Note: Descriptions are shown in the official language in which they were submitted.
` 104~3Q4
This applica-tlon is a div. of Cdn. S.N. 269,017, filed
December 31, 1976, ~hich is a div. o Cdn. S.N. 197,007, filed
April 8, 1974.
The present invention relates generally to systems for
providing a visual and a corresponding magnetically encoded record
of data and more particularly~ a system wherein the recorded data
is stored on a single medium in both visual and magnetic modes with
fixed positional correlation therebetween.
Prior art systems of the type presently under
consideration typically employ permanent magnets mounted on type
bars of a typewriter, the permanent magnets being located either
within or below the print font. In these systems, the magnetic
data is recorded coincidentally as visual data is typed on an
opaque paper sheet having a magnetic backing thereon or impregnated
~ with magnetic material. When a key of the typewriter is struck,
by an operator's finger, permanent magnets are translated into ~ -
contact with, or in close proximity to, the magnetic portion of
the sheet thereby generating magnetic flux on the surface of the
sheet being imprinted. Paper thickness and magnetic character-
istics prevent effective recording through a paper sheet to a
magnetic backing record with permanent magnets that strike the
sheet from the paper or front side~ Hence, those systems wherein
magnetic data is recorded by relying upon magnetic flux being
transmitted through a sheet of paper to a magnetic backing are
most likely not sufficient to enable detection of the magnetically
recorded data without appreciable error. While errors may not be
introduced~by recording on a sheet of paper having magnetic
material, such as ferroma~netic particles, impregnated therein,
such a sheet generally takes on the dark hue of the black
particles embedded therein making it difficult to discern the
data visually recorded th~reon. Also, erasure of typed material
from paper having magnetic material embedded therein is impractical
because of adverse effects on the appearance of the printed
material on the sheet and irregularities likely to be introdued by
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erasing on the magnetic surface. Such irre~ularities ma~ cau~e
problems in correctly detecting recorded ma~netic ~lux during
read-back.
Another disadvantage of systems wherein permanent magnets
are carried on the faces of type bars is t~at codes for space,
tab or carriage return functions cannot be included wlthout pro-
viding special type bars on the typewriter. Without tab or
carriage return codes being introduced onto the magnetic medium,
the time required for reading out information from the magnetic
record is considerably increased over the time required for
records that carry such information. If no space code is provided
on the recording medium, it is essent;al that the medium carry
some suitable type of timing or synchronizing tracks, in which
case the recorded data cannot be considered as self-clocking or
self-synchronized.
Another disadvantage of systems employing permanent
magnets on type bar faces is that the magnet flux level decreases
in response to each mechanical strike against a platen. Even-
tually, the magnetic flux level in the magnets could quite
conceivably be reduced to a point where sufficient magnetic flux
is not recorded on the magnetic medium and accuratereproduction
of data during read-back does not occur. While magnets may be
recharged through the utilization of special equipment, the
recharging operation is a costly and time-consuming operation.
In addition, an operator is not usually apprised as to when
recharging is necessary.
In certain prior art systems permanent magnets are
carried within the character head itself. These systems, in
addition to suffering from the previously discussed disadvantages,
are likely to have the character head structure so weakened
15~4~)304
mechanically that a head might be broken after little use.
Another disadvantage attendant with systems wherein magnets are
mounted on the head is that small characters, sucH as commas and
periods, cannot carr~ the magnets because there i~ not enough
surface area on the character head for more that one magnet.
In consequence, a character such as a period or comma that is
always located in the lower center portion of the key face cannot
be distinguished if a permanent magnet is embedded in the
character itself.
Systems wherein permanent magnets are placed beneath
the print character head are beset by additional problems. In
general, only upper case print fonts can be utilized ~n such
systems because the lower case character is usually replaced with
a magnet structure. While some systems proposed have both upper
and lower case fonts, with two magnets extending below the
characters, it is believed that these systems are not practical
because different typewriters have different sized platens and
platens frequently become so out-of-round after any extended
period of use. The problems of platen size and out-of-roundness
are also prevalent-with the systems wherein a magnet replaces a
lower case character because the magnet and the upper case character
must both simultaneously strike a rounded portion of the platen.
Another problem associated with having a magnet below
the print character is that the magnetically recorded data may
not properly be written onto the magnetic medium at the bottom of
the page. As is well known, typing personnel frequently are not
aware of the fact that they are typing on the last line of a
sheet of paper, or type below a point where the paper stays
horizontally aligned with the result that magnetically recorded
data below the line becomes difficult to detect accurately.
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11~)4~304
The possibility of incomplete erasures of erroneous magnetic
bits is also likely in these systems.
In a second class of prior art systems, electric signals
are generated in response to the activation of each key on a
typewriter keyboard, with different codes representing each
key. In response to the electric signals, different discrete
areas or spots on a magnetic recording member are magnetized at
a plurality of horizontal and vertical matrix positions having a
total area equal approximately to the area required for a
character. Because a plurality of horizontal parallel lines are
utilized to represent each character magnetically, a single head
is not feasible for reading back all of the data associated with
a particular character. Moreover, because the number of
magnetic spots recorded for each character is variable and the
spots are at different positions, the record formed with these
systems is not self-clocking and hence synchronizing tracks
must be provided.
In addition to the aforementioned problems, this system
; typically suffers from a lack of complete keyboard encoding
functions, such as spacing, carriage return, shifting between
upper and lower case and character deletion.
The aforementioned disadvantages of known prior art
systems are essentially overcome by the system of the invention
disclosed. The instant system utilizes a single, flexible re-
cording medium, to record in the visually readable and magnetic
modes. More specifically, the medium is constituted of a paper
sheet of suitable color, such as white, having a portion of one
surface covered with a thin, ferromagnetic film or strip. In
response to each key activation of an encoding typewritter, bi-
polarity magnetic data bits are applied to discrete surfaceareas of the magnetic film. The magnetic data representative of
1'~J4~)3~4
each character i9 applied to the magnetic film by mean8 of a
coreless magnetic re~ordin~ he~d ~ormed of a plurality of
conductors. Each conductor is selectively pulsed by a current
in accordance with a code representative of the selected and
depressed key. In one particular embodiment, eight bits.Are
recorded for each character of functional operation ~e.g., space
bar activation). Included are shift key and parity bits,
whereby both lower and upper case characters may be inscribed on
and read from the record and self-clocking can be realized. By
applying bi-polarity data to the magnetic record the.same number
of bits is recorded for each charactex~ By applying this data
to the record serially,monotracks of data are obtained which
represent serial character and functional key selection and
acti~ations, and therefore the record is completely self-clocking
and no synchronizing track is required.
The magnetic recording head is positioned above and ~ .
behind the location where a type bar comes into contact with a -
sheet on the platen and the conductor of the recording head are ~ :
preferably in direct contact with the surface of the magnetizable
film to achieve optimum flux-coupling between current-carrying
conductors of this head and the magnetic recording medium. By
positioning the recording head above the point where the type
bar contacts the sheet the problem of run-off of data magnetically
recorded at the bottom of the page is obviated. The problem of
run-off at the top of the sheet normally does not arise because - .
an operator normally allo~s enough spacing or heading at the top
of each page to permit contact between the recording head and the
magnetizable film. --
A magnetic recording head constructed in accordance .
with the present invention comprises a plurality of conductors,
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having extremely small cross-sectional areas, positioned to con-
tact the magnetic recording medium. In a typical recording head,
36 conductors are provided, with eight of the conductors supplying
flux to the record and the remaining conductors serving as spacers
between the flux-supplying conductors. In one embodiment, the
conductors comprise a plurality of single turn wires, whereas in
a second embodiment the conductors take the form of extremely thin
strips. In both embodiments, the several conductors have parallel
longitudinal displaced axes. The conductors are topologically
arranged so that the magnetic flux recorded thereby never exceeds
the space required for the largest character typed by non-propor-
tional typewriters.
To enable sufficient bi-polarity magnetic flux to be
imparted by the conductors to the magnetic medium, the conductors
are pulsed with currents having an extremely large peak amplitude
and a short enough duration to prevent the conductors from being
destroyed. We have found that current pulses having approximately
20 amperes peak value and 30 microsecond duration impart sufficient
flux to the record to enable accurate results to be attained.
The circuit utilized for generating these pulses comprises essen-
tially a capacitor and a switch, such as a silicon-controlled
rectifier. Charge stored on the capacitor is dumped throu~h the
silicon-controlled rectifier when a gate electrode of the rectifier
is activated.
It is,--accordingly, an object of the present invention
to provide a new and improved medium embodying human readable
alphanumeric and magnetic data in fixed relative positional
relationships and a system for encoding such data on the medium.
A further object of the present invention is to provide
a new and improved medium carrying human readable and magnetically
recorded data, wherein the magnetically recorded data are self-
clocking, and a system for recording such data on the medium.
~4~3~)4
An additional object of the invention is to provide a
system for typing human readable visual characters and for record-
ing magnetic data on a paper sheet having a magnetic backing,
wherein magnetic flux is applied directly to the backing without
being transmitted through the paper.
A further object of the invention is to provide a sheet
carrying human readable and magnetic data in single spaced line
relationship of upper and lower case alphanumeric characters, and
to a system for recording same.
1~Although the invention disclosed has various novel
aspects, the invention of particular note in this divisional ;
application comprehends in one broad aspect a recording head for
recording and erasing magnetic data on a magnetizable medium which
comprises a support of electrical insulating material, magnetic
erase means including a plurality of interconnected, electrically
conductive segments having erase surfaces thereof positioned in
alignment on the support for receiving an electrical erase signal,
and magnetic recording means comprising a plurality of spaced,
individual recording conductors mounted intermediate different
pairs of the segments for individually receiving coded electrical
recording signals. Preferably, a multiplicity of the recording ~ ;
conductors are mounted on the head, and the magnetic erase surfaces
space the recording conductors substantially equal distances apart.
In prior art systems for recording visual and magnetic
data in a prescribed, fixed positional relationship wherein
erasing is proposed, selectively erasing magnetically recorded
. . .
":.: ' . .
1041)304
data from the record is accomplished by saturating the magnetic
medium. In accordance with a preferred disclosed aspect of the
present system, erasing of the medium is accomplished by degaus-
sing. In degaussing, the magnetic flux of the erased area is
reduced below a detectable level for read-back purposes. This
is accomplished by feeding a multiplicity of low duty cycle bi-
polarity pulses to the record head. The first pulse in the multi-
plicity has a relatively high amplitude and succeeding pulses
decrease successively in amplitude. In this manner the magnetic
flux level on the area of the magnetic record beneath the head
is successively reduced, eventually to a level where the read
circuit cannot discern a polarized magnetic bit in the area
of erasure.
In accordance with the erasing apparatus utilized in the
present invention, all of the conductors in the head assembly
are connected to be responsive to the erasing pulses. Thus, if
perfect alignment between the paper and the write head is not
maintained, as is likely to occur when a sheet is removed from
a typewriter and then re-inserted, previously recorded bits for
a particular character are usually erased.
The above and still further aspects, features and
advantages of the present invention will become apparent upon
consideration of the following detailed description of several
specific embodiments thereof, especially when taken in conjunc-
tion with the accompanying drawings, wherein:
Figure 1 is a perspective view illustrating the position
of the recording head of the present invention relative to a
platen and sheet of paper on which human readable and magnetic
data are written, the upper left hand portion of the sheet
being folded to depict magnetic bits applied thereto by
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1~4~304
the recording head in direct correspondence to the characters
typed on the ~ront o~ tHe paper sheet.
