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BACKGROUND OF THE INVENTION  
         [0001]    A pier or dock is known to extend from a marina or shoreline into a body of water to provide a landing for watercraft, or to provide limited access to the water such as for fishing. An end of the pier is usually attached to an offshore piling in the water. Typically, the end of a smaller pier is movably attached to the piling in order for the end of the pier to move up and down in response to tidal, wave or wake actions. Otherwise a small pier, for instance, could be submerged and unusable during a high tide.  
           [0002]    Conventional roller arrangements are known to permit the pier to rise and lower around pilings as the tide comes in and recedes. However, some piers known as “finger piers” with relatively narrow widths and long lengths present lateral stability problems, which conventional rollers do not address. Specifically, conventional roller arrangements do not adequately stabilize the finger pier to prevent lateral instability or twisting. For example, a boat wake acting on a 4-foot wide finger pier can turn the finger pier into a “rolling log,” making it difficult to walk upon.  
           [0003]    Twisting is due to the creation of a “moment” that results when a first force is applied on one part of the pier without an equal and opposite force directly along the first force&#39;s line of action. More specifically, the moment urges a rotation about a given point or axis, which may be better understood with reference to a moment arm or lever arm corresponding to the moment.  
           [0004]    The moment arm is a perpendicular distance d between the line of action of a force F and a center of the moment. A magnitude of the moment of the force F acting about the point is directly proportional to the distance d of the force F from the point. Therefore, the magnitude of the moment can be defined as the product of the force F and the moment arm d expressed as:  
           magnitude of moment=force×distance= F×d.    
           [0005]    If the moment is to be taken about the point due to the force F, then in order for the moment to develop, the line of action cannot pass through that point. Alternatively, if the line of action does go through the point, the moment is zero because the magnitude of the moment arm is zero; thus, no twisting will occur.  
           [0006]    Imagine two people standing on either side of a pier that is movably attached to a piling. Further assume that both people weigh 200 pounds (lbs) and stand 12 inches (in.) on laterally opposite sides of the piling. Each person creates a moment of 2,400 in.-lbs (200 pounds×12 inches). The center of the moments in this case is zero since 2,400 in.-lbs minus 2,400 in.-lbs results in a total moment of zero; i.e., a state of equilibrium exists on the pier. If one of the people would suddenly climb aboard a boat tied alongside the pier, the weight of the remaining person would no longer be counterbalanced. The pier would twist down on the side of the remaining person. In other words, the force (weight) F of the person still standing on the pier would have created a moment as defined above.  
           [0007]    A device is needed that smoothly raises and lowers the pier and also stabilizes the pier to reduce rolling and twisting under most water surface conditions.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    In general, the present invention is directed to a dock stabilizer that permits a dock or pier to smoothly raise and lower in response to most normal tidal, wave, and wake actions. Furthermore, the dock stabilizer reduces rolling and twisting actions of the pier to make the pier easier to walk upon. The component parts of the invention are simple, reliable, and economical to manufacture and use.  
           [0009]    In one aspect of the invention, a dock stabilizer is provided with a base for attachment about a piling on a dock. A plurality of rollers are attached to the base with a first roller disposed axially apart from a second roller such that the base is interposed between the first and second rollers. A third roller is located laterally apart from the first roller such that the piling is interposed between the first and third rollers. A fourth roller is located laterally apart from the second roller such that the piling is interposed between the second and fourth rollers. The first and third rollers and the second and fourth rollers cooperate to equalize a moment arm formed substantially perpendicular to the piling and parallel to the dock to reduce twisting and rolling of the dock.  
           [0010]    Other aspects and advantages of the invention will be apparent from the following description and the attached drawings, or can be learned through practice of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The above and other aspects and advantages of the present invention are apparent from the detailed description below in combination with the drawings, in which:  
         [0012]    [0012]FIG. 1 is a perspective view of a dock stabilizer according to an aspect of the present invention;  
         [0013]    [0013]FIG. 2 is a perspective view of an unstabilized finger pier;  
         [0014]    [0014]FIG. 3 is a partial perspective view of a dock rollingly disposed about a piling in a conventional manner;  
         [0015]    [0015]FIG. 4 is a perspective view of the dock stabilizer stabilizing a finger pier;  
         [0016]    [0016]FIG. 5 is another perspective view of the dock stabilizer similar to FIG. 4 in which the finger pier is stabilized during use by a user; and  
         [0017]    [0017]FIG. 6 is a partial plan view of another embodiment according to a further aspect of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    Detailed reference will now be made to the drawings in which examples embodying the present invention are shown. The drawings and detailed description provide a full and detailed written description of the invention and the manner and process for making and using it so as to enable one skilled in the pertinent art to make and use it. The drawings and detailed description also provide the best mode of carrying out the invention. However, the examples set forth herein are provided by way of explanation of the invention and are not meant as limitations of the invention. The present invention thus includes modifications and variations of the following examples as come within the scope of the appended claims and their equivalents.  
