CA1094632A - Rotary electrical printer and method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A rotary electrical printer is described. The printer includes rotor, means for rotating the rotor and at least one group of styli secured to the rotor. Feed means is pro-vided for moving sheet recording material past the rotor in a direction transverse to the direction of rotation of the rotor with the styli contacting the sheet. The group of styli includes a plurality of axially-spaced styli. Control means is provided for selectively energizing the styli to cause each stylus to form a dot on the sheet at a selected location and thereby form images from transverse rows and circumferential columns of such dots. The styli in the group are positioned closely adjacent to one another so as to be capable of forming a group of continuous columns of dots during a single pass of the styli over said recording sheet.

Description

This invention relates to image recording and printing, and particularly to rotary printing. In its pre-ferred embodiment, the invention is disclosed in use in a rotary printer of the type in which images are formed by electrical discharges selectively positioned on discharge-sensitive paper.
As the speed of modern data-processing equipment has increased, so has the need for a high-speed, low-cost data printer Very high-speed data printers have been lC d~veloped~ However, such printers usually are very com-plex and expensive~ Much ch~aper printers have been devised, but usually such printers are slow, and also are complicated.
As a result, the cost of such printers, in terms of dollars per unit of printing speed (character per second~, has been undesirably high~ Furthermore, such prior printers have been unduly complicated and large. The maintenance costs have been relatively high, and the loss of operating time due to malfunction also has been undesirably large. Also, many prior printers are very noisy in operation.
In accordance with the foregoing, it is a major object of the present invention to provide a recorder or printer whose speed is relatively high and whose cost is low; a printer whose cost per unit of speed is very modest.
Furthermore, it is an ob~ect to provide such a printer which is small, simple and reliable. Furthermore, it is an ; object to provide such a device which is relatively smooth and quiet in operation so that it does not disturb people when printing.
In accordance with the present invention there is provided a rotary electrical printer including a rotor, 10~3~

means for rotating the rotor and at least one group styli secured to the rotor. Feed means is provided for moving sheet recording material past the rotor in a direction transverse to the dlrection of rotation - la -3~

of the rotor with the styli contacting the sheet. The group of styli includes a plurality of axially-spaced styli. Control means is provided for selectively energizing the styli to cause each stylus to form a dot on the sheet at a select~d location and thereby form images from transverse rows and circumferen-tial columns of such dots. The styli in the group are posi-tioned closely adjacent to one another so as to be capable of forming a group of continuous columns of dots during a single pass of the styli over said recording sheet.
Styli control means may be provided for changing the position of the printing produced by at least one of the styli, the control means comprising means for changing the time separation between successive actuations of the print members. By this means 7 the relative positions of the printed images can be adjusted on the record member without movement of the styli on the rotor. This avoids the nec-essity for re-balancing the rotor and other adverse effects which might be caused by mechanical adjustment of the styli.
Preferably, the record surfacQ has the form of a strip of electrical discharge-sensitive paper which is wrapped part-way around the rotor when making contact with the print mem~ers. It also is preferred that the paper ; strip be moved transversely across the rotor in a direction perpendicular to the plane of rotation of the rotox.

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It is prcferred that the characters be formed into ~ords which extend longitudinally of the record strip, and that the strip be wid~ enough to accommodate a number of lines of text matter to be printed. Coded infor~ation representing the characters is stored in an electrical memory and then read out in a sequency such that each print head prints characters in vertical columns, the characters in each colu~n being loca~ed in different lines of text matter. Thus, during each pass across the record strip, each head will print not just one character, but as many characters as there are lines of characters to be printed. In the preferred device, there are three such heads so that for each revolution of the rotor the number of characters which will be printed is equal to three times the number of lines of text. As a result, rather high printing speeds can be achieved with moderate rotor speeds.
It is also within the scope of the invention to print the words across the strip rather than longitudinally. In this case, the printing speed also will be relatively high.
In accordance with a further feature of the invention, ~ the electrical position signals for indicating the position of the rotor are produced by indicia which rotate w~th the rotor and which are spaced apart by the desired spacing between dots in the printed images. Preferably, the indicia are opaque lines on a transparent disc mounted on the same shaft as the rotor.
2S A plurality of detectors is provided for detecting the indicia. It is desired that the number of detectors equal the number of recording heads. One of the detectors remains stationary, and the other two can be adjusted angularly around the disc to effectively alter the enabling and disabling of each 106~S3~ , of -the three stylus heads without actually moving any of the heads. This permits adjustment of character alignment to compensate for uneven stylus wear and similar problems, without any mechanical adjustment of the heads on the rotor.
The memory which is used to store the character codes desirably is one into which data can be recirculated so as to repeat the printed text to make duplicate copies.
The paper strip preferably is fed continuously past the rot at a speed which is directly proportional to the rotor speed. This ensures the same spacing between characters or lines (depending on which direction words are printed in) regardless of the rotor speed. This is accomplished compact].y by gearing a paper feed roller to the same shaft as the one which drives the rotor.
The shaft is driven by a D.C. motor which has relatively high torque at low speeds, is xelatively in-expensive, and which can be operated by batteries so as to make the printer portable.
The paper feed roller extends outwardly from a housing. A cl~ved guide fits over the housing to guide the paper into a cylindrical slee~e which is used as a platen which supports the recording paper, and upon which the styli ride when not contacting the paperO The paper feed roller mates with an idler roller mounted in the guide, and pulls paper from a roll.
Paper from the roll passes over a guide bar which is located approximately in the plane of travel of the top of the arched paper through the printer. The guide 6~

bar is located so as to force the paper to bend through a substantial angle so that the point of delivery of the paper to theprinter will remain approximately the same despite variations in the diameter of ~he paper roll. This prevents jamming and bunching of the paper.
Especially simple means are provided for electrically connecting the conductive portion o the paper to the return connection of the voltage supply; that i5, electrical grounding means. This should be provided in order to ensure electrical discharges between the styli and the paper. One embodiment consists of a helical spring on a curved rod. The preferred embodiment is one in which the paper drive wheel is made of metal and is used to ground the paper, thus serving two functions simultaneously.
Because the speed of the paper feed, the timing disc and th~ rotor all are equal or directly proportional to one another at all times, the printer will operate accurately ; at a very wide range of speeds. In order to ensure that the blackness and readability o the printing is relatively uniform despite such speed variations, an automatic blackness control circuit is provided. The speed of the rotor is sensed, and the voltage applied to the styli is varied directly with the speed so that higher voltages are applied at higher speeds, and vice versa. This promotes relatively uniform blackness of the printed images.
A mechanism is providedwhich automatically retracts the styli away from the recording paper when the rotor speed drops below a pre-determined minimum. Preferably, the styli are retracted by means of springs. The styli are - 5 ~

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caused to automatically engage th~ recording paper when the rotor attains the desired minimum speed by means of centrifugal forces which act against the springs and hold the styli in contact with the paper. This prevents the styli from scratching or tearing the recording paper when new paper is fed through the printer, and it makes it easy to remove the rotor containing the styli from the printer.
The invention also provides a simple and eco-nomical adjustment mechanism for adjusting the axial positions of the styli. Furthermore, another simple mechanical structure is provided for adjusting the radial extent of the styli so as to compensate for wear, and for alignment purposes.
The invention also provides means for easily mounting and removing the rotor from the printer by means of a simple slide latch. A spring is provided for pushing the rotor off of the drive shaft when the latch is loosened.
The result of the foregoing features is a printer which meets the objects set forth above. That is, the printer is notably small, simple in construction and light-weight. Nonetheless, it is fast, relatively inexpensive and easy to maintain, and is quiet in operation.
The foregoing and other objects and advantages of the invention will be set forth in or apparent from the following description and drawings.
In the drawings:
Figure 1 is a front perspective view of a printer contructed in accordance with the present invention;

