Casing for a machine, with several parallel screws, for treating materials

A process for the production of a casing for n parallel screws of a treatment machine, which screws penetrate into one another and are caused to rotate inside said casing, the internal wall of said casing comprising n adjacent cylindrical sectors each subtending an angle A and having a radius r and each covering one said screw over that part of the periphery of said screw which is outside the zone of penetration of said screw, said process comprising:

• producing n shells, each of which has an internal face in the form of a cylindrical sector having a radius r and subtending an angle B, said angle B being less than said angle A;
• producing n guide bars, each of which has two concave faces forming a V, each said concave face being in the form of a cylindrical sector having a radius r and subtending an angle ##EQU7## the axes of said concave faces being parallel and spaced apart by a distance equal to the distance between the axes of said screws;
• connecting said guide bars to one another by means of joining members so that the axes of said concave faces coincide in pairs;
• and
• fixing each shell to two guide bars so that the axis of the internal face thereof coincides with the axes of the corresponding concave faces of said guide bars, and so that the unit consisting of a respective said shell and of two adjacent said guide bars forms a cylindrical sector subtending an angle A.