Patent ID: 7901063

Claim:
An ink circulation system for use in a drop on demand inkjet printing apparatus, the ink circulation system comprising: an inkjet printhead arranged to eject ink drops therefrom; a supply path arranged to supply an ink to the inkjet printhead and a return path arranged to return a surplus of the ink, that is not used to eject ink drops from the inkjet printhead; a refresh path arranged to couple the return path with the supply path to refresh the supply path with the surplus of the ink returned by the return path; and an active through-flow ink degassing unit arranged to control a dissolved gas level of the ink, the active through-flow ink degassing unit including an ink entry arranged to receive a flow of ink and an ink exit arranged to deliver a flow of degassed ink; wherein the active through-flow degassing unit further includes a vacuum connection arranged to apply a vacuum, and a semi-permeable membrane arranged to provide a surface area where the ink and the vacuum come into direct contact with each other without the ink penetrating the semi-permeable membrane.