WO1980002769A1

WO1980002769A1 - Isolated multiple core magnetic transducer assembly

Info

Publication number: WO1980002769A1
Application number: PCT/US1980/000648
Authority: WO
Inventors: R Herman
Original assignee: New World Computer Co Inc
Priority date: 1979-06-01
Filing date: 1980-05-30
Publication date: 1980-12-11
Also published as: JPS56500630A; EP0029458A1; EP0029458A4

Abstract

Magnetic transducer assembly (1) including a plurality of magnetic cores (2a-d) affixed to a nonmagnetic slider (4), the slider having a multiplicity of fluid bearing surfaces (7a-d) for supporting the magnetic transducer assembly on a fluid bearing proximate to a rotating surface such as a magnetic disc. Each magnetic core has a corresponding slider fluid bearing surface of equal width, the magnetic cores being affixed to the trailing edge (3) of the fluid bearing surfaces. The slider provides additional fluid bearing surfaces (8a-b) intermediate the corresponding fluid bearing surfaces.

Description

DESCRIPTION

ISOLATED MULTIPLE CORE MAGNETIC TRANSDUCER ASSEMBLY

This invention relates generally to magnetic transducers and more particularly to a magnetic transducer assembly with multiple magnetic cores and a non-magnetic integral slider. Reference is made to the following co-pending applications concurrently filed with this application: Serial No. 44,535, filed June 1, 1979 and entitled "Actuator Apparatus for Magnetic Disc Recording Systems"; Serial No. 44,533, filed June 1, 1979 and entitled "Gas Circulation and Filtration Apparatus for Magnetic Disc Recording Systems"; and Serial No. 44,536, filed June 1, 1979 and entitled "Suspension Device for Magnetic Transducers". The above-referenced applications are assigned to ehe same assignee as this application and disclose and claim subject matter related to the present application.

Magnetic disc recording systems commonly utilize a plurality of magnetic transducers that are positioned near the surface of a rotating disc. These magnetic transducers are separated from the surface of the rotating disc by a relatively thin fluid bearing, to form what is commonly called a "flying" head. While some magnetic disc recording systems position one magnetic core adjacent to each magnetic track contained on the surface of the disc, other systems employ fewer magnetic cores and means for alternatively positioning these cores adjacent to the desired tracks.

Generally, the magnetic transducers used in either of the above systems include a plurality of magnetic cores that are carried in some manner upon a slider riding upon a thin fluid bearing proximate to the surface of the rotating disc. A exemplary julti-channel magnetic head is disclosed in Solyst U.S. Patent No. 3,579,214. However, the slider disclosed therein is formed from a ferromagnetic block which is relatively expensive and magnetically couples together the multiple magnetic cores, thereby creating interference between adjacent cores. A second exemplary magnetic transducer is commonly termed a Winchester slider as referenced in Wiseley U.S. Patent No. 4,141,050, column 2, lines 50-56. The Winchester slider employe three fluid bearing surfaces each having a magnetic core embedded therein. However, the magnetic cores and fluid bearing surfaces must be relatively wide to support the transducer assembly, thus requiring a relatively wide track and consequently diminishing the storage capacity of the magnetic disc. A third example of a multi-channel magnetic transducer assembly is disclosed in Neace U.S. Pat. No. 3,792,492 which describes an assembly of a plurality of magnetic cores mounted on a non-magnetic spacer which is bonded into a slotted air bearing member. This transducer assembly requires that the magnetic core and spacer combination be fitted into the air bearing member, increasing the manufacturing complexity and cost, and additionally increasing the total mass of the magnetic core, spacer and air bearing member combination.

The magnetic transducer assembly of the present invention, on the other hand, provides relatively narrow magnetic cores that are fixed to a non-magnetic slider in a generally low mass combination, thus overcoming the limitations descrid above. In an exemplary embodiment, the magnetic transducer assembly comprises a plurality of magnetic cores bonded to the trailing edge of a non-magnetic ceramic slider to form a flying head for magnetic disc. The surface of the slider nearest the disc includes a plurality of fluid bearing surfaces for supporting the magnetic transducer assembly on a fluid bearing near a rotating disc, and also includes leading edge surfaces. Trailing edge surfaces are provided by the magnetic cores, and a magnetizing coil is wound around each magnetic core.

