Centering device

Abstract

A centering device (1) for centering a flat workpiece (700-706) includes: a centering station (100), the centering station (100) including at least first and second clamping mechanisms (300, 301) for clamping the workpiece (700-706); and a conveying device for conveying the workpiece (700-706) to the centering station (100) along a traveling direction. The first and second clamping mechanisms (300, 301) are respectively movable horizontally by first and second guide devices (200, 201) and can rotate freely about an axis.

Description

Technical Field

[0001] The present invention relates to a centering device for centering a flat workpiece, particularly a sheet metal blank to be processed in a press, comprising: a centering station having at least first and second clamping devices for clamping the workpiece; and a conveying device for conveying the workpiece to the centering station in a conveying direction. Background Technology

[0002] Pre-punched sheet metal parts, or "blanks," are typically further processed in a press (such as a multi-station press or stamping line). Before actual processing in the press, the supplied blanks must usually be split or separated, cleaned, and oiled if necessary. For the blanks to be further processed precisely in the press, they must be accurately positioned and oriented in a predetermined orientation after the aforementioned operations and before being introduced into the press.

[0003] Workpieces requiring centering are typically present as sheet metal blanks. These blanks may lose their predefined position during transport or cleaning operations, particularly in the event of improper transport. To minimize this risk, it is previously known that workpieces are clamped simultaneously at multiple locations via robotic arms and grippers for lifting and centering. However, such devices are expensive to acquire, and the corresponding methods for converting to new workpieces are very complex and costly.

[0004] Methods for positioning and orientation are also known, in which centering is performed by means of mechanical sliders and stops. However, these methods have the following drawbacks: when changing the type of blank, the sliders and stops must be repositioned and reoriented in a cumbersome manner. Furthermore, when machining irregularly shaped metal sheets or multiple small metal sheets, a large number of sliders and stops are required to ensure correct positioning. Mechanical sliders also have the disadvantage that the blank may be damaged during centering.

[0005] Known solutions have complex designs or are difficult to adapt to new workpiece types; that is, they are not easily applicable to any desired workpiece. Summary of the Invention

[0006] The object of the present invention is to provide a centering device that belongs to the technical field stated at the beginning and that can be widely used while having a compact and simple design.

[0007] The objective is achieved by the features of claim 1. According to the invention, both the first and second clamping devices are horizontally movable via the first and second guiding devices, respectively, and both the first and second clamping devices are freely rotatable about an axis.

[0008] Therefore, a particularly simple centering device is provided by a solution that can be implemented in a technically simple manner. Clamping devices for clamping workpieces and guiding devices for moving the clamping devices are known to those skilled in the art, and can further be implemented in a technically particularly simple manner. Furthermore, the guiding device, which contrasts particularly with the driven balls of a ball table or ball plate, can be controlled in a particularly simple and precise manner.

[0009] Centering is made particularly simple by clamping the workpiece, preferably with two freely rotatable clamping devices; in particular, centering can be achieved with particularly simple control by using exactly two clamping devices that can rotate freely about an axis. For centering the workpiece, it is clamped, preferably by at least two clamping devices. After the workpiece has been clamped, a guide device is actuated to center the workpiece. Since the clamping devices are now rotatably mounted, rotation of the workpiece can be initiated simply, generated by the two guide devices. Due to the free rotatability of the clamping devices, only the distance between the clamping devices must be kept constant during centering, and the rotation generated during centering can be initiated by the freely rotatable clamping devices.

[0010] The clamping device is preferably mounted on the first guide device so that it can rotate freely about a vertical axis, preferably exclusively. If the clamping device is pivotable, the axis of rotation can also be oriented non-vertically.

[0011] The centering device allows the workpiece to rotate by an angle greater than 90°, making it applicable to a particularly wide range of fields. Furthermore, it is conceivable that the guiding clamping device allows them to engage with each other, for example, along the conveying direction, thus enabling rotation around an angle greater than 180°.

[0012] The term "centering" will be understood below to refer to a change in the position and / or orientation of a workpiece in a plane. Centering typically occurs via translation, rotation, or a combination of translation and rotation. In the context of centering, the workpiece is preferably transferred from its actual position to a desired position by superimposed translations / rotations. The actual position is typically the workpiece orientation along which the workpiece is transferred to the centering station, and the desired position is the workpiece orientation along which the workpiece intends to leave the centering station.

[0013] In method 532 for centering a flat workpiece, particularly a sheet metal blank to be processed in a press, the following steps are performed: a) Determine the current position and orientation of a workpiece being conveyed on a conveying device using a detection device; b) Transfer the workpiece to the center station; c) The workpiece is clamped by means of first and second clamping devices, which are rotatable about an axis; d) Orient the workpiece based on the current position and the desired position using the guiding device.

[0014] These method steps provide a method for centering a workpiece that can be implemented in a particularly simple manner. Determining the workpiece's position before reaching the centering station allows for the design of the centering station in a particularly compact and simple manner. In particular, the centering station and the detection device can therefore be formed independently of each other and maintained, upgraded, or repaired independently, thereby simplifying the operation and maintenance of the centering device.

