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REFERENCE TO RELATED APPLICATIONS 
       [0001]    Priority is hereby claimed to the filing date of U.S. provisional patent application 61/738,618 entitled Universal Inside Corner Patch for Membrane Roofing filed on Dec. 18, 2012 and to the filing date of U.S. provisional patent application 61/825,239 entitled Self Adhesive Universal Inside Corner Patch for Membrane Roofing filed on May 20, 2013. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention disclosed herein relates generally to membrane roofing for low slope roofs such as those found on commercial buildings and more specifically to sealing or patching corners formed by protrusions extending upwardly from commercial roof decks when installing a membrane roof on the deck. 
       BACKGROUND 
       [0003]    Polymeric membranes are commonly used to seal flat or low slope roofs of commercial buildings. Such membranes may be made of a variety of thermoplastic materials including, without limitation, Polyvinyl Chloride (PVC), PVC Alloys or Compounded Thermoplastics such as Tripolymer Alloy (TPA), Thermoplastic Olefin (TPO), Chlorinated Polyethylene (CPE), and Ethylene propylene diene terpolymer (EPDM). The most common types of commercial roofing membranes are made of PVC or TPO. The invention may be described herein for the sake of clarity primarily within the context of TPO membrane roofing. It will be understood, however, that the invention is not limited to TPO roofing membranes but applies to any other type of membrane used to roof and waterproof commercial and other buildings having low slope roofs. 
         [0004]    When roofing a low slope roof, webs of membrane material are rolled out on a roof and adhered or bonded along their seams to provide a waterproof barrier atop the deck of the roof. Commercial roofs virtually always have protrusions that project upwardly from the roof deck. Such protrusions include, for example, HVAC ducts, ventilation ducts, rectangular protrusions for skylights and other features, parapets, and others. Non-circular protrusions such as rectangular protrusions define outside corners where the edges of the protrusion meet the roof deck. Other protrusions, such as parapets, form inside corners where two walls of the parapet meet the roof deck. Other protrusions that form inside and outside corners also may be present. In order to seal the roof, these corners must be sealed against water penetration. Traditionally, roofers would fabricate corner patches in the field by cutting, trimming, and configuring a scrap piece of membrane material until it fit a particular corner. This is a time consuming process, requires skill, and sometimes does not result in a good fitting leak proof patch. 
         [0005]    More recently, prefabricated outside corner patches have been developed for sealing outside corners of protrusions on a commercial roof. U.S. Pat. No. 8,161,688, owned by the assignee of the present application, discloses a radially scalloped outside corner patch that, when spread out, conforms to substantially orthogonal outside corners of a protrusion. Pending U.S. patent application Ser. No. 13/454,674, also owned by the assignee of the present application, discloses a universal outside corner patch that is designed to conform to non-orthogonal outside corners of a protrusion. The disclosures of these documents are hereby incorporated by reference in their entireties. Accordingly, the convenient sealing of outside corners, both orthogonal and non-orthogonal, defined by protrusions from a commercial roof has been addressed. 
         [0006]    Inside corners have been a different story. For orthogonal inside corners (corners formed by two inside walls that meet that meet each other and the roof deck at 90 degree angles), corner patches are available that are molded with three orthogonal sides that fit against the orthogonal sides and roof deck of an inside corner. However, inside corners often are not orthogonal and traditional inside corner patches do not fit well. When a corner patch does not fit well, it can lead to leaks at these corners over time. In cases where an inside corner includes a surface at an angle of more than a few degrees difference from 90 degrees, traditional inside corner patches cannot be used at all. A need exists for a universal inside corner patch that can conform to non-orthogonal inside corners or inside corners where one or more walls forming the corner meets the other walls or the roof deck at an angle significantly different than 90 degrees. Such a universal inside corner patch should also be equally usable just like pre-molded patches to seal orthogonal inside corners. It is to the provision of such a universal inside corner patch and to a method of sealing inside corners that the present invention is primarily directed. 
