EP0027559A1 - Device for driving and controlling the ribbon feed in a high speed printer - Google Patents

Abstract

The command and control of the ribbon drive are carried out by the control unit (300) comprising a control element (301) which delivers drive signals to the motors (49, 50) driving the ribbon receiving coils, via the analog control stages (302, 303). If one of the receiving coils is not driven (no ribbon or slack in the ribbon), no signal is delivered on the lines (305 and 306) and the element (301) controls the reversal of the movement of the ribbon. This inversion command is repeated either until the appearance of a signal on the lines (305 or 306) indicating that the ribbon is normally stretched, or for a determined number of times, the element (301) then generating a malfunction signal on the line (305).

Description

The present invention relates to command and control assemblies for driving a ribbon and more particularly to control systems which remove slack from the ribbon at the same time as they perform automatic test operations.

High speed printers, including wire matrix printers, which use ink ribbons, often encounter many difficulties in controlling the movement of the ribbon and in maintaining the proper position and tension of said ribbon. To date, it has not been possible to produce devices for monitoring and controlling the ribbon drive of a high speed printer.

The present invention remedies this shortcoming and relates to a control means, located in a wire matrix printer operating at high speed, to ensure the removal of slack from the ribbon, the appropriate positioning of said ribbon and the execution of test operations. when the printer is started up, for example when it is switched on or after replacing the ribbon with a new ribbon, these results are obtained by means of a command and control device for the ribbon drive d '' a high-speed printer which has two ribbon take-up reels with which drive stepper motors are respectively associated, these reels and their associated motors being able to rotate in both directions, each of the reels then serving as the ribbon take-up reel (driving motor) or as a ribbon supply reel (driven motor). The control device

comprises a control element which delivers ribbon drive control signals to said motors during the operation of the machine, each of these motors, when it is not excited and that it does not drive the ribbon, delivering transmitter signals to the control element to indicate the movement of the ribbon and to determine the operating conditions of this ribbon.

• La Figure 1 est une représentation schématique simplifiée du sous-système de l'imprimante dans lequel le dispositif de la présente invention est incorporée.
• La Figure 2 représente la console de l'imprimante comportant un certain nombre d'éléments composant l'imprimante y compris le dispositif d'alimentation de feuilles.
• La Figure 3 est une vue de l'avant de l'imprimante.
• La Figure 4 est une vue éclatée de divers ensembles composant l'imprimante, comprenant l'ensemble d'alimentation de feuilles, l'ensemble d'impression et l'ensemble d'entraînement du ruban.
• Les Figures 5 et 6 représentent un élément protecteur de ruban qui est utilisé dans l'imprimante décrite ici.
• La Figure 7 est une vue de dessus prise légèrement de l'arrière de l'imprimante, et montre l'ensemble d'alimentation de feuilles.
• La Figure 8 représente un certain nombre d'éléments électriques et de blocs de commande du sous-système d'impression.
• La Figure 9 représente un circuit de commande d'entrai- nement du ruban pour l'imprimante, ce circuit utilisant un microcalculateur.
• La Figure 10 représente certains signaux caractéristiques rencontrés pendant le fonctionnement des moteurs d'entraînement du ruban.
• La Figure 11 représente un programme utilisé pour éliminer le mou du ruban et assurer la détection d'erreurs.
• La Figure 12 est un programme utilisé pendant les opérations normales d'entraînement du ruban.

Other objects, characteristics and advantages of the present invention will emerge more clearly from the description which follows, made with reference to the drawings appended to this text, which represent a preferred embodiment thereof.

• Figure 1 is a simplified schematic representation of the printer subsystem in which the device of the present invention is incorporated.
• Figure 2 shows the printer console with a number of printer components including the sheet feeder.
• Figure 3 is a front view of the printer.
• Figure 4 is an exploded view of various assemblies making up the printer, including the sheet feed assembly, the print assembly, and the ribbon drive assembly.
• Figures 5 and 6 show a protective tape which is used in the printer described here.
• Figure 7 is a top view taken slightly from the rear of the printer, showing the sheet feed assembly.
• Figure 8 shows a number of electrical components and control blocks for the printing subsystem.
• Figure 9 shows a ribbon drive control circuit for the printer, this circuit using a microcomputer.
• Figure 10 shows some characteristic signals encountered during operation of the ribbon drive motors.
• Figure 11 shows a program used to remove slack from the tape and to detect errors.
• Figure 12 is a program used during normal tape drive operations.

