Abstract:
A trim guard, that surrounds wooden posts sunken into the ground, as well as other embedded structures is disclosed. The trim guard protects the posts or support structures from mechanical abrasion from devices such as rotary weed trimmers.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to mechanical sleeves that protect fence posts, mailbox posts, or any structure that is embedded into the earth, from deterioration from environmental elements and mechanical abrasion such as weed cutting devices. The sleeve is designed to surround the post or other structure and drain water away from the structure, thereby reducing corrosion from metallic structures and reducing degradation from biological agents and attendant rotting. 
         [0002]    While a preferred embodiment of the invention will be illustrated with respect to protecting wooden fence posts from attack by rotary string trimmers used in landscaping and ground maintenance operations it will be appreciated that the invention is not limited to this application, but has wider utility in connection with protecting any in-ground object which is subject to repeated attack by equipment which has the tendency of destroying the aesthetic appearance or the structural integrity of the object. 
       BACKGROUND OF THE INVENTION 
       [0003]    Devices intended to protect fence posts or other structures that are embedded into the ground are well known. An example is found in U.S. Pat. No. 5,503,371, invented by Bies, fully incorporated herein by reference. Bies shows an article and method of maintaining wooden fence posts from attack by landscaping equipment in which the base of the post is encircled with a hard plastic cuff. The plastic cuff has a smoother surface than the post such that string cutters used in edging around the fence post create a smoother and cleaner cut of the vegetation with the cuff as a backing while protecting the post from attack by the tip of the string element. 
         [0004]    U.S. Pat. No. 5,328,156 to Hoke, fully incorporated herein by reference, shows a generally “U” shaped self-adhering plastic extrusion that is firmly fitted to the bottom portion of a chain link or wooden fence without fasteners. Upstanding walls of the elongated plastic body are tapered towards the center having a neck for accepting the fence and a curved bottom to provide a channel on each side to rapidly drain off water. The tapered walls grip the fence in frictional engagement to hold the body member in place. The assembly includes short coupler members shaped to slide longitudinally in close frictional engagement over the outer surface of the body members where abutting ends are found. Couplers help secure the body members in place and cover the joint. A raised central ridge running along the length of the bottom positions the edge protector with respect to the bottom of the fence and holds the bottom of the fence elevated above drainage channels to protect the fence from moisture or termite damage. 
         [0005]    U.S. Pat. No. 4,845,889 to Taylor, fully incorporated herein by reference, discloses a lawn trimmer shield for protecting trees, plants and the like against damage from being struck by the rotating string of a lawn trimmer/weed cutter. The shield comprises two wall sections of hollow substantially semi-cylindrical shape which are hingably connected via a hinge. Each of the wall sections has a chamfered ground engaging edge which facilitates trimming close to the ground adjacent the shield. Handles are provided for facilitating installation and removal of the shield. Spikes are provided proximate the ground engaging edge for securing the shield close to the ground when it is installed about a tree, plant or the like. 
         [0006]    U.S. Pat. No. 4,349,989 to Snider, fully incorporated herein by reference, shows a fence guard for installation along a fence line for the purpose of preventing or retarding the growth of grass, weeds and other vegetation under and along a fence, which fence guard includes an elongated grass shield fitted along the straight runs of the fence line adjacent to the fence posts and extending outwardly from one or both sides of the fence line to cover the ground and grass along the fence. A swivel joint for attachment to the base of fence posts in the fence line at points where the fence changes direction; specially configured gate plates for mounting to the base of the gate posts installed in the fence and corner post plates provided at the base of each fence post in the fence line at points where a 90 degree directional turn is achieved, or where several fence lines meet, to match cooperating lengths of the grass shield. 
         [0007]    U.S. Pat. No. 3,571,972 to Carter, fully incorporated herein by reference, shows a device for enveloping upright elements such as trees, posts and the like at ground level to inhibit the growth of vegetation. A collar is formed of flexible water resistant sheet material and a main opening is formed therein from which a main slit extends to the outer edge of the sheet of material, the main slit being for the purpose of facilitating envelopment of a tree trunk and the like. A plurality of radial inner slits are formed in the sheet and extend outwardly from the central opening to define a plurality of flexible fingers which are disposed against the tree trunk or post to inhibit plant growth. Preferably the sheet is of laminated construction and the inner slits are formed in such manner that the fingers formed in the two laminated sheets are disposed in staggered relationship and the main slits in the two sheets are disposed out of coincidence with each other. 
