Patent Publication Number: US-10760274-B2

Title: System and method to produce a bituminous membrane superficially covered by grain-based decorations

Description:
PRIORITY CLAIM 
     This application claims priority from Italian Patent Application No. 102016000102772 filed on Oct. 13, 2016, the disclosure of which is incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to a system and method to produce a bitumen-based membrane superficially covered by grain-based decorations. 
     In particular, the present invention concerns a system for producing a belt-shaped/laminated sheath or membrane produced by means of a bitumen-based mixture or blend, for example a modified bitumen, air-blown bitumen or distilled bitumen, and superficially covered by grain decorations. The membrane subject of the present invention can be suitably applied in the building sector to produce waterproofing and/or sealing layers and preferably, but not necessarily, for covering roofs, and/or any part of a building; to which the following description shall make explicit reference, without any loss of generality. 
     BACKGROUND OF THE INVENTION 
     It is known that the bitumen-based membranes of the type described above have a multilayer structure comprising: a central supporting layer which is produced by means of a film made of flexible material trapped between two outer bituminous layers, an upper layer and a lower layer, opposite each other. Some types of bituminous membranes used to waterproof roofs have a larger surface covered by an outer granular layer which, in addition to protecting the membrane from atmospheric agents, is distributed on the surface to form a predefined decorative design, which generally represents the modular elements traditionally used for covering roofs, for example shingles, or flat or curved tiles. 
     The above-mentioned surface decoration of the membrane can be provided by different methods, some of which entail rotating an application drum provided with surface cavities, moving the bitumen-based membrane below the application drum, filling the cavities of the drum with covering grains, temporarily maintaining the covering grains in the cavities until the latter reach a certain angular position in which the grains are released from the cavities and are thus deposited by gravity on the surface to be decorated of the membrane below. 
     U.S. Pat. No. 5,812,369 describes a method of the type described above in which the grains are retained in the cavities by means of a flexible belt wound in a ring around a plurality of wheels and arranged at the back of the application drum so as to superficially envelop the semi-circumference of the drum arranged on the side where the grains are deposited, thus temporarily occluding the cavities during the rotation of the application drum. 
     The technical problem of this solution is that, during the feeding phase, some grains are deposited on the outside of the cavities and remain trapped between the belt and the surface of the application drum and are deposited in an uncontrolled manner on the membrane, causing irregularities/blurring on the lines/contours of the decoration which therefore spoil the decorative pattern. Furthermore, the grains trapped between the drum and the belt superficially abrade both the application drum and the belt itself. If said abrasion is continuous, in the long term it will damage both the drum and the belt which consequently have to be replaced, resulting in increased costs in terms of production, maintenance, machine standstills, etc. 
     WO 2015 125 089 A1 also describes a method of the type described above, in which the grains are temporarily retained in the cavities prior to depositing thereof by means of an occlusion roller made of elastically deformable material, instead of a flexible belt. The occlusion roller is positioned in contact with the application drum on the side on which the grains are deposited, thus partially deforming on the same side and therefore forming a sliding elastic surface portion which compresses the grains inside the cavities and cleans the surface of the drum during the rotation thereof. 
     The technical problem associated with this solution is represented by the fact that the occlusion roller, being made of deformable elastic material and being continually pressed against the drum, is subject to rapid wear by the latter and consequently has to be replaced often, with all consequent drawbacks. 
     Furthermore, depositing of the grains is often inaccurate. In fact, positioning of the roller axis on the horizontal centreline plane on which the drum axis lies and sizing of the sliding elastic surface portion which extends below the horizontal centreline plane are such that discharge of the grains from the cavity can commence when the cavity is positioned in the lower portion of the roller, well below the horizontal centreline plane thereof. In this way, the cavity is free to discharge when it is already substantially facing the membrane. Consequently, the initial discharge of the grains is carried out in an uncontrolled manner, i.e. not gradual, and can cause blurring on the lines of the decoration which impair the aesthetic effect thereof. 
     The Applicant has therefore carried out a detailed, study with the aim of identifying a simple and inexpensive solution for implementing a method to produce a bitumen-based membrane superficially covered by grain-based decorations which overcomes the technical problems highlighted above. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is therefore to make available a solution for achieving the above objective. 