Figure 2 is a cross-sectional view taken along lines
2-2 of Fig. 1 of the composite sheet o~ paper and a ~lexible
magnetizable ~acking integral therewith, and additionally depicts
typical electrical current wave~orms ~or writing bipolarity
magnetic bits onto the magnetizable backing.
Figure 3 is a cross-sectional view of the composite
paper sheet and magnetizable backing taken along the direction
of recording and additionally depicts voltage waveforms derived
when the flux pa~terns from ~he backing are read.
Figure 4 is a perspective view, in combination with
a circuit block diagram, of one embodiment of a typewriter-
encoder constructed in accordance with the present invention
Figure 5 is a sectional view taken through the lines
5-5, Fig. 4, showing the relationship between the magnetic
recording head of the present invention in combination with other
parts of the typewriter mechanism, appearing with Fig. 1.
Figure 6 is an enlarged, perspective view of a
portion of a recording head frame and flux-producing windings
constructed in accordance with the present invention. ~-
Figure 7 is a perspective view illustrating a system
for vacuum drawing the magnetizable backin~ into contact with
the windings of the recording head.
Figure 8 is a perspective view of a modification of a
magnetic recording head wherein thin, metal strips are utilized
as recording conductors.
Figure 8A illustrates a typical arrangement of the
interconnected metal strips to provide a recording section for
the recording head.
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Figure 9 is a perspective view illustrating a magnetic
recording head of the type illustrated by Fig. 7 utilized in
con~uction with a conventional typewrIter having a ball-type
printing element.
Figure 10 illustrates a system ~or magnetically erasing
discrete areas immediately preceding or ~ollowing a discrete
area on which amagnetic recording is to be made.
Figure 11 illustrates a system for supplying recording
current to the recordi~g head and for manually initiating magnetic
erasure of discrete magnetizable areas immediately prior to
recording on such areas.
Figure 12 illustrates a system for automatically
initiating magnetic erasure of discrete magnetizable areas
immediately prior to recording on such areas.
Figure 13 is one embodiment of a circuit diagram for
producing and supplying recording currents to the recording
head to produce magnetic bits on the magnetizable backing.
Figure 14 is a schematic diagram of a source of erase
currents for the systems of Fig. 10-12, inclusive.
Figure 15 is a perspective view of one embodiment of
a reading apparatus constructed in accordanc~ with the present
invention.
Figure 16 is a sectional view taken along lines 16-16
of Fig. 15, illustrating the apparatus for maintaining a sheet
in situ on the read head of Fig. 15.
Figure 17 is an enlarged view of mechanism for indexing
the read head from line-to-line in the embodiment of Fig. 15; and
Figure 18 is a block diagram of circuitry for reading
or printing out information recei~ed and decoded from the
reading apparatus of Fig. 15.
104~)304
THE VISUAL AND MAGNETIC R$CORDING MEDIUM
se~ore proceedi~n~ wi~tH tne det~led descr;ption o~
the apparatus of the present invention, a typical illustration
of the data recorded by this apparatus may be had by reference
to Figs. 1 and 2. In these f~gures, there is illu~trated a
sheet of conventional bond paper 21 hav~n~ a thickness on the
order of 2 to 3 mils and a flexible backing sheet, coating,
film or layer 22 composed of a highly magnetizable material,
such a~ Fe2O3 or Fe3O4, upon which magnetic data bits can be
recorded and stored. The layer 22 typically has a thicknes~
on the order of 0.5 mil, and may be applied to the entire surface
of one side of the pap~r sheet 21 by conventional methods.
Printed on paper sheet 21 are conventionaltypewritten
alphanumerlc characters, Fig. 1, each of which requires essentially
the same discrete surface area. Typical conventional type-
writers are designed to print ten characters per inch with each -~
line spaced approximately 0.16 inch apart. On this exemplary
basis, each discrete area alloted to, and occupied by, an~ -
,, ~ ,, ,~ . .
~; ~ alphanumeric character has a width dimension of approximately
20 100 mils and a height dimension of approximately 160 mils. Both
upper and lower case letters of a complete fifty-key typewriter
keyboard can be printed on sheet 21 in single spaced line
relationship, if desired. Human readable characters on the same
line can be imprinted in succession and adjacent to each other
on sheet 21, as in accordance with printing normally associated
with and obtainable from a conventional typewriter.
As may be seen from Fig. 1, in vertical alignment with
each alphanumeric character printed on sheet 21, there is a
particular combination of eight bits of bipolarity magnetic data
properly coded to repre~ent any single key on the typewriter
keyboard. The data bits are depicted as short vertical lines
which to~ether form a single track of magnetic bits on layer 22.
- . .- ..:, . : - . . .
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1~)4~304
An exemplary combination of eight bits is illustr~ted in Fiy. 1,
The area encompassing the eight bits is approximately the same
width as a typewritten character. Similarly, since these eight
bits are the binary-coded representation of one particular
character the height of each of the eight bits is approximately
the same as that of the character. Each group of eight bits is
recorded simultaneously (or in situ) on the magnetic layer 22
in response to a corresponding key actuation at a position
slightly above the corresponding key characterization, whereby
a prescribed, fixed or one-to-one positional relationship is
provided, between a generated character line and a corresponding
multibit magnetic-data track comprised of a succession of
eight-bit groups. Hence, in Fig. 1 in the word "HEADING" the
letter "A" is typewritten on a line at a position immediately
below that whereexemplary magnetic bits corresponding thereto
are recorded, but the relative positions of the recorded visible
and magnetic data along the width dimension of the sheet are
aligned.
Therefore, the horizontal rows of alphanumeric data
are parallel to, but offset a fixed distance from, the rows of
single tracks of magnetic data on the magnetizable side of the
recording medium. Each alphanumeric character is also in a
prescribed vertical relationship (typically aligned) with each
group of eight magnetic bits which are uniquely coded to represent
that particular character.
The eight bits of recorded data representing one typed
character are illustrated in Figure 2 as oval lines carrying
arrow heads indicating the polarity of the magnetism of the
particular recorded bit; the bit polarity is also indicated by
the relative positions of the magnetic north and south poles, N
and S, on the leftand right sides of the associated oval lines.
Hence, magnetic l bits are represented by these mutually
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~04~3V4
tangential oval lines havin~ arrowheads point~n~ in the clockwise
direction, as well as N and S on the left and right sldes thereof.
Magnetic O ~its are of the oppos~te magneti~c polar~ty and are
represented by two mutually tangential oval lines having arrow
heads pointing in the counterclockwise direction, as well as by
magnetic poles S and N on the left and right sides, respectively,
of the associated oval lines. The first six magnetic bits of
each eight bit group, Fig. 2, indicate which key on the
typewriter keyboard is depressed while the seventh b~t indicates
if the shift lever is depressed while the character is recorded
(upper or lower case character~. The last or eighth bit is
used as a parity bit for error checking.
The parity check employed is such that an odd number
of 1 and 0 bits is derived for each character. To illustrate,
for lower case letter "a", the first six bits may be 101001 ~ ;
while the seventh bit is a 1 bit to indicate that the shift
lever was not activated and the eighth bit is also a 1 bit to
provide the desired parity check. Upper case letter "A" would
have the same first six bits as "a", namely lOlOQl, but the
seventh bit is recorded as a 0 bit to indicate that the shaft
key was activated on the keyboard and the last bit is recorded
as 0 bit to provide the required odd parity check.
MAGNETIC RECORDING - GENRRAL
The eight magnetic bits for each key are created
simultaneously on layer 22 by applying a corresponding number of
rapidly changing electrical currents to the alloted area on the
layer. Each magnetic bit so formed includes a north pole N and
a south ~ole S laterally spaced from each other by a relatively
small distance with the orientation~ of the poles along the
width dimen~ion of the paper indicating the code of the recorded
character. Each magnetic bit center i8 spaced from an adjacent
bit center a distance sufficient to provide adequate separation
,~ .
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.... . .
.. . .
1046~3~4
between ad~acent magnetized areas to obtain a sufficiently
well-defined voltage waveform to satisfy the particular system
readback requirements. A single track of magnetic bit groups
is formed on layer 22 in positional correspondence with a line
of characters on sheet 21. As a result, a self-synchronized
reading apparatus may be employed to readout the magnetic record.
~ ith reference to Figs. 4-7 of the drawings, there is
illustrated one embodiment of the instant recording apparatus
for simultaneously writing a human readable and a magnetic
record on the sheet 21 and the layer 22, respectively. The
apparatus, Fig. 4, comprises a conventional electric typewriter
26 with a full fifty-key keyboard having upper and lower case
characters, as well as a backspace key 27, a spec;al erase
key 28 for erasing magnetic data, a space bar 29, a carriage
return key 30, and a shift key 31.
Erase key 28, space bar 29, carriage return key 30 and
shift key 31 all have permanent magnets 32 fixedly mounted on
lower extensions thereof. Each of the magnets is movable past
an associated reed switch 35 upon depression of its associated
key or bar; the reed-like contacts of each switch closing in
response to the movement of a magnet therepast.
Electrical signals produced upon reed switch closure
indicate which of the erase key 28, space bar 29, carriage
return key 30 or the shift key 31 has been depressed by the
typist. In addition to the special signals derived in response
to depression of keys 28, 30 and 31 and bar 29, a signal is
similarly derived upon depression of any of the remaining keys
on the typewriter keyboard.
In addition to these signals, all signals produced in
response to the depression o~ the remaining keys on keyboard,
other than erase key 28, and the shift key 31 and fed to a diode
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1()4V3~)4
coding matrix designated generally by numeral 36 via a multi-
lead cable 37. The electr~cal signals ~ed to the matrix are
obtained from closures of individual switches, thé state of
which, as mentioned above, are under the control of magnets
associated with individual keys on the keyboard. Assuming that
the remaining keys total ~ifty, there will be fifty additional
switches and fifty additional connecting leads. Matrix 36 is
constructed so that if any one of the fifty leads is connected
to ground in response to closure of an associated switch by
activation of a selected key on the keyboard, eight predeter- ~ -
mined binary electrical signals are simultaneously produced on
eight conductors leading out of the matrix. The first six bits
indicate which key of the keyboard has-been depressed, the
seventh bit indicates whether the shift key 31 has been depressed
and the eighth bit is employed as a parity check. Special
codes are associated with spacer bar 29 and carriage return key
30, whereby the binary bit combination for these keys is
different from that of any other keys, while preserving the
parity check. To preserve the parity check for upper case
characters, diode coding matrix 36 includes means for inverting
the parity bit for each character ~n response to activation of
shift key 31, as well as means for generating a 0 bit as the
seventh bit if the shift key 31 is activated. The eight
predetermined signals obtained from the output of the diode
coding matrix 36 are applied to the recording circuit 39. High
amplitude current pulses generated at 39 pass thru the normally
closed relay contacts of a switching circuit 38 to recording head
41, fixedly mounted above a platen 42 in typically horizontal
alignment with a type guide 43.
