Nozzles for
single screw extruder annular shaped plastic products including a stationary column, a rotary head rotatably carried by the stationary column by at least one roller bearing cooperating along at least one cylindrical interface, with the stationary member including at least two supply conduits for the plastic
twin screw extruder and the rotary head including a corresponding number of continuation flow passages so that the plastic material can be transferred from the stationary column to the rotary head at the cylindrical interface. The cylindrical interface includes a portion having a predetermined diameter so that one of the supply conduits and its corresponding continuation passage is located at a predetermined intermediate location along that portion of the cylindrical interface, and that continuation passage includes the at least one roller bearing, and the nozzle includes packing glands located on opposite sides of the roller bearing along that cylindrical interface, so as to prevent plastic material from leaking from the nozzle.
When manufacturing tubular or hose-shaped products of plastics
sheet production extruder matter several problems are encountered, which depend upon the passage of the plastics matter through a nozzle, from which the matter is extruded. Homogenity and an even temperature are important.
In order to increase the strength of the product, it has been proposed to merge two or more part-flows of molten plastics matter at a common slot. Such procedure further makes it possible to use plastics of different colours and/or quality, so the product will have different colours inside and outside.
Rolling bearings in the nozzle part are subjected to high loads, but cannot be lubricated in the same manner as in conventional machines, as the grease would contaminate the plastics matter. The bearings must furthermore be located in such a manner as to prevent plastics from leaking out.
The aim of the present
twin screw extruder is to propose a nozzle for producing tubular or hose-shaped
single screw extruder, where a good control of the quality of the plastics flow is obtained, and where it is possible to locate the bearings in advantageous positions, and to provide an efficient lubrication with small risk of leakage.
