Patent Application
20070257971
This invention relates generally to the field of digitally controlled printing and liquid patterning devices, and in particular to continuous ink jet systems in which a liquid stream breaks into drops, some of which are selectively deflected.
Traditionally, digitally controlled liquid patterning capability is accomplished by one of two technologies. In each technology, a patterning liquid is fed through channels formed in a printhead. Each channel includes a nozzle from which drops of liquid are selectively extruded and deposited upon a medium. When color marking is desired, each technology typically requires independent liquid supplies and separate liquid delivery systems for each liquid color used during printing.
The first technology, commonly referred to as “drop-on-demand” ink jet printing, provides liquid drops for impact upon a recording surface using a pressurization actuator (thermal, piezoelectric, etc.). Selective activation of the actuator causes the formation and ejection of a flying drop that crosses the space between the printhead and the pattern receiving media, striking the media. The formation of printed images or other patterns is achieved by controlling the individual formation of liquid drops, based on data that specifies the pattern or image.
Conventional “drop-on-demand” ink jet printers utilize a pressurization actuator to produce the ink jet drop at orifices of a print head. Typically, the pressurization is accomplished by rapidly displacing a portion of the liquid in individual chambers that supply individual nozzles. Displacement actuators are most commonly based on piezoelectric transducers or vapor bubble forming heaters (thermal ink jet). However, thermomechanical and electrostatic membrane displacement has also been disclosed and used.
U.S. Pat. No. 4,914,522 issued to Duffield et al., on Apr. 3, 1990 discloses a drop-on-demand ink jet printer that utilizes air pressure to produce a desired color density in a printed image. Liquid in a reservoir travels through a conduit and forms a meniscus at an end of an inkjet nozzle. An air nozzle, positioned so that a stream of air flows across the meniscus at the end of the liquid nozzle, causes the liquid to be extracted from the nozzle and atomized into a fine spray. The stream of air is applied at a constant pressure through a conduit to a control valve. The valve is opened and closed by the action of a piezoelectric actuator. When a voltage is applied to the valve, the valve opens to permit air to flow through the air nozzle. When the voltage is removed, the valve closes and no air flows through the air nozzle. As such, the liquid dot size on the image remains constant while the desired color density of the liquid dot is varied depending on the pulse width of the air stream.
The second technology, commonly referred to as “continuous stream” or “continuous” ink jet printing (CIJ), uses a pressurized liquid source which produces a continuous stream of liquid drops. This technology is applicable to any liquid patterning or selection application. Conventional continuous ink jet printers utilize electrostatic charging devices that are placed close to the point where a filament of working fluid breaks into individual drops. The drops are electrically charged and then deflected to an appropriate location by an electric field of self-image charge in a grounded conductor. When no drop deposition is desired at a particular location on the receiver medium, the drops are deflected into an liquid capturing mechanism, a drop catcher or gutter, and either recycled or discarded. When a print or pattern drop is desired, the drops are not deflected to the drop catcher and are allowed to strike the receiver media. Alternatively, deflected drops may be allowed to strike the media, while non-deflected drops are collected in the liquid capturing mechanism.
Conventional continuous ink jet printers utilize electrostatic charging devices and deflector plates that require addressable electrical components that must be very closely and precisely aligned to the continuous streams of patterning liquid without touching them. The patterning liquid, the liquid, must be sufficiently conductive to allow drop charging within a few microseconds. While serviceable, these electrostatic deflection printheads are difficult to manufacture at low cost and suffer many reliability problems do to shorting and fouling of the drop charging electrodes and deflection electric field plates. A continuous ink jet system that does not rely on drop charging would greatly simplify printhead manufacturing, and eliminate the need for highly conductive working fluids.
U.S. Pat. No. 3,709,432, issued to Robertson, on Jan. 9, 1973, discloses a method and apparatus for stimulating a filament of working fluid causing the working fluid to break up into uniformly spaced liquid drops through the use of transducers. The lengths of the filaments before they break up into liquid drops are regulated by controlling the stimulation energy supplied to the transducers, with high amplitude stimulation resulting in short filaments and low amplitudes resulting in long filaments. A flow of air is generated uniformly across all the paths of the fluid at a point intermediate to the ends of the long and short filaments. The air flow affects the trajectories of the filaments before they break up into drops more than it affects the trajectories of the liquid drops themselves. By controlling the lengths of the filaments, the trajectories of the liquid drops can be controlled, or switched from one path to another. As such, some liquid drops may be directed into a catcher while allowing other liquid drops to be applied to a receiving member. The physical separation or amount of discrimination between the two drop paths is very small and difficult to control.
