Radial spherical plain bearings are standardised according to DIN 12240, Part 1. In hydraulic cylinders, typically types E (DO) and types W (LO) with expanded inner ring are used.
Form E (DO)
Form W (LO)
Basically, spherical bearings are never entirely free from clearance, which is why this bearing clearance must be accounted for at the reversal point of the cylinder movement.
Spherical plain bearings are used
Depending on the cylinder series, different types of spherical plain bearings are used.
The spherical plain bearing design requires maintenance as standard. These must be lubricated regularly in accordance with the load and spherical bearing manufacturer's recommendations.
Special spherical plain bearings, such as maintenance-free or with lower bearing clearance, are available on request.
Spherical plain bearings requiring maintenance are lubricated either at the grease nipple on the bracket, at the grease nipple via the pin or directly on the pin.
Fixation of bearing
The spherical plain bearings are pressed into the lugs of the rod eyes or cylinder tubes. They are either permanently fixed and crimped with several marks or alternatively fixed with removable snap rings.
with snap ring
Being plain bearings, all spherical bearings have a certain bearing clearance. This describes how far the inner ring can be moved in relation to the outer ring.
This bearing clearance, also called bearing play, manifests itself when the bearing is installed. It is therefore necessary to use a bearing housing and pin with the correct tolerances. The bearing clearance depends on the dimensions and the bearing clearance-group.
Bearings of the normal clearance group N are suitable for normal applications of hydraulic cylinders, while bearings with narrow clearance group 2 are used for cylinders intended for dynamic requirements with very small amplitudes.
Radial and axial bearing clearance
|Diameter in [mm]||Bearing clearance group in [µm]|
|above||up to||Group N||Group 2|
|12||20||40 - 82||10 - 40|
|20||35||50 - 100||12 - 50|
|35||60||60 - 120||15 - 60|
|60||90||72 - 142||18 - 72|
|90||140||85 - 165||18 - 85|
|140||200||100 - 192||18 - 100|
Radial bearing clearance of spherical bearings requiring maintenance according to ISO 12240-1, type E or W
Group N = normal clearance
Group 2 = narrow clearance Spiel
The bearing clearance indicated in the table only applies to the fits recommended by the bearing manufacturers.
The fits specified in the standards for hydraulic cylinders and accessories may differ from them. The bearing clearance must be calculated in each individual case.
However, the bearing clearance can be reduced to suit the application by selecting the appropriate internal clearance group.