Recirculating Ballscrews for Bionics

It may happen that operators, for various reasons, need a grip support, almost a substitute for their own hand. In order to help Bioservo Technologies develop the Ironhand bionic glove, Eichenberger Gewinde has supplied its recirculating ballscrews, which ensure speed, precision and minimum space requirements.

by Michela Zanardo

Impaired hand function can therefore have serious consequences at work as well as at home. The mission of a technology and development company from Sweden, Bioservo Technologies, is to manufacture bionic, power-generating products for people with reduced muscle strength or for additional strength requirements. The goal of finding the latest revolutionary innovation for the perfect drive solution has led Bioservo Technologies to Eichenberger Gewinde: the combination of the skills of the two companies gives birth to Ironhand.

A help for both operators and companies
Weak hands can result in numerous challenges for people working on tasks that require a lot of gripping. Pain or lack of strength can lead to sickness-related absences. In critical situations, tasks may even have to be re-defined. This may affect the overall company as well as the physical and mental health of the individual. By providing tools, people can master their daily tasks again and/or return to their work. This means companies lose fewer qualified employees with key competencies, and individuals remain integrated in the world of work.
Ironhand is based on Soft Extra Muscle technology and was launched in 2019. The modular system consists of a glove covering five fingers, and a drive system. Pressure sensors integrated in the power hand control servomotors in the device. This provides the wearer with particularly strong grip.
Eichenberger Gewinde boldly uses exotic materials, thread shapes and dimensions outside the norm. Unusual geometries, the company’s own interfaces, special materials and hardening procedures offer some extras. In co-operation with Bioservo’s team, Eichenberger Gewinde has developed the ideal thread drive solution for Ironhand.

It works as a real hand
Ironhand consists of a lightweight glove with a wearable control unit that is carried as a backpack. It is able to increase the user’s gripping strength by up to 80 N within milliseconds. The key components of this kit are five electrically powered, cold-rolled ballscrews by Eichenberger Gewinde. It is these ballscrews that convert the rotational motion of the small servomotors into linear motion.
The function of Ironhand is similar to that of our hands: a hand motion is usually initiated by the muscles in the forearm; those muscles pull on the tendons that are attached to the five fingers. Ironhand works in the same way: the pressure-sensitive sensors in the fingertips of the glove recognise when the user grasps an object. A microcomputer calculates the required power. Servomotors drive five intricate ballscrews of 5×2 mm (Ø 5 mm, pitch 2 mm). They are connected with the fingers of the glove by thin wires. These fine connections move the fingers, and the additional strength is created by the slimline glove. The higher the pressure on the sensors, the more power the glove delivers. So Ironhand recognises how the user grasps an object and intuitively and automatically adapts the gripping motion.

Precision and minimum spatial conditions
Restricted assembly space with heavy loads is a frequent challenge. Silent motions within limited space are required. High positioning accuracies must be accomplished when trying to achieve the smallest lifts and high dynamics, when in constant use; the focus is on safety and reliability. Maintenance intervals, service life and, not least, cost also play important roles. Using individual designs or special manufacturing processes, Eichenberger Gewinde adapts its products to the application in question. The cold-formed, inductively hardened Ironhand ballscrews, with the dimensions of 5×2 mm, combine speed, precision and minimum spatial conditions. Additionally, the perfect pitch ratio of the screw increases motion efficiency.