Note: Descriptions are shown in the official language in which they were submitted.
8484
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 ~odern data-processing equipment
has increased, so has the need for a high-speed, low-cost
data printer. Very high-speed data printers have been
developed. However, such printers usually are very com-
plex and expensive. Much cheaper 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 object 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,
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 direction of rotation
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3.~ 8~
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 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, 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 surface 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 members. 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 rotor.
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32-643
4 ~ ~
It is prcferred that the ch~racters be fornled into
~ords which extend longitudinally of the record strip, and
that the strip be wide enough to accommodate a number of lines
of text matter to be printed. CGded 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 ~ertical columns, the characters in each col~n being located
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 ~hich rotate with the rotor
and which are spaced apart by the desired spacing between dots
in the printed images. Preferably, the indicia are o?aque lines
on a transparent clisc mounted on the same shaft as the rotor.
A plurality of detectors is provided for detecting
the indicia. It is desired that the number of detectors equal
the nu~ber 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
-
of the three stylus heads without actually moving any of
the heads. This permits adjustment of character aligilment
to compensate for uneven stylus wear and similar problems,
without any mechanical adjustmert 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 wnich 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 compactly 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 higsh torque at low speeds, is relatively 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 curved guide fits over the housing to guide
the paper into a cylindrical sleeve which is used as a
platen which supports the recording paper, and upon which
the styli. ride when not contacting the paper. 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
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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 the paper roll. This prevents
jamming and bunching of the paper.
Especially simple means are provided for
electrically connecting the conductive portion of the paper
to the return connection of the voltage supply; that is,
electrical grounding means. This should be provided in
1~ 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.
lS Because the speed of the paper feed, the timing
disc and the 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 of the printing is relatively
uniorm 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
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. . ..
caused to automatically engage the 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
thé 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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L
~1~8484
Figure 2 is a rear perspective view of the printer
shown in Figure 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 l through 5, and is partiaily
schematic;
Figure 8 is a set of waveform diagrams demonstrating
the operation of the timing disc and associated electronic
circuitry;
Figures 9 and lO 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 being
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 another embodiment of the printer of the
present invention;
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48~
Figure 15 is an elevation view, partly cross-
sectional, taken along line 15-15 of Figure 1~;
Figure 16 is another elevation view of the rotor
shown in Figures 14 and 15;
Figure 17 is a side elevation 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.
The printer 20 includes a base plate 22, a cylindrical housing
24, a cylindrical sleeve 26 which is 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 for rotating the rotor 28. A timing
disc 54 (Figure 2) for timing the printing also is mounted
on the shaft 48.
Electrical discharge-sensitive paper 36 is stored
in a roll 34 contained in a dispenser 32. The paper 36 passes
upwardly from theroll 34 over a straight guide bar 35 towards
a curved paper guide 38. The guide 38 is hinged to the 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
most inside surface. After the printing has been farmed on
the undersurface of the paper 36, the paper emerges from the
left edse of the sleeve 26 as shown in Figure 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. The rotor 28 has three stylus heads62, 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 stylus heads passes over the recording paper, it will
produce at least one printed character.
1~84~3~
It is preferred that the words be printed on the
strip as shown in Figure 3; that is, in the longitudinal
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 o a single stylus head; the column s 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 capabilities of the printer
when operating in such a mode are comparable with those in
the 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, both of which already have been described. The motor 30
is mounted on an end plate 70 for the housing 24 by means
Or 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 toothed wheel
52 which is secured to the shaft 48. The sizes of the
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.
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 128 are held against the retainer 108
by means of a threaded nut 114 which screws onto threads 49
(Figure 4) on the left end of the shaft 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 ~evel gear 94 on the shaft 96 which drives the paper
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.. .. . . . . . . . . . . .
feed roller 56 at a speed substantially slower than that
of the rotor 28.
The feed roller 56 mates with-an idler roller
98 which is mounted on a shaft 100 in the curved paper guide
38. A cover 102 fits over the idler roller 100 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.
PA~ER GROUNDING MEANS
Figure 10 shows schematically the eiectrical
circuit formed when a spark is formed between a stylus 68
and the paper 36. The conductive 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.
I This 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
is secured to the end plate 70 in the manner shown in Figure
4 and which is connected to gLound. The ends of the spring
58 are held in place by means of retaining rings 61.
As it is shown in Figure 5, the rod 60 curves
forwardly as well as into an arc so that it fits underneath
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84
the right edge of the cover 38. The upper portion of the coils
of the spring resiliently press a~ainst 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
undersurface 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 pass easily
through the guide 38.
PAPER 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
15 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 3~. Substantial
movement of the dispensing point is undesirable in that it
tendP 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.
: . . . ......................... .. . .... .. . . . ..
