Note: Descriptions are shown in the official language in which they were submitted.
~Z~344~
APPARATUS FOR SYNCHRONIZING CARRIER SPEED AND
PRINT CHARACTER SELECTION IN ON-THE-FLY PRINTING
DESCRIPTION
Back~round of the Invention
.
5 l. Field of the Invention
.
This invention relates to a movable disk printer and in
one of its aspects to such a printer in which printing is
provided while at least a movable carriage on which the
movable disk is mounted is on-the-fly. More specifically,
10 this invention relates to the synchronization of a movable
disk which rotates for a variable distance with the car-
riage moving at a variable velocity so that the moving
carriage reaches a selected print position coincident with
the rotatable disk's arrival at the print character
, 15 selected for said print position.
2. Description of Prior Art
Printers which utilize a rotating disk with characters on
the periphery thereof are well known. Several of such
printers are commercially available. Rotating disk
.
AT3-78-031
: .
_ . . .. . _ _ ............... . . _ . _ . . .... . . .
. . ~ :
~z~46
- printers can be divided into 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 ~e
5 divided into a first category where the disk constantly
rotates and into a second category where the mo~ion of the
disk is intermittent. In printers with a constantly
rotating disk, printing takes plac~e when the hammer strikes
the rotating disk. Rotation of the disk is not stopped
10 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.
An alternate division of disk printers can be made by
lS 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
20 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
25 the rotating disk time to move to the desired character.
Th`e following are some of the issued and pending patents
which show rotating disk printers:
The Willcox U. S. Pat. No. 3,461,235 issued Aug. 12, 1969,
shows a disk printer with a constantly rotating disk. The
30 carrier stops at each print position.
AT9-78-031
~28446
The Ponzano U.S. Patent No. 3,707,214, issued 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 U.S. Patent No. 3,356,199, issued 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 in each print position.
The Giani U.S. Patent No. 3,742,845, issued July 3, 1973,
shows in Fig. 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 U.S. Patent No. 3,794,150, issued February 26,
1974, discloses a drum printer which includes an incre- -
menting carrier. The carrier stops at each print position
until the drum rotates to the desired position.
.
U.S. Patent No. 4,101,006, issued July 18, 1978, of Jensen
et al, discloses a carrier control system for a start-stop
disk printer in which the carrier normally traverses at a
predetermined 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.
AT9-78-031
';
~28496
U.S. Patent No. 4,030,591, Martin et al, issued June 21,
1977, discloses a rotating disk printer where the carrier is
moving at a variety of velocities when the printing by the
firing of the print hammer takes place. Thus, the firing of
the print hammer must be timed dependent on the velocity of
the carrier or carriage at the particular instance.
In U.S. Patent No. 3,858,509, issued January 7, 1975, a
rotating disk printing apparatus is disclosed in which the
striking force applied to the hammer can be varied between
"light" and "hard". However, in that patent the printing is
not done on-the-fly and there is no need to coordinate the
speed of the carriage and the travel time of the print
hammer to insure that the position of the character to be
printed is at the print impact point at the time it is
caused to strike the printing medium.
U.S. Patent No. 4,035,781, L.H. Chang, issued July 12, 1977,
mentions a procedure in a printer wherein upon a failure to
print, at least one retry to print is made before the
apparatus is stopped for an error correction routine. This
patent does not involve on-the-fly printing wherein the
carrier is never stopped. In the apparatus of the patent,
the carrier appears to stop at each print position. Thus,
it appears to be-unrelated to the problem of synchronization
of time related parameters in on-the-fly printers.
Further developments with rotating disk printers covered in
a Kane et al U.S. Patent No. 4,189,246, issued February 19,
1980, relate to rotating disk printers in which the carrier
is moving at a variety of velocities, the rotatable char-
acter disk is rotating over a variety of distances and the
AT9-78-031
;
.
1~84~6
print hammer is driven at a variety of forces in order to
achieve consistent and high print quality. Thus, the app-
roach in U.S. Patent No. 4,189,246 adds a Eurther element,
i.e., variable hammer force, which, unlike the apparatus of
U.S. Patent 3,858,509, must be coordinated with a variable
carriage velocity and variable disk rotation distance in
order to achieve the desired synchronization of selected
print character with the selected carrier with the selected
carrier print position. Actually, as set forth in U.S.
