US 3864692 A
An ink jet printer in which ink droplets issuing from a source serially pass through an electrically energizable deflection field which is activated at regularly recurring intervals. Deflection of the drops occurs along different trajectories toward a recording medium because of the variable time each droplet is subjected to the energized deflection field. The droplets which are deflected have the same physical or electrical characteristics and are not given differing charges, for example, before entry into the deflection field. Both electrically chargeable droplets and magnetic droplets may be used as the marking fluid when directed according to time dependent deflection. Generally, the deflection field is of sufficient length to include simultaneously all droplets which will comprise a full character stroke on the recording medium and the deflection signal is a square wave selectively applied. However, deflection fields may be shortened and the applied signal may either increase or decrease with time during the energizing interval. In addition, apparatus may be included to produce deflection along either of two coordinate axes and means are disclosed to select droplets required for printing while discarding others during issuance of the droplets from the source at a fixed generation rate.
Claims available in
Description (OCR text may contain errors)
United States Patent 1 McDonnell et al.
[ 1 Feb. 4, 1975 TIME DEPENDENT DEFLECTION CONTROL FOR INK JET PRINTER  Inventors: James A. McDonnell, Binghamton;
Robert E. McGuire; Raymond Radlinsky, both of Endwell, all of NY.
 Assignee: International Business Machine Corporation, Armonk, NY.
 Filed: Sept. 26, 1973  Appl. No.2 401,006
Primary Examiner-Joseph W. Hartary Attorney, Agent, or Firm-K. P. Johnson INK SOURCE  ABSTRACT An ink jet printer in which ink droplets issuing from a source serially pass through an electrically energizable deflection field which is activated at regularly recurring intervals. Deflection of the drops occurs along different trajectories toward a recording medium because of the variable time each droplet is subjected to the energized deflection field. The droplets which are deflected have the same physical or electrical characteristics and are not given differing charges, for example, before entry into the deflection field. Both electrically chargeable droplets and magnetic droplets may be used as the marking fluid when directed according to time dependent deflection. Generally, the deflection field is of sufficient length to include simultaneously all droplets which will comprise a full character stroke on the recording medium and the deflection signal is a square wave selectively applied. However, deflection fields may be shortened and the applied signal may either increase or decrease with time during the energizing interval. In addition, apparatus may be included to produce deflection along either of two coordinate axes and means are disclosed to select droplets required for printing while discarding others during issuance of the droplets from the source at a fixed generation rate.
15 Claims, 10 Drawing Figures NOZZLE OUTGOING TRAJECTORIES TIME SEQUENCE DEFLECTION SIGNAL GEN.
PATENTEDFEB 4% 3.8641592 SHEET 10F a INK SOURCE 2 Z OUTGOING L/ Z/ TRAJECTOR'ES o o o T r 14 TIME SEQUENCE/I6 DEFLECTION FIG. i SIGNAL GEN.
DEFLECTION VOLTAGE T|MEP PRINT 2 POSITION o 0 0 o o O 0 DROP NUMBER o o o o o 0 0 o o HORIZONTAL VERTICAL DEFLECTION DEFLECTION SIGNAL GEN. SIGNAL GEN.
PATENTEDFEB 4W5 3.864.692
E o o CONTROLLED CHARGE VOLTAGE F I G 5 DROPLET SELECTI 44 VOLTAGE CONTROLLED CHARGE VOLTAGE PATENTED 4|975 3.864.692
sum 30F 3 INK SOURCE;
NOZZLE v TIME'SEOUENCE DEFLECTION 65"SIGNAL GENERATOR FIG. 7
TIME SEQUENCE DEFLECT|0N 65 SIGNAL GENERATOR FIG. 8
TIME DEPENDENT DEFLECTION CONTROL FOR INK JET PRINTER BACKGROUND OF THE INVENTION The present invention relates to graphic display recorders and more particularly to ink jet printers employing selectively directed droplets for forming characters and the like on a recording medium.
