Abstract: In a convention throttle-controlled internal combustion engine (1, 2) equipped with a supercharger which has the form of a compressor (10) provided with screw rotors (14, 15) arranged in a compression chamber, the supercharger is inactive at part engine loads. Since the engine normally operates at part loads for about 95% of its running time, efficiency is correspondingly poor. This drawback is overcome with the arrangement according to the invention in which the screw compressor (10) is provided on the inlet side (20) thereof with a capacity regulating device (22) which is operated by a gas pedal, or accelerator, and which when the engine is only partially loaded, is adjusted to a corresponding position in which the compressor (10) operates as an expander (3) of variable throttle effect on the engine inlet side (3) and transmits power to the engine, thereby replacing the conventional gas throttle.

Abstract: A screw compressor for intermittent operation, preferably for supplying a pneumatic brake system of an automotive vehicle with compressed air, comprises, in the high pressure end wall (4) of the compressor, a wall plate (14) which seals against the casing wall (2) of the compressor and which can be withdrawn axially of the compressor out of sealing engagement with the casing wall and into a space (16) which is provided in the high pressure end wall, the space (16) communicating with the compressor inlet (12), to thereby fully unload the compressor.