High Speed Dot Matrix Printer

Abstract

An elongated paper document is advanced preferably at a constant rate although incremental advancement may be employed if desired. A plurality of reciprocating solenoid assemblies are mounted in stationary fashion in a closely spaced arrangement and are each provided with reciprocating print wires for impacting an inked ribbon against a paper document. The free ends of the print wires which impact the inked ribbon are slidably mounted within suitable bearings provided within an elongated movable plate with the bearings arranged to align the free ends of the print wires along an imaginary straight line. Means are provided for moving the movable plate substantially in a horizontal direction transverse to the movement of the paper document so as to selectively print a row of dots. The movable member may be guided along a slight incline to compensate for constant paper movement during a printing operation. After completion of the first row, the movable member is reset to the start position which together with the advancement of the paper document places the printer in readiness for selective printing of the next row of dots. Seven rows of dots with a five column width each define alphanumeric characters. Alternatively, the printer may be employed for curve or graph plotting. High speed operation is obtained through the movement of print wires having extremely low mass as compared with conventional printers.

Description

The present invention relates to printers and more particularly to high speed printers of the dot matrix type which are adapted to provide extremely high speed printing while providing extremely low mass for the moving parts to provide printing speeds not heretofore possible through conventional designs.

BACKGROUND OF THE INVENTION

Dot matrix printers are well known in the art and are typically comprised of a matrix of print wires (conventionally arranged in an ordered matrix of seven rows and five columns having 35 print wires in all) in which the print wires are selectively packed against an inked ribbon which, in turn, is driven against the paper document to form any desired characters. The print wires are then physically shifted or moved, in unison, in a direction transverse to the movement of the paper document so as to move the print wires to the next print position. Upon completion of a single line of characters or symbols, the print wire bundle making up the five by seven matrix is rapidly shifted back to the starting position, the document is advanced and the next line of characters is printed in a similar fashion.

In order to reduce the amount of mass required to be moved at high speed during the printing operation, an improved version of the aforementioned technique has been developed and is set forth in detail in copending applications Ser. No. 35,405, filed May 7, 1970 now U.S. Pat. No. 3,703,949, issued Nov. 28, 1972 and Ser. No. 179,457, filed Sept. 10, 1971, assigned to the assignee of the present invention, wherein the five by seven matrix of print wires is replaced by a set of substantially vertically aligned print wires which are advanced in stepwise fashion five times per character to form substantially the same five by seven dot matrix as that described hereinabove. The print wires are incrementally advanced one additional step to provide the appropriate spacing between adjacent characters. The print wire assembly is advanced in this manner to complete a line of characters after which the print wire assembly is rapidly stepped in the reverse direction to return to the start position; the paper document is advanced and the next line of characters is printed in a similar fashion. This arrangement, however, requires the acceleration, movement and deceleration of the print wires at a very high repetitive rate and over a substantial distance (usually 8-12 inches) thereby severely limiting the printing speed and increasing down-time due to the wearing of the moving components. Also, the distance traveled by the print head for one line of characters is double the width of the line of print.

Still another technique which has been developed to further enhance the printing speed of the dot matrix printers is described in U.S. Appliction Ser. No. 204,024, filed Dec. 2, 1971 abandoned in favor of U.S. application Ser. No. 345,000, filed Mar. 26, 1973 and assigned to the assignee of the present application. In an effort to further reduce the amount of movement experienced by the print wire assembly, the print wires and their actuating solenoids are mounted upon a movable mounting assembly with the free ends of the reciprocating print wires being arranged substantially along an imaginary straight line. In one preferred embodiment, wherein it is desired to provide 80 characters per line, and in accordance with a five by seven matrix, the print wires selectively print a first row of dots with each print wire printing the first row of ten characters per line. Thus, the movable assembly is reduced to experiencing a movement which is effectively 1/8 the distance of the entire length of a line of characters. In the case where the paper document is continuously advanced, the mounting assembly moves along a slight incline so as to compensate for constant paper movement while at the same time providing a horizontal dot row. Thus, the mounting assembly undergoes movement which is effectively one-tenth of a line of characters in the print position and one-tenth in the return position providing mechanical movement which is equal to one-fifth of the length of a line of characters whereas in the printers described hereinabove in U.S. Pat. No. 3,703,949 and U.S. application Ser. No. 179,457 the print wire assemblies undergo movement which is double the length of a line of characters. It can thus be seen that the print wire assembly of application Ser. No. 345,000 reduces the amount of physical movement of the parts by one-tenth that experienced in the printers of U.S. Pat. No. 3,703,949 and application Ser. No. 179,457.

Whereas all of the above techniques have led to significant increases in printing speeds and reduction in the amount of moving parts, it is still nevertheless desirable to provide printers capable of even higher operating speed while at the same time significantly reducing the mass of the moving parts thereby requiring techniques which constitute a significant departure in design and operating concepts.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is characterized by providing a high speed impact printer of the dot matrix type in which the print wires undergo significantly reduced linear movement transverse to their longitudinal axes relative to present day techniques and in which the need for physically moving the actuating solenoids is completely eliminated so as to achieve print speeds not heretofore possible.

