Patent Publication Number: US-11639585-B2

Title: Support layer for supporting an artificial turf assembly, and artificial turf system

Description:
TECHNICAL FIELD 
     The present invention relates to a support layer for supporting an artificial turf assembly, and to an artificial turf system. The support layer of the present invention may be used as supporting layer for artificial turf systems, for example for use in athletic fields (e.g. soccer fields), for equestrian applications, in ornamental lawns and gardens, and in children&#39;s playgrounds. 
     BACKGROUND 
     Artificial turf is widely used for athletic fields/courses for playing sports such as soccer, field hockey, football, rugby, golf, etc., and for playgrounds as well as for equestrian use. An artificial turf system is known and it typically buildup of a base layer or foundation layer (e.g. compacted sand or dirt, concrete, asphalt, gravel, or other compacted particulate or granulate material; said foundation layer being graded so that water will not form pools on the field), a support layer (e.g. according to the present invention) and the artificial turf (comprising a porous turf backing to which a plurality of plastic grass-like filaments/strands are attached, preferably comprising an infill material between approx. the lower half to two-third of the vertically arrange filaments). 
     SUMMARY 
     In an aspect, the invention relates to a support layer, for supporting an artificial turf assembly. Said support layer has been formed of a polymeric foam, preferably having a density of between 20 and 70 gram per liter, such as a polyolefin foam; and has an upper side and a lower side. In use the support layer has been placed with the lower side thereof on a base surface and supports, on the upper side thereof, the artificial turf assembly. The support layer comprises a plurality of through drainage holes extending from the upper side to the lower side for allowing liquid such as rain water to flow via the plurality of drainage holes from the upper side to the lower side, and also comprises a plurality of channels at the lower side for allowing liquid such as rain water to flow through the channels along the lower side, wherein each of said plurality of drainage holes debouches into one of the plurality of channels. In certain aspects, at least partial drainage holes may be formed on peripheral edges of the support layer that form complete drainage holes when one support layer is assembled and/or connected to another support layer. These partial drainage holes being configured to direct water from an upper side of the support layer to a lower side of the support layer. An effect of the support layer according to the invention is the provision of shock absorption and dewatering to the artificial turf covering said support layer thereby improving safety and user-friendliness for users of said artificial turf. 
     In an embodiment the support layer may have been formed as a plate element, preferably being a rectangular plate element. Alternatively the support layer may be provided on a roll. 
     In an embodiment the plurality of channels extend mutually parallel and are fluidly connected to each other by means of a plurality of cross channels. This way, any liquid such as rain water may easily flow along the lower side of the layer. 
     The plurality of cross channels may have a smaller cross sectional area than the plurality of channels, the plurality of cross channels preferably having a smaller width and/or a smaller depth than the plurality of channels. 
     In an embodiment the plurality of channels extend in a length direction, the plurality of cross channels extending, mutually parallel, at an angle in the range of 20 to 90 degrees, preferably from 20 to 60 degrees, more preferably from 30 to 50 degrees, to the length direction. 
     In an embodiment the support layer comprises a plurality of individual elevated portions and/or sloped portions formed on the upper side of the support layer that are angled towards one or more the drainage holes. An effect of the elevated portions and/or sloped portions is an improved drainage of liquid to the individual drainage holes. 
     The plurality of elevated portions may be dome, pyramid, truncated pyramid, cone, truncated cone or tetrahedron shaped. They preferably are pyramid shaped. 
     Each of the plurality of elevated portions may have at least three of the plurality of drainage holes along the circumference thereof preferably wherein each of the elevated portions has a triangular or quadrilateral shape, in plan view, wherein a drainage hole is present at each of the corners of said shape. Each of the plurality of elevated portions preferably has a quadrilateral shape, further preferably square shape, in plan view, wherein a drainage hole is present at each of the four corners of said quadrilateral shape. 
     The plurality of drainage holes are provided in parallel rows extending in a first direction, the holes in each of the rows being spaced apart at a constant pitch, so as to define an area between each at least three directly adjacent drainage holes, preferably between four directly adjacent holes, wherein an elevated portion of the plurality of elevated portions is formed on each area. 