Ink jet printers are well known. Examples of such printers are disclosed in U.S. Pat. No. 2,600,129, issued June 10, 1952 to C. H. Richards; U.S. Pat. No. 3,596,275, issued July 27, 1971 to R. G. Sweet; U.S. Pat. No. 3,500,436, issued Mar. 10, 1970 to R. W. Nordin; and U.S. Pat. No. 3,510,878, issued May 5, 1970 to C. E. Johnson, Jr.
Character printing with a stream of ink droplets is generally accomplished electrostatically in the prior art by selectively deflecting the stream repeatedly along one direction while the recording medium on which the ink is deposited moves at a slower velocity along a second orthogonal direction. This results in a matrix type of printing in which droplets not required are directed to a gutter or else not produced. Each desired droplet is given an electrical charge at the time of formation that corresponds with its assigned position along the line of deflection and directed through an electrostatic field of constant strength. The several droplets are there deflected in proportion to their respective charges.
This type of printing requires sophisticated electrical circuitry. The charges for each desired droplet must be accurately established and maintained through the duration of printing in order to provide uniformly spaced and accurately placed droplets on the record medium. Because of the aerodynamic effects and interdrop electrical characteristics, compensation circuits are usually required to maintain the uniform spacing of droplets. In addition, changes in ink temperature or viscosity affeet the time of drop breakoff and hence the charge placed on the droplet; this is overcome by using synchronizing circuits which rely on further detection devices to maintain proper droplet charge.
When printing with magnetic ink droplets, it has been found that although no charging is required, the magnetic deflection field must be varied for each droplet in order to attain the proper droplet spacing. This, therefore, requires a series of magnetic deflection elements between the droplet formation point and recording medium for the selective application of various and suitable deflection energies. This is done by either providing a single magnetic field and varying the flux density or by providing a succession of magnetic fields which can be selectively energized as each droplet progresses toward the record surface. As with the electrostatic printing, such control circuits become complex, expensive and are usually difficult to maintain at the proper stability.
It is accordingly a primary object of this invention to provide improved ink droplet printing apparatus for producing graphic displays such as alphanumeric characters.
Another important object of this invention is to provide ink droplet printing apparatus in which droplet deflection is accomplished by energizing the deflection field at selected predetermined times and the droplets, having uniform charges or latent magnetization, are
given trajectories toward a recording medium according to their time in the field.
Another object of this invention is to provide ink droplet printing apparatus in which the ink droplets used for printing are equally charged and the deflection field is electrically or magnetically energized for regular intervals of time to establish different droplet trajectories.
Another object of this invention is to provide ink droplet printing apparatus in which the droplets are se lectively charged at either of two levels and may optionally be synchronously charged with droplet production or asynchronously charged.
A still further object of this invention is to provide ink droplet printing apparatus in which droplets are given deflection trajectories according to the time that is spent in either an electrostatic deflection field or a magnetic deflection field.
Another object of this invention is to provide ink droplet printing apparatus having a pair of selectively energizable deflection fields between a droplet source and recording medium in which droplets are given deflection in proportion to the time spent in either of said fields.
SUMMARY OF THE INVENTION The foregoing objects are attained in accordance with the invention by serially producing a stream of like-charged ink droplets, directing them through a selectively energizable deflection field toward a recording medium, and selectively energizing the field in accordance with the position of the droplets therein so as to cause said droplets to assume a trajectory dependent upon the time each droplet is subjected to the field. In a simple case, the field is merely turned on and then off when the series of droplets is between the plates. Thereby, each successive droplet later in the series is subjected to the field for a longer period and will have a greater deflection from its initial path of travel. The droplets are preferably produced in sufficient number to record a full line of the recording matrix if every droplet is present. When using charged droplets in an electrostatic field, each of the droplets to be used in the series is given a like charge and droplets to be discarded are given a different or no charge. Charging pulses may be provided for a predetermined time until the selected series is fully charged or may be synchronously applied by energizing the droplets as each is produced. The ink drop printing apparatus of the invention can also be used with magnetic ink droplets. Of course, in this case no charge is placed on the droplets but they are likewise produced in a sufficient number in a series to complete one line of the matrix in the case where a full line is required. Unwanted magnetic droplets may be deflected by an auxillary device from the character forming deflection field. The deflection field is preferably energized for regularly recurring time intervals and the magnitude of the energizing signal may be constant or in some cases varied.
