Patent ID: 7568371

Claim:
In a stretch-forming machine of the type wherein a pair of opposed curving jaw assemblies grip opposite end edge portions of a metal sheet for initially stretching the metal sheet into a yield state, and forming the metal sheet into a predetermined curved configuration, the improvement wherein each jaw assembly comprises: a) a jaw comprising an array of adjacent grippers moveable relative to each other to collectively define the curve of the jaw for gripping a respective one of the opposite end edge portions of the sheet from adjacent a first corner area to adjacent a second corner area of the sheet; b) a moveable yoke connected to the jaw; c) a pivot assembly connecting the yoke to a beam way for pivoting the jaw about a laterally extending pivot axis defined by a contact point between the metal sheet and at least one centrally-positioned gripper, the pivot assembly being aligned with the laterally extending pivot axis at the contact point within sheet-gripping openings defined by respective ones of the grippers, such that the centrally-positioned gripper pivots about the contact point of the pivot axis during pivotal movement of the centrally-positioned gripper thereby maintaining the contact point in about the same position during pivoting; and d) at least one actuator for pivoting the jaw about the pivot axis and urging grippers adjacent the centrally-positioned gripper in a stretching direction to further progressively stretch the first and second corner areas of the metal sheet while minimizing further elongation along a central area of the metal sheet proximate the centrally-disposed gripper.