CA1191048A - Random droplet liquid jet apparatus and process - Google Patents
Random droplet liquid jet apparatus and processInfo
- Publication number
- CA1191048A CA1191048A CA000395424A CA395424A CA1191048A CA 1191048 A CA1191048 A CA 1191048A CA 000395424 A CA000395424 A CA 000395424A CA 395424 A CA395424 A CA 395424A CA 1191048 A CA1191048 A CA 1191048A
- Authority
- CA
- Canada
- Prior art keywords
- droplets
- liquid
- random
- orifices
- fluid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/07—Ink jet characterised by jet control
- B41J2/115—Ink jet characterised by jet control synchronising the droplet separation and charging time
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/02—Ink jet characterised by the jet generation process generating a continuous ink jet
- B41J2/025—Ink jet characterised by the jet generation process generating a continuous ink jet by vibration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/02—Ink jet characterised by the jet generation process generating a continuous ink jet
- B41J2/03—Ink jet characterised by the jet generation process generating a continuous ink jet by pressure
Landscapes
- Treatment Of Fiber Materials (AREA)
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
- Ink Jet (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Coating Apparatus (AREA)
- Telephone Function (AREA)
- Manufacturing Of Micro-Capsules (AREA)
- Nozzles (AREA)
Abstract
RANDOM DROPLET LIQUID JET APPARATUS AND PROCESS
ABSTRACT
Fluid or liquid jet marking apparatus and process wherein the treating fluid or liquid (10) is in the form of ink, dyestuff or other printing, marking or coloring medium, is delivered under pressure to an array of jet orifices (14) from which the medium issues continuously as streams (16) that break randomly into discrete droplets in flight. The moving random droplets are selectively charged as they pass through a selectively energizable electrostatic field (18). The paths of charged droplets are controlled by a deflection means (20) which establishes a second electrostatic field through which the droplets pass. Depending on whether the droplets are charged, they are either caught by a collector (22), or impinge on a receiving substrate such as a textile, paper or any other desired medium, product or substance.
In the apparatus, the streams (16) break up randomly into droplets. Since the apparatus is not provided with a separate stimulator, vibrator or perturbation device, the orifice plate can have virtually an unlimited cross-machine length. It has been found that by controlling certain equipment parameters, such random droplet breakup can occur within a narrow distribution around a mean droplet size to produce results very much the same as with perturbed systems that use separate, regularly cyclical varicosity inducing means, and in many cases are superior to perturbed systems in a large variety of applications as the length of the orifice plate is not limited in size. The undesirable effects of droplet to droplet size and spacing variation become narrowed with increased pressure on the fluid or liquid supply and decreased diameter of the jet orifices.
ABSTRACT
Fluid or liquid jet marking apparatus and process wherein the treating fluid or liquid (10) is in the form of ink, dyestuff or other printing, marking or coloring medium, is delivered under pressure to an array of jet orifices (14) from which the medium issues continuously as streams (16) that break randomly into discrete droplets in flight. The moving random droplets are selectively charged as they pass through a selectively energizable electrostatic field (18). The paths of charged droplets are controlled by a deflection means (20) which establishes a second electrostatic field through which the droplets pass. Depending on whether the droplets are charged, they are either caught by a collector (22), or impinge on a receiving substrate such as a textile, paper or any other desired medium, product or substance.
In the apparatus, the streams (16) break up randomly into droplets. Since the apparatus is not provided with a separate stimulator, vibrator or perturbation device, the orifice plate can have virtually an unlimited cross-machine length. It has been found that by controlling certain equipment parameters, such random droplet breakup can occur within a narrow distribution around a mean droplet size to produce results very much the same as with perturbed systems that use separate, regularly cyclical varicosity inducing means, and in many cases are superior to perturbed systems in a large variety of applications as the length of the orifice plate is not limited in size. The undesirable effects of droplet to droplet size and spacing variation become narrowed with increased pressure on the fluid or liquid supply and decreased diameter of the jet orifices.
Description
~9~ B
RANDOM DROPLET LIQUID JET APPA~TUS AND PROCESS
FIELD OF THE INVENTION
This lnvention relates to the field of non-contact fluid marking devices which are commonly known as "ink je_.t devices.
THE PRIOR ART
Ink jet devices are shown generally in U.S.
Patent No. 31373r437, issued March 12, 1968, to Sweet & Cumming: No. 3,560,988, issued February 2, 1971 to Rrick; No. 3,579,721, issued May 25, 1971 to Raltenbach; and No. 3,596,275, to Sweet, issued July 27, 1971. In all of those devices, jets (very narrow streams) are created by forcing a supply of recordinq fluid or ink from a manifold through a series of fine orifices or nozzles. The chamber which contains the ink or the orifices by which the jets are formed are vibrated or "stimulated" so that the jets break up into droplets of uniform size and regular spacing.
Each stream of drops is formed in proximity to an associated selective charging electrode which establishes electrical charges on the drops as they are formed. The flight of the drops to a receiving substrate is controlled by interaction with an electrostatic deflection field through which the drops pass, which selectively deflects them in a trajectory toward the substrate, or to an ink collection and recirculation apparatus (commonly called a "gutter~) which prevents them from contacting the ~ubstrate.
While it has been known that a fine liquid jet will break into discrete droplets under its inherent thermal and acoustic mot;on even in the absence of any external perturbations, it has heretofore generally been believed that specifically ~9~
calibrated separate perturbation at or near the natural frequency of drop formation was a practical necessity to produce droplets that are regularly spaced, sized, and timed across the orifice array to permit proper use OL the apparatus. Printing with charged drops requires relatively precise control of the droplet paths to the ultimate positions on the receiving substrate, and drop size, spacing, and charge level have generally been regarded as critical factors. Thus, Sweet requires perturbation means for assuring that droplets in the stream are spaced at regular intervals and are uniform in size.
As noted in Sweet, the stream has a natural tendency, due at least in part to the surface tension of the fluid, to break up into a succession of droplets. ~owever, as is easily observed in a jet of water squirted through a garden hose nozzle, the droplets are ordinarily not uniform as to dimension or frequency. In order to assure that the droplets will be substantially uniform in dimension and frequency, Sweet provides means for introducing what he refers to as "regularly spaced varicosities~ in the stream.
These varicosities create undulations in the cross~
sectional dimension of the jet stream issuing from the nozzle. They are made to occur at or near the natural frequency of formation of the droplets. As in Sweet, this frequency may be typically on the order of 120,000 cycles per second.
A wide variety of varicosity inducing means are now known in the art. For example, Rrick utilizes a supersonic vibrator in the piping through which ink is fed from the source to the apparatus; and in Raltenbach, the ink is ejected through orifices formed in a perforated plate which is vibrated continuously at a resonant frequency.
Since the advent of the Sweet approach, non-contact marking devices utilizing fluid droplet streams have become commercially developed. Rowever, so far as is known to me, it has been a characteristic of ink jet devices that all ~f them utilize some type of varicosity inducing means or "stimulator" to induce regular vibrations into the stream to provide regularity and uniformity of the droplets.
As noted in Stoneburner U.S. Patent No.
3,88~,508, issued May 6, 1975, proper stimulation has been one of the most difficult problems in the operation of jet drop recorders. For hiqh quality recording it has been necessary that all jets be stimulated at the same frequency and with very nearly the same power to cause break-up of all the streams into uniformly sized and regularly spaced drops.
Furthermore, it is necessary that drop generation not be accompanied by generation of "satellite dropsn, and that the break-up of the streams into drops occur at a predetermined location in proximity to the charging electrode, both of which are dependent on the power of delivery at each jet.
Stoneburner shows means for generating a traveling wave along the length of an ink supply manifold of which an orifice plate forms one side. The wave guide so formed is tapered or progressively decreased in width along its length, to counteract and reduce the natural tendency toward attenuation of the drop stimulating bending waves as they travel down the length of the orifice plate.
BRIEF DESCRIPTION OF THE PRE:SENT_INVENTION
In practice, there is often an undesirable interaction between the stimulator and the structure 34~
of the ink delivery system. This adverse effect may show up as a tendency for the overall system to achieve non-uniform stimulation across the orifice array due to ref lected and interfering waves (as referred to in Stoneburner, just discu.ised), such that certain orif ices do not rece;ve appropriate stimulation while others have too much. The system thus has "cusps" or null points that are reflected as degradations in the quality of droplet deposition.
Furthermore, with these variations in power, satellite or very small droplets tend to form in between each of the larger droplets and cause difficulties within the system in that these fine droplets tend to escape and be dispersed into the surrounding area or beyond the acceptable target area limits. Satellite droplet formation is a sensitive function of the properties of the ink or treating liquid being used so that the problem of stimulation is further complicated.
