WO2024096866A1 - Capteurs capillaires de matrice de tête d'impression - Google Patents

Capteurs capillaires de matrice de tête d'impression Download PDF

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Publication number
WO2024096866A1
WO2024096866A1 PCT/US2022/048481 US2022048481W WO2024096866A1 WO 2024096866 A1 WO2024096866 A1 WO 2024096866A1 US 2022048481 W US2022048481 W US 2022048481W WO 2024096866 A1 WO2024096866 A1 WO 2024096866A1
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WO
WIPO (PCT)
Prior art keywords
fluid
capillary
capillary pressure
reservoir
fluid reservoir
Prior art date
Application number
PCT/US2022/048481
Other languages
English (en)
Inventor
Matthew SUNDHEIM
James Michael GARDNER
Ronald J. Ender
Original Assignee
Hewlett-Packard Development Company, L.P.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hewlett-Packard Development Company, L.P. filed Critical Hewlett-Packard Development Company, L.P.
Priority to PCT/US2022/048481 priority Critical patent/WO2024096866A1/fr
Publication of WO2024096866A1 publication Critical patent/WO2024096866A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/17—Ink jet characterised by ink handling
    • B41J2/175—Ink supply systems ; Circuit parts therefor
    • B41J2/17503—Ink cartridges
    • B41J2/17556—Means for regulating the pressure in the cartridge
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
    • B41J2/04555—Control methods or devices therefor, e.g. driver circuits, control circuits detecting current
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
    • B41J2/0458—Control methods or devices therefor, e.g. driver circuits, control circuits controlling heads based on heating elements forming bubbles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2/14016—Structure of bubble jet print heads
    • B41J2/14153—Structures including a sensor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/17—Ink jet characterised by ink handling
    • B41J2/175—Ink supply systems ; Circuit parts therefor
    • B41J2/17503—Ink cartridges
    • B41J2/17513—Inner structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/17—Ink jet characterised by ink handling
    • B41J2/175—Ink supply systems ; Circuit parts therefor
    • B41J2/17566—Ink level or ink residue control

Definitions

  • Printing devices may be used for printing on and/or copying a sheet of print medium.
  • printing device may utilize fluid ejection devices that include ink for printing and/or copying.
  • Fluid ejection devices may be refillable or non-refillable. As the fluid ejection device is utilized, the ink in a fluid reservoir of the fluid ejection device may become low. The refillable fluid ejection device may receive additional ink and the non-refillable fluid ejection device may be replaced.
  • FIG. 1 is a block diagram of an example of a fluid ejection device.
  • FIG. 2A illustrates a top-down view of an example of a printhead die of a fluid ejection device including fluid in a capillary in contact with a first fluid sensor.
  • FIG. 2B illustrates a top-down view of an example of a printhead die of a fluid ejection device including a fluid not in contact with a first fluid sensor.
  • FIG. 2C illustrates a top-down view of an example of a printhead die of a fluid ejection device including a fluid not in contact with a second fluid sensor.
  • FIG. 3 illustrates a top-down view of an example of a printhead die of a fluid ejection device including a plurality of fluid sensors.
  • FIG. 4 illustrates a side view of an example of a fluid ejection device of a printing device and a top-down view of a printhead die of the fluid ejection device.
  • FIG. 5 is a block diagram of an example of a printing device.
  • a user may utilize a printing device for various purposes, such as for business and/or recreational use.
  • a printing device can include any hardware device with functionalities to physically produce representation(s) (e.g., text, images, models, etc.) on a physical print medium. Examples of printing devices include, for instance, an inkjet printing device, (e.g., a thermal inject (T! J) device, an All-In-One (AIO) printing device, etc.), among other types of printing devices.
  • a printing device can further include other functionalities such as scanning, faxing, and/or other printing device functionalities, and can perform print jobs when in receipt of a print job request from a computing device or other network (e.g., Internet) connected device.
  • the printing device includes a fluid ejection device implemented as a fluid drop jetting printhead that ejects drops of ink through a plurality of orifices or nozzles toward print media so as to print onto the print media.
  • a print medium may be a type of suitable sheet or roll material, such as paper, card stock, transparencies, polyester, plywood, foam board, fabric, canvas, photopolymers, plastics, composite, metal, wood, build material for additive printing, and the like.
  • the fluid ejection device may supply a print substance such as an ink to the printhead die from a reservoir that stores the ink.
  • the fluid ejection device may be non-refillable (e.g., a replaceable printer cartridge) or fillable and/or refillable (e.g., as used in a Continuous Ink Supply System (CISS), though examples are not so limited).
  • CISS Continuous Ink Supply System
  • the fluid ejection device For the fluid ejection device to operate (e.g., eject ink onto a print medium), the fluid ejectors and chambers of the printhead die are primed.
  • the printhead die may be physically located below the reservoir.
  • the fluid ejection device may rely on a negative capillary pressure to overcome the forces of gravity to hold ink primed into the printhead from leaking out of the printhead while not in use.
  • capillary pressure refers to a pressure within the fluid ejection device that results from the interaction between the contents of the fluid ejection device and the walls of the fluid ejection device.
  • the term “print job” may refer to different things, based on the context of the sentence. For example, in the context of a process, it refers to the process of forming markings such as text and/or images by transferring a print material (e.g., ink) to a medium, in the context of printing device output, it refers to the resulting media with markings formed thereon. And in the context of a yet intangible printing device output, it may refer to a set of signals or instructions that may yield a tangible print job when processed by the printing device.
  • a print material e.g., ink
  • the ink volume is increased, increasing the saturation level of the porous media and decreasing the negative capillary pressure within the fluid ejection device.
  • the porous media and ink stored in the reservoir ages, the porous media can outgas or oxidize changing a contact angle between the contents of the reservoir and the walls of the reservoir and/or the ink can lose water or other volatile components, resulting in the changing of the capillary pressure within the fluid ejection device.
  • the capillary pressure within the fluid ejection device may fluctuate while the system is idle, during use, and/or during replenishment.
