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Publication numberUS3769469 A
Publication typeGrant
Publication dateOct 30, 1973
Filing dateJun 28, 1972
Priority dateJun 28, 1972
Also published asCA998470A1, DE2329693A1
Publication numberUS 3769469 A, US 3769469A, US-A-3769469, US3769469 A, US3769469A
InventorsM Garnier, R Nelson
Original AssigneeIbm
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Trim erase mead assembly for providing a uniform erase field
US 3769469 A
Abstract
A magnetic recording transducer assembly including an erase core assembly for erasing the edges of a newly written track immediately after it is written by a write transducer is disclosed. The erase assembly comprises an erase core member and a coil. The core member comprises a flexible strip of magnetic material, each end of the strip having first and second parallel leg portions spaced apart a distance corresponding to the desired width of the track after erasure. A housing positions the core member in operating relationship to the write transducer. Additional means fixes the core member relative to the housing to maintain the first and second leg portions of the core member in parallel relationship for a throat height distance which is less than the length of the legs and to maintain the width of erase gaps such that the erase flux field is substantially uniform over a range of current above the minimum required to saturate the core in the throat height region. The housing has a first surface adapted to be positioned in a recording relationship to the track. The core is bent to position the ends of the strip normal to the plane of the first surface in spaced apart relationship whereby the legs define erase gaps in the first housing surface for erasing the edges of the track.
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United States atent 1191 Garnier et a1.

[ Oct. 30, 1973 TRIM ERASE HEAD ASSEMBLY FOR PROVIDING A UNIFORM ERASE FIELD [75] Inventors: Michael F. Garnier; Roland D.

Nelson, both of San Jose, Calif.

[22] Filed: June 28, 1972 [21] Appl. No.: 266,947

51 110.01. Gllb 5/22 58 Field of Search 179/1002 1), 100.2 c; 340/1741 F; 346/74 MC [56] References Cited UNITED STATES PATENTS 3,155,949 11/1964 Tibbetts 179/1002 D 3,504,134 3/1970 Miyata 179/1001 C 3,684,841 8/1972 Boemme.. 179/1001 D 3,668,332 6/1972 Anderson.... 179/1002 C 3,562,443 2/1971 B08 6! a1. 179/1002 D OTHER PUBLICATIONS Dortort et al., Multi-Track Magnetic Head, RCA Tech. Notes, RCA TN No. 214, Jan. 1959.

[5 7] ABSTRACT A magnetic recording transducer assembly including an erase core assembly for erasing the edges of a newly written track immediately after it is written by a write transducer is disclosed. The erase assembly comprises an erase core member and a coil. The core member comprises a flexible strip of magnetic material, each end of the strip having first and second parallel leg portions spaced apart a distance corresponding to the desired width of the track after erasure. A housing positions the core member in operating relationship to the write transducer. Additional means fixes the core member relative to the housing to maintainthe first and second leg portions of the core member in parallel relationship for a throat height distance which is less than the length of the legs and to maintain the width of erase gaps such that the erase flux field is substantially uniform over a range of current above the minimum required to saturate the core in the throat height region. The housing has a first surface adapted to be positioned in a recording relationship to the track. The core is bent to position the ends of the strip normal to the plane of the first surface in spaced apart relationship whereby the legs define erase gaps in the first housing surface for erasing the edges of the track.

16 Claims, 6 Drawing Figures ERASE CURRENT SOURCE PATENIEU 081 30 I975 FIG. 2

FIG. 6;"

BOma I Erase ERASE CURRENT SOURCE FIG. 3

TRIM ERASE HEAD ASSEMBLY FOR PROVIDING A UNIFORM ERASE FIELD BACKGROUND OF THE lNVENTlON 1. Field of the Invention This invention relates to a magnetic transducer with an erase core assembly and, more particularly, an erase core assembly that will provide an erase flux field that is substantially uniform over a range of current above the minimum required to saturate the core in the throat height region.

