AU6223473A - Electronic printer - Google Patents

Description

Regulation 9

COMMONWEALTH OF AUSTRALIA j

PATENTS ACT 1952-1969

62.234 m APPLICATION FOR A PATENT

WE, TEXAS INSTRUMENTS INCORPORATED, a

Corporation of the State of Delaware, United

States of America, having its principal place

of business at 13500 North Central Expressway,

Dallas, Texas, United States of America, hereby

apply for the grant of a Patent for an invention

entitled "ELECTRONIC PRINTER" which is described

in the accompanying Complete Specification.

Our address for service is care of COLLISON CO.,

Savings Bank Building, 97 King William Street,

Adelaide, South Australia, 5000.

This application is a separate application

made by virtue of sub-section of section

49A of the Patents Act 1952-1969 in respect of

an invention disclosed in the complete specification

lodged in respect of Application No. 64320/60.

Dated this 5th day of November, 1973.

TEXAS INSTRUMENTS INCORPORATED, By their Patent Attorneys, COLLISON CO. G. E. HABEL.

TO:

THE COMMISSIONER OF PATENTS, WODEN, 2606. A.CT. WODEN, A.C.T. 2606.

I

COMMONWEALTH OF AUSTRALIA Form PATENTS ACT 1952-1969

COMPLETE SPECIFICATION (ORIGINAL)

62,234 t73 FOR OFFICE USE Class lae*l Application Number: L4 3i 7, 3 Lodged: 7 -i

a o 6o F 3 11;,2 4 1: /oT (S Pff(c/o.31 o- 1 4 1 7C S/3 Complete Specification-Lodged: 7 '1 73 Published: Priority:

Related Art:

TO BE COMPLETED BY A. LLICANT Name of Applicant: TEXAS INSTRUMENTS INCORPORATED

Address of Applicant: 13500 North Central Expressway, Dallas, Texas 75222, United States of America.

Actual Inventor: JAMES 4AWJ. BRENNAN, JR., DONALD FRANK BOREN and HERMON LLOYD POPE

Address for Service: care of COLLISON CO., Savings Bank Building, 97 King William Street, Adelaide, South Australia

Complete Specification for the invention entitled: "ELECTRONIC PRINTER"

The fu w'ing statement is a full description of this invention, including the best method of performing it known tc&, US:

I This invention relates generally to an electronic

printer for time shared computers,

Input-output terminals currently in use are

relatively slow compared to computer operating speeds

and data transmission rates. Slow input speed is the

result primarily of the relatively slow rate at which

an operator can encode the data by means of a conventional

typewriter type keyboard. This is particularly

disadvantageous when used in time sharing computer

applications because the central processor is tied

up for the erire period that an operator at one of

the remote stations is inputting data to the processor

by means of the keyboard. In addition, the input-output

stations presently in use have been relatively slow in

printing out, relatively expensive, relatively bulky,

and quite noisy.

This invention is concerned with an input-output

station which utilizes an MOS shift register storage

means for accumulating a predetermined number of

characters prior to responding to polling from the

central processing unit of a time sharing system. The

output fromnt the accumulator is then transmitted to the

central processing unit in response to polling at the

maximum rate the data transmission link allows. The station utilizes an elsctronic printer which provides the

capability of directly printing out data from the central

processing unit at the maximum data transmission rate.

In addition, the electronic printer is silent in operation,

is more reliable, is smaller in size, lower in weight than previously available stations, and provides for an auxiliary input and auxiliary output device.

There is thus provided according to the invention

an electronic printer comprising an electronic printing

device for printing characters onto a sheet of a

recording medium being kept in a supporting means for

causing contact between said printing means and the

recording medium at each printing position, said

printing means being movable across the sheet of

recording medium and can be positioned at each printing

position, a carriage, said printing means being mounted

on said carriage and movable along guiding means by a

first stepping motor. A counter for stepping the

stepping motor and means coupled between said counter

and the windings of the stepping motor for deenergizing

all motor windings in response to a return carriage signal.

In order to more fully understand the invention

reference may be made to the following detailed

description of an illustrative embodiment, when read

in conjunction with the accompanying drawings, wherein:

Figure 1 is a schematic logic diagram of an

input-output station in accordance with the present

invention;

Figure 2 's a simplified sectional view of an

input-output station in accordance with the present

invention;

Figure 3 is an end view of the electronic printer

of the input-output terminal of Figure 2;

Figure 4 is a front elevational view of the

electronic printer of Figure 3;

Figure 5 is a schematic diagram illustrating the

cable system of the electronic printer of Figure 3;

Figure 6 is a plan view of the electronic printer

of Figure 3;

Figure 7 is a partial vertical sectional view cf

a portion of the paper advance mechanism of the electronic

printer of Figure 3;

Figure 8 is a transverse sectional view of the

electronic printer of Figure 3 looking toward the

left-hand end of the device with a carriage at the

left-hand margin;

Figure 9 is a schematic circuit diagram of the

electronic controls of the electronic printer;

Figure 10 is a schematic logic diagram of the

coitrol logic shown in Figure 9;

Figure 11 is an isomet-ic view of the rear face of

of the printhead and heat sink of the electronic printer

of Figure 3;

Figure 12 is an enlarged view of the printhead shown

in Figure 11;

Figure 13 is a sectional view taken substantially on

lines 13-13 of Figure 12, and

Figure 14 is a schematic circuit diagram of the

temperature compensation circuit of Figure 9.

Description of Figure 1 Logic

Referring now to the drawings, an input-output station in accordance with the present invention is indicated generally by the reference numeral 10 in the schematic logic diagram of Figure i. The input-output station 10 is adapted to operate with a conventional data set 12 used to transmit serial-by-bit data by existing telephone data link. For example, the data set may be a Bell Telephone System type 103F2 and may be linked by telephone line with an IBM (Registered Trade Mark) 360

Model 30 computer utilizing an IBM 2702 transmission

control unit. Utilizing such a sy3tem, a rate of fifteen

characters per second can be achieved, the limiting

factor being the telephone line data link.