To manufacture the exemplary embodiment, a notched surface of a ferrite block is joined to a first surface of a ferrite plate. The obverse surface of the ferrite plate is next joined to a block of non-magnetic ceramic material such as barium titanate. A channel is machined into a first surface of the ceramic block parallel to the ferrite block and plate to form a suitable mounting surface. On the opposite side of the ceramic block and perpendicular to the ferrite block and plate, a plurality of notches are formed into the assembly of the ferrite block and plate as well as the ceramic block, to define the fluid bearing surfaces.

Portions of the ferrite block and plate are then removed to define individual magnetic cores that are Isolated by the non-magnetic ceramic block. Individual magnetic transducers including four magnetic cores are machined from the assembly of the ferrite block, ferrite plate and ceramic block. A hydrodynamic leading edge is then formed on the leading edge of the fluid bearing surfaces of the magnetic transducers, and a trailing edge is formed on the magnetic cores of the transducers. It is thus an object of this invention to provide an improved magnetic transducer assembly with multiple magnetic cores.

It is another object of this invention to provide a magnetic transducer assembly with multiple magnetic cores bonded to non-magnetic material.

It is a further object of this invention to provide a magnetic transducer assembly with multiple magnetic cores that are bonded to a single non-magnetic slider.

It is yet another object of the present invention to provide a magnetic transducer assembly with relatively narrow magnetic cores supported by a non-magnetic slider.

These and other objects and advantages of the present invention will be apparent from the following description and accompanying drawings.

Figure 1 is a perspective view of the magnetic transducer assembly depicting the fluid bearing surfaces and the magnetic cores.

Figure 2 is a perspective view of the magnetic transducer assembly depicting the fluid bearing surfaces and the magnetic cores.

Figures 3-7 illustrate the magnetic transducer assembly manufacturing steps.

Figure 8 is a perspective representation of a plurality of magnetic transducer assemblies in use.

Turning now to the drawings, the magnetic transducer assembly 1 of the present invention, as shown in Figures 1 and 2, comprises a plurality of magnetic cores 2a-d, bonded to the trailing edge 3 of a non-magnetic ceramic slider 4. The surface 5 of the slider 4, shown in detail in Figure 2 and the surface nearest the disc during normal operation, is machined to form a plurality of track fluid bearing surfaces 7a-d and ancillary fluid bearing surfaces designated typically at 8a and 8b. A leading edge angled surface 9a-f is formed into each fluid bearing surface of the slider 6 and trailing edge angled surfaces 10a-d are formed into each magnetic core 2a-d. A magnetizing coil 11a-d is wound around each of the magnetic cores 2a-d.

An exemplary process for forming an individual magnetic transducer assembly begins as shown in Figure 3 with a ferrite block 13 that has a first upper surface 14 into which are formed notches 15 and 16. Each notch 15 and 16 typically has two surfaces 17 and 18 perpendicular to the surface 14 and an angled sidewall 19 formed nearest the centerline of the ferrite block 13 and angled approximately thirty degrees from surface 14. The ferrite block 13 also as a second lower surface 20 that is opposite and parallel to the surface 14. Once the notches 15 a-d 16 are formed, the ferrite block 13 is rotated about its longitudinal axis and the surface 14 is bonded to a first upper surface 25 of a ferrite plate 27 as shown in Figure 4. The bonding technique utilizes a glass 28, as is well known to those skilled in the art, to achieve a gap 29 between the ferrite block 13 and the ferrite plate 27 in the range of twenty-five micro-inches to seventy-five micro-inches. An exemplary manufacturer of magnetic transducer assemblies utilizing such techniques is Magnetic Arts, 1310 Industrial Avenue, Escondido, California 92025.

