Fluid circulation

Among other things, an apparatus for use in fluid jetting is described. The apparatus includes a printhead including a flow path and a nozzle in communication with the flow path that has a first end and a second end. The apparatus also includes a first container fluidically coupled to the first end of the flow path, a second container fluidically coupled to the second end of the flow path, and a controller. The first container has a first controllable internal pressure and the second container has a second controllable internal pressure. The controller controls the first internal pressure and the second internal pressure to have a fluid flow between the first container and the second container through the flow path in the printhead according to a first mode and a second mode. In either mode, at least a portion of the fluid flowing along the flow path is delivered to the nozzle when the nozzle is jetting. The first mode has the first internal pressure higher than the second internal pressure and the second mode has the second internal pressure higher than the first internal pressure. The fluid flows from the first container to the second container according to the first mode and flows from the second container to the first container according to the second mode.

TECHNICAL FIELD

This disclosure generally relates to fluid circulation in a fluid ejector.

BACKGROUND

An ink jet printer typically includes an ink path from an ink supply to an ink nozzle assembly that includes nozzles from which ink drops are ejected. Ink drop ejection can be controlled by pressurizing ink in the ink path with an actuator, which may be, for example, a piezoelectric deflector, a thermal bubble jet generator, or an electrostatically deflected element. A typical printhead has a line of nozzles with a corresponding array of ink paths and associated actuators, and drop ejection from each nozzle can be independently controlled. In a so-called “drop-on-demand” printhead, each actuator is fired to selectively eject a drop at a specific pixel location of an image, as the printhead and a printing media are moved relative to one another.

A printhead can include a semiconductor printhead body and a piezoelectric actuator. The printhead body can be made of silicon, which is etched to define ink chambers. Nozzles can be formed in the silicon body, or defined by a separate nozzle plate that is attached to the silicon body. The piezoelectric actuator can have a layer of piezoelectric material that changes geometry, or bends, in response to an applied voltage. The bending of the piezoelectric layer pressurizes ink in a pumping chamber located along the ink path.

Printing accuracy can be influenced by a number of factors, including the uniformity in size and velocity of ink drops ejected by the nozzles in the printhead and among the multiple printheads in a printer. The drop size and drop velocity uniformity are in turn influenced by factors, such as the dimensional uniformity of the ink paths, acoustic interference effects, contamination in the ink flow paths, and the uniformity of the pressure pulse generated by the actuators. Contamination or debris in the ink flow can be reduced with the use of one or more filters in the ink flow path.

SUMMARY

In one aspect, the disclosure describes an apparatus for use in fluid jetting. The apparatus comprises a printhead including a flow path and a nozzle in communication with the flow path. The flow path has a first end and a second end. The apparatus also includes a first container fluidically coupled to the first end of the flow path, a second container fluidically coupled to the second end of the flow path, and a controller. The first container has a first controllable internal pressure and the second container has a second controllable internal pressure. The controller controls the first internal pressure and the second internal pressure to have a fluid flow between the first container and the second container through the flow path in the printhead according to a first mode and a second mode. In either mode, at least a portion of the fluid flowing along the flow path is delivered to the nozzle when the nozzle is jetting. The first mode has the first internal pressure higher than the second internal pressure and the second mode has the second internal pressure higher than the first internal pressure. The fluid flows from the first container to the second container according to the first mode and flows from the second container to the first container according to the second mode.

Implementations may include one or more of the following features. The fluid flowing from the first container to the nozzle in a direction opposite to the direction in which the fluid flows from the second container to the nozzle. The first internal pressure and the second internal pressure are both lower than the atmospheric pressure. A difference between the first and second internal pressures is larger than a difference between the atmospheric pressure and the first or second internal pressure. The controller controls a rate of the fluid flow between the first and second containers to be higher than the rate of the fluid delivery from the first or second container to the nozzle when the nozzle is jetting. For a given period of time, an amount of the fluid flown between the first and second containers is at least 10 times an amount of fluid jetted by the printhead when the printhead is jetting a fluid. A rate of the fluid flow through the flow path is about 5% or less of a velocity of a fluid droplet ejected from the nozzle. The apparatus also includes a sensor to sense a fluid level in each of the first container and the second container. The controller controls the first and second internal pressures to be in the first mode when the sensed fluid level in the second container is below a predetermined value. The controller controls the first and second internal pressures to be in the second mode when the sensed fluid level in the first container is below a predetermined value. The first container is in a first chamber and the second container is in a second chamber, and the first and second containers are flexible and contain substantially no air. Each of the first and second chambers is connected to a vacuum source to provide adjustment to the first and second internal pressures. The flow path is about 1 micron to about 30 microns upstream of the nozzle, e.g., measured along a path in which the fluid flows. The first and second containers are self-contained fluid reservoirs. The first and second containers are mounted on a housing that is connectable to the printhead. The connection between the housing and the printhead is switchable between a first state in which the first and second containers are in fluid communication with the flow path and a second state in which the first and second containers are fluidically disconnected from the flow path.

