INKJET PRINTHEAD ASSEMBLY WITH COMPACT REPOSITIONABLE SHUTTER

Abstract

An inkjet printhead assembly includes a repositionable shutter mechanism adapted to block a slot through which drops of ink ejected from the array of nozzles pass before they impinge on the print medium. The shutter mechanism includes an actuator rod having a first actuation feature, and a repositionable shutter blade extending in a cross-track direction having first and second tabs affixed to its ends. The first tab includes a second actuation feature that engages with the first actuation feature of the actuator rod. An actuator is configured to translate the actuator rod, thereby pivoting the repositionable shutter blade about the pivot axis between a first pivot position where the shutter blade blocks the slot and a second pivot position where the shutter blade is moved away from the slot so that drops of ink can pass through the slot.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly assigned, co-pending U.S. patent application Ser. No. 15/163,235, entitled: “Modular printhead assembly with common center rail”, by M. Piatt et al.; to commonly assigned, co-pending U.S. patent application Ser. No. 15/163,243, entitled: “Printhead assembly with removable jetting module”, by J. Brazas et al.; to commonly assigned, co-pending U.S. patent application Ser. No. 15/163,249, entitled: “Inkjet printhead assembly with repositionable shutter”, by D. Tunmore et al.; to commonly assigned, co-pending U.S. patent application Ser. No. 15/299,749, entitled: “Modular printhead assembly with tilted printheads,” by D. Tunmore; and to commonly assigned, co-pending U.S. patent application Ser. No. ______ (Docket K002124), entitled: “Inkjet printhead assembly with repositionable shutter mechanism,” by D. Tunmore, each which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention pertains to the field of inkjet printing and more particularly to an inkjet printhead assembly including a repositionable shutter.

BACKGROUND OF THE INVENTION

In the field of high speed inkjet printing it is desirable to be able to print across the width of the print medium in a single pass of the print medium past a print station. However, for many applications the desired print width exceeds the width of the available printheads. It is therefore necessary to arrange an array of printheads such that each printhead in the array prints a print swath, and the set of print swaths cover the entire print width. Whenever the printed image is made of a set of print swaths, it is necessary to align or stitch each pair of adjacent print swaths to each other such that the seam between adjacent print swaths is not visible.

For such printing applications it is desirable to provide some means to accurately align the array of printheads relative to each other to provide consistency in the stitching of the print swaths. Even with improvements in the reliability of the printheads, it is desirable to provide means for removing and replacing individual printheads within the array of printheads. The structure for aligning the printheads into an array should therefore enable individual printheads to be removed from the array and replaced with another printhead with minimal change in the alignment of the printheads and their corresponding print swaths.

Commonly assigned U.S. Pat. No. 8,226,215 (Bechler et al.) provides a structure for aligning a plurality of printheads, with the printheads arranged in two staggered rows of printheads. It uses a printhead baseplate that includes sets of kinematic alignment features, one set for each printhead, to engage with alignment features on the printheads in order to provide repeatable alignment of the printheads.

Even with a fixed alignment of the array of printheads there is some variation in the quality of the stitching. It has been determined that the amplitude of the stitching variation depends in part on the spacing between the nozzle arrays in the two rows of printheads, with a smaller spacing between the rows yielding less variation in the stitching. It has also been found that as the desired print width increases, the cost for manufacturing the alignment baseplate to accommodate the increased print width increases significantly. There remains a need to provide an improved alignment system that can more readily accommodate wider print widths and provide a reduced spacing between the nozzle arrays in the rows of printheads.

In the field of continuous inkjet printing, each printhead includes a drop generator, which includes an array of nozzles, and drop selection hardware, which includes a mechanism to cause, for each of the nozzles in the array, the trajectories of printing drops to diverge from the trajectories of non-printing drops. An ink catcher is used to intercept the trajectory of the non-printing drops from each nozzle. It has been found that a skew of the drop selection hardware relative to the nozzle array can contribute to a skew of the images printed by the printhead relative to the print swaths of other printheads in an array of printheads. There remains a need for an improved system for aligning the drop selection hardware of a printhead relative to the nozzle array of a printhead.

In the field of continuous inkjet printing, it has been common to provide a shutter mechanism for sealing an outlet of the printheads to prevent ink from passing through the outlet during startup/shutdown and other maintenance procedures of the printhead. The shutter is then displaced from the outlet during the operation mode of the printhead to enable print drops to be emitted through the outlet and deposited onto the print medium. Prior art shutter arrangements have been found to limit the spacing between printhead rows, and to limit the effectiveness for performing various maintenance operations. There remains a need for a compact repositionable shutter mechanism.

SUMMARY OF THE INVENTION

The present invention represents an inkjet printhead assembly including a printhead module with a repositionable shutter, includes:

a jetting module including an array of nozzles extending in a cross-track direction for printing on a print medium traveling along a media path from upstream to downstream;

a slot through which drops of ink ejected from the array of nozzles pass before they impinge on the print medium;

an ink catcher positioned on one side of the slot for catching non-printing drops of ink ejected from the array of nozzles, the ink catcher including an ink channel for drawing ink away from the slot;

a shutter mechanism including:

• • an actuator configured to translate an actuator rod along a translation direction between a first actuator position and a second actuator position, the actuator rod including a first actuation feature;
  • a repositionable shutter including:
    • a shutter blade extending in a cross-track direction from a first end to a second end;
    • a first tab affixed to the first end of the shutter blade, the first tab including a second actuation feature that engages with the first actuation feature of the actuator rod; and
    • a second tab affixed to the second end of the shutter blade;
    • wherein the repositionable shutter is adapted to rotate around a pivot axis passing through the first and second tabs between a first pivot position and a second pivot position, such that when the repositionable shutter is rotated into the first pivot position the shutter blade blocks drops of ink from passing through the slot and diverts the ink into the ink catcher, and when the repositionable shutter is rotated into the second pivot position the shutter blade is moved away from the slot so that drops of ink can pass through the slot; and

wherein when the actuator rod is translated into the first actuator position a first torque is applied to the repositionable shutter through the first and second actuation features, thereby pivoting the repositionable shutter into the first pivot position, and when the actuator rod is translated into the second actuator position a second torque is applied to the repositionable shutter through the first and second actuation features, thereby pivoting repositionable shutter into the second pivot position.

This invention has the advantage that the repositionable shutter mechanism is compact and inexpensive to manufacture.

It has the additional advantage that the repositionable shutter mechanism can be easily removed and replaced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block schematic diagram of an exemplary continuous inkjet system according to the present invention;

FIG. 2 shows an image of a liquid jet being ejected from a drop generator and its subsequent break off into drops with a regular period;

FIG. 3 shows a cross-section view of an inkjet printhead of the continuous liquid ejection system according to this invention;

FIG. 4 shows a first example embodiment of a timing diagram illustrating drop formation pulses, the charging electrode waveform, and the break off of drops;

FIG. 5 shows a top view of an exemplary printhead assembly including a staggered array of jetting modules;

FIG. 6 shows an exemplary modular printhead assembly including a plurality of printhead modules mounted onto a central rail assembly in accordance with the present invention;

FIG. 7 illustrates additional details of the rail assembly in the modular printhead assembly of FIG. 6;

FIG. 8 illustrates additional details of the jetting modules in the modular printhead assembly of FIG. 6;

FIGS. 9A-9E illustrate exemplary alignment tab configurations;

FIG. 10 illustrates additional details of the mounting assemblies in the modular printhead assembly of FIG. 6;

FIG. 11 shows a top view of the modular printhead assembly of FIG. 6;

FIGS. 12A-12D show cross-section views of the modular printhead assembly of FIG. 6;

FIGS. 13A-13B show side views of the modular printhead assembly of FIG. 6;

FIG. 14 is an exploded view showing components of a shutter mechanism including a repositionable shutter according to an exemplary embodiment;

FIG. 15A-15B show side views of an exemplary shutter mounting system;

FIGS. 16A-16C illustrate the operation of the repositionable shutter of FIG. 14 using an actuator mechanism;

FIG. 17 illustrates the removal of the repositionable shutter of FIG. 14;

FIG. 18 illustrates an alternate repositionable shutter configuration including a spring that applies a bias force to the actuator mechanism;

FIG. 19 illustrates an alternate repositionable shutter configuration where the actuator components are on an opposite side of the pivot axis from the ink catcher;

FIG. 20 shows additional details of the repositionable shutter configuration of FIG. 19;

FIGS. 21A-21B illustrate the operation of the repositionable shutter configuration of FIG. 19;

FIG. 22 illustrates the removal of the repositionable shutter of FIG. 19; and

FIG. 23 illustrates an alternate repositionable shutter configuration having a vertical actuator rod.

It is to be understood that the attached drawings are for purposes of illustrating the concepts of the invention and may not be to scale. Identical reference numerals have been used, where possible, to designate identical features that are common to the figures.

DETAILED DESCRIPTION OF THE INVENTION

The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. References to “a particular embodiment” and the like refer to features that are present in at least one embodiment of the invention. Separate references to “an embodiment” or “particular embodiments” or the like do not necessarily refer to the same embodiment or embodiments; however, such embodiments are not mutually exclusive, unless so indicated or as are readily apparent to one of skill in the art. The use of singular or plural in referring to the “method” or “methods” and the like is not limiting. It should be noted that, unless otherwise explicitly noted or required by context, the word “or” is used in this disclosure in a non-exclusive sense.

