Arrangement for controlling the edge of pulp mass in a web former and a method for controlling the edge of pulp mass

A method for controlling the edge of a pulp mass in a web former defining a wedge-shaped space extending in a machine direction between two opposing and converging wires for receiving the pulp mass, the web former further having opposing side edges, and the wires being supported to define the wedge-shaped space by respective chamber units, each chamber unit including at least one chamber for receiving the water removed from the pulp mass, said method comprising:

• directing a pressurized injection fluid through at least one channel defined by and extending through at least one edge control element of an edge control device, the at least one edge control element being disposed between opposing chamber units about at least one side edge of the web former, and laterally extending at least partially between the opposing wires, the at least one channel being configured to direct the pressurized injection fluid outwardly therefrom, toward at least one of the opposing wires and the opposing chamber units, such that the pressurized injection fluid forms a seal between the at least one edge control element and the at least one of the opposing wires and the opposing chamber units, thereby substantially preventing the pulp mass from spreading laterally outward past the side edges of the web former.