Bending machines, in particular press brakes, equipped with a position measuring system

Abstract

The invention relates to a bending machine, in particular a press brake, having an upper beam 7 and a lower beam 9. The upper beam 7 is movable in the direction of a main axis y of the bending machine 1 relative to the lower beam 9 in order to form a workpiece which can be inserted between the upper beam 7 and the lower beam 9 through the front of the bending machine 1 by bending along a bending line extending in the width direction z of the bending machine 1. The bending machine 1 comprises at least one position measuring system 11 for measuring and monitoring, respectively, a measuring and monitoring position of the upper beam 7 relative to a reference position during the work process, the position measuring system 11 being designed such that a linearly movable measuring unit 12 of the position measuring system 11 follows the movement of the upper beam 7 in the direction of the main axis y and moves in the process along a fixed linear element 13. The linearly movable measuring unit 12 of the position measuring system 11 is held relative to the upper beam 7 by a connecting element 14 which is designed to be resistant to deformations in the direction of the main axis y and elastic in the width direction z and / or depth direction x of the bending machine 1.

Description

Technical Field

[0001] The present invention relates to a bending machine equipped with a position measurement system, particularly a press brake.

Background Art

[0002] In a bending machine, the deformation of a workpiece is achieved by a vertically movable upper beam pressing a workpiece placed on a lower beam located below the upper beam. To control the adjustment path of the upper beam and further to control the deformation process of the workpiece, it is known to provide a position measurement system in the bending machine, by which the position of the upper beam is determined relative to a reference position during the deformation process.

[0003] For example, a bending machine is known from European Patent Application Publication No. 1902792 (EP1902792A2), which includes a position measurement device for determining the adjustment path of a press beam that can be adjusted using a drive device between an upper inversion position and a lower inversion position. By using this position measurement device, the stroke position can be confirmed. The position measurement device is composed of optoelectronic measurement devices arranged at both end regions on opposite sides of the press beam, and the respective positions are determined by linear scales. European Patent Application Publication No. 1902792 (EP1902792A1) does not provide any details regarding the design of the position measurement device.

[0004] The forces and deformations on the bending machine that occur during the deformation process of the workpiece change the absolute and relative positions of the position measurement system, particularly in the direction of the main axis of the bending machine along which the upper beam moves relative to the lower beam. Due to those forces and deformations, the achievable angular accuracy is adversely affected. To minimize the reduction of angular accuracy as much as possible, other known solutions use joints, spherical supports, etc. to separate the position measurement system from unwanted deformations of the bending machine and transfer a position signal with as high accuracy as possible to the machine control.

[0005] However, the drawback of these solutions is that the supports or connections required for the position measurement system cannot be designed to have no play at all because relative movement cannot occur without any play in the supports or connections required for the position measurement system. Therefore, the deformation caused as a result of thermal expansion and member fatigue cannot be completely compensated for either. The measurement results obtained erroneously thereby have an adverse effect on the result of the bending process, which is undesirable.

[0006] International Publication No. 03 / 072278 (WO03 / 072278A1) discloses a method for reducing the bending angle error when bending a metal sheet in a bending press composed of a stationary lower tool and a bending beam provided with an upper tool driven by a linear axis. The inversion point below the bending die is pre-calculated based on a preset specified value of the bending angle and the force path process measured during the bending process. The force path process is measured by a position transducer and a force transducer and processed inside a control unit.

[0007] European Patent Application Publication No. 1011886 (EP1011886A1) discloses a press brake for bending a metal sheet, which has a measurement and control system operating on at least four points of the bending angle. The press brake includes a vertically reciprocating elongated upper bending punch, a fixed elongated lower bending matrix having at least a longitudinal bending groove, and feeler means for measuring each bending movement of the metal sheet when bending inside the bending groove in order to control and command the bending parameters of the bending process in the press brake by a data processing logic unit. The feeler means operates using at least four bending detection points. All the detection points are divided into two sets consisting of bending detection points, that is, one set is on one side and the other set is on the other side, and are designed to be symmetric in number and position with respect to the vertical plane along each corresponding plate bending line of the resulting bent plate.

