Abstract:
The disclosures made herein are directed to artificial turf systems and installation techniques that are adapted for providing a target maximum shock rating (i.e., “Gmax” rating) without the use of compliant infill materials such as, for example, crumbled rubber. More specifically, such disclosures are directed to artificial turf systems and installation techniques that achieve such target maximum shock rating without the use of compliant infill materials even in applications where the artificial turf system is installed over a substantially non-displacing support surface such as asphalt or crushed stone. Furthermore, such artificial turf systems and installation techniques can be specifically configured for use on a support surface that is substantially impermeable to liquid that might drain off of or through the artificial turf.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The disclosures made herein relate generally to artificial turfs and, more particularly, to artificial turf systems and installation techniques that are adapted for providing a target maximum shock rating (i.e., “Gmax” rating). 
       BACKGROUND 
       [0002]    Artificial turf sports playing surfaces (i.e., artificial turf sports surfaces) are becoming increasingly popular as a replacement for natural grass in stadiums, on golf courses, on play ground areas, on sports playing fields, and the like. Artificial turf sports surfaces require less maintenance than natural grass surfaces, and do not require water, chemicals or sunlight for satisfactory performance and sustainability, thereby enhancing their environment impact with respect to natural grass surfaces. Artificial turf sports surfaces require no sunlight, can be laid indoors, and can even be made to be portable for allowing it to be laid and removed as and when needed for use. Artificial turf sports surfaces offer unmatched versatility because they can be placed in totally dry regions, regions of high rainfall, extreme heat conditions and cold regions. 
         [0003]    Most artificial turfs are comprised of rows of flat ribbons, strips, twisted yarns, fibrillated yarns, texturized yarns and like (i.e., the artificial grass blades). The artificial grass blades are tufted such that a first end is engaged with the synthetic backing material (e.g., within holes thereof) and such that a second end is above a top surface of the backing material. The first end of the artificial grass blades are then bonded into the synthetic backing material in a manner that is intended to prevent removal of the artificial grass blades from the backing material. 
         [0004]    As used in artificial turf sports playing surfaces, artificial turf is laid over a support surface with a bottom face of the backing material facing the support surface. With the artificial grass blades stand vertically in the backing material, the space between the artificial grass blades is then filled with fine granulated or ground particulate materials such as sand, polymer granules, ground or granulated rubber, polymer foam etc (i.e., the infill). The infill is provided to a specified depth with respect to a free length of the artificial grass blades (i.e., length above the backing material) such that it supports the artificial grass blades in the vertical position and also provides impact cushioning for the comfort and safety of individuals engaged in activity on the artificial turf sports playing surface. The free length of the artificial grass blades is typically dependent upon an intended end use of the playing surface. The artificial grass blades act like grass and extend above the level of infill so that they simulate the aesthetic characteristics and, to some degree, behavior of natural grass. 
         [0005]    It is well known that preferred types of infill traditionally have included a compliant granular component that serves to meet a desired (e.g., required) maximum shock rating. In particular, crumbled rubber made from recycled rubber (e.g., vehicle tires) is a compliant granular component that has been used in infill material for artificial turf sports playing surfaces for decades. However, there have become concern that the use of certain such compliant granular component such as crumbled rubber can be a health hazard. This has prompted some governmental jurisdictions to require certain disclosures and warning regarding the potential hazardous materials used in artificial turf sports playing surfaces. For example, California has passed legislation referred to as “Proposition 65”, which provides that persons doing business in California may not expose individuals to chemicals known to cause cancer and/or reproductive toxicity without first giving clear and reasonable warning, nor discharge such chemicals into drinking water. 
         [0006]    Due at least partially to the potential that crumbled rubber made from recycled rubber may include carcinogens, crumbled rubber is a material that is subject to the notice provision of Proposition 65. As such, the use of crumbled rubber made from recycled rubber has fallen out of favor as a material for infill in artificial turf sports playing surfaces. Although crumbled rubber made from virgin rubber materials is not is subject to the notice provision of Proposition 65, its cost often prohibits it from use as an in-fill material for artificial turf sports playing surfaces. 
