A-B 440G-T27121 Safety Interlock Switch

A-B 440G-T27121 Safety Interlock Switch

 

 

The Allen-Bradley 440G-T27121 is a Guardmaster TLS-GD2 safety interlock (guard locking) switch, used to lock and monitor machine safety doors in industrial automation systems.

Product Information

• Brand: Allen-Bradley (Rockwell Automation)
• Series: Guardmaster TLS-GD2 / 440G-T series
• Part Number: 440G-T27121
• Type: Solenoid Safety Interlock / Guard Locking Switch
• Function: Door locking + safety circuit monitoring

Key Electrical Data

• Supply voltage: 24V AC/DC
• Contacts:
  • 2 × NC safety contacts
  • 1 × NO auxiliary contact
  • Solenoid control contacts included
• Actuation: Tongue (keyed actuator, not included)
• Lock type: Power-to-unlock (typical TLS-GD2 configuration)

Working Principle

This device is used on protective doors or guards:

• When machine is running → door is locked
• PLC/safety system keeps solenoid energized
• When safe condition is reached → power is applied/removed depending logic → lock releases
• Door status is monitored via safety contacts

It ensures operators cannot open the guard while machinery is running.

Main Functions

• Physical locking of safety doors
• Safety circuit feedback (door open/closed status)
• Machine stop interlock protection
• Integration with safety PLC or safety relay systems

Typical Applications

• CNC machine safety doors
• Robotic work cells
• Packaging machines
• Press machines
• Conveyor safety guarding
• Automated production lines

Key Features

• High locking force (industrial safety-grade design)
• IP67 protection for harsh environments
• Multiple safety contacts for redundant monitoring
• Designed for ISO/IEC safety standards (machine guarding systems)
• Compatible with PLC safety circuits

Precautions

• Actuator (tongue key) is usually sold separately
• Must be correctly aligned with door mechanism
• Requires proper safety circuit design (not direct load switching)
• Not suitable as a normal electrical switch (it is a safety device)
• Wiring must follow safety category requirements (ISO 13849 / IEC 62061 systems)