EP1772204A1

EP1772204A1 - "Bending press for pieces of sheet metal with integrated manipulator in a rear positioning device"

Info

Publication number: EP1772204A1
Application number: EP06115768A
Authority: EP
Inventors: Francesco Vaudano
Original assignee: Crea SRL
Current assignee: Crea SRL
Priority date: 2005-10-07
Filing date: 2006-06-21
Publication date: 2007-04-11
Also published as: ITTO20050705A1

Abstract

Bending press for pieces of sheet metal, comprising:
- a stationary support structure (12, 14, 16) bearing a fixed tool holder table (18) and a movable tool holder table (20) able to move in a vertical plane, and
- a positioning device (24) situated on the rear side of the fixed tool holder table (18) and bearing at least one retaining element (28) able to be positioned in such a way as to define a reference surface against which is thrust an edge of a piece to be bent (P). The retaining element is provided with at least one gripping element (40a, 40b, 54, 56) rotatable around a horizontal axis (42) and able to be actuated around said axis of rotation (42) under the command of a numeric control unit, in such a way that during the bending operation the gripping element (40a, 40b, 54, 56) can hold the piece and follow the movement of the lap bent by the piece.

Description

The present invention relates to a bending press for pieces of sheet metal.
The document EP-A-619151 describes a bending press according to the preamble to claim 1, comprising a rear positioning device with a retaining element adjustable in the vertical and horizontal direction and forming an arresting surface for positioning the pieces of sheet metal to be bent. A pincer is movably mounted at the end of the retaining element, in such a way as to allow the gripping and manipulation of the pieces to be bent thanks to the vertical and horizontal displacement of the retaining element. The pincer is held in position against the retaining element by means of a flexible tie rod operated by a pneumatic actuator. During the bending operation, the pincer moves away from the retaining element following the movement of the bent lap of the piece. At the end of the bending operation, the pincer and the piece held thereby are returned against the retaining element by the flexible tie rod operated by the pneumatic actuator.
In the solution described in the document EP-A-619151 , the manipulator integrated in the positioning device allows to move the piece of sheet metal solely in the vertical and horizontal direction. The fact that the pincer is connected to the retaining element by means of a flexible member does not allow commanded movements of the pincer when the pincer is moved away from the retaining element. Moreover, during the bending operation, the pincer is not able to support the lap of the piece being bent.
The object of the present invention is to provide an enhanced solution that allows to exploit the rear retaining elements of the positioning device as members for sustaining and manipulating the pieces of sheet metal during the bending operation.
According to the present invention, said object is achieved by a bending press having the characteristics set out in the claims.
The present invention shall now be described in detail with reference to the accompanying drawings, provided purely by way of non limiting example, in which:

Figure 1 is a perspective view of a bending press according to the present invention,
Figure 2 is a rear perspective view of the bending press of Figure 1,
Figure 3 is a schematic perspective view of the positioning device indicated by the arrow III in Figure 1,
Figure 4 shows a different grip mode of the positioning device of Figure 3,
Figures 5 and 6 are two schematic lateral views showing the positioning and gripping of pieces of sheet metal with different length of the flange to be bent,
Figures 7 through 13 are schematic views showing the sequence of execution of a bend in the brake according to the present invention,
Figure 14 is a perspective view of a variant of the positioning device according to the invention, and
Figures 15 through 18 are lateral views illustrating the operation of the positioning device of Figure 14.

