Sheet metal working tool with a relatively movable hold-down device held on the upper part of the tool and with a drive device and an adjusting device for this hold-down device.

Abstract

Sheet metal working tool (100) for forming and / or cutting sheet metal material (200), comprising a lower tool part and an upper tool part between which the sheet metal material (200) is arranged and can be formed and / or cut by lowering the upper tool part, wherein the upper tool part has a relatively movable hold-down device (120) with which the sheet metal material (200) can be pressed against the lower tool part during forming and / or cutting and thereby fixed in a defined area, characterized in that the upper tool part has at least one drive device (150) which engages with the relatively movable hold-down device (120) when the upper tool part is raised (B) and carries the hold-down device (120) along, and that furthermore at least one actuating device (170) acting between the hold-down device (120) and the lower tool part with a coil spring, a disc spring, a fluid spring,a hydraulic cylinder or a bellows cylinder is provided which, even before the engagement of the drive device (150), pushes the hold-down (120) away from the lower part of the tool and thereby reduces the weight on the hold-down (120), so that the subsequent engagement of the drive device (150) can take place largely without impact.

Description

[0001] The invention relates to a press-mounted sheet metal working tool for forming and / or cutting sheet metal material, comprising a lower tool part and an upper tool part, wherein the upper tool part has at least one relatively movable hold-down device. In particular, it is a pressing, forming, or trimming tool.

[0002] A sheet metal working tool of the type in question is known from DE 10 2009 037 854 A1. The previously known sheet metal working tool has a lower tool part that can be mounted on a press table and an upper tool part that can be attached to a press ram. By means of the press ram, the upper tool part can be lowered from a top dead center (TDC) to a bottom dead center (BDC) (downward movement or closing movement), whereby the sheet metal material located between the upper and lower tool parts is formed and / or cut. Furthermore, the upper tool part has a relatively movable hold-down device which, during the downward movement of the upper tool part, first contacts the sheet metal material in order to fix it in a defined area (typically the edge area) during the forming and / or cutting process by pressing it against the lower tool part.The hold-down device is actuated by a ram cushion device belonging to the press or alternatively by spring and / or adjusting devices in the tool.

[0003] In contrast to a drawing tool, the blank holder in a trimming and / or forming tool does not serve to influence the flow of sheet metal material, but rather to fix the sheet metal material by pressing it against the other tool part (especially the lower tool part). The blank holder is attached when the sheet metal working tool is closed, before the forming or cutting process begins. The blank holder force or surface pressure generated by the blank holder must be sufficient to securely fix the sheet metal material or component during the forming (or forming) or cutting (or trimming) process.

[0004] After reaching bottom dead center, or after completing the forming and / or cutting operation, the upper part of the tool is brought back to top dead center by means of the press ram by lifting it (upward movement or opening movement). The relatively movable blank holder must be moved along with it. The sheet metal working tool known from DE 10 2009 037 854 A1 has a spring device for this purpose (see paragraph

[0047] ) which presses the blank holder against the ram cushion via a bolt. The force of the spring device must overcome the weight of the blank holder, which is impossible due to the effects of inertia with larger or heavier blank holders (which can weigh up to 6000 kg and more) and / or with higher ram speeds and the associated higher press stroke rates, such as those that can be achieved with modern servo presses.

[0005] It is therefore an object of the invention to show a way in which high blank holder weights and / or high ram speeds can be handled with regard to the opening movement in a sheet metal working tool of the type mentioned at the outset.

[0006] This problem is solved by a sheet metal working tool according to the invention with the features of claim 1. Advantageous embodiments and further developments result from both the dependent claims and the following explanations.

[0007] The upper part of the sheet metal working tool according to the invention has at least one drive element which engages with the relatively movable blank holder when the upper part of the tool is lifted and carries the blank holder along in the upward movement (i.e., towards the top dead center). Furthermore, the sheet metal working tool according to the invention has at least one adjusting device acting directly between the blank holder and the lower part of the tool, which pushes the blank holder away from the lower part of the tool even before the drive element engages, thereby reducing the effective weight force on the blank holder, so that the subsequent engagement of the drive element on or with the blank holder can occur smoothly or at least largely smoothly, or without jerking.