[0008] Therefore, it is necessary to avoid external forces on the position measurement system in order to prevent plastic deformation and resulting damage to the position measurement system, as well as measurement errors of the position measurement system.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object of the present invention is to provide a position measurement system in a bending machine that is functionally improved and has high precision during the bending process. In particular, this position measurement system should be more robust against deformation of the bending machine.

Means for Solving the Problems

[0011] This object is achieved by the bending machine according to claim 1. Further developments of the present invention are described in the dependent claims.

[0012] The bending machine according to the present invention includes an upper beam and a lower beam. The upper beam is movable in the direction of the main axis of the bending machine with respect to the lower beam in order to form a workpiece, particularly a plate, inserted or insertable between the upper beam and the lower beam through the front surface of the bending machine by bending along a bending line. The bending line extends in the width direction of the bending machine. The main axis direction corresponding to the working direction of the bending machine preferably extends in the vertical height direction (vertical direction) of the bending machine.

[0013] In the following, when terms are used in connection with up or down, or in relation to the working direction or the (vertical) height direction, these terms always refer to the vertical up and down direction in the operating position of the bending machine, i.e., the position of its intended use.

[0014] This bending machine is designed in particular as a press brake, but the bending machine may also be a pressing and bending machine, a rotary bending machine, etc.

[0015] The bending machine includes at least one position measurement system for measuring and monitoring the position of the upper beam and the position to be measured and monitored with respect to the reference position during the working process. The position measurement system is designed such that the linearly movable measurement unit of the position measurement system moves along a fixed linear element in the process following the movement of the upper beam in the direction of the main axis. Preferably, the fixed linear element is a measuring ruler along which the linearly movable measurement unit of the position measurement system moves.

[0016] According to the present invention, the linearly movable measurement unit of the position measurement system is held against the upper beam by a connecting element designed to be resistant to deformation in the direction of the main axis and further elastic in the width direction and / or the depth direction of the bending machine.

[0017] The bending machine according to the present invention has the advantage that the deformation of the bending machine occurring during the deformation process is almost completely separated from the position measurement system due to the elasticity of the connecting elements in the width direction and / or the depth direction of the bending machine, and in the case of deformation of the bending machine, only the connecting elements are particularly reversibly deformed. Therefore, the unwanted deformation of the bending machine does not affect the measurement results. Instead, only the position of the upper beam in the direction of the main axis is determined by the position measurement system.

[0018] In a preferred embodiment, a connection element that is resistant to deformation is designed as a torsion element having spring elasticity in the width direction and / or the depth direction of the bending machine. It is particularly preferred if this connection element is designed as a torsion element that is elastic in both the width direction of the bending machine and the depth direction of the bending machine, in particular having spring elasticity. This enables deformation in the width direction and the depth direction of the bending machine and separates them from the position measurement system, in particular from components that move relative to one another. Due to the material and / or shape of the torsion element, the elasticity in the width direction and the depth direction of the bending machine can be selected and automatically adjusted to maintain a play-free state even in the event of a change in the situation. For example, wear of the machine guide may change the distance between a moving machine element and a fixed machine element. Here, the torsion element adapts to the situation independently.

[0019] A further advantageous embodiment realizes that the connection element has a lower rigidity than the fixed linear element held against the lower beam and its receptacle in the width direction and / or the depth direction of the bending machine. Preferably, the connection element has a lower rigidity than the fixed linear element held against the lower beam and its receptacle in both the width direction and the depth direction of the bending machine. This preferred design facilitates the separation of the position measurement system from any deformation that may occur in the bending machine.

[0020] Generally, the connection element can be geometrically designed with little material use in the desired deformation directions, i.e., the width direction and / or the depth direction of the bending machine, in order to deform elastically as a result of the application of forces due to the deformation of the bending machine. Thus, in the main axis direction (i.e., the working direction), the connection element is characterized by a relatively large amount of material in order to achieve a higher resistance to deformation.