2. Description of the Prior Art The use of magnetic heads to record and reproduce information has become quite important in recent years. The criticality of improving the magnetic characteristics of such heads has become more pronounced since magnetic recording technology is constantly attempting to improve the areal density of information recorded and reproduced on a magnetic medium. Accordingly, the industry is constantly attempting to improve the track density, more commonly known as increasing the number of tracks per inch across the record surface of the magnetic medium. The track density is dependent upon the width of a track of information and thus requires minimizing the effective width of the transducing gap of a magnetic transducer. One method of reduction is to utilize a read/write transducer having a large gap width and to provide erase means for erasing the edges of the written track immediately after it is written. In this manner, a narrow track of information will be effectively written and additionally, a wide track will be read by the transducer during the read mode upon deactivation of the erase means. This invention is directed toward a magnetic transducer having an improved erase capability that provides a constant erasure for relatively large variations in erase current amplitude.

Recording transducers directed toward the concept of erasing tracks of information have long been known to the art. It must be remembered that recording over a track of magnetic information reorients the domains of the magnetic record media and accomplishes an erasure of the information previously recorded on' .the track. Several examples of techniques and means for providing magnetic erasure are noted; simultaneously erasing a plurality of tracks is shown in U. S. Pat. No. 2,987,582 to Naiman; the concept of tunnel erasing edges of a track by providing tunnel erase means on a magnetic transducer is shown in U. S. Pat. No. 3,155,949 to Tibbetts.

The Naiman patent shows an erase head having a plurality of toothlike pole pieces for selectively erasing a plurality of channels on a magnetic record. The erase bar of this type extends the full width of the record medium and is adapted to be fixed relative thereto. However, this patent does not show erasing the edges of a previously written track and would be inapplicable on accessing systems because of the cumulative tolerance buildup in view of the pole-tip per track arrangement.

The Tibbetts patent describes a tunnel erase record ing head which includes a read/write element and an erase element that is fixed in alignment with the read/- write element for erasing both edges of the path. However, the readback signal of each track remaining after edge-erasure will continuously decrease as the current through the erase means is increased. Thus, at some point when the erase current is high enough the entire track of magnetic information will be erased.

In order to overcome the above-noted defects a novel magnetic recording transducer having an erase core assembly for erasing the edges of a newly written track immediately after it is written by a write transducer has been devised wherein the transducer provides an erase flux field that is uniform over a range of current magnitudes above the minimum required to saturate the core in the throat height region. The erase core comprises a flexible strip of magnetic material, each end of the strip having first and second parallel leg portions spaced apart a distance corresponding to the desired width of the track after erasure. The core is bent to position the ends of the strip substantially normal to the plane of a first surface of a housing in which the core member is positioned. The ends are maintained in a spaced-apart relationship whereby the first legs define a first erase gap for erasing one edge of the track and the second legs define a second erase gap for erasing the opposite edge of the track. In addition, means for fixing the core member relative to the housing to maintain the first and second leg portions in parallel relationship for a throat height distance which is less than the length of the legs is included. This core fixing means also maintains the width of the erase gaps. This transducer lends itself to low cost fabrication and can be used with electrical components having a wide variance in electric and magnetic characteristics since the same erase flux field is produced over a wide variation of erase current magnitudes.

Accordingly, it is an object of this invention to provide a simple rugged magnetic recording transducer for use in a magnetic recording system having a simple erase core assembly that provides a substantially constant erasure for relatively large variations in erase current amplitude.

It is another object to provide an erase core assembly for a magnetic recording transducer for erasing the edges of a newly written track immediately after it is written by a write transducer, the assembly comprising an erase core member, a coil, a housing for positioning the core member 'in operating relationship to the write transducer, the housing having a first surface adapted to be positioned ina recording relationship to the write transducer, the housing having a first surface adapted to be positioned in a recording relationship to the track, the core member comprising a flexible strip of magnetic material, the end of the strip having first and second parallel leg portions spaced apart a distance corresponding to the desired width of the track after erasure, the core being bent to position the ends of the strip substantially normal to the plane of the first surface in a spaced apart relationship whereby the first legs define a first erase gap in the first surface for erasing one edge of the track and the second legs define a second erase gap in the first surface for erasing the opposite edge of the track, and means for fixing the core member relative to the housing to maintain the first and second leg portions in parallel relationship by a throat height distance which is less than the length of the leg and to maintain the width of the erase gap such that the erase flux field is substantially uniform over a range of current above the minimum required to saturate the core in the throat height region.

