Abstract:
An inkjet printhead is configured to reduce the likelihood of media coming into contact with a printhead face. The inkjet printhead includes a housing, an aperture plate having a plurality of apertures in an aperture area through which inkjet ejectors eject ink, and a pair of members aligned with a direction of media movement and extending along a length of the aperture area, the pair of members being configured to lift media away from the plurality of apertures in the aperture area.

Description:
TECHNICAL FIELD 
     The process and device described below relate to imaging devices and, more particularly, to inkjet printheads in inkjet imaging devices. 
     BACKGROUND 
     Drop on demand inkjet technology for producing printed images has been employed in products such as printers, multifunction products, plotters, and facsimile machines. Generally, an inkjet image is formed by selectively ejecting ink drops from a plurality of drop generators or inkjets, which are arranged in a printhead, onto an image receiving substrate. For example, the image receiving substrate may be moved relative to the printhead and the inkjets may be controlled to emit ink drops through nozzles formed in the printhead at appropriate times. The timing of the inkjet activation is performed by a printhead controller, which generates firing signals that activate the inkjets to eject ink. The ink ejected from the inkjets is liquid ink, such as aqueous, solvent, oil based, curable ink, or the like, which is stored in containers installed in the printer. Alternatively, the ink may be loaded in a solid or a gel form and delivered to a melting device, which heats the ink to generate liquid ink that is supplied to a printhead. 
     The ejected ink travels through an air gap between the printhead face and the image receiving substrate. The greater the distance between the printhead face and the image receiving member, the greater the expelled ink drop speed and consistency required to travel this distance and land on the substrate at the position intended for the ejected ink drops. 
     Inkjet printers that print images on precut sheets of print media are referred to as cut sheet inkjet printers. Cut sheet inkjet printers strip media sheets from a supply of media sheets stacked on an input tray. A media conveyer transports each stripped media sheet through a print zone of the printer. The inkjets eject ink onto the print media as the media conveyer transports the print media through the print zone. After receiving ink from the inkjets, the media conveyer transports the stripped media sheet to an output tray. Once received by the output tray the media sheets are collected by a user or received by another printing system for further processing. 
     The media conveyer transports the media sheets through the print zone where the printheads are operated to eject ink onto a surface of the media sheets. Accordingly, an air gap is required that is large enough to enable sheets of different thicknesses to pass by the printheads. If the airgap is too large the resultant image quality will suffer because of poor placement of the ink drops on the sheet medium. These competing restrictions on the air gap between the printheads and the media sheets can be balanced provided the media sheets stripped from the input tray are flat and free from creases or other imperfections. Some media sheets stripped from the input tray, however, may include creases and other imperfections. As the media conveyer transports these media sheets, the imperfect portions of the media sheet may pass through the print zone at a distance too close to the printheads for accurate placement of the ink drops. Additionally if the media sheet were to actually touch the printhead at any point there is significant danger of disrupting the complete functioning of one or more of the jets. This disruption might be either temporary or permanent but in either case the image quality will suffer significantly. Consequently, image quality may be affected by the close passage of the media sheets to the printhead. For example, some nozzles in the printhead may become clogged by particulate matter carried by a media sheet and image streaks and/or missing pixels may be produced in the printed image. Therefore, control of the distance between media surfaces and the printhead faces in the print zone is useful. 
     SUMMARY 
     An inkjet printhead is configured to reduce the likelihood of media coming into contact with a printhead face. The inkjet printhead includes a housing, an aperture plate having a plurality of apertures in an aperture area through which inkjet ejectors eject ink, and a pair of members aligned with a direction of media movement and extending along a length of the aperture area, the pair of members being configured to lift media away from the plurality of apertures in the aperture area. 
     The inkjet printheads configured to reduce contact between media and a printhead face may be incorporated in an inkjet printhead array. The inkjet printhead array includes a plurality of printheads arranged to eject ink in a continuous line across media passing by the plurality of printheads, each printhead having an aperture plate having a plurality of apertures through which inkjet ejectors eject ink, and a pair of members positioned proximate the plurality of printheads and aligned with a direction of media movement past the plurality of printheads, the pair of members being configured to lift media away from the plurality of apertures in the aperture plates of the plurality of printheads. 
     An alternative embodiment of an inkjet printhead array is configured to reduce contact between media and the printheads in the array without requiring each printhead to be configured with a nozzle protector. The inkjet printhead array includes a plurality of printheads arranged to eject ink in a continuous line across media passing by the plurality of printheads, each printhead in the plurality of printheads including a housing, an aperture plate having a plurality of apertures in an aperture area through which inkjet ejectors eject ink, and a pair of members aligned with a direction of media movement and extending along a length of the aperture area, the pair of members being configured to lift media away from the plurality of apertures in the aperture area. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The foregoing aspects and other features of the present disclosure are explained in the following description, taken in connection with the accompanying drawings. 
