Source: http://www.google.com/patents/US5880914?dq=7,446,777
Timestamp: 2016-02-06 14:18:41
Document Index: 1844257

Matched Legal Cases: ['art 11', 'arts 11', 'art 1', 'arts 1', 'arts 1', 'art 12', 'arts 1', 'arts 1']

Patent US5880914 - Recording and/or reading device with magnetic heads and method for the ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsDisclosed is a recording and/or reading device with magnetic heads including at least two magnetic heads. A magnetic circuit for the closing of the magnetic flux has a pad common to both heads. A first pole of a first type magnetically couples the common pad to the gap of the first head through a non-magnetic...http://www.google.com/patents/US5880914?utm_source=gb-gplus-sharePatent US5880914 - Recording and/or reading device with magnetic heads and method for the manufacture thereofAdvanced Patent SearchPublication numberUS5880914 APublication typeGrantApplication numberUS 08/926,687Publication dateMar 9, 1999Filing dateSep 10, 1997Priority dateJul 26, 1994Fee statusLapsedAlso published asDE69514585D1, DE69514585T2, EP0694910A1, EP0694910B1Publication number08926687, 926687, US 5880914 A, US 5880914A, US-A-5880914, US5880914 A, US5880914AInventorsJean-Claude LehureauOriginal AssigneeThomson-CsfExport CitationBiBTeX, EndNote, RefManPatent Citations (55), Referenced by (4), Classifications (14), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetRecording and/or reading device with magnetic heads and method for the manufacture thereof
US 5880914 AAbstract
Disclosed is a recording and/or reading device with magnetic heads including at least two magnetic heads. A magnetic circuit for the closing of the magnetic flux has a pad common to both heads. A first pole of a first type magnetically couples the common pad to the gap of the first head through a non-magnetic link. A second pole of a second type, separated from the first pole by a non-magnetic interval, magnetically couples the common pad to the gap of the second head. Such a device finds applications to a system for recording and/or reading, notably on magnetic tapes.
1. A recording/reading device, comprising:first and second magnetic heads, including respectively first and second gaps; a magnetic substrate including a common pad to the first and second magnetic heads; a first pole and a second pole surmounting said common pad; a magnetic circuit for closing a magnetic flux having said pad common to the first and second magnetic heads, wherein said first pole magnetically couples the common pad to the first gap of the first magnetic head through a non-magnetic link, and said second pole magnetically couples the common pad to the second gap of the second magnetic head; and a non-magnetic interval having a predetermined thickness and surface separating the first pole from the second pole. 2. A device according to claim 1, wherein the predetermined thickness and surface of the non-magnetic interval are such that the first pole controls a recording/reading operation of the first magnetic head and such that the second pole controls a recording/reading operation of the second magnetic head.
The present invention relates to a recording and/or reading device with magnetic heads arranged so as to prevent this variability of performance characteristics.
The invention will be understood more clearly and other characteristics and advantages of the invention shall appear from the following description of its embodiments, this description being made with reference to the appended drawings, of which:
FIGS. 1a, 1b show partial views, respectively from the front and in a section along the axis a--a of a known matrix device with magnetic head.
This device is formed by a grooved magnetic substrate 10 with substantially square-shaped projecting pads arranged in the form of a matrix network. The pads are referenced 11, 12, 13 . . . Two pads of one and the same column have the same reference. The subscript number of each pad reference corresponds to the rank of the column. The pads cannot be seen in FIG. 1a.
Row excitation conductors L and column excitation conductors C are positioned in the grooves 3 and are covered and/or embedded in a non-magnetic material. Each pad 11, 12, I3 is surmounted by a pole P1, P2, P3. The poles of one and the same column bear the same reference and the number in this reference corresponds to the rank of the column. All the poles (except of course the edge poles) have a part 11a with a greater surface area that corresponds substantially to the surface area of a pad 11 and two protruding features 11b that extend two of their corners diagonally. These protruding features 11b surmount the intersection between two grooves 3. A gap 41, 42 . . . is made between two facing protruding features 11b. The gaps 41, 42 are placed above the intersection of a row conductor L and a column conductor C. All the gaps located above the same column conductor C have the same subscript number.
A magnetic head M1 for example has a magnetic circuit for the closing of the flux formed by the two neighboring pads 11, 12 located diagonally in the matrix network, the portion of the substrate 10 that connects these two pads, the poles P1, P2 that surmount each of these pads 11, 12 and the gap 41 between these two poles P1, P2. Head MI also has the column conductor C and the row conductor L which intersect beneath the gap 41.
Similarly, the magnetic head M2 having a pad 12 in common with the magnetic head M1 comprises a magnetic circuit formed by the two pads 12 and 13, the substrate portion 10 that connects them, the two poles P2, P3 which surmount each of these pads and the gap 42 between the two poles P2, P3. Head M2 also includes the two conductors C, L that intersect beneath the gap 42. These two heads M1 and M2 also have a common pole P2. The method for making the poles and the gap consists of the deposition, at one in every two columns of pads, of a first magnetic layer designed to form the first poles P1, P3 of each head, covering the other pads with a non-magnetic layer that includes at least one flank of the first layer, covering the non-magnetic layer with a second magnetic layer designed to form the second poles P2 . . . of each head.
