WO2013167803A1

WO2013167803A1 - Method of measuring a workpiece in bending, a measuring device, a measuring carriage as well as a press brake

Info

Publication number: WO2013167803A1
Application number: PCT/FI2013/050493
Authority: WO
Inventors: Hannu Alitalo
Original assignee: Aliko Oy Ltd
Priority date: 2012-05-07
Filing date: 2013-05-06
Publication date: 2013-11-14
Also published as: FI20125492L

Abstract

The invention relates to a method of measuring a workpiece in a press brake. The invention further relates to a measuring device, a measuring carriage as well as a press brake. The workpiece (8) is measured by the measuring device (16) which is moved in its longitudinal direction (A) during measurement. The measuring device is provided with a supporting arm (29) in which a measuring carriage (30) is arranged by means of a joint (31). The measuring carriage is provided with contact members (41) which follow a surface of the workpiece during the measurement. A position of the measuring carriage with respect to the supporting arm is determined by means of a measuring member (40), and measurement data is used for determining deformation of the workpiece and for controlling operation of the press brake (1).

Description

Method of measuring a workpiece in bending, a measuring device, a measuring carriage as well as a press brake

Background of the invention

[0001] The invention relates to angular measurement, and measurement of an angle or curvature of a workpiece bent by means of a press brake bending machine in particular.

[0002] The invention further relates to a measuring device and a measuring carriage which may be used for measuring, in a press brake, an angle or curvature formed on a workpiece. The invention further relates to a press brake equipped with a measuring device.

[0003] The field of the invention is described in closer detail in the preambles of the independent claims of the application.

[0004] It is possible to manufacture various products of sheet material by bending. A press brake can be used for rectilinear bending, in which the bending axis is straight. In a press brake, sheet material is bent in one direction between press brake bending tools. Such press brake bending tools include a male die and a female die. Typically, bending in a press brake is carried out as free bending, in which a sheet is bent so that the sheet is not pressed against the entire surface of a tool but wherein the angle of an edge being formed is affected by adjusting the mutual distance between the tools. The structure of a press brake is made as robust as possible; nevertheless, deformations occur in the structure and in the long beams in particular, because the pressing forces are great and the distances between support points are long. Consequently, bending suffers from inaccuracy because of deflections. In addition, tolerances in the material may cause measuring errors. In order to solve this drawback, the press brake is equipped with a measuring device so as to enable a workpiece to be measured after a first pressing phase, adjustment to be carried out on the basis of measurement results, as well as a second pressing phase to be performed. However, the existing measuring devices are defective.

Brief description of the invention

[0005] An object of the present invention is to provide a novel and improved method, measuring device, measuring carriage, and press brake.

[0006] The method according to the invention is characterized by using the measuring device which is provided with a measuring carriage pro- vided with at least two contact members arranged at a distance from one another; pressing, during the measurement, the measuring carriage against the flank surface of the workpiece, whereby the measuring carriage, supported by the contact members, settles along the direction of the flank surface to be measured; and determining an angular position of the measuring carriage and determining, on the basis of the angular position, an angular position of the flank surface of the workpiece.

[0007] The measuring device according to the invention is characterized in that the measuring head comprises a measuring carriage pivotally connected by a joint to the supporting arm; the measuring carriage is provided with at least two contact members located at a distance from one another, the contact members following a surface of the workpiece to be measured and affecting a position of the measuring carriage with respect to the supporting arm; and the measuring member is arranged to determine an angular position between the supporting arm and the measuring carriage.

[0008] The measuring carriage according to the invention is characterized in that the measuring carriage has a rotatable frame; the rotatable frame has a joint; the rotatable frame is further provided with at least two contact members located at a distance from one another, the contact members following the surface of the workpiece to be measured and affecting a position of the measuring carriage with respect to the joint; and the measuring carriage is provided with at least one measuring member for determining an angular position of the joint.

[0009] The press brake according to the invention is characterized in that the measuring device is as claimed in independent claim 5.

[0010] The idea underlying the disclosed solution is that the deformation of the workpiece is measured by means of the measuring carriage. During measurement, the carriage is moved in a longitudinal direction of the workpiece. The measuring carriage comprises contact members that follow the surface to be measured. The measuring carriage is supported on the supporting arm by means of a joint, in which case the carriage turns into an angular position according to the surface to be measured with respect to the joint. A turning position of the joint is measured, and the measurement result is used for determining deformation of the workpiece. The operation of the press brake may be controlled on the basis of the deformation of the workpiece. [0011] An advantage of the disclosed solution is that the measurement is carried out by means of a relatively simple measuring device which is inexpensive and easy to install in the press brake. The measuring device is also reliable and safe since the measurement is not based on using optics or a laser.

