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Abstract

A spin casting apparatus, method of manufacture for producing a molded article from a polyurethane material, shown as a non-pneumatic tire, where a mold that is formed in sections or halves and has an inner cavity formed to have the shape of the article to be manufactured and is separable to release that article after manufacture. The mold is secured to a support plate of the apparatus that is journaled to turn axially imparting a centrifugal force into the mold. The support plate is connected to or is arranged to be connected to a motor assembly for turning, and includes a clamping arrangement for maintaining the mold halves together on the support plate. An annular trough is formed in the mold immediately adjacent to a mold interior cavity inner circumference to receive a polyurethane material liquid passed thereto, and to, in turn, pass that liquid through a trough annular opening or ports into the mold cavity. The polyurethane material is selected to begin to react, forming a foam, as support plate turning is initiated, providing immediate centrifugal forces into the material to uniformly distribute it throughout the mold cavity, compacting it against the cavity walls to form an article having a uniformly increasing porosity from a dense outer circumference to its inner circumference. The preferred polyurethane material is composition of polyisocyanates, with water as a polyol, and preferably includes a blowing agent to produce carbon dioxide gas during curing and provides for, after mixing, a time delay in seconds to allow the mixture to fill the mold annular trough and at least partially travel into the mold cavity, before the mixture begins to react. An article, such as a bicycle, wheel chair tire, or the like, can be formed in the apparatus and by the method to have a non-porous ring-shaped outer skin, with a foam interior, and has a uniform declining density in porosity from its outer surface to its interior and may include a wire loop, or the like, molded into a tire bead, as a tension retainer member.

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First Claim