Pneumatic system is cost-effective machine guard

A novel obstruction detection system based on technology transfer from the rail industry has great potential as a cost-effective solution for machine guarding and operator safety.

Guarding systems using light curtains, interlocks and other high tech solutions would be great if they were not so expensive.

Hoerbiger-Origa reckons it has advanced the state of the art of machine guarding and operator safety with the development of an obstruction detection system based on technology transfer from the rail industry.

Powered doors, machine guards, handling systems and assembly machines are commonplace in most industrial environments, and so are the inherent risks of trapping.

Whether it is products or people that are at risk, it is essential that an adequate level of protection is provided.

It is a fact of industrial life that some applications do require very complex and expensive guarding, for many applications a simpler solution can be envisaged.

Hoerbiger-Origa's design team have been working on obstruction detection solutions for many years within the rail industry and made the decision to apply this knowledge to produce solutions for use in the industrial and manufacturing worlds.

The objective was to produce low cost yet effective alternatives to the existing technologies so that safety and integrity could be achieved without incurring excessive costs.

"Our rail doors operate by monitoring the back pressure in the pneumatic cylinders that drive the doors to and fro", explains Hoerbiger-Origa's Mark Prew.

"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".

The designers looked at what was required before the current concept could 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 team 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 in fact monitors for rapid decelerations that would be indicative of an obstruction occurring.

The controller also monitors pressure for rapid decay, and its timer function compares actual parameters with preset expectations, variations from which would indicate a problem.

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

As the team worked towards a final design they realised that they had produced a very 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.

It 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, biparting solutions, short, medium and long stroke configurations, and multilayered backup detection.

Prew sums up: "We have developed a very versatile system that is suitable for a wide spectrum of applications.

It provides a cost effective alternative to more complex detection systems while still maintaining many of their functions".

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