Method and device for manufacturing a double-walled, thermoplastic tube with a connecting sleeve

A method for manufacturing a double-walled, thermoplastic tube, the method comprising:

• a) extruding a first tube into a mould tunnel comprising at least one row of moulds guided on a path,
• b) forming the first tube into a corrugated shape in at least one first section and expanded into a connecting sleeve in at least one second section,
• c) extruding a second tube into the first tube and pressing the second tube against the corrugation troughs of the first tube,
• d) applying a first pressure that is above atmospheric pressure to the space between the first and second tubes while the first tube is given a corrugated shape and the second tube is extruded into the first tube,
• e) switching the first pressure to a second pressure with a compressed gas controller to apply the second pressure to the space between the first and second tubes at a specified time proximate to expansion of the first tube into a connecting sleeve, where the second pressure is less than or equal to the first pressure and above atmospheric pressure,
• f) applying a third pressure above atmospheric pressure to an inside of the second tube during extrusion of the second tube into the first tube during formation of the connecting sleeve to press the second tube against the first tube, and
• g) applying the first pressure to the space between the first and second tubes after application of the second pressure.

A method for manufacturing a double-walled, thermoplastic tube, the method comprising:

• extruding a first tube into a mould tunnel having at least one corrugated section and at least one connecting sleeve section,
• extruding a second tube into the first tube,
• supplying a gas having a first pressure that is above atmospheric pressure through a gas duct to the space between the first and second tubes while the first tube is being extruded into the at least one corrugated section and the second tube is extruded into the first tube,
• switching the pressure of the gas being supplied from the gas duct to the space between the first and second tubes from the first pressure to a second pressure at a time proximate to expansion of the first tube into a connecting sleeve with a compressed gas controller, where the second pressure is less than or equal to the first pressure and above atmospheric pressure, and
• switching the pressure of the gas being supplied from the gas duct to the space between the first and second tubes to the first pressure with the compressed gas controller after supplying the gas at the second pressure.