GB820277A - Improvements in or relating to the manufacture of gramophone records - Google Patents

Abstract

820,277. Moulding gramophone records. PHILIPS ELECTRICAL INDUSTRIES Ltd. Jan. 6, 1956 [Jan. 11, 1955], No. 547/56. Class 87(2). [Also in Groups VIII, XI and XXXVIII] Gramophone records are made from a composite sheet material comprising a core layer of electrically-conducting material and surface layers of resinous material, an electric current being passed through the core layer to heat it and soften the resinous surface layers to enable the latter to take the impression of matrices. Fig. 4 shows one example of such material, consisting of a central layer 27 of paper fibre faced with two aluminium foils 28, 29, and two outermost layers 30, 31 of resinous material, the foils being bare at the edges. Such material is fed in the form of a strip 5, Figs. 1 and 2, to a press comprising stamps 1, 2 to which are secured matrices 3, 4. The strip rests on rollers 8, 9 and the bare edges of the strip are clamped between terminals 10, 12 and 11, 13 by which electric current is passed through the core to heat the strip. The strip being hot, the terminal members 10, 11 are raised to cut off the current and the matrices are moved towards each other to press the strip, a knife 14 cutting a central hole and knives 18, 19 cutting a circular disc from the strip. Such a cut-out disc is shown at 26, Fig. 2. It is not completely cut out, being connected to the strip by portions 22 ... 25. The next part of the strip to be operated upon is shown at 27. Cooling channels 16, 17 in the stamps control the temperature. Another form of the composite material comprises a core layer of a mixture of paper fibres and graphite with polyvinyl chloride-acetate copolymer deposited in situ on the core layer from aqueous suspension. A third form comprises a central non-conductive layer, e.g. of fibre or resin, covered with metal foil on both sides, e. g. as is shown in part in Fig. 5, in which the core layer consists of a non-conducting central calendered fibrous material covered on each side with a tape of metal foil wound in the form of a spiral. In using such a material the centre of a spiral constitutes one contact for the electric current and the end 32 of the spiral is the other contact, the knife 14 acting as a current supply to the centre. Other forms of core layers are made by mixing natural or synthetic resin or cardboard material with carbon or metal powder. The resinous covering layers may be of shellac or vinyl resin or phenolaldehyde or other thermosetting resin, and may be affixed to the core by adhesive or deposited from solution or dispersion.