Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1988-11-17
1990-01-30
Van Balen, William J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
427212, 4274071, 4274073, 428 17, 428 95, 4283044, 4283179, 428327, B32B 516
Patent
active
048973025
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION is concerned with synthetic sporting surfaces and particularly although not exclusively sporting surfaces suited to the game of tennis.
There are many synthetic sporting surfaces which purport to combine advantages of natural playing surfaces such as grass, clay, cinders, etc. with advantages of synthetic materials such as wearability, weatherability and the like. Prior art synthetic sporting surfaces may be broadly classified in two groups:
artificial turf comprising tufted fibrous material, and;
solid surfaces comprising a cushioned or stiff integral layer of a synthetic material.
The present invention is concerned with surfaces of the "solid" type although it should be understood that for many sporting applications surfaces according to the invention may be superior to "artificial turf" sporting surfaces.
Previously known "solid" sporting surfaces may be broadly categorized as "cushioned" and "hard" surfaces.
Of the prior art cushioned surfaces the most effective and most durable, comprise a cast layer of liquid polyurethane polymer containing particles of a resilient material such as pulverized rubber from reclaimed motor car tyres and the like and these surfaces may be constructed as solid or porous structures.
A solid structure may typically comprise a polyurethane liquid polymer containing pulverized rubber particles having a particle size in the range 2 mm-5 mm in the ratio of about 10 parts by weight of polymer and 4 parts by weight of rubber particles. The mixture is then cast onto a previously prepared surface of concrete, asphalt, timber, compacted earth or the like to form a layer of between 6 mm-20 mm in thickness. A pigmented (usually red iron oxide) surface coat of synthetic rubber or polyurethane polymer or a mixture thereof is then applied as both a decorative and wear layer.
Generally speaking these "solid" surfaces are used only as indoor sporting surfaces for indoor tennis. While quite effective initially as a surface for serious competition tennis, these surfaces nevertheless suffer a number of disadvantages. "Solid" polyurethane/rubber surfaces are extremely expensive due to the high polyurethane polymer content. In addition a "dog-bone" wear pattern develops between opposing base lines after a period of use. Apart from being unsightly when viewed by both live and television audiences, the dog-bone shaped depression gives rise to uneven ball bounce which is unacceptable to players.
Although attempts have been made to patch the dog-bone wear pattern by casting a fresh layer of polyurethane top coat into the depression, these attempts have been generally unsuccessful. When casting a fresh layer of top coat into the wear depression, it is very difficult to match the colour of the fresh layer to that of the surrounding original layer and thus the undesirable visual appearance of the dog-bone wear pattern can be worsened by repair. A particular disadvantage of such repair methods is that unless extreme caution is taken, delamination can occur between the original and repaired surfaces at the edges. This can be quite dangerous for players if they trip on a lifted edge.
Although the abovementioned problems may be avoided by casting a fresh layer of polyurethane resin over the entire surface of the tennis court, the high cost of materials is virtually prohibitive. This of course negates the possibility of frequent changes to the colour scheme of a tennis court as is often required for television purposes.
Another type of surface usually employed on outdoor tennis courts comprises a porous structure to assist in drainage of rainwater. The porous surface is constructed from a clear liquid polyurethane polymer containing rubber particles or other particulate materials. A porous structure is achieved by mixing the liquid polyurethane polymer and rubber particles in the ratio of about 1 part by weight of polymer and 5 parts by weight of rubber particles and applying the mixture to an outdoor surface to a thickness of between 6 mm-25 mm. The resultant structure when cured contains p
REFERENCES:
patent: 4054706 (1977-10-01), Shapiro
A. V. Syntec Pty Ltd.
Van Balen William J.
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