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111~48~
i
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 omitted.
As it can be seen in Figure 6, the points of
contact between the styli 68 and the circle 125 which represents
the 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 andthe 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.
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.
~18~8~
The lower twb-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 ~aper 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). The 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 single wide black line 168 applied to the disc. Ideally,
the three sensors A, B and C would be 120 apart from o~e
another, as are the three stylus heads 62, 64 and 66. However,
the construction of the housing 24 and the paper guide 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
circumferentially with respect to the disc 54 so as to adjust
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8~
'
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 ~astened 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 shown) comprising a small piece of film which is 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 54 has be~ 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 is pivotably
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.
34~
connected at 152 to a mounting bracket 150. The bracket
154 has a long arm with a longitudinal groove 156.
Still referring to Figures 4, 11 and 12, two
adjustment cam devices 158 and 160 are provided. Each has a
body which is fitted rotatably into a hole in the end 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 s 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. However, in general, each of the thin, closely-spaced
lines 166 times 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 of 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
left hand corner of Figure 9, and the styli 68 are shown in the
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1~848~
upper right-hand corner of the drawing. The slip-ring disc
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 Figure 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 (labelled groups 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 strip.
Of course, if the use of a wider strip is desired, then the
styli can be energized selectively 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 consisti'ng of six 480 bit shift-registers.
Connected to theoutput 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 203. The dot matrix signals are adapted to enable
selected ones of the five styli which are in contact with the
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.. . .
~8~8~
th~ paper strip to be energized so as to form one row of
dots in a particular character to be printed.
The codeconverter 202 is addressed by means of
three input leads 264,266 and 268 in order to produce on
the output lines 203 successively the 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 forty
characters long. By the addition of more shift registers,
the storage capacity of the memory 200 can be increased. With
a paper strip width of four inches and characters approximately
3/16th inch high, and with minimum spacing between lines, up
to t~enty-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 storage capacity to the memory.
In fact, if the characters are prinied in a single line, and
if a "FIFO" 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 providea for
reading and writing to and from the memory 200. 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 delivered to one input of
a gate 218. During data entry, a D-type flip-flop 236
. . . ' . . - .. , . ' :'.
3484
(lower left-hand corner o 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 AND 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 iine 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
230 to the clock inputof 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 of
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 is 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.
- 20 -
, . , ,, . . .,, ., . , ., , .............. ~. - : ........ ..
.. . . . . . . . . . . . ..
84
The change of flip-flop 236 to the "set"
condition enables gate 219 and thus makes it 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 that data no longer can be written into the memory
from the input lines 204.
SETTING THE EN~ MARGIN 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 permits the printer
to start printing in order to provide a definite unprinted
margin on the paper between the matter to be printed and
the c7~t end of the paper strip.
COLUMN SYNC SIGNAL GEME~ATION
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, Band C shown in Figure 9 may be ampllfiers
and Schmitt trigger circuits for the amplification and
wave-shaplng 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 counter. These sisnals are developed in t~le
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 both flip-flops 300 and 302 receive the B sensor
signal on thier "clear" leads.
.. ,, . ., ., . , ., . ...... , . . . -. . ......... , . .. . ~ , .
j - : ~ 21 - ~ - -
.'' . - ' ,
~118~L8~
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-transistor,
S 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 flip-flops 302
and 300 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 sensorC,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
166, 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 marks 166 is 224.1
away, and there still are several marks 166 left to pass
through sensor C. iThus, the counter counts up to two before
the wide pulse 168iends and the counter again is cleared.
This produces 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.
After the wide pulse passes sensor B, but before
the thin lines reach sensor B, the counter remains cleared,
and no "column sync" signal is produced. After the thin
.. . . . . . . . . . . . .
.
~18~8~
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
S "column sync" signal. As a result, the "column sync"
signal is produced 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 sync"
signals 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 start 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 another D-type flip-flop
251 which changes state and develops a signal on its Q
output 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 fro~
the A sensor through to the clock input of the flip-flop 254.
Thus, the first of the pulses developed by the thin lines
- 23 -
, . . . . .. . . . ~ . .... . . . . . . . .
,' . , . . , , '
~1~8484
166 on thè 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 A sensor also time the later operation of the flip-
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 anotherNANDgate 260 whose other input also
is high due to being connected to the Q output of another
D 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 ROM 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 of its inputs are in the same state.
One of the inp~ts of each of the gates 272 is
connected t~ the outpu- -~f a three-input positive NAND gate
270. The output of gate 270 enables each cf 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-flop 254 is "set" in order to
enable printing. Lead 276 is connected to one output
terminal 284 of a multiplexer circuit 282 (in the lower
right hand portion of Figure 9) which, as it will be
,, , , . , . , , . ~ . . . . .
