GB1592602A

GB1592602A - Data printers

Info

Publication number: GB1592602A
Application number: GB8368/77A
Authority: GB
Original assignee: Sycor Inc
Current assignee: Sycor Inc
Priority date: 1977-02-09
Filing date: 1977-08-28
Publication date: 1981-07-08
Also published as: SE7702053L; IT1075626B; JPS5398735A; NL7800946A; FR2380144A1; DE2710525A1; DE2710525C2; JPS574951B2; CA1099818A; FR2380144B1

Description

(54) DATA PRINTERS (71) We, SYCOR, INC., a Corporation of the State' of Delaware, United States of America, of 100 Phoenix Avenue, Ann Arbor, Michigan, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to data printers and, more particularly, to setting and varying the margins and line spacing of printed data.

There have been proposals for various mechanical means whose adjustment or manipulation before printing begins, 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 extremities 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 accomplished 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. For example, where the printing surface is paper entrained over a roller, the printing surface 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 mechanical 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 effect be moved inwardly by the insertion of blank data either at the beginning or ending of the line. The blank data can be inserted by the operator of the printing machine before the affected line 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 the use of punched cards. To move a left-hand margin of a line of printed data 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 of a left-hand margin, or to the left of a right-hand margin).

According to the present invention, a data printer has at least one print head, means for holding printable stock in position relative to such print head for printing thereby, means for effectively moving the print head and stock relative one another for printing characters in a horizontal alignment, and a control system comprising: manually actuable control key means and means coupled thereto for producing electrical print head position signals whose codes are determined directly by control key actuation, said signals being selectively applied to condition a digital memory which operatively controls at least one or the other of a margin-sefting means or line-advancing means, said margin-setting means being operatively coupled to said control key means and coupled to said means for relatively moving said print head and stock to limit printing to a defined horizontal area ending on at least one side at a selected position in said horizontal alignment whose code is stored in said memory, in response to said signals; the line-advancing means being operatively associated with the means for relatively moving the print head and stock to cause advancement of the stock transversely relative to each such horizontal line of characters thereby spacing the latter from the next ensuing printed character line, said signals when applied to condition said line-advancing means acting to digitally control a part of the latter in dependence upon selected actuation of said control key means so as to set the amount of spacing which will subsequently occur between certain successive printed character lines.

Thus, the invention provides 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 manual control key means such as push-buttons. 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. Preferably means are provided for controlling the direction of printing i.e., printing a data line either from the left or the right, as a function of minimum printing time.

Variation of margins and line spacing both before and during printing can be used to eliminate a variety of printing problems. For 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 right of the printed matter with respect to the physical edges of the form, can be compensated for by an adjustment of the margins or line spacing of the printed data. Similarly, variations in the loading of the preprinted form into the printing machine can be compensated for by varying margins and line spacing.Also, if the input instructions governing the printing of data contain an error resulting in mispositioning of the printed data, the machine operator can make adjustments in margins and line spacing to compensate for the error without the need for correcting the input instructions. In all the above cases, the corrections are quickly and easily accomplished by the operator, and need be done only once if the desired correction is repetitive.

The invention may be carried into practice in various ways but one data printer embodying the invention and its method of operation will now be described by way of example with reference to the accompanying drawings, in which: Figure I is a fragmentary front perspective view of the print head, drive, and platen of the printer; Figure 2 is a functional block diagram of the control system of the printer; Figure 3 is a functional flow diagram of the printer when SETUP (or SETFORM) state is initiated; Figure 4 is a functional flow diagram of the printer when the LEFT-HAND MARGIN function is initiated; Figure 5 is a functional flow diagram of the printer when the LINE FEED function is initiated; Figure 6 is a functional flow diagram of the printer when the UP function is initiated; Figure 7 is a functional flow diagram of the printer when the RIGHT function is initiated;; Figure 8 is a functional flow diagram of the printer when the DOWN function is initiated; Figure 9 is a functional flow diagram of the printer when the LEFT function is initiated; Figure 10 is a functional flow diagram of the printer when the STOP state is initiated; Figure 11 is a functional flow diagram of the printer when the RUN state is initiated; and Figure 12 is a functional flow diagram of the printer when the TOP OF FORM function is initiated.

