Safety method and safety device for a machine, especially a bending press

A potentially dangerous machine is secured to protect against injuries and has first and second tool parts that define an opening gap between them. At least the first tool part is movable relative to the second tool part in a movement direction during an operating cycle for deforming a workpiece between them by reducing a size of the opening gap in the movement direction. The protected zone precedes the first tool part and extends over at least a portion of the opening gap in the direction of relative movement. The protected zone is monitored with an optoelectronic sensor, and a danger signal is generated in response to a breach of the protected zone. When the size of the opening gap in the movement direction becomes smaller than the protected zone, the size of the protected zone is correspondingly reduced until during subsequent closing movements of the first tool part substantially the entire opening gap is within the protected zone.