Note: Descriptions are shown in the official language in which they were submitted.
DESCRIPTION OF THE PRIOR ART
Printers which utilize a rotating disk with characters
on the periphery thereof are well known. Several such
printers are commercially available. Rotating dlsk printers
can be divided in categories by either focusing on how the
disk rotates or by focusing on how the carrier traverses.
Focusing on how the disk rotates, such printers can be
divided into a first category where the disk constantly
rotates and into a second category where the motion of the
disk is intermittent. In printers with a constantly rotating
disk, printing takes place when the hammer strikes the
rotating disk. Rotation of the disk is not stopped each
time a character is printed. In printers with a disk that
intermittently rotates, the disk is rotated to the desired
print position and then stopped. There is no disk rotation
while printing takes place.
EN974012
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1 An alternate division of disk printers can be made by
focusing upon the motion of the carrier. In some printers,
the traverse of the carrier is stopped each time printing
takes place. In other printers the carrier is moving at the
instant when printing occurs. In both the type where the
carrier is moving when printing occurs and in the type where
the carrier is stopped when printing occurs, the disk may or
may not be rotating at the time of printing. In some printers
where the carrier is moving at a fixed speed when printing
takes place, the carrier is slowed down and stopped between
print positions in order to give the rotating disk time to
move to the desired character.
The following are some of the issued and pending patents
- which show rotating disk printers:
: .
The Willcox patent 3,461,235 shows a disk printer with
a constantly rotating disk. The carrier stops at each print
position.
The Ponzano patent 3,707,214, which issued on December
26, 1972, discloses a disk printer which has separate controls
for a print wheel and its carrier. The print wheel and the
carrier move by the shortest distance to the next selected
position. The print wheel and the carrier stop at each
print position.
The Robinson patent 3,356,199, which issued on December
5, 1967, describes a rotating disk printer wherein the disk
is constantly rotating. The type elements on the disk are
in a particular spiral configuration. The carrier also
moves at a constant speed which is synchronized with the
motion of the disk in such a manner that the desired character
can be printed
: '
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in each print position.
The Giani patent 3,742,845, which issued on July 3, 1973, shows
in FIGURE 11 a drum printer which has a constantly rotating drum.
It is suggested that this drum could be mounted on a carrier. The
carrier would have to stop at each print position in order to give
the rotating drum time to rotate to the desired character.
The Cahill patent 3,794,150, which issued February 26, 1974,
discloses a drum printer which includes an incrementing carrier. The
carrier stops at each print position until the drum rotates to the
desired position.
Canadian Application Serial No. 238,095 of Jensen et al, filed
October 20, 1975, discloses a carrier control system for a start-
stop disk printer in which the carrier normally traverses at a pre-
determined speed. Printing always occurs at the same predetermined
speed; however, if there is not sufficient time to rotate the disk
to the next desired character, the carrier is slowed down between print
positions and then returned to the predetermined speed.
None of the above references show a printer where the carrier
is moving at a plurality of different speeds when printing occurs
and where the firing of the print hammer is timed dependent upon the
speed of the carrier
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l in each print position.
SUMMARY OF THE INVENTION
Generally stated, it is an object of this invention to
provide a printer with improved performance.
Another object of the present invention is to provide a
start-stop disk printer which has improved throughput.
Another object is to provide an improved method of
printing.
More specifically, it is an object of this invention to
provide for controlling the speed of the carrier in accordance
with the time required to position the print wheel at the
desired position.
Another object of the invention is to control the speed
of the carrier and to control hammer firing time with respect
to carrier speed.
Another object of this invention is to control carrier
speed in such a way that proportionally-spaced printing can
be done with a high throughput speed.
The present invention provides a start-stop disk printer
which has one motor for controlling the disk and another
motor for controlling the carrier movement. As in all
mechanical systems, the mechanical characteristics of these
motors and other related mechanical components impose physical
limitations such as maximum speeds, maximum accelerations
and maximum decelerations. The present invention is directed
to maximizing the performance of the printer by controlling
the carrier traverse, disk rotation, and hammer firing such
that the maximum capacities of the motors and other physical
components can be utilized more fully than possible in the
prior art
EN974012 -4-
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1 control schemes.