The example embodiments of the present invention are illustrated schematically and not to scale for the sake of clarity. One of the ordinary skills in the art will be able to readily determine the specific size and interconnections of the elements of the example embodiments of the present invention.

As described herein, the example embodiments of the present invention provide a printhead or printhead components typically used in inkjet printing systems. However, many other applications are emerging which use printheads to emit liquids (other than inks) that need to be finely metered and deposited with high spatial precision. As such, as described herein, the terms “liquid” and “ink” refer to any material that can be ejected by the printhead or printhead components described below.

Referring to FIG. 1, a continuous printing system 20 includes an image source 22 such as a scanner or computer which provides raster image data, outline image data in the form of a page description language, or other forms of digital image data. This image data is converted to half-toned bitmap image data by an image processing unit (image processor) 24 which also stores the image data in memory. A plurality of drop forming transducer control circuits 26 reads data from the image memory and apply time-varying electrical pulses to a drop forming transducers 28 that are associated with one or more nozzles of a printhead 30. These pulses are applied at an appropriate time, and to the appropriate nozzles, so that drops formed from a continuous inkjet stream will form spots on a print medium 32 in the appropriate position designated by the data in the image memory.

Print medium 32 is moved relative to the printhead 30 by a print medium transport system 34, which is electronically controlled by a media transport controller 36 in response to signals from a speed measurement device 35. The media transport controller 36 is in turn is controlled by a micro-controller 38. The print medium transport system shown in FIG. 1 is a schematic only, and many different mechanical configurations are possible. For example, a transfer roller could be used in the print medium transport system 34 to facilitate transfer of the ink drops to the print medium 32. Such transfer roller technology is well known in the art. In the case of page width printheads, it is most convenient to move the print medium 32 along a media path past a stationary printhead. However, in the case of scanning print systems, it is often most convenient to move the printhead along one axis (the sub-scanning direction) and the print medium 32 along an orthogonal axis (the main scanning direction) in a relative raster motion.

Ink is contained in an ink reservoir 40 under pressure. In the non-printing state, continuous inkjet drop streams are unable to reach print medium 32 due to an ink catcher 72 that blocks the stream of drops, and which may allow a portion of the ink to be recycled by an ink recycling unit 44. The ink recycling unit 44 reconditions the ink and feeds it back to the ink reservoir 40. Such ink recycling units are well known in the art. The ink pressure suitable for optimal operation will depend on a number of factors, including geometry and thermal properties of the nozzles and thermal properties of the ink. A constant ink pressure can be achieved by applying pressure to the ink reservoir 40 under the control of an ink pressure regulator 46. Alternatively, the ink reservoir can be left unpressurized, or even under a reduced pressure (vacuum), and a pump can be employed to deliver ink from the ink reservoir under pressure to the printhead 30. In such an embodiment, the ink pressure regulator 46 can include an ink pump control system. The ink is distributed to the printhead 30 through an ink channel 47. The ink preferably flows through slots or holes etched through a silicon substrate of printhead 30 to its front surface, where a plurality of nozzles and drop forming transducers, for example, heaters, are situated. When printhead 30 is fabricated from silicon, the drop forming transducer control circuits 26 can be integrated with the printhead 30. The printhead 30 also includes a deflection mechanism 70 which is described in more detail below with reference to FIGS. 2 and 3.

Referring to FIG. 2, a schematic view of continuous liquid printhead 30 is shown. A jetting module 48 of printhead 30 includes an array of nozzles 50 formed in a nozzle plate 49. In FIG. 2, nozzle plate 49 is affixed to the jetting module 48. Alternatively, the nozzle plate 49 can be integrally formed with the jetting module 48. Liquid, for example, ink, is supplied to the nozzles 50 via ink channel 47 at a pressure sufficient to form continuous liquid streams 52 (sometimes referred to as filaments) from each nozzle 50. In FIG. 2, the array of nozzles 50 extends into and out of the figure.

Jetting module 48 is operable to cause liquid drops 54 to break off from the liquid stream 52 in response to image data. To accomplish this, jetting module 48 includes a drop stimulation or drop forming transducer 28 (e.g., a heater, a piezoelectric actuator, or an electrohydrodynamic stimulation electrode), that, when selectively activated, perturbs the liquid stream 52, to induce portions of each filament to break off and coalesce to form the drops 54. Depending on the type of transducer used, the transducer can be located in or adjacent to the liquid chamber that supplies the liquid to the nozzles 50 to act on the liquid in the liquid chamber, can be located in or immediately around the nozzles 50 to act on the liquid as it passes through the nozzle, or can be located adjacent to the liquid stream 52 to act on the liquid stream 50 after it has passed through the nozzle 50.

In FIG. 2, drop forming transducer 28 is a heater 51, for example, an asymmetric heater or a ring heater (either segmented or not segmented), located in the nozzle plate 49 on one or both sides of the nozzle 50. This type of drop formation is known and has been described in, for example, U.S. Pat. No. 6,457,807 (Hawkins et al.); U.S. Pat. No. 6,491,362 (Jeanmaire); U.S. Pat. No. 6,505,921 (Chwalek et al.); U.S. Pat. No. 6,554,410 (Jeanmaire et al.); U.S. Pat. No. 6,575,566 (Jeanmaire et al.); U.S. Pat. No. 6,588,888 (Jeanmaire et al.); U.S. Pat. No. 6,793,328 (Jeanmaire); U.S. Pat. No. 6,827,429 (Jeanmaire et al.); and U.S. Pat. No. 6,851,796 (Jeanmaire et al.), each of which is incorporated herein by reference.

Typically, one drop forming transducer 28 is associated with each nozzle 50 of the nozzle array. However, in some configurations, a drop forming transducer 28 can be associated with groups of nozzles 50 or all of the nozzles 50 in the nozzle array.

Referring to FIG. 2 the printing system has associated with it, a printhead 30 that is operable to produce, from an array of nozzles 50, an array of liquid streams 52. A drop forming device is associated with each liquid stream 52. The drop formation device includes a drop forming transducer 28 and a drop formation waveform source 55 that supplies a drop formation waveform 60 to the drop forming transducer 28. The drop formation waveform source 55 is a portion of the mechanism control circuits 26. In some embodiments in which the nozzle plate is fabricated of silicon, the drop formation waveform source 55 is formed at least partially on the nozzle plate 49. The drop formation waveform source 55 supplies a drop formation waveform 60 that typically includes a sequence of pulses having a fundamental frequency f_O and a fundamental period of T_O=1/f_O to the drop formation transducer 28, which produces a modulation with a wavelength λ, in the liquid jet. The modulation grows in amplitude to cause portions of the liquid stream 52 to break off into drops 54. Through the action of the drop formation device, a sequence of drops 54 is produced. In accordance with the drop formation waveform 60, the drops 54 are formed at the fundamental frequency f_O with a fundamental period of T_O=1/f_O. In FIG. 2, liquid stream 52 breaks off into drops with a regular period at break-off location 59, which is a distance, called the break-off length, BL from the nozzle 50. The distance between a pair of successive drops 54 is essentially equal to the wavelength λ of the perturbation on the liquid stream 52. The stream of drops 54 formed from the liquid stream 52 follow an initial trajectory 57.

The break-off time of the droplet for a particular printhead can be altered by changing at least one of the amplitude, duty cycle, or number of the stimulation pulses to the respective resistive elements surrounding a respective resistive nozzle orifice. In this way, small variations of either pulse duty cycle or amplitude allow the droplet break-off times to be modulated in a predictable fashion within ±one-tenth the droplet generation period.

Also shown in FIG. 2 is a charging device 61 comprising charging electrode 62 and charging electrode waveform source 63. The charging electrode 62 associated with the liquid jet is positioned adjacent to the break-off point 59 of the liquid stream 52. If a voltage is applied to the charging electrode 62, electric fields are produced between the charging electrode and the electrically grounded liquid jet, and the capacitive coupling between the two produces a net charge on the end of the electrically conductive liquid stream 52. (The liquid stream 52 is grounded by means of contact with the liquid chamber of the grounded drop generator.) If the end portion of the liquid jet breaks off to form a drop while there is a net charge on the end of the liquid stream 52, the charge of that end portion of the liquid stream 52 is trapped on the newly formed drop 54.

