CA1218683A

CA1218683A - Sports ground covering

Info

Publication number: CA1218683A
Application number: CA000439695A
Authority: CA
Inventors: Pierre Zurkinden
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-10-25
Filing date: 1983-10-25
Publication date: 1987-03-03

Abstract

ABSTRACT OF THE DISCLOSURE

A sports ground covering has a lower cushioning layer, an upper wear-resistant layer, and an intermediate reinforcing iron netting. Both the layers contain rubber chips produced from old vehicle tires. The lower cushioning layer contains interspersed spherical expanded clay, which gives the layer resilience and makes it independent of atmospheric humidity during production.

Description

This invention relates to a sports ground covering.
Swiss Patent No. 601,567 describes a sports ground covering having a lower layer for cushioning or damping impact actions on the covering and a thinrier wear-resis-tant coating applied there-to. The lower or cushioning layer can be stabi-lized by a reinforcing iron net-ting and con-tains, apar-t ~rom rubber chips made from old vehicle tires bound with polyure-thane, mineral additives, enabling the elasticity of the layer to be se-t at a desired value.
] Sports ground coverings constructed in this way have excellent characteristics. However, certain problems occur during their production as a result of the use of mineral additlves. Due to -the Eact that they consist of chippings, concrete rubble and/or sand, the additives are hygroscopic. The moisture proportion contained -therein consequently varies within certain limits. During -the produc-tion of the cushioning layer the moisture c031tent of the additives largely depends on how and where they were stored beforehand. It is quite possible for the moisture content to change during the production of the spor-ts ground ~overing because -the contents can be lower during the late afternoon than in the morning. ~s a resul-t, the properties oE the covering change.
In addition, due to -their porosi-ty, the additives also partly absorb the binder, i.e. -the polyurethane, to a degree which is partly dependent on the particle size of the minerals and makes accurate me-tering of the binder more difficul-t.
During manufacture, it is necessary -to depend on -the values obtained through experience, but this can only gradually be acquired and sports ground coverings must have the correct composition from the outse-t. Additional problems are caused by the Eact that ~or excessiv~ly high moisture con-ten-ts of the mineral additives the polyuretane tends to expand.

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An objec-t of the invention is to replace this additive by a more sui-table ma-terial, which not only simplifies produc-tion but also enables part of the production process to be carried out in advance so that in si-tu it is only necessary to earry ou-t the actual installation of the covering.
According to the presen-t invention there is provided a sports ground covering comprising a lower layer for cushioniny or damping impact effects on the covering, an upper wear-resis-tant coating applied thereto, and an in-termediate reinforcing netting for stablizing -the cushioning layer, the two layers eomprising rubber chips bound with polyurethane, said lower layer also containing expanded clay interspersed therein.
The invention will now be descri~ed in more detail, by way of example only, with referenee to the aecompanying draw-ings, in which the single Figure is a perspec-tive view of a partly cut-away spor-ts ground covering.
In ~he Figure the sports ground covering has a lower eushioning layer 1, an upper or wear-resistant eoating 2, and an intermediate reinforcing iron netting 3, which s-tabilizes layer 1. Both layers comprise rubber chips, produced from old vehicle -tires, bound with polyurethane. The complete eovering is applled to a gravel layer (no-t shown) which allows the drainage of rain water and melted snow. Instead of the cushioning layer 1 eontaining mineral additives as in -the prior art, it now has interspersed therein expanded clay 5, preferably in -the form of small balls. This expanded clay has the following advantages:
1. It is not porous and is -therefore no-t hygroscopic. Thus, it always has -the same specifie gravity, regardless of atmospherie humidity present during the produetion or during the storage of the expanded elay. This constant bulk density provides a eover-ing of constant quality. ~lhe frequently observed expansion ofthe polyurethane used as a binder for the rubber chips, which ~2~

OCcurs when the wa-ter content of -the mineral additives is too high, is no longer observed.
Due to the lack of porosity not only is the absorption of water prevented, but also the absorption of part of the poly-urethane. Thus, the latter can be metered in an accurate man-ner, further contributing to the uniformity of the covering. In addition, much less polyurethane is required than hitherto.

2. Due to this uniformi-ty, it is not only possible to indust-rially prepare the ac-tual expanded clay, but also -the cushioning layer containing it, so -that the layer only has to be laid on site. Such prefabrication was possible with mineral addi-tives, but led to -the difficulty -that duxing transpor-ta-tion part of said additives were separated again from the layer material, mainly due to -the unavoidable vibrations. The expanded clay balls are completely integrated into the material and avoid this problem .

3. The constant specific gravity of the expanded clay balls also permits uniform production when the ball diameters differ.
Thus, there is no dependence of the quali-ty on the particle size, as was encountered in the hitherto used minerals.

4. Expanded clay is more elastic than mineral additives. As a result, not only is the covering more elastic, but it is also less sensitive to extreme temperature variations.
The aEorementioned use of expanded clay makes it possible to obtain a very robust and hard-wearing sports ground covering.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A sports ground covering comprising a lower layer for cushioning or damping impact effects on the covering, an upper wear-resistant coating applied thereto, and an inter-mediate reinforcing netting for stablizing the cushioning layer, the two layers comprising rubber chips bound with polyurethane, said lower layer also containing expanded clay interspersed therein.

2. A sports ground covering as defined in claim 1, wherein said expanded clay is in the form of small balls.