Abstract:
The present disclosure provides a method for producing detectable warnings ( 16 ) on substrate surfaces ( 14 ), which includes providing a mat ( 30 ) with a top surface ( 38 ) and a bottom surface ( 36 ) and a pattern of mat through holes ( 34 ) extending through the mat ( 30 ). The through holes ( 34 ) comprise a lower portion ( 44 ) defining a lower mat opening ( 33 ) and an upper portion ( 32 ) defining an upper mat opening ( 35 ), wherein the upper mat opening ( 35 ) is larger in transverse dimension than the lower mat opening ( 33 ). The method further includes placing the mat ( 30 ) on a substrate surface ( 14 ), wherein the bottom surface ( 36 ) of the mat ( 30 ) is adjacent the substrate surface ( 14 ), and injecting into the mat through holes ( 34 ) a viscous substance ( 40 ) having the ability to cure into a solid. The method further includes removing the mat ( 30 ) at the appropriate time to form raised detectable warnings ( 16 ) on the substrate surface ( 14 ).

Description:
BACKGROUND 
     Detectable warnings, a distinctive surface pattern of domes detectable by cane or underfoot, are used to alert people with vision impairments of their approach to streets and hazardous drop-offs. The ADA Accessibility Guidelines (ADAAG) require these warnings on the surface of curb ramps, which remove a tactile cue otherwise provided by curb faces, and at other areas where pedestrian ways blend with vehicular ways. They are also required along the edges of boarding platforms in transit facilities and the perimeter of reflecting pools. 
     The technical specifications of the ADA require that detectable warnings on walking surfaces have a specific truncated dome pattern. This unique pattern is intended to provide a consistent and uniform surface that is distinctive from other materials and, therefore, recognizable as a warning to pedestrians that they are approaching a potentially dangerous area. Under the “Revised Draft Guidelines for Accessible Public Rights-of-Way,” the ADAAG specifically requires that detectable warnings consist of a surface of truncated domes aligned in a square or radial grid pattern. 
     SUMMARY 
     The present disclosure provides a method for producing detectable warnings on substrate surfaces, which includes providing a mat with a top surface and a bottom surface and a pattern of mat through holes extending through the mat. The through holes comprise a lower portion defining a lower mat opening and an upper portion defining an upper mat opening, wherein the upper mat opening is larger in transverse dimension than the lower mat opening. The method further includes placing the mat on a substrate surface, wherein the bottom surface of the mat is adjacent the substrate surface, and injecting into the mat through holes a viscous substance having the ability to cure into a solid. The method further includes removing the mat at the appropriate time to form raised detectable warnings on the substrate surface. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of the present disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of detectable warnings formed on a target, substrate surface; 
         FIG. 2  is a top perspective view of a mat including a plurality of openings, wherein the mat is secured to a target substrate surface and a blended material is injected into the openings; 
         FIG. 3A  is a cross-sectional view of blended material being injected into the openings of the mat of  FIG. 2 ; 
         FIG. 3B  is a cross-sectional view of the mat of  FIG. 3A  being removed from the target substrate surface; 
         FIG. 3C  is a cross-sectional view of the blended material adhered to the target surface after the mat of  FIG. 3A  has been removed from the target surface; 
         FIG. 3D  is a cross-sectional view of the blended material adhered to the target surface, wherein the material has slumped partially to begin forming detectable warnings; 
         FIG. 3E  is a cross-sectional view of detectable warnings formed on a target surface as shown in  FIG. 1 ; and 
         FIG. 4  is a cross-sectional view of blended material being injected into an alternate embodiment of the mat of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a substrate or target surface  14  having a pattern of detectable warnings in the form of truncated domes  16  formed thereon is shown. The truncated domes  16  are illustrated as arranged in an “in-line” or “square” pattern as shown in  FIG. 1 . The rows of truncated domes may instead be rotated (for example at 45 degrees) in relation to the substrate surface  14  to produce an offset pattern. Preferably, the truncated domes are spaced at least 1.6″ from the center of one truncated dome to the center of the adjacent truncated dome, and no more than 2.4″ apart for both the in-line pattern and the offset pattern. In addition, a multiple sinusoidal pattern in a stacked relationship, as shown in U.S. Pat. No. 5,385,770, may instead be used to provide a greater likelihood that an object in constant contact with surface  14  will encounter a truncated dome  16  in the shortest distance. For ease of illustration and clarity, only the in-line pattern is shown. 
