10 is designed to produce a uniform orientation and consistency of fibers laid down in the cross machine direction on the wire 12 this uniformity starts with an attenuator not shown disposed upstream relative to the headbox for damping pressure pulses caused by the stock pumping equipment the stock then flows into the manifold 16 the manifold is tapered in a cross machine direction either linearly or parabolically so that the pressure within the manifold remains constant in the cross machine direction the job of each tube 24 an example of which is best shown in fig4 is to change the direction of the stock flow from the cross machine direction to the machine direction each tube has an upstream section 54 which is generally cylindrical and which receives stock from the manifold 16 the upstream section 54 is joined at an expansion joint 61 to a flattened downstream section 60 which discharges stock onto the wire 12 the length of the upstream section 54 of the tube 24 is selected so the flow becomes completely symmetrical and aligned in the machine direction the flow then undergoes a sudden expansion at the juncture 61 with the downstream section 60 the sudden expansion creates shear for improved fiber dispersion and also creates head loss for cross machine uniformity because flow through a pipe 24 is dependent on the entire pressure drop a large pressure drop caused at the expansion joint 61 reduces the effect of upstream pressure variations.