Abstract:
A modular energy absorbing system sandwiched between an impact-receiving upper surface and a lower foundation. The energy absorbing system has one or more interconnected modules that cooperate to absorb and distribute impact forces applied thereto. Each module has one or more frustoconical support structures. At least some of the frustoconical support structures have bases that underlie the upper impact-receiving surface such as a football field or a basketball court.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a Continuation-In-Part of U.S. Ser. No. 14/533,438 filed on Nov. 5, 2014 and Ser. No. 13/865,483 filed on Apr. 18, 2013, the disclosures of which are incorporated herein by reference in their entirety 
    
    
     TECHNICAL FIELD 
     Several embodiments of this disclosure relate to articles of manufacture and methods for providing a surface underlayment system with interlocking resilient anti-slip shock tiles or modules. 
     BACKGROUND 
     To reduce injury in sporting events, a playing surface is sometimes provided with an underlayment system that absorbs and redistributes energy, thereby cushioning the blow when for example a player falls to the ground after being tackled. In an industrial setting, flooring systems are sometimes provided that absorb forces generated by repeated footfalls. Playground systems also require some means of absorbing energy to reduce the risk of serious injury when a child falls on the surfaces beneath and around playground structures. 
     Against this background, it would be desirable to provide an article of manufacture and its method of making that includes a surface underlayment system with interlocking resilient anti-slip shock tiles or modules that accommodate thermal expansion or contraction and can be usefully deployed indoors or outdoors in all weather conditions. 
     Ideally the tiles could be economically nested or stacked before transportation to a job site, would have a minimal installed cost; be compatible with a lower foundation and an upper surface between which they are interposed; and require little to no maintenance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a first embodiment that depicts one way in which two adjacent retention system tiles or modules may become interlocked in a partially overlapping configuration; 
         FIG. 2  is a top view which illustrates two modules that have become interlocked; 
         FIG. 3  is a sectional view taken along the line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a sectional view taken along the line  4 - 4  of  FIG. 2 ; 
         FIG. 5  illustrates a perspective view of an alternate embodiment of a frustoconical energy absorbing support structure; 
         FIG. 6  is a sectional view thereof along the line  6 - 6  of  FIG. 5 ; 
         FIG. 7  is a top view of a second embodiment of a single module; 
         FIG. 8  is an enlarged perspective view of a portion of the second embodiment; 
         FIG. 9  is also an enlarged view of a portion of the second embodiment as seen from a different vantage point from that of  FIG. 8 ; 
         FIG. 10  is an enlarged perspective view of portions of two modules after they are juxtaposed; 
         FIG. 11  is a view of the underside of the embodiment depicted in  FIG. 8 ; and 
         FIG. 12  is a view of the underside of the embodiment depicted in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     One aspect of this disclosure involves a first embodiment of a modular surface underlayment system  10  ( FIGS. 1-6 ) that lies between an upper surface  12  and a lower foundation  14  as best shown in  FIG. 3 . Other embodiments ( FIGS. 7-12 ) are discussed below. In each embodiment, the system  10  has interconnected, preferably one or more thermoplastic tiles or modules  16  that cooperate to manage energy absorption or distribution following a blow imparted to the upper surface  12  from above, while maintaining their structural interrelationship in the face of thermal expansion and contraction responses to changing environmental conditions. Each module  16  is configured to cushion the blow by absorption and/or re-distribution laterally. 
     In more detail, at least some of the modules  16  have an array of preferably frustoconical energy absorbing support structures  15 . Optionally, ribs (not shown) connect at least some of the frustoconical structures  15 . As used herein the term “frustoconical” includes a generally conical structure, the end of which has been truncated, perhaps by a planar or undulating surface (bottom surface  18 ,  FIG. 3 ) that may be parallel or inclined to its top surface  20 . The bottom surface  18  is also termed what in the game of chess is sometimes called a “rook”. 
     The bottom surface  18  of the frustoconical energy absorbing support structures  15  may or may not be circular. It could for example be oval, elliptical, square, rectangular, triangular, hexagonal or generally polygonal. Effectively the structures  15  serve as support pillars with sidewalls  24  ( FIG. 3 ) that rise from the bottom surface  18  and are configured to support the weight for instance of a 250 lb. person without collapsing. In response to impact, depending on the impacting force, the sidewalls  24  buckle and may or may not spring back to or towards an undeflected configuration, thereby absorbing or redistributing at least some of the forces that accompany impact upon the upper surface  12 . 
