Abstract:
A printhead protection apparatus moves between printheads in a printer between a position where cross-members in a frame block media irregularities from striking the faces of the printheads and a position where the cross-members are retracted between adjacent printheads to enable the faces of the printheads to be wiped. The frame of the apparatus encompasses the printheads and the cross-members connected to the frame move between adjacent printheads.

Description:
TECHNICAL FIELD 
     This disclosure is directed to printers that use printheads to form ink images on media and, more particularly, to mechanisms for protecting the printheads in such printers from errant media. 
     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 ink image is formed by selectively ejecting ink drops from a plurality of ejectors or inkjets, which are arranged in an array within 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 eject 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. The ink is stored in containers installed in the printer and the containers are fluidly connected to the printheads. 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 ink by an inkjet 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 where the printheads are located. The inkjets of the printheads 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. In continuous sheet printers, media is pulled from a rotating roll and actuators driving rollers propel the sheet through the printer past the printheads and post-printing processing equipment to a take-up roll. 
     In cut-sheet printers, some media sheets stripped from the input tray may include creases and other imperfections. Additionally, water from the ink landing on a media sheet can cause a portion of the sheet to curl, which increase the sheet&#39;s height above the transport. In continuous sheet printers, the risk of sheet curl is also present. If a portion of a media sheet actually touches the face of a printhead, a significant danger exists 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 suffers significantly. Therefore, protecting printheads in cut sheet and continuous sheet printers from media passing by the printheads would be useful. 
     SUMMARY 
     A new apparatus helps protect the faceplate of printheads arranged in an array within a printer. The apparatus includes a frame having four members, each member having a first end and a second end, the first end of a first member is connected to the first end of a second member and the second end of the first member is connected to the first end of a third member and the first end of a fourth member is connected to the second end of the second member and the second end of the fourth member is connected to the second end of the third member, a plurality of cross-members mounted to the frame, each cross-member having a first end and a second end, the first end of each cross-member is connected to the first member of the frame and the second end of each cross-member is connected to the fourth member, the cross-members being separated from an adjacent cross-member by a distance corresponding to a width of a printhead in a direction perpendicular to a path of media movement in the plane of the media movement, each cross-member between positioned adjacent to at least one printhead in a plurality of printhheads that are oriented parallel to one another, an actuator operatively connected to the frame, the actuator being configured to move the frame between a first position and a second position, when the frame is in the first position, a portion of each cross-member extends into a space between the printheads and the media passing the printheads, and when the frame is in the second position, no portion of each cross-member extends into the space between the printheads and the media passing the printheads, and a controller operatively connected to the actuator. The controller is configured to operate the actuator to move the frame between the first and second positions to extend the portions of the cross-members into the space between the printheads and the media passing the printheads selectively. 
     A printer incorporates the apparatus to help protect the faceplate of printheads arranged in an array within a printer. The printer includes a plurality of printheads arranged in an array and oriented to be parallel to one another, the printheads being configured to eject drops of ink, a media transport configured to move media past the printheads in a media movement direction to receive the drops of ink ejected by the printheads, a frame having four members, each member having a first end and a second end, the first end of a first member is connected to the first end of a second member and the second end of the first member is connected to the first end of a third member and the first end of a fourth member is connected to the second end of the second member and the second end of the fourth member is connected to the second end of the third member, a plurality of cross-members mounted to the frame, each cross-member having a first end and a second end, the first end of each cross-member is connected to the first member of the frame and the second end of each cross-member is connected to the fourth member, the cross-members being separated from an adjacent cross-member by a distance corresponding to a width of one printhead in a direction that is perpendicular to the media movement direction in the plane of the media movement, each cross-member between positioned adjacent to at least one printhead in the plurality of printhheads, an actuator operatively connected to the frame, the actuator being configured to move the frame between a first position and a second position, when the frame is in the first position, a portion of each cross-member extends into a space between a plane formed by faces of the printheads and a plane through which the media passes by the printheads, and when the frame is in the second position, no portion of each cross-member extends into the space between the plane formed by the faces of the printheads and the plane through which the media passes the printheads, and a controller operatively connected to the actuator, the media transport, and the printheads in the plurality of printheads. The controller is configured to operate the media transport to move media past the printheads in the media movement direction, to operate the printheads to eject ink drops onto the media as the media passes the printheads, and to operate the actuator to move the frame between the first and second positions to extend the portions of the cross-members into the space between the plane formed by the faces of the printheads and the plane through which the media passes the printheads selectively. 
