Abstract:
A printhead chip for an inkjet printhead includes a substrate. A plurality of nozzle arrangements is positioned on the substrate. Each nozzle arrangement includes nozzle chamber walls and a roof that define a nozzle chamber. The roof defines an ink ejection port that is in fluid communication with the nozzle chamber. An actuator is displaceable, in a substantially rectilinear manner, with respect to the substrate. An ink-ejecting mechanism is angularly displaceable with respect to the substrate to eject ink from the ink ejection port. A translation to rotation conversion mechanism is interposed between the actuator and the ink-ejecting mechanism to convert rectilinear movement of the actuator into angular displacement of the ink-ejecting mechanism.

Description:
REFERENCED PATENT APPLICATIONS  
       [0001]    This application is a continuation-in-part application of U.S. application Ser. No. 09/112,767. The following patents/patent applications are hereby incorporated by reference:  
                                                   6,227,652   6,213,588   6,213,589   6,231,163   6,247,795       09/113,099   6,244,691   6,257,704   09/112,778   6,220,694       6,257,705   6,247,794   6,234,610   6,247,793   6,264,306       6,241,342   6,247,792   6,264,307   6,254,220   6,234,611       09/112,808   09/112,809   6,239,821   09/113,083   6,247,796       09/113,122   09/112,793   09/112,794   09/113,128   09/113,127       6,227,653   6,234,609   6,238,040   6,188,415   6,227,654       6,209,989   6,247,791   09/112,764   6,217,153   09/112,767       6,243,113   09/112,807   6,247,790   6,260,953   6,267,469       09/425,419   09/425,418   09/425,194   09/425,193   09/422,892       09/422,806   09/425,420   09/422,893   09/693,703   09/693,706       09/693,313   09/693,279   09/693,727   09/693,708   09/575,141       09/113,053   09/855,094   09/854,762   09/854,715   09/854,830       09/854,714   09/854,703   09/855,093   09/854,815   09/854,825       09/864,377   09/864,380   09/900,178   09/864,379   09/864,378       09/864,334   09/864,332   09/864,343   09/864,342   09/866,786       09/874,757   09/900,174   09/900,160   09/900,175   09/900,177       09/900,159   09/900,176   09/922,274   09/922,275   09/922,158       09/922,159   09/922,036   09/922,047   09/922,029   09/922,207       09/922,112   09/922,105   09/942,549   09/942,605   09/942,548       09/942,603   09/942,604                  
 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable  
         FIELD OF THE INVENTION  
         [0003]    This invention relates to an ink jet printhead chip. More particularly, this invention relates to an inkjet printhead chip that includes a motion conversion mechanism.  
         BACKGROUND OF THE INVENTION  
         [0004]    As set out in the above referenced applications/patents, the Applicant has spent a substantial amount of time and effort in developing printheads that incorporate micro electr-mechanical system (MEMS)-based components to achieve the ejection of ink necessary for printing.  
           [0005]    As a result of the Applicant&#39;s research and development, the Applicant has been able to develop printheads having one or more printhead chips that together incorporate up to 84000 nozzle arrangements. The Applicant has also developed suitable processor technology that is capable of controlling operation of such printheads. In particular, the processor technology and the printheads are capable of cooperating to generate resolutions of 1600 dpi and higher in some cases. Examples of suitable processor technology are provided in the above referenced patent applications/patents.  
           [0006]    Common to most of the printhead chips that the Applicant has developed is a component that moves with respect to a substrate to eject ink from a nozzle chamber. This component can be in the form of an ink-ejecting member that is displaceable in a nozzle chamber to eject the ink from the nozzle chamber.  
           [0007]    As is also clear from the above applications, Applicant has developed a number of ways in which to achieve the ejection of ink from the respective nozzle chambers. A majority of these are based on the selection of a material having a coefficient of thermal expansion that is such that, on a MEMS scale, expansion upon heating and subsequent contraction upon cooling can be harnessed to perform work. The material is formed to define at least part of a thermal actuator that includes a heating circuit. The heating circuit is shaped to be resistively heated when a current passes through the circuit. The current is supplied to the circuit in the form of pulses at a frequency that depends on the printing requirements. The pulses are usually supplied from a CMOS layer positioned on a substrate of the printhead chip. The pulses are shaped and have a magnitude that is also dependent on the printing requirements. The generation and control of the pulses is by way of a suitable microprocessor of the type described in the above referenced applications.  