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Figure 2 is a rear perspective view of the printer shown in ~igure 1, with the paper guide raised, and with some of the paper removed;
Figure 3 shows a section of the paper recording strip used in the printer of Figure 1 and bearing a reproduction of printing actually produced by the printer;
Figure 4 is an exploded front perspective view of the printer shown in Figure l;
Figure 5 is a cross-sectional view taken along line 5-5 of Figure l;
Figure 6 is an elevation view of the rotor of the device of Figure 1 taken in the direction of line 6-6 of Figure 5;
Figure 7 is an elevation view of the timing disc of the device shown in Figure 1 through 5, and is partially schematic;
Figure 8 i5 a set of waveform diagrams demonstrating the operation o the tirning disc and associated electronic circuitry;
Figures 9 and 10 comprise the electrical control circuit of the printer shown in Figures 1 through 5;
Figures ll and 12 are partially schematic elevation views of a component of the printer, with the component beir.g shown in two different operating positions in the two figures;
Figure 13 is a plan view, partially schematic, illustrating another emdobiment of the invention;
Figure 14 is a side elevation view, partly in cross-section, of anothex embodiment of the printer of the presentinvention, 63~

Figure 15 is an elevation view, partly cross-sectional, taken along line 15 15 of Figure 14;
Figure 16 is another elevation view of the rotor shown in Figures 14 and 15;
Figure 17 is a side ele~ation view of one of the print heads of the printer shown in Figures 14, 15 and 16;
Figure 18 is an end elevation view of the print head shown in Figure 17; and Figure 19 is a cross-sectional, broken-away view of a portion of the Figure 14 structure taken along line 19-19 of Figure 14.

GENERAL DESCRIPTION

Figures 1 and 2 show an embodiment 20 of the : printer constructed in accordance with the present invention.
lS The printer 20 includes a base plate 22, a cylindrical housing 24, a cylindrical sleeve 26 which i5 used as a platen, a rotor 28 mounted on a shaft 48 so as to rotate in the sleeve 26, and a drive motor 30 or rotating the rotor 28. A timing disc 54 (Figure 2) for timing the printing also is mounted on the shaft 48.
Electrical discharge-sensiti~e paper 36 is stored in a roll 34 contained in a dispenser 32. The paper 36 passes upwardly ~rom theroll 34 over a straight guide bar 35 towards a curYed paper guide 38. The guide 38 is hinged to thç outer surface of the housing 24 at 40 so that it can be raised easily in the manner shown in Figure 2. As it is shown in Figure 1, a latch 42 holds the guide 38 down when the printer is in operation.

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Referring to Figure 2, a drive roller 56 is provided which pulls the paper from the roll 34, drawing it through the curved guide 38 so that the paper forms an arc, and feeds the paper through the sleeve 26 near its upper moct inside surface. After the printing has been formed on the undersurface of the paper 36, the paper emerges from the left edse of the sleeve 26 as shown in Fiyure 1. A paper tear ring 46 is provided at the left edge of the sleeve 26.
The ring 46 has a serrated upper edge 47 to permit a length of the paper strip to be torn off easily.
The undersurface (that it, the concave surface) of the paper strip 36 is coated first with a dark material, and then with a light-colored material such as aluminum or zinc oxide which can be eroded or vaporized away by an elec~
trical discharge or spark. ~he rotor 28 has three stylus heads 62, 64 and 66 each with five parallel equidistant axially-spaced styli 68 (see Figures 5 and 6).
As it will be explained in greater detail below, the paper feed roller 56 and the rotor 28 are driven contin-uously by the drive motor 30. The styli are selectivelyenergized so as to form images on the underside of the paper by the formation of dots in a five dot by seven dot matrix.
An example of printing produced by the printer 20 is shown in Figure 3. Each stylus head has five wires, which is enough to produce all the dots for the horizontal portions of characters to be printed. Thus, each time one of the ~tylus heads passes ovex the recording paper~ it will produce at least one printed character.

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It is preferred that the words be printed on the strip as shown in Figure 3; that is, in the longikudinal direction indicated by the arrow 31. Furthermore, when several lines of text are to be printed, the data is stored in a memory in the device and is read out so that each stylus head will print an entire vertical column of characters, one character from each of the lines. For example, the first column A of characters in Figure 3 was printed by a single pass of a single stylus head; the column B was printed by a single pass of a second stylus head, and column C was printed by a single pass of a third stylus head. Since there are three stylus heads, three columns of characters are printed per revolution of the rotor. Thus, the number of characters per revolution which the device will print is equal to three times the number of lines being printed.
Of course, it also is possible to form words in a vertical direction instead of in the horizontal direction shown in Figure 3. The speed c~pabilities of the printer when operating in such a mode are comparable with those in ~0 ~he other mode.
The printer 20 now will be described in detail.
DRIVE SYSTEM

Now referring to Figures 4 and 5, the drive system of the printer 20 includes the shaft 48 and the drive motor 30, hoth of which already have been described. The motor 30 is mounted on an end plate 70 for the housing 24 by means o~ screws 80. To the output shaft 76 of the motor 30 is secured a toothed drive wheel 78 which drives a toothed-timing belt 50 (see Figures 2 and 4) to drive large t~d wheel 52 which is secured to the shaft 48. The sizes of the 63~

wheels 78 and 52 are such as to produce a speed reduction of four to one. The timing disc 54 is secured to the wheel 52 and thus is secured to the shaft 48.
The shaft 48 is mounted in ball bearings 72 in the end plate 70, and a retainer 74 is secured to the right end of tne shaft. (See Figure 5). Another end plate 88 is provided at the opposite end of the housing 24. The shaft rotates in ball bearings 92 in the end plate 88, and is retained by a retainer 108 secured to the shaft.
The rotor 28 is mounted on a spacer 110 (see Figure 4 as well as Figure 5) by means of screws, and the spacer is similarly attached at its other end to a slip-ring disc 104 which abuts against the retainer 108. The spacer, slip ring, and rotor lZ8 are held against the retainer 108 by means of a threaded nut 114 which screws onto threads 49 (E'igure 4) on the left end of the sha~t 48. Thus, the rotor 28, the spacer 110, the slip-ring disc 104, the gear wheel 52 and the timing disc 54 all rotate together at the same speed.
The rubber paper feed roller 56 is driven by gearing coupling it to the shaft 48. As it is shown in Figures 4 and 5, the roller 56 is rotatably mounted on a shaft 96 which is secured in an upper extension 89 (See Figure 4) of the end plate 88. A slot 91 is provided through which the upper surface of the roller 56 extends.
A lower extension 90 of the end plate 88 forms the bearing support for a shaft 84 to which is secured a worm gear 86 which meshes with a worm 82 secured to the shaft 48.
This combination drives a bevel gear 92 which meshes with another bevel gear 94 on the shaft 96 which drives the paper feed roller 56 at a speed substantially slower thar that of the rotor 28.
The feed roller 56 mates with an idler roller 98 which is mounted on a shaft lO0 in the curved paper guide 38. A cover 102 fits over the idler roller lO0 to protect it.
As it can be seen in Figure 5, the recording paper 36 is pinched tightly between the two rubber rollers 56 and 98 so that the rotation of the roller 56 will pull the paper through the printer substantially without any slippage.
PAPER GROUNDING MEANS

Figure lO shows schematically the electrical circuit formed when a spark is formed between a stylus 68 and the paper 36. The conducti~e under-surface 39 of the preferred recording paper must be connected to the return terminal of the voltage supply 69 which is connected to the stylus 68 in order to produce electrical discharges. Since that return terminal is grounded, the undersurface of the paper must be grounded.
~his is accomplished by a means of a unique grounding device which is shown in Figures 2, 4 and 5.
The grounding device consists of a helical conductive spring 58 which is wound around a curved metal rod 60 which lS secured to the end plate 70 in the manner shown in Figure . : 25 4 and which is connected to ground. The ends of the spring : 58 are held in p~ace by means of retaining rings 61.
: As it i-- shown in Figure 5, the rod 60 curves forwArdly as well as into an arc so that it fits underneath ,_ .

