Abstract:
An ink jet print head has a plurality of nozzle arrangements. Each nozzle arrangement defines a nozzle chamber from which ink can be ejected. Each nozzle chamber is configured so that the ink is ejected from each nozzle chamber in a first direction with respect to each nozzle chamber. Each nozzle arrangement has an ink ejection mechanism that is operatively arranged with respect to each nozzle arrangement, for ejecting ink from each nozzle chamber. The ink ejection mechanisms are each displaceable in a second direction relative to the nozzle chambers, the second direction being substantially at right angles to said first direction, to facilitate the ejection of ink from the nozzle chamber.

Description:
RELATED APPLICATIONS AND CROSS REFERENCES  
       [0001]    This application is a continuation-in-part application of U.S. application Ser. no. 09/113,061. U.S. application Ser. no. 09/113,061 09/112,818 09/112,772 09/112,754 09/112,811 09/112,812 09/112,813 are hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to an ink jet printhead that incorporates laterally displaceable actuator mechanisms.  
         BACKGROUND OF THE INVENTION  
         [0003]    The Applicant has invented a page width printhead which is capable of generating text and images of resolutions as high as 1600 dpi.  
           [0004]    The printhead is manufactured in accordance with a technique that is based on integrated circuit fabrication. An example of such a technique is that which is presently used for the fabrication of micro electromechanical systems. It will be appreciated by those skilled in the art that such techniques are carried out largely in a planar fashion. This means that the layers of material are deposited and then selectively etched to define the required structure. This fabrication technique is well known and will therefore not be described in further detail here.  
           [0005]    The Applicant has filed many patent applications covering the use of these techniques to fabricate the page width printhead mentioned above. The page width printhead can incorporate up to 84 000 nozzle arrangements. Each nozzle arrangement includes a micro electromechanical actuator that is displaceable to eject ink from a nozzle chamber of each nozzle arrangement.  
           [0006]    An important factor in this field of technology is chip size. The larger the chip, the more expensive the printhead. Accordingly, it is important that the chip be kept as thin as possible. Conventionally, the actuators are positioned to be displaceable in a direction corresponding to that of the direction of drop ejection. Drop ejection usually takes place in a direction substantially normal to a plane in which the chip is positioned. It follows that the chip must be made thick enough to accommodate movement of the actuators. This can result in the chip being excessively thick and thus costly.  
           [0007]    The Applicant has devised a way of overcoming this problem with the present invention.  
         SUMMARY OF THE INVENTION  
         [0008]    According to the invention, there is provided an ink jet print head which comprises a substrate;  
           [0009]    at least one nozzle arrangement positioned on the substrate, , the, or each, nozzle arrangement defining a nozzle chamber from which ink can be ejected, the nozzle chamber being configured so that the ink is ejected from the, or each, nozzle chamber in a first direction that is substantially normal to the substrate, and the, or each, nozzle arrangement having an ink ejection mechanism that is operatively arranged with respect to the, or each, nozzle arrangement, for ejecting ink from the, or each, nozzle chamber, wherein the ink ejection mechanism is displaceable in a second direction relative to the, or each, nozzle chamber, the second direction being in a plane substantially parallel to the substrate.  
           [0010]    The invention will now be described, by way of example only, with reference to the accompanying drawings. The specific nature of the following description is not to be construed as limiting in any way the scope of the above summary 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    In the drawings,  
         [0012]    [0012]FIG. 1 shows a partly sectioned view of a nozzle arrangement of a first embodiment of a printhead, in accordance with the invention;  
         [0013]    [0013]FIG. 2 shows an exploded view of a nozzle arrangement of a second embodiment of a printhead, in accordance with the invention; and  
         [0014]    [0014]FIG. 3 shows an exploded view of a nozzle arrangement of a third embodiment of a printhead, in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    In FIG. 1, reference numeral  10  generally indicates a nozzle arrangement of a first embodiment of a printhead, in accordance with the invention.  
         [0016]    The printhead is in the form of a page width printhead. It follows that those of ordinary skill in the field of printhead manufacture will appreciate that the nozzle arrangment  10  is one of many such nozzle arrangements. For ease of reference, one such nozzle arrangement is shown.  
         [0017]    As set out in the preamble, the printhead is manufactured using integrated circuit fabrication technology. In particular, the printhead is manufactured with techniques that are used for the manufacture of micro electromechanical systems. Such techniques use a process of deposition and subsequent etching to achieve a final product. The Applicant has covered these manufacturing techniques as applied to printheads in other patents and patent applications. It is therefore not within the scope of this specification to detail such steps.  
         [0018]    In this particular example, the nozzle arrangement  10  includes a wafer substrate  12 . A pair of opposed side walls  14 , an end wall  38  and a roof portion  16  are positioned on the substrate  12  to define a nozzle chamber  18 . The roof portion  16  defines an ink ejection port  20 .  
         [0019]    The end wall  38  is defined by a filter structure  40  so that ink entering the nozzle chamber  18  is filtered.  
