Tire Bead Metal Cable Anchoring for Mounting Ease
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Solution Overview
Problem
The rigidity of tire beads in bead-wire-less tires makes them difficult to mount and demount, especially for large tires, and using high-elongation cables or low-rigidity anchoring rubber compromises road behavior or tire life.
Innovation Solution
A tire design featuring a metal cable with two layers, where the inner layer has M wires wound at pitch p1 and the outer layer has N wires wound at pitch p2, allowing for ovalization and improved mounting ability without compromising road behavior, using a rubber composition with a secant tensile modulus greater than 20 MPa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bead rigidity is increased to improve road behavior and tire life, then the mounting and demounting difficulty increases
Solution Approach 1:
The bead structure is segmented into two functional zones: an inner bead core zone with high rigidity for road behavior, and an outer bead edge zone with lower rigidity for mounting. The bead core uses stiff anchoring rubber and radial reinforcing members, while the bead edge uses softer rubber composition that allows ovalization during mounting operations.
Solution Approach 2:
Different rubber compositions are used in different regions of the bead. The anchoring rubber in the bead core has high rigidity (modulus > 20 MPa) for road behavior, while the bead edge rubber has lower rigidity for mounting ease. The radial reinforcing members are positioned to provide localized stiffness where needed while allowing deformation at the bead edge.
2Ease of operation
If high-elongation cables are used to improve mounting ability, then the tire life and road behavior deteriorate
Solution Approach 1:
The invention extracts the mounting function from the cable material properties and transfers it to the bead structure design. Instead of relying on cable elongation for mounting, the bead edge is designed to ovalize and pass over the rim flange, with the cable serving only its structural reinforcement function in the bead core.
Solution Approach 2:
Conventional wisdom suggests using high-elongation cables for mounting ease, but this invention inverts the approach by using standard rigidity cables with a specially designed bead structure that provides mounting ease through structural deformation rather than material elongation.
3Ease of operation
If low-rigidity anchoring rubber is used to improve mounting ability, then the road behavior and grip properties deteriorate
Solution Approach 1:
The rubber composition is segmented into two distinct zones: anchoring rubber in the bead core with high rigidity (modulus > 20 MPa) for road behavior, and bead edge rubber with lower rigidity for mounting. This segmentation allows each zone to optimize its properties for its specific function without compromising the other.
Solution Approach 2:
Different rubber compositions are applied locally to different bead regions. The anchoring rubber maintains high modulus for road behavior while the bead edge rubber provides compliance for mounting operations, achieving both requirements through spatial differentiation of material properties.
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 solution enhances the deformability of tire beads, simplifying mounting and demounting while maintaining high road behavior and tire life, without the need for expensive high-elongation treatments or low-rigidity anchoring rubbers.
Implementation Method 1
the great rigidity of the beads could cause difficulties when mounting and/or demounting the tires... the beads may cross 'humps' which form an obstacle to the passage of said beads
Implementation Method 2
cooperating with an adjacent portion of the carcass reinforcement by means of an appropriate rubber composition... transmitting the forces between the radial reinforcing members and the anchoring reinforcing members
Implementation Method 3
a rubber composition of reduced rigidity, having an elasticity modulus of between 10 and 20 MPa at a deformation of 10%, and a high creep resistance
Data Source
AI summary
Tire having a crown, a crown reinforcement, sidewalls and beads, a carcass reinforcement passing into the sidewalls and anchored in the beads. The anchoring is accomplished, in at least one bead, by a circumferential alignment of an anchoring reinforcing member oriented circumferentially and cooperating with a rubber composition. The anchoring reinforcing member is a metal cable having a construction M+N with an inner layer C1 of M wires of diameter d1 wound together in a helix at a pitch p1 , this layer C1 being surrounded by an outer layer C2 of N wires of diameter d2 wound together in a helix at a pitch p2. This anchoring cable satisfies (d1, d2, p1 and p2 being expressed in mm): 2≦M≦4, M+3≦N ≦M+7, 0.25 <d1 <0.40, 0.25 <d2 <0.40, 3.5 <p1 <7<p2<14.