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REFERENCE TO PRIOR APPLICATION DATA  
       [0001]    This application is a continuation-in-part of copending application Ser. No. 10/357,113 filed on Feb. 3, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to fasteners employed to fasten a covering material to an underlying substrate. More particularly, the invention relates to a stress plate with a fastener for fastening a membrane, such as a roof membrane or roofing insulation, to a roof deck, a wall, concrete, stone, plaster, steel deck or wood.  
           [0004]    2. Reported Development  
           [0005]    Fasteners are conventionally employed in the building industry for fastening or clamping a flexible membrane, such as an insulation membrane to a substrate, such as a roof deck. The fasteners typically comprise a large head portion and a shank portion. In use, the shank portion is driven through the membrane into the underlying substrate to anchor the fastener thereinto, while the head portion holds the membrane against the substrate and prevent removal thereof by wind lift. The undersurface of the head portion is typically provided with gripping means so that the membrane is prevented from moving or sliding under the fastener. The gripping means are typically designed not to penetrate completely through the membrane in order to prevent atmospheric moisture from entering into the substrate through the holes which tend to be made by the gripping means. It is also important that the gripping means are spread/distributed in the undersurface of the head portion of the stress plate in order prevent tearing of the membrane. Conventional fasteners are illustrated by the following references.  
           [0006]    U.S. Pat. No. 4,787,188 discloses a stress plate for securing a roof membrane to a roof deck. The stress plate is circular having a top surface and a bottom surface with a central circular opening for receiving a screw for fastening the stress plate over a roof membrane and to the roof deck. The stress plate is equipped with four gripping prongs of triangular shape which are circumferentially spaced from each other by 90°.  
           [0007]    In use a first membrane is applied to a roof deck surface, then the membrane is secured to the roof deck surface with the stress plate and the screw. A top sheet or membrane is lapped over the first membrane to cover the stress plate and welded to the first membrane. The four gripping prongs in the stress plate grip the first sheet and hold the same on top of the roof deck without tearing.  
           [0008]    U.S. Pat. No. 5,049,018 discloses a fastener for gripping a substrate material. The fastener is of a unitary piece comprising a head portion, a shaft portion, and a hook portion at the end of the shaft portion, wherein the hook portion has an outwardly and upwardly extending resilient end portion. The end portion has an end surface which provides gripping contact with a wall of a hole in a substrate into which the fastener is inserted.  
           [0009]    It is apparent that the reference invention is directed to a fastener the construction of which insures that the fastener will not be dislodged by wind uplift from the hole of the substrate.  
           [0010]    U.S. Pat. No. 5,163,798 relates to a fastener assembly which is employed to secure plies or membranes of roofing, felt and paper to prevent the materials from being blown off the base roofing material before the base material is sufficiently hardened.  
           [0011]    The assembly comprises a fastener and a retainer plate. The assembly includes a fastener plate which defines a substantially rectangular opening. The fastener includes a head and a pair of legs which are integrally hingably connected to the head. The legs have a contoured distal portion and an angular side configuration so that at least one of the legs is forced apart as the fastener is driven into the base material.  
           [0012]    We have observed that under windy conditions the prior art fasteners need improvement in securely holding a flexible membrane on a substrate without the gripping means penetrating the flexible membrane, and without tearing the flexible membrane.  
           [0013]    Accordingly, an object of the present invention is to provide a new and improved stress plate with a fastener to allow attachment of one or more flexible membranes to an underlying substrate without tearing the flexible membrane or allowing it to slip out from under the stress plate.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention comprises two non-integral components: a stress plate, and a fastener. In use the stress plate and the associated fastener attach and firmly hold a flexible membrane to an underlying substrate, such as a roof deck. The stress plate has a top surface and a bottom surface and is provided with multiple barbs extending vertically outwardly from the bottom surface and having sufficient length to grip the flexible membrane preferably without puncturing therethrough. The stress plate further includes an opening in its central portion to allow a fastener, such as a screw, therethrough for attachment of the stress plate to the underlying substrate. The opening may be circular, rectangular or square.  
           [0015]    The present invention comprises sixteen preferred embodiments.  
           [0016]    In the first embodiment of the invention the stress plate is circular having an opening in its center portion and three dome-shaped concentric ribs or protuberances rising above the top surface of the stress plate for providing sufficient strength thereto. The radius of the concentric ribs increases from the center opening to the outer circumference of the stress plate. Separating the first and second concentric ribs there is a first concentric depression or dimple, and separating the second and third concentric ribs there is a second concentric depression or dimple. A flat surface extends between the third rib and the edge or circumference of the stress plate. In preferred embodiments, the circular stress plate can range in diameter from about 1 to about 5 inches. At least one of the first or second dimples or the flat surface is provided with multiple pairs of barbs.  
           [0017]    The first dimple optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configurations. The groups of barbs are approximately evenly spaced from each other. Optionally, the barbs can be located in the second dimple. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of triple barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0018]    In the second embodiment of the invention the stress plate is elliptical having an opening in its center portion and three dome-shaped concentric ribs or protuberances rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second concentric ribs there is a first concentric depression or dimple, and separating the second and third concentric ribs there is a second concentric depression or dimple. A flat surface extends between the third rib and the edge or circumference of the stress plate. At least one of the first or second dimples or the flat surface is provided with multiple groups of triple barbs.  
           [0019]    The first dimple optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to twelve groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of triple barbs are approximately evenly spaced from each other. Optionally, the barbs can be located in the second dimple. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of triple barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0020]    In the third embodiment of the invention the stress plate is of square configuration having an opening in its center portion and three dome-shaped concentric ribs or protuberances running parallel to each other and to the edge of the stress plate rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second ribs there is a first depression or dimple, and separating the second and third ribs there is a second depression or dimple. A flat surface extends between the third rib and the edge or circumference of the stress plate. At least one of the first or second concentric dimples or the flat concentric surface is provided with multiple groups of triple barbs.  
