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US 5,248,366 AGranted
Method for helical cutting of a flexible tubular sheet of polymeric material
OwnerOle-Bendt Rasmusseninventor
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OwnerOle-Bendt Rasmusseninventor
Estimating the term…
Flexible tubular film is helically cut into a flat strip by feeding the tubular film in flattened form from a supply source to a film feeding means advancing the flat film tube at a predetermined velocity to a tube expansion zone in which the flat tube is expanded into a generally cylindrical tube and passed axially over a hollow mandrel slightly less in external diameter than the diameter of the expanded tube to be cut helically while on the mandrel into a flat strop that is removed at an angle to the mandrel axis. The tube is expanded in the zone by inflation with air fed through the mandrel in a direction countercurrent to the direction of tube movement and under a pressure sufficient to render the expanded tube stiff as it slides over the mandrel and resistant to deformation while being helically cut. The advance and expansion of the flat tube in the expansion zone is positively controlled by moving surfaces contacting the film, which surfaces define a diverging expansion zone and are driven at a velocity substantially at least as great as the predetermined velocity of advance of the flat film tube to the expansion zone.
In a method of helically cutting a flexible tubular film of substantially predetermined diameter into a flat strip in which said tubular film is supplied in flattened form from a supply source to a first position, advanced at a substantially predetermined velocity from said first position to an expansion zone where it is expanded from said flat form into generally cylindrical tubular form, passed over a hollow cylindrical mandrel disposed within said cylindrical tubular form axially of said mandrel, and while on said mandrel helically cut into a flat strip, and said flat strip is removed from the mandrel at an angle to the mandrel axis, the improvement wherein said mandrel is hollow with an external diameter sightly less than the diameter of the expanded tubular film, and comprising the steps of expanding said flattened tubular form in said expansion zone by inflation with air continuously supplied through said hollow mandrel in the direction of said first position under a pressure such as to spread said flattened tubular film into a stiff cylindrical tube that makes a sliding fit with said mandrel and resists deformation during the helical cutting, and positively controlling the advance and expansion of the flattened tube in said expansion zone by means of moving surfaces defining a diverging expansion zone while driving said moving surfaces at a velocity at least substantially as great as the predetermined velocity of advance of said film from said first position to said expansion zone.
In a method of helically cutting a flexible tubular film into a flat strip in which said tubular film is supplied from a supply source to a first position in a flattened tubular form, advanced from said first position to an expansion zone where it is expanded from said flattened form into generally cylindrical tubular form, passed over an elongated mandrel axially thereof, and while on said mandrel helically cut into a flat strip, and said flat strip is removed from the mandrel, the improvement in which the expanded tubular film is cut in a cutting zone that has a fixed location relative to the mandrel axis, and wherein the film supply source is in the form of a reel of said film upstream of said first position, said reel being rotatable about its longitudinal axis with said axis being fixed and generally coaxial with the axis of said mandrel, and comprising the steps of withdrawing the film from the reel periphery and then advancing the film from said reel to said first position substantially axially of the reel.
Dependencies are inferred from the claim text.