The novel control mechanism of this invention moves the
carrier at several different speeds depending upon the
particular sequence of characters being printed. The particu-
lar time the print hammer is fired is varied depending upon
the speed of the carrier when the particular character is
printed.
The foregoing and other objects, features and advantages
of the invention will be apparent from the more particular
description of a preferred embodiment of the invention as
illustrated in the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIGURE 1 shows a printer apparatus adapted for use with
the present invention.
FIGURES 2A and 2B are curves showing carrier velocity
versus carrier displacement and carrier velocity versus time
in one type of prior art printer.
FIGURES 3A and 3B show curves of carrier velocity
versus carrier displacement and carrier velocity versus time
in another type of prior art device.
FIGURE 4 shows the allowable carrier velocities when
the printer is operated in accordance with the present
invention.
FIGURE 5 shows a curve showing an example of carrier
velocity versus carrier displacement when a printer is
operated in accordance with the present invention.
FIGURE 6 iS a schematic circuit diagram of the circuitry
which drives the step motors in the present invention.
FIGURE 7 iS a table showing the speeds selected
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1 under various conditions and the data stored in memory table
T7.
FIGURE 8 is a table showing the timing words stored in
memory table T8.
FIGURE 9 is a diagram of a data string as stored in
memory location T9.
FIGURES 10A and 10b comprise a flow diagram of the
program executed by the processor shown in FIGURE 6.
FIGURE 11 shows the position of the characters on the
disk.
DESCRIPTION OF A PREFERRED EMBODIMENT
FIGURE 1 shows the main mechanical components of the
present printer. They are shown somewhat schematically
since such components are well known and the present invention
is directed to the control mechanism for the two stepper
motors 3 and 8 and not to the mechanical components per se.
As shown in FIGURE 1, a laterally sliding carrier 1 is
mounted on guides la and lb and carries a rotatable print
wheel or disk 2 driven by a stepping motor 3. The carrier 1
is driven by a toothed belt 7 which is driven by a stepping
motor 8 (the teeth on the belt are not shown). Alternatively,
motor 8 could drive a lead screw which in turn could drive
carrier 1.
The type disk 2 comprises a disk having a number of
movable type elements such as the flexible spokes or type
fingers 9A, 9B, 9C, etc. Printing of any desired character
is brought about by operating a print hammer 10, which is
actuated by a solenoid 11, both of which are mounted on the
carrier 1. When the appropriate type
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1 finger approaches the print position, the solenoid 11
actuates the hammer 10 into contact with the type finger,
driving it into contact with the paper 12. An emitter wheel
13 attached to and rotating with the type disk 2 cooperates
with a magnetic sensor 13a to produce a stream of emitter
index pulses for controlling the operation of the printer.
The emitter has a series of teeth each of which corresponds
to one finger 9A, 9B, 9C, etc. A home pulse is generated
for each revolution of the print wheel by a single tooth on
another emitter (not shown). The printer controls can thus
determine the angular position of the type disk 2 at any
time by counting the pulses received since the last line
pulse. A toothed emitter 15 is mounted on the shaft of the
motor 8 and in conjunction with a transducer 15a provides
pulses which indicate the position of the carrier 1.
Stepper motors 3 and 8 are activated by conventional
drive circuits 21 and 22. Examples of the type of drive
circuitry that could be used are shown in U.S. Patent
3,636,429.
The actions of positioning the carrier 1 and positioning
the print wheel 2 are, in general, independent except that
coordination is required at the instant printing occurs.
Both the type disk 2 and the carrier 1 must be in a selected
position (but they need not be at rest) when the hammer 10
strikes the type disk 2. Due to the amount of inertia
involved, it is often possible to reposition the type disk 2
more quickly than the carrier 1. Therefore, it is the
repositioning time of the carrier which primarily limits the
speed of
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1 printing.
