GB634764A - Improvements relating to the manufacture of moulded articles from moulding powders - Google Patents

Abstract

634,764. Moulding buttons, slides &c. from different ly-coloured moulding powders. HORNFLOWA, Ltd., and WINTER, H. A. M. Jan. 29, 1948, No. 2720. Addition to 566,837 and 588,635. [Class 87 (ii)] In Specification 588,635 a process is described in which a mould comprising parts A<SP>1</SP> A<SP>2</SP>, B, C, Fig. 1, is filled with heaps of differently-coloured moulding powders G, F<SP>1</SP> F<SP>2</SP> (by a method described in Specification 566,837), the combined heap is then pressed into a volume small enough to be contained in the middle mould part A<SP>1</SP>, as shown in Fig. 2, the part A<SP>2</SP> is separated from the remaining mould parts and turned upside down, graining recesses formed by the mould part C are filled with powder, and the material is then pressed a second time. The product of that process is a tablet or preform that is to be moulded later under heat and pressure, for finally setting the moulding powder, into a finished button or other article. In the present process, which results in the production of a finished article, the plunger K<SP>1</SP>, Fig. 2, employed for the preliminary compression of the powder to form a tablet in the part A<SP>2</SP>, has a moulding face corresponding substantially in shape to the moulding face of a second plunger K2, Fig. 6, which is used to press the tablet out of the part A<SP>2</SP> and against the mould top B<SP>2</SP> to mould the final product, for which purpose the parts K2, B<SP>2</SP> are formed with flash lands L<SP>1</SP>, L<SP>2</SP> surrounding the shaped mould parts, so as to co-operate in the manner of an open flash mould and extrude superfluous material through the narrowing gap formed between the flash lands as they close. The (hot) mould is kept closed as shown in Fig. 6, until the material has been cured, and may then be placed between a pair of cooled platens in a power press to improve the surface of the moulded article and facilitate its subsequent removal from the mould. The extrusion shown in Fig. 6 results in the basic material forming the peripheral portion of the preform being forced out, leaving coloured material showing at the edge. A semi-positive type mould (Fig. 7, not shown) may be used, the flash in this case being extruded into a gap in the mould parts. To reduce transference of heat from the platen P, Fig. 8, to the tool plate T that carries the plunger K, the plunger stands proud of the plate and the plate does not contact the platen. The plunger is secured to the plate by means of a spring clip S.