U.S. Pat. No. 4,190,844, issued to Taylor, on Feb. 26, 1980, discloses a single jet continuous ink jet printer having a first pneumatic deflector for deflecting non-printing drops to a catcher and a second pneumatic deflector for oscillating printing drops (Taylor '844 hereinafter). A printhead supplies a filament of working fluid that breaks into individual liquid drops. The liquid drops are then selectively deflected by a first pneumatic deflector, a second pneumatic deflector, or both. The first pneumatic deflector has a diaphragm that either opens or closes a nozzle depending on one of two distinct electrical signals received from a central control unit. This determines whether the liquid drop is to be deposited on the medium or not. The second pneumatic deflector is a continuous type having a diaphragm that varies the amount a nozzle is open depending on a varying electrical signal received the central control unit. This deflects printed liquid drops vertically so that characters may be printed one character at a time. If only the first pneumatic deflector is used, characters are created one line at a time, being built up by repeated traverses of the printhead.
While this method does not rely on electrostatic means to affect the trajectory of drops it does rely on the precise control and timing of the first (“open/closed”) pneumatic deflector to create printed and non-printed liquid drops. Such a system is difficult to manufacture and accurately control. The physical separation or amount of discrimination between the two drop paths is erratic due to the uncertainty in the increase and decrease of air flow during switching resulting in poor drop trajectory control and imprecise drop placement. Pneumatic operation requiring the air flows to be turned on and off is necessarily slow in that an inordinate amount of time is needed to perform the mechanical actuation as well as time associated with the settling any transients in the air flow. Further, it would be costly to manufacture a closely spaced array of uniform first pneumatic deflectors necessary to extend the Taylor '844 concept to a plurality of closely spaced jets.
U.S. Pat. No. 5,963,235 issued to Chwalek, et al., on Oct. 5, 1999 discloses a continuous ink jet printer that uses a micromechanical actuator that impinges a curved control surface against the continuous stream filaments prior to break-up into droplets (Chawlek '235 hereinafter). By manipulating the amount of impingement of the control surface the stream may be deflected, along multiple flight paths. While workable, this apparatus tends to produce large anomalous swings in the amount of stream deflection as the surface properties are affected by contact with the working fluid.
U.S. Pat. No. 6,509,917 issued to Chwalek et al., on Jan. 21, 2003, discloses a continuous ink jet printer that uses electrodes located downstream of the nozzle, closely spaced to the unbroken fluid column, to deflect the continuous stream filament before breaking into drops (Chawlek '917 hereinafter). By imposing a voltage on the electrodes drops may be steered along different deflection paths. This approach is workable however the apparatus prone to electrical breakdown due to a build up-of conductive debris around the deflection electrodes.
U.S. Pat. No. 6,474,795 issued to Lebens, et al., on Nov. 5, 2002 discloses a continuous ink jet printer that uses a dual passage way to supply fluid to each nozzle (Lebens '795 hereinafter). One fluid passageway is located off-center to the nozzle entry bore and has a micromechanical valve that regulates the amount of flow that is supplied. The off-center flow from this passageway causes the jet to be emitted at an angle. Thus by manipulating this valve, drops may be directed to different deflection pathways. This approach is workable however the printhead structure is more complex to fabricate and it is difficult to achieve uniform deflection from all of the jets in a large array of jets.
U.S. Pat. No. 6,079,821, issued to Chwalek et al., on Jun. 27, 2000, discloses a continuous ink jet printer that uses actuation of asymmetric heaters to create individual liquid drops from a filament of working fluid and deflect those liquid drops (Chwalek '821 hereinafter). A printhead includes a pressurized liquid source and an asymmetric heater operable to form printed liquid drops and non-printed liquid drops. Printed liquid drops flow along a printed liquid drop path ultimately striking a print media, while non-printed liquid drops flow along a non-printed liquid drop path ultimately striking a catcher surface. Non-printed liquid drops are recycled or disposed of through a liquid removal channel formed in the catcher.
