Adjustable printhead mounting

A system includes a mounting assembly to mount a printhead to a frame having a length in a first direction and a width in a second direction. The mounting assembly includes a fixed component affixed to the frame and a movable component that can move relative to the fixed component. A first pair of flexures connects a first end of the fixed component to a first end of the movable component, and a first adjustment mechanism is positioned at the first end. A second pair of flexures connects a second end of the fixed component to a second end of the movable component, and a second adjustment mechanism is positioned at the second end. A connector couples the mounting assembly to the printhead such that movement of the movable component imparts movement to the printhead. The first adjustment mechanism and the second adjustment mechanism can be operated individually or together.

BACKGROUND

The following description relates to depositing fluid onto a medium. 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, for example, a piezoelectric transducer, a thermal bubble jet generator, or an electrostatically deflected element. A typical printhead module has a line or an array 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 module, each actuator is fired to selectively eject a drop at a specific location on a medium. The printhead module and the medium can be moving relative one another during a printing operation.

In one example, a printhead module can include a substrate and an actuator. The substrate can include a flow path body, which can be made of silicon and can include microfabricated flow paths and pumping chambers. The substrate can also include a nozzle layer secured to the flow path body, and nozzle layer can include nozzles formed therein. The actuator can include a layer of piezoelectric material that changes geometry, or flexes, in response to an applied voltage. Flexing of the actuator pressurizes ink in a pumping chamber located along the ink path.

Printing accuracy can be influenced by a number of factors. Precisely positioning the nozzles relative to the medium can be necessary for precision printing. If multiple printhead modules are used to print contemporaneously, then precise alignment of the nozzles included in the printhead modules relative to one another also can be critical for precision printing.

SUMMARY

A mounting assembly for a fluid ejection module configured to deposit a fluid onto a medium is described. A system can include a mounting assembly to mount a fluid ejection module to a frame having a length in a first direction and a width in a second direction. The mounting assembly can include a fixed component configured to affix to the frame and a movable component adapted to move relative to the fixed component and the frame. The mounting assembly can also include a first pair of flexures connecting a first end of the fixed component to a first end of the movable component, a first adjustment mechanism positioned at the first end, a second pair of flexures connecting a second end of the fixed component to a second end of the movable component, and a second adjustment mechanism positioned at the second end. The mounting assembly can also include a connector configured to couple the mounting assembly to the fluid ejection module such that movement of the movable component imparts corresponding movement to the fluid ejection module. The first adjustment mechanism and the second adjustment mechanism are configured to be operated individually to rotate the first or second end of the movable component, respectively, and to be operated together to translate the movable component in an angular (non-zero) direction relative to the first direction and the second direction.

A system can include a frame having a length in a first direction and a width in a second direction. A system can also include a mounting assembly configured to mount a fluid ejection module to the frame. The mounting assembly can include a fixed component configured to affix to the frame, a movable component configured to move relative to the fixed component and the frame, and a first adjustment mechanism positioned along a first axis that is orthogonal to a first surface of the movable component and that is proximate to a first end of the movable component. The mounting assembly can also include a second adjustment mechanism positioned along a second axis that is orthogonal to the first surface of the movable component and that is proximate to a second end of the movable component. The mounting assembly can also include a connector configured to couple the mounting assembly to the fluid ejection module such that movement of the movable component imparts corresponding movement to the fluid ejection module. The first adjustment mechanism and the second adjustment mechanism can be configured to be operated individually to rotate the movable component about the second axis and the first axis, respectively, and are configured to be operated together to translate the movable component in an oblique angular direction relative to the first direction and the second direction.

Implementations can include one or more of the following features. A length of each flexure in the first and second pair of flexures can be identical such that the fixed component and the movable component remain substantially parallel to one another while moving relative to one another. The first adjustment mechanism can be positioned between the first pair of flexures and the second adjustment mechanism can be positioned between the second pair of flexures. A first edge of the fixed component, a first edge of the movable component, and the first pair of flexures can together foam a parallelogram configuration that is substantially maintained upon movement of the movable component. A second edge of the fixed component, a second edge of the movable component, and a second pair of flexures can together also faun a parallelogram configuration that is substantially maintained upon movement of the movable component.