` FIGURES 2A and 2B illustrate one prior art technique
- for controlling a start-stop disk printer wherein the speed
of the carrier is constant. A constant velocity is selected
such that the disk has time to rotate to any desired position
in the time required for the carrier to move between character
positions. It is noted that in such printers the velocity
selected must be very low, herein designated LV. FIGURE 2A
shows the carrier velocity in this type of printer with
respect to the horizontal displacement of the carrier as it
traverses the various print positions. FIGURE 2B shows the
carrier velocity with respect to time. As shown by these
figures, the carrier velocity is constant both with respect
to time and with respect to carrier position.
The carrier velocity LV must be such that the time
required for the carrier to move from one print position to
the next is greater than the longest time required to position
the disk under the worst-case conditions. This technique is
reasonably satisfactory in a low speed printer or if the
time needed to reposition the disk is always about the same.
However, in a high performance printer with a servo or step
motor driven disk, the disk repositioning time may vary over
a wide range, such as 6 to 48 milliseconds, depending on the
angle between successive characters. By placing frequently
used characters adjacent to each other on the disk, most
repositioning cycles can be completed in the short end of
the range with just an occasional longer cycle for infrequently
used characters or infrequent character sequences. A constant
velocity carrier is not then
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1 desirable because it limits the printing speed and it does
not take advantage of the fact that the disk is repositioned
very quickly in most cycles.
FIGURES 3A and 3B illustrate a prior art system wherein
the motion of the carrier is stopped at each print position.
FIGURE 3A shows carrier velocity relative to carrier dis-
placement, and FIGURE 3B shows the carrier velocity relative
to time. It is noted that during the time spans A, B, and C
the carrier is stopped waiting for the disk to be positioned.
This occurs because in this type of system the time to
position the carrier is always the same, but the time to
position the disk varies. Times A, B, and C would be zero
only if the carrier required more time to move between
positions than the longest time required to position the
; disk. In such a system, the carrier is accelerated at its
maximum possible acceleration rate and then decelerated at a
maximum possible deceleration rate between character positions.
- It is noted that the average velocity designated AV in
FIGURE 3B is relatively small. This relatively low average
velocity limits the overall speed of the printer.
FIGURE 4 shows the allowable carrier velocities with
the present invention. In the particular embodiment shown,
there are four allowable velocities designated Vl to V4.
These velocities are chosen so that the carrier 10 can
accelerate or decelerate between any two velocities (except
zero) within the space between adjacent print positions. If
the carrier starts from zero velocity, it is only accelerated
to Vl at the first print position.
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1 A change from Vl to 0 and back to Vl is possible in one
column width.
FIGURE 5 shows an example of the carrier velocity
versus carrier displacement when the present invention is
employed. In this example, the carrier accelerates to
velocity Vl between print positions 0 and 1, it accelerates
to velocity V3 between print positions 1 and 2. The velocity
remains constant between print position 2 and 3. Between
print positions 3 and 4 the velocity increases to V4; between
print positions 4 and 5 the velocity decreases to Vl; between
print positions 5 and 6 the velocity increases to V3; and
between print positions 6 and 7 the velocity decreases to
Vl. The particular velocity at which the carrier moves
between print positions is determined by a combination of -~
two factors designated namely:
a. The number of positions which the disk must rotate
in order to be positioned to print the next charac-
ter.
b. The distance the carrier must move in order to
print the next character. Whether or not there
are any spaces between characters which are being
printed determines the distance the carrier must
move between characters.
FIGURE 7 shows the carrier speed which is selected
under various conditions. For example, if the disk must
move 12 positions, the carrier accelerates or decelerates to
velocity V3. It is noted that under certain conditions
where the rotation of the disk is very large (that is,
between 45 and 48 positions), the
EN974012 -10-
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1 speed goes from Vl to 0 and back up to Vl between print
positions.