In accordance with the above objects it is another object to provide a transducer assembly wherein the means for fixing the erase core member is integral and unitary with the housing and which includes a wedgeshaped portion with the vertex extending proximate to and slightly spaced from the first surface of the housing. the distance between the vertex and the first surface controlling the throat height distance.

In accordance with the above objects, it is still another object to provide an erase core assembly wherein the erase core member includes a nonmagnetic shim fixedly positioned within the erase gaps extending upwardly into the bent erase core member from the ends and further extending across at least the width of the legs.

It is yet another object to provide an erase core assembly as set forth above which comprises a nonmagnetic leg spacer, firmly positioned laterally between the first leg portions and the second leg portions for maintaining the respective legs aligned and spread apart.

Still a further object is to provide a transducer assembly for use on a flexible magnetic medium wherein the first surface of the housing includes an outwardly directed smooth continuous contour having an apex point nearest the plane of the magnetic medium, the erase gaps being aligned perpendicular to the track and on opposite sides of the apex with respect to the associated write gap of the write transducer and further comprising means for maintaining the flexible medium in complicance with the write gap and the erase gaps.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the magnetic transducer of this invention comprising the novel erase core assembly.

FIG. 2 is a side elevational view of a section of the transducer illustrated in FIG. 1 taken through lines 2-2 of FIG. 1.

FIG. 3 is a graph illustrating the variation in track signal level as a function of the erase current through the erase core assembly.

FIG. 4 is a blown-up plan view of the gap area of the magnetic transducer shown encircled in FIG. 1.

FIG. 5 is a plan view of the erase core member prior to its fabrication into the magnetic'transducer.

FIG. 6 is a side elevation'view of a section of the erase core taken through lines 6--6 of FIG. 4 illustrating the throat height region during a fabrication step.

DESCRIPTION OF THE INVENTION Referring now to the drawings, and more particularly FIGS. 1 and 2 thereof, there is shown in a magnetic recording system a magnetic transducer assembly, generally designated by the numeral 10, positioned by accessing means 18 with its read/write gap 19 and its erase gaps 26 and 27 in a contacting transducing relationship with a selected one of a plurality of tracks 17 on a moving magnetic medium 16. A pressure pad assembly 65 maintains the medium in compliance with the transducers. The medium is illustrated as being a flexible disk which is the preferred environment for this invention, although it is recognized that the transducer assembly is operable in magnetic tape or drum recording systems and with rigid magnetic mediums.

The transducer assembly 10 includes a read/write assembly 70 and an erase core assembly 30 assembled within a housing, generally designated 11. The C- shaped core 13 of assembly 70 having coil 14 wound therearound is fixedly positioned within a recess in a first housing portion 12 so that the ends of the C are flush with a locating surface 15 of the first housing portion 12.

The L-shaped core 21 of the assembly 70 is similarly fixedly positioned within a corner end cavity in a second housing portion 20. The erase core assembly 30 is positioned in the second housing portion in an abutting relationship with the L-shaped core 21 and around a supporting wedge-shaped portion 23 that also controls the throat height of the erase gaps. The wedge 23 is inserted within the erase core assembly 30 and con strained by an angled mating surface 61 of the second housing portion 20 and by a third cover housing portion 60. Fasteners 62 secure portions 60 and 20 together and bolts 29 secure portion 20 against the locating surface of portion 12. A first housing surface 25 comprising surface segments of the three housing portions 12, 20 and 60 and having an outwardly directed spherical contour encompasses the gap region of the transducer assembly. The smooth contoured convex shape reduces wearing between the transducer and the moving medium and by providing the read/write gap 19 and the erase gaps 26 and 27 on opposite sides of the apex 26 of the surface 25, constant compliance between the gap and the medium is facilitated. Surfaces of the housing away from the gap are relieved to reduce interference with the rotating disk assembly.

