The essence of the new design is that the rotor has pivoting hammers, each hammer has the shape of a circle section with an angle of at least 35°, and the attaching point of the hammer coincides with the axis of symmetry of the circle section near its base. This design prevents the particles of fragmented material, when struck by the hammers, from moving in a circular path and forming a rotating ring. In- stead, the particles move approximately radially with re- spect to the screen. This results in a quicker passage of the material through the screen. Figure 2 shows the design of