One very important aspect of the present invention is
that the firing of hammer 10 must be controlled and timed
dependent upon the speed at which the carrier is moving when
a particular character is printed so that the flight time of
the hammer and its drive circuits does not cause misalignment
of the characters. In the prior art techniques, such as
those illustrated in FIGURES 2A and 2B, the hammer could
10 always be fired when the carrier was at a particular position
in relation to the character being printed. For example, if
six pulses of the stepper motor were required to drive the
carrier between adjacent print positions, the hammer could
always be fired after the fifth drive pulse.
In the prior technique illustrated in FIGURES 3A and
3B, the hammer could always be fired when both the carrier
: and the print disk were stopped. With the present invention,
as will be seen later, the hammer firing must be controlled
dependent upon the particular speed at which the carrier is
moving when a particular character is printed.
The circuitry which operates the components shown in
FIGURE 1 in accordance with the present invention is shown
in FIGURE 6. Stepping motor drive circuits 21 and 22, shown
in FIGURE 1, are activated by the circuitry shown in FIGURE
6. The data which is to be printed comes from a data source
612. In response to this data, the circuitry shown in
FIGURE 6 generates a series of pulses on lines 21A, 21B,
22A, and 22B which activate drive circuits 21 and 22 such
that stepper motors 3 and 8 move the carrier and the disk to
the correct positions to print the data supplied by data
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1 source 612. The signals on lines 21s and 22B indicate the
direction which the stepper motor should move. Signals on
lines 21A and 22A indicate how far the motors should move.
Each pulse on line 21A causes motor 8 to move one step and
each pulse on line 22A causes motor 3 to move one step.
The main components of the circuitry which generates
the appropriate pulses in response to the data supplied by
data source 612 are: processor 610, shift register memories
615 and 617, counters 630 and 631, and zero detector 616.
Data source 612 gives a series of signals on line 612B
which represent characters and spaces such as "all good men
come to the aid of their country". When data is available
on output 612B, line 612A is activated. If data is available
on line 612B when a data request signal appears on line 610B
one element of data called a "datum" is gated through gate
613 to processor 610.
Data source 612 can be a conventional data buffer or a
keyboard input device such as a typewriter. Processor 610
can be a commercially available computer such as the IBM
20 System/7. The processor 610 receives the data, makes certain
calculations and then sends a series of numbers out to
carrier shift register memory 615 and disk shift register
memory 617. If the hammer is to be fired in a particular
column, the processor 610 also activates one of the lines
610Vl to 610V4 to indicate the speed at which the carrier is
being driven. These lines control the timing of the hammer
firing.
The processor 610 has two tables stored in its memory.
These are represented in FIGURE 6 as areas
EN974 012 -12-
1056~'0~
1 T7 and T8. Processor 610 also has two data storage areas
which are represented by areas T9 and TR.
The data stored in table T7 indicates the speed at
which the carrier is moved under various conditions. This
- data is shown in FIGURE 7.
The information in table T8 is the particular numbers
which the processor 610 supplies to memories 615 and 617 in
order to move the stepper motors 3 and 8 at particular
velocities. These numbers are shown herein in FIGURE 8,
where the notation Nl, N2, etc. represents particular timing
values appropriate for various carrier speed changes and
print wheel movements. Specific examples are given later.
Storage area T9 is a shift register storage used to
store three elements of data. This is illustrated in FIGURE
9. The elements of data are termed Datum 1, Datum 2, and
Datum 3. Generally, Datum 1 and Datum 2, and Datum 3 indicate
characters which are to be printed as follows:
Datum 1 The character in the process of being printed, -
i.e., the character for which commands to move the
carrier and the disk, and to fire the hammer have
just been given. (See below for a discussion of
start up.)
Datum 2 The character to be printed after the next move of
carrier and disk.
Datum 3 The character to be printed after the next two
moves of the carrier and disk.
The number of spaces which the carrier must move between
printing Datum 1 and printing Datum 2 is hereinafter designated
move A and the number of spaces which
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1 the carrier must move between printing Datum 2 and Datum 3
is herein designated move s.
