Abstract: Apparatus for stabilizing a jet flow (J) discharged from a headbox slice channel (16) of a paper machine and for controlling the edge area of a paper or board web. In the flow direction (F) of the stock suspension, the slice channel (16) narrows and converges in the edge areas thereof, on both sides in cross direction of the web formed. The top wall (25) of an apron beam (24) forms the bottom wall of the slice channel (16). The slice channel (16) is defined by a planar top wall (14), which is hinge-jointed at the upstream edge of adjustment of the slice opening (15). At the level of the bottom wall (25), the slice channel (16) narrows and converges linearly from the full width (L.sub.max) of a turbulence generator (13) down to the width (L.sub.0) of the slice opening. At the level of the top wall (14) of the slice channel (16) the width of the slice channel (16) is essentially retained the same and equal to the width (L.sub.0) of the slice opening.

Abstract: The invention relates to a headbox of a paper or board making machine, particularly a hydraulic headbox, which has an inlet header section (1) with a manifold tube section (2) and an equalizing chamber (3) in the stock suspension flow route, a turbulence generator section (4) following the equalizing chamber (3), after which a tapered slice section (8) is located, through which the stock suspension is discharged onto the wire. The headbox also has an attenuation chamber (6) for pressure variations, which defines one or several air spaces (7) under the flow channel of the stock suspension, the spaces being connected with the flow channel by way of a connecting channel (5). The air space or spaces (7) are preferably confined by subjacent frame structures including a bottom wall (16) and vertical walls (18) and walls (19) defining the flow channel from below.