Abstract:
A method for manufacturing a substrate having a textured surface. The method including the steps of: providing a substrate having a surface; applying a coating material onto the surface of the substrate; texturing the coating material on the surface of the substrate to form a textured coating; exposing the textured coating on the substrate to ultraviolet light for a duration of time sufficient to fully cure the textured coating on the substrate; and thereby forming a fully cured textured surface on the substrate.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to the field of construction materials. More specifically, this invention relates to textured wallboards, as might be used in new construction or home remodeling, and the methods for their manufacture. 
         [0003]    2. Description of Related Art 
         [0004]    Various types of wallboards have been used for years in the construction trades. The most common form of wallboard used today is drywall, which is also known as plasterboard, gypsum board and sheetrock. Drywall is formed of gypsum plaster pressed between two sheets of relatively thick paper. Drywall itself is not structural and requires the building of an underlying wall, typically formed from a framework of 2×4 lumber, to which the drywall is secured. After securing the drywall on the wall, seams between adjacent sheets of the drywall must be taped, mudded and sanded, and the smooth, unfinished exterior surface must thereafter be primed and painted. If a textured surface is desired, the texture is applied after the drywall is hung, either before or after the priming of the exterior surface, by spraying on the texture material or other means. 
         [0005]    Another form of wallboard is cement board. Cement board has either wood flakes or cellulose fiber, bonded together by cement, to form the panel. Texture is applied to cement board in similar fashion, but usually cement board is used as a backing board and is covered with tile. 
         [0006]    A further type of wallboard is one made of magnesium oxide, and which is often referred to as magnesia board. These boards are often used in place of drywall and are not a paper faced panel. In addition to being fire resistant, these boards are also not susceptible to mold and mildew. For the latter reasons, magnesia boards are often used in place of drywall. Magnesia boards can also be incorporated into preformed wall systems, such as the insulated wall systems often used in the remodeling trade for refinishing basements. 
         [0007]    One method of applying a texture to this type of wallboard involves providing a series of generally parallel textile strands, yarns or strings that are laid upon and adhesively secured to the board&#39;s surface. After the adhesive dries, the strands are trimmed. The textured panel can thereafter be primed and painted. Issues can arise, however, should one of the stands become dislodged from the board surface, either during manufacturing and installation or after installation. 
       SUMMARY 
       [0008]    In overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a novel method for forming a panel or board having a textured surface. 
         [0009]    In one aspect of the invention, a method is provided for manufacturing a substrate having a textured surface, the method including the steps of: providing a substrate having a surface; applying a coating material onto the surface of the substrate; texturing the coating material on the surface of the substrate to form a textured coating; and exposing the textured coating on the substrate to ultraviolet light for a duration of time sufficient to fully cure the textured coating on the substrate and thereby form a fully cured textured surface on the substrate. 
         [0010]    In another aspect, the step of applying the coating material to the surface of the substrate includes the step of first applying the coating material to a pair of counter rotating rollers. 
         [0011]    In a further aspect, the step of applying the coating material to the surface of the substrate includes contacting at least one roller with the surface of the substrate thereby transferring coating material from the roller to the surface of the substrate. 
         [0012]    In yet another aspect, the step of applying the coating material to the surface of the substrate includes roll coating the substrate in a coating station. 
         [0013]    In still a further aspect of the invention, the surface of the substrate is planar. 
         [0014]    In another aspect, the invention includes moving the substrate along a conveyor system during the coating, texturing and curing steps. 
         [0015]    In a further aspect of the invention, the step of texturing the coating material on the surface of the substrate includes drawing the substrate with the coating material thereon past a doctor blade or board, the doctor blade having a profiled edge and the profiled edge contacting at least the coating material and thereby forming a texture in the coating material that corresponds with the shape of the profiled edge. 
         [0016]    In a still further aspect of the invention, the profiled edge has a series of recesses formed therein. 
         [0017]    In yet another aspect of the invention, the series of recesses is a random series of recesses. 
         [0018]    In still another aspect of the invention, the series of recess is a repeating series of recesses. 
         [0019]    Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a perspective view of production line for forming textured wall boards according to the principles of the present invention; 
           [0021]      FIG. 2  is an enlarged view of the coating station and the texturing station seen in  FIG. 1 ; 
           [0022]      FIG. 3  is a downstream view of the doctor blade of the coating station showing the profiled edge that imparts the pattern or texture onto the coating on the surface of the substrate; and 
           [0023]      FIG. 4  is a perspective view of a resultant wallboard manufactured in accordance with the principles of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Referring now to the drawings, a production line for practicing a method in accordance with the principles of the present invention is illustrated therein and generally designated at  10 . The production line  10 , which is best seen in  FIG. 1 , is configured to continuously apply and fully form a texture surface on planar substrates  12 . As such, the production line  10  has various stations for achieving this process. These stations principally include an in-feed station  14 , a coating station  16 , a texturing station  18 , a curing station  20  and an out-feed station  22 . While described herein as having specific stations, it will be readily apparent to those skilled in the art that variations on the stations are possible, as is the incorporation of additional stations and components into the production line  10 . 