     Each two adjacent drainage holes in neighbouring rows may be spaced apart at a distance, wherein said distance is equal to the pitch, defining a square area between four directly adjacent drainage holes, which area is thus covered by one of the elevated portions. 
     Drainage holes, preferably each drainage hole, of the plurality of drainage holes may have a widened entrance portion at the upper side of the support layer. As a result, drainage of liquid at the upper side of the support element is improved. In an embodiment the widened entrance portion is star-shaped or cross-shaped in plan view, each arm of the shape being sloped, that means gradually sinks into the support layer from a free end of the arm towards the hole. In certain aspects, each arm of one widened entrance portion is spaced apart and discontinuous relative to another arm of another widened entrance portion. In certain aspects, arms from each entrance portion are axially aligned with arms from another entrance portion(s) but are spaced apart and are not fluidly connected to one another on the upper side of the support layer. 
     In an embodiment at least two of the arms extend in line with the direction of extension of the rows. In case of a cross-shaped entrance portion preferably the remaining two arms extend perpendicular to the direction of extension of the rows. In case of rectangular or square elevated portions, the arms thus each extend in between a part of the circumference of two respective adjacent elevated portions. 
     An elevation of each of the plurality of elevated portions may be in the range of 1 to 5 mm. A maximum thickness of the support layer may be in the range of 10 to 80 mm, in the range of 10 to 70 mm, in the range of 15 to 70 mm, in the range of 10 to 65 mm, in the range of 15 to 65 mm, 10 to 60 mm, 15 to 60 mm, 10 to 55 mm, 15 to 55 mm, 10 to 50 mm, 15 to 50 mm, 10 to 45 mm, 15 to 45 mm, such as between 20 and 80 mm, such as between 20 and 65 mm, such as between 20 and 55 mm, such as between 20 and 45 mm, wherein any of the endpoints falling within the above disclosed ranges may serve as endpoints for any additional range(s) falling there between (but not explicitly disclosed above). A depth of the plurality of channels may be in the range of 25 to 75 percent of a total thickness of the support layer, preferably in the range of 30 to 50 percent. Said polymeric foam may have a material density of between 20 and 70 gram per liter, preferably between 30 and 50 gram per liter. In case that the support layer is in the form of a plate element, the surface area in plan view of the support plate element is in the range of 0.5 to 4 m 2 , preferably wherein the plate element is rectangular having a length in the range of 0.5 to 4 m and a width in the same range, the length further preferably in the range of 1 to 2 m, still further preferably about 1.6 m, the width further preferably in the range of 1 to 1.5 m, still further preferably about 1.15 m. 
     Said polymeric foam may be a polyolefin foam, preferably a polyethylene foam (expanded polyethylene) or polypropylene foam (expanded polypropylene) or a mixture thereof. The polymer of the foam may be a homopolymer, e.g. a homo-polypropylene or a homo-polyethylene, or it may be a co-polymer, e.g. a copolymer of ethylene and propylene. Mixtures of homopolymers and/or co-polymers may also be envisaged. In addition, mixture of the same type of polymer may be used having a different density, for example a first EPP having a first density and a second EPP having a second density. Other examples of suitable materials are expanded polylactic acid (EPLA), expanded polystyrene (EPS) and mixture of all of these. The materials for use in the support layer according to the present invention may be so-called virgin (new) materials or may be recycled materials. Mixture of virgin and recycled materials may also be used. Any combination of type of polymer, density of polymer and origin (virgin versus recycled) may be used. In other words, said polymeric foam may be a polyolefin foam, preferably a polyethylene foam (expanded polyethylene EPE), polypropylene foam (expanded polypropylene EPP), polylactic acid foam (expanded polylactic acid EPLA), polystyrene foam (expanded polystyrene EPS), co-polymer foam comprising at least monomers, preferably ethylene and propylene, or one or more mixtures of these polymeric foams. 
     The support layer may have connecting elements at a circumferential edge thereof for connecting the support layer to further support layers such that the support layers are flush with respect to each other, preferably wherein the connecting elements are arranged for connecting the layer to a further layer in a form-closed manner such as a dovetail joint. This way, a large area may be covered by a plurality of support layers, preferably being in the form of plate elements, which plurality of support layers are effectively connected to each other. 
     The invention also relates to an artificial turf system, comprising
         an artificial turf assembly,   a support layer according to the invention, preferably said support layer being in the form of a plurality of panel elements as described above, supported on a base surface such as a layer of sand, wherein the (plurality of panel elements of the) support layer forms, at the upper sides thereof, a closed support surface supporting the artificial turf assembly.       

