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Патент USA US2407175

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Sept» 3, 1945-
. Filed Nov. 14, 1940
3 Sheets-Sheet 1
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A57-¿1e @e4/ch’
GMW-Hf@ /Vfazz
HANS Merz.
SePt- 3; ‘1946-
P. oRLlcH Erm.
Filed Nov. 14, 1940
s sheets-sheet 2
Sept. >3, 1946.
„ P, oRLlcH' Erm.
Filed Nov. 14, 1940
3 Sheets-Sheet 3
Patented Sept. 3, 1946
Peter Orlich, Günther Negel, and Hans Hartz,
Kiel, Germany; vested in the Alien Property
` Application November 14, 1940, Serial No. 365,646
In Germany May 2, 1939
3 Claims.
This invention pertains to sound-emitting de
vices of the kind operated by a compressed gas,
invention the tuning is achieved by making the
greatest distance between the openings and the
such as whistles and sirens. Some features of
the invention are particularly concerned with
Walls of the air chamber equal to an uneven
multiple of one-quarter of the emitted wave
the emission of signals for echo sounding devices. Cil length.
Referring first to Fig. 1 of the drawings, I5 is
One object of the invention is to improve the
an air chamber of a siren having a rotor I1 and
efficiency of sound-producing devices of this kind.
' Another object, pertaining especially to sound
emitters for aircraft, is to provide a more com
driven by a motor 2|. The air chamber is sup
plied With compressed -air by an inlet nipple 3|.
pact construction and one which enables the 10 Inside the air chamber is a differential valve 24,
known per se, the valve surfaces ‘I and 8 of which
sound emitter to be integrated with the structure
of the aircraft.
Another object is to improve the operation of
the valve controlling the sound emission.
Another object is to improve the synchroniza
„have different areas and rest upon corresponding
seats of the air chamber. The differential valve
is held in closed position by an electromagnet 9.
However, due to the diiîerences in the respective
areas Vof the two valve surfaces, upon opening of
tion of the signal emission of an echo sounding
the magnet circuit the valve is released and is
device and the start of a measuring apparatus
moved by the compressed air in the direction
for determining the time interval between the
indicated by the arrow. Thereby the air in the
signal emission and echo reception.
Another object is to reduce the liability of the 20 chamber can flow out through the openings I6
sounding apparatus to be disabled by becoming
and I 8 of the stator and the rotor I‘I, respectively.
This construction is particularly adapted for
sirens used for echo sounding devices built into
Another object is to provide an improved gov
aircraft and intended to emit intermittent sound.
ernor mechanism suitable for, though not limited
In accordance with the invention. the air charn
to, use on the rotor of a siren or its driving motor. 25
ber IU is adapted to the sounding frequency by
Other objects will appear from the following
making the distance between the openings IG and
specification, in which several illustrative ern
the upper end I2 of the air chamber an uneven
bodiments of the invention will be described, with
multiple of M4. In this connection it is impor
reference to the accompanying drawings, wherein
Fig. l is an axial section of a siren embodying 30 tant that especially in those cases in which the
inner walls are constituted by the armature of
a differential valve, the valve surfaces at I2 con
Fig. 2 is an axial section of a modification of
stitute as large a fraction of the end surface as
the inventive siren, together with its _driving
possible and the curved zone I3 is kept relatively
motor and compressor, in an arrangement illus
small, so that the tuning can be carried out in a
trating several features of the invention;
clean-cut manner. In cases in which it is not
Fig. 3 is a whistle sound emitter, with asso
necessary to produce such accurate tuning, itis
ciated compressor and driving motor; and
preferable to give the air chamber a strictly cy
Fig. 4 is an axial section of part of a motor
lindrical shape, with flat end faces. In all cases
showing a governor mechanism in accordance
40 the relations vare best secured if the air chamber
with the invention.
