CA2145385A1 - Method and system for drop marking and a drop deflector for use therewith - Google Patents
Method and system for drop marking and a drop deflector for use therewithInfo
- Publication number
- CA2145385A1 CA2145385A1 CA002145385A CA2145385A CA2145385A1 CA 2145385 A1 CA2145385 A1 CA 2145385A1 CA 002145385 A CA002145385 A CA 002145385A CA 2145385 A CA2145385 A CA 2145385A CA 2145385 A1 CA2145385 A1 CA 2145385A1
- Authority
- CA
- Canada
- Prior art keywords
- high voltage
- drops
- deflection
- deflection electrode
- electrode
- 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.)
- Abandoned
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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
- B41J2/075—Ink jet characterised by jet control for many-valued deflection
- B41J2/08—Ink jet characterised by jet control for many-valued deflection charge-control type
- B41J2/09—Deflection means
Landscapes
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
Abstract
Deflection electrodes (90, 92) create a region of high electric field intensity and an ink mist neutralization region (96). High field intensity is achieved by spacing the deflection electrodes (90, 92) closer together than has hitherto been possible. The higher deflection field intensity facilitates full ink drop deflection and character size although the effective length of the electrodes (90, 92) may be substantially less than those in conventional ink jet printing heads. Insulative material (94) is placed over the high vol-tage deflection electrode to obviate high voltage arcing. The insulated electrode and the ink drops to be deflected may be of the same polarity permitting an ink mist neutralization region (96) to be located on the low voltage electrode (90).
Description
21~3~5 METHOD AND SYSTEM FOR DROP MARKING AND A
DROP DEFLECTOR FOR USE THEREWITH
This invention relates generally to the field of high speed printing of characters on printing media, such as paper sheets, labels or the like. More specifically, it relates to non-impact type printing utilizing bny droplets of electrically conductive ink forced through a nozzle or orifice under pressure and commonly referred to as drop marking or ink jet pri"ling. The structure defining the orifice is subjected to ullrdsGn,c vibrations which are usually produced by a piezoelectric crystal driven by an oscillator circuit and cause the inkstream to break up at a regular drop rate as it leaves the orifice. The drop rate is plopGIlio"al to the rate of vibration.
The stream of ink drops is directed past a charge electrode or ring where selected drops are charged. By synchronizing the charge on the ring witn the drop for~"dlion rate, the charge on each drop is discretely controlled.
The drops are next directed past a drop deflection means comprising a pair of electrodes which have a potential difference of several thousand volts to establish an electric field between the electrodes. Uncharged ink drops are not deflected by the electric field and continue along their initial trajectory which is preferably directed towards a gutter which collects the uncharged drops for recirculation back to the nozzle. The charged ink drops are deflected from their initial trajectory by the influence of the electric field and follow trajectories dependent on the level of their respective charge. The result is the ability to direct drops of ink to selected positions Wo 94/08792 3~,$ pcr/GBs3/o2 along a line on a printing medium by controlling the electrical charge which a drop receives. This ability is used, in conjunction with movement of the nozzle, to generate predetermined markings, such as alphanumeric characters.
It is well known that, for any given ink drop charge, the angular change in the trajectory of the ink drop will be a direct function of the electric field intensity between the deflection electrodes through which the charged ink drop passes, and the time taken for the ink drop to travel therethrough. It is also well known that the size of the printed character is directly related to the " ,axir"um obtainable angular change in the trajectory of the ink drops and the distance of the medium from the drop deflection means. Consequently, to obtain characters or print sizes of a predetermined minimum height, it is necessary to define both the minimum field intensity and the minimum deflection electrode length to achieve the required angular change of trajectory.
For a given character size, any increase of the field inlensily will enable a reduction in the length of the deflection electrodes which, in turn, translates into an advantageous decrease in both the overall size of the print head and the spacing between the ink nozzle and the printing medium. The shortest nozzle to printing medium spacing generally yields the best quality print. However, the field intensity may not be increased without limit because inter-electrode electrical arcing occurs at elevated field inlensilies. One known prior art ink jet printer, for example, utilizes 5,000 volts to energize deflection electrodes spaced in parallel relationship 3/16 inch apart (that is about 0.48 cm), which translates into about 10,500 volts/cm.
Substantially increasing the resulting field intensity can result in arcing.
wo 94/08792 214 a ~ 8 ~ pcr/GB93/o2lol There is also a problem with ink mist collecting on deflection electrodes. This mist unavoidably forms upon impact of the ink drops with the print medium and/or the collection gutter. This ink mist has an electrical charge which in a collected form can influence the deflection field in an uncG"l~ollable manner. It is well-known to utilize the electrical attraction, between the ink mist having a first charge polarity and the tip of the high voltage electrode having the opposile polarity, to neutralize the ink mist.
As herei. ,a(lar described, it is also known for the drop deflection means to have its electrodes diverging in the direction of the drop trajectories to provide room for the diverging drops and to increase the field intensity at the entrance between the electrodes. Due to the closer spacing of the electrodes at the er,l,d"ce it is also known to insulate the high voltage electrode in the vicinity of the entrance to prevent inter-electrode arcing.
It is accord;ngly known from the prior art for a drop marking system to include means for emitting a stream of marking drops, means for charging selected drops, drop deflection means for deflecting the charged drops to follow a trajectory different from a trajectory followed by the uncharged drops whereby certain drops will mark a medium whilst other drops will be intercepted by the catcher, the drop deflection means including a high voltage electrode and a low voltage electrode, means for maintaining the low voltage electrode at ground or nearly at ground, means for applying a high voltage to the high voltage electrode sufficient to create an electric field between the electrodes to deflect the charged drops, and insulation material covering part of the high voltage electrode to innibit arcing between the electrodes.
21~3385~
It is also known from the prior art for a drop deflector, for a drop m~rking system in which a stream of m~.~ing drops are to be emitted and selected drops are to be charged for deflection along a trajectory different from a trajectory followed by the uncharged drops, to include a high voltage deflection electrode and a low voltage deflection electrode, means for Illainta nil~g the low voltage deflection electrode at ground or nearly at ground, rneans for applying a high voltage to the high voltage deflection electrode sufficient to create an electric field between adjacent surfaces of the deflection electrodes to deflect the charged drops, and insulation m~t~ri~l covering part of the said ~-lj~ent surface of the high voltage deflection electrode to inhibit arcing between the deflection electrodes.
According to one aspect of the present invention a drop m~rking system, or a drop deflector for a drop m~rking system, is provided wherein the insulation m~t~ri~l covering subst~nti-lly the entire surface of the high voltage deflection electrode adj~r,ert to the low voltage deflection cle~tlode wl,,,~ the electric field strength and in_ mist discharge can be increased by op~ g the high voltage deflection electrode at a voltage which would othenvise cause arcing b.,t~ce~ the low and high voltage deflection ele~llodes, the imped~nce of the insulating ~ t~ plt~ ting the establi~hm~nt of corona (;ull.,.lts and wherein the means for applying the high voltage to the high voltage deflection electrode is arranged to apply the high voltage at the same polarity as the charge to be given to the select~d drops whereby the charged drops will be repelled by the high voltage defl~tion elecl~odc towards the low voltage deflection electrode. Preferably the deflection electrodes are plates which diverge in the direction of the drop tr~je~to~ ;~s wh~ the electric field will be ~llollge r at the entr~n~ of the drop deflection means than at its exit.