     Embodiments of the support layer according to the invention as described above are also applicable for the artificial turf system according to the present invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention is described hereinafter with reference to the accompanying drawings in which an embodiment of the present invention is shown and in which like reference numbers indicate the same or similar elements. 
         FIG.  1    shows, in plan view, an embodiment of a support layer according to the present invention, 
         FIG.  2    shows section II-II of  FIG.  1   , 
         FIG.  3    shows a front view of the layer of  FIG.  1   , 
         FIG.  4    shows section IV-IV of  FIG.  1   , 
         FIG.  5    shows detail V of  FIG.  2   , 
         FIG.  6    shows detail VI of  FIG.  1   , 
         FIG.  7    shows detail VII of  FIG.  1   , 
         FIG.  8    shows, in bottom view, the support layer of  FIG.  1   , 
         FIG.  9    shows detail IX of  FIG.  8   , 
         FIG.  10    shows detail X of  FIG.  8   , 
         FIG.  11    shows an artificial turf system according to the present invention, 
         FIG.  12    shows, in 3-dimensional view, a part of an upper side of the support layer of  FIG.  1   , 
         FIG.  13    shows a perspective view of a second embodiment of the support layer, 
         FIG.  14    shows a top view of the second embodiment of the support layer, and 
         FIG.  15    shows section B-B of  FIG.  14   . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1 - 10  and  12    show a support layer  1  according to the invention. The support layer is arranged for supporting an artificial turf assembly  30  in use. The support layer  1  is in that case part of a plurality of such support layers  1  of a support system  50  according to  FIG.  11   , the system  50  further comprising an artificial turf assembly  30 , that means, an assembly forming a surface of synthetic fibers made to look like natural grass, most often used in sports arenas but for residential lawns as well. The plurality of support layers  1  is then supported on a base surface  32  such as a layer of sand, and form, at upper sides  2  thereof, a closed support surface supporting the artificial turf assembly  32 . 
     The support layer  1  is in the form of a rectangular support plate element formed of a polymeric foam and has an upper side  2  and a lower side  3 , wherein, as mentioned, in use the support layer  1  has been placed with the lower side  3  thereof on a base surface and supports, on the upper side  2  thereof, the artificial turf assembly. At least in the present example, a length of the layer  1  is about 1.6 m and a width about 1.15 m. 
     The support layer is prepared from a polymer foam, preferably from expandable polyolefin beads that are expansion molded to provide the support layer. In an embodiment, the support layer consists of one or more expanded polypropylene (EPP) and/or one or more expanded polyethylene (EPE) materials or other materials. Co-polymeric foams may also be used as (part of) the polymeric foam. In addition, mixture of the same type of polymer may be used having a different density, for example a first EPP having a first density and a second EPP having a second density. Other examples of suitable materials are expanded polylactic acid (EPLA), expanded polystyrene (EPS) and mixture of all of these. The materials for use in the support layer according to the present invention may be so-called virgin (new) materials or may be recycled materials. Mixture of virgin and recycled materials may also be used. Any combination of type of polymer, density of polymer and origin (virgin versus recycled) may be used. 
     With “consists of” is meant consists for at least 90 wt. %, more preferably at least 95 wt. % of said expanded polymer. Other constituents may be for example fillers, colorant, stabilizers and other additives known to a person skilled in the art. The polymeric foam is preferably a so-called closed cell foam. The method of expansion molding using a closed mold under pressure is known in the art and will not be further explained here; usually steam is used to expand the polymeric beads which are optionally provided with an adhesive coating. 
     The support layer  1  comprises a plurality of through drainage holes  6  extending from the upper side  2  to the lower side  3  for allowing liquid such as rain water to flow via the plurality of drainage holes  6  from the upper side  2  to the lower side  3 . The drainage holes  6  are evenly distributed over the support layer  1 . At least in the present example a diameter of the holes is about 4 mm but may alternatively be in the range  1  to  20 , preferably 3 to 10 mm. 
     The through drainage holes ensure that water, e.g. due to rain, is drained and removed from the artificial grass surface. The structure of the through drainage holes having widened entrance portion also ensures that any infill that is washed out will be trapped. The size and frequency of the drainage holes may be selected depending of the desired water extraction rate, which depends on the expected maximum rain fall in a certain geographical area where the support layer is to be used. 
     The support layer  1  also comprises a plurality of channels  4  at the lower side  3  for allowing liquid such as rain water to flow through the channels  4  along the lower side  3 . A depth d of the channels is about 50 percent of a total thickness t of the layer  1 . 
     The channels provided at the lower surface of the support layer preferably line up over the full length and width of the ground covering support structure allowing water to run to the sides of the field. This efficient water draining by water flow in the channels at the bottom side of the support layer is increased by a slope of e.g. 0.5% in the height of the base layer towards the sides of the filed in the same orientation as the channels. 
     Each of the drainage holes  6  debouches into one of the channels  4 . The channels  4  extend mutually parallel over the entire lower side  3  of the support layer  1  and are fluidly connected to each other by means of a plurality of cross channels  8 . The cross channels have a width which is about 50 percent of the width of the channels  4  and have a depth which is about 50 percent of the depth of the channels  4 . See  FIG.  5   . The channels  4  extend in a length direction  10 , whereas the cross channels  8  extends, also mutually parallel, at an angle α of about 35 degrees to the length direction  10 , over the entire lower side  3  of the support layer  1 . 
     The support layer also has a plurality of individual—preferably pyramid shaped—elevated portions  14  at the upper side  2 . The elevated portions of the support layer provide improved drainage of the support layer by sloping towards the holes. The drainage holes  6  are provided in parallel rows  12  extending in a first direction  15 , at 45 degrees to the length direction  10 . The holes  6  in each of the rows  12  are spaced apart at a constant pitch p of about 42 mm, so as to define an area  13  between each four directly adjacent drainage holes  6 . Also, each two adjacent drainage holes  6  in neighbouring rows  12  are spaced apart at a distance r of about 42 mm, wherein the distance r is thus equal to the pitch p, thereby defining a square area  13  between four directly adjacent drainage holes  6 . See  FIGS.  6  and  7   . Each time an elevated portion  14  is formed on one of the areas  13 . Thus, each elevated portion  14  has four drainage holes  6  along the circumference thereof, wherein a drainage hole  6  is present at each of the corners of said shape, except for some further elevated portions  14 ′ at the sides of the layer. 
     As in particular shown in  FIGS.  3  and  4   , each drainage hole has a widened entrance portion  16  at the upper side  2  of the support layer  1 , to facilitate drainage to a larger extent. The widened entrance portion  16  is cross-shaped in plan view. The cross shape has four arms  18 , each arm  18  being sloped, as shown in  FIG.  4   . As the figures show, two of the arms  18  extend in line with the direction of extension  15  of the rows  12 , while the remaining two arms  18  extend perpendicular to direction  15 . Below the entrance portion  18 , the holes  6  have a main portion  19  which is of circular cross section but which may alternatively be of other cross sectional shapes such as square, oval or triangular, for example. 
     In an embodiment of the present invention, the widened entrance portion has a width of between 3 and 6 mm, preferably between 4 and 5 mm, such as between 4.2 and 4.8 mm. 
     In an embodiment of the present invention, the widened entrance portion has an angle with respect to the surface of the upper side of between 140° and 180°, preferably between 150° and 170°, such as between 160° and 165°. 
     The special effect of drainage holes with widened entrance portions is that these allow for an improved drainage as compared with holes not having these widened entrance portions; this without negatively affecting properties, such as shock absorption of the support layer. 
     Moreover, in a support layer having a plurality of individual elevated portions  14  at the upper side  2  and drainage holes with widened entrance portions, the elevated portions have a double function; i.e. water drainage to the drainage holes and uniform shock absorption in the support layer. 
     A support layer being formed of expanded polypropylene EPP and having pyramid shaped elevated portions  14  at the upper side  2 , in which each drainage hole has a widened entrance portion  16  at the upper side  2  of the support layer, was tested according to the European Synthetic Turf Organisation (ESTO) Performance Guide for Shockpads. The results can be seen in the following table. 
     The widened entrance portion  16  has a width of 4.5±1 mm and an angle with respect to the surface of the upper side  2  of 161.6°±5%. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 Requirement 
               