The voltage on the charging electrode 62 is controlled by the charging electrode waveform source 63, which provides a charging electrode waveform 64 operating at a charging electrode waveform 64 period 80 (shown in FIG. 4). The charging electrode waveform source 63 provides a varying electrical potential between the charging electrode 62 and the liquid stream 52. The charging electrode waveform source 63 generates a charging electrode waveform 64, which includes a first voltage state and a second voltage state; the first voltage state being distinct from the second voltage state. An example of a charging electrode waveform is shown in part B of FIG. 4. The two voltages are selected such that the drops 54 breaking off during the first voltage state acquire a first charge state and the drops 54 breaking off during the second voltage state acquire a second charge state. The charging electrode waveform 64 supplied to the charging electrode 62 is independent of, or not responsive to, the image data to be printed. The charging device 61 is synchronized with the drop formation device using a conventional synchronization device 27, which is a portion of the control circuits 26, (see FIG. 1) so that a fixed phase relationship is maintained between the charging electrode waveform 64 produced by the charging electrode waveform source 63 and the clock of the drop formation waveform source 55. As a result, the phase of the break off of drops 54 from the liquid stream 52, produced by the drop formation waveforms 92-1, 92-2, 92-3, 94-1, 94-2, 94-3, 94-4 (see FIG. 4), is phase locked to the charging electrode waveform 64. As indicated in FIG. 4, there can be a phase shift 108, between the charging electrode waveform 64 and the drop formation waveforms 92-1, 92-2, 92-3, 94-1, 94-2, 94-3, 94-4.

With reference now to FIG. 3, printhead 30 includes a drop forming transducer 28 which creates a liquid stream 52 that breaks up into ink drops 54. Selection of drops 54 as printing drops 66 or non-printing drops 68 will depend upon the phase of the droplet break off relative to the charging electrode voltage pulses that are applied to the to the charging electrode 62 that is part of the deflection mechanism 70, as will be described below. The charging electrode 62 is variably biased by a charging electrode waveform source 63. The charging electrode waveform source 63 provides charging electrode waveform 64, also called a charging electrode waveform 64, in the form of a sequence of charging pulses. The charging electrode waveform 64 is periodic, having a charging electrode waveform 64 period 80 (FIG. 4).

An embodiment of a charging electrode waveform 64 is shown in part B of FIG. 4. The charging electrode waveform 64 comprises a first voltage state 82 and a second voltage state 84. Drops breaking off during the first voltage state 82 are charged to a first charge state and drops breaking off during the second voltage state 84 are charged to a second charge state. The second voltage state 84 is typically at a high level, biased sufficiently to charge the drops 54 as they break off. The first voltage state 82 is typically at a low level relative to the printhead 30 such that the first charge state is relatively uncharged when compared to the second charge state. An exemplary range of values of the electrical potential difference between the first voltage state 82 and a second voltage state 84 is 50 to 300 volts and more preferably 90 to 150 volts.

Returning to a discussion of FIG. 3, when a relatively high level voltage or electrical potential is applied to the charging electrode 62 and a drop 54 breaks off from the liquid stream 52 in front of the charging electrode 62, the drop 54 acquires a charge and is deflected by deflection mechanism 70 towards the ink catcher 72 as non-pint drops 68. The non-printing drops 68 that strike the catcher face 74 form an ink film 76 on the face of the ink catcher 72. The ink film 76 flows down the catcher face 74 and enters liquid channel 78 (also called an ink channel), through which it flows to the ink recycling unit 44. The liquid channel 78 is typically formed between the body of the catcher 72 and a lower plate 79.

Deflection occurs when drops 54 break off from the liquid stream 52 while the potential of the charging electrode 62 is provided with an appropriate voltage. The drops 54 will then acquire an induced electrical charge that remains upon the droplet surface. The charge on an individual drop 54 has a polarity opposite that of the charging electrode 62 and a magnitude that is dependent upon the magnitude of the voltage and the coupling capacitance between the charging electrode 52 and the drop 54 at the instant the drop 54 separates from the liquid jet. This coupling capacitance is dependent in part on the spacing between the charging electrode 62 and the drop 54 as it is breaking off. It can also be dependent on the vertical position of the breakoff point 59 relative to the center of the charge electrode 62. After the charge drops 54 have broken away from the liquid stream 52, they continue to pass through the electric fields produced by the charge plate. These electric fields provide a force on the charged drops deflecting them toward the charging electrode 62. The charging electrode 62, even though it cycled between the first and the second voltage states, thus acts as a deflection electrode to help deflect charged drops away from the initial trajectory 57 and toward the ink catcher 72. After passing the charging electrode 62, the drops 54 will travel in close proximity to the catcher face 74 which is typically constructed of a conductor or dielectric. The charges on the surface of the non-printing drops 68 will induce either a surface charge density charge (for a catcher face 74 constructed of a conductor) or a polarization density charge (for a catcher face 74 constructed of a dielectric). The induced charges on the catcher face 74 produce an attractive force on the charged non-printing drops 68. The attractive force on the non-printing drops 68 is identical to that which would be produced by a fictitious charge (opposite in polarity and equal in magnitude) located inside the ink catcher 72 at a distance from the surface equal to the distance between the ink catcher 72 and the non-printing drops 68. The fictitious charge is called an image charge. The attractive force exerted on the charged non-printing drops 68 by the catcher face 74 causes the charged non-printing drops 68 to deflect away from their initial trajectory 57 and accelerate along a non-print trajectory 86 toward the catcher face 74 at a rate proportional to the square of the droplet charge and inversely proportional to the droplet mass. In this embodiment the ink catcher 72, due to the induced charge distribution, comprises a portion of the deflection mechanism 70. In other embodiments, the deflection mechanism 70 can include one or more additional electrodes to generate an electric field through which the charged droplets pass so as to deflect the charged droplets. For example, an optional single biased deflection electrode 71 in front of the upper grounded portion of the catcher can be used. In some embodiments, the charging electrode 62 can include a second portion on the second side of the jet array, denoted by the dashed line electrode 62′, which supplied with the same charging electrode waveform 64 as the first portion of the charging electrode 62.

In the alternative, when the drop formation waveform 60 applied to the drop forming transducer 28 causes a drop 54 to break off from the liquid stream 52 when the electrical potential of the charging electrode 62 is at the first voltage state 82 (FIG. 4) (i.e., at a relatively low potential or at a zero potential), the drop 54 does not acquire a charge. Such uncharged drops are unaffected during their flight by electric fields that deflect the charged drops. The uncharged drops therefore become printing drops 66, which travel in a generally undeflected path along the trajectory 57 and impact the print medium 32 to form a print dots 88 on the print medium 32, as the recoding medium is moved past the printhead 30 at a speed V_m. The charging electrode 62, deflection electrode 71 and ink catcher 72 serve as a drop selection system 69 for the printhead 30.

FIG. 4 illustrates how selected drops can be printed by the control of the drop formation waveforms supplied to the drop forming transducer 28. Section A of FIG. 4 shows a drop formation waveform 60 formed as a sequence that includes three drop formation waveform 92-1, 92-2, 92-3, and four drop formation waveforms 94-1, 94-2, 94-3, 94-4. The drop formation waveforms 94-1, 94-2, 94-3, 94-4 each have a period 96 and include a pulse 98, and each of the drop formation waveforms 92-1, 92-2, 92-3 have a longer period 100 and include a longer pulse 102. In this example, the period 96 of the drop formation waveforms 94-1, 94-2, 94-3, 94-4 is the fundamental period T_O, and the period 100 of the drop formation waveforms 92 is twice the fundamental period, 2T_O. The drop formation waveforms 94-1, 94-2, 94-3, 94-4 each cause individual drops to break off from the liquid stream. The drop formation waveforms 92-1, 92-2, 92-3, due to their longer period, each cause a larger drop to be formed from the liquid stream. The larger drops 54 formed by the drop formation waveforms 92-1, 92-2, 92-3 each have a volume that is approximately equal to twice the volume of the drops 54 formed by the drop formation waveforms 94-1, 94-2, 94-3, 94-4.

As previously mentioned, the charge induced on a drop 54 depends on the voltage state of the charging electrode at the instant of drop breakoff. The B section of FIG. 4 shows the charging electrode waveform 64 and the times, denoted by the diamonds, at which the drops 54 break off from the liquid stream 52. The waveforms 92-1, 92-2, 92-3 cause large drops 104-1, 104-2, 104-3 to break off from the liquid stream 52 while the charging electrode waveform 64 is in the second voltage state 84. Due to the high voltage applied to the charging electrode 62 in the second voltage state 84, the large drops 104-1, 104-2, 104-3 are charged to a level that causes them to be deflected as non-printing drops 68 such that they strike the catcher face 74 of the ink catcher 72 in FIG. 3. These large drops may be formed as a single drop (denoted by the double diamond for 104-1), as two drops that break off from the liquid stream 52 at almost the same time that subsequently merge to form a large drop (denoted by two closely spaced diamonds for 104-2), or as a large drop that breaks off from the liquid stream that breaks apart and then merges back to a large drop (denoted by the double diamond for 104-3). The waveforms 94-1, 94-2, 94-3, 94-4 cause small drops 106-1, 106-2, 106-3, 106-4 to form. Small drops 106-1 and 106-3 break off during the first voltage state 82, and therefore will be relatively uncharged; they are not deflected into the ink catcher 72, but rather pass by the ink catcher 72 as printing drops 66 and strike the print medium 32 (see FIG. 3). Small drops 106-2 and 106-4 break off during the second voltage state 84 and are deflected to strike the ink catcher 74 as non-printing drops 68. The charging electrode waveform 64 is not controlled by the pixel data to be printed, while the drop formation waveform 60 is determined by the print data. This type of drop deflection is known and has been described in, for example, U.S. Pat. No. 8,585,189 (Marcus et al.); U.S. Pat. No. 8,651,632 (Marcus); U.S. Pat. No. 8,651,633 (Marcus et al.); U.S. Pat. No. 8,696,094 (Marcus et al.); and U.S. Pat. No. 8,888,256 (Marcus et al.), each of which is incorporated herein by reference.