[0021] In a preferred embodiment, a connecting element that is resistant to deformation in the direction of the main axis is formed as a flat piece that extends such that its main side surface lies within a plane orthogonal to the width direction, and the long side of the main side surface extends in the depth direction of the bending machine. The flat piece is elastic, particularly spring-elastic, in the width direction and / or the depth direction of the bending machine and represents a torsional element that is resistant to deformation in the main axis direction. This flat piece enables a partially elastic connection of the linearly movable measuring unit. Additionally, it allows for deformations in undesirable directions and has a high fatigue strength that separates them from components that are movable relative to each other, particularly from the linearly movable measuring unit and the fixed linear element, in the position measuring system. Such a flat piece can be provided easily and at low cost. The elasticity can be selected based on the material and / or shape of the flat piece.

[0022] According to a further preferred embodiment, the connecting element has a section with a weakening element. In a first variant, the weakening element is formed by reducing the thickness of the member in the width direction compared to a section without a weakening element. Alternatively or additionally, the weakening element is formed by one or more indentations. Further alternatively or additionally, the connecting element is formed from two or more interconnected material layers using a sandwich method, and the material is interrupted in at least one of the material layers in the section with the weakening element. By selecting or combining the above options for the weakening element, the elasticity of the connecting element that is resistant to deformation can be adjusted. In this regard, it is possible to adapt to the type and / or size and / or design of the bending machine.

[0023] According to a further preferred embodiment, the section with the weakening element in the connecting element is formed closer to the upper beam than to the linearly movable measuring unit in the depth direction. This promotes the elasticity in the width direction and / or the depth direction of the bending machine that has simultaneous resistance to deformation in the main axis direction.

[0024] According to a further advantageous embodiment, the connecting element resistant to deformation has, or is formed from, spring steel. This connecting element can also be made of, or formed from, a material having properties similar to high elasticity.

[0025] According to a further preferred embodiment, the connecting element is held on the lower surface of the upper beam and in a section located outside in the width direction of the upper beam. Attaching the connecting element, and thus the position measuring system, at a position where it is less affected by deformation with respect to the machine frame of the bending machine is advantageous for the desired feature of the lowest possible potential impact on the position measuring system due to potential deformation of the machine frame.

[0026] This approach is based on the consideration that the positions least affected by deformation are located at the outer ends of the upper and lower beams. For example, relative movement and / or elongation due to thermal expansion can reliably achieve the result when bending the workpiece if the distance of the measurement point between the upper beam and the lower beam changes by the same amount. However, unwanted torsion or bending of the fixed linear element can be equally avoided.

[0027] A further preferred embodiment realizes that the connecting element is held directly against the upper beam or via a receptacle. This preferably has high rigidity.

[0028] In a further preferred embodiment, the connecting element is held against the slider of the linearly movable measuring unit, and the sensing element of the linearly movable measuring unit is fixed to the slider.

[0029] According to a further preferred embodiment, the connecting element is removably arranged with respect to the upper beam and the linearly movable measuring unit via respective fastening means such as screws. This enables the connecting element to be quickly replaceable, for example when the operating conditions change. As a result, a modular bending machine can be provided. For example, a connecting element that is resistant to deformations having various material properties can be used in the main axis direction when particularly large deformations are expected during the working process or during a change in geometric conditions. This is particularly effective in situations where there are large changes in the bending length or force. Even when damage, i.e., damage to the connecting element, occurs, it can be quickly replaced, which reduces the downtime of the processing machine.

[0030] According to a further preferred embodiment, the connecting element, as well as the attachment part of the connecting element to the linearly movable measuring unit and the upper beam, is thermally conductive. This enables a parallel expansion of the position measurement system and the machine frame of the bending machine and is effective for the desired deformation characteristics and accuracy requirements.