The system 10 includes a data set interface 14 which

is adapted to convert serial-by-bit character codes to the

necessary logic levels of "request to send", "clear to send",

"data terminal ready", "data set ready", and "carrier data"

in the conventional manner. In addition, serial-by-bit

data is transmitted from interface 14 over line 16, and the

same type of data is received over line 18. The serial-by-bit

data is transmitted from the interface 14 to a converter

by way of line 22, and serial-by-bit data is received from

the converter 20 by way of line 24.

The converter 20 is a shift register having parallel

data inputs on channel 26 and parallel data outputs on

channel 28 in addition to the serial input 22 and serial

output 24. The converter thus performs serial-to-parallel

conversion of data received from the data set interface 14,

and performs parallel-to-serial conversion of data output to the data set interface 14.

The parallel-by-bit data from the converter

is passed through a selectively enabled switching network

represented by OR gate 30 to a :single character buffer 32.

The parallel data in buffer 32 is continuously available

to an electronic printer 34, which will hereafter be

described in detail, by way of channel 36, and to an auxiliary

output device 37 of any desired type by way of channel 38.

The electronic printer 34 has the capability of printing

character data at the maximum transmission rate.

The parallel-by-bit data produced by a conventional

keyboard and encoder device 40 and the data encoded by the

auxiliary input device 39 may be selectively, in the

alternative, passed thrc-igh gate 30 by way of channels

42 and 44, respectively, and stored in buffer 32. This

data is printed out by the electronic printer 34 as it is

encoded to permit the operator of the keyboard to read what

is being encoded. The character in the buffer 32 is also

stored in an accumulator register 48 by way of channel

The accumulator register 48 is comprised of a number of

shift registers equal to the number of parallel bits

contained in the data, each MOS shift register having a

number of bits corresponding to a complete line of data

produced by the electronic printer 34. For example, if

the electronic printer 34 is capable of printing a fifty

character line, the shift registers of the accumulator 48

would include at least fifty bits plus end of address and

new line code characters at the beginning and end of the block of data. The output from the accumulator register

48 is passed through level converters 54 and gated out by

way of channel 56, gate 58, channel 60, and gate 62 to

the converter 20 at the appropriate time as will hereafter

be described.

All data passing through gate 30, whether from the

converter 20, keyboard encoder 40, or output of the

auxiliary device 37, is continually applied to a static

command decode circuit 64 by way of channel 63. The

command decode circuit 64 produces eights logic signals

on lines 65-72 which are indicative, respectively, of the

end of transmission (EOT), poll character for station (POLL),

keyboard address, auxiliary input address, electronic printer

address, auxiliary output address, end of address (EOA)

received, and "yes" received.

When an end of transmission signal EOT is received,

a reset flip-flop 74 is set, which in turn resets the

entire system. When the station poll character is

received, the poll flip-flop 76 is set which in turn

enables the keyboard flip-flop 78, the auxiliary input

flip-flop 80, the printer flip-flop 82, and the auxiliary

output flip-flop 84. Then when a keyboi address, an

Luxiliary input address, a printer address, or an auxiliary

output address is decoded, the respective flip-flops are

set.

When the keyboard flip-flop 78 is set, gates 86 and

88 are enabled. If the MOS acciumulator register 48 is full,

as detected by the MOS full detector 90, gate 86 enables gate 58 through OR gate 96 so that data stored in register 52 is gated out. If the MOS storage 48 is not full, gate 88 produces an output which triggers the "No" flip-flop 92 through OR gate 94. Then when the MOS accumulator 48 is filled, the output from gate

88 ceases, the "No" flip-flop 92 is reset, and the data

from the MOS accumulator register 52 is gated out as a

result of the signal through gates 86, 96, and 58. The

same procedure is followed when the auxiliary input rather

than the keyboard is addressed by the computer as the

result of the operation of AND gates 98 and 100. Thus, the input

from either the keyboard or the auxiliary device is selected

by the central processing unit of the computer.

When the printer is addressed, the printer flip-flop

82 is set, thus enabling gates 102, 104 and 106. Then if

the electronic printer 34 is not ready, as indicated by

a low state on line 105, gate 104 sets "No" flip-flop 92

through gate 94. When the electronic printer is ready,

gate 102 sets "Yes" flip-flop 108 through OR gate 110

and gate 106 is enabled by line 114 if the text flip-flop

112 is high as a result of receiving an end of address

record over channel 71. This gates out a print strobe

when a timing pulse is applied to gate 106 by the timings

circuit 116.

When the auxiliary output device is addressed on

line 70, the auxiliary output flip-flop 84 is set, thus

enabling gates 117, 118, 120. These three gates then

function ir the same manner as gates 102, 104 and 106, dependent upon the status of the ready line 122 from the auxiliary device 37, and line 114 from the text flip-flop 112.

A "Yes" flip-flop 124 is set whenever the printer is

addressed and ready, whenever the auxiliary output is

addressed and ready, or whenever a longitudinal redundancy

check is satisfactory as will presently be described. An

end of block flip-flop 126 is set by line 127 whenever a

line shift is detected in the last storage space of the

accumulation register 48. A command encrder 128 produces

an appropriate character whenever the flip-flops 124 and

126 are set and this character is transferred by channel

130 through gate 62 and channel 26 to the converter

The content of the buffer 32 is also continually

applied to a longitudinal redundancy check (LRC) circuit 132.

The circuit 132 performs a conventional longitudinal redundancy

check on all incoming data received from the central

processing unit and then compares the locally generated LRC

number with the LRC number received from the central processing

unit immediately following the receipt of an end of block decode

signal from the command decode 64 which sets end of block

(EOB) flip-flop 133. In addition, the YRC circuit 132

generates an LRC number for all outgoing data. The LRC number is transmitted by way of channel 134, gate 136,

channel 138 and gate 62 after an end of block character (EOB)

has been send from encoder 128. This results from the

detection of a line shift character in the last storage

space of the accumulation register 52 and the setting of EOB

U flip-flop 126 by line 127, to in turn set the enable LRC

flip-flop 139 and gate out the LRC number through gate 136.

