Abstract:
An improved cinch strap and backup plate, used to form an enlap joint between two overlapping roofing panels, is disclosed. The backup plate is provided with horizontally extending shoulders which protrude outwardly from each end of the plate. One shoulder provides support for the endlap joint during its assembly, while the other shoulder provides support for later installed endlap joints. The cinch strap is configured to conform to the contour of the roofing panels. The cinch strap is provided with spines which provide structural support, and drainage channels which help to clear moisture from the roof. The cinch strap is configured so as to engage other, aligned cinch straps in a head-to-tail arrangement. The improved cinch strap and backup plate provide a structurally stronger, weatherproof endlap joint.

Description:
BACKGROUND OF THE INVENTION 
     There are many possible ways to provide a roof for a structure. One way to roof a structure is through the use of metallic roofing panels. The art of roofing structures with metallic roofing panels has advanced to the use of standing seam roofing panels. Standing seams are formed when raised longitudinal edges of roofing panels engage to form a longitudinal ridge running from the peak to the gutter of a roof. 
     Standing seam metallic roofing panels are normally manufactured from galvanized steel or GALVALUME (TM) and then may be painted or coated with a protective film. The individual panels may vary in width from one to several feet, and may be up to thirty feet in length. 
     In erecting a structure, walls or columns of the building are first built and rafters, which form the primary roof support, are carried by the walls or columns. These rafters usually span the width of the structure. Joists, or purlins, are load across the rafters, are supported by the rafters, and are normally installed perpendicularly to the rafters, thereby defining the roof line. The purlins extend along the length of the building. Insulation may be laid across the joists. 
     A standing seam roofing system may then be installed. Roofing panels are joined together along adjacent longitudinal sides in a male/female joint to form the standing seams. It is known in the art how to attach the roofing panels to the joists, or purlins. 
     In structures where the distance from the peak to the gutter line is greater than the maximum length of a single roofing panel, it may be necessary to install two or more lengths of roofing panels to provide a roof. Endlap joints are formed where the end of one panel overlaps the end of an abutting panel. It will be understood by one skilled in the art that the lower end of the roofing panel, located nearest to the peak of a roof, will overlap the upper end of an abutting roofing panel, located closer to the gutter line of the roof, in a shingle-like manner. 
     At the point where the two roofing panels overlap, creating an endlap joint, it is necessary to secure the panels together in order to maintain the structural integrity of the roof and to provide a weatherproof seal between the panels. In Gulf Coast aareas where frequent high winds and heavy rains are experienced, it is necessary to maintain an endlap joint that can provide a seal against driving rain and still be strong enough to resist the lifting force of high winds. Very frequently, the atmosphere in the interior of the structure may be air-conditioned. In the process of doing this, the atmospheric pressure may become greater than the pressure in the building and rain-water running over the roof may be sucked through the endlap joint if the joint is not watertight. 
     In areas of the countery where roofing systems experience seasonal snow loadings, it is imperative to provide an endlap joint of sufficient strength to resist the occasionally high stresses placed on the roof by the snow in order to protect the structural integrity of the roof. 
     Finally, the endlap joint formed by the overlapping roofing panels must be strong enough to resist &#34;live loads&#34; occasioned by workmen walking on the roof during maintenance of the structure. 
     The present invention provides a means for creating an endlap joint between overlapping roofing panels that provides structural strength to the roofing system while maintaining a watertight seal against environmental forces. 
     SUMMARY OF THE INVENTION 
     To assemble an endlap joint in accordance with the present invention, a first, lower roofing panel is placed adjacent to a roofing panel which forms the lower half of the already assembled endlap joint. It will be understood by one skilled in the art that a &#34;lower&#34; element in a roofing system refers to an element that is nearer the gutter line than the peak of the roof. Similarly, a &#34;higher&#34; element is an element located nearer to the peak of the roof. The first roofing panel is placed so that the longitudinal edge of the panel nearest to the installed panel engages the edge of that panel and creates a standing seam. The first roofing panel is placed so that the upper end of the panel is positioned adjacent to the upper end of the adjacent, already installed roofing panel. 