In order to better show the advantages of the device of the present invention, it will be described as part of a wire matrix printer operating at high speed, capable of printing a high number of lines. per minute on continuous strips of paper.

Figure 1 is a schematic representation of an exemplary system which includes a main system 1 and the printing subsystem 2 which itself includes a printer control unit 3 and a set of circuits electronic printing 4. The control and data signals are delivered from the main system via the interface 5 and the execution and control signals are delivered by the printing control unit 3 to the electronic printing circuits 4 via the control bus bar 6. The status signals are supplied by the printing control unit 3 to the main system 1 via the interface 5. D in a conventional manner, the main system 1 generates information comprising orders and data and monitors the states. The print control unit 3 receives the control and data signals, decodes the commands, searches for errors and generates status information, controls the printing and spacing and conducts print diagnostics. The electronic printing circuits 4 execute decoded orders from the control unit, control all the operations of the printer, control the print wires, control the motors, detect transmitter signals from the printer and control the lights on the operator control panel and the switching circuits. These same electronic circuits control the drive-platinum mechanism, the ribbon drive, the carriage carrying the print head (i.e. the control unit), the operator control panel and the printer detectors.

The various elements of the system such as the control unit and the electronic circuits of the printer include one or more microprocessors or microcomputers for analyzing orders and data and for controlling operations.

Figures 2 and 3 show various elements of the printer _- all of which are housed in the console 10. Also shown are various access panels or covers such as elements 11, 12 and 13. The upper cover 11 has a window 14 which, when it is closed, allows the operator to observe the movement of the paper during the operation of the printer. The sheets (documents) 15 are delivered from a stack 16 and can be driven up or down as seen in Figures 2 and 3 by means of a sheet feeding assembly 20-which comprises one or more sets of sheet driving elements such as the upper tractor assembly comprising the driving elements 90 and 91. A sheet guiding element 28 guides the latter, after printing, towards a stack which is not shown but is located below the printing mechanism and at the rear of the printer console. The printer includes a printing assembly 30 which is generally disposed horizontally relative to the sheets 15 at the printing station 32. The printing assembly 30 is shown more clearly in other figures. This is also true for the printer ribbon drive assembly 40 which is arranged in the vicinity of the front of the printer. The print control unit 3 and its associated microprocessors are generally arranged behind the side cover 13.

A ribbon 41 is wound on one of the reels 42 or 43. Each ribbon box will preferably contain a protective ribbon element 46 located between the printing assembly 30 and the sheets 15 to keep the ribbon 41 in proper alignment and to minimize ink stains on the sheets 15. Two motors drive the ribbon 41 in a reciprocating movement between the spools 42 and 43. The print control unit detects any jams of the ribbon and the end of the process (EOR). A ribbon jam turns on a light and stops printing. An EOR state reverses the ribbon drive direction.

The printer includes an operator control panel 26 which is comprised of multiple control keys, two LEDs, a two-position on / off power switch, and the operator display panel.

A 16-position operating mode switch 65 has a direct position which allows printing to be controlled by the user system. All other positions are independent and do not allow printing to be started by the user system.

FIGS. 4 to 7 are detailed representations of the sheet feeding assembly 20, the printing assembly 30 and the ribbon drive assembly 40.

The sheet feed assembly 20 has end plates (side frames) 21 and 22 which carry the various sheet feed mechanisms including a drive motor 23 which drives the elements tractors 90 to 93 by means of the toothed belt 109 and a plate 29 arranged behind the sheets and against which the printing wires 33 are applied during printing. The motor 23 comprises a sheet feed transmitter assembly 24. A transmitter indicates the end of the paper and the jamming of the sheets.

The printing assembly 30 comprises a base 75 carrying various mechanisms comprising the printing motor 76 represented in phantom lines in order to be able to more easily represent other elements, and which is excited to drive a printing head carriage 31 with the control assembly 77 in a horizontal back-and-forth movement to effect printing on a sheet inserted in the printer. The printing assembly also drives a printing emitter 70 comprising an emitting glass 71 and an optical detection assembly 72.