In another aspect, the disclosure features a method for use in fluid jetting. The method comprises delivering a fluid at a controlled flow rate from a first container to a second container along a flow path in a printhead along a first direction and delivering the fluid at a controlled flow rate from the second container to the first container along the flow path in the printhead along a second direction opposite to the first direction. A portion of the fluid flowing in the flow path is delivered to a nozzle in communication with the flow path when the nozzle is ejecting the fluid. A portion of the fluid flowing in the flow path is delivered to the nozzle in communication with the flow path when the nozzle is ejecting the fluid.

Implementations may include one or more of the following features. The fluid flowing from the first container to the nozzle in a direction opposite to the direction in which the fluid flows from the second container to the nozzle. A pressure difference between an internal pressure of the first container and an internal pressure of the second container is maintained. Each internal pressure of the first and second containers is maintained to be lower than an atmospheric pressure. The pressure difference between either internal pressure of the first and the second containers and the atmospheric pressure is maintained to be smaller than the pressure difference between the internal pressure of the first container and the internal pressure of the second container. The first and second containers are flexible and the pressure difference is maintained by applying different pressures to exterior surfaces of the flexible first and second containers. A fluid level in the first and second containers is sensed and a fluid delivery direction from the first and second directions is selected based on the sensed fluid level. Delivering the fluid in the selected direction comprises adjusting the internal pressures of the first and second containers. The controlled flow rate is about 5% or less of a velocity of a fluid droplet ejected by the nozzle.

In another aspect, the disclosure features an apparatus for use in fluid jetting. The apparatus comprises a printhead including a flow path and a nozzle in communication with the flow path, the flow path having a first end and a second end; a first container fluidically coupled to the first end of the flow path, the first container having a first controllable internal pressure; a second container fluidically coupled to the second end of the flow path, the second container having a second controllable internal pressure; and a controller to control the first internal pressure and the second internal pressure to have a fluid flow between the first container and the second container through the flow path in the printhead. At least a portion of the fluid flowing along the flow path is delivered to the nozzle when the nozzle is jetting, the first internal pressure being higher than the second internal pressure.

Implementations may include one or more of the following features. The fluid flowing from the first container to the nozzle in a direction opposite to the direction in which the fluid flows from the second container to the nozzle. The first internal pressure and the second internal pressure are both lower than atmospheric pressure. The first container is in a first chamber and the second container is in a second chamber, and the first and second containers are flexible and contain substantially no air each of the first and second chambers is connected to a vacuum source to provide adjustment to the first and second internal pressures. The first and second containers are self-contained fluid reservoirs. The first container contains the fluid and the second container is empty before use.

Implementations may include one or more of the following advantages. An assembly having a printhead module attached to a cartridge containing self-contained fluids can be used for testing operations, such as test printing. The cartridge can include two separate chambers each enclosing a fluid container capable of providing the fluid to nozzles of the printhead module to be jetted. The fluid can be recirculated between the two fluid containers to prevent the fluid from drying along one or more fluid paths in the system or at the nozzles. Particles in fluid can be kept in suspension in the fluid to maintain the quality of the fluid. For example, the fluid can have a high uniformity. Further, air bubbles along the fluid paths can be removed by the recirculation flow. The fluid recirculation can be performed during the fluid jetting. The entire assembly can be disposed of following the testing operation, avoiding having to flush clean a printhead module between tests.

Details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages may be apparent from the description and drawings, and from the claims.