     This objective is achieved by the present invention which is relative to a system and method to produce a bitumen-based membrane superficially covered by grain-based decorations as described in the attached claims. 
     The present invention further concerns a machine for decorating a bitumen-based membrane by means of covering grains as described in the attached claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting embodiment example thereof, in which: 
         FIG. 1  schematically shows a system for producing a bitumen-based membrane superficially covered by grain-based decorations produced according to the teachings of the present invention; 
         FIG. 2  schematically shows a machine for depositing grain-based decorations on the membrane comprised in the system shown in  FIG. 1 , and subject of the present invention; 
         FIG. 3  schematically shows the application drum of the machine for depositing grain-based decorations shown in  FIG. 2 ; 
         FIG. 4  is a front elevation view of an embodiment of the machine for depositing grain-based decorations subject of the present invention; 
         FIG. 5  is a section I-I of the machine shown in  FIG. 4 ; 
         FIG. 6  is a perspective view of a grain retention device comprised in the machine subject of the present invention; 
         FIGS. 7 and 8  are photographs of the decorated surface of two bituminous membranes obtained by implementing the method subject of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described in detail with reference to the attached Figures to allow a person skilled in the art to produce it and use it. Various modifications to the embodiments described will be immediately evident to persons skilled in the art and the general principles described can be applied to other embodiments and applications without departing from the protective scope of the present invention, as defined in the attached claims. Therefore, the present invention must not be considered limited to the embodiments described and illustrated, but must be given the widest protective scope in accordance with the principles and characteristics described and claimed herein. 
     The meaning of some terms used in the present description and in the claims, will now be defined. 
     By “membrane” we mean a flat multilayer structure with predefined width based on a bituminous mixture, comprising: at least one central supporting layer which is produced by means of a central tape or film made of flexible paper, plastic material or fabric or any similar flexible material, and at least two lower and upper bituminous layers, fixed on respective larger lower and upper surfaces, opposite each other, of the central supporting layer so as to trap/embed said central supporting layer in a stable manner. The membrane can be ribbon-shaped/laminated and be sized so that it can be wound to form a roll/coil. The membrane subject of the present invention is further structured to be preferably used, for example, as a waterproofing and decorative bituminous membrane for roof. It is understood that the use of the membrane is not limited to application on a roof; other types of application can be envisaged, such as applications for covering/coating any other surface/wall of a dwelling/building. 
     By “bituminous mixture” it is understood a mixture or compound based on natural hydrocarbons or residues deriving from the distillation or refining of oil and mixed in a known way, and therefore not described in detail (forming tar, asphalt or in general a mixture of high viscosity hydrocarbons), to which a certain quantity of polymer material is preferably, but not necessarily, added. The polymer material can comprise: APP (acronym for atactic polypropylene) and/or SBS (acronym for Styrene-Butadiene-Styrene) and/or polyolefins (for example APAO—Amorphous Poly Alpha Olefin and/or TPO thermoplastic polyolefins), and/or styrene-butadiene-styrene (SBS), and/or styrene-ethylene-butadiene-styrene (SEBS), and/or resins, or similar substances. 
     By the term “covering grains” we mean flakes or fragments or tiny solid particles finely chopped (dimensions smaller than 1.5 mm); they can comprise for example granules, sand, grit, and can be composed of minerals, for example slate, basalt, ferrite or any similar mineral. 
     With reference to  FIG. 1 , the number 1 indicates a system that carries out a process/method for producing a membrane  2  superficially covered by a decoration formed of covering grains  3 . 
     According to a preferred embodiment shown in  FIG. 1 , the system  1  can comprise: a forming station  4  designed to preform/prefabricate the membrane  2 , and a coating station  5  designed to superficially coat, at least partially, the preformed membrane  2  with coating grains  3 . 
     The system  1  can further comprise membrane feeding/moving means provided, for example, with idle/motorized rollers (not illustrated) rotated by relative drive units, for example electric motors controlled by an electronic control unit  10  for feeding the membrane  2  along a direction A, preferably approximately horizontal, for example rectilinear, thus crossing in sequence the forming station  4  and the coating station  5 . 