the right edge of the cover 38. The upper portion of the coils of the spring resiliently press against the underside of the paper 36 and force it upwardly against the guide 38. The many coils of the spring provide numerous relatively closely spaced contacts to make good grounding contact with the undersurfac of the paper.
This combination ground connection and paper tensioning means also serves a third function; that of helping to shape the paper into an arc so that it will pa~s easily through the guide 38.
PAl'ER DISPENSING

As it is shown in Figures 1, 2, 4 and 5, the paper roll 34 is stored on a spindle 120 whose ends fit into slots 118 in a pair of end plates 122 of the dispenser 32. The plates 122 are secured to the base plate 22 of the printer.
The friction created by the various components of the dis-penser tends to prevent over-run of the paper feed roll after paper feeding has stopped.
As it is most readily apparent in Figure 5, the bar or roller 35 serves the funciton of causing the paper coming from the roll 34 to be bent through a substantial angle before passing on towards the printer. However, the bar always delivers the paper at approximately the same height to the printer, which would not be the case if the paper were pulled directly from the roll 34. Substantial movement of the dispensing point is undesirable in that it tends to cause bunching or wrinkling of the paper and thus prevents smooth feeding of the paper. Therefore, the dispenser 32 dispenses the paper strip to the printer uniformly and smoothly.

9;qL~32 ROTOR CONSTRUCTION
Figure 6 shows the construction of the rotor 28 and the positions ofits three stylus heads 62, 64 and 66.
Figure 6 is a partially schematic view of the rotor 28, taken in the direction of line 6-6 of Figure 5, with the spacer 110 and other elements omitt~d.
As it can be seen in Figure 6/ the points of contact between the styli 68 and the circle 125 which represents thQ internal surface of the platen sleeve 26, are indicated by reference numerals 119, 121, and 123. The styli 68 are mounted in a solid epoxy resin base which is secured to a bracket 128 which is mounted on the rotor 28. The bracket 128 has a curved slot 130 with a screw 132 to allow the stylus head to be moved outwardly or inwardly to increase or decrease the pressure of the styli on the platen or the paper on the platen.
As it can be seen in Figure 6, the angle between the styli and the radius lines extending through the points 119, 121 and 123, is approximately 70. The angle formed between the styli 68 and the tangent line 127 at point 119 therefore is 20. Thus, the styli travel over the platen and the paper at an angle substantially less than perpendicular.
This makes for smoother operation of the mechanism and reduces the likelihood of the styli tearing the paper when the styli cross over fromthe platen ontothe edge of the paper.
Referring again to Figure 5, it can be seen that the platen sleeve 26 is of a diameter substantially larger than that of the housing 24. This is necessary so that the paper 36 will enter the inside surface of the platen sleeve.

The lower two-thirds 116 of the rear edge of the sleeve 26 is of a smaller diameter so that it will fit onto the flange 93 of the endplate 88 where it is fastened in place by means of three screws ~not shown).
The paper tear ring 46 is fitted into a recess 95 in the inside surface of the front edge of sleeve 26.
As it also is apparent from Figure 5, each of the stylus heads 62, 64 and 66 is connected to terminals at the rear of the slip-ring board 104 by means of wires 112 ~also see Figure g). Th~ terminals connect through the board 104 to the slip-rings on the other side of the board 104.
It also should be noted that the stylus heads 62 and 64 are shown in Figure 5 rotated from their actual positions so that they can be illustrated more clearly.
DISCHARGE TIMING STRUCTURE
The timing of the formation of dots by the styli is important to the accurate printing of characters and other images~ Referring now to Figures ~, 4, 5 and 7, this timing function is provided by means of the transparent disc 54 which has a series of thin opaque black lines 166 (Figure 7) and a si.ngle wide black line 168 applied to the disc. Id2ally, the three sensors A, B and C would be 120 apart from one ; another, as are the three stylus heads 62, 64 and 66. However, the construction of the housin~ 24 and the paper ~uide 38 does not permit this. Because of such constructional re-straints, sensors A and C are placed 180 apart from one another, and sensors A and B are placed 60 apart. Sensor B
is fixed in position. However, sensorsA and C are movable cirsumferentially with respect to the disc 54 so as to adjust 4~3;~
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the timing of the start and stop of printing by the stylus heads relative toone another. This makes it relatively easy to make the initial head alignment, and also makes it possible to easily adjust for uneven wear of the styli and other causes of misalignment of the printing without moving the stylus heads. This avoids unbalancing the rotor and makes the adjustment process quite simple.
TIMING ADJUSTMENT
Referring to Figures 4, 11 and 12, as well as Figure 7, sensor B, the fixed sensor, includes a detector structure 146 fastened to a mounting plate 148. The detector structure 146 includes a U-shaped housing, one arm of which includes a small light emitting diode (LED) 153 ~Figure 11) which shines its light towards the other arm which contains a small photo-transistor 155 to detect the light. A mask (not ~hown) comprising a small piece of film which i6 opaque except for a small thin slit covers the photo-transistor so as to admit only that light which falls on the thin slit.
The detector 146 of sensor B is inserted through a hole 138 in the housing 24 and is secured in place after the disc 5~ has been mounted in the housing. The two arms of detector 146 fit around the edge of the disc so that the light from the LED shines through the disc in the area where the markings 166 and 168 are located and is detected by the phototransistor.
Each of the other sensors A and C also includes an identical detector 146. The detector 146 in each sensor A
and C is mounted on an L-shaped bracket 154 which i pi~otably 3~:

connected at 15~ to a mounting bracket 150. The bracket 154 has a long arm with a longitudinal groove 156.
Still referring to Figuxes 4, 11 and 12, two adjustmen~ cam devices 158 and 160 are provided. Each has a hody which is fitted rotatably into a hole in theend plate 70 of the housing 24 and has aslotted head which permits the device to be turned with a screwdriver. Each device 158 and 160 also has an eccentrically-mounted pin 162 or 164. As it is shown in Figures 11 and 12, the pin 162 or 164 fits into the groove 156. As the head of the cam device 158 or 160 is rotated, the arm of the bracket 154 is raised upwardly or lowered about the pivot point 152 so as to change the location at which the detector senses the lines 166 and 168.
The pivot points 152 are shown schematically in Figure 7.

The detailed operation of the disc 54 and the sensors A, B and C in timing the printing of the printer will be explained in detail in connection with Figures 8 through 10. ~owever, in general, each of the thin, closely-spaced lines 166 time~ the placement of one dot (or one row of up to five dots), and the wide pulse mark 168 serves as a reference mark. Very precise adjustments in the printing placement can be made by use of the cams 158 and 160 to move slightly the location of either or both o~ the sensors A and C
relative to the sensor B so as to change the relative starting and stopping times for printing produced by the stylus heads.