FIG. 5 is a diagram of an exemplary inkjet printhead assembly 112. The printhead assembly 112 includes a plurality of jetting modules 200 arranged across a width dimension of the print medium 32 in a staggered array configuration. The width dimension of the print medium 32 is the dimension in cross-track direction 118, which is perpendicular to in-track direction 116 (i.e., the motion direction of the print medium 32). Such printhead assemblies 112 are sometimes referred to as “lineheads.”

Each of the jetting modules 200 includes a plurality of inkjet nozzles arranged in nozzle array 202, and is adapted to print a swath of image data in a corresponding printing region 132. Commonly, the jetting modules 200 are arranged in a spatially-overlapping arrangement where the printing regions 132 overlap in overlap regions 134. Each of the overlap regions 134 has a corresponding centerline 136. In the overlap regions 134, nozzles from more than one nozzle array 202 can be used to print the image data.

Stitching is a process that refers to the alignment of the printed images produced from jetting modules 200 for the purpose of creating the appearance of a single page-width line head. In the exemplary arrangement shown in FIG. 5, three jetting modules 200 are stitched together at overlap regions 134 to form a page-width printhead assembly 112. The page-width image data is processed and segmented into separate portions that are sent to each jetting module 200 with appropriate time delays to account for the staggered positions of the jetting modules 200. The image data portions printed by each of the jetting modules 200 is sometimes referred to as “swaths.” Stitching systems and algorithms are used to determine which nozzles of each nozzle array 202 should be used for printing in the overlap region 134. Preferably, the stitching algorithms create a boundary between the printing regions 132 that is not readily detected by eye. One such stitching algorithm is described in commonly-assigned U.S. Pat. No. 7,871,145 (Enge), which is incorporated herein by reference.

The two lines of nozzle arrays 202 in the staggered arrangement are separated by a nozzle array spacing 138. It has been found that larger nozzle array spacings 138 result in larger amplitudes of the stitching variation, even after stitching correction algorithms are applied. Therefore, it is desirable to reduce the nozzle array spacing 138 as much as possible. With prior art arrangements for mounting the nozzle arrays 202, such as that described in the aforementioned, commonly-assigned U.S. Pat. No. 8,226,215 there is a limit to how small the nozzle array spacing 138. These methods also get expensive and cumbersome when it is necessary to accommodate larger and larger print widths. These limitations are addressed with the modular inkjet printhead assembly described herein.

FIG. 6 shows an exemplary modular printhead assembly 190 including a plurality of printhead modules 260 in accordance with the present invention. Each printhead module 260 includes a jetting module 200 and a mounting assembly 240. The printhead modules 260 are mounted onto a central rail assembly 220, which includes a rod 224 attached onto the side of a beam 222 that faces the print medium 32. The print medium 32 moves past the printhead assembly 190 in an in-track direction 116. The mounting assembly 240 extends across the width of the print medium 32 in a cross-track direction 118.

In the illustrated configuration, the printhead assembly 190 includes three printhead modules 260, with one being mounted on a downstream side 226 of the rail assembly 220, and two being mounted on an upstream side 228 of the rail assembly 220. An advantageous feature of this modular printhead assembly 190 design is that wider print medium 32 can be supported by simply extending the length of the rail assembly 220 and adding additional printhead modules 260. By alternating the printhead modules 260 between the downstream side 226 and the upstream side 228 of the rail assembly 220, the associated nozzle arrays 202 can be stitched together with appropriate overlap regions 134 (see FIG. 5).

FIG. 7 shows additional details for an exemplary embodiment of the rail assembly 220 of FIG. 6. The rail assembly 220 includes rod 224, which is attached to the bottom side of beam 222 (i.e., the side that faces the print medium 32 (FIG. 6). Mounting brackets are attached to the beam 222 for used for clamping the mounting assembly 240 to the rail assembly 220.

In the illustrated configuration, the rod 224 has a cylindrical shape, and the bottom side of the beam 222 has a concave profile that matches the shape of the outer surface of the rod 224. In other configurations, the beam and the rod 224 can have different shapes. For example, the bottom side of the beam 222 can have a v-shaped groove that sits on the outer surface of the rod 224. In another example, the rod 224 can have a cylindrical shape around a portion of the circumference, but can have a flat surface on one side to facilitate attaching the rod 224 to a beam 222 having a flat bottom side. The rod 224 can be attached to the beam 222 using any appropriate means. For example, bolts can be inserted through holes in the rod 224 into corresponding threaded holes in the bottom side of the beam 222.

The beam 222 includes a series of notches 223 that are adapted to receive tabs on the jetting modules 200 and the mounting assemblies 240 (FIG. 6) as will be discussed later. In an exemplary embodiment, two notches 223 are provided for each of the printhead modules 260 (FIG. 6) at locations corresponding to the positions of the tabs, which are preferably provided in proximity to first and second ends the jetting modules 200 and the mounting assemblies 240. (Within the context of the present disclosure, “in proximity” to an end means that the distance between the end and the notch is no more than 20% of the distance between the two ends.) In the illustrated configuration, the notches 223 extend all the way through the beam 222. In other configurations, the notches 223 may extend only part of the way through. As will be discussed later, the beam also includes rotational alignment features 225 that are adapted to engage with a corresponding datum on the mounting assemblies 240 or the jetting modules 200.

FIG. 8 shows additional details for an exemplary embodiment of the jetting module 200 of FIG. 6. A nozzle array 202 (not visible in FIG. 8) extends across the width of the jetting module 200 in the cross-track direction 118. Fluid connections 216 and electrical connections 217 connect to other components of the printer system 20 (FIG. 1).

The jetting module 200 includes first and second alignment tabs 204, 205 spaced apart in the cross-track direction 118 that are configured to be inserted into the notches 223 in the beam 222 and engage with the rod 224 of the rail assembly 220 (FIG. 7). In order to define the desired position of the jetting module 200 relative to the rail assembly 220 requires constraining six degrees of freedom using six alignment features. The first alignment tab 204 provides a first alignment datum 210 and a second alignment datum 211. The second alignment tab 205 provides a third alignment datum 212 and a fourth alignment datum 213. The engagement between the first and second alignment tabs 204, 205 with the rod 224 define four degrees of freedom (x, z, θ_x, θ_z).

The jetting module 200 also includes a rotational alignment feature providing a fifth alignment datum 214 (not visible in FIG. 8), which is adapted to engage with a corresponding rotational alignment feature associated with the beam 222 to define the fifth degree of freedom (θ_y). The rotational alignment feature associated with the beam 222 may be on the beam 222 itself, or can be on the mounting assembly 240, which is in a predefined position relative to the beam 222. In the illustrated configuration, the fifth alignment datum 214 is on the bottom surface of the jetting module 200, and contacts a component of the mounting assembly 240 (see FIG. 12B).

The jetting module 200 also includes a cross-track alignment feature providing a sixth alignment datum 215, which is adapted to engage with a corresponding cross-track alignment feature on the rail assembly 220 to define the sixth degree of freedom (y). In the illustrated configuration, the sixth alignment datum 215 is provided on a side face of the second alignment tab 205, and the corresponding cross-track alignment feature on the rail assembly 220 is provided by a side face of the corresponding notch 223 in the beam 222. While the sixth alignment datum 215 is shown on the inside face of the second alignment tab 205, one skilled in the art will recognize that it could alternatively be on the outside face. In other configurations, the sixth alignment datum 215 can be a side face of the first alignment tab 204, or can be provided by some other feature on the jetting module 200.

The first and second alignment tabs 204, 205 of the jetting module 200 can take any appropriate form. FIGS. 9A-9E illustrate a number of exemplary configurations that can be used. Each configuration includes a “v-shaped” notch 206, which is formed into the alignment tab 204. The notch 206 has two faces 207, 208, each of which provides a corresponding alignment datum 210, 211 at the location where the alignment tab 204 contacts the rod 224. In the illustrated examples, the faces 207, 208 are oriented at 90° to each other, but this is not a requirement. Fixtures can be provided during the manufacturing process for the jetting module 200 to accurately machine the positions of the faces 207, 208 relative to the position of the nozzle array 202, so that the nozzle array 202 can be accurately aligned relative to the rail assembly 220.

In FIG. 9A the notch 206 has sharp corners and includes a horizontal face 207 and a vertical face 208. The alignment tab 204 of FIG. 9B is similar except that the outer corners include fillets 201 and the inner corner includes an endmill 203. The alignment tab 204 of FIG. 9C includes protrusions 209 which provide the contact points (alignment datum 210 and alignment datum 211) with the rod 224. For example, the protrusions 209 can be ball bearings that provide a single point of contact. In FIGS. 9D and 9E the notches 206 are rotates so that the faces 207, 208 are diagonal. In FIG. 9D, the faces 207, 208 are oriented at ±45° relative to the horizontal. In FIG. 9E, the face 207 tilts backward by a small angle (e.g., about 10°). This has the advantage that the downward weight of the jetting module 200 will have the effect of pulling the jetting module 200 toward the rail assembly 220.