The ribbon drive assembly 40 comprises a support frame 44, a cover 45 and drive motors 49 and 50.

In order to load the paper into the printer, the sheet feeder assembly 20 pivots and moves away from the base 75 at pivot points 80 (80a) and 81 (81a) to allow the paper to be fed into the machine. The latches 83 and 84 are lifted by the operator so that the ends 83a and 84a are released from the eccentric fingers 85 and 86 of the sheet feeding device. The sheet feeder then pivots away from the operator as seen in Figures 2 to 4 and to the right as seen in Figure 6. This provides access to the drive devices 90-93 so that the operator can load the paper. The sheet feed assembly is then closed and relocked by the latches 83 and 84 to allow normal operation of the machine. While the sheet feeder assembly is rotated rearward to return it to service, a switch 94 prohibits operation of the machine. This switch is actuated by a tab 95 of the sheet feeding assembly when the latter is closed.

Figures 4 to 7 also show the sheet feeding assembly which comprises means allowing an adjustment of the machine according to the thickness of said sheets. As previously noted, the entire sheet feeder assembly pivots rearward and clears from the rest of the printer around pivot points 80 and 81. In the closed position, the sheet feeder assembly allows a spiral guide element 96 to urge a finger 97 from the main carriage shaft 98 of the printing assembly 30. The adjustment of the spiral guide element 96 is such that it causes the rotation of the main carriage shaft 98. The element 96 is retained in position by a spring loaded locking assembly. This assembly comprises a spring loaded finger which engages in the notches of the element 96 so as to be maintained in the position established by the operator. Are associated with the shaft 98, eccentrics such as the part 98a of the left end of the shaft 99 comprising the stud 100 on which the lock 83 engages. The rotation of the shaft 98 thus releases the locks 83 and 84, which modifies the distance separating the ends of the printing wires 33 from the platen 29. This adjustment allows the printer to receive sheets of various thicknesses. The printer can handle sheets ranging in thickness from 1 to 6.

Paper is supplied by the four sets of tractor elements 90-93. Two are arranged above the printing line and two below the printing line. Pressure drive elements. Individual drive elements include drive chains to which doiats are attached separated by an appropriate distance allowing their engagement in the holes of the sheet. For example, the drive element 90 comprises a drive chain 101 having fingers 102. The chain 101 is driven by a wheel 103 fixed to a shaft 104 which also drives the wheel and the chain of the drive element. drive 91. The drive elements 92 and 93 are driven from the shaft 105. Due to the fact that the drive elements are arranged above and below the printing line, the printer can move the paper in either direction. The normal sheet feeding direction is up in Figures 2, 3, 4 and 6. However, it is also possible to feed the paper down.

The drive of the shafts 104 and 105 in rotation and the feeding of the sheets are ensured by the motor 23 in the appropriate direction, which causes the pulleys 106 and 107 to be driven (to which the shafts 104 and 105 are connected) from from the engine pulley and via the toothed drive belt 109. The cover 110 protects the belt 109 and the pulleys 106-108 during their rotation. The sheet feed transmitter assembly 24 includes a transmitter wheel 47 bearing marks to indicate its rotation and a light-emitting diode assembly 48 used to indicate the amount of rotation of the motor 23 in one or the other. another direction and, consequently, the importance of the movement of the sheets when they are driven by the motor 23.

The printer's ability to feed paper in two directions has certain advantages. For example, in order to better see the print line when the stop button is pressed by the operator, the paper can be moved up a few centimeters above its normal position so that it can be easily read and adjusted to its proper position. When the start key is pressed, the paper is returned to its normal printing position and the print line is no longer visible to the operator. The printer can also be used in case tracing operations are necessary. In this case, a plot can be obtained by calculating one point at a time and moving the paper up and down like a plotter rather than calculating the complete curve and printing it from the top at the bottom as for the scanning of a frame.

