Browse Prior Art Database

Web Tension Sensing Devices

IP.com Disclosure Number: IPCOM000050187D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 36K

Publishing Venue

IBM

Related People

Buchholz, MH: AUTHOR [+2]

Abstract

Sensors can be used to control the tension of a magnetic tape in a reelto reel tape drive. An air-pressure sensing transducer is mounted in a magnetic head adjacent to the transducers. In other embodiments, a moving capacitor plate, a piezoelectric device, or an optical device is placed in the path of the tape to control the tape tension.

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Web Tension Sensing Devices

Sensors can be used to control the tension of a magnetic tape in a reelto reel tape drive. An air-pressure sensing transducer is mounted in a magnetic head adjacent to the transducers. In other embodiments, a moving capacitor plate, a piezoelectric device, or an optical device is placed in the path of the tape to control the tape tension.

As shown in Fig. 1, a pressure-sensitive transducer can be mounted in a magnetic head adjacent to the read and write transducers. The flying height of the tape is critical to the output from the magnetic head. The flying height is controlled by the air pressure generated by the moving tape at the transducer magnetic gap. Monitoring this air pressure at the transducers by the pressure sensor provides a critical control over the tape tension by controlling the reel drive motors. As shown in Fig. 1, a transducer 1 sensitive to air pressure is mounted at the rear of a head 2 containing a read gap 3 and a write gap 4. A tap hole 5 is formed through the head from the face to the transducer 1 to allow the transducer to sense the air pressure at the face of the head 2.

The transducer 1 can thereby sense the air pressure formed between the moving magnetic tape 6 and the head 2. The output of transducer 1 is directed to the servo system for controlling the reel drive motors.

Tension analog feedback for the servo control can use a capacitive, piezoelectric or optical device to generate analog voltage amplitudes proportional to the tape tension. Fig. 2 shows the embodiment which utilizes capacitance. In Fig. 2, the position of the moving capacitor plate 10 is proportional to the tension in the tape 11. The moving capacitor plate 10 is positioned between a lower capacitor plate 12 and an upper capacitor plate 13. An alternating current reference voltage is placed between the upper and lower c...