Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
This invention pertains in general to electromagnetic ~ :
transducers, and, more particularly, to transducers for converting
electrical energy into movements or sounds, and/or movements or
sounds into electrical energy.
Electromagnetic transducers for converting movements
or forces (such as sound) into electrical energy, or for converting
electrical energy into movements or forces (such as sound), include
an electrically-conductive movable element (armature) and a sta-
tionary magnetic element (stator) for applying magnetic flux thereto. -
Forces applied to the armature, as a result of magnetic flux vari-
ations, convert electrical energy into movements, and in the case
of a speaker, soundO Alternately, physical forces on the armature ~ ;
(such as in the case of microphones) oreate changes in the magnetic
flux and generate electrical signals due to the movement of the ` -
. ,~ . -~ . .
armature. ` -
In the prior art speakers, the armature is located in a ; ~ `
magnetic field and is generally secured near the center of the
diaphragm (speaker cone). The armature usually includes a coil that
,;,: ~
receives the electrical signals to be converted into soundu The high
frequencies are generated on the center of the diaphragm while the
intermediate and base frequencies are generated over the entire `~
,,
surface of the coneO Such an arrangement has poor efficiency at ~ -
high frequencies and, as a result, usually has a degraded high fre~
quency response.
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. . .
In order to obtain an improved high-frequency re~ponse,
a small "tweeter" type speaker cone has been mounted within the
center of the large speaker cone to get greater power output at
high frequencies. Other arrangements include separate base and
tweeter speakerss electrically interconnected with cross-over
networks to provide an overall high-fidelity response. In either
case, great care must be taken in the design and manufacture ;~
thereof so that the frequency response of the combination provides
a continuous transition between high and low frequency ranges, or
else certain frequencies will be attenuated, or peaked, resulting in
an undesirable frequency response.
The present day speakers use a magnetic structure that
is cup-shaped, with an inner pole piece extending through the center
of the opening. The open edge of the cup forms one magnetic poLe,
while the free end of the inner pole piece forms the other magnetic
pole. The air gap between the pole pieces is reduced to increase
the concentration of magnetic flux. In order to achieve greater
magnetic flux density and higher power output in the high-frequency
range, the permanent magnets used in the magnetic assembly of the
prior art are increased in size so that the speakers are very often
rated in "pounds" of magnet (i. e., two pound magnet speaker, etc. ).
This increased size and weight add further structural requirements
to the speaker housing so that the speaker will not warp. These
requirements add to the cost of the speaker. In addition, there is
a point of diminishing returns wherein added incremental sizes of
... , , . , ., ,. . . ~ .
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magnets will produce diminishing amounts of additional power output
at the high-frequency range. Furthermore, since it is the strength
of the magnetic flux density through the armature that determines
the efficiency and the output of the speaker, the size of the magnet
(in pounds) may be misleading in cases where poor magnetic flux
coupling is provided as a result of poor design.
In order to reduce the size and weight of the magnetic
structure of speakers, various peripherally-driven transducers ;
were designed, such as, for example, those disclosed in the U. S.
10 Patents Nos. 2, 520, 646 and 2, 535, 757, issued on August 29, 1950, `
and December 26, 1950, respectively, to E. E. Moth and J. J. ~` 9
Root, respectively. These transducers include armature plates
secured to the periphery of the diaphragm and a combined perma-
nent magnettand electromagnetic stator arrangement to impart
varying magnetic flux to the armature. Such an arrangement pro-
vides sufficient power and fidelity for telephone purposes as set
forth in U. S. Patent No. 2, 520, 646. The arrangement disclosed
in U. S. Patent No. 2, 537, 757 may have provided sufficient fidelity
over twenty years ago, but would probably be considered poor in
20 today's standards. The limited fidelity results from the inherent
disadvantages in driving a speaker by modulating the magnetic flux
of the stator through the use of a stator coil. The coil required to
provide the necessary flux variation introduces a large reactive
impedance in the circuit that Limits its overaLl frequency response.
It was found that greater efficiency and higher frequency responses
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would be achieved with the coil mounted on the movable armature
as in most present day speakers.