The fluid ejection module can have a width in a third direction and include an array of nozzles formed on a nozzle face. The first adjustment mechanism and the second adjustment mechanism can be configured to operate individually to rotate a first or second end of the fluid ejection module, respectively, and to operate together to translate the fluid ejection module in the third direction such that the array of nozzles can be aligned relative to the frame and relative to an array of nozzles included in an adjacent fluid ejection module also mounted to the frame.

At least one of the first adjustment mechanism and the second adjustment mechanism can include an eccentric bearing. The eccentric bearing can be configured such that operating a corresponding adjustment mechanism can cause the eccentric bearing to at least partially orbit an axis through a center of the corresponding adjustment mechanism, the axis being substantially perpendicular to the fixed component. A system including a mounting assembly can also include a motor connected to at least one of the first adjustment mechanism and the second adjustment mechanism. The motor can be connected to one of the first adjustment mechanism or the second adjustment mechanism by reduction gears. A mounting assembly can also include a fluid inlet providing a fluid path through the fixed component and the movable component toward the fluid ejection module.

Implementations of this disclosure can realize none, some, or all of the following advantages. The use of two pairs of flexures in a mounting assembly can maintain a nozzle face parallel to the fixed component, thereby facilitating accurate alignment of the nozzle face. Use of an eccentric bearing offset from a screw axis permits relatively large angular movements to produce relatively small translations, thereby facilitating accuracy of alignment. Further, translating the nozzle face at an oblique angle relative to a desired adjustment direction increases accuracy of adjustment because a relatively large translation produces a relatively small adjustment in the desired adjustment direction. Use of two adjustment mechanisms permits adjustment of the fluid ejection module by both translation and rotation.

DETAILED DESCRIPTION

A fluid ejection module and a mounting assembly for the fluid ejection module are described. An exemplary fluid deposited by the fluid ejection module is ink. However, it should be understood that other fluids can be used, for example, electroluminescent material used in the manufacture of light emitting displays, liquid metals used in circuit board fabrication, or biological fluid.

A mounting assembly to mount a fluid ejection module to a frame is described. The frame is configured to position and support one or more fluid ejection modules near a medium. The mounting assembly includes a fixed component, which is configured to affix to the frame, and a movable component. The movable component is adapted to move relative to the fixed component and the frame, whereas the fixed component does not move relative to the frame. The fixed component and the movable component are connected by a first and a second pair of flexures. The first pair of flexures connects a first end of the fixed component to a first end of the movable component and the second pair of flexures connects a second end of the fixed component to a second end of the movable component. A first adjustment mechanism is positioned at the first end, for example, between the first pair of flexures, and a second adjustment mechanism is positioned at the second end, for example, between the second pair of flexures. The mounting assembly further includes a connector configured to couple the mounting assembly to the fluid ejection module.

Movement of the movable component imparts corresponding movement to the fluid ejection module. For example, the first adjustment mechanism and the second adjustment mechanism can be operated individually to rotate the first end or second end of the movable component, respectively. When the movable component rotates, the fluid ejection module also rotates. The frame has a length in an x direction and a width in a y direction. In one implementation, the first and second adjustment mechanism can be operated together to translate the movable component in an angular direction relative to the x and y directions. Similarly, when the movable component translates in a direction, the fluid ejection module also translates. In this manner, an array of nozzles included on a nozzle face of the fluid ejection module can be aligned to the frame and/or to an adjacent fluid ejection module also coupled to the frame, as shall be described in further detail below.

FIG. 1Ais a perspective view of a printing apparatus101including an implementation of multiple mounting assemblies100arranged within a frame110. Each mounting assembly100is configured to mount a fluid ejection module to the frame110. The mounting assemblies100include fixed components120that affix to the frame110. In the implementation shown, each fixed component120includes apertures125configured to receive a connector (e.g., a screw) for fastening the fixed components120to the frame110. The frame110includes bores115that align with the apertures125of the fixed component120. Other techniques to affix the fixed components120to the frame110can be used, and the one described is but one example.

Each mounting assembly100can include a first adjustment mechanism130and a second adjustment mechanism140. In the particular implementation shown, the first adjustment mechanism130includes a first adjustment screw135, and the second adjustment mechanism140includes a second adjustment screw145. The adjustment screws135,145can be configured so as to be accessible from above each mounting assembly100. Each mounting assembly100can include a fluid inlet150and a fluid outlet160, which are discussed in more detail below.

