Electronic controller for cyclically operating machinery

Claim 1

An electronic controller for a cyclically operating mechanical device comprising: two safety channels of different circuit construction, simultaneously having identical control functions and acting upon respectively associated operating members, of which a first of said safety channels is constructed with hard-wired switching logic and a second of such safety channels with microcomputer circuitry, including at least a microprocessor having a control program and a check program, said check program effecting a self-check of all components of said second safety channel, said channels having respective output signals; a common safety stage connected to both channels, which upon the occurrence of unequal output signals of the two safety channels places the device in a safe state; a self-check facility, different from said self-check of said second channel for effecting self-check of the first safety channel, the self-checks of said channels being effected periodically within the cycle periods; and amplifiers connected to the outputs of the safety channels and having output signals applied to a comparator for monitoring equality and synchronism of said two safety channels, said comparator having an output signal, the output signal of the comparator and output signals of the self-check facilities acting upon said common safety stage.