Apparatus for measuring out pulverulent materials

In apparatus for measuring out pulverulent materials, which apparatus includes a screw presenting a side root surface and positioned, and rotatably mounted, in a barrel open at at least one of its ends, the improvement wherein the thread of said screw extends from said surface and is interrupted between only two diametrically opposite generatrices of the latter for causing said side surface to consist of a single threaded zone and a single smooth zone, and said apparatus further comprises fixed scraping means cooperating with said threaded zone of said screw, said fixed scraping means comprising several teeth lined up along an axis parallel to the longitudinal axis of the barrel, the distance between said teeth being equal to, or a multiple of, the pitch of the thread, each of said teeth having a profile such that it meshes with, and occupies substantially the entire space between, two consecutive threads of said screw, and drive means to rotate and reciprocate said screw in order to allow said threads to synchronously mesh with said teeth of said scraping means.