. . .. . . . , . . . . . :
34
explained further below, always receives the pulses
produced by the thin lines 166 in the sensors A, B and C.
'~hus, 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 printed.
Since there are seven dots verti~ally 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 264 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 two has been selected
by connecting line 257 to line 264, on the ninth count by
- 25 -
,: ., ,, ,,, ,. ,. , ,, . , .... .. .. , ..... ~, . ...... - . . .
. . . , . - . .. . , . . ~ .. . . ~ ~ .. ... .
8~8~
the row counter 262, line 264 goes high, and this sets
flip-flop 258. 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 222 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 200 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
20 277 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 263, and the printing
of the next character in the column is started. The next
character is 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 of characters has been completed.
- 26 -
, ~,,, . ... . . ,.. , ... , ., - - ~ ., - ,. .. . ..... . ... .. . . ....
.
8~8~
LINE COUNTER
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 of 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 ihe flip-
flop 254 now is cleared. This disables the printer until
it is time to start the next vertical column of characters
when the next print head is in position to start printing.
DOT TIMING
The dot timing circuit 210 includes, in addition
20 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 describes the operation of the multiplexer:
- 27 -
.
,, . . . . - . . .. . . . .
TRUTH TABLE F~R MULTIPLEXER 282
291 292 284 286 Function Permitted
(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 counter 214 includes a pair of
J-K type flip-flops 304 and 306. When the first pulse
from the divide-by-117 counter 288 changes the state of
flip-flop 304, this changes the data at the output lines
284 and 286 in accordance 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 way, first the A signals then the B signals and
then the C signals are delivered to the circuit to control
the printing.
Referring now to Figure 8, the "column sync"
signal occurs at time to~ and the sensor timing signals
start shortly thereafter, at time tl. Referring now
particularly to the "B" sensor waveform in Figure 8, it
can be seen that the B sensor starts producing timing
pulses at time t2. 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 the print-enable flip-flop 254. When the
counter 288 has counted 117 pulses (one-third of the 351
pulses produced by the thin mark.s 166 on the disc)
. . . - - 28 -
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 of 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 enabled to start printing at t7, until the line
counter stops the printing at t8. men the column sync pulse
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 memory 200 has been read out;and printed.
During the readout of information from the me~lory
200, the shift register 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 p~ovided
which delivers a pulse over line 234 to return flip-flop
236 to its initial state, de-energize the motor drive
circuit 208, and stop the motor. This same circuit also
resets any of the shift registers or flip-flops which have
- 29 -
. .
, . . - . .... , , . : ............ . ., . . - -, . .
.. . .
~1848~
.
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 printin~
job 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 connected
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
desired.
AUTOMATIC BLACKNESS CONTROL CIRCUlT
In accordance with another feature of the
invention an automatic blackness control circuit 215 is
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
the inputs of the amplifiers 314 in order to increase
or decrease the voltage applied to the styli in accordance
with the speed of the rotor.
Tne pulses delivered 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 tachometer 308 have constant widths, since
,, . . . , , , . "
- 30 -
.
84
their widths are determined only by the characteristics
of the multivibrator. However, since the time periods
between the pulses varies with the speed o~ the rotor,
the output of the inteigrator 310 varies in direct proportion
to the rotor speed. This increases or decreases the out-
put of the amplifier 312, and the 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 o~ [from] 500
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
characters 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.
- 31 -
. .
3L~ 18~8~
USES AND VARIATIONS
It is envisioned that the present invention 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 easily.
The printer of the present invention is so small (e.g. 4
inches by 4 inches by 8 inches or smaller) 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
discharge 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
.. ,. . . . . . : . . . ..
., .. .. , . . . . . . . ., . . . , ,~ , ......... : - , ,. ~ .- , , i
- . . . . ..
~8~84
of styli for each of the heads. In such an embodiment,
each of the push rods is actuated by 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 be
varied, as can the number of styli in each head. However,
the use of three print heads, with each printing one
column of characters 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 st~rting
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 he displaced longitudinally by a small
amount from the place where the first line starts. It
has been found, advantageously, that this slight amount
of skew usually is not objectionable in data printers,
and need not be compensated for. However, if it becomes
objectionable in a particular use ofthe 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 ~
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.
- 33 -
, ... . . , , . , . .. . . . . , ,. . . . -
. .- . - . , , , . ...... . . . .
--
` lli8~84
Although a mechanical system has been described
f~r 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 each of the heads so as to cause the
printing by that head to lead or lag the printing of the
others bya 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 lS, each stylus head includes five
closely-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
- 34 -
,. . . .. . . . . ; . . . ~ , . . .. . ..