[0015] The conveying device preferably includes at least one conveyor belt. Therefore, workpieces can be transported quickly and accurately. The conveyor belt can be, for example, in the form of a magnetic belt, whereby the workpiece can be fixed in place during transport. Instead of a magnetic belt, other conveyor belts known to those skilled in the art can also be provided, such as vacuum belts. Given a suitable selection of the conveyor belt surface, the workpiece can also be fixed on the conveyor belt via friction between the workpiece and the conveyor belt.

[0016] In variations, other conveying devices may also be provided, such as conveyor plates, support rollers, ball bearing plates, etc.

[0017] In a particularly preferred embodiment, the centering device is formed such that the workpiece is positioned on a support surface during the centering operation by means of clamping and guiding devices. Therefore, particularly large or deformable workpieces (e.g., large metal sheets) can be oriented in a gentle manner. For this purpose, the workpiece does not necessarily have to be on a conveyor belt. In a preferred embodiment, the workpiece is positioned on a support surface different from the support surface of the conveyor belt during centering (see below). Alternatively, for centering, the workpiece can also be completely or partially lifted off the conveyor belt or raised.

[0018] The conveyor belt preferably comprises a plurality of parallel conveyor belt strips spaced apart from each other, wherein lifting units having workpiece support surfaces are arranged in the gaps between two conveyor belt strips, wherein, when the workpiece support surfaces are raised, the workpiece is uniquely located on the workpiece support surfaces. Therefore, workpieces conveyed on the conveyor belt can be raised in a simple manner. Raising the workpiece is particularly advantageous for centering the workpiece if centering on the conveyor belt itself is not suitable. This is usually the case when the conveyor belt is formed so that the orientation of the workpiece does not change during transport. It is generally desirable that the orientation of the workpiece does not change during transport; in particular, the orientation of the workpiece (after centering) is intended to remain unchanged, for example, during further transport. Preferably, the lifting units are pneumatically operated, i.e., the lifting units include pneumatic cylinders by means of which the workpiece support surfaces can be raised and lowered directly or indirectly. Instead of pneumatic cylinders, the lifting units may also include other drive devices, such as spindle drives, hydraulic cylinders, etc.

[0019] In this variant, the lifting unit between the conveyor belts can be omitted. In this case, for centering, the workpiece can be located on the conveyor or clamped, lifted, and centered from above by a clamping device.

[0020] During operation, in order to clamp the workpiece, the clamping device is preferably lowered simultaneously (see below), and the workpiece is lifted off the conveyor belt by means of the lifting unit.

[0021] In a variation, the clamping device can first be moved downwards to secure the workpiece, after which the lifting unit, along with the workpiece and the clamping device, moves upwards. In this case, the clamping device can move upwards actively or passively, together with the lifting unit.

[0022] The workpiece support surface preferably has a coefficient of friction lower than that of the workpiece support surface of the conveyor belt. This ensures that, when the workpiece support surface is raised, the workpiece located on the workpiece support surface can move against lower frictional resistance, especially for centering. Therefore, the workpiece can be accurately and effectively centered with greater acceleration and lower risk of damage.

[0023] In the variant, different coefficients of friction may not be required.

[0024] The surface of the lifting unit preferably includes a ball plate arranged such that, when the lifting unit is raised, the workpiece rests on the balls of the ball plate. For this purpose, the balls of the ball plate are mounted in a rotatable manner, resulting in the workpiece being able to move against the lowest possible resistance, particularly for centering, via a clamping device.

[0025] In variations, other devices can be provided to reduce the resistance between the support surface and the workpiece during centering. Air cushions, for example, can also be provided as alternatives to ball bearings.

[0026] The centering station preferably further includes third and fourth clamping devices, each of which can be moved horizontally by means of third and fourth guide devices, respectively. It is particularly advantageous to have more than two clamping devices available, especially for large workpieces. This reduces the load on individual clamping devices, thereby enabling an efficient method for centering larger workpieces. However, depending on the arrangement of the clamping devices, it is also possible to simultaneously center multiple individual workpieces that are adjacent to each other or one behind the other, thus further increasing the efficiency of the method for centering workpieces.

[0027] In variations, the third and fourth clamping devices can be omitted. However, it is also conceivable to provide three or more than four clamping devices, and in particular, for example, five, six, seven, eight or more guiding devices. The preferred number of guiding devices ultimately depends on the type of use, and in particular on the size, stability, weight, maximum load capacity, number of workpieces to be processed in parallel, and other factors.

[0028] Particularly preferably, the method uses exactly two clamping devices to center the workpiece.

[0029] One of the guiding devices preferably includes a first linear guide for moving the clamping device along the conveying direction and a second linear guide for moving the first linear guide at a right angle to the conveying direction. This provides a particularly simple and therefore cost-effective Cartesian guide. The Cartesian guide has the advantages of a cost-effective design, simple control, and minimal additional maintenance. Here, the orientation of the first linear guide at a right angle to the conveying direction has the advantage that the centering device can have a compact design overall. Therefore, the large overhang of the centering station exceeding the width of the conveyor belt can be substantially eliminated in the centering station. In particular, the second linear guide allows two or more second linear guides to be guided on this first linear guide.