is at any rate made in the form of a solid of
Sirens have an air chamber which is inserted
in the compressed'air supply line just in front
If the outer walls of the air chamber are not
of the outlet openings of the rotor, in order to
straight as in the example, but are to la certain
produce a uniform flow of air. Such an aircham
ber is used in all kinds of sirens, including those' 4.5 degree curved, as indicated by the dash line I4,
features of the invention;
the straight line distance from the openings‘IB
to the end faces at I2 is not the criterion for
determining the Wave length, but rather the
a cylindrical surface, as well as those whose open
ings are in a disk.
length of the shortest curved connecting line
According to the invention the efficiency of 50 between said openings I6 and said end faces at I2.
such sirens is considerably improved by tuning
It is important in some cases to design the siren
the air chamber to the emitted frequency. This
for two or more operating frequencies, as in the
driven pneumatically as well as those driven by
a motor and likewise those whose openings lie in
tuning causes stationary air waves to beset up
with a loop at the openings and a node at the
case of the air protective sirens. In such cases
there may be used either a plurality of passages
most remote wall areas. In accordance with the 55 for the air stream within the air chamber, one
example of which would be a smooth cylinder
and the other a curved conduit, for example, a
spiral channel; or the air chamber can be tuned
to a common multiple, for instance, the least
common multiple of the two signal frequencies.
So, for example, a siren with frequencies of 1800
caused by the spring action of the air compressed
in the air cushion. These axial vibrations cause
a repeated closing and opening of the diiîerential
valve so that the true sound signal is mislead
ingly interfered with by these vibrations, whereby
the desired signal is furthermore unnecessarily
and 3000 cycles 4per second can be used if :its air
chamber is tuned to three-fourths of 1800 cycles
or with five-fourths of 3000 cycles.
measuring elevation above ground, the danger
In order to utilize the good properties of thecompressed air-operated sound emitter in accord
exists that the echo» coming in may go into the
outlets of the sound signal emitted. This disad
ance with the invention to the full extent, it is
advisable to connect the sound emitter with a
ring-shaped horn; for it has been >shown that
other horn shapes allow sub-maxima of the di
rectional characteristic of the» sound emitter to
occur, which are perpendicular to the main'direc
vantage is eliminated by providing in the part
of the enclosing wall 25 of the stator which is
parallel to the valve plate 25, bleed ports 28 in
In the use of such devices an erroneous
indication was given because at small heights they
path of the direct sound beam between the sender
and receiverand the path ofthe reflected sound
beam are almost the same; that is, in the use of
the sound emitter with a tuned air chamber, the
advantage achieved is nullified by the use of an
unsuitable sound horn. It is particularly advan
tageous for benefit of thesound characteristics to
construct the ring horn of the sound emitter as
a so-'called exponential horn7 that is a horn
extended. V~If such devices are used as a sound
emitter for air-sounding devices or devices for
suitable number and size to weaken the cush
ioning eiIect to such an extent that the air
cushion does not act as a spring upon the valve,
so that the valve is not set in vibration.
Heretofore the compressed air for driving a
siren, or whistle, of an air sounding unit has been
either taken from a compressed air container,
such as a steel flask, or it has also been suggested
to use the exhaust gases of the aircraft. The use
of exhaust gases, however, has the disadvantage
that the superatmospheric pressure which is
available is much too small, to produce the loud
sound impulse required in practice. The use of a
steel flask has seemed up to now the best means
of supplying the compressed air, although it al
tially. along its length. The construction of the 30 ways had the disadvantage that it had to be ex
sound horn as an exponentially expanding ring
changed fro-m time to time and a relatively long
horn has an additional advantage; the motor
compressed air conduit was required. An im
used to drive .the ~rotor of the siren can be built
portant improvement of the whole signal emitting
into the Ainner space of the inner horn. Thereby
apparatus of an air sounding unit is now pro
the whole `sound emitting unit is reduced to a
vided, by producing the compressed air by a com
small height. Furthermore, it is thereby possible
presser which is arranged in the immediate vi
to build the'sound emitter into a part of the body
cinity of the sound emitting apparatus. By this
of the aircraft, for example, into its deck. Since
means not only -is there an important saving of
for aerodynamic'reasons the outer surface of the
space and weight, as against the known units
aircraft must be smooth, the sound emitter is 40 operating with a steel flask, and the exchange of
brought 'into the inside of the part of the body
the steel?lasks done away with, but in addition
of the aircraft on which it is mounted, such as
to that the following advantage is achieved: It
the'fuselage. This, however, requires a break in
has been found in the operation of echo
the static vframe of the fuselage. It is therefore
sounding. units on aircraft that a difficulty oc
important to build in the sound emitter in such
curred in unfavorable weather conditions, caused
a way that the outer horn constitutes a stress
by the icing of the transmitting device, as a re
sustaining unit of the aircraft fuselage. This
sult of which in whistles the Whistle openings were
manner of building in the unit is, furthermore,
closed and in sirens the rotor was frozen fast.
