Abstract: A milling apparatus comprises a container with a plate extending across the container and movable relative thereto by an oscillator which communicates oscillatory movement to the plate at right angles to its plane. The oscillation can be tuned so that the natural frequency of oscillation of the plate and communication means is the same as or a whole number multiple of the oscillation frequency of the oscillator. The oscillator comprises a rotatable eccentric member driven to provide mechanical oscillations. The plate within the container acts to agitate grinding elements provided within the container. The container can either be used in a batch mode by moving the plate from an inlet to an outlet or in a continuous flow mode in which the comminuted material passes the plate from an inlet to an outlet.

Abstract: A cavitator comprising a cavitator plate mounted within a container is vibrated by an oscillator comprising a mechanically rotatable eccentric body to provide low frequency high power vibration. A mechanical linkage between the oscillator and the cavitator plate is tuned so that the frequency of oscillation matches the natural frequency of vibration of the linkage. The tuning can be achieved by modifying the length of the linkage or by choosing the necessary properties of the linkage or by varying the frequency of vibration of the oscillator. Various possible linkages include a pipe formed in sections, an elongated beam supported at its nodes, an annular pipe, and a pipe arrangement with overlapping section. The arrangement is of particular advantage when used with complex cavitator plates including vanes, paddles or rods or when using a cage grinder incorporating a plurality of balls for acting upon the material.