Patent 4,189,246, the variations in impact force of the
hammer are manifested by corresponding variations in hammer
flight time. Thus, in order to achieve synchronization for
printing a character, the apparatus depends on the synchro-
nization of three time-related variables: the variable
distance the character disk must rotate, the variable
velocity of the carriage, and the variable flight time of
the hammer. However, in U.S. Patent 4,189,246, the escape-
ment velocity, i.e., carrier speed, is constant ketween each
pair of characters but may vary from one character pair to
the next character pair depending on the relative distance
on the print disk between the characters in each pair. This
necessitated that relatively large tolerances be set on the
time for the carrier to escape to insure that the print disk
would have sufficient time to complete its rotation before
the carrier arrived at the next print position. The con-
sequence of this reduced throughput due to slower carrier
velocities.
:
; U.S. Patent No. 4,178,108 issued December 11, 1979, by M.H.
Kane offered an improvement to U.S. Patent 4,189,246 by pro-
viding means for correcting errors that occur when the print
disk rotation and the carrier escapement lose synchroniza-
tion. Loss of synchronization occurs when the carrier
escapes to the next print position before the print disk
AT9-78-031
~Z84~6
rotates the next character into posi-tion to be printed while
the carrier is still in motion, i.e., on-the-fly. U.S.
Patent 4,178,108 compensates for loss of synchronization by
stopping the carrier, reversing its motion and then re-
starting carrier motion in the direction of printing toregain synchronization. U.S. Patent 4,178,108 teaches that
the tolerances of the escapement time can be reduced since
loss of synchronization can be corrected. It further
teaches that tolerances must be maintained such that loss of
synchronization, and the resulting stopping of the carrier,
will occur infrequently enough that throughput will still be
improved over the tolerances required where occasional loss
of synchronization cannot be tolerated.
SUMMARY OF THE INVENTION
The present invention is directed to on--the-fly printing
apparatus wherein carrier means movable at variable velo-
cities from a first print position on-the-fly past a
second print position are coordinated with character
printing means, for example, a rotatable disk, having a
plurality of movable characters which are adapted to
imprint upon the application of an impact force. The
movable characters are controlled by character selection
means which move the characters over variable distances
during the movement of the carrier means from a first
selected character coincident with the carrier at the
first print position to a second selected character coin-
cident with the carrier at a second print position. The
apparatus further includes control means for controlling
movement of the carrier means and the character selection
means into coincidence at a print position such as said
second print position. Such control means further includes
AT9-78-031
~ ~ . .. .
~z~
means for synchronizing the carrier escapement time to the
print disk rotation time by varying the carrier escapement
velocity between print positions including acceleratlng
and/or decelerating the carrier ve:Locity such that total
5 escapement time coincides with print disk rotation time,
resulting in higher printing speeds and higher throughput
than heretofore achievable.
BRIEF DESCRIPTION OF THE DRAWING
.
Fig. 1 shows a printer apparatus adapted for use with the
10 present invention.
Fig. 2 is a schematic diagram, in block form, of the cir-
cuitry for controlling the operation of the printer appa-
ratus in Fig. 1.
Fig. 3 is a table of escapement velocities as related to
15 selection time magnitudes.
Fig. 4 is a table of delay times for escapement motor
drive as related selection time magnitude and escapement
velocity.
Fig. 5 contains graphs showing combinations of velocities
20 utilized to move the carrier certain distances as examples
of carriage movement during printing.
Fig. 6 is a table showing the control bits for producing
the velocity profile shown in Graph A of Fig. 5.
Fig. 7 is a flow diagram depicting the sequence of opera-
25 tions executed by the escapement controller shown in
Fig. 2.
AT9-78-031
.
~lZ84~;
DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 shows the main mechanical components of a printer
of the well-known type which utilizes a rotating disk with
characters on the periphery thereof. A laterally sliding
5 carrier 1 is mounted on a guide rod la and a lead screw 7
and carries a rotatable print wheel or disk 2 driven by a
stepping motor 3. The carrier 1 is driven by lead screw 7
which is driven by a stepping motor 8. Alternatively,
motor 8 could drive a belt which in turn could drive
10 carrier 1. The lead screw 7 is threaded such that each
step of stepper motor 8 represents one increment of escape-
ment for the carrier 1.
A type disk 2 comprises a disk having a number of movable
type elements such as the flexible spokes or type fingers
15 9A, 9B, 9C, etc. Printing of any desired character is
brought about by operating a print hammer 10, which is
- acutated by a solenoid 11, both of which are mounted on
carrier 1. When the appropriate type finger approaches
the print position, solenoid 11 actuates hammer 10 into
20 contact with the selected type finger, driving it into
- contact with a paper 12 or other printing medium. An
emitter wheel 13 attached to and rotating with type disk 2
cooperates with a sensor FB2 to produce a stream of emitter
index pulses for controlling the operation of the printer.
