Multi-Material Spring Structure for Flexible Joints With Smooth Surfaces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing flexible, non-load bearing joints and cylindrical structural columns fail to simultaneously maintain mechanical rigidity and allow for large global displacements while preserving a smooth outer surface, especially under changing configurations and load conditions.
Innovation Solution
A flexible multi-material structure comprising a spring skeleton with repeating cells filled with infill materials, such as foamed or monolithic elastomers, where the spring skeleton can be made of steel and polycarbonate blends, and the infill materials include silicones or polyurethane, with a Poisson ratio of 0.1 to 0.3, providing a balance of radial and torsional stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a monolithic flexible structure is used, then large global displacements are allowed, but mechanical rigidity and radial stiffness are insufficient
Solution Approach 1:
The invention uses a composite structure combining a flexible outer elastomeric material with an embedded stiff spring skeleton. The elastomer allows large global displacements and bending, while the spring skeleton provides radial stiffness and mechanical strength. This composite approach resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The structure implements local quality by having different regions with different stiffness characteristics. The outer elastomeric surface provides flexibility for large displacements, while the embedded spring skeleton in specific locations provides radial stiffness. The spring cells are strategically positioned to provide stiffness where needed while allowing flexibility elsewhere.
2Length of moving object
If a flexible structure is used, then large global displacements are allowed, but the outer surface smoothness deteriorates
Solution Approach 1:
The invention uses a flexible elastomeric outer shell that maintains surface smoothness while allowing large global displacements. The continuous elastomeric surface acts as a smooth skin over the internal spring skeleton, preventing surface irregularities during articulation and bending.
Solution Approach 2:
The composite of elastomer and spring skeleton allows the smooth elastomeric surface to carry the bending deformation while the internal skeleton maintains structural integrity, preventing surface buckling or wrinkling during large displacements.
3Strength
If radial stiffness is increased, then radial displacement is prevented, but bending flexibility is reduced
Solution Approach 1:
The spring skeleton is positioned and oriented to provide radial stiffness in the radial direction while allowing bending flexibility in the tangential direction. The cellular structure of the springs creates anisotropic mechanical properties, being stiff radially but flexible for bending.
Solution Approach 2:
The elastomer-spring composite creates directional stiffness characteristics where the spring skeleton dominates radial response while the elastomer dominates bending response, achieving both radial stiffness and bending flexibility simultaneously.
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 structure effectively withstands loads and maintains a smooth surface during articulation, minimizing actuation energy and preventing radial displacement, while allowing for significant bending and torsional deformation without buckling, as validated by finite element analysis and experimental measurements.
Implementation Method 1
the Poisson ratio of the infill material may be about 0.1 to 0.3
Implementation Method 2
the infill material may consist of one or more of foamed and monolithic elastomers
Implementation Method 3
a spring skeleton comprising a plurality of repeating cells
Data Source
AI summary
A flexible multi-material structure comprises a spring skeleton comprising a plurality of repeating cells, the cells filled with an infill material, wherein the spring skeleton is one of a machined spring structure and a wave spring structure. The spring skeleton may comprise one of steel and polycarbonate blends, and the infill material may consist of one or more of foamed and monolithic elastomers. The foamed and monolithic elastomers consist of one or more of silicones, polyether, and polyurethane. The Poisson ratio of the infill material is about 0.1 to 0.3. The repeating cells of the spring skeleton have a predetermined wall thickness (t), wall height (h), and revolution symmetry.