WO2003029013A1 - Derouleur de bande - Google Patents

Derouleur de bande Download PDF

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Publication number
WO2003029013A1
WO2003029013A1 PCT/GB2002/004405 GB0204405W WO03029013A1 WO 2003029013 A1 WO2003029013 A1 WO 2003029013A1 GB 0204405 W GB0204405 W GB 0204405W WO 03029013 A1 WO03029013 A1 WO 03029013A1
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WO
WIPO (PCT)
Prior art keywords
spool
tape
motor
diameter
tape drive
Prior art date
Application number
PCT/GB2002/004405
Other languages
English (en)
Inventor
Keith Buxton
Original Assignee
Zipher Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zipher Limited filed Critical Zipher Limited
Publication of WO2003029013A1 publication Critical patent/WO2003029013A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J33/00—Apparatus or arrangements for feeding ink ribbons or like character-size impression-transfer material
    • B41J33/14—Ribbon-feed devices or mechanisms
    • B41J33/34—Ribbon-feed devices or mechanisms driven by motors independently of the machine as a whole
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B15/00—Driving, starting or stopping record carriers of filamentary or web form; Driving both such record carriers and heads; Guiding such record carriers or containers therefor; Control thereof; Control of operating function
    • G11B15/02—Control of operating function, e.g. switching from recording to reproducing
    • G11B15/026—Control of operating function, e.g. switching from recording to reproducing by using processor, e.g. microcomputer

Definitions

  • the present invention relates to a tape drive, for example a tape drive which may form part of a transfer printer which makes use of tape-supported inks, or a label applicator which applies tape-supported labels to a substrate.
  • a tape drive for example a tape drive which may form part of a transfer printer which makes use of tape-supported inks, or a label applicator which applies tape-supported labels to a substrate.
  • a tape which is normally referred to as a printer tape and carries ink on one side, is presented between a printhead and a substrate with the ink-carrying side facing the substrate.
  • the printhead is operative to transfer ink from the tape on to the target substrate which may be for example paper or a flexible film.
  • the target substrate which may be for example paper or a flexible film.
  • transfer label printers and thermal transfer coders print directly onto substrates such as packaging materials manufactured from flexible film or card.
  • Tape is normally delivered to the end user in the form of a spool of tape wound onto a core.
  • the end user pushes the core onto a tape spool support, pulls the free end of the tape to release a length of the tape, and then engages the free end of the tape with a further spool support.
  • the spool supports are mounted on a cassette which can be readily mounted on a printing machine.
  • the printing machine includes a transport means for driving the two spools in a tape transport direction so as to unwind tape from one spool (deemed the supply spool) and wind tape onto the other spool (deemed the take-up spool).
  • the printing apparatus transports tape between the two spools along a predetermined path past the printing head. In some applications tape transport is in only one direction, but in other applications tape may be transported in both directions alternately.
  • printers of the above type rely upon a wide range of different approaches to the problem of how to drive the tape spools. Some rely upon stepper motors, others on DC motors, to directly or indirectly drive the spools. Generally, in commercially available printers, only the take-up spool is driven in the tape transport direction and some form of "slipping clutch” arrangement is connected to the supply spool to provide a resistive "drag" force so as to ensure the tape is maintained in tension during the printing and tape winding processes and to prevent tape over-run when it is desired to bring the tape to rest. It will be appreciated that maintaining adequate tension is an essential requirement for the proper functioning of the printer.
  • the initial outside diameter of the supply spool decreases and the initial outside diameter of the take-up spool increases.
  • the tape tension will vary in proportion to the diameter of the supply spool. Given that it is desirable to use large supply spools so as to minimise the number of times that the tape has to be replenished, this is a serious problem.
  • a slipping clutch is very difficult to set up. This is because the initial large diameter and associated large inertia of the supply spool means that a high drag level is required in order to avoid over- run of the supply spool during operation. As the supply spool reduces in size, the tension of the tape increases, and the previously necessary high drag level results in excessive tape tension. This can result in over tensioning, causing tape breakage, or stalling of the motor driving the tape up spool, particularly if the tape is driven at high speed or is accelerated and decelerated at high rates. Thus the problems associated with slipping clutch arrangements limit the performance of printers by limiting the maximum acceptable rate of acceleration, rate of deceleration and speed of the tape transport system.
  • the speed of the tape must track that of the substrate whilst printing is occurring during each printing cycle, but generally the tape is stopped or driven in the opposite directions between printing cycles.
  • the speed of the substrate (which is often determined by the speed of associated manufacturing equipment) can change rapidly. High rates of tape acceleration and deceleration are therefore required.
  • the diameter of the supply spool is not directly monitored however, but rather is calculated on the basis that the sum of the cross-sectional areas of the two spools is known and is approximately constant throughout the tape transfer process (hereinafter the "conservation of area principle"). This assumption is only valid however if for all tapes the sum of the cross-sectional areas is always the same, and all the tape is supported by one particular spool at the outset of the tape transfer process. In the real world such conveniently predictable circumstances often do not arise. Circumstances cannot be reliably predicted for various reasons. It is not always possible to start with all the tape on one spool, and with a known spool diameter.
  • different spools of tape may have different diameters because they have different lengths of tape on them or tape of different thickness.
  • a tape cassette to a printer that carries a tape partially wound on one spool and partially wound on the other.
  • a different tape for example a tape with ink of a different colour.
  • some of a tape may be discarded so as to make it possible to use the remainder. This results in a length and volume of tape which is entirely unpredictable.
