Crushers with ring-shaped track and roller

Grinder, including at least one annular track with a horizontal axis (14), at least one roller (16) capable of travelling over the said track, means for pressing the roller against the track, and means for displacing the material from one edge to the other of the track in such a way that it passes several times beneath the roller before being discharged, with the gap between the roller (16) and the track (14) decreasing in the direction of advance of the material to be crushed, wherein the said gap between the roller (16) and the track (14) decreases from the edge of the track located on the side of supply of the material to be crushed to a distance from this edge at least equal to 80% of the width of the track, and in that this gap then rapidly increases to form a decompression area (19) on the crushed material discharge side, and in that the track (14) is constituted by a ring integral with a coaxial drum (10) which forms a discharge chamber (15) on one side of the track, and an annular barrier (17) is provided at the end of the discharge chamber the furthest from the track to maintain, in the said chamber, a layer of crushed material the thickness of which is such that it practically reaches the edge of the roller in the plane of the adjacent edge of the track.