Patent ID: 7208899
Filing Date: 2007-04-24
Classification: G05B

Abstract:
1. A device for emergency-stopping a servomotor by shutting off a power supply to the servomotor, using one or more signal systems for generating and transmitting emergency-stop signals, comprising: an emergency-stop switch and first and second emergency-stop signal circuits provided in each of the signal systems, said emergency-stop switch having two contacts included in said first and second emergency-stop signal circuits, respectively, to be manually opened and closed simultaneously; a processor for performing monitoring of open/closed states of said first and second emergency-stop signal circuits to issue a shut-off command to shut off the power supply to the servomotor when at least one of said first and second emergency-stop signal circuits indicates an open state; and first and second switching means provided in said first and second emergency-stop signal circuits, respectively, for opening/closing first and second common lines used in the signal systems for connection with a power source of the signal circuits, according to commands from said processor, wherein said processor performs checking of the first emergency-stop signal circuit by issuing an opening command to said first switching means when said first and second emergency-stop signal circuits are closed and thus electric power is supplied to the servomotor so as to confirm that said first emergency-stop signal circuit indicates an open state without issuing the shut-off command, and issues a closing command to said first switching means after the confirmation, while continuing monitoring of the open/closed state of the second emergency-stop signal circuit, and performs checking of the second emergency-stop signal circuit by issuing an opening command to said second switching means when said first and second emergency-stop signal circuits are closed and thus the electric power is supplied to the servomotor so as to confirm that said second emergency-stop signal circuit indicates an open state without issuing the shut-off command, and issues a closing command to said second switching means after the confirmation, while continuing monitoring of the open/closed state of the first emergency-stop signal circuit, the checking of said first and second emergency-stop signal circuits being performed alternatively and periodically.