E~,f~ ly the low voltage deflection electrode has an llnin~lll tDd portion positioned to AMENDED SHEET
IPF~/FP
2I4a38~
attract and neutralize the charge on mist produced by charged drops striking the medium.
It is also known from the prior art for a method of deflecting selected charged drops from a first trajectory to another t~je~tory to comp,ull~.se passing a stream of charged and uncharged drops through an electric field generated between a high voltage deflection electrode and a low voltage deflection electrode.
According to another aspect of the present invention a method of deflecting se!ect~
charged drops from a first trajectory to another haje~;lOly includes insulating the surface of the high voltage deflection electrode adjacent to the low voltage deflection electrode to enable operation at a voltage which would otherwise cause arcing b~l~ecn the low and high voltage deflection electrodes, the in~d~..ce of the insulating m~t~ri~l preventing the establi~hn~r t of corona cu~
The method may include applying the high voltage to the high voltage defl~tion electrode with the same polarity as the charge on the charged drops wll~,.~y the charged drops will be repelled by the high voltage deflection electrode tOwalds the low voltage deflection electrode.-There is no suggestion from the prior art that the benefits of an increased i~t~_nsilyelectric field and neutralization of ink mist can be obtained by fully j~C~ ng the high voltage deflection electrode to prevent arcing or of using the grounded electrode for ink mist control.
The present invention employs this ar~n~nt by using the high voltage electrode to repel the drops rather than at~act them. The grounded electrode attracts ink mist to neutralize it thereby avoiding any ~ubsl-nl;~l effect on field AMENDED SHEET
IPEA/EP
wo 94/08792 21 ~ 5 :~ 8 5 pcr/GB93/o2lo1 strength. This permits the high voltage electrode to be completely insulated to prevent arcing.
Because of the electrically insulative coating over the high voltage deflection electrode, the deflection electrodes can be spaced closer than uninsulated or partially insulated electrodes which depend only on avoiding a dielectric breakdown of the air to maintain a voltage difference that supports an electric field. Higher electrical potentials can be used resulting in est~blisl,r"ent of a greater intei,sily electric field, which for the same length of drop travel from the nozzle to the printing medium, increases the deflection amplitude at the printing medium. Conversely a given deflection amplitude at the printing medium can be achieved with a correspondingly shorter length of drop travel.
i The present invention therefore provides a print head having deflection electrodes of decreased length.
The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-Figure 1 is a schematic block diagram of a known drop marking system utilizedin an ink jet printer produced by Videojet Systems Intemational, Inc. and sold under their Trade Mark EXCEL;
- Figure 2 is an enlarged diagrammatic view of the ink jet printer head shown in Wo 94/08792 21 ~ 5 3 8 ~ pcr/GB93/o2lol Figure 1 illustrating details of the drop deflector; and Figures 3, 4,5 and 6 are diagrams similar to Figure 2 but illustrating alternative forms of drop deflector, in accordance with the present invention, for use with a drop marking system such as that shown in Figure 1.
Referring to Figure 1, a drop marking system has a tank 10 for a supply of electrically conductive ink which is withdrawn by pump 12 and supplied under pressure to nozzle 14 via a regulator 16 and a conduit 18 in a conventional manner. The resistivity of the ink is preferably in the range of 100 ohm-cm to 1500 ohm-cm.
The nozzle 14 has a small orifice 20 through which the ink is emitted. The orifice 20 is preferably defined in a jewel 22 located in the end of the nozzle 14. A
piezoelectric transducer 24 is fitted in abutting contact with the nozzle 14 and is driven, generally at an ultrasonic rate, by conventional oscillator/character generator circuitry 26. The ink sl,ea"" emitted from the orifice 20 by virtue of the pressure from pump 12, is broken up by the transducer 24 into a series of ink drops 28. The above described operation of the ink nozzle is well known and is disclosed in more detail, for example, in U.S. Patent No.3,972,474. The nozzle 14 together with the orifice 20 and transducer 24 constitute a means for emitting a stream of ink drops along a trajectory T1 aligned with an ink catcher or gutter 36.
A charge electrode or ring 30 is provided along the trajectory T1 near the orifice 20 and functions to charge selected individual ink drops 28, as they break off from the stream in the proximity of the ring 30, thus trapping a selectea charge on each wo 94/08792 pcr/GB93/o21 21~5385 8 selected ink drop. A positive potential is placed on ring 30 to cause a negative charge on the selected ink drops 28 which are identified in Figures 1 and 2 by individual minus signs. The oscill~tor/character generator 26 generates a time variant video signal on line 27 generally in the form of a pulse train of varying amplitude which is synchronized with the oscillator drive to the transducer 24 to f~cilit~te the discrete control of the ",agr,ilude of the charge acquired by each selected ink drop passing through the ring 30.
All of the ink drops 28 thereafter pass along the trajectory T1 into a spaced deflection system which is indicated generally by arrow 32 and comprises divergent linear deflection electrodes 52 and 54. The electrode 52 is grounded as shown at 53 but the electrode 54 is connected to a means 55 for applying high voltage sufficient to create an electric field between the electrodes 52 and 54 to deflect the selected charged drops 28. All of the uncharged drops 28 are unaffected by this electric field and continue along their initial trajectory T, until intercepted by the gutter 36 and returned through conduit 38 to the ink reservoir. However the selected negatively charged drops 28 are deflected by the electric field towards the positively charged high voltage electrode 54 and follow different trajectories such as T2 which are directed towards a medium 34 such as paper or other printable material to be marked by the selected ink drops.
The deflection or displacement of a given ink drop as it passes through a uniform electric field is given by the following relationship:-WO 94/08792 PCl`/GB93/02101 92l~S38~
107 EX Z02q X = 2md Vjo where:-x is the deflection amplitude at the surface of the print medium;
q is the charge on the ink drop;
Ex is the electric field inlensily bel~/ecn planar shaped deflection electrodes;
Vjo is the initial drop velocity;
md is the mass of the ink drop; and zO is the axial ~li;,~nce from the point of drop fo""ation to the print surface.
Thus the deflection ~x" of each drop is in direct proportion to the magnitude of the charge ~q" placed thereon. If no charge is placed on the drop, it passes deflection system 32 along a sl,digl ,t, undeflected path into gutter 36 and is not printed on the medium 34.
It is also apparent that the ink drop deflection UX" is directly related to the intellsil~ of the electric field ~Ex~ which acts upon each charged ink drop as it passes through the deflection system 32 towards the print medium 34. Accordillgly any increase in the field intensity "Ex'' will result in a linear increase in the ink drop deflection "x". Thus, consiste,ll with maintaining a predetermined character size (i.e.
maximum drop deflection), it will be appreciated that the axial distance ,,zOu travelled by the ink drops may be reduced if the electric field intensity ~Ex'' is correspondingly increased.