Peripherally-driven electroacoustic transducers have ;
been developed wherein the cup-shaped magnetic speaker structure
of the prior art is used along with a coiL attached to the peripheral
edge of a diaphragm extending into the air gap. Because of the
massive magnetic structure invoLved (wherein essentially the
entire central portion of the cup-shaped magnet is formed
speaker iron), the arrangement, as a practical matter, is limited
in size, for use as a microphone, or as a tweeter speaker, Any
increase in size to provide a good base frequency response would
be prohibitive because of weight and cost.
Electromagnetic transducers are presently being used
in control apparatus, such as a pneumatic controller (for converting
electrical signals into pressure, or pressure into electrical signals)
that employ the same cup-shaped magnetic structure as presently i
used in speakers to drive a ringishaped armature. Because of the
weight and size of such a magnetic structure, and the lack of avail-
able space, the forces, or electrical signals, produced by such
transducers are rather limited. As a result, intricate lever ~
mechanisms must be used with such transducers to provide the -
desired conversion and hence add to the expense of such apparatus.
It would be highly desirable if a transducer could produce the forces,
or electrical signals, needed for such control apparatus without
requiring the massive and heavy magnetic structure, particularly
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so if greater forces or higher amplitude electrical signals couLd be
produce(d without requiring additional space,
In addition to the foregoing, the electroacoustic trans-
ducers of the prior art are highly directional. Most of the acoustic
energy generated by the electroacoustic devices is directed in a
cone-shaped patterrl fromthe center of the diaphragm. If an
omnidirectional speaker arrangement is desired, a large number
of speakers are required to be mounted in some sort of directional
array so that the combined effect of all the speakers provides the
10 desired affect. Such an arrangement is quite expensive, requiring
many speakers.
It is therefore an object of this invention to provide a ~ `
new and improved electromagnetic transducer for converting
electrical energy into movement, and/or converting movement -
into electrical energy,
It is also an object of this invention to provide a new and
improved electromagnetic transducer that can function as either a
speaker, a microphone, or a control device.
It is still a further object of this invention to provide a
20 new and improved electroacoustic transducer that produces
increased power output at the high frequency range.
It is also an object of this invention to provide a new and
irnproved electroacoustic transducer that is relatively light weight ~-
and can produce a wide range of frequenciesJ including the high,
intermediate and low-frequency ranges with a single diaphragm.
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It is another object of the present invention to
provide a new and improved electroacoustic transducer that is
omnidirectional in its sound propagation.
BRIEF DESCRIPTION OF T'HE INVENTION
Thus the present invention provides an electro-
acoustic transducer comprising: a diaphragm; tubular shaped
current conduction means secured to said diaphra~m along a
peripheral edge thereof; concentric tubular shaped open ended
magnetic flux translative elements providing at least one
tubular shaped air gap therebetween for receiving said current
conduction means; and permanent magnet means mounted between
said elements so that said elements concentrate magnetic flux ''
from said permanent magnet means through said air gap.
In certain embodiments the transducer of the
invention includes an elongated rim-shaped magnetic means
having poles of opposite magnetic polarity providing an air ; -
gap that has the same general elongated configuration as the
magnetis means. Current conduction means, such as, for
example, a coil, having the s~me general configuration as ~ ','
the air gap, is positioned to extend within the air gap and is ,
responsive to the current flow therethrough to produce move-
ments, or is responsive to a force applied thereto to generate
electrical signals.
In the case of an electroacoustic transducer
embodying the invention, the current conduction means is
secured to a diaphragm adjacent the peripheral edge thereof -~-
so that forces are applied to, or received from, the
diaphragm periphery. ,
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l~V63~
In accordance with an embodiment of the invention,
the magnetic means provides an air gap that has an elongated
shape. The air gap can be continuous or discontinuous.
The current conduction means has the same elongated shape
as the air gap and is mounted to extend within the air gap
for movements transverse the flow of magnetic flux. The
magnetic means, the air gap, and the current conduction
means can have any regular tubular shape such as, for
example, annular, polygon, etc., or can have a serpentine
shape.
In another embodiment the invention provides a -
transducer comprising: a pair of tubular shaped magnetic
flux translative elements mounted in a substnatially con~
centric arrangement for providing therebetween at least one
tubular shaped air gap, one af said pair of elements being ~-
open at both ends while the other one of said pair of
elements being open at at least one end, and permanent
magnetic means mounted between said pair of elements for
providing magnetic flux flow through said elements and said
air ~ap current conduction means having a shape to fit ~ ~within said air gap, and means for mounting said current ;conduction means so that at least a portion thereof extends
within said air gap so that in response to a current flow
through said current conduction means said current conduction ~ ~;means moves within said air gap.
