Abstract:
The invention relates to a machine for stamping, bending and/or mounting of sheet metal parts with at least one upper housing part  14  and at least one lower housing part  16 . Preferably, several are arranged in a row. On each housing part  14, 16  the carriage apparatus  20  is engaged by a motor. In order to increase the productivity of the machine, the carriage is driven by a program-controlled synchronous motor. In one embodiment a gear is positioned between motor and carriage which is formed preferably as an eccentric disc, connecting rod or elbow lever. The program-controlled synchronous motor is embodied as a torque motor and coupled by the gear member with the carriage.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates to a machine for stamping, bending and/or mounting sheet metal parts, comprising a plurality of housing boxes which are vertically aligned and connected. Several housing boxes can be arranged in a row. Each housing box contains an upper housing part and optionally a lower housing part. The upper and lower housing parts are horizontally aligned and connected to each other in each housing box. Each housing part contains at least one carriage apparatus including a carriage guide, which engages a motor. 
     Moreover, the invention relates to a method for operating such a machine. 
     The present invention relates in general to an indexed advancing machining device in which a workpiece is subjected to stamping, bending, deepdrawing or other machining processes, wherein all machining processes are carried out by a cycled, indexed, stepwise advancement of the workpiece from one to the next processing step. The workpiece is thus subjected sequentially to a series of machining processes until the entire machining process is completed by the final process. The individual machining processes are carried out in a single system. Depending on the workpiece and the number of required process steps, a plurality of machines can be sequentially positioned in a modular arrangement according to EP 0 875 311. They are suitable especially for the mass production of sheet metal pieces because of their high production capacity, their short workpiece throughput times, and their high degree of automation. 
     EP-A 0 103 885 teaches a machine in which elongate upper and lower housing parts are connected to one another by spacing bodies at their ends to form a frame. At the front side and at the backside of each housing part, a number of carriage apparatus are fastened on which, in turn, corresponding tools are mounted for the workpiece to be produced, respectively. Worm gear shafts are provided in the housing parts and their end faces are flush with the housing parts. Several such housing frames can be connected to one another at their end faces wherein the connection of the drive shafts is realized by curved teeth couplings. 
     DE-A 195 35 949 teaches a machine in which housing parts extend between two vertical end beams, and the arrangement of several housing parts with their end face is not suggested. 
     EP-A 0 127 156 discloses a machine in which the housing comprises two horizontal supports and two vertical supports, wherein fixedly arranged torque output locations are provided in all four supports for coupling with a carriage apparatus. 
     DE-C 40 10 115 shows a machine for stamping, bending and mounting which, however, differs from the machine of the present invention in that the housing is used with closed front plates, wherein a central wheel is supported in the housing and a plurality of star-shape arranged carriage apparatuses are in driving engagement with the circumference of the wheel. Several such machine housings can be sequentially arranged in a modular fashion. The synchronization of the central wheels in all individual machine housings and, even more, of their starshape arranged and radially operating carriage apparatus is a problem because of the required angular gears and couplings. 
     The number of sequentially performed bending processes differs depending on the type of the product to be produced. Often, the bending device has a stamping device upstream; in some situations, however, the latter is not needed. The known machines are too large for simple bending parts because they are designed for eight or more carriage apparatuses or a multiple thereof. Even when all positions are not occupied by carriage apparatuses, angular gears that are not required, are running so that energy consumption and wear are unnecessarily high. 
     DE 195 36 036 teaches connecting individual machining units to a crankshaft drive so that the individual bending stamps can be activated or deactivated as selected. This is achieved by a piston cylinder arrangement which is moved by pressure medium actuation as a unit by the crankshaft so that the apparatus becomes active. By venting the cylinder, the apparatus is deactivated and the piston runs without load in the cylinder in a reciprocating fashion. 