Wo 94/08792 pcr/GB93/o2lol 21~5385 As previously indicated, the field intensity "EXU cannot be increased without limit due to dielectric breakdown of the air separating the spaced deflection electrodes 52 and 54. Naturally, the presence of moisture, ink droplets and ink mist significantly reduces the maximum field intensities which can be maintained. Practical maximum field intensities are approximately 10-15 kv/cm. Such restricted deflection field i"tensilies limit the maximum drop deflection achievable in a short drop transit space and, therefore, necessitate longer deflection systems.
Convenlional drop deflectors have uninsu'~ted high and low voltage deflection electrodes parallely spaced at a spacing of about 3/16 inch, that is about 0.48 cm, and their perfor")a"ce is limited by the field density that can reliably be created with this arrangement.
Figure 2 illustrates, in greater detail, the improved deflection system taught by Videojet Systems l"ler"dlional, Inc. in which a higher field i"lensily than conventional is achieved. The linear deflection electrodes 52 and 54 diverge, in the direction of the ink drop travel, from a drop entrance 58 of relatively close spacing adjacent the ring 30 to a drop exit 60 of maximum spacing adjacent the medium 34 and the gutter 36.
The means 55 places a fixed positive high DC potential, typically about 5000 volts, on the high voltage upper electrode 54 with respect to the grounded voltage lower electrode 52, in conventional fashion, to generate an electric field 56 therebetween intended to accelerate or attract the selected negatively charged ink drops 28 upwardly as they pass from the entrance 58 to the exit 60.
wo 94/08792 ~14 ~ 3 8 -~ pcr/GB93/o2lol The divergence of the deflection electrodes 52 and 54 causes the electric field 56 to be highly non-uniform with a substantially greater field intensity at its entrance 58 than at its exit 60. This non-uniformity defines a region of high field intensity generally at the entrance 58 which exerts the great~st force for deflecting the charged ink drops.
The desi~ed high field intensity in the region of the enl,a"ce 58 is achieved by spacing the deflection electrodes 52, 54 substantially closer together in the e~Lrd~lce region 58 than is conventional. Whilst other known systems generally position the deflection electrodes at a uniform 3/16 inch (0.48 cm) spacing, the drop entrance 58 ot the Figure 2 structure may be reduced to 3t32 inch (0.24 cm) or even 1/16 inch (0.12 cm), thereby tripling the electric field intensity in this region. The electrodes 52 and 54 diverge to a spacing of between about 3/16 and 5/16 inch (that is 0.48 cm to 0.80 cm) at the drop exit 60.
Elevated electric field intensities of this magnitude would conventionally be impracticable as they would be accompanied by excessive arcing in the narrowed gap adjacent the entrance 58, particularly in the presence of the conductive ink drops and mist. The arrangement illustrated in Figures 1 and 2 overcomes this problem by positioning a dielectric insulation material 62 over the portion of the high voltage electrode 54 generally in the entrance region of high electric field intensity. The dielectric insulation material 62 can be Teflon FEP which exhibits a dielectric strength (236 KV/cm) six times that of air, and therefore, a relatively thin 1/10 inch (0.25 cm) layer of this material provides an additional 5,900 volts dielectric strength thereby wo 94/0829~ j 3 8 ~ pcr/GB93/o2lol doubling the maximum useable electric field intensity.
However, in the prior art device of Figure 2 it is necessary for the high voltage deflection electrode 54 to have its exit end 66 left uninsulated and exposed to provide for mist neutralization and collection.
It is well known that ink drops i-"pacti"g on a print medium create an ink mist which can accumulate to form an u---~d-,le-l electric field which, in turn, will deflect charged ink drops from their inlended trajectories. In the prior art device of Figure 2, negatively charged ink mist 64 is allld-;ted to the exposed end 66 of the positively charged high voltage electrode 54 (generally 1/8 -1/4 inch (that is 0.32 - 0.64 cm) of the electrode is left exposed) where, upon contact with that electrode, the mist is electrically neutralized. While the prior art device shown in Figure 2 has been highly satisfactory, there remains the possibility of arcing which, because the ink drops conldin volatile solvents, can result in combustion. This possibility is increased by use of the high voltage electrode for conl,olli,1g mist. As mist builds up, changes in the field occur and evaporation of the solvent decreases the dielectric strength of the air gap between the plates increasing the likelihood of arcing.
With reference to Figure 3 a stream of ink drops 80 are emitted by a nozzle 84 through a jcwcllcd orifice 86 and selected drops are appropriately charged by charge electrode 88. The deflection structure consists of a pair of plates defining deflection electrodes 90 and 92. Uncharged drops pass along trajectory T, to the gutter or catcher 36 as before while charged drops pass along trajectory T2 to mark the WO 94/08792 214 5 3 8 5 PCJ'/GB93/02101 substrate 34. The upper electrode 90 is grounded, or nearly so, to provide the low voltage electrode while the lower electrode 92 is maintained at a negative voltage on the order of 2,000 to 5,000 volts to provide the high voltage electrode. The entire high voltage electrode 92 is surrounded by an insulating layer 94 which can be of any suitable insulating material such as that previously discussed in connection with the prior art insulabng layer 62 in Figure 2. It should parbcularly be noted that, because the electrode 92 is completely enc~ps~ ted, arcing between the electrode cannot occur under ordinary operating conditions. The ink drops selected for marking the subsl,ate 34 are negatively charged and are therefore repelled by the high voltage electrode 92, as indicated in the drawing, to cause a deflection onto a trajectory, such as T2, to mark the substrate 34.
Bec~llse the high voltage electrode is completely encapsulated in insulating material, it cannot be used for mist control. However, this function is provided by the low voltage electrode 90 due to the use of negatively charged drops, that is the same polarity as the high voltage electrode 92. Thus mist, which forms when the drops impact on the sul,slldte 34, is attracted to an end 96 of the grounded electrode 90.
Because the high voltage electrode plate 92 is encapsulated in a material of high dielectric strength having very high resistivity (of the order of a thousand volts/mil and 1000 Megohm-cm), shorting the surface of the high voltage electrode 92 to ground, or to the opposite grounded electrode plate 90 will not collapse the electrode field.
Furthermore corona currents will not be established because of the high impedance of the encapsulating material 94.
W094/08792 2~ ~S38 pcr/GB93/o2lo1 In order to obtain the full benefits of the present invention, the high voltage encapsulated electrode 92 is preferably of the same polarity as the charge on the ink drops 80. The other electrode 90 is preferably substantially at ground potential. The charged drops will be repelled from the high voltage electrode 90 rather than, as in the prior art, all,acted thereto. This ensures that the ùncor,l,ollable charged satellites 98 cc"sliluting the mist will not gather on the high voltage electrode 92 and interfere with the es~ lisl""ent of the desired field. Instead, the u-,coul,olled satelliles 98 gather on the end 96 of the oppos;"y grounded electrode 90 and are discharged leaving the field undisturbed. The plates are shown as planar but may have other geometries.
