Abstract:
A method of manufacturing roofing shingles including the steps of coating a continuously supplied shingle mat with roofing asphalt to make an asphalt-coated sheet, the asphalt-coated sheet having at least one prime region, applying alternate granules onto the at least one prime region, applying prime granules over the alternate granules to form a granule-covered sheet, and cutting the granule-covered sheet into shingles.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to roofing shingles. More particularly, this invention relates to roofing shingles manufactured with more efficient use of raw materials. 
       BACKGROUND OF THE INVENTION 
       [0002]    A common method for the manufacture of asphalt shingles is the production of a continuous strip of asphalt shingle material followed by a shingle cutting operation which cuts the material into individual shingles. 
         [0003]    In the production of the continuous strip of asphalt shingle material, a substrate such as an organic felt or a glass fiber mat is passed into contact with a coater containing liquid asphalt to form a tacky asphalt coated strip. Subsequently, the hot asphalt coated strip is passed beneath one or more granule applicators which apply the protective surface granules to portions of the asphalt coated strip to form a granule coated sheet. The granule coated sheet is cooled and subsequently cut into individual shingles. 
         [0004]    In the manufacturing process, the asphalt coated strip is conceptually divided into an equal number of prime lanes, and headlap lanes. The prime lanes receive an application of prime granules while the headlap lanes receive an application of headlap granules. Headlap granules are normally covered by subsequently laid shingles, whereas prime granules remain exposed. Prime granules are more resistant to attack by long term exposure to sunlight, and consequently prime granules are more expensive than headlap granules. It would be advantageous if shingles could be manufactured with more efficient use of raw materials. 
       SUMMARY OF THE INVENTION 
       [0005]    According to this invention there is provided a method of manufacturing roofing shingles. The method comprises the steps of coating a continuously supplied shingle mat with roofing asphalt to make an asphalt-coated sheet, the asphalt-coated sheet having at least one prime region, applying alternate granules onto the at least one prime region, applying prime granules over the alternate granules to form a granule-covered sheet, and cutting the granule-covered sheet into shingles. 
         [0006]    According to this invention there is also provided an apparatus for manufacturing roofing shingles, the roofing shingles having at least one prime region. The apparatus comprises an asphalt coater configured to receive a shingle mat traveling in a machine direction. The asphalt coater is configured to coat the shingle mat with asphalt. The apparatus further includes a source of alternate granules and at least one alternate granule applicator positioned downstream from the asphalt coater. The at least one granule applicator is configured to apply alternate granules onto the at least one prime region. The apparatus also includes a source of prime granules and at least one prime granule applicator positioned downstream from the at least one alternate granule applicator. The at least one prime granule applicator is configured to apply prime granules over the alternate granules to form a granule-covered sheet. A drum is positioned downstream from the at least one prime granule applicator. The drum is configured to press the prime granules into the sheet and remove the granules which are not adhered to the granule-covered sheet. A cutter is positioned downstream from the drum. The cutter is configured to cut the granule-covered sheet into shingles. 
         [0007]    Various advantages of this invention will become apparent to those skilled in the art from the following detailed description of the invention, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic elevational view, partially in cross section, of a portion of an apparatus for making shingles according to the method of the invention. 
           [0009]      FIG. 2  is a schematic plan view of a portion of an asphalt-coated sheet, showing a roofing shingle, made according to the method of this invention. 
           [0010]      FIG. 3  is an enlarged schematic cross-sectional elevational view of the prime lane of the roofing shingle illustrated in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    Composite shingles, such as asphalt shingles, are a commonly used roofing product. Asphalt shingle production generally includes feeding a base material from an upstream roll and coating it first with a roofing asphalt material, then a layer of granules. The base material is typically made from a fiberglass mat provided in a continuous shingle membrane or sheet. It should be understood that the base material can be any suitable support material. 
         [0012]    Composite shingles may have a headlap region and a prime region. The headlap region may be ultimately covered by adjacent shingles when installed upon a roof. The prime region will be ultimately visible when the shingles are installed upon a roof. 
         [0013]    The granules deposited on the composite material shield the roofing asphalt material from direct sunlight, offer resistance to fire, and provide texture and color to the shingle. The granules generally involve at least two different types of granules. Headlap granules are applied to the headlap region. Headlap granules are relatively low in cost and primarily serve the functional purposes of covering the underlying asphalt material for a consistent shingle construction, balancing sheet weight and preventing overlapping shingles from sticking to one another. Colored granules or other prime granules are relatively expensive and are applied to the shingle at the prime regions. Prime granules are disposed upon the asphalt strip for both the functional purpose of protecting the underlying asphalt strip and for the purpose of providing an aesthetically pleasing appearance of the roof. 
