System and method for attenuating the drying of ink from a printhead during periods of printer inactivity

Abstract

A capping station is configured for storing printheads during printer inactivity to preserve the viscosity of the ink in the nozzles of the printheads. Each capping station has a receptacle, a planar member having a shaft that moves bidirectionally within an opening in a floor of the receptacle, a source of cleaning fluid, and a vacuum source. A controller is operatively connected to actuators to move the receptacle so a seal on an upper wall of the receptacle engages a printhead housing and to move the planar member within the receptacle. The controller also operates a pump to move cleaning fluid through the receptacle and to operate the vacuum source to pull ink from the nozzles of a printhead to the faceplate of the printhead. The planar member is moved proximate the faceplate so the ink forms a film that preserves the viscosity of the ink in the nozzles.

Claims

1. A capping station for storing printheads during periods of printhead inactivity comprising: a receptacle having at least one wall and a floor configured to enclose a volume partially, the at least one wall of the receptacle having a first opening and the floor having an opening; a seal mounted to an upper surface of the at least one wall of the receptacle; a planar member having a shaft extending perpendicularly from the planar member through the opening in the floor of the receptacle; a vacuum source operatively connected to the first opening in the receptacle; a first actuator operatively connected to the receptacle, the first actuator being configured to move the receptacle bidirectionally in a direction aligned through the opening in the floor of the receptacle; a second actuator operatively connected to the shaft, the second actuator being configured to move the shaft bidirectionally in the opening of the floor; and a controller operatively connected to the first actuator, the second actuator, and the vacuum source, the controller being configured to operate the first actuator to move the receptacle and engage the seal with a printhead housing that surrounds a printhead faceplate, operate the vacuum source to apply a slight vacuum to volume enclosed by the printhead faceplate, the at least one wall, and the floor when the seal engages the printhead housing, and operate the second actuator to move the planar member proximate the printhead faceplate to form a film with ink pulled from nozzles in the printhead faceplate between the planar member and the printhead faceplate.

2. The capping station of claim 1, the planar member further comprising: a base section; and an ink receiving surface.

3. The capping station of claim 2 wherein the base section is made of hydrophobic material and the ink receiving surface is made of hydrophilic material.

4. The capping station of claim 3, the at least one wall of the receptacle further having a second opening and a third opening; and the capping station further comprising: a fluid source fluidly connected to the second opening; a pump operatively connected between the second opening and the fluid source, the pump being configured to pull fluid from the fluid source; a valve being operatively connected to the third opening, the valve being configured to move between a first position that opens the third opening and a second position that closes the third opening; and the controller being operatively connected to the pump and the valve, the controller further configured to: operate the valve to open the third opening and operate the pump to pull fluid from the fluid source and into the volume of the receptacle through the second opening and out of the receptacle through the third opening; and operate the valve to close the third opening and deactivate the pump to stop fluid flow through the volume of the receptacle.

5. The capping station of claim 4, the controller being further configured to: operate the valve and the pump to enable fluid flow through the volume of the receptacle and then stop the fluid flow through the volume of the receptacle before the controller operates the vacuum source to apply a slight vacuum to the volume of the receptacle.

6. The capping station of claim 5 wherein the seal is comprised essentially of an elastomeric material.

7. A method for operating a capping station to store printheads during periods of printhead inactivity comprising: operating a first actuator with a controller to move a receptacle having at least one wall and a floor that partially enclose a volume within the receptacle so a seal mounted to an upper surface of the at least one wall of the receptacle engages with a printhead housing that surrounds a printhead faceplate; operating a vacuum source with a controller to apply a slight vacuum to the volume enclosed by the printhead faceplate, the at least one wall, and the floor when the seal engages the printhead housing; and operating with the controller a second actuator operatively connected to a shaft that extends perpendicularly from a planar member within the volume of the receptacle through an opening in the floor of the receptacle to move the planar member proximate the printhead faceplate to form a film with ink pulled by the slight vacuum from nozzles in the printhead faceplate between the planar member and the printhead faceplate.

8. The method of claim 7 further comprising: operating with the controller a valve operatively connected to a second opening in the at least one wall of the receptacle to open the second opening and operating with the controller a pump interposed between a fluid source and a third opening in the at least one wall of the receptacle to pull fluid from the fluid source into the volume of the receptacle through the through opening and out of the receptacle through the third opening; and operating with the controller the valve to close the third opening and deactivate the pump to stop fluid flow through the volume of the receptacle.