FIG. 10 shows additional details for an exemplary embodiment of the mounting assembly 240 of FIG. 6. The mounting assembly 240 includes third and fourth alignment tabs 244, 245 protruding from a frame 242. The alignment tabs 244, 245 are spaced apart in the cross-track direction 118 and are configured to be inserted into the notches 223 in the beam 222 and engage with the rod 224 of the rail assembly 220 (FIG. 7). The alignment tabs 244, 245 of the mounting assembly 240 can take any appropriate form that provides two contact points with the rod 224, such as those shown in FIGS. 9A-9E.

In order to define the desired position of the mounting assembly 240 relative to the rail assembly 220 requires constraining six degrees of freedom using six alignment features. The third alignment tab 244 provides a seventh alignment datum 250 and an eighth alignment datum 251. The fourth alignment tab 245 provides a ninth alignment datum 252 and a tenth alignment datum 253. The engagement between the alignment tabs 244, 245 with the rod 224 therefore define four degrees of freedom (x, z, θ_x, θ_z).

The mounting assembly 240 also includes a rotational alignment feature providing an eleventh alignment datum 254, which is adapted to engage with a corresponding rotational alignment feature 225 (FIG. 7) on the beam 222 to define the fifth degree of freedom (θ_y). In the illustrated configuration, the eleventh alignment datum 254 is a ring that protrudes slightly from the upper cross-piece of the frame 242.

The mounting assembly 240 also includes a cross-track alignment feature providing a twelfth alignment datum 255, which is adapted to engage with a corresponding cross-track alignment feature on the rail assembly 220 to define the sixth degree of freedom (y). In the illustrated configuration, the twelfth alignment datum 255 is provided on a side face of the fourth alignment tab 244, and the corresponding cross-track alignment feature on the rail assembly 220 is provided by a side face of the corresponding notch 223 in the beam 222. While the twelfth alignment datum 255 is shown on the outside face of the fourth alignment tab 205, one skilled in the art will recognize that it could alternatively be on the inside face. In other configurations, the twelfth alignment datum 255 can be a side face of the third alignment tab 245, or can be provided by some other feature on the mounting assembly 240.

A mounting assembly clamping mechanism 310 is used to apply a clamping force to the mounting assembly 240 clamping it to the rail assembly 220. The clamping force causes the seventh alignment datum 250, the eighth alignment datum 251, the ninth alignment datum 252, and the tenth alignment datum 253 of the mounting assembly 240 to engage with the rod 224, and causes the eleventh alignment datum 254 of the mounting assembly 240 to engage with the corresponding alignment feature 225 (FIG. 7) on the beam 222. In the illustrated configuration, the mounting assembly clamping mechanism 310 is provided by three bolts 312. One of the bolts 312 is shown on one side of the mounting assembly 240 in proximity to the third alignment tab 244. This bolt 312 threads into a threaded hole 316 on the mounting bracket 229 (see FIG. 7), which is attached to the beam 222. Likewise, another bolt 312 (not visible in FIG. 10) will be on the other side of the mounting assembly 240 in proximity to the fourth alignment tab 245. A third bolt 312 would be inserted through the bolt hole 314 shown in the top rail of the frame 242 and into a threaded hole 318 on the beam 222 at a position corresponding to the rotational alignment feature 225 (see FIG. 7). It will be obvious to one skilled in the art that a variety of other types of mounting assembly clamping mechanisms 310 can be used in accordance with the present invention, including various spring clamp arrangements.

In the illustrated exemplary embodiment, the ink catcher 72 is attached to the frame 242 of the mounting assembly 240. The charging electrode 62 is then attached to the ink catcher 72. A shutter mechanism 352 is also attached to the frame 242 of the mounting assembly 240. The shutter mechanism 352 is used to block the path of ink between the nozzles 50 and the print medium 32 (see FIG. 3) when the jetting module 200 is not being used to print image data. Motor 371 is a component of the shutter mechanism 352. The shutter mechanism 352 will be discussed in more detail later.

A jetting module clamping mechanism 300 is provided for each jetting module 200. In the illustrated exemplary embodiment, the jetting module clamping mechanism 300 is a component of the mounting assembly 240. The jetting module clamping mechanism 300 applies a force to the associated jetting module 200 that causes the first alignment datum 210, the second alignment datum 211, the third alignment datum 212 and the fourth alignment datum 213 of the associated jetting module 200 to engage with the rod 224 and causes the fifth alignment datum 214 to engage with a corresponding rotational alignment feature associated with the beam 222. In the illustrated configuration, the fifth alignment datum 214 is on the bottom surface of the jetting module 200, and contacts a corresponding rotational alignment feature the mounting assembly 240. As can be seen in FIG. 12B, the rotational alignment feature in this example is on a top surface of the ink catcher 72, which is a component of the mounting assembly 240, and will therefore have a defined positional relationship to the beam 222.

In the illustrated exemplary embodiment, the jetting module clamping mechanism 300 is a spring loaded toggle clamp mechanism that can be operated by a human operator who is installing the jetting module 200 into the printhead assembly 190 (FIG. 6). The spring loaded toggle clamp mechanism includes a handle 302 connected to two spring plungers 304 using a lever mechanism. When the operator lifts the handle 302, the two spring plungers 302 are pushed against corresponding surfaces of the jetting module 200, thereby pushing the jetting module against the rail assembly 220. Additional details of the spring loaded toggle clamp mechanism can be seen more clearly in FIG. 12D.

A cross-track force mechanism 320 is also provided for each jetting module 200. In the illustrated exemplary embodiment, the cross-track force mechanism 300 is a leaf spring mechanism which is attached to the frame 242 of the mounting assembly 240. When the jetting module is inserted into the mounting assembly 240, the leaf spring applies a cross-track force on the jetting module 200 (to the right with respect to FIG. 10), which causes the sixth alignment datum 215 (see FIG. 8) to engage with a corresponding cross-track alignment feature on the beam 222. In this case, the inner surface of the second alignment tab 205 is pushed against the side face of the corresponding notch 223 in the beam 222. The cross-track force mechanism 320 also serves to apply a cross-track force on the mounting assembly 240 (to the left with respect to FIG. 10), which causes the twelfth alignment datum 255 to be pushed against the side face of the corresponding notch 223 in the beam 222, thereby engaging with a corresponding cross-track alignment feature on the beam 222. In other configurations, the cross-track force mechanism 320 can utilize other types of spring mechanisms, or can utilize any other type of force mechanisms known in the art that are adapted to provide a cross-track force (e.g., screw mechanisms, hydraulic mechanisms or toggle clamp mechanisms).

FIG. 11, shows a top view of the printhead assembly 190 of FIG. 6, which includes one printhead module 260 mounted on the downstream side 226 of the rail assembly 220, and two printhead modules 260 mounted on the upstream side 228 of the rail assembly 220. Some aspects of the various components can be seen more clearly in this view. The cut-lines are shown corresponding to the views of FIGS. 12A-12D.

FIG. 12A corresponds to cut-line A in FIG. 11, which passes through the center of the left-most printhead module 260. FIG. 12B is an enlarged view of the region 380 in FIG. 12A, showing additional details. A number of features of the printhead assembly 190 can be observed in these view. Slots 350 are provided in the lower surface of each printhead module 260 corresponding to the in-track positions of the nozzle arrays 202. The nozzle array spacing 138 is defined by the in-track distance between the two slots 350. As discussed earlier, it is desirable to minimize the nozzle array spacing 138 to reduce stitching errors. An advantage of the exemplary embodiment of printhead assembly 190 is that the slots 350 can be positioned quite close to the rail assembly 220. This is partially due to the fact that the ink catcher 72 is positioned upstream of the nozzle array 202 for the jetting module 200 on the upstream side 228 of the rail assembly 220, and the ink catcher 72 is positioned downstream of the nozzle 202 array for the jetting module 200 on the downstream side of the rail assembly 220. Because the ink catchers 72 extend out a significant distance from the nozzle arrays 202, prior art system where the ink catchers 72 were all positioned on the same side of the nozzle arrays 202 required that the nozzle array spacing 138 be significantly larger.

The eleventh alignment datum 254 on the frame 242 of the mounting assembly 240 can also be seen. The mounting assembly clamping mechanism 310 (FIG. 10), pushes the alignment datum 254 into a corresponding rotational alignment feature 225 on the beam 222 of the rail assembly 220.

FIG. 12B shows an enlargement of the region 380 in FIG. 12A, and more clearly illustrates the portion of the printhead assembly 190 in the vicinity of the nozzle array 202. Undeflected printing drops 66 pass through a slot 350 formed between a repositionable shutter blade 356 and the lower plate 79 of the ink catcher 72. The repositionable shutter blade 356 can be selectively repositioned to block the slot 350, as will be discussed in more detail later. The liquid channel 78 of the ink catcher 72 draws away non-printing drops 68 (FIG. 4) for recycling. In the illustrated configuration, the fifth alignment datum 214 of the jetting module 200 is provided by a protrusion which extends from the lower surface of the jetting module. The fifth alignment datum 214 contacts an upper surface of the ink catcher 72, which provides the rotational alignment feature 256. The ink catcher 72 is a component of the mounting assembly 240, which is mounted onto the rail assembly 220 in a predefined location, with the rotational alignment being defined relative to the beam 222 as has been discussed earlier. The rotational alignment feature 256 is therefore indirectly associated with the beam 222, even though it is not directly on the beam 222. In other embodiments, the fifth alignment datum 214 can be located in a different position on the jetting module 200. For example, the fifth alignment datum 214 can be a protrusion on the face of the jetting module that faces the beam 222. The rotational alignment feature 225 can then be a point on the beam 222, or on the frame 242 (FIG. 10) of the mounting assembly 240.

