The present disclosure relates generally to inkjet printing systems, and more particularly to a device for maintaining printheads of an inkjet printing system and a method of operating such a device.
Inkjet printing systems typically include one or more print units, and each print unit has one or more printheads. A controller controls the printhead to eject a fluid (such as ink or another composition) onto a medium. Each printhead includes a nozzle plate that includes a plurality of orifices (nozzles) through which ink from inside the printhead may be controllably ejected.
A printhead typically includes a fluid chamber in fluid communication with one or more of the nozzles. Pressure inside of the fluid chamber is increased relative to ambient air pressure to force a drop of fluid through the nozzle(s). One type of printhead uses a piezoelectric element that deforms a wall of the fluid chamber to reduce the volume thereof and thereby increase the pressure within the fluid chamber. Alternately, a heating element may be used to vaporize some of the fluid (or a constituent of the fluid such as a fluid carrier or a solvent) in the fluid chamber to form a bubble therein, which increases the pressure inside the fluid chamber. In either case a controller controls the current that is passed through the piezoelectric element to control the deformation thereof or controls the current through the heating element in turn to control the temperature thereof so that drops are formed when needed. Other types of inkjet technologies known in the art may be used in the printing systems described herein.
In a printing system, the printhead is secured to a mount and disposed such that the nozzles of the printhead are directed toward the medium. In some embodiments, more than one printhead may be secured to the mount in a one- or two-dimensional array. Further, some printing systems may include a plurality of mounts, wherein each mount has one or more printheads disposed therein in a one- or two-dimensional array. In such systems, the plurality of mounts may be disposed in the printing system in a one or two-dimensional array and the nozzles of the printheads in these mounts are directed toward the medium.
Dried ink, dust, paper fibers, and other debris can collect on a nozzle plate or in one or more nozzles of the printhead and prevent proper ejection of ink from such nozzles. The controller of a printing system can undertake periodic cleaning cycles during which ink is purged from the nozzle(s) to release any debris in or near such nozzle(s). The purged ink and/or debris must be removed from the nozzle plate in the vicinity of the nozzles, for example, by wiping, so that such purged ink and/or debris does not collect on the nozzle plate and dry to create further debris that will later interfere with ejection of ink from nozzles of the printhead.
According to one aspect, a printhead maintenance station for cleaning a nozzle plate of a printhead of a print unit includes a wiper bar, a wiper secured to the wiper bar, a wiper cleaning assembly, and an actuator. The wiper is stored in the wiper cleaning assembly when not in use. The controller operates the actuator to rotate the wiper bar to move the wiper from the wiper cleaning assembly to a wiping position, and causes relative movement of the printhead maintenance station and the print unit to wipe the nozzle plate with the wiper.
According to another aspect, a method of operating a print head maintenance station to clean a nozzle plate of a printhead of a print unit, wherein the printhead maintenance station includes a wiper bar having a wiper secured thereto, and a wiper cleaning assembly, includes the steps of disposing the wiper in a wiper cleaning assembly and operating an actuator to rotate the wiper bar to move the wiper from the wiper cleaning assembly to a wiping position. The method includes the further step of moving the print unit relative to printhead maintenance station thereby wiping the nozzle plate with the wiper.
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In some embodiments, each printhead 106 of the print unit 102 may print a particular color of ink. As may be apparent to one of skill in the art, the print unit 102 may include, for example, four printheads 106 that print cyan, magenta, yellow, and black ink to form four-color images on the medium 104. The print unit 102 may also include one or more other printheads 106 that print a custom color ink, a white ink, a metallic ink, and/or the like. Each printhead 106 includes a nozzle plate having a plurality of nozzles (orifices) and during operation ink or another liquid may be ejected through such nozzles and deposited on the medium 104. The medium 104 may be coated or uncoated paper, plastic, polyethylene, a metal, and/or any substrate on which ink or another material ejected by the printhead 106 may be deposited.
The printing system 100 includes a controller 112 to coordinate relative movement between the print unit 102 and the medium 104, operation of the printheads 106 to print an image on the medium 104, and maintenance of the printheads 106. In some embodiments, during printing, the medium 104 may be transported in a direction parallel to a first axis 114 while the print unit 102 is transported in a direction parallel to a second axis 116 perpendicular to the first axis 114. In other embodiments, the print unit 102 may be transported in directions parallel to both the first axis 114 and the second axis 116, while the medium 104 is transported parallel to the first axis 114.