The present invention is comprised of a printing machine frame having mounted thereon in stationary fashion a plurality of print wire actuating solenoids. In one preferred embodiment, wherein it is desired to print 132 characters per line, 132 print wire actuating solenoids are mounted in a stationary fashion upon the printer machine frame.

The printer machine frame is further provided with means for mounting a document advancing apparatus which may either be a rotatable platen or a tractor advancing assembly for advancing the paper document in either continuous or incremental fashion. The solenoids are mounted in front of the platen assembly and are each provided with a slender print wire mechanically coupled to a solenoid armature for actuation thereof. The free ends of the print wires are all positioned in close proximity to the surface of the paper document to be impacted. An inked ribbon spanning the space between a take-up and feed reel is positioned to span the paper document and to be impacted by the print wires to effect the printing of dot rows.

An elongated movable deflection plate is positioned adjacent the free ends of the print wires and is provided with a plurality of openings preferably aligned along an imaginary straight line. Suitable bearings are provided within each of the openings and they are each adapted to receive the free end of an associated print wire to maintain the free ends thereof in alignment along the aforesaid imaginary straight line while enabling the print wires to experience reciprocating movement. In the case where the paper document is advanced in a continuous manner, the deflection plate is preferably guided along a slight incline to compensate for paper movement and thereby assure printing of a dot row along an imaginary straight and preferably horizontal line. This arrangement may be eliminated in instances where the paper document is advanced in incremental fashion.

Printing is performed by moving the deflection member to the start position which is typically the left-hand end of the paper document. The deflection plate is moved at a substantially constant rate while the print actuating solenoids are activated to cause the free ends of the print wires to impact the inked ribbon against the paper document. In a preferred embodiment, the deflection plate deflects the print wire over a distance equal to five adjacent dots (i.e. one character) which is a distance of the order of one-twelfth of an inch. Since only the forward ends of the print wires undergo deflection, the amount of mass which is moved during the printing of any row is reduced to an absolute minimum.

The printer electronics is comprised of input means for receiving data in either serial or parallel fashion and feeding the data in parallel fashion into a multistage shift register capable of storing a multiplicity of binary words each representing a particular character or symbol.

Once the register, which is capable of storing coded representations of a full line of characters, is fully loaded, or is loaded to the desired amount (i.e., to respectively print a full line or less than a full line) the contents of each stage of the register (containing the binary bits representing a character or symbol) are applied to conversion means for each character which may, for example, be a character generator adapted to provide output signals in binary form at selected ones of its plurality of output terminals which represent the first dot row of the line of characters to be printed. These signals are, in turn, employed to selectively trigger the operation of the print wire actuating solenoids to cause "dots" at spaced intervals along the first dot row to be printed. The deflection member then moves a very small distance (of the order of 1/60 of an inch) to the right to cause selective printing of the next dot position within the first dot row. A counter is employed for "remembering" the position of the deflection plate at any given instant. The state of the counter controls that dot position of the first dot row which is outputted to the associated solenoid for controling the solenoid to print the proper dot at each position within the row.

The stepping operation continues, in the preferred embodiment, over a distance equal to five adjacent dot positions until all the dots along the first dot row have been printed. The deflection assembly is then returned to the start position and movement of the paper document at that time automatically maintains the appropriate dot spacing between the first and second dot rows. The second and remaining dot rows of the five by seven matrices are formed in a similar fashion.

Upon completion of the seventh dot row, the document feed device is caused to operate to separate the completed line of characters from the next line of characters to be printed. During this stepping operation, the binary code groups of the next line of characters are shifed into the register and as soon as the register is loaded (either completely or to the extent desired) the operation is continued for the next line of characters in a similar fashion.

Perfect registration of the dot patterns in each dot row are assured through the use of a registration means which enables actuation of each solenoid only at the precise position of printing and which further serves as the means for advancing the counter which "remembers" the position of the deflection means at any given instant.

The same technique as has been described hereinabove may be employed for curve or graph plotting with only slight modifications being required in the printer electronics, as will be more fully described.

OBJECTS OF THE INVENTION

It is therefore one object of the present invention to provide a novel high speed impact printer of the dot matrix type in which printing of characters is undertaken in a partially serial and partially parallel fashion for each line of characters and in a serial by line fashion to form characters and/or symbols and to plot curves.

Another object of the present invention is to provide a novel high speed impact printer in which the mass of the moving parts is significantly reduced and further in which the amount of physical movement undergone by the impacting members is remarkably reduced as compared with present day techniques.

Still another object of the present invention is to provide a novel high speed impact printer of the dot matrix type incorporating a print wire assembly in which the print wire actuating solenoids are mounted in stationary fashion and in which the print wires are all simultaneously deflected toward each print position.

BRIEF DESCRIPTION OF THE FIGURES

The above as well as other objects of the present invention will become apparent when reading the accompanying description and drawings in which:

FIG. 1 is a perspective view showing a dot matrix impact printer designed in accordance with the principles of the present invention.

FIG. 1a is a perspective view showing a portion of the printer of FIG. 1 in greater detail.

FIG. 1b is an end view showing the registration means employed in the embodiment of FIGS. 1 and 1a.