In another embodiment the present invention provides
an electroacoustic transducer comprising: a first metallic
element having an open ended tubular shape; a second
metallic element, having substantially the same tubular
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shape as said first element but having smaller dimensions
so that the second element is posit:ioned in a substantially
concentric relation with said first element; permanent
magnet means mounted between the first and second elements
and adjacent one end of each of said elements so that the
other end of each of said first and second elements define
an air gap therebetween and wherein magnetic flux flows
from said permanent magnet means through a path including
said elements and said air gap; current conduction means,
having substantially the same configuration as said air gap, ~ :;
mounted for movement within said air gap, and diaphragm
means, having substantially the same geometric configuration
as the area enclosed by said current conduction means,
extending across said current conduction means and attached
thereto. ~ .
In another embodiment the present invention provides
an electroacoustic transducer comprising: a stator including
a plurality of tubular shaped open ended magnetic flux
translative elements positioned in a substantially concentric
relation for providing two separate air gaps that have sub-
stantially the same tubular shape as said elements and are
located adjacent and parallel to each other with a separation
in between, and permanent magnet means mounted between said
elements to provide magnetic flux flow through said elements
and said air gaps; current conduction means, having sub-
stantially the same configuration as said air gaps; means
for mounting said current conduction means so that said
current conduction means extends within both air gaps for -
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free movement, in response to a current flow therethrough,
in a direction transverse the direction of magnetic flux
flow through said air gaps, and diaphragm means connected
to said current conduction means adjacent the peripheral
edge of the diaphragm means enclosing at least the area
defined by the shape of the current conduction means and
extending through said separation between said air gaps.
In another embodiment the present invention provides
an electromagnetic transducer comprising: stator means
including first and second tubular shaped open ended ~ :
magnetic flux translative elements, the second element
having smaller dimensions than the first element so that
the second element is positioned in a substantially con- -
centric relation within the second element, first and second : -
tubular shaped pole pieces extending from said first and `~ ~!
second elements, respectively, and adjacent one end thereof .~
so that said first and second pole pieces define a tubular ~. .
shaped air gap therebetween,and permanent magnet means
mounted between said first and second elements with opposite ; .
poles facing separate ones of first and second elements
so that magnetic flux flows from said permanent magnet
means through a path including the first and second.:elements
and said air gap, the cross-sectional area of the permanent
magnet means, transverse the direction of magnetic flux
flow, is substantially greater than the crass-sectional
area of the air gap, transverse the direction of magnetic ~ :
flux flow, and current conduction means, having substantially .. ::
. .
the same tubular shape as said air gap, movably mounted in - ~
said air gap. ` .
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Since the magnetic means has a tubular rim-type shape,
it provides a light-weight, low-cost, means for providing an elongated
air gap having high density magnetic flux flowing therethrough. The
combination of the elongated air gap and the current conduction means
located thereint provides for an arrangement wherein the diaphragm
is driven at its outer extremities ~peripherally), resulting in a sub-
stantially larger working area for the generation of high frequencies
than with the conventional center-driven diaphragm and thereby
greatly increasing the efficiency of the speaker. Furthermore,
10 since the high frequencies are generated along the peripheral edge
of the diaphragm, depending upon the diaphragm shape, the speaker
can provide an on~nidirectional high-frequency pattern of sound - `
propagation,
The electromagnetic transd~lcer can be built with two units
back-to-back for use as a stereo speaker. In addition to the fore- -
going, the diaphragm can be made of clear plastic, or glass, to
provide a transparent center portion. ~ `
The electromagnetic transducer can also include two
parallel air gaps adjacent each other with the cùrrent conduction
20 means (arrnature) extending Lnto both air gaps for providing further
magnetic flux for driving the armature.
Alternately, the electromagnetic transducer can include
two air gaps located in tandem with separate current conduction ~
~ .' ~, ., '.
means located in each air gap. With such an arrangement, such
current conductions means (armature) can drive separate elements,
or can be interconnected in tandem to drive a single element.
