US3555558A

US3555558A - Ink drop writing apparatus with data synchronizing means

Info

Publication number: US3555558A
Application number: US792271*A
Authority: US
Inventors: David M Sherman
Original assignee: AB Dick Co
Current assignee: AB Dick Co; Videojet Technologies Inc
Priority date: 1969-01-21
Filing date: 1969-01-21
Publication date: 1971-01-12
Anticipated expiration: 1988-01-12
Also published as: DE1965456A1; FR2031123A5; GB1297106A; JPS493206B1

Abstract

IN AN INK DROP WRITING APPARATUS IN WHICH A RECIPROCATING CARRIAGE CARRIES INK DROP EMITTING APPARATUS, WHICH INK DROPS ARE EMITTED THROUGH AN ELECTRIC FIELD TOWARD PAPER, AND IN FLIGHT ARE DEFLECTED IN ACCORDANCE WITH VIDEO SIGNALS FOR PRODUCING INTELLIGIBLE INFORMATION ON SAID PAPER, MEANS ARE PROVIDED, IN ACCORDANCE WITH THIS INVENTION, FOR INSURING THAT DESPITE VARIABLES, SUCH AS DIFFERENT CARRIAGE START-UP TIME AND ACCELERATION, A UNIFORM LEFTHAND MARGIN IS PRODUCED ON THE PAPER, AND ALSO THAT PRINTING FREE FROM TIMING ERRORS OCCURS.

Description

Jan. 12, RM N 3,555,558

INK DROP WRITING APPARATUS WITH DATA SYNCHRONIZING MEANS Filed Jan. 21, 1969 2 Sheets-Sheet l 5O symc \HDEO 52 S\6NAL SIGNAL FUELD SOURCE. IQOUQCE BMTD RE5ERVO\R \8 TRANSDUCER j 22 v CHARGING WASTE PROQ ART TUNNEL REsERvonz NOW \5 THE TSME 48 INK DROP WRWER GEAR MOTO R BOX 70 FQOM 58 62 6ATE589 MOTOR FIG 4 CONTROL 72 so 40 4 76 6 J 6 lie! 5% A 7% El *JLJLJLII H ILILJ JLILJLJLJLJLILI E E.

Al W //v vE/vro/e 74 DA v/o M. SHERMAN By A wrap/v5 Y5 Jan. 12, 1971 p, SHERMAN 3,555,558

INK DROP WRITING APPARATUS WITH DATA SYNCHRONIZING MEANS Filed Jan. 21, 1969 2 Sheets-Sheet I F- 90 i7 4 I 8% ARmAeE 87 STOP DATA END POsmoN K DETECTOR 2 DATA g f SOURCE v as I 5mm DATA gitffi DETECTOR 9! 6 59 f 5TART 5H \FT 8 B T START OF CARRlAGE CLOCK REGSTER HEADING Sl6NAL emu/m5 DECODER TO MOTOR GATES CONTROL f g RES ET COUNTER V 1 Q4 uPDATE eTRoBE ESEQ O0 REGASTER CARR E 6 DATA R ET SYNCHROWZER gsfig cuzcurrs DETECTOR DATA CHARACTER \eNAL GEN 9 TRANSFER sTRoBE cmcunvb \02 START V DEO To I aewu C,HARG)NC; cwecuw TUNNEL \04 A06 7 T 25 HO \oo\ HZ 400 Hz, r 20 OSOLLATOR I D\\/1DER 1 v Q T RESET CARWAGE 22 PRINT DOS \TION DETECTOR 1 /Q2 V Q1 5131 Q uPDATEsTRosE Q n4 H2. 2 I 15%. 1 lNVE/VTOR DA V/D M. Sf/EQMAN By & a

. ff/ M 3/- 5 Patented Jan. 12, 1971 3,555,558 INK DROP WRITING APPARATUS WITH DATA SYNCHRONIZING MEANS David M. Sherman, La Grange, Ill., assignor to A. B. Dick Company, Chicago, Ill., a corporation of Illinois Filed Jan. 21, 1969, Ser. No. 792,271 Int. Cl. G01d.15/18;B41j3/04 US. Cl. 34675 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to apparatus for writing with ink drops which are charged by a video signal and directed through an electric field, to 'be deflected in accordance with the charge, and more particularly to improvements therein.

An ink drop writing apparatus has been developed, wherein ink is applied under pressure to a nozzle. The nozzle is vibrated in response to a synchronizing signal which is also used for synchronizing video signals. The vibrated nozzle causes an ink jet, which is emitted therefrom, to break up into uniform drops at a distance away from the tip of the nozzle. The rate of such drop formation is determined by the vibration rate. A means for charging each drop is provided at the location at which the ink stream begins to break into drops. This means usually is a conductive tube or cylinder. Video signals are applied between the nozzle and cylinder in response to which a drop assumes a charge determined by the amplitude of the video signal at the time that the drop breaks away from the jet stream.

The drop thereafter passes through a fixed electric field, as a result of which it is deflected by an amount determined by the amplitude of the charge on the drop.

At the boundary of the electric field there is positioned a writing medium upon which the drop falls. Since the deflection of the drop is determined by the charge on the drop, the arrangement enables one to write information with the ink which is carried by the video signal.

The vibrating nozzle is carried by a carriage which is made to reciprocate along a predetermined path while the paper upon which writing is to occur is moved in a path which is orthogonal to the path of the carriage. One of the problems which arose with this apparatus is that because of variables such as variations in the carriage start-up time and carriage acceleration, and the presence of data, the paper upon which the writing occurred would have an irregular left-hand margin. Thus, the visual presentation of'the results of writing with the ink jet writer was not commercially acceptable and tended to cause irritation to a reader.

OBJECTS AND SUMMARY OF THE INVENTION An object of this invention is to provide apparatus whereby an ink jet writing system, of the type described can provide a uniform left-hand margin despite variations in carriage start-up and acceleration. This is achieved by sensing that data is available, starting carriage motion, sensing when the carriage reaches a predetermined location spaced from the lefthand edge of the carriage path of travel which is a sufficient distance to insure that the carriage is up to its proper speed, and then permitting writing to commence. Also logic circuits are provided to sense whether or not the circuit provide the video signals to the charging tunnel are in condition for providing correct character video signals. If not, a delay is provided to enable this to occur.

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 drawing of a prior art ink drop writing system.

FIG. 2 is a schematic drawing illustrating the mechanical arrangement for writing with the ink drop writer.

FIG. 3 is a schematic drawing showing photocell placement along the carriage travel path.

FIG. 4 is a block schematic diagram illustrative of an embodiment of this invention.

FIG. 5 is a block schematic diagram illustrative of a data synchronizer circuit which is shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic drawing of a presently known arrangement which is shown to alford a better understanding of the invention.

An ink reservoir 10 provides ink under pressure to tubing 12 which is flexible. An electromechanical transducer 14 is usually placed adjacent to or around the tubing. The transducer is driven in response to signals from a source 16. The transducer serves to vibrate and/or compress the tubing 12 in the region of the nozzle 18. This results in an ink jet 20 being emitted which, at a short distance downstream, breaks up into drops 22, which are formed at a rate determined by'the frequency of the vibration. In the region where the stream 20 breaks down into drops, a charging tunnel 24 is provided. This comprises a conductive cylinder to which video signals from a video signal source 26 are applied. The video signals establish a field Within the charging tunnel so that the ink drops which are formed therein assume a charge determined by the amplitude of the video signal present at the time the drop separates from the ink jet.

Downstream of the charging tunnel there are usually placed a pair of electrodes 28 which are connected to a field bias source 30. As a result there is established between the electrodes a constant electric field. The ink drops, which bear charges in accordance with the video signal, enter this field and are deflected by an amount which is proportional to the amplitude of the charge. This enables intelligent writing to occur on a writing medium 32, which is moved at some synchronous rate past the electrodes. Drops which do not bear a video charge are captured by a tube or trough 34 Which is judiciously placed at one side so as to capture these drops. It leads to a waste reservoir 36. The paper moves into the plane of the drawing whereby its motion, together with the deflection of the drops, may be used for forming intelligible characters.

In order to write lines of information across a wide sheet of paper, an arrangement such as is schematically represented in FIG. 2 may be employed. By Way of illustration, the ink drop writer 40 is attached to a traveling nut 42, which is free to move on jonrnally supported lead screw 44. At the top of the ink drop writer is a nut 46 which is free to slide along a rod 48. Accordingly, as the lead screw 44 is rotated in one direction or the other, the ink drop writer will move in a direction dictated by this rotation along a path parallel to the lead screw.

By ink drop writer is here meant a housing which supports the ink reservoir 10, tubing 12, transducer 14, nozzle and charging tunnel 24. The video and sync signal sources are placed elsewhere and are connected to the ink drop writer by wires. The function of the deflection electrodes 28 is performed by a pair of spaced plates 41 which extend along the path of travel of the ink drop writer and are placed so that the stream of drops pass between them on their way to the paper. A trough (not shown) identical to the tube 34 is provided which extends adjacent to the bottom plate.

The paper 50 upon which writing is to occur moves in a direction vertical to the direction of the path of motion of the ink drop writer. A motor 52 has a first shaft 54 extending therefrom to a half sector gear 56. The motor has a second shaft 58 extending therefrom to a gear box 60, which functions to reverse the direction of rotation of the shaft 62. This reverse motion is communicated through a shaft 62 to another half sector gear 64 in which it terminates. The sector gears are cut so that as the motor rotates, the sector gear 56 engages a gear 66 atached to one end of the lead screw, to rotate the lead screw 44 so that the ink drop writer is moved from left to right. When the ink drop writer reaches the right-hand end of the lead screw, the sector gear 56 is disengaged from the gear 66 and a sector gear 64 engages a gear 68 on the other end of the lead screw. This results in the lead screw being rotated in the opposite direction thereby returning the ink drop writer to its home position on the lefthand side of the lead screw. Motor control apparatus 70 serves the function of energizing the motor to rotate over the interval required for the ink drop writer to make one round trip path along the lead screw. The motor control then waits until it receives a signal which enables the motor to again function to cause the ink drop writer to make a round trip path.

FIG. 3 is a schematic drawing which shows the placement of three photocells for detecting when the ink drop writer has attained three positions along its path of travel. Photocell 72, in conjunction with the light source 74, operates to detect when the ink drop writer carriage 40 has reached the home position at the left-hand end of its path of travel. Photocell 76, in conjunction with light source 78, indicates when the carriage has attained the right hand end of its path of travel. Photocell 80, in conjunction with its light source 82, indicates when the carriage, after leaving the home position, has arrived at a location at which it no longer is accelerating but is moving at a constant speed along its path of travel. It should be understood that the placement of the photocells as shown in FIG. 3 occurs on the structure shown in FIG. 2, but is not shown in the drawing of FIG. 2 in order to preserve clarity in the drawing.

FIG. 4 is a block schematic diagram illustrative of how this invention insures a uniform left-hand margin with the apparatus described. A data source 84 provides the information which is to be printed by the ink drop writer. The data source may be any of the known data supply systems such as magnetic cores, magnetic tape, or may be keyboard originated or information coming over a line. The data source can be rendered operative to transfer data into a register 86 by a signal from the carriage return detector 88, which includes photocell 72 and light source 74. The data source operation is stopped by a signal from the carriage end position detector 90, which includes the photocell 76 and light source 78.

In an embodiment of this invention that was actually built and operated, the data from the source was presented serially and each character consisted of eight binary bits. These were entered serially into an eight bit register 86, being shifted by clock signals. A 2 kHz. clock signal source 87 provided clock signals for the data source 84. The clock signal source output was also applied to a shift clock source 90, which reshaped the signals so that they were suitable for shifting the eight bit register 86. The output of the 2 kHz. clock signal source is also applied to a divide by eight circuit, 92. The divide by eight circuit merely constitutes a counter having an eight count capacity.

The data from the source is arranged so that at the biginning of each line that is to be written a code is placed which signifies the beginning of a line of data. This code is identified by decoding gate circuits 89 labeled as Start of Heading Decoder. These gate circuits merely constitute a set of AND gates which produce an output only when they sense the presence of the code representative of the beginning of a line of data. This output signal is applied to the motor control 70 to instruct it to start moving the ink drop writer carriage to the right. The output of the start of the heading decoder is also applied to the divide by eight counter, 92, to cause it to reset.

The eight bit register contents are transferred in parallel to a data buffer register 94, in response to an update strobe signal. The update strobe signal is the eighth count output of the divide by eight counter, 92. The contents of the data buffer register are applied to a character signal generator circuit 96. This circuit performs the function of converting an eight bit code into character representative signals which in this case is a train of signals suitable for application to the ink jet apparatus for printing. The character signal generator circuit is enabled to transfer out the character signals to a video signal circuit 102 only in the presence of a data transfer strobe signal which is received from a data synchronizer circuit 98.

The data synchronizer circuits 98, are reset and thus enabled to commence functioning in the presence of an output signal from the carriage print position detector 100. This includes the photocell and light source 80, 82, shown on FIG. 3. This photocell is enabled to produce a signal when the carriage reaches the position from which it Will travel to the end of its path with no further change in velocity. Also, should the data synchronizer circuit 98 receive simultaneously a carriage print position signal and a signal from the divide by eight counter, it will delay the provision of a data transfer strobe signal for a period of 10 microseconds. The reason for this is that the data buffer register is being filled with new data at the time of the occurrence of the update strobe. Should the data transfer strobe occur during the interval when the data buffer register is being filled, the character signal generator circuit will function improperly since an improper code signal will be provided to it. The effect of the delay of 10 microseconds is negligible on the printed copy. When the speed of the carriage of the ink drop writer is compared with 10 microseconds, the eye cannot discern the ditference between a character which is printed without delay, and one which is printed with delay.

The character signal generator circuit, as previously indicated may be any one of the well known character generator circuits which converts a coded input representatrve of characters to a train of output signals which can be used to control the position of an electron beam, in con unction with a television scanning raster deflection of the electron beam to display characters. The analogy of the mechanical motions provided for the ink drop writer to a television type scanning raster may be seen from the fact that the writing paper moves vertically and the ink drop writer carriage moves transversely to the paper. Drops from the ink drop writer are either permitted to reach the paper or are deflected into the waste reservoir in response to the presence or absence of video signals. The circuits required for character generation are essentially the same, except of course allowance is made for the reduced speed of operation of the ink jet printer.

The output of the character signal generator circuit 96 is applied to a video signal generator circuit which converts the signals received to signals suitable for application to the charging tunnel. The data transfer strobe which is the output of the data synchronizer circuit is applied to the video signal generator circuit 102 which converts to a form suitable for application to the charging tunnel 24.

FIG. is a block diagram illustrating the details of the data synchronizer circuit 98. A 100 kHz. oscillator 4 applies its output to a divide by 400 counter circuit 106, and as clock signals to a first flip-flop 108, and a second flip-flop 111. The divide by 400 circuit 106 is reset in the presence of a carriage print position detector signal. The output of the divide by 400 circuit 106, consisting of 250 hertz signals, is applied as one input to a first NAND gate 110, and to a second NAND gate 112. In the presence of the output from the divide by 400 counter 106, with the update strobe signal being absent, then the NAND gate 112 is enabled to apply its output through an inverter 114 to an OR gate 116. The output of the OR gate, which is applied to the I input terminal of a JK flip-flop 111, upon the occurrence of the next clock pulse from the 100 kHz. oscillator, causes the flipflop 111 to be driven to the state with its Q output high whereupon a NOT Data Transfer strobe signal is obtained from its 6 output. Flip-flop 111 is reset upon the occurrence of the following clock pulse by virtue of the fact that its Q output is connected to its K input. With its Q output now being high, this following clock pulse returns the JR flip-flop to its stable state with its 6 output high.

Should an update strobe signal be provided by the divide by eight counter 92 at the time of the occurrence of an output from the divide by 400 counter l-06, then NAND gate 112 is inhibited from operation by virtue of the input received from the inverter circuit 118. However, NAND gate 110 is enabled. Its output is applied through an inverter circuit 120 to the J input terminal of JK flip-flop 108. Upon the occurrence of the next clock input from the 100 kHz. oscillator 104, this flipflop is driven to its set state whereupon the negative going output from the 6 output terminal of the flip-flop 108 is applied, through an inverter 12 2 to the OR gate [116. As in the previous case, the output of the OR gate drives the flip-flop 111 to its set state thus providing the NOT Data Transfer strobe signal. Flip-flop 108 and flip-flop 111 will both be reset upon the occurrence of the following clock pulse in view of their respective connections from the Q output terminals to their K input terminals.

The delay of the data transfer strobe signal which is caused by the introduction of flip-flop 108 into the circuit which drives flip-flop 111 is a one clock interval. The clock interval here is the time between two output pulses of the 100 kHz. oscillator :104, or 10 microseconds. This is sufficient to enable the data buffer register to load up.

The data synchronizer circuit shown in FIG. 5 will function continuously to insure that the data buffer register has been loaded with a character before the data transfer strobe is provided.

There has been described above a novel, useful and simple system for insuring a margin alignment and a freedom from error in printing, in an ink drop writing system.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art and consequently it is intended that the claims be interpreted to cover such modifications and equivalents.

What is claimed is:

1. In an ink drop writing system of a type wherein a source of data provides data signals to a means to convert said data signals to video signals and an ink drop forming mechanism projects ink drops toward a writing medium spaced therefrom means for applying video signals to said ink drops from said means to convert said data signals to video signals to determine the trajectory of said drops, and there is a carriage means for carrying said ink drop forming mechanism reciprocally along a path from a starting position to a finishing position, means for insuring Nertical alignment of characters written by said ink drop writing system at the beginning of a line of characters comprising:

means for detecting when said ink drop forming mechanism reaches its starting position and providing a starting signal indicative thereof,

a buffer register having its input coupled to said data signal source and its output to said means to convert data signals to video signals,

means responsive to said starting signal to enable the flow of data from said source of data to said buffer register,

means for detecting the first of said data signals to flow from said data signal source and providing a heading signal indicative thereof,

means for initiating motion of said carriage means responsive to said heading signal,

a source of update strobe signals,

means for applying update strobe signals from said source to said buffer register to enable it to accept data signals from said data source,

means for generating data transfer signals,

means for applying said data transfer signals to said means to convert data signals to Video signals and to enable transfer of video signals to said means for applying video signals, and

means responsive to the presence of an update strobe signal to delay the application of a data transfer signal until said buffering register has been loaded with data signals.

2. In an ink drop writing system as recited in claim 1 wherein there is included a means for detecting when said ink drop forming mechanism reaches a predetermined position at which its velocity is constant and providing a write signal indicative thereof, and

means for resetting said update strobe signal source responsive thereto,

said system also including means for detecting when said ink drop forming mechanism reaches its finishing position and providing a stop signal indicative thereof, and

means for terminating the flow of data signals from said source of data signals to said buffer register.

3. In an ink drop writing system as recited in claim 1 wherein said means responsive to the presence of an update strobe signal to delay the application of a data transfer signal until said buffer register has been loaded with data signals includes a source of clock pulses,

means for generating a data transfer signal responsive to a clock pulse signal,

a delay means connected to said means for generating a data transfer signal,

first gate means for applying a clock pulse signal from said source to said means for generating a data transfer signal to activate it,

means for inhibiting operation of said first gate means in the presence of an update strobe signal, and

second gate means for applying a clock pulse signal from said source to said delay means, for generating a delayed data transfer signal in the presence of an update strobe signal.

4. In an ink drop writing system of a type wherein a source of data provides data signals to a means to convert said data signals to video signals and an ink drop forming mechanism projects ink drops toward a writing medium spaced therefrom, means for applying video signals to said ink drops from said means to convert said data signals to video signals to determine the trajectory of said drops, and there is a carriage means for carrying said ink drop forming mechanism reciprocally along a path from a starting position to a finishing position, means for insuring vertical alignment of characters Written by said ink drop writing system at the beginning of a line of characters comprising:

a buffer register,

means responsive to said starting signal for enabling the fiow of data signals from said data signal source to said buffer register,

means for initiating motion of said carriage means responsive to said head signal,

a source of update strobe signals,

means for resetting said update strobe signal source responsive to said start signal,

means for enabling said buffer register to receive data responsive to said update strobe signals,

means for detecting when said ink drop forming mechanism reaches a predetermined position at which its velocity is constant and providing a write signal indicative thereof,

means for generating data transfer signals,

means for resetting said means for generating data transfer signals responsive to a write signal,

means for enabling said means to convert data signals to video signals to transfer said video signals to said means for applying signals responsive to data transfer signals,

means to detect when said ink drop forming mechanism reaches its finishing position and providing a stop signal indicative thereof, and

means responsive to said stop signal to terminate said fiow of data signals from said source of data signals to said buffer register.

5. In an ink drop writing system as recited in claim 4 wherein said means responsive to said data transfer signals for enabling said means to convert data signals to video signals to transfer said video signals to said means for applying video signals includes:

means for delaying the application of a data transfer signal to said means to convert data signals to video signals in the presence of an update strobe signal for an interval required to insure that said buffer register has been loaded with data signals.

6. In an ink drop writing system as in claim 5 wherein said means responsive to the presence of an update strobe signal to delay application of a data transfer signal to said means to convert data signals to video signals includes a source of clock pulses, having an interval between pulses at least equal to the time required to load said buffer register,

a first and a second flip-flop circuit each having a first and second input and a clock input, corresponding first and second outputs, and assuring a state with one of its outputs high in response to the one of its two inputs to which an input signal is applied when a clock signal is applied to its clock input,

means for applying clock pulses from said source ,to said first and second flip-flop circuit clock inputs, a first and second NAND gate,

means connecting said first NAND gate output to said first flip-flop first input,

means connecting said second NAND gate output to said second flip-flop first input,

means connecting said first flip-fiop second output to said second flip-flop first input,

means connectingclock pulses from said source to one input to said first and second NAND gates,

an inverter circuit having an input and an output connected to an input to said second NAND gate, and

means for applying an update strobe signal to said inverter circuit input and O S & 1 i d first NAND gate input whereby said second flip-flop produces a data transfer signal upon the occurrence of a first clock pulse and in the absence of an update strobe signal, and produces a data transfer "signal upon the occurrence of a second clock pulse in'th'e presence of an update stro'be signal.

References Cited UNITED STATES PATENTS JOSEPH W. HARTARY, Primary Examiner US. Cl. X.R. 1786.6