This invention relates to an ink jet printhead. More particularly, the invention relates to an ink jet printhead that includes tilt-compensating ink ejection ports.
Ink jet printheads of the type manufactured using micro-electromechanical systems technology have been proposed in a construction using nozzle chambers formed in layers on the top of a substrate with nozzle chambers formed in the layers. Each chamber is provided with a movable paddle actuated by some form of actuator to force ink in a drop through the nozzle associated with the chamber upon receipt of an electrical signal to the actuator. Such a construction is typified by the disclosure in International Patent Application PCT/AU99/00894 to the Applicant.
The present invention stems from the realisation that there are advantages to be gained by dispensing with the paddles and causing ink drops to be forced from the nozzle by decreasing the size of the nozzle chamber. It has been realised that this can be achieved by causing the actuator to move the nozzle itself downwardly in the chamber thus dispensing with the paddle, simplifying construction and providing an environment which is less prone to the leakage of ink from the nozzle chamber.
Furthermore, Applicant has identified that it would be useful to incorporate a mechanism whereby ink ejection ports could be kept clear of obstructions, such as dried ink or paper dust.
According to an aspect of the present disclosure, a nozzle arrangement for ejecting ink includes a substrate defining an ink supply passage; a first endless wall extending from the substrate and bounding the ink supply passage; an elongate actuator operatively anchored at a fixed end to the substrate and at a location external to the confines of the first endless wall, the actuator configured to reciprocally bend towards and away from the substrate on receipt of an electrical current; and a cover terminating a free end of the actuator, the cover defining a second endless wall suspended from the cover within the confines of the first endless wall to define an ink chamber with the first endless wall, the cover further defining an ink ejection port through which ink in the ink chamber is ejected. The reciprocal bending of the actuator towards and away from the substrate varies a volume of the ink chamber and effects ejection of ink from the ink chamber through the ink ejection port. The first and second endless walls define a gap therebetween, a width of the gap being conducive to the formation of a fluidic seal effected via surface tension of the ink.
Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described by way of example only with reference to the accompanying drawings in which:
It will be appreciated that a large number of similar nozzles are simultaneously manufactured using MEMS and CMOS technology as described in our co-pending patent applications referred to at the beginning of this specification.
For the purposes of clarity, the construction of an individual ink jet nozzle arrangement will now be described.
Whereas in conventional ink jet construction of the type described in our above referenced co-pending patent applications, ink is ejected from a nozzle chamber by the movement of a paddle within the chamber, according to the present invention the paddle is dispensed with and ink is ejected through an ink ejection port in a movable portion of a nozzle chamber defining structure, which is moved downwardly by a bend actuator, decreasing a volume of the nozzle chamber and causing ink to be ejected from the ink ejection port.
Throughout this specification, the relative terms “upper” and “lower” and similar terms are used with reference to the accompanying drawings and are to be understood to be not in any way restrictive on the orientation of the nozzle arrangement in use.
Referring now to
An ejection port is defined by rim 9 located in the roof portion 6 so as to define an opening for the ejection of ink from the nozzle chamber as will be described further below.
The roof portion 6 and downwardly depending sidewalls 7 are supported by a bend actuator 10 typically made up of layers forming a heated cantilever which is constrained by a non-heated cantilever, so that heating of the heated cantilever causes a differential expansion between the heated cantilever and the non-heated cantilever causing the bend actuator 10 to bend as a result of thermal expansion of the heated cantilever.
A proximal end 11 of the bend actuator 10 is fastened to the substrate 1, and prevented from moving backwards by an anchor member 12 which will be described further below, and the distal end 13 is secured to, and supports, the roof portion 6 and sidewalls 7 of the nozzle arrangement.