         [0007]    Therefore, an artificial turf system and associated installation technique that provides a desired shock rating while utilizes an infill material that is cost effective, that resist compaction and that is known to be non-hazardous would be advantageous, desirable and useful. 
       SUMMARY OF THE DISCLOSURE 
       [0008]    Embodiments of the present invention are directed to artificial turf systems and installation techniques that are adapted for providing a target maximum shock rating (i.e., “Gmax” rating) without the use of compliant infill materials such as, for example, crumbled rubber. More specifically, embodiments of the present invention are directed to artificial turf systems and installation techniques that achieve such target maximum shock rating without the use of compliant infill materials even in applications where the artificial turf system is installed over a substantially non-displacing support surface such as asphalt or crushed stone. Still further, such artificial turf systems and installation techniques can be specifically configured for use on a support surface that is substantially impermeable to liquid that might drain off of or through the artificial turf. 
         [0009]    In one embodiment of the present invention, an artificial turf installation comprises a base structure, a layer of resilient material, an artificial turf, and infill material. The base structure is formed from a layer of compacted aggregate material. The base structure defines a turf support surface; a layer of resilient material having opposing sides. The layer of resilient material extends over and is supported on the base structure with a first side thereof facing the base structure. The artificial turf includes a plurality of spaced-apart rows of synthetic grass blades and a primary. An upper end portion of the synthetic grass blades extends above a first side of the primary and a lower end portion of the synthetic grass blades extents through the primary to a second side thereof. The primary extends over and is supported by the layer of resilient material such that the first second side of the primary faces the second side of the layer of resilient material. The layer of infill material on the first side of the primary between the spaced-apart rows of synthetic grass blades. The layer of infill material defines a playing surface that is below the upper end portion of at least a portion of the synthetic grass blades. The infill material consists of a particulate having an exterior surface comprising a polymeric material. 
         [0010]    In another embodiment of the present invention, a method of forming a sports playing surface. The method begins with providing a base structure by depositing a layer of asphalt and compacting the layer of asphalt to define a turf support surface. A layer of resilient material is provided on top of the turf support surface and an artificial turf is provided on top of the layer of resilient material. The artificial turf includes a plurality of spaced-apart rows of synthetic grass blades and a primary. An upper end portion of the synthetic grass blades extends above a first side of the primary and a lower end portion of the synthetic grass blades extents through the primary to a second side thereof. A layer of infill material is provided on the first side of the primary between the spaced-apart rows of synthetic grass blades. The layer of infill material defines a player support surface that is below the upper end portion of at least a portion of the synthetic grass blades. The infill material consists of a polymer-coated granular material. 
         [0011]    These and other objects, embodiments, advantages and/or distinctions of the present invention will become readily apparent upon further review of the following specification, associated drawings and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a cross-sectional view showing a view showing an artificial turf installation in accordance with an embodiment of the present invention. 
           [0013]      FIG. 2  is a cross-sectional view of an artificial turf and layer of infill material in accordance with an embodiment of the present invention. 
           [0014]      FIG. 3  is an illustrative view showing a particulate configured in accordance with an embodiment of the present invention, in which the particulate has an exterior surface comprising a polymeric material. 
           [0015]      FIG. 4  is a flow diagram showing a method for creating an artificial turf installation in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  shows an artificial turf installation  100  configured in accordance with a preferred embodiment of the present invention. Advantageously, the artificial turf installation  100  provides target shock absorption performance (e.g., compliance with California&#39;s proposition 65 legislation) while utilizes an infill material that is cost effective, that resist compaction and that is known to be non-hazardous. To this end, the artificial turf installation  100  achieves such target shock absorption performance without the use of compliant infill materials even in applications having a substantially non-displacing installation substructure and installation base such as asphalt over crushed stone, road base, soil or the like. Furthermore, the artificial turf installation  100  is substantially impermeable to liquid that might drain off of or through the artificial turf thereof. 
