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

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

Such protection devices are known for example from DE 2750234 B1, DE 19717299 A1, WO 97/25568, the EP 0264349 B1, EP 0146460 A2 or DE 10232795 A1 and serve primarily the operator to protect and prevent, for example, the hand sandwiched between the two machine parts and tools or is injured. Of course, the light barrier arrangement also prevent by the moving first machine part unintentionally between him and the second machine part got damaged or objects be destroyed, with a self-destruction or damage is prevented. Without additional measures would at the end of the closing movement of the first machine part shortly before Reaching the workpiece to be machined at a stand, since the lowermost laser beam would be interrupted when the first machine part up to the safety distance to the workpiece has approached. In order to prevent this, in the known Guards the light barrier arrangement against End of the closing movement disabled. This can only therefore to be accepted, because the same dangerous of the Rapid speed to a safer creep speed is switched. This creep speed However leads disadvantageously to a reduction of the Working cycle and thus to slow down the operations.

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

This object is inventively achieved by a protective device solved with the features of claim 1.

By the switching means according to the invention can for each Of workpiece creep speed phase as short as held possible. For flat workpieces are only Photocells activated in the distance level, the safety distance a have for the first machine part. This Safety distance corresponds to the braking power of the first machine part or is slightly larger. The at least one second light barrier which in the spacer layer the first machine part is upstream, prevents an inter- the machine parts into skidding hand is injured by this second light barrier through the inside hand slipping is already broken before a break in the first Photocell is carried out by a fingertip. This at least a second light barrier in the distance level must, however, necessarily in the machining of box-shaped workpieces be disabled, otherwise can not be processed would. Simultaneously with this deactivation, however, the at least enabled a third light barrier, which in the arranged work trajectory of the first machine part is, therefore, with a designed as a punch first machine part below the level spacing. 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. Automatic switching Although done in the creep speed here earlier, then, when the third light barrier reaches the workpiece, However, by switching the deactivation achieved this third light barrier in flat workpieces are, because at least then minimizes the creep phase becomes.

are of the measures listed in the dependent claims Advantageous developments and improvements of the claim 1 specified protective device possible.

By disabling device for disabling Plurality of third light barriers one by one and finally the first light barrier in each case before an interruption by the workpiece to be machined or by the second machine part is reached, a further margin improvement. The gradual deactivation may even a einrutschender while the reduced closing speed Finger or hand einrutschende be recognized.

To a permanent deactivation of the photoelectric after reaching of the workpiece or the second machine part automatically To prevent automatic are advantageously Switch-on means intended to reactivate the light barriers, in particular through the opening movement of the first are triggered 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 and the third light barrier and the third Light barriers with each other is expediently less than the diameter of the smallest between the machine parts selected movable body part of an operator, Thus, in particular smaller than the diameter of a small Fingers. The safety distance is therefore, for example, between 6 and 14 mm, respectively.

To deactivate the at least one light barrier arrangement is in an advantageous embodiment of a cam control with limit switches with the deactivation device connected. Alternatively, to disable and be provided a measuring system. It is preferably the Position measuring system associated with a learning means by which the Deactivation positions by interrupting at least the lowermost photocell storable at a Lernhub or are adjustable. Finally, there is an alternative way for deactivating also to provide a timing control means to connect to the deactivation device.

In an advantageous embodiment of the invention, the Beams of the second and / or third light barriers each a light band or a light surface form, the or each represented by a sensor array, in particular a camera chip can be detected. 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 in the following description, explained in more detail. Show it:<dl tsize="7"><dt>figure 1</dt><dd>a longitudinal side view of the invention with the Protective device provided press brake,</dd><dt>figure 2</dt><dd>a cross-side view of the illustrated in Figure 1 Press brake in a simplified representation with deactivated third light barrier and between the Tools eintauchendem finger,</dd><dt>figure 3</dt><dd>the same representation in completely submerged Finger,</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 Dipped fingers and</dd><dt>figure 6</dt><dd>an arrangement with a plurality of second and third light barriers, and </dd><dt>figure 7</dt><dd>an alternative arrangement with a plurality of second and third light barrier.</dd></dl>

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

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

In each case at the mutually opposite narrow sides of the Upper tool 10 are guides 15, 16 attached to the upper tool 10, for example screwed. The attachment can of course are in principle also indirectly, the is, which are then attached to a holder guides 15, 16, the not shown through a holder for the Upper tool 10 is connected thereto.

In the guides 15, 16 are brackets 17, 18 for three Photocells 19 - 21 in a vertical adjustment movement movable, whose direction is shown by the double arrows B and which corresponds to the working direction of movement A. Each of the Photocells 19 - 21 is in a conventional manner from a laser transmitter and a laser receiver, wherein the laser transmitter on the one support 17 and the laser receiver are arranged on the other holder 18th It is in principle also possible to reduce the number of channels in that the transmitted beam of the transmitter by a beam splitter is divided into a plurality of transmitting light beams. furthermore It is also possible to expand the transmission beam parallel. Other options, the number of stations and the number of save receiver, are indicated at the outset DE 19717299 A1. Instead of laser light beams can of course also other known types of Light beams are used.

The first photoelectric sensor 19 and the second photocell 20 are in a distance plane perpendicular to the direction of working movement A arranged that to a safe distance from the upper tool 10 comprises at least the braking distance of the top tool 10 corresponds. The first light barrier 19 below the upper die 10 in its working movement plane or sheet or slightly staggered at this, while the second light barrier 20 toward the operator to about 30 to 50 mm is set to front. The third photocell 21 is below the first photocell 19 is also substantially in the labor movement plane or web of the upper tool 10. and is thus further from the upper tool 10 located opposite the first light barrier 19. The distance between the first photocell 19 and the third Light barrier 21 essentially corresponds to the difference between the diameter of a human fingertip and the diameter of the part of the finger that is after the stop are the closing movement in the working plane can.

