Protecting and positioning in one device.
In-plant logistics solutions increasingly use self-driving shuttle systems, known as side-tracking skates, between the conveyors. They permit goods being conveyed to be shifted perpendicular to the direction of transport in an automated fashion.
More and more areas are being automated where products were traditionally moved manually or by forklift truck to intermediate buffers or transported to packaging lines. This level of automation with shuttle systems, generally known also as side-tracking skates or distribution cars, provides a solution which guarantees greater flexibility and the major advantage that these areas remain practically open, allowing people to walk through unhindered or free moving corridor supply vehicles to drive through.
However, with this advantage comes the need to ensure the protection of workers in the area, which is typically done using safety laser scanners on these vehicles or systems.
Leuze offers the solution
Leuze’s Rotoscan RS4 safety laser scanner is considered highly suitable for this type of application as it has the ability to measure distance and detect a vehicle position with absolute accuracy.
Gerry Bryant, managing director of Countapulse Controls, cites as an example a solution implemented in the paper processing industry where the guillotined paper is placed onto pallets and then shrink-wrapped for protection. The pallets are then transported via roller and belt conveyors and the sideways distribution of the pallets to the various plant areas is implemented via side-tracking skates.
“Firstly, in this type of application it is necessary to protect personnel in the areas where the side-tracking skates pass and secondly it is necessary to track and determine the exact positioning of the side-tracking skates at all times,” says Bryant.
The Rotoscan RS4 Safety Laser Scanner fulfils both requirements in one device and has an integrated interface for the optimum connection to Profibus DB (Profisafe). One of the main features is the intelligent MotionMonitoring function, which makes the devices predestined for use in mobile applications such as side-tracking skates. Apart from reliable protection for the transportation path, this function permits robust and accurate measurement of speeds and distances: up to six speed values can be monitored.
If necessary, protective field adjustments can be applied in the form of extended protective fields at higher speeds. Moving personnel do not interfere with the robust distance measurement in this case. The current measurement value is given a ‘quality’ rating and the respective rating or measurement quality of the data determines the subsequent behaviour of the Safety Laser Scanner.
Bryant explains that in practice this lets people move through the sensor’s measuring field without triggering a stop signal, depending on the distance and speed of a side-tracking skate. In-plant movements on the transportation path thus do not interfere with the operation of the shuttle – without restricting the safety of persons in the path.
The robust distance measurement can also be used to position the vehicles, and the new measuring procedure of the Rotoscan RS4 permits measurements of the distance to defined reference planes. This can be used to determine positions precisely.
Just as for the side-tracking skates on which pallets with paper stacks are transported to the packaging machines, the conveyor segments of the vehicles can stop at the loading and discharge stations with millimetre precision to transfer the pallets. The braking, stopping and loading at the roller conveyors is also monitored.
For more information contact Gerry Bryant, Countapulse Controls, +27 (0)11 615 7556, [email protected], www.countapulse.co.za
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