               
                 Property 
                 Test Condition 
                 Result 
                 ESTO Guide 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Thickness (mm) 
                 EN 9863-1 
                 23.4 
                 ≥8 mm 
               
               
                 Mass (g/m 2 ) 
                 EN 9863-1 
                 885 
                 — 
               
               
                 Density (g/L) 
                 Calculated from 
                 38 
                   
               
               
                   
                 mass 
                   
                   
               
               
                 Shock Absorption 
                 Individual result 
                 69.1 
                 ≥25% 
               
               
                 Triple A - (%) 
                 Dry at 23 ± 2° C. 
                   
                   
               
               
                   
                 Individual result 
                 69.1 
                 — 
               
               
                   
                 Frozen 
                   
                   
               
               
                 Vertical Deformation 
                 Individual result 
                 8.8 
                 — 
               
               
                 Triple A - (mm) 
                 Dry at 23 ± 2° C. 
                   
                   
               
               
                 Water Permeability 
                 EN 12616 
                 60000 
                 ≥500 
               
               
                 (mm/h) 
                   
                   
                   
               
               
                 Horizontal water  
                 ESTO Guideline 
                   
                   
               
               
                 flow (l/s · m) 
                 0.1% Slope 
                 0.388 
                   
               
               
                   
                 0.3% Slope 
                 0.645 
                   
               
               
                   
                 0.5% Slope 
                 0.800 
                   
               
               
                 Tensile Strength  
                 Unaged 
                 0.18 
                 ≥0.15 
               
               
                 (MPa) 
                 EN 12230 
                   
                   
               
               
                   
                 After Air Ageing 
                 0.19 
                   
               
               
                   
                 EN 13817/EN  
                   
                   
               
               
                   
                 12230 
                   
                   
               
               
                 Tensile Properties 
                 — 
                 105 
                 ≥75% 
               
               
                 % of unaged value  
                   
                   
                   
               
               
                 (%) 
               
               
                   