           [0021]    The first dimple preferably optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to twelve groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of triple barbs are approximately evenly spaced from each other. Optionally, the barbs can be located in the second dimple. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0022]    In the fourth embodiment of the invention the stress plate is of rectangular configuration having an opening in its center portion and three dome-shaped ribs or protuberances running parallel to each other and to the edge of the stress plate rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second ribs there is a first depression or dimple, and separating the second and third ribs there is a second depression or dimple. A flat surface extends between the third rib and the edge or circumference of the stress plate. At least one of the first or second concentric dimples or the flat concentric surface is provided with multiple groups of triple barbs.  
           [0023]    The first dimple optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of triple barbs are approximately evenly spaced from each other. Optionally, the barbs can be located in the second dimple. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0024]    In the fifth embodiment of the invention the stress plate is circular having an opening in its center portion and two dome-shaped concentric ribs or protuberances rising above the top surface of the stress plate for providing sufficient strength thereto. The radius of the first concentric rib close to the opening is smaller than the radius of the second concentric rib close to the circumference of the stress plate. Separating the first and second concentric ribs there is a concentric depression or dimple. A flat surface extends between the second rib and the edge or circumference of the stress plate. At least one of the dimples or flat surface is provided with multiple groups of triple barbs.  
           [0025]    The first dimple optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of triple barbs are approximately evenly spaced from each other. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of triple barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.  
           [0026]    In the sixth embodiment of the invention the stress plate is elliptical having an opening in its center portion and two dome-shaped concentric ribs or protuberances rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second concentric ribs there is a first concentric depression or dimple. The edge or circumference of the stress plate terminates in a substantially flat surface. At least one of the dimple or flat surface is provided with multiple groups of triple barbs.  
           [0027]    The dimple optionally can be provided with groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly space from each other. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of triple barbs each of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0028]    In the seventh embodiment of the invention the stress plate is of square configuration having an opening in its center portion and two dome-shaped ribs or protuberances running parallel to each other and to the edge of the stress plate rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second ribs there is a depression or dimple. A flat surface extends between the second rib and the edge or circumference of the stress plate. At least one of the dimple or flat surface is provided with multiple groups of triple barbs.  
           [0029]    The dimple optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly space from each other. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0030]    In the eighth embodiment of the invention the stress plate is of rectangular configuration having an opening in its center portion and two dome-shaped ribs or protuberances running parallel to each other and to the edge of the stress plate rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second ribs there is a depression or dimple. A flat surface extends between the second rib and the edge or circumference of the stress plate. At least one of the dimple or flat surface is provided with multiple groups of triple barbs.  
           [0031]    The dimple optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of triple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of triple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of triple barbs each of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0032]    In the ninth embodiment of the invention the stress plate is circular having an opening in its center portion and three dome-shaped concentric ribs or protuberances rising above the top surface of the stress plate for providing sufficient strength thereto. The radius of the concentric ribs increases from the center opening to the outer circumference of the stress plate. Separating the first and second concentric ribs there is a first concentric depression or dimple, and separating the second and third concentric ribs there is a second concentric depression or dimple. A flat surface extends between the third rib and the edge or circumference of the stress plate. In preferred embodiments, the circular stress plate can range in diameter from about 1 to about 5 inches. At least one of the first or second dimples or the flat surface is provided with multiple groups of quadruple barbs.  
           [0033]    The first dimple optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configurations. The groups of barbs are approximately evenly spaced from each other. Optionally, the barbs can be located in the second dimple. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of quadruple barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0034]    In the tenth embodiment of the invention the stress plate is elliptical having an opening in its center portion and three dome-shaped concentric ribs or protuberances rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second concentric ribs there is a first concentric depression or dimple, and separating the second and third concentric ribs there is a second concentric depression or dimple. A flat surface extends between the third rib and the edge or circumference of the stress plate. At least one of the first or second dimples or the flat surface is provided with multiple groups of quadruple barbs.  
           [0035]    The first dimple optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to twelve groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of quadruple barbs are approximately evenly spaced from each other. Optionally, the barbs can be located in the second dimple. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of quadruple barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0036]    In the eleventh embodiment of the invention the stress plate is of square configuration having an opening in its center portion and three dome-shaped concentric ribs or protuberances running parallel to each other and to the edge of the stress plate rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second ribs there is a first depression or dimple, and separating the second and third ribs there is a second depression or dimple. A flat surface extends between the third rib and the edge or circumference of the stress plate. At least one of the first or second concentric dimples or the flat concentric surface is provided with multiple groups of quadruple barbs.  
           [0037]    The first dimple preferably optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to twelve groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of quadruple barbs are approximately evenly spaced from each other. Optionally, the barbs can be located in the second dimple. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0038]    In the twelfth embodiment of the invention the stress plate is of rectangular configuration having an opening in its center portion and three dome-shaped ribs or protuberances running parallel to each other and to the edge of the stress plate rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second ribs there is a first depression or dimple, and separating the second and third ribs there is a second depression or dimple. A flat surface extends between the third rib and the edge or circumference of the stress plate. At least one of the first or second concentric dimples or the flat concentric surface is provided with multiple groups of quadruple barbs.  
           [0039]    The first dimple optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of quadruple barbs are approximately evenly spaced from each other. Optionally, the barbs can be located in the second dimple. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs approximately evenly spaced from each other.  
