Abstract:
The invention concerns a bending machine comprising a machine frame, an upper bar equipped with a tool and a lower bar likewise equipped with a tool, the upper bar and the lower bar being mounted mutually mobile on the frame. The machine comprises at least one drive means for moving the tools of the lower and upper bars towards each other, so as to shape a plate-shaped part to be machined located between said tools. The invention aims at providing that the force exerted by the tools of the lower and upper bars should be the highest possible, at the least possible cost. Therefor, the drive means comprises at least one displacement drive element, to develop an opening and closing movement of the upper bar and the lower bar relative to each other, and at least one force drive element to exert a higher force that that of the displacement drive element, so as to shape the part to be machined which is located between the upper bar tool and the lower bar tool, the displacement drive element being immobilized and locked during the forming operation.

Description:
This application is a continuation of international application number PCT/EP2003/006730 filed on Jun. 26, 2003. 

   The present disclosure relates to the subject matter disclosed in international application number PCT/EP2003/006730 of Jun. 26, 2003 and German application number 102 45 778.6 of Sep. 26, 2002, which are incorporated herein by reference in their entirety and for all purposes. 
   BACKGROUND OF THE INVENTION 
   The invention relates to a bending machine comprising a machine frame, an upper beam having an upper beam tool and a lower beam having a lower beam tool, the upper beam and the lower beam being mounted such that they can move relative to one another on the machine frame, and at least one drive for moving the upper beam tool and the lower beam tool toward one another in order to act on a workpiece made from flat material and located between the two beams. 
   Bending machines of this type are known from the prior art. In these bending machines, the drive is usually dimensioned such that it can generate sufficient forces to hold a workpiece securely between the upper beam and the lower beam. 
   However, this solution has the drawback that if a speed of the relative movement between upper beam and lower beam which is required for the desired processing times of the workpieces is to be reached, the forces with which the upper beam tool and the lower beam tool can act on the workpiece are limited or require a level of outlay which is not economically justifiable. 
   Therefore, the invention is based on the object of improving a bending machine of the generic type in such a manner that forces which are as high as possible are applied to the workpiece by the upper beam tool and lower beam tool at the lowest possible cost. 
   SUMMARY OF THE INVENTION 
   In a bending machine of the type described in the introduction, this object is achieved, according to the invention, by virtue of the fact that the at least one drive comprises at least one displacement drive for generating an opening and closing movement of the upper beam and the lower beam relative to one another and at least one force drive for generating a greater force than the displacement drive in order to deform the workpiece disposed between the upper beam tool and the lower beam tool, and in that the displacement drive is stationary and blocked during deformation. 
   The advantage of the solution according to the invention is to be regarded as residing in the fact that the displacement drive can generate a rapid relative movement between upper beam and lower beam, whereas the force drive opens up the additional option of applying high forces to the workpiece by the upper beam tool and lower beam tool in order thereby to be able to deform this workpiece. 
   In this context, the term deform is to be understood as meaning shaping of a workpiece by the interaction of upper beam tool and lower beam tool. Deformation of this nature comprises, for example, closing and compression of bends or folds, stamping of beads or any other form of deformation operations carried out on flat materials. 
   The force drive can be of particularly expedient configuration if the force drive is formed such that during the generation of a force which moves the upper beam tool and the lower beam tool toward one another, its speed of displacement is lower than that of the displacement drive. 
   This in particular enables the driving power for the force drive to be kept at a low level despite the large force generated and also allows the rapid displacement movements which take place over long displacement distances to be transferred to the displacement drive. 
   It is particularly expedient if the force that can be generated by the force drive exceeds the force that can be generated by the displacement drive by a factor of at least two, preferably at least five, even more preferably at least ten. 
   In the explanation of the invention which has been given thus far, no further details have been provided as to the way in which the drive is disposed relative to the upper beam and the lower beam. An advantageous exemplary embodiment provides that the at least one drive, which comprises in each case one displacement drive and one force drive, is disposed at an end of the upper beam. 