Operation of Figure 1 Logic

In operation, assume that data is to be transmitted

to the central processing unit. The operator of the

keyboard 40 first presses the clear button which resets

all flip-flops and puts an end of address (EOA) code in

the first character of the MOS accumulation register 48.

The operator then proceeds to enter data from the keyboard

into the accumulation register 48 by way of gate 30 and

buffer 32. When the operator has either filled the line,

or entered all of the data, the return carriage button

is pushed which generates a new line code which is also entered

in the accumulation register

As soon as the new line character is received by the

first-in storage space of the accumulation register, all

characters are stepped through the register until the end

of address (EOA) character is detected at the first-out storage

space, indicati that the MOS register is full. This

resets the Cext flip-flop 112 by way of channel 113 to

disable print strobes through gate 106, and sets the MOS

full flip-flop 90 to enable gates 86 and 98 by way of line 93.

Then when the central processing unit polls the station,

poll flip-flop 76 is set, thus enabling flip-flops 78,

82 and 84. Then when the keyboard is polled, keyboard

flip-flop 78 is set, thus enabling gate 58 through gate 96.

Data is then sent from accumulation register 52 to the

computer over channel 60, gate 62 and converter 20 at the maximum rate jermitted by the data link, the rate being clocked by the timing circuit 116.

When the new line character is detected in the

first-out storage space of the accumulator register 48, the

end of block flip-flop 126 is set by line 127 so that an

end of block character is transmitted on channel 130

following the new line character. The output from the

end of block flip-flop 126 also sets the enable LRC flip-flop

139 which in turn enables gate 136 so that the LRC number

is transmitted following the end of block character.

After the central processing unit has performed the

longitudinal redundancy check, a "yes" is transmitted by

the central processing unit. When the "yes" code is

decoded by the command decode 64, the station 10 goes

into the idle state.

If an end of address EOA character is received from

the computer, text flip-flop 112 is set by line 71, thus

enabling either gate 106 or 120. The central processing

unit may then send data whj:h will be printed out without

further addressing the station or electronic printer.

Any time that data is to be transmitted by the computer

to station 10, the station is ,olled to set POLL flip-flop

76 and either the electronic printer 34 is addressed to

set flip-flop 82, or the auxiliary output device 37 is

addressed to set flip-flop 84. Then when an end of address

signal is transmitted, text flip-flop 112 is set by channel 71

to enable gate 106 or 120. If the printer is addressed and

is ready, the output of gate 102 sets the "Yes" flip-flop 124

I

and a "yes" is transmitted to the computer indicating

that the printer is ready. If the auxiliary output

device is addressed and is ready, then a "yes" is

transmitted to the computer. The data is then printed

out by the addressed output device at the rate received

from the computer. When the end of block (EOB) character

is received from the computer, the end of block flip-floD

133 is set, thus enabling the longitudinal redundancy

check circuit 132. The next character from the computer

is the longitudinal redundanc7 check number which is

compared with the longitudinal redundancy check number

generated locally during receipt of the last data block.

If the LRC numbers agree, "Yes" flip-flop 124 is set

by channel 135 and a "yes" is transmitted to the computer.

If the LRC numbers do not agree, the "No" flip-flop 92

is set by line 137 of a "no" transmitted to the computer.

If a "yes" is transmitted to the computer, additional

data may be sent by preceding the data with an end of

address (EOA) character. If an end of transmission

character (EOT) is sent instead, the reset flip-flop 74

is set through line 65 and the entire station 10 is cleared.

Description of Figures 2-8

The input-output station 10 is shown in the

simplified longitudinal sectional view of Figure 2 and is

comprised of a keyboard and encoder section 40, an

electronic printer 34, and an electronic circuitry package

140 which includes all of the circuitry of Figures 1, 9,

and 14. As previously mentioned, the keyboard and encoder is of conventional design and includes t'e electronics necessary to produ,e the seven parallel bit binary code representative of the characters on the conventional typewriter keyboard, together with the nececssary'control codes. The mechanical aspects of the electronic printer 34 are shown in the detailed views of Figures 3-8. The electronic circuitry is illustrated in Figures 9-14.

Referring now to Figures 3-8, the electronic printer

34 has a support comprised of a base plate 150 to which are

attached -ight-hand and left-hand end plates 152 and 154,

respectively. As can best be seen in Figures 4 and 8, a

carriage indicated generally by the reference numeral 156

is slidably mounted on a pair of cylindrical rods 158 and

160. The upper rod 158 i, pivotally journaled in the end

plates 152 and 154. The lower rod 160 is connected to the

upper rod 158 by right- and left-hand arms 162 and 164.

The left-hand arm 164 has a bell crank portion 166 which

is connected by a spring 168 to the base pla'e 150.

The carriage 156 includes a channel portion 170

2C. which has apertures in the flange portions receiving

the rods 158 and 160, and a heat sink 172 which is

connected to the channel 170 by a pair of standoffs 174

(see Figure An electronically controlled thermal

printing matrix 176, which will hereafter be described in

greater detail, is bonded to the interior face of the heat

sink 172. An extension 160a of the rod 160 extends to

the left of the arm 164. A metal tab 178 is connected to

the end of the extension 160a. A magnet 180 is mounted

I on the left-hand face of the left-hand upright support

plate 154 in a position to hold the tab 178 when the lower

rod 160 is pivoted inwardly. The rod 160 is also connected

to the piston rod 182 of the dash pot 184 which is also

mounted on the left-hand face of the left-hand upright

support-plate 154. When the tab 178 is pushed inwardly

against the magnet 180, the upper end of the heat sink 172

and thus the printhead 176 is pivoted outwardly and held

so as to permit loading of the paper as will presently be

described. The dash pot 184 prevents the spring 168 from

damaging the printhead 176 as it is returned by physically

breaking the hold of the magnet 180.

