US 3,941,546 AGranted

Apparatus and process

AssigneeE. I. Du Pont de Nemours and Company

InventorMartval John Hartig

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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.

Claims3

Dependent claims

An apparatus for preparing heat-shrinkable plastic tubing by radially expanding lengths of plastic tubing to a larger diameter within a cylinder which comprises

a. a heat-resistant flexible sheet looped into cylindrical shape to form a restraint, the loop being formed by looping one end of said sheet back upon the opposite end so that a portion of the surface along one of the ends abuts a portion of the same surface of the sheet along the other end;
b. a pair of clamps extending longitudinally along the portions of the cylindrically shaped sheet which abut to form the cylinder, positioned such that the ends of the sheet which abut are between the clamps so that at least one looped end of the sheet can be moved between the clamps to a distance from said clamps on the side of the clamps opposite the cylindrical shape, and
c. means located at each end of the cylindrically shaped sheet to provide (1) a pressure-tight fitting between the inside and outside of said plastic tubing, and (2) a gas conduit through the fitting.

Dependencies are inferred from the claim text.