25 The emitter has a series of teeth each of which correspond
to one finger 9A, 9B, 9C, etc., of the printing disk. A
homing pulse is generated for each revolution of the print
wheel by a single tooth on another emitter (not shown).
The printer control can thus determine the angular position
30 of type disk 2 at any time by counting the pulses received
since the last homing pulse. A toothed emitter lS is
AT9-78-031
.
- . - . .
1~2~4~6
mounted on the shaft of the motor 8 and in conjunction
with a sensor FBl pxovides pulses which indicate the
position of the carrier 1.
Stepper motors 3 and 8 are activated by conventional drive
5 circuits 21 and 22. Examples of the type of drive cir-
cuitry that could be used are shown in U.S. Patent 3,636,429.
A hammer solenoid 11 is actuated by a hammer drive circuit
23 which is also conventional.
The actions of positioning the carrier 1 and positioning
10 the print wheel 2 are, in general, independent except that
coordination is required at the instant printing occurs.
Both type disk 2 and carrier 1 must be in a selected posi-
ton (but they need not be at rest), when hammer 10 strikes
type disk 2.
15 Referring now to Fig. 2, a schematic diagram is illustrated
of circuitry which may be utilized to provide the appropriate
control signals to the escapement motor drive circuit 21,
to print wheel drive circuit 22, and to the hammer drive
circuit 23. The data which is to be printed comes from a
20 data source (not shown), which may be a conventional data
buffer or a keyboard input device such as a typewriter.
~- Data from the data source is conducted to the input of a
suitable computer or microprocessor, only the output of
which is illustrated in Fig. 2, and the microprocessor can
25 be any suitable commercially available microprocessor or
computer such as the IBM System 7. The processor receives
the input data and will make certain calculations and then
send a series of binary numbers out on either an address
bus 40 or a data bus 41 as illustrated in Fig. 2. In
30 response to the data received from the microprocessor, the
circuitry in Fig. 2 generates appropriate drive pulses to
AT9-78-031
,
~lZ~4~;
circuits 21, 22, and 23 in order to cause stepper motors 8
and 3 to move the carrier 1 and the disk 2 to the correct
positions, and to activate the print hammer 10 in orde~ to
print the data supplies by the data source. The output
5 signals to each of the drive circuits 21 and 22 include
information indicating the direction in which the stepper
motor should move and the number of steps to be moved, it
being understood that one pulse is provided by the appro-
priate drive circuit for each step of the motors 3 and 8.
10 As illustrated in Fig. 2, the circuitry of this invention
includes a plurality of buffer registers indicated gener-
ally by the reference number 42 which receive appropriate
information from the microprocessor through address bus 40
and data bus 41. Buffer registers 42 include an operating
15 state register 43, which controls the direction of movement
of carrier, a hammer energy register 43 which stores data
concerning initiation time and duration of the hammer
energy pulse, and a selection register 46 which receives
and stores data from the microprocessor concerning the
20 selection of the characters on the printing wheel 2. In
order to load data into the buffer registers 42 from the
microprocessor, address data from the microprocessor bus
is inputted into a command decode circuit 47 and from
there through a control bus 48 to the respective buffer
25 registers. Likewise, data from data bus 41 of the micro-
processor is routed through data bus in gate 49 and data
bus 50 to respective inputs of the buffer registers 42.
The microprocessor is also connected through the control
bus 48, a data available line 51, and a data request line
30 52 to a sequence control circuit 53 which controls the
sequence of operation of the circuitry of Fig. 2 and of
the microprocessor, as hereinafter explained. Since
printing is accomplished by the present invention while
AT9-78-031
.
,
~28~9~6
carrier 1 is in motion, it is necessary to provide buf~er
registers 42 in order that data from the processor may be
stored therein prior to actual usage, to permit the micro-
processor to accummulate subsequent data and to permit new
5 data to be stored in the buffer registers when the pre-
viously stored data has been dumped. In this manner, the
data is available to the operating registers described
below when needed in order to permit the continuous opera-
tion of the system.