  • a system which can only stabilise tape tension when used with a cassette that when first mounted on the printer has all of the tape supported on one tape spool, the tape being of known length and thickness, does not therefore fully address the problem.
  • labelling machines are known in which a tape carrying a series of adhesive labels is initially supported on a supply spool and transported to a take-up spool. The labels are peeled off the tape between the supply and take-up spools such that the diameter of the supply spools when initially installed is greater than the diameter of the take-up spool after all of the tape (minus labels) has been transferred to the take-up spool.
  • US 4,294,552 describes a tape drive in which two stepper motors are used, a first motor driving a take-up spool in a conventional manner, and the second motor being configured such that its motor windings provide drag.
  • a substantially constant drag current is passed through the windings of the second motor using cross-coupled connections from the first stepper motor.
  • This tape drive suffers from the significant disadvantage that the constant drag current will not result in a constant tension being applied to the tape.
  • EP 0 546 303 discloses a tape drive comprising two stepper motors each coupled to a respective tape spool.
  • the tape transport direction is reversible and the primary objective is achievement of uniform tape velocity, with tape tension control a secondary consideration.
  • the motor coupled to the supply spool operates in regenerative mode, thus generating drag.
  • the motor coupled to the take-up spool is driven by pulse width modulated sine waves so as to generate constant torque.
  • the angular velocity of the take-up motor is controlled by reference to a look-up table.
  • Tape tension is controlled by connecting the windings of the motor coupled to the supply spool to a variable load.
  • the drag provided by the supply spool motor is varied, but there are only four possible drag magnitudes.
  • the relative radii of the tape spools is calculated from the angular velocity of the supply motor.
  • the angular velocity of the take-up motor is then controlled so as to maintain a given linear tape speed. Tape tension is not stabilised by taking account of supply spool diameter variations.
  • US 5,490,638 describes a tape drive in which two stepper motors are provided, one being coupled to each of the tape spools.
  • the supply spool motor drags because its windings are connected to a resistive load.
  • the amount of drag is controlled by controlling the level of the load current at a desired value. That load current can be set to one of a number of possible values by selecting one of a number of resistors that form part of a potentiometer that sets the current level. Again however the circuit is set up to maintain constant tape velocity and tape tension control is a secondary issue.
  • US 4,573,645 describes a tape drive in which the two tape spools are coupled to respective stepper motors.
  • the stepper motor coupled to the supply spool acts as a generator and the loading of the generator is controlled by driving current through load resistors.
  • the magnitude of the current driven through the load resistors is controlled to compensate for changes in spool diameters.
  • this compensation relies upon knowledge of the initial diameter of the supply spool which is not generally predictable for the reasons discussed above and furthermore assumes that the sum of the cross-sectional areas of the two spools of tape remains constant. In the real world it is not acceptable to have to rely on the assumption that the initial diameter of a supply spool is predetermined and the cross sectional area of the supply and take-up spools is constant.
  • a tape drive comprising first and second motors, first and second tape spool supports on which respective first and second spools of tape may be mounted, each spool being driveable by a respective motor, and a controller for controlling the motors such that the tape may be transported from the second spool to the first spool, wherein the first motor is a stepper motor, and the controller is operative to energise the first stepper motor to draw the tape in a tape transport direction on to the first spool and to control the second motor such that the second motor resists rotation of the second spool in the direction of tape transport, means being provided to determine the diameter of the spool supported by the second spool support, and to vary control of the second motor as a function of the determined diameter of the spool supported by the second spool support, the function being such that tension in the tape is maintained within predetermined limits.
  • the diameter determining means may comprise means for measuring the diameter of the second spool, for example an optical arrangement which may comprise at least one optical emitter positioned such that a shadow is cast by at least the second spool, at least one optical detector adapted to detect the position of an edge of the shadow, and means to determine the diameter of the second spool from the detected position of the edge of the shadow.
  • an optical arrangement which may comprise at least one optical emitter positioned such that a shadow is cast by at least the second spool, at least one optical detector adapted to detect the position of an edge of the shadow, and means to determine the diameter of the second spool from the detected position of the edge of the shadow.
  • the emitter or the detector may be mounted on a translatable carriage, such that components of the optical arrangement are displaced through a position corresponding to the shadow edge.
  • a detector may be mounted on the translatable carriage with two emitters positioned such that the first and second spools cast shadows edges of which are located on a track along which the detector is displaced.
  • an emitter may be mounted on the translatable carriage with two detectors positioned such that the edges of shadows cast by the first and second spools are displaced past the detectors as the emitter is displaced on the carriage.
  • an emitter and a detector may be mounted on the carriage, with a mirror positioned to reflect light from the emitter to the detector, at least the second spool being located between the carriage and mirror such that the second spool obstructs reflection of light from the emitter to the detector to an extent dependent upon the diameter of the second spool.
  • the detector comprises an elongate array of detectors positioned such that the shadow edge moves along the length of the array as the diameter of the second spool changes.
  • the tape drive may be part of a printer which operates cyclically with each cycle including a printing operation, and the diameter of the second spool may be measured at intervals between successive printing cycles.
  • the diameter of the second spool may be calculated.
  • means may be provided for monitoring tape transport and rotation of at least one motor, and means may be provided for calculating the diameter of the second spool from the measured tape transport and motor rotation.
  • the current diameter of the second spool may be estimated from a previously determined spool diameter and subsequent operation of the tape drive.
