Reinforcing ridges are formed so as to project from corner portions of peripheral walls, and an opening end edge is made thick-walled, so that an ink cartridge having a sufficient rigidity can be molded using vapor impermeable soft synthetic resins. In addition, shape keeping ribs are formed so as to...http://www.google.de/patents/US6250750?utm_source=gb-gplus-sharePatent US6250750 - Ink cartridge and loading mechanism for ink cartridge