     A new method of operating a printer helps protect the faceplate of printheads arranged in an array within a printer. The method includes operating with a controller a media transport to move media past a plurality of printheads in a media movement direction, operating with the controller the printheads to eject ink drops onto the media as the media passes the printheads, and operating with the controller an actuator operatively connected to a frame having a plurality of cross-members that extend between a first member of the frame and a second member of the frame, the operation of the actuator moves the frame having the plurality of cross-members from a first position to a second position to extend portions of the cross-members into a space between a plane formed by faces of the printheads and a plane through which the media passes the printheads selectively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and other features of an apparatus that helps protect printheads in a printer from strikes by passing media are explained in the following description, taken in connection with the accompanying drawings. 
         FIG. 1  depicts a print zone in a printer having an apparatus for protecting the printheads from irregular media structures. 
         FIG. 2  is a perspective view of a rectangular cross-member used in the apparatus shown in  FIG. 1 . 
         FIG. 3  is a perspective view of an elliptical and circular cross-member that can be used in the apparatus of  FIG. 1 . 
         FIG. 4  is a side view of the print zone shown in  FIG. 1  in which the cross-members of the apparatus for protecting the printheads from irregular media structures are positioned between the printheads and the media being printed. 
         FIG. 5  is a side view of the print zone shown in  FIG. 1  in which the cross-members of the apparatus for protecting the printheads from irregular media structures are positioned in the gaps between the printheads to enable wiping of the printhead faces. 
     
    
    
     DETAILED DESCRIPTION 
     A print zone  10  in which an array of printheads  14  are located with a configuration of guide members is shown in  FIG. 1 . The printheads  14  are arranged in a 1×29 array. The printheads are oriented parallel to one another to enable adjacent printheads to form a straight line of ink drops across a sheet of media moving past the printheads in direction indicated by the P arrow. That is, the plane of the media is parallel to a plane formed by the faces of the printheads  14 . Each printhead  14  has a shoulder that prevents the edges of the faces  20  of adjacent printheads from contacting one another. Thus, the shoulders form gaps  24  between adjacent printheads  14 . A frame  28  has cross-members  18  that oriented at the same angle as the printheads  14  are to the media movement direction P. The frame  28  is operatively connected to an actuator  32 , which is operatively connected to a controller  36 . The actuator  32  is configured to move the frame  28  into and out of the plane formed by the faces  20  of the printheads  14 . Although the printheads  14  are shown as being oriented at an acute angle to the media direction P, the printheads could be oriented at other angles including being perpendicular to the media direction P. The direction CP is the cross-process direction, which is perpendicular to the media movement direction P in the plane of the media movement. 
     In further detail, the frame  28  includes four members  100   a ,  100   b ,  100   c , and  100   d . Each member has two ends. One end of member  100   b  is connected to one end of member  100   a  and the other end of member  100   b  is connected to one end of member  100   d . Similarly, one end of member  100   c  is connected to the other end of member  100   a  and the other end of member  100   c  is connected to the other end of member  100   d . Frame  28  can be formed by connecting the four members  100   a ,  100   b ,  100   c , and  100   d  mechanically by brazing, welding, fasteners, or adhesives. Alternatively, the members can be formed into frame  28  integrally by injection molding or casting. The length of the frame  28  in the cross-process direction CP exceeds the distance from a rightmost printhead and a leftmost printhead. Likewise, the width of the frame  28  in the media movement direction P exceeds the width of the printheads in the media movement direction P. That is, the frame  28  is configured to encompass the printhead array in the print zone  10  in a plane parallel to the faces of the printhead array. 
     As shown in  FIG. 2 , an exemplary cross-member  18  is a member having two ends and a rectangular cross-section, although the cross-members can be configured with elliptical  18 ′, circular  18 ″, or other cross-sections as shown in  FIG. 3 . A longitudinal axis of cross-member  18  has a length from one end to the other end of the cross-member  18  that spans the distance between member  100   b  and  100   c  of frame  28 . The two ends of the cross-member  18  can be connected perpendicularly to the members  100   b  and  100   c  or the two ends can be connected at an angle as shown in  FIG. 1 . The orientation of the cross-member ends to the longer members of the frame  28  depends upon the orientation of the printheads  14  in the array of printheads. Thus, the cross-members  18  and the frame  28  can form a parallelogram as shown in  FIG. 1  to accommodate the slanted orientation of the printheads, although other configurations in the shape of a rectangle, for example, can be used to accommodate printheads oriented in a more orthogonal manner. The distance between adjacent cross-members  18  in the frame  28  is slightly larger than between adjacent printheads in the direction of the media movement past the printheads. The width of a cross-member  18  is slightly less than the distance between adjacent printheads in the cross-process direction CP. The height of a cross-member  18  in a direction perpendicular to the plane in which the media moves past the printheads is less than a distance from the face of a printhead to the top of the member to which the printhead is mounted. In some embodiments, the cross-members  18  are connected to the members  100   b  and  100   c  of frame  28  mechanically by brazing, welding, fasteners, or adhesives. In other embodiments, the cross-members  18  can be integrally formed with the frame  28  by injection molding or casting. The first cross-member  18  is positioned adjacent to the rightmost printhead as shown in  FIG. 1 . 
