Tape drive and printing apparatus

• US 20040146331A1
• Filed: 03/16/2004
• Published: 07/29/2004
• Est. Priority Date: 09/11/2000
• Status: Active Grant

• Current Assignee: Videojet Technologies Incorporated (Veralto Corp.)
• Original Assignee: Zipher Limited
• Inventors: McNestry, Martin, Buxton, Keith, Hart, Philip
• Granted Patent: US 7,150,572 B2
• Time in Patent Office: Days
• US Class Current: 400/615.2
• CPC Class Codes: B41J 2/325 by selective transfer of ink from ink carrier, e.g. from ink ribbon or sheet
• CPC Class Codes: B41J 33/00 Apparatus or arrangements for feeding ink ribbons or like character-size impression-transfer material
• CPC Class Codes: B41J 33/14 Ribbon-feed devices or mechanisms
• CPC Class Codes: B41J 33/16 with drive applied to spool or spool spindle
• CPC Class Codes: B41J 33/34 driven by motors independently of the machine as a whole
• CPC Class Codes: B41J 33/36 with means for adjusting feeding rate
• CPC Class Codes: B41J 33/54 for ensuring maximum life of the ribbon B41J33/38 takes precedence
• CPC Class Codes: B65H 2220/09 indicating that several of an entity are present
• CPC Class Codes: B65H 23/1806 in reel-to-reel type web winding and unwinding mechanism, e.g. mechanism acting on web-roll spindle
• CPC Class Codes: B65H 2555/26 Stepper motors
• CPC Class Codes: B65H 2701/372 Ink ribbons
• CPC Class Codes: G01B 11/08 for measuring diameters

Abstract

A tape drive for use in for example transfer printing apparatus to drive a printer ribbon. The printer ribbon is mounted on two spools each of which is driven by a respective stepper motor. A controller controls the energisation of the motor such that the ribbon is transported in at least one direction between spools mounted on the spool support. The controller is operative to energise both motors to drive the spools of ribbon in the direction of ribbon trasport to achieve push-pull operations. Ribbon tension is monitored to enable accurate control of ribbon supply and ribbon takte up, the ribbon tension being monitored by monitoring power supply to the two stepper motors.

Claims

1. A tape drive comprising two motors at least one of which is a stepper motor, two tape spool supports on which spools of tape may be mounted, each spool being drivable by a respective motor, and a controller for controlling the energisation of the motors such that the tape may be transported in at least one direction between spools mounted on the spool supports, wherein the controller is operative to energise both motors to drive the spools of tape in the direction of tape transport.

2. A tape drive according to claim 1, wherein the controller is arranged to control the motors to transport tape in both directions between the spools.

3. A tape drive according to claim 1 or 2, wherein both of the motors are stepper motors.

4. A tape drive according to claim 1, 2 or 3, wherein the controller is operative to monitor tension in a tape being transported between spools mounted on the spool supports and to control the motors to maintain the monitored tension between predetermined limits.

5. A tape drive according to claim 4, wherein means are provided to monitor the power supplied to at least one of the motors and to calculate an estimate of tape tension from the monitored power.

6. A tape drive according to claim 5 as dependent upon claim 3, comprising a power supply, and a stepper motor drive means for supplying current sequentially to windings of the stepper motors from the power supply, the power being monitored by means for monitoring the magnitude of voltage and/or current supplied to the motors and/or the motor drive means.

7. A tape drive according to claim 6, comprising a regulated power supply providing a substantially constant voltage to the stepper motor drive means, the monitoring means monitoring the magnitude of current supplied to the stepper motor drive means.

8. A tape drive according to claim 7, wherein each stepper motor is energised by a respective motor drive circuit, a respective low resistance resistor is connected in series with each motor drive circuit, and voltage signals developed across the series resistors are monitored to monitor the current supplied to the motors.

9. A tape drive according to claim 8, wherein the voltage signals are converted to digital signals which are supplied to a microcontroller which controls the generation of motor control pulse trains which are applied to the motor drive circuits.

10. A tape drive according to claim 7, 8 or 9, wherein the means for monitoring current is operative to monitor current over a predetermined period of time.

11. A tape drive according to claim 10, wherein the monitoring means is operative only during periods in which tape transport speed is substantially constant.

