Patent ID: 7163164

Claim:
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 , 4 a , 4 b ) attached to the receptacle and dividing the receptacle into an upper part ( 5 ) located above comb ( 4 , 4 a , 4 b ) and a lower part ( 6 ) located underneath comb ( 4 , 4 a , 4 b ) characterised in that said fixed comb ( 4 , 4 a , 4 b ) 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.