US 4,573,645 A · Ribbon tension control

Abstract

A ribbon tension control for controlling the tension of ribbon traveling between a rotating supply spool and a rotating take-up spool varies the amount of braking torque applied to the supply spool to hold ribbon tension constant as the distribution of ribbon between the spools changes. A generator rotationally coupled to the supply spool produces braking torque to resist the rotation of the spool when the generator windings are electrically loaded. The loading of the generator is controlled by processing feedback signals emitted by the generator to provide periodic load switching signals. Processing of the feedback signal is accomplished in the exemplary embodiment by a drag lookup table which is addressed by the feedback signal. The drag lookup table produces a duty cycle value which is used to determine the duty cycle of the switching signal, which, in turn, controls the electrical loading of the generator. Because electrical loading of the generator at the switching signal rate modulates the feedback signal which it emits, the period of the switching signal is sufficiently different from that of the feedback signal to permit separation of the feedback signal from the switching signal.

Claims27

Dependent claims

A ribbon tension controller for controlling the tension of a fixed length of ribbon as it is transferred from a rotating supply spool to a rotating take-up spool, said ribbon tension controller comprising:

alternating current generator means coupled to said supply spool for producing braking torque to resist the rotation of said supply spool;
control means for producing a digital ribbon tension control signal related to the relative lengths of the fixed length ribbon then present on said spools;
and
dynamic electrical braking means for dynamically varying the braking torque produced by said generator means, said braking means including switching means, electrically coupled to said generator means and to an electrical load, for selectively coupling said load to said generator means in response to said digital control signal.

1 more element

A tape transport apparatus for controlling the tension of a length of ribbon as it is transferred from a rotating supply spool to a rotating take-up spool, said apparatus comprising:

electrical drive means mechanically coupled to said take-up spool for rotating said take-up spool to wind said ribbon onto said take-up spool;
electrical alternating current generator means mechanically coupled to be driven by said supply spool for producing braking torque to resist the rotation of said supply spool;
electrical control means for detecting ribbon motion and for producing a corresponding digital ribbon tension control signal related to the desired ribbon tension;
and
digital switching means, electrically coupled to an electrical load and to said generator means, for varying the braking torque produced by said generator means by selectively connecting said load to said generator means in response to said digital control signal.

2 more elements

A tape transport apparatus for controlling the tension of a length of ribbon as it is transferred from a rotatable supply spool to a rotatable take-up spool, said apparatus comprising:

means for generating a first electrical signal;
drive means rotationally coupled to said take-up spool for winding said ribbon from said supply spool onto said take-up spool at a linear velocity proportional to said first electrical signal;
alternating current generator means rotationally coupled to said supply spool for producing a second electrical signal at an output thereof proportional to the angular velocity of said supply spool and for producing braking torque to resist the rotation of said supply spool;
control means responsive to said first and second signal for producing a third electrical signal proportional to the ratio of the angular velocity at which said supply spool is rotating to the angular velocity at which said take-up spool is being controlled to rotate;
periodic signal generating means responsive to said third signal for producing a first periodic pulse train, the duty cycle of the pulses of said pulse train bearing a predetermined relationship to said third signal;
electrical load means for resisitively loading said generator means causing said generator means to produce braking torque;
and
switch means for connecting said load means to said generator means when a pulse of said periodic pulse train is present.

5 more elements

Dependencies are inferred from the claim text.

Ribbon tension control

Life of this patent

Ribbon tension control

Life of this patent

Abstract

Claims27