[0008] Preferably, this positioning device comprises a linearly guided and force-actuated actuating element that can perform an actuating stroke. Preferred methods for applying force to the actuating element are listed below.

[0009] To manage the effects of inertia with larger or heavier blank holders and / or at higher ram speeds, the upper part of the sheet metal working tool according to the invention has at least one, in particular rigid, drive element that moves with the upper part of the tool. During the upward movement, this drive element engages directly or indirectly with the blank holder, which initially rests on the lower part of the tool. This engagement occurs particularly at a defined position of the upper part of the tool or a specific press ram position. Upon engagement, a positive fit is established between the drive element and the blank holder, so that during the further upward movement of the upper part of the tool, the blank holder is carried along and lifted by the positive fit established during the upward movement.

[0010] The engagement of the moving drive unit with the still stationary blank holder occurs more or less abruptly or jerkily. Due to a high blank holder mass and / or a high ram speed, this leads to impacts or shocks that can damage the sheet metal working tool and / or the press. To prevent such impacts, at least one adjusting device, acting primarily directly between the blank holder and the lower tool body, is provided. This device pushes or detaches the blank holder from the lower tool body even before the drive unit engages, thereby reducing the weight (or even pre-accelerating) the blank holder, so that the subsequent engagement of the drive unit can be largely impact-free.

[0011] An actuating device acting between the blank holder and the lower tool part is understood to be an assembly consisting of several individual components, which can, in particular directly, generate a compressive force between the blank holder and the lower tool part, thereby creating a distance between these components. The force can be introduced directly or indirectly into the blank holder and / or the lower tool part. It is preferably provided that such an actuating device is arranged in an outer tool area of ​​the sheet metal working tool according to the invention. An outer tool area is, in particular, an area of ​​the sheet metal working tool according to the invention that lies outside the tool's working surfaces and is preferably also easily accessible from the outside.

[0012] If necessary, the hold-down device can be set into an upward movement by means of at least one actuating device even before the engagement of the drive device, whereby the actuating device would function as a pre-acceleration device.

[0013] Preferably, the drive device comprises a drive element that can be brought into a positive engagement with the hold-down device, either directly or indirectly, in order to subsequently apply lifting forces to the hold-down device. Particularly preferred is the drive device being a rigid tie rod attached directly or indirectly to a frame of the upper tool part, which, in particular, has at least one drive element at its lower axial end, such as a drive disc, a drive hook, or the like, which, when the upper tool part is lifted, strikes the hold-down device to drive it along. The drive element and / or the hold-down device can be equipped with damping elements in the contact area to dampen the impact. Such damping elements can be, for example, spring elements made of polyurethane or other special plastics that have a spring-like and damping effect.

[0014] Since the preceding and / or subsequent explanations sometimes refer only to one drive device and one actuating device, it should be expressly pointed out that the sheet metal working tool according to the invention can have several drive devices and / or several actuating devices, which may be identical or different in terms of their design and / or properties. It is preferred that the drive devices and / or the actuating devices on a sheet metal working tool according to the invention are designed for synchronous operation and are arranged accordingly in the sheet metal working tool.

[0015] Preferably, the at least one adjusting device is arranged on the hold-down and presses against the lower part of the tool. It is also preferred that the at least one adjusting device is arranged on the lower part of the tool and presses against the hold-down. The sheet metal working tool according to the invention can have several adjusting devices that are arranged differently, i.e., both on the lower part of the tool and on the upper part of the tool.

[0016] Preferably, the actuating force that can be generated, particularly at bottom dead center, by all actuating devices combined, essentially corresponds to the weight or force of the hold-down device. This allows the hold-down device to have an effective weight load of zero kilograms at the moment the drive device engages (i.e., the force of the hold-down device is effectively canceled out), which is highly advantageous with regard to the inertia effects that occur when the drive device engages and the hold-down device is subsequently pulled along.

[0017] It can also be provided that the total or combined actuating force generated by all actuating devices, particularly at the bottom dead center, is less than the weight or weight force of the hold-down device. This ensures that the hold-down device has a reduced weight load at the moment the drive device engages, which is advantageous with regard to the inertia effects that occur when the drive device engages and the hold-down device is subsequently pulled along.

