7 MECHANICAL APPARATUS FOR HANDLING OF BULK MATERIALS; PARTS AND FITTINGS THEREFOR, NAMELY CONVEYORS, DUST SEPARATORS AS COMPONENTS OF APPARATUS FOR HANDLING BULK MATERIALS, MIXERS, DISCHARGE DEVICES AS COMPONENTS FOR DRAINING BULK MATERIALS FORM CONTAINERS, FILTERS BEING PARTS OF MACHINES, VALVES, NAMELY SLIDE VALVES, FLAP VALVES, DIVERTER VALVES AND ROTARY VALVES, ALL BEING PARTS OF MACHINES, DISTRIBUTION DEVICES, NAMELY PIPES, TUBES, TUBES AND HOSES, ALL BEING PARTS OF MACHINES, PUMPS AND BLOWERS FOR THE PRESSURE-CONVEYING OF GRANULATED BULK MATERIALS, COMPRESSORS FOR MACHINES, AND CLASSIFIERS FOR SEPARATING BULK MATERIAL DEPENDENT ON PARTICLE SIZE