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No tools needed to build an island

01 May, 2001

No tools needed to build an island

The fluid power specialist Asco Joucomatic has developed a pair of technologies that it claims will make it easier to assemble and interconnect pneumatic installations. The technologies, which have taken two years to develop, are:

• an easy-to-assemble family of pneumatic spool valve islands designed to be flexible, both in their installation and the type of control they perform; and

• a communications system that that can connect up to 127 valves and other devices over a distance of up to 2.5km and link them to a field bus network.

The Mega valve islands allow almost any combination of valves to be assembled rapidly without tools, simply by clipping them into position. Once completed, an island is IP65 rated. Up to 16 of the 18mm-wide valves can be fitted on an island which can, in turn, be mounted directly onto machines, as well as in panels. Replacing a monostable valve with a bistable version (which is the same size) takes about 90 seconds.

The valves, which can handle flow rates of up to 900 l/min and will last for at least 40 million cycles, are available in double 3/2, 5/2 or 5/3 solenoid air-operated spool formats, and have 1.6W push/pull coils. Users can mix and match components, allowing the islands to be supplied with two or three different pressure levels from -0.9 bar (a vacuum) to 8 bar.

There is a choice of technologies for connecting the islands:

• a "classic" connection using a size 15 connector with optional LED indicators and electrical protection;

• a multiwire (25 or 37) connection via a sub-D connector;

• an easy-connect AS-i interface that can supervise eight monostable or four bistable spool valves; or

• Asco Joucomatic`s new "intelligent" valve connection system (VCS).

The VCS uses a flat, two-wire cable similar to an AS-i cable (but green rather than yellow) to connect up to 127 valve connectors and 254 sensors in a loop. The two ends of the loop terminate at a control module that, in turn, links to a bus system such as Profibus DP, Interbus S or DeviceNet. Asco Joucomatic claims that the system is at least 30% cheaper to install than conventional technologies, and that the savings grow as you add more devices.

Like the Mega system, the VCS is tool-free - closing a connector lid onto the cable at any point, pierces it to make a pair of connections with conductors. It also slices through the cable between these connections, forcing the current to pass through the connector which houses an ASIC chip that checks for terminal overheating, short-circuits and low voltages. Any faults can be located and diagnosed via LEDs on the loop control module.

The connectors, which also act as repeater stations, can be up to 20m apart. If the maximum of 127 are daisy-chained, a 2.5km loop can be created and, in this worst case, the time taken to respond is a maximum of 3ms. For shorter loops or fewer connectors, the response rate is faster.

If the main cable current capacity of 3.1A is insufficient, a second cable can be added, carrying up to 10A. Extra power supply modules can be added anywhere on the loop, if needed. You can also add extra connectors and the system will reconfigure itself automatically.

As well as Asco Joucomatic`s own valves, cylinders and solenoids, the VCS system can support other manufacturers` products via adaptors. There are plans to add an analogue capability later this year.

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