10 In addition to the buffer registers described, the circuit
of Fig. 2 also incluAes a plurality of operating registers
61, 62, and 64, and an escapement controller 63. A system
reset signal on line 73 is input to sequence control 53
and distributed to the operating registers and escapement
15 controller for initializing the system at power on or
after a system failure. In general, upon receipt of
appropriate load command, the operating registers receive
and store the information contained in the buffer regis-
ters 42j thus permitting the buffer registers to then
20 intake new data while the data in the operating registers
is being acted on. As illustrated in Fig. 2, an operating
state output register 61 is provided to receive and store
data from operating state register 43, a hammer delay and
energy register 62 is provided to receive and store data
25 from hammer energy register 44, and a selection downcounter
64 is provided to receive and store data from selection
register 46. The escapement controller is provided to
receive the selection data from the selection register 46
and to generate escapement velocity profiles based on the
30 selection time magnitude as will hereinafter be described
in detail. The outputs of the respective registers 61,
62, and 64 are connected as shown in Fig. 2 to escapement
motor control logic 66 for controlling the direction of
AT9-78-031
. . . ~
: . :
l~Z8~46
12
motion of carrier 1, to hammer control logic 65 for con-
trolling the actuation of print hammer 10, and to selection
motor control logic 67 for controlling the motion of print
wheel 2. The output of the escapement controller 63 is
5 connected to escapement motor control logic 66 for control-
ling the escapement velocity of the carrier 1.
Referring to Fig. 3 there is shown in outline form a table
of next velocity values stored in the escapement controller
63 for printing the next character. The tahle is arranged
10 as a matrix having a number of columns j equal to the
number of selection time magnitudes S for rotating the
print disk 2 and a number of rows i equal to the number of
velocity values N at which the carrier 1 may be moving
when printing occurs. The selection time magnitude S is
15 determined by the time required to rotate the print disk 2
from its present position to the position of the next
character to be printed. In the preferred embodiment,
motor 3 is capable of bidirectional rotation so that the
maximum number of selection times j is one-half of the
20 number type fingers. The number of carrier velocities i
at printing can occur is a designer's choice limited only
by technology. In the preferred embodiment a range is set
from zero to ten inches per second. The selection time
magnitude S and the velocity N are combined to access the
25 next velocity table of Fig. 3 to produce a velocity value
V at which the carrier will be moving when the selected
~ character is printed in order to synchronize selection and
;~ escapement. The escapement controller 63 receives from
the selection register 46 the magnitude of the selection
30 time, S, for rotating the print disk to the next printing
character. The selection magnitude S is combined with the
velocity N of the carrier which is stored in a register in
AT9-78-031
_ _ _ , _ . . . , . : .
: - . . :
~2B44~6
13
escapement controller 63 to access the table and provide a
next velocity V which is required to synchronize the
carrier movement with the print disk rotation.
Referring to Fig. 4, a second table which is stored in the
5 escapement controller 63 is shown which contains the delay
times used to control the escapement stepper motor 8 to
provide carrier transition from the velocity N at which
the last character was printed to the next velocity V at
which the next character will be printed. The table of
10 Fig. 4 contains one matrix of values for each of the next
velocities V from the table of Fig. 3. Each matrix of the
table of Fig. 4 is arranged into columns corresponding to
the selection time magnitude for the next character to be
printed and rows corresponding to the number of carrier
15 increments between print positions. Recall the carrier
increments are determined by stepper motor 8 and the
threads on the lead screw 7. The preferred embodiment of
the invention is described for illustrative purposes only
using a 10 pitch printer, i.e. a printer which prints ten
20 characters per inch with each character occupying a fixed
amount of space. It will be understood that some other
pitch, such as 12 pitch could be selected or that propor-
tional spacing can be employed within the scope of this
invention. In the preferred embodiment the stepper motor
25 8 and lead screw 7 accomplish 240 steps per inch which
provides 24 increments for each character of escapement.
This requires that stepper motor 8 make 24 steps between
printing characters coincident with the selection time
magnitude of the print disk 2. The matrix of the table of
30 Fig. 4 which corresponds to the next velocity V is accessed
using the selection time magnitude S and the escapement
increment density value D to provide a delay time t. The
delay time t is the time between drive pulses to the
AT9-78-031
46
14
escapement stepper motor 8 which controls the escapement
velocity. The series of delay times t from the delay
table combine to change the carrier velocity to the next
velocity V in the selection time S.
