In U.S. Pat. No. 3,765,216 a basic form of extruding feedstock through a die was disclosed. In U.S. Pat. No. 3,922,898 dated Dec. 2, 1975, there is disclosed a different form of apparatus where, by applying a gripping pressure greater than the yield strength of the feedstock material throughout the length of the passageway, two-sided gripping could be utilized to extrude feedstock. In this patent it was also stated that in order for the extrusion to take place, it was necessary to lubricate the two ungripped sides of the feedstock.
USPTO Backgrounds
USPTO Backgrounds