               
            
           
         
       
     
     It can be seen in Table 1 that the support layer complies with the Guidelines of the ESTO Performance Guide for Shockpads. 
     Moreover, this support layer complies with the European EN 15330-1 standard and the latest FIFA Quality Concept for Artificial Turf. This support layer shows improved water drainage when compared to support layers not having the elevated portions and widened drainage holes having a widened entrance portion; furthermore, the shock absorption is uniform over the whole are of this support layer. 
     The different properties of the support layer according to the invention are measured or calculated under the following conditions. 
     The thickness and the mass are measured according to EN 9863-1 (CSN EN ISO 9863-1: Geosynthetics—Determination of thickness at specified pressures of 2016). The density is calculated from the mass. 
     The Shock absorption is measured according to the Guidelines of the ESTO at 23±2° C. and when the sample, i.e. the shockpad, is frozen, for example at a temperature ≤0° C. 
     The vertical deformation is measured with a dry sample at 23±2° C. 
     The water permeability is measured according to EN 12616 (CSN EN 12616; Surfaces for sports areas—Determination of water infiltration rate.) 
     The Horizontal water flow is measured according to ESTO Guidelines at three different slopes, e.g. 0.1%, 0.3% and 0.5%. 
     The Tensile strength is measured for an unaged sample according to EN 12230, whilst for a sample after air ageing is measured according to EN 13817/EN 12230 (DIN EN 12230: Surfaces for sports areas—Determination of tensile properties of synthetic sports surfaces). The Tensile properties are further given by the percentage of unaged value; this is calculated according to the ESTO Guidelines. 
     In an embodiment the support layer according to the invention has a shock absorption, measured according to the ESTO Guidelines, at 23±2° C. higher than 25%, preferably higher than 50%, more preferably higher than 80%, for example higher than 90%. 
     In an embodiment the support layer according to the invention has a shock absorption, measured according to the ESTO Guidelines, when said support layer is frozen, for example at a temperature 0° C., higher than 25%, preferably higher than 50%, more preferably higher than 80%, for example higher than 90%. 
     In an embodiment the support layer according to the invention has a water permeability, measured according to EN 12616, higher than 500 mm/h, preferably higher than 1000 mm/h, more preferably higher than 10000 mm/h, even more preferably higher than 50000 mm/h; for example, 60000 mm/h. 
     In an embodiment an unaged support layer according to the invention has a tensile strength, measured according to EN 12230, of at least 0.15 MPa, preferably, higher than 0.15 MPa, more preferably higher than 0.16 MPa, for example, 0.18 MPa. 
     In an embodiment a support layer according to the invention and after air ageing has a tensile strength, according to EN 13817/EN12230, of at least 0.15 MPa, preferably, higher than 0.15 MPa, more preferably higher than 0.16 MPa, for example, 0.19 MPa. 
     Thus, relative to a reference level  24  of the upper side  2 , the slope of the arms  18  starts at this level  24  and slopes down to a lower level  25 , at which level  25  the entrance portion  18  transitions into the main, circular, portion  19  of the hole. Also, the pyramid shaped elevations  14  start at the reference level  24  and rise to a top level  27 . Consequently, the upper side  2  has flat surface portions  28  between elevated portions  14  and (entrance portions  18  of) holes  6 . The shorter the arms  18  are, the larger the flat portions  28  will be. The flat portions  28  thus transition into, bottom surfaces of, the arms  18 , in the example of the figures, as shown in  FIG.  4   , at an angle of about 20 degrees, in the direction  15 , and transition into upwardly sloped surfaces of the pyramid shape of elevations, at an angle of about 10 degrees, transverse to the direction  15 . Also see  FIG.  12   . 
     An elevation e of each elevated portion  12  is about 3 mm. A maximum thickness t of the support layer  1  is about 25 mm. Also, the polymeric foam has a material density of between 30 and 50 gram per liter, such as between 30 and 40 gram per liter. Also, the polymeric foam of which the support layer  1  is made, is a polyethylene foam. 
     The impact characteristics are measured using standardized testing procedures, such as for example but not limited to ASTM-F355 in the U.S. and EN-1177 in Europe and FIFA 2015 FQP test methods e.g. FIFA test methods 04a, 05a, 13. For example for soccer fields, the FIFA provides strict rules regarding impact that the artificial turf system has to comply to. The present support layer complies with the latest FIFA (Fédération Internationale de Football Association) Quality Concept for Artificial Turf, the International Artificial Turf Standard (IATS) and the European EN15330 Standard. Typical shock, or energy, absorption and deformation levels from foot impacts far such systems are within the range of 55-70% shock absorption and about 4 millimeters to about 9 millimeters deformation, when tested with the Berlin Artificial Athlete (EN14808, EN14809). Vertical ball rebound is about 60 centimeters to about 100 centimeters (EN12235), Angled Ball Behavior is 45-70%, Vertical Permeability is greater than 180 mm/hr (EN12616) along with other standards, such as for example energy restitution. 