     A cross section of a truncated dome  16  bonded to substrate  14  is shown in  FIG. 3E . Inclined peripheral surfaces  20  may have curved upper and lower transitions  22  and  24  with upper surface  26  and substrate  14 , respectively, so that an object such as a cane, shoe, or foot, as well as an implement such as a shovel or squeegee, will not jam or lodge in the otherwise sharp corners or edges created at these interfaces. Beneficially, these curved transitions  22  and  24  increase the truncated dome&#39;s resistance to dislodgment from lateral impacts by permitting a certain degree of impact redirection. To comply with R304.1 (as mentioned in the background section of this application), the truncated domes  16  are at least 0.9″ in diameter along the bottom of the truncated dome  16 , and no more than 1.4″ in total diameter. Along the top of the truncated dome, the diameter is at least 50 percent and no more than 65 percent of the base diameter. The truncated domes  16  are approximately 0.2″ in height. 
     Other truncated shapes and sizes may also be used as detectable warnings. For instance, as shown in U.S. Pat. No. 5,385,770, additional designs may include an elongated elliptical design, a diamond shaped design, an asymmetrical elongated elliptical design, or a dumbbell design. Each detectable warning is characterized as having an inclined peripheral surface and somewhat rounded or curved transitions between both the lower substrate  14  and the upper surface of the detectable warning. 
     Now referring to  FIG. 2 , a mat  30  or similar element may be used to create the afore-described detectable warnings or truncated domes  16  on a substrate surface  14 . The mat  30  may consist of either a rigid, flexible, or semi-flexible material, where the mat  30  may be formed using a molding technique, such as injection molding. The mold may include an upper and lower portion, and each portion of the mat mold may contain a portion of a mold cavity. The mold may also include inwardly extending projections that generally conform to the shape of the through holes  34  to form the through holes  34  during the molding process. 
     Referring to  FIGS. 2 and 3C , each through hole  34  formed during the molding process represents a mold for forming the desired truncated domes  16  on the substrate surface  14 . The through holes  34  are shown as being of an inverted frusto-conical shape and include a lower portion  44  defining a lower mat opening  33  and an upper portion  32  defining an upper mat opening  35 . Preferably, the diameter of the lower mat openings  33  on the mat bottom surface  36  are about 0.50 inches to 0.90 inches and the diameter of the upper mat openings  35  on the mat top surface  136  are about 150% to 225% larger. However, it should be appreciated that through holes  34  of different sizes may be used to form various-sized detectible warnings  16 . The through holes  34  may be arranged in a desired pattern to enhance the detectability of the target surface. 
     Now referring to  FIGS. 2 and 3A , the truncated domes  16  are formed by first placing the mat  30  on a substrate surface  14 . The mat  30  may include a sealant or adhesive surface (not shown) on the mat bottom surface  36  so that the mat  30  temporarily adheres to the substrate surface  14 . After the mat  30  is placed upon the substrate surface  14 , a viscous material  40  is injected into and fills each through hole  34 . The material  40  is injected into the through holes  34  by using a manually operated squirt bottle or other manually operated or powered device. The material  40  may also be infused into the through holes  34  with a squeegee or similar device. After the material  40  has been injected or infused into all the through holes  34 , the mat  30  is removed. 
     Referring to  FIG. 3B , when the mat  30  is lifted from the substrate surface  14 , the material  40  in the lower portion  44  of the through hole  34  falls downwardly through the lower mat opening  33  and adheres to the substrate surface  14  to form an initial base portion  42 . The material  40  is of a consistency such that it slumps slightly when it falls to the substrate surface  14 . At the same time the initial base portion  42  is being formed, the material  40  in the upper portion  32  of the through hole  34  is gravitationally forced downwardly and inwardly towards the center of the through hole  34 . Referring to  FIG. 3C , the material  40  from the upper portion  32  falls through the lower mat opening  33  onto the initial base portion  42  to form an initial annular top ring  50 . 
     The material  40  in the initial annular ring  50  continues to fall inwardly and downwardly into the initial base portion  42  and causes the initial base portion  42  to slump further and become larger in size and diameter, as shown in  FIG. 3D . The ring  50  continues to fall into the base portion  42  until a truncated dome  16  having a base diameter of approximately 0.9″ to 1.4″ is formed, as shown in  FIG. 3E . The shape and size of the upper surface  26  of the truncated dome  16  is defined by the initial annular ring  50 , which is formed by material  40  that falls through the lower mat opening  33  in the mat bottom surface  36 . Thus, the dome upper surface  26  is roughly the same size and shape as the lower mat opening  33 , or about 50 to 60 percent of the base  27  diameter. 