  • fluid ejection devices may include a sensor to measure a volume of ink within the fluid reservoir.
  • the sensor may measure a reduction of fluid in the reservoir due to use of the fluid during a print job and/or due to porous media outgassing or oxidizing and/or loss of water or other volatile components of the fluid caused over time by age. Differing volumes of fluid within the reservoir creating different capillary pressures within the fluid ejection device may cause fluctuations in print quality.
  • the sensor may measure a volume of ink added to the fluid reservoir so that the volume added is equal to the amount of ink used during printing. In some examples, there may be a time between use of ink, the addition of ink, and a stabilization of the capillary pressure within the fluid reservoir.
  • Print devices that utilize sensors to measure ink volume may add ink to the fluid reservoir while the capillary pressure within the fluid reservoir is still stabilizing from a print job.
  • Fluid presence sensors can be located within the printhead die of the fluid ejection device and in contact with ink entering the printhead die from the reservoir in order to monitor the level of ink within the fluid reservoir.
  • the fluid presence sensors enable detection of whether to add ink to the fluid reservoir based on a saturation curve (e.g., a relationship between the capillary pressure and a saturation level within the fluid reservoir) of the fluid reservoir Utilizing the saturation curve of the fluid reservoir allows for compensation of fluctuations in capillary pressures within the fluid ejection device and allows the fluid ejection device to stabilize (e.g , reach an equilibrium) before a replenishment.
  • Adding ink to the fluid ejection device in accordance with the saturation curve may reduce the risk of the fluid reservoir being overfilled and/or the risk of reduction of negative capillary pressure, which can reduce the chance of ink leakage. Additionally, preventing the negative capillary pressure from being reduced past the point of overcoming gravitational forces. As a result, as compared with previous approaches, the fluid ejection device may be utilized longer without negative effects on print quality, reducing the frequency of fluid ejection device replacement, increasing efficiency, and reducing cost, resources, and waste.
  • FIG. 1 is a block diagram of an example of a fluid ejection device 102.
  • the fluid ejection device 102 may include a fluid reservoir 104.
  • the fluid reservoir 104 may include a fluid 106, (e.g., ink in various colors, such as black, cyan, magenta, yellow, etc.) to be utilized during a print job process, and a porous media 108.
  • a fluid 106 e.g., ink in various colors, such as black, cyan, magenta, yellow, etc.
  • the fluid ejection device 102 may include a printhead die 110 fluidically connected to the fluid reservoir 104 to receive fluid 106 from the fluid reservoir 104.
  • the printhead die 110 may be fluidically sealed and connected to a fluid path of the fluid ejection device 102 (e.g., as is further illustrated in FIG. 4).
  • the printhead die 110 may be physically located below the fluid reservoir 104 and a negative capillary pressure of the fluid reservoir 104 may hold fluid 106 from leaking from the printhead die 110 while the fluid ejection device 102 is not in use and/or hold excessive fluid 106 from being transferred to a sheet of print medium during the print job process.
  • the porous media 108 of the fluid ejection device 102 may be at a first capillary pressure.
  • the first capillary pressure can be a capillary pressure of a porous media of a fluid reservoir while the fluid reservoir is above a first threshold capacity (e.g., is not low on fluid).
  • the printhead die 110 may include a capillary 112 sized to have a capillary pressure equal to the first capillary pressure of the porous media 108.
  • the capillary 112 may indude a first fluid sensor 114 arranged to contact fluid 106 in the printhead die 110. in some exampies, the capillary 112 may comprise a small bore located within a layer of the printhead die 110.
  • the capillary 112 and the first fluid sensor 114 may be arranged such that the first fluid sensor 114 is to be in contact with the fluid 106 in the capiliary 112 while the fluid reservoir 104 exceeds the first threshold capacity and the capiliary pressure of the porous media 108 is at the first capiliary pressure (e.g., as is further illustrated in FIG. 4).
  • the capillary 112 and the first fluid sensor 114 may be arranged such that the first fluid sensor 114 is not to be in contact with the fluid 106 while the fluid reservoir 104 is below the first threshold capacity and the capillary pressure of the porous media 108 exceeds the first capillary pressure.
  • the porous media 108 of the fluid ejection device 102 may be at a second capillary pressure.
  • the second capillary pressure can be a capillary pressure of a porous media of a fluid reservoir while the fluid reservoir is below a first threshold capacity and above a second threshold capacity (e.g., is low on fluid).
  • the printhead die 110 may further include a gradient channel.
  • the gradient channel may include straight walls descending from the capiliary 112.
  • the gradient channel may be a curved gradient channel 116.
  • the curved gradient channel 116 may be formed in the printhead die 110 such that the size of the curved gradient channel 116 decreases (e.g., descends) and the capillary pressure of the curved gradient channel 116 increases as the curved gradient channel 116 extends from the capillary 112.
  • a first end of the curved gradient channel 116 may be fluidicaily connected to the capillary 112, as is further illustrated in FIG. 2A.
  • the first end of the curved gradient channel 116 may be sized to have a capillary pressure equal to the second capiliary pressure of the porous media 108.
  • the curved gradient channel 116 may include a second fluid sensor 118 arranged to contact fluid 106 in the curved gradient channel 116 of the printhead die 110.
  • the curved gradient channel 116 and the second fluid sensor 118 may be arranged such that the second fluid sensor 118 is to be in contact with the fluid 106 in the curved gradient channel 116 while the fluid reservoir 104 exceeds the second threshold capacity and the capillary pressure of the porous media 108 is at the second capillary pressure, as is further illustrated in FIG. 2B.
  • the curved gradient channel 116 and the second fluid sensor 118 may be arranged such that the second fluid sensor 118 is not to be in contact with the fluid 106 while the fluid reservoir 104 is below the second threshold capacity and the capillary pressure of the porous media 108 exceeds the second capillary pressure.
  • the first threshold capacity is greater than the second threshold capacity and the first capillary pressure of the porous media 108 is less than the second capillary pressure of the porous media 108.
