Abstract: The method produces glass tubes having a predetermined inner profile according to a Vello-method or Down-Draw method, wherein molten glass emerges from an outlet orifice of a melt feed and is drawn over a shaping body to form a hollow drawing bulb, and the drawing bulb is drawn over a profile forming body downstream of the shaping body to form the predetermined inner profile. To enable a reliable, risk-free positioning of the profile forming body within the drawing bulb, the profile forming body is axially moved either from below the shaping body via an inner space of the glass tube or via an inner bore of a shaft supporting the shaping body until reaching an operational position in the inner space of the glass tube. An apparatus for performing the method is also described.

Abstract: The invention relates to a method and apparatus for manufacturing glass tubes having a predetermined inner profile according to a Vello-method or Down-Draw-method, wherein molten glass 6 emerges from an outlet orifice 12 of a melt feed 2 and is drawn over a shaping body 3 so as to form a hollow drawing bulb 50, and the drawing bulb 50 is drawn over a profile forming body 4 positioned downstream of the shaping body 3 to form the predetermined inner profile. In order to enable a reliable and riskless positioning of the profile forming body 4 in an operational position within the drawing bulb 50, according to the invention the profile forming body 4 is moved in axial direction either from below the shaping body 3 via the inner space of the glass tube 5; 5? or via an inner bore 31 of a shaft 30 supporting said shaping body until reaching an operational position in the inner space of said glass tube 5; 5?.

Abstract: The device for homogenizing a glass melt has at least one stirring device, which includes a rotatable stirrer shaft (10) and stirrer paddles (11, 11?, 11?). The stirrer paddles are arranged at intervals from each other along the stirrer shaft to produce an essentially axially oriented conveying effect on the glass melt. To improve homogenization while simultaneously saving on noble metal material, the stirrer paddles (11, 11?, 11?) are each provided with a built-in element (11E). The built-in element (11E) has an edge (11K), which extends from the stirrer shaft (10) in a radial direction (R) along a rear paddle area (11B) with an edge length which is less by a specified distance (X) than the length (L) of the paddle area (11B) in a radial direction (R). These built-in elements provide a marked reduction in bubble formation.