           [0040]    In the thirteenth embodiment of the invention the stress plate is circular having an opening in its center portion and two dome-shaped concentric ribs or protuberances rising above the top surface of the stress plate for providing sufficient strength thereto. The radius of the first concentric rib close to the opening is smaller than the radius of the second concentric rib close to the circumference of the stress plate. Separating the first and second concentric ribs there is a concentric depression or dimple. A flat surface extends between the second rib and the edge or circumference of the stress plate. At least one of the dimple or flat surface is provided with multiple groups of quadruple barbs.  
           [0041]    The first dimple optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of quadruple barbs are approximately evenly spaced from each other. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of quadruple barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.  
           [0042]    In the fourteenth embodiment of the invention the stress plate is elliptical having an opening in its center portion and two dome-shaped concentric ribs or protuberances rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second concentric ribs there is a first concentric depression or dimple. The edge or circumference of the stress plate terminates in a substantially flat surface. At least one of the dimple or flat surface is provided with multiple groups of quadruple barbs.  
           [0043]    The dimple optionally can be provided with groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly space from each other. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of quadruple barbs each of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0044]    In the fifteenth embodiment of the invention the stress plate is of square configuration having an opening in its center portion and two dome-shaped ribs or protuberances running parallel to each other and to the edge of the stress plate rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second ribs there is a depression or dimple. A flat surface extends between the second rib and the edge or circumference of the stress plate. At least one of the dimples or flat surface is provided with multiple groups of quadruple barbs.  
           [0045]    The dimple optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly space from each other. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0046]    In the sixteenth embodiment of the invention the stress plate is of rectangular configuration having an opening in its center portion and two dome-shaped ribs or protuberances running parallel to each other and to the edge of the stress plate rising above the top surface of the stress plate for providing sufficient strength thereto. Separating the first and second ribs there is a depression or dimple. A flat surface extends between the second rib and the edge or circumference of the stress plate. At least one of the dimple or flat surface is provided with multiple groups of quadruple barbs.  
           [0047]    The dimple optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight groups of quadruple barbs each barb of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other. The flat surface of the stress plate adjacent to the edge optionally can be provided with a multiplicity of groups of quadruple barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten groups of quadruple barbs each of which may be of triangular, rectangular, or semi-circular configuration. The groups of barbs are approximately evenly spaced from each other.  
           [0048]    Both the triple and the quadruple barbs may be arranged in a group or in a row configuration to form the multiplicity of barbs. Each embodiment may consist of a multiplicity of triple barbs in a group or row configuration, or a multiplicity of quadruple barbs in a group or row configuration. Furthermore, each embodiment may consists of a multiplicity of triple barbs and quadruple barbs arranged in an alternating configuration. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0049]    The invention will be further described with respect to the accompanying drawings wherein:  
         [0050]    [0050]FIG. 1 is a top, perspective view of the circular stress plate having three ribs and multiple groups of triple barbs thereon and fastener;  
         [0051]    [0051]FIG. 2 is a side elevational view thereof;  
         [0052]    [0052]FIG. 3 is a top plan view thereof;  
         [0053]    [0053]FIG. 4 is a bottom perspective view thereof;  
         [0054]    [0054]FIG. 5 is a top perspective view of the elliptical stress plate having three ribs and multiple groups of triple barbs thereon and fastener;  
         [0055]    [0055]FIG. 6 is a side elevational view thereof;  
         [0056]    [0056]FIG. 7 is another side elevational view thereof;  
         [0057]    [0057]FIG. 8 is a top plan view thereof;  
         [0058]    [0058]FIG. 9 is a bottom perspective view thereof;  
         [0059]    [0059]FIG. 10 is a top perspective view of the square stress plate having three ribs and multiple groups of triple barbs thereon and fastener;  
         [0060]    [0060]FIG. 11 is a side elevational view thereof;  
         [0061]    [0061]FIG. 12 is a top plan view thereof;  
         [0062]    [0062]FIG. 13 is a bottom perspective view thereof;  
         [0063]    [0063]FIG. 14 is a top perspective view of the rectangular stress plate having three ribs and multiple groups of triple barbs thereon and fastener;  
         [0064]    [0064]FIG. 15 is a side elevational view thereof;  
         [0065]    [0065]FIG. 16 is another side elevational view thereof;  
         [0066]    [0066]FIG. 17 is a top plan view thereof;  
         [0067]    [0067]FIG. 18 is a bottom perspective view thereof;  
         [0068]    [0068]FIG. 19 is a is a top perspective view of the circular stress plate having two ribs and multiple groups of triple barbs thereon and fastener;  
         [0069]    [0069]FIG. 20 is a side elevational view thereof;  
         [0070]    [0070]FIG. 21 is a top plan view thereof;  
         [0071]    [0071]FIG. 22 is a bottom perspective view thereof;  
         [0072]    [0072]FIG. 23 is a top perspective view of the elliptical stress plate having two ribs and multiple groups of triple barbs thereon and fastener;  
         [0073]    [0073]FIG. 24 is a side elevational view thereof;  
         [0074]    [0074]FIG. 25 is another side elevational view thereof;  
         [0075]    [0075]FIG. 26 is a top plan view thereof;  
         [0076]    [0076]FIG. 27 is a bottom perspective view thereof;  
         [0077]    [0077]FIG. 28 is a is a top perspective view of the square stress plate having two ribs and multiple groups of triple barbs thereon and fastener;.  
