OPTICAL SAFETY DEVICE FOR MOUNTING ON A MOVING MEMBER

摘要

Safety apparatus and method for protecting an object entering into the path of a moving blade in a press brake (10). The apparatus includes laser emitters (22) and receivers (24) for mouting in fixed relationship to the leading edge (36) of the blade (18) to provide a plurality of light beams (26) in advance of the blade (18). A controller (51) including halting means (57) for halting advancing movement of the blade in response to certain contingencies is provided. These contingencies include those involving interruption or obstruction of the light beams (26) and those which are indicative of a fault with the press or the safety apparatus itself. Accordingly the controller (51) also includes laser control and processing means (54), blade movement control means (56) and blade position processing means (58) which operate in conjunction with the halting means (57) to enable overriding control of the movement of the blade (18). The laser control and processing means further include pulsing means (55) to pulse the emitted light beams (26) in a unique manner so that each beam (26) can be differentiated from the others and also from ambient light sources. Vibration sensing means is also provided to enable discrimination between normal and abnormal vibration of the laser emitters (22) and receivers (24). The method involves use of mute point set a prescribed height above the material to be pressed whereby operation of the halting means (57) is associated with the position of the blade (18) relative to the mute point, whereby sensing of the laser beams for interruption or obstruction is muted after the blade (18) reaches the mute point. Different arrangements for setting the mute point are also described.