The erase core assembly 30 comprises an erase core member 35, best illustrated in FIG. 5 of the drawings. As shown therein the core member is a unitary flexible strip of magnetic material having at each of its respective ends 36 and 37, mating first leg portions 38 and 40, respectively, and second leg portions 39 and 41, respectively. The legs at each end are parallel to one another and spaced apart by windows 49 at a distance corresponding substantially to the desired width of the track after erasure. Intermediate the ends 36 and 37, the core member 35 includes a wider lower reluctance region 42 having a shoulder 43. As illustrated in FIG. 2, an erase coil 44 is positioned around the core in an abutting relationship with shoulder 43. The leads of the coil 44 are connected to an appropriate terminal associated with the housing portion 20 for connection to an erase current source 45. The flexible magnetic core is bent and thereafter annealed into a teardrop shape with the ends 36 and 37 positioned substantially normal to the plane of the first housing surface 25 in a spaced-apart relationship whereby the first legs 38 and define a first erase gap 46 in the first surface for erasing one edge of the track 17 and the second legs 39 and 41 define a second erase gap 47 in the first surface 25 for erasing the opposite edge of the track 17.

The wedge-shaped portion 23 is inserted into the cavity 22 within the second housing portion 20 with its vertex 24 extending proximate to and slightly spaced from the first surface 25 of the housing 11. The distance between the vertex 24 and the first surface 25 controls the throat height 48 of the erase core member 35. It has been found that when the wedge-shaped portion 23 subtends an angle of between 20 and at the vertex 24 it provides adequate structural support for the erase core assembly when mating against the throat height defining surface 63 of the housing 20 while allowing sufficient throat leakage flux between the upper legs comprising each erase gap. However, the preferred embodiment is achieved when the angle is 45.

The assembly of the erase core member 35 is illustrated in FIGS. 2 and 6. As shown, one end 37- of the core member 35 is positioned in the corner of the cavity against the back surface of the L-core 21 and bent outwardly into the cavity 22. After the erase coil 44 is positioned against shoulder 43 the other core end 36 is conformed against the surface of the wedge portion 23 the extremities of the core up to approximately onehalf the length of the legs as defined by window regions 49 extending externally of the housing surface 25. A non-magnetic shim 50, preferably made of brass and having spaced-apart legs 52 separated by a window opening 51 is inserted internally within the erase core member between the ends 36 and 37 with its legs 52 disposed against the respective legs 38 and 39. A nonmagnetic brass leg spacer 55 having a parallelapiped shape is firmly positioned laterally between both the first leg portion and the second leg portion thus maintaining the respective legs of the erase core member aligned, parallel and spread apart. Securing the third cover housing portion 60 to portion 20 with surface 61 mating with a similarly shaped surface of wedge 23 and throad height defining surface 63 abutting end 36 constrain the core member 35 in the housing with a desired throat height 48. It should be noted that the bifurcated legs extend internally above the apex and onto the wedge surface. Thereafter the extremities of the several erase core assembly pieces extending beyond surface 25 are severed. Then the first housing surface 25 is ground and lapped into a segment of a sphere defining an apex point 26 laterally midway between the erase core pole tip portions 38 and 39 and on a longitudinal axis between the read/write gap 19 and the erase gaps 46 and 47.

The gap region of the magnetic transducer is illustrated in FIG. 4. As shown, the C-shaped core 13 has a magnetic pole piece 56 laterally bounded by nonmagnetic stainless steel laminations 57. A nonmagnetic shim 58 defining the read/write gap 19 separates the pole piece 56 from magnetic pole piece 27 of L-shaped core 21, also bounded by nonmagnetic laminations 28. The nonmagnetic shim 58 is introduced between the pole pieces prior to securing the housing portions 12 and together. The legs 38 and 39 are positioned against the core 13 and maintained laterally separated by the nonmagnetic leg spacer 55. The legs 52 of shim 50 prevent legs 40 and 41 from closing in on legs 38 and 39 respectively so as to maintain the desired erase gap width 46 and 47. Thus, the ends of the strip of magnetic material are substantially normal to the plane of the first surface 25, the first and second leg portions of the erase core member are maintained parallel and spaced apart. Epoxy 54 is used to secure the erase elements in position. Alternatively, another shim (not shown) could be used to separate the core 13 from the erase member elements.

