Air Sifting or Separating Machine Having Discharge Regulation

An air sifting or separating machine for a dry separation of raw material, comprising:

• a material feed mechanism;
• at least one carrier member that is provided with openings and is adapted to receive material from said material feed mechanism that is to be sifted or separated;
• a discharge mechanism for heavy material and light material layered on said carrier member during a sifting or separating process;
• means for passing a pulsating air stream, as working air, through said carrier member to loosen up and layer the material fed to said carrier member into a heavy material layer, which acts as a sifting or separating bed, and into a light material layer that is disposed on the heavy material layer;
• a control device, for said discharge mechanism, disposed at a downstream end of said carrier member as viewed in a direction of transport of the material, wherein said control device is operative via a radiometrical measurement of a thickness of the material, and wherein said control device is comprised of a source of radiation mounted on a wall of said sifting or separating machine, and of an associated scintillation unit that is adapted to measure absorption of radiation given off by said source of radiation;
• a protective pipe, wherein said scintillation unit is disposed within said protective pipe, and wherein said protective pipe is freely mounted at a suitably set distance from said source of radiation and within the sifting or separating bed in a stream of the material;
• and
• a support mechanism for carrying said protective pipe, wherein said support mechanism is connected to said sifting or separating machine and extends over said carrier member.