Patent ID: 8794744

Claim:
An inkjet unit, wherein the inkjet unit comprises a liquid compartment that forms a liquid receiving cavity that receives and contains therein a liquid and a jetting nozzle extending in an axial direction from the liquid receiving cavity to a distal end that forms a liquid discharge opening adapted to confront a workpiece, a piezoelectric ceramic module comprising a contact wall that is positioned against an outer wall of the liquid compartment so as to selectively compress the outer wall of the liquid compartment, the liquid receiving cavity being in communication with the liquid discharge opening to allow the liquid contained in the liquid receiving cavity to jet outward through the liquid discharge opening toward the workpiece when the outer wall of the liquid compartment is compressed by the piezoelectric ceramic module, the inkjet unit further comprising a gas supply device, the gas supply device being arranged outside the liquid compartment, the gas supply device and the liquid compartment together delimiting a gas flow channel, the gas flow channel having a gas spray orifice that is arranged to surround an outer wall of the jetting nozzle in such a way that the jetting nozzle projects beyond the gas spray orifice and is exposed to an external atmosphere to allow the liquid jetted through the liquid discharge opening to spray directly to the workpiece without being mixed with a gas that is discharged through the gas spray orifice to the external atmosphere, the gas spray orifice comprising a plurality of sub-orifices that are spaced from each other, the plurality of sub-orifices being arranged to surround the outer wall of the jetting nozzle, whereby the gas discharged through the gas spray orifice is prevented by the outer wall of the jetting nozzle from mixing with the liquid jetted through the liquid discharge opening, the gas being guided by and moving along the outer wall of the jetting nozzle in the axial direction toward the distal end so as to form a circumferential gas curtain around and outside the outer wall of the jetting nozzle and movable relative to the outer wall of the jetting nozzle to prevent a spill of the liquid from moving in a direction transverse to the axial direction and attaching to the outer wall of the jetting nozzle.