9. The method of claim 8 further comprising: operating the valve and the pump with the controller to provide fluid flow through the volume of the receptacle and then stop the fluid flow through the volume of the receptacle before operating the vacuum source with the controller to apply a slight vacuum to the volume of the receptacle.

10. A printer comprising: a plurality of printheads; a capping station for each printhead in the plurality of printheads, each capping station including: a receptacle having at least one wall and a floor configured to enclose a volume partially, the at least one wall of the receptacle having a first opening and the floor having an opening; a seal mounted to an upper surface of the at least one wall of the receptacle; a planar member having a shaft extending perpendicularly from the planar member through the opening in the floor of the receptacle; a vacuum source operatively connected to the first opening in the receptacle; a first actuator operatively connected to the receptacle, the first actuator being configured to move the receptacle bidirectionally in a direction aligned through the opening in the floor of the receptacle; a second actuator operatively connected to the shaft, the second actuator being configured to move the shaft bidirectionally in the opening of the floor; and a controller operatively connected to the first actuator, the second actuator, and the vacuum source, the controller being configured to operate the first actuator to move the receptacle and engage the seal with a printhead housing that surrounds a printhead faceplate, operate the vacuum source to apply a slight vacuum to volume enclosed by the printhead faceplate, the at least one wall, and the floor when the seal engages the printhead housing, and operate the second actuator to move the planar member proximate the printhead faceplate to form a film with ink pulled from nozzles in the printhead faceplate between the planar member and the printhead faceplate.

11. The printer of claim 10, the planar member of the capping station further comprising: a base section; and an ink receiving surface.

12. The printer of claim 11 wherein the base section of the planar member is made of hydrophobic material and the ink receiving surface of the planar member is made of hydrophilic material.

13. The printer of claim 12, the at least one wall of the receptacle of the capping station further having a second opening and a third opening; and the capping station further comprising: a fluid source fluidly connected to the second opening; a pump operatively connected between the second opening and the fluid source, the pump being configured to pull fluid from the fluid source; a valve being operatively connected to the third opening, the valve being configured to move between a first position that opens the third opening and a second position that closes the third opening; and the controller being operatively connected to the pump and the valve, the controller further configured to operate the valve to open the third opening and operate the pump to pull fluid from the fluid source and into the volume of the receptacle through the second opening and out of the receptacle through the third opening; and operate the valve to close the third opening and deactivate the pump to stop fluid flow through the volume of the receptacle.

14. The printer of claim 13, the controller of the capping station being further configured to: operate the valve and the pump to enable fluid flow through the volume of the receptacle and then stop the fluid flow through the volume of the receptacle before the controller operates the vacuum source to apply a slight vacuum to the volume of the receptacle.

15. The printer of claim 14 wherein the seal is comprised essentially of an elastomeric material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing aspects and other features of a system and method that enable ink at the nozzles of a printhead to maintain a low viscosity state are explained in the following description, taken in connection with the accompanying drawings.

(2) FIG. 1A is a schematic drawing of an aqueous inkjet printer that prints ink images directly to a web of media and that attenuates evaporation of fast drying inks from the printheads of the printer and FIG. 1B is a side view showing the positions of the printhead array and capping stations during printing operations.

(3) FIG. 2A is a schematic drawing of a printhead capping system used in the printer of FIG. 1A and FIG. 1B that preserves the viscosity of a fast-drying ink during a period of inactivity and FIG. 2B depicts the structure of the planar member in the printhead capping system of FIG. 2A.

(4) FIG. 3A, FIG. 3B, and FIG. 3C are schematic diagrams of the printhead capping station shown in FIG. 2 being used to attenuate the evaporation of fast drying inks from the printheads of the printer during periods of printhead inactivity.

(5) FIG. 4 is a flow diagram of a process for capping a printhead in the printer of FIG. 1 so evaporation of fast drying inks from the printheads of the printers is reduced.

(6) FIG. 5 is a schematic diagram of a prior art ink delivery system that is used in prior art printers for purging only.

(7) FIG. 6A and FIG. 6B are schematic diagrams of a prior art capping station.

