Abstract:
A piling is supported substantially horizontally upon a carrier including at least two pairs of roller wheels on at least two separate bases spaced from each other and with the piling resting upon the roller wheels. A two part spray head mixes and sprays a coating material, such as a PTMEG type material, onto a lateral surface of the piling. Elongate spray passes are followed by partial rotation of the piling upon the roller wheels and further spray passes until a full layer of coating is applied. After early layers of coating material have been applied to the piling, a squeegee is passed longitudinally against the surface while pressing against the surface, to cause a tight bond. Thereafter, additional layers of coating material are applied to achieve the desired thickness for the overall coating. Finally, the outermost surface is worked with a squeegee to produce a desired surface finish.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit under Title 35, United States Code §119(e) of U.S. Provisional Application No. 61/988,529 filed on May 5, 2014. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The following invention relates to methods for coating of elongate structures. More particularly, this invention relates to methods for coating elongate structures such as pilings while utilizing a spray head to spray coating material onto the elongate structure in layers, and also including working of the material coating layers physically at least somewhat. 
       BACKGROUND OF THE INVENTION 
       [0003]    Marine pilings are used in a variety of different marine environments to provide structural support for docks, piers and other coastline physical structures. The pilings are generally characterized by having a cylindrical form which has dimensions which are exceptionally longer than their diameter. For instance, pilings can range in length from dozens of feet to well over one hundred feet in length. 
         [0004]    The material from which pilings are typically formed is some type of wood. In a typical example, Douglas Fir wood is effectively utilized. The piling is formed from the entire trunk of the tree in a typical embodiment, which trunk has been de-limbed and debarked. Other finishing of the surface of the wood might include some degree of shaping of the outer cylindrical surface, cutting to length, and potentially treating, such as pressure treating, as is known in the art. The pilings are also characterized in that they have a slightly greater diameter at one end than the other end. The smaller diameter end is typically placed downward and the piling is driven into the ground at a desired location to a desired depth based on structural and engineering requirements at the site. Other portions of the structure are mounted in a variety of different ways to upper ends of the pilings. 
         [0005]    Because significant mid-portions of the pilings come in direct contact with the water (and typically salt water of the marine environment) unique difficulties are presented. The marine environment is harsh on the piling, causing the piling to diminish in structural strength over time. Depending on how the wood material is treated, these treatments can pose a hazard to the marine environment, such as by harmful chemicals leaching into the water and causing harm to marine life. 
         [0006]    In the prior art, piling systems have had to be designed in a manner striking a balance between these difficulties to achieve a piling structure which has an acceptably long life with the desired structural strength, while also avoiding damage to the marine environment. Furthermore, the marine environment where pilings are utilized often involves significant amounts of boating traffic. This boating traffic can include very large seagoing vessels in many instances. These vessels exert significant forces on the pilings themselves when the pilings are impacted by such vessels, such as when the vessel is docking adjacent a structure in which the pilings are incorporated, and also from wave and tidal action which causes vessels to move against pilings. 
         [0007]    Such abrasive and impact loads on the surface of the pilings provide another source of damage to the pilings, both from individual incidents and over time. Such impact damage also presents further opportunity for materials associated with the pilings to enter into the marine environment and exacerbate any damage which might be caused to the marine environment, such as by leaching of pressure treating chemicals into the marine environment after impact loads are encountered against the surface of the pilings. 
         [0008]    One piling which has been effective in balancing these difficulties and producing a piling of both long life and environment hazard avoidance is a piling which has been coated with a sufficiently thick layer of a polyurea solid coating. Such coatings act to encapsulate any pressure treating materials to which the wood has been subjected and provide a resilient outer surface which can deflect impact loads of at least a low and moderate level. While such coated pilings can be coated with a variety of different materials, one material which has been found to be exceptionally desirable is polytetramethylene ether glycol, known by the acronym PTMEG. Such PTMEG coated pilings have found themselves to be the product of choice for many designers seeking to maximize piling strength and longevity, as well as environmental hazard avoidance. 
         [0009]    The PTMEG is a two component polyurea elastomer coating which has been in existence since the mid-1980s. Such polyurea systems have sometimes been characterized as modified two component polyurethane systems. While they both may have some characteristics in common, polyurea systems are actually a unique technology from polyurethane systems. 
