METHOD AND APPARATUS FOR PLASTICALLY FORMING HELICAL INTERNAL GEARS AND HELICAL GEARS

摘要

The invention concerns the extrusion of helical internal gears and helical gears by pushing materials (5) processed to any type of blank into a die unit (2,3) successively by means of a punch (17), i.e., by passing the materials (5) once through the die unit (2,3). This die unit (2,3) comprises an outer contour restraining container (2) into which metal materials (5) each having a central bore are to be inserted, a die (3) placed contiguously below the container, these container (2) and die (3) being arranged to be circumferentially rotatable relative to each other, and upper and lower mandrels (13,16) disposed inside the container (2) and the die (3) in alignment with their axes, respectively, and interconnected for being circumferentially rotatable relative to each other. The metal materials (5) being successively pushed into gaps between the upper mandrel (13) and the container (2) and between the lower mandrel (16) and the die (3) by means of a punch (17) to mold helical internal gears (21). The outer peripheral surface of the lower mandrel (16) has formed therein an approach area (161a) in which the peripheral surface is gradually varied into a teeth shape of helical internal gear and a product configuration area (161b) continuously extended from the approach area and having a complete teeth shape of the helical internal gear (21).