FIG. 1Bis a planar view of the bottom of the printing apparatus101shown inFIG. 1A. The nozzle faces160of the fluid ejection modules200mounted in the frame110by the mounting assemblies100are shown. In the implementation shown, each nozzle face160includes nozzles170arranged in columns forming a 2-D array of nozzles. In one particular example, each nozzle face160includes 64 columns with 32 nozzles per column, for a total of 2048 nozzles. In this implementation, the short edges of the nozzle faces160are at an angle (e.g., an oblique angle) relative to the frame110, e.g., angle α. That is, the width of the nozzle faces160extends in the w direction, whereas the width of the frame110extends in the y direction, as is illustrated in the vector diagram. Similarly, the long edges of the nozzle faces160are at an angle (e.g., an oblique angle) relative to the frame110, e.g., angle γ. That is, the length of the nozzle faces160extends in the v direction, whereas the width of the frame110extends in the x direction. A medium upon which a fluid would be deposited by the fluid ejection modules200would, in one implementation, be positioned square to the frame110, i.e., having edges aligned in the x and y directions.

Referring now toFIGS. 2 and 3, the mounting assembly100shall be described in further detail. For illustrative purposes,FIG. 2is a perspective view of an a single fluid ejection module200mounted in the frame110by the mounting assembly100.FIG. 3shows the mounting assembly100in isolation.

The fluid inlet150and the fluid outlet160are configured for carrying fluid to and from, respectively, the fluid ejection module200. The fluid inlet150can be fitted with a fluid supply tube (not shown), and the fluid outlet160can be fitted with a fluid return tube (not shown). In one example, the fluid supply tube and the fluid return tube can be made of an elastomeric rubber or other flexible material.

A first pair of flexures210and a second pair of flexures220(FIG. 4) connect the fixed component120to a movable component230. The movable component230is configured or adapted to move relative to the frame110and/or the fixed component120. The movable component230is also configured or adapted to effect movement of the fluid ejection module200. In the example shown, each flexure is of substantially an identical length, such that the fixed component and movable component maintain a substantially parallel relationship to one another. In the implementation shown, the first adjustment mechanism130controls movement of the movable component230by manipulation of the first adjustment screw135, and the second adjustment mechanism140controls movement of the movable component230by manipulation of the second adjustment screw145. The first adjustment mechanism130and the second adjustment mechanism140can be positioned at opposite ends of the fixed component120. In this implementation, the first adjustment mechanism130and the second adjustment mechanism140are positioned between the first pair of flexures210and the second pair of flexures220, respectively. Alternatively, the adjustment mechanisms130,140can be positioned alongside the pairs of flexures210,220or elsewhere. A connector240attached to a bottom surface of the movable component230can connect the mounting assembly100to the fluid ejection module200. In the implementation shown, a printhead mounting screw235secures the connector240to the movable component230, although other techniques to affix the connector240can be used. In one implementation, the connector240can be formed integral to the movable component230.

As is shown most clearly inFIG. 3, the first pair of flexures210, an edge212of the fixed component120, and an edge214of the movable component230form a parallelogram configuration. The second pair of flexures220, an edge of the fixed component120, and an edge of the movable component230also form a parallelogram configuration. The parallelogram configuration allows the movable component230to move relative to the fixed component120while remaining substantially parallel to the fixed component120. Advantageously, the connector240, fluid ejection module200, and more importantly the nozzle face160also remain substantially parallel to the fixed component, and therefore substantially parallel to the medium upon which a printing fluid is to be deposited. It can be important to maintain the distance between the nozzle face and the medium substantially constant as well as consistent across the nozzle face160.

In the implementation shown, the first pair of flexures210and the second pair of flexures220are oriented at an angle (e.g., an oblique angle) relative to the frame110. In particular, the face of each parallelogram is oriented in the w direction, that is, parallel to the short edges of the nozzle face160(seeFIG. 1B). In this implementation, the first pair of flexures210and the second pair of flexures220are arranged at the same angle relative to the frame110. Orienting the pairs of flexures210,220in this manner can allow the movable component230to translate in the w direction when both adjustment mechanisms130,140are adjusted in the same direction by the same amount.

In some implementations, the flexures can be formed from thin sheets of material with a high modulus of elasticity and a high yield strength. For example, the flexures can be composed of a plain carbon steel, a spring steel, a stainless steel, or other suitable material. If one adjustment mechanism is rotated while the other remains stationary, the flexures of the stationary mechanism may undergo some twisting, however, the fixed component120and the movable component230will remain substantially parallel to one another.

