Commercial port operations use rail-bound Automated Stacking Cranes (ASC) to process high volumes of shipping containers. These and other applications that require long e-chain travels are expected to benefit from Igus’ drive-chain.
Forty years ago, container ships held an average of 1,000 containers. Today, giants of the Triple-E-Class load almost 24,000 containers. This rising trend means that ports must continuously modify their infrastructure, including automated stacking cranes that load containers onto trucks and tow wagons. These huge overhead cranes cover distances of several hundred metres and more on rails. In many cases, the motor cables must track the movement of the ASC cranes.
Justin Leonard, director of the e-Chains business unit at igus UK, said: "For lengths of more than 1,000 metres, however, enormous tensile and thrust forces act on the e-chains. To prevent this and to optimise the longevity of the energy supply systems in such extreme applications, we are the first manufacturer in the world to develop an energy chain with its own drive."
The drive-chain design concept works as follows: so-called drive blades are mounted in the chain’s outer radius, with which the e-chain is driven along the lower run. On the lower rail, there are motor-driven friction wheels on the sides and rollers on the top. When the crane starts, the friction wheels’ motors also start. The lower run moves over the rail, a synchronized movement in which hardly any forces acting on the chain links via the carrier.
"This means that we achieve minimal load, low wear and long running times over distances of 1,000 metres and more," Leonard added.
In addition, igus is working on an alternative drive concept where the friction wheels are replaced by linear electric drives.
Energy supply systems with their own drive are an alternative to an energy supply system that has been used in ASC cranes: motorised steel drums that collect the motor cables, often working in two directions when the fixed point of the line is in the middle of the route.
According to Igus, the problem with this system is if the crane approaches this fixed point, it must brake to enable the cable routing to be pivoted, leading to a loss of time. Also, motor drums can weigh 4 to 6 tonnes which increases the energy consumption of the crane.
“Since the drive-chain runs uninterrupted on the rail, ASC cranes no longer have to brake near the fixed point in the middle, so they can work more productively," Leonard continued. "At the same time, the e-chain system does not increase the total weight and nor therefore the required drive power of the system. Due to the system’s lower weight, speeds of six m/s are possible even over long distances. These factors combined are major advantages from which more and more port operators around the world are benefiting."