  • the fluid 106 in the fluid reservoir 104 may be at a first level while the fluid reservoir 104 exceeds the first threshold capacity and the capillary pressure of the porous media 108 is at the first capillary pressure and the fluid 106 in the fluid reservoir 104 may be at a second level, lower than the first level (e.g. , less fluid 106), while the fluid reservoir 104 exceeds the second threshold capacity and the capillary pressure of the porous media 108 is at the second capillary pressure.
  • FIG. 2A illustrates a top-down view of an example of a printhead die 210 of a fluid ejection device 202 including fluid 206 in a capillary 212 in contact with a first fluid sensor 214.
  • the fluid ejection device 202 may include the capillary 212 and the first fluid sensor 214 located in the printhead die 210
  • the capillary 212 and the first fluid sensor 214 may be arranged such that the first fluid sensor 214 is to be in contact with the fluid 206 while the fluid 206 of a fluid reservoir of the fluid ejection device 202 exceeds a first threshold capacity and a capillary pressure of a porous media is at a first capillary pressure.
  • the capillary 212 and the first fluid sensor 214 may be arranged such that the first fluid sensor 214 is to be in contact with the fluid 206 while a variable capillary pressure of the porous media is equal to a static capillary pressure of the capillary 212.
  • the printhead die 210 may further include a curved gradient channel 216 fluidicaliy connected to the capillary 212 at a first end 220 of the curved gradient channel 216.
  • the first end 220 of the curved gradient channel 216 may be sized to have a capillary pressure equal to a second capillary pressure.
  • the second capillary pressure may be a greater capillary pressure than the first capillary pressure and the capillary pressure of the capillary 212.
  • the curved gradient channel 216 may supply fluid 206 to the capillary 212.
  • the curved gradient channel 216 may include a second fluid sensor 218.
  • the curved gradient channel 216 and the second fluid sensor 218 may be arranged such that the second fluid sensor 218 is to be in contact with the fluid 206 while the fluid 206 of the fluid reservoir of the fluid ejection device 202 exceeds a second threshold capacity and while a variable capillary pressure of the porous media is less than or equal to a static capillary pressure of the first end 220 of the curved gradient channel 216.
  • the printhead die 210 may further include a capillary choke 224 fluidically connected to a second end 222 of the curved gradient channel 216.
  • the capillary choke may have a bore size smaller than the capillary.
  • the capillary choke 224 may be fluidically connected between the curved gradient channel 216 and a fluid reservoir of the fluid ejection device 202.
  • the capillary choke 224 may be sized to have a capillary pressure greater than the second capillary pressure.
  • the capillary choke 224 may be arranged to be in contact with fluid 206 entering the printhead die 210 from the fluid reservoir to supply fluid 206 from the fluid reservoir to the curved gradient channel 216 and the capillary 212.
  • fluid 206 may be present in the capillary choke 224, the curved gradient channel 216 and in contact with the second fluid sensor 218, and the capillary 212 and in contact with the first fluid sensor 214.
  • FIG. 2B illustrates a top-down view of an example of a printhead die 210 of a fluid ejection device 202 including a fluid 206 not in contact with a first fluid sensor 214.
  • the fluid ejection device 202 may include a capillary 212 and the first fluid sensor 214 located in the printhead die 210.
  • the printhead die 210 may further include a curved gradient channel 216 fluidically connected to the capillary 212 and comprising an increasing capillary gradient having a greater capillary pressure than a capillary pressure of the capillary 212.
  • the capillary 212 may be sized to have a capillary pressure equal to a first capillary pressure of a porous media of a fluid reservoir of the fluid ejection device 202.
  • the curved gradient channel 216 may be sized to have a capillary pressure, at an end of the curved gradient channel 216 connected to the capillary 212, equal to a second capillary pressure of the porous media of the fluid reservoir.
  • the second capillary pressure may be greater than the first capillary pressure.
  • the capillary pressure of the curved gradient channel 216 may increase as the curved gradient channel 216 extends away from the capillary 212.
  • the fluid ejection device 202 may eject drops of fluid 206 (e.g., ink) onto a print medium.
  • fluid 206 e.g., ink
  • the capillary pressure in the fluid reservoir may increase (e.g., become more negative).
  • fluid 206 may be drawn out of the capillary 212, away from the first fluid sensor 214, and into the curved gradient channel 216, as is illustrated in FIG. 2B.
  • the printhead die 210 may further include an opening 226 (e.g., a small hole in the printhead die 210).
  • the opening 226 may be connected to the capillary 212 and vented to atmospheric or humidified air (e.g., air) to back-fill the capillary 212 with air while the capillary pressure of the porous media exceeds the first capillary pressure.
  • air may be drawn into the capillary 212 taking the physical place of the fluid 206 (e.g., back-filling the fluid 206).
  • the capillary pressure of the porous media of the fluid reservoir increases to exceed the first capillary pressure and the capillary pressure of the capillary 212.
  • fluid 206 may flow out of the capillary 212 and into the fluid reservoir and air, via the opening 226, may back-fill the capillary 212.
  • the first fluid sensor 214 may detect fluid 206 is not in the contact with the first fluid sensor 214 indicating that the fluid ejection device 202 is below the first threshold capacity (e.g., below a first specific level of fluid 206 or ink).
  • the first fluid sensor 214 may send a signal to the fluid ejection device 202.
  • the fluid ejection device 202 may send a signal to a processor of a print device.
  • the processor may generate a notification to indicate that the fluid reservoir is low on fluid 206.
  • the processor may transmit a signal to a computing device (e.g., a desktop, a laptop, a mobile device, etc.) to indicate that the fluid reservoir is low on fluid 206.
  • the processor may instruct the computing device to display the received notification.
  • the fluid ejection device 202 may be non-refillable and the notification may indicate that the fluid ejection device 202 may have a limited amount of use before a replacement.
  • the fluid ejection device 202 may be fillable/refillable and the notification may trigger a receipt of fluid 206 into the fluid reservoir (e.g., as is further illustrated in FIG. 4).
