Light Curtains Overview 275

American National Standards Institute

ANSI. A private, nonprofit organization that administers and coordinates voluntary standards and systems for products, services, and systems in the U.S. The American National Standards Institute sets forth safety guidelines for installing and using presence-sensing devices such as light curtains.

ANSI

American National Standards Institute. A private, nonprofit organization that administers and coordinates voluntary standards and systems for products, services, and systems in the U.S. ANSI sets forth safety guidelines for installing and using presence-sensing devices such as light curtains.

ANSI B11.19

A document published by the American National Standards Institute that sets standards for safeguarding and risk reduction in operating machinery. ANSI B11.19 includes guidelines for light curtains and other presence-sensing devices.

area access control

AAC. A safeguarding method that uses a light curtain with a single beam to guard the area near a machine performing a hazardous operation. Area access control light curtains can only guard against the entry of an operator's whole body.

automated assembly line

An assembly line in which the majority of tasks are performed by automated machines. Automated assembly lines require little or no human interaction.

automatic restart

A setting for light curtains that allows machine operations to automatically restart after an obstruction in the sensing field is removed. Automatic restart is commonly used in POC applications.

blanking

A feature of light curtains that allows an operator to disable one or more sections of the sensing field. Blanking is used to allow necessary objects such as workpieces or other equipment to pass through the sensing field without halting machine operations.

bypassing

The act of completely disabling a light curtain or other safety device. Bypassing should never be done during any machine operation.

cascading

A feature of light curtains that allows them to be connected together. Cascading enables several light curtains to act as one when guarding a hazardous operation.

control reliability

The capability of a device to achieve a safe state in the event of damage or internal failure. Control reliability is required for light curtains and many other safeguarding devices.

dynamic blanking

A feature of light curtains that enables a light curtain to recognize the pattern of beam interruptions caused by expected objects. Dynamic blanking allows expected objects to pass through the sensing field while still protecting against the entry of people or unexpected objects.

earplugs

A protective device that is inserted in the ear to block noise. Earplugs protect against hearing loss.

effective aperture angle

The maximum angle of deviation between the transmitter and receiver units of a light curtain. A narrower effective aperture angle provides greater protection from interference, but less flexibility in placement.

fixed blanking

A feature of light curtains that disables specific sections of the sensing field. Fixed blanking is used to allow stationary objects to intersect with the sensing field.

floating blanking

A feature of light curtains that allows a specific number of beams to be interrupted at any location in the sensing field. Floating blanking is used to allow moving objects to pass through the sensing field.

frequency

A measurement of the number of times a light wave repeats in one second. Frequency is measured in hertz (Hz).

hard hats

A lightweight, protective head covering used to protect the head from impacts, bumps, and electric shock. Hard hats have a shock-absorbing lining with a headband and straps that suspend the shell away from the skull.

infrared

Invisible light energy emitted by heated objects. Infrared light is often used in presence-sensing devices.

International Electrotechnical Commission

IEC. An international organization that prepares and publishes all standards for electrical, electronic, and related technologies. The International Electrotechnical Commission developed the specifications for Type 2 and Type 4 light curtains.

light curtains

A type of presence-sensing device consisting of a field of light that stops a machine when the light is blocked by an object. Light curtains prevent mechanical parts from striking employees and equipment.

light-emitting diodes

LEDs. A semiconductor device that emits a narrow spectrum of light in a forward direction. Light-emitting diodes are used to create the sensing fields of light curtains.

lockout/tagout

A method of protecting employees from accidental machine startup by locking and labeling devices. Lockout/tagout renders a tool or machine inoperable.

machine guards

A rigid shield or cover that encloses hazardous areas on a machine. Machine guards prevent accidental machine contact with body parts and prevent debris, such as chips, from exiting the machine.

machine tool

A power-driven machine that is used to manufacture parts by guiding a tool to shape workpieces. Common examples of machine tools include the press brake, the lathe, and the shear machine.

manual restart

A setting for light curtains that requires an operator to manually restart machine operations after the sensing field is obstructed. Manual restart is commonly used in PAC applications.

maximum operating range

The maximum distance allowed between the transmitter and receiver units of a light curtain. The maximum operating range of a light curtain will be shortened if mirrors are used to bend its light beams.

minimum object resolution

The diameter of the smallest object that the sensing field of a light curtain can reliably detect. Minimum object resolution is determined by the amount of space between light beams in the sensing field.

minimum safe distance

The minimum distance allowed between a light curtain and a hazardous operation. Minimum safe distance can be calculated using values and equations found in ANSI B11.19.

muting

A feature of light curtains that allows an operator to temporarily disable the entire sensing field. Muting is used to allow people or objects to pass through the sensing field during non-hazardous portions of machine operations.

Occupational Safety and Health Administration

OSHA. A government agency under the Department of Labor that sets the standards for working conditions in the U.S. The Occupational Safety and Health Administration ensures that employees work in safe and healthy environments.

OSHA

Occupational Safety and Health Administration. A government agency under the Department of Labor that sets the standards for working conditions in the U.S. OSHA ensures that employees work in safe and healthy environments.

