Patent Publication Number: US-2009235605-A1

Title: Method of Making A Modular Synthetic Floor Tile Configured For Enhanced Performance

Description:
RELATED APPLICATIONS 
     The present application is a continuation in-part application, which claims the benefit of U.S. patent application Ser. No. 11/732,714, filed Apr. 3, 2007, which claims the benefit of U.S. patent application Ser. No. 11/244,723, filed Oct. 5, 2005, which claims the benefit of U.S. Provisional Application No. 60/616,885, filed Oct. 6, 2004. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to synthetic floor tiles, and more particularly to a modular synthetic floor tile in which its elements are designed and configured to enhance the performance characteristics of the floor tile through optimization of various design factors. 
     BACKGROUND OF THE INVENTION AND RELATED ART 
     Numerous types of flooring have been used to create multi-use surfaces for sports, activities, and for various other purposes. In recent years, the technology in modular flooring assemblies or systems made of a plurality of modular floor tiles has become quite advanced and, as a result, the use of such systems has grown significantly in popularity, particularly in terms of residential and portable game court use. 
     Modular synthetic flooring systems generally comprise a series of individual interlocking or removably coupling floor tiles that can either be permanently installed over a support base or subfloor, such as concrete or wood, or temporarily installed over a similar support base or subfloor from time to time when needed, such as in the case of a portable game court installed and then removed in different locations for a particular event. These floors and floor systems can be used both indoors or outdoors. 
     Modular synthetic flooring systems utilizing modular synthetic floor tiles provide several advantages over more traditional flooring materials and constructions. One particular advantage is that they are generally inexpensive and lightweight, thus making installation and removal less burdensome. Another advantage is that they are easily replaced and maintained. Indeed, if one tile becomes damaged, it can be removed and replaced quickly and easily. In addition, if the flooring system needs to be temporarily removed, the individual floor tiles making up the flooring system can easily be detached, packaged, stored, and transported (if necessary) for subsequent use. 
     Another advantage lies in the types of materials that are used to construct the individual floor tiles. Since the materials are engineered synthetics, the flooring systems may comprise durable plastics that are extremely durable, that are resistant to environmental conditions, and that provide long-lasting wear even in outdoor installations. These flooring assemblies generally require little maintenance as compared to more traditional flooring, such as wood. 
     Still another advantage is that synthetic flooring systems are generally better at absorbing impact than other long-lasting flooring alternatives, such as asphalt and concrete. Better impact absorption translates into a reduction of the likelihood or risk of injury in the event a person falls. Synthetic flooring systems may further be engineered to provide more or less shock absorption, depending upon various factors such as intended use, cost, etc. In a related advantage, the interlocking connections or interconnects for modular flooring assemblies can be specially engineered to absorb various applied forces, such as lateral forces, which can reduce certain types of injuries from athletic or other activities. 
     Unlike traditional flooring made from asphalt, wood, or concrete, modular synthetic flooring systems present certain unique challenges. Due to their ability to be engineered, the configuration and material makeup of individual floor tiles varies greatly. As a result, the performance or performance characteristics provided by these types of floor tiles, and the corresponding flooring systems created from them, also varies greatly. There are two primary performance characteristics, beyond those described above (e.g., shock absorption), that are commonly considered in the design and construction of synthetic floor tiles for athletic purposes: 1) traction or grip of the contact surface, which is a measure of the coefficient of friction of the contact surface; and 2) contact surface abrasiveness, which is a measure of how much the contact surface abrades a given object that is dragged over the surface. 
     In order for the contact surface of a flooring system to provide high performance characteristics, such as those that would enable athletes to quickly start, stop, and turn, the contact surface must provide good traction. Currently, efforts have been undertaken to improve the traction of synthetic flooring systems. Such efforts have included forming nubs or a pattern of protrusions that extend upward from the contact surface of the individual floor tiles. However, such nubs or protrusions, while providing somewhat of an improvement in traction over the same surface without such nubs, significantly increases the abrasiveness of the contact surface, and therefore the likelihood of injury in the event of a fall. Indeed, such nubs create a rough or coarse surface. In addition, the existence of nubs or protrusions creates irregular or uneven surfaces that may actually reduce traction depending upon their configuration and size. 
     Another effort undertaken to improve traction has involved forming a degree of texture, particularly an aggressive texture, in the upper or top surfaces of the various structural members or elements defining the contact surface of the flooring system. However, this only marginally improves traction, primarily because the texture, although seemingly aggressive, is unable to be pronounced enough to have any significant effect on the surface area of an object moving about the contact surface. This is particularly the case in the event the object comprises a large surface area (as compared to the surface area of the contact surface) and exerts a large normal force, such as an athlete whose shoe surface area and large normal force almost negate such practices. 
     With respect to the performance characteristic of abrasiveness of the contact surface of the flooring system, many floor tile designs sacrifice this in favor of improved traction. Indeed, the two most common ways to increase traction discussed above, namely providing raised nubs or other protrusions and providing aggressive texture on the contact surface, function to negatively increase the abrasiveness of the floor tiles and the flooring system in most prior art floor tiles. Thus, although a flooring system may provide good traction, there is most likely a higher risk for injury in the event of a fall due to the abrasive nature of the flooring system. 
     Abrasiveness may further be compounded by the sharp edges existing about the tile. Indeed, it is not uncommon for individual floor tiles to have a perimeter around and defining the dimensions of the floor tile consisting of two surfaces extending from one another on an orthogonal angle. It is also not uncommon for the various structural members extending between the perimeter and defining the contact surface to also comprise two orthogonal surfaces. Each of these represents a sharp, rough edge likely to abrade, or at least have a tendency to abrade, any object that is dragged over these edges under any amount of force. The combination of current traction-enhancing methods along with the edges of sharp perimeter and structural members, all contribute to a more abrasive contact surface. 
     SUMMARY OF THE INVENTION 
     In light of the problems and deficiencies inherent in the prior art, the present invention seeks to overcome these by providing a unique floor tile and flooring system designed to provide an increase of traction without the abrasiveness of prior related floor tiles and systems. Rather than providing raised nubs or an abrasive aggressive texture to increase traction about the contact surface of the floor tile, the present invention increases traction by enhancing or increasing the coefficient of friction about the contact surface while simultaneously maintaining low abrasiveness or a low abrasion index about the contact surface. The coefficient of friction of any given floor tile manufacture in accordance with the present invention may be enhanced or increased by striking an optimized and careful balance between various design factors, such as the ratio of surface area to the size of the openings of the contact surface. Stated differently, the coefficient of friction of the contact surface may be manipulated and selected by balancing various design factors, such as the size of the contact surface openings, the geometry of such openings, as well as the size and configuration of the various structural members defining such openings. Each of these, either individually or collectively, function to affect the coefficient of friction depending on their configuration. In any given embodiment, each of these parameters may be manipulated and optimized during design and manufacture to provide a floor tile having enhanced performance characteristics. 
     A floor tile formed in accordance with an effort to optimize various design constraints, such as the above-discussed parameters, also benefits from being much less abrasive as compared to other prior related floor tiles. Abrasiveness may be further reduced by providing blunt edges or transition surfaces along the perimeter of the floor tile, as well as the various structural members defining the openings and contact surface. 
