Patent ID: 8297744

Claim:
A functional liquid supply apparatus comprising: a plurality of sub tanks which supply functional liquid to a plurality of ink jet type functional liquid droplet ejection heads via a head side channel respectively, a tank unit which replenishes the functional liquid to the plurality of sub tanks by pressurized liquid feeding, a functional liquid channel having a main channel of which an upstream side is connected to the tank unit, a branch channel of which an upstream side is connected to the main channel, and a plurality of branching channels of which an upstream side is connected to the branch channel and a downstream side is connected to each of the sub tanks, a plurality of branching channel opening and closing devices which is provided on each of the branching channels and replenishes the pressurized functional liquid fed from the tank unit to each of the sub tanks by opening and closing action, and a liquid feeding control device which controls the tank unit, the tank unit including: a pair of main tanks which stores the functional liquid; a liquid pressurizing and feeding device connected to the pair of the main tanks; a switching device having a pair of tank channels of which an upstream side is connected to the pair of the main tanks and a downstream side is connected to the main channel and a pair of tank opening and closing valves interposed in each tank channel, and which is capable of switching the pressurized liquid of the functional liquid fed from the pair of the main tanks alternatively, a pair of weight measuring apparatuses which measure a weight of each main tank, and a pair of bubble detection sensors discretely provided on each tank channel and detecting a bubble in the functional liquid flowing in each tank channel, wherein the liquid feeding control device makes the switching device switch from one main tank side to the other main tank side when the functional liquid of the one main tank is consumed to a predetermined weight and the bubble is detected in a corresponding one tank channel based on measurement results of the pair of weight measuring apparatus and detection results of the pair of bubble detection sensors.