Draw-process methods, systems and tooling for fabricating one-piece can bodies

Apparatus for carrying out redraw of work product drawn from a circular cut edge blank of high tensile strength flat-rolled double-reduced steel can stock into a can body of increased side wall height in relation to the drawn work product, comprising in combination

• redraw tooling including
• a sleeve-like redraw die of tubular cross section
• a redraw punch, and
• a redraw clamping ring,
• each being symmetrically disposed during redraw usage for movement in relation to a common central longitudinal axis, and further including
• positioning means including surface means partially defining a cylindrical configuration for fixing the location of the drawn work product for redraw,
• the positioning means cylindrical configuration and size providing during redraw usage for relative movement of the redraw die in a direction parallel to the common central axis through the positioning means free of any requirement to move the positioning means from the redraw area during such redraw usage,
• the redraw die presenting:
• a redraw cavity defined by an internal side wall, an outer periphery side wall, with both internal and outer periphery side wall being symmetrically disposed with relation to such central longitudinal axis and having a circular configuration in a plane perpendicularly transverse to such axis,
• the redraw cavity internal side wall being recess tapered in the amount of about one half degree so as to present a larger cross sectional area in a plane perpendicularly transverse to such central axis with increasing penetration into the redraw cavity,
• a redraw die endwall providing for solely planar clamping by presenting a redraw die planar clamping surface disposed to extend radially from the entrance zone of the redraw cavity in a plane which is perpendicularly transverse to the common central axis of the redraw die cavity,
• a unitary curvilinear redraw die cavity entrance transition zone between the redraw die end-wall and the redraw die cavity internal side wall,
• the redraw die planar clamping surface extending to a redraw die transition zone at the redraw die outer periphery side wall,
• the redraw die outer periphery side wall defining a cylindrical configuration conforming to that partially defined by the surface means of the positioning means to enable movement within such surface means during redraw usage,
• the redraw cavity entrance zone presenting a curvilinear surface between the redraw cavity internal side wall and the redraw die planar clamping surface,
• such cavity entrance curvilinear surface when projected onto a plane perpendicularly transverse to such central axis having a radius in the range of about 0.02" to about 0.035";
• the redraw punch means including
• a substantially cylindrical configuration redraw punch which is symmetrical with respect to such central axis as aligned for redraw usage,
• an endwall having at least a peripheral portion defining a planar surface disposed in a plane which is perpendicularly transverse to the common central axis of the redraw punch,
• a side wall having a circular configuration in a plane perpendicularly transverse to such central axis and a diameter providing for sheet metal clearance during redraw usage so as to provide for relative movement of the redraw punch into such redraw cavity in which the diameter of the drawn work product is decreased in the range of about 15% to about 30%, and
• a compound curvilinear transition zone of predetermined surface area between the redraw punch endwall and side wall;
• the redraw clamping ring presenting
• a circular toroidal configuration in a plane perpendicularly transverse to such central axis which is symmetrically disposed for and during redraw usage in coaxial relationship with, and radially exterior of, the redraw punch,
• the toroidal configuration redraw clamping ring presenting a planar endwall clamping surface disposed in a plane perpendicularly transverse to such central axis;
• a substantially cylindrical configuration outer peripheral side wall, symmetrical to such central axis and having a diameter which for redraw usage is approximately equal to the internal diameter of a drawn work product side wall while allowing for tool clearance, and
• a curvilinear-surface transition zone for such redraw clamping ring between its planar endwall clamping surface and its outer periphery side wall surface,
• such redraw clamping ring transition zone as projected onto a clamping surface plane which is perpendicularly transverse to such central axis for redraw usage occupying less than about 40% of the projection of the curvilinear-surface juncture, between the endwall and side wall of the drawn work product, onto such clamping surface plane such that during redraw usage the dimension relationship provides for the curvilinear juncture at the closed end of the drawn work product to be initially reshaped to that of the redraw clamping ring curvilinear-surface transition zone with can stock sheet metal which is radially outward of and contiguous to the redraw punch being clamped solely between planar clamping surfaces of the redraw die and redraw clamping ring during redraw usage which provides for fabrication of a redrawn can body;
• such a redrawn can body including
• a closed endwall,
• a cylindrical configuration side wall having a predetermined diameter which is in the range of about 15% to about 30% less than the diameter of the drawn work product,
• the redrawn can body having a uniform height extending from its closed end toward its axially opposite open end,
• flange metal extending about the full periphery of such redrawn can body about its open end,
• such flange metal being disposed at completion of such redrawn usage in a plane which is at or near to perpendicularly transverse to such common central axis of the redraw tooling,
• a side wall height which is greater than the height of the side wall of such drawn work product, and
• a compound curvilinear juncture between the closed end wall and redraw side wall having an interior surface area which is approximately equal to the surface area of the redraw punch curvilinear transition zone.

