Protective device for machines such as bending presses, cutting machines, punching machines or the like.

The invention relates to a protective device for machines such as bending presses, cutting machines, stamping machines or the like, in which a first machine part operating movements against a second machine part performs, with the first machine part mounted by means of a holding device photoelectric arrangement, in particular laser light barrier arrangement which is perpendicular to a distance level to work plane of movement of the first part has a first light barrier and at least one second light barrier, extend their light beams parallel to the longitudinal direction of the first part, and the spacing layer comprises a a safe distance from this first machine part, wherein the first light barrier substantially in the labor movement plane or sheet the first machine part is arranged, and with a light beam interruption in the labor movement stopping blocking device.

Such protection devices are, for example, from DE 2750234 B1, DE 19717299 A1, WO 97/25568, EP 0264349 B1, EP 0146460 A2 or DE 10232795 A1 and serve to primarily protect the operator and to prevent that for example the hand is pinched or injured between the two machine parts and tools. Of course, the light barrier arrangement can prevent destruction that by moving first machine part inadvertently came between him and the second machine part items damaged or with a self-destruction or damage is prevented. Without additional measures would at the end of the closing movement the first machine part come shortly before reaching the workpiece to be machined to a halt because the lowest laser beam would be interrupted when the first machine part has approached the workpiece up to the safety distance. To prevent this, in the known protection devices, the light barrier arrangement is deactivated at the end of the closing movement. This can only be accepted, therefore, since it is simultaneously switched from the dangerous rapid speed to a safer creep speed. However, this slow speed leads disadvantageously to a reduction in the working cycle and thus to slow down the operations. A generic protection device is known from DE 202 17 426 U.

It is therefore an object of the invention to keep the working phase with reduced speed as short as possible, in the processing of box-shaped and flat workpieces.

This object is achieved by a protective device having the features of claim 1.

By switching the invention can be maintained for each type of workpiece creep speed phase as short as possible. For flat workpieces only the photocells are activated in the distance plane, having a safe distance from the first machine part. This safety margin corresponds to the braking power of the first part or is slightly larger. The at least one second light barrier, which is upstream of the first machine part in the distance level, prevents an in slipping between the machine parts hand is hurt by this second light barrier is already interrupted by the inside skidding hand before an interruption of the first light barrier is carried out by a fingertip , This at least one second light barrier in the distance layer must however necessarily in the machining of box-shaped workpieces are disabled, otherwise no processing would be possible. Simultaneously with this deactivation, however, the at least a third light barrier is activated, which is disposed in the working path of movement of the first machine part, that is at a upper tool formed as the first machine part distance below the plane. This third photocell accepts thereby quasi the safety function of the second light barrier in the processing of box-shaped workpieces, so prevents jamming of the last moment into slipping hand. The automatic switchover to the creep speed is indeed here earlier, when the third light barrier reaches the workpiece, however, by switching disabling this third light barrier in flat workpieces can be achieved because at least then again the creep phase is minimized.

The measures specified in the dependent claims, advantageous refinements and improvements of the claim 1 protection device are possible.

By deactivating device for deactivating the plurality of third light barriers one by one and finally the first light barrier is in each case from being interrupted by the workpiece to be machined or by the second machine part achieved a further improvement in safety. The gradual deactivation may even be recognized a einrutschender while the reduced closing speed finger or einrutschende hand.

To prevent permanent deactivation of the light barriers to reaching the workpiece or the second machine part automatically, automatic switch-on means to reactivate the light barriers are provided in an advantageous manner, which can be triggered in particular by the opening movement of the first machine part or by limit switches. The safety distance in the working movement direction between the first machine part and the first light barrier and between the latter and the third light barrier and the third photoelectric one another is advantageously smaller than the diameter of the smallest movable between the machine parts body part of an operator selected, ie, in particular smaller than the diameter of a small Fingers. The safety distance is therefore, for example, range from 6 to 14 mm.

To deactivate the at least one light barrier arrangement a cam control with limit switches connected to the deactivation device in an advantageous embodiment. Alternatively, it can be provided for deactivating a measuring system. It is preferably the measuring system learning means allocated by the deactivation positions by interrupting at least the lowest photoelectric barrier in a Lernhub storable or adjustable. Finally, an alternative way to disable also consists in connecting a timing means with the deactivation device.

In an advantageous embodiment of the invention, the light beams of the second and / or third light barriers can each have a light band or a light surface form, the or that can be detected in each case by a sensor array, in particular a camera chip. It may also here a successive deactivation of protective field areas, also continuously carried out.