           [0008]    On a macroscopic scale, it is counter-intuitive to use the expansion and subsequent contraction of material in order to achieve the performance of work. Applicant submits that the perceived slow rate of expansion and contraction would lead a person of ordinary skill in the field of macroscopic engineering to seek alternative energy sources.  
           [0009]    On a MEMS scale, however, Applicant has found that expansion and contraction of such a material can be harnessed to perform work. The reason for this is that, on this scale, expansion and contraction are relatively rapid and can transmit relatively high force.  
           [0010]    There remains an issue of range of movement. While the expansion and contraction are both rapid and forceful, Applicant has found that it would be desirable for a mechanism to be provided whereby such rapidity and force of movement could be amplified at a region where the work is required to eject the ink.  
           [0011]    A majority of the nozzle arrangements covered by the above applications and patents use differential expansion in the thermal actuator to achieve bending of the thermal actuator. This bending movement is transmitted to an ink-ejecting component that is either rectilinearly or angularly displaced to eject the ink.  
           [0012]    Applicant has found that it would be desirable for simple rectilinear expansion of a thermal actuator to be transmitted to an ink-ejecting component, since such simple rectilinear expansion on a MEMS scale is relatively efficient.  
           [0013]    The Applicant has conceived this invention in order to achieve the desired transmission and amplification of motion mentioned above.  
         SUMMARY OF THE INVENTION  
         [0014]    According to the invention, there is provided a printhead chip for an inkjet printhead, the printhead chip comprising  
           [0015]    a substrate; and  
           [0016]    a plurality of nozzle arrangements that is positioned on the substrate, each nozzle arrangement comprising  
           [0017]    nozzle chamber walls and a roof that define a nozzle chamber with the roof defining an ink ejection port that is in fluid communication with the nozzle chamber;  
           [0018]    an actuator that is displaceable, in a substantially rectilinear manner, with respect to the substrate;  
           [0019]    an ink-ejecting mechanism that is angularly displaceable with respect to the substrate to eject ink from the ink ejection port; and  
           [0020]    a translation to rotation conversion mechanism interposed between the actuator and the ink-ejecting mechanism to convert rectilinear movement of the actuator into angular displacement of the ink-ejecting mechanism.  
           [0021]    The ink-ejecting mechanism may include an ink ejection member that is positioned in the nozzle chamber and is angularly displaceable with respect to the substrate to eject ink from the ink ejection port.  
           [0022]    The actuator may have a fixed portion that is fixed to the substrate and a working portion that is capable of thermal expansion when heated to be displaced in said substantially rectilinear manner.  
           [0023]    The translation to rotation conversion mechanism may include a pivot member that is pivotal with respect to the substrate. The pivot member may be connected to the working portion of the thermal actuator to pivot upon displacement of the working portion. The ink ejection member may be connected to the pivot member so that the ink ejection member is angularly displaced upon expansion of the working portion.  
           [0024]    The nozzle chamber walls and the roof may be dimensioned so that the nozzle chamber is elongate and has a generally rectangular shape when viewed in plan. The nozzle chamber walls may thus include a distal end wall, a proximal end wall and a pair of opposed side walls, the pivot member being positioned adjacent the proximal end wall and the ink ejection port being positioned adjacent the distal end wall.  
           [0025]    Each ink ejection member may be shaped to correspond generally with a plan profile of each nozzle chamber so that an end of the ink ejection member is positioned adjacent the ink ejection port.  
           [0026]    Each pivot member and each ink ejection member may be configured so that the ink ejection member is between approximately 20 and 60 times longer than an effective lever arm defined by the pivot member. In particular, each ink ejection member may be approximately 40 times longer than the effective lever arm defined by the pivot member.  