     The membrane feeding/moving means  6  and the forming station  4  of the membrane  2  are of known type and consequently will not be further described apart from specifying that the forming station  4  can be structured to carry out the following operating phases: unwind from a roll or coil  7  a layer designed to form the central supporting layer  8  of the membrane  2 , feed forward the supporting layer  8  immersing it, for a section of its travel, in a controlled manner, in an impregnation tank  9  containing the hot bituminous compound in a semi-liquid and viscous state, thus causing the bituminous blend to adhere/attach to the opposite larger surfaces of the supporting layer  8  so as to form the lower and upper bituminous layers of the preformed membrane  2 . 
     With reference to  FIGS. 1 and 2 , the coating station  5  comprises at least a grain application machine  11 , which is designed to receive covering grains  3  and deposits the covering grains  3  in a controlled manner on the hot semi-solid membrane  2  just preformed (still partially viscous at least on the surface), during the movement of the same along the direction A, thus forming on the preformed membrane  2  a superficial decorative covering on the basis of at least a predefined pattern. 
     According to a preferred embodiment shown in  FIGS. 1, 2 and 3 , the grain application machine  11  comprises an application drum  12 , which can be arranged above the membrane  2  at a determinate distance therefrom, to rotate around an axis B, thus receiving the covering grains  3  in a loading region  12   a  on the surface of the drum  12  and associated with an angular rotation interval Δα of the application drum  12 , and deposits the covering grains  3  on the upper surface of the membrane  2  below, when the application drum  12 , during the rotation, cross approximately an angular deposition position of the drum  12 . Preferably, but not necessarily, the axis B can be horizontal and orthogonal to the direction A. 
     The grain application machine  11  further comprises a grain loading device  13 , which is arranged at the loading region  12   a  of the application drum  12  and is structured to load the covering grains  3  in a controlled/dosed manner, in the loading region  12   a  of the application drum  12 . 
     According to a preferred embodiment example shown in  FIGS. 1 and 2 , the application drum  12  can have a preferably cylindrical shape with a circular section. The application drum  12  can be made preferably, but not necessarily, of rigid non-deformable material, for example metallic or plastic material and the like. The application drum  12  can be rotated around the axis B by a drive unit provided with an electric motor M (shown in  FIG. 4 ) preferably controlled by an electronic control system comprising for example the electronic control unit  10  and mechanically connected to the application drum  12  by means of a mechanical motion transmission system of known type and therefore not described in detail. 
     On the outer cylindrical surface of the application drum  12  cavities  15  are obtained, which are structured to each contain a predefined quantity of covering grains  3  and are arranged on the surface according to a predefined geometric distribution which depends on the superficial decorative covering to be produced on the membrane  2 . 
     As regards the grain loading device  13 , it can comprise a hopper  16 , which is arranged approximately beside the upper part of the application drum  12  substantially at the back thereof, and has in the lower part, i.e. on the bottom, an opening  18  which faces the loading region  12   a  of the surface of the drum  12 . The opening  18  is obtained on the bottom of the hopper  16  so that the covering grains  3  which come out of the opening  18  are deposited in the loading region  12   a  thus entering the cavities  15  therein. 
     According to a preferred embodiment example shown in  FIG. 2 , the hopper  16  is arranged so that the opening  18  is conveniently positioned facing the surface portion of the drum  12  within the angular rotation interval Δα. 
     In the example illustrated in  FIGS. 2 and 3 , the angular rotation intervals Δα ranges between an angle α 2  and an angle α 2  both determined with respect to the horizontal centreline plane O of the drum  12  passing through the axis B. According to a preferred embodiment example, the angle α 1  is approximately 37° while the angle α 2  is approximately 45°. 
