Trapezoidal non-pneumatic tire with supporting and cushioning members
Patent 4921029 Issued on May 1, 1990. Estimated Expiration Date: May 22, 2009. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
A trapezoidal non-pneumatic tire ("TNPT") is integrally molded from a stiff, resilient elastomeric material with particular specifications, to form a unitary structure comprising outer and inner cylindrical coaxial members ("hoops"), the outer being wider than the inner. The outer hoop is supported and cushioned by a plurality of circumferentially spaced apart, planar rib members (ribs) and a planar central web member (web) which connects the hoops at their circumferential center lines. The web lies in a plane perpendicular to the rotational axis of the TNPT. The ribs extend axially along the inner and outer hoops, connecting them, and the edges of the ribs lie along the opposite faces of the web. The ribs are angled in the range from 15° to 75° to radial planes which intersect them at their radially inner ends, and the ribs on one side of the web are angled oppositely from those on the other. A rubber tread is secured to the outer surface of the outer hoop. The coaction of the structural elements of the TNPT provides a load-supporting structure which, in operation, is subjected to continuous compression and tensile forces as it travels over the ground. Deformation and buckling characteristics of the TNPT are derived from its unique trapezoidal shape which results in an interaction of the structural elements such that the outer hoop is not pulled under the wheel as much as the outer hoop would have been, had the shape of the TNPT been rectangular. The trapezoidal shape provides the TNPT with improved "handling" characteristics in hard turns without sacrificing a "ride" which is suprisingly similar to that of a conventional pneumatic tire.