Separating stones from wood, e.g. wood chips or sawed timber, by analysing noise inside vibrating boxes to detect presence of stones

摘要

Small pieces of wood are transported in a forwards direction by tilting and vibrating boxes (6) inside the separation machine. Noise from inside the box, which varies according to the wood material hardness and density, is processed electronically, and any noise caused by a stone striking against the inside of the box is converted into an electric signal for carrying out stone separation. The separation machine includes a trough having an inlet end with a rotating roll and an outlet end with one or more reversible, clad rolls for the wood. The machine contains a number of enclosing, vibrating box constructions. The box constructions are provided with measuring devices (10) for recording any change in frequency and amplitude/noise level.