Ink jet printing apparatus

Ink jet printing apparatus for printing documents being transported along an independently operated conveyor comprising:

• a control console;
• a printing arm movably mounted on said control console for movement between a storage position which is clear of said conveyor and a printing position above said conveyor;
• tachometer means supported by said printing arm for sensing the speed of movement of said documents and generating a corresponding tachometer signal;
• printing control means mounted within said control console for receiving said tachometer signals and generating printing control signals in synchronism therewith;
• a print head carriage movably supported by said printing arm;
• print head positioning means for adjusting the vertical position of said carriage relative to said printing arm;
• and
• an ink jet printing head mounted on said carriage;
• said ink jet printing head comprising means for generating a plurality of printing jets arranged in at least one line extending in a sideward direction generally transverse to the direction of document travel along said conveyor, and means for controlling the printing operation of said printing jets in response to said printing control signals.