[0012] The idea of an embodiment is that measurement data is used for controlling deflection compensation of the beams of the press brake. One beam or both beams of the press brake or a table of the press may be provided with adjusting units for producing so-called crowning. This enables the bending of the workpiece to be made uniform over the entire bending length, although the press brake always exhibits some flexibility.

[0013] The idea of an embodiment is that measurement data is used for adjusting the length of a working stroke of the press brake. This means that after measurement, in the second phase of the bending, the distance of the male die from the female die may be adjusted, enabling a bend of the workpiece between the male die and the female die to be made as desired.

[0014] The idea of an embodiment is that both flank surfaces of a bend formed on the workpiece are measured. The measurement may be carried out either from the outer surface side or from the inner surface side of the workpiece. On the basis of measurement results, angular values of the bend in question are determined in a control unit over a section of the measured longitudinal measuring cycle.

[0015] The idea of an embodiment is that the press brake is used for bending one half of a tubular piece with a curved cross section. This enables the curvature of the inner surface of the bent workpiece to be measured by means of one or more measuring devices.

[0016] The idea of an embodiment is that two parallel flank surfaces of a workpiece are measured and deviations in the parallelism of these flank surfaces are determined on the basis of the measurement results. Measurement data is used for forming corrective control parameters, and a second press brake bending procedure is carried out so as to make the flank surfaces in question parallel. This embodiment may be utilized when producing components for structures that are to be formed from two halves. This embodiment enables e.g. division surfaces of the beams to be made dimensionally accurate. Further, it is possible to measure the parallelism of the flanks of any bending profile. [0017] The idea of an embodiment is that a workpiece having a tubular cross-sectional profile bent thereon is measured. One, two or more flank surface(s) of such a workpiece may be measured in order to determine the dimensions and shape of the tube.

[0018] The idea of an embodiment is that the workpiece is measured over its entire length. The measuring device may then be run from end to end of the workpiece. If several measuring devices are provided one after the other, the length to be measured may be divided between them in some appropriate manner.

[0019] The idea of an embodiment is that the workpiece is measured over selected one or more measurement lengths which are smaller than the total length of the workpiece.

[0020] The idea of an embodiment is that at least one measuring device is connected to the lower beam or the table of the press brake.

[0021] The idea of an embodiment is that at least one measuring device is connected to the upper beam of the press brake.

[0022] The idea of an embodiment is that at least one measuring device is connected to the press brake bending tool of the press brake, i.e. to the male die or the female die.

[0023] The idea of an embodiment is that at least one measuring device is connected to a deflection compensation device which is provided in the press brake and which may be located on a side of the press brake.

[0024] The idea of an embodiment is that the frame of the measuring device comprises a horizontal frame and a vertical frame. The horizontal frame is by means of a linear bearing connected to horizontal guides to be fastened to the press brake, in which case the horizontal frame is movable along the guides in a longitudinal direction of the press brake. Further, between the vertical frame and the horizontal frame are provided vertical guides, which are perpendicular to said horizontal guides, and linear bearings, making the vertical frame movable in a vertical direction with respect to the horizontal frame. One or more supporting arms of the measuring device are fastened to an upper part of the vertical frame. The upper part of the vertical frame may be provided with a projection-like section which is directed towards the press brake. The projection-like section may be a rigid fixed part or, in some cases, it may also be an articulated arm that can be turned mechanically or by means of an actuator. [0025] The idea of an embodiment is that the frame of the measuring device comprises a horizontal frame and a rotatable vertical frame. The horizontal frame is by means of a linear bearing connected to the horizontal guides to be fastened to the press brake, in which case the horizontal frame is movable along the guides in the longitudinal direction of the press brake. The vertical frame is by means of a turning joint arranged in the horizontal frame, enabling the vertical frame to be turned towards or away from the workpiece. Further, the vertical frame may be extendable and contractable.