         [0014]    The description and drawings disclose a method and apparatus for manufacturing an asphalt shingle having a predetermined percentage of alternate granules disposed beneath the prime granules on the prime region of the shingle. Referring now to the drawings, there is shown in  FIG. 1  an apparatus  10  for manufacturing asphalt-based shingles according to the invention. The illustrated manufacturing process involves passing a continuous sheet in a machine direction (indicated by an arrow  12 ) through a series of manufacturing operations. The sheet usually moves at a speed from about 300 feet/minute to about 800 feet/minute. However, other speeds can be used. 
         [0015]    In a first step of the manufacturing process, a continuous sheet of shingle mat  14  is payed out from a roll (not shown). The shingle mat  14  can be any type of substrate suitable for use in reinforcing asphalt-based roofing shingles, such as a nonwoven web of glass fibers. The shingle mat  14  is fed, in machine direction  12 , through a coater  16  where a coating of asphalt  18  is applied to the shingle mat  14 . The asphalt coating  18  can be applied in any suitable manner. In the illustrated embodiment, the shingle mat  14  contacts a supply of hot, melted asphalt  18  to completely cover the shingle mat  14  with a tacky coating of asphalt  18 . However, in other embodiments, the asphalt coating  18  could be sprayed on, rolled on, or applied to the shingle mat  14  by other means. Typically the asphalt coating is highly filled with a ground mineral filler material, amounting to at least about 60 percent by weight of the asphalt/filler combination. In one embodiment, the asphalt coating  18  is in a range from about 350° F. to about 400° F. In another embodiment, the asphalt coating  18  can be more than 400° F. or less than 350° F. The shingle mat  14  exits the coater  16  as an asphalt-coated sheet  20 . The asphalt coating  18  on the asphalt-coated sheet  20  remains hot. 
         [0016]    The asphalt-coated sheet  20  is shown in more detail in  FIG. 2 . As shown, the asphalt-coated sheet  20  for the three-wide apparatus  10  comprises six distinct regions or lanes including three headlap lanes h 1 , h 2 , and h 3 , and three prime lanes p 1 , p 2 , and p 3 . An exemplary roofing shingle is shown by a phantom line  22  and may be cut from asphalt-coated sheet  20  as shown. In this manner, three roofing shingles of any length desired may be cut from each such section of asphalt-coated sheet  20 . Each shingle  22  would contain one headlap lane h 1 , h 2 , or h 3 , and one respective adjacent prime lane p 1 , p 2 , or p 3 . Accordingly, the shingle  22  includes a headlap region  26  and a prime region  24 . 
         [0017]    The headlap region  24  of the shingle  22  is that portion which is covered by adjacent shingles when the shingle  22  is ultimately installed upon a roof. The prime region  26  of the shingle  22  is that portion which remains exposed when the shingle  22  is ultimately installed upon a roof. 
         [0018]    In this embodiment, the shingle  22  is cut from the asphalt-coated sheet  20  to be three feet long by one foot wide. As further shown in  FIG. 2 , the shingle  22  includes two cut-out regions  28  which define three tabs  30 . It will be apparent to one skilled in the art that the asphalt-coated sheet  20  may be manufactured having a wide variety of widths to allow different numbers of shingles to be cut therefrom. For example, some roofing shingle manufacturing plants use an asphalt-coated sheet (not shown) which is sufficiently wide to allow four, one foot wide shingles to be cut therefrom. Such a wider asphalt-coated sheet would include an additional headlap region, and an additional prime region. One skilled in the art will also recognize that roofing shingles of different sizes, i.e. roofing shingles having different lengths and/or widths, may be cut from the asphalt-coated sheet  20 . 
         [0019]    Referring again to  FIG. 1 , the asphalt-coated sheet  20  is passed beneath an alternate granule applicator  34 . The alternate granule applicator  34  is configured to apply alternate granules  36  onto the prime lanes p 1 , p 2 , and p 3  at a predetermined, adjustable feed rate. The alternate granule applicator  34  can be of any type of applicator, blender or dispenser, having an adjustable feed rate and being suitable for applying alternate granules  36  onto the asphalt-coated sheet  20 , such as for example a fluted roll applicator, gravity feed applicator or an auger-type dispenser. Although one alternate granule applicator  34  is shown in the embodiment illustrated in  FIG. 1 , any suitable number and configuration of alternate granule applicators  34  can be used. The alternate granule applicator  34  is fed from an alternate granule hopper  35  via an alternate granule hose  35   a . The alternate granule hopper  35  can be any hopper suitable for supplying alternate granules  36  to the alternate granule applicator  34 . 