[0031] In the following, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0033] In the following, embodiments of the present invention will be described based on a bending machine in the form of a press brake. A perspective view of the press brake indicated by reference numeral 1 is shown in FIG. 1. In FIG. 1, and further in FIGS. 2 to 6, a spatial coordinate system is shown to explain the directions of the bending machine 1. The x-direction corresponds to the depth direction of the bending machine 1, and a workpiece to be bent is inserted into the bending machine 1 in the x-direction through the front surface of the bending machine 1. On the other hand, the z-direction is the width direction of the bending machine 1. The depth direction x and the width direction z exist in a horizontal plane. The y-direction is the vertical direction and corresponds to the height direction y of the bending machine 1. The main axis of the bending machine 1 extends in the y-direction of the coordinate system and is hereinafter also referred to as the working direction.

[0034] The bending machine 1 includes, among other things, a frame 2 including two side stands 3, 3' and a frame plate 4. An upper beam 7 and a lower beam 9 are provided on the front surface of the bending machine 1. The front surface of the upper beam 7 is indicated by reference numeral 7a, and the front surface of the lower beam 9 is indicated by reference numeral 9a. A tool table 10 exists at the upper edge of the lower beam 9, and a lower tool is fixed to the tool table 10 during the operation of the bending machine 1. On the other hand, the upper beam 7 has a tool receptacle 8 for fixing a corresponding upper tool. During the operation of the bending machine 1, a plate (not shown) is inserted into the space between the upper beam 7 and the lower beam 9, and then the upper beam 7 is moved downward in its working direction, whereby the upper tool is pushed into the lower tool, thereby deforming the plate. The bending machine 1 is fixed to the floor using fixing means 26, 26' corresponding to each corner at the corners of the bending machine to ensure a stable installation state of the bending machine during the bending process.

[0035] The hydraulic actuator is used to move the upper beam 7 in the working direction. The upper beam 7 is approximately positioned above the reinforcing plate 5 and extends between the side stand 3 and the side stand 3'. In the view of FIG. 1, only two hydraulic cylinders 6 and 6' of the actuator are shown. The hydraulic cylinders 6 and 6' are attached to the frame plate 4 and positioned in the recesses of the upper beam 7. The corresponding cylinder rods are connected to the upper beam 7 in the region of these recesses and can move the upper beam 7 in the direction of the main axis, i.e., the working direction or the vertical direction y.

[0036] During the working process in which the upper beam 7 is moved in the main axis direction (i.e., the vertical direction y) of the bending machine 1 with respect to the lower beam 9, two position measurement systems 11, 11' are provided on the bending machine 1 to measure and monitor the positions of the upper beam 7 with respect to the reference position respectively. In an exemplary embodiment, the bending machine 1 is shown with two separate position measurement systems 11, 11'. It should be noted that in order to realize the measurement and monitoring of the position of the upper beam 7, it is sufficient to provide only a single position measurement system 11 or 11' for the bending machine.

[0037] As can be more clearly seen from FIGS. 2 to 4, the position measurement systems 11, 11' are arranged and held at the outer ends of the upper beam 7 and the lower beam 9 on opposite sides of each other, and the position measurement systems 11, 11' extend into the interior of the machine body formed by the side stands 3, 3', the frame plate 4 and the reinforcing plate 5. This is most clearly shown, for example, in the detailed perspective view of FIG. 3.

[0038] The position measurement system will be described in detail below with reference to the position measurement system 11 shown in FIGS. 5 and 6 in the detailed perspective view and top view from the rear. The design of the position measurement system 11' shown in FIGS. 2 to 4 is structurally identical to that of the position measurement system 11 and is, as an example, only mirror-inverted with respect to the vertical x-y plane.

[0039] The position measuring system 11 has a linearly movable measuring unit 12 and a fixed linear element 13. The linearly movable measuring unit 12 has a slider 21 and a sensing element 22 fixed to the slider 21. The linearly movable measuring unit 12 of the position measuring system 11 is held against the upper beam 7 by a connecting element 14 that is resistant to deformation in the direction of the main axis, i.e., the vertical direction y.