[0026] The idea of an embodiment is that the supporting arm is by means of a joint arranged in the frame, enabling the supporting arm to be turned in order to place the measuring carriage against the workpiece in a desired manner. The supporting arm may also be provided with more joints, or an appropriate joint mechanism may be provided between the supporting arm and the frame. This embodiment enables the measuring carriage to be placed against the outer surface and the inner surface of the workpiece.

[0027] The idea of an embodiment is that the contact member is placed in a physical contact with the press-brake-bent workpiece.

[0028] The idea of an embodiment is that the contact member is a rolling member pivotally mounted to the rotatable frame.

[0029] The idea of an embodiment is that the contact member is a wheel.

[0030] The idea of an embodiment is that the contact member is a roller or a corresponding cylindrical rolling member.

[0031] The idea of an embodiment is that the contact member is a ball.

[0032] The idea of an embodiment is that the contact member is a slide which can be slidingly moved along the surface of the workpiece.

[0033] The idea of an embodiment is that the contact member is a slide pin or a slide block. Such a contact member may be manufactured from a plastic material, ceramics or hardened steel with good sliding properties and durability.

[0034] The idea of an embodiment is that the contact member is a pressure medium element, such as an air bag element. In such a case, the contact member and the workpiece have a contact through the pressure medium, whereby the contact member follows the surface of the workpiece and affects the angular position of the measuring carriage. [0035] The idea of an embodiment is that the contact member is a member forming a magnetic field. In such a case, a magnetic field is formed between the contact member and the workpiece, due to the influence of which the contact member follows the surface of the workpiece at a physical distance from the surface to be measured. However, the contact member transmits forces on the measuring carriage that turn it into an angular position according to the surface of the workpiece. The contact member according to this embodiment is thus not in a physical contact with the workpiece but the contact member does, however, produce the forces necessary for implementing the measuring principle disclosed in this application.

[0036] The idea of an embodiment is that the measuring member is an angle sensor arranged in connection with a turning joint provided between the supporting arm and the measuring carriage.

[0037] The idea of an embodiment is that the measuring member is a laser configured to measure the turning angle of the measuring carriage with respect to the supporting arm.

[0038] The idea of an embodiment is that the measuring carriage is used for measuring the surface of a workpiece provided with holes or recesses.

[0039] The idea of an embodiment is that the measuring carriage comprises three, four or more contact members located at a distance from one another. In such a case, the measuring carriage may retain its position with respect to the surface of the workpiece even if one contact member passes over a hole in the workpiece. The other contact members enable one contact member to travel across the hole or recess without affecting the measurement.

[0040] The idea of an embodiment is that the measuring carriage comprises elongated bar-like or cylindrical contact members whose length is selected to be greater than the dimension parallel with the surface of the holes or recesses in the surface of the workpiece to be measured. In such a case, the contact member travels across the hole or recess in the workpiece without affecting the measurement.

[0041] The idea of an embodiment is that during measurement, the measuring carriage is pressed against the surface of the workpiece to be measured. [0042] The idea of an embodiment is that the measuring carriage is by means of the supporting arm pressed against the surface of the workpiece to be measured.

[0043] The idea of an embodiment is that the measuring carriage is provided with means for pressing it against the surface of the workpiece to be measured.

[0044] The idea of an embodiment is that two, three or more measuring devices are arranged one after the other in the longitudinal direction on one side or on both sides of the press brake. The measuring devices provided one after the other may be arranged to move on the same guide, or they may have guides of their own.

[0045] The idea of an embodiment is that the measuring device comprises two, three, four or more measuring units. Each measuring unit comprises at least one supporting arm and measuring carriage. The measuring units may be arranged side by side, in which case the measuring units are with respect to one another located at a different distance from the gap. Such a measuring device enables the flank surface of the workpiece to be measured at several points simultaneously. The measuring carriages of adjacent measuring units may be partially overlapping with respect to one another.

[0046] The idea of an embodiment is that for the duration of the work phase of the press brake, i.e. pressing, the measuring device is driven to a measuring device position provided at an end of the press brake. When the measuring device has been driven into this position, it will not interfere with the pressing or visibility of the workpiece and, on the other hand, it is protected against dents.

[0047] The idea of an embodiment is that in the measuring carriage, the distance between the contact members is at least 20 mm, usually 20 to 500 mm. A typical distance is 50 to 200 mm. When the contact members are sufficiently far away from one another, a necessary turning moment is ensured which makes the measuring carriage to turn with respect to the supporting arm.

