Abstract: Tooth assemblies upon the breaker rings of the rotor of the apparatus each include tooth and seat components having abutting surfaces that prevent forward, rearward, inward and lateral movement of the tooth relative to the seat and rotor. Outward tooth movement during operation of the apparatus is prevented by a pin that extends generally parallel to the rotor axis through aligned bores within the tooth and its seat. The pin is shielded from damaging impacts with the material being ground and from detrimental bending stresses, and is releasably retained within the bores by a detent that permits convenient removal of the pin when replacement or repair of the tooth is required.

Abstract: The grinding chamber of the apparatus has first and second grinding sections having perforate wall sections overlying the outlet of the apparatus. The perforate wall of the first grinding section underlies the rotor of the apparatus and has an arcuate shape. The perforate wall of the second grinding section extends generally tangentially upwardly and outwardly from the downstream end of the perforate wall of the first grinding section. The second grinding section is larger than the first, and may include breaker bars which deflect the material being ground toward the perforate wall of such section.

Abstract: Shear pins indirectly interconnecting breaker rings and shaft components of the rotor assembly of the apparatus are so located and mounted as to be readily replaceable when sheared by relative rotative movement between the components. Relative rotative movement of the components is detected and changes the operating condition of the drive motor and/or a signaling device associated with the apparatus.

Abstract: A breaker tooth member for apparatus for the reduction of solid material such as wood, plastics, metal and the like comprises a metal head having an integral projecting mounting shank having an enlarged portion adjacent the head adapted to fit snugly in an enlarged mounting bore portion of a support ring, the head being formed opposite the shank with a recess having a flat back face intersecting a ledge defining a locking formation, and an integral harder wear resistant metal sharp edged element is mounted in the recess flush against the back face, that element being correspondingly formed along one edge to interlock with said ledge, and the element is fixed on the head by a plurality of pins having tight friction fit in aligned bores in the head and the element.