Abstract: A rotary piston pump in which a slide valve has a pivot bearing at each of its ends which supports a sliding block and wherein a theoretical slide valve length in the position in which the axes of symmetry of the shell rotor and slide valve are superimposed, is equal to the sum of the length along the slide valve measured between the pivot bearings plus two times the thickness of a sliding block measured between its pivot bearing and the wall of the shell. The sliding blocks have an outer surface with a curvature between the curvature of the outer surface of the rotor and the maximum curvature of the wall of the shell.

Abstract: A control arrangement for effecting the reconveyance of exhaust gas over a larger engine operating range, while concurrently constructing the control to be more sensitive and better correlated with any particular thermal and/or mechanical operating condition of the internal combustion engine. The arrangement includes a multiple-position valve located in the conducting path of the control conduit, which is so located and constructed whereby the control pressure chamber of the control pressure chambers of the adjusting device are selectively subjected to a gas pressure and/or atmospheric pressure present in the intake conduit of the internal combustion engine upstream and/or downstream of the dosing arrangement for the combustion air or, respectively, the provided fuel-air mixture, or in the path of an accumulator associated with the control conduit.