EP1797973A1

EP1797973A1 - Combined panel bender-press brake machine

Info

Publication number: EP1797973A1
Application number: EP06115780A
Authority: EP
Inventors: Giovanni Vidotto
Original assignee: Crea SRL
Current assignee: Crea SRL
Priority date: 2005-12-16
Filing date: 2006-06-21
Publication date: 2007-06-20
Also published as: ITTO20050880A1

Abstract

A panel bending machine comprising:
- a fixed lower table (3),
- a movable upper table (4),
- a plurality of blank holder tools (1,2) borne by the lower table (3) and by the upper table (4) and able to hold a piece of sheet metal (12) in a fixed position, and
- a bending device (5) comprising a support structure (8) bearing two mutually opposite bending tools (6, 7) in fixed position with respect to each other.

The upper table (4) is movable relative to the lower table (3) in a vertical plane, and a plurality of bending punches and dies (19, 20) are provided, susceptible to be mounted on the upper table and on the lower table (3, 4) to replace the blank holder tools (1, 2).

Description

The present invention relates to machines for bending pieces of sheet metal.
In the prior art, there are two types of machines able to bend pieces of sheet metal: press brake machines and panel benders.
A press brake machine typically comprises a stationary support structure and two tables, whereof a first one is stationary whilst the second table is movable relative to the first along a rectilinear direction. The tables bear respective bending punches and dies co-operating with each other in a bending plane. The principle whereon press brake machines are based consists of bending a piece of sheet metal by effect of the mutual interpenetration of the bending punches and dies. During the bending operation, the opposite laps of the piece of sheet metal situated at opposite parts relative to the bending plane rotate towards each other as the punches and the die mutually inter-penetrate. Panel benders are machines based on a different operating principle from that of press brake machines. The operating principle whereon panel benders are based consists of keeping the piece of sheet metal still between a pair of blank holder tools and in executing the bending operation by means of a bending device that is movable relative to the piece of sheet metal.
Figure 1 of the accompanying drawings schematically shows the typical structure of a known panel bending machine. With reference to Figure 1, the panel bending machine according to the prior art comprises a pair of blank holder tools 1, 2 borne by a fixed lower beam 3 and by a mobile upper beam 4. The panel bending machine comprises a bending device 5 which comprises two mutually opposite bending tools 6, 7 fastened on a "C" shaped support structure 8. The structure 8 of the bending device 5 is provided with vertical and horizontal translation movements and with oscillation movements, indicated by the double arrow 9, whose combined action is such as to allow the bending action forcing a free edge 10 of a piece to be bent 12 in the direction of bending.
The upper table 4 is generally supported by a structure able to rotate around a fixed axis, so that the movement of the movable table 4 relative to the fixed table 3 is a circular movement, schematically represented by the double arrow 11.
In traditional panel bending machines, the piece of sheet metal to be bent 12 is actuated on a horizontal support plane. The actuation of the piece 12 is normally performed by means of a manipulator 13 provided with a pincer 14 able to enclose the piece of sheet metal 12 between two horizontal faces. The dimensions of the pincer 14 are small, in order to approach the pincer as far as possible to the blank holder tools 1, 2.
The support of the sheet metal piece 12 in order to maintain it flat is provided by means of a fixed bearing plane, coplanar with the bearing plane of the fixed blank holder tool 2. The manipulator 13 is provided with a translational movement 15 along a direction perpendicular to the tables 3, 4 and with a rotation movement 16 around a vertical axis.
Figures 2 and 3 outline the operation of a standard panel bending machine. The bending is accomplished by effect of the movement of the support structure 8 bearing the bending tools 6, 7 whilst the piece 12 is held between the blank holder tools 1, 2.
With reference to Figure 4, the oscillating structure 8 of the bending device 5 is provided with shuttles 17 which are movable along guides parallel to the bending line. Such shuttles 17 support bending tools positioned inwards relative to the bending tools 6, 7 integral with the oscillating structure 8. The tools borne by the shuttles 17 enable to execute the bending of lateral fins 18 of pieces of the type shown in Figure 5.
Known panel bending machines are often provided with tool changing systems which enable to configure the blank holder tool in order to adapt to the geometry and to the dimensions of the piece being machined. Figure 6 schematically shows the change of the blank holder tools 1 for the upper table 4 of a panel bending machine.
The sheet metal pieces 12 can be loaded and unloaded manually or, as in most automated systems, by means of an additional system for handling the pieces.
Panel bending machines are characterised by high productivity and by a high degree of automation compared to the bending process carried out by means of press brake machines. However, known panel bending machines have some limitations. For example, the bent piece must be such as to have, after bending, all the bends above the plane whereon slides the piece of sheet metal moved by the manipulator. Figure 7 shows an admissible combination of bends whilst Figure 8 shows a bend condition that is not achievable with known panel bending machines. In some machines, the presence of flanges is allowed below the plane whereon the piece of sheet metal slides only for the last side of the piece to be bent, because the piece is ejected from the machine by means of an accessory that makes the piece slide parallel to the line of the tools.
Moreover, the precision obtained for the bent flange is generally inferior to the one obtained by a press brake machine.
The dimensions of the piece to be bent are limited by the dimensions of the manipulator pincer. The thickness of the sheet metal piece to be bent is limited, because the stresses at stake to perform the bending operation by means of a panel bending machine would be too high and would require particularly heavy and costly mechanical structures.
Panel bending machines have a high cost, which further grows if an additional manipulator has to be added for loading/unloading the bent pieces.
Lastly, since some types of bending operations cannot be executed by a panel bending machine, in some cases the bending of the semi-finished piece output by the panel bending machine has to be completed with additional work performed by a press brake machine.
Comparing a panel bending machine with a press brake machine, the following is noted:

