Browse Prior Art Database

SENSING SYSTEM FOR DETECTING FAILED JETS ON INK JET DEVICES

IP.com Disclosure Number: IPCOM000027679D
Original Publication Date: 1998-Oct-31
Included in the Prior Art Database: 2004-Apr-08
Document File: 4 page(s) / 192K

Publishing Venue

Xerox Disclosure Journal

Abstract

Thermal ink jet printers typically use large arrays of jets or nozzles linearly aligned in a printhead face to eject ink droplets onto a recording medium. A persistent problem for a printing system is the failure of one or more jets to eject ink in proper alignment or to eject ink at all. Figures 1-3 show an optical scanning device which enables a printer in an automated mode to determine which jets in a larger array of jets are either not printing or are expelling misdirected droplets.

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XEROX DISCLOSURE JOURNAL

SENSING SYSTEM FOR DETECTING FAILED JETS ON INK JET DEVICES John D. Sotack

Proposed Classification
U. S. C1.347/023 Int. CL B41j 02/165

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XEROX DISCLOSURE JOURNAL - Vol. 23, No. 5 September/October 1998 21 1

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SENSING SYSTEM FOR DETECTING FAILED JETS ON INK JET DEVICES(CONT'D)

INTEGRATED SENSOR SIGNAL

DISPLACEMENT

FIG. 3

CONTROL

PROCESS DIRECTION

FIG. 4

212 XEROX DISCLOSURE JOURNAL - Vol. 23, No. 5 September/October 1998

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SENSING SYSTEM FOR DETECTING FAILED JETS ON INK JET DEVICES(CONT'D)

Thermal ink jet printers typically use large arrays of jets or nozzles linearly aligned in a printhead face to eject ink droplets onto a recording medium. A persistent problem for a printing system is the failure of one or more jets to eject ink in proper alignment or to eject ink at all. Figures 1-3 show an optical scanning device which enables a printer in an automated mode to determine which jets in a larger array of jets are either not printing or are expelling misdirected droplets.

FIG. 1 is an end view of a print zone 10 of a printer employing either a partial width array or a full width array to form line images 12 on a paper sheet 14. An optical scanning sensor 16 comprises a single line 128 element charged coupled device (CCD) photosensitive array camera 18. The camera is imaged by light from a color light emitting diode (LED) assembly 20 (red, green and blue LEDs) reflecting from line 12 through lens
22. Since the inks are subtractive colors, each will reflect essentially no light when illuminated by its primary color. Sensor 16 is gapped from the paper by a spacer 23 that is part of the sensor.

FIG. 2 shows a test image 30 which has been printed on sheet 14 by a stationary full width printhead printing in cyan. Image 30 consists of four rows of process direction lines 32. Each row contains lines 32 followed by a 3-pixel wide blank area. Because each row contains lines printed by a very faint pixel, coverage for every jet is obtained by printing four rows of lines, each offset a pixel from the previous. The sheet 12 is indexed in the process direction following imaging of each row. For purposes of demonstrating the failed jet sensing concept, it is assumed that the 17th jet from the left end has failed leaving a space at area A.

Sensor 16 is monitored on a translation mechanism which enables the sensor to be scanned in a direction parallel to the full width array and perpendicular to the process direction. The task of the sensor is to identify all failed or misaligned jets by scanning each row of line segments of image 30. After image 30 is printed, the paper is stepped until the frst row is opposite the translation path of the sensor. The sensor is then translated from...