         [0019]    The present invention is generally directed to a dock stabilizer with a plurality of roller assemblies that permit the dock or pier to smoothly raise and lower in response to most normal tidal, wave, and wake action. Furthermore, the dock stabilizer reduces rolling or twisting action of the pier to make the pier easier to walk upon. Although the exemplary dock stabilizer, described in detail below is made of marine-grade aluminum and is square in shape, the invention is not limited to the exemplary materials, sizes, and shapes discussed herein. For instance, the invention is intended for use with any size of pier, dock, and the like and with pilings of various sizes and shapes.  
         [0020]    The Figures show a dock stabilizer generally designated by the numeral  10 . The dock stabilizer  10  includes a plurality of roller assemblies  12 ,  20  with a plurality of rollers  14 ,  16 ,  22 ,  24  attached by bars  18   a, b, c, d  to a frame assembly or base  26 . The dock stabilizer  10 , the bars  18   a, b, c, d,  and the base  26  are manufactured of marine-grade aluminum and are therefore virtually impervious to attack from salts and other corrosives found in or near most bodies of water, such as oceans, harbors, and inland waterways. It should be understood, however, that the foregoing elements of the dock stabilizer  10  can be made from any type of metal, plastic such as high density polyurethane (HDPE), treated wood, or other durable material. It should be further understood that fewer or additional rollers and bars of various sizes and shapes can be provided. Therefore, the invention is not limited to the illustrated enhancements.  
         [0021]    With particular reference to FIG. 1, a perspective view of the dock stabilizer  10  shows a first roller assembly  12  with a first roller  14  and a second roller  16  attached to the base  26  via a plurality of bars  18   a, b.  Also in this example, a second roller assembly  20  is disposed apart from the first roller assembly  12  and is similarly attached to the base  26  via a plurality of bars  18   c, d.  The rollers  14 ,  16 ,  22 ,  24  have respective rolling faces  14   a,    16   a,    22   a,    24   a  that roll substantially parallel to an axis A of a piling P (see FIG. 4). The base  26  and the roller assemblies  12 ,  20  are shown squarely arranged to accommodate the square-shaped piling P (see FIG. 4) but other arrangements can be provided to accommodate any shape of piling as will be described below.  
         [0022]    As shown in FIG. 1, the first roller  14  and the second roller  16  are axially aligned on opposite sides of the base  26 . Similarly, the second roller assembly  20  has a third roller  22  and a fourth roller  24  disposed opposite each other on opposite sides of the base  26 . FIG. 1 further shows each of the bars  18   a, b, c, d  with respective portions on axially opposite sides of the base  26 . Bars  18   a, b, c, d  have portions with lengths L 1 , L 2 , which in this example are between from about 2 inches to about 14 inches in length such that the rollers  14 ,  16 ,  22 ,  24  are disposed from about 2 inches to about 14 inches from the base  26 . Although the bars  18   a, b, c, d  can be any desired length, 2 inches to about 14 inches control rocking of a finger pier of about 4 feet in width by reducing the moment about the piling P toward zero. An operation of the dock stabilizer  10  will be described in further detail below.  
         [0023]    In this exemplary embodiment the rollers  14 ,  16 ,  22 ,  24  are made from an ultra high molecular weight (UHMW) material to withstand most dockside conditions. However, the rollers  14 ,  16 ,  22 ,  24  can be made of metal such as aluminum or stainless steel, or a plastic such as high density polyurethane (HDPE), a rubber or any other durable material. It should also be noted that although the plurality of rollers  14 ,  16 ,  22 ,  24  are illustrated in FIG. 1 as cylinders, they can be wheels, tapered rollers, or other rolling mechanisms suitable for rollingly stabilizing the dock D in relation to the piling P.  
         [0024]    Also shown in FIG. 1, the base  26  of the dock stabilizer  10  includes a protrusion or skirt  28 , which is sized to fit about an outer surface of the piling P. The base  26  and skirt  28  define a complementary opening  30  through which the piling P passes. The base  26  further includes means for attaching the base to the dock D, such as a plurality of holes  32   a  and complementary bolts  32   b  (see FIG. 4). In this example, the holes  32   a  are defined about a perimeter of the base  26  for insertion of the bolts  32   b  into the dock D. It is to be noted that any suitable means for attaching the base  26  to the dock D can be used in lieu of or in addition to holes  32   a  and bolts  32   b,  such as nails, screws, rivets and the like. Additionally, adhesives, clamps or other attachment mechanisms may be used to secure the base  26  to the dock D.  