While the ink jet printer disclosed in Chwalek '821 works extremely well for its intended purpose, the amount of physical separation between printed and non-printed liquid drops is limited which may limit the robustness of such a system. Simply increasing the amount of asymmetric heating to increase this separation will result in higher temperatures that may decrease reliability.
U.S. Pat. No. 6,505,921 issued to Chwalek, et al. on Jan. 14, 2003, discloses and claims an improvement over Chwalek '821 whereby a plurality of thermally deflected liquid streams is caused to break up into drops of large and small volumes, hence, large and small cross-sectional areas (Chwalek '921 hereinafter). Thermal deflection is used to cause smaller drops to be directed out of the plane of the plurality of streams of drops while large drops are allowed to fly along nominal “straight” pathways. A uniform gas flow is imposed in a direction perpendicular and across the array of streams of drops of cross-sectional areas. This perpendicular gas flow applies more force per mass to drops having smaller cross-sections than to drops having larger cross-sections, resulting in an amplification of the deflection acceleration of the small drops. Such gas flow deflection amplification can provide needed additional separation between drops to be captured in a gutter versus drops that are allowed to deposit on a medium. However, to be effective, the apparatus of Chwalek '921 requires a substantial difference in large and small drop volumes which has the effect reducing printing speed as time and liquid volume is spent creating large drops.
U.S. Pat. No. 6,508,542 issued to Sharma, et al. on Jan. 21, 2003, also discloses and claims an improvement over Chwalek '821 that uses a gas flow to amplify the spatial separation between drops traveling along two diverging pathways, so as to improve the reliability of drop capture (Sharma '542 hereinafter). Sharma '542 teaches a gas flow that is emitted in close proximity to a gutter drop capture lip and that is generally opposed to both the nominal and thermally deflected flight paths of drops. The gas flow of Sharma '542 is illustrated as further splitting the drops into two pathways and is positioned so that the gas flow is losing convergence at a point where the thermally deflected drops are physically separating.
Effectively, the apparatus and method taught by Sharma '542 increases drop pathway divergence by reducing the drop velocity in the direction of the media and gutter. That is, by slowing the flying drops, more time is provided for the off-axis thermal deflection acceleration imparted at the nozzle to build up into more spatial divergence by the time the capture lip of the gutter is reached. The interaction of the gas flow of Sharma '524, and the diverging drop pathways, will also be very dependent on the time varying pattern of drops inherent in image or other pattern printing. Different drop sequences with be differently deflected, resulting in the addition of data dependent drop placement error for the printed drops. Further, the approach of Sharma '542 may be unsuitable to implement for a large array of jets as it is difficult to achieve sufficiently uniform gas flow behavior along a wide slit source so that the point of transition to incoherent gas flow would occur at the same distance from the nozzle for all jets of the array.
Notwithstanding the several inventions described above, there remains a need for a robust, high speed, high quality liquid patterning system. Such a system may be realized using continuous ink jet technology that does not rely on drop charging and electrostatic drop deflection. Further, such a system could be realized if sufficient drop deflection can be achieved to allow robust drop capturing without sacrificing print speed and pattern resolution by the formation of large volume drops or long flight paths from nozzle to medium. Finally, such a system requires simplicity of design that facilitates fabrication of large arrays of closely space jets.
The foregoing and numerous other features, objects and advantages of the present invention will become readily apparent upon a review of the detailed description, claims and drawings set forth herein. These features, objects and advantages are accomplished by constructing a drop deflector apparatus for a continuous drop emission system comprising a plurality of drop nozzles emitting a plurality of continuous streams of a liquid that breaks up into streams of drops of substantially uniform drop volume having nominal flight paths that are substantially parallel and substantially within a nominal flight plane. A plurality of path selection elements is provided corresponding to the plurality of continuous streams of drops operable to firstly deflect individual drops from the corresponding continuous stream of drops along a first deflection flight path diverging from the nominal flight path. Further, a plurality of gas nozzles is provided which generate a plurality of localized gas flows, positioned along one of the first deflection flight paths or the nominal flight paths, wherein the localized gas flows are oriented so as to cause a substantial second deflection of one of the firstly deflected drops or the nominal drops in a direction perpendicular to the nominal flight plane without causing a substantial deflection of drops following the other of the first deflection flight paths or the nominal flight paths.
