Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-02-18
2001-07-17
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06260951
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods of manufacture of printing apparatus, particularly methods of manufacture of droplet deposition apparatus such as inkjet printheads.
Apparatus for deposition of droplets of ink or other fluid are well known. As shown, for example, in EP-A-0 278 590 (belonging to the present applicant and incorporated herein by reference), they comprise one or more ink ejecting chambers from which droplets of ink are ejected, generally via a nozzle, towards a substrate on which an image is to be printed.
To ensure correct positioning of the printed image on the substrate, it is necessary to position the ink ejecting chambers and/or their nozzles accurately relative to the substrate. This is particularly important where several printheads are used to print several overlapping images of different colours (normally cyan, magenta, yellow and black) to provide a full-colour printed image.
Typically, a printer mechanism is employed to hold the substrate relative to a reference surface on the printhead. The printhead is in turn manufactured such that the reference surface lies a fixed distance from the ink ejecting chambers and/or their nozzles of the printing unit (where a printhead has an array of ink ejecting chambers, the reference surface may be positioned relative to a particular one (e.g. the first) of the ink ejecting chambers). However, a tight tolerance on this fixed distance is necessary if the overall positioning of the printhead relative to the substrate is to be to the high accuracy required. Manufacturing the printhead to such tight tolerances may be difficult to achieve, however, and will depend, inter alia, on the material of the printhead, its form and overall dimensions. The present invention seeks to avoid these difficulties.
SUMMARY OF THE INVENTION
Accordingly, the invention consists a method of locating a reference surface on a printing apparatus, the apparatus comprising a printing unit having at least one printing element and mounted on a support member; the method comprising the steps of: positioning the apparatus such that said printing element is located at a first predetermined position; positioning a reference member having said reference surface such that said reference surface is located at a second predetermined position; said first and second positions being in a predetermined spatial relationship; and fixing the reference member to said support member, thereby to fix said reference surface in a predetermined position relative to said printing element.
By this method, it is possible to align the printing elements of a printing apparatus with the reference surface independently of any intermediate printhead structure, thereby avoiding any difficulties that may be associated with such an intermediate structure. and any manufacturing difficulties associated therewith.
Where the printing apparatus is droplet deposition apparatus such as an inkjet printhead, the term ‘printing element’ covers not only an ink ejecting chamber in a printhead but also the respective nozzle, where this is present.
The present invention also consists in a method of manufacturing a printing apparatus that includes a printing unit comprising a droplet ejection unit having at least one printing element, said at least one printing element comprising a nozzle for droplet ejection formed in a nozzle plate, and a support member for said droplet ejecting unit; the method comprising the steps of: mounting said droplet ejecting unit on said support member; thereafter forming at least one nozzle in said nozzle plate of the droplet ejecting unit; and thereafter arranging a reference member such that a reference surface of said reference member is located at a predetermined position relative to said at least one nozzle; and fixing the reference member to said support member.
As before, such a method allows the nozzles of a droplet deposition apparatus to be aligned with the reference surface independently of any intermediate printhead structure, thereby avoiding any difficulties that may be associated with such an intermediate structure. Furthermore, since the relative positioning of nozzle and reference surface only takes place after the droplet ejecting unit has been mounted on its support member, the mounting process need only be carried out to an accuracy appropriate to the relative location of the unit and the support member rather than to an accuracy appropriate to the relative location of a nozzle of unit and a reference surface of the support member.
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Harvey Robert A.
Ingham Ian
Le N.
Marshall O'Toole Gerstein Murray & Borun
Vo Anh T. N.
Xaar Technology Limited
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