Abstract: A multistage continuous rotary screw press assembly with the helical or spiral collars, vanes or ribs of each stage within the casing separated from those of an adjacent stage in the direction of material feed through the casing by a transition zone in which fixed material impingement elements, for example, knives, are mounted for dividing the material as it is expressed from one stage to the next adjacent stage in the material feeding direction.

Abstract: An improved double-roll crusher is provided which is especially suitable for crushing bones having a relatively low content of soft matter, the crusher being of the general type comprising two parallel rolls, each comprising an assembly of alternating toothed cutting discs and spacers so disposed that cutting discs on one roll extend radially into the spaces between adjacent cutting discs on the opposing roll in an alternating manner, wherein the improvement comprises forming the toothed cutting discs so that the gap between adjacent teeth is trapezium-shaped, the sides of the teeth make a rake angle of 1.degree.-20.degree., the upper face of each tooth is beveled 5.degree.-35.degree., and the length of the larger base of the trapezium is close to the maximum desired particle size.