U.S. patent number 3,685,144 [Application Number 05/063,902] was granted by the patent office on 1972-08-22 for method of making a magnetic transducer.
This patent grant is currently assigned to The National Cash Register Company. Invention is credited to Cebern B. Trimble.
United States Patent |
3,685,144 |
Trimble |
August 22, 1972 |
METHOD OF MAKING A MAGNETIC TRANSDUCER
Abstract
A planar magnetic transducer comprising a planar coil means, in
the general shape of a spiral, with at least a portion of the coil
means being sandwiched between the pole ends of two magnetic
circuit plates. The method utilizes printed circuit techniques to
batch-fabricate single end bifilar coil transducers which may be
miniature in size.
Inventors: |
Trimble; Cebern B. (Dayton,
OH) |
Assignee: |
The National Cash Register
Company (Dayton, OH)
|
Family
ID: |
26743930 |
Appl.
No.: |
05/063,902 |
Filed: |
August 14, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
668528 |
Sep 18, 1967 |
3549825 |
|
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Current U.S.
Class: |
29/603.14;
G9B/5.097; G9B/5.086; G9B/5.094; 360/123.01; 29/603.15;
29/603.25 |
Current CPC
Class: |
G11B
5/3163 (20130101); G11B 5/313 (20130101); G11B
5/3179 (20130101); Y10T 29/49046 (20150115); Y10T
29/49044 (20150115); Y10T 29/49064 (20150115) |
Current International
Class: |
G11B
5/31 (20060101); G11b 005/42 (); H01f 007/06 () |
Field of
Search: |
;29/603,625 ;179/1.2C
;346/74MC ;340/174.1F ;336/200 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Campbell; John F.
Assistant Examiner: Hall; Carl E.
Parent Case Text
This application is a division of application Ser. No. 668,528,
filed on Sept. 18, 1967, U.S. Pat. No. 3,549,825 by Cebern B.
Trimble for Magnetic Transducer with Planar Spiral Coil Extending
into the Gap.
Claims
I claim:
1. The method of producing a magnetic transducer comprising the
steps of:
a. forming a recess on one side of a non-magnetic substrate;
b. forming a generally planar first magnetic plate in said recess,
with said plate having a pole end and a back end;
c. insulatingly supporting and forming over said plate and one side
a coil means in the general shape of a spiral so that the outer
turn thereof lies near said pole end, and the inner turn of said
coil means lies near said back end;
d. and insulatingly supporting and forming a second magnetic plate
over said coil means with said second plate having a pole end
positioned opposite the pole end of said first plate and having a
back end magnetically coupled to the back end of said first
magnetic plate, and with at least the outer turn of said coil means
being positioned between said pole ends.
2. The method as claimed in claim 1 in which said step (c)
comprises the steps of:
e. forming the first of a plurality of generally spirally shaped
coil windings so as to position the outermost portion thereof near
said pole end of said first magnetic plate;
f. forming the second winding of said plurality in superposed
relationship with said first winding while simultaneously joining
one end of said first winding with one end of said second winding;
and
g. forming additional windings as required according to the
technique of step (f) so as to join one end of each preceding
winding with one end of the winding being currently formed so as to
form said coil means into a multilayered single coil.
3. The method of producing a magnetic transducer comprising the
steps of:
a. forming a first magnetic plate on a non-magnetic substrate, with
said plate having a pole end and a back end;
b. depositing a first thin film of insulation over the entire
surface of said substrate and plate;
c. depositing a layer of conductor metal over said insulation;
d. forming a coil means in the general shape of a spiral of said
conductor metal;
e. depositing a second thin film of insulation over said first film
of insulation and said coil means;
f. removing portions of said second film of insulation near said
back end of said first plate to expose said back end and to expose
the ends of said coil means; and
g. forming a second magnetic plate on said second film of
insulation and said back end to magnetically couple said back end
with said second magnetic plate, said second plate having a pole
end which is spaced from said pole end of said first magnetic plate
to produce a transducer gap with an outer portion of said coil
means being positioned between said pole ends.