In this manner the present invention permits increased field intensity without adverse inter-electrode arcing, thereby permitting a shorter printhead. This can be accomplished without sacrificing the ink mist neutralizing function. The high voltage electrode is completely encapsulated in an insulating material. The uninsulated electrode is preferably grounded or at a very, IGmil ,al voltage (say not more than 100 volts) and utilized for the mist neutralization function. Because the ink drops and high voltage electrode are of the same polarity, the high voltage electrode repels the drops to cause deflection, rather than attracting the drops as in the prior art.
Figures 4, 5 and 6 illustrate altematives to Figure 3 and only the features of difference will be described, the same reference numerals being used to indicate equivalent parts.
In Figure 4 the polarity of the high voltage supply and the charge on the drops WO 94/08792 21 ~ 5 3 8 ~ PCJ'/GB93/02101 have been reversed so that they are both positive. The upper low voltage electrode 90 is still grounded, or nearly so.
The arrangement of the electrodes in Figures 3 and 4 can be altered to suit specific operating requirements. For instance, the gutter 36 could be repositioned to collect ink drops from one of the deflected trajectories such as T2, and the relative positions of the electrodes 90, 92 can be reversed.
In Figure 5 the high voltage electrode 92 is of positive polarity whereas the selected drops are given a negative charge so that they will be attracted from trajectory T1 to another trajectory, such as T2 or T3, dependent on the level of charge.
The end 96 of the low voltage electrode 90 may be kept at a low positive voltage to collect satellites 98 from the vicinity of the catcher 36. Other satellites may alternatively be removed, if desired, by suction or by using a separate uninsulated electrode of appropriate potential.
In Figure 6 the positions of the low voltage electrode 90 and the high voltage electrode 92 have been reversed so that the medium 34 will be marked by uncharged drops along trajectory T, and by charged drops along trajectories such as T2. The drops for recirculation are the most heavily charged drops which pass along trajectory T3 to the catcher 36.
Whilst the general features of the invention are shown in and described with reference to Figure 3, the subsequent Figures 4, 5 and 6 indicate several variations Wo 94/08792 ~ 85 pcr/GBs3/o21ol 2~3 of the manner in which some features may be re-arranged.
Although the electrodes 90 and 92 illustrated in Figures 3 to 6 are shown as being the same size as the electrodes 52 and 54 of Figures 1 and 2, it should be particularly noted the increased field strength provided by the present invention enables a given drop deflection to be achieved using electr~Jes which are correspondingly shorter (in the direction of the trajectories T" T2, etc) than hitherto possible. This increases print accuracy and reduces evaporation from the recirculated drops which have less exposure to the ambient environment.
The relative disposition of the electrodes 90, 92 may be as shown but, if desired, could be parallely spaced provided the deflected drops can escape through the drop exit 60. However, due to the increased field intensity it is also possible that the angular diverge of the electrodes may also be increased.
DROP DEFLECTOR FOR USE THEREWITH
This invention relates generally to the field of high speed printing of characters on printing media, such as paper sheets, labels or the like. More specifically, it relates to non-impact type printing utilizing bny droplets of electrically conductive ink forced through a nozzle or orifice under pressure and commonly referred to as drop marking or ink jet pri"ling. The structure defining the orifice is subjected to ullrdsGn,c vibrations which are usually produced by a piezoelectric crystal driven by an oscillator circuit and cause the inkstream to break up at a regular drop rate as it leaves the orifice. The drop rate is plopGIlio"al to the rate of vibration.
The stream of ink drops is directed past a charge electrode or ring where selected drops are charged. By synchronizing the charge on the ring witn the drop for~"dlion rate, the charge on each drop is discretely controlled.
The drops are next directed past a drop deflection means comprising a pair of electrodes which have a potential difference of several thousand volts to establish an electric field between the electrodes. Uncharged ink drops are not deflected by the electric field and continue along their initial trajectory which is preferably directed towards a gutter which collects the uncharged drops for recirculation back to the nozzle. The charged ink drops are deflected from their initial trajectory by the influence of the electric field and follow trajectories dependent on the level of their respective charge. The result is the ability to direct drops of ink to selected positions Wo 94/08792 3~,$ pcr/GBs3/o2 along a line on a printing medium by controlling the electrical charge which a drop receives. This ability is used, in conjunction with movement of the nozzle, to generate predetermined markings, such as alphanumeric characters.
It is well known that, for any given ink drop charge, the angular change in the trajectory of the ink drop will be a direct function of the electric field intensity between the deflection electrodes through which the charged ink drop passes, and the time taken for the ink drop to travel therethrough. It is also well known that the size of the printed character is directly related to the " ,axir"um obtainable angular change in the trajectory of the ink drops and the distance of the medium from the drop deflection means. Consequently, to obtain characters or print sizes of a predetermined minimum height, it is necessary to define both the minimum field intensity and the minimum deflection electrode length to achieve the required angular change of trajectory.
For a given character size, any increase of the field inlensily will enable a reduction in the length of the deflection electrodes which, in turn, translates into an advantageous decrease in both the overall size of the print head and the spacing between the ink nozzle and the printing medium. The shortest nozzle to printing medium spacing generally yields the best quality print. However, the field intensity may not be increased without limit because inter-electrode electrical arcing occurs at elevated field inlensilies. One known prior art ink jet printer, for example, utilizes 5,000 volts to energize deflection electrodes spaced in parallel relationship 3/16 inch apart (that is about 0.48 cm), which translates into about 10,500 volts/cm.
Substantially increasing the resulting field intensity can result in arcing.
wo 94/08792 214 a ~ 8 ~ pcr/GB93/o2lol There is also a problem with ink mist collecting on deflection electrodes. This mist unavoidably forms upon impact of the ink drops with the print medium and/or the collection gutter. This ink mist has an electrical charge which in a collected form can influence the deflection field in an uncG"l~ollable manner. It is well-known to utilize the electrical attraction, between the ink mist having a first charge polarity and the tip of the high voltage electrode having the opposile polarity, to neutralize the ink mist.
As herei. ,a(lar described, it is also known for the drop deflection means to have its electrodes diverging in the direction of the drop trajectories to provide room for the diverging drops and to increase the field intensity at the entrance between the electrodes. Due to the closer spacing of the electrodes at the er,l,d"ce it is also known to insulate the high voltage electrode in the vicinity of the entrance to prevent inter-electrode arcing.
It is accord;ngly known from the prior art for a drop marking system to include means for emitting a stream of marking drops, means for charging selected drops, drop deflection means for deflecting the charged drops to follow a trajectory different from a trajectory followed by the uncharged drops whereby certain drops will mark a medium whilst other drops will be intercepted by the catcher, the drop deflection means including a high voltage electrode and a low voltage electrode, means for maintaining the low voltage electrode at ground or nearly at ground, means for applying a high voltage to the high voltage electrode sufficient to create an electric field between the electrodes to deflect the charged drops, and insulation material covering part of the high voltage electrode to innibit arcing between the electrodes.
21~3385~
It is also known from the prior art for a drop deflector, for a drop m~rking system in which a stream of m~.~ing drops are to be emitted and selected drops are to be charged for deflection along a trajectory different from a trajectory followed by the uncharged drops, to include a high voltage deflection electrode and a low voltage deflection electrode, means for Illainta nil~g the low voltage deflection electrode at ground or nearly at ground, rneans for applying a high voltage to the high voltage deflection electrode sufficient to create an electric field between adjacent surfaces of the deflection electrodes to deflect the charged drops, and insulation m~t~ri~l covering part of the said ~-lj~ent surface of the high voltage deflection electrode to inhibit arcing between the deflection electrodes.
According to one aspect of the present invention a drop m~rking system, or a drop deflector for a drop m~rking system, is provided wherein the insulation m~t~ri~l covering subst~nti-lly the entire surface of the high voltage deflection electrode adj~r,ert to the low voltage deflection cle~tlode wl,,,~ the electric field strength and in_ mist discharge can be increased by op~ g the high voltage deflection electrode at a voltage which would othenvise cause arcing b.,t~ce~ the low and high voltage deflection ele~llodes, the imped~nce of the insulating ~ t~ plt~ ting the establi~hm~nt of corona (;ull.,.lts and wherein the means for applying the high voltage to the high voltage deflection electrode is arranged to apply the high voltage at the same polarity as the charge to be given to the select~d drops whereby the charged drops will be repelled by the high voltage defl~tion elecl~odc towards the low voltage deflection electrode. Preferably the deflection electrodes are plates which diverge in the direction of the drop tr~je~to~ ;~s wh~ the electric field will be ~llollge r at the entr~n~ of the drop deflection means than at its exit.
E~,f~ ly the low voltage deflection electrode has an llnin~lll tDd portion positioned to AMENDED SHEET
IPF~/FP
2I4a38~
attract and neutralize the charge on mist produced by charged drops striking the medium.
It is also known from the prior art for a method of deflecting selected charged drops from a first trajectory to another t~je~tory to comp,ull~.se passing a stream of charged and uncharged drops through an electric field generated between a high voltage deflection electrode and a low voltage deflection electrode.
According to another aspect of the present invention a method of deflecting se!ect~
charged drops from a first trajectory to another haje~;lOly includes insulating the surface of the high voltage deflection electrode adjacent to the low voltage deflection electrode to enable operation at a voltage which would otherwise cause arcing b~l~ecn the low and high voltage deflection electrodes, the in~d~..ce of the insulating m~t~ri~l preventing the establi~hn~r t of corona cu~
The method may include applying the high voltage to the high voltage defl~tion electrode with the same polarity as the charge on the charged drops wll~,.~y the charged drops will be repelled by the high voltage deflection electrode tOwalds the low voltage deflection electrode.-There is no suggestion from the prior art that the benefits of an increased i~t~_nsilyelectric field and neutralization of ink mist can be obtained by fully j~C~ ng the high voltage deflection electrode to prevent arcing or of using the grounded electrode for ink mist control.
The present invention employs this ar~n~nt by using the high voltage electrode to repel the drops rather than at~act them. The grounded electrode attracts ink mist to neutralize it thereby avoiding any ~ubsl-nl;~l effect on field AMENDED SHEET
IPEA/EP
wo 94/08792 21 ~ 5 :~ 8 5 pcr/GB93/o2lo1 strength. This permits the high voltage electrode to be completely insulated to prevent arcing.
Because of the electrically insulative coating over the high voltage deflection electrode, the deflection electrodes can be spaced closer than uninsulated or partially insulated electrodes which depend only on avoiding a dielectric breakdown of the air to maintain a voltage difference that supports an electric field. Higher electrical potentials can be used resulting in est~blisl,r"ent of a greater intei,sily electric field, which for the same length of drop travel from the nozzle to the printing medium, increases the deflection amplitude at the printing medium. Conversely a given deflection amplitude at the printing medium can be achieved with a correspondingly shorter length of drop travel.
i The present invention therefore provides a print head having deflection electrodes of decreased length.
The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-Figure 1 is a schematic block diagram of a known drop marking system utilizedin an ink jet printer produced by Videojet Systems Intemational, Inc. and sold under their Trade Mark EXCEL;
- Figure 2 is an enlarged diagrammatic view of the ink jet printer head shown in Wo 94/08792 21 ~ 5 3 8 ~ pcr/GB93/o2lol Figure 1 illustrating details of the drop deflector; and Figures 3, 4,5 and 6 are diagrams similar to Figure 2 but illustrating alternative forms of drop deflector, in accordance with the present invention, for use with a drop marking system such as that shown in Figure 1.
Referring to Figure 1, a drop marking system has a tank 10 for a supply of electrically conductive ink which is withdrawn by pump 12 and supplied under pressure to nozzle 14 via a regulator 16 and a conduit 18 in a conventional manner. The resistivity of the ink is preferably in the range of 100 ohm-cm to 1500 ohm-cm.
The nozzle 14 has a small orifice 20 through which the ink is emitted. The orifice 20 is preferably defined in a jewel 22 located in the end of the nozzle 14. A
piezoelectric transducer 24 is fitted in abutting contact with the nozzle 14 and is driven, generally at an ultrasonic rate, by conventional oscillator/character generator circuitry 26. The ink sl,ea"" emitted from the orifice 20 by virtue of the pressure from pump 12, is broken up by the transducer 24 into a series of ink drops 28. The above described operation of the ink nozzle is well known and is disclosed in more detail, for example, in U.S. Patent No.3,972,474. The nozzle 14 together with the orifice 20 and transducer 24 constitute a means for emitting a stream of ink drops along a trajectory T1 aligned with an ink catcher or gutter 36.
A charge electrode or ring 30 is provided along the trajectory T1 near the orifice 20 and functions to charge selected individual ink drops 28, as they break off from the stream in the proximity of the ring 30, thus trapping a selectea charge on each wo 94/08792 pcr/GB93/o21 21~5385 8 selected ink drop. A positive potential is placed on ring 30 to cause a negative charge on the selected ink drops 28 which are identified in Figures 1 and 2 by individual minus signs. The oscill~tor/character generator 26 generates a time variant video signal on line 27 generally in the form of a pulse train of varying amplitude which is synchronized with the oscillator drive to the transducer 24 to f~cilit~te the discrete control of the ",agr,ilude of the charge acquired by each selected ink drop passing through the ring 30.
All of the ink drops 28 thereafter pass along the trajectory T1 into a spaced deflection system which is indicated generally by arrow 32 and comprises divergent linear deflection electrodes 52 and 54. The electrode 52 is grounded as shown at 53 but the electrode 54 is connected to a means 55 for applying high voltage sufficient to create an electric field between the electrodes 52 and 54 to deflect the selected charged drops 28. All of the uncharged drops 28 are unaffected by this electric field and continue along their initial trajectory T, until intercepted by the gutter 36 and returned through conduit 38 to the ink reservoir. However the selected negatively charged drops 28 are deflected by the electric field towards the positively charged high voltage electrode 54 and follow different trajectories such as T2 which are directed towards a medium 34 such as paper or other printable material to be marked by the selected ink drops.
