Device for grinding up non-metallic pieces

A device for grinding (1) non-metal parts (2) comprising at least one motor-driven rotating shaft (11) inside a receptacle that receives non-metal parts that are to be ground, said shaft (11) having a plurality of teeth (8) intended to shred and grind said non-metal parts (2), said teeth (8) being arranged radially in rows around the periphery of shaft (11) so as to cooperate, when they rotate, with teeth (15) of at least one fixed comb (4, 4a, 4b) attached to the receptacle and dividing the receptacle into an upper part (5) located above comb (4, 4a, 4b) and a lower part (6) located underneath comb (4, 4a, 4b) characterised in that said fixed comb (4, 4a, 4b) comprises an electrically conducting base (41, 42) held at a specific potential and an electrically conducting surface (14) that faces the upper part (5) of the receptacle and is electrically insulated from said base (41, 42) and held at a potential that is different to that of base (41, 42) so as to detect the presence of metal parts by making the electrical circuit thus produced.