Method and apparatus for controlling heaters in a continuous ink jet print head

#The present invention relates to a method and apparatus for operating heaters of a print head in a continuous ink jet to provide a stream of ink droplets. In particular, the present invention relates to a method and apparatus for generating a pulsetrain to operate the heaters of the print head to allow variation in pulse width and/or pulse period.

#Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because of various advantages such as its non-impact, low noise characteristics and system simplicity. For these reasons, ink jet printers have achieved commercial success for home and office use and other areas.

#Traditionally, color ink jet printing is accomplished by one of two technologies, referred to as drop-on-demand and continuous stream printing. Both technologies require independent ink supplies for each of the colors of ink provided. Ink is fed through channels formed in the print head. Each channel includes a nozzle from which droplets of ink are selectively extruded and deposited upon a medium. Each technology requires separate ink delivery systems for each ink color used in printing. Ordinarily, the three primary subtractive colors, i.e. cyan, yellow and magenta, are used because these colors can produce up to several million perceived color combinations.

#FIG. 1 is a schematic block diagram of an asymmetric heat-type continuous ink jet printing apparatus capable of implementing the method of the present invention.

#FIG. 2 is a schematic diagram of an exemplary embodiment of a nozzle provided on the print head.

#FIG. 3 is a schematic diagram of one configuration of a print head in accordance with one embodiment having a plurality of nozzles showing the circuitry of SIDE 1.

#As will be evident from the discussion below, the present invention provides an effective method for controlling the heaters of a print head in a continuous ink jet printer. In this regard, it should initially be noted that whereas the method as applied to a specific example is described, the present invention is not limited thereto but may be applied to other embodiments where the configuration of the printer, print head and/or heaters is different than that shown in the various figures.

#FIG. 1 is a schematic block diagram of an asymmetric heat-type continuous ink jet printer system 1 capable of implementing the method of the present invention. The printer system 1 includes an image source 10 such as a scanner or computer which provides raster image data, outline image data in the form of a page description language, or other forms of digital image data. This image data is processed by an image processing unit 12 which also stores the image data in a memory (not shown). In this regard, the image processing unit 12 may perform various image enhancing algorithms, color correction to match the output devices, etc. A heater control circuit 14 which is controlled in the present embodiment by the micro-controller 24 reads data from the image memory and applies electrical pulses to a heater 50 that applies heat to a nozzle that is part of a print head 16. These pulses are applied at an appropriate time, and to the appropriate nozzle as described in further detail below, so that drops formed from a continuous ink jet stream will print spots on a recording medium 18 in the appropriate position designated by the data in the image memory and in the appropriate darkness or pixel graytone value.

#Recording medium 18 is moved relative to print head 16 by a recording medium transport system 20 which is electronically controlled by a recording medium transport control system 22 which in turn, is controlled by a micro-controller 24. The recording medium transport system is shown in FIG. 1 as a schematic only, and many different mechanical configurations are possible in various embodiments. For example, a transfer roller could be used as recording medium transport system 20 to facilitate transfer of the ink drops to recording medium 18. Such transfer roller technology is well known in the art. In the case of page width print heads, it is most convenient to move recording medium 18 past a stationary print head. However, in the case of scanning print systems, it is usually most convenient to move the print head along one axis (the sub-scanning direction) and the recording medium along an orthogonal axis (the main scanning direction) in a relative raster motion.