ELECTRICAL CONTROL CIRCUITRY

Figure 9 shows the electrical control circuit for the printer 20. The drive motor 30 is shown in the lower lef~ hand corner of Figure 9, and the styli ~8 are shown in the J
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upper right-hand corner of the drawing. The slip-ring disc i 104, the brushes 106 contacting the slip-rings and the wires 112 leading from the slip-rings to the styli also are shown in the upper right hand corner. It is evident from F gure 9 that each of the slip-rings is continuous so that each of the brushes 106 continuously is in contact with three styli, one from each of the three stylus heads.
The position of each such stylus is the same in each of the heads. That is, the outermost brush is connected to the first stylus in each head; the next brush to the second stylus, and so forth. This means that the styli in all three heads (labelledgroups A, B and C in Figure 9) are energized simultaneously. Therefore, the paper strip 36 should not extend more than one-third of the circumference of the platen 26. Otherwise~ extraneous printing will be done on the s~rip.
Of course, if the use of a wider strip is desired, then the styli can be energized s lectively by means of segmented slip-rings.
D.C. is supplied throughout the control circuit by either a D~C. power supply, if 117 volts 60 Hz power is the available source, or from a battery.
In the central upper portion of Figure 9 is shown a memory 200 consisting of six 480 bit shift-registers.
Connected to the output of memory 200 is an ROM code converter 202 commonly called a "character generator", which converts character identification signals from the memory 200 into corresponding dot matrix signals appearing on five output lines Z03. ~he dot matrix signals are adapted to enabl~
selec~ed ones of the five styli which are in contact with the the paper strip to be energized so as to form one row of dots in a particular character to be printed.
The code converter 202 is addressed by means of three input leads 264,266 and 268 in order to produce on the output lines 203 successively th~ information to form seven successive rows of dots for a given character, thus enabling the printing of the character in 5x7 dot matrix form. This procedure will be described in greater detail below.
DATA ENTRY
The memory 200 has a capacity sufficient to store characters for twelve lines of text, each line being for~y characters long. By the addition of more shift registers, the storage capacity of the memory 200 can be increased. With a paper skrip wldth of four inches and characters approximately 3/16th inch high, and with minimum spacing between linesO up to twenty-four lines can be printed across the paper strip.
The lines can be made about as long as one desires, if one is willing to add the necessary st~rage capacity to the memory.
In fact, if the characters are printed in a single line, and if a "FIF0" memory is used instead of the memory 200, the line can have a virtually unlimited length.
Data is applied to the six input lines 204 to the memory 200. A memory control circuit 206 is provided for reading and writing to and from the memory Z00. A high-frequency clock signal ~e.g.l M H z~ is applied over input line 226 to one input of a NAND gate 228. Strobe pulses are applied, at a somewhat lower frequency, over another input line 216. The strobe pulses are deli~ered to one inpu~ of a gate 218. During data entry, a D type flip-flop 236 6~

(lower left-hand corner of Figure 9) is in the reset condition in which a signal appears on output Q and none appears on the output Q. The "low" signal on Q enables gate 218 which delivers strobe pulses through another gate 220 and an ~ND gate 222 over a read/write line 224 to the memory 200. The strobe pulses cause data to be entered on the common data entry line 225 to the shift registers in the memory.
When the flip-flop 236 is reset, the Q signal from flip-flop 236 is applied over a line 244 to inhibit a gate 219 to prevent the reading of data through that - gate~
Simultaneously with the read-in of data to the memory 200, the output of gate 222 is delivered over line L5 230 to the clock input of another shift register 232 which also has a storage capacity of 480 bits and is identical - to the shift registers in the memory of 200. The shift register 232 is used as a detection device to detect when the memory 200 is full, and to signal the start o the printing operation.

START MOTOR
When the shift register 232 is full, it sends out an output signal over line 234 to the clock input of the flip-flop 236. This "sets" the flip-flop and creates a signal on the Q output line which i~ sent over line 238 to a motor drive circuit 208, which is a semi-conductor relay which completes the circuit to the drive motor 30 and starts it running.

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The change of flip-flop 236 to the "set"
condition enables gate 219 and thu~ makes i~ possible to read data out of the memory during printing, as it will be described below. Also, gate 218 is disabled by the signal on Q, so tha~ data no longer can be written into the memory from the input lines 204.

SETTING THE END ~RGIN ON THE RECORD STRIP
The operation of the flip-flop 236 also causes a change of state on its Q lead, and this actuates a margin counter circuit. A counter 246 counts two "column sync" signals representing two revolutions of the timing disc 54 (not shown in Figure 9) before it permlts the printer to start printing in order to provide a definlte unprinted margin on the paper between the matter to be printed and the c~t end of the paper s~rip.
. COLUMN SYNC SIGNAL GENERATION
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At the lower right-hand edge of Figure 9 are shown the three sensors A,B and C shown in Figures 4 and 7 which detect the narrow timing marks 166 and the wide timing mark 168 on the spinning disc 54. Included in the detectors A, B and C shown in Figure 9 may be amplifiers and Schmitt ~rigger circuits for the amplification and wave-shaping of the pulses from the detectors.
The "column sync" signals shown in the waveform diagrams of Figure 8 are the ones that are counted by the margin counterO These signals are developed in the following manner. A column sync counter 212 is provided.
It includes two J-K type flip-flops 300 and 302. Flip-flop 302 receives the signal from the C sensor on its clock input, and bo~h flip-flops 300 and 302 receive the B sensor signal on thier "clear" leads.

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Referring now to Figure 7 of the drawings, the disc 54 ro~ates counter-clockwise. The sensors, A, B
and C produce signals when a transparent portion of the disc 54 is between the LED and the photo-trar.sistor, allowing light to reach the latter. Therefore, whenever a transparent area of the disc 54 is opposite the B
sensor, the "clear" input leads of the 1ip-flops 302 and ~00 are driven low so as to reset the column sync counter 212. When the wide mark 168 (2.5 times as wide as any of the marks 166) passes through the sensor B~ this temporarily removes the "clear" signal from the flip-flops 300 and 302, and enables them to count pulses received from the sensor C, which now senses the narrow marks 166. Although it might seem that the thin marks 166 are ending at the time the wide mark 168 first is detected by sensor B, this is not so because the wide mark 168 is 64.1 from the forward end of the train of marks 166l whereas sensor B nominally is only 60 from sensor A. Therefore~ sensor C then is 220 clockwise away from sensor B, and the end of the thin maxks 166 is 224~1 away, and there still are several marks 166 left to pass through sensor C~ Thus, the counter counts up to two before the wide pulse 168 ends and the counter again is cleared.
Thisproduces an output pulse on Q of flip-flop 300.
This pulse is the "column sync" signal shown in Figure 8 and appearing on line 248 of Figure 9~
Aft~r the wide pulse passes sensor ~, but before the thin lines reach sensor B, the counter remains cleared, andno"column sync" signal is produced. After the thin - 22 ~

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lines 166 reach sensor B, and also later when both sensors B and C sense the thin lines,;the counter 212 is reset once for every transparent space between thin lines, and cannot, therefore, count to two and cannot produce a "column sync'l signal. As a result, the "column sync"
signal is pr~duced only once per revolution of the disc 54, at the time when the wide mark 168 passes through sensor B~
As it has been noted above, the "column syncl' signal~ are delivered over line 248 to the margin counter 246 which counts two of the signals. The counter 246 then delivers an output signal over line 250 to star-t the printing operation~ -STARTING PRINTING
-Referring to the lower central portion of Figure 9, the signal on line 250 of the margin counter 246 is delivered to the clock input of ano~her D-type flip-flop 251 which changes state and develops a signal on its Q
outp~t line. This signal is supplied over line 254 to the margin counter to inhibit it, and also is supplied over line 252 as a "start" signal to a print-enabling flip-flop 254~
Flip-flop 254 is a D-type flip-flop which is clocked by signals applied to its clock lead 253 from an AND gate 290 which is in the right-central portion of Figure 9~ AND gate 290 receives an enabling input on its lower lead, and is enabled by pulses from the A sensor received over line 298. This, in effect,sends the pulses fron the A sensor through to the clock input of the flip-flop 254.
Thus, the first of the pulses developed by the thin lines ii3;~

