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BACKGROUND 
     The present invention relates generally to the construction of a roofing shingle. In particular, the present invention relates to the construction of an asphalt roofing shingle utilizing a unique combination of exposure dimension and arrangement of color striations thereon to create a greater visual impact than existing asphalt shingles. 
     Asphalt shingles (sometimes also often referred to as composite shingles) are one of the most commonly used roofing materials. Asphalt shingles typically comprise an organic felt or fiberglass mat base on which is applied an asphalt coating. The organic felt or fiberglass mat base gives the asphalt shingle the strength to withstand manufacturing, handling, installation and servicing, and the asphalt coating provides resistance to weathering and stability under temperature extremes. An outer layer of mineral granules is also commonly applied to the asphalt coating to form a weather surface which shields the asphalt coating from the sun&#39;s rays, adds color to the final product, and provides fire resistance. 
     Asphalt shingles are typically manufactured as strip shingles, laminated shingles, interlocking shingles, and large individual shingles in a variety of weights and colors. Even though asphalt shingles offer significant cost, service life, and fire resistance advantages over wood shingles, wood shingles are often preferred due to their pleasing aesthetic features, such as their greater thickness as compared to asphalt shingles, which results in a more pleasing, layered look for a roof. 
     Various asphalt shingles have been developed to provide an appearance of thickness comparable to wood shingles. Examples of such asphalt shingles are shown in U.S. Pat. No. 5,232,530 entitled “Method of Making a Thick Shingle”; U.S. Pat. No. 3,921,358 entitled “Composite Shingle”; U.S. Pat. No. 4,717,614 entitled “Asphalt Shingle”; and U.S. Pat. Des. No. D309,027 entitled “Tab Portion of a Shingle.” Each of these patents is incorporated by reference herein in its entirety. 
     In addition to these patents, significant improvements in the art of roofing shingles have been disclosed and patented in U.S. Pat. Nos. 5,369,929; 5,611,186; and 5,666,776; each entitled “Laminated Roofing Shingle”, issued to Weaver et al. and assigned to the Elk Corporation of Dallas. These patents disclose laminated roofing shingles having a color gradient or gradation thereon to create the illusion of thickness or depth on a relatively flat surface. These patents are also incorporated by reference herein in their entireties. The present invention substantially improves on the roofing shingles described in the above-identified patents. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a roofing shingle that includes a unique combination of exposure dimension and arrangement of color striations thereon to provide a greater visual impact than existing asphalt shingles. In accordance with one aspect of the present invention, there is provided a laminated roofing shingle having a first shingle sheet and a second shingle sheet. The first shingle sheet has a headlap section and a buttlap section, the buttlap section being about 7 inches or greater in height and including a plurality of tabs which are spaced apart to define one or more openings between the tabs. Each of the tabs has a relatively uniform color throughout the tab. The relatively uniform color throughout the tab may very in contrast between each of the tabs. The second shingle sheet is attached to the underside of the first shingle sheet and has portions exposed through the openings between the tabs. The second shingle sheet has at least first, second, third, and fourth horizontal striations thereon across at least partial portions of the second sheet which are exposed through the openings between the tabs. The first striation has a substantially uniform dark color throughout a first quadrilateral area. The second striation includes a second elongated quadrilateral area below the first striation. The second striation has a substantially uniform color throughout the second quadrilateral area. The third striation includes a third elongated quadrilateral area below the second striation. The third striation has a substantially uniform color throughout the third quadrilateral area, which is lighter than the color of the second striation. The fourth striation includes a fourth elongated quadrilateral area below the third striation. The fourth striation has a substantially uniform color throughout the fourth quadrilateral area, which is lighter than the color of the third striation. At least the second, third, and fourth striations provide a color gradation on at least partial portions of the second sheet which are exposed through the openings between the tabs. The color of the first striation may be selected to be consistent with (i.e., to continue) the color gradation of the second through fourth striations. 