       DISCLOSURE OF THE INVENTION 
       [0008]    Wood most often used for large fenced areas, horse and cattle farms, parks, golf courses and the like are typically soft, less expensive pressure treated pine poles six to eight feet in length. Fence contractors will generally install such posts using hydraulic post extractors to remove a weakened or broken post, or power augers for digging holes for a new fence. Pressure treated pine is a relatively soft wood and will not stand up under the abrasive action of the plastic or nylon string cutter. Nylon has a tensile strength of 22,000 PSI, an impact strength of 2.2 to 2.6 ft. lb./in and a compressive strength of 29,400 PSI. The wood fibers are eroded away by the abrasive action of the tip of the nylon string exposing the untreated substrate to rapid enabling attack from moisture and insects which enter the post at the erosion zone near the ground line. The sleeves of the present invention can be made of any hard plastic or thermo-setting resin such as polyvinylchloride having an ultraviolet stabilizer additive to prevent discoloration and deterioration over time from the ultraviolet rays of the sun. The resin should have a flexibility without cracking or breaking down to approximately 15 degree F. allowing for installation during cold weather conditions. Depending on costs, other high density plastics may be used such as HDPE (high density polyethylene) having a tensile strength of 34,800 PSI, impact of 0.4 to 4.0 ft. lb./in. and compression of 3,000 PSI; or acrylonitrile butadiene styrene (ABS) having a tensile strength of 7,000 PSI, impact of 2.0 to 6.0 ft. lb./in. and a compression strength of 12,500 PSI are just two examples of the plastic other than PVC which may be used for the sleeves. Posts having the sleeve installed will not need to be repainted near the ground line resulting in further cost savings in both labor and material. Posts are generally spray painted or brush painted with external enamel, usually white in the horse farm industry. Alternatively a creosote based material having a black, matt finish is applied to the fence post providing a protective covering. The sleeve, if installed prior to installation of the posts, or before extensive edging has occurred will protect wood from being removed by the abrasive action of the string cutter. However, even if installed after substantial erosion has occurred fence life will be increased and fence maintenance expenditures significantly reduced for the land owner. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0009]      FIG. 1  shows the invention in its broadest application, from the top and bottom. As can readily be seen the sleeve of the instant invention is split diagonally, enabling the sleeve to be assembled over a wooden post or other support. Snap detents ( 1 ) are provided on each of the two diagonal halves, which can be easily connected either before the post or other support is installed, or after the post has been secured to the ground. In this way, the invention can be utilized either with a new post, that has not been installed, or can later be added to posts that are already sunken into the ground or otherwise installed, such as supported on a concrete footer. 
           [0010]    Flange, or vertical collar ( 2 ) extends vertically above horizontal supporting plate ( 3 ). The purpose of the vertical collar is to protect the post or other structure from string in a rotary trimmer, as well as to protect the portion of the post that contacts the ground from other environmental degradation. Additionally, the vertical flanges ( 2 ) can be used to secure the sleeve to the post by screws, adhesive, or other means known in the art. 
           [0011]      FIG. 2  shows the detents ( 1 ) in greater detail. Each half has a rectangular extension designated by ( 4 ) that overlaps the other half of the trim guard. Studs ( 5 ) extend perpendicular from the rectangular extension and are in register with corresponding openings in the supporting plate ( 3 ). When the two halves are assembled, the studs ( 5 ) are pressed through the corresponding openings. An interference fit between the studs ( 5 ) and the openings ( 6 ) establish a secure fastening of the two diagonal halves. As can be appreciated from  FIG. 2 , the top of the studs ( 5 ) can be further provided with a flange that operates as a detent, that snaps over the opening when the two diagonal halves are pressed together. 
           [0012]    Although the studs ( 5 ) and openings ( 6 ) are shown in vertical alignment, where the underlying fence post defines vertical, the studs ( 5 ) and openings ( 6 ) could equally be horizontal. In this embodiment, the studs would extend horizontally from the diagonal half, and a flange would extend vertically from the opposite diagonal half. The studs ( 5 ) would then resiliently snap, in detent like fashion with an interference fit, through openings in the vertically extending flange of the opposite half of the trim guard. 
           [0013]      FIG. 3  shows the sleeve from the top view, with the side views on the right and under the top view. As can be seen, ridge support means ( 7 ) are provided on each right angle corner of the vertical flanges. The purpose of the ridge support means is to provide greater strength, particularly in the corners where they are located, in order to reduce stress concentration at the corners. 
