Patent Grant
8801129
This invention relates generally to the field of digitally controlled printing devices, and in particular to continuous printing systems in which a liquid stream is selectively broken off into drops having a small volume and drops having a large volume.
Printing systems that deflect drops using a gas flow are known; see, for example, U.S. Pat. No. 4,068,241, issued to Yamada, on Jan. 10, 1978. Such printing systems rely on the ability to generate distinct sizes of drop—a “print drop” of a given size, and a “catch drop” of distinctly different size. Differential deflection of the drops of different sizes is employed to cause print drops to impinge on the substrate and the catch drops to be collected and re-circulated through the ink delivery system.
In thermally stimulated continuous inkjet printing (see, for example Jeanmaire et al. U.S. Patent Application Publication No. 20020085071 A1 and Chwalek et al, In U.S. Pat. No. 6,079,821), periodic heat pulses are applied to individual heaters embedded in a nozzle array. The periodic heat pulses drive capillary break-up of jets formed at each nozzle to produce an array of drops. The period of the pulse waveform determines the ultimate size of drop formed after jet break-up. Because the jet responds most sensitively to disturbances at a characteristic frequency fR known as the Rayleigh frequency, drops are most effectively produced at a fundamental size corresponding to a volume of fluid given by πr2U/fR, where r is the jet radius and U is the jet velocity.
In U.S. Pat. No. 6,851,796, which issued on Feb. 8, 2005, an ink drop forming mechanism selectively creates a stream of ink drops having a plurality of different volumes traveling along a first path. An air flow directed across the stream of ink drops interacts with the stream of ink drops. This interaction deflects smaller drops more than larger drops and thereby separates ink drops having one volume from ink drops having other volumes.
As the drop selection mechanism described above depends on drop size, it is necessary for large-volume drops to be fully formed before being exposed to the deflection air flow. Consider, for example, a case where the large-volume drop is to have a volume equal to four small-volume drops. It is often seen during drop formation that the portion of the ink stream that is to form the large-volume drop will separate from the main stream as desired, but will then break apart before coalescing to form the large-volume drop. It is necessary for this coalescence to be complete prior to passing through the drop deflecting air flow. Otherwise the separate fragments that are to form the large-volume drop will be deflected by an amount greater than that of a single large-volume drop. Similarly, the small-volume drops must not merge in air before having past the deflection air flow. If separate small-volume drops merge, they will be deflected less than desired.
The distance over which the large-volume drop forms upon coalescence of is fragments is known as the drop formation length (DFL), denoted herein as LD. The details of the large-drop waveform and the physical properties of the jet determine the size of LD. For the purposes of printing, smaller drop formation lengths are advantageous, as the drops are then available for size separation at distances closer to the nozzle plate, and the distance over which the drops must travel prior to separation is reduced. Thus a smaller drop formation length helps reduce the size of the printhead and reduces the risk of incomplete large drop formation and reduces the risk of unintended merging of small drops.
It has been found that ink coverage levels are excessive when printing on certain print media, resulting loss of acuity and discernable gray levels. While the ink coverage level can be reduced through the use of smaller nozzles or by reducing the ink pressure or increasing the frequency of drop formation, these options have shortcomings. Conversely, on other substrates the ink coverage levels can be insufficient, resulting in lack of optical density and voids in the printed regions. While the ink coverage level can be altered through the use of different nozzles sizes or by adjusting the ink pressure or the frequency of drop formation, these options can also have shortcomings. If different nozzle sizes are to be used for different print media, then it would be necessary to produce and maintain an inventory of a number of distinct printheads each having a distinct nozzle size. Reducing the ink pressure or raising the frequency of drop formation can result in reducing the stimulation perturbation wavelengths toward the Rayleigh cutoff limit. As the perturbation wavelengths are reduced toward the Rayleigh cutoff limit, the drop formation can become excessively sensitive to small changes in ink properties, nozzle size, ink pressure, and stimulation amplitude. Increasing the ink pressure or reducing the frequency, on the other hand, can increase the formation of satellite drops, which can reduce printhead reliability.
Thus there is a need for waveforms that provide a means to alter the size of the large drops relative to the small drops. The present invention addresses these needs.