Another and major limiting factor of the known perturbed ink jet systems resulting from the stimulator is that the traveling waves generated by the external or artificial perturbation means substan-tially limit the length of those devices. From a practical standpoint, such known devices are limited to cross-machine orifice plate lengths no greater than 10.5 inches (26.67 cm~ where there are 120 jets to the inch and the artificial perturbation means is operating at 48 kilocycles. At higher frequencies the possible length of the orifice plates is reduced, while at lower fre~uencies the length might be lengthened.
There are numerous disadvantages associated with such orifice plate limitations. The primary disadvantage is encountered in trying to build a perturbed orifice system suitable for treatment of continuous length broad width goods, for example including those in the textile field, wallpaper, paper or other continuous length broad width goods or in continuously or intermittently fed forms of other wide substrates or materials, where any such goods, subs-trates or materials range in width from about one foot to about several yards. Experience shows that it is extremely difficult and, practically speaking, almost impossible to combine two or more of the limited length perturbed orifice plates across the needed distance in a manner that will permit the uniform continuous treating of such goods or materials sufficiently to mask the separation between the perturbed orifice plate sections, and/or to mask the effect of their mutually different operational patterns. It becomes increasing-ly difficult to obtain a satisfactory result as the number of such short length perturbed orifice plates is increased to span increasing widths of goods to be treated.
With the present invention, however, where no artificial or external perturbation is being used (unless random perturbations are used), there is virtually no limitation on the length of the orifice plate or the extent over which such orifices can be made available for use across the width of a wide or narrow substrate or receiving medium. Thus, textile paper or other substrates having widths varying from a few feet to many yards can be treated as they are moved or otherwise indexed beneath a single, machine-wide orifice structure. A plurality of such machine-wide orifices can of course be operated in tandem or in some predetermined manner or sequence to accomplish any desired result.
It has been found that although droplet break-up in an unperturbed (unless random perturbations 4~3 are used) continuous jet system is a random process, the distribution of random droplet sizes and spacings is nevertheless quite narrow. I have also found that at smaller orifice sizes and higher fluid pressures, the variations among randomly generated droplets can be made sufficiently narrow so that the resulting random droplet streams become useful, for example, in applying color patterns or any type of treating agent or agents to textiles or for applying indicia or treatments to a variety of other surfaces employing a variety of liquids.
This "narrow random distribution" effect is utilized according to a preferred form of the invention in apparatus having; a source of treating liquid which is to be applied under higher pressure than is normally used for eguivalent accuracy of droplet placement; a series of jet orifices of smaller diameter than usual, for equivalent droplet placement accuracy, through which orifices the treating liquid or coloring medium ~0 is forced as fine streams that break randomly into discrete droplets; electrode means for imparting electrostatic charges to the drops as they form; and deflection means for directing the paths of selected droplets in the streams toward a receiving substrate or toward a gutter or other collecting means. Further, the charging electrode is more extensive than with a stimulated system since the break-off point may vary more in both space and time.
Neither the apparatus nor the process has perturbation means that would impart regular cyclical vibrations or cause the liquid being applied to break into droplets more uniform than their unperturbed, random size distribution (however random perturbations can be used).
To achieve a given accuracy of droplet place-4~
rnent, or "droplet misregistration value", an unpertur-bed system with the same flow rate requires a different orifice size and presure from those of a perturbed system. The orifice size must be smaller than would be used to achieve the same accuracy in a conventional perturbed system, typically no more than about 70% the orifice diameter of a per~urbed system having the same accuracy of droplet placement or droplet misregis-tration value. The liquid head pressure is also, or alternatively, substantially higher, preferably at least about four times that of a perturbed system with corresponding accuracy. Further, it is desirable that the charging voltage be higher, by a factor of at least about 1.5 ~imes.
For purposes of this specification and claims, the term "droplet misregistration value" is defined as the offset distance or variation from a straight line, drawn in a direction perpendicular (i.e. the "cross-machine" direction) to the direction of travel of the substrate, of a mark on the substrate when all jets in an array perpendicular to the direction of motion of the substrate are switched at the same time from being caught by the gutter to being delivered to the substrate.
The perturbations that cause drop break-off in unstimulated jets generally arise from the environment in which the system is found. Generally these fluctuations are produced by the normal sound and acoustic motion that are inherently present in the fluid. However, in some "noisy" environments, unwanted external perturbations, for example, factory whistles, vibrations from gears and other machine movements, and even sound vibrations from human voices, can have an overpowering influence and cause a change in the means break-off point of the jets in an unstimulated system.
In a modified embodiment of this invention, the system can be irregularly stimulated, as by a noise source which generates random vibrations. I believe this embodiment can be found useful where the apparatus is to be used in a noisy area. In such an environment, the application of the irregular noise vibration will surprisingly produce more regular results from jet to jet than application of regular cyclical vibrations.
In view of the above, the method or process of the present invention, for randomly generating liquid droplets and for applying selectively these droplets to a moving substrate surface, comprise preferably the following steps:
a) pressurizing a source of liquid;
b) feeding the pressurized liquid to an array of spaced apart liquid jet orifices extending in a cross-machine direction transverse of the direction of movement of the substrate surface;
c) acoustically coupling random perturbation to the liquid to actively induce random drop formation process in fluid streams issuing from the orifices;
d) selectively activating a charging electro-de means disposed downstream of the orifices and ex-tending over the zone of random drop formation to impart electrical charges to the drops as they pass thereby; and e) deflecting electrically charged droplets away from the substrate downstream of the charging step.
Other objects, features and characteristics of the present invention as well as the process, and operation and functions of the related elements and the combination of parts, and the economies of manufacture, will become more apparent from the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures.
B.RIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIGURE 1 is a diagrammatic cross-section illustration of a binary continuous fluid or liquid jet apparatus in accordance with the invention;
FIGURE 2 is a diagrammatic perspective illus-tration showing the droplet charging means and the droplet deflecting means;
FIGURE 3 is a schematic illustration of a modified embodiment of the invention wherein the appa-ratus is stimulated by a random noise generator that drives an acoustic horn; and FIGURE 4 is a diagrammatic illustration of another embodiment of a random noise perturbed system in accordance with the invention, wherein a series of piezoelectric crystals apply random noise perturbations to a wall of the fluid or liquid supply manifold or chamber.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
PRESENT INVENTION:
While this invention may be similar to previously known ink jet recording apparatus in that similar results can be achieved, the basic operating principle of the present invention differs radically from such known ink jet recording systems.
As shown diagrammatically in Figures l and 2, the apparatus includes a supply or source of treating liquid 10 under pressure in a manifold or chamber that supplies an orifice plate 12 having a plurality of jet orifices 14 extending in a "cross-machine" direction of the apparatus as shown in Figure 2. Streams or jets of liquid 16 forced through the orifices 14 pass through electrostatic droplet charging means 18, 18, which selectively imparts to the liquid charges that are retained on the droplets as the streams break into discrete droplets.
The charging plates 18, 18, must be sufficiently extensive in length and have a dimension wide enough in the direction of jet flow to charge droplets regardless of the random points at which their break-off occurs. In prior art apparatus, the perturbations caused break-off to occur in a narrow zone, downstream of the orifices. Here, without regu-lar or separate artificial or external perturbation, the point of break-off varies more widely. In order to assure that all late-to-break off droplets are charged, the ribbonlike charging plates 18-18 must provide a field that extends to the region of breakoff of such droplets. In practice, the ribbonlike charging plates should preferably have a dimension of about lOOd inches (lOOd cm) in the direction of jet flow, where d is the orifice diameter in inches or centimeters. Their width or dimension in the direction of droplet flow could range from a size greater than about 30d to less than about 300d. Charging voltages to charge plates 18,18 preferably range from about 50 to about 200 volts.
After charging, the droplets in flight then pass a deflecting ribbon or means 20 which directs the paths of the charged droplets toward a suitable gutter or collector 22. Uncharged drops proceed toward a receiving substrate 24 (e.g., a textile), which is supported by and may be conveyed in some predetermined manner by means not shown, relative to the apparatus, in the direction of arrow 26 (i.e., a longitudinal direction transverse to the "cross-machine" direction previously defined). The deflector ribbon or means 20 is preferably operated at voltages ranging from about 1000 to about 3000 volts.
Reference may be had to known ink jet devices for further details of structural elements suitable for use in such apparatus.
In part, the structure of the present invention differs frorn the prior art in that the streams break up into droplets in response to a variety of factors including internal factors such as surface tension, internal acoustic motion, and thermal motion, rather than re~ular external perturbation. No regular varicosity inducing means are utilized, in contrast to what has heretofore been believed essential. Droplet formation takes place randomly.
