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SHEET FLATNESS CONTROL WITH AN ACTIVE BACKSIDE DRYER IN A THERMAL INK JET PRINTER

IP.com Disclosure Number: IPCOM000027733D
Original Publication Date: 1999-Apr-30
Included in the Prior Art Database: 2004-Apr-09
Document File: 4 page(s) / 152K

Publishing Venue

Xerox Disclosure Journal

Abstract

Disclosed is a design of an imaging zone for a Thermal Ink Jet (TIJ) printer that keeps a sheet of paper flat to maintain a precise printhead-to-paper gap control, regardless of paper thickness. Paper is kept flat by tensioning it prior to imaging and by locating its image side directly to the printhead. Additionally, this imaging zone provides a wide drying zone for a non-contacting backside radiant heater and provides for acceptably small lead and trail edge margins for the user's document.

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

SHEET FLATNESS CONTROL WITH AN ACTIVE BACKSIDE DRYER IN A THERMAL INK JET PRINTER
Steven R. Moore
Thomas F. Szlucha
John H. Looney

Proposed Classification
U. S. C1. 347/101 Int. C1. B41j 2/01

Disclosed is a design of an imaging zone for a Thermal Ink Jet (TIJ) printer that keeps a sheet of paper flat to maintain a precise printhead-to-paper gap control, regardless of paper thickness. Paper is kept flat by tensioning it prior to imaging and by locating its image side directly to the printhead. Additionally, this imaging zone provides a wide drying zone for a non-contacting backside radiant heater and provides for acceptably small lead and trail edge margins for the user's document.

XEROX DISCLOSURE JOURNAL - Vol. 24, No. 2 MarcWApril1999 45

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Page 2 of 4

SHEET FLATNESS CONTROL WITH AN ACTIVE BACKSIDE DRYER IN A THERMAL INK JET PRINTER (Cont'd)

One difficult parameter to control in a scanning carriage TIJ printer is the printhead-to- paper gap. Ideally, this gap should be kept uniform across the entire scan width of the printer. The average gap should be kept as small as possible to minimize the pixel placement error caused by misdirected jets. However, if the gap is too small, sheet deformations such as curl and cockle (localized swelling caused by wet ink) can cause the printhead to touch the sheet, resulting in a smudge. The average gap, therefore, is dictated by the sheet flatness that can be achieved.

A common approach to maintaining sheet flatness is to impact a reverse bend in the sheet just prior to imaging. The sheet is driven at an oblique angle against a flat platen surface and the beam strength of the sheet is utilized to create a flat zone. This approach is not suitable for a flat zone length of at least 16.25 millimeters because the length is too long to be reliably achieved. Moreover, this approach does not counteract sheet deformations such as cockle.

The disclosed imaging zone design does not rely on a sheet's beam strength to maintain flatness control. The design is illustrated in the accompanying figure where a control nip 12 is responsible for feeding the sheet's lead edge into the imaging zone. The sheet's lead edge is allowed to travel a calibrated distance along a paper path 14 until it is secured in the distance, causing the sheet to become tensioned. The available drive force at an output nip 16 limits the amount of tensioning. Once the available drive force is exceeded, the sheet lead edge begins to slip at output nip 16, maintaining a constant tension.

The sheet height relative to printhead 20, which is located above a radiant dryer 30, is controlled b...