the outlet socket 12 at the upper edge of the agitator panel 13 this panel is clamped against the bounding wall of portion 11 by means of a central clamp rail 21 and two shorter end clamping rails 22 which abut the agitator panel at the side thereof which is provided with the covering 15 and are secured to the bounding wall of portion 11 by screw connections 23 comprising screws which extend through the clamping rail and the bounding wall and nuts tightened against the outside of the bounding wall with a lock washer there between thus it will be seen that the upper edge of the agitator panel is tightly engaged with the inner surface of the bounding wall so as to prevent pulverulent material received by the bin from penetrating between the agitator panel and the bounding wall considering the fact that the bounding wall of the conical lower portion 11 is it is preferred to arrange several separate clamp rails as shown herein though it is also possible within the scope of the invention to have a single rail which extends continuously along the upper edge of the agitator panel the problem referred to above is encountered not only.