The present inventions are also configured to have a gas nozzles associated with each drop emission nozzle or, alternatively, a gas nozzle shared with two adjacent drop emission nozzles.
The present inventions are additionally configured to use path selection elements comprising at least one of a heater apparatus that non-uniformly heats the corresponding continuous stream of liquid, an electrostatic force apparatus that attracts the corresponding continuous stream of liquid in the direction of the first deflection flight path, a moveable surface in contact with the corresponding continuous stream of liquid that is moveable in the direction of the first deflection flight path or a flow valve in a fluid path leading to the corresponding continuous stream of liquid wherein the flow valve is operable to cause an asymmetric flow through the corresponding one of the plurality of drop nozzles.
The present inventions further include methods of forming a liquid pattern on a medium based on pattern data comprising providing a plurality of drop nozzles emitting a plurality of continuous streams of drops of substantially uniform drop volume having nominal flight paths that are substantially parallel, substantially within a nominal flight plane and that impinge the medium. Further forming the liquid pattern by firstly deflecting individual drops from the plurality of continuous streams of drops, based on pattern data, along first deflection flight paths that diverge from the nominal flight path while remaining substantially within the nominal flight plane and then secondly deflecting drops traveling along one of the first deflection flight paths or the nominal flight paths in a direction perpendicular to the nominal flight plane by a plurality of localized gas flows without causing a substantial deflection of drops following the other of the first deflection flight paths or the nominal flight paths. The secondly deflected drops are captured in a drop catcher thereby forming the liquid pattern on the media comprised of drops that are not secondly deflected.
These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.
In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in which:
FIGS. 5(a) and 5(b) show schematic top views of a single continuous stream of fluid with and without the application of a synchronizing thermal energy perturbation according to a preferred embodiment of the present invention;
FIGS. 6(a), 6(b) and 6(c) show representations of energy pulse sequences for stimulating synchronous break-up of a fluid jet by heater resistors and first deflection by heater resistors according to a preferred embodiment of the present invention;
FIGS. 7(a), 7(b) and 7(c) show representations of balanced energy pulse sequences for stimulating synchronous break-up of a fluid jet by heater resistors and first deflection by heater resistors according to a preferred embodiment of the present invention;
FIGS. 8(a) and 8(b) show schematic top views of a single continuous stream of drops being firstly deflected to one side then the other side by heater resistors according to a preferred embodiment of the present invention;
FIGS. 14(a) and 14(b) shows a schematic front view and a top view of an electrostatic deflection apparatus for firstly deflecting drops according to a preferred embodiment of the present 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. Functional elements and features have been given the same numerical labels in the figures if they are the same element or perform the same function for purposes of understanding the present inventions. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art.
Referring to
The liquid pattern deposition system further includes a source of the image or pattern data 410 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 bitmap image data by controller 400 and stored for transfer to a multi-jet drop emission printhead 10 via a plurality of printhead transducer circuits 412 connected to printhead electrical interface 20. The bit map image data specifies the deposition of individual drops onto the picture elements (pixels) of a two dimensional matrix of positions, equally spaced a pattern raster distance, determined by the desired pattern resolution, i.e. the pattern “dots per inch” or the like. The raster distance or spacing may be equal or may be different in the two dimensions of the pattern.
Controller 400 also creates drop synchronization signals to the printhead transducer circuits that are subsequently applied to printhead 10 to cause the break-up of the plurality of fluid streams emitted into drops of substantially the same size and with a predictable timing. Printhead 10 is illustrated as a “page wide” printhead in that it contains a plurality of jets sufficient to print all scanlines across the medium 300 without need for movement of the printhead itself.