     The present invention resides in a method for enhancing the performance characteristics of a modular synthetic floor tile, comprising arranging (or configuring) a plurality of interconnecting structural members to define an upper contact surface of the floor tile having a plurality of openings; shaping (or configuring) each of said structural members to comprise a thickness sufficient to support a load about said upper contact surface and having a contact flat defining a portion of said upper contact surface, said contact flat comprising a smooth surface and having a width between 0.03 and 0.08 inches; and configuring said upper contact surface with a dry static coefficient of friction of at least 0.6 and an abrasion index no greater than 20. 
     The present invention also resides in a method for enhancing the performance characteristics of a modular synthetic floor tile, said method comprising: arranging a plurality of interconnecting structural members to define an upper contact surface of the floor tile having a plurality of openings; sizing each of said openings to comprise an area between 0.06 in 2  and 0.12 in 2 ; shaping each of said structural members to comprise a thickness sufficient to support a load about said upper contact surface and having a contact flat defining a portion of said upper contact surface, said contact flat comprising a width between 0.03 and 0.08 inches, and a transition surface extending from said contact flat to a side surface of said structural member, said transition surface defining a portion of said upper contact surface and providing said structural members with a blunt edge; and configuring said upper contact surface with a dry static coefficient of friction of at least 0.6 and an abrasion index no greater than 20. 
     The present invention further resides in a modular synthetic floor tile comprising: a plurality of interconnecting structural members defining an upper contact surface of the floor tile having a plurality of openings, said plurality of structural members comprising a contact flat defining a portion of said upper contact surface and having a width between 0.03 and 0.08 inches, said openings comprising an area between 0.06 in 2  and 0.12 in 2 , said upper contact surface having a dry static coefficient of friction of at least 0.6, and said upper contact surface having an abrasion index of no greater than 20. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings merely depict exemplary embodiments of the present invention they are, therefore, not to be considered limiting of its scope. It will be readily appreciated that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Nonetheless, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  is a flowchart depicting a method for making an upper contact surface of a modular synthetic floor tile, in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  is a flowchart depicting a method for making an upper contact surface of a modular synthetic floor tile, in accordance with another exemplary embodiment of the present invention; 
         FIG. 3  illustrates a perspective view of an exemplary upper contact surface and support base of a modular synthetic floor tile, made in accordance with an exemplary embodiment of the present invention; 
         FIG. 4  illustrates a top view of the exemplary upper contact surface and support base of a modular synthetic floor tile of  FIG. 3 ; 
         FIG. 5  illustrates a bottom view of the exemplary upper contact surface and support base of a modular synthetic floor tile of  FIG. 3 ; 
         FIG. 6  illustrates a cut-away sectional view of the exemplary upper contact surface of  FIG. 3 ; 
         FIG. 7   a  is a schematic representation of a frictional force diagram of a flat surface; 
         FIG. 7   b  is a schematic representation of a frictional force diagram of an exemplary upper contact surface made in accordance with the method of the present invention; 
         FIG. 8  illustrates a top view of another exemplary upper contact surface of a modular synthetic floor tile made in accordance with the method of the present invention; 
         FIG. 9  illustrates a cut-away sectional view of the exemplary upper contact surface of  FIG. 8 , along section lines A-A and B-B; 
         FIG. 10  illustrates a partial sectional side view of an exemplary upper contact surface made in accordance with an exemplary embodiment of the present invention, and an object acting on the openings and structural members of the upper contact surface; 
         FIG. 11  illustrates a partial top view of the exemplary upper contact surface of  FIG. 9 ; 
         FIG. 12  illustrates a cut-away sectional view of another exemplary upper contact surface, formed in accordance with the method of the present invention; and 
         FIG. 13  illustrates a top view of a modular synthetic floor tile in accordance with still another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following detailed description of exemplary embodiments of the invention makes reference to the accompanying drawings, which form a part hereof and in which are shown, by way of illustration, exemplary embodiments in which the invention may be practiced. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that various changes to the invention may be made without departing from the spirit and scope of the present invention. Thus, the following more detailed description of the embodiments of the present invention is not intended to limit the scope of the invention, as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the present invention, to set forth the best mode of operation of the invention, and to sufficiently enable one skilled in the art to practice the invention. Accordingly, the scope of the present invention is to be defined solely by the appended claims. 
     The following detailed description and exemplary embodiments of the invention will be best understood by reference to the accompanying drawings, wherein the elements and features of the invention are designated by numerals throughout. 
     The present invention describes a method and system for enhancing the performance characteristics of a synthetic flooring system comprising a plurality of individual modular floor tiles. The present invention discusses various design factors or parameters that may be manipulated to effectively enhance, or even optimize, the performance characteristics of individual modular floor tiles, and the resulting assembled flooring system. Although a floor tile possesses many performance characteristics, those of coefficient of friction and abrasiveness are the focus of the present invention. 
     Generally speaking, it is believed that the coefficient of friction of a modular synthetic floor tile may be enhanced by balancing and manipulating a plurality of various design considerations or parameters, such as the geometry of the openings in the upper contact surface of the floor tile, the size of the openings, the surface area of the upper contact surface as expressed by the size of the contact area, or contact flat, on the top surface of the structural members, and the geometry of a transition surface which can extend between the horizontal top surface and the vertical side faces of the structural member. Other design parameters, such as material makeup, are also important considerations. The present invention contemplates the balance of one of these factors with at least one additional one to achieve the desired performance characteristics. 
     With respect to the surface area of the upper contact surface, and particularly the various structural members making up or defining the upper contact surface, it has been found that the coefficient of friction or traction of a floor tile, and ultimately an assembled flooring system, may be enhanced by manipulating the ratio of surface area to opening area (which is directly related to or dependant on the size of the openings). A floor tile comprising a plurality of openings formed in its contact surface for one or more purposes (e.g., to facilitate water drainage, etc.) will obviously sacrifice to some extent the surface area compared to the opening area. However, the size of the openings and the thickness of the top surfaces of the structural members making up the openings (which top surfaces at least in part define the upper contact surface, and particularly the surface area of the upper contact surface) may be manipulated to achieve a floor tile having a greater or reduced coefficient of friction. 
     With respect to the size of the openings in the upper contact surface, these also can be manipulated to enhance the coefficient of friction. It has been discovered that the openings can be configured to releasably receive and apply a compression force to objects, such as the foot or sole of the shoe of the user, acting on or moving about the contact surface of the floor tile that are sufficiently pliable. Openings too small may not adequately receive any portion of an object, thus leaving the surface rather slick and reducing the overall traction of the floor tile, while openings too large may limit the area of the object being acted on by the openings, as well as increase the abrasiveness of the floor tile. 
     With respect to the geometry of the openings in the upper contact surface, it has been discovered that certain openings are able to enhance the coefficient of friction of a floor tile better than others, particularly when other design considerations fall outside optimal ranges. Specifically, openings having a plurality of well-defined angles, either acute or obtuse (as defined below) function to enhance the coefficient of friction by applying a compression force to suitably pliable objects acting on or moving about the contact surface. By providing a plurality of well-defined angles in some or all of the openings of a modular synthetic floor tile, and with the openings being large enough to receive a portion of the sole or foot of the user, the openings are able to essentially wedge a portion of the sole or foot in those segments of the openings formed by the well-defined angles. By doing so, one or more compression forces are induced and caused to act on the object, which compression forces function to increase the coefficient of friction. Nonetheless, such well defined angles are not required to provide optimal conditions about a surface of a floor tile when taking into consideration other design factors or parameters that may be balanced against one another to achieve the desired overall performance characteristics of high traction and low abrasiveness. 