12. A tape drive according to claim 10 or 11, wherein the predetermined period of time corresponds to a predetermined length of tape transport.

13. A tape drive according to any one of claims 5 to 12, wherein calibration data is recorded for the or each stepper motor, the calibration data representing power consumption for the stepper motor at each of a series of step rates under no tape load conditions, and a measure of tape tension is calculated by reference to a measure of motor step rate, the calibration data related to the step rate, and power consumed by the motor.

14. A tape drive according to any preceding claim, comprising means for monitoring the outside diameters of the tape spools, and means for calculating tape tension by reference to the monitored diameters.

15. A tape drive according to claim 14, wherein the outside diameter monitoring means is operative to monitor the outside diameter of the spools for each of a plurality of diameters which are mutually inclined to each other.

16. A tape drive according to claim 14 as dependant upon claim 3 and claim 13, comprising means for calculating a measure of tension t, the controller being operative to maintain t between predetermined upper and lower limits, where:

t=N((V₁/x₂)−

(V₂/x₁))/(V₂r₁+V₁r₂)

and;

V₁ is a measure of power supplied to a first motor acting as a take-up spool drive motor;

V₂ is a measure of power supplied to a second motor acting as a supply spool drive motor;

r₁ is the radius of a spool of tape driven by the first motor;

r₂ is the radius of a spool of tape driven by the second motor;

x₁ is a calibration factor for the first motor related to the step rate of the motor;

x₂ is a calibration factor for the second motor related to the step rate of the motor; and

N is a calibration scaling factor.

17. A tape drive according to claim 16, wherein the controller implements a control algorithm to calculate a length of tape to be added to or subtracted from the tape extending between the spools in order to maintain the value t between the predetermined limits and to control the stepper motors to add or subtract the calculated length of tape to the tape extending between the spools.

18. A tape drive according to any one of claims 7 to 15 as dependant upon claim 3, comprising means for deriving a measure of the difference or ratio between the currents supplied to the two motors, and means for controlling stepping of the motors in dependence upon the difference or ratio measure.

19. A tape drive according to claim 18, wherein the controlling means maintains motor speed constant during periods in which the difference or ratio measure is within each of a series of tolerance bands defined between upper and lower limits, and means are provided for adjusting the tolerance bands in dependence upon the ratio of the outside diameters of the spools.

20. A tape drive according to claim 18 or 19, wherein the controlling means implements a control algorithm to calculate a length of tape to be added to or subtracted from the tape extending between the spools in order to maintain the difference or ratio measure between the upper and lower limits and to control the stepper motors to add or subtract the calculated length of tape to the tape extending between the spools.

21. A tape drive according to claim 16, 17, 19 or 20, comprising means for inputting a value corresponding to tape width, and means for adjusting the predetermined limits to take account of tape width.

22. A tape drive according to claim 21 as dependent upon claim 17 or 20, wherein the control algorithm comprises gain constants, and the gain constants are adjusted to take account of tape width.

23. A tape drive according to claim 17, 20 or 22, wherein the control algorithm operates cyclically such that during one cycle the length of tape to be added or subtracted is calculated and during a subsequent cycle the motors are controlled to adjust the amount of tape between the spools.

24. A tape drive according to claim 16, 17, 19, 20, 21, 22 or 23, comprising means for generating a fault-indicating output if the measure falls below a minimum acceptable limit below the lower limit.

25. A tape drive according to claim 14 or any claim dependant upon claim 14, wherein the diameter monitoring means comprises an optical sensing system including at least one light emitter and at least one light detector arranged such that an optical path is established therebetween, a transport mechanism supporting at least one part of the optical sensing system and drivable so as to cause the optical path to sweep across a space within which spools to be measured will be located, and a controller operative to control the transport mechanism, to detect positions of the transport mechanism in which the output of the detector changes to indicate a transition between two conditions in one of which the optical path is obstructed by a spool and in the other of which the optical path is not obstructed by that spool, and to calculate the spool diameters from the detected positions of the transport mechanism in which the detector output changes.

26. A tape drive according to claim 25, wherein one of the emitter and detector is mounted on the transport mechanism, the other being fixed in position relative to the spools of tape.