         [0010]    Two component polyurea systems are typically known for a very rapid dry time (typically less than thirty seconds), achieved without the use of a catalyst, as is required with two component polyurethane systems. This rapid dry time is very consistent/uniform over a broad ambient temperature range. While the fast reaction/rapid dry time is virtually unaffected by ambient moisture, the presence of a moisture on a substrate must be considered when achieving adhesion to that substrate. This is all made possible by unique chemistry of raw materials used to develop the two component polyurea systems. Two component fast set polyurea systems typically do not contain any solvents or volatile organic compounds (VOCs). 
         [0011]    Polyurea systems with a slower/modified reactivity and set time when used in spray application generally provide better wetting and adhesion to the substrate, such as a piling surface. These systems are also used in concrete joint filling applications. The main distinguishing characteristic with the polyurea technology over polyurethanes is that amine terminated (—NH2) resins are used rather than hydroxyl terminated (—OH) resins, commonly referred to as polyols. The reaction of the amine terminated resins with the isocyanate component results in the formation of a urea linkage. Since this is a polymer and these units repeat, the term polyurea then applies. The basic reaction to form the polyurea involves combining an isocyanate prepolymer with polyamine to produce the polyurea polymer. The resulting polyurea physical properties result in highly desirable characteristics for the coating of pilings, such as described above. 
         [0012]    For such a PTMEG coated piling to have the very best performance, it is important that a strong bond be provided between the PTMEG polyurea coating and the underlying wood material. It is also desirable that a relatively smooth outer surface be provided. It is also desirable that the PTMEG coating be of substantially uniform thickness. Furthermore, difficulties can be encountered during the PTMEG application process due to the unique manner in which the PTMEG needs to be handled and applied. Accordingly, a need exists for a process for applying coatings to pilings such as PTMEG so that a piling having optimal performance characteristics can be provided, and in a manner which can efficiently be performed in a safe and economical fashion. 
       SUMMARY OF THE INVENTION 
       [0013]    With this invention, a process is defined for applying a coating such as PTMEG to pilings or other elongate wood structural elements. Initially, a piling or other elongate wood structure is identified which is to receive the coating of PTMEG or other similar material. When similar materials to PTMEG are referred to, those materials which require spray application as well as some physical working of the material surface are considered to be in this category and benefit from the process of this invention. The wood material is selected having a moisture content of less than 19% to 22%. The wood can be treated or untreated and still be usable according to this invention. If the wood is not sufficiently dry, the wood can be dried before performing this process. While Douglas fir is one acceptable wood material, other woods or wood-like elongate structures could similarly be utilized according to the process of this invention. 
         [0014]    Initially, the wood is inspected for splinters and any other debris adhering thereto. The wood is cleaned to remove splinters, such as with a wire brush. The wood is also preferably blasted with compressed air to further remove debris and loose wood fibers from the outer surface. 
         [0015]    An inspection step is next performed to identify large checks or cracks within the piling. Any large checks or cracks are filled in advance of the PTMEG coating process. Such filling can involve filling with caulk or covering with tape. Small cracks and other imperfections are effectively filled with the PTMEG coating and do not need to be filled or covered. When the wood material has been appropriately prepped by having been cleaned, inspected and any checks/cracks filled or covered, the wood material is ready for coating. 
         [0016]    The wood material is preferably supported upon rollers to allow the elongate structure to be effectively positioned within a coating environment. The coating environment is preferably an enclosed housing, such as a building having dimensions sufficient to accommodate the length of the piling or other elongate wooden material to be coated. To manage such positioning, a pair of carriers are preferably provided. The carriers include a base with a pair of support wheels extending up from an upper surface of the base, with the pair of wheels in a common plane generally perpendicular to a longitudinal axis of the piling. The base can be supported upon caster wheels so that the carriers can be moved about with the elongate piling supported thereon. The caster wheels or other supports can be locked in position once the piling is positioned where desired. Because the piling is supported upon a pair of wheels over each carrier, the piling is held in fixed location but can have its orientation rotated about its longitudinal axis (about arrow B of  FIG. 1 ). While two carriers are shown in  FIG. 1 , more than two carriers could be utilized if needed, such as for exceptionally long pilings. 
