Patent Application
20220074221
The present invention relates generally to the preservation of wooden structures that are set in the ground, such as fence posts, and thus subjected to degradation over time due to water-induced rot. The invention includes the use of plastic coatings that prevent ground rot associated with that portion of the post that is set in the ground, and near ground rot or above-ground rot induced by the premature removal of pressure treatment fluids from the wood when the wood is physically damaged by, for example, string trimming machines.
A variety of different types of wood can be used for fence posts. Cypress, cedar and redwood are naturally resistant to insects, weather and ground rot, but are relatively expensive compared to pine. However, all four types of wood are relatively soft, and require pressure treatment with wood preservative products to extend the useful life of the post.
Wood preservative products used in pressure treating fence posts and other wooden structures intended for sustained outdoor use are those that control wood degradation due to fungal rot or decay, sap stain, molds, or wood-destroying insects. A typical preservative chemical is ACQ, or alkaline copper quaternary, which is a water-based wood preservative that prevents decay from fungi and insects (i.e., it is a fungicide and insecticide). It also has relatively low risks, based on its components of copper oxide and quaternary compounds. Water-based preservatives like ACQ leave a dry, paintable surface. ACQ is registered by the U.S. Environmental Protection Agency for use on lumber, timbers, landscape ties, fence posts, building and utility poles, land, freshwater and marine pilings, sea walls, decking, wood shingles, and other wood structures.
ACQ, and similar chemicals, can be applied by pressure treatment or dipping. Pressure treatment of lumber or posts requires immersing the wooden object in a liquid preservative and placed in a pressure chamber. High pressures within the chamber forces the chemical into the wood fibers, with the goal of forcing the chemical into the core of each piece of wood. This process is much more effective than simply soaking the wood in the chemical. However, at least with respect to commercially available pine fence posts, the chemical typically does not penetrate the wood more than a couple millimeters, which means that the post will have no, or reduced, chemical protection if the outer surface of the post is scarred or gouged more than a couple millimeters in depth.
One source of gouging for fence posts is the common string trimmer, known as “weed eaters.” String trimmers typically have a rotary head that is spun fast enough that two monofilament nylon strings are forced outward by centrifugal force to thereby become stiff enough to “eat” through grass, weeds, and slight, woody plants. A string trimmer works on the principle that a line spun fast enough is held out from its center (the rotating reel) very stiffly by centrifugal force, such that as the hub rotates faster, the line become more difficult to bend and thus acts as a cutting tool. Although the line is circular in cross section, the ends have a circular edge that acts like the edge of a knife to cut through plant material, such as grass and weeds, and softer tree barks.
In the course of repetitive use of string trimmers around fence posts, an outer surface of the post can be, and often is, eroded or gouged by the high-speed line by a depth sufficient to remove pressure treatment preservatives, paints or stains which usually protect the post from rot-inducing moisture. Thus, a need exists for an inexpensive, cost effective way of protecting fence posts and other wooden structures from scaring, gouging or erosion caused by string trimmers.
In one aspect of the present invention, a method of treating a fence post having a below-ground portion and an above-ground portion includes the steps of applying a plastic coating circumferentially around the post at an area of the post which, during trimming, is in contact with a high-speed rotating line, the plastic coating, when solidified, forming a hard, plastic protective sleeve bonded permanently to the post.
The step of applying a plastic coating further may include spraying, dipping or painting a liquid thermosetting material.
Preferably, the thermosetting material is selected from the group consisting of phenolic resin, urea-melamine, polyester and epoxy resin.
The plastic protective sleeve preferably has a thickness of between one and three millimeters, and has a hardness, fracture toughness and tensile strength to a degree sufficient to resist abrasion from the high-speed rotating line, but not significantly greater. The degree to which the sleeve is abrasion resistant can be selected depending on the cost of materials, such that if higher resistant materials are more costly, lower resistant materials can be used. The protective sleeve extends for a length sufficient to protect the post during weed and grass trimming. In preferred uses, the length can range from about a few inches to about one foot.
If it is desired to extend the life of post from underground deterioration from moisture, the sleeve can extend downward for the full extent of the post's in-ground portion, and cover the post's bottom, thereby forming a watertight sleeve having an above-ground portion that protects the post from abrading, erosion or cutting by string trimmers.
In one aspect of the invention, protective sleeve is provided for in situ retrofitting around a pre-set post, by applying a protective material around the post beginning at about ground level and extending upwardly for a length sufficient to avoid abrasion by a high-speed rotating line of a string trimmer. In another aspect of the invention, the protective sleeve is formed on the post before the post is set.
The protective sleeve is preferably made of a thermoplastic material selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), polyethylene terephthalate (PET), polyvinylchloride (PVC), polypropylene, polyester, acrylic, e.g., Lucite, cellulosic, acrylonitrile butadiene styrene (ABS), polycarbonate, acetyls, polytetrafluoroethylene (PTFE), and mixtures and variants thereof.
Preferably, the sleeve has a hardness or other material properties sufficient to resist abrasion from a string trimmer. When the sleeve is made of plastic material, it may be applied to the post, before it is set in the ground, by dipping, spraying, coating or otherwise applying in liquid form to cover the bottom and that portion of the post which will be set in the ground, to thereby resist degradation due to moisture.