In the implementation shown, a fluid supply tube250is fitted to the fluid inlet150, and a fluid return tube260is fitted to the fluid outlet160. A connector tube310is arranged between the fluid outlet160and the movable component230. In some implementations, the connector tube310passes through the moveable component230and allows fluid to flow from the fluid ejection module200to the fluid outlet160. Alternatively, the connector tube310can be arranged between the fluid outlet160and a fluid passage in the movable component230. Another connector tube (not shown) can be provided between the fluid inlet150and the movable component230. The connector tube310can be made of an elastomeric rubber or other flexible material to allow the movable component230to move relative to the fixed component120without disrupting the fluid connection of connector tube310.

FIG. 4is a perspective, cross-sectional view of the implementation of the mounting assembly100shown inFIG. 3, rotated relative to the view shown inFIG. 3. The first adjustment mechanism130and surrounding components are shown in cross-section. The connector tube310has a connector tube bottom surface315that interfaces with the connector240. The compressive force applied by the printhead mounting screw235can effect a fluid-tight compression seal between the connector tube bottom surface315and the connector240. Alternatively, in implementations where the connector tube310does not pass through the movable component230, the bottom surface of the movable component230can form a fluid-tight compression seal against the connector240.

The first adjustment screw135has a screw axis430oriented longitudinally and located at the center of the first adjustment screw135; the first adjustment screw135rotates about the screw axis430. The first adjustment mechanism130includes an eccentric bearing440having an eccentric bearing axis450located at its center and oriented parallel with the screw axis430. The eccentric bearing440also rotates about the screw axis430. That is, the eccentric bearing440rotates about an axis that is offset from the eccentric bearing's center axis (i.e., eccentric bearing axis450), and the eccentric bearing440can also orbit around the screw axis430. The eccentric bearing440is mounted to the lower end of the first adjustment screw135. The distance between the screw axis430and the eccentric bearing axis450is the offset amount “e”. The offset e can also be referred to as an eccentricity e.

Because the eccentric bearing430is mounted relative to the first adjustment screw135in an offset manner, manipulation of the first adjustment screw135causes the eccentric bearing axis450to orbit the screw axis430, as is further described below. The eccentric bearing440is positioned in a bore442in the movable component230. As the eccentric bearing440orbits about the screw axis430, the exterior surface of the bearing440exerts pressure against the interior surface of the bore442, thereby moving the movable component230. The distance between the screw axis430and the eccentric bearing axis450determines the range of relative motion between the fixed component120and the movable component230. In other implementations, the bore442can be configured as a slot or gap between two surfaces of the movable component230and does not necessarily have to be configured as a bore, per se.

FIGS. 5A,5B, and5C are schematic representations showing the relative movement of the eccentric bearing440about the adjustment screw135. The perimeter of the bore442is shown as a broken line. The bore442is configured such that movement is imparted to the inner surface of the bore442, and therefore to the movable component230, in the w direction only. However, in other configurations, movement in more than one direction can be accomplished by changing the configuration of the bore442. To achieve movement in only the w direction, the bore442is configured such that the inner surface of the bore442contacts the exterior surface of the eccentric bearing440at two opposing points across the diameter of the bearing440.

The screw axis430of the adjustment screw135is shown, which is also the axis of rotation of both the adjustment screw135and the eccentric bearing440. A contact point542between the inner surface of the bore442and the exterior surface of the eccentric bearing440is shown. InFIG. 5A, the contact point542is at its leftmost position in terms of the w axis. As the eccentric bearing440rotates counter-clockwise about the screw axis430, the contact point542moves toward the right in the w direction.FIG. 5Bshows the position of the eccentric bearing440when the first adjustment screw135has been rotated 90 degrees counter-clockwise relative to its position inFIG. 5A. The contact point542has moved in the w direction by a distance equal to the offset e.

FIG. 5Cshows the position of the eccentric bearing440when the first adjustment screw135has been rotated 90 degrees counter-clockwise relative to its position inFIG. 5B. The contact point542has again moved in the w direction by a distance equal to the offset e. The total displacement of the contact point542between the position inFIG. 5Aand the position inFIG. 5Cis equal to 2e in the w direction. This is the right-most position of the contact point542. The contact point542will begin to translate back toward the left in the w direction as the eccentric bearing440continues to rotate counter-clockwise about the screw axis430. That is, a half-turn of the adjustment screw135translates the contact point542by its maximum displacement of 2e. As an example, the distance 2e can be between about 1 micron and about 1000 microns, such as about 200 microns, although other distances are possible depending on the implementation.