the panel bending machine is generally more productive than a press brake machine, even if the latter is served by robots;
the panel bending machine allows some types of bend that are more difficult to obtain on a press brake machine, but it does not allow types of bend or special work operations that are instead possible on press brake machines; and
the press brake machine has lesser limitations with respect to the dimensions of the piece and to its geometry.

The object of the present invention is to provide a panel bending machine with an improved structure, able to combine the advantages of a traditional panel bending machine with those of a press brake machine, to reduce the limitations of the panel bending machine in terms of geometry of the piece and type of allowable bends, as well as to reduce costs integrating in the manipulator the functions of loading/unloading the piece.
According to the present invention, said object is achieved by a panel bending machine having the characteristics set out in the claims.
The characteristics and the advantages of the present invention shall become readily apparent in the detailed description that follows, with reference to the accompanying drawings, provided purely by way of non limiting example, in which:

Figures 1 through 8, already described above, illustrate a known panel bending machine,
Figure 9 is a schematic perspective view of a panel bending machine according to the present invention,
Figure 10 is a lateral view of the panel bending machine according to the present invention with a possible manipulator configuration,
Figure 11 is a perspective view of the manipulator of Figure 10,
Figures 12 through 15 are schematic lateral views illustrating the work cycle of a panel bending machine according to the present invention,
Figures 16 through 19 illustrate an example of disengagement of the piece of sheet metal even in the presence of downwards bends,
Figure 20 is a perspective view that illustrates a bent piece provided with bends both along the outer edge and internal to the piece of sheet metal,
Figures 21, 22 and 23 schematically illustrate a combined cycle of panelling and pressure bending for the production of the piece illustrated in Figure 20,
Figures 24 through 27 illustrate four manipulator variants with different degrees of freedom, and
Figure 28 illustrates a variant in which an anthropomorphic robot is used,
Figure 29 illustrates a variant in which the same manipulator, in addition to serving the panel bender, serves other machines (e.g. press brake machines, riveting machines, welding machines, etc.), and
Figure 30 illustrates a variant in which the tables and the bending device of the panel bending machine are upset around a horizontal axis, in order to have the piece of sheet metal to be bent in vertical position.