Lord Rayleigh explored the dynamics of fluid jets around the beginning of the 20th century. He found that a fluid stream issuing under pressure from a jet orifice breaks into indiv 7 ~/
/
,",/
r~
4~3 droplet-to-droplet intervals that statistically averaqe 2~ r, where r is the radius of the o~ifice producing the jet. The droplet diameters average about 2.11 d. ~owever, these spacings and size~ are only averages. Actual br. ;k-up is a random process;
the actual droplet size and spacings vary. The actual sizes and spacings follow normal distribution curves around the means defined by the Rayleigh formulae and in experiments since Lord Rayleigh's work I have found that the average ;s now better represented by the expression 4.51d with 4.51 being an observed or measured number. For example, ~n apparatus having an ~ ink pressure P of 12 psig and an orifice diameter of .002~, the mean droplet size is about ~004~. The normali~ed standard deviation of the droplet sizes (that is, the standard deviation of droplet size, divided by the mean droplet size) is about .1; that is, 68% of the droplets are within .0004~ of the mean droplet size of .004~ Further, the break-off point varies from jet to jet by up to six drop spacings.
These variances are too wide for utility in many applications. When intending to print a horizontal line across a substrate, all jets are commanded to print at the same time by removinq voltage ~rom the charge plate at all jet positions. It can be seen that if all jets break up into droplets at the same time and at the same distance from the orifice plate, the system will ~imultaneously cause all jets to start issuing uncharged drops and these drops will proceed to the substrate in step.
For the normal1zed standard deviaton of droplet size of approximately 0.1, a~ is encountered in practice, thl~ corre~pond3 to a~out a 32% chance the droplet will be larger or smaller by that amount and the spot size on the substrate will correspond-ingly vary by that size. This produce~ variation inthe apparent uniformity of a horizontal line. This efect will be minor, however, in that for a deviation of .l with a droplet of .004~ in diameter, the S var~ation will only be .001~.
In fllght from the point of break-off, larger drops have more mass than smaller drops, in proportion to the third power of the ratio of their diameters.
The fluid dynamic force from passage through air that tend~ to slow them down i~ proportional to the square of the ratio of their d~ameter~ so that larger drop~
tend to maintain faster speeds in traveling to the substrate. Assuming, however, that all jets break off at the same time, for an or;fice diameter of .003", a di~tance to the substrate of one inch, a jet velocity of 400 inches per second, and a deviation of .1 in the drop diameter, the misregistration on the substrate i~
les~ than two thousandths of an inch.
In the event one jet breaks off closer to the orifice plate than the mean break-off point of all ~ets by some number n of mean drop spacings (half the total spread~ the resulting droplet ~which I shall ca~l the ~late droplet~) will have a further distance to travel to the substrate than a droplet from the mean breakoff point ~which I shall call the ~mean droplet~. To date, the total spread of drop spacings I have noticed i8 about 6 or +3 and -3 about the mean. However, drop spacings can vary ~rom thl~, for example, from about 2 to about 8 but will generally be qreater than abq~t 1. If V is the ~et velocitY in ~ ches per second (or cm~sec), ~ tile orifi oe diameter in in~l~s (or cm), and V' thç rate of movement of the subs'crate in inches per second (or cm~sec), the arrival of the late drcplet at the ~ub~trate will occur about n (4. 51d~V) second~ after 35 the arrival of the ~ean dropletO During this time 4~
interval the moving substrate will have traveled a distance of n (4.51d) V'/V inches. By way of example, at a substrate speed of 60 inches per second (corresponding to a substrate moving at 100 yards per minute~, a jet velocity of 800 inches per second, an orifice diameter of ~003 inches, and with n=6, the misregistration error is .0061 inches. It is to be noted that if d were ~ times larger and V twice smaller~ the error would be 2 ~~larger, or about .017 inches. Thus, the use of the smaller diameter orifice and the higher pressure fluid in an unstimulated system can achieve smaller misregistration errors than might initially be expected as compared to a regular periodic stimulation or perturbed system of conventionalorifice diameter and pressure.
In devices heretofore available, regular periodic stimulation or perturbation means have been required to narrow the distribution in drop size to essentially zero, to achieve acceptable misregistration error. However, I have found that errors due to the distribution of drop sizes can be substantially reduced by certain conditions. This can be seen from the following analysis. The normalized standard deviation of droplet size remains constant as the diameter of the orifice is made smaller and also as the pressure P is increased, in the absence of perturbing means. If the orifice diameter is reduced by, say, K (e.g. a factor of the square root of two (~~ ), the area of the ori-fice is accordingly decreased by K (e.g. a factor of two). If, however, at the same time stream velocity is increased by a factor of K2 (e.g. two), the net flow from the orifice remains constant.
For similar charge and deflection fields the drop trajectories will remain constant, but the natural frequency now is K3 (e.g. 2 ~) higher and there are ~.
~,_'f 4~1 therefore now K3 ~e.g. 2~ ) as many drops formed per unit time, and the time of flight to the substrate for any given drop is reduced by l/K2 (e.g. halved). If the breakup point with a full sized jet varied over six drop spaces due to the random nature of break-up, as is often the case, a print error would occur of six times the break-of~ time interval times the speed of the substrate. With the smaller, higher pressure jet, the same error in break-off distance would result in an error only l/K (e.g. 1/2 ~-) as great, (e.g. that is,
RANDOM DROPLET LIQUID JET APPA~TUS AND PROCESS
FIELD OF THE INVENTION
This lnvention relates to the field of non-contact fluid marking devices which are commonly known as "ink je_.t devices.
THE PRIOR ART
Ink jet devices are shown generally in U.S.
Patent No. 31373r437, issued March 12, 1968, to Sweet & Cumming: No. 3,560,988, issued February 2, 1971 to Rrick; No. 3,579,721, issued May 25, 1971 to Raltenbach; and No. 3,596,275, to Sweet, issued July 27, 1971. In all of those devices, jets (very narrow streams) are created by forcing a supply of recordinq fluid or ink from a manifold through a series of fine orifices or nozzles. The chamber which contains the ink or the orifices by which the jets are formed are vibrated or "stimulated" so that the jets break up into droplets of uniform size and regular spacing.
Each stream of drops is formed in proximity to an associated selective charging electrode which establishes electrical charges on the drops as they are formed. The flight of the drops to a receiving substrate is controlled by interaction with an electrostatic deflection field through which the drops pass, which selectively deflects them in a trajectory toward the substrate, or to an ink collection and recirculation apparatus (commonly called a "gutter~) which prevents them from contacting the ~ubstrate.
While it has been known that a fine liquid jet will break into discrete droplets under its inherent thermal and acoustic mot;on even in the absence of any external perturbations, it has heretofore generally been believed that specifically ~9~
calibrated separate perturbation at or near the natural frequency of drop formation was a practical necessity to produce droplets that are regularly spaced, sized, and timed across the orifice array to permit proper use OL the apparatus. Printing with charged drops requires relatively precise control of the droplet paths to the ultimate positions on the receiving substrate, and drop size, spacing, and charge level have generally been regarded as critical factors. Thus, Sweet requires perturbation means for assuring that droplets in the stream are spaced at regular intervals and are uniform in size.
As noted in Sweet, the stream has a natural tendency, due at least in part to the surface tension of the fluid, to break up into a succession of droplets. ~owever, as is easily observed in a jet of water squirted through a garden hose nozzle, the droplets are ordinarily not uniform as to dimension or frequency. In order to assure that the droplets will be substantially uniform in dimension and frequency, Sweet provides means for introducing what he refers to as "regularly spaced varicosities~ in the stream.
These varicosities create undulations in the cross~
sectional dimension of the jet stream issuing from the nozzle. They are made to occur at or near the natural frequency of formation of the droplets. As in Sweet, this frequency may be typically on the order of 120,000 cycles per second.
A wide variety of varicosity inducing means are now known in the art. For example, Rrick utilizes a supersonic vibrator in the piping through which ink is fed from the source to the apparatus; and in Raltenbach, the ink is ejected through orifices formed in a perforated plate which is vibrated continuously at a resonant frequency.
Since the advent of the Sweet approach, non-contact marking devices utilizing fluid droplet streams have become commercially developed. Rowever, so far as is known to me, it has been a characteristic of ink jet devices that all ~f them utilize some type of varicosity inducing means or "stimulator" to induce regular vibrations into the stream to provide regularity and uniformity of the droplets.
As noted in Stoneburner U.S. Patent No.
3,88~,508, issued May 6, 1975, proper stimulation has been one of the most difficult problems in the operation of jet drop recorders. For hiqh quality recording it has been necessary that all jets be stimulated at the same frequency and with very nearly the same power to cause break-up of all the streams into uniformly sized and regularly spaced drops.
Furthermore, it is necessary that drop generation not be accompanied by generation of "satellite dropsn, and that the break-up of the streams into drops occur at a predetermined location in proximity to the charging electrode, both of which are dependent on the power of delivery at each jet.