When the processor 610 interrogates data source 612 for
an element of data and data source 612 does not have data
available (which is indicated by the absence of a signal on
line 612A0 a special character is inserted into the data
string which is hereinafter called a "no data" condition.
The "no data" character has the following properties:
It has zero width (i.e., no carrier motion is required).
Its position on the wheel is defined as the position of
the previously printed character (home position upon
initial start-up).
It is never printed.
Thus, the "no data" character never calls for any
action on the part of the printer except for stopping the ;
carrier when there is no more data. Thus, the "no data"
characters serve as precursors to fill the registers or
memories and permit starting the printing process. Similarly,
when no more data is available, they serve as chasers and
permit completion of all the printing for which the data
source has asked.
With the information at the next three characters
(including "no data") available, the processor 610 can
decide the appropriate sequences for the motors and hammer.
The manner in which this is done is described in detail
later.
Storage area TR contains three storage registers herein-
after termed R0, Rl, and R2. The numbers stored in these
registers indicate the number of spaces between
EN974012 -14-
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~:'
1 adjacent characters. This data indicates the number of
print positions that the carrier must move. This data is
stored for both move A and move B.
Carrier shift register memory 615 and disk shift regis-
ter memory 617 are first-in first-out memories which may
merely consist of a plurality of shift registers. Each
memory can store up to 64 words. Each word has a plurality
of bits. Each word is shifted through the memory in parallel.
The bits of each word represent a number (which is translated
into a time delay or a speed) and a bit indicating direction.
The circuitry shown in FIGURE 6 operates as follows:
Processor 610 puts a series of numbers in memories 615
and 617. The numbers from memories 615 and 617 are gated
through gates 615A and 617A to down counters 630 and 631.
Down counters 630 and 631 receive a series of clock pulses
on inputs 630A and 631A. The signals on lines 630A and 631A
cause the counters to decrement to zero. Each counter has
associated therewith a zero detector designated 630C and
631C. When a counter reaches zero count, the respective
detector emits a pulse to the carrier step motor drive
circuits 21 and 22. Thus, if, for example, the number
"1500" is transferred into the counter 630, then after 1500
clock pulses occur, the counter reaches zero and a pulse is
produced on line 2lA.
In the specific example described herein, the stepper
motor 8 and toothed belt 7 are such that when six pulses are
applied to stepper motor 8, carrier 1 moves one print position.
The system operation will be illustrated by showing how the
processor 610
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1 causes a series of six pulses to go to the carrier step
motor drive circuit 21.
In order to move carrier 1 one print position, processor
610 supplies six numbers to carrier shift register memory
615. The magnitude of these numbers represents the timing
of the six pulses which go to carrier step motor drive 21.
These six numbers are sequentially sent to down counter 630.
After each number is sent to down counter 630, a series of
clock pulses decrement the counter to zero. When the counter
reaches zero a pulse is generated on line 21A which moves
motor 8 one step and carrier 1 one-sixth of a column width.
The pulses on line 21A also go through OR circuit 640 and
AND gate 641 to delay circuit 642. After a very short
(e.g., one-half microsecond) time delay introduced by delay
642, another number is gated from carrier shift register
memory 615 to down counter 630 and the process repeats
itself.
As explained above, six numbers in memory 615 are
required to generate six pulses on line lA and to thereby
move the carrier one column width. Each set of six numbers
in memory 615 is separated from the preceding set of six
numbers by a word which contains all zeros. A word with all
zeros is placed in memory 615 by processor 610 after it
places every six numbers in the memory. The all zeros
separator word is detected by circuit 616 which generates an
"operation complete" signal. This causes the processor 610
to gate more information into memories 615 and 617 and it
also initiates the activation of hammer drive circuit 660 as
will be explained later.
EN974012 -16-
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1 The magnitude of the six numbers placed in memory 615
determine the duration between pulses that appear on line
21A and, hence, the speed of step motor 8 and carrier 1.
Similarly, numbers placed in memory 617 control the motion
of disk step motor 3.
