Patent GB-1036236-A (GB)
Title: Improvements in or relating to tape feeding apparatus
IPC: G11B15/48
Filed: 1964-09-16
Abstract: 1,036,236. Automatic speed and tension control. AMPEX CORPORATION. Sept. 16,1964 [Nov. 14,1963], No. 37785/64. Heading G3R. [Also in Division H2] A magnetic tape is driven by a single capstan coupled to reversible motor 12, under the control of data processing equipment which provides signals to energize the motor. When the apparatus is commanded by the data processing equipment to change from a non-operative condition to a normal speed forward drive, a flip-flop 60 provides a signal of predetermined amplitude and negative polarity to cause amplifier 65 to charge capacitor 73 at a constant rate, thus accelerating the capstan at a proportional rate. A positive-going voltage at the output of amplifier 65 is applied to the power amplifier 72. When the tape is stationary and a signal is received flip-flop 62 is energized to provide a negative pulse to amplifier 75 for energizing relay 68. A positive D.C. signal is applied through contacts 68a, 70a, to summing device 64, capacitor 80 being connected in parallel with capacitor 73. In addition, resistor 81 is shunted across resistor 71, and the output of amplifier 65 is connected to amplifier 75 through resistor 83. The signal applied to amplifier 75 is in the form of a short duration pulse derived by the differentiating action of capacitor 76. However, capacitors 73, 80 are charged sufficiently to provide a signal to amplifier 75 which maintained the energization of relay 68. The acceleration time constant is greatly increased by connecting the capacitors 73, 80 in parallel when low-to-high speed operation is demanded. If the rewind command is given while the tape is moving at normal speed, the tape is decelerated and then starts acceleration in the reverse direction at the slower rate. The higher final rewind speed is achieved by virtue of the connection of resistors 71, 81, in parallel, the lower resistance of the parallel circuit providing a higher input current to the power amplifier 72. If,when the system is operating in the rewind mode, it is commanded to stop, relay 70 is actuated to open contacts 70a to remove the input signal from amplifier 65. Capacitors 73, 80, discharge to cause the capstan motor to decelerate at a slow rate until relay 68 is de-energized to disconnect capacitor 80 and provide a quicker rate of deceleration. When the rewinding of the tape has been completed in the reverse direction at high speed, it may be stopped and advanced at normal speed to a desired position. A photosensor sends a signal to flip-flop 60 which reduces the output of summing device 64 to zero. The high speed command signal is removed, and the tape is then accelerated in the forward direction at a high rate. The tape is then stopped when a pulse from the photo-sensor turns off the flip-flop 60. The system may operate automatically to carry out a search for a particular block of information at high speeds, and upon location of the information to automatically return to a lower reading speed in the forward direction. When a high-speed signal is applied to flip-flop 106, and a reverse signal to flip-flop 86, the tape is accelerated at a slower rate to the high speed at which the search is to be effected. A position mark detector on the tape delivers a pulse to gates 103,104, and re-sets the flip-flop 106. The resulting output from flip-flop 91 is passed through gates 87, 89, to reverse the signal delivered to amplifier 93. The capstan is decelerated and then accelerated at high rate to the lower speed for reading in the forward direction. When a head detects a position mark on the tape, a pulse through gate 103 causes the capstan to decelerate and stop at the position mark. A combination of current limiter and amplifier 93 forms a ramp function generator comprising a bridge arrangement of four diodes each connected in a forward-conducting direction with respect to bias voltages. The bridge circuit receives a signal from summing device 92 and applies a signal to power amplifier 96. A further diode-bridge is connected in the forward-conducting direction with respect to the bias voltages and provides a constant current output to an inverter amplifier when the signal from junction 92 exceeds a given level. The output of the inverter amplifier is connected through resistor 95 to power amplifier 96, Fig.4 (not shown). The tape may be associated with supply and take-up reels, one capstan being in continual engagement with the tape and positioned between the reels. Vacuum boxes provide loop storage on either side of the capstan between the reels, Fig. 1 (not shown).