Abstract: The invention relates to a focusing drive (15) having a linear stroke carriage (6) for carrying and moving an optics carrier in the direction of focus, the focusing drive (15) comprising: a focus carrier (1) having at least one linear guidance system (3) having a rail (4) extending in the direction of focus and having at least one carriage (5) movably supported on the rail (4); and a direct drive (2) for moving a piston (10) supported movably in the direction of focus, which piston is in turn joined to the linear stroke carriage (6) of the focusing drive (15), the linear stroke carriage (6) being joined to the at least one carriage (5) of the linear guidance system (3). This focusing drive (15) makes do with few components without linkage elements, and is significantly quieter.

Abstract: The invention relates to a focusing drive (15) having a linear stroke carriage (6) for carrying and moving an optics carrier in the direction of focus, the focusing drive (15) comprising: a focus carrier (1) having at least one linear guidance system (3) having a rail (4) extending in the direction of focus and having at least one carriage (5) movably supported on the rail (4); and a direct drive (2) for moving a piston (10) supported movably in the direction of focus, which piston is in turn joined to the linear stroke carriage (6) of the focusing drive (15), the linear stroke carriage (6) being joined to the at least one carriage (5) of the linear guidance system (3). This focusing drive (15) makes do with few components without linkage elements, and is significantly quieter.

Abstract: The invention relates to a refractory part for a device for regulation or interruption of a jet of steel, characterized in that it is formed from a refractory material essentially consisting ofa) 61 to 77% by weight of grains having an alumina content of more than 50% by weight and a melting point higher than 1800.degree. C., andb) 39 to 23% by weight of a binding phase having a X-ray diagram in which the most intense lines are the lines characteristic of a sialon of the formula Si.sub.6-z Al.sub.z N.sub.8-z where z ranges from 2.5 to 4.Application in particular as plate in a slide closing device.

Abstract: The invention relates to new refractories with a high content of alumina and the process for their production. The refractories are made up of alumina particles held by a binder capable of withstanding a reducing atmosphere at 850.degree. C. The refractories are characterized by low porosity and high mechanical strength and are also inert towards coal ashes and slags at these temperatures. The binder used in the refractories consists of a combination of aluminum nitride and aluminum oxycarbide. The carbon required to the formation of the carbon oxide may be introduced in a form of carbon black or graphite, or may originate from a decomposition of a provisional or organic binder.