Embodiments of the invention are shown in the drawing and explained in more detail in the following description. Show it:<dl id="dl0001"><dt>figure 1</dt><dd>a longitudinal side view of a bearing the protective device according to the invention the press brake,</dd><dt>figure 2</dt><dd>a cross-side view of the press brake in a simplified representation with deactivated third light barrier and between the tools eintauchendem finger shown in Figure 1,</dd><dt>figure 3</dt><dd>the same representation in completely submerged fingers,</dd><dt>figure 4</dt><dd>the arrangement of Figure 2 but with deactivated second photocell and editing a box-shaped workpiece,</dd><dt>figure 5</dt><dd>the same arrangement as figure 4, but with completely immersed finger and</dd><dt>figure 6</dt><dd>an arrangement with a plurality of second and third light barrier, and </dd><dt>figure 7</dt><dd>an alternative arrangement with a plurality of second and third light barriers.</dd></dl>

The press brake illustrated in Figures 1 and 2 consists essentially of a trained as punch 10 first machine part, which is movable against a fixed, configured as a lower tool 11 second machine part. The opposing labor movement direction A is characterized by a double arrow. Of course, may be designed to be movable in an alternative embodiment also the upper tool is fixed and the lower tool. The plate-like, elongated upper tool 10 has a working area 12 with wedge-shaped cross-section, while the lower tool 11 has a corresponding wedge-shaped groove 13, in which the working area 12 is engaged in the work movement and thereby to lie on the lower tool 11, machined plate 14 bends or abkantet.

The remaining regions of the known press brake are not shown for simplicity. The cross-sectional shape of the work area 12 and the trough 13 can of course vary.

In each case at the mutually opposite narrow sides of the upper tool 10 guides 15, 16 are attached to the upper tool 10, for example screwed. The mounting can of course in principle also be carried out indirectly, that is, the guides 15, 16 are then attached to a holder, which is connected via an unillustrated bracket for the upper tool 10 therewith.

In the guides 15, 16 brackets 17, 18 for three light barriers 19 are - 21 movable in a vertical adjustment movement whose direction is shown by the double arrows B and corresponding to the working direction of movement A. Each of the light barriers 19 - 21 consists in known manner of a laser transmitter and a laser receiver, wherein the laser transmitter to the one bracket 17 and the laser receiver arranged on the other holder 18th In principle it is also possible to reduce the number of stations in that the transmitted beam of the transmitter is split by a beam splitter into a plurality of transmitting light rays. Furthermore, it is also possible to expand the transmission beam parallel. Other ways to save the number of stations and the number of recipients are described in the initially mentioned DE 19717299 A1. Instead of laser light beams can be used by light beams, of course, other known species.

The first light barrier 19 and the second light barrier 20 are arranged in a plane perpendicular to the distance working movement direction A, which has a safe distance from the upper tool 10, which corresponds to at least the braking distance of the top tool 10th The first light barrier 19 is arranged offset below the upper die 10 in its working plane of movement or track or easy to this, while the second light barrier 20 is set to front toward the operator by approximately 30 to 50 mm. The third photocell 21 is also disposed below the first light barrier 19 substantially in the working plane of movement or web of the upper tool 10 and is therefore further away from the upper die 10 located opposite the first light barrier 19. The distance between the first light barrier 19 and the third photocell 21 substantially corresponds to the difference between the diameter of a human finger tip and the diameter of the part of the finger, which may be located in the machining plane after stopping the closing movement.

The protective effect of the safety device described is that the closing movement between the upper tool 10 and lower tool 11 is abruptly stopped when one of the laser beams of the light barrier 19 - 21 is interrupted, so if an object gets in the path of movement. Since such press brakes or similar machines are usually manually operated, is above all the risk of the hand or the arm of an operator enters the working trajectory, which could result in a pinching or severing by the closing movement. The safety distance between the upper tool 10 and the distance layer 22 should be such that, for example, no finger can be interposed. On the other hand this safeguard level should be such that in case of interruption of a laser beam, the closing movement may be slowed down or stopped in time before the obstacle. The safety distance is therefore, for example, range from 6 to 14 mm.

The adjustment of the light barrier arrangements or the brackets 17, 18 carried on the upper tool by displacement in the guides 15, 16 may, for example according to DE 19717299 A1 mentioned at the outset. It may be 10123562 A1 also provided an automatic positioning device according to DE. moves the upper tool 10 against the lower tool 11, so the light barriers are being interrupted by the workpiece 14 at the end of the closing movement, which would lead to an immediate movement stop, so that the desired operation can not be performed. By means of a deactivation device, this is prevented, which may be accommodated, for example in one of the brackets 17, 18 or any other body of the machine. This deactivation device each disabled a light barrier by means of a switching device just before a break through the workpiece 14 or the lower tool 11 would occur. At the same time, a changeover from the previous operating speed in a creep feed with substantially reduced speed for safety reasons. With the backward movement of the upper die is then a re reactivate the light barriers, which could also take place in the upper end position before the next operation principle. The deactivation apparatus may be effected in known manner by a position measuring system, a cam control with limit switches or a time-synchronous control.