4. The method as claimed in claim 3 in which said forming step (a)
comprises:
h. etching a recess in the surface of said substrate;
i. depositing a permalloy to overfill said recess; and
j. abrading the excess permalloy so that the top thereof lies in
the plane of said surface to form said first magnetic plate.
5. The method as claimed in claim 4 in which said forming step (d)
comprises the steps of:
k. delineating the portions of said conductor metal to be removed
so that upon the removal thereof said coil means will be produced;
and
L. etching away said portions of step (k) down to said first film
of insulation to produce said coil means.
6. The method of producing a bifilar magnetic transducer comprising
the steps of:
a. forming a first magnetic plate on a non-magnetic substrate with
said plate having a pole end and a back end;
b. depositing a first thin film of insulation over the entire
surface of said substrate and plate;
c. depositing a layer of conductor metal over said insulation;
d. delineating portions of said conductor metal to be removed so
that, upon the removal thereof, a desired first coil in the general
shape of a spiral will be produced by the metal remaining;
e. etching away said portions of step (d) down to said first film
of insulation to produce said first coil with spaces between
adjacent turns thereof;
f. depositing a second thin film of insulation over said first coil
and said first film of insulation from step (e);
g. depositing a second layer of conductor metal over said second
film of insulation;
h. delineating portions of said second layer of conductor metal to
be removed so that upon the removal thereof, a desired second coil
in the general shape of a spiral will be produced by the metal
remaining;
i. removing said portions of said second layer of metal down to
said second film of insulation while leaving said metal of step (g)
in said spaces between the turns of said first coil to thereby form
discrete turns of said second coil of said transducer;
j. depositing a third thin film of insulation over said second
coil;
k. depositing a layer of permalloy metal on said third film of
insulation;
L. delineating portions of said permalloy metal of step (k) to be
removed so that, upon the removal thereof, a desired second
magnetic plate having a pole end and a back end will be produced by
the permalloy metal remaining; and
m. joining said back ends of said first and second plates and
exposing the ends of said coils for making connections thereto.
7. The method as claimed in claim 6 in which said forming step (a)
comprises the steps of:
n. etching a recess in the surface of said substrate;
o. depositing a permalloy to overfill said recess; and
p. abrading the excess permalloy so that the top thereof lies in
the plane of said surface to form said first magnetic plate.
8. The method of producing a bifilar magnetic transducer comprising
the steps of:
a. forming a recess on one side of a non-magnetic substrate;
b. forming a generally planar first magnetic plate in said recess,
with said plate having a pole end and a back end;
c. insulatingly supporting and forming over said plate and one side
a plurality of spirally shaped, planar coil windings for first and
second multi-turn coils, the windings of said first and second
coils being alternated in generally superposed relationship, with
at least the outermost turn of the windings of said first and
second coils being positioned near said pole end;
d. forming a second magnetic circuit plate over said plurality of
windings, with said second plate having a pole end positioned
opposite the pole end of said first plate and having a back end
magnetically coupled to the back end of said first plate, and with
at least one of the outermost turns of the windings of said first
and second coils being positioned between said pole ends; and
e. connecting the ends of the windings of said first coil to form
one continuous multilayered winding, and similarly connecting the
ends of the windings of said second coil to form one continuous
multilayered winding.
9. The method of producing a magnetic transducer comprising the
steps of:
a. etching a recess in a surface of a non-magnetic substrate;
b. depositing a permalloy to overfill said recess;
c. abrading the excess permalloy so that the top thereof lies in
the plane of said surface to form a first magnetic plate;
d. depositing a thin film of insulation over the entire said
surface of said substrate;
e. depositing a thin layer of metal over the entire surface of said
insulation to form a plating electrode;
f. electro-plating a conductor metal over said thin layer of metal
to a desired thickness;
g. delineating the portions of said conductor metal to be removed
so that, upon the removal thereof, a desired coil configuration
will be produced by the conductor metal remaining;
h. etching said portions down to said film of insulation to produce
said coil configuration;
i. depositing a second thin film of insulation over said surface of
said substrate and said coil configuration;
j. delineating an area near one end of said first plate to be
removed;
k. etching said area of step (j) to expose said first magnetic
plate thereat;
L. depositing a second thin layer of metal over the surface of said
second film of insulation and the portion of the first magnetic
plate as exposed from step (k);
m. depositing a layer of permalloy metal on said second thin layer
of metal; and
n. delineating portions of said permalloy metal of step (m) to be
removed so that, upon the removal thereof, a desired second
magnetic plate will be produced by the permalloy metal remaining.