FIG. 12C corresponds to cut-line B in FIG. 11, which passes through alignment tab 244 of the mounting assembly 240 in the left-most printhead module 260 in FIG. 11 (i.e., the upstream printhead module 260 on the right-hand side of FIG. 12C). It can be seen that the alignment tab 244 is inserted partway through the notch 223 in beam 222, and that the seventh alignment datum 250 and the eighth alignment datum 251 are in contact with the rod 224.

FIG. 12D corresponds to cut-line C in FIG. 11, which passes through the alignment tab 204 of the jetting module 200 in the left-most printhead module 260 in FIG. 11 (i.e., the upstream printhead module 260 on the right-hand side of FIG. 12C). Cut-line C also passes through the spring plunger 304 of the upstream printhead module 260. The handle 302 of the jetting module clamping mechanism 300 for the upstream printhead module 260 has been pushed upward into the engaged position, so that the spring plunger 304 is applying a force onto an angled surface along one side of the jetting module 200. This pushes the alignment tab 204 of the jetting module 200 tightly against the beam 222 of the rail assembly 220. It can be seen that the alignment tab 204 is inserted partway through the notch 223 in beam 222, and that the first alignment datum 250 and the second alignment datum 251 are in contact with the rod 224. A second spring plunger 304 (not visible in FIG. 12D) is similarly applying a force onto an angled surface along the other side of the jetting module 200, thereby engaging the second alignment tab 205 with the rod 224. A downward component of the force provided by the jetting module clamping mechanism 300 also pushes downward on the jetting module 200 so that the fifth alignment datum 214 engages with the corresponding rotational alignment feature 256 on the mounting assembly 240 (as discussed with respect to FIG. 12B). The handle 302 of the jetting module clamping mechanism 300 for the downstream printhead module 260 on the left side of FIG. 12D has been pushed downward into the released position, so that the spring plungers 304 have been pulled away from the jetting module 200. This enables the jetting module 200 to be extracted from the printhead assembly 190 (e.g., for maintenance).

FIG. 13A shows a side view of the printhead assembly 190 of FIG. 6 as viewed from the downstream side 226. One printhead module 260 is visible on the downstream side 226 of the rail assembly 220, with the other two printhead modules 260 being behind the rail assembly 220 on the upstream side 228 (FIG. 6).

FIG. 13B shows an enlargement of the region 382 in FIG. 13A, and more clearly illustrates the portion of the printhead assembly 190 in the vicinity of the one of the notches 223 in the beam 220. Alignment tab 245 of the mounting assembly 240 (see FIG. 10) and alignment tab 205 of the jetting module 200 (see FIG. 8) in the left printhead module 260 behind the rail assembly 220 are visible within the notch 223. The leaf spring which serves as the cross-track force mechanism 320 (see FIG. 10) is visible between the alignment tabs 205, 245. The cross-track force mechanism 320 applies a cross-track force to both the mounting assembly 240 and the jetting module 200.

In the illustrated exemplary embodiment, the cross-track force mechanism 320 pushes the mounting assembly 240 to the left so that the alignment datum 255 on the outer face of the alignment tab 245 contacts the left face of the notch 223, which serves as the corresponding cross-track alignment feature associated with the beam 222. As discussed earlier, in other embodiments, other features on the mounting assembly 240 can serve as the alignment datum 245.

Similarly, in the illustrated exemplary embodiment, the cross-track force mechanism 320 pushes the jetting module 200 to the right so that the alignment datum 215 on the inner face of the second alignment tab 205 contacts the right face of the notch 223, which serves as the corresponding cross-track alignment feature associated with the beam 222.

In other embodiments, other features on the jetting module 200 can serve as the alignment datum 215. For example, the alignment datum 215 can be on outer face of the first alignment tab 204. As the cross-track force mechanism 320 pushes the jetting module 200 to the right, the spacing between the alignment tabs 204, 205 and the spacing between the alignment tabs 244, 245 can be arranged such that the outer face of the first alignment tab 204 comes into contact with the inner face of the third alignment tab 244 (see FIG. 10) on the mounting assembly 240. In this case, the inner face of the alignment tab 244 serves as the corresponding cross-track alignment feature associated with the beam 222. Since the mounting assembly 240 is mounted onto the rail assembly 220 in a predefined location, with the cross-track alignment being defined relative to the beam 222 as has been discussed earlier, the cross-track alignment feature on the alignment tab 244 is therefore indirectly associated with the beam 222, even though it is not directly on the beam 222.

FIG. 14 is an isometric view showing a shutter mechanism 352 including a repositionable shutter 354. The repositionable shutter 354 extends in a cross-track direction 118 from a first end to a second end. Tabs 358 (i.e., lever arms) are affixed to the first and second ends of a shutter blade 356. In the illustrated embodiment, both tabs 358 include actuation features (i.e., grooves 410), through which a torque can be applied to rotate the repositionable shutter 354 around a pivot axis 362. When the repositionable shutter 354 is pivoted into a first pivot position, the shutter blade 356 blocks drops of ink from passing through the slot 350 and diverts the ink into the ink catcher 72 (see FIG. 12B). When the repositionable shutter 354 is pivoted into a second pivot position, the shutter blade 356 is moved away from the slot 350 so that drops of ink can pass through the slot 350. In a preferred configuration, the shutter blade 356 includes an elastomeric tip 357 adapted to seal against the lower plate 79 of the ink catcher 72 when the repositionable shutter 354 is in the first pivot position (see FIG. 16A).

In the illustrated exemplary configuration, the tabs 358 include circular holes 364 coaxial with the pivot axis 362. Shafts 366 are adapted to be mounted into the holes 364 in the tabs 358, such that the shafts 366 and the holes 364 are all coaxial with the pivot axis 362. The repositionable shutter 354 is detachably mounted to the mounting assembly 240 (FIG. 10) by sliding the shafts 366 of the repositionable shutter 354 into mounting grooves 368 on the frame 242 of the mounting assembly 240 as illustrated in FIGS. 15A-15B, which show side views of the shutter mounting system.

The top of the mounting grooves 368 define stops 384 for the shafts 366 to position the shutter blade 356 so that the elastomeric tip 357 (see FIG. 14) properly seals against the lower plate 79 of the ink catcher 72 (see FIG. 12B) when the shutter is pivoted to the first pivot position. A latch mechanism 386 retains the shafts 366 against the stops 384 of the mounting grooves 368. The stops 384 are preferably positioned so that the pivot axis 362 of the repositionable shutter 354 is positioned between the nozzle array 202 (FIG. 12B) and the slot 350.

In the illustrated exemplary configuration, the mounting grooves 368 have a groove axis 396 (i.e., the groove center) that includes a small bend 388 to the left. When the shaft 366 is inserted into the mounting groove 368 and engages the stop 384, the bend 388 forms a small indent 389 in the left edge of mounting groove 368, thereby helping to define the vertical position of the shaft 366, and therefore the vertical position of the repositionable shutter 354. Removal of the repositionable shutter 354 requires the shaft 366 to be shifted slightly to the right before it can be lowered down the mounting groove 368.

Latch mechanisms 386 retain the shafts 366 at the first and second ends of the repositionable shutter 354 at the stops 384 of the mounting grooves 368. The latch mechanisms 386 include a latch plate 390 configured to pivot around a pivot axis 392. A spring 391 biases the latch plate 390 so that latch keeper 394 contacts a portion of the shaft 366 opposite where the shaft 366 contacts the stop 384, as shown in FIG. 15A. The latch mechanism 386 must be manually pivoted using a pivoting motion 395 so the latch keeper 394 is shifted away from the shaft 366 to allow the shaft 366 to be extracted from the mounting groove 368, as shown in FIG. 15B.

The pivot axis 392 of the latch mechanism 386 is preferably positioned such that the pivoting motion 395 of the latch keeper 394 is roughly perpendicular to the orientation of the mounting groove axis 396 at the end of the mounting groove 368. Such an orientation ensures that shaft 366 of the repositionable shutter 354 cannot apply a force on the latch mechanisms 386 to pivot the latch keeper 394 out the way.

An angled face 398 of the latch plate 390 facing the entrance to the mounting groove 368 is steeply tapered so that contact with the shaft 366 as it is being inserted into the mounting groove pivots the latch plate 390, allowing the shaft 366 to inserted all the way to the stop 384. The latch plate 390 can then pivot back to the latched position (see FIG. 15A) with the latch keeper 394 in place behind the shaft 366. A pin 400, which passes through an opening 402 in the latch plate 390 limits rotation of the latch plate 390.

