Patent Application
20140176634
The present invention relates to controlling condensation of vaporized liquid components of inkjet inks during inkjet ink printing.
In an ink jet printer, a print is made by ejecting or jetting a series of small droplets of ink onto a paper to form picture elements (pixels) in an image-wise pattern. The density of a pixel is determined by the amount of ink jetted onto an area. Control of pixel density is generally achieved by controlling the number of droplets of ink jetted into an area of the print. To produce a print containing a single color, for example a black and white print, it is only necessary to jet a single black ink so that more droplets are directed at areas of higher density than areas with lower density.
Color prints are generally made by jetting, in register, inks corresponding to the subtractive primary colors cyan, magenta, yellow, and black. In addition, specialty inks can also be jetted to enhance the characteristics of a print. For example, custom colors to expand the color gamut, low density inks to expand the gray scale, and protective inks such as those containing UV absorbers can also be jetted to onto a paper to form a print.
Ink jet inks are generally jetted onto the paper using a jetting head. Such heads can jet continuously using a continuously jetting print head, with ink jetted towards unmarked or low density areas deflected into a gutter and recycled back into the ink reservoir. Alternatively, ink can be jetted only where it is to be deposited onto the paper using a so-called drop on demand print head. Commonly used heads eject or jet droplets of ink using either heat (a thermal print head) or a piezoelectric pulse (a piezoelectric print head) to generate the pressure on the ink in a nozzle of the print head to cause the ink to fracture into a droplet and eject from the nozzle. Inkjet printing is commonly used for printing on a cellulose based paper, however, there are numerous other materials in which inkjet is appropriate. For example, vinyl sheets, plastic sheets, textiles, paperboard, and corrugated cardboard can comprise the print media. For simplicity, the term paper will be used to refer to any form of print media, upon which the inkjet system deposits ink or other liquids. Additionally, although the term inkjet is often used to describe the printing process, the term jetting is also appropriate wherever ink or other liquids is applied in a consistent, metered fashion, particularly if the desired result is a thin layer or coating.
Ink jet printers can broadly be classified as serving one of two markets. The first is the consumer market, where printers are slow; typically printing a few pages per minute and the number of pages printed is low. The second market consists of commercial printers, where speeds are typically at least hundreds of pages per minute for cut sheet printers and hundreds of feet per minute for web printers. For use in the commercial market, ink jet prints must be actively dried as the speed of the printers precludes the ability to allow the prints to dry without specific drying subsystems.
Inkjet inks generally comprise up to about 97% water or another jettable carrier fluid such as an alcohol that carries colorants such as dyes or pigments dissolved or suspended therein to the paper. Ink jet inks also conventionally include other materials such as humectants, biocides, surfactants, and dispersants. Protective materials such as UV absorbers and abrasion resistant materials may also be present in the inkjet inks. Any of these may be in a liquid form or may be delivered by means of a liquid carrier or solvent. Conventionally, these liquids are selected to quickly vaporize after printing so that a pattern of dry colorants and other materials forms on the receiver soon after jetting.
Commercial inkjet printers typically print at rates of more than fifty feet of printing per minute. This requires printheads 10A, 10B and 10C to eject millions of droplets 12A, 12B and 12C of inkjet ink per minute. Accordingly, substantial volumes of liquids are ejected and begin evaporating at each of printheads 10A, 10B and 10C during operation of such printers.
When an ink jet image is printed on an absorbent paper, the inkjet ink droplets penetrate and are rapidly absorbed by the paper. As the ink is absorbed into the paper, the carrier fluid in the ink droplets spread colorants. A certain extent of spreading is anticipated and this spreading achieves the beneficial effect of increasing the extent of a surface area of the paper covered by the inkjet ink color. However, where spreading exceeds an expected extent, printed images can exhibit any or all of a loss of resolution, a decrease in color saturation, a decrease in density or image artifacts created by unintended combinations of colorants.
Absorption of the carrier fluid from inkjet inks can also have the effect of modifying the dimensional stability of an absorbent paper. In this regard it will be appreciated that the process of paper fabrication creates stresses in the paper that are balanced to create a flat paper stock. However, wetting of the paper causes the paper fibers to expand and partially or completely releases initially balanced stresses. In response, the paper cockles and distorts creating significant difficulties during subsequent paper handling, printing, or finishing applications. Cockle and distortion can degrade color to color registration, color saturation, and can also degrade any stitching of the print made when multiple jetting modules are used in combination to form a continuous imaging area across a width of the print. In addition, cockle and distortion of a print can impede the ability of a printing system to print front and back sides of a paper in register, often referred to as justification.
Further, in some situations, the jetting of large amounts of inkjet ink onto an absorbent paper can reduce the web strength of the paper. This can be particularly problematic in printers such as inkjet printing system 2 that is illustrated in
Semi-absorbent papers absorb the ink more slowly than do absorbent papers. Inkjet printing on semi-absorbent papers can cause liquids from the inkjet ink to remain in liquid form on a surface of the paper for a period of time. Such ink is subject to smearing and offsetting if another surface contacts the printed surface before the carrier fluid in the ink evaporates and the colorant is fixed. Air flow caused by either a drying process or by the transport of the paper can also distort the wet print. Finally, external contaminants such as dust or dirt can adhere to the wet ink, resulting in image degradation.
To avoid these effects, high speed inkjet printed papers are frequently actively dried using one or more dryers such as dryers 16A, 16B and 16C shown in
However, the increased rate at which carrier fluid evaporates creates localized concentrations of vaporized carrier fluid 17. Further around printing heads 10A, 10B and 10C, movement of paper 6 through printer 2 drags air and carrier fluid along with paper 6 forming current 15 of air that carries a meaningful portion of vaporized carrier fluid 17 therein that travels along with printed paper 6 as printed paper 6 moves from print head 10A, to printhead 10B and on to printhead 10C. Accordingly, when a printed portion of paper 6 reaches second printing area 10B a second inkjet image is printed and a concentration of vaporized carrier fluid 17 in the portion of current 15 moving with paper 6 is further increased. A similar result occurs at printhead 10C.
These concentrations increase the probability that vaporized carrier fluids 17 will condense on structures within printer 2 that are at a temperature that is below a condensation point of the evaporated carrier fluid. Such condensation can have a variety of effects on mechanical and electrical systems in printer 2. Further, there is the risk that such condensation will form droplets 19 on structures such as printhead 10B or printhead 10C from which they can fall, transfer or otherwise come into contact with a printed paper 6 so as to create image artifacts on paper 6. This risk is particularly acute for structures that are in close proximity to paper 6. Although the evaporated and condensed carrier fluid is substantially clear, as it contacts surfaces that have colorant deposits such deposits mix with the carrier fluid giving it color that detracts from the printed image when deposited there upon.
Additionally, there is the risk that such condensation forms in such locations where the condensation can combine with carrier fluid in ink droplets jetted toward a receiver to create image artifacts and can also interfere with droplet formation and/or can negatively influence the flight path taken by the droplets. Accordingly, it is desirable to provide some level of protection against the formation of such droplets of condensation at the printhead.
It will also be appreciated that it is frequently the case that several printheads are used in proximity to form what is known in the art as a printing module or linehead. Concentrations of vaporized carrier fluid can vary significantly at different printheads in the printing module. In part this occurs because the air current 15 carries vaporized carrier fluid along the receiver 6 as receiver 6 is moved from printhead to printhead such that the amount of vaporized carrier fluid in air current 15 increases as receiver 6 passes each print head.
U.S. Pat. No. 6,340,225 entitled: “Cross floor care system for inkjet printer” and U.S. Pat. No. 6,390,618 entitled “Method and apparatus for inkjet print zone drying.” These describe systems that blow air through a printing zone to enhance printing efficiency and to reduce cost. It will be appreciated that such systems introduce air flow that cuts across the printing zone between the printheads and the receiver and that therefore can disrupt the trajectory of the ink droplets and introduce image artifacts in to the receiver.
Accordingly, what is also needed are new printers and air flow systems for printers that can create without creating unwanted image artifacts.