     A channel-shaped backup plate is inserted below the first panel and is positioned adjacent to, and aligned with, a backup plate that has already been assembled into the adjacent endlap joint. A backup plate according to the present invention is provided with a horizontal &#34;shoulder&#34; which extends outward horizontally from the raised ends of the plate. A shoulder of the plate is positioned so that it rests on top of a shoulder of an adjacent, installed plate. 
     A second roofing panel is then placed adjacent to the upper roofing panel of the already assembled endlap joint. The second roofing panel is placed so that a longitudinal edge of the panel forms a standing seam with the upper panel of the already assembled endlap joint. The second panel is positioned so that its lower end overlaps the first roofing panel and the backup plate beneath it. 
     A cinch strap according to the present invention is then placed over the second panel so that the upper longitudinal edge of the strap is positioned over the upper edge of the backup plate. In accordance with the present invention, one end of the strap has been formed so as to be engageable with the exterior contour of the standing seam formed by the junction of the four roofing panels. The strap is placed so that this formed end overlaps the standing seam and abuts an end of the adjacent cinch strap of the already assembled endlap joint. 
     Finally, self-drilling fasteners are applied to preformed holes in the cinch strap. The fasteners draw this strap and the backup plate together, thereby sandwiching the two roofing panels between them to form the endlap joint. 
     When assembling an endlap joint according to the present invention, a tape mastic or sealant is applied between the two roofing panels at the point at which they overlap each other and the backup plate in order to aid in the formation of a watertight joint. 
     During application of the fasteners to the cinch strap, the endlap joint must be supported. A common method of supporting the endlap joint has been placing workers, often on scaffolding, beneath the backup plate who manually support the plate, and thereby the endlap joint, during assembly. This method has been both costly and time consuming. Another, more common method of assembling endlap joints involves pre-punching holes in the cinch strap, roofing panels, and backup plate and inserting fasteners through the aligned, preformed holes. Although this method may at first appear to be an easy way to assemble endlap joints, it has been found to have several practical drawbacks. 
     Initially, this latter method has proven to be very difficult to accomplish in the field. Due to the nature of the tolerances associated with standing-seam roofing systems and their assembly in the field, it is difficult, as a practical matter, to align all the preformed holes in each of the cinch strap, backup plate, and roofing panels. To further complicate matters, once the roofing panels engage and interlock with adjacent panels to form the standing seam, it is not practical to slide the panels longitudinally along the seam. Therefore, the holes in each of the panels must be aligned before both panels engage the adjacent roofing panels; this is often a laborious process. 
     There is a second major drawback to pre-punched hole method of assembling endlap seams. As stated, it is often necessary to position and reposition the roofing panels in order to align the pre-punched holes. Once this is accomplished, it is still necessary to align the holes in the cinch strap and backup plate with the holes in the roofing panels. Often, a rod is inserted into the holes to align them. The insertion of the rod, and the jockeying of the various components, often damages the mastic positioned between the roofing panels resulting in an imperfect water seal in the endlap joint. 
     The present invention avoids all the above-mentioned difficulties. According to the present invention, the endlap joint is supported by the backup plate through the use of the horizontal shoulder of the backup plate resting on top of the shoulder of the adjacent plate in the already assembled endlap joint. Because the backup plate is so supported, it is no longer necessary to have the plate independently supported during assembly of the endlap joint, and because the plate is so supported self-drilling fasteners may be used without resorting to pre-punched holes in the component. 
     Other roofing systems have relied solely on retaining tabs, formed in the backup plate, to support the plate during assembly of the endlap joint. This has not proven to be entirely effective and additional plate support is often required. The additional support that is required to effectively support the backup plate during assembly of the endlap joint is efficiently provided by the support shoulders of a backup plate according to the present invention. 
     Further, once the roof has been completely assembled, the overlapping horizontal shoulders of the aligned backup plates will provide additional support to the whole roof. This additional support helps to protect the integrity of the entire roofing system during periods of heavy weather or when workmen are walking about on the roof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of an assembled endlap joint according to the present invention. 
     FIG. 2 is an exploded view of the components comprising an endlap joint according to the present invention. 
     FIG. 3 is a plan view of a backup plate incorporating the present invention. 
     FIG. 4 is a side view of the backup plated depicted in FIG. 3 facing the lower side of the backup plate. 
     FIG. 5 is an end view of the backup plate depicted in FIG. 3. 