         [0020]    The phrase “alternate granules” as used herein, is defined to include any granules having a cost less than the cost of the prime granules. In one embodiment, the cost of the alternate granules  36  can be in a range from about 20 percent to about 70 percent of the cost of the prime granules. Alternatively, the alternate granules  36  can be less than 20 percent or more than 70 percent of the cost of the prime granules. As previously mentioned, the alternate granules  36  shield the roofing asphalt material from direct UV rays from sunlight, offer resistance to fire, and provide texture and color to the shingle. After application to the asphalt-coated sheet  20 , the alternate granules  36  are substantially enveloped by the asphalt coating  18 , requiring the alternate granules  36  to be resistant to temperatures in a range from about 350° F. to about 400° F. Alternatively, the alternate granules  36  can be heat resistant to temperatures in excess of about 400° F. The alternate granules  36  can include granules from many sources. Examples of sources of alternate granules  36  include recycled prime granules, granules applied to non-weather exposed areas of the shingle (headlap granules), relatively inexpensive natural rock granules, granules produced from scrap ceramics, granules from scrap and excess building materials and slag materials from metal refining and coal burning. The alternate granules  36  can also be prime granules of such low grade so as to unsuitable for use as prime granules. Examples of low grade prime granules include prime granules having defective coloring, an inconsistent or thinner than desired ceramic coating, inconsistent granule sizing or a larger or smaller than desired size. In one embodiment as shown in  FIG. 3 , the alternate granules  36  are approximately the same size as the prime granules  57 . In another embodiment, the alternate granules  36  can be larger or smaller than the prime granules  57 . 
         [0021]    Applying alternate granules  36  to the prime lanes p 1 , p 2 , and p 3  of the asphalt-coated sheet  20  defines a partial alternate granule coated sheet  38 . As further illustrated in  FIG. 1 , the partial alternate granule coated sheet  38  is passed beneath a series of granule applicators  56  and  58  for applying prime and headlap granules onto the partial alternate granule coated sheet  38 . The granule applicators  56  and  58  can be of any type suitable for applying onto the partial alternate granule coated sheet  38 . An example of a granule applicator,  56  and  58 , is a granule applicator of the type disclosed in U.S. Pat. No. 5,599,581 to Burton et al., which is hereby incorporated by reference, in its entirety. Additionally, a granule valve such as the granule valve disclosed in U.S. Pat. No. 6,610,147 to Aschenbeck may also be used. U.S. Pat. No. 6,610,147 to Aschenbeck is also incorporated by reference in its entirety. The prime granule applicator  56  is fed from a prime granule hopper  60  via a prime granule hose  60   a . The prime granule hopper  60  can be any hopper suitable for supplying prime granules  57  to the prime granule applicator  56 . 
         [0022]    Although two granule applicators  56  and  58  are shown in the embodiment illustrated in  FIG. 1 , any suitable number and configuration of granule applicators can be used. For example, a series of two prime granule applicators can be used, wherein the granule applicator  56  can be used to apply prime granules  57  onto the prime lanes p 1 , p 2  and p 3 . Similarly, the granule applicator  58  can be used to apply headlap granules  59  on the headlap lanes h 1 , h 2  and h 3 . Applying prime granules  57  and headlap granules to the partial alternate granule coated sheet  38  defines a granule-covered sheet  62 . In another embodiment, additional granule applicators can be used for additional granule drops, such as different colors, sharp demarcations and background granules. 
         [0023]    In the embodiment shown in  FIG. 1 , subsequent to the application of the alternate granules  36  onto the prime lanes p 1 , p 2  and p 3  by the granule applicator  34 , the application of the prime granules  57  by the granule applicator  56  onto the prime lanes p 1 , p 2  and p 3 , substantially forces, by the weight of the prime granules  57 , the alternate granules  36  into the asphalt coating  18 . As shown in  FIG. 3 , substantially all of the alternate granules  36  are completely enveloped within the asphalt coating  18 . It will be understood that the phrase “substantially all” is defined as within the range of from about 60 percent to about 90 percent of the alternate granules  36 . The range of the alternate granules  36  enveloped within the asphalt coating  18  can be verified by microscopic examination of a cross-sectional portion of the prime region  24  of the shingle  22 . As will be explained later in more detail, subsequent shingle manufacturing operations also press the alternate granules  36  and the prime granules into the asphalt coating  18 . 
         [0024]    As further shown in  FIG. 3 , while substantially all of the alternate granules  36  are enveloped by the asphalt coating  18 , some of the alternate granules  36  will be visible on the prime region  24  of the shingle  22 . In order to maintain the desired appearance of the prime region  24  of the shingle  22 , the color of the alternate granules  36  can optionally be coordinated with the ingredient color of the prime granules  57 . In one embodiment, the alternate granules  36  are in the same color family as the ingredient color of the prime granules  57 . The phrase “color family” is defined as having a total color difference ΔE* between the alternate granules  36  and the prime granules  57  within +/−5, where ΔE*=((ΔL*) 2 +(Δa*) 2 +(Δb*) 2 ) 1/2  based on the CIE L*, a* b* color scale. In another embodiment, the alternate granules  36  can have a total color difference ΔE* more than or less than +/−5. Alternatively, another desired appearance of the prime region  24  can be achieved by using alternate granules  36  in a different or contrasting color family. In another embodiment where the alternate granules  36  contain multiple colored ingredients, there is at least one ingredient color in the alternate granules  36  having a total color difference ΔE* with the ingredient color of the prime granules  57  within +/−5 based on the CIE L*, a* b* color scale. 
