Sandal Construction with Rigid Inserts for Adjustable Strap Movement
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Solution Overview
Problem
Conventional sandal constructions are heavy and lack adequate cushioning and adjustability, particularly when the midsole is compressed under the weight of the wearer.
Innovation Solution
A sandal construction featuring a multilayer sole with a rubber outsole and an EVA midsole, incorporating strap inserts made of a rigid polymeric material like TPU, which facilitate the movement of an adjustable strap through the midsole, even when compressed, by using embedded web and upright sleeves to guide the strap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a firm and heavy material is used for the midsole to permit lengthwise movement of the strap, then the strap adjustability is improved, but the sandal becomes heavier and less cushioned
Solution Approach 1:
The midsole is segmented into two distinct components: a lightweight cushioning material (EVA) for the main body and rigid strap inserts for strap guidance. This segmentation allows each component to perform its specialized function without compromising the other - the EVA provides cushioning and light weight while the rigid inserts enable strap movement.
Solution Approach 2:
The sandal employs composite construction by combining EVA (a lightweight, cushioning material) with rigid strap inserts (made from materials like acetal, nylon, or TPU). This composite approach allows the midsole to simultaneously achieve light weight and cushioning from the EVA while obtaining strap movement capability from the rigid inserts, resolving the contradiction between weight and strap adjustability.
2Ease of operation
If a firm material is used for the midsole to maintain strap movement capability under compression, then the strap adjustability is improved, but the cushioning is reduced
Solution Approach 1:
The midsole is divided into cushioning zones (EVA material) and structural guidance zones (rigid strap inserts). The EVA portions compress to provide cushioning under the wearer's weight, while the rigid strap inserts maintain their shape to continue guiding strap movement even when the EVA is compressed.
Solution Approach 2:
By combining EVA (providing cushioning) with rigid strap inserts (providing structural stability for strap movement), the midsole achieves both cushioning and strap adjustability under compression. The rigid inserts prevent the passage from deforming when the EVA compresses, maintaining strap movement capability.
3Weight of moving object
If a lightweight and cushioned material like EVA is used for the midsole, then the sandal becomes lighter and more comfortable, but the strap movement becomes difficult when compressed
Solution Approach 1:
The rigid strap inserts act as intermediaries between the lightweight EVA material and the strap. They provide a stable, non-deforming passage through which the strap moves, mediating between the compressible EVA and the strap to ensure smooth adjustment even when the EVA is compressed under weight.
4Adaptability or versatility
If a single adjustable-length strap is laced through passages in the midsole, then the adjustability is improved, but the midsole material must be firm and heavy
Solution Approach 1:
The midsole is segmented into cushioning material and rigid strap inserts, allowing the passages to be defined by the rigid inserts rather than the overall midsole material. This segmentation enables the use of lightweight EVA while maintaining the structural integrity needed for strap movement through the passages.
Data Source
AI summary
A sandal construction providing lightweight, highly adjustable sandals. The sandal includes an EVA midsole configured to receive the wearers footwear and an outsole configured to engage the ground. The sandal includes an upper having a heel assembly that seats the heel of the wearer's foot and a strap that retains the forward portion of the wearer's foot. The forefoot strap is a single, adjustable length strap that passes over the wearer's foot and is slidably threaded through passages in the sole. The midsole includes embedded strap inserts that define portions of the passages to receive and facilitate lengthwise movement of the strap. The strap inserts are substantially more rigid than the EVA. Each strap insert may include a web shepherding the strap across the bottom of the midsole and a pair of upright sleeves that shepherd the strap through at least a portion of the thickness of the midsole.