Referring to Figure 1, the elements of a data printing machine include, for illustration, a print head 10 laterally driven along a roller-type platen 12 by a worm-gear or lead screw-type drive 14. The worm-gear drive 14 is rotationally coupled (as by a drive belt) to an encoder 24, which produces electrical pulses in response to rotation of the worm-gear, or lead screw, which also produces lateral movement of printing head 10. Thus, the train of 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 of the platen 12, for vertically driving a printing surface such as paper from a roll between the print head 10 and the platen 12.A digitally encoding keyboard 36 (Figure 2) is electrically coupled to the printing machine, as discussed hereinafter, to provide an input from the operator of the printing machine for control of the machine. The 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 the platen 12. The print head 10 is positioned laterally along the platen 12 so that adjacent dot positions can be used to form coherent groupings of dots representing characters such as numbers and letters. The output of the 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 the platen 12 to limit the ultimate allowable travel of the print head 10 to locations between the two limit switches. For example, physical engagement by the print head 10 of the limit switches can actuate the switches. The encoder 24 can be of the type having a disc with light-interrupting means with two pairs of associated light-emitting diodes and photo-transistors to produce quadrature-related signals including an electrical pulse for each printed dot location, as described for example in our copending Patent application No.

8369/77, (Serial No. 1592603) filed concurrently herewith.

Referring to Figure 2, a functional block diagram of a printing machine control system includes the aforementioned encoder 24, which is coupled to control logic and memory, designated by the numeral 32, through the sequential connection of a direction-anddisplacement logic decoder 26, an up-down counter 28, and a comparator 30. The control logic and memory 32 also has inputs from the keyboard 36, and from 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 the print head 10, to a buffer 46 for controlling 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 carriage drive servo, power amplifier, motor 56.

Carriage drive servo, power amplifier, motor 56 is coupled to receive an input from control logic 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 surface by print head 10 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 38 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 0 to 5 volts. In addition to translating voltage levels, interface 40 can also match impedance levels and filter out noise from data source 38.Voltage signals transmitted from interface 40 to data source 38 indicate the availability of interface 40 to receive data.

Paper feed controller 54 applies a voltage signal to power amplifier and stepping motor 52 causing the paper to move one increment. In one embodiment of this invention, twelve incremental steps are required to move the paper one line. Paper feed controller 54 includes logic and memory circuits for determining the last instructions sent to amplifier motor 52 and for determining how many more increments are required to complete one line. Control character decoder 42 decodes characters from data source 38 which are not to be printed but, instead, are used to indicate such actions as line feed, carriage return, horizontal tab and various other control functions. For example, a single character representing the spacing of a certain number of lines is converted into an order for a discrete number of line spacings equalling the desired vertical distance.Paper feed controller 54 receives voltage signals indicating how many vertical line spacings are desired and sends to step motor 52 voltage signals indicating the number of incremental steps required to equal the desired number of vertical line spacings.

Needle controller 48 operates in a manner analogous to paper feed controller 54. A character can have for example, 10 vertical 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 which the character is to start. Needle controller 48 has an input from buffer 46 which initiates printing action when print head 10 is in the desired lateral position.

The connection from decoder 26 to carriage servo, power amplifier, motor 56 sends pulses indicating movement of the print head to a carriage servo controlling the carriage motor. Typically, the servo expects a given pulse repetition rate and controls the motor to either increase the speed of movement of print head 10 if the pulse repetition rate received is too low or decrease movement of print head 10 if the pulse repetition received is too high.

The pulse repetition rate is also used to stop the driving of print head 10 by carriage servo, power amplifier, and motor 56. That is, if a given time period of say, for example, 50 milliseconds, passes without pulses indicating movement of print head 10 when movement of print head 10 is expected, such as during printing, the carriage motor shuts down because it is assumed that print head 10 has reached a lateral limit of travel or has been laterally jammed. It can be appreciated that the servo controlling the carriage 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 then determined by the motor characteristics.

In general, margin and line spacing setting and variation is initiated by an operator at keyboard 36 and implemented in the printing machine through control logic and memory 32. That is, the desired performance of the printing machine is controlled through keyboard 36. Information about the actual condition or position of the print head is necessary for control logic and memory 32 to develop voltage signals for obtaining desired performance of the printing machine (i.e., movement of the print head) and is supplied by encoder 24, which in fact monitors movement of print head 10. Needle controller 48 and the control logic and memory unit 32 coordinate printing action.

