Sensing apparatus for cyclically operated apparatus

摘要

A can lid forming apparatus includes means for attaching a can opening key. A proximity field sensor is mounted in a doming die of the apparatus and generates a pulse logic signal as a can lid with a staked key is formed by the doming tool. A timing disc rotates in synchronism with each cycle of the tool and generates a pair of logic signals. A key monitor circuit is connected to respond to the signals to establish a latch, check latch and reset latch sequence for each cycle of the tooling. If the latch is not set, an appropriate output signal is generated indicating a key is missing from the lid. If the latch is not reset after being set, indicating a build-up of aluminum fines or the like on the probe, an appropriate signal is generated by a preconditioned probe monitoring curcuit. The latter is connected to respond to the pulse logic signal and the reset signal to continuously check on the generation of the output pulse of the probe and produce a stop or alarm output if the logic pulse signal is not formed; indicating a sensor malfunction of the absence of the key.