Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Patent
1996-09-25
1998-06-30
Johnstone, Adrienne C.
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
152526, 152532, 152534, 152535, B60C 918, B60C 920, B60C 922
Patent
active
057728100
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a tire with radial carcass reinforcement anchored on both sides to at least one bead wire and having a crown reinforcement consisting of at least two so-called working plies which are superimposed and formed of wires or cables which are parallel in each ply and crossed from one ply to the next, forming angles of at most 45.degree. in absolute value with the circumferential direction of the tire.
Such a tire, more particularly of the "heavy vehicle" type, having a form ratio H/S of at most 0.80 and intended for a vehicle of medium or large tonnage, has a crown reinforcement which also comprises a ply of metal wires of cables of low stretchability which form an angle of between 60.degree. and 90.degree. with the circumferential direction, said ply, known as a triangulation ply, being located radially between the carcass reinforcement and the first crown ply known as working ply. The triangulation ply forms with the two working plies a triangulated reinforcement which exhibits little deformation under the various stresses which it suffers, the triangulation ply having the essential role of taking up the forces of transverse compression to which all the reinforcements are subjected in the region of the crown of the tire.
Certain existing tires, known as "highway" tires, are intended to travel at high speed over increasingly long distances due to the improvement in the network of highways and the increase in the highway networks throughout the world. The conditions under which such a tire is called upon to travel undoubtedly permit an increase in the number of miles traveled, there being less wear of the tire; on the other hand, the life of the tire and in particular of the crown reinforcement is strongly penalized.
The stresses present at the level of the crown reinforcement and, more particularly, the shear stresses between the two crown working plies, together with a substantial increase in the operating temperature at the level of the ends of the shorter working ply, result in the appearance and propagation of cracks in the rubber at the level of said ends, despite the presence at the junction of the edges of the working crown plies of a thickened layer of rubber.
SUMMARY OF THE INVENTION
In order to overcome the above drawbacks and to lengthen the life of the crown reinforcement of the type of tire in question, the tire, in accordance with the invention, comprises a radial carcass reinforcement surmounted by a crown reinforcement formed, in direction radially from the inside to the outside, of at least one triangulation ply of non-stretchable metal wires or cables which form an angle of between 60.degree. and 90.degree. with the circumferential direction and of two working plies formed of non-stretchable metal wires or cables crossed from one ply to the next and forming an angle of between 10.degree. and 45.degree. with the circumferential direction. It is characterized by the fact that the first working ply radially adjacent on the outside of the radially outermost triangulation ply is of a smaller width than the width of said triangulation ply, the second working ply, radially above the first, having a larger axial width than the width of the triangulation ply; and the edges of the said second working ply covering the edges of said triangulation ply so the radial distances between the respective cables of the two plies at the level of said edges are at most equal to 1.5 mm over an axial distance equal to at least 2% of the axial width of the triangulation ply.
By radial distance between two respective cables of the two plies there is understood the thickness of rubber measured radially between the upper and lower generatrices respectively of said cables.
A variant of the invention which is particularly beneficial for the life of the crown reinforcement consists in associating a ply of circumferential metal elements with the above architecture, said ply having an axial width of less than the width of the first working ply and located radiall
REFERENCES:
patent: 4696335 (1987-09-01), Tsukagoshi et al.
Compagnie Generale des Etablisse-Ments Michelin - Michelin & Cie
Johnstone Adrienne C.
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