     Other aspects of the present invention include methods for manufacturing the above-described laminated shingle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings in which: 
     FIG. 1 is a perspective view of a laminated shingle incorporating one embodiment of the present invention; 
     FIG. 2 is a top plan view of the shingle of FIG. 1; 
     FIG. 3 is a front plan view of the shingle of FIG. 1; 
     FIG. 4 is a left side view of the shingle of FIG. 1; 
     FIG. 5 is a perspective view of a partial roofing section covered with shingles incorporating one embodiment of the present invention; 
     FIG. 6 is an isometric, schematic drawing of a sheet of roofing material incorporating one embodiment of the present invention from which components for the shingle of FIG. 1 may be obtained; 
     FIG. 7 is an exploded isometric view showing shingle components taken from the sheet of roofing material in FIG. 6 which may be used to form the shingle of FIG. 1; 
     FIG. 8A is an exploded isometric view showing shingle components taken from a sheet of roofing material according to another embodiment of the present invention; and 
     FIG. 8B is an enlarged drawing of a portion of a backer strip of FIG. 8A with transition stripes disposed between adjacent horizontal striations. 
     FIG. 9 is a top plan view of a laminated shingle wherein the tabs have different color contrasts from one another. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A laminated shingle  20  according to an exemplary embodiment of the present invention is shown in FIGS. 1 to  4 . The laminated shingle  20  preferably comprises a first shingle sheet  30  attached to a second shingle sheet  50 . First shingle sheet  30  has a generally rectangular configuration defining a headlap section  32  of the laminated shingle  20 , with a plurality of tabs  36  extending therefrom to define a buttlap section  34  of the laminated shingle  20 . Tabs  36  may also be referred to as “dragon teeth.” A plurality of openings  38  are formed between adjacent tabs  36 . The second shingle sheet  50  also has a generally rectangular configuration and is disposed beneath tabs  36  with portions of the second shingle sheet  50  exposed through the plurality of openings  38 . 
     Various techniques such as glueing or self-sealing adhesive strips (not shown) may be used to attach the second shingle sheet  50  to the underside of the first shingle sheet  30 . The resulting laminated shingle  20  has a generally rectangular configuration defined in part by longitudinal edges  22  and  24  with lateral edges  26  and  28  disposed therebetween. Longitudinal edge  22  is defined by an end of headlap section  32  and constitutes the upper edge of the laminated shingle  20 . Longitudinal edge  24  is defined by an end of buttlap section  34  and constitutes the lower (or leading) edge of laminated shingle  20 . A plurality of self sealing adhesive strips  40  are preferably disposed on the exterior of first shingle sheet  30  between headlap section  32  and buttlap section  34 . 
     First shingle sheet  30  may sometimes be referred to as a “tab sheet” or a “dragon tooth sheet,” and second shingle sheet  50  may sometimes be referred to as a “backer strip” or “shim.” In addition, openings  38  formed between adjacent tabs  36  with portions of backer strip  50  disposed thereunder may sometimes be referred to as “valleys.” Depending upon the desired application and appearance of each laminated shingle  20 , tabs  36  may have equal or different widths and may have a square, rectangular, trapezoidal, or any other desired geometric configuration. In the same respect, openings  38  may have equal or different widths and may have a square, rectangular, trapezoidal or any other desired geometric configuration. As will be explained later in more detail, laminated shingles  20  may be formed from a sheet  80  of roofing material shown in FIG. 6 with tabs  36  and opening  38  formed as a “reverse image” of each other. 
     For one embodiment of the present invention, laminated shingle  20  may be formed from a fiberglass mat (not shown) with an asphalt coating on both sides of the mat. If desired, the present invention may also be used with shingles formed from organic felt or other types of base material. The present invention is not limited to use with shingles having a fiberglass mat. 
     The exposed outer surface or weather surface  42  for shingle  20  is defined in part by tabs  36  and the portions of backer strip  50  which are exposed through openings  38  between adjacent tabs  36 . Weather surface  42  of laminated shingle  20  may be coated with various types of mineral granules to protect the asphalt coating, to add color to laminated shingle  20  and to provide fire resistance. For some applications, ceramic coated mineral granules may be used to form the outer layer comprising weather surface  42 . Also, a wide range of mineral colors from white and black to various shades of red, green, brown and any combination thereof may be used to provide the desired color for shingle  20 . The underside of shingle  20  may be coated with various inert minerals with sufficient consistency to seal the asphalt coating. 
