Polyurethane Injection Molded Boot Assembly
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Solution Overview
Problem
Conventional waterproof boots, such as those made of rubber or neoprene with a vulcanized rubber outer layer, are often inflexible, heavy, and costly to manufacture, with the vulcanization process potentially reducing the elasticity of the neoprene inner layer.
Innovation Solution
A waterproof boot assembly featuring a neoprene sock with an injection-molded polyurethane (PU) layer on selected areas, such as the heel, ankle, and shin, while leaving other portions uncovered, providing a lightweight, flexible, and comfortable fit, and a manufacturing method that encases the foot portion and integrates a PU midsole for cushioning and shock attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rubber is used as the waterproof material with sufficient thickness, then strength and puncture resistance are improved, but flexibility and weight are worsened
Solution Approach 1:
The patent uses a composite construction combining neoprene (a flexible rubber-like material) with a thinner rubber waterproof layer. The neoprene provides flexibility and light weight while the thinner rubber layer provides the necessary waterproofing and puncture resistance, resolving the contradiction between strength and weight by using materials with complementary properties rather than relying on thick rubber alone.
Solution Approach 2:
The patent applies rubber material selectively only where waterproofing is needed, rather than using thick rubber throughout the entire boot. The thinner rubber layer is placed specifically on the waterproofing surfaces, while other areas use lighter neoprene, optimizing the balance between puncture resistance and weight reduction.
2Reliability
If rubber is vulcanized onto the neoprene outer layer, then waterproofing is improved, but manufacturing complexity and cost are increased
Solution Approach 1:
The patent extracts the vulcanization step from the manufacturing process entirely, replacing it with an injection molding process. The waterproof rubber layer is applied and secured without requiring vulcanization, thereby simplifying the manufacturing process and reducing complexity while maintaining the waterproofing function.
Solution Approach 2:
The patent replaces the thermal-chemical vulcanization process with a mechanical injection molding process. Instead of using heat and chemical reactions to bond the rubber layer to the neoprene, the invention uses injection molding to form and attach the rubber layer, substituting a simpler mechanical process for a complex thermal-chemical one.
3Reliability
If heat is applied during the vulcanization process, then waterproofing is improved, but the neoprene elasticity is worsened
Solution Approach 1:
The patent replaces the heat-intensive vulcanization process with a cold or low-heat injection molding process. This substitution eliminates the high temperature exposure that would damage neoprene elasticity, while still achieving effective waterproofing through the injection molded rubber layer's proper bonding and sealing.
Solution Approach 2:
The patent converts the potential harm of heat exposure during waterproofing into a benefit by using an injection molding process that can be performed at lower temperatures. This approach maintains neoprene elasticity while still achieving effective waterproofing, turning what would be a harmful thermal process into a gentler, more compatible manufacturing method.
4Duration of action of stationary object
If the boot is made entirely of rubber, then durability is improved, but flexibility and comfort of fit are worsened
Solution Approach 1:
The patent combines neoprene and rubber in a composite structure where neoprene provides flexibility and comfort of fit, while the thinner rubber layer provides durability and waterproofing. This composite approach allows each material to contribute its advantageous properties, resolving the contradiction between durability and flexibility.
Solution Approach 2:
The patent applies different materials to different parts of the boot based on their functional requirements. The neoprene is used in areas requiring flexibility and comfort, while the rubber layer is applied specifically where durability and waterproofing are needed, optimizing both properties through localized material selection.
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 results in a lightweight, waterproof, and comfortable boot that maintains neoprene elasticity, offering improved fit and durability with reduced manufacturing costs through a single injection molding process.
Implementation Method 1
an outer layer of injection molded material on selected portions of the neoprene sock's outer surface
Implementation Method 2
integrates a PU midsole for cushioning and shock attenuation
Data Source
AI summary
A footwear assembly having an upper that comprises a neoprene sock with a foot portion integrally connected to a leg portion. The foot portion has heel, vamp and under-foot portions. The leg portion has front shin, side wall, and rear calf-side portions. The upper has a unitary, outer, injection molded layer molded directly onto the foot and shin portions of the neoprene sock, while the sidewall and rear calf-side portions remain substantially uncovered by the injection molded layer. The injection molded layer encases the foot portion of the neoprene sock. The injection molded layer on the shin portion defines a shin guard portion having a necked down area integrally connected to the injection molded layer at the vamp portion, wherein the shin guard extends upwardly from the necked-down portion in an outwardly diverging shape away from the vamp.