A third rod 186 and a paper advance drive shaft 188

(see Figure 8) extend between the upright support plates

152 and 154 and form a track upon which a pressure pad

carriage 190 is slidably mounted. The pressure pad

carriage supports a pressure pad 192 which is substantially

the same size as the printing matrix of the printhead 176

in mating contact with th- printing matrix. The pressure pad 192 includes a thin hard metal plate connected to the

pressure pad carriage 190 by a resilient block. The hard metal plate provides an abrasive resistant surface,

while the resilient block provides self-alignment to

assure uniform contact over the face of the flat matrix.

Both the printhead carriage 156 and the pressure pad

carriage 190 are moved from left to right across the

respective tracks 158-160 and 186-188 by a carriage

stepping motor 194 and cable system. The cable system

-1 A- includes a drum 196 mounted dircctly on the shaft of the stepping motor 194. The opposite ends of a cable

198 are secured in grooves 200 and 202 in drum 196

to form an endless loop. A length of the cable 198

greater than the distance of travel of the carriage 156

is wound around drum 196 at each end. As illustrated in

the schematic diagram of Figure 5, the cable 198 extends

around a pulley 204 journaled on the right-hand upright

152 to a second pulley 206 mounted on the left-hand

upright 154 to form a first reach 198a. The c -le

continues around pulley 208 journaled on the right-hand

upright 152, pulley 210 journaled on the left-hand upright

154, and back around pulley 212 mounted on the right-hand

upright 152 to form reaches 198b, 198c, and 198d. The

cable 198 is wound on the drum 196 in such a manner as

to unwind and pass around pulley 204 as it is wound onto

the drum from around pulley 212 at the same point on the

drum. The printhead carriage 156 is connected to reach

198a, and the pressure pad carriage 190 is connected to

23. reach 198c so that the two carriages are always moved in

the same direction and in synchronism by the cable system.

An electrical cable takeup carriage 214 is comprised

of a U-shaped plate having a base portion 216 extending

parallel to the rod 160 and right-hand and left-hand

arm portions 218 and 220 having sliding bearings 222 which

ride on the print carriage rods 158 and 160. A pair of

pulleys 224 and 226 are joirnaled on the base portion 216.

A second cable 228 (see Figure 5) extends from the

U right-hand upright 152 around the left-hand pulley 226,

back around the right-hand pulley 224 and then is

anchored at the left-hand upright 154. The cable 228

is not shown in Figure 4, or 6 to simplify the drawings.

A spool 230 is also journaled on the takeup carriage 214 and

a fla- multiple wire electrical cable 232 extends from

an anchor bracket 234 on the left-hand upright 154

around the spool 230 to the carriage 156. As the carriage

156 moves between the left-hand position 156a shown in

dotted outline in Figure 5 and the right-hand position

shown in solid outline, the spool 230 is moved one-half

the distance as represented by the dotted position 230a

as a result of the cable 228, thus keeping a slack out of

the multilead electrical cable 232.

A helical spring 236 is fixed to the left-hand

end of the shaft of the stepping motor 194 and to the

left-hand upright 154 by the bracket 238. The spring 236

preloads the shaft of the stepping motr! 194 with sufficient

torque to maintain the carriage 156 at its full left-hand

26. position when the windings of motor 194 are open-circuited,

and th torque of the spring is increased as the motor 194

steps the carriage from left to right. However, since

the spring 236 has a substantial length, the torque loading

on the motor shaft is not significantly increased from a

percentage standpoint, particularly since the shaft rotates

only about three and one-half revolutions. When the windings

of the stepping motor 194 are open-circuited, the torqcue

of spring 236 drives the drum 196 in a direction to very rapidly move the printhead carriage 156 and the pressure pad carriage 190 to the left-hand margin position.

A system for supporting and feeding thermally

sensitive paper 240 from a large roll is comprised of

a right-hand support 242 which is connected to the

right-hand upright by standoffs 243 and a left-hand

support 244 which is connected to the left-hand upright

154. The supports 242 and 244 have identical V-shaped

grooves 246 and 248 at the upper end for receiving the

stub axles 250 and 252 projecting from the support for

the roll of paper. The sheet of paper 240 proceeds

upwardly from the periphery of the roil around a buffer

roller 254 which is journaled on arms 256 and 258, see

Figure 6, which in turn are journaled on the supports 242

and 244, respectively, at pivot points IvIng on axis 260.

The arms 256 and 258 are biased upwardly by the straps

261 wound around drums 263 and urged downwardly by springs

265. The arms pivot against the force of the spring

between the upper position shown in solid outline in

Figure 3 and the position shown in dotted outline. The

paper 240 then proceeds around a fixed, cylindrical,

lower shelf 262, up between the printhead 176 and the

pressure pad 192, and over a fixed, cylindrical, upper

shelf 264 which terminates in an upwardly extending flange

portion 266. A guide trough 268 is disposed beneath the

lower shelf 262 to assist in causing the paper to pass

upwardly in front of the lower shelf 262.