27. A tape drive according to claim 25, wherein both the emitter and detector are mounted on the transport mechanism, the optical path between the emitter and detector being established by a mirror located at the side of the spools remote from the transport mechanism and arranged to reflect light from the emitter back to the detector.

28. A tape drive according to claim 25, 26 or 27 as dependent upon claim 15, wherein the diameter monitoring means is operative to monitor the spool diameters with the spools in a first position, to rotate the spools to at least one further position, and to monitor the spool diameters in the or each further position, the calculated spool diameters enabling an accurate assessment of spool eccentricity and outer circumference.

29. A tape drive according to claim 25, 26, 27 or 28, wherein the transport mechanism comprises a print head transport mechanism of a transfer ribbon printer.

30. A tape drive according to claim 14 or any claim dependent upon claim 14, wherein the diameter measuring means comprises mean for calculating the ratio of the diameters of the spools.

31. A tape drive according to claim 30 as dependant upon claim 3, wherein the ratio calculating means comprises means enabling a first stepper motor driving a take up spool and disabling a second stepper motor driving a supply spool such that the second stepper motor acts as a generator, means for generating pulses from the second stepper motor, the pulse rate being proportional to motor speed, means for detecting the generated pulses to produce a measure of the rotation of the second stepper motor, means for monitoring stepping of the first stepper motor to produce a measure of the rotation of the first stepper motor, and means for comparing the measures of the rotations of the motors to calculate the ratio of the outside diameters of the spools.

32. A tape drive according to claim 31, comprising means for calculating an updated diameter for at least one spool from a ratio between the spool diameters as initially monitored, a current ratio between the spool diameters, and the diameter of at least one spool as initially monitored.

33. A tape drive according to any preceding claim incorporated in a transfer printer for transferring ink from a printer ribbon to a substrate which is transported along a predetermined path adjacent to the printer, the tape drive acting as a printer ribbon drive mechanism for transporting ribbon between first and second ribbon spools, and the printer further comprising a printhead arranged to contact one side of the ribbon to press an opposite side of the ribbon into contact with a substrate on the predetermined path, a printhead drive mechanism for transporting the printhead along a track extending generally parallel to the predetermined substrate transport path and for displacing the printhead into and out of contact with the ribbon, and a controller controlling the printer ribbon and printhead drive mechanisms, the controller being selectively programmable either to cause the ribbon to be transported relative to the predetermined substrate transport path with the printhead stationery and displaced into contact with the ribbon during printing, or to cause the printhead to be transported relative to the ribbon and the predetermined substrate transport path and to be displaced into contact with the ribbon during printing.

34. A tape drive according to claim 33, wherein the drive mechanism is bi-directional such that ribbon may be transported from the first spool to the second spool and from the second spool to the first.

35. A tape drive according to claim 34, wherein the printhead is mounted on a printhead carriage that is displaceable along the track, first and second carriages being provided which are interchangeable and are shaped such that with one carriage in position on-the track the printhead is disposed so as to enable printing on a substrate travelling in one direction along the substrate transport path and with the other carriage in position on the track the printhead is disposed so as to enable printing on a substrate travelling in the other direction along the substrate transport path.

36. A tape drive according to any preceding claim incorporated in a printing apparatus comprising a housing, a printhead mounted on a printhead support assembly which is displaceable relative to the housing in a direction parallel to a print ribbon path along which a ribbon is driven by the tape drive, a first drive mechanism for displacing the printhead support relative to the housing, a roller which in use supports a substrate to be printed on the side of the ribbon path remote from the print head, a second drive mechanism for displacing the printhead relative to the printhead support assembly to a printing position in which a portion of the printhead bears against the roller or any substrate or ribbon interposed between the printhead and roller, and a controller for adjusting the first drive mechanism to adjust the angular position of the printhead relative to the rotation axis of the roller.

37. A tape drive according to any preceding claim incorporated in a printing apparatus comprising a housing, a printhead mounted on a printhead support assembly which is displaceable relative to the housing in a direction parallel to a print ribbon path along which a ribbon is driven by the tape drive, a first drive mechanism for displacing the printhead support relative to the housing, a peel off roller mounted on the printhead support assembly and displaceable with the printhead in the said parallel direction, and a second drive mechanism for displacing the printhead relative to the printhead support assembly and peel off roller between a ready to print position adjacent the print ribbon path and a printing position in which the printhead would contact a print ribbon on the path, wherein a cam mechanism is provided which is engaged as a result of displacement of the printhead support assembly to a predetermined position and when engaged causes retraction of the printhead away from the ready to print position to a position spaced from the peel roller and the print ribbon path.

