Patent ID: 7207504
Filing Date: 2007-04-24
Classification: B02C

Abstract:
1. A grinder for producing small particles from material, comprising: a housing having an inner wall; a rotatable mechanical member in the housing having a periphery adjacent the inner wall; a drive for driving the rotatable member for causing the rotatable member to create an annular flow of air between the periphery of the member and the inner wall, and for establishing a grinding zone between the periphery and the inner wall which comprises: (a) a first region in which a heavy gas is established, the first region being between the inner wall and an intermediate position between the periphery of the member and the inner wall; (b) a second region for receiving relatively large particles compared to the particles which make up the heavy gas, the second region being between the intermediate position and the periphery of the mechanical member; and (c) a shear zone between the first and second regions at the intermediate location; and wherein the relatively large particles received in the first region come into contact with the heavy gas particles across the shear zone where the relatively heavy particles are comminuted into smaller particles, some of which add to the heavy gas within the first region and the other of which form small particles of a size which do not behave as a heavy gas, and wherein the small particles, together with some of the particles which make up the heavy gas and other larger particles from the first region move out of the grinding zone with an annular flow of air from the grinding zone and travel to a first collection outlet for collection or fall back to the mechanical member and again travel to the first region for further grinding in the grinding zone; and wherein the rotatable member comprises a disc having vanes for creating the annular flow of air between the periphery of the disc and the inner wall, said vanes having an arcuate shape for directing air in the same direction as intended rotation of the disc for accelerating gas particles from an inner peripheral portion of the vanes to the periphery of the disc to create sufficient acceleration to enable the gas to exit the vanes in the direction of rotation of the disc without producing any substantial turbulence.