From Figures 4, 6 and 8 it will be noted that the lower shelf 262 and the upper shelf 264 are spaced apart to provide a longitudinally extending groove

270. The pressure pad 192 projects through the groove

270 to a point slightly beyond the cylindrical curvature

of the lower and upper shelves 262 and 264, as can best

be seen in Figure 8. The lower and upper shelves 262 and

264 are mounted on a pair of slotted sleeves 272 (see

Figure 7) and 274 which are journaled on the line feed

drive shaft 188 by bearings 278. Paper drive rollers

280 and 282 are splined to the drive shaft 188 at each

end of the shelves 262 and 264 and have resilient rims

with radii very slightly larger than the radii of curvature

of the cylindrical shelves 262 and 264. A drive sheave 284

is splined to the shaft 188. Shaft 188 is rotatably

journaled in the right-hand and left-hand uprights

152 and 154. A pair of idler rollers 286 and 288 are

journaled on a shaft 289 which extends between the

ends of arms 290 and 292 vchich in turn are pivotally

mounted on a rod 294 which extends betweer the right-hand

and left-hand uprights 152 and 154. The arms 290 and 292 are

connected to helical springs 296 and 298, respectively,

which are disposed around the rod 294 and anchored by

clamps 300 and 302 so as to continually urge the rollers

286 and 288 toward the respective drive rollers 280 and

282, to clamp the edges of the paper 240 between the

idler rollers 286 and 288 and drive rollers. A roller

303 is also journaled on the center of shaft 289 to assist

in guiding the paper. A second stepping motor 304 is mounted

on the outer face of the right-hand upright support 152

B

and has a shaft extending leftward into a rotary dash

pot 306. A drive sheave 308 is mounted on the housing

of the dash pot 306 and drives a toothed belt 310 which

passes around sheave 284 on the feed roller shaft 188.

Thus, as the motor 304 is stepped as will hereafter be

described, the continuous sheet of paper 240 from the

roll is advanced, one line at a time, by the rollers

280 and 282.

Description of Electronic Printer Control Circuitry

The circuitry for operating the electronic printer 34

is shown in the schematic block diagram in Figure 9. The

data output from the buffer 32 is fed both to a control

logic circuit 320 and to an MOS array character generator

circuit 322. The control logic 320 decodes control

characters from the data to provide a data bit on line

324 representative of whether an upper case or lower case

character upshift or downshift) is to be printed.

The control logic 320 also prevents operation of the

printer if a parity check is not satisfactory, and provides

a print and step cycle, a back space cycle, a carriage

return and line feed cycle, and a line feed only cycle.

During the print and step cycle, the control logic 322 also

produces a positive-going print pulse on line 326, a

negative-going print pulse on line 327, and a printer not

ready signal on line 105. The character generator circuit

decodes seven parallel bits, plus complements, to selectively

turn the buffer stage 420 and heater element transistor

424 "on" during the print cycle to produce the proper

character. A temperature compensation circuit 450 senses the temperature of printhead 176 by means of diode 452 prior to the print cycle, and then sets the supply voltage to the printhead at a level to produce a predetermined temperature during the print cycle.

Referring now to the detailed logic diagram of

Figure 10, the printhead carriage stepping motor 194 has

four windings, each of which moves the shaft of the motor

to a predetermined position when energized. A reversible

counter 318 is reset to a count of one when the printhead

carriage 156 returns to the left-hand margin by a logic

on line 338. The counter is then incremented one

count at the end of each print pulse by line 336 going

from a logic to a logic A decoder 328 decodes

the count of counter 318 and energizes the outputs 330-333

by operating the appropriate transistor switches during

counts one through four, respectively, to step the

printhead carriage from left to right across the page.

One of th. outputs 330-333 is always energized so as to

maintain the printhead carriage in position against the

force of the carriage return spring 236. When a carriage

return signal is received on line 334, indicated by a

logic the count decoder is disabled so that all power

is removed from winding circuits 330-333, thus permitting

the motor to bc freely driven by the carriage return spring

236, without back EMF. The counter 316 counts in the reverse

mode whenever line 340 is at a logic level.

The paper feed stepping motor 304 has two windings

which are energized from outputs 342 ard 343 which are controlled by the transistor switches operated by the outputs of NAND gates 344 and 345, respectively. Neither of the windings of the paper feed stepping motor 304 is energized except while stepping the motor. However, the motor has a high holding torque when de-energized to hold the paper in position.

The incoming control characters are decoded by the

decoder 346 which produces a logic level on the

appropriate output line 348-352, respectively whenever a

"back space", "upper case", "lower case", "carriage return"

or "new line only" character is received. In addition,

the paper is rapidly advanced by repeated carriage return

cycles as long as line 354 goes to a logic level on

command from the keyboard.

An upper case latch UC comprised of NAND gates 356

and 357 is set to the logic state to produce a logic

at the top output 324 whenever upper case line 349

goes to a logic level, and is set to a logic state

whenever lower case line 350 goes to a logic level.

A carriage retur- latch CR comprised of NAND gates

358 and 359 is set to a logic state in response to

a logic level on line 351 and a print strobe on

line 336, and allows the carriage to return to the left

margin position closing a left l.mit switch which produces

a logic on input 360. The carriage return latch CR

is reset by the first print strobe after the printhead

carriage closes the limit switch.

A new line latch NL comprised of NAND gates 362 and 363 is set to a logic state in response to a logic level on line 352, and a print strobe on line

336, and is reset to a logic state in response to

line 364 from NAND gate 394 going to a logic state.

A master timing latch MT comprised of NAND gats 366

and 367 is set to a logic state whenever lines 350, 354,

351 and 352 are at a logic level and a print strobe is

gated through gate 368. The master timing latch MT is

reset to a logic level in response to the output

of NAND gate 394 going to a logic level.

A print cycle latch PC comprised of NAND gates 370 and

371 is set to the logi- level whenever the output of

NAND gate 368 goes to a logic level in response to a

print strobe, and is reset to a logic level whenever

line 372, which is the output of NArD gate 374, goes to

a logic level.

The logic output from the master timing latch MT

and the output from the carriage return latch CR are ORed

through NOR gate 376 to disable NAND gate 368 and prevent 21). the passage of a print strobe during either a carriage

return cycle or a print cycle. The logic output of

the master timing latch MT turns an oscillator circuit 378

"on" to clock a two-stage counter comprised of J-K flip-flops

380 and 381.