DETAILED DESCRIPTION

A printhead module generally includes a printhead body with multiple nozzles that are in fluid communication with an external fluid supply to allow for a continuous printing operation. In certain applications, a printhead module that can be effectively operated using a relatively small volume of a fluid, e.g., for a fluid testing operation, is desirable. The printhead module can include a fluid supply assembly designed for a relatively small volume of a printing fluid, and the fluid supply assembly can be attachable to the printhead body. In some implementations, the fluid supply assembly is a non-refillable fluid supply assembly, e.g., a single-use printing fluid supply cartridge. Such a device is described in U.S. Pat. No. 7,631,962, which is incorporated by reference.

After use, the printhead body and the fluid supply assembly can be discarded. For example, when testing printing fluids of different colors or qualities, each type of fluid is contained within a fluid supply assembly and printed using a printhead body that is not used to print any other types of printing fluids. There would be no need to flush clean the fluid supply assembly or the printhead body when testing different printing fluids.

Referring toFIG. 1, an assembled system10(or a printhead module10) for use, e.g., in test printing, includes a printhead body16and a fluid supply assembly12, e.g., in the form of a cartridge12that can be attached to the printhead body16. The fluid supply assembly12contains two fluid containers14a,14bto supply a fluid to a printhead body16. One or more nozzles18(only one nozzle shown in the figure) of the printhead body16can be activated to eject fluid drops20to form a pattern on a substrate (not shown). The pattern can be studied to evaluate the quality of the fluid, the image effect of the printing, or the design of the printhead module16.

The two fluid containers14a,14beach can be a self-contained fluid reservoir that communicates with each other through a fluid path24extending from each fluid container14a,14b, and passing through the printhead body16. In this context, self-contained means that during the printing operation, fluid is not supplied into the reservoir from a source outside the fluid containers14a,14b. Rather, the fluid to be used is the fluid contained within the self-contained fluid containers14a,14b. For convenience, we name the fluid path24from the fluid container14aand outside the printhead module16as24a, the fluid path24from the fluid container14band outside the printhead module16as24b, and the fluid path24within the printhead module as24c. The fluid path24ccan be formed in an MEMS die (seeFIGS. 5 and 6below) and is upstream of the nozzle18. The fluid can flow back and forth through the flow path24between the two fluid containers14a,14bto recirculate the fluid between the two containers. During the flow, a portion of the fluid is directed to the nozzle18when needed, e.g., when fluid droplets20are being jetted. The fluid to be jetted by the printhead module16can be delivered from either of the fluid containers14a,14b.

The recirculation (or circulation) of the fluid between the two containers14a,14bcan improve printing quality, e.g., by preventing the fluid from drying at any location along the fluid path or approximate the nozzle18. Particles in the fluid can be kept in suspension in the fluid without substantial coagulation to maintain the quality, e.g., uniformity of viscosity and/or avoidance of large particles that could clog the fluid path or nozzle, of the fluid. In some implementations, air bubbles generated along the fluid path24can be carried with the flow and be removed at the containers14a,14b, e.g., by rising to the surface of the fluid in the containers14a,14b. The test printing results from the system10contain few artifacts generated by fluid drying, air bubbles, or fluid quality variations. The system10resembles a real printing system (that is not used only for testing), and the test printing results can provide a true representation of the elements that are being tested, e.g., the quality of the fluid.

In the assembled system10, to prevent the fluid from automatically flowing out of an inactivated nozzle18and control the fluid flow between the containers14a,14b(explained in more detail below), the fluid pressure in each fluid container14a,14bis controlled. In the example shown inFIG. 1, the fluid containers14a,14beach includes a flexible wall36a,36bthat transfers the pressure in each chamber22a,22bof the cartridge12to the fluid inside the containers14a,14b. Each chamber22a,22bencloses a respective fluid container36a,36b. The pressure within each chamber22a,22bcan be adjusted using a pressure control device28, e.g., one or more pumps or vacuum sources, connected to the chambers through openings30a,30b, respectively. The chambers22a,22bare sealed from each other and the pressure in each chamber can be independently adjusted by the pressure control device28.