         FIG. 1A  is a perspective view of an inkjet printhead, as disclosed herein, the printhead having a nozzle protector configured to prevent contact between nozzles in the printhead and print media. 
         FIG. 1B  is a side view of the inkjet printhead of  FIG. 1A . 
         FIG. 2  is a frontal view of an inkjet printhead array that may include a plurality of inkjet printheads such as those depicted in  FIG. 1A  and  FIG. 1B . 
         FIG. 3A  is a side view of the ink jet printhead of  FIG. 1A  with the nozzle protector engaging a leading edge of a media sheet. 
         FIG. 3B  is a side view of the ink jet printhead of  FIG. 1A  with the nozzle protector engaging central portion of a media sheet. 
         FIG. 3C  is a side view of the ink jet printhead of  FIG. 1A  with the nozzle protector engaging a trailing edge of a media sheet. 
         FIG. 4A  is a frontal view of the inkjet printhead array of  FIG. 2  with a leading edge of a print medium passing over the inkjet printhead array. 
         FIG. 4B  is a frontal view of the inkjet printhead array of  FIG. 2  with a trailing edge of a print medium passing over the inkjet printhead array. 
         FIG. 5A  is a frontal view of an alternative inkjet printhead array having a plurality of inkjet printheads and a nozzle protector. 
         FIG. 5B  is a side view of the printhead array of  FIG. 5A . 
         FIG. 6A  is a frontal view of the inkjet printhead array of  FIG. 5  with a leading edge of a print medium passing over the inkjet printhead array. 
         FIG. 6B  is a frontal view of the inkjet printhead array of  FIG. 5  with a trailing edge of a print medium passing over the inkjet printhead array. 
     
    
    
     DETAILED DESCRIPTION 
     The apparatus and method described herein make reference to printheads and printhead arrays adapted for use in a printing system. The term “print medium” refers to any article with a surface suited to having ink printed onto it, with paper being a common example. A “printhead” as used herein refers to a device that ejects a fluid, such as ink, onto a print medium. Each printhead has an aperture plate with a plurality of apertures, also known as nozzles, etched into the aperture plate&#39;s surface. These nozzles eject ink droplets onto the print medium. A “printhead array” as used herein refers to an assembly of at least two printheads positioned relative to one another to print over an area of a print medium. For example, in a common type of print array, two or more printheads are placed in staggered positions so that the entire printable surface of a print medium may be covered in ink. 
     A printhead  100  with a nozzle protector is depicted in  FIG. 1A . The printhead  100  has an outer housing  104  that surrounds an exposed aperture plate  108 . The aperture plate  108  has a plurality of nozzles  112  formed through its surface. Each of the nozzles  112  is configured to eject ink droplets away from the surface of the aperture plate  108 . A nozzle protector has two members  116 A and  116 B disposed on the housing. In the embodiment of  FIG. 1A , the nozzle protector members  116 A and  116 B are a pair of raised members that are placed on either side of the aperture plate  108 . Each nozzle protector member  116 A and  116 B extends beyond the length of the area of aperture plate  108  containing nozzles, where the length of the aperture plate is defined as the dimension of the aperture plate  108  that is aligned to the direction of movement of a print medium over the printhead  100 , indicated by arrow  124 . The nozzle protector members  116 A and  116 B are also aligned to the direction of travel of a print medium traveling over the printhead  100 . In the example embodiment of  FIG. 1 , the nozzle protector members  116 A and  116 B each have a ramp,  120 A and  120 B, respectively. The ramps  120 A and  120 B are placed in the print media path such that the leading-edge of a print medium traveling in direction  124  engages the ramps  120 A and  120 B before the print medium begins to travel over the exposed aperture plate  108 . The ramps  120 A and  120 B allow a print medium to engage the nozzle protector members in a smooth manner, lifting the print medium away from the aperture plate  108 , and mitigating potential paper jams. While  FIG. 1A  shows nozzle protector members  116 A and  116 B placed beside aperture plate  108 , the nozzle protector members may be incorporated into the aperture plate in alternative embodiments. These nozzle protector members extend along the length of areas in the aperture plate that contain nozzles. Many aperture plate designs have dimensions that are greater than the length and width of the area where nozzles are formed in the aperture plate. In these designs, the nozzle protector members may be positioned to extend beyond the length of the area bearing nozzles, but are not required to extend along the entire length of the aperture plate. 