The end of ribbon and jamming detections are ensured, in this assembly, by a pin wheel 112 arranged just above the lower left drive device. The studs of this wheel protrude through a cutout 113a formed in the tilting cover 113. This studded wheel is not driven by any mechanism but is simply carried by a bearing. The studs of the wheel engage in the perforations for driving the paper when the latter is pulled by the drive assemblies. A small optical transmitter disc 115 is mounted on the other end of the shaft 114 relative to the spike wheel. The marks carried by this disk are detected by a photo-transistor assembly with light-emitting diodes 116 and the information is delivered to the electronic circuits of the subsystem. Electronic circuits, check that the marks are passed to the photo-transistor at a certain preset frequency when the paper is fed. If the mark is not detected during this time, the machine is stopped because either the paper is finished or a paper jam has occurred.

The frames 88 and 89 carrying the drive elements 90-93 can be adjusted to the left or to the right by a coarse adjustment operation in order to adjust the machine according to the size of the sheets used for a particular application. After an appropriate positioning, the frames are locked in position on the shaft 67 by locking screws such as the locking screw 87. All the drive elements are driven by the two shafts 104 and 105 from the motor 23 as described above. The position of the motor is adjusted in the lateral frame 21 by means of the recesses 120 in order to ensure an appropriate tension of the belt 109.

Apart from the coarse adjustment, it is also possible to carry out a fine adjustment to adjust the position of the printing on the sheets in very small steps. This operation is ensured by a notched button 66 which urges the shaft 67 to which the two frames of the drive elements are fixed. This shaft floats laterally between the lateral frames 21 and 22. The notches of the button urge the threads of the right end of the shaft 67. The button is held in a fixed position by a fork 68. The button 66 therefore remains in a fixed position and the notches laterally drive the shaft 67 to the left or to the right, depending on the direction in which the button 66 is turned. In order to make up for the play, the shaft 67 is always returned in one direction by a spring 69 arranged on the left end of the shaft. When the paper leaves the top of the drive elements, it is guided up and towards the rear of the machine and down by the guide 28.

In order to ensure that the distance between the fingers of the upper drive elements corresponds to that between the fingers of the lower drive elements, an adjustment operation is carried out. This adjustment operation is ensured by the introduction of a template or a piece of paper into the drive assembly, which places the lower fingers in an appropriate position relative to the upper fingers. This operation is ensured by loosening a collar 121 located on the end of the shaft 104. Once this position is obtained, the collar 121 is tightened and indeed, the upper set of drive elements is in correspondence with the lower clearance so that the perforations of the paper are correctly requested by the two sets of elements drive. Sheets can be driven brought into the sheet feeding mechanism by turning the button 122. This button simply biases the upper drive shaft 104 of the upper drive assembly and via the toothed belt 109 , causes the lower drive assembly to rotate.

Figures 4 and 7 show a carriage 31 comprising a control unit 77 and the support 78; this carriage can receive all the print heads with their wire control devices 35 and the print wires 33. This assembly is structured so as to be able to receive 2 to 8 or 9 groups of print heads from eight order each. Thus, a printer having eight groups of printheads, as shown in Figure 4, has 64 print wire control devices and 64 associated print wires. Only two control devices 35 are shown in Figure 4. The other 62 control devices would be arranged in the openings 133, some of which have been shown. To ensure that the print wires have a long service life, lubrication assemblies 134 containing grease wicks are arranged near the print wires. The print thread controllers control the threads to print dots that form characters. The carriage 31 is driven back and forth by an endless screw 36 controlled by the motor 76. The endless screw 36 drives the carriage in a back and forth movement by means of nuts attached to the carriage. When the carriage 31 is disposed on the far left as seen in Figure 4 (right in Figure 7), it is said to be in its "rest position". When the carriage is in its rest position, a cam 37, fixed to the carriage, urges a finger 38 fixed to the main carriage shaft 98. If the machine has not carried out printing for a certain time, (de the order of a few seconds), the unit control command indicates to the carriage that it must move completely to the left, in which case the cam 37 urges the finger 38 to drive the main carriage shaft 98 in rotation by approximately 15 °. Eccentric fingers such as finger 100 described above are mounted at each end of the shaft. These fingers urge the latches 83 and 84 so that the distance between the printing assembly and the paper drive assembly is controlled by the latches. When the shaft 98 is rotated, the eccentrics associated with the locks 83 and 84 separate the paper drive assembly from the printing assembly.