FIG. 6is a perspective, cross-sectional view of an implementation of the mounting assembly100attached to the fluid ejection module200. The fluid ejection module200is but one example of a fluid ejection module200that can be mounted to the frame110by way of the mounting assembly100. Other configurations of fluid ejection modules can also be mounted to the frame110using the mounting assembly100. For illustrative purposes, the example fluid ejection module200is described in further detail below.

Fluid can enter an upper supply chamber610of the fluid ejection module200from the fluid inlet150. Fluid can pass from the upper supply chamber610through a supply filter620into a lower supply chamber630. From the lower supply chamber630, fluid can pass through an interposer640into a substrate160, which can be composed of silicon. The substrate160can include a fluid passage or multiple passages and at least one nozzle170, as shown inFIG. 1B, described above. In some implementations, the fluid passage or passages can be microfabricated. Fluid that is not ejected through any of the nozzles170can exit the substrate160into lower return chamber660. Fluid can pass from the lower return chamber660through a return filter670(optionally) and into an upper return chamber680. Fluid can pass from the upper return chamber680through connector240and connector tube310into fluid outlet160and through fluid return tube260.

In some implementations, a portion of the fluid passing through the fluid ejection module does not enter the substrate160, but instead can bypass the substrate160and pass directly from the lower supply chamber630to the lower return chamber660. This bypass flow can facilitate a higher overall flow rate of fluid through the fluid ejection module200, which can, for example, remove contaminants from the fluid ejection module200and facilitate temperature control of the fluid ejection module200.

The fluid ejection module200can include a plurality of actuators to cause fluid to be selectively ejected from each of the fluid passages. That is, a flow path from each fluid passage to a corresponding nozzle can be associated with an actuator that provides an individually controllable MEMS fluid ejector. The substrate160can include a flow-path body, a nozzle layer and a membrane layer. The flow-path body, nozzle layer and membrane layer can each be silicon, e.g., single crystal silicon. The fluid flow path can include a fluid inlet, an ascender, a pumping chamber adjacent the membrane layer, and a descender that terminates in a nozzle formed through the nozzle layer. Activation of the actuator causes the membrane to deflect into the pumping chamber, forcing fluid out of the nozzle.

FIGS. 7A,7B, and7C are schematic representations of one of the nozzle faces160of one of the fluid ejection modules200shown inFIG. 1B.FIG. 7Ashows a nozzle face160in a starting position. The nozzle face160has nozzles170. Starting positions of a first bearing axis710and a second bearing axis720are marked near opposite ends of the nozzle face160. Each ofFIGS. 7A,7B, and7C has a vector diagram showing x, y, v, and w directions. The x and y directions are parallel and perpendicular to the length of the frame110, respectively. The v and w directions are parallel with the long edges and short edges, respectively, of the nozzle face160.

Angular misalignment of a nozzle face160can result in printing defects because fluid droplets may not be deposited in intended positions in the x direction, the y direction, or both. Misalignment can result from one or more fluid ejection modules being mounted at an incorrect angle relative to the frame110, or from deformities in the frame110, or from other causes. One or both of the first adjustment mechanism130and the second adjustment mechanism140can be adjusted to rotate or translate the nozzle face160.

Referring toFIG. 7B, the starting position of the nozzle face160is shown in broken lines. An adjusted position of the nozzle face160is shown in solid lines. This adjusted position can be achieved by adjusting the second adjustment mechanism140to move the second end of the movable component230, while keeping the first end of the movable component fixed, i.e., the first adjustment mechanism130is kept fixed. By only adjusting the second end of the movable component230, the corresponding end of the nozzle face160rotates slightly about the first end, i.e., about the first bearing axis710by an angle θ relative to the starting position of the nozzle face160. The relative movement is shown in an exaggerated manner inFIG. 7Bto illustrate the relative movement. Because the fixed component120remains parallel to the movable component230, the rotation can occur, in some implementations, because of some twisting of the flexures220. Adjustments of this kind can be used to correct angular misalignment of the nozzle face160and/or to achieve translation in the x and y directions, as any rotation in the θ direction achieves some translation in the x and the y directions.