With reference to Figs. 1, 5 and 6, a magnetic recording
head 41 is fixedly mounted to an arm 45 havln~ an enlarged inner
end 46 fixedly mounted on a hollow shaft 47 which in turn is
mounted integral with the frame of the typewriter. With the
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104~3~)4
head 41 fixedly positioned centr~lly o~ the typewriter rame in
typical alignment with the type guide 43. The shaft 47, which
carries the arm 45 and ~ead 41, IS typically on the order o~
three times the length of the platen 42 in order to permit the
recording of magnetic characters at either edge of the medium
21,22. Signals from switch 38 are coupled to head 41 ~y conductors
sheathed in a cable 48 and inserted into the sha~t 4 7 and emerging
from the interior of the shaft and the arm 45 ~y way of a bore
46A extending transversely through a portion of the arm and the
shaft. Each of the conductors forming cable 48 is connected to
one terminal pin of a standard multiterminal connector plug 60,
which is manually insertable into connector receptacle 59 of
head 41, as indicated by Figs. 1 and 5.
MA(~IETIC RECORDING - DETAILS OF :EæCORDING HEAD ~.
With general reference to ~g. 6, thè head 41 is -
characterizable as a coreless magnetic head having three sections
A,B and C; each equal in width, and typically 100 mils wide, with
each section performing a different function determined ~y a
selected mode of typewriter operation. The first section designa-
ted A, comprises a plurality of turns, typically 52, of a single,
continuous conductor having two end leads 49A and 49B, respectively,
which are energized when it is required to erase (by degaussing)
a pre~iously recorded character. During an erase mode, in section
B, between sections A and C, a discrete magnetizable area of the
backing 22 is erased before a recording is made thereon, thereby
ensuring a greater accuracy and integrity to recording.To this end,
fringe areas at both ends of record section B' are degaussed by
appropriately energiz~ng spaced windin~s separating section B'
from sectionq A and C, re8pectively. Similarly, section A
during the erase mode era~es the discrete record area and adjacent
fringe areas of a previously recorded character. The
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104!~)304
deguassing of fringe areas also reduces the possibility of
nonerased, previously recorded magnet~c bits remaining on a
reinserted, slightly misaligned paper 21 in the typewriter. In
section C, adjoining section B, an area is similarly erased while
a preceding character is recorded in section B'. Section C is
formed by a plurality of turns of a single, continuous conductor
having lead ends 51A and 51B, respectively.
Typically, each conductor is constituted by a copper
wire having a diameter of 1.75 mils coated with an electrical
insulating layer of polyurethane of 0.1 mil thickness. Each
conductor is wound evenly around a mandrel-like portion 58 of
the head frame 41'so that an elongated section of each
convolution is in physical contact with the layer 22. ~ecause
each section of conductor is coated with insulation, short
circuiting is prevented between mutually ad~acent conductors.
Parts of the recording head 41 other than the conductors wound
,
upon the portion 58, are preferably composed of a suitable
insulating material, such as a polymer~c or epoxy resin. ~-
For each magnetic bit recorded on the backing 22, only
every fifth winding or turn of section B (Fig. 6~ is energized and
:
the remaining four windings or turns for that bit are utilized as
spacers between the energized windings. Eight single conductors
~; are interleaved between certain juxtaposed but spaced-apart
oonvolutions of the continuous winding on the mandrel 58. Each
such recording conductor forms less than a complete turn on the
mandrel and typically has a portion of length suitably affixed
to only the top, bottom and front surfaces of the mandrel as
~iewed in Fig. 6. Also, each recording conductor is separated
by four spaced turns which are merely spacers, and are not
supplied with signals. In Fig. 6,numerals 53-1 and 53-2 designate
the recording windings for the first and second bits a~ a character,
:
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104~3Q4
respectively, and the spacer turns are designated 54. The
seventh and eighth record windings are designated 53-7 and
53-8, respectively. of course, it is to be understood that the
dimensions illustrated in Fig. 6 are greatly exaggerated and
that the total lateral distance between record winding 53-1 for
the first bit of a chara,cter and record winding 53-8 for the last
~eighth)bit of that character is typically on the order of 68
mils. In the manner described for spacing windings 53-1 and
53-2 for recording the first and second bits, four spacer
conductors are utilized to maintain precise separation between
each of the six remaining record wind;ngs 53-3. . .53-8 from one
another. Thus, section A is defined by the windings connected
to leads 49A and 49B, section B is defined by the windings
connect,ed to leads 50A and 60B, said section C is defined by
the windings connected to leads 51A and 51B, with leads 49B,
50A and 50B, 51A, respectively, being commonly connected at
single terminals. Leads 49B, 50A and 50B, 51A extend from a
continuous winding, as disclosed above, and recording lead
pairs 53-lA, 53-lB,..53-8A, 53-8B, extend from less than single
complete turns of corresponding recording windings 53-1. . .53-8.
I,t may be noted that no magnetic core material is
employed in the head 41 and that turns having insulation thereon
are utilized as spacers between adjacent recording turns.
Sufficient magnetic flux is applied by windings 53-1, 53-2...53-8
,to magnetic backing 22 by pulsing these turns with high intensity
currents and by allowing these turns to contact the backing 22.
As described, infra, ciruitry is provided to pulse windings 53-1,
53-2...53-8 with currents having peak magnitudes on the order of
20 amperes for approximately 10 microseconds. Such currents
create enough flux around the windings to appropriately change the
magnetic state of a defined, adjacent area of the layer 22. The
extremely large amplitude currents do not overheat the conductors
to thepoint to rupture because of the extremely short time
duration of these pulses.
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1~46~304 .
OTHER EMB~pIMENT~ OF THE ~ECORDING HEAD
Section B of the head 41 may be modi~fi~ed such that two
separate adjacent windings are utilized for recording each ~it.
In such a configuration, the current flow~ng through a first one
of the two windings is in a direction opposite to the current
flowing through the second one of the'two windings for the same
bit, whereby the first winding is switched to a first current
source when the particular bit is a binary 1 and the second
winding is switched to a second current source when a binary O is
to be recorded. As in the case of the Fi~. 6 embodiment, the
recording windings for each bit are separated by four spacer
windings to provide the desired fringe spacings on either side of
each magnetic area commensurate with the area required for a
character.
Fig. 7 illustrates another embodiment of a recording
head, designated 41, wherein contact between backing 22 and a
surface 58' of the head 41 is maintained by a plural;ty of
apertures 89 extending perpendicular to the surface of the head
that contacts backing 22. Apertures 89 are'formed in the head
41 during the manufacture thereof and commun~cate w~th'a common
bore~90 connected to a suitable source of fluid pressure, such as
a vacuumpump (not shown). The pump applies a subatmospheric
pressure of approximately 13 pounds per square inch to the backing
22 by way of the aperture 89, this vacuumbeing sufficient to
maintain the record medium in firm contact with the recording
windings 53-1...53-8, and is controlled by a solenoid valve 91-1,
Fig. 1, installed in tube 91. Alternately, an above atmospheric
pressure applied via tube 90, may be controlled by an in-line
solenoid valve installed in the tube 91.
According to still another embodiment of the invention,
the longitudinal axes of erase and recording windings are mutually
-20-
'
1~4~3Q4
orthogonal, that is, positioned at right angles to each other.
In such case the erase windings are located one character
position on either side of the intermediate sect~on B of Fig. 6
to enable erasing prior to recording or in response to depression
of say a backspace key. Thus, the two erase windings would be
positioned orthogonal to-the windings depicted in sections A and
C, respectively, in Fig. 6.
Another embodiment of the invention would place all of
the record and erase conductors mutually parallel to each other
and spaced one character apart with their respective longitudinal
axes aligned. Thus, the two erase windings and record windings
would be positioned orthogonal to the windings depicted in
sections A, C and B, respectively of Fig. 6.
A further embodiment would place the reaord conductors
orthogonal to the erase conductors and one character apart from
one another. Thus, the record windings would be orthogonal to the
record winding depicted in section B of Fig. 6.
The windings of the head 41 may be made in the form of
thin, flat conductive strips ~Fig. 8 and 8A) having a dimension Y
perpendicular to the plane of the backing 22 substantially~ greater
than dimension X. Dimension X is proportioned to give a current
density that is nearly equal to its counterpart wire conductor
of Fig. 6.
All other factors being equal, the substantially greater
amount of metal available in the strip-like windings provides a
somewhat longer lifetime of wear of the recording windings. Fig.
8 illustrates one set of identical spacer strips 95-1, 95-2 corre-
sponding to two of the spacer windings 54 in section B of Fig. 6
of the recording head prior to connection in electrical series.
-30 The strip designated 96 depicts a recording strip ~correspo~di~
to one of the recording windings 53-1...53-~ of Fig. 6. Numeral
-21-
.
~04Q304
97 designates a strip corresponding to the first winding of the
head to which the lead 49A is joined, Fig. 6. The strips 98-1 and
98-N illustrate representative erase strips in section A of the
recording head.
Fig. 8A depicts a typical electrical series connection
of the various spacer strips 95 to each other and to an adjacent
strip 98-N as well as a series connection of the terminal strip
97 to a juxtaposed erase s'rip 98-l. The strip 98-l is electrically
connected to the strip 97 which receives erase current pulses via
10 the lead 49A. The edges and sides of the various strips may be
coated with a layer of a suitable electrical insulating material
to prevent short circuits therebetween. The material may be a
suitable epoxy compound which adheres to all surfaces of the
strips except the forwardmost edge of each strip leg which contacts
the backing 22. It will be noted that in order to interleave the
recording strip 96 between t~o other strips such .-s the strips
95-1 and g8-~, the two parallel legs of each strip are bent in
opposite directions out of the strip plane, Fig. 8 and passed
between the bifurcated arms of the strip 96. A physical and
20 electrical connection is then made between the respective down-
wardly and upwardly extending end portions of the strips 95-l
and 98-N. Connections are similarly effected between all
juxtaposed strips save the strips utilized for recording, such
as the strip 96.
MAGNETIC Fd~:CORDING - DETAILS OF TYPEWRITER MECHANISM
To ensure that the record windings designated 53-l,
53-2...53-8 are in virtual contact with the magnetic surface of
the layer 22 Fig. 5, the head 41 is placed directly above platen
30 42 and is contoured along the lower surface to conform closely
with the cylindrical portion of platen 42 immediately above the
point where type bar 25 strikes the sheet 21.
_22--
104~3U4
To maintain the layer 22 in contact with conductors
53-1...53-8, platen 61 is mounted on c~rriage assembly 50
approx~mately dIrectly a~ove platen 42 and has its longitudinal
axis extending parallel to the longitudinal axis of the lower
platen. Platens 42 and 61 carr~ radially-pro~ecting pins 62 ~or
engaging pinholes 63 located a ~ixed distance inwardly o~ the
margins of sheet 21 to prov~de a positive pin feed for the paper
sheet and to maintain the sheet in horizontal alignment.
Referring to Figs. 4 and 5, the magnetizable backing 22
is pressed into firm contact with the conductors 53-1.~.53-8 by
a transparent hold-down plate 64 spanning opposed columns of pins
62~ Pins 65 mounted stationary on carriage assembly 50 hinge the
upper right-hand end of the plate 64, as viewed in Fig. 5, for
pivotal movement thereon. The lo~er left end of the plate 64
includes pins 66 that selectively engage bores, not shown in
abutment 67 ~hat is also fixedly mounted to carriage assembly
50. Hold-down plate 64 has a section of enlarged width at the
lower end thereof for forcing the backing 22 into good electrical
contact with the conductors 53-1...53-8 of head 41.
Proper registry is maintained despite rubbing between
both face8 of the sheet 21 and backing 22 by the clamping action
of elongated spring clips 68. Clips 68 are connected at each
end of plate 64 so that a longitudinal slot 69 formed in the
clips 68 accommodates the pins 62 of platen 61 as the pins rotate.
me ends of clips 68, Fig. 5, remote from the hinge pin 65, are
connected to the plate 64 and are configured to extend parallel
to the semicircular upper portion of the plate 64 to enable the
sheet 21 to issue freely from under upper platen 61. Platens 42
and 61 are rotated together in synchronism by a belt drive 70
so that pins 62 positively eng,age and drive the paper sheet 21
and the backing 22.
