Method and apparatus for forming a can end with controlled thinning of formed portions of the can end

Abstract

A can end blank is initially cupped and a central portion of the cup is rolled up with an annular portion of the cup being free formed without substantial contact with any tooling except to prevent overextension of the free formed material and to define a final geometry of the free formed material as the forming press reaches a bottom of its forming stroke. The free forming may be accomplished by controlling the motion of a crown ring using a delay cam assembly so that the motion of the crown ring is independent of the motion of the rest of the tooling which is controlled by the motion of the ram or punch assembly of the forming press.

1 . A method for forming a can end with controlled thinning of formed portions of the can end, the method comprising:
 cutting a can end blank from a sheet of material in a forming press;   clamping a portion of the can end blank between a first tool and a second tool in a generally horizontal orientation;   forming a cup in the can end blank with a third tool and a fourth tool to form a cupped can end blank;   clamping a portion of the cupped can end blank between a fifth tool and a sixth tool;   controlling the sixth tool independently of the first through fifth tools of the forming press to move in a generally vertical direction substantially in synchronism with the fifth tool as the forming press operates to form the can end;   contacting a central portion of an outer surface of the cup with a seventh tool to hold the central portion of the cup stationary as the clamped portion of the cupped can end blank is moved downward so that the material between the central portion of the cup and the clamped portion of the cupped can end blank is free formed without substantial contact with any of the first through seventh tools; and   providing an eighth tool associated with the seventh tool to prevent overextension of free formed material, wherein the fourth tool retracts so that the third tool extends beyond the fourth tool to define a final geometry of free formed material as the forming press reaches a bottom of a forming stroke.   
     
     
         2 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 1  wherein controlling the sixth tool comprises:
 configuring a delay cam; and 
 coupling the delay cam to the sixth tool so that the delay cam controls movement of the sixth tool independently of the first through fifth tools of the forming press. 
 
     
     
         3 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 2  wherein configuring a delay cam comprises:
 forming an up-dwell cam portion that maintains the sixth tool in a raised position within the forming press; 
 forming a first cam operating portion that moves the sixth tool from the raised position within the forming press to a lowered position within the forming press; 
 forming a down-dwell cam portion that maintains the sixth tool in the lowered position within the forming press; and 
 forming a second cam operating portion that moves the sixth tool from the lowered position within the forming press to the raised position within the forming press. 
 
     
     
         4 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 1  wherein providing an eighth tool associated with the seventh tool to prevent overextension of the free formed material comprises securing the eighth tool to the seventh tool so that free formed material contacts the eighth tool if at all at the bottom of the forming stroke of the forming press. 
     
     
         5 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 4  wherein securing the eighth tool to the seventh tool is such that free formed material contacts the eighth tool if at all during about a final 0.002 to 0.004 inch of the forming stroke of the forming press. 
     
     
         6 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 4  wherein the eighth tool is adjustably secured to the seventh tool. 
     
     
         7 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 1  wherein the third tool, the seventh tool and the eighth tool define the final geometry of the free formed portion of the cupped can end blank at the bottom of the forming stroke of the forming press. 
     
     
         8 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 1  further comprising positioning the fourth tool within the forming press in accordance with material required to be free formed within the forming press. 
     
     
         9 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 8  wherein positioning the fourth tool within the forming press comprises spacing the fourth tool relative to a piston of the forming press. 
     
     
         10 . A method for forming a can end with controlled thinning of formed portions of the can end as claimed in  claim 9  wherein spacing the fourth tool relative to a piston of the forming press comprises selecting a spacer that extends between the fourth tool and the piston of the forming press. 
     
     
         11 . A method for free forming a portion of a can end with controlled thinning of formed portions of the can end, the method comprising:
 providing a forming press having a fixed base and an upper punch assembly that is stroked relative to the fixed base;   moving the upper punch assembly of the forming press from a top stroke position toward a bottom stroke position; and   controlling a crown ring supported for movement in the fixed base of the forming press so that movement of the crown ring is independent of the stroke of the upper punch assembly of the forming press.   
     
