Patent GB-996106-A (GB)
Title: Tape rewind control
IPC: H02P5/48
Filed: 1963-09-30
Abstract: 996,106. Automatic tension control. SPERRY RAND CORPORATION. Sept. 30,1963 [Oct. 10,1962], No. 38402/63. Heading G3R. [Also in Division H2] Reels 10, 12, are driven by motors 32, 34, a magnetic tape 14 passing into vacuum loop boxes 18, 28, to form loops 19, 29. Capstan 24 is driven by motor 48 associated with clutch 52 and brake 54, forward and reverse signals for the capstan being applied to lines 66, 68. The clutch and brake are . controlled in accordance with the sense of a signal at terminal 86, a trigger circuit 100 responding to signals from lines 66, 68, to release brakes 96, 98, and establish the desired loop-lengths in preparation for operation of capstan 24. The box 18 has a plurality of apertures 112-121 connected to individual vacuum-operated switches, the box 28 being similarly constructed, and, with the loops oriented as shown, the system is prepared for transport of the tape from right to left, the opposite balancepoints of the tape being established for reverse movement. The voltage across resistor 252 is a function of the length of loop 19, a servo amplifier 320 responding to deviations between the actual and desired lengths of the loop to control motor 32 in a corrective sense. Re-winding operation. The system is modified so that the tape may be re-wound from reel 12 to reel 10 in a rapid manner. A signal on line 68 prepares the tape for backward movement and puts the loops into the positions shown. A signal at terminal 86 maintains the brakes 96, 98 released, clutch 52 being engaged and brake 54 released to allow movement of the capstan. However, air under pressure floats the tape over the capstan so that motion of the capstan does not affect the tape. Energization of solenoid 25f disconnects resistors 262-271 associated with box 28 and closes contacts 325a, 325<SP>c</SP>, in the control circuit associated with box 18. Solenoid 25f also closes contacts 289a, 289b, whereby a potential is developed across resistor 292 which corresponds with that across resistor 252 when apertures 114-116 are exposed to vacuum. The reel 10 is driven at a speed proportional to the amount of loop 19 below aperture 114, the speed being a maximum when the loop is below aperture 116. The reel 10 is reversed when the loop is above aperture 114. The balance point control amplifier 200 is also modified by energisation of solenoid 25f so that the balance point for servo amplifier 420 corresponds with the position of loop 19 opposite aperture 120. Initially, the higher vacuum in box 18 causes some tape to enter from box 28, the motor 34 operating at maximum speed to unreel the tape. The motor 32 maintains loop 19 opposite aperture 114 until loop 29 extends beyond one of the ports 190, whereupon more tape moves from box 28 toward box 18. The speed of the reel 10 increases as the loop 19 drops until the loop reaches aperture 117 and the speed of the reel 112 is reduced. If the loop 19 falls below aperture 120, the motor 34 is reversed to shorten loop 29. The application of full vacuum to loop 29 reduces the rate of transfer of tape until the loop 19 rises above the aperture 120. When the reel 10 contains the greater portion of tape, it removes tape from box 18 faster than it is unreeled, the loop 19 remaining in the upper part of box 18 substantially opposite aperture 114. During this period, the tape is unreeled at a maximum rate. Removal of the signal from solenoid 25f reestablishes the vacuum on capstan 24 and restores the system to normal operation. Specification 920,788 is referred to.