Safety device of press brake and controlling method of press brake

A safety device of a press brake which includes an upper table for holding a punch, a lower table for holding a die, and an actuator which lowers and raises the upper table, the safety device comprising:

• a projector which is mounted on the upper table, and configured to emit laser light in such a way that the laser light passes through between the punch and the die;
• an optical receiver which is mounted on the upper table, comprising a photodetector which detects the laser light passing through between the punch and the die, and configured to determine whether the optical receiver is in a light receiving state of receiving the laser light, or in a light obstructing state of not receiving the laser light;
• and
• a safety controller configured, when the actuator lowers the upper table for performing a bending processing by sandwiching a material arranged on the die between the punch and the die, to control lowering of the upper table to stop, when it is determined that the optical receiver is in the light obstructing state in a period in which a condition is satisfied that a first distance between a tip on the die side of the punch and an upper end of the punch side of the material is equal to or greater than a second distance between the tip of the punch and the photodetector, and to control the lowering to continue without stopping the lowering of the upper table even when it is determined that the optical receiver is in the light obstructing state in a period in which a condition is satisfied that the first distance is less than the second distance, wherein
• the safety controller comprises:
• a comparator configured to compare the first distance with the second distance so as to output a first output value when the first distance is equal to or greater than the second distance, and to output a second output value when the first distance is less than the second distance;
• and
• an AND circuit which receives the first or second output value from the comparator, and a light obstructing output value or a non-light obstructing output value from the optical receiver, and configured to output a lowering stop signal of the upper table, only when the AND circuit receives the first output value from the comparator and the light obstructing output value from the optical receiver.