         [0078]    [0078]FIG. 29 is a side elevational view thereof;  
         [0079]    [0079]FIG. 30 is a top plan view thereof;  
         [0080]    [0080]FIG. 31 is a bottom perspective view thereof;  
         [0081]    [0081]FIG. 32 is a top perspective view of the rectangular stress plate having two ribs and multiple groups of triple barbs thereon and fastener;  
         [0082]    [0082]FIG. 33 is a side elevational view thereof;  
         [0083]    [0083]FIG. 34 is another side elevational view thereof;  
         [0084]    [0084]FIG. 35 is a top plan view thereof;  
         [0085]    [0085]FIG. 36 is a bottom perspective view thereof;  
         [0086]    [0086]FIG. 37 is a top, perspective view of the circular stress plate having three ribs and multiple groups of quadruple barbs thereon and fastener;  
         [0087]    [0087]FIG. 38 is a side elevational view thereof;  
         [0088]    [0088]FIG. 39 is a top plan view thereof;  
         [0089]    [0089]FIG. 40 is a bottom perspective view thereof;  
         [0090]    [0090]FIG. 41 is a top perspective view of the elliptical stress plate having three ribs and multiple groups of quadruple barbs thereon and fastener;  
         [0091]    [0091]FIG. 42 is a side elevational view thereof;  
         [0092]    [0092]FIG. 43 is another side elevational view thereof;  
         [0093]    [0093]FIG. 44 is a top plan view thereof;  
         [0094]    [0094]FIG. 45 is a bottom perspective view thereof;  
         [0095]    [0095]FIG. 50 is a top perspective view of the square stress plate having three ribs and multiple groups of quadruple barbs thereon and fastener;  
         [0096]    [0096]FIG. 51 is a side elevational view thereof;  
         [0097]    [0097]FIG. 52 is a top plan view thereof;  
         [0098]    [0098]FIG. 53 is a bottom perspective view thereof;  
         [0099]    [0099]FIG. 54 is a top perspective view of the rectangular stress plate having three ribs and multiple groups of quadruple barbs thereon and fastener;  
         [0100]    [0100]FIG. 55 is a side elevational view thereof;  
         [0101]    [0101]FIG. 56 is another side elevational view thereof;  
         [0102]    [0102]FIG. 57 is a top plan view thereof;  
         [0103]    [0103]FIG. 58 is a bottom perspective view thereof;  
         [0104]    [0104]FIG. 59 is a is a top perspective view of the circular stress plate having two ribs and multiple groups of quadruple barbs thereon and fastener;  
         [0105]    [0105]FIG. 60 is a side elevational view thereof;  
         [0106]    [0106]FIG. 61 is a top plan view thereof;  
         [0107]    [0107]FIG. 62 is a bottom perspective view thereof;  
         [0108]    [0108]FIG. 63 is a top perspective view of the elliptical stress plate having two ribs and multiple groups of quadruple barbs thereon and fastener;  
         [0109]    [0109]FIG. 64 is a side elevational view thereof;  
         [0110]    [0110]FIG. 65 is another side elevational view thereof;  
         [0111]    [0111]FIG. 66 is a top plan view thereof;  
         [0112]    [0112]FIG. 67 is a bottom perspective view thereof;  
         [0113]    [0113]FIG. 68 is a is a top perspective view of the square stress plate having two ribs and multiple groups of quadruple barbs thereon and fastener;  
         [0114]    [0114]FIG. 69 is a side elevational view thereof;  
         [0115]    [0115]FIG. 70 is a top plan view thereof;  
         [0116]    [0116]FIG. 71 is a bottom perspective view thereof;  
         [0117]    [0117]FIG. 72 is a top perspective view of the rectangular stress plate having two ribs and multiple groups of quadruple barbs thereon and fastener;  
         [0118]    [0118]FIG. 73 is an enlarged top plan view of three triangular barbs in a group configuration;  
         [0119]    [0119]FIG. 74 is an enlarged top plan view of three triangular barbs in a row configuration;  
         [0120]    [0120]FIG. 75 is an enlarged top plan view of three rectangular barbs in a group configuration;  
         [0121]    [0121]FIG. 76 is an enlarged top plan view of three rectangular barbs in a row configuration;  
         [0122]    [0122]FIG. 77 is an enlarged top plan view of three semi-circular barbs in a group configuration;  
         [0123]    [0123]FIG. 78 is an enlarged top plan view of three semi-circular barbs in a row configuration;  
         [0124]    [0124]FIG. 79 is a cross-sectional view illustrating the use of the stress plate and the fastener for attaching a roof membrane to a roof deck.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0125]    Reference is now being made to the drawings wherein like numerals represent like parts throughout the figures showing the various embodiments of the present invention.  
       First Embodiment—Circular with Three Ribs  
       [0126]    [0126]FIGS. 1-4 relate to a preferred first embodiment of the present invention in which the circular stress plate is generally designated at  10  and the fastener is generally designated at  12 . The two components are non-integral and when put together, constitute the invention. The circular stress plate  10  has a round or rectangular opening  14  in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with three concentric dome-shaped ribs: rib  16  is the closest to the opening; rib  20  is farthest from the opening; and rib  18  is between ribs  16  and  20 . The ribs serve as reinforcements to the stress plate. Separating rib  16  from rib  18  there is a concentric depression or dimple  22 , and separating rib  18  from rib  20  there is another concentric depression or dimple  24 . An essentially flat surface  26  extends between rib  20  and the circumferential edge  28  of the stress plate. Dimple  22  is provided with multiple groups of triple barbs  30  (six pairs are shown), and flat surface  26  is also provided with multiple groups of triple barbs (eight pairs are shown). The individual barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The groups of barbs are approximately evenly spaced from each other. The individual barbs forming the triple barbs may be in a group configuration as shown, or may be in a row configuration (not shown).  