In the figures 2 and 3 the case of machining a flat workpiece 14, for example of a sheet is shown. The activation device has a switching device for alternative disabling the second light barrier 20 and the third light barrier 21. When bending a flat workpiece according to Figures 2 and 3, the third photocell 21 is deactivated, which is symbolized by a crossed representation. Active only the light barriers 19 and 20. If thus there is no irregular interruption of the light barriers 19, 20, the switch will only be made to creep speed when the light barrier 19, 20, ie the distance plane 22 reaches the workpiece 14th Only during this short distance corresponding to at least the braking distance of the top tool 10, this has to be moved at creep speed. One finger can not be inserted between the upper tool 10 and the workpiece 14 in this small distance.

The second photocell 20 serves to increase the safety. Without this second light barrier 20 could be the case that in the creep speed work movement is indeed stopped by interrupting the first light barrier 19 by a quick hand movement shortly before the transition, however, could still be applicable inserted during the braking phase by a rapid flick of the hand, she would still pinched in the region of their greater height. This prevents the second light barrier 20 which has already initiates of Figure 2 by interruption due to the rapidly inserted hand the braking before the first light barrier 19 is interrupted. Even in far inserted finger according to Figure 3 thus takes the upper tool 10 in time to a standstill.

If a box-shaped workpiece 25 is to be bent, cut or stamped in accordance with Figures 4 and 5 or with correspondingly arranged workpiece stops or brackets, the upstream light barrier 20 to make the processing impossible. In this case, the changeover of the deactivation apparatus is actuated with the effect that after the changeover, the photocell 20 deactivated, and for the light barrier 21 is activated. The photocell 21 now ensures that the protective effect due to the loss of the light barrier 20 is not reduced. The now precedes down photocell 21 detects the first fingertip and passes via a disruption to the braking of the upper tool 10th Figure 5 shows that even with fast fingers inserted there is no danger that this will be pinched or injured. However, it must be accepted that a longer route with a reduced speed in the creep speed has to be covered, as they slowly phase already starts upon reaching the workpiece 25 through the photocell 21st

Another security improvement can also be achieved that only the photocell 21 is deactivated just before it reaches the workpiece 25th The light barrier 19 remains active, so that even with a reduced closing speed a einrutschender fingers can still be detected.

The embodiment illustrated in Figure 6 shows that the number of light barriers can be exacerbated in the distance layer 22 and through additional light barriers 26, 27 before and by further light barriers 28 to 30 behind the working plane. This variety of photoelectric effect that can not be passed gripped therebetween, so that the security is increased. Of course, can also be arranged, for example, just before the processing level, a number of such light barriers. The alternative activation of the photocells naturally also applies to this embodiment. So the light barriers 20, 26 to 30 on the one hand and the light barriers are there alternative 21 and 31 respectively alternatively activated depending on whether a flat workpiece 14 or a box-shaped workpiece 25 is present.

The number of light barriers below the upper tool in the working plane of movement or web may be supplemented, as already explained in the embodiment, a light barrier 31. As shown in Figures 4 and 5, the light barriers 31, 21 are each turned off one after the other, always just before a these photocells reaches the workpiece.

In the further embodiment shown in Figure 7 second light barriers 32 to 36 no longer arranged in a common distance plane 22 with the first light barrier 19, but in an inclined curved arrangement of upper tool 10 so that these light barriers 32 to 36 form a barrier, which makes a passage to put your hand to the workspace below the upper die 10 without interruption of the light barrier impossible or prevented. Here, the arrangement and number of these second light barriers 32 to 36 also vary. There are assemblies in an oblique line at an angle or in any other possible formations forming the barrier described. By the switching means are in each case either the second light barriers 32 to 36 on the one hand or the third photoelectric barriers 21, 31 zusammem with the first light barrier 19 on the other hand alternatively activated.

Alternatively or additionally, also the second light barrier on the opposite side of the upper tool 10 may be arranged accordingly. The training and embodiments described for the other embodiments are of course also be realized in this embodiment.

Alternatively, several light barriers arranged in rows, these could also be replaced by light bands or light areas, which can be detected by means of sensor arrays, for example, the camera chip. So could for example according to Figures 6 and 7, the light barriers 19, 21 and 31 by a band of light and arranged in the spacing layer 22 photoelectric sensors or light barriers 32 to 36 replaced by a second light band or a light surface, said light bands alternatively by means of switching the deactivation device is activated or can be disabled.