During a print cycle, or a back space cycle, signified

by the carriage return latch CR and new line latch NL both

being in the logic level so that the output of NOR gate

382 is a logic gate 374 produces a logic on line 372 when flip-flop 380 complements to the logic state on the first pulse from oscillator 378. The logic "0" at the output of gate 374 causes the output of gate 390 to go to a logic level which is stored on capacitor

392. Then when flip-flop 380 complements to the logic

state on the second pulse from oscillator 378, the

output from gate 384 goes back to a logic which results

in a logic pulse out from gate 394 to reset the

flip-flops 380 and 381 and the master timing latch MT.

In the event either carriage return latch CR or new line

latch NL is in the logic state, the logic output

of NOR gate 382 will disable NAND gate 374, thus preventing

the resetting of flip-flops 380 and 381 and master timing

latch MT after the second count. Instead, the flip-flops

380 and 381 and master timing latch MT are reset on the

fourth count when the outputs of gates 374, 384 and 390 are

all at a logic level and the output of gate 394 goes to

a logic level.

In the operation of the circuit of Figure 10, the

application of power to the circuit automatically sets

upper case latch UC to the lower case mode, resets new

line latch NL, resets the print cycle latch PC, and

institutes a carriage return cycle by setting carriage

return latch CR as a result of applying a logic to

reset input 390 by logic circuitry that is not illustrated.

When the carriage return latch is set, the logic on line

334 de-energizes the printhead carriage stepping motor so

that spring 236 returns the carriage to the left margin

I and closes the left limit switch, thus applying a logic to the input of the NAND gate 361 to enable the gate to reset the CR latch on the next strobe pulse. The true output of the CR latch also disables gate 368 through the circuit including NAND gate 375 and NOR gate 376. The output of gate 376 also produces a "printer not ready" indication on output 105. The true output of the CR

Jatch also resets the counter 318 to the reference count

through NAND gate 383. Then on the next print strobe on

line 336, the cz 4iage return latch CR is reset and the

system is ready for operation with the printhead carriage

at the left-hand margin and the counter 318 at the count

of one and the carriage stepping motor 194 energized.

The upper case UC is initially set to the lower case

state and this information fed to the character generator.

Any time that an upper case character is decoded, latch UC

is st to the logic state and all subsequent characters

will be upter case until such time as a lower case code

is again received. During the presence of either an upper case

or a lower case signal, the print strobe is blocked from

the master timing latch MT at gate 368 through NOR gate 341.

If a line of data is to be printed, the next print

strobe received on line 336 is passed through gate 368 to

set the master timing latch MT and the print cycle latch PC.

The complement output of the print cycle latch is gated

out by gate 339 and inverted on line 326 to produce a

positive print pulse which results in the energization of the

character generator, and a complementary negative pulse on

I line 327 to operate the temperature compensation circuit

to print a character. The true output of the master

timing latch MT is gated through NOR gate 376 to disable

gate 368 and produce a printer not ready indication on

line 105. The complement output of the master timing

latch MT sets the oscillator 378 in operation. As soon

as the first flip-flop 380 is complemented by the first

pulse from the oscillator i78: the output of NAND gate 374

goes to zero, thus resetting the print cycle latch PC.

This terminates the print cycle pulse on lines 326 and 327, and

increments the counter 326 as line 336 falls to a logic "0"

The zero output from gate 374 causes the output from gate

390 to be a logic which is stored on capacitor 392.

Then when the output of gate 374 goes back to a logic "1"

when flip-flop 381 complements on the next pulse from

the oscillator 378, the output of gate 394 goes to a logic

which resets flip-flops 380 and 381 and the master

timing latch 1r1, thus terminating the print cycle. Thus,

a character has been printed and the printhead carriage

stepped one space to the right immediately after the

counter 326 was incremented at the end of the print

pulse. This procedure is repeated to print characters

across the line.

If a back space signal is decoded at any time prior

to a print strobe on line 336, the logic level on line

340 causes the counter 326 to be conditioned to count in

the reverse mode, while line 341 disables gate 339 so

so that no output print strobe is produced on lines 326

I and 327 during the back space.

In the event a carriage return character is decoded,

the gate 368 is disabled through NOR gate 337. Then the

next print strobe sets the carriage return latch CR and the

master timing latch MT to the logic states through

gate 335. When the master timing latch is set at a

logic state, the print ready line 105 goes to logic

and gate 368 is disabled by gate 376, and oscillator

378 is set in operation. Also, when the carriage return

latch CR is set at the logic state, gate 374 is

disabled through gate 382 and the output of gate 329 goes

to a logic thus enabling gate 327. The complement

output of the carriage return latch CR is then at a logic

which open circuits all of the windings to the carriage

stepping motor 194, thus permitting the spring 236 to

return the carriage to the left-hand margin and close

the left limit switch. The true output of the CR latch

also resets the counter 318 through gate 383. Since

gate 374 is disabled, the counter comprised of flip-flops 380 and 381 proceeds to the count of four before being

reset by the output of gate 366. As flip-flop 380 goes

through the second and fourth counts the logic level

on the complement output of flip-flop 380 complements

flip-flop 325. The true output of flip-flop 325 in

conjunction with the output of gate 327 is decoded by

gates 344 and 345 to cause the paper drive stepping motor 304

to advance two steps, which corresponds to a single line

advance of the paper. When the output of gate 394 goes to zero at the count of four, the cycle is ended by resetting flip-flops 380 and 381 and the master timing latch MT. The next print strobe then resets the carriage return latch through gate 36. to complete the carriage return cycle during which the carriage was returned to the left margin, and the paper advanced ready to print a new line.

In the event a new line only character is decoded,

gate 368 is again disabled through gate 337. Then on

the next print strobe, the new line latch NL and the

master timing latch MT are both set as a result of the

outpuL of gate 325 going to a logic level. The

true output of the new line latch NL then enables gate 327

through gate 329, and disables gate 374 through gate 382.