  • the capillary pressure of the fluid reservoir may decrease and the fluid 206 may flow into the capillary 212 until the capillary pressure of the fluid reservoir reaches the first capillary pressure, as such the capillary 212 of the printhead die 210 may be primed or reprimed with fluid 206.
  • the fluid 206 flows into the capillary 212, air in the capillary 212 may be pushed through the opening 226 and out of the capillary 212.
  • the capillary pressure reaches the first capillary pressure, the level of fluid 206 in the fluid reservoir increases to the first threshold capacity and fluid 206 flows into contact with the first fluid sensor 214 (e.g., as illustrated in FIG. 2A).
  • the signal may indicate that the fluid level of the fluid ejection device 202 is at the first threshold capacity and for the fluid reservoir to cease receiving fluid 206.
  • the printhead die 210 may further include a capillary choke 224 fluidically connected to a second end 222 of the curved gradient channel 216.
  • the capillary choke 224 may be fluidically connected between the curved gradient channel 216 and a fluid reservoir of the fluid ejection device 202.
  • the capillary choke 224 may be arranged to be in contact with fluid 206 entering the printhead die 210 from the fluid reservoir to supply fluid 206 from the fluid reservoir to the curved gradient channel 216 and the capillary 212 and to receive fluid 206 from the capillary 212 and the curved gradient channel 216.
  • FIG. 2C illustrates a top-down view of an example of a printhead die 210 of a fluid ejection device 202 including a fluid 206 not in contact with a second fluid sensor 218.
  • the fluid ejection device 202 may include a capillary 212 and a first fluid sensor 214.
  • the printhead die 210 may include a curved gradient channel 216, and the second fluid sensor 218 located in the curved gradient channel 216.
  • the curved gradient channel 216 may include a first end 220 fluidically connected to the capillary 212 and sized at the connection with the capillary 212 to have a capillary pressure equal to a second capillary pressure of a fluid reservoir of the fluid ejection device 202.
  • the printhead die 210 may further include a capillary choke 224 fluidically connected to a second end 222 of the curved gradient channel 216.
  • the capillary choke 224 may be connected between the curved gradient channel 216 and the fluid reservoir and arranged to be in contact with fluid 206 entering the printhead die 210 from the fluid reservoir.
  • the capillary choke 224 may have a capillary pressure greater than a capillary pressure of the curved gradient channel 216.
  • the capillary choke 224 may be sized to have a bubble pressure greater than a threshold internal printhead die pressure to block air from an opening 226 in the printhead die 210 from entering the capillary choke 224.
  • the term “bubble pressure” refers to the pressure differential used to force air through a wetted orifice.
  • the threshold internal printhead die pressure may be a highest negative pressure that a printhead die is to have during the life of a fluid ejection device 202.
  • the capillary choke 224 may be sized (e.g. , have a diameter) such that the surface tension between the fluid 206 and the walls of the capillary choke 224 creates a capillary pressure greater than an internal printhead die pressure.
  • the diameter of the capillary choke 224 may be sized large enough so that internal pressures of the fluid ejection device 202 may cause fluid 206 from the fluid reservoir to travel into and through the capillary choke 224. Additionally, the diameter of the capillary choke 224 may be sized small enough that air from the opening 226 may be blocked from traveling into and through the capillary choke 224 to the fluid reservoir and causing air pockets in the fluid 206.
  • the curved gradient channel 216 may extend from the capillary 212, at a location sized such that the capillary pressure equals the second capillary pressure of the fluid reservoir, to the capillary choke 224, at a location sized such that the capillary pressure exceeds the threshold internal printhead die pressure.
  • Each wall of the curved gradient channel 216 may arc inwardly between the first end 220 and the second end 222 of the curved gradient channel 216.
  • the second fluid sensor 218 may be arranged between the first end 220 and the second end 222 of the curved gradient channel 216 and at substantially the same distance away from each arced wall of the curved gradient channel 216 (e.g., substantially center of the walls).
  • the term “substantially” intends that the characteristic does not have to be absolute but is ciose enough so as to achieve the characteristic.
  • “substantially center” is not limited to absolute center.
  • the level of fluid 206 may decrease within the fluid reservoir of the fluid ejection device 202.
  • a negative capillary pressure within the fluid reservoir may increase (e.g., become more negative) and fluid 206 may be drawn out of the capillary 212, away from the first fluid sensor 214, and into the curved gradient channel 216, as is illustrated in FIG. 2B.
  • Air may displace the fluid 206 by back-filling the capillary 212 via the opening 226 in the printhead die 210.
  • the first fluid sensor 214 may detect fluid 206 is not in the contact with the first fluid sensor 214 indicating that the fluid ejection device 202 is below a first threshold capacity.
  • the level of fluid 206 in the fluid reservoir may further decrease and a negative capillary pressure within the fluid reservoir may further increase (e.g., during an extended print job and/or multiple consecutive print jobs).
  • fluid 206 may be drawn from the capillary 212, the first fluid sensor 214, the curved gradient channel 216, and the second fluid sensor 218, as is illustrated in FIG. 2C.
  • Air may further displace the fluid 206 by back-filling the curved gradient channel 216 via the opening 226 in the printhead die 210.
  • the second fluid sensor 218 may detect fluid 206 is not in the contact with the second fluid sensor 218 enabling an indication that the fluid ejection device 202 is below a second threshold capacity.
  • the capillary 212 and the curved gradient channel 216 are de-primed (e.g., fluid 206 is not present in the capillary 212 and the curved gradient channel 216).
  • the second fluid sensor 218 may send a signal to the fluid ejection device 202.
  • the fluid ejection device 202 may send a signal to a processor of a print device.
  • the processor may generate a notification to indicate a level of fluid 206 in the fluid reservoir.
  • the level of fluid 206 may be very low (e.g., below the second threshold capacity).
  • the processor may transmit a signal to a computing device (e.g., a desk top, a mobile device, etc.) to indicate that the fluid reservoir is very low on fluid 206.
  • the processor may instruct the computing device to display the received notification.
  • the fluid ejection device 202 may be non-refillable and the notification may indicate that the fluid ejection device 202 may have a limited amount of use before a replacement.