38. A tape drive according to claim 37, wherein the cam mechanism comprises a plate mounted on the housing and defining a slot, and a pin extending from a pivotal member mounted on the printhead support assembly, engagement of the pin in the slot as a result of displacement of the printhead support assembly to the predetermined position causing the pivotal member to rotate from a first position in which it supports the printhead to a second position in which the printhead is free to move to the position spaced from the peel roller and the print ribbon path.

39. A tape drive according to claim 38, wherein the pivotal member is mounted on a displaceable member mounted on the printhead support assembly, displacement of the displaceable member from a retracted to an extended position when the pivotal member is in the first position causing the printhead to move from the ready to print from the printing position.

40. A tape drive according to any preceding claim incorporated in a printing apparatus comprising a printhead, the tape drive serving as a printing ribbon drive mechanism for advancing a printing ribbon between the printhead and a path along which in use a substrate to be printed is advanced, the print apparatus further comprising means for applying the printhead to a ribbon supported in the drive mechanism, the printhead comprising an array of printing elements each of which may be selectively energised to release ink from a portion of ribbon contacted by that element, and a controller for controlling energisation of the printing elements and the advance of the ribbon so as to perform a series of printing cycles each of which includes a printing phase during which relative movement between the printhead and ribbon results in the printhead traversing a predetermined length of ribbon and a non-printing phase during which the ribbon is advanced a predetermined distance relative to the printhead, wherein the controller is arranged selectively to energise different groups of printing elements during successive printing cycles, the groups of elements being distributed on the printhead such that different groups contact different portions of the ribbon, and the controller is arranged to advance the ribbon such that the said predetermined distance of ribbon advance is less that the said predetermined length of ribbon, the groups of printing elements being energised such that that ribbon is advanced by at least said predetermined length of ribbon in the interval between any two printing phases in which the same group of printing elements are energised.

41. A tape drive according to claim 40, comprising two groups of printing elements, wherein said predetermined distance of ribbon advance is at least half the said predetermined length of ribbon.

42. A transfer printer for transferring ink from a printer ribbon to a substrate which is transported along a predetermined path adjacent the printer, comprising a printer ribbon drive mechanism for transporting ribbon between first and second ribbon spools, a printhead arranged to contact one side of the ribbon to press an opposite side of the ribbon into contact with a substrate on the predetermined path, a printhead drive mechanism for transporting the printhead along a track extending generally parallel to the predetermined substrate transport path and for displacing the printhead into and out of contact with the ribbon, and a controller being selectively programmable either to cause the ribbon to be transported relative to the predetermined substrate transport path with the printhead stationery and displaced into contact with the ribbon during printing, or to cause the printhead to be transported relative to the ribbon and the predetermined substrate transport path and to be displaced into contact with the ribbon during printing.

43. A transfer printer according to claim 42, wherein the drive mechanism is bi-directional such that the ribbon may be transported from the first spool to the second spool and from the second spool to the first.

44. A printer according to claim 42, wherein the ribbon drive mechanism comprises at least one stepper motor to drive at least one ribbon spool in the direction of tape transport.

45. A printer according to claim 42 or 43, wherein the ribbon drive mechanism comprises two stepper motors each driving a respective one of the first and second ribbon spools in the direction of tape transport.

46. A printer according to claim 45, comprising means for monitoring ribbon tension and means for controlling the stepper motors to maintain the monitored tension within predetermined limits.

47. A printer according to claim 42, 43, 44, 45 or 46, wherein the printhead drive mechanism comprises a stepper motor coupled to the printhead.

48. A printer according to claim 42, 43, 44, 45, 46 or 47, wherein the printhead is mounted on a carriage that is displaceable along the track.

49. A printer according to claim 48 as dependent upon claim 43, comprising first and second carriages which are interchangeable and are shaped such that with one carriage in position on the track the printhead is disposed so as to enable printing on a substrate travelling in one direction along the substrate transport path and with the other carriage in position on the track the print head is disposed so as to enable printing on a substrate travelling in the other direction along the substrate transport path.

