Precision control of the compressed air drives

Multi-axis pneumatics and piezo-based pressure regulation are helping an OEM produce almost infinitely flexible shrink-wrapping machines which can be adapted to suit almost any situation

Multi-axis pneumatics and piezo-based pressure regulation are helping an OEM maintain its claim of being able to produce almost infinitely flexible shrink-wrapping machines which can be adapted to suit almost any situation.

EDL-John Quinn Packaging incorporate many innovations into their machine designs, including sealing jaws that open by as much as 400mm (far more than on standard shrink wrappers), overhead pushers to drive the product through the wrapping station (more adaptable than conventional conveyors), and extensive use of cutting edge technologies such as Airfit Tecno, the piezo-based pressure regulator from Hoerbiger-Origa.

"Precision control of the compressed air drives is very important on our machines," says Bill Lewis of EDL-John Quinn.

"There is a lot of sequencing and product throughput speeds have to be spot on.

The Tecno regulator does us proud and in fact we have tested it to levels that we would never need on real machines".

In fact John Quinn began specifying Tecno on all its machines almost as soon as the range was launched by Hoerbiger-Origa because it allowed a substantial simplification and size reduction of the control panel compared to previous solutions.

"We've worked with Hoerbiger-Origa and their innovative technologies since Day 1, right back to the infancy of rodless pneumatic cylinders, upon which our machine design flexibility is built".

These cylinders, complete with integral guides, play the vital role of pushing the product through a wall of shrink wrap, the first stage of the wrapping process.

Positioning is critical if a neat wrap is to ensure, hence the Tecno regulators.

The original attraction to a rodless solution was the compactness that resulted because there was now extending rod to accommodate.

Once the product is fully into the package station the pushers retract and the jaws close, driven by small Hoerbiger-Origa piston cylinders, to cut and seal the shrink wrap.

In fact all of the pneumatics on any John Quinn machine are from Hoerbiger-Origa, including valves, fittings and filters.

"There is pressure to swap to other suppliers," reveals Lewis, "But Hoerbiger-Origa is part of our quality assurance.

We know their products are Rolls-Royce standard and they provide tremendous tech support.

In fact our design team is not complete without a Hoerbiger-Origa engineer!".

Rodless cylinders were invented nearly 30 years ago.

Their key element is the sliding seal, which allows the load bearing yoke to be connected laterally to the air-driven piston within the cylinder rather than having to use a longitudinal piston rod which can become very awkward and cumbersome on long stroke applications.

As the period of patent protection drew to a close Hoerbiger-Origa set about developing several new ideas to maintain their position as innovators in machine design, one of which was the use of piezo technology in pressure regulation.

Tecno combines piezoelectric technology and precision miniature component engineering to completely redefined user expectations for speed and precision of air pressure control.

Smaller than a computer mouse, Tecno can handle a flow rate of up to 380 litres/min, providing pilot, main pressure regulator valve and electronic controls in a single package.

At its heart, instead of conventional solenoid technology, is a piezo chip which functions as a continuously operating 3/2 way pilot control valve.

By applying a variable signal of less than 0.25W to a cantilevered piezo element between inlet and outlet, the control airflow may be varied.

The output pressure control signal is then amplified via a diaphragm mechanism to control the main pressure regulating valve.

Control air consumption is less than 0.6 Nl/min, making it far quieter than solenoid-operated valves.

A reaction time of less than 7ms provides an almost instantaneous response and enables the output control to be cycled at speeds in excess of 40Hz.

Furthermore, the Tecno regulator does not compromise speed for precision, as the output accuracy is also maintained to within 0.2%.

Responsiveness to highly dynamic situations has also been enhanced with the new version, making Tecno the perfect choice for applications in which precise pressure profiles are required.

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