   This could be configured such that the drive is disposed only on one side of the upper beam and of the lower beam. It is particularly expedient if in each case one of the drives according to the invention is disposed on both sides of the upper beam and the lower beam. 
   Thus far, no further details have been given as to the way in which the displacement drive and force drive are disposed relative to one another. By way of example, it would be conceivable for the force drive to be disposed in such a way that it is operative in any partial region between a beam and the tool associated with this beam, whereas the displacement drive serves to move the upper beam and lower beam toward one another. 
   However, it is particularly advantageous if the force drive and the displacement drive are combined to form a drive unit which as a whole is operative only between the upper beam and the lower beam, so that both the force drive and the displacement drive effect a relative movement between the upper beam and the lower beam. 
   Where the present invention speaks of the drive unit effecting a relative movement of the upper beam with respect to the lower beam, and in so doing acts on the upper beam and the lower beam, it is not necessarily imperative that the drive unit must only act directly on the upper beam and the lower beam. In many cases, one of the beams, in particular the lower beam, is fixedly connected to the machine frame. In a situation of this nature, the drive unit likewise acts only between upper beam and lower beam in the context of the invention if the drive unit engages on the machine frame, since the latter is fixedly connected to one of the beams and therefore the drive unit is also connected between this beam that is fixedly connected to the machine frame and the movable beam. 
   No further details have been given as to the configuration of the displacement drive itself. 
   To ensure that the force drive can become active when the displacement drive is inactive and therefore blocked, an advantageous solution provides for the displacement drive to comprise a blocking device which is active when the drive is stationary. This blocking device creates the possibility of ensuring that the displacement drive, in any event when stationary, does not execute any movement whatsoever and therefore the entire force of the force drive can become active. 
   As an alternative or in addition to the provision of a blocking device, another favorable solution provides that the displacement drive is blocked by a self-locking action when it is stationary. This solution has the advantage that the blocking device can be dispensed with or at least, if it is still present for safety reasons, can be configured in such a way that the forces which it has to absorb are lower. 
   No further details have been provided as to the configuration of the displacement drive. A particularly expedient solution provides that the displacement drive is formed as a spindle drive, comprising a threaded spindle and a spindle nut. 
   This solution is particularly expedient if the spindle nut is drivable by a drive motor. 
   To generate a self-locking action in the region of the drive of the spindle nut, an expedient solution provides that the spindle nut is driven by means of a self-locking transmission. 
   Thus far, no further details have been given as to the configuration of the force drive. According to a particularly expedient solution, the force drive is formed as a hydraulic drive. 
   To make the hydraulic drive as small and compact as possible, it is preferably provided that the hydraulic drive comprises a plurality of piston surfaces which act in parallel. 
   The hydraulic drive could be active indirectly, i.e. via an intermediate transmission, but it is particularly expedient if the hydraulic drive is disposed so as to act directly in the drive unit, i.e. the hydraulic drive itself effects the relative movement of upper beam and lower beam, without the need for any intermediate transmission. 
   To allow efficient operation of the hydraulic drive, it is preferably provided that a hydraulic unit of the hydraulic drive be disposed at one of the beams. 
   As an alternative to providing a directly operating hydraulic drive, in another preferred exemplary embodiment of the solution according to the invention it is provided that the force drive comprises a lever transmission with a drive for this. 
   In this case, the drive for the lever transmission may either be a pivot drive or a linear drive. It is even conceivable for the linear drive provided to be a pneumatically or hydraulically actuable cylinder. 
   A very wide range of solutions are conceivable with regard to the control of the bending machine according to the invention having the displacement drive and the force drive. 
   By way of example, it would be conceivable for the displacement drive and force drive to be used in parallel. In this case, however, it would be necessary for the displacement drive to be formed to be self-locking, so that the force drive can then act with the greater force in any position of the displacement drive. 
   The bending machine according to the invention can be made simpler if a control unit is provided, which actuates either the displacement drive or the force drive, so that in particular the displacement drive does not have to operate under conditions in which the greater force of the force drive is active. 
