Method and apparatus for helical cutting of a tubular film
OwnerOle-Bendt Rasmusseninventor
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Abstract
A method of forming a film (1) of molten polymer material, by extruding said material in a direction (2) out of a narrow exit slot (3), which is an integral part of a wider die chamber (4) of which the major dimension of extension is parallel with the major dimension of the exit slot (3), characterized in that the molten polymer material is formed into one or more flows generally parallel with said major dimension of the exit slot (3), each said flow being pumped in a re-circulating arrangement from the chamber inlet (7) to the outlet (8) through conduits connecting the inlet to the outlet, while fresh molten polymer material is administered from a reservoir into each re-circulating flow.
Claims21
A method of forming a flat film by mono-extrusion of a molten thermoplastic polymer material, by feeding the material into at least one inlet section of an elongated die-chamber heated to a temperature above a melting range of the polymer material and extruding the molten polymer material out of a narrow exit slot, which is parallel with a longitudinal direction of the die-chamber, and making a major part of the polymer material contents of the elongated die-chamber flow generally parallel with a longitudinal die-chamber direction and out of at least one outlet section of the die-chamber, from where the flow is recirculated back into the at least one inlet section of the elongated die-chamber.
A method of forming a mono-extrusion film comprising:
- feeding a polymer material into at least one inlet of an elongated die-chamber heated to a temperature above a melting range of the polymer material further including at least one outlet and a narrow exit slot,
- forming at least one flow of the molten polymer material between the at least one inlet and the at least one outlet, where the at least one flow has a flow direction parallel with a longitudinal dimension of the die-chamber and generally perpendicular to an extrusion direction through the exit slot,
- extruding a portion of the molten polymer material through the exit slot in the extrusion direction to form the mono-extrusion film, and
- re-circulating the at least one flow back to the at least one inlet producing at least one recirculating flow,
- where a throughput of the at least one re-circulating flow exceeds a throughput of the extruded film.
Dependencies are inferred from the claim text.