Apparatus for blow-moulding hollow bodies

Claim 1

Apparatus for blow-moulding preheated parisons of thermoplastic material comprising, in combination, a mold defining an elongated cavity having a closed end and a mandrel receiving end, an elongated mandrel extending into said mold cavity through said mandrel receiving end, said mandrel having an inner end disposed adjacent the cavity closed end, an outer end adjacent said cavity mandrel receiving end and an exterior surface, a passage longitudinally extending through said mandrel intersecting said inner end, an elongated elastic tubular rubber bellows encompassing said mandrel within said mold cavity having an inner closed end adjacent said mandrel inner end and a sealed end sealed to said mandrel outer end, said bellows having a variable radial wall thickness increasing in thickness from said sealed end toward said bellows'' inner closed end whereby inflation of said bellows by a pressurized medium entering said passage causes said bellows to initially longitudinally extend toward said cavity closed end prior to significant radial bellows expansion occurring, means for mounting an elongated heated parison of thermoplastic material within said mold cavity encompassing said bellows whereby inflation of said bellows initially elongates said parison prior to significant radial expansion thereof within said cavity, and a vent passage defined in said mandrel and positioned so as to be communicable with the interior of a parison placed thereon and with the atmosphere to vent the interior of said parison during expansion thereof by said bellows.