CA1155962A - Printwheel homing apparatus - Google Patents

Abstract

PRINTWHEEL HOMING APPARATUS

Abstract of the Disclosure In a printwheel type of printer using a selection stepper motor for driving the printwheel, means are provided for performing printwheel homing operation upon occurrence of predetermined events. Such an event, is detected and reported to microprocessor means which drive motion means for bringing the printer carriage assembly to a first extreme left position where a stop element fixed relative to the printwheel rotation is made to enter the path of another stop element attached to rotate with the printwheel.
Subsequently, the selection stepper motor driving the printwheel is driven for a number of steps at least equal to one motor revolution to ensure reaching inhibition of the printwheel rotation by bringing the rotating stop element into contact with the relatively fixed stop element.
The carriage is then moved back to the left margin writing position where the relatively fixed stop element is withdrawn from the path of the other stop element and the angular printwheel home position is noted and stored by the microprocessor means.

Description

'3 ~ ~

P~INTWHEEL HOMING APP~RATUS

Back~round of the In~ention This invention relates to electromechanical impact printing devices of the type employing a rotary type-face-carrier.
More particularly, this invention relates to a homing system for printing systems of the kind noted wherein the rotary type-face-carrier is rotated for character selection purposes. -:, RQtary printing systems are known in which the printhead comprises a rotary type-face-carrier, e.g., a printwheel, including a plurality of resilient pads or fin~ers bearin~
printing elements. The printhead is located on a carriage for translation from one print position to the next along -a print line direction during printing operations. This operation is performed by translaling the carriage from 15 ]eft to right and back, using a series of cables and pulleys ~`
driven by a D.C. motor controlled by electronic circuitry.
As the carriage-head assen~ly is moved from a print position to the next along the print line direction, the type-face-carrier is rotated about its axis for character selection purposes. rrhis operation rotates the printwheel until the pad bearing the char~cter to be print~d faces ~he desired print position and is aligned with the striking end of a printhammer also mounted on the carriage~ Printing is then performed while the carriaqe îs momentarily stopped by actuating the printham~er to impress the character borne by the pad a~ainst an inking ribbon and a print receiving medium. After the printhammer rebounds toward its original rest position, the printwheel is ro~ated so that the next 3 ~

proper character pad is aligned with the printhammer, while the carriage is translated to the next character print location where the next character is to be printed.
This process continues until a complete line has been printed, after which the carriage is returned to the next line starting position, e.g., which could either be the left margin position or the end of the following line in case of bi-directional printing, and the print receiving medium is moved in preparation for the printing of the next line of chaxacters.

Proper operation of such rotary printing systems depends on a number of factors among which the proper character selection is one of the most critical. In so called closed-loop systems, the rotary printwheel cooperates with position sensing devices enabling the system associated logic e~uipment to determine permanently which character faces the printhammer. For instance, the printwheel includes detection marks or indicia which can be detected by a printwheel home detector during printwheel rotation.
In response to detection of the detection marks, a printwheel home signal is generated by the detector and transmitted to the logic circuitry which controls the operation of a motor used to rotate the printwheel. With some additional logic and/or printwheel angular position detection means, the system is kept permanently aware of the printwheel angular situation. Such detection systems are generally located on the translatin~ carriage addin~ weight thereto.

All of the necessary bulky and expensive sensing equipment used in the closed-loop systems may be avoided provided aj few additional logic and control means are added to the m~chine. In so called open loop systems, no expensive sensin~ means is used to permanently track the printwheel angular position and report it to the system control unit.
The system needs only to know which character was last printed and which one should ~e next, to determine through a table look up operation the required printwheel angular displacement to be performed.

_, .

Naturall~, before printing first starts, i.e., ~hen the powex is turned on, and even from time to time during normal printing operation, when a predetermined event occurs, both closed and opell loop systems need some kind of homing operation to put the printwheel into a home angular position, i.e., a reference position, known to the system.
This operation is fairly simple when dealing with closed loop type of equipment. For instance, the printwheel may be commanded to rotate in a given direction u~ to a velocity corresponding to the movement of a predetermined number of character element spaces per time unit and then h~ continuously rotated in that same direction at this velocity until the printwheel home detector dPtects a home mark on the wheel ~ predetermined number oE times.
When this occurs, a signal i5 generated indicating home position to the system which will -then track the wheel rotation through a control of the rotation driving means.