The sleeve is preferably made of a thermosetting material selected from the group consisting off phenolic resin, urea-melamine, polyester and epoxy resin, and mixtures and variants thereof.
The sleeve, when made of a plastic material, can be applied as a retrofit in situ, with a plastic material, which is either the thermosetting or thermoplastic. An example of a thermoplastic material includes a sheet of plastic material that is wrapped around a post and then heated until the plastic melts to come into intimate, permanent contact with the wooden post. As the heated material cools, it becomes a solid protective hand or sleeve around the post. For thermosetting materials, a liquid plastic material can be applied around the post in a plastic state, and then heated sufficiently to form a solid, protective sleeve.
Other materials, other than plastics, can be used to form the protective sleeve. For example, certain fabrics, including woven cotton, can be wrapped around the post and permanently affixed thereto by any suitable means, including staples, nails, or adhesives, plastics, etc. Similarly, metal bands can be used to form the sleeve, such as adhesively hacked metal tape which is wrapped around the post at the around where the post will be at ground level and slightly above.
Ceramic materials can be used to form the sleeve, or can be used as an additive in a liquid plastic material to enhance the abrasion resistance of the material. Materials, such as clay, are inexpensive compared to the costs of resins, adhesives, and plastics, so the addition of a ceramic additive will both enhance abrasion resistance and decrease cost.
In another aspect of the invention, preformed sleeve segments can be made to fit around the post at about ground level. For a post with a circular cross-section, the sleeve would include two C-shaped sections that are placed on opposite sides of the post at about ground level, and then connected either to each other or separately to the post to form a cylindrical sleeve. For a half post (of the type where a post of circular cross section is split longitudinally to form two posts each have a D-shape in cross-section), the sleeve would include a pre-formed C-shaped portion, and a flat portion, which combine to form a D-shaped sleeve. Posts having a square cross-sectional shape, commonly used in urban and suburban fencing, could include a “square U” shaped portion and a flat portion, when combined forming a sleeve having a square cross-sectional shape. In any post cross-section, the two portions can be connected to each other or to the post by any conventional means. For aesthetic reasons, the two portions should be sized to make a clean fit, although excess material can be trimmed after installation.
The invention also contemplates elastic materials that can be wrapped around the post, similar to an “Ace” bandage used on athletes and horses to prevent injury. Once wrapped around the post, a liquid plastic, adhesive or other material that either air-dries or thermos-sets into a hard coating, can be used to enhance the protective abilities of the wrap.
As an environmental aspect of the invention, waste plastic can be collected, shredded and placed into a heating chamber, whereupon the material is heating to form a plastic slurry. The lower end of a post is then dipped in the slurry and removed, and then the slurry-covered lower portion of the post is cooled or otherwise thermoset until the slurry forms a solid plastic shield or boot covering the lower end of the post.
Other aspects of the invention will become apparent in view of the following detailed description and claims.
Referring to
The boards 18, 20 and 22 are typically made of oak, typically one inch thick by six inches wide, and most typically have three boards, but four board fences are also commonly employed. The boards are typically nailed to the posts.
The posts 12, 14 and 16 are secured in the ground by first digging a posthole. The lower end portions 12a, 14a and 16a of the posts 12, 14 and 16 are placed in the post holes and then held tightly in place by packed dirt, or in the case of urban and suburban uses with smaller numbers of posts, concrete (typically ready-mix concrete) can be poured into the hole dried to create a firm hold in the vertical upright position. The ground 24 is shown as a horizontal line extending between the posts 12, 14 and 16, and is shown cutaway to reveal the lower portions of the post being permanently set in the ground.
Other means of setting posts in the ground are available, particularly for large volumes of fencing, such as in agricultural settings where fence posts can be set for miles. Farm fencing can carry wire instead of boards, such as strands of barbed wire, or American wire, “chicken” wire, and other forms that are supported on posts. The lower end of the post can be shaped to a point and driven in the ground with post driver, as are known and available as tractor-driven implements. Some post drivers need no tapering or sharpening of the end of the post to be drive to a sufficient depth to be stable and strong.
The ground 24 absorbs rainwater and maintains a permanent moisture content that eventually will lead to rot of a wooden post. Once the lower portion of the post rots, the entire post must be replaced, at cost and inconvenience. Pressure treatment of wooden posts is designed to extend the life of a post.
In the normal course of maintenance, grass 26 and other plant growth grows under the fence boards and around the posts. It is common practice to use a string trimmer 28, sometimes called a “weed eater,” is used to trim the plant growth under the fence and around the posts. When the high-speed line of the string trimmer hits a post, over time, the surface of the post is eroded by the line. The amount of erosion, over the course of months and years of trimming, will be sufficient to cut into the post to penetrate the depth of pressure treatment fluid, thus exposing untreated wood to moisture. When this happens, the post will lose its protection from rot at around the ground level of the post, which is also a place where moisture from the ground or from rain, can wick into the post and cause rot over times.
