The best Twin Screw Extuder you are seeking for
The invention relates to twin screw extruder comprising a cylinder having twin bores therein to receive the twin screw and enclosed by a cylindrical casing, with at least one passage to allow heating or cooling fluid to flow between the cylinder and the casing. A difficulty encountered in the Single Screw Extruder heating or cooling of cylinders in twin screw extruder where the bores partially overlap, is that the portions of the cylinder which absorb the greatest quantity of heat per unit are inwardly directed wedge-shaped sheet production extruder projections at the sides of the region where the twin bores overlap.
Such wedge-shaped projections can be cooled adequately only with a large technical outlay. In previously proposed twin screw extruder, the cylinder enclosing the twin screw is in extended form, i.e. it is constructed with two flat outer faces each extending parallel with the plane in which the axes of the twin bores lie. This cylinder, which is difficult to produce in its basic shape, has a helical groove cut into its periphery, to guide the heating or cooling fluid around the cylinder in a helical path..
The cylinder is surrounded by a circular casing and the gaps between the upper and lower surfaces of the cylinder and the inner wall of the casing are filled with separate chordal segments. Such a twin screw extruder is expensive to manufacture and it is difficult to maintain a seal between the cylinder and the segments. The invention has among its objects to provide a twin screw extruder of the above described kind wherein positive guidance of the heating or cooling fluid is obtained at relatively low manufacturing cost using favourably shaped basic components.
According to the invention there is provided a twin screw extruder comprising a cylinder having twin bores therein to receive the twin screw of the extruder and a circular casing, with at least one passage to permit heating or cooling fluid to flow between the cylinder and the casing, in which the cylinder has a generally circular outside contour with a first set of grooves and a second set of grooves forming parts of said at least one passage.extending obliquely to the longitudinal axis of the cylinder and formed in the outer surface of the cylinder, the bottom walls of the grooves extending parallel to a plane which includes the two longitudinal axes of the twin bores with the first set of grooves lying on one side of said plane, and the second set of grooves lying on the other side of said plane, the inclination of said first set of grooves to said axis being opposite to the inclination of said second set of grooves to said axis, and the inside of the casing containing spaced recesses forming further parts of said at sheet production extruder least one passage and, The twin screw extruder is thus positively guided in said at least one passage between the cylinder and the casing in a helical path without any great outlay in manufacture.