Recording medium 300 is moved relative to printhead 10 by a recording medium transport system 250, which is electronically controlled by a media transport control system 414, and which in turn is controlled by controller 400. The recording medium transport system shown in
Pattern liquid is contained in a liquid reservoir 418 under pressure. In the non-printing state, continuous drop streams are unable to reach recording medium 300 due to a fluid gutter (not shown) that captures the stream and which may allow a portion of the liquid to be recycled by a liquid recycling unit 416. The liquid recycling unit 416 reconditions the liquid and feeds it back to reservoir 418 via printhead fluid outlet 210. The liquid recycling unit may also be configured to apply a vacuum pressure to outlet 210 to assist in liquid recovery and control of the gas flow through printhead 10. Such liquid recycling units are well known in the art. The liquid 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 liquid. A constant liquid pressure can be achieved by applying pressure to liquid reservoir 418 under the control of liquid supply controller 424 that is managed by controller 400.
The liquid is distributed via a liquid supply line entering printhead 10 at liquid inlet port 42. The liquid preferably flows through slots and/or holes etched through a silicon substrate of printhead 10 to its front surface, where a plurality of nozzles and printhead transducers are situated. In some preferred embodiments of the present inventions the printhead transducers are resistive heaters. In other embodiments, more than one transducer per jet may be provided including some combination of resistive heaters, electric field electrodes and microelectromechanical flow valves. With printhead 10 fabricated from silicon, it is possible to integrate some portion of the printhead transducer control circuits 412 with the printhead.
A secondary drop deflection apparatus, described in more detail below, is configured downstream of the liquid drop emission nozzles. This secondary drop deflection apparatus comprises a plurality of localized gas flows that impinge individual drops in the plurality of streams of drops flying along predetermined paths based on pattern data. A supply of pressurized gas 420, controlled by the controller 400 through a gas pressure control apparatus 422, is connected to printhead 10 via gas supply inlet 95
Localized gas flows 96 are produced by gas deflector apparatus 98 which is formed of a gas distribution manifold 91 with a gas flow nozzle layer 93 and gas distribution manifold cover 97. Pressurized gas 90 is supplied from an external source via pressurized gas inlet 95. The pressurized gas 90 flows through a distribution system to a gas flow separation passageway 92 that ends in a gas flow nozzle 94. The gas flow emitted by gas flow nozzle 94 is a highly localized gas jet 96 that is arranged to forcefully impinge individual drops 84 in stream 122 that fly through it, deflecting them to the fluid capture apparatus 200. The localized gas flow may be visualized as a truncated cone shaped flow of high velocity gas having an initial cross sectional area equal to that of gas flow nozzle 94 and diverging in a Gaussian distribution of velocity with distance away from gas nozzle layer 93. The cross-sectional area of the cone of localized gas flow is characterized as the aerial extent, or diameter Dgf, from the center of the flow out to the first standard deviation of gas flow velocity, Vg.
Gas flow nozzles 94 are spaced away from the path of the stream of drops 122 by a distance Sgf that is chosen to be small enough that the diameter of localized gas flow 96, Dgf, has not diverged to an extent large enough to substantially impinge more than one drop in drop stream 122 at a time. Several factors are involved in the selection of separation distance, Sgf, including the area or effective diameter, Dgn, of gas nozzle 94, the pressure of the supplied gas 90, the diameter of the drops, Dd, the spacing or wavelength, λd, of drops in the synchronized stream of drops and the spacing Sdn of drop nozzles, hence drop streams, along the array of drop streams in printhead 10. As a general rule, the diameter of the gas flow, Dgf, at separation distance Sgf should not exceed the drop diameter Dd. The array of gas flow nozzles 94 is positioned downstream from the drop generator nozzle layer 14 an appropriate distance Lg, to be explained further hereinbelow.
The pressurized gas source 420 for the gas deflector apparatus 98 can be of any type and may include any number of appropriate plenums, conduits, blowers, fans, etc. Gas distribution manifold 91 may be any appropriate shape. The nature of the gas used may be any that is economically available and is safe and effective for the liquid pattern application system involved, for example air, nitrogen, argon, and the like.
Fluid capture apparatus 200 is comprised of a fluid capture manifold 220 having a captured fluid return passage 202 and formed with a drop capture or gutter lip 206. Gutter lip 206 defines the cleavage point between drops that are captured and drops that are permitted to fly to medium 300. Drops must be sufficiently deflected by localized gas flows 96 to travel downward in the illustration, below gutter lip 206. Fluid capture apparatus 200 is illustrated with a porous media component 204 that serves as a landing surface 214 for drops 84 deflected by localized gas flows 96. It is desirable that gas deflected drops impinge the porous landing surface rather than impact gutter lip 206 to minimize the production of liquid mist.