           [0027]    In a particular embodiment, the ink ejecting mechanism may be in the form of an active ink-ejecting structure. The active ink-ejecting structure may at least partially define the nozzle chamber and the roof that defines the ink ejection port that is in fluid communication with the nozzle chamber. The active ink-ejecting structure may be pivotally connected to the substrate. The actuator may be connected to the active ink-ejecting structure so that the active ink-ejecting structure is angularly displaced with respect to the substrate upon displacement of the actuator, to eject ink from the ink ejection port.  
           [0028]    The printhead chip may be the product of an integrated circuit fabrication technique. The substrate may include a silicon wafer substrate and a CMOS layer positioned on the silicon wafer substrate, the CMOS layer being connected to the actuator of each nozzle arrangement to provide the actuator with electrical driving pulses.  
           [0029]    The substrate may have a plurality of ink inlet channels defined therein, one inlet channel opening into each respective nozzle chamber.  
           [0030]    The invention extends to an inkjet printhead that includes at least one printhead chip as described above. 
       
    
    
       [0031]    The invention is now described, by way of examples, with reference to the accompanying drawings. The following description is not intended to limit the broad scope of the above summary.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]    In the drawings,  
         [0033]    [0033]FIG. 1 shows a schematic sectioned side view of a nozzle arrangement of a first embodiment of a printhead chip, in accordance with the invention, for an inkjet printhead, in a quiescent condition;  
         [0034]    [0034]FIG. 2 shows a schematic sectioned side view of the nozzle arrangement of FIG. 1;  
         [0035]    [0035]FIG. 3 shows a schematic plan view of the nozzle arrangement of FIG. 1; and  
         [0036]    [0036]FIG. 4 shows a schematic sectioned side view of a nozzle arrangement of a second embodiment of a printhead chip, in accordance with the invention, for an ink jet printhead. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]    In FIGS.  1  to  3 , reference numeral  10  generally indicates a nozzle arrangement for a first embodiment of an ink jet printhead chip, in accordance with the invention.  
         [0038]    The nozzle arrangement  10  is one of a plurality of such nozzle arrangements formed on a silicon wafer substrate  12  to define the printhead chip of the invention. As set out in the background of this specification, a single printhead can contain up to 84000 such nozzle arrangements. For the purposes of clarity and ease of description, only one nozzle arrangement is described. It is to be appreciated that a person of ordinary skill in the field can readily obtain the printhead chip by simply replicating the nozzle arrangement  10  on the wafer substrate  12 .  
         [0039]    The printhead chip is the product of an integrated circuit fabrication technique. In particular, each nozzle arrangement  10  is the product of a MEMS-based fabrication technique. As is known, such a fabrication technique involves the deposition of functional layers and sacrificial layers of integrated circuit materials. The functional layers are etched to define various moving components and the sacrificial layers are etched away to release the components. As is known, such fabrication techniques generally involve the replication of a large number of similar components on a single wafer that is subsequently diced to separate the various components from each other. This reinforces the submission that a person of ordinary skill in the field can readily obtain the printhead chip of this invention by replicating the nozzle arrangement  10 .  
         [0040]    An electrical drive circuitry layer  14  is positioned on the silicon wafer substrate  12 . The electrical drive circuitry layer  14  includes CMOS drive circuitry. The particular configuration of the CMOS drive circuitry is not important to this description and has therefore been shown schematically in the drawings. Suffice to say that it is connected to a suitable microprocessor and provides electrical current to the nozzle arrangement  10  upon receipt of an enabling signal from said suitable microprocessor. An example of a suitable microprocessor is described in the above referenced patents/patent applications. It follows that this level of detail will not be set out in this specification.  
         [0041]    An ink passivation layer  16  is positioned on the drive circuitry layer  14 . The ink passivation layer  16  can be of any suitable material, such as silicon nitride.  
         [0042]    The nozzle arrangement  10  includes nozzle chamber walls in the form of a distal end wall  18 , a proximal end wall  20  and a pair of opposed sidewalls  22 . A roof  24  spans the walls  18 ,  20 ,  22 . The roof  24  and the walls  18 ,  20 ,  22  define a nozzle chamber  26 . The roof  24  defines an ink ejection port  28  in fluid communication with the nozzle chamber  26 . The walls  18 ,  20 ,  22  and the roof  24  are dimensioned so that the nozzle chamber  26  has a rectangular shape when viewed in plan. The ink ejection port  28  is positioned adjacent a distal end  52  of the nozzle chamber  26 .  