  • the fluid ejection device 202 may be filiable/refillable and the notification may trigger a receipt of fluid 206 into the fluid reservoir (e.g., as is further illustrated in FIG. 4).
  • the capillary pressure of the fluid reservoir may decrease and the fluid 206 may flow into the curved gradient channel 216.
  • air in the curved gradient channel 216 may be pushed out of the curved gradient channel 216, into the capillary 212, and out through the opening 226.
  • the level of fluid 206 in the fluid reservoir increases to the second threshold capacity as fluid 206 flows into contact with the second fluid sensor 218 (e.g., as illustrated in FIG. 2B).
  • the signal may indicate that the fluid level of the fluid ejection device 202 is at the second threshold capacity and that the level of fluid 206 in the fluid reservoir is low.
  • the curved gradient channel 216 of the printhead die 210 may be primed or reprimed with fluid 206.
  • the height of the capillary 212, the curved gradient channel 216 and the capillary choke 224 within the printhead die 210 may be the same.
  • the length of the curved gradient channel 216 from the second end 222 to the first end 220 and the arc of the curved gradient channel 216 may be sized for priming and/or repriming the curved gradient channel 216 with fluid 206 from the capillary choke 224.
  • a net capillary force (F o ) of the channel may be calculated.
  • the arc of the walls of the curved gradient channel 216 may be sized to have a specific capillary force (e.g., capillary pressure) according to Equation 1 below:
  • the net capillary force (F o ) of a channel may be calculated as a cosine of a half-angle (0) of a junction and a contact angle (0) of a fluid in the channel multiplied by a height (/?) of the channel and a cosine of the half-angle (0) of the junction multiplied by a width (w) of the channel, multiplied by two times a fluidair surface tension (y) of the channel.
  • the half-angle (0) of a junction refers to the angle between the center of the curved gradient channel 216 at a location in which the wall of the curved gradient channel 216 connects with the capillary choke 224 and a point on the wall of the curved gradient channel 216.
  • the contact angle (0) of a fluid in the channel refers to the wetted angle of the fluid 206 to the wall in the curved gradient channel 216, as is illustrated in FIG. 2B.
  • the fluid-air surface tension (y) of the channel refers to the force between liquid molecules that enables the liquid surface to resist external forces.
  • the curved gradient channel 216 may be sized to prime and/or reprime with fluid 206 at a specific capillary pressure. For example, as fluid 206 is received into the fluid reservoir and the capillary pressure within the fluid reservoir decreases (e.g. , becomes less negative) the capillary pressure may decrease below the prime/reprime specific capillary pressure enabling fluid 206 to flow into the curved gradient channel 216. [0055] As the fluid ejection device 202 continues to receive fluid 206, the capillary pressure of the fluid reservoir may continue to decrease and the fluid 206 may flow into the capillary 212 until the capillary pressure of the fluid reservoir reaches the first capillary pressure.
  • the capillary 212 of the printhead die 210 may be primed or reprimed with fluid 206.
  • the arc and angle of the curved gradient channel 216 may be shaped to promote a gradual filling of fluid 206 into the curved gradient channel 216 and the capillary 212.
  • the gradual filling may minimize fluid 206 flowing to and contacting the second fluid sensor 218 and/or the first fluid sensor 214 prematurely (e.g., indicating a false capillary pressure of the fluid reservoir and a false volume of fluid).
  • FIG. 3 Illustrates a top-down view of an example of a printhead die 310 of a fluid ejection device 302 including a plurality of fluid sensors.
  • the printhead die 310 may include a capillary 312 and an opening 326 vented to air.
  • the printhead die 310 may further include a first curved gradient channel 316 including a first end 320 fluidically connected to the capillary 312 and a second end 322 fluidically connected to a first end of a second curved gradient channel 328.
  • the second curved gradient channel 328 may have a second end fluidically connected to a capillary choke 324.
  • the walls of the first curved gradient channel 316 may arc inwardly toward the center of the first curved gradient channel 316 and the width between the walls may expand from the second end 322 to the first end 320 of the first curved gradient channel 316.
  • the first curved gradient channel 316 may be sized to have a specific net capillary force (e.g. , capillary pressure) as previously described in connection with FIG. 2C via Equation 1.
  • the walls of the second curved gradient channel 328 may arc inwardly toward the center of the second curved gradient channel 328 and the width between the walls may expand from the capillary choke 324 to the second end 322 of the first curved gradient channel 316.
  • the second curved gradient channel 328 may be sized to have a specific net capillary force (e.g., capillary pressure) as previously described in connection with Equation 1.
  • the printhead die 310 may include a first fluid sensor 314 arranged to enable detection of fluid within the capillary 312, a second fluid sensor 318 arranged to enable detection of fluid within the first curved gradient channel 316 and/or a third fluid sensor 330 arranged to enable detection of fluid within the second curved gradient channel 328.
  • the first fluid sensor 314 may be arranged to be in contact with fluid in the capillary 312 while the fluid reservoir exceeds a first threshold capacity and to not be in contact with fluid while the fluid reservoir is below the first threshold capacity.
  • the second fluid sensor 318 may be arranged to be in contact with the fluid in the capillary 312 while the fluid reservoir exceeds a second threshold capacity and to not be in contact with fluid while the fluid reservoir is below the second threshold capacity.
  • the third fluid sensor 330 may be arranged in the second curved gradient channel 328 to be in contact with fluid in the second curved gradient channel 328 while the fluid reservoir exceeds a third threshold capacity and to not be in contact with fluid while the fluid reservoir is below the third threshold capacity.
  • the level of fluid may decrease causing the capillary pressure of a porous media of the fluid reservoir to increase and as the fluid reservoir is replenished with fluid, the level of fluid may increase causing the capillary pressure of the porous media to decrease.
  • the capillary pressure of the porous media of the fluid reservoir may be at a first capillary pressure and fluid in the printhead die 310 may be in contact with the third fluid sensor 330, the second fluid sensor 318, and the first fluid sensor 314.