[0048] The idea of an embodiment is that the supporting arm of the measuring device is extendable and contractable linearly, and in addition the length of the supporting arm is measured by means of at least one measuring member. This embodiment enables, for instance, a radius of a workpiece bent into an arc to be measured. [0049] The idea of an embodiment is that the measuring carriage is by means of a turning joint arranged in the rigid frame part of the measuring device, in which case the turning angle is determined with respect to the frame part. The frame part may be provided with a projection which forms a supporting arm for the measuring carriage. The measuring device with a rigid structure may be dimensioned and positioned such that the measuring carriage automatically settles at a correct measurement point on the flank surface of the piece to be measured when the measuring device is being run. On the other hand, it is possible to adjust the location of the measuring device in a transverse direction and in a height direction so that the measuring device may be pre-set for measurement.

Brief description of the figures

[0050] Some embodiments are explained in more detail in the accompanying drawings, in which

Figure 1 is a schematic front view of a press brake;

Figure 2 schematically shows, as viewed in a longitudinal direction of a workpiece, an arrangement for measuring parallelism of flanks of the workpiece;

Figure 3 schematically shows, as viewed in the longitudinal direction of a workpiece, an arrangement for measuring an angle bent on the workpiece;

Figure 4 is a schematic view of a measuring device;

Figure 5 schematically shows, as viewed in the longitudinal direction of a workpiece, a measuring carriage of the measuring device, the carriage being provided with wheels rolling against a surface of the workpiece;

Figure 6 schematically shows, as viewed in the longitudinal direction of a workpiece, a measuring carriage of the measuring device, the carriage being provided with slide members sliding against the surface of the work- piece;

Figure 7 schematically shows, as viewed in the longitudinal direction of a workpiece, a measuring carriage of the measuring device, the carriage being provided with rollers rolling against the surface of the workpiece;

Figure 8 schematically shows, as viewed perpendicularly to a surface of a workpiece, a measuring carriage of the measuring device, both ends of the carriage being provided with two wheels;

Figure 9 schematically shows, as viewed in the longitudinal direction of a workpiece, a measuring carriage of the measuring device, contact mem- bers in the carriage forming a fork-like head to be arranged against the surface of the workpiece;

Figure 10 schematically shows, as viewed in the longitudinal direction of a workpiece, an alternative measuring device whose vertical frame is rotatable with respect to a joint;

Figure 11 schematically shows, as viewed in the longitudinal direction of a workpiece, an angular measurement arrangement wherein an upper beam of a press is provided with a measuring device for measuring internal curvature of the workpiece, and

Figure 12 schematically shows a measuring device which may be fastened to the upper beam of a press brake for measuring an angle or curvature of a workpiece; and

Figure 13 shows as a simplified diagram phases associated with measurement.

[0051] For the sake of clarity, the figures show some embodiments in a simplified manner. In the figures, like reference numerals identify like elements.

Detailed description of some embodiments

[0052] The vertical press brake 1 shown in Figure 1 comprises a frame 2 including at least ends 2a and 2b which may be supported against a floor. Between the ends 2a, 2b are supported an upper beam 3 and a lower beam 4, which are elongated pieces. The beams 3 and 4 may be plate structures. The lower beam 4 may be connected by fastening pins 5 or corresponding connecting members to the ends 2a, 2b, whereby it may be stationary. The upper beam 3 may be moved in a vertical direction by means of powered members 6a and 6b. The powered members 6a, 6b may be hydraulic cylinders by means of which the upper beam 3 may be moved towards the lower beam 4 during press brake bending and, correspondingly, away from the lower beam 4 during a return movement. Between the upper beam 3 and lower beam 4 a gap 7 is provided in which a workpiece 8 to be press brake bent may be arranged. The opposite longitudinal edges of the beams 3, 4 have support surfaces 9 to which press brake bending tools may be fastened. A male die is typically fastened to the upper beam 3 while a female die is fastened to the lower beam 4. For the sake of clarity, Figure 1 shows no press brake bending tools.