While the requirement for homing operation is obviously even more critical with open loop type of equipment ~here 2a any error in homing operation would lead to a totally incorrect subsequent printing, no sensing equipment is normally available in such type of equipment, which could be used for homing purposes.

Some open loop printers have been equipped with optoelectronic or with electromagnetic type of sensors especially intended for homing purposes. These devices and their read out electronics are relatively expensive.

Summary of the In ention An object of the invention is to provide simple and inexpensive but yet ~eli~ble homing means for printing systems usin~ type-face-c~rriers which are positioned into printing position through~ at least, rot~tion about one given ~xis.

., . ~ . , 3 ~ ~
According to the present in~ention, inexpensive means are provided for performing homing of a rotary -type-face-carrier to be used with equipment in which khe positioning of a character to be printed, with respec-t to printing position, is performed through linear displacement of a carriage supporting a printhead and rotation of the type-face-carrier attached to said printhead about at least one given direction. Initial type-face-carrier homing operation is performed when specific situations occur such as detection of printer power-on setting, by automatically shifting the carriage within the printer housinq limits, in a direction parallel to the record medium holder, i.e., platen, down to a given extreme position where a stop element fixed relative to the rotation of the type-face-carrier about the at least one given direction, is made to extend within the path of another stop element attached to rotate with the type-face-carrier. The type-face-carrier rotation means are then excited to rotate the type-face-carrier a sufficient angle to ensure mechanical engagement of one stop element in contact with the other, which stops the type-face-carrier and inhibits it from further rotating. Then the carriage is automatically moved to a given position where the relatively fixed stop element is made to clear the path of the other stop element.

A fuller understandin~ of the nature and advantages of the invention will derive ~rom the ollowing detailed descrip-tion in con~unction with the accompanying drawings.

Brief Descri tion of the D~awin~~

FIG. 1 is a top pl~ne vie~ o~ a rotary type of printer e~bod~ving the in~enti~n.

FIG. 2 is a block diagram of the logic controlling the printer motors o~ the invention.

_5~ 5 9 ~ ~
FIGS. 3A and 3B show one embodiment of the stop elemen-ts of the invention.

FIGS 4A and 4B show another embodiment of the stop ele~ents of the invention.

FIG. 5 shows a timing diagram to be used to perform the homing function.

FIG. 6 represents a motor driver circuit arrangement for a three phase stepper motor.

Detailed Description of the Invention FIG. 1 shows a top plane view of a rotary type of printer embodying the invention. The printer has left and right side plates 2 and 4, and a base 6, for housing the mechanlcal components, most of the electrical components and some of the electronic and logic parts of the machine The rest of the circuits wil~ be located in a separate housing not shown.

carriage assembly 8 is slidingly supported by a shaft 10, and can be shifted between said left and right side plates

2 and 4 by a belt and pulley assembly 12 driven by a carriage stepper motor 14. Carriage assembly 8 includes a base plate 16 which provides support for the rotatable type-face-carrier, e.~., printwheel 18, for a type-face-carrier rotation means, i.e., the selection stepper motor 20 which rotates the printwheel 18, for the hammer 2~ and driver 23 assembl~, and for a ribbon c~rtrid~e 24 interposing an inkin~ ribbon 26 between printwheel 18 and record medium holder or pl~ten 28. The pl~ten 28 is rotatably secured to the side plates 2 and 4 to support the record medium (not shown). T~e platen 28 is provided with conventional platen knobs 30 and 31 3a and with automatic motion means (not shown) which enable rotating the platen to transfer the reco~d or print receiving medium from one printing line position to another.

The printer is also provided with a printwheel homing device including a first (58~ and a second (61) stop elements which will be described further onO

In operation, feeding the carriage motion means, i.e., carriage stepper motor, 14 with signals provided by electronic and lo~ic control circuitry (see FIG. 2) causes the belt and pulley assembly 12 to move the carriage assembl~ 8 from left to right or vice-versa alon~ a print line direction and from one print position to the next.
While shifting the carriage assembly 8, the printwheel 18 is also rotated about its axis by the selection stepper motor 20 for character selection purposes in order to present the pad bearing the character to be printed in front of a printing position on the record medium, and within the path of hammer 22. With the selected pad positioned, driving the driver 23 will make the hammer 22 strike thé printing character against the inking ribbon 26 and print receiving medium and print the selected character.

