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Forms Feeding and Printhead Gap Compliance System in a Low End Printer

IP.com Disclosure Number: IPCOM000111211D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 155K

Publishing Venue

IBM

Related People

Veals, ER: AUTHOR

Abstract

In any printing mechanism, the need for a compliant system that accepts multi-styles of printing media, yet preserves very precise tolerances to maintain consistent print registration and print quality, has always been a delicate and sometimes unachievable balance. The features outlined herein comprise the central components for achieving this balance in a printing mechanism that supports continuous, uniform thickness print media and inserted multi-part thickness media (forms) utilizing two separate and distinct feed mechanisms. The features are a unique combination of proven engineering principles that accomplish this basic operational balance.

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Forms Feeding and Printhead Gap Compliance System in a Low End Printer

      In any printing mechanism, the need for a compliant system that
accepts multi-styles of printing media, yet preserves very precise
tolerances to maintain consistent print registration and print
quality, has always been a delicate and sometimes unachievable
balance.  The features outlined herein comprise the central
components for achieving this balance in a printing mechanism that
supports continuous, uniform thickness print media and inserted
multi-part thickness media (forms) utilizing two separate and
distinct feed mechanisms.  The features are a unique combination of
proven engineering principles that accomplish this basic operational
balance.

1.  An automatic printhead-to-paper gap compliance system is
    activated when forms are inserted in the document feed mechanism
    (Fig. 1).  Regardless of the forms being used, this system
    utilizes the form thickness to move the printhead and printhead
    guide system to compensate for the thickness of that particular
    form.  This maintains a nearly constant printhead-to-paper
    distance, regardless of the form thickness.

          This compensating motion occurs when the back-up (pressure
    roll) shaft is moved by inserting the form.  This motion is
    transferred through the forms compensation bearing to the forms
    compensation plate and is equal on each end via the forms
    compensation torsion shaft.  The printhead guide shaft is
    attached to the forms compensation plates through bushings at
    each end.  The printhead/carrier combination traverses this guide
    shaft.  Thus, when any form is inserted anywhere in the document
    path, the printhead is moved back (away from the platen) to
    compensate for this additional thickness.  This function prolongs
    the printhead life by allowing it to operate at or near its
    optimum gap through the many varieties of printing media.

2.  An integral spring in the forms compensation bearing reduces the
    effects of manufacturing variations (tolerances, run-out, etc.,)
    of the forms feeding shafts on the forms compensation mechanism.
    This spring absorbs the run-out, etc., from both the forms
    feeding and pressure roll shafts without imparting this motion to
    the forms compensation function.

          This spring is molded in the inside diameter of the forms
    compensation bearing (Fig. 2).  It exerts a small force on the
    pressure roll shaft to maintain constant contact with the feed
    roller shaft.  This spring absorbs the manufacturing variations
    of both of these shafts, while preventing this motion from being

    transmitted to the forms compensation components.  The design
    dictates that the bearing orientation is always the same in the
    assembly.

          This integral spring also...