The current required to energize the print controllers is applied to them by the wiring assemblies 73, Figure 7, one set being provided for each group of eight controllers. The wiring, such as the cable 73a, Figure 4, is arranged in the machine in a semicircular loop so that when the carriage 31 is moved back and forth, the cable can be wound according a certain radius and therefore undergoes no undue stress. This loop is formed and maintained by a steel flange 74. In this case, a set of cables is provided for each group of eight control elements or a maximum of eight groups of cable holding flanges on each machine.

The ribbon drive assembly 40 of the printer is shown mainly in Figures 3, 4 and 7. Figure 3 shows the spools 42 and 43 which carry the ribbon on each side of the machine near the front of .this. These reels carry, in a conventional manner, 150 meters of a 3.8 cm wide nylon ribbon. Figure 4 shows flanges 118 and 119 which hold the ribbon coils 42 and 43 respectively. The coil 43 is driven, for example, by the motor 50, via the pinion 132 which drives a corresponding pinion 123 machined in the underside of the flange 119, the movement then being transmitted to the spool 43. In a feeding direction, the ribbon leaves the left spool 42, passes through the balusters 125 and 126, Figures 3, 4 and 7, passes through the front of the assembly ribbon drive located between the print heads 34 and the sheets 15, then passes through the balusters 127 and 128 and enters the straight ribbon spool 43. The protective element for the ribbon is generally disposed between the balusters 126 and 127 and is mounted on two flexible fastening elements 130 and 131.

Figure 5 shows a protective tape 46 more particularly used in the printer shown in Figures 3, 4 and 7. Figure 6 is a sectional view taken along lines 8-8 of Figure 7. The element protective 46 has an elongated opening 46a extending substantially over its entire length. The opening allows the print wires 33 to be applied against the ribbon in the printer through the protective element in order to ensure printing on the sheets 15. The element 46 has slots at its opposite ends 46b and 46c which facilitate its mounting in the printer on the flexible elements 130 and 131 of the ribbon drive assembly as shown in Figures 3, 4 and 7. The element 46 and the ribbon 41 are shown slightly at an angle in Figures 3, 5 and 7, which is a more normal position in the printer. The tape drive assembly 40 is also disposed slightly at an angle to the horizontal in order to establish the slightly offset angular position of the element 46 and of the tape 41. In this condition, the opening 46a is in horizontal position with respect to the printing wires 33 and to the sheet 15.

The characters that are printed consist of dots printed on the paper. These dots are printed by wires which are mounted in groups of eight on a carriage 31 which is moved back and forth in front of the printing line. Printing is bidirectional, complete printing lines being formed from right to left and from left to right.

A character is formed on an area eight points high and nine points wide. Two of the 9 point positions on a horizontal line (1 and 9) are provided for inter-character spacing, and any thread can print a point in four of the other seven point positions on the horizontal line (2 to 8). The printer can print 10 characters per inch (1 inch = 2.54cm) or 15 characters per inch.

Most printed characters use the top seven threads in the group to print a character in a format (or matrix) that is 7 points high and 7 points wide. The eighth thread (the bottom one) is used for certain lowercase characters, special characters and underline.

The number of groups of printing threads varies according to the printer model and these groups can be in a conventional manner, 2, 4, 6 or 8 in number. The printing speed increases with the number of groups of sons. There are, for example, 16 sets of characters stored in the printer control unit. Any of these sets can be used for the main system program.

Figure 8 shows various interesting blocks of the printer. A power supply unit 245 delivers drive and control power to the unit. The on / off switch 240 controls the power supply 245. From the power supply, the hood interlock switch 242 conditions and deconditions the 48 volt drive which controls most of the printing logic 243. Logic 243, once conditioned, searches the operator control panel 26 for information regarding the operations to be performed. Mode switch 65 tells the logic what type of operation in test procedure must be carried out. The printing assembly 30 is controlled by the printing logic at the same time as the paper feeding assembly 20. The transmitting devices 24 and 70 deliver position information to the printing logic. The printing logic also controls and enters into conversational relation with the interface panel 247 and transfers information to other parts of the printer. The ribbon motors 49 and 50 are all or nothing controlled by the printing logic 243 which receives inputs from the ribbon control assembly to determine the occurrence of an end of ribbon condition. The command 252 ensures the passage of the print head in the appropriate position at the appropriate time for the triggering of the control devices. The paper control 253 is a control block which brings the paper to the desired positions. Fans 254-258 are used to control the temperature inside the machine. The printing logic 243 comprises two microprocessor adapter blocks 200 and 210. The first is the CMA communication adapter which accepts an input and transfers it to the second which is the CTA control adapter which actually controls the printer.