The true output of the master timing latch MT causes the

print ready line 105 to go to a logic and disables

gate 369, and the complement output sets the oscillator

378 in operation. The flip-flops 380 and 381 again

proceed to a count of fou.l before being reset by the output of gate 394, and the paper drive stepping motor

is stepped on the counts of two and four as previously

described. The logic output from gate 394 resets

the master timing MT and new line NL latches to end

the cycle.

The MOS character generator 322 is of the type

described in U.S. Patent No. 3,540,919. The character

generator 322 receives a total of seven parallel bits

of information including the back space information on

line 324 from the cortrol logic 320 and the complement of each. Six bits of the information plus their complements are received on inputs 400 and an additional bit and its complement are input on lines 402 and 403.

The twelve inputs 400 are arranged in parallel relationship

and extend normal to a number of parallel character

output lines 404. There is one output line 404 for each

character to be generated, typically eighty. Each of the

lines 404 is connected to ground through an MOS transistor

406. The gates of MOS transistors 406 are connected to

a negative voltage source so that the transistors function

as load resistors. The input lines 400 are connected to

the gates of input decoding MOS transistors 408. The

sources of the input decoding transistors 408 are

connectable to a positive voltage source through a

bipolar switching transistor 410, and the drains are

connected to the character output lines 404. Fifty

output lines 412 (two outputs for each element of

the electronic printhead) extend normal to the character

lines 404. ?n MOS transistor 414 is provided to connect

each of the outputs 412 that is required to generate the

character in the matrix represented by the character line

404 to ground. The data inputs 402 controlMOS transistors

416, and inputs 403 control MOS transistors 417 so as to

select which of a pair of output lines 412 are to be

connected to the gate of an MOS output buffer 418 which

controls current supplied through bipolar transistor 410

to the base of bipolar transistor 420 used to drive the

bipolar transistor 424 which controls current through the heater resistor 426 of each element of the electronic printhead during the print cycle. The MOS circuit 322 is enabled by the print pulse on line 326 from the control logic 320 which turns bipolar transistors 422 and 410

"on" to connect the positive voltage terminal to the

sources of MOS transistors 408 and 418.

Thus, during a pr-nt cycle when transistor 410 is

turned Lhe character lines 404 are normally at

a positive potential determined by the values of the

load resistances 406 so long as any one of the transistors

408 connected to the particular character line 404 is

This results in the transistor 414 controlled

by the particular output line 404 being turned "off" and

the element controlled by output line 412 being

If, however, all of the transistors 408 connecting the

positive voltage supply to the particular character line

404 are turned "off", as will be the case only when the

particular combination of logic inputs designates the

character represented by the particular character line 404,

then the output line 404 is at ground potential and all

of the output lines 41.. ecessary to form that character

will be connected to ground by an MOS transistor 414.

The information on lines 402 finally selects between

two differently coded output lines 412 to ultimately turn

"on" the output transistor 418 for the particular elements

necessary to generate the character. The MOS circuit 322 is

an integrated circuic contained in a single package.

Referring now to Figures 11-13, the printhead 176

I'wc

which is mounted upon the heat sink 172 is of the

type described and claimed in its various aspects

Great Britain Patent No. 1,235,197 and U.S. Patent

No. 3,501,615. The printhead 176 is comprised of a

5 x 5 matrix of semiconductor mesas 428 which are

thermally isolated one from the other by air gaps

as best seen in Figure 13, and which are bonded to a

ceramic chip 432 by a thermally insulating epoxy layer

434. The transistor 424 (see Figure 9) and resistor 426

for each mesa is diffused in the interior face adjacent

the epoxy layer. The transistor 420 for each of the

twenty-five mesas is formed in the face of a semiconductor

chip 436 generally in the area designated by the dotted

outline 438 in Figure 12 and the circuits completed

by thin metallic film leads formed on the surface of

the semiconductor mesas 428 and chip 436 adjacent the

epoxy layer 434. The ceramic chip 432 is then bonded

to the metallic heat sink 172. The leads to the driver

circuit for the mesas terminate around the periphery

of the semiconductor chip 436 and are bonded to

leads formed on a printed circuit template 440 mounted

on the heat sink 172. The leads on the printed circuit

440 are soldered to the leads carried by the multilead

strap cable 232.

Referring now to Figure 14, the temperature

compensation 450 includes a temperature sensing diode 452

which is located on the chip 436 adjacent to the matrix

of thermal elements 428 generally in the position indicated in Figures 12 and 13. A constant voltage is established at point 454 by a Zener diode 456 so that current flows through resistor 458, the temperature sensing diode

452, and the common return line from all of the

transistors 420 and 424 on the printhead 176. The

resistance of the common return is represented by

resistor 460.

The voltage at point 462 is sampled through switch

464 and stored on capacitor 466 except during each

negative going print cycle. Thus, whenever input 327

from the control logic 320 is at a positive voltage

level so that transistors 470 and 472 are turned "on"

and point 474 is positive, switch 464 is turned "on".

Then during the negative going print cycle on line 327,

the switch 464 is turned "off".

The voltage on capacitor 466 is applied to the

noninverting input of an operational amplifier 476. The

output of amplifier 476 is passed through a pair of output

stages 478 and 480 to an output 482 which is connected to

provide collector current to all of the transistors 420

and 424 of the printhead. Resistor 485 provides a load

when all elements of the printhead are turned "off" during

a print cycle, such as would be required to produce a

space. A feedback resistor 484 connects the output 482

back to the inverting input of amplifier 476. The

inverting input is also connected throilIh a variable

resistance 486 to the sliding contact of a voltage

divider 488 which is connected across the reference Zener 456.

~iilrsL~-n--V1 .ur~-

U The inverting input is also connected through a

resistor 490 and a second sw/itch 492 to ground, and

alternatively through a variable resistance 494 to a

voltage supply of about -9.0 volts at point 496, as

established by the Zener diode 498 and the negative

voltage at terminal 500. The switch 492 is also

controlled by transistors 470 and 472 and thus is

turned "off" during the print cycle, and "on" during

the sample cycle.

