Heat retaining shield in glass gob former

Glass gob forming apparatus which comprises one or more axially reciprocatable plungers each mounted above a respective orifice in the floor of a refractory trough such that on axial reciprocation of the plunger(s) in use of the apparatus molten glass is forced out of the trough through the orifice(s) in the form of gobs, the plunger(s) being surrounding by a refractory cylinder which extends into molten glass in the refractory trough in use, there being provided a refractory heat-insulating tubular shield within the cylinder around the plunger(s) to reduce heat loss from molten glass within the cylinder during use, the heat shield being above the molten glass level within the cylinder and being in the form of a blind tube mounted coaxially within the refractory cylinder, the closed end of the tube facing towards the trough floor and the plunger(s) extending through openings in the end of the tube, the refractory cylinder being spaced from the plunger(s) and the blind tube heat shield extending substantially across the space thereby formed to provide heat insulation.