The printer ribbon drive assembly consists of two stepper motors that drive a ribbon between 2 spools. While one of the motors drives the ribbon, the other motor is rotated by the ribbon and generates tension in one of its phases. This voltage is detected and stored in intermediate memory to give a transmitter signal. The frequency of the appearance of the emitting signals depends on the relative windings of the tapes on the coils and these signals appear in a conventional manner every four to six steps of the motor. A motor pitch is defined as a 2 ° rotation of the motor. The reception of these transmitting signals indicates that the ribbon is present on the reel which is unwound and that the ribbon is driven. When the transmitting signals disappear, the motors are reversed, the one that was fired now providing the drive and the other engine generating the transmitting signals. The criterion used to control the reversal or the reversal of the movement of the ribbon is the disappearance of the transmitting signals during a given number of steps of the drive motor.

Figure 9 shows the ribbon drive control unit 300. This control block comprises a control element, such as a microcomputer 301 delivering drive signals to the analog control stages 302 and 303 for the left and right 49 and 50, respectively.

The microcomputer or control element includes an unalterable memory, a random access memory, an interface and chronology units and can be any type of commercially available microcomputer. As an example, this microcomputer could be an Intel 8748 EPROM microcomputer which includes an unalterable programmable and erasable memory. From the control stage 302, there is a transmitting line 305 which returns to the microcomputer 301 and from the control stage 303, there is a transmitting line 306 which returns to the microcomputer 301. When the line 312 "Power supply restoration" is energized, the block is conditioned, line 315 "Error +" is energized and line 316 "Busy +" is de-energized. Before operation can start, line 315 is restored either by exciting the "Error restore-" line 311 or by entering diagnostic mode. The normal movement of the ribbon is caused by the conditioning of the "Operation-" line 310. Block 304 makes it possible to improve the voltage leaving the card of the control block.

There may be a problem when the ribbon control is first activated. The microcomputer 301 which controls the drive of the ribbon gives an initial sense to its movement. If the direction of this movement that there is no ribbon on one of the supply coils, no transmitting signal appears on line 305 or line 306, element 301 then commanding a reversal of the displacement of the ribbon until that a transmitting signal is detected. If there is a little slack in the ribbon, no transmitting signal is also received. The generation of a ribbon malfunction signal is delivered on line 315 if no transmitting signal is detected after a predetermined number of reversals.

Figure 10 shows examples of signals for one of the motors at different test points, including phase A and phase B signals. Each time the motor phase changes, a current surge appears on the line + 48-volts. This current surge is caused by the phase change and causes the application of an initial 48-volt pulse to the motor to cause it to drive. A sawtooth support current is also shown in the Figure. The control current in the different motors increases in a repetitive configuration. This current is represented in the form of a half-sawtooth signal comprising a flat in its middle part. This is because the control current increases as it approaches the motor poles. The high voltage ground current in the motor changes, as shown in the figure, with each change of the motor phase. The induced reaction signals are not shown in Figure 10 but are of a lower level and measured in tenths of a millivolt.

A device is provided in the control and drive circuits of FIG. 9 for removing slack from the ribbon with the application of a minimum stress thereto and for carrying out a diagnosis within the framework of the slack removal process. . This will take place after loading a new ribbon or when powering up, for example.

In short, the microcomputer 301 controls a motor on 32 step, each step of the motor corresponding to a rotation of 2 ° of said motor. If no transmitter signal is received, the direction of the drive is then reversed and the other motor is driven in 32 steps while the microcomputer searches for transmitter signals. This drive reversal and control process continues until a transmitting signal is received or six reversals have occurred. If there is an error indication, this indicates that there was too much slack in the belt.

