Split-Tube Flexure Joint with Greater Range of Motion


Vanderbilt University researchers have developed an improved flexure based revolute joint which has better properties than a conventional flexure joint. Its split tube design enables a greater range of motion and withstands more load than conventional flexures while eliminating stick-slip and backlash behaviors.

Addressed Need

Machines are sensitive to backlash and coulomb friction requiring elimination or minimization of surface forces especially on the small/micro scale or in zero gravity conditions
Precision motion, small scale and zero gravity conditions require open-loop systems opposed to conventional sliding and rolling which result in stick-slip behavior
Conventional flexures have no backlash or coulomb friction however they are limited by:
• Limited range of motion exhibiting plastic deformation around 5-10 degrees
• Stiffness along the axis of rotation
• Off-axis compliance resulting in buckling twist-bend

Technology Description

This flexure-based joint offers significantly better properties than a conventional flexure. It utilizes a split tube design comprised of a thin-walled hollow shaft of variable wall thickness with a slit and two arms. Elements of the design are adjustable depending on the required strength or stiffness. Additionally, compound and simple orientations can be combined to achieve optimal properties. Overall, this design capitalizes on the differences in mechanics between its open and closed sections with respect to torsion, bending and compression in order to minimize torsional stiffness and maximize all other stiffness.

Unique Properties and Competitive Advantages

Reduced stiffness along the axis of rotation
Off-axis stiffness significantly greater than conventional flexures
Greater range of motion (over 5 times that of conventional flexures)
Withstand greater loads before buckling (3 times that of conventional flexures)
No backlash, coulomb friction or stick-slip behavior
Can be lubricant free permitting use in clean environments

Intellectual Property Status

U.S. Patent Number 6,585,445 was issued July 1, 2003.
For publication information, Goldfarb Publication
For lab information: Goldfarb Lab

Michael GoldfarbJohn Speich
Licensing manager: 
Ashok Choudhury

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