US Patent 7276271 Polymer fiber tubular structure having kinking resistance

An apparatus for forming a tubular structure from a liquefied polymer, the apparatus comprising: (a) a dispenser for dispensing the liquefied polymer; (b) a precipitation electrode being at a first potential relative to the dispenser, the precipitation electrode being designed and constructed for generating a polymeric shell thereupon; and (c) a mechanism for increasing a local density of the polymeric shell in a plurality of predetermined sub-regions of the polymeric shell, thereby to provide a tubular structure having an alternating density in a longitudinal direction.