that may be differently oriented when installed. Broadly, the lock structure comprises first and second edge structures and a nailing area located somewhere between the edge structures. 
     As is common in the industry, the siding panels described herein can be composed of a variety of plastic materials. Preferably, the panels are composed primarily of PVC resins. The capstock or exterior layer is formulated to have a good appearance and to be weather, wear and impact resistant. The substrate or interior layer is formulated primarily for stiffness and strength. Nevertheless, other constructions including only one material or more than two materials could be used to form the layers or plies of the siding panel. 
     In the embodiments of the invention in which an additional material is co-extruded onto the panel, co-extrusion refers to two or more extrudates. Co-extrusion includes the use of an identical material as that of the siding panel or a different material. A high strength material that could be used is preferably a compounded, reinforced PVC material. One such material is known as GEON Fiberloc 925 GR30 manufactured by GEON Corporation. Another alternative material is known as Tuf-Stif manufactured by Georgia Gulf Corporation. Other high strength materials including other plastics or materials (e.g., graphite or boron) may also be used. 
     The siding panels described herein are preferably made of thermoplastic material. The structural advantages of the channel nailing hem are also adaptable to panels made of metal sheets as well, and the invention is not limited to vinyl siding. 
     The above discussion concerns the preferred embodiments of the present invention. Various other embodiments as well as many changes and alterations may be made without departing from the spirit and broader aspects of the invention as defined in the claims.