Nozzle arrangement with ejection apertures having externally projecting peripheral rim

1. A nozzle arrangement for ejecting ink, the nozzle arrangement comprising:

a substrate assembly defining an ink inlet passage and including heater element drive circuitry;

a nozzle chamber structure formed on the substrate assembly, the nozzle chamber structure defining nozzle chambers in fluid communication with the ink inlet passage and apertures through which ink in each of the nozzle chambers can be ejected; and

heater elements positioned between the drive circuitry and the apertures, the heater elements being connected to the drive circuitry to be individually supplied with current to eject ink from one of the apertures respectively, wherein

each of the apertures has an externally projecting peripheral rim.

2. A nozzle arrangement as claimed in claim 1 , wherein each of the heater elements is an elongate conductor having at least one arcuate portion.

3. A nozzle arrangement as claimed in claim 2 , wherein each of the heater elements is shaped to define at least one discontinuous annulus that defines said at least one arcuate portion.

4. A nozzle arrangement as claimed in claim 3 , wherein each of the heater elements is shaped to define a plurality of concentric discontinuous annuli comprising any one of three or five discontinuous annuli.

5. A nozzle arrangement as claimed in claim 4 , wherein each adjacent pair of broken annuli is interconnected by a respective pair of parallel arms.

6. A nozzle arrangement as claimed in claim 2 , wherein the arcuate portion is of substantially uniform diameter and terminates in a pair of enlarged contacts at either end.

7. A nozzle arrangement as claimed in claim 6 , wherein each of the heater elements is suspended by the enlarged contacts such that the arcuate portion is spaced from the aperture and the drive circuitry.