Stoneburner shows means for generating a traveling wave along the length of an ink supply manifold of which an orifice plate forms one side. The wave guide so formed is tapered or progressively decreased in width along its length, to counteract and reduce the natural tendency toward attenuation of the drop stimulating bending waves as they travel down the length of the orifice plate.
BRIEF DESCRIPTION OF THE PRE:SENT_INVENTION
In practice, there is often an undesirable interaction between the stimulator and the structure 34~
of the ink delivery system. This adverse effect may show up as a tendency for the overall system to achieve non-uniform stimulation across the orifice array due to ref lected and interfering waves (as referred to in Stoneburner, just discu.ised), such that certain orif ices do not rece;ve appropriate stimulation while others have too much. The system thus has "cusps" or null points that are reflected as degradations in the quality of droplet deposition.
Furthermore, with these variations in power, satellite or very small droplets tend to form in between each of the larger droplets and cause difficulties within the system in that these fine droplets tend to escape and be dispersed into the surrounding area or beyond the acceptable target area limits. Satellite droplet formation is a sensitive function of the properties of the ink or treating liquid being used so that the problem of stimulation is further complicated.
Another and major limiting factor of the known perturbed ink jet systems resulting from the stimulator is that the traveling waves generated by the external or artificial perturbation means substan-tially limit the length of those devices. From a practical standpoint, such known devices are limited to cross-machine orifice plate lengths no greater than 10.5 inches (26.67 cm~ where there are 120 jets to the inch and the artificial perturbation means is operating at 48 kilocycles. At higher frequencies the possible length of the orifice plates is reduced, while at lower fre~uencies the length might be lengthened.
There are numerous disadvantages associated with such orifice plate limitations. The primary disadvantage is encountered in trying to build a perturbed orifice system suitable for treatment of continuous length broad width goods, for example including those in the textile field, wallpaper, paper or other continuous length broad width goods or in continuously or intermittently fed forms of other wide substrates or materials, where any such goods, subs-trates or materials range in width from about one foot to about several yards. Experience shows that it is extremely difficult and, practically speaking, almost impossible to combine two or more of the limited length perturbed orifice plates across the needed distance in a manner that will permit the uniform continuous treating of such goods or materials sufficiently to mask the separation between the perturbed orifice plate sections, and/or to mask the effect of their mutually different operational patterns. It becomes increasing-ly difficult to obtain a satisfactory result as the number of such short length perturbed orifice plates is increased to span increasing widths of goods to be treated.
With the present invention, however, where no artificial or external perturbation is being used (unless random perturbations are used), there is virtually no limitation on the length of the orifice plate or the extent over which such orifices can be made available for use across the width of a wide or narrow substrate or receiving medium. Thus, textile paper or other substrates having widths varying from a few feet to many yards can be treated as they are moved or otherwise indexed beneath a single, machine-wide orifice structure. A plurality of such machine-wide orifices can of course be operated in tandem or in some predetermined manner or sequence to accomplish any desired result.
It has been found that although droplet break-up in an unperturbed (unless random perturbations 4~3 are used) continuous jet system is a random process, the distribution of random droplet sizes and spacings is nevertheless quite narrow. I have also found that at smaller orifice sizes and higher fluid pressures, the variations among randomly generated droplets can be made sufficiently narrow so that the resulting random droplet streams become useful, for example, in applying color patterns or any type of treating agent or agents to textiles or for applying indicia or treatments to a variety of other surfaces employing a variety of liquids.
This "narrow random distribution" effect is utilized according to a preferred form of the invention in apparatus having; a source of treating liquid which is to be applied under higher pressure than is normally used for eguivalent accuracy of droplet placement; a series of jet orifices of smaller diameter than usual, for equivalent droplet placement accuracy, through which orifices the treating liquid or coloring medium ~0 is forced as fine streams that break randomly into discrete droplets; electrode means for imparting electrostatic charges to the drops as they form; and deflection means for directing the paths of selected droplets in the streams toward a receiving substrate or toward a gutter or other collecting means. Further, the charging electrode is more extensive than with a stimulated system since the break-off point may vary more in both space and time.
Neither the apparatus nor the process has perturbation means that would impart regular cyclical vibrations or cause the liquid being applied to break into droplets more uniform than their unperturbed, random size distribution (however random perturbations can be used).
To achieve a given accuracy of droplet place-4~
rnent, or "droplet misregistration value", an unpertur-bed system with the same flow rate requires a different orifice size and presure from those of a perturbed system. The orifice size must be smaller than would be used to achieve the same accuracy in a conventional perturbed system, typically no more than about 70% the orifice diameter of a per~urbed system having the same accuracy of droplet placement or droplet misregis-tration value. The liquid head pressure is also, or alternatively, substantially higher, preferably at least about four times that of a perturbed system with corresponding accuracy. Further, it is desirable that the charging voltage be higher, by a factor of at least about 1.5 ~imes.
For purposes of this specification and claims, the term "droplet misregistration value" is defined as the offset distance or variation from a straight line, drawn in a direction perpendicular (i.e. the "cross-machine" direction) to the direction of travel of the substrate, of a mark on the substrate when all jets in an array perpendicular to the direction of motion of the substrate are switched at the same time from being caught by the gutter to being delivered to the substrate.
The perturbations that cause drop break-off in unstimulated jets generally arise from the environment in which the system is found. Generally these fluctuations are produced by the normal sound and acoustic motion that are inherently present in the fluid. However, in some "noisy" environments, unwanted external perturbations, for example, factory whistles, vibrations from gears and other machine movements, and even sound vibrations from human voices, can have an overpowering influence and cause a change in the means break-off point of the jets in an unstimulated system.
In a modified embodiment of this invention, the system can be irregularly stimulated, as by a noise source which generates random vibrations. I believe this embodiment can be found useful where the apparatus is to be used in a noisy area. In such an environment, the application of the irregular noise vibration will surprisingly produce more regular results from jet to jet than application of regular cyclical vibrations.
In view of the above, the method or process of the present invention, for randomly generating liquid droplets and for applying selectively these droplets to a moving substrate surface, comprise preferably the following steps:
a) pressurizing a source of liquid;
b) feeding the pressurized liquid to an array of spaced apart liquid jet orifices extending in a cross-machine direction transverse of the direction of movement of the substrate surface;
c) acoustically coupling random perturbation to the liquid to actively induce random drop formation process in fluid streams issuing from the orifices;
d) selectively activating a charging electro-de means disposed downstream of the orifices and ex-tending over the zone of random drop formation to impart electrical charges to the drops as they pass thereby; and e) deflecting electrically charged droplets away from the substrate downstream of the charging step.
Other objects, features and characteristics of the present invention as well as the process, and operation and functions of the related elements and the combination of parts, and the economies of manufacture, will become more apparent from the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures.
B.RIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIGURE 1 is a diagrammatic cross-section illustration of a binary continuous fluid or liquid jet apparatus in accordance with the invention;
FIGURE 2 is a diagrammatic perspective illus-tration showing the droplet charging means and the droplet deflecting means;
FIGURE 3 is a schematic illustration of a modified embodiment of the invention wherein the appa-ratus is stimulated by a random noise generator that drives an acoustic horn; and FIGURE 4 is a diagrammatic illustration of another embodiment of a random noise perturbed system in accordance with the invention, wherein a series of piezoelectric crystals apply random noise perturbations to a wall of the fluid or liquid supply manifold or chamber.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
PRESENT INVENTION:
While this invention may be similar to previously known ink jet recording apparatus in that similar results can be achieved, the basic operating principle of the present invention differs radically from such known ink jet recording systems.
As shown diagrammatically in Figures l and 2, the apparatus includes a supply or source of treating liquid 10 under pressure in a manifold or chamber that supplies an orifice plate 12 having a plurality of jet orifices 14 extending in a "cross-machine" direction of the apparatus as shown in Figure 2. Streams or jets of liquid 16 forced through the orifices 14 pass through electrostatic droplet charging means 18, 18, which selectively imparts to the liquid charges that are retained on the droplets as the streams break into discrete droplets.
The charging plates 18, 18, must be sufficiently extensive in length and have a dimension wide enough in the direction of jet flow to charge droplets regardless of the random points at which their break-off occurs. In prior art apparatus, the perturbations caused break-off to occur in a narrow zone, downstream of the orifices. Here, without regu-lar or separate artificial or external perturbation, the point of break-off varies more widely. In order to assure that all late-to-break off droplets are charged, the ribbonlike charging plates 18-18 must provide a field that extends to the region of breakoff of such droplets. In practice, the ribbonlike charging plates should preferably have a dimension of about lOOd inches (lOOd cm) in the direction of jet flow, where d is the orifice diameter in inches or centimeters. Their width or dimension in the direction of droplet flow could range from a size greater than about 30d to less than about 300d. Charging voltages to charge plates 18,18 preferably range from about 50 to about 200 volts.