     With continued reference to  FIG. 1  and to  FIG. 4 , the cross-members  18  are fixedly mounted at each end to the frame  28  as described above to enable the cross-members to be moved in response to the actuator  32  moving the frame  28 . In  FIG. 4 , the process direction P is into the plane of the figure. Each cross-member  18  fits within one of the gaps  40  between adjacent printheads  14 . The cross-members are sufficiently rigid that they do not deform when struck by irregular media, such as wrinkle  50  in the cross-process direction CP passing through the print zone  10 . That is, they have a cross-sectional area that is large enough and made with a rigid material that impact with irregular media deflects the irregular structure rather than causing the cross-member to deform. Thus, the cross-members are thicker than wires and are more appropriately called rods or the like. The width of the cross-members in the cross-process direction CP, however, cannot exceed the distance across the gaps between adjacent printheads  14 . Additionally, the height of the cross-members  18 , as shown in  FIG. 4 , cannot be equal to the height of the gaps between adjacent printheads to provide sufficient volume for retracting the cross-members  18  within the gaps so the surface of the cross-members closest to the media path becomes at least flush with the plane formed by the faces  20  of the printheads  14 . Thus, the cross-members  18  are unsupported by the member  54  to which the printheads  14  are mounted. This structure differs from previously known cross-member structures that either contact or are close enough to an underlying support structure that the portions of the cross-members that extend past a printhead into the gap G between the printheads and the media  56  are deflected into the underlying face of a printhead or other support member to prevent the cross-member from exiting the gap G completely. That is, these previously known protection devices require an underlying support member to preserve the structural integrity of the cross-member in the gap G. The frame  28  and cross-members  18  are sufficiently rigid that the cross-members  18  do not deflect into the gap between adjacent printheads when struck by irregular media features, such as the wrinkle  50  shown in  FIG. 4 . 
       FIG. 5  depicts the protection apparatus described above during a maintenance operation on the printheads  14 . The controller  36  operates actuator  76  to move a member  64  into the print zone  10 . A wiper  72  is mounted to the member  64 . The controller  36  is also configured to pivot the member  64  so the wiper  72  can be rotated into contact with the faces  20  of the printheads  14  and rotated out of contact with the faces. After the wiper  72  is rotated into contact with the faces  20 , the controller  36  operates the actuator  76  to move the member  64  in the media process direction to wipe the faces  20  of each printhead  14  in the print zone  10 . This wiping typically occurs after a purging operation has been performed on one or more of the printheads. To prevent the wiper from bumping over or becoming stuck on the cross-members  18 , the controller  36  operates the actuator  32  ( FIG. 1 ) to move the frame  28  away from the gap between the printhead faces  20  and the media path to retract the cross-members  18  into the gaps between the printheads  14  or the gap beside the rightmost printhead as shown in the figure. In this position, the cross-members  18  are close to or contact the member  54  and the end of the cross-members opposite the end contacting the member  54  are completely within the gaps between adjacent printheads. Consequently, the cross-members  18  do not interfere with the wiper  72  as it moves through the print zone  10  to wipe each of the printheads  14 . The actuator  76  can be configured to move the member  64  bidirectionally so the wiper  72  can return through the print zone  10  to wipe the face  20  of each printhead  14  in the opposite direction. Regardless whether the wiper  72  travels unidirectionally or bidirectionally through the print zone  10 , once the wiper  72  completes the wiping operation and exits the print zone  10 , the controller  36  operates the actuator  32  to move the frame  28  toward the media path to return the cross-members to the positions shown in  FIG. 4  to guard the faces  20  of the printheads  14  from irregular media structures. It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements may be subsequently made by those skilled in the art that are also intended to be encompassed by the following claims.