   To allow controlled use of the high force that can be generated by the force drive, it is preferably provided that the force that can be generated by the force drive can be controlled by the control unit, so that the use of the full force of the force drive can be effected in a controlled manner only during the respectively corresponding processing operations. 
   A particularly advantageous solution in this respect provides for the control unit to use the force drive as a function of the respective processing operation. 
   This would provide the option, for example, of performing the fixing using the displacement drive, which generates sufficient force, during normal bending operations using a bending beam, in which the workpiece is merely clamped, i.e. fixed, between upper beam tool and lower beam tool, and consequently the force drive need not be used at all for this purpose. 
   In this case, the force drive is then only used in situations in which deformation of the workpiece, i.e. for example bending of a fold, closing of a fold or any type of further deformation processes is to be carried out by the upper beam tool and the lower beam tool. 
   However, in order not to make the control outlay excessively complex, in another advantageous exemplary embodiment of a bending machine according to the invention it is provided that the control unit finally actuates the force drive during clamping of the workpiece in order for the latter to be bent by means of a bending beam, so that the force drive is always ultimately responsible for generating the force which acts on the workpiece. 
   As an alternative or in addition to the above, it is provided that the control unit finally actuates the force drive each time the workpiece is acted on by means of the upper beam tool and the lower beam tool in order to be processed, so that in any event the force that can be generated by the force drive can be utilized for the processing. 
   Further features of the invention form the subject matter of the following description and of the illustration in the drawing of a number of exemplary embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a perspective front view of a bending machine according to the invention; 
       FIG. 2  shows a section on line  2 — 2  in  FIG. 1 ; 
       FIG. 3  shows a section on line  3 — 3  in  FIG. 1  for a first exemplary embodiment of a bending machine according to the invention; 
       FIG. 4  shows an enlarged illustration of a region A in  FIG. 3 ; 
       FIG. 5  shows an illustration of an excerpt from a first example of a deformation on the basis of a section similar to that shown in  FIG. 3  in the region of upper beam tool and lower beam tool; 
       FIG. 6  shows an illustration similar to that shown in  FIG. 5  of a second example of a deformation; 
       FIG. 7  shows a section similar to that shown in  FIG. 3  through a second exemplary embodiment of a bending machine according to the invention, and 
       FIG. 8  shows a section similar to that shown in  FIG. 3  through a third exemplary embodiment of a bending machine according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An exemplary embodiment of a bending machine according to the invention, illustrated in  FIG. 1 , comprises a machine frame which is denoted overall by  10  and has side columns  12  and  14 , between which, as illustrated in  FIG. 2 , an upper beam  16  and a lower beam  18  extend. 
   By way of example, the lower beam  18  is fixedly connected to the columns  12  and  14 , while the upper beam  16  is movable relative to the lower beam  18 . 
   Furthermore, the upper beam  16  carries an upper beam tool  20  and the lower beam  18  carries a lower beam tool  22 , between which a workpiece  24  made from flat material, for example from sheet metal, can be clamped in such a way that a strip of this material which projects beyond the upper beam tool  20  and the lower beam tool  22  can be bent out of a plane  28  that can be defined by the lower beam tool  22  and the upper beam tool  20 . 
   For this purpose, the bending machine is provided, for example, with a bending beam  30 , which extends between bending beam holders  32  disposed at its ends and can move with these bending beam holders  32  about a pivot axis  34 , the pivot axis  34  preferably lying above the clamping plane  28 . 
   The bending beam in this case acts, by means of a bending beam tool  36 , on the strip  26  of the workpiece that is to be bent over, with the entire bending beam  30  being pivotable about the pivot axis  34 . 
   To displace the upper beam  16  in a direction of movement  40  relative to the lower beam  18 , so that the workpiece  24  is either acted on by the upper beam tool  20  of the upper beam  16  and pressed onto the lower beam tool  22  of the lower beam  18 , or the workpiece  24  can move freely between the upper beam  16 , which has been lifted off the lower beam  18 , and the lower beam  18  itself, the bending machine according to the invention is provided with a drive, which is controllable by a control unit  42  and comprises two drive units  46  and  48 , which are in each case disposed in end regions  52  and  54  of the upper beam  16  and of the lower beam  18  and effect a relative movement between the upper beam  16  and the lower beam  18 , in the situation illustrated by way of example cause the upper beam  16  with the upper beam tool  20  to be lifted off the workpiece  24  resting on the lower beam  18  with the lower beam tool  22 , or cause the upper beam tool  20  to act on the workpiece  24  toward the lower beam tool  22 . 