After charging, the droplets in flight then pass a deflecting ribbon or means 20 which directs the paths of the charged droplets toward a suitable gutter or collector 22. Uncharged drops proceed toward a receiving substrate 24 (e.g., a textile), which is supported by and may be conveyed in some predetermined manner by means not shown, relative to the apparatus, in the direction of arrow 26 (i.e., a longitudinal direction transverse to the "cross-machine" direction previously defined). The deflector ribbon or means 20 is preferably operated at voltages ranging from about 1000 to about 3000 volts.
Reference may be had to known ink jet devices for further details of structural elements suitable for use in such apparatus.
In part, the structure of the present invention differs frorn the prior art in that the streams break up into droplets in response to a variety of factors including internal factors such as surface tension, internal acoustic motion, and thermal motion, rather than re~ular external perturbation. No regular varicosity inducing means are utilized, in contrast to what has heretofore been believed essential. Droplet formation takes place randomly.
Lord Rayleigh explored the dynamics of fluid jets around the beginning of the 20th century. He found that a fluid stream issuing under pressure from a jet orifice breaks into indiv 7 ~/
/
,",/
r~
4~3 droplet-to-droplet intervals that statistically averaqe 2~ r, where r is the radius of the o~ifice producing the jet. The droplet diameters average about 2.11 d. ~owever, these spacings and size~ are only averages. Actual br. ;k-up is a random process;
the actual droplet size and spacings vary. The actual sizes and spacings follow normal distribution curves around the means defined by the Rayleigh formulae and in experiments since Lord Rayleigh's work I have found that the average ;s now better represented by the expression 4.51d with 4.51 being an observed or measured number. For example, ~n apparatus having an ~ ink pressure P of 12 psig and an orifice diameter of .002~, the mean droplet size is about ~004~. The normali~ed standard deviation of the droplet sizes (that is, the standard deviation of droplet size, divided by the mean droplet size) is about .1; that is, 68% of the droplets are within .0004~ of the mean droplet size of .004~ Further, the break-off point varies from jet to jet by up to six drop spacings.
These variances are too wide for utility in many applications. When intending to print a horizontal line across a substrate, all jets are commanded to print at the same time by removinq voltage ~rom the charge plate at all jet positions. It can be seen that if all jets break up into droplets at the same time and at the same distance from the orifice plate, the system will ~imultaneously cause all jets to start issuing uncharged drops and these drops will proceed to the substrate in step.
For the normal1zed standard deviaton of droplet size of approximately 0.1, a~ is encountered in practice, thl~ corre~pond3 to a~out a 32% chance the droplet will be larger or smaller by that amount and the spot size on the substrate will correspond-ingly vary by that size. This produce~ variation inthe apparent uniformity of a horizontal line. This efect will be minor, however, in that for a deviation of .l with a droplet of .004~ in diameter, the S var~ation will only be .001~.
In fllght from the point of break-off, larger drops have more mass than smaller drops, in proportion to the third power of the ratio of their diameters.
The fluid dynamic force from passage through air that tend~ to slow them down i~ proportional to the square of the ratio of their d~ameter~ so that larger drop~
tend to maintain faster speeds in traveling to the substrate. Assuming, however, that all jets break off at the same time, for an or;fice diameter of .003", a di~tance to the substrate of one inch, a jet velocity of 400 inches per second, and a deviation of .1 in the drop diameter, the misregistration on the substrate i~
les~ than two thousandths of an inch.
In the event one jet breaks off closer to the orifice plate than the mean break-off point of all ~ets by some number n of mean drop spacings (half the total spread~ the resulting droplet ~which I shall ca~l the ~late droplet~) will have a further distance to travel to the substrate than a droplet from the mean breakoff point ~which I shall call the ~mean droplet~. To date, the total spread of drop spacings I have noticed i8 about 6 or +3 and -3 about the mean. However, drop spacings can vary ~rom thl~, for example, from about 2 to about 8 but will generally be qreater than abq~t 1. If V is the ~et velocitY in ~ ches per second (or cm~sec), ~ tile orifi oe diameter in in~l~s (or cm), and V' thç rate of movement of the subs'crate in inches per second (or cm~sec), the arrival of the late drcplet at the ~ub~trate will occur about n (4. 51d~V) second~ after 35 the arrival of the ~ean dropletO During this time 4~
interval the moving substrate will have traveled a distance of n (4.51d) V'/V inches. By way of example, at a substrate speed of 60 inches per second (corresponding to a substrate moving at 100 yards per minute~, a jet velocity of 800 inches per second, an orifice diameter of ~003 inches, and with n=6, the misregistration error is .0061 inches. It is to be noted that if d were ~ times larger and V twice smaller~ the error would be 2 ~~larger, or about .017 inches. Thus, the use of the smaller diameter orifice and the higher pressure fluid in an unstimulated system can achieve smaller misregistration errors than might initially be expected as compared to a regular periodic stimulation or perturbed system of conventionalorifice diameter and pressure.
In devices heretofore available, regular periodic stimulation or perturbation means have been required to narrow the distribution in drop size to essentially zero, to achieve acceptable misregistration error. However, I have found that errors due to the distribution of drop sizes can be substantially reduced by certain conditions. This can be seen from the following analysis. The normalized standard deviation of droplet size remains constant as the diameter of the orifice is made smaller and also as the pressure P is increased, in the absence of perturbing means. If the orifice diameter is reduced by, say, K (e.g. a factor of the square root of two (~~ ), the area of the ori-fice is accordingly decreased by K (e.g. a factor of two). If, however, at the same time stream velocity is increased by a factor of K2 (e.g. two), the net flow from the orifice remains constant.
For similar charge and deflection fields the drop trajectories will remain constant, but the natural frequency now is K3 (e.g. 2 ~) higher and there are ~.
~,_'f 4~1 therefore now K3 ~e.g. 2~ ) as many drops formed per unit time, and the time of flight to the substrate for any given drop is reduced by l/K2 (e.g. halved). If the breakup point with a full sized jet varied over six drop spaces due to the random nature of break-up, as is often the case, a print error would occur of six times the break-of~ time interval times the speed of the substrate. With the smaller, higher pressure jet, the same error in break-off distance would result in an error only l/K (e.g. 1/2 ~-) as great, (e.g. that is,
2.12 in this example instead of six or only 35% of the error above). That is, an unperturbed (or randomly perturbed) system with drop formation points that vary by about six drop spaces may be made to have smaller than expected (and perhaps about the same) droplet misregistration error as compared to a periodically stimulated system having drop formation points that vary by only about two drop spaces if the orifice diameter and stream volocity are decreased and increased respectively by factors K and K where K is about equal to the square root of two. Furthermore, fluctuations in density would now be averaged over K3 (e.g. 2 ~~) drops; (e g. if there is a 32% chance that the drop radius for the larger orifice case varied 10%, with a corresponding volume variation of 33~, there would only be a 9% chance the smaller orifice system would so vary).
Though a regularly stimulated system can in principle be designed to deliver with high accuracy, in practice errors occur of up to two drop spacings. With an unstimulated system, the break-off point can vary over six to seven drop spacings, but by reducing orifice size and increasing pressure, this error can be reduced to that of a stimulated system with the larger orifice size, while still offering the advantage of substantially unlimited orifice plate length.
In general for this purpose, the orifice size may be in the range of 00035 to .020 inches; and the fluid or liquid pressure may be in the range of 2 to 500 psig. The value of droplet misregistration error can be less than about 0.1 inch for applications on substrates having a relatively smooth surface while for application to substrates having relatively unsmooth, rough or fibrous surfaces the droplet misregistration error can be less than about 0.4 inches, or even 0 9 inches where such misregistration could be acceptable, such as where the printing or image will only be viewed from a distance.
More specifically I have found that general applications of a liquid to treat a substrate require an orifice diameter of about 0.004 inches, with the center to center spacing of orifices being about 0.016 inches. The liquid head pressures behind the orifices can vary from about 2 to about 30 psig. However, the preferred pressure range varies from about 3 to about 7 psig. The substrate can move at a velocity (V') of about 0 to about 480 inches per second with a preferred narrower range varying from about 5 to about 150 inches per second and the most preferred rate being about 60 inches per second (100 yards per minute).
~ ore general ranges for the parameters invol-ved, including the orifice and pressure ranges, are a jet velocity (V) ranging from about 200 to about 3200 inches per second with the more preferred velocity range varying from about 200 to about 500 inches per second for a general purpose liquid applicator and the most preferred jet velocity being a~out 400 inches per second. Also, in certain instances substrates might be moved at rates faster than 480 inches per second, and this apparatus could have applicability to print at ^~3 such substrate feed rates.
