Single pass ribbon cartridge for impact printers having means to prevent incorrect insertion

A ribbon cartridge containing a ribbon for an impact printer comprising

• a cartridge housing,
• first and second reels rotatably mounted in said housing, each reel supporting a portion of an inventory of a ribbon web running in a path along one end of said cartridge housing from said first to said second reel,
• said cartridge housing having an open end opposite said one end, and
• a blocking element mounted in said housing adjacent to and blocking a portion of said open end in a position closer to one of said reels than to the other.

In an impact printer having means for receiving a ribbon cartridge and means for driving only one reel in said cartridge,

• the improvement comprising apparatus permitting the engagement of said cartridge and receiving means whereby only said one reel engages said driving means comprising
• a ribbon containing cartridge housing,
• first and second reels rotatably mounted in said housing, each reel supporting a portion of an inventory of a ribbon web running in a path along one end of said cartridge housing from said first to said second reel,
• said cartridge housing having an open end opposite said one end, and
• a rib mounted in said housing facing and blocking a portion of said open end in a position closer to said first reel than to said second reel, and
• wherein said receiving means includes a stop element disposed so as to impede said rib to stop the engagement of said cartridge and said receiving means when said cartridge is being inserted into said receiving means in a direction toward the engagement of said first reel with said driving means.