In apparatus for making a multi-ply smooth surfaced paper web from stock having a slurry of fibers in a liquid carrier, the combination comprising:
- a headbox having a lower wall and an upper wall and including means defining an upper stock chamber and a lower stock chamber for low consistency fibrous stock to form outer surface plies for a finished web;
- said headbox including means defining an intermediate stock chamber between said upper and lower chambers for high consistency fibrous stock for an intermediate ply between said outer plies;
- first and second delivery means connected respectively to said upper and lower chambers for delivering low consistency fibrous stocks for the outer surface plies;
- an intermediate stock delivery means connected to said intermediate chamber for delivering a high consistency stock thereto;
- a slice chamber connected to receive stock from said stock chambers and extending from the headbox and having upper and lower slice walls respectively connected to said upper and lower headbox walls and tapering toward each other leading to a slice opening to discharge onto paper web forming surface means;
- said slice chamber having an upper slice chamber portion and having a lower slice chamber portion respectively connected to receive stock from said upper and lower headbox chambers and directed to discharge from said slice opening onto said forming surface means as separate ply layers to provide upper and lower outer surface plies for the multi-ply paper web;
- means for maintaining fine scale fiber distributing turbulence in the stock which is directed by said upper and lower slice chamber portions to said slice opening;
- a rigid intermediate portion of the slice chamber positioned between said upper and lower slice chamber portions and defined between rigid upper and lower intermediate portion walls which face one another and separate said upper and lower slice chamber portions;
- said intermediate portion walls having cooperating facing undulating surfaces defining a tortuous fiber distributing flow passageway which communicates in high consistency stock receiving relation at its upstream end with said intermediate stock chamber and has its downstream end adjacent to said slice opening for discharging an intermediate ply layer between said low consistency stock outer surface ply layers;
- said passageway including an upstream part comprising a straight-on section having a downstream end abrupt right angular juncture with a right angular elongated straight jog section which has at its downstream end an abrupt acute angle juncture with the upstream end of a downstreamwardly elongated straight slanting section of substantial length, which, in turn, has at its downstream end an abrupt obtuse angle juncture with the upstream end of a sinuous section of substantial length and having a series of smoothly curving sinuous loops which progressively diminish in length and height from said obtuse angle juncture in a downstream direction for maintaining said uniform fiber distribution after the high consistency stock has been subjected to vigorous fiber distributing agitation of the fibers in the stream;
- and a generally straight terminal section of substantial length extending from the downstream end of said sinuous section toward the end of said passageway for modulating and smoothing flow of said intermediate ply layer to its joining with the outer ply layers, so that said outer ply layers on engaging said intermediate ply layer will present substantially smooth outer surfaces for the multi-ply paper web.