EP3438345A2

EP3438345A2 - Mat made of waterproof plastic material for the sub-base of synthetic turfs or pavings and the like

Info

Publication number: EP3438345A2
Application number: EP18185327.6A
Authority: EP
Inventors: Giuseppe De Maria
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-08-01
Filing date: 2018-07-24
Publication date: 2019-02-06
Also published as: IT201700088166A1; EP3438345A3; US20190040592A1

Abstract

A mat (10) made of waterproof plastic material for the sub-base of synthetic turfs or pavings and the like, adapted to be arranged between a bed surface (201) and a covering layer (202), comprising:
- a membrane (101) which comprises a lower face (12) adapted to be rested on the bed surface (201) and an upper face (11) adapted to be covered by the covering layer (202);
- one or more coupling elements (50a, 50b) for mutual interconnection with other mats (10') so as to compose a single turf for the complete covering of a predetermined bed surface (201); the lower face (12) and the upper face (11) comprising a plurality of ribs (30, 40, 70) adapted to absorb and return mechanical stresses; the ribs (30, 40, 70) comprise longitudinal lines (30) which form channels (31) for the horizontal draining of the water on the upper face (11).

Description

The present invention relates to a mat made of waterproof plastic material for the sub-base of synthetic turfs or pavings and the like.
More in particular, the invention relates to a mat particularly but not exclusively useful and practical for providing playing fields made of synthetic grass.
The use of synthetic grass in playing fields has constituted a considerable advantage with respect to natural grass it requires less maintenance and allows a greater number of hours of use as it does not need water, chemical products or sunlight. Synthetic grass, that is applied in contexts in which, due to weather conditions, natural grass would not be able to grow, allows to play different sports even in extremely hot or cold regions. Obviously, some measures are nevertheless necessary. For example, if it used in high-rainfall contexts, correct runoff of rainwater must be ensured so as to avoid the forming of puddles or leaks of water in the ground below, which can jeopardize the use of the playing field.
In fact a ground, in order to be considered approved, i.e., suitable for carrying out a specific game, must comply with constraints imposed by the competent authorities (such as for example FIFA, amateur national leagues or the International Rugby Board) that might require for example that the ground is capable of absorbing to some extent shocks, such as impacts, falls, the passage of players and equipment.
These requirements might not be met in the event of adverse weather conditions. Therefore, when the synthetic grass is placed, it is necessary on the one hand to identify the requirements to be met (for example, for a rugby field, the shock absorption index must have a value that is higher than that of a tennis field) and on the other hand to ensure that the performance of the ground is met during the game.
In the prior art there are examples of materials that, when used together with synthetic grass, have the goal of improving ground performance.
A first example of the prior art is constituted by materials made of polyethylene foams with millings for water disposal. These materials not only require the additional installation of a sheath for waterproofing the sub-base but also show low resistance to compression and the risk of crushing in the short term with reduction of their draining ability.
A second example of the prior art is constituted by geocomposite materials made of polypropylene and wrapped with geotextile material. These materials, too, require the additional installation of a sheath in order to waterproof the sub-base and also show low resistance to compression and poor performance particularly in terms of shock absorption.
A third example of materials of the prior art comprises sheets made of polypropylene and molded by injection as grids provided with an underlying wing. These materials, besides being rigid and prone to break if subjected to loads, require an elaborate installation due to the need to fix the sheets with metal eyelets in order to avoid their movement. Moreover, in this case also it is necessary to lay a waterproofing sheath and geotextile material on the surface.
Another example is constituted by materials molded in polyethylene sheets that require the use of a waterproofing sheath. These materials are very expensive.
A last example is constituted by the use of a plurality of rubber mats, usually quadrangular and provided with ribs, which are arranged side by side so as to cover the entire surface of the playing field.
Even rubber mats of the known type, albeit very useful and practical, are lacking in some aspects.
First of all it is very difficult, during laying, to obtain perfect spreading and precise alignment of the various mat portions.
Furthermore, because of the intense and repeated stresses (such as for example rebounds, "sliding tackles" of the players, treading, transit of apparatuses and heavy equipment...) to which they are subjected during use, the mat portions tend to move and misalign.
Another disadvantage of mat portions of the known type is constituted by the fact that water draining is uneven and undesired accumulations of water form following rainfall, with consequent formation of puddles and accordingly, over time, also of hollows and/or bulges in the turf above.
Another very important drawback, which occurs in mat portions of the known type, is constituted by thermal expansion.
In fact, following the rise of the temperature, the material of which the mats are made expands and the mats increase their dimensions considerably (expansions up to 5 mm on a width of 1200 mm have been observed) and thus push against each other, with consequent creation of corrugations, bulges, misalignments.
Vice versa, following the lowering of the temperature, the material contracts, with the consequent creation of tractions, stresses, misalignments and ruptures.
The aim of the present invention is to overcome the limitations of the background art highlighted above, providing a new mat capable of obviating the problems caused by thermal expansion and contraction.
Within the scope of this aim, an object of the present invention is to provide a mat that is easy to deploy and at the same time ensures stability and correct alignment over time.
Another object of the invention is to provide a mat that avoids unwanted accumulations of rainwater.
A further object of the invention is to provide a mat that is easy to manufacture and economically competitive if compared with the prior art.
Another object of the invention is to provide a synthetic turf arrangement that ensures good-level and lasting performance and an efficient draining of rainwater.
Another object of the present invention is to provide a method for producing a mat portion adapted to be used as sub-base for synthetic turfs.
This aim and these and other objects that will become better apparent hereinafter are achieved by a mat according to claim 1.
This aim and these and other objects are also achieved by a ground according to claim 10.
This aim and these and other objects are also achieved by a method according to claim 11.
Further characteristics and advantages will become better apparent from the description of a preferred but not exclusive embodiment of a mat according to the invention, as well as of a method for producing the mat, illustrated by way of non-limiting example with the aid of the accompanying drawings, wherein:

