Metal working – Method of mechanical manufacture – Electrical device making
Patent
1988-03-14
1989-10-31
Hall, Carl E.
Metal working
Method of mechanical manufacture
Electrical device making
360126, G11B 542
Patent
active
048767905
DESCRIPTION:
BRIEF SUMMARY
The invention relates to magnetic information recording and playback technique, more particularly to a method for producing a magnetic head usable for information recording playback. The term "information recording" covers sound recording on a magnetic carrier, video recording technique, as well as digital information recording. For the sake of simplicity the examples disclosed in the present specification will relate to conventional tape recording applications, however, any other recording and reading application is considered as equivalent.
The development of information recording technique has created a small number of head types.
A conventional and widely used head comprises a magnetic core made of profiles soft-iron sheets in a laminated arrangement, and there is provided an air gap between the sheets just across the frontal zone which abuts the magnetic carrier. A coil is wound around the core for connection with appropriate electronic circuits. Such heads are held in a head support and have a magnetic shielding around them. These heads proved to be popular, they had fairly good electrical properties (at least in sound recording applications) and their manufacture was not too expensive. A basic drawback of such heads was that the soft core material was soon worn by the frictional effects of the tape.
The development of the art has introduced chromium-dioxide and metal tape materials which have been much harder than normal tapes, and the laminated cores were unable to endure the wear caused by such medias.
In an improved technology a hard coating is provided on such heads, whereby the surface hardness has become sufficiently high. The problem with such heads lies in that the coating material increases the effective air gap to twice its thickness, and in most applications the high frequency response of the recording has become much worse than without such coatings.
Another head strucure family is based on the use of ferrite or glass ceramic materials. These materials have sufficient hardness to endure increased wear and they are also preferable regarding their frequency response. A drawback with such heads lies in the comparatively low value of permeability, whereby their electric signals are at a lower level than in case of permalloy cores. The greatest drawback of such heads lies in the difficulties during manufacture. These hard materials are hard to be formed and tooled, and their production is costly and it requires much time and work. A further drawback of such heads lies in their low heat conductivity. In operation, the effect of friction might cause extreme temperatures in the vicinity of the air gap, and at their elevated temperatures a recrystallisation might take place at the boundary surface of the glass and the ferrite material, which virtually increases the air gap and decreases frequency response. The thermal stresses may often lead to small cracks which mean the end of their useful life.
The object of the invention is to provide a method for producing a magnetic head which not only has good electrical properties, but can be manufactured with reasonable costs and has improved wear-resistant properties.
The invention is based on the discovery that for increasing the hardness of the soft-cored heads, the hard material should be arranged between the soft-iron sheets rather than on the head. If a hard material like e.g. titanium nitride is deposited on the main surface of the iron sheets forming the core, then the hardness of the so-obtained laminar sandwich structure will vary along the width of the information carrier (the tape) as a comb-like function. Since the tape has sufficient rigidity in the stretched state over small distances, the tape is sliding on the hard edges only and causing no wear to the soft iron material between the hard coatings.
This effect is similar to the passing of the wheels of a car above the grating of a sewer or the like. The wheel cannot get in between the iron rails if the rails are arranged in a sufficient density.
It has been experienced that even as thin c
REFERENCES:
patent: 2850582 (1958-09-01), DeRaemy
patent: 3683126 (1972-08-01), Krause
patent: 4156882 (1979-05-01), Delagi et al.
Bolla Istvan
Csanyi Istvan
Grimm Istvan
Stenczinger Sandor
Budapesti Radiotechnikai Gyar
Hall Carl E.
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