Abstract:
An in-line process for forming pre-finished siding manufactured from cellular poly vinyl chloride comprising embossing, milling, parting, punching, and coating the poly vinyl chloride such that the resulting siding is suited for use in an environment exposed to a wide range of fluctuating temperatures and moisture. The process accommodates the natural expansion and contraction of cellular poly vinyl chloride by producing a novel milled clapboard configuration that, when used as siding, can be installed to create a historically correct clapboard installation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/745,531 filed on Apr. 25, 2006. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally directed to a process for preparing a siding material. More particularly, the present invention relates to a process for preparing cellular polyvinyl chloride materials for use as siding on buildings to mimic traditional, cedar wood clapboard siding. 
     2. Background of the Invention 
     Traditionally, siding, e.g., housing siding, is made from cedar wood, fiber cement, engineered wood, and vinyl. Each of these materials, however, has certain inherent problems when used as siding. 
     For example, siding made from cedar wood tends to absorb moisture, and to, consequently, warp, decay, and rot. Additionally, insects are attracted to the wood, and, therefore, contribute to the decay. Furthermore, when painted, the wood tends to blister, peel, and crack. 
     Although it absorbs less water than wood siding materials, fiber cement siding does absorb some moisture. Additionally, painted fiber cement siding suffers some of the same problems as does painted wood siding. To reduce the moisture and paint problems, the cut edges of the fiber cement siding must be carefully treated. Furthermore, fiber cement is unduly heavy, brittle, requires specialized tools and instruments for installation, and debris formed during its installation may create health risks. For these reasons, then, fiber cement siding is difficult to install. 
     With regards to engineered wood, all engineered wood includes wood flour. Accordingly, similar to the wood siding, wood flour absorbs water, swells, warps, decays, rots, attracts insects and sheds paint. 
     Vinyl siding is formed into 12 foot clapboards from thin sheets of rigid poly vinyl chloride (“PVC”). The use of vinyl siding improves upon the use of wood, in that vinyl does not warp or rot to the same degree as does wood. However, formed vinyl clapboards are very light and hollow giving them a flimsy look and feel. Additionally, vinyl siding must be overlapped to accommodate expansion and contraction. As a result, a tell-tale sign of vinyl versus wood siding is the overlapping joint that appears every 12 feet on all vinyl siding installations. Also, vinyl siding must be inserted into ‘j-channel’ installed around windows, doors and at all corners in order to accommodate expansion and contraction of the PVC with changes in temperature. Further, vinyl siding chalks over time; i.e. a white powder rises to the surface; especially on darker colors, thereby diminishing the appearance of the siding. 
     An improved product for use as siding is cellular PVC. Similar to rigid vinyl siding manufactured from PVC, cellular PVC siding expands and contracts about ¼ inch per 14 foot clapboard with changes in temperature of about 50 degrees Fahrenheit. The prior art has attempted to restrict such expansion and contraction by a variety of techniques, e.g., by applying the cellular PVC siding with heavier than normal nailing (as is the common practice for installing cellular PVC trimboard). This, however, has not been effective. Rather, what is needed is a process for forming cellular PVC siding, wherein the process itself accommodates the fact that cellular PVC siding expands and contracts when exposed to certain temperatures. 
     BRIEF SUMMARY OF THE INVENTION 
     The above-discussed drawbacks and deficiencies of the prior art are greatly reduced or eliminated by a novel in-line process for preparing a novel configured cellular PVC clapboard for use as siding, wherein the process utilizes novel material removal, product handling, and finishing techniques. The novel process accommodates the natural tendency of cellular PVC siding to expand and contract when exposed to certain temperatures to form a novel milled clapboard configuration that, when used as siding, can be installed to create a historically correct clapboard installation, i.e., to create identical dimensions to cedar clapboard and the appearance of “butted” joints. 