  • estimating means may be provided which is operative to estimate the current diameter on the assumption that the total cross-sectional area of the supply and take-up spools is a constant.
  • the first and second motor are stepper motors
  • the second motor is connected to a load
  • means are provided to control current drawn by the load as a function of the determined diameter.
  • a feedback circuit may be connected to the load, the feedback circuit being configured to maintain the current drawn by the load at a required level determined by the controller.
  • the circuit may be arranged periodically to connect the load to the windings of the second stepper motor in accordance with a pulse width modulated signal, adjustment of the pulse width modulated signal providing adjustment of the average load.
  • the feedback circuit may comprise a first filter which provides a DC value indicative of the current passing through the load, a second filter which provides a DC value indicative of the pulse width modulated signal, and means for comparing the DC values to provide a feedback signal.
  • the feedback circuit may further comprise a sawtooth function generator arranged to generate a sawtooth signal, and means for comparing the feedback signal and the sawtooth signal to provide a sawtooth modulated feedback signal which controls the connection means.
  • the load may be connected to the windings by a transistor which is turned on and off by the pulse width modulated signal.
  • Diodes may be connected between windings of the second stepper motor and the load to prevent flow of current from the load to the windings, and the controller may be provided with enable means configured to ensure that current is passed from the windings of the second stepper motor to the load only when drive current is not being supplied to the second stepper motor.
  • Each element of the tape drive which is provided for the second stepper motor may be in addition provided for the first stepper motor and vice versa, such that tape may be transported from the first reel to the second reel, that is the tape may be driven in both directions between the spools.
  • the second motor is a stepper motor
  • the second motor could be a DC motor, in which case drive current to the DC motor is controlled as a function of the determined diameter, for example such that the drive current is directly proportional to the determined diameter.
  • Figure 1 is a schematic illustration of components of a tape drive in accordance with the present invention
  • Figure 2 illustrates an embodiment of the present invention in which a calibrator is responsive to inputs received from a tape spool drive motor and a tape spool diameter measurement device;
  • Figure 3 is a schematic representation of a tape spool diameter measuring device suitable for use in the embodiment of Figure 2;
  • Figure 4 is a schematic illustration of dimensions of tape spools which may be used in the calculation of an estimate of changes in tape spool diameter as a result of tape transport between spools;
  • Figure 5 is a schematic illustration of an embodiment of the present invention in which a calibrator receives inputs from a tape transport measurement device and a supply spool drive motor
  • Figure 6 is a schematic illustration of an embodiment of the invention in which a take-up spool is driven by a stepper motor, a supply spool is driven by a DC motor, and a calibrator is responsive to inputs from optical sensors such as those illustrated in Figure 3 and the stepper motor driving the take-up spool;
  • Figure 7 illustrates a further embodiment of the present invention in which both take-up and supply spools are driven by stepper motors and a calibrator is responsive to inputs from both the stepper motors and a tape transport measurement device in the form of a roller which contacts the tape;
  • FIG 8 is a more detailed illustration of components illustrated in Figure 7;
  • Figure 9 illustrates waveforms generated by windings of a stepper motor in the embodiments of the invention illustrated in Figure 8.
  • Figure 10 is an illustration of a further embodiment of the invention which is of the same general type as that shown in Figure 8 but has a modified stepper drive control circuit.
  • a first drive motor 1 which is a stepper motor is coupled to a tape spool support (not shown) on which a first tape spool 2 is supported.
  • the tape spool 2 acts as a take-up spool, drawing tape from a second tape supply spool 3 which is coupled to a second drive motor 4.
  • the motor 4 could be either a DC motor or a stepper motor.
  • the tape follows a path from the supply spool 3 to the take-up spool 2 around a pair of idler rollers 5 and 6.
  • the length of tape extending between the rollers 5 and 6 extends parallel to a path indicated by line 7 along which in use a substrate which is to be printed is transported.
  • a printhead 8 is positioned so that the tape is located between it and the substrate path 7 so as to enable the transfer of ink from the tape to a substrate on that path 7.
  • the printhead may be stationary relative to the idler rollers 5 and 6 or may be transportable in a direction parallel to the idler rollers 5 and 6 as indicated by arrow 9.
  • the motor 1 is driven by a drive 10 and the motor 4 is driven by a drive 11.
  • the two motors drives are controlled by a controller 12.
  • the controller is also connected to a calibrator 13 which provides an input to the controller representative of the outside diameter of at least the supply spool 3.
  • the motor 1 is driven at a speed appropriate to the particular application in which the printer is deployed. The manner in which this speed is determined is not of direct relevance to the present invention.
  • the motor 4 however is controlled by the drive 11 so as to resist rotation of the supply spool 3. This results in the generation of a torque which operates on the supply spool 3 in a direction opposite to the direction of tape transport. This torque and the diameter of the supply spool 3 determines the tension in the tape extending between the idler rollers 5 and 6.
  • the calibrator 13 is provided to deliver to the controller an input 14 representative of that diameter.
  • the calibrator 13 may derive the necessary supply spool diameter measurement in any appropriate manner.
  • One general arrangement which relies upon an initial direct measurement of spool diameter and thereafter calculation of changing spool diameter over time is illustrated in Figure 2.
  • the same reference numerals are used in Figures 1 and 2 for like components.
  • the calibrator receives an output from a spool diameter measurement device 15 which delivers to the calibrator 13 a signal representative of the diameter of the supply spool 3.