166 on the code disc in the A sensor, together with the the "start" signal on' line 252, causes a change of state in the flip-flop 254. The subsequent clock pulses from the ~ sensor also time the later operation of the ~lip-flop 254. This operation of flip-flop 254 changes the state of the Q output line 256 and the Q output line 274.
Simultaneously, the "high" signal on line 256 is applied to one input of anotherNAND gate 260 whose other input also is high due to being connected to the Q output of another ~ type flip-flop 258, which is "cleared" at this time~
ROW COUNTER
The output of gate 260 enables the row counter 262 whose function is to count the rows of dots being printed, as well as the spaces in-between lines of characters;
to address the ~OM code converter 202 over address lines 264, 266 and 268 and cause it to deliver its information through AND gates 272 and amplifiers 314 to the brushes 106 and then to the styli 68. Of course, none of the AND gates 272 will produce a proper output signal unless both o its inputs are in the same state.
One of the inputs of each of the gates 272 is connected to the output of a three~input positive NAND yate 270. The output of gate 270 enables each of the AND gates : 272 when the signal on each of input leads (274 and 276) is in the proper state. The signal on line 274 is in the proper state whenever flip-fIop 254 is "se~" in order to enable printing. Lead 276 is connected to one output terminal 284 of a multiplexer circuit 282 (in ~he lower right hand portion of Figure 9) which, as it will be ~i9 ~632 explained further below, always receives the pulses produced by the thin lines 166 in the sensors A, B and~C.
Thus, the gate 270 is enabled repeatedly by the timing pulses produced by the thin lines 166, but only during the short duration of those pulses.
The timing pulses also are delivered from line 284 to the row counter 262 over a line 263. The row counter counts the time pulses and thus steps through its addressing routine and counts the number of rows being printedO
Since there are seven dots vQrtically in each character, the row counter steps through seven pulses~ repeatedly changing the combination of outputs on lines 264, 266 and 268 to sequentially address the ROM code converter 202.
On the eighth count line 271 of the row counter goes !'high". This inhibits the gate 270 and sends an enabling signal over the "clear" line 277 to enable flip-flop 258. Flip-flop 258 does not actually change its state at this time because it is a "D" type device which requires a clock pulse on the clock input to enable it to change.
The signal on line 271 also is sent to the line counter 278 to advance it by one count.

LINE SPACING SELECTION
The clock output line 257 of the flip-flop 258 actually can be connected to either line 264 or 268 in order to select the spacing between lines of characters.
Line 2&4 is energized when the counter 262 counts up to two, and line 268 is energized when the counter 262 counts to five~
Assuming a line spacing of ~wo has been selected by connecting line 257 to line 264, on the ninth count by 4~i3Z

the row countex 262, line 264 goes high, and this sets flip-flop 2580 If a line spacing of five is selected, the same action takes place at a count of twelve instead of nine.

READING THE NEXT CHARACTER
When flip-flop 258 is set, its Q output goes high and delivers a signal to activate a one-shot multi-vibrator 261 in the memory control circuit 206 in the upper left portion of Figure 9. The one-shot multi-vibrator produces a pulse which is delivered through gates 219, 220 and 2~2 to read/write line 224 to read out from memory 200 the information for another character. It should be noted that the information for the first character already appeared on the output leads of the memory 2U0 because that was the first information that was stored in the memory 200.
The setting of flip-flop 258 causes its Q output to go low, which causes the output of gate 260 to go high and reset all of the outputs of the row counter of 262 to zero. The resulting low signal on lines 271 and 277 resets flip-flop 258 and again enables gate 270 to permit the next character to be printed.
The row counter 262 now starts anew to count timing pulses received over the line 263l and the printing of the next character in the column is started. The next character i5 printed in the same manner as the first character, and the process is repeated until a character has been printed in each of the twelve or twenty-four lines in which characters are to be printed. Thus one column o~ characters has been completed.

3~2 LINE COU~ITER
The signal on output lead 271 from the row counter 262 also is delivered to a line counter 278 which counts the number of lines which have been printed in any pass of a print head over the record strip. Two different connections are provided to the line counter 278, one enabling the internal circuitry to count up to twelve lines, the other enabling it to count up to twenty-; four lines at the option cf the user.
Assuming that twelve lines are to be printed, after the twelfth character has been printed by a particular print head, the line counter 278 delivers an output signal over line 280 to an AND gate 282 which also receives an input from flip-flop 236 over line 240 so that the flip-flop 254 now is cleared. This disables the printer until it is time to start the next vertical c~lumn of characters when the next print head is in position to start printing.
DOT TIMING
The dot timing circuit 210 includes, in addition to the multiplexer 282 and the column sync counter 212, a data select counter 214 and a divide-by-117 counter 288.
The multiplexer 282 connects different input signals to the output leads 284 and 286 depending upon the state of the input lines 291 and 292. The following table descrlbes the operation of the multiplexer:
' ;

' ., ~0~ 32 TRUTH TABLE FOR MIJLTIPI.EXER 2 ~32 291 292 284!; 286 Function Permit~ed ~1) 0 0 A B Print. Column A

(2) 1 0 B C Print Column B

(3) 0 1 C - Print Column C
Column Sync Signal Resets to Condition (1) The data select c~unter 214 includes a pair of J-K type flip-flops 304 and 306. When the first pulse from the divide-~y-117 counter 288 changes the state of flip-flop 304, this changes the data at the output lines 284 and 286 in accordan~e with the above table. When the next pulse is received from the circuit 288, the state of the second flip-flop 306 is changed, and data on lines : 284 and 286 change again in accordance with the table.
. In this wayl first the A signals then the B signals and then the C signals are delivered to the circuit to control the printing.
~20 Referring now to Figure 8, the "column sync"
signal occurs at time tol and the sensor timing signaIs start shor~ly thereafter, at time tl. Referring now : particula~ly to the "B" sensor waveform in Figure 8, it can be seen that the B s~nsor starts produ~ing timing ~: 25~ pulses at time t2O Referring again to Figure 9, the pulses from sensor B are delivered over output lead 286 of the multiplexer to the divide-by-117 counter 288. Printing by the "A" stylus head ends at t3 (Figure 8~ when the line : counter cLears th print-enable flip-flop 254. When the ~30 countex 2~8 has counted 117 pulses (one-third of the 351 pulses produced by the thin marks 166 on the disc~