As shown in Fig. 5, a second lower surface 26 of the ferrite plate 27 is similarly bonded to a ceramic base 40, which is preferably barium titanate or other suitable material. A pair of notches 41 and 42 are formed then into opposing surfaces 43 and 44, respectively, of the ceramic base 40. The surfaces 43 and 44 and notches 41 and 42 are paralled to notches 15 and 16. A surface 45 of the ceramic base 40 is opposite from ferrite plate 27 and is adjacent to surfaces 43 and 44. The ferrite block 13, ferrite plate 27, and ceramic base 40 are parted along a plane 50 which is substantially intermediate and parallel to the surfaces 43 and 44, resulting in two essentially identical bar assemblies 51 and 52. Each bar assembly 51 and 52 has a forward surface 53 and 54, which originally comprised the surface 45 of the ceramic base 40, and a trailing surface 55 and 56 which originally comprised the surface 20 of the ferrite block 13. Additionally, two new fluid bearing surfaces 60 and 61 are formed. The surface 60 is opposite from and parallel to the surface 44 of bar assembly 51; the surface 61 is similarly opposite from and parallel to the surface 43 of the bar assembly 52.

The bar assemblies 51 and 52 then are rotated and aligned as shown in Fig. 6 such that the forward surface 53 of the bar assembly 51 abuts the trailing edge 56 of the bar assembly 52, and such that the surfaces 44 and 43 are coplanar, thus aligning the fluid bearing surfaces 60 and 61. Track gas bearing surfaces 7a-d, and ancillary gas bearing surfaces 8a and 8b shown in Figs. 2 and 6 are machined into the fluid bearing surfaces 60 and 61 perpendicular to the notches 41 and 42. The pattern of track fluid bearing surfaces 7a-d and ancillary bearing surfaces 8a-b may be repeated across the length of the bar assemblies 51 and 52, although those skilled in the art will recognize that the pattern shown in Figure 6 may be varied without harmful result. The assemblies 51 and 52 are again rotated as illustrated in Fig. 7 such that the fluid bearing surface 60 of the bar assembly 51 abuts the surface 43 of bar assembly 52, the assemblies 51 and 52 being further aligned such that a plane 78 perpendicular to the track fluid bearing surfaces 7a-d and passing through an edge 79 of the track fluid bearing surfaces 7a-d will pass through an edge 80 of the corresponding track fluid bearing surface 81. Additionally, the forward surfaces 53 and 54 are aligned to be coplanar. Once so positioned, grooves 85a-d are formed through the ferrite material remaining from the ferrite block 13 and the ferrite plate 27 to define magnetic cores typically designated 2a-d.

Individual magnetic transducer assemblies generally designated 1 as shown in Figs. 1 and 2 are parted from the bar assemblies 51 and 52 of Fig. 7 along planes typically designated 105 and 106 that are perpendicular to the track fluid bearing surfaces 7a-d and ancillary fluid bearing surfaces 8a and 8b, the planes 105 and 106 being selected so as to define a magnetic transducer assembly 1 containing four magnetic cores 2a-d and the associated track fluid bearing surfaces 7a-d, and two ancillary fluid bearing surfaces 8a and 8b.

The fluid bearing surfaces of the magnetic cores 7a-d (Fig. 2) are then ground to define a trailing edge angle into trailing edges lOa-d which may, for example, be on the order of eight degrees. The trailing edge angle may begin approximately within five-thousandths an inch from the gap originally formed at 29 (Fig. 4) and generally designated 29a-d in Fig. 2. The magnetic transducer assembly 1 is further ground to define a leading edge angle on the order of one-half degree into leading edges 9a-f which extend approximately forty-thousands of an inch from the leading edge surface 131. It will be remembered that the surface 131 was originally part of the forward surface 54 of the bar assembly 52. To complete the magnetic transducer assembly 1, a length of wire 94 is wound through each magnetic core 2a-d in a manner that is well known in the art to form magnetizing coils lla-d.

In operation, five typical magnetic transducer assemblies 100 through 104 as shown in Fig. 8 are affixed to a suspension spring 141 at notches such as the notch 140 of the magnetic transducer assembly 1 in Fig. 1. The suspension spring 141 magnetic transducer assemblies 100 through 104 toward the surface of a disc 142 rotating in a direction indicated by arrow 150. A suitable suspension apring 141 is disclosed in co-pending application Serial No. 44,536, filed June 1, 1979. The nominal spacing between typical magnetic cores 2a-d of a typical magnetic transducer assembly 1 is equal to the distance between nine tracks of recorded information of the surface of disc 142, as also described in U.S. Patent Application Serial No. 44,536, filed June 1, 1979. As the suspension spring 141 traverses the surface of the disc 142 a distance perpendicular to the direction of rotation that is equal to the distance between eight tracks of recorded information, magnetic transducer assemblies 100 through 104 will be moved across a total of 160 tracks of information.

