Variable size inlets in inkjet printhead

Abstract

A nozzle arrangement for an ink jet printhead includes a substrate. Nozzle chamber walls are arranged on the substrate to define a nozzle chamber. An ejection actuator is operatively positioned with respect to the nozzle chamber and is displaceable between an inoperative condition and an operative condition to eject ink from the nozzle chamber. The ejection actuator includes an actuating mechanism to facilitate such displacement. A refilling actuator is operatively positioned with respect to the nozzle chamber and is displaceable between an inoperative condition and an operative condition to direct ink into a zone in which the ink can be acted on by the ejection actuator, subsequent to the ejection of ink from the nozzle chamber. The refill actuator includes an actuating mechanism to facilitate such displacement.

We claim  
     
         1 . An inkjet nozzle arrangement including: 
 at least one first actuator;    at least one second actuator;    said at least one first actuator and said at least one second actuator defining at least part of at least one inlet to a nozzle chamber;    said at least one first actuator being displaceable from a respective rest position to a respective displaced position;    said at least one second actuator being displaceable from a respective rest position to a respective displaced position;    the first and second actuators being configured to increase the effective area of the at least one inlet when at least one of said actuator is in a displaced position compared to when in the respective rest position.    
     
     
         2 . The arrangement of  claim 1  wherein the at least one first actuator is at least one ejection actuator and the at least one ejection actuator is configured to eject ink from the nozzle chamber on movement from the rest position to the displaced position.  
     
     
         3 . The arrangement of  claim 2  wherein the at least one ejection actuator is configured to also draw ink into the nozzle chamber on movement from the rest position to the displaced position.  
     
     
         4 . The arrangement of  claim 1  wherein the at least second actuator is a refilling actuator and wherein the at least one refilling actuator is configured to direct or draw ink into the nozzle chamber on movement from the rest position to the displaced position.  
     
     
         5 . A nozzle arrangement as claimed in  claim 1 , which is the product of an integrated circuit fabrication technique.  
     
     
         6 . A nozzle arrangement as claimed in  claim 5 , in which the substrate includes a wafer substrate and a drive circuitry layer positioned on the wafer substrate, the drive circuitry layer being connected to both the at least one first actuator and the at least one second actuator.  
     
     
         7 . A nozzle arrangement as claimed in  claim 6 , in which the wafer substrate is etched to define the nozzle chamber walls.  
     
     
         8 . A nozzle arrangement as claimed in  claim 7 , in which an etch stop layer is positioned on the wafer substrate, in opposition to the drive circuitry layer, the etch stop layer defining a roof wall of the nozzle chamber and an ink ejection port in fluid communication with the nozzle chamber.  
     
     
         9 . A nozzle arrangement as claimed in  claim 8 , wherein the at least one first actuator is an ejection actuator and the at least one second actuator is a refill actuator, both actuators being defined by a layer of expansion material that is positioned on the drive circuitry layer to span an inlet of the nozzle chamber so that the actuators are substantially co-planar, the expansion material having a coefficient of thermal expansion which is such that heating and subsequent expansion of the material is sufficient to perform work.  
     
     
         10 . A nozzle arrangement as claimed in  claim 9 , in which the inlet has a substantially rectangular cross section in a plane parallel to the etch stop layer with the ejection actuator anchored at one side of the inlet and the refill actuator anchored at an opposed side of the inlet, the actuators both being substantially rectangular and dimensioned to be partly received in the nozzle chamber with free ends of the actuators positioned adjacent each other.  
     
     
         11 . A nozzle arrangement as claimed in  claim 9 , in which the etch stop layer defines the ink ejection port in a position generally aligned with the ejection actuator so that movement of the ejection actuator towards the etch stop layer into an ejection zone results in the ejection of ink from the ink ejection port.  
     
     
         12 . A nozzle arrangement as claimed in  claim 9 , in which the refill actuator is positioned so that displacement of the refill actuator into the nozzle chamber serves to drive ink from a remaining zone of the nozzle chamber into the ejection zone and to permit the ingress of ink from the ink supply into the nozzle chamber subsequent to the ejection actuator being displaced from its operative condition into its inoperative condition.  
     
     
         13 . A nozzle arrangement as claimed in  claim 9 , in which the actuating mechanism of both the ejection actuator and the refill actuator is in the form of a heating element positioned in each actuator proximate an outer surface of each actuator so that activation of the heating elements results in a heating and subsequent expansion of a portion of each actuator proximate the outer surface so that the actuators are bent into the nozzle chamber.  
     
     
         14 . An ink jet printhead which comprises 
 a substrate; and    a plurality of nozzle arrangements positioned on the substrate, each nozzle arrangement comprising:    at least one first actuator;    at least one second actuator;    said at least one first actuator and said at least one second actuator defining at least part of at least one inlet to a nozzle chamber;    said at least one first actuator being displaceable from a rest position to a displaced position;    said at least one second actuator being displaceable from a rest position to a displaced position;    the first and second actuators being configured to increase the effective area of the at least one inlet when at least one actuator is in the displaced position compared to when in the respective rest position.    
     
     
         15 . A method of ejecting ink from a nozzle arrangement of an ink jet printhead, the nozzle arrangement including a substrate, nozzle chamber walls arranged on the substrate to define a nozzle chamber, at least one micro-electromechanical ejection actuator that is displaceable between an inoperative and an operative condition to facilitate the ejection of ink from the nozzle chamber and at least one micro-electromechanical refill actuator that is displaceable between an operative condition and an inoperative condition to direct ink into a zone in which the ink can be acted upon by the ejection actuator, the method including the steps of: 
 supplying the nozzle chamber with ink;    activating the, or each, ejection actuator so that ink is ejected from the nozzle chamber; and    activating the, or each, refill actuator at a predetermined time after activation of the, or each, ejection actuator so that ink is directed into said zone to be acted upon again by the, or each, ejection actuator, if required.    
     
     
         16 . A method as claimed in  claim 15 , which includes the steps of: 
 activating the, or each, ejection actuator so that the, or each, ejection actuator is displaced from its inoperative condition to its operative condition;    de-activating the, or each, ejection actuator so that the, or each, ejection actuator returns to its inoperative condition; and    activating the, or each, refill actuator subsequent to the, or each, ejection actuator returning to its inoperative condition.  17 . A method of operating an ink ejection nozzle having at least one first micro-electro mechanical actuator that is displaceable upon receipt of an electrical signal and at least one second micro-electro mechanical actuator that is displaceable upon receipt of an electrical signal, the method including, sequentially:    providing a first signal to the at least one first actuator, to cause ejection of ink from the nozzle;    removing the first signal;    providing a second signal to the at least one second actuator, to encourage ingress of ink into the nozzle.