Because of the simplified deflection control means much of the expense necessitated by the circuits for the electrostatic control means heretofore known has been eliminated. Ink droplet charging can be done in a binary fashion either synchronously or asynchronously and the deflection field energization may be accomplished on a regularly recurring time cycle even though relatively complex characters have to be formed. The
invention has the advantage of not being restricted to field energization signals of constant amplitude but other signals such as ramp or step signals may be applied if desired to produce the necessary deflection trajectories for the droplets. The deflection technique is suitable for use with either electrostatic deflection fields or with magnetic deflection fields and carries with it the above named advantages in either case.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically illustrates an ink drop deflection apparatus constructed in accordance with the principles of the invention.
FIG. 2 is a timing diagram showing relationship between a signal applied to a deflection field and the impact positions of ink droplets responding thereto.
FIG. 3 is a modification of the apparatus shown in FIG. 1 in which a second selectively energizable deflection field has been added to enable two dimensional deflection.
FIGS. 4a and 4b illustrate another waveform that may be applied to the deflection field and the relationship of the droplet trajectories in accordance therewith.
FIG. 5 is a diagram of'an ink droplet printing apparatus in which a gutter is used to receive all unwanted ink droplets.
FIG. 6 illustrates an aperture plate in conjunction with the apparatus of FIG. 3 in which improperly charged droplets and unwanted droplets can be eliminated.
FIG. 7 is a schematic diagram of ink droplet printing apparatus for magnetic ink which incorporates the principles of the invention.
FIG. 8 is a schematic diagram of magnetic ink droplet deflection-apparatus in which unwanted droplets can be eliminated.
FIG. 9 is a timing diagram showing both a time and amplitude variable energization signal for a magnetic deflection field and showing the relative trajectories of ink droplets deflected by the field so energized.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. I a stream of ink droplets 10 issues from a nozzle 11 which is supplied with ink under pressure from source 12. The nozzle and ink source, which may be of types well known in the art, produce a stream of ink in the order of 0.001 inches in diameter which breaks up into individual droplets in the vicinity of the charging electrode 13. As each droplet breaks from the filament of ink issuing from the nozzle, it carries with it an electric charge. In the diagram shown, each droplet receives the same charge and the droplets pass serially between a pair of deflection electrodes 14 and 15 which areeach connected to opposite polarities of a time sequence deflection signal generator 16. The generator periodically energizes plates l4, 15 to create a transverse electrostatic field of the polarity indicated. At the moment, it may be assumed that generator 16 produces square wave pulses which vary between zero and a positive value. The system is synchronized such that the deflection plates are initially uncharged and the droplets are produced in series in a group. When the first droplet of the group reaches the end of deflection plates 14 and 15, to the right, and is about to emerge therefrom, the last droplet ofthe group has-just entered between the plates. At this time, an electric field at a fixed value is established between plates 14 and 15 from signal generator'l6 and will remain until the last droplet in the series reaches the right hand edge of the plates.
When this occurs, each of the equally charged droplets in the group will be influenced by the electric field between plates 14 and 15 for a different amount of time. The first droplet of the group which is about to emerge from the plates will experience electric field for the shortest amount of time and the last droplet of the group, which has just entered between the plates, will experience the field for the greatest amount of time as it travels the entire length of the deflection plates. Intermediate drops of the groups will be influenced by the electric field for differing time periods and will acquire a transverse velocity component proportional to the time-integral of the field they experience. Since they have a substantially constant velocity, this is, in turn, proportional to the distance integral of the field, from the position of the droplet at the instant the field is turned on to the end of the field region or termina tion of the field. The first droplet will experience little or no deflection as it leaves the field region at the time the field is set up, whereas the last drop is fully deflected since it travels the full length of the field region under the influence of the field. The uniformly spaced intermediate drops acquire equal increments of transverse velocity because of the electric field distribution along the length of the deflection plates 14 and 15 is uniform. After traveling along the trajectories toward the recording surface, not shown, the deflection droplets are arranged to produce a line scan which is approximately linear. The deflection plates can be of a length to allow sufficient droplets therebetween to comprise a character stroke or one line of a matrix arrangement of droplets.
