Patent ID: 6902651

Claim:
Tube bank structure of the headbox of a papermaking machine having a plurality of flow tubes for flowing raw material of paper (stock) arranged in the tube bank, wherein each of said flow tubes has a smaller diameter pipe portion of a circular cross-sectional configuration in the upstream side defining an inlet opening for the stock, and a larger diameter flow tube portion, the larger diameter flow tube portion consisting of a larger diameter pipe portion, having a length L 1 and an inner diameter D 2 , of a diameter larger than that of said smaller diameter pipe portion and connected to said smaller diameter pipe portion, a succeeding tapered pipe portion, having a length L 2 , changing smoothly in sectional configuration from circular one to rectangular one toward downstream to be enlarged smoothly in cross-sectional area to be succeeded by a rectangular pipe portion, having a length L 3 , defining an outlet opening for the stock, wherein L 1 +L 2 +L 3 =(3.5˜7)× D 2 .