Ink jet printing method and apparatus

摘要

A method and apparatus for controlling the flow of ink in an ink jet printing system which includes an ink supply reservoir and an ink jet print head comprising an ink inlet, and ink outlet and an ink cavity between the inlet and outlet in fluid communication with a plurality of closely spaced orifices. Valve means are included in the ink inlet and ink outlet, and the valve means are both open to provide an operative mode in which the ink cavity is filled with pressurized ink and a stream of ink is produced from each of the orifices. An idle mode is established periodically when printing is not desired by substantially simultaneously closing both valve means to interrupt the flow of pressurized ink through the print head. The ink then in the print head drains until the surface tension forces at the orifices exceed the pressure within the head. The result is a positive pressure within the print head which is sealed off with the result that no contaminant material is drawn into the print head.