Abstract: A method and apparatus for protecting a mixing apparatus for producing strand-shaped explosives and propellants in a twin-shaft screw extruder, the housing of which is formed of housing parts connected to a clamping device acting under hydraulic pressure. In order to compensate for excessive pressure and to prevent abrupt opening of the mixing chamber, the torque developed at the screw shafts is continuously monitered and fed to a control and storage device together with temperature and pressure values measured at the end of the screw shaft in the material being processed. If one of the measure values exceeds a permissable limit, a signal is produced to change the operating condition of the screw extruder, particularly to stop and withdraw the extruder from the housing, to halt the drive motor of the extruder shafts and to open the extruder housing by relieving the clamping device.

Abstract: A method for the multi-stage compression of a mass in a press, especially an extrusion press containing plastic or elastic masses. The mass to be extruded is precompressed up to a preliminary pressure by the rapid advance of the pressure piston. The initial advance takes place at a high rate without the occurrence of impermissibly high temperatures of the mass or the enclosed gas. The subsequent compression to higher pressure levels takes place in a sequence of stages in each of which the rate of advance of the pressure piston is constant. The rate of advance is increased from stage to stage until a final extrusion pressure is reached. An apparatus for carrying out the method of the invention includes a hydraulic flow rate regulator which is controlled on the basis of signals that are related to the pressure measured in the hydraulic system. The pressure signals may be derived by potentiometers energized by pressure-dependent switches.

Abstract: A method for pressure buildup in a pressing cylinder of a press for a plastic or elastic material, wherein the material, under the influence of the advance of a plunger, is initially precompressed slowly to reach a pre-extrusion pressure and then the pressure is raised and adjusted to the extrusion pressure for the material and maintained at this level. The differential quotient of the pressure rise as a function of time is predetermined as a criterion for reaching the pre-extrusion pressure, and compression is carried out up to this point at a constant low plunger advance rate, with a constant rise in pressure thereafter up to the extrusion pressure.A circuit for carrying out the method includes at least one valve incorporated in the hydraulic feed line to the hydraulic cylinder in which the piston is positioned. The valve is controllable initially by a volume sensor and then by a pressure-rise control means for the hydraulic fluid.