Method for redrawing a one-piece cup-shaped work product drawn from high tensile strength double-reduced flat-rolled steel can stock precoated with organic coating and draw lubricant into a can body of decreased diameter and increased side wall height in relation to the diameter and side wall height, respectively, of the work product, comprising

• disposing a redraw die having a redraw cavity and a planar clamping surface on the exterior surface side of the cup-shaped work product in symmetrical relationship to the common central axis of the work product,
• disposing a redraw punch and a sleeve-like redraw clamping member having a planar clamping surface toward the interior surface side of such work product cup in symmetrical relationship to the common central axis of such work product,
• selecting the redraw punch for redraw usage to have a diameter providing for sheet metal and tooling clearance during relative movement of the redraw punch into the redraw cavity to decrease the work product side wall diameter by about 15% to 30%,
• disposing the redraw clamping member coaxially with the redraw punch during redraw usage in symmetrical relationship to the common central axis of the redraw punch and work product,
• selecting the redraw clamping ring peripheral side wall to have a diameter which is approximately equal to the internal diameter of the drawn work product side wall while allowing for tooling clearance, selecting the redraw clamping ring curvilinear transition zone at its peripheral side wall so that as projected during redraw usage onto a clamping surface plane which is perpendicularly transverse to the common central axis it occupies less than about 40% of a projection of the drawn work product compound curvilinear juncture between its endwall and side wall onto such clamping surface plane,
• providing for relative movement during redraw usage of the redraw clamping member and redraw punch parallel to such common central axis so as to
• initially reshape the configuration of such compound curvilinear juncture of the cup-shaped down work product to that of the compound curvilinear transition zone at the outer periphery of the redraw clamping member;
• clamping drawn work product can stock radially outwardly of and contiguous to the redraw punch between the planar clamping surfaces of the redraw die and clamping ring while moving the redraw punch into the redraw cavity to form a redrawn can body having a closed endwall with
• a predetermined cross sectioned dimension which is between about 15% to 30% less than the corresponding dimension of the drawn work product,
• interrupting relative movement of the redraw punch into the redraw cavity so as to
• provide flange metal extending about the full periphery of the redrawn can body about its open end,
• such flange metal being disposed at completion of the redraw relative movement in a plane which is substantially perpendicularly transverse to such common central axis.

A redraw die for redrawing a one-piece cup-shaped work product drawn from flat-rolled sheet metal can stock pre-coated with an organic coating and draw lubricant,

• such redraw die having
• a tubular configuration with an inner side wall and an outer side wall in symmetrical relationship with each other and a common central axis of the redraw die and a cup-shaped work product during redraw usage,
• an endwall presenting a planar clamping surface on such redraw die,
• curvilinear-surface transition zones unitary respectively with each of the inner and outer redraw die side walls and the redraw die planar clamping surface,
• each such transition zone having a curvilinear surface which at one of its arcuate ends is in tangential contact with the redraw die planar clamping surface and at its remaining arcuate end is in tangential contact with its respective redraw die side wall, forming a redraw die cavity entrance zone between the redraw die clamping surface and the redraw die inner side wall and a peripheral transition zone between the redraw die clamping surface and the redraw die outer side wall, and, in which
• each such redraw die curvilinear surface transition zone is formed about multiple radii of curvature of differing lengths as measured in a plane which includes such common central axis.

A redraw clamping tool for use in redrawing a cup-shaped work product drawn from flat-rolled sheet metal to decrease the cross sectional area of the cup-shaped work product in a plane perpendicularly transverse to its common central axis and increase its side wall height;

• such clamping tool having
• an elongated sleeve-like configuration, symmetrical about its central longitudinal axis, with a working surface at one of the longitudinal ends;
• such working surface comprising a planar clamping surface endwall lying in a plane which is at or near perpendicularly transverse to its central longitudinal axis at such longitudinal end of the clamping tool,
• an outer peripheral side wall surface and an inner side wall surface which are in symmetrical relationship to each other about such central axis,
• a transition zone surface between the planar surface endwall and the outer peripheral side wall surface,
• such transition zone surface being curvilinear as viewed in cross section in a plane which includes such central axis, and in tangential contact with the planar endwall surface and the outer peripheral side wall surface,
• such transition zone surface presenting a composite of a plurality of curvilinear surfaces formed about at least two radii of curvature of different lengths such that a projection of such composite of curvilinear surfaces transition zone onto a plane which is perpendicularly transverse to such central axis occupies a less cross sectional dimension in such plane than the maximum radius of curvature utilized in forming such transition zone surface.