     The support layer according to the invention may be in the form of a panel or plate several of which are used together to cover the base layer forming a ground-covering support system. The plates or panels according to the invention may be configured to have a puzzle-shape, such as by dovetail shaped joints as mentioned below, allowing interlocking connection to obtain a support system that is stable and does not have shifting of the separate support panels relative to each other. 
     As  FIGS.  1  and  8    show in particular, the support layer  1  is of a generally rectangular shape and has connecting elements at a circumferential edge  37  thereof, in the form of dovetail joints  36   a  &amp;  36   b , for connecting the support layer  1  to further such support layers  1  and such that the connected support layers  1  are flush with respect to each other and form a closed surface for supporting thereon the artificial turf assembly  30 . As shown, the layer  1  has male dovetail joints  36   a  on its left and bottom side in the view of  FIG.  1   , and has female dovetail joints  36   b  on its right and upper side in the view of  FIG.  1   . This way, the layer  1  can be easily and in a form closed manner be connected to further of such layers  1 . 
       FIGS.  13 - 15    depict a second embodiment of the support layer(s)  100  as disclosed herein. In particular.  FIG.  13    depicts a perspective view of a second embodiment of the support layer  100 ,  FIG.  14    shows a top view of the second embodiment of the support layer  100 , and  FIG.  15    shows section B-B of the support layer  100  of  FIG.  14   . The support layer  100  of the second embodiment may be made from substantially the same materials, in substantially the same way, and performs in a substantially similar manner as that mentioned above regarding the first embodiment (i.e., support layer  1 ). Furthermore, the lower side  103  of the support layer  100  including the channels  104  formed thereon of the second embodiment may have substantially the same conformation as disclosed above in  FIGS.  2 - 5 , and  8    when disclosing the first embodiment. 
     Also, similar to the first embodiment and in view of  FIG.  11   , the second embodiment of the support layer  100  may be arranged for supporting an artificial turf assembly  30  while in use. In view of  FIG.  11   , support layer  100  may be included within system  50  instead of support layer  1  (i.e., support layer  100  may be substituted for support layer  1  in system  50 ). In this aspect and in view of  FIG.  11   , the support layer  100  of the second embodiment is part of a plurality of such support layers  100  of a support system  50  according to  FIG.  11   , the system  50  further comprising an artificial turf assembly  30 , that means, an assembly forming a surface of synthetic fibers made to look like natural grass, most often used in sports arenas but for residential lawns as well. The plurality of support layers  100  is then supported on a base surface  32  such as a layer of sand, and form, at upper sides  2  thereof, a closed support surface supporting the artificial turf assembly  32 . 
     In view of  FIGS.  11 ,  13 , and  14   , the support layer  100  is in the form of a rectangular support plate element formed of a polymeric foam and has an upper side  102  and a lower side  103 , wherein, as mentioned above, when in use the support layer  100  has been placed with the lower side  103  thereof on a base surface and supports, on the upper side  102  thereof, the artificial turf assembly. In certain aspects, a length of the layer  100  ranges from about 1.4 m to 1.6 m and a width ranges from about 1.10 to 1.15 m. In certain aspects, a length of the layer  100  is about 1.58 m and a width ranges is about 1.12 m. 
     In certain aspects and as further shown in  FIGS.  13  and  14   , each support layer  100  includes at least partial drainage holes  106  formed on the circumferential edges (peripheral edges)  137  (including the corners) of the support layer  100 , and as further shown in  FIGS.  14  and  15   , the support layer  100  further includes a complete drainage hole formed approximately in the center of each support layer  100 . Each drainage hole  106  has a predetermined shape. For example, in certain preferred aspects, the partial drainage holes are semi-circular shaped (half circles) while the complete drainage hole is preferably circular shaped. It should be further noted that each partial drainage hole  106  formed on the circumferential edges (peripheral edges)  137  is configured to form complete drainage holes when one or more support layer(s)  100  are assembled and/or connected to another support layer. For example and in view of  FIGS.  13  and  14   , it should be readily appreciated and understood, that four support layers  100  should be aligned and connected to one another to form a complete drainage hole from the partial drainage holes  106  formed on a corner of the support layer(s)  100 . Likewise, only two support layers  100  need to be aligned and connected to one another when forming a complete drainage hole  106  positioned approximately mid-span along each of the circumferential edges  137  (peripheral edges) of each support layer. 