In some implementations, the amount of fluid in the containers14a,14bis small and the fluid pressures within the containers14a,14bare substantially the same as the fluid pressures in the chambers22a,22b, respectively. Each container14a,14bcan be air-free or under a vacuum before the fluid is filled into the container. In some implementations, a system10can have one of the fluid containers14a,14bfilled with a desired amount of fluid, e.g., 0.25 ml to 10 ml, 0.5 ml to 3 ml, or 1.5 ml, and the other one of the fluid containers empty and airless. In some implementations, the fluid containers14a,14bmay contain some air. In some implementations, the fluid containers contain a gas but do not contain oxygen gas. The fluid path24can be controlled to be airless or free of oxygen. An airless system or a system free of oxygen can prevent air or oxygen dissolving into the fluid to affect the quality of printing or quality of the fluid. In some implementations, the system10can be assembled under an inert atmosphere.

The fluid in each containers14a,14bis maintained at a selected negative pressure, e.g., −0.5 inch of water to −20 inches of water or −6 inches to −7 inches of water, depending on factors such as size of the orifice or nozzle18. When the nozzle18is not activated to eject droplets20, the negative pressure prevents the fluid from automatically seeping out of the nozzle18and at the same time prevents air from being drawn into the printhead module16from the nozzle18. Referring toFIGS. 1 and 1A, the negative pressure in the fluid balances the combined forces of fluid source pressure (produced by the height location of the fluid containers14a,14brelative to the printhead module16, which can be positive or negative), capillary action, and atmospheric pressure to maintain a meniscus34on an fluid-air interface at the nozzle18. When the nozzle18(or the pumping chamber) is activated, the meniscus34can allow the fluid to be jetted out of the nozzle18readily. Such a negative pressure in the fluid is maintained during the flow circulation between the containers14a,14b, and also during fluid jetting from the nozzle18. During fluid jetting, the fluid pressure in the vicinity of the nozzle18(e.g., upstream of the nozzle18and in a pumping chamber (not shown)) can be changed by an actuator, e.g., a piezoelectric actuator.

The direction of fluid flow along the fluid path24is controlled by a difference between the fluid pressures in the fluid containers14a,14b. For example, when the fluid pressure in the container14ais higher than the fluid pressure in the container14b, the fluid flows from the container14atowards the container14b(as an arrow32shows). The pressure control device28maintains the negative pressure in the fluid (in the containers14a,14bor at the printhead body16) and, e.g., at the same time, generates the pressure difference between the pressures within the chambers22a,22b. The rate of the fluid flow can be affected by the value of the pressure difference and other factors, such as the dimensions of the flow path24.

The amount of recirculation fluid between the two fluid containers can be about 1/1000 to about 10 times the maximum amount of fluid jetted by the print body16in a given time period. The recirculation fluid flow rate (i.e., the amount of recirculation fluid passing by a cross-section of the flow path24per second) can be selected based on the need of the system. In some implementations, the ratio of the recirculation fluid flow rate to the amount of fluid jetted depends on the duty cycle of the printing or percentage of the jetting nozzles per unit time period, e.g., be lower when the printing is operating at a higher duty cycle. The recirculation fluid flow velocity can be controlled to prevent effects on, e.g., errors in, fluid jetting trajectories because the recirculation fluid is in communication with the nozzle18, e.g., flows past the nozzle18.

The value of the pressure difference between the two fluid containers can be chosen based on the desired flow rate, the characteristics of the fluid, e.g., viscosity, the design of the flow path24, and other factors. In some implementations, the value of the pressure difference is pre-chosen based on the assembly10and the fluid while the direction of the pressure difference can be changed dynamically. The assembly10switches the direction of the pressure difference to drive the fluid flow in the desired direction. For example, when the pressure in the fluid container14ais higher than the fluid pressure in the fluid container14b, the fluid flows from the fluid container14ato the fluid container14b. When the direction of the pressure difference is reversed (i.e., the fluid container14bhas a higher pressure than the fluid container14a), the flow direction is reversed. In some implementations, the value of the pressure difference is about 0.1 inch of water up to 100 inches of water.