     Finally, it has also been discovered that blunting the edges between the horizontal top surface, or contact flat, and the vertical sides or faces of the structural members bounding the openings can further improve the coefficient of friction by providing an oblique surface against which the sole or foot of the user can find additional purchase. This can be accomplished by providing a transition surface between the top surface and side faces that is designed to eliminate the sharp edge that would otherwise exist between these two surfaces. The transition surface may comprise a curved configuration, such as an arc or radius, or may comprise a linear configuration, such as a chamfer, with the linear segment extending downward on an incline from the top surface. The transition segment may also comprise a combined linear and nonlinear configuration. The concept of a blunt transition surface may also be applied to the series of structural members making up the perimeter of the floor tile. 
     It is contemplated that all of these design parameters may be carefully considered and balanced for a given floor tile. It is also contemplated that each of these design parameters may be optimized for a given floor tile design. Optimized does not necessarily mean maximized. Indeed, although it will most likely always be desirable to maximize the coefficient of friction of a particular floor tile, this may not necessarily mean that each of the above-identified design parameters is maximized to achieve this. For a given floor tile, the coefficient of friction may be best enhanced by some design parameters giving way to some extent to other design parameters. Thus, each one is to be carefully considered for each floor tile design. In addition, there may be instances where the coefficient of friction may not always be maximized. For example, aesthetic constraints may trump the ability to maximize the coefficient of friction. In any case, it is contemplated that by manipulating the above-identified design parameters that the coefficient of friction for any given floor tile may be enhanced, or optimized, to some degree. 
     To illustrate, it may not be possible, in some instances, to maximize the ratio of surface area to opening area for a particular floor tile. However, this does not mean that the ratio cannot nevertheless be optimized. By optimizing this ratio, taking into account all other design parameters, the overall coefficient of friction of the floor tile may be enhanced to some degree, even in light of other overriding factors. 
     It has also been discovered that the coefficient of friction can be enhanced without the need for providing texture in the contact surface, as exists in many prior related designs. Indeed, the present invention advantageously provides a flat, planar contact surface without texture to achieve an enhanced coefficient of friction. As discussed above, in some cases texture can reduce the coefficient of friction of the floor tile, thus making objects acting on the contact surface more prone to slipping. By providing a flat, planar contact surface, the entire surface area is able to come into contact with an object. 
     In a related aspect, it has been discovered that the coefficient of friction of a floor tile can be enhanced without the need for additional raised or protruding members extending upward from the contact surface, as also is provided in many prior related designs. 
     While it is desirable to enhance the coefficient of friction or traction for a given floor tile, it is also desirable to simultaneously reduce the tendency of the floor tile to abrade an object. Generally speaking, the abrasiveness of a floor tile, and subsequent assembled flooring system, may be reduced by limiting the tendency of the floor tile to abrade an object acting on or moving about the contact surface of the floor tile. By forming various transition surfaces between each of the edges and top surfaces of the structural members and the perimeter, a softer, smoother contact surface is created. In addition, the interface between adjacent tiles is also softened due to the transition surface along the perimeter. 
     DEFINITIONS 
     The term “tile performance” or “performance characteristic,” as used herein, shall be understood to mean certain measurable characteristics of a flooring system or the individual floor tiles making up the flooring system, such as grip or traction, ball bounce, abrasiveness, shock absorption, durability, wearability, etc. As can be seen, this applies to both physical related characteristics (e.g., those types of characteristics that enable the flooring system to provide a good playing surface, or that affect the performance of objects or individuals acting on or traveling about the playing surface), and safety related characteristics (e.g., those types of characteristics of the floor tile that have a tendency to minimize the potential for injury). For example, traction may be described as a physical performance characteristic that contributes to the level of play that is possible about the contact surface. Abrasiveness may be termed a safety-related performance characteristic, although it is not necessarily an indicator of how well the flooring system will affect or enable sports or activity play and at what level. Nonetheless, the ability to minimize injury and enable safe play, particularly in the event of a fall, is an important consideration. 
     The term “traction,” as used herein, shall be understood to mean the measurement of coefficient of friction of the flooring system (or individual floor tiles) about its contact surface. 
     The term “traction index” as used herein, shall be understood to mean the average dry coefficient of friction, which is a composite value of both the dynamic and static values as tested under dry conditions. 
     The terms “abrasive” or “abrasiveness,” as used herein, shall be understood to mean the tendency of the flooring system (or individual floor tiles) to abrade or chafe the surface of an object that drags or is dragged across its contact surface. One test for abrasion is the standardized ASTM (American Society for Testing and Materials) F1015-3 Test, entitled “Standard Test Method for Relative Abrasiveness of Synthetic Turf Playing Surfaces.” 
     The term “acute,” as used herein, shall be understood to mean an angle or segment of structural members intersecting one another on an angle less than 90°. 
     The term “right-angle,” as used herein, shall be understood to mean an angle or segment of structural members intersecting one another on an angle equal to 90°. 
     The term “obtuse,” as used herein, shall be understood to mean an angle or segment of structural members intersecting one another on an angle greater than 90°. 
     The term “transition surface,” as used herein, shall be understood to mean a surface or edge extending between a top surface or contact flat of a structural member or perimeter member, and a face or side surface of that member to provide a soft or blunt transition between the top surface and the face. Such a transition surface can function to reduce abrasiveness and improve traction of the flooring system. A transition surface may comprise a linear segment, a round segment having a radius or an arc to provide a rounded edge, or any combination of these. 
     The term “quadrilateral,” as used herein, shall be understood to mean a polygon with four sides or edges and four vertices or corners. Quadrilaterals can include squares, rectangles, and diamonds (rhombus) and variations thereof. 
     The term “area of the opening” or “aperture area,” as used herein, shall be understood to mean the calculated or quantifiable area or size of the open space or aperture of the opening as defined by the structural members making up the opening and defining its boundaries. Commonly known area calculations are intended to provide the aperture area of the opening(s) measured in any desirable units, such as in 2 , mm 2  or cm 2 . 
     Traction and Abrasiveness 
     One of the more important challenges in the construction of synthetic floor tiles and corresponding flooring systems is the need to provide a contact surface having adequate traction or grip. Traction refers to the friction existing between a drive member and the surface it moves upon, where the friction is used to provide motion. In other words, traction may be thought of as the resistance to lateral motion when one attempts to slide the surface of one object over another surface. Traction is particularly important where the synthetic flooring system is to be used for one or more sports-related or other similar activities. 
     The level of traction a particular flooring system (or individual floor tile) provides may be described in terms of its measured coefficient of friction. As is well known, coefficient of friction may be defined as a measure of the slipperiness between two surfaces, wherein the larger the coefficient of friction, the less slippery the surfaces are with respect to one another. One factor affecting coefficient of friction (or traction) is the magnitude of the normal force acting on one or both of the objects having the two surfaces, which normal force may be thought of as the force pressing the two objects, and therefore the two surfaces, together. Another factor affecting coefficient of friction is the type of material from which the surfaces are formed. Indeed, some materials are more slippery than others. To illustrate these two factors, pulling a heavy wooden block (one having a large normal force) across a surface requires more force than does pulling a light block (one having a smaller normal force) across the same surface. And, pulling a wooden block across a surface of rubber (large coefficient of friction) requires more force than pulling the same block across a surface of ice (small coefficient of friction). 
     For a given pair of surfaces, there are two types of friction coefficient. The coefficient of static friction, μ s , applies when the surfaces are at rest with respect to one another, while the coefficient of kinetic friction, μ κ , applies when one surface is sliding across the other. 
