Metal Box Corporation

David A Dick

Glyn Staines

Leonard W Reed

Robert M Barr

James William Nicholas

Melvin Edward Robinson

Peter E Butcher

Rickworth Folland

Desmond P Smith

A process of forming biaxially oriented tubular articles by repeatedly performing a cycle of operations which includes engaging a thermoplastic tube by a first clamping member over a first region at a trailing end of the tube and engaging the tube by a second clamping mechanism over a second region at a spacing from the first region so as to define between the clamping mechanisms a portion of the tube to be longitudinally stretched and radially expanded; moving the clamping mechanisms apart to stretch the tube portion therebetween longitudinally; admitting pressure fluid into the tube portion to expand it radially and form a biaxially oriented bubble adjacent the leading end of the tube, and severing a substantial part, but not all, of the bubble from the tube to form the tube with a radially outwardly flared end as the leading end of the tube for the succeeding cycle of operations.

Process of forming a biaxially oriented thermoplastic tube including the

A food container comprising an open-ended cylindrical body which is made of a crystallizable polyethylene terephthalate material, and end closures at each end of the body forming with the body a closed container, the body material being biaxially oriented and the container body having been head-set, while restrained against radial or axial shrinkage, at a temperature between about 180.degree. C. and about 240.degree. C., whereby the container is able to withstand hot-filling, pasteurization or sterilization temperatures of up to about 120.degree. C. without undergoing shrinkage of its linear dimensions by more than 3%.

Dimensionally stable thermoplastic tubular articles

Methods for forming tubular closed-ended articles of thermoformable

For heat-setting tubular articles (such as can bodies) of an at least partly biaxially oriented crystallizable polymer, preferably a saturated linear polyester such as polyethylene terephthalate, e.g. for thermally processable food containers, a tube of the polymer is fitted over a mandrel and clamped at its ends to the mandrel at a temperature below the glass transition temperature of the polymer. The tube is then heated, e.g. by inserting a heater 28 into the interior of the mandrel, above the temperature to which it is to be heat-set (at least 60.degree. C. above for PET) whereupon it shrinks into contact with the mandrel but is restrained from axial or further radial shrinkage. The tube and mandrel are cooled to below the heat-set temperature and the tube may then be cut into can body sections by knives engaging in circumferential grooves. Contact between the tube and mandrel is released, e.g. by forcing compressed air out through small holes in the mandrel surface to allow the tube and mandrel to be separated. Tubular bodies with one closed end can be heat-set on a mandrel with a correspondingly shaped end.

Method and apparatus for making dimensionally stable thermoplastic

A method and apparatus are described for flanging a tubular article of a crystallizable thermoplastic polymer, particularly of a saturated linear polyester material such as polyethylene terephthalate, which has been heat-set to an elevated temperature, e.g. for producing bodies for processable food and beverage containers. The open end of the tubular body is applied to a flanging die and heated to a flanging temperature above the glass transition temperature but below the heat-set temperature of the polymer. The tubular body and the die are forced together so that the softened end of the tubular article is forced to move outwards until it abuts against a stop ring to form the flange. The residual shrinkage in the polymer material helps it to take up the precise contours of the die and to form a well-defined flange. The flanged end is then cooled, preferably to a temperature at least 20.degree. C. below the flanging temperature, before releasing the tubular body 10 from the die.

Methods and apparatus for flanging tubular polymer articles

Biaxially oriented tubular articles which are destined to provide bodies for processable food containers are made from an elongate tube of thermoplastics material as it emerges from an extruder. The manufacturing process comprises repeatedly performing a cycle of operations each including the following steps:

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Wantage, United Kingdom

David A Dick