SICK has released the T 4000 multi electronic safety interlock, offering switching distances of up to 15mm. Up to four RFID sensors can be connected to a single evaluation unit and it offers high immunity to impacts and vibrations.
Applications include the protection of access doors to robot cells or in protective barriers along production and assembly lines. Separate door signalling outputs are provided, with which each connected sensor can be individually assigned to the particular door and evaluated.
The system has EN 954-1 Category 4 certification. Its reading head is mounted on the fixed part of a guard and connected to the evaluation unit by a cable, available in two versions for the simultaneous connection of two or four sensors. The actuator - a transponder - is mounted on the access door in such a way that it is located at a safe switching distance of 15mm from the reading head during machine operation. The energy required for transmission of the transponder code is transferred from the reading head to the actuator by induction.
The entire monitoring process takes place via radio frequency identification (RFID). While the machine is operating the bit pattern of the code is continuously compared with the stored code. If the codes match, the safe relay outputs and the separate semiconductor outputs for each door are released and the robot can start. Opening of the protective equipment is detected by interruption of the data communication and the hazardous movement of the machine is immediately stopped. The same occurs if the power supply is interrupted or if the actuator is damaged. In such cases there is no need to replace the entire system. Only the actuator need be replaced, because the evaluation device can learn any number of codes. As only the last code that was learned is valid, and multiple teach-in of the same actuator to the same evaluation device is impossible, the system is highly tamper-proof.
The sensor's large response range offsets tolerances between the door and the protective barrier, reliably preventing false alarms. The lock's immunity to impacts and vibrations is particularly important when safeguarding elevators, palletisers and depalletisers, or machines for securing loads. Movable covers on machines can also be monitored with the electronic safety system to prevent unauthorised reaching into a running machine.