[0040] The fixed linear element 13, which is designed, for example, as a measuring ruler, is fixed to a lower beam (not shown in FIG. 5) using a receptacle 19 that is resistant to deformation, thereby coming to rest adjacent to the tool holder 10 in the width direction z. The fixed linear element 13 is attached to the lower beam 9 and thereby fixed to the bending machine 1 via the receptacle 19.

[0041] When the upper beam 7 moves in the working direction, i.e., the main axis direction or the height direction y, the linearly movable measuring unit 12 of the position measuring system 11 moves along the fixed linear element 13 in the process following the movement of the upper beam 7. For this purpose, the slider 21 of the linearly movable measuring unit 12 is moved along the fixed linear element 13 by a guide 25 (see FIG. 6). When the linearly movable measuring unit 12 moves relative to the fixed linear element 13, its sensing element 22 moves along the fixed linear element 13, enabling the position of the upper beam 7 relative to a predefined reference position to be determined during the working process.

[0042] The structural design of the guide 25 shown in FIG. 6, in which elements of the slider 21 engage around corresponding elements of the fixed linear element, is merely exemplary. Generally speaking, internal or external guides of the slider 21 along the fixed linear element 13, which are known in principle, could also be considered as alternatives.

[0043] The receptacle 20 is provided on the lower surface 7b of the upper beam 7 and connects the connecting element 14, which is resistant to deformation, to the upper beam 7. The receptacle 20 of the upper beam 7 is exemplarily formed in an "L" shape. One of the two legs of the receptacle 20 is removably or non-removably fixed to the lower surface 7b of the upper beam 7. Of the two legs, the other leg extending in the main axis direction, i.e., the height direction y, is used to fix the end of the connecting element 14 on the processing machine side. The other end of the connecting element 14 on the measurement system side is fixed to the slider 21 of the linearly movable measurement unit 12.

[0044] Since the section of the upper beam 7 located on the outside in the width direction z is less affected by deformation during the sheet metal bending process compared to other sections, it is preferable that the connecting element 14 is fixed via the receptacle 20 on the section of the upper beam 7 located on the outside, as shown in FIGS. 1 to 5. This is advantageous for the accuracy of the position measurement system during the bending process, especially among other aspects described below.

[0045] The connecting element 14 is fixed to the receptacle 20 of the upper beam 7 and further to the slider 21 using one or more fastening means 23, for example screws, and in both cases, the connecting element 14, the receptacle 20 of the upper beam 7, and the linearly movable measurement unit 12 can be made removable. This allows for easy replacement of the connecting element 14 according to existing operating conditions.

[0046] In the exemplary embodiment shown here, two fastening means 23 are respectively provided to fix the connecting element 14 to the receptacle 20 and the slider 21. Between each pair of the fastening means 23, here as an example, to facilitate fixation and correct alignment with the receptacle 20 and the slider 21, the connecting element has adjustment elements 24, for example in the form of holes, corresponding to each pair of the fastening means 23. For this purpose, the receptacle 20 and the slider 21 may have protrusions corresponding to the adjustment elements 24, and these protrusions engage with the associated adjustment elements 24.

[0047] The connection of the slider 21 to the upper beam 7 following the stroke of the upper beam 7 is made only via the deformation element 14. Therefore, this element is the only connecting element associated with the influence on undesirable deformations of the processing machine body. These deformations are undesirable in the width direction z and the depth direction x. The measurement data of the upper beam 7 is desirable and appropriate only in the height direction y, i.e., the main axis direction.

[0048] Deformations of the processing machine body that have an adverse effect on position measurement can occur, for example, when the upper beam 7 does not move parallel to the lower beam 9 in the main axis (height axis y) direction, resulting in an inclination of the posture of the upper beam 7. When using two position measurement systems 11, 11' with the upper beam 7 as shown in FIGS. 1 to 4, this leads to undesirable simultaneous movement in the width direction z. Allowing this deformation leads to poor bending results and damage to the position measurement systems 11, 11'. Similarly, such adverse effects occur in the depth direction x when the processing machine body expands as a result of the force applied during bending and the upper beam 7 moves relative to the processing machine body.

