Abstract:
The present invention relates to a system and method for printing an extruded sheet in which ink is applied over the extruded sheet. The extruded sheet is at an elevated temperature. The ink cures immediately upon contact with the extruded sheet having an elevated temperature. In one embodiment, at least one print roller applies a background color to the sheet and a plurality of print rollers apply one or more additional colors for forming a pattern or image on the sheet. For example, the pattern or image can have a wood grain appearance. The extruded sheet can be sized for use as a vinyl siding product.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a system and method for printing an extruded sheet in which ink is directly applied to the extruded sheet with one or more print rollers.  
           [0003]    2. Description of the Related Art  
           [0004]    It is often desirable to enhance the appearance of plastic articles, such as vinyl siding. U.S. Pat. No. 5,662,977 describes a process for manufacturing plastic siding panels with an embossed three dimensional pattern. The embossed pattern can resemble a natural wood grain. In the process, a decorative wood grain foil is transferred to an extruded plastic sheet. The wood grain foil is formed of multiple synthetic resinous paint coats printed or cast on a temporary carrier sheet. A three dimensional wood grain texture is embossed on the surface of the laminate. Following the embossing, the foil is stripped away and the wood grain resin is transferred to the extruded plastic sheet. This patent has the drawback of using high temperatures and pressures in order for proper embossing.  
           [0005]    Other techniques have incorporated an accent color pattern within the article. U.S. Pat. No. 5,232,751 describes a method for making a vinyl sheet article including color patterns. A colorant is mixed with a top coat compound. The compound is heated and processed so that the melted colorant spreads axially in the direction of extrusion. The color-striated compound is fused with the substrate compound.  
           [0006]    U.S. Pat. No. 5,869,176 describes a method for extruding plastic articles having an accent color pattern. Pellets of a capstock base material such as polyvinyl chloride (PVC) are combined with accent color pellets. The accent color pellets are alloyed masses of a resin and pigment which are larger than the powder particles of the base material. During extrusion, the accent color pellets soften and disperse later than the base material to produce accent color streaks simulating wood-grain. The above described color accent techniques have the shortcoming of being difficult to control the incorporated color pattern.  
           [0007]    It is desirable to provide a system and method for printing color or a pattern of colors on an extruded sheet which can be precisely controlled.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention relates to a system and method for printing an extruded sheet in which heat curable ink is applied over the extruded sheet. The extruded sheet is at an elevated temperature. The ink cures immediately upon contact with the extruded sheet having an elevated temperature. The extruded sheet can be received against a rotating drum. The drum can include a plurality of perforations to enable a vacuum to be applied to the drum for holding the extruded sheet against the drum. Alternatively, the extruded sheet is received on a rotating belt. The rotating belt can include a plurality of perforations to enable a vacuum to be applied to the belt for holding the extruded sheet against the belt. At least one print roller is positioned adjacent the drum to apply ink on the extruded sheet. In one embodiment, at least one print roller applies a background color to the sheet and a plurality of print rollers apply one or more additional colors for forming a pattern or image on the sheet in registration with one another. For example, the pattern or image can have a wood grain appearance. The extruded sheet can be sized for use as a vinyl siding product.  
           [0009]    The invention will be more fully described by reference to the following drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    For a better understanding of the present invention, reference may be made to the accompanying drawings.  
         [0011]    [0011]FIG. 1 is a side elevational view of a system for printing an extruded material.  
         [0012]    [0012]FIG. 2 is a front elevational view of a printing apparatus used in the system of the present invention.  
         [0013]    [0013]FIG. 3 is a schematic diagram of a print roller and application of ink to the print roller.  
         [0014]    [0014]FIG. 4A is a front and top perspective view of a portion of the printing apparatus.  
         [0015]    [0015]FIG. 4B is a top perspective view of a portion of the printing apparatus.  
         [0016]    [0016]FIG. 5 is a perspective view of hose connection for a cooling apparatus used with the printing apparatus.  
         [0017]    [0017]FIG. 6 is a side elevational view of the printing apparatus.  
         [0018]    [0018]FIG. 7A is a schematic diagram of an alternative system for printing an extruded material.  
         [0019]    [0019]FIG. 7B is a schematic diagram of a belt used in the system of FIG. 7A. 
     
    
     DETAILED DESCRIPTION  
       [0020]    Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.  