     A side view of the printhead  100  and nozzle protector member  116  is depicted in  FIG. 1B . This view shows the nozzle protector member  116 , including the ramp  120  that is aligned with the direction of media travel indicated by arrow  130 . The nozzle protector member  116  slopes away from the surface of housing  104  to a predetermined distance at the top of the ramp  120 . In the embodiment of  FIG. 1B , the nozzle protector member  116  rises a predetermined distance of 0.5 mm, but alternative embodiments may use different heights to maintain a desired distance between the printhead and print media. The nozzle protector member  116  may be formed as an extension of the printhead housing  104 , such as by forming the printhead housing from a polymer and extruding the nozzle protector member  116  from the housing&#39;s surface. Alternatively, the nozzle protector member may be formed separately and attached to the surface of the housing via an adhesive layer between the bottom of the nozzle protector member and the housing. Still other embodiments may weld the nozzle protector member and housing together, or use mechanical means including screws or bolts. In embodiments using mechanical connections such as screws, the nozzle protector member may be removed by unscrewing the nozzle protector member and removing it from the housing. In still other embodiments, the nozzle protectors may be separate members positioned at either end of the printhead. 
     A frontal view of a printhead array  200  having printheads with nozzle protectors is depicted in  FIG. 2 . The printhead array  200  holds a plurality of printheads  204 A- 204 D. Multiple copies of the printhead  100  shown in  FIGS. 1A and 1B  may be used in the example embodiment of  FIG. 2 . The printheads  204 A- 204 D in printhead array  200  are staggered such that there is a degree of overlap between adjacent aperture plates  208 A- 208 D. For example, aperture plate  208 A is overlapped by aperture plate  208 B along the direction of print media travel indicated by arrow  224 . The staggered arrangement allows for printheads  204 A- 204 D to eject ink droplets in a continuous line onto a print medium passing over the printhead array  200  without leaving gaps in ink coverage on the print medium. While  FIG. 2  depicts a total of four printheads  204 A- 204 D, alternative printheads may use fewer or greater numbers of printheads in the array. Additionally, while the printhead array  200  of  FIG. 2  has printheads arranged in two rows, alternative staggering arrangements using three or more rows are also envisioned. 
     In the embodiment of  FIG. 2 , each of the printheads  204 A- 204 D contains nozzle protector members exemplified by nozzle protector members  216 A and  216 B. As in  FIG. 1A  and  FIG. 1B , these members are disposed along length of the aperture plate  208 A, extending beyond the area of aperture plate  208 A containing nozzles, and are aligned with the direction of media travel indicated by arrow  224 . Each of the nozzle protector members  216 A and  216 B has a ramp  220 A and  220 B, respectively. Alternative embodiments of the nozzle protector members seen in  FIG. 2  may have different widths to aid the movement of a print medium over the printhead array. In one alternative embodiment, nozzle protector member  216 B could have an extended width with one end attached to printhead  204 A, and the other end attached to  204 C. This configuration allows a wider nozzle protector member to engage a print medium across the entire gap between printheads. 
     A side view of a printhead  300  with a nozzle protector member being engaged by a print medium with a curled leading edge is depicted in  FIG. 3A . The print medium  330  in  FIG. 3A  has a curled leading edge  332 . As the print medium travels in direction  320 , the curled leading edge  332  engages the nozzle protector member  308 , beginning with the ramp  312 . The ramp  312  allows the print medium  330  to engage the nozzle protection member  308  gradually, preventing the paper from deforming which could lead to jams or reduced print quality. The print medium  330  travels along the nozzle protection member  308  which blocks the print medium  330  from contacting the surface of the housing  304 , and the aperture plate with print nozzles (not shown). 
     A side view of the printhead  300  from  FIG. 3A  being engaged by a print medium with a distorted central portion is depicted in  FIG. 3B . In this example, a print medium  334  has a distortion  336 . The print medium is engaged with the nozzle protection member  308  which prevents the distortion  336  from extending the print medium  334  into contact with the housing  304 , which also contains the aperture plate with print nozzles (not shown). The example depicted in  FIG. 3B  shows the nozzle protection member  308  engaging the print medium  334  along the entire length of nozzle protection member  308 , blocking the print medium  334  from contacting the apertures in the aperture plate. 
     A third view of the printhead  300  being engaged by a print medium with a curled trailing edge is depicted in  FIG. 3C . In this example, the print medium  338  has a curled trailing edge  340 . The curled trailing edge engages with the nozzle protection member  308  instead of curling down to contact the housing  304 . The contact with the nozzle protection member  308  lifts the print medium  338  away from the surface of the housing  304 , and aperture plate (not shown). As the print medium travels in the direction indicated by arrow  320 , the curled edge  340  remains in contact with the nozzle protection member  308 , and is blocked from contact with the aperture plate and nozzles. 
