Typewriting machines – Including adjustment for optimum printing plane – Responsive to thickness of record-medium
Reexamination Certificate
2000-01-06
2001-06-26
Eickholt, Eugene (Department: 2854)
Typewriting machines
Including adjustment for optimum printing plane
Responsive to thickness of record-medium
C400S613000, C400S613200
Reexamination Certificate
active
06250823
ABSTRACT:
TECHNICAL FIELD
The present invention relates in general to impact printers, and in particular, to a cover-platen opening mechanism in such printers.
BACKGROUND INFORMATION
Printers used in point-of-sale applications frequently need to have a paper supply reloaded by an operator who may be new to the job, or otherwise untrained. Moreover, it is often necessary that the paper be reloaded while customers are waiting to be served. Impact printers require close tolerances between the printhead and the platen. As a consequence, impact printers according to the prior art require the threading of paper through the printing mechanism, and a simultaneous manipulation of feed actuating mechanisms to load the paper in order that the relationship of the printhead and paper maintain the required tolerance. Moreover, the implementation of alternate paper feed paths in order to provide for the printing of form documents, as well as printing onto paper supplied in bulk, is difficult to implement in point-of-sale impact printers according to the prior art. The close tolerances between the printhead and the platen must be maintained in the presence of forms having different thickness paper. This is precluded in the impact printing mechanisms in printers having a platen and printhead with a fixed relative position, according to the prior art.
Thus, there is a need in the art for a mechanism that allows simple drop-and-load paper loading while maintaining tight head gap tolerances, and in which form thickness compensation is accommodated.
SUMMARY OF THE INVENTION
The present invention addresses the previously mentioned needs by providing a cover-platen opening mechanism that permits drop-in replacement of a paper supply roll without the necessity of threading the paper through the platen and printhead mechanism. At the same time, the cover-platen opening mechanism according to the principles of the present invention maintains the required platen-printhead spacing tolerances.
In a cover-platen opening mechanism according to the principles of the present invention, a platen shaft longitudinally affixed to the platen forms a pivotal attachment to a cover frame. A protrusion on a first end portion of the platen provides a bearing surface for engaging a spring. The platen has a stop attached to a pre-determined one of a first and a second end portion. The stop engages positioning means that displaces in response to the thickness of a form document onto which printing is to be performed. The spacing between the platen and a printhead is thereby adjusted in response to the thickness of the form document.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.
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Harris Richard Hunter
Myers Robert Andrew
Thomas Jeff David
Eickholt Eugene
Flynn John D
International Business Machines - Corporation
Winstead, Sechrest & Minick, LLP
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