         [0025]    [0025]FIG. 1 further shows a plurality of additional guide rollers  34   a, b  disposed laterally apart from each other about the base  26  substantially perpendicular to the first and second roller assemblies  12 ,  20 . The guide rollers  34   a, b  assist with an up and down movement of the dock D as the tide goes in and out or as wake and wave actions cause the dock D to rise and fall under normal circumstances.  
         [0026]    In FIG. 2 a piling P′ is shown passing through an opening O′ of an unstabilized dock D′. With a weight W′ placed on one side of the unstabilized dock D′, the unstabilized dock D′ twists due to creation of a moment by a force F′ of the weight W′. By way of example, if the weight W′ weighs 200 lbs and sits approximately 12 inches (d′) from the piling P′, the weight W′ creates a moment of 2,000 in.-lbs (200 lbs×12 inches). Since there is no equalizing force to offset the moment created by the weight W′, the dock D′ is twisted as indicated by a twist angle θ relative to a horizontal plane H.  
         [0027]    By way of comparison, FIG. 3 shows a conventional roller assembly R that allows the dock D′ to raise and lower smoothly along the piling P′. However, the conventional roller assembly R does not counteract the moment as described above with respect to FIG. 2 to prevent the dock D′ from twisting.  
         [0028]    [0028]FIG. 4 shows the dock stabilizer  10  operably placed about the piling P with the roller assemblies  12 ,  20  aligned substantially parallel to an axis A of the piling P. In this example, the base  26  is secured to the dock D by bolts  32   b,  as described above. The roller assemblies  12 ,  20  zeroize moments to provide equilibrium on the dock. More specifically, the length L 1  of the arms  18   a, b, c, d  cooperate with the opposing length L 2  of the bars  18   a, b, c, d  to counteract moments (see FIG. 1). This aspect of the invention may be better understood with respect to an exemplary operation of the dock stabilizer  10  with reference to FIG. 5.  
         [0029]    As shown in FIG. 5, a user U weighing 200 lbs creates a moment of 2,000 in.-lbs in a similar manner as described above. Also as described with respect to FIG. 2 above, the 2,000 in.-lbs moment would usually cause the dock D to twist to a side upon which the user U is standing. However, a movement M 1  of the first roller  14  and the bars  18   a, b  is opposed by a movement M 2  of the roller  24  and the bars  18   c, d  (see FIG. 1) on the underside of the dock D. In this example, the length L 1  of bars  18   a, b  is offset by the length L 2  of bars  18   c, d  to counteract the moment of the user U and prevent the dock D from twisting. In other words, as the user U walks along one side of the dock D in FIG. 5, the first roller  14  and the fourth roller  24  contact the piling P to equalize the moment of the user U.  
         [0030]    As briefly introduced, alternative embodiments of the invention will accommodate different sizes and shapes of various pilings and the like. For instance, in another aspect shown in FIG. 6, a partial top plan view of a roller assembly  112  is shown. A similar roller assembly (not shown) would face substantially opposite of the roller assembly  112 . In this embodiment, rollers  114   a, b, c  are attached to a base  126  via bars  118   a, b  and contact a piling P″ in a manner similar to the foregoing embodiment. In this alternative arrangement, a rolling face  114   b ′ rolls substantially parallel to an axis A″ of the piling P″. The remaining rollers  114   a, c  may intermittently contact the piling P″ during times of specific wave or tidal actions that move the dock D″ from side to side.  
         [0031]    In a further aspect of the invention, the rollers  114   a, b, c  are self-aligning rollers that automatically contact and align on the surface of the piling P″ as the dock D″ moves from side to side; i.e., one or more faces of the rollers  114   a, b, c  contact and conformingly adjust to any shape of the surface of the piling P″.  
         [0032]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention. For example, specific shapes of various elements of the illustrated embodiments may be altered to suit particular applications. It is intended that the present invention include such modifications and variations as come within the scope of the appended claims and their equivalents.

Summary:
A dock stabilizer is provided that attaches about a piling on a dock or a pier to stabilize the dock or pier. In one aspect, the dock stabilizer utilizes a plurality of roller assemblies that are spaced axially and laterally apart from one another to reduce twisting or rocking of the dock. At least one of the roller assemblies may have a roller disposed a predetermined distance from the surface of the dock to counteract a moment arm and provide equilibrium on the dock.