Torque-resistant cables for vertical order pickers of up to twelve meters

Challenge

The deflection principle for cable guidance has already been used by Still for smaller order picking devices and has proven to be very successful. For the EK-X type series the lateral guide of the roller was improved slightly due to the greater cable lengths – and then the initial tests quickly showed that unfortunately, in this case, this solution did not work. Volker Haspel, who is responsible for electrical engineering at Kion Systems: "The cables that we used, twisted and looked like a corkscrew. Shortly afterwards they failed in the test. The testing of such cables is definitely a complex task. They execute relative motions in the lift frame and high dynamics occur when moving the order picker. Moreover, you have to take the tensile force that occurs here into account, which is different than the situation with energy chain cables". “

Solution

Tests in the laboratories of both companies showed: The special chainflex cable structure with cores wound in bundles also works very well on the rollers. Thereby the cores are first wound in bundles, which in turn are braided with a small pitch length around a core element. This core element is not used as a filler, rather it is designed as a strain relief element. In appearance the result is highly reminiscent of a steel rope. To additionally support this stable braiding construction a jacket is extruded under pressure to supplementally guide the wires in the longitudinal direction. All of these measures result in the fact that the forces occurring in the cable are minimized and the construction remains intact.
 
Also the special materials of the jacket and its workmanship are significant additional aids for durability. It was shown that the shape of the roller does not have an influence on service life. The decision was clear for the Still designers; the cable was defined as the standard for the lift frame of the EK-X.A chainflex cable with cores wound in bundles and TPE jacket is used which are between 4.50 and 16 metres long in the order pickers. There is no question that they are highly stressed. In many applications the devices are in continuous use, which means that the lift frame is always in motion. The chainflex cables move under these conditions just like they move in many thousands of energy chain applications. With this cable Still has found a solution for a task that arose through the changed geometry of lift frame and guide roller. The cable specialists at igus have also gained an insight: now they know that their cables are not only chain-suitable, but they have also proven to be effective in roller guides.