Control logic and memory 32 can include, for example, programmable read only memories (PROM), random access memories (RAM), microprocessor chip and input output devices which transmit developed voltage signals to and from other components such as the print head assembly, the keyboard, the paper advance, the encoder assembly and all switches. An example of a switch is a contact which is open when there is paper in the printer and closed when there is no paper. Advantageously, logic and memory 32 also has an operator accessible configuration switch which enables the operator to select a single or a double line feed and set a default form length for use when the form length has not been otherwise defined. That is, the switch would alter the voltage signal sent to paper feed controller 54 to change the paper feed.The microprocessor chip used can be, for example, an Intel 8080 microprocessor in combination with an Intel 8224 clock generator and driver.

The clock generator driver can be driven by, for example, an 18 MHz crystal-controlled oscillator and provides the timing and control signals for the internal operation of the Intel 8080 microprocessor.

The horizontal position of print head 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 address. When the printing machine being described is energised for operation, print head 10 is assigned, by control logic and memory 32, a given arbitary address number larger than the total number of dot positions along platen 12. That is, a portion of the memory of control logic and memory 32 receives and stores binary bits representative of a print head 10 address larger than the total number of dot positions along platen 12. Initially, such information can be provided by an operator at keyboard 36.Print head 10 is then slewed slowly to the right, for example, and one bit, or binary unit, is added for each dot position traversed (in accordance with encoder pulses) until a right side limit is reached. As already noted, the right side limit can be indicated by an absence of encoder pulses for a period of time such as 50 milliseconds or limit switches which are actuated by the physical presence of print head 10 and complete a circuit indicating movement of print head 10 to the right must be stopped. The advantage of detecting a pause or a "time out" in the encoding pulse is that lateral jamming of print head 10 can 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 move print head 10 to the right.When the limit is reached, a signal is applied to 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 left 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 described in the aforementioned copending application filed on even date herewith. Briefly, the voltage level of one of the signal outputs of direction and displacement logic decoder 26 establishes the sign (i.e. direction of print head) of the voltage pulses (i.e., incremental distance traveled 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 numbers 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 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 representing the desired location of the print head and generates voltage signals representing the difference between the two locations. That is, the output of comparator 30 is a voltage signal representing 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.

Lateral position addresses for print head 10 are also used in the process of determining whether the next sequential data line should be printed forward or backward to minimize printing time. In so doing, the data to be printed is compiled in whole lines in buffer 46, allowing for determination of whichever 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 132 characters, is governed by the control logic and memory unit 32. Until buffer 46 is filled or other instructions are received, line compilation prevails as the primary processing activity of the printing machine before actual printing. An example of buffer 46 is a random access memory.The print head address at the particular location where the preceding printed line happens to end (since each line may well begin or end at a place other than the extreme left margin or the extreme right margin) is compared to the address for the beginning character of the next data line and also to the address of the ending character of the next data line. The distance from the print head to the beginning character of the data line is computed by finding 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 difference between the address of the print head and the address of the last character of the data line.

The print head is then moved to the location of the closest such character, at the beginning or end of the next data line, to print in forward or reverse sequence depending upon whether the first or last character is closest.

A conventional drive motor, such as a stepper motor, driven by an appropriate power amplifier (together shown as unit 52) is mechanically coupled to the pin feed 20 (which may alternatively be a tractor device or friction feed mechanism) such that the motor actuates the pin feed or other paper-advance component to vertically advance printing paper in relation to print head 10. The number of steps that the step motor drives the paper-advance device after a line of data has been printed determines the vertical spacing to the next line to be printed. For example, in one embodiment, twelve steps are used to obtain a six line-per-inch density and nine steps are used to obtain an eight line-per-inch density. In the preferred embodiment, a normal line feed (one-sixth of an inch) is comprised of twelve paper-advance steps and takes approximately thirty milliseconds of execution time.A normal line feed refers to the amount of vertical movement of the printing surface for each line of printed data. If double line feed is enabled, a line feed operation causes a twenty-four step paper-advance motion in approximately forty-eight milliseconds.

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: Key Set Form State 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 reset to zero. A pair of depressions defines the form length.

The form length definition is the number of lines of paper advance resulting from the use of the LINE FEED key between the two most recent TOP OF FORM entries. A zero count is not valid.

Vertical Uses page line Go to next Stope 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 directly after a Top of Form entry causes all verti cal tab locations to be cleared.