[0053] Figure 1 shows in an exaggerated manner and in dashed line 10 the deflection of the support surface 9 of the upper beam 3 under the influence of press brake bending forces. The upper beam 3 is supported at its ends, but no support is provided in the middle. Because the beam is typically several metres long, the beam 3 slightly deflects into an arc in the middle, even though its structure is constructed to be considerably rigid in respect of deflection. In order to compensate for this deflection, the press brake 1 is equipped with several adjusting units 1 that may be arranged in the structure of the lower beam 4. The adjusting units 11 may be arranged along the entire length of the lower beam 4 at a predetermined distance L from one another. The distance L may be 500 mm, for instance. Each adjusting unit 11 may comprise an eccentric mechanism 12 and an actuator 13 to affect its turning position. The actuator 13 may be a hydraulic cylinder that may be connected through a crank or a corresponding transmission member to act on the eccentric 12. By means of the adjusting units 1 , the support surface 9 of the lower beam 4 may be bent into a curve as shown in dashed line 14 in the figure. The purpose is then to bend the support surface 9 of the lower beam 4 so that it becomes parallel with the support surface of the upper beam 3 that bends during the press brake bending. The magnitude of an angle being formed on the piece during press brake bending is then equal along the entire press brake bending length.

[0054] The eccentric mechanism 12 of the adjusting unit 11 transmits the force generated by the actuator 13 to the beam 4, in which case the beam 4 bends at said adjusting unit 11. Thus, the adjusting units 11 have a local effect on the deflection of the support surface 9. The adjusting units 11 are independent devices that may be controlled irrespective of one another. The operation of the press brake 1 may be controlled by one or more control units 15 that may also control the adjusting units 11. The control unit 15 may comprise a processor or it may be a programmable logic, for example. One or more control strategies may be set in the control unit 15 to control the adjusting units 11. Further, the press brake 1 may have one or more measuring devices 16 for measuring the deformation of a press-brake-bent piece. The measuring device 16 may be arranged in first guides 17 provided in the lower beam 4 of the press brake, or in second guides 18 provided in the upper beam 3. This enables the measuring device 16 to be moved, supported by the guide 17, 18, in a longitudinal direction A of the press brake 1 , whereby the measuring device 16 moves in a direction of an angle or curve formed on the workpiece 8. The measurement may thus be carried out simultaneously with driving the measuring device 16 in the direction A. The measuring device 16 may be arranged on both sides of the press brake, which enables both flanks of a bend formed on the workpiece 8 to be measured without removing the workpiece from the gap 7. Measurement data may be transmitted from the measuring device 16 to the control unit 15 which, on the basis of measurement results, may determine the need for deflection compensation and control the adjusting units 11 individually. Additionally, the measurement may be used for determining a magnitude of a bent angle and thus for adjusting the length of stroke of the press, i.e. the distance of the male die from the female die may be adjusted so that a desired sought-after angle for bend or sought-after curvature is achieved in free bending when a curved shape is formed by bending.

[0055] Figure 2 shows a measuring arrangement wherein parallelism of bent flanks 19 and 20 of the workpiece 8 is measured. If the measurement reveals any deviation from parallelism, in a second phase of the bending an angle 21 may be pressed by a male die 22 further towards a female die 23 in order to achieve a sought-after value.

[0056] Both sides of the press brake 1 are provided with measuring devices 16a, 16b which are by means of the guides 17 supported on the lower beam 4 and which may be moved by one or more drive motors M along the linear guides 17 in the longitudinal direction A of the workpiece. The measuring device 16 comprises a frame 24 which may be provided with a first frame part 25 and a second frame part 26. The first frame part 25 is supported on the guides 17, and the second frame part 26 may be moved in a vertical direction C with respect to the first frame part 25. The second frame part 26 may be provided with a projection part 27 which is directed towards the gap 7. The projection part 27 is fixed or, alternatively, it may be moved in a transverse direction B, or its length may be changed. A supporting arm 29 is by means of a joint 28 connected to a section of an outermost end of the projection part 27. In the supporting arm 29 is arranged a measuring carriage 30 which may be placed against the surface 19, 20 of the workpiece 8 to be measured. The measuring carriage 30 is connected by means of a joint 31 to the supporting arm 29. The position of the measuring carriage 30 with respect to the supporting arm 29 is measured during measurement, when the measuring carriage 30 is moved in the longitudinal direction A of the workpiece.

[0057] The measuring carriage 30 may be placed in a versatile manner at different measurement points against the workpiece 8, when the second frame part 26 may be moved in the vertical direction C and the supporting arm 29 may be turned with respect to the joint 28. The moving may be carried out by means of actuators. The actuator may be an electric motor. The second frame part 26 and the supporting arm 29 may also be used for producing a force to continuously keep the measuring carriage 30 against the work- piece 8 during measurement.