     It will be appreciated that the terms “top”, “bottom”, “upper” and “lower” should be construed as non-limiting. For example any of the modules  10  could be inverted. In that case the bottom surface  18  could become juxtaposed with and lie below the upper surface  12 . 
     In a preferred embodiment, the top surfaces  20  of the frustoconical structures  15  interface with the upper surface  12 , such as an artificial turf or a hard playing surface. The top surfaces  20  are generally planar and are roughly parallel to the bottom surfaces  18 . Where the frustoconical structure  15  has a bottom surface  18  that resembles a rook with crenellations, the crenellations have upper edges that are generally co-planar (see,  FIGS. 5, 6 ). 
     In one preferred embodiment (see, e.g.,  FIGS. 1-4 ), the modules  10  provide mutual support. They coordinate with and connect to one another, despite having features described below that accommodate thermal expansion and contraction. To attach adjacent modules  10 , oval female troughs or recesses  44  ( FIG. 3 ) are provided in a peripheral edge flange of a module that engage male protuberances  46  in a peripheral edge flange of an adjacent module. The oval female recesses  44  are oriented so that they are preferably substantially aligned with a major component of a direction of thermal expansion and contraction. When a male protuberance  46  is engaged by a female recess  44 , unidirectional relative movement therebetween can be accommodated without the buckling of adjacent modules  10 . 
     If desired, lugs  50  and grooves  52  ( FIG. 3 ) can be provided in the walls of male  46  and female  44  members (or vice-versa) to provide a snap-fit engagement mechanism between adjacent modules  10 . The lugs  50  and grooves  52  may be defined continuously or intermittently in the sidewall  44 ,  46 . Optionally, a flooring surface  12  can be laminated to the underlayment system  10 . In this embodiment, the cone array  15  and male members  46  are covered by the flooring surface  12  and the female members  44  exposed. When the laminated system is snapped together, the sides of the flooring surface butt together, thereby creating a continuous surface. 
     The modular energy absorbing system  10  may include a number (n) of modules  10  (where 1&lt;n&lt;1,000,000) depending on the desired footprint on the lower foundational surface  14  over which the system  10  is installed. 
     One feature of the disclosed structure is that when the upper surface  12  overlies the modules  10 , a firm feel under foot is experienced that is relatively uniform over the middle region of a module  10  and over its edges or peripheral flanges that overlap with those of adjacent modules  10 . Preferably, the weight of for example, a pedestrian or player is distributed evenly over multiple frustoconical structures  15  associated with one or more modules. 
     In some cases, (e.g.,  FIGS. 5, 6 ) a module  16  is positioned so its undulating cone top surface  18  engages an underlying foundation or support structure  14 . Undulations are provided to enable point contact between the surface  18  and the underlying support surface  14 , as contrasted with an area of contact. If desired, apertures  19  can be provided in at least some of the cone bottom surfaces  18  for drainage and weight reduction. One purpose of the rook-like feature is that when there is a hole  19  in the contoured surface, the hole  19  does not plug when placed adjacent to a flat surface such as a concrete floor or flat planar surface  14 . If the rook feature is not present then the perforation seals against the flat surface  14  and prevents water from draining through the system. 
     Once the complete modular system  10  has been installed, it may be covered with an upper surface  12 , such as a basketball arena or gymnasium floor or layers of permeable materials like synthetic turf, natural grass, sedum, geotextiles, and the like to create a finished surface that is both functional and aesthetically pleasing. A preferred embodiment has a geo textile both above and beneath the underlayment system  10 . The lower geotextile prevents the system  10  from settling into the lower foundation  14  and fine particulates from migrating upward. The upper geotextile prevents the migration of infill materials such as sand and crumb rubber through the carpet and into underlying recesses. Filled, or partially filled recesses, have a reduced ability to attenuate impacts. If desired, the system can utilize green products in the upper surface  12 . As used herein the term “green product” includes products that have these among other attributes:
         Energy efficient, durable and often have low maintenance requirements.   Free of Ozone depleting chemicals, toxic compounds and don&#39;t produce toxic by-products.   Often made of recycled materials or content or from renewable and sustainable sources.   Obtained from local manufacturers or resources.   Biodegradable or easily reused either in part or as a whole.       