If the incoming stream of droplets is continuous and uniformly spaced, a new group is located in position between deflection plates 14 and 15 at approximately the time the last drop of the first group of droplets has left the deflection plate region. This second group of droplets is given a line scan deflection because the deflection field is now reduced to zero because of the termination of the square wave signal from generator 16. The difference with the second group of droplets is that the last droplet in that group receives little or no deflection because the electric field between the deflection plates is turned off at approximately the time it enters the region between the plates. The foremost drop of the group is fully deflected because electric field was on during nearly the whole of its transit time. Likewise, the intermediate droplets are deflected proportional amounts. Thus, the scan direction reverses for the second group of droplets.
If a third group of droplets follows normally spaced behind the second group, it enters the region between deflection plates 14 and 15 when the electric field is zero and is scanned when the field is switched on again by the next positive square-wave pulse from generator 16. The result is a scan moving back and forth in a vertical direction. Naturally the scan can be made to travel back and forth in a horizontal direction if the deflection plates are rotated degrees about the nominal droplet path.
FIG. 2 illustrates the relationship between the deflection of the groups of droplets discussed above and the square wave voltage signal applied to deflection plates 14 and 15 of FIG. 1. It will be seen that the droplets are proportionately deflected in one direction when the square wave pulse is present to establish a transverse deflection field, and the droplets are deflected in the opposite direction when the deflection voltage returns to zero.
In FIG. 1 a scheme is shown for deflecting the ink droplets back and forth in one dimension, that is, the vertical direction. Since all the droplets have the same charge, it is possible, if required, to provide another scan direction by passing the droplets between a second pair of deflection plates, positioned, for example, orthogonal to the first pair of deflection plates. With this technique, a matrix scan can be created without moving the recording surface. Referring to FIG. 3, a system having two pairs of deflection plates is shown. A stream of equally charged ink droplets is produced using a structure described for FIG. 1. The stream of droplets is directed between the first pair of deflection plates -21 which are connected to a source of square wave voltage 23 similar to signal source 16 of FIG. 1. The droplets are deflected back and forth in a one dimensional scan as described in relation to FIG. 1, except that the direction of scan is horizontal due to the position of deflection plates 20 and 21. The deflected droplets emerging from plates 20 and 21 pass between a second pair of deflection plates 24 and 25 where they are deflected in the second direction such as vertical to produce a second scan that is relatively slow. Because of the relative slowness of the scan, the droplet transit time is not critical and the scan can be established by a field produced by a ramp voltage from a deflection signal generator 26 connected to plates 24 and 25, just as with the conventional cathode ray tube deflection signal. Transit time of the droplets through deflection plates 24 and 25 may have the effect of delaying the deflection and distorting it fora period equal to the transit time near the leading and trailing edges of those plates. These effects can be nullified by initiating the ramp voltage before the first active droplet of the complete raster scan enters the electric field region between the second set of deflection plates 24 and 25 and ending only after the last active droplet has emerged.
The deflection voltage from signal generator 26 need not be a ramp voltage; a staircase deflection voltage signal such as applied to deflection plates 20 and 21 may also be employed provided that deflection plates 24 and 25 are long enough to encompass all the droplets in the raster. Whether a ramp deflection voltage signal or a staircase voltage signal is used, a zig-zag raster is obtained as illustrated on recording medium 27.
The invention has been described assuming that the signal generator produces regularly spaced square waves and that the charged ink droplets are produced continuously. The result was a zig-zag raster scan on the recording medium. If the droplets are produced in groups of a length sufficient to produce one line of a matrix, with a gap created between droplet groups, it will be obvious that parallel lines having a single sweep direction can be produced. With this in mind, another modification of droplet control is shown in FIGS. 4a and 4b.
