Abstract: An automatic pressure valve primarily intended for use in compressors comprising a closing element in the form of a plate, a valve seat with a valve seat face, springs and a stop, the closing plate being so situated in the closed state of the valve that the face of the plate at the cylinder side is below the outer dead center position of the piston. In its top position, the closing element forms with the valve seat face a toroidal shaped gap which in axial section is similar in shape to a De Laval nozzle. The closing element is moved to its lower position, namely into contact with the valve seat face by lowering of the piston on which it rests.