Line Advance paper in Go to next Stop at next Feed Line Feed line. line feed.

units until key is re leased. A normal line feed (1/6 inch) is comprised of 12 paper advance steps and takes approxi mately 30 ms. to execute. If a double line feed is enabled, a line feed operation causes a 24 step paper advance in approximately 48 msec. Paper ad vance begins with slow movements in single unit increments and gradually accele rates to slew speed.

Motion stops when the key is released.

LEFT Move head left Go to left Move Left-Hand until key is side of Margin left one released or platen dot position limit en countered RIGHT Move head right Go to right Move Left-Hand until key is side of Margin 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 ation DOWN Add one step NONE Add one step to to next Line next Line Feed feed operation operation LEFT Save head Go to soft NONE MARGIN location as Left-hand Left-Hand Margin Margin Posi- position tion SET Move head to Move head to NONE FORM left side & load position permit set-up and go to SET FORM state RUN Initiate print- Initiate NONE ing and go to printing and RUN state go to RUN state STOP Stop any head Stop any head Suspend printing, motion and go and paper ad- Stop motion and to STOP state vance motion go to STOP state In the above table, three operational states of the printing machine are listed along the horizontal axis and examples of keys on the keyboard are listed along the vertical axis. The three machine states, set form, stop and run, are mutually exclusive, and each state defines the printer condition as a result of operator keyboard entries and determines the effect of, or a printer response to, succeeding keyboard entries. - Accordingly, a key can be used to initiate different, although related, printer responses dependent upon the printer state, effectively expanding the number of key entries available to the operator.

In general, the set form 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 movement of the print head and vertical movement of the printing surface. For example, in a particular printing operation this information may include a left-hand margin location, top of form location, form length specification and vertical tab locations. To facilitate a set-up procedure in which horizontal or vertical locations can be efficiently established, the capability is provided to cause print head or paper-advance motion in incremental steps for relatively slow motion, or in a continuous movement for relatively fast motion.The operator can choose the speed of movement of print head 10 by either a momentary depression or a continuous depression of a key, such as LEFT, causing print head movement. The acceleration of the print head is determined by the print head motor characteristics. However, the final slewing speed of print head 10 may be chosen to be equal to the printing speed of print head 10 as controlled by carriage servo, amplifier, motor 56. That is, the voltage applied to motor 56 by actuation of keyboard 36 (e.g., by actuation of the LEFT or RIGHT key) can be of the same magnitude as the voltage applied to motor 56 during normal printing, which is determined by setting of the servo controlling motor 56 in relation to the pulse repetition rate received from decoder 26.Print head motion 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 preferably characterized by a continuing 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 of 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. For example, to change a left-hand margin position, four sequential operator actions are necessary: (a) Enter the set torm state by depression of the "Set Form" key.

(b) Move the print head to a particular position on the paper corresponding to the desired margin setting by using the appropriate key (LEFT and RIGHT keys).

(c) Indicate setting of the new desired margin position by depression of the left-hand margin (Left Margin) key.

(d) Enter (or register) the Left Margin entry by initiating either the Stop or Run state, by depression of the "Stop" or "Run" key.

This sequence is advantageous because a new left-hand margin is not effective until steps a, b, c and d have been completed. The previously 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 when a left-hand margin is not available to the printing machine. Advantageously, a left-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 margin is not entered at keyboard 36 by the operator.

Inward of the left and right physical extremes of print head movement "soft limits" are.

established to stop physical movement of the print head past these "soft limit" positions. As noted above, upon the first depression of the set form key, the print head is moved to the left until the left side limit is encountered. An offset of approximately a three-character distance is added to the left limit dot position and the result is stored as the location of the left edge of the printer (termed a "soft limit" position). More specifically, the location of the print head expressed as a binary number address is stored when the print head is positioned at the left side limit. To this binary 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 which causes print head travel to the left edge will result in termination of motion left at the soft limit position. Similarly, a soft limit is established for the right edge of the printer by subtracting approximately a three-character distance from the physical right side limit dot position on the first encounter with that limit. A recurring excursion of the print head to the physical limits may indicate either drift due to digital errors or a complete loss of control as a result of a hardware malfunction or other such major problem.

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. Operator keyboard entries, in general, cause motion horizontally or vertically to set location with 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 adjustment of horizontal and vertical print position, and 2) conditional or immediate stop of printer activity. Fine adjustment, consisting of only very limited increments such as (for example) one dot position left or right or one paper advance step up or down for each key depression, allows minor changes to horizontal and vertical positioning established in the set form state. In particular, the left-hand margin can be moved to the left or to the right and the new location of the left-hand margin retained for all future data lines.Fine adjustments of 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 positional changes are realized on the next printed line.

