Head unit and liquid ejection apparatus

A liquid ejection apparatus comprising a plurality of head units installed in the liquid ejection apparatus, the plurality of head units each comprising:

• a head module comprising a nozzle surface in which a plurality of nozzles are opened;
• a casing connected to the head module;
• a first connector connected to the liquid ejection apparatus and comprising a first communication opening communicating with a first communication liquid passage formed in the liquid ejection apparatus;
• a second connector connected to the liquid ejection apparatus and comprising a second communication opening communicating with a second communication liquid passage formed in the liquid ejection apparatus;
• a first liquid-passage tube disposed in the casing and fluidically connected to the first communication opening;
• a first branch-liquid-passage tube disposed in the casing and fluidically connected to the first liquid-passage tube;
• a second branch-liquid-passage tube disposed in the casing and fluidically connected to the first liquid-passage tube;
• a first tube joint disposed in the casing and connecting the first liquid-passage tube to the first branch-liquid-passage tube and the second branch-liquid-passage tube such that the first branch-liquid-passage tube and the second branch-liquid-passage tube branch off from the first liquid-passage tube;
• a second liquid-passage tube disposed in the casing and fluidically connected to the second communication opening;
• a third branch-liquid-passage tube disposed in the casing and fluidically connected to the second liquid-passage tube;
• a fourth branch-liquid-passage tube disposed in the casing and fluidically connected to the second liquid-passage tube;
• and
• a second tube joint disposed in the casing and connecting the second liquid-passage tube to the third branch-liquid-passage tube and the fourth branch-liquid-passage tube such that the third branch-liquid-passage tube and the fourth branch-liquid-passage tube branch off from the second liquid-passage tube,
• wherein the head module comprises:
• a first liquid-passage opening fluidically connected to the first branch-liquid-passage tube;
• a second liquid-passage opening fluidically connected to the second branch-liquid-passage tube;
• a third liquid-passage opening fluidically connected to the third branch-liquid-passage tube;
• and
• a fourth liquid-passage opening fluidically connected to the fourth branch-liquid-passage tube, and
• wherein the first tube joint is disposed between the second connector and the second tube joint when viewed in a direction parallel with the nozzle surface.