Fine printing, coloring, and/or imaging of substrates similar to the results obtainable from a regularly perturbed system can be obtained with the present invention by using an orifice having a diameter of about 0.0013 inches with appropriate center to center spacing. The pressures will be greater than in the general application circumstances above and will range from about 15 to about 70 psig, with the preferred pressure being about 30 psig. Here jet velocities will preferably vary from about 600 to about 1000 , , lS
/
B
inches per second with the preferred velocity being about 800 inches per second.
The viscosities of the ink, colorant or treating liquia are limited only by the characteris-5 tics of the particulac treating liquid or coloringmediu~ relative to the ocifice dimension. From a practical standpoint, the liquid or medium will generally have a viscosity less than about 100 cps and pceferably about 1 to about 25 cps.
Since the present invention can ~roduce applicators of virtually almost any ori~ice plate length, as discussed previously, the ranqe of application, unlike the previously discussed regularly ~rturbed systems, is extremely broad. This is because the jet lS ocifices can not only be constructed in very short lengths, such as a few centimeters or inches, they can also extend for any desired distance for example,0.1 inch to 15 feet or longer. Accordingly, the present invention is uniquely suitable for use with wide webs or where relatively large surfaces are to be colored or printed with indicia of some type. One example is printing, coloring or otherwise plaring images on textiles but it should be clearly unaerstood this is not the only application of this invention. In a similac manner the characteristics of the receiving substcate can vary markedly.
In textile applications all textile ~yes and dyestuffs ana colorants can be used, being either natural o~ synthetic, so long as they are compatible with the material from which the orifice plate is constructed, such as stainles5 steel or other chemically resistant materials or combinatlons thereof, and are compatible as well with the orifice dimensions which are desired to be use~. (Large particle mate~ials can cau se unwa n tea clogg I ng . ) ~, ~9~1~48 Suitable textile dyes include reactive, vatt dlsperse.
direct, acid, basic, al~zarine, azoicO naph~hol, pigmen~ and sulphur dye~. Included among ~uitable colorant~ are ink~, tints, vegetable dyes, lakes, mordant~ and mineral color~.
Included among the types of treating liquids are any des~red printing, coloring or image forming agents or mediums, including fixatives, dispersants, salt~, reductant~, oxidant~, bleaches, resist~, fluorscent brighteners and gum~ as well a~ any other known chemical fini~hing agents ~uch a~ various resins, and reactant~ and component~ thereof, in addition to numerous additi~es and modifying agents.
It is believed that all such materials could be effectively employed acco~ding to the present invention to produce desired effects on a variety of substrates, a~ or example, all types of paper and paper like product~, cloth and textlle webs of various woven, knitted, needled, tu~ted, felted, batt, spun, bonded and other non woven types, metal sheet, plastic3, glass, gypsum and similar composition board, varlous laminates including plywood, veneers, chipboara, various fiber and re~in composltes, like Masonite, or any other materlal as well a~ on a ~ariety of ~urface~ including flat, curved, smooth, roughened, or variou~ other forms.
The apparatus shown in Figures 1 and 2 is unperturbed. As previou~ly mentioned, background or other vibrations in the area of u~e can themselves ~omet~me3 act as perturbation means and produce unaesirable variable re~ults. Fi~ures 3 and 4 show a modified embodiment of the apparatu~, wherein the qyste~ i5 not regularly perturbed, but i8 ~ub~ect to ~rregular or no~e perturba~on, which overrlde~ or ma~ks ~uch background vibration.
LO41~3 In ~$gure 3 ~he noi~e source includes an amplifier 30 which applie~ noise from a resistive or other electrical ~ource 32, to a transducer such as an acoustic horn 34. The horn imparts the noi~e vibrations to the fluid or the mani~oldO These random perturbations may be applied to the ~luid us1ng prior art transducer~; but the perturbation they apply herein i~ irregular, not regular.
In Figure 4, the nose transducer is a set of piezoelectric crystals 40 which are mounted to wall 42 of the fluid manifold 12. Other types of transducers may be used, as known in the art. The dif~erence is that the~ are operated in a narrow band of random frequencie~, not at regular frequencies.
It is desirable that the central frequency of the noise approximate the natural frequency of droplet breakup. This is about V/4.51 d cycles per second where d ~s the jet diameter in inches and V the velocity of the jet in inches per second. The band width is desirably less than about 12,000 cycles/
~econd, so that the random vibrations are most efective in achieving breakoff.
While the invention ha~ been descr ibed in connection with what i~ presently considered to be the most practical and preferred embodiments, it i~ to be understood that the invention i3 not to be limited to the disclosed embodiments but on the contrary, i5 intended to cover variou~ modifications and equivalent arrangements included within the ~pirit and scope of the appended claims, which scope i5 to be accorded the broadeYt interpretation ~o aQ to encompas~ all such ~odifications and equivalent s~ructures.
B
Though a regularly stimulated system can in principle be designed to deliver with high accuracy, in practice errors occur of up to two drop spacings. With an unstimulated system, the break-off point can vary over six to seven drop spacings, but by reducing orifice size and increasing pressure, this error can be reduced to that of a stimulated system with the larger orifice size, while still offering the advantage of substantially unlimited orifice plate length.
In general for this purpose, the orifice size may be in the range of 00035 to .020 inches; and the fluid or liquid pressure may be in the range of 2 to 500 psig. The value of droplet misregistration error can be less than about 0.1 inch for applications on substrates having a relatively smooth surface while for application to substrates having relatively unsmooth, rough or fibrous surfaces the droplet misregistration error can be less than about 0.4 inches, or even 0 9 inches where such misregistration could be acceptable, such as where the printing or image will only be viewed from a distance.
More specifically I have found that general applications of a liquid to treat a substrate require an orifice diameter of about 0.004 inches, with the center to center spacing of orifices being about 0.016 inches. The liquid head pressures behind the orifices can vary from about 2 to about 30 psig. However, the preferred pressure range varies from about 3 to about 7 psig. The substrate can move at a velocity (V') of about 0 to about 480 inches per second with a preferred narrower range varying from about 5 to about 150 inches per second and the most preferred rate being about 60 inches per second (100 yards per minute).
~ ore general ranges for the parameters invol-ved, including the orifice and pressure ranges, are a jet velocity (V) ranging from about 200 to about 3200 inches per second with the more preferred velocity range varying from about 200 to about 500 inches per second for a general purpose liquid applicator and the most preferred jet velocity being a~out 400 inches per second. Also, in certain instances substrates might be moved at rates faster than 480 inches per second, and this apparatus could have applicability to print at ^~3 such substrate feed rates.
Fine printing, coloring, and/or imaging of substrates similar to the results obtainable from a regularly perturbed system can be obtained with the present invention by using an orifice having a diameter of about 0.0013 inches with appropriate center to center spacing. The pressures will be greater than in the general application circumstances above and will range from about 15 to about 70 psig, with the preferred pressure being about 30 psig. Here jet velocities will preferably vary from about 600 to about 1000 , , lS
/
B
inches per second with the preferred velocity being about 800 inches per second.
The viscosities of the ink, colorant or treating liquia are limited only by the characteris-5 tics of the particulac treating liquid or coloringmediu~ relative to the ocifice dimension. From a practical standpoint, the liquid or medium will generally have a viscosity less than about 100 cps and pceferably about 1 to about 25 cps.
Since the present invention can ~roduce applicators of virtually almost any ori~ice plate length, as discussed previously, the ranqe of application, unlike the previously discussed regularly ~rturbed systems, is extremely broad. This is because the jet lS ocifices can not only be constructed in very short lengths, such as a few centimeters or inches, they can also extend for any desired distance for example,0.1 inch to 15 feet or longer. Accordingly, the present invention is uniquely suitable for use with wide webs or where relatively large surfaces are to be colored or printed with indicia of some type. One example is printing, coloring or otherwise plaring images on textiles but it should be clearly unaerstood this is not the only application of this invention. In a similac manner the characteristics of the receiving substcate can vary markedly.
In textile applications all textile ~yes and dyestuffs ana colorants can be used, being either natural o~ synthetic, so long as they are compatible with the material from which the orifice plate is constructed, such as stainles5 steel or other chemically resistant materials or combinatlons thereof, and are compatible as well with the orifice dimensions which are desired to be use~. (Large particle mate~ials can cau se unwa n tea clogg I ng . ) ~, ~9~1~48 Suitable textile dyes include reactive, vatt dlsperse.
direct, acid, basic, al~zarine, azoicO naph~hol, pigmen~ and sulphur dye~. Included among ~uitable colorant~ are ink~, tints, vegetable dyes, lakes, mordant~ and mineral color~.
Included among the types of treating liquids are any des~red printing, coloring or image forming agents or mediums, including fixatives, dispersants, salt~, reductant~, oxidant~, bleaches, resist~, fluorscent brighteners and gum~ as well a~ any other known chemical fini~hing agents ~uch a~ various resins, and reactant~ and component~ thereof, in addition to numerous additi~es and modifying agents.