-23-
;
.
104~3~4
MAGNETIC RECORDING-
GEN~:RAL DESC~IPTION OF RECORDING OPERATION
The magnetic bits are recorded on the magnetic backing 22
simultaneously as a corresponding character is typed onto the
sheet 21. A typical recording is initiated by an operator
depressing a selected character key on the key~7oard Fig. 4 where-
upon the corresponding type bar is driven by conventional means to
rotate about a pivot in the usual manner. A cohventional single
type bar and cam drive therefor is depicted by Fig. 12 and referred
10 to generally by the numeral 80. The wiper 81 affixed near the
pivot end of the type bar sweeps past a contact 84 to close a
normally open switch or switches. When the corresponding switch
closes, ground potential is applied to the conductor connected
to one side of the switch and included among the conductors
grouped in the cable 37. In response to the grounding of this
particular conductor, diode coding matrix 36 generates eight
binary signals in parallel on its eight output conductors.
These elght signals are fed through switch 38 to recording circuit
39, Fig. 13, and to conductors 53-1...53-8, inclusive, Fig. 6.
Each of conductors 53-1.. 53-8 receives, by way of its associated
leads and terminal connections to the block 59, a differen~t
predetermined, uni~ue binary signal with the binary 1 signals
flowing through the conductors in one direction and the binar~ 0
signals flowing through the conductors in an opposite direction.
The contact 84, Fig. 12 may be a multiple contact device coded
to perform the function of the diode coding matrix 36, Fig. 4.
Switch contact 83 is used when it is desired to generate an
erase signal prior to recording.
The binary 1 and O currents flowing in conductors
53-1.. 53-8, inclusive, cause magnetic fl~lxes of opposite
directions to be generated, dependent upon the polarity of the
currents applied to the respective leads and windings. For
example, if it is assumed that the current pulses applied to
--24--
104~304
the first two windin~s 53-] and 53-2 are ~9 indicated by the
waveforms o~ Fig. 2, a binary l posltive current ~lows throu~h
winding 53-1, whereupon a clockwi~se flux is induced by that winding
in the region surrounding it. Simultaneously a binary 0 negative
current flows through winding 53-2 whereupon a counterclockwise
flux is induced in the area surrounding the winding. In response
to the clockwise and counterclockwise fluxes derived from conductors
53-1 and 53-2 the surface areas of backing 22 directly in contact
with these conductors are magnetized in oppos~te directions,
typically across a 3 mil width o~ the backing 22. With adjacent
conductors 53-1 and 53-2 sufficiently separated from each other
by, for example, 10 mils, the centers of the flux concentrations
resulting from current flows through these conductors, are like-
wise separated by 10 mils. ~he fringing effects of the magnetic
flux may spread approximately 1.5 mils to either side of the
center of the win~ing, so that there is ~pproximately a 7 mil
gap between adjacent flux areas on the backing 22. The 7 mil
spacing between the extremities of the magnetic bits recorded on
the backing 22 is provided by the four spacing windings 54
interposed between adjacent recording windings 53-1 and 53-2.
Because of the spacing between ad;acent recorded bits, the
magnetic data storedon the backing 22 may be readily read out by
a conventional magnetic read head. The current pulses required
to drive the record windings are typically pulses having very
steep leading edges and slowly declining trailing edges.
Typically the pulses having a maximum amplitude on the order of
20amperes and drop to a value of less than one ampere in a time
interval of approximately 100 microseconds.
The entire operation described for recording magnetic
bits on the bac~.ing 22 occurs in less time than the interval
between activation of the type bar and release of platen 42 prior
-25-
~ 14q~304
~mechanisms on the typewriter. Switches 116 and 117, which may ~e
of the electronic type are illustrated as be~ng mechanical
switches for ease ~f explanati~on o~ operation, it being under-
stood that each key on the typewriter keyboard has a single switch
such as 116 or 117 associated with it. If the first bit in a
character being recorded is a 1 ~it, switch 117 is drlven from
its normally open state to a closed state upon pivoting of its
associated type bar mechanism, thereby placlng ground on one
coordinate of the diode matrix 36. This causes the matrix to
generate eight binary coded output~ulses which activate different
control devices in the stages 1...8 inclusive. The binary output
signals of the matrix 36 are uniquely coded to represent each
alphanumeric typewriter key. The stages 1...8, inclusive, thereby
convert the binary output of the matrix into corresponding
directionally-coded record~ng currents. Switch 116 remains open
during closure of switch 117 since its associated key is not
depressed during this typing interval. Switch 117 remains closed
until its associated type bar mechanism, in its return movement,
travels a predetermined distance from the paper or platen
whereupon the switch reopens. Thus, only one switch, such as
117 is closed at any one time.
Terminals 112 and 113 are connected through matrix
diodes 118-lM and ll9-lM, coupling diodes 118 and 119 as well as
resistors 120 and 121, to the gate electrodes of silicon-controlled
rectifiers 122 and 123, respectively. The gate electrode of
silicon-controlled rectifier ~SCR) 122 is connected to the
reference -6 volt potential at terminal 124 through a resistor
125. The gate electrode-of SCR 123 is connected to contact lOlB
at one side of winding 53-1 through a resistor 126. The other
contact lOlA formed on the other side of winding 53-1 is connected
to the reference voltage at terminal 124 through 0.2 ohm resistor
127, such resistor being utilized to monitor the current through
-27-
. . : . .
104~3~4
to the type bar striking it. ~t is i~,~ortant that the magnetiG
bîts ~e recorded on the backin~ 22 w~th'the pl~ten 42 statIonary
to maintain the recorded bits in alignment.
MAGNETIC RECOP~ING -'ALPHANUMERIC CHARACTERS
Reference is now made to Fig. 13 of the drawings wherein
there is illustrated a circuit diagram o~ an exemplary one of the
sources of recording currents illustrated in Fig. 12. Each source
delivers recording pulses having waveforms as described
hereinabove to a corresponding recording windings3-1,...53-8 and
comprises a low impedance switch through which the charge from
a previously charged capacitor is dumped into an associated
recording winding. The recording mode is initiated by the
operator depressing a selected one of the keys on the keyboard
shown in Fig. 4 which causes the associated key type bar to pivot
toward the platen. While so pivoting, the type bar mechanism
closes a switch associated therewith prior to impact of the type
bar with the paper or platen.
As mentioned hereinabove, eight individual recording
stages or circuits are provided, with each stage being fed a
properly coded signal obtained from the matrix 36 in response
to a switch closure caused by pivotal movement of the typè bar
mechanism. In turn, each stage generates a short duration,
high amplitude pulse for feeding one of windings 53-1...53-8.
The direction of the current pulse through any one winding is
dependent upon which of two circuit inputs is activated. Since
each stage is essentially identical to the other seven, a
description of only the stage for the winding 53-1 suffices.
This stage, referred to as block 1 in Fig. 13 ! includes
a pair of input terminals 112 and 113 which are selectively
connected to ground potential at terminals 114 and 115 by
operation of one of the switches 116 and 117 which are
respectively operatively associated with two different type bar
-26-
.. ..
~04~304
winding 53-1. Hence, when the system is in a quiesce~t condition
and switches 116 and 117 are both open, resistors 125 and 126
apply approximately a -6 volt D.C. potent~al to the gate electrodes
of SCRs 122 and 123, respectively, to maint~in these rectifiers
in a cut-off condition.
Under quiescent conditions, the anodes of silicon-
controlled rectifiers 122 and 123 are connected to a +B3 volt D.C.
supply at terminal 128 via the path through contact 129 of relay
130, and the parallel paths through hold-off diodes 132 and 133,
which are respectively connected in series with resistors 134 and
135. The cathode of silicon-controlled rectifier 122 is connected
to the -6 volt D.C. potential at terminal 124. Resistor 127 and
winding 53-1 have an extremely small series impedance and since
- there is no current flowing, except a small leakage current, there
is very little voltage drop, and therefore, the cathode electrode
of SCR 123 is also maintained at approximately -6 volts D.C. at
quiescence.
Bipolar high ampere pulses may also be fed through
winding 53-1. As illustrated, the anodes of SCRs 122 and 123
are respectively connected to one electrode of each of capacitors
137 and 138. The other electrode of capacitor 137 is connected
to contact lOlB, resistor 126 and the anode of SCR 123 while
capacitor 138 is connected directly to the -6 volt D.C. source
at terminal 124. Current derived from the initial charge on
capacitor 137 passes thru winding 53-1 w~th the current flowing
from left to right, Fig. 13, in response to SCR 122 being rendered
in a closed circuit condition while current ~lows in the opposite
direction through winding 53-1 in response to current derived from
capacitor 138 when the anode-cathode path of SCR 123 is closed.
Current flow from left to right typically corresponds to the
recording of a 0 bit whereas current flow from right to left
-28-
1~4~304
typically corresponds to the recording of a 1 ~it.
Normally closed contact ~rm 129 couples the positive
D.C. voltage at terminal 128 to capaci~ors 137 and 138 during
the interval when no key on the keyboard is activated~ Contact
arm 129 is open circuited during virtually the entire interval
when a key on keyboard is depressed in response to activation of
relay coil 130 whereby the current supplied by capacitors 137 and
138 to winding 53-1 is of predetermined duration. Relay coil
130 is connected in the collector circuit of NPN power transistor
139 and is shunted by reverse biased protecting diode 141. The
emitter of transistor 139 is connected directly to the negative
voltage at terminal 124. ~he base o~ transistor 139
is connected to the negative supply at terminal 124 through
resistor 142 and is connected to termLnals 112 and 113 through
isolating diodes 144 and 145 and matrix diodes 118-lM and 119-lM
respectively.
Under normal operating conditions,transistor 139 is
maintained in a non-conducting condition by the negat~ve voltage
applied to its base through resistor 142 thereby~ causing the base
and emitter to be at the same voltage level. With transistor
139 non-conducting, contact arm 129 is closed, whereby capacitors
137 and 138 are fully charged through components 132, 134 and
135 respectively to a potential of, for example, ~35 volts. The
charge is maintained on capacitors 137 and 138 under quiescent
conditions because the anode-cathode paths of SCRs 122 and 123 are
cut-off. In response to a depression of a key on the keyboard
one of switches 116 and 117 is closed to apply a forward bias to
the base of a power transistor 139. For~ard biasing transistor
139 causes relay 130 to be energize~,opening contact arm 129.
The triggering of eighth SCR 122 or 123, ho~ever, occurs
before the contact arm 129 opens because the response of the relay
-29-
104~)304
130 is substantially slower thc~n that of the SCRs . In response
to closing one of contacts 116 or 117, the char~e on one of the
capacitors 137 or 138 is immediately conducted through the
anode-cathode path of the SCR having its gate electrode connected
to the closed switch. Capacitors Cl and C2 are su~ficiently large,
having a magnitude of 12 microfarads, and t~e forward impedance of
SCRs 122 and 123, is low enough so that a current pulse having
the required amplitude and duration is produced. Because of the
extremely low impedance in the resistance-capacitance circuit
connecting winding 53-1 to the selected one of capac~tors 137 or
138, virturally all of the significant current flow occurs in the
winding within 30 microseconds.
