Removing gas from a printhead

A method of removing gas from a printhead is provided. A sealing material may be applied to orifices of a printhead from external the printhead to restrict passage of fluid through the orifices. Ink may be moved through a printhead conduit disposed in fluid communication with the orifices to create an inward suction adjacent the orifices so that the gas is displaced from adjacent the orifices.

BACKGROUND

Printers may create printed output on a print medium by firing ink droplets at the print medium from nozzles of a printhead. To prepare the nozzles for firing initially, the nozzles are primed with ink, to replace gas with ink. The nozzles and their supply compartments then should be maintained relatively free of gas bubbles to maintain consistent firing of the nozzles.

DETAILED DESCRIPTION

The present teachings provide methods of removing gas from a printhead, and particularly from orifices (nozzles) and/or from firing compartments of the printhead disposed adjacent the orifices. A sealing material may be applied to the orifices from external the printhead to produce sealed orifices. The sealing material may separate internal gas inside the printhead from external gas outside the printhead and may restrict passage of fluid through the sealed orifices, such as passage of air and/or ink. The sealing material may be a solid sealant or a liquid sealant, such a viscous liquid, among others. In some embodiments, the sealing material may be a glycol. The sealing material may be configured to withstand a greater inwardly directed pressure than ink, while restricting entry of external gas through the orifices and into the printhead.

Ink may be moved through a printhead conduit disposed in fluid communication with the sealed orifices. The printhead conduit may operate as a venturi (a constricted tube) that so that ink movement may create a reduced pressure in the printhead conduit, according to Bernoulli's principle. The reduced pressure thus may provide an inwardly directly pressure drop (a net inward pressure or suction) between the sealed orifices and the printhead conduit, so that the ink (and/or the sealing material) displaces internal gas from adjacent the sealed orifices. The displacement of internal gas may effect (1) priming of the printhead with ink, and/or (2) servicing of the printhead to remove trapped gas from adjacent the sealed orifices (such as gas in the sealed orifices themselves and/or in firing compartments disposed adjacent the sealed orifices), among others.

Apparatus configured to remove gas from orifices and/or firing compartments of a printhead are also disclosed. The apparatus may include an inkjet printer. The apparatus also may include a service station with an applicator configured to apply a sealant to orifices of a printhead. The apparatus may include a pressure or flow controller configured to move ink through a conduit of the printhead, disposed between an ink supply chamber and a receiver compartment. The movement of ink may remove internal gas of the printhead from adjacent the orifices. The apparatus also may be configured to remove the sealant mechanically and/or by firing ink from the orifices into a spittoon, among others. The methods and apparatus disclosed herein may provide a more economical and/or effective approach to priming printheads and/or removing gas from the printheads. For example, the methods and apparatus disclosed herein may waste substantially less ink than a vacuum applied to the printhead orifices from external the printhead, which can suck substantial quantities of wasted ink from the printhead as the vacuum removes air.

FIG. 1shows an embodiment of a printer20configured for removal of gas from printheads22of the printer after application of a sealing material to the printheads. Printer20may be any suitable type of printer, such as an inkjet printer, among others. Printer20may include a colorant application assembly24and a media movement mechanism26.

Gas, as used herein, may include air and/or any gas-phase substance or mixture disposed in or adjacent the printhead and/or the ink. Accordingly, gas may be introduced into an ink supply during packaging of the ink or fabrication of the printhead, may be evolved by chemical reaction in the ink, may escape from a dissolved condition or by evaporation, and/or may enter from an opening in the ink supply or printhead, such as air entering through an ink supply chamber, an ink reservoir, and/or a printhead nozzle, among others.

Colorant application assembly24may be configured to dispense one or more liquid colorants, hereafter termed ink, from printheads22to selected positions of a print medium28, such as paper. Each printhead may include nozzles (orifices) and firing elements, such as heaters or piezoelectric elements, disposed adjacent the orifices. The printheads may be configured to reciprocate on carriage rod30to dispense swaths of ink to the selected positions of the print medium. The colorant application assembly may include a plurality of ink reservoirs32holding ink of different colors and in fluid communication with printheads22. The ink reservoirs may be disposed adjacent the printheads as part of a cartridge and movable on the carriage rod during printhead scanning along a scan axis, for on-axis supply of ink. Alternatively, as shown in the present illustration, the ink reservoirs may be spaced from the printheads, for example, connected thereto using supply tubing34. Accordingly, the ink reservoirs32may be stationary as the printheads reciprocate on carriage rod30.