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the invention, the invention resides in a method for operating a jetting module comprising providing a jetting module including a nozzle and a drop forming mechanism; providing a liquid to the jetting module under pressure sufficient to cause a liquid stream to jet from the nozzle; providing a small-drop waveform, the small-drop waveform having a starting endpoint and a trailing endpoint, the time between the starting endpoint and the trailing endpoint being the small-drop period XS, the small-drop waveform including a small drop volume-control pulse, the small-drop volume-control pulse having a centroid, the centroid of the small-drop volume-control pulse being at a first defined time relative to a predefined one of the starting endpoint and the trailing endpoint of the small-drop waveform; providing a large-drop waveform, the large-drop waveform having a starting endpoint and a trailing endpoint, the time between the starting endpoint and the trailing endpoint being the large-drop period XL, where XL=N*XS and N is an integer greater than one, the large-drop waveform including a large-drop volume-control pulse, the large-drop volume-control pulse having centroid; wherein the centroid of the large-drop volume-control pulse being at a second defined time relative to the corresponding one of the starting endpoint and the trailing endpoint of the large-drop waveform, the second defined time being different from the first defined time; applying to the drop forming mechanism a sequence of drop formation waveforms in which a small-drop waveform applied after another identical small-drop waveform causes a small drop of volume Vs to be formed; applying a small-drop waveform after a large-drop waveform causes a small drop of volume Vs2 to be formed, where VS2 is not equal to VS; applying a large-drop waveform after another identical large-drop waveform causes a large drop of volume VL to be formed, where VL˜N*Vs; and applying a large-drop waveform after a small-drop waveform causes a large drop of volume VL2 to be formed, where VL2 is not equal to VL.
In the detailed description of the example embodiments of the invention presented below, reference is made to the accompanying drawings, in which:
a-c are prior art waveforms for creating large and small drops;
a-d are waveforms of the present invention for creating large and small drops;
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 can take various forms well known to those skilled in the art. In the following description and drawings, identical reference numerals have been used, where possible, to designate identical elements.
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 inkjet 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
Referring to
Recording medium 32 is moved relative to printhead 30 by a recording medium transport system 34, which is electronically controlled by a recording medium transport control system 36, and which in turn is controlled by a micro-controller 38. The recording medium transport system 34 shown in
Ink is contained in an ink reservoir 40 under pressure. In the non-printing state, continuous ink jet drop streams are unable to reach recording medium 32 due to an ink catcher 42 that blocks the stream and which can permit 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 reservoir 40. Such ink recycling units 44 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 ink reservoir 40 under the control of ink pressure regulator 46. Alternatively, the ink reservoir 40 can be left unpressurized, or even under a reduced pressure (vacuum), and a pump is employed to deliver ink from the ink reservoir 40 under pressure to the printhead 30. In such an embodiment, the ink pressure regulator 46 can include an ink pump control system. As shown in
The ink is distributed to 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 mechanisms, for example, heaters, are situated. When printhead 30 is fabricated from silicon, drop forming mechanism control circuits 26 can be integrated with the printhead 30. Printhead 30 also includes a deflection mechanism (not shown in
Referring to
Liquid, for example, ink, is emitted under pressure through each nozzle 50 of the array to form filaments of liquid 52. In
Jetting module 48 is operable to form liquid drops having a first size or volume and liquid drops having a second size or volume through each nozzle 50. To accomplish this, jetting module 48 includes a drop stimulation device 28, also commonly called a drop forming device, for example, a heater or a piezoelectric actuator, that, when selectively activated, perturbs each filament of liquid 52, for example, ink, to induce portions of each filament to breakoff from the filament and coalesce to form drops 54, 56.
In
As discussed in these references, the volume of the drops formed by the activation of the drop forming device depends on the frequency or period of activation of the heater. A high frequency of activation of the drop forming device results in small-volume drops being formed and a low frequency of activations results in the formation of large-volume drops. When drop forming activation pulses are applied to the drop forming device, the drop forming devices perturb the liquid stream flowing past the drop forming device. The perturbation travels with the liquid of the liquid stream, to form a point where the jet pinches off to separate a newly formed drop from the rest of the jet. As the time interval between successive drop forming activation pulses increases, the length of the liquid stream between the resultant pinch points increases, yielding a drop of increased volume. Depending on the time intervals between activation pulses in this manner, large-volume drops and small-volume drops of any desired volume ratio can be created, ranging up to 10:1.