     According to a preferred embodiment shown in  FIGS. 1 to 6 , the grain application machine  11  further comprises a grain retention device  20 , which is arranged beside the drum  12  on the opposite side of the opening  18  of the hopper  16  with respect to the vertical centreline plane V of the drum  12  passing through the axis B, in contact with the drum  12 ; this maintains the covering grains  3  in the cavities  15  when the latter are in a retention surface region  12   b  of the drum  12  within an angular rotation interval Δβ distinct from and subsequent to the angular rotation interval Δα in the direction R of rotation of the drum  12 . Preferably the direction R can correspond to the feed direction A of the membrane  2 . In  FIGS. 2 and 3 , R is anticlockwise and the direction A of the membrane is oriented towards the right side of the drawing. 
     In the example illustrated, the angular rotation interval Δβ is between an angle β 1  and an angle β 2  both determined with respect to the horizontal centreline plane O of the drum  12  passing through the axis B. According to a preferred embodiment example, the angle β 1  can be approximately 125° while the angle α 2  can be approximately 180° while the angular rotation interval Δβ can be approximately 55°. 
     According to a preferred embodiment shown in  FIGS. 2, 3, 5 and 6 , the grain retention device  20  comprises a scraping device  21  comprising a scraper shaped so as to present a scraping face  21   a  arranged in contact with the retention region of the drum  12  in order to slide on it. 
     According to a preferred embodiment, the scraping device  21  can conveniently be made of a sintered polymer based material. 
     The Applicant has found that the scraping device  21  can be conveniently made of sintered polyethylene preferably at low pressure and high density. In fact, the Applicant has found that the scraping device  21  made of sintered polymer material, for example sintered polyethylene, has the technical effect of a high resistance to wear and, since it is self-lubricating, significantly reducing the surface wear on the drum  12 . Tests carried out by the Applicant have shown that a sintered polyethylene particularly appropriate for producing the scraping device  21  can have a friction coefficient ranging from approximately 0.2 to 0.25, and a specific weight ranging from approximately 0.935 g/cm 3  to 0.98 g/cm 3 . The tests performed by the Applicant have also highlighted that, for example, the sintered polyethylene named “POLIZENE®” could be appropriate for producing the substantially non-deformable scraping device  21 . 
     According to a possible embodiment example shown in  FIG. 2 , the scraping device  21  is angularly fixed with respect to the drum  12  so that it remains in contact with the retention region  12   b  of the drum  12  during rotation thereof. 
     As shown in  FIGS. 3, 4, 5 and 6 , the scraping device  21  can comprise, for example, a scraper defined by an elongated shaped bar which extends along a longitudinal axis approximately parallel to the axis B and can have a cross section approximately polygonal, preferably square or rectangular. It is understood that the shape of the scraping device  21  is not limited to the sections listed above but can have different shapes suitable for retaining the grains  3  in the retention region. 
     According to a possible embodiment example shown in  FIGS. 2, 3 and 6 , the scraping face  21   a  can be approximately arcuate, i.e. it has a section transverse to the longitudinal axis of the scraping device  21  having approximately the shape of a circle section. Preferably, the circle section can be approximately complementary to the portion of the transverse section of the drum  12  defining the retention region  12   b.    
     According to a preferred embodiment shown in  FIGS. 3 and 6 , the arcuate scraping face  21   a  forms at its ends with the lateral walls of the scraping device  21  a first edge and a second edge. In the example of  FIG. 3 , the first edge of the scraping device  21  is arranged so as to form an angle with the horizontal centreline plane O corresponding to the angle β 1 . In the example of  FIG. 3 , the second edge of the scraping device  21  is arranged so as to form an angle with the horizontal centreline plane O corresponding to the angle β 2 . 
     According to a preferred embodiment shown in  FIGS. 2 and 5 , the grain retention device  20  can further comprise a mechanical device  22  which is structured so as to exert a force on the scraping device  21  to maintain the scraping face  21   a  preferably in contact (in abutment) in a substantially adherent and uniform manner on the retention region of the drum  12  along the entire axial length of the scraper  21 . 
     According to a possible embodiment example shown in  FIGS. 2 and 6 , the mechanical device  22  can comprise a rod or shaft  24  which can be positioned above the drum  12  and extends along a longitudinal axis approximately parallel to the axis B. The mechanical device  22  can further comprise a plurality of approximately vertical rocker arms or arms  25  which support at the bottom the scraping device  21  and at the top pivot on the shaft  24  so as to freely oscillate around it. 