suitable for all kinds of shapes of horns, so that
This dan-ger occurs above all in echo sounding
it constitutes a distin'ct'feature of the invention 50 devices used for landing purposes and therefore
in itself.
usually having a measuring range of only one
Fig. 1 exemplifies the latter construction of
hundred or a few hundred meters, because these
the inventive siren. The air currents ñowing
devices are not operated constantly, but are set
out of the ports í S and >I8 flow into a sound horn,
in operation only shortly before the landing. By
whose cross-sectional area increases exponen
which consists of an outer horn wall I9 and an
inner horn Wall 20. These two horn walls are
. producing the'compressed air by the use of a com
pressor near the sound emitter, the compressed
cf exponential form, In the hollow of the ’inner
horn 20 is lodged a motor 2l which drives the
air is supplied at a temperature much above the
atmospheric temperature. The compressed air
supplied by the compressor'necessarily has a tem
The outer horn I9 is constructed as a
stress-sustaining part of the aircraft fuselage
and merges with the outer ‘wall of the fuselage
perature of about 100° C. or more. Now if care is
taken to avoid any substantial loss of heat on the
way from the compressor to the sound emitter it
self, the whistle or siren is pre-warmed. The pilot
4|. In front of the opening of the horn there
is preferably stretched’a screen or diaphragm 23.
Fig. 1 also shows an additional improvement of
can therefore switch in the sounding apparatus
the sound emitterof an echo vsounding device in 65 »a‘few minutes before the landing,l if he knows or
accordance with the invention. Since the axial
forces and accelerations occurring during the
movement of the diiïerential valve 24`provided
in the air chamber to produce very short sound
impulses may become too largeand lead'to injury
of the’device, there is enclosed between the 'valve
plate 25 next to the outlet ports and the enclos
ing wall 26 of the air chamber, an air cushion 2l.
This device, known per se, h'as the disadvantage
fears'that the transmitter may have become iced,
and thereby can thaw it out.
In >the arrangements known heretofore, which
used the exhaust gases of the motors as an op
erating medium for the siren or the whistle, it is
true that gases of elevated temperature were
used; however, as previously indicated, such de
vices have rnot proven to be useful in practice.
An additional advantageous arrangement of
that the valve has imparted to it axialvibrations 75 the echo sounding apparatus in accordance with
the invention consists in driving the compressor
as well as the rotor of the siren by one and the
same motor; that'is, a motor is used for driving
the compressor, which kis required for other func
tions on the aircraft. In this way the arrange
ment of a special motor and thereby an increase
in the weight and space requirements are avoided.
between the motor 'I1 and the rotor 19. In this
case, to be sure, it is necessary to provide a speed
regulator for the compressor motor.
` A special form of the inventive conception
consists in the use of a pump and impact mech
anism as a compressor, which commends itself
particularly for use in air sounding units on ac
This advantage is naturally also achieved if the
compressor is operated directly by the aircraft
count of its compact construction and small
space requirements.
In Fig. 3 is shown a sound emitter of an air
motor. Such a device is desirable for the use of a 10
whistle as the sound emitter.
sounding unit in accordance with the invention,
using such an impact mechanism compressor.
