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Патент USA US3073926

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Patented Jan. l5, 'i963
axis and along the line 1-1 of FIG. 2 of a sound re
producer embodying the present invention;
Philip lB. Williams, Lombard, and Harry E. Ailen and
Charles R. Hohmann, La Grange, lll., assignors to The
Muter Company (Jensen Manufacturing Company Di
vision), Chicago, lli.
Fiied Nov. 24, 1958, Ser. No. 775,798
2 Claims. (5l. 179-1155)
within the range of voice communication.
Loudspeakers have many uses which require that their
FIG. 2 is a cross-sectional view taken at the line 2_2
of FlG. l; and
FIG. 3 is an enlarged detail view, in cross-section, of
a portion of the structure shown in FIG. l.
Referring to «the drawing, the field magnet 1 includes
a cere plate 2, a pair of permanent magnetsectors 3, and
a top plate 4, all held securely together by bolts 5. TheA
core plate 2 and the top plate 4 are preferably composed
of soft iron. lA central core member 6 and a core tip
or inner pole piece 8 are bolted together and to the core
pla-te 2 by a «screw 9. The inner pole piece 8 extends
through a round hole ¿la provided in the center of the top
plate to form an outer pole piece, the inner and outer
This invention relates to sound reproducers, and more
particularly refers to loudspeakers which are blast-proof,
pressure-proof, and water-proof, and which are designed
for the intelligible transmission of sound of frequencies
working parts be water-proof. For example, speakers
pole pieces being spaced to form an annular magnetic
which must be used out-of-doors must be protected
gap. A centering ring lil of a non-magnetic material, such
against the deteriorating etiects of the weather, partic
ularly where 'the speakers are exposed to rain, ice, snow
as brass or aluminum, is aiiixed to the top plate and serves
and salt water atmospheres.
Water frequently causes 20
to center the core tip 3 within the hold 4a in top plate 4.
Positioned over `the core tip S, covering the upper face
corrosion of the various parts of the speaker, while lower
of this inner pole piece, and extending into the magnetic
temperatures may cause Water to freeze around the mov
»iany speakers are used by the military forces where ex
gap between the core 4tip and the top plate is an elas
tomeric centering body il. Embedded within the center
ing body is a voice coil l2 and a portion `of a voice coil
bobbin d3. The bobbin and voice coil are maintained
treme demands are made upon them for performance un
concentric with the magnetic gap by the centering body.
der adverse weather conditions.
A conical diaphragm ißt» is affixed at its throat to the ex
ing parts of a speaker and, particularly in the magnetic
gap, to destroy completely the operation of the speaker.
For example, loud
speakers are generously distributed throughout naval
posed end of the voice coil bobbin 13.
The centering body ll may be formed by any of sev
ships both on deck and below decks. Loudspeakers on
deck are exposed tothe elements such as salt water spray 3 O eral different methods. It may be formed by applying
an elastomer-base adhesive primer to the surfaces of the
and must necessarily be protected. Even more stringent
pole pieces and the voice coil assembly, inserting the
demands are made upon loudspeakers used in the sub
voice coil lassembly within the magnetic gap, filling the
marine service. Here loudspeakers mounted on the open
space between the voice coil assembly and the pole pieces
deck and bridge are completely covered with sea water
with RTV Silastic elastomer, and then allowing the
when the submarine is submerged, and yet they must be
elastomer to set while the proper spacing of the voice
immediately ready for operation when the submarine sur
coil assembly is maintained.
faces. They must remain operable even though sub
A preferred method is to prepare the voice coil as
jected to 4freezing conditions which would immobilize an
sembly by mounting the voice coil on the bobbin and
ordinary loudspeaker.
