Headbox of a paper machine with edge feed arrangements

A headbox of a paper machine having a width, lateral edges and a middle region defined between the lateral edges along the width of the headbox, comprising

• an inlet header for stock,
• a slice duct from which a suspension jet of the stock is discharged, and
• a turbulence generator arranged between the inlet header and the slice duct,
• a dilution profiling system utilizing a feedback-connected regulation system to control the cross-direction basis weight profile of a paper web produced by the paper machine, the dilution profiling system comprising
• a dilution feed header for a dilution liquid or a stock suspension having a consistency lower than the consistency of the stock in the inlet header,
• means for fluidly coupling the dilution feed header to the middle region of the headbox along the width of the headbox between the inlet header and the slice duct, and
• regulation means associated with said fluid coupling means for regulating the flow of the dilution liquid or stock suspension having a consistency lower than the consistency of the stock in the inlet header through said fluid coupling means,
• the headbox further comprising
• conduit means arranged between the dilution feed header and the slice duct for passing flows of the dilution liquid or stock suspension having a consistency lower than the consistency of the stock in the inlet header from the dilution feed header along the lateral edges of the headbox to form edge flows such that only the dilution liquid or stock suspension having a consistency lower than the consistency of the stock in the inlet header flows at the lateral edges of the headbox until a downstream end of said turbulence generator, and
• control means arranged in connection with said conduit means for regulating the velocity of each of said edge flows to control a transverse velocity component of the stock suspension jet such that the cross-direction fiber orientation profile of the web produced from the stock suspension jet is controlled.

A method for controlling the cross-direction fiber orientation profile of a paper web produced from a stock suspension jet discharged from a headbox and the basis weight profile of the web, comprising the steps of:

• directing a stock suspension from an inlet header of the headbox through a plurality of turbulence tubes in a turbulence generator, the turbulence tubes being situated alongside one another in a direction transverse to the stock flow direction and in vertical rows situated in a middle region along the width of the headbox between lateral edges of the headbox,
• directing a dilution liquid from a dilution header through a plurality of feed ducts each leading into a respective one of the vertical rows of turbulence tubes situated in the middle width region of the headbox,
• regulating the flow of dilution liquid through each of the feed ducts to thereby control the basis weight profile of the web,
• passing flows of the dilution liquid from the dilution header along the lateral edges of the headbox to thereby constitute edge flows, and
• regulating the velocity of each of the edge flows to control a transverse velocity component of the stock suspension jet such that the cross-direction fiber orientation profile of the web produced from the stock suspension jet is controlled.