Figure 1 is a perspective view of a possible embodiment of a mat according to the invention;
Figure 2 is a perspective view of two portions of mats arranged side by side;
Figure 3 is a perspective view of two portions of connected mats;
Figure 4 is a plan view of the upper face of the mats of Figure 2;
Figure 5 is a sectional view, taken along the plane V, of the mats of Figure 4;
Figure 6 is a bottom perspective view of the lower faces of the mats of Figure 3 connected;
Figure 7 is a bottom perspective view of the lower faces of the mats of Figure 2 arranged side by side;
Figure 8 is a plan view of the lower face of the mats of Figure 2;
Figure 9 is a sectional view taken along the plane V of the mats of Figure 8;
Figure 10 is a schematic view of a system for the production of the mat according to the present invention;
Figure 11 is a view of a playing field in which multiple mats according to the present invention are used.

With reference to the above figures, the mat, generally designated by the numeral 10, is adapted to be arranged between a bed surface 201 and a covering layer 202. The bed surface 201 is usually constituted by the natural ground 201a on which generally a layer of stabilizing material 201b is laid. The covering layer 202 is constituted preferably by synthetic grass 202c, with sand, gravel or any other type of walking or covering surface inside it.
More precisely, the mat 10 is designed to be connected to other mats 10', so as to compose a single turf for the complete covering of a preset bed surface 201 (for example for the complete covering of a football field). For this purpose, the mat 10 comprises at least one coupling element 50a, 50b for mutual interconnection with other mats 10'. In the preferred and illustrated embodiment, the coupling element 50a, 50b is constituted by two concave protrusions 50a, 50b, which are mutually complementary, each arranged at a longitudinal end of the mat portion 10 and shaped so as to be mutually coupled, forming a waterproof engagement system.
Again with reference to the cited figures, the mat 10 comprises a membrane 101 which in turn comprises a lower face 12 adapted to be rested on the bed surface 201 and an upper face 11 adapted to be covered by the covering layer 202.
Both the upper face 11 (shown in Figures 1 to 4) and the lower face 12 (shown in Figures 6, 7 e 8), comprise a plurality of ribs 30, 40, 70 adapted to absorb and return mechanical stresses.
In practice, these ribs 30, 40, 70 are protrusions of the membrane 101, which protrude from the two faces 11, 12 and form, as will be explained hereinafter, lines 30, ridges 40, channels 31 and receptacles 71 having shapes and dimensions that depend on the specific use for which the mat 10 is intended. In particular, the mat 10, according to the invention, is characterized by a flexing parameter associated with the deformation of said ribs 30, 40, 70. It is thus possible to set this flexing parameter, for example based on the specifications imposed by regulations for a specific playing field, by sizing conveniently the ribs 30, 40, 70.
According to the invention, the mat 10 further comprises at least one expansion joint 20 adapted to compensate for the thermal deformations by deforming.
The expression "expansion joint" 20 designates a deformable element, comprising a cavity and/or concavity, that joins two longitudinal portions (10a, 10b) of the mat and preferably occupies the entire length of the mat 10.
In the preferred and illustrated embodiment, the expansion joint 20 is shaped like an arch with a substantially C-shaped cross-section and the cavity oriented downward (i.e., toward the bed surface 201 when the mat 10 is laid), which occupies the entire width of the mat 10 and in practice divides the mat 10 into two or more distinct longitudinal portions 10a, 10b mutually connected by said expansion joint 20 (see Figure 1).
The expansion joint 20 has the characteristic of being easily deformable; in this manner, when the membrane 101 is subjected to a thermal expansion, the expansion joint 20 deforms by contracting its own cavity, allowing the two longitudinal portions 10a, 10b to move closer and thus preventing the overall dimensions of the mat 10 from varying.
Likewise, when the membrane 101 is subjected to a contraction following a temperature decrease, the expansion joint 20 deforms, widening its own concavity, allowing the two longitudinal portions 10a, 10b to move apart and thus preventing the total dimensions of the mat 10 from varying.
In this manner the problems caused by thermal expansion and contraction to which mats of the known type are subjected are avoided.
Furthermore, the expansion joint 20 keeps the mat 10 stretched by keeping the longitudinal portions 10a, 10b separate. In this manner, the deployment of the mat 10 is easier and more precise.