   In a first exemplary embodiment of a bending machine according to the invention, illustrated in  FIG. 3 , each of the drive units, in this case the drive unit  46  illustrated, comprises a displacement drive  56  and a force drive  58 , the two of which are directly coupled to one another, so that the drive unit  46  on one side acts on a bearing element  62 , which is fixedly connected to the upper beam  16 , and on the other side acts on the lower beam  18  via a bearing element  64  fixedly connected to the lower beam  18 . 
   The drive unit  46  is in this case constructed in such a way that both the displacement drive  56  and the force drive  58 , either alternately or together, act on the bearing element  62  and on the bearing element  64 , depending on how they are actuated by the control unit  42 . 
   In the first exemplary embodiment, illustrated in  FIG. 3 , the displacement drive  56  comprises a threaded spindle  66  which is held nonrotatably and extends with its longitudinal axis  68  running transversely with respect to the clamping plane  28 , passing through a spindle nut  70 , which is held such that it cannot slide in the direction of the longitudinal axis  68  of the threaded spindle  66  by two bearings  72  and  74  but can rotate about the longitudinal axis  68  in the bearing element  64 , which is formed as a bearing housing. 
   Driving of the spindle nut  70  and therefore rotation of the latter relative to the threaded spindle  66  then effects displacement of the threaded spindle  66  in the direction of its longitudinal axis  68  and therefore in the direction toward the upper beam  16  or away from the upper beam  16 . 
   For the spindle nut  70  to be driven in rotation, the spindle nut is provided on its peripheral side with external toothing  76  in which a worm  78  engages, so that the worm  78  and the external toothing  76  together form a worm transmission. 
   The worm  78  can be driven by a common drive shaft  80 , which extends between the two drive units  46  and  48  and for its part is drivable, via a step-down transmission  82 , by a motor  84 , so that the spindle nuts  70  of the two drive units  46  and  48  can always be driven synchronously with one another by means of the motor  84 . 
   The displacement drive  56  as a whole, i.e. the combined unit made up of threaded spindle  66 , spindle nut  70 , worm transmission  76 ,  78 , step-down transmission  82  and motor  84 , is formed in such a way that when the motor  84  is stationary, on account of the self-locking action it blocks a movement of the threaded spindle  66  in the direction of its longitudinal axis  68 . 
   The threaded spindle  66  is fixedly connected by one end  88 , preferably the end  88  facing the upper beam  16 , to a piston rod  92  of a triple piston  94 , which, as illustrated in  FIGS. 3 and 4 , comprises three annular piston surfaces  102 ,  104 ,  106  which are disposed in succession in the direction of a longitudinal axis  96  of the piston rod  92  and facing which are disposed cylinder chambers  112 ,  114 ,  116  in a cylinder housing  118 , it being possible for hydraulic medium to be fed to the cylinder chambers  112 ,  114 ,  116  simultaneously via a distribution passage  120  in the cylinder housing  118 , so that a considerable force can be generated with a small configuration of the force drive  58  by medium being applied to the piston surfaces  102 ,  104 ,  106 . 
   The cylinder chambers  112 ,  114 ,  116  are fed by a hydraulic unit  122 , which is preferably disposed located at the upper beam  16  and is actuable by the control unit  42 , in order to generate pressurized hydraulic medium so as to move the piston  94  relative to the cylinder housing  118 . 
   The cylinder housing  118  for its part is located on the bearing element  62  fixedly connected to the upper beam  16 , specifically on a side of the bearing element  62  which is remote from the lower beam  18 , so that application of hydraulic medium to the cylinder chambers  112 ,  114 ,  116  leads to the cylinder housing  118  acting on the bearing element  62  and causing it, together with the upper beam  16 , to move toward the lower beam  18 , so that the cylinder housing  118  is displaced relative to the piston rod  92  in the direction of the lower beam  18 . 
