device for controlling the drive of a elektromotorischen bandwickelrolle magnetbandes, depending on the position of a bandschlaufe, between a bandtransportrolle and bandwickelrolle through a measuring line is held

摘要

1,262,558. Automatic position control. INTERNATIONAL BUSINESS MACHINES CORP. Sept.26, 1969 [Oct.8, 1968], No.47508/69. Heading G3R. In a system in which a capstan drive transports tape from one reel through a column loop store to another reel, signals from a number of loop position detectors spaced along the column control the reel motors through logic circuitry to reduce variations in the length of the loop. In Fig. 1, magnetic tape 12 forms a loop in a vacuum column 10 which receives or supplies tape according to whether the capstan (not shown) is moving the tape in the forward or backward direction shown. The output polarities of photo-electric or pressureresponsive switch type detectors 1-6, which depend on whether the loop of tape is positioned above or below them, automatically control, through logic circuits, a reversible motor driving a tape reel 11 to correct deviations of the loop from a desired position between detectors 3 and 4. The arrangement of AND, OR and inverter circuits is such that if, for example, in the case of a forwardly driven tape, the loop enters the zone between detectors 5 and 6 from above, the reel motor is energized to remove tape from the column, but, if entry into this zone is from below, the reel motor is not energized so that it continues to move the loop towards its desired position by coasting. When the loop is between detectors 4 and 5, a further control system operates in a similar manner except that the reel motor is only energized if the loop has arrived at its position between detectors 4 and 5 from one between detectors 2 and 3 on the other side of its desired position. When the loop is between detectors 3 and 4, the reel motor is dynamically braked. The reel motor is not energized if the loop is above its desired position in the case of a forwardly driven tape. In the case of a backwardly driven tape, control systems associated with detectors 1-3 control operation of the reel motor in the reverse direction in a manner similar to that in which it is controlled in a forward direction by detectors 4-6. If the capstan is stopped, detectors 1-6 co-operate to restore the loop to its desired position. Safeguards are provided to prevent simultaneous removal of the tape from the column by the capstan and the reel motor and to prevent energization of the reel during braking. In a modification, a large number of vacuumoperated switches at different levels apply pulses from a voltage divider to pulse detectors controlling the logic circuits to give more accurate positioning.