Patent Application
20070247497
The present invention relates generally to inkjet printers, and more specifically, to devices, methods, and systems for supplying ink to inkjet printer printheads.
Ink jet printers are used commonly in offices and home printing applications. They are popular due to their low cost of operation, low energy use and quiet operating features. Ink jet printing involves the ejection of tiny ink droplets through small holes, in a controlled manner, to create the desired image on the media intended to receive the image. Ink is supplied from an ink reservoir to a printhead, which includes various passageways from the reservoir to a plurality of firing chambers having nozzle orifices. Energy is applied to the ink from an ink droplet generator near each orifice, which may include the application of electrostatic attraction, the application of oscillating forces from piezo elements, the application of heat from heating elements or the like.
It is known to provide the nozzle orifices in a printhead cartridge that is mounted on a carriage that may support one or more such printheads. The carriage traverses back and forth across the medium being printed, and ink droplets are emitted as the carriage moves. One of the ways in which ink jet printing can be made faster is simply to move the carriage faster as the ink droplets are emitted. In doing so, it is desirable to minimize the amount of ink contained within the cartridge carried on the carriage, to reduce the weight and thus the momentum of the carriage. Further, the repeated and abrupt reversal in movement direction of the carriage traversing back and forth across the media can create turbulence in the ink, which in turn can cause printing problems due to air absorption, ink foaming and the like.
For some large printing devices, such as plotters used to create drawings, posters or other large printing jobs; or for printers such as color printers and printers designed for high volume print service utilizing large volumes of ink in relatively short time periods, carrying a reasonable volume of ink in the ink cartridge on the carriage has become impractical. If a small volume of ink is carried to reduce weight and momentum of the carriage, frequent change is necessary as the ink supply is rapidly diminished. Alternatively, carrying a large volume of ink in the cartridge makes the cartridge large and heavy, neither of which is desirable for a fast moving carriage.
To satisfy the goal of reducing carriage weight, and to provide adequate ink volumes for printers requiring such, it has been known to provide large volume, off carriage ink reservoirs. A flexible tube connects the ink reservoir to the ink cartridge on the carriage, and only a small amount of ink needs be carried within the cartridge itself.
However, the use of off-carriage ink reservoirs presents its own unique set of problems. It is most often necessary to operate an off carriage ink delivery system at a slight negative or back pressure, to prevent ink dripping from the nozzles. However, back pressure that is too high can result in the printhead becoming deprimed, creating additional printing problems. Further, high back pressure can draw air into the ink supply system, which then can become trapped within the ink, causing even further printing problems.
Additionally, when an emptied ink reservoir is removed from the system and replaced with a fill ink reservoir, air can be introduced into the ink delivery tubing. The trapped air will eventually enter the cartridge or accumulate in a critical location and an accumulation of air in the cartridge or critical location can prematurely end the life of a cartridge by starving the printhead for ink.
What is needed is an ink delivery system that overcomes the aforementioned problems by providing for air removal in the system while simultaneously providing ink to a printhead.
According to one embodiment of the invention, there is disclosed an ink delivery system. The system includes an ink container, operable to interface with and provide ink to a printhead, where the ink container and the printhead are positioned on a moveable carriage. The system also includes an ink supply item, operable to transmit ink to the ink container via an ink conduit, and a vacuum source, coupled to an upper portion of the ink container via an air conduit, where the vacuum source is operable to pull air from the ink container by generating negative pressure in the ink container.
According to one aspect of the invention, the vacuum source is a low pressure pump. The vacuum source can also be a diaphragm pump. According to another aspect of the invention, the ink container further includes a screen operable to interface with a felt of the printhead. According to yet another aspect of the invention, the screen is operable to prevent air from entering the ink container from the printhead. Furthermore, the ink container can include a filter operable to filter the air pulled from the ink container by the vacuum pump. The filter may be a hydrophobic material, and can prevent ink from entering the air conduit.