FIG. 2 is a drawing useful in explaining solenoid carriage and paper movement.

FIG. 3 is a block diagram showing the electronics employed in the printer of FIG. 1.

FIG. 4 shows the manner in which characters are generated by the printer of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The printer of the present invention is an impact printer which, when printing characters utilizes a five by seven dot matrix to produce each character when in the printing mode or, alternatively, utilizing any of a plurality of the print wires when operating in the curve plotting mode. The unit, in one preferred embodiment, prints an array of from 80 to 132 characters per line. The printer, in one embodiment, is capable of printing eighty characters per line with paper widths varying between eight and nine inches. The device utilizes an elongated paper document moved by a platen and generates of the order of six lines of characters to the inch in the vertical direction, with ten characters per inch in the horizontal direction. The printer requires no special paper and can produce an original plus seven copies with the seventh copy being quite legible.

PRINTING METHOD

The printing of characters is accomplished by moving the paper document (in the preferred embodiment) in a substantially constant speed upon the platen by mechanical movement. The top row of dots (i.e. the first dot row) of all characters are formed in the following manner:

The printer in the embodiment capable of printing eighty characters per line, is provided with eighty solenoids mounted in tightly spaced fashion. In the case where each line comprises eighty characters, the solenoid print wires are mounted within the movable deflection member and are spaced at approximately one-tenth inch intervals. With each character comprised of five dot positions (i.e. five dot columns per character) the solenoids are actuated the maximum of six times per dot row and the movable deflection member is stepped a distance of the order of one-tenth inch at a substantially constant rate to complete each dot row of a line of characters. The mounting assembly is then returned to the start (i.e., left-hand-most) position in readiness to print the next dot row of the line of characters. Seven rows of dots are printed to form a line of (up to 132) characters, each character being defined by an associated five by seven matrix pattern, the sixth dot position providing the spacing between adjacent characters.

Each individual solenoid forms a single character in a fashion which is most analogous to the manner in which an electron beam scans the face of a cathode ray tube (i.e., in the line-by-line fashion employed, for example, in television receivers).

Accurate spacing of the dots in each row, and hence the time of printing, is initiated by the strobe pulse derived from an optical pick-up head which cooperates with a stationary slotted Mylar strip having a slot provided for each dot position along the horizontal row of dots. A slit spacing of one dot size between characters is provided.

The printing of characters is accomplished by the print wires which are solenoid driven to move the print wires against the inked ribbon to produce dots on the original copy. The actuation of the solenoids occurs only during the generation of the strobe pulse derived from the optical pick-up head. This pulse has the duration of the order of 450 microseconds with a relaxed time (return time) of 550 microseconds. The characters are printed such that one dot row of each of the characters in a line of characters is printed in a row by row fashion. Seven rows of dots are printed, thereby forming a five by seven dot matrix for each character printed within a line of characters. Spacing between horizontal rows of dots is of the order of 0.015 inches and between character lines is of the order of the spacing between five horizontal rows of dots.

COORDINATION BETWEEN PAPER MOVEMENT AND SOLENOID MOVEMENT

The movement of the paper document, in one preferred embodiment, is constant regardless of the fact that single line feeds or multiple line feeds are desired. Single motor means is employed as a source for all of the motive power necessary in the printer such as, for example, for moving the platen or paper drive and for moving the movable deflection member. Appropriate gearing or other mechanical mechanisms are provided for coupling the output of the motor to each of the movable means. Obviously, the inked ribbon may be driven by the same motor source through appropriate gearing. The deflection means is horizontally aligned and moves along a path which is aligned at a slight incline relative to the horizontal direction to synchronize relative vertical movement of the print wires with vertical movement of the paper to assure printing of a horizontally aligned straight row of dots. During the return stroke, the relative downward movement of the solenoid mounting assembly cooperates with the continuous upward movement of the paper to provide accurate spacing between horizontal rows of dots.

DOT REGISTRATION

Character registration control is provided by a character registration control circuit whose mechanical features will be more fully described hereinbelow and which is adapted to generate an optical signal developed by the movement of an optical pick-up head and cooperating light source relative to an intervening encoded Mylar strip when the printer is printing a row of dots. The optical signal is converted into an electrical pulse to initiate the timing for the printing of each line as well as serving as the means for advancing the row counter which "remembers" the dot position within each dot row which is being printed. The completion of each row is also remembered by a second counter means so as to provide means for "remembering" the particular dot row being printed at any time.