Condensation control systems are provided for use with a printing module having a plurality of inkjet printheads that eject ink droplets of an ink having an evaporative carrier fluid toward a receiver that is moved past the printing module by a receiver transport system. In one embodiment, the condensation control system. In one embodiment a condensation control system has a barrier between the inkjet printheads, a plurality caps with each cap positioned at one of the plurality of inkjet printheads and extending from the barrier toward the receiver to create higher flow areas between the inkjet printheads and the receiver, with the caps being separated to create lower resistance flow channels between the caps and further having openings through which ink droplets can pass from the inkjet printheads through the higher resistance flow areas and onto the receiver, a cross-module airflow generation system generating a cross-module airflow to remove a portion of any vaporized carrier fluid from between the barrier and the receiver. Differences between a lower resistance to the cross-module airflow in the lower resistance flow channels and a higher resistance to the cross-module airflow in the higher resistance flow areas cause the cross-module airflow to flow through the cross-module airflow channels so that any portion of the cross-module airflow entering the higher resistance flow areas does not create variations in the travel paths of the ink droplets that are sufficient to form an observable artifact in a print made on the receiver using the ink droplets.
Unless otherwise stated expressly herein the drawings are not to scale.
In the embodiment of
Receiver transport system 40 generally comprises structures, systems, actuators, sensors, or other devices used to advance a receiver 24 from an input area 32 past print engine 22 to an output area 34. In
In an alternate embodiment illustrated in
Inkjet printing system 20 is operated by a printing system controller 82 that controls the operation of print engine 22 including but not limited to each of the respective printing modules 30-1, 30-2, 30-3, 30-4 of first print engine module 26 and second print engine module 28, receiver transport system 40, input area 32, to form inkjet images in registration on a receiver 24 or an intermediate in order to yield a composite inkjet image on receiver 24.
Printing system controller 82 operates inkjet printing system 20 based upon input signals from a user input system 84, sensors 86, a memory 88 and a communication system 90. User input system 84 can comprise any form of transducer or other device capable of receiving an input from a user and converting this input into a form that can be used by printing system controller 82. Sensors 86 can include contact, proximity, electromagnetic, magnetic, or optical sensors and other sensors known in the art that can be used to detect conditions in inkjet printing system 20 or in the environment-surrounding inkjet printing system 20 and to convert this information into a form that can be used by printing system controller 82 in governing printing, drying, other functions.
Memory 88 can comprise any form of conventionally known memory devices including but not limited to optical, magnetic or other movable media as well as semiconductor or other forms of electronic memory. Memory 88 can contain for example and without limitation image data, print order data, printing instructions, suitable tables and control software that can be used by printing system controller 82.
Communication system 90 can comprise any form of circuit, system or transducer that can be used to send signals to or receive signals from memory 88 or external devices 92 that are separate from or separable from direct connection with printing system controller 82. External devices 92 can comprise any type of electronic system that can generate signals bearing data that may be useful to printing system controller 82 in operating inkjet printing system 20.
Inkjet printing system 20 further comprises an output system 94, such as a display, audio signal source or tactile signal generator or any other device that can be used to provide human perceptible signals by printing system controller 82 to an operator for feedback, informational or other purposes.
Inkjet printing system 20 prints images based upon print order information. Print order information can include image data for printing and printing instructions. Print order information can be received from a variety of sources. In the embodiment of
In the embodiment of inkjet printing system 20 that is illustrated in
Inkjet printheads 100 can use any known form of inkjet technology to jet ink droplets 102. These can include but are not limited to drop on demand inkjet jetting technology (DOD) or continuous inkjet jetting technology (CD). In “drop-on-demand” (DOD) jetting, a pressurization actuator, for example, a thermal, piezoelectric, or electrostatic actuator causes ink droplets to jet from a nozzle only when required. One commonly practiced drop-on-demand technology uses thermal actuation to eject ink droplets 102 from a nozzle. A heater, located at or near the nozzle, heats the ink sufficiently to boil, forming a vapor bubble that creates enough internal pressure to eject an ink drop. This form of inkjet is commonly termed “thermal ink jet (TIJ).”
In “continuous” ink jet (CIJ) jetting, a pressurized ink source is used to produce a continuous liquid jet stream of ink by forcing ink, under pressure, through a nozzle. The stream of ink is perturbed using a drop forming mechanism such that the liquid jet breaks up into droplets of ink in a predictable manner. One continuous printing technology uses thermal stimulation of the liquid jet with a heater to form droplets that eventually become print droplets and non-print droplets. Printing occurs by selectively deflecting one of the print droplets and the non-print droplets and catching the non-print droplets. Various approaches for selectively deflecting droplets have been developed including electrostatic deflection, air deflection, and thermal deflection. The inventions described herein are applicable to both types of printing technologies and to any other technologies that enable jetting of droplets of an ink consistent with what is claimed herein. As such, inkjet printheads 100 are not limited to any particular jetting technology. In the embodiment of
In the embodiments that are shown in
As ink droplets 102 are formed, travel to receiver 24, and are heated for drying, receiver 24 emits vaporized carrier fluid 116. This raises the concentration of vaporized carrier fluid 116 in a gap 114 between barrier 110 and target area 108. This effect is particularly acute in gaps 114 between printing module 30-1 and a target area 108 within which receiver 24 is positioned.
It will be noted that as carrier fluid is frequently water, terms such as moisture, humid, and humidity, may be used in this specification that in a proper sense relate only to water in either a liquid or gaseous form. For simplicity, these terms are also terms are intended to refer to the liquid and gaseous forms of non-aqueous solvents or carrier fluids in a corresponding manner. In various embodiments herein ink droplets 102 are generally referred to as delivering colorants to receiver 24 however, it will be appreciated that in alternate embodiments ink droplets 102 can deliver other functional materials thereto including coating materials, protectants, conductive materials and the like.
During printing, inkjet printing modules such as inkjet printing module 30-1, rapidly form and jet ink droplets 102 onto receiver 24. This process adds vaporized carrier fluid 116 to the air in gap 114-1, creating a first concentration of vaporized carrier fluid 116-1 and also increasing a risk of condensation on downstream portions of the barrier 110.
Further, as receiver 24 moves in the direction of receiver movement 42 (left to right as shown in
Receiver 24 then passes beneath dryer 50-1 which applies energy 52-1 to heat receiver 24 and any ink thereon. The applied energy 52-1 accelerates the evaporation of the water or other carrier fluids in the ink. Although such dryers 50-1, 50-2, and 50-3 often include an exhaust system for removing the resulting warm humid air from above receiver 24, some warm air with vaporized carrier fluid 116 is carried along by moving receiver 24 as it leaves dryer 50-1. As a result, a third concentration of carrier fluid entering in third gap 114-3 between nozzle arrays 104A and 104B and target areas 108A and 108B at inkjet printing module 30-3 is greater than second concentration of vaporized carrier fluid 116-2. Similarly, printing of ink droplets 102 at inkjet printing module 30-3 creates a fourth concentration of vaporized carrier fluid 116-4 exiting gap 114-3. To the extent that receiver 24 remains at an increased temperature after leaving dryer 50-1, carrier fluid from the ink droplets 102A and 102B can be caused to evaporate from receiver 24 at a faster rate further adding moisture into gap 114-3 such that the fourth concentration of vaporized carrier fluid 116-4 is found in gap 114-4 after receiver 24 has been moved past inkjet printing module 30-2 and dryer 50-1.
Accordingly, where multiple inkjet printing modules 30 jet ink onto receiver 24, concentrations of vaporized carrier fluid 116 near a receiver 24 can increase in like fashion cascading from a first concentration of vaporized carrier fluid 116-1 to a second concentration of vaporized carrier fluid 116-2, to a third concentration of vaporized carrier fluid 116-3 and so on. As such, the risk of condensation related problems increases with each additional printing undertaken by inkjet printing modules 30-2, 30-3, and 30-4 downstream of dryer 50-1 it is necessary to reduce the risk that these concentrations will cause condensation that damages the printer or the printed output.
This embodiment of condensation control system 118 includes caps 130A and 130B at each of printheads 100A and 100B. Caps 130A and 130B have shields 132A and 132B and thermally insulating separators 160A and 160B respectively. An energy source 180 provides energy that can be applied to cause shields 132A and 132B to be heated and a control circuit 182 controls an amount of energy that is applied to control the heating of shields 132A and 132B.
