Priming apparatus for liquid ink writing instruments

#In the printing and recording arts, it has been known for some years to deliver ink to the printing or recording pen through small conduits. More particularly, this type of ink delivery system has found special application in ink jet printers and in capillary-type recording pens. In such systems, it occasionally occurs that gases evolve from the ink during operation or during periods of shutdown which can cause flow reductions or outright blockage of ink flow during subsequent operation. Also, the ink may evaporate away from the ink jet or pen outlet, so that the writer is not ready to perform when just actuated, but must await movement of ink back to the outlet. Numerous attempts have been made to overcome the problem of gas evolution in the printing ink by means such as improved ink chemistries and various apparatus for removing gas bubbles from the ink as they form. Various caps have been provided to reduce evaporation. While these approaches have achieved a degreee of success, a need has continued to exist for a simple, reliable priming system which can be used to ensure that the ink lines leading to the ink jet or other pen are filled with ink and free of air bubbles at the time the printer is started.

#The primary object of the invention is to provide a simple, improved priming apparatus for use with ink jet and capillary recording pens or similar writing or printing instruments.

#A further object of the invention is to provide such an apparatus which combines the function of the droplet charging ring used in ink jet printers during printing with the further function of drop removal from the ink jet during priming.

#FIG. 1 shows a schematic view of a priming system according to the present invention, as particularly configured for application to an ink jet printer.

#FIG. 2 shows a section view of the unique priming pump according to the invention.

#FIG. 2a shows a view taken on line a--a of FIG. 2 indicating the details of the inlet and outlet valves for the priming pump.

#There follows a detailed description of preferred embodiments of the invention, reference being made to the drawings in which like reference numbers identify like elements of structure in each of the several Figures.

#With reference to FIG. 1, an apparatus according to the invention is illustrated schematically. Means for applying ink to a suitable medium are provided such as an ink jet printing head 10 of the type disclosed in U.S. Pat. Nos. 3,902,083 and 3,840,758, illustrated schematically; however, those skilled in the art will recognize that a capillary pen could also be used. In operation of an ink jet type printer, droplets are emitted from the printing head and then passed through electrical deflection circuitry of a type known in the art before impinging upon the recording medium (not shown) in the desired pattern to form alphanumeric characters. In a capillary printing system, the pen physically contacts the recording medium; however, delivery to the pen is via a thin capillary-type conduit in a manner somewhat similar to that used in ink jet printers. A source of ink 12 such as a capped bottle is provided which holds a quantity of ink 14 in its lower portion. A conduit 16 extends from printing head 10 to source 12 and down into source 12 to a location below the upper surface of the ink. Preferably, a filter 18 is provided at the lower end of conduit 16 to prevent particulate matter from reaching and potentially clogging the printing head.

#Control circuitry 20 is provided in ink jet applications which charges and deflects the ink drops as necessary to form desired alphanumeric characters in accordance with techniques now well known in the art. Circuitry 20 is connected to the ink jet printing head 10 by means of a conductor 22 and to ink source 12 by means of a conductor 24 which extends down within source bottle 12 into the ink 14 so as to establish proper electrical continuity between the ink and the associated driving and deflection circuitry.