of the sector is free of the liquid phase which was passing therethrough with the prior art sector having an internal volume of 19 63 liters reference b it was found that the internal volume of the sector was never completely filled with the liquid phase which passes therethrough and that as shown in fig4 the commencement of discharge of the liquid phase occurs when the sector has already covered an angle u03b3 of about 172 5 u00b0 with respect to its starting position in respect of which u03b3 is equal to 7 5 u00b0 fig4 in association with fig3 clearly illustrates the beginning of discharge of the liquid phase in fact if we consider the starting position 30 of a sector which has just been immersed with respect to the level dd 39 of the suspension in the trough 37 corresponding to 50 immersion of the drive shaft 32 that position 30 corresponds to an angle u03b3 which is in fact equal to 7 5 u00b0 when the disc 32 comprises for example 24 sectors with an apex angle of 15 u00b0 when the sector 30 reaches position 33 it has already covered an angle of 172 5 u00b0 with respect to its starting position and the angle u03b3 as measured in the direction of rotation of the disc 32 is then 180 u00b0 beyond u03b3 180 u00b0 the sector occupies the position 34 corresponding to the drainage angle u03b1e then in position 35 it passes into the blowing region corresponding to the angle u03b1s in the course of which the cake deposited on the faces of the sector is deflected by deflectors 36 finally the sector 35 passes into a non productive region represented by the angle u03b1m referring to fig3.