In the off-axis configuration shown in the present illustration, printheads22may be included in a printhead arrangement36including ink supply chambers38. Each supply chamber may receive ink for its respective printhead from a corresponding ink reservoir32using supply tubing34.

Media movement mechanism26may be configured to move a print medium before, during, and/or after colorant application assembly24dispenses ink onto the print medium. The media movement mechanism may define a path of media travel, from an input site38to an output site40, that is disposed orthogonally to a scan axis along which the printheads reciprocate. The printheads may be configured to reciprocate in a print zone42adjacent the print medium for dispensing ink to the print medium. The printheads also may travel to a service zone44separate from, or overlapping, the print zone and including a service station46, as described in more detail below.

FIG. 2shows a schematic representation of selected aspects of printer20. Printer20may include colorant application mechanism24, a service station46for servicing aspects of the colorant application mechanism, and a processor60for controlling operation of the colorant application mechanism and/or service station.

Colorant application mechanism24may be configured to move ink between one or more ink reservoirs32and one or more printheads22. To simplify the presentation, a single ink reservoir and printhead are shown in the present illustration. The ink reservoir may supply ink to a printhead assembly62through channel34. The ink may travel into supply chamber38of printhead assembly62, to nozzle supply conduit64, and then out nozzles (orifices)66. Alternatively, nozzles66may be sealed so that ink travels through nozzle supply conduit, past nozzles66, and to receiver compartment68, as indicated by the arrows shown at69(or in reverse, from receiver compartment68to supply chamber38, among others). A printhead assembly, as used herein, is a printhead and any attached ink compartment(s), such as a supply chamber and/or receiver compartment, among others. A printer may include a plurality of printhead assemblies, termed a printhead arrangement.

Colorant application mechanism24may include at least one pressure or flow controller70to control fluid movement within the colorant application mechanism. The pressure controller may include a pump72(or pumps). The pump may be any mechanism for exerting a pressure on ink directly, or on a container holding ink, including pressurized gas, a vacuum pump, a mechanical pump (syringe, rotary, peristaltic, etc.), and/or the like. The pressure controller also or alternatively may include one or more valves74operable to permit or restrict fluid movement between ink compartments.

Service station46may be any portion of the printer configured to service printhead22. The service station may be substantially stationary, so that the printhead is moved to the service station, the service station may move to the printhead, or a combination thereof, as indicated at76. Service station46may include a nozzle sealant applicator78configured to apply a sealant80to the printhead from sealant reservoir82. Service station46also may include a waste reservoir or spittoon84to receive ink and/or sealant from the printhead, particularly ink and/or sealant ejected from the printhead by actuation of firing elements of the printhead.

The sealant or sealing material may be solid, liquid, a combination thereof (such as a gel), among others. A solid sealing material may include a resilient member, such as formed of plastic or rubber, that is pushed against the printhead to create a seal. A liquid sealing material may be any suitable liquid. Exemplary liquid sealing materials are viscous. Viscous, as used herein, means having a greater viscosity than the viscosity of ink in the printhead. In some examples, the viscosity may be about 2 to 250 centipoise. Alternatively, or in addition, the sealing material may have a burst pressure greater than the burst pressure of ink in the printhead. The “burst pressure” for a fluid, as used herein, is the pressure at which the fluid's sealing capacity is lost, that is, the pressure at which a fluid sealing an orifice permits entry of external gas through the orifice. In some examples, a sealing material may be soluble in ink and may be miscible, that is soluble at any ratio of sealing material to ink. Exemplary sealing materials may be alcohols, particularly polyols or diols, such as glycols or polymers thereof.

Exemplary glycols or glycol polymers that may be suitable include dipropylene glycol, ethylene glycol, propylene glycol, and/or polyethylene glycol, among others.