In this embodiment, printing module 30-1 has a first plurality of printheads 100A arranged along a first print line 123 and a second plurality of printheads 100B arranged along a second print line 125. As is shown in
A barrier 110 separates target areas 108A and 108B from other components of printing module 30-1 to limit the extent to which any airborne or other environmental contaminants can enter into printing module 30-1. For example, in various embodiments, barrier 110 is a barrier to water vapor or other evaporates, as well as inks, paper fragments, colorants, dust, dirt or other foreign materials. Optionally, barrier 110 can also act as a thermal barrier to limit the extent to which heat from the target areas 108A and 108B can enter into printing module 30-1. In the embodiment illustrated in
In some embodiments, this is done by positioning faces 106A and 106B through passageways 124A and 124B so that faces 106A and 106B protrude from passageways 124A and 124B. In other embodiments, faces 106A and 106B can be even or generally even with second surface 122, and in still other embodiments faces 106A and 106B can be positioned between second surface 122 and first surface 120. In further embodiments, faces 106A and 106B can be positioned behind barrier 110.
In the embodiment that is illustrated here, barrier 110 provides a support for inkjet printheads 100A and 110B, however this is not necessary.
As is shown in
In other embodiments, at least one printhead 100A and cap 130A are arranged along first print line 123 and at least one printhead 100B and cap 130B are arranged along second print line 125. In still other embodiments, at least three printheads are provided with at least one printhead of the at least three printheads arranged along first print line 123 and at least one of the at least three printheads arranged along second print line 125. In still other embodiments a plurality of printheads 100 can be provided with caps 130 with a first portion of the plurality arranged along first print line 123 as printheads 100A and caps 130A and a second portion of the plurality of printheads 100 and caps 130 arranged along second print line 125 as printheads 100B and caps 130B.
First shield 132A and second shield 132B are non-porous and serve to prevent condensation from accumulating on faces 106A and 106B of printheads 100A and 100B. Shields 132A and 132B also provide some protection from physical damage to inkjet printheads 100 and barrier 110 that might be caused by an impact of receiver 24 against a face 106A of printhead 100A, against a face 106B of printhead 100E or against barrier 110. First shield 132A and second shield 132B can take the form of plates or foils and films.
Generally, shields 132A and 132B span at least a width dimension and a length dimension over nozzle arrays 104A and 104B of printheads 100A and 100B. Shields 132A and 132B therefore provide surface area that is relatively large compared to a small thickness that is, for example, on the order of about 0.3 mm. In other embodiments, first shield 132A and second shield 132B can have a thickness in the range of about 0.1 mm to 1 mm.
In certain embodiments, shields 132A and 132B can have a low heat capacity so that a temperature of shields 132A and 132B will rise or fall rapidly and in a generally uniform manner when heated or otherwise exposed to energy from an energy source and otherwise will act to rapidly approach an ambient temperature. In certain circumstances, this ambient temperature will be below a condensation temperature of the vaporizable carrier fluid in printing regions 136A and 134B. This creates a risk that condensation will form on shields 132A and 132B.
Accordingly, shields 132A and 132B are actively heated so that they remain at a temperature that is at or above the condensation temperature of any vaporized carrier fluid 116 in printing regions 136A and 136B. Increasing the temperature of shield 132 reduces or prevents condensation from forming and accumulating on a face 140 of shield 132 that faces target area 108.
Shield 132 can be made of a material having a high thermal conductivity, such as aluminum or copper. The high thermal conductivity of such an embodiment of shield 132 helps to distribute heat more uniformly across shields 132A and 132B so that the temperature of shields 132A and 132B maintain a generally uniform temperature to reduce the risk that condensation will form on localized regions of lower temperature of shields 132A and 132B. Optionally shields 132A and 132B can be made from a non-corrosive material such as a stainless steel.
To prevent condensation from forming on shields 132A and 132B, shields 132A and 132B can optionally have a higher emissivity (e.g., greater than 0.75) to better absorb thermal energy. For example, shields 132A and 132B optionally can be made having a black color and optionally can have an anodized or matte finish to enhance absorption. Alternatively, shields 132A and 132B can be another dark color. Absorption of the thermal energy radiating onto shields 132A and 132B can passively increase the temperature of shields 132A and 132B to reduce an amount of energy required to actively heat the shields 132A and 132B above the condensation temperature of vaporized carrier fluid 116.
Alternatively, other embodiments shields 132A and 132B can be made of a material having a lower thermal conductivity, such as for example, a ceramic material. In still other embodiments, shield 132 can be made from any of a stainless steel, a polyamide, polyimide, polyester, vinyl and polystyrene, and polyethylene terephthalate.
As is illustrated in
In one embodiment, openings 138A and 138B can be shaped or patterned to closely correspond to an arrangement of nozzle arrays 104A and 104B in an inkjet printing module such as inkjet printing module 30-1. One example of this type is illustrated in
As is shown in
In the embodiment of
In general, it will be appreciated that the amount of vaporized carrier fluid 116 that enters first shielded regions 134A and 134B is best limited by providing openings 138A and 138B with a smallest cross-sectional distance 144 that is highly restrictive without negatively influencing drop transit. Accordingly, in some embodiments, smallest cross-sectional distance 144 of openings 138A and 138B can be defined as a function of a size of an ink droplet 102A and 102B such as 150 times the size of an average weighted diameter of ink droplets 102A and 102B ejected by an inkjet printhead 100. For example, in one embodiment, the smallest distance can be on the order of less than 300 times an average diameter of ink droplets while in other embodiments, the smallest cross-sectional distance 144 of an opening 138 can be on the order of less than 150 times the average diameter of ink droplets 102 and, in still other embodiments, the smallest cross-sectional distance 144 of an opening 138 can be on the order of about 25 to 70 times the average diameter of a diameter of ink droplets 102A and 102B.
In other embodiments, a smallest cross-sectional distance 144 of an openings 138A and 138B can be determined based upon the expected flight envelope of ink droplets 102A and 102B as ink droplets were to travel from nozzle arrays 104A and 104B to target areas 108A and 108B. That is, it will be expected that ink droplets 102A and 102B will travel nominally along a flight path from nozzle arrays 104A and 104B to target areas 108A and 108B and that there will be some variation in a flight path of any individual ink droplet 102A and 102B relative to the nominal flight path and that the expected range of variation can be predicted or determined experimentally and can be used to define a smallest cross-sectional distance 144 of one or more opening 138A and 138B such that an opening 138A and 138B has a smallest cross-sectional distance 144 that does not interfere with the flight of any inkjet droplet from a nozzle arrays 104A and 104B to target areas 108A and 108B.
Returning now to
Thermally insulating separators 160A and 160B can be permanently fixed to faces 106A and 106B, to barrier 110 or to shields 132A and 132B using adhesives, welding, and mechanical fasteners and the like. Thermally insulating separators 160A and 160B can also integrally formed with shields 132A and 132B and can for example be formed from a common substrate.
In other embodiments, thermally insulating separators 160A and 160B can be removably mounted to faces 106A and 106B, to barrier 110 or to shields 132A and 132B. For example, in one embodiment, thermally insulating separators 160A and 160B can comprise magnets that are joined to selected regions of shield 132A and 132B. In other embodiments, shields 132A and 132B is positioned between barrier 110 and target areas 108A and 108B by a plurality of thermally insulating separators 160A and 160B. Such a plurality of thermally insulating separators 160A and 160B can take the form of pins, bolts, or other forms of connectors that in combination form a perimeter for caps 130A and 130B that substantially or completely resists airflow into shielded regions 134A and 134B.
Thermally insulating separators 160A and 160B can be made to be thermally insulating through the use of thermally insulating materials including but not limited to air or other gasses, Bakelite, silicone, ceramics or an aerogel based material. Thermally insulating separators 160A and 160B can also be made to be thermally insulating by virtue a shape or configuration, such as by forming thermally insulating separators 160A and 160B to have a tubular construction or other construction that provides, for example, a relatively large surface area as opposed to cross-sectional area or that has other features that allow thermally insulating separators 160A and 160B to radiate. In one embodiment of this type, a poor thermal insulator such as stainless steel can be made to act as a thermal insulator by virtue of assembling the stainless steel in a tubular fashion. Optionally, both approaches can be used.