The two stepper motors 14 and 20 ~see FIG. 2) are driven by motor dri~er circuits 32 and 34 controlled by logic circuitry composed of one master microprocessor 36, two separate slave microprocessors 38 and 40 provided with associated external memories 42 and 44 and output ports 46 and 48 respectively. These slave microprocessors 38 and 40 are respectiv~ly intended for driving the carriage stepper motor 14 and the selection stepper motor 20. Other slave microprocessors (not shown) are used for performing other printer functions not involved in homing operations.

The depressing of any character key (not shown~ on the printer board 50 shown in FIG. 1 is detected and reported to the master microprocessor 36 ~s a comm~nd. The master microprocessor 36 identi~ies the command, defines the functions to be performed and distributes the jo~s to the slave microprocessors. The master microprocessor 36 is also kept aware of the eyolution of the functions under

3~

performance by the slaves in order to synchronize these functions with each othex. The 51 ave microprocessors used to control stepper motor operations have to provide se~uences of coded signals based on both the type of mov~
to be performed by the stepper motor involved and the type of stepper motor used. The step-phase relationship of each stepper motor is defined through a phase table Tl (not shown~ comprising a set of binary words permanently stored into the internal memory of the associated slave micro-processor 38 or 40, while the corresponding externalmemory 42 or 44 stores profiles. A profile consists of sequence of phase and time data selected by the designer for performing a specific and complete move ox sequence of stepper motor steps with the best possible efficiency and reliability. Knowing the actual position of a stepper motor and the desired next position, the slave microprocessor controlling that stepper motor feeds the corresponding motor driver circuit with a sequence of data derived from a profile, which data are then converted by said motor driver circuit intc sets or trains of time varying current pulses fed into the motor phase cixcuits in accordance with the indications of the phase table of the motor involved. The motor acceleration and speed rates depend on the shapes of the current pulse trains applied to selected motor phases. The motor direction of rotation depends on the oxder in which the different phases are switched on and off.

In normal printing operation the depressin~ of a character key on the printer board is reported to the master microprocessor 36 through its status and data input as a command issued from a c~mmand source. Prior to any effective impact printin~ operation, the carriage assembly h~s to be ~oved along the print line to face the correct print position. This job is devoted to the slave microprocessor 38, In addition, the printwheel 18 has to be rotated to present the adequate pad to ~c~ the hammer 22. This function is devoted to the slave n~icroprocessor 40. Both -8~ nl operations are initiated and synchxonized ~y the master microprocessor 36. For inst~nce, the selected character to be printed is identified by the master mlcroprocessor 36 and this identity is reported to the slave microprocessor 40 which stores it into one of its internal registers (R2) while the identity of the last character printed has been transferred from register R2 into a register,Rl. Also stored in the slave microprocessor 40 internal memory is a table T2 (not shown) identifying the sequence of charac-ter distribution about the printwheel 18 periphery. Proper angul~r rot~tion of the printwheel 18 for character selection purposes involves the following operations to be controlled by the slave microprocessor 40. First the table T2 is consulted in order to determine the angular rotation to be performed by the printwheel 18 to move from the position identified by the contents of register Rl to the position identified by the contents of register R2. Then, based on this information, the profile in external memory 44 is addressed. This provides a selected microprogram to be read into the slave microprocessor 40, which then addresses the taple Tl. The phase-table data is in turn used to control the stepper motor driver circuit 34 through the output ports 48.

The contents of R2 is shifted into R1 setting the system ready for a new character selection operation.

With similar means and in a similar manner, the slave microprocessor 38 together with its external memory 42, the output ports 46 and the motor driver circuit 32 will drive the carriage stepper motor 14 to bring the carriage assembl~ 8 to the ~dequate position ~lon~ the printing line.

Due to the dependency of the angular printwheel movement upon the contents of Rl, any error in said Rl contents would tend to propagate to subse~uent printin~. A correct setting of this register is thus particularly important.
In addition, when the power is turned off the registers R1 LE9-7g-004 g 1~
and R2 are reset to zero. Therefore, upon power-on, a homing function must be performecl, i.e., the prir,twheel 18 should be first set to a position known to the slave microprocessor 40 (i.e., loaded into its register Rl) and qualified as printwheel hcme position. In closed loop type systems, sensing devices are available, which, with some additional electronics and logic, could help in performirlg the homing functicn. In open loop type systems, the homing function can be performed with a good price-efficiency relationship, using the stop ele~ents of this invention in conjunction with the logic of FIG. 2 and control loyic.