According to an optional characteristic, there are also connection means 50a, 50b for mutually connecting various mats 10, 10' made to match up during deployment, for even greater assurance of stable alignment.
In the example shown there is a single expansion joint 20, but according to the invention the mat 10 can comprise further expansion joints 20 that divide the mat into a plurality of sectors 10a, 10b.
In the preferred and illustrated embodiment, with particular reference to Figures 6, 7 and 8, the ribs 30, 40, 70 form on the lower face 12 a plurality of receptacles 71.
The expression "receptacle" 71 is understood to reference an open sector delimited by walls 70. Preferably, the receptacles 71 have a square shape, forming, on the lower face 11, a grid with a specific spacing (i.e., the distance between the ribs 70 that constitute the walls 70 of the receptacles 71).
In the same embodiment, as shown in particular in Figures 1 to 4, on the upper face 11 the ribs 30, 40, 70 comprise longitudinal lines 30 that form channels 31 for the horizontal draining of water.
In other words, the ribs 30 form, on the upper face 11, straight walls, which are mutually parallel, extend transversely from one side to the other of the mat 10 and form between them a series of channels 30 in which water can flow.
In fact, as will be described hereinafter in an example of application of a plurality of mats according to the invention, the mats 10, 10' are usually arranged so as to have an appropriate inclination that facilitates the draining of water on the upper face 11.
The presence of the channels 31 cause a draining of water that is uniform along all of the upper face 11 and prevents the forming of unwanted stagnations.
Preferably, on the upper face 11, the ribs 30, 40, 70 also comprise transverse ridges 40 that are less high than the longitudinal lines 30 and are adapted to create accumulations of water.
In practice, these transverse ridges 40 are perpendicular to the longitudinal lines 30, connecting to each other said longitudinal lines 30 and forming barriers that retain a water layer on the bottom of the channels 31.
The advantage of this solution resides in that the water layer retained by the transverse ridges helps to keep the temperature of the system low and uniform.
Here, it should be noted that this water layer, contrary to the unwanted accumulations of water that the invention seeks to avoid, has a depth equal to the height of the transverse ridges 40 and can be thus conveniently preset so as to not interfere with the overlying covering layer 202.
Advantageously, the transverse ridges 40 have a spacing that is equal to the spacing of the receptacles 41, i.e., the distance between the transverse ridges 40 is equal to the distance between the walls 70 that form the receptacles 71 and each transverse ridge 40 is arranged at an underlying wall 70. In this manner, the transverse ridges 40 also help to strengthen the structure of the mat 10 without jeopardizing its flexibility.
According to an optional and advantageous characteristic, on the longitudinal lines 30 there are one or more cuts 60 for the passage of water between at least two channels 31. In practice, the cuts 60 create passages through the longitudinal lines 30 by means of which the water can drain from one channel 31 to the other. In this manner a more even distribution of the water flow is allowed and excessive hydraulic pressures are avoided in the event of intense rainfall.
Optionally, the mat 10 further comprises one or more holes 111 for the passage of water through the membrane 101, i.e., for the draining of a certain quantity of water from the covering layer 202 toward the bed surface 201.
In practice, in the preferred embodiment, all the elements described so far are provided by the shaping of a single piece of waterproof plastic material. Preferably, this waterproof plastic material is constituted by a mixture 90 composed of 15-25% thermoplastic polymer and 75-85% rubber obtained from used tires (ELTs, end-of-life tires).
Moreover, the mat 10 can further comprise a filter (not shown) interposed between the upper face 11 and the covering layer 202, preferably composed of a nonwoven fabric (NWF) or needle-tufted fabric, for filtering the sand that arrives from the covering layer 202 and for protection from solar radiation.
A preferred method for the production of mats 10 according to the invention is shown schematically in Figure 10. According to this method, the thermoplastic mixture 90 exits in the plastic state from a flat head of an extruder 81 and it is then calendered by passing between two conveniently contoured rollers 82a, 82b. As known in the art, calendering is a process that is performed in machines (calenders) composed of rollers with parallel axes, having an adjustable distance, which rotate at low speed; it consists in making the plastic material pass in the semisolid state between the pairs of rollers.