[0049] These adverse effects are eliminated or at least significantly reduced by the deformation element 14. The term "deformation resistance" of the connecting element 14 refers to the deformation resistance in the main axis direction, i.e., the height direction y. The connecting element 14 is designed, for example, in contrast, as a torsion element designed to have elasticity, particularly spring elasticity, in the width direction z of the bending machine 1 and / or in the depth direction x of the bending machine 1. Preferably, the elasticity is provided in both the width direction z and the depth direction x of the bending machine 1.

[0050] Therefore, unwanted torsion or bending due to forces and deformations occurring during the bending process with respect to the processing machine body and / or the processing machine axis of the bending machine 1 is not transmitted to the fixed linear element 13. The connecting element 14 having elasticity in the width direction z and / or the depth direction x of the bending machine 1 substantially separates the deformation of the processing machine body from the position measuring system 11. Instead, only the connecting element 14 is deformed, particularly reversibly deformed. This deformation is reversible because when the processing machine body is unloaded, the connecting element returns to its original shape at the end of the working process or the bending process. This has the advantage that unwanted deformation of the processing machine body of the bending machine 1 does not affect the measurement result, and only the position in the main axis direction of the upper beam 7, that is, the height direction y, is determined by the slider 21 and the sensing element 22 fixed thereto.

[0051] Intentionally, the connecting element 14 has at least one partially elastic member with high fatigue strength that allows deformation in unwanted directions, that is, in the width direction z and / or the depth direction x, thereby separating them from the position measuring system 11, particularly the slider 21.

[0052] The connecting element 14 is designed as an elastic element in the above-mentioned preferred directions, while the receptacle 19 of the lower beam 9 and the receptacle 20 of the upper beam 7 are designed to be relatively more rigid. This combination substantially separates the deformation of the processing machine body from the position measuring system 11 by the deformation of the connecting element 14 as required.

[0053] The connecting element 14, which is resistant to deformation, is generally designed with little material used in the desired elastic directions, that is, the width direction z and / or the depth direction x, in order to be elastically deformable as a result of the application of force. In the main axis direction (height direction y), the connecting element 14 is characterized by a relatively large amount of material to achieve higher resistance to deformation.

[0054] In the exemplary embodiment shown in the figures, the connecting element 14 is designed as a flat piece that meets the above requirements. The main front and back surfaces 14a, 14b of the flat piece extend in a vertical x-y plane perpendicular to the width direction z. The connecting element 14 designed as a flat piece has a long edge or side that extends in the depth direction x of the bending machine 1. This long side is the longest side of the flat piece and is significantly longer than the other two sides in the height direction y and the width direction z. This is most clearly shown, for example, in FIG. 5.

[0055] To achieve the desired elastic properties, the connecting element 14 has a section 15 with a weakening element 18 that weakens the member (FIG. 6). The section 15 with the weakening element 18 has a length l 15 and a thickness d 15 . The section 15 where the member is weakened is present between two sections 16, 17 where the member is not weakened. The sections 16, 17 each have a length l 16 and l 17 as well as a thickness d 16 and d 17 . The total length l of the connecting element 14 is the sum of the lengths l 15 , l 16 , l 17 of the sections 15, 16, 17, that is, l = l 15 + l 16 + l 17 . The thicknesses d 16 and d 17 of the sections 16, 17 where the member is not weakened are the same in this exemplary embodiment, that is, d 16 = d 17 . At the same time, the thicknesses d 16 and d 17 of the sections 16, 17 where the member is not weakened in this exemplary embodiment are greater than the thickness d 15 of the section 15 where the member is weakened, that is, d 15 < d 16 and d 15 < d 17 .