Current will not flo~ through the winding 53-1 after
capacitor 137 or 138 is discharged and the circuit from terminal
128 has been opened. Similarly, the gated SCR 122 (or 123) is
cut off after the discharge of the capacitor connected to its
anode because of the open circuit condition of contact arm 129
preventing any current flow through components 132, 134 or 133,
135 respectively.
As mentioned hereinabove, each of the remaining seven
sources of recording currents is substantially the same as the
described source except that the other circuits do not have their
input terminals 112 and 113 connected to the base of transistor
139. It is necessary that only one of the driver circuits be
connected to selectively forward bias transistor 139 during the
period when the selected key is depressed.
MAGNETIC RECORDING--SPECIAL FUNCTIONS~: S~IFTING
The seventh and eighth stages differ slightly from the
remaining stages such difference resulting from a need to reverse
the polarity of the shi~t key and parity indicating magnetic bits
when shift key 31 (FIGURE 4) is depressed.
-30-
1~4~)3Q4
To record the operation of the shift key, the seventh
source o~ recording currents shown in Fig. 13 is utilized. This
stage includes a single lead 118A that is energized whenever any
of the alphanumeric keys on the key~oard are depressed lead 118A
of the seventh stage is normally coupled through a reed switch
contact arm 35-1 and resistor 121 to the gate electrode of SCR
123, whereby the winding 53-7 connected to the seventh stage
is supplied with current from capacitor 138 in response to each
key activation. When current is received from capacitor 138 it
represents the recording of a 1 bit. If the shift key 31 is
depressed to make a shift from the lower to the upper case, the
arm 35-1 changes state resulting from magnetization by the
permanent magnet 32 moving sufficiently close to reed switch 35.
During each shift period lead 118A is connected through
closed contact arm 35-1 and resistor 120 to the gate electrode of
~CR 122 of the seventh stage. Energization of the gate electrode
of SCR 122 results causing capacitor 137 to discharge current
through the winding 53-7 in the opposite direction, thereby
representing the recording of a 0 bit. Therefore, the direction
in which the winding 53-7 of the recording head is selectively
energized with bipolar currents indicating the status o~ shift
key 31 is accomplished without resorting tc complex circu;try.
Typically, a recorded 1 bit represents lower case and a recorded
0 bit represents the upper case.
MAGNETIC RECORDING--SE'ECIAL FUNCTIONS: PARITY CHECK
_ .
To provide reversal of the parity bit derived from the
eighth output lead of matrix 36, reed switch contact arms 35-2
and 35-3 are driven from the position shown to make with contact
terminals 146 and 147 in response to depression of shift key 31.
The arms 35-2 and 35-3 are similarly operated by the permanent
magnet 32 attached to the lower end of the stem joined to shift
key 31. The arms 35-2 and 35-3 are normally closed so that they
are respectively connected through resistors 120 and 121 to the
-31-
1~)40304
gate electrode of SCRs 122 and 123 o the eighth stage. In
response to activation o~ shi~t key~ 31, the positions o~ switch
arms 35-2 and 35-3 are translated to make with contacts 146 and
147 which are connected respectively through resistors 121 and 122
to the gate electrodes of SCRs 123 and 122. Thus, the parity
bit indicating signal, ge~erated by stage 8, is reversed whenever
the shift key 31 is depressed. Conseauently,parity is maintained
by the shi~t key control of both the seventh and eighth recording
stages.
MAGNETIC RECORDING--SPECIAL FUNCTIONS:_SPACING,
GE RETURN P.ND TABULATING
Depression of a keyboard key representing any other
special functions other than erasing, such as forward spacing,
carriage return or tabulating causes closure o~ an associated
reed switch contact and generation of a unique, corresponding
code by the matrix 36 in a manner similar to that described
hereinabove for alphanumeric character recording. That is,
the code generated by the matrix 36 is recorded on the backing 22
and utilized subsequently in readout. The back space function,
however, is not encoded on the backing 22~
In order to selectively inhibit an encoding operation,
inhibit or no-code key, designated NC in Fig. 4, is provided on
the typewriter keyboard and, when depressed, operates in
conjunction with circuitry illustrated by Fig. 13 to inhibit the
generation of recording signals. Preferably, the key NC is
translucent and includes a lamp L which is illuminated by a +28
volt source when the key is depressed. Moreover, the key ~C
preferably includes a conventional latch mechanism (not shown~
which latches up and keeps the NC circuit at essentially gr~und
potential until the key is again depressed, thereby eliminating
any requirement that the operator hold the key depressed during
-32-
~04(~304
the no-coding interval. The no-code key i9 typically utilized
to permit complete ~reedom o~ carrI~ge movement ~y operation o~
the spacing key without causing the encoding of a spacing function
on the backing 22 each time the spacer key is depressed.
As will be evident, provisions may also be made for
the performance of other special functions; the above examples
being principally illustrative of the recording capabilities
of the instant invention.
Figure 9 illustrates another embodiment of a recording
system wherein a conventional, rotatable ball-type printing head
90 is mechanically coupled to the magnetic recording head 41
through a cable 91. The coupling is by means of a system of
freely rotatable pulleys 92 and is such that the head 41 remains
directly opposite the head 90 at all positions of the head 90.
In certain conventional typewriters which utilize ball
or cylindrical printing heads to type characters onto paper
mediums, the logic utilized to effect the requisite incremental ;~
angular displacements of the head 90, whereby the selected
character is rotated opposite the paper immediately prior to the
imprinting thereof, typically provides representative coding
which may then be supplied directly to the diode matrix 36
for initiating operation of the aforedescribed encoding circuitry
associated with the head 41. Thus, in such systems the problem
of generating binary voltage pulses representing the selected
key on the keyboard is significantly reduced.
EMBODIMENTS OF THE MAGNETIC RECORDING CIRCUITS
There are two possible embodiments of the recording
circuits for the head îllustrated by Fig. 6. One embodiment is
depicted by Fig. 13 wherein the recording currents are supplied
directly and continuo~sl~ that is, without any means of
-33-
1~4~3Q4
interruption, to xeco~ding ~indings 53~1...53~8. Thus, for
wind~ng 53~1~ termInals 1~1~ and lOlB are cont~nuousl~ connected
to leads 53-lA and 53-lB, respectively, In this embodiment,
the windings 54, Fig. 6, in section B~ serve solely as spacers
for the recording windings and the leads 50A and 50B may be
open circuited or otherwise preclud~d from receiving current.
A second embodiment is dep~cted by Fig. 11 wherein the
recording currents, Fig. 13, are supplied by way of interruptable
circuits to the lead-ins o~ the recording windings. In this
embodiment, the spacer and record windings in section B may
also serve as erase windings. The means by which the former
windings are made to serve during an erase mode is described
hereinbelow.
MAGNETIC ERASE
Apparatus is provided for erasing the bits associated
with a character when the operator realizes that a mistake has
been made. When this occurs the operator backspaces carriage
assembly 50 of Fig. 4 by depressing the standard backspace key
27 until the character that needs correcting is centered between
the spaced-apart vertical guide bars of the type guide 43. After
the character in error and type guide 43 are aligned, the
operator depresses error correction erase key 28 which causes
a permanent magnet mounted on the key extension to sweep past
and close the associated reed switch in the process as indicated
in Fig. 14.
Generally summarized, in response to the closure of
this switch, erase control 71 derives a signal that is applied to
energize relays shown in Fig. 11, and then erase circuit 72.
The signal applied by erase control terminal T2, energizes relays
to connect in electrical series the terminals joined to the
leads 50A and 50B and the terminals joined to the recording
windings 53-1...53-8, inclusive, thereby connecting all
-34-
104~)304
windings in section B i~ electrical ser~es. Tnus~,current
supplied to a wind~ng in section B flows ~n the same d~rection
through all other windings in that section and hence any current
applied from terminal T3, to relay contact KlB flows the entire
width of a character space on the back~ng 22.
After relays Kl and K2 have been energized so that all
of the windings in section B are connected together in series,
erase circuit 72 responds to the energizing of relay 157 to
generate a plurality of short duty cycle current pulses having a
waveform similar to a damped sinusoid with a duration on the
order of 100 milliseconds. The current supplied by erase circuit
72 to switch 38 has a peak magnitude of approximately 20 amperes
and a duty cycle on the order of 0.1 to prevent overloading of
windings 53-1...53-8. ~ecause of the damped sinusoid waveform
of the pulses applied by erase ¢ircuit 72 through contacts of
relays Kl and K2 to the series-connected windings in Section B,
the magnetic flux is removed by degaussing from the area where
the character desired to be erased is located and the magnetic
flux is removed throughout the entire area of the character
sought to be erased because the windings in section B are all
connected series-aiding. Hence, if the printed character and
the magnetic data associated with it are not perfectly aligned -
with type guide 43, the magnetic bits representing the character
are nevertheless erased.
Magnetic erasures may be made on either side of a
character centered between the spaced, vertical bars of the type
guide 43, Fig. 4. As illustrated by the embodiment of Fig. 10, `'~
this is accomplished by connecting terminals T3 and T~ of a
source of erase currentc~ Fig. 14, either to the lead pair 49A,
49B or to the lead pair 51A, 51B. The selective connection of
the terminals T3 and T4 to either lead pair may be effected by
-35-
104~304
manual operation o a double thxo~double pole switch S~-l. In
this mode, the terminals Tl and T2 of Pig. 14 are only connected
as ~nd~cated by Fig. la~ The circuit arrangement i~llustrated by
Fig. 10 thereby provides one with a choice of erase modes, that
is, erasure either to the right or to the left of each recorded
character. The actual`e~asure (,by degaussing), may oacur when
the keyboard erase key 28, F~g. 14, is depressed or automatically
upon activation of each'type bar mechanism. The latter can be
accomplished by providing an extra set of contacts ~AE-l and
KAE-2 on the relay 130, Fig. 13, and having these contacts
connected in parallel with the contacts of switch 35, Fig. 14
with Tl connected to T2 as indicated in Figure 10.
Magnetic erasures may also be made immediately before
and in the area where a new character is to be encoded. Additional
modes of erasure may be accomplished manually by depressing the
keyboard erase key 28, Fig. 14, and/or automatically by utilizing
the movement of the type ~ar mechanism. The respective circuits
utilized to implement manual and/or automatic erasure of the
area on the backing 22 corresponding to the portion of the
recording medium centered between the bars of the type guide 43
is illustrated by Figs. 11 and 14 considered in conjuction with ''
each other and by Figs. 11, 12 and 14, similarly considered. ,~
Briefly summarized, the manual erasure mode contemplates
depression of keyboard erase key 28, Fig. 14, which then initiates
the application of erase current to the area on the backing 22
prior to recording on essentially that same area and therefore
is used mainly to make corrections of previously recorded data.
The automatic mode contemplates initiating the application of
the erase current to the specified area on the backing 22 upon,
normal operation of the keybar mechanism~ Since both modes require
an appropriate source of erase current, a suitable source
according to this invention is disclosed hereinbelow.
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.
104~304
EMBODIM~NT OF ERASE CURRENT SOURCE
Figure 14 Illustrates a deta~led schemat~c diagram o~
a circuit 72 for generating erase currents. Basically, circuit
72 produces a succession of relatively low-duty cycle, bipolarity
pulses, the amplitudes of which decrease with each succeeding
pulse. The first pulse produced has a peak current of 20 amperes
and the succeeding pulses decrease in amplitude by approximately
10 per cent, whereby the pulses have an envelope approximating
a damped sinusoid. Each pulse has a maximum duration on the
order of 100 microseconds with a duty cycle of approximately
10 per cent, whereby the pulse amplitude reaches a virtually
negligible value of about 1 milliampere within 100 microseconds
after the first pulse is initiated.
