A turbulence-creating device is mounted to the roof, such that high winds flowing across the roof are caused to become turbulent, thereby interfering with the laminar flow and lift which would otherwise be created. The turbulence-creating devices comprise generally V-shaped or curved spoilers, many of which are pivotally mounted to a vertical mast attached to the roof such that the spoilers face in the direction of the oncoming wind and are shaped to disturb the laminar flow, thereby preventing lift from being generated. In some embodiments, fixed omnidirectional spoilers with curved sides are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) on U.S. Provisional Application No. 60/764,193 entitled A ERODYNAMIC  R OOF  L IFT -P REVENTION  D EVICE , filed on Feb. 1, 2006, by Charles J. VendenBerg, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a system and method to prevent wind damage to roofs. In areas where high winds can occur, wind damage to roofs, and particularly flat roofs or shallow pitched roofs, can be significant. The laminar flow of high velocity winds across the surface of a flat roof generates lift which frequently results in detachment of roofing material, particularly where large sheets of material are joined along seams and only adhesively attached to the underlying roof support members at spaced locations. The lift caused by high winds across the surface of a roof initially tends to lift the roofing fabric or covering from the edges of the roof, followed by the tearing and removal of the entire roof covering, and subsequently the underlying roof structure. Such winds typically accompany severe storms, such as hurricanes, and, upon the destructive removal of the roof covering, further damage to the building structure and its contents results due to the intrusion of wind and rain directly into the building. 
     Some efforts have been made to provide structures at the edge of a roof to prevent the initial tearing of roof material from the surface of the roof, however, such structure is not effective in the central area of the roof on relatively large buildings which, during storms, can lift away, be torn, and otherwise destroyed by the lift forces caused by laminar flow of wind across the flat or slightly inclined roof surface. Accordingly, there exists a need for a system by which an entire roof surface is protected from the lift forces generated by high winds flowing along the surface of the roof during storms. 
     SUMMARY OF THE INVENTION 
     The system of the present invention addresses this need by providing a turbulence creating device which is mounted to a roof in sufficient number and spaced such that high winds flowing across the roof are caused to become turbulent, thereby interfering with the laminar flow and lift which would otherwise be created. Thus, the system of the present invention provides protection for the entire roof by preventing lift forces from being generated along the entire roof surface. 
     In a preferred embodiment of the invention, the turbulence-creating devices comprise generally V-shaped or curved spoilers which are pivotally mounted to a vertical mast attached to the roof such that the spoilers face in the direction of the oncoming wind and are shaped to disturb the laminar flow, thereby preventing lift from being generated. In some embodiments, fixed omnidirectional spoilers are provided. The spoilers may also generate a downward force which tends to secure the roof in place during high wind conditions. The configurations of the generally V-shaped, curved, or fixed spoilers provide the desired turbulent effect on the wind as well as provide downward forces for the roof structure. 
