US Patent 9403367 Printing machine

A printing machine has a printing unit which has a printing-material conducting element that can be rotated about an axis of rotation defining an axial direction and at least four printing heads. Four positioning devices are arranged, by the use of each of which, at least one printing head can be arranged at least either in a respective printing position associated with the printing head or in a respective idle position associated with a printing head. At least one first printing head of the printing heads can be arranged either in a first printing position associated with that first printing head or in a first idle position associated with that first printing head. At least one second printing head of the printing heads can be arranged at least either in a second printing position associated with that second printing head or in a second idle position associated with that second printing head. Each respective idle position is configured as a respective maintenance position, in which a maintenance device configured as a cleaning device is or can be associated with at least one nozzle of the respective printing head. The maintenance device is arranged in such a way that the maintenance device can be moved along a provision path at least partially orthogonally to the axial direction.