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

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

Research output: Contribution to conferencePaperAcademicpeer-review

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Abstract

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

Conference

Conference33rd ASPE Annual Meeting 2018
Abbreviated titleASPE 2018
CountryUnited States
CityLas Vegas
Period4/11/189/11/18

Fingerprint

Hinges
Prosthetics
Reinforcement
Stiffness
Loads (forces)
Leaf springs
Buckling

Cite this

Boers, B., Naves, M., Garcia Rodriguez, L. A., & Brouwer, D. M. (2018). Inverted curved flexure hinge with torsional reinforcements in a printed prosthetic finger. Paper presented at 33rd ASPE Annual Meeting 2018, Las Vegas, United States.
Boers, Bas ; Naves, Mark ; Garcia Rodriguez, Luis Alberto ; Brouwer, Dannis Michel. / Inverted curved flexure hinge with torsional reinforcements in a printed prosthetic finger. Paper presented at 33rd ASPE Annual Meeting 2018, Las Vegas, United States.6 p.
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Boers, B, Naves, M, Garcia Rodriguez, LA & Brouwer, DM 2018, 'Inverted curved flexure hinge with torsional reinforcements in a printed prosthetic finger' Paper presented at 33rd ASPE Annual Meeting 2018, Las Vegas, United States, 4/11/18 - 9/11/18, .

Inverted curved flexure hinge with torsional reinforcements in a printed prosthetic finger. / Boers, Bas; Naves, Mark ; Garcia Rodriguez, Luis Alberto; Brouwer, Dannis Michel.

2018. Paper presented at 33rd ASPE Annual Meeting 2018, Las Vegas, United States.

Research output: Contribution to conferencePaperAcademicpeer-review

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N2 - 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.

AB - 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.

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Boers B, Naves M, Garcia Rodriguez LA, Brouwer DM. Inverted curved flexure hinge with torsional reinforcements in a printed prosthetic finger. 2018. Paper presented at 33rd ASPE Annual Meeting 2018, Las Vegas, United States.