FR2719619A1 - Artificial grass material - Google Patents

Abstract

The ground covering material has implanted tufts (3,5) on a carrier (1), which are rot-proof and resistant to ultra-violet rays, with a latex backing (7). The smooth straight tufts (3) are alternated with shorter crimped tufts (5). Also claimed is a tufting operation with needles to insert the tufts into the carrier material in straight rows, with alternating straight tufts (3) and shorter crimped tufts (5).

Description

 SYNTHETIC GRASS AND METHOD FOR THE PRODUCTION THEREOF.

 tdel'invention.

 The present invention relates to a so-called synthetic turf, that is to say a covering intended for soils which imitates natural turf, both from the point of view of appearance and from the point of view of physical properties and which is used. for the exercise of sports.

 The invention also relates to a method enabling the production of such a synthetic turf in a relatively simple and inexpensive manner.

Technological background
Many sports, such as football, hockey, etc. are practiced on specially landscaped grounds with regard to flatness and whose soil is provided with a turf cover and more specifically, which has been specially sown using herbaceous species, generally selected.

 These soils have intrinsic properties, in particular resilience. Climatic conditions and other factors, notably related to use, however cause deterioration over time and seasons and in any case make regular maintenance necessary (reseeding, regular mowing, rolling, etc.).

 The succession of frost and thaw, heavy rain and snow cause, in particular, major deterioration to most natural terrains, and in some cases lead to their closure.

 There is therefore an advantage in being able to have a covering imitating the grass made of a synthetic material, hereinafter referred to as "synthetic grass" as a partial or total replacement for soils made up of natural grass.

 However, such recoveries must reconcile imperatives of mechanical properties (for example bouncing balls, slippage, hooking for crampons or specific soles according to the types of sport of shoes etc). In addition, synthetic materials have the major drawback of causing overheating and even burns when, as a result of a fall, a player slides on a synthetic surface. On the market, synthetic turf has already been proposed consisting of relatively long, smooth and flexible threads which make it possible to avoid these overheating or burns.

 However. this type of product does not have sufficient "hold", that is to say both resilience properties and sufficient stability for the exercise of most sports and athletes, used to a natural grass . believe that "synthetic" products do not fully meet their expectations.

Aims of the present invention
The present invention aims to reconcile safety requirements, in particular safety linked to the risk of overheating or burns for players with "holding" properties, ie essentially mechanical behavior of the covering, comparable to those of natural turf. , enough for athletes to accept the substitution of natural grass for synthetic grass.

 Additionally, the invention aims to obtain a product which from the point of view of maintenance and weather resistance is superior to natural grass and in particular which makes it possible to play in all weathers and which requires only limited maintenance.

 The invention also aims to provide a process both from the point of view of the cost price and from the point of view of the ease of installation and the ease of manufacture, making it possible. under acceptable financial conditions, consider replacing the natural turf with synthetic turf.

 Other objects, advantages and particularities of the invention will appear on reading the description which follows.

Element features of the invention
The invention provides a synthetic grass consisting of an implantation of rot-resistant and W-resistant son in a support, preferably a canvas, also having these properties, and optionally provided on the back with a latex coating intended to stabilize the whole. , characterized in that the product consists of an alternation of smooth straight wires and crimped wires, so that the crimped wires are set back relative to the height of the smooth straight wires.

 Advantageously, the length of the smooth straight wire is between 15 and 20 mm and is preferably of the order of 18 millimeters, while the crimped wire, for the same length in the stretched state, has under its crimped profile 65 to 85% of the height of the smooth straight wire. This means that on the finished product, the crimped yarns show a shrinkage of 15 to 35% compared to the height of the straight smooth yarns.

 Straight smooth and crimped yarns are preferably polyolefin yarns, such as yarns composed of polypropylene and polyethylene, and preferably specially treated to improve the coefficient of friction in order to obtain good sliding properties and thus reduce the risk. burns in the event of a fall.

 The alternation rhythm of smooth straight yarns and crimped yarns, as well as the nature of each of these types of yarns can be adapted to obtain a synthetic turf which best corresponds to the sport for which said turf is intended.

 The threads are arranged in alternating rows, successively constituted by one or more (preferably two) rows of smooth straight threads and one or more (preferably two) rows of crimped threads.

 The term wire must be understood in the broad sense and applies in particular to very thin strips of the order of a millimeter or a fraction of a millimeter having a thickness of the order of a few tenths or a few hundredths of a millimeter.

 The manufacture of synthetic turf is carried out by a technique akin to the known technique of "tufting" consisting of implanting in a row using a suitable needle, a continuous thread on a support such as a canvas, alternating however the rows as indicated above.

 An alternation of a row of straight smooth wires and a row of crimped wires or two rows of straight wires and two rows of crimped wires seems to be the most suitable solution for synthetic turf intended for exercise. sports such as football or hockey, in particular with regard to the characteristics of rebound, comfort and quality of play. The interaction of the foot with the surface, regardless of the type of shoes used (with or without crampons ) is completely satisfactory.

 A particularly advantageous embodiment of the manufacturing process consists in implanting wires having differential shrinkage properties during a heat treatment (which is very often the case for smooth straight wires compared to crimped wires, even if they are of the same chemical nature), shave them in a conventional manner at the same height in their stretched form and take advantage of the hot latex operation in order to both fix the wires and obtain, thanks to the removal differential, the product as desired, that is to say a product for which the crimped wires are even further back compared to the straight wires. Indeed, already by their shape, the crimped yarns appear at a lower level than the smooth straight yarns and the latexing operation only increases this shrinkage.

 This procedure makes the best use of conventional tufting techniques and facilitates production at a reasonable cost.