The non-magnetic layer is designed to form the gaps 41, 42. The last steps are the machining, polishing and cutting steps which are used to make the poles flush and to demarcate them as well as the gaps.
In this type of device, there remains a non-magnetic link 5 beneath the second formed poles P2 . . . and this non-magnetic link 5 connects two gaps 41, 42 that are located on either side of the second poles P2.
The gaps 41, 42 connected by this non-magnetic link 5 are symmetrical. The two gaps 41 and 42 associated with a non-magnetic link portion are oriented in opposite directions. The two successive magnetic heads M1, M2 that possess these gaps 41 and 42 are not identical. They are opposite. This leads to differences in level between the recordings made by these two heads when they are crossed by a flux of a same intensity.
FIG. 2 gives a partial cross-sectional view of a variant of a known type of recording and/or reading device with magnetic heads. In this variant, the magnetic substrate, instead of being a one-piece unit, is formed by the joining of two superimposed elementary substrates. The first substrate 10a is grooved with projecting parts 11 ', 12 ', 13 ' positioned in a matrix network. Row conductors L and column conductors C are arranged in the grooves 3. The second elementary substrate 10b is a composite substrate. Second elementary substrate 10b is formed by a magnetic block 261, 262, 263 . . . arranged in the same matrix network and separated by a non-magnetic material 25. The blocks 261, 262, 263 . . . are sized so that each covers a projecting part 1'1, 1'2, 1'3 . . . and the non-magnetic material 25 covers the space between the projecting parts 1'1, 1'2, 1'3. The joining of the two substrates 10a and 10b can be done by bonding. The projecting parts 1'1, 1'2, 1'3, each covered with a block 261, 262, 263 . . . , form pads.
The poles P1, P2, P3 . . . and the gaps 41, 42, 43 are formed in the same way as here above, with the poles surmounting the pads 261, 262 and the gaps surmounting the non-magnetic material 25.
In this variant, the gap of each head is tilted with respect to the surface of the composite substrate 10b and the tilts of the gaps 41, 42 of two successive heads having a common pad are supplementary.
This tilt further aggravates the differences in performance characteristics between two heads having linked gaps. The reference α represents the obtuse angle formed by the gap 41 with the upper surface of the first formed pole Pi and α' represents the acute angle formed by this gap 41 with the upper surface of the second formed pole P2.
FIGS. 3a and 3b show partial views respectively in a front and cross-sectional view (along the axis b--b) of an exemplary recording and/or reading device with magnetic heads according to the invention. These two figures are comparable to FIGS. 1a and 1b. They again show the same grooved substrate 10 with projecting pads 11, 12, 13 arranged in a Cartesian reference system. Row excitation conductors L and column excitation conductors C are positioned in the grooves 3 and are embedded and/or covered with a non-magnetic material such as resin. For greater clarity, the conductors cannot be seen except in FIG. 3b. Poles P'0, P'1, P'2, P'3, P'4 . . . are positioned on the pads 11, 12, . . . but now a pad 11, 12 is covered with a pair of poles, respectively P'0, P'1 for the pad 11, P'2 and P'3 for the pad 12 etc. . . . . In one pair of poles, for example P'2, P'3, a first pole P'2 of a first type magnetically couples the pole 12 with the gap 4'1 of a first magnetic head M'1 through a non-magnetic link 50. The second pole P'3 of a second type magnetically couples the pad 12 with the gap 4'2 of a second magnetic head M'2. The first type of pole P'3 is separated from the second type of pole P'2 by a non-magnetic interval 52.
In the example shown in FIGS. 3a, 3b, the non-magnetic interval that surmounts a pad has the same subscript number as itself. The non-magnetic intervals that surmount the pads of one and the same column are preferably aligned. The pads 11, 12 . . . are pads common to two magnetic heads. The poles P'0, P'1, P'2 have a part 12a with a greater surface area corresponding to about half the surface area of a pad 11, 12, 13 . . . and at least one protruding feature 12b that extends one of their corners towards an intersection of excitation conductors C, L. The protruding features 12b of two poles, for example P'2, P'3 surmounting one and the same pad 12 are preferably directed along a diagonal of the pad 12. The gaps 4'1, 4'2 . . . are made between two facing protruding features 12b. These gaps 4'1, 4'2 . . . are positioned above the intersection of a row conductor L and a column conductor C above a groove 3. The gaps 4'1 of one and the same column are preferably positioned so as to be aligned. The rows of gaps and non-magnetic intervals may preferably be substantially parallel.
The magnetic head M'1 has a magnetic circuit for closing the flux formed by the pad 11, the pad 12, the portion of the substrate 10 that links them, the pole P'1, the pole P'2 and the gap 4'1 between them. It also has the column conductor C and the row conductor L which intersect beneath the gap 4'1.
