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`Revolutionary` bearings challenge angular contacts

01 August, 2003

`Revolutionary` bearings challenge angular contacts

THK claims to have come up with a "revolutionary concept" in the form of cross roller bearings that can replace traditional angular contact bearings, in low-to-medium speed applications requiring 360 degree of rotation. The new approach is said to provide up to four times more stiffness, for improved rotational accuracy, and can handle high loads.

Unlike traditional mechanisms, which have angular ball bearings in face-to-face contact, the new approach uses a sequence of cylindrical rollers at right angles to each other in a sealed, 90-degree V-groove. There are two rings which rotate independently, with the individual rollers separated by precision spacer retainers, designed to hold the roller securely while maximising the roller`s line contact.

This design allows a single bearing to handle loads in all directions, while the increased contact area of the cylindrical rollers means they can carry much larger loads. Other claimed advantages include: enhanced rotational stability, smoothness and accuracy; reduced noise and frictional losses; and the elimination of roller skew. The bearings, supplied preloaded, need no adjustment.

There are several versions of the cross roller bearings:

• a thin, lightweight, low-profile model (the RA) with inner ring diameters from 50-200mm, for low load-bearing applications, such as robotic joints, where high levels of stiffness are needed;

• a version (RE) with a split inner ring for outer ring rotation; and

• a range (RB) with split outer rings and single inner rings delivering high rotational accuracy in applications where precise inner ring rotation is needed. Their inner ring diameters range from 20-1,250mm.

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