6~2 the counter 288 produces an output signal which is delivered to one input of an AND gate 294 whose other input is con-nected to the Q line o flip-flop 300. Thus, AND gate ' 294 is enabled and sends a signal over line 296 to clear the line counter 278. This removes the output from the line counter on line 280 and thereby disables AND gate 282 and causes the print-enable flip-flop 254 to change state and start the "B" print head to printing another column of characters. This~,occurs at time t4, a short time after t3.
From time t4 to t6, the "B" stylus head prints characters. At t6, the line counter again operates to stop the printing. In the meantime, timing pulses from the "C" sensor have been delivered to the counter 288 since t5. When counter 288 again produces an output after having counted 117 pulses from sensor C, the third stylus head is ena~led to start printing at t7, until the line counter stops the printing at t8. Then the column sync pNlse occurs again at to and the printing process is repeated again for another revolution of the rotor 28. This is repeated over and over again until all of the infcrmation in the memcry 200 has been read out and printed.
During the readout of information from the memory 200, the shift resister 232 shifts the same number of times as each of the shift registers in the momory. When register 232 is full, a circuit (not shown) is provided which delivers a pulse over line 234 to return flip-flop 236 to its inîtial state, de-energi~e the motor drive circuit 208, and stop the motor. This same circuit also resets any o the shift registers or flip-flops which have -- :29 --not already been reset, in order to prepare the circuit for the next printing job., REPEAT PRINTING
It if is desired to repeat the same prin~ing joh to make duplicate copies of the text, this can be accomplished simply as follows. Prior to loading the memory, the "R strobe" input to the shift register 232 and the "R"
! input to the shift registers in the memory 200 are co~nec~ed together and to a low signal source. The shift registers are of a type in which this causes the data to be re-circulated and re-stored in the shift registers of the memory 200 instead of being destructively read out. The same is true for the shift register 232. Thus, in this mode of operation, the printer automatically will print the same text matter again and again, as many times as desiredO
AUTOMATIC B~ACKNESS CONTROL CIRCUIT
In accordance with another feature of the ;~ invention an automatic blackn~ss control circuit 215 is 2b provided. This circuit comprises a one~shot multi-vibrator tachometer 308 whose output is delivered to an integrator circuit 310 whose output is amplified by a linear amplifier 312. The output of the'amplifier 312 is delivered to th'e inputs of the amplifiers 314 in order to increase 2S or decrease the voltage applied to the styli in accordance with the speed of the rotox., '' The pulses delivere~ over line 284 have a frequency which is directly proportional to the rotor speed, since these are the fine pulses produced successively by the lines 166 in sensors A, B and C. The pulses at the output of the tachomet2r 308 have constant widths, since ~ 30 -their widths are determined only by the characteristics of the multivibrator. However, since the time periods between the pulses ~aries with the speed oE the rotor, the output of the integrator 310 varies in direct proportion to the rotor speed. This increases or decreases the out-put of the amplifier 312, and thc amplifiers 314. As an example, in a preferred embodiment of the invention which has been built and successfully tested, the voltage applied to the styli was 50 at a printing speed of [from] 500 ; 10 characters per second. At 3,000 characters per second and the same number of lines and line spacing, the stylus voltage was 70 volts.
By means of the automatic blackness control circuit, the blackness and readability of the printed characters is maintained at a relatively constant level despite such wide variations in speed of the rotor. As a demonstration example, highly satisfactory printing has been produced when the rotor is merely rotated by hand at a very low speed, as well as at speeds of up to 3,000 characters per second~
It should be understood that the speed of 3,000 charactexs per second is not believed to be the upper limit of speed for this device~ This speed will vary with the number of lines of characters being printed, etc.
However, it is a significant advantage of the invention that a speed of up to 3,000 characters per second has been achieved in a relatively low cost, simple and compact machine.

.~ ~

.

3;2 USES AND ~IARIATIONS
It is envisioned that the present inven~ion will have wide utility in printing alphanumeric characters. For example, it is believed that this invention will be especially useful in producing "hard copy" from a cathode ray tube or television screen at a computer terminal or elsewhere.
The "page" of data appearing at any one time on the cathode ray tube screen can be printed out as a unit rather easil~.
The printer of the present invention is so small (e.g. 4 inches by 4 inches by 8 inches or smallerl that it can be fitted into the same module with many cathode ray tube display screens.
The printer can be used advantageously in many applications where small size is important. For example, the printer is useful in aircraft, spacecraft, police, fire and other emergency vehicles.
It is believed that the printer of the present invention will make excellent low-cost, reliable stock quotation printer, especially when operated in the mode in which the printing is composed in a single line.
As one alternative embodiment of the invention, the logic circuitry of a computer terminal can be used to replace some of the control circuitry shown in Figure 9.
Alternatively, the printer control signals can be provided by specially programming a general purpose computer.
Although it is preferred that the electrical dis~harge process be used in the present invention, the three print heads on the rotor also can have other con~
structions. One is the use of a group of push-rods instead

4~,3~2 of styli for each of the heads. In such an embodiment, each of the push rods is act~ated b~ an electro-magnet to strike an inked ribbon or the like in order to form characters in dot matrix form on ordinary paper. Devices forming dots from ink s~milarly can be used to form characters from dots on ordinary paper.
The number of print heads on the rotor can ~e varied, as can the number of styli in each head. However, the use of three print heads, with each printing one column of chaxacters per pass, has been found to have decided advantages. It will be noted in Figure 3 that there is a slight variation from left to right of the starting point of the top and bottom lines of print. This is because, as the rotor is rotating, the recording paper is continuously moving, which means that the position at which the last line starts will be displaced longitudinally by a small amount from the place where the first line starts. It has been found, advantageously, that this slight amount o~ skew usually is not objectionable in data printers, and need not be compensated for. However, if it becomes objectionable in a particular use of~he printer, the skew can be compensated in the manner shown in Figure 13.
Figure 13 is a schematic plan view of a printer like that shown in the previous figure of the drawings, except that the direction of paper feed is at an angle 4 of 2 degrees and 4 minutes from the longitudinal axis of the printer, an angle which is sufficient to compensate for the skew produced by the printer. Of course, if variations in the number of heads and/or stylus wires are made, the compensation angle ~ can be varied as necessary.

~o~

Although a mechanical system has been described for alignment of the printing by the three heads, one in which the adjustment is made by turning the cam wheels 158 and 160, the same adjustment can be made by purely electronic means~ In this modification, the same function can be performed by the adjustment of counters which time the start of printing by ~ach of the heads so as to cause the printing by that head to lead or lag the printiny of the others by a certain amount. With present technology, however, it is believed that the mechanical adjustment described above gives good precision at a lower cost than it would require to obtain the same precision by electronic means.

REMOVABLE ROTOR CONSTRUCTION
Figure 14 shows a rotary printer 20 which is substantially the same as the printer shown in the previous Figures of the drawings, except for the rotor structure at the left end of the printer, and the paper grounding structure.
Referring now to Figures 14 and 15, three stylus heads 420 are pivotably mounted on the inside surface of the rotor 28. Only two heads 420 are shown in Figure 15, and only one of those heads is shown in Figure 14, in order to maintain the clarity of the drawings.
Referring now to Figures 17 and 18, as well as to Figures 14 and 15, each stylus head includes five cl~sely-spaced parallel stylus wires 68 which are molded into a stylus support 424. Electrical energy is distributed to the styli by means of a printed circuit panel 426 which is secured to the support 424. This assembly is secured to an L-shaped slide member 428. Member 428 slides in a groove in a mounting block 422. An adjustment screw 432 i5 threadedly engaged with the depending lower portion 430 of the slide 428, and is rotatably engaged with the body 422. Thus, by turning the screw 432 ~he slide 428 is moved and the position of the styli 68 on the body can be adjusted.
Each of the three stylus heads is pivotably mounted on the rotor 28 by means of a support structure which is shown in Figures 14 and 19 and will be described in greater detail below.
Each stylus head 420 has an arm 434 secured to the body 422 extending in a direction perpendicular to the direction of extent of the styli 68. At the end of the arm 434 is an enlarged hollow portion 436 which is filled with lead or contain a heavy metal inserted 438. The insert 438 provides a relatively large mass for use in the centri-fugal extension of the styli into engagement with the recording paper 36.
Referring now to Figure 15, attached to each arm 434 is a tension spring 454 whose other end is attached to a pin 456 which entends parallel to the drive shaft 48.
The point o~ connection between the spring 457 and the arm 434 is between the block 422 andthe end 436 of the arm 434.
The foregoing structure operates to automatically retract the styli 68 away from the recording paper 36 when the speed of rotation of the rotor 28 drops below a pre-determined minimum speed, e.g. 500 revolutions per minute or so. The tension springs rotate the print heads 420 about their pivot axis, indicated at 452, in a clockwise direction. This moves the styli away from the 3~

paper 36.
When the rotor 28 starts rotating, certrifugal force acts on the heavy inserts 438 at the ends of the arms 434, applies tension to the springs, and rotates the arms 434 counter-clockwise. When the desired speed has been reached the styli 68 engage the surface of the recording paper 36.
A stop structure is provided so that an increase in rotational speed does not cause the styli 68 to press too hard against the paper 36. This stop structure consists of a cam 458 ~Figure 2) and a screw 460. The back edge of the body 422 of each print head engages th~ cam so as to stop the counter-clockwise rotation of the printhead due to centrifugal force and stabilize the positions of the styli 68 at the desixed location. This location can be varied by turning the screw 460.