Prior to the operation of the tmperature

compensation circuit 450, the sliding contact of

voltage divider 488 is first adjusted so that the

voltage at the sliding contact is equal to the voltage

at the sample point 462 when the diode 452 is at

ambient temperature. This voltage is typically

+0.7 volt. Next, the print pulse is activated at

a slow rate and variable resistor 494 is adjusted until

,he output voltage at point 482 is at the level necessary

to achieve the desired darkness of print. Next, the print rate is increased to the maximum an.icipated rate

and variable resistor 486 adjusted to achieve the same

print quality, thus producing approximately the same

output voltage at 482.

In the operation of the circuit 450, the average

temperature of the printhead is sensed by means of the

voltage drop across diode 452 prior to each print cycle,

and the power applied to the printhead during the print

cyc- is then adjusted according to the previously sensed temperature. For example, when the printing rate is slow, the offset potential voltage across the diode

452 is alproximately 0.7 volt so that 0.7 volt is

stored on capacitor 466 during the sampling period

when switch 464 is open. Switch 492 is also open

during this sampling period so that point 493 is essentially

shorted to ground. This configuration results in an

output voltage of approximately +3.0 volts at 482 to

keep the amplifier from going into saturation, but

not sufficiently high to produce printing. In addition,

all of the printheads are "off" so that no printing

can result. During the print cycle, switches 464 and 492

are closed and at least part of the elements of the

printhead will usually be turned Closing sampling

switch 464 prevents voltage surges at point 462 due to

increased IR drop across resistor 460 and heating of

the printhead from being applied to the amplifier 476

with resulting inaccuracies and instabilities. Closing

of switch 492 pulls point 493 more negative, requiring

a higher voltage at the output 482 to balance the

amplifier. However, as the temperature of the diode

452 increases, due to an increase in printing rate or

the nature of the characters being printed, or to a lesser

extent due to an increase in the ambient temperature,

the offset voltage across the diode 452 decreases, thus

decreasing the voltage stored on capacitor 466 and

applied to the input of amplifier 476 during the print

cycle. For example, an increase in the temperature in the printhead of 50 C results in a lowering of the voltage by 0.1 volt to about 0.6 volt. The inverting input is then maintained only at approximately 0.6 volt during the print cycle so that the output voltage at

482 need not be as high as would otherwise be necessary

to balance the amplifier 476. The output voltage required to balance the amplifier is further reduced

by the current that then passes through resistor 486,

which compensates for the increased cooling rate at

higher printhead temperatures.

Although a preferred embodiment of the invention has

been described in detail, it is to be understood that

various changes, substitutions, and alterations can be

made therein without departing from the spirit and scope

of the invention as defined by the appended claims.

Lt~crulic~ -34-

Claims (1)

1. I The claims defining the invention are as follows:-

   i. Electronic printer comprising an electronic

   printing device for printing characters onto a sheet

   of a recording medium being kept in a supporting means

   for causing contact between said printing means and the

   recording medium at each printing position, said printing

   means being movable across the sheet of recording medium

   and can be positioned at each printing position, a carriage,

   said printing means being mounted on said carriage and

   movable along guiding means by a first stepping motor.

   A counter for steppingthe stepping motor and means coupled

   between said counteL and the windings of the stepping

   motor for de-energizing all motor windings in response

   to a return carriage signal.

   2. Printer according to Claim 1 including switching

   means for deactivating said first stepping motor, and by

   at least one biasing means, especially by a spring,

   for returning the carriage to a starting position.

   3. Printing means according to Claim i, including

   a first logic circuitry for producing a print signal

   rendering operative the print head in response to a

   print strobe and for then providing a stepping pulse for

   the counter.

   4. Printing means according to Claim 1 wherein

   the counter car. be reset by a return cairiage signal.

   Printing means according to Claim 3 including a second logic circuit for blocking print signals in response to a return carriage signal.

   6. Printer according to Claim 1 including a

   line feed stepping device for the recording medium.

   7. Printing means according to Claim 6 wherein

   said line feed stepping device comprises a stepping motor

   following third logic circuit for stepping said motor

   in response to a carriage return signal or a line feed

   stepping signal.

   Dated this 5th day of November, 1973.

   TEXAS INSTRUMENTS INCORPORATED, By their Patent Attorneys, COLLISON CO.

   1 -36-

   READY FIG. I I0-. -122

   CONVERTER SERIAL-TO -PARALLEL-IN PARALLEL-TO-SERIAL-OUT

   226

   I 24 -22 SREQUEST TO SEND CLEAR TO SEND DATA SET DATA TERMINAL READY INTERFACE TA DATA SET READY ET TRANSM!TTED DATAI 2 RECEIVED DATA -18 CARRIER DETECT

   FIGZ I II z AUXI LIARY A 48 36 9BUFF 3 INPUT killLU OUTPU ION CONLVEVRLERS DVCIDEVICE 1- 7 12 NrSER 39.. 3 3 R CHECK 13 36

   BUFFEREN TION JLR F/F 114 .4 EOB~ EL RE PRINTE ELECTRONIC READY _tNABL PRINTER "05 10SROBE XT KEYBOARD 40 30 COMMAND DECODE All I 2ENCODER (STATIC) 764 jSqm 42 DTC 64R 28 67 '44 -9 6 'POLL ICHAR 71 T0 CONVERTER KEYBOARD SERIAL-TO -PARALLEL-IN F/F PARALLEL-TO-SERIAL-OUT AUX INPUT PRINTER a 800 F/F to AUX OUTPUT 0O REq ~~77 PRIN r./F :OT4 92N

   62 F 12 COMMAND 886 ENCODER PUT DOW' 24 _22 128 REQUEST TO SEND CLEAR TO SEND DATA SET DATA TERMINAL READY INTERFACE 84 F/F 124 DATA DATA SET READY SET TRANSMITTED DATAl 116 RECEIVED DATA -18 CARRIER DETECT