A controller26determines the direction of fluid flow based on the fluid levels in each container14a,14b, and instructs the pressure control device28to form a desired pressure difference between the two containers to drive the fluid flow. In some implementations, the fluid levels are sensed by fluid level sensors36a,36blocated within the containers14a,14b, respectively. Examples of the sensors36a,36bcan include contact sensors that touch the fluid containers14a,14b. Other sensors (not shown) suitable for use can include optical sensors, which can be placed outside of the containers14a,14b, proximity sensors, or magnetic sensors, such as reed switches. The sensors36a,36bcan communicate with the controller26through a wire (not shown) or wirelessly. In some implementations, the sensors36a,36band the controller26are connected by one or more optical fibers for communication, e.g., data delivery.

The controller26can be programmed to store criteria for use in forming the instructions to the pressure control device28or other associated devices, e.g., the printhead body16, based on the sensed fluid levels in the containers14a,14b. For example, the criteria can be a minimum fluid level. Under some stored criteria, the controller26can function as shown inFIG. 2. Upon receiving50the sensed fluid levels in the containers14a,14bfrom the sensors36a,36b, the controller26compares the sensed fluid levels with the stored criteria. The controller26first determines52whether the sensed fluid levels in both containers14a,14bare both lower than a predetermined minimum level (PML). If yes, the controller26instructs54the printhead module16to stop printing because the sensed fluid levels indicate that the fluid in the containers14a,14bis running out. In addition, the controller26can also provide a signal to the user to indicate that the fluid level is low and the cartridge12may be discarded or needs to be refilled (discussed later). The pressure control device28can also be instructed to stop working, although maintaining the negative pressure for the fluid meniscus at the nozzle18may be desirable so that the fluid does not leak. If no, then the controller26determines56whether the sensed fluid levels are both higher than the predetermined minimum level. If yes, the fluid flow conditions, e.g., direction or rate, along the fluid path24between the two containers14a,14bdo not need to be changed. The controller26keeps receiving50the sensed fluid levels and monitors the fluid flow. If no, the controller26further determines58whether the current flow direction in the fluid path24is from the container having the high flow level to the container having the low flow level. If yes, the fluid flow conditions do not need to be changed, and the controller26keeps receiving50the sensed fluid flow levels and monitors the fluid flow. If no, then the controller26instructs60the pressure control device28to reverse the pressure difference between the two containers14a,14bso that the fluid flow direction is reversed.

The controller26can also use other criteria and function in ways different from that described inFIG. 2to control the fluid flow between the two containers14a,14b. The criteria can be set at the controller26when the system10is manufactured or can be set/reset by any user of the system10. The criteria can be selected practically, e.g., how much fluid needs to be in the system10to allow the printhead body16to effectively print, or how much fluid is initially filled in the containers14a,14b. For example, when one of the fluid containers is fully filled, and the other one is partially filled, the criteria (e.g., the predetermined minimum level) have to be reasonably high because not all fluid in the full container can be circulated into the partially filled container. The predetermined minimum level can also be affected by the sensitivity and reliability of the sensors36a,36bfor sensing the ink levels in the two containers14a,14b. Examples of the predetermined minimum level can be 0.1 ml to about 0.2 ml. The predetermined minimum level can also be a percentage, e.g., 5%-20%, of the total initial fluid amount in each container or in both containers.

The controller26can be implemented with circuitry, e.g., a programmable microcontroller, or other hardware, software, firmware, or combinations. The controller26can also communicate with a controller (not shown) controlling the fluid jetting of the printhead module16. In some implementations, the controller26can control both the pressure control device28and the fluid jetting. The controllers can be powered by one or more batteries (not shown) in the system10and can coordinate to control the fluid jetting and the fluid flow for fluid recirculation, e.g., simultaneously. Fluid recirculation in a printhead is also discussed in U.S. Pat. No. 7,413,300, U.S. Pat. No. 5,771,052, U.S. Pat. No. 6,357,867, U.S. Pat. No. 4,891,654, U.S. Pat. No. 7,128,406, and U.S. patent application Ser. No. 12/992,587, the entire contents of which are incorporated herein by reference.

