Abstract: In operation of a screw extruder, particularly a pin extruder, processing a rubber or a plastic mixture, troubling disturbances and on occasion heavy damage occur when foreign bodies are introduced into the extruder with the material to be processed causing damage to the extruder structure. In order to avoid this damage one possibility is to shut off the extruder at a sufficiently early time and of course immediately when an appropriate dangerous condition is detected. Therefore the drive torque which is taken by the extruder screw shaft is compared with the mass pressure in the mixture to be processed. As soon as this compared value no longer follows the functional dependence of the normal operating parameters such as the rotation speed of the extruder shaft, viscosity of the mixture, temperature lowering of the tempering medium, the volume increase of the mixture drawn in the extruder inlet or the like, the extruder is automatically shut off since a disturbance by foreign bodies is assumed.

Abstract: In the production of profiles from rubber and/or plastic mixtures, the throughput of the extruder should be kept constant. To this end, an identification of the mixture of material to be processed is fed in the form of a code to a computer system in which the characteristic mixture properties and the set-point operating values for a given profile to be made by the extruder are stored in memory. During the extrusion process, at least one operating variable, preferably the pressure occurring in the mixture of material being processed, is measured continuously, the difference between a measured value at a given time and the corresponding set-point value of the operating variable stored in memory is formed, and this difference is used as a control variable for a governing system for the speed or rpm of the extruder which is operated by the computer system.

Abstract: A shear head in which an extruded vulcanizable composition meets preheated reinforcing strands has a compartment adjacent a mouth of the head which is evacuated to reduce the danger of gases affecting adhesion of the strands to the composition.