The sealant applicator may be any mechanism for applying sealant80to the printhead. The form of the applicator may be in accordance with the type of sealant used. For example, with a solid sealant, the sealant applicator may be a structure or device for placing the solid sealant against the printhead, such as a cantilever or spring, among others. With a liquid sealant, the sealant applicator may be a structure that spreads the liquid sealant, such as a pad or brush, among others. Alternatively, or in addition, the sealant applicator may be a structure configured to spray the sealant on the printhead, to dip the printhead into the sealant, and/or the like.

Processor60may be any data-processing controller included in the printer or disposed in a separate apparatus, such as a computing device in communication with the printer. The processor may be configured to control operation of pump72and valve(s)74, such as determining when and how much ink flows from ink reservoir32to printhead assembly62. The processor also may be configured to control when and how much sealant80is applied to the printhead and to coordinate application of sealant and movement of ink through nozzle supply conduit64. Accordingly, the processor may be coupled to a sensor that senses a property of ink from a subset or all of the nozzles. For example, the sensor may measure a property such as droplet size, droplet trajectory, and/or presence/absence of ink or fired droplets. Data from the sensor may be processed by the processor to determine if the printhead should be serviced to remove gas and/or prime nozzles. Accordingly, the processor may be configured to automatically initiate application of the sealing material and/or movement of ink through the supply conduit to the receiver compartment based on the sensor data. Alternatively, or in addition, the processor may be configured to initiate removal of gas from printheads at predefined intervals or based on instructions received from a user through a user interface. The processor further may be configured to control removal of the sealing material from the printhead and to coordinate this removal with movement of ink into nozzle supply conduit64after application of the sealing material.

FIG. 3shows a sectional view of selected aspects of printhead assembly62and pressure controller70from printer20. Printhead assembly may include a body102, at least one printhead22, and a carrier104joining the printhead to the body.

Body102may define one or more compartments for holding fluid, such as ink or air. For example, in the present illustration, body102defines a supply chamber38configured to hold ink106to be fired from the printhead. Body102also may define a receiver compartment68separated from supply chamber38by internal wall108. The body may be formed of any suitable material, such as a plastic, metal, glass, or ceramic, among others.

Body102may define a plurality of channels for movement of ink into and through the body and/or for regulating pressure in the body. For example, body102may define body channels110,112for supplying ink to the body and between supply chamber38and receiver compartment68. First body channel110may function as an inlet channel to receive ink from an ink reservoir. Second body channel112may function as an outlet (or inlet) channel for ink and/or gas and/or may be used for pressure regulation of the body. Each of body channels110,112, respectively, may be regulated by a pump72a,72band/or at least one valve74a,74b. Each pump may be operable to create a positive or negative pressure in the body relative to the ambient pressure.

Body102also may define first and second openings114,116. First opening114may by a chamber outlet to permit ink to flow to printhead22and/or to receiver compartment68from supply chamber38. First opening114may be covered by a filter118to remove particulates from the ink. Second opening116may be an inlet for receiver compartment68, to permit ink and/or gas to travel into the receiver compartment. In some embodiments, second opening116may function as an inlet to carry ink to printhead22and/or supply chamber38from receiver compartment68.

Body also may define an intake orifice120and a diaphragm orifice122. Intake orifice120may be covered by a bubbler screen124configured to adjust the body pressure by permitting passage of external air into the body if the body pressure becomes too negative. Diaphragm orifice122may be attached to a diaphragm or deformable member126that forms an external gas compartment128of variable volume. Deformable member126may function, for example, to maintain a more constant pressure in supply chamber38as ink is removed from the supply chamber.

Carrier104may be configured to provide fluid communication between body102and printhead22. Carrier104may define passages130,132that extend between printhead22and body102. In some examples, first passage130may function as an inlet to carry ink to printhead22, and second passage132may function as an outlet to carry ink and/or gas from printhead22to receiver compartment68. Ink flow between the first and second passages may be encouraged or discouraged according to the open or closed status of valve74band/or the pressure difference between the passages produced by pump(s)72aand/or72b. Carrier104may be formed of any suitable material, including ceramic, glass, plastic, silicon, metal, and/or the like.

Printhead22and/or carrier104may define a supply conduit64in fluid communication with the nozzles/orifices66of the printhead and providing fluid communication between passages130,132. Accordingly, ink entering supply conduit64from first passage130may be expelled from the nozzles and/or may travel to second passage132. In some embodiments, the supply conduits may be a plurality of distinct conduits, for example, one or more distinct conduits for each column of nozzles.