     These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a flat roofed building showing locations of airfoils on the roof of the building by the dotted line circles and showing one embodiment of an airfoil spoiler mounted to the roof of the building; 
         FIG. 2  is an enlarged perspective view of the spoiler shown in  FIG. 1 ; 
         FIG. 3  is a top plan view of the spoiler shown in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the spoiler, taken along section line IV-IV of  FIG. 3 ; 
         FIG. 5  is a front elevational view of an alternative embodiment of the spoiler shown in  FIG. 2 , including several apertures formed through the body of the spoiler; 
         FIG. 6  is a perspective view of an alternative design for a three-dimensional curvilinear spoiler having a raised central section with apertures therethrough; 
         FIG. 7  is a front elevational view of the spoiler shown in  FIG. 6 ; 
         FIG. 8  is a top plan view of the spoiler shown in  FIG. 6 ; 
         FIG. 9  is a perspective view of another embodiment of the invention showing a generally plow blade-shaped spoiler design; 
         FIG. 10  is a front elevational view of the spoiler of  FIG. 9 ; 
         FIG. 11  is a top plan view of the spoiler design of  FIG. 9 ; 
         FIG. 12  is a perspective view of another configuration of a generally plow blade-shaped design, with the configured ends having apertures therethrough; 
         FIG. 13  is a front elevational view of an alternative embodiment of the spoiler of  FIG. 12 ; 
         FIG. 14  is a top plan view of yet another embodiment of a spoiler; 
         FIG. 15  is a perspective view of an alternative design for a three-dimensional curvilinear spoiler having a raised central section with a freewheeling turbulence producing fan mounted therein; 
         FIG. 16  is a front elevational view of the spoiler shown in  FIG. 15 ; 
         FIG. 17  is a perspective view of an alternative design for a three-dimensional curvilinear spoiler having a raised central section with a wind generator mounted therein; 
         FIG. 18  is a front elevational view of the structure of  FIG. 17 ; 
         FIG. 19  is a perspective view of an alternative embodiment of an air foil which may be employed in an installation such as illustrated in  FIG. 1 ; and 
         FIG. 20  is a perspective view of another alternative embodiment of an air foil which may be employed in an installation such as illustrated in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The spoilers of the invention can be employed for either flat roofs  22  or slightly pitched roofs of a building  20  ( FIG. 1 ) to disturb high velocity laminar airflow which would otherwise reduce the air pressure at the surface of the roof causing lift, which could tear the roof from the building. The surface  23  of roof  22  is typically comprised of a covering sheet of water-impervious material, such as tar paper, PVC, or other sheet material, which comprise individual strips joined at seams by seals and adhesively attached to the underlying roof support sheeting. The roof support sheeting is frequently made of plywood or chipboard sheets. Often surface  23  will include small pea-sized stones, such as pea gravel, to assist in holding the water-impervious material to the underlying structure. Nonetheless, under high wind conditions encountered during wind storms, such as sheer winds, and hurricanes, the surface material  23  frequently lifts off the roof and, in many cases, takes the underlying support structure with it. 
     By mounting a plurality of spaced-apart spoilers  10 , which are rotatably mounted and shaped to automatically align in response to the wind force (arrows F in  FIG. 2 ) to face into the wind at the surface of the roof, the airflow becomes turbulent preventing or greatly reducing lift forces. Many spoilers, such as spoiler  10  of  FIGS. 1-3 , is pivotally mounted by a housing  12  to a bearing  14 , such as shown in  FIG. 4 , coupling the spoiler  10  to a mast  16  which is suitably attached to a mounting flange  18 . Flange  18  is secured to the roof  22  by fasteners  19  ( FIGS. 2 and 3 ), such as bolts, in a sealed manner. These spoilers pivot to align with the wind due to the generally V-shaped design (as viewed from the top) as they disturb the laminar flow which otherwise occurs during a wind storm. This turbulence prevents the laminar flow from decreasing the air pressure immediately adjacent the roof and eliminates or greatly reduces the lift which otherwise tends to lift the roof sheeting and underlayment from the building structure. 
     Depending on the building size and, therefore, the roof area, several airfoils may be employed and spaced at appropriate spaced-apart locations  15  ( FIG. 1 ) to cause the turbulence of the wind flow path across the surface  23  of the roof  22 , thereby preventing damage to the roof. In many cases, the airfoil is designed to align with the wind and is V-shaped to cause a sufficient amount of turbulence to prevent laminar flow immediately adjacent the roof in the area served by the airfoil. The spoilers  10  can be molded of a suitable polymeric material, such as polycarbonate, glass-reinforced nylon, or fiberglass. Alternatively, they can be stamped or otherwise formed of metal, such as aluminum, steel, or stainless steel. If formed of aluminum or steel, they may be treated by anodizing or galvanizing or otherwise covered to provide weather resistance. 
