Patent ID: 8262209

Claim:
A circulating type ink supply system comprising: an upstream ink tank; an upstream ink flow channel connected at one end thereof to the upstream ink tank; a nozzle branch portion connected to the other end of the upstream ink flow channel and being in communication with a nozzle configured to discharge ink; a downstream ink flow channel connected at one end thereof to the nozzle branch portion; a downstream ink tank connected to the other end of the downstream ink flow channel and configured to store the ink flowed from the upstream ink tank via the upstream ink flow channel, the nozzle branch portion, and the downstream ink flow channel; a feedback flow channel configured to return the ink in the downstream ink tank to the upstream ink tank; a circulating mechanism configured to circulate the ink stored in the upstream ink tank from the upstream ink flow channel through the nozzle branch portion, the downstream ink flow channel, the downstream ink tank, and the feedback flow channel to the upstream ink tank; and a printing mechanism configured to discharge the ink branched at the nozzle branch portion from the nozzle portion for printing, wherein: with reference to ink at an atmospheric pressure at a level of the nozzle, an energy per unit volume, which is determined by a sum value of a static pressure and a potential energy of the ink in the upstream ink tank, both when the circulation of the ink is stopped and when the circulating mechanism operates does not exceed an energy per unit volume of the referenced ink.