Separation distances 150A and 150B create a shielded regions 134A and 134B that provide air gap 139 between faces 106A and 106B and shields 132A and 132B. Air gap 139 provides additional thermally insulation between, shields 132A and 132B and faces 106A and 106B to allow shields 132A and 132B to have a temperature that is greater than a temperature of faces 106A and 106B without heating printheads 100A and 100B to an unacceptable level. While a larger air gap 139 between faces 106A and 106B and shields 132A and 132A provides a desirable level thermal insulation, this is not mandatory and air gap 139 does not need to be large. To keep the flight path from nozzle arrays 104A and 104B to target areas 108A and 108B small, which is desired for maintaining the best print quality, air gap 139 should be kept small. In one embodiment, air gap 139 is between about 0.5 and 5.0 mm tall however, other sizes are possible and may be more useful or practical for particular machine configurations.
Thermally insulating separators 160A and 160B can have a fixed size to define a fixed separation or can vary with temperature so that a greater air gap 139 is provided when conditions are hotter. In one embodiment, thermally insulating separators 160A and 160B can incorporate a material that is thermally expansive so that thermally insulating separators 160A and 160B expand the extent of separation distances 150A and 150B between either or both of shields 132A and 132B and barrier 110 in response to any of an increase in a temperature of matter that is in contact with the thermally expansive thermally insulating separators 160A and 160B such as contact with faces 106A and 106B, second surface 122, shields 132A and 132B or air in printing regions 136A or 136B.
The thermal insulation provided by air gap 139 in turn allows shields 132A and 132B to be actively heated to a temperature that is above a condensation point for the vaporized carrier fluids in printing regions 136A and 136B while allowing printheads 100A and 100B to remain at cooler temperatures, including, in some embodiments, temperatures that are below a condensation temperature of the vaporized carrier fluids in printing regions 136A and 136B.
It will be appreciated however that the condensation temperature in a first printing region 136A can differ significantly from the condensation temperature in a second printing region 136B. This can occur for a variety of reasons. For example, first printing region 136A and second printing region 136B can have different concentrations of vaporized carrier fluid 116, different temperatures, different heating or cooling rates, printing loads, printhead temperatures, and different exposure to factors such as ambient humidity, airflow, receiver temperature, printhead temperature, variations in an amount of ink used for printing. These conditions can also change rapidly and dynamically across a plurality of printheads in the printing module.
Accordingly, in the embodiment illustrated in
There are a number of ways in which this can be done. In one embodiment, energy source 180 supplies electrical energy and control circuit 182 includes logic circuits that determine an extent to which electrical energy is supplied to a first electrical heater 172A that causes first shield 132A to heat and a second electrical heater 172B that causes the second shield 132B to heat. Control circuit 182 controls the transfer of electrical energy to first electrical heater 172A and separately controls the transfer of electrical energy to second electrical heater 172B. In one embodiment, electrical heaters 172A and 172B are in the form of resistors or other known circuits or systems devices that convert electrical energy into heat. In certain embodiments, electrical heaters 172A and 172B can comprise a thermoelectric heat pump or “Peltier Device” that pumps heat from one side of the device to another side of the device. Such a thermoelectric heat pump can be arranged, for example, to pump heat from a side 142A of shield 132A confronting first printing region 136A to a side 143A of shield 132A that is in contact with thermally insulating separators 160A and shielded regions 134A. Such electrical heaters 172A and 172B can be joined to shields 132A and 132B or shields 132A and 132B can be made from a material or comprise a substrate that can heat in response to applied electrical energy.
In a further embodiment, energy source 180 can comprise a heater that heats a plurality of contact surfaces that are in contact with shields 132A and 132B and control circuit 182 can control an actuator in energy source 180 such as a motor that controls an extent of contact between shields 132A and 132B and the contact surface or can control an amount of heat supplied by the energy source to each of the contact surface.
In another embodiment of, thermally insulating separators 160A and 160B can be made of materials that expand when subject to a change in electromagnetic fields about the materials and in such embodiments, an electro-magnetic signal can be provided by a control circuit 182 cooperate with a energy source 180 to create appropriate electromagnetic conditions to induce expansion or contraction of the thermally insulating separators 160A and 160B. For example, in one embodiment of this type, thermally insulating separators 160A and 160B that are formed from a material that expands when exposed to electrical energy can be connected in series with electrical heaters 172A and 172B such that whenever power is applied to electrical heaters 172A and 172B, such electrical power also is applied to thermally insulating separators 160A and 160B causing thermally insulating separators 160A and 160B increase the gap between shields 132A and 132B and printheads 100A and 100B.
It will be appreciated that in other embodiments, caps 130A and 130B can be attached to printheads 100 as shown in
Attachment of caps 130A and 130B to barrier 110 can allow smaller separation distances between faces 106 of printheads 100 and shields 132A and 132B. For example, in some embodiments where printheads 100A and 100B are mounted to barrier 110, printheads 100A and 100B can be recessed relative to faces 106A and 106B of printheads 100A and 100B. This approach also enables printheads 100A and 100B to have greater thermal isolation from shields 132A and 132B.
Any other known mechanism and control system that can be combined to permit controlled heating of adjacent but thermally isolated surfaces can be used toward this end. Control circuit 182 can take any of a variety of forms of control circuits known in the art for controlling energy supplied to heating elements. In one embodiment, printing system controller 82 can be the control circuit. In other embodiments, control circuit 182 can take the form of a programmable logic executing device, a micro-processor, a programmable analog device, a micro-controller or a hardwired combination of circuits made cause printing system 20 and any components thereof to perform in the manner that is described herein.
The heating of shields 132A and 132B can be uniform or patterned. In one embodiment of this type, a heater 172 can take the form of a material that heats when electrical energy is applied and that is patterned to absorb applied energy so that different portions of shield 132 heat more than other portions in response to applied energy. This can be done for example, and without limitation, by controlled arrangement or patterning of heaters 172 on shields 132A and 132B. Such non-uniform heating of shields 132A and 132B can be used for a variety of purposes. In one embodiment, shields 132 can be adapted to heat to a higher temperature away from respective openings 138 than proximate to openings 138.
It will be appreciated from the foregoing that portions of shield 132A and 132B are located between portions of the face of the printheads 100A and 100B and target areas 108A and 108B to limit the extent to which vaporized carrier fluid 116 passes from printing regions 136A and 136B to shielded regions 134A and 134B. In certain embodiments, this also advantageously limits the extent to which any radiated energy can directly impinge upon the faces 106A and 106B of the printheads 100A and 100B.
In the embodiment illustrated in
In another embodiment, sensors 86A and 86B can comprise a liquid condensation sensor located proximate to shields 132A and 132B and that are operable to detect condensation on faces 140A and 140B of shields 132A and 132B. Sensors 86A and 86B are further operable to generate a signal that is indicative of the liquid condensation, if any, that is sensed thereby. The signals from sensors 86A and 86B is transmitted to control circuit such as printing system controller 82 so that printing system controller 82 can control an amount of energy supplied by energy source 180 to cause shields 132A and 132B to heat according to the sensed condensation.
In still another embodiment, sensors 86A and 86B can comprise temperature sensors located proximate to shields 132A and 132B operable to detect a temperature of shields 132A and 132B and further operable to generate a signal that is indicative of the temperature of shields 132A and 132B. The signal from sensors 86A and 86B can be transmitted to control circuit such as printing system controller 82 so that control circuit 182 can control an amount of energy supplied by energy source 180 to cause shields 132A and 132B to heat according to the sensed temperature.
In yet another embodiment, sensors 86A and 86B can comprise receiver temperature sensors that are operable to detect conditions that are indicative of a temperature of receiver 24 such as an intensity of infra-red light emitted by receiver 24 and further operable to generate a signal that is indicative of temperature of receiver 24. The signal from receiver temperature sensors 86A and 86B can be transmitted to a control circuit 182 such as printing system controller 82 so that control circuit 182 can control an amount of energy supplied by energy source 180 to cause shields 132A and 132B to heat according to the sensed temperature of receiver 24 when receiver 24 is in first printing region 136A and in second printing region 136B.
As is shown in the embodiment of
Supplemental shields 234A and 234B are positioned apart from second surface 122 of barrier 110 by separation distances 154A and 154B that are less than projection distances 152A and 152B of caps 130A and 130B. Preferably, supplemental shields 232A and 232B are sealed or substantially sealed against caps 130A and 130B to limit the transit of vaporized carrier fluid 116 into shielded regions 134A and 134B.
