Patent Application
20150143866
The invention relates to a press table or press beam for a press brake of the type outlined in the introductory part of claim 1.
A problem which arises when bending workpieces, especially those with long bend edges, is that the bend angle obtained along the bend edge after the bending operation is not constant because the forming forces cause a flexion at the press beam or press table supporting the bending tool, which cannot be entirely prevented even if opting for a very solid construction. As a result, the depth by which a bending punch moves down is shorter at the workpiece center than at the ends of the bend edge, making the forming angle likewise less pronounced.
A known way of preventing these workpiece faults is to impart to the workpiece support surface on an active press table or press beam a certain degree of outwardly convex curvature using appropriate devices during a bending operation, which corresponds to the flexion of the non-actively deformable press beam or press table. The support surfaces supporting the bending tools therefore extend approximately parallel with one another and the depth to which a bending punch moves down along the bend edge is constant, thereby also resulting in a uniform forming angle.
A press brake on which a convex curvature can be imparted to the press table or press beam, also referred to as cambering, by means of a pre-stressing device is known from AT 351896 B. The press table or press beam comprises two half-panels which can be biased towards one another by means of a pre-stressing device, as a result of which an outwardly convex curvature can be imparted to the tool support surface. Other possible embodiments disclosed for the pre-stressing device are wedge arrangements or hydraulic cylinders.
The disadvantage of this system is that the pre-stressing forces expended by such pre-stressing devices in order to impart the curvature are transmitted as concentrated loads at predefined positions and thereby result in a curvature contour which matches the flexion of the press beam to only a slight degree because the latter is highly dependent on the positioning of the workpiece and the length of the bend edge.
The objective of the invention is to propose a press brake whereby a curved contour can be imparted to the press table or press beam which enables a high bending accuracy with uniform forming angles to be obtained for many applications whilst nevertheless being based on a simple construction.
The objective is achieved by the invention by means of a press table or a press beam of the generic type having the characterizing features of claim 1.
Due to the fact that the actuator comprises a hose arrangement disposed between the mutually facing pressure surfaces resting against the latter and fillable with hydraulic fluid, which extends substantially in the longitudinal direction of the beam element, the curved contour of the beam element is caused by a uniform load and not by concentrated loads. Since the forming forces generated during the operation of bending the workpiece likewise constitute a uniform load and thus results in a bending line corresponding to the flexion of the deformed, non-actively adjustable press beam or press table, the curved contour caused by the hose arrangement on the actively adjustable press table or press beam represents a better approximation of the flexion than would be the case if using concentrated loads to pre-stress the beam element on the active press table or press beam. Furthermore, the hose arrangement is a simple component for generating the pre-stressing action and hydraulic units are provided on most press brakes for driving the press beam, which can also be used to supply the hose arrangement with pressurized fluid.
A high rigidity can be obtained for a press table or press beam of a slim construction if the beam element and the support beam element are of a plate-shaped designed, overlap with one another in at least certain portions and extend substantially parallel with the working plane or press plane. A high bending strength of the beam element prevents a situation in which, when working with workpieces with shorter bend edges which act more or less like concentrated loads, local deformation or flexion occurs in the beam element, as could otherwise occur due to the flexible hose arrangement under concentrated loads.
It is also of advantage if the beam element or the support beam element forms a U-shaped cross-section in at least certain portions with a base and adjoining arms and the beam element extends around the support beam element or the support beam element extends around the beam element at least partially on either side by means of the arms. The hose arrangement contained between the pressure surfaces is therefore disposed in the interior of the press table or press beam and is well protected against mechanical damage. This also results in a good mutual guiding action and lateral support for the beam element and support beam element.
To enable even beam elements with a very high bending strength to be pre-stressed, it is of advantage if the hose arrangement has a working length between the pressure surfaces which approximately corresponds to the distance between two connecting points on the beam element. This enables a uniform load to be applied to the entire bending length, thereby resulting in a high pre-stressing force.