In Fig. 2 there is shown an illustrative embodi
ment of such a device. 11 is a driving motor
95 is a whistle, which is separated by a check
which drives the rotor 19 of a siren through a
valve 96 from a compression chamber 91 enclosed
step-up transmission gear 18 and a compressor 15 by a cylinder 91a. Within the compression
chamber reciprocates a piston 98 against a spring
8| through a reduction gear 80.` The transmission
99, the reciprocation being caused by means of
gear 18 is connected by a shaft 82 to rotor 19 not
rigidly, but through an elastic coupling 83. Also
a cam |00, which is driven by a worm wheel |0|
operated by the worm I0|a of~ a motor |02. An
there is mounted on the hollow shaft 84 which
connects the elastic coupling “83 with the rotor 20 additional check valve |03 serves for suction of
the atmospheric air into the compression cham
19, a centrifugal governor 85 providing for a con
ber 91. A switch |04 arranged in the compres
stant rotary speed of the rotor 19. 86 is the inner
sion space is adapted to control the time measur
wall of a ring horn set in front of the outlet ports
ing mechanism of an echo sounding device, not
81 of the rotor, the outer wall of the horn being
indicated at 88 and being also of the exponential
Said switch |04 being pressure responsive can
form. The elastic coupling 83 and the centrifugal
beV connected, for example, with the measuringgovernor 85, which is advantageously constructed
as a centrifugal braking governor, are arranged
mechanisms of the kind shown in the copending
applications of Peter Orlich and Hans Hartz,
within the hollow-space 89 enclosed by the wall 86.
From the >compressor 8_| the compressed air is 30 Serial No. 285,310, filed July 19, 1939, and of
conducted through a conduit 90 into the tuned air
Peter Orlich, Günther Negel, and Hans Hartz,
chamber 9| of the siren. It is particularly ad
Serial No. `365,647, ñled November 14, 1940, or
Patent No. 2,032,893 to Bernhard Settegast and
vantageous to construct the air chamber 9| in
Wilhelm Rudolph. Measuring apparatus of this
such a way, vas shown in thel example, that the
whole, or atleast the greatest part of the shaft 35 type operate upon the principle of measuring the
interval between the instant of emission of the
of the rotor, is surrounded by it. Hereby the
sound signal and the instant of reception of the
uniform heating of the moving parts of the siren,
echo. Accordingly, the measuring mechanism
as well as all parts of the rotor, is accomplished.
which measures this time interval must be set in
Also upon replacement'of the siren by a whistle
such a construction of the air 'chamber is desir 40 operation at the same instant as the signal is
emitted. The emission of the signal is generally
able. The inner wall of the air chamber 9| is
repeated periodically and usually the signal
formed, in known manner, by an electromagnet
transmitter is set in operation by some kind of
armature 92 serving as a valve for controlling the
an electric device. Heretofore, the transmitter
supply of air to the ports 81, and the air induc
tion ports 93 of the compressor 8| are provided, , i and the measuring `mechanism have been simul
taneously controlled by a control member, for
in known manner, with am pressure regulating
example, a shaft rotating at constant speed. In
valve `94. rI‘he electromagnet armature 92 is
practice, disadvantages of this system have oc
shown again as a differential valve.
curred which are due to the fact that electrical
The length of the compressed air conduit 90
control'effected by means of relays or switches,
and the heat insulation of the same are made to
particularly mechanical switches or similar trans
conform to the conditions prevailing in the com
mitting members, is not absolutely exact and
pressor 8|. Under certain conditions it is neces
consequently no correct synchronism between the
sary to provide the conduit 90 with heat insula
signal emission and the setting in operation of
tion, if this conduit is notaltogether eliminated,
the measuring device is afforded. This disad
and to arrange on the compressor 8| .itself cooling
vantage is satisfactorily avoided by using said
fins, so that on the one hand the temperature
pressure responsive switch |04 automatically
necessarily arising from the compressionof the
actuated by the inventive sound emitter of Fig. 3
gases does not become too high and create a fire
to set in operation the mechanism for measuring
hazard, while on the other hand a further cooling
of the air conducted to the tuned air chamber 9| 60 the length of time for the transmission of the
is prevented. >At very high temperatures of the
It is obvious that the motors for driving the
air, to be sure, and with the simultaneous use of
rotor of the siren and the time-measuring appa
good insulation of the compressor 8| against the
ratus are to be kept at a constant speed. For
surrounding conditions, it may be indicated to
this purpose centrifugal governors are frequently
cool the compressed air first on the outer wall
used, in which a switch contact is closed under 1
of the air chamber 9|, whereby it is prevented
the innuence of centrifugal force, this switch
that the whole siren is subjected to excessive and
controlling any part of the motor, either the field
damaging heating after being thawed and the
or the armature. In the known governors it is
rotor set in operation.
