NOZZLE ARRANGEMENT FOR AN INK JET PRINTER HAVING SYMMETRICALLY ARRANGED ACTUATORS
Provided is a nozzle arrangement for an ink jet printer. The arrangement includes a wafer substrate with a layer of drive circuitry, said substrate defining an ink supply channel through the substrate leading to an ink chamber with sidewalls and a roof having a fixed portion fast with the substrate and a movable portion displaceable with respect to the fixed portion and defining an ink ejection port. The arrangement also includes an ink ejection arrangement for ejecting ink from the ink chamber via the port, said ink ejection arrangement having four symmetrically arranged thermal bend actuators each connected to a respective side of the movable portion to displace said movable portions in a rectilinear manner relative to the fixed portions during ink ejection.
1 . A nozzle arrangement for an ink jet printer, said arrangement comprising:
a wafer substrate with a layer of drive circuitry, said substrate defining an ink supply channel through the substrate;
sidewalls and a roof arranged on the substrate and defining an ink chamber in fluid communication with the ink supply channel and having a fixed portion fast with the substrate and a movable portion displaceable with respect to the fixed portion and defining an ink ejection port; and
an ink ejection arrangement for ejecting ink from the ink chamber via the port, said ink ejection arrangement having a plurality of symmetrically arranged thermal bend actuators each connected to a respective side of the movable portion to displace said movable portions in a rectilinear manner relative to the fixed portions during ink ejection.
2 . The nozzle arrangement of claim 1 , wherein the actuators are connected to the drive circuitry layer for control of the actuators.
3 . The nozzle arrangement of claim 1 , in which the fixed portion includes a static ink ejection structure having an inner wall and an outer wall that together define a wall portion, an inwardly directed ledge being positioned on the inner wall so that said ledge extends into the nozzle chamber.
4 . The nozzle arrangement of claim 3 , having a sealing formation which is positioned on the outer wall to extend outwardly from the wall portion so that the sealing formation and the ledge define an ink displacement formation.
5 . The nozzle arrangement of claim 4 , wherein the sealing formation includes a re-entrant portion that opens towards the substrate with a lip positioned on the re-entrant portion to extend horizontally from the re-entrant portion.
6 . The nozzle arrangement of claim 5 , wherein the sealing formation and the sidewalls are configured so that, when the nozzle arrangement is in a quiescent condition, the lip and a free edge of the sidewalls are in horizontal alignment with each other, so that a distance between the lip and the free edge is such that an ink meniscus is defined between the sealing formation and the free edge when the nozzle chamber is filled with the ink.
7 . The nozzle arrangement of claim 6 , wherein when the nozzle arrangement is in an operative condition, the free edge is interposed between the lip and the substrate and the meniscus stretches to accommodate such movement, so that when the chamber is filled with ink, a fluidic seal is defined between the sealing formation and the free edge of the sidewalls.