Apparatus for continuously manufacturing calibrated round or profiled glass tubes and glass tubes made by same

Abstract

The apparatus for continuously manufacturing a calibrated round or profiled glass tube with a predetermined inner profile has a melt feed with an outlet opening for molten glass, a shaping body for forming a hollow drawing bulb from the molten glass, a profile forming body positioned downstream of the shaping body, and a device for changing a distance between the shaping body and the profile forming body to vary a wall thickness of the glass tube. The molten glass from the outlet opening is drawn over the shaping body to form the drawing bulb and the drawing bulb is drawn over the profile forming body so that inner circumferential surfaces of the drawing bulb are deformed while bearing on outer surfaces of the profile forming body to form the predetermined inner profile of the glass tube.

1 . An apparatus for continuously manufacturing a calibrated round or profiled glass tube having a predetermined inner profile, said apparatus comprising
 a melt feed with an outlet opening for molten glass;   a shaping body for forming a hollow drawing bulb from the molten glass;   a profile forming body positioned downstream of the shaping body; and   means for changing a distance between the shaping body and the profile forming body to vary a wall thickness of the glass tube;   whereby the molten glass from the outlet opening is drawn over the shaping body to form the hollow drawing bulb and the hollow drawing bulb is drawn over the profile forming body so that inner circumferential surfaces of the hollow drawing bulb are deformed while bearing on outer surfaces of the profile forming body to form the predetermined inner profile of the glass tube.   
   
   
       2 . The apparatus according to  claim 1 , wherein the profile forming body is disposed downstream of the shaping body in the direction of gravity. 
   
   
       3 . The apparatus according to  claim 1 , wherein the means for changing the distance between the shaping body and the profile forming body varies a length over which the inner circumferential surfaces of the drawing bulb abuts against or bear on the outer surfaces of the profile forming body. 
   
   
       4 . The apparatus according to  claim 1 , wherein the means for changing the distance between the shaping body and the profile forming body comprises a movable shaft held in a longitudinal bore of a shaping body shaft and wherein the movable shaft is guided linearly within the longitudinal bore. 
   
   
       5 . The apparatus according to  claim 4 , wherein at least one of process air and protective gas is passed through the longitudinal bore to the profile forming body. 
   
   
       6 . The apparatus according to  claim 1 , wherein the shaping body is arranged in the vicinity of the outlet opening and wherein the shaping body is axially movable to stop the molten glass from emerging from the outlet opening so that the profile forming body can be exchanged. 
   
   
       7 . The apparatus according to  claim 6 , wherein the profile forming body and the shaping body are held rotationally fixed relative to the outlet opening of the melt feed. 
   
   
       8 . The apparatus according to  claim 1 , wherein the shaping body is formed by a slowly rotating, tubular body such that a continuous strand of molten glass emerging from the outlet opening runs onto the slowly rotating tubular body, thus forming a drawing bulb at a lower end of the slowly rotating body. 
   
   
       9 . The apparatus according to  claim 8 , wherein the profile forming body is rotated synchronously with the slowly rotating tubular body. 
   
   
       10 . The apparatus according to  claim 1 , further comprising means for deflecting the glass tube horizontally and for drawing off the glass tube having the predetermined inner profile after the calibration or profiling at the profile forming body. 
   
   
       11 . A calibrated round or profiled glass tube having a predetermined inner profile, manufactured by means of a method wherein: molten glass emerges from an outlet opening of a melt feed and is drawn over a shaping body so as to form a hollow drawing bulb, and the hollow drawing bulb is drawn over a profile forming body positioned downstream of the shaping body so that inner circumferential surfaces of the hollow drawing bulb are deformed while abutting against outer surfaces of the profile forming body to form the predetermined inner profile and wherein the wall thickness of the glass tube is varied by changing a distance between the shaping body and the profile forming body, wherein a maximum fluctuation of an inner diameter of the glass tube is less than 0.4% of the inner diameter of the glass tube. 
   
   
       12 . The glass tube according to  claim 11 , wherein the maximum fluctuation of the inner diameter of the glass tube is less than 0.25% of the inner diameter of the glass tube. 
   
   
       13 . The glass tube according to  claim 12 , wherein the maximum fluctuation of the inner diameter of the glass tube is less than 0.2% of the inner diameter of the glass tube. 
   
   
       14 . The glass tube according to  claim 11 , wherein a maximum fluctuation of an outer diameter of the glass tube is less than 0.45% of the outer diameter of the glass tube. 
   
   
       15 . The glass tube according to  claim 14 , wherein the maximum fluctuation of the outer diameter of the glass tube is less than 0.3% of the outer diameter of the glass tube. 
   
   
       16 . The glass tube according to  claim 15 , wherein the maximum fluctuation of the outer diameter of the glass tube is less than 0.25% of the outer diameter of the glass tube. 
   
   
       17 . The glass tube according to  claim 11 , wherein an outer diameter of the glass tube is in a range between 20 mm and 100 mm. 
   
   
       18 . The glass tube according to  claim 17 , wherein said range is between 40 mm and 80 mm. 
   
   
       19 . The glass tube according to  claim 18 , wherein the outer diameter is 60 mm. 
   
   
       20 . The glass tube according to  claim 11 , wherein a wall thickness of the glass tube is in a range between 1 mm to 3 mm. 
   
   
       21 . The glass tube according to  claim 20 , wherein said wall thickness of the glass tube is 2 mm.