[0030] In a variation, the guiding device may include a first linear guide for moving the clamping device perpendicular to the conveying direction and a second linear guide for moving the first linear guide along the conveying direction. It is also conceivable that the first and second linear guides do not extend parallel to each other. For example, the tracks of the first linear guides for the first and second guiding devices may be perpendicular to each other. Finally, one or more of the guiding devices may also take the form of a robot, which may in particular have four, five, six, or more axes.

[0031] The first linear guides of the first and second guides are preferably arranged parallel to each other, and the second linear guides of the first and second guides are arranged aligned with each other. Particularly preferably, the first linear guides of the first and second guides comprise a track guide transverse to the conveying direction, preferably a single track guide, on which the first linear guide is movable transversely to the conveying direction. Aligned track guides or a shared track guide for the first linear guides of the two guides allow for a compact or cost-effective design of the centering device once again. Here, the two first linear guides can be moved via a dedicated drive device, resulting in their independent control. However, it is acceptable here that the two first linear guides cannot intersect each other.

[0032] In a variant, the first linear guide can also be guided on separate track guides and specifically arranged parallel to each other.

[0033] The first linear guide preferably includes a belt drive for moving the clamping device and / or the second linear guide includes a belt drive for moving the first linear guide. Particularly preferably, both the first and second linear guides include belt drives. The use of belt drives has the advantages of enabling high acceleration and rapid movement with high precision. Furthermore, the acquisition and maintenance of belt drives are cost-effective. However, it is also conceivable that only the first or only the second linear guide includes a belt drive, while other linear guides include additional drive mechanisms, such as spindle drives, pneumatic or hydraulic drives, rack and pinion drives, linear motors, etc.

[0034] In a variation, a drive mechanism other than a belt drive can be provided for both the first and second linear guides. In this case, the drive mechanism does not necessarily need to be formed identically in both the first and second linear guides. Thus, the first linear guide may include a spindle, while the second linear guide is operated by a linear motor.

[0035] Preferably, the clamping device can be lowered and raised, preferably pneumatically, particularly relative to the first linear guide. Thus, the clamping device can be easily guided to the workpiece so that it can be clamped. For this purpose, the clamping device includes a lifting mechanism, wherein the lifting direction is preferably vertically oriented and preferably perpendicular to the support surface of the conveyor belt. The lifting mechanism can be configured such that the workpiece can be held without force relative to the lifting direction. In this case, the workpiece will be pulled above the support surface of the conveyor belt or ball bearing for centering. This embodiment is particularly advantageous for large and / or flexible workpieces that can deform, especially under their own load, as deformation of the workpiece and thus distortion of its orientation can be avoided after lowering. Alternatively, the lifting mechanism can also be configured such that the workpiece can be actively raised and lowered by means of the lifting mechanism. Thus, smaller or dimensionally stable workpieces can be centered in a frictionless manner. The lifting mechanism can also be configured such that forceless holding in the vertical direction and active raising of the workpiece are possible.

[0036] In a variant, the descent and elevation of the clamping device relative to the first linear guide can be omitted. Furthermore, the alternative clamping device can be designed to be raised and lowered relative to the first linear guide, and the first linear guide, together with the clamping device, can also be designed to be raised and lowered relative to the second linear guide. Finally, the guide as a whole can also be designed to be raised and lowered.

[0037] The clamping device can be pneumatically raised, particularly against restoring force (preferably against spring force). Thus, the clamping device is lowered without energy. This arrangement is advantageous because it allows the clamping device to move downwards with a constant force while the spring relaxes. This force can be preset in a simple manner by selecting a spring with the desired spring constant. Particularly preferably, the clamping device is lowered solely by spring force. Therefore, the pressure applied to the workpiece can be controlled in a simple way. The clamping device is preferably pneumatically raised. This allows for particularly rapid movement, i.e., the clamping device can be rapidly raised after centering. This results in shorter cycles during centering, thus producing a particularly efficient method.

[0038] In variations, the clamping device can also be designed to be raised and lowered in an alternative manner. Lowering can also occur by gravity. Furthermore, in principle, raising, rather than lowering, can overcome spring force. Therefore, during the operation of the guiding device, damage to the centering device can be avoided in the event of a malfunction in the lifting device (e.g., a leak in the pneumatic device). Furthermore, both raising and lowering can be pneumatically achieved using a so-called pneumatic spring. In addition, alternatives to pneumatic devices include rack and pinion drives, hydraulic drives (especially those with short strokes), and magnetic drives, etc.

[0039] The clamping device preferably includes a suction cup for clamping the workpiece. This is particularly beneficial in the case of already pneumatically actuated lifting devices, where existing infrastructure can be better utilized. Therefore, for example, the conveyor belt can also be designed as a vacuum belt. The suction cup also allows the workpiece to be clamped in a particularly gentle manner. Furthermore, clamping the workpiece using a suction cup has proven to be particularly simple, as essentially only a workpiece area corresponding to the diameter of the suction cup is required.