       Second Embodiment—Elliptical with Three Ribs  
       [0127]    [0127]FIGS. 5-9 relate to a preferred second embodiment of the present invention in which the elliptical stress plate is generally designated at  10 ′ and the fastener is generally designated at  12 ′. The two components are non-integral and when put together, constitute the invention. The elliptical stress plate  10 ′ has a round or rectangular opening  14 ′ in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with three concentric dome-shaped ribs: rib  16 ′ is the closest to the opening, rib  20 ′ is farthest from the opening; and rib  18 ′ is between ribs  16 ′ and  20 ′. The ribs serve as reinforcements to the stress plate. Separating rib  16 ′ from rib  18 ′ there is a concentric depression or dimple  22 ′, and separating rib  18 ′ from rib  20 ′ there is another concentric depression or dimple  24 ′. An essentially flat surface  26 ′ extends between rib  20 ′ and the circumferential edge  28 ′ of the stress plate. Dimple  22 ′ is provided with multiple groups of triple barbs  30 ′ (six pairs are shown), and flat surface  26 ′ is also provided with multiple groups of triple barbs (eight pairs are shown). The individual barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The groups of barbs are approximately evenly spaced from each other. The individual barbs forming the triple barbs may be in a group configuration as shown, or may be in a row configuration (not shown).  
       Third Embodiment—Square with Three Ribs  
       [0128]    [0128]FIGS. 10-13 relate to a preferred third embodiment of the present invention in which the square stress plate is generally designated at  40  and the fastener is generally designated at  42 . The two components are non-integral and when put together, constitute the invention. The square stress plate  40  has a round or rectangular opening  44  in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with three concentric dome-shaped ribs: rib  46  is the closest to the opening; rib  50  is farthest from the opening; and rib  48  is between ribs  46  and  50 . The ribs serve as reinforcements to the stress plate. Separating rib  46  from rib  48  there is a concentric depression or dimple  52 , and separating rib  48  from rib  50  there is another concentric depression or dimple  54 . An essentially flat surface  56  extends between rib  50  and the circumferential edge  58  of the stress plate. Dimple  52  is provided with multiple groups of triple barbs  60  (eight pairs are shown), and flat surface  56  is also provided with multiple groups of triple barbs (eight pairs are shown). The individual barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The groups of barbs are approximately evenly spaced from each other. The individual barbs forming the triple barbs may be in a group configuration as shown, or may be in a row configuration (not shown).  
       Fourth Embodiment—Rectangular with Three Ribs  
       [0129]    [0129]FIGS. 14-18 relate to a preferred fourth embodiment of the present invention in which the rectangular stress plate is generally designated at  40 ′ and the fastener is generally designated at  42 ′. The two components are non-integral and when put together, constitute the invention. The rectangular stress plate  40 ′ has a round or rectangular opening  44 ′ in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with three concentric dome-shaped ribs: rib  46 ′ is the closest to the opening; rib  50 ′ is farthest from the opening; and rib  48 ′ is between ribs  46 ′ and  50 ′. The ribs serve as reinforcements to the stress plate. Separating rib  46 ′ from rib  48 ′ there is a concentric depression or dimple  52 ′, and separating rib  48 ′ from rib  50 ′ there is another concentric depression or dimple  54 ′. An essentially flat surface  56 ′ extends between rib  50 ′ and the circumferential edge  58 ′ of the stress plate. Dimple  52 ′ is provided with multiple groups of triple barbs  60 ′ (ten pairs are shown), and flat surface  56 ′ is also provided with multiple groups of triple barbs (eight pairs are shown). The individual barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The groups of barbs are approximately evenly spaced from each other. The individual barbs forming the triple barbs may be in a group configuration as shown, or may be in a row configuration (not shown).  
       Fifth Embodiment—Circular with Two Ribs  
       [0130]    [0130]FIGS. 19-22 relate to a preferred fifth embodiment of the present invention in which the circular stress plate is generally designated at  70  and the fastener is generally designated at  72 . The two components are non-integral and when put together, constitute the invention. The circular stress plate  70  has a round or rectangular opening  74  in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with two concentric dome-shaped ribs: rib  76  is an inner rib close to the opening, and rib  78  is an outer rib spaced from the inner rib toward the circumferential edge  88  of the stress plate. The ribs serve as reinforcements to the stress plate. Separating rib  76  from rib  78  there is a concentric depression or dimple  82 . An essentially flat surface  86  extends between rib  78  and the circumferential edge  88  of the stress plate. Dimple  82  is provided with multiple groups of triple barbs  90  (eight pairs are shown), and flat surface  86  is also provided with multiple groups of triple barbs (eight pairs are shown). The individual barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The groups of barbs are approximately evenly spaced from each other. The individual barbs forming the triple barbs may be in a group configuration as shown, or may be in a row configuration (not shown).  
       Sixth Embodiment—Elliptical with Two Ribs  
       [0131]    [0131]FIGS. 23-27 relate to a preferred sixth embodiment of the present invention in which the elliptical stress plate is generally designated at  70 ′ and the fastener is generally designated at  72 ′. The two components are non-integral and, when put together, constitute the invention. The elliptical stress plate  70 ′ has a round or rectangular opening  74 ′ in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with two concentric dome-shaped ribs: rib  76 ′ is an inner rib close to the opening, and rib  78 ′ is an outer rib spaced from the inner rib toward the circumferential edge  88 ′ of the stress plate. The ribs serve as reinforcements to the stress plate. Separating rib  76 ′ from rib  78 ′ there is a concentric depression or dimple  82 ′. An essentially flat surface  86 ′ extends between rib  78 ′ and the circumferential edge  88 ′ of the stress plate. Dimple  82 ′ is provided with multiple groups of triple barbs  90 ′ (six pairs are shown), and flat surface  86 ′ is also provided with multiple groups of triple barbs (eight pairs are shown). The individual barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The groups of barbs are approximately evenly spaced from each other. The individual barbs forming the triple barbs may be in a group configuration as shown, or may be in a row configuration (not shown).  