   Furthermore, a set of disk springs  124  is provided on an opposite side of the bearing element  62  from the cylinder housing  118 , which set of disk springs  124  is supported on one side against the bearing element  62  and on the other side against a support ring  126 , which simultaneously produces a connection to the end  88  of the spindle  66 . 
   The set of disk springs  124  causes the bearing element  62 , together with the upper beam  16 , to move in the direction away from the lower beam  18  when the cylinder chambers  112 ,  114 ,  116  are unpressurized and therefore the cylinder housing  118  can move toward the piston  94  and away from the lower beam  18 . 
   The dimensions of the set of disk springs  124  are such that without pressure being applied to the cylinder chambers  112 ,  114 ,  116  the cylinder housing  118  is displaced away from the lower beam  18  until it comes to a mechanical stop. 
   Furthermore, by way of example, the threaded spindle  66  is fixed such that it cannot rotate relative to the upper beam  16  by means of a nonpositive lock effected by the prestressed set of disk springs  124 , which fixes the unit composed of support ring  126 , piston rod  92  and threaded spindle  66  such that it cannot rotate with respect to the bearing  62 . 
   In the solution according to the invention, it is now possible to use the displacement drive  56  to move the upper beam  16  and the lower beam  18  very quickly relative to one another, for example at speeds of the order of magnitude of 50 to 100 mm/sec, without this displacement drive  56  being able to apply high forces, so that it is impossible for a high force to be generated between the upper beam tool  20  and the lower beam tool  22 . 
   However, for many bending operations carried out by means of the bending beam  30  for example, the force is sufficient to clamp the workpiece  24 . 
   If high forces are required, the force drive  58  can be used, this drive being able to generate a force which is more than double, preferably more than five times, particularly preferably more than ten times, that of the displacement drive  56 . However, the force drive  58  only allows velocities of the relative movement between the upper beam  16  and the lower beam  18  in the region of a few millimeters per second or less. 
   The much higher force which can be generated by the force drive  58  offers the advantage, however, of realizing, with the bending machine, as illustrated in  FIG. 5  or  FIG. 6 , also additional operations, for example deformation of the workpiece. By way of example, it is possible, as illustrated in  FIG. 5 , to bend over the workpiece  24  between the upper beam tool  20  and the lower beam tool  22 , i.e. to press together a strip  26  which has been bent over onto the workpiece  24  over a region  25 , thereby effecting what is known as a closed fold without any cavity between the strip  26  and the region  25  of the workpiece  24 . 
   On the other hand, however, it is also possible, for example, as illustrated in  FIG. 6 , to stamp a bead  23 , for example, into the workpiece  24  by means of the force drive  58  by suitable shaping of the upper beam tool  20  and lower beam tool  22 . 
   In the simplest case, the force drive  58  is always used with the displacement drive  56  stationary, without the force of the force drive  58  having any adverse effect on the displacement drive  56  such that the latter would likewise be displaced, since—as has already been explained—the displacement drive  56  is formed to be self-locking. 
   In principle, given a self-locking form of the displacement drive  56 , it would also be conceivable, in parallel with the displacement drive, for example while the workpiece  24  is being acted on by the upper beam tool  20  in order to be pressed onto the lower beam tool  22 , to start up the force drive  58  at the same time as and in addition to the displacement drive  56 , but on account of the force action of the force drive  58  this would lead to the displacement drive  56  being blocked when the force drive  58  unfurls its full force, and therefore to the motor  84  likewise being blocked. 
   Furthermore, in one particular embodiment of the solution according to the invention, it is also conceivable for the hydraulic unit  122  to be formed in such a way that it can be used to predetermine the force generated by the force drive  58  in a metered and controlled way, so that different forces generated by the force drive  58  can be used depending on the manner of processing of the workpiece  24 . 