FIGS. 1 and 1a are perspective views shown in somewhat exploded fashion to facilitate an understanding of the invention in which the printer 10 is comprised of an elongated mounting bracket 11 secured upon the machine frame F for mounting the solenoids 12 thereto in a stationary fashion. In one preferred embodiment, the forward ends of each of the solenoids are provided with threaded portions 12a which threadedly engage the tapped apertures 11a provided in mounting plate 11. Each of the solenoids is further provided with a slender print wire 13 extending outwardly from the forward end of each solenoid and mechanically coupled to the solenoid armatures (not shown for purposes of simplicity) which cooperate with the solenoid field coils (also not shown for purposes of simplicity) to provide for reciprocating movement of the print wires. Copending applications Ser. No. 152,598 and Ser. No. 37,815 show typical solenoid assemblies which may be employed to great advantage in the present invention. A detailed description of the solenoid assemblies will be omitted herein for purposes of simplicity, it being understood that the above-mentioned copending applications are incorporated herein by reference thereto. For purposes of understanding the present invention it is sufficient to understand that the armatures and print wires are normally biased to maintain the print wires a small but spaced distance from the inked ribbon. Energization of the solenoid field coils cause the armatures and hence the print wires to be moved in the direction shown by arrow 14 so as to impact the ribbon 15 against the paper document 16. Deenergization of the solenoid field coil causes the armatures and hence the print wires to come under the influence of spring members (not shown for purposes of simplicity) to return the armatures and print wires back to the undeflected or non-print position.

The paper document 16 which is preferably an elongated member of indeterminate length is entrained about a platen 17 mounted to rotate about a shaft 18 which is coupled to a single drive motor M employed to serve as the motive source for all physical movement within the printer.

The inked ribbon 15 is reeled between a supply and a take-up reel 19 and 20, respectively, which reels are selectively mechanically coupled to the single motor means M for moving the ribbon 15 in the direction shown by arrow 21. Rollers 22a-22d are spring loaded and act to maintain the inked ribbon extending between supply and take-up reels 19 and 20 under tension. Energization of the solenoid field coils cause the associated print wires to be impacted against the inked ribbon 15 which, in turn, is driven against the paper document 16 to cause the dots to be formed. Total linear movement of the print wires in the direction of arrow 14 is of the order of 0.015 inches. Under normal operation, the free end of each print wire is approximately 0.006 inches from the ribbon and paper. This close spacing may be utilized due to the fact that a great deal of the force is absorbed by the ribbon and the paper upon impact.

The print wires extend through a first stationary mounted plate 23 provided with a plurality of jewel bearings 24 positioned within apertures provided within plate 23 so as to provide a bearing for each of the print wires extending therethrough which has an extremely low coefficient of sliding friction. The jewel bearings 24 mounted within plate 23 act as a fulcrum to control the bending or deflection of the print wires 13 in a manner to be more fully described.

Printer 10 is further comprised of a movable deflection plate 25 having a plurality of openings provided therein for receiving jewel bearings 26. The free ends of the print wires 13 each extend through an associated one of the jewel bearings 26 which provide an extremely low coefficient of sliding friction between the jewel bearings and the print wires.

As shown best in FIG. 1a, deflection plate 25 has a pair of elongated V-shaped grooves 25a and 25b provided on opposite sides thereof and near the lower edge thereof. A pair of rails 27 and 28 are arranged in spaced parallel fashion and are slightly inclined at a desired angle relative to the longitudinal axis 17a of platen 17. However, bearings 26 are aligned horizontally so as to form a slight angle with the inclined rails 27 and 28. Deflection plate 25 is positioned to slide between rails 27 and 28. The rails 27 and 28 are each provided with V-shaped elongated grooves 27a and 28a, respectively. A plurality of cylindrical bearings 29 are provided within the grooves 27a and 25b in rail 27 and plate 25. Similar bearings 20 are provided to rollingly engage groove 28a in rail 28 and groove 25a in deflection plate 25.

A shaft 31, arranged to rotate in a direction shown by arrow 32, is coupled to the single drive motor of the printer by suitable mechanical means not shown for purposes of simplicity so as to drive shaft 31 in the direction shown by arrow 32. A cam member 33 is fixedly secured to shaft 31 so as to rotate therewith. Cylindrical member 33 is provided with a shuttle cam flange 33a fixedly secured thereto and adapted to have its peripheral portion slidingly engage a pair of spaced downwardly extending projections 25c and 25d provided along the underside of deflection plate 25 for the purpose of reciprocating the deflection plate in the forward (print) direction shown by arrow 34 and subsequently in the reverse or return direction shown by arrow 35 with the forward and return operations occurring during one revolution of shuttle cam 33.

Dot registration is obtained by means of a slotted Mylar strip 40 fixedly secured to the machine frame by any suitable means. An assembly 41 secured to the underside of deflection plate 25 is provided with two downwardly extending portions 42 and 43 which serve to mount a light sensitive pick up device 44 and a light source 45 as shown best in FIG. 1b. The registration strip 40 is provided with a plurality of narrow slits 40a arranged at spaced intervals, with the spacing therebetween being exactly the same as the spacing between adjacent dots printed within any dot row. The preferable form of the registration strip is one in which the entire registration strip is opaque with the narrow slits 40a being transparent so as to permit the passage of light therethrough from light source 45, which light is picked up by the light sensitive device 44 to generate an output pulse which serves to permit energization of the solenoids only when their associated print wires are in registration with one of the slits and further serves to develop a pulse to advance the "remembering" counter which serves to " remember" the dot position being printed.