FIGURE 8 shows that for each possible carrier speed
change there is a particular series of numbers that must be
placed in memory 615. For example, to change from velocity
V2 to velocity Vl, the numbers N13 to N18 must be placed in
memory 615. The actual value of numbers N13 to N18 depends
upon the characteristics of the particular circuitry and the
particular motors. For example, with a conventional stepping
motor and with timing signals at microsecond intervals the
following numbers could be stored in the memory to change
from a carrier speed of six inches per second to a carrier
speed of zero.
2777 2777 2777 2777 5000 5000
The following numbers would be used for a constant speed of
six inches per second
2777 2777 2777 2777 2777 2777
The following numbers would be used to change from nine
inches per second to six inches per second
3900 2200 0 2777 2777 2777
Similarly, an example of the actual numbers N93 to N96
placed in memory 617 to obtain a disk rotation of four units
could be (each number in memory 617 moves disk 2 one unit)
1400 1130 1018 2130
In practice, the easiest way to determine the actual
numbers Nl to N1286 is by trial and error. Various numbers
are placed in memories 615 and 617
EN974012 -17-
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1 and the resultant velocities are measured. By trial and
error, one can determine which particular number will gener-
ate a particular desired velocity profile.
Each word placed in memories 615 and 617 has a multibit
number which is gated out on lines 615D and 617D, plus a
direction bit which appears on outputs 615E and 617E. The
bits on lines 615E and 617E control the direction of motion
of the step motors.
The operation begins when a pulse appears on line 610A.
The pulse on line 610A goes through OR circuit 640 and AND
gate 641, through delay element 642 and it gates the first
number from carrier shift register memory 615 to down counter
630. Inverter 643 receives the same clock pulses as appear
on lines 630A and 631A and it produces an out-of-phase
clock pulse so that the information in shift register memory
615 and 617 is not gated to down counters 630 at an inappro-
priate time. Logical elements 650, 651, 652, and 653 perform
a similar timing and gating function to logical elements
640, 641, 642, and 643.
An important facet of this present invention is that
the timing of the firing of hammer 10 is dependent upon the
speed of carrier 1. Six pulses on line 21A are required to
move carrier 1 between adjacent print positions. After the
sixth pulse is supplied to circuit 21 counter 630 is loaded
with the sixth number and the firing of the hammer is initiated
by the "all zero detector" 616 on line 616A; however, a
variable amount of delay is introduced by delay circuits
672A to 672D, dependent upon the speed at which the carrier
is being driven. The length of each delay 671 is chosen so
that the length of the delay plus the hammer flight time is
equal to the time required to move the carrier one-sixth of
a column width at the particular velocity.
EN974ol2 -18-
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1 The manner in which the hammer drive circuit 660 is
activated is as follows: The signal on line 616A activates
hammer drive circuit 660 through AND gates 671A to 671D,
single shot delay elements 672A to 672D, and OR gate 673.
If the hammer is to be fired, the processor 610 provides a
signal on one of the lines 610Vl to 610V4 indicating the
particular velocity at which the carrier step motor 8 is
being driven. This combination of signals activates one of
the single shot delay elements 672A to 672D which in turn
activates hammer driver circuit 660. Thus, the hammer
driver circuit 660 is activated at a particular time which
is dependent upon the particular velocity at which the
carrier is moving past a particular print position. The
length of delay introduced is shorter if the velocity is
higher.
FIGURE lOA and 10B is a flow diagram of the specific
operations performed by processor 610. The details of the
flow diagram will now be explained by explaining each block
in the flow diagram.
Block 81 The processor 610 determines if the data source
612 has data available by interrogating line 612A.
Block 82 If an element of new data called a "new datum" is
available, an interrogation is made to determine
if it is a space.
Block 83 A count indicating the number of spaces between
two adjacent characters is accumulated and recorded
in register RO in storage area TR, and new data is
requested.
EN974012 -19-
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.: ,
1 slock 84 When a printable character arrives after a space,
the count in register Rl is transferred to register
R2. This count represents a value termed S for
move A.