     The inventive process comprises a series of specially designed milling cutters, saws and punching apparatus with supporting precision product guiding, registration and transport. The process further comprises removal of material via specially designed material removal tools having cutting edges and coatings which have been specifically developed for the high speed machining, sawing and punching of cellular PVC. The inventive process utilizes novel techniques for the mitigation of electrostatic buildup that is inherent in cellular PVC processing, handling, swarf removal and collection. Finally, the inventive process incorporates an in-line, high speed application and accelerated curing of a uniquely formulated, two-part polyurethane finish. 
     Accordingly, the invention relates to a novel process for converting large cellular PVC sheets for use as pre-finished siding. These large sheets are readily available from many sources and therefore can be obtained at low cost. The subject process utilizes this material in a very efficient way to produce pre-finished cellular PVC siding, with its many inherent advantages, at a cost comparable to conventional primed and field coated wood clapboard siding. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic depicting an exemplary process; 
         FIG. 2   a  is a schematic depicting an exemplary profiling operation comprising milling of the ends, radii, and lower assembly grooves on a cellular PVC board; 
         FIG. 2   b  is a schematic depicting an exemplary profiling operation comprising milling of the faces and qualifying the thickness of the cellular PVC board depicted in  FIG. 2   a;    
         FIG. 2   c  is a schematic depicting an exemplary profiling operation comprising milling of the upper assemblies and saw grooves on the cellular PVC board depicted in  FIG. 2   a;    
         FIG. 3  is a schematic depicting an elevational cross-sectional view of an exemplary parting operation; 
         FIG. 4   a  is a schematic depicting a full scale exemplary 4 inch cellular PVC board having a two-up configuration and formed by the inventive process, wherein measurements are in inches; 
         FIG. 4   b  is a schematic depicting a 4× scaled version of the clapboard depicted in  FIG. 4   a , wherein measurements are in inches; 
         FIG. 5   a  is a schematic depicting a side view of an exemplary 4 inch cellular PVC clapboard formed by the inventive process, wherein measurements are in inches; 
         FIG. 5   b  is a schematic depicting a view of a face of the clapboard depicted in  FIG. 5   a , wherein measurements are in inches; 
         FIG. 6   a  is a schematic depicting a full scale exemplary 6 inch cellular PVC board having a two-up configuration and formed by the inventive process, wherein measurements are in inches; 
         FIG. 6   b  is a schematic depicting a 4× scaled version of the clapboard depicted in  FIG. 6   a , wherein measurements are in inches; 
         FIG. 7   a  is a schematic depicting a side view of an exemplary 6 inch cellular PVC clapboard formed by the inventive process, wherein measurements are in inches; and 
         FIG. 7   b  is a schematic depicting a view of a face of the clapboard depicted in  FIG. 7   a , wherein measurements are in inches. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Disclosed herein is a novel, in-line, method for preparing cellular PVC materials for use in siding. An exemplary method for preparing the cellular PVC materials for such use comprises an optional step of embossing both the front and back surfaces of cellular PVC sheets and cutting them into more usable sized boards. The cellular PVC boards are milled to specification using a novel apparatus, the process of which will be explained in greater detail below. Each milled board is parted into two clapboards utilizing a specially modified bandsaw. Additionally, slots are punched through the clapboards for installation purposes. Furthermore, the clapboards are cleaned, coated and cured. Through the process, cellular PVC siding is prepared which exhibits reduced expansion and contraction properties as compared to conventionally prepared cellular PVC siding. The process is more specifically discussed with reference to the Figures. 
     Referring to  FIG. 1 , an exemplary process begins with the receipt of full pallets, each pallet comprising a stack of cellular PVC sheets. The pallets are placed onto a platform. Single cellular PVC sheets are then sequentially vacuumed picked by an automated gantry pick and place destacker from the top of the stack and placed onto a powered conveyor. The powered conveyor feeds the cellular PVC sheets end to end through an optional embossing process. 
     The embossing process includes an infra-red heater array that warms and, therefore, softens the surfaces of the cellular PVC sheets for embossing by patterned pinch rollers. In an exemplary embodiment, these patterned pinch rollers apply approximately 6,000 pounds of force to apply a wood grain to the top and bottom surfaces of each cellular PVC sheet, at a rate of approximately 20 feet per minute (“ft/min”). 
