Reset and Bypassing Safety Light Beams

Three Different Reset Possibilities

Supervised Manual Reset (Figure 1)

When the Spot light beam is broken Vital gives stop signals to dangerous machines inside the guarded area and the reset indication lamp is on. A new start of the machine requires a reset of the light beam. The reset button must be placed so that it cannot be reached from inside the guarded area and so that it has to be activated from outside the machine. When the reset button has been activated, i.e. the reset inputs have been both closed and opened, the outputs from the Vital are activated, the reset indication lamp is off and the machine can be started. High demands are placed on the reset function, a fault must not lead to the ready signal being given when someone has interrupted the light beam. (See connection example HD3800A)

Figure 1 - Reset push button with lamp indication.

Supervised Time Resetting (Figure 2)

To reset the light beam, push button 1 must first be pressed and then push button 2 (within the predetermined preset time). This prevents unintentional resetting when someone is within the hazardous area. This is especially important when the area which is being protected by the light beam is not clearly visible from outside.

When time resetting is performed the safety timer relay JSHT1 A/B is used together with the Vital. This allows pre-reset times (in steps from 5 to 40 seconds) to be set. (See connection example HE3811A)

Figure 2 - Both buttons 1 and 2 need to be pressed (in sequence) within the pre-reset time to reset the Spot light beam.

Automatic Reset (Figure 3)

Automatic reset is utilized for example when a light beam is used to monitor an area. In this case when the light beam is interrupted this indicates that the robot is operating in the area allowing it to be stopped if a person enters into the same area. When the light beam is clear, the Vital is reset automatically.

Figure 3 - Unbroken light beam b indicates that the industrial robot is outside area B. Area B can now be entered without stopping the robot.

Bypassing (Figure 4)

For the transport of materials, the light beams, grids or curtains can be bypassed just before they are interrupted. The bypassing is achieved by sensors which detect the auto carrier and give signals direct or via a safety relay to the Vital.

In the connection examples you can find a number of different solutions. (See connection example HE3824C-E)

Figure 4 - Automatic bypassing when auto carrier passes.