[0018] Furthermore, it can be provided that the total or combined actuating force generated by all actuating devices, particularly at the bottom dead center, is greater than the weight or the weight force of the hold-down device. This allows the hold-down device to be pre-accelerated or set into an upward movement even before the drive devices engage, which is particularly advantageous with regard to the inertia effects that occur when the drive device subsequently engages and the hold-down device is then carried along.

[0019] Preferably, the actuating stroke achievable with the at least one actuating device is equal to or greater than the hold-down stroke. The hold-down stroke is the relative movement, or the associated travel distance, of the hold-down relative to the upper tool part after the hold-down has come into contact with the lower tool part and the upper tool part continues to move to its bottom dead center. This will be explained in more detail below in connection with the figures. However, the actuating stroke achievable with the actuating device can also be smaller than the hold-down stroke, which will also be explained in more detail below in connection with the figures.

[0020] An adjusting device can have or comprise at least one spring assembly. Such a spring assembly can be, for example, a coil spring, a disc spring, a block spring (e.g., a rubber or elastomer spring), a fluid spring (e.g., a gas spring), or the like, wherein the adjusting device comprises several identical or different spring assemblies. An adjusting device is particularly designed and arranged in the sheet metal working tool according to the invention such that the at least one spring assembly comprised therein is tensioned when the upper part of the tool or the hold-down is lowered and automatically relaxes again when the upper part of the tool or the hold-down is raised.

[0021] It is particularly preferred that at least one actuating device is designed with an integrated damping function or damping effect, wherein this damping function is realized in particular by damping elements and / or damping devices installed in the actuating device. Thus, shock absorption can be achieved when the hold-down device is placed directly or indirectly onto the actuating device or onto the actuating element of the actuating device. The proposed actuating device would therefore be advantageous for reducing stress both when closing and opening the sheet metal working tool.

[0022] Typically, during the upward movement of the upper tool part, the blank holder holds the sheet metal material or forming part in place until the active elements of the sheet metal working tool (such as blades, forming jaws, etc.) no longer touch the sheet metal material. Therefore, the blank holder force must typically be greater than the stripping force or release force of the active elements from the sheet metal material.

[0023] The invention is explained in more detail below by way of an example with reference to the schematic figures, wherein the features explained below and / or shown in the figures can be general features of the invention, irrespective of specific combinations of features. Fig. Figure 1 shows a sheet metal working tool according to the invention in a schematic sectional view, wherein the upper part of the tool is located at bottom dead center. Fig. Figure 2 shows the sheet metal working tool from Fig. 1, wherein the upper part of the tool is in an upward movement and the hold-down device is still resting on the lower part of the tool. Fig. Figure 3 shows the sheet metal working tool from Fig. 1, wherein the upper part of the tool is in an upward movement and carries the hold-down with it.

[0024] Fig. Figure 1 shows a sheet metal working tool according to the invention, designated as 100 in its entirety. The sheet metal working tool 100 is installed in a press and comprises a lower tool part attached to the press table 10 and an upper tool part attached to the press ram 20. A sheet metal material 200 can be arranged between the upper tool part and the lower tool part and formed and / or cut in a known manner, whereby the upper tool part attached to the press ram 20 is lowered from a top dead center (TDC) towards the stationary lower tool part to a bottom dead center (BDC) and then raised again to the top dead center.

[0025] The upper part of the tool includes a frame or base plate 110 to which a relatively movable hold-down device 120 is attached. This device presses the sheet metal material 200 against a punch 130 belonging to the lower part of the tool during forming and / or cutting, thereby fixing it in at least one defined area or section. This prevents, for example, an already formed area of ​​the sheet metal material 200 from being undesirably deformed further. Fastening elements and guides for the hold-down device 120 are not shown. Reference numeral 140 denotes a frame or base plate belonging to the lower part of the tool. A die belonging to the upper part of the tool is not shown.