The system10can be implemented as an assembly70shown inFIGS. 3A-3D. The controller26and the pressure control device28can be separate from the assembly70and be attached to the openings72a,72b. The assembly70includes a fluid supply assembly74attached to a printhead housing76. A printhead body78is connected to the printhead housing76. The fluid supply assembly74includes two fluid containers80a,80bin two separate chambers74a,74bto supply a jetting fluid to the printhead body78. The fluid supply assembly74can be similar to the cartridge12ofFIG. 1, the fluid containers80a,80b, and the chambers74a,74bcan have similar features to those of the fluid containers14a,14b, and the chambers22a,22b. The printhead body78can have features, e.g., flow path and nozzles, like the flow path24cand the nozzles18ofFIG. 1. Each chamber74a,74bincludes an opening72a,72bto be connected to a pressure control device (such as the pressure control device28ofFIG. 1). The fluid contained in the containers74a,74bis recirculated between the containers and supplied to the printhead body78in a manner, e.g., through flow paths80a,80b, similar to that described inFIG. 1.

In particular,FIGS. 3B and 3Dare cross-sectional perspective views of the assembly70depicted inFIG. 3Ataken along line3B-3B.FIG. 3Cis a cross-sectional perspective view of the assembly70taken along line3C-3C. The fluid supply assembly74includes the self-contained fluid containers80a,80b, at least one of which containing a small volume of a fluid, such as ink. Like the containers14a,14b, the fluid containers80a,80bare flexible containers, similar to bags, and shall be referred to as fluid bags, although other forms of self-contained fluid containers can be used. The fluid bags80a,80bcan be filled with the fluid before or after the fluid supply assembly74is attached to the printhead housing76. In some implementations, the total amount of fluid filled in the fluid bags80a,80bdoes not exceed the capacity of one fluid bag80aor80b. For example, the fluid bag80acan be fully filled with the fluid while the fluid bag80bis empty. In some implementations, up to about 75% of the total capacities of the two fluid bags80a,80bcan be filled with the fluid. The unfilled capacity in either one or both of the fluid bags80a,80bprovides room for the fluid to be recirculated between the two bags.

The fluid bags80a,80bcan be sealed after the fluid is filled into the bags. The fluid remains in the fluid bags until it is used. Seals84a,84b, e.g., O-rings, form seals between the fluid bags80a,80band the printhead housing76. Referring particularly toFIGS. 3B and 3D, the embodiments depicted include a double snap-fit connection, whereby the fluid supply assembly74can be first attached to the printhead housing76in position A, the closed position (FIG. 3B). In the closed position, the fluid paths82a,82bare closed and the fluid bags74a,74bare not in fluid communication with the printhead body78. Prior to commencing a printing operation, the fluid supply assembly74is moved into position B, the open position (FIG. 3D). In the open position, the fluid bags74a,74bare in fluid communication with the printhead body78via the open fluid paths82a,82b.

To connect the fluid supply assembly74to the printhead housing76in the closed position A, a user aligns the male connectors115protruding from the fluid supply assembly74with the corresponding female connectors117formed in the printhead housing76and exerts enough force to engage the male connectors115with the female connectors117at position A (FIG. 3B), but not too much force so as to engage the female connectors117at position B (FIG. 3D). The user should receive enough tactile feedback when mating the fluid supply assembly74to the printhead housing76to determine when position A has been reached.

To move the fluid supply assembly74into the open position B with respect to the printhead housing76, a user exerts additional force to engage the male connectors115with the female connectors117at position B. The male connectors115have enough flexibility to bend under pressure to disengage from the female connectors117at position A and snap into engagement at position B. The female connectors117can be configured to facilitate this movement, for example, by having angled faces as depicted that encourage the similarly angled male connectors115to slide out of engagement upon the exertion from a downward force. The above describes one implementation of a double snap-fit connection. Other configurations of a double snap-fit connection can be used, as well as other types of connections that allow for a closed and an open position.