     In EP 0 875 311 a system is described in which the stations are switched on and off as selected by engageable and disengageable bevel gears. These bevel gears are mounted on a spline shaft penetrating the machining units, wherein the energy and the movement of the individual machining units is delivered by a common drive motor to the individual machining units via the aforementioned shaft. The common drive shaft ensures that all machining units operate synchronously to one another and synchronously to the advancing cycle of the workpiece to be machined. If it is desired to produce a new workpiece on such a system of machining units, not only must the individual tools be exchanged and optionally individual stations be switched on or off, but also the respective tool stroke must be adjusted to the exchange of the eccentric apparatus. This requires an exchange of the eccentric discs which move the carriage apparatus. The eccentric discs also determine the carriage stroke because of their eccentricity. After the eccentric discs are exchanged, their angle adjustment must also be corrected so that the machining units move in a precisely timed manner with the advancement of the workpiece. Retooling times of four to six hours are required for such a tool exchange and adjustment of the machine to a workpiece that is to be newly produced. The cooperation of the workpiece advancement and the machining units must be precisely adjusted to each other with respect to timing and may not change even for working cycles of, for example, 500 strokes per minute. Due to the high cycle frequency for strokes of typically 40 to 50 mm, the machining units must not only receive considerable cutting forces but also considerable acceleration forces. Upon running in the machine, it is desirable that the stations can be operated individually, and a common reference position must be adjustable in a reproducible manner. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to increase the productivity of a machine for stamping, bending, and/or mounting of sheet metal parts, and especially, to reduce the required retooling times for the adjustment of the eccentric discs. 
     A carriage apparatus is driven by a program-controlled synchronous motor. The movement cycle of the synchronous motor can be programmed. Instead of using an eccentric disc, the stroke can be adjusted easily by a program change. An exchange of eccentric discs is not required. Accordingly, the retooling time is advantageously reduced. 
     Because the controlling torque of the synchronous motor is exceeded due to high frequency and partially high shaping forces, it is advantageous for a gear, such as an eccentric disc, connecting rod, or elbow lever, to be positioned between the motor and carriage apparatus. High processing forces can be generated without the need for a large synchronous motor due to the corresponding gear reduction. 
     In connection with rotary gears such as eccentric discs, it is especially advantageous when the program-controlled synchronous motor is a rotation motor, preferably a torque motor, which is coupled to the carriage apparatus via the gear membrane. The stroke can be easily changed because the synchronous motor is operated only over a portion of its range. This means that the drive only employs a minimal angular range of the eccentric disc. This reduces the stroke. Accordingly, there is no need for a new eccentric disc. Neither an exchange of the eccentric disc is required during retooling nor the critical adjustment of the angular position for synchronization of the process steps. For both the running of the machine and the individual stations, respectively, the individual synchronous motor of the station can be controlled separately which facilitates control during retooling considerably. In this manner, individual stations can also be switched on or off as desired without having to mechanically intervene in the energy flow. This means that gear members such as movable clutches and angular gears are not needed. 
     In a further embodiment the motors of several sequentially arranged housing parts are exchangeable with one another. With such a standardized interface between the motors and the housing parts, the individual machine can be constructed very flexibly. Not only can individual stations be switched on and off electronically in a simple manner, but an excess number of motors can also be avoided, and they can be used in other machines or at other locations. The employed synchronous motors have an especially high output with a small volume when the motor is water-cooled. The resulting heat loss can thus be directly dissipated away from the machine. Problems with non-uniform heating of the machine are advantageously prevented. The machine maintains its precision even over extended production periods. 
     The individual housing parts can be sequentially arranged despite the water-cooled motors in a convenient, quick, and easy way when the housing parts have a cooling water inlet and cooling water return lines for the motors correlated therewith which are adjusted relative to one another in regard to their position. When connected sequentially, the individual housing parts form a common cooling water inlet and return line. These lines can be connected to one another, for example, by quick couplings. 
     In another embodiment the machine of the present invention comprises a memory-programmable control which comprises a current measuring device and an evaluation circuit which produces a signal as soon as set point limit values of a working cycle current are surpassed or no longer reached. As soon as a tool begins to turn dull, the required cutting and bending forces increase so that the current uptake of the motor also increases. Upon surpassing a predetermined limit value, the machine can thus be shut down and preventive servicing of the tool can be performed. Thus, the machine will not accidentally produce rejects. The same holds true when falling below a predetermined limit value, for example, due to tool breakage. When tool breakage occurs, the machine can also be shut down and a tool exchange can be carried out. 
     Also, the machine, upon surpassing or falling below the limit value, automatically will shut down. In this way, the machine will not accidentally produce rejects. As soon as tool breakage or tool wear occurs, which could lead to intolerable changes on the workpiece, the machine will automatically shut down. 
     The machine has a standardized and modular composition because the upper and the lower housing parts are components of a uniform narrow housing box whose front side has correlated therewith not more than one upper and one lower carriage apparatus. Such housing parts can be variably arranged in sequence and adjusted to the respective tool. 
     In certain situations it is advantageous where the torque motor has a continuous shaft which is provided with output hubs at both ends. For example, this allows symmetrical force introduction into a press by means of an elbow lever. Moreover, rear and front housing parts with their carriage apparatus can be driven by a common torque motor because the torque motor has two output shaft ends. 
     According to a further embodiment of the invention, the carriage apparatus is provided with eccentric discs which project past the narrow housing boxes such that between two neighboring housing boxes an optionally two-part spacer block is connected by screwing. This increases the spacing of the output shafts of neighboring housing boxes so that carriage strokes of 50 mm and more can be performed. Such simple intermediately positioned spacer blocks also allow a precise grid length and cutting length adjustment which may be required because of shaping of the workpieces during machining. 
     The machine according to a further embodiment has a front and rear housing box row wherein each front housing box is connected to a rear housing box at the top and bottom via a connecting plate and screws. As an alternative, connecting plates extending over the entire length of the housing box row can be provided. Both housing box rows have their own drive motors. 
     It is also advantageous to eliminate several drive motors for the individual carriage apparatus when a gear is connected between the motor and carriage apparatus and the gear is formed as a central wheel with pinions. The carriage apparatus is engaged with and driven by the gear wheel. A correspondingly stronger torque motor drives a larger central gear wheel. The pinions engage this central gear wheel and, in turn, drive the carriage apparatus whose axes are arranged radially to the axis of the central wheel. In this way, several carriage apparatuses can be driven simultaneously by a central wheel and the number of required individual drives is advantageously reduced. 
     The retooling time can be further reduced because the carriage apparatus is designed as a component group with the motor. 
     Moreover, it is an object of the invention to provide a method for operating the machine of the present invention while avoiding complicated exchange of eccentric discs. 
     The object in regard to the method is solved in that the rotation motor can be reversibly operated over only a selected angular range. Depending on the size of the angular range which is used, the stroke that is generated will change for the same eccentric disc. An exchange of the eccentric disc for the purpose of stroke change can therefore advantageously be eliminated. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a central vertical section of a housing box with torque motors; 
     FIG. 2 is a front view of two housing boxes screwed to one another; 
     FIG. 3 is a front view of three housing boxes screwed to one another and of a spacer block; 
     FIG. 4 is a front view of a machine with two presses and four housing boxes as bending devices; 
     FIG. 5 is a vertical section of several front and rear housing boxes; 
     FIG. 6 is a plan view onto a machine similar to FIG. 5 with four housing boxes as bending devices, respectively; 
     FIG. 7 is a view of a housing box with twice the width and two drives; 
     FIG. 8 is a vertical sectional view of the double wide housing box according to FIG. 7; 
     FIG. 9 is a vertical section of the double wide housing boxes with two symmetrically arranged torque drives; 
     FIG. 10 is a press according to FIG. 9 with different arrangement of the drives; 
     FIG. 11 is a press according to FIGS. 9 and 10 but with a single drive with two symmetrically arranged output shaft ends; 
     FIG. 12 is a front view of an eccentric disc; 
     FIG. 13 is a front view of an individual carriage apparatus; 
     FIG. 14 is a vertical cross sectional view of the individual carriage apparatus according to section line XIV—XIV of FIG. 13; 
     FIG. 15 is a front view of a machine with two housing boxes with linearly driven carriage apparatus, a central wheel with several carriage apparatus in a different embodiment, and a press; 
     FIG. 16 is a front view of a housing box with central wheel; and 
     FIG. 17 is a vertical sectional view of the central wheel according to section line XVII—XVII in FIG.  16 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, in which like reference numerals are used to refer to the same or similar elements, FIG. 1 shows a preferred embodiment of the present invention. A housing box  10  is mirror-symmetrical to a central horizontal plane  12  and has an upper housing part  14  and a lower housing part  16  which are both connected to one another to form a single part. The housing box  10  is cost-efficiently produced from a block of steel casting, ferro casting or a light metal casting, and, in particular, after surface machining of the bottom surface, is highly precisely milled in a clamped position. In this connection, a front wall  18  is machined such that parts of a carriage apparatus  20  can be correlated with the housing box  10 . The carriage guides  28  in the form of guide strips for the carriage are connected to the front wall  18  of each housing box  10  in a positive locking way and are screwed thereto. Also, in the area of the central horizontal symmetry plane a tool receiving surface  30  is milled which serves for a positive-locking receiving of a tool base plate  32  of a tool  34  wherein also the tool base plate  32  can be screwed onto the front wall  18 . In the embodiment according to FIGS. 1 through 6, an upper and a lower motor housing, which contains the torque motor  24 , respectively, is inserted into each housing box  10 . The housing boxes  10  are sufficiently wide so that the eccentric discs  38  mounted on the output shafts  22  of neighboring housing boxes  10  do not touch one another. The eccentric discs  38  for a carriage stroke of 40 mm result constructively in a minimal width of the housing boxes  10  of 176 mm. Larger eccentric discs, for example, for a carriage stroke of 50 mm, will result in a housing box width of approximately 200 mm. 