IN FIGS. 4a and 4b, there is shown a technique of extending the line length in a matrix wherein the deflection electrodes are halfthe length ofa series of droplets which are to make up the matrix line of print. This is accomplished by square wave signals which occur alternately, positively and negatively with respect to a zero potential line as indicated in FIG. 4a. The time in this example is divided into equal increments with the beginning and ending of the increments designated :1, t2, t3, :4. In FIG. 4b, a pair of deflection plates 30 and 31 are shown, between which successive groups of serially arranged ink droplets are directed toward a recording medium not shown. Considering the group of droplets denoted by heavy lines, at time [1, a positive square wave is applied to deflection plates 30 and 31 for the time 11 and 12. As seen in FIG. 4b, the first droplet of the series of charge droplets is about to enter the deflection field and will be subjected to the transverse force of the field during its entire traversal from the bcginning ofthe deflection plates to the end of the deflection plates. The succeeding three drops will experience the deflection force, each for a slightly less interval of time and the fifth drop in the series will just start to enter the deflection field at time 12 when the square wave signal is terminated. Each of the first four droplets will have received varying transverse velocity components during the passage through the field and during the time required for the fifth droplet to travel to the end of the deflection field, which is not energized, no transverse forces will be experienced by the last five droplets. However, at time [3, a negative square wave is applied to the deflection electrodes and as the last four droplets continue in such a field, they will receive transverse velocity components in the direction opposite to the first four. It will be noted that the center droplet of the series does not experience any deflection force, since the deflection field was terminated as it entered the plates 30, 31 and the field was energized just as that droplet left the deflection plates. With this technique, a longer matrix can be generated at the recording surface.
The description thus far has indicated that a series of droplets generated should be formed in groups to coincide with the regularly recurring deflection field energization. FIG. 5 illustrates how ink droplets can be formed continuously and then selectively eliminated to form groups or to form voids within a group which may be required for the matrix line of a character being formed. Droplets issue continuously from nozzle 35 and pass between charging electrodes 36, then between deflection electrodes 38 and 39 while proceeding toward recording medium 40. However, charging electrodes 36 are intermittently controlled to place charges only on certain of the droplets issuing. The uncharged droplets, as they pass through the deflection field, cannot be deflected from their nominal path, and will be collected in a gutter 41 which, as is usual in the art, is connected by a vacuum pump to the ink supply for the nozzle for reuse. Those droplets that are charged will be deflected in accordance with the excitation voltage on deflection plates 38 and 39. With the apparatus as shown, it is preferable to place a bias voltage on deflection plates 38 and 39 to deflect all charged droplets above gutter 41. The applied control signal can then be superimposed upon the bias signal to achieve the desired droplet deflection.
It has been mentioned above that the charge voltage for droplets at the charging electrode may be asynchronously applied rather than synchronously. By this is meant that the charge voltage is not applied in timed relation with each droplet at breakoff from the filament extending from the nozzle. As seen in FIG. 6, droplets issue from nozzle 35 and form droplets in the vicinity of charge electrodes 36 which are controlled by charge circuit 37. Charge circuit 37 will apply the binary (charge or no charge) signal for the time necessary to charge the droplets required within or for a matrix line on the recording medium. As both the charged and uncharged droplets proceed toward the recording medium 40, they pass between two pairs of orthogonally disposed deflection plates. One pair is selection electrodes 42 and 43 controlled by selection voltage circuit 44. This circuit is essentially a continuous bias voltage which has the effect of deflecting all charged droplets from the uncharged droplets. Simultaneously all droplets proceed between vertically disposed deflection electrodes 38 and 39 which operate with the time dependent on-off deflection signal as described earlier with regard to FIGS. 1-4. Interposed between record ing medium 40 and the selection and deflection electrodes 42, 43 and 38, 39- is a mask or plate 45 which has a gutter opening 46 and a print opening 47. Opening 46 communicates with'a duct 48 which returns to a sump, not shown. Mask 45. is fitted with a collection channel 50 at the bottom thereof which is connected to a duct 51 which likewise returns to the sump.