       Seventh Embodiment—Square with Two Ribs  
       [0132]    [0132]FIGS. 28-31 relate to a preferred seventh embodiment of the present invention in which the square stress plate is generally designated at  100  and the fastener is generally designated at  102 . The two components are non-integral and, when put together, constitute the invention. The square stress plate  100  has a round or rectangular opening  104  in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with two concentric dome-shaped ribs: rib  106  is an inner rib close to the opening, and rib  108  is an outer rib spaced from the inner rib toward the circumferential edge  118  of the stress plate. The ribs serve as reinforcements to the stress plate. Separating rib  106  from rib  108  there is a concentric depression or dimple  112 . An essentially flat surface  106  extends between rib  108  and the circumferential edge  118  of the stress plate. Dimple  112  is provided with multiple groups of triple barbs  120  (eight pairs are shown), and flat surface  116  is also provided with multiple groups of triple barbs (eight pairs are shown). The individual barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The groups of barbs are approximately evenly spaced from each other. The individual barbs forming the triple barbs may be in a group configuration as shown, or may be in a row configuration (not shown).  
       Eighth Embodiment—Rectangular with Two Ribs  
       [0133]    [0133]FIGS. 32-36 relate to a preferred eighth embodiment of the present invention in which the rectangular stress plate is generally designated at  100 ′ and the fastener is generally designated at  102 ′. The two components are non-integral and, when put together, constitute the invention. The rectangular stress plate  100 ′ has a round or rectangular opening  104 ′ in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with two concentric dome-shaped ribs: rib  106 ′ is an inner rib close to the opening, and rib  108 ′ is an outer rib spaced from the inner rib toward the circumferential edge  118 ′ of the stress plate. The ribs serve as reinforcements to the stress plate. Separating rib  106 ′ from rib  108 ′ there is a concentric depression or dimple  112 ′. An essentially flat surface  106 ′ extends between rib  108 ′ and the circumferential edge  118 ′ of the stress plate. Dimple  112 ′ is provided with multiple groups of triple barbs  120 ′ (eight pairs are shown), and flat surface  116 ′ is also provided with multiple groups of triple barbs (eight pairs are shown). The individual barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The groups of barbs are approximately evenly spaced from each other. The individual barbs forming the triple barbs may be in a group configuration as shown, or may be in a row configuration (not shown).  
       Ninth Embodiment—Circular with Three Ribs  
       [0134]    FIGS.  3740  relate to a preferred ninth embodiment of the present invention in which the circular stress plate is generally designated at  130  and the fastener is generally designated at  132 . The two components are non-integral and when put together, constitute the invention. The circular stress plate  130  has a round or rectangular opening  134  in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with three concentric dome-shaped ribs: rib  136  is the closest to the opening; rib  140  is farthest from the opening; and rib  138  is between ribs  136  and  140 . The ribs serve as reinforcements to the stress plate. Separating rib  136  from rib  138  there is a concentric depression or dimple  142 , and separating rib  138  from rib  140  there is another concentric depression or dimple  144 . An essentially flat surface  146  extends between rib  140  and the circumferential edge  148  of the stress plate. Dimple  142  is provided with multiple quadruple barbs  150  (six are shown), and flat surface  146  is also provided with multiple quadruple barbs (eight are shown).  
       Tenth Embodiment—Elliptical with Three Ribs  
       [0135]    [0135]FIGS. 41-45 relate to a preferred tenth embodiment of the present invention in which the elliptical stress plate is generally designated at  130 ′ and the fastener is generally designated at  132 ′. The two components are non-integral and when put together, constitute the invention. The elliptical stress plate  130 ′ has a round or rectangular opening  134 ′ in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with three concentric dome-shaped ribs: rib  136 ′ is the closest to the opening, rib  140 ′ is farthest from the opening; and rib  138 ′ is between ribs  136 ′ and  140 ′. The ribs serve as reinforcements to the stress plate. Separating rib  136 ′ from rib  138 ′ there is a concentric depression or dimple  142 ′, and separating rib  138 ′ from rib  140 ′ there is another concentric depression or dimple  144 ′. An essentially flat surface  146 ′ extends between rib  140 ′ and the circumferential edge  148 ′ of the stress plate. Dimple  142 ′ is provided with multiple quadruple barbs  150 ′ (six are shown), and flat surface  146 ′ is also provided with multiple quadruple barbs (eight are shown).  
       Eleventh Embodiment—Square with Three Ribs  
       [0136]    [0136]FIGS. 46-49 relate to a preferred eleventh embodiment of the present invention in which the square stress plate is generally designated at  160  and the fastener is generally designated at  162 . The two components are non-integral and when put together, constitute the invention. The square stress plate  160  has a round or rectangular opening  164  in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with three concentric dome-shaped ribs: rib  166  is the closest to the opening; rib  170  is farthest from the opening; and rib  168  is between ribs  166  and  170 . The ribs serve as reinforcements to the stress plate. Separating rib  166  from rib  168  there is a concentric depression or dimple  172 , and separating rib  168  from rib  170  there is another concentric depression or dimple  174 . An essentially flat surface  176  extends between rib  170  and the circumferential edge  178  of the stress plate. Dimple  172  is provided with multiple quadruple barbs  180  (eight are shown), and flat surface  176  is also provided with multiple quadruple barbs (eight are shown).  
       Twelfth Embodiment—Rectangular with Three Ribs  
       [0137]    [0137]FIGS. 50-54 relate to a preferred twelfth embodiment of the present invention in which the rectangular stress plate is generally designated at  160 ′ and the fastener is generally designated at  162 ′. The two components are non-integral and when put together, constitute the invention. The rectangular stress plate  160 ′ has a round or rectangular opening  164 ′ in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with three concentric dome-shaped ribs: rib  166 ′ is the closest to the opening; rib  170 ′ is farthest from the opening; and rib  168 ′ is between ribs  166 ′ and  170 ′. The ribs serve as reinforcements to the stress plate. Separating rib  166 ′ from rib  168 ′ there is a concentric depression or dimple  172 ′, and separating rib  168 ′ from rib  170 ′ there is another concentric depression or dimple  174 ′. An essentially flat surface  176 ′ extends between rib  170 ′ and the circumferential edge  178 ′ of the stress plate. Dimple  172 ′ is provided with multiple quadruple barbs  180 ′ (ten are shown), and flat surface  176 ′ is also provided with multiple quadruple barbs (eight are shown).  
