Compact Vertical-Motion Isolator Using Negative-Stiffness Flexures
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Solution Overview
Problem
Existing vibration isolators face challenges in achieving low system natural frequencies and high isolation performance at higher frequencies due to limitations in compact design and structural resonant responses, particularly in vertical-motion isolation systems.
Innovation Solution
The design incorporates a negative-stiffness-producing mechanism using compressible flexures arranged in a stacked or side-by-side configuration, allowing for a compact size without compromising performance by overlapping flexure lengths, which enables the isolator to operate with longer compressed flexures and achieve lower natural frequencies and increased vertical displacement ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional vibration isolators use traditional spring and damper combinations, then they can provide basic vibration isolation, but they cannot achieve low system natural frequencies and high isolation performance at higher frequencies simultaneously
Solution Approach 1:
The patent combines positive-stiffness springs with negative-stiffness mechanisms (buckled flexures) to create a composite suspension system. This composite structure achieves low effective stiffness and low natural frequencies while maintaining high isolation performance, resolving the contradiction between isolation effectiveness and system complexity.
Solution Approach 2:
The patent changes the stiffness parameter by introducing negative-stiffness mechanisms that counteract the positive stiffness of conventional springs. By adjusting the buckling load and flexure geometry, the system achieves tunable low natural frequencies while maintaining structural integrity and isolation performance.
2Reliability
If the isolator uses longer compressed flexures to achieve lower natural frequencies, then the isolation performance improves, but the isolator size increases
Solution Approach 1:
The patent arranges multiple flexures in a nested or overlapping configuration where the lengths of flexures overlap rather than extending linearly. This nesting approach allows longer effective flexure lengths for lower natural frequencies while minimizing the overall isolator volume and footprint.
Solution Approach 2:
The patent transitions from a linear arrangement of flexures to a three-dimensional stacked configuration. By arranging flexures in multiple layers or dimensions, the system achieves the equivalent of longer flexures without increasing the linear dimensions of the isolator, thus reducing overall volume while maintaining isolation efficiency.
3Volume of moving object
If the isolator is designed to be compact, then the space requirement is reduced, but the ability to achieve low natural frequencies and high isolation performance is compromised
Solution Approach 1:
The patent uses three-dimensional stacking of overlapping flexures to pack more functional length into a smaller volume. This dimensional approach allows compact isolator design while maintaining the flexure length necessary for low natural frequencies and high isolation performance.
Solution Approach 2:
The composite suspension system integrates positive and negative stiffness elements in a compact arrangement, achieving high isolation performance in a reduced volume by optimizing the spatial distribution of stiffness-contributing components.
4Ease of manufacture
If conventional isolators use simple spring structures, then the device is easy to manufacture, but they exhibit high structural resonant responses that limit isolation performance
Solution Approach 1:
The patent uses flexible flexures with controlled buckling behavior instead of simple rigid springs. These flexible elements provide inherent damping and distribute stress more evenly, reducing structural resonant responses while maintaining manufacturing feasibility through standard flexure fabrication methods.
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
This approach results in more compact vertical-motion isolators that maintain high isolation efficiency across a wide range of frequencies, including very low natural frequencies, surpassing the capabilities of conventional isolators.
Implementation Method 1
loading a particular elastic structure which forms the isolator or a portion of it to approach the elastic structure's point of elastic instability
Implementation Method 2
loading the structure to approach its point of elastic instability... causes a substantial reduction of either the vertical or the horizontal stiffness of the isolator
Implementation Method 3
a support spring for providing positive stiffness in the vertical direction and having force-supporting capability in the vertical direction for supporting the object
Implementation Method 4
designed to reduce the transmission of unwanted vibration between an object and its surroundings, commonly called vibration isolators or suspension devices
Data Source
AI summary
A vertical-motion vibration isolator utilizes negative-stiffness-producing mechanism which includes a plurality of compressed flexures, each having a particular length in the compressed direction of the flexure and being oriented in a horizontal direction, wherein the plurality of compressed flexures are positioned relative to each other such that the length of each compressed flexure substantially overlaps the length of each of the other compressed flexures. At least some of the plurality of compressed flexures can be positioned in a stacked arrangement. The arrangement of compressed flexures forming a portion of the negative-stiffness mechanism can reduce the size of the isolator without compromising vibration isolation performance.