     A printhead array having a leading edge of a print medium moving over the printhead array is depicted in  FIG. 4A . In  FIG. 4A , print medium  420  travels over the printhead array  400  in the direction indicated by arrow  412 . While traveling over printheads  404 A and  404 C, the print medium  420  passes over nozzle protector members  408 A and  408 B on printhead  404 A, and  408 C and  408 D on printhead  404 C. If the print medium  420  is curled or otherwise distorted, the nozzle protector members maintain separation between the print medium  420 , and the nozzles in the aperture plates  406 A and  406 B. 
     A printhead array having a trailing edge of a print medium moving over the printhead array is depicted in  FIG. 4B . As in  FIG. 4A , the print medium  420  moves over printhead array  400  in the direction indicated by arrow  412 . In  FIG. 4B , the print medium  420  is moving over the printheads  404 B and  404 D. Printhead  404 B has nozzle protector members  416 A and  416 B, and printhead  404 D has nozzle protector members  416 C and  416 D. If the print medium  420  is curled or distorted, the nozzle protector members  416 A- 416 D block the print medium  420  from contacting the nozzles in the surfaces of the aperture plates  406 C and  406 D. 
     An alternative embodiment of a printhead array with a nozzle protector is depicted in  FIG. 5A . In this embodiment, printhead array  500  has printheads  504 A- 504 D placed in a staggered arrangement similar to that of  FIG. 2 . Printheads  504 A- 504 D have aperture plates  508 A- 508 D, respectively. Each aperture plate has a plurality of apertures  516 A- 516 D, or nozzles, that eject ink from the printhead. The printhead array  500  has a housing  502  containing the printheads  504 A- 504 D and a nozzle protector including a pair of raised members  512 A and  512 B. These nozzle protector members are aligned with the direction of movement of a print medium passing over the printhead array  500 , indicated by arrow  524 . The nozzle protector members  512 A and  512 B each extend along the combined lengths of all the printheads  504 A- 504 D in the printhead array  500 . As with the nozzle protector members shown in  FIG. 1A  and  FIG. 1B , nozzle protector members  512 A and  512 B each include a ramp,  520 A and  520 B, which extends away from the printhead array  500 . The ramps  520 A and  520 B are placed in the print media path such that the leading-edge of a print medium traveling in direction  524  engages the ramps  520 A and  520 B before the print medium begins to move over the exposed aperture plate  508 . 
       FIG. 5B  depicts a side view of the printhead array  500  of  FIG. 5A . The printhead array  500  has housing  502  supporting nozzle protector member  512 . The nozzle protector member  512  has a ramp  520  that extends from the housing  502  to the top of nozzle protector member  512 , at a predetermined distance from the housing  502 . The ramp  520  is aligned with the direction of movement of a print medium, indicated by arrow  526 . 
     While the nozzle protector members  512 A and  512 B shown in  FIG. 5A  and  FIG. 5B  have a similar shape to those depicted in  FIG. 1A  and  FIG. 1B , the dimensions chosen for nozzle protector members  512 A and  512 B may differ. For example, nozzle protectors  512 A and  512 B have longer lengths and wider widths in order to accommodate the size of the entire printhead array. Additionally, the predetermined distance that the nozzle members  512 A and  512 B extend from the printhead array housing  502  may be a different distance than for nozzle protector members used with a single printhead. 
     A print medium moving over the printhead array of  FIG. 5A  is depicted in  FIG. 6A  and  FIG. 6B . Print medium  620  moves over the printhead array  600  in the direction indicated by arrow  624 .  FIG. 6A  depicts the leading edge of print medium  624  passing over printheads  604 A and  604 B. If the print medium  624  is curled or distorted, the nozzle protection members  612 A and  612 B block the print medium  624  from contacting the nozzles in aperture plates  608 A and  608 B. The print medium moves over the printhead array  600  with a trailing edge shown in  FIG. 6B . If the trailing edge is curled or distorted, the nozzle protections members  612 A and  612 B extend along the length of printheads  604 C and  604 D, and block the print medium  624  from contacting the nozzles in aperture plates  608 C and  608 D. 
     Although many of the figures discussed above show the printheads in an upward facing direction for ease of illustration, the reader should appreciate that most printing systems orient printheads in a downwardly facing or horizontally facing configuration and that the protective structure described herein may be applied to all such configurations. If the printhead faces downwardly, then the media is moved by the protective structure downwardly away from the printhead. If the printhead is oriented to eject ink horizontally, then the media is moved by the protective structure in a generally horizontal direction away from the printhead. Additionally, if a printhead faces upwardly, the media is lifted in upwardly away from the printhead. 
     Those of ordinary skill in the art will recognize that numerous modifications may be made to the specific implementations described above. Therefore, the following claims are not to be limited to the specific embodiments illustrated and described above. The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.