Self-scraping mixers

A self-cleaning mixer comprising a housing having a top and side wall members which together define an inner chamber, said inner chamber having an inner face, at least two blades rotatably mounted within the housing, said blades having a cross section defined by at least two arcs of a circle having the same length and the same radius R, and means for rotating these blades about their axes, said blades being arranged and dimensioned so that during their rotation their edges scrape the inner face of the inner chamber as well as the lateral faces of each blade, these blades remaining constantly staggered in relation to each other by the same angle A when they are in mutual contact, the inner face of the inner chamber and the outer faces of the blades extending along truncated cones having the same apex with the axes of rotation of the blades passing through this apex wherein the radius R is given by the formula:

• ##EQU5## in which the coefficient K is equal to cos A/2, D is the diameter of the envelope circle of the cross-section of a blade during its rotation and m is given by the formula:
• ##EQU6## where angle B is the semi-angle at the apex, at least equal to 5 degrees, of the envelope conical surface of a blade during its rotation.