Road structure – process – or apparatus – Pavement – Including bed
Reexamination Certificate
1997-09-24
2001-05-08
Lillie, Eileen D. (Department: 3673)
Road structure, process, or apparatus
Pavement
Including bed
C404S035000, C052S391000
Reexamination Certificate
active
06227759
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates generally to a skating surface, and more particularly relates to a plastic skating surface, wherein the skating surface comprises at least two sheets of plastic welded together. The effects of expansion and contraction of the skating surface is limited to the outer perimeter of the skating surface. An expansion plate overlaps the outer perimeter of the skating surface, thereby defining a fixed outer edge of the skating surface.
II. Discussion of the Related Art
Plastic has been used for over 20 years as a surface upon which one can skate using either hockey or figure skates. At this time such products are not generally accepted by the hockey community nor by the figure skating community even though certain individuals have endorsed them or are selling such products. Sales of such products are generally limited to very small surfaces (typically 30-40 feet square) compared to entire hockey rinks (200′×85′) or even smaller training areas of perhaps 3,000 to 6,000 square feet. For over 20 years the market has rejected plastic ice as a meaningful competitor or supplement for refrigerated ice.
The basic thermal expansion and contraction properties of plastic have been the major factor in limiting the commercial viability of “plastic ice”. Those parties knowledgeable in plastics and their commercial applications understand that plastic products are subject to expansion and contraction in relation to changes in the air temperature around the plastic. For example, HMD (high molecular density) plastic if applied to an entire ice arena 200 feet long would expand and shrink about 2 feet, given a 70-80 degree change in temperature. The present invention involves a strategy for dealing with these scientifically determined characteristics of plastic. Before the present invention, welding technologies for plastics had not been applied to plastic surfaces for skating and/or hockey playing or training areas.
Those companies making products for skating and/or hockey related purposes have all employed various forms of tongue-and-groove or interlocking designs as their method of locking the plastic in place and in dealing with expansion and contraction. The principle disadvantages of these existing and former products include price, and the expansion and contraction problems associated with the linear coefficients of thermal expansion and contraction for plastics. Price becomes a factor primarily because of the need to have a system that compensates for the above-mentioned expansion and contraction characteristics.
When we started researching this problem, while seeking a low cost surface viable for use in training skaters and hockey players as a supplement to refrigerated ice surfaces, we discovered the existing companies had products with essentially the same characteristics all apparently designed to compensate for expansion and contraction. These surfaces generally employed relatively small (23″×23″to 48″×48″) surfaces that were about one inch thick and employed tongue-and-groove methods of attachment. We also observed thinner plastic surfaces of a rectangular nature that also employed tongue-and-groove joints. These surfaces failed due to warping at the perimeter of each piece including the joints, as a result of the natural expansion and contraction from temperature changes.
Installing tongue-and-groove sections is costly because of the time needed to install many pieces. The largest such known product comes in 4′×4′ sections. A 60′×100′ training area of 6,000 square feet would require about 375 such pieces to be fit together, each piece dependent upon laying other pieces. In contrast, according to the present invention, 25 plastic sheets 30′×8′ may be welded together to form a training area having the same square footage. Laying such sections, prior to welding can be done in less than one hour by one crew.
Typically, the tongue and groove plastic skating surface is expensive due to the nature of their design and installation practices. A skating surface made according to the present invention should cost less than one-half the cost of a plywood backed tongue and groove system.
Another product similar to the tongue and groove product is made by bonding 0.25″ plastic to 0.5″ sheets of high quality plywood. The product is also milled with grooves on all four sides of the plywood core to allow joining by pieces of plastic which fit into the grooves of adjoining pieces. This process of production is also expensive because of the need to bond the ¼ inch plastic on either side of the wood, cut the resulting pieces into squares and then mill the sides to create the grooves. Typically, such products retail at a price in excess of $24.00 a square foot even for full-sized rinks. Hence, a need exist for an economical plastic skating surface that directs the expansion and contraction of the skating surface to an outer edge of the skating surface. The present invention addresses these and other needs.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide a plurality of plastic sheet material aligned edge to edge in a common plane, wherein the edges of adjacent sheets are welded together to thereby form a single continuous skating surface that directs the expansion and contraction of the skating surface to an outer periphery of the skating surface. Without any limitation intended, the preferred embodiment of the present invention utilizes a high molecular weight (HMW) polyethylene polymer. The HMW polyethylene is used in a plastic injection molding process to produce a molded large sheets of plastic ¼ to ½ inch thick. In the preferred embodiment, the plastic sheets are ⅜ of an inch thick, 32 feet long and 8 feet wide. Those skilled in the art will appreciate that the plastic sheets may be manufactured having dimensions that are either longer or thicker or in any combination thereof.
In the preferred embodiment, the skating surface comprises at least two sheets of plastic laid side by side and welded together thereby forming a single continuous piece of plastic. The single continuous plastic skating surface restricts the effects of expansion/contraction to the perimeter of the surface. The expansion/contraction of the skating surface can be calculated and steps can be taken to accommodate each direction of movement. For example, the manufacture of a 30′×100′ training area in accordance with the present invention would involve about 12 sheets of plastic welded together. If temperature fluctuations could be limited to changes of 70-80 degrees (a reasonable assumption for use in insulated buildings) then the overall skating surface would expand about 12 inches along its length and 4 inches along its sides. Hence, when installing the sheets in a confined area, the installation would need to accommodate a 2 inch expansion along each side and a 6 inch expansion at each end. This can easily be done by installing the plastic in such a manner that it either has unoccupied space around all four sizes or has “kick boards” that float slightly above the plastic and extend over the plastic by 2 inches on the sides and 6 inches on the ends. The details of such a kick board will be apparent to those skilled in the art.
If desired, a larger sheet of plastic, such as 17,000 square foot (a standard 200′×85′) hockey rink surface, or a much smaller surface, is anchored by a number of commercially available means of “pinning” the sheet in the middle so that its heat-change-induced movement is restricted to a limited area at the parameter of the surface. Pinning the sheet allows for the construction of dasher boards or kick boards (boards used hockey rinks) suspended over the plastic in such a manner as to allow the plastic to expand and contract without either buckling or shrinking outside the confines of the dasher boards.
In other unrelated
Fricke Leonard S.
Sims Carl W.
Addie Raymond W
Lillie Eileen D.
Nikolai Mersereau & Dietz, P.A.
TecLink International Ltd.
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