According to another embodiment of the invention, there is disclosed a method of controlling ink flow in an ink jet printer. The method includes providing an ink container, where the ink container supplies ink to a printhead, and pumping air from the ink container using a vacuum pump, where the vacuum pump is operable to remove air from an upper portion of the ink container. The method also includes automatically supplying ink to the ink container upon the generation of negative pressure in the ink container resulting from the pumping of air from the ink container by the vacuum pump.
According to one aspect of the invention, the method includes supplying ink to the ink container from an ink supply item coupled to the ink container via an ink conduit. According to another aspect, the ink container supplies ink to the printhead via at least one screen that interfaces with a felt of the printhead. The method can also include maintaining pressure in the ink container such that the at least one screen maintains contact with ink within the printhead.
According to yet another aspect of the invention, the vacuum pump is operable to remove air from an upper portion of the ink container via at least one filter. The at least one filter can include a hydrophobic material. Additionally, the ink container can be operable to supply ink to the printhead via at least one screen that interfaces with the printhead. According to another embodiment, air may be pumped from the ink container using a diaphragm pump.
According to yet another embodiment, there is disclosed an ink container for use in an ink delivery system. The ink container includes at least one ink reservoir operable to receive ink from an ink supply item via an ink conduit, a common air chamber, open to the at least one ink reservoir, and an air removal opening for interfacing with the common air chamber. Additionally, the air removal opening is operable to expel air from the at least one ink reservoir resulting from negative pressure in the common air chamber.
According to one aspect of the invention, the ink container also includes an air drain positioned in between the common air chamber and the at least one ink reservoir. The air drain may also include a filter operable to cover the air drain. According to another aspect of the invention, the ink container can include at least one film operable to seal the common air chamber.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
The ink container 22 is normally carried on a carriage that traverses back and forth in close proximity to the media upon which the printed image is being formed. The ink container 22 engages the printhead 15, which has an array of nozzles (not shown) from which ink droplets are emitted in the desired pattern and sequence for creating the desired image on the media intended to receive the printed image. As described in greater detail with respect to
It will be appreciated that the ink supply item 12 includes a housing that encloses an ink reservoir (not illustrated), which may be a flexible bladder or the like, as those skilled in the art will readily understand. The ink supply item 12 may also include an outlet (not illustrated) that connects to the ink conduit 20. According to one aspect of the invention, the ink supply item 12 is mounted in a stationary manner in the printing device, and remains in place even as the carriage carrying ink container 22 traverses back and forth during a printing operation. Thus, the ink supply item 12 may be off carriage, as opposed to the ink container 22 and printhead 15, which may be both on carriage. The ink conduit 20 is sufficiently long and flexible to move as required, to maintain fluid flow communication between ink container 22 and ink supply item 12, even as the ink container 22 is moved during printing. According to another embodiment of the present invention, the ink supply item 12 may also be carried on the carriage such that it is on carriage.
As is shown in
The filter 25 provided at the interface of the air conduit and the air removal portion 27 of the ink container 22 is operable to allow air to enter the air conduit 18 while preventing ink from entering the air conduit 18. According to one aspect of the invention, the filter is constructed of a hydrophobic mesh material, such as porous treated polysulphone, treated acrylic copolymers, porous polytetrafluoroethylene, or other treated polymers. Various hydrophobic materials are available from sources such as Pall Corp or Gore Corp. A suitable hydrophobic material for the filter 25 does not wet easily, and therefore retains a no-liquid pass property even as the material is contacted by ink from within the ink container 22. This property can be significant as the ink level within the ink container 22 may rise to the level of the filter 25 during operation of the ink delivery system 10. It will be appreciated that while only a single filter 25 is illustrated in the side view of the ink delivery system 10 shown in
Referring again to
Because the ink supply item 12 is positioned at a lower height than the ink container 22 in the ink delivery system 10, the screen's 24 ability to prevent air from entering the ink container 22 prevents the ink within the ink container from draining back into the ink supply item 12. Additionally, it will be appreciated that air is accumulated within the ink container 22 away from the screen 24 to prevent high pressure from developing at the ink supply interface with the printhead 15, which could prevent the printhead 15 from being resupplied with ink.