Alternatively, the connecting points or bolts may be disposed, relative to the height of the beam element, in the half spaced at a distance apart from the support surface in the working direction, thereby resulting in a more homogeneous bending curve of the beam element.
If a pivot bearing is provided at the connecting points between the beam element and support beam element, a bending line of the beam element is obtained which is substantially brought about solely by the uniform load of the hose arrangement, which prevents disruptive inner tensions in the press table or press beam because slight mutual changes of angle are not impeded.
Similar advantageous effects can also be obtained if a slide bearing is provided at the connecting points because changes in length between the connecting points induced by the deformation of the beam element and support beam element are not impeded.
Increased ability for movement between the beam element and support beam element can also be achieved if at least one bending-resistant element extends respectively from the connecting points on the beam element to a fixing point on the support beam element.
If the arms of the U-shaped beam element are retained by means of at least one cross-connector at a fixed distance from one another after the hose arrangement as viewed from the support surface, the stability of the press table or press beam is increased, preventing deformation or cambering transversely to the pressing direction.
The hose arrangement may comprise at least two hose portions extending parallel with one another, which are hydraulically connected in parallel, so that the force transmitted to the pressure surface of the beam element is distributed over several contact lines or contact surfaces. The force transmission is therefore more uniform and load peaks on the hose arrangement as well as the beam element and support beam element are reduced.
Handling and assembly of the hose arrangement is made easier if adjacent parallel hose portions are connected to one another to form a hose assembly. The connection may be established by welding or adhesive along sleeve lines of the hose portions.
The hose arrangement may comprise two or more hose assemblies disposed one above the other in the pressing direction, thereby enabling the deformation height to be increased if one hose assembly is not sufficient to generate the required maximum camber. The hose assemblies may be separated by a stiff intermediate layer.
The pressure surfaces on the beam element and/or support beam element may have concave recesses for partially accommodating the hose arrangement, thereby reducing load peaks on the hose arrangement and preventing undefined deformation of the hose arrangement.
For bending operations in which it is not necessary to camber the press table or press beam, the beam element is placed in contact with the support beam element in the region of the pressure surfaces with the hose arrangement devoid of pressure. The bending strength and strength of the beam element is therefore supplemented by that of the support beam elements.
To impart greater flexibility to the hose arrangement and hence also greater deformability, the hose arrangement may comprise a hose portion with a strengthening material made from a synthetic fiber braid.
The pressurized fluid supply unit connected to the hose arrangement may have at least one substantially leakage-free valve, in particular a seat valve or cartridge valve to provide easy control of the filling volume and hence the pressure and camber height. An existing pre-tensioning can therefore easily be maintained because the pressure does not drop once the valve is closed.
To enable operation of the valve to be easily integrated in an existing control device of the press brake and obtain a rapid and sensitive adjustment of the filling volume and camber height, it is of advantage if the valve has an electromagnetic operating unit.
In particular, the valve may be actuated by a pulse-width modulator.
To provide a clearer understanding, the invention will be described in more detail below with reference to the appended drawings.
These are highly schematic, simplified diagrams illustrating the following:
Firstly, it should be pointed out that the same parts described in the different embodiments are denoted by the same reference numbers and the same component names and the disclosures made throughout the description can be transposed in terms of meaning to same parts bearing the same reference numbers or same component names. Furthermore, the positions chosen for the purposes of the description, such as top, bottom, side, etc., relate to the drawing specifically being described and can be transposed in terms of meaning to a new position when another position is being described. Individual features or combinations of features from the different embodiments illustrated and described may be construed as independent inventive solutions or solutions proposed by the invention in their own right.
As illustrated in
Such flexion 7 of the press beam 4 or press table 3 causes a workpiece 2 to be pushed down into the bending die to a less pronounced depth at the center of the edge to be bent by the bending punch than at the ends of the bend edge, as a result of which a different bend angle can occur on the bent workpiece 2 along the bend edge, which means that such a workpiece could possibly need additional work or may be totally unusable. The forces 9 causing the respective flexion 7 on the press table 3 or press beam 4 are indicated in
A way of preventing detrimental effects on a workpiece 2 due to flexion 7 of the press table 3 or press beam 4 is known from the prior art and involves taking active counter-measures on the press table 3. As illustrated in
The concave bottom face 13 of the press beam 4 caused by flexion 7 co-operates with the convexly cambered top face 14 of the press table 3, thereby resulting in a uniform penetration depth of the bending punch into the workpiece 2 along the bend edge and hence also a much more constant bend angle along the bend edge.
