Ink jet printing apparatus

Claim 1

A printhead assembly for a drop-on-demand ink jet printer, comprising: an ink reservoir having an outlet for excess ink; a printhead being mounted adjacent the ink reservoir and having at least one ink channel that communicates with the reservoir at a location below the reservoir outlet, said at least one ink channel providing a restriction to ink flow and having an ink ejecting orifice at one end of the channel and means operable to cause droplets of ink to be expelled from the orifice for depositing on a recording medium, whereupon the channel is replenished with ink drawn in from the reservoir by capillary action; an ink supply source; an ink supply line from the source to said ink reservoir through which ink is, in turn, drawn into the reservoir from the ink source when ink droplets are expelled from the channel orifice and the channel is replenished from the reservoir; means for delivering ink along the supply line from the source to the ink reservoir when the printhead is not expelling ink droplets, the means for delivering ink being used only to prime the printhead assembly; and said reservoir outlet presenting a restriction to ink flow equal to, or greater than the restriction to ink flow presented by the printhead, the outlet restriction presenting a low restriction to air flow, whereby ink delivered to the ink reservoir by said ink delivering means, to prime the printhead assembly, forces air out of the ink reservoir through said reservoir outlet, so that ink is not forced into the printhead and through the channel orifice until the ink level in the ink reservoir reaches said reservoir outlet.

Claim 11

A method of priming a printhead assembly for a drop-on-demand ink jet printer comprising an ink reservoir connected to a printhead having ink channels communicating with droplet ejecting orifices, which have a predetermined ink flow impedance, the method comprising the steps of: (a) providing a conduit from a flexible ink supply container to the ink reservoir for movement of ink therethrough; (b) providing an outlet in an upper portion of the ink reservoir for unrestricted flow of air therethrough; (c) connecting the ink reservoir to the channels of the printhead with a sealed passageway located in a lower portion of ink reservoir, so that the sealed passageway is below the ink reservoir outlet; (d) moving ink from the supply container through the conduit into the ink reservoir by capillary action during printing and under pressure during priming of the printhead assembly; (e) restricting the flow of ink from the outlet of the printhead reservoir by a flow impedance of ink through the reservoir outlet that is equal or greater than the flow impedance of ink exiting through the printhead orifices; (f) expelling air from the reservoir through the outlet and concurrently filling the reservoir with ink by the movement of ink into the reservoir from the supply container through the conduit, thereby priming the printhead assembly because ink will not flow from the printhead nozzles until the air has been removed from reservoir and replaced with ink; and (g) collecting ink exiting from the outlet of the reservoir and from the printhead orifices during the priming of the printhead.

Claim 12

A method of priming a printhead assembly for a drop-on-demand ink jet printer comprising an ink reservoir connected to a printhead having ink channels communicating with droplet ejecting orifices, which have a predetermined ink flow impedance, the method comprising the steps of: (a) providing a conduit from a flexible ink supply container to the ink reservoir for movement of ink therethrough; (b) providing an outlet in an upper portion of the ink reservoir for unrestricted flow of air therethrough; (c) connecting the ink reservoir to the channels of the printhead with a sealed passageway located in a lower portion of ink reservoir, so that the sealed passageway is below the ink reservoir outlet; (d) moving ink from the supply container through the conduit into the ink reservoir by capillary action during printing and under pressure during priming of the printhead assembly; (e) restricting the flow of ink from the outlet of the printhead reservoir by a flow impedance of ink through the reservoir outlet that is equal or greater than the flow impedance of ink exiting through the printhead orifices; (f) expelling air from the reservoir through the outlet and concurrently filling the reservoir with ink by the movement of ink into the reservoir from the supply container through the conduit, thereby priming the printhead assembly because ink will not flow from the printhead nozzles until the air has been removed from reservoir and replaced with ink; and (g) collecting ink exiting from the outlet of the reservoir and from the printhead orifices during the priming of the printhead.