         [0017]    The artificial turf installation  100  includes an installation substructure  105  and a base structure  110  formed over the installation substructure  105 . The base structure  110  is preferably bordered by a substantially fixed structure such as, for example, a turf securing structure  112  (e.g., composite nailer board) and/or a curbing structure  114  (e.g., concrete curbing). A layer of resilient material  115  overlays the base structure  110 , preferably without any intervening structure therebetween. Artificial turf  120  overlays the layer of resilient material  115 , preferably without any intervening structure therebetween. A layer of infill material  125  is dispersed within the blades  130  of the artificial turf  120 . 
         [0018]    The installation substructure  105  can comprise a layer of compacted crushed rock or other load bearing material layer. In some embodiments, the installation substructure  105  can be, for example, 3 to 4 inches of class-2 road base compacted to 90% to 95%. The installation substructure  105  serves the function of providing a high-density and high strength structural layer that can withstand formation of the base structure  110  (e.g., paving), static loading of the base structure  110  (e.g., weight of the base structure  110  itself), and dynamic loading of the base structure  110  (e.g., foot traffic, vehicle traffic, and/or the like). Other suitable configurations and/or material for the installation substrate  105  will be apparent to a skilled person in view of the disclosure herein. 
         [0019]    The base structure  110  can consist of a layer of compacted aggregate composition. Asphalt is a preferred aggregate composition. In some embodiments, the base structure  110  can be, for example, 2 to 4 inches of asphalt. A preferred characteristic of asphalt is that it includes a binder that enhances longevity and strength of compaction as well as reduced permeability. Concrete is yet another material from which the base structure  110  can be formed. Other suitable configurations and/or material for the base structure  110  will be apparent to a skilled person in view of the disclosure herein. For example, it is contemplated that the base structure  110  can comprise a preformed structure (e.g., in roll or tile form) that exhibits similar characteristics as would a suitably thick layer of asphalt. 
         [0020]    The layer of resilient material  115  is preferably in the form of a pad (i.e., a shock pad). The pad can be formed of a unitary material (e.g., cast or extruded foam) or can be formed discrete particles of resilient material that are fused, bonded or otherwise held together to form a unified piece of material. In this respect, the layer of resilient material  115  has opposing surfaces and extends over the base structure  110  such that it is supported on the base structure with a first side thereof facing the base structure  110 . 
         [0021]    Referring now to  FIGS. 1 and 2 , the artificial turf includes a plurality of spaced-apart rows of synthetic grass blades  130  and a primary  140 . An upper end portion of the synthetic grass blades  130  extends above a first side of the primary  140  and a lower end portion of the synthetic grass blades  130  is engaged with the primary  140 . In preferred embodiments, the lower end portion of the synthetic grass blades  130  extends through the primary to be exposed at a second side thereof. In some embodiments, the lower end portion of the synthetic grass blades  130  is secured to the primary  140  via a layer of material applied onto the second side of the primary  140  over the second end portions of the synthetic grass blades  130 . In preferred embodiments, an average minimum length of the synthetic grass blades  130  is between about 0.75 and 2.5 inches and is preferably about 1.75 inches. Materials from which the synthetic grass blades  130  and the primary  140  are made are well-known to a skilled person. Furthermore, commercially-available artificial turfs are well-known and include synthetic grass blades and primary made from such well-known materials. 
         [0022]    Referring to  FIGS. 1 and 2 , the layer of infill material  125  covers the first side of the primary between the spaced-apart rows of synthetic grass blades  130 . The layer of infill material  125  defines a playing surface  145  that is below the upper end portion of at least a portion of the synthetic grass blades  130 . Preferably, the infill material  125  is homogeneous throughout its entire depth from the primary to the playing surface. A thickness T of the layer of infill material  125  can be equal to or greater than substantially 75% a length L of the synthetic grass blades  130 . In the case of synthetic grass blades  130  having a range of lengths L, the thickness T of the layer of infill material  125  can be equal to or greater than substantially 75% an average of the range of lengths L (i.e., average length) of the synthetic grass blades  130  or can be equal to or greater than substantially 75% a shortest of the range of lengths L (i.e., average minimum length) of the synthetic grass blades  130 . 
