DEVICE FOR INPUTING A GAS INTO THE CAVITY OF AN INJECTION MOLD FOR PRODUCING HOLLOW PLASTIC BODIES

摘要

In the case of apparatuses of this type, there is the disadvantage that the fitting of the needle-shaped injection nozzle, by which the gas is introduced into the mould cavity, is problematical, since the previously injected polymer melt can very quickly solidify like a skin in the outer boundary region due to cooling, so that a reliable penetration of the injection nozzle or piercing of the skin already formed is not ensured. Furthermore, a lifting-off of the polymer melt in the piercing region of the gas injection nozzle can occur, with loss of gas. It is the aim of the invention to avoid these disadvantages and to achieve a reliable insertion of the needle without damage and without the risk of boundary zones of already fed-in polymer melt lifting off, as a result of which accurate metering of the quantity of gas fed in is achieved in the mass production of hollow plastic bodies. This object is achieved by the end (17) of the gas injection nozzle (8) which faces the mould cavity (3) protruding freely until approximately in the centre of the part of the mould cavity (3) assigned to the gas injection nozzle. The invention is used in particular in the mass production of hollow plastic bodies which consist with preference of partly crystalline polymers, for example polyamide. …IMAGE…