chips suspension is withdrawn by a pump 303 through a withdrawal space 206 the shaft 106 not shown in this drawing passes through a penetrating opening 202 in the bucket shaped outlet 201 fig5 a and 5 b show a fourth preferred embodiment where the surface of the outlet line 302 is partially or fully perforated strainer holes or slits 205 from the perforated surface a fraction q 2 of the fluid in the chips suspension is withdrawn by a pump 303 through a withdrawal space 206 arranged around the perforated strainer holes or slits 205 in the outer surface of the outlet line fig6 a shows a fifth preferred embodiment of how the strainer surface of the bucket shaped outlet which consists of strainer holes or slits 205 may appear the complete surface is perforated in this case fig6 b shows a sixth preferred embodiment in which parts of the strainer surface are perforated by strainer holes or slits 205 fig6 c shows a seventh preferred embodiment in which parts of the strainer surface are perforated with strainer holes or slits 205 fig7 a and 7 b shows a side view and a top view of the bucket shaped outlet 201 where scraper arms 207 have been arranged on a shaft 106 with the aim of maintaining the strainer holes or slits in the strainer surfaces of the bucket shaped outlet clean such that they do not become clogged fig8 a and 8 b show an eighth preferred embodiment of the bucket shaped outlet 201 where the outlet has a bottom surface 203 similar to that shown in fig4 a and 4 b parts of preferably the complete bottom surface 203 are perforated with strainer holes or.