Patent ID: 6277896
Filing Date: 2001-08-21
Classification: B29C

Abstract:
A method for manufacturing a monolithic plastic object, which object defines a sandwich-like structure with a foam core and closed skin, and wherein the method comprises the steps of:(1) providing an injection moulding device with a plastic plasticizing and injection device and a mould which includes at least two mould parts displaceable relative to each other by displacing means, which mould parts in a closed first extreme position define a mould device and in an open second extreme position release a formed object for removal, wherein the displacing means are adapted to move the mould parts at a chosen speed;(2) providing foaming means for causing foaming in the mould cavity of plastic injected into the mould cavity;(3) providing gas feed means for feeding gas under pressure to the mould cavity to temporarily render the foaming means effectively inactive;(4) energizing the gas feed means;(5) energizing the plasticizing and injection unit in the first extreme position of the mould in order to inject heated plastic into the mould cavity, which plastic is a mixture of two plastics, wherein the first plastic is a non-type A plastic and the second plastic is a type A plastic that constitutes a maximum of 20 percent by mass of the mixture, and wherein the type A plastic is a plastic with high melt strength compatible with the first plastic;(6) ending the energizing of the gas feed means;(7) ending the energizing of the plasticizing and injection unit;(8) energizing the displacing means such that the mould parts move apart in accordance with a chosen velocity progression; and(9) causing the formed object to cool to a chosen temperature, fully opening the mould cavity and removing the cooled and formed object.