As was mentioned hereinabove, rails 27 and 28 are arranged at a very slight incline relative to the horizontal direction to assure the printing of a dot row in which all of the dots are aligned along an imaginary straight line which preferably is parallel to the horizontal direction. For example, considering FIG. 2, numeral 60 represents the dot printed at time t.sub.0. Immediately thereafter, the free ends of the solenoid print wires are deflected to move to a positon to print dot 61. During this time dot 60 has moved upwardly to location 60' due to the fact that the paper is being continuously advanced at a constant rate of speed in the direction shown by arrow A. Due to the incline of rails 27 and 28, the free ends of the print wires move along dotted line 64 to print dot 62. During this time the paper document moves upward (arrow A) moving the first dot from location 60' to 60" and moving the second dot from position 61 to position 61'. By diagonal movement of the free ends of the print wires, all three dots are caused to lie along a straight line (dotted line 63). It should be noted that the spacing between the dots in FIG. 2 has been exaggerated to facilitate an understanding of the operation, typical spacing between dots being of the order of 0.018 inches. It should also be further noted that the angle of inclination as represented by dotted line 64 has been exaggerated to further faciliatate an understanding of the cooperation of movement of the deflection plate and continuous paper movement to achieve printing of a dot row along an imaginary straight line which preferably is parallel to the horizontal direction.

The speed of movement of platen 17 and hence paper document 16 is further chosen so that during the time it takes the movable deflection plate 25 to move from its right-hand most position to its left-hand most position (during a return operation) the paper document 16 has moved a distance equal to half the spacing between adjacent rows of dots forming a character. This is aided by the fact that whereas movable deflection plate 25 moves upward and to the right during printing, it moves downward and to the left during carriage return. In one embodiment, the paper moves a distance equal to the radius of the dot during printing so that during a carriage return, the movement of both the paper and the carriage through one radius each amounts to combine movement of one diameter of a dot.

Whereas the preferred embodiment of FIG. 1 shows the use of a shuttle cam for providing the desired printing and return movement of the print wire deflection plate 25, it should be understood that any other suitable means may be employed such as the cam device 97 shown in FIG. 1b of copending application Ser. No. 204,024 or alternatively a timing belt device may be employed, depending upon the needs of the user.

Stationary plate 23 containing jewel bearings 24 act as a fulcrum for each of the print wires 13 to control the bending which each print wire undergoes as the deflection plate 25 moves the free ends of the print wires in unison during a line printing operation.

FIG. 4 shows the dot patterns for some typical characters capable of being printed by the device of the present invention, with the dot spacing of FIG. 4 being exaggerated to simplify their understanding. The solid circles indicate dots to be printed. In each case, the order of printing is dot row 1, dot positions 1, 2, 3, 4, 5 (for each print wire) until dot row 1 is completed; dot row 2, dot positions 1, 2, 3, 4, 5, until dot row 2 is completed; and so forth until seven dot rows have been completed thereby completing one line of characters. Appropriate selection of dots in each 5.times.7 matrix (which contains 35 different dot positions) permits the printing of any desired characters as typified by the characters shown in FIG. 4.

FIG. 3 shows a block diagram of one preferred electronic scheme 70 for operating the printer mechanism of FIG. 1. The apparatus 70 of FIG. 3 is comprised of a data entry means 71 which, for example, may be an external source such a computer adapted to output data in the form of input information to the printer. Data may be in the form of a six-bit binary code capable of representing up to 64 different characters, numerals or other symbols. The output lines of the date entry block are shown as being coupled to the input of a two-phase clock 74 and a counter 75 as well as the input of register 76.

The zero backfill circuit 72 provides a capability of "backfilling" of register with "blank" characters in the case where a line of print is to contain less than the total number of characters which the printer is capable of printing per line.

Print cycle circuit 73 comprises a settable and resettable flip-flop, for example, to indicate the initiation of a print cycle and thereby indicating that a search for the next group of dots to be printed should be performed during such print cycle. The solenoids such as, for example, the solenoids 12 of FIG. 1, are operated by a pulse having a time duration of the order of 450 microseconds. The relaxed time between adjacent solenoid drive pulses is of the order of 550 microseconds and it is during this time interval in which the search for the next group of dots is performed in readiness for the next dot printing operation, as will become obvious upon a description of the operation of the electronics of FIG. 3.

Clock pulse source 74, which has its input connected to the outputs of each of the electronic circuits identified as blocks 71-73 is a clock pulse source which has a capability of generating two lagging clock pulses source to operate data register 76. One such suitable two-phase clock source may, for example, be a clock pulse source and one shot multivibrator triggered by the clock pulse source for developing a first output from the clock pulse source and a second output (lagging the first output) from the one shot multivibrator. However, any other type of clock pulse source and register may be employed if desired, it being understood that the register 76 is of the type in the present application, which utilizes two time separated clock pulses for advancement thereof.

The outputs of each of the circuits 71-73 are simultaneously coupled to the input of counter 75 which develops a pulse at its output 75b for each five pulses applied to its input 75a. The output of counter 75 is simultaneously applied to the input of counter 76 and a timing pulse decoder 77. Counter 76 develops a pulse at its output for each group of eight pulses applied to its input 76a. The outputs of all of the stages of counter 76 are also simultaneously applied to one input of timing pulse decoder circuit 77. Timing pulse decoder 77 is comprised of a counter plus logical decoding circuitry for developing an output signal at only one of its 80 outputs 77a at any given instant. Each of its output lines are coupled to associated input lines of an 80 bit buffer register 83 which operates in a manner to be more fully described.

