Patent ID: 6481481
Filing Date: 2002-11-19
Classification: B60C,Y10T

Abstract:
A reinforced rubber membrane,used as a tread support means for a tire, and forming with said tire and its mounting rim a travelling assembly which is capable of travel when the tire is subject to a loss of pressure, the rim having a flange and a rim seat, the rim having a nominal diameter DS and the flange having an external diameter DR, inflated during use to a pressure p0 greater than the pressure p1 of the cavity of the tire, and having, in the inflated state, a crown radius RM less than the loaded radius RE of the tire used at its recommended pressure, said membrane being reinforced in its crown by at least two plies of cords or cables parallel to each other in each ply and crossed from one ply to the next, at least one of said plies being a so-called hooping ply composed of at least one layer of cords or cables, oriented circumferentially and having a breaking load per cm of ply making it possible firstly to resist the tension due to the maximum centrifugal force to which the tire is subjected, increased by the tension due to the pressure differential p0âˆ’p1 existing during normal travel, and secondly the breaking of the cords or cables for a pressure differential p0âˆ’pâ€²1 greater than p0âˆ’p1, and reinforced in each of its sidewalls by at least one ply, the membrane being characterized in that, viewed in meridian section, the sidewall reinforcement ply is anchored in each lower part of the sidewall by winding around an inextensible annular reinforcement element, which does not break under the action of the tension induced by the action of the sidewall ply and the internal diameter D of which is between the value DR and a value equal to DS minus the product of the width LS of the rim seat and the tangent of the angle of inclination of said seat, said sidewall reinforcement ply being formed of reinforcement elements, each element comprising a core surrounded by a helically wound cord or cable, the said core having a breaking load which is firstly greater than the tension, per element of ply, due to the pressure differential p0âˆ’p1 and to the maximum centrifugal force to which said element is subjected, and secondly such that it permits the breaking of said elements of the sidewall ply for a pressure differential p0âˆ’pâ€²1 greater than p0âˆ’p1 and after the breaking of the elements of the hooping ply, and said reinforcement element of the sidewall ply having a curve, representing the tension as a function of the relative elongation &egr;, having, for an elongation greater than the elongation at break &egr;A of the core, a segment in which the variation in the tractive force as a function of the elongation is substantially zero, the elongation at break &egr;R of the reinforcement element being at least equal to the ratio of the difference between the internal meridian length of the tire and the external meridian length of the membrane to the external meridian length of the membrane.