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.
A dewatering device for the web-forming or wet section of a papermaking machine comprises foils arranged transverse to a forming wire, that is to say, extend in the cross-machine direction. Force or powering elements act upon the foils so as to exert a force or pressure upon the forming wire, and thus, bring about dewatering and sheet formation of a layer of fiber stock suspension reposing upon the forming wire. The force elements are constructed and positioned such that additional moments are generated which counteract tilting moments produced by the frictional force present between the foils and the forming wire. In certain arrangements, the force elements also can be interconnected with one another.
A dewatering instrument for a paper machine twin-wire former for improving the fiber dispersion performance while avoiding the decrease in strength of formed paper in its thickness directions. In the dewatering instrument, dewatering inhibiting blades have plane sections for supporting a wire and inclined surfaces for defining wedge-shaped spaces spreading out toward the upstream side in the wire traveling direction with respect to a wire plane formed on a wire entry side of the plane sections. Angles (wedge-angles) between the inclined surfaces and the wire are set to become sequentially smaller as a whole in proportion as the dewatering inhibiting blades are positioned on the further downstream side in the flowing direction of a paper raw material liquid. Or, the dimensions of the wedge-shaped spaces defined between the inclined surfaces and the wires are made to become sequentially larger as a whole in proportion as the dewatering inhibiting blades are positioned on a further downstream side in the flowing direction of a paper raw material liquid. With the configurations of the dewatering inhibiting blades, the dewatering pressure peak value increases in accordance with advancing toward the downstream.
The temperature of the ceramic elements of a supporting or wiping strip that is assigned to a wire or a felt in a paper production facility, is controlled by guiding a cooling carrier medium or a heating carrier medium through the supporting or wiping strip. For that purpose, the supporting or wiping strip is formed with at least one channel, through which the carrier medium for heat or for cold is pumped.
A dewatering instrument of a twin-wire former allows the angles at which the wires are wrapped around the dewatering blades to be adjusted even during operation so that pulsating pressure applied to the paper stock may be set appropriately according to the prevailing paper making condition. The respective dewatering blades of the dewatering instrument are supported by two support bodies, the first one of which is fixed and pivotably supports the blade, and the second one of which is movable to pivot the blade about the first. For example, the second support body may be a flexible tube which is inflatable and deflatable. When the blade is pivoted, the attitude of the land of the blade is changed so that the wrap angles of the wires with respect to the land of the dewatering blade are adjusted.
A rib construction for a draining device in a paper machine in which a loading rib is used to support and/or to load a wire or wires in a paper machine and/or to doctor water from the face of a wire or wires. The rib is loaded by pressure of a medium. Between the rib and its frame part, a pressure space is formed and defined by a flexible belt and into the loading pressure is passed into this pressure space. The flexible belt defines the pressure space so that the area of effect of the loading force is independent from the movement of the rib toward the wire(s).
