EGLASSTREK DOUBLE-WALLED PGM-PIPE FOR LOW PRESSURE FINER/OVERFLOW FUSION PROCESS

The present development (Patent application) relates to a process and a device for monitoring and controlling temperature during glassmaking, in particular during the making of TFT/LCD glass by Low Pressure Refiner or by Overflow Fusion process.  As regards the process, this object is achieved in that the riser- or down- pipe and/or the muffle- or chamberpipe is heated directly by electrical current flow. The pipe is made of an electrically conductive heat-resistant material (e.g. PGM – Platinum Group Metals) and is provided with terminals for guiding current. 

In this connection preferable is an embodiment in which in particular the riser- or downpipe and/or muffle- or chamberpipe the lower section thereof is constructed as a double-walled pipe, that is to say as a pipe in which both the inner wall and the outer wall are electrically conductive, with the inner and outer walls being directly connected to one another at one end of the pipe, preferably at the downstream end of the pipes, but the two pipes walls otherwise separated from one another and electrically insulated from one another, with the inner pipe and outer pipe each having a power terminal at the other end, e.g. preferably the upstream end, of the outlet pipe. Between the inner and outer walls, either a corresponding air gap or vacuum or indeed an insulating material, may be provided.

The double-walled construction in particular of the lower section of the outlet pipe has the particular advantage that direct heating of the pipe wall is possible over the entire length of the riser- or downpipe, although the downstream end of the pipes reaches into the muffle- or chamberpipe and in general also into the glass melt in the vertical section of the muffle- or chamberpipe, with the result that it is impossible to mount power contacts in this region. By connecting the outer wall and the inner wall one behind the other, however, it is possible to provide both power terminals, that of the inner pipe and that of the outer pipe, outside the muffle- or chamberpipe and preferably in the vicinity of the upstream end of the riser- or downpipe.