Supplemental shields 232A and 232B can be heated by convection flows of air 189 heated by receiver 24 to an elevated temperature. This can reduce the possibility that vaporized carrier fluids will condense against supplemental shield 232. Optionally, supplemental shields 232 can be actively heated in any of the manners that are described herein. Supplemental shields 232 can also be made in the same fashion and from the same materials and construction as shields 132A and 132B.
In the embodiment that is illustrated in
In still another embodiment, first shield 132A can comprise a flexible or bendable sheet that is held in tension by the thermally insulating separator 160 with the thermally insulating separator 160 acting as a frame.
Alternatively, first shield 132A can be adapted to change dimension in a manner that accommodates changes in dimension of barrier 110 and inkjet printheads 100 due to heating or cooling.
In still another embodiment first shield 132A can be joined to thermally insulating separator 160A in a manner that allows first shield 132A and thermally insulating separator 160A to move relative to each other to accommodate change in dimension of the barrier 110, inkjet printheads 100 due to heating or cooling. This can be done for example where first shield 132A and thermally insulating separator 160A are magnetically joined to each other or where thermally insulating separator 160A is magnetically joined to barrier 110. In one example of this, thermally insulating separator 160A can comprise a magnet such as a ceramic magnet or a polymeric magnet while barrier 110 and shield 132A can be made from or made to incorporate magnetic materials. It will be appreciated that in other embodiments second cap 130B can likewise incorporate any of the features described herein with reference to shield 132A.
As is shown in
Co-linear airflow 214A and 214B can optionally be used to provide one or more of the advantages of: providing greater control over air/ink interactions that influence drop placement, a buffer against the effect of any crossing air flow 216, creating an air cushion that resists movement of receiver 24 toward shields 132A and 132B and providing additional protection against the possibility that receiver 24 will be moved toward and strike shields 132A and 132B. Further, co-linear airflows 214A and 214B can be conditioned by an optional air conditioning system 228 so that co-linear airflows 214A and 214B have any or all of a controlled temperature, pressure, flow rate or humidity to provide controlled environmental conditions in first shielded region 136A and second shielded region 136B and also so that co-linear airflows 214A and 214B have properties that are useful in drying ink that has been applied to receiver 24 or otherwise achieving the effects described herein. In one example, co-linear airflows 214A and 214B can be heated in a manner that is calculated to raise the temperature of shields 132A and 132B.
In this embodiment, condensation control system 118 includes barrier 110, caps 130 and a cross-module airflow generation system 220. Cross-module airflow generation system 220 provides a cross-module airflow 240 at an entrance area 223 of a cross-module flow path 236 between receiver 24, barrier 110, caps 130A and 130B to reduce the concentration of vaporized carrier fluid 116.
As is also shown in
Cross-module airflow 240 can be supplied at a rate of between 20 and 100 cubic feet per minute with a preferential flow rate of 25 cubic feet per minute in some embodiments. For example, an inkjet printing system 20 can have a controller such as printing system controller 82 and sensors such as sensors 86 that provide data from which the controller can determine at least two of an expected or measured range of concentrations of a vaporized carrier fluid 116 to be removed by the cross-module airflow 240, expected or measured resistance to cross-module airflow 240 in lower resistance flow channels 252 and higher resistance flow areas 250, expected or measured temperatures of the air between receiver 24 and barrier 110, expected or measured evaporation or condensation temperatures of any vaporized carrier fluid 116, the temperature of the air used in cross-module airflow 240, a temperature of any vaporized carrier fluid 116 in any entrained air 242 moving with receiver 24 during printing, and wherein the controller establishes a rate of cross-module airflow based upon the determined data from the sensors and known differences between the airflow resistance in the higher resistance flow areas 250 and the lower resistance flow channels 252. In one embodiment of this type, printing system controller 82 additionally determine a volume of cross-module airflow to be supplied between the barrier and the receiver based upon at least one of a type of ink to be used in printing, a speed of receiver movement and a range of a volume of ink droplets to be emitted per unit time during printing.
In another embodiment, the relative proportion of cross-module airflow 240 through higher resistance flow areas 250A and 250B to the proportion of cross-module airflow 240 traveling through lower resistance flow channels 252 at a particular flow rate can be determined by printing system controller 82 based upon the resistance to cross-module airflow in the higher resistance flow areas 250A and 250B by clearance distances 248A and 248B between caps 130A and 130B and receiver 24, by the resistance to cross-module airflow 240A in the lower resistance flow channels 252. Here, printing system controller 82 can select a volume of cross-module airflow per unit time based in order to achieve a threshold ratio that will prevent image artifacts from occurring.
It will be appreciated that cross-module airflow 240 like most other flows will follow the path of least resistance through cross-module flow path 236. Accordingly, in the embodiment of
Here higher resistance flow areas 250A and 250B are created by providing regions in which cross-module airflow 240 is required to flow through a small clearance distance 248A and 248B between comparatively large surfaces of caps 130A and receiver 24 and between caps 130B and receiver 24 respectively. Any portion of cross-module airflow 240 entering into clearance distances 248A is likely to contact either or both of cap 130A and receiver 24 and similarly any portion of cross-module airflow 240 entering into clearance distance 248B is likely to contact either or both of cap 130B and receiver 24. This friction creates what is known as a surface drag on such flows. The surface drag resists cross-module airflow 240 creating higher resistance flow areas 250A between caps 130A and receiver 24 and between higher resistance flow areas 250B and receiver 24.
For example as is shown in the embodiment of
In this embodiment, lower resistance flow channels 252 are defined by an entrance distance 238 between second surface 122 of barrier 110 that is at least three times as large as clearance distances 248A and 248B in the higher resistance flow areas 250A and 250B and by cap separation distances 255 which are also at least three times as large as clearance distances 248A and 248B. Accordingly, a much smaller proportion of the cross-module airflow 240 that flows through lower resistance flow channels 252 contacts a surface and therefore there is substantially less resistance to flow in lower resistance flow channels 252.
It is possible therefore to control the proportion of cross-module airflow 240 traveling through higher resistance flow areas 250A and 250B relative to the proportion of cross-module airflow 240 traveling through lower resistance flow channels 252 controlling the resistance to cross-module airflow 240 in the higher resistance flow areas 250A and 250B relative to the resistance to cross-module airflow 240 in lower resistance flow channels 252.
In the embodiment of
In one embodiment, cap separation distances 255A between caps 130A and 130B are between 2 mm to 15 mm while cap extension distances 246A and 246B between second surface 122 and a portion of caps 130A and 130B in the higher resistance flow areas 252A and 252B are between about 2 mm to 6 mm and while clearance distances 248A and 248B are between about 0.5 to 2.0 mm. In other embodiments, a cap separation distance 255 between caps 130A and 130B can be at least about 0.1 to 0.2 times a width of nozzle arrays 104A and 104B respectively.
Only a portion of cross-module airflow 240 passes into higher resistance flow areas 250A and 250B and both the energy and volume of this portion of cross-module airflow 240 is reduced by the resistance to flow from the higher resistance to flow in higher resistance flow areas 250A and any portion of cross-module airflow 240 that enters higher resistance flow areas 250A and 250B is required to travel at least a threshold distance 297A and 297B along direction of receiver movement 42 within the higher resistance flow areas 250A before reaching first print line 123 or second print line 125 so that the resistance to flow causes such portions to lack the energy necessary to deflect ink droplets in a manner that can create image artifacts. While the threshold distances 297A and 297B that are useful in any printer design will be a function of various aspects of the printer, in certain embodiments, threshold distance 297 can be for example between about one to ten times a clearance distance 248. There is however sufficient flow through these higher resistance flow areas 250A and 250B to reduce a concentration of vaporized carrier fluid 116 in higher resistance flow areas 250A and 250B such that the risk of condensation buildup is reduced.
This arrangement protects against the possibility that any cross-module airflow 240 that does pass through higher resistance flow areas 250 will negatively influence placement of ink droplets 102A and 102B as they travel to receiver 24 and allows cross-module airflow generation system 220 to introduce a much greater volume of cross-module airflow 240 into entrance area 223 without creating unwanted variations in trajectories of ink droplets 102A and 102B than is possible without caps 130 A and 130B.