By creating pulses having initial amplitudes equal to
the amplitude of the recording pulses and successively reduced
amplitude levels to the head windings comprising series-connected `
windings 53-1...53-8, and series-connected erase winding from
50A to 50B, the flux level of the magnetic data in the area on
I backing 22 is finally reduced to a level less than one which can
be detected or read with read out circuitry and particularly
the read out circuitry disclosed subsequently. The successi~ely
decreasing amplitude erase pulses thru windings 53-1...53-8 and
series-connected erase winding 50A to 50B causes the area on
backing 22 to have reduced magnetism because the medium is
successively driven through smaller and smaller B-H curves, in a
manner well known to those in the magnetic recording art.
The circuit 72 comprises a conventional free-running
multivibrator 151 for alternately triggering the gate electrodes
of SC~s 152 and 153. SCRs 152 and 153 alternately ieed
bipolarity current pulses from capacitors 154 and 155, respect-
ively to series-connected windings of the head 41. The current
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pulses fed by SCRs 152 and 153 to the head windings decrease in
amplitude because the anode~cathode volta~e applied ~cross the
SCRs is reduced each time an SCR is triggered. Reduction of the
anode-cathode voltage of each SCR is accomplished, generally, by
connecting the anode-cathode circuit paths across a aapacitor
156 which is connected in a relatively long time-constant circuit.
Resistor 174-2 has a value of 0 to several ohms,
depending on the value of capacitors 154,155. To enable the first
positive erase pulse to be greater than the amplitude of the
first negative erase pulse, capacitor 155 has a larger value of
capacitance than capacitor 154 or alternatively, if capacitor
154 and 155 are of the same value then resistor 174-2 is used
- to decrease the amplitude of the negative erase pulse.
To trigger the normally inoperative multivibrator 151
into operation, a D.C. energizing potential for the multivibrator
is applied thereto by closure of normally-open contact 156 of
a relay 157. A relay with mercury wetted contacts is used for
the relay 157 to prevent contact bounce or chatter. The coil
of relay 157 is selectively energized through its connection of
Tl and T2 to the circuit shown in Fig. 11. As mentioned above,
a switch 35 is selectively closed in response to movement of
magnet 32 that is attached to an extension of erase key 28.
Hence, in response to depression of erase key 28, a circuit
is completed to energize the coil of relay 157 from the positive
voltage source +Bl to ground, to energize the relay coil and
close contact arm 156. To provide contact protection of the
contact arm 156, the arm is shunted by the series combination of
resistor 159 and capacitor 161.
In response to the application of +Bl to multivibrator
151, the multivibrator commences constant frequency oscillation.
The multivibrator comprises a pair of unijunction transistors 162
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and 163 that are connected in a conventional oscillating circuit
that need not be specifically~ descri~bed. The oscillating circuit
includes potentiometers 164 and 165 that are respecti~ely
connected t~ru resistors to the emitters o~ uni~unctions 162
and 163. The sliders of potentiometers 164 and 165 are adjusted
so that unijunction 163 always commences conducting prior to
unijunction 162. The values of the resistors and capacitors
connected to the emitters of unijunctions 162 and 163 are selected
so that a pulse is derived from each of the unijunctions once
approximately every 300 microseconds.
Bases 166 and 167 of unijunctions 162 and 163 are -
respectively connected through load resistor 168 and winding 169
to terminal 171 at a potential of, for example, -6 volt. The
voltages developed across resistor 168 and inductance 169 are
respectively applied to the gate electrodes of SCRs 152 and
153, whereby each of the SCRs is triggered into conductive
state as unijunctions 162 and 163 are rendered conductive. In
response to SCRs 152 and 153 conducting, the charge accumulated ~ -
- on capacitors 154 and 155, respectively, is discharged in
opposite directions through series-connected windings in the
head 41.
The voltage induced in winding 169 in response to
conduction of unijunction 163 is coupled to secondary winding 172,
that is shunted by oscillation-damping diode 173. One end of
winding 172 is connected to the cathode of SCR 153 while the
other end of the winding is connected through limiting resistor
174 to the SCR gate electrode. The voltage developed across
resistor 168 in response to conduction of unijunction 1~2 is
coupled to the gate electrode of SCR 152 via the current limiting
voltage divider comprising resistors 174~1 and 174~2.
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,' ,,'~, ' :
: ,. ,
~0403(~4
Connected in s~r~es wLth ca~acitors 154 and 155 are
relati~vely h~gh Q coi~ls 175 and 176, res~ect~vel~. One end o~
co~l 175 is connected to terminal T4 whi~le one end o~ coi~l 176
is connected to a slightly ne~ative voltage -B of, for example,
-6 volts at terminal 171 and through resistance 174-3 to the
terminal T3. Coils 175 and 176, togetner wIth capacitors 154
and 155, respectively, form low impedance series resonant circuits
which have a half cycle oscillation period on the order of 100
microseconds to reduce the anode voltage for SCRs 152 and 153
The SCRs are cut off in response to the oscillating voltage
derived from the series resonant circuit subsequently to their
activation in response to an output from oscillator 151.
The anode-cathode paths of SCRs 152 and 153 are
energized through isolating diodes 177 and 178, which are series-
connected respectively to current limiting resistors 179 and 180.
Power to diodes 177 and 178 and the anodes of SCRs 152 and 153
is derived from an approximately +130 volt supply connected to
terminal 182 through resistor 183 that has a relatively large
~alue, on the order of 5,000 ohms. Resistor 183, together with
capacitor 156, forms a relatively long-time constant c~rcuit.
In operation under quiescent conditions, capacitors 154
and 155 are charged to approximately the voltage between terminals
182 and 171, while capacitor 156 is charged to the slightly lower
voltage between terminal 182 and ground. Under quiescent
conditions, no voltage is applied to unijunctions 162 and 163,
whereby multivibrator 151 is not operating.
In response to depression of key 28, contact 156 is
closed, so that multiv~brator 151 commences operation. Unijunction
163 invariably is triggered into a conducting stage prior to
unijunction d~ode 162 because o~ the positions for the sliders
of potentiometers 164 and 165, whereby a current is fed to
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... .. . . . .
- , :. . .
- 104()304
winding 169. In response to current being fed through winding
169, a volta~e is induced ~n secondary 172 and coupled to the
gate electrode of SCR 153.
The voltage applied to the gate of SCR 153, drives the
SCR anode-cathode to its lo~ impedance state and the charge stored
on capacitor 155 is appli~d to terminal T4 and is discharged thru
windings 53-1...53-8 and series connected erase windings from 50A
to 50B. The current derived from capacitor 155 has a tendency
to oscillate because of its series connection with inductance
10 176. When the oscillating current reaches zero value, within ~
10 microseconds of the gate for SCR 153 being activated, the - -
anode-cathode path of SCR 153 is cut off.
Capacitor 156 now supplies additional charge to
capacitor 155, charging the latter capacitor to a voltage -~
approximately 20 per cent less than the voltage to which it was ~ ;~
previously charged. The reduced voltage occurs because the
capacitor 156 voltage decreases as it transfers charge to
capacitor 155. In response to the charge transfer from capacitor
156 to capacitor 155, the voltage across the former capacitor
is reduced. Even though capacitor 156 is connected to a
positive supply at $erminal 182, it cannot be recharged to its
former value prior to the next pulse from multivibrator 151
because of the relatively large t30 millisecond) time constant of
the circuit in which it is connected.
While current is being supplied by capacitor 155 to the
head windings, the resistance-capacitance time constant circuits
of multivibrator 151 are discharging and recharging, whereby
within 100 microseconds after SCR 153 is originally gated into
conduction, unijunction 162 is rendered in a conducting condition.
In response to unijunction 162 conducting, tHe gate electrode
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of SCR 152 is energized, establishing a ]ow impedance path
from capacitor 15A through terminal T3 and the head windings.
The current from capacitor 154 to the head windings
flows in a direction opposite to that ~rom capacitor 155,
where~y a second current pulse, of opposite direction to the
first pulse, is suppled through windings 53-1...53-8 and
series-connected erase windings from 50A to 50B. The second
current pulse has a lower amplitude than the first because
capacitor 154 has a lower capacity than capacitor 155 or
alternately due to resistor 174-2.
The resonant circuit comprising capacitor 154 and
inductor 175 is arranged so that a 10 microsecond pulse is
delivered to the head windings, i.e. the second pulse has the
same duraiion as the first pulse supplied to the windings by
capacitor 155. Thereby, the anode-cathode path of SCR 152 is
rendered in a nonconducting state after one-half cycle of the
high frequency current applied to it.
After the charge on capacitor 154 has been discharged
in the recording windings and SCR 152 has cut off, capacitor
154 is supplied with additional charge by capacitor 156. The
charge transferred from capacitor 156 to capacitor 154 is reduced ~ - -
over the charge formerly maintained across the capacitor, whereby
the current delivered to the windings by capacitor 154 and
SCR 152 in response to the next activation of unijunction 162
and multivibrator 151 has a peak value less than the current
supplied by the capacitor the first time the SCR was activated.
The decrease in current supplied by capacitors 154 and 155 is
approximately 10 per cent during each cycle, whereby the peak
amplitude of the current fed by capacitor 155 to the head
windings the first time that SCR 153 is activated is on the order
of 20 amperes while the peak current supplied by the capacitor
to the windings the second time that SCR 153 is triggered is
. ~
, -, , .
104~304
approximately 16.2 ampers. Similarly, the initial peak
current ~uppliedby capacitor 154 to th~ w~ndings is on the order
o~ 18.~ amperes while the second current pulse :l~ed to tl~e windi~ngs
l~y capacitor 154 has a magnitude of approximately 14.6 amperes.
Capacitors 154 and 155 are alternately discharged to
generate approximately 10 cycles of positive and negative
decreasing amplitude puls~as over an ~nterval of approxImately
six milliseconds. After about three milliseconds the amplitude
of the pulses has decreased to nearly zero and the erasing mode ~ `
may be terminated by releasing the erase key 28. When this
occurs, the associated reed switch 35 opens, contact 156 opens
and voltage is removed from multivibrator 151.
SYSTEM FOR MANUALLY ERASING AREA
PRIOR TO RECORDING THEREON
.
The erase currents flowing through the terminals T3
and T4, Fig. 11, are selectively applied to the windings of
section B by manual initiation of the circuitry illustrated by
Fig. 11. Following depression of the erase key 28 and consequent
closure of its associated switch 35, Fig. 14, current from a
+Bl source flows through terminal T2 to relay K3, Pig. 11.
Two relays Kl and K2 are utilized typically because
of the large number of contacts involved. As an examination of
the circuit will bear out, relay K4 cannot be energi~ed until
both relays Kl and K2 have pulled in because a set of contacts
KlA and K2A from each relay are connected in series with the
relay K4 energizing circuit. Relay K4 is energized upon
closure of contacts KlA and K2A and the time it takes to pull
- in provides additional delay to insure that all contact bounce
attributable to the pulling in of relays Kl and K2 is over
before +Bl i9 coupled through relay K4 contacts out to mercury
relay 157 of Fig. 14. As disclosed above, the circuit of Fig. 14
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.. . . . . .
.: , ~ . , ;
:. . - . .
