the pitch and shape of the treating thread portion of intermeshing rotary screws are within the professional knowledge of the expert the alternative embodiment of the apparatus as illustrated in fig4 and 5 is distinguished from the embodiment shown in fig1 to 3 merely by the fact that the plane outlet restricting closure element is not a flap but a kind of wedge body 15 presenting a plane inclined surface 16 to the material under discharge through aperture 10 and collar 10a which also in this embodiment has a generally outwardly flaring configuration as shown in fig5 and an oblique mouth opening by means 12 12a similar to those described in connection with the embodiment according to fig1 to 3 body 15 to shiftable between a position in which its plane surface 16 closes the plane opening defined by collar 10 and selective positions in which said plane surface 16 selectively uncovers the plane opening bounded by the free end of collar 10a in its shifting movement body 15 is supported by a bearing surface 17 carried by bed structure 13 as far as operation is concerned the description given in connection with the embodiment according to fig1 to 3 also applies to the embodiment according to fig4 and 5 it will be understood that other types of outlet closures may be provided within funnel like structures such as collars 13 permitting attachment.