     Bores  40  are provided in the sidewalls of the housing boxes  10  so that neighboring housing boxes  10  can be screwed to one another easily. This is achieved by machine screws  42  as illustrated in FIG.  2 . Feather keys  44  provide exact guiding in the external grooves of the housing boxes  10 . 
     FIG. 3 illustrates a first embodiment of a sheet metal machining and mounting machine with four housing boxes screwed together wherein three housing boxes  10  are furnished with carriage apparatuses and a further housing box  11  is provided which is screwed onto the end. Drive distribution boxes would normally be required at the ends, but can be eliminated due to the use of torque motors. In the prior art such drive distribution boxes are required so that the upper and lower drive shafts can be connected to one another in driving connection. In the prior art, angular gears are provided in the drive boxes which are driven by an electric motor, which in this case is also required because each carriage apparatus must be driven by its own torque motor. The drive shafts, which in the prior art drivingly connect bending devices for common driving with a single motor and which in the present invention would otherwise extend along the geometric axis  50  to be pushed through the angular gears, can also be eliminated. 
     FIG. 4 illustrates a larger machining apparatus which is comprised of the same basic units, i.e., the housing boxes  10  and  11 . In addition, two stamping presses  52 ,  54  are integrated into the modular system. The assembled complete housing can still go without the otherwise provided motor drives at the ends. 
     Spacer blocks  56  are arranged between two housing boxes  10 . The spacer blocks  56  permit the use of larger eccentric discs for the carriage apparatus of the housing boxes  10  illustrated to the left. Moreover, such spacer blocks  56  can change the grid and cutting lengths according to the workpieces to be shaped. 
     FIG. 5 shows a vertical sectional view of a twin housing which is comprised of a front row of housing boxes  10  and a rear row of housing boxes  10  wherein the bottom wall of the housing boxes of both rows is screwed onto the sub structure, while at the top both housing box rows are connected to one another by a connecting plate  58  and screws. The formed housing supports carriage apparatus  20  on the front side and on the rear side. According to FIGS. 5 and 6, the connecting plate  58  extends across both housing box rows. As an alternative, each pair of front and rear housing boxes  10  can be provided with its own correspondingly narrow connecting plate. 
     FIG. 7 shows a housing box of double width for a stamping press. The carriage apparatus  20  is driven by two output shafts  22  of two torque motors. On the output shafts  22 , two eccentric discs are seated which drive the carriage apparatus  20 . 
     FIG. 8 illustrates in vertical section a similar embodiment as FIG.  7 . On the output shaft  22  of the torque motor  24 , two sensing rollers  27  of the carriage apparatus  20  glide on a double eccentric disc  38 . 
     FIG. 9 shows a different arrangement of a press in which two torque motors are aligned axially in the housing box  10 . The connecting rod  31  is moved by means of an eccentric  29  which is arranged on the output shaft  22 , so that the tool  34  carries out a corresponding stroke. 
     FIG. 10 shows an alternative arrangement of two torque motors for driving a press. In this arrangement, the drive is realized by the drive shaft  22  acting on the eccentric  29 . The latter drives the tool  34  by means of a connecting rod  31 . 
     FIG. 11 shows a principally similar type of drive. However, a torque motor is shown which has output shafts in the interior on both sides, which drive the connecting rod by means of the eccentric. 
     In all cases the torque motors have an identically designed housing whose housing mantle is cooled at the inner side by a cooling channel  25 . The motors themselves are round and have in addition a torque support for supporting them on the housing box  10 . 
