Abstract:
An ink jet printer that includes a printhead configured to eject ink. The printhead is housed in a housing. A capping device is pivotally fastened with respect to the housing to be pivotal into and out of capping engagement with the printhead. The mechanism includes an arm pivotally mounted with respect to the housing and a capping leg extending transversely from the arm to cap the printhead.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   The present application is a Continuation of U.S. application Ser. No. 10/503,887 filed on Aug. 09, 2004, now issued U.S. Pat. No. 7,144,107, which is a 371 of PCT/AU03/00151 filed on Feb. 12, 2003. 

   FIELD OF THE INVENTION 
   The following invention relates to improvements in portable printer technology. More particularly, though not exclusively, the invention relates to a capping device for a hand-held drop-on-demand printer having a fixed printhead for ejecting droplets of ink onto a sheet of print media external to the printer. 
   BACKGROUND 
   Prior art drop-on-demand printers incorporate a supply of print media and employ a print media feed mechanism to transport the print media past the printhead or printheads to effect printing onto the print media. Our co-pending application (AP43) entitled “Manually Moveable Printer with Speed Sensor” discloses a portable, hand-held drop-on-demand inkjet printer having a fixed printhead. The printer can print an image onto a sheet external to the printer by passing the casing of the printer over and across the print media as the nozzles of the printhead eject ink. 
   During non-use periods of the printer, a capping device seals the printhead from the surrounding atmosphere to prevent evaporation of ink and the consequential blockage of the nozzles. 
   The present application is directed to specific capping arrangements for portable printers, particularly, though not exclusively, for portable printers of the type disclosed in co-pending application AP43, the contents of which are specifically incorporated herein by cross-reference. 
   Co-Pending Applications 
   Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the applicant or assignee of the present invention simultaneously with the present application: 
                                                   PCT/AU03/00154   PCT/AU03/00151   PCT/AU03/00150           PCT/AU03/00145   PCT/AU03/00153   PCT/AU03/00152           PCT/AU03/00168   PCT/AU03/00169   PCT/AU03/00170           PCT/AU03/00162   PCT/AU03/00146   PCT/AU03/00159           PCT/AU03/00171   PCT/AU03/00149   PCT/AU03/00167           PCT/AU03/00158   PCT/AU03/00147   PCT/AU03/00166           PCT/AU03/00164   PCT/AU03/00163   PCT/AU03/00165           PCT/AU03/00160   PCT/AU03/00157   PCT/AU03/00148           PCT/AU03/00156   PCT/AU03/00155                        
The disclosures of these co-pending applications are incorporated herein by cross-reference.
 
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   DISCLOSURE OF THE INVENTION 
   There is disclosed herein a portable printer comprising: 
   a housing, 
   a printhead affixed within the housing and including a plurality of ink ejection nozzles configured to eject droplets of ink toward a sheet of print media external to the housing in a printing operational mode, and 
   a capping device including an arm having a capping region that covers the ink ejection nozzles when the printer is in a non-printing operational mode and moves away from the nozzles to enable ejection of ink en route to a sheet of print media in said printing operational mode. 
   Preferably the arm is attached by a pivot to the housing. 
   Preferably the arm includes an activation region to one side of the pivot and a leg to the other side of the pivot, the leg extending in a direction substantially normal to the activation region and including said capping region. 
   Preferably an elastomeric pad is attached to the capping region. 
   Alternatively the arm is formed of a resilient, elastically deformable material being affixed at an end thereof to the housing. 
   In this alternative the housing can include a fulcrum and said arm includes an activation region to one side of said fulcrum and a leg to the other side of the fulcrum, the leg extending in a direction substantially normal to the activation region and including said capping region. 
   Alternatively again, the housing can have mounted thereto a wheel by which the housing rides over a sheet of print media in said printing operational mode, the wheel having associated therewith a friction clutch, the friction clutch including activation means for deflecting said capping region of the arm upon rotation of said wheel in said printing operational mode. 
   In this alternative said activation means can comprise a peg projecting from the friction clutch. 
   In this alternative the arm can be formed from an elastically deformable material including a deviation and wherein the peg bears against the deviation. 
