Pneumatics blows away light curtains

Guarding systems using light curtains and interlocks are great but expensive. Now, Hoerbiger-Origa has an alternative – an obstruction detection system based on technology transfer from the rail industry.

Guarding systems using light curtains, interlocks and other high tech solutions would be great if they were not so expensive. Now Hoerbiger-Origa has developed an alternative – an obstruction detection system based on technology transfer from the rail industry.

Rail doors safety systems operate by monitoring the back pressure in the pneumatic cylinders that drive the doors to and fro. In normal operation the pressure remains within specific operating limits, but the back pressure will rapidly drop away if an obstruction is detected. It’s simple to detect this change in either back pressure or drive pressure and rapidly reverse the flow of air to reopen the doors minimising the contact time against the obstruction.

So the Hoerbiger-Origa designers looked at what was required for the rail concept to be transferred to the manufacturing sector.

The rail doors constituted a relatively low and steady load, producing a low risk and the team realised that a high performance sensing technique would be needed for greater or fluctuating loads. The designers got to work on concepts based around an optical encoder combined with a small intelligent controller that would allow displacement, speed and time lapse to all be monitored.

The encoder monitors for rapid decelerations that would be indicative of an obstruction occurring. The controller also monitors pressure for rapid decay, while it’s timer functions compares actual parameters with pre-set expectations, variations from which would indicate a problem.

Further, the flexibility in the controller allows it to react to obstructions in different ways, i.e. reverse movement on detection, hold position on detection, back off then hold position, back off and retry, or dump all air.

As the designers worked towards a final design they realised that they had produced a versatile concept that could be suitable for many applications. Not just powered doors for enclosing working spaces when tools are in use, but also for conveyor transfer stations, centring operations, powered lifts, handling applications and many other situations.

The new system can be used vertically, horizontally and at all angles in between; there is independent and variable speed control in all directions; and variable or lockable pressure control to give the right power for any given application.

Extras that can be added include passive brakes for added security, dual direction obstruction detection, bi-parting solutions, short, medium and long stroke configurations, and multi layered backup detection.

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