         [0043]    A plurality of ink inlet channels  30  is defined through the substrate  12  and the layers  14 ,  16 . Each ink inlet channel  30  is in fluid communication with a respective nozzle chamber  26 . Further, an opening  32  of each ink inlet channel  30  is aligned with the ink ejection port  28  of its associated nozzle chamber  26 .  
         [0044]    An anchor formation in the form of a pair of anchors  34  is fast with the substrate  12  on a proximal side of the nozzle chamber  26 . An actuator in the form of an electro thermal expansion actuator  36  is fast with the anchor  34  and extends towards the proximal end wall  20 . The thermal expansion actuator  36  is of a conductive material and is shaped to define an electrical heating circuit. The actuator  36  is of a material that has a coefficient of thermal expansion that is such that, when heated and subsequently cooled, expansion and contraction of the material can be harnessed to perform work on a MEMS scale. An example of a suitable material is Aluminum Titanium Nitride. In particular, the thermal expansion actuator  36  has a pair of arms  38  that are interconnected by a bridge portion  40 . The actuator  36  has a fixed portion defined by fixed ends  42  of the arms  38  that are fast with respective anchors  34 .  
         [0045]    Each of the anchors  34  are configured to provide electrical connection between the fixed ends  42  and the electrical drive circuitry layer  14 . In particular, the anchors  34  are configured to provide electrical connection between one fixed end  42  and a negative contact and the other fixed end  42  and a positive contact. The electrical drive circuitry layer  14  is connected to a microprocessor of the type described in the above referenced patents/applications so that electrical current pulses of suitable shape and magnitude can be supplied to the actuator  36 .  
         [0046]    The bridge portion  40  of the actuator  36  defines a working portion of the actuator  36 .  
         [0047]    The nozzle arrangement  10  includes a pivot member  44  that is pivotally arranged on the proximal end wall  20 . The bridge portion  40  of the actuator  36  is connected to the pivot member at a position intermediate a pivot point, indicated at  46 , defined by the pivot member  44  and the proximal end wall  20 . It is to be understood that the pivot point  46  can be defined by any number of configurations of the pivot member  44  and the proximal end wall  20 . For this reason, the pivot point  46  is indicated schematically only. In one possible embodiment, the proximal end wall  20  could define the pivot member  44 . In this case, the pivot point  46  would be defined between the proximal end wall  20  and the sidewalls  22 . In particular, this would entail hingedly connecting the proximal end wall  20  to the sidewalls  22 .  
         [0048]    It will be appreciated that, in any event, the pivot member  44  is to form part of the proximal end wall  20 . Thus, a sealing member  48  is provided intermediate the pivot member  44  and the ink passivation layer  16 . The sealing member  48  is configured to accommodate pivotal movement of the pivot member  44  upon expansion and subsequent contraction of the thermal expansion actuator  36 .  
         [0049]    The nozzle arrangement  10  includes an ink ejection member in the form of a paddle  50 . The paddle  50  is dimensioned to correspond generally with the nozzle chamber  26 . In particular, the paddle  50  is dimensioned so that an end portion  54  of the paddle  50  is positioned intermediate the ink ejection port  28  and the opening  32  of the ink inlet channel  30 .  
         [0050]    The paddle  50  and the pivot member  44  are configured so that the paddle  50  is approximately 40 times longer than an effective lever arm, indicated at  56 , defined by the paddle  50  and the pivot member  44 . It should be noted that the lever arm  56  is only shown schematically because of the wide variety of different possible configurations available for defining the lever arm  56 . Further, a ratio of paddle length to lever arm length can vary widely from the 40:1 ratio. This could depend on a number of factors such as driving signal strength and actuator material.  
         [0051]    It will be appreciated that a maximum extent of movement of the paddle  50  takes place at the end portion  54  of the paddle  50 . Furthermore, this extent of movement is up to 40 times greater than a range of movement of the effective lever arm  56 . It follows that the expansion of the thermal actuator  36  is substantially amplified at the end portion  54 , therefore facilitating the ejection of ink  58  from the ink ejection port  28  as indicated at  60  in FIG. 2. When the actuator  36  cools, subsequent contraction of the actuator  36  causes an amplified extent of movement of the end portion  54  back into a quiescent position shown in FIG. 1. This results in separation of the ink  60  from the ink  58  to form an ink drop  62 .  
