Apparatus for mixing bulk materials
This invention relates to an apparatus for mixing bulk materials, such as granulated polyamide and other granular materials, which can be used in the chemical and food industries. 
     Apparatus for mixing bulk materials is known, and can comprise a vertical screw or outer elevator (fed by a horizontal screw), arranged under devices for displacing and mixing the material. In several cases in the upper part of the apparatus there is provided a second horizontal screw for mixing the fresh incoming material with the material introduced by the elevator. 
     It is a drawback of an apparatus of such design that it has a large number of movable parts which can be damaged, giving rise to the stopping of work during repair. 
     It is an object of the invention to avoid the drawbacks of known apparatus for mixing bulk materials by providing an apparatus for mixing bulk materials which is of simple design and operable to achieve a high degree of mixing. 
     This object is achieved by providing the apparatus, which comprises a vertical cylinder and an inclined bottom, along its axis with an internal pipe, and on its outer side there is fastened a vertical pipe, these pipes being connected at their bottom ends to a centrifugal ventilator (blower), while at the upper end of the internal pipe there is disposed a mixer. This mixer comprises two oppositely converging cones, connected at their bases and provided with blades at their outer surface. The mixer (rotor) is attached to rotate freely about an axis, which is fastened to the cover of the apparatus. 
     The advantageous features of the apparatus of the invention are its simple design, its reliability in operation and the high degree of mixing. Furthermore, it can be used for cooling the material and dust removal. 
    
    
     For a better understanding of the invention, reference should be made to the accompanying drawing, the sole FIGURE of which illustrates a preferred embodiment of the invention in a vertical elevational view, partly broken away of an apparatus in accordance with the present invention. 
    
    
     The apparatus for mixing bulk materials comprises a vertical cylinder 2 with bottom 15, which is suitably inclined in order to avoid any stagnant zones, to which there a fastened pipe connections 1 and 16. To pipe connection 16 there is fastened a pneumatic shut-off valve 17. 
     Along the axis of vertical cylinder 2 there is disposed an internal pipe 3, above which, in the cover 10 of the apparatus, there is fixed a mixer 13. This mixer comprises a long cone 4 and an upper cone 6, which are connected at their bases. To the bottom cone 4 there are fastened bow-shaped curved blades 5 while the upper cone is formed with radial blades 7. The mixer is attached freely to the shaft 8, which is fastened to the cover 10. 
     To the upper part of the vertical cylinder 2 there is connected an outer pipe 14. At the inlet of this pipe in the vertical cylinder 2 there is provided a sieve 12. The bottom end of the outer pipe 14 is connected to the suction flange (intake side) of ventilator or blower 18. The outlet flange of this ventilator (discharge side) is connected to the internal pipe 3. On top of vertical cylinder 2 there are provided an access hatch 9 and a pipe 11 for fresh incoming material. 
     The apparatus of the present invention operates as follows: 
     Ventilator 18 is switched on, which sucks gas from the vertical cylinder 2 through pipe 14. Sieve 12 prevents entry of particles of the material into pipe 14 and ventilator 18. The gas entrains the solids entering through pipe connection 16 and valve 17, and returns it back through the internal pipe 3 into vertical cylinder 2. 
     The flow coming out of the internal pipe 3 imparts a rotational motion to mixer 13 due to the bow-shaped curved blades 5, fastened to bottom cone 4. The rotation of radial blades 7 of the upper cone 6 causes the uniform spraying of the fresh material entering through pipe 11 which is trained on the mixer 13 and its mixing with the material recirculating through the internal pipe 3. The mixed material is discharged through pipe connection 1.