PAC

Perimeter access control. A safeguarding method that guards the area near the machine performing a hazardous operation. PAC light curtains create a perimeter around the machine and guard against the entry of an operator's arms or body into the protected area.

pallets

A low, portable platform on which goods and materials are stacked for storage or transportation. Pallets are also known as skids.

pass-through hazard

A safety risk that occurs when an operator is able to fit between the sensing field of a presence-sensing device and the hazardous machine operation it guards. The existence of a pass-through hazard means that presence-sensing devices should never be set to automatic restart.

penetration depth factor

The distance that a small body part such as a finger might travel beyond the sensing field of a light curtain before a larger body part such as a hand interrupts one of the beams. Penetration depth factor can be calculated using guidelines found in ANSI B11.19.

perimeter access control

PAC. A safeguarding method that guards the area near the machine performing a hazardous operation. Perimeter access control light curtains create a perimeter around the machine and guard against the entry of an operator's arms or body into the protected area.

personal protective equipment

PPE. Any of the various articles of clothing or safeguarding devices that are used to prevent injury in the workplace. Common examples of personal protective equipment include safety glasses, gloves, masks, gowns, and earplugs.

photoelectric sensors

A type of sensor that detects the presence of an object through the use of a beam of light. Photoelectric sensors do not physically contact the object being detected.

pinch point

Any place in which two moving components come together. Pinch points can cause injury if a body part comes into contact with the area.

POC

Point of operation control. A safeguarding method that guards only the point of operation on a machine tool. POC light curtains are placed close to the point of operation and typically guard against the entry of an operator's fingers, hands, or arms into the protected area.

point of operation

The area where the tool comes into contact with the workpiece. The point of operation is typically the most hazardous area of the machine and should be protected by primary safeguarding methods.

point of operation control

POC. A safeguarding method that guards only the point of operation on a machine tool. Point of operation control light curtains are placed close to the point of operation and typically guard against the entry of an operator's fingers, hands, or arms into the protected area.

PPE

Personal protective equipment. Any of the various articles of clothing or safeguarding devices that are used to prevent injury in the workplace. Common examples of PPE include safety glasses, gloves, masks, gowns, and earplugs.

presence-sensing device initiation

PSDI. A feature that allows a presence-sensing device to initiate new a machine operation after a predetermined number of interruptions. Presence-sensing device initiation is only permitted in limited circumstances.

presence-sensing devices

A mechanism used to detect the location of people or objects near hazardous areas of a machine. Presence-sensing devices often use pressure-sensitive mats or light curtains.

press brake

A type of stamping machine with an open frame and a long, narrow bed. Press brakes are often used for bending operations, and they are typically manually operated.

primary safeguarding

A device or barrier on a machine that prevents point of contact hazards. Primary safeguarding devices includes machine guards and some presence-sensing devices.

protective field height

The height of the sensing field of a light curtain. The protective field height should be tall enough to prevent anyone from reaching over the top of the sensing field.

pullback devices

A set of cables attached to an operator's hands, wrists, or arms that pulls the operator's hands back if they come too close to a dangerous area. Pullback devices prevent accidental contact between operators and hazardous machine operations.

receiver unit

A device that detects beams of light. The receiver unit of a light curtain only detects the beams of infrared light sent by the transmitter unit.

robotic work cell

The area composed of a robot and any external devices or equipment that interact with the robot. Robotic work cells are often guarded by light curtains and other presence-sensing devices.

safety glasses

Protective eyewear, usually made of thick plastic, that shields the eyes from flying debris. Safety glasses offer protection from impact, dust, chips, splashes, and sometimes ultraviolet light.

safety professional

An expert in safety procedures who provides advice, support and analysis to manufacturing workplaces. Safety professionals may have a variety of different specializations or certifications.

safety shoes

Footwear that protects the feet from impact, electric shock, and/or heat. Safety shoes sometimes include reinforced toe areas.

secondary safeguarding

Any device, barrier, or equipment that works together with primary safeguarding devices. Secondary safeguarding devices includes fences, alarms, and some presence-sensing devices.

sensing field

An area of space monitored by a device that detects the presence of people or objects. A sensing field may by monitored via many different methods of detection, including electromagnetic fields, electrostatic fields, or beams of light.

soundproof

A material that absorbs or dampens sound waves, reducing the amount of noise in an area. Soundproof materials are often used as safety equipment to protect operators from the hazardous levels of noise created by some machine operations.

transmitter unit

A device that emits beams of light. The transmitter unit of a light curtain sends an array of infrared light.

Type 2 light curtains

A category of light curtains that offer lower levels of protection. Type 2 light curtains are appropriate for low-risk situations and are used as secondary safeguarding devices.

Type 4 light curtains

A category of light curtain that offer higher levels of protection. Type 4 light curtains are appropriate for high-risk situations and are used as primary safeguarding devices.

ventilation systems

A series of devices designed to remove potentially hazardous air from a work area and replace it with clean air. Ventilation systems are often composed of ductwork, exhaust hoods, filters, and fans, among other components.