     The maximum possible friction force between two surfaces before sliding begins is the product of the coefficient of static friction and the normal force: F max , =μ s N. It is important to realize that when sliding is not occurring, the friction force can have any value from zero up to F max . Any force smaller than F max  attempting to slide one surface over the other will be opposed by a frictional force of equal magnitude and opposite in direction. Any force larger than F max  will overcome friction and cause sliding to occur. 
     When one surface is sliding over the other, the friction force between them is always the same, and is given by the product of the coefficient of kinetic friction and the normal force: F=μ κ N. The coefficient of static friction is larger than the coefficient of kinetic friction, meaning it takes more force to make surfaces start sliding over each other than it does to keep them sliding once started. 
     These empirical relationships are only approximations. They do not hold exactly. For example, the friction between surfaces sliding over each other may depend to some extent on the contact area, or on the sliding velocity. The friction force is electromagnetic in origin, meaning atoms of one surface function to “stick” to atoms of the other surface briefly before snapping apart, thus causing atomic vibrations, and thus transforming the work needed to maintain the sliding into heat. However, despite the complexity of the fundamental physics behind friction, the relationships are accurate enough to be useful in many applications. 
     If an object is on a level surface and the force tending to cause it to slide is horizontal, the normal force N between the object and the surface is just its weight, which is equal to its mass multiplied by the acceleration due to earth&#39;s gravity, g. If the object is on a tilted surface such as an inclined plane, the normal force is less because less of the force of gravity is perpendicular to the face of the plane. Therefore, the normal force, and ultimately the frictional force, may be determined using vector analysis, usually via a free body diagram. Depending on the situation, the calculation of the normal force may include forces other than gravity. 
     Material makeup also affects the coefficient of friction of an object. In most applications, there is a complicated set of trade-offs in choosing materials. For example, soft rubbers often provide better traction, but also wear faster and have higher losses when flexed—thus hurting efficiency. 
     Another important challenge in the production of synthetic flooring systems is the reduction of the abrasiveness of the contact surface. Abrasiveness may be thought of as the degree to which a surface tends to abrade the surface of an object being dragged over the surface. A common test for abrasiveness of a surface comprises dragging a friable block over the surface under a given load. This is done in all directions over the surface. The block is then removed and weighed to determine its change in weight from before the test. The change in weight represents the amount of material that was lost or scraped from the block. 
     The more abrasive a floor tile is the more it will have a tendency to abrade the skin and clothes of an individual, and thus cause injury and damage. Therefore, it is desirable to reduce abrasiveness as much as possible. However, because traction is considered more desirable, abrasiveness has often been sacrificed for an increase in traction (e.g., by providing protrusions and/or texture about the contact surface). Unlike many prior art designs, the present invention advantageously provides both an increase in traction and a reduction in abrasiveness. 
     DESCRIPTION 
     With reference to  FIG. 1 , illustrated is a method  10  for making an upper contact surface of a modular synthetic floor tile having a high traction index and a low abrasion index, in accordance with one exemplary embodiment of the present invention. The method includes the operation of choosing  12  a shape for a plurality of openings in the upper contact surface. The openings can be given the shape of a polygon, and can be organized in a repeating pattern across the face of the contact surface. Each opening can have a uniform area of the opening, or aperture area, and be bounded on all sides by structural members having a uniform thickness. The shapes can be selected from the group consisting of triangles, quadrilateral, pentagons, and hexagons, or any other shape that allows for a repeatable pattern of openings, with each opening having a uniform aperture area and a perimeter defined and bounded by structural members that are of uniform thickness. In other embodiments, the areas and structural member thicknesses may be non-uniform. 
     The method also includes the operation of sizing  14  the uniform aperture area of each of the plurality of openings to releasably receive a portion of the sole or foot of the user. The dimensions of the aperture area of the opening can be configured to receive and apply a compression force to objects, such as the foot or sole of the shoe of the user acting on or moving about the contact surface of the floor tile, and afterwards release the portion of the foot or sole of the shoe. In an exemplary embodiment of the present invention, the uniform aperture area of each of the plurality of openings can be selected to be between 0.06 in 2  and 0.12 in 2 . 
     The method further includes shaping  16  each of the structural members to comprise a constant thickness that is sufficient to support the loading generated by the user without substantial deformation and having a smooth contact flat the defines a portion of the upper contact surface. The plurality of structural members bounding the perimeter of each opening, or at least the subset of structural members directly under the foot or sole of the shoe of the user at any one moment, can be designed with a thickness great enough to resist and support the vertical and lateral loads that can be generated by the user while engaging in activities on the surface of the modular tile, such as starting, stopping, running, jumping, landing, twisting, changing direction, etc. The structural members can be configured to withstand these loadings without substantial deformation, so that the openings and the top contact flat maintain their configuration and the tile retains its performance characteristics throughout all aspects of the activity. In an exemplary embodiment of the present invention, the plurality of structural members can be given a constant thickness between 0.09 in and 0.13 in. 
     The method of the present invention may also include the step of configuring  18  each of the structural members with transition surfaces between the smooth contact flat and the side faces of structural members to provide the upper contact surface with an average dry static coefficient of friction greater than 6.0 and an ASTM F1015 Abrasion Index of less than 20. As stated hereinabove, the challenges of simultaneously providing both a high coefficient of friction, or traction index, with a low abrasion index may or may not be appreciated by one having skill in the art. It can be demonstrated, both historically and with current examples in the prior art, that a high coefficient of friction is typically associated with a high abrasion index, as the two most common ways of increasing traction, namely providing raised nubs or other protrusions and providing aggressive texture on the contact surface, both function to negatively increase the abrasiveness of the floor tiles and the flooring system in most prior art floor tiles. Forming a top contact surface that simultaneously provides a coefficient of friction greater than 0.6 and an abrasion index (as measured by the ASTM F1015-e test) of less than 20, is a significant advancement in the state of the art and is achieved through careful balance of certain design parameters discussed herein. 
     The present invention is particularly advantageous over the prior art by providing a measurable standard of performance for both the traction and abrasion indexes. The traction index is the average dry coefficient of friction, which is a composite value of both the dynamic and static values as tested under dry conditions, and should be greater than 0.60. The methods of testing and ascertaining the values for both static and dynamic coefficients of friction are readily available to one having skill in the art. The abrasion index of the present invention can be measured using the standardized ASTM (American Society for Testing and Materials) F1015-3 Test, entitled “Standard Test Method for Relative Abrasiveness of Synthetic Turf Playing Surfaces,” and should be less than 20. 
     The transition surface between the top contact surface and the side faces of each of the plurality of structural members does not in and of itself provide the upper contact surface with a high traction index and low abrasion index, but instead can be the final factor working in combination with other factors to achieve the desired performance. These other factors can include the shape of the opening with multiple, well-defined corners, and the size or area of the opening which allows a portion of the sole of the shoe or foot of the user to be temporarily and removably captured and restrained while moving over the flooring surface. 
     The transition surface can function to provide an oblique surface, relative to the upper contact surface, which is better able to restrain and absorb the lateral forces generated by the sole or foot of the user during movement over the floor tile. The transition surface can include a curved configuration, such as an arc or radius, or may comprise a linear configuration, such as a chamfer, with the linear segment extending downward on an incline from the top surface. The transition segment may also comprise a combined linear and nonlinear, or curved, configuration. 
