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Magnetically Latched Floating Platen

IP.com Disclosure Number: IPCOM000038055D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Ballance, MK: AUTHOR [+3]

Abstract

A magnetically latched floating platen, in a wire matrix serial printer, prevents platen movement when printing on thin documents (single sheets) and is effectively unlatched by insertion of a heavy document (passbook).

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Magnetically Latched Floating Platen

A magnetically latched floating platen, in a wire matrix serial printer, prevents platen movement when printing on thin documents (single sheets) and is effectively unlatched by insertion of a heavy document (passbook).

As shown schematically in the Figure, some wire matrix serial printers, for use in applications such as a bank teller station, are designed with a floating platen 1. The platen is supported by springs 2 at each end, permitting downward movement to accommodate various thickness documents (single sheets, multi- part forms, passbooks, etc.), thus maintaining a constant printhead to printing surface gap so as to maintain uniform print wire contact force and assure uniform printing density. Adjustable stops 3 permit adjustment of the initial printhead to platen gap.

In practice, since the platen is supported only at the ends, the support force is lighter on the ends than it is in the middle. Therefore, its resistance to downward movement, caused by printing pressure, varies across its length, resulting in light printing on the edges of documents and heavy printing in the center. If, during printing, the printing force exceeds the platen support force, the platen will move away, and some print wires with shorter strokes may not contact the paper, resulting in missing dots.

In the present embodiment, this problem is resolved by providing the stops with permanent magnets 4, and embedding armatures 5 in the platen. It i...