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Патент USA US2110505

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March 8, 1938.
Filed March 2, 1936
2, 1 1 0,505
Patented Mar. 8, 1938
UNITED stares eAra-nr orrlce
0101’ Ingemar. Harald Ekman, ‘Stockholm,
Application 'March 2, 1936,~ Serial No. 66,710
In Sweden February 12, 1935
5 Claims. (Cl. 116-147)
A well-known type of sirens for signaling pur
poses bases its action upon the use of a ?uid
under pressure, usually compressed air generated
by means of a rotary compressor wheel or de~
5‘ livered from a separate reservoir, the air being
discharged from a chamber at certain deter
mined intervals into the open air through a
sound aperture or apertures from which there
may lead horns for controlling the direction or
10 directions of the sound. In sirens of this type,
the sound is produced by variations. of the pres
sure in said ‘chamber obtained as a result of
the alternate opening
ture or apertures. If
15* only guide and direct
act also as discharge
and closing of said aper
horns are used, they not
the sound vibrations but
passages for the-exhaust
?uid, thereby interfering with the formation of
the sound vibrations. In another well-known
type of sirens, the‘ sound producer comprises a
20:1 diaphragm vibrated either by means of an elec
tromagnetic force or by the action of compressed
air.‘ In the last-mentioned case the diaphragm
is situated in a sound chamber to which. leads
a pipe for the compressed air in such away as
25: to have its mouth opposite the diaphragm. The
sound chamber'is provided with a horn, and
the vibrations of the diaphragm are produced by
means of a fluid under pressure, that is to say,
a pressure above or below atmospheric, which
is‘ intermittently admitted to the surface of the
diaphragm remote from said sound aperture or 10
apertures under the control of a valve mecha
nism, the operation of which is independent of
the vibrations of the diaphragm.
In the accompanying drawing an embodiment
of the invention is shown in axial section in the
single figure
In the embodiment‘ shown the: numeral I in
dicates a, preferably circular, diaphragm which
is inserted as an intermediate wall in a chamber
formed between a bottom piece 2 and a cover
3 both of which are formed with peripheral
?anges, between which the circumferential por
tion of the diaphragm is clamped. ' Said ?anges
are held together by screws 4% extending through
suitable washers 5 of a thickness equal to that 25
of the diaphragm, or somewhat thicker, there ’
the diaphragm acts as a valve for said pipe in
being left a space between the inner periphery
order to periodically discharge a quantity of
of the annular washer and the outer periphery
of the diaphragm suf?cient to- permit a radial
expansion of the diaphragm, which is necessary, 30
for instance, if the diaphragm, when in opera‘
compressed air through the horn, thereby giving
30': rise to a natural vibration therein.
In this type
of sirens the force, whether it’ is produced by
an electromagnet or by compressed air, may only
act upon a restricted portion of the diaphragm
near its centre, so that only diaphragms of rather
35v smml dimensions may be-used. In case of larger
diaphragms of substantial mass,’ the whole dia
phragm cannot take part in the vibration as a
result of such a concentrated action, particu—
larly not at high frequencies, so that the vibra
40 5 tion will be limited to the central portion of the
diaphragm. As a strong sound requires a large
diaphragm, the range of use of sirens of this
type will be correspondingly limited. It is fur
ther to be noted that in sirens haw'ng a dia
45. phragm operated by means of compressed air,
the horn acts as an outlet for the exhaust air
and will, as a result, cause such an interference
with the sound vibrations as that already re
ferred to- hereinbei‘ore in connection with the
501 description of the ?rst stated type.
The object of this invention is to provide a
siren by which the above stated‘ drawbacks are
overcome, and which presents, in addition, sev
eral great advantages.
which a diaphragm is provided as a soundpro
ducing member in a. chamber formed withv a
constantly open sound aperture or apertures on
one side of the diaphragm. The principal char
acteristic feature of the invention involves. that
The invention relates to that type of sirens in
tion, is. heated by a hot gas used as an operat
ing fluid. In‘ the embodiment shown the bottom
piece 2 represents at the same time an end wall
of a pressure chamber 6 adapted to receive a 35
compressed gas which may be admitted thereto
by a pipe 7 or the like, leading, for instance,
from a. rotary compressor located outsidev said
Extending centrally through the
chamber 6 is
the space 8
diaphragm l
shaped slide
tures H,
shaft 8.
a rotatable shaft 8 projecting into
between the end wall 2 and the
and carrying in said space a disk
valve ii} having two- sets of aper
12, concentrically surrounding the
The apertures H are situated above a
set of apertures 53 leading to the pressure cham
ber 6 and, similarly, the apertures l2 are situ
ated above a set of apertures M leading to the
The cover 3 is. provided with a central port
from whichv projects a horn i5.
‘ .
" The shaft 8 is adapted to be rotated at a vary
ing number of revolutions, as for instance, by an
' electric motor or the like. The apertures ll, l2 of
the slide valve In and the apertures l3, M of the
end. wall 2 are so related with'respect to each
other that upon the rotation of shaft 8,1the space‘
‘ 9 between the diaphragm I and the slide valve
III will ‘be alternately communicated- with the
pressure chamber ,6 and the atmosphere. As a
result of this operation, the diaphragm will be
alternately subjected to a pressure above atmos
pheric and to the atmospheric pressure and will,
consequently, vibrate at a frequency determined
made in many ways without departing from the
principle of the invention.
