Valve unit for interrupting or releasing a flow of a medium along a hollow duct, use thereof in a dosing system for the metered discharge of said medium, and method for the metered discharge of a medium

A valve unit is disclosed for the interruption or release of a pressurized flow of a medium along a hollow duct, which flows along the hollow duct, as well as a preferred use of the valve unit in a dosing system and a method for the metered discharge of a medium from a cartridge-needle configuration, with a cartridge connected to the needle configuration via at least one hollow duct with an open cartridge end, to which a pressurizing means is applied, which is capable of driving the medium provided inside the cartridge in the direction of the needle configuration for discharge by applying pressure. The invention has at least in a section along the hollow duct in which at least one first magnet unit is mounted to be axially movable longitudinally along the flow direction of the medium through the hollow duct, for generating a first magnetic field, a second magnet unit providing second magnetic field interacting with the first magnetic field in such a way that a magnetic force which mutually attracts the magnet units axially acts between the first and the second magnet units, and a mechanical stop along the hollow duct, against which the first magnet unit is drivable using a retention force which may be generated by the magnetic force.