     The embossed, or the non-embossed (depending on whether embossing was done), cellular PVC sheets are then conveyed end to end, precisely registered against a datum edge and fed into a gang rip saw that will, depending upon the size of the desired finished clapboard, simultaneously cut the cellular PVC sheet into multiple (e.g., 4 or 6) parallel cellular PVC boards at a rate of about 20 ft/min. The gang rip saw cuts the sheet at a width which is calculated to minimize waste. Accordingly, in an exemplary embodiment, the width of the individual boards is preferably generated by a waste minimizing, two-up configuration, i.e. each board will yield two back-to-back clapboards, wherein the creation of back-to-back ½ inch thick clapboards is especially preferred. 
     The cut cellular PVC boards are then conveyed by a cross-feed conveyor into the infeed section of a moulder, i.e., profiling machinery. This infeed section precisely registers the cellular PVC boards against a datum edge and sequentially feeds them, end to end, in continuous strip fashion through the moulder. 
     Referring to  FIGS. 1 and 2 , the moulder, at a speed of about 100 ft/min, precisely feeds the cellular PVC boards through a series of specially designed milling operations to achieve the desired profile from the relatively irregular boards. More specifically, each of the individual milling operations incorporates specially contoured tools specifically designed for cellular PVC, thereby providing novel qualifying cuts on all surfaces of each board, as necessary, to standardize the milled dimensions of each finished board to yield a two-up back-to-back clapboard configuration. 
     Additionally, each milling head comprises uniquely constructed swarf removal ductwork incorporating static dissipation techniques. The static dissipation techniques include electrically connecting any component contacting the cellular PVC board in the milling operations to earth ground through the use of a high amperage copper wire network. 
     Referring to  FIG. 2   a , in an exemplary embodiment, milling cutters  22  and  24 , each operating at about 8,000 revolutions per minute (“rpm”), flank the ends  23  and  25  of a cellular PVC board  26 , which is registered against a horizontal datum edge  28  and a vertical datum edge  30 . Milling cutters  22  and  24  respectively mill ends  23  and  25 , the radii  27  and  29 , and the lower assembly grooves  31  and  33  of cellular PVC board  26 . In an exemplary embodiment, each of lower assembly grooves  31  and  33  respectively comprises a throat opening dimension  35  and  37  of about 0.080 inch, which has proven to be critical to ease of assembly in the field. Additionally, milling cutters  22  and  24  also qualify the width of cellular PVC board  26 . 
     Once milling cutters  22  and  24  have completed their tasks, cellular PVC board  26  continues through the milling process while remaining registered against horizontal datum edge  28  and vertical datum edge  30 . At this point, milling cutters  32  and  34  are employed. Referring to  FIG. 2   b , in an exemplary embodiment, milling cutters  32  and  34  respectively mill faces  39  and  41  of cellular PVC board  26 . Such milling preferably occurs at a speed of about 8,000 rpm to achieve the desired profile. The two-up configuration requires this profile to have extremely precise angles to maximize cross-sections of certain areas while minimizing waste. Additionally, in an exemplary embodiment, milling cutter  32  qualifies a thickness  40  of cellular PVC board  26  in the vicinity of what will be an upper assembly groove 43 to about 0.500 inch, plus 0.028 inch, minus 0.000 inch. 
     Referring to  FIG. 2   c , in an exemplary embodiment, after milled by milling cutters  32  and  34 , cellular PVC board  26  remains registered against horizontal datum edge  28  and vertical datum edge  30 , and upper assembly grooves  43  and  45  and saw grooves  60  and  62  are respectively milled by specially designed milling heads incorporating two-tiered multiple milling cutter arrays  36  and  38  at a speed of about 12,000 rpm. In a particularly preferred embodiment, each of upper assembly grooves  43  and  45  respectively comprise a throat opening dimension  51  and  53  of about 0.080 inch, as this dimension is critical to ease of assembly in the field. Additionally, it is important that the location of saw grooves  60  and  62  be precise to help locate the critical parting cut that separates the two-up clapboards. 