Possible embodiments of a press table 3 proposed by the invention will be described below, and the structural characteristics and features described can literally be transposed to a displaceable press beam 4 and therefore apply not only to a press table 3 but also to a press beam 4, the support surface for a bending die 15 or a bending punch 16 which can actively be altered from a planar initial position to a convex, outwardly curved shape.
The base 23 of the U-shaped beam element 17 constituting the support surface 18 on its own would have a very low bending strength but because of the connection to the arms 21 parallel with the working plane 22, the beam element 17 overall has a relatively high bending strength, as is generally required of press brakes 1. The connection between the base 23 and the arms 21 may specifically comprise a positive connection parallel with the working plane 22, thereby resulting in a stable force transmission between the base 23 and arms 21. Another option is a one-piece, e.g. welded, connection between the base 23 and arms 21.
The beam element 17 is connected to a support beam element 24 of approximately the same length, which likewise has a plate-shaped main structure and extends approximately parallel with the working plane 22. In the embodiment illustrated as an example, the support beam element 24 is disposed in the interior of the U-shaped beam element 17 and is enclosed between the two arms 21. Connecting points 25 are provided on the beam element 17 at which it is connected by means of connecting elements 26, for example in the form of bolts 27, to the support beam element 24. The beam element 17 and the support beam element 24 therefore overlap in the region of the arms 21.
The bolts 27 extend at a right angle to the working plane 22 of the press brake 1 and extend through both the arms 21 of the beam element 17 and the support beam element 24. Such a design of press table 3 or press beam 4 with mutually overlapping portions of beam element 17 and support beam element 24 may also be described as a sandwich layout.
The beam element 17 has a pressure surface 28 facing the support beam element 24 and in the embodiment illustrated as an example lies on the inner face of the base 23. The support beam element 24 also has a pressure surface 29 which faces the pressure surface 28 on the beam element 17. To enable an active camber 12 to be imparted to the support surface 18 of the beam element 17 as illustrated in
The actuator 30 is provided in the form of a hose arrangement 33 extending in the longitudinal direction of the beam element 17 which can be filled with hydraulic fluid 34. In the embodiment illustrated as an example, the hose arrangement 33 comprises three mutually parallel hose portions 35, which are supported on both the pressure surface 28 of the beam element 17 and the pressure surface 29 on the support beam element when filled with hydraulic fluid 34 and thus transmit the adjusting force 32 to the beam element 17.
The three mutually parallel hose portions 35 of the hose arrangement 33 illustrated in
The press table 3 may be designed so that when the hose arrangement 33 is not filled or is without pressure, the beam element 17 is supported to the side of the hose arrangement 33 with support surface 28 on support surface 29 of the support beam element 24, so that when the press brake 1 is being operated without activating the cambering device, the bending strength of the beam element 17 is additionally enhanced by the bending strength of the support beam element 24.
The hose arrangement 33 comprises flexible hose portions, the strength of which is selected so that they can withstand the maximum pressures that will be generated by the hydraulic fluid 34 without bursting. In one advantageous embodiment, hoses incorporating a strengthening material made from a synthetic fiber braid are used because they have a higher elasticity than hoses with a metal braid and can therefore cover longer adjustment paths when creating the camber 12.
The hose arrangement 33 preferably has a working length between the pressure surfaces 28 and 29 which approximately corresponds to the distance between two connecting points 25 on the beam element 17. The total free bending length of the beam element 17 and a uniform load can therefore be applied by the hose arrangement 33, thereby creating a camber 12 which is approximately parallel with the flexion 7 of the press beam 4.
