Reported Development 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.

U. S. Patent 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°.

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.

U. S. Patent 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.

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.

U. S. Patent 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.

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.

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.

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 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 pairs of 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.

The present invention comprises eight embodiments.

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.

The first dimple optionally can be provided with a multiplicity of pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight pairs of triangular, rectangular, or semi-circular barbs approximately evenly space 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 pairs of barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten pairs of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.

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 pairs of barbs.

The first dimple optionally can be provided with a multiplicity of pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to twelve pairs of triangular, rectangular, or semi-circular barbs 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 pairs of barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten pairs of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.

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 pairs of barbs.

The first dimple preferably optionally can be provided with a multiplicity of pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to twelve pairs of triangular, rectangular, or semi-circular barbs 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 pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to sixteen pairs of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.

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 pairs of barbs.

The first dimple optionally can be provided with a multiplicity of pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to fourteen pairs of triangular, rectangular, or semi-circular barbs 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 pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to sixteen pairs of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.

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 dimple or flat surface is provided with multiple pairs of barbs.

The first dimple optionally can be provided with a multiplicity of pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight pairs of triangular, rectangular, or semi-circular pair of barbs 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 pairs of barbs extending downward from the bottom surface of the stress plate, and preferably, four to ten pairs of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.

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 pairs of barbs.

The dimple optionally can be provided with a multiplicity of pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to eight pairs of triangular, rectangular, or semi-circular barbs 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 pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to ten pairs of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.

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 pairs of barbs.

The dimple optionally can be provided with a multiplicity of pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to twelve pairs of triangular, rectangular, or semi-circular barbs 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 pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to sixteen pairs of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.

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 pairs of barbs.

The dimple optionally can be provided with a multiplicity of pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to fourteen pairs of triangular, rectangular, or semi-circular barbs 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 pairs of barbs extending 90° downward from the bottom surface of the stress plate, and preferably, four to sixteen pairs of triangular, rectangular, or semi-circular pairs of barbs approximately evenly spaced from each other.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further described with respect to the accompanying drawings wherein: FIG. 1 is a top, perspective view of the circular stress plate having three ribs thereon and fastener; FIG. 2 is a side elevational view thereof; FIG. 3 is a top plan view thereof; FIG. 4 is a bottom perspective view thereof; FIG. 5 is a top perspective view of the elliptical stress plate having three ribs thereon and fastener; FIG. 6 is a side elevational view thereof, FIG. 7 is another side elevational view thereof; FIG. 8 is a top plan view thereof; FIG. 9 is a bottom perspective view thereof; FIG. 10 is a top perspective view of the square stress plate having three ribs thereon and fastener; FIG. 11 is a side elevational view thereof ; FIG. 12 is a top plan view thereof ; FIG. 13 is a bottom perspective view thereof; FIG. 14 is a top perspective view of the rectangular stress plate having three ribs thereon and fastener; FIG. 15 is a side elevational view thereof; FIG. 16 is another side elevational view thereof; FIG. 17 is a top plan view thereof; FIG. 18 is a bottom perspective view thereof; FIG. 19 is a is a top perspective view of the circular stress plate having two ribs thereon and fastener; FIG. 20 is a side elevational view thereof ; FIG. 21 is a top plan view thereof; FIG. 22 is a bottom perspective view thereof; FIG. 23 is a top perspective view of the elliptical stress plate having two ribs thereon and fastener; FIG. 24 is a side elevational view thereof; FIG. 25 is another side elevational view thereof; FIG. 26 is a top plan view thereof; FIG. 27 is a bottom perspective view thereof; FIG. 28 is a is a top perspective view of the square stress plate having two ribs thereon and fastener; FIG. 29 is a side elevational view thereof ; FIG. 30 is a top plan view thereof ; FIG. 31 is a bottom perspective view thereof; FIG. 32 is a top perspective view of the rectangular stress plate having two ribs thereon and fastener; FIG. 33 is a side elevational view thereof; FIG. 34 is another side elevational view thereof; FIG. 35 is a top plan view thereof ; FIG. 36 is a bottom perspective view thereof ; FIG. 37 is an enlarged top plan view of the pair of triangular barbs; FIG. 38 is an enlarged top plan view of the pair of rectangular barbs ; FIG. 39 is an enlarged top plan view of the pair of semi-circular barbs; and FIG. 40 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 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 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 pairs of barbs 30 (six pairs are shown), and flat surface 26 is also provided with multiple pairs of barbs (eight pairs are shown). The pairs of barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The pairs of barbs are approximately evenly spaced from each other.

