US Patent 9067424 Ink cartridge and mount/demount mechanism for the same

An ink cartridge includes: an ink storage container configured to store ink; a socket portion provided at one end of the ink storage container and configured to be fitted to and detached from a joint portion of a printing machine; an ink supply port provided in the socket portion; an inside plug configured to seal an ink passage to the ink supply port by using a biasing force coming from a direction of the ink storage container; and an inside plug lock portion configured to lock the inside plug at a position where the inside plug is pressed by an insertion shaft, and maintain a locked state of the inside plug independently of a retreating of the insertion shaft to a retreat position after a locking of the inside plug.