[0040] In variations, the clamping device can also be designed in another way. Therefore, the clamping device may include, for example, an electromagnet. Furthermore, the clamping device may include an actively actuated gripper. A hook may also be provided, which can engage, for example, behind an edge region of the workpiece. Other possible designs of clamps are also familiar to those skilled in the art.

[0041] The centering device preferably includes a detection device for detecting the position and orientation of the conveyed workpiece. The position and orientation of the workpiece can then be corrected by the centering device based on this detected information. Therefore, the detection device is arranged upstream of the centering station so that the actual position can be determined before centering.

[0042] In a variant, the detection device can also be surrounded by a centering station. In this case, the actual position can be identified by means of the centering station itself, for example, by clamping points of a pre-defined clamping device on the workpiece.

[0043] The detection device preferably includes a line camera arranged upstream of the centering station with respect to the conveying direction. Therefore, the line camera is positioned in the workpiece feed path and preferably extends laterally relative to the workpiece feed path. Thus, the position and orientation of the workpiece are detected by the line camera during feed. The line camera can be designed in a simple manner, allowing for accurate detection of position and orientation, and, compared to other detection devices such as cameras, does not require, for example, sophisticated image processing.

[0044] However, in the variant, another detection device can also be provided, such as a camera, a sensor grid, etc.

[0045] In a preferred embodiment, the line camera is arranged in the transition between the two conveyor belts, particularly in the gap, and includes a scanner preferably vertically positioned below the support surface of the workpiece and a reflector vertically positioned above the space through which the workpiece is conveyed. Thus, the workpiece is scanned from below.

[0046] In a variant, the workpiece can be scanned from above. For this purpose, the scanner is positioned vertically above the workpiece's support surface. Furthermore, photographs can be taken from above to detect the workpiece's actual position. In principle, the apparatus may also include a detection device located downstream of the centering station along the conveying direction to compare the workpiece's position after centering with the desired position. However, this detection device can be omitted.

[0047] The centering device preferably includes a control unit designed to control the centering based on measurement data from a line camera, thereby achieving the desired orientation of the workpiece. Here, the light and dark contours of the workpiece are preferably determined by the line camera. This yields data that can be processed in a simple manner, allowing for precise positioning and orientation of the workpiece.

[0048] The detected contour can be specifically compared with a desired contour, representing the expected position and orientation of subsequent processing stations. The deviation between the light and dark contour and the desired contour is evaluated by the controller in a manner known per se and converted into corrections, such as rotation angle corrections, to be implemented in the longitudinal and transverse directions. These corrections are then implemented by the guiding device so that the positioned and oriented workpiece corresponds to the desired contour.

[0049] Other advantageous embodiments and combinations of the features of the present invention will emerge from the following detailed description and throughout the patent claims. Attached Figure Description

[0050] In the accompanying drawings used to explain exemplary embodiments: Figure 1 A schematic illustration of a side view of the centering device transverse to the conveying direction is shown; Figure 2 A schematic illustration of a side view of the centering device along the conveying direction with the clamping device lowered is shown. Figure 3 A schematic illustration of a side view of the centering device along the conveying direction is shown with the clamping device raised. Figure 4 A schematic diagram of a plan view of the centering device is shown; Figure 5 A cross-sectional view of the Cartesian guide device is shown along the conveying direction; Figure 6 A cross-sectional view of the Cartesian guide device is shown, transverse to the conveying direction, when the clamping device is raised; Figure 7 A cross-sectional view of the Cartesian guide device is shown, transverse to the conveying direction, with the clamping device lowered. Figures 8 to 12 A schematic diagram of a plan view of a Cartesian guide device with four clamping devices during the processing of different workpieces is shown. Figure 13 A schematic diagram of a plan view of a Cartesian guide device with six clamping devices during the processing of three workpieces is shown. Figures 14 to 16 A schematic diagram of a plan view of a Cartesian guide device with eight clamping devices during the processing of different workpieces is shown. Figure 17 A schematic diagram of a plan view of a Cartesian guide device with four clamping devices is shown, in which two workpieces are rotated by an angle of 90°; Figure 18 A schematic diagram of a plan view of a Cartesian guide with four clamping devices is shown, in which two workpieces are centered from an arrangement adjacent to each other to an arrangement behind another.

[0051] In principle, identical components are given the same reference numerals in the accompanying drawings. Detailed Implementation

[0052] Figure 1 A schematic illustration of a side view of the centering device 1 in the direction of transport is shown.

[0053] In the current situation, the centering device 1 includes a means for conveying the workpiece ( Figure 1 A conveyor belt 400 (not shown). For this purpose, the conveyor belt 400 includes a plurality of conveyor belt strips 410 oriented parallel to the conveying direction. The conveyor belt 400 includes a substructure 420 on which the conveyor belt strips 410 are mounted. The conveyor belt strips 410 are driven by a drive unit (not shown), particularly by one or more electric motors. In operation, the individual conveyor belt strips 410 are driven at the same speed (m / s), particularly in straight sections.