Description
BACKGROUND OF THE INVENTION
This invention relates to magnetic transducers for use in magnetic
recording and reproduction and to the method of making the
same.
One of the problems encountered in magnetic transducers of the
prior art is the high cost of producing them. The high cost is due
primarily to the watch-maker type of mechanical precision required
in fabricating said transducers.
The bulk of prior-art magnetic transducers are generally cubic in
form with the coil thereof being wound around at least one of the
legs of the magnetic core thereof. While this type of transducer
provides adequate performance when properly utilized, a
considerable amount of leakage flux is present between the pole
tips thereof and across the many faces of the transducer core.
Leakage flux is redundant, and the only useful flux in the
transducer is that which extends beyond the core area to the area
of the recording media with which the transducer is used. Leakage
flux, however, in this prior-art transducer is of little concern
because the core reluctance is small in comparison to the total
leakage field reluctance. The core reluctance is relatively small
in these prior-art transducers because of the large cross-sectional
area of the core, compared to the mean flux path length, and
because the permeability of the core material is high. When such
prior-art transducers are used in magnetic switching arrangements
where the information transfer rate is increased to enhance system
performance, the increased switching rate results in a reduction of
the permeability of the core material thereof, which in turn
results in an inadequate performance of the transducer.
In contrast with the prior-art transducers, the transducers of this
invention have a reduced high frequency fall-off in applications
involving increased information transfer rates. The transducers of
the instant invention also have several redundant leakage flux
circuits requiring a relatively low core reluctance. Inherently,
the core reluctance will be small in the transducers of this
invention because of a short flux path length resulting from the
miniaturization of the transducers.
The transducers of the present invention are batch fabricated
through the use of high resolution optical masks along with
advanced chemical machining and thin film deposition techniques
which provide for reduced costs of fabrication and result in
accurately formed, high performance transducers having a deposited
coil of high winding density. In addition, the batch-fabrication
techniques mentioned facilitate the production of multi-head
transducers.
SUMMARY OF THE INVENTION
The magnetic transducers of this invention include generally a
first magnetic circuit plate which is deposited on a non-magnetic
substrate. A conductor coil means, in the general shape of a
spiral, is then deposited on said first magnetic plate and said
substrate and is insulated therefrom. Over the coil means is
deposited a second magnetic circuit plate which is insulated
therefrom. The first and second magnetic circuit plates have pole
ends which are spaced apart to receive at least a portion of said
coil means therebetween and to provide the gap for the transducer.
The coil means include modifications for a single conductor coil, a
bifilar coil construction, and a multi-layered bifilar coil
construction. The invention also includes a modification in which
the first and second magnetic circuit plates lie in planes which
intersect each other.
The general method of producing the transducers of this invention
utilizes chemical machining and deposition techniques to batch
fabricate the transducers. The first magnetic circuit plate
previously mentioned is deposited on a non-magnetic substrate, and
a layer of conductor material is deposited thereover, with
insulation layers being deposited where necessary. The layer of
conductor metal is then masked to delineate the shape of the coil
required. Chemical machining techniques are then employed to etch
away the unwanted conductor material to leave the desired coil
configuration. On top of the coil there is deposited the second
magnetic circuit plate, having a pole end which is spaced from the
pole end of the first magnetic circuit plate to produce the gap for
the transducer. Additional steps, to be described later, are
required for the various modifications of transducers disclosed
herein.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a general perspective view of a magnetic transducer of
the prior art.
FIG. 2 is a plan view of one embodiment of the magnetic transducer
of this invention, showing the deposited magnetic plates and the
generally, spirally shaped coil.
FIG. 3 is generally a cross-sectional view taken along the line
3--3 of FIG. 2, showing more details of the transducer
construction.
FIG. 4 is a plan view of another embodiment of this invention,
showing a transducer having a bifilar coil construction.
FIG. 5 is generally a cross-sectional view taken along the line
5--5 of FIG. 4, showing more details of the bifilar coil
construction.