       SUMMARY 
       [0007]    Briefly described, a universal inside corner patch is disclosed for sealing inside corners formed by protrusions such as parapets from a low slope commercial roof when covering and sealing the roof with membrane roofing material. Preferably, the body of the corner patch is made of the same material as a membrane used to cover the roof deck. In one embodiment, the universal inside corner patch comprises a body having a central portion and a peripheral portion. A cutout is formed in the body extending from the peripheral portion toward the central portion thereof. The cutout defines in the body a skirt portion having an edge on one side of the cutout and a flap portion on an opposite side of the cutout. Folding locations, which can be fold lines or other indicia, on the body correspond to respective angles of an inside corner to be patched. 
         [0008]    When the skirt portion is overlapped with the flap portion with the edge of the skirt portion registering with one of the folding locations, the inside corner patch is configured to conform to an inside corner with an angle corresponding to that folding location. The folding locations may correspond to inside corners with significantly acute angles such as 70 degrees and significantly obtuse angles such as 120 degrees. A self-adhesive coating may be provided on the back surface of the body to help hold the corner patch in its folded configuration and in place on the roof. The self-adhesive coating may be covered with a peel-off protective sheet. These and other aspects, features, and advantages of the invention disclosed herein will become more apparent to the skilled artisan upon review of the detailed description set forth below taken in conjunction with the accompanying drawing figures, which are briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a plan view of a universal inside corner patch that embodies principles of the invention in one embodiment. 
           [0010]      FIG. 2  is a plan view of the universal inside corner patch of  FIG. 1  emphasizing a configuration for a 110 degree inside corner. 
           [0011]      FIG. 3  is a perspective view of the corner patch of  FIG. 2  folded and welded to form an inside corner patch for a 110 degree inside corner. 
           [0012]      FIG. 4  is a plan view of a universal inside corner patch that embodies principles of the invention in another embodiment. 
           [0013]      FIG. 5  is a plan view of the universal inside corner patch of  FIG. 4  emphasizing a configuration for an 80 degree inside corner. 
           [0014]      FIG. 6  is a perspective view of the universal inside corner patch of  FIG. 5  folded and sealed to fit an 80 degree inside corner. 
           [0015]      FIG. 7  is a top plan view of a universal inside corner patch configured to conform to a valley of arbitrary angle. 
           [0016]      FIG. 8  is a perspective view of the universal inside corner patch of  FIG. 7  folded to fit a valley. 
           [0017]      FIG. 9  is a perspective view of the back of a universal inside corner patch showing a backing sheet being peeled away from a self-adhesive backing according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Referring now in more detail to the drawing figures, wherein like reference numerals, where appropriate, indicate like parts throughout the several views,  FIG. 1  illustrates a universal inside corner patch that embodies principles of the invention in one preferred form. The corner patch  11  is cut from a piece of roofing membrane material such as TPO that preferably is the same as the material of the membrane to be used to cover a roof deck. Most preferably, the material has a flexural modulus of between 1,500 psi and 20,000 psi. In the illustrated embodiment, the patch is circular in shape, although this is not a limitation of the invention. The patch  11  comprises a body  12  that is divided by fold lines  13  and  14  into four quadrants, Q 1 , Q 2 , Q 3 , and Q 4 . In the illustrated embodiment, the quadrants are orthogonal inasmuch as the fold lines  13  intersect one another at 90 degree angles. However, this is not a limitation of the invention and the quadrants may be other than orthogonal according to application specific needs. 
         [0019]    Quadrant Q 1  is characterized by an angular or pie-shaped cutout  16  extending from the perimeter of the body  12  toward a center portion thereof. A smaller relief cut  17  extends from the center of the body  12  radially outwardly to meet the cutout  16 . The function of the relief cut  17  will be described in more detail below. The cutout  16  and the relief cut  17  together partially sever the material of quadrant Q 1  from the body of the patch to form a lap or flap portion  18 . Radially extending fold lines  19 ,  21 ,  22 , and  23  are defined in the flap portion  18  and the fold lines correspond to folds to be made in the flap portion  18  for various angles of inside corners to be sealed with the corner patch. In the illustrated embodiment, for instance, fold line  19  corresponds to an inside corner angle to be patched of 90 degrees, fold line  21  to an angle of 100 degrees,  22  to 110 degrees, and  23  to 120 degrees. 