     According to the present invention, the buttlap section  34  (the exposed section of the shingle when it is laid up on a roof) is made about 7 inches or greater and four or more horizontal striations are provided on the surface of backer strip  50  which is exposed through openings  38 . The horizontal striation nearest the headlap section of the shingle is made a uniformly dark color. Other horizontal striations are each made of a uniform color which together provide a color gradient or gradation according to the teachings of U.S. Pat. Nos. 5,369,929; 5,611,186; and 5,666,776, which are incorporated herein by reference in their entireties. The color of the striation nearest the headlap section may be selected to be consistent with (i.e., to continue) the color gradation of the other horizontal striations. 
     Using the foregoing unique combination of buttlap section (exposure) dimension and arrangement of color striations, the laminated shingle according to the present invention provides a significantly greater visual appearance than existing laminated shingles. While the improvement in visual appearance is applicable to all types of roofs, it is especially significant on low-sloped roofs (i.e., those roofs having less than six feet of rise for every twelve feet of run). 
     While many different shingle dimensions may be utilized with the present invention, the following exemplary dimensions and number of shingles per square are suitable for easy handling and packaging of the shingles: 
     1. 38 inch length, 7.9 inch exposure height, 17.8 inch overall height, and 48 shingles/square; 
     2. 36 inch length, 8 inch exposure height, 18 inch overall height, and 50 shingles/square; 
     3. 36 inch length, 8.3 inch exposure height, 18.6 inch overall height, and 48 shingles/square; and 
     4. 36 inch length, 9 inch exposure height, 20 inch overall height, and 44 shingles/square. 
     Returning to FIGS. 1 through 4, the exemplary embodiment shown includes a backer strip  50  with four horizontal striations  52 ,  54 ,  56 , and  58 . Striation  58 , the striation adjacent the headlap section of the shingle, is a uniformly dark-colored striation. The horizontal striations  52 ,  54 , and  56  are colored striations that provide a color gradient or gradation from a light color near the leading edge  24  to a dark color near the upper portion of each opening  38 . The color of the horizontal striation  58  may be selected to be consistent with (i.e., to continue) the color gradient or gradation of the other striations (so that striations  52  through  58  altogether provide a color gradient or gradation). Preferably, the height of each striation is approximately equal. In addition, for aesthetic reasons it is preferred that the height of each striation be in the range of one to two inches. 
     The number of horizontal striations and the width of each striation on backer strip,  50  may be varied depending upon the desired aesthetic appearance of the resulting laminated shingle  20 . It is preferred, however, for a shingle to have an exposure height of 7 to 9 inches and four to six horizontal striations thereon. 
     Each striation may have a different color to establish the desired amount of contrast. For the purposes of this patent application, a different color may include a different tone. In addition, contrast for purposes of this patent application is defined as the degree of difference in the tone or shading between areas of lightest and darkest color. For some applications, a gradual change in contrast associated with a large number of striations may provide the appearance of depth or thickness associated with wood or other natural products. Also, the amount or degree of contrast in the color gradient exposed in each opening  38  may be varied depending upon the desired aesthetic appearance. An important feature of the present invention is the ability to vary the color gradient and the amount of contrast to provide the desired illusion or appearance of thickness on the finished roof. 
     As shown in FIG. 5, a plurality of laminated shingles  20  may be installed on a roof or other structure (not shown) to provide protection from the environment and to provide an aesthetically pleasing appearance. The normal installation procedure for laminated shingles  20  includes placing each shingle  20  on a roof in an overlapping configuration. Typically, buttlap section  34  of one shingle  20  will be disposed on the headlap section of another shingle  20 . Self-sealing adhesive strips  40  are used to secure the overlapping shingles  20  with each other. Also, a limited lateral offset is preferably provided between horizontally adjacent rows of shingles  20  to provide an overall aesthetically pleasing appearance for the resulting roof. 
     FIGS. 6 and 7 show one procedure for fabricating a laminated shingle  20  from a sheet  80  of roofing material. Various procedures and methods may be used to manufacture sheet  80  from which shingles incorporating the present invention may be fabricated. Examples of such procedures are contained in U.S. Pat. No. 1,722,702entitled “Roofing Shingle”; U.S. Pat. No. 3,624,975 entitled “Strip Shingle of Improved Aesthetic Character”; U.S. Pat. No. 4,399,186 entitled “Foam Asphalt Weathering Sheet for Rural Roofing Siding or Shingles”; and U.S. Pat. No. 4,405,680 entitled “Roofing Shingle.” Each of these patents is incorporated by reference herein in its entirety. 