FIG. 6 is a plan view of another embodiment of this invention,
showing a plurality of transducers mounted in side-by-side relation
for multi-track operation.
FIG. 7 is a general view in perspective of one embodiment of this
invention, showing a plurality of transducers arranged on a
substrate for multi-track, read-write operation.
FIG. 8 is a general view in perspective of another embodiment of
this invention, showing a transducer with its magnetic circuit
plates lying in two different planes which are at right angles to
each other.
FIGS. 9 to 13 inclusive are cross-sectional views showing various
stages in the method of producing a bifilar transducer according to
this invention.
FIG. 14 is a plan view of another embodiment of this invention,
showing a bifilar transducer with its coils produced in a plurality
of layers.
FIG. 15 is a cross-sectional view taken along the line 15--15 of
FIG. 14, showing more details of the bifilar coil construction.
FIG. 16 is a plan view of another embodiment of this invention,
showing a transducer having a plurality of multi-layered single
turns connected together to form a single coil.
FIG. 17 is a cross-sectional view taken along the line 17--17 of
FIG. 16, showing more details of the transducer shown therein.
FIG. 18 is a cross-sectional view taken along the line 18--18 of
FIG. 16, showing more details of the transducer shown therein.
FIG. 19 is a cross-sectional view taken along the line 19--19 of
FIG. 16, showing more details of the transducer shown therein.
FIG. 20 is a cross-sectional view taken along the line 20--20 of
FIG. 16, showing more details of the transducer shown therein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
FIG. 3 shows a first embodiment of this invention, which includes
two magnetic transducers 20 and 22, which are mounted on the same
substrate 24 to form a read-write transducer. Because these
transducers 20 and 22 may be identical, a discussion of the
construction of the transducer 20 will follow.
The transducer 20 (FIGS. 2 and 3) has a generally planar
construction when compared with the prior-art transducer 26 shown
in FIG. 1. The transducer 20 includes the substrate 25 having a
recess 23 formed therein to receive the first magnetic circuit
plate 30. The top of the plate 30 (as viewed in FIG. 3) lies in the
same plane as does the surface 32 of the substrate 24, which may be
of glass. A layer of insulation 34 is then deposited on the surface
32 and the plate 30 to insulate the plate 30 from the individual
turns of the coil 36. If the magnetic circuit plate 30 is made of
ferrite material, the insulation layer 34 is generally not needed;
however, if said plate is made of permalloy material, the layer 34
is needed.
After the insulation layer 34 is deposited on the surface 32 and
the plate 30, the coil 36 is formed thereon as shown in FIGS. 2 and
3. The coil 36 is generally spiral in shape, with its innermost
turn beginning at 38 (FIG. 2) and its outermost turn ending at 40.
The techniques used for producing the various elements of the
transducer 20 will be later described in detail.
After the coil 36 is formed on the insulation layer 34 (FIG. 3), a
layer of insulation 42 is deposited on the coil 36, so as to fill
the spaces between adjacent turns thereof and to insulate the coil
from the second magnetic circuit plate 44. The plate 44, when
deposited, also has projections 46, which fill the spaces in the
pockets of insulation formed between adjacent turns of the coil 36.
The second plate 44 has a pole end 48, which is positioned opposite
the pole end 50 of the first magnetic plate 30, as shown in FIG. 3,
and the second plate 44 has a back end 52, which is in contact with
the back end 54 of the first magnetic plate. When looking at the
first and second magnetic plates 30 and 44 respectively (as viewed
in FIG. 2), it is apparent that they are offset from each other.
Being offset from each other in this manner reduces the leakage
flux across the plates 30 and 44. The reluctance of the magnetic
path in the plates 30 and 44 is lower with no gap at the back ends
54 and 52 as shown, although the transducer is operative with a gap
at said back ends.
The transducer 22 shown in FIG. 3 is identical to the transducer 20
just described; however, it is placed on the opposite side of the
substrate 24. When so positioned, the transducers 22 and 24
together provide a read-write magnetic transducer head. FIG. 6
shows a plurality of transducers 22 positioned in side-by-side
relation on a common substrate 56 for multi-track applications.