The y direction is the direction of travel of the medium on which fluid is deposited by a fluid ejection module200. Incorrect positioning of a nozzle face160in the y direction can result in incorrect droplet deposition. Inconsistent (e.g., non-uniform) positioning of nozzles170in the y direction between multiple fluid ejection modules200can be corrected by controlling the relative timing of ejection of fluid from the nozzles170. Thus, if the nozzles170of a first fluid ejection module200are offset by a certain distance in the y direction relative to the nozzles170of a second fluid ejection module200, then the time at which the nozzles170of the second fluid ejection module200eject fluid can be advanced or delayed such that all of the nozzles170will deposit fluid on the medium in desired positions in the y direction. Alternatively, the first adjustment mechanism130and the second adjustment mechanism140can be adjusted to move one or more of the fluid ejection modules200to align the nozzles170in the y direction.

Incorrect positioning of a nozzle face160in the x direction can cause visible printing errors, e.g., streaks or lines on the medium. These printing errors cannot be corrected by adjusting the timing of fluid ejection from the nozzles on different fluid ejection modules200because the medium moves in the perpendicular y direction. The first adjustment mechanism130and the second adjustment mechanism140corresponding to a fluid ejection module200can be adjusted to translate the movable component230and with it the fluid ejection module200. This translation occurs in a w direction, shown inFIG. 1B, and this translation has a component in the x direction and a component in the y direction.

Referring toFIG. 7C, a starting position of the nozzle face160is shown in broken lines. An adjusted position of the nozzle face160is shown in solid lines. When the first adjustment mechanism130and the second adjustment mechanism140are adjusted in the same direction by an equal amount, the nozzle face160translates in the w direction. A translation in the w direction produces a translation in the y direction and a translation in the x direction. Because a translation in the w direction produces a relatively smaller translation in the x direction, greater accuracy of translation can thus be obtained than if the movable component230were adjusted in the x direction directly. The flexures210,220can be oriented such that translation in the w direction produces a greater translation in the y direction than in the x direction. In such a configuration, accuracy of adjustment in the x direction can be further improved. In some implementations, the translation in the y direction can be compensated for (e.g., canceled out) by adjusting the timing of fluid ejection, relative to translation of the medium, such that adjustment in the w direction only results in adjustment in the x direction.

Adjustments more complex than those shown inFIGS. 7A,7B, and7C are possible. For example, if the first adjustment mechanism130and the second adjustment mechanism140are adjusted by unequal amounts, the movable component230can be both rotated and translated. Various movements are possible depending on the amount by which, and the direction in which, each of the adjustment mechanisms130,140is adjusted.

To allow the movable component230to translate in the w direction shown inFIG. 1B, the width of the first pair of flexures210and the second pair of flexures220can, in some implementations, be arranged as shown in perspective view inFIG. 2. Such implementations can be used, for example, where the flexures are formed from thin sheets of material. Thin sheets of material can resist deflection in tension, but offer less resistance to deflection in a direction perpendicular to their width. Where the flexures are made of thin sheets of material, the width of the flexures can be arranged perpendicular to the w direction, thus allowing deflection in the w direction.

Alignment of fluid ejection modules200can be performed by rotating the first adjustment screw135, the second adjustment screw145, or both. Referring again toFIGS. 7A,7B, and7C, rotating the second adjustment screw145causes rotation of the fluid ejection module200around the first bearing axis710. Similarly, rotating the first adjustment screw135can cause rotation of the fluid ejection module200around the second bearing access720. In some implementations, rotating both adjustment screws135,145by a same amount in a same direction can cause translation of the fluid ejection module200. Rotating both adjustment screws135,145can cause various combinations of rotation and translation of the fluid ejection module200.

Adjustment of the adjustment screws135,145can be performed during operation of the fluid ejection module200, and adjustment can be made in light of information gathered regarding the alignment of the fluid ejection module200. Such alignment information can be gathered during operation of the fluid ejection module200. For example, sensors, such as optical sensors, can sense where fluid has been ejected from the fluid ejection module or where fluid has contacted a medium, and alignment information can be generated from the output of these optical sensors.

