A thermal transfer printer incorporating a tape drive comprising a first torque-controlled motor and a second position-controlled motor, two tape spool supports on which spools of tape may be mounted, each spool being drivable by a respective one of said motors, and a controller for controlling the energization of the motors such that the tape may be transported in at least one direction between spools mounted on the spool supports. The controller is arranged to determine a control signal to be provided to the torque-controlled motor to set the tape tension, and to provide said control signal to the torque-controlled motor, determination of the control signal including determination of a component intended to compensate for the inertia of a spool of tape driven by the torque-controlled motor.
1. A thermal transfer printer for selectively transferring an ink material carried on a tape to a substrate intended to receive printing to transfer an image from the tape to the substrate, the printer comprising:
two spool supports for spools of tape carrying ink material, with the tape being wound on the spools and with a span of tape being held in tension between the spools, the tape spools being carried on and driveable by the respective spool supports, and the tape being of the single strike type for which a region of fresh tape must be made available for printing each image to the substrate during a printing operation;
a print head positioned at the span of tape between the tape spools, the print head being mounted for selective movement between an extended position adjacent the span of type between, the spools and a retracted position spaced apart from the span of tape between the tape spools and comprising heating elements selectively energized for transferring ink material on the span of tape between the tape spools to the substrate when the print head is moved to its extended position and into contact with the tape while the tape is in contact with the substrate to print an image, wherein the print head is moved to its retracted position between printings of consecutive adjacent images on the substrate;
a tape drive for selectively transporting tape between the spools of tape comprising a first torque-controlled motor and a second position-controlled motor, each driving a spool of tape via its spool support, wherein at least one of the motors is selectively controllable to operate either as a torque-controlled motor or a position-controlled motor;
the tape drive further comprising a controller configured to control the energization of the motors to transport the tape in a first direction and a second direction between the spools, wherein the first and second directions of tape transport being generally opposite to one another;
the controller further being configured to selectively control energization of the first or second motors such that one of the motors is operated as a position-controlled motor during transport of the tape in the first and second tape transport direction to drive its spool support to a commanded angular position to take-up or supply a predetermined length of tape to the span of tape between the spools;
the controller further being configured, when the tape is transported in either the first direction or second direction to control energization of at least one of the motors to operate as a torque-controlled motor to drive a spool support to deliver a predetermined level of torque to set tension in the span of tape extending from one spool to the other spool;
the controller further being configured to determine a motor drive current to be provided to the motor being operated as a torque-controlled motor to set tension in the span of tape extending from one spool to the other spool, wherein the controller is configured to determine a level of current that compensates for an inertia of the spool of tape and spool support driven by the torque-controlled motor and that is, between printings of consecutive adjacent images on the substrate, added to or subtracted from a level of current that drives the torque-controlled motor at steady state for tape transport when printing an image,
wherein when the tape is transported in a first direction the first motor is operated as a torque-controlled motor arranged to drive a tape spool supplying tape and the second motor is operated as a position-controlled motor arranged to drive a tape spool taking up tape, the torque-controlled motor being driven in a second direction opposite to the first direction, and when the tape is transported in the second direction the second motor is operated as a torque-controlled motor arranged to drive a tape spool supplying tape and the first motor is operated as a position-controlled motor arranged to drive a tape spool taking up tape, the torque-controlled motor being driven in the first direction.