         [0017]    Before the first coat of coating material, such as PTMEG, is applied, the coating material application spray equipment is prepped for operation. This preparation includes calculating how much coating material is likely to be required based on square footage of the surface of the piling and the number of layers of material to be applied, as well as the thickness of the layers of material. Spray equipment is checked to make sure that a sufficient amount of material is ready for application. The spray equipment is configured to be of a type which can both heat the material to be applied and also combine two separate components of the material together, such as in a one-to-one ratio, before being sprayed from the equipment. The spray equipment thus includes some means for heating the material and keeping it at a minimum temperature (typically at least 175° F.). The spray equipment also is configured to pressurize the spray to approximately 3,000 psi. Most preferably, the two separate components of the PTMEG are routed from heated pressurized separate supplies to a combining spray nozzle, and not combined until they reach the spray nozzle. 
         [0018]    A first layer of PTMEG material is then sprayed onto the elongate piling or other wood structure to be coated. Each layer of PTMEG involves passing a spray head along a longitudinal axis from a first end to a second end. The piling or other structure is then rotated, such as 90° and the coating of the first layer continues. After the piling has been rotated and passes of spray have been applied so that all of the surface of the piling has received a first coat, the first layer is complete. After this first layer is complete, a second layer is applied upon the first layer in the same fashion that the first layer was applied. 
         [0019]    After two coats have been applied, a squeegee is mechanically brought into contact with the surface of the piling and passed along the surface of the piling longitudinally. These passes of the squeegee occur from a first end to a second end, followed by turning of the piling and then again passing along the surface of the piling until all of the PTMEG material has had the squeegee pressed there against. The squeegee is passed over the surface in a manner applying force against the outer surface of the PTMEG, tending to press the PTMEG into the wood somewhat. This squeegee action assists in strengthening the bond between the PTMEG coating and the outer surface of the wood. 
         [0020]    A visual inspection after the squeegee procedure will determine whether cracks of a small variety that were not filled are being effectively filled by the PTMEG. If not, further squeegeeing can occur until such cracks are no longer visible. Furthermore, if bubbles appear in the PTMEG during the squeegee process, these bubbles can be inspected to ensure that no bare wood is exposed inside the bubbles (and if so the squeegee work can continue to avoid any exposed wood remaining). 
         [0021]    After this initial squeegeeing procedure has been completed over the entire surface of the piling, further layers of PTMEG are applied in the same fashion that the first layer and second layer were applied. In a typical embodiment, twelve total layers of PTMEG are sequentially applied to the outer surface of the piling or other elongate wood structure. The number of coats could vary based on specifications called for by a designer. After the final layer of PTMEG has been applied, the squeegee is again used in a process similar to that described above, except to provide a smooth final finish surface for the coated piling free from any discernible surface imperfections. 
         [0022]    If multiple pilings or other structures are to be coated, another piling can be brought into position and coated with PTMEG in the same manner as the first, by following the same procedure. The piling which has already been coated can be left to have the PTMEG coating cool and cure into its final surface finish. It is then ready to be transported to a desired location for use. Finally, spray equipment can be shut down in a manner which is consistent with operating instructions for the spray equipment and to keep the spray equipment sufficiently clean and prepped for reuse in the future. 
       OBJECTS OF THE INVENTION 
       [0023]    Accordingly, a primary object of the present invention is to provide a method for applying a coating such as PTMEG to an outer surface of an elongate structure such as a piling with the coating having a secure bond to the surface of the piling. 
         [0024]    Another object of the present invention is to provide a method for applying a coating such as PTMEG or similar material as a coating to an outer surface of an elongate structure such as a piling with the coating having a smooth outer surface. 
         [0025]    Another object of the present invention is to provide a method for applying a coating, such as PTMEG, to an outer surface of an elongate structure such as a piling with the coating having a desired thickness made up of multiple individual layers. 
         [0026]    Another object of the present invention is to provide a coating for pilings which protects the piling from damage and corrosion. 
