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IP.com Disclosure Number: IPCOM000027645D
Original Publication Date: 1998-Jun-30
Included in the Prior Art Database: 2004-Apr-08

Publishing Venue

Xerox Disclosure Journal


In order to keep a thermal ink jet printhead printing reliably, each channel must be fired at a time interval which depends on the ink and drop generator design, but is, in general, of the order of 30 seconds. Typically, these maintenance drops are ejected into a waste container in the capping station of the printer. Moving the printhead over to the waste container takes time and affects printing. The maintenance efficiency of a printer could be quantitatively written as the ratio of the number of non-printing maintenance cycles (in this case, waste dump spits) to the number of printed documents. Maintenance spits must be performed every L seconds to guarantee drop-on-demand performance. L in this case is roughly equivalent to the latency of the drop generator system. In a full width array 20 ppm printer, several pages are printed during a typical 30-40 sec. latency period. For segmented, single cartridge printers, 1 to 2 latency periods would expire for every printed color page. Drop on demand for those jets used only at the end of the page would definitely require some form of maintenance during that page's printing. An algorithm can be devised which will allow the drop generator to spit color ink onto pre-printed black portions of a document. Sparsely located color pixels in a black background should not significantly alter the appearance of the black printed areas. This scheme would improve the maintenance efficiency of the printer by reducing the number of color-related, non-printing maintenance cycles.