         [0021]    [0021]FIG. 1 illustrates a side elevational view of a system for printing on extruded material  10  in accordance with the teachings of the present invention. Extruded sheet  12  exits extruder  13 . Extruder  13  can be any conventional extruder such as for example a Cincinnati Milicron.  
         [0022]    Extruded sheet  12  can be formed of an extrudable plastic substrate material. For example, extruded sheet  12  can be formed of polyvinylchloride (PVC), polystyrene, acrylonitrile-butadiene-styrene (ABS), nylon, ethylene-vinyl acetate (EVA), polycarbonate, polyethylene, polypropylene, polyethylene terepthalate, thermoplastic olefins, acrylonitrile-styrene-acrylic (ASA), and alloys, blends or coextrusions of these resins. Extruded sheet  12  exits extruder  13  at an elevated temperature. For example, the elevated temperature can be in the range of about 250° F. to about 450° F. and preferably about 390° F.  
         [0023]    Extruded sheet  12  enters printing apparatus  14 . Extruded sheet  12  is contacted by first rotating roll  15  and second rotating roller  16  of printing apparatus  14 . First rotating roller  15  is placed opposite second rotating roller  16  to form a nip there between. Extruded sheet  12  is flattened between first rotating roller  15  and second rotating roller  16 .  
         [0024]    Positioning rollers  17  press extruded sheet  12  against drum  18 . Preferably, surface  19  of drum  18  has a plurality of perforations  20 , as shown in FIG. 2. Vacuum pump  21  pulls a sufficient vacuum to hold extruded sheet  12  against drum  18 . Surface  19  of drum  18  is preferably formed of a flexible material to provide a flexible surface to allow extruded sheet  12  to lay flat against drum  18  during application of vacuum, as shown in FIG. 3. For example, surface  19  of drum  18  can be formed of natural rubber, silicon rubber or styrene-butadiene (SBR) rubber.  
         [0025]    Print rollers  21  are positioned at predetermined positions P 1 -P n  adjacent drum  18  as shown in FIG. 1 and FIG. 3. Positions P 1 -P n  can be closely spaced. For example, positions P 1 -P n  can each be spaced about 18 inches to about 24 inches from one another. Each of print rollers  21  at respective positions P 1 -P n  can apply ink  22  of the same color or a different color to extruded sheet  12 . Each of print rollers  21  can be selectively activated to print in order to formulate a combination of colors. In the embodiment, shown in FIG. 1, five print rollers  21  are used at respective positions P 1  to P 5 . Print rollers  21  print the same color on extruded sheet  12  at position P 1  and P 2  to form a background color covering the entire extruded sheet  12 . For example print rollers  21  at positions P 1  and P 2  can print any number of background colors such as colonial white, antique linen, desert tan, natural clay, country suede, light maple, sterling gray, granite gray, rustic cedar and ivy green. Alternatively, either print roller  21  at position P 1  or at position P 2  can be used to apply a color to extruded sheet  12 . Print rollers  21  at one of respective positions P 3 -P 5  can apply ink  22  to form a pattern on extruded sheet  12 . For example, each of print rollers  21  at positions P 3 -P 5  can apply ink to textured or patterned surface formed on the respective print roller  21  to print one of the primary colors: red, yellow or blue. A suitable print roller  21  is a gravure cylinder. The gravure cylinder can be engraved with a pattern or image. It will be appreciated that any conventional print roller could be used in accordance with the teachings of the present invention.  
         [0026]    Extruded sheet  12  is held against drum  18  to provide precise registration between adjacent cylinders. For example, print rollers  21  at position P 1  can have a circumference of about 18 inches for printing about 18 inches on extruded sheet  12  and print roller  21  at position P 2  prints in registration adjacent to the area printed by print roller  21  at position P 1 .  
         [0027]    Ink  22  can be a heat cured ink. For example, ink  22  can be a plasticol ink which cures at a temperature in the range of about 140° F. to about 200° F. Accordingly, ink  22  cures immediately upon contact with extruded sheet  12  which has an elevated temperature. Alternatively, ink  22  can be an evaporable ink or any conventional ink which cures upon contact with a material having an elevated temperature.  
         [0028]    [0028]FIGS. 4A and 4B illustrate apparatus which can be used in system  10  for application of ink  22  to print roller  21 . Pump  23  (not shown) pumps ink  22  to ink inlet  24 . Ink inlet  24  dispenses ink  22  onto doctor blade  25 . Pump  23  can be adjusted to supply the desired amount of ink  22  to doctor blade  25 . Doctor blade  25  extends along the width of print roller  21 . Doctor blade  25  spreads ink  22  over surface  26  of print roller  21 . Excess ink  22  is removed by doctor blade  25 .  