Referring again toFIGS. 5A-5C, the offset e permits a relatively large angular movement of an adjustment screw to be converted into a relatively small displacement of an eccentric bearing440. This arrangement facilitates precise control of the position of the fluid ejection module200. The size of the offset e can be selected to achieve a desired range of movement of the eccentric bearing440in light of design factors such as manufacturing design tolerances. The manufacturing design tolerances of the various components of the mounting assembly100, fluid ejection module200, and frame110can be summed to find a total manufacturing design tolerance. The offset e can be selected such that the range of motion of the fluid ejection module200is greater than or equal to the total manufacturing design tolerance. In this way, the position of the fluid ejection module200can be adjusted to compensate for manufacturing design tolerances. For example, the offset e can be between about 0.5 microns and about 500 microns, such as about 100 microns.

In some implementations, the adjustment screws can be turned by hand. Set screws can be provided to hold the adjustment screws in a fixed position when not adjusting, and the set screws can have a nylon tip. A set screw with a nylon tip can create friction to hold an adjustment screw in place without deforming or otherwise damaging the adjustment screw. In these and other implementations, the adjustment screws can be turned by a motor rather than by hand, and the motor can be controlled, for example, manually or by a computer. Where adjustment of the adjustment screws is performed by motors, stepper motors can be used, and gear reduction can be used to increase the accuracy of adjustment. In some implementations, gear reduction can produce the result that the motor cannot be “back-driven” by forces exerted on the adjustment screw, thus potentially obviating the need for a set screw.

In some implementations, the motors can be stepper motors with a home sensor. In one implementation, a Hall effect sensor is used to determine a home position, e.g., the position of the adjustment screws135,145at which the magnetic field is either the highest or the lowest. A Hall effect sensor measures the strength of a magnetic field. In this implementation, a magnetic disk is affixed to each adjustment screw135,145. As the magnetic disk moves nearer the Hall effect sensor, the magnetic field increases, and as the magnetic disk moves away from the Hall effect sensor, the magnetic field decreases. The Hall effect sensor is used to sense the position of the magnetic disk, from which the position of the adjustment screws135,145can be determined.

In one implementation, the Hall effect sensor can be used in conjunction with an encoder on the motor to sense a rotation position. In one example, the encoder pulses 1024 times per revolution of each adjustment screw135,145. Each pulse corresponds to four counts, and thus one revolution of each adjustment screw135,145is the equivalent of 4096 counts. The positions of the adjustment screws135,145can be controlled at the level of counts, thereby providing high resolution positioning of the adjustment screws135,145, which can result in high resolution alignment of the nozzles170.

In some implementations, the motors can include a high gear reduction gearbox, for example, a 1000 to 1 gear ratio. In another implementation, one or both of the motors can be a DC motor with a high gear reduction gearbox and an encoder. In other implementations, other suitable motors can be used.

The pairs of flexures210,220can be pre-stressed in some implementations to facilitate consistent accuracy of adjustment and/or alignment. For example, the pairs of flexures210,220can be pre-curved before installation in the mounting assembly100. When installed, the pairs of flexures210,220can be held in a substantially straight position by the movable component230, which is in turn held by the eccentric bearing440attached to the first adjustment screw135. The pairs of flexures210,220are thus in a pre-stressed state because they are elastically bent away from their free positions. This pre-stress tends to hold the components of the mounting assembly100in a consistent position. Without being confined to any particular theory, this holding effect results from the force of the pre-stress pushing all of the components in the same direction and thereby taking up any looseness between the components of the mounting assembly100. Again without being confined to any particular theory, the pre-curve can be made sufficiently large that the flexures exert force in the same direction throughout rotation of the adjustment screw135, thereby facilitating consistency of adjustment throughout rotation.

In some implementations, a mask or template can be used to visually align the fluid ejection module200with the frame110, another fluid ejection module200, or both. For example, a mask or template can be aligned with the frame110. Cameras with a suitably sized field of view can be used to view the nozzle face160from a perspective similar to the perspective ofFIG. 1B, and nozzles or markings on the nozzle face160can be aligned with locations on the mask or template.

The use of terminology such as “front,” “back,” “top,” and “bottom” throughout the specification and claims is for illustrative purposes only, to distinguish between various components of the printhead module and other elements described herein. The use of “front,” “back,” “top,” and “bottom” does not imply a particular orientation of the printhead module. Similarly, the use of horizontal and vertical to describe elements throughout the specification is in relation to the implementation described. In other implementations, the same or similar elements can be orientated other than horizontally or vertically as the case may be.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, instead of set screws or motors, a friction fit, potentially aided by a spring, can be used to prevent adjustment screws from turning when not being adjusted. Accordingly, other embodiments are within the scope of the following claims.