Since the magnetic pole piece 27 is laterally wider than magnetic pole piece 56, even if a slight misalignment occurs when securing the pole pieces together, the entire edge of pole piece 56 would still be adjacent a magnetic return path through pole piece 27. Moreover, the leg spacer 55 is substantially equal in width to the magnetic pole piece 27, and the outer boundaries of the erase core member are aligned with the outer boundaries of the stainless steel laminations 28, thus assuring a generally tight fit and alignment within the slot formed by mating portions 20 and 60.

FIG. 3 is a graph depicting the magnitude of the signal levels of a track on the magnetic medium as a function of the erase current. When a write current source of a given magnitude energizes the read/write transducer, a signal level corresponding in readback voltage to that described by curve 80, is written on track 17. This written signal is substantially constant. In accordance with this invention the erase transducers are always energized when the read/write transducer is in the write mode for erasing the edges of the written track. Curve 85 illustrates the signal remaining after erasure of the track edges for the novel transducer assembly described herein. For small values of erase current, a decrease in track signal initially occurs. However, once a minimum erase current is exceeded, the signal level remaining after erasure becomes relatively constant. The head of this invention utilizes an erase current of milliamps as shown by operating point 86. This operating point is on the flat portion of the curve, being greater than the point 87 which is the minimum current required to obtain a uniform and constant erase flux flield. From curve it is noted that even if the electrical or magnetic characteristics of this novel transducer assembly or its associated electronics are slightly varied, either individually or for a batch of heads, the signal remaining on the track after erasure would be the same as long as the erase current exceeded point 87. Thus, manufacturing tolerances are loosened on the dimensions of the transducer assembly components and on the erase driver electrical components, whereby manufacturing cost is drastically reduced without a reduction in head performance.

For purposes of illustration, curve 82 depicts the variation in signal for a normal tunnel erase transducer. It is seen that as the erase current increases the signal remaining after erasure continuously decreases, approaching zero at high erase currents. Since there is no constant signal region, the transducer erase characteristics are consequently extremely sensitive to variations in the operating point, thus requiring that the tolerance of each head be separately controlled during manufacture.

In order to describe the constant erasure process, it should be noted that the ends of the erase core legs contact the magnetic medium, have facing surfaces in the throat height region and become gradually separated at a 45 angle above the throat. Accordingly, magnetic flux passing through one of the legs encounters the least reluctance in a path longitudinally through the medium across the erase gap and up the 1 other leg, and thus will flow primarily through this path.

This flux is known as the fringing or erase flux. It is solely this erase flux which provides the tunnel erasing mechanism for erasing the edges of the written track. However, in order to provide a constant erase field and prevent the erasing flux from varying in magnitude the erase core member is driven by a magnetomotive force that saturates the medium and the pole tip region. Normally, an erase core material is not saturated since it is only necessary to provide an erase field intensity at the erase gap which is in excess of the coercivity level of th medium. After the medium is saturated an increase in flux through the core will contribute verylittle to the fringe erase field, and will primarily flow across the facing surfaces of the erase core legs in the throat height region as a gap leakage flux. saturating the throat height region effectively increases the gap width between the facing legs, thereby causing a very high reluctance in this region. This is seen as point 87 in FIG. 3. Consequently, additional flux flowing through the core member will leak off the legs above the throat closing a path internally within the erase core member. This flus is known as throat leakage flux. The nonmagnetic wedge 23 doesnot effect the flow of this flux although it is physically in the path. Neither the gap leakage flux nor the throat leakage flux contributes to the erasing process and thus has no effect on the amplitude of the written track signal.

The erase core is desirably stamped from a precisely rolled sheet stock of a high permeability iron alloy. The dimensions used in constructing the core member are dependent upon the magnetic material used. The shim 50 has been chosen to provide a relatively large erase gap width of approximately 3 mils, thus making erasure less sensitive to throat height variations. Accordingly, the throat height can vary between 1 and 7 mils While still achieving constant erasure. The core legs having a reduced cross section with respect to that of the core body are 60 mils long, thus providing a large surface for closure of the throat leakage flux.

