GLASS ENGINEERING FOR CATHODE RAY TUBE MANUFACTURE (i)
Posted by STEVE MYCIUNKA on
In the very early days of television, the bulbs for cathode ray tubes (CRT) were blown by hand, however, due to volume requirements, most CRT bulbs were moulded, being made in two parts with the flattened end termed the face-plateand the pear shaped body termed the cone. As the separate parts were delivered to the Mullard factory, at this stage in the early 1950s that means the Blackburn works, the first stage after inspection for blemishes was to join the parts. Any components marred by blemishing were returned to the glass moulders for re-melting - waste not want not!
Joining was carried out using a multi stage joining machine with the face-plate and cone being held on a loading jig whilst touching each other, the fixture then commences to revolve and was moved to successive stations where gas blowpipe flames of increasing intensity played on all areas of the join until the individual parts were welded together, successive stations then reduced the glass temperature gradually with the bulbs finally being placed into an annealing furnace where they were left to cool to ambient temperature slowly hence relieving any heat induced stresses.
So, that's the cone and faceplate sorted, next time we'll look at the manufacture and attachment of the CRT necks.
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