Patent GB-1161328-A (GB)
Title: Apparatus for Producing Articles such as Hollow Containers
IPC: B29C41/36
Filed: 1966-10-21
Abstract: 1,161,328. Moulding plastic substances. CONTINENTAL CAN CO. Inc. 21 Oct., 1966 [21 Oct., 1965], No. 47361/66. Heading B5A. A container is moulded by introducing an electrostatically charged powdered moulding material into a mould 12 having an electrostatic charge of opposite polarity whereby the powder is uniformly distributed over the mould surface from a dispensing means rotating relative said surface, the temperature of which powder is controlled to fuse and then rigidify the material, after which the container is removed from the mould. Examples of material used are polyethylene, polystyrene, polypropylene and polyurethane. In one embodiment the charged powder is fed to a U-shaped channel 18 which is then enclosed by the two parts of a split mould 12; the channel and mould are connected to opposite poles of a high potential source 60 and the channel is axially rotated by a pulley drive 26 so that the powder is thrown from the channel and through a screen 30. A shaft 32 with adjustable blades 33 is rotated within the channel in an opposite direction by a pulley drive 38, and is also reciprocated axially by a crank drive 56, 58. The channel loading source 70<SP>1</SP> has separate compartments for different materials. The mould may be cooled by a fluid coolant sprayed into it from an axially located conduit. In order to direct the particles to desired areas, electrodes may be placed around the mould, which may be of glass, and connected to potentials of different magnitude. A number of adjustable corona wires may extend from the channel. If, for example, a two colour container is desired, some electrodes could be charged to attract the first colour of moulding powder and the remaining electrodes charged to repel it; with the introduction of the second colour the potentials on the electrodes would be reversed. In the embodiment of Fig. 10 the powder is fed to the rotating surface of a male mould 114 located within a stationary housing 124 supplied with the charged powder from a hopper 128. Opposed potential is applied to the mould and hopper. The hopper may include a rotary bladed powder dispenser whereby the powder is fed through a slot 130 and on to the mould; the slot may include corona pins for electrostatically charging the powder. The male mould includes means for retracting it from the housing, passages for the flow of heating and cooling fluid and ejector means for removing the moulded article. Such ejector means may include a plate 154 movable axially by mechanical means or by air pressure. Foamed containers may be produced by mixing a foaming agent with the powder and then heating the coated mould 114 in a steam chamber. The latter may constitute a female mould determining the outer surface of the container. To produce a double walled container, the inner wall is formed on a male mould, and the outer wall is separately formed in a female mould; the moulds are then brought together and the walls united by heating or cooling. By such means one wall may be of a foamed plastic, and one wall may be spaced from the other. The moulded container may be removed from the female mould by introducing thereinto an oppositely charged male mould. In a further embodiment, fibres are uniformly deposited on a hot tacky plastic layer on a mould surface; since the fibres stand at right angles to the mould surface due to the electrostatic effect, an oppositely charged electrode is swept over the fibres causing them to be flattened on to the plastic layer in a desired direction. A further plastic layer may then be applied followed by a further deposite of fibres which are similarly treated. In the case of a split mould 260, Fig. 26, after the plastic coating 262 and fibres have been applied, a rotatable probe 266 with adjustable electrostatically charged electrodes 276 is advanced through the mould causing the fibres to be flat.