Abstract:
A bending system comprising a series of bending stations, each equipped with a bending head. Workpieces are conveyed from one bending station to the next by grippers suspended from a two-axis gantry, that preferably grasp the workpiece at an intermediate portion. Each bending head grasps the tube at a different intermediate position, and in the preferred embodiment each bending station is capable of rotating to position the bending dye such that the free end of the workpiece being bent can be oriented in the bending plane without interference by an adjacent bending station. These features reduce the space requirements of the system considerably. A multi-level dispensing apparatus may be provided to load the bending heads. The bending system is preferably operated by computer, allowing the bending of long workpieces to precise configurations under the control of a single operator.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to industrial equipment. In particular, this invention relates to a bending system for bending wires, tubes and other elements, for example for use as components in manufacturing.  
       BACKGROUND OF THE INVENTION  
       [0002]     Bent components are used in manufacturing many different types of articles and machines. For example, many of the fluid conduits in an automobile are bent to a predetermined shape for installation on an automobile assembly line. In such situations the component must be shaped to exacting tolerances, particularly in the case of for example brake lines which carry brake fluid from the master braking cylinder to the wheel cylinders, in order to ensure that the conduits fit into the space for which they are designed and conduits are stable in motion.  
         [0003]     One popular bending method is known as “draw bending”, in which the workpiece is held in position and bent by a bending arm around a dye having a set radius of curvature. Where multiple bends are required in different directions, rather than changing the direction of motion of the bending arm and the orientation of the dye, after each bend the workpiece is rotated to the next bending plane so that the bend can be effected by actuating the bending arm in the same direction, to the desired angle. Such a device is known as a “rotary draw bender.” 
         [0004]     To bend components within very high tolerances, rotary bending heads have been developed that combine different types of actuators, for example a hydraulic gripper for gripping the tube can be combined with an electric motor for rotating the tube to the bending plane and pneumatic or hydraulic actuators for effecting the actual bending of the tube by the bending arm.  
         [0005]     A conventional rotary bending head comprises a set of jaws for gripping one end of the tube; a bending arm extending forwardly of the jaws and having a grasping end, for holding the tube during bending and rotation; and a dye having a specific bending radius movable to the bending point on the tube, the dye being sized depending upon the diameter of the tube and the desired radius of curvature of the bend. The arc of motion of bending arm is limited to the bending plane, so the tube is rotated until the desired bend direction falls into the bending plane, at which point the bending arm is actuated to effect the bend to the desired angle. In a typical case this process occurs multiple times on a particular tube, for example in the case of a brake line.  
         [0006]     However, such prior art rotary bending heads have significant limitations. The time that it takes to apply multiple bends to a tube depends upon a number of factors, including the rotational speed of the bending jaws. Prior to each bend, the jaws must rotate the tube to an angular orientation in which the desired bend direction lies in the bending plane. This rotation cannot commence until the previous bend is completed, and in order to maintain precise tolerances the rotation must completely cease before the next bend begins. In the case of a tube to which multiple bends are to be applied, the time spent rotating the tube to the bending position for each successive bend can constitute the majority of the time taken to complete the bending process. In industries such as the automobile parts industry, where a typical run through the bending apparatus to fill a single order can involve hundreds of thousands of tubes, this wasted time can have a significant unnecessary overhead cost.  
         [0007]     Moreover, the tube bending head so described as capable of bending tubes only up to a certain length, i.e. approximately 1.3 meters (4 feet), at the maximum rotational speed of the jaws. Because of the mechanical disadvantage obtained by grasping the tube at one end, in longer tubes the inertia of the free end of the tube will cause the tube to wobble, to the point where the tube is likely to be out of alignment at the moment the bend occurs, unless the rotational speed of the jaws is reduced. With the jaws rotating at maximum speed, as a long tube is rotated the free end of the tube tends to twist and lag behind the gripped end of the tube, so that the bending point may not have rotated fully into the bending plane at the precise moment that the bending arm is applied to the tube. Also, if the tube is heavy enough inertia can cause the tube to slip in the gripper at full speed. All of these problems result in reduced tolerance and, in many cases, inaccurate bends, which requires that many of the component be discarded. This problem is also wasteful and time consuming over many thousands or hundreds of thousands of workpieces.  
         [0008]     It would accordingly be advantageous to provide a bending apparatus that is capable of maintaining high rotational speeds when rotating the tube into the bending plane over successive bends, without reducing the accuracy or tolerances in the finished product, and to be capable of bending tubes longer than 1.3 meters (4 feet) quickly and without reducing the accuracy or tolerances in the finished product.  