  • the calibrator 13 also receives an input from the supply spool motor 4 representative of angular rotation of the motor 4, that input being derived for example from a shaft encoder or (if the motor 4 is a stepper motor) a motor step counting device.
  • An initial measurement of the outside diameter of the spool 3 is made at least when the spools 2 and 3 are first coupled to the motors 1 and 4. Thereafter, given knowledge of the thickness of the tape supported on the spool and the number of revolutions of spool 3 (derived from knowledge of the number of revolutions of the motor 4), the changing diameter of the supply spool 3 can be calculated as described above.
  • tape tension can be controlled purely on the basis of knowledge of the diameter of and torque applied to the supply spool 3, preferably the diameters of both the take-up and supply spools 2,
  • Figure 3 illustrates such an arrangement in which the diameters of both spools are measured and the rotation of both motors is monitored.
  • Figure 3 shows a direct connection between the motor 1 and the calibrator 13 to enable rotation of the take-up spool 2 by the motor 1 to be monitored.
  • the motor 1 will step or not step in response to step pulses delivered by the drive 10.
  • the drive 10 delivers step pulses in response to control signals from the controller 12.
  • rotation of the motor 1 is locked in synchronisation with the operation of both the drive 10 and the controller 12, and therefore motor rotation can be monitored indirectly by monitoring the operation of either the drive 10 or the controller 12.
  • the spool diameter measuring apparatus illustrated in Figure 3 provides measurements of the diameters of both the supply spool 3 and the take- up spool 2.
  • Two optical emitter devices 16 and 17 are located beneath the spools 2, 3 and are used in conjunction with a detector 18 mounted on a carriage 19, the carriage being displaceable in a direction indicated by line 20 so that in one extreme position the detector 18 is located at a position indicated by broken line 21 and at the other extreme the detector 18 is located at the position indicated by broken line 22.
  • the carriage 19 could also serve to transport the printhead of the device in some embodiments of the invention. As the detector 18 is moved to the left in Figure 3 from the position indicated by line 22, initially only emitter 16 is energised.
  • the detector 18 is in the shadow of the spool 2, but as soon as the detector 18 crosses the plane indicated by line 23 an output signal will be generated by the detector 18. This is coupled by a flexible cable 24 to the calibrator 13. The detector 18 is then advanced further towards the position indicated by line 21 and its output disappears as the detector crosses the plane indicated by line 25. The carriage then continues until the detector 18 is at the position indicated by line 21. The carriage is then returned after the emitter 16 has been deenergised and the emitter 17 has been energised.
  • the detector 18 is initially in the shadow cast by the spool 3 but will generate an output as soon as it reaches the plane indicated by the line 26.
  • the carriage 19 continues to advance until that output disappears as the detector 18 crosses the plane indicated by the line 27.
  • the position at which the planes indicated by lines 23, 25, 26 and 27 intersects the path of the detector 18 can be determined.
  • the distance between the axes of rotation of the spools 2 and 3 is known and is indicated in Figure 3 as dimension A.
  • the perpendicular distance between the track followed by the detector 18 and the plane in which the emitters 16 and 17 are located is also known (dimension B in Figure 3).
  • the distance between the track followed by the detector 18 and the plane including the axes of the spools 2 and 3 is also known (dimension C in Figure 3). From these dimensions the diameters Dl and D2 of the take-up and supply spools 2 and 3 can be readily derived using simple trigonometry.
  • Two emitters 16 and 17 which are alternately energised are used to ensure that on each traverse of the detector 18 the detector always enters an area of shadow cast by at least one of the spools regardless of spool diameter.
  • the calculation of the spool diameters would be somewhat simpler if the planes indicated by lines 23, 25, 26 and 27 were perpendicular to the direction of displacement of the detector 18.
  • This can be achieved by for example replacing the emitters 16 and 17 with a mirror extending parallel to the direction of displacement of the carriage 19 and arranging both a transmitter and a detector on the carriage 19, the transmitter and detector being spaced apart in a direction parallel to the tape spool axes. With such an arrangement the detector would detect light only when both it and the emitter are located on a plane perpendicular to the mirror which is not obstructed by a tape spool.
  • the spool diameter measurement device as described with reference to Figure 3 is dependent upon movement of the detector 18 which can conveniently be achieved by mounting the detector 18 on the carriage used to transport the printhead. In “intermittent” printers the printhead is displaced relative to the tape and substrate during each printing cycle. In “continuous” printers however in which both the substrate and ribbon are moved past a stationary printhead there is no need to provide a traversing carriage and therefore the spool diameter measurement system as described in Figure 3 can only be applied if an otherwise unnecessary transport mechanism is provided to move the detector 18. It would however be possible to avoid the need for such a transport mechanism if, rather than relying upon a moving detector 18, a linear array of detectors was provided extending along the path traversed by the detector 18 in the arrangement as described in Figure 3.
  • Dsc and D TC are previously measured supply and take-up spool diameters respectively.
  • the current diameter ratio R is defined by:
  • This may also be arranged as:
  • Re is the ratio of the previously measured take-up spool to supply spool diameters.
  • the measured spool diameters ratio Re the measured supply spool diameter Dsc, and the current spool diameters ratio R are known
  • an estimate of the current diameter of either or both reels Ds or D T can be derived.
  • the thickness of the tape can be measured or is known from knowledge of the thickness of tapes provided by the tape supplier, and the number of rotations of the supply spool is known on the basis of the output to the calibrator 13 from the motor 4. This makes it possible to determine the current reel diameter ratio (R).