   In a further alternative the arm can be attached to the housing by an integral spring and the printer further comprises an eccentric cam upon a shaft, the eccentric cam bearing against the arm and rotatable to deflect the arm so as to move said capping region away from the nozzles to enable ejection of ink in said printing operational mode. 
   In yet a further alternative, the printer can include a solenoid within the housing disposed with respect to the arm such that upon energization of the solenoid magnetic force draws the arm thereto so as to move said capping region away from the nozzles to enable ejection of ink in said printing operational mode. 
   In this alternative the arm can have attached thereto a metal plate to interact with the solenoid. 
   In this alternative the arm can include an integral spring interacting with the solenoid so as to bias the arm away from the solenoid. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred forms of the present invention will now be described by way of example only with reference to the accompanying drawings wherein: 
       FIG. 1  is a schematic cross-sectional end elevational view of a portable printer showing a first capping device in a capped position; 
       FIG. 2  is a schematic cross-sectional end elevational view of the portable printer of  FIG. 1  with the first capping device shown in an uncapped position; 
       FIG. 3  is a schematic cross-sectional end elevational view of a portable printer having a second type of capping device, in a capped position; 
       FIG. 4  is a schematic cross-sectional end elevational view of the printer of  FIG. 3  with the second capping device, in an uncapped position; 
       FIG. 5  is a schematic cross-sectional end elevational view of a portion of another printer having a third type of capping device, in a capped position; 
       FIG. 6  is a schematic cross-sectional elevational view of a portion of the printer of  FIG. 5  with the third capping device in an uncapped position; 
       FIG. 7  is a schematic front elevational view of a friction clutch used in the embodiment of  FIGS. 5 and 6 ; 
       FIG. 8  is a schematic cross-sectional end elevational view of a portion of a printer having a fourth type of capping device, in a capped position; 
       FIG. 9  is a schematic cross-sectional end elevational view of a portion of the printer of  FIG. 8  with the fourth capping device shown in an uncapped configuration; 
       FIG. 10  is a schematic cross-sectional end elevational view of a portion of a printer having a fifth type of capping device, in a capped configuration; and 
       FIG. 11  is a schematic cross-sectional end elevational view of the portion of the printer of  FIG. 10  with the fifth capping device shown in an uncapped configuration. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the accompanying drawings there are schematically depicted a number of different capping configurations for a portable printer. The portable printer is intended to eject droplets of ink onto a sheet of print media as the printer is held by hand and moved across the sheet of print media. A typical internal configuration of a printhead and associated hardware in a portable printer for which the capping devices disclosed herein are applicable is disclosed in co-pending application entitled “Manually Moveable Printer with Speed Sensor” (AP43) cross-referenced above. 
   In  FIGS. 1 and 2  of the accompanying drawings there is schematically depicted in cross-section, a printer housing  10  having located therein a fixed printhead  11 . The printhead  11  has a print chip  12  extending throughout its full width, that is, the width of an image to be printed. A first embodiment of a capper arm  13 , which may be metallic or formed of other material such as plastics, is pivotally mounted at  14  to the printer housing  10 . The capper arm  13  resides at the exterior of the housing  10  and includes a leg  28  to which there is affixed an elastomeric pad  16  which seals against the chip  12  in the capped configuration depicted in FIG.  1 . The elastomeric pad  16  is moved away from the print chip  12  by leg  28  to enable printing in the configuration depicted in  FIG. 2 . 
   The capper arm  13  includes an activating region  15  to which finger force can be applied as indicated by arrow F shown in  FIG. 2 . The application of such finger force causes pivoting of the capper arm  13  about pivot  14 . A spring (not shown) can return the capper arm to the position shown in  FIG. 1 . 
   A second embodiment of the capping device is depicted in  FIGS. 3 and 4 . In this embodiment, the capper arm  13  is formed of a resilient, elastically deformable material such as metal or plastics. In a particular preferred embodiment, the capper arm  13  is formed of stainless steel. The capper arm  13  is fixed at  17  to the printer housing  10  at one end thereof A fulcrum  14  (depicted schematically) resides alongside the transition of the capper arm  13  to the leg  29 . 
   Upon the application of finger force F as indicated in  FIG. 4 , the capper arm  13  deforms, resulting in the leg  29  moving to the position depicted in  FIG. 4  so as to draw the elastomeric pad  16  away from the print chip  12  for printing purposes. Upon release of the finger force F, the resilience of the capper returns it to the configuration depicted in  FIG. 3  wherein the elastomeric pad  16  seals against the print chip  12 . 