         [0009]     Further, it would be advantageous to provide a series of bending heads in an apparatus, in order to effect bends of many different radii and complete the entire bending procedure without having to change the bending dye. However, positioning each bending stations far enough away from adjacent bending stations so that the workpiece can be bent without interference by an adjacent bending station would take up considerable floor space.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention overcomes these disadvantages in a bending system which is capable of bending long tubes, wires and other elements into complex three dimensional configurations, with the same tolerances and precision as short tubes and without reducing the rotational speed of the bending head.  
         [0011]     The invention accomplishes this by providing a series of bending stations, each equipped with a bending head. The workpieces are conveyed from bending station to bending station by grippers that preferably grasp the workpiece at an intermediate portion, rather than at one end. This reduces the length of workpiece from the gripping point to the free ends, commensurately reducing twisting and wobbling of the workpiece during bending and significantly diminishing the likelihood of slippage of the workpiece in the gripper during rotation.  
         [0012]     The bending stations may also be spaced from one another a distance which is shorter than the length of a workpiece, because each bending head grasps the tube at a different intermediate position so the bending stations do not interfere with one another. Moreover, in the preferred embodiment each bending station is capable of rotating, to position the bending dye such that the free end of the workpiece being bent can be oriented in the bending plane without interference by an adjacent bending station. These features reduce the space requirements of the system considerably.  
         [0013]     In the preferred embodiment a two-axis gantry is provided to convey a workpiece to each successive bending station after the previous bending station has completed its bending cycle (which may involve multiple bends). Also, in the preferred embodiment a multi-level dispensing apparatus is provided to load the bending heads. A movable loader arm can pick a workpiece off of any shelf of the dispensing apparatus, which increases the speed of operation by avoiding the need to wait for next workpiece to fall into the loading position on the shelf after a workpiece has been loaded to the first bending station.  
         [0014]     The bending system is preferably operated by computer, so that parallel processing by multiple bending stations can be effected quickly and without interruption. The bending system according to the invention accordingly facilitates the bending of workpieces such as long tubes, wires and other elements to precise configurations under the control of a single operator, thus saving up to two-thirds of the labour involved in bending workpieces with a single bending head. The bending system of the invention is also relatively compact, since the bending stations can be closer together than the length of each workpiece, due to the versatility in the position at which the grippers grasp the workpiece and the ability to rotate each bending station to a position where it can bend a portion of the workpiece without interference by adjacent bending stations.  
         [0015]     Moreover, bending of long tubes and wires can be effected without slippage of the tube in the gripper or inertial twisting or wobbling of the workpiece, thereby significantly reducing and even potentially eliminating the number of workpieces which must be discarded due to failure to meet tolerances.  
         [0016]     The present invention thus provides a bending system, comprising a series of bending stations spaced from one another, each bending station comprising a bending head for bending a workpiece through a bending envelope defined along a bending plane, a series of grippers suspended from a gantry, for conveying the workpiece from one bending station to another bending station, and at least one of the bending heads being rotatable, to thereby adjust the position of the bending envelope relative to adjacent bending stations, whereby the bending head can be rotated to bend the workpiece without interference from adjacent bending stations.  
         [0017]     The present invention further provides a bending system, comprising a series of bending stations spaced from one another, each bending station comprising a bending head for bending a workpiece through a bending envelope defined along a bending plane, a series of grippers suspended from a gantry, for conveying the workpiece from one bending station to another bending station, and a multi-level dispensing apparatus comprising a movable loader arm for picking a workpiece off of a shelf of the dispensing apparatus and conveying the workpiece to a gripper.  
         [0018]     The present invention further provides a method of bending an elongated workpiece using a series of bending stations spaced from one another, each bending station comprising a bending head for bending a workpiece through a bending envelope defined along a bending plane, comprising the steps of: a. rotating at least one of the bending heads to position the bending envelope so that the workpiece can be bent without interference from adjacent bending stations, b. conveying the workpiece along the series of bending stations, and c. bending the workpiece as the workpiece is conveyed to each bending station. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     In drawings which illustrate by way of example only a preferred embodiment of the invention,  
         [0020]      FIG. 1  is a perspective view of a two-axis gantry for the bending system of the invention, taken from above;  
         [0021]      FIG. 2  is a perspective view of the gantry of  FIG. 1 , taken from below;  
         [0022]      FIG. 3  is perspective view of a gripping arm suspension rail in the gantry of  FIG. 1 ;  
         [0023]      FIG. 4  is an elevational view of a gripping arm;  
         [0024]      FIG. 5A  is a top plan view of the bending stations in the bending system of  FIG. 1 ;  
         [0025]      FIG. 5B  is a schematic plan view of the bending stations during a bending run; and  
         [0026]      FIG. 6  is a schematic elevation of the bending system of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]     The bending system of the invention will be described herein in the context of bending tubes  2 , for example tubes used for fluid conduits in an automobile such as brake lines. However, it will be appreciated that the principles of the invention apply to bending any bendable elongated member, and the invention is not intended to be limited to any particular type of workpiece.  