Block 85 The count in register RO is transferred to register
Rl. This count represents the value S for move B.
Register RO is set to zero after its contents are
transferred to register Rl.
Block 86 The new datum is inserted into the left end of the
data string in storage area T9 (FIGURE 9). This
data string has three elements of data. The new
datum is always entered at the left and each time
a new datum is entered, the data presently in the
register is shifted one place to the right.
Block 87 Interrogation is made to determine whether or not
the carrier is stopped. If the carrier is stopped,
special action must be taken.
Block 88 The third element of data in the data string is
interrogated to determine if it is a "no data"
condition.
Block 89 The second element of data in the data string is
interrogated to determine if it is a "no data"
condition. If yes, request more data.
Block 90 The amount of wheel rotation for moves A and B is
calculated. This is done by calculating the
number of intermediate characters on the wheel.
(See FIGURE 11.)
EN974012 -20
10562(~7
1 For example, a move from A to D is three spaces.
It is noted that the disk has 96 characters. If
desired, some characters could be repeated. If
characters are repeated, the smallest amount of
possible rotation would be chosen. Eurthermore,
frequently used characters could be grouped.
Block 91 The number of positions which the carrier will
have to advance for moves A and B is determined by
adding one to the numbers in registers Rl and R2.
0 Block 92 Table T6 (FIGURE 7 herein) in the memory of
computer 610 is interrogated to determine the
carrier speeds for moves A and B.
Block 93 The actual speed for move A is se7ected as the
lower of the permissible speeds for move A and
move B. The reason the lower of the two speeds is
chosen is to insure that the carrier will always
be going slow enough to allow the disk motor to
complete its move prior to the carrier having
moved one column and to be certain the carrier can
stop if that is required.
Block 94 Table T8 (EIGURE 8 herein) in the memory of computer
610 is interrogated to determine the sequence of
commands which need be sent to memory 615 and 617
in order to execute move A. If multiple columns
are to be moved (i.e., the count in register R2 is
more than one), Table T8 will be addressed more
than once with the total sequence for the move
EN974012 -21-
`--` 10562~V7
1 being several sets of six numbers.
Block 95 Line 616A is interrogated to determine if the
previous operation is complete. This interrogation
is repeated until an operation complete signal is
received on line 616A.
Block 96 The commands necessary (found in Block 94) to
execute move A are sent by processor 610. This
includes: sending six numbers to memory 615 in
order to move the carrier, sending a series of
numbers to memory 617 in order to move the disk,
and sending a signal on the appropriate one of the
hammer firing lines 616Vl, 616V2, 616V3, or 616V4.
Request new data.
Block 97 If Block 88 found that the third element of data
in the data string was a "no data" condition,
Block 97 interrogates the second element of data
to determine if it also is "no data" condition.
BlocX 98 If the third element of data is a "no data" condition
and the second element of data is not a "no data"
condition, Block 98 specifies the speed for move A
as being the smallest non-zero speed.
Block 99 If both the second and third elements of data are
a "no data" condition the carrier must be stopped.
The sequence of commands to stop the carrier is
extracted from Table T8 (FIGURE 8 herein).
Block 100 The system waits for a signal on line 616A to
indicate that the operation is complete. t
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. . .
1 No operation proceeds until this signal arrives.
Block 101 The commands necessary to stop the carrier (found
in Block 99) are sent to memory 615 and new data
is requested.
Block 102 If the carrier is stopped and the second element
of data is a "no data" condition, more data is
requested.
Block 103 The amount of disk rotation for move A is obtained
as explained with reference to Block 90.
Block 104 One is added to the amount in register Rl to
determine the amount of carrier advance.
Block 105 The sequence of commands is obtained from Table T8
in memory as in Block 94.
Block 106 (FIGURE 10A) An interrogation is made of the data
in data string T9 (shown herein in FIGURE 9) to
determine if all three datums are a "no data"
condition. If they are, more data is requested.
Block 107 A new "no data" datum of information is inserted
in the data string in Table T9.