     The method of the present invention can further comprise designating a radius of curvature for the transition surface extending between the top contact surface and the side faces of each of the plurality of structural members, as well as designating the width of the contact flat on the top contact surface that is bounded on both sides by the curved transition surface. The width of the contact flat is not equal to the previously selected overall width of the structural members, but is the remainder of the overall value after subtracting the width of the curved transition surface from both edges. In an exemplary embodiment of the present invention, the width of the contact flat can be between 0.03 in and 0.08 in, and the radius of curvature to be between 0.01 in and 0.05 in. 
     The flowchart of  FIG. 2  depicts another method  20  for making an upper contact surface of a modular synthetic floor tile, in accordance with an exemplary embodiment of the present invention. The method includes the steps of arranging  22  (or configuring) a plurality of interconnecting structural members to define an upper contact surface of the floor tile having a plurality of openings, shaping  24  (or configuring) each of the structural members to comprise a thickness sufficient to support a load about the upper contact surface and having a contact flat that defines a portion of the upper contact surface a smooth surface and having a width between 0.03 and 0.08 inches, and configuring  26  the upper contact surface with a dry static coefficient of friction of at least 0.6 and an abrasion index no greater than 20. 
     With reference to  FIGS. 3-6 , illustrated is an exemplary upper contact surface and support base of a modular synthetic floor tile  110 , the upper contact surface  114  being made in accordance with one exemplary embodiment of the present invention. As shown, the floor tile  110  comprises an upper contact surface  114 , shown as having a grid-type or lattice configuration, that functions as the primary support or activity surface of the floor tile  110 . In other words, the upper contact surface  114  is the primary surface over which objects or people will travel, and that is the primary interface surface with such objects or people. The upper contact surface  114  thus inherently comprises a measurable degree or level of traction and abrasiveness that will contribute to and affect the performance characteristics of the floor tile  110 , or more specifically the performance of those objects and people acting on the floor tile  110 . The level of traction and abrasiveness of the floor tile is discussed in greater detail below. 
     The floor tile  110  further comprises a plurality of structural members that make up or define the grid-type upper contact surface  114 , and that provide structural support to the upper contact surface  114 . In the exemplary embodiment shown, the floor tile  110  comprises a first series of rigid parallel structural members  118  that, although parallel to one another, extend diagonally, or on an incline, with respect to the perimeter  126 . The floor tile  110  further comprises a second series of rigid parallel structural members  122  that also, although parallel to one another, extend diagonally, or on an incline, with respect to the perimeter  126 . The first and second series of structural members  118  and  122 , respectively, are oriented differently and are configured to intersect one another to form and define a plurality of openings  130 , each opening  130  having a geometry defined by a portion of the structural members  118  and  122  configured to intersect with one another at various intersection points. In the embodiment illustrated in  FIG. 3 , the structural members  118  and  122  are configured to form openings  130  having a diamond shape, in which the structural members that define each individual opening are configured to intersect or converge on one another to form opposing acute angles and opposing obtuse angles, as measured between imaginary axes extending through the points of intersection of the structural members  118  and  122 . 
     As will be discussed below, the structural members used to form the floor tile and to define the contact surface in any embodiment herein may comprise other configurations to define a plurality of differently configured openings in the upper contact surface, or openings having a different geometry. As discussed herein, the present invention provides a way to enhance traction of the contact surface by providing suitable openings, such as those that have at least one well-defined angle, as defined herein. This does not necessarily mean however, that each and every opening in the contact surface will comprise at least one well-defined angle. Indeed, an upper contact surface may have a plurality of openings, only some or none of which have at least one well-defined angle. This may be dictated by the configuration of the structural members and the resulting particular geometry of the openings in the contact surface, as is discussed in more detail below. 
     Circumscribing the upper contact surface  114  and the general dimensions of the floor tile  110  is a series of perimeter structural members  126 , which function as a boundary for the floor tile  110 , as well as an interface with adjacent floor tiles configured to be interconnected with the floor tile  110 . The perimeter  126  also comprises a top surface  142  and an outer face or perimeter wall  146 , which extends around the floor tile  110 . The top surface  142  of the perimeter is generally planar with the top surface of the various structural members  118  and  122 . As such, the perimeter  126  and the structural members  118  and  122  each function to define at least a portion of the contact surface  114 . 
     The floor tile  110  is square or approximately square in plan, with a thickness T that is substantially less than the plan dimension L 1  and L 2 . Tile dimensions and material composition will depend upon the specific application to which the tile will be applied. Sport uses, for example, frequently call for floor tiles having a square configuration with side dimensions (L 1  and L 2 ) being either 9.8425 inches (metric tile) or 12.00 inches. Obviously, other shapes and dimensions are possible. The thickness T may range between 0.25 and 1 inches, although a thickness T between 0.5 and 0.75 inches is preferred, and considered a good practical thickness for a floor tile such as that depicted in  FIG. 3 . Other thicknesses are also possible. The floor tiles can be made of many suitable materials, including polyolefins, such as polypropylene, polyurethane and polyethylene, and other polymers, including nylon. Tile performance may dictate the type of material used. For example, some materials provide better traction than other materials, and such should be considered when planning and installing a flooring system. 
     The floor tile  110  further comprises a support structure (see  FIG. 5 ) designed to support the floor tile  110  or above a subfloor or support surface, such as concrete or asphalt. As shown, the bottom of the floor tile  110  comprises a plurality of vertical support posts  154 , which give strength to the floor tile  110  while keeping its weight low. The support posts  154  extend down from the underside of the contact surface, and particularly the structural members  118  and  122 . The support posts  154  may be located anywhere along the underside of the floor tile surface, and the structural members, but are preferably configured to extend from the points of intersection, each one or a select number, of the structural members, as shown. In addition, the support posts  154  may be any length or offset lengths, and may comprise the same or different material than that of the structural members  118  and  122 . 
     A plurality of coupling elements in the form of loop and pin connectors are disposed along the perimeter wall  146 , with loop connectors  160  disposed on two contiguous sides, and pin connectors  164  disposed on opposing contiguous sides. The loop and pin connectors  160  and  164 , respectively, are configured to allow interconnection of the floor tile  110  with similar adjacent floor tiles to form a flooring system, in a manner that is well known in the art. It is also contemplated that other types of connectors or coupling means may be used other than those specifically shown and described herein. 
     As shown in  FIG. 6 , the structural members  118  can further comprise a smooth, planar top contact surface or flat  134  forming at least a portion of the upper contact surface  114 , and opposing sides or vertical side faces  138 - a  and  138 - b  oriented transverse to the top contact flat  134 . The contact flat  134  may comprise different widths (as measured along a cross-section of the structural member) that may also be optimized to contribute to the overall enhancement of the coefficient of friction. The side faces  138 - a ,  138 - b  can be perpendicular to the top contact flat  134 . In the exemplary embodiment shown, however, the structural member  118  can taper slightly from its base to the contact flat  134 , resulting in tapered side faces  138 - a ′ and  138 - b ′ that can be oriented at an near-perpendicular angle with respect to the top contact flat  134 . Although not shown in detail, the structural members  122  comprise a similar configuration, each also having a top contact flat and opposing faces. 