         [0025]    Referring again to  FIG. 1 , the output of the alternate granule applicator  34  is controlled such that the alternate granules  36  constitute a predetermined percentage of the total volume of all granules which ultimately envelop within the prime lanes p 1 , p 2 , and p 3  of the asphalt-coated sheet  20 . In one embodiment, the predetermined percentage of alternate granules  36  is within a range from about 5 percent to about 20 percent of the total volume of all granules which ultimately adhere to the prime lanes p 1 , p 2 , and p 3  of the asphalt-coated sheet  20 . For example, if a total of thirty pounds (30 lbs.) of granules adhere to each 100 square feet of a prime lane p 1 , p 2  and p 3 , approximately 10 percent or three pounds (3 lbs), of these granules would be alternate granules  36 . It will be appreciated however, that the amount of alternate granules  36  may vary. In one embodiment, the amount of alternate granules  36  can vary depending on the color difference between the alternate granules  36  and the prime granules  57 . In this embodiment, if both the color of the alternate granules  36  and the prime granules  57  substantially match each other in overall color, a much higher percentage of alternate granules  36  can be applied. 
         [0026]    In one embodiment as shown in  FIG. 1 , the application of the headlap granules  59  to the headlap lanes h 1 , h 2  and h 3  of the asphalt-coated sheet  20  occurs after the application of the alternate granules  36  and the prime granules  57  to the prime lanes p 1 , p 2  and p 3 . Alternatively, the application of the headlap granules  59  to the headlap lanes h 1 , h 2  and h 3  may occur before or at the same time as the application of the alternate granules  36  and the prime granules  57  to the prime lanes p 1 , p 2  and p 3 . 
         [0027]    As shown in  FIG. 1 , after all the granules are deposited on the asphalt-coated sheet  20 , the granule-covered sheet  62  is turned around a slate drum  64  to press the alternate granules  36 , prime granules  57  and headlap granules  59  into the asphalt coating  18 . The slate drum  64  temporarily inverts the granule-covered sheet  62  so that the excess and non-adhering granules fall off. The excess granules fall into a backfall hopper  70 . The backfall hopper  70  is configured to accumulate the recovered granules for later use as alternate granules  36 . 
         [0028]    In one embodiment as shown in  FIG. 1 , while the granule-covered sheet  62  is inverted, a backdust applicator  72  is positioned to apply a thin layer of backdust material  74  to a bottom surface  76  of the granule-covered sheet  62 . The backdust material  74  is configured to adhere to the bottom surface  76  of the granule-covered sheet  62  and results in a substantially less tacky bottom surface  76  for downstream shingle production operations. In one embodiment, the backdust material  74  is sand. Alternatively, the backdust material  74  can be any material, such as for example natural rock dust or small glass particles, sufficient to adhere to the bottom surface  76  of the granule-covered sheet  62  and result in a substantially less tacky bottom surface  76 . 
         [0029]    Subsequent to the application of the backdust material  74 , the granule-covered sheet  62  is turned around a sand drum  78  to press the backdust material  74  into the bottom surface  76  of the granule-covered sheet  62 . 
         [0030]    The granule-covered sheet  62  is passed between a pair of press rolls  80 ,  82  that further press the alternate granules  36 , prime granules  57  and headlap granules  59  into the granule-covered sheet  62 . 
         [0031]    As further shown in  FIG. 1 , downstream from the press rolls,  80  and  82 , the granule covered-sheet  62  is passed through a cooling section  84 . The cooling section  84  is configured to sufficiently cool the granule-covered sheet  62  to allow downstream manufacturing operations. In one embodiment, the cooling section  84  includes rollers allowing the granule-covered sheet  62  to be passed up and down while being sprayed with water to cool the hot asphalt coating  18 . In another embodiment, any means of cooling the granule-covered sheet  62  can be used. 
         [0032]    Downstream from the cooling section  84 , the granule-covered sheet  62  is subsequently fed through a cutter  86  that cuts the granule-covered sheet  62  into individual shingles  22 . The cutter  86  may be any type of cutter, such as for example a rotary cutter, sufficient to cut the granule-covered sheet  62  into individual shingles  22 . 
         [0033]    The principle and mode of operation of this invention have been described in its preferred embodiments. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described without departing from its scope.