There are situations that require a little external positive pressure. This concept can even be applied to lift tables. Read here what we have done to prevent a 6-metre shaft from bending ...
The end customer was faced with the following problem. In his production process, PVC tarpaulins are wound up on a 6-metre long shaft. But due to the length of the shaft and the increasing weight of the tarpaulin, the shaft bent. Unfortunately, to an extent that was too much for the winding machine to cope with.
We provided the customer with a lift table that supports the shaft by generating counter-pressure. Basically, a small scissor lift table would have been sufficient to apply the counter-pressure in the middle of the bending shaft. However, the customer wanted the widest possible support for the PVC tarpaulin, so we decided to use a tandem lift table.
Deviation from our standard design
In contrast to our standard lift tables, we decided to arrange the lift cylinders vertically to simplify the control loop for this specific case.
The customer uses pedestal bearings on the very long and narrow platform to mount several support shafts for the winding machine. The scissor lift now moves with a defined pressure from below against the 6-metre-long shaft and so prevents the shaft from bending.
The exact pressure level is determined by means of a force-displacement diagram, whereby the pressure value is set by an adjustable pressure relief valve and the displacement is measured by a cable length sensor.
Easy to move out of the way
As soon as the PVC tarpaulin has been fully wound up, the full shaft must be replaced with an empty one. The lift table has forklift pockets to move it out of the way when the shaft is replaced.
Flat bars with locating holes were attached to the underside of the lift table to reposition it once the shaft has been replaced. This simple solution enabled the set-up times to be reduced to an acceptable level.