[0026] In the Fig. In the illustration shown in Figure 1, the upper part of the tool is at bottom dead center. At this point, the forming and / or cutting operation is generally complete. Subsequently, the upper part of the tool is lifted again by means of the press ram 20 and moved back to top dead center. This upward movement of the upper part of the tool is illustrated by arrow B. During this movement, the relatively movable hold-down device 120, which can weigh up to several tons, must be carried along. For this purpose, the sheet metal working tool 100 according to the invention has at least one and preferably several drive devices 150, as explained in more detail below.

[0027] In the example shown, a drive device 150 comprises at least one rigid and axially extending tie rod 151, which extends through the hold-down device 120 via a bore or recess and is attached to the frame 110 at its upper axial end. The attachment to the frame 110 can be effected, for example, by screwing. A disc-shaped drive element 152 is arranged at the lower axial end of the tie rod 151. When the upper part of the tool is lifted, this drive element engages with the relatively movable hold-down device 120, such that it makes contact with the hold-down device 120 from below at the edge of the bore and subsequently presses against the hold-down device 120 from below to carry it along during the upward movement B.

[0028] The drive element 152 is a spring assembly, resulting in a soft or damped engagement between the drive element 150 and the hold-down device 120. The spring assembly 152 comprises at least one elastic body (e.g., made of polyurethane or rubber) positioned between an upper and a lower disc. However, the spring assembly 152 can also be designed differently. The structurally defined spring travel or damping travel of the spring assembly or spring element 152 can, for example, range from 2 mm to 25 mm.

[0029] Despite the spring mechanism 152, impacts can occur with heavy hold-downs 120 and / or at high ram speeds due to inertia effects if the drive element 152 strikes the hold-down 120 during the upward movement B and jerkily or abruptly carries it along in the upward movement B, potentially resulting in high accelerations of up to 25g and more. To avoid such impacts, the sheet metal working tool 100 according to the invention has at least one and preferably several adjusting devices 170, as explained in more detail below.

[0030] The actuating device 170, arranged by way of example on the lower part of the tool, comprises a longitudinally movable rod-like actuating element 173, which is mounted in a spring housing or spring accumulator 175. A mechanical spring assembly, 176, arranged in the spring housing 175, is designated by reference numeral 176, which is by way of example a coil spring. By pressing the actuating element 173 into the spring housing 175, the spring assembly or coil spring 176 is tensioned, resulting in a force being applied to the actuating element 173, depending on the spring characteristic curve (force versus displacement).

[0031] The spring assembly 176 can optionally be pre-tensioned and thus permanently tensioned. Instead of at least one coil spring, at least one disc spring or at least one fluid spring, such as a gas spring, can also be provided. The adjusting device 170 can comprise several spring assemblies of the same or different spring types. Alternatively, the adjusting device 170 can be designed as a hydraulic cylinder, a bellows cylinder (i.e., without a spring assembly), or in some other way. Furthermore, the adjusting device 170 can also be arranged directly or indirectly on the hold-down device 120. The sheet metal working tool 100 can also have at least one adjusting device 170 arranged on the lower part of the tool and at least one adjusting device arranged on the hold-down device 120.

[0032] When the sheet metal working tool 100 closes, i.e., when the upper part of the tool is lowered towards the lower part, the hold-down device 120 comes into contact with the actuating element 173 of the actuating device 170. During the further downward movement, the actuating element 173 is pressed into the spring housing 175 by the hold-down device 120, thereby tensioning the spring device 176 and generating a compressive force against the hold-down device 120 or upwards according to the spring characteristic curve.

[0033] The adjusting device 170 can also be used to achieve shock damping during the downward movement or when closing the sheet metal working tool 100, particularly when the blank holder 120 is placed on the tool base or on the punch 130. Preferably, the adjusting device 170 is equipped with corresponding damping elements and / or damping devices to enable such a damping function. Preferably, the sheet metal working tool 100 is designed such that, during the downward movement, the blank holder 120 first rests on the adjusting element 173 of the adjusting device 170 and only then on or comes into contact with the punch 130, so that the impact of the blank holder 120 on the punch 130 or on the tool base can be dampened by the adjusting device 170. This is particularly advantageous with high blank holder masses and / or high ram speeds.