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In some embodiments, the controller 112 initiates the maintenance cycle after the print unit 102 has been operated for a predetermined period of time since the last maintenance cycle. In other embodiments, if the medium 104 is a web 118 (
In some cases, the controller 112 may stop the transport of the web 118 or the carrier 124 when the maintenance cycle is initiated. In other cases, the movement of the web 118 or the carrier 124 is uninterrupted while the maintenance cycle is undertaken, for example, if the maintenance cycle coincides with a roll change or a paper splice, or when a gap is present between discrete media 104 placed on the carrier 124. It should be apparent that the maintenance cycle could be undertaken at any time the printheads 106 are not being used to print, with or without stopping the transport of the medium 104, the web 118, and/or the carrier 124.
The printhead maintenance station 130 is disposed in the printing system 100 such that the printhead maintenance station 130 does not interfere with transport of the web 118 and/or the carrier 124. In some embodiments, the printhead maintenance station 130 remains stationary while the print medium 104 and the print unit 102 are transported relative to one another during printing.
In other embodiments, the printhead maintenance station 130 moves in synchrony with the print unit 102 when the print unit 102 moves in the direction parallel to the first axis 114 and remains stationary when the print unit 102 moves in the direction parallel to the second axis 116. In such embodiments, when the maintenance cycle is initiated, the print unit 102 needs to move only in the direction parallel to the second axis 116 to be in position for maintenance. In some embodiments, when a maintenance cycle is initiated the print unit 102 may remain stationary relative to the axes 114 and 116 and the printhead maintenance station 130 may move toward the print unit 102.
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When the print unit 102 is printing (
When a maintenance cycle is initiated, the controller 112 causes the print unit 102 to move relative to the printhead maintenance station 130 until the print unit 102 is at a first maintenance position at which the nozzle plate 156 of each printhead 106 is aligned with the catch trough 150 associated with such printhead 106 (
After the ink has been purged, the wipers 152 are moved from the retracted position (
Thereafter, the print unit 102 and the printhead maintenance station 130 are moved relative to one another until the wiping portion 160 of each wiper 152 contacts the first edge 162 of the nozzle plate 156 of the printhead 106 associated with such wiper 152 (
The print unit 102 and the printhead maintenance station 130 are then moved relative to one another such that the wiping portion 160 of each wiper 152 remains in contact with and wipes the nozzle plate 156 of the printhead 106 associated with the wiper. Such movement is undertaken until the print unit 102 reaches a second maintenance position at which the wiping portion 160 reaches a second edge 164 of the nozzle plate 156 (
It should be apparent that the print unit 102 and the printhead maintenance state 130 may be moved relatively to one another repeatedly (for example, back and forth) between the first maintenance position and the second maintenance position during a maintenance cycle before the wipers are retracted into the housing 154. Such repeated movement may be undertaken, for example, to more thoroughly wipe the nozzle plates 156 of the printhead 106 during the maintenance cycle.
If additional printing is to be undertaken, the controller 112 may cause the print unit 102 to return to the printing position shown in
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A first actuator 222a has a drive shaft 224a coupled to the first wiper bar 192a adjacent the first end wall 210. A second actuator 222b includes a drive shaft 224b coupled to the second wiper bar 192b adjacent to the second end wall 208. The actuators 222a and 222b synchronously drive the first and second wiper bars 192a and 192b, respectively, in opposite directions toward the extended and retracted positions. The belts 218 and 220 transmit the torque developed by each actuator 222a and 222b to both wiper bars 192a and 192b.
The first actuator 222a and the second actuators 222b may be, for example, motors, air cylinders, or other devices operable to rotate the first wiper bar 192a and second wiper bar 192b, respectively. In a preferred embodiment, the actuators 222a and 222b may be pneumatic motors or air cylinders. However, it should be apparent to one of ordinary skill that other types of motors may be used including different fluidic motors or induction motors of any suitable type, such as an induction motor, a direct current motor, a stepper motor, and the like.