         [0020]      FIGS. 2 and 3  illustrate use of the universal inside corner patch of  FIG. 1  for sealing an inside corner with one of its three walls extending upwardly from a roof deck at an obtuse angle of, in this example, 110 degrees. Referring to  FIG. 2 , the patch  11  is first folded along selected fold lines to form the shape of the patch. More specifically, quadrants Q 2 , Q 3 , and Q 4  are folded upwardly in a direction out of the page in  FIG. 2  along fold lines  13  and  14 . Quadrant Q 1  is folded along the 110 degree fold line  22  such that the flap portion  18  moves upwardly out of the page in  FIG. 2 . The edge  15  of quadrant Q 4  on one side of the pie-shaped cutout  16  is moved into registration with the now folded 110 degree fold line  22  as indicated by arrow  24  in  FIG. 2 . The portion of quadrant Q 4  that overlaps the flap portion  18  is referred to herein as the skirt portion. At this point, the shape of the corner patch is essentially formed. 
         [0021]    The flap portion can be adhered to the back of skirt portion if desired to hold the shape of the corner patch while it is moved into a corner to be patched. Alternatively, the folded patch can simply be placed into the corner and then massaged into a good close fit before it is adhered and sealed to surrounding TPO material. In one embodiment, described in more detail below, a self adhesive coating covered by a peal-off protective sheet is provided on the back side of the corner patch. In this embodiment, the protective sheet may be peeled off before or during the folding process so that the skirt portion of quadrant Q 4  self-adheres to the flap portion  18  when the patch is folded to retain the folded shape of the patch. 
         [0022]      FIG. 3  illustrates the shape of an inside corner patch folded as described in the previous paragraph. As can be seen, the flap portion  18  is folded behind the skirt portion of quadrant Q 4  with the edge  15  of the skirt portion defined by the pie-shaped cutout being registered with the 110 degree fold line  22 . A portion of quadrant Q 1  between the 90 degree fold line and the 110 degree fold line forms an extension of quadrant Q 2  so that the total angular extent of quadrant Q 2  and the extension is 110 degrees. It will thus be appreciated that quadrant Q 4  forms an angle of 110 degrees with respect to quadrant Q 3 . At the same time, quadrant Q 2  forms an angle of 90 degrees with respect to quadrant Q 3 . Accordingly, in this configuration, the corner patch  11  fits snuggly into an inside corner defined by the intersection of roof deck  8  with upstanding walls  7  and  9 , where wall  9  extends upwardly from the roof deck  8  at an angle of 110 degrees. The corner patch can then be bonded and sealed to the surrounding membrane material in a conventional manner to seal the corner. Thus, the universal inside corner patch of this invention reliably seals an obtuse inside corner. 
         [0023]      FIG. 4  illustrates a universal inside corner patch very similar to that of  FIG. 1 , except this inside corner patch can be folded to accommodate both acute and obtuse inside angle corners. Similar to  FIG. 1 , the corner patch  28  of  FIG. 4  is cut from a piece of roofing membrane material such as TPO or other material that preferably is the same as that used to cover a roof deck. The patch  28  comprises a body  29  that is divided by fold lines  31  and  32  into four quadrants, Q 1 , Q 2 , Q 3 , and Q 4 . The fold lines  31  and  32  intersect one another at 90 degree angles in this embodiment. 