     The structural members  118  can further comprise a transition surface  136  extending between the top contact flat  134  and the side faces  138 - a  and  138 - b . The transition surface  136  is designed to eliminate the sharp edge that would otherwise exist between the horizontal contact flat  134  and side faces  138 - a  and  138 - b . The transition surface  136  may comprise a curved configuration, such as an arc or radius, with a radius of curvature r ts  as shown. The radius of curvature r ts  of the curved transition surface may be between 0.01 and 0.05 inches, and is preferably 0.02 inches. In another aspect the transition surface may comprise a linear configuration, such as a chamfer, with the linear segment extending downward on an incline from the top surface. The angle of incline of the linear segment may be anywhere from 5 to 85 degrees, as measured from the horizontal plane of the contact flat  134 . Still further, the transition segment may comprise a combined linear and nonlinear configuration. 
     One effect of the transition surface  136  is to soften the edge of the structural members, thus reducing the abrasiveness of the floor tile or the tendency for the floor tile to abrade an object dragged over its surface. However, the transition surfaces  136  can also affect the coefficient of friction, or traction index, of the floor tile. By eliminating the sharp edge that would otherwise exist between the top contact flat  134  and side faces  138 - a  and  138 - b , the transition surfaces  136  on either side of the structural member  118  can reduce the width of the top contact flat  134 . Whereas the top contact flat  134  without transition surfaces would have a smooth, planar strip with a width equal to the thickness of the top of the structural member, or t sm , the transition surfaces reduce the width of the planar strip to that of a contact flat  134  having a width or thickness t cf . 
     As shown in  FIGS. 7   a - 7   b , the transition surfaces can also improve the traction index of the upper contact surface of the modular synthetic floor tiles. As can be readily appreciated by one having skill in the art, a flat surface  50  can be subjected to a load force  60  which is applied at an angle  62  to the surface. In order to support this load in equilibrium (i.e. without slipping), the surface  50  must be capable of responding with an equal and opposite reaction force  64  to counteract the load force  60 . For a flat planar surface, as the one depicted in  FIG. 7   a , the reaction force  64  is comprised of two components: a normal force component  66  and a friction force component  68 . 
     This same principle applies to the structural members  118  of the present invention, which top contact flat  134  forms a portion of the upper contact surface of the floor tile. When a load force  60  is applied to the narrow contact flat on the top of the structural member, the contact flat surface responds with a reaction force  64  which is comprised of a normal component  66  and a friction component  68 . However, if the same object that applies load force  60  is allowed to partially enter into opening  130  located to the side of the structural member  118 , the object also will contact and press against transition surface  136  with load force  70 . And in order to maintain equilibrium, a reaction force  72  must also be generated at the transition surface to balance the load force  70 . However, since the load force  70  is applied at angle  72  which is nearly perpendicular to the curve of the transition surface  136  at the point of contact, the reaction force  74  is comprised primarily, if not entirely, of a normal component  76 . 
     It will be appreciated that in order for the transition surface  136  to substantially contribute to the overall reaction force, or traction index, which keeps the moveable object from slipping, the openings  130  must be sufficiently large and the surface of the object must be sufficiently pliable to allow a portion of the object to descend below the level of the contact flats  134 , enter the opening  130  and contact the transition surface  136 . It can also be appreciated that the contribution of the transition surface  136  to the overall reaction force is not required to be a reaction derived from a frictional interaction between the two surfaces, per se, but instead can be a normal, or direct, reaction force  74  in response to a perpendicular load. 
     With reference to  FIGS. 8 and 9 , illustrated is another exemplary upper contact surface  214  of a modular synthetic floor tile  210 , made in accordance with the method of the present invention. Similar to the embodiment shown in  FIGS. 3-6 , the upper contact surface  214  is formed with a plurality of quadrilateral openings  230  defined by a plurality of structural members  218 , shown as having a grid-type or lattice configuration. However, in the embodiment of  FIG. 8  the quadrilateral openings  230  have the shape of a square. The top surfaces  234  of the plurality of structural members  218  serve as the primary support or activity surface of the floor tile  210 . In other words, the upper contact surface  214  is the primary surface over which objects or people will travel, and that is the primary interface surface with such objects or people. The upper contact surface  214  thus inherently comprises a measurable degree or level of traction and abrasiveness that will contribute to and affect the performance characteristics of the floor tile  210 , or more specifically the performance of those objects and people acting on the floor tile  210 . 
     Circumscribing the upper contact surface  214  and the general dimensions of the floor tile  210  is a perimeter  226 , which functions as a boundary for the floor tile  210 , as well as an interface with adjacent floor tiles that includes loop connectors  260  disposed on two contiguous sides, and pin connectors  264  disposed on opposing contiguous sides. The loop and pin connectors  260  and  264 , respectively, are configured to allow interconnection of the floor tile  210  with similar adjacent floor tiles to form a flooring system, in a manner that is well known in the art. 
     As shown in further detail in  FIG. 9 , which focuses on the top contact surface portion of the modular floor tile, the structural members  218  can define an upper contact surface  214  comprised, in part, by smooth, horizontal top contact flats  234  forming at least a portion of the upper contact surface  214 , and vertical side faces  238  oriented perpendicular to the top contact flats  234 . The thickness of the structural members  218  can vary both from top to bottom, as with a tapered structural member, as well as along the length of the structural member as it encounters various hole configurations. However, it has been discovered that the structural members can also be given a constant thickness (as measured along a cross-section of the structural member just below the contact flat  234 ) that may be optimized to contribute to the overall enhancement of the coefficient of friction. The thickness of the structural members t sm  may be between 0.07 inches and 0.11 inches, and is preferably about 0.09 inches. 
     The upper contact surface  214  can also have transition surfaces  236  extending between the top contact flats  234  and the side faces  238 . The transition surfaces  236  may comprise a curved configuration, such as an arc or radius, with a radius of curvature r ts . The radius of curvature r ts  of the curved transition surfaces may be between 0.01 inches and 0.05 inches, and is preferably 0.02 inches. In another aspect the transition surfaces may comprise a linear configuration, such as a chamfer, with the linear segment extending downward on an incline from the top surface. The angle of incline of the linear segment may be anywhere from 5 to 85 degrees, as measured from the horizontal, and will preferably be between 30 and 60 degrees. Still further, the transition surface may comprise a combined linear and nonlinear configuration. 
     On any one structural member  218 , the transition surface  236  is designed to eliminate the sharp edge that would otherwise exist between the top contact flat  234  and the side faces  238 . This has the effect of reducing the abrasiveness of the floor tile or the tendency for the floor tile to abrade an object dragged over its surface. If not for the transition surface, the contact flat  234  would connect with the side faces at a sharp 90° angle, and the width of the contact flat  234  would be equal to the thickness of the structural member  218 . However, by eliminating the sharp edge that would otherwise exist between the top contact flat  234  and side faces  238 , the transition surfaces  236  on either side of the structural member  218  can reduce the width of the top contact flat  234 . Furthermore, the width of the contact flat can be optimized to contribute to the overall enhancement of the coefficient of friction. In one embodiment of the present invention, the width of the top contact flat  234  can be between 0.03 inches and 0.08 inches, and is preferably about 0.05 inches. 
     The side faces  238  and the transition surfaces  236  of the structural members serve to define the plurality of openings  230  in the upper contact surface  214  of the floor tile. The walls of the opening  238  can be perpendicular to the contact flat  234 , or can be provided with a slight taper (see  FIG. 6 ). The openings can be configured with a variety of shapes and sizes, including triangles, squares, diamonds and other polygons, as well as hemispheres, circles or other random shapes. The openings can also be configured to vary across the upper contact surface of the floor tile in repeatable patterns that include openings of different sizes and shapes, as well as non-repeatable or random patterns that can emulate natural surfaces and surroundings. However, it has been discovered that the area of the openings  230 , or aperture areas, as measured near the top contact flat  234 , can also be given a constant or uniform value that can be optimized to contribute to the overall enhancement of the coefficient of friction. The aperture area of each of the plurality of openings can be uniformly sized to be between 0.06 in 2  and 0.12 in 2 , and is preferably about 0.09 in 2 . 
