Tape transport having variable torque constant reel and capstan drive motor

Claim 2

A magnetic tape transport comprising: a pair of reel drive motors, each disposed to drive a different reel of tape with rotary motion and each including at least one wound field producing a component of magnetic field flux and a motor torque constant varying with the current therethrough; a capstan positioned along a tape path extending between the pair of reels to drive magnetic tape intermediate the pAir of reels; a capstan motor connected to drive the capstan at a first maximum speed during intermittent program operation and at a speed greater than the first speed during rewind operation; a pair of buffer loop forming devices positioned along the tape path to form a buffer loop of magnetic tape between the capstan and a reel of tape on each side of the capstan; a magnetic head positioned along the tape path intermediate the capstan and one of said pair of tape buffer loop forming devices; and a motor control system including circuitry for driving at least one of the at least one wound field of each reel drive motor with a first current producing a first torque constant during intermittent program operation and with a second current producing a second torque constant substantially less than the first torque constant during rewind operation.

Claim 3

The tape transport as set forth in claim 1 above, wherein the capstan motor includes at least one wound field producing a component of magnetic flux and a motor torque constant varying with the current through the wound field and wherein the motor control system further includes capstan motor circuitry driving at least one of the at least one capstan motor field windings with a first current producing a first torque constant during intermittent program operation and with a second current producing a second torque constant substantially less than the first torque constant during rewind operation.

Claim 4

The tape transport as set forth in claim 1 above, wherein each reel motor includes a field generator producing a constant component of magnetic field flux and a constant component of a motor torque constant and wherein the first current produces a component of magnetic field flux in support of the constant component and the second current produces a component of magnetic field flux in opposition to the constant component.

Claim 5

The magnetic tape transport as set forth in claim 3 above, wherein the capstan motor includes at least one wound field producing a component of magnetic flux and a motor torque constant varying with the current therethrough and wherein the motor control system further includes capstan motor circuitry driving at least one of the at least one wound field of the capstan motor with a first current producing a first torque constant during intermittent program operation and with a second current producing a second torque constant substantially less than the first torque constant during rewind operation.

Claim 6

A bidirectionally and intermittently operable magnetic tape transport comprising: a pair of reels defining the ends of a tape path; a pair of buffer loop forming elements positioned along a tape path intermediate the pair of reels; a capstan disposed to control tape motion intermediate the pair of tape loop elements; a magnetic head positioned along a tape path intermediate the tape loop elements; a pair of reel motors connected to drive the pair of reels in response to signals from reel motor control circuitry, said reel motors having first permanent magnet field generators and second wound field generators; and reel motor control circuitry connected to control the reel motors, the reel motor control circuitry including field control circuitry for variably energizing the wound fields to provide a first torque constant for intermittent operation and a second torque constant for rewind operation.

Claim 7

A bidirectionally and intermittently operable magnetic tape transport comprising: a pair of reels defining the ends of a tape path; a pair of buffer loop forming elements positioned along a tape path intermediate the pair of reels; a capstan disposed to control tape motion intermediate the pair of tape loop elements; a magnetic head positioned along a tape path intermediate the tape loop elements; a pair of reel motors connected to drive the pair of reels in response to signals from reel motor control circuitry, said reel motors having first permanent magnet field generators and second wound field generators; and reel motor control circuitry connected to control the reel motors, the reel motor control circuitry including field control circuitry for variably energizing the wound fields to provide a first torque constant for intermittent operation and a second torque constant for rewind operation.

Claim 8

The tape transport as set forth in claim 5 above, wherein the field control circuitry changes between first and second torque constant energizations in a controlled manner.

Claim 9

The tape transport as set forth in claim 6 above, wherein the field control circuitry prohibits step function changes between the first torque constant and the second torque constant.

Claim 10

The tape transport as set forth in claim 7 above, wherein the field control circuitry changes the wound field energizations to vary the torque constants approximately linearly between the first and second torque constants.

Claim 11

The tape transport as set forth in claim 8 above, wherein the field control circuitry changes the wound field energizations to vary the torque constants in a manner causing the torque constants to lie approximately inversely proportional to the speed of the respective motors between the first and second torque constants.

Claim 12

The tape transport as set forth in claim 6 above, wherein the field control circuitry responds during rewind operation to begin the transitions of motor field energizations from first torque constant energizations to second torque constant energizations only after the reel motors have reached normal program operation speeds.