         [0028]     The bending system  10  of the invention comprises a series of bending stations  20 ,  22 ,  24 ,  26 , shown in  FIGS. 5 and 6 . There are four bending stations in the embodiment illustrated, however it will be appreciated that more or fewer bending stations may be employed, depending upon the complexity of the bending to be accomplished and the desired output of the system.  
         [0029]     Each bending station comprises a pedestal  28 , which is rotatably mounted into a floor  12  of the system  10 , and a bending head  30  having a bending arm  32  that follows an arcuate path about a dye  34  along a bending plane B, as is conventional. The bending plane B in the embodiment illustrated (shown as a dotted line in  FIG. 6 ) is generally horizontal and the bending stations  20 ,  22 ,  24  and  26  are preferably equally spaced along the floor  12  of the system  10 , to simplify control requirements.  
         [0030]     Tubes  2  are unloaded from a tube loader  90  and delivered to the first bending station  20 , and then unloaded from each bending station and delivered to the next successive bending station, by a movable gripper  50 , illustrated in detail in  FIG. 4 . The gripper  50  comprises a gripper arm  52  suspended from its upper end and gripper jaws  54  mounted to its lower end. The gripper jaws  54  are contained within a rotatable disk  62 , which in the embodiment shown is rotated by a drive servo or mechanical drive  56  actuated by a servo motor (not shown) via pulley  58  and extending around bearings or sprockets  60  such that the servo or mechanical drive  56  is held engaged against a ribbed peripheral edge  64  of the gripper disk  62 . The jaws  54  are actuated by pneumatic or hydraulic cylinders  66  contained within the disk  62 , and the disk  62  is in turn rotatably mounted to the arm  52  by a bearing (not shown) engaging the peripheral edge.  
         [0031]     The movable gripper  50  is suspended from a two-axis gantry  40 , illustrated in  FIGS. 1 and 2 . The gantry  40  comprises a main frame  42  supported by legs  44  and having, for each gripper  50  (five in the embodiment illustrated), a movable crossbeam  46 , best seen in  FIG. 3 . The crossbeams  46  are slidably mounted to the side rails  42   a  of the frame  42  and movable along a first (“x”) axis within a set range by an electric motor or other actuator (not shown) driving a pinion along a rack, or via any other suitable drive system. The particular drive system used to move the crossbeams  46  in the “x” direction along the gantry frame  42  is a matter of selection.  
         [0032]     A gripper  50  is preferably provided for each bending station  20 ,  22 ,  24 ,  26  plus one extra gripper  50  for unloading from the last station  26  and depositing the bent workpiece  2  onto an unloading shelf or tray  8  (shown in  FIG. 6 ). Each gripper  50  is independently movable longitudinally along the gantry  40 , i.e. in the “x” direction, via the movable crossbeams  46 , for unloading a tube  2  from the loader  90  or one bending station and delivering it to the next bending station or the unloading shelf  8 . Each gripper  50  is also independently movable transversely across the gantry  40 , along a second (“y”) axis, by a sliding mount  70 , best seen in  FIG. 3 , actuated by a servo or mechanical drive  72  (shown in  FIG. 1 ). This allows the gripper  50  to load the tube  2  at a point where the jaws  54  can most conveniently grasp the tube  2  at an intermediate point for the next bend, which: 
        allows the gripper  50  to longitudinally align the next bending point of the tube  2  with the dye  34 ;     effectively doubles the length of tube  2  which can be rotated at a given speed without risking inertial twisting or wobbling of the workpiece or slippage at the gripper jaws  34 ;     allows multiple bends to be effected at each bending station  20 ,  22 ,  24  or  26  before the tube  2  is unloaded and moved to the next bending station. After each bend the gripper jaws  54  rotate the tube  2  to the bending plane for the next successive bend and, if necessary, the bending head  34  is raised or lowered between bends to change the bend radius for successive bends by aligning the tube  2  with a different level of a multi-level bending dye  34 ; and     allows the gripper  50  to grasp a partially bent tube  2  at the most convenient point of the tube  2  to maximize the use of the space around the bending stations  20 ,  22 ,  24 ,  26  because the tube  2  can be bent from either side of the gripper  50 .        