     The size of the spoilers can be varied depending upon the application, although an about 3 to about 5 foot wingspan W ( FIG. 3 ) is a typical width. The vertical height H ( FIG. 2 ) may vary from about 12 to about 24 inches, and the mast height is selected to achieve the desired turbulence. The thickness of the molded polymeric spoilers is from about 1 to about 2 inches. Typically, the mast  16  positions the lower edge  36  of the spoiler  10  about 6 to 8 inches from the roof surface  23 . The bearings  14  are selected to withstand the anticipated wind loads as in the diameter of the mast  16  and its mounting flange  18 . The bearing is conventionally coupled to the mast and secured within the spoiler housing  12  by a plurality of set screws  13  ( FIG. 4 ) to assure the free rotation of the spoiler to align with the wind. 
     The spoiler  10 , shown in  FIGS. 1-4 , comprises a body  30  which includes a pair of legs  32  and  34  which are integrally formed, as by molding using the materials described above, and are joined at the center  33  to housing  12  at an angle ∝, as best seen in  FIG. 3 , of from about 90° to about 150°. Each leg  32  and  34  includes an upper edge  35  and a lower edge  36 . The legs include concave surfaces  37  between edges  35  and  36  with cup-shaped enclosed ends  38  and  39 . The junction of the concave surfaces  37  of legs  32  and  34  form a vertically extending edge  31  extending between upper edge  35  and lower edge  36  and assists in dividing the force of the wind on the spoiler evenly, such that it aligns with the incoming wind, causing the otherwise laminar flow to become turbulent, spiraling around horizontal axes parallel to the surface  23  of the roof. This breaking up of the laminar wind prevents it from causing lift forces sufficient to damage the roof. 
     The spoiler shown in  FIGS. 1-4  may include a plurality of apertures, as shown by the spoiler  10 ′ in  FIG. 5 , in which the spoiler shape is identical to that shown in  FIGS. 1-4  but the legs  32 ′ and  34 ′ include a plurality of apertures  40  extending therethrough, which reduce the wind resistance of the spoiler and further increase the turbulence by providing additional passageways via apertures  40  through which the wind can pass. Apertures  40  have a diameter of approximately one-third that of the height H of the spoiler, namely, from about 4 to about 8 inches in diameter to provide the desired passage of wind therethrough. 
     An alternative embodiment of the spoilers shown in the earlier figures is shown in  FIGS. 6-8  where a curvilinear spoiler  50  is shown. Spoiler  50  is mounted to the surface of a roof utilizing a mounting flange  18 , mast  16 , and housing  12  and bearing  14 , similar to the mounting in the previous embodiments. The spoiler  50  has a generally curved and concavely shaped body, as viewed in  FIG. 8 , with a forwardly curved and raised upper center section  52  and a forwardly and outwardly curved lower lip  54  which extends along the entire length of the spoiler body. Spoiler  50  is curved, as shown in  FIG. 8 , occupying an arc β of approximately 90°-140°. The ends  56  and  58  of spoiler  50  occupy approximately one-quarter of the overall width of the spoiler, while the center section occupies at least approximately one-half. The height of the end sections  56  and  58  are from about 12 to about 24 inches. The height of the curved dome of the center section  52  is at least twice that of legs  56 ,  58  (i.e., about 24 to about 48 inches). Preferably, spoiler  50  includes a pair of apertures  51  for the passage of wind therethrough. Apertures  51  have a diameter similar to apertures  40  shown in the  FIG. 5  embodiment, although they can have a somewhat larger diameter inasmuch as they are formed in the increased height center section  52  of the spoiler. As can be seen in  FIGS. 6 and 8 , the top lip  53  of the center section  52  of the spoiler  50  does not extend forwardly as does the lower lip  54  and, therefore, the wind striking the spoiler, in addition to being disturbed, will tend to push downwardly on the spoiler  50  to improve the resistance of the roof to wind damage. 
