Correlation of Viscosity Measurements With Flow of Glass*

Abstract

The following paper describes the transformation from the rule‐of‐thumb state to a scientifically controlled process of the filling of the glass insulation into the brass shells for incandescent lamp bases. It is divided into three parts: (a) the development of the platinum alloy dies or orifices, (b) determination of the flow of glass through the platinum dies or orifices, and (c) automatic control of glass‐stream temperature by means of radiation pyrometers. For three decades or more this process has been in operation. Wonderful strides have taken place in the development of the machinery needed until at present the medium screw base (No. 102) for general home lighting is filled with glass and the glass is shaped at the rate of 220 per minute. Actually 12,000 bases are processed per hour by this machine, which is known as a glass base machine. In brief, the process consists of indexing a brass shell and eyelet held in a proper holder under a flowing stream of glass, cutting the stream, pressing the glass into shape, cleaning the glass from the eyelet holes, and blowing the hot base off into an annealer for cooling. Control of the glass stream lagged woefully behind the development of the machines and represented a strictly rule‐of‐thumb handling. The crux of the difficulty was the constantly varying size of the orifice through which the glass is delivered to the glass base machine. A porcelain die was used for this purpose and quickly enlarged due to erosion. The development of a platinum alloy‐lined refractory die solved the problem of the varying size of the orifice. While this development was being carried on, the field of automatic control for the oil‐fired tank was kept continually in mind and various promising installations were experimented with. Thus when the unvarying orifice was developed, the whole process of control was immediately available. The present status of this work as here described does not represent a perfect solution but only the present situation which is subject to further improvement.