As discussed earlier, the shutter mechanism 352 is adapted to be actuated by applying a torque through the tabs 358 of the repositionable shutter 354. This can be accomplished with an actuator 370 as illustrated in FIGS. 16A-16C. In the illustrated exemplary configuration, the actuator 370 includes a motor 371 which rotates a lever 373 mounted onto a shaft 372 of the motor 371. The lever 373 can be rotated between a first position shown in FIG. 16A and a second position shown in FIG. 16B.

The lever 373 is attached to a first end of a pushrod 374. The opposite end of the pushrod 374 includes an actuation feature that engages an associated actuation feature of the repositionable shutter 354 as shown in FIG. 16C, which shows additional details of region 430 of FIG. 16B. In the illustrated exemplary configuration, the actuation feature of the pushrod 374 is a pin 404 that engages the actuation feature of the repositionable shutter 354 (i.e., the groove 410). It will be obvious to one skilled in the art that other types of actuation features can be used in accordance with the present invention to provide the required engagement between the pushrod 374 and the repositionable shutter 354.

By means of the engagement of the pin 404 with the groove 410, the actuator 370 can move the pushrod 374 to the left to provide a counter-clockwise torque on the repositionable shutter 354 thereby pivoting the repositionable shutter 354 into the first position (see FIG. 16A) such that the shutter blade 356 (FIG. 14) block drops of ink from passing through the slot 350. Similarly, the actuator 370 can move the pushrod 374 to the right to apply a clockwise torque on the repositionable shutter 354 thereby pivoting the repositionable shutter 354 into the second position (see FIG. 16B) so that drops of ink can pass through the slot 350. As the actuator 370 rotates the repositionable shutter 354 between the first and second positions, the pin 404 is free to slide along the groove 410. In the illustrated configuration, the pin 404 slides up the groove 410 (i.e., moves farther away from the pivot axis 362 of the repositionable shutter 354) as the repositionable shutter 354 pivots from the first position to the second position. (The amount and direction that the pin 404 slides within the groove 410 will depend on the placement of the engagement point between the pin 404 and groove 410 relative to the shutter pivot point 362.) As the actuator can provide the torque on the shutter to shift it in either direction between the first and the second positions, springs that act directly on the repositionable shutter 354 to bias it into a closed (first) position (such as those shown in FIG. 14 of commonly-assigned U.S. patent application Ser. No. 15/163,249, which is incorporated herein by reference) are not required. The elimination of the need for springs that act directly on the repositionable shutter 354 frees up space around the repositionable shutter 354, and facilitates easier removal and installation of the repositionable shutter 354 for printhead maintenance purposes.

The removal of the repositionable shutter 354 is shown in FIG. 17, which is a cross-sectional view similar to FIG. 16C showing region 430 of FIG. 16B. A portion of the frame 242 of the mounting assembly 240 (FIG. 10) including the mounting groove 368 is shown using phantom lines. The use of the open-ended groove 410 in the tab 358 of the repositionable shutter 354 allows the actuation feature of the repositionable shutter 354 to easily disengage from the pin 404, which serves as the actuation feature of the pushrod 374 as the shaft 366 of the repositionable shutter 354 is moved down the mounting groove 368. Similarly, the groove 410 can easily engage the pin 404 as the process is reversed when the repositionable shutter 354 is being installed.

When the repositionable shutter 354 is removed from the printhead module 260 (FIG. 6), the pushrod 374 is limited in how far it can drop by contact with a wall feature 412 of the mounting assembly 240 (FIG. 10). A second wall feature 414 limits the upward travel of the pushrod 374, ensuring that the pin 404 of the pushrod does not slide out of the open groove 410. Through the use of such features, the position of pushrod 374 can be maintained within an appropriate range to facilitate engagement of the actuation feature (i.e., groove 410) of the repositionable shutter 354 with the corresponding actuation feature (i.e., pin 404) of the pushrod 374 while the repositionable shutter 354 is being installed.

In an alternate embodiment (not shown) the groove 410 of the repositionable shutter 354 and the pin 404 of the pushrod 374 can be interchanged such that the actuation feature of the repositionable shutter 354 is a pin and the actuation feature of the pushrod 374. In other embodiments, any other types of appropriate actuation features known in the art can be used to engage the repositionable shutter 354 with the pushrod 374 such that the lateral motion of the pushrod causes the repositionable shutter 354 to pivot around the shaft 366.

In the embodiment shown in FIGS. 16A-16B, a stepper motor 371 provides the force to actuate the repositionable shutter 354 back and forth between the first and the second positions. In alternate embodiments, such as that shown in FIG. 18, a spring 416 attached to the lever 373 is used to apply a bias force to rotate the lever 373 to the first position, and via the pushrod 374 and to rotate the repositionable shutter 354 to its first position where the slot 350 is blocked. This provides a failsafe feature where the shutter closes when power is removed from the actuator. The opposite end of the spring 416 from is attached to the mounting assembly 240 through conventional means that are not shown. In other embodiments, a spring is coupled directly between the pushrod 374 and the mounting frame 240 to apply a force on the pushrod that biases both the repositionable shutter 354 and the lever 373 into their first positions. In both of these embodiments, the spring 416 is located remote from the repositionable shutter 354; freeing up space adjacent to the shutter blade 356 (FIG. 14) and making it easier to remove and reinstall the repositionable shutter 354. In other embodiments (not shown), a solenoid actuator is used instead of a motor 371 to provide the actuation force to the pushrod 374.

FIG. 19 illustrates an alternate embodiment of a repositionable shutter 354 for use in a printhead module having a different mounting frame configuration. Only portions of the printhead module are shown to highlight the repositionable shutter 354 and the actuator mechanism. An ink catcher 72 and drop deflection mechanism 70 are shown along with a mount 418 for the repositionable shutter 354. The shutter mount 418 includes mounting grooves 368, which are similar to those of the previous embodiments. The mounting groove 368 of this embodiment extends farther after the bend 388 (see FIG. 15B) than the previous embodiments. When the repositionable shutter 354 is installed with the shafts 366 in the mounting grooves 368, the shafts 366 are secured in place by latch mechanism 386, which is similar to the previously described latch mechanism.

Unlike the earlier embodiments in which the torque to pivot the repositionable shutter 354 was applied at the tabs 358 near each end of the shutter blade 356 (see FIG. 14), the illustrated embodiment is configured to apply the actuator torque to a central portion 420 of the repositionable shutter 354. In the previous embodiment, the actuator motor 371 was mounted to the mounting assembly 240 near the back side of the catcher 72. In this embodiment, the actuator mechanism is located on the back side of the repositionable shutter 354 (i.e., the side farthest from the catcher face 74). In an exemplary configuration, the actuator mechanism components (e.g., pushrod 374, pushrod guide 432, channel 422 and slide mechanism component 424) associated with a particular printhead module 260 are arranged so that they will fit between the printhead modules 260 mounted on the opposite side of the rail assembly 220 (see FIG. 6). In alternate configurations (not shown), the actuator mechanism components can be arranged to apply the actuator torque in proximity to the ends of the shutter blade 356, or at some other location along the shutter blade 356, rather than in the central portion 420 as shown in FIG. 19. In such embodiments, the actuator mechanism components (e.g., pushrod 374, pushrod guide 432, channel 422 and slide mechanism component 424) would be attached at a desired location along the repositionable shutter 354.

In this configuration, the actuation feature of the repositionable shutter 354 is configured as a T-shaped channel 422, which is open on one end as can be seen in FIG. 20 (which is a close up view of region 434 in FIG. 19). The actuation feature of the pushrod 374 is a T-shaped slide mechanism component 424 that can be inserted into the T-shaped channel 422 of the repositionable shutter 354. The T-shaped slide mechanism component 424 is extended in length, in a direction parallel to a slide motion direction 426.

The actuation motor 371 is connected to pushrod 374 via a lever 373 (which rotates on shaft 372 of motor 371) and a linkage arm 428 as shown in FIGS. 21A-21B. The pushrod 374 passes through a pushrod guide 432 that restricts the motion of the pushrod 374 to a single degree of freedom translation, (i.e., left and right). Activation of the motor 371 causes the pushrod 374 to move left or right between a first position (see FIG. 21B) and a second position (see FIG. 21A). Actuation of the pushrod 374 to the left as shown in FIG. 21B causes the T-shaped slide mechanism component 424 of the pushrod 374 to slide upward along the channel 422 thereby causing the repositionable shutter 354 to pivot around its axis 362 into a first position where the shutter blade 356 blocks drops of ink from passing through the slot 350 and diverts the ink into the ink catcher 72. Actuation of the pushrod 374 to the right as shown in FIG. 21A causes the T-shaped slide mechanism component 424 of the pushrod 374 to slide downward along the channel 422 thereby causing the repositionable shutter 354 to pivot around its axis 362 into a second position where the shutter blade 356 is moved away from the slot 350 so that drops of ink can pass through the slot 350.