FIG. 7 shows a plurality of transducers 20 and 22 arranged on
opposite sides of a common substrate 24 to form a plurality of
read-write transducers for multi-track applications. The entire
arrangement shown in FIG. 7 may be encapsulated in plastic 57
(shown in dashed lines) to form a flying platform which may be
moved relative to the record media.
FIGS. 4 and 5 show a second modification of this invention, in
which the transducer 58 is bifilar. The method for producing this
modification and the modification shown principally in FIG. 2 is
substantially the same; however, more of the details of the method
are brought out in a discussion of the second modification.
Therefore, a detailed discussion of the method for producing the
transducer 58 of this invention will now be presented.
The transducer 58 (FIGS. 4 and 5) is produced on the substrate 60
as follows. The substrate 60 may be made of glass, as previously
explained, and a thin layer of tantalum (not shown) is R. F.
sputtered on the substrate by conventional techniques. A thin layer
of gold (not shown) is similarly sputtered on the layer of
tantalum. A conventional photo resist is then positioned over the
gold layer to delineate the shape of the recess 62 into which the
first magnetic circuit plate 64 will be positioned. The photo
resist is then exposed and developed, conventionally, leaving the
gold layer exposed for the area where the recess 62 will be formed.
The exposed gold layer is then etched away by a conventional
solution of aqua regia to expose the layer of tantalum, where the
recess 62 will be formed. The layer of tantalum is then etched away
by a conventional solution of hydrofluoric nitrate, which also
etches the glass substrate 60 to the desired depth to form the
recess 62. The tantalum and gold layers mentioned in this paragraph
are utilized to form a strong bond to the substrate 60.
After the recess 62 is formed in the substrate 60, a layer of
tantalum, followed by a layer of gold, is R. F. sputtered on the
surface of the recess 62 by the techniques already explained. The
layer of gold serves as a plating electrode for electrode
positioning a permalloy material in the recess 62, which is
overfilled. After overfilling, the excess permalloy is abraded
down, so that the top thereof (as viewed in FIG. 5) of the first
magnetic plate 64 lies in the same plane as the top surface 66 of
the substrate 60. A layer of glass insulation 68 is then R. F.
sputtered over the surface 66 and the plate 74 by conventional
techniques.
Once the layer of glass insulation 68 (FIGS. 5 and 9) is deposited
on the magnetic circuit plate 64, a layer of conductor material is
adhered thereto as follows. First, a layer of tantalum is sputtered
on the layer 68, and over the tantalum, a layer of gold is
deposited by the techniques already explained. This layer of gold
(not shown) is actually a plating electrode for the layer of
conductor material, such as copper, which is deposited thereon to
the desired thickness, the copper layer being used to form the
first coil 70, shown in FIGS. 4, 5, and 9 through 13.
The first coil 70 is produced as follows. After the layer of
conductor material is deposited on the insulation layer 68 (best
shown in FIG. 9), a photo resist mask 72 is placed over the layer
of conductor material to delineate the desired shape of the coil
70, and the chemical machining techniques already described are
used to remove the unwanted portions of conductor material, leaving
the individual turns of the coil 70 separated from one another. The
insulating layer 68 serves as a stop for said machining techniques.
The coil 70 has the general shape of a spiral, with its inner turn
74 starting near the back gap 76 (FIG. 5) of the first magnetic
plate 64, and the outer turn thereof being located near the pole
end 78 of the circuit plate 64 and ending at the terminal 80 (FIG.
4).
After the first coil 70 is deposited and formed, the photo resist
mask 72 (FIG. 9) is removed by conventional techniques, and the
transducer 58 is cleaned in preparation for depositing a second
layer 82 of glass insulation by the R. F. sputtering technique
already mentioned. After the layer 82 is deposited, a thin layer of
tantalum (not shown) is deposited thereon, which is followed by a
thin layer of gold, which is deposited thereover by said sputtering
technique. The gold layer (not shown) serves as a plating electrode
for the layer of conductor metal 84, which is deposited thereover
to the desired thickness, as shown in FIG. 11.