     The mechanical device  22  can further comprise a plurality of counterweights  26  which are mechanically coupled/connected to the arms  25  preferably via stems  27  fixed to the arms  25 . The counterweights  26  are designed to exert a force which pushes the scraping face  21   a  against the drum  12  in a direction approximately radial to it. According to a possible embodiment shown in  FIG. 4 , the arms  25  can be arranged parallel and equidistant from one another along the scraping device  21  so that the counterweights  26  distribute the force exerted on the scraping face  21   a  in a uniform manner over the entire axial length thereof. 
     As regards the hopper  16 , according to an convenient embodiment, it can have on the bottom two lower walls, preferably but not necessarily flat and reciprocally inclined so as to converge at the ends. The two lower walls delimit with their ends the opening  18 . In the example illustrated in  FIGS. 2, 3 and 5 , a wall  16   a  defines a slide which favours the loading of the grains  3  in the cavities  15  in the loading region  12   a.    
     The wall  16   a  can be conveniently arranged on a plane radial to the drum  12  and passing through the axis B so as to be inclined by an angle γ with respect to the horizontal plane O. The Applicant has found that said inclination favours the controlled loading of the grains  3  in the cavities  15 . 
     The Applicant has also found it convenient to produce the hopper  16  so that the other bottom wall  16   b  extends towards the drum  12  on a plane substantially tangent to the drum  12 . Said positioning advantageously prevents the raising of an excessive number of granules since the wall  16   b  performs a smoothing action on the cylinder  12 . 
     In an embodiment example shown in  FIG. 2 , the wall  16   a  can present a terminal portion folded inwards, which supports in a stable manner a scraper  28  arranged approximately in contact with the drum  12 . The scraper  28  is structured to scrape the grains  3  from the surface of the drum  12  during loading, thus causing them to enter the cavities  15 . The scraper  28  is further structured to clean the grains  3  from the contact surface of the drum  12 . 
     In an embodiment example shown in  FIGS. 4 and 5 , the scraper  28  can comprise for example a rectangular plate-like body with an elongated shape, which extends along an axis parallel to the axis B and has a preferably approximately rectilinear free end which is arranged in contact with the drum  12  for approximately the entire axial length thereof. 
     In the example illustrated, the scraper  28  extends from the folded terminal portion of the wall  16   a , preferably coplanar with it, so that it is inclined with respect to the horizontal plane O preferably by an angle corresponding approximately to the angle α 1 . The Applicant has found that the scraper  28  can be advantageously made of sintered polyethylene preferably at low pressure and high density. It is understood that the scraper  28  could be integrated in the terminal part of the wall  16   a  or be formed therefrom. 
     With reference to  FIG. 2 , the hopper  16  can further comprise preferably at the wall  16   b , a dosing door  29  moving on a movement plane from and towards a closing position of the opening  18 , therefore adjusting the quantity of covering grains  3  loaded from the hopper  16  into the cavities  15  of the drum  12 . 
     Preferably, the movement plane of the dosing door  29  can be approximately tangent to the drum  12 . Preferably the movement plane can be tangent to the drum  12  and the movement of the dosing door on the plane allows variation of the angle α 2 . 
     According to one embodiment, the dosing door  29  can be mounted in a sliding manner on the wall  16   b  of the hopper  16  by means of appropriate guides (not illustrated), to move over the movement plane, from and towards the contact end of the scraper  28  with the drum  12 , in order to vary the dimension of the opening  18  and therefore adjust the quantity of grains discharged from the hopper  16 . The dosing door  29  can be moved on the movement plane via electric movement means (not illustrated), for example linear electric actuators or electric motors driven by an electronic control system, for example the electronic control unit  10 . The dimension of the opening  18  can be varied to dose the quantity of grains  3  loaded on the drum  12  on the basis of one or more control parameters of the system  1  and/or of the membrane  2 . For example, the control parameters can be the feeding speed of the membrane  2 , and/or the density of grains  3  to be deposited on the membrane  2 , and/or the dimensions of the grains. 
