Patent Number: 6,293,143

Title: Ink level sensing device and method therefor

Abstract: The invention relates to an ink level sensing apparatus including an ink cartridge having an ink chamber containing ink and having at least one substantially transparent side panel adjacent the ink chamber. A fluorescent material is disposed in the ink chamber, the fluorescent material being substantially insoluble in the ink and having a specific gravity which is sufficiently lower than the ink to provide an interface between the ink and the fluorescent material. A relatively narrow band light source for emitting light at a first wavelength along a light path through the substantially transparent side panel of the ink cartridge is provided for exciting the fluorescent material. A photosensor for receiving light emitted from a fluorescent material at a second wavelength when the excited fluorescent material crosses the light path is provided, wherein the first and second wavelengths are substantially different. The apparatus provides a means for sensing ink level in an ink cartridge in a reliable relatively inexpensive way.

Inventors: Denton; Gary Allen (Lexington, KY), Routt, Jr.; Wilson Morgan (Lexington, KY)

Assignee: Lexmark International, Inc.

International Classification: B41J 2/175 (20060101); G01F 23/284 (20060101); G01F 23/292 (20060101); G01F 023/00 (); B41J 002/195 (); G01J 001/42 ()

Expiration Date: 09/25/2018