After the layer of conductor metal 84 is deposited, those areas 86
which are positioned above the turns of the coil 70 (as viewed in
FIG. 11) are abraded down to the level of the glass insulation 82
above said turns, so that the top of the metal layer 84 lies in the
same plane as the top of the glass layer 82, as shown in FIG. 12.
The abrasion operation produces the discrete turns of the second
coil 88, and, as can be seen from FIG. 12, the turns of the second
coil 88 are insulated from the turns of the first coil 70 and lie
between adjacent turns of the first coil 70. As can be seen from
FIG. 4, the second coil 88 has one terminal 90 near the back end of
the first magnetic circuit plate 64 and the other terminal at 92,
with the outer turn of said coil positioned near the pole end 78 of
the first magnetic plate 64.
Prior to forming the second magnetic circuit plate 94, the portion
of the transducer 58 near the back gap end 76 of the first magnetic
circuit plate 64 is cleared away by using photo resist masks (not
shown) and conventional chemical machining techniques to expose the
end 76 of the plate 64 (FIG. 5). After the back gap end 76 is
exposed, a third layer of glass insulation 96 (FIG. 5) is deposited
over the entire second coil 88 and the substrate 60 except for the
area of of the back gap end 76. A suitable mask (not shown) can be
positioned over the back gap end 76 to prevent the deposition of
the glass layer 96 thereon, and it can be removed after the layer
96 is deposited to expose the end 76.
The second magnetic circuit plate 94 (FIGS. 5 and 13) is formed as
follows. After the third layer 96 of insulation is deposited, a
thin layer of tantalum (not shown) is deposited thereover, and a
thin layer of gold (not shown) is deposited over the tantalum. The
gold layer serves as a plating electrode for depositing a layer of
desired thickness of permalloy material thereon, the permalloy
material being formed into the second magnetic circuit plate 94
through utilizing a photo resist mask and the chemical machining
techniques already described. The second magnetic circuit plate 94
has the general shape shown in FIG. 4. As shown in FIG. 4, the
plates 64 and 94 are generally "C" shaped, with their pole ends
overlapping to form the transducer gap, with portions of the first
and second coils 70 and 88, respectively, lying between said pole
ends, as better shown in FIG. 5.
FIG. 8 is a general view in perspective of another embodiment of
this invention, showing a transducer 97 having portions of its
magnetic circuit plates 99 and 101 lying in two mutually
perpendicular planes. The transducer 97 is mounted on a substrate
103 by the techniques already mentioned, with a few following
exceptions. Instead of being mounted in one plane, the first
magnetic circuit plate 99 is deposited in a recess which extends
into the mutually perpendicular facer 105 and 107 of the substrate
103, these faces joining along a common edge 109. The transducer 97
includes a coil 111, which is similar to the coil 36 (shown in FIG.
2) and which is positioned between the magnetic circuit plates 99
and 101 by the techniques already described. The circuit plate 99
has one portion lying in the face 105 and a second portion 113
lying in the face 107. The circuit plate 101 has a portion
positioned generally parallel to the face 105 and a second portion
115 lying in the face 107. The portions 113 and 115 are spaced
apart to form the transducing gap of the transducer 97, and the
tops of the portions 113 and 115 are in the same plane as the top
of the face 107 as viewed in FIG. 8. The coil 111 is provided with
terminals 117 and 119 to connect it to external circuitry. A
transducer 121, identical to the transducer 97, may be positioned
in opposed relation on the substrate 103 to provide a read/write
transducer.
FIGS. 14 and 15 show another modification of a bifilar transducer
made according to this invention; however, in this transducer 98,
each individual coil thereof is composed of a plurality of
multi-layered windings, each winding being in the general shape of
a spiral and said windings being interconnected to form said coil.
The transducer 98 is supported on a substrate 100, which may be
glass and which has recesses formed therein to receive the first
magnetic circuit plate 102 according to the techniques already
explained. An insulating layer 104 is then deposited over the
entire substrate 100 and the first plate 102. On top of the layer
104, the first winding 106 of the first conductor coil is formed as
previously explained, with this one exception. Near the back end
108 of the first plate 102, certain portions (like 110 and 112 in
FIG. 15) of the conductor material from which the winding 106 was
formed are not removed when the winding 106 is formed. These
portions 110 and 112 are isolated from the winding 106 and are used
merely as fillers to facilitate the construction of the transducer
98, as will be explained later. The beginning of the first winding
of the first coil starts at 114 and ends at 116 (FIG. 14).