[0056] The lengths l of the section 15 where the member is weakened and the sections 16, 17 where the member is not weakened 15 , l 16 , l 17 , and the thickness d 15 , d 16 , d 17 are generally selected according to the bending machine 1, its shape conditions, and / or the forces generated during the bending process. Preferably, the length l of the section 16 where the member fixed to the receptacle 20 of the upper beam 7 is not weakened 16 is smaller than the length l of the section 17 where the member fixed to the slider 21 is not weakened, i.e., l 17 < l 16 < l 17 is true.

[0057] The section 15 provided with the weakening element 18 can be formed such that the material thickness decreases in the width direction z as shown in FIGS. 5 and 6 when compared with the sections 16, 17 having no weakening element at all. Alternatively or additionally, the weakening element 18 can also be formed by one or more depressions (not shown in the symbolic representation). In this case, the thicknesses d 16 and d 17 of the sections 16, 17 where the member is not weakened can correspond to the thickness d 15 of the weakened section 15, i.e., d 15 = d 16 = d 17 is true. The thicknesses d 16 and d 17 of the sections 16, 17 where the member is not weakened can alternatively be greater than the thickness d 15 of the section 15 where the member is weakened, i.e., d 15 < d 16 and d 15 < d 17 is also possible.

[0058] In a further alternative, the connection element resistant to deformation can also be formed from two or more interconnected material layers using a sandwich method. In this regard, in section 15 with the weakening element 18, the material is interrupted in at least one of the other material layers (not shown in the figure). In section 15 with the weakening element 18, one or more indentations can also be provided.

[0059] The connection element 14 can be made of or have spring steel. Alternatively or additionally, similar materials with high elasticity can be used.

[0060] The material of the connection element resistant to deformation and its receptacles 19, 20 for the lower beam 9 and the upper beam 7 advantageously has thermal conductivity. This enables parallel expansion of the position measurement system 11 and the machine tool body.

[0061] The embodiments of the invention described above offer many advantages.

[0062] The fastening means 23 used to hold the connection element 14 resistant to deformation for the upper beam 7 and the linearly movable measuring unit 12 enables a modular system in which the connection element 14 can be quickly exchanged in a simple manner when the operating conditions change. For example, if particularly large deformations of the machine tool body are expected, or if the shape conditions change, for example, the bending length or force is greater, connection elements resistant to deformation made of different materials with different material properties can be used. In addition, the connection element 14 can be quickly exchanged when damage occurs. This can reduce the downtime of the machine tool.

[0063] The use of the connection element 14 resistant to deformation does not require lubrication means or special maintenance means and thus provides a reliable position measurement system by simple and inexpensive means.

[0064] The connection of the connection element to the upper beam 7 and the linearly movable measurement unit 12 enables optimal position control in the main axis direction by ensuring that there is no play between the fixed linear element 13 and the linearly movable measurement unit 12 that moves relative to it. A connection without play prevents vibrations from occurring as a result of changes in control parameters. This improves the measurement accuracy.

Explanation of Signs

[0065] 1 Bending machine, 2 Frame, 3, 3' Side stand, 4 Frame plate, 5 Reinforcing plate, 6, 6' Hydraulic cylinder, 7 Upper beam, 7a Front surface of the upper beam, 7b, 7b' Lower surface of the upper beam, 8 Tool receptacle, 9 Lower beam, 9a Front surface of the lower beam, 10 Tool holding part, 11, 11' Position measurement system, 12 Linearly movable measurement unit, 13 Fixed linear element, 14 Connection element, 14a Main side surface of the connection element, 14b Main side surface of the connection element, 15 Section where the member is weakened, 16 Section where the member is not weakened, 17 Section where the member is not weakened, 18 Weakening element, 19 Receptacle of the lower beam 9, 20 Receptacle of the upper beam 7, 21 Slider, 22 Sensing element, 23 Fastening means (e.g., screw), 24 Adjusting element (e.g., hole), 25 Guide, 26, 26' Fixing means, l Length of the connection element 14, l 15 Length of section 15, l 16 Length of section 16, l 17 Length of section 17, d 15 Thickness of section 15, d 16 Thickness of section 16, d 17 Thickness of section 17.

