Nozzle guard for an ink jet printhead
View Patent ↗A nozzle guard ( 80 ) for an ink jet printer with an array ( 14 ) of nozzles ( 22 ) and respective ink ejection means for ejecting ink onto media to be printed. The nozzle guard ( 80 ) has ink containment formations ( 146 ) that stop any misdirected ink droplets or ink leakage from damaged nozzles interfering with the operation of surrounding nozzles or dropping onto the media. To maintain print quality and to stop the supply of ink to damaged nozzles, each containment formation ( 146 ) has an ink sensor. The nozzle or nozzles ( 22 ) within the containment formation are disabled if a predetermined amount of ink is present.
1. A printhead for an ink jet printer, the printhead including:
a substrate carrying an array of nozzles for ejecting ink onto media to be printed, each nozzle incorporating a bend actuator for ejecting ink from a nozzle chamber, the bend actuator being arranged to cause refilling of the nozzle chamber from a supply of ink after ink ejection;
an apertured guard positioned over at least one of the nozzles such that ejected ink passes through an aperture and onto the media;
the guard and the at least one nozzle at least partially defining a containment formation for isolating leaked or misdirected ink from the at least one nozzle from at least some of the other nozzles in the array;
means to detect a predetermined amount of ink in the containment formation; and
nozzle fault circuitry connected to the detection means, the nozzle fault circuitry arranged to stop supply of ink to the at least one nozzle by disabling the associated bend actuator if the predetermined amount of ink is detected by the detection means.
2. A printhead according to claim 1 wherein each nozzle in the array has a respective containment formation to isolate it from all the other nozzles in the array and each of the containment formations has one of said detection means.
3. A printhead according to claim 1 wherein the containment formations isolate predetermined groups of nozzles from the other nozzles in the array; wherein
the detection means and nozzle fault circuitry associated with each of the containment formations is configured to stop further supply of ink to the predetermined group upon sensing a predetermined level of ink in the containment formation.
4. A printhead according to claim 1 wherein the detection means has a pair of electrical contacts positioned in the containment formation such that an accumulation of the predetermined amount of ink closes an electrical circuit such that a comparator of the fault detection circuit disables the actuator.
5. A printhead according to claim 4 wherein the nozzle guard is formed from silicon.
6. A printhead according to claim 4 wherein the nozzle guard further includes fluid inlet openings for directing fluid through the passages, to inhibit the build up of foreign particles on the nozzle array.
7. A printhead according to claim 6 the fluid inlet openings are positioned remote from a bond pad of the nozzle array.
8. A printhead according to claim 1 wherein the containment formation further includes containment walls extending from the guard to the exterior of each of the nozzles.
9. A printhead according to claim 1 wherein the detection means provides feedback for a fault tolerance facility to adjust the operation of other nozzles in the array to compensate for the damaged nozzle.