         [0025]    At the initiation of a method in accordance with the principles of the present invention, the substrates  12  are loaded onto a conveyor assembly  24 , such loading occurring either by an automated transfer mechanism or manually. The conveyor assembly  24  then carries the substrates  12  along the production line  10  and through the in-feed station  14 , the coating station  16 , the texturing station  18 , the curing station  20  and the out-feed station  22  The conveyor assembly  24  may utilize various means to convey the substrates  12  through the stations  14 - 22 . In a preferred embodiment, the conveyor assembly  24  employs an endless conveyor belt  26  that is driven by an electric motor (not shown) about a series of rollers  30 . With the substrates  12  loaded onto the conveyor assembly  24 , the substrates  12  are advanced by the conveyor belt  24  from the in-feed station  14  into the coating station  16 . 
         [0026]    The coating station  16  is a roll coater having a pair of rollers, which are herein referred to as a nip or coating roller  32  and a conditioning or doctor roller  34 . Driven by an electric motor (not shown), the nip roller  32  and the conditioning roller  34  are counter-rotating relative to one another such that, as seen in the illustrated drawings, the nip roller  32  rotates in a clockwise direction (the bottom of the roller  32  adjacent to the conveyor belt  26  moving in the direction of movement of the belt  26 ) and the conditioning roller  34  rotates in a counter clockwise direction. While the nip roller  32  and the conditioning roller  34  may be constructed from a variety of materials, a preferred material for the nip roller  32  is ethylene propylene diene monomer (EPDM) and the preferred material for the conditioning roller  34  is chrome plated steel, each rollers  32 ,  34  being formed so as to have a smooth exterior surface. 
         [0027]    At the upper side of the rollers  32 ,  34  (the side of the rollers away from the conveyor belt  26 ) a trough  36  is defined by the adjacent curvatures of the rollers  32 ,  34 . This trough  36  may therefore be described as the generally triangular space between the nip roller  32  and the conditioning roller  34 , where the two rollers rotate toward one another. 
         [0028]    With the rollers  32 ,  34  counter rotating, a viscous coating material  38  is dispensed into the trough  36 . The coating material  38  may be dispensed into the trough  36  at a central location, or it may be dispensed at multiple locations along the length of the trough  36 . Accordingly, a wide variety of dispensing mechanisms (not shown) could be used for this purpose. The dispensing mechanism also can either continuously supply the coating material into the trough  36  or only periodically dispense the coating material  38 . The rate at which the material  38  is provided into the trough  36  will depend, at least in part, on the rate at which the material  38  is being transferred to the substrate  12 . 
         [0029]    At least when received centrally in the trough  36 , because of its viscous nature, the coating material  38  will initially pool in the central region of the rollers  32 ,  34 . This collected pool of coating material  38  will eventually elongate, as a result of the rotating action of the nip and conditioning rollers  32 ,  34 . The elongated coating material  38  forms a log  42  within the trough  36  that extends approximately the entire length of the nip and conditioning rollers  32 ,  34 . As the coating material  38  is elongated by the counter rotating action of the rollers  32 ,  34 , a certain amount of the coating material  38  adheres to the nip roller  32 . The coating material&#39;s affinity for the chrome plated steel of the conditioning roller  34  is less than that for the EPDM material of the nip roller  32  and, therefore, a lesser amount of the coating material  38  adheres to the conditioning roller  34 . 
         [0030]    The nip roller  32  is positioned such that the nip roller  32  contacts the upper surface  44  of the substrate  12 , as the substrate  12  is being conveyed on the conveyor belt  26  through the coating station  16 . It is therefore desirable for the rotational speed of the nip roller  32  to correspond with the speed at which the substrates  12  are being conveyed in the production line  10 . In a preferred embodiment, substrates  12  are being conveyed by the conveyor belt  26  at the rate of about 16 feet/minute. By contacting the upper surface  44  of the substrate  12 , an amount of the coating material  38  is transferred from the nip roller  32  to the upper surface  44  of the substrate  12 . 
         [0031]    With the coating material  38  applied to the upper surface  44  of the substrate  12 , this coated substrate  12  next encounters the texturing station  18  of the production line  10 . In the texturing station  18 , the coating material  38  on the substrate  12  is provided with a texture or pattern that becomes the ultimate surface texture/pattern on the resulting wall board  13 . In the illustrated embodiment, this is achieved by providing a doctor blade  46  downstream of the nip roller  32  and before the curing station  20 . 