The deflection or displacement of a given ink drop as it passes through a uniform electric field is given by the following relationship:-WO 94/08792 PCl`/GB93/02101 92l~S38~
107 EX Z02q X = 2md Vjo where:-x is the deflection amplitude at the surface of the print medium;
q is the charge on the ink drop;
Ex is the electric field inlensily bel~/ecn planar shaped deflection electrodes;
Vjo is the initial drop velocity;
md is the mass of the ink drop; and zO is the axial ~li;,~nce from the point of drop fo""ation to the print surface.
Thus the deflection ~x" of each drop is in direct proportion to the magnitude of the charge ~q" placed thereon. If no charge is placed on the drop, it passes deflection system 32 along a sl,digl ,t, undeflected path into gutter 36 and is not printed on the medium 34.
It is also apparent that the ink drop deflection UX" is directly related to the intellsil~ of the electric field ~Ex~ which acts upon each charged ink drop as it passes through the deflection system 32 towards the print medium 34. Accordillgly any increase in the field intensity "Ex'' will result in a linear increase in the ink drop deflection "x". Thus, consiste,ll with maintaining a predetermined character size (i.e.
maximum drop deflection), it will be appreciated that the axial distance ,,zOu travelled by the ink drops may be reduced if the electric field intensity ~Ex'' is correspondingly increased.
Wo 94/08792 pcr/GB93/o2lol 21~5385 As previously indicated, the field intensity "EXU cannot be increased without limit due to dielectric breakdown of the air separating the spaced deflection electrodes 52 and 54. Naturally, the presence of moisture, ink droplets and ink mist significantly reduces the maximum field intensities which can be maintained. Practical maximum field intensities are approximately 10-15 kv/cm. Such restricted deflection field i"tensilies limit the maximum drop deflection achievable in a short drop transit space and, therefore, necessitate longer deflection systems.
Convenlional drop deflectors have uninsu'~ted high and low voltage deflection electrodes parallely spaced at a spacing of about 3/16 inch, that is about 0.48 cm, and their perfor")a"ce is limited by the field density that can reliably be created with this arrangement.
Figure 2 illustrates, in greater detail, the improved deflection system taught by Videojet Systems l"ler"dlional, Inc. in which a higher field i"lensily than conventional is achieved. The linear deflection electrodes 52 and 54 diverge, in the direction of the ink drop travel, from a drop entrance 58 of relatively close spacing adjacent the ring 30 to a drop exit 60 of maximum spacing adjacent the medium 34 and the gutter 36.
The means 55 places a fixed positive high DC potential, typically about 5000 volts, on the high voltage upper electrode 54 with respect to the grounded voltage lower electrode 52, in conventional fashion, to generate an electric field 56 therebetween intended to accelerate or attract the selected negatively charged ink drops 28 upwardly as they pass from the entrance 58 to the exit 60.
wo 94/08792 ~14 ~ 3 8 -~ pcr/GB93/o2lol The divergence of the deflection electrodes 52 and 54 causes the electric field 56 to be highly non-uniform with a substantially greater field intensity at its entrance 58 than at its exit 60. This non-uniformity defines a region of high field intensity generally at the entrance 58 which exerts the great~st force for deflecting the charged ink drops.
The desi~ed high field intensity in the region of the enl,a"ce 58 is achieved by spacing the deflection electrodes 52, 54 substantially closer together in the e~Lrd~lce region 58 than is conventional. Whilst other known systems generally position the deflection electrodes at a uniform 3/16 inch (0.48 cm) spacing, the drop entrance 58 ot the Figure 2 structure may be reduced to 3t32 inch (0.24 cm) or even 1/16 inch (0.12 cm), thereby tripling the electric field intensity in this region. The electrodes 52 and 54 diverge to a spacing of between about 3/16 and 5/16 inch (that is 0.48 cm to 0.80 cm) at the drop exit 60.
Elevated electric field intensities of this magnitude would conventionally be impracticable as they would be accompanied by excessive arcing in the narrowed gap adjacent the entrance 58, particularly in the presence of the conductive ink drops and mist. The arrangement illustrated in Figures 1 and 2 overcomes this problem by positioning a dielectric insulation material 62 over the portion of the high voltage electrode 54 generally in the entrance region of high electric field intensity. The dielectric insulation material 62 can be Teflon FEP which exhibits a dielectric strength (236 KV/cm) six times that of air, and therefore, a relatively thin 1/10 inch (0.25 cm) layer of this material provides an additional 5,900 volts dielectric strength thereby wo 94/0829~ j 3 8 ~ pcr/GB93/o2lol doubling the maximum useable electric field intensity.
However, in the prior art device of Figure 2 it is necessary for the high voltage deflection electrode 54 to have its exit end 66 left uninsulated and exposed to provide for mist neutralization and collection.
It is well known that ink drops i-"pacti"g on a print medium create an ink mist which can accumulate to form an u---~d-,le-l electric field which, in turn, will deflect charged ink drops from their inlended trajectories. In the prior art device of Figure 2, negatively charged ink mist 64 is allld-;ted to the exposed end 66 of the positively charged high voltage electrode 54 (generally 1/8 -1/4 inch (that is 0.32 - 0.64 cm) of the electrode is left exposed) where, upon contact with that electrode, the mist is electrically neutralized. While the prior art device shown in Figure 2 has been highly satisfactory, there remains the possibility of arcing which, because the ink drops conldin volatile solvents, can result in combustion. This possibility is increased by use of the high voltage electrode for conl,olli,1g mist. As mist builds up, changes in the field occur and evaporation of the solvent decreases the dielectric strength of the air gap between the plates increasing the likelihood of arcing.
With reference to Figure 3 a stream of ink drops 80 are emitted by a nozzle 84 through a jcwcllcd orifice 86 and selected drops are appropriately charged by charge electrode 88. The deflection structure consists of a pair of plates defining deflection electrodes 90 and 92. Uncharged drops pass along trajectory T, to the gutter or catcher 36 as before while charged drops pass along trajectory T2 to mark the WO 94/08792 214 5 3 8 5 PCJ'/GB93/02101 substrate 34. The upper electrode 90 is grounded, or nearly so, to provide the low voltage electrode while the lower electrode 92 is maintained at a negative voltage on the order of 2,000 to 5,000 volts to provide the high voltage electrode. The entire high voltage electrode 92 is surrounded by an insulating layer 94 which can be of any suitable insulating material such as that previously discussed in connection with the prior art insulabng layer 62 in Figure 2. It should parbcularly be noted that, because the electrode 92 is completely enc~ps~ ted, arcing between the electrode cannot occur under ordinary operating conditions. The ink drops selected for marking the subsl,ate 34 are negatively charged and are therefore repelled by the high voltage electrode 92, as indicated in the drawing, to cause a deflection onto a trajectory, such as T2, to mark the substrate 34.
Bec~llse the high voltage electrode is completely encapsulated in insulating material, it cannot be used for mist control. However, this function is provided by the low voltage electrode 90 due to the use of negatively charged drops, that is the same polarity as the high voltage electrode 92. Thus mist, which forms when the drops impact on the sul,slldte 34, is attracted to an end 96 of the grounded electrode 90.