. A.DJUSTMENT OF THE STYLI
The radial extent of the styli 68 can be adjusted, as it has been stated above, simply by turning the screw 432 in order to extend the styli radially outwardly or move them inwardly in ordex to adjust them, or in order to com-pensate for wear or dislocation of the initial positions of the styli.
Each of the stylus heads 420 also can be adjusted axially (in a direction parallel to the drive shaft 48) by means of the structure shown in detail in Figure 19, and also in Figure 14. An adjustment screw 412 is provided with its head on the outer surface of the rotor disc 28. The screw has a smooth shaft 446 which fits into and slides within a sleeve 448 which acts as a bearing, both for the shaft 446, and also for the inner surface of the block 422.
As it is shown in Figure 17, the block 422 is provided - 3~ -~0~ ;3~

with a large hold 442 into which the sleeve 448 fits,- and a small threaded hold 444 in a plate 440 (see Figure 18) attached to one side of the stylus head.
Referring again to Figure 19, the screw is held in place by means of a snap-ring 450 which fits into a groove in the end of the shaft 446. The shaft 446 has a threaded end 452 which fits into the threaded hole 444.
The adjustment of the head is made simply by inserting a screwdriver into the slot in the head 412 of the adjustment screw and turning it. This causes the distance between block 422 and disc 28 to change, thus providing axial alignment of each print head. This helps ensure that each of the characters in the printing produced by the printer will be properly spaced from the characters printed by each of the other stylus heads.
ROTOR MOUNTING AND DISMOUNTING
The rotor 28 is mounted on the sha't 48 by ; means of the structure shown in Figure 14. A hub 400 is provided. The rotor 28 is secured to the hub by means of four screws 402 (see Figure 16). Secured to the other end of the hub 400 is the slip-ring disc 104 which makes electrical contact with the electrical circuitry of the printer, in the manner described in greater detail above~
A stop member 108 is provided on the shaft.
The hub 400 has a central recess in which the pins 456 are located. These are the pins to which the springs 454 are attached.
Still referring to Figure 14, the hub 400 has a recess 457 in its rear portion into which is inserted a ccmpression spring 459. The compression spring bears against the stop member 108 and the hub 400 to thrust the rotor outwardly off of the shaft 48 and thus assist in removlng it.
Referring now to Figure 16, the rotor 28 is secured to the end of the drive shaft 48 by means of a latch mechanism. The latch mechanism includes a latch me~ber or plate 404 with two perpendicular end tabs 406 again~t which one can press in order to slide the member 404.
The member 404 is secured to the outer surface of the rotor 28 by means of a pair of rivets 410 which bear against the slide 404 in a pair of elongated slots. Bowed washers ~not shown) are positioned between the rivet neads and the slide in order to ensure a constant frictional engagement between the slide and the surface of the rotor, thus holding the slide in the position to which it is moved~
The slide 404 has a slot with an enlarged opening 408 whose diameter is slightly larger than the end of the dri~e shaft 48 n The drive shaft 48 has a circumferential groove 418 (see Figure 14) into which the edges of the slide 406 in the slot fits in order to grip the end of the shaft 48.
Thus, simply by sliding the slide 406 downwardly~
as shown in Figure 16, the slide will release its engagement "
with the end of the shaft so that the disc can be removed.
Then, the spring 459 pushes outwardly on the rotor and assists in removing it.
When replacing the rotor 28, the end of the shaft 48 is inserted through the hole 408, and the slide 404 is pushed upwardly to re-engage the slide with the end of the shaft and secure the rotor in place.

:~0~;3~

The above-described rotor mounting and stylus adjusting structure is highly advantageous. Whenever it is desired to remove the rotor from the printer, or whenever it is desired to start a new strip of recording paper through the printer, the styli 68 will not interfere because they are retracted and out of engagement with the recording paper. Furthermore, the printer reaches proper printing speed more qulckly because the friction of the styli against the paper is absent until the desired minimw~ operating speed has been reached.
The device provides means for axially adjusting the styli without removing the rotor from the printer.
This adjustment can be made simply by turning the screws 412 which are exposed at the open left end of the printer.
A simple mechanical means also is provided for adjusting the ef~ective length of the styli, simply by turning the screws 43~. This makes it easy to initially align the styli for producing printing which is properly aligned and easy to read. Two of the three photocells and the related electronic circuitry used in the embodiment de~crihed above in Figures 1-13 for circumferential adjust-ment and timing of the operation of the styli can be eliminated because of the provision of mechanical adjustment b~l the use of screws 432~
The rotor is made very easy to remove by the ; provision of the simple slide latch shown in Figure 16.
The ease of removal is augmented by the use of the spring 459.
The movement of the styli towards and away from the recording paper can be accomplished by other than centrifugal means, if desired. For example, the styli can be extended by solenoids actuated a certain length ~f time after rotation of the styli has started.
The same solenoids can be used to retract and hold the styli out of contact with the paper after the rotor has started decelerating or after it has come to a stop. rrhe solenoids can be actuated manually, if desired.
ALTERNATIVE PAPER GROUNDING STRUCTURE
Figure 14 also shows an alternative structure for grounding the recording paper 360 Instead of the curved spring structure 58 described above, the paper feed wheel 55 is made of metal (steel, e.g.), and is grounded by means of a brush 461. The brush 461 contacts the end of the axle 96 upon which wheel 56 is mounted. This structure provides an advantageous rolling ground contact to ground the recording paper. This eliminates the wear and friction caused by a sliding contact, and minimizes scratching of the paper.
Furthermore, making the wheel 56 of metal instead of rubber prevents the wheel 56 from becoming idented due to its pressing against the wheel 98 when at rest Ior a substantial time.
MATERIA~S AND spEcIFIcArIoNs Following are specifications for some of tha materials and components of a printer which has been con-structed and successfully tested in accordance with thepresent inventicn.
Suitable recording paper is readily available.
Suitable paper~, coated with a black opaque material and then coated with eithex aluminum or zinc oxide, have been obtained from Fitchberg C~P.I., Scranton, Pennsylvania, and from Atlan-Tol Industries. The preferred paper has a total thickness of 0.002 inch. The aluminum-coated paper - ~0 9~ 6~

is desirable because it often requires lower stylus voltages in order to vaporize the aluminum coating to expose the black material underneath.
Styli which have been used successfully have a diameter of 0.007 inch, and are spaced approximately 0.016 inch from one another, center-line to center-line. The desired spacing of the dots on the paper is approximately 0.016 inch, both in the horizontal and in the vertical direction. It should be noted, howe~er, that sometimes there is a small ~ertical extension of the dots due to the rotation of the rotor. When printing characters, this sometimes improves the printing in that it tends to fuse the dots together into solid vertical lines.
The material of the styli is thoriated tungsten.
The most desired range of angles between the styli and the platen is 60 to 70 (see Figure 6).
It is preferred that as much of the body of the printer as possible be molded out of plastic in order to achieve low cost and light weightO Thus, although the main drive ~haft 48 is made of metal, the housing 24 and many other parts are molded out of reinforced plastic material such as glass fiber-filled polystyrene, which has good strength and wear properties.
The platen 26 preferably is molded out of glass fiber-filled "SAN" ~styrene-acrylonytrile polymer), or out of glass fiber-illed "Lexan" polycarbonate plastic material or nylon. A platen made of S~N and 30~ short (e.g., less than 1~32" long) glass fiber has been found to have excellent characteristics, in that it is elec$rically non-conductive, and yet does not wear away significantly under the erosion of the styli, despite the fact that they are made~of a very hard metal.
A D. C. motor which has been found to be suit-able for driving the printer is manufactured by Barber-Coleman Co., part number FYOM-63200-51. It has a diameter of 1.26 inches and a length of 1.95 inches. Its operating voltage is 12 volts D.C. and has a torque output of 1 ounce-inch at 4400 R.P.M. and 1.3 Amperes.
The optical sensors 146 used to sense the marks 13 on the timing disc 54 are made by Optron Corporation. The sensor is called an "optical switch", part number OBP800.
Also suitable is a similar device made by Spectronic, Part No. PNSPX 1872-s. The sensor has been modified simply hy adding a mask as described above in the specification.
The code used to encode characters is the well-known code called "ASCII II". This is advantageous since code converters for use with such a code are readily available.
In the electrical control circuit of Figure 9, certain of the components will be identified specifically below. The components are readily available from several different sources unless it is indicated otherwise.