FIGS. 3A and 3B show one embodiment of the stop elements of the invention. A printwheel 18 comprising resilient pads 52 which support print characters 54 on their extremities is shown. The printwheel including a hub 56 is adapted to be made to rotate with the motor shaft 57 by the selection stepper motor 20 (FIG. 1), to bring any selected pad into a predetermined printin~ position located on the hammer 22 (FIG. 1~ path. The printwheel hub 56 is provided with a first stop element or knob 58, which can be a .060 inch molded ~e~er fixed at any desired ~ixed angle from the printwheel home pad position. This knob 58 is attached to rotate with the printwheel 18. The home pad 60 has been selected to ~e the third pad to the left of the pad set into printing position when the printwheel 18 is stopped, as shown on FIG. 3B. But no matter what the printwheel home pad angular position is, the homing opera~ion should identify and bring the home pad 60 with the printing position.

A second stcp ele~,ent 61 i attached to the le~t side plate 2 of the printer housin~. This second stop element 61 comprises essentially a br~cket 62, carryin~ a l~tch 64.
The bracket 62 is vertically adjustable while the latch 64 is adjusta~le~ The latch 64 can rotate about an axis or pivot 66 parallel to the rotation axis of the . . . ~_ ,.

-10~ J:3~
printwheel 18. Under norm~l printing conditions, the farthest left position to be reached by the c~rriage assembly 8 of FIGo 1~ iOe~ ~ the left printing margln position is such ~hat, while the printwheel 18 rotates ~o~
character selection pur~oses, the kncb 58 scans a path normally out of the space limits into which the latch 64 (see FIG. 3A) extends. This second stop element is shown on FIG. 3A in a rest position with a limiting member 68 forbidding the latch 64 to rotate clockwise any further under the impetus o~ a return spring 70.

Upon power~on detection, the logic control of FIG~ 2, i.e., master-slave arrangement 36-38 and driver circuit 32 drives the carriage stepper motor 14 to bring the carriage assembly 8 ~o an extreme left position where the side plate 2 prevents the carriage assembly 8 from moving any further left by havin~ the base plate 16 abutting against said side plate 2.
There, the latch 64 engages into the rotary path limits which would be ~canned by the knoh 58 while the printwheel 18 would rotate (see dashed lines on FIGS. 3A and 3B~.

The printwheel selection stepper motor 20 may be detented or not during this time. ~en the carriage assembly 8 i5 made tc reach that first extreme left position, the knob 58 is at random orientation. If the printwheel 18 rotates in clockwise direction, then the knob 58 might hit the latch 64 below the position shown on FIG. 3B.
Then due to its chamfer sha~ed end, the latch 64 rota-tes about its pivot 66 in counterclockwise direction away from limiting member 68, to enable moving the carriage assembly 8 ~urther to the desixed extreme left positionO Now, when the carxiage assembly 8 is at that position, the slave microprocessor 40 driYes the selection stepper motor 20 ~ith a fixed set o~ instructions such that said selecticn motor 20 would normally be ste~ped more ~han one revolution in counterclockwise direction, This ~ssures that the printwheel 18 will be rotated enough for the knob ~8 to reach the latch 64 which has returned against the limiting LE9~79-004 :~;35~

member 68 under the impetus of the return spring 70 as in FIGS. 3~ and 3B. The selection stepper motor 20 might be still electrically driven until the end of the fixed set of inskructions while it is mechanically non-rotating without this bein~ detrimental to the motor. After the last instruction is executed, the printwheel 18 is made to rotate clockwise for a predetermined number of steps depending upon the angular position of the home pad 60 with respect to printing position in order to bring said home pad into printing position. This number of steps has been selected to be three with the arran~ement of FIGS. 3A and 3B. Then the carriage assembly 8 is made to move to the left margin writing position ~see FIG. 3A) where the latch 64 clears the path of knob 58. At completion of boming operation, the contents of the table T2 at the address corresponding to the home pàd~ is loaded and stored into register R1 acting as storage means for identifying the present angular position of the printwheel 18~

