Patent ID: 8693159

Claim:
A safety system for use in controlling an industrial device, comprising: a plurality of safety switches, each safety switch including at least two contacts wherein the contacts of each safety switch are activated in tandem responsive to a single trigger and wherein a first contact of each of the safety switches is connected in series with a control voltage to define a first safety signal; a safety relay having a plurality of inputs and a plurality of outputs, wherein a first input of the safety relay is configured to receive the first safety signal, wherein the first safety signal is in a first state when the first contact of each of the safety switches is closed and wherein the safety signal is in a second state when the first contact of at least one of the safety switches is open, a second input of the safety relay is configured to receive a second safety signal, wherein the second safety signal is in a first state when a second contact of each of the safety switches is closed and wherein the safety signal is in a second state when the second contact of at least one of the safety switches is open, a third input of the safety relay is connected to a command signal for the industrial device, a first output of the safety relay is configured to generate a first signal corresponding to the state of the first safety signal, and a second output of the safety relay is configured to generate a second signal corresponding to the state of the second safety signal; and a controller having: a first input configured to receive the first signal corresponding to the state of the first safety; a second input configured to receive the second signal corresponding to the state of the second safety signal; a plurality of additional inputs wherein each additional input corresponds to one of the plurality of safety switches and is configured to receive an input signal from one of the contacts of the corresponding safety switch; a processor configured to: generate an interlock when the first and second inputs indicate the state of the first safety seal is different than the state of the second safety signal, identify which of the plurality of safety switches triggered the interlock, and reset the interlock when the identified safety switch is triggered and the first and the second inputs indicate the state of the first safety signal is the same as the state of the second safety signal; and an output configured to generate a signal corresponding to the interlock; and a switch connected in series with the command signal for the industrial device, wherein the switch is selectively opened and closed as a function of the signal corresponding to the interlock from the output of the controller.