     Extensive testing was conducted on a number of modular synthetic floor tiles, some of which were formed in accordance with the present invention. The tests included measured average dry dynamic coefficient of friction, measured average dry static coefficient of friction, and measured abrasion index in accordance with the ASTM F1015-3 Test. Table 1 below sets forth a representative sample of the tested floor tiles and the results obtained. 
     As a result of the testing, it has been discovered that two, three or all four of the above-mentioned design parameters, specifically the aperture area of the openings  230 , the thickness of the structural members  218 , the width of the top contact flat  234 , and the type and configuration of the transition surface  236 , can be simultaneously optimized together to provide an upper contact surface  214  of the floor tile having a high coefficient of friction and a low index of abrasion. While it can be appreciated by one having skill in the art that a plurality of structural members  218  having an upper contact surface  214  comprised of smooth contact flats  234  and transition surfaces  236  may have a low index of abrasion, it is not intuitive that this same 
                     TABLE 1                  Measured Coefficients of Friction and Abrasion Index                                                                 Measured   Measured                   Uniform   Width of   Radius of   Avg. Dry   Avg. Dry   Measured           Upper Contact   Aperture   Contact Flat   Transition   Dynamic   Static   Abrasion           Surface   Area (in. 2 )   (in.)   Surface (in.)   COF   COF   Index                                                         Tile #1   Flat, Smooth Top   0.0562   0.155   None   0.45   0.58   Not Tested       Tile #2   Flat, Smooth Top   0.0576   0.100   0.020   0.50   0.56   Not Tested       Tile #3   Flat, Smooth Top   0.0807   0.050   0.020   0.65   0.60   8.71       Tile #4   Flat, Smooth Top   0.0986   0.050   0.020   0.75   0.60   6.06       Tile #5   Flat, Smooth Top   0.0930   0.085   None   0.63   0.56   8.06       Tile #6   Ridges   0.058   0.153   Round Rib   0.52   0.64   47.98       Tile #7   Circular Protrusions   0.070   0.165   Round Rib   0.58   0.64   36.60       Tile #8   Ridges &amp; Protrusions   .0087/.0654   0.127   n/a   0.49   0.59   28.42       Tile #9   Circular Protrusions   0.0397   0.101   None   0.57   0.57   23.30       Tile #10   Ridges   0.101   0.081   None   0.58   0.63   25.70       Tile #11   Ridges   0.059   0.135   Round Rib   0.42   0.57   47.00       Tile #12   Ridges   0.059   0.125   Round Rib   0.43   0.60   37.68       Tile #13   Ridges   0.071   0.145   Round Rib   0.42   0.59   47.94                    
configuration could, when balanced with other relative design parameters as discussed herein, provide a high coefficient of friction.
 
     Referring back to  FIG. 7 , it is thought that the high coefficient of friction is formed by both a friction-based reaction force  64  generated at the contact flat  134 , and a normal reaction force  74  generated at the transition surface  136 . However, in order for an object moving on the upper contact surface of the floor tile to come into contact with the transition surface, which is below the level of the top contact surface, a portion of the object must descend below the level of the contact flats  134 , enter the opening  130  and contact the transition surface  136 . 
     Returning to  FIG. 9 , the contact between the object and the transition surface  236  is only possible if the openings  230  are large enough relative to the thickness of the structural members  218  to allow the bottom surface of the object to bend into the openings  230 . It is further considered that a structural member  218  with a wide contact flat  234  would not encourage bending and deformation of the object into the openings  230  as much as an upper contact surface  214  having narrow contact flats  234  connected with two adjacent transition surfaces  236 . Thus, it is hypothesized that the contact flat  234  must be thin enough to encourage bending over the structural members  218  and into the openings  230 , which bending places the bottom surface of the object into a position to be contacted and acted upon by the transition surfaces  236 . 
     The shape or geometry of the openings in the upper contact surface can also be a factor that contributes to the performance of the floor tile, as it has been discovered that certain openings are able to enhance the coefficient of friction of a floor tile better than others. Specifically, openings having a plurality of well-defined angles, either acute, right (90°) or obtuse, function to enhance the coefficient of friction by applying a compression force to suitably pliable objects acting on or moving about the contact surface. By providing at least one well-defined angle, or at least one segment of structural members that form a well-defined angle, assuming an appropriate size, the opening will comprise a wedge or wedge-like configuration that may receive the suitably pliable object therein as the object moves about the contact surface. Indeed, the opening may be configured to receive the object as the object is subject to a load or force causing the object to press against the contact surface. Furthermore, any lateral movement of the object about the contact surface, while still subject to the downward pressing load or force, will cause the portion of the object within the opening to press against the sides of the opening, or rather the structural members defining the opening. If the lateral movement is such so as to cause the portion of the object within the opening to press into the wedge formed by the well-defined angle, various compression forces will be induced that act on the object, which compression forces function to increase the coefficient of friction. 
     More specifically, each of the openings are configured to receive and at least partially wedge a portion of an object acting on the contact surface to enhance the coefficient of friction of the floor tile, and to provide increased traction about the contact surface. Indeed, the floor tile is configured with an enhanced coefficient of friction, which is at least partially a result of the size and geometry of the openings in the contact surface. For example, an object, such as a shoe being worn by an individual participating in one or more sports or activities, acting on or moving about the contact surface may be received within the openings, including the wedged segment of the openings. In other words, at least a portion of the object may be caused to extend over the edges of the structural members of the contact surface and into the openings in the floor tile. This is particularly the case if the object is at least somewhat pliable. 
     As the object is caused to further move laterally across the contact surface in a direction toward the well-defined angle (such as in the case of an individual initiating movement in a certain direction), the object will be further forced into the wedge of the opening comprising the well-defined angle. As this occurs, one or more compression forces are created by the various structural members on the portion of the object extending below the contact surface and into the openings, which compression force increases as the object is further wedged into the acute segment of the opening. As the object is wedged into the opening, and as the compression force on the portion of the object within the opening increases, the coefficient of friction is observably increased, which results in increased traction about the contact surface. 
     In operation, the compression force functions to increase the force necessary to remove the object from the opening. Stated differently, in order to progress in its movement about the contact surface, the object must be removed or drawn from the opening(s). In order to be removed or drawn from the opening(s), any compression forces acting on the wedged portion of the object, as applied by the structural members defining the opening(s), must be overcome. This increase in force required to draw the object from the openings and to move the object about the contact surface enables the floor tile and the resulting flooring system to exhibit enhanced performance characteristics as the traction about the contact surface is increased. 
     It is noted that the compression forces that act on the object to increase traction are small enough so as to not significantly increase the drag on the object, which might otherwise result in a reduction of efficiency of the object as it moves or is caused to be moved about the contact surface. In other words, an object moving about the contact surface will not encounter any noticeable drag nor any reduction in efficiency. Quite the contrary, it is believed that the increase in coefficient of friction or traction produced by the acute segments in the openings of the floor tile will instead function to increase the efficiency of the object&#39;s movements by reducing the amount of slide or slip about the contact surface. This perceived increase in efficiency far outweighs any negative effect that an object might experience as a result of a slight increase in drag. 
