VALVE TYPES & MANUFACTURING TECHNIQUES (xvii) - B7G & B9A VALVE ASSEMBLY - SEALING -

Today, we shall look at valve sealing.  First off, the cage-base assembly was inserted into the bottom end of the envelope and then mounted vertically onto a rotating table on the sealing machine.  At the first station on the table, the location of the electrode assembly with respect to the bottom of the valve was automatically adjusted. The aligned assembly then passed through a four stage sealing process where gas blow pipes played upon the the walls of the envelope at a point exactly opposite the rim of the glass base.  Gradually, the glass softened and hence the envelope and base were fused together and with gentle pressure from forming guides, the join was shaped and minor irregularities were smoothed out.

The final product of the sealing process is shown in the photo above as '3'.