FIGS. 4A and 4~ show a simpler arrangement for the second stop element. An interposer 72 is now mounted on the carriage assembly 8 and an adjustable screw 74 is inserted into the left side plate 2. The intlerposer 72 is made to be slidable or reciprocable in a plane parallel to the path of first stop element 58 and is maintained out of said path under the impetus o a spring 76 except when the carriage is shiEted to the left against the adjustable screw 74. FIG. 4A shows the second stop element with interposer 72 positioned out of the path of the knob 58 by the spring 76 being relaxed, ~hile FIG. 4B shows the same second stop element wîth the spring 76 compressed whereby the interposer 72 is made to extend within the path of knob 58.

As mentioned before, homing operations are needed when the printer power is se~ on~ But such a need m~y also occur while the printer is operating. With reference to FIG. 2, , ~ `3 the need for performing the homing operations will be decoded by the master microprocessor 36 detecting the occurrence of a predetermined event, e.g., the setting on o~ the print0r electric power or the detection o~ a specific S instruction. Upon detection of such an event, the master microprocessor 36 controls the logic flow between the two slave microprocessors 38 and 40, as shown on the timing dia~ram of FIG. 5.

FIG. 5 shows a timin~ diagram for performing the printwheel 18 homing function using a 3-phase ninety six steps variable reluctance stepper motor as selection motor 20, and a 6-phase four hundred and twenty steps variable reluctance stepper motor as carriage motor 14. Starting at time zero zones A through D show the timing schedule for the carriage motor 14, while zones E through ~ show the timing schedule for the selection motor 20 for the same period of time.

For the Carriage Stepper Motor 14-Zone A: Accelerate the carrlage assembly 8 to 5.81 inches~sec.
Zone B: ~ove the carriage assembly 8 to the left at 5.81 inches/sec~ fox 3188 motor steps, i.e., 13.2 inches.
~one C: Move the carriage assembly 8 to the left for 180 steps at 20 milliseconds per step.
(This is to ensure that the carriage assembly 8 reaches the extreme left position, to offset any bounce-away that may occux and to keep the c~r~iage assembly 8 at the left stop].
3Q Zone D: W~it 650 milliseconds and then move the caxriage assembly 8 to the right down to the left writing mar~in position, for 72 steps (This moYe ~ssures that the knob 58 clears the xelatively fixed second stop member so the printwheel 18 can rotate in either direction freely).

LE9~79-004 ~13-For The Selection Motor 20:
Zone E: Initialize the selection motor 20 to reach a normal speed in counterclockwise direction ~nd then wait up to 4 seconds (delay to ensure that the carriage asse~bly 8 has reached the extreme left position re~ardless of where i~
was at the time of power-on)~
Zone F: Run the selection motcr 20 for 48 steps in counterclockwise direction and wait 50 milliseconds.
Zone G: Run the selection motor 20 in coun~erclockwise direction for 48 steps with 20 milliseconds delay after each step, then wait for 50 milliseconds.
Zone H: Rotate the printwheel l8 3 steps in clockwise direction to the home position, then wait 20 milliseconds.

NOTES: (l) Whenever one of the stepper motors 14 and 20 reaches a stop position, it could still be driven for a shork period of time without being deteriorated. This enables performing the functions defined in the above mentioned zones, using predetermined microprograms stored in the microprocessor memories wi1:hout any consideration of the actual location of the carriage assembly 8 and printwheel 18 at power-on.

(2) The last printwheel step (Zone H) is only due to the fact that the home pad 60 has been selected to be three steps away from printing position when the first and~
second stop elements are made to come into contact with each ot~er. However, the home pad 60 could be selected at an~ known angul~x position from the ~irst stop element 5~.

(3~ The stepper motors 14 and 20 cannot reach a glven speed instantaneously. The~ should, first, ~e brought to that speed at a selected acceleration ratei The above functions are performed b~ having stored micro-programs run the microprocessors to control the motor driver circuits 32 and 34 to feed the necessary time varyiny current signals into the motor coil phasès.

FIG. 6 shows a motor driver circuit arrangement for a three phase stepper motcr. The motor driver cixcuit is made of three double transistor current amplifiers Tl-2, T3-4 ~nd T5-~- driving the different motc,r pkases. A
resistor R is used on each motor phase to decrease the motor coil time constant, while a series diode-resistor arrangement Rd is used on each motcr pha~se to provide a return current path to the motor phase coil just turned off.