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BP~IEF DESCRIPTION OF THE: DRAV~rlNGS
. . _
Figure 1 is a perspective view of an embodiment of an -
electromagnetic transducer, including the invention, having a ~ ~,
round or disc-shaped configuration;
Figure 2 is a front view of the electromagnetic trans-
ducer of Figure 1 with the diaphragm removed;
Figure 3 is a side view of the diaphragm of t~,f~ec'~ro-
magnetic tra~s~oer;~ioiFigure 1;
Figure 4 is a front view of the diaphragm of Figure 3;
Figure 5 is a side view of the electromagnetic transducer ~ ;
of Figure 1;
Figure 6 Is a sectional view of the electromagnetic trans- ~;
ducer of Figure 1 taken along the lines 6-6;
Figure 7 is a sectional view of the air gap portion of the
electromagnetic transducer of Figure 1 including a pair of "()^7'
rings for maintaining the diaphragm within the air gap; :
Figure 8 is a sectional view of a portion of the electro-
magnetic transducer of Figure 1 taken along the lines 8-8 and
using a flexible ring for maintaining the diaphragm within the air
20 gap;
Figure 9 is a sectional view of the electromagnetic
transducer of Figure 1 taken along lines 9-9 of Figure 5;
Figure 10 is a sectional view of the electromagnetic ~-.. - -
transducer of Figure 1 taken along lines 10-10 of Figure 5, with
the diaphragm removed;
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37~a~
Figure 11 is an enlarged view of a portion of the diaphragm
of the electromagnetic transducer of Figure 1 taken along Lines 11-11
of Figure 3; ~
Figure 12 is a perspective vi.ew of a second embodiment of
an electromagnetic transducer, including the ir~vention, having a
generally rectangular shape;
Figure 13 is a perspective view of a third embodiment of
an electromagnetic transducer, including the invention, having a
generally triangular shape;
Figure 14 is a fourth embodiment of an electromagnetic
transducer, including the invention, including two transducers back-
to-back for stereo operation; ~:
Figure 15 is a sectional view of a fifth embodiment of an
electromagnetic transducer, including the invention, wherein the :.
armature extends within two air gaps; : ;
Figure 16 is a front view of the annular-shaped electro-
magnetic transducer of Figure 1 with the diaphragm removed and
with the air gap separated into sections;
Figure 17 is a side view of a diaphragm for the elecit~o- :
20 magnetic transducer of Figure 16 having segments removed from
the edge thereof to fit within the sectorized air gap and having a
continuous coil wound around the edge thereof; :
Figure 18 is a modification of the diaphragm of Figure 17
having a plurality of separate coils secured to the peripheral edge
of the diaphragm; ~ :
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Figure 19 is a sectional view of a sixth embodiment of an
electromagnetic transducer, including the invention, having two
armatures that can function as a control device;
Figure 20 is a side ~riew oE the electromagnetic trans-
ducer of Figure 19; and ~ !
Figure 21 is a plane view of a magnetic structure for an
electromagnetic transducer, including the invention, wherein the
air gap has a "U" shaped serpentine configuration.
.
DETAILED DESCRIPTION OF THE INVENTION
An electromagnetic transducer including the invention has
a magnetic structure with an ~longat~dl continuous or discontinuous
air gap. The magnetic structure defines a closed curve (i. e., ~; '
outlines a closed geometric configuration) and has a hollow rim- ~;
type shape, such as the annular or tubular shape of a ring, or the
straight-sided tukular shape of an outline of a polygon, such as a -
rectangle, a triangle, or a serpentine configuration. The air gap
has the same general shape as the magnetic structure. ~ ,
The electromagnetic transducers of Figures 1-18 are
described in the context of electroacoustic transducers for con-
verting electrical signals into sounds ~speakers) and/or for
converting sounds into electrical energy (microphones). In all
such cases, the armature is connected to the periphery of a dia~
phragm to apply forces thereto, or to receive forces therefrom.
With a diaphragm as an input or output device, the magnetic ar na~
structure takes on a regular tubular hollow form (annular, poLygon,
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etc. ) to apply or receive forces Erom the periphery of the diaphragm,
However, it is to be un derstood that the electromagnetic transducer
of Figures 1 - 18 also can function as a force transducer for use in
a variety of controL apparatus, wherein the diaphragm is removed
and some sort of coupling device, such as, for example, a lever
system, is secured to the armature to provide îor the transLation
of the armature movement. The Figures 19 - 21 are described in
the context of specialized control system transducers wherein dia- ;
phragms are not required and the magnetic structure and air gap
10 can take more the complex serpentine tubular forms. By tubular
shaped we mean any rim-type shape structure wherein an empty or
hollow space is encompassed or surrounded by the rim-shaped -
structure.