  • the calibrator 13 receives an input representative of spool diameter measurement from the measurement device 15 and an input representative of rotation of the motor 4 and delivers output 14 to the controller, the output 14 representing the instantaneous diameter of the supply spool 3.
  • the controller 12 may incorporate a processor with a pre-loaded value representing a target tension. That target tension will determine the input to the motor drive 11 from the controller 12, the motor drive 11 being controlled so as to drive the motor 4 in a manner such that as the supply spool radius decreases the motor torque also decreases so as to maintain the tape tension substantially constant.
  • the spool diameter measurement is achieved using an optical system as illustrated in Figure 3.
  • Alternative arrangements are possible however which do not rely upon direct measurement of spool diameter but rather calculate the spool diameter on the basis of signals representing tape transport and spool rotation.
  • Such an arrangement is schematically illustrated in Figure 5, again the same reference numerals being used as in Figure 1 where appropriate.
  • a tape transport measurement device 28 is positioned at some point adjacent the tape transport path so as to be able to generate an output 29 from which the length of tape dispensed in a given period can be derived.
  • the output 29 is applied to the calibrator 13 which also receives an output 30 from the motor 4, the output 30 being representative of rotations of the supply spool 3.
  • the calibrator 13 calculates from the length of tape transported past the device 28 in a given period and the number of revolutions of the spool 3 in that same period the circumference of the spool 3 on the basis that:
  • the radius of the spool 3 can be calculated from the circumference and hence all the information required to control tape tension is available.
  • FIG 6 this illustrates an embodiment of the invention intended to draw tape only in one direction, the take-up spool 2 being driven by a stepper motor and the supply spool 3 being driven by a DC motor.
  • the calibrator 13 is shown coupled to an optical sensing device 31 which could be for example of the type illustrated in Figure 3 and which delivers to the calibrator information representing the diameters of both the supply spool 3 and the take-up spool 2 during an initial calibration phase before the tape is transported for printing purposes.
  • the take-up spool 2 is driven to rotate in a clockwise direction (as viewed in Figure 6) by the stepper motor 1, thereby winding the tape onto the take-up spool 2.
  • the take-up spool 2 is driven by the stepper motor 1 so as to rotate through a predetermined number of angular steps, the number of steps being controlled by the controller 12.
  • the amount of tape wound onto the take-up spool 2 is dependent upon the size of each angular step and the diameter of the take-up spool 2 (including tape already wound on the spool). If X steps of ⁇ degrees per step are taken, and the take-up spool has a diameter D, the amount of ribbon wound onto the spool is determined by:
  • the supply spool 3 is driven by the DC motor 4 so as to provide torque in an anti-clockwise direction as viewed in Figure 6.
  • the torque provided by the DC motor 3 determines tension in the tape.
  • the magnitude of the tension is determined by both the torque generated by the DC motor 4 and by the radius of the supply spool 3 as discussed above.
  • the motor 4 is a DC motor
  • the DC motor current is controlled in accordance with the following equation:
  • C is the drive current provided to the motor 4
  • T is the required tension
  • R is the radius of the supply spool 3
  • K is a constant which converts the DC motor current to the torque generated by the DC motor 4.
  • the output 14 of the calibrator 13 indicates the current radius of the supply spool 3 calculated on the basis of an initial calibration measurement of the diameters of the supply spool 3 and the take-up spool 2 and monitoring of rotation of the stepper motor 1, that rotation when taken in combination with the known diameter of the take-up spool 2 enabling the calculation of the current diameters of both of the spools.
  • the controller 12 also supplies stepper pulses to the stepper motor drive 10 so as to control rotation of the take-up spool 2.
  • the DC motor-based arrangement of Figure 6 is advantageous when compared with prior art mechanical slipping clutch arrangements as it enables a relatively constant tape tension to be maintained regardless of changes in the diameter of the supply spool 3.
  • a disadvantage however with the embodiment of Figure 6 is that the DC motor and its associated drive controller is expensive.
  • the arrangement of Figure 6 does not lend itself to bi-directional drives which are advantageous in many applications.
  • An alternative embodiment of the invention which is capable of bi-directional drive is illustrated in Figure 7.
  • the embodiment of Figure 7 corresponds in general terms with the arrangement illustrated in Figure 5 and the same reference numerals are used where appropriate in Figures 5 and 7.
  • a non-slip free-running roller 32 which forms part of tape transport measurement device 28 is in contact with the tape between the rollers 5 and 6. Rotation of the roller 32 is detected by a suitable detector which provides the output 29 indicative of tape transport to calibrator 13.
  • the calibrator 13 also receives an output from the motor 4 which in this embodiment is a stepper motor and a further output 33 from the stepper motor 1. (As discussed above with reference to Figure 3, it will be appreciated that as the output 33 is representative of rotation of the stepper motor 1 the required motor rotation information could and in practice generally would be derived from either the motor drive 10 or the controller 12 rather than the motor).
  • the controller 12 provides stepper pulses to the motor drive circuit 11 which in turn generates a drive current that operates the stepper motor 4.
  • the controller 12 also provides an enable signal El to the stepper motor drive 11.
  • the second drive circuit 10 also receives stepper pulses and an enable input E2 from the controller 12.