DETAILED DESCRIPTION

(8) For a general understanding of the environment for the system and method disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein, the word printer encompasses any apparatus that produces ink images on media, such as a digital copier, bookmaking machine, facsimile machine, a multi-function machine, or the like. As used herein, the term process direction refers to a direction of travel of an image receiving surface, such as an imaging drum or print media, and the term cross-process direction is a direction that is substantially perpendicular to the process direction along the surface of the image receiving surface. Also, the description presented below is directed to a system for preserving the operational status of inkjets in an inkjet printer during periods of printer inactivity. The reader should also appreciate that the principles set forth in this description are applicable to similar imaging devices that generate images with pixels of marking material.

(9) FIG. 1A illustrates a high-speed aqueous ink image producing machine or printer 10 in which a controller 80 has been configured to perform the process 400 described below to operate the capping system 60 (FIG. 1B) so the ink at the nozzles of the printheads 34A, 34B, 34C, and 34D maintain a low viscosity state during periods of printhead inactivity. As illustrated, the printer 10 is a printer that directly forms an ink image on a surface of a web W of media pulled through the printer 10 by the controller 80 operating one of the actuators 40 that is operatively connected to the shaft 42 to rotate the shaft and the take up roll 46 mounted about the shaft. In one embodiment, each printhead module has only one printhead that has a width that corresponds to a width of the widest media in the cross-process direction that can be printed by the printer. In other embodiments, the printhead modules have a plurality of printheads with each printhead having a width that is less than a width of the widest media in the cross-process direction that the printer can print. In these modules, the printheads are arranged in an array of staggered printheads that enables media wider than a single printhead to be printed. Additionally, the printheads can also be interlaced so the density of the drops ejected by the printheads in the cross-process direction can be greater than the smallest spacing between the inkjets in a printhead in the cross-process direction. Printer 10 can also be a printer that has a media transport system that replaces the moving web W to carry cut media sheets past the printheads for the printing of images on the sheets.

(10) The aqueous ink delivery subsystem 20, such as the one shown in FIG. 5, has at least one ink reservoir containing one color of aqueous ink. Since the illustrated printer 10 is a multicolor image producing machine, the ink delivery system 20 includes four (4) ink reservoirs, representing four (4) different colors CYMK (cyan, yellow, magenta, black) of aqueous inks. Each ink reservoir is connected to the printhead or printheads in a printhead module to supply ink to the printheads in the module. Pressure sources and vents of the purge system 24 are also operatively connected between the ink reservoirs and the printheads within the printhead modules, as described above, to perform manifold and inkjet purges. Additionally, although not shown in FIG. 1A, each printhead in a printhead module is connected to a corresponding waste ink tank with a valve as described previously with reference to FIG. 5 to enable the collection of purged ink during the manifold and inkjet purge operations previously described. The printhead modules 34A-34D can include associated electronics for operation of the one or more printheads by the controller 80 although those connections are not shown to simplify the figure. Although the printer 10 includes four printhead modules 34A-34D, each of which has two arrays of printheads, alternative configurations include a different number of printhead modules or arrays within a module. The controller 80 also operates the capping system 60 and one or more actuators 40 that are operatively connected to components in the capping system 60 to preserve the low viscosity of the ink in the nozzles of the printheads in the printhead modules as described more fully below.

(11) After an ink image is printed on the web W, the image passes under an image dryer 30. The image dryer 30 can include an infrared heater, a heated air blower, air returns, or combinations of these components to heat the ink image and at least partially fix an image to the web. An infrared heater applies infrared heat to the printed image on the surface of the web to evaporate water or solvent in the ink. The heated air blower directs heated air over the ink to supplement the evaporation of the water or solvent from the ink. The air is then collected and evacuated by air returns to reduce the interference of the air flow with other components in the printer.

(12) As further shown, the media web W is unwound from a roll of media 38 as needed by the controller 80 operating one or more actuators 40 to rotate the shaft 42 on which the take up roll 46 is placed to pull the web from the media roll 38 as it rotates with the shaft 36. When the web is completely printed, the take-up roll can be removed from the shaft 42. Alternatively, the printed web can be directed to other processing stations (not shown) that perform tasks such as cutting, collating, binding, and stapling the media.