     
         12 . A method for free forming a portion of a can end with controlled thinning of formed portions of the can end as claimed in  claim 11  wherein controlling a crown ring comprises:
 configuring a delay cam; and 
 coupling the delay cam to the crown ring so that the delay cam controls movement of the crown ring independently of the stroke of the upper punch assembly of the forming press. 
 
     
     
         13 . A method for free forming a portion of a can end with controlled thinning of formed portions of the can end as claimed in  claim 12  wherein configuring a delay cam comprises:
 forming an up-dwell cam portion that maintains the crown ring in a raised position within the fixed base of the forming press; 
 forming a first cam operating portion that moves the crown ring from the raised position within the fixed base of the forming press to a lowered position within the fixed base of the forming press; 
 forming a down-dwell cam portion that maintains the crown ring in the lowered position within the fixed base of the forming press; and 
 forming a second cam operating portion that moves the crown ring from the lowered position within the fixed base of the forming press to the raised position within the fixed base of the forming press. 
 
     
     
         14 . A method for free forming a portion of a can end with controlled thinning of formed portions of the can end as claimed in  claim 13  further comprising positioning a redraw stop in the fixed base of the forming press to prevent overextension of free formed material. 
     
     
         15 . An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly movable relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled, the apparatus comprising:
 a draw punch carried by the upper punch assembly of the forming press;   a draw pad supported for movement in the fixed base of the forming press, the draw punch and draw pad being aligned with one another for clamping a can end blank;   a pre-panel punch carried by a piston of the upper punch assembly of the forming press;   a die center carried by the upper punch assembly of the forming press, the die center surrounding the pre-panel punch which is movable relative to the die center, the pre-panel punch and die center engaging the can end blank as the can end blank is clamped between the draw punch and draw pad to commence formation of a cup in the can end blank to form a cupped can end blank;   a crown ring supported for movement in the fixed base of the forming press and having an upper surface defining a contour for a crown of the can end, movement of the crown ring being controllable independent of a forming stroke of the upper punch assembly;   a knockout carried by the upper punch assembly, the knockout being aligned with the crown ring for engaging a portion of the cupped can end blank as the cupped can end blank is drawn from the draw punch and draw pad so that the cupped can end blank is clamped between the knockout and the crown ring with an outer surface of the cup extending toward the fixed base; and   a panel punch mounted to the fixed base, the panel punch being positioned and sized so that it contacts a central portion of the outer surface of the cup of the cupped can end blank to hold the central portion of the cup stationary as the clamped portion of the cupped can end blank is moved downward so that the material between the central portion of the cup and the clamped portion of the cupped can end blank is free formed without substantial contact with any tooling of the forming press, the pre-panel punch retracting so that the die center extends beyond the pre-panel punch to define a final geometry of the free formed material as the forming press reaches a bottom of its forming stroke.   
     
     
         16 . An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in  claim 15  further comprising a redraw stop coupled to the panel punch and positioned to prevent overextension of free formed material. 
     
     
         17 . An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in  claim 16  wherein the redraw stop is adjustably coupled to the panel punch. 
     
     
         18 . An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in  claim 15  further comprising a delay cam coupled to the crown ring to control movement of the crown ring independent of the forming stroke of the upper punch assembly of the forming press. 
     
     
         19 . An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in  claim 18  wherein the delay cam is configured to define an up-dwell cam portion that maintains the crown ring in a raised position within the fixed base of the forming press, to define a first operating cam portion that moves the crown ring from the raised position within the fixed base of the forming press to a lowered position within the fixed base of the forming press, to define a down-dwell cam portion that maintains the crown ring in the lowered position within the fixed base of the forming press, and to define a second cam operating portion that moves the crown ring from the lowered position within the fixed base of the forming press to the raised position within the fixed base of the forming press. 
     
     
         20 . An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in  claim 15  wherein the pre-panel punch is positioned within the upper punch assembly of the forming press in accordance with an amount of material required to be free formed within the forming press. 
     
     
         21 . An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in  claim 20  further comprising a spacer between the pre-panel punch and the piston of the upper punch assembly of the forming press to position the pre-panel punch within the upper punch assembly of the forming press.