Abstract:
A device that includes a frame equipped with guiding means, blank holder modules to be moved along the guiding means, means for blocking independently each blank holder module in a specific position, a magazine of end modules located near each end of the guiding means and gripping and handling means for grasping an end module to fix the end module to a blank holder module and vice-versa.

Description:
This application is a 371 of PCT/FR97/01227, filed Jul. 7, 1997. 
    
    
     The present invention relates to a device for adapting the size of a jaw. 
     BACKGROUND OF THE INVENTION 
     A jaw is a machine tool part designed for machining elements in the form of sheets, such as sheet metal, that holds the machined sheet firmly. Jaws are found, for example, in drawing machines and bending brakes. 
     The size of the jaw must be adapted to the size of the sheet metal to be machined and to the operation carried out. To be able to machine pieces of sheet metal of different sizes on the same machine tool, it is necessary to be able to change the size of the jaw. 
     Adapting the entire jaw to the size of the sheet metal to be machined without manual intervention is known. 
     The main drawback of conventional systems for adapting the size of a jaw automatically is that this operation takes a relatively long time, thus limiting productivity in relation to flexibility. The time required to machine the sheet metal is less than the time taken to adapt the jaw in known systems. Hence, a user will endeavor to fabricate several parts with the same size before changing the size of the jaw. 
     Moreover, for optimization reasons, manufacturers recommend first running operations requiring a short jaw on the machine tool equipped with a modular jaw, and subsequently, running operations requiring a long jaw. The user, thus, has to adjust the machining sequence to these constraints. 
     SUMMARY OF THE INVENTION 
     The goal of the invention is to furnish a device enabling the size of a jaw to be adapted very rapidly to improve the flexibility of a machine tool designed to receive this jaw and enable the various machining operations to be conducted in any sequence without thereby affecting cycle time. 
     For this purpose, the device it proposes consists of a frame provided with guide means, jaw modules designed to move along the guide means, means for independently locking each jaw module into a given position, a magazine of end modules located near each end of the guide means and gripping and handling means for gripping an end module in a magazine to position the end module against a jaw module and withdraw an end module positioned against a jaw module to replace it in a magazine. 
     The configuration of the jaw can then be changed very rapidly. One need only move the jaw modules not used for making a predefined bend toward the ends of the guide means and regroup the jaw modules needed for this bending operation at the center of the guide means then, with the aid of gripping means, bring an end module to each end of the group of jaw modules to form a jaw of the desired size for making the bend. All these operations can be conducted rapidly, because the jaw modules can move at the same time as the end modules. 
     Advantageously, a module, called a central module, is mounted in a fixed position relative to the frame. The movable jaw modules are located on each side of the central module. The jaw modules on a given side of the central module are all similar, and the jaw modules on one side of the central module have a different length in the direction of the guide means than those located on the other side of the central module. The central module then serves as a stop when the jaw modules are being moved. The different lengths of the jaw modules on one side and on the other side of the central module enables a greater variety of different jaw lengths to be offered. If, for example, all the jaw modules and the central module are 100 mm long, the assembly formed by the jaw modules and the central module will always be a multiple of 100 mm long. On the other hand, if the jaw modules on one side are 100 mm long and those on the other side are 50 mm or 150 mm long, it will also be possible to have total lengths that are multiples of 50 mm. Of course, other values and other length ratios are possible. 
     In a preferred embodiment, the guide means are comprised of at least one rectilinear rail integral with the frame. In this case, advantageously, the jaw modules are mounted on two parallel rails between which is guided a drive bar, and the locking means enable each jaw module, independently of the others, to be coupled to either the drive bar or the guide rails. To move the jaw modules, one need only join them to the drive bar and move the latter with these modules. The other jaw modules that are not supposed to move remain coupled to the frame. To shift all the jaw modules that are to be moved, one need only move the drive bar once in one direction with the modules moving in the same direction, then move the jaw modules that are supposed to move, in the other direction. 
     In a preferred embodiment, each jaw module has a locking part that can move perpendicularly to the guide rails. The locking part has a U-shaped section perpendicularly to the guide rails with the end of one arm of the U being in a lengthwise groove provided in a rail. The other arm end of the U is opposite the other guide rail and the drive bar projects between these two arms. A spring pretensions the locking part in one direction making the locking part coupled to the frame or the drive bar. An actuator is provided to act against the spring to make the locking part coupled to the drive bar or the frame. 
     To drive the drive bar, it is provided with a rack meshing with a gear driven by a motor. Other means are of course possible: the bar can, for example, be connected to an actuator or to a linear motor. 
     In the device according to the invention, the gripping and handling means may be a gripper moving lengthwise on the frame. Other solutions such as a manipulator robot are also possible. 
     The invention also proposes using a device such as that described above on a machine designed to make bends in a piece of sheet metal, having two jaws and one bending tool. In such a machine, there is no point in having two modular jaws; a single jaw is generally sufficient. 