4 O aiiixing it thereto by means of an epoxy resin. The dia
Still another requirement for yreproducers used in sub
marine service and to some extent in other military serv
ice is that they be resistant to extreme shocks and pres
sure changes, such as would be caused by the detonation
phragm i4 may also be cemented to the bobbin 13 at
this time by means of an epoxy resin. The sub-assembly
comprising the bobbin, voice coil and diaphragm is then
of depth charges near the submarine. Speakers of known 4-5 placed in a mold ñxture which maintains the voice coil
assembly centered within the mold cavity. The liquid
construction have not proved adequate for withstanding
elastomer is then poured into the mold through the in
such extreme shock.
side of the tube formed by the bobbin. The elastomer
It is `an object of the present invention to provide a
flows under the voice coil and bobbin and rises into a
sound reproducer which is not adversely affected by ex
posure to Water or other potentially harmful agents and 50 cavity between the mold and the outside of the voice
coil and part of the bobbin, completely covering and
which, even when submerged in sea water over an ex
embedding the voice coil and the lower portion of the
tended period, will remain operable.
bobbin. It is advantageous to contour the mold cavity
I-t is a further object of the present invention to pro
in such a manner that the introduction of elastomer over
vide a sound reproducer which is extremely resistant to
shock land pressure surges, and which will withstand the 55 and above that required to embed the voice coil forms
a web integral with the inner portion of the elastomeric
extreme pressures encountered by submarines while sub
merging to great depths.
Other objects and advantages of the present invention
will become more apparent from the following discus
body in the form of a partition across the entire inner
diameter of the bobbin. It is additionally advantageous
to pour a surplus of elastomer into the bobbin cavity to
make the web thick enough so that it extends to and
seals itself to the inner surface of the throat of the dia
sion and from the appended drawings.
According to the present invention, an annular elas
phragm, forming a water-tight seal. The sub-assembly
tomeric centering body having the speaker voice coil
is inserted into the magnetic gap by forcing the centering
substantially embedded therein is disposed in the mag
body axially into the magnetic gap until the web 11a
netic gap formed by the pole pieces of the loudspeaker
ñeld magnet. The centering body serves the function of 65 comes to rest against the core tip. Conveniently, the cen
tering body is dimensioned to completely till the mag
centering the voice coil within the gap and allowing it
to vibrate axially, and of providing a biasing force to
urge the voice coil to its normal position. It also pre
vents water and `other corrosive elements as well as dirt
netic gap.
If desired, an adhesive may be applied to
cement the centering body to the pole pieces.
The diaphragm supporting frame is comprised of a
plurality of spacing posts l5 aflixed at one end to the
from entering the magnetic gap vand impeding the normal
70 upper plate 4 by any suitable means such as silver solder
operation of the speaker.
ing. The diaphragm rim 14a is clamped in position by
ln the drawings:
FIG. 1 is a cross-sectional view, taken through the
means of clamping rings 16 and screws 17, gaskets 18
being interposed, if desired. A protecting cover 19,
having a skirt 19a depending therefrom, is also held in
place by the screws 17 and offers physical protection for
tion to permit proper operation of the speaker' and
marine service and has continued to function even after
continued and repeated submersion in salt water, even at
very low temperatures. It has also withstood tests in
which it was subjected to the pressures of explosive blasts.
îts ability to withstand such forces is due to a large extent
to the fact that the throat of the cone is firmly, albeit
also to assure equalization of pressure at both surfaces
resiliently, supported by the core tip 8. The elastomeric
the diaphragm 14. A plurality of apertures 20 are pro
vided in the cover, both in its face and in the skirt por
of the diaphragm.
centering body serves `as a cushion to receive and limit
Insulated leads 21 are brought out from the voice coil
and are connected Vto a terminal strip 27 to which ex
ternal connections may be made.
The disposition of the sector magnets 3 is shown in
FIG. 2. This structure is utilized here in preference to
a ring magnet, in order to allow better access to, and
more space for the terminal strip, and, when desired, to
permit an activating coil to be inserted about the central
shocks. Web 11a of this centering body serves both to
l0 contribute to the sealing of the voice coil region of the
speaker from water and other deleterious external agents,
magnet for the purpose of magnetizing it, and for the
subsequent removal of the coil. If desired, however,
Y and to prevent more than normal movement of the voice
coil assemblyl inwardly in consequence, for example, of
blast pressures exerted upon exposed external parts of the
, As a study of the drawing will clearly show, almost all
surfaces of the loudspeaker, including front and back sur
faces of the relatively fragile diaphragm, are openly ex
where other means are provided for bringing out the voice
posed to ambient atmosphere or other iiuid so that a shock
coil leads, a continuous ring magnet may be used.