Porous media component 204 may also be formed with a slot 212 that is opposite the location of gas flow nozzles 94, that is, located at a distance Lgf downstream of drop generator nozzle layer 14. A vacuum or negative pressure source is applied to the fluid capture manifold by the liquid recycling unit 416 via fluid capture outlet 208. A flow of captured gas and liquid 62 is established as indicated by flow lines 210. Captured fluid 62 is separated from captured gasses by the liquid recycling unit 416 for possible re-introduction into the liquid reservoir. The fluid capture apparatus captures both the localized gas flows produced by gas deflector 98 as well as drawing in ambient gases entrained by the deflected drops 84.
A front face view of a single nozzle 50 of a preferred printhead embodiment is illustrated in
Two resistive heaters, side one heater 30, and side two heater 38, are formed on a front face layer on opposite sides of the nozzle bore, wherein the term “side” means along the direction of the array of nozzles as is seen in
The spacing away from the nozzle rim and the width of the side heaters along the direction of the array of nozzles are an important design parameters. Typically the inner edge of the side heater resistors is positioned approximately 1.5 microns to 0.5 microns away from the nozzle edge. The outer edge, hence width, of the side heater resistors is typically placed 1 micron to 3 microns from the inner edge of the side heater resistors.
One effect of pulsing side heaters 30 and 38 on a continuous stream of fluid 62 is illustrated in a top side view in FIGS. 5(a) and 5(b). FIGS. 5(a) and 5(b) illustrates a portion of a drop generator substrate 12 around one nozzle 50 of the plurality of nozzles. Pressurized fluid 60 is supplied to nozzle 50 via liquid supply chamber 48 and flow separation passageway 44. Nozzle 50 is formed in drop nozzle front face layer 14, and possibly in thermal and electrical isolation layer 26. Side heater resistors 30 and 38 are also illustrated.
In
In
FIGS. 6(b) and 6(c) illustrate two pulse sequences that may be used to not only synchronize jet break-up but also to deflect a portion of the fluid in a sideward deflection. For example in
Alternatively,
FIGS. 7(a), 7(b) and 7(c) show representations of balanced energy pulse sequences for stimulating synchronous break-up of a fluid jet by heater resistors and first deflection by heater resistors according to additional preferred embodiments of the present inventions. The energy pulses applied to the side one 30 and side two 38 heaters are adjusted so that the same amount of energy in total is applied to the heaters during each drop synchronization period. Balancing the energy pulses in this manner ensures that a relatively constant average power is applied to the heaters adjacent each jet, so that a relatively constant amount of waste heat is dissipated by thermal management pathways that are provided for each jet.
For the purpose of understanding the present inventions it is necessary only to recognize that the application of asymmetric heat at the nozzle of a continuous jet can deflect the jet. Practically achievable deflection amounts are of the order of a few degrees. For the present inventions it is assumed that thermal deflection or deflection by other means to be discussed below, achieves deflections of 0.5 to 2.0 degrees away from the nominal, undeflected flight paths of undeflected drop streams.
The intended position of the localized gas flows is particularly indicated by the flow drawn between drop nozzles 50j and 50j+1. The array of gas flow nozzles is positioned a distance Sgf away from the drop nozzle array axis. Pressurized gas 90 is forced through the gas flow nozzles 94, creating a localized jet of gas having a peak velocity of Vg, and a spatially diverging, generally Gaussian profile 99. For the purposes of the present inventions, an important design parameter is the effective cross-sectional diameter, Dgf, of the localized gas flow 96 at the distance Sgf from the gas flow nozzle plate 93. The effective cross-sectional diameter of the localized gas flow 96 is designated as the effective diameter of the first standard deviation in gas velocity as measured or calculated from modeling. Typically, the diameter of the gas flow, Dgf, is less than twice the uniform drop diameter, Dd, being emitted, that is, Dgf<2 Dd. For increased latitude to variations in gas flow nozzle diameters, shapes and gas distribution manifold pressure variations, it is preferable to design the localized gas flow diameter to be equal to or less than the operating drop diameter, Dgf≦Dd. This condition is met if the gas nozzle effective diameter is equal to or less than the drop nozzle diameter, Dgn≦Ddn, and the spacing Sgf is approximately 20 Dgn or less, Sgf≦Ddn.
