Glass tube

Abstract

Two conventional thick-walled, drawn, fused quartz tubes 1,2 are arranged the one within the other. At their forward end of them, each is gripped in a collet 3,4. These forward collets are supported for travel along a track 5 by a distance equivalent to the length of the tubes. A heating, and drawing, station 6 is arranged a short distance back in the length of the tubes from an initial position of the forward chucks. At its furthest end, the outer tube is gripped by a tensioning collet 8, itself supported on the track. The collets are arranged to be driven along the track by respective stepper motors 9,10,11. At the heating station, heaters in the form of burners 12 are provided for heating the outer tube. Heat is applied at a rate to soften the outer tube. The forwards stepper motors draw the forward collets 3,4 such that the outer tube stretches. The rear, tensioning collet 8 moves forwards more slowly, whereby the outer tube is stretched sufficiently to reduce it in diameter into contact with the inner tube.

Dependencies are inferred from the claim text.