Compression mould assembly for producing glass articles of uneven thickness

TLDR: In this article, a compression mold assembly for producing a glass article having a zone of reduced thickness as compared with the rest of the article comprises a plunger 1 and complementary mould 2 having opposed molding surfaces adapted to compress there between a glass mass to the desired form, the moulding surfaces of each mould being formed of (i) carbon steel containing less than 0A3% by wt. carbon, or (ii) ferritic stainless steel or ferritic heat-resistant steel, except for the portion of the molding surface of at least one of the moulds, which

Abstract: 1,164,988. Making moulds. TOKY SHIBAURA ELECTRIC CO. Ltd. 20 Feb., 1968, No. 8282/68. Heading B3A. [Also in Division C1] A compression mould assembly for producing a glass article having a zone of reduced thickness as compared with the rest of the article comprises a plunger 1 and complementary mould 2 having opposed moulding surfaces adapted to compress therebetween a glass mass to the desired form, the moulding surfaces of each mould being formed of (i) carbon steel containing less than 0A3% by wt. carbon, (ii) ferritic stainless steel or ferritic heat-resistant steel containing less than 0A4% by wt. carbon, or (iii) austenitic stainless steel or austenitic heatresistant steel, except for the portion of the moulding surface of at least one of the moulds, which provides the zone of reduced thickness in the article, said portion being formed of a selffluxing nickel-chromium-boron base alloy having a Rockwell hardness of less than 45. The surface of the plunger 1 is formed by fusing the Ni-Cr-B alloy to the body of the plunger, which is of heat resisting steel, and parts are removed by cutting to form the bottom portion of the mould surface 16. A ring 10 is slidably mounted around the upper part of plunger 1 and has a boss-like portion 12 which seats on a recessed ledge 12 in the upper edge of mould 2. The moulds are preferably made of heat resisting steel containing 13% by wt. of chromium. That area of the plunger designed to form the area of reduced thickness may have a composition in per cent by wt., of Ni 90, Cr 5, B 1, Fe+Si+ C 4 and a Rockwell hardness of 20, or Ni 80, Cr 11, B 3, Fe + Si + C 6 and a Rockwell hardness of 40. The preferred range is Ni 75-90, Cr 4-18, B 0A75-4A5 and Fe+Si+C less than 10. The mould assembly is preferably used for cathode-ray tube cone portions.