Safety Light Curtains
Mostly found in factories, plants, warehouses and manufacturing facilities, safety light curtains form invisible
safety barriers or perimeters around automated robotic machinery, compactors, feeders and access points for automated machine assemblies that could injure or kill workers. They are composed of a receiver and transmitter, both of which are long, identical bars that emit LED lights. In order to work correctly, they must be lined up perfectly to transmit the light beams from one to another. They are mounted on brackets, rails or the floor. Light curtains are usually invisible, although sometimes they emit a series of red beams. Because they do not physically block the object they are protecting, light curtains are much like
brake monitors, which are also invisible
machine guards that work in vehicle or machine breaking systems. Often, light curtains work in conjunction with fencing or other barriers to increase safety even more. If an obstruction or penetration occurs, a stop signal is instantly and automatically sent to the machine's system. This shuts down the machinery altogether. All light curtains must be
OSHA approved and go though routine maintenance to ensure they are working properly.
All safety light curtains are divided into three types: type two, three or four. These designations are decided based on how dangerous the machinery is, how often workers come close to it and the severity of the potential damage if the light curtain is breached. Type two is for the lowest risk hazard and only self-checks when it is turned on or reset. Type three is used in higher risk situations, and requires that more than a single part must fail before it loses functionality. Type four curtains continuously check themselves and are reserved for only the most hazardous of applications where workers are frequently exposed and interact with the machinery. Light curtains can be many meters wide and are able to dart around corners with the use of mirrors. All safety light curtains have specific options and limitations that must be addressed when determining which is best for an application. Spanning distance is how far the transmitter and receiver may separate and still transmit light. They have different resolutions, which is the smallest sized object that the curtain can detect. These are divided into finger, hand and body resolution. Hand and finger detection is used when an operator's hands are near the machinery, while body detection is for light curtains that form a perimeter around a machine.