  • the controller 12 When it is desired to wind the tape onto the spool 2, the controller 12 provides a "high" enable signal E2 to the drive circuit 10 together with pulses which control rotation of the motor 1 that drives the spool 2 in the clockwise direction. The controller 12 provides a "low” enable signal to the stepper drive 11 so that the circuit 11 generates no drive current. Windings of the motor 4 are connected to a programmable load circuit. Since no drive current is provided to the stepper motor 4, the motor resists the drive to which it is subjected by tension in the tape coupled to the supply spool 3. This resistance produces a "drag” torque which tensions the tape. The drag torque is dependent upon the current generated in the motor windings of the motor 4 as it is forced by the tape to rotate.
  • the generated current, and hence the tension, is determined by the characteristics of the load circuit. It will be appreciated that the arrangement of Figure 7 can be operated in both possible tape transport directions simply by reversing the manner in which the two stepper motors are controlled. Thus if the spool 2 is the take-up spool, the motor 1 is driven whereas the motor 4 provides drag. If the take-up spool is spool 3, the motor 4 is driven and the motor 1 provides drag torque.
  • roller arrangement of Figure 7 is purely schematic, showing the roller 32 in contact with one side of a straight length of tape.
  • the tape path would be such that the tape would be deflected around the roller 32 to reduce the risk of tape/roller slippage.
  • the roller 32 could be positioned between two idler rollers with the roller 32 deflecting the tape into a space occupied by the roller 32 between the idler rollers.
  • FIG. 8 A load circuit suitable for generating the drag torque discussed above is illustrated in Figure 8.
  • Figure 8 also shows components corresponding to the stepper motor 4, stepper drive 11, controller 12 and calibrator 13.
  • a corresponding load circuit and a corresponding drive circuit are connected to the other stepper motor 1 of Figure 7.
  • the stepper motor 4 is provided with drive current by the stepper drive circuit 11 which is controlled by the control circuit 12. Outputs from the drive current circuit 11 are connected to bases of four transistors 34 to 37.
  • the collector of each transistor is connected to a winding of the stepper motor 4, (the windings being labelled in figure 8 as A, A , B and B .
  • An opposite end of each winding is connected to a DC positive supply voltage.
  • the emitter of each transistor 34 to 37 is connected to ground.
  • the control circuit 12 To operate the stepper motor, the control circuit 12 provides a high enable signal El to the drive current circuit 11 together with a series of pulses.
  • the drive current circuit 11 is provided with sequencing control logic which turns on the transistors 34 to 37 in a predetermined order. As each transistor 34 to 37 is turned on it draws current through a corresponding motor winding, thereby advancing the stepper motor. The number of steps through which the stepper motor is advanced is determined by the number of pulses generated by the control circuit.
  • the sequencing control logic provided by the drive current circuit 11 may provide half step, full step or microstep control.
  • the load circuit shown in figure 8 comprises four diodes 38 to 41 each of which has an input connected to the output end of a respective motor winding A, A , B and B . Outputs of each of the diodes 38 to 41 are connected together and are connected to a power resistor 42.
  • a transistor 43 is connected between the power resistor 42 and the DC positive supply voltage.
  • the transistor 43 is controlled by an active load drive circuit 44 which provides a pulse width modulated signal to the base of the transistor 43.
  • a logic inverter 45 is connected between the enable output of the control circuit 12 and the active load drive circuit, to ensure that the active load drive circuit 44 is turned on only when the drive current circuit 11 is turned off.
  • the control circuit 12 also provides a pulse width modulated signal which is passed to the active load drive circuit 44.
  • the base voltage of the active load drive circuit 44 is referenced to the DC positive supply voltage. This means that a level shift circuit 46 is required to raise the level of the enable signal and the pulse width modulated signal passed to the active load drive circuit 44. A separate positive bias voltage on input 47 provides power to the active load drive circuit 44.
  • the load circuit is used to control the amount of work carried out by the stepper motor 4 when it is forced to rotate by tape being pulled from the supply spool (i.e. when pulled from left to right in figure 7).
  • Each winding of the motor 4 behaves as a generator and generates an AC waveform, as shown by the rectified waveforms in figure 9. Rectification of the generated motor voltage is provided by the diodes 38 to 41.
  • the arrangement of diodes assumes a two phase stepper motor. It will be appreciated that for example a five phase stepper motor could also be used, and where this is the case more diodes would be required.
  • the voltage seen at the power resistor 42 will be the peak of each separate waveform (this is due to the blocking effect of each diode). If the motor is pulled faster or slower then the output voltage generated will be correspondingly increased or decreased.
  • the active load drive circuit 44 controls the amount of net current that is allowed to flow through the power resistor 42 by adjusting the duty cycle of the pulse wave modulated signal provided to the base of the transistor 43.
  • a high duty cycle will result in a large load current being drawn through the power resistor 42, whereas a low duty cycle will result in a small load current being drawn through the power resistor 42.
  • the stepper motor 4 In order to generate a large load current the stepper motor 4 must work hard, and this is reflected in a high drag torque.
  • a low duty cycle will result in a smaller load current being drawn through the power resistor 42. Less work is required in order to generate the smaller load current, and the drag torque provided by the stepper motor will be correspondingly reduced.
  • the duty cycle of the pulse wave modulated signal passed to the transistor 43, and hence the load current drawn through the power resistor 42, is controlled by the control circuit 12.
  • the duty cycle of the pulse width modulated signal must be high in order to provide a required amount of tension to the ribbon (the tension is proportional to the drag torque and inversely proportional to the radius of the spool).
  • the control circuit 12 is provided with a signal 14 from the calibration 13 indicating the radius of the supply spool to enable stabilisation of tape tension.