  • the capillary pressure of the porous media may be at a second capillary pressure and fluid may be in contact with the third fluid sensor 330 and the second fluid sensor 318 and may not be in contact with the first fluid sensor 314 in the capillary 312. As such, air may back-fill the capillary 312 via the opening 326.
  • the capillary pressure of the porous media may be at a second capillary pressure and fluid may be in contact with the third fluid sensor 330 and may not be in contact with the second fluid sensor 318 in the first curved gradient channel 316 and the first fluid sensor 314 in the capillary 312. As such, air may back-fill the capillary 312 and the first curved gradient channel 316 via the opening 326.
  • the capillary pressure of the porous media may be greater than the second capillary pressure and fluid may not be in contact with the third fluid sensor 330 in the second curved gradient channel 328, the second fluid sensor 318 in the first curved gradient channel 316, or the first fluid sensor 314 in the capillary 312. As such, air may backfill the capillary 312, the first curved gradient channel 316, and the second curved gradient channel 328 via the opening 326.
  • the first fluid sensor 314, the second fluid sensor 318, and the third fluid sensor 330 may enable detection of fluctuating capillary pressures within the fluid ejection device 302.
  • the fluid sensors may send signals to the fluid ejection device 302.
  • the fluid ejection device 302 may send a signal to a processor of a print device.
  • the processor may generate a notification to indicate a level of fluid in the fluid reservoir.
  • the processor may determine, based on the signal received from the fluid ejection device 302, a capillary pressure of print nozzles located adjacent to the capillary choke 324 in the printhead die 310.
  • the fluid ejection device 302 may be fillable/refillable and based on the notification or the capillary pressure of the print nozzles, a receipt of fluid into the fluid reservoir may be triggered (e.g., as is further illustrated in FIG. 4).
  • the printhead die 310 may include the capillary 312, the first curved gradient channel 316, and the second curved gradient channel 328, each including a fluid sensor, although examples are not so limited.
  • the capillary 312, the first curved gradient channel 316, and the second curved gradient channel 328 may each include multiple fluid sensors or may not include a fluid sensor.
  • the printhead die 310 may include a plurality of curved gradient channels (e.g., 3, 4, 5, etc.), each channel having the same or varying quantities of sensors (e.g., one, multiple, or no sensors).
  • the level of fluid within the fluid reservoir and capillary pressures within the printhead die 310 may be determined in increments, a notification of levels and/or pressures may be generated by a printing device, and the fluid reservoir may be replenished in accordance with the fluid level within the fluid reservoir and/or the capillary pressures within the printhead die 310.
  • FIG. 4 illustrates a side view of an example of a fluid ejection device 402 of a printing device 400 and a top-down view of a printhead die 410 of the fluid ejection device 402.
  • the fluid ejection device 402 may include a fluid reservoir 404 and the printhead die 410 including the same or similar elements as the fluid reservoir 104 and the printhead die 110 as referenced in FIG.
  • the fluid reservoir 404 may include a fluid 406 (e.g., ink) and a foam 408.
  • the fluid reservoir 404 may further include humidified air 432.
  • the printhead die 410 may include a capillary 412 and a first fluid sensor 414.
  • the fluid reservoir 404 may be fluidicaily connected to the printhead die 410.
  • the printhead die 410 may receive fluid 406 from the fluid reservoir 404.
  • the fluid ejection device 402 may include a standpipe and a plenum 438 fluidicaily connected to the fluid reservoir 404 and the printhead die 410 to supply fluid 406 from the fluid reservoir 404 to the printhead die 410.
  • the capillary 412 of the printhead die 410 may be sized to have a capillary pressure equal to a first capillary pressure of the foam 408 and may include the first fluid sensor 414.
  • the first fluid sensor 414 may be arranged to be in contact with fluid 406 in the capillary 412 while the fluid reservoir 404 exceeds a first threshold capacity and a capillary pressure of the foam 408 is at the first capillary pressure and to not be in contact with fluid 406 while the fluid reservoir 404 is below the first threshold capacity and the capillary pressure of the foam 408 exceeds the first capillary pressure.
  • the printhead die 410 may include a curved gradient channel 416 including a first end fluidicaily connected to the capillary 412 and sized to have a capillary pressure equal to a second capillary pressure of the foam 408.
  • the curved gradient channel 416 may include a second fluid sensor 418 arranged to be in contact with fluid 406 in the curved gradient channel 416 while the fluid reservoir 404 exceeds a second threshold capacity and the capillary pressure of the foam 408 is at the second capillary pressure and not to be in contact with the fluid 406 while the fluid reservoir 404 is below the second threshold capacity and the capillary pressure of the foam 408 exceeds the second capillary pressure.
  • the first threshold capacity may be greater than the second threshold capacity. Additionally, the first capillary pressure of the foam 408 may be less than the second capillary pressure of the foam 408.
  • the printhead die 410 may further include a capillary choke 424 fluidicaily connected between a second end of the curved gradient channel 416 and the fluid reservoir 404 (e.g., via the standpipe and plenum 438).
  • the capillary choke 424 may be arranged to be in contact with fluid 406 entering the printhead die 410 from the fluid reservoir 404, to pass the fluid 406 between the curved gradient channel 416 and the fluid reservoir 404.
  • the capillary choke 424 may be sized to have a bubble pressure greater than a threshold internal printhead die pressure to block air from an opening 426 in the printhead die 410 from entering the capillary choke 424 and the fluid reservoir 404.
  • the capillary choke 424 may be fluidically connected to a fluid ejection nozzle 434 of the printhead die 410.
  • the first fluid sensor 414 and the second fluid sensor 418 may be utilized to enable a detection of the capillary pressure of the foam 408 in the fluid reservoir 404 and to monitor pressure levels at the fluid ejection nozzle 434.
  • the fluid ejection device 402 may further comprise a fluid receiving port 436 fluidically connected to the fluid reservoir 404.
  • the fluid receiving port 436 may supply fluid 406 to the fluid reservoir 404.