   By way of example, it would be conceivable for the force drive  58  to apply lower forces when it is merely intended to clamp the workpiece  24  between the upper beam tool  20  and the lower beam tool  22 , whereas greater forces are applied when it is intended to deform the workpiece  24  by the action of the upper beam tool  20  and the lower beam tool  22  instead of just clamping the workpiece  24 . 
   In a second exemplary embodiment of a bending machine according to the invention, illustrated in  FIG. 7 , in the drive unit  46 ′ the displacement drive  56  is formed in the same way as in the first exemplary embodiment. By contrast, the force drive  58 ′ is not formed as a direct-acting hydraulic drive, but rather as a lever transmission  130  having a long lever  132  and a short lever  134 , in which case, starting from a common pivotal connection point  136 , the long lever  132  is connected to the upper beam  16  by means of a pivot point  138 , whereas the short lever is connected to a force-transmission rod  142  by means of a pivot point  140 , the force-transmission rod  142  for its part in turn being connected to the end  88  of the threaded spindle  66 . 
   Displacement of the common articulation point  136  in the direction toward a dead center position and away from the latter therefore makes it possible to vary the distance between the pivot points  138  and  140  and therefore likewise to generate a great force for moving the upper beam  16  relative to the lower beam  18 . 
   For this purpose, a linear drive  142  is provided for moving the pivot point  136 , which linear drive may, for example, be a hydraulic drive, or alternatively may also be a spindle drive. For its part, the linear drive  142  is likewise connected to the upper beam  16 , via a pivot point  144 , and can therefore move with the upper beam  16 . 
   In a third exemplary embodiment of a bending machine according to the invention, illustrated in  FIG. 8 , each of the drive units in this case comprises the drive unit  46 ″, a force drive  58 , which corresponds to that of the first exemplary embodiment, while the displacement drive  56 ′ is formed by a hydraulic cylinder  150 , which can be fed by a hydraulic unit  152  in order to move the upper beam  16  upward and downward away from the lower beam  18 . 
   To allow the force drive  58  to be used when the hydraulic cylinder  150  is stationary, the hydraulic cylinder  150  must likewise be able to absorb the forces applied by the force drive  58 . Since this can only be realized with difficulty using the hydraulic cylinder  150 , the displacement drive  56 ′ is provided with a blocking device  154 . The latter comprises on the one hand a toothed rod  158  arranged as an extension of a piston rod  156  of the hydraulic cylinder  150  and two holding jaws  162  and  164 , which are toothed on the front side, are disposed in a housing  160  that has the toothed rod  158  passing through it, and can be moved toward or away from the toothed rod  158  by means of pressure chambers  166  and  168 , respectively, with the holding jaws  162  and  164  engaging in a positively locking manner in the toothed rod  158  in the position in which they are forced toward the toothed rod  158 . 
   As soon as the hydraulic cylinder  150  becomes stationary, therefore, the holding jaws  162  and  164  are pressed onto the toothed rod  158  by the hydraulic unit  152  and thereby fix it in a positively locking manner with respect to the housing  160  and therefore with respect to the lower beam  18 . 
   If the displacement drive is to be moved, the application of pressure to the holding jaws  162  and  164  is released, and therefore so is the positively locking fixing of the toothed rod  158  relative to the lower beam  18 , so that the displacement drive  56 ′ can operate under the action of the hydraulic cylinder  150 . 
   It is preferable for the hydraulic unit  152  to be operated in such a way that it inevitably activates the blocking device  154  each time the hydraulic cylinder  150  is stationary, and therefore the displacement drive  56 ′ is automatically blocked with respect to movement when the hydraulic cylinder  150  is stationary, so that in a stationary position the displacement drive  56 ′ is always able to absorb the forces which may be generated by the force drive  58 . 
   In both the second exemplary embodiment and the third exemplary embodiment, the operation of the displacement drives  56 ,  56 ′ and of the force drives  58 ,  58 ′ can take place in the same way as in the first exemplary embodiment, by means of the control unit  42 , and consequently in this respect reference is made in full to the statements made in connection with the first exemplary embodiment.