In the operation of the structure of FIG. 6, droplets issuing from nozzle 35 are either charged or not charged depending upon whether they are required for printing. Those desired are all charged to a common level, while those not required are given no charge. As the continuous series ofdroplets passes into the electric field established between electrodes 42, 43, those carrying a charge will be deflected toward opening 47 in mask 45. Droplets uncharged will continue to opening 46 in the mask and return through duct 48 to the sump for reuse. Since charging has occurred asynchronously some droplets. may have received their charge during the time of transition from the zero voltage on plates 36 to full value or during the transition in the opposite direction and not be fully charged or uncharged. These droplets when passing between electrodes 42 and 43 will be only partially deflected toward opening 47 from opening 46 and will impact mask 45 between the two openings thereby draining into channel 50. When the fully charged droplets reach vertical deflection electrodes 38 and 39, the desired time deflection signal is applied or removed from those electrodes to produce the required vertical change in trajectory. These droplets will continue through opening 47 and impact recording medium 40. Deflection electrodes 38 and 39 are controlled as described with regard to FIG. 1.
The technique of time dependent deflection of ink droplets is also readily adaptable to printing with magnetic ink, as illustrated in FIG. 7. Magnetic ink is supplied from pressurized source 60 to nozzle 61 and issues therefrom as a stream, subsequently breaking into droplets. The droplets, however, are not charged as is the case with electrostatic deflection. The droplets are directed between the pole pieces 62 of an electromagnet 63 which is energized by winding 64 for selective periods of time to subject each of the droplets in the series to different durations of transverse forces as the droplets traverse the nominal flight path. Energization is done with an intermittently controlled signal generator 65. During their travel, the droplets enter the magnetic field of the electromagent 62 and experience a transverse force in the direction of the higher density flux paths. In other words, the transverse forces will be downward and deflection will occur in proportion to the time each droplet is subjected to the applied forces. As described with reference to FIG. 1, if successive series of droplets are formed and directed through the magnetic field, a signal such as a regularly applied square wave can be used to produce successive parallel lines on recording medium 66 if the recording medium is moved laterally of the stream.
Since it is more practical to generate magnetic ink droplets continuously, unwanted droplets must be eliminated. One technique for selective elimination is shown in'FlG. 8. Droplets of magnetic ink are formed by nozzle 61 and directed as in FIG. 7 between pole pieces 62 of electromagnet 63 having winding 64. The winding is controlled by time sequence deflection signal generator 65. The ink droplets have a nominal path which will impact recording medium 66 at the desired print area. To this point the structure of FIG. 8 is similar to that of FIG. 7; however, in order to achieve the selectivity of ink droplets, horizontal selector magnet 67 is arranged so that its pole pieces 68 are on opposite sides above and below the droplet path. The selector magnet also has a control winding 69 thereon which is connected with a suitable signal source for intermittently applying energizing current to produce a magnetic flux field about the droplet path. The selector magnet 67 is a thin ferromagnetic material which is less than the drop-to-drop spacing so that when energized the selector magnet will operate only on a single drop. As droplets pass along their nominal path the selector magnet can be intermittently energized which will create a leftward deflection due to the flux gradient causing the selected drops to depart sufficiently from the desired drops to enter a gutter 70. Desired drops will continue to pass between the pole pieces 62 of the vertical deflection magnet 63 so that ink droplets are deflected according to the time subjected to the field of magnet 63. Droplets deflected from the nominal path by selector magnet 67 will also be vertically influenced by the electromagnet 63 but gutter 70 is made to have a sufficiently long vertical opening to catch such deflected droplets.
In certain instances, particularly deflection of magnetic ink, the amount of droplet deviation provided by an electromagnet may not be sufficient to produce the length ofline scan desired. This may be due to the electromagnet characteristics or the lack of space between the nozzle and recording medium. A technique of extending the scan distance is to superimpose a ramp signal on the time sequence deflection signal which is applied to the vertical scan magnet. This, of course, applies a greater transverse force to the droplets during the time that they are within the activating magnetic field. The deflection signal may be longer than the traversal time required for a droplet through the magnetic field. It should also be noted that such a technique is equally applicable to electrostatic embodiment of FIG. 1. Although a ramp has been shown in FIG. 9, other wave forms may be employed to attain the desired droplet deflection.