     To provide at least one well-defined angle, the opening will consist of one or more shapes or geometries having a well-defined angle. Some of the geometries contemplated comprise quadrilaterals, such as squares, rectangles and diamond-shaped openings, triangular openings, and other geometries having polygonal shapes, such as pentagons, hexagons, octagons, etc. Each of these shapes are made up primarily of linear segments or sides. Moreover, openings comprising various nonlinear or curved segments or sides are also contemplated, such as circles, ovals, etc. Although these do not have well defined angles, they still can operate similar to openings made up of linear segments in that they can effectively provide a wedge-like function. 
     As discussed hereinabove, the openings must be appropriately sized in order to be able to receive a portion of the object therein. Indeed, openings too small will have the effect of reducing the amount of the object that may be received into the opening, as well as the extent to which the object extends into the opening. As such, and as discussed above, the size of the opening for a given floor tile may be optimized. 
     The size of an opening may be measured in one of several ways. For instance, each of the openings will comprise a perimeter defined by the various structural members making up the perimeter. A measurement of this perimeter, taken along all sides, will provide a general size of the opening. It is contemplated that an optimal sized opening, measured in this way, will comprise a perimeter measurement ranging from 1.0 inches to 1.5 inches. 
     Another way the openings may be determined is by measuring their length and width, as taken from the two furthest points of the opening existing along x-axis and y-axis coordinates. It is contemplated that an optimal sized opening, measured in this way, will comprise a length ranging from 0.25 inches to 0.75 inches and a width ranging from 0.25 inches to 0.75 inches. 
     Still another measurement of the size of an opening may be in terms of its area, or rather its opening area as defined herein. Indeed, the openings may comprise an area ranging from 0.06 in 2  to 0.12 in 2 . 
     The size of the openings is directly related to the ratio of surface area to opening area. Indeed, the size of the openings may dictate the surface area provided by the top surfaces of the structural members, and thus the contact surface. Conversely, the surface area of the top surfaces of the structural members, and thus the contact surface, may dictate the size of the openings. As can be seen, these two are inversely related. An increase in one will decrease the other. As such, the ratio of these two design parameters is significant as the manipulation of this ratio provides another way to modify and enhance the coefficient of friction of the floor tile. 
       FIGS. 10 and 11  illustrate in greater detail how the shape and size of the openings in the upper contact surface can improve the traction index, or coefficient of friction, for an individual participating about a flooring system comprising a plurality of modular floor tiles formed in accordance with the present invention. Specifically,  FIGS. 10 and 11  illustrate a portion of the sole  304  of a shoe (not shown) of an individual as acting on and moving about the upper contact surface  314  of a present invention floor tile  310  during a sporting event or other activity. The openings  330 - a  and  330 - b  comprise a diamond shaped geometry similar to the ones illustrated in  FIGS. 3-5 , and the shape and profile of the structural members  318  and  322  can further include transition surfaces  336  and contact flats  334  which cooperatively act to enhance the coefficient of friction. 
     As one or more force normal F N  act on the sole  304  of the shoe (assuming a suitable degree of pliability within the sole), such as that caused by the weight of the individual wearing the shoe and/or any movements initiated by the individual, a portion of the sole  304  is caused to be received into the openings  330 - a  and  330 - b  formed in the contact surface  314  of the floor tile  310 , which portion of the sole  304  is identified as portion  306 . The openings  330 - a  and  330 - b  are sized so as to permit this, as is the narrow width of the contact flat that provides for increased bending and deflection of the sole of the shoe into the openings. 
     Furthermore,  FIG. 11  illustrates the effect of any lateral forces F L  acting on the sole  304  of the shoe. As shown, in the event one or more lateral forces F L  is caused to act on the sole  304 , and therefore the portion  306  of the sole  304  received in the opening  330 , in the direction of one of the opposing well-defined angles α of the opening  330 , this will cause the portion  306  of the sole  304  to wedge within the well-defined angle α defined by the side faces  338  and transition surfaces  336  of structural members  318  and  322 . As this happens, one or more compression forces F C  are induced by the structural members  318  and  322 , which act on the portion  306  of the sole  304  of the shoe within the opening  330  to essentially squeeze the portion  306 , as indicated by the several longitudinal lines of the sole  304  that converge upon one another within the acute angle of the opening  330 . As discussed above, this effectively functions to increase the coefficient of friction about the contact surface  314 . 
     In summary, it has been discovered that the degree of the well-defined angles, the size of the openings, the thickness of the structural members, the width of the contact flats and the radius of curvature of the transition surface may all be manipulated to enhance the coefficient of friction of the floor tile. 
       FIGS. 12 and 13  illustrate additional exemplary floor tile embodiments, each one comprising a plurality of openings or depressions having at least one well-defined angle. For example, shown in  FIG. 12  is an exemplary embodiment of an upper contact surface  414  similar to the upper contact surface depicted in  FIGS. 8-9 , with the exception that the upper contact surface  414  has depressions  430  instead of through openings. The depressions can be defined by structural members  418  which comprise an upper contact flat  432 , a transition surface  436  and side faces  418 , and can be deep enough to allow a portion of an object moving on the upper contact surface  414  to enter the depression and be acted upon by the transition surfaces and the well-defined angles. The depression can have a bottom surface  440  that may or may not include a drain hole  442 . While a contact surface with depressions that hold or temporarily retain water may not be preferable for outdoor applications, it may prove beneficial in indoor applications by providing a high traction, low abrasion contact surface with a stiffer, stronger support base. 
       FIG. 13  illustrates an exemplary floor tile  510  as having a upper contact surface  514  comprising a plurality of openings  530  having a triangular shaped geometry, and is provided to further illustrate a preferred aspect of the present invention in which each of the plurality of openings in the upper contact surface have a uniform area of the opening, or aperture area, and is bounded and defined on all sides by structural members having a uniform thickness. The shapes can be selected from the group of shapes consisting of triangles, quadrilateral, pentagons, and hexagons, or any other shape that allows for a repeatable pattern of openings having well-defined angles, and with each opening having a uniform aperture area and a perimeter defined and bounded by structural members that are of uniform thickness. 
     The foregoing detailed description describes the invention with reference to specific exemplary embodiments. However, it will be appreciated that various modifications and changes can be made without departing from the scope of the present invention as set forth in the appended claims. The detailed description and accompanying drawings are to be regarded as merely illustrative, rather than as restrictive, and all such modifications or changes, if any, are intended to fall within the scope of the present invention as described and set forth herein. 
     More specifically, while illustrative exemplary embodiments of the invention have been described herein, the present invention is not limited to these embodiments, but includes any and all embodiments having modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those skilled in the art based on the foregoing detailed description. The limitations in the claims are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the foregoing detailed description or during the prosecution of the application, which examples are to be construed as non-exclusive. For example, in the present disclosure, the term “preferably” is non-exclusive where it is intended to mean “preferably, but not limited to.” Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims. Means-plus-function or step-plus-function limitations will only be employed where for a specific claim limitation all of the following conditions are present in that limitation: a) “means for” or “step for” is expressly recited; and b) a corresponding function is expressly recited. The structure, material or acts that support the means-plus function are expressly recited herein. Accordingly, the scope of the invention should be determined solely by the appended claims and their legal equivalents, rather than by the descriptions and examples given above.