Once a transmitting signal is received, the motor which ensures the training continues this training on 4x32 is on 128 steps, then takes place a reversal of direction. The other motor provides 32-step drive and if no transmitter signal is received, an error condition is present. If a transmitting signal is received in this direction, the test has been passed.

Thus, transmitting signals were received in both directions to verify the correct operation of the ribbon and any slack was removed in the latter without applying any excessive tension to it.

The diagram in Figure 11 begins with the transition to diagnostic mode and at this time the command is applied to one of the motors, for example the right motor, and a maximum of 6 drive reversals can be achieved. Then the program goes to junction "X" and controls the drive of the right motor on 32 steps. These are numbers of reversals and arbitrary steps. Other values could be used if desired. When the right engine provides the drive, the microcomputer 301 searches for transmitter signals from the other engine, that is to say from the left engine, in this case. A test is performed to determine if a change in the transmitting signal has been detected. If no change in the transmitting signal has been detected after the right motor has been turned to 32 steps, a drive reversal is initiated and the drive of the other motor begins. Then we decide perform a test and find out how many rollovers have occurred. In the event that 6 drive reversals have occurred, this indicates that each motor has been driven three times in 32 steps and that there is excessive slack in the ribbon or no ribbon. The ribbon movement is stopped and the line "Error +" 315, Figure 9 is excited. If less than 6 reversals have occurred, the program returns to junction "X" and starts the drive of the other motor which has not been previously selected. The program continues on this loop until transmitting signals have been received or 6 reversals have occurred. When at least one transmitting signal has been received, this indicates that the ribbon is present and is wound on the reel currently being driven. The motor associated with this coil is then driven in 128 steps (4x32), which is a new arbitrary number chosen only to ensure a sufficient number of transmitting signals so that the difference in the diameters of the ribbon on the coils does not have effect on the end result. After 128 steps, a reversal is initiated and the motor which was driven in rotation now provides the drive and the transmitting signals are tested in the opposite direction. The motor is now controlled in 32 steps to drive the ribbon in this direction, then a test is carried out to determine whether transmitting signals have been received in this direction. If no transmitting signal has been received, this indicates that there has been an error and the movement is stopped. If a transmitting signal has been received, this indicates that at this level, transmitting signals have been received in both directions. There is tape on the spool and no problem exists in the system at this time.

This diagram indicates the operations allowing the ribbon to be fed from the two coils and a lower tension is therefore applied to said ribbon. Any slack in the tape is removed. In addition, the ribbon drive and the transmitter signals are tested in both directions.

The removal of slack, during normal training of the ribbon, can be effective by the introduction of a period of neutralization of the inversion of the ribbon drive direction during which the transmitting signals are not tested. During this time, a motor drives a large number of steps in a given direction. Referring to Figure 12, it can be seen that the ribbon is first primed and the neutralization of direction reversal is conditioned, for example, for 50 to 100 steps of the motor. When an operating signal is received, the first phases of the motor are started and the reverse conditioning is tested. If the inversion is not yet conditioned, an end of neutralization inversion test is then carried out and the command is returned to the "Y" junction.

When the inversion is conditioned, the test of the transmitting signals begins. If a transmitter signal was received while the engine was running on 32 steps, control then passes to junction "Z". At this instant, the microcomputer 301 verifies the distance traveled by the ribbon since the direction reversal or the start. If a sufficient distance has been traveled, the "1 inversion" indicator is cut, no record of a previous inversion is known and the command passes to the "Y" junction.

The "W" junction is reached if no transmitter signal is received for 32 steps from the motor. In this case, a test is carried out to see if there has already been a reversal (the "1 reversal" indicator is lit). In this case, there were two reversals over a short distance of travel and a ribbon jam occurred.

If no inversion has been recently performed, this is the first and the indicator "1 inversion" is conditioned, the inversion for a short sequence is neutralized and the movement is conditioned in the opposite direction.