[0054] The centering device 1 also includes a second conveyor belt 500, which is part of the centering station 100. The conveyor belt 500 similarly includes a plurality of conveyor strips 510, which are oriented parallel to each other along the conveying direction and driven similarly to conveyor belt 400. The support surfaces of the conveyor belts are substantially in the same plane, resulting in the ability to transfer workpieces from conveyor belt 400 to conveyor belt 500.

[0055] A gap is provided between conveyor belts 400 and 500, through which workpieces can be conveyed in the direction from conveyor belt 400 to conveyor belt 500. Therefore, the gap exists transversely to the conveying direction. A line camera 600 is mounted below the support surface of the conveyor belts, in the region of the gap. By means of the line camera 600, workpieces guided above the gap can be detected, and their orientation and position can be determined. A reflector 601 for reflecting the light emitted by the line camera 600 is positioned above the support surface of the conveyor belts. Positioning below the support surfaces of conveyor belts 400 and 500 allows for a particularly compact design of the centering device 1.

[0056] The fixed center station 100 also has a Cartesian guidance device 200, in Figure 1 The image plane includes two second linear guides 250 and 251 that extend perpendicularly and parallel to the image plane. On each of the two second linear guides 250 and 251, a first linear guide 210 with a clamping device 300 and a first linear guide 212 with a clamping device 302 are respectively arranged, such that the first and second linear guides can move laterally and horizontally in the transport direction. The clamping devices 300 and 302 are movable along the transport direction on the two first linear guides 210 and 212, and can be raised and lowered relative to the second linear guides 210 and 212 (see below). Figures 5 to 7 ).

[0057] Figure 2 A schematic illustration of a side view of the centering device 1 along the conveying direction is shown with the clamping devices 210 and 211 lowered. Figure 2 Now shown in particular is a separate conveyor belt 510, which extends parallel to the conveying direction and about Figure 2 The individual conveyor belt strips 510 extend orthogonally to the plane of the paper. Therefore, the individual conveyor belt strips 510 are shown as approximately square.

[0058] Figure 2 A lifting unit 530 is also shown, by means of which the conveyed workpiece 700 can be raised through the gaps between the conveyor belts 510. The lifting unit includes a plurality of ball bearing plates (see...). Figures 5 to 7 The ball bearing plate 531 is connected via a base plate 533 and can be guided through the gaps between the conveyor belts 510, resulting in the formation of a support surface for the workpiece 700, which is configured to be higher than the support surface of the conveyor belts. The ball bearing plate 531 can be raised by means of one or more pneumatic cylinders (not shown).

[0059] exist Figure 2In this configuration, workpiece 700 is clamped by clamping devices 210 and 211, and lifting unit 530 is positioned in an upper position where workpiece 700 is not in contact with conveyor belt 510. Figures 5 to 7 The details of this aspect are described in more detail. In this configuration, the workpiece 700 can now be centered by means of the Cartesian guide 200. For this purpose, the individual linear guides 210, 211, and 250 (linear guide 251 is invisible and located behind linear guide 250) move based on the actual position determined by the line camera 600 and the known desired position in order to transfer the workpiece 700 to the desired position.

[0060] Figure 3 A schematic illustration of a side view of the centering device along the conveying direction is shown with the clamping devices 210 and 211 raised. After the workpiece 700 has been transferred to the desired position, the lifting unit 530 moves downward on one hand, and the clamping devices 300 and 301 move upward on the other hand, thereby placing the workpiece 700 back on the conveyor belt 500, which can then be further transported by the conveyor belt 500, particularly, for example, to a press for further processing of the workpiece 700.

[0061] Figure 4 A schematic diagram of a plan view of the centering device 100 is shown, wherein in each case, the workpiece 700 is guided along the conveying direction on the conveyor belt 400 and downstream of the Cartesian guides 200-203. Therefore, Figure 4 The diagram illustrates the state during a transition cycle, where workpiece 700 has just been oriented, and another workpiece 700 is positioned before the entrance of centering station 100. In this configuration, centering station 100 has a Cartesian guide 200 with two second linear guides 250, 251, which are offset laterally parallel to the conveying direction. Each of the two second linear guides 250, 251 includes two first linear guides 210, 211 and 212, 213, respectively, and clamping devices 300, 301 and 302, 303 hold each of the first linear guides 210, 211 and 212, 213. In this configuration, the first linear guides 210, 211 and 212, 213 can be moved laterally to the conveying direction by means of the second linear guides 250, 251. The clamping devices 300, 301 and 302, 303 can move along the conveying direction by means of the first linear guides 210, 211 and 212, 213 respectively.

[0062] The following Figures 5 to 7 The Cartesian guide device 200 and, in particular, the clamping device 300 are shown in detail.

[0063] Figure 5 A cross-sectional view of the Cartesian guide 200 along the conveying direction is shown. In this figure, the second linear guide 250 can be seen in the cross-section. The first linear guide 210 is movably held thereon via a drive belt 260. The second drive belt 261 provides support for the first linear guide 211 (not visible in this figure). The first linear guide 210 also includes a drive belt 220 by means of which the clamping device 300 can be moved along the conveying direction.