         [0052]    The paddle  50  includes reinforcing ribs  64  to strengthen the paddle  50 . This is necessary due to the relative length of the paddle  50  and a resultant bending moment exerted on the paddle  50 .  
         [0053]    It will be appreciated that, in light of the above referenced applications and patents, the nozzle arrangement  10  is suited for fabrication with an integrated circuit fabrication technique. Furthermore, the pivot member  44  and pivot point  46  can be defined by any number of micro mechanical arrangements. For example, a flexible member may be formed intermediate the pivot member  44  and the sidewalls  22  or proximal end wall  20  that is distorted to accommodate pivotal movement of the pivot member  44 .  
         [0054]    In FIG. 4, reference numeral  70  generally indicates a nozzle arrangement of a second embodiment of a printhead chip, in accordance with the invention, for an inkjet printhead. With reference to FIGS.  1  to  3 , like reference numerals refer to like parts, unless otherwise specified.  
         [0055]    The nozzle arrangement  70  includes an active ink-ejecting structure  72 . The active ink-ejecting structure  72  has a roof  74  and walls  76  that extend from the roof  74  towards the substrate  12 . The roof  74  defines an ink ejection port  78 . The roof  74  and the walls  76  together define a nozzle chamber  80 .  
         [0056]    The walls  76  comprise a proximal end wall  82 , an opposed distal end wall  84  and a pair of opposed sidewalls  86 . The ink ejection port  78  is positioned adjacent the distal end wall  84 , while the opening  32  of the ink inlet channel  30  is positioned adjacent the proximal end wall  82 .  
         [0057]    The proximal end wall  82  is pivotally mounted on the substrate  12  so that the active ink-ejecting structure  72  is pivotal with respect to the substrate  12 . In particular, the active ink-ejecting structure  72  is pivotal in the direction of an arrow  88  to an extent that is sufficient to facilitate the ejection of ink from the ink ejection port  78 .  
         [0058]    The roof  74  and the walls  76  are dimensioned so that the nozzle chamber  80  is rectangular and has a length that is more than 3 times a height of the nozzle chamber  80 . This, together with the fact that the ink ejection port  78  and the opening  32  are positioned at opposite ends of the nozzle chamber  80  facilitates the retardation of ink flow from the ink ejection port  78  towards the opening  32  when the structure  72  is pivotally displaced towards the substrate  12 . This flow is referred to as backflow and is highly undesirable.  
         [0059]    The bridge portion  40  of the actuator  36  is fixed to the proximal end wall  82 . Thus, on heating and subsequent expansion of the actuator  36  in the manner described above, the ink-ejecting structure  72  is pivoted towards the substrate  12 . Upon cooling and subsequent contraction of the actuator  36  in the manner described above, the ink-ejecting structure  72  is pivoted away from the substrate  12 . This reciprocal movement of the ink-ejecting structure  72  results in the ejection of an ink drop from the ink ejection port  28 .  
         [0060]    The bridge portion  40  is connected to the proximal end wall  82  at a position in which a length of the ink-ejecting structure  72  is up to 40 times greater than a length of an effective lever arm, indicated at  92 . It follows that pivotal movement of the effective lever arm  92  as a result of displacement of the bridge portion  40  upon heating and subsequent cooling of the actuator  36  can be amplified by a factor as high as 40. It has been found by the Applicant that this facilitates efficient ink drop ejection.  
         [0061]    The nozzle arrangement  70  includes a sealing structure  90  that extends from the ink passivation layer  16 . The walls  76  overlap the sealing structure  90  so that a fluidic seal is defined between the sealing structure  90  and the walls  76  when the nozzle chamber  80  is filled with ink.  
         [0062]    Applicant believes that this invention provides a means whereby simple thermal expansion and contraction, in a rectilinear manner, can be converted into useful work by converting the motion into amplified pivotal motion.