Process for cold forming a metal tube with an inwardly thickened end

Claim 1

A process for extruding a tubular metal part having an inwardly flared end portion, in a press, having a support base and a pressure ram movable towards said base, comprising: positioning a relatively short tubular blank within a die mounted upon the base in alignment with the ram, the die having an open inlet end with a blank receiving portion and an outlet end having an inwardly extending annular shoulder whose inner cross-sectional dimension is smaller than that of the blank receiving portion to form an extrusion throat, and with the die being open at the outlet end for passing the extruded blank therethrough; ram pushing the blank partway through the die shoulder for thereby extruding a portion of the blank therethrough to form a substantially uniform, relatively thin wall tubular barrel portion on the blank, with the end portion of the blank remaining in the die blank receiving portion thereby forming an outwardly flared, that is, thicker outwardly extending wall portion on the blank end; next, inserting a second, identical blank into the die blank receiving portion in end to end contact with the first mentioned blank; then ram pushing the second blank towards the die shoulder, thereby forcing the said end portion of the first mentioned blank completely through the die shoulder and out of the die outlet opening, to simultaneously force the thicker wall portion thereof to move radially inwardly, that is, causing the thicker wall portion to reverse and extend inwardly relative to the said barrel portion, so that the now finished extruded first blank is formed as an elongated tube of uniform external cross-section and with its inner cross-sectional shape having a portion which is of smaller cross-sectional size at an end of the tube, relative to the inner cross-sectional size of the remaining portion of the tube; and then continuing the ram pushing of said second blank to repeat the steps of pushing the blank partway through the die shoulder and then repeating the cycles of inserting a new blank and ram pressing for thereby continually extruding such tubular parts.