An ink cartridge incorporating a memory chip includes a housing having a top wall, a bottom wall and plural side walls defining the exterior of the cartridge for enclosing a supply of ink. The bottom wall having an aperture formed therein to provide an opening through the exterior surface of the bottom wall. A pocket-like structure is formed within the bottom wall and/or on an inside surface of the bottom wall. A substrate including a memory chip is received in the pocket-like structure, the substrate including at least one electrical contact that faces the aperture so as to be accessible by a contact member external to the cartridge when the cartridge is mounted in a printer's cartridge receiving receptacle.

An ink jet carriage assembly for an off-axis ink delivery ink jet printer including a movable print carriage; a plurality of ink jet printhead cartridges removably supported by the movable print carriage having cartridge septums for accepting respective ink delivery needles; a humidor structure located adjacent the cartridge septums for collecting ink from ink delivery needles when air is purged from ink delivery tubes connected to the ink delivery needles, and for containing or enclosing the ink delivery needles to prevent ink evaporation from the ink delivery tubes. A dummy cartridge collects ink from an ink delivery connector when air is purged from an ink delivery tube connected to the ink delivery connector.

A color ink jet printing device has an off-board ink reservoir for each color being printed. Each reservoir comprises at least two separately replaceable cartridges from which ink is supplied under positive pressure to refill replaceable printhead cartridges. A visual indicator is provided for each off-board cartridge to indicate when the cartridge is empty and this indicator is turned on if the ink supply in the cartridge is exhausted during a refill operation. Printing is not stopped until all off-board cartridges holding one color of ink are empty. At this time the empty cartridges that held any color ink, are replaced. After each operator intervention to replace empty cartridges, the volume of each color ink will be (N-1)/N of maximum reservoir capacity where N is an integer greater than one and represents the number of cartridges in the reservoir. The empty status of a reservoir cartridge is determined by sensing the level of ink in the printhead cartridge a fixed time interval after initiation of a refill operation from the reservoir cartridge.

A thermal ink jet printhead for a printer has a temperature sensor attached thereto for monitoring the operating temperature thereof. A maximum printhead operating temperature is stored in a memory of the printer's control circuitry and, if the printhead temperature sensed by the temperature sensor during a printing operation exceeds the maximum operating temperature stored is the memory, a signal is generated indicating that the printhead has stopped ejecting ink droplets and must be checked for depriming or a depleted ink supply.

An ink cartridge for an inkjet printer includes a housing for supporting an ink supply in a cavity within the cartridge housing and a color or ink type discrimination structure connected to the cartridge housing, the color discrimination structure being when assembled a generally cylindrical structure having a keyway formed therein wherein the color or ink type discrimination structure may be oriented through rotation about the central axis of the cylindrical structure in one of plural allowable orientations when the cartridge housing is assembled or after assembly to define a color or ink type of ink in the cartridge. Thus, the same structure or parts may be used in different cartridges containing ink of different colors but yet provide color discrimination.