. The arrangement of the compressor, as well as 70 usual to provide a lever that also operates the
the coupling of the sound emitter, is not limited
switch contact, eccentric to the axis of rotation,
to the form shown. Instead of the elastic cou
so that centrifugal force acts vdirectly upon the
pling 83, for example, any other non-rigid cou
switch lever. This has the disadvantage, how
pling can be used, for example, a friction cou
ever, that the switch lever, on account of its ec-`
pling._ It isv even possible to use a. rigid coupling
centric position, forms only a chord within the
available circle, which -`defines-‘the .limits of 'the
rotary-part ',of'the governor.` Consequently, the
length of the switchlever in comparison with the
dimensions of thefwholecentrifugal‘governor is
is mounted upon the r.switch lever :I | I. The abil
ity of the half l(ball ‘| |1 ‘toshift enables this ele
ment .always :tofcon-form` uniformly to .the bear
ingpoints of the 'ballsl |8. It is of coursegneces
relatively smalh resulting also . in a relatively 5 sary to take care .that Ythe axis of symmetry of
small extent of .moi/ement, which is furthermore
the cause of arrelatively large irregularity. Now
it-is'particularly desirable in air sounding appa
the ball bearing .H8 and >the half Vball |.|'| ,is -as
nearly as. possibleon‘the axis of rotation..
The above-described conception whereby the
ratus according to the invention -to provide a
disadvantages of .the previouslyknown centrifu
switching movement .as -large as possible .for the l0 gal governors are removed is not limited .tothe
givenA ltotal dimensions of the centrifugal gov
illustrative form shown in Fig. 4.
ernor Vand‘thereby'to .achieve the greatest ‘possible
The elements of theinvention can obviously
accuracyA of the governor, by constructing the
be used .either 'individually or in any combina
centrifugal lgovernor armas .a bellcrank lever,
the end point ofonezleg of which visarranged on 15
We claim:
aîa'rocking axis :at the periphery of 'the rotating
1. In a siren, a casing enclosing `an'air cham
housing or other carrier., and the free -leg of which
ber, means for delivering compressed vair to said
extends to the axis of rotation, wherefit acts upon
chamber, said casing having ports for emitting
anon-rotatingswitch lever. In contrast to the
compressed air from vsaid air chamber, a rotor
usual centrifugaly governors .the yswitch `is there- 2Q mounted adjacent said ports, and means for driv
fore'stationary, in la centrifugal governor accord
ing said rotor at a predetermined speed, said rotor
ing to the invention. Forthis reason the gov
having ports coacting with said casing ports to
ernorisparticularly suited for regulating the ñeld`
control the emission of compressed air from said
of îamotor, because Aall >collectors are eliminated.
air chamber to produce a sound of definite fre
In Fig. 4 is shown an illustrative embodiment 25 quency, a valve seat and a vdifferential valve in
of such Va governor. ||9 is the armature'of a
said air chamber coacting to control the flow vof
motor, which rotateswithin a >field frame |05.