     Again referring to  FIG. 1 , once milled, the now profiled cellular PVC boards exit the moulder, and are fed by a cross-feed conveyor into a gravity chute that reorients the profiled cellular PVC boards from traveling flat to traveling on edge. 
     Referring to  FIGS. 1 and 3 , the profiled cellular PVC boards, now traveling on edge, are carefully and precisely guided end to end into a band type sawing machine at a rate of about 100 ft/min. Each cellular PVC board registers against a horizontal datum surface  48  and a vertical datum surface  50 . The cellular PVC board is driven through the parting process by a special drive wheel  52 , preferably a urethane drive wheel. A precisely guided parting band saw blade  54  traveling at a feed speed of about 60 meters per second parts board  56  into two, identically profiled cellular PVC clapboards. 
     Additionally, in an exemplary embodiment, specially developed band saw blade  54  leaves a kerf of not more than about 0.050 inch thick. The saw blade precisely-follows the two pre-milled saw grooves  60  and  62  in order to achieve the proper parting cut location. The location, angle and kerf width of this parting cut is generated by the finished clapboard profile, including assembly grooves and nailing flanges common to all exposure sizes of clapboard as well as the common thickness of ½ inch. The location and angle of this parting cut is crucial to the functioning of the siding. If the cut is slightly out of position it will destroy the assembly groove profiles thereby rendering the clapboard impossible to assemble in the field. 
     Again referring to  FIG. 1 , the parted cellular PVC clapboards exit the sawing machine and are reoriented to a lying flat position with the cosmetic surface up and similarly aligned. The cellular PVC clapboards are transferred and then fed end to end at a rate of about 200 ft/min into a uniquely designed, continuous motion, slotting machine where an uninterrupted row of nailing slots are punched into the cellular PVC clapboards. These slots are utilized, during installation, to fasten the cellular PVC clapboards to the structure being sided. 
     The cellular PVC clapboards exit the slotting machine and are then transferred and fed end to end through a laser marking station where a manufacturing logo and date code can be laser etched onto the backside of the cellular PVC clapboard. After this step, the cellular PVC clapboards travel into a cleaning and de-ionizing module at a rate of about 200 ft/min. This specially designed module subjects the cellular PVC clapboard to high intensity de-ionizing air jets which minimize static charge built up through the milling and handling process. The cellular PVC clapboard then continues through a brushing and vacuuming section to thoroughly clean and prepare the cellular PVC clapboard for painting. 
     The cellular PVC clapboard then continues traveling at a speed of about 200 ft/min through a paint application booth where specially configured and positioned spray guns uniformly apply a two-component polyurethane based coating to the exposed surfaces of the cellular PVC clapboard. In an exemplary embodiment, five spray guns are utilized in the coating step. Furthermore, in an exemplary embodiment, the spray guns apply a coating having a thickness of about 4 millimeters to the cellular PVC clapboard. 
     The cellular PVC clapboard is then fed into a specially constructed drying tunnel. This drying tunnel will provide to each PVC clapboard about 10 minutes of flash-off time at ambient temperature, about 20 minutes of cure time at approximately 125 degrees Fahrenheit, and about 10 minutes of cool down to ambient temperature before handling. In an exemplary embodiment, the drying tunnel will process about six clapboards per minute. 
     The inventive process discussed above results in cellular PVC siding that can be installed according to historically accurate installation methods. That is, the cellular PVC siding formed from the novel process disclosed herein, exemplary embodiments of which are disclosed in  FIGS. 4   a - 7   b , can be installed according to installation methods accepted for the installation of cedar clapboard siding. This, then, eases installation and adds to the aesthetic appeal of synthetic siding materials. In addition to forming a uniquely configured cellular poly vinyl chloride clapboard for use in siding, the inventive process disclosed herein also provides for the precise profiling, cutting, and sawing of the cellular PVC sheets, boards, and clapboards to ensure proper fit and use in the field. 
     Although the principles of the present invention have been illustrated and explained in the context of certain specific embodiments, it will be appreciated by those of skill in the art that various modifications beyond those illustrated can be made to the disclosed embodiment without departing from the principles of the present invention.