Many drops 84, drawn as open fill, are firstly deflected by side deflectors such as the heater resistors discussed above in connection with
The slight first deflection imparted to the fluid forming drops 84 accumulates to an “off-axis” amount of approximately one-half the drop nozzle spacing Sdn after traveling the distance Lgf, the position of the localized gas flows 96. Typically, first deflection means will impart approximately a deflection of 0.50 to 2.00 to the fluid at the nozzle. Therefore Lgf will typically be in the following range:
where Sdn is the drop nozzle spacing. For drop nozzle spacing in the range 84 microns to 21 microns, Lgf will be typically in the range: 300 microns to 4800 microns. For a preferred embodiment wherein the nozzle spacing is ˜42 microns for 600 dpi printing and the first deflection is ˜1°, Lgf˜1200 microns according to Equations 1 and 2.
Localized gas flows 96 are indicated in
The localized gas flows 96 are designed to impart minimal deflection to undeflected drops 82 so as not to cause errors in the landing positions of the liquid pattern forming drops 82. Gas flows 96 may set up a low velocity, generally uniform, gas flow that slightly and equally deflects all drops following nominal flight paths. Such uniform deflection of printing drops is acceptable and has the affect of slightly shifting the position of liquid pattern formation relative to the receiving medium. However, the velocity of deflection gas flows, where they intersect the flight paths of nominal drops, is constrained by design so that the undeflected drops 82 are not substantially deflected out of the nominal flight plane in a pattern-data-dependent fashion. A substantial pattern-dependent deflection would be one that shifted the landing point of a drop by more than 30% of a raster distance.
In
An alternative preferred embodiment of the present inventions is illustrated in
Further preferred embodiments of the present inventions are illustrated in
For these embodiments wherein firstly deflected drops are used to form the liquid pattern, the localized gas flows 96 are designed to impart minimal deflection to firstly deflected drops so as not to cause errors in the landing positions of these liquid pattern forming drops. The velocity of deflection gas flows, where they intersect the flight paths of firstly deflected drops, is constrained by design so that the firstly deflected drops 82 are not substantially deflected out of the nominal flight plane in a pattern-data-dependent fashion. A substantial pattern-dependent deflection would be one that shifted the landing point a drop by more than 30% of a raster distance.
Additional embodiments of the present inventions may be configured using asymmetric first deflection means other than the resistive heaters apparatus discussed heretofore. FIGS. 14(a) and 14(b) illustrate an electrostatic deflection apparatus that may be used to perform the first deflection.
Electrostatic first deflection may be used in combination with any of the embodiments of the gas deflection subsystem and fluid capture subsystem previously discussed. A liquid patterning apparatus equipped with asymmetric electrostatic first deflection will function in analogous fashion to one equipped with asymmetric resistive heating. That is, the system may be configured to print with undeflected drops as discussed in connection with
A side view of the nozzle region of such a drop generator is illustrated in
The microvalve structure of
The plurality of valve closure actuators are opened and closed based on liquid pattern data. The result is a set of drops that travel along nominal flight paths when the valve is closed or along first deflection paths when the valve is opened. Microfluid flow first deflection may be used in combination with any of the embodiments of the gas deflection subsystem and fluid capture subsystem previously discussed. A liquid patterning apparatus equipped with asymmetric microfluid flow first deflection will function in analogous fashion to one equipped with asymmetric resistive heating. That is, the system may be configured to print with undeflected drops as discussed in connection with
Methods of liquid pattern deposition that utilize localized gas flow for secondary drop deflection may be apparent from the above discussion of the numerous apparatus embodiments of the present inventions. For sake of clarity, some preferred methods of forming a liquid pattern on a medium are illustrated schematically in
In the set of methods schematically illustrated in
In the set of methods schematically illustrated in
The inventions have 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 inventions.