[0058] If a bending angle 21 is measured, the measuring carriage 30 of the right-hand measuring device 16b may be arranged at an alternative measurement point 32 shown in the figure. In such a case, the magnitude of the bending angle 21 and the deviations along the length of the workpiece are determined in the control unit on the basis of measurement data produced by both measuring devices 16a, 16b.

[0059] Figure 3 shows a measuring arrangement wherein the magnitude of the bending angle 2 of the workpiece 8 is measured. The measuring carriage 30 of the left-hand side measuring device 6a is arranged against an inner surface 33 of the flank since the measurement cannot be carried out against the short left-hand flank of the workpiece. Figures 3 and 4 together show that a measuring head 30 may be placed in a versatile manner against different surfaces of the workpiece 8.

[0060] Figure 4 shows in greater detail the construction of the measuring device 16 applied in Figures 2 and 3. The first frame part 25, i.e. the horizontal frame, comprises linear bearings 34 enabling the horizontal frame to be connected to horizontal guides. The second frame part 26, i.e. the vertical frame, comprises vertical guides 35. Between the frame parts 25, 26 are provided second linear bearings 36 which enable the vertical frame to move in the vertical direction C. The upper part of the second frame part 26 is provided with a projecting part 37 to which the supporting part 29 is connected by the joint 28. The supporting arm 29 may be turned by means of a first turning motor 37 which may be arranged in connection with the joint 28. The turning motor 37 may be locked to be non-turning after the measuring carriage 30 has been set in place for measurement. A sensor 38 may also be provided in connection with the joint 28 for determining the turning position of the joint. The measuring carriage 30 is connected to the supporting arm 29 by means of a joint 31. In connection with the joint 31 may be provided a second turning motor 39 which enables the measuring carriage 30 to be turned into a position roughly corresponding to the position of the surface to be measured. After the measuring carriage 30 has by means of the vertical frame 26, the supporting arm 29 and the second turning motor 39 been placed against the surface to be measured, the second turning motor 39 may be released. After the turning motor 39 has been released, the measuring carriage 30 may freely turn with respect to the joint 31. In such a case, the measuring carriage 30 follows the surface to be measured, and this motion is transmitted to the joint 31 whose position may be measured by a sensor or a corresponding measuring member 40. The measuring carriage 30 is provided with contact members 41 moving along the surface of the workpiece.

[0061] Figure 5 shows a measuring carriage 30 provided with two contact members 41 arranged at a distance from one another. The contact members 41 are wheels 42 pivotally mounted to a rotatable frame 43.

[0062] In Figure 6, the contact member 41 of the measuring carriage 30 is a slide 44 which may be slidingly moved along the surface of the workpiece. The contact member may be a slide pin or a slide block.

[0063] In Figure 7, the contact member 41 of the measuring carriage 30 is a roller 45 or a corresponding cylindrical rolling member.

[0064] The measuring carriage 30 shown in Figure 8 comprises four contact members 41 located at a distance from one another. The contact members 41 may be of any type shown above. In Figure 8, the contact members are wheels 42. Owing to the several contact members 4 , the measuring carriage 30 may retain its position with respect to the surface of the workpiece 8 even if one contact member 41 passes over a hole 46 or recess in the work- piece. The second contact members 41 retain their contact with the surface to be measured, enabling one contact member to pass over the hole 46 or recess without affecting the measurement. The measuring carriage 30 may comprise a bogie structure 47 for the contact members 41. In such a case, the bogie 47 comprises two axles 48 whose ends are provided with wheels 42, twin wheels or rollers. The axles 48 are interconnected by means of the rotatable frame 43.

[0065] Figure 9 shows a measuring carriage 30 wherein the contact members 41 form a fork-like piece 49. In such a case, the measuring carriage 30 has no separate rotatable frame 43 but it is an integrated part of the forklike piece 49. It is to be noted that the number of branches may be larger than two, as shown in the figure, i.e. the number of branches may be three, four, or more. [0066] For the sake of clarity, Figures 5 to 9 show no measuring member for determining the turning angle of the joint 31.

[0067] Figure 10 shows an alternative measuring device 16, a lower part of its second frame part 26, i.e. the vertical frame, being provided with a joint 50 enabling the vertical frame 26 to be rotated in the transverse direction B. The vertical frame 26 may further be provided with means for extending and contracting it. In addition, the length of the supporting arm 29 may be variable.

