Tire with two treads having between treads a reinforcement ring

Details Tire with two treads having between treads a reinforcement ring Tire with two treads having between treads a reinforcement ring

1995-08-18

1997-07-08

Johnstone, Adrienne C.

Resilient tires and wheels

Tires, resilient

Anti-skid devices

152451, 152454, 152528, 152531, B60C 300, B60C 1100

Patent

active

056456581

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a tire having two separate treads, spaced axially apart by a connecting zone which is formed of a central groove and a reinforcement ring arranged radially below said groove, the carcass reinforcement of said tire extending from one bead to the other, passing below said ring.
The tire in question, generally of a aspect ratio H/B of at most 0.60, rests on the ground with a contact surface which is as large as possible. This tire, as described in French application 2 187 560, thus has good adherence on dry ground and, due to the presence of the connecting zone between the two treads, very good adherence on wet ground.
Such a tire, which is intended primarily for high-speed vehicles, has however a number of drawbacks due to the speed and in particular irregular transverse and/or circumferential wear.


SUMMARY OF THE INVENTION

In order to overcome said drawbacks, the present invention proposes a tire having two treads which are spaced axially from each other by a connecting zone comprising a groove and, in its middle, a reinforcing ring of a radius less than that of the treads, characterized by the fact that the reinforcement ring has a curve of the circumferential tension load as a function of the relative elongation which is non-linear, monotonic and increasing, and has at each of its points a tangent the slope of which is positive it being formed of three segments OA, AB and BR, a first segment OA for which the circumferential tensile rigidity is substantially constant permitting easy elongation of the ring, a second segment BR for which the of circumferential tensile rigidity is substantially constant and greater than the rigidity of the first segment OA, the two segments OA and BR being connected by a strongly curved segment AB, said curve C being included within a region of the plane bounded by two curves C1 and C2, each of which curves is formed of successive linear segments: origin O to a point A1 of a relative elongation equal to 0.01 and having a slope of 12.times.10.sup.4 daN, followed by a second segment extending beyond the point A1 and having a slope of 28.times.10.sup.4 daN; origin O to a point A2 of a relative elongation equal to 0.01 and having a slope of 2.times.10.sup.4 daN, a second segment extending from the point A2 to a point B2 of a relative elongation equal to 0.025 and having a slope of 4.times.10.sup.4 daN, this second segment being followed by a third segment extending beyond the point B2 and having a a slope of 6.times.10.sup.4 daN.
Thus, under the effect of the centrifugal force due to the speed, the reinforcement ring of the connecting zone can easily stretch up to a given relative elongation and thus permit the two interior edges of the two treads to increase their radii, this variation in the interior radii being then similar to the variation of the radii of the axially exterior edges of the treads.
The tire in question can thus retain a tread profile the transverse curvatures of which are substantially constant as a function of the speed of travel, which permits more uniform wear of the tread and accordingly a longer wear life.
By elongation of a ring with an interior diameter .phi. there is understood the difference in circumferential lengths of the ring placed under circumferential tensile load. If .phi.' is the interior diameter of the ring under tensile load, the elongation is .pi.(.phi.'--.phi.) and the relative elongation is (.phi.'--.phi.)/.phi..
The slope of the tangent to a curve is the ratio of the increase in the tensile load (force) to the unit increase of relative elongation. If 1% relative elongation is taken as unit increase, then the slope is given in daN, a unit of force. This slope measures, at each point of the curve representing the tensile load as a function of the relative elongation, the circumferential tensile rigidity of the ring for a given relative elongation.
The ring of the invention therefore has a increasing circumferential tensile rigidity as a function of the relative elongation be

REFERENCES:
patent: 2990869 (1961-07-01), Riley
patent: 3830273 (1974-08-01), Boileau
patent: 4945967 (1990-08-01), Tavazza et al.
patent: 5277236 (1994-01-01), Takatsu et al.
patent: 5407701 (1995-04-01), Reuter
patent: 5419383 (1995-05-01), Iwamura

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