Discover the purpose and applications of safety light curtains, which help ensure user safety during routine operations.
What is a Safety Light Curtain?
Light curtains can automatically interrupt the operation of potentially dangerous devices or machinery if a human operator is present. These safeguards may also go by a variety of other names, including “light screens” and “optical guards.” Whatever their name, these devices can help ensure user safety during routine operations like maintenance, while also giving the operator greater freedom and flexibility in an industrial environment.
How Do Light Curtains Work?
The light curtain consists of two parts: a transmitter and a receiver.
- The transmitter contains multiple LEDs that send pulses of infrared light to the receiver. The pulses emit in sequence, such as from top to bottom, and each pulse releases at a specific frequency.
- The receiver pairs with the transmitter to “expect” these pulses in the right sequence and timing, thereby eliminating (or nearly eliminating) the possibility of interference from other light sources.
When an opaque object passes between the transmitter and receiver, that object interrupts the reception of pulses. This interruption triggers the connected device or machinery to stop.
Light curtains differ from other photoelectric sensors in that they have self-monitoring circuitry. In the event of a fault in their operation, this circuitry sends an automatic stop signal, ensuring that the connected device will not function unless an effective safeguard is present.
Light Curtain Applications: Point of Operation vs Perimeter Control
Manufacturers and industrial facilities employ light curtains as a safety mechanism in two general situations: point of operation and perimeter.
- Point of operation. For these guards, users install a light curtain at the site of material handling, such as under a hydraulic press, to ensure that no one can enter the danger zone while the machine is operating.
- Perimeter. In contrast, perimeter guards refer to delineating a whole working space or room, such as for a robotic arm. These guards can ensure that no person or object enters the boundary of the machine’s movement.
Light curtains offer advantages over other types of safeguards, such as physical barriers. It’s easier to access a machine guarded by a light curtain than one guarded by a physical barrier. A light curtain barrier makes it easier and more efficient to perform both routine maintenance and semi-automatic processes that require human intervention.
Safety Light Curtain Operation: Installation Considerations
It should go without saying that the operator must place the machine’s reactivation and reset switch outside the light curtain’s defined area to reactivate the machine safely. Additionally, you should only use a light curtain to control machines that are capable of stopping at any point in their operation cycle. If the controlled device – like a full revolution clutch press, for example – will still finish its cycle or stroke after the circuitry issues its stop signal, that machine is not a good candidate for a light curtain.
Operators can use light curtains to safeguard either a specific point of hazardous operation or the entire perimeter of the space defined by the movement of a machine. When compared to traditional safeguards like physical barriers, the automatic nature of light curtains makes it easier and more efficient to service machines or to perform semi-automatic operations.