Abstract: An ink jet printer includes a movable carriage supported above an ink-receiving medium by a rail defining a carriage axis, with a cartridge holder mounted on said carriage having a plurality of cartridge compartments each receiving a respective thermal ink jet printer cartridge. Each cartridge is provided with three datum surfaces located on the perimeter of a sidewall of the cartridge, and sufficiently spaced apart from each other and from the center of gravity of the cartridge to provide accurate and stable alignment. More particularly, the nozzle plate of the cartridge is attached to a lower surface of snout portion such that the Y axis of the nozzle plate is substantially parallel to the first sidewall, with the first and second datum surfaces at the front and rear of a lower end of the ink reservoir portion straddling the snout and the third datum surface at an upper end of the ink reservoir portion.

Abstract: Precise alignment between two or more nozzle plates affixed to print cartridges installed in a single carriage of an ink printer is achieved by machining datum projections on each print cartridge after its nozzle plate has been permanently secured to the print cartridge. The machined datum projections on the print cartridge contact surfaces on the carriage when the print cartridge is installed in the carriage such that the dimensions of the datums affect the position of the cartridge, and hence the nozzle plate, within the carriage.

Abstract: In a printer carriage adapted for holding multiple pen cartridges in separate compartments, each carriage compartment includes one or more key-coded barriers at an entrance to the compartment to provide a first level carriage lockout scheme against non-matching cartridge tabs. A second level carriage lockout is provided to differentiate between different families of print cartridges which successfully pass through the first level lockout, which second level is based on predetermined barrier floor configurations in the bottom of each carriage compartment which block non-matching wings on particular print cartridge families.

Abstract: Precise alignment between two or more nozzle plates affixed to print cartridges installed in a single carriage of an ink printer is achieved by machining datum projections on each print cartridge after its nozzle plate has been permanently secured to the print cartridge. The machined datum projections on the print cartridge contact surfaces on the carriage when the print cartridge is installed in the carriage such that the dimensions of the datums affect the position of the cartridge, and hence the nozzle plate, within the carriage.