Tube treating and method
AssigneeThe Dow Chemical Company
InventorDavid H. Dawson
Life of this patent
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Abstract
Synthetic resinous thermoplastic tubing is reduced radially in diameter with minimal increase in length by passing the tube through a plurality of successively smaller dies wherein a minor portion of the die moves relative to a major portion of the die during the reduction step. Plastic tube is obtained which has a tendency to expand radially with a minimal alteration in its length. Such tubing is particularly suitable for lining of pipe.
Claims5
A method for the preparation of a synthetic resinous tube capable of radial expansion and generally without change of length of the tube upon expansion, the steps of the method comprising
- providing a synthetic resinous thermoplastic tube having a diameter greater than a desired diameter,
- introducing a portion of the tube into a plurality of die plates having successively smaller circular openings therein, the tube having a region of decreased diameter generally adjacent the die plate having the smaller opening and a region of major diameter generally adjacent the die plate having the largest port opening,
- moving at least one of the die plates towards the region of major diameter thereby reducing the diameter of a portion of the tube while maintaining the conduit in fixed relation to at least a major portion of the remaining die plates, subsequently, in sequence,
- moving each said plurality of die plates in hereinbefore described manner to provide a synthetic resinous thermoplastic tube having reduced diameter, the foregoing steps being performed at a temperature between the glass temperature of the resinous tube and the softening temperature.
Dependencies are inferred from the claim text.