3484
an L-shapedslide member 428. Member 428 slides in a
groove in a mounting block 42 . An adjustment screw 432
is threadedly engaged with the depending lower portion
430 of the slide 42~, and is rotatably engaged with the
body 422. Thus, by turning the screw 432 the 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 therotor 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 of 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 42(~ about their pivot axis, indicated at 452, in a
clockwise direction. This moves the styli away from the
,, . . . . . . . .
., .: . . . - . . . :........ . ...... .,, .... .. . . , ., .. ... .. , . . . - . . ..
- 35 -
_ _ . __ _
8~34
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 tothe 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 bacX edge
of the body 422 of each print head engages the 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 desired location. This location can be
varied by turning the screw 460.
ADJUSTMENT OF THE STYLI
The radial extent of the styli 68 can be adjllsted,
as it has.~een stated above, simply by turning the screw
432 in order to 2xtend the styli radially outwardly or move
them inwardly in order to adjust them, or in order to com-
pensate for wear or dislo ation 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 surfac~ 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
.. ~ ;. . . . . . . .- . .
.. , ~ .. . .. ., , , , . . . . . . , .. . ., . , . ~ . . . .. . . .... . ... ..
~- 36 -
., , , . . . . . . . .. . , . . . . ,. -- .
- 111848~
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
~rinted by each of the other stylus heads.
ROTOR MOUNTING AND DISMOUNTING
Th~ ro~or 28 is mounted on the sha't 48 by
.. . .
means of the'';'r~cture 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
20 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
30 against the stop member 108 and the hub 400 to thrust the
'_ 37 ~
.. . . . . . ...
. : .. . . .
8413~
rotor outwardly off of the shaft 48 and thus assist in
removing 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
member or plate 404 with two perpendicular end tabs 406
against 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
drive shaft 48. 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
2~ 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.
- 38 -
. .
., . .. , .. ,. , ,~ , . , .. , , . . , . ., ~. . .... . .. ..
. .
~1~8~
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 quickly because the friction of the
styli against the paper is absent until the desired
minimum operating speed has been reached.
The device provides means for axially adjusting
the styli without removing the rotor fromthe 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 ~ffective length of the styli~ simply by
turning the scr~ws 432. 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 elec Y~onic circuitry used in the embodiment
described above ,~ 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~ 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 ~59.
The movement of the styli towards and away from
the recording paper can be accomplished by other
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, ~ . .,, . ,. . ..,." ... , ,. . ,... ...,., , , .. .., . ..~, . - ,.. ...
.,,, ,. ,. - . ... .. . .
111848~
~ ~~ than centrifugal means, if desired. For example, the
styli can be extended by solenoids actuated a certain
length of 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 36. 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
15 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 ror a
substantial time.
MATERIALS AND SPECIFICATIONS
.
Following are specifications for some of the
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 papers, coated with a black opaque material and
then coated with either 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 thick~ess of 0.002 inch. The aluminum-coated paper
.. . . . . . . . . . .......... ~ . . . . ...
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.
8~8~
is desirable because it often requires lower stylus
voltages in order to vapori~e 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, however, that sometimes
there is a small vertical 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 weight. Thus, although
the main drive shaft 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-filled "Lexan" polycarbonate plastic
material or nylon. A platen made of SAN and 30~ short
(e.g., less than 1/32" long) glass fiber has been found to
have excellent characteristics, in that it is electrically
non~conductive, and yet does not wear away significantly
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.. ..
~118~84
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
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 by
adding a mask as described above in the specification.
The code used to encode characters is the well-
known code called "ASCIT 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
Corp. operates on ASCII II
code.
Shift registers in ~emory Intergrated circuit shift
200 and Shift Register 232 registered 2529, with data
recirculation feature.
"Flip-Flops" 236, 251, 254, 74LS integrated circuit D
258 type (flip-flops) bi-stable
multivibrators.
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1~1t34~
"Flip-Flops" 300, 302, 304 74LS73 J-K type integrated
and 306 circuit (flip-flops) bi-stable
multivibrators.
Multiplexer 282 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 integrated
circuit plus NOR gate.
Integrator 310 A741 operational differential
amplifer with capacity feed-
back.
One-shot tachometer 308 An integrated circuit 74LS121
one-shot multivibrator.
AND gates 272 Integrated circuit No7403
NAND gates
Gates 222, 282, 294, 290 Integrated circuit 74LS08 AND
gates.
Counter 288 ~~ Two 74LS193 integrated
circuit counters connected
as a divide-by 117 circuit.
OR Gates 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 ma~ occur to
those skilled in the art and these can be made without
departing from the spirit or scope of the invention.
This application is a division of Canadian
Application Serial No. 260,724, filed September 8, 1976.
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