Universal stem mold apparatus

In an apparatus for manufacturing a molded glass stem for an electron tube, said stem comprising a tubulation, a body integral therewith having a plurality of fillets and a plurality of lead-in conductors extending through said fillets, said apparatus comprising a plurality of lower stem mold assemblies and a plurality of pre-heating, heating, forming and annealing stations, said forming stations including at least one primary forming station having a primary upper stem mold assembly, and at least one secondary forming station having a secondary upper stem mold assembly, said primary upper stem mold assembly including a plurality of lead-weights and primary fillet-forming means, said secondary upper stem mold assembly including a plurality of lead-weights and secondary fillet-forming means extending, wherein the improvement comprises

• a primary universal stem mold including a first mold block having a glass-contacting surface and an oppositely disposed second surface, said primary fillet-forming means including a plurality of longitudinal fillet-forming openings formed in said glass-contacting surface and extending through said first mold block, and
• a plurality of primary inserts replaceably disposed within said openings in said first mold block, each of said inserts having a first end and an oppositely disposed second end with a recess provided in said first end thereof for contacting the glass of the stem to preshape said fillets, each of said inserts having a lead-accommodating opening therein extending from said recess into said insert, said second end of each of said inserts being in contact with a different one of said lead-weights to retain said primary inserts within said openings in said first mold block of said primary universal stem mold,
• a secondary universal stem mold including a second mold block having a glass-contacting surface and an oppositely disposed second surface, said secondary fillet-forming means including a plurality of longitudinal fillet-forming openings formed in said glass-contacting surface and extending through said second mold block;
• and
• a plurality of secondary inserts replaceably disposed within said openings in said second mold block, each of said inserts having a first end and an oppositely disposed second end with a lead-in conductor orienting recess provided in said first and thereof for directing said lead-in conductor into a lead-accommodating opening extending from said orienting recess into said insert, said secondary insert being spaced from the glass contacting surface of said second mold block, said fillets being shaped by capillary action between the glass of said stem and the wall surrounding said longitudinal fillet-forming openings formed in said second mold block of said secondary upper stem mold assembly, said second end of each of said inserts being in contact with a different one of said lead-weights to retain said secondary inserts within said openings in said second mold block of said secondary universal stem mold.