[0064] The clamping device 300 includes a base plate 311, at one end of which a retainer 312 for connection to a drive belt 220 is fastened. At the opposite end of the base plate 311, a cylinder 313 is fastened, in which a piston 314 is mounted in a vertically movable manner. The piston 314 is connected to a piston rod 317, which includes a suction cup 315 at its vertically lower end. A compression spring 316 is arranged vertically below the piston, driving the piston 314 in an upward direction, and thus also driving the suction cup 315 in an upward direction. To lower the suction cup, compressed air is filled into the space in the cylinder 313 vertically above the piston 314. In this way, the piston 314 moves downward against the spring force, thereby lowering the suction cup 315. Figure 5 In this configuration, spring 316 is substantially relaxed (except for the force of gravity acting upon it), and suction cup 315 is in an elevated state. Suction cup 315 is actively actuated by means of negative pressure (vacuum). The compressed air and vacuum connections are not shown in the accompanying drawings, but their arrangement is readily apparent to those skilled in the art. Suction cup 315 is freely rotatable, and consequently, the workpiece can also be rotated for centering purposes.

[0065] Figure 6 A cross-sectional view is shown transversely through the Cartesian guide 200 in the conveying direction with the clamping device 300 raised. It can be clearly seen, particularly based on the first linear guide 210, that the line of sight is now along the conveying direction. Two separate conveyor belts 510 are visible in the area of ​​the conveyor belt 500, with a lifting unit 530 arranged between these two conveyor belts 510. The lifting unit 530 includes ball plates 531, which can be raised and lowered respectively by means of one or more lifting cylinders. The ball plates 531 are connected to the base plate 533 via a support 532 (see...). Figure 2 and Figure 3 In this case, it can be pneumatically actuated. In order to center the workpiece 700 set in the centering station 100, the clamping device 200 (i.e., the suction cup 315) is now lowered and the workpiece 700 is raised from the conveyor belt 510 by the lifting unit 530 having ball plates 531.

[0066] Figure 7A cross-sectional view is shown transversely through the Cartesian guide 200 in the transport direction with the clamping device 300 lowered and the lifting unit 530 raised. In this state, the workpiece 700 can now be oriented by means of the Cartesian guide 200. For this purpose, all (in this example, four) clamping devices 300-303 can move independently of each other in the plane to achieve the desired position of the workpiece 700.

[0067] According to the aforementioned configuration, different centering operations on multiple workpieces can be performed simultaneously using the centering device 1, depending on the circumstances. For this purpose, the number of linear guides can be varied.

[0068] Figures 8 to 12 A schematic diagram of a plan view of a Cartesian guide 200 having four clamping devices during the processing of different workpieces 700-706 is shown, wherein workpieces 700-706 are, for example, rectangular. However, it will be clear to those skilled in the art that any conceivable form of workpiece can be centered by means of a centering device, provided that such a surface exists on which the clamping device 300 can clamp the workpiece.

[0069] Figure 8 An arrangement of four clamping devices 300-303 is shown, wherein the workpiece 700 is clamped at diagonally opposite ends by means of only two opposing clamping devices 301 and 302. Here, the workpiece 700 occupies substantially the entire width of the conveyor belt 500 along the current orientation.

[0070] Figure 9 It shows that according to Figure 8 The arrangement is such that, in each case, the workpiece 701 is clamped at opposite diagonal ends by means of pairs of clamping devices 300, 302 and 301, 303. Here, two workpieces 701 arranged adjacent to each other in the lateral direction occupy essentially the entire width of the conveyor belt 500 along the current orientation. Thus, it is shown that even multiple workpieces 701 can be simultaneously centered by means of the centering device 1.

[0071] Figure 10 It shows that according to Figure 8 The arrangement of the workpieces, in each case, involves clamping the workpiece 702 relative to each other at the center by means of pairs of opposing clamping devices 300, 302 and 301, 303. The workpiece 702 has a smaller size compared to the workpiece 701. Therefore, it is shown that the centering device is essentially independent of the workpiece size.

[0072] Figure 11 It shows that according to Figure 8The arrangement is such that, in each case, the workpiece 703 is clamped by two clamping devices 300, 301 and 302, 303 arranged adjacent to each other. Thus, it is shown that multiple workpieces 703 arranged one behind another can also be simultaneously centered by the centering device 1.

[0073] Figure 12 It shows that according to Figure 8 The arrangement is such that, in each case, workpieces 704 and 705 are clamped at opposite diagonal ends by means of pairs of clamping devices 300, 302 and 301, 303 respectively. Here, workpieces 704 and 705 have different dimensions transverse to the conveying direction. Therefore, it is shown that workpieces 704 and 705 of different dimensions can also be simultaneously centered by means of the centering device 1.

