This invention relates to an ink tank for an ink jet printhead.
Ink jet printheads include an ink tank (reservoir), some form of pressure regulator, an ejector chip (such as a heater chip) with nozzle plate, a filter, and ink passages to carry ink from the ink reservoir to the ejector chip. The ejector chip jets the ink out through the nozzle plate. The ink reservoir can be integral with the printhead or can be a separate, removable tank. A printhead with ink reservoirs contained in separate, removable tanks should be able to continue operating after the tank is removed and replaced. When a tank is removed, air can be drawn into the printhead and can cause some or all of the ink ejection nozzles to be starved of ink, which can cause print defects. Additionally, in a replaceable tank system the ink ejector chip may fill with air if the tank is run too low.
In order for the ink ejector chip to eject ink droplets, ink must be present in or at the chip. If air is present in the ink ejector chip, the chip may not effectively eject droplets and may not effectively draw ink from the tank or reservoir. It is therefore often necessary to purge the air from the printhead after a new tank is installed. This process is referred to as retiring the printhead. The present invention provides an apparatus that reprimes the printhead when a new tank is installed.
The present invention provides an ink tank with one or more ink reservoir chambers, and a priming piston or pistons incorporated into the tank. The piston can be activated by a linkage in the printer such that when the tank is first installed, the piston will be actuated. This draws a volume of ink out of the ink exit orifice, through the ink channels in the printhead, and into the ink ejector chip, thereby retiring the printhead.
Accordingly, it is a first aspect of the present invention to provide an ink tank for an inkjet printer, including: a tank body having at least one chamber for holding ink, and at least one outlet through which ink may pass to feed ink to a printhead; at least one priming cylinder in fluid communication with the at least one chamber and enclosing a displacement volume; and at least one piston capable of sliding longitudinally within the at least one priming cylinder, whereby at least a portion of the displacement volume is expelled into the at least one chamber upon actuation of the piston. The piston can include a section containing at least one annular ring around its lateral surface, where the annular ring forms a seal with the wall of the priming cylinder. In one more detailed embodiment, the piston can include a section containing helical rings around its lateral surface, where the gap between adjacent helical rings forms a circuitous vent path through which air can travel. In an alternate more detailed embodiment, the piston can include a section containing a serpentine path on its lateral surface, where the serpentine path forms a vent path through which air can travel.
Either of these more detailed embodiments may be practiced with the following variations. The priming cylinder can include a first orifice in fluid communication with atmosphere, and second and third orifices in fluid communication with the chamber. The first orifice of the priming cylinder can be in fluid communication with the second and third orifices of the priming cylinder if the piston is positioned at the beginning point in its stroke. The first orifice of the priming cylinder can be isolated from fluid communication with the second and third orifices of the priming cylinder if the piston is positioned such that its annular rings are located between the first and second orifices of the priming cylinder. At least a portion of the displacement volume can be expelled into the chamber if the piston is positioned such that its annular rings are located between the first and second orifices of the priming cylinder, and if the piston slides longitudinally toward the second and third orifices of the priming cylinder. The second orifice of the priming cylinder can be in fluid communication with atmosphere if the piston is positioned such that the second orifice of the priming cylinder is located between the at least one annular ring and the helical rings.
In an alternative embodiment of the first aspect of the present invention, the tank body has an open top, a separate lid component covering the open top of the tank body, and the priming cylinder is molded integrally with the lid. This alternative embodiment may be practiced with all the variations and detailed embodiments described above.
It is a second aspect of the present invention to provide an ink tank for an inkjet printer, including: a tank body having a plurality of chambers for holding ink, each of the plurality of chambers having an outlet through which ink may pass to feed ink to a printhead; a plurality of priming cylinders, each of which is in fluid communication with one of the plurality of chambers, and each of which encloses a displacement volume; and a plurality of pistons, each of which is capable of sliding longitudinally within one of the plurality of priming cylinders, whereby at least a portion of each of the plurality of displacement volumes is expelled into one of the plurality of chambers upon actuation of the plurality of pistons. The second aspect of the present invention may be practiced in all the variations and embodiments described above for the first aspect.
It is a third aspect of the present invention to provide a method for priming an inkjet printhead comprising the steps of: providing an ink tank having: (a) a tank body having at least one chamber for holding ink, and at least one outlet through which ink may pass to feed ink to a printhead; (b) at least one priming cylinder in fluid communication with the at least one chamber and enclosing a displacement volume; and (c) at least one piston capable of sliding longitudinally within the at least one priming cylinder; and actuating the piston such that least a portion of the displacement volume is expelled into the at least one chamber. In a detailed embodiment, the step of actuating the piston comprises the act of sliding the piston longitudinally within the priming cylinder. In a more detailed embodiment, the act of sliding the piston longitudinally within the priming cylinder is performed by application of a force by a mechanism external to the ink tank. The piston can include a section containing at least one annular ring around its lateral surface, where the annular ring forms a seal with the wall of the priming cylinder. The piston can include a section containing helical rings around its lateral surface, where the gap between adjacent helical rings forms a circuitous vent path through which air can travel. Alternatively, the piston can include a section containing a serpentine path on its lateral surface, where the serpentine path forms a vent path through which air can travel.
The present invention provides an ink tank with one or more ink reservoir chambers, and a priming piston or pistons incorporated into the tank. The piston can be activated by a linkage in the printer such that when the tank is first installed, the piston will be actuated. This draws a volume of ink out of the ink exit orifice, through the ink channels in the printhead, and into the ink ejector chip, thereby retiring the printhead. Since the ink ejector chip primarily ingests air when the tank is emptied, a reprime is particularly needed when a new full tank is installed.
As seen in
As discussed above, when the ink tank is shipped to customer, the piston is in the starting position shown in
Upon installation of the ink tank in a printer, the ink exit orifice 23 is unsealed, and the ink tank is ready for priming. Priming is performed by sliding the piston to the left inside the cylinder, which can be accomplished by application of force to the piston by a mechanism in the printer in the exemplary embodiment. With reference to
This invention provides a priming piston that allows the tank to be vented during shipping, sealed and pressurized during priming, and control evaporation and venting after prime.
Having described the invention with reference to exemplary embodiments, it is to be understood that the invention is defined by the claims and it not intended that any limitations or elements describing the exemplary embodiment set forth herein are to be incorporated into the meanings of the claims unless such limitations or elements are explicitly listed in the claims. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.
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Number | Date | Country | |
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20060119673 A1 | Jun 2006 | US |