         [0027]    Another object of the present invention is to provide a method for coating a piling which simplifies the coating process and avoids damage to the piling, coating equipment or danger to personnel applying the coating. 
         [0028]    Another object of the present invention is to provide a piling coating method which is suitable for coating exceptionally long pilings, including pilings as long as one hundred feet long or more. 
         [0029]    Other further objects of the present invention will become apparent from a careful reading of the included drawing figures, the claims and detailed description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  is a perspective view of a portion of a platform, such as a dock, with the platform supported upon pilings such as coated pilings according to this invention and illustrating one form of elongate structure to be coated according to a method of this invention. 
           [0031]      FIG. 2  is a perspective view of a piling or other elongate structure such as a wood core for a piling, supported upon rollers/carriers during a piling coating method of this invention, and with the piling shown in broken lines. 
           [0032]      FIG. 3  is a perspective view of an end of the piling after it has been coated, and with a portion of the coating cut away to reveal a cross-section of the coating of the piling. 
           [0033]      FIG. 4  is a perspective view of a portion of that which is shown in  FIG. 2  and illustrating movement of the piling during the coating procedure, as well as orientation of a spray head and squeegee during various different steps in the piling coating process. 
           [0034]      FIG. 5  is a perspective view of a squeegee with an arcuate blade for use in the process of this invention as one working tool to enhance a bond between the coating and the surface of the piling and to improve a surface finish of the coated piling. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0035]    Referring to the drawings, wherein like reference numerals represent like parts throughout the various drawing figures, reference numeral  10  is directed to a coated piling such as that which can be used in a marine environment, such as to support a dock D or other platform in a marine environment ( FIG. 1 ). Other elongate structural members or other items can also be coated, especially with PTMEG, or other similar coatings, according to the method of this invention. 
         [0036]    In essence, and with particular reference to  FIGS. 2 and 4 , basic details of the coated piling  10  and method for coating the piling  10  are described, according to a preferred embodiment. A wood core  20 , for such as a piling is initially provided without a coating  30 . This outer coating  30  is applied according to a method of this invention by placing the wood core  20  upon a set of at least two carriers  40 . Each carrier  40  rotatably supports the wood core  20  thereon. A spray head  50  is placed proximate to the outer surface of the wood core  20  and a layer of PTMEG (or other similar material) is sprayed onto an outer surface of the wood core  20 . The spray head  50  is moved longitudinally (along arrow A of  FIG. 4 ) to apply a coating to the wood core  20 . After a pass of the spray head  50  from one end to the other, the wood core  20  is rotated (along arrow B of  FIG. 4 ) to present a portion of the wood core  20  outer surface which has not yet received a layer of the outer coating  30 . The passage of the spray head  50  then continues to occur (along arrow A) to complete this first layer of the outer coating  30 . A squeegee  60  is also used by pressing against layers of the outer coating  30 , typically early in the process to enhance a bond between layers of the outer coating  30  and the outer surface of the wood core  20 , and to provide a smooth outer surface  38  of the outer coating  30  at an end of the coating process. 
         [0037]    More specifically, and with continuing reference to  FIGS. 2 and 4 , specific details of the coated piling  10  and process for coating the coated piling  10  are described, according to a preferred embodiment of this invention. The coated piling  10  includes the wood core  20  with an outer coating  30  of PTMEG or similar material. The wood core  20  is an elongate linear structure formed by delimbing and debarking the trunk of a tree, and particularly a tree which is predisposed toward growing straight and tall. One such tree would be a douglas fir tree. The wood core  20  would typically have some degree of taper built thereinto with the smaller diameter at a lower end and a larger diameter at an upper end. The wood core thus includes a cylindrical lateral surface and two ends which are generally flat. As discussed in detail above, it is desirable for the wood core  20  to be coated with an outer coating  30  of PTMEG or similar material to improve its performance, especially in the marine environment. 
         [0038]    The outer surface of the wood core  20 , when initially provided, has some degree of imperfections therein. These imperfections can include splinters, debris and checks (holes gouged out of the outer surface of the wood core). The outer coating  30  preferably has a smooth outer surface  38  and a bond  35  defining an inner surface of the outer coating  30  adjacent the outside of the wood core  20 . This bond  35  is preferably a secure bond between the wood core  20  and the outer coating  30 . 