The fluid paths82a,82bare opened or closed based on the relative position of the fluid supply assembly74and the printhead housing76. The fluid paths82a,82binclude upper portions81a,81bwithin the fluid supply assembly74and extending from respective fluid bags80a,80b. The upper portions81a,81bends at the bottom surfaces of outlet heads118a,118bof the fluid supply assembly74. The fluid paths82a,82balso include lower portions124a,124bformed in the printhead housing76. When the fluid supply assembly74is in the position A ofFIG. 3B, the upper portions81a,81band the lower portions124a,124bdo not connect. Instead, the seal84a,84bare in contact with the bottom surface of the outlet heads118a,118band close the flow paths82a,82b. A spring114in the outlet head118exerts a downward force compressing the seal110. The fluid in the fluid bags80a,80bcannot flow past the bottom surface of the outlet heads118a,118b. When the fluid supply assembly74is in the position B ofFIG. 3D, the bottom of the outlet heads118a,118bcontact the lower portions124a,124b, which can compress the spring114within the outlet heads118a,118b. The seals84a,84bare positioned past the distal end of the lower portions124a,124bof the fluid paths82a,82band are not in contact with the bottom of the outlet head118. The flow paths82a,82bare no longer blocked by the seal110. The fluid can thereby flow from the fluid bags80a,80bto the printhead body78. Detailed designs of the fluid path to enable such flow control are discussed, e.g., in U.S. Pat. No. 7,631,962, the entire content of which is incorporated herein by reference.

In some implementations, the fluid supply assembly74is permanently attached to the printhead housing76, i.e., cannot be detached without breaking a component of the assembly74or housing76. Once the fluid contained within the fluid bags80a,80bhas been used, the assembly70can be discarded. The fluid bags80a,80bare filled via the outlet heads118a,118bbefore attaching the fluid supply assembly74to the printhead housing76. The assembly70thereby provides a self-contained disposable testing unit that uses only a small volume of test liquid. Because the assembly70is only used once, testing can occur without flushing clean printhead modules between tests.

The system10ofFIG. 1can also be implemented in assemblies different from those shown inFIGS. 3A-3D. For example, the control of the flow path82a,82bbetween the fluid bags80a,80band the printhead body78(FIGS. 3A-3D) can be differently performed using different structures and/or mechanisms. Some sample structures are described in U.S. Pat. No. 7,631,962.

The printhead body16in the system10can be any type of printhead body. Referring toFIG. 4, a printhead body100includes a fluid ejection module, e.g., a quadrilateral plate-shaped printhead module, which can be a die103fabricated using semiconductor processing techniques. The fluid ejector further includes an integrated circuit interposer104over the die103and a lower housing322discussed further below. A housing110supports and surrounds the die103, integrated circuit interposer104, and lower housing322and can include a mounting frame142having pins152to connect the housing110to a print bar. A flex circuit201for receiving data from an external processor and providing drive signals to the die can be electrically connected to the die103and held in place by the housing110. Tubing162and166can be part of the fluid paths24a,24bofFIG. 1and are to be connected to the cartridge12ofFIG. 1to supply a fluid to the die103.

Referring toFIG. 5, the die103includes a substrate122, e.g., a silicon-on-insulator (SOI) wafer and the integrated circuit interposer104. Within the substrate122, fluid paths242are formed to recirculate the fluid along the M direction (single arrow) or along the N direction (double arrow) between an inlet176and an outlet172(e.g., of the tubing162,166ofFIG. 4) while delivering the fluid to a pumping chamber174to be jetted from a nozzle126. In implementations, the inlet176can be connected to the fluid container14aand the outlet172can be connected to the fluid container14bofFIG. 1. In the example shown in the figure, the pumping chamber174is part of the flow path242. Each fluid path242includes an inlet channel176leading to the pumping chamber174, and further to both the nozzle126and the outlet channel172. The fluid path242further includes a pumping chamber inlet276and a pumping chamber outlet272that connect the pumping chamber174to the inlet channel176and outlet channel172, respectively. The fluid path can be formed by semiconductor processing techniques, e.g., etching. In some embodiments, deep reactive ion etching is used to form straight walled features that extend part way or all the way through a layer in the die103. In some embodiments, a silicon layer286adjacent to an insulating layer284is etched entirely through using the insulating layer as an etch stop. The pumping chamber174is sealed by a membrane180and can be actuated by an actuator formed on the surface of the membrane180opposite to the pumping chamber174. The nozzle126is formed in a nozzle layer184, which is on an opposite side of the pumping chamber174from the membrane180. The membrane180can be formed of a single layer of silicon. Alternatively, the membrane180can include one or more layers of oxide or can be formed of aluminum oxide (AlO2), nitride, or zirconium oxide (ZrO2).