     FIG. 12 shows an eccentric disc whose outer contour is followed by the sensing roller  27 . The sensing roller  27  is conventionally connected to the carriage apparatus. When the eccentric disc  38  is rotated for example between 0° and 45°, it performs a maximum stroke. The same holds true when it is rotated, for example, in the clockwise direction from 0° to 45° wherein it passes through an angular range of 315°. The transmission of the rotational movement is different, depending on which angular range is used for operating the eccentric disc. The advantage of the torque motor is that the rotation of the eccentric disc can be pre-programmed. The torque motor can also be carried out in a reversing direction over a portion of the angular range so that only partial strokes can be performed. 
     In FIG. 13 the front view of an individual carriage apparatus  26  is shown. Parts with identical function are provided with the same reference numerals as in the other figures. In contrast to the carriage apparatus as illustrated in FIG. 1, FIG. 14 shows a vertical sectional view of an individual carriage apparatus in which the carriage  20  is mounted within the guide  28  on an adaptor plate  62 . The adaptor plate  62  is at the same time formed as a housing for the torque motor  24 . In this way, the adaptor plate  62  can be fastened as a component group, which also integrates the torque motor  24 , by means of feather keys  44  on the front side of a housing part. This component group comprises all required drive parts of the carriage  20 . The torque motor  24  drives the two eccentric discs  38  by its output shaft. A lower sensing roller  27  whose axle is fixedly connected with the carriage  20 , drives the carriage in the workpiece direction. The upper roller  27  whose axle is fixedly connected with the return plate  61 , which is, in turn, fixedly connected to the carriage  20 , returns the carriage after it has performed a machining step. 
     In FIG. 15 several such linearly driven individual carriage apparatuses are illustrated which can be screwed onto the housing boxes as component groups. A linear intake  64  for material is provided on the left side of the illustrated machine. Toward the right, two upper and two lower linearly driven carriage apparatuses  26  follow. Downstream thereof, a housing box  10  with central wheel  65  is positioned. The station comprises a total of eight carriage apparatuses driven by the central wheel  65 . Three of the carriage apparatuses are respectively positioned in the vertical direction, above and below the central wheel axle  66 , and in addition, one is positioned to the right and one to the left, with an axle which is slanted relative to the horizontal. 
     To the right, upper and a lower housing parts  14  and  16  are provided with further carriage apparatus  26 . The machine ends with a stamping press  52 . The construction of the station with a central wheel drive can be seen in particular in FIGS. 16 and 17. In FIG. 17, the carriage apparatuses are not illustrated in order to simplify the drawing. In the housing box  10 , a single torque motor  24  is provided as a drive for the carriage apparatus  26 . The movement axes of these carriage apparatuses  26  are arranged radially relative to the central wheel axle  66 . Accordingly, the carriage apparatuses  26  are fastened with hammer head screws (not represented) engaging annular grooves  67  on a central clamping plate  68 . The clamping plate  68  is part of the housing box  10 . Behind this clamping plate, the outer toothing  69  of central wheel  65  is engaged by a pinion  70  which drives the carriage apparatus  26 . In this way, the eight carriage apparatuses of the embodiment can be driven by a single torque motor which reduces the capital expenditure for the drive motors significantly. 
     The machine according to the invention for bending, stamping etc. is characterized in that drive shafts penetrating the housing parts, which are to be coupled to angular gears in each housing part, can advantageously be eliminated. Due to the minimal mass of the employed motors, the machine hardly coasts when shut down. Moreover, the bending and stamping force can be continuously measured during a working cycle for quality control. The individual stations can be switched on and off as desired without having to initiate complicated retooling work. 
     While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 
     LIST OF REFERENCE NUMERALS 
       10  housing box 
       11  housing box, drive distribution box 
       12  horizontal plane 
       14  upper housing parts 
       16  lower housing parts 
       20  carriage apparatus 
       22  drive shafts 
       24  torque motor 
       26  carriage apparatus 
       27  sensing rollers 
       28  carriage guides 
       29  eccentric 
       30  tool receiving surface 
       31  connecting rod 
       32  tool base plate 
       34  tools 
       38  eccentric discs 
       40  bores 
       42  machine screws 
       44  feather keys 
       45  cooling channels 
       46  angular gears 
       48  electric motor 
       50  geometric axis 
       52  stamping press 
       54  stamping press 
       56  spacer blocks 
       58  connecting plate 
       60  bearing ring 
       61  return plate 
       62  adaptor plate 
       63  output axle 
       64  linear intake 
       65  central wheel 
       66  central wheel axle 
       67  annular grooves 
       68  clamping plate 
       69  outer toothing 
       70  pinion 
       71  component group