The realization at the end of the screw
If the viscosity is lower, the conveying rate through the extruder screw is also reduced, so that with the outer ring stationary, the planetary pump would have too high of a conveying rate and an underpressure would result in the transition zone. Pursuant to the present invention it is then possible for the outer ring to rotate somewhat. In so doing, the conveying rate of the planetary pump is reduced, so that again the same conveying rates exist between planetary pump and extruder screw. The setting of the brake can either be prescribed on the basis of empirical values as a function of the viscosity of the material that is to be conveyed, or there is effected an automatic adaptation that is then based, for example, upon a pressure measurement in the transition zone between sheet production extruder screw and planetary pump. With this embodiment, a control device is activated by the pressure sensor that is provided there, and in turn sets the force of the brake.
In a modified embodiment, it is also possible, instead of the brake, to use a separate drive motor that permits an even more sensitive adjustment. The inventive approach makes it possible to realize a load-symmetrical conveyance. The helical gearing of the planetary pump, in other words also of the planetary pinions, permits a volumetric conveyance. The helical gearing can have any suitable angle, for example an angle of 10to 60 degrees, preferably somewhat greater than 20 degrees.
The planetary pump is self-cleaning, and can support the end of the screw. Due to the realization at the end of the screw, an economical manufacture is possible, and the occurrence of leakage streams through gears or pinions toward the outside, as with a gear pump, is not possible. As a consequence of the planetary pump, a good output can be realized, and there results a volumetric conveyance that is independent of the material to be conveyed. On the other hand, the inventive approach ensures that the planetary pump will always be supplied with material, so that it will also always convey. In a manner known per se, an extrusion nozzle , which is indicated only schematically, is provided on the output side.It can be seen how the planetary carrier supports the planetary pinions. Relatively large recesses are provided so that the material that is to be extruded need overcome only low resistance to flow.The specification incorporates by reference the disclosure of German priority.The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims. Further advantages, details and features can be seen from the following description of one exemplary embodiment with the aid of the drawing.