Method and device for protecting a sheet metal working machine by means of a laser beam.

The present invention relates to a method and a protection device by means of a laser beam, to a working machine of a sheet such as bending press, shearing, bending machine or other similar machine.

Are already known machines of the aforementioned type protection devices which comprise a generator set of at least one horizontal laser beam, said assembly comprising, on one side of the machine, an emitter of the laser beam and, on the other side of the machine, a receiver of this laser beam, the emitter and the receiver being located in the same horizontal plane. The thus produced laser beam is located at a height relative to a reference plane, which depends on the height of docking is to dire.de the height of the upper surface of the sheet relative to this reference plane. In the case of a press brake the safety in which the laser beam is located height depends on the height of the folding Vee used and the thickness of the sheet to be bent. This clearance height is equal to the sum of the height of the folding V-shaped and the thickness of the sheet increased by a distance which is less than the thickness of a finger and which is chosen less than 8 mm.

It is therefore understandable that it is necessary to constantly adjust the clearance height which is the laser beam, the thickness of processed sheets, pitch bending Vés etc.

The present invention aims to provide a method and a protection device that will eliminate any interpretation of the part of the user of the machine, as regards the correct positioning of the laser beam, and to automatically ensure the position thereof from the only information necessary for the production, that is to say the height berthing at which the movable element of the machine just meet the sheet metal shearing, roll or to fold.

For this purpose this protection method by means of a laser beam, to a working machine of a sheet, such as a bending press, a shearing machine, a bending machine or other similar machine, comprising a movable tool verti cally toward the sheet supported on a support, is characterized by determining the safety height should go where the horizontal laser beam relative to a horizontal plane of reference, to ensure user protection the machine, by adding to the height of the attachment surface, that is to say the height of the upper surface of the sheet relative to the reference plane, a safety distance less than 8 mm, is moved vertically the emitter of the laser beam, is continuously measured the effective height of the laser beam emitted from the reference plane, the effective height of the laser beam is compared with the predetermined safety height and stops the vertical movement of the emitter of the laser beam when the height of the beam becomes equal to the clearance height.

The invention also relates to a -protection device, by means of a laser beam, to a working machine of a sheet, comprising a movable tool vertically in the direction of the support sheet on a support, a set horizontal laser beam generator having on one side of the machine, an emitter and, on the other side of the machine, a receiver of the laser beam, so as to automatically control the stopping of the machine when the laser beam is intercepted, characterized in that it comprises means for vertically moving the transmitter and receiver of the laser beam, means for measuring the effective height of the emitter of the laser beam relative to a reference plane, means for calculating a safe height should go where the laser beam by adding to the height of the docking surface, that is to say the height of the upper surface of the sheet relative to the reference plane, a safe distance less than 8 mm, means for comparing the effective height of the issuer of the security with the calculated height of the laser beam and to stop the vertical motion of the transmitter when the height of the laser beam becomes equal to the precalculated safety height.

The method and device according to the invention have the advantage that the user of the machine is only to be programmed, for example by means of keyboards or from a digital program, the two variable values ​​that constitute the thickness of the sheet metal to be worked and, in the case of press brakes, height folding Vee. This information having been introduced in the protective device according to the invention, it automatically causes the vertical displacement of the emitter of the laser beam and, correspondingly, that of the receiver, so that the protection of the laser beam is placed exactly at the height desired, and regardless of the thickness of the sheet metal working.

hereinafter described, by way of nonlimiting example, an embodiment of the present invention, with reference to the accompanying drawings wherein:<ul><li>The single figure is a block diagram of a protection device according to the invention applied to a press brake.</li></ul>

The protective device shown in the drawing is associated to a press brake which is schematically and partially shown having a frame 1 on the upper part of which is a matrix, for example, by a folding Ve 2 and above which is movably mounted a vertically cross-sectional tool corresponding to that of the matrix, that is to say a folding blade 3, in the particular case. This press brake is designed to fold a sheet Vee 4 variable thickness e. The protection of this press brake is ensured by means of a horizontal laser beam 5 which extends in the vertical plane of the folding blade 3. This laser beam is produced by a transmitter 6, on one side of the machine in this case the right side, and it is sensed by a receiver 7 located on the opposite side that is to say the left side, the transmitter 6 and receiver 7 being coaxial.