The microprocessors used ma~ be conventional commercially available ~icroprocessors such as Intel 8085 for the master ~unction and Intel 8Q41 for the slave functions.

Attached are a set of program~ used for performing the homir.g function using the above mentioned Intel Systems~ The main part of the attachment consists of two programs, one for the "SELECTION MOTOR" 20, the other for the "CARRIAGE MOTOR" 14.
These programs calI for subroutines such as SYGETPHS for initialization purposes; SYDELAY for counting delays; or SYSL~XPR. ~YGETPHS and SYDELAY subroutines (not shown) are conventional initializing and counting routines. The "CARRIAGE MOTOR" program alss re~uires two profiles designated by "~ome Profile" and "$hort Tab Pro~ile" respectively.

It is recognized that the carriage assem~ly 8 could be driven to the right side frame extreme position to effect the homing operation although the le~t side frame extreme position is preferred due to its proximit~ to the normal print starting 30 point~

While the invention has been particularly shown ~nd described with re~erence to the pre~erred embodiments thereof, it will ~e understood ky those skilled in the art that the foregoing and other changes in fonm and~details may be ~ade thérein without departing from the sF~irit and scope of the invention.
*Trade Mark Q~
,,~

SELECTION ~IOTOR
*********************~*************************************~*********~*
* 1. SET PWASE TABLE POI~TE~ TO TOP OF PHASE
* TABLE;
S~SLHOME MOV R7,5ZINITFT-X OlGO' CALL SYG~TPHS (TO INITIALIZE) OUTl P1,A
* 1. DELAY FO~ CA~RI~R TO REACH ABSOlUTE
* LEFT h~RCIN (4 SEC.);
MOV R4,X C8 SYZSHCDL ~OV A,X 06 CALL SYDELAY (TO COUNT 4 SEC) DJNZ R4,SYZSHCDL
* 1. LOAD CO~PARE TIME REGJST~R FO~ MOV~ 48;
MOV R3,SZCTLONC
* 1. SET CONTROL ~ORD POINT~R TO MOVE 48 MOV RO,SZMVLONG
* 1. SET ~4RIABLE RUNS RECIST~R ~OR MOVE 48 MOy R6,X 25 * 1. EXECUTE 48-STEP ~OVE;
CALL SYSLEXPR
* 1. POIST-~OVE DElAX (50 MSEC);
MOV R4,X 05 SYZSHSDL M~V A,131 CALL SYD~LAY (TO COUNT 50 MSEC) DJNZ R4,SYZSHSDL
1. SET MOVE COUNTER TO 48;

MOV R4,48 * 1. REPEAT
SYZSHONE SEL RBO
* 2. . LOAD COI~PARE TIME REGISTER FOR M~VE 1;
MOV R3,SZCT1 * 2. . SET CONTROL WORD POINTER TO MOV~ 1;
MOV RO,S2MV1 * 2. . CLR PAGE FLAG;
MOV A,R5 ANL A,SZCl,RPAG
MOV R5,A
* 2. . EXECUTE 1-STEP MOVE;
CAlL SYSLEXPR
* 2. . POST-MOVE DELAY (20 MSEC);
MOV A,X 06 CALL SYDE~AY (TO COUNT 20 MSEC?
* 2. 0 DECRE~EN~ ~OVE COUNTER;

* 1. UNTIL MOVE COUNTER = O
DJNZ R4,SY2SHONE
* 1. ENDREPEAT;
SEL RBO
* 1. POST-MOVE DELAY (50 ~SEC);
MOV R4,X 05 SXZSHEDL MOV A,131 CALL SYDELAY (TO COUNT 5a MSEC) DJNZ R4,SYZSHEDL
* 1. LO~D COMPARE T1~1E REGISTER FOR MOVE 3;
MOV R3,SZCT3 -16- ~ V ~
* 1. SET CONTROL h~RD PO,TNTER TO M0VE 3;
* 1. SET DIRECTION TO PLUS & CLR PACE FLAC;
MOV A,R5 ANl A,SZCLBDP
MOV R5,A
* 1. EXECUTE 3-STEP MOVE;
CALl SYSLEXPR
* 1. POST-MOVE DELAY ( 20 MSEC);
MOV A,X'06' CALL SYDELAY (TO COUNT 20 MSEC) * 1. EXIT TO DECODE ROVTINE;
*******************~***************************************************
* ENDSEGMENT (SYSLHOME);

