Machine for indirect ink-jet printing

A method for changing a printing roller in an indirect digital printing machine comprising:

• providing at least a printing unit comprising:
• a plurality of rollers which are mutually tangential and counter-rotating for transferring ink to a printing support, the plurality of rollers comprising at least a first printing roller and a counter-roller;
• a printing head configured for emitting ink onto the first printing roller when the first printing roller is in a working position at the counter-roller;
• a displacement device configured for moving the printing head towards and away from the first printing roller;
• a second printing roller initially arranged in a respective waiting position spaced from the working position;
• a transfer device configured for operating between the waiting position and the working position, the transfer device is connected to the second printing roller for moving the second printing roller from the waiting position to the working position;
• when the first printing roller ends a printing cycle, the first printing roller is configured to be removed from the working position and the second printing roller substituting the second printing roller for the first printing roller at the working position;
• the method comprising the steps of:
• moving the printing head away from the first printing roller then in the working position;
• removing the first printing roller from the working position;
• moving, by means of the transfer device, the second printing roller from the waiting position into the working position to thereby substitute the second printing roller for the first printing roller at the working position;
• moving the printing head towards the second printing roller when the second printing roller is in the working position.

A printing unit configured for an indirect digital printing machine, the printing unit comprising:

• a plurality of rollers which are mutually tangential and counter-rotating for transferring ink to a printing support, the plurality of rollers comprising at least a first printing roller and a counter-roller;
• a printing head configured for emitting ink onto the first printing roller when the first printing roller is in a working position at the counter-roller;
• a displacement device configured for moving the printing head towards and away from the first printing roller;
• a second printing roller initially arranged in a respective waiting position spaced from the working position;
• a transfer device configured for operating between the waiting position and the working position, the transfer device is connected to the second printing roller for moving the second printing roller from the waiting position to the working position;
• when the first printing roller ends a printing cycle, the first printing roller is configured to be removed from the working position, and the second printing roller is configured for substituting the second printing roller for the first printing roller at the working position;
• a removal position spaced from the working position;
• an additional transfer device which operates between the working position and the removal position;
• the first printing roller being connected to the additional transfer device for the first printing roller being moved by the additional transfer device from the working position to the removal position;
• the working position is located between the removal position and the waiting position;
• and
• the transfer device and the additional transfer device comprise guide rails extending respectively between the waiting position and the working position and between the working position and the removal position, the first and the second rollers being slidingly associated with each of the rails for sliding along the rails.