Machines for extruding tubes

Claim 1

A MACHINE FOR THE CONTINUOUS PRODUCTION OF AN IMPERMEABLE TUBE COMPRISING A PERMEABLE REINFORCING SLEEVE HAVING AN IMPERMEABLE INTERNAL COATING OF THERMOPLASTIC MATERIAL, SAID MACHINE COMPRISING AN EXTRUSION HEAD HAVING A PASSAGE EXTENDING THROUGH IT AND TERMINATING IN AN EXTRUSION ORIFICE, A MANDREL WITHIN SAID PASSAGE, SAID MANDREL BEING ADAPTED TO SUPPORT THE REINFORCING SLEEVE AND BEING PROVIDED ALONG PART OF ITS LENGTH INSIDE THE PASSAGE WITH INTERNAL PASSAGES COMMUNICATING WITH SAID EXTRUSION ORIFICE AND TERMINATING AT ITS FORWARD END IN A PORTION OF SMALLER CROSS-SECTION, CLAMPING MEANS INSIDE THE HEAD AND EXTERNAL TO THE MANDREL WHICH COACT WITH SAID MANDREL AT SPACED POINTS TO LOCATE IT IN POSITION, MECHANISM FOR MOVING SAID CLAMPING MEANS BEING EFFECTIVE ALTERNATELY IN RELATION TO THE MANDREL TO HOLD THE SLEEVE AND MANDREL ALTERNATELY AND INTERMITTENTLY AT SAID SPACED POINTS WITHIN SAID EXTRUSION HEAD, MEANS FOR DRAWING THE SLEEVE CONTINUOUSLY UNDER TENSION OVER THE MANDREL AND THROUGH THE PASSAGE AND THE EXTRUSION ORIFICE, AND MEANS FOR INJECTING THERMOPLASTIC COATING MATERIAL UNDER PRESSURE INTO THE EXTRUSION HEAD EXTERIORLY OF SAID SLEEVE, WHEREBY SOME OF SAID COATING MATERIAL IS FORCED THROUGH THE SLEEVE AND INTO THE INTERNAL PASSAGES OF THE MANDREL AND IS EXTRUDED THROUGH THE ORIFICE AS AN INTERNAL COATING ON THE SLEEVE AS THE LATTER IS DRAWN THROUGH THE HEAD.