COMPONENT IDENTIFICATION
Rom Code Converter 202 2512 "Character Generator" -Manufactured by Signetics CorpO operates on ASCII II
code.

Shift registers in Memory Intergrated circuit shift 200 and Shift Register 232 xegistered 2529, with data recirculation feature.

"Flip-Flops" 236, 251, 254, 74LS integrated circuit D
258 type (flip-flops) bi-stable multivibrators.

"Flip-Flops" 300, 302, 304 74LS73 J-K type integrated and 306 circuit (flip-flops) bi-stable I multivibxators.
Multiplexer 2S2 Integrated circuit multi-plexer type 74153.
Row counter 262 Integrated circuit 4 bit-counter connected as a divide-by-16 circuit.
Margin space counter 246 74LS90 integrated circuit counter connected as a divide-by-2 circuit.
Line counter 278 74LS190 integrated circuit counter with 74SL74 flip-flop connected at the input as a divide-by-2 circuit.
Gate 270 Number 7427 inte~rated circuit plus NOR gate.
Integrator 310 A741 operational differential amplifer with capacity feed-back.
One-shot tachometer 308 An integrated ci cuit 74LS121 one-shot multivibra~or.
AND gates 272 Integrated circuit No7403 NA~D gates 25 Gates 222, 282, 294, 290 Integrated circuit 74LS08 AND
yates.
Counter 288 Two 74LS193 integrated circuit counters connected as a divide-by 117 circuit.
30 OR ~ates 218, 219 and 220 74LS02 integrated circuit NOR gates.

The above description of the invention is intended ~` to be illustrative and not limiting. Various changes or modifications in the embodiments described may occur to those skilled in the art and these can be made without departing from the spirit or scope o the invention.

.

Claims (20)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a rotary electrical printer including a rotor, means for rotating said rotor, at least one group of styli secured to said rotor, feed means for moving sheet recording material past said rotor in a direction transverse to the direction of rotation of said rotor with said styli contacting said sheet, said group including a plurality of axially-spaced styli, and control means for selectively energizing said styli to cause each stylus to form a dot on said sheet at a selected location and thereby form images from transverse rows and circumferential columns of such dots, the styli in said group being positioned closely adjacent to one another so as to be capable of forming a group of continuous columns of dots during a single pass of said styli over said recor-ding sheet.

2. A device as in claim l which prints characters by forming them from dots, there being, in said group the same number of styli as required to form all of the dots in one of the horizontal and vertical portions of each of said characters so that one pass of a head over said sheet will be capable of producing at least one printed character.

3. A device as in either of claims 1 and 2 in which alphabetic characters are printed to form words, said sheet being electro-sensitive paper having the form of an elon-gated strip, said feed means being adapted to move said strip longitudinally past said rotor, there being a plural-ity of said groups of styli on said rotor, said styli being spaced apart by the desired distance between dots in the printed characters, said control means including means for causing said words to be formed longitudinally on said strip.

4. A device as in claim 2 in which said electrical con-trol means includes data storage means for storing text data in full page form, with information describing successive lines of text matter, and means for reading out said data in the order in which the characters will appear in succes-sive columns of the printed text.

5. A device as in claim 4 in which said data storage means includes means for selectively recirculating and re-storing data read out from said memory so as to provide duplicates of printed messages.

6. A device as in claim 3 including data storage and control means for storing and controlling the printing of text matter in a single line, said data storage means in-cluding a FIFO memory.

7. A device as in claim 1 including position indicating means bearing indicia for rotating with said rotor and pro-ducing electrical position signals corresponding to positions of said rotor at which dots are to be printed, said control means being responsive to said electrical signals for energizing said styli.

8. A device as in claim 7 including styli control means for changing the position of the printing produced by at least one of said styli, said control means comprising means for changing the time separation between successive actuations of said styli.

9. A device as in claim 7 in which said device includes a plurality of said groups of styli spaced angularly on said rotor, said position indicating means includes a plurality of stationary indicia detectors near said indicia, said detectors being adapted to produce said position signals in response to detection of said indicia, said control means including means for adjusting the angular position of one of said detectors with respect to said rotor.

10. A printer as in any of claim 7 through 9 in which said position indicating means includes a disc with indicia comprising alternating opaque and transparent linear areas on said disc, the arcuate spacing between adjacent opaque areas being proportional to the desired spacing of the dots from one another, and a detector comprising a lamp and a photocell, said photocell being positioned to re-ceive light from said lamp modified by the linear areas on said disc.

11. A device as in any of claims 7 through 9 for printing characters and words in lines, spacing means for setting the spacing between characters in successive positions traversed by said rotor, said spacing means comprising means for counting said position signals and disabling said styli from printing for a predetermined count.

12. A device as in any of claims 7 through 9 including means for moving a record surface across said rotor trans-versely to the plane of rotation of said rotor and in a position to contact said styli for printing, means for causing the printing of characters on said sheet so as to form words extending in the direction of travel of said record surface, and means for causing the spacing between adjacent characters to be determined by the spacing between successive passes of said styli across said sheet.

13. A device as in any of claims 7 through 9 including drive motor means for moving said recording sheet over said rotor, means for driving said rotor for a predetermined distance while disabling said styli to provide a starting margin for the images to be printed on said sheet.

14. A printer as in claim 1 including discharge means for applying an electrical voltage to each of said styli and creating an electrical discharge between each stylus and said sheet to create said dot, means for detecting the speed of movement of said rotor relative to said sheet, and means for varying the voltage applied to each stylus approximately in direct proportion to said speed.

15. A method for the electrical printing of alphanumeric characters by recording dots on recording material, said method comprising rotating a rotor bearing a plurality of axially spaced styli so as to move said styli across a curved sheet of said recording material wrapped at least part-way around said rotor, providing indicia for indicating the positions of said rotor, detecting said indicia with at least one detector which produces electrical position-indicating pulses, energizing said styli selectively with said pulses to produce images on said recording material, and including the step of making the number of said styli equal to the number needed to form the dots in a row or column of dots forming a character so that each group of styli forms at least one character per pass over said recording material.

16. A method as in claim 15 in which there are a plur-ality of angularly spaced groups of said styli on said rotor and including the step of starting and stopping the actuation of said styli in timed sequence by the use of electrical actuation signals, and adjusting the timing between successive actuation signals to align the images produced by the styli on said paper.

17. A method as in claim 16 in which said detecting step is performed by a plurality of stationary detectors spaced angularly from one another, there being one such detector for every angular stylus position, said adjusting step comprising moving at least one of said detectors re-lative to another.

18. A method as in claim 15 including the step of storing in an electrical memory coded character information in a format in which columns of vertically aligned characters are stored in sequence, and reading out said information in the same sequence so that each stylus group prints a column of characters during each pass over said recording medium.

19. A method as in claim 18 including the step of re-storing the information in said memory and reading it out again to make duplicate copies of the text.

20. A method as in any of claims 15 through 17 in which said recording material is in strip form, the width of said strip being less than the circumferential distance on said rotor between adjacent styli, and including the step of enabling all of said styli simultaneously, but causing only the styli in contact with said paper to produce printing.