Abstract: The material exchange column contains a packing which can be installed in the horizontal position of the column. The column has a ring gap between the packing and the column wall in which collars are arranged. The latter each comprise a band-shaped region (30) which lies in contact with the packing. At the upper edge of the band-shaped collar regions there adjoin spring-elastically connected surface pieces which produce a bridge to the wall and which are provided for a return conduction of the liquid from the wall to the packing during the operation of the column. It applies at least for some of the collars that the latter have elevations in their band-shaped regions which hold the ring gap open in a form-stable manner under the load of the packing when the column lies horizontally.

Abstract: A self-advancing conical boring tool with a tapered frame for supporting roller cutters, each of which has a frusto-conical body with a plurality of teeth randomly disposed about its periphery. Each roller cutter is constrained within a pair of thrust bearings and a pair of self-aligning spherical roller bearings for free rotation about an axis that is both oblique and skewed relative to a longitudinal axis of the tool. A flexible diaphragm is captively held to the frame proximate each roller cutter and forms a pressure compensated chamber for a bearing lubricant, one face of the diaphragm being adjacent a thrust bearing and the other face of the diaphragm being exposed to the environment through a vent.

Abstract: A self-advancing conical boring tool with frusto-conical roller cutters rotatably mounted to a tapered frame by means of self-aligning spherical roller bearings. Each roller cutter is constrained within a pair of spherical roller bearings for free rotation about an axis that is both oblique and skewed relative to a longitudinal axis of the frame.