     In view of the above and  FIGS.  13 - 15   , it should be further appreciated that the upper side  102  of each support layer  100  is generally planar (i.e., unlike the first embodiment does not include elevated portions) but may be slightly sloped to direct water towards each partial and/or complete drainage hole  106  formed on the support layer  100 , which further facilitates water drainage from the upper side  102  of each support layer to the lower side  103  of each support layer via the drainage holes  106 . In further view of  FIGS.  13 - 15   , the upper side  102  of each support layer  100  further includes a widened entrance portion  116  (similar to widened entrance portion  16  in  FIG.  4    of the first embodiment) directly adjacent to and surrounding each partial and complete drainage hole  106  formed on each support layer  100 . The widened entrance portion  116  preferably has a predetermined shape, which includes a star shape or a cross shape  118  when formed in the center of the support layer  100  (or at least a partial cross shape  118  when formed along the circumferential edges of each support). The cross shape  118  (or partial cross shape  118  formed along the circumferential edges of each support) include individual arms. Each individual arm begins and is directly connected to the uppermost surface of the upper side  102  and continuously descends/extends with a constant slope (or substantially constant slope) towards and is directly connected to its corresponding complete or partial drainage hole  106 . This arrangement further facilitates water drainage from the upper side  102  (e.g., an uppermost surface) of the support layer  100  through the drainage hole into the lower side  103  of the support layer. 
     As further shown in  FIGS.  13  and  14    and with reference to a first axis (A 1 ) and a second axis (A 2 ), the arms of the cross shape  118  (or partial cross shape  118 ) of the widened entrance portions  116  are axially aligned along a first or second axis with arms of other cross shapes (or partial cross shapes  118 ) formed on the upper side  102  of the support layer. (The third through sixth axes (i.e., A 3 , A 4 , A 5 , A 6 ), as shown in  FIG.  14   , similarly depict additional, contemplated axial alignments of each arm positioned along the circumferential edges in the support layer  100 .) Although each arm of the cross shape (or partial cross shape) is axially aligned with another arm of another cross shape (or partial cross shape) formed on the upper side  102  of the support layer  100 , these axially aligned arms are not fluidly connected to one another. Instead, each axially aligned arm is separated by reference portion  124 , which is part of the upper most (or outermost) portion of upper side  102  and is substantially planar and/or is slightly sloped towards each arm that it separates. Thus, in this aspect reference portion  124  separates an arm from another arm but further directs water flow towards a desired arm and ultimately the desired drainage hole  106  (i.e., complete or partial drainage hole) of each support layer  100 . 
       FIG.  15    further depicts a cross section of support layer  100  of B-B of  FIG.  14   . In view of  FIG.  15    and the above disclosures, it should be readily apparent how the upper side  102 , widened entrance portion(s)  116 , and cross-shape(s) (and/or partial cross shapes)  116  direct water towards drainage holes  106  (or partial drainage holes) and how water is directed into at least one of the plurality of channels  104  formed on the lower side  103  of the support layer  100 . In  FIG.  15   , “d” represents the depth of each channel  104  formed on the lower side  103 , which is about 50 percent of a total thickness “t” of the layer  100 . It should be noted that the thickness of the support layer  100  range from 10 to 80 mm, from 10 to 70 mm, from 15 to 70 mm, from 10 to 65 mm, from 15 to 65 mm, from 10 to 60 mm, from 15 to 60 mm, from 10 to 55 mm, from 15 to 55 mm, from 10 to 50 mm, from 15 to 50 mm, from 10 to 45 mm, from 15 to 45 mm, wherein any of the endpoints falling within the above disclosed ranges may serve as endpoints for any additional range(s) falling there between (but not explicitly disclosed above). 
     As discussed above, the support layer  100  shown in  FIGS.  13 - 15    may be in the form of a panel or plate, and in view of  FIG.  11   , several support layers may be connected and used together to cover the base layer forming a ground-covering support system  50 . The plates or panels according to the invention may be configured to connect to one another and may have a puzzle-shape, such as by dovetail shaped joints, allowing interlocking connection to obtain a support system that is stable and does not have shifting of the separate support panels relative to each other. The support layer  100  is of a generally rectangular shape and has connecting elements (not shown) positioned on and/or extending from circumferential edge(s)  137  thereof; these connecting elements may be in the form of dovetail joints, for connecting the support layer  100  to another support layer  100  and such that the connected support layers  100  are flush with respect to each other and form a closed surface for supporting thereon the artificial turf assembly  30 . In certain aspects, the layer  100  may have male dovetail joints on its left and/or bottom side, and may have female dovetail joints on its right and/or upper side such that multiple support layers can be easily connected to one another to achieve a desired overall dimension. 
     Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope thereof. 
     The following clauses define several aspects and embodiments of the invention. 
     1. A support layer ( 1 ,  100 ) for supporting an artificial turf assembly ( 30 ), said support layer being formed of a polymeric foam and having an upper side ( 2 ,  102 ) and a lower side ( 3 ,  103 ), wherein in use the support layer ( 1 ) has been placed with the lower side ( 3 ,  103 ) thereof on a base surface and supports, on the upper side ( 2 ,  102 ) thereof, the artificial turf assembly, the support layer ( 1 ,  100 ) comprising a plurality of through drainage holes ( 6 ,  106 ) extending from the upper side ( 2 ,  102 ) to the lower side ( 3 ,  103 ) for allowing liquid such as rain water to flow via the plurality of drainage holes ( 6 ,  106 ) from the upper side ( 2 ,  102 ) to the lower side ( 3 ,  103 ), and also comprising a plurality of channels ( 4 ,  104 ) at the lower side ( 3 ,  103 ) for allowing liquid such as rain water to flow through the channels ( 4 ,  104 ) along the lower side ( 3 ,  103 ), wherein each of said plurality of drainage holes ( 6 ,  106 ) debouches into one of the plurality of channels ( 4 ,  104 ), wherein said support layer ( 1 ,  101 ) comprises a plurality of individual elevated portions ( 14 —first embodiment only) at the upper side ( 2 ) of the support layer ( 1 ) and said plurality of individual elevated portions ( 14 ) are dome, pyramid, truncated pyramid, cone, truncated cone or tetrahedron shaped, preferably, pyramid or dome shaped. 
     2. A support layer ( 1 ,  100 ) for supporting an artificial turf assembly ( 30 ), said support layer being formed of a polymeric foam and having an upper side ( 2 ,  102 ) and a lower side ( 3 ,  103 ), wherein in use the support layer ( 1 ,  100 ) has been placed with the lower side ( 3 ,  103 ) thereof on a base surface and supports, on the upper side ( 2 ,  102 ) thereof, the artificial turf assembly, the support layer ( 1 ,  101 ) comprising a plurality of through drainage holes ( 6 ,  106 ) extending from the upper side ( 2 ,  102 ) to the lower side ( 3 ,  103 ) for allowing liquid such as rain water to flow via the plurality of drainage holes ( 6 ,  106 ) from the upper side ( 2 ,  102 ) to the lower side ( 3 ,  103 ), and also comprising a plurality of channels ( 4 ,  104 ) at the lower side ( 3 ,  103 ) for allowing liquid such as rain water to flow through the channels ( 4 ,  104 ) along the lower side ( 3 ,  103 ), wherein each of said plurality of drainage holes ( 6 ,  106 ) debouches into one of the plurality of channels ( 4 ,  104 ); and wherein drainage holes ( 6 ,  106 ), preferably each drainage hole, of the plurality of drainage holes have a widened entrance portion ( 16  or arms  118 ) at the upper side ( 2 ,  102 ) of the support layer ( 1 ,  101 ). 
     3. A support layer ( 1 ,  100 ) for supporting an artificial turf assembly ( 30 ), said support layer being formed of a polymeric foam and having an upper side ( 2 ,  102 ) and a lower side ( 3 ,  103 ), wherein in use the support layer ( 1 ,  101 ) has been placed with the lower side ( 3 ,  103 ) thereof on a base surface and supports, on the upper side ( 2 ,  102 ) thereof, the artificial turf assembly, the support layer ( 1 ,  100 ) comprising a plurality of through drainage holes ( 6 ,  106 ) extending from the upper side ( 2 ,  102 ) to the lower side ( 3 ,  103 ) for allowing liquid such as rain water to flow via the plurality of drainage holes ( 6 ,  106 ) from the upper side ( 2 ,  102 ) to the lower side ( 3 ,  103 ), and also comprising a plurality of channels ( 4 ,  104 ) at the lower side ( 3 ,  103 ) for allowing liquid such as rain water to flow through the channels ( 4 ,  104 ) along the lower side ( 3 ,  103 ), wherein each of said plurality of drainage holes ( 6 ,  106 ) debouches into one of the plurality of channels ( 4 ,  104 ), wherein said support layer ( 1 ,  101 ) comprises a plurality of individual elevated portions ( 14 —first embodiment only) at the upper side ( 2 ,  102 ) of the support layer ( 1 ,  100 ) and said plurality of individual elevated portions ( 14 ) are dome, pyramid, truncated pyramid, cone, truncated cone or tetrahedron shaped, preferably, pyramid or dome shaped; and wherein drainage holes ( 6 ), preferably each drainage hole, of the plurality of drainage holes have a widened entrance portion ( 16  or arms  118 ) at the upper side ( 2 ,  102 ) of the support layer ( 1 ,  100 ). 
     The foregoing description provides embodiments of the invention by way of example only. The scope of the present invention is defined by the appended claims. One or more of the objects of the invention are achieved by the appended claims.