         [0024]    Quadrant Q 1  is characterized by an angular or pie-shaped cutout  33  extending from the perimeter of the body  28  toward a center portion thereof. A smaller relief cut  34  extends from the center of the body  12  radially outwardly to meet the cutout  33 . The cutout  33  and the relief cut  34  together partially sever the material of quadrant Q 1  from the body of the patch to form a lap or flap portion  36 . Radially extending fold lines  36 ,  37 ,  38 ,  39 , and  41  are defined in the flap portion  36  and these fold lines correspond to folds to be made in the flap portion  36  for various angles of inside corners, both acute and obtuse, to be sealed with the corner patch. In the illustrated embodiment, for instance, fold line  38  corresponds to an inside corner angle to be patched of 90 degrees, fold line  39  to an obtuse angle of 100 degrees, and  76  to an acute angle of 70 degrees. 
         [0025]      FIGS. 5 and 6  illustrate application of the universal corner patch of  FIG. 4  to seal an acute inside corner having a wall that defines an angle of, in this example, 80 degrees. The process is similar to that just described in the previous paragraph for an obtuse angle. Referring to  FIG. 5 , the corner patch is folded along fold lines  31  and  32  in a direction out of the page in  FIG. 5  until quadrant Q 2  forms an angle of 90 degrees with respect to quadrant Q 3  and quadrant Q 3  forms an angle of 90 degrees with respect to quadrant Q 4 . The lap or flap portion  26  of quadrant Q 1  is then folded upwardly out of the page along the 80 degree fold line  37 . Skirt portion of quadrant Q 4  is overlapped onto the flap portion  26  until the edge  30  comes into registration with the 80 degree fold line, as illustrated by arrow  50  in  FIG. 5 . The corner patch can then be tacked in this configuration if desired; or, where an adhesive backing is present, the skirt portion adheres itself to the flap portion upon contact. As shown in  FIG. 6 , the universal corner patch, when configured as just described, fits snuggly into an inside corner where one wall  46  forms a right angle with respect to a roof deck  48  and an adjacent wall  47  forms an acuter angle of, in this case, 80 degrees with respect to the roof deck  48 . The corner patch can then be adhered to surrounding membrane material in a conventional manner, or it may self adhere where an adhesive backing is present, to seal the corner. 
         [0026]      FIGS. 7 and 8  illustrate an alternate embodiment of the invention for use to seal valley corners of various angles. In this embodiment, a patch  51  is cut from a membrane material such as TPO into a shape having a semi-circular portion to the left in  FIG. 7 . The right side of the patch  51  in  FIG. 7  comprises a pie-shaped cutout  56  and a relief cut  57  that separate the material of the patch into a first leg  58  and a second leg  59 . Fold lines  53 ,  54 , and  61  define quadrants Q 2  and Q 3  in the semicircular left portion of the patch. Fold line  61  corresponds to a 90 degree fold. The patch  51  further comprises fold lines arrayed about the 90 degree fold line  61  corresponding to acute and obtuse angle folds of various degrees. In the illustrated embodiment, for example, there is shown a 70 degree fold line  63 , an 80 degree fold line  62 , a 110 degree fold line  64 , and a 120 degree fold line  66 . While specific angles are indicated in the drawing, it will be understood by the skilled artisan that other and different angles are possible within the scope of the invention. 
         [0027]    To adapt the universal valley patch  51  for sealing a valley  71  ( FIG. 8 ) of a particular angle, the patch  51  is folded upwardly out of the page in  FIG. 7  along fold lines  53  and  54 . The patch is then folded along a fold line corresponding to the angle of a valley to be sealed with the patch. In  FIG. 8 , for example, a valley having an angle  71  that is equal to α+β is shown. The edge  72  of the patch is folded over as shown by arrow  67  until it registers with the fold line corresponding to the valley angle, whereupon the patch can be tacked in this configuration or it may self adhere where an adhesive backing is present. The patch is then placed in the valley, where it conforms to the angle of the valley and can be adhered to surrounding membrane material to seal the valley, as illustrated in  FIG. 8 . 