5 Fig. S shows four graphs as examples of selection times
required to rotate the print disk 2 from a first selected
print character to a second selected print character and
the corresponding escapement velocities used to synchronize
the escapement with the selecton time. The horizontal leg
10 of each graph represents the incremental escapement den-
sity, d, between characters. As previously stated, the
preferred embodiment of this invention is described as a
fixed pitch printer which prints ten characters per inch
of escapement. The lead screw 7 contains 240 increments
15 per inch, therefore giving 24 increments of escapement per
character position as shown in the graphs. The vertical
leg of each graph in Fig. 5 represents the carrier velocity
in inches per second. In operation, the escapement con-
troller 63 provides a signal to the escapement motor
20 control logic 66 which determines the frequency at which
- the stepper motor 8 is pulsed by the escapement motor
drive circuit 21. The delay between pulses to the stepper
motor 8 determines the velocity of the carrier. As is
readily apparent, a small delay between pulses to the
25 stepper motor 8 causes the carrier to move at a higher
velocity and conversely a longer delay between pulses to
the stepper motor causes the carrier to move at a lower
velocity.
Fig. 6 is a table of delay times for corresponding to the
30 escapement graph A of Fig. 5 and Fig. 7 is a flow diagram
.
AT9-78-031
.
- : , . . . . ,: ~ ~ .
~28~46
8 of the operation of the escapement controller 63. ~efer-
ring now to Figs. 5, graph A, 6, and 7 in combination a
typical escapement of the carrier from one print position
to the next will be described. In Fig. S, graph A, it is
5 shown that the selection time equals 27.684 milliseconds.
This is the time required ~or the print wheel to rotate
from the character just printed to the next printing
character. This time is stored in the selection register
46. The graph A in Fig. 5 assumes that the carrier is
10 moving at six inches per second when the selection time is
generated in the selection register 46. Referring to Fig.
7, the initial value of the velocity register is set to
zero at block 101 when the system is turned on or in
response to a system reset at block 102. When the start
15 line is energized by the sequence control 53 (Fig. 2) the
escapement controller tests the start line at block 103.
When it is determined that a start signal has been set,
the selection magnitude is read from the selection regis-
ter by the escapement controller at block 104. Assuming
20 the carrier velocity is six inches per second, the velo-
city register will contain 6. At block 107, the density
counter is set equal to one representing the first incre-
ment of escapement toward-the printing of the next charac-
ter. The value of the density counter is tested at block
25 108 to determine if it is less than or equal to 24, the
incremental position at which the next character is to be
printed. If the result of the test is affirmative then
the escapement controller 63 outputs a signal to the
escapement motor control logic 66 to step the escapement
30 motor 8 at block 109. The velocity, selection, and density
values are then combined to access the delay table tFig.
4) to determine the amount of delay to be executed prior
to the next motor step. Referring to graph A of Fig. 5
.
AT9-78-031
.
:
16
and Fig. 6 it can be seen that for the first increment of
escapement density, D, the escapement velocity is six
inches per second. The binary value representing the
delay time between pulses to the stepper motor to maintain
S escapement at six inches per second is counted down at
blocks 112 and 113 in Fig. 7. When the delay time has
been counted down an increment is added to the density
counter at block 114 and a branch :is taken back to block
108 to test the magnitude of the density counter contents.
10 If it is still less than or equal to 24 a pulse is output
once again at 109 to step the motor 8 and the delay is
accessed from the delay table using the velocity and se-
lection at the new density (Fig. 4). At the ourth incre-
ment, 0 = 4, the delay time is increased and correspond-
15 ingly the carrier velocty is decelerated to S.5 inches/second. At D = 5, D = 6, D = 7, D = 8, and D = 9 the
carrier is further decelerated until the next print velo-
city of three inches per second is attained. The delay
value is then constant for the remaining increments of
20 this carrier escapement. When the density counter exceeds
24, the carrier has escaped to the next print position and
a branch is taken to block 105. The value of the selection
magnitude and the velocity register value are combined to
access the next velocity table (Fig. 3) at block 105. As
25 was previously stated, the velocity value that is accessed
in the next velocity table is the escapement velocity
value for the carrier at the time the next character is to
be printed. In graph A this value is three inches per
second. At block 106 the velocity register is set equal
30 to the next velocity value. A finish signal is set at
block 111. A branch is then taken back to block 102 and
the process is repeated for the next character.
AT9-78-031
~ . . _, . , , _ _. .
~2~4~6
While the invention has been particularly shown and
described wlth reference to a particular embodiment, it
will be understood by those skilled in the art that vari-
ous changes in form and detail may be made without depart-
5 ing from the spirit and scope of the invention.
'' ,1
AT9-78-031
- , .
- :