 
         [0037]     The sliding mount  70  may be moved by a servo or mechanical drive  72  as shown, or by a rack and pinion or any other suitable drive system, and the particular drive system used to move the sliding mount  70  in the “y” direction along the gantry frame  42  is a matter of selection.  
         [0038]     Preferably the grippers  50  all move substantially in unison in the “x” direction. This simplifies synchronization of the loading and unloading of the various bending stations  20 ,  22 ,  24 ,  26  for efficient parallel processing.  
         [0039]     For greater versatility, some of the grippers  50 —particularly those loading and holding for the first two stations  20 ,  22  where the free ends of the tubes  2  are still quite long—may have a set of slip-jaws  36  disposed spaced from the dye  34  and preferably movable in the direction of the “y” axis independently of the gripper  50  (see bending station  20  in  FIG. 6 ). The slip jaws  36  surround the tube  2  to retain it axially, but do not prevent the tube  2  from rotating. This further reduces unwanted wobbling of the tube  2  during the bending operation, by providing a second support point along the tube  2  spaced from the primary gripping point at the gripping jaws  54 . For proper operation of the optional slip jaws  36  the workpiece  2 , while held in a stable position, must be able to rotate completely freely within the slip-jaws  36  as any resistance to rotation of the tube  2  to the bending plane B may cause the tube to twist and potentially slip in the gripper jaws  54 .  
         [0040]     Rotation of the bending stations  20 ,  22 ,  24 ,  26  does not need to be controlled during the bending process, because each bending station  20 ,  22 ,  24 ,  26  can be rotated to the desired orientation manually before the bending process begins, based on the particular bends being performed by each particular bending station and the length and direction of the free ends of the tube  2  during the bending procedure, and is locked into the desired rotational position by a releasable latch or pin  23 . Preferably each bending station  20 ,  22 ,  24 ,  26  also has some degree of vertical adjustability, for example four to six inches from the floor  12 , allowing the station to accommodate multi-level bending dyes  34  of varying sizes without interfering with the operation of the gantry  40 . This allows bends of different radii to be effected by a single bending station during each bending run, and reduces the need to change bending heads for different bending runs. In addition the bending head  30  itself moves along a vertical (“z”) axis relative to the pedestal so that the bending dye  34  can be moved into the bending plane B (stations  22  and  26  in  FIG. 6 ) for bending or retracted out of the path of the grippers  50  (stations  20  and  24  in  FIG. 6 ) while tubes  2  are being moved between stations. The bending heads  30  can also be controlled to raise the bending dye  34  to a specific level, in order to align a particular level of a multi-level bending dye  34  with the level of the gripper  50  (i.e. the bending plane B).  
         [0041]     Alternatively, or additionally, the grippers  50  could be designed to be extendable in the “z” direction, to move the workpiece  2  to the level of the bending dye  34 . However, because it is preferable to move the workpiece  2  as little as possible during the bending operation to avoid unwanted inertial flexing and wobbling, it is advantageous to instead move the dye  34  to the level of the workpiece  2  as in the preferred embodiment shown.  
         [0042]     Each bending head  30 , crossbeam  46  and gripper  50  is operated by a computer  14 , which directs the position and motion of the gripper  50 ; the angular orientation of the gripper jaws  54  through rotation of the servo motor (not shown) in the gripper arm  52 ; the opening and closing of the jaws  34  via pneumatic/hydraulic actuators  66 ; actuation of the bending arm  32 ; and the timing of the bending cycle at each station  20 ,  22 ,  24 ,  26 . The computer  14  also controls the loader  90 .  
         [0043]     In the preferred embodiment, shown in  FIG. 6 , the loader  90  has multiple levels. Three levels  92 ,  94 ,  96  are provided in the embodiment illustrated. This allows for loading a greater volume of tubes  2 , faster unloading of tubes  2  from the loader  90 , and restocking of the loader  90  without disrupting the bending cycle. Each loading level or shelf  92 ,  94 ,  96  is inclined to allow the tubes  2  to slide to the front (gantry side) of a shelf  92 ,  94  or  96  for pickup by the pickup bar  98  disposed on a track  97 , and is provided with an actuator  99  with a catch  99   a  that releases one tube  2  at a time to the front of the shelf. The pickup bar  98  rotates between a position in which pickup jaws  98   a  face the tubes  2  (generally horizontal) and a position in which pickup jaws  98   a  face the first gripper  50 , and also travels vertically along the track  97 , enabling the pickup bar  98  to grasp a tube  2  from any shelf  92 ,  94 ,  96  and feed it to the first (nearest) gripper  50 . Although the loader  90  so described and illustrated is gravity fed, it is also possible to provide a powered loader which would load the front of each shelf using an actuator.  
