US4219855A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Thin film magnetic head
Assignee: International Business Machines Corp
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Filing: 1978-12-21
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Granted: 1980-08-26
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Expires: 1998-12-21
Abstract
Abstract A thin film magnetic transducer comprises a non-magnetic substrate and a pair of magnetic pole pieces having different widths. The width of the first pole piece deposited on the substrate is greater than that of the second pole piece to prevent a problem associated with misregistration between the pole pieces, which may occur during manufacture. Such misregistration generally results in a "wraparound", so that the edge of the second pole piece would have an extended portion forming an angle to the normal magnetic transitions created by the pole pieces. The width of the second pole piece is slightly less than the effective width of the data track recorded on a magnetic medium, and the data track width is relatively independent of the dimension of the first pole piece.
Inventors
- 👤 Robert E. Jones, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 19:57
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/127; G11B5/31; G11B5/3163; G11B5/3109; G11B5/3116; G11B5/313
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
118 words
A thin film magnetic head assembly comprising: a nonmagnetic substrate having an air bearing surface; a first pole piece layer having a predetermined width at one end deposited on said substrate; a nonmagnetic material deposited on said first pole piece layer to form a transducing gap; a second pole piece layer deposited on said nonmagnetic material having a width at one end less than that of said first pole piece, said width dimension being determinative of the width of the recorded data track, said one ends of said pole piece layers being disposed in a common plane with said air bearing surface, said pole piece layers being coextensive and centered relative to a centerline which bisects said layers.
Claim 2
Dependent Claim
118 words
A thin film magnetic head assembly comprising: a nonmagnetic substrate having an air bearing surface; a first pole piece layer having a predetermined width at one end deposited on said substrate; a nonmagnetic material deposited on said first pole piece layer to form a transducing gap; a second pole piece layer deposited on said nonmagnetic material having a width at one end less than that of said first pole piece, said width dimension being determinative of the width of the recorded data track, said one ends of said pole piece layers being disposed in a common plane with said air bearing surface, said pole piece layers being coextensive and centered relative to a centerline which bisects said layers.
Claim 3
Dependent Claim
23 words
A thin film magnetic head assembly as in claim 1, including electrically conductive means disposed adjacent to and between said pole piece layers.
Claim 4
Dependent Claim
33 words
A thin film magnetic head assembly as in claim 1, wherein the width of said first pole piece layer is greater than that of said second pole piece layer by less than 15%.
Claim 5
Dependent Claim
34 words
A thin film magnetic head assembly as in claim 1, wherein the width of said first pole piece is about 40 microns, and the width of said second pole piece is about 35 microns.
Claim 6
Dependent Claim
18 words
A thin film magnetic head assembly as in claim 1, wherein said pole piece layers are substantially parallel.
Claim 7
Dependent Claim
22 words
A thin film magnetic head assembly as in claim 1, wherein the thicknesses of said pole piece layers are substantially the same.
Claim 8
Dependent Claim
22 words
A thin film magnetic head assembly as in claim 6, wherein said thicknesses are in the order of 2 to 3 microns.
Claim 9
Dependent Claim
21 words
A thin film magnetic head assembly as in claim 1, wherein the thickness of said gap material is about 1 micron.
Claim 10
Dependent Claim
19 words
A thin film magnetic head assembly as in claim 1, wherein said pole piece layers are formed from Permalloy.
Claim 11
Dependent Claim
58 words
A thin film magnetic head assembly, as in claim 1, wherein said pole piece layers P1 and P2 obey the relationship: ##EQU2## where 3σ is the three sigma variation, MR is the amount of misregistration as measured between the centerline bisecting said pole piece layers, and P1W and P2W are the widths of the respective pole piece layers.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-08-26 | 1984-02-25 | 1984-08-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-08-26 | 1988-02-25 | 1988-08-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-08-26 | 1992-02-25 | 1992-08-26 | $7700.00 | Window Closed / Lapsed |