  • the diodes 38 to 41 isolate the load circuit from the drive current circuit 11, since they effectively block current flow from the drive current circuit.
  • the load circuit transistor 43 is disabled by the active load drive circuit 44 during conventional motor drive.
  • a disadvantage of the load circuit shown in figure 8 is that the drag torque generated by the stepper motor 4 is dependent upon the speed of rotation of the stepper motor. This will not affect operation of the circuit if the speed of rotation of the take-up spool (2 in figure 7) is unchanging or varies in a known manner, as the load circuit can be calibrated appropriately before operation. However, when the speed of rotation of the take-up reel is variable and cannot be included in a calibration of the active load, the drag torque generated by the stepper motor will include unwanted variation.
  • a circuit which overcomes this disadvantage is shown in figure 10.
  • the components shown in figure 10, other than the load circuit, correspond to those shown in figure 8 and are not therefore described further.
  • the load circuit itself is substantially modified.
  • the power resistor 42 is connected between the transistor 43 and the DC positive supply voltage.
  • a first filter formed by a resistor 48 and capacitor 49 is connected to the pulse width modulated signal output from the control circuit 12.
  • a second filter formed by a resistor 50 and capacitor 51 is connected across the power resistor 42.
  • the output of the second filter is connected to the inverting input of an operational amplifier 52, and the output of the first filter is connected to the non- inverting input of the operational amplifier 52.
  • the output of the operational amplifier 52 is connected to the non-inverting input of a second operational amplifier 53.
  • a sawtooth ramp generator 54 is connected to the inverting input of the operational amplifier 53.
  • the output from the second operational amplifier is connected to the base of the transistor
  • the first filter filters and averages the pulse width modulated voltage output by the control circuit 12 (and shifted by the level shift circuit 46) to provide a DC voltage.
  • the second filter filters and averages the pulse width modulated current passed by the transistor 43 (i.e. the current generated by the windings of the stepper motor 4) to provide a DC voltage.
  • the first operational amplifier 52 compares the required current as determined by the control circuit 12 with the generated current.
  • the operational amplifier 52 amplifies the difference between the required current and the generated current and passes the amplified difference signal to the second operational amplifier 53.
  • the second operational amplifier 53 subtracts a sawtooth waveform, having a repeat frequency of 10 to 100 kHz, from the amplified difference signal.
  • the output from the second operational amplifier 53 is a variable pulse width modulated waveform that will adjust the average current generated by the stepper motor 4 to keep it relatively constant and at the level required by the control circuit 12. In this way the drag torque provided by the stepper motor 4 is made independent of the level of electromotive force induced in the stepper motor 4.

Abstract

La présente invention concerne un dérouleur de bande comprenant : un premier et un second moteur ; un premier et un second support de bobine de bande sur lesquels une première et une seconde bobine de bande respectives peuvent être montées, chacune de ces bobines pouvant être entraînée par un moteur respectif ; et une unité de commande chargée de commander les moteurs de sorte que la bande soit acheminée de la seconde bobine vers la première bobine. Le premier moteur est un moteur pas-à-pas. L'unité de commande est conçue pour faire fonctionner le premier moteur pas-à-pas pour qu'il entraîne la bande dans un sens d'entraînement de bande sur la première bobine et pour commander le second moteur de sorte qu'il empêche la rotation de la seconde bobine dans le sens d'entraînement de la bande. Le diamètre de la bobine reposant sur le second support de bobine est mesuré et la commande du second moteur varie en fonction du diamètre déterminé de la bobine reposant sur ce second support, la tension dans la bande étant maintenue dans des limites prédéfinies. Le second moteur peut aussi être un moteur pas-à-pas, ou un moteur à courant continu. Le diamètre de la bobine de bande peut être mesuré, par exemple optiquement, ou calculé, par exemple à partir de la distance d'entraînement de la bande et de la rotation du moteur correspondant mesurées.