         [0039]    To keep the outer surface  38  smooth and to promote this secure bond  35 , the outside of the wood core  20  is cleaned of any debris and any splinters are removed therefrom. Furthermore, a desirable moisture level for the wood core  20  is achieved before the process begins. If desired, the wood core  20  can be treated, such as with a pressure treating or other wood preservative, before applying the outer coating  30 . Loose splinters are also removed. If large cracks or checks exist on the surface they are filled. 
         [0040]    The outer coating  30  typically extends over the lateral sides of the wood core  20 . End caps can be provided at ends of the wood core  20  to complete the encapsulation of the wood core  20 , at least at an upper end thereof. This end cap, in one embodiment, is formed from a material compatible with or the same as PTMEG. The end cap can be prefabricated and attached to the end of the wood core  20  or can be applied thereto such as with a spraying technique. The process of this invention is primarily associated with the application of the outer coating  30  rather than the placement of the end caps. 
         [0041]    The outer coating  30  has a thickness comprised of accumulation of multiple separate layers of PTMEG or similar material sprayed onto the outside of the wood core  20 , building up this outer coating  30  to a desired thickness. In one embodiment a thickness of this coating is between one-half inch and one inch in thickness. Other thicknesses for the outer coating  30  could also be provided. 
         [0042]    To support the wood core  20  during the application of the layers forming the outer coating  30 , the wood core  20  is preferably oriented with a longitudinal axis extending approximately horizontally and resting upon a pair of the carriers  40 , which provide a preferred form of roller support for the wood core  20 . A pair of such carriers  40  are preferably provided spaced longitudinally from each other. Each carrier  40  includes a base with support wheels  44  extending upward therefrom. The support wheels  44  (also referred to as “rollers”) are rotatably supported upon axles  46  which are pivotably attached to upper ends of frames  48  extending upward from an upper surface of the base  42 . Caster wheels  49  are preferably provided below the base  42  to allow the carrier  40  to roll upon an underlying horizontal surface. 
         [0043]    The two support wheels  44  are preferably oriented within common planes and with their axles  46  parallel to each other and extending horizontally. A saddle space is thus provided between the two support wheels  44  into which the wood core  20  can rest. The wood core  20  can then be rotated relatively easily about a central longitudinal axis (along arrow B of  FIG. 4 ). The caster wheels  49  are preferably lockable and unlockable so that the entire wood core  20  can be moved upon the carriers  40  in a variety of different directions when the caster wheels  49  are unlocked, but the caster wheels  49  can be locked when desired so that the carriers  40  are kept from moving and the wood core  20  is prevented from any movement other than rotation about the longitudinal axis (arrow B of  FIG. 4 ). 
         [0044]    To apply the outer coating  30 , a spray head  50  is utilized. This spray head  50  can be any of a variety of different spray heads or similar devices which bring two separate components together, mix them together and spray them out of a tip  52  thereof. The particular spray head  50  disclosed herein has a tip  52  downstream from a mixer  54 . A trigger  56  is manipulatable by a hand of the user to cause mixed PTMEG or similar material to be sprayed out of the tip  52  of the spray head  50  when the trigger  56  is depressed. 
         [0045]    A pair of hoses  58  connect to the spray head  50  upstream of the mixer  54 . These hoses  58  are preferably held together by a keeper  59  so that the two hoses  58  can be managed together. The hoses  58  extend to separate reservoirs and pumps which are preferably coordinated together so that they deliver a desired ratio of two separate materials along each hose  58 . For instance, if the two components of the PTMEG or similar mixture are to be provided in a 1-to-1 ratio, the pumps are timed so that they deliver a common amount of flow rate through each hose  58 . Preferably, the pumps and associated preparation equipment also includes heating apparatus so that the components supplied through the hoses  58  are not only pressurized but also heated to an optimal temperature. Curing of the PTMEG or similar material after being sprayed from the spray head  50  occurs by both cooling and reaction of the two components together. The resulting outer coating  30  has a consistency and hardness similar to a soft plastic or a hard rubber and which is non-porous. 