The actuators can be individually controllable actuators401supported by the substrate122. Multiple actuators401are considered to form an actuator layer, where the actuators can be electrically and physically separated from one another but part of a layer, nonetheless. The substrate122includes an optional layer of insulating material282, such as oxide, between the actuators and the membrane180. When activated, the actuator causes the fluid to be selectively ejected from the nozzles126of corresponding fluid paths242. Each flow path242with its associated actuator401provides an individually controllable MEMS fluid ejector unit. In some embodiments, activation of the actuator401causes the membrane180to deflect into the pumping chamber174, reducing the volume of the pumping chamber174and forcing fluid out of the nozzle126. The actuator401can be a piezoelectric actuator and can include a lower electrode190, a piezoelectric layer192, and an upper electrode194. Alternatively, the fluid ejection element can be a heating element.

The integrated circuit interposer104includes transistors202(only one ejection device is shown inFIG. 5and thus only one transistor is shown) and is configured to provide signals for controlling ejection of fluid from the nozzles126. The substrate122and integrated circuit interposer104include multiple fluid flow paths242formed therein.

Referring toFIG. 6, the fluid can flow from a fluid supply, e.g., one of the fluid containers14a,14bofFIG. 1, through the lower housing322of the printhead body100(FIG. 4), through the integrated circuit interposer104, through the die103, and out of the nozzles126in the nozzle layer184. The lower housing322can be divided by a dividing wall130to provide an inlet chamber132and an outlet chamber136. The fluid from the fluid supply can flow into the fluid inlet chamber132, through fluid inlets101in the floor of the lower housing322, through fluid inlet passages476of the lower housing322, through the fluid paths242of the die103, through fluid outlet passages472of the lower housing322, out through the outlet102, into the outlet chamber136, and to the fluid return, e.g., the other one of the fluid containers14a,14bofFIG. 1. During fluid recirculation, the flow direction can also be opposite to what is described above. A portion of the fluid passing through the die103can be ejected from the nozzles126.

Each fluid inlet101and fluid inlet passage476is fluidically connected in common to the parallel inlet channels176of a number of MEMS fluid ejector units, such as one, two or more rows of units. Similarly, each fluid outlet102and each fluid outlet passage472is fluidically connected in common to the parallel outlet channels172of a number of MEMS fluid ejector units, such as one, two or more rows of units. Each fluid inlet chamber132is common to multiple fluid inlets101. And each fluid outlet chamber136is common to multiple outlets102. The terms “inlet” and “outlet” do not indicate the flow directions. In other words, the fluid can be provided to the pumping chambers in the die103from the inlets101or from the outlets102, depending on the flow direction between the two fluid supplies. Printhead modules are discussed in U.S. patent application Ser. No. 12/833,828, the entire content of which is incorporated herein by reference.

In other implementations, each fluid container14a,14bcan include a fluid refill port so that the system10can be reused. For example, when the fluid in the containers is substantially used up, the same fluid can be refilled into the containers through the refill port. In some implementations, the used containers can be cleaned and a different fluid can be filled into the containers for test printing. The fluid container14a,14bcan be the same as the chambers22a,22b. In other words, the fluid can be directly stored in the chambers22a,22bwithout the containers14a,14b. The pressure of the fluid in different chambers22a,22bcan be similarly controlled using the pressure source28and the controller26, as explained previously. The flow paths24a,24b,24ceach may correspond to multiple flow paths in implementations.

In other implementations, the fluid containers14a,14bdo not include any sensing devices to determine the fluid levels in the containers. The system10can be programmed to stop printing when a full bag of fluid is emptied by recirculation and jetting. No fluid flows back from a second bag back to the emptied bag. Such a design can reduce the cost of the system10. Generally, in this embodiment, one of the fluid containers, e.g., container14a, is full and the other container, e.g., container14b, is empty before jetting. To fully use the fluid contained in the fluid container14a, the print head body16can be programmed to jet until no fluid is left in the fluid container14a.

The fluid can include ink of various colors and properties. A food grade printing fluid can also be used. In some implementations, the fluid can also include non-image forming fluids. For example, three-dimensional model pastes can be selectively deposited to build models. Biological samples can be deposited on an analysis array. Circuitry forming materials can also be used.

All publications, patent applications, patents, and other references mentioned herein are incorporated by reference herein in their entirety.