     FIG. 6 is a plan view of the cinch strap incorporating the present invention. 
     FIG. 7 is a side view of the cinch strap depicted in FIG. 6. 
     FIG. 8 is an end view of the cinch strap depicted in FIG. 6. 
     FIG. 9 is another section view of an assembled endlap joint according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, an endlap joint according to the present invention is comprised of six different types of components: a backup plate 20; a lower roofing panel 80; tape mastic or sealant 85; an upper roofing panel 90; a cinch strap 30; and a plurality of fasteners 100. 
     Details of the backup plate 20 will be discussed first. Referring to FIGS. 1-5 and 9, each backup plate 20 is defined by a length (depicted in FIG. 3 as &#34;l&#34;), corresponding directionally to the width of the roofing panels 80 and 90, and a width (depicted in FIG. 3 as &#34;w&#34;). A backup plate 20 according to the present invention is basically channel-shaped and configured to follow at least part of the interior configuration of the roofing panels 80 and 90. Positioned at the ends 30 of the backup plate 20 are laterally outward extending shoulders 22. Each shoulder 22 may be used to support the backup plate 20, and to provide support for an adjacent backup plate. 
     In one embodiment of the present invention, a backup plate 20 may be formed from sheet, or coil, steel in a metal stamping operation. 
     Preferably, the outwardly extending shoulders 22 of the backup plate 20 are provided adjacent to the upper edge 32 of the backup plate 20. In accordance with the present invention, the shoulders 22 extend outwardly from the ends 30 of the backup plate 20 beyond the centerline of the upstanding seams formed by adjacent, interlocked roofing panels. 
     Preferably, the width of the shoulders 22 equal approximately one third of the width of the backup plate 20. 
     In accordance with the present invention, a plurality of retaining tabs 26 are provided adjacent the upper edge 32 of the backup plate 20 in order to receive an upper end of the lower roofing panel 80. 
     The backup plate 20 is provided with a vertical reinforcing surface 24, which extends downwardly from the upper edge 32 of the backup plate 20, and a longitudinal support groove 28 formed in the backup plate 20 adjacent to, and parallel with, the lower edge 34 of the plate 20. 
     In a preferred embodiment of the present invention, the retaining tabs 26 extend upwardly from the upper edge 32 of the backup plate 20, then horizontally toward the lower edge 34 of the plate 20, parallel to the plate 20. The tabs 26 are formed in the plate 20 so that the thickness of the lower roofing panel 80 may be received between the upper surface 21 of the plate 20 and the lower surface 27 of the horizontal sections of the retaining tabs 26. The retaining tabs 26 may generally be one inch square. 
     The cinch strap will now be discussed. Referring to FIGS. 1, 2, and 6-8, each cinch strap 36 is defined by a length, which corresponds to the width of the surface of the upper roofing panel 90, and a width. A first raised end 44 which is engageable with a portion of one surface of a standing seam. A second raised end 42 which is generally in the shape of an inverse &#34;V&#34; is configured to engage the outer contour of the opposite standing seam formed by the roofing panel 90. It will be understood that defining raised end 42 as an &#34;inverse V-shape&#34; is in no way limiting the configuration of end 42, but rather is used to describe how end 42 is configured to engage the standing seam formed by the roofing panels. 
     In the embodiment depicted in FIGS. 2 and 9, raised end 42 is composed of a number of connected surfaces. Referring particularly to FIG. 7, raised end 42 is attached to the elongated main body portion 37 by a raised base surface 39 which is configured to engage a portion of a standing seam. A first upwardly directed side surface 41 extends upwardly and outwardly from base surface 39, following the contour of the standing seam. A first substantially horizontal surface 43, a second upwardly directed side surface 45, a first downwardly directed side surface 47, and a second substantially horizontal surface 49 define a summit which engages, and caps, the peak of the standing seam. Finally, a second downwardly directed side surface 51 extends outwardly from the second substantially horizontal surface 49, and is engageable with the end 44 of an adjoining cinch strap. 