50. A printer according to claim 49, wherein a peel off roller is mounted adjacent the print head, the position of the peel off roller relative to the printhead being reversible.

51. An apparatus for measuring the diameters of two spools of tape mounted on a tape drive mechanism which is drivable to, transport tape between the spools, comprising an optical sensing system including;

at least one light emitter and at least one light detector arranged such that an optical path is established therebetween, a transport mechanism supporting at least part of the optical sensing system and drivable so as to cause the optical path to sweep across a space within which spools to be measured will be located, and a controller operative to control the transport mechanism, to detect positions of the transport mechanism in which the output of the detector changes to indicate a transition between two conditions in one of which the optical path is obstructed by a spool and in the other of which the optical path is not obstructed by that spool, and to calculate the spool diameters from the detected positions of the transport mechanism in which the detector output changes.

52. A printing apparatus comprising a housing, a printhead mounted on a printhead support assembly which is displaceable relative to the housing in a direction parallel to a print ribbon path, a first drive mechanism for displacing the printhead support relative to the housing, a roller which in use supports a substrate to be printed on the side of the ribbon path remote from the printhead, a second drive mechanism for displacing the printhead relative to the printhead support assembly to a printing position in which a portion of the printhead bears against the roller or any substrate or ribbon interposed between the printhead and roller, and a controller for adjusting the first drive mechanism to adjust the angular position of the printhead relative to the rotation axis of the roller.

53. An apparatus according to claim 52, wherein the portion of the printhead that bears against the roller or any substrate or ribbon interposed between the printhead and roller, is the portion of the printhead that contains selectively energisable printing elements.

54. An apparatus according to claim 53, wherein the elements are linearly arranged along the portion of the printhead.

55. An apparatus according to 54, wherein the linear array of elements is arranged along an edge, or parallel in close proximity to an edge of the printhead.

56. A printing apparatus comprising a housing, a printhead mounted on a printhead support assembly which is displaceable relative to the housing in a direction parallel to a print ribbon path, a first drive mechanism for displacing the printhead support relative to the housing, a peel off roller mounted on the printhead support assembly and displaceable with the printhead in the said parallel direction, and a second drive mechanism for displacing the printhead relative to the printhead support assembly and peel off roller between a ready to print position adjacent the print ribbon path and a printing position in which the printhead would contact a print ribbon on the path, wherein a cam mechanism is provided which is engaged as a result of displacement of the printhead support assembly to a predetermined position and when engaged causes retraction of the printhead away from the ready to print position to a position spaced from the peel roller and the print ribbon path.

57. A printing apparatus comprising a printhead, a printing ribbon drive mechanism for advancing a printing ribbon between the printhead and a path along which in use a substrate to be printed is advanced, means for applying the printhead to a ribbon supported in the drive mechanism, the printhead comprising an array of printing elements each of which may be selectively energised to release ink from a portion of ribbon contacted by that element, and a controller for controlling energisation of the printing elements and the advance of the ribbon so as to perform a series of printing cycles each of which includes a printing phase during which relative movement between the printhead and ribbon results in the printhead traversing a predetermined length of ribbon and a non-printing phase during which the ribbon is advanced a predetermined distance relative to the printhead, wherein the controller is arranged selectively to energise different groups of printing elements during successive printing cycles, the groups of elements being distributed on the printhead such that different groups contact different portions of the ribbon, and the controller is arranged to advance the ribbon such that the said predetermined distance of ribbon advance is less than the said predetermined length of ribbon, the groups of printing elements being energised such that the ribbon is advanced by at least said predetermined length of ribbon in the interval between any two printing phases in which the same group of printing elements are energised.

58. A method for controlling a tape drive comprising two motors at least one of which is a stepper motor, two tape spool supports on which spools of tape may be mounted, each spool support being drivable by a respective motor, and a controller for controlling the energisation of the motors such that tape may be transported in at least one direction between spools mounted on the spool supports, wherein the controller energises both motors to drive the spools of tape in the direction of tape transport.

