Replaceable ink bag and ink cartridge with replaceable ink bag

An ink cartridge with replaceable ink bag, comprising:

• a cartridge body, an ink bag and a lid body;
• wherein:
• the cartridge body being a hard-shell container with an opening;
• inner walls on long side of the cartridge body comprising at least a retention block, a gap existing between the retention block and an inner bottom of the cartridge body;
• the ink body further comprising an ink amount trigger, a bag body and a positioning element;
• the bag body being a bag container with changeable shape, filled with ink, the bag body further comprising a first bag surface and a second bag surface, disposed oppositely, the first bag surface being partially glued to the ink amount trigger, the ink amount trigger moving towards a predefined direction as the amount of remaining ink decreasing;
• the second bag surface being partially glued to the positioning element;
• surroundings of the positioning element having at least a retention element;
• when assembled, the retention element being inserted between the retention block and the inner bottom for fixing the ink bag inside the cartridge body;
• and
• the lid body being removably engaged to the cartridge body for opening and closing the opening of the cartridge body.