  • the printing device 400 in response to the fluid 406 being in contact with the first fluid sensor 414 or the second fluid sensor 418, the printing device 400 may indicate a particular level of fluid 406 in the fluid reservoir 404. Based on a level of fluid 406 in the fluid reservoir 404 in a fillabie/refiilable fluid ejection device 402, the fluid reservoir 404 may receive additional fluid 406 via the fluid receiving port 436.
  • the fluid reservoir 404 may be refilled via the fluid receiving port 436 based on a saturation curve of the fluid reservoir 404.
  • the saturation curve may define a relationship between the capillary pressure and a media saturation of the fluid reservoir 404. For example, the more fluid 406 in the fluid reservoir 404 (and less foam 408), the greater the media saturation level. Correspondingly, the less fluid 406 (and more foam 408) in the fluid reservoir 404, the lower the media saturation level.
  • the volume of fluid 406 in the fluid reservoir 404 decreases, decreasing a media saturation and causing the capillary pressure of the foam 408 to exceed the first capillary pressure.
  • the capillary pressure of the foam 408 increases (e.g., becomes more negative) to cause fluid 406 to flow from the first fluid sensor 414 and the capillary 412 into the fluid reservoir 404.
  • the media saturation may continue to decrease.
  • the capillary pressure of the foam 408 continues to increase causing the curved gradient channel 416 to back-fill with air via the opening 426 and the fluid 406 to flow from the second fluid sensor 418 and the curved gradient channel 416 into the capillary choke 424 and the fluid reservoir 404.
  • the capillary pressure of the foam 408 is greater than the capillary pressure of the capillary 412 to cause the fluid 406 at the capillary 412 and the first fluid sensor 414 to flow through the curved gradient channel 416 into the capillary choke 424 and into the fluid reservoir 404.
  • air may back-fill the capillary 412 via the opening 426 connected to the capillary 412.
  • the first fluid sensor 414 may detect that the fluid 406 is not in contact with the first fluid sensor 414.
  • the fluid reservoir 404 in a fillable/refillable device may receive fluid 406 via the fluid receiving port 436 in response to the first fluid sensor 414 detecting fluid 406 is not in contact with the first fluid sensor 414, enabling detection of the fluid reservoir 404 being below the first threshold capacity.
  • the fluid reservoir 404 may receive fluid 406, increasing the media saturation of the fluid reservoir 404.
  • the capillary pressure of the foam 408 decreases and may cause fluid 406 to flow from the fluid reservoir 404 into the capillary 412 and the first fluid sensor 414 as the capillary pressure of the foam 408 reaches the first capillary pressure.
  • fluid 406 may no longer be received from the fluid receiving port 436. In this way, the fillable/refillable fluid ejection device 402 may be supplied and/or resupplied with fluid 406.
  • the capillary pressure of the foam 408 In a delayed reception of fluid 406 in a fillable/refillable fluid ejection device 402, as the media saturation continues to decrease the capillary pressure of the foam 408 continues to increase. The media saturation may decrease below the second threshold capacity. In response to the fluid reservoir 404 being below the second threshold capacity, the capillary pressure of the foam 408 is greater than the capillary pressure of the curved gradient channel 416 to cause the fluid 406 at the capillary 412, the first fluid sensor 414, the curved gradient channel 416, and the second fluid sensor 418 to flow into the capillary choke 424 and into the fluid reservoir 404.
  • air in response to the opening 426 being vented to air, air may back-fill the capillary 412 and the curved gradient channel 416 via the opening 426 connected to the capillary 412.
  • the second fluid sensor 418 may detect that the fluid 406 is not in contact with the second fluid sensor 418.
  • the fluid reservoir 404 may receive fluid 406 via the fluid receiving port 436 in response to the second fluid sensor 418 detecting fluid 406 is not in contact with the second fluid sensor 418, enabling detection of the fluid reservoir 404 being below the second threshold capacity.
  • the first fluid sensor 414 and the second fluid sensor 418 may detect a resistance across contacts in order to detect the presence of fluid 406.
  • the fluid 406 may cause a low resistance across the fluid sensor contacts.
  • the air may cause a high resistance across the fluid sensor contacts.
  • the low resistance may indicate that fluid 406 is in contact with the fluid sensor and the high resistance may indicate fluid 406 is not in contact with the fluid sensor.
  • the first fluid sensor 414 and the second fluid sensor 418 may be impedance sensors.
  • the impedance sensor may provide a voltage signal indicating a wet or dry state. For example, while fluid 406 is in contact with the impedance sensor the voltage signal may indicate a wet state and while fluid 406 is not in contact with the impedance sensor the voltage signal may indicate a dry state.
  • first fluid sensor 414 and the second fluid sensor 418 may be a resistance sensor or an impedance sensor; however, examples are not so limited and other types of sensors conducive to sensing fluid 406 are also contemplated (e.g., capacitive sensor, etc.).
  • FIG. 5 is a block diagram of an example of a printing device 500.
  • a memory resource 542 is part of the printing device 500 that can be communicatively coupled to a fluid ejection device.
  • the printing device 500 include a processor 540 communicatively coupled to the memory resource 542.
  • the memory resource 542 includes instructions 544, 546, 548, 550, stored on the memory resource 542 and executed by the processor 540 to perform particular functions.
  • the processor 540 may include, but is not limited to: a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a metal-programmable cell array (MPCA), a semiconductor-based microprocessor, or other combination of circuitry and/or logic to orchestrate execution of instructions 544, 546, 548, 550.
  • the printing device 500 includes instructions 544, 546, 548, 550, stored an a machine- readable medium (e.g., memory resource 542, non-transitory computer-readable medium, etc.) and executable by the processor 540.
  • the printing device 500 utilizes a non-transitary computer-readable medium storing instructions 544, 546, 548, 550, that, when executed, cause the processor 540 to perform corresponding functions.
  • the memory resource 542 may be electronic, magnetic, optical, or other physical storage device that stores executable instructions.