         [0020]    The nozzle arrangement  10  includes an ink ejection mechanism in the form of a linear actuator  22 . The linear actuator  22  includes a magnetic rod  24  that is positioned in a plane substantially parallel to a plane in which the substrate  12  is positioned. A pair of spaced guide formations  26  are arranged on the substrate  12 , with the magnetic rod  24  being displaceably positioned between the guide formations  26 . The guide formations  26  and the rod  24  are configured so that the rod  24  is restrained to be displaced linearly between opposed edges  28  of the substrate  12 .  
         [0021]    The magnetic rod  24  defines a number of spaced magnetic poles  30  along its length. A number of electromagnetic devices  32  are positioned on each side  34  of the magnetic rod  24 . The electromagnetic devices  32  and the magnetic poles  30  are configured so that selective activation of the electromagnetic devices  32  results in movement of the magnetic rod  24 . In particular, the electromagnetic devices  32  are connected to drive circuitry, indicated generally at  34 , so that stepped motion of the magnetic rod  24  can be achieved. It will be appreciated that the drive circuitry  34  can be connected to a sophisticated control system so that exact backwards and forwards control of the magnetic rod  24  can be achieved.  
         [0022]    A plunger  36  is mounted on an end of the magnetic rod  24  to be received between the side walls  14  of the nozzle chamber  18 . The plunger  36  is displaceable, via actuation of the rod  24  towards and away from the end wall  28  to eject ink from the ink ejection port  20 .  
         [0023]    In FIG. 2, reference numeral  50  generally indicates a nozzle arrangement of a second embodiment of a printhead, in accordance with the invention. With reference to FIG. 1, like reference numerals refer to like parts, unless otherwise specified.  
         [0024]    In this particular example, the nozzle chamber  18  is defined by a recess  52  that is etched in the substrate  12 . The recess  52  is generally rectangular in cross section. A floor  54  of the recess  52  has a first portion  56  with an arcuate profile and a second portion  58  that defines an inlet  60 .  
         [0025]    The nozzle arrangement  50  has a coiled actuator  62 . The coiled actuator  62  includes a coiled, composite arm  64 . The arm  64  is composed of a heating element  66  embedded in a thermal expansion material, in this case polytetrafluoroethylene (PTFE)  68 . PTFE has a coefficient of thermal expansion which is such that PTFE can do work when heated to expand. The heating element  66  is embedded in the PTFE  68  such that, upon heating of the PTFE  68  by the heating element  66 , the PTFE  68  expands so that the composite arm  64  uncoils to a degree.  
         [0026]    The heating element  66  is connected to the drive circuitry  34  at  70 . It follows that, with the drive circuitry  34  connected to a suitable control system, selective partial uncoiling of the arm  64  can be achieved. PTFE is inherently resilient. It follows that, when the PTFE  68  cools, the arm  64  returns to its coiled state.  
         [0027]    An ink displacement member in the form of a paddle  72  is connected to an end of the arm  64 . The paddle  72  is received in the nozzle chamber  18  above the inlet  60  when the arm  64  is in its coiled state. When the arm  64  uncoils, as set out above, the paddle  72  is driven across the nozzle chamber  18  into a position above the first portion  56  of the floor  54  of the recess  52 . The arcuate profile of the first portion  56  facilitates the ejection of ink from the nozzle chamber  18 .  
         [0028]    In FIG. 3, reference numeral  80  generally indicates a nozzle arrangement of a third embodiment of a printhead, in accordance with the invention. With reference to FIGS. 1 and 2, like reference numerals refer to like parts, unless otherwise specified.  
         [0029]    The nozzle arrangement  80  includes a nozzle chamber  82  that is defined by four side walls  84  and a roof wall  86 . The roof wall  86  defines an ink ejection port  88  from which ink is ejected, in use.  
         [0030]    The nozzle chamber  18  is rectangular so that an opposed pair of walls  84 . 1  are major walls, while the remaining walls  84 . 2  are minor walls. The inlet  60  is positioned proximate one of the minor walls  84 . 2  while the ejection port  88  is positioned proximate the other, opposed, minor wall  84 . 2 .  
         [0031]    The nozzle arrangement  80  also includes a coiled actuator  86 . In this example, the paddle  72  is received in the nozzle chamber  18  via a slot  88  defined in one of the walls  84 . In particular, the paddle  72  is positioned above the inlet  60  when the arm  64  is in its coiled condition and is driven towards said opposed minor wall  84 . 2  when the arm  64  is partially uncoiled. This serves to pressurize the ink in the chamber  82 , thereby ejecting the ink from the chamber  82 .  
         [0032]    In all three of the examples given, it is important to note that the actuators are displaced in a plane substantially normal to the plane of ink ejection. As set out in the preamble, this form of printhead is manufactured in a planar fashion. The fact that the actuators are arranged to be displaced in this fashion, results in a substantial simplification of the fabrication process. The primary reason for this is that the whole actuator is positioned on the substrate, rather than extending into the substrate.  
         [0033]    Also as set out in the preamble, the cost of a page width printhead chip increases dramatically with the thickness of the chip. The primary reason for this is that the chip must be of a length sufficient to span at least part of a printing medium. The present invention, as indicated in the examples described above, provides a means whereby these costs can be greatly alleviated. This is achieved by providing actuators which do not require a minimum thickness of the chip in which to operate.