With reference to Figures 1 and 2, the number 10 designates a bending press for pieces of sheet metal. The bending press 10 comprises a fixed base structure including two lateral uprights 12 joined together by an upper cross member 14 and by a lower cross member 16.
The bending press 10 comprises a lower tool holder table 18, fixed relative to the base structure, and an upper tool holder table 20, movable in a vertical plane and actuated by two actuators 22.
On the rear side of the brake 10 there is a positioning device 24 comprising a horizontal beam 26 parallel to the lower tool holder table 18. The horizontal beam 26 is movable in the vertical direction and along a horizontal direction that is orthogonal with respect to the tool holder tables 18, 20. The horizontal beam 26 bears two retaining elements 28, each of which is provided with a translation movement along the horizontal beam 26 in a parallel direction to the line of the tools of the bending press 10.
The two retaining elements 28 are provided with respective abutment surfaces against which an edge of a piece of sheet metal to be bent goes to bear. The abutment surfaces of the retaining elements 28 can be arranged in a predetermined position with respect to the bending tools thanks to the horizontal and vertical motion of the beam 26. The abutment surfaces of the retaining elements 28 constitute a reference surface for positioning the pieces of sheet metal which defines the length of the lap to bend, i.e. the distance of the edge of the piece from the bending line.
The motion of the beam 26 and of the retaining elements 28 is commanded by electric motors (not shown) controlled numerically by the numeric control unit of the machine. The control unit defines the position of the retaining elements and, consequently, the position of the reference surface for the bearing of the rear edge of the sheet metal pieces, according to the bending program of the piece.
With reference to Figure 3, the arrows 30, 32 indicate the direction of displacement of the horizontal beam 26 and the arrows 34 indicate the direction of displacement of each retaining element 28 along the beam 26. Each retaining element 28 comprises a base 36 that is mounted able to slide along the beam 26 in the direction indicated by the arrows 34. Each retaining element 28 also comprises a retaining body 38 which bears the retaining surfaces for positioning pieces of sheet metal P.
The retaining body 38 of each retaining element 28 bears at least one gripping element able to grip a piece of sheet metal P. In the example illustrated in Figure 3, each retaining body 38 is provided with two gripping elements 40a, 40b. In the embodiment illustrated by way of example in Figure 3, the gripping elements 40a, 40b are pincer gripping elements. Alternatively, the gripping elements could be of the type with suction cups or magnets or each retaining element 28 could be provided with one or more pincer gripping elements and with one or more suction cup or magnet gripping elements.
The retaining bodies 38 of the retaining elements 28 are articulated to the respective bases 36 around common horizontal axis 42 parallel to the bending line. Each retaining element 38 is provided with an electric motor (not shown), numerically controlled, which commands the rotating motion of the retaining element 38 around the axis 42. The motors that command the rotation of the retaining elements 38 are controlled by the same numeric control elements that manages the motion of the beam 26, of the retaining elements 28 and of the movable table 20 of the bending press.
The gripping elements 40a, 40b are configured in such a way as to be able to grip a piece to be bent both on a side parallel to the bending line (Figure 3) and on sides of the piece P that are perpendicular to the bending line (Figure 4).
The gripping elements 40 are situated at the distal ends of the retaining elements 28 and they are intended to grip pieces with small flanges to be bent. The gripping elements 40b are situated in an intermediate position between the gripping elements 40a and the axis of rotation 42 and they are intended to grip pieces with large flanges to be bent (Figure 6).
Figures 5 and 6 show a piece of sheet metal to be bent P positioned between a punch 44 and a die 46, respectively fastened to the upper tool holder table 20 and to the lower tool holder table 18.
As shown in Figure 6, for bending large flanges, the retaining elements 28 also support the piece P in optimal fashion even in the presence of a flexion of the piece (phenomenon that is the more accentuated the larger and thinner the manipulated piece).
Figures 7 through 13 illustrate the working sequence of the positioning device 24 described previously. In the first step, shown in Figure 7, the operator introduces the piece P between the bending tools 44, 46 of the bending press and pushes the piece P to abut against the retaining elements 28, as occurs in a normal bending press. This operation could also be performed by means of a manipulator robot positioned on the front side of the press.
Gripping the piece of sheet metal P and positioning the piece P between the bending tools could also be accomplished by the positioning device 24 using the gripping elements provided on the retaining elements 28, as described in detail in the Italian patent application no. T02004A 000842 by the same Applicant.
When the piece P is situated between the punch and the die 44, 46 and is held by the gripping pincers 40a of the retaining elements 28, the bending step starts. In a first step shown in Figures 8 and 9, the positioning device 24 positions the piece P in such a way that the flange to be bent has the desired length. Simultaneously, the punch moves towards the die (Figure 10) and starts bending the piece. During the bending operation (Figure 11) the positioning device follows the motion of the flange under the command of the numeric control unit. During the bending operation the flange is held by the gripping elements 40a. This is made possible by the rotating motion of the abutment bodies 38 around the axis 42. At the end of the bending operation, the positioning device 24 repositions the piece P for the execution of a second bend (Figure 12) and the cycle is repeated for each subsequent bend (Figure 13).
During the bending operations, the operator does not intervene directly on the piece, since the piece is manipulated by the motorised retaining elements 28 of the positioning device 24. The operator's intervention may be necessary during the upsetting and/or unloading of the piece or to execute bends that are not obtainable with the system described above. In the first case, the retaining elements are positioned in such a way as to hand the piece to the operator and, on the operator's command, the pincers are opened. The operator upsets the piece and hands it back to the positioning device 24 pushing the piece 24 to abut against the reference surfaces of the retaining elements. At this point, the piece is gripped by the gripping elements and the cycle of automatic manipulation of the piece resumes.
The positioning device 24 according to the present invention could also be provided with support structures to prevent the piece of sheet metal from flexing. The positioning device could also be provided with integrated systems for loading and unloading and/or upsetting the piece. If the piece cannot be manufactured or completed with automatic manipulation by the device 24, the retaining elements can be used as the traditional retainers of bending presses.
Figure 14 shows a variant of the positioning device according to the present invention. In the variant of Figure 14, each retaining element 28 comprises a retaining body 46 fixed relative to the base 36 and provided with abutment surfaces 48 against which is thrust to bear the edge of the piece for its positioning with respect to the bending line. Each retaining element 28 is further provided with a gripping element 50 with a part 52, fixed relative to the retaining body 46 and to the base 36 and a rotating part 54, rotatable relative to the fixed part 52 around the axis 42. The rotating part 54 bears the means for gripping the piece of sheet metal which can be of the pincer type (as illustrated in the figure) or with suction cups or magnets.
Figures 15 through 18 show a possible working sequence of the positioning device shown in Figure 14. As is readily apparent, this configuration of the device allows to perform upsetting operations on the piece in order to execute bends on opposite sides of the piece. Figure 15 shows the device at the end of the first bend, Figure 16 shows the step of upsetting the piece and Figures 17 and 18 show the positioning of the piece for the execution of the second bend and the step of executing the second bend.
In both embodiments described above, the bending lines need to be parallel to the axis of rotation 42 of the gripping elements. The retaining elements 28 can be provided with further degrees of freedom with respect to the embodiments described above, in order to allow the execution of bends along lines that are not parallel to the grip area.
The two retaining elements could also be provided with mutually independent vertical and horizontal translation movements in an orthogonal direction to the bending line.
The retaining elements of the solution according to the present invention are preferably interchangeable, so that the positioning device can be adapted to pieces having different geometry. The interchangeability of the gripping elements allows to use the positioning device 24 also to replace the bending tools in automatic. To do so, the gripping elements suitable for gripping and manipulating pieces of sheet metal are automatically replaced with gripping elements suitable for gripping and manipulating the bending tools.
The system according to the present invention can also be combined with a bending robot. In this case, the retaining elements according to the present invention can co-operate with the bending robot to execute the bends, e.g. subdividing the bending cycle into some steps to be performed by the bending robot and into other steps to be performed by the positioning device 24. The device 24 can also be used to upset the piece as an auxiliary manipulating element assisting the main manipulator robot.
The advantages of the present invention are the following:

ability to exploit an automatic device normally present on bending presses to conduct more operations than those whereto the device is normally dedicated;
ease of application to bending presses, since the retaining elements currently present on the press can be replaced;
ability to relieve the operator of the need to accompany the piece of sheet metal during the bending operation;
ability to free the front area of the brake from the bulk of any accompanying devices and/or manipulator robots which would limit access to the operator;
ability to enhance the operator's safety, since (s)he is not forced to hold the piece with his/her hands during the bending operation;
ability to enhance flexibility in the case of integrated cell with bending robot, and
reduction in cycle times.

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

Bending press for pieces of sheet metal, comprising:
- a stationary support structure (12, 14, 16) bearing a fixed tool holder table (18) and a movable tool holder table (20) able to move in a vertical plane, and

- a positioning device (24) situated on the rear side of the fixed tool holder table (18) and bearing at least one retaining element (28) able to be positioned in such a way as to define a reference surface against which is thrust an edge of a piece to be bent (P) to position said piece with respect to the bending line,
in which the positioning device (24) is provided with at least one gripping element (40a, 40b, 54, 56) for gripping and manipulating the piece of sheet metal,
characterised in that said gripping element (40a, 40b, 54, 56) is rotatable around a horizontal axis (42) and it can be actuated around said axis of rotation (42) under the command of a numeric control unit, in such a way that during the bending operation the gripping element (40a, 40b, 54, 56) can hold the piece and follow the movement of the lap bent by the piece.
Bending press as claimed in claim 1,
characterised in that said retaining element (28) comprises a base (36) and a retaining body (38) that is rotatable relative to the base (36) around said horizontal axis (42), the retaining body (38) bearing at least one gripping element (40a, 40b).
Bending press as claimed in claim 1,
characterised in that each retaining element (28) comprises a base (36) and a retaining body (46) that is fixed relative to the base (36), the retaining element (28) comprising a gripping element (50) including a first part (52), fixed with respect to the base (36) and a rotatable part (54) bearing gripping means (56) for gripping pieces of sheet metal.
Bending press as claimed in any of the previous claims, characterised in that said first gripping element (40a, 40b, 50) is replaceable.
Bending press as claimed in claim 1,
characterised in that the positioning device (24) comprises a beam (26) that is movable in the vertical direction and in the horizontal direction orthogonally to the bending line, the beam (36) bearing two retaining elements (28) movable along the beam (26) along a direction that is parallel to the bending line and provided with respective gripping elements (40a, 40b, 54, 56).
Bending press as claimed in claim 5,
characterised in that the gripping elements of said retaining elements (28) are rotatable around a common horizontal axis (42) parallel to the bending line.
Bending press as claimed in claim 1,
characterised in that the retaining elements (28) provided with gripping elements (40a, 40b, 54, 56), are provided with mutually independent translation motions in the vertical and horizontal direction, orthogonal to the bending line.
Bending press as claimed in any of the previous claims, characterised in that the interchangeable gripping element further provides for the use of gripping elements suitable for replacing the bending tools.