This sliding motion of the slide mechanism component 424 of the pushrod 374 in the slide mechanism component (i.e., channel 422) of the repositionable shutter 354 results in the slide mechanism component 424 being farther from the pivot axis 362 of the shutter rotation when the repositionable shutter 354 is in the first position of FIG. 21B than it is when the repositionable shutter 354 is rotated to the second position of FIG. 21A. As the repositionable shutter 354 rotates around its pivot axis 362, the channel axis 436 of the T-shaped channel 422 also rotates. To accommodate such a change in the orientation of the channel 422, the T-shaped slide mechanism 424 is pivotably attached to the pushrod 374 at pivot 438. The engagement of the T-shaped slide mechanism component 424 of the pushrod 374 with the T-shaped channel 422 of the repositionable shutter 354 enables a bidirectional torque to be applied to the repositionable shutter 354 so that it can be actuated back and forth between the first position and the second position, without the need for springs acting directly on the repositionable shutter 354.

As illustrated in FIG. 22, the open end of the channel 422 enables the slide mechanism component 424 of the pushrod 374 to be easily engaged with the channel 422 when the repositionable shutter 354 is being mounted in the printhead module 260, and to be easily disengaged when the repositionable shutter 354 is dismounted from the printhead module 260. In some embodiments, the slide mechanism component 424 can include a stop 440 to limit how far the slide mechanism component 424 can rotate around the pivot 438 and thereby maintain slide mechanism component 424 at an orientation that facilitates engagement with the channel 422 during installation of the repositionable shutter 354 into the printhead module 260.

In the embodiments of the repositionable shutter 354 discussed, the pushrods 374 have been oriented, and displaced during actuation in approximately a horizontal direction. The invention is not limited to such an orientation. FIG. 23 illustrates an alternate embodiment in which the pushrod 374 is oriented vertically.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

PARTS LIST

• 20 system
• 22 image source
• 24 image processing unit
• 26 control circuits
• 27 synchronization device
• 28 drop forming transducer
• 30 printhead
• 32 print medium
• 34 print medium transport system
• 35 speed measurement device
• 36 media transport controller
• 38 micro-controller
• 40 ink reservoir
• 44 ink recycling unit
• 46 ink pressure regulator
• 47 ink channel
• 48 jetting module
• 49 nozzle plate
• 50 nozzle
• 51 heater
• 52 liquid stream
• 54 drop
• 55 drop formation waveform source
• 57 trajectory
• 59 break-off location
• 60 drop formation waveform
• 61 charging device
• 62 charging electrode
• 62′ charging electrode
• 63 charging electrode waveform source
• 64 charging electrode waveform
• 66 printing drop
• 68 non-printing drop
• 69 drop selection system
• 70 deflection mechanism
• 71 deflection electrode
• 72 ink catcher
• 74 catcher face
• 76 ink film
• 78 liquid channel
• 79 lower plate
• 80 charging electrode waveform 64 period
• 82 first voltage state
• 84 second voltage state
• 86 non-print trajectory
• 88 print dot
• 92-1 drop formation waveform
• 92-2 drop formation waveform
• 92-3 drop formation waveform
• 94-1 drop formation waveform
• 94-2 drop formation waveform
• 94-3 drop formation waveform
• 94-4 drop formation waveform
• 96 period
• 98 pulse
• 100 period
• 102 pulse
• 104-1 large drop
• 104-2 large drop
• 104-3 large drop
• 106-1 small drop
• 106-2 small drop
• 106-3 small drop
• 106-4 small drop
• 108 phase shift
• 112 printhead assembly
• 116 in-track direction
• 118 cross-track direction
• 132 printing region
• 134 overlap region
• 136 centerline
• 138 nozzle array spacing
• 190 printhead assembly
• 200 jetting module
• 201 fillet
• 202 nozzle array
• 203 endmill
• 204 alignment tab
• 205 alignment tab
• 206 notch
• 207 face
• 208 face
• 209 protrusion
• 210 alignment datum
• 211 alignment datum
• 212 alignment datum
• 213 alignment datum
• 214 alignment datum
• 215 alignment datum
• 216 fluid connections
• 217 electrical connections
• 220 rail assembly
• 222 beam
• 223 notch
• 224 rod
• 225 rotational alignment feature
• 226 downstream side
• 228 upstream side
• 229 mounting bracket
• 240 mounting assembly
• 242 frame
• 244 alignment tab
• 245 alignment tab
• 250 alignment datum
• 251 alignment datum
• 252 alignment datum
• 253 alignment datum
• 254 alignment datum
• 255 alignment datum
• 256 rotational alignment feature
• 260 printhead module
• 300 jetting module clamping mechanism
• 302 handle
• 304 spring plunger
• 310 mounting assembly clamping mechanism
• 312 bolt
• 314 bolt hole
• 316 threaded hole
• 318 threaded hole
• 320 cross-track force mechanism
• 350 slot
• 352 shutter mechanism
• 354 repositionable shutter
• 356 shutter blade
• 357 elastomeric tip
• 358 tab
• 362 pivot axis
• 364 hole
• 366 shaft
• 368 mounting groove
• 370 actuator
• 371 motor
• 372 shaft
• 373 lever
• 374 pushrod
• 380 region
• 382 region
• 384 stop
• 386 latch mechanism
• 388 bend
• 389 indent
• 390 latch plate
• 391 spring
• 392 pivot axis
• 394 latch keeper
• 395 pivoting motion
• 396 groove axis
• 398 angled face
• 400 pin
• 402 opening
• 404 pin
• 410 groove
• 412 wall feature
• 414 wall feature
• 416 spring
• 418 mount
• 420 central portion
• 422 channel
• 424 slide mechanism component
• 426 slide motion direction
• 428 linkage arm
• 430 region
• 432 pushrod guide
• 434 region
• 436 channel axis
• 438 pivot
• 440 stop

Claims

1. An inkjet printhead assembly including a printhead module with a repositionable shutter, comprising: a jetting module including an array of nozzles extending in a cross-track direction for printing on a print medium traveling along a media path from upstream to downstream;a slot through which drops of ink ejected from the array of nozzles pass before they impinge on the print medium;an ink catcher positioned on one side of the slot for catching non-printing drops of ink ejected from the array of nozzles, the ink catcher including an ink channel for drawing ink away from the slot;a shutter mechanism including: an actuator configured to translate an actuator rod along a translation direction between a first actuator position and a second actuator position, the actuator rod including a first actuation feature;a repositionable shutter including: a shutter blade extending in a cross-track direction from a first end to a second end;a first tab affixed to the first end of the shutter blade, the first tab including a second actuation feature that engages with the first actuation feature of the actuator rod; anda second tab affixed to the second end of the shutter blade;wherein the repositionable shutter is adapted to rotate around a fixed pivot axis passing through the first and second tabs between a first pivot position and a second pivot position, such that when the repositionable shutter is rotated into the first pivot position the shutter blade blocks drops of ink from passing through the slot and diverts the ink into the ink catcher, and when the repositionable shutter is rotated into the second pivot position the shutter blade is moved away from the slot so that drops of ink can pass through the slot; andwherein when the actuator rod is translated into the first actuator position a first torque is applied to the repositionable shutter through the first and second actuation features, thereby pivoting the repositionable shutter into the first pivot position, and when the actuator rod is translated into the second actuator position a second torque is applied to the repositionable shutter through the first and second actuation features, thereby pivoting repositionable shutter into the second pivot position.

2. The inkjet printhead assembly of claim 1, wherein the first actuator feature is a pin extending from the actuator rod and the second actuator feature is a groove formed in the first tab, and wherein the pin is adapted to fit within the groove thereby engaging the second actuation feature with the first actuation feature.

3. The inkjet printhead assembly of claim 1, wherein the first actuator feature is a grooved formed in the actuator rod and the second actuator feature is a pin extending from the first tab, and wherein the pin is adapted to fit within the groove thereby engaging the second actuation feature with the first actuation feature.

4. The inkjet printhead assembly of claim 1, wherein the repositionable shutter is removable from the inkjet printhead assembly.

5. The inkjet printhead assembly of claim 4, further including a first shaft extending from the first tab and a second shaft extending from the second tab, the first and second shafts being coaxial with the pivot axis, and wherein the first and second shafts are adapted to removably engage with corresponding first and second mounting grooves on a frame of the printhead module.

6. The inkjet printhead assembly of claim 5, further including first and second latch mechanisms configured to latch the respective first and second shafts into the corresponding first and second mounting grooves.

7. The inkjet printhead assembly of claim 5, wherein the second actuation feature of the repositionable shutter is adapted to disengage from the first actuation feature of the actuator rod when the repositionable shutter is disengaged from the printhead module by sliding the first and second shafts out of the corresponding first and second mounting grooves.

8. The inkjet printhead assembly of claim 1, wherein the actuator includes a motor having a motor shaft, the motor being coupled to the actuator rod using a pivoting lever, and wherein the actuator rod is translated between the first and second actuator positions by rotating the motor shaft to reposition the pivoting lever.

9. The inkjet printhead assembly of claim 1, wherein the ink channel of the ink catcher is formed between a catcher body and a lower plate, and wherein the shutter blade has an elastomeric tip that seals against the lower plate of the ink catcher when the repositionable shutter is pivoted into the first pivot position.

10. The inkjet printhead assembly of claim 1, wherein the pivot axis is positioned between the array of nozzles and the slot.