Wear is a very important consideration since the transducer is designed for and used in a contact recording environment. The housing is fabricated from stainless steel which is noncorrosive, nonmagnetic and reduces head-disk wear problems. The spherical contour of the housing surface also reduces wear and allows a more even wrapping of the medium over both the read/write gap and the erase gaps.

It has been shown that this invention provides an improved magnetic transducer assembly in which the leg portions of the erase core member are maintained in a parallel relationship for a throat height distance which is less than the length of the legs and the width of the erase gaps are maintained at a constant separation such that the erase flux field is substantially uniform over a range of current above the minimum required to Samrate the cor in the throat height region. Since this transducer has a small write gap to erase gap spacing and therefore excellent head-to-rnedium compliance characteristics, it is useful in efficiently recording high density information.

While there has been described, what are at present, considered to be the preferred embodiments of the magnetic transducer assembly with an erase core in accordance with the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A magnetic transducer assembly for cooperating with a relatively moving magnetic medium comprising:

a read/write transducer including a plurality of elements for writing a track of information on the magnetic medium;

an erase core assembly for erasing the edges of said written track immediately after it is written by said read/write transducer; and

a housing for carrying said read/write transducer and said erase core assembly and having a first surface with an outwardly directed smooth continuous contour having an apex point nearest the plane of said magnetic medium adapted to be positioned in a recording relationship to said track,

said erase core assembly comprising:

an erase core member including a flexible strip of magnetic material, each end of said strip having first and second parallel leg portions spaced apart a distance corresponding substantially to the width of said track after erasure, said core being bent to position the ends of said strip substantially flush with said first surface in spaced apart relationship whereby said first legs define a first erase gap in said first surface for erasing one edge of said track and said second legs define a second erase gap in said first surface for erasing the opposite edge of said track, and

a coil associated with said erase core member,

said housing comprising:

a first portion for carrying at least one of said plurality of elements of said read/write transducer,

a second portion for carrying at least another of said plurality of elements of said read/write core and having a cavity therein for carrying said erase core assembly,

a third mating portion for fixedly constraining said erase core member within said housing,

means for fixing said erase core relative to said housing to maintain said first and second leg portions in parallel relationship for a throat height distance which is less than the length of said legs and to maintain the width of said erase gap such that the flux field is substantially uniform over a range of current above the minimum required to saturate said erase core in the throat heigh region,

said erase gaps being aligned perpendicular to said track and on an opposite side of said apex with respect to the associated write gap of said write transducer, and

means for maintaining said flexible medium in compliance with said write gap and said erase gaps.

2. The magnetic transducer assembly as set forth in claim 1, wherein said first surface of said housing is spherically shaped.

3. The magnetic transducer assembly as set forth in claim 1, wherein said housing includes a wedge-shaped portion disposed within said cavity with the vertex extending proximate to and slightly spaced from said first surface of said housing,

said bent erase core abutting said write transducer for closely positioning said erase gaps to the associated write gap of said write transducer and extending over said wedge-shaped portion,

said third mating portion mating with said second portion for constraining said erase core therebetween and for maintaining said first and second leg portions said parallel relationship and to maintain said width of said erase gaps.

4. An erase core assembly for a magnetic recording transducer for erasing the edges of a newly written track immediately after it is written by a write transducer, said assembly comprising:

an erase core member,

a coil,

a housing for positioning said core member in operating relationship to said write transducer, said housing having a first surface adapted to be positioned ina recording relationship to said track, said core member comprising:

a strip of-magnetic material, each end of said strip havingfirst and second parallel leg portions spaced apart a distance corresponding substantially to the desired width of said track after erasure, said core being positioned with the ends of said strip substantially normal to the plane of said first surface in spaced apart relationship whereby said first legs define a first erase gap in said first surface for erasing one edge of said track and said second legs define a second erase gap in said first surface for erasing the opposite edge of said track, and

means for fixing said core member relative to said housing to maintain said first and second leg portions in parallel relationship for a throat height distance which is less than the length of said legs and to maintain the width of said erase gaps such that the erase flux field is substantially uniform over a range of current above the minimum required to saturate said core in the throat height region.

5. The erase core assembly as set forth in claim 4, wherein said means for fixing said core member is integral and unitary with said housing.