There has been described improved ink jet printer structure which uses ink droplets having a binary type of charge, being either charged or uncharged and which permits the use of a simplified deflection circuit. The technique is also adaptable to magnetic ink jet printers.
While the invention has been particularly shown and described with reference to preferred embodiments, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention. What is claimed is: 1. A fluid drop control system comprising: means for directing a series ofdrops ofmarking fluid of like deflection characteristics along a path;
selectively energizable means adjacent said path for establishing a deflection field simultaneously encompassing said drop series and having a force component transversely of said path acting to deflect said drops moving along said path; and
means for energizing said deflection means for a predetermined time to subject each drop in said series of drops to said transverse force for different times for unidirectional deflection and impart to each drop in said series a different trajectory from said path beyond said deflection means according to the time subjected to said force.
2. Apparatus as described in claim 1 wherein said energizing means is operable for regular intervals of time.
3. Apparatus as described in claim 1 wherein said deflection means is energizable by electrical signals.
4. Apparatus as described in claim 1 wherein saiddirecting means produces drops in a series uniformly spaced from each other.
5. Apparatus as described in claim 1 wherein the energy supplied by said energizing means is of a constant level during said predetermined time.
6. Apparatus as described in claim 1 wherein said means for energizing said deflection means is also operable to vary the magnitude of energization during each predetermined time period.
7. A fluid droplet marking system comprising:
a recording medium:
means for directing droplets of marking fluid of like deflection characteristics of substantially uniform size serially along a path towards said recording medium;
selectively energizable deflection means between said directing means and said recording medium for establishing a force component encompassing a series of said droplets and acting transversely thereon as said droplets are moving along said path to deflect said droplets therefrom; and
means for uniformly energizing said deflection means for a predetermined time to simultaneously act on a plurality of said droplets to induce unidirectional deflection and to cause each said droplet in said series to be deflected according to the time subjected to said force and follow a different trajectory from said path toward said recording medium.
8. Apparatus as described in claim 7 comprising second selectively energizable deflection means between said directing means and said recording medium for establishing a force component transversely of said path and in a direction different from the force component of the first-mentioned deflection means to deflect said drops from said path; and
second means for energizing said second deflection means for a second predetermined time for altering the trajectory of selected ones of said droplets passing from the first deflection means toward said recording medium.
9. Apparatus as described in claim 8 wherein said deflection means and said second deflection means are arranged to act simultaneously on said droplets when energized.
10. Apparatus as described in claim 7 further including means for inhibiting certain selected droplets from said directing means from reaching said recording medium.
11. Apparatus as described in claim 7 wherein said deflection means is a pair of electrically energizable plates on opposite sides of said path and said energizing means produces an electrical field therebetween; and
further including charging means between said directing means and said deflection means for establishing a uniform electrical charge on selected ones of said droplets.
12. Apparatus as described in claim 11 wherein said charging means includes a source of binary voltage signal selectively operable for applying charging voltage only to selected ones of said droplets from said directing means, leaving others of said droplets in said series uncharged and not deflectable by said deflection means; and
interceptor means located between said directing means and said recording medium for intercepting and collecting said uncharged droplets. 13. Apparatus as described in claim 7 wherein said energizing means applies a square wave signal to said deflection means.
14. Apparatus as described in claim 7 wherein said energizing means includes means to establish a bias energy level on said deflection means.
15. A fluid drop control system comprising: means for producing drops of marking fluid having like deflection characteristics in a force field and directing a series of said drops along a path;
selectively energizable means adjacent said path for establishing a deflection fleld simultaneously encompassing said drop series and having a force component transversely of said path acting to deflect said series of drops moving along said path; and
means for energizing said deflection means for a predetermined time to subject each drop in said series of drops to said transverse force for different times according to the position of each said drop in said series while moving past said selectively energizable means and impart to said drops unidirectional deflection and in different trajectories from said path beyond said deflection means.