Locking switches are designed to prevent accidental or deliberate access while the machine is in motion. The mechanical locking feature is ideal for machines that have to finish a sequence, a program, or coast to a stop before the interlocked guard can be opened. The switches allow the guard to be mounted closer to the hazard than non-locking switches.
The operating principle of these switches is simple. When the actuator enters the switch, it engages with and operates a tamper-resistant locking mechanism, closing the contacts. This locks the actuator in and holds the guard closed. When the contacts are closed and the mechanism is locked in, the machine is allowed to start.
To open the guard, a separate signal is required to energize the solenoid which releases the locking mechanism after the machine has stopped or the cycle has finished. A timer or stopped-motion detector can be used for this signal. The timer can be used on machines with a consistent coast down time. The stopped-motion detector is available for machines that have a variable or inconsistent coast down time. If power is lost, a supervised override mechanical release that is built into the switch can be used.