       
    
    
       [0014]    All the sharp angles in the invention are rounded, to reduce strength concentration, and attendant failure at those sharp corners where stress failures are most common. As can be seen in the two profiles accompanying  FIG. 3 , the corners between the upright vertical flanges ( 2 ) and base ( 3 ) are well rounded. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    In the preferred embodiment, the trim guard of the instant invention is constructed of polyvinylchloride. However, any polymeric material with the necessary impact strength is suitable, for instance polyethylene, polybutylene, or polypropylene. Copolymers are also suitable, such as ABS copolymer. It must be remembered the trim guard is intended for outdoor use. Therefore, the material selected must possess the requisite thermal properties, i.e. it must not become overly brittle at cold winter temperatures and at the same time it must not become unnecessarily soft at higher summer temperatures. Polyvinylchloride plasticized with dioctylthalate or doctyladipate, and epoxidized soy bean oil, is commonly used in these temperature extremes. The material must also be resistant to radiant degradation, normally encountered when polymeric materials are exposed to sunlight. Any material selected absolutely must be impact resistant to mechanical abrasion, as when a string rotary trimmer cuts vegetation around the trim guard. 
         [0016]    As can be appreciated from consideration of the structural configuration of the horizontal supporting plate, grass or other plants are prevented from growing anywhere near the post or other embedded support. Because the horizontal supporting plate rests directly on the ground, and is very thin, a rotary power or hand mower can pass over the horizontal support plate, thereby easily trimming plant growth that protrudes outside of the horizontal support structure. If the vertical collar fits tightly around the post, then all that is necessary to remove plant material from around the post is to simply mow over the horizontal support structure, thereby completely eliminating the added burden of using a rotary string cutter. 
         [0017]    Metals usable to make the instant trim guard would include aluminum, steel, especially stainless steel, copper, brass, or alloys of these metals. Most important when using metals for the trim guard is to remember that the metals must be corrosion resistant, as they are intended for outdoor use. If metals are selected, it is critical to remember that the metal be similar to the post or other support encased. This will reduce the junction potential between dissimilar metals that encourages corrosion because anodic/cathodic action due to the junction of dissimilar metals. In this application, the trim guard is particularly suitable for high-voltage power line supporting structure, or metallic sign posts, etc. 
         [0018]    Although the Figures show the device in a rectangular configuration, it must be understood that any shape is usable with the trim guard. Round trim guards, for round posts, half-round trim guards for half-round posts, are contemplated within the scope of the trim guard. In any of these embodiments, the trim guard is split in half and attached in the manner shown with the rectangular species. Most important is that the trim guard fit as closely as possible to the underlying post or support structure. In this fashion, weeds, grass or other vegetation is inhibited from growing between the trim guard and the post or other underlying structure. 
         [0019]    It is also contemplated that adhesive or other material, such as a resiliently compressible material can provided between the trim guard and the post. This will act to further inhibit the growth of vegetation between the post and trim guard. In another embodiment of the instant invention, an herbicide is interposed between the trim guard and post, such as in an adhesive polymeric matrix, or other adhesive matrix. In yet another embodiment of the invention, a herbicide is included in the polymeric matrix of the weed guard itself, and is constantly dispersed by diffusion from the weed guard. 
         [0020]    Biocides that inhibit bacterial growth are also within the scope of the invention. Such biocides are intended to diffuse into the underlying post, thereby inhibiting bacterial decomposition of the post. Bacterial decomposition is the usual mode of failure in wooden posts, particularly where the post is submerged into the soil. Bacteria from the ground invades the wood, and rots the wood. By diffusing the biocide into the post, rot is considerably slowed down. 
         [0021]    Insecticides are also within the scope of the invention, impregnated in the plastic matrix of the vertical collar or interposed in a compressible matrix between the vertical collar and the embedded support. 
         [0022]    When the instant invention is used with metallic support structures, corrosion inhibitors could also be incorporated. The corrosion inhibitors could be dispersed within a polymeric matrix of the surrounding sleeve, or they could be impregnated into an adhesive matrix that interposes between the sleeve and underlying supporting structure. Corrosion inhibitors, biocides, or herbicides or other additives that are impregnated into an interposed matrix could be reapplied, as the additive is depleted from the matrix. Conveniently, new additive in liquid form could be poured into the matrix and allowed to saturate the matrix for fresh dispersion.