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NW5, 1946.
‘
O. SOLDAN
2,410,528
MICROPHONE
Filed Sept. 29, 1941
M’If/WUQ
,
5/
0770
60404”.
‘
‘
2,410,528
Patented Nov. 5, 1946
UNITED STATES ‘PATENT OFFICE
2,410,528
MICROPHONE
Otto Soldan, Falkensec, Osthaveland, Germany;
vested in the Alien Property Custodian
Application September 29, 1941, Serial No. 412,893
In Germany October 26, 1940
1 Claim.
(Cl. 179—122)
1
2
This invention relates to a microphone having
a pressure compensation chamber which elimi
nates the changes in tension caused in the in
terior of the case by the in?uence of the ambient
temperature. To this end, the operating dia
phragm and the carbon chamber of such micro
phones are arranged in a closed chamber of the
case, the chamber being de?ned by a sealing dia
phragm from the operating side and by a ?exi
wall of the chamber I9 as well as to the inner
wall of the edge I5 of the case 4, bent at right
angles in order to attain a completely air-tight
seal of this portion of the case chamber. Since
the protective wall ‘I with its portion II extends
at the rear side of the case 4 up to the opening
for the contact nipple I3’, the hollow space I6 be
hind the ?xed electrode 2 is also protected against
moisture by the intermediate wall II. The cup
shaped member II of the ?xed electrode 2 is not
in direct engagement with the latter, but only
with the felt ring I4 so that a path of communi
cation I8 from the space I6 behind the electrode
2 to the pressure compensation chamber I9 prop
ble water-tight protective wall from the opposite
side.
_
It has been found that this chamber must be
tested for air-tightness, which entails connect
ing a testing device to the chamber. This is ac
complished according to the invention by pro
viding the chamber of the case enclosed by the
sealing diaphragm and the water-tight protec
15
er is thereby provided, which path enables
through the openings 20 arranged in the electrode
cup-shaped member II a free access of air from
the one space to the other. The hollow space I 5
is closed in the central portion of the rear wall
of the chamber for the air-tightness, said open
ing being accessible from outside and capable of 20 of the case by the contact nipple l3. This con
tact member is provided with a bore 2I which is
being closed.
closed by a screw 22 and enables after the loosen
Since the arrangement of this opening in the
ing of the screw the fastening of a control gauge,
protective wall of the chamber itself is disad
for instance, of a manometer or the like for test
vantageous, as its ?exibility would thereby be im
- ing the pressure compensation chamber for air
paired, and since such an arrangement also in
tightness.
volves a particular opening in the case, the open
In this manner, it is possible to test such pres
ing capable of being closed is arranged accord
sure compensation chambers for air-tightness
ing to the invention in the contact member
without impairing the construction of such a
mounted at the rear side of the case, which mem
microphone.
ber projects into a space arranged behind the
What is claimed is:
?xed electrode and closed by the protective wall,
In a microphone, an outer casing, ?xed and
said space being in communication with the pres
movable electrodes in said casing, said ?xed elec
sure compensation chamber, the portion of the
trode and casing forming a space between them
cup-shaped member for the ?xed electrode ex
behind the ?xed electrode, a diaphragm secured
tending in this path of communication being pro
to said movable electrode for operating the same,
vided for this purpose with one or more openings.
a protective casing for said parts comprising a
In the accompanying drawing is shown an em
protective diaphragm in front of said operating
bodiment of the invention in diagrammatic form
diaphragm and a ?exible pressure compensating
in which the single ?gure shows a sectional view
diaphragm in the rear thereof, said compensat
of one half of the sealed microphone case ac
ing diaphragm having a peripheral portion sealed
cording to the invention. In the microphone
to said protective diaphragm and forming a space
case 4 is arranged the carbon chamber I which
between said ?exible diaphragm and operating
is de?ned by the ?xed electrode 2 and the felt ring
diaphragm, extending around said ?rst named
I4. The chamber is closed by the operating dia
phragm 3 provided with the movable electrode 45 space, said ?rst-named casing having an opening
whereby said spaces are in free communication
2'. To seal these parts, a diaphragm 6 is em
with each other, said ?rst named casing being
ployed consisting of a water-tight foil and ar
formed with a second opening communicating
ranged at the operating side. In this case the
diaphragm 6 rests directly on the operating dia
with said ?rst named space and with» the outer
phragm 3 and is preferably glued to the ?exible 50 atmosphere and means for closing said opening.
water-tight protective wall ‘I forming the lower
OTTO SOLDAN.
tive wall with an opening so as to enable a testing
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