         [0029]    Print rollers  21  can be lowered and raised adjacent drum  18  for respectively selective printing of ink  22  from respective print rollers  21  at positions P 1 -P 5  to extruded sheet  12 . In the embodiment shown in FIGS.  4 A- 4 B, crank  26   a  is coupled to end  27   a  of print roller  21  and crank  26   b  is coupled to end  27   b  of print roller  21 . Crank  26   a  and crank  26   b  can be selectively rotated for lowering and raising respective ends  27   a  and  27   b  respectively towards and away from drum  18 . Doctor blade  25  can be lowered and raised respectively toward and away from drum  18  with handle  28 . It will be appreciated that other apparatus can be used by one of ordinary skill in the art for raising and lowering print roller  21  and doctor blade  25  respectively.  
         [0030]    All of print rollers  21  can be coupled to one another to provide simultaneous rotation of print rollers  21 . Each of print rollers  21  can be coupled to toothed disc  29 . Toothed discs  29  are attached by axle  30  to end  27   a  of print roller  21 . Chain  31  is received on respective toothed discs  29  of each of print rollers  21 . Chain  31  is coupled to a rotation motor (not shown) for rotation of chain  31  and simultaneously rotating respective print rollers  21 .  
         [0031]    Print rollers  21  can be chilled with cooling apparatus  40  to prevent ink  22  from curing until contact with extruded sheet  12 , as shown in FIG. 4A and FIG. 5. Cooling motor  42  can be attached with a hose (not shown) to inlet  41  to circulate a cooling liquid to manifold  43 . Hose connections  44  are attached to manifold  43 . A respective hose  45  can be attached to hose connections  44  and end  27   b  of each print roller  21 . Upon attachment of hose  45 , cooling liquid can circulate in aperture  46  within print roller  21  from end  27   b  of print roller  21  to end  27   a  of print roller  21 . A suitable cooling liquid is water or glycol.  
         [0032]    Extruded sheet  12  is received between embossing rollers  48  of printing apparatus  14  as shown in FIG. 1. Embossing rollers  48  can provide a desired texture to extruded sheet  12 .  
         [0033]    After printing with printing apparatus  14 , extruded sheet  12  is drawn through cooling tank  49 , as shown in FIG. 1. Cooling tank  49  is filled with a cooling liquid at a temperature in the range of about 40° F. to about 80° F. for cooling extruded sheet  12 . Downstream of cooling tank  49  is a cutoff mechanism  50 . Cutoff mechanism  50  cuts extruded sheet  12  to appropriate lengths. For example cutoff mechanism  50  can cut extruded sheet  12  into a predetermined length for forming a siding panel.  
         [0034]    Mount  52  mounts protrusion  53  from each side of drum  18  to extension  54  of frame  55 , as shown in FIGS. 1, 2 and FIG. 6. Mount  52  allows rotation of drum  18 . Motor  56  is coupled by arm  57  to protrusion  53 . Motor  56  rotates drum  18  in a clockwise direction. Mount  58  attaches each print roller  21  to frame  55 . Print roller  21  is received on shaft  59  coupled to mount  58 . Mounts  58  are coupled to upper portion  61  of frame  55 . Positioning rollers  17  and embossing roller  48  are mounted by mounts  60  to upper portion  61  of frame  55 , as shown in FIG. 1. Upper portion  61  of frame  55  is positioned above drum  18  and follows the shape of drum  18 .  
         [0035]    [0035]FIGS. 7A and 7B illustrate an alternative system for printing an extruded material  70 . Extruded sheet  12  enters printing apparatus  72 . Extruded sheet  12  is received on surface  73  of rotatable belt  74 . Belt  74  can be formed of a flexible material and can have a plurality of perforations  75  as shown in FIG. 7B. Vacuum chamber  76  pulls a sufficient vacuum to hold extruded sheet  12  against belt  74 . Surface  73  of belt  74  is preferably formed of a flexible material to allow extruded sheet to lay flat against belt  74  during application of vacuum. Print rollers  12  P 1 -P n  are positioned adjacent belt  74 . Print rollers P 1 -P n  operate as described above.  
         [0036]    It is understood that the above-described embodiments are illustrative of only a few of the many possible specific embodiments which can represent applications of the principles of the invention. Numerous and varied other arrangements can be readily derived in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention.