1. Field of the Invention
This invention relates to an apparatus for sealing a rotatable tubular member in a stationary housing which surrounds the end of the tubular member, comprising a gripping device, which is secured to the outside peripheral surface of the rotatable tubular member and rotates with the tubular member, and a sealing element, which is radially movably disposed in the gripping device and rotates with the latter and is in sealing relation to the housing.
2. Discussion of Prior Art
Rotatable tubular members, particularly in rotary kilns, must be sealed at their charging and/or discharge ends in order to prevent or minimize an escape of gases and dusts and an ingress of air. For this purpose the gap between the rotatable tubular member and the stationary housing, which surrounds the end of the tubular member, must be sealed. As a sliding sealing element is required to seal the gap and in most cases is exposed to elevated temperatures, dust and gases, the sliding sealing element is subjected to heavy wear. Additionally, the rotatable tubular member is axially displaced as a result of thermal expansion and owing to the nature of its bearings and also performs continual radial movements because the axis of the rotatable tubular member never coincides exactly with the center line of the housing but performs a gyratory motion about the center line of the housing. Particularly these continual radial movements of the rotatable tubular member impose high stresses on the sliding sealing elements.
The periodical "Zement--Kalk--Gips" No. 5, 1971, contains on pages 208 to 215 a summary of arrangements for sealing rotary kilns. Whereas some of the sealing arrangements disclosed there are structurally expensive, none of them can prevent a heavy wear particularly as a result of the axial movement of rotary kilns.
German Pat. No. 17 50 881 discloses a sealing arrangement comprising a tubular section which surrounds the outside peripheral surface of the rotatable tubular member and has on the inside an annular flange, which overlaps a ring that is secured to the outside peripheral surface of the rotatable tubular member. On the other side the flange is forced against the ring by thrust members, which are connected to the ring by screws. The flange and the tubular section are radially displaceable and are connected to the rotatable tubular member by chains so that the flange and the tubular section rotate with the rotatable tubular member. A sealing ring composed of a plurality of segments is secured to the stationary housing and surrounds and supports the tubular section. Owing to the asymmetrical loading of the tubular section, the gyratory motion of the end of the tubular member and the frictional contact between the flange of the tubular section and the gripping device, the radial displacement results in an additional load. The sealing segments always subjected to contact pressure wear heavily, the pressure contact of the sealing segments and the gripping device are highly liable to be deranged, and the sealing arrangement is highly expensive and can be mounted only with difficulty.