In some embodiments, the wiper bars 192 of the maintenance sections 132 of the printhead maintenance station 130 are moved in a direction perpendicular to a longitudinal axis of the wiper 152 approximately 180 degrees between the extended (i.e., wiping) position and the cleaning and storage (i.e., retracted) position.
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Each wiper cleaning assembly 252a, 252b, . . . , and 252f includes a chamber 254a, 254b, . . . , and 254f, respectively, into which the wiper 152a, 152b, . . . , and 152f associated with such cleaning assembly may be retracted for cleaning and storage. The controller 112 (see
Each chamber 254 includes a fluid intake port 256 and fluid purge port 258. An input end 260 of the fluid intake port 256 is coupled to a fluid supply line 262. The fluid supply line 262 is coupled via a three-way valve 264 to a cleaning fluid supply 266 and a pressurized gas supply 268. An output end 270 of the fluid intake port 256 is in fluid communication with the chamber 254 so that any fluid introduced into the fluid intake port 256 is deposited into such chamber 254.
In the illustrated embodiment, the fluid purge port 258 of each chamber 254 is coupled to a waste tank 272. In some embodiments, one waste tank 272 may be coupled to each fluid purge port 258. In other embodiments, one waste tank 272 may be coupled to a plurality of fluid purge ports 258 and/or multiple waste tanks 272 may be coupled to one or more fluid purge ports 258.
To clean the wipers 152, for example, after such wipers 152 have been used to wipe the nozzle plate 156 as described above in connection with
To prevent the cleaning fluid and/or the pressurized gas introduced in the chambers 254 from escaping into the housing 154, a gasket 255 may surround each wiper 152 and/or the blade holder 300 which secures the wiper 152. When the wiper 152 is disposed in the chamber 254, the gasket 255 may form a seal that isolates the chamber 254 and the wiper 152 from the rest of the housing 154. In some embodiments, the gasket 255 or another gasket may be disposed around the opening of the chamber 254 to provide such seal.
After the wiper 152 is disposed in the chamber 254, the controller 112 actuates the three-way valve 264 so that the fluid supply line 262 is coupled to the cleaning fluid supply 266. The controller 112 then actuates a pump 274 to force cleaning fluid from the cleaning fluid supply 266 into the fluid supply line 262, through the fluid intake port 256, and into the chamber 254. As the chamber 254 fills with the cleaning supply fluid the cleaning fluid flows across the wiper 152 and into the fluid purge port 258. Such flow of cleaning fluid dislodges any ink and debris on the wiper 152 and carries such ink and/or debris therewith through the fluid purge port 258 and into the waste tank 272.
After the cleaning fluid is forced past the wipers 152 for a predetermined amount of time, the controller 112 operates the three-way valve 264 to couple the fluid supply line 262 to the pressurized gas supply 268 to introduce pressurized gas into the chamber 254. The pressurized gas in the chamber 254 flows past the wiper 152 and exits the chamber 254 through the fluid purge port 258. The flow of pressurized gas carries any cleaning fluid in the chamber 254 and/or on the wiper 152 and dries the chamber 254 and/or the wiper 152. In some embodiments, the waste tank 272 may include a port 276 open to the environment through which the pressurized gas may be released. The port 276 may include a filter that traps fluids and/or particles.
After allowing the pressurized gas to flow through the chamber 254 for a predetermined amount of time, the controller 112 closes the three-way valve 264. The wipers 152 may remain in the chambers 254 until the wipers 152 are needed to wipe the nozzle plates 156, although the wipers may be moved to the extended position at any time.
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It should be apparent that one or more filters may be disposed in one or both of the fluid line 262 or 282 to trap any contaminants in the fluids that flow therethrough.
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Numerous modifications to the present embodiments will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is presented for the purpose of enabling those skilled in the art to make and use the embodiments and to teach the best mode of carrying out same. The exclusive rights to all modifications which come within the scope of the appended claims are reserved.
This application claims the benefit of U.S. Provisional Patent Application No. 62/303,721, filed Mar. 4, 2016. The entire contents of this application are incorporated herein by reference.
Number | Date | Country | |
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62303721 | Mar 2016 | US |