Figures 3-12 show the logical flow diagram for activating a button on keyboard 36 labeled - as the first box in the logical flow. The machine states which are considered 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 assigned to the current head position, and the margins, vertical spacing and length of the form to be printed are assigned arbitrary or default values which are used unless otherwise changed.

As shown in Figure 3, a logical process upon activation of the set-up (or sometimes referred to as set-form) state includes first questioning whether the machine state -is in state zero, and if not, in state three, and if not, in state one. The left margin and vertical control parameters which are entered during this logical flow are not fixed until the printer is advanced to either a stop or run state. The particular left-hand margin established in this logical flow is a "soft" left-hand margin a three character distance inward (or to the right) of the physical left limit position. Referring to Figure 4, initiating the left margin function causes interrogation of the machine state and action upon the left-hand margin depending upon the state of the machine.Referring to Figure 5, when the line feed function is initiated the printer state is interrogated and, for example, if it is in the set condition the paper is advanced until the line feed key is released. Although typically each unit of line feed is the equivalent of single spacing, if desired, each unit of line feed can be the equivalent of double spacing which would occur where indicated by an asterisk (*). Further, paper motion indicated at block (A) continues until the key is released, even if the out of paper switch is set. Referring to Figure 6, the logical flow of the up function is shown. In accordance with one embodiment of this invention, a normal line feed (at the point indicated by an asterisk [*]) 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 step from the next line feed, after which feed the number of steps returns to the initial value. In Figure 7, when the right function is initiated and the machine is in the run state the added dot position (occurring at block [A]) to the left-hand margin is realized on the next printed line. When the machine 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. Figure 8 shows the logical flow of the down function and, as in Figure 6, a normal line feed (occuring 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, after which feed the number of steps returns to the initial value.

Figure 9 shows a logical flow upon actuation of the left function which is analogous to the right function logical flow shown in Figure 7. Figures 10 and 11 show the logical flow for the initiation of stop and run machine states respectively. The logical flow diagram for the top of form function is shown in Figure 12 and is advantageously used in conjunction with a printing surface which is separated into sequentially coupled repetitive forms. Basically, in the set state information is entered about the form length in lines, in the run state a stop is caused after the next top of form operation, and in the stop state the paper is advanced to the top of form position.

Various modifications and variations will no doubt occur to those skilled 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 disclosed herein. Similarly, the particular sequence of steps for establishing either a margin or a spacing between lines may be varied from that disclosed herein.

WHAT WE CLAIM IS: 1. A data printer having at least one print head, means for holding printable stock in position relative to such print head for printing thereby, means for effectively moving the print head and stock relative one another for printing characters in a horizontal alignment, and a control system comprising: manually actuable control key means and means coupled thereto for producing electrical print head position signals whose codes are determined directly by control key actuation, said signals being selectively applied to condition a digital memory which operatively controls at least one or the other of a margin-setting means or - line-advancing means, said margin-setting means being operatively coupled to said control key means and coupled to said means for relatively moving said print head and stock to limit printing to a defined horizontal area ending on at least one side at a selected position in said horizontal alignment whose code is stored in said memory, in response to said signals; the line-advancing means being operatively associated with the means for relatively moving the print head and stock to cause advancement of the stock transversely relative to each such horizontal line of characters thereby spacing the latter from the next ensuing printed character line, said signals when applied to condition said line-advancing means acting to digitally control a part of the latter in dependence upon selected actuation of said control key means so as to set the amount of spacing which will subsequently occur between certain successive printed character lines.

2. A data printer as claimed in Claim 1 in which the said means coupled to said control key means produces different particular ones of said electrical signals upon selective control key means actuation, certain of said different signals being 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 selective control key means actuation to index relative movement of said print head and print stock by limiting ensuing printing to a defined horizontal area ending on two lateral sides at different particular positions in said horizontal alignment thereof.

3. A data printer as claimed in Claim 2 in which 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 said indexing of relative movement may be changed by subsequent control key means actuation to a different position than that previously set by control key means actuation.

4. A data printer as claimed in Claim 1 or Claim 2 or Claim 3 in which the manually actuable control key means 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.