It is believed that all such materials could be effectively employed acco~ding to the present invention to produce desired effects on a variety of substrates, a~ or example, all types of paper and paper like product~, cloth and textlle webs of various woven, knitted, needled, tu~ted, felted, batt, spun, bonded and other non woven types, metal sheet, plastic3, glass, gypsum and similar composition board, varlous laminates including plywood, veneers, chipboara, various fiber and re~in composltes, like Masonite, or any other materlal as well a~ on a ~ariety of ~urface~ including flat, curved, smooth, roughened, or variou~ other forms.
The apparatus shown in Figures 1 and 2 is unperturbed. As previou~ly mentioned, background or other vibrations in the area of u~e can themselves ~omet~me3 act as perturbation means and produce unaesirable variable re~ults. Fi~ures 3 and 4 show a modified embodiment of the apparatu~, wherein the qyste~ i5 not regularly perturbed, but i8 ~ub~ect to ~rregular or no~e perturba~on, which overrlde~ or ma~ks ~uch background vibration.
LO41~3 In ~$gure 3 ~he noi~e source includes an amplifier 30 which applie~ noise from a resistive or other electrical ~ource 32, to a transducer such as an acoustic horn 34. The horn imparts the noi~e vibrations to the fluid or the mani~oldO These random perturbations may be applied to the ~luid us1ng prior art transducer~; but the perturbation they apply herein i~ irregular, not regular.
In Figure 4, the nose transducer is a set of piezoelectric crystals 40 which are mounted to wall 42 of the fluid manifold 12. Other types of transducers may be used, as known in the art. The dif~erence is that the~ are operated in a narrow band of random frequencie~, not at regular frequencies.
It is desirable that the central frequency of the noise approximate the natural frequency of droplet breakup. This is about V/4.51 d cycles per second where d ~s the jet diameter in inches and V the velocity of the jet in inches per second. The band width is desirably less than about 12,000 cycles/
~econd, so that the random vibrations are most efective in achieving breakoff.
While the invention ha~ been descr ibed in connection with what i~ presently considered to be the most practical and preferred embodiments, it i~ to be understood that the invention i3 not to be limited to the disclosed embodiments but on the contrary, i5 intended to cover variou~ modifications and equivalent arrangements included within the ~pirit and scope of the appended claims, which scope i5 to be accorded the broadeYt interpretation ~o aQ to encompas~ all such ~odifications and equivalent s~ructures.
B
Claims (19)
1. An apparatus for randomly generating liquid droplets and for selectively applying such liquid droplets to a moving substrate surface, said apparatus comprising:
- a source of pressurized liquid;
- an array of spaced apart liquid jet orifices extending in a cross-machine direction trans-verse to the direction of movement of said substrate surface, each of said orifices being in fluid communication with said source of pressurized fluid;
- random signal generation means acoustically coupled to said liquid for actively induc-ing random drop formation processes in fluid streams issuing from said orifices;
- charging electrode means disposed downstream of said orifices and extending over the zone of random drop formation for selectively imparting electrical charges to said drops as they are randomly formed; and - deflection electrode means disposed downstream of said charging electrode means for deflecting electrically charged droplets away from the substrate surface.
- a source of pressurized liquid;
- an array of spaced apart liquid jet orifices extending in a cross-machine direction trans-verse to the direction of movement of said substrate surface, each of said orifices being in fluid communication with said source of pressurized fluid;
- random signal generation means acoustically coupled to said liquid for actively induc-ing random drop formation processes in fluid streams issuing from said orifices;
- charging electrode means disposed downstream of said orifices and extending over the zone of random drop formation for selectively imparting electrical charges to said drops as they are randomly formed; and - deflection electrode means disposed downstream of said charging electrode means for deflecting electrically charged droplets away from the substrate surface.
2. Apparatus as in claim 1, wherein said ran-dom signal generation means generates and utilizes noise signals only within a predetermined range of frequencies.
3. Method for randomly generating liquid droplets and for selectively applying such liquid droplets to a moving substrate surface, said method comprising:
- pressurizing a source of liquid;
- feeding said pressurized liquid to an array of spaced apart liquid jet orifices extending in a cross-machine direction transverse to the direction of movement of said substrate surface;
- acoustically coupling random pertur-bations to said liquid to actively induce random drop formation processes in fluid streams issuing from said orifices;
- selectively activating a charging electrode means disposed downstream of said orifices and extending over the zone of random drop formation to impart electrical charges to said drops as they pass thereby; and - deflecting electrically charged drop-lets away from the substrate surface downstream of said charging step.
- pressurizing a source of liquid;
- feeding said pressurized liquid to an array of spaced apart liquid jet orifices extending in a cross-machine direction transverse to the direction of movement of said substrate surface;
- acoustically coupling random pertur-bations to said liquid to actively induce random drop formation processes in fluid streams issuing from said orifices;
- selectively activating a charging electrode means disposed downstream of said orifices and extending over the zone of random drop formation to impart electrical charges to said drops as they pass thereby; and - deflecting electrically charged drop-lets away from the substrate surface downstream of said charging step.
4. Method as in claim 3, wherein said acoustic coupling step utilizes noise signals only within a predetermined range of frequencies.
5. Apparatus for applying liquid droplets to a moving substrate surface along a cross-machine dimension substantially in excess of 10.5 inches, said apparatus comprising:
- a source of pressurized fluid;
- random drop generation means in fluid communication with said source including spaced apart liquid jet orifices extending in an unbroken array along said cross-machine dimension and random signal generation means acoustically coupled to said fluid for randomly generating droplets in the fluid streams issuing from the orifices in a manner substantially independent of the cross-machine dimension by avoiding stationary standing acoustic waves or other phenomena associated with regular periodic perturbations that would, if regular periodic perturbations were used, limit the maximum cross-machine dimension;
- charging electrode means disposed downstream of said orifices and extending over the zone of random drop formation for imparting electrical charges to said drops as they pass thereby; and - deflection electrode means disposed downstream of said charging electrode means for de-flecting electrically charged droplets away from the substrate surface.
- a source of pressurized fluid;
- random drop generation means in fluid communication with said source including spaced apart liquid jet orifices extending in an unbroken array along said cross-machine dimension and random signal generation means acoustically coupled to said fluid for randomly generating droplets in the fluid streams issuing from the orifices in a manner substantially independent of the cross-machine dimension by avoiding stationary standing acoustic waves or other phenomena associated with regular periodic perturbations that would, if regular periodic perturbations were used, limit the maximum cross-machine dimension;
- charging electrode means disposed downstream of said orifices and extending over the zone of random drop formation for imparting electrical charges to said drops as they pass thereby; and - deflection electrode means disposed downstream of said charging electrode means for de-flecting electrically charged droplets away from the substrate surface.
6. Apparatus as in claim 5, wherein said random drop generation means generates and utilizes noise signals only within a predetermined range of frequencies.
7. Method for applying liquid droplets to a moving substrate surface along a cross-machine dimen-sion substantially in excess of 10.5 inches, said method comprising:
- pressurizing a source of fluid;
- randomly generating droplets from said fluid using spaced apart liquid jet orifices extending in an unbroken array along said cross-machine dimension and coupling random perturbations to said liquid for randomly generating droplets in the fluid streams issuing from the orifices in a manner substantially independent of the cross-machine dimension by avoiding stationary standing acoustic waves or other phenomena associated with regular periodic perturbations that would, if used, limit the maximum cross-machine dimen-sion;
- selectively activating a charging electrode means disposed downstream of said orifices and extending over the zone of random drop formation for imparting electrical charges to said drops as they pass thereby; and - deflecting electrically charged drop-lets away from the substrate surface.
- pressurizing a source of fluid;
- randomly generating droplets from said fluid using spaced apart liquid jet orifices extending in an unbroken array along said cross-machine dimension and coupling random perturbations to said liquid for randomly generating droplets in the fluid streams issuing from the orifices in a manner substantially independent of the cross-machine dimension by avoiding stationary standing acoustic waves or other phenomena associated with regular periodic perturbations that would, if used, limit the maximum cross-machine dimen-sion;
- selectively activating a charging electrode means disposed downstream of said orifices and extending over the zone of random drop formation for imparting electrical charges to said drops as they pass thereby; and - deflecting electrically charged drop-lets away from the substrate surface.
8. Method as in claim 7, wherein said random drop generation step utilizes noise signals only within a predetermined range of frequencies.
9. Apparatus as in claim 1, wherein said random signal generation means comprises:
- a noise source providing electrical noise signals at an output;
- a selective bandpass filter connected to receive said electrical noise signals from the noise source output and to pass therethrough to a filtered output only the portion of such signals occurring within a predetermined band of frequencies; and - an electro-acoustic transducer connect-ed to receive said filtered output signals and to convert same to corresponding mechanical vibrations.