         [0046]    In a preferred form of the invention, a squeegee  60  is provided particularly for working of the PTMEG or similar material after it is sprayed as a layer onto the wood core  20 . The squeegee  60  preferably includes at least one handle  62  with a head  64  at a distal end of the handle  62  and with a blade  66  on the head  64 . This blade  66  is preferably arcuate, most preferably with a curvature approximately similar to that of the outside of the wood core  20 . 
         [0047]    The squeegee  60  provides two functions. First, layers of PTMEG or similar material which are first applied to the wood core  20  benefit from being pressed into the outside of the wood core  20  so that the PTMEG extends into small cracks and other roughened surface features on the outside of the wood core  20  to provide a secure bond  35  between the outer coating  30  and the wood core  20 . Later, the squeegee  60  can be utilized after a final layer of outer coating  30  has been sprayed onto the wood core  20  to provide a smooth outer surface for the outer coating  30 . In one embodiment, the squeegee  60  can merely be a flexible piece of planar rubber which has been curved to have a desired curvature and is held in two hands to be run longitudinally with a flat edge curved to pass along the outside of the wood core  20  (along arrow A of  FIG. 4 ). 
         [0048]    In practicing the method of this invention, the wood core  20  is initially placed upon multiple carriers  40 . A first layer of PTMEG or similar material is then sprayed from the spray head  50  (which has been prepped for supply under pressure of two different components to the mixer  54  from the hoses  58 , and then discharged from the tip  52  of the spray head  50 . A portion of the outside of the wood core  20  is sprayed with this material (along arrow C of  FIG. 4 ) in the form of a spray S. A layer of PTMEG or similar material is applied to the outside of the wood core  20  from one end to the other. This spray path will only cover part of the radial lateral surface of the wood core  20 . Thus, the wood core  20  is rotated (along arrow B of  FIG. 4 ) and the spray process is continued to add another pass of spray material onto a surface of the wood core  20 . Multiple passes (along arrow A) with the spray head  50 , followed by multiple rotations (about arrow B of  FIG. 4 ) results in a complete single layer of PTMEG or similar material being provided as part of the outer coating  30 . 
         [0049]    After at least one such layer has been applied, and most preferably after two such layers have been applied, the squeegee  60  is utilized (by passing along arrow A of  FIG. 4 ) to press the PTMEG or similar material into the outside of the wood core  20  to form a tight bond  35 . The squeegee  60  runs longitudinally (along arrow A) and then for convenience, the entire wood core  20  can be rotated (about arrow B) before further passage of the squeegee (along arrow A) until all surfaces of the wood core  20  have had the squeegee  60  applied thereto to press a layer of the outer coating  30  into the outside of the wood core  20 . 
         [0050]    The process of coating is then continued with the spray head  50  with both longitudinal motion of the spray head  50  (along arrow A of  FIG. 4 ) interposed by rotation of the wood core  20  (about arrow B of  FIG. 4 ) to apply successive additional layers of PTMEG or similar material. After about ten layers (and most preferably twelve layers) in total have been applied, all of the desired PTMEG or similar material has been applied to form the outer coating  30 . A final finish of the outer surface  38  is prepared by running the squeegee  60  over the outer surface  38  once more to provide a desired surface finish. Most preferably, this surface finish is a smooth surface finish free of bubbles or other imperfections. 
         [0051]    The coated piling  10  is complete and can be allowed to cool and finally cure. If multiple wood cores  20  are to be coated, the spray head  50  can be kept active by bringing a new wood core  20  located upon separate carriers  40  into position for treatment of a new wood core  20 . After the last wood core  20  has been coated, a cleaning regimen is pursued with the spray head  50  and associated hoses  58  so that the spray head  50  and associated equipment including hoses  58  are ready for reuse in the future. 
         [0052]    This disclosure is provided to reveal a preferred embodiment of the invention and a best mode for practicing the invention. Having thus described the invention in this way, it should be apparent that various different modifications can be made to the preferred embodiment without departing from the scope and spirit of this disclosure. When structures are identified as a means to perform a function, the identification is intended to include all structures which can perform the function specified.