[0034] While the hold-down device 120 sits on the lower part of the tool or on the punch 130, it is actuated in a known manner by a ram cushion device belonging to the press or alternatively by spring and / or adjusting devices installed in the sheet metal working tool 100, i.e., subjected to force, so that the hold-down device 120 can fix the sheet metal material 200 accordingly.

[0035] Starting from the in Fig. In the lowest position of the upper tool part shown in Figure 1, it is moved upwards by means of the press ram 20. The blank holder 120 initially rests on the sheet metal material 200 or on the punch 130 before being carried along in the upward movement B by the engaging drive devices 150, as explained above. However, before the drive devices 150 engage with the blank holder 120 during the upward movement B, the actuating devices 170, by means of the actuating elements 173, already press against the blank holder 120 from below (for which purpose the blank holder 120 is designed with corresponding contact surfaces), thereby reducing the force acting on the blank holder 120 by the total force applied by all spring devices 176. This phase of the upward movement is described in Figure 1. Fig. Figure 2 shows that when the adjusting devices are arranged on the hold-down device 120, they push the hold-down device 120 away from the lower part of the tool, which would lead to a reduction in the effective weight load in an analogous way.

[0036] The reduction of the effective weight force or load on the blank holder 120, effected by the adjusting devices 170, leads to more favorable inertia effects even before the drive devices 150 engage. This allows the subsequent engagement of the drive devices 150 with the blank holder 120, during which the blank holder 120 is pulled along more or less abruptly in the upward movement B at the beginning of the drive movement, to occur largely without shock or jerk. The loads occurring on the sheet metal working tool 100, and especially those occurring on the drive devices 150, are thereby significantly reduced. The press loads can also be considerably reduced by the proposed tool design measures. As a result, the dynamic loads on the entire system are significantly reduced.Furthermore, any vibrations that occur can also be dampened.

[0037] Furthermore, with appropriate design of the actuating devices 170 or their spring devices 176, a pre-acceleration of the hold-down device 120 can also be achieved before the drive devices 150 engage with the hold-down device 120, so that the hold-down device 120 is already moved upwards in the direction of the upward movement B before the drive devices 150 engage. In this case, a particularly "soft" engagement of the drive devices 150 with the hold-down device 120 is enabled. Such pre-acceleration of the hold-down device 120 is made possible in particular by the fact that the actuating force that can be generated jointly by all actuating devices 170 is greater than the weight or greater than the effective weight force of the hold-down device 120, so that the actuating devices 170 can lift the hold-down device 120 when it is decoupled, i.e., no longer actuated by the plunger cushion device or the like.

[0038] After the essentially shock-free engagement of the drive devices 150 with the hold-down device 120, the latter is moved upwards together with the upper part of the tool, whereby the hold-down device 120 and the adjusting devices 170 finally come out of contact. This phase of the upward movement is described in Fig.Figure 3 shows that in this phase, the hold-down device 120 is suspended from the base plate 110, with the weight load of the hold-down device 120 being transmitted only via the tie rods 151 belonging to the drive devices 150. After the drive devices 150 engage the hold-down device 120, the initial movement of the hold-down device 120 can be supported for a short distance (i.e., over a certain distance) by the actuating devices 170, which, for example, allows for a smoother initial acceleration of the hold-down device 120. During rebound, the spring devices 176 gradually lose spring force, an effect which can be reduced, for example, by a non-linear spring characteristic curve or by preload. When the hold-down device 120 reaches a certain height during the upward movement B, the actuating elements 173 of the actuating devices 170 finally disengage, which is determined by the structurally predetermined extension length.the stroke of the actuating elements 170 is determined.

[0039] The contact phase or contact duration between the actuating devices 170, or their actuating elements 173, and the hold-down device 120 during a work cycle can be specified by the structural design of the actuating element stroke or the actuating stroke on the actuating devices 170. A work cycle comprises lowering the upper tool part from TDC to BDC and subsequently raising the upper tool part from BDC to TDC. The contact phase between the hold-down device 120 and an actuating device 170 corresponds at least to the time period during which the hold-down device 120 rests on the lower tool part or on the punch 130. In particular, however, it is intended that the contact phase between the hold-down device 120 and the actuating devices 170 exceeds this time period during which the hold-down device 120 rests on the lower tool part or on the punch 130.The actuating elements 173, which sit on the punch 130, exceed the height of the die holder 120, so that the actuating elements 173 come into contact with the die holder 120 even before the die holder 120 is placed on the punch 130 and only come out of contact again after the die holder 120 is lifted off the punch 130. This advantageously allows shock damping when the die holder 120 is placed on the lower part of the tool and / or a smooth initial acceleration of the die holder 120 after the engagement of the drive devices 150 (as explained above).

