Ink delivery apparatus for inkjet printhead

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 said reservoir when some ink in the reservoir is delivered to the printhead and in response to the ink delivery replenishes some ink to said reservoir from an ink supply source, is characterized in that:

• said pressure regulator and ink replenishment mechanism includes a pressure regulator membrane that air-tightly covers an opening in said reservoir and is compliant to maintain substantially constant negative pressure in said reservoir by deforming inwardly when some ink in said reservoir is delivered to the printhead and by returning outwardly when some ink is replenished to said reservoir, and a replenishment activator that is connected to said pressure regulator membrane outside said reservoir to avoid being exposed to the ink and which initiates ink replenishment to said reservoir when said pressure regulator membrane deforms inwardly and terminates ink replenishment when said pressure regulator membrane returns outwardly.

An ink delivery apparatus for an inkjet printhead, comprising an ink reservoir for the printhead, and an ink conduit that empties into said ink reservoir, is characterized in that:

• a valve membrane air-tightly covers an opening in said reservoir and normally caps said ink conduit to prevent said ink conduit from emptying into said reservoir, but is compliant to uncap said ink conduit to allow said ink conduit to empty into said reservoir.

A method of replenishing ink in a reservoir that drains ink to a printhead in a drop-on-demand inkjet printer, comprising:

• deforming a compliant valve membrane to uncap an ink conduit to allow the ink conduit to replenish ink in the reservoir, when a compliant pressure regulator membrane is deformed because ink has been drained from the reservoir to the printhead;
• and
• returning the compliant valve member recap the ink conduit to prevent the ink conduit from replenishing ink in the reservoir, when the compliant pressure regulator membrane is returned once ink is replenished to the reservoir.