5. A data printer as claimed in Claim 4 in which 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.

6. A data printer as claimed in Claim 5 in which said means for producing electrical signals is so operative upon actuation of said control key means with said print head in said position of alignment.

7. A data printer as claimed in any of the preceding Claims in which the line-advancing means is responsive to particular electrical signals produced by control key means actuation by varying the spacing between certain character lines in incremental amounts as a function of particular control key means actuation.

8. A data printer as claimed in Claim 7 in which the line-advancing means is responsive to repeated electrical signals produced by repeated control key means actuation by varying the spacing between certain character lines in incremental amounts related in number to the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of form function is shown in Figure 12 and is advantageously used in conjunction with a printing surface which is separated into sequentially coupled repetitive forms. Basically, in the set state information is entered about the form length in lines, in the run state a stop is caused after the next top of form operation, and in the stop state the paper is advanced to the top of form position. Various modifications and variations will no doubt occur to those skilled 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 disclosed herein. Similarly, the particular sequence of steps for establishing either a margin or a spacing between lines may be varied from that disclosed herein. WHAT WE CLAIM IS:

1. A data printer having at least one print head, means for holding printable stock in position relative to such print head for printing thereby, means for effectively moving the print head and stock relative one another for printing characters in a horizontal alignment, and a control system comprising: manually actuable control key means and means coupled thereto for producing electrical print head position signals whose codes are determined directly by control key actuation, said signals being selectively applied to condition a digital memory which operatively controls at least one or the other of a margin-setting means or - line-advancing means, said margin-setting means being operatively coupled to said control key means and coupled to said means for relatively moving said print head and stock to limit printing to a defined horizontal area ending on at least one side at a selected position in said horizontal alignment whose code is stored in said memory, in response to said signals; the line-advancing means being operatively associated with the means for relatively moving the print head and stock to cause advancement of the stock transversely relative to each such horizontal line of characters thereby spacing the latter from the next ensuing printed character line, said signals when applied to condition said line-advancing means acting to digitally control a part of the latter in dependence upon selected actuation of said control key means so as to set the amount of spacing which will subsequently occur between certain successive printed character lines.

number of repeated control key means actuations.

9. A data printer as claimed in any of the preceding Claims which includes a print head drive means coupled to the print head for laterally positioning the print head at any of a plurality of mutually-spaced known positions along a print head lateral travel path, and a print medium drive means for incrementally advancing a print medium with respect to the printing head in a manner whereby successive lines of data printed on the print medium 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 the print head and the print head drive means, for determining the lateral position of the print head along said path relative to a known reference location therealong; memory means operatively coupled to said position monitoring means and said medium drive means for storing indicia representative of said lateral position of said print head, representative of said known reference location, representative of a given left-hand margin position and indicia representative of certain of said plurality of distance increments of print medium advancement; control means coupled to said memory means, to said position-monitoring means, to said print medium drive means, and to the print head and the print head drive means for controlling the position of the print head relative to the print medium and said travel path, and actuating the print head to print along said path; and a keyboard which consitutes said manually actuable control key means and is 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 said control signals to set said left-hand margin position and the vertical spacing between printed lines.

10. A data printer as claimed in Claim 9 in which: an actuating means is included within the keyboard 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; a storage means is included within said memory means for storing indicia representative of the changed number of distance increments representing said changed vertical spacing; and a print medium positioning means is included within said control means for controlling said medium drive means to position said print medium so that said certain successive lines of data printed on said medium have said changed vertical spacing between lines.

11. A data printer as claimed in Claim 9 or Claim 10 in which the position-monitoring means includes: an encoder coupled to the print head drive means for producing an electrical output signal in response to lateral movement of the print head along said travel path; and logic means coupled to said encoder for generating a print head binary number address defining each location of the print head relative to said known reference location as the head moves along its said travel path past said known position.

12. A data printer as claimed in Claim 11 in which the logic means includes: incrementing means 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 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.

13. A data printer as claimed in any of Claims 11 or 12 in which the keyboard includes: 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.

14. A data printer as claimed in Claim 13 in which the 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.

15. A data printer as claimed in Claim 13 or Claim 14 in which said left-direction control means includes a left acceleration mans for applying a signal to the print head drive means as long as said left-direction control means remains actuated, said signal 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.

16. A data printer as claimed in any of Claims 9 to 15 in which the 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.

17. A data printer arranged to operate substantially as described herein with reference to the accompanying drawings.