     Such a machine, or bending brake, can adapt the size of its jaw during the time taken for the bent piece of metal to leave and the metal to be bent to take its place. For sheets to be bent on two opposite sides, the invention proposes a machining center, characterized by having two bending brakes according to the invention, the two bending brakes being opposite each other and able to move toward or away from each other, and by a conveyor designed to convey the pieces of sheet metal being located between the two bending brakes. The conveyor can also be provided with a central rotator which is placed between the two bending brakes and is able to turn the sheets to be bent on four sides—or more. 
     In any event, the invention will be properly understood with the aid of the description that follows with reference to the attached schematic drawings that show a device according to the invention as a nonlimiting example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of this invention will be described in detail, with reference to the following drawings wherein like numerals represent like elements and wherein: 
     FIG. 1 shows a machine designed to bend pieces of sheet metal, provided with a device according to the invention, 
     FIGS. 2 and 3 are schematic front views showing the device in two different positions, 
     FIG. 4 shows a drive mechanism for jaw modules, 
     FIG. 5 is a cross section on an enlarged scale along line  5 — 5  in FIG. 4, 
     FIG. 6 is a cross section on an enlarged scale along line  6 — 6  in FIG. 4, 
     FIGS. 7 to  10  represent several possible configurations of a device according to the invention, 
     FIG. 11 shows in a side view two bending brakes opposite each other, each of them provided with a device according to the invention, and 
     FIG. 12 is a perspective view of an end module. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     As one application example of a device for adapting the size of a jaw, FIG. 1 shows a sheet metal bending brake provided with such a device. 
     This bending brake has a bench  2 , a brush table  4  designed to receive a sheet of metal (not shown in this figure) to be bent, a bending tool  6 , a fixed lower jaw  8 , an upper jaw  10  mounted on an arm  12  pivoting around an axis  14 , and a manipulator robot  16  to move the sheets to be bent. 
     The width of upper jaw  10  is modular. Thus, the bending brake can be adapted to numerous sheet dimensions and several types of bending. The means whereby the size of jaw  10  is modified are described below. 
     FIGS. 2 and 3 show schematically upper jaw  10  of the bending brake of FIG.  1  and the device that varies its width. Jaw  10  has several jaw modules  18 ,  19 , all of similar 
     These modules are guided on the two parallel rails  22 . Between these two rails  22  is a space forming a groove in which a drive bar  40  is guided. This drive bar  40  is provided with a rack  42  at one of its ends, with which a gear  44  driven rotationally by a motor (not shown) meshes. 
     Each jaw module  18 ,  19  is provided with a device that either joins it to rails  22  or joins it to drive bar  40 . When drive bar  40  moves, it brings with it the jaw modules  18 ,  19  attached to it, the others remaining stationery. Thus, it is possible to move each jaw module individually, or in a group of jaw modules, or any other conceivable combination. 
     FIGS. 5 and 6 show a cross section of a jaw module  18  and its associated locking device. The latter comprises in particular a locking part  46 , a spring  48 , and a pneumatic actuator  50 . 
     Locking part  46  is placed in a recess provided in the side of the jaw module that faces rails  22 . This recess is such that the locking part can move perpendicularly to rails  22 . In a sectional plane perpendicular to rails  22  (FIGS.  5  and  6 ), locking part  46  has a generally U-shaped cross section. The arms of the U point to rails  22 . The end of a first arm fits into a groove  52  provided longitudinally in a rail  22 . The second arm faces the other guide rail  22 . Drive bar  40  projects from the two rails  22  and is located between the two arms of locking part  46 . The second arm of this part  46  faces drive bar  40 . 
     At its first arm, the locking part is subjected to the action of spring  48 , which urges the first arm of the locking part toward drive bar  40 . At the second arm is pneumatic actuator  50 . The latter can urge locking part  46  against spring  48  and thus push the second arm in the direction of drive bar  40 . 
     FIG. 5 shows the position of jaw module  18  when actuator  50  is not acting. Spring  48  then urges locking part  46  toward drive bar  40 . The first arm of this locking part  46  then abuts the wall of groove  52  provided in a rail  22 . By reaction, jaw module  18  moves in the opposite direction, namely leftward in FIG.  5 . Module  18  then abuts the outer face of rail  22  opposite spring  48 . Thus, the jaw module is locked onto the two rails  22  and is thus coupled to frame  20 . 
     FIG. 6 shows the position of jaw module  18  when actuator  50  acts. Actuator  50  then pushes locking part  46  so that its second arm abuts drive bar  40 . By reaction, jaw module  18  moves in the direction opposite to the direction of movement of locking part  46 , namely rightward in FIG.  6 . The dimensions of the various guide grooves guiding jaw module  18  on rails  22  are such that jaw module  18  then abuts drive bar  40 , not rail  22  opposite pneumatic actuator  50 . Thus, jaw module  18  is coupled to drive bar  40 . 
