Title: Apparatus and process

Abstract: In the apparatus for preparing heat-shrinkable plastic tubing by radially expanding lengths of plastic tubing to a larger diameter within a rigid cylinder by heating the cylinder externally and pressurizing the interior of the extruded plastic tubing with gas to cause the tubing to radially expand against the interior walls of the rigid cylinder, The improvements which comprise: A. employing in place of the rigid cylinder a heat-resistant flexible sheet looped into a cylindrical shape to form a restraint, B. employing a pair of clamps extending longitudinally along the cylindrical shaped sheet along the portions of the sheet which meet and abut to form the cylinder, positioned such that the ends of said sheet are between the clamps, and C. employing means for heating the tubing comprising a device for injecting a hot gas into the interior of the extruded plastic tubing.

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Inventors: Hartig, Martval John (Wilmington, DE, US)

Application Number: 451119
Filing Date: 1974-03-14
Publication_date: 1976-03-02
Assignee: E. I. Du Pont de Nemours and Company (Wilmington, DE)
Primary Class(es): 425/526 249/173, 264/573, 425/392
Other Classes:
US Patent Ref:

1762440	Jun, 1930	Howe	249/173.
3257689	Jun, 1966	Weyer	425/387.
3296344	Jan, 1967	Timmerman	264/95.
3454257	Jul, 1969	Dupuis	249/173.
3600488	Aug, 1971	Yazawa	425/72.
3611516	Oct, 1971	O'Conner et al.	249/173.
3647340	Mar, 1972	Sakurai et al.	425/326.
3679167	Jul, 1972	Jupiter et al.	249/173.
3752630	Aug, 1973	Takagi et al.	425/392.
3836111	Sep, 1974	Binder	249/173.

Other Refs: 39-433038-16245

, 1964	JA
, 1963	JA

Primary Examiner: Husar, Francis S.
Assistant Examiner: Rowold, Carl
Attorney: