CA1099818A - Method and apparatus for setting and varying margins and line spacing on data printers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The specification discloses a method and apparatus for setting and varying margins, line spacing and printing direction of a data printing machine by a machine user before and during printing by use of a keyboard with push-button control which is coupled to a digital controller to input information about the actual and the desired location of a print head relative to a printing surface, in response to which the controller outputs signals which control relative motion of the print head and indexes its relative position, from the actual to the desired direction and location.

Description

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1) Field o-E the Invention This invention relates generally to the control and operation of data printing machines; and, more parti-cularly, to setting and varying the margins and line spacing of printed data and determining the direction of printing.

2) Prior Art The prior art teaches various mechanical means whose adjustment or manipulation before printing begins 7 or during interruption in printing, will institute changes in the margins and spacing between lines of printed data. For example, mechanical limits or stops can control the extre-mities of travel of a print head and can be adjusted to a desired position before printing begins. Similarly, varying the spacing between lines of printed data is usually accom-plished by such means as manual adjustment of a mechanical gearing arrangement or slip clutch which vertically moves a printing surface in relation to a printing head. FOT
example, the printing surface (i.e. paper entrained over a roller) can be moved by freeing the roller -from its normal drive mechanism and freely rolling it a desired distance, thereby moving the paper with the roller.
Once me~hanical margins have been established for a printing machine, it is known that either the left-hand or right-hand margin of a line of printed data can in ef~ect be moved inwardly by the insertion of blank data either at the beginning or ending of the line. The blan~ data can be inserted by the operator of the printing machine beore the affected lin~e starts to print, or can be included in the data introduced into the printing machine. A frequently used method of introducing data into a printing machine is A

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1 the use of punched cards. To move a le-~t-hand margin o~ a line of printed ~ata to the right, the punched card would include blank data representative of the desired amount of movement to the right of the left-hand margin. In either case, operator insertion or data insertion, the insertion of blank data would vary a given margin only for a single line of printed data, and subsequent variation of a margin would require subsequent additional introduction of blank data.
Also, variation of the margins can only be inwardly relative to the particular margin (i.e., to the right o-f a left-hand margin, or to the left of a right-hand margin).
SUMMARY OF THE INVENTION
This invention provides a method and apparatus for setting, and for varying both the margins and the spacing between printed lines of data, both before and during printing by a printing machine, merely by operation of a push-button control. For example, the left-hand margin of a data line can be moved to the left or the right during printing and once set the margin will be maintained, without additional instructions, for all subsequent printed data lines until the margin is changed again by printing machine operator action. An embodiment of this invention can also include control of the direction of printing, i.e., printing a data line either from the left or the right, as a function of mlnimum printing time.
A data printing machine in accordance with the invention has a print head which can be driven laterally across a platen and which, by a corled address, can be uniquely located when positioned at a number of equally spaced, fixed positions along the platen. One of the fixed positions lS used as a reference location by an encoder

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l indicating the relative position of the print head A paper drive is used to vertically position a printing surface in relation to the print head. The data printing machine further includes a memory, an electronic controller and a keyboard coupled together for enabling an operator to control printing, selection of left-hand margin location7 variation to the left or right of the left-hand margin - location, selection of data line spacing and variation of data line spacing. The memory is coupled to the encoder and paper drive and stores the lateral position of the print head, the reference location~ the left-hand margin position, and the line spacing. The electronic controller controls the relative position of the print head and the printing surface and actuates printing. The keyboard provides an interface for transmission of data between the data printing machine and the printing machine opera~or.
Variation of margins and line spacing both before and during printing in accordance with an embodiment of this invention can be used to eliminate a variety o printing problems. ~or example, if a printing machine is being used to complete blank spaces in an otherwise preprinted form, a positional printing error in the preprinted portion of the form, e.g., a misalignment to the bottom and rlght of the printed matter with respect to the physical edges of the form, can be compensated for by an adjustment o-f the margins or line spacing of the printed data. Similarly, variations in the loading of the preprinted form into the printin~
machine can be compensated for by varying margins and line spacing. Also, i the input instructions governing the printing of data contain an error resulting in misposi-tioning of the prin~ted data, the machine operator can make ~ ~ 9 ~ 1 ~

1 adjustments in margins and line spacing ~o compensate for the error without the need for correcting the input instru-ctions. In all the above cases, the corrections are quickly and easily accomplished by the opera~or, and need be done only once if the desired correction is repetitive.
The determination of whether printing forward or printing backward is the quickest way to print a given data line makes use of numerical addresses, re~erenced to a fixed horizontal re~erence location, representing the horizontal (or lateral) position of the ends of the next data line to be printed and the horizontal position of the print head.
The advantages of basing a numerical address for determining horizontal position of the print head upon a fixed location instead of a variable location such as the preceding loca-tion to the left of the print head is that any error is not cumulative. More particularly, i~ each address is indepen-dently related to the address of a fi~ed point instead of successively related to the addresses of previous printing pOSitiOIlS, an error in one address is not cumulativé and does not lead to errors in all subsequent addresses.
BRIEF DESCRIPTION OF lHE DRA~INGS
Fig. 1 is a fragmentary ~rontal perspective view of a printing machine print head, drive, and platen which can be used in accordance with an embodiment of this in-vention;
Fig. 2 is a functional block diagram of a printing machine control system in accordance with an embodiment o-f this invention;~
Fig. 3 is a functional flow diagram of a machine in accordance with an embodiment of this invention when SET-UP (or SETP0RM~ state is initiated;

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1 Fig. 4 is a ~unctional -Elow diagram of a machine in accordance with an embodiment of this invention when the LEFT-HAND MARGIN ~unction is initiated;
Fig. 5 is functional flow diagram o-~ a machine in accordance with an embodiment of this invention when the LINE
PEED function is initiated;
Fig. 6 is a functional flow diagram of a machine in accordance with an embodiment of this invention when the UP function is initiated;
Fig. 7 is a functional flow diagram of a machine in accordance with an embodiment of this invention when the RIGHT function is initiated;
Fig. 8 is a functional flow diagram of a machine in accordance with an embodiment o this invention when the DOWN function is initiated Fig. 9 is a functional flow diagram o a machine in accordance with an embodiment of this invention when the LEFT function is initiated;
Fig. 10 is a functional flow diagmram of a machine in accordance with an embodiment of this invention when the STOP state is initiated;
Fig. 11 is a functional flow diagram of a machine in accordance with an embodiment of this in~ention when the RUN state is initiated; and Fig. 12 is a functional flow diagram of a machine in accordance with an embodiment of this invention when the TOP OF FORM function is initiated.
DETAILED DESCRIPTION OP THP, PREPERRED EMBODIMENT
Referring to Fig. 1, the elements of a p~inting machine operated and controlled in accordance with an embodiment of this in~ention include, or illustration, a , . ~ , . . . .
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1 prin~ head 10 laterally driven along a roller-type platen 12 by a worm-gear or lead screw-type drive 14. Worm-gear drive 14 is rotationally coupled ~as by a drive belt) to an encoder 24, ~hich produces electrical pulses in response to rotation o-f the worm-gear, or lead screw, which also produces lateral movement of printing head 10. Thus, the train o-f pulses from the encoder corresponds directly to print head travel and position. A pin-feed drive element 20 has paper-driving sprockets or pins at both ends o~ platen 12, for vertically driving a roll of paper or other printing surface between print head 10 and platen 12. A digitally encoding keyboard 36 (Fig. 23 is electrically coupled to the printing machine, as discussed hereinafter, to provide an lnput ~rom the operator of the printing machine -for control of the machine. Print head 10 can be of the type, for example, having a single column of solenoid-driven impact needles or stylii for forming dots on a printing surface supported by platen 12. Print head 10 is positioned laterally along platen 12 so that adjacent dot positions can be used to orm coherent groupings of dots representing characters such as numbers and letters. The output of encoder 24 can be monitored to detect pulse interruptions indicating a left or right~hand physical limit has been reached. Alternatively, left-hand and right-hand limit switches may be used at the extreme ends of platen 12 to limit ~the ultimate allowable travel of print head 10 to locations between the two limit switches. ~or example, physical engagement by print head 10 of the limlt switches can actuate the switches. Encoder 24 can be of the type having a disc with light-interrupting means with two pairs o~ associated light-emitting diodes and photo-transistors to produce quadrature-rela~ed signals .

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8~3 l including an electrical pulse for each printed dot location as described for example in ~rench Patent No. 2,294,852, issued July 16, 1976. A similar encoder i.s shown in ~. S.
Patent No. 3,891,077, issued June 4, lg75.
P~eferring to Fig. 2, a functional block diagram of a printing machine control system in accordance with an embodiment of this i.nvention includes the aforementioned encoder 24, which is coupled to control logic and memory, designated by the numeral 32, through the sequential con-nection of a direction-and-displacement logic decoder 26, an up-down counter 28~ and a comparator 30. I'he control logic and memory 32 also has inputs from a keyboard 3~ 9 and a data source 38, through an input-output interface 40. Control logic and memory 32 has outputs coupled to a carriage drive servo, power amplifier, motor 56 for controlling lateral movement of print head lO, to a buffer 46 for ccntrolling flow of data to activate print head needles~ to comparator 30~for supplying a desired lateral location for print head 10~ and to interface 40 for controlling flow of data from data source 38. Buffer 46 is connected to a needle-drive power amplifier 44 through the sequential connection of a needle controller 48 and a character generator read only memory 50. Control logic and memory 32 is connected to a power amplifier and step motor 52 through the sequential connection of a control character decoder 42 and a paper feed controller 54. Direction and displacement. logic decoder 26 is coupled to up-down counter 28 and carri,a,ge drive servo, power amplifier~ motor 56.
Carriage drive servo, power amplifier, motor 56 is ' 1 coupled to receive an input from control lagic and memory 32 and determines the right and left movement of the print head along the platen. The data which is eventually printed on the printing sur-face by print head lO is supplied at data source 38. A typical source can be, for example, a magnetic memory containing information describing a particular paragraph to be printed. Interface 40 is adapted to adJust the level of the voltage signals from data source 3g to the level required by control logic and memory 32'. For example, if control logic and memory 32 uses transistor logic, voltage applied to logic and memory 32 should be in the range of about O to 5 volts. In addition to translating voltage levels, interface 40'can also match'`impedance levels and filter out noise fr'om data source '38. Voltage 'signals transmitted from interface 40 to data source'3g indicate the availabi'lity of interface 40 to recei've data.
Paper feed controller 54 applies' a voltage signal to power amplifier and stepping~ motor 52 causing the' paper to move one incr'ement. In one'embodiment of this -invention, twelve incr'emental step.s are required to move the' paper one line. Paper feed controller 54 includes' logic and' memory circuits for determining the last inst-ructions sent-to amplifier motor 52 and or dete~rmining how many more 'in-crements are required to complet'e one line. Control char-acter decoder 42 decodes characters from data source'38 which'are not to be printed but, instead, are'used to indicate such'actions as -line feea, carriage return, hbri-zontal tab and various othe'r control functions. For example, a single'character representing the spacing of a certain numbe~r of lines is converted into an order for a discret'e numbe'r of line spacings e~'ualling the' desirea vertical 1 distance. Paper feed controller 54 recei~es ~oltage signals indicating ho~ many vertical line spacings a.re desi-red and sends to step motor 52 voltage signals indicating the num~er of incremental steps required to equal the desired nurnber o-f ver~ical line spacings.
Needle controller ~8 operates in a manner analo-gous to paper feed controller 54. A character can have for example, 10 ~ertical segments much the same as each line can have a plurality of horizontal segments. Needle'controller 48 has an output of voltage signals representing the'next character to be printed and the vertical column in whi'ch the character is to star*. Needle'controller 48 has an input from buffer 46 which'initiate-s' printing action whe'n print head lO is in the des'ired lateral positi:on.
The connection from decoder 26 to. carriage se:r~o, power amplifier, motor 5~ sends pulses' indicating~ mo~ement of the print head to a carriage servo controlling the ' carriage motor. ~ypically, the' servo expec'ts: a given pulse repetiti.on rate and controls the' mo~or to ei'ther increase the speed of movement of print he`ad lO'if the' pulse repeti-tion rate recei~ed is too low :or decrease movement o-f print head lQ if the pulse- repetition recei'ved is too high.' The pulse .repet'ition rate'is also used to stop the''dri~ing of print he'ad 10 by carriage se:ryo7 power amplifier, and motor 5~. That .is 7 if a gi.~en' ti:me period of say, far example, 50 milliseconds, passes' witho'ut pulses' indicating n~ovement of print he'ad lO'when movement o print head 10 is expected, such.'as during printing, the carriage'motor shuts. down because it is assumed that print he'ad 10 has reached a 3Q lateral limit of tra~el' or has been lateral:ly ja~mea. It can be appreciated that :the :se~'yo contr~lling the carriage -lQ-.

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1 motor can be set to produce a, variety of different speeds of lateral movement. Further, the carriage motor is typically operated by applying a normal drive voltage to the motor the acceleration or slowing of the motor is the'n determined by the motor characteristics.
In general,~ margin and line spacing settin~ and variation is initiated 'by an operator at ke'ybo'ard 36 and implemented in the printing machine through'control logic and memory 32. That is, the des'ired per~ormance'of the printing machine is controlled through keybo'ard 36. In-formation about the' actual condition or position o-E the print head is neces'sary for control logic 'and memory 32 to develop voltage signals for obtaining des'ired per~ormance of the printing machi'ne (i.e., movement of the'print head~ and is supplied by encoder 24, which'in fact monitors movement of print head 10. Needle'controller ~8 and *he control logic and memory unit 32 coordinate printing act'ion.
Control logic and memory 32 can include,' ~or example, programmable'read only memories ~PROM)', rando~
2Q access memories (RAM), microprocessor chip and input/output devices' which transmit de~eloped voltage'signals ~o and ~rom othe'r components such'as the' print head assembly, the' keyboard, the paper advance, the encoder assembl'y and all switches'. ~n example'of a swi'tch''is a contact wh'ich'is open when the're is paper in the''printer and closed wh'en the~re is no paper. Advantageously, logic and memory 32' also has an operator accessible con-figuration switch'whi'ch'enabl'es' the operato~r to selec't ~ single'or a double line~ feed and set a default ~orm lengt~'for use'when the -form length has no~
3Q been other~i'se defined. That-is, the' swi"tGh'would alter the voltage signal sent to paper fee'd controller 54 ta change .
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l the paper feed. The microprocessor chip used can be, :Eor example, an Intel 8080 microprocessor in combination with an Intel~8224 clock generator and driver. The cloc~ generator driver can be driven by, ~or example, an 18 MHz crystal-controlled oscillator and provides the timing and control signals for the internal operation o~ the In~el gO~0 micro-processor.
The horizontal positi:on o-~ print he'ad 10 at each position along platen 12 is described by a binary number corresponding to a single dot position along platen 12.
Thus~ one dot can be printed at each discrete binary ad-dress. Whenever a printing machine in accordance wi.th an embodiment o~ this invention is energizea for operation, print head 10 is assigned, by control logic and memory 32, a given arbitary address ~umbe'r larger than the' total nu~ber of dot positions along plate:n 12. That is, a portion of the memory of control logic and memory 32 receives' and stores binary bits: repres'entative of a print head lO'address larger ~han the total number of do~ positions along platen 12.
Initially, such'information can be provided by an operator at keyboard 36. Print he`ad 10 i5 then slewe:d slowly to the right,: for example, and one bit, or binary unit~ is added for each dot positi:on traversed ~in accordance with'encoder pulses) until a right side limit is reache'd. As already noted, the'right side :limit can be i.ndicated by an absence of encoder pulses for a per'i.od of time such'as 50 milli- i seconds or limit switches which are actuated by the' physical presence of print head 10 and complete a circuit i:ndicating moyement of print head 10 to the'right must be stopped. The advantage of dete:ct'ing a pause'or a "time out" in the' encoding pulse is that late:ral jamming of print head 10 can ~ ~rRC~ k 1 also be detected at locations other than the lateral limits.
Slewing is caused by a signal output from control logic and memory 32 to carriage power amplifier and carriage motor 56 for actuating motor 56 to moYe print head 10 to the right.
When the limit is reached, a signal is applied ~o control logic and memory 32 which in turn applies a signal to carriage power amplifier and motor 56 causing the carriage and print head to stop moving. The position is stored as the right side limit position. Print head 10 is then slowly slewed to the lef~ and one bit is subtracted for each dot position traversed until a left side limit is reached.
The binary number address of print head 10 when it is located at the left side limit is used as a fixed reference point for all lateral positions of print head 10 along platen 12. The distance between the left and right side limit positions is then computed and thus determines the number of characters which can be printed in the established platen width.
The logical signal processing of the output of encoder 24 by direction and displacement logic decoder 26 is more fully descri'bed in the aforementioned French and United States patents. Briefly, the voltage level of one of the signal outputs of direction and displace-ment logic decoder 26 establishes the sign (,i.e., direction of print head) of the voltage pulses (i.e., incremental distance travelled by the print head) of the other of the signal outputs of decoder 26. Voltage signals sent from counter 28 to comparator 30 represent binary rlumbers indicating the actual location of the print head along the platen. Comparator 30 also receives voltage signals from control logic and memory 32 representing the ~s ~1 .. .. .

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1 binary number address of the location where the' printing head is desired to be located by the operator. Comparator 30 compares the voltage signals representing the actual location of the print head with the voltage signals repre-se~ting the desired location of the print head and generates voltage signals representing the difference'be'tween the two locations. That is, t~e output of comparat~r 30 is a voltage signal represen~ing the position -from which the distance from the actual location to the desired location of the print head is determined in the control logic and memory 32.
Late-ral posi-tion addresses for print he'ad lO are also used in the process o determining whe't'he'r the' next se~quential data line sho'uld be printed for~ard or backward to minlmize'printing time. In so doing, ,the' data to be printed is compiled in ~hole'lines' in buffer 46, allowing ~or dete~rmination of whiche'ver print direction will optimize throughput. The'flow ,of printable'data from data source 38 to buffer 46, which'stores a whole line'of data, for example 2Q 132 characters, is governed by the control logic and memory unit 32. Until buffer 46 is filled or othe'r instrUctiQns are'recei'ved 9 line compilation prevails as the' primary processing activity of the printing machine be'fore actual printing. An example of buf-fer 46 is a random acc'es's memory. The'~print head address at the' particular location ~here the' preceding printed line happens to end ~since each line may well be~gin or end at a place other than the extreme left margin or the extreme ~ight' margin) is comp~red to the address for the' beginning c,haracter o~ the next data line and a,lso to the''address o the ending charact'er of the next data line. The' distance fr'om the print head to the' be'-.
~ - ' ' .' , ' 1 ginning character o~ the data line is computed by ~inding the difference between the'address of the print head and the address of the beginning character of the' data line.
Similarly, the distance from the print head to the' ending character of the data line 'is computed by finding the diference between the address of the print he'ad and the' address :of the last character of the data line. The print head is then moved to the' location of the' closest su-ch character, at the beginning or end of the'.next data line, to print in forward or reverse'sequence depending upon whe'ther the first-or last characte.r is closes't.
A conventional drive motor, such'as a stepper moto.r, driven by an appropriate.power amplifier ~together sho~n as unit) 52:is mech'anica'lly coupled to the'.pin feed 2Q
(which may also be:'a tracer device'or friction: fee'd mechanism~
such~that the motor actuates khe' pin fee~d or other paper-adv~ance component to ver:ti.cally advance'printi.ng paper in relati:on to print head 10.' The' number of steps that:the' step motor drives the' paper-ad-vance'device'afte:r a line of data has bee'n printed dete:rmines the''vertical spacing to t~e next line to be printed. For example, in one `embo'd'imen.t, twel've'steps are used to. obtain a six line-per-inch'density and nine steps are used to obt'ain an eight':line-per-inch' density. In the preferred emobodiment 9 a normal line feed ~one-sixth:of an inch)' i5 comprise~a of t~e:lve paper-advance steps and takes' approximatel'y thirty milliseconds:of execu-tion time. A normal line~ fee'd refers to the''amount of vertical movement o-f the p~in~ing surface for each line of printed data. If double'line'fee'd is enabl:ed, a line feed 3Q. operation causes a twenty-four step' paper-advance'motion i.n approximately fort~-eight' milli:sec'onds.

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1 Following is a table showing the response of a data printing machine in accordance with the foregoing to actuation of different keys on keyboard 36:
~EY SET FORM ST~TE STOP STATE RUN STATE
Top of Any "Top of Form" Machine advan- Machine stops Form entry in the set ces to next at next Top state causes the Top of Form of Form page line count to be res'et to zero. A pair of depressions defines the form length~
The form length'de-' finition is the number of lines' of paper advance resulting from the use of the LINE FEED
ke~ betwe~en the two most recent TOP OP
FOR,M entries. A
zero coun~ is not vali,d.
Vertical Uses page'line' Go to next Stop at next Tab count as VERTICAL Vertical Tab Vertical Tab TAB location. If position. position.
a tab exists at that line, it is cleared. A depres-sion of the' Verti-cal Tab Key directl~
after a Top of Form entry cause$ all verti-cal tab locations to be cleared.
Line Ad~ance paper in Go to next Stop at next Feed Line'Feed line. line'~ed.
units until key is re-leased. A normal line fee'd (l/6,inch) is comprised of 12 paper ad~ance'steps and takes approxi-matel~ 30' ms. to execute~. If a -double line fee'd is enabled',,a line feed operation causes' a ~4 step paper ad~ance in approximatel'y 48 msec. Paper ad-vance begins with slow m~v'emen*s : , , 1 in sing].e unit increments and gradually accele-rates to slew speed.
Motion stops when the key is released.
LEFT Move head le-ft Go to left Moyc Left-Hand until key is side of Margin le-ft one released or platen dot position limit en-countered RIGHT Move head right' Go to right Mo~e Le:Et-lland until key is side of Mar~in right one released or platen dot position limit en-countered UP Subtract one' NONE Subtract one step from next step -from next Line Feed oper- Line Feed oper-ation atian DOWN ~dd one step NONE Add one step to to next Line next Line Feed feed operation operation LEFT Save head Go to soft NON~
MARGIN location as Let-Hand Left-Hand Marg~n Margin Posi- positi-on tion SET FORM Move head to ~ove head to NONE
left side ~ load positi:Qn permit set-up and go to SET
FORM state RUN Initiate print-- Initiate NQNE
ing and go ta printing and RUN state' go to RUN state' STOP Stop any he'ad Stop any he'ad Suspend printing, motion and go and paper ad- Stop motion and to S~OP state: vance motion go to STOP state In the above table,' three' operational state~s of the printing machine are listed along the horizontal axis and examples of keYs on the keyboard are listed alon.g the vertical axis. The three machine states 9 set form, stop and run, are mutually exclusive,' and each state. defines the printer condition as a res'ult of operator keybo'ard entries and det'ermines the''ef-.~ec:t of, or a printe:~ response-to, .

1 succeeding keyboard entries. Accordingly, a key can be used to initiate dif-ferent, al~hough rela~ed, prin~er responses dependent upon the printer state, effectively expanding the number of key entries available to the operator.
In general, the set ~orm state permits the operator to input horizontal and vertical positional information, by operating the appropriate keys in the keyboard. Such information is used to control horizontal mo~ement o~ the print head and vertical movemen~ of the printing surEace.
For example, in a particular printing operation this in-for-mation may include a let-hand margin location, top of form location, form length specification and vertical tab loca-tions. To Eacilitate'a set-up procedure in whi'ch hori-zontal or vertica] locatlons can be'efficiently es'tabl'ished, the capability is provided to cause print head or paper-advance motion in incremelital step's -for rel'atively slow motion, or in a continuous mo~ement -for relatively ~ast motion. The operator can choose the spee'd of movement of print he'ad 10 by eithe'r a momentary depres'sion or a con-tinuous depression of a key, such as LEF~, causing print head movement~ The accel'eration of the print head is determined by the print he'ad motor characteristics. How-e~er, the final slewing spee'd of print he'ad lO'may be chosen to be equal to the'printing speed of print head 10 as controlled by carriage ser~o, amplifieT, motor 56. That is, the' voltage applied to motor 56 by actuakion o-E key'board 36 ~e.g., by actuation of ~he LL~T or RIGHT ke~ can be' o-f the same magnitude as the'voltage applied to motor 56 during normal printing, which'is determined by se~ting of the servo controlling motor 56 in relation to the' pulse repetition rate recei'~ed~ fr'om dec'oder 26. Print head motion 1 or paper movement in the set form state continues as long as the respective key is depressed (or until a limit is encountered), and is pre-ferably characterized by a con-tinuing motion rate acceleration from slow, small discrete increments to faster slew speeds.
When set-up is complete, the operator may advance the printer state to stop or run by depressing a stop key or a run key. As a result o either action, the' positional information inputed in the' set -form state is fixed and can only be changed, except for fine adjustments in the run state, by returning to the set form state. Por example, to change a left-hand margin position, four sequential operator actions are necessary:
a) Fnter the set orm state by depression o-f the "Set Form" key.
b) Move the''print head to a particu]ar position on the paper corresponding to the'desired margin setting by using the' appropriate key (LEFT and RIGHT keys).
c) ~ndicate 'set'ting of the' new des'ired margin position by depression oE the' left-hand margin ~Left Margin? key.
d) Enter (or regist-er? the Left Margin ent~y by initiating either the Stop or Run state, by depression of the' "Stop" or "Run" key.
This se~uence is advantageous because'a new 'left-hand margin is not effective until steps a, b, c and d have been com-plet'ed. The pre~iously set or assumed left-hand margin is not lost until the new left-hand margin is set, or, in other words, there is no time wh'en a left-hand margin is not available~'to t~e printing~machine. ~dvantageo'usly, a left-- , " ': .

1 hand margin is assumed by the printer if the operator makes no left-hand margin entry. That is, a left-hand margin can be included in control logic and memory 32 and can be used at all times a different left-hand margln is not entered at keyboard 36 by the operator.
Inward of the left and right physlcal extremes of prlnt head movement "so-ft limits" are established to stop physical mo~ement of the print head past these- "soft limit"
positions. As noted above, upon the first:dep:ression of the set form key, the print head is mo~ed to the' left until the left side llmlt is encountered. An offset:of approximately a three-character distance is added to the left .limit dot position and the res'ult is -stored as the location of the left edge`of the printer (termed a "soft l'imit" postion).
More specifically, the locati.on of the print head expres'sed as a binary number address is stored when the''print .head is positioned at the left side limit. To this bin~ry number address is added a binary number representing the horizontal distance required to contain approximately three characters. The'resulting binary number address represents the.soft limit position. Any later action wh:ich. causes print head tra~el to the'left edge'will result in termina-tion of motian left at:the' soft limit position. Similarly, a soft limit .is es'~ablished for the right-edge'o thc printer by subt:racting approximateIy a t~ree.-character distance'from the' physical right side limit dot positi.on on the first encounter with'that limit. A recurring excursion of the print he~ad ta: the' physical limits may indicate either dri~t due to digital errors or a complete loss o~ control as a result of a hardware'malfunct'ion or other such''majo-r probl'em.
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1 In the STOP state, the printer is considered to be "off line". No changes to set-up conditions are permitted regardless of any key depressions as long as the printer is in the stop state. The operator has the assurance that despite print head or paper-advance motion initiated by a specific key entry, no parameters established in the set form state or -fine adjusted in the run state will be altered or lost. Opera~or keyboard entries, in general, cause motion horizontally or vertically to set location wi'th a single key depression. Printer functions in the stop state are intended to facilitate loading of paper without loss or change of set-up data.
The run state is the "on line" condition of the printer. In this machine'state, two types of functions can be commanded from the keyboard: 1) fine'adju~s~ment of horizontal and vertical print position, and 2~ conditional or immediate stop of printer activi~y. Fine adjustment, consi-sting of only ~ery limited increments such'as Cfor example? one dot position left or right' or one~'paper adYance step up or down for each key depression, allows minor changes' to horizontal and vertical positioning es'tablished in the'~set form state. In particular, the left--hand margin can be moved to the let or to the' right and the new loca-tion of the left-ha`nd margin retained for all future data lines. Fine adjustments o one dot or one paper-advance step ~per key depression) are not applied to the line being printed at the' time the adjustments are entered and posi-tional changes are realized on the' next printed line.
Figs. 3-12 sho'w the' logical flow diagr'am for activating a button on keyboard 36 labeled as the' first box in the'logical flow. ''rhe'machi'ne states which are con-~3 ~

1 sidered in the flow diagram are indicated by zero ~) for power initiated, one (1) for set, two (2) for stop and three (3) for run. In the logical flow diagram the Y indicates a yes answer and N indicates a no answer. The logical flow concludes in an idle condition which means the machine is ready to accept another instruction, i.e. the actuation of another button on keyboard 36. When the power is turned on, an arbitrary value is assi-gned to the current head position, and the margins, vertical spacing and length'of the form to be printed are assigned arbitrary or de-fault values which are used unless othe'rwise changed.
As shown in Fig. 3, a logical proces's upon activa-tion of the set-up (or so~etimes referred to as set-form~
state includes first questioning whethe'r the machine state is in state zero, and if not 9 in state three, and if not, in state'one. The left margin and vertical control parameters ~hich are entered during this logical flow are not fixed until the printer is adYanced to either a stop or run state.
The partîcular left-hand margin established in this logical flow is a "soft" left-hand margin a ~hree`character distance in~ard ~or to the right) of the physical left limit position.
Referring to Fig. 4, initiating the left margin function causes interrogation of the' machine stat~ and action upon the' left-hand margin depending upon the state of the ma-chine. Referring to Fig. 5,~ when the line feed function is initiated the printer state 'is interrogated and, for e~a~ple, if it is in the set condition the' paper is advanced until the line fee'd key is released. Although typically each unit of line feed is the equivalent o-E single spacing, if de-3Q sired, each unit of line feed can be' the equivalent of double sp~cing which would occur where indicated by an 1 asterisk (*). ~urther, paper motion indicated at block (A) continues until the key is released, even if the out of paper switch is set. Referring to Fig. 6~ the logical -flow of the up function is shown. In accordance with one embodi-ment of this invention, a normal line feed (at the point indicated by an ast-erisk [*]) is comprised of 12 paper-advance steps and the initiation of the up-key is limited to 12 sequential key depressions. An actuation of the up function subtracts one st-ep from the next line feed, after which eed the number of steps returns to the initial value.
In Fig. ~, when the right, function is initia~ed and the machine'is in the run state the'added dot position (oc-curring at block [A])' to the left-hand margin is realized on the next printed line. ~hen the machi'ne is in the set state ' (occurring at block :[B]) the right head movement continues until the key is released. When the machine is in the stop state the print head is moved to the right side'limit. Fig.
S shows the`'logical flow of the' down function and, as in Fig. 6, a normal line feed (occurring at asterisk [*]) is comprised of 12 paper-advance'steps. Again, as the logical flow diagram shows,,the particular action taken depends on the machine state.' In a set or run state'actuation of the down function adds one step to the next line~ feed, a-f*er which eed the number of steps ret'urns to the initi-al value.
Fig. 9 shows a logical flow upon actuation of the left Eunction which'is analogous to the right, function logical flow shown in Fig. 7. Figs. lO and 11 show the'logical flow for the'initiation of stop and run machi'ne states respec-tively. The logical, flow diagram for the top oE form function is shown in Fig. 12 and is advantageously used in conjunct'ion with a printing surf~ace which is sep'arated into ~9~

1 sequentially coupled repetitiVe :Eorms. Basically, in the set state information is entered about the form length in lines, in the run state a stop is caused a-fter the next top of form operation, and in the stop state the paper is advanced to the top of form positi:on.
Various modifications and variations will no doubt occur to those ski.lled in the art to which this invention pertains. For example, the particular rate of incremental response :of margin change or line spacing change can be varied from that disclose-d herein. Similarly, the par-ticular se-quence of steps for establishing ei'the'r a margin or a spacing between lines.may be. varied -from that :disclosed herei'n. These and all othe'r variations which:basically rely on the te~achlngs through'which thi's disclosure'has advanced the art are properly consi:dered within t.he.scope of this invention.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

A control system for a data printer of the general type having at least one print head and means for holding printable stock in position relative to such print head for printing thereby, and also having drive means including a bi-directional and incrementally controllable drive apparatus for effectively moving the print head and stock relative one another such that the print head may print horizontally aligned characters, said control system comprising:
at least one manually actuable control key device and means coupled thereto for producing electrical signals in response to selected control key actuation, said signals being applied to condition at least one of a margin-setting means or line-advancing means; said margin-setting means operatively coupled to said control key-responsive signal-producing means and coupled to said drive means, said margin-setting means including means conditionable by said electrical signals and operative to index the relative movement of print head and printer stock by selectively enabling said drive apparatus in a manner limiting printing to a defined horizontal area ending on at least one side at a selected one of said particular positions in said horizontal alignment; said line-advancing means operatively associated with means for moving said print head and stock transversely relative to each such horizontal line of characters thereby spacing the latter from the next ensuing printed character line, said control key device operative to produce other signals which when applied to said line-advancing means acting to condition the latter so as to cause same to set the amount of spacing between certain successive printed character lines in relation to actuation of said control key.

The control system for a data printer according to claim 1 wherein said means coupled to said control key device produces different particular ones of said electrical signals upon repeated selective control key actuation, certain of said different signals representative of different particular positions in such horizontal alignment, and said margin-setting means including means conditionable by different particular ones of said electrical signals produced upon repeat selective control key actuation to re-index allowable relative movement of said print head and print stock by differently enabling said drive apparatus so as to change at least one of the margins for ensuing printing.

The control system for a data printer according to claim 2 wherein said margin-setting means conditioned by said electrical signals is condition-retaining for subsequent printing and is condition-alterable by subsequent different particular electrical signals representative of a different position, such that a margin may be changed by subsequent control key actuation to a different position than that previously set by control key actuation.

The control system for a data printer according to claim 3 wherein said manually actuable control key device includes a control key and means coupled thereto for initiating said effective relative print head and print stock movement upon actuation of such control key and for stopping such movement upon deactuation of such control key, and wherein said means for producing electrical signals representative of a particular position is operative to produce signals representative of a given particular position when said print head has been moved relative to said stock into alignment with such given particular position.

The control system for a data printer according to claim 4 wherein said means for producing electrical signals is operative to produce signals representative of any of a plurality of different given particular positions when said print head has been moved into alignment with a selected one such given position.

The control system for a data printer according to claim 5 wherein said means for producing electrical signals is so operative upon actuation of said control key device with said print head in said position of alignment.

The control system for a data printer according to claim 1 wherein said line-advancing means is responsive to particular electrical signals produced by control key actuation by varying the actuation of a drive motor powering a line-advancement mechanism, thereby varying the amount of line advancement and the spacing between certain character lines as a function of particular control key actuation.

The control system for a data printer according to claim 7 wherein said line-advancing means is responsive to repeated electrical signals produced by repeated control key actuation by varying the spacing between certain character lines in incremental amounts related in number to the number of repeated control key actuations.

The control system for a data printer according to claim 1, including a print head drive means coupled to said print head for laterally positioning said print head at any of a plurality of mutually-spaced known positions along a print head lateral travel path, and a print media drive means for incrementally advancing a printing media with respect to said printing head in a manner whereby successive lines of data printed on said printing media along said print head lateral travel path have a plurality of distance increments between adjacent lines of data, and including a positioning means comprising:
a position-monitoring means operatively coupled to at least one of said print head and said print head drive means, for determining the lateral position of said print head along said path relative to a known reference location therealong, memory means operatively coupled to said position-monitoring means and said media drive means for storing indicia representative of said lateral position. of said print head along said travel path, representative of said known reference location relative to said travel path, representative of a given left-hand margin position com-prising one of said known positions along said lateral travel path, and indicia representative of certain of said plurality of distance increments of print media advancement;
control means coupled to said memory means, to said position-monitoring means, to said print media drive means, and to said print head and said print head drive means for controlling the position of said print head relative to said printing media and said travel path, and actuating said print head to print along said path; and a keyboard coupled to said control means for providing an interface for transmission of control signals from an operator to said control means, said control means selectively responding to certain of said control signals to set said left-hand margin position by inputting address information to said memory means which comprises indicia representative of a particular position along said lateral travel path and responsive to certain other of said control signals to set the vertical spacing between printed lines by inputting indicia to said memory means representative of certain of said plurality of distance increments of print media advancement.

A control system for a data printer according to claim 9 wherein:
said keyboard includes an actuating means for actuating a change in the number of said distance increments between certain successive lines of printed data to change the vertical spacing between said certain successive printed lines;
said memory means is operative to store indicia representative of the changed number of distance increments representing said changed vertical spacing; and said control means includes a print media positioning means for controlling said media drive means to position said printing media so that said certain successive lines of data printed on said media have said changed vertical spacing between lines.

A control system for a data printer according to claim 10 wherein said position-monitoring means includes an encoder coupled to said print head drive means for producing an electrical output signal in response to lateral movement of said print head along said travel path;
and including:
logic means coupled to said encoder for generating a print head binary number address defining each location of said print head relative to said known reference location as the head moves along its said travel path past said known position;
a left-hand margin set key coupled to said memory means for causing storage, upon actuation, of the particular print head binary number address for the head position at the time of actuation as a left-hand margin position;
a left-direction head drive control means coupled to said print head drive means and to said memory means for moving said print head to the left of said left-hand margin position, in order to reset such margin leftward; and a right-direction head drive control means coupled to said print head drive means and to said memory means for moving said print head to the right of said left-hand margin position, in order to reset such margin rightward.

A control system for a data printer according to claim 11 wherein said keyboard includes:
an up-line position means for decreasing by steps of at least one the number of said distance increments between a successively printed pair of lines of data, and a down-line position means for increasing by steps of at least one the number of said distance increments between a successively printed pair of lines of data.

A control system for a data printer according to claim 12 wherein said keyboard includes:
a set-up state control means for enabling said left-direction head drive control means to move said print head to the left as long as said left-direction means are enabled, and for enabling said right-direction head drive control means to move said print head to the right as long as said right-direction means are enabled; and a run state control means for enabling said left-direction head drive control means to move said left-hand margin to the left a predetermined number of said mutually-spaced positions for each operation of said left-direction control means, and for enabling said right-direction head drive control means to move said left-hand margin to the right a predetermined number of said mutually-spaced positions for each operation of said right-direction control means.

A control system for a data printer according to claim 13 wherein said left-direction control means includes a left acceleration means for applying a signal to said print head drive means as long as said left-direction control means remains actuated, said signals causing accelerating movement of said print head to the left, and wherein said right-direction control means includes a right acceleration means for applying a signal to said print head drive means as long as said right-direction control means remains actuated thus causing accelerating movement of said print head to the right.

A control system for a data printer according to claim 11 wherein said logic means includes:
incrementing means operatively coupled to said encoder for adding a binary unit to the binary number address of said mutually-spaced positions along said path in response to said print head traversing each of said spaced positions while moving in a first direction;
and decrementing means operatively coupled to said encoder for subtracting a binary unit from said binary number addresses in response to said print head traversing each of said fixed positions while moving in a second direction, opposite from said first direction.

A method of controlling a data printer of the type having a print head which is moved laterally by a drive means along a horizontal print path and past a plurality of mutually-spaced print positions disposed along said print path, and periodically moving the printing media transversely with respect to said print path such that successive lines of data printed on said printing media have predetermined vertical spacing between lines of data, said method including the steps of:
laterally moving said print head to a desired initial margin position along its said travel path;
actuating a control element while said print head is located at said margin position and thereby producing a coded signal which identifies said initial margin position;
storing said coded signal in a digital memory device using a digital electrical control means to selectively energize the print head drive means in a manner effecting precise control over the positioning of the print head thereby, and using said stored coded signal with said control means to return the print head to said initial margin position thereby controlling subsequent positioning of data printed by said print head so that rows of data printed thereby have an end indexed at said desired margin position.

The method in accordance with claim 16, including the further step of changing the margin from that initially set by changing the stored coded signal which identifies the initial desired margin position, said stored coded signal being changed by use of digital signal inputs which are functions of control key actuation and which are not dependent on the instantaneous position of the print head.

The method in accordance with claim 17, wherein said stored coded signal is changed by applying pulses to digital circuit elements, each control key actuation being correlated to a particular number of such pulses producing a particular amount of margin change.

The method in accordance with claim 17, wherein said margin is shifted in one direction by changing the stored coded signal through a first type of digital number shift, and the same margin is shifted in the opposite direction by changing the stored coded signal through a second type of digital number shift.

The method in accordance with claim 16, including the steps of moving the print head laterally to first one and then the other of both left and right desired margin positions, actuating a control element while the print head is located at each such margin position to thereby input two different coded signals each identifying one of such margin positions, storing said coded signals separately in a digital storage means, and subsequently using said stored coded signals in said digital control means to limit print head travel to said two margin positions by selective energization of the print head drive means.

A method of printing data as recited in claim 16 wherein said step of periodically moving the printing media to provide for vertical line spacing includes:
vertically advancing said printing media with respect to said print head by a plurality of incremental movements between successive single-spaced printed lines having a standard spacing, a standard line spacing between successive lines comprising at least three such vertical increments;
selecting a desired non-standard line spacing by adjusting the particular number of said vertical movement increments which are to be included in a subse-quent line advance;
producing and digitally storing coded signals indicative of the number of increments setting said.
desired non-standard line spacing;
using said stored signals to subsequently advance said printing-media so that a pair of successive lines of data are subsequently printed at the desired non-standard line spacing.

A method of printing data as recited in claim 21 further comprising:
selectively increasing or decreasing the number of said vertical increments between certain successive printed lines of data by actuation of a manually-controllable key which inputs signals affecting a change in the digitally-stored coded signals.