The location of erosion of a post is illustrated in
As shown in
In a preferred embodiments, the band 30 and the boot 32 are made of a thermoplastic material, such as a thermoplastic polyester selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), polyethylene terephthalate (PET), polyvinylchloride (PVC), polypropylene, polyester, acrylic, e.g., Lucite, cellulosic, acrylonitrile butadiene styrene (ABS), polycarbonate, acetyls, polytetrafluoroethylene (PTFE), and mixtures and variants thereof. Thermoplastic materials can be applied in liquid form at elevated temperatures, and when cooled they form hard, solid surfaces. In the case of the band 30, the hardness of the thermoplastic material will resist abrasion from string trimming around the posts of a fence. Many of these plastics are in widespread use for beverage containers, plastic wrappings, plastic packaging and the like, and are thus considered relatively inexpensive.
The band 30 can be retrofitted in situ by applying the plastic material around the post and then having the plastic material cool to become solid, or heated to be solid, depending on whether the plastic is thermosetting or thermoplastic. In that case, the band will start at ground level and extend upwardly by a length sufficient to shield the post from abrasion by high-speed rotating string trimmers. If the post is not yet set in the ground, the band can be applied using a variety of means, and the boot 32 can be formed by dipping the post in liquid plastic material. The post could also be coated with plastic material by other means, such as with a brush or roller. Two part epoxy resins can also be mixed and applied, and air dried
Virtually any thermoplastic material can be used, with the preferred choices depending on cost, availability and environmental factors. Nylon, or polyamides, can be used either in the monomer or polymer form. High density polyethylene (HDP) is particularly advantageous because it has a relatively low melting point and is available both in commercial quantities from plastics suppliers, and also as scrap or waste, as many bottles and packaging are made of the material and can be collected, shredded, melted and recycled as post protecting sleeves. Generally, preferred plastic materials will have a relatively low melting point so that the material can be applied in heated, liquid form to the post, by brushing, rolling, spraying, dipping or any other suitable means, and then as the liquid plastic cools, it will harden on and bond to the post.
Alternatively, a thermosetting material can be used, whereby the plastic material is applied to the post in liquid form and then heated to a temperature sufficient to harden and permanently bond to the post. Virtually any thermosetting plastic can be used, although particularly preferred materials are selected from the group consisting of phenolic resin, urea-melamine, polyester and epoxy resin.
Once heated, or cooled, the plastic material hardens and adheres to the post and provides a permanent harrier to high speed rotating lines from string trimmers. For cost and efficiency, and ease of handling, it is preferred to use thermosetting plastics that have low melting points, and thermosetting plastics that have a relatively high transition temperature (from liquid to solid state).
Other materials besides plastics can be used as barriers to abrasion. For example, cotton fabrics, similar to those used to make clothing, can be cut into bands and adhered in place using adhesives or other means. Cotton fabric, or cotton polyester blends, tends to resist abrasion from string trimmers, but suffers from being less permanent and less protective, although fabric will nonetheless be effective. Sleeves can also be made of aluminum, rubber, synthetic rubber and other elastomers if pre-formed to be attached to the post at the ground level.
Although preferred embodiments have been described whereby plastic bands are formed in situ as a retrofit after a post is set in the ground, and where the plastic bands or boots are formed on the post before setting in the ground, other embodiments include preforming plastic or metal hands or sleeves and installing them on the posts after the posts are set in the ground. FIG. 7 shows in sequence a method of making a band for protecting a circular cross-sectional post at or around the ground level of the post. First, a short length of PVC pipe 34, of an inner diameter approximately the same as the outer diameter of the post The pipe 34 is cut longitudinally into two halves, forming two arcuate sections 36 and 38. Each section is placed around the post at the zone of abrasion, at the ground level and extending upwardly from there, and then secured in place by any appropriate means, such as nails 40 or screws, pins, staples, etc. PVC piping is preferred because it is in abundant supply and relatively inexpensive. For “half post” cross-sections of a generally D-shape, one arcuate section can be couple with a flat piece of PVC to form the “D” shape and thereby encase the post at the ground level and slightly above.
In another aspect of the invention, waste plastic 42, such as from plastic beverage containers, can be shredded and placed in a heating chamber 44 whereupon a heating element 46 is activated to convert the solid waste plastic into a liquid slurry. As seen in
Sleeves according to the present invention can easily be made using injection molding or 3-D printing to make two complementary parts of a sleeve that can be assembled on the post in situ. Referring to
As seen in
Commercially available two-part epoxy resins, of the type used for coating wood tabletops, can be used as coatings on the post at the area exposed to string trimming. Typically, the two part resins come with a resin and a hardener that are mixed just before use in a mixing container in a 1 to 1 ratio. The epoxy cures after application to a hard, clear finish.
Whether a resin or thermoplastic or thermosetting material, when in liquid form, the material can be augmented with a ceramic powder, such as clay or silica, to enhance the abrasive resistance, and UV resistance. Adding a ceramic powder, or any other inorganic constituents, can also reduce the cost of application, as these materials are less expensive than resins and other plastics.
Although specific embodiments of the present invention have been described, it will be understood by those of skill in the art that there are other embodiments that are equivalent to the described embodiments. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiments, but only by the scope of the appended claims.