What I claim is:—
l; A‘ siren, comprising means'formin'g. a cham
ber, a diaphragm inserted as a sound producing
member in said chamber so as to divide it into
two spaces, said chamber having a constantly
open sound emission port opening to one of said
spaces, said chamber also having'separate ad
by the speed of rotationof ‘the shaft 8 and the
number of apertures. When ‘the diaphragm is
pressed upwards under the action of a pressure
mission and discharge apertures opening to the 10
other of said spaces fora driving fluid, a rotary
slide valve having apertures to control both said
above atmospheric, it will‘ act as a piston in the
space l6 between the diaphragm and the cover 3.
alternately admit and discharge driving ?uid to
The height of said space should be so determined
that the principal part of the air in the chamber
admission and said discharge apertures so as to
and from said other space.
‘ 2. A siren, comprising means forming: a sound
' I6 will be discharged into the horn as a result
chamber having two oppositely disposed walls, one
of the upward movement of the diaphragm. Due
of said walls having a constantly open sound port,
to the increase of pressure to which the air in
the horn is now subjected, immediately followed
by a reduction of pressure, as soon as the aper
tures l4 are uncovered and the pressure above
atmospheric hitherto acting on the lower side of
a’ diaphragm inserted in said chamber so as to
the diaphragm ceases, allowing the diaphragm
, to return to its original position by its inherent
elasticity, a sound vibration will be produced.
It is evident that in this operation, the horn need
only act to transmit the sound vibration, but does
not ‘act as an outlet pipe for the exhaust ?uid,
:- because the diaphragm closes the horn with rela-v
tion to the pressure chamber 6. _At each vibra—
tion the quantity of driving ?uid that may be
divide it into two separate spaces, each facing 20
a separate one of said walls, means forming a.
driving ?uid chamber situated outside the other
one of said walls, said other wall having a set of
apertures connecting the driving fluid chamber
with the space facing said other wall, said other 25
wall having another set of apertures leading from
the space between the diaphragm ‘and the said,
other wall to the atmosphere, and a rotary slide
valve having apertures therein inserted in said
last-mentioned space to control said two sets of
apertures in alternation.
;1 de?nite number of such quantities. ' In order to
3. A siren, comprising two end walls and a.
peripheral wall forming a sound chamber, one of
said end walls having a constantly open sound
port, a diaphragm mounted in said ‘chamber
avoid undue losses 'of driving ?uid, it is thus
advisable to‘make the volume of the space 9 as
clamped loosely at its periphery in said peripheral
wall to allow of expansion thereof, said diaphragm
contained in the space 9 is allowed to escape,
and to each individual-tone there corresponds a
small as possible by limiting the height of said
space to what is strictly necessary for allowing
40 the return vibration of the diaphragm. This is
'due to the'fact that the diaphragm also performs
a fully developed negative vibration, below its
central‘ position.
The apertures formed in the slide valve [0 and‘
45 the rigid end wall 2, by which the frequency is
determined, act also to’ determine to a certain ex¢
dividing the sound chamber into two ‘separate
spaces, each facing a separate one of the end
walls, means forming a driving fluid chamber.
outside the other end wall, said other end wall
having a set of apertures, communicating the
driving ?uid chamber with the space adjacent
said other wall, said other wall being provided
with another set of apertures leading from the 45,
space between the diaphragm‘ and the said other
tent the curve rep’resenti'ng‘th'e vibrations of the
diaphragm. , It is thus possible,'by suitably shap
wall to the atmosphere, and a rotary slide valve
having apertures therein inserted in said last
ing these apertures, to obtain an adequate shape’ mentioned space to control said two sets of aper
50 of this curve, allowing the apertures to regulate tures in alternation.
the admission and discharge of the driving ?uid
4. A siren having, in combination, means form,
and thus also the variations ‘of pressure upon the ing a sound chamber said means including two‘
diaphragm in agreement with each angular varia- . end walls and a peripheral wall, one of said end
tion‘ during the rotation of the slide valve in a walls having a sound emission port and the other
end wall having inlet and? outlet apertures for a 56
55 predetermined manner. If desired, provisions
'may be made toallow the driving ?uid to expand
driving ?uid, a diaphragm inserted in said 'pe-
vin a certain degreein the space 9 below the dia
< It has been stated hereinbefore that the use of
ripheral wall so as to divide the'sound chamber
into two separate spaces each facing, an indi
vidual one of said end walls, both of said spaces
a ?uid under pressure for the operation of the
having a height perpendicular to the diaphragm 60
diaphragm in the manner described involves that
which is substantially only as great as is neces
phragm before discharged to the atmosphere. .
the power will act simultaneously upon the whole
sary to permit the vibrations of the diaphragm'
and a rotary'valve having apertures therein for
p the action of an electromagnetic or mechanical, controlling said inlet and outlet aperturesmount
ed adjacent said other end wall.
“I. force which is restricted to a smaller area.‘ As
the mass of a gaseous ?uid under pressure isvery
5. A siren as claimed in claim 1, in which the
small and the outlet velocity of such a ?uid discharge aperture of the other-chamber is situ
through the slide valve apertures of the siren in-,v ated ‘near its periphery in‘ order to allow the
creases