     With reference to  FIG. 3 , the cavities  15  are obtained on the surface of the drum  12  one approximately beside the other in approximately adjacent positions, having relative longitudinal axes preferably arranged in positions approximately radial to the drum  12 . Preferably, the longitudinal axes of the cavities  15  can be approximately coplanar to the plane on which the scraper  28  lies. 
     With reference to a preferred embodiment, shown in  FIG. 3 , the cavities  15  have a longitudinal axis F and can be formed by an inner portion  15   a  and an outer portion  15   b . The inner portion  15   a  can have an approximately triangular axial section whereas the outer portion  15   b  can have an approximately trapezoidal axial section. The Applicant has found that the trapezoidal section allows complete emptying of the cavities, a condition that cannot be obtained for example with a rectangular section in which the grains tend to get caught in the cavity. 
     Preferably the oblique sides of the outer portion  15   b  form an angle θ less than 90° with the outer surface of the drum  12  which surrounds the cavity  15 . 
     The density and reciprocal positioning of the cavities  15  on the surface of the drum  12  depends on the decoration to be provided and/or the aesthetic effect to be obtained. 
     In the example shown in  FIG. 1 , the system  1  comprises a plurality of grain application machines  11 , which are arranged one after the other in the feed direction A. In the example illustrated, the machines are structured to provide on the membrane respective decorations that graphically represent the modular elements used for cover roofs, such as shingles, and flat or curved tiles. 
     A first application machine  11  can be structured to deposit on the upper face of the preformed hot and semi-solid membrane  2  that is fed forward below the drum  12 , first fine/thin grains to provide on said face lines that define the edge/contour of the graphic modular element. Preferably, the grains defining the contour of the modular elements can be black. The first grains are deposited in a controlled manner on the hot semi-solid membrane  2  thus embedding/sinking into the surface thereof. Preferably the first grains can have a granulometry smaller than approximately 0.7 mm, preferably smaller than or equal to approximately 0.63 mm. 
     A second application machine  11 , arranged downstream of the first application machine  11 , can be structured to deposit on the upper face of the membrane  2  second large grains, i.e. thicker than the first grains, so as to completely cover the upper face. Preferably the large grains can have a granulometry ranging between approximately 0.7 and approximately 1.5 mm, preferably ranging from approximately 0.63 mm to approximately 1.25 mm. 
     During the application, a certain quantity of second grains is deposited over the first grains which prevent sticking thereof to the membrane  2  while another quantity of grains is deposited in the uncovered bituminous areas of the membrane  2  and remain stuck thereto, thus colouring the inner space delimited by the contours. Preferably, the large grains defining the larger visible surface of the modular elements can be red or green or other similar colours. 
     During a subsequent cooling phase, the membrane  2  changes its state from semi-solid to solid, and the grains  3  deposited are rigidly/stably fixed on the surface of the membrane  2  thus defining the permanent surface decoration. 
     The second grains that remain free, i.e. not attached to the face of the membrane  2 , can be easily separated therefrom. For this purpose, the system  1  can comprise, for example, a recovery tank for recovering the grains arranged downstream of the second application machine  11 , while the movement means can be structured to overturn the cooled membrane  2  above the grain recovery tank thus inverting/overturning the upper face so that the second grains left free (not attached) are deposited by gravity in the tank below. It is understood that the free grains could be sucked by a suction device (not illustrated) or separated from the membrane by other separation means of known type. 
     From the above description it is evident that the structure of the application machine  11  allows the grains to be conveniently dosed and distributed accurately on the membrane  2  without causing overlapping thereof, thus guaranteeing complete fixing of all the grains deposited thereon. Advantageously, in the system provided with two application machines and produced as described above, this results only in an overlapping of large grains on the contours of the decoration obtained with fine grains of the membrane. This prevents mixing between fine and large grains and allows complete recovery of the large grains with all the consequent advantages in terms of reduction of waste and costs. 
     It has therefore been shown that the present invention allows achievement of the above objectives. 
     Lastly, it is clear that modifications and variations can be made to the method, the machine and the system described and illustrated here without departing from the scope of the present invention defined by the attached claims.