20 pressure Wave substantially neutralizes itself by exerting
The elastomeric centering body 11 may be composed
of any suitable elastomeric material. Among such ma
terials are natural rubber, artificial rubbers such as buta
diene polymers and copolymers, acrylonitrile polymers,
silicone rubbers, or other elastomers known in the art.
The type of elastomer will be dictated by the intended use
of the loudspeaker.
For example, where low stiffness
Iits forces against opposite surfaces of the speaker parts.
Pressures exerted against web 11a of the voice coil center
ing body have no effect since it is backed up by the end
of core tip it.
Despite its ruggedness, the present reproducer is fully
operative to provide a Satisfactory level of intelligible
sound communication over an extended area.
of the moving system is desired, an elastomer which is
more resilient may be used. On the other hand, where
l. A blast-proof water-proof loudspeaker comprising a
stiff diaphragm characteristics are desired, an elastomer 30 iield magnet defining a magnetic gap and a diaphragm
having less resiliency may be used. To decrease stiffness
supporting frame mounted on said magnet, an elastomeric
even further, a foamed elastomer may be used and may
be foamed in place within the gap around the voice coil.
voice coil centering body positioned Within and substan
tially filling said magnetic gap, said centering body sup
ported by and having a portion thereof maintained in fixed
Alternatively, the centering body may be preformed and
the voice coil, centering body and voice coil bobbin, and 35 relationship with said field magnet, a voice coil bobbin, a
diaphragm may be prefabricated as a unit. For uses in
voice coil mounted on said bobbin centrally positioned
situations where the reproducer will be submerged under
within said magnetic gap and substantially embedded and
water at low temperatures for extended periods, elas
Sealed within said elastomeric centering body, a conical
tomers having good low temperature elastic properties
diaphragm affixed at the throat thereof to said bobbin
may advantageously be used. A preferred material is a
and clamped at its periphery to said frame, both the front
silicone rubber marketed under the trademark “RTV
and back surfaces of said diaphragm being exposed to
ambient atmosphere, and a web integral with said center
The core plate 2 and the top plate 4 should be com
ing body defining a transverse partition adapted to seal
posed of soft iron. The sector magnets 3 and the central
said bobbin against the passage'of fluid therethrough.
core element 6 should preferably be made of a material
2. A voice coil diaphragm sub-assembly adapted for
having strong permanent magnetic properties such as
insertion Ainto the magnetic gap of a held magnet to co
Alnico V. Other materials such as ceramic magnetic
operate therewith to form a blast-proof water-proof loud
materials may be used. The core tip 8 may be composed
speaker, said sub-assembly comprising an annular elasto
either of soft iron or of a permanent magnetic material.
meric voice coil centering body, a cylindrical bobbin, a
lf desired, soft iron may be used for either the sectors 3 50 conical diaphragm aiiixed at the throat thereof to said
or the central magnet 7, as a sutiiciently strong magnetic
bobbin, a voice coil mounted on said bobbin and corn
field may be produced by the remaining permanent mag
pletely embedded within said centering body, and a web
integral with said centering body defining a transverse
For normal uses, the speaker cone or diaphragm 14
partition adapted to seal said bobbin against the passage
may be made of any common material used in the art. 55 of fluid therethrough.
However, where the cone must withstand the effects of
sea Water and shocks such as that produced by the detona
tion of depth charges, care must be used in the choice
of suñiciently durable material. A suitable cone designed
to withstand these forces may be produced by molding 60
the cone from a plurality of layers of a ñnely woven
References Cited in the tile of this patent
fabric impregnated with a phenolic resin, which is sub
sequently molded and cured under pressure and heat.
The present loudspeaker has proven itself to be remark
ably suitable for use where it is to be subjected to the 65
ravages of extended submersion in salt water. It has
been tested under the conditions encountered by sub
Bostwick ______________ __ July 30, 1946
Mounce _____________ __ Aug. 11, 1953
Levy ________________ __ July 17, 1956
Germany _________ ...._.___ Dec. 14, 1953
France _______________ __ Aug. 6, 1956
France ________________ __ Jan. 7, 1957
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