Single stroke, draw and trim die assembly

A die assembly for drawing and trimming sheet material, comprising

• (a) a first die means for applying to one surface of the sheet material a draw forming force in one direction along a draw forming axis said first die means including a fixed draw punch over which sheet material is drawn,
• (b) a second die means mounted for reciprocal movement relative to said first die means between a retracted position and an advanced position along said draw forming axis for applying to the other surface of the sheet material an opposing draw forming force to draw form the sheet material into a desired shape as said second die means moves from its retracted position to its advanced position, said second die forming means including a draw ring having an interior aperture configured to complement the exterior shape of said draw punch and allow said draw ring to telescopically advance over said draw punch as said second die means moves from its retracted position to its advanced position;
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• (c) trimming means for cutting away a portion of the drawn sheet material when said second die means is in its advanced position, said trimming means including
• (1) a trim die ring having a first trim cutting edge in the shape of the sheet material portion to be cut, said trim die being mounted in a fixed position on one of said die means, and
• (2) a trim punch mounted on said first die means having a second trim cutting edge, said trim punch being mounted on the other said die means for movement in a trim plane generally transverse to said draw forming axis to create a shear cutting action between said first and second trim cutting edges to trim the drawn sheet material in a plane transverse to said draw forming axis, said trim die ring being mounted so that said first trim cutting edge is positioned exactly opposite said second trim cutting edge when said second die means is in its advanced position, said draw ring being mounted for limited movement in said trim plane in response to movement of said trim punch;
• and
• (3) actuating means for holding said trim punch in a first position in which the trim punch is in alignment with said fixed draw punch to allow the sheet material to be drawn over said fixed draw punch and said trim punch and for displacing said trim punch within said trim plane when said second die means is in its advanced position, said actuating means including
• (a) a cam support plate oriented generally parallel to said trim plane, a lower mounting plate upon which said trim punch is mounted, a wobble plate for supporting said mounting plate in a spaced parallel position with respect to said cam support plate and for allowing said lower mounting plate to move in a plane parallel to said trim plane and cam means for displacing said wobble plate, said lower mounting plate and trim punch as a unit in four successive strokes in opposite directions along two perpendicular axes located within the trim plane,
• (b) a slide retainer fixed to said cam support plate and containing a central cavity and radially directed channels opening into said central cavity arranged along two perpendicular axes, four thrust members mounted for reciprocal movement within said channels, respectively, each said thrust member having a thrust imparting end in sliding engagement with said wobble plate and a thrust receiving end located within said central cavity and a rotatable cam mounted within said central cavity for rotation about an axis perpendicular to the trim plane, said rotatable cam having a profile which successively engages said thrust receiving ends and causes successive pairs of said thrust members to be displaced radially, one thrust member is displaced inwardly by movement of said wobble plate.