Stretch roll forming

Abstract

A method of forming includes applying a stretching force along a linear axis of a work piece and forming the work piece while the stretching force is applied.

What is claimed is: 
     
         1 . A method of forming comprising,
 applying a stretching force in a region where a work piece is being formed, along a length of the work piece by controlling a torque applied to a plurality of sets of rollers that contact the work piece, wherein controlling the torque includes operating a first set of rollers with a first predetermined torque to pull the work piece in a first direction and operating a second set of rollers with a second predetermined torque to pull the work piece in a second, opposite direction; and,   simultaneously roll forming the work piece in the region where the stretching force is being applied, while stretching an entire cross-section of the work piece along its length,   wherein roll forming includes bending the work piece to have a radius along at least one of a yaw axis, a pitch axis, and a roll axis.   
     
     
         2 . The method of  claim 1  wherein applying the stretching force includes, exerting a tensile force by the use of a plurality of sets of rollers in contact with the work piece. 
     
     
         3 . The method of  claim 1 , wherein the radius is determined by the relative locations of one or more rollers of the sets of rollers. 
     
     
         4 . Then method of  claim 1 , wherein the radius is not the same as that of a roller of the sets of rollers. 
     
     
         5 . A method of applying traction forces to a surface of a work piece through at least one grip comprising,
 contacting the work piece with the at least one grip over two or more contact regions along which the surfaces of the work piece and the at least one grip are substantially conformal and where the at least one grip and the work piece exert normal forces on each other, where at least two traction forces are transmitted to the work piece, wherein contact between the at least one grip and the work piece occurs at two or more rollers, balls, or tractor elements which are pressed onto the surface of the work piece and are driven so as to apply the at least two traction forces to the work piece,   where the at least two traction forces act in opposing directions and stretch an entire cross-section of the work piece over a stretching region; and   simultaneously plastically deforming the stretching region to have a radius along at least one of a yaw axis, a pitch axis, and a roll axis.   
     
     
         6 . A work piece forming system comprising:
 a plurality of consecutive set of rollers for exerting a stretching force along a linear axis of a work piece where each set of rollers comprise at least one roller disposed proximate to each of the opposed top and bottom surfaces of a work piece, and   a controller coupled to the sets of rollers to control the torque applied to at least one set of rollers.   
     
     
         7 . The system of  claim 6  and further including,
 a frame to which the plurality of consecutive sets of rollers are affixed, the frame having adjustment means for controlling the position of at least one set of rollers. 
 
     
     
         8 . The system of  claim 6  and further including,
 at least one sensor configured to measure strain existing in the work piece between sets of rollers. 
 
     
     
         9 . The system of  claim 6  where the controller receives an input signal from at least one sensor. 
     
     
         10 . The system of  claim 6  and further including,
 first endless loop tractor belts each having inside and outside surfaces and interconnecting adjacent rollers proximate to the top and bottom surface of the work piece where the outside surface of each belt makes contact with a respective surface of the work piece, and 
 a flexible raceway comprising a plurality of stacked plates disposed proximate the inside surface of each tractor belt. 
 
     
     
         11 . The system of  claim 10  and further including,
 a plurality of needle rollers positioned between the respective raceways and the inside surface of the respective endless loop belt. 
 
     
     
         12 . The system of  claim 10  and further including,
 a second endless and rotatable loop belt into which the needle rollers are serially attached, said second endless loop belt disposed within the loop of the first endless loop belt. 
 
     
     
         13 . The system of  claim 12  and further including,
 a plurality of hydraulic cylinders in operative contact with the raceways for selectivity providing bending forces to the stacked plates. 
 
     
     
         14 . A method of applying traction forces to a top and bottom surface of a work piece comprising:
 providing first sets of rollers disposed proximate to each of the top and bottom surfaces of the work piece, where each of the first sets of rollers comprises at least one roller,   enveloping the first sets of rollers proximate to the top surface of the work piece by a first endless loop tractor belt;   enveloping the first sets of rollers proximate to the bottom surface of the work piece by a second endless loop tractor belt;   said first and second tractor belts each having inside and outside surfaces;   providing one or more flexible raceway surfaces disposed proximate the inside surface of each tractor belt;   wherein the flexible raceway surface acts to press a portion of the outside surface of the respective tractor belt against the respective surface of the work piece,   wherein each of the one or more flexible raceway surfaces are bendable between configurations of different curvature; and   controlling a torque applied to at least one roller of each of the first sets of rollers to drive the endless belts.