The method, according to the invention, entails that the rollers 82a, 82b of the calender are conveniently contoured so as to give the mixture 90 the shape of the finished mat 10, without requiring further processes.
Preferably, the clearance between the two rollers 82a, 82b is approximately 0.3 mm, so as to create a strong compression on the finished part.
Moreover, the rollers 82a, 82b are cooled, thus causing, besides the plastic deformation, also the cooling of the mixture 90. Preferably, this cooling occurs by bringing the rollers 82a, 82b to a temperature of approximately 7°C, so that the shrinkages of the material are minimal.
Figure 11 shows an example of a playing field 500 made of synthetic grass, in which multiple mats 10, 10' according to the invention are used.
The playing field 500 shown comprises a plurality of mats 10, 10' interposed between a bed surface 201 and a covering layer 202. In greater detail, in the illustrated example, the bed surface 201 comprises a base of natural ground 201a on which stabilized ground 201b or inert recovered materials mixed with stabilizing agents are deposited. The stabilized ground 201b is hard and consolidated and is adapted to accommodate a plurality of mats 10, 10', so as to give them such an inclination as to allow horizontal draining, i.e., toward the longitudinal sides of the playing field, of water.
Multiple mats 10, 10' are then arranged on the stabilized ground 201b and are mutually connected by means of the coupling elements 50a, 50b, so as to form a single waterproof turf, even with glue on the joint. Although the figure shows only two mats 10, 10', the person skilled in the art understand without any inventive effort that other mats can be added until the entire playing area is covered.
Finally, the mats 10, 10' are covered by a covering layer 202 which in this example comprises, in the following order, crushed siliceous sand 202a, rubber granules 202b, synthetic grass 202c. The mats 10, 10' according to the present invention, together with the layers 202a, 202b, 202c, allow to absorb shocks, contain vertical deformation and stresses so as to meet the international regulations of the competent authorities, such as FIFA, with shock absorption of the system starting from 55% up to 70% and vertical deformation from 4 mm to 8 mm. Optionally, between the covering layer 202 and the mats 10, 10' it is possible to insert, if advantageous, a filter of the non-woven fabric, NWF, type.
As already explained, although the turf has been presented mainly with regard to use on playing fields, it could also find other applications where the draining of water is required, such as for example in landfills, terraces, gardens as casing of tubes or also as protective layer under dry-lay pavings, road pavings, ballasts, etcetera.
In practice it has been found that the mat according to the present invention achieves the intended aim and objects since is capable of obviating the problems caused by thermal expansion and contraction.
Another advantage of the mat according to the invention is that it is easy to lay, ensuring at the same time stability and correct alignment over time.
A further advantage of the mat according to the invention is that it avoids unwanted accumulations of water.
Another advantage of the mat according to the invention is that it is easy to provide and economically competitive if compared with the background art.
A further advantage of the mat according to the invention is that it allows the provision of playing fields that give the greatest assurances of reliability and safety in use and meet all the parameters set by regulations.
The mat thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the accompanying claims.
All the details may furthermore be replaced with other technically equivalent elements.
In practice, the materials used, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.
To conclude, the scope of the protection of the claims must not be limited by the illustrations or preferred embodiments shown in the description by way of example, but rather the claims must comprise all the characteristics of patentable novelty that reside in the present invention, including all the characteristics that would be treated as equivalents by the person skilled in the art.
The disclosures in Italian Patent Application No. 102017000088166 from which this application claims priority are incorporated herein by reference.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

