Abstract:
Apparatus and method for forming compound shaped surfaces. A skin conforming to the visual shape of the surface being formed is prepared from a blank sheet of material that is cut to size and includes any desired stamped-out detailing or notched edges or lines. Disposable strips of material are used to form hems in the skin. A preforming die is used to create tight bends or outer contours in the skin. A liner of the desired size and detailing is formed along with two-shaped side flanges. A plurality of ribs or silhouettes are provided and placed into the skin to form and maintain the desired final shape. The pre-formed liner is then assembled to the skin, the ribs being disposed between the liner and the skin.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to formation of curved surfaces such as vehicle body panels. 
     2. Description of the Prior Art 
     Various processes are known in the art for forming curved surfaces, such as compound curved vehicle body panels. In most cases, jigs are used to form such panels. Spacers used between the outer skin and the inner panel are used to hold and maintain the shape of the structures. In the prior art, these spacers are structurally a part of the inner panel. 
     There is thus a need for an apparatus and method for forming compound curved surfaces, such as vehicle body panels, without using jigs or the like. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide apparatus and method for forming compound curved surfaces. 
     It is a further object of this invention to provide such apparatus and method particularly adapted to form curved vehicle body panels. 
     It is still further an object of this invention to carry out the foregoing objects without using jigs or the like. 
     These and other objects are preferably accomplished by forming compound shaped surfaces including the step of conforming a visual shape of the surface being formed from a blank sheet of material that is cut to size and includes any desired stamped-out detailing or notched edges. Disposable strips of material are used to form hems in the skin. A preforming die is used to create tight bends in the skin thereon. A liner of the desired size and detailing is formed along with two spaced side flanges. A plurality of ribs or silhouettes are provided and placed into the skin to form and maintain the desired final shape. The pre-formed liner is then assembled to the skin, the ribs being disposed between the liner and the skin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the outer skin of the body panel or structure to be formed in accordance with the teachings of the invention; 
     FIG. 2 is a perspective view of the skin of FIG. 1 illustrating a first process step in forming the panel or structure of the invention; 
     FIG. 3 is a perspective view of the skin of FIGS. 1 and 2 illustrating another processing step; 
     FIG. 4 to 6 are perspective views of subsequent steps in processing the skin of FIG. 1; 
     FIG. 7 is a perspective view of a liner to be used with the skin of FIG. 1 in forming a body panel or structure in accordance with the teachings of the invention; 
     FIG. 8 is a perspective view of the liner of FIG. 7 illustrating a subsequent step in the processing thereof; 
     FIG. 9 is a perspective view of a sheet of material used to form structural silhouettes in accordance with the teachings of the invention; 
     FIG. 10 is a perspective view of two identical and one reversed image silhouettes formed from similar sheets of material as shown in FIG. 9 oriented in the position in which they will be assembled to the skin and panel of FIGS. 1 and 7; 
     FIG. 11 is a perspective view illustrating the assembly of two of the silhouettes of FIGS. 10 to the skin of FIG. 6; 
     FIG. 12 is a perspective view showing a subsequent step in the assembly of the silhouettes of FIG. 11; 
     FIG. 13 is a perspective view illustrating the third silhouette of FIG. 10 assembled to the liner of FIG. 7; 
     FIG. 14 is a perspective view illustrating the assembly of the liner of FIG. 13 to the skin of FIG. 12; 
     FIG. 15 is a perspective view illustrating the final processing of the parts of FIG. 14; and 
     FIG. 16 is a perspective view of two vehicle door panels formed in accordance with the teachings of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1 of the drawing, a blank sheet 10 of any suitable material, is shown. Since the invention contemplates the formation of making contoured vehicle body panels, the use of electro-galvanized, cold-rolled steel of 14 to 24 gage is preferred. Of course, any other standard sheet metal, such as aluminum or stainless steel, may be used along with other suitable gage thicknesses. 
     Sheet 10 may also be of any suitable dimensions depending of course on the final body panel size desired. For example, sheet 10 may be 26&#34;×33&#34;; 30&#34;×30&#34;; 15&#34;×40&#34;, etc. 
     Sheet 10 is intended to be the outer skin of the final body panel and may be stamped or cut for special details of the final panel. For example, cut-out areas 11, 12 are provided on opposite elongated edges 13, 14, respectively. Corners 15 through 18 are cut at a 45° angle. A latch pocket cavity 19 and lock hole 20 therefore is stamped out. 
     As seen in FIG. 2, areas where tight bending will occur are shown at lines 21 through 28. A conventional two piece press break hemming die 36 is used to form flanges that is, one edge, e.g., edge 13, of sheet 10 is disposed in a generally V-shaped cavity 37 in die portion 38 and a mating die portion 39, having an end 40 conforming generally to cavity 37, is pressed down in the direction of arrow 41. This forms an angled hem or flange 35. Flanges or hems 33, 34 have been formed in like manner. 