     As the material  40  ceases slumping, the material  40  cures to form the truncated dome  16 , as shown in  FIG. 3E . Once the truncated dome  16  has formed and cured, a final coat of viscous catalyzed material may be applied to the substrate surface  14  and the truncated domes  16  to smoothen any abnormalities or blemishes and help ensure an even appearance. 
     The truncated domes  16  of the present disclosure may be formed from material  40 , which may comprise a methacrylate monomer blended with binders, pigments, and an abrasive. Ideally, the blended material has good abrasion resistance, chemical resistance, and longevity. The material  40  may be a viscous substance that is selected from the group consisting of polyester, polyethylene, polyurethane, polypropylene, polymethacrylate, polystyrene, polystyrene-acrylonitrile, polyvinylchloride, vinyl chloride acetate, nylon, rayon, acetate, acetate butyrate, rubber, methylmethacrolate, and polycarbonate. In one form of the present invention, the composition of the detectable warnings may be a methacrylate monomer blend having glass fiber binders, pigments, and reflective material. The use of a methacrylate monomer helps engender strong bond characteristics with normally encountered substrate surfaces such as asphalt, concrete, steel, and wood. The use of glass fibers enhances structural properties of the detectable warnings, increases traction, and reduces the amount of resin mixture needed for any given application. The percentage pigment chosen provides adequate color contrast under the provisions of the ADA. The use of reflective material such as glass spheres or beads enhances low light detection of the detectable warnings and further decreases the amount of monomer needed. Finally, the percentage abrasive not only increases the potential coefficient of friction of the warnings, but also provides additional strength as an aggregate and decreases the overall amount of resin needed for a given application. 
     Now referring to  FIG. 4 , wherein corresponding numerals increased by  100  refer to like elements, a further embodiment of the mat  130  is depicted. The mat  130  is substantially the same as mat  30  except that the through holes  134  include a lower generally circular portion  144  defining a lower mat opening  133  and an upper curved portion  132  defining an upper mat opening  135 . The lower circular portion  144  extends from the mat bottom surface  136  at least partially through the mat thickness. The upper curved portion  312  extends from the lower circular portion  144  to the mat upper surface  138 . The upper curved portion  132  extends upwardly and outwardly towards the mat top surface  138  so that the diameter of the upper mat opening  135  is larger than the diameter of the lower circular portion  144  and the lower mat opening  133 . 
     Preferably, the diameter of the lower mat openings  134  (and the diameter of the lower circular portion  144 ) are about 0.50 inches to 0.90 inches and the diameter of the upper mat openings  135  on the mat top surface  136  are about 150% to 225% larger. The through holes  134  may be arranged in a desired pattern to enhance the detectability of the target surface. 
     The mat  130  is used to form truncated domes  116  (not shown) in substantially the same way as with mat  30 . Each through hole  134  in the mat  130  represents a mold for forming the desired truncated domes  116  on the substrate surface  114 . After the mat  130  is placed upon the substrate surface  114 , a viscous material  140  is injected into and fills each through hole  134 . After the material  140  has been injected or infused into all the through holes  134 , the mat  130  is removed. When the mat  130  is lifted from the substrate surface  114 , the material  40  in the lower circular portion  144  falls downwardly through the lower mat opening  134  and adheres to the substrate surface  114  to form an initial base portion  142 . 
     The material  140  is of a consistency such that it slumps slightly when it falls to the substrate surface  114 . At the same time the initial base portion  142  is being formed, the material  140  in the upper curved portion  132  of the through hole  134  is drawn downwardly and inwardly towards the center of the through hole  134 . The material  140  from the upper curved portion  132  falls through the lower mat opening  133  and onto the initial base portion  142  to form an initial annular ring  150 . The material  140  in the initial annular ring  150  continues to fall inwardly and downwardly into the initial base portion  142  and causes the initial base portion  142  to slump further and become larger in size and diameter. The ring  150  continues to fall into the base portion  142  until a truncated dome  116  having a base diameter of approximately 0.9″ to 1.4″ is formed. The shape and size of the upper surface  126  of the truncated dome  116  is defined by the initial annular ring  150 , which is formed by material  140  that falls through the lower mat opening  133  in the mat bottom surface  136 . Thus, the dome upper surface  126  is roughly the same size and shape as the lower mat opening  133 , or about 50 to 60 percent of the base diameter. When the material  140  has ceased slumping, the material  140  cures to form the truncated dome  116 . 
     While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.