The actual program to implement the above described
flow diagram on a commercially available IBM System/7 is a
direct state-of-the-art translation of the above flow diagram.
Various other embodiments of the present invention are
possible. For example, it is possible to design a system
which has an infinite variety of speeds at which a carrier
can traverse between print positions. Such a system would
require more complex logic; however,
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1 it would achieve increased speea, thus presenting a cost
benefit trade-off which must be made in the design.
At each print position, the system would calculate the
desired velocity of the carrier in order to arrive at the
next print position. This calculation could take into
account the following parameters:
1. There is a certain maxlmum allowable velocity
(hereinafter called CVN) due to the inherent
limitations of the carrier mechanism.
2. If the carrier were to travel at a constant velocity
between adjacent print positions, the CVN velocity
would be different for the traverse between successive
print positions because of the fact that the print
wheel need rotate different amounts. In order to
simplify the calculation, the system could restrict
the velocity of the carrier at each print position
to a velocity which is less than the CVN velocity.
3. The mechanical aspects of the carrier also dictate
that there is a maximum allowable acceleration. ~-
The velocity chosen must not require more than
this maximum allowable acceleration.
4. The mechanical characteristics of the carrier also
impose a maximum allowable deceleration. It is t
important that the carrier speed at any print
position be such that the carrier can, in fact,
decelerate to the desired speed before the next
print position.
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' . ' ' , ,, ': . ~ "
. ~ ~ . . . ..
10562107
1 The embodiment of the invention shown herein does not
have proportional spacing. That is, the amount that the
carriage moves for each character is identical to the amount
moved for any other character. The present invention could
also be advantageously utilized in a proportional spacing
system. In a proportional spacing system, each character is
considered as having a particular number of units of width.
For example, the letter "W" would have seven units of width
whereas the letter "i" would have three units of width. The
velocity of the carrier is calculated utilizing the number
of units of space which the character must move rather than
the number of columns which the carrier must move. In a
proportional spacing system, the logic would determine the
number of units which the carrier must move to print a
particular datum. Depending upon the particular series of
datums which are to be printed and whether or not there are
any spaces between these datums, particular velocities would
be chosen.
Other embodiments of this invention are also possible.
However, they would all involve the fundamental principle
that the hammer firing must be timed in relationship to the
particular velocity which the carrier is moving when a
particular character is printed.
One method of timing the hammer firing is shown herein.
Other equivalent methods could also be utilized. For example,
one could have another counter which is counted to zero in a
manner similar to counter 630 and 631. The processor would
insert a number in this counter depending upon when the
hammer should be fired for the particular carrier velocity
at which a
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~056~V7
1 character is printed. Other alternate equivalent means of
timing the hammer in relation to the carrier speed are also
possible.
As shown herein the carrier moves at four speeds. A
system using more or less speeds could be utilized. One
could also use a continuously variable range of speeds;
however, this would complicate correct firing of the print
hammer. A system with continuously variable speeds would
have to use a counter which is loaded with a number and
counted to zero to time hammer firing.
As shown herein, the carrier is moving at one of several
possible velocities when each character is printed. However,
one of the allowable velocities could be zero.
The term "hammer flight time" is used herein to mean
the length of time between when the beginning of the hammer
fire signal appears and when the type hits the paper.
It is noted that in FIGURE 8, for all units of disk
rotation other than one there are as many timing numbers as
there are units of rotation required because one timing
number causes one unit of rotation. For example, for 4
units of rotation, numbers N93 to N96 are used. However, if
only one unit of rotation is desired, three timing numbers
N85 to N87 are used. These numbers could be
1400F 2000R 2000F
where F and R indicate the direction bits. With these
numbers, one gets a forward pulse, a reverse pulse, and a
forward pulse, the net of which is one step forward.
While the invention has been particularly shown and
described with reference to a preferred embodiment thereof,
it will be understood by those skilled in the art that
various changes in form and details may be made therein
without departing from the spirit and scope of the invention.
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