   In the first and second embodiments of the capping device shown in  FIGS. 1 to 4 , a user grasps the printer housing  10  and in doing so, inherently applies a force F to the activation region  15  of the capper arm  13 . There may be provided a switch within the printer housing and associated with the capper arm  13  such that application of finger force F depresses the switch to set the printhead  11  into a printing operational mode. 
   In  FIGS. 5 to 7  of the accompanying drawings there is schematically depicted a third embodiment of a capping device incorporating a friction clutch. In this embodiment, the printer housing  10  has mounted thereto one or more wheels  18 , at least one of which can be associated with an optical sensor as described in the cross-referenced application AP43 entitled “Manually Moveable Printer with Speed Sensor”. One of the wheels, ie. wheel  18  in this example, can have associated with it a friction clutch  19 . Wheel  18  and clutch  19  can be mounted upon a common shaft  30  ( FIG. 7 ) and biased against each other such that rotation of wheel  18  causes rotation of clutch  19  until something stops the clutch  19  from spinning, whereupon wheel  18  continues to rotate with a dynamic frictional engagement between it and the non-rotating clutch  19 . In the embodiment depicted, the friction clutch  19  has a peg  20  extending laterally from it. This peg  20  is received behind a deviated portion  21  of the capper arm  13 . In this embodiment, the capper arm  13  is attached within the printer housing  10  such that portion  29  moves in a linear fashion, ie. it is guided to move in a straight line. Upon rotation of friction clutch  19 , the peg  20  bears against the deviated portion  21  of capper arm  13  to move it in the direction indicated by arrow C ( FIG. 6 ). This, in turn, draws the elastomeric pad  16  away from the chip  12 . It should be appreciated in this regard that wheel  18  is riding upon the print media  22  to effect wheel rotation in the direction indicated by arrow W in  FIG. 6 . When the printer housing  10  is lifted away from the print media  22 , rotation W ceases, whereupon resilience of the capper arm  13  pushes the peg  20  back to the position depicted at  FIG. 5  and at the same time returns the elastomeric pad  16  to seal the print chip  12  as shown in  FIG. 5 . 
   In a fourth embodiment of the capping device shown in  FIGS. 8 and 9 , there is provided an internally driven camshaft  24  including an eccentric cam  23 . Camshaft  24  might be selectively rotated by means of an electric motor for example. In this embodiment, the capper arm  13  is mounted to a pivot  14  and is biased by an integral spring  25  against the eccentric cam  23 . That is, the integral spring  25  biases the leg portion  28  of the capper arm  13  to the position depicted in  FIG. 8  whereat the elastomeric pad  16  seals over chip  12 . When the camshaft  24  is rotated such that the eccentric cam rotates into the position depicted in  FIG. 9 , the capper arm  13  deforms integral spring  25  while the elastomeric pad  16  moves away from the print chip  12 . 
   In  FIGS. 10 and 11  of the accompanying drawings, there is depicted a fifth embodiment of the capping device wherein the capper arm  13  is activated by an internal solenoid  26 . In this embodiment, the capper arm  13  slides linearly between the positions depicted in  FIGS. 10 and 11 . The capper arm  13  includes an integral spring  25  that bears against solenoid  26 . As an alternative, the spring  25  could bear against some other fixed internal structure of the printer housing  10 . Attached to the capper arm  13  is a metallic plate  27  to be attracted to the solenoid  26  by magnetic interaction therewith. Application of electric current to the solenoid  26  creates a magnetic field drawing the metal plate  27  thereto. This in turn draws the capper  13  to the uncapped position where the elastomeric pad  16  has moved away from the print chip  12  to enable printing to commence. 
   When the solenoid is no longer receiving electric current, its magnetic field diminishes or ceases enabling the spring  28  to return the capper arm  13  to the capped position depicted in  FIG. 10 . 
   It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, the elastomeric pad need not be affixed to the capper arm itself. Instead, it might be attached to the printhead  11  so as to surround the print chip  12  and come into sealing contact with a smooth surface of leg  28  of capper arm  13 .