Claim 13

A tape transport having at least one tape driving element positioned along a tape path, the tape transport comprising a motor connected to drive the tape driving element, the motor including at least two field generators each generating a component of magnetic field flux with the flux component generated by at least one of said field generators being variable, and a field controller connected to vary the flux component generated by the variable flux field generator to provide at least two different torque constants for different tape transport operating conditions.

Claim 14

A tape transport having at least one tape driving element positioned along a tape path, the tape transport comprising a motor connected to drive the tape driving element, the motor including at least two field generators each generating a component of magnetic field flux with the flux component generated by at least one of said field generators being variable, and a field controller connected to vary the flux component generated by the variable flux field generator to provide at least two different torque constants for different tape transport operating conditions.

Claim 15

The tape transport as set forth in claim 11 above, wherein the field controller includes circuitry causing changes in the torque constant of the motor to be made in a controlled manner not a step function change.

Claim 16

The tape transport as set forth in claim 12 above, wherein the field controller causes the rate of change of the torque constant with respect to time to remain approximately constant as the torque constant is changed between two values.

Claim 17

The tape transport as set forth in claim 13 above, wherein the field controller changes the torque constant in response to a command to change from one nominal operating speed to a second nominal operating speed and the rate of change of torque constant with respect to time is selected such that time required to accelerate between the two operating speeds is approximately equal to the time to change between the corresponding torque constants.

Claim 18

The tape transport as set forth in claim 12 above, wherein the field controller changes the torque constant in a manner causing the product of motor speed and the torque constant to be maintained approximately constant.

Claim 19

The tape transport as set forth in claim 11 above, wherein the first operating condition is an intermittent program operating condition having a first nominal full speed, and wherein the field controller does not permit the product of torque constant and speed at speeds above the first nominal full speed to exceed twice the product of torque constant and speed at the first nominal full speed.

Claim 20

The tape transport as set forth in claim 11 above, wherein the two different torque constants vary in magnitude by a ratio of at least five to one.

Claim 21

The tape transport as set forth in claim 11 above, wherein the two different torque constants vary in magnitude by a ratio of at least six to one.

Claim 22

A tape transport having a pair of tape storage devices, a tape path extending between the tape storage devices, at least one tape buffer disposed along the tape path, a capstan disposed to drive tape along the tape path, and comprising: a capstan motor connected to drive the capstan, the capstan motor including a first magnetic field generator and a second magnetic field generator generating a variable magnetic field; a motor control system connected to control the second magnetic field generator to vary the torque constant of the capstan motor in accordance with a predetermined pattern.

Claim 23

A tape transport having a pair of tape storage devices, a tape path extending between the tape storage devices, at least one tape buffer disposed along the tape path, a capstan disposed to drive tape along the tape path, and comprising: a capstan motor connected to drive the capstan, the capstan motor including a first magnetic field generator and a second magnetic field generator generating a variable magnetic field; a motor control system connected to control the second magnetic field generator to vary the torque constant of the capstan motor in accordance with a predetermined pattern.

Claim 24

The tape transport as set forth in claim 19 above, wherein the motor control system includes means for maintaining the torque constant at a predetermined magnitude when motor speed is below a selected motor speed and means for maintaining the torque constant generally inversely proportional to motor speed as the motor accelerates between the selected motor speed and a higher motor speed.

Claim 25

The tape transport as set forth in claim 20 above, wherein the motor control system includes an armature passing armature current in series through magnetic fields generated by the first and second magnetic field generators and wherein the motor control system controls the second magnetic field generator to provide a second magnetic field about the armature current which is similar in polarity to the first magnetic field at the selected motor speed and opposite in polarity to the first magnetic field at the higher motor speed.

Claim 26

In a magnetic tape transport having at least one reel for moving a length of magnetic tape bidirectionally at a nominal speed during normal programming operations and at a speed substantially higher than the nominal speed during rewind, and a power supply, a motor drive system coupled to drive the reel, the motor drive system comprising a variable torque constant motor and means providing the motor with a first torque constant for normal programming operation and a second torque constant different from the first torque constant for rewind, said motor drawing a nominal, substantially fixed amount of current from the power supply independent of the torque constant thereof.