In the same way, the magnetic head M'2 which has the pad 12 in common with the head M'1 has a magnetic circuit formed by the common pad 12, the pad 13 and the substrate portion that links them, the poles P'3 and P'4 and the gap 4'2 between these two poles. Head M'2 also has the row conductors L and column conductors C which intersect beneath the gap 4'2.
The two poles P'2, P'3 of a pair contribute to defining two gaps 4'1, 4'2 belonging to successive heads M'1, M'2. The pole P'2 of the first type participates in the working of the head M'1 and the pole P'3 of the second type in the working of the head M'2. However, it may be the case, if the thickness and surface of the non-magnetic interval 52 are appropriate, that the two poles of the pair P'2 and P'3 both play a part in the selective operation either of the first magnetic head M'1 or of the second magnetic head M'2.
In the example described, the non-magnetic link 50 links a non-magnetic interval 52 in passing beneath one of the poles P'2 of a first type of a pair surmounting the same pad 12 as the interval 52, to the gap 4'1 to the definition of which a contribution is made by the first type pole P'2 of the pair. The non-magnetic interval 52, the gap 4'1 and the non-magnetic link 50 are formed by a same layer of magnetic material. Preferably, the non-magnetic interval 52, the gap 4'1 and the non-magnetic link have the same thickness.
At two consecutive pads 11, 12, 13, this link 50 is located on the same side of the non-magnetic interval 52, 53 with which it is linked.
FIG. 3b clearly shows that two consecutive heads M'1, M'2 are now identical at the poles and the gaps. The gaps 4'1, 4'2 of these two heads are no longer linked. When they are crossed by fluxes of a same intensity, they generate a same level of recording.
The poles P'0, P'1, P'2, P'3, P'4 are formed above the composite elementary substrate 10b as well as the gap 4'1, 4'2.
The magnetic blocks 261, 262 . . . of the magnetic substrate are each covered with two poles, respectively P'0 and P'1, P'2 and P'3 etc. and these two poles are separated by the non-magnetic interval, respectively 51, 52 . . . The magnetic blocks contribute to forming pads. FIG. 4a again shows also the non-magnetic links 50 between a non-magnetic interval 52 and a gap 4'1 formed in passing beneath a first type of pole P'2.
However now the gaps 4'1 and 4'2 are tilted instead of being perpendicular to the surface of the composite substrate 10b and therefore that of the pads. The gaps 4'1 and 4'2 Of two successive magnetic heads M'1 and M'2 preferably have the same tilt. The differences in performance between two successive magnetic heads M'1, M'2 having a common pad are eliminated. In this variant, the non-magnetic intervals 51, 52 are also tilted with respect to the surface of the composite substrate 10b and hence that of the pads. The tilts of two non-magnetic intervals 51, 52 are preferably the same.
A plate 27 of a non-magnetic material covers the substrate 10 and the poles P'0, P'1, P'2 . . . , the gaps 4'1, 4'2 and the non-magnetic intervals 51, 52, 53 are deposited on the plate 27.
The method starts with a magnetic substrate 10, made of ferrite for example, grooved with the pads 11, 12, 13 arranged in a matrix network and having row conductors L and column conductors C. These conductors are positioned in the grooves 3 and embedded in a non-magnetic material such as glass for example.
First, a first layer 21 of magnetic material is deposited above the substrate 10 or the non-magnetic plate. This layer 21 forms bands directed along the columns of pads and they cover a part of each pad 11, 12, 13. This layer will have a flank 24' on the pads 11, 12, 13.
This mask is designed to protect the zones that have to be covered with non-magnetic material. This mask has one edge that passes through the gaps 4'1, 4'2 and through the non-magnetic intervals 51, 52, 53. In this way, the first magnetic layer 21 has one flank 24 above the grooves between two pads.
This non-magnetic layer 22 is designed to form the gaps 4'1, 4'2, the non-magnetic intervals 51, 52 and the non-magnetic links 50.
The contour of the poles is then cut out. In the example described, each pole P'0, P'1, . . . occupies substantially half of the surface area of a pad 11, 12 . . . Other configurations are possible. The cutting out operation also demarcates the gaps and the non-magnetic intervals. It is preferable that the non-magnetic intervals 52 should be entirely contained in the surface area of the pads so as to prevent leakage fields.
As a variant, instead of using a single-piece substrate, it is possible to use a substrate formed by the joining of two elementary superimposed substrates such as the one shown in FIG. 4a. The first elementary substrate 10a is obtained conventionally by grooving a block of magnetic material such as ferrite to obtain the projecting parts 1'1, 1'2, 1'3.
The second elementary substrate 10b is obtained by making grooves in a piece of magnetic material to obtain the blocks 261, 262, by filling the grooves with a magnetic material 25. The two substrates 10a, 10b are assembled by bonding for example so that the projecting parts 1'1, 1'2 are covered with the blocks 261, 262. Machining is then used to eliminate the base of the second substrate 10b. The row conductors L and column conductors C are positioned in the grooves of the first substrate 10a. The poles, the gaps and the non-magnetic intervals are then deposited on the second substrate 10b.
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