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Safety interlock switch adds escape release

A Rockwell Automation - Allen-Bradley Guardmaster product story

Edited by the Engineeringtalk editorial team Aug 10, 2005

Improved safety provision for machine operators is provided by Allen-Bradley Guardmaster's introduction of a new escape release facility for its TLS-GD2 safety interlock switch.

Improved safety provision for machine operators is provided by Allen-Bradley Guardmaster's introduction of a new escape release facility for its TLS-GD2 safety interlock switch.

The escape release complements the operation of the manual override on the TLS-GD2, providing an easily accessible means of escape for an operator trapped within a guarded area, in the event that a machine is accidentally switched on while its guard door is closed.

The new escape release facility is provided to allow intentional unlocking of the TLS-GD2 guard interlock switch from inside a hazardous enclosure, without the use of tools, as is the case with manual overrides.

In the event of an emergency condition, it is manually activated by a large pushbutton, triggering positively guided contacts that stop machine operation and unlock the actuator of the TLS-GD2 to allow operator escape from the hazardous area.

The machine then remains in this stopped condition even after the escape release pushbutton is released; until power is then restored and the actuator locked (unless, of course, it has already been removed from the switch).

Unlike some competing designs, the position of TLS-GD2 escape release means that it is freely accessible within a walk-in guarded area, and that guarding does not have to be specially designed to accommodate it.

In addition, the fact that the TLS-GD2 offers the facility for four possible actuator entry positions and three possible conduit entries means that it is easily integrated into most types of hinged, sliding and removable guarding systems.

Like the standard TLS-GD2, the escape release version offers the best price/performance ratio and integrates the most features in its class.

It is designed with a stainless steel actuator entry which protects the switch against poor guard alignment and wear; has onboard locked/unlocked status indication and optional manual key release functions; and provides the highest holding force in its class, at 2000N.

Compact and robust, the TLS-GD2 protects not only machine operators, but also machines and tooling from damage in production situations where machine overrun times mean that normal safety switches on their own may not be sufficient to provide adequate safety provision.

The TLS- GD2 locks shut a machine guard door until an electrical signal - from a PLC or Allen-Bradley Guardmaster CU3 timer, for example, allows release.

When securely closed, the locking mechanism has been designed to withstand forces in excess of 2000N.

Moreover, with its 100% solenoid rating, the TLS -GD2 will not burn out or reach excessive temperatures.

Also, unlike most other locking switches, the unique design of the TLS-GD2 means that the force exerted is not directly applied to the solenoid, thereby giving the switch extended life.

Also underlining its quality of construction, the TLS-GD2 solenoid lock incorporates monitoring, positive guided safety contacts (one safety and one auxiliary).

These break the safety circuit when the lock is energised (ie to release), and provide indication of the switch state.

The subsequent removal of the actuator operates two further positive operating safety contacts and an auxiliary or monitoring circuit.

This means that the TLS-GD2 can offer the OEM and end-user a total of five available output contacts to monitor guard position, lock engagement and solenoid condition in either dual or single channel safety control systems.

The TLS-GD2 escape release version is available in three switching capacities, 24, 110 and 230V, to satisfy most market requirements.

In applications that require additional security the safety switch can be used in conjunction with PLCs and Allen-Bradley Guardmaster CU1 timers, CU2 stop motion detectors or Minotaur monitoring relays.