Tape transport with overspeed limit servo control

Claim 2

In a magnetic tape transport whereiN tape is driven past an electromagnetic head and onto a motor-driven reel and a vacuum column buffers tape between the head and the reel, a method for limiting tape overspeeding at the reel relative to the tape speed past the head by limiting the torque applied to the reel by the motor, the method comprising the steps of: a. metering the rotational speed of the reel and providing a first signal indicative thereof; b. dividing the vacuum column into regions of preassigned lengths; c. providing a second signal which changes in value each time the tape loop passes between a pair of adjacent regions; and d. disabling the motor form applying torque to the reel with the tape in any particular region when the first and second signals provided for that particular region reach a predetermined relationship.

Claim 3

The method of claim 1, wherein the disabling step includes adding the second signal to the first signal, the motor being cut off when the first and second signals cancel.

Claim 4

The method of claim 1, wherein the disabling step includes providing a third signal indicative of the sum of the first and second signals and cutting off the motor when the third signal is zero.

Claim 5

The method of claim 3, wherein the disabling step further includes clamping the third signal between a preselected maximum positive and negative value, the motor thereby producing a maximum positive and negative output reel-driving torque.

Claim 6

In a magnetic tape transport wherein tape is driven past an operational zone, through a vacuum column, and onto a motor-driven reel, apparatus for limiting the torque applied to the reel by the motor comprising: a. means metering the angular velocity of the reel for providing a control signal indicative thereof; b. means dividing the column into regions of preassigned lengths for detecting passing of the loop between adjacent regions; c. means responsive to the detecting means for providing a reference signal indicative of the particular region in which the tape loop is positioned; d. means adding the control signal and reference signal; and e. means responsive to the output of the adding means for cutting off the applied torque to the reel by the motor whenever the control signal and reference signal reach a predetermined relationship.

Claim 7

In a magnetic tape transport wherein tape is driven past an operational zone, through a vacuum column, and onto a motor-driven reel, apparatus for limiting the torque applied to the reel by the motor comprising: a. means metering the angular velocity of the reel for providing a control signal indicative thereof; b. means dividing the column into regions of preassigned lengths for detecting passing of the loop between adjacent regions; c. means responsive to the detecting means for providing a reference signal indicative of the particular region in which the tape loop is positioned; d. means adding the control signal and reference signal; and e. means responsive to the output of the adding means for cutting off the applied torque to the reel by the motor whenever the control signal and reference signal reach a predetermined relationship.

Claim 8

In a magnetic tape transport wherein tape is driven past an electromagnetic head and onto a motor-driven reel and a vacuum column buffers tape between the head and the reel, apparatus for limiting tape overspeed at the reel relative to the tape speed past the head by limiting the torque applied to the reel by the motor, the apparatus comprising: a. first means metering the rotational speed of the reel for providing a first signal indicative thereof; b. second means dividing the vacuum column into regions of preassigned lengths for sensing when the tape passes between regions; c. third means for providing a distinct second signal of preassigned value for each regional position of the tape loop; and d. fourth means responsive to the first and second signals for disabling the motor from applying torque to the reel whenever the first and second signals provided in that particular region reach a predetermined relationship.

Claim 9

In a magnetic tape transport wherein tape is driven past an electromagnetic head and onto a motor-driven reel and a vacuum column buffers tape between the head and the reel, apparatus for limiting tape overspeed at the reel relative to the tape speed past the head by limiting the torque applied to the reel by the motor, the apparatus comprising: a. first means metering the rotational speed of the reel for providing a first signal indicative thereof; b. second means dividing the vacuum column into regions of preassigned lengths for sensing when the tape passes between regions; c. third means for providing a distinct second signal of preassigned value for each regional position of the tape loop; and d. fourth means responsive to the first and second signals for disabling the motor from applying torque to the reel whenever the first and second signals provided in that particular region reach a predetermined relationship.

Claim 10

The apparatus of claim 6 wherein the first means includes a reel-driven tachometer.

Claim 11

The apparatus of claim 6, wherein the second means includes a plurality of loop position sensors spacially disposed throughout the vacuum column, the regions being defined therebetween.

Claim 12

The apparatus of claim 6, wherein the fourth means includes means for adding the first and second signals and for cutting off the motor when the first and second signals cancel.

Claim 13

The apparatus of claim 6, wherein the fourth means includes means for providing a third signal indicative of the sum of the first and second signals, the motor being cut off when the third signal is zero.

Claim 14

The apparatus of claim 10, wherein the third means further includes meanS for clamping the third signal between preselected maximum positive and negative values, the motor thereby producing a maximum positive and negative output reel-driving torque.

Claim 15

In a magnetic tape transport wherein tape is driven past an operational zone and onto a motor-driven reel and a vacuum column buffers tape between the head and the reel, apparatus for limiting tape overspeeding at the reel relative to the tape speed past the zone by limiting the torque applied to the reel by the motor, the apparatus comprising: a. a plurality of loop position sensors spacially disposed throughout the column and defining a plurality of regions therebetween; b. means coupled to the loop position sensors for establishing a first signal which changes between two preassigned values each time the tape passes a distinct one of the sensors; c. a reel-driven tachometer for generating a second signal indicative of the rotational speed of the reel; d. means adding the first and second signals for generating a third signal indicative of their sum; e. amplifier means responsive to the third signal for generating a reel drive motor control signal; and f. clamp means coupled to the amplifier means for limiting the maximum positive and negative values of the control signal thereby limiting the maximum positive and negative reel-driving torque.

Claim 16

In a magnetic tape transport wherein tape is driven past an operational zone and onto a motor-driven reel and a vacuum column buffers tape between the head and the reel, apparatus for limiting tape overspeeding at the reel relative to the tape speed past the zone by limiting the torque applied to the reel by the motor, the apparatus comprising: a. a plurality of loop position sensors spacially disposed throughout the column and defining a plurality of regions therebetween; b. means coupled to the loop position sensors for establishing a first signal which changes between two preassigned values each time the tape passes a distinct one of the sensors; c. a reel-driven tachometer for generating a second signal indicative of the rotational speed of the reel; d. means adding the first and second signals for generating a third signal indicative of their sum; e. amplifier means responsive to the third signal for generating a reel drive motor control signal; and f. clamp means coupled to the amplifier means for limiting the maximum positive and negative values of the control signal thereby limiting the maximum positive and negative reel-driving torque.

Claim 17

The apparatus of claim 12, wherein the amplifier means has an input terminal coupled to the adding means and an output terminal coupled to the motor through the clamp means.

Claim 18

The apparatus of claim 13, further comprising a reel servo control circuit coupled between the clamp means and the motor and responsive to the control signal for controlling the torque generated by the motor.

Claim 19

The apparatus of claim 13, wherein the amplifier means includes an operational amplifier having a feedback path between its output and input, the clamp means being included in the feedback path.

Claim 20

The apparatus of claim 13, wherein the clamp means comprises: a. a diode clamp coupled to the output of the amplifier means; and b. an operational amplifier having an input coupled to the diode clamp and an output coupled to the input of the amplifier means.