       Thirteenth Embodiment—Circular with Two Ribs  
       [0138]    [0138]FIGS. 55-58 relate to a preferred thirteenth embodiment of the present invention in which the circular stress plate is generally designated at  190  and the fastener is generally designated at  192 . The two components are non-integral and when put together, constitute the invention. The circular stress plate  190  has a round or rectangular opening  194  in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with two concentric dome-shaped ribs: rib  196  is an inner rib close to the opening, and rib  198  is an outer rib spaced from the inner rib toward the circumferential edge  218  of the stress plate. The ribs serve as reinforcements to the stress plate. Separating rib  196  from rib  198  there is a concentric depression or dimple  212 . An essentially flat surface  216  extends between rib  198  and the circumferential edge  218  of the stress plate. Dimple  212  is provided with quadruple barbs  220  (eight are shown), and flat surface  216  is also provided with multiple quadruple barbs (eight are shown).  
       Fourteenth Embodiment—Elliptical with Two Ribs  
       [0139]    [0139]FIGS. 59-63 relate to a preferred fourteenth embodiment of the present invention in which the elliptical stress plate is generally designated at  190 ′ and the fastener is generally designated at  192 ′. The two components are non-integral and, when put together, constitute the invention. The elliptical stress plate  190 ′ has a round or rectangular opening  194 ′ in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with two concentric dome-shaped ribs: rib  196 ′ is an inner rib close to the opening, and rib  198 ′ is an outer rib spaced from the inner rib toward the circumferential edge  218 ′ of the stress plate. The ribs serve as reinforcements to the stress plate. Separating rib  196 ′ from rib  198 ′ there is a concentric depression or dimple  212 ′. An essentially flat surface  216 ′ extends between rib  198 ′ and the circumferential edge  218 ′ of the stress plate. Dimple  212 ′ is provided with multiple quadruple barbs  220 ′ (six are shown), and flat surface  216 ′ is also provided with multiple quadruple barbs (eight are shown).  
       Fifteenth Embodiment—Square with Two Ribs  
       [0140]    [0140]FIGS. 64-67 relate to a preferred fifteenth embodiment of the present invention in which the square stress plate is generally designated at  230  and the fastener is generally designated at  232 . The two components are non-integral and, when put together, constitute the invention. The square stress plate  230  has a round or rectangular opening  234  in its center portion through which the fastener is inserted when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with two concentric dome-shaped ribs: rib  236  is an inner rib close to the opening, and rib  238  is an outer rib spaced from the inner rib toward the circumferential edge  248  of the stress plate. The ribs serve as reinforcements to the stress plate. Separating rib  236  from rib  238  there is a concentric depression or dimple  242 . An essentially flat surface  246  extends between rib  238  and the circumferential edge  248  of the stress plate. Dimple  242  is provided with multiple quadruple barbs  250  (eight are shown), and flat surface  246  is also provided with multiple quadruple barbs (eight are shown).  
       Sixteenth Embodiment—Rectangular with Two Ribs  
       [0141]    [0141]FIGS. 68-72 relate to a preferred sixteenth embodiment of the present invention in which the rectangular stress plate is generally designated at  230 ′ and the fastener is generally designated at  232 ′. The two components are non-integral and, when put together, constitute the invention. The rectangular stress plate  230 ′ has a round or rectangular opening  234 ′ in its center portion through which the fastener is inserted, when the stress plate is employed for attaching and firmly holding a roof membrane to an underlying roof deck. The stress plate is provided with two concentric dome-shaped ribs: rib  236 ′ is an inner rib close to the opening, and rib  238 ′ is an outer rib spaced from the inner rib toward the circumferential edge  248 ′ of the stress plate. The ribs serve as reinforcements to the stress plate. Separating rib  236 ′ from rib  238 ′ there is a concentric depression or dimple  242 ′. An essentially flat surface  246 ′ extends between rib  238 ′ and the circumferential edge  248 ′ of the stress plate. Dimple  242 ′ is provided with multiple quadruple barbs  250 ′ (eight are shown), and flat surface  246 ′ is also provided with multiple quadruple barbs (eight are shown).  
         [0142]    [0142]FIGS. 73, 74,  75 ,  77  and  78  show the triple barbs in enlarged top plan views used in the stress plate and are integral therewith.  
         [0143]    [0143]FIG. 73 shows equilateral triangles in a group of three in the stress plate, the sharp points of the triangles extend outwardly from the bottom surface of the stress plate.  
         [0144]    [0144]FIG. 74 shows equilateral triangles in a row of three in the stress plate, the sharp points of the triangles extend outwardly from the bottom surface of the stress plate.  
         [0145]    [0145]FIG. 75 shows rectangular barbs in a group of three. In the stress plate the rectangular barbs extend outwardly from the bottom surface of the stress plate.  
         [0146]    [0146]FIG. 76 shows rectangular barbs in a row of three. In the stress plate the rectangular barbs extend outwardly from the bottom surface of the stress plate.  
         [0147]    [0147]FIG. 77 shows a pair of semi-circular barbs in a group of three. In the stress plate the semi-circular barbs extend outwardly from the bottom surface of the stress plate.  
         [0148]    [0148]FIG. 78 shows a pair of semi-circular barbs in a row of three. In the stress plate the semi-circular barbs extend outwardly from the bottom surface of the stress plate.  