LE9-79 no4 CA~RIAGE MOTOR
*************************~**~*~********~*********~*k~****** ***~*~**~**
SYCRHO~E EQU *
* 1. INITIALIZE PHASE TABLE;
CALL SYPTINIT
* 1. INITIALIZE FLACS (DIR, EOP*, lS*, * EOR* SET & NO~, CN2, VAR RESET);
MOy R5,X'E9' * 1. SET CONT~OL WORD POINTE~ TO HOIl~E PROFILE
*

MOV R6,5ZLTAB-1 * 1. LOAD RlJN COUNTER WITH FIRST LEVEL STEPS;
MOV R4,5Z~LSTPS
* 1. LOAD SZTHOLD ~ITH FIRST LEVEL TIME;
MOV R1,SZTHOLD
~OV @R1,5ZELTI~F
* 1. CET E~IRST PHASE & STO~E Ih' SZPHOLD;
CALL SYNEWPHS
* 1. REPE~T
SXZCHACC E~U *
* 2. . CALL (SYSTEP) OUTPUT PHASE, LOAD &
* START T~ER;
CALL SXSTEP
* 2. . CALL (SYNXT~OV) DETE~'IINE NEXT PHASE
* & TIME;
CALL SYNXT~OY
*

* 2. . ~AIT FO~ TIMER TO EXP~E;
SYZCH~TA JTF SYZCHSTA
JMP SYZCHWTA
* 2. . STOP T1MER~COUNTER;
SYZCHSTA STOP TCNT
* 1.,UNTIL END OF PROFILE FLAG ACTIVE
MOV A,R5 * 1. ENDREPEAT;
*

* 1. SET RUN COUNTE~ TO 180 STEPS
MOV R49X'B4' * 1. REPEAT
SYZCHSLW EQV *
* 2. . GET NBXT PHASE ~ROM SZPHOLD & OUTPUT
* TO MOTOR;
MOV R1,SZPHOLD
MOV A,@R1 OVTL P1,A
* 2. . DECREMENT RUN COUNTER;
DJ~Z R4,SYZCHM
JMP SYZC~YYR
* 2. . CAlL (SYNE~PHS) DETEfiMINE NEXT PHASE;
SYZCH~YL CALL SXNE~PHS
2. . DELAY 20 ~SEC;
MOY R3,X' 01 ' CALL SYLNGDLY
* 1. UNTIL RUN COUNTER = ZERO
JMP SYZCHSL~
* 1. ENM EPEAT;

~E9-79-OQ4 -18~ 5 SYZCHMYR EQU *
* 1~ DEL~Y 100 MSECi MOV R3.Xta5~
CALL SYLNGDLY
* 1. SET CWP TO SHORT .TAB (3 IPS OTF) * PROFILE;
MOV R6,SZ3IPS
* 1. SET EOP*, LS*, NOW, YAR. & EOR* FLA5S, * AND CLEAR DIR & C~2 FLAGS;
MOY 45,X173' * 1. LOAV VARIABhE RUNS REGISTER WITH #RUNS
* FOR 72 STEP MOYE;
MOV R3,X'32' * 1. CALL (SYSLEXPR) EXECUTE -~72 STEP MOVE;
CfiLL SYSLEXPR
* 1. EXIT PROCESS ROUl'INE;
***********************"***********************************************
* EIWSEG~ENT (SYCRI~OME), *************************************~t*****************************~*~
SYSLEXPR
* 1. CALL (SYNXTMOV) DETERMINE PHASE AND
* DEI,AY AT FIRST STOP
CALL SYNXTMOV
* 1. REPEAT
* 2. . CALL (SYSTEP~ SF,ND NE~ PHASE TO MOTOR
* lOAD & START TIMER
SYZMXSTP CALL SYSTEP
* 2. . CALL (SYNXTMOV) DETER~INE P}~ASE &
* , DELAY OF NEXT STEP;
CALL SYNXTMOV
* 2. . ~AIT FOR TIMER TO EXP~RE;
SYZMX~AI JTF SYZMXTST
JMP SYZMX~AI
* 2. . STOP Tl'MER/COUNTFR;
SYZ~IXTST STOP TCNT
* 1. UNTIL END OF PROFILE FLAG IS ACTIVE
MOV A,R5 * 1. ENDREPEAT;
* 1. RF,TURN TO CALLING ROUTINE-***********************************************************************
* ENDSEG~ENT (SYSlEXPR);

HC~E P~FILE
# SI'EPS: DELZ~.Y (~IS):

SHORT TAB PP~OF:~;E
rEæs~ DEC~Y (]IS~
14 lq~0 What is claimed is:
.

