A device for conveying a mixture of substances includes a delivery cylinder having perforations and is configured to separate, through the perforations, mixture components from the mixture of substances. A material feed space is connected to an inlet side of the delivery cylinder and delivery line is connected to the outlet side. A delivery piston is reciprocatable through the material feed space and the delivery cylinder. A closure member is disposed at the outlet side of the delivery cylinder or in the delivery line and is movable between open and closed positions. A control unit is operable to move the delivery piston and a drive mechanism operable to move the closure member. The control unit is configured to respond to displacement signals of the delivery piston so as to cause a closing movement of the closure member and is configured to respond to output signals of an upstream pressure sensor so as to cause an opening movement of the closure member.