As described above, the printhead 15 may be a vented printhead, and the ink required for operation will be provided directly from the felt, which receives the ink from the ink container 22. The felt in the printhead 15 can also include and/or be replaced by foam or fibrous materials. Ink used from the felt creates the pressure demand for ink replenishment. A non-vented printhead can have a flexible member to replace the capacitance function of the felt. Additionally, the removal of air from the ink container 22 supply subsystem so that ink is always against the screen, or supplied to the printhead keeping the pressure drop low. With this air removal configuration the ink delivery system 10 can be shipped dry and then primed with ink during a machine initialization process. The air removal stops when ink is against filter 25, at this time the vacuum system only exerts pressure on the filter 25 and no longer on the ink container 22.
It will be appreciated by one of ordinary skill in the art that the height of ink in the off-carriage ink supply item 12 and the backpressure of ink in the felt of a vented printhead 15 are in equilibrium in the ink delivery system 10. Ink flows in or out of the printhead 15 to maintain this equilibrium. As an illustrative example, with all backpressures measured relative to the nozzle plate, if under normal conditions the ink supply item 12 ink fluid height is 4 cm below the printhead chip, then the printhead backpressure will be −4 cmH2O when equilibrium exists. Continuing with this illustrative example, if the printhead backpressure increases to −5 cmH2O then a 1 cmH2O pressure draw to resupply ink to the printhead 15 is created. Ink will continue to flow until this differential is eliminated. The higher the backpressure difference the faster the ink is replenished to the printhead 15.
It will also be appreciated that during normal printing operations ink is supplied by the printhead 15. In the short term the ink is replaced by a combination of ink coming from the ink container 22 and air coming in through a vent in the printhead 15. As air comes into the printhead 15 the backpressure increases and pulls ink through the ink supply path until the air is replaced with ink. The printing and ink resupply system (which includes the ink container 22, ink conduit 20, and ink supply item 12) act asynchronously. The printhead 15 supplies peak flow requirements while the resupply subsystem replenishes ink at a delayed and normally slower rate. Instead of pulling air into the printhead 15 a non-vented printhead supplies part of the ink by changing volume. The volume change increases backpressure and will decrease and reach equilibrium when the ink is re-supplied and the volume returns to normal. A non-vented printhead system without volumetric changes requires all the demand volume to come from outside of the printhead.
In this design an extra chamber is used to remove air from the system. Therefore, an air receptacle 34 is positioned in the ink container 29, which receives an air conduit (not illustrated) that pumps air out of the ink container 29. The air conduit may be received into a conduit receptacle within or connected to the air receptacle similar to the ink conduit receptacles 36a, 36b, 36c, 36d. As described in detail below, the air receptacle 34 includes an air removal opening in the ink container 29 that receives air from each of the ink reservoirs 30a, 30b, 30c, 30d, specifically, from air drains 32a, 32b, 32c, 32d that are integrated into the ink container 29.
Each air drain 32a, 32b, 32c, 32d is exposed to, or open to, an associated ink reservoir and permits air from the ink reservoir to flow through a respective filter (not illustrated) to the air conduit (not illustrated) via the air receptacle 34. According to one aspect of the invention, the air drains 32a, 32b, 32c, 32d may be covered by one or more filters that prevent the flow of ink within the ink reservoirs 30a, 30b, 30c, 30d into the air conduit. The back side of the ink container 29 of
As shown in
For illustrative purposes, the general location of the ink reservoirs 30a, 30b, 30c, 30d are illustrated with dashed lines in
It will be appreciated that ink from the printhead will wet the one or more screens such that a large quantity of air will not be pulled into the ink container from the printhead. Thus, the pump, which may be a low pressure vacuum pump, is actuated as many times as required (blocks 86, 88) to remove the air from the ink container and replace it with ink. This ink comes primarily from the ink supply item although initially a small amount comes from the printhead. Air stops being removed from the system when ink covers the filters (block 90). Additional pump actuation does nothing to the system since the pressure generated is limited so ink is not pulled through the filters. To achieve backpressure equilibrium between the printhead and off carrier ink source, ink may either come into or leave the printhead. Periodic actuation of the pump can remove any air that may accumulate over time.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
