Patent ID: 8763939

Claim:
A method of crushing material comprising the steps of: feeding the material to a rotor; crushing the material by said rotor to pieces of different sizes; forwarding said pieces of different sizes to at least two secondary crushing rotors; hitting the pieces of a first size on impact surfaces of the first secondary crushing rotor; hitting the pieces of a second size on the impact surfaces of the second secondary crushing rotor; adjusting an angle between the impact surface of the each secondary crushing rotor with respect to the movement directions of these material pieces to a value from approximately 76 to approximately 104 degrees at the moment of the impact, hitting said pieces on said impact surfaces at a time interval between impacts of the first and second secondary crushing rotors defined with use of the expression Δ t =(0.7 . . . 1.3)( R 1 /V 1 −R 2 /V 2 ), where R 1 is a distance from a place, where the most distant from the rotor rotation axis point of the impact surface of the rotor is at the minimum distance from the end of a feed track, to the place, where the first secondary crushing rotor hits the material pieces of said first size, R 2 is a distance from the place, where the most distant from the rotor rotation axis point of the impact surface of the rotor is at the minimum distance from the end of the feed track, to the place, where the second secondary crushing rotor impacts the pieces of said second size, V 1 is an average velocity of the pieces of said first size forwarded towards the first secondary crushing rotor, and V 2 is an average velocity of the pieces of said second size forwarded towards the second secondary crushing rotor.