In a preferred embodiment, the initial length of the ferrite block 13, the ferrite plate 27 and the ceramic base 40 is approximately eight inches; thus a plurality of magnetic transducer assemblies typically designated 1 are manufactured at one time, resulting in a relatively low-cost low-mass magnetic transducer assembly with narrow track widths and magnetically isolated magnetic cores.

Having thus described one embodiment of my invention in detail, it is to be understood that numerous equivalents and alternatives do not depart from the invention will be apparent to those skilled in the art, given the teachings herein. Thus, my invention is not to be limited to the above description but is to be of the full scope of the appended claims.

Claims

Claims:

1. A magnetic transducer assembly for recording or retrieving information from a moving magnetic surface while supported by a fluid bearing betweenthe moving magnetic surface and the magnetic transducer assembly, comprising: a plurality of magnetic cores each having an outside surface, and a first gap, a slider of non-magnetic material having a first surface for supporting said magnetic transducer assembly against said fluid bearing, a second surface opposite said first surface for mounting said slider to suspension means, and a bonding surface adjacent to said first surface and said second surface, said outside surface of each said magnetic core being affixed to said bonding surface, positioning each said first gap proximate said first surface to support and substantially magnetically isolate said magnetic cores.

2. A magnetic transducer assembly as in claim 1 wherein each said magnetic core comprises a generally

C-shaped member having a back portion and a first and second leg portion extending from said back portion and a first and second leg portion extending from said back portion to define said generally C-shaped member, said first and second leg members each having an end, and a plate member having a first surface being bonded to said ends to define a magnetic circuit having said first gap and a second gap between said C-shaped member and said plate member, and said second surface of said plate member forms said outside surface.

3. A magnetic transducer assembly as in claim 1 wherein said first surface of said slider additionally includes an adjoining leading edge surface inclined from the plane defined by said first surface for more readily forming said fluid bearing.

4. A magnetic transducer assembly as in claim 3 wherein said leading edge surface is inclined approximately one-half degree from said plane.

5. A magnetic transducer assembly as in claim 1 hwerein said magnetic cores are additionally formed to include core fluid bearing surfaces adjoining said first surface.

6. A magnetic transducer assembly as in claim 5 wherein said core fluid bearing surfaces are additionally formed to include an adjoining trailing edge surface inclined from a plane defined by said first surface.

7. A magnetic transducer assembly as in claim 6 wherein said trailing edge surfaces are inclined approximately 8 degrees from said plane.

8. A magnetic transducer assembly as in claim 1 wherein said fluid bearing surface is formed to include a plurality of track fluid bearing surfaces and ancillary fluid bearing surfaces substantially parallel to the direction of travel of said moving magnetic surface.

9. A magnetic transducer assembly as in claim 8 wherein each said first gap is colinearly aligned with a correspondingly said track fluid bearing surface.

10. A magnetic transducer assembly as in claim 9 wherein said track fluid bearing surfaces and said first gaps are of equal width.

11. A magnetic transducer assembly as in claim 8 wherein said ancillary fluid bearing surfaces are intermediate said track fluid bearing surfaces.

12. A magnetic transducer assembly as in claim 8 wherein said ancillary fluid bearing surfaces are fluid-dynamically isolated from said track fluid bearing surfaces.

13. A magnetic transducer assembly for recording or retrieving information from a moving magnetic surface while supported by a fluid bearing surface between the moving magnetic surface and the magnetic transducer assembly, comprising, a plurality of magnetic cores each comprising a generally C-shaped member having a back portion and first and second leg portions extending from said back portion to define said generally C-shaped member, said first and second leg members each having an end, and a plate member having a first surface and a second and opposite surface, said first surface being bonded to said ends to define a magnetic circuit having a first and a second gap between said generally C-shaped member and said plate member; a slider of non-magnetic material having a first surface formed to include a plurality of track fluid bearing furfaces and ancillary fluid bearing surfaces substantially parallel to the direction of travel of said moving surface for supporting said magnetic transducer assembly against said fluid bearing, and a bonding surface adjacent to said first surface, said track fluid bearing surfaces and said ancillary fluid bearing surfaces each additionally formed to include an adjoining leading edge surface inclined from a plane defined by said track fluid bearing surfaces and said ancillary fluid bearing surfaces; and said second surface of said plate member of each magnetic core being affixed to said bonding surface, positioning each said first gap proximate to said first surface and colinearly aligning said first gap of each magnetic core with a corresponding said track fluid bearing surface to support and substantially magnetically isolate said magnetic cores, each said magnetic core additionally formed to include an adjoining trailing edge surface inclined from a plane defined by said track fluid bearing surfaces and said ancillary fluid bearing surfaces,

