Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Reexamination Certificate
2000-04-12
2004-01-06
Watkins, III, William P. (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
C428S119000, C428S141000, C428S220000, C238S014000, C404S019000, C052S177000, C004S582000, C015S215000, C015S238000
Reexamination Certificate
active
06673417
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to anti-slip floor tiles and their method of manufacture.
BACKGROUND OF THE INVENTION
Ceramic floor tiles and other hard floor surfaces are easily maintained and withstand heavy traffic, but such floors can be slippery when soiled or wet. This problem is especially dangerous for floors in doorways, kitchens, and bathrooms where soil, such as oil, grease, sand, or water, can be deposited onto the floor. A minimum floor tile slip resistance coefficient of approximately 0.20 to 0.25 is required to prevent slipping. That coefficient can be measured following the American Society for Testing and Materials (“ASTM”), Standard Testing Procedure (“STP”) F-1677-96. See
Measurement of Slip Between the Shoe and Ground During Walking
; Perkins, P. J., ASTM STP 649, pp. 71-87 (1978) for a general discussion of slip resistance coefficients, which is herein incorporated by reference in a manner consistent with this disclosure. Accordingly, research has been conducted on anti-slip floor materials. Such floor materials previously available are prepared, for example, by embedding abrasive foreign particles (i.e., particles made from a material different than that of the hard floor) on the surface layer of the hard floor, or by covering the hard floor surface with a flexible continuous rubbery sheet with random deformable or compressible rubbery particles distributed throughout the rubbery sheet.
Abrasive particles can be incorporated into certain floor surfaces by mixing sand, aluminum oxide, carbide particles, or another grit in paint or glaze and painting or glazing the floor surface with the mixture. Abrasive particles having a composition different from that of the floor surface can also be included in the floor surface such that the particles protrude from the floor surface. In either case the abrasive particles tend to wear and detach from the surface with time. Additionally, the concentration of the particles on the surface varies randomly, thereby resulting in non-uniform results.
U.S. Pat. Nos. 3,227,604, 4,239,797 and 4,336,293, for example, disclose floor materials having grit or particles embedded in or distributed throughout the surface layer. These materials have the drawback that the surface layer, if worn by walking, no longer retains non-slip properties. Furthermore, the embedded particles tend to separate from the surface with time.
U.S. Pat. No. 3,676,208 to Griffin discloses a floor surface wherein glass spheres are incorporated into a surface adhesive film. An epoxy-type resin containing a significant concentration of minuscule solid spheres, such as glass beads, is coated onto a floor surface. This grit-containing epoxy mixture increases the slip resistance of the floor, but it is believed that it does not provide sufficient slip resistance when heavily coated with water or grease.
U.S. Pat. No. 3,030,251 discloses non-slip sheet articles comprising an essentially-continuous, flexible, readily-deformable, rubbery underlying matrix within which a multitude of discrete flexible resilient non-adhesive particles are distributed. However, the particles are not exposed. While the particles have lower abrasion resistance than the matrix layer, they are non-adhesive and are therefore easily releasable.
An object of the present invention is to overcome the foregoing drawbacks of conventional floor materials and to provide anti-slip floor tiles having high durability, uniform performance, and high slip resistance coefficients.
A further object of the present invention relates to a method for manufacturing anti-slip floor tiles having high durability, uniform performance, and high slip resistance coefficients.
SUMMARY OF THE INVENTION
The anti-slip floor tiles of the present invention are textured with a pattern of spikes. The spikes can be spaced in any suitable pattern which results in an adequate slip resistance coefficient (i.e., a slip resistance coefficient of at least about 0.20, preferably at least about 0.25) under any use condition (i.e., dry, wet, greasy or greasy/wet). For a tile of this invention which is greasy/wet (i.e., greasy and wet) the adequate slip resistance coefficient is also at least about 0.20, preferably at least about 0.25. In contrast some tiles of the prior art have slip resistance coefficient of as low as about 0.13 under greasy/wet conditions. Further, the tiles of this invention maintain slip resistance coefficients of at least about 0.20, preferably at least about 0.25 under greasy/wet conditions even after simulated wear. The distance between adjacent spikes (also referred to herein as “distance between spikes”) can range from about 5 mm to about 20 mm, with the minimum distance between spikes being about 5 mm. In a preferred embodiment of the invention, the spikes are spaced in a substantially uniform pattern with about 11 mm between adjacent spikes.
The spikes are preferably pyramidal or conical in shape. Further, the top of the spike can optionally be shaped so as to produce a substantially flat upper surface. The height and base width of the pyramidal spikes (or the height and diameter of the conical spikes) are important to slip resistance coefficients. Preferred spike dimensions range from about 0.2 to about 3.0 mm in height and from about 0.8 to about 3.0 mm in base width for pyramidal spikes. For conical spikes, preferred spike dimensions range from about 0.2 to about 3.0 mm in height and from about 0.8 to about 3.0 mm in diameter. Whenever reference is made herein to a height and base width (or diameter) of the spikes, it is intended to reference the height and base width of the pyramidal-shaped spikes or the height and diameter of the conical-shaped spikes. The spike angle (i.e., the angle of a sidewall of the spike with respect to the horizontal plane of the base of the spike as shown in the Figures) is defined by the height and base width (or diameter) of the spikes.
Another embodiment of the invention is drawn to a process for manufacturing anti-slip floor tiles which comprise an exterior surface that is textured with a pattern of spikes, preferably a substantially uniform pattern of spikes, said process comprising the steps of:
a) pressing a suitable powder composition on a mold, said mold comprising an upper punch, a mold frame, a lower punch, and a filler box, thereby forming a pressed tile,
b) extracting said pressed tile from said mold, and
c) firing the resulting pressed tile to form said anti-slip floor tile
wherein the surface texture is formed from the upper punch of the mold which includes spike-shaped indentations.
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Milligan, “Abrasive Products in the Building Industry”, 1935, Industrial and Engineering Chemistry, vol. 27, No. 10, pp. 1123 1124.
Crossville Ceramics Company
Hunton & Williams LLP
Watkins III William P.
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