6. The erase core assembly as set forth in claim 4, wherein said means for fixing said core member includes a wedge-shaped portion with the vertex extending proximate to and slightly spaced from said first surface of said housing.

7. The erase core assembly as set forth in claim 6, wherein said distance between said vertex and said first surface of said housing defines said throat height distance.

8. The erase core assembly as set forth in claim 6, wherein said wedge-shaped portion forms an angle of between and 70 at said vertex.

9. The erase core assembly as set forth in claim 4, wherein said erase core member includes a nonmagnetic shim fixedly positioned within said erase gaps extending upwardly into said erase core member from said ends across at least the width of said legs.

10. The erase core assembly as set forth in claim 4, wherein said erase core member includes a substantially wider portion of reduced reluctance, the boundary of said wider portion forming a shoulder, and wherein said coil abuts said shoulder.

11. The erase core assembly as set fort in claim 4, and

further comprising a non-magnetic leg spacer, firmly positioned laterally between said first leg portions and said second leg portions, thus maintaining said respective legs aligned and spread apart.

12. The erase core assembly as set forth in claim 4, wherein said erase core abuts said write transducer for closely positioning said erase gaps to the associated write gap of said write transducer.

13.The erase core assembly as set forth in claim 4, wherein said means for fixing said core member abuts said erase core member.

14. The erase core assembly as set forth in claim 4,

and further comprising mating means for fixedly constraining said erase core member within said housing. 15. The erase core assembly as set forth in claim 4, wherein said strip is flexible, bent into position and is a nickel-iron alloy having a high permeability.

16. In a magnetic recording system, the combination comprising:

a flexible magnetic medium, a magnetic transducer assembly cormpsing:

a read/write transducer including a read/write gap; an erase core assembly; a housing for carrying said read/write transducer and said erase core assembly; said housing having a first spherically shaped surface adapted to be positioned in a recording relationship to said magnetic medium; said erase core assembly including a strip of magnetic material that is positioned with its ends against said first surface, each end of said strip having spaced-apart first and second parallel leg portions, respective first and second leg portions each defining an erase gap; means for fixing said core member within said housing to maintain said first and second leg portions in parallel relationship for a throat height distance which is less than the length of said legs and to maintain the width of said erase gaps such that the erase flux field is substantially uniform over a range of current above the minimum required to saturate said core assembly in the throat height region, and means for maintaining said flexible magnetic medium in compliance with said read/write gap and said erase gaps.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3155949 *Nov 24, 1961Nov 3, 1964IbmTunnel erase magnetic transducer
US3504134 *Jul 13, 1966Mar 31, 1970Ncr CoMultiple magnetic head with a strip core having a common base portion
US3562443 *Sep 14, 1967Feb 9, 1971Philips CorpComposite recording/playback head with two trim erase heads oriented at an angle to the record/playback head
US3668332 *Aug 26, 1970Jun 6, 1972Xerox CorpMagnetic recording heat which accurately defines the width of the recording track
US3684841 *Dec 30, 1969Aug 15, 1972Honeywell IncMulti-channel magnetic transducer structure having full width erase head in non-magnetic housing
Non-Patent Citations
Reference
1 *Dortort et al., Multi Track Magnetic Head, RCA Tech. Notes, RCA TN No. 214, Jan. 1959.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4819092 *May 8, 1987Apr 4, 1989Colorado Memory Systems, Inc.Apparatus for writing signal density information on a magnetic medium
US6564307Aug 18, 1999May 13, 2003International Business Machines CorporationMethod, system, and program for logically erasing data
EP0052706A1 *Sep 16, 1981Jun 2, 1982International Business Machines CorporationSafeguarding of data recorded on disk by tunnel erase magnetic head assembly
WO1994024669A1 *Apr 5, 1994Oct 27, 1994Univ WashingtonMagnetic recording head with continuously monitored track following servo
Classifications
U.S. Classification360/118, G9B/5.156, G9B/5.4
International ClassificationG11B5/265, G11B5/127, G11B5/48, G11B5/187, G11B5/147
Cooperative ClassificationG11B5/488, G11B5/265, G11B5/127
European ClassificationG11B5/265, G11B5/127, G11B5/48D