Abstract:
A tube bending apparatus which provides an improved method for the operator to input shape changes into the control and a method of calculating revised machine movements to better achieve the desired workpiece shape.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefits of Provisional Patent Application No. 60/485,724 filling date Jul. 10, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to apparatus and methods for the bending of rigid workpieces, particularly tubes, such as used in automotive structures, exhaust systems, heat exchangers and aircraft hydraulic systems, but including pipe, rod and wire.  
       BACKGROUND OF THE INVENTION  
       [0003]     In prior apparatus used for bending of pipe and tube, such as used in automobile exhaust systems, heat exchangers and aircraft construction, there are three main components, the tube positioning mechanism, the bend head and the controller.  
         [0004]     The controller causes the tube positioning mechanism to grip one end of the tube and position the tube in the desired longitudinal and axial position in relation to the bend head. The bending head comprises a rotary bend die, an opposing clamp die which clamps a section of the tube immediately preceding the section of the tube where the bend is to be formed, and a pressure die located directly behind the clamped section of the tube. The controller causes the tube to be pulled around the rotary bend die, the pressure die moves substantially in unison with the tube while resisting the radial reaction force of the tube action on the pressure die. Thus the pressure die and rotary bend die cause the tube to be squeezed therebetween during the bending operation. The controller causes a sequence of positioning and bending movements to produce the desired shape and number of bends in the workpiece.  
         [0005]     Many variable factors such as the type of material, tube wall thickness, shape of tube section to be formed, the radius of the bend and the like contribute to the “springback” characteristics of the tube and need to be considered when tube bending with rotary draw bending machinery is carried out. The movements of the bending apparatus are adjusted to compensate for the “springback” characteristics. The tube produced is compared to the shape desired using known equipment and further adjustments are made to the movements of the apparatus to produce a tube of the desired shape. The operator of the bending apparatus is able to modify the shape parameters in the controller to change the shape of tubes bent subsequent. In prior apparatus the operator can modify the shape parameters using two methods. The first method involves modifying the length of a straight between two bends in the workpiece, or the rotation between two bends, or the depth of a bend, or any combination of these. The second method involves changing the coordinates of the intercepts of the centerlines of the straights of the workpiece.  
         [0006]     These prior methods require experience and skill on the part of the operator. In practice there may be many iterations of bending, measuring and modification needed, with a high number of tubes being used, before tubes of acceptable accuracy are manufactured, which results in increased tube scrap.  
         [0007]     Although commercially acceptable tubes are manufactured with apparatus hereinbefore described, there is a need for pipe bending means which are capable of producing bent tubes of consistent quality on a repeated basis with fewer iterations of adjustment.  
       SUMMARY OF THE INVENTION  
       [0008]     It is an object of the present invention to provide an improved method for the entry of shape parameter adjustments by the operator of the tube bending apparatus.  
         [0009]     It is a further object of the present invention to provide the operator with verification that the entered shape changes will improve the outcome of the bending process.  
         [0010]     It is a yet further object to provide means for the control computer to compensate the movements of the bending apparatus to produce a tube that closer matches the desired shape in fewer iterations with reduced scrap.  
         [0011]     It is a yet still further object of the invention to provide the operator a method to enter shape adjustments during the manufacture of multiple bent tubes due to material variations and tool wear.  
         [0012]     These and other objects of the invention will become apparent from a reading of this specification as a whole.  
         [0013]     Accordingly, in one aspect the invention provides a method of modifying the parameters of the desired tube shape in the control, the method comprising 
        a) bending the workpiece to form a complete bent tube and comparing the shape of this tube to the desired shape using conventional inspection methods.     b) The operator is able to display a visual representation of the desired bent tube on the control display.     c) The operator will use the control to select which bend or straight requires modification. The control will display the visual guides and move menu superimposed on the selected bend or straight.     d) The operator will then select the visual guide, or button, appropriate to the direction of the desired shape modification and enter a value for the magnitude of the desired adjustment.     e) The control will display the revised tube shape in relation to the unmodified tube shape.     f) The operator will accept the revised tube shape or make additional adjustments, until satisfied that the modifications will improve the acceptability of the tube shape, at which time the operator accepts the revised tube shape.     g) The control will then calculate revised movements for the bending apparatus to bend the modified desired shape.        
 
         [0021]     In another aspect the invention can provide a portable means to enter the desired shape modification remotely into the control of the bending apparatus.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  is a diagrammatic view of the bending apparatus control display according to the invention with visual guides superimposed on a bend within the visual representation of the bent tube.  
         [0023]      FIG. 2  is a diagrammatic view of the control display on conventional bending apparatus with the visual representation of the bent tube.  
         [0024]      FIG. 3  is a diagrammatic view of the bending apparatus control display according to the invention with the bend selected and showing the visual guide, a move command menu and a visual representation of the revised bent tube shown in relation to the unmodified tube shape.  
         [0025]      FIG. 4  is a diagrammatic view of the bending apparatus control display according to the invention with the visual guides superimposed on a straight within the visual representation of the bent tube.  
         [0026]      FIG. 5  is a block diagram representing the method to be followed in modifying a tube shape according to the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]     The invention provides an improved method for the operator of the tube bending apparatus to modify the movements of the bending apparatus to change the shape of the workpiece produced.  
         [0028]     The invention enables the operator to make changes to the overall shape by making changes to a bend in relation to it&#39;s current position within the workpiece by specifying modifications to shape and position in relation to the current position and orientation of that bend. In previous apparatus modifications are made to the individual shape elements such as length between bends, rotation between bends and angle of bend or in relation to the coordinate system of the entire workpiece.  
         [0029]     The choice of modifications to improve the shape of the workpiece using prior apparatus requires experience and skill from the operator. Modifying individual shape elements on one bend will change the entire shape unless compensating modifications are made to other shape elements within the workpiece. Modifying the part shape in relation to the coordinate system of the entire workpiece is not simple because the bend to be modified rarely lies true to a plane within the coordinate system.  
         [0030]     The controller of prior apparatus enables the operator to display a visual representation of the desired workpiece shape on the computer monitor of the tube bending apparatus controller as shown in  FIG. 2  and select a bend for shape modification.  
         [0031]     The invention provides an improved method enabling the apparatus to display a menu of options to move the position of the bend or the adjacent straights in relation to the existing position and orientation of the plane of the bend selected. The menu can be a conventional drop down menu or visual guides as shown in  FIG. 1 .  
         [0032]     The operator selects the direction and inputs the distance for the move. The improved method according to the invention then enables the apparatus to display the resulting shape as an overlay as shown in  FIG. 3 . The operator can accept the change or make subsequent changes. Once satisfied, the operator authorizes the invention to calculate revised movements for positioning and bending subsequent workpieces in the tube bending apparatus.  
         [0033]     Although this disclosure has described and illustrated certain preferred embodiments of the invention, it is to be understood that the invention is not to be restricted to those particular embodiments. Rather, the invention includes all embodiments which are functional equivalents of the specific embodiments and features that have been described and illustrated.