As can best be seen in FIG. 14, the first winding 118 of the second
coil of the transducer starts at 120 and ends at 122. The
individual turns of the winding 118 are located slightly above and
between the individual turns of the winding 106 of the first coil,
as shown in FIG. 15, by the techniques already described in
relation to the embodiment shown in FIGS. 4,5, and 9 through 13
inclusive. The winding 118 is insulated from the winding 106 by a
layer 123 of glass insulation. The top of the winding 118 and the
top of the insulation layer 123 lie in the same plane, over which
another layer 125 of glass insulation is deposited.
After the layer 125 of glass insulation is deposited, a second
winding 124 of the first coil of the transducer 98 is formed
thereon, as shown in FIGS. 14 and 15, with the filler portions 126
and 128 (FIG. 15) being formed at the same time. After the second
winding 124 is formed, it is insulated by a layer 130 of glass
insulation. The winding 124 begins at 132 (FIG. 14) and ends at
134.
After the second winding 124 of the first coil of the transducer 98
is formed, the second winding 136 of the second coil is formed on
the layer 130 of glass insulation already deposited by the
techniques already described. The top of the winding 136 lies in
the same plane as the top of the insulation layer 130, as viewed in
FIG. 15, and another layer of glass insulation 138 is deposited
over this plane. The winding 136 starts at 140 and ends at 142
(FIG. 14) and has the generally spiral shape shown.
The third winding 144 of the first coil and the third winding 146
of the second coil (FIGS. 14 and 15) are formed in the same manner
as the other windings of the transducer 98. The winding 144 starts
at 148 and ends at 150 (FIG. 14). The winding 146 starts at 152 and
ends at 154. Both windings 144 and 146 are generally spiral in
shape and generally overlie the other windings of their respective
coils, and are insulated from each other by a layer 156 of glass
insulation. The filler portions 158 and 160 are formed at the same
time that the winding 144 is formed. The top of the winding 146
lies in the same plane as the top of the layer 156 of glass
insulation, and another layer 162 of glass insulation is deposited
over this plane.
The fourth winding 168 of the first coil and the fourth winding 170
of the second coil of the transducer 98, as shown in FIGS. 14 and
15, are formed by the same techniques as the other windings
thereof, and the windings 168 and 170 are insulated from each other
by the layer 172 of glass. The fourth winding 168 starts at 174 and
ends at 176 (FIG. 14), and the fourth winding 170 starts at 178 and
ends at 180, both said windings having the generally spiral shape
shown. The filler portion 182 (FIG. 14) is formed when the winding
168 is formed.
After the windings 168 and 170 are formed, a layer 184 of glass is
deposited over all the safe windings of the transducer 98, as shown
in FIG. 15. The filler portions 110, 126, 158, and 182, previously
mentioned, provide a gradual slope for better supporting the back
end of the second magnetic circuit plate 186 on the layer 184 of
insulation.
In order to connect the individual windings of the first and second
coils of the bifilar transducer 98 shown in FIGS. 14 and 15, the
following construction is used. The individual windings
(106,124,144, and 168) of the first coil are connected together as
follows. A terminal conductor strip 188 is connected to the
starting end 114 of the first winding, as shown in FIG. 14. In
order to expose the end 114 prior to securing the strip 188
thereto, it was necessary to take steps to remove the various
layers of glass insulation which may have been deposited thereover
during the process of producing the transducer 98. These steps are
conventional and need not be recited here in detail. The remaining
end 116 of the first winding 106, after being exposed, is connected
to the beginning end 132 of the second winding 124 by the conductor
strip 190, which may be deposited by conventional techniques. The
remaining end 134 of the second winding 124 is connected to the
beginning end 148 of the third winding 144 by the conductor strip
192. In a similar manner, the remaining end 150 of the third
winding 144 is connected to the beginning end 174 of the fourth
winding 168 by the conductor strip 194. The remaining end 176 of
the fourth winding 168 has a terminal conductor strip 196 connected
thereto, as shown in FIG. 14.