For the protection of such a press brake, the laser beam 5 is located above the plate 4 at a safe distance away from the upper surface 4a of the sheet surface which constitutes the attachment surface . This distance d is chosen to be less than the thickness of a finger and less than 8 mm practice.

According to the invention the transmitter 6 and the receiver 7 of the laser beam 5 are mounted to move vertically under the control of the respective motors 8 and 9. These motors can be made by precision actuators of electrical type, which are integral with the frame 1 of the machine.

The protective device further comprises an adder circuit 11 which receives at its input representing the thickness e signals of the sheet 4 to be folded, the height h of bending Vee 2, and a constant value which corresponds to the safety distance d. This adder 11 is connected at its output to a first input of a comparator 12 having two inputs. The second input of the comparator 12 is connected to a position sensor 13 which measures at all times the effective height H of the emitter 6 with respect to a horizontal reference plane P which may be that one of the press table. The comparator 12 is connected, è release, two devices 14, 15 respectively controlling the supply of electric actuators 8, 9.

The operation of the device according to the invention is as follows:<ul><li>The user of the press brake previously entered values ​​corresponding to the thickness of the sheet to fold and the height h of folding Vee. This introduction can be performed using two keyboards 16, 17 or even from a digital program. E and h values ​​are added in the adder circuit 11, to the safety distance d and the adder circuit 11, provides at its output a signal corresponding to the sum thus obtained. Moreover, the position sensor 13 provides the second input of the comparator 12 a signal H corresponding to the actual height of the laser emitter 6. Since both signals have different values, the comparator 12 emits at its output a signal transmitted to feeder 14 which raises or lowers, fast speed, the transmitter 6, depending on the position he is occupying. The comparator 12 also supplies a signal, with a slight difference, to the feed device 15 associated with the electric actuator 9 controlling the movement of the receiver 7. The latter is then moved vertically in the same direction as the transmitter 6 to a speed substantially similar but not necessarily identical to that of the transmitter.</li></ul>

When the transmitter is 6 reach the position where the actual H 5 laser beam height is equal to the pre-calculated safe height d + e + h, the comparator 12, noting that equality, acts on the device 14 to stop transmitter 6. from that moment the laser beam is emitted to be desired safety H height. The receiver 7 which moves slower than the transmitter 6 continues its movement until it is aligned with the transmitter 6. At this time the receiver photodiode 7 detects the laser beam 5 that has been stabilized and it acts via a feedback circuit 18, the power device 15, for stopping the electric actuator 9 associated with the receiver 7 so that the receiver 7 is stopped in the axis of the transmitter 6 at the desired height H security.

Although in the accompanying drawings the transmitter 6 and receiver 7 have been shown as being aligned coa- xialement, it is preferable in practice to arrange them vertically in mobile enclosures and to provide means, such as mirrors or fibers optical horizontally for deflecting the laser faiceau so that it becomes parallel to the folding Vee 2. such an arrangement can accommodate these sets in vertically arranged on both volumes either side of the machine. '

To ensure the inhibition of the laser beam 5 at the end of downward travel of the folding blade 3, that is to say when the latter intercepts the beam there is provided a limit relay 19 integral with the whole vertically mobile transmitter comprising the laser 6. This limit relay 19 therefore moves vertically with the transmitter 6 and is actuated, the end of the downward stroke of the folding plate 3 by a stop or a ramp 21 integral this blade. This limit relay 19 is connected so as to allow the continuation of the downward movement of the blade 3, once the latter has intercepted the laser beam 5.

The device according to the invention may also comprise means controlling the inhibition, which is required to cross the beam 5, by substituting the normally energy transmitted by the laser beam striking a stream, is performed in a time very short, depending on the approach speed of the folding blade 3. This can be materialized by a delay of the order of 0 to 0.1 s. After that, fault blanking the beam conc.erné unsafe recover. This allows to prohibit any error or fraud to neutralize the laser beam during the descent of the press.

In case the mobile upper tool have variable heights, it is possible to automatically inhibit the adequate range laser beam, considering the limits tolerated by the timer, by replacing the fixed stop mounted on the support of the mobile tool or by a height-adjustable abutment with quick release lock or by a cell to electronic reflex system very narrow beam or possibly beam derived from the laser transmitter which detect the profile tool with a reflective coating such as that known under the name "SCOTCHLIGHT" .If possitive response the corresponding receiving cell give an order of inhibition.

The method and the device according to the invention also apply in the case of using a second protection beam passing through the folding itself Vee.