With reference to Figure 9, the panel bending machine according to the present invention comprises a fixed lower table 3 and a movable upper table 4. The upper table 4 is provided with an up and down motion in a vertical plane and it is actuated by one or more actuators (not shown) of the hydraulic, electromechanical or mixed type.
In practice, the upper table 4 and the lower table 3 are perfectly equivalent to the structure of a traditional press brake machine.
Unlike traditional panel making machines and press brake machines, on the tables 3, 4 can be mounted the blank holder tools 1, 2 as in common panel bending machines or pairs of bending dies and punches 19, 20 for pressure-bending. The blank holder tools 1, 2 and the bending tools 19, 20 can be mounted manually by an operator or automatically by means of an additional manipulator (not shown). As Figure 9 schematically shows, the change of the tools involves both the upper table 4 and the lower table 3.
In a possible variant, the tool changing operation can be performed by the same manipulator that actuates the piece during the bending operations, which carries out the tool change operation before production is started, by means of an appropriate gripping member.
In Figure 9, the bending tools 19, 20 are mounted on respective supports 21 which are mounted on the tables 3, 4. This arrangement enables to pre-assemble the bending tools 19, 20 on the supports 21 in order to quicken the mounting of the bending tools on the tables 3, 4. However, this does not exclude that the bending tools 19, 20 can be mounted directly on the tables 3, 4. In a variant, not shown herein, the bending tools 19, 20 can be engaged on the blank holder tools 1, 2. In this case, it is not necessary to remove the blank holder tools 1, 2 to ready the machine to operate with the bending tools 19, 20.
The shuttles 17 of the bending device 5 are provided with respective abutments provided with position sensors 22 which serve for the alignment of the piece and as an abutment for the piece during pressure bending operations.
With reference to Figure 10, the traditional manipulator of known panel bending machines is replaced by a manipulator with multiple degrees of freedom, able to manipulate the piece of sheet metal 12 to be bent by means of interchangeable gripping members, which can be suction cup, magnetic or mechanical pincers. Figure 10 shows a Cartesian manipulator with four degrees of freedom provided with a translation along a horizontal axis 23 that is orthogonal to the tables 3, 4 of the panel bending machine, a movement in the vertical direction 24, an axis of rotation 25 of the gripping member 26 around a horizontal axis, and an axis of rotation 27 of the gripping member around an axis that is orthogonal to the previous one. The four axes are arranged serially, i.e. the last axis 27 is positioned downstream of the axis of rotation 24, which in turn is downstream of the axis of vertical translation 24 which, lastly, is located downstream of the axis of translation 23 orthogonal to the tables 3, 4. Figure 11 shows a perspective view of such a manipulator. The configuration of the manipulator shown in Figures 10 and 11 assures the minimum degrees of freedom to execute the manipulation of the piece of sheet metal both during the loading and unloading operation, and during the bending steps. In particular, the manipulator shown in Figures 10 and 11 allows to raise and to manipulate the piece of sheet metal along the horizontal plane or along any plane parallel to a plane passing through the third axis 25 of the manipulator. The third axis 25 enables to incline the grip member 26 to follow the sheet metal during the bending operations with dies and punches.
Figures 12 through 15 show a work cycle in panel bending machine mode, comprising the steps of drawing a piece (Figure 12), approaching the bend (Figure 13), bending (Figure 14) and unloading (Figure 15). The manipulator, by means of the rotation around the axis 25, orients the gripping member 26 in such a way as to be able to withdraw the flat piece of sheet metal stacked in one or more loading stations. In these loading stations, the pieces of sheet metal may be planar, inclined or vertical. The machine can be provided with appropriate systems to separate the pieces of sheet metal and measuring the thickness of the sheet metal itself. After completing the withdrawal operation, the manipulator executes the bending cycle in combination with the tables 3, 4, whereon the blank holder tools 1, 2 are mounted, and with the bending device 5 provided with the tools 6 and 7. At the end of the bending cycle, the piece is unloaded by the manipulator in one or more unloading stations.
With reference to Figures 16 through 17, the vertical movement of the gripping device 26 allows to insert and to disengage the piece 12 between the blank holder tools 1, 2 even in the presence of bends that are located below the plane of grip of the sheet metal piece.
Figures 21 through 22 illustrate a combined panel-making and pressure-bending cycle for the production of a piece illustrated in Figure 20. The piece 20 is provided with an inner flange which cannot normally be obtained with a standard panel bending machine or it can be obtained only under certain conditions and with special and costly equipment. Figure 21 schematically shows the panel- bending operation for the bending of the outer edges. Thereafter, after the replacement of the blank holder tools with the bending punches and dies, the bending of the inner flange is executed. Before the pressure bending operation, a measurement and alignment operation can be carried out with the sensors mounted on the shuttles 17 of the oscillating structure. As shown in Figures 22 and 23, during the pressure bending operation, the gripping device 26 rotates around a horizontal axis that is parallel to the bending line to accompany the bent lap during the bending operation (Figure 23).
Figure 24 shows a Cartesian manipulator provided with a spherical wrist, which allows a higher number of degrees of freedom and hence a greater dexterity in the manipulation of the piece and in the types of bend achievable. To the degrees of freedom of the manipulator of Figure 11 has been added an axis of rotation 28, orthogonal relative to the plane defined by the axes of rotation 25, 27.
Figure 25 shows a Cartesian manipulator provided, in addition to the spherical wrist, as in the manipulator of Figure 24, with an additional axis of translation 29 along a horizontal direction parallel to the tables. The manipulator of Figure 25 allows to move the piece on stations positioned along the longitudinal axis of the tables, eliminating the constraint of having the bending station in the centreline of the tables.
Figure 26 shows a manipulator with the same degrees of freedom of the manipulator of Figure 25 but provided with a gripping organ 26 that is mechanical instead of with suction cups.
Figure 27 shows an additional variation in which to the manipulator shown in Figures 25, 26 has been added a further degree of freedom constituted by a vertical axis of rotation 30 of the entire manipulator. In this way, the radius of action and hence the capacity to load/unload the pieces is increased.
Figure 28 shows an additional variant in which the Cartesian manipulator is replaced by an anthropomorphic robot with six axes of rotation indicated with the references 31 through 36.
Figure 29 is a plan view that illustrates an additional variant of the manipulators of Figure 25 and 27 in which the axis of translation 23 is positioned parallel to the tables 3, 4 of the panel bending machine, and the axis of translation 29 is orthogonal to the tables 3, 4. In this case, the manipulator is able to serve both the panel bending machine, and an additional machine 37 to perform complementary operations. Machine 37 could be a bending machine, if one does not intend to exploit the possibility of executing the bending operation using the tools 19, 20 mounted on the tables 3, 4 of the panel bending machine, or a riveting machine, a tack welding machine, or another machine required to complete the work cycle of the piece of sheet metal 12.
Figure 30 shows a variant of the present invention in which the whole bending structure has been rotated by 90° relative to the horizontal axis. In this way, the tables 3, 4 are horizontal instead of vertical. The piece of sheet metal 12 during the bending operations is maintained vertical. In this way, the flexing effect due to the weight of the piece of sheet metal itself is drastically reduced.
Naturally, without altering the principle of the invention, the construction details and the embodiments may be widely varied from what is described and illustrated herein, without thereby departing from the scope of the invention, as defined by the appended claims.

