Teekanne GmbH of Düsseldorf is one of Europe's biggest tea merchandisers. At the start of 1996, the company decided to abandon the use of foil packaging for tea cartons and to change over to the use of packaging materials which would seal in the flavor. Thus, it was necessary to rethink the control concept for the existing packaging and transport system. The system takes up a great deal of room, stretching as it does over more than 80 meters, and functions as a link between 20 automatic filling machines and the final packaging station.
At the same time as the filling mechanism is operating, the cartons are being folded and glued in carton aligning stations. The finished cartons are then transported to the filling machines via a clever carton logic system resembling a shunting yard. The various tea specialities are sorted into the arriving packages at the filling machines.
The subdistribution boards with
INTERBUS-ST modules are installed
directly on the conveyor lines
A great number of light barriers, valves and motors is required in order to control this fully automatic process. The old, conventional contactor control system had to bow out and be replaced by a PLC in order for the required level of flexibility to be achieved. For reasons of time, the usual complex and cost-intensive parallel cabling was replaced by a modern automation concept incorporating INTERBUS.
The short time interval referred to worked in INTERBUS' favor because it was possible to separately test each prefabricated, decentralized subdistribution board comprising INTERBUS-ST modules for picking up the signals from the jam light barriers as well as the contactors which are also decentralized and are used for activating the conveyor belt motors. This enormous time saving was one of the principal reasons for using INTERBUS in the Teekanne plant.
INTERBUS CMD monitors the system
Before the tea specialties such as rose hip, peppermint and chamomile teas are transported to the final packaging station by the conveyor line, it is necessary to seal the cartons using a carton sealer. Roverna Verpackungsmaschinen GmbH of Fernwald is a specialist in this field. They use INTERBUS as well.
A PC is used as the control medium of a carton sealer. It utilizes the modern and standardized IEC 1131-3 programming language.
The exchange of signals between the packaging and transport system and the carton sealers takes place through an I/O coupling via INTERBUS. Thus, the entire system takes the form of a homogenous INTERBUS network. This aspect is particularly significant for the maintenance personnel.
The uniform configuration and diagnosis tool, INTERBUS CMD, permits the entire INTERBUS system to be monitored easily and clearly. If there is a jam in the conveyor system, it must be possible to switch off the individual belts within a specific time, working back from the location of the malfunction. This is in order to guarantee the quality of the packaging. It is achieved by a group switch-off which is configured using INTERBUS CMD. The conveyor system restarts automatically and runs in normal mode after the malfunction has been corrected. Following this, the tea cartons reach the final packaging station, which is also controlled by INTERBUS. All in all, it is a well thought-out and elegant solution.
Dipl.-Ing.
Andreas Baaske,
Teekanne GmbH, Düsseldorf,
Dipl.-Ing. Peter Engelhardt