The embodiment of the electroacoustic transducer illus-
trated in Figures 1 - 11 includes an annular or tubular-shaped
housing 10, having a magnetic structure that provides a tubular
ring-shaped air gap 120 The air gap 12 provides the magnetic flux
for producing the transducer action~ A diaphragm 14, having the ~ ;
general form of the geometric configuration enclosed by the air
20 gap 12, is mounted with the peripheral edge 30 thereof extending
within the air gap 12. The diaphragm 14 has the general form of a
disk, with a slight convex shape, and with the peripheral edge 30 ;
thereof folded over to extend transverse (generally normal) to the
plane of the diaphragm 14 and into the air gap 12. The edge 30 of
the diaphragm 14 follows the same general ring shape as that of
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the air gap 12. Current conduction means, such as a coil 18, is
attached to the diaphragm 14 adjacent to the peripheral edge 30
~as illustrated in Figures 3 and 4) so that when the edge 30 of the
diaphragm 14 is positioned in the air gap 12, the current conduc-
tion means also extends within the air gapO The current conduction
means or coil 16 i9 wound in the form of a ring, the same general
tubular shape configuration as the air gap 12.
The housing 10 of the electroacoustic transducer is :`
formed with an inner metallic annular-shaped element or ring 18,
10 and an outer annular shaped element or ring 20. Magnetic means
22 is mounted between the inner and outer rings 18 and 2û, with
the opposite poles thereof positioned adjacent to the inner and ~ :~
outer rings 18 and 20 as illustrated in Figures 6, 8, and 9. The .
magnetic means 22 can be a solid continuous or ring-type ceramic,
or rare earth magnet, or can comprise a plurality of ceramic
magnets mounted adjacent to each other as (illustrated in Fig. 9)
to provide the overall affect of a continu,ous annular-shaped magnet. `;. :.
The width of the magnets 22, as viewed in :Figures 6 and 8 is less
than the width of the rings 18 and 20. The magnets 22 are mounted
... . . . .
20 adjacent an end of the rings 18 and 20, opposite the end that extends
toward the diaphragm 14. A pair of annular or ring-shaped pole ~
pieces 24 and 26 are mounted adjacent the end of the inner and outer ~ ~ :
rings 18 and 20, opposite the end adjacent the magnets 22. The air
.. ;~ .
space between the pole pieces 24 and 26 defines the annular or ring-
shaped air gap 12 through which magnetic flux flows. Since the two
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6;~7~3
rings 1~ and 20 cover the entire ends of the magnets 22, substantiaLly
all of the magnetic flux from the magnets flows through the easy fLux
path (the path of low impedance) which extencls from the magnets
through a ring, through a pole piece, through the air gap, through
the other pole piece, and back through the other ring to the magnetæ.
The effect of the two r.ings~8 and 20 and the two pole pieces 24 and
26 is to concentrate substantially all of the magnetic flux from the
magnets 22 across the air gap 12, The magnetic flux radiating
from the large cross-sectional area of the magnets 22 is concen-
trated into a much smaller cross-sectional area of the air gap 12 `
thereby providing an extremely concentrated magnetic flux in the
air gap.
As illustrated in Figures 3, 4, and 11, the current con-
duction means, or coil 16, is wound around the peripheral edge 30
of the diaphragm 14 in a direction parallel to the edge, The coil 16
is fastened by cement to the diaphragm 14 adjacent the edge 30.
As previously mentioned, the folded end 30 of the diaphragm 14 and
the coil 16 have substantially the same annular-shaped configuration
as the air gap 12, so that the diaphragm end 30, and the coil 16
20 mounted thereon, are inserted into the air gap 12, The coil 16 and
the end 30 of the diaphragm 14 are loosely mounted in the air gap 12
for free movement back and forth in a direction transverse the flow
of magnetic flux, as illustrated by the arrows 36.