 Other production techniques can of course be envisaged depending on the circumstances and the production equipment available.

 These yarns will be dyed in the mass and provided with the necessary treatments, superficial or in the mass, generally used for this type of products, for example agents for protection against ultraviolet radiation, priming agents such as lubricants, etc. known to specialists.

 When in use, the product, which is generally delivered in the form of a roll, is laid flat in strips on the ground and loaded with fine, dry sand at the rate of 6 to 15 kg per m2 which fills the gaps between the wires and which ensures a ballast in order to fix the unrolled strips firmly on the ground. The strips arranged in parallel can be joined together by any suitable technique.

Additional fixings can be provided, in particular at the ends of the, by suitable means such as stapling, etc.

 Usually. for a product whose installation is envisaged by this technique, three rows per centimeter (with the above-mentioned alternation) are sufficient.

 It is also possible to provide more than three rows per centimeter, that is to say to use a denser product in which case, it is possible to remove the ballast sand, this lawn then preferably being fixed by bonding in plain on a specially adapted support surface.

 Another solution for laying the product according to the invention consists in providing a sufficiently heavy coating on the back of the product, for example a PVC type coating, which allows the turf to be held in place by its sole weight.

 Of course, depending on the circumstances and in particular on the sport practiced, numerous variants can be envisaged. It should also be noted that the product as described does not see its uses limited to the sports indicated. This type of product may also be suitable for the practice of athletics in general, tennis, whether indoor or outdoor.

 The invention will be described in more detail by way of illustration of a particularly preferred embodiment with reference to the accompanying drawings.

drawingdescription
Figure 1 shows a wire called crimped as it is commercially available, having a thickness of 0.070 mm, a width of about 1.5 mm.

 Figure 2 shows in section the product according to the invention, according to a preferred arrangement constituting an alternation of two rows of crimped son and two rows of straight son. Other alternations are of course possible.

 In Figure 2, there is shown a support fabric 1 provided with a tufting consisting of two rows of straight son 3 and two rows of crimped son 5. According to a preferred embodiment of the invention, the alternating rows have were obtained by the conventional tufting technique on the support fabric 1 in pitted loops using a conventional needle.

 The strands are then shaved to the same length in their stretched state, which means that the crimped strands 5, because of their profile, already have a lower level than the straight straight strands after being cut.

 This arrangement is further accentuated by a latexing operation which consists in an operation of applying a latex 7 by heat treatment on the back of the product which causes a differential shrinkage so that the crimped threads 3 on the finished product are even shorter than the smooth straight wires 5, so as to obtain a total shrinkage of between 15 and 35%.

 As previously indicated, most of the crimped yarns, compared to smooth straight yarns of the same kind, exhibit differential shrinkage due to the increase in crimping during the thermal coating operation, such so that we finally get the desired shrinkage.

Claims (11)

 1. Synthetic grass consisting of an implantation of rot-proof and W-resistant son (3,5) in a support (1), preferably a canvas, also having these properties, and optionally provided with a latex coating on the back ( 7) intended to stabilize the assembly, characterized in that the product consists of an alternation of smooth straight wires (3) and crimped wires (5), so that the crimped wires (5) are set back relative at the height of the smooth straight wires (3).  2. Synthetic grass according to claim 1 characterized in that the length of smooth straight son (3) is between 15 and 20 mm, and is preferably of the order of 18 mrn.  3. Synthetic grass according to claim 1 or 2 characterized in that the crimped son (5) for a length in the stretched state corresponding to that of straight smooth son (3), have under their crimped profile a shrinkage of 15 to 35 % in relation to the height of the smooth straight wires (3).  4. Synthetic grass according to any one of the preceding claims, characterized in that the yarns (3,5) are polyolefin yarns, preferably yarns composed of polypropylene or polyethylene, and preferably specially treated to improve the coefficient of friction in order to obtain good sliding qualities and thus reduce the risk of burns in the event of a fall.  5. Synthetic grass according to any one of the preceding claims, characterized in that the wires (3,5) are arranged in alternating rows, constituted successively by one or more (preferably two) rows of smooth straight wires (3) and a or several (preferably two) rows of crimped threads (5).  6. A method of manufacturing synthetic grass according to any one of the preceding claims by a technique related to the known technique of "tufting" consisting of implanting in row using a suitable needle, a continuous wire on a support such a canvas, characterized in that rows of smooth straight threads (3) and curly threads (5) are alternated.  7. Method according to claim 6 characterized in that one implements smooth straight wires (3) and crimped (5) having differential shrinkage properties during a heat treatment, in that they are shaved conventionally to same length and in that one takes advantage of the hot latex operation operating at the same time fixing the wires and obtaining, thanks to the differential shrinkage, the product as desired, this latex operation completing the difference already obtained by the crimp of the crimped wire (5).  8. Use of a synthetic grass according to any one of claims 1 to 5 characterized in that the product which is generally delivered in the form of a roll is laid flat in strips on the ground and loaded with fine dry sand 2 to reason of 6 to 15 kg per m which fills the interstices between the wires and which ensures a ballasting in order to fix the strips unrolled firmly on the ground.  9. Use of a synthetic turf according to claim 8 characterized in that the strips arranged in parallel are joined together by any suitable technique and by additional fastenings in particular at the ends of the strips.  10. Use of a synthetic grass according to any one of claims 1 to 5 characterized in that this grass is fixed by bonding in plain on a specially adapted support surface.  11. Use of a synthetic turf according to any one of claims 1 to 5 characterized in that this turf is provided with a sufficiently heavy coating on the back so as to keep the turf in place by its sole weight.