Typically, one drop forming device 28 is associated with each nozzle 50 of the nozzle array. A drop forming device 28 can be associated with groups of nozzles 50 or all of nozzles 50 of the nozzle array.
When printhead 30 is in operation, drops 54, 56 are typically created in a plurality of sizes or volumes, for example, in the form of large drops 56, a first size or volume, and small drops 54, a second size or volume from each of the nozzles 50 in the nozzle array. A drop stream 58 including drops 54, 56 follows a drop path or trajectory 57.
Printhead 30 also includes a gas flow deflection mechanism 60 that directs a flow of gas 62, for example, air, past a portion of the drop trajectory 57. This portion of the drop trajectory 57 is called the deflection zone 64. As the flow of gas 62 interacts with drops 54, 56 in deflection zone 64 it alters the drop trajectories. As the drop trajectories pass out of the deflection zone 64 they are traveling at an angle, called a deflection angle, relative to the undeflected drop trajectory 57.
Small drops 54 are more affected by the flow of gas than are large drops 56 so that the small drop trajectory 66 diverges from the large drop trajectory 68. That is, the deflection angle for small drops 54 is larger than for large drops 56. When the volume ratio between the large-volume drops 56 and the small-volume drops 54 is greater than 2:1, the flow of gas 62 provides sufficient drop deflection and therefore sufficient divergence of the small and large drop trajectories 66, 68 so that catcher 42 (shown in
When catcher 42 is positioned to intercept large drop trajectory 68, small drops 54 are deflected sufficiently to avoid contact with catcher 42 and strike the print media. As the small drops 54 are printed, this is called small drop print mode. When catcher 42 is positioned to intercept small drop trajectory 66, large drops 56 are the drops that print. This is referred to as large drop print mode.
Referring to
Drop stimulation device 28, also called a drop forming device or drop forming mechanism, (shown in
Positive pressure gas flow structure 61 of gas flow deflection mechanism 60 is located on a first side of drop trajectory 57. Positive pressure gas flow structure 61 includes first gas flow duct 72 that includes a lower wall 74 and an upper wall 76. Gas flow duct 72 directs gas flow 62 supplied from a positive pressure source 92 at downward angle θ of approximately a 45° relative to liquid filament 52 toward drop deflection zone 64 (also shown in
Upper wall 76 of gas flow duct 72 does not need to extend to drop deflection zone 64 (as shown in
Negative pressure gas flow structure 63 of gas flow deflection mechanism 60 is located on a second side of drop trajectory 57. Negative pressure gas flow structure 63 includes a second gas flow duct 78 located between catcher 42 and an upper wall 82 that exhausts gas flow 62 from deflection zone 64. Second duct 78 is connected to a negative pressure source 94 that is used to help remove gas flowing through second duct 78. An optional seal(s) 84 provides an air seal between jetting module 48 and upper wall 82.
As shown in
Gas supplied by first gas flow duct 72 is directed into the drop deflection zone 64, where it causes large drops 56 to follow large drop trajectory 68 and small drops 54 to follow small drop trajectory 66. As shown in
Alternatively, deflection can be accomplished by applying heat asymmetrically to filament of liquid 52 using an asymmetric heater 51. When used in this capacity, asymmetric heater 51 typically operates as the drop forming mechanism 28 in addition to the deflection mechanism. This type of drop formation and deflection is known having been described in, for example, U.S. Pat. No. 6,079,821, issued to Chwalek et al., on Jun. 27, 2000.
Deflection can also be accomplished using an electrostatic deflection mechanism. The electrostatic deflection mechanism can facilitate drop charging and drop deflection using a single electrode per jet, like the one described in U.S. Pat. No. 4,636,808, or through the use of separate drop charging and drop deflection electrodes. Typically an individual drop charging electrode is associated with each jet, as described in U.S. Pat. No. 4,636,808. Alternative electrostatic deflection mechanisms use a single drop charging electrode for an array of nozzles, as described in U.S. Pat. No. 7,938,516 or U.S. Published Application No. 20100033542.
