Footwear Sole Structure with Offset Tensile Member for Nonlinear Bending Stiffness
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Solution Overview
Problem
Conventional sole structures in athletic footwear lack optimal resistance to flexion, particularly in the forefoot region, leading to inadequate support and stability during dorsiflexion, as they do not effectively manage the transition in bending stiffness with increasing flex angles.
Innovation Solution
A sole structure featuring a first sole plate with a recess containing tensile members fixed at the forward and rear ends, with a midportion that is initially transversely offset and straightens under dorsiflexion, providing a piecewise bending stiffness that increases at a predetermined flex angle, enhancing resistance to further flexion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional sole structures are used, then the footwear provides basic cushioning and motion control, but the bending stiffness does not increase sufficiently during dorsiflexion, leading to inadequate support and stability
Solution Approach 1:
The tensile member is configured with an initial transverse offset that allows it to remain relatively slack during early dorsiflexion, then progressively engage and straighten as flexion increases. This dynamic behavior enables the sole structure to transition from a more flexible state during initial movement to a stiffer state during greater dorsiflexion, resolving the contradiction between ease of operation and bending stiffness.
Solution Approach 2:
The patent changes the physical state and geometric configuration of the tensile member through dorsiflexion. The member transitions from a curved, offset configuration to a straightened configuration, fundamentally altering its mechanical properties and load-bearing capacity. This parameter change enables the sole to provide progressive stiffness increase without compromising initial flexibility.
2Strength
If the sole structure provides increased resistance to flexion, then support and stability are improved, but the complexity of the sole structure increases due to the additional tensile member configuration
Solution Approach 1:
The tensile member serves multiple functions simultaneously: it provides structural reinforcement, acts as a progressive stiffness mechanism, distributes ground reaction forces, and guides the flexion pattern of the sole. By consolidating these multiple functions into a single structural element, the patent achieves improved support and stability without proportionally increasing complexity.
Solution Approach 2:
The tensile member functions as a flexible structural element that transitions from a compliant, curved state to a rigid, straightened state under load. This flexible-thin-film approach allows the complex mechanical behavior to be achieved with a relatively simple, thin structural component rather than a bulky or multi-component assembly.
3Strength
If the tensile member is straightened under dorsiflexion, then bending stiffness increases, but the offset distance decreases from the initial transverse offset
Solution Approach 1:
The tensile member is deliberately given a curved geometry with an initial transverse offset rather than being straight. This curvature is essential to the mechanism: it allows the member to accommodate initial dorsiflexion movements while progressively storing elastic energy and engaging tensile forces. As dorsiflexion continues, the curvature decreases as the member straightens, directly converting the shape change into increased bending stiffness.
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 sole structure offers increased bending stiffness during dorsiflexion, providing improved support and stability by maintaining tension in the tensile members, which translates to enhanced resistance to flexion and better distribution of ground reaction forces.
Implementation Method 1
The midportion of the at least one tensile member is transversely offset from both the forward end and the rear end by a first offset distance when the sole structure is in an unflexed, relaxed state. The midportion of the at least one tensile member is transversely offset from both the forward end and the rear end by a second offset distance less than the first offset distance when the sole structure is dorsiflexed in the forefoot region.
Data Source
AI summary
A sole structure for an article of footwear comprises a first sole plate with a foot-receiving surface, a ground-facing surface opposite the foot-receiving surface, and an opening in the ground facing surface extending at least partway through the first sole plate and from a lateral side to a medial side of the first sole plate in a forefoot region. The first sole plate has a first wall at a forward extent of the opening, a second wall at a rear extent of the opening, and at least one tensile member disposed in the opening. The tensile member has a forward end fixed to the first wall, a rear end fixed to the second wall. A midportion of the at least one tensile member is transversely offset from both the forward end and the rear end by a first offset distance when the sole structure is in an unflexed, relaxed state.