     An alternative embodiment of the spoiler is shown in  FIGS. 9-11  in which a generally plow-shaped spoiler  60  is shown and, likewise, is mounted to the surface  23  of a roof  22  by means of a mounting flange  18 , securing bolts  19 , a mast  16 , and a housing  12  including a suitable bearing, as in the first embodiment. The spoiler  60  is also generally V-shaped as is spoiler  10  in the  FIGS. 1-4  embodiment and was formed in a V at about the same angle. The legs  62  and  64  of the spoiler thus converge at an angle of from about 90° to about 150°. The legs, however, have a generally vertically extending rear wall  61  and a concave surface  63  which join at a center edge  65 . The lower lip  66  of the spoiler  60  is generally horizontal and extends forwardly in a generally plow-shaped configuration, as best seen in  FIG. 9 . This configuration allows a more robust body for the spoiler  60  in the fillet area  67  ( FIG. 9 ) and, as in the proceeding embodiment, responds to the wind impinging upon the spoiler by not only causing wind to become turbulent, thereby preventing the lifting effect, but also tends to push downwardly on the spoiler for assisting in holding the roof in place. 
     The ends of the spoilers shown in the preceding four embodiments may be configured to provide further turbulence as, for example, shown in the spoilers of  FIGS. 12-14 . These spoilers likewise are generally V-shaped forming an angle, such as shown by angle α in  FIG. 3 , of from about 90° to about 150°, and may include apertures, such as apertures  72  near the tip of spoiler  70  shown in  FIG. 12 . Each of the spoilers have ends which may include a tapered edge, such as  74  shown in  FIGS. 12 and 13 , and are downwardly curved at  75  to provide additional wind disturbing edges at the outermost edge of the spoilers. 
     Spoiler  80 , shown in  FIG. 14 , likewise has a generally V-shaped, plow-like configuration with a forwardly projecting upper lip  82  and tapered outer edges  84  and  86 . The body of spoiler  80  is likewise generally concave shaped, as is the body of spoiler  10  shown in  FIGS. 1-4 . The upper lip  82  of spoiler  80  extends forwardly a lesser degree than the lower lip  88 . 
     Each of these embodiments have dimensions and construction materials commiserate with that described in the first embodiment of  FIGS. 1-4  and may optionally include a plurality of apertures, as shown in the embodiment of  FIG. 5 . 
     The embodiments in  FIGS. 15 and 16  comprise a spoiler which has a configuration somewhat similar to that shown in the embodiment of  FIGS. 6-9 , namely, curvilinear spoiler  90  with a smoothly curved, rounded lower section  92  having rounded ends  93 . Lower section  92  is generally concave with a forwardly extending lip  91  which circumscribes an arc β similar to that of the  FIGS. 6-8 . Spoiler  90  extends upwardly in an integral raised center section  94  which is significantly higher than the upper section  52  of the  FIGS. 6-8  embodiment. The center section  94  is from about two to about four feet in the vertical direction and includes a large central aperture  95 , the edge of which supports four orthogonal support struts  96  supporting a bearing  97  of a freewheeling fan  98 . Thus, the spoiler  90 , as shown in  FIGS. 15 and 16 , provides additional turbulence through the action of the wind spinning the four blades of fan  98 , causing additional turbulence as the wind passes through aperture  95 . The diameter of aperture  95  is from about 18 to about 36 inches, while the diameter of the four-bladed fan  98  is from about 17 to about 35 inches. The material and width of the spoiler  90  is substantially the same as in prior embodiments, although the thickness may be somewhat greater than the about 1-2 inch thickness of the remaining embodiments to support the struts  96  and fan  98  therein. Spoiler  90  is curved in a semicircle and has a radius of curvature of from about 24 to about 48 inches. 