59. A method of controlling a transfer printer for transferring ink from a printer ribbon to a substrate which is transported along a predetermined path adjacent the printer, wherein a printer ribbon drive mechanism transports ribbon between first and second ribbon spools, a printhead is arranged to contact one side of the ribbon to press an opposite side of the ribbon into contact with a substrate on the predetermined path, a printhead drive mechanism transports the printhead along a track extending generally parallel to the predetermined substrate transport path and displaces the printhead into and out of contact with the ribbon, and a controller controls the printer ribbon and printhead drive mechanisms, the controller being selectively programmed either to cause the ribbon to be transported relative to the predetermined substrate transport path with the printhead stationary and displaced into contact with the ribbon during printing, or to cause the printhead to be transported relative to the ribbon and the predetermined substrate transport path and to be displaced into contact with the ribbon during printing.

60. A method for measuring the diameters of two spools of tape mounted on a tape drive mechanism which is drivable to transport tape between the spools, wherein an optical sensing system including at least one light emitter and at least one light detector is arranged such that an optical path is established therebetween, a transport mechanism supporting at least part of the optical sensing system and is driven so as to cause the optical path to sweep across a space within which spools to be measured are located, and a controller which controls the transport mechanism detects positions of the transport mechanism in which the output of the detector changes to indicate a transition between two conditions in one of which the optical path is obstructed by a spool and in the other of which the optical path is not obstructed by that spool, the spool diameters being calculated from the detected positions of the transport mechanism in which the detector output changes.

61. A method for adjusting the position of a printhead in a printing apparatus comprising a housing, a printhead support assembly on which the printhead is mounted and which is displaceable relative to the housing in a direction parallel to a print ribbon path, a first drive mechanism for displacing the printhead support relative to the housing, a roller which in use supports a substrate to be printed on the side of the ribbon path remote from the printhead, and a second drive mechanism for displacing the printhead relative to the printhead support assembly to a printing position in which a portion of the printhead bears against the roller or any substrate or ribbon interposed between the printhead and roller, and a controller for adjusting the first drive mechanism to adjust the angular position of the printhead relative to the rotation axis of the roller, wherein the printhead is positioned adjacent the roller, a test print is performed, the first drive mechanism is adjusted to change the angular position of the printhead relative to the rotation axis of the roller, a further test is performed, the adjustment and test processing being repeated until a satisfying print quality is achieved.

62. A method for controlling the retraction of a printhead during printer ribbon replacement in a printing apparatus comprising a housing, a printhead support assembly on which the printhead is mounted and which is displaceable relative to the housing in a direction parallel to a print ribbon path, a first drive mechanism for displacing the printhead support relative to the housing, a peel off roller mounted on the printhead support assembly and displaceable with the printhead in the said parallel direction, and a second drive mechanism for displacing the printhead relative to the printhead support assembly and peel off roller between a ready to print position adjacent the print ribbon path and a printing position in which the printhead would contact a print ribbon on the path, wherein when printer ribbon replacement is required the printhead support assembly is displaced to a predetermined position, a cam mechanism is positioned so as to be engaged as a result of displacement of the printhead support assembly to the predetermined position, the cam mechanism when engaged causing retraction of the printhead away from the ready to print position to a position spaced from the peel roller and the print ribbon path.

63. A method for controlling a printing process in a printing apparatus comprising a printhead, a printing ribbon drive mechanism for advancing a printing ribbon between the printhead and a path along which in use a substrate to be printed is advanced, and means for applying the printhead to a ribbon supported in the drive mechanism, the printhead comprising an array of printing elements each of which may be selectively energised to release ink from a portion of ribbon contacted by that element, wherein the energisation of the printing elements and the advance of the ribbon is controlled so as to perform a series of printing cycles each of which includes a printing phase during which relative movement between the printhead and ribbon results in the printhead traversing a predetermined length of ribbon and a non-printing phase during which the ribbon is advanced a predetermined distance relative to the printhead, different groups of printing elements are selectively energised during successive printing cycles, the groups of elements being distributed on the printhead such that different groups contact different portions of the ribbon, and the ribbon is advanced such that the said predetermined distance of ribbon advance is less than the said predetermined length of ribbon, the groups of printing elements being energised such that the ribbon is advanced by at least said predetermined length of ribbon in the interval between any two printing phases in which the same group of printing elements are energised.