         [0149]    The length of the barbs may vary depending on the thickness of the roof membrane which is to be attached to the underlying roof deck. Typically, the length of the barbs would be in the range of 0.1-1.0 centimeter or more, and preferably in the range of 0.2-0.5 centimeter.  
         [0150]    The barbs are formed by cutting the same from the surface of the stress plate and bending them  90 ° from the surface of the stress plate. The barbs can be formed by a conventional dye punching process.  
         [0151]    The stress plates are made of materials including galvanized or galvalume carbon steel and stainless steel. Softer metals such as copper or aluminum may also be used, however, the thickness of the stress plate should be larger to provide sufficient integrity to the stress plate. The thickness of the stress plate typically is about 0.05-0.1 cm. The fastener is typically a screw of 4 to 10 cm long having thread thereon.  
         [0152]    [0152]FIG. 79 is a cross-sectional view illustrating the use of the stress plate and the fastener for attaching a roof membrane to a roof deck. Lower membrane  260  is positioned over insulation  262  which is over the roof deck surface  264 . Inserting fastener  268  through stress plate  266 , insulation  262  and into roof deck  264 . Upper membrane  270  is then lapped-over portions of the lower membrane covering the stress plate  266 . The upper membrane is secured to the lower membrane by the welded seam  272 .  
         [0153]    Wind Uplift Test  
         [0154]    Comparative wind uplift tests were conducted on the triple and quadruple barb stress plates of the present invention, and the single barb stress plate. The wind uplift test measures the resistance of the roofing system to high wind currents. The triple and quadruple barb stress plates were found to have superior resistance to high wind currents as compared to single barb stress plates.  
                                                                                                                                                                                                             PARTS LIST                   First and Second Embodiments - Circular and       Elliptical with Three Ribs                Stress plate, generally designated   10, 10′           Fastener, generally designated   12, 12′           Opening in center portion   14, 14′           Ribs   16, 16′, 18, 18′,               20, 20′           Depressions or dimples   22, 22′, 24, 24′           Flat surface of stress plate   26, 26′           Circumferential edge of stress plate   28, 28′           Triple barbs   30, 30′            Third and Fourth Embodiments - Square and       Rectangular with Three Ribs                Stress plate, generally designated   40, 40′           Fastener, generally designated   42, 42′           Opening in center portion of stress plate   44, 44′           Ribs   46, 46′, 48, 48′,               50, 50′           Depressions or dimples   52, 52′, 54, 54′           Flat surface of stress plate   56, 56′           Circumferential edge of stress plate   58, 58′           Triple barbs   60, 60′            Fifth and Sixth Embodiments - Circular and       Elliptical with Two Ribs                Stress plate, generally designated   70, 70′           Fastener, generally designated   72, 72′           Opening in center portion of stress plate   74, 74′           Ribs   76, 76′, 78, 78′           Depressions or dimples   82, 82′           Flat surface of stress plate   86, 86′           Circumferential edge of stress plate   88, 88′           Triple of barbs   90, 90′            Seventh and Eighth Embodiments - Square and       Rectangular with Two Ribs                Stress plate, generally designated   100, 100′           Fastener, generally designated   102, 102′           Opening in center portion of stress plate   104, 104′           Ribs   106, 106′, 108,               108′           Depressions or dimples   112, 112′           Flat surface of stress plate   116, 116′           Circumferential edge of stress plate   118, 118′           Triple barbs   120, 120′            Ninth and Tenth Embodiments - Circular and       Elliptical with Three Ribs                Stress plate, generally designated   130, 130′           Fastener, generally designated   132, 132′           Opening in center portion of stress plate   134, 134′           Ribs   136, 136′, 138,               138′, 140, 140′           Depressions or dimples   142, 142′, 144,               144′           Flat surface of stress plate   146, 146′           Circumferential edge of stress plate   148, 148′           Quadruple barbs   150, 150′            Eleventh and Twelfth Embodiments - Square and       Rectangular with Three Ribs                Stress plate, generally designated   160, 160′           Fastener, generally designated   162, 162′           Opening in center portion of stress plate   164, 164′           Ribs   166, 166′, 168,               168′, 170, 170′           Depressions or dimples   172, 172′, 174,               174′           Flat surface of stress plate   176, 176′           Circumferential edge of stress plate   178, 178′           Quadruple barbs   180, 180′            Thirteenth and Fourteenth Embodiments - Circular and       Elliptical with Two Ribs                Stress plate, generally designated   190, 190′           Fastener, generally designated   192, 192′           Opening in center portion of stress plate   194, 194′           Ribs   196, 196′, 198,               198′,           Depressions or dimples   212, 212′           Flat surface of stress plate   216, 216′           Circumferential edge of stress plate   218, 218′           Quadruple barbs   220, 220′            Fifteenth and Sixteenth Embodiments - Square and       Rectangular with Two Ribs                Stress plate, generally designated   230, 230′           Fastener, generally designated   232, 232′           Opening in center portion of stress plate   234, 234′           Ribs   236, 236′, 238,               238′′           Depressions or dimples   242, 242′           Flat surface of stress plate   246, 246′           Circumferential edge of stress plate   248, 248′           Quadruple barbs   250, 250′            Using the Stress Plate                Lower membrane   260           Insulation   262           Roof deck   264           Stress plate   266           Fastener (screw)   268           Upper membrane   270           Welded seam   272                      
 
         [0155]    Having described the invention with reference to its preferred embodiments, it is to be understood that modifications within the scope of the invention will be apparent to those skilled in the art.

Summary:
A two-piece fastener plate and fastener assembly and method of securing a roof membrane to a roof deck wherein the fastener is reinforced with concentric dome-shaped ribs separated by concentric depressions or dimples. The concentric depressions or dimples are provided with multiple triple or quadruple barbs for gripping the roof membrane when the fastener secures the roof membrane to the roof deck.