Because the high voltage electrode plate 92 is encapsulated in a material of high dielectric strength having very high resistivity (of the order of a thousand volts/mil and 1000 Megohm-cm), shorting the surface of the high voltage electrode 92 to ground, or to the opposite grounded electrode plate 90 will not collapse the electrode field.
Furthermore corona currents will not be established because of the high impedance of the encapsulating material 94.
W094/08792 2~ ~S38 pcr/GB93/o2lo1 In order to obtain the full benefits of the present invention, the high voltage encapsulated electrode 92 is preferably of the same polarity as the charge on the ink drops 80. The other electrode 90 is preferably substantially at ground potential. The charged drops will be repelled from the high voltage electrode 90 rather than, as in the prior art, all,acted thereto. This ensures that the ùncor,l,ollable charged satellites 98 cc"sliluting the mist will not gather on the high voltage electrode 92 and interfere with the es~ lisl""ent of the desired field. Instead, the u-,coul,olled satelliles 98 gather on the end 96 of the oppos;"y grounded electrode 90 and are discharged leaving the field undisturbed. The plates are shown as planar but may have other geometries.
In this manner the present invention permits increased field intensity without adverse inter-electrode arcing, thereby permitting a shorter printhead. This can be accomplished without sacrificing the ink mist neutralizing function. The high voltage electrode is completely encapsulated in an insulating material. The uninsulated electrode is preferably grounded or at a very, IGmil ,al voltage (say not more than 100 volts) and utilized for the mist neutralization function. Because the ink drops and high voltage electrode are of the same polarity, the high voltage electrode repels the drops to cause deflection, rather than attracting the drops as in the prior art.
Figures 4, 5 and 6 illustrate altematives to Figure 3 and only the features of difference will be described, the same reference numerals being used to indicate equivalent parts.
In Figure 4 the polarity of the high voltage supply and the charge on the drops WO 94/08792 21 ~ 5 3 8 ~ PCJ'/GB93/02101 have been reversed so that they are both positive. The upper low voltage electrode 90 is still grounded, or nearly so.
The arrangement of the electrodes in Figures 3 and 4 can be altered to suit specific operating requirements. For instance, the gutter 36 could be repositioned to collect ink drops from one of the deflected trajectories such as T2, and the relative positions of the electrodes 90, 92 can be reversed.
In Figure 5 the high voltage electrode 92 is of positive polarity whereas the selected drops are given a negative charge so that they will be attracted from trajectory T1 to another trajectory, such as T2 or T3, dependent on the level of charge.
The end 96 of the low voltage electrode 90 may be kept at a low positive voltage to collect satellites 98 from the vicinity of the catcher 36. Other satellites may alternatively be removed, if desired, by suction or by using a separate uninsulated electrode of appropriate potential.
In Figure 6 the positions of the low voltage electrode 90 and the high voltage electrode 92 have been reversed so that the medium 34 will be marked by uncharged drops along trajectory T, and by charged drops along trajectories such as T2. The drops for recirculation are the most heavily charged drops which pass along trajectory T3 to the catcher 36.
Whilst the general features of the invention are shown in and described with reference to Figure 3, the subsequent Figures 4, 5 and 6 indicate several variations Wo 94/08792 ~ 85 pcr/GBs3/o21ol 2~3 of the manner in which some features may be re-arranged.
Although the electrodes 90 and 92 illustrated in Figures 3 to 6 are shown as being the same size as the electrodes 52 and 54 of Figures 1 and 2, it should be particularly noted the increased field strength provided by the present invention enables a given drop deflection to be achieved using electr~Jes which are correspondingly shorter (in the direction of the trajectories T" T2, etc) than hitherto possible. This increases print accuracy and reduces evaporation from the recirculated drops which have less exposure to the ambient environment.
The relative disposition of the electrodes 90, 92 may be as shown but, if desired, could be parallely spaced provided the deflected drops can escape through the drop exit 60. However, due to the increased field intensity it is also possible that the angular diverge of the electrodes may also be increased.
Claims (9)
1. A drop marking system including means (14,84,86) for emitting a stream of marking drops, means (80) for charging selected drops, drop deflection means (32) for deflecting the charged drops to follow a trajectory (T2) different from a trajectory (T1) followed by the uncharged drops whereby certain drops will mark a medium (34) whilst other drops will be intercepted by the catcher (36), the drop deflection means (32) includes a high voltage deflection electrode (92) and a low voltage deflection electrode (90), means (53) for maintaining the low voltage deflection electrode (90) at ground or nearly at ground, means (55) for applying a high voltage to the high voltage deflection electrode (92) sufficient to create an electric field between adjacent surfaces of the deflection electrodes (90,92) to deflect the charged drops, and insulation material covering part of the said adjacent surface of the high voltage deflection electrode (92) to inhibit arcing between the deflection electrodes (90,92), characterised in that the insulation material (94) covers substantially the entire surface of the high voltage deflection electrode (92) adjacent to said low voltage deflection electrode (90) whereby the electric field strength and ink mist discharges can be increased by operating the high voltage deflection electrode (92) at a voltage which would otherwise cause arcing between the low and high voltage deflection electrodes (90,92), in that the impedance of the insulating material (94) prevents the establishment of corona currents and in that the means (55) for applying the high voltage to the high voltage deflection electrode (92) is arranged to apply the high voltage at the same polarity as the charge to be given to the selected drops whereby the charged drops will be repelled by the high voltage deflection electrode (92) towards the low voltage deflection electrode (90).
2. A system, as in Claim 1, characterised in that the deflection electrodes (90,92) are plates which diverge in the direction of the drop trajectories whereby the electric field will be stronger at the entrance (58) of the drop deflection means (90,92) than at its exit (60).
3. A system, as in Claim 1 or Claim 2, characterised in that the low voltage deflection electrode (90) has an uninsulated portion (96) positioned to attract and neutralize the charge on mist produced by charged drops striking the medium (34).
4. A drop deflector, for a drop marking system in which a stream of marking drops are to be emitted and selected drops are to be charged for deflection along a trajectory (T2) different from a trajectory (T1) followed by the uncharged drops, including a high voltage deflection electrode (92) and a low voltage deflection electrode (90), means (53) for maintaining the low voltage deflection electrode (90) at ground or nearly at ground, means (55) for applying a high voltage to the high voltage deflection electrode (92) sufficient to create an electric field between adjacent surfaces of the deflection electrodes (90,92) to deflect the charged drops, and insulation material covering part of the said adjacent surface of the high voltage deflection electrode (92) to inhibit arcing between the deflection electrodes (90,92), characterised in that the insulation material (94) covers substantially the entire surface of the high voltage deflection electrode (92) adjacent to the low voltage deflection electrode (90) whereby the electric field strengh can be increased by operating the high voltage deflection electrode (92) at a voltage which would otherwise cause arcing between the low and high voltage deflection electrodes (90,92), in that the impedance of the insulating material (94) prevents the establishment of corona current and in that the means (55) for applying the high voltage to the high voltage deflection electrode (92) is arranged to apply the high voltage at the same polarity as the charge to be given to the selected drops whereby the charged drops will be repelled by the high voltage deflection electrode (92) towards the low voltage deflection electrode (90).