compressed air from said chamber to said ports,
Upon the armature is a Vsupport |06, which re
the armature of »said valve constituting an inner
volves with it and :carries upon its periphery a
wall of the .airA chamber and designed to recip
pivot |01, about which a bell 4crank |08`is yroclr- 30 rocate in the direction of- ’its longitudinal axis,
able. The leg of this bell crank |08 which is
the configuration of the-armature being such as
parallel to the axis Aof rotation is shorter than
to form an outer curved surface defining a rela
the other and isalso loaded with a greater'mass
tively small curved Zone within the air chamber,
than"V the other. Herebyit is aohievedthat both
whereby said ai-r chamber is tuned to said fre
the greatest possiblecentrifugal forcev and the 35 quency so that standing sound Waves are set up
greatest‘possible switching movement of the 'free
with a loop at said ports and a node at the end
end of the bell crank lever |08 occurs. Opposite
of said air chamber most remote from said ports,
the vbell -crank lever |08 is symmetrically arranged
the distance from said ports through said air
a second bell crank lever |09, which is likewise
chamber to the most remote part of the inner
rockable upona pivot | |-0 at the periphery ofthe 4o wall of said casing being equal to an uneven
carrier |05. By Vthe arrangement of two sym
multipleof one fourth of the wave length of the
metrical Acentrifugal governor :lever arms there yis
emitted -sound waves.
simultaneously provided la balance of the whole
2. In a siren, a casing enclosing 4an air cham
system. This is, however, not absolutely essen
ber, lmeans for delivering compressed air to said
tial to ‘ the device.
One lever arm would be 4_3
On the other hand lobviously three or
more lever arms could be'used, with- an increase
chamber, said casing having ports for emitting
compressed air from said air chamber, a rotor
mounted adjacent said ports, and means for driv
ing said rotor at a predetermined speed, said
rotor having ports coacting with said casing _ports
The free ends of Vthe bell crank levers ,|08 and , ,j to control the emission of compressed air 4from
|09 act upon -a switch arm `| | |, which‘ismade as "
said Aair chamber lto produce a sound of definite
large as possible, that is, the rocking axis ||2 of
frequency, a valve seat and a differential valve
the switch lever is `>likewiseplacedat >the periph
in -said- air chamber coacting to control the íiow
ery of the governorand secured ,to‘ithehousing
of compressed air from said chamber to said
||3 `of the governor. The housing ||3 forms a , ..
ports, the armature of said valve constituting an
unit with the frame m5V of the motor. At the U"
inner wall of the air chamber and designed to
free end of the switch arm |||`is a contact H4,
reciprocate in the direction of Vits longitudinal
the contact surface »of `which‘is fixed Yto any sta
axis, the configuration of the armature being
tionary part, preferably upon the housing || 3,
ofthe centrifugal force, and‘thereby amore exact
operation of 'the governor would be provided.
such as to `forman outer curved surface defining
and is perpendicular to the axis lof rotation. The
switch arm ||| is held by a spring ||5 at aiden (il) a .relatively small curved zone within the air
chamber, whereby, said air' chamber is tuned to
nite normal distance from the contact face ||4.
said frequency sothat standing sound waves
The tension of the fspring ||5 .isadjustabla in
are vset up rwith a. loop at >said ports ,and a .node
known manner, by a setscrew H6, which ’ is
at the end of .saidair chamber most remotefrom
screwed into the :housing H3.V
A particular feature of `the construction‘of lthis (i5 saidv ports,„said„air chamber having the. form
of a lsolid ,ofrevolution with plane end surfaces
device is to be seeninthe'fact thatithe `Contact
and a height -equal to an uneven multiple of
between the free ends` of the centrifugal governor
lever arms |00 and |09 and the` switch lever |||
one-fourth of the wave length yoffsaid definite
is constructed asra ball bearing. Upon the free ) frequency.
ends of the bell crank levers |08 vand |09 sits a
3;.In a.siren.for producinga sound of pre
half ball | I1, which can >be Vmoved laterally with
determined wave length, wall means forming an
in narrow limits in slots in thellever arms |08
axially` extending annular chamber having an
and |09. The counter bearing of the vhalfïball
outlet at one-endthereof, vibration _producing
| |'| is-constructed as la ball bearing || 8, which 75 means Aincluding a circular row -of ports surround
ing said outlet and being positioned a ñxed dis
tance from the opposite end of said annular
chamber which distance is equal to an uneven
multiple of one-fourth of the Wave length of the
emitted sound waves, said chamber having as
its inner peripheral wall a surface of revolution,
said Wall means having as part thereof a recip
rocating diiîerential valve axially movable to
open and close said outlet, and means to supply
to said chamber a compressed gas of controlled
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