Apparatus for damping pulp stock pressure fluctuations in a headbox

Claim 1

A paper machine headbox comprising header means for receiving pulp stock, distribution pipe means communicating with said header means for receiving pulp stock therefrom and conveying the pulp stock beyond said header means, flow-equalizing means communicating with said distribution pipe means downstream of said header means for receiving the pulp stock from said distribution pipe means and equalizing the flow of the pulp stock, turbulence passage means communicating with said flow-equalizing means downstream of said distribution pipe means for receiving the pulp stock from said flow-equalizing means and conveying the pulp stock beyond said flow-equalizing means while reducing turbulence in the flowing pulp stock, and lip slice means communicating with said turbulence passage means downstream of said flow-equalizing means for receiving the pulp stock from said turbulence passage means and delivering the pulp stock to a lip slice which forms part of said lip slice means and through which the pulp stock discharges from the headbox, said header means and flow-equalizing means forming a pair of means for respectively providing chambers in which pulp stock is situated while flowing from said header means to said lip slice means, and at least one of said pair of means including a wall means comprising a solid plate which defines part of said chamber of said one means and which is operatively connected with part of said one means for movement with respect to the remainder of said one means for altering the volume of said chamber thereof, said plate having an inner surface for contacting the pulp stock to respond to pressure fluctuations therein so as to move in response to said pressure fluctuations to change the volume of the chamber of said one means, said plate having an outer surface which is directed away from the chamber of said one means, and enclosure means for enclosing a gas such as air under pressure, said enclosure means having a hollow interior for holding therein the gas under pressure and said outer surface of said plate defining part of the hollow interior of said enclosure means so that through said plate the gas under pressure in said enclosure means acts on the pulp stock in the chamber of said one means for damping pressure fluctuations in the pulp stock.