Inverted curved flexure hinge with torsional reinforcements in a printed prosthetic finger

Bas Boers, Mark Naves, Luis Alberto Garcia Rodriguez, Dannis Michel Brouwer

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    Flexure-based finger joints for prosthetic hands have been studied, but until now they lack stiffness and load capacity. In this paper we present a design which combines large range of motion, stiffness and load capacity, with a torsional overload protection mechanism. Five design considerations which increase grasp force and limit the stress values are presented: (1) Due to the inverted flexure attachment, the flexures are loaded mainly in tension, avoiding buckling of flexures. (2) Curved flexures have been used of which one straightens out at large deflection angles to improve load capacity at large deflections. (3) To achieve high torsional loads, one of the flexures is outfitted with triangular torsional stiffeners, which increase the out-of-plane stiffness significantly, while only slightly increasing the actuation stiffness. (4) The entire joint is rotated by 20˚ so the combination of actuation and contact forces lead to mainly axial forces in the curved leaf spring, avoiding excessive internal bending.
    The presented prosthetic flexure-based finger joint is able to achieve 20N of contact force with an additional 5N of out of plane load over the entire 80˚ range of motion, which is a major improvement over existing prosthetic flexure-based finger designs.
    Original languageEnglish
    Number of pages6
    Publication statusPublished - 4 Nov 2018
    Event33rd ASPE Annual Meeting 2018 - Red Rock Casino Resort Spa, Las Vegas, United States
    Duration: 4 Nov 20189 Nov 2018
    Conference number: 33


    Conference33rd ASPE Annual Meeting 2018
    Abbreviated titleASPE 2018
    Country/TerritoryUnited States
    CityLas Vegas


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