with individual expansion lugs
The Vorwald expansion chucks of the Series 834 are suitable for unwinders without shafts. The expansion of the expansion leafs takes place centrally.
The roughened and hardened surface of the steel leafs permits the greatest possible torque transmission with cardboard, steel and plastic cores.
The functional principle is based on the inclined plane that lies in the winding direction. Through the existing web tension of the winding material a torque acts on the expansion chuck via the reel diameter. This torque makes cylindrical rollers inside the expansion chuck run up an inclined plane thereby pressing the expansion leafs outwards. An additional medium such as compressed air is not required for the activation.
The clamping force of the expansion chuck varies depending on the web height and the given braking torque of the unwinding machine. An important condition is that both expansion chucks must be braked and that a minimum torque of 0.05 x the reel weight acts on the expansion chucks. A further very important advantage of this arrangement is the absolutely concentric clamping of the cores, because all expansion leafs expand uniformly to the same extent. This makes very high winding speeds achievable.
Based on the Vorwald standard the expansion chucks are customised according to the modular design principle.