Figure 12 is a description of the ribbon movement sequence. At the start, some initialization procedures are performed and a rollover neutralization indicator is conditioned. Then the command goes to the "Y" junction. The program remains at this point until the movement of the ribbon is excited by the conditioning of the "Operation" line 310, Figure 9. At this moment, one of the motors is started and a test is carried out to determine if a possibility exists to execute a reversal. If the microcomputer is in a period in which the reversal is not possible, it modifies a deconditioning account, checks the end of this reversal deconditioning time, and returns to the "Y" junction. If reversal is possible, the test of the transmitting signals then takes place. Then a test is performed to determine if a transmitter signal has been received within a period of 32 steps from the motor. If a transmitting signal has been received, the program then goes to the "Z" junction. At junction "Z", the program tests and modifies a count of the displacement of the ribbon indicating the total movement of the ribbon. If this displacement account has reached a certain value, generally of the order of 10 meters, which corresponds to approximately 16,000 engine steps, the "1 inversion" indicator is then reset (or restored) and future ribbon reversals will not cause the ribbon to jam. The program then goes to the "Y" junction. If a reversal or reversal of the tape drive direction is detected while the "1 reversal" indicator is conditioned, a ribbon jam is then indicated. If no transmitter signal has been received for 32 steps from the motor, the program goes to junction "W". At this time, the "1 inversion" indicator is tested. If this indicator is on, this indicates that two inversions have been detected within a slight displacement of the ribbon and that there is a jamming of the ribbon. If this indicator is cut, this indicates that it is a first inversion or an inversion following a long movement of the ribbon. The indicator "1 inversion" is then conditioned and the "Inversion neutralization" indicator is also conditioned. The movement of the other motor is conditioned and we return to the "Y" junction.

Although the essential characteristics of the invention applied to a preferred embodiment of the invention have been described in the foregoing and represented in the drawings, it is obvious that a person skilled in the art can provide all of them. modifications of form or detail which he judges useful, without departing from the scope of said invention.

Claims (8)

1.- Device for command and control of the ribbon drive of a high speed printer which comprises: two ribbon take-up reels (42, 43) (41) which are respectively associated with drive stepper motors (49, 50), these reels and their associated motors being able to rotate in both directions, each of the reels then serving as ribbon take-up reel (driving motor) or as ribbon supply reel (driven motor); this device being characterized in that it further comprises: a control element (301) which delivers ribbon drive control signals to said motors during the operation of the machine, each of these motors when it is not energized and when it does not drive the ribbon , delivering transmitting signals to the control element to indicate the movement of the ribbon and to determine the operating conditions of this ribbon. 2.- Device according to claim 1, characterized in that in addition: each of the motors, when it is not energized, only delivers an emitting signal if it is actually driven, the control element detecting the appearance of these signals, means for removing slack from the ribbon are connected to the control element, these means control the rotation of the motors and, after starting the ribbon, commanding the reversal of the ribbon drive if no emitter signal has appeared after the driving motor has rotated N not, this reversal command being carried out by de-excitation of the driving motor and excitation of the driven motor and being carried out either until the appearance of a transmitter signal, or, if there is no transmission of transmitter signals, a predetermined number (P) of times. 3.- Device according to claim 2, characterized in that, if a transmitting signal is detected by the control element before said P inversions, this detection indicating that there is a ribbon on the coils, said motor control element causing it to continue its rotation during SxN step, then commands a reversal of the ribbon drive and finally detects if a new transmitter signal is emitted by the new driven motor, in which case the ribbon is tensioned and ready to function correctly. 4.- Device according to claim 2, characterized in that if no transmitter signal is transmitted after the P inversions, the control element delivers an error signal indicating excessive slack or the absence of ribbon. 5.- Device according to claim 3 or 4, characterized in that N is between 20 and 50, P is between 2 and 8 and S is between 2 and 6. 6.- Device according to claim 2, characterized in that in addition: means for neutralizing the inversion of the ribbon are controlled by the control element, these means being able to neutralize the detection of the emitting signals delivered by the driven motor and this, during a predetermined number R of rotational steps of the driving motor, these neutralization means acting during a new displacement of the ribbon when the ribbon drive system is in normal operation, and R being larger than N. 7.- Device according to claim 6, characterized in that: measuring means are connected to the control element to determine the distance traveled by the tape since the previous reversal or since said new displacement and to determine, when said neutralization means are no longer operational, if two reversals of the ribbon drive occurred in order to deliver a ribbon jam signal. 8.- Device according to any one of the preceding claims, characterized in that said control element is constituted by a microcomputer independent of the central control unit of the printer.

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