For example,
Other characteristics of printing module 30-1 will also have an influence on the design and arrangement of caps 130A and 130B and these include but are not limited to characteristics such as a cross-sectional area of cross-module flow path 236, and any expected extent of variations in relative position of receiver 24 and nozzle arrays 104A and 104B. These factors can influence the extent to which caps 130A and 130B can extend from second surface 122 toward receiver 24 as it will be desirable to avoid contact between caps 130A and 130B and receiver 24.
There are a variety of factors that influence the design and arrangement of caps 130A and 130B of a condensation control system 118 and many of these factors are based on the characteristics of printing module 30-1. As an initial matter, it will be appreciated for any printing module, such as printing module 30-1 a primary design consideration will be the physical layout of printheads 100A and 100B, nozzle arrays 104A and 104B and faces 106A and 106B. Any arrangement of caps must capable of fitting within the physical layout of printheads 100A and 100B while still operating. Another factor is a printing distance or a range of printing distances over which inkjet nozzle arrays 104A and 104B are designed to eject ink droplets 102A and 102B during printing. Such factors can provide design constraints within which the characteristics of caps 130A and 130B can be determined.
Additional considerations can include but are not limited to rates of transport of receiver 24, the air flow characteristics of the materials used for caps 130A and 130B, evaporation rates of vaporized carrier fluid 116, expected printing rates, and the like. In certain embodiments, the placement arrangement of nozzle arrays 104A and 104B of printheads 100A and 100B will be determined first and the locations, shapes, sizes and other characteristics of condensation control system 218 can be determined based upon the design of the printheads 100A and 100B. In other circumstances the need for a condensation control system 118 that has controlled cross-flow and the requirement of providing caps 130A and 130B can be used as a design factor that influences the design, selection, arrangement or other characteristics of printheads 100A and 100B. These and other characteristics of printing module 30-1 can influence the design of caps 130A and 130B as well as the design of cross-module flow path 236.
It will be appreciated from the above that by providing controlled patterns of resistance to cross-module airflow 240, it becomes possible to provide a volume of cross-module airflow 240 pass through cross-module flow paths 236 that is sufficient to reduce the risk that vaporized carrier fluid 116 will condense into artifact creating droplets without such airflow creating errors in the placement of ink droplets 102A and 102B.
Printing systems are expected to work without error when operated at any of a wide variety of different operating conditions. For example, printing speeds, printing densities, receiver types and environmental conditions can vary widely. Such conditions can influence the flow of cross-module airflow 240 through caps 130A and 130B and can interact with the structures of printing module 30-1, with receiver 24 and with condensation control system 118 in different ways under different conditions. Under many conditions, an arrangement of caps 130A and 130B will operate as described above.
However, in other conditions interactions between cross-module airflow 240, receiver 24, caps 130A and 130B and barrier 110 can create flow patterns that can cause at least a portion of cross-module airflow 240 to pass through higher resistance flow areas 250A or 250B to create drop placement errors and associated image artifacts. For example, under certain conditions, airflow related conditions such as backpressure, recirculation, turbulence and other conditions can be created that give rise to unstable or higher pressure airflows in cross-module flow path 236 and that can, in turn, create image artifacts.
Accordingly, condensation control system 118 of
The cross-module airflow control features shown the embodiment of
Deflection surfaces 270A and 272A begin at vertices 274A and are sloped relative to direction of receiver movement 42 at generally equal deflection angles 291A and 293A to divide the cross-module airflow 240 and to guide different portions of cross-module airflow 240 into different ones of the lower resistance flow channels 252. In this embodiment, caps 130A have a mirror symmetry about a central axis 276A that extends along direction of receiver movement 42 through a center of caps 130A and through vertices 274A. Deflection surfaces 270A and 272A are illustrated as being generally flat and angles 291A and 293A can be for example between about 20 and 70 degrees. In other embodiments deflection surface 270A and 272A extend away from vertices 274A at a slope of between 0.25 and 1.0 relative to the direction of receiver movement 42. In still other embodiments, deflection surfaces 270A and 270B can have surfaces that are curved, bent or otherwise shaped to provide controlled deflection of cross-module airflow 240 without creating turbulence, recirculation, or backpressure as discussed above. In some embodiments, it can be effective to use deflection surfaces 270A and 272A that are curved in a convex manner.
In some embodiments of this type, caps 130A have vertices 274A that extend upstream from nozzle array 104A by a cap lead-in distance 294A that is greater than one fourth of a nozzle array width 298A of nozzle array 104A. In other embodiments, it can be useful provide cap 130A having vertices 274A that extend upstream from a nozzle array 104A by a threshold distance 297A that is greater one third of the length of a nozzle array width 298A of nozzle array 104A. In still other embodiments, caps 130A can be shaped so that a vertex 274A extends upstream from nozzle arrays 104A by a threshold distance 297A of at least ten times more than a clearance distance 248A between a cap 130A and receiver 24.
In the embodiment illustrated in
It will be appreciated that the above described embodiments of deflection surfaces 270A and 270B are shaped to divide cross-module airflow 240 so that cross-module airflow 240 is divided generally evenly and flows about caps 130A of first print line 123 in a generally balanced fashion. However, this in turn assumes that cross-module airflow 240 is not significantly unbalanced when incident on deflection surfaces 270A and 270B. To help ensure such balance, the embodiment of
As is also illustrated in
A further aspect of the embodiment of
In the embodiment that is illustrated in
In the embodiment that is illustrated in
In this embodiment, deflection surfaces 270B and 272B are shown shaped in a concave fashion corresponding to a convex shape of trailing surfaces 286A and 288A. In the embodiment illustrated this is done to create approximately constant width lower resistance flow channels 252 between caps 130A of first print line 123 and caps 130B of second print line 125. This establishes a uniform flow through the channel and inhibits the formation of recirculation zones, which can track condensation, along the trailing edges of the caps 130A. In certain embodiments deflection surfaces 270B and 272B extend away from vertices 274B at a slope of between 0.1 and 1.0 relative to the direction of receiver movement 42.
Also in this embodiment, at least one of caps 130B has a vertex 274B that extends upstream from nozzle array 104B by a threshold distance 297B that is greater one fourth of a nozzle array width 298B of nozzle array 104B. In other embodiments, it can be useful to define such shapes to provide a pattern of caps 130B that extend upstream from a nozzle array 104B by a threshold distance 297B so that resistance to flow in higher resistance flow areas 250B reduces the energy of any portion of the cross-module airflow 240 entering the higher resistance flow area 250B to a level that is below a level that is necessary to deflect ink droplets 102B in a manner that can create image artifacts. In one embodiment, the threshold distance 297B can be greater than about a quarter of a width of a nozzle array 104B about which cap 130B is located. In other embodiments, a threshold distance 297B can be at a distance that is at least ten times more than a clearance distance 248B between cap 130B and receiver 24 in a higher resistance flow area 250B formed between cap 130B and receiver 24.
It will be appreciated that the terms vertex and vertices have been used generically as a reference to a point of caps 130A and caps 130B where deflection surfaces 270A and 272A meet and where deflection surfaces 270B and 272B meet such that portions of cross-module airflow 240 on one side of such a vertex or vertices are deflected by deflection surfaces 270A and 270B respectively and such that portions of cross-module airflow 240 on another side of such a vertex or such vertices are deflected by deflection surfaces 272A and 272B respectively. In some cases these points may comprise a proper vertex of a triangle; however in other cases these points may take other forms such as tangent points on a curved surface. The terms vertices and vertexes are used herein to encompass any point of any geometry that meets the above described conditions.
As is noted above, cross-module airflow 240 will seek paths of least resistance to flow, according to the extent to which cross-module airflow 240 is deflected along a width direction 57 as cross-module airflow 240 passes through a cross-module flow path 236, there is a risk that enough of cross-module airflow 240 will escape from cross-module flow path 236 to limit the efficacy of condensation control system 118, particularly with respect to second print line 125.
