Browse Prior Art Database

Rewind of Magnetic Tape

IP.com Disclosure Number: IPCOM000075077D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Holman, BJ: AUTHOR [+2]

Abstract

High-speed rewind of magnetic tape is accomplished by backward rotation of file reel 1, machine reel 2 and proportionally controlled backward rotation of capstan 3. The motors which rotate the reels are controlled by position sensors L1, L2, R1 and R2. These sensors sense the position of tape loops 4 and 5 in machine vacuum column 6 and file vacuum column 7. During rewind the tape moves from column 6 to column 7. A long loop of tape is maintained in column 7 and a short loop is maintained in column 6.

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Rewind of Magnetic Tape

High-speed rewind of magnetic tape is accomplished by backward rotation of file reel 1, machine reel 2 and proportionally controlled backward rotation of capstan 3. The motors which rotate the reels are controlled by position sensors L1, L2, R1 and R2. These sensors sense the position of tape loops 4 and 5 in machine vacuum column 6 and file vacuum column 7. During rewind the tape moves from column 6 to column 7. A long loop of tape is maintained in column 7 and a short loop is maintained in column 6.

Digital tachometers 8, 9 and 10 measure the speed of the tape at the capstan and at the reel side of each of the vacuum columns. The output frequency of the tachometers increases as the tape speed increases.

The tachometer outputs are compared by frequency comparators 11 and 12. The comparators have two possible outputs, "reel fast" or "reel slow", and a third output which is proportional to the difference in the output frequencies of the two tachometers being compared.

This difference output is used to proportionally control the duty cycle of capstan motor 13, in accordance with the position of the tape loops in the columns. The control order for the capstan motor is shown in View B.

Considering the file vacuum column 7, if the loop is between sensors R1 and R2, a capstan coast is instituted when "file-reel- slow" is signalled by the frequency comparator, and the time duration of this coast interval is proportional to the difference output....