of the gaps 280 u2032 between the bars 238 u2032 increases between the upper end 234 u2032 and the lower end 236 u2032 of the screen 232 u2032 fig1 shows a graph comparing relative chip compaction in a pulp digester when using the standard right cylinder screen assembly shown in fig1 a the diverging screen assembly shown in fig2 a and the screen assembly in accordance with certain preferred embodiments of the present invention shown in fig3 a 11b the results for the standard screen are depicted using a solid line the results for the diverging screen are depicted using a dashed line having elongated dashes and the results for the screen assembly of the present invention are depicted using a dashed line having shorter dashes the x axis in the graph represents the height of the screen assembly starting 0 1 meter above the screen wherein the cover plate is located the y axis in the graph shows the relative compaction of the chip column the chip columns in the three different systems i e standard screen diverging screen screen of the present application all have the same absolute starting value at 0 2 meter above the upper end of the screen the graph shows that compaction for the standard screen and diverging screen increases at the transition between the cover plate and the screen in contrast the compaction level for the present invention actually decreases at the transition because the upper cover plate diverges the peak value of the compaction is at the location where there is no axial flow vector at all after peak value the compaction is decreased rapidly by counter current wash flow thus the graph of fig1 shows that the screen assembly of the present.