Novel Direct Drive Bearing System Cuts Noise Levels by 50% on CT Scanner

Precision bearings and a novel direct drive system have been developed for the latest CT scanners, helping to cut noise levels in half and enabling faster examination times.

Since the 1970s, computer tomography (CT) scanners have been used by hospitals and other medical establishments to scan part or all of a patient’s body for diagnosis purposes.



However, on their latest models, CT scanner manufacturers are now demanding machines and components that are quieter for patients, more compact and which enable faster examination times.

A direct drive system for CT scanners was developed recently by the Schaeffler Group for a number of leading CT scanner manufacturers. The ‘SIMTUS’ system, for example, incorporates a novel, integrated mechatronic turning unit, which not only helps to halve noise levels on the CT scanners from 12dbA to 6dbA, but also enables images to be generated and recorded 50% faster than previous machines.

SIMTUS utilises a special, low noise CT scanner bearing originally developed for helicopters; a novel, direct drive ring motor/segment motor; a position measuring module; and high precision components and bearing rings – all supplied by the Schaeffler Group.

The design, manufacture and supply of the complete SIMTUS system was carried out by the Schaeffler Group over the course of 12 months, using bearings from its ‘INA and FAG’ range, ‘IDAM’ drives and from its super-precision ‘Barden’ range of bearings. In total, the CT scanner machine and patient table utilise eight linear guidance systems, one CT main bearing, two slewing rings and one X-ray tube bearing unit.

SIMTUS incorporates a custom-designed, thin section bearing, which uses ceramic rolling elements for current insulation. The bearing not only offers the high accuracy required by the application, but also provides low noise levels and a longer operating life.

The IDAM ‘HSRV’ direct drive ring motor also offers a number of technical advantages for the customer. It is designed to operate at low temperatures, with high speed capability, high efficiency, low vibration levels and low noise. The segment motor was designed as a modular unit with a variable number of segments, allowing more space for other scanner components.

The rotor (rotating part) is fitted with permanent magnets. The stator (housing component) is equipped with coils that are subjected to current. This creates a magnetic field, which is followed by the permanent magnets in the rotor, inducing rotation. This principle is known as ‘direct drive’.

Barden’s super precision X-ray bearings were used to support the spinning X-ray anode, which rotates at speeds in excess of 10,000 rpm under extreme conditions. The operating environment is high voltage, high temperature (400°C to 500°C) in a vacuum down to 10-8 torr. The key benefit here is this system enables the X-ray scanner to generate and record high resolution images up to 50% faster than conventional machines.

The two, four-point contact slewing rings were customised by the from Schaeffler’s standard bearing range, enabling the gantry to slowly swivel by up to ±30°. The four point contact ball bearings were supplied ready to install, greased for life and provide smooth running (swivelling), high accuracy and high stiffness.

The key benefit of the gantry bearings is that they are maintenance-free, a low cost design and have a small width, which meant the number of parts were reduced for the customer.

The patient table on the machine also uses bearings from the Schaeffler Group. Low noise was again important for this application. Six ‘KUVE’ linear guides are used at various points on the table, offering high load carrying capacity, low noise, functional reliability and high rigidity. The four-row linear ball bearing and guideway assembly incorporates quad spacers between the balls, which siginificantly reduce the running noise. The low displacement resistance enables the table to be adjusted with high positioning accuracy. The guidance system operates virtually maintenance-free for its entire operating life, due to a lubricant reservoir integrated adjacent to the loaded raceways.

Reiner Thalacker, Head of Consumer Products at the Schaeffler Group comments: “The innovative development of the large thin-section bearings made it possible to bring the new generation of high performance turning units to market maturity, for use in high end CT scanners.

“It is the patients who benefit most from this technology transfer. The new CT scanners are more precise thanks to the bearing technology and are much quieter than previous generations – while significantly reducing examination times.”

As well as CT scanners, the Schaeffler Group is active in many other areas of the medical and healthcare industry, with applications for bearings and linear guides in dentist drills, dentist chairs, guidance systems for precision grinding of optical lenses, ophthalmology, ceiling stands in operating theatres, and for automated laboratory analysis equipment.

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