- a noise source providing electrical noise signals at an output;
- a selective bandpass filter connected to receive said electrical noise signals from the noise source output and to pass therethrough to a filtered output only the portion of such signals occurring within a predetermined band of frequencies; and - an electro-acoustic transducer connect-ed to receive said filtered output signals and to convert same to corresponding mechanical vibrations.
10. Apparatus as in claim 9, wherein said selective bandpass filter includes means limiting said predetermined band of frequencies to a bandwidth of less than about 12,000 cycles/second.
11. Method as in claim 3, wherein said random perturbations are generated by bandpass filtering electrical noise signals and by converting the resul-tant filtered electrical signals to corresponding mechanical vibrations.
12. Method as in claim 11, wherein said band-pass filtering includes limiting the bandwidth of filtered electrical signals to less than about 12,000 cycles/second.
13. Method as in claim 3, 4 or 7, wherein said substrate comprises a continuous length textile mate-rial moving transverse to said cross-machine direction.
14. Method as in claim 11, wherein said substrate comprises a continuous length textile material moving transverse to said cross-machine direction.
15. Method as in claim 12, wherein said subs-trate comprises a continuous length textile material moving transverse to said cross-machine direction.
16. A textile substrate product selectively treated with liquid dye in accordance with the method of claim 3, 4 or 7.
17. A textile substrate product selectively treated with liquid dye in accordance with the method of claim 14.
18. A textile substrate product selectively treated with liquid dye in accordance with the method of claim 12.
19. In a liquid jet printing apparatus where droplets of pressurized liquid issuing from an array of orifices are selectively controlled to pass or not to pass onto a substrate surface, the improvement com-prising:
- random perturbation means coupled to said liquid for artificially inducing random drop formation processes in streams of fluid issuing from said orifices.
- random perturbation means coupled to said liquid for artificially inducing random drop formation processes in streams of fluid issuing from said orifices.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US23132681A | 1981-02-04 | 1981-02-04 | |
| US231,326 | 1988-08-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1191048A true CA1191048A (en) | 1985-07-30 |
Family
ID=22868750
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000395424A Expired CA1191048A (en) | 1981-02-04 | 1982-02-02 | Random droplet liquid jet apparatus and process |
Country Status (23)
| Country | Link |
|---|---|
| EP (2) | EP0057472B1 (en) |
| JP (1) | JPS58500014A (en) |
| KR (1) | KR880001453B1 (en) |
| AR (1) | AR229416A1 (en) |
| AT (2) | ATE57138T1 (en) |
| AU (2) | AU550059B2 (en) |
| BR (1) | BR8205986A (en) |
| CA (1) | CA1191048A (en) |
| DE (2) | DE3279204D1 (en) |
| DK (1) | DK437182A (en) |
| ES (1) | ES509282A0 (en) |
| FI (1) | FI75225C (en) |
| GB (1) | GB2108433B (en) |
| GR (1) | GR78350B (en) |
| HK (1) | HK52786A (en) |
| IE (1) | IE53454B1 (en) |
| IN (1) | IN157640B (en) |
| MX (1) | MX160194A (en) |
| NO (1) | NO823317L (en) |
| NZ (1) | NZ199622A (en) |
| PT (1) | PT74383B (en) |
| WO (1) | WO1982002767A1 (en) |
| ZA (1) | ZA82705B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4644369A (en) * | 1981-02-04 | 1987-02-17 | Burlington Industries, Inc. | Random artificially perturbed liquid jet applicator apparatus and method |
| US4650694A (en) * | 1985-05-01 | 1987-03-17 | Burlington Industries, Inc. | Method and apparatus for securing uniformity and solidity in liquid jet electrostatic applicators using random droplet formation processes |
| JP2915635B2 (en) * | 1990-08-31 | 1999-07-05 | キヤノン株式会社 | Ink jet recording device |
| US6508546B2 (en) * | 1998-10-16 | 2003-01-21 | Silverbrook Research Pty Ltd | Ink supply arrangement for a portable ink jet printer |
| US6733116B1 (en) | 1998-10-16 | 2004-05-11 | Silverbrook Research Pty Ltd | Ink jet printer with print roll and printhead assemblies |
| US7431427B2 (en) | 2002-06-13 | 2008-10-07 | Silverbrook Research Pty Ltd | Ink supply arrangement with improved ink flows |
| FR2890595B1 (en) * | 2005-09-13 | 2009-02-13 | Imaje Sa Sa | GENERATION OF DROPS FOR INK JET PRINTING |
| RU2602996C1 (en) * | 2015-08-04 | 2016-11-20 | Федеральное государственное автономное образовательное учреждение высшего образования "Национальный исследовательский Томский политехнический университет" | Device to generate series of moving fluid drops |
| RU2606090C1 (en) * | 2015-09-28 | 2017-01-10 | Федеральное государственное автономное образовательное учреждение высшего образования "Национальный исследовательский Томский политехнический университет" | Device for generating series of moving liquid drops |
| CN117283989B (en) * | 2023-10-30 | 2024-06-11 | 武汉国创科光电装备有限公司 | Arrayed electrofluidic jet printing method and device for ink jet printing |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH425838A (en) * | 1965-09-29 | 1966-12-15 | Paillard Sa | Tubular needle for writing with inkjet |
| US3484793A (en) * | 1966-05-02 | 1969-12-16 | Xerox Corp | Image recording apparatus ink droplet recorder with optical input |
| US3656171A (en) * | 1970-12-08 | 1972-04-11 | Mead Corp | Apparatus and method for sorting particles and jet prop recording |
| DE2154472C3 (en) * | 1971-11-02 | 1975-05-15 | Casio Computer Co., Ltd., Higashiyamato, Tokio (Japan) | Nozzle arrangement for an inkjet printer |
| US3798656A (en) * | 1972-07-28 | 1974-03-19 | Ibm | Ink return system for a multijet ink jet printer |
| JPS5633750B2 (en) * | 1973-07-25 | 1981-08-05 | ||
| JPS5912476B2 (en) * | 1973-09-21 | 1984-03-23 | ミノルタ株式会社 | Inkjet generator |
| US3898671A (en) * | 1973-12-12 | 1975-08-05 | Teletype Corp | Ink jet recording |
| US4005435A (en) * | 1975-05-15 | 1977-01-25 | Burroughs Corporation | Liquid jet droplet generator |
| JPS5528859A (en) * | 1978-08-23 | 1980-02-29 | Ricoh Co Ltd | Image recording method |
-
1982
- 1982-01-26 IE IE159/82A patent/IE53454B1/en unknown
- 1982-01-29 IN IN68/DEL/82A patent/IN157640B/en unknown
- 1982-02-01 NZ NZ199622A patent/NZ199622A/en unknown
- 1982-02-02 CA CA000395424A patent/CA1191048A/en not_active Expired
- 1982-02-03 AU AU82035/82A patent/AU550059B2/en not_active Ceased
- 1982-02-03 MX MX191249A patent/MX160194A/en unknown
- 1982-02-03 JP JP57500885A patent/JPS58500014A/en active Pending
- 1982-02-03 WO PCT/US1982/000140 patent/WO1982002767A1/en active IP Right Grant
- 1982-02-03 ES ES509282A patent/ES509282A0/en active Granted
- 1982-02-03 BR BR8205986A patent/BR8205986A/en unknown
- 1982-02-03 AR AR288335A patent/AR229416A1/en active
- 1982-02-03 PT PT74383A patent/PT74383B/en unknown
- 1982-02-03 GB GB08227548A patent/GB2108433B/en not_active Expired
- 1982-02-04 AT AT86104112T patent/ATE57138T1/en not_active IP Right Cessation
- 1982-02-04 EP EP82100804A patent/EP0057472B1/en not_active Expired
- 1982-02-04 ZA ZA82705A patent/ZA82705B/en unknown
- 1982-02-04 EP EP86104112A patent/EP0196074B1/en not_active Expired - Lifetime
- 1982-02-04 GR GR67210A patent/GR78350B/el unknown
- 1982-02-04 AT AT82100804T patent/ATE38493T1/en active
- 1982-02-04 KR KR8200470A patent/KR880001453B1/en active
- 1982-02-04 DE DE8282100804T patent/DE3279204D1/en not_active Expired
- 1982-02-04 DE DE8686104112T patent/DE3280256D1/en not_active Expired - Fee Related
- 1982-09-24 FI FI823289A patent/FI75225C/en not_active IP Right Cessation
- 1982-10-01 NO NO823317A patent/NO823317L/en unknown
- 1982-10-01 DK DK437182A patent/DK437182A/en not_active Application Discontinuation
-
1986
- 1986-04-29 AU AU56818/86A patent/AU574573B2/en not_active Ceased
- 1986-07-10 HK HK527/86A patent/HK52786A/en unknown
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