         [0028]      FIG. 9  illustrates one embodiment of the inside corner patch of this disclosure that includes a self-adhering feature to hold the corner patch in its folded configuration and adhere the corner patch in place in a corner. The corner patch  61  comprises a body  62  with a cutout  63  as described in detail above. The back surface of the body  62  is coated with a self-adhering coating  66  that may be covered with a peel-away protective release layer  64 . The adhesive can be in the form of a tape or a hot melt adhesive made with greater than about 50% butyl polymer or a blend of butyl polymers and Styrene copolymers such as butadiene Styrene (SBS), Styrene ethylene butylenes Styrene (SEBS), Styrene ethylene-propylene (SEP), or Styrene ethylene-propylene Styrene (SEPS). The adhesive may further comprise less than about 30% of a aliphatic or aromatic hydrocarbon tackifier resin, less than about 10% fillers such as clay, talc, CaCO3, MgO, Mg(OH)2, less than about 5% thermal stabilizers, antioxidants, and processing aids. A functional coating hot melt adhesive that meets the AFERA 5001 standard is one example of an appropriate adhesive for use in the present invention. The thickness of the adhesive coating may be in the range of from 5 to 40 mils and preferably from 10 to 20 mils. The adhesive can be reinforced with an appropriate material such as a thin porous laid polyester fiber mat having a preferred thickness less than 15 mils to add strength. 
         [0029]    To fold and then apply the corner patch of  FIG. 9 , the release layer  64  is peeled away and the patch body  62  is folded as described above to match the angle of the inside corner to be sealed. When so folded, the flap portion  18  ( FIG. 2 ) adheres to the now exposed adhesive on the back of the skirt portion to hold the patch in its folded configuration. The patch can then be applied to an inside corner defined in a roof and pressed to adhere the patch in place. Heat may be applied if desired to seal the patch further in the corner by liquefying the hot melt adhesive so that it bonds to the surfaces that meet at the inside corner. 
         [0030]    The invention has been described herein in terms of preferred embodiments and methodologies considered by the inventors to represent the best mode of carrying out the invention. It will be understood by the skilled artisan; however, that a wide range of additions, deletions, and modifications, both subtle and gross, may be made to the illustrated and exemplary embodiments without departing from the spirit and scope of the invention. For instance, while several different materials have been mentioned as roofing membrane materials, the term “membrane” should be construed as including any web material that may be used to seal the roof of a commercial or residential building where corners are encountered and need to be sealed. The inside corner patches in the illustrated embodiments are generally circular. However, other shapes such as, for instance, square, rectangular, oval-shaped, and others may be substituted within the scope of the invention. Pie-shaped cutouts have been illustrated and described above; however, this is not a limitation of the invention and cutouts of other shapes such as curved, for example, may be used. 
         [0031]    The corner patches have been described with fold lines corresponding to specific angles such as 80 degrees or 110 degrees. These angles are shown and described for clarity of explanation, but do not represent limitations of the invention. In fact, the corner patches of this invention may accommodate obtuse and acute angled inside corners of virtually any angle within the physical restraints of the material from which the patch is made and its geometry. The patch may be placed in a corner of unknown angle, for example, and massaged and shaped in place to conform itself to the corner without the installer ever actually measuring or knowing the angle of the corner. These and other modifications and substitutions may suggest themselves to persons of ordinary skill in the art and such should be construed to be within the scope of the invention disclosed herein.

Summary:
A universal inside corner patch for patching inside corners formed by protrusions from a commercial low slope roof is disclosed. The universal inside corner patch includes a body having a central portion and a peripheral portion. A cutout is formed in the body extending from the peripheral portion to the central portion thereof. The cutout defines in the body a skirt having an edge on one side of the cutout and a flap having an edge on an opposite side of the cutout. Folding locations such as lines or other indicia on the body correspond to respective angles of an inside corner to be patched. When the skirt portion is overlapped with the flap portion with the edge of the skirt portion registering with one of the folding locations, the inside corner patch is configured to conform to an inside corner with an angle corresponding to the one of the folding locations. An adhesive may be disposed on a back surface of the body for adhering and sealing the corner patch in place.