Interlock Switches with Guard Locking

Choosing Interlock Switches with Guard Locking components

Guard-locking interlocks have two safety functions in one device: position monitoring (is the guard closed?) and locking (is the guard mechanically held closed?). Both must work correctly, and the locking mechanism's behavior on power loss (de-energized to lock vs. de-energized to unlock) determines fail-safe behavior under power failure.

Specs to confirm before ordering:

Exact OEM part number with all option codes
Locking principle: power-to-unlock (locked when power is removed — fail-safe locked) or power-to-lock (locked only when power is applied — fail-safe unlocked)
Holding force — typically 1000 N to 8000 N depending on guard design and hazard
Solenoid voltage: 24 VDC most common, sometimes AC variants
Coding level: uncoded, low-coded, high-coded RFID
Number of monitoring and lock contacts
Manual release options: emergency release (inside the cell), bypass key, or auxiliary unlock
Mounting style and actuator approach direction
IP rating — IP65 standard, IP67/IP69K for washdown
Cable or M12 connector style

Common gotchas: "power-to-unlock" devices are the safer choice for most machine guarding — on power loss the guard remains locked, preventing access to a coasting machine. "Power-to-lock" devices fail safer for fire-egress scenarios but are less common in machinery. Holding force ratings assume properly aligned actuators and an unsprung guard; springs in the guard add to the force the lock has to resist. Emergency unlock features must be accessible from the hazardous side — a person trapped inside must be able to open the guard. The lock contact is separate from the guard-position contact; the safety controller must evaluate both.

Typical applications: press brake and stamping press access doors, large-machine perimeter gates where machinery coasts after stop command, oven and cure-chamber doors with thermal hazard, large robot cell entry gates, and ride-control access doors at theme parks and industrial test cells. On legacy installations, in-kind replacement preserves the locking behavior, holding force, and validated safety logic.

For obsolete guard-locking interlocks, send the OEM part number for a sourcing quote.

Power-to-unlock vs. power-to-lock — which do I need?

Power-to-unlock (locked on power loss) is the typical choice for machine guarding because the guard stays locked while a coasting machine decelerates. Power-to-lock is used in egress scenarios where doors must release on power loss. Match the original — switching the principle changes the fail-safe behavior.

Do you stock obsolete guard-locking interlocks?

Yes. Discontinued Schmersal AZM170/AZM190, retired Euchner CES-A-LNA, end-of-life Allen-Bradley TLS3 are sourced through our supplier network.

What is the holding force I need?

Per ISO 14119, holding force is sized to the foreseeable force a person could apply to open the guard. Typical machine guards specify 1300 N, 2000 N, or higher. Match the original specification rather than guessing.

Does the device include an emergency release?

Most current guard-locking interlocks offer optional emergency release from inside the cell — important for personnel trapped inside. The option is part-number-coded; we will state which variants include it.

Can I substitute a higher-coded version?

Substituting a higher-coded (more defeat-resistant) version usually preserves or improves the safety case, but the actuator pairing must match. Test fit and update the safety documentation.

What is the warranty?

12-month functional warranty on the switch and solenoid. Safety-function performance is the integrator's responsibility.

Interlock Switches with Guard Locking

Pilz 512110 Safety Interlock Switch

Pilz 540010 Safety Sensor

Pilz 540050 Coded Magnetic Safety Switch

Pilz 570270 Safety Sensor

Pilz 570271 Safety Sensor

Pilz 570280 Safety Sensor

Pilz 570281 Safety Sensor

Pilz 570400 Safety Sensor

Pilz 570460 Safety Sensor

Pilz 570493 Safety Sensor

Pilz 570500 Safety Interlock Switch

Pilz 570501 Safety Interlock Switch

Pilz 570502 Safety Interlock Switch

Pilz 570510 Safety Interlock Switch

Pilz 570511 Safety Interlock Switch

Pilz 570520 Safety Interlock Switch

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