Producing multi-layered glass tubes by Danner-traction-principle, comprises introducing first and second strands made of first and second glasses to a circulating drawing blowpipe over first and second nozzles to form glass layers

摘要

The method comprises introducing a first strand (STA) made of a first glass (A) to a circulating drawing blowpipe (3) over a first nozzle (2A) to form a first glass layer (WA), and introducing a second strand (STB) made of a second glass (B) to the circulating drawing blowpipe over a second nozzle (2B), which is spatially arranged to the first nozzle in a drawing direction (Z). The second glass overdraws the first glass to form a second glass layer applied on the first glass layer. The second strand is introduced to the drawing blowpipe over a heated conductive element. The method comprises introducing a first strand (STA) made of a first glass (A) to a circulating drawing blowpipe (3) over a first nozzle (2A) to form a first glass layer (WA), and introducing a second strand (STB) made of a second glass (B) to the circulating drawing blowpipe over a second nozzle (2B), which is spatially arranged to the first nozzle in a drawing direction (Z). The second glass overdraws the first glass to form a second glass layer applied on the first glass layer. The second strand is introduced to the drawing blowpipe over a heated conductive element arranged between the first nozzle and the second nozzle. The conductive element corresponds to a platinum guide plate that surrounds the drawing blowpipe in a cover-like manner, where N strands made of different glasses are introduced to the blowpipe over N nozzles that are distanced to each other and N glass overdraws (N-1) glass to form a glass tube consisting of N glass layers. The inner first glass layer is formed from the first glass (A), which is high-graded, homogeneous and/or acid-resistant than the second glass (B), which forms the outer second glass layer and is a stable carrier glass. One of the first and second glasses is a color glass. The inner first glass layer is thinly formed than the outer second glass layer. The thickness of the glass layers are variably formed by adjusting the introduction of the strands and/or dimension of the nozzles.