     The embodiment shown in  FIGS. 17 and 18  is a spoiler having a geometry substantially the same as spoiler  90 , with the exception that the bearing  97  is replaced with a generator  107  which is driven by fan blades  108  with generator  107  supported by orthogonal struts  106  extending from the edges of aperture  105  in the raised center section  104  of the spoiler  100 . Again, the lower section  102  is concavely curved with rounded ends  103  to, in essence, scoop the wind, as in the previous embodiment shown in  FIGS. 15 and 16 , upwardly into the aperture  105  where the generator is activated by the wind. The conductors (not shown) leading from the generator  107  extend through one of the struts  106  which is hollow and to slip rings on housing  12  which interface with conductors leading through mast  16  to the building where conductors from each of the plurality of generators, positioned such as shown in  FIG. 1 , are coupled to an electrical control circuit, such as an inverter or other power control circuit which converts the voltage from the generator to one which can be employed either to charge a battery pack for subsequent conversion to 110 volt AC or one which operates an inverter directly. Such power control and inverting circuits are well known in the wind generating industry and can be of conventional design. The generator  107  can be a DC or an AC generator. 
     Alternative embodiments to the previously described rotatable spoilers are shown in  FIGS. 19 and 20 .  FIGS. 19 and 20  show omnidirectional fixed spoilers which can be positioned in an array in spaced relationship in rows and columns on a roof as shown by the installation of  FIG. 1 . In  FIG. 19 , an omnidirectional spoiler  120  is shown which has a generally square shape (as viewed from the top) and includes four concavely curved side walls  121 - 124 , which are joined at curved intersecting corners  125 . The side walls are integrally formed with a convexly domed top  126  at the upper edges of the side walls that flare out at the bottom to form a peripheral flange  127  extending around the spoiler  120  and which receives fasteners, such as lug bolts  128 , for securing the spoiler  120  to the surface  23  of a roof  22 . The length of each of the side walls  121 - 124  is from about 3 feet to about 6 feet, while the height of the integrally molded spoiler  120  is from about 18 inches to about 24 inches measured from the flange  127  to the top of domes top  126 . The spoiler  120  can be economically manufactured by blow molding, injection molding, or the like out of a polymeric material, such as PVC, although a more robust material, such as polycarbonate, glass-reinforced nylon, fiberglass, or the like, or a weather-impervious metal or treated metal can be employed, such as aluminum, galvanized steel, or the like, in which case they can be formed by progressive die stamping. The fixed spoiler  120  has the advantage of being somewhat less expensive to manufacture in that it has no moving parts and does not require bearings or a mounting mass and can be shipped in a nesting relationship to an installation for subsequent mounting to a roof in an array as shown in  FIG. 1 . 
       FIG. 20  shows an alternative embodiment of an omnidirectional spoiler  130 , which is manufactured of the same materials as discussed in connection with spoiler  120  and has a circular or round configuration as viewed from the top and a peripheral side wall  131  which is concavely curved and terminates at its lower edge in a peripheral mounting flange  132 . Spoiler  130  integrally includes a convexly domed circular top  133 . The spoiler  130  is mounted to the surface  23  of a roof  22  by means of a plurality of fasteners, such as lug bolts  134 . As in the embodiment of  FIG. 19 , the overall dimensions of the spoiler  130  includes a diameter of from about 3 feet to about 6 feet and a height of from about 18 inches to about 24 inches. In either of the omnidirectional spoilers shown in  FIGS. 19 and 20  regardless of the wind direction, a linear wind will always impinge upon a concavely curved surface and the domed top of the device and, therefore, be deflected upwardly in a spiral pattern to cause turbulence to the wind and reduce or eliminate lifting effect on the roof itself. 
     Thus, with the system of the present invention, a variety of different configured spoilers can be provided for causing turbulence of wind across the surface of a flat or relatively low pitched roof to prevent lifting forces during high wind conditions. In one embodiment, the spoiler incorporates a wind driven generator for combining the turbulence generating effect together with the generation of electrical power not only during a severe wind storm but whenever sufficient wind is present to operate the generators. The system of the present invention provides protection against roof damage during high wind conditions and assists in maintaining the roof's integrity during storms. 
     It will become apparent to those skilled in the art that various modifications to the preferred embodiment of the invention as described herein can be made without departing from the spirit or scope of the invention as defined by the appended claims.