'
~)4~)304
insures that the lamp located on typewriter ~h~ch illuminates
the exase k~y 28 l~ghts when erasing. There IS no arc~ng or
i~ncrease ~n contact res~stance o~ the contacts o~ ~ig. 11
utilized in switching the windings of section B since these relay
contacts are closed prior to initiating the generation of the
erasin~ current. The diodes across the relay coils of the relays
Kl...K4 are for relay contact protection to prevent arcing.
Upon release of the erase key 28 current is removed
from the relay K3 causing this relay and the relays Kl, K2 and
K4 to drop out and restore the contacts controlled by the relays
Kl and K2 to the positions shown in Fig. 11. The windings in
section B are then conditioned to receive recording signals from
the sources 1-8, inclusive. The recording signals are produced
- in the manner and by the means described above.
SYSTEM FOR AUTOMATICALLY ERASING
AREA PRIOR TO RECORDl~NG THEREON : :
Fig. 12 illustrates a conventional electric typewriter
mechanism designated generally by the numeral 80. The mechanism
includes a flexible electrical wiper 81 mounted on type bar
mechanism 82 so as to wipe firstly across a common electrically
; conductive strip 83 and then across an insulated spacing and
hence across a discrete conductive spot or area 84 which is
associated with a particular character. A lead connects each
area 84 to eight diodes of the diode matrix 36. Ground is applied
; to the lead when contact is made between the wiper and the area
84. Ground potential traces through the wiper 81 by way of the
type bar mechanism 82 and the grounded typewriter frame. The
wiper 81, in wiping across areas 84, may be considered operation-
ally equivalent to the closing o~ ~witch 116 or 117, Fig. 13, to
effect encoding.
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. ~, ... . . .. . .
. . ..
1()41~)304
When the wiper 81, ~i~. 12 sweeps across the strip 83,
ground potential is applied to a resistor coupled to the base of
transistor 85 caus~ng transi~stor 85 to turn on and apply
energizing current to the relay 86. In response to this current,
the relay ~6 pulls in, closes contact K86 and thereby applies
voltage +Bl to the terminal T2/ Tig. 11. The application o~
voltage +Bl to terminal T2 of Fig. 14 causes voltage +Bl to
appear at contact arm 156, in the absence of the presence or
operation of the switch 35 and the keyboard erase key 28. As
discussed hereinabove, energization o~ the relay coils occur in
the sequence, first K3, then Kl and K2, K4 and lastly 157.
Energizing 157 causes voltage to be applied thru contact arm 156
to multivibrator 151 causing the erase circuit to supply erase
currents to all windings thereby effecting erasure of the
magnetizable area prior to recording in that area constituting
aection B of the recording head 41. The relatively slow sweep
of the wiper 81, Fig. 12, across the common strip 83 and the
relatively large spacing between this strip and adjacent area
84 permits the erase operation to be completed before a recording
is initiated by the wiper 81 contacting and sweeping across an
aligned area 84.
It will be evident that the manual and automatic erase
modes may be used together, with the manual erase, utilized
selectively in instances where no recording on the same mag-
netizable area is desired after typing erasure is performed.
Having now described the embodiments by which data is
permanently recorded on the mediums 21 and 22, a reading system
will now be described for translating at will the magnetic data
stored on the backing 22 back into groupings of electrical pulses
corresponding to each particular character of the ~tored data.
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1~4~t3~4
RE~DI~IG S~STEM
Reference is now made to P~gs. 3 and 15 ~or a considera-
t;on of the technlques involved in reading the bi~ts recorded on
single lines of backing 22. In Fig. 3, the magnetic bits along
a line of backing 22 are arranged so that they were derived in
response to binary bits indicative of 1, a, 1, 0, 0, 1, 1, 1, and
the magnetic areas along backing 22 are polarized, respectively,
in accordance with said bits as north-south, south-north, north-
south, south-north, south-north, north-south, north-south, north-
south. In response to the north-south magnetic polarization,
lines of flux extend from backing 22 ln a clockwise direction,
while the south-north magnetic areas have fluxes in the opposite,
counterclockwise direction.
To read the magnetic spots along a line of backing 22,
a conventional magnetic recording or read-out head 191 is provided.
Head 191 includes a pair of pole faces 192 and 193 positioned
to be in engagement with backing 22 and separated ~rom` each other by
air gap 194. Reading head 191 is translated along a line of
binary magnetic coded data on backing 22 from left to right, as
viewed in Figs. 3 and 15. Head 191 carries winding 195, that is
wound about the legs of the head, and derives an output wltage
commensurate with the rate of change of flux in the reading head.
As head 191 scans from left to right across backing 22,
voltages indicative of flux rate of change are induced in winding
195, as indicated by waveform 196. The vertical segments of
- waveform 195 are aligned with the flux patterns derived from
backing 22 as the head is translated. Hence, when head 191 is
positioned to the left of the four magnetic bits in layer 22, Fig.
3, there is no voltage induced in winding 195. As head 191
translates to the right, the north pole o~ the first bit is
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104()304
encountered, causing a clockwise circulation o~ flux ~rom pole
ace 192 to pole face 193. In response to the clockwise ~ -
circulation of flux between pole faces lg2 and lg3, there is
induced in winding~l95 a positive ~oltage. When head 191 reaches
the center of the first bit that is recorded, there is no rate
of change of flux, whereby zero output voltage is derived from
winding 195. As head 191 progresses farther to the right, beyond
the center of the first bit, the rate o~ change of flux across
gap 194 is decreasing, whereby a negative output voltage is
derived from winding 195.
After head 191 has cleared the flux pattern occurring
as a result of the first 0 bit recorded on backing 22, there is a
gap where no magnetic flux is recorded on the backing. In
response to a lack of flux in the gap between the first and
second bits, a zero voltage is derived from winding 195. The
zero voltage between these bits has a duration considerably in
excess of the zero voltage between the poles of the first bit
because of the substantial separation between adjacent magnetic
bits. As a consequence, detection problems encountered with the
instant record are reduced as co~pared to records that have bits
with very small separations.
Further translation of head 191 to the right, Fig. 3,
results in passage of the leftmost portion of the next bit on
sheet 22 within gap 194 of head 191. Because the flux at the
leading edge of the binary bit is counterclockwise, the rate
of change of flux from pole face 192 to pole face 193 through
head 191 is in the counterclockwise direction, whereby a negative
voltage is induced in pick-up winding 195. As head 191 progresses
to the center of the first binary 1 bit, a zero rate of change
of flux is again airculated in 194, whereby a zero voltage is
`' ' - ,'`; :~ , .
- ~ .
` 104~304
produced by the winding 195. A~ head 191 translates to the
right side of the binary bit, a positive voltage is induced in
winding 195. In the manner described, the voltage waveform 196
is sequentially derived from the winding lg5 as the head 191
translates from left to right past the recorded bits to produce
the voltage waveform of the eight dipulses indicative to the eight
recorded bits as shown in Fig. 3. T~e eight bits, 10100111 are
indicative of one visual character such as a lower case "a".
Utilizing well-known magnetic recording read-out
techniques for binary information, only every other peak voltage
generated by winding 195 is utilized for sensing binary data.
For example, if the leading edge of the voltage generated in
response to each passage of head 191 over a magnetic north-south
or south-north section on backing 22 is considered as possessing
the binary data, the first positive peak in waveform 196, below
the north pole of the first bit on backing 22, is read to provide
a binary 1 indication for the first bit encountered by head 191.
As the head progresses, the first negative peak voltage is
discarded but the second negative peak voltage, commensurate with
the south pole of the first 0 bit is read to provide an indication
of the binary 0 value of the magnetic recorded data. The remaining
bits are read-out in similar fashion. No clock track is required
to perfOrmthe read-out since the read-out system is "self-clocking".
As seen from Fig. 3, the magnetic data recorded on the
backing 22 has a length along the longitudinal axis of the sheet
considerably in excess of pole faces 192 and 193 and gap 194
between them. By forming the magnetic data as lines having a
length considerably in excess of the effective reading area of
head 191, any problems of vertical alignment of sheet 21 when it is
placed in recording typewriter 26 or on a reader are obviated.
m us, if paper sheet 21 is not straight in typewriter 26, the
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recorded magnetic data has a tendency to move in ~ transverse
direction relative to he~d 191 during t~e re~d~out process. If
head 191 had a readi~ng area commenSurate w~th the length of each
recorded magnetic bit 23, the reader would very~ likely pick up
magnetic bits from an ad~acent line to provide a possible erroneous
indication of the bits in-the line being scanned. It is under-
stood, of course, that the relationship between the reading area
of head 191 and the length of magnetic bits 23 can be reversed,
whereby the recorded bits have a relatively short length in the
middle of each line and the effective reading area of head 191
is approximately e~ual to the line spacing of recorded visual
characters.
A preferred embodiment of the apparatus utilized for
reading characters from backing 22 utilizing head 191 is
illustrated in Fi~5.15, 16 and 17. In this figure, read head
191 detects each of the binary bits for all the characters on a
particular line. Head 191 scans each line and reads a number of
times equal to the number of characters recorded on the particular
line. After all of the characters on a particular line have been ~ ;~
read, the reader is advanced to the next line by moving it
longitudinally relative to the length of backing sheet 22.
The reader of Fig. 16 comprises a drum 201 mounted for
rotation at both ends in the direction indicated by the arrow at
a relatively constant velocity of, for example, 125 inches per
second. A synchronous motor 208 drives the drum and all mechanism
unted thereon. A constant speed motor 208 is not essential
because each of the recorded binary bits has a finite magnetization
area associated with it to provide for seIf-clocking.
The exterior surface o~ the drum 201 is covered with
a polyurethane foam sheet 2ao, upon which`~s laid the upper
Surface or printed side of sheet 21. The ferromagnetic backing
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. . .
,
-` 1041J304
22 carrying the recorded ma~netic data is therehy carried by
drum 201 as its outer peripheral sur~ace when the system is in
use. Backing 22 is normally ~n contact with t~e edge o~ nead 191
when binary bits are bei~ng read ~rom the record. Because of the
resilient nature o~ sheet 200, Fig. 16, contact ~etween head 191
and backing 22 does not cause excessive damage to the magnetic
layer. In fact, it has been found through experimentation, that
the same area on backing 22 can be read in excess of 20,000 times
even though there is physical contact between the backing 22 and
head 191.
Sheet 21 and backing 22, in composite form, are
maintained in situ on drum 201 by clamping cams 209 and 210 having
the ends affixed to end plates of drum 201. Cams 209 and 210
extend the length of drum 201 and are accommodated for limited
movement in enlarged apertures 214 and 215. Each of the plates
211 and 212 is connected to tensioned springs 216 and 217 -
respectively, that bias rods 209 and 210 into pressing the
respective lower and upper edges of the backing 22 against shoulders
218 and 219 sloping radially inwardly of the drum body to define
the longitudinal edges of a flat sector 220 of overall
rectangular configuration. The apertures 214 and 215 are of
sufficient size to allow the rods 209 and 210 to firmly engage
both drum shoulders.
The spring bias applied to rods 209 and 210 prevents
sheet 21 from being displaced on the drum 201 as the drum rotates.
After one edge of backing 22 has been clamped in situ by rod
209, the sheet is wound about foam layer 200 and the other edge
of the backing is pulled over the shoulder 219. Rod 210 is
raised from the shoulder 219 and the othex edge of the backing is
smoothed down and over the shoulder 219. ThQ rod 210 ls then
released and allowed to snap into place holding the paper firmly
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~ ' ' ' .
``` 1~)4~)304
against foam layer 200 covering the shoulder 219 during drum
rotation.
