Apparatus for making high speed corrugated plastic tubing

A high speed corrugator for producing corrugated thermoplastic tubing, comprising:

• a pair of complementary upper and lower mold assemblies each comprising an endless chain of articulately interconnected mold blocks and means for guiding the mold blocks along an endless track having a forward run and a return run, each mold block being complementary to a respective mold block of the other assembly, said mold blocks cooperating in pairs along said forward run to form an axially extending tunnel defining a tubular mold having a corrugated wall,
• each mold assembly further comprising an air distributing duct extending along the return run of the endless track and positioned to distribute cooling air to the exposed interior faces of the mold blocks therealong,
• blower means connected to said air distributor ducts for supplying cooling air thereto,
• means associated with said assemblies for driving the endless chains in synchronism for progressively moving the mold blocks along said endless tracks,
• an extrusion head adapted to be fitted to the nozzle of an extrusion machine for forming a tube of thermoplastic material therefrom,
• means positioning the mold assemblies so as to locate the extrusion head at the entrance to said tunnel coaxially therewith,
• a tubular member connected to and extending axially from the extrusion head along said tunnel,
• first baffle means mounted on the tubular member and defining with the extrusion head a first air space,
• second baffle means mounted on the tubular member and spaced axially from the first baffle means to define therewith a second air space,
• said extrusion head including first air duct means for introducing pressurized air to the first air space for expanding the extruded tube of thermoplastic material to conform to the wall of the tubular mold,
• and said tubular member including second air duct means separate of first air duct means for introducing cooling air to the second air space for cooling the molded thermoplastic material within said tubular mold.

An extrusion head for use in combination with a corrugator for the continuous production of corrugated thermoplastic tubing, the corrugator providing a tubular mould into which a tube of thermoplastic material is extruded and expanded by blow moulding to conform to the mould, the extrusion head being adapted to be fitted to the nozzle of an extrusion machine and comprising:

• a tubular body providing an annular passage for the extrusion of said material and terminating in an annular orifice,
• a tubular member mounted within the tubular body and extending axially therefrom,
• a first baffle member mounted on the tubular member and spaced axially from said orifice,
• a second baffle member mounted on the tubular member and spaced axially from the first baffle member,
• the tubular body providing a first air duct terminating at an opening between said orifice and the first baffle member,
• the tubular member defining a second air duct terminating at a plurality of openings distributed axially along the tubular member at positions between said first and second baffle members,
• the extrusion head further including an adaptor block providing a first air inlet communicating with the first air duct for introducing pressurized air thereto, and a second air inlet communicating with the second air duct for introducing cooling air thereto.