GB393222A - Improvements in or relating to the production of hollow moulded articles - Google Patents

Abstract

393,222. Disintegratable moulding- cores; mould-opening devices. S O C. ITALIANA PIRELLI, 21, Via Fabio Filzi, Milan, Italy. Jan. 16, 1933, No. 1469. Convention date, Jan. 15, 1932. [Class 87 (ii).] Dispersible cores for the manufacture of rubber and like articles are formed of a hydrated crystalline salt which is soluble in its water of crystallization upon being heated. Sodium hyposulphite, sodium thiosulphate, sodium sulphate decahydrate, hydrated sodium carbonate, borax, sodium acetate, crystallized' calcium chloride, potassium sodium tartrate, disodium phosphate and sodium ammonium phosphate are given as examples of materials. Mixtures of the above ingredients can be used and a proportion of inert filling-material, for example, moulding or siliceous sand, clay, diatomaceous earth, sawdust, powdered cotton waste, and the like. Specific examples of actual mixtures used include equal parts by weight of sodium: thiosulphate and either sand or moulding sand, or of sodium thiosulphate, sand, and moulding sand. These mixtures disintegrate at about 49‹ C. Another example of a mixture disintegrating at 32‹ C., comprises two parts by weight of sodium sulphate decahydrate, two parts sand, and one part moulding sand. A third example disentegrating at 58‹ C. comprises two parts by weight of sodium acetate, twoparts sand and one part moulding sand. A fourth example disintegrating at 125‹ C. comprises two parts by weight of borax, two parts sand and one part moulding sand. As applied to the manufacture of a core for a superballoon tyre cover, the material for a half core is placed in the jacketed lower half 1 of a mould round a central metal bush 8, which is positioned by the boss 7. Rings 11, 12 are then placed in position, and finally the topmember 2 is assembled or the pin 10 and rotated to distribute the material with or without applied pressure. Heat is then applied to the jackets to melt the material sufficiently to sinter it into a coherent body. To open the mould the screws 13 are used to prise the top mould member from off the ring 12 and similar screws then used in the holes 14 to prise the part core and ring 11 from the mould member 1. Fig. 2 shows the assembled core, the two bushes 8 being placed end-to-end and clamped by a screwed ring 18 to the rotary metal sleeve 16. The cores may be removed from the articles by breaking them up mechanically or by water dispersion in cases where the heating would mar the finished product. Specifications 350,227 and 381,658 are referred to.