Plain bearings in electric wheelchairs

Profile

• What was needed: drylin W profile guides
• Requirements: Resistance to outdoor use and high loads; a maintenance-free and lubrication-free profile guide.
• Industry: medical equipment
• Success for the customer: A mechanism optimally adapted to the body's own joint functions.

Problem

The Motion Solutions GmbH – 'moso' for short – has set itself the task of ensuring or maintaining the mobility of its physically disabled customers. The company develops and manufactures a wide range of tools that are characterised by innovative functions, for example, by the special mobility of the seat systems.
For people who cannot stand on their own, Motion Solutions customises and distributes the "EasyStand Evolv" standing trainer. They bring the user into the standing position at the push of a button and without any other intervention. This strengthens the active and passive musculature, stabilises the cardiovascular system, treats contractures and brings the users to the same level as their standing fellow human beings.
The structure of such a device is anything but simple. The mechanics must be adapted to the body's joint function. During the entire standing up process, shearing motion should not occur on the backrest or on the seat surface, and all system components that touch and guide the body must be in the same positional relationship throughout the entire standing up and sitting down phases.
In addition, it has a so-called "delordosing", which brings the pelvis into the orthopaedically correct position when standing, by shifting the seat surface according to the user's needs as an additional movement.

Solution

The moso engineers have implemented this push-out with a drylin W profile guide, or more precisely a drylin WJ200QM housing bearing with an angular contour , which exerts a leverage effect on the delordosing system . It runs on a profile rail guide and is equipped with a clamping device, which synchronises the radius of movement in relation to the standing. This is just one of many examples of the use of igus plain bearings in Motion Solutions' rehabilitation equipment and wheelchairs. For more than ten years, the designers have been using the exceptionally compact plain bearings, which do not require lubrication and are suitable for outdoor use without restrictions. The bearings have to prove that they are also suitable for high loads in other devices in the moso product range. Prime example is the "Leo 350 XXL": An electric wheelchair for people with disabilities, who weigh up to 350 kilograms and are up to 2.20 metres tall. The wheelchair itself is extremely manoeuvrable and compact. Here, for example, in the longitudinal adjustment as well as in the (optional) height adjustment of the seat system, drylin® linear guides again provide for mobility and stability. The seat tilt can also be highlighted, which means that the seat can be tilted upwards to the rear by 45 degrees and forward, as an entry and exit aid. Here, plastic bearing bushings are used as well as in the drive and steering system of the Leo 350. They also prove themselves in the case of high mechanical loads such as shocks caused, for example, by driving over the curbs, as well as by the twists to which the chassis is subjected in practice.