FIG. 4shows a sectional view of printhead22and carrier104. In this example, printhead22and carrier104cooperatively define supply conduit64. Supply conduit64may extend lengthwise along the printhead, according to the arrangement of nozzles66. In the present illustration, nozzles66are arranged in a pair of adjacent columns.

Printhead22may include a substrate152, firing elements154formed on or in the substrate, and an orifice layer156connected to the substrate. The orifice layer and substrate may define a plurality of firing compartments158each including a firing element154, such as a heater or a piezoelectric element, that can be selectively energized to expel ink from its respective nozzle66. The substrate may be any suitable material, particularly a semiconductor, such as silicon, or an insulator, such as glass.

FIG. 5shows another sectional view of printhead22and carrier104, taken through a column of nozzles66. To simplify the presentation, a relatively small number of nozzles are shown. However, the printhead may have any suitable number of nozzles. In exemplary embodiments, each column of nozzles may have 150, 300, or 600 orifices.

FIG. 5indicates a flow path170(open arrows) of ink through supply conduit64. Ink may enter supply conduit64from first passage130of the carrier and exit the supply conduit at second passage132of the carrier. Flow of the ink may create a pressure drop directed inwardly from orifices66and firing compartments158to the printhead conduit, so that there is a net inward pressure at the orifices, shown at172. This pressure drop may be created according to Bernoulli's principle, for example, by pushing ink through supply conduit64of smaller diameter at a greater speed than in flanking passageways.

FIGS. 6–10show printhead configurations produced during performance of a method of removing gas from printhead22. For simplification, only a single nozzle66and firing compartment158are shown in fluid communication with supply conduit64.

FIG. 6shows printhead22in an unprimed configuration. In this unprimed configuration, supply conduit64, and particularly nozzle66and firing compartment158, may be free of ink and filled with gas, generally air. The unprimed configuration may be the configuration of the printhead before its first use, that is, as sold to consumers. Alternatively, the unprimed configuration may be produced after the printhead has been used for printing, for example, by operating the printhead with a shortage of ink or as a desired condition of the printhead, such as produced during cleaning or the ink used. Alternatively, the printhead at this stage may be primed with ink, but may include trapped gas, such as pre-existing air bubbles, in one or more of the orifices, firing compartments, and/or in supply conduit64, among others.

FIG. 7shows printhead22during application of a sealing material190to an external surface192of the printhead. External surface192may be defined by orifice layer156or an orifice plate, among others. The sealing material may be applied to external surface192so that the sealing material covers and seals some or all of the orifices66of the printhead, shown at194. Sealing an orifice, as used herein, means that the sealing material restricts passage of fluid through the orifice, for example, passage of external gas196into the printhead. Accordingly, a sealed orifice provides a hermetic restriction that separates internal gas198from external gas196. Sealing material190may be a viscous liquid applied by contact of the printhead with an applicator202. The applicator may be absorbent or nonabsorbent. In some examples, the applicator may include an elastomeric material, such as ethylene propylene diene monomer (EPDM) rubber.

FIG. 8shows printhead22during movement of ink106through supply conduit64after application of sealing material190to seal the orifice. Movement of the ink may create a reduced pressure in the supply conduit so that internal gas198in firing compartment158enters supply conduit64as gas bubbles204and is replaced by ink106moving in a direction opposite to the gas bubbles.

FIG. 9shows printhead22in a primed condition after the internal gas has been replaced substantially by ink106, shown at206. Sealing material190now may be removed for operation of the primed printhead.

FIG. 10shows printhead22firing droplets208from orifice66. Such droplets initially may include a substantial amount of sealing material190, shown at210, which may decrease as additional droplets are fired, shown at212. Alternatively, or in addition, sealing material may be removed from printhead22by a mechanical approach, such as wiping off the sealing material, and/or may be washed off by external application of a suitable solvent.

It is believed that the disclosure set forth above encompasses multiple distinct embodiments of the invention. While each of these embodiments has been disclosed in specific form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. The subject matter of this disclosure thus includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. Similarly, where the claims recite “a” or “a first” element or the equivalent thereof, such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements.