| 摘要 |
A headbox contains a rigid lower lip which is directed towards a dewatering surface, a wire or the like, guided over a rotating cylinder or roll, and a rigid upper lip having a rigid lip portion which, in conjunction with a portion or section of the dewatering surface neighboring the lower lip downstream with respect to the flow of the stock suspension, delimits a sheet forming chamber or space. The lip portion is provided at the region of the sheet forming chamber with step or groove-like depressions or recesses extending transversely with respect to the direction of flow of the stock or fiber suspension. These recesses serve to form recirculation turbulence which supports the marginal flow of the stock suspension. With this arrangement the effect of the wall friction upon the flow velocity is practically eliminated, so that with a flow velocity of the stock suspension which is adjusted in accordance with the travel speed of the dewatering surface, there is ensured for a uniform forming of the suspended fibers of the stock suspension in the lengthwise and transverse direction of the paper which is to be fabricated.
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