The protective effect of the protective device is described in that the closing movement between the upper tool 10 and Lower tool 11 is stopped abruptly when one of the laser beams the light barrier 19 - 21 is interrupted when Thus, an object comes into the movement path. Since such Press brakes or similar machines usually hand operated are, there is above all the risk that the hand or the arm of an operator in the work trajectory gets what by a pinching or severing the closing movement could result. The safety distance should be between the upper tool 10 and the distance plane 22 therefore be such that, for example, no finger interposed can be. On the other hand is te this safeguard be so great, that during an interruption a laser beam, the closing movement currently in time can be slowed or stopped the obstacle. The safety distance Therefore, for example, 6-14 mm set.

The adjustment of the light barrier arrangements or brackets 17, 18 at the upper tool by displacement in the guides 15, 16, for example, according to the initially indicated DE 19717299 A1 done. There may also be automatically positioning device according to DE 10123562 A1 provided be. moves the upper tool 10 against the lower tool 11, so at the end of the closing movement the photocells be interrupted by the workpiece 14, which leads to would result in an immediate movement stop, so that the desired Operation could not be performed. With The aid of a deactivation device, this is prevented, for example in one of the holders 17, 18 or can be accommodated 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 would take place 11th Simultaneously, a switching occurs from the previous operating speed in a Slow speed with significantly reduced rate of Safety. In the backward movement of the upper tool then a re-reactivation of photocells, which in principle also in the upper end position before could be the next step. The deactivation device can in a conventional manner by a position measuring system, a cam control with limit switches or by a time-synchronous control carried out.

In the figures 2 and 3, the case of processing a flat blank 14, shown, for example, a sheet. The activation device has a switching means for alternatively deactivating the second photoelectric barrier 20 and the third light barrier 21. When bending a flat workpiece according to Figures 2 and 3, the third photocell 21 deactivated, which by a slash Representation is symbolized. Active are therefore only the photoelectric sensors 19 and 20. If no irregular Interruption of the light barriers 19, 20 is carried out is, the switchover to the creep speed only takes place when the light barrier 19, 20, that is, the distance layer 22, the Workpiece 14 reached. Only during this short distance, corresponding to at least the braking distance of the upper tool 10, it must be moved at creep speed. A finger can in this small distance is no longer between Upper tool 10 and workpiece 14 are pushed.

The second photocell 20 serves to increase the safety. Without this second light barrier 20 could be the case, that by a quick hand motion just before the Transition to creep speed work movement through Interruption of the first photocell 19 is stopped, but if could by a quick flick of the hand during the braking phase are still been pushed to the Region of their greater height would still squeezed. This prevents the second light barrier 20 of Figure 2 by interruption due to the rapidly inserted Hand the braking operation already initiates, before the first light barrier 19 is interrupted. Even in far inserted Finger according to Figure 3 is thereby the upper tool 10 still in time to a standstill.

If a box-shaped workpiece 25 according to Figures 4 and to 5 is bent, cut or punched or correspondingly arranged workpiece stops or brackets , the upstream light barrier 20 processing to make impossible. In this case, the switching means the deactivation apparatus is actuated with the effect that disabled after switching the light barrier 20 and for the light barrier 21 is activated. The photocell 21 now ensures that the protective effect due the elimination of the light barrier 20 is not reduced. The now precedes down photocell 21 detects as first fingertip and passes by the interruption A braking operation of the upper tool 10th Figure 5 shows that even with quickly inserted his fingers no longer a threat is that this is clamped or injured. there but must be taken into account that a longer Way back down at a reduced speed in creep mode must be because these slow phase already achieve the workpiece 25 using the light barrier 21st

Another security improvement can also be achieved be that only deactivates the light barrier 21 is just before it reaches the workpiece 25th The Photocell 19 remains active, so that even when reduced closing speed a einrutschender finger nor can be detected.

The embodiment illustrated in Figure 6 shows that the number of light barriers exacerbated in the distance plane 22 can be and through additional light barriers 26, 27 in front and behind by further light barriers 28 to 30 the working plane. This causes the plurality of light barriers, that no longer pass grasped therebetween can, so that the security is increased. Of course several such light barriers, for example only be before machining plane. The alternative Activation of photocell relates course also this embodiment. So are there alternative the light barriers 20, 26 to 30 on the one hand and the light barriers 21 and 31 are alternatively activated depending on 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 labor movement plane or sheet may be supplemented, In the embodiment, a light barrier 31. As illustrated in Figures 4 and 5, the light barriers can 31, 21 respectively off in succession, always short before one of these light barriers reaches the workpiece.

In the further embodiment shown in Figure 7 are second photoelectric sensors 32 to 36 is no longer in a common Distance plane 22 with the first light barrier 19, but in an inclined curved arrangement of upper tool 10 is arranged such that these photocells 32 to 36 form a barrier that a passage to put your hand to the workspace below the upper die 10 without interruption one makes these photoelectric impossible or prevented. Here, the arrangement and number of these second Photocells 32 to 36 also vary. Arrangements are in an oblique line at an angle or in other Formations possible to form the barrier described. By switching each be either the second light barriers 32 to 36 on the one hand or the third Light barriers 21, 31 zusammem with the first light barrier 19 On the other hand, alternatively activated.

Alternatively or additionally, may also second photocells on the opposite side of the upper tool be 10 arranged accordingly. The to the other embodiments described embodiments and configurations of course, also in this embodiment, realizable.

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