Impact extrusion method, tooling and product

Abstract

A hollow preform impact extruded from a metal billet to produce a progressing wall at a transition wall thickness. An axially forward portion of the progressing wall is ironed by extrusion past an extrusion point to form a sidewall portion of a lesser thickness. Extruding is stopped while some of the billet remains to form the closed bottom end. The preform has a bottom portion, a sidewall portion and a transition wall portion extending between the bottom portion and the sidewall portion. The transition wall portion is thicker than the sidewall portion and can be formed into at least part of the rim of an expansion shaped container. An impact extrusion punch has a central axis, an axially forward, impact surface for impacting metal to be extruded, a transition region for directing material displaced by the impact surface and a rear extrusion point for ironing material extruded past the transition region.

1 . An expandable metal preform for an expansion shaped metal container having a closed bottom, a rim and a sidewall, the preform comprising,
 a closed end; and   a tubular wall extending from the closed end and defining a longitudinal axis of the preform;   the closed end including a bottom forming portion with a bottom wall thickness and the tubular wall including a sidewall forming portion with a sidewall thickness;   the preform further including a rim forming portion intermediate the bottom forming portion and the sidewall forming portion, the rim forming portion including a transition wall adjacent the bottom forming portion and having a transition wall thickness larger than the sidewall thickness.   
     
     
         2 . The preform of  claim 1 , wherein the transition wall thickness differs from the bottom wall thickness. 
     
     
         3 . (canceled) 
     
     
         4 . (canceled) 
     
     
         5 . The preform of  claim 1 , wherein the rim forming portion is part of the tubular wall or part of the closed end. 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . (canceled) 
     
     
         9 . The preform of  claim 1 , wherein the transition wall thickness varies in a circumferential, radial and/or axial direction of the preform, or the transition wall includes circumferentially alternating first and second regions having the transition wall thickness and a reduced wall thickness respectively, the second regions optionally including convex and/or concave deformations for increased rigidity. 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . (canceled) 
     
     
         13 . (canceled) 
     
     
         14 . (canceled) 
     
     
         15 . The preform of  claim 1 , wherein the tubular wall has a spacing from the axis, the rim forming portion is part of the tubular wall and the transition wall has an axial width equal to (a) about 5% to about 80% of the spacing from the axis, (b) about 30% to about 53% of the spacing from the axis, or (c) about 36% to about 47% of the spacing from the axis. 
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . The preform of  claim 15 , wherein (a) the spacing from the axis is about 18 mm and the axial width is about 36% of the spacing from the axis, or (b) the spacing from the axis is about 19 mm and the axial width is about 47% of the spacing from the axis. 
     
     
         19 . (canceled) 
     
     
         20 . (canceled) 
     
     
         21 . The preform of  claim 1 , wherein the rim forming portion is part of the closed end and the transition wall has an axial width equal to about 36% to about 47% of a spacing of the tubular wall from the central axis. 
     
     
         22 . (canceled) 
     
     
         23 . (canceled) 
     
     
         24 . (canceled) 
     
     
         25 . (canceled) 
     
     
         26 . (canceled) 
     
     
         27 . An impact extrusion punch for insertion into an impact extrusion die, the punch comprising
 a body with a central axis;   an axially forward, impacting end;   an axially rearward, driven end for attachment to a press;   an impact surface on the impacting end for impacting metal to be extruded;   a transition region rearward of the impacting end for directing material displaced by the impact surface; and   a rear extrusion point for ironing material directed past the transition region, the rear extrusion point being adjacent a rearward end of the transition region.   
     
     
         28 . The impact extrusion punch of  claim 27 , wherein the transition region includes a peripheral shoulder of the impact surface and a land portion extending rearward from the peripheral shoulder. 
     
     
         29 . The impact extrusion punch of  claim 28 , wherein a rearward end of the land portion is positioned at a different spacing from the axis than a forward end of the land portion at the peripheral shoulder, and either the rearward end is positioned further from the axis than the forward end or the rearward end is positioned closer to the axis than the forward end. 
     
     
         30 . (canceled) 
     
     
         31 . (canceled) 
     
     
         32 . The impact extrusion punch of  claim 29 , wherein the impact surface is generally circular and the land portion is frusto-conical. 
     
     
         33 . The impact extrusion punch of  claim 28 , wherein the land portion has an axial length equal to (a) about 5% to about 80% of a spacing of the land portion from the central axis, (b) about 30% to about 53% of a spacing of the land portion from the central axis, or (c) about 36% to about 47% of a spacing of the land portion from the central axis. 
     
     
         34 . (canceled) 
     
     
         35 . (canceled) 
     
     
         36 . The impact extrusion punch of  claim 27 , further comprising a thinning extrusion point for further thinning of ironed sidewall material extruded past the rear extrusion point. 
     
     
         37 . The impact extrusion punch of  claim 27 , wherein the rear extrusion point includes an extrusion shoulder for ironing the material directed past the transition portion, the extrusion shoulder extending outward from the rearward end of the transition portion to a larger spacing from the central axis than the rearward end. 
     
     
         38 . (canceled) 
     
     
         39 . A method of impact extruding a hollow preform having a longitudinal axis,
 a closed bottom end and an axially extending tubular wall, the method comprising the steps of   impacting a metal billet for plasticizing the material of the billet and displacing and directing the plasticized material for forming an axially progressing tubular transition wall at a transition wall thickness;   ironing an axially forward portion of the progressing transition wall on a radially inner surface by forcing the forward portion past an extrusion point to form a sidewall having a sidewall thickness smaller than the transition wall thickness; and   stopping the impacting while some of the billet remains, to form the closed bottom end.   
     
     
         40 . The method of  claim 39 , wherein the impacting is stopped when the billet is reduced to a bottom wall thickness that differs from the transition wall thickness. 
     
     
         41 . (canceled) 
     
     
         42 . (canceled) 
     
     
         43 . The method of  claim 39 , wherein the ironing of the first sidewall portion is commenced after an axial progression of the progressing wall of about 5 mm to about 15 mm, or about 5% to about 80% of a spacing of the progressing wall from the axis. 
     
     
         44 . The method of  claim 43 , wherein the axial progression of the progressing wall is (a) about 6 mm to about 10 mm, or about 30% to about 53% of the spacing from the axis; or (b) about 7 mm to about 9 mm, or about 36% to about 47% of the spacing from the axis. 
     
     
         45 . (canceled) 
     
     
         46 . The method of  claim 44 , wherein the spacing of the progressing wall from the axis is about 18 mm and the axial progression of the progressing wall is about 7 mm, or about 36% of the spacing from the axis. 
     
     
         47 . The method of  claim 44 , wherein the spacing of the progressing wall from the axis is about 19 mm and the axial progression of the progressing wall is about 9 mm, or about 47% of the spacing from the axis.