Due to the particularity of its structure and the diversity of on-site conditions, the slewing bearing of Cat excavator is prone to damage to the slewing bearing, slewing ring gear or slewing motor due to oil leakage. Therefore, the leakage should be prevented and handled in time. This paper will introduce some maintenance methods summarized from practice.
Structure and lubrication principle of rotary bearing
In fact, the grease lubrication of the rotary part of the excavator is divided into two cavities: the rotary bearing lubrication cavity and the rotary ring gear lubrication cavity.
The lubrication of the rotary bearing is completed by filling the lubricating grease through the lubricating nozzle located on the outer ring of the rotary bearing, and the lubrication of the rotary gear ring is completed by the pre added grease. The rotary bearing has two inner and outer (or upper and lower) rubber strips as oil seals. The outer oil seal is fixed on the inner ring (fixed plate) of the rotary bearing of the lower frame to prevent external dust and sundries from entering the rotary bearing. The inner oil seal is located on the outer ring (moving plate) of the bearing to prevent the grease in the rotary gear ring from entering the bearing. The rotary gear ring and the rotary bearing use the same brand of grease.
The rotary oil seal gradually thins from thick to thin, and finally forms a sharp angle. Only the elastic part of the rubber itself presses the end face of the rotary bearing by the deformation of the rubber to achieve the sealing effect (Fig. 2 shows the shape before the deformation of the sealing strip) . this kind of seal has a slight effect on preventing grease leakage, but the pressure is not high. Once the pressure increases due to excessive oil filling or the increase of working temperature, the grease will still leak through the oil seal. Under normal circumstances, the leakage amount is related to many factors, such as the filling amount, the working speed and frequency of the rotating part, as well as the on-site temperature. Therefore, there is a risk to the normal operation Fuzziness related to abnormal leakage.
