Process of bending laminated metal sheet

Abstract

This invention improves on the process of bending in a conventional progressive stamping press a flat laminated metal sheet around a corner edge of a die block to form a generally straight piece-part corner, and comprises the steps of forming extended concavely rounded depressions in the opposite sheet faces at the sheet locations of the intended corner, then locating and clamping the sheet with the depressed regions aligned along a die block corner, and then mechanically bending the sheet with said depressed sheet regions aligned over the die block corner edge. The sheet depressions can be aligned essentially opposite one another, being rounded concavely and of a high width-to-depth ratio and of a depth to reduce the sheet to between 80-30% of its original thickness. The sheet depressions might occur at one stamping press station by opposing press tools each having a convex rounded working edge elongated along the length of the intended corner, with the blank bending occurring at a subsequent stamping press station.

What is claimed is:  
     
         1 . A method of folding, with a conventional stamping press, a generally flat laminated metal sheet about a corner to form a three-dimensional piece, the combination comprising the steps of: 
 locating the sheet at a first press station, and striking a press tool having a convexly rounded working edge elongated substantially along the entire length of the intended piece corner against a sheet face at the location of said intended piece corner, for forming an elongated concavely rounded depressed region therein and thereby reducing the sheet thickness between adjacent main and fold sheet portions;    locating the sheet at a second press station to have the main sheet portion supported on a press block with the depressed region aligned adjacent a press block corner and the fold sheet portions cantilevered beyond the press block corner to an adjacent clearance space; and    holding the main sheet portion against the press block while moving a folding tool against the fold sheet portion for bending said sheet about the press block corner at the depressed region.    
     
     
         2 . A method of folding a laminated metal sheet according to  claim 1 , further wherein opposed striking press tools are used for forming concavely rounded depressed regions in the opposite sheet faces at essentially opposite locations proximate said intended piece corner operable for reducing the sheet thickness between the adjacent main and fold sheet portions.  
     
     
         3 . A method of folding a laminated metal sheet according to  claim 2 , further wherein each depressed region is of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness.  
     
     
         4 . A method of folding a laminated metal sheet according to  claim 2 , further comprising each depressed region having a depth between 10-35% of the original blank thickness, leaving the thinnest part of the sheet at the intended corner between 80-30% of the original sheet thickness.  
     
     
         5 . A method of folding a laminated metal sheet according to  claim 2 , further wherein each depressed region has a high width-to-depth ratio, the width being at least twice and up to many times the depth.  
     
     
         6 . A method of folding a laminated metal sheet according to  claim 4 , further wherein each depressed region is of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness.  
     
     
         7 . A method of folding a laminated metal sheet according to  claim 6 , further wherein each depressed region has a high width-to-depth ratio, the width being at least twice and up to many times the depth.  
     
     
         8 . A method of folding a laminated metal sheet according to  claim 2 , further wherein each depressed region is of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness, and each depressed region having a depth between 10-35% of the original blank thickness, leaving the thinnest part of the sheet at the intended corner between 80-30% of the original sheet thickness.  
     
     
         9 . A method of folding a laminated metal sheet according to  claim 2 , further comprising each depressed region having a depth between 10-35% of the original blank thickness, leaving the thinnest part of the sheet at the intended corner between 80-30% of the original sheet thickness, and each depressed region having a high width-to-depth ratio, the width being at least twice and up to many times the depth.  
     
     
         10 . A method of folding a laminated metal sheet according to  claim 2 , further wherein each depressed region being of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness, and each depressed region having a high width-to-depth ratio, the width being at least twice and up to many times the depth.  
     
     
         11 . A method of folding, with a conventional stamping press, a generally flat laminated metal sheet about a corner to form a three-dimensional piece, the combination comprising the steps of: 
 forming opposed elongated concavely rounded depressed regions in opposite sheet faces substantially along the entire length of and at the sheet location of the intended piece corner and between adjacent main and fold sheet portions;    supporting the main sheet portion on a press block with the depressed region aligned adjacent a press block corner and holding it there, and moving a fording tool against the fold sheet portion cantilevered beyond the press block corner to an adjacent clearance space for bending said sheet about the press block corner at the depressed region.    
     
     
         12 . A method of folding a laminated metal sheet according to  claim 11 , further comprising each depressed region being of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness, each depressed region having a depth between 10-35% of the original sheet thickness, leaving the thinnest part of the sheet at the intended corner between 80-30% of the original sheet thickness, and each depressed region having a high width-to-depth ratio, the width being at least twice and up to many times the depth.