(13) Operation and control of the various subsystems, components and functions of the machine or printer 10 are performed with the aid of a controller or electronic subsystem (ESS) 80. The ESS or controller 80 is operably connected to the components of the ink delivery system 20, the purge system 24, the printhead modules 34A-34D (and thus the printheads), the actuators 40, the heater 30, and the capping station 60. The ESS or controller 80, for example, is a self-contained, dedicated mini-computer having a central processor unit (CPU) with electronic data storage, and a display or user interface (UI) 50. The ESS or controller 80, for example, includes a sensor input and control circuit as well as a pixel placement and control circuit. In addition, the CPU reads, captures, prepares and manages the image data flow between image input sources, such as a scanning system or an online or a work station connection, and the printhead modules 34A-34D. As such, the ESS or controller 80 is the main multi-tasking processor for operating and controlling all of the other machine subsystems and functions, including the printing process.

(14) The controller 80 can be implemented with general or specialized programmable processors that execute programmed instructions. The instructions and data required to perform the programmed functions can be stored in memory associated with the processors or controllers. The processors, their memories, and interface circuitry configure the controllers to perform the operations described below. These components can be provided on a printed circuit card or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits can be implemented with a separate processor or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with discrete components or circuits provided in very large scale integrated (VLSI) circuits. Also, the circuits described herein can be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits.

(15) In operation, image data for an image to be produced are sent to the controller 80 from either a scanning system or an online or work station connection for processing and generation of the printhead control signals output to the printhead modules 34A-34D. Additionally, the controller 80 determines and accepts related subsystem and component controls, for example, from operator inputs via the user interface 50 and executes such controls accordingly. As a result, aqueous ink for appropriate colors are delivered to the printhead modules 34A-34D. Additionally, pixel placement control is exercised relative to the surface of the web to form ink images corresponding to the image data, and the media can be wound on the take-up roll or otherwise processed.

(16) As shown in FIG. 1B, a plurality of capping stations 60 are positioned behind the printhead modules 34A, 34B, 34C, and 34D during printing operations. When one of more printheads need long term storage, the corresponding printhead is raised by the controller 80 operating one of the actuators 40 and the corresponding capping station 60 is moved opposite and underneath the raised printhead by the controller 80 operating another one of the actuators 40. The controller 80 then operates the actuators, printhead, and capping station components as described in more detail below to preserve the operational status of the printhead during a period of printhead inactivity. When the printhead is returned to operational status, the controller 80 operates the actuators 40 to lift the printhead from its capping station, return the capping station to a position behind the printhead, and lower the printhead to its printing position.

(17) Using like numbers for like components, a capping station that can attenuate the evaporation of quickly drying inks from printheads is shown in FIG. 2A. The capping station 60 includes a receptacle 204, a sealing member 208, a fluid inlet 212, a vacuum connection 216, a fluid outlet 220, and a perimeter seal 224. The receptacle 204 is a housing having at least one wall and a floor that partially surrounds a volume of air. The sealing member 208 is a T-shaped member having a planar member 228 that is supported by a shaft 232 that extends through an opening 236 in the floor of the receptacle 204. The planar member 228 has a length and width that corresponds to a horizontal cross-section of the volume within the receptacle 204. One of the actuators 40 is operatively connected to the shaft 232 and is configured to move the shaft bidirectionally within opening 236 to raise and lower the planar member 228 within the receptacle 204. The controller 80 is operatively connected to the actuators 40 to operate one of the actuators to move the planar member 228 within the receptacle 204. Another actuator 40 is operatively connected to the receptacle 204 and the controller 80 to enable the controller to operate the actuator and move the receptacle vertically. The perimeter seal 224 is mounted along the perimeter of the receptacle at an upper surface of the wall of the receptacle 204. This seal is made of an elastomeric material that hermetically seals the volume within the receptacle 204 when the controller 80 operates one of the actuators 40 to move the receptacle vertically toward the printhead 240 so the perimeter seal contacts printhead housing 244 and surrounds the perimeter of the nozzle faceplate 248 of the printhead 240.

(18) With continued reference to FIG. 2A, the fluid inlet 212 is fluidly connected with a source of cleaning fluid 252. A pump 256 is interposed between the fluid inlet 212 and the fluid source 252 and is connected to controller 80 so the controller can operate the pump to move cleaning fluid from the source 252 into the receptacle 204 through the fluid inlet 212. Once the volume of the receptacle is filled when the receptacle is pressed against the printhead housing 244, the cleaning fluid exits the receptacle through the fluid outlet 220. A valve 260 is interposed between the fluid outlet 220 and a used fluid reservoir (not shown). The controller 80 is operatively connected to the valve 260 so the controller operates the valve to open and close the fluid outlet 220 from the receptacle 204. A vacuum source 264 is operatively connected to the vacuum inlet 216 and the controller 80 so the controller can operate the vacuum source 264 to apply a vacuum to the volume within the receptacle 204 selectively.

