Composite Spring Assembly for Nonlinear Knee Joint Support
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Solution Overview
Problem
Existing orthotic and prosthetic devices often struggle to provide a non-linear spring response that effectively supports knee joints during rehabilitation, while also ensuring comfort and preventing joint damage.
Innovation Solution
The use of composite springs made from alternating layers of carbon fiber and fiberglass materials, combined with a dampening member and adhesive, to create a composite spring assembly that provides a preselected non-linear spring response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear spring response is used in orthotic devices, then the device structure is simple, but it cannot provide effective support during knee rehabilitation and may cause joint damage
Solution Approach 1:
The patent transforms the linear spring response into a non-linear response by changing the geometric parameters of the spring. Specifically, the spring is designed with a variable cross-sectional area along its length, where the width varies according to a predetermined function. This geometric parameter change enables the spring to provide different stiffness at different compression stages, delivering soft support during early rehabilitation and firmer support as healing progresses, thereby resolving the contradiction between support effectiveness and device simplicity.
Solution Approach 2:
The patent employs composite materials consisting of alternating layers of carbon fiber-reinforced polymer and fiberglass-reinforced polymer. This composite structure combines the high strength and stiffness of carbon fiber with the toughness and damage resistance of fiberglass. The layered composite construction enables the spring to achieve the desired non-linear mechanical response while maintaining reliability and preventing joint damage during knee rehabilitation.
2Reliability
If a non-linear spring response is implemented, then knee joint support is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The patent divides the spring into multiple discrete layers, with each layer consisting of alternating carbon fiber and fiberglass reinforcement. This segmentation allows each layer to be manufactured and cured independently, then stacked to form the complete spring. The segmented approach simplifies the manufacturing process by enabling modular production, quality control at the layer level, and easier adjustment of the non-linear response characteristics through layer configuration rather than complex monolithic molding.
Solution Approach 2:
The patent achieves the non-linear spring response through controlled variation of geometric parameters during the manufacturing process. The width of the spring varies along its length according to a predetermined function, and this geometric progression can be implemented using standard composite layup techniques with progressively varying tooling or masking. This approach to parameter change maintains ease of manufacture by using conventional composite fabrication methods rather than requiring complex post-processing or assembly operations.
3Strength
If the adhesive strength is high, then the composite spring layers are strongly bound, but the dampening effect is reduced
Solution Approach 1:
The patent applies different adhesive properties at different locations within the composite structure. The adhesive is formulated and applied to provide optimal bond strength at the fiber-matrix interfaces where structural integrity is critical, while allowing controlled slip and energy dissipation at the inter-layer boundaries. This local differentiation of adhesive quality enables the spring to maintain structural strength while simultaneously providing the desired dampening effect for shock absorption during knee rehabilitation.
Solution Approach 2:
The patent uses a composite adhesive system that combines materials with different mechanical properties. The adhesive formulation includes components that provide strong initial bonding to ensure layer cohesion, while also incorporating viscoelastic elements that enable energy dissipation through controlled deformation. This composite adhesive approach resolves the contradiction between maintaining strong inter-layer bonds and providing sufficient dampening to reduce impact forces on the knee joint.
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 composite spring assembly effectively supports knee joints with a non-linear spring response, enhancing comfort and preventing joint damage by controlling the energy release during movement.
Implementation Method 1
The composite spring generally provides an appropriate elastic response for the composite spring assembly
Implementation Method 2
The dampening member may facilitate dampening of the elastic response during spring-back of the composite spring
Implementation Method 3
A strength adhesive (e.g. epoxy) is generally used to bind the carbon fiber materials and the fiberglass materials
Data Source
AI summary
Composite springs, composite spring assemblies, medical devices including the same, and methods of making and using the same are disclosed. The composite springs may comprise alternating layers of carbon fiber and fiberglass materials. A strengthening adhesive, such as an epoxy, may be used to bind the carbon fiber and fiberglass materials. A dampening member may be attached to the composite spring, thereby at least partially defining a composite spring assembly. The dampening member may dampen elastic/spring forces of the composite spring. The composite spring assembly may be attached to an orthotic device to provide a non-linear spring response during movement of the device.