Counters 75 and 76 collectively form a counter capable of developing a count of 80, i.e. of generating an output pulse at 76b for every 80 pulses applied at input 75a. The function of this counting operation will be described in detail hereinbelow.

Output line 76b of counter 76 is coupled to the input line 78a of counter 78. Output 78b of counter 78 is coupled to the input 80a of divide by 10 counter 80 whose output 80b is coupled to the input 81a of a second divide by ten counter 81 whose output 81b is coupled to the input 84a of a multiplexer 84.

Divide by six counter 78 is further provided with a plurality of outputs 78c from each of its stages, each of which are coupled to associated inputs of a column decoder 79 having five output lines 79a which are coupled to associated input lines of character generator 85 which will be described hereinbelow.

Data register 82 has the capability of storing 80 characters each character being comprised of six data bits. The output of data register 82 (six binary bits) is coupled to six associated inputs 85a of character generator 85 and are simultaneously coupled through feed-back loop 82b to associated input lines 82c of data register 82. The shift pulse input 82d of data register 82 is coupled to the output 74b of clock 74, while the data input lines 82a are coupled to the data entry device 71 or any other suitable external source which provides the input data for the printing operation. In the system block diagram as shown, data may be first provided in serial fashion with each six bits being converted into parallel fashion by a suitable serial to parallel converter, if desired. The operation of the electronic circuitry of FIG. 3 is as follows:

Let it first be assumed that data register 82 has been filled with 80 characters, i.e. that each character position in a line of 80 characters is to receive a character, number or other symbol. Once this has occurred, the first character (of six data bits) loaded into register 82 will have been shifted 80 positions from the left-hand most stage of register 82 to the right-hand most stage so as to have the state of its data code appearing at the six outputs of register 82 at the right-hand end thereof. At this time, data entry device 71 will provide a shift pulse which is applied to the input of divide by ten counter 75 and simultaneously to clock source 74. The outputs of counters 75, 76, 78, 80 and 81 will all be binary zero at this time. The six data bits in the right-hand most stage of register 82 will be simultaneously applied to the input of character generator 85. At this time, column decoder 79 will provide an output pulse at the left-hand most output line causing the character generator to provide a seven bit output which represents the seven dot positions in the first column of the first character to be printed in the line of characters (note, for example, FIG. 4 in which the dots of column 1 will be caused to appear at the seven output positions 85c of character generator 85). These seven bits are simultaneously applied to associated inputs 84b of multiplexer 84.

Row counter 81 is provided with four output lines 81b which are coupled to associated input lines 84a of multiplexer 84 with the binary code of these lines representing the particular row being printed at any given time. As is noted in FIG. 5, the printing of seven rows constitutes the printing of one line of characters or other symbols. Initially, row counter 81 is set at zero which is interpreted by multiplexer 85 as an indication that the dot in the particular column of dots to be printed for dot row one is that dot position which should be selected. Multiplexer 84 operates as a decoder in which only of the seven input lines 84b is coupled to its output line 84c at any given instant. The condition or state of the bit in column 1, dot row 1, of the first character is coupled to the input of 80 bit buffer register 83 which is comprised of eighty bistable flip-flops each of which is capable of storing one binary bit regardless of its binary state. The correlation can be seen between the eighty storage flip-flops and the 80 solenoids provided in the printer for the embodiment in which a capability of 80 characters per line is provided. It should be obvious that any other line length may be utilized and in fact embodiments have been developed in which up to 132 characters per line capacity has been provided. In such embodiments it would be obvious to provide a buffer register 83 having 132 stages with the other circuitry also being modified accordingly.

The output of timing pulse decoder 77 is comprised of 80 output lines only one of which is enabled at any given time. The operation is such that the first or left-hand most output line is enabled during start-up of the first line of characters to be printed to indicate that a dot position (i.e. in the first dot row and first column) of the first character will be stored in the bistable flip-flop associated with this position.

The next pulse from clock source 74 advances all of the coded characters stored in register 82 one position to the right. The coded character stored in the right-hand most position is recirculated through feedback path 82b so as to be redeposited in the first position or left-hand-most stage of register 82.

The second character comprised of a six-bit code is applied to associated inputs 85a of character generator 85. Simultaneously therewith column decoder 79 remains in the zero count state since data from the first column of dots of the remaining 79 characters has yet to be loaded into buffer register 83 and subsequently printed. The output code generated by column decoder 79 therefore represents the fact that the first column (i.e., column 1- see FIG. 4) of the second character is to appear at the output leads 85c of character generator 85. These seven outputs which represent the state of the bits in column one of the second character are simultaneously applied to the inputs 84b of multiplexer 84. Row counter 81 at this time remains at a zero count indicating that the dot in row one column one (for the second character) is to be selected. Since timing pulse decoder 77 has received only one output pulse from divide by ten counter 75, the output signals of decoder 77 appearing at 77a enable only the second flip-flop register to receive one bit which represents the dot condition (i.e. a dot or no dot) of the first column in dot row one of the second character.