Claim 27

In a magnetic tape transport having at least one reel for moving a length of magnetic tape bidirectionally at a nominal speed during normal programming operations and at a speed substantially higher than the nominal speed during rewind, and a power supply, a motor drive system coupled to drive the reel, the motor drive system comprising a variable torque constant motor and means providing the motor with a first torque constant for normal programming operation and a second torque constant different from the first torque constant for rewind, said motor drawing a nominal, substantially fixed amount of current from the power supply independent of the torque constant thereof.

Claim 28

The invention as set forth in claim 22, wherein the motor includes at least one fixed field and at least one field winding for generating a variable field, and further comprising a drive circuit coupled between the power supply and the at least one field winding, the drive circuit being operative to energize the at least one field winding with a direct current of one sense to provide the first torque constant and a direct current of opposite sense to provide the second torque constant.

Claim 29

The invention as set forth in claim 23, wherein the motor includes a permanent magnet for generating one component of a magnetic field having a total net flux which is increased when the field winding is energized with the direct current of one sense and which is decreased when the field winding is energized with the direct current of opposite sense.

Claim 30

A magnetic tape transport comprising: a pair of rotatable reels adapted to have the opposite ends of a length of magnetic tape wound thereon; means disposed along a tape path extending between the rotatable reels for processing the magnetic tape including capstan means for driving the tape and magnetic head means for recording, reading and erasing information stored on the tape; a pair of vacuum chambers arranged to form buffering loops of tape on opposite sides of the processing means; sensor means associated with the vacuum chambers for providing indications of the positions of the tape loop within the vacuum chambers; a pair of motors respectively coupled to drive the pair of reels; and servo means coupled to the motors and responsive at least to the sensor means to drive the reels bidirectionally and within a nominal speed range so as to maintain nominal lengths of the tape loops during normal operation of the tape transport and to drive the reels at a speed substantially greater than the nominal speed range during rewind of the tape transport; each of the pair of motors including a plurality of separate field generating means, the energization of at least one but not all of which is changed as necessary to enable the motor to operate with a first torque constant for normal operation and with a second torque constant different from the first torque constant for rewind.

Claim 31

A magnetic tape transport comprising: a pair of rotatable reels adapted to have the opposite ends of a length of magnetic tape wound thereon; means disposed along a tape path extending between the rotatable reels for processing the magnetic tape including capstan means for driving the tape and magnetic head means for recording, reading and erasing information stored on the tape; a pair of vacuum chambers arranged to form buffering loops of tape on opposite sides of the processing means; sensor means associated with the vacuum chambers for providing indications of the positions of the tape loop within the vacuum chambers; a pair of motors respectively coupled to drive the pair of reels; and servo means coupled to the motors and responsive at least to the sensor means to drive the reels bidirectionally and within a nominal speed range so as to maintain nominal lengths of the tape loops during normal operation of the tape transport and to drive the reels at a speed substantially greater than the nominal speed range during rewind of the tape transport; each of the pair of motors including a plurality of separate field generating means, the energization of at least one but not all of which is changed as necessary to enable the motor to operate with a first torque constant for normal operation and with a second torque constant different from the first torque constant for rewind.

Claim 32

The invention as set forth in claim 25, wherein each motor includes a permanent magnet for providing a first field and at least one winding for providing a second field when energized.

Claim 33

The invention as set forth in claim 26, wherein the at least one winding is energized in one sense to provide the first torque constant and in an opposite sense to provide the second torque constant.

Claim 36

The method of operating a tape transport as set forth in claim 28 above, wherein the step of controlling includes the steps of maintaining the torque constant constant at selected lower operating speeds and varying the energization of the second field generator to maintain the torque constant generally inversely proportional to motor speed as the motor accelerates over a selected range of motor operating speeds greater than said selected lower operating speeds.

Claim 37

The method of operating a tape transport as set forth in claim 20 above, wherein the selected lower operating speeds are speeds encountered during program operation and the motor accelerates over the selected range of motor operating speeds greater than said selected lower operating speeds during rewind.

Claim 38

The method of operating a tape transport as set forth in claim 29 above, the step of varying includes the step of varying the second field generator energization approximately linearly between energizations of opposite polarity and equal magnitude as the motor accelerates over the range of operating speeds greater than said selected lower operating speeds.