Browse Prior Art Database

Magnetic Shield for Disk File

IP.com Disclosure Number: IPCOM000086553D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Elliott, JF: AUTHOR [+3]

Abstract

Fig. 1 shows an actuator mechanism for a disk file of the type disclosed in United Kingdom Patent Specification 1,342,495. The actuator consists of an arm 1 mounted for rotational motion about a pivot 2. A record/playback head 3 is supported at one end of the arm 1 and a voice coil 4 cooperating with a fixed E-shaped permanent magnetic stator 5 is supported on a former 6 at the other end of the arm. By energizing the voice coil 4 with drive currents of appropriate magnitude and polarity, the head 3 can be moved from one track to another over a rotating disk surface 7 in order to perform transducing operations thereon.

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Magnetic Shield for Disk File

Fig. 1 shows an actuator mechanism for a disk file of the type disclosed in United Kingdom Patent Specification 1,342,495. The actuator consists of an arm 1 mounted for rotational motion about a pivot 2. A record/playback head 3 is supported at one end of the arm 1 and a voice coil 4 cooperating with a fixed E- shaped permanent magnetic stator 5 is supported on a former 6 at the other end of the arm. By energizing the voice coil 4 with drive currents of appropriate magnitude and polarity, the head 3 can be moved from one track to another over a rotating disk surface 7 in order to perform transducing operations thereon.

With high bit density recordings, a phenomenon known as "bit shift" caused by stray flux from the stator 5 can be a problem. The direction of the stator magnetic flux in the vicinity of the record/ playback head 3 is represented by arrow 8 and is seen to have a large component in the sensitive direction 9 across the gap of the head 3. Screening of the head by the addition of a mu-metal shield to the arm 1 is undesirable with this particular actuator, since it adds to the inertia of the mechanism.

The solution adopted is shown in Fig. 2. Here a fixed thin mu-metal shield 10 is supported extending over the disk surface 7 in the vicinity of the head 3. The shape of the shield 10 is determined experimentally to deflect the flux in the vicinity of the head 3 so that it has only a small component 8 in the sensitive direction...