Equipment for heating molten glass which flows through the conditioning section of a precrucible

摘要

A method and apparatus for preventing the side-to-side temperature differences which occur in a precrucible for molten glass, in its conditioning section, immediately before the feed, are described. Glass leaving a refiner, on normally passing along the precrucible, passes through a pair of cooling sections and from there to the conditioning section. Heat is applied to the glass in the precrucible through gas burners spaced along the sides, above the level of the glass. The flames of the gas burners lie above the upper surface of the glass in the precrucible. Cooling can be achieved through air or by means of submerged heat removers. Typical precrucibles for feeding machines for the shaping of vessels can contain glass with a depth of 15 cm, and a width of 91 cm, decreasing to 56 cm at the inlet to the pot. Having a plurality of electrodes which enter the glass in the conditioning section through the side wall thereof and connecting electrodes adjacent to the opposite poles of a source of power supply, heat can be applied through the Joule effect locally to the side walls of the glass in the precrucible. The glass which enters from the refiner is conditioned in an optimal operation so that its temperature away from the centre of the flowing glass immediately before entering the feed is approximately the same as at the surface, close to the bottom and in the zone lying between these two points. A three-level thermocouple is located along the central line at approximately 23 cm from the feed to monitor these temperatures and help the operator control the actual temperature of the glass. Three levels of thermocouples are located on the opposite sides of the precrucible and approximately 20 cm from the central line. The three pairs are positioned at the same depths relative to those along the central line. The output from the thermocouple at the centre of the right hand side is used as the control temperature for a temperature-limiting circuit connected to the electrodes. The temperature-limiting circuit has an adjustment temperature indicator whose level is selected by the operator and this chosen level is compared with that of the output from the central side electrode. Typically the operator will choose the set temperature which is the temperature which he desires to obtain for the thermocouple temperature indicators along the central line. Ideally all these temperatures will be concordant and then the temperature of the glass will be a temperature which ensures optimum working properties for the glass.