This operation is continued until a dot condition in dot row one, column one of all 80 characters are loaded into the 80 stages of buffer register 83. The outputs at each of the 80 flip-flop stages of register 83 are coupled to solenoid drive circuits which, in turn, are coupled to associated outputs of the solenoids (12 of FIG. 1). The print carriage is moving at this time and moves into the first position in which the photo cell and light source are moved into registration with the first slit or transparent opening provided in registration strip 40. It should be noted that the light source 45 and photo cell 44 are preferably in alignment with any one of the jewel bearings 26 provided in deflection plate 25. When the registration between one of the registration slits and light source 45 and photocell 44 occurs, the light sensitive pickup 44 develops a pulse due to the registration condition to activate a strobe circuit 86 which develops a sharp output pulse sufficient to enable the outputs of buffer register 83 to energize the solenoid drivers. It should be noted that the 80 dot position conditions of the aforementioned characters (1-80) are all loaded within less than 500 microseconds. Since the movable deflection plate requires of the order of 550 microseconds to deflect the print wires from one registration position to the next, it can be seen that the operation of loading of the 80 bits occurs well before the time in which these 80 bits exert control over their associated solenoid drivers.

After the completion of 80 shift operations, the characters are now back in their original position with the first character being in the right-hand most stage and the last character to be loaded in the register being in the left-hand most stage. At this time the operation recycles itself except that the column decoder 79 has now received an output signal from divide by six counter 78 due to the fact that divide by eight counter 76 has developed a pulse at its output 76b to indicate that eighty shift operations have occurred. At this time, column decoder 79 accepts the pulse to cause its next output line to be activated, thereby causing the character generator 85 to provide a seven bit output representative of the dot conditions of the second column for the first character. Counters 80 and 81 have yet to be triggered, causing the output of row counter 81 to continue to condition multiplexer 84 so as to accept the binary state representing the dot condition in dot row one, column two of the first character (see FIG. 4). This binary bit is singled out to appear at output 84c of multiplexer 84. Timing pulse decoder 77 develops an output wherein only its left-hand most line is active to load the bit appearing at the output of multiplexer 84 into the stage of buffer register 83 which represents the first character. This operation continues until the binary bits representing the dot conditions of dot row one, column two dot positions of the 80 characters are now loaded into buffer register 83. Again, it should be noted that this operation occurs in less than 500 microseconds so that these bits are in actuality "waiting" for the deflection assembly to move to the next registration position.

The above operation continues until all dots in dot row one, column two for the 80 characters have been printed. The operation set forth hereinabove continues until all five column positions in the first dot row for the 80 characters have been printed.

Divide by five counter 78 counts the number of columns which have been printed. The capability of counting five columns is provided in spite of the fact that a space is provided between the end of each character and the beginning of the next character since there is no need to move the print wire deflection means through six dot positions. Alternatively, however, it is possible to move the print wire deflection means 25 through six positions in instances where it is desired to print or plot curves.

Since each solenoid in the preferred embodiment of the present invention has been designed to print one character (there being a capability of printing eighty characters per line with eighty solenoids) the output of counter 78, upon completion of the first dot row, advances row counter 81 to enable it to condition multiplexer 84 to select the data bit representing the dot positions in dot row 2 for the first line of eighty characters. Since divide by five counter 78 will have been reset after the entire first dot row of a line of 80 characters has been printed, column decoder 79 again causes character generator 85 to be conditioned to provide output information at its output lines 85c which represent the dots to be printed in the first column of any character which is presented at its input lines 85a.

The cycle is then repeated for the second through seventh rows in the first line of characters, at which time an output from row counter 81 is employed to indicate that a line of characters has been completed after the seventh row has been printed, in order to provide an output pulse to cause a speed up in the movement of the paper document to provide adequate spacing between the line of characters just printed and the next line of characters about to be printed, which spacing is typically of the order of five dot rows. Paper advancement may be controlled through the mechanical apparatus described in application Ser. No. 241,782, filed 4/6/72 and assigned to the assignee of the present invention.

The character generator 85 may be likened to a magnetic core or solid state memory device having a first set of inputs 85a and a second set of inputs 85b which "intersect" at predetermined positions within the character generator to develop pulses at the output lines 85c which are representative of the appropriate intersections selected. The input lines 85a apply a six binary bit code capable of selecting any one of 64 different characters, numerals or other symbols. The particular column in the five by seven matrix of the character selected is outputted to output lines 85c depending upon which of the column inputs is activated. One suitable character generator which may be employed is the Texas Instrument Co. Character Generator designated as Model No. TMS 4103. Obviously, any other character generator may be employed depending only upon the needs of the user.

Curve plotting is performed by converting register 82 into an 80 bit register for storing only one binary bit per stage with the dot positions in each stage representing the dots to be printed. In this instance the character generator and multplexer need not be employed and register 82 is adapted to function in the same manner as buffer register 83 to selectively print the dots in each dot row.

