The bottom bearing (5) is located in an oil bath (8) and generates by rotation of the driving spindle (2) an oil mist that is further reinforced by the rotary element (12). This oil mist lubricates the top bearing (4). The pulley (7) is provided above the top bearing (4). In the event of an oil leak at the top bearing (4), there is no danger of oil reaching the driving belt (6), since the force of gravity causes the leaking oil to flow down to the bottom of the housing (3).