[0074] Figure 13 A schematic plan view of a Cartesian guide device 200 with six clamping devices 300-305 is shown during the processing of three identical workpieces 705. In each case, the workpiece 705 is clamped at its center at opposite ends by means of pairs of oppositely arranged clamping devices 300, 302 and 301, 303 and 304, 305. Thus, it is shown that three workpieces 705 arranged adjacent to each other can also be simultaneously centered.

[0075] Figures 14 to 16 A schematic plan view of a Cartesian guide device 200 with eight clamping devices 300-307 is shown, illustrating its operation during the processing of different workpieces. Figure 14 In, similar to Figure 13 The workpiece 705 is clamped, wherein three of the workpieces are replaced, and now all four of the workpieces are simultaneously centered. Figure 15 With Figure 14 A similar approach illustrates that not all four workpieces 705 to be centered must necessarily have the same orientation. In the present case, two workpieces 705 are oriented transversely to their longitudinal direction and oriented along the conveying direction. Figure 16 Similarly, four workpieces 705 are shown, all now oriented laterally to the transport direction.

[0076] Figure 17A schematic plan view of a Cartesian guide device 200 with four clamping devices 300-303 is shown, in which two workpieces 706 are rotated by 90°. Before centering, the workpieces 706 are oriented transversely to their longitudinal direction from the transport direction. The first workpiece 706 is clamped diagonally by clamping devices 300, 302, and the second workpiece 706 is clamped diagonally by clamping devices 301, 303. To perform the rotation, clamping devices 300, 302 and 301, 303 now move toward each other by means of first guide devices 250, 251, respectively. Simultaneously, clamping devices 300, 302 and 301, 303 move away from each other, such that the distances between clamping devices 300, 302 and 301, 303 remain constant. If the travel of the first linear guides 210-213 is large enough, or if the workpiece can be clamped between the clamping devices with a sufficiently small distance, rotation around an angle greater than 90° is also possible. If the clamping devices 301 and 303, and 300 and 302, can intersect each other along the conveying direction (which would require the clamping devices to be guided transversely to the conveying direction between the second linear guides 250 and 251, for example, on a centerline via the linear guides), then rotation of the workpiece 706 around an angle greater than 180° is possible.

[0077] Figure 18 A schematic plan view of a Cartesian guide 200 with four clamping devices 300-303 is shown, wherein two workpieces 705 are centered from an adjacent arrangement to an arrangement further back. Prior to centering, the workpieces 705 are oriented adjacent to each other in a direction transverse to their longitudinal direction in the transport direction. The first workpiece 705 is clamped by clamping devices 302, 303 in the region of its leading edge along the transport direction, and the second workpiece 705 is clamped by clamping devices 300, 301 in the region of its trailing edge along the transport direction. To perform movement, clamping devices 302, 303 are now moved along the transport direction by means of first linear guides 212, 213, respectively, and clamping devices 300, 301 are moved in the opposite direction to the transport direction by means of first linear guides 210, 211, respectively. They are then moved toward each other by means of first guides 250, 251 until they are arranged one behind the other with respect to the transport direction.

[0078] It should be noted that, in order to determine the center, one or more workpieces can be clamped multiple times, thus making it possible for multiple workpieces to be positioned in any desired manner relative to each other.

[0079] Conveyor belt 400 does not necessarily have to have conveyor belt strips 410, but may also include a single conveyor belt with a full transport width. Alternatively to conveyor belt 400, another feeder conveyor, such as a roller conveyor, may also be provided.

[0080] Although, in the current configuration, the first linear guides 210-217 and the second linear guides 250, 251 are driven by a transmission belt, they may also include other drive mechanisms, such as spindle drives, rack drives, etc. Other variations are known to those skilled in the art.

[0081] The line camera 600 can also be positioned in another manner. Alternatively, other detection devices can be provided to determine position and orientation before centering.

[0082] Although a Cartesian guidance device is shown exclusively in this exemplary embodiment, it will be apparent to those skilled in the art that other guidance devices may also be provided. In particular, individual or all of the Cartesian guidance devices may be replaced by robots, etc., in known ways.

[0083] In summary, it should be noted that the present invention provides a centering device, which, combined with a simple design, can be used in a particularly variable manner.

Claims

1. A method for centering a flat workpiece, particularly a sheet metal blank to be processed in a press, comprising the following steps: The current position and orientation of the workpiece are determined by means of a detection device, which is located upstream of the centering station; The workpiece is conveyed to the fixed center station along the conveying direction; The workpiece is clamped at at least two spaced-apart positions by a first clamping device and a second clamping device, each clamping device being able to rotate freely about an axis. The workpiece is raised from the support surface of the conveyor belt; The first clamping device and the second clamping device are moved horizontally by a corresponding guiding device, while maintaining the distance between the clamping devices; as well as Based on the determined current position, the workpiece is oriented to the desired position through a combination of translational and / or rotational movements.

2. The method of claim 1, wherein, The conveying of the workpiece along the conveying direction to the centering station is performed by means of a conveying device, and the lifting of the workpiece from the support surface of the conveyor belt includes: The workpiece is lifted from the support surface of the conveying device by means of a lifting unit, such that the workpiece rests on the support surface of the lifting unit, and the support surface of the lifting unit has a lower coefficient of friction than the support surface of the conveying device.