         [0044]     In operation, tubes  2  of the desired size are loaded into one or more of the three levels  92 ,  94 ,  96  of the loader  90 . The pickup bar  98  grasps a tube  2  from one of the loader levels and feeds the tube  2  to the gripper  50  closest to the loader  90 . The gripper  50  grasps the tube  2  at an intermediate point, and the associated crossbeam  46  moves the gripper  50  in the “x” direction toward the first bending station  20 , until the tube  2  is in transverse alignment with the bending die  34 . The gripper  50  then moves in the “y” direction to align the dye  34  with the specific position on the tube  2  to be bent. Preferably the tube  2  has been grasped by the gripper  50  generally centrally, minimizing the lengths of the free ends of the tube  2  extending beyond the periphery of the station  20 , and thus reducing the tube bending “envelope.” With the tube  2  in position for bending by the first bending station  20 , the bending head  30  is moved along the “z” direction (i.e. vertically) to bring the bending dye  34  in alignment with the tube  2 . The bending arm  32  is actuated to force one of the extending free ends of the tube  2  around the bending dye  34 , which bends the tube  2  to the required angle and radius.  
         [0045]     If the control program calls for further bending by the first bending station  20 , the gripper  50  moves in the “y” direction to align the dye  34  with the next point on the tube  2  to be bent and the disk  62  rotates the tube  2  to the required angular orientation, so that bending along the bending plane B bends the tube  2  in the proper direction.  
         [0046]     When the bending cycle at the first bending station  20  is complete, which may for example be when the next bend requires a dye  34  with a different radius or the tube  2  needs to be repositioned in the gripper  50 , the bending head  30  is retracted to the rest position out of the path of travel of the gripper  50 . The disk  62  in the next successive gripper  50  rotates until the opening in its disk  62  is facing the tube  2 . The crossbeam  46  suspending the next successive gripper  50  moves in the “x” direction toward the first bending station  20 , and when the tube enters the jaws  54  the jaws  54  in the next successive gripper  50  close to grasp the tube  2 , and the jaws  54  in the first gripper  50  open to release the tube  2 . The crossbeam  46  suspending the next successive gripper  50  then moves in the “x” direction back toward the second bending station  22 , and the bending cycle commences at the second bending station  22  in the same fashion as that described above in relation to the first bending station  20 .  
         [0047]     Once the first gripper  50  has released the tube  2 , the first gripper  50  returns to the loader  90  to pick up another unbent tube  2  from stock at the same time that the second gripper  54  moves over to the second bending station  22  with the partially bent tube  2   a . One or more bends are effected at the second bending station  22 , following which the third gripper  50  moves over to the second bending station  22 , retrieves the partially bent tube  2   b  from the second bending station  22  and conveys it to the third bending station  24 . Likewise, a partially bent tube  2   c  is retrieved from the third bending station  24  by the fourth gripper  50  and moved to the fourth bending station  26 , which performs then final bends on the tube  2   c , following which the fifth and last gripper arm  50  retrieves the completely bent tube  2   d  from the fourth bending station  26  and deposits it onto the unloading shelf  8 . It will be apparent that all of the bending operations can operate in parallel in order to maximize the output of the apparatus.  
         [0048]     The bending operation is substantially entirely controlled by a single computer  14 . Typically, setting up the system  10  for a tube bending run involves roughly approximating the bends required at each bending station, programming the computer  14  to effect the bends in sequence at the designated points on the tube  2 , running a number of tubes  2  through the bending system  10 , and correcting any deviations from the desired finished product. When the tube bending system  10  starts to output fully bent tubes  2   d  conforming to the required specifications, a single operator can operate the tube bending system  10  simply by monitoring the bending operation at each bending station  20 ,  22 ,  24  and  26  to ensure the quality of the finished product, each tube  2  being bent identically (within established tolerances) to all previous tubes  2 . The operator merely needs to ensure that the loader  90  is kept stocked with unbent tubes  2 , and that no interruptions occur in the bending cycle at each of the bending stations. It is possible to monitor and even control the operation remotely, by providing a suitable communications link to the computer  14 .  
         [0049]     Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims.