Design of a multifunctional body powered prosthetic hand

Abstract

Nowadays the design of prosthetic hands is mainly focused on myo-electric control for more functionality. And easy producible 3d printed prosthetics to lower the costs of a custom prosthesis. As a result of this change of focus, the body powered prosthetic hands currently on the market are mainly simple clamping mechanisms with no innovative functions. Looking back into the history of hand prosthetics many body powered prosthetic hands housed a couple of innovative design choices to increase the functionality. Some examples of this are the Pringle-Kirk arm and the Despinasse hand. As a counter reaction to this movement, a new body powered prosthetic hand is designed. The new prosthetic hand will be based on the innovative solutions of the past and will bring back more functionalities to the body powered prosthetics. The new design housed fingers made out of cylindrical springs, in combination with leaf springs. This is all actuated via a dependency mechanism in the hand palm, this combination allows for very flexible fingers that can grab complexly shaped objects and still offer a multi finger grip. The first tests revealed that the leaf springs limited the motion of the fingers and further testing without the leaf springs showed a setup with only cylindrical springs was a better solution. The second test was focused on pinch force, although the maximum acquired pinch force was not high, a sturdy grip should be possible based on literature, this does need further testing to validate. For the continuing of the prototyping testing of the dependency mechanism was done, initial testing at a larger scale showed promising results, little to no loss of force. The conclusion that can be drawn based on these tests is that there are certainly parts of prosthetic hands of the past that are worth taking a closer look at.