Second Embodiment-Elliptical with Three Ribs 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 pairs of barbs 30' (six pairs are shown), and flat surface 26'is also provided with multiple pairs of barbs (eight pairs are shown). The pairs of barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The pairs of barbs are approximately evenly spaced from each other.

Third Embodiment-Square with Three Ribs 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 pairs of barbs 60 (eight pairs are shown), and flat surface 56 is also provided with multiple pairs of barbs (eight pairs are shown). The pairs of barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The pairs of barbs are approximately evenly spaced from each other.

Fourth Embodiment-Rectangular with Three Ribs 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 pairs of barbs 60' (ten pairs are shown), and flat surface 56'is also provided with multiple pairs of barbs (eight pairs are shown). The pairs of barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The pairs of barbs are approximately evenly spaced from each other.

Fifth Embodiment-Circular with Two Ribs 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 pairs of barbs 90 (eight pairs are shown), and flat surface 86 is also provided with multiple pairs of barbs (eight pairs are shown). The pairs of barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The pairs of barbs are approximately evenly spaced from each other.

Sixth Embodiment-Elliptical with Two Ribs 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 pairs of barbs 90' (six pairs are shown), and flat surface 86'is also provided with multiple pairs of barbs (eight pairs are shown). The pairs of barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown).

The pairs of barbs are approximately evenly spaced from each other.

Seventh Embodiment-Square with Two Ribs 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 pairs of barbs 120 (eight pairs are shown), and flat surface 116 is also provided with multiple pairs of barbs (eight pairs are shown). The pairs of barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The pairs of barbs are approximately evenly spaced from each other.

Eighth Embodiment-Rectangular with Two Ribs 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 pairs of barbs 120' (eight pairs are shown), and flat surface 116'is also provided with multiple pairs of barbs (eight pairs are shown). The pairs of barbs are either triangular (as shown), or rectangular (not shown), or semi-circular (not shown). The pairs of barbs are approximately evenly spaced from each other.

FIGS. 37,38 and 39 shows the pairs of barbs in top plan view used in the stress plate and are integral therewith.

FIG. 37 shows a pair of equilateral triangles in the stress plate the sharp points of the triangles extend outwardly from the bottom surface of the stress plate.

FIG. 38 shows a pair of rectangular barbs. In the stress plate the rectangular barbs extend outwardly from the bottom surface of the stress plate.

FIG. 39 shows a pair of semi-circular barbs. In the stress plate the semi- circular barbs extend outwardly from the bottom surface of the stress plate.

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.

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.

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.

FIG. 40 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 130 is positioned over insulation 132 which is over the roof deck surface 134. Inserting fastener 138 through stress plate 136, insulation 132 and into roof deck 134. Upper membrane 140 is then lapped-over portions of the lower membrane covering the stress plate 136. The upper membrane is secured to the lower membrane by the welded seam 142.

Wind Uplift Test Comparative wind uplift tests were conducted on the double. 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. For example, a three second burst of wind at 175 miles per hour can exert a negative pressure of 90 pounds per square foot on the roof system.

The roofing system consists of : a steel roof deck, an insulating layer placed on the roof deck, and a roof membrane placed on the top of the insulating layer. The respective plates were then attached to the roofing system by inserting the respective fasteners through the stress plates, the roof membranes, and the insulating layer and into the steel roof deck and holding the roofing system at 15 pounds per square feet intervals starting at 30 pounds per square feet for sixty seconds or until failure.

Failure of the roofing system was measured by the membrane tearing around the stress plates.

The roofing system having the double barb stress plate passed the wind uplift test at 60 seconds at 90 pounds of pressure per square feet, while the roofing system having the single barb stress plate failed at 47 seconds at 75 pounds of pressure per square feet. 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' Pairs of 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' Pairs of barbs60, 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' Pairs 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' Pairs of barbs120, 120' Using the Stress Plate Lower membrane 130 Insulation 132 Roof deck 134 Stress plate 136 Fastener (screw) 138 Upper membrane 140 Welded seam 142 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.