Pepperl+Fuchs Blog

Machine Safeguarding with Safety Edges

Posted by Tom Corbett on Thu, Aug 22, 2013

Unique photoelectric sensors for edge monitoring

Moving machine parts, closing edges of doors and gates, and even automated guided vehicles (AGV) all have the potential to cause workplace injuries. Health and Safety regulations require that workers be protected from preventable injuries. But without the proper protection in place, worker safety can be at risk. One way to provide this protection is by machine safeguarding.

Safety edgesSafeguarding is when a device is used to prevent dangerous contact with machinery or equipment. When triggered, the device stops the dangerous process before injury can occur. Many times safeguarding is done with safety light curtains. Light curtains, as the name suggests, create a curtain of light that can detect objects as small as a finger. When any of the beams are blocked, the output of the sensor changes and the dangerous process stops.

But what happens when the area to be safeguarded is a small pinch or crush point like on the closing edges of doors or protective covers? Or when the danger is a collision risk from AGVs? All are applications where mounting a pair of large light curtains isn’t possible. For these types of edge monitoring applications, the PSE4 Safety Edge provides an ideal solution.

The PSE4 Safety Edge is a complete edge monitoring system that consists of a:

  • Safety controller
  • Unique thru-beam photoelectric sensors
  • Rubber sensor strip
  • Optional aluminum mounting strip

Assembling a safety edge requires no special tools or technical expertise. And with no configuration or programming, the safety edge easily integrates into existing processes and control systems.

The safety edge works by placing the unique thru-beam emitter and receiver inside the ends of the rubber sensor strip to create an optical light path. The light bounces around the smooth inner surface of the mounting strip, which allows the strip to curve a certain amount without completely blocking the light. When a person or object places pressure on the rubber sensor strip, the rubber deforms and the light path is interrupted. The safety controller monitoring the photoelectric sensors detects the interruption, causing its forced-guided relay contacts to open and stop the dangerous process.

How a safety edge worksThe thru-beam photoelectric sensors are fully encapsulated and rated IP68, making them resistant to dust and moisture. The rubber sensor strip features a two-chamber design that allows actuations that occur in the end area to push the emitter and receiver into the lower chamber to ensure the light path is still broken. When used in conjunction with the safety controller which monitors and detects faults in the photoelectric sensors or wiring, the safety edge meets Performance Level e according to EN ISO 13849-1. Performance Level e provides the best reliability and is equivalent to that required at the highest level of risk.

The PSE4 Safety Edge is a simple and reliable safeguarding solution. It provides a high level of worker safety by monitoring the edges of dangerous processes or hazards where protection from conventional devices is not possible. Plus, the safety edge meets the latest machine safety design standards, EN ISO 13849-1.

EN ISO 13849-1 has become the global machine safety design standard and replaces EN 954. It provides safety requirements and guidance on the principles for the design and integration of safety-related parts of control systems (SRP/CS), including the design of software. Performance Levels are determined through a detailed hazard and risk analysis.

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Topics: Light Grids, Photoelectric Sensors

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