Electrical safety circuit for machine - has safety switches to connect either of two safety circuits to supply voltage

摘要

The safety circuit (S) which controls the operation of a machine is connected across the supply line through the change-over switch (do) to the contacts (1,2) and through the change-over switch (d). These change-over switches are actuated either separately or by a common relay. When these change-over switches (d,do) are actuated, one switch (do) is connected to the supply voltage whilst the other switch (d) is connected to the safety circuit (S1). Thus is any fault in the safety circuit (S) causes the relays to operate and cuts out the active circuit (S), the safety circuit (S1) comes into operation so that the machine is still protected.