Method for the production of a hollow cylinder made of synthetic quartz glass with the aid of a holding device, and appropriate holding device for carrying out said method
In a previously known method for producing a hollow cylinder made of synthetic quartz glass, a silicon-containing compound is flame-hydrolyzed and SiO 2 particles are deposited layer by layer on a rotating support, resulting in the production of an elongate porous soot body ( 5 ) having a central internal bore. Said soot body is dehydrated, doped, or vitrified, a process during which the soot body is held in a vertical direction inside a treatment oven by means of a holding device ( 9 ) comprising an elongate holding body ( 1 ) which protrudes into the internal bore of the soot body and is made of a material having a higher softening temperature than quartz glass. The aim of the invention is to create a method which is based on the previously known method and by means of which the purity of the hollow cylinder is maintained during said heating process while requiring little time and material for aftertreating the internal bore. Said aim is achieved by providing a gas-impermeable envelope ( 2 ) made of synthetic quartz glass between the holding body and the soot body. The holding device that is appropriate for carrying out the inventive method is characterized by the fact that a gas-impermeable envelope made of synthetic quartz glass is provided between the holding body and the soot body.
1 . A method for producing a hollow cylinder ,said method comprising: producing an elongate porous soot body having a central internal bore by flame hydrolysis of a silicon-containing compound and layerwise deposition of SiO 2 particles on a rotating support, holding said soot body while said soot body is dehydrated, doped or vitrified in a vertical orientation in a treatment furnace by means of a holding device which comprises an elongate holding body which protrudes into the internal bore of the soot body and is made of a material having a higher softening temperature than quartz glass, and wherein a gas-impermeable cladding of synthetic quartz glass is provided between the holding body and the soot body.
2 . The method according to claim 1 , wherein the soot body is collapsed onto the quartz glass cladding during vitrification.
3 . The method according to claim 1 , wherein the quartz glass cladding is configured as a cladding tube of quartz glass which surrounds the holding body at least in part.
4 . The method according to claim 3 , wherein the cladding tube of quartz glass has a wall thickness ranging from 1 mm to 25 mm.
5 . The method according to claim 3 , wherein the cladding tube of quartz glass surrounds the holding body so as to define therebetween an annular gap having a mean gap width of not more than 5 mm.
6 . The method according to claim 3 , wherein the soot body surrounds the cladding tube of quartz glass so as to define therebetween an annular gap having a mean gap width of not more than 2 mm.
7 . The method according to claim 3 , wherein the SiO 2 particles are deposited in layers on the cladding tube of quartz glass.
8 . The method according to claim 1 , wherein the quartz glass cladding extends along a substantial length of the internal bore of the soot body.
9 . The method according to claim 1 , wherein the soot body is vitrified in the treatment furnace.
10 . The method according to claim 1 , wherein the soot body is provided with a dopant in the treatment furnace.
11 . The method according to claim 1 , wherein the soot body stands with a lower face end thereof on a support base connected to the holding body , from which the quartz glass cladding extends along the holding body.
12 . A holding structure for use in the de-hydration, doping or vitrification of an elongate porous soot body having a central internal bore in a vertical orientation, said holding structure comprising: an elongate holding body which protrudes into the internal bore of the soot body and is made of a material having a higher softening temperature than quartz glass, and a gas-impermeable cladding of synthetic quartz glass supported between the holding body and the soot body.
13 . The holding device according to claim 12 , wherein the quartz glass cladding is configured as a cladding tube of quartz glass which surrounds the holding body at least in part.
14 . The holding device according to claim 13 , wherein the cladding tube of quartz glass has a wall thickness ranging from 1 mm to 25 mm.
15 . The holding device according to claim 13 , wherein the cladding tube of quartz glass surrounds the holding body so as to define therebetween an annular gap having a mean gap width of not more than 5 mm.
16 . The holding device according to claim 13 , wherein the soot body surrounds the cladding tube of quartz glass so as to define therebetween an annular gap having a mean gap width of not more than 2 mm.
17 . The holding device according to claim 13 , wherein the cladding tube of quartz glass is part of the soot body.
18 . The holding device according to claim 12 , wherein the quartz glass cladding extends along a substantial length of the internal bore of the soot body.
19 . The holding device according to claim 12 , wherein the holding body is connected to a support base from which the quartz glass cladding extends along the holding body.