5. A drop deflector, as in Claim 4, characterised in that the deflection electrodes (90,92) are plates which diverge in the direction of the drop trajectories whereby the electric field will be stronger at the entrance (58) of the drop deflection means (90,92) that at its exit (60).
6. A drop deflector, as in Claim 4 or Claim 5, characterised in that the low voltage deflection electrode (90) has an uninsulated portion (96) positioned to attract and neutralize the charge on mist produced by the charged drops striking a target (34).
7. A method of deflecting selected charged drops from a first trajectory (T1) to another trajectory (T1), comprising passing a stream of charged and uncharged drops through an electric field generated between adjacent surfaces of a high voltage deflection electrode (92) and a low voltadge deflection electrode (90), characterised by insulating the said adjacent surface of the high voltadge deflection electrode (92) to enable operation at a voltage which would otherwise cause arcing between the low and high voltage deflection electrodes (90,92), the impedance of the insulating material (94) preventing the establishment of corona currents.
8. A method, as in Claim 7, characterised by applying the high voltage to the high voltage deflection electrode (92) with the same polarity as the charge on the charged drops whereby the charged drops will be repelled by the high voltage deflection electrode (92) towards the low voltage deflection electrode (90).
9. A method, as in Claim 8, characterised by using the low voltage electrode (90) to attract satellite droplets and to neutralize the charge thereon.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US96013892A | 1992-10-13 | 1992-10-13 | |
| US960,138 | 1992-10-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2145385A1 true CA2145385A1 (en) | 1994-04-28 |
Family
ID=25502835
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002145385A Abandoned CA2145385A1 (en) | 1992-10-13 | 1993-10-11 | Method and system for drop marking and a drop deflector for use therewith |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPH08501997A (en) |
| CN (1) | CN1090815A (en) |
| AU (1) | AU5153193A (en) |
| CA (1) | CA2145385A1 (en) |
| GB (1) | GB2285604A (en) |
| TW (1) | TW240197B (en) |
| WO (1) | WO1994008792A1 (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2763870B1 (en) * | 1997-06-03 | 1999-08-20 | Imaje Sa | ELECTRICALLY CONDUCTIVE LIQUID SPRAY CONTROL SYSTEM |
| GB2337485B (en) | 1998-05-20 | 2000-06-14 | Linx Printing Tech | Ink jet printer and deflector plate therefor |
| JP3794406B2 (en) * | 2003-01-21 | 2006-07-05 | セイコーエプソン株式会社 | Droplet ejection device, printing device, printing method, and electro-optical device |
| WO2005123392A1 (en) * | 2004-06-17 | 2005-12-29 | Videojet Technologies Inc. | System for aligning a charge tunnel of an ink jet printer |
| GB0701233D0 (en) * | 2007-01-23 | 2007-02-28 | Videojet Technologies Inc | A continuous stream ink jet print head |
| KR101339987B1 (en) * | 2007-12-24 | 2013-12-10 | 삼성전자주식회사 | Apparatus for measureing drop mass deviation and controlling method of thereof and pattern forming system using thereof and controlling method of pattern forming system using thereof |
| JP5725800B2 (en) * | 2010-06-24 | 2015-05-27 | キヤノン株式会社 | Liquid discharge head |
| JP5946322B2 (en) * | 2012-05-22 | 2016-07-06 | 株式会社日立産機システム | Inkjet recording device |
| US9452602B2 (en) * | 2012-05-25 | 2016-09-27 | Milliken & Company | Resistor protected deflection plates for liquid jet printer |
| JP6022391B2 (en) * | 2013-03-28 | 2016-11-09 | 株式会社日立産機システム | Inkjet recording device |
| CN104417063B (en) * | 2013-08-21 | 2016-03-23 | 北大方正集团有限公司 | A kind ofly reduce the method and device of overlapping neat error effect |
| WO2018235378A1 (en) * | 2017-06-20 | 2018-12-27 | 株式会社日立産機システム | Ink jet recording apparatus |
| CN108790405B (en) * | 2018-04-19 | 2019-07-09 | 华中科技大学 | A kind of electrohydrodynamic printing head that can eliminate drop charges |
| US10913294B2 (en) * | 2019-05-14 | 2021-02-09 | Electronics For Imaging, Inc. | Printing systems and associated structures and methods having ink drop deflection compensation |
| CN110525048B (en) * | 2019-08-30 | 2020-10-09 | 合肥京东方卓印科技有限公司 | Device, system and method for measuring volume of ink drop |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4047184A (en) * | 1976-01-28 | 1977-09-06 | International Business Machines Corporation | Charge electrode array and combination for ink jet printing and method of manufacture |
| US4031561A (en) * | 1976-05-03 | 1977-06-21 | The Mead Corporation | Startup apparatus and method for jet drop recording with relatively movable charge plate and orifice plate |
| JPS5567468A (en) * | 1978-11-15 | 1980-05-21 | Fuji Xerox Co Ltd | Ink jet recorder |
| JPS55166258A (en) * | 1979-06-11 | 1980-12-25 | Ricoh Co Ltd | Ink jet recording device |
| US4249189A (en) * | 1979-09-04 | 1981-02-03 | The Mead Corporation | Ink jet printer having improved deflection electrode |
| JPS5655265A (en) * | 1979-10-11 | 1981-05-15 | Ricoh Co Ltd | Multiple deflecting electrode structure for liquid jet recorder |
| JPS56123872A (en) * | 1980-03-05 | 1981-09-29 | Ricoh Co Ltd | Ink jet recording device |
| JPS599061A (en) * | 1982-07-09 | 1984-01-18 | Hitachi Ltd | Charge modulation type ink jet printer |
| FR2573008B1 (en) * | 1984-11-13 | 1988-01-08 | Imaje Sa | INK JET SINGLE JET PRINTHEAD |
-
1993
- 1993-10-11 WO PCT/GB1993/002101 patent/WO1994008792A1/en active Application Filing
- 1993-10-11 CA CA002145385A patent/CA2145385A1/en not_active Abandoned
- 1993-10-11 JP JP6509753A patent/JPH08501997A/en active Pending
- 1993-10-11 AU AU51531/93A patent/AU5153193A/en not_active Abandoned
- 1993-10-11 GB GB9505256A patent/GB2285604A/en not_active Withdrawn
- 1993-10-12 CN CN 93115004 patent/CN1090815A/en active Pending
- 1993-11-08 TW TW82109354A patent/TW240197B/zh active
Also Published As
| Publication number | Publication date |
|---|---|
| AU5153193A (en) | 1994-05-09 |
| GB2285604A (en) | 1995-07-19 |
| JPH08501997A (en) | 1996-03-05 |
| CN1090815A (en) | 1994-08-17 |
| TW240197B (en) | 1995-02-11 |
| GB9505256D0 (en) | 1995-05-10 |
| WO1994008792A1 (en) | 1994-04-28 |
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| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19960411 |