Tubular workpieces of oriented polymers such as polyethylene polyester and PVC are formed by drawing a workpiece over an expanding former in the absence of any force perpendicular to the axis of the workpiece. The processes do not require the use of any liquid lubricant. They enable greater degrees of expansion and hence orientation in the direction perpendicular to the axis to be achieved and result in products of improved appearance and strength.
申请公布号
US5910346(A)
申请公布日期
1999.06.08
申请号
US19950479518
申请日期
1995.06.07
申请人
BTG INTERNATIONAL LIMITED
发明人
WARD, IAN MACMILLAN;CRAGGS, GORDON;SELWOOD, ALAN;TARAIYA, AJAY KUMAR