Precision-folded, high strength, fatigue-resistant structures and sheet therefor

Abstract

Precision-folded, high strength, fatigue-resistant structures and a sheet therefore are disclosed. To form the structures, methods for precision bending of a sheet of material along a bend line and a sheet of material formed with bending strap-defining structures, such as slits or grooves, are disclosed. Methods include steps of designing and then separately forming longitudinally extending slits or grooves through the sheet of material in axially spaced relation to produce precise bending of the sheet when bent along the bend line. The bending straps have a configuration and orientation which increases their strength and fatigue resistance, and most preferably slits or arcs are used which causes edges to be engaged and supported on faces of the sheet material on opposite sides of the slits or arcs. The edge-to-face contact produces bending along a virtual fulcrum position in superimposed relation to the bend line. Several slit embodiments suitable for producing edge-to-face engagement support and precise bending are disclosed. With these teachings, forming numerous three-dimensional load-bearing structures from a two dimensional sheet are enabled. Examples of straight and curved beams, chassis, and exoskeletons are disclosed.

1 - 59 . (canceled) 
     
     
         60 . A three-dimensional structure, said structure comprising:
 a folded sheet of material having at least two portions, each portion including a plurality of bending strap-defining structures formed therein, the strap-defining structures being positioned to define a plurality of bend lines and produce bending of the sheet of material along the bend lines; and   an alignment structure for aligning and securing the two portions together;   wherein aligning and securing the alignment structure causes longitudinal bending of the sheet of material in a direction transverse to the bend lines.   
     
     
         61 . The sheet of material as defined in  claim 60  wherein,
 each bending line has adjacent strap-defining structures defining a bending strap having a longitudinal strap axis oriented and positioned to extend across the bend line.   
     
     
         62 . The method as defined in  claim 61  wherein,
 the longitudinal strap axis extends at an oblique angle to the respective bend line.   
     
     
         63 . The sheet of material as defined in  claim 62  wherein,
 the strap-defining structures are slits formed to extend through the sheet of material.   
     
     
         64 . The sheet of material as defined in  claim 63  wherein,
 the slits have a kerf dimension and jog distance causing edge-to-face engagement of the sheet of material on opposite sides of the slits during bending of the sheet of material.   
     
     
         65 . The sheet of material as defined in  claim 62  wherein,
 the strap-defining structures are grooves formed to a depth not extending through the sheet of material.   
     
     
         66 . The sheet of material as defined in  claim 60  wherein,
 the three-dimensional structure is a hollow curved beam.   
     
     
         67 . The sheet of material as defined in  claim 60  wherein,
 the alignment structure comprises a plurality of attachment tabs along at least one of the plurality of bend lines.   
     
     
         68 . The sheet of material as defined in  claim 67  wherein,
 the attachment tabs are formed to extend through attachment slots provided in a second sheet of material to secure the second sheet of material to the first named sheet of material thereby securing the longitudinal bend in the first named sheet of material.   
     
     
         69 . The three-dimensional structure as defined in  claim 60  wherein,
 the first portion and the second portion are bent to curve longitudinally along the bend lines and the three-dimensional structure is a curved, four-sided, hollow box beam.   
     
     
         70 . The sheet of material as defined in  claim 60  wherein,
 at least two of the plurality of bend lines are non-linear.   
     
     
         71 . The sheet of material as defined in  claim 60  wherein,
 at least two of the plurality of bend lines are spaced from each other and non-parallel.   
     
     
         72 . The method as defined in  claim 60  wherein,
 the periphery of the sheet of material includes at least one cut that defines a first leave portion and a second leave portion, wherein the first leave portion and second leave portion are interleaved with each other.   
     
     
         73 . The method as defined in  claim 60  wherein,
 the alignment structure comprises openings in the first portion and second portion for adjustably setting the longitudinal bending of the sheet of material, wherein an opening in the first portion align with a corresponding opening in the second portion.   
     
     
         74 . The method as defined in  claim 60  wherein,
 the openings correspond to a predetermined longitudinal bend curvature.   
     
     
         75 . The method as defined in  claim 60  wherein,
 the three-dimensional article is U-shaped.   
     
     
         76 . A hollow beam comprising:
 a first sheet of material formed for bending along a plurality of first sheet bend lines, the first sheet of material being formed with a plurality of bending strap-defining structures positioned proximate each of the first sheet bend lines, and the bending strap-defining structures being configured to produce bending, and the first sheet of material being bent along the first sheet bend lines; and   a second sheet of material secured to the first sheet of material to form a curved hollow beam having side walls.   
     
     
         77 . The hollow beam of  claim 76  wherein,
 the bend lines are bend curves having a non-linear portion, and the first sheet of material is bent along the first sheet bend curves to produce an open, curved channel.   
     
     
         78 . The hollow beam of  claim 77  wherein,
 the first sheet of material is bent along the first sheet bend curves to produce an open, curved channel with flange portions.   
     
     
         79 . The hollow beam of  claim 77  wherein,
 a cross-sectional area of the channel converges.   
     
     
         80 . The hollow beam as defined in  claim 76  wherein,
 the plurality of bending strap-defining structures are a plurality of slits, and wherein the slits in the first sheet of material are arcuate.   
     
     
         81 . The hollow beam as defined in  claim 76  wherein,
 the hollow beam is longitudinally-curved in a direction transverse to at least one of the first sheet bend lines.   
     
     
         82 . A method of forming a three-dimensional article from a two-dimensional sheet of material, the method comprising:
 providing a sheet of material having at least two portions and an alignment structure for securing the two portions together, each portion including a plurality of bending strap-defining structures formed therein, the strap-defining structures being positioned to define a plurality of bend lines, each bending line having adjacent strap-defining structures defining a bending strap having a longitudinal strap axis oriented and positioned to extend across the bend line, and the strap defining structures being configured and positioned to produce bending of the sheet of material along the bend lines;   bending the sheet of material along the bend lines to produce a three-dimensional structure;   bending the sheet of material in a longitudinal direction transverse to at least one of the bend lines whereby the alignment structure comes into alignment; and   securing the two portions together to form a longitudinally-curved three-dimensional structure.   
     
     
         83 . The method as defined in  claim 82  wherein,
 along at least one of the plurality of bending lines, strap-defining structures on one side of the bending line have a greater length than strap-defining structures on an opposite side of the bending line.