[0068] In the embodiment shown in Figure 1 1 , the upper beam 3 of the press brake is provided with a measuring device 16. Guides 18 may be fastened to a flank of the upper beam 3, and the frame 24 of the measuring device is movably connected to these guides. It is also possible that both flanks of the upper beam 3 are provided with measuring devices 16. In Figure 1 1 , the press brake 1 is used for bending one half of a tubular piece with a curved cross section. The measuring device 16 enables the curvature of the inner surface of the bent workpiece 8 to be measured. It is also possible to measure a radius of curvature since the supporting arm 29 may be extendable and contractable and the length of the supporting arm 29 may be measured by a sensor or a corresponding measuring member.

[0069] It is also possible that in Figure 1 1 the supporting arm 29 is by means of a turning joint fastened to the frame 24, enabling the supporting arm 29 and the measuring carriage 30 therein to be turned into a desired angular position.

[0070] The measuring device 16 shown in Figure 12 comprises a plurality of measuring units 51 a to 51 d, i.e. in this case four units. Each measuring unit 51 comprises at least one supporting arm 29 and measuring carriage 30. The measuring units 51 may be arranged side by side, in which case the measuring units 51 are, when viewed in the transverse direction B, located at a distance from one another. Such a measuring device 16 enables the flank surface of the workpiece 8 to be measured at several points simultaneously. The measuring carnages 30 of adjacent measuring units 51 may be partially overlapping with respect to one another. The measuring units 51 may be alternately located on different sides of the frame 24. The supporting arm 29 of the measuring unit 51 may be connected by a linear bearing 52 to a guide 53 provided in the frame 24, enabling the measuring unit 51 to be moved with respect to the frame 24. The distance of the measuring carriage 30 from the frame 24 may be measured by means of the measuring device provided in connection with the supporting arm or by means of any other measuring device. This measurement data may be used in the control unit for determining the magnitude of the radius of the workpiece 8.

[0071] Figure 13 is a simplified diagram showing features and work phases associated with the measurement.

[0072] In some cases, features disclosed in this application may be used as such, regardless of other features. On the other hand, when necessary, features disclosed in this application may be combined in order to provide various combinations.

[0073] The drawings and the related description are only intended to illustrate the idea of the invention. Details of the invention may vary within the scope of the claims.

Claims

1. A method of measuring a workpiece in a press brake, the method comprising:

measuring at least one flank surface of a workpiece (8) bent by the press brake (1 ) by means of at least one measuring device (16);

carrying out the measurement when the workpiece (8) resides in a gap (7) of the press brake;

moving the measuring device (16), supported by guides (17, 18), in a longitudinal direction of the gap and measuring the workpiece (8) during the moving;

communicating measurement data from at least one measuring member (40) of the measuring device (16) to at least one control unit (15); and determining in the control unit (15) on the basis of the measurement data control parameters for controlling operation of the press brake (1 );

c h a r a c t e r i z e d by

using the measuring device (16) which is provided with a measuring carriage (30) provided with at least two contact members (41 ) arranged at a distance from one another;

pressing, during the measurement, the measuring carriage (30) against the flank surface of the workpiece (8), whereby the measuring carriage (30), supported by the contact members (41 ), settles along the direction of the flank surface to be measured; and

determining an angular position of the measuring carriage (30) and determining, on the basis of the angular position, an angular position of the flank surface of the workpiece (8).

2. A method as claimed in claim 1 , c h a r a c t e r i z e d by using in the measurement at least two measuring carriages (30), measuring both flank surfaces of a bend formed on the workpiece

(8); and

determining, on the basis of measurement results, a magnitude of an angle of the bend.

3. A method as claimed in claim 1 or 2, c h a r a c t e r i z e d by using in the measurement at least two measuring carriages (30), measuring two parallel flank surfaces of the workpiece (8); determining, on the basis of measurement results, deviations in the parallelism of the flank surfaces; and using measurement data for forming corrective control parameters for a new press brake bending procedure.

4. A method as claimed in any one of the preceding claims, c h a r a c t e r i z e d by

using the measurement data for controlling deflection compensation of beams (3, 4) of the press brake.

