Adjustable ledge for the sheet forming zone of a papermaking machine

摘要

The ledge is arranged transverse to the machine direction in a substantially flexure resistant manner and is adjustable for guiding the wires between which a web of material is formed. The ledge contains a guide surface which faces the wires and has a special contour. For improved control of the pressure changes occurring in the region of the ledge, the ledge contains a supporting member and a pressing member which contains the guide surface. A pressing device is supported at the supporting member and the pressing member can be adjusted in a direction relative to the wires as well as relative to the supporting member by using the pressing device for simultaneously elevating the pressing member and inclining the pressing member with respect to the machine direction. Advantageously the pressing device constitutes a hose which is subjected to a pressurizing medium and thereby deformable. The hose is at least partially imbedded into the supporting member such that its deformation causes movement of the pressing member. For simultaneously inclining the pressing member during such movement, a connecting member is provided between the pressing member and the supporting member. The ledge permits the adjustment of optimum pressures along a sheet forming zone whereby the sheet formation is improved.