In use, ink is supplied to the nozzle chamber through conduit 2 and opening 3 in any suitable manner, but typically as described in our previously referenced co-pending patent applications. When it is desired to eject a drop of ink from the nozzle chamber, an electric current is supplied to the bend actuator 10 causing the actuator to bend to the position shown in
When the electric current is cut off, the actuator 10 reverts to the straight configuration as shown in
In one form of the invention, the opening 3 in floor portion 5 is relatively large compared with the cross-section of the nozzle chamber and the ink droplet is caused to be ejected through the nozzle rim 9 upon downward movement of the roof portion 6 by viscous drag in the sidewalls of the aperture 2, and in the supply conduits leading from the ink reservoir (not shown) to the opening 2. This is a distinction from many previous forms of ink jet nozzles where the “back pressure” in the nozzle chamber which causes the ink to be ejected through the nozzle rim upon actuation, is caused by one or more baffles in the immediate location of the nozzle chamber. This type of construction can be used with a moving nozzle ink jet of the type described above, and will be further described below with specific reference to
In order to prevent ink leaking from the nozzle chamber during actuation i.e. during bending of the bend actuator 10, a fluidic seal is formed between sidewalls 7 and 8 as will now be further described with specific reference to
The ink is retained in the nozzle chamber during relative movement of the roof portion 6 and floor portion 5 by the geometric features of the sidewalls 7 and 8 which ensure that ink is retained within the nozzle chamber by surface tension. To this end, there is provided a very fine gap between downwardly depending sidewall 7 and the mutually facing surface 16 of the upwardly depending sidewall 8. As can be clearly seen in
In order to make provision for any ink which may escape the surface tension restraint due to impurities or other factors which may break the surface tension, the upwardly depending sidewall 8 is provided in the form of an upwardly facing channel having not only the inner surface 16 but a spaced apart parallel outer surface 18 forming a U-shaped channel 19 between the two surfaces. Any ink drops escaping from the surface tension between the surfaces 7 and 16, overflows into the U-shaped channel where it is retained rather than “wicking” across the surface of the nozzle strata. In this manner, a dual wall fluidic seal is formed which is effective in retaining the ink within the moving nozzle mechanism.
As has been previously described in some of our co-pending applications, it is desirable in some situations to clear any impurities which may build up within the nozzle opening and ensure clean and clear ejection of a droplet from the nozzle under actuation. A configuration of the present invention using a projection in combination with a moving nozzle ink jet is shown in the accompanying
As can be seen in
As the roof portion 6 returns to its original position upon straightening of the bend actuator 10 as shown in
It will be appreciated that as the bend actuator 10 is bent causing the roof portion to move downwardly to the position shown in
The correction of this non-perpendicular movement can be achieved by providing the nozzle rim 9 with an asymmetrical shape as can be clearly seen in
By carefully tailoring the shape and characteristics of the nozzle rim 9, it is possible to completely compensate for the tilting of the roof portion 6 during actuation and to propel the ink drop from the nozzle in a direction perpendicular to the floor portion 5.
Although, as described above, the backpressure to the ink held within the nozzle chamber may be provided by viscous drag in the supply conduits, it is also possible to provide a moving nozzle ink jet with backpressure by way of a significant constriction close to the nozzle. This constriction is typically provided in the substrate layers as can be clearly seen in
The bend actuator which is formed from a heated cantilever 28 positioned above a non-heated cantilever 29 joined at the distal end 13 needs to be securely anchored to prevent relative movement between the heated cantilever 28 and the non-heated cantilever 29 at the proximal end 11, while making provision for the supply of electric current into the heated cantilever 28.
The non-heated cantilever 29 is provided with outwardly extending tabs 32 which are located within recesses 33 in the sidewall 31, giving further rigidity, and preventing relative movement between the non-heated cantilever 29 and the heated cantilever 28 in the vicinity of the anchor 27.
In this manner, the proximal end of the bend actuator is securely and firmly anchored and any relative movement between the heated cantilever 28 and the non-heated cantilever 29 is prevented in the vicinity of the anchor. This results in enhanced efficiency of movement of the roof portion 6 of the nozzle arrangement.
The present application is a continuation of U.S. application Ser. No. 11/545,566 filed on Oct. 11, 2006, now issued with U.S. Pat. No. 7,581,819, which is a continuation of U.S. application Ser. No. 11/015,012 filed on Dec. 20, 2004, now issued as U.S. Pat. No. 7,134,741, which is a continuation of U.S. application Ser. No. 10/893,378 filed on Jul. 19, 2004, now issued as U.S. Pat. No. 6,994,425, which is a continuation of Ser. No. 10/303,347 filed on Nov. 23, 2002, now issued as U.S. Pat. No. 6,767,077, which is a continuation of Ser. No. 09/693,313 filed on Oct. 20, 2000, now issued as U.S. Pat. No. 6,505,916, the entire contents of which are herein incorporated by reference.
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Child | 12538162 | US | |
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Child | 11545566 | US | |
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Child | 10303347 | US |