Artificial grass mats known up to now comprise plastic tubes with the shape of blades of grass, made from plastics like for instance polypropylene, polyethylene and teflon provided on a support layer. Said fields are widely used to play ball sports like soccer and hockey but said fields have one well-known disadvantage. When someone falls down on the artificial grass and especially upon making a sliding-tackle on it local high temperatures are developed which may cause nasty wounds. Generally, one tries to prevent such hurting by keeping the artificial grass field wet which is especially applied on hockey fields. However it is difficult to adjust the amount of water required.

Moreover, it requires a lot of water to keep the artificial grass field in such a condition that the hurting caused by making sliding-tackles on it is minimized.

In EP patent 1080274 an artificial lawn with hollow blades of grass in a U-form has been described. In this way the artificial blades of grass receive liquid from the rain and humidity in the air in general and/or by spraying. Through small openings in the lateral walls of tufts of said blades above or in the support layer, air that prevents the water can escape. Through these small openings in the lateral walls of tufts of said blades in the water-storing layer, water may additionally be taken up from that layer. However in this way only a small amount of water can be adsorbed additionally. When these artificial blades of grass are applied it is moreover not easy to regulate the quantity of liquid that will be kept by those blades of grass and besides this the application of sprinkling is water and time-consuming.

The object of the present invention is therefore to provide a field of artificial grass which field may be supplied with liquid in a controllable and easy way.

The invention provides therefore a field of blades of grass of the type stated in the preamble comprising capillaries as: a. capillary tubes between the blades of grass and/or b. capillary nerves inside the artificial blades of grass, with one end of the capillaries located in a liquid adsorbing and releasing layer.

Said hollow capillaries have generally a substantial straight thread-like form, with about the same size of opening at both opposite sides. The capillaries may be slightly bended particularly at their ends. By the capillary effect the capillary tubes and nerves upon losing liquid will fill it selves again from the liquid adsorbing and releasing layer.

The capillary tubes are present between artificial blades of grass and optionally natural blades of grass.

In case the field of artificial grass according to the invention comprises capillary tubes those are preferably made of silicone material. Other suitable materials are polypropylene, polyethylene and teflon.

Preferably, the liquid adsorbing and releasing layer in the field of artificial grass according to the invention comprises one or more of the materials felt and cotton. Those natural materials have a large capability both to adsorb and release liquid.

In a preferred embodiment of the invention the field of artificial grass according to the invention is provided with a liquid storing layer. Generally this liquid storing layer is put under the liquid adsorbing and releasing layer. Preferably this layer comprises rubber, more preferably sintered rubber, capable of storing a lot of liquid for instance by irrigation, and releasing the liquid again as soon as the liquid adsorbing and releasing layer needs it.

According to another preferred embodiment at least some of the capillary tubes and/or at least some of the capillary nerves of the field of artificial grass comprise a liquid conductor. Said liquid conductor comprises for instance one or more of the following hydrophilic materials: cotton and sponge. Those liquid conductors may be applied as a hydrophilic layer on the interior wall of said capillary tubes or capillary nerves, particularly made of cotton. Preferably however at least some of the liquid conductors fully fill the capillaries for instance with an nucleus of sponge or a thick wire of cotton, to enlarge the capillary effect.

According to another aspect of the invention a process is provided to prepare a field of artificial grass by weaving said capillaries in the support layer at such a height that one end is located in the liquid adsorbing and releasing layer. Generally the usual artificial blades of grass present in the support layer will be woven with there bottom end in the support layer. The support layer is for instance made of latex.

In this way the present invention provides processes to prepare the two types of artificial grass field. In case the artificial grass field comprises artificial blades of grass together with separate capillary tubes like for instance hollow threads with openings at the two ends, especially silicone threads, wherein optionally liquid conductor material is applied said capillary tubes are woven in a method known in the art together with the blades of grass in support layer of the artificial grass. In case capillary nerves are applied within the artificial blades of grass wherein optionally liquid conductor material is applied the blades of grass including the capillary nerves are woven in a method known in the art in the support layer of the artificial grass. However the capillary tubes and the blades of grass with capillary nerves have at least to reach the liquid adsorbing and releasing layer with liquid as for instance the felt layer, or to stretch out in said layer to be able to adsorb the liquid.

According to yet another aspect of the invention a process to improve the quality of an existing field of grass is provided by the application of capillary tubes between blades of grass or capillary nerves within the artificial blades of grass or both in an already existing field of natural or artificial grass in which case generally the liquid will be adsorbed up from the groundwater. In this way the capillary tubes or capillary nerves are for instance applied to repair the bad parts of an artificial or natural grass field.

Generally the tubes and nerves which are to be applied in this way have to be about 10- 25 cm, preferably between about 15-20 cm, to be able to reach the groundwater.