14. A magnetic transducer assembly as in claim 13 wherein said leading edge surface is inclined approximately one-half degree from said plane.

15. A magnetic transducer assembly as in claim 13 wherein said trailing edge surface is inclined approximately 8 degrees from said plane.

16. A magnetic transducer assembly as in claim 13 wherein said ancillary fluid bearing surfaces are intermediate said track fluid bearing surface and are fluid-dynamically isolated therefrom.

17. A magnetic transducer assembly as in claim 13 wherein said track fluid bearing surfaces and said first gap are of equal width.

18. A magnetic transducer assembly for recording or retrieving information from a moving magnetic surface while supported by a fluid bearing between the moving magnetic surface and the magnetic transducer assembly, comprising, a plurality of magnetic cores each comprising a generally C-shaped member having a back portion and first and second leg portions extending from said back portion to define said generally C-shaped member, said first and said second legs each having an end, and a plate member having a first surface and a seconq and opposite surface, said first surface being bonded to said ends to define a magnetic circuit having a first and second gap between said C-shaped member and said plate member; a slider of non-magnetic material hving a first surface formed to include a plurality of track fluid bearing surfaces and ancillary fluid bearing surfaces substantially parallel to the direction of travel of said moving magnetic surface for supporting said magnetic transducer against said fluid bearing, a second and opposite mounting surface for mounting said slider to suspension means, and a bonding surface adjacent to said first and second surfaces, said track fluid bearing surfaces and said ancillary fluid bearing surfaces each additionally formed to include an adjoining leading edge surface inclined approximately one-half degree from a plane defined by said track fluid bearing surfaces and said ancillary fluid bearing surfaces, said ancillary fluid bearing surfaces being formed intermediate said track fluid bearing surfaces and fluid-dynamically isolated therefrom; said second surface of said plate member of each magnetic core being affixed to said bonding surface, positioning each said first gap proximate said first surface and colinearly aligning said first gap of each magnetic core with a corresponding said track fluid bearing surface to support and substantially magnetically isolate said magnetic cores, said magnetic cores additionally formed to include a magnetic core fluid bearing surface adjoining said track fluid bearing surfaces, said magnetic core fluid bearing surface further including an adjoining trailing edge surface inclined approximately eight degrees from a plane defined by said track fluid bearing surfaces and said magnetic core fluid bearing surface adjoining said track fluid bearing surfaces, said magnetic core fluid bearing surface further including an adjoining trailing edge surface inclined approximately eight degrees from a plane defined by said track fluid bearing surfaces and said ancillary gas bearing surfaces.

19. A magnetic transducer assembly for recording or retrieving information from a moving magnetic surface while supported by a fluid bearing therebetween comprising a magnetically impermeable member having a first surfact for aerodynamically supporting said magnetic transducer assembly against said fluid bearing and a second surface adapted for mounting said assembly on a suspension means, said first surface having a leading edge and a trailing edge, and a plurality of magnetic cores formed integrally with said magnetically impermeable member and forming the trailing edge thereof.

20. A method of forming a magnetic transducer assembly comprising the steps of bonding a plate of magnetically permeable material to a block of such material to form a predetermined gap therebetween, bonding the assembly of said magnetically permeable block and plate to a magnetically non-permeable base, forming an aerodynamic bearing surface on one face of said base, forming a trailing edge on the assembly of said block and plate, machining said block and plate assembly to form a plurality of magnetic cores, and winding a coil on each of said magnetic cores.

21. The method of claim 20 wherein the step of forming an aerodynamic bearing surface includes forming a plurality track bearing surfaces.