It can be seen from the foregoing description that the present invention provides a printer capable of character printing or curve plotting wherein a long row of dots is printed while the movement of the print wires is reduced to an amount of the order of one nth of the total length of the line of print where n represents the number of print wires provided for each row of dots. The amount of mass which is caused to move during the printing operation is also remarkably reduced as compared with conventional devices since the solenoids which actuate the print wires are mounted in a stationary fashion and only the free ends of the print wires are deflected to perform the printing operation.

Claims

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

1. An impact printer for forming dot patterns upon a movable document comprising:

a deflection assembly movable over a small distance in a direction transverse to the direction of movement of said paper document positioned adjacent said document;

a plurality of impact means each mounted in a stationary fashion adjacent said deflection assembly so as to experience no movement during printing;

each of said impact means including a reciprocating print wire and means for driving said wire against said document at high speed;

the free ends of said wires adapted to impact said document being arranged at closely spaced intervals within openings provided in said deflection assembly, said openings being arranged along an imaginary line substantially in alignment with the direction of movement of said deflection assembly;

means for selectively energizing said impact means during movement of said deflection assembly in the printing direction, whereby the distance travelled by said deflection assembly and hence the free ends of the print wires in printing one line of dots is 1/Nth the total length and is of the order of the width of one character of said line where N represents the number of impact means;

register means having N storage stages for storing N binary signals representative of the N dots to be printed in the next row of dots;

buffer storage means having a plurality P of stages, each stage being associated with one of said driving means;

means for transferring a group of P binary signals stored in selected stages of said first storage means to said buffer storage means wherein the binary signals are transferred from P positions in said first storage means, said positions being at intervals in said first storage means which are N/P apart in said first storage means;

means coupled to said buffer storage means for selectively energizing said impact means at each dot position in a line of dots across said document during movement of said deflection assembly in the printing direction, whereby the distance traveled by said deflection assembly in printing one line of dots is 1/Pth the length of said line where P represents the number of impact means.

2. The printer of claim 1 wherein the free ends of said print wires are arranged at equally spaced intervals whereby each print wire is adapted for printing 1/Nth of the total number of dots per row.

3. The printer of claim 1 further comprising means for continuously moving said document;

means for moving said deflection assembly;

means for guiding said deflection assembly to move along an angle of inclination adapted to cause each row of dots to lie along a straight line even though the paper document is moving during the printing of each row of dots.

4. The printer of claim 1 further comprising means coupled to said first storage means for generating a plurality of character signal groups, each of said groups comprising a plurality of rows of signals collectively representing a character;

means coupled to said character generating means for sequentially coupling row signals to associated ones of said impact means for printing a plurality of characters.

5. The printer of claim 1 further comprising means coupled to said moving means for driving said carriage assembly.

6. Means for controlling the print assembly of a dot matrix impact printer wherein an M row by N column matrix of dots represents each character of symbol comprising a movable member movable a distance of the order of the width of one character and a plurality of fixedly mounted solenoids positioned adjacent said movable member and arranged to experience no movement in the direction of movement of said movable member:

a paper document and means for moving said paper document simultaneously with the movement of said movable member; each of said solenoids including print wires having their free ends mounted within an associated opening provided in said movable member;

said control means comprising:

register means having a plurality of stages for storing the binary coded representation of characters to be printed on one line of said paper document;

means for shifting said characters out of said storage means;

said register means including means for recirculating characters shifted out of said output stage back into the input stage upon the occurrence of a shift pulse;

first means for counting the number of shift pulses applied to said register to identify the character in the output stage of said register;

second means for identifying the column of dots being printed by said print assembly;

third means for identifying the character being printed by each solenoid;

fourth means for identifying the row of the characters being printed;

means coupled to said second means for determining the column being printed;

character generator means coupled to the output stage of said register and the column determining means for providing an output representing the dots of the Nth column of the character presently stored in the output stage;

means coupled to said character generator means and said fourth means for selecting only one of the row position dots determined by said fourth means;

buffer storage means having a plurality of storage positioned equal in number to the number of solenoids being coupled to said dot selection means and said first means for storing the output of dot selection means in the storage position associated with the solenoid which is assigned to print the dot being stored;

registration means sensing the movement of said movable member for generating pulses controlling the time at which said solenoids are simultaneously operated;

each of said solenoids being coupled to an associated one of the storage positions of said buffer storage means;

said buffer storage means being enabled by said registration means to selectively operate said plurality of solenoids after said buffer storage means is loaded.

7. The device of claim 6 further comprising means for generating a code identifying the last character to be loaded into said register;

means responsive to said first counting means and said code generating means for filling the remainder of said register means with blank character data until said register positions are completely filled.

8. The device of claim 6 further comprising means coupled to said second means for causing a shift of N.sub.c /S.sub.n characters in said register when the dots in the first row of the first group of characters has been printed where N.sub.c = the total number of characters in a line of characters and S.sub.n = the number of solenoids.

9. The device of claim 6 wherein T = maximum number of characters per line;

S.sub.n = number of solenoids and the number stages in said buffer register;

said first counting means being capable of counting to a capacity of T;

said second counting means being capable of counting to a capacity of T(N+1); and

said third counting means being capable of counting to a capacity of T(N+1) .times. T/S.sub.n.