Claims

A panel bending machine comprising:
- a fixed lower table (3),

- a movable upper table (4),

- a plurality of blank holder tools (1,2) borne by the lower table (3) and by the upper table (4) and able to hold a piece of sheet metal (12) in a fixed position, and

- a bending device (5) comprising a support structure (8) bearing two mutually opposite bending tools (6, 7) in fixed position with respect to each other, in which the support structure (8) is movable along a vertical direction and a horizontal direction and it is provided with an oscillating movement to execute, by means of the bending tools (6, 7), the bending of a piece (12) held by said blank holder tools (1, 2),
characterised in that the upper table (4) is movable relative to the lower table (3) in a vertical plane, and in that it comprises a plurality of bending punches and dies (19, 20) susceptible to be mounted on the upper table and on the lower table (3, 4) to replace the blank holder tools (1, 2).
Panel bending machine as claimed in claim 1, characterised in that it comprises a Cartesian manipulator for the actuation of pieces of sheet metal, provided with a translational movement along a horizontal direction (23) that is orthogonal to said tables (3, 4), a translation movement along a vertical direction (24) that is parallel to said tables (3, 4), a first movement of rotation around a horizontal axis (25) parallel to said tables (3, 4) and a second movement of rotation (27) around an axis that is orthogonal to said first axis of rotation (25).
Panel bending machine as claimed in claim 2, characterised in that the manipulator device comprises an additional movement of rotation around an axis (28) orthogonal to a plane passing through said first and second axis of rotation (25, 27).
Panel bending machine as claimed in claim 3, characterised in that the manipulator comprises an additional movement of translation along a horizontal direction (29) parallel to said tables.
Panel bending machine as claimed in claim 4, characterised in that the manipulator devices comprises a fourth movement of rotation around a vertical direction (30).
Panel bending machine as claimed in claim 4, characterised in that it comprises an anthropomorphic robot for the manipulation of pieces of sheet metal, provided with at least six rotational degrees of freedom (31-35).
Panel bending machine as claimed in claim 4, characterised in that the bending device (5) comprises two adjustable shuttles (17) which can be displaced relative to the support structure (5) along a direction parallel to said tables (3, 4), said shuttles (17) being provided with respective position sensors (22).
Panel bending machine as claimed in claim 4, characterised in that the bending punches and dies (19, 20) are mounted on supports (21) able to be mounted on the tables (3, 4) to replace the blank holder tools (1, 2) .
Panel bending machine as claimed in claim 1, characterised in that the bending punches and dies (19, 20) are able to be mounted directly on the tables (3, 4) to replace said blank holder tools (1, 2).
Panel bending machine as claimed in claim 1, characterised in that the bending punches and dies (19, 20) are able to be mounted on said blank holder tools (1, 2).
Panel bending machine as claimed in claim 1, characterised in that the two tables (3, 4) and the bending device (5) are upset relative to a horizontal axis, in such a way that the tables (3, 4) extend in a horizontal plane.
Panel bending machine as claimed in claim 1, characterised in that the two tables (3, 4) and the bending device (5) are upset relative to a horizontal axis, in such a way that the tables (3, 4) extend in an inclined plane with any inclination.
Panel bending machine as claimed in claim 11, characterised in that the piece of sheet metal (12) is held vertical during the bending operations in order to reduce or eliminate the flexion effects caused by the weight of the sheet metal itself.
Panel bending machine as claimed in claim 4 or 5, characterised in that the direction of translation (23) is parallel to the table (3, 4), and the direction (29) is orthogonal to the tables instead of parallel.
Panel bending machine as claimed in claim 1, characterised in that the manipulator is able to serve both the panel making machine and other machine tools (37) in order to complete the work cycle of the piece.