T.~.9--79-004

Claims (9)

The embodiments of the invention in which an ex-clusive property or privilege is claimed are de-fined as follows.

1. A type face-carrier homing apparatus for an electronic impact printer comprising:
a housing provided with side plates;
a record medium holder positioned within said housing between said side plates;
a carriage assembly slidingly supported to move in parallel direction to said record medium holder;
carriage assembly motion means for moving said carriage assembly;
a rotatable type-face-carrier bearing printing types, said type-face-carrier being attached to move with said carriage assembly;
type-face-carrier rotation means for rotating the type-face-carrier for character selection purposes;
a first stop element attached to rotate with said rotatable type-face-carrier;
a second stop element fixed relative to the rotation of said rotatable type-face-carrier;
means responsive to the detection of a predetermined event for driving said carriage assembly motion means to bring said carriage assembly into a first given extreme position where said second stop element is made to extend within the path of said first stop element when said type face-carrier rotates;
means for driving said type-face-carrier rotation means to rotate said type-face-carrier and bring said first stop element into contact with said second stop element so as to prevent said type face-carrier from rotating any further;

means for subsequently driving said carriage assembly motion means to bring said carriage assembly into a second given position where said second stop element is made to extend out of the path of said first stop element;
storage means; and, loading means for loading the information characterizing the angular position of the home pad of said rotatable type-face-carrier as stopped, into said storage means.

2. A type-face-carrier homing apparatus according to Claim 1, wherein said first stop element is a knob attached to the type-face-carrier to scan a circular path concentric with said type-face-carrier, during rotation of said type-face-carrier.

3. A type-face-carrier homing apparatus according to Claim 2, wherein said second stop element is attached to a side plate of the printer housing.

4. A type-face-carrier homing apparatus according to Claim 3 wherein said second stop elements includes:
a bracket element;
means for rigidly connecting said bracket element to one side plate of the printer housing;
a chamferred latch element;
pivot means for pivotally connecting said latch element to said bracket element in a plane parallel to the path of said first stop element limiting member means for limiting the movement of said latch about said pivot, in one direction, and, return spring means connected for bringing said latch back to its rest position whenever it is pivoted away from said rest position.

5. A type-face-carrier homing apparatus according to claims 1 or 2 wherein said type-face-carrier is a printwheel.

6. A type-face-carrier homing apparatus according to claims 3 or 4 wherein said type-face-carrier is a printwheel.

7. A printwheel homing apparatus for an electronic impact printer including:
a housing provided with side plates;
a platen positioned within said housing between said side plates;
a carriage assembly reciprocatable along said platen within said housing;
a carriage assembly motion means for moving said carriage assembly along said platen;
a printwheel attached to move with the carriage and provided with a home pad;
a stepper motor means for rotating the printwheel for character selection purposes;
a first stop element attached to rotate with the printwheel and placed at a fixed angle with respect to said home pad;
a second stop element fixed relative to said printwheel;
processor means responsive to the detection of a predetermined event, for driving said carriage assembly motion means to bring said carriage assembly into a first given extreme position where said second stop element is made to extend within the path of said first stop element when said printwheel is made to rotate;
processor means for subsequently driving said stepper motor means for a number of steps sufficient for driving said stepper motor for at least one full revolution, therefore ensuring that said first stop element will come into contact with said second stop element and stop said printwheel from rotating;
means for driving said stepper motor means for a predetermined-number of steps for bringing said home pad into printing position;
storage means; and, loading means for loading the information relating to the identity of the character borne by said home pad into said storage means.

8. A printwheel homing apparatus for an electronic impact printer according to Claim 7, wherein said carriage assembly motion means includes a stepper motor.

9. A printwheel homing apparatus according to Claim 7 or Claim 8 wherein said second stop element is attached to the printer housing.