As shown in
In typical printheads, the jetting module 48 contains a large number of nozzles 50, each with an associated drop forming device 28. Each drop forming device 28 receives sequences of drop formation waveforms 27 from a corresponding waveform source 98. The drop formation waveforms 27 typically are waveforms of the voltage applied to the drop forming device 28. Alternatively the drop formation waveforms 27 can be waveforms of the current applied to the drop forming device 28. While the drop forming device can be actuated to form large drops and small drops of any desired volume ratio up to 10:1, including both integer and non-integer ratios, the mechanism control circuits 26 containing the waveform sources 98 for the array of drop forming devices 28 become unacceptably complex if the periods of the one or more large-drop waveforms are not all equal to each other. Similarly, the periods of the one or more small-drop waveforms should also be equal to each other to avoid inacceptable control circuit complexity. Furthermore to avoid unacceptable complexity in the control circuits, the period of the large-drop waveforms should be equal to the period of the small-drop waveforms times an integer N; 2≦N≦10. In prior art systems having arrays of nozzles and independent drop selection per nozzle, these limitations on the periods of the large-drop waveforms and the small-drop waveforms have restricted the volume ratio of large-volume drops to small-volume drops to integer values.
The present invention overcomes this limitation of the art by providing a jetting module 48 including a nozzle 50 and a drop forming mechanism 28; providing a liquid to the jetting module 48 under pressure sufficient to cause a liquid stream to jet from the nozzle 50; providing a small-drop waveform, the small drop waveform having a starting endpoint and a trailing endpoint, the small-drop waveform having a small-drop period XS, the small-drop waveform including a small drop volume-control pulse, the small-drop volume-control pulse of the small-drop volume-control pulse having centroid, the centroid of the small-drop volume-control pulse being at a first defined time relative a predefined one of the starting endpoint and the trailing endpoint of the small-drop waveform; providing a large-drop waveform, the large-drop waveform having a starting endpoint and a trailing endpoint, the large-drop waveform having a large-drop period XL, where XL=N*XS and N is an integer greater than one, the large-drop waveform including a large-drop volume-control pulse, the large-drop volume-control pulse having centroid; wherein the centroid of the large-drop volume-control pulse being at a second defined time relative to the corresponding one of the starting endpoint and the trailing endpoint, the second defined time being different from the first defined time; applying to the drop forming mechanism a sequence of drop formation waveforms in which a small-drop waveform applied after another identical small-drop waveform causes a small drop of volume Vs to be formed; applying a small-drop waveform after a large-drop waveform causes a small drop of volume Vs2 to be formed, where VS2 is not equal to VS; applying a large-drop waveform after another identical large-drop waveform causes a large drop of volume VL to be formed, where VL˜N*Vs; and applying a large-drop waveform after a small-drop waveform causes a large drop of volume VL2 to be formed, where VL2 is not equal to VL.
To enable the invention to be better understood, prior art waveforms for the formation of large drops 56 and small drops 54 will first be described, and then waveforms for several embodiments of the invention will be described.
For this embodiment, delaying the drop forming pulse 122 within the large-drop waveform 120 caused the centroid 126 of the drop forming pulse 122 to be at a time interval T2 relative to the starting endpoint 130 of the large-drop waveform 120. This time interval is different from the time interval T1 between the centroid 106 of the drop forming pulse 102 of the small-drop waveform 100 and the starting endpoint 130 of the small-drop waveform 100. When consecutive small-drop waveforms 100 are applied to the drop forming mechanism 28, a small drop of volume VS is formed. When consecutive large-drop waveforms 120 are applied to the drop forming mechanism 28, a large drop of volume VL is formed, where VL=3VS. Applying a large-drop waveform 120 immediately after a small-drop waveform 100 causes a small drop to be formed having a volume VS2, which is different from VS. Applying a small-drop waveform 100 immediately after a large-drop waveform 120 produces a large drop having a volume VL2, which is different from VL. In this embodiment, the volume VS2 is larger than VS, and the volume VL2 is less than VL.