     Referring particularly now to FIG. 6, in a preferred embodiment of the present invention, the cinch strap 36 is provided with a pair of longitudinal reinforcing spines 40. A plurality of transverse drainage channels 38 are provided which facilitate the drainage of rainwater and the like from the roof by facilitating the flow of water from one longitudinal side of the cinch strap 36 to the other. The drainage channels 38 are formed perpendicular to the longitudinal centerline of the cinch strap 36. In order to facilitate the drainage of water from the top of the cinch strap 36, reinforcing spines 40 may intersect raised ends 42 and 44 and not intersect the drainage channels 38 located proximate ends 42 and 44. Further, reinforcing spines 40 may intersect only one side of the drainage channels 38 provided proximate the transverse centerline of the strap 36 in order to provide a path for water to drain. 
     In a preferred embodiment, the cinch strap is formed to accommodate a ribbed roofing panel. Ribs are generally provided in the planar web, or substantially flat, horizontal, main body portion 37 of the roofing panels 80 and 90. In this embodiment of the invention, deformations 46 are provided in the strap 36, thereby allowing the strap to conform to the contour of the roofing panel 90. Roofing panels 80, 90 may be ribbed in order to increase their structural strength. 
     Reinforcing spines 40 perpendicularly intersect deformations 46 and drainage channels 38 formed throughout the strap. Holes 48 are formed along the longitudinal centerline of the strap 36 in order to receive self-drilling fasteners 100 which, when applied to the endlap joint, draw the backup plate 20 and the cinch strap 36 together, thereby sandwiching the roofing panels 80 and 90 between them. 
     The length of the cinch strap 36 is such that contoured end 42 of the straap 36 extends down the outer face of the standing seam formed with the preinstalled roofing panels so that the end 42 of the strap 36 engages the end of 44 of an already installed cinch strap, as depicted in phantom in FIG. 7. 
     There are several advantages to forming the end 42 of cinch strap 36 to overlap the standing seam formed by the roofing panels. The resultant endlap joint is structurally stronger when the cinch strap 36 engages the standing seam over the top of the seam. Additionally, a more aesthetically-pleasing roof results when the aligned cinch straps 36, arranged in a head-to-tail relationship, completely cover the standing seams formed by the adjacent roofing panels. 
     Referring now to FIGS. 1 through 9, when assembling an endlap joint according to the present invention, a first lower roofing panel 80 is positioned so that the upper end 87 of the roofing panel 80 is adjacent to the upper end of an already installed roofing panel while the remainder of the roofing panel 80 extends toward the gutter line. 
     A longitudinal edge of the first roofing panel 80 engages the longitudinal edge of the already installed roofing panel to form a standing seam. 
     A backup plate 20 is positioned adjacent to an already installed backup plate so that a shoulder 22 of the backupu plate 20 rests on top of a shoulder 22 of the already installed adjacent plate. 
     The backup plate 20 is positioned so that the upper end 87 of roofing panel 80 is inserted beneath the plurality of retaining tabs 26. 
     A second, upper roofing panel 90 is then positioned over roofing panel 80 and the backup plate 20. The second roofing panel 90 is positioned so that the lower edge 91 of the panel 90 is positioned above the lower edge 34 of the backup plate 20 while the remaining portion of the roofing panel 90 extends over the upper edge 32 of the backup plate 20 toward the peak of the roof. 
     A longitudinal edge of the second roofing panel 90 engages a longitudinal edge of an adjacent roofing panel that has already been installed to form a standing seam. 
     A cinch strap 36 is then placed over the second roofing panel 90. The cinch strap 36 is positioned so that the lower edge of the strap 36 is approximately three inches from the upper edge 32 of the backup plate 20. The contoured end 42 of the strap 36 is placed over the standing seam formed by the combination of roofing panels 80, 90, and the two already installed roofing panels. The contoured end 42 engages the end 44 of an already installed adjacent cinch strap in a head-to-tail relationship. 
     Finally, a plurality of self-drilling fasteners 100 are inserted into preformed holes 48 in the cinch strap 36. The self-drilling fasteners 100 draw the cinch strap 36 toward the backup plate 20 thereby sandwiching roofing panels 80 and 90 between them and creating a structurally strong, water-tight endlap joint. 
     The method may then be repeated until the entire roof is in place. 
     Various modifications and improvements may be made to the disclosed embodiment without departing from the overall scope and spirit of the invention. For example, a tape mastic or sealant 85 may be placed between the overlapping roofing panels 80 and 90 in order to enhance the seal of the endlap joint.