PCT/GB2002/004405 2001-09-28 2002-09-30 Derouleur de bande WO2003029013A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0123303.0 2001-09-28
GB0123303A GB0123303D0 (en) 2001-09-28 2001-09-28 Tape drive

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WO2003029013A1 true WO2003029013A1 (fr) 2003-04-10

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FR2846908A1 (fr) * 2002-11-05 2004-05-14 Eurocodic Sa Machine a etiqueter a transfert thermique avec controle de rembobinage et procede pour l'impression multiple d'etiquettes
GB2404896A (en) * 2003-08-14 2005-02-16 Markem Tech Ltd Ribbon transport mechanism having tensioning means
US7052194B2 (en) 2003-04-22 2006-05-30 Markem Technologies Limited Apparatus and method for controlling a ribbon transport mechanism
WO2008107648A1 (fr) * 2007-03-07 2008-09-12 Zipher Limited Dérouleur de bande
WO2008119927A1 (fr) * 2007-03-31 2008-10-09 Zipher Limited Dérouleur de bande
GB2448305A (en) * 2007-03-07 2008-10-15 Zipher Ltd Tension monitoring and control in a tape drive
GB2449676A (en) * 2007-05-31 2008-12-03 Zipher Ltd Printing apparatus having a controller configured to provide control signals in response to comparing measured with predetermined criterion
CN101663173A (zh) * 2007-03-31 2010-03-03 赛福尔有限公司 带驱动装置
GB2471846A (en) * 2009-07-14 2011-01-19 Illinois Tool Works Label printer for a weighing scale
GB2482167A (en) * 2010-07-22 2012-01-25 Markem Imaje Ltd Tape drive and a method of operation of the tape drive
GB2507771A (en) * 2012-11-09 2014-05-14 Markem Imaje Ltd Tape drive and method of operation of a tape drive
US8961045B2 (en) 2007-03-07 2015-02-24 Videojet Technologies (Nottingham) Limited Tape drive
WO2015059449A1 (fr) * 2013-10-21 2015-04-30 Videojet Technologies Inc. Entraînement de bande et imprimante à transfert
US9145000B2 (en) 2013-02-13 2015-09-29 Dover Europe Sàrl Printing apparatus and method of operating a printing apparatus
US9233553B2 (en) 2000-09-11 2016-01-12 Videojet Technologies (Nottingham) Limited Tape drive and printing apparatus
US9238375B2 (en) 2013-02-12 2016-01-19 Dover Europe Sàrl Tape drive and method of operation
US9272531B2 (en) 2013-02-13 2016-03-01 Dover Europe Sarl Tape drive and method of operation of a tape drive
WO2016067051A1 (fr) * 2014-10-31 2016-05-06 Videojet Technologies Inc. Entraînement de bande et imprimante à transfert
US9340052B2 (en) 2011-08-10 2016-05-17 Markem-Imaje Industries Limited Motor control system
CN111559182A (zh) * 2020-05-25 2020-08-21 厦门墨逦标识科技有限公司 基于光学测量的打印机色带移动控制方法及装置
US11260650B2 (en) 2017-06-28 2022-03-01 Videojet Technologies Inc. Transfer printer and method
US11745528B2 (en) 2017-06-29 2023-09-05 Videojet Technologies Inc. Tape drive

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GB2396847B (en) * 2002-11-05 2006-01-11 Eurocodic S A Thermal transfer label printer with rewind control, and method for multiple label printing
FR2846908A1 (fr) * 2002-11-05 2004-05-14 Eurocodic Sa Machine a etiqueter a transfert thermique avec controle de rembobinage et procede pour l'impression multiple d'etiquettes
US7052194B2 (en) 2003-04-22 2006-05-30 Markem Technologies Limited Apparatus and method for controlling a ribbon transport mechanism
GB2404896A (en) * 2003-08-14 2005-02-16 Markem Tech Ltd Ribbon transport mechanism having tensioning means
CN101678685B (zh) * 2007-03-07 2011-09-14 赛福尔有限公司 带驱动装置
WO2008107648A1 (fr) * 2007-03-07 2008-09-12 Zipher Limited Dérouleur de bande
GB2448305A (en) * 2007-03-07 2008-10-15 Zipher Ltd Tension monitoring and control in a tape drive
GB2448305B (en) * 2007-03-07 2009-03-11 Zipher Ltd Tape drive
GB2448395B (en) * 2007-03-07 2009-05-06 Zipher Ltd Tape drive
GB2448395A (en) * 2007-03-07 2008-10-15 Zipher Ltd A tape drive for a thermal printer
US8961045B2 (en) 2007-03-07 2015-02-24 Videojet Technologies (Nottingham) Limited Tape drive
CN101663173A (zh) * 2007-03-31 2010-03-03 赛福尔有限公司 带驱动装置
WO2008119927A1 (fr) * 2007-03-31 2008-10-09 Zipher Limited Dérouleur de bande
GB2449676A (en) * 2007-05-31 2008-12-03 Zipher Ltd Printing apparatus having a controller configured to provide control signals in response to comparing measured with predetermined criterion
WO2008146002A1 (fr) * 2007-05-31 2008-12-04 Zipher Limited Dispositif d'entraînement de ruban
GB2449676B (en) * 2007-05-31 2009-08-26 Zipher Ltd Tape Drive
GB2471846A (en) * 2009-07-14 2011-01-19 Illinois Tool Works Label printer for a weighing scale
US8517618B2 (en) 2009-07-14 2013-08-27 Illinois Tool Works Inc. Weighing scale with cassette device that moves print head upon insertion with label printer
US8665301B2 (en) 2010-07-22 2014-03-04 Markem-Imaje Limited Tape drive and method of operation of a tape drive
GB2482167B (en) * 2010-07-22 2016-06-08 Markem-Imaje Ind Ltd Tape drive and method of operation of a tape drive
GB2482167A (en) * 2010-07-22 2012-01-25 Markem Imaje Ltd Tape drive and a method of operation of the tape drive
US9340052B2 (en) 2011-08-10 2016-05-17 Markem-Imaje Industries Limited Motor control system
US9975366B2 (en) 2011-08-10 2018-05-22 Markem-Imaje Industries Limited Motor control system
GB2507771B (en) * 2012-11-09 2020-03-04 Dover Europe Sarl Tape drive and method of operation of a tape drive
US9144999B2 (en) 2012-11-09 2015-09-29 Dover Europe Sàrl Tape drive and method of operation of a tape drive
EP2730422A1 (fr) * 2012-11-09 2014-05-14 Markem-Imaje Limited Dispositif d'entraînement de bande et procédé de fonctionnement associé
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US9272531B2 (en) 2013-02-13 2016-03-01 Dover Europe Sarl Tape drive and method of operation of a tape drive
US9770930B2 (en) 2013-10-21 2017-09-26 Videojet Technologies Inc. Tape drive and transfer printer
CN105324247A (zh) * 2013-10-21 2016-02-10 录象射流技术公司 磁带驱动器和转移打印机
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