Process and apparatus for blow moulding a hollow body from thermoplastic material

摘要

After enclosing a preform in a blow mould, a rod is introduced through the blowing mandrel. Subsequently, the stretching rod is displaced mechanically by means of a roller guide on a curved track and the preform is thereby prestretched axially by a certain partial length. In the process, a wall section of the preform, which is preferably shaped during blow moulding into a tapering neck section, is drawn out to a thinner wall thickness. After the prestretching, the preform is further stretched by means of the blowing air, the stretching rod being driven in such a way that it constantly guides the bottom of the preform centrally, and at the same time is opened out to form the finished hollow body.