     See, http://www.isustainableearth.com/green-products/what-is-a-green-product 
     It will be appreciated that the upper surface  12  can be laid across or secured to one or more modules  10 . Optionally, a flooring surface  12  can be laminated to the underlayment system  10 . In this embodiment, the cone array  15  and male members  46  are covered by the flooring surface  12  and the female members  44  exposed. When the laminated system is snapped together, the sides of the flooring surface butt together, thereby creating a continuous surface. Optionally, anti-friction lugs  23  ( FIG. 3 ) are provided in the upper surface  20  to eliminate or reduce slippage between the energy absorbing module  10  and the upper surface  20 . Similarly, anti-friction lugs can be provided in the bottom surface  18  of at least some frustoconical structures  15  to reduce slippage over the lower foundation  14 . 
     This disclosure now turns to other embodiments ( FIGS. 7-12 ), in which a long channel  50  is punctuated by traverse ribs  53 . Optionally, longitudinally oriented ribs  55  may be provided between the transverse ribs  53  ( FIG. 7 ). Such structures provide a positive engagement or adequate snap retention between adjacent tiles, panels or modules. Without the ribs  53 , the long continuous channel  50  may open up too easily and adjacent tiles may undesirably slide or become separated prematurely. Between the long interlocked channels  50  and the lugs  23  ( FIGS. 3, 7 ) a shallow u-shaped channel  56  runs along one side of the module  16 . The channel  56  allows for expansion and contraction perpendicular to the channel  50 . 
     It will be appreciated that the disclosed underlayment system may not only underlie artificial turf but also other flooring systems. The drainage holes  19  are optional. In some applications, for example where the upper impact-receiving surface includes an impermeable surface such as a running track, gym floor, floor tile, etc., there may or may not be a benefit from having the rook top  18 . These include turf underlayment, playground underlayment, and other systems where the underlayment lies between a wear surface and a drainage system. 
     One aspect of the system disclosed is that interaction between plastic and a flat surface may be noisy. For example, the system may flutter when displaced relative to the surface above or below and generate sound at a decibel level that may be objectionable. Therefore, alternate embodiments include a thin foam or felt layer interposed between the upper surface  12  and the disclosed energy absorbing system. For instance, most turf systems are installed over a compacted stone base. In such applications, a permeable non-woven or woven PP geo textile not only deadens the noise but also prevents the disclosed system from settling substantially into the stone base or the stone base from migrating up between the frustoconical structures  15 . This thin layer promotes drainage but also prevents relative movement or migration of adjacent layers. In an indoor environment, placement of a foam or felt pad underneath the energy absorbing system would tend to deaden that noise. 
     It will be appreciated that the underlayment systems may or may not be recoverable. For example, a non-recoverable polypropylene or thermoplastic urethane or other thermoplastic may be suitable for use in basements when moisture and mildew could otherwise be an issue. In such applications, the energy absorber  10  would not crush significantly, let alone recover to or toward an undeflected state. Instead of cushioning the blow by deformation, resistance to impact would be relatively inelastic. Then in the absence of drainage holes, the disclosed system would constitute a reservoir or vapor barrier. As used herein the term “thermoplastic” means “a polymer material that becomes pliable with heat, and with sufficient temperature, a liquid. When cooled, thermoplastics return to solid.” See, http://lookup.computerlanguage.com/host_app/search?cid=C999999&amp;term=thermoplastic&amp;lookup.x=0&amp;lookup.y=0 
     Besides injection molding, one method by which to manufacture the disclosed system is thermoforming. Such approaches enable easy performance tuning by changing sheet thickness and material type that is thermoformed over the tool. It will be appreciated that thermoforming lends itself to rapid high volume manufacturing and low manufacturing costs. Ideally, a polyolefin thermoplastic, such as a polypropylene copolymer, offers an optimal balance of cost and performance. Additional materials may be compounded into the thermoplastic, such as flame retardant packages, to meet customer building codes or performance criteria. 
     The system can be easily and economically be transported to the job site due to the high packaging density (nesting) of the modules  10 . Besides the above advantages, the system is light in weight and low in cost to manufacture. 
     In summary, the disclosed system offers at least these benefits: minimal installed costs; compatibility with existing foundations; and little to no maintenance. 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The Figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.