Continuous ink jet printing with improved drop formation

#Reference is made to commonly assigned, co-pending U.S. patent applications Ser. No. 09/751,232 and Ser. No. 09/750,946 filed Dec. 28, 2000 in the names of David L. Jeanmaire et al., and Ser. No. 09/910,097 filed Jul. 20, 2001 in the name of David L. Jeanmaire et al.

#This invention relates generally to the field of digitally controlled printing devices, and in particular to continuous inkjet printers wherein a liquid ink stream breaks into droplets, some of which are selectively deflected.

#Traditionally, digitally controlled color printing capability is accomplished by one of two technologies. The first technology, commonly referred to as “drop-on-demand” ink jet printing, provides ink droplets for impact upon a recording surface using a pressurization actuator (thermal, piezoelectric, etc.). Selective activation of the actuator causes the formation and ejection of a flying ink droplet that crosses the space between the printhead and the print media and strikes the print media. The formation of printed images is achieved by controlling the individual formation of ink droplets, as is required to create the desired image. Typically, a slight negative pressure within each channel keeps the ink from inadvertently escaping through the nozzle, and also forms a slightly concave meniscus at the nozzle, thus helping to keep the nozzle clean.

#Other features and advantages of the present invention will become apparent from the following description of the preferred embodiments of the invention and the accompanying drawings, wherein:

#FIG. 1 is a schematic plan view of a printhead made in accordance with a preferred embodiment of the present invention;

#FIGS. 2(a)-2(d) consists of a series of diagrams illustrating a frequency control of a heater and drop formation;

#The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art.

#FIG. 1 shows an ink droplet forming mechanism 19 of a preferred embodiment of the present invention. Ink droplet forming mechanism 19 includes a printhead 17, at least one ink supply 14, and a controller 13. Although ink droplet forming mechanism 19 is illustrated schematically and not to scale for the sake of clarity, one of ordinary skill in the art will be able to readily determine the specific size and interconnections of the elements of the preferred.

#In a preferred embodiment of the present invention, printhead 17 is formed from a semiconductor material (silicon, etc.) using known semiconductor fabrication techniques (CMOS circuit fabrication techniques, micro-electro mechanical structure (MEMS) fabrication techniques, etc.). However, it is specifically contemplated and, therefore within the scope of this disclosure, that printhead 17 may be formed from any materials using any fabrication techniques conventionally known in the art.