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Патент USA US3079480

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Feb. 26, 1963
_ M. CAMRAS
'
3,079,470
MAGNETIC TRANSDUCER HEAD
Filed Dec. 21, 1959
2 Sheets-Sheet 1
226
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223
224
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Marvin CammS
HE
Feb‘. 26, 1963 ‘
MLCAMRAS
'
‘Filed Dec}. 21; 1959
3,079,470
MAGNETIC TRANSDUCER HEAD'
-
2 Sheets-Shed 2
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LE1? a. 772L471"
1.77
.
3
illustrated in FIGURE 6, while tape receiving surfaces
244 and 245 are shaped, and surfaces such as indicated
at 2% and 247 are made ?at and coplanar.
As indicated in FIGURE 8, a yoke 25% is formed of
ferrite material, with surfaces 25s” and 25% polished
?at and in the same plane to receive surfaces 246 and
247 of the gap unit shown in FIGURE 7. By way of
example, the yoke 250 may be formed of single crystal
ferrite with the directions of easy magnetization as indi
cated by the arrows 252 and 253 to conform with the
?ux path in the yoke. However it is preferable to make
the yoke of sintered ferrite, which may be “molded” into
the correct shape, and which is formed of a composition
having superior magnetic properties including high initial
permeability, high saturation flux density, and a high
enough ICurie point to insure stability at normal operating
temperatures.
FIGURE 9 illustrates the ?nal assembly with coils 256
and 257 and non-magnetic side plates 258 and 259 applied
to the assembly of yoke 25% and gap subassembly 261
of FIGURE 7. The side plates facilitate mounting of
the assembly and serve to strengthen and reinforce the
gap unit in its mounting with the yoke 250. In many
cases, the side plates 258 and 259 may be omitted and
surfaces 246 and 24-7 and Edda and 25% glued in place.
FIGURE 10- illustrates a further ferrite head con?gu
ration indicated generally by the reference numeral 3%.
The head
may comprise two core parts 331 and
4
comprising a pair of C-shaped core parts of ferrite ma
terial de?ning a ring-type head. In this embodiment, the
end faces 343a and 3420 are relatively spaced, While faces
341i) and 3423b may be in direct contact. In FIGURE
12, the upper gap is formed by thin pieces of metal mag
netic material such as Mumetal pieces 344 and 345, so
that the gap remains sharp even though the adjacent
errite material of core parts 342,1 and 342 is somewhat
irregular. The gap between the Mumetal parts 344 and
10 345 may be provided by vacuum depositing a suitable
non-magnetic material such as discussed above on one
or both of the confronting surfaces 344a and 345a of the
pole piece members 344 and 345. In FIGURE 12, the
‘gap material 350 may be deposited on face 344a to com
pletely till the gap in the magnetic circuit including core
parts 341 and 342 and pole piece members 344 and 345.
The assembly of FIGURE 12 including windings 351
and 352 may be embedded in an epoxy resin casing as in
dicated by the dash line 355. It‘ is found that the sand
wich including pole piece parts 344 and 345 and gap
material 35%) should be kept very thin in the direction
etween faces 341a and 342a to avoid interference effects
that produce a notch in the response curve at an audible
frequency.
In each of the illustrated embodiments, the gap in
the magnetic circuit is preferably less than 5 microns
and is provided by metal deposited on one or more of
the gap de?ning faces of the confronting magnetic parts.
3&2 of a suitable ferrite material such as “Ferroxcube,”
Vacuum deposition of the gap material is preferred for
this material comprising a manganese-zinc-ferrite com 30 accuracy, although plating can be used. Copper is a
position. The part 301 may comprise a relatively straight
bar of rectangular cross-section having edge portions de
desirable material for gap spacers because of its high
conductivity and because a copper gap is readily ob
?ning planar gap faces 3illla and 1161b. The other part
3612 is of a generally C-shape and has planar gap de?ning
edge faces 3ii2a and 36% confronting the faces 361a
and 3611). The core part 382 may have a winding 304
wound thereon prior to assembly of the core part 392
with the core part 3021. The edge gap de?ning face 3010,
servable under a microscope in contrast to the core pieces.
Facilities for evaporating metal are common in the
302b, and having a total thickness between the confront
ing gap faces which is preferably below 5 microns. When
fronting relation to form a non-magnetic gap, said blocks
having a direction of easy magnetization perpendicular
to the plane of said confronting surfaces.
2. A magnetic head comprising a pair of homogeneous
optical industry for coating lenses and mirrors. Evap
orated metal on plastic is also widely used for decorative
emblems.
The present application is a continuation-in-part of
3951b and 362a and 3652b may have a suitable non-mag
Serial No. 723,304 ?led March 24, 1958.
netic gap material vacuum deposited thereon to a thick 40
It will be apparent that many modi?cations and varia
ness of one micron, for example. Examples of suitable
tions may be effected without departing from the scope
gap materials are aluminum, gold, chromium, titanium
of the novel concepts of the present invention.
and silicon. The reference numerals 3%, 3%7, 3% and
I claim as my invention:
'
Sit-9 indicate diagrammatically gap material vacuum de
1. A magnetic head comprising a pair of single crystal
posited on the respective gap faces 301a, 302a, 301b, 45 ferrite blocks having ?at planar surfaces thereof in con
the core parts 301 and 3€l2 are assembled with their re
spective gap layers in contact, the gay layers 3%, 307
and 303, see completely ?ll the gaps in the magnetic cir 50 non-sintered ferrite members having respective surfaces
cuit de?ned by the core parts 391 and 302. The head
in confronting relation to de?ne a non-magnetic gap
between said members.