     FIGS. 7 to  10  show several possible jaw configurations, among numerous others, obtained by associating jaw modules  18 ,  19  with end modules  36 ,  37 . FIG. 7 shows a configuration in which all the jaw modules  18 ,  19  are grouped around central module  28  and an end module  36 ,  37  is located at each end. 
     FIG. 8 shows another configuration. When changing from the configuration of FIG. 7 to that of FIG. 8, several steps are necessary, but they can be effected very rapidly. End modules  36 ,  37  are first replaced in their respective magazines. The three leftmost jaw modules  18  in FIGS. 7 and 8 are coupled to drive bar  40 . The latter is moved leftward. The pressure in actuators  50  corresponding to these three jaw modules  18  is released. These modules thus become coupled to rails  22  and are fixed relative to frame  20 . The three rightmost jaw modules  19  in FIG. 7 are then coupled to drive bar  40 , subjecting the corresponding actuators  50  to pressure. All the other jaw modules  18 ,  19  remain coupled to rails  22  and are fixed relative to frame  20 . Drive bar  40  moves rightward, bringing with it the three jaw modules  19 . 
     While these movements of jaw modules  18 ,  19  are taking place, grippers  26  grip each end module  36 ,  37  in a corresponding magazine  24 ,  25  and position it on module  18 ,  19  forming the end of the jaw. 
     If, in the bending operation to be carried out by the bending brake, it is not necessary to have an end module at the end of the jaw, end modules  36 ,  37  can remain in place and be between two jaw modules  18 ,  19 , as shown in FIG.  9 . The time necessary for changing the configuration can then be slightly reduced. 
     FIG. 10 shows a configuration in which an end module  37  is placed directly on central module  28 . Thus, it is possible to have a narrow jaw. 
     By judiciously choosing the widths of jaw modules  18 ,  10  and end modules  36 ,  37 , it is possible to cover an entire range of widths for the jaw obtained with a predetermined incrementation. The dimensional example, indicated below, enables all widths multiples of 5 mm to be obtained, starting at the width of 310 mm. 
     Thus, for example, one can choose jaw modules  18  with a width of 100 mm, which in the example shown in the drawing are at the left of central module  28 , jaw modules  19  with a width of 150 mm, which will be to the right of central module  28 , four end modules  36  associated with magazine  24  and hence destined to be mounted on jaw modules  18  with dimensions 80 mm, 90 mm, 100 mm, and 105 mm, and four end modules  37  associated with magazine  25  and hence destined to be mounted on jaw modules  19 , measuring 80 mm, 85 m, 95 mm, and 105 mm. If, as shown in FIGS. 7 to  10 , the jaw has five 100 mm jaw modules  18  and four 150 mm jaw modules  19 , it is possible to assemble the various modules  28 ,  18 ,  19 ,  36 ,  37  to obtain any jaw width that is a multiple of 5 mm and is between 310 mm and 1310 mm. 
     Of course, the movement of grippers  26  and drive bar  40  can be controlled by a computer (not shown) which, depending on the necessary jaw width and the type of bend to be created, calculates the configuration to be adapted and the paths of the various elements, then supplies this information to a central control system that controls the movement of these elements. 
     The design of the modular jaw as described above allows a very rapid transition from one configuration to the next, lasting about ten seconds. Thus, it becomes possible to change the configuration at the same time as changing the sheet metal or the position of this sheet. Contrary to machines known to date, which require about ten times the setup time, the jaw configuration can be changed without taking extra time. 
     It then becomes conceivable to place two bending brakes opposite one another, as shown in FIG. 11. A conveyor, not shown, brings a piece of sheet metal  54  to a position between the two bending brakes. A central rotator  56  is located between the two bending brakes to rotate a sheet of metal that is to be bent on four sides, or more. Of course, to adapt to the various dimensions of the sheet and the type of bend to be made, the two bending brakes must be able to move away from and toward each other. For this purpose, they are both mounted on a common base  58 . A computer and a central control system can be provided to calculate and control the movements of the two machines on common base  58 , but they can also control the modular jaws of the two machines. 
     It goes without saying that the invention is not confined to the embodiment described above as a nonlimiting example; on the contrary it covers all variants. 
     Thus, for example, each jaw module could be equipped with drive means enabling it to move by itself on the guide means. The drive bar would be replaced by a fixed rack extending over the entire length of the frame and each jaw module would be equipped with a motor with a gear at the end of its shaft. A brake would prevent the gear from turning, thus, locking the module onto the frame. The modules could be guided on guide columns. 
     The device enabling the size of a jaw to be adapted is not necessarily adapted to a bending brake a machine for bending around a specific radius. It can be mounted on any machine having a jaw such as a machine used to bend at an angle. 
     The size, shape, and number of the modules are provided only as examples to illustrate the invention. It is of course possible to multiply the number of modules to increase the number of possible configurations.