     As seen in FIG. 3, a plurality, such as three, of disposable flat strips of sheet metal, such as strips 29, 30, and 30&#39; are provided disposed inside of flanges 33 to 35 prior to flattening of the same. Strips 29, 30, and 30&#39; are of a greater thickness than the material of the liner 50 (FIG. 7) that will be subsequently assembled to sheet 10. Strips 29, 30, and 30&#39; are thus used as separators in the bending and forming of hems or flanges 33 to 35. 
     As seen in FIG. 4, a conventional straight flattening die 42 comprising of mating die portions 43, 44 is used to flatten hem or flange 35 by pressing the edges together. Strips 29, 30, and 30&#39; remain in place trapped within flanges 33 to 35. 
     As seen in FIG. 5, a special pre-forming die 45 having upper and lower portions 46, 47, respectively, is used to crease sheet 10 within the areas indicated by phantom lines 25 to 28 to form the contoured or upraised midportion 48 shown in FIG. 6. It can be seen that, in FIG. 5, the mating portions of die 45 are configured to form the contoured portion 48. Strips 29, 30, and 30&#39; are now removed and the remaining hem or flange 49 is formed at an angle of about 150° as heretofore discussed using die 36 of FIG. 2. 
     As seen in FIG. 7, a second sheet 50 of metal, similar to sheet 10, of the desired gage is provided. As discussed about with respect to sheet 10, the measurements and materials may vary; however, sheet 50 is preferably about 2&#34; longer in length than sheet 10 and about 2&#34; shorter in width. Sheet 50 which will be the liner of the completed body panel, is then stamped for any special detail, such as a latch pocket access cavity 51. A plurality of 3/16&#34; holes 52 are also stamped about the periphery along sides 53, 54. These holes 52, as will be discussed with respect to the silhouettes or stiffeners of FIGS. 9 and 10, correspond to one end flange of the silhouettes or stiffeners and may be evenly spaced apart, e.e., about 5&#34; apart. Phantom lines 55, 56 adjacent one side 57 and like phantom lines 58, 59 adjacent the opposite side 60 indicate where bending operations will be carried on. 
     As seen in FIG. 8, Z-shaped flanges are formed as is well known in the art at sides 57, 60. 
     Referring now to FIG. 9, a silhouette or stiffener 61, of sheet metal, is provided of the desired gage and is pre-cut to size in any suitable manner. Stiffener 61 is cut along dotted trace line 63 to form equally spaced teeth 66 along one arcuate path. Thus, as seen in FIG. 10, a plurality of spaced slots 67 are formed along edge 64 allowing this edge to be bent into a curved flange 68. The other edge 65 is then bent in the opposite direction forming a Z-shaped section. Two identical stiffeners 61 and one reversed or mirror image stiffener 61&#39; are shown in FIG. 10 in their proper orientation. 
     The assembly of three stiffeners, such as stiffeners 61, 61&#39; of FIG. 10, to the skin 10 will now be discussed. Skin 10 is oriented as in FIG. 11. A first stiffener 61 is disposed on top of skin 10 with flange 68 of stiffener 61 located adjacent and under the flange 35. A hammer or mallet may be used to hammer one of the stiffeners 61 in the direction of arrow 70 to lock the same in position. The reversed or mirror image stiffener 61&#39; is mounted under flange 33 in like manner (see arrows 71). The final position of the stiffeners 61, 61&#39; mounted to skin 10 is shown in FIG. 12. A welding gun 69 is used to tack weld the stiffeners (or any other parts) at spaced locations to hold the parts together during assembly. 
     The other stiffener 61 is now spot welded along flange 65&#39; (see the dotted lines in FIG. 13) to liner 50 as shown. Other means than welding may be used such as riveting or bolting. Any other accessories desired to be mounted to liner 50 may also be installed thereon at this stage. 
     As seen in FIG. 14, the flanged edges 57 of liner 50 is slid under hem 34 of skin 10 (with stiffeners 61, 61&#39; assembled thereto as in FIG. 12) in the direction of arrow 72 with flanged edge 60 of liner 50 slid under hem 49 of skin 10 as indicated by arrow 73. The final installation of liner 50 to skin 10 and stiffener 61, 61&#39; is shown in FIG. 15. The flanges and hems may be pressed together using flattening dies. For example, as seen in FIG. 15, a conventional flattening die 420, having mating portions 430, 440 may be used along the straight end edges. A special flattening die 420&#39;, having mating portions 430&#39;, 440&#39; may be used along the curved side edges. The flanges and hems may also be spot welded using a welding gun 69 at spaced locations, if desired. Holes 52 are provided so that the resulting other weld lumps may be ground off in the finishing process. Also, if desired, blind rivets or metal screws may be used instead of welding. Finally, a pair of finished vehicle door panel assemblies 100, 101 are shown in FIG. 16 formed in accordance with the teachings of the invention. All rough surfaces, including any weld lumps around holes 52 have been ground off in the finishing process leaving a smooth surface. 
     It can be seen that a multiple compound curved body panel is formed without the need of using expensive jigs or the like. A pressure brake die is used to form tight bends as in FIG. 5. Curved silhouettes or stiffeners are used to form and maintain the shape of the body panel.