In the embodiment described above, the timing of the drop forming pulse 122 of the large-drop waveform 120 was shifted so that the leading edge of the drop forming pulse 122 was not at the starting endpoint 130 of the large-drop waveform 120, while the leading edge of the drop forming pulse 102 of the small-drop waveform 100 was at the starting endpoint 130 of the small-drop waveform 100. As described above, this reduced the volume of a large drop created by a large-drop waveform 120 followed by a small-drop waveform 100; VL2<VL, and increased the volume of a small drop created by a small-drop waveform 100 followed by a large-drop waveform 120; VS2>VS. In an alternate embodiment shown in
In the embodiments of the invention described above, the leading edge of drop forming pulse or volume-control pulse of either the small-drop waveform or the large-drop waveform was at the starting endpoint of the waveform, while the volume-control pulse of the other of the small-drop waveform or the large-drop waveform was delayed so that the leading edge of the delayed volume-control pulse was not at the starting endpoint of the corresponding waveform. The centroid of the drop forming pulse of the small-drop waveform is at a first time interval T1 relative to the starting edge of the small-drop waveform. The centroid of the drop forming pulse of the large-drop waveform is at a second time interval T2 relative to the starting edge of the large-drop waveform. The second time interval T2 is different from the first time interval T1.
In each of these embodiments, varying the amount by which the timing of the drop-forming pulse of the small-drop waveform and/or of the large-drop waveform is shifted varies the difference T2−T1, the volume difference between VL2 and VL and the volume difference between VS1 and VS can be varied. By appropriate selection of the timing of the drop-forming pulses, the volume difference between the small drop VS2 and small drop volume VS, |VS2−VS| can be selected to be greater than of 0.03*VS, or greater than 0.05*VS, or greater than and 0.1*VS. It tends not to be practical to adjust the drop-forming pulse timings to produce a volume difference between the small drop VS2 and small drop volume VS, |VS2−VS|, of greater than 0.3*VS.
The embodiments described above have a large-drop waveform with a period of XL which is equal to three times the period XS of the small-drop waveform. When consecutive large-drop waveforms are applied, the resulting large drop has a volume VL=3*VS. The invention is not limited to a factor of three in waveform periods between the large-drop waveforms and the small-drop waveforms. In general, the ratio between the large-drop waveform period and the small-drop waveform period can be any integer value. The ratio in the periods will be denoted by N. In the more generalized form, the consecutive small-drop waveforms produce small drops of volume VS, and consecutive large-drop waveforms produce large drops of volume VL, where VL=N*VS. Applying a large-drop waveform immediately after a small-drop waveform causes a small drop to be formed having a volume VS2, which is different from VS. Applying a small-drop waveform immediately after a large-drop waveform produces a large drop having a volume VL2, which is different from VL.
U.S. Pat. No. 8,087,740 discloses that drop formation pulses can be composed of a packet of sub-pulses. This is effective when the time between the sub-pulses is less than the response time of the drop forming device, for example when the time between the sub-pulses is less than the thermal response time of heater used as a drop forming device. In such cases, the packet of sub-pulses acts on the liquid jet as a single pulse having a leading edge corresponding to the leading edge of the first sub-pulse in the packet and a trailing edge corresponding to the trailing edge of the last sub-pulse in the packet. The centroid of the drop-forming pulse in such cases corresponds to the centroid of the integrated packet of the sub-pulses rather than to centroid of one of the sub-pulses.
The present invention permits the drop volume of the large drops and the small drops to be adjusted. In some embodiments, a plurality of sets of small-drop waveforms and large-drop waveforms are defined, each set of defined waveforms producing different print drop volumes. In one embodiment, one of the sets of small-drop waveforms and large-drop waveforms is selected and employed for printing based at least in part on the desired print drop volume. On another embodiment the flow rate of ink through the printhead nozzles is measured. Based at least in part on the measured flow rate a set of waveforms is selected for use in the printhead from the plurality of defined sets of small-drop waveforms and large-drop waveforms. In some embodiments, the selected set of waveforms is stored in the printhead. In other embodiments, the plurality of defined sets of small-drop waveforms and large-drop waveforms, are stored in memory of the printing system controller.