As illustrated in
As illustrated in
In the embodiment illustrated in
The extent of the camber can be fixed by the regulated intake of hydraulic fluid 34 and the associated regulated pressure increase in the hose arrangement 33. For example, during a bending operation, it is possible to calculate the flexion 7 of the press beam on the basis of workpiece parameters or detect it by means of an appropriate measuring system during the bending operation and on this basis, the camber 12 can be set to the same dimension by regulating the intake of hydraulic fluid 34. If calculating the anticipated flexion 7 of the press beam 4 beforehand, the camber 12 of the press table 3 can also be set prior to running the bending operation. If measuring flexion 7 during the bending operation, the camber 12 is likewise adjusted to the right fit during the bending operation. In addition, it is also possible to measure the camber 12, in other words the camber of the support surface 18, during the bending operation, and the camber 12 can then be regulated by a subsequent adjustment adapted to the measured or calculated flexion 7 of the press beam 4.
The hose arrangement 33 is supplied with hydraulic fluid 34 by means of a pressurized fluid supply unit 42 incorporating at least one substantially leakage-free valve 43, so that when the valve is closed, the fluid pressure can be easily kept constant during a bending operation. The valve 43 is a seat valve or cartridge valve, for example. The valve 43 is preferably operated by means of an electromagnetic operating unit, as a result of which the hose arrangement 33 can be supplied with hydraulic fluid 34 in a simple manner integrated in the control device of the press brake 1. The valve 43 may be activated in particular by means of a pulse-width modulator 44, which can be integrated in the pressurized fluid supply unit 42 or provided by the control device of the press brake 1.
The hose arrangement 33 may also be of a multi-layered design, for example by disposing two of the hose assemblies illustrated in
As illustrated in
In this embodiment, it is not bolts serving as the connecting elements 26 between the beam element 17 and support beam element 24 as described in connection with
Here too, the use of a pressure segment 47 between the beam element 17 and support beam element 24 results in a slide bearing 51 and a pivot bearing 52, which enables the beam element 17 and support beam element 24 to be bent by the hose arrangement 33 as well as by bending forces during the bending operation without creating a high degree of stress in the press table 24. In this embodiment, the bottom face of the pressure segment 47 is of an arcuately curved design and the top face 49 is a flat surface.
In this embodiment, the pressure segment 47 has a curved shape on both the bottom face 48 and the top face 49 and thus has a lenticular cross-section. The bottom face 48 is inserted in a co-operating recess in the cross-connector 40 and the curved top face 49 is inserted in a sliding piece 53 which is mounted by the top face in a guide recess 55 with a flat slide surface 54 so as to be displaceable on the bottom face of the support beam element 24. Again in this embodiment, a slide bearing 51 and a pivot bearing 52 are formed at the connecting point 25.
In spite of the fixed connection at the connecting point 25 on the cross-connector 40 and on the fixing point 57, increased movement occurs between the beam element 17 and the support beam element 24 due to the length of the bending-resistant element 56, which is useful when actively creating the camber 12. The ability to allow relative movement can be enhanced by providing additional slots 58, for example, as indicated by broken lines in
The embodiments illustrated as examples represent possible variants of the press table or press beam, and it should be pointed out at this stage that the invention is not specifically limited to the variants specifically illustrated, and instead the individual variants may be used in different combinations with one another and these possible variations lie within the reach of the person skilled in this technical field given the disclosed technical teaching. Accordingly, all conceivable variants which can be obtained by combining individual details of the variants described and illustrated are possible and fall within the scope of the invention.
All the figures relating to ranges of values in the description should be construed as meaning that they include any and all part-ranges, in which case, for example, the range of 1 to 10 should be understood as including all part-ranges starting from the lower limit of 1 to the upper limit of 10, i.e. all part-ranges starting with a lower limit of 1 or more and ending with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1 or 5.5 to 10.
The objective underlying the independent inventive solutions may be found in the description.
Above all, the individual embodiments of the subject matter illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| A 175/2012 | Feb 2012 | AT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AT2013/050032 | 2/8/2013 | WO | 00 |
