Patent ID: 8360563

Claim:
A liquid droplet jetting apparatus which jets liquid droplets of a liquid stored in a main tank, comprising: a main-tank attachment section to which the main tank is detachably attached; a sub tank having a liquid storage chamber communicating with the main tank attached to the main-tank attachment section; a liquid droplet jetting head having: nozzles from which the liquid droplets are jetted; channels, each of which communicates with the sub tank and guides the liquid flowed from the sub tank to the nozzles; and a pressure applying mechanism which applies, to the liquid in the channels, a pressure directed toward the nozzles to jet the liquid droplets from the nozzles; a volume changing mechanism which changes a volume of the liquid storage chamber of the sub tank; a counter-flow preventing mechanism which prevents a counter flow of the liquid toward the main tank from the liquid storage chamber of the sub tank; and a controller which controls the volume changing mechanism to change the volume of the liquid storage chamber and to suppress a pressure fluctuation in the liquid storage chamber in a liquid-droplet jetting mode of jetting the liquid droplets with the pressure applied by the pressure applying mechanism, and which controls the volume changing mechanism to change the volume of the liquid storage chamber and to transport the liquid in the liquid storage chamber to the liquid droplet jetting head in a purge mode of discharging the liquid in the liquid droplet jetting head forcibly from the nozzles; wherein the counter-flow preventing mechanism is a non-return valve mechanism including a valve element which is movable toward an opening position to open the channel upon receiving a flow of the liquid from the main tank directed toward the liquid storage chamber, and which is movable toward a closing position to close the channel upon receiving a counter flow of the liquid from the liquid storage chamber toward the main tank; wherein the valve element is not moved to the closing position by the counter flow due to the pressure fluctuation inside the liquid storage chamber in the liquid jetting mode, and is moved toward the closing position by the counter flow due to pressure fluctuation in the liquid storage chamber in the purge mode; wherein the valve element is arranged at an inflow port of the liquid formed in a sub tank, the valve element including: a shaft which has one end inserted in the inflow port with a clearance space with respect to the inflow port; and an umbrella portion which is elastic and is projected in an umbrella shape folding back from the other end of the shaft; and wherein a projection extending in a radial umbrella portion is formed on a surface of the umbrella portion, the surface facing the shaft.