     Sheet  80  is preferably formed from a fiberglass mat placed on a jumbo roll (not shown) having a width corresponding to the desired sheet  80 . Laminated shingles  20  are typically fabricated in a continuous process starting with the jumbo roll of fiberglass mat. As previously noted, laminated shingle  20  may also be fabricated using organic felt or other types of base material. 
     Sheet  80  shown in FIG. 6 preferably comprises a fiberglass mat with an asphalt coating which both coats the fibers and fills the void spaces between the fibers. A powdered mineral stabilizer (not shown) may be included as part of the asphalt coating process. A smooth surface of various inert minerals of sufficient consistency may be placed on the bottom surface of sheet  80  to seal the asphalt coating. 
     Top surface  82  is preferably coated with a layer of mineral granules such as ceramic coated stone granules to provide the desired uniform color portions and the color gradient portions associated with weather surface  42  of shingle  20 . Typically, the mineral granules are applied to the sheet  80  while the asphalt coating is still hot and forms a tacky adhesive. 
     FIG. 6 shows a schematic representation of a roller  86  and mineral granule hopper  90  which may be used to provide the desired granular surface coating to sheet  80 . The hopper  80 , which may be any hopper which is well known in the art, includes a plurality of partitions  91  which divide the hopper  90  into three sets of compartments: a set of compartments  92 ,  94 ,  96  and  98  at each end of the hopper and a central compartment  99  between the ends. The central compartment  99  of hopper  90  contains a uniform mixture of the mineral granules which will produce the desired color on dragon teeth or tabs  36  and the other portions of first shingle sheet  30  which will be exposed to the environment. This transfer of mineral granules is sometimes referred to as a “color drop.” The rotation of roller  86  and the movement of sheet  80  are coordinated to place the desired color drop on each shingle  20 . 
     For the embodiment of the present invention shown in FIGS. 6 and 7, each first shingle sheet  30  will have the same uniform mixture of mineral granules on both the headlap section and the buttlap section. For the embodiment shown in FIGS. 1 to  4 , headlap section  32  may have the same layer of mineral granules as buttlap section  34  or headlap section  32  may have a neutral or non-colored layer of mineral granules. The surface layer on headlap section  32  may be varied as desired for each application. 
     Different colored mineral granules corresponding to the desired color of horizontal striations  52 ,  54 ,  56 , and  58  are preferably placed in the appropriate compartments  92 ,  94 ,  96 , and  98 , respectively. As sheet  80  passes under roller  86 , mineral granules from the appropriate compartment in hopper  90  will fall onto roller  86  and will be transferred from roller  86  to top surface  82  of sheet  80 . The volume or pounds per square foot of mineral granules placed on surface  82  is preferably the same throughout the full width of sheet  80 . However, by dividing the hopper  90  into compartments, the color of various portions of sheet  80  may be varied including providing horizontal striations  52 ,  54 ,  56 , and  58  for backer strip  50 . 
     It is important to note that conventional procedures for fabricating shingles having an exterior surface formed by mineral granules include the use of granule blenders and color mixers, along with other sophisticated equipment to ensure a constant uniform color at each location on the exposed portions of the shingles. Extensive procedures are used to ensure that each color drop on a sheet of roofing material is uniform. The color drop between shingles may be varied to provide different shades or tones in color. However, within each color drop, concerted efforts have traditionally been made to insure uniformity of the color on the resulting shingle associated with each color drop. 
     Once the color drop process is complete, the sheet  80  is allowed to cool. After the sheet  80  is cooled, it is then cut. As shown by dotted lines  84 ,  86 , and  88  in FIG. 6, sheet  80  may be cut into four horizontal lengths or lanes  60 ,  62 ,  64 , and  66 . The width of lanes  62  and  64  corresponds with the desired width for first shingle sheet  30 . The width of lanes  60  and  66  corresponds with the desired width for second shingle sheet  50 . 