(19) The planar member 208 is shown in more detail in FIG. 2B. The planar member 208 includes a base section 268 that joins shaft 232 and an ink receiving surface 272. The ink receiving surface, which contacts fluid held between the nozzle faceplate 248 and surface 272, is made of hydrophilic material, which has a high surface energy, while the base section 268 is made of hydrophobic material, which has a low surface energy. These material choices ensure the ink from the printhead stays on the hydrophilic surface 272 to form a film having a uniform thickness. When the planar member 208 is slowly moved so cleaning fluid on the surface 272 mixes with ink on the faceplate 248 to form this film, it squeezes the film to ensure any air bubbles entrained in the film escape through the fluid outlet 220 before the valve 260 is closed.

(20) Using like numbers for like components, the capping station 60 that can attenuate the evaporation of quickly drying inks from printheads is shown in use in FIG. 3A, FIG. 3B, and FIG. 3C. This system 60 differs from the one shown in FIG. 5A and FIG. 5B in that controller 80 is configured to perform the process 400 shown in FIG. 4 between print jobs or other periods of printhead inactivity to operate the capping station to reduce ink drying at the nozzles of the printhead 240 in one of the modules 34A, 34B, 34C, and 34D. FIG. 4 depicts a flow diagram for the process 400 that operates the capping system 60 to cover the faceplate of the printhead with a film to preserve the viscosity of the ink in the nozzles at the low viscosity. In the discussion below, a reference to the process 400 performing a function or action refers to the operation of a controller, such as controller 80, to execute stored program instructions to perform the function or action in association with other components in the printer. The process 400 is described as being performed with capping station 60 in the printer 10 of FIG. 1A and FIG. 1B for illustrative purposes.

(21) The process 400 of operating the capping station 60 is now discussed with reference to FIG. 4 and the illustrations of FIG. 3A, FIG. 3B, and FIG. 3C. When the printhead is to be capped for a relatively long period of printer inactivity, the controller 80 operates one or more actuators to move the printhead opposite the capping station 60. The controller 80 then opens the valve 260 and operates the pump 256 to pull cleaning fluid from the cleaning fluid source across the planar member 208 and out through the fluid outlet 220 (block 404 and FIG. 3A). When the ink receiving surface of the planar member is clean and a film of cleaning fluid established on that surface, the controller 80 deactivates the pump 256, closes the valve 260, and operates one of the actuators 40 to move the receptacle 204 toward the printhead to engage the printhead housing 244 so the perimeter seal 224 hermetically seals the volume between the planar member 208 and the nozzle faceplate 248 (block 408 and FIG. 3B). Once the volume between the nozzle faceplate and the planar member is sealed, the controller 80 operates the vacuum source 264 to apply a slight vacuum to the volume within the receptacle 204 (block 412). As used in this document, a slight vacuum means a negative pressure sufficient to pull the ink levels in the nozzles to the surface of the faceplate without purging the inkjets. This vacuum action forms an ink barrier on the faceplate that helps prevent air bubbles and particulate matter from entering the nozzles of the printhead. In one embodiment, this slight vacuum is 125 Pa. Once the vacuum is established, the controller 80 operates one of the actuators 40 to move the shaft 232 within the opening 236 so the ink receiving surface 272 of the planar member 208 is proximate but not contacting faceplate 248 (block 416 and FIG. 3C). The ink at the faceplate 248 and the cleaning fluid on the ink receiving surface 272 mix to form a film that is effective for preserving the viscosity of the ink at the nozzles so the ink in the nozzles does not dry out. In one embodiment, the gap between the faceplate 248 and the ink receiving surface 272 of the planar member 228 is in a range of about 250 microns to about 500 microns. One examples of a cleaning fluid that can be used in the capping station is Nippon Kayaku Kayajet CL-66. Once the period of inactivity is completed and the printhead is to be returned to operational status (block 420), the controller 80 deactivates the vacuum source and operates the actuators to pull the planar member into the receptacle 204 and to pull the perimeter seal away from the printhead housing (block 424).

(22) It will be appreciated that variants of the above-disclosed and other features, and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.