         [0023]    In preferred embodiments of the present invention, an artificial turf installation is configured for achieving target shock absorption performance. In such preferred embodiments, the layer of resilient material  115  and the layer of infill material  125  can be jointly configured to provide a level of vertical compliance (i.e., impact damping) that leads to the Gmax rating not exceeding 130 g&#39;s being achieved (i.e., the target Gmax rating), such as determined by testing in accordance with ASTM F355-A. To this end, it is preferred in some embodiments for the layer of resilient material  115  to provide at least 90% of the vertical compliance required for achieving the target Gmax rating, with the remaining portion of the required vertical compliance being provided by the layer of infill material  125 . 
         [0024]    A preferred embodiment of the layer of resilient material  115  can be a preformed shock pad. One example of such a preformed shock pad is commercially-available from Schmitz Foam Products under the product designation of ProPlay Sport  23 D, which is a thermal bonded (closed-celled) cross-linked polyethylene foam having the following physical and functional characteristics: thickness of about 23 mm thick; unit mass of about 4.0 kg/sq. meter; tensile strength of about 260 kPa (i.e., about 46 psi); compressive strength at 25% compression (e.g., compressed to about 17 mm thick) of about 188 kPa; compressive strength at 50% compression (e.g., compressed to about 12 mm thick) of about 571 kPa; and compressive strength at 75% compression (e.g., compressed to about 6 mm thick) of about 2920 kPa. In view of the disclosures made herein, a skilled person will appreciate other implementations of a layer of resilient material that provides necessary physical and functional characteristics that suitably contribute to the vertical compliance of an artificial turf installation configured in accordance with the present invention. 
         [0025]    A preferred embodiment of the infill material  125  consists of a particulate having an exterior surface comprising a polymeric material. As shown in  FIG. 3 , in preferred embodiments, the particulate having the exterior surface comprising the polymeric material is a polymer-coated granular material such as, for example, acrylic coated sand  200 . The acrylic coated sand  200  includes a sand particle  205  that is fully or partially covered by a layer of acrylic material  210 . The layer of acrylic material  210  approximates the exterior shape of the sand particle  205 . However, thickness of the layer of acrylic material  210  and considerations such as its as-formed viscosity and surface tension can cause the layer of acrylic material  210  to smooth out inward depressions/cavities/valleys in the sand particle  205 , thereby resulting in the acrylic coated sand  200  having a smoother exterior surface than the sand particle  205 . This smoother exterior surface (and slightly larger average diameter of the acrylic coated sand  200 ) advantageously reduces an ability for the acrylic coated sand  200  to pack together. Furthermore, the layer of acrylic material  210  provides additional strength that reduces the potential for the sand particle  205  to fracture into two or more smaller pieces, which further reduces an ability for the acrylic coated sand  200  to pack together. A key benefit to the acrylic coated sand  200  being resistance to packing together is that being less packed results in a layer of the acrylic coated sand  200  offering greater cushion effect as compared to a layer of uncoated sand particles having nominally the same thickness (e.g., 75% the length L of the grass blades). In view of the disclosures made herein, a skilled person will appreciate other implementations of the infill material  125  in which it has an exterior surface comprising a polymeric material (e.g., a fully polymeric granular material) 
         [0026]      FIG. 4  shows a method  400  of creating an artificial turf installation in accordance with an embodiment of the present invention. The method  400  can begin with an installation substrate formation step  405  being performed such as to form, for example, the installation substructure  105 . After performing the installation substrate formation step  105 , a base structure formation step  410  is performed such as to form, for example, a layer of asphalt on top of the installation substrate. Thereafter, a resilient material layer providing step  415  is performed such as to lay, for example, a shock pad on top of the base structure. After the resilient material layer providing step  415  is performed, an artificial turf installing step  420  is performed such as to provide artificial turf (e.g., Artificial turf  120 ) on top of the resilient material layer, followed by an infill depositing step  425  being performed creating a layer of infill material (e.g., a layer of the acrylic coated sand  200 ) on top of a primary of the artificial turf between rows of synthetic grass bladed that are engaged with and extending above the primary. 
         [0027]    Although the invention has been described with reference to several exemplary embodiments, it is understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the invention in all its aspects. Although the invention has been described with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed; rather, the invention extends to all functionally equivalent technologies, structures, methods and uses such as are within the scope of the appended claims.