A mat (10) made of waterproof plastic material for the sub-base of synthetic turfs or pavings and the like, adapted to be arranged between a bed surface (201) and a covering layer (202), comprising:
- a membrane (101) which comprises a lower face (12) adapted to be rested on said bed surface (201) and an upper face (11) adapted to be covered by said covering layer (202);

- one or more coupling elements (50a, 50b) for mutual interconnection with other mats (10') so as to compose a single mat for the complete covering of a predetermined bed surface (201);
said lower face (12) and said upper face (11) comprising a plurality of ribs (30, 40) adapted to absorb and return mechanical stresses;
characterized in that said ribs (30, 40, 70) comprise longitudinal lines (30) which form channels (31) for the horizontal draining of the water on said upper face (11).
The mat (10) according to claim 1, characterized in that on said upper face (11) said ribs (30, 40, 70) also comprise transverse lines (40) which are lower than said longitudinal lines (30) and are adapted to create accumulations of water.
The mat (10) according to claim 1 or 2, characterized in that one or more cuts (60) for the passage of water between at least two of said channels (31) are provided on said longitudinal lines (30).
The mat (10) according to one or more of the preceding claims, characterized in that said ribs (70) form a plurality of receptacles (71) on said lower face (12).
The mat (10) according to claims 2 and 4, characterized in that said transverse lines (40) have a spacing that is equal to the spacing of said receptacles (71).
The mat (10) according to one or more of the preceding claims, characterized in that it is divided into at least two longitudinal portions (10a, 10b) which are mutually connected by means of an expansion joint (20) adapted to compensate for the thermal expansions and contractions by deforming.
The mat (10) according to one or more of the preceding claims, characterized in that it comprises furthermore one or more holes (111) for the passage of water through said membrane (101).
The mat (10) according to one or more of the preceding claims, characterized in that said waterproof plastic material is constituted by a mixture (90) composed of 15-25% thermoplastic polymer and 75-85% rubber, said rubber being obtained from used tires.
The mat (10) according to one or more of the preceding claims, characterized in that it further comprises a filter which is interposed between said upper face (11) and said covering layer (202), said filter comprising material of the nonwoven fabric (NWF) type.
A playing field (500), particularly for soccer fields and the like, comprising a bed surface (201) and a covering layer (202), said covering layer comprising at least one layer of synthetic grass (202c), characterized in that it comprises, between said covering layer (202) and said bed surface (201), a plurality of mats (10, 10') according to one or more of the preceding claims.
A method for providing a mat (10) made of waterproof plastic material for the sub-base of synthetic turfs or pavings and the like, characterized in that it comprises the steps of:
- providing a waterproofing mixture (90) which comprises thermoplastic material;

- making said mixture (90) exit in the plastic state from an extruder (81);

- calendering said mixture (90), making it pass between two cooled contoured rollers (82a, 82b), so that said rollers (82a, 82b) create a pressure on said mixture (90), giving it the shape of a mat, and at the same time cool said mixture (90).
The method according to claim 11, characterized in that said rollers (82a, 82b) are contoured so as to impart to said mixture (90) the shape of a mat (10) according to one or more of claims 1 to 9, and in that said rollers (82a, 82b) are cooled to a temperature comprised between 5°C and 8°C, cooling said mixture (90).