3. The method of claim 2, wherein, The supporting surface of the lifting unit includes a ball plate with freely rotatable balls, and the ball plate is arranged such that the workpiece can be located on the balls of the ball plate when the lifting unit is raised.

4. The method according to claim 2, wherein, The conveying device includes at least one conveyor belt, and the conveyor belt includes a plurality of parallel conveyor belt strips spaced apart from each other, wherein the lifting unit is arranged in the gap between two conveyor belt strips.

5. The method according to claim 1 or 2, wherein, One of the guiding devices includes a first linear guide for moving the clamping device along the conveying direction and a second linear guide for moving the first linear guide at a right angle to the conveying direction.

6. The method according to claim 1 or 2, wherein, The detection device includes a line camera, which is arranged upstream of the fixed center station with respect to the transmission direction.

7. The method according to claim 6, wherein, The centering station is controlled based on the measurement data from the line camera, so that the desired orientation of the workpiece can be achieved.

8. The method according to claim 6, wherein, The line camera determines the light and dark contours of the workpiece.

9. The method according to claim 8, wherein, The workpiece orientation includes: comparing the detected current position with the stored desired profile, and generating a correction signal for the guiding device.

10. The method according to claim 1 or 2, wherein, During the centering process, the workpiece is rotated more than 90°.

11. A centering device (1) for centering flat workpieces (700-706), particularly sheet metal blanks to be processed in a press, comprising: A centering station (100) having at least a first clamping device and a second clamping device (300, 301) for clamping the workpiece (700-706); and a conveying device for conveying the workpiece (700-706) to the centering station (100) along a conveying direction, wherein the first clamping device and the second clamping device (300, 301) are both capable of horizontal movement via a first guide device and a second guide device (200, 201), and wherein the first clamping device and the second clamping device (300, 301) are uniquely capable of free rotation about an axis, and the first clamping device and the second clamping device are capable of moving independently of each other in a plane to achieve the desired position of the workpiece.

12. The centering device (1) according to claim 11, characterized in that, The conveying device includes at least one conveyor belt (500).

13. The centering device (1) according to claim 12, characterized in that, The conveyor belt (500) includes a plurality of parallel conveyor belt strips (510) spaced apart from each other, wherein lifting units (530) having workpiece support surfaces are arranged in the gaps between two conveyor belt strips, such that when the workpiece support surfaces are raised, the workpieces (700-706) can be uniquely located on the workpiece support surfaces.

14. The centering device (1) according to claim 13, characterized in that, The workpiece support surface has a friction coefficient that is smaller than that of the workpiece support surface of the conveyor belt strip (510).

15. The centering device (1) according to claim 14, characterized in that, The surface of the lifting unit (530) includes a ball plate (531) arranged such that when the lifting unit is raised, the workpiece (700-706) can be positioned on the balls of the ball plate (531).

16. The centering device (1) according to any one of claims 11 to 15, characterized in that, The centering station (100) further includes a third clamping device and a fourth clamping device (302, 303), wherein the third clamping device and the fourth clamping device (302, 303) are rotatable about the axis and are each rotatable by means of the third guide device and the fourth guide device (200-203), respectively.

17. The centering device (1) according to any one of claims 11 to 16, characterized in that, One of the guiding devices (200-203) includes a first linear guide (210) for moving the clamping device (300) along the conveying direction and a second linear guide (250) for moving the first linear guide (210) at right angles to the conveying direction.

18. The centering device (1) according to claim 17, characterized in that, The first linear guides (210, 211) of the first guide device and the second guide device are arranged in parallel to each other, and the second linear guides (250) of the first guide device and the second guide device (210, 211) are arranged aligned with each other.

19. The centering device (1) according to any one of claims 17 and 18, characterized in that, The first linear guide (210, 211) includes a belt drive for moving the clamping device, and / or the second linear guide (250) includes a belt drive for moving the first linear guide.

20. The centering device (1) according to any one of claims 17 to 19, characterized in that, The clamping device (300) can be lowered and raised, preferably pneumatically raised and / or lowered, particularly relative to the first linear guide (210).

21. The centering device (1) according to claim 20, characterized in that, The clamping device (300) is pneumatically raised, particularly against restoring force and preferably against spring force.

22. The centering device (1) according to any one of claims 11 to 21, characterized in that, The clamping device (300) includes a suction cup (315) for clamping the workpiece (700-706).

23. The centering device (1) according to any one of claims 11 to 22, characterized in that, The centering device includes a detection device for detecting the position and orientation of the conveyed workpiece (700-706).

24. The centering device (1) according to claim 23, characterized in that, The detection device includes a line camera (600), which is arranged upstream of the fixed center station (100) with respect to the transmission direction.

25. The centering device (1) according to claim 24, characterized in that, The centering device includes a control device designed to control the centering station (100) based on measurement data from the line camera (600), thereby enabling the desired orientation of the workpieces (700-706) to be achieved.

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