Process for the manufacture of rods of thermoplastic material, having internal capillary ducts, for the preparation of pen nibs incorporating capillary ink ducts

Claim 1

A process for manufacturing a pen nib with capillary ink passages which is capable of providing a fine script without vibration, comprising heating a mass of thermoplastic material to a temperature higher than that at which it fuses, extruding from said mass of thermoplastic material a rod through a die so shaped as to form inside the rod a longitudinal opening of star-shaped cross section characterized by a plurality of substantially parallel sided ducts that communicate with each other at the center of said cross section, said ducts being separated by wedge-shaped segments of said thermoplastic material, said segments being spaced from each other and being alternately long and short and at least two diametrically opposed long segments being even longer than the other long segments, said variations in segment length resulting in the disposition of the inner points of said segments at different distances from the center of said rod, cooling the extruded rod to a temperature lower than at which the thermoplastic material fuses, and mechanically drawing the cooled rod to reduce its outside diameter and also to reduce the width of said channels until said channels have a wedge-like shape tapering toward the central axis of the rod and at least said two segments contact each other.