Radial spherical plain bearing
Use in hydraulic cylinders
Radial spherical plain bearings are standardised in Part 1 of DIN 12240. In the hydraulic cylinder, forms E (DO) and W (LO) with a widened inner ring are particularly used.
Form E (DO)
Form W (LO)
In principle, however, spherical plain bearings are never free of play, and therefore their bearing clearance must be taken into account at the reversal point of the cylinder movement.
Spherical plain bearings are used
- as pivot mounting with spherical plain bearing for mounting on the cylinder body
- in the spherical rod eye with spherical plain bearing for mounting on the piston rod
- on the protection tube for cylinder mounting
Depending on the cylinder series, different types of spherical plain bearings are used.
Lubrication
The standard version of the spherical plain bearings requires maintenance. These must be lubricated regularly according to the load and the spherical plain bearing manufacturer's recommendation.
Special spherical plain bearings, such as maintenance-free or with reduced bearing clearance, are available on request.
The lubrication of the spherical plain bearings requiring maintenance is carried out either at the grease nipple on the clevis, at the grease nipple via the pivot pin or directly on the pivot pin.
Mounting bearing
The spherical plain bearings are pressed into the clevises of the spherical rod eyes or cylinder tubes. They are either permanently installed and flanged with several marks on the circumference or alternatively fastened with removable retaining rings.
permanently installed
with retaining ring
Bearing clearance
All spherical plain bearings have a certain bearing play as plain bearings. The inner ring can be moved relative to the outer ring by this amount.
This bearing play, also called bearing clearance, occurs in the installed state. For this, it is necessary that both the bearing housing and the pivot pin are used with the correct tolerances. The size of the bearing clearance depends on the dimensions and the bearing clearance group.
For normal use of a hydraulic cylinder, bearings with normal play of group N are suitable; for cylinders with dynamic requirements at very small amplitudes, bearings with reduced bearing clearance group 2 are used.
Radial and axial bearing clearance
|
Diameter in [mm] |
Bearing clearance group in [µm] | ||
| over | 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 plain bearings requiring maintenance according to DIN ISO 12240-1, form E or W
Group N = normal play
Group 2 = reduced play
However, the bearing clearance given in the table only applies to the fits recommended by the bearing manufacturers.
The fits specified in the standards for hydraulic cylinders and accessories sometimes deviate from this. A calculation of the bearing clearance is recommended in individual cases.
By selecting the appropriate bearing clearance group, the play can be reduced to suit the application.