Abstract: An ink delivery apparatus for an inkjet printhead, comprising an ink reservoir for delivering some ink at a slight negative pressure to a printhead, and a pressure regulator and ink replenishment mechanism that maintains substantially constant negative pressure in the reservoir when some ink in the reservoir is delivered to the printhead and in response to the ink delivery replenishes some ink to the reservoir from an ink supply source, is characterized in that: the pressure regulator and ink replenishment mechanism includes a pressure regulator member that air-tightly covers an opening in the reservoir and is compliant to maintain substantially constant negative pressure in the reservoir, and a replenishment activator connected to the pressure regulator member outside the reservoir to avoid being exposed to the ink and which initiates ink replenishment to the reservoir when some ink in the reservoir is delivered to the printhead.