Secondary headbox for overlay application in board formation

Claim 1

In combination with a board forming fourdrinier having a base sheet forming on the wire thereof, a secondary headbox capable of handling slurries of high solids consistencies positioned above and across the fourdrinier's machine direction, said headbox comprising: a. a slurry feed header; b. a first chamber into which the slurry from said header is introduced, said chamber including an underflow baffle beneath which the slurry initially passes and a driven perforated roll into and through which the slurry flows whereby the slurry is mixed and evenly distributed across the width of said chamber; c. a first weir over which the slurry from the first chamber passes into a second chamber; d. a second chamber having a baffle positioned therein under which the slurry flows, the lower edge configuration of said baffle conforming to the hydraulic flow of the slurry whereby any slurry turbulence is dampened, said baffle being positioned from the wall of said second chamber whereby the flow of the slurry through the chamber is controlled; e. a second weir over which the slurry flows out of the second chamber onto a declined apron; and f. a baffle positioned from and forming a nip opening with the leading edge of said declined apron whereby slurry flow direction onto the base sheet is controlled, the lower edge of said baffle terminating in a straight edge parallel to the leading edge of the declined apron and positioned from 0 inches to about 3 inches below said leading edge whereby slurry flow is directed vertically downward onto the base sheet carried by the fourdrinier wire passing thereunder.