  • a non- transitory machine-readable medium (e.g., the memory resource 542) may be, for example, a non-transitory MRM comprising Random-Access Memory (RAM), read-only memory (ROM), an Electrically-Erasable Programmable ROM (EEPROM), a storage drive, an optical disc, and the like.
  • the non-transitory machine-readable medium e.g., the memory resource 542) may be disposed within a controller and/or computing device.
  • the executable instructions 544, 546, 548, 550 can be “installed” on the device.
  • the non-transitory machine-readable medium (e.g., the memory resource 542) can be a portable, external or remote storage medium, for example, that allows a computing system to download the instructions 544, 546, 548, 550, from the portable/external/remote storage medium.
  • the executable instructions may be part of an “installation package.”
  • the non-transitory machine-readable medium (e.g., the memory resource 542) can be encoded with executable instructions for determining whether a fluid level of a fluid ejection device exceeds a threshold capacity.
  • the memory resource 542 includes instructions 544 that are executed by the processor 540 to determine a fluid reservoir exceeds a first threshold capacity and a second threshold capacity in response to a capillary and a first fluid sensor being in contact with a fluid in a printhead die.
  • the capillary and the first fluid sensor may be arranged to contact the fluid entering the printhead die of a fluid ejection device of the printing device 500.
  • the capillary may be sized to have a capillary pressure equal to a first capillary pressure of a foam of the fluid reservoir. As the fluid reservoir is depleted, the fluid reservoir may drop below the first threshold capacity increasing a capillary pressure of the foam above the first capillary pressure and the capillary pressure of the capillary. Due to the pressure increase of the reservoir, fluid may be drawn out of the capillary, away from the first fluid sensor, and into the reservoir.
  • the memory resource 542 includes instructions 546 that are executed by the processor 540 to determine the fluid reservoir is below the first threshold capacity in response to the first fluid sensor not being in contact with the fluid in the printhead die.
  • the printhead die may include an opening connected to the capiliary adjacent to the first fluid sensor.
  • the capillary may be vented to air to back-fill the capillary. As air back-fills the capillary, fluid from the capillary may flow through a curved gradient channel and into a capillary choke of the printhead die and into the fluid reservoir.
  • the capillary choke may be sized such as a capillary pressure of the capillary choke exceeds a threshold internal printhead die pressure to block the air from entering the capillary choke and flowing into the fluid in the fluid reservoir.
  • the memory resource 542 includes instructions 548 that are executed by the processor 540 to determine the fluid reservoir is below the second threshold capacity in response to a second fluid sensor located in the curved gradient channel not being in contact with the fluid in the printhead die.
  • a first end of the curved gradient channel may be fluidically connected to the capillary and sized to have a capillary pressure equal to a second capillary pressure of the foam of the fluid reservoir.
  • a second end of the curved gradient channel may be fluidically connected to the capillary choke and the capillary choke may be fluidically connected to the fluid reservoir.
  • the memory resource 542 may include instructions 550 that are executed by the processor 540 to cause the printing device 500 to indicate a fluid level of the fluid reservoir based on whether the fluid reservoir exceeds the first threshold capacity or the second threshold capacity (or multiple threshold capacities in the example of multiple curved gradient channels and sensors as described in reference to FIG. 3).
  • the instructions may include detecting whether the fluid is in contact with the first fluid sensor or the second fluid sensor to determine the fluid level of the fluid reservoir (or multiple sensors as described in reference to FIG. 3).
  • the processor 540 may cause, based on the level of fluid in the fluid reservoir, fluid to be added to the fluid reservoir via a fluid receiving port.
  • Fluid may be added while the printing device 500 is not performing a print job (e.g., not printing). For exampie, fluid may be added while the printing device 500 is in between print jobs and/or the printing device 500 may pause printing to add fluid in response to the detection of the fluid level of the fluid reservoir.
  • the instructions executed by the processor 540 may include detecting whether the fluid is in contact with the first fluid sensor or the second fluid sensor (or multiple sensors as described in reference to FIG. 3) and determining a pressure level at a fluid ejection nozzle of the printhead die based on detecting whether fluid is present at the first fluid sensor or the second fluid sensor.
  • the pressure at the fluid ejection nozzle may be determined and monitored while the printing device 500 is idle and may be determined and monitored while the printing device 500 is printing.
  • the processor 540 may cause fluid to be added to the fluid reservoir via the fluid receiving port.

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  • Ink Jet (AREA)

Abstract

L'invention concerne un exemple de dispositif qui peut comprendre un dispositif d'éjection de fluide, comprenant un réservoir qui contient un milieu poreux, et une matrice de tête d'impression reliée au réservoir et comprenant un capillaire dimensionné pour avoir une pression capillaire égale à une première pression capillaire du milieu poreux et comprenant un premier capteur disposé pour être en contact avec le fluide tandis que le réservoir se trouve à une première capacité de seuil et une pression capillaire du milieu poreux se trouve à la première pression capillaire, et un canal à gradient courbe relié au capillaire et dimensionné pour avoir une pression capillaire égale à une deuxième pression capillaire du milieu poreux et comprenant un deuxième capteur disposé pour être en contact avec le fluide dans le canal à gradient courbe lorsque le réservoir dépasse un deuxième seuil de capacité et que la pression capillaire du milieu poreux est égale à la deuxième pression capillaire.
PCT/US2022/048481 2022-10-31 2022-10-31 Capteurs capillaires de matrice de tête d'impression WO2024096866A1 (fr)

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PCT/US2022/048481 WO2024096866A1 (fr) 2022-10-31 2022-10-31 Capteurs capillaires de matrice de tête d'impression

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5079570A (en) * 1989-10-18 1992-01-07 Hewlett-Packard Company Capillary reservoir binary ink level sensor
WO2021126189A1 (fr) * 2019-12-18 2021-06-24 Hewlett-Packard Development Company, L.P. Structures capillaires

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5079570A (en) * 1989-10-18 1992-01-07 Hewlett-Packard Company Capillary reservoir binary ink level sensor
WO2021126189A1 (fr) * 2019-12-18 2021-06-24 Hewlett-Packard Development Company, L.P. Structures capillaires

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