
Light Curtains

Industrial environments can be dangerous and operator safety must be the top priority when operating and maintaining hazardous machinery. Traditionally, physical barriers, such as pull-back restraints and sliding gates, were used to protect operators from hazardous machines. Now, a light curtain barrier can be used instead, allowing operators easier access to perform routine tasks, maintenance and repair.
Light curtains are considered presence detection devices and have two important components: a transmitter and a receiver. The transmitter sends infrared light beams to the receiver in a known sequence and at a specific frequency. The receiver anticipates the beams of light in the known sequence and frequency, reducing the possibility of interference from other light sources. When an object passes between the transmitter and receiver, the light from the transmitter is interrupted and not received by the receiver, triggering a stop signal. This stop signal is typically sent to a safety relay, which will remove power from the machine.
Light curtains are generally used in two situations: perimeter and point of operation. Perimeter guards protect the boundary or perimeter of an entire working space around a machine. Light curtains used in perimeter guarding applications are generally selected for torso detection and ensure that no person or object enters the boundary of the machine’s movement. Point of operation guards are installed at the site of material handling or the pinch point. Light curtains used in point of operation guarding are selected for finger and hand detection and are used in applications such as hydraulic presses, riveting, stamping and automated assembly machinery.
Products
Limit switches are electromechanical switches that operate based on the movement or presence of an object. They are designed to detect the presence of an object using an actuator connected to a series of contacts to detect the presence and proximity or absence of a material or object. When the switch’s actuator is moved by an object it will change the state of an electronic contact set. This movement signals that some preset limit has been reached. There are many different ways a switch can be actuated depending on the type of switch that is being used. Some use a roller and lever, some use a button or plunger, while others might use a rotating arm and rod attached to the main body of a switch. The type of switch that is used will largely be dictated by the specific application.
Where are limit switches used? Limit switches can be used to tally or count items, so that when a limit is reached, the switch will open or close. This open and closing action can be counted by a controller allowing the action to be totalized. Limit switches can be used as safety interlocks to prevent machine parts from moving any further when specific point is reached. Limit switches are also commonly used in larger control systems. For example, when a certain limit is reached, the actuator can deactivate or activate a device to prevent it from malfunctioning.