[0040] The relative movement between the frame 110 and the hold-down 120 after the hold-down is placed on the tool base, or the distance of this relative movement, is referred to as the hold-down stroke. Preferably, the stroke of the actuating elements 173 on the actuating devices 170 corresponds at least to this hold-down stroke and is, in particular, greater than this hold-down stroke. Especially with regard to achieving pre-acceleration of the hold-down 120 (as explained above), this ensures that the hold-down 120 can be pre-accelerated over its entire travel distance (i.e., from its bottom dead center) until the engagement of the drive devices 150 (and optionally beyond). However, the stroke of the actuating devices 170 can also be less than the hold-down stroke.

[0041] To achieve specific tool properties, all adjusting devices 170 on the sheet metal working tool 100 according to the invention can be identical or different. Furthermore, depending on their design and configuration, these adjusting devices 170 can perform their function synchronously or asynchronously. The same applies to the drive devices 150.

[0042] In contrast to the example shown in the figures and explained above, the actuating device 170 can also be operated by motor (e.g. with an electric motor), pneumatically and / or hydraulically. Reference symbol list 10 press table 20 press rams 100 sheet metal working tools 110 Base plate, frame (tool top) 120 hold-downs (tool top) 130 stamps (tool base) 140 Base plate, frame (tool base) 150 Drive device (holding device) 151 tie rods 152 Spring assembly 170 Actuator 173 Actuator 175 Spring housings 176 Spring assembly 200 Sheet metal material (molded part) B Upward movement

Claims

Sheet metal working tool (100) for forming and / or cutting sheet metal material (200), comprising a lower tool part and an upper tool part between which the sheet metal material (200) is arranged and can be formed and / or cut by lowering the upper tool part, wherein the upper tool part has a relatively movable hold-down device (120) with which the sheet metal material (200) can be pressed against the lower tool part during forming and / or cutting and thereby fixed in a defined area, characterized in that the upper tool part has at least one drive device (150) which engages with the relatively movable hold-down device (120) when the upper tool part is raised (B) and carries the hold-down device (120) along, and that furthermore at least one actuating device (170) acting between the hold-down device (120) and the lower tool part with a coil spring, a disc spring, a fluid spring,a hydraulic cylinder or a bellows cylinder is provided which, even before the engagement of the drive device (150), pushes the hold-down (120) away from the lower part of the tool and thereby reduces the weight on the hold-down (120), so that the subsequent engagement of the drive device (150) can take place largely without impact. Sheet metal working tool (100) according to claim 1, characterized in that the adjusting device (170) is arranged on the hold-down device (120). Sheet metal working tool (100) according to claim 1, characterized in that the adjusting device (170) is arranged on the lower part of the tool. Sheet metal working tool (100) according to any one of claims 1 to 3, characterized in that the actuating force that can be generated jointly by all actuating devices (170) is essentially equal to or greater than the weight of the hold-down device (120). Sheet metal working tool (100) according to one of claims 1 to 3, characterized in that the actuating force that can be generated jointly by all actuating devices (170) is less than the weight of the hold-down device (120). Sheet metal working tool (100) according to one of the preceding claims, characterized in that the adjusting device (170) is arranged in an outer tool area. Sheet metal working tool (100) according to one of claims 1 to 6, characterized in that the actuating stroke that can be generated with the actuating device (170) is equal to or greater than the hold-down stroke. Sheet metal working tool (100) according to one of claims 1 to 6, characterized in that the actuating stroke that can be generated with the actuating device (170) is smaller than the hold-down stroke. Sheet metal working tool (100) according to one of claims 2 to 8, characterized in that the adjusting device (170) is designed with an integrated damping function.

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