     The cut along dotted line  86  corresponds with the desired pattern for dragon teeth  36  and associated openings  38 . For some applications, more than four lanes may be cut from a sheet of roofing material similar to sheet  80 . The number of lanes is dependent upon the width of the respective sheet of roofing material and the desired width of the resulting shingles. 
     Sheet  80  may also be cut laterally to correspond with the desired length for the resulting first shingle sheet  30  and second shingle sheet  50 . As shown in FIG. 7, each lateral cut of sheet  80  results in two backer strips  50  and two first shingle sheets  30  which may be assembled with each other to form two laminated shingles  20 . The resulting laminated shingles  20  may be packaged in a square for future installation on a roof as is well known in the art. 
     The cutting of sheet  80  and the assembly of laminated shingles  20  may be performed in a number of ways. For example, the laminated shingles  20  may be produced through an off-line lamination process in which the sheet  80  is cut both longitudinally and laterally and then the tab sheets and backer sheets which are produced are matched and attached together. Alternatively, and more preferably, the laminated shingles  20  may be produced in a continuous in-line lamination process in which the sheet  80  is cut longitudinally by a rotary die cutter, producing horizontal lengths (such as lanes  60 ,  62 ,  64 , and  66 ) which consist of continuous tab sheet strips and backer sheet strips. The tab sheet strips and backer sheet strips are joined and adhered together to produce laminated shingle strips through means well known in the art. The laminated shingle strips may then be passed through a cutting cylinder, which cuts the strips into individual shingles. After discrete shingles are formed, they can be processed with commonly used apparatus for handling shingles, such as a shingle stacker to form stacks of shingles and a bundle packer to form shingle bundles. 
     It is important to note that a color gradient of the present invention may be placed on shingles using various procedures and various types of materials. The present invention is not limited to shingles formed by the process shown in FIGS. 6 and 7. 
     FIG. 8A is an exploded isometric view showing shingle components taken from a sheet of roofing material according to another embodiment of the present invention. In the embodiment of FIG. 8A, as better shown in FIG. 8B which is an enlarged drawing of a portion of a backer strip of FIG. 8A, transition stripes  152  and  154  are disposed between adjacent pairs  52 / 54  and  54 / 56  of the horizontal striations  52 ,  54  and  56 . Each transition stripe has a color value that is a mixture of the colors associated with the two horizontal striations adjacent to the transition stripe. The transition stripes may be used when the difference in contrast between adjacent horizontal striations is sufficiently great that a shingle would present a confused or disjointed appearance without the transition stripes. The transition stripes may be applied as described in U.S. Pat. No. 5,611,186, which is incorporated by reference herein in its entirety. 
     FIG. 9 illustrates a laminated shingle according to the present invention wherein the backer strip  50  has four horizontal striations  52 ,  54 ,  56  and  58 , and wherein each of the tabs  36  has a relatively uniform color throughout each tab and different color contrasts between each tab. 
     Although the present invention has been described with reference to certain preferred embodiments, various modifications, alterations, and substitutions will be apparent to those skilled in the art without departing from the spirit and scope of the invention, as defined by the appended claims.

Summary:
There is provided a laminated roofing shingle having a first shingle sheet and a second shingle sheet. The first shingle sheet has a headlap section and a buttlap section, the buttlap section being about 7 inches or greater in height and including a plurality of tabs which are spaced apart to define one or more openings between the tabs. Each of the tabs has a relatively uniform color throughout the tab. The second shingle sheet is attached to the underside of the first shingle sheet and has portions exposed through the openings between the tabs. The second shingle sheet has at least first, second, third, and fourth horizontal striations thereon across at least partial portions of the second sheet which are exposed through the openings between the tabs. The first striation includes a first elongated quadrilateral area with a substantially uniform dark color throughout the first quadrilateral area. The second striation includes a second elongated quadrilateral area below the first striation. The second striation has a substantially uniform color throughout the second quadrilateral area. The third striation includes a third elongated quadrilateral area below the second striation. The third striation has a substantially uniform color throughout the third quadrilateral area, which is lighter than the color of the second striation. The fourth striation includes a fourth elongated quadrilateral area below the third striation. The fourth striation has a substantially uniform color throughout the fourth quadrilateral area, which is lighter than the color of the third striation. There are also provided methods for manufacturing the above-described laminated shingle.