3. A magnetic head comprising a pair of magnetic
members of homogeneous ferrite material having re
magnetic gap de?ned by the gap layers 3tl6 and 387. 55 spective surfaces in confronting relation to de?ne a non
The assembly of FIGURE 10 may be secured in assem
magnetic gap less than about 5 microns in length in the
3% may cooperate with a magnetizable record medium
312 which travels successively across the top edges of
the core parts 3531 and 3'92 in coupling relation to the non
bled relation by any suitable means, for example by
potting the assembly in epoxy resin as indicated diagram
matically by the dash line 315.
FIGURE 11 shows an embodiment which is entirely
direction spanning said blocks.
4. A magnetic head comprising a pair of single crystal
ferrite members having respective surfaces in confront
ing relation to de?ne a non-magnetic gap.
similar to the embodiment of FIGURE 10, except that 60
5._ A magnetic head comprising a pair of single crystal
a second C-shaped ferrite core part 326* is substituted
ferrite members having ?at planar surfaces in confront
for the core part 301 in FIGURE 10 and carries a second
ing relation to form a non-magnetic gap for coupling to
coil 321. Corresponding primed reference numerals are
a magnetic record medium, and a yoke structure of
given to similar parts. The end faces 320a and 32% are
sintered ferrite material forming a loop magnetic circuit
65
provided with vacuum deposited layers ‘as indicated dia
with said single crystal ferrite members and the non
grammatically at 323 and 324 which together with the
magnetic gap therebetween.
layers 307' and 369’ of non-magnetic material completely
6. A magnetic head comprising a pair of single crystal
?ll the gaps in the magnetic circuit .de?ned by the core
ferrite members having ?at planar surfaces in confront
parts 302' and 323. The total gap length of each gap 70 ing relation and having an evaporated ?lm of non-mag
in the magnetic circuit is preferably less than 5 microns
netic material deposited on at least one of said surfaces
and may, for example, be 2 microns. The gap spacer
and rigidly determining the spacing between said sur
may be of any of the materials mentioned in connection
faces to de?ne a non-magnetic gap for coupling to a
with FIGURE 10.
magnetic record medium.
’ FIGURE 12 illustrates a magnetic transducer head 340 75
7. A magnetic head comprising “a pair of homogeneous
3,079,470
5
non-sintered ferrite members having respective surfaces
in confronting relation to de?ne a non-magnetic gap for
coupling to a magnetic record medium, and a yoke
structure of sintered ferrite material forming a loop
6
of non-magnetic material deposited upon at least one
of said surfaces to rigidly determine the spacing there
> between and to de?ne a non-magnetic gap for coupling
to a magnetic record medium.
magnetic circuit with said homogeneous non-sintered
ferrite members and the gap therebetween.
8. A magnetic head comprising a pair of single crystal
12. A magnetic head comprising a pair of single crystal
ferrite members having respective surfaces in confront
ing relation and having an evaporated ?lm deposited on
at least one of said surfaces of approximately one-quar
ter micron thickness to rigidly determine the spacing
members to a magnetic record medium, a yoke structure ll) between said members and to de?ne a non-magnetic gap
for coupling to a magnetic record medium.
of sintered ferrite material included in .a loop magnetic
circuit with said single crystal ferrite members, means
References Cited in the ?le of this patent
de?ning a path of travel of a record member successively
UNITED STATES PATENTS
across said single crystal ferrite members and in cou
ferrite members having respective surfaces in confront
ing relation to provide a region for coupling of the
pling relation to said region provided by said surfaces, 15
and a magnetoelectric transducing element coupled to
said loop magnetic circuit.
9. A magnetic head comprising a pair of homogeneous
non-sintered ferrite members having respective surfaces
in confronting relation to de?ne a non-magnetic gap 20
between said members and having side surfaces disposed
at right angles to said confronting surfaces, and unitary
side plate means of non-magnetic material in contact
with said side surfaces of the respective ferrite members
and spanning the gap therebetween.
25
10. A magnetic head comprising a pair of homogeneous
non-sintered ferrite members having respective surfaces
in confronting relation to de?ne .a non-magnetic gap
between said members, a yoke structure forming a loop
magnetic circuit with said ferrite members and the gap 30
therebetween, and side plate means of non-magnetic
material laterally contacting a side surface of each of
the ferrite members and of the yoke structure and span
ning the gap between the ferrite members.
11. A magnetic head comprising a pair of homogeneous
non~sintered ferrite members having respective surfaces
in confronting relation and having an evaporated ?lm
2,261,412
2,346,555
2,585,932
2,592,652
2,692,978
2,706,752
12,724,663
2,809,237
2,818,514
2,862,066
2,866,011
2,919,312
2,945,919
Reeve ________________ __ Apr. 2,
Cobb _______________ __ Apr. 11,
Hare _______________ __ Feb. 19,
Buhrendorf __________ __ Apr. 15,
Galt ________________ __ Oct. 26,
Dupy _______________ __ Apr. 19,
Bond _______________ __ Nov. 22,
Bergmann ____________ __ Oct. 8,
Goerty ______________ __ Dec. 31,
Thiele ______________ .._ Nov. 25,
Kornei ______________ ._ Dec. 23,
Rosenberger _________ ..._ Dec. 29,
Neumann ____________ __ July 19,
1941
1944
1952
1952
1954
1955
1955
1957
1957
1958
1958
1959
1960
FOREIGN PATENTS
669,458
713,371
893,385
Great Britain _________ __ Apr. 2, 1952
Great Britain _________ _- Aug. 11, 1954
Germany ____________ _._ Oct. 15, 1953
OTHER REFERENCES
Proceedings of the IRE, October 1956, pp. 1343, 1344;
available in the USPO Scienti?c Library.
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