Claims

1. A bending machine, in particular a press brake, having an upper beam (7) and a lower beam (9), the upper beam (7) being movable in the direction of a main axis (y) of the bending machine (1) relative to the lower beam (9) in order to form a workpiece, which can be inserted between the upper beam (7) and the lower beam (9) through a front surface of the bending machine (1) by bending along a bending line, the bending line extending in the width direction (z) of the bending machine (1), the bending machine (1) comprising at least one position measuring system (11) for measuring and monitoring, respectively, the position of a measuring object of the upper beam (7) relative to a reference position during a working process, the position measuring system (11) being designed such that a linearly movable measuring unit (12) of the position measuring system (11) follows the movement of the upper beam (7) in the direction of the main axis (y) and moves along a fixed linear element (13) fixed relative to the lower beam (9) during the working process, the linearly movable measuring unit (12) of the position measuring system (11) is held against the upper beam (7) by connecting elements (14) designed to be resistant to deformations in the direction of the main axis (y) and elastic in the width direction (z) and / or depth direction (x) of the bending machine (1), 13. A bending machine, characterized in that the connecting element (14) is designed as a torsion element that is designed to be spring elastic in the width direction (z) and / or the depth direction (x) of the bending machine (1), and one end of the connecting element (14) is fixed to the linearly movable measuring unit (12) and the other end is fixed to the upper beam (7).

2. 2. The bending machine according to claim 1, characterized in that the connection element (14) has a lower stiffness in the width direction (z) and / or the depth direction (x) of the bending machine (1) than the fixed linear element (13) and its receptacle (19) held against the lower beam (9).

3. 3. A bending machine according to claim 1 or 2, characterized in that the connecting element (14) resistant to deformation in the direction of the main axis is formed as a flat piece extending such that its main sides (14a, 14b) lie in a plane perpendicular to the width direction (z), the long sides of the main sides (14a, 14b) extending in the depth direction (x) of the bending machine.

4. 4. Bending machine according to claim 3, characterized in that the connecting element (14) has a section (15) provided with a weakening element (18).

5. 5. The bending machine according to claim 4, characterized in that the weakened elements (18) are formed by reducing the thickness of the member in the width direction (z) compared to sections (16, 17) that do not have a weakened element.

6. 5. A bending machine according to claim 4, characterized in that the weakening element (18) is formed by one or more depressions.

7. 5. The bending machine according to claim 4, characterized in that the connecting element (14) is formed from two or more interconnected material layers using a sandwich method, with a material interruption in at least one of the material layers in the section (15) provided with the weakening element (18).

8. 5. The bending machine according to claim 4, characterized in that the section (15) with the weakened element (18) of the connecting element (14) is formed closer to the upper beam (7) in the depth direction (x) than to the linearly movable measuring unit (12).

9. 2. Bending machine according to claim 1, characterized in that the connecting element (14) comprises or is made of spring steel.

10. 2. The bending machine according to claim 1, characterized in that the connecting element (14) is held on the lower surface (7b) of the upper beam (7) and on a section of the upper beam (7) that is located on the outside in the width direction (z).

11. 2. A bending machine according to claim 1, characterized in that the connecting element (14) is held against the upper beam (7) either directly or via a receptacle (20).

12. 2. The bending machine according to claim 1, characterized in that the connecting element (14) is held against a slider (21) of the linearly movable measuring unit (12) and a sensing element (22) of the linearly movable measuring unit (12) is fixed against the slider (21).

13. 13. The bending machine according to claim 1 or 12, characterized in that the connecting element (14) is detachably arranged on the upper beam (7) and on the linearly movable measuring unit (12) by respective fastening means (23).

14. 14. The bending machine according to claim 13, characterized in that the connection element (14) and its attachment to the linearly movable measuring unit (12) and to the upper beam (7) are thermally conductive.

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