The individual windings (118,136, 146, and 170) of the second coil
of the bifilar transducer 98 are connected to form one continuous
coil as follows. The first winding 118 has a terminal conductor
strip 198 connected to the beginning end 120 thereof, as shown in
FIG. 14. The ends of the several windings of said second coil are
exposed by removing any insulation layers which may be present
thereover, as previously explained. The remaining end 122 of the
first winding 118 is connected to the beginning end 140 of the
second winding 136 by the conductor strip 200. The remaining end
142 of the second winding 136 is connected to the beginning end 142
of the third winding 146 by the conductor strip 202. In a similar
manner, the remaining end 152 of the third winding 146 is connected
to the beginning end 178 of the fourth winding 170 by the conductor
strip 204. The remaining end 180 of the fourth winding 146 has a
terminal conductor strip 206 connected thereto as shown.
After the first and second coils of the bifilar transducer 98 are
connected as just explained, a protective layer 208 (FIG. 15) of
glass insulation may be deposited thereover to protect the
individual windings and conductor strips. The second magnetic
circuit plate 186 is then formed on the transducer 98 by the
techniques already explained. As is apparent from FIG. 15, portions
of the first and second coils lie between the first and second
magnetic circuit plates 102 and 186, respectively, and the pole
ends 208 and 210, respectively, thereof are spaced apart to produce
the transducer gap. The back ends 108 and 212 of the plates 102 and
186, respectively, may be joined as shown in FIG. 15, or they may
be spaced apart according to design requirements.
FIGS. 16 through 20 show another transducer 214 of this invention;
however, this transducer has a single coil, which is made of a
plurality of multi-layered, single-turn conductor windings as
follows. The transducer 214 is supported on a substrate 216, which
may be glass, and the substrate has recesses formed therein into
which the first magnetic circuit plate 218 (having a pole end 220
and a back end 222) is positioned and formed according to the
techniques previously described. A thin planar layer 224, of glass
insulation, is then deposited over said substrate 216 and circuit
plate 218. The first turn 226 is formed on the glass layer 224 and
has terminal ends 228 and 230 and the general shape shown in FIG.
16. On top of the first turn 226, there is deposited a second layer
232 of glass insulation. The second turn 234 is formed on the
second layer 232 and has the general shape best shown in FIG. 16.
The second turn 234 of the coil has one end 236 thereof connected
to the end 230 of the first turn 226, and its other end terminates
at 238. It is apparent from FIG. 16 that the individual turns (226,
234) of the coil, when connected in series, conform to the general
shape of a spiral.
After the second turn 234 of the transducer 214 is formed, a layer
240 of glass insulation is deposited thereover, and the third turn
242 is then formed on the layer 240 (FIGS. 16, 17, 18, 19, and 20).
The turn 242 has the general shape shown in FIG. 16 and has one end
244 connected to the end 238 of the second turn 244, and the
remaining end thereof terminates at 246. On top of the third turn
242 is deposited a layer 248 of glass insulation, over which is
deposited the fourth turn 250 of the coil. The fourth turn 250 has
one end 252 connected to the end 246 of the turn 242 and its other
end terminating at 254. A suitable connecting terminal 256 (FIG.
16) is connected to the end 254 of the fourth turn 250, and a
similar terminal 258 is connected to the beginning end 228 of the
first turn 226 to enable the transducer to be connected to external
circuitry. A layer 260 of glass insulation is then deposited over
the fourth turn 250.
The second magnetic circuit plate 262 is then formed on the layer
260 according to the techniques already described. The plate 262
has a pole end 264 (best shown in FIG. 17) and a back gap end 266.
The pole end 264 is spaced from the pole end 220 of the first plate
218 to form the gap of the transducer 214, with portions of its
coil positioned between said pole ends. The back ends 222 and 266
of the plates 218 and 262, respectively (FIG. 17), may be connected
as shown, or they may be spaced apart according to design
requirements.
While the forms of the invention shown and described herein are
admirably adapted to fulfill the requirements primarily stated, it
is to be understood that it is not intended to confine the
invention to the forms or embodiments disclosed herein, for it is
susceptible of embodiment in various other forms.
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