US3827057A

US3827057A - Selective charging magnitude compensation

Info

Publication number: US3827057A
Application number: US00320325A
Authority: US
Inventors: V Bischoff; R Keur
Original assignee: AB Dick Co
Current assignee: AB Dick Co; Videojet Technologies Inc
Priority date: 1973-01-02
Filing date: 1973-01-02
Publication date: 1974-07-30
Anticipated expiration: 1991-07-30
Also published as: DE2364881B2; CA1001213A; JPS509332A; JPS5322019B2; DE2364881A1; GB1442798A; BE809359A

Abstract

In an ink drop printer, the charge on a just formed drop is stored and used to provide a compensating charge for the next drop, to be formed in order to avoid the adverse effects of the charge on the just formed drop.

Description

[111 3,827,057 [451 July 30, 1974 SELECTIVE CHARGING MAGNITUDE COMPENSATION Inventors: Vincent E. Bischoff, River Grove; Robert I. Keur, Niles, both of Ill.

Assignee: A. B. Dick Company, Chicago, Ill. Filed: Jan. 2, 1973 Appl. No.: 320,325

Primary Examiner.loseph W. Hartary Attorney, Agent, or Firm'-Lindenberg, Freilich, Wasserman, Rosen & Fernandez [57] ABSTRACT In an ink drop printer, the charge on a just formed [52] US. Cl. 346/75 rop is stored and used to provide a compensating [51] Int. Cl. G01d 18/00 charge o th next p, to be formed i order to [58] Field of Search 346/75 avoid th ad rs ffe ts f th charg n the just formed drop. [56] References Cited UNITED STATES PATENTS 8 Claims, 2 Drawing Figures 3,631,511 l2/l97l Keuretal. 346/75 DE A Vl DEO comp comp ANAL GEN NETWORK I I I A E) C 20 58 GAIN g ES Q" CONTROL C NETWORK [30 V {32 {54 V DAT-A CHARACTER VlD VlD SOURCE GEN PRoc AMP l6 24A 0) K g 22 b INK g 4 g Q o REJERVOW TRANSDUCER 6 o 0 Q o G VOLTA6E CATCHER PATENTEBJuLamsm v) DEO com D QQMP ANAL GEN NETWORK I A-Elvc pa GAIN SYSTEM CONTROL CLOCK NETWORK PO P2 {54 r 40 DATA CHARACYER WD 5 v19 SOURCE GEN p AMP \6 \O) \2 /\g 22 EL-5223M; \4 I I4 Q INK RE ERVO\R TRANSDUCER 5 0 o a 6 0 24B. 2 H\G:H -n 28 VOLTAGE CATCHER f? 1 W5 fi CLOCK G FF \/\D K Q FF v ,54 6O 50 B Q 72 62 C Q56 74 c o L CK- DELAY FF I BACKGROUND OF THE INVENTION The present invention relates to ink drop printing apparatus, and more particularly, to an improved arrangement for charging drops.

In a U.S. Pat. No. 3,631,511, it was shown that one of the problems which arises in ink drop printing apparatus is that a drop which is charged, and which is just broken from the-ink jet stream has an electric field which operates on the immediately following drop being formed and charged in a manner to depress or lower the charge, which that drop will receive from the video signal. Similar, but lesser degree effects are caused by the drops which precede the one justbroken from the ink jet stream. As a result, the following ink drop is not properly deflected by the following electric field. This results in printing which is not as good as it should be, or which is imprecise with respect to character formation. In order to avoid these effects, increased drop spacing, as well as guard drops, that is, drops with no charge, are used for spacing charged drops. These techniques however slow up the printing process or have undesirable effects.

U.S. Pat. No. 3,631,511, proposes an arrangement for compensating for the effects on a drop being formed, of a charge on the drop which has just been formed by detecting whether or not a just formed drop has had a charge applied to it, and if it has, then a compensating voltage is added to the video charging voltage being applied to charge the next drop being formed, whose amplitude varies with the amplitude of the charging voltage. This arrangement does charge, but since the charge applied to a drop does vary, it does not completely and/or accurately compensate for the adverse effects of the charge of a just formed drop on the next drop being formed.

OBJECTS AND SUMMARY OF THE INVENTION An object of this invention is to compensate accurately the charge to be applied to a drop being charged for the effects of a charge on a drop which has already been formed and charged.

Yet another object of the present invention is the provision of an arrangement for improving the printing quality and speed of an ink drop printer.

These and other objects of the present invention are achieved in an arrangement wherein means are provided for storing the fact that a video signal has been applied to a just formed drop, together with the amplitude of that video signal. In that event, a compensating charge is applied to the succeeding drop being formed, which is determined be the amplitude of the charge on the already formed drop, to thereby accurately compensate for the effects of the charge, on the already formed drop.

The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block schematic diagram illustrative of this invention in an ink drop printing arrangement FIG. 2 is a schematic block diagram of an embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a known type of ink jet printer, which also includes a schematic representa tion of the circuitry required, in accordance with this invention.

An ink jet printer, basically includes an ink reservoir 10, which holds ink under pressure. A pipe 12, discharges the ink from the ink reservoir in the form of a stream 14, which is directed at writing paper 16. An electromechanical transducer 18 squeezes the nozzle at a frequency determined by the output of the sync signal generator or system clock 20. The periodic nozzle squeezing causes periodic narrowing or necking of the ink jet 14, so that drops 14 are formed along the path of the ink jet stream on its way to the paper 16. These drops are substantially uniformly sized and regularly spaced. A small ring 22 is placed at a drop charging location along the ink jet 14, where it begins to break into drops. The drops are formed within the ring and pass out of it through an electric field, which is established by two spaced plates, respectively 24A and 243. A high voltage deflection field is established between these plates from a high voltage source 26. Drops which are not used in the process of writing on the paper, are not charged and are caught by a waste catcher 28. The charged drops are deflected between the plate 24A and 243, in a manner so they avoid the waste catcher and are directed upon the paper at a location determined by the amplitude of a charge on a drop.

Information for charging the drops, which determines what characters are printed on the paper 16, is provided by video signals from a data source 30. These signals may be digital or analog in form. They are applied to a character signal function generator 32, at a rate determined by the output of the system clock 20. The binary character signal fucntion generator 32, processes its input in binary digital form, finally converting the digital signals into a series of electric signals which represent the voltages to be successively used to charge successive drops. These voltages are applied to a video processor 34, which converts a signal to a form suitable for charging the drops so that they will be deposited in a desired pattern on the paper. The output of the video processor is applied to a video amplifier 40.

The character being printed is usually constructed by deflecting the drops vertically and moving the paper horizontally, or by moving the entire ink jet printing horizontally, the paper being stationary and the drops being deflected vertically as the ink jet printing assembly is moved. In either event, the signals out of the character generator comprise a sequence of voltages whose amplitudes are determined by the character desired to be printed.

In accordance with this invention, a digital output (represented by A, B, and C) is taken from the character generator. The character generator usually includes a Y column counter which converts the video signal received from the data source 20 into a digital count. This digital count, here represented as A, B, and C, constitutes the desired discrete charge levels for the droplets. The charge level is applied to the video processor 34, the A, B, and C digital count is applied to the Referring to FIG. 2, there, shown in more detail, is a schematic representation of what is included in

blocks

36, 44 and 46 of FIG. 1. The video analyzer 46 indicates whether a particular drop is to be compensated based upon whether a previous drop was charged. The video analyzer comprises a I, K flip-flop with video signals applied to its K input and video signals to its .I input. It also has a clock input. The Q output of the analyzer 46 is connected as the enabling inputs to

NAND gates

58, 60, and 62.

In the presence of a video signal being applied to the video processor, the flip-flop 46 is reset with its Q output high. In the absence of such a video signal, a video" signal is applied to the J input of the flip-flop and its Q output goes high.

Three data storage registers or, flip-

flops

52, 54 and 56 have their respective Q outputs connected, as second required inputs, to the NAND gates. One input to each of the flip-

flops

52, 54 and 56 is a clock signal, which is applied through a delay circuit 57, the other inputs are the respective binary signal inputs A, B and C. The data on lines A, B, and C are entered in the re spective flip-flops toward the trailing end of a system clock pulse as a result of the time delay caused by the delay circuit 45. This data is stored thereby, and will be available during the next or successive drop formation period.

The compensation network 36, includes a ladder of binary weighted resistors respectively 70, 72 and 74, to which the respective outputs of

NAND gates

58, 60 and 62 are connected. The other ends of

resistors

70, 72 and 74 are commonly connected to a compensation magnitude control potentiometer 50. The NAND gates function as current switches. These switches are selected by the outputs of the flip-

flops

52, 54 and 56.

The gain of the video amplifier 40, is controlled by the compensation network 36 as follows. As more of the

gates

58, 60, and 62 are enabled, the compensation network actuates the gain control network 38 to increase the gain of the video amplifier 40. A reduction in the number of

gates

58, 60, and 62 enabled, operates to reduce the gain of the video amplifier 40.

From what has been described thus far, it will be understood that upon the trailing edge portion of a clock pulse the video signal, if any, being used to charge a drop being formed is stored in flip-

flop

52, 54 and 56. In the event the succeeding drop is to be charged, when the next video signal arrives, flip-flop 46 serves to enable

gates

58, 60 and 62 whereby the gain of the video amplifier 40 is established so that the amplitude of the charge which will be applied to the drop then being formed is the video signal amplified sufficiently to include compensation for the charge applied to the preceding drop. In the absence of a gain control voltage which occurs when no charge is applied to the preceding drop, the gain factor of the video amplifier is set at some nominal value, whereby no compensation is applied to the video voltage which is being used to charge a drop. It can be appreciated from the foregoing, that the present invention generates a gain control voltage which represents a function identical to the video amplifier charging function, delayed in time by one drop period. This is an analog function of the preceding drop charge which is then used to determine the gain to be given to the video signal intended for use as the next drop charge.

There has accordingly been described and shown herein a novel and useful arrangement for establishing the amplitude of a charge to be applied to a drop which includes compensation for the value of the charge which was applied to an immediately preceding drop.

What is claimed is:

1. In an ink drop system, an arrangement for compensating the charge to be applied to a drop being formed to correct for the effects of the charge on a drop which was just previously formed comprising:

means for storing a representation of a voltage which was used to charge a drop which was just previously formed, and

means for amplifying a voltage to be applied to charge the next drop to be formed following said previously formed drop by an amount which is a function of said stored representation of a voltage to thereby provide a voltage for charging said next drop which includes compensation for the charge on said drop which was previously formed.

2. In an ink drop system as recited in claim 1 wherein there is included:

means for sensing that said next drop to be formed is to be charged and providing an output indicative thereof, and

means, enabled responsive to said output, to convert said representation of a voltage in said means for storing into said function for controlling the gain of said means for amplifying.

3. In an ink drop system, an arrangement for compensating a charge to be applied to a drop being formed to correct for the effects of the charge on a drop which was just previously formed comprising video signal means for providing an output comprising a representation of a voltage used for charging each drop,

means for storing an output of said video signal means comprising a representation of the voltage which was used to charge a drop which was just previously formed,

means for sensing that a representation of a voltage is being provided by said video signal means to charge a drop being formed immediately following said just previously formed drop and providing an output indicative thereof,

first means, enabled responsive to said output from said means for sensing, for converting said representation of a voltage stored by said means for storing into a representative gain control voltage, and

second means for converting said representation of a voltage used for charging a drop immediately following said just previously formed drop into a drop charging voltage,

amplifier means for amplifying said drop charging voltage, being provided by said second means for converting, by an amount determined by said representative gain control voltage to thereby compensate for the effects of the charge on the just previously formed drop.

4 In an ink drop printer as recited in claim 3 wherein said means for storing comprises:

flip-flop means for storing a digital representation of the voltage used to charge the previously charged drop,

said means for converting, enabled responsive to an output from said means for sensing comprises: gate means connected to receive outputs from said means for storing and said means for sensing, and

resistor means connected to receive output from said gate means for converting said output from said gate means into a representative gain control voltage.

5. In an ink drop printing means as recited in claim 4 wherein said means for sensing comprisesa flip-flop having a first output responsive to a voltage being applied thereto from said video signal means and a second output when no voltage is applied thereto from said video signal means, and

means connecting said first output to said gate means.

6. In an ink drop printing system, an arrangement for compensating the charge to be applied to a drop being formed to correct for the effects of the charge on a drop which was just previously formed comprising:

character generator means for providing analog signals for charging drops and a digital signal representative of each analog signal,

means for storing a digital signal representative of an analog signal used to charge the drop which was previously formed,

means for sensing that an analog signal is being provided by said video signal means for charging a drop being formed and providing an output indicative thereof,

gate means connected to receive output from said means for storing and enabled responsive to an output from said means for sensing for converting said digitalsignal stored in said means for storing into an analog control signal,

drop charge amplifying means to which analog signals from said character generator are applied for amplifying said analog signals for application for charging a drop being formed, and

means for controlling the gain of said drop charge amplifying means responsive to said analog control signal whereby said output of said drop charge amplifying means is an analog signal for charging a drop being formed compensated for the charge applied to a just previously charged drop.

7. In an ink drop system, the method of compensating the charge to be applied to a drop being formed to correct for the effects of a charge on a drop which was just previously formed, comprising the steps of:

storing a voltage representative of the charge applied to said just previously formed drop until the next drop is being formed, and

amplifying a voltage to be applied to charge said next drop by an amount which is a function of said stored voltage representative of the charge applied to said just previously formed drop to provide a voltage to charge said next drop which is compensated for the charge on said just previously formed drop.

8. The method recited in claim 7 wherein there is included the steps of:

sensing that the next drop being formed following said just previously formed drop is to be charged and providing an output indicative thereof, and converting the stored voltage representative of the charge applied to said just previously formed drop in the presence of said output into a function for controlling amplification.

Claims

1. In an ink drop system, an arrangement for compensating the charge to be applied to a drop being formed to correct for the effects of the charge on a drop which was just previously formed comprising: means for storing a representation of a voltage which was used to charge a drop which was just previously formed, and means for amplifying a voltage to be applied to charge the next drop to be formed following said previously formed drop by an amount which is a function of said stored representation of a voltage to thereby provide a voltage for charging said next drop which includes compensation for the charge on said drop which was previously formed.

2. In an ink drop system as recited in claim 1 wherein there is included: means for sensing that said next drop to be formed is to be charged and providing an output indicative thereof, and means, enabled responsive to said output, to convert said representation of a voltage in said means for storing into said function for controlling the gain of said means for amplifying.

3. In an ink drop system, an arrangement for compensating a charge to be applied to a drop being formed to correct for the effects of the charge on a drop which was just previously formed comprising video signal means for providing an output comprising a representation of a voltage used for charging each drop, means for storing an output of said video signal means comprising a representation of the voltage which was used to charge a drop which was just previously formed, means for sensing that a representation of a voltage is being provided by said video signal means to charge a drop being formed immediately following said just previously formed drop and providing an output indicative thereof, first means, enabled responsive to said output from said means for sensing, for converting said representation of a voltage stored by said means for storing into a representative gain control voltage, and second means for converting said representation of a voltage used for charging a drop immediately following said just previously formed drop into a drop charging voltage, amplifier means for amplifying said drop charging voltage, being provided by said second means for converting, by an amount determined by said representative gain control voltage to thereby compensate for the effects of the charge on the just previously formed drop. 4 In an ink drop printer as recited in claim 3 wherein said means for storing comprises: flip-flop means for storing a digital representation of the voltage used to charge the previously charged drop, said means for converting, enabled responsive to an output from said means for sensing comprises: gate means connected to receive outputs from said means for storing and said means for sensing, and resistor means connected to receive output from said gate means for converting said output from said gate means into a representative gain control voltage.

5. In an ink drop printing means as recited in claim 4 wherein said means for sensing comprises a flip-flop having a first output responsive to a voltage being applied thereto from said video signal means and a second output when no voltage is applied thereto from said video signal means, and means connecting said first output to said gate means.

6. In an ink drop printing system, an arrangement for compensating the charge to be applied to a drop being formed to correct for the effects of the charge on a drop which was just previously formed comprising: character generator means for providing analog signals for charging drops and a digital signal representative of each analog signal, means for storing a digital signal representative of an analog signal used to charge the drop which was previously formed, means for sensing that an analog signal is being provided by said video signal means for charging a drop being formed and providing an output indicative thereof, gate means connected to receive output from said means for storing and enabled responsive to an output from said means for sensing for converting said digital signal stored in said means for storing into an analog control signal, drop charge amplifying means to which analog signals from said character generator are applied for amplifying said analog signals for application for charging a drop being formed, and means for controlling the gain of said drop charge amplifying means responsive to said analog control signal whereby said output of said drop charge amplifying means is an analog Signal for charging a drop being formed compensated for the charge applied to a just previously charged drop.

7. In an ink drop system, the method of compensating the charge to be applied to a drop being formed to correct for the effects of a charge on a drop which was just previously formed, comprising the steps of: storing a voltage representative of the charge applied to said just previously formed drop until the next drop is being formed, and amplifying a voltage to be applied to charge said next drop by an amount which is a function of said stored voltage representative of the charge applied to said just previously formed drop to provide a voltage to charge said next drop which is compensated for the charge on said just previously formed drop.

8. The method recited in claim 7 wherein there is included the steps of: sensing that the next drop being formed following said just previously formed drop is to be charged and providing an output indicative thereof, and converting the stored voltage representative of the charge applied to said just previously formed drop in the presence of said output into a function for controlling amplification.