Bearing for Ceiling Mounts in Operating Theatres

An ultra-compact, lightweight bearing solution with integrated electromechanical brake has been developed for ceiling mounts in medical operating theatres. The same bearing unit can also be used in examination tables, mammography devices, X-ray cameras, surgical microscopes and stair lifts. Schaeffler's ZAXB bearing unit incorporates an AXS angular contact roller bearing that supports high axial loads and tilting moments.

This ensures that the numerous medical devices, computers and monitors can be moved to their optimal ergonomic positions smoothly and reliably. The integral electromechanical brake ensures secure location, once the desired position has been found. Compared with conventional bearing systems with separate brake, the ZAXB is much lighter and more compact. At the same time, the unit is a closed system, which means there is less exposure to aggressive cleaning chemicals that could damage the materials used.

Ceiling mounts in operating theatres have to support a growing number of increasingly heavy devices, while also enabling quiet, vibration-free positioning. Classic mechanical components play a 'supporting' role in this context. The bearings must exhibit high static load safety and tilting rigidity in the smallest possible installation space. At the same time, their inside diameter should be relatively large to allow the supply lines and cables to pass through easily.

The unit with integrated brake comprises an outer ring with fixing thread, an inner ring with coil and pressure springs, an adjusting nut with fixing thread, an anchor plate with axial movement facility and a lining plate that is connected to the outer ring. There are also two double direction axial angular contact roller bearings in an 'O' arrangement. As a result of this 'O' arrangement and the contact angle of 60deg, the bearing unit provides high load-carrying capacity and exhibits significant radial stiffness.

The bearing rings and adjusting nut are precision-turned parts made from high-strength steel, while the axial roller and cage assemblies and axial bearing washers are manufactured using non-machining methods. The integrated brake prevents the bearing unit from rotating when the current is turned off, as the anchor plate is pressed against the brake lining by springs. Therefore, the ceiling mount is safely fixed. When current is supplied, an electromagnet pulls the anchor plate against the springs and releases the brake lining so that the unit can rotate and be brought smoothly into another position.