In another embodiment, the invention is used to reduce coverage variations across the printhead nozzle array produced by variations is nozzle geometry. From the plurality of defined sets of waveforms, one set of small-drop waveforms and large-drop waveforms is used to create drops from a first portion of the nozzle array, and a second set of small-drop waveforms and large-drop waveforms is used to create drops from a second portion of the nozzle array.
It has been found that the invention, by altering the volume of the print drop, alters the momentum of the print drop. As a result of the change in momentum of the print drop the deflection of the print drop by the drop deflection mechanism can be altered. As a result the impact location of the print drop on the print media can be altered. By appropriate use of the drop volume altering waveforms, fine adjustments can be made to the width of character strokes for improved image quality purposes. In some embodiments of the invention, the set of waveforms used for printing can include a small drop waveform and a first large-drop waveform and a second large-drop waveform. The second large-drop waveform has a period equal to the period of the first large-drop waveform, the second large-drop waveform including a large-drop forming pulse, wherein the waveform of the second large-drop waveform is distinct from the waveform of the first large-drop waveform. In certain embodiments, the centroid 186 of the drop forming pulse of the small-drop waveform is at a first time interval T1 relative to the one of the endpoints of the small-drop waveform and the centroid 186 of the drop forming pulse of the first large-drop waveform is at a second time interval T2 relative to the corresponding endpoint of the large-drop waveform; and where the second time interval T2 is different from the first time interval T1. The second large-drop waveform has a drop forming pulse having a centroid at a third time interval T3 relative to the corresponding endpoint of the second large-drop waveform. The third time interval T3 is different from the second time interval T2.
In some embodiments of the invention, the set of waveforms used for printing can include a first small-drop waveform and a second small-drop waveform and a large-drop waveform. The second small-drop waveform has a period equal to the period of the first small-drop waveform, the second small-drop waveform including a small-drop volume-control pulse. The waveform of the second small-drop waveform is distinct from the waveform of the first small-drop waveform. The centroid 186 of the drop forming pulse of the first small-drop waveform is at a first time interval T1 relative to the predetermined one of the starting endpoint and the trailing endpoint of the small-drop waveform, centroid 186 of the drop forming pulse of the second small-drop waveform is at a third time interval T3 relative to the corresponding one of the starting endpoint and the trailing endpoint of the second small-drop waveform and the centroid 186 of the drop forming pulse of the large-drop waveform is at a second time interval T2 relative to the corresponding starting endpoint and the trailing endpoint of the large-drop waveform.
Similarly in some embodiments of the invention the set of waveforms used include a first small-drop waveform and a second small-drop waveform and a large-drop waveform. The second large-drop waveform has a period equal to the period of the first large-drop waveform, the second large-drop waveform including a large-drop volume-control pulse. The waveform of the second large-drop waveform is distinct from the waveform of the first large-drop waveform. The centroid 186 of the drop forming pulse of the first large-drop waveform is at a first time interval T1 relative to the predetermined one of the starting endpoint and the trailing endpoint of the first large-drop waveform and the centroid 186 of the drop forming pulse of the second large-drop waveform is at a second time interval T2 relative to the corresponding one of the starting endpoint and the trailing endpoint of the second large-drop waveform, and the centroid of the drop forming pulse of the small drop waveform is at a third time interval relative to the corresponding one of the starting endpoint and the trailing endpoint of the small-drop waveform. The use of multiple large-drop waveforms or multiple small-drop waveforms provides more flexibility in terms of the amount of ink that can be printed on a pixel.
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.
This application claims the benefit of U.S. Provisional Patent Application No. 61/608,674, filed Mar. 9, 2012, entitled “Method for Altering Drop Size in a Continuous Inkjet Printer” by Robert Link et al, which is incorporated herein by reference in its entirety.
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|---|---|---|---|
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| 4636808 | Herron | Jan 1987 | A |
| 6079821 | Chwalek et al. | Jun 2000 | A |
| 6457807 | Hawkins et al. | Oct 2002 | B1 |
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| Number | Date | Country | |
|---|---|---|---|
| 20130235103 A1 | Sep 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61608674 | Mar 2012 | US |