5. A measuring device for measuring a workpiece in a press brake, the measuring device comprising:

at least one linear guide (17, 18) fastenable to the press brake (1 ); a frame (24) supported on the linear guide (17, 18);

at least one drive motor (M) for moving the measuring device (16) on the linear guide (17, 18) with respect to a press-brake-bent workpiece (8) during measurement;

at least one supporting arm (29) connected to the frame (24) and movable with respect to the frame (24); and

at least one measuring head which is arranged in the supporting arm (29) and in connection with which at least one measuring member (40) is provided for measuring the press-brake-bent workpiece (8);

c h a r a c t e r i z e d in that

the measuring head comprises a measuring carriage (30) pivotally connected by a joint (31 ) to the supporting arm (29);

the measuring carriage (30) is provided with at least two contact members (41 ) located at a distance from one another, the contact members (41 ) following a surface of the workpiece (8) to be measured and affecting a position of the measuring carriage (30) with respect to the supporting arm (29); and

the measuring member (40) is arranged to determine an angular position between the supporting arm (29) and the measuring carriage (30).

6. A measuring device as claimed in claim 5, c h a r a c t e r i z e d in that

the frame (24) comprises a horizontal frame (25) and a vertical frame (26);

the horizontal frame (25) is by means of a linear bearing (34) connected to the guides (17), enabling the horizontal frame (25) to be moved along the guides (17) in a longitudinal direction (A) of the press brake (1 ); between the vertical frame (26) and the horizontal frame (25) are provided vertical guides (35), which are perpendicular to said guides (17), and linear bearings (36), making the vertical frame (26) movable in a vertical direction (C) with respect to the horizontal frame (25); and

the supporting arm (29) is fastened to an upper part of the vertical frame (26).

7. A measuring device as claimed in claim 5 or 6, characterized in that

the supporting arm (29) is extendable and contractable linearly; and the measuring device (16) comprises at least one measuring member for determining a length of the supporting arm (29).

8. A measuring carriage for measuring a workpiece in a press brake,

characterized in that

the measuring carriage (30) is provided with a rotatable frame (43); the rotatable frame (43) is provided with a joint (31);

the rotatable frame (43) is further provided with at least two contact members (41) located at a distance from on another, the contact members (41) following a surface of the workpiece (8) to be measured and affecting a position of the measuring carriage (30) with respect to the joint (31 ); and

the measuring carriage (30) is provided with at least one measuring member (40) for determining an angular position of the joint (31).

9. A measuring carriage as claimed in claim 8, characterized in that

the contact member (41) is a rolling member pivotally mounted to the rotatable frame (43);

the rotatable frame (43) is an elongated piece, the contact members (41) being provided in end sections thereof; and

the joint (31) is located in a middle section of the rotatable frame (43), in a section between the contact members (41).

10. A measuring carriage as claimed in claim 8 or 9, character i z e d in that

the measuring carriage (30) comprises at least three contact members (41 ) located at a distance from one another.

11. A press brake, comprising:

a frame (2) with at least ends (2a, 2b); an elongated movable upper beam (3) and an elongated fixed lower beam (4) which are arranged vertically on top of one another and between which a gap (7) is provided for a piece (8) to be press-brake-bent;

powered members (6a, 6b) for moving the upper beam (3) with respect to the lower beam (4);

and in which the opposite longitudinal edges of the beams (3, 4) are provided with support surfaces (9) for fastening press brake bending tools (22, 23);

deflection compensation means for compensating for deflection of the beams (3, 4) and for setting the support surfaces (9) in parallel regardless of press brake bending forces directed to the beams (3, 4);

and which deflection compensation means include several adjusting units (11) provided with an eccentric mechanism (12) arranged to be turned by means of an actuator (13);

at least one measuring device (16) for measuring deformation of the workpiece (8) after the press brake bending; and

at least one control unit (15) for controlling operation of the press brake (1) on the basis of received control data and measurement data obtained from the measuring device;

characterized in that

the measuring device (16) is as claimed in independent claim 5.

12. A press brake as claimed in claim 11, characterized in that at least one measuring device (16) is connected to the lower beam (4) or a table of the press brake (1 ) .

3. A press brake as claimed in claim 11 or 12,

characterized in that

at least one measuring device (16) is connected to the upper beam (3) of the press brake (1 ) .

14. A press brake as claimed in any one of preceding claims 11 to

13,

characterized in that

at least one measuring device (16) is connected to a tool (22, 23) of the press brake (1) .