The diaphragm 14 and the coil 16 can be held in place in
the air gap 12 by the use of a flexible rubber cem~nt. Alternatively,
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the coil 16 and the diaphragm 14 can be held in place by a pair of
"O" rings 34 as illustrated in Figure 7. The "O" rings 34 have a
cross-sectional diameter in the order of one-ilalE the diameter of
the air gap 12 and extend around the entire length thereof. The
"O" rings 34 have a thickness so that when the coil 16 and the clia-
phragm end are placed thereon, a loose fit is accomplished so that
the coil 16 and the diaphragm 14 are free to move back and forth
transverse the magnetic field. Another method of maintaining the
coil16 and the end of the diaphr agm 14 within the air gap 12 is
illustrated in Figure 8. A plastic ring 35 is attached to the outer
annular member 20 to extend beyond the end thereof. A very thin
nylon cloth ring 33 is attached at one end to the plastic ring 35 and
at the other end to the diaphragm 14.
In response to a force applie d to the diaphragm 14, an ~ ~
electrical signal is generated across the coil leads 3B wherein the - ~ ~ -
electroacoustic transducer functions as a pickup device, such as
a microphoneO Alternatively, in response to a current flow through
the coil 16, the diaphragm 14 is forced to move along the direction
of the arrows 36 to function as a receiver, or as a speaker. The
movement of a coil within a magnetic flux as a result of a physical
force applied thereto for producing electricity, or the movement of
a coil with a magnetic flux in response to a current flow there~
through for producing sound, are well-known phenomena and do not
require any further explanation. Hence, as can be seen in the
electromagnetic transducer of the invention, the electromotive ~ `
~:,
force is applied along the peripheral edge of the diaphragm 14 thereby
providing a large working area for the transLation of forces to and
from the diaphragm 14,
It should be understood that the electromagnetic trans~
ducer of the invention can have any type of overall configuration.
For example, the air gap 12 can have the tubular form of a polygon .
rather than the ring shape, such as the rectangular tubular conflg-
uration illustrated in Figure 12, or the triangular tubuLar ~`~
configuration illustrated in Figure 13, For the purposes of simpli- ~ -
fying the explanation of the electromagnetic transducers of .
Figures 12 and 13, the same elements in Figures 12 and 13 as in ~ ~ -
Figures 1 - 11 are designated by the same reference numerals,
aLthough the configuration or shape of the elements differ. As : . -
illustrated in Figures 12 and 13, the inner and outer metallic
elements, and the magnetic means mounted therebetween (not shown), ~ ~ -
define an air gap 12 having the tubular configuration of the outline of
a polygon (such as the rectangle of Figure 12 or the triangle of .l . :
Figure 13). In each of the embodiments of Figures 12 and 13, the
peripheral edge of the diaphragm 14 is bent to form an angle trans- ~ :
verse to the plane of the diaphragm 14 and has the same general ~
:.-, . .
shape or configuration as the air gap 12 (rectangle, triangle, etc~
In addition, the current conduction means or coil 16 (not shown) is
attached adjacent to the peripheral edge of the diaphragm 14 and
extends within the air gap 12 (In a manner as previously discussed
with regard to Figures 1 - 11). As in the case of the transducer of
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Figures 1 - 11, the diaphragm 14 of Figures 12 and 13, and the
current conduction means attached thereto, are free to move back -
and forth within the air gap 12 in a direction transverse to the flow
of magnetic flux, in the same manner as discussed above, and
therefore is free to function as either a microphone or as a
speaker. ;
Figure 14 illustrates two electromagnetic transducers '
of the type illustrated in Figures 1 - 11 positioned back-to-back to ~
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provide a double speaker configuration for producing a stereo
10 effect. When the two electromagnetic transducers 10A and 10B
are mounted adjacent to each other as illustrated in Figure 12, a
partition 44 is positioned between the two transducers (along the -
side opposite that having the diaphragms 14A and 14B) to prevent
the interPerence of sound wave therebetween. If a more prominent
stereo effect is desired, the transducers 10A and 10B can be
separated from each other depending upon the distance between the
listener and the transducers. ~
The air gap 12 of Figures 1 - 15 is illustrated as having ;
the shape of a continuous closed curve. If, for some reason, the
20 continuous air gap is not desired, such as, for example, because
of the use of very thin rings 18 and 20 for cost reduction or weight `
reduction purposes, the air gap 12 can be broken into a plurality of
sectors by the non-metallic (plastic) separators 40 to strengthen
the structure (as illustrated in Figure 16). In this case, the dia-
phragm 14 is fitted with grooves or slots 42, one for each of the
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separators 40 (Figure 17) so that the peripheral edge of the diaphragm
14 has the same configuration as the air gap and fits within the air
gap. The coil 16 is wound around the p~eripheral edge 30 with portions
thereof bent to bypass the slots 42. It should be understood that the
size of the separators 40 can be increased in si~e substantially over
that illustrated in Figure 16 to provide a plurality of separat~rair
gaps and the electromagnetic transducer will still function, but less
effectively.