The problems of hurting the skin when someone falls down on artificial grass are solved by the application of the new field of artificial grass of the invention in which system the supply of the liquid is provided by irrigation in stead of by the rain, which means that the quantity of liquid supplied may be regulated. The field will be irrigated either by supplying water to the liquid adsorbing and releasing layer, or more preferred, by supplying water to a water storing layer from which layer water will be released to the liquid adsorbing and releasing layer. The liquid needed is preferably added by spraying but will of course also originate from nature as for instance rain.

To provide the capillary tubes and capillary nerves according to the invention with a maximum capillary effect the openings at both ends are about the same. In this way, when the liquid adsorbing and adsorbing layer such as a felt layer is wet the

capillary tubes and/or nerves will adsorb an amount of liquid, generally water, what is as large as possible and which will be released when there is a pressure on the artificial grass, especially when a sliding-tackle is made on the grass field. In that case liquid from the capillary tubes and/or from the capillary nerves adsorbed up from the felt layer will be released upon contact of someone's body with the artificial blades of grass. This liquid has a sort of quenching function especially when someone's skin is hurt like burned by the artificial grass field. After the sliding-tackle made the capillary nerves and capillary tubes are active to adsorb liquid again. Moreover, the constant process of evaporation will bring on the sportsman or sportswoman a feeling of cool grass which causes generally a large advantageous psychological effect.

The new capillary artificial grass field is formed when the new capillary grass mat comprising blades of grass, capillaries between or inside the artificial blades of grass and a support layer is applied on a second layer made of material which is able to adsorb liquid and to release it easily, for instance made of felt. Preferably, this new capillary grass mat is glued with said layer. In a preferred embodiment the layer able to adsorb the liquid is applied on a third layer with liquid storing properties being a fine, porous mat as for instance a rubber mat lying on a flatted bottom of for instance sand. Said porous mat has three targets: first of all like shock absorbing device, secondly like liquid reservoir and thirdly for a good bond of the layer able to adsorb the liquid as for instance the felt layer which forms a part of an optimal playing field.

The present invention will be further elucidated with reference to the annexed figures of preferred embodiments of the invention with in: figure 1: slightly bended capillary tube (1) comprising a liquid conductor (2) which tube ends in the felt liquid adsorbing and releasing layer (3) figure 2: slightly bended capillary nerve (4) in a green blade (5) filled with a liquid conductor (2) which nerve ends in the felt liquid adsorbing and releasing layer (3) figure 3: substantially straight capillary nerve (5) inside artificial blades of grass (6) comprising a liquid conductor (2) which nerve ends in the underground of sand (7)

figure 4: artificial grass field has been depicted in normal position (A) and after a sliding- tackle (B), with slightly bended capillary tube (1) some of which filled with a liquid conductor (2), which tubes end in felt, the liquid adsorbing and releasing layer (3), artificial grass blades (8) in the latex support layer (9); the liquid storing layer (10) of rubber, particularly hydro rubber is located under the liquid adsorbing and releasing layer (3) and above the underground of sand (7).

The figures are schematic and not drawn to scale. Some dimensions are highly exaggerated for the sake of clarity.

In the figures preferred embodiments of the invention have been presented.

Figure 1 depicts a capillary tube comprising a slightly bended thread fully filled with a water conductor (2), extending from the thread to enlarge the capillary effect.

Figure 2 depicts a capillary nerve (4) inside an artificial blade of grass (5), also fully filled with a water conductor (2). Upon the application of the capillary tube and/or the capillary nerve the liquid is taken up from the liquid adsorbing and releasing layer, as for instance a felt layer.

Figure 3 represents a substantially straight capillary nerve (6) inside artificial blades of grass (5) comprising a liquid conductor (2) which nerve ends in the underground of sand (7). The capillary of this embodiment may advantageously be applied to repair an existing damaged natural or artificial field of grass. Applying this embodiment the ground water will be adsorbed by the capillary nerve.

In figure 4 the same type of capillary tubes (1) comprising a water conductor has been depicted as in figure 1 together with capillary tubes (1) without water conductor between artificial blades of grass. The artificial blades of grass are attached to a support layer or mat (9), while the capillary tubes are attached on the liquid adsorbing and releasing layer (3). Under this layer the water storing layer (10) is applied from which layer the water is supplied to the liquid adsorbing and releasing layer (3). Finally, the water storing layer covers the underground, usually sand (7). In the left side of this figure under A, the artificial grass blades with tubes are present before someone has touched it.

Under B the situation of the artificial grass has been depicted after a sliding-tackle where water is released from the capillary tubes which water prevents wounds caused by the local development of high temperatures.

It will be appreciated that the invention is in no way restricted to the embodiments given in this description. For instance, due to the system of three layers (support layer, liquid adsorbing and releasing layer and water storing layer) as disclosed and the possibility of independent variation thereof the field of artificial grass may be adapted to various ball sports like tennis, soccer, korfball, rugby, baseball, and the like.

Also for indoor sports and sport activities on covered locations the artificial field of grass according to the invention may be applied. Particularly, also the air humidity in the indoor space may be improved in this way.