To move reading head 191 relat~ve to ~acking 22 after
each character on a particular line has ~een read, the head is
clamped to the vertical extension 221 of a block 222, Figs. 15
and 17, which is horizontally indexed to traverse the surface 200.
The block 222 slides upon a rail 223 fixedly mounted at ~oth
ends thereof to vertical supports 224. The rail 223 is parallel
to the axis of rotation of the drum 201.
The block 222 includes a bearing 225 which mounts a pawl
226 for rotation. Pawl 226 engages teeth 228 of rack 229 that is
reciprocally driven by rotation of an eccentric cam 231, an
increment equal to the d~stance between the apecies of adjacent
rack teeth. This distance is equal to the center-to-center
lateral distance between adjacent discrete magnetized areas.
Hence, with reference to Fig. 1, the peak-to-peak
distance between the rack teeth 228 would be equal to the magnetic
track spacing or type line spacing. Cam 231 is coupled to the
output shaft of solenoid 232 which is energized each time that a
complete line of characters on backing 22 has been read and
decoded. Activation of solenoid 232 causes cam 231 to be rotated
through one-quarter of a revolution, whereby pawl 226 is indexed
along the teeth 228 of rack 229 from right to left, as viewed in
Fig. 17, the distance of one character. To maintain rack 229 in
alignment with bar 223 and reading head 191 in contact with backing
22, the rack is mounted for recip~ocation parallel to the rail
223 on bearings 234 suitably nested in the supports 224.
Circuitry suitable for decoding or reading information
from magnetic read-out head 191 and coupling the information to
an appropriate output device such as typewriter 250 is
schematically illustrated in Fig. 18. In a typical system, the
1~4~304
read-out system will generally be at a location removed ~rom head
191. In lieu o~ typewrIt~r 250, the decoded si~gnals may be
employed as the read-in ~or a computer or the li~ke.
Since the record 22 includes no tim~ng channels and
rotation thereof is not necessarily synchronous because the
magnetic bits are self-clocking, apparatus is provided in the
decoding system for establishing pulses required for sensing a
particular character. In addition, because the typewriter 250
is unable to respond at the same speed as bits are derived from
head 191, provision is made to reduce the rate at which signals
are applied to the typewriter. To this end, typewriter 250
prints only a single character for each revolution of drum 201.
Hence, during the first revolution of a particular line, the
- first character recorded on backing 22 is printed by typewriter
250, during the second revolution of drum 201 for the same line,
the typewriter prints the second character, and so on. ~ ;
To establish the self-clock;ng feature and enable only
a single character to be printed by typewriter 250 during each
revolution of drum 201 a magnet 300 is mounted to project from
one end plate 301 of the drum 201. Mounted stationary in align-
ment with the path of magnet rotation are reed switches 302 and
303. The switches 302 and 303 are oriented such that magnet 300
closes the switch 303 just after the drum 201 rotates the sheet
21 from contact with the read head 191 and then closes the switch
302 just before the sheet 21 resumes contact with the read head.
Switches 302 and 303 reopen after the magnet passes them. Th~
read head, from the time switch 303 closes until switch 302 closes
~just before the magnetic sheet again makes contact with the
read head~ de~ines a dead zone or time interval during which the
typewriter 250 is operated to type out the decoded character
on a suitable medium. One character is t~ped out for each
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complete revolution, except ~or a typewriter carxiage shift from
lower to-upper case c~aracters ox ~ sh~t ~rom ~pper ~o lower
case characters. CarrIage sh~fti~ng requi~res one full revolution
of the drum.
SYSTEM FOR OPERATING. AN BLECTRIC
TYPEWRITER TO PRINT OUT RECORDED INFORMATION
With reference to Fig. 18, power is ~irst applied to all
components of the drum reader system, except the eleven AND gates
305-1...305-11. Wlth ~e sheet 21 properly positioned on the drum,
the drum has the magnetically recorded information (for the line
that is to be typed out) aligned with the read head 191 which
has been previously m~ved to its extreme right-hand position as
viewed in Fig. 15. Flip-flop 306 is reset by momentarily
pressing push-button switch 345. This provides an inhibit
signal to AND gate 305-12 and will prevent type out after applying
power to all of the gates 305-1...305-11. Power is then applied
to these gates that control operation of electric typewriter 250.
To start the type out it is necessary to momentarily ~ -
press push-button switch 310. Normal reaction time of a person
~20 pressing the switch 310 should insure it being depressed for at
least one reader drum revolution. The signal generated by,
switch 310 is inverted by inverting amplifier 311 and "ANDED"
with the differentiated output from flip-flop 312. This occurs ~-
when switch 302 is closed by the magnet 300 rotating past it
causing flip-flop 312 to be reset. The differentiated output
of flip-flop 312 is applied to the S2T input of flip-flop 313 causin~
this flip-flop to set. Flip-flop 306 ~s also simultaneously
SET and upon changing state removes an inhibit signal from gate
305-12 which, however, still remains inhibited because of the
in~ibit signal provided at the Q input thereof by flip-flop 312.
Thus, the AND gates 305-1... 305-11 and 305-15 are inhibited.
With gates 305-1...305-11 inhibited, all data transfer to
typewriter 250 is also ~nhibited. When flip-flop 306 sets, it
-53-
1~4~304
also triggers monostable multivibrator 315 which resets a first
counter 316 to all binary zeroes ~"O's"l~ and si~multaneous-ly
resets a second counter 317 to all "O's" except ~or a "1" which is
automatically placed in the least signifi~cant bit counter stage.
Any output from the counter 317 caused by the resetting of that
counter is also inhibited. The system therefore is fully reset
just before the backing 22 makes contact with the read head 191.
When the backing 22 makes initial contact with the
read head, the relatively low amplitude signal (about 15 mullivolts
peak-to-peak) generated at the read head 191 output is amplified
by amplifier 321. The pulse generated by the positive half
cycle of the signal appears at amplifier output 322 and the
pulse generated by the negative half cycle appears at amplifier
output 323. The pulse appearing at amplifier output 323 triggers
a Schmitt trigger circuit 325 which serves to square up the
signal waveform at output 323 so that it can be sampled and
cause information to be shifted into a shift register 326 when a
shift pulse occurs. The 322 and 323 outputs from amplifier 321
are "OR'D" together by an OR gate 327 and squared by Schmitt
trigger 328 and then divided by 2 by a divider circuit 329. The
output of circuit 329 is delayed by means of a conventional delay
circuit 331 for about 20 microseconds and applied to an input
of an AND gate 333 by way of monostable 332 which shapes received
pulses into suitable shift pulses. Thus, each fuil period of the
input from the read head 191 produces a single pulse that is time
delayed sufficiently to sample the second half of the input
waveform at substantially the center of its squared-up waveform.
After eight successive waveforms have been sampled representing
a particular recorded character in the line being scanned and
the eight representative pulses created therefrom are fed serially
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' , ' ' , .,
1~4~3~4
into the shift register 326 and into a divide-by-eiyht circuit 337
coupled to the output of AND gate 333. upon receivi~ng eight suc-
cessive pulses, the circui~t 337 puts a count of "li' into the least
significant stage of the counter 316 and since counter 317 was
previously reset to a count ~f "1" a coincidence in count between
the least significant stages of two counters is detected by count
coincidence detector 335 and a reset pulse IS generated by
the detector 335. This pulse causes flip-flop 313 to reset and
also reset counter 316, and inhibit the gate 333 from feeding any
more shift pulses into the register 326 or into the circuit 337.
Thus, the eight bits representing the first character are stored
in the shift register. ~hen the magnetic backing 22 rotates beyond
contact with the read head 191, switch 303 closes and sets
- flip-flop 312 which causes the inhibit signal to be removed from
the Q flip-flop output and AND gate 305-12 for a time interval
beginning at the instant switch 303 closes and extending to the
time when switch 302 closes. During the interval, the gate 305-12
is enabled and in turn enables the gates 305-1...305-11 thereby
permitting the coded information that was previously serially
fed into the shift register 326 to be read out in parallel and
supplied to the electric typewriter 250. The typewriter receives
a six bit binary code via gates 305-1...305-6 and a print trigger
pulse ~ia gate 305-7 that causes the typewriter 250 to type out
the corresponding character.
Closure of switch 303 also caused flip-flop 312 to send
in another count to counter 317 by enabling AND gates 305-12 and
305-15 assuming no typewriter shift is required. With a count of
two in the counter 317, the next cycle initiated when switch 302
closes again will cause the binary pulses fed serially into the
shift register 326 to be stopped after the eight bits associated
-55-
l~4~3a4
with the second m~gnetically xecorded character has been stored
in the register 326. As the second group o~ pulses representing
bits of the second character are fed into t~e regi~ster 326, the
first group of bits representing the first character is shifted
completely out of the shift register. The complete line is read
character by character until a carria'ge return signal is decoded
by "AND" gate 305-10.
The logic for enabling the gate 305-10 is coincident
enabling signal at output J of gate 305-12, and a six bit logic
ABCDEF to be obtained by connecting the first six input leads
of gate 305-10 to appropriate output leadsABCDEF of shift register
326. The shift register generates this logical output when the
read head 191 scans a "carriage return" coded area on the backing
22 and stores in the register 326. When the gate 305-10 is
enabled the change in output level signals an associated carriage
return mechanism in the typewriter 250 to similarly return its
carriage. The enabling of the carriage return 305-10 further
energizes the solenoid drive 232 to reciprocate the rack 229,
Fig. 17, once so as to index the head 191 opposite the next line
of characters.
Similarly, the space function is implemented by the
AND gate 305-11 receiving coincidental appropriately coded input
signals on leads ABCDEF from the register 326 and an enabling
signal from output J of gate 305-12. Each time the gate 305-11
is enabled, the ccrresponding spacing mechanism in the typewriter
- 250 is activated once.
The functions of shift and unshift are performed under
the control of a conventional carriage shi~t detector and control
circuit 340. The detector 340 recei~es a logical input from the
seventh stage of the shift register 326, that is from the lead
-56-
11~34~3~4
designated by the letter ~, and in so doing, detects the
necesslty to shift. ~h~n a pulse correspondin~ to a ~it IS
produced on lead ~, for example, the detector 340 enables the
gate 305-9 and disables the gate 3a5-8 causing thè typewriter
250 to shift from lower case characters to upper case characters.
Type out and further feeding of shift pulses to the register 326
i9 inhibited for one complete drum revolution to permit the
shift to be accomplished.
An O bit on lead G drives the logic 340 to inhibit the
gate 305-9 and enable the gate 305-8 thereby causing the type-
writer to unshift to lower case or remain in the lower case if
previo~sly in lower ca~e. The shift position of the typewriter
is monitored and as a check ma~ be fed back to the logic 340 by
way of lead 341 for comparison with the state of the control
logic circuity. A parity circuit 344 is also incorporated in
system to inhibit further type out or-to leave a space if parity
is not maintained. A parity circuit (not shown) could also be
devised to merely inhibit the type out of any single character
that did not pass parity check.
Type out and operation of the circuitry may be stopped
by momentarily pressing push-button switch 345. Closure of
switch 345 operates to reset flip-flop 306 which disables the
control gate 305-12. To restart the type out it is necessary to
momentarily press push-button 310 as previously described.
While we have described and illustrated several specific
embodiments of our invention, it will be clear that additional
~ariations of the details of construction which are specifically
illustrated and described may be made without departing from the
true spirit and scope of the invention ~s def~ned in the appended
claims.
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