         [0032]    As noted above, the doctor blade  46  imparts the textured/pattern into the coating material  38  on the substrate  12 . To achieve this, the doctor blade  46  has a profiled lower edge  48  that is encountered by the coating material  38 . This is more readily seen in  FIGS. 2 and 3 . The peripheral edge  48  is provided with a series of recesses  50  that correspond to the desired pattern or texture that is to be formed in the coating material  38  on the substrate  12 . The recesses  50  may have common depths or be of different depth, and may be equally spaced on the profiled edge  48  or spaced at different or repeating intervals. Additionally, the recesses  50  themselves can have a variety of shapes, including, without limitation, semi-circular, oval, ellipsoidal, rectangular or another polygonal shape, and partial portions thereof. The recesses  50  may also be provided along the profiled edge so as to define either a random series of recesses or a repeating series of recesses. 
         [0033]    As the coated substrate  12  is conveyed past the doctor blade  46 , the recesses  50  of the profiled edge  48  shape the coating material  38 , which results in the pattern of the profiled edge  48  being transferred to the coating material  38 . To achieve this, the profiled edge  48  of the doctor blade  46  brought into contact the upper surface  44  of the substrate  12 . The profiled edge  48  may, however, only contact the coating material  38  in order to form the texture therein. 
         [0034]    If the texture is to form a linear design on the wall board  13 , then the doctor blade  46  is maintained stationary relative to the passing substrate  12 . However, in an alternative embodiment, the doctor blade  46  need not remain stationary. Rather, it can be moved either transversely relative to the movement of the substrates  12  or it can be moved in a vertical direction (normal to the surface  44  of the substrate  12 ) to form a non-linear pattern or uneven surface. 
         [0035]    It should also be noted that the doctor blade  46  can be provided in different configurations. For example, the doctor blade  46  could be provided in the form of an additional roller having a patterned surface which imprints the coating material  38  with the texture. In a further embodiment, the doctor blade  46  could be provided as a plate having a pattern formed on its surface, and which is periodically pressed into the coating material  38  so as to form a texture therein. 
         [0036]    Once the texture has been formed in the coating material  38  on the substrate  12 , the substrate  12  is then transferred to the curing station  20 . The curing station  20  of the present invention uses ultraviolet (UV) light within a UV oven  52  to cure the coating. While the term “oven” is used herein, it should be understood that the UV oven  52  need not necessarily develop or provide heat, other than that which is incidentally formed in the UV oven  52  by the UV lamps. To achieve this, the UV oven  52  is provided with series of UV lamps or sources  54  that emit an amount of ultraviolet light that is sufficient to fully or substantially fully cure (dry and harden) the coating material  38  within the time period that the substrate  12  is located within the UV oven  52 , which may be only about 15 to 30 seconds. As a result of this photochemical process, upon exiting the UV oven  52  the coated substrate  12  has been converted into the wallboard  13  and has a hardened, textured surface provided thereon. From the UV oven  52  of the curing station  20 , the wall board  13  proceeds to the out-feed station  22  where the wallboard  13  may be stacked and packaged for shipment or transferred for further process. As an example of further processing, the finished wallboard  13  may be transferred to another production line where the textured surface of the wallboard  13  has a primer or paint coating applied to it. Notably, these primer/painting stations could be fully integrated with the production line  10  of  FIG. 1 , if desired. 
         [0037]    The substrates  12  utilized in the present invention are generally planar and are constructed of a material that is suitable for the desired purpose, which as described herein is for use as wallboard, although the invention is not intended to be limited the manufacture of products only for such purposes. Once preferred substrate  12  is a board or panel known as a magnesia board or a magnesium oxide board. As the later name implies, this substrate  12  includes magnesium oxide as one of its principal components. In such a board, magnesium oxide is combined with a cement product, and a variety of other materials, the combination of which is then cast to form a rigid panel. Since the manufacturing of magnesium oxide boards is well known, further discussion of this technology is not provided herein. 
         [0038]    As it is apparent from the prior discussion, the coating material  38  used in the present invention is a UV curable material. Such materials are often based upon epoxy, acrylates, urethane acrylates, polyester acrylates, polyether acrylates, amino modified polyether acrylates, acrylic acrylates and various other acrylates. Such coatings can also be based upon unsaturated polyester with styrene, for example. The above identification of chemical families is only intended to be illustrative and should not be considered as limiting the chemical family upon which the UV coating materials used with the present invention can be based. The particular composition of the UV coating material will ultimately depend on the intended end use of the wallboard  13  and the desired performance characteristics. 
         [0039]    As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from spirit of this invention, as defined in the following claims.