Device with a connecting valve

The device has two propulsion stroke-producing drives with pneumatic or hydraulic displacement systems having supply conduits. One of the supply conduits is closed by a main valve unit (161) that is arranged in a main valve chamber when the other conduit is opened. A non return valve chamber is provided in the main valve unit, and a spring loaded non return valve unit (182) is arranged in the non-return valve chamber, where the non return valve unit connects the conduits with each other when the latter conduit is relieved.