Abstract: In the operative position shown in FIG. 4 a printing roller abuts the cylindrical surface of an impression roller to cause ink to be transferred from an anilox roller via the printing roller to the impression roller. The gear wheel on the impression roller meshes with a gear on the printing roller which in turn meshes with a gear on the anilox roller to cause rotation of those three rollers.The printing roller and the anilox roller can be moved to the right, when viewed in FIG. 4, to move their co-operating cylindrical surfaces out of contact with each other, and yet still leave their gears in mesh in order to enable the printing roller to be changed and yet maintain the rotation of the anilox roller. A clutch is provided to enable the printing roller to be stationary when being changed, or to enable the printing roller to be correctly aligned with the impression roller when brought back into co-operation therewith.