Abstract: A positioning device for a positioning element, which is rotationally displaceable about a first axis, including a positioning member engaged with the positioning element. The positioning member is rotatable about a second axis perpendicular to and spaced from the first axis. The positioning device further includes a slotted link disposed on the positioning element and arranged radially about the first axis, a threaded spindle rotatable about a fixed point, and a link block inserted into the slotted link it cannot be turned. The link block is defined by a spindle nut engaged with the threaded spindle. The thread pitch of the threaded spindle corresponds to a predefined range of the positioning angle of the positioning element such that the positioning element is displaceable within the range of the positioning angle by two rotations of the threaded spindle or less.

Abstract: The invention relates to a procedure for manufacture of a quartz glass body by deposition of SiO2 particles on the outer surface of a cylindrical mandrel rotating around its longitudinal axis under formation of an essentially cylindrical porous blank with an inside bore hole, and by removing the mandrel and sintering of the blank, characterized in that the mandrel in the area of one of the ends of the successively forming blank is surrounded by a shaping element rotating at the same rotation velocity as the mandrel, such shaping element having a core area facing the blank which is at least partially removably embedded into the front face of the successively forming blank and which is removed before sintering after having widened the inside bore hole of the blank with a shape complementary to that of the core area.