If, for some reason, a plurality of coils are desirable
10 instead of a single coil, a pLurality of coils 16A, 16~, etc., (Fig. 18)
can be located along the peripheral edge 30 in an arrangement so
that when the diaphragm 14 is located ~ithin the air gap 12 only one-
half the coils 16A and 16B (separated by the dashed line 46) extend
within the air gap. ~ -
In the emb odiment of the electromagnetic transducer of
the invention of Figure 15, rather than having the air gap extending
outward as illustrated in Figures 1-14 and 16-2OJ the transducer of
Figure 15 includes two air gaps 50 and 52, both extending inward. :
The air gap 50 is part of the magnetic flux path for the annular-
20 shaped magnet 60, the metallic ring 56, and the annular pole piece
58. The air gap 52 is part of the magnetic flux path for the magnet
62, the ring 56, and the pole piece 64. The pole pieces 58 and 64
are bent inward at the free ends to extend toward the ring 56 to
reduce the size of the air gaps 50 and 52. A flat planar disk-shaped
diaphragm 58 is fastened along its peripheral edge to an insulating
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ring 70. The insulating ring 70 is fastened to the metallic ring 56
by a thin nylon cloth ring 72. A coil 74 is wound around the insu-
lating ring 70 in a manner so that the coil 74 extends into both of
the air gaps 50 and 52. The direction of the magnetic flux through
the air gaps 50 and 52 is of a polarity, and the coil 74 is wound 90
that the current flow in the coil produces an additive force in the
air gaps 50 and 52 to move the coil and the diaphragm 14 in the
direction of the arrows 76. Although the transducer of ~igure 15
is described as being annular or ring-shaped, it is to be under-
stood that the transducer can have any tubular-type form, such as ;
polygon shapes (triangular, rectangularJ etc. ).
The tubu3lar-shapedJ hollow~ magnetic structure pro- ~ -
viding an elongated air gap 12 (in the form of a closed curve, or
in sections of a closed curve) in combination with the diaphragm 14 ; --
(having the edge thereof of the same stlape as the air gap 12)
including a coil along its peripheral edge (formed to fit within che
air gap 12) provides an arrangement wherein electromotive forces
are transmitted between the pole pieces 24 and 26 and the diaphragm
14 over the entire, or portions of, t~Ze peripheral edge of the
20 diaphragm. The combination of the peripheral edge of the diaphragm
and the coil attached thereto provides a large working area, wherein
the entire~ or a large part of the peripheral edge 30 is exposed to the
electromotive forces. This provides a highly-efficient arrangement,
particularly at the high-frequency range. In the case wherein the
transducer of the invention functions as a speaker, the high-frequency
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signals are generated along the entire circumference or peripheral
edge of the diaphragm 14, thereby providing a substantially greater
transducing area for the generation of high frequencies. As a
result, the single diaphragm 14, in an electroacoustic transducer
including the invention, provides a wide r ange of frequencies wherein
~ . .
the effectîve power output at the high-frequency range approaches ~ ~
that of the lower-frequency ranges. There is no need for "tweeter" ;~ ;;
speakers to accentuate the high frequencies~ The entire broad
range of audio frequencies are generated by the single diaphragm 14. ~
In addition to the foregoing, it should be noted that since the high `
frequencies are generated at the circurmference or peripheral edge
30 of the diaphragm 14, the propagation of the high-frequency signals - -
,, . - .
appears to be in all directions, essentially providing the effect of an
omnidirectional speaker. This is because the direction of music and -
sound is primarily detected by the human ear from the propagation of
the high-frequency sounds. The propagation pattern of the high ;
frequencies from the electroacoustic transducer including the ~ `
invention approaches a pattern of 360 and therefore it is very diffi~
cult for the listener to detect the source of the sound.
