Browse Prior Art Database

Tape Presence Sensor

IP.com Disclosure Number: IPCOM000088956D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Crawford, RP: AUTHOR [+2]

Abstract

A photo-optical tape-presence sensing device with a fail-safe feature immediately senses tension loss so as to prevent loss of data stored on the tape.

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Tape Presence Sensor

A photo-optical tape-presence sensing device with a fail-safe feature immediately senses tension loss so as to prevent loss of data stored on the tape.

A sensing device 1 (Fig. 1) is mounted adjacent an idler roll 2 downstream of where tape 3 makes a 90-degree direction change so that the tape stiffness will carry the tape away from the device if tension is lost.

Device 1 preferably comprises a housing 4 containing two spaced phototransistors A, B (Fig. 2) mounted opposite a single light source 5, such as a light-emitting diode. These phototransistors A, B are mounted opposite source 5 to verify that tape 3 is confined within a specific area z.

Signals from the phototransistors A, B are "ANDed" with only the following specific one of the four Boolean conditions indicating acceptable positioning of the tape: A . B

The other three Boolean conditions indicate the following: A . B indicates light source or phototransistor B has failed or become contaminated. A . B and A
. B indicate that the tape is out of position.

Note that if phototransistor A fails during running, the loss of tension will be sensed as A and B when the loose tape crosses the B beam. Additional checks may be made when tape 3 is not threaded. For example, with no tape threaded, only A and B would be acceptable. If desired, the output from phototransistor B could be used to servo the light source as current to compensate for aging and contamination.

If the fail-safe feature is no...