Patent ID: 9725352
Date: 2017-08-08
CPC Classifications: B23K,C03B

Claim:
1. A method for producing a tube ( 22 ) of glass by forming a hollow cylinder ( 2 ) from the glass with a first outer diameter D 1 in that said cylinder, while rotating about a rotation axis ( 6 ), is softened in portions in a heating zone ( 20 ) which is moved at a relative feed rate Va, and the softened portion is radially expanded under an action of a centrifugal force and/or of an internal overpressure applied in a bore ( 7 ) of the hollow cylinder ( 2 ) so as to form a deformation zone ( 30 ), and the tube ( 22 ) is continuously shaped with a second outer diameter D 2 which is greater than the first outer diameter D 1 , wherein the radial expansion of the softened portion is carried out at a location-dependent radial expansion rate Vr, a profile of which along the deformation zone has a maximum value Vr,max which is smaller than 2 times the relative feed rate Va.