In addition to the foregoing, the diaphragm 14 of the
electroacoustic transducer including the invention can be made of a
variety of thin, fairly-rigid materials, such as, for example, clear
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plastic or glass. VVith a clear plastic or glass diaphragm, the
electroacoustic transducer appears as a hollow ring, or polygon~
shaped tube, with a clear "see-through" center. Eence, various
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novelty items can be included within the speaker, such as, for
example, lighting or color effects wherein the intensity of, and a - ~ -
frequency of, illumination and color thereof i9 a function of the `~
amplitude and frequency of the sound being produced (psychedelic
effects). Furthermore, the embodiment of the transducer of
Figure 12 has the added advantage wherein the rectangular -
diaphragm 14 and the elements forming the air gap 12 can be
built about the front of a television tube with the clear diaphragm ~;
14 positioned across the face television tube. Such an arrange-
10 ment provides a "see-through" speaker for viewing the television
screen wherein the diaphragm functions as the source of sound ~-
and a very large speaker, having extremely excellent acoustical
fidelity, for television sets requiring very little extra space. ;
The embodiment of electromagnetic transducer illustrated
in Figures 19 and 20 is described in the context of a transducer for
use in control systems, such as, for example, lens focusing, or a
pneumatic controller. The transducer includes an annular, tubular~
shaped magnet 100 (of the type specified above) providing the magnetic ;
flux for the transducer. The magnet 100 is secured between an outer ; ~
metallic sleeve 102 and an inner metallic sleeve 104, both of which ~ -
extend beyond opposite ends of the magnet 100, The outer sleeve 102
includes the bends 106 and 108 so that the portions3~$~hhes~1eeee~102
and 104 that extend beyond the magnet 100 are brought in close
proximity to define two annular, tubular-shaped air gaps 110 and
112. The dimensions of the air gaps 110 and 112 extending along the
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direction of the axis 114 of the transducer and are substantially
longer than the corresponding dimensions of the transducer of
Figures 1 - 18 since it is movement, rather than sound, to be
the input or output signal.
Separate current conduction means ~armatures 116 and
118) are positioned in separate ones of the air gaps and are
mounted on the rings 120 and 122. The rings 120 and 122 include
a plurality of tabs 124 which extend into the guideways 126 to pro-
vide bearing surfaces for the armatures. The item to be controlled
10 is secured to the rings 120 and 122, For example, the coils 116
and 118 can be driven by a differential amplifier to provide a cor-
responding differential movement from the coils. Alternatively, -
the coils 116 and 118 can be driven in parallel and the coils con-
nected to a lever mechanism in an aiding tandem management.
If the transducer is to beused in an optical system, the lens or -~
lenses can be secured to the rings 120 and 122. The armatures ~;
can be coupled to drive a single lens or can drive separate lenses.
In addition, similar transducers of the type illustrated in Figures 18
and 20 can be stacked in a tandem arrangement, so that the trans- ;
2G ducer can provide a variety of functions in response to a large com-
bination of input signals. ; ~Ç
Although the transducer of Figures 19 and 20 is illustrated
as having an annular tubular shape, it is to be understood that it can ; ~ -
have a variety of tubular shapes, such as triangular, rectangular,
oval, etc., depending upon the specific design requirements.
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At times, the space provided for a control transducer may
be limited and weight may be a problern, The air gap of the trans- ;
ducer of the invention can be increased by providing a serpentine
type of configuration, such as the "U" shaped configuration of
Figure 21 wherein the elongated length of the air gap is increased
over that provided by the regular tubular-shaped configurations of
Figures 1 - 20. As illustrated in Figure 21, the transducer
includes an inner "U" shaped metallic element 130 and an outer
"U" shaped metallic element 132 having a "U" shaped magnet
structure (not shown) disposed therebetweenO A pair of "U" shaped ~ - ~
pole pieces 134 and 136 extend toward each other from the elements ~ 7
130 and 132 to define a continuous "U" shaped air gap 138 defining
a closed curve. The armature for the transducer of Figure 21 will
also have a "U" shape to conform with the air gap 138. As can be
seen, since the length of the air gap 138 is greater than that pro~
vided by a tubular configuration of that of Figures 1 - 20, a greater
working area is provided and, therefore, a greater output verses
space is achieved by this arrangement. It should be understood
with the transducer of the invention that any type of serpentine ;-
closed curve air gap configuration can l~e provided, depending upon
the design reqoirer.~erlts and the :pace avaiiable.
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