Pen printer

A pen printer for converting data into printed form on a print sheet placed on a platen, comprising:

• means, including a plurality of ink pens movable into direct contact with said print sheet, for printing information on said print sheet in different colors;
• a pen carriage mounted for reciprocating movement above said platen, said pen carriage having means for removably attaching each of said ink pens juxtaposed in the direction of movement of said pen carriage, said pen carriage has a plurality of cartridge guide slots for receiving said respective ink pens thereon, lock members rotatably mounted on said pen carriage, each of said lock members having a hook resiliently urged for engagement with corresponding one of said ink pens, and resilient means for urging said ink pens to hold the same in engagement with said hooks, respectively;
• pen actuators mounted on said pen carriage apart from said ink pens, said pen actuators being free from attachment to said ink pens, and each pen actuator being responsive to an electrical signal for bringing a corresponding one of said ink pens toward said platen into contact with said print sheet;
• a carriage actuator responsive to an electrical signal for moving said pen carriage;
• a sheet feed mechanism responsive to arrival of said pen carriage to at least one of first and second predetermined positions separated from each other for feeding said print sheet a predetermined length on said platen;
• and
• a control circuit for converting said data into electrical signals to control said pen actuators and said carriage actuator.