Measuring and testing – Tire – tread or roadway
Reexamination Certificate
2001-12-11
2004-05-04
Oen, William (Department: 2855)
Measuring and testing
Tire, tread or roadway
Reexamination Certificate
active
06729179
ABSTRACT:
The invention relates to a method for testing tires and to an apparatus for implementation thereof, intended in particular but not exclusively for tires of heavy road haulage vehicles (lorries and the like).
DESCRIPTION OF RELATED ART
A phenomenon typically affecting these kinds of tires (alternatively spelled “tires”) consists of the breaks which reveals itself as a clean cut on the side of the tire (alternatively spelled “tire”), extending circumferentially thereto and along which a cutting-off of the radial cords forming the carcass of the tire occurs. This phenomenon is known to persons skilled in the art by the name of “zipper break.”
The reinforcing cords of tire carcasses for heavy road haulage generally consist of metallic wires and are much stronger than textile cords commonly used in the carcasses of car tire. As a results it is difficult to understand how this type of break occurs, especially when taking into account that failure may occur after only a short distance traveled by the tire.
In other words, said “zipper break” cannot be attributed to the normal wear to which a tire is subject following prolonged use over time or in particularly severe conditions (heavy load, rough road surface, etc.), and does not fall within the other known forms of tire breaks.
Consequently, it is difficult, if not impossible, to understand and reproduce with the usual methods (computer analysis, experiments, etc.) the conditions that—in real driving conditions—lead to the “zipper break” of tires. Additionally, this problem renders it difficult, if not impossible, to provide tire structures for lorries and the like specifically designed to prevent this particular type of break.
SUMMARY OF THE INVENTION
The present invention aims at remedying this situation.
The invention arises from Applicant's perception that the “zipper break” is caused by abnormal and occasional working conditions of the sidewall of the tire, capable of causing a particular fatigue stress in the carcass structure.
An example of these stresses is the so-called “kissing”, i.e. the interference which occurs between two tires mounted side by side on the same axle (such as the twinned tires in the lorries) in the event of an excessive load acting on them, or when one of the tires is operating with an inflation pressure lower than that of the other tire or both the tires have a pressure which is lower than the nominal operating pressure.
Therefore, on the basis of said perception, the present invention provides a method for testing tires and an apparatus for carrying out said method, suitable for reproducing the conditions which, during use, give rise to the phenomenon of “zipper break”.
The characterising features of said method and of the abovementioned apparatus are set out in the following claims.
REFERENCES:
patent: 4651787 (1987-03-01), Appl
patent: 5328084 (1994-07-01), Billieres
patent: 5458176 (1995-10-01), Rhyne
patent: 5616859 (1997-04-01), Rhyne
Crema Fabrizio
Di Bernardo Carlo
Oen William
Pirelli Pneumatici S.p.A.
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