Tyre Bead Stiffener Low Permeability
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Solution Overview
Problem
Heavy goods vehicle tires face issues with endurance under excessive loads and inflation pressures, leading to carcass reinforcement unwinding and damage due to inadequate protection in the bead area, particularly cracking and premature wear of stiffener reinforcement elements.
Innovation Solution
A tire design featuring a radial carcass reinforcement with a stiffener made of unhooped metal cables with saturated layers exhibiting low permeability, and a reduced thickness of polymeric mixtures between the stiffener and the carcass reinforcement upturn, enhancing the tire's resistance to stress and preventing unwinding and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If layers of reinforcing elements or stiffeners are added to protect the carcass reinforcement in the bead zone, then the resistance of the tire to excessive stresses is improved, but the stiffener reinforcement elements are damaged by breaks in compression zones and cracking of the polymeric mixtures
Solution Approach 1:
The patent changes the geometric parameters of the stiffener, specifically reducing the offset distance between the end of the carcass reinforcement upturn and the stiffener from conventional values to less than 15 mm. This parameter change allows the stiffener to better follow the curvature of the bead during tire deformation, reducing compression stresses and preventing breaks and cracking while maintaining protection against excessive stresses.
Solution Approach 2:
The patent makes the stiffener configuration dynamic by allowing it to closely follow the curvature changes of the bead during tire operation. By reducing the offset, the stiffener can adapt to the dynamic deformation of the tire bead, maintaining optimal positioning that prevents both excessive stress damage and compression zone failures.
2Object-affected harmful factors
If the ends of the carcass reinforcement upturn and stiffener are offset to avoid crack propagation, then damage to the bead area is reduced, but the protection effect is diminished and the tire endurance is reduced
Solution Approach 1:
The patent optimizes the offset parameter to a specific range (less than 15 mm) that balances two competing requirements: it is small enough to maintain protection against crack propagation but large enough to prevent direct stress concentration at the interface. This precise parameter control enables the stiffener to protect the bead area while maintaining tire endurance under excessive loads and inflation pressures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design significantly improves the tire's endurance by reducing the risk of carcass reinforcement unwinding and cracking, while maintaining the stiffener's integrity, even under intense braking and overload conditions, thereby extending the tire's lifespan and performance.
Implementation Method 1
the reinforcing elements of at least one stiffener being unhooped metal cables with saturated layers exhibiting in the so-called permeability test a flow rate of less than 5 cm³/min
Data Source
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AI summary
The invention relates to a tyre with a radial carcass reinforcement which is made up of at least one layer of reinforcing elements which is anchored in each of the beads by being wrapped around a bead wire, said wrapped-around portion of carcass reinforcement being reinforced by at least one layer of reinforcing elements or stiffener. According to the invention, the reinforcing elements of at least one stiffener are unwrapped metal chords with saturated layers which in the test known as the permeability test return a flowrate of less than 5 cm3/mn and the thickness of the polymer compounds separating the stiffener from the end of the wrapped-around portion of carcass reinforcement is strictly less than 3.5 mm.