Accordingly, in the embodiment of
While the airflow containment provided by sidewalls 115 and 117 helps to ensure the efficacy of cross-module airflow 240 there is a potential that interactions between sidewalls 115 and 117 and cross-module airflow 240 can create recirculation zones, backpressure, turbulence or other conditions that can create airflows that disrupt printing either at first print line 123 or at second print line 125. To reduce the possibility that this will occur, a side flow control structure 280A is provided at an end of first print line 123 and side flow control structure 280B is positioned at an opposite end of second print line 125. Side flow control structure 280A is generally shaped and sized to correspond to the shapes and size of an adjacent cap 130A and is positioned between sidewall 117 and the adjacent cap 130A so as to create a higher resistance flow area 250C and a lower resistance flow channel 252 that has flow characteristics that are similar to the flow characteristics of lower resistance flow channels 252 between caps 130A. Similarly, side flow control structure 280B is generally shaped and sized to correspond to the shapes and size of an adjacent cap 130B and is positioned between sidewall 115 and an adjacent cap 130B so as to create a higher resistance flow area 250C and a lower resistance flow channel 252 that has flow characteristics that are similar to the flow characteristics of lower resistance flow channels 252 between caps 130A.
Side flow control structures 280A and 280B can be integral to sidewalls 115 and 117 or can be separate therefrom. Where caps 130A and 130B are heated as discussed in various embodiments above, side flow control structures 280A and 280B can be heated in a similar manner. Additionally, where useful side flow control structures 280A and 280B can have openings (not shown) similar to the openings 138 of caps 130A and 130B if required or useful to better control cross-module airflow 240. Additionally, where useful an air flow can be directed out of such openings in the side flow control structures 280A and 280B that is similar to the co-linear air flow provided through the openings 138 of the caps 130A and 130B.
Also shown in
An additional cross-module airflow control feature illustrated in the embodiment of
In this embodiment the use of vacuum ports 226A, 226B, 226C, 226D and 226E to provide vacuum suction makes it is possible to provide vacuum suction within limited ranges of positions along width direction 57 that are aligned with lower resistance flow channels 252. For example, as is shown here, in this embodiment vacuum ports 226B, 226C, and 226D are aligned with confluences 296 and therefore help to ensure that pressure buildups do not occur at such confluences 296 and in regions that flow into confluences 296. By providing vacuum suction in limited areas that align with lower resistance flow channels 252 the effect of the vacuum suction in higher resistance flow areas 250B is spatially limited. This lowers the risk that such vacuum suction will, itself, induce flows of in higher resistance flow areas 250B that have a potential for causing print artifacts. The extra vacuum flow removes moist air from the local vicinity of the printhead exit in addition to the air passing underneath the printhead. In some cases, this can allow greater vacuum suction to be used than would be possible in alternative embodiments where vacuum suction is provided generally across an exit area 225 of cross-module flow path 236.
In this embodiment, additional vacuum ports 226A and 226E are shown that optionally provide vacuum suction along sidewalls 115 and 117 respectively to reduce the possibility that pressures can build up proximate thereto. The vacuum suction applied by vacuum ports 226A-226E can be, in one embodiment, about 60 to 65 cubic feet per minute. While in other embodiments, the vacuum suction applied by vacuum ports 226A-226E can be in a range of between about 30 to 100 cubic feet of air per minute.
It will be appreciated that the symmetrical shapes and arrangements illustrated in
In this regard, it will be appreciated that, to maintain optimal print quality, the spacing between for example an ink droplet catcher or a nozzle of the printhead 100 and receiver 24 should be kept to a minimum. However, to maintain large volumes of cross-module airflow 240 additional space is required. This embodiment enables the spacing between barrier 110 and receiver 24 to be large while still allowing a nozzle to receiver spacing to be maintained at a preferred smaller distance. By providing additional clearance between first surface 120 of barrier 110 and receiver 24, the risk of print defects caused by the receiver 24 contacting barrier 110 or moisture on barrier 110 is therefore reduced.
The embodiment that is illustrated in
Receiver matching plate 330 reduces air leakage under receiver 24 so that to provide more uniform airflow conditions across width direction 57 of printing module 30 so as to prevent creation of airflow between receiver 24 and barrier 110 that can create ink droplet placement errors either through deflection of receiver 24 or through deflection of ink droplets.
As is discussed above, and as is shown in
This effect is conceptually illustrated in
In this embodiment, the downstream high pressure air 342A and 342B flow through higher resistance flow areas 250A and 250B and into lower resistance flow channels 252 to flow with cross-module airflow 240 through lower resistance flow channels 252.
Returning to
The volume of co-linear airflow 214A and 214B and the downstream high pressure air 342A and upstream high pressure air 340B created thereby can benefit in certain circumstances from the use of a condensation control system 118 that provides additional features in order to allow the use of both cross-module airflow 240 and co-linear airflows 214A and 214B in order to reduce the risks that condensation will form in the cross-module flow path 236 while not creating airflows that cause errors in the placement of ink droplets 102A and 102B.
As is shown in
A plurality of interline positioning surfaces 392 are provided between first print line 123 and second print line 125. Receiver 24 is positioned by interline positioning surfaces 392 as receiver 24 passes from first print line 123 to second print line 125 such that while receiver 24 is between first print line 123 and second print line 125, receiver 24 is positioned at a far distance 396 that is greater than first print line distance 244A and second print line distance 244B. This provides an integration volume 390 between caps 130A, 130B, barrier 110 and receiver 24 where co-linear air flows 214A and 214B and cross-module airflow 240 can merge without creating flows that can enter the higher resistance flow areas 250A and 250B to create print artifacts on receiver 24.
In the embodiment that is illustrated here, far distance 396 is at least 30% greater than a first print line distance 244A and a second print line distance 244B between receiver 24 and barrier 110 at second print line 125 to create integration volume 390. In other embodiments, far distance 396 can be between about 25 to 100 percent greater than first print line distance 244A and second print line distance 244B. While in still other embodiments far distance 396 can be between about 35 to 40 percent greater than the first print line distance 244A and the second print line distance 244B. In one example embodiment, far distance 396 is 6 mm while first print line distance 244A is about 4 mm, second print line distance 244B is about 4 mm and clearance distances 248A and 248B are about 1 mm.
In some situations the aggregate flow of co-linear airflow 214 into integration area 390 by printheads 100A at a first print line 123 and a printheads 100B at second print line 125 in a printing module can create, generally, a positive pressure within integration volume 390 that helps to drive co-linear airflows 214A and 214B that flows into integration volume 390 into the lower resistance flow channels 252. For example, in some circumstances such aggregate co-linear airflow 214A and 214B can provide for example and without limitation 200 percent of the volume of air per unit time that is supplied by cross-module airflow 240. However, it will be appreciated the positive pressure should be lower than a pressure of the portion 241 of cross-module airflow 240 that flows through lower resistance flow channels 252 to avoid creating back pressure, turbulence or other problems in lower resistance flow channels 252 that can cause artifact inducing flows into higher resistance flow areas 250A and 250B.
In other situations, cross-module airflow 240 flowing through the lower resistance flow channels 252 draws co-linear airflow from integration area 390 into lower resistance flow channels 252 for flow therewith by creating a suction in lower resistance flow channels 252 proximate integration area 390. The suction in lower resistance flow channels 252 can be supplemented by vacuum applied proximate to lower resistance flow channels 252 by vacuum ports 226 as is illustrated for example with respect to
There are a variety of different ways in which interline positioning surfaces 392 can be used to position receiver 24. In the embodiment that is illustrated in
Optionally, in other embodiments of this type, printing support surfaces 410A and 410B can be incorporated, at least in part into the area to which vacuum is applied by vacuum manifold 424. In such embodiments, seals 428 and 430 and vacuum manifold 424 can be arranged accordingly.
In some embodiments, a single vacuum source 440 can be used to provide a vacuum force 442 to multiple vacuum manifolds 424 located at different positions along width direction 57 or to a single vacuum manifold 424 having multiple ports arranged along width direction 57. Additionally, in some embodiments, vacuum source 440 can be located remotely from condensation control system 118 such as an external vacuum system, which is connected to the one or more vacuum manifolds 424 of condensation control system 118 by means of vacuum ducts (not shown).
When a vacuum force 442 is output by vacuum manifold 424 during printing, the vacuum force 442 acts on receiver 24 between printing support surfaces 410A and 410B and pulls receiver 24 towards vacuum manifold 424 until further movement of receiver 24 toward vacuum manifold 424 is stopped by the presence of interline positioning surfaces 392. The intensity of the vacuum force 442 applied by vacuum source 440 need be no greater than that which is necessary to draw receiver 24 against interline positioning surfaces 392. This causes receiver 24 to flow along a non-linear path between first print line 123 and second print line 125 and to pull away from barrier 110 using a force that is evenly applied to receiver 24 lowering the risk receiver 24 will be damaged during such bending and allowing such bending to occur without requiring contact with side of receiver 24 a printed side of receiver 24. As is discussed in greater detail above, this has the effect of creating an advantageous but not always necessary integration volume 390 in which a co-linear airflow 214A and 214B, downstream high pressure air 342A and upstream high pressure air 340B can be integrated and ultimately incorporated into one of lower resistance flow channels 252 for transport along with cross-module airflow 240.
The intensity of the vacuum force 442 applied to receiver 24 can be based on particular print job characteristics. The print job characteristics include, but are not limited to, a weight of receiver 24 and a content density of the image to be printed on receiver 24.
In other embodiments, other methods for guiding receiver 24 along a path that generates an integration volume 390 can be used, including but not limited to creating an electrostatic attraction between receiver 24 and interline positioning surfaces 392 such as by inducing first electrostatic charge on receiver 24 and by inducing a second, opposite, electrostatic charge on the interline positioning surfaces 392.
In further embodiments, receiver 24 can be caused to move between first print line 123 and a second print line 125 along a non-linear path between first print line 123 and a second print line 125 by inducing a running buckle in receiver 24. Such a running buckle can be created by causing temporary reduction in a speed at which receiver 24 is moved at a position that is downstream of the position of the desired running buckle relative to a position that is upstream of the position of the desired running buckle. This can be done, for example, where printing support surface 410A comprises a roller that is rotated to advance receiver 24 toward second printing support surface 410B which also comprises in this embodiment a roller that is at least temporarily operated at a rate of rotation that advances receiver 24 at a slower rate. This difference in rate of causes a buckle to form and the buckle can be maintained as a running buckle so long as after a desired extent of buckle is formed to rates of movement of receiver 24 at printing support surface 410A and at printing support surface 410B are generally equalized.
In still other embodiments, interline positioning surfaces 392 can comprise structures such as rails, pinch rollers, turn bars or other forms of guides that are arranged relative to frame 382 and printing support surfaces 410A and 410B to cause receiver 24 to move away from barrier 110 in a manner that creates integration volume 390. In some cases, this will involve controlled contact with a printed surface of receiver 24; however, in certain embodiments such contact can be acceptable such as where such contact can be done in an unprinted edge area of receiver 24.
In any of the above described embodiments of condensation control system 118 it may be necessary or useful under certain circumstances to use other characteristics of caps 130A and 130B to help define the differences in resistance to cross-module airflow 240 provided in higher resistance flow areas 250A and 250B and in lower resistance flow channels 252, to reduce the extent to which condensation can occur on caps 130A and 130B and to help manage the flow of any condensation that does form on caps 130A and 130B. One way to accomplish this is by providing lower surface energy surfaces 350A and 350B that are positioned to confront higher resistance flow areas 250A and 250B and by providing higher surface energy surfaces 352A and 352B to confront lower resistance flow channels 252. This can be done, generally, in any of the above described embodiments.
For example,
Examples of materials that have a surface energy below 32 ergs/cm2 include but are not limited to Polyethylene, Polydimethylsiloxane, Polytetrafluoroethylene (PTFE), Polytrifluoroethylene (P3FEt/PTrFE), Polypropylene-isotactic (PP), Polyvinylidene fluoride (PVDF). Examples of materials that have a surface energy above about 40 ergs/cm2 include but are not limited to Polyethyleneoxide (PEO); Polyethyleneterephthalate (PET); Polyvinylidene chloride (PVDC) and Polyamide, Polyimide, metals such as stainless steel, silicon, ceramics such aluminum oxide. Accordingly, in an embodiment such as the embodiment illustrated in
In some embodiments, the surface energies of caps 130A and 130B will be determined by material properties of the materials used to form caps 130A and 130B. For example, in the embodiment of
In other embodiments, caps 130A and 130B can be coated with materials that will provide lower surface energy surfaces 350A and 350B confronting higher resistance flow areas that have, for example, surface energies that are below about 32 ergs per square centimeter. Similarly caps 130A and 130B can be coated with materials that will provide higher surface energy surfaces 352A and 352B confronting lower resistance flow channels 252 that have, for example, surface energies that are above about 40 ergs per square centimeter.
In still other embodiments, caps 130A and 130B can be differently processed to increase the surface energies of surfaces that confront lower resistance flow channels 252 such that these surfaces have surface energies that are above about 40 ergs per square centimeter. In one embodiment this can be done by bombarding a polymeric surface of a cap 130A that is made using a material such as a polyolefin with ions. This can be done using a flame treatment, which delivers reactive ions via a burning gas jet, or by corona surface treatment which bombards the surface with ions from a corona wire or mesh. In still other embodiments, a plasma surface treatment can be used. Here an ionized gas is discharged against a surface that will confront a lower resistance flow channel 252 to increase the surface energy of the surface. In still another embodiment, electron-beam (e-beam) irradiation can be used to increase the surface energy of a material used to make a cap 130A or 130B.
Optionally, barrier 110 can also have a second surface 122 that also has surface energy that is above 40 ergs per square centimeter. This can be done by making barrier 110 using a material that has such a surface energy, by coating barrier 110 using a material having such surface energy or by processing barrier 110 using a material that has such a surface energy. The materials and processes described above for providing surfaces of portions of caps 130A and 130B that have surface energies above 40 ergs per centimeter squared can likewise be used here to provide such surface energies with respect to second surface 122 of barrier 110. Optionally barrier 110 can have a second surface 122 having a surface energy that is higher than the surface energy of surfaces 352A and 352B preferably by at least five ergs/cm. Thus if the surface energy of surfaces 352A and 352B are 40 ergs/cm2, the surface energy of second surface 122 should be about 40 ergs/cm2 in this embodiment.
As is shown in the embodiment of
In other embodiments such abutment should provide a continuous transition higher surface energy surfaces 350A and 350B to lower surface energy surfaces 350A and 350B.
However, as is shown in
Surface energy is measured by determining the contact angle between droplets of diiodo-methane and distilled water and the surface being measured. The polar and dispersive contributions to the surface energy are determined using these liquids and the interfacial energy calculated using the Good-Girifalco approximation.
One embodiment of a method for operating a printing system is provided in
In the embodiment of
Additionally, as is shown in
Printing system controller 82 and appropriate and known humidity, temperature, and flow sensors 86 can be used to measure such data and that memory 88 can contain data fields that can provide data from which printing system controller 82 can determine expected conditions based for example on heuristic data determined during previous printing operations with inkjet printing system 20 or based previous printing operations that have been performed by printers other than inkjet printing system 20 but having similar components. Optionally printing system controller 82 can consider the printing instructions and image data or any other information in a job order in order to determine the rate of cross module airflow to be used during a printing job.
It will also be appreciated that the drawings provided herein illustrate various arrangements components of various embodiments of condensation control system 118. Unless otherwise stated herein, these arrangements are not limiting. For example and without limitation, inkjet printing system 20 is illustrated with sensors 86, electrical heater 172 and energy source 180 being positioned on a face side 140 of shields 132 that confront printing region 136. However, in other embodiments, and unless stated otherwise these components can be located on sides 142 of shields 132 that confront shielded regions 134.
In various embodiments one or more of steps 510, 512 or 514 can be used, such as guiding airflow between caps 130A and 130B (step 510) and integrating airflow (step 512) which can be done for example, by urging the receiver away from the barrier along a path that leads the receiver to a far distance that is greater than the first barrier distance and the second barrier distance to create an integration volume between the first print line and the second print line where co-linear air flow and cross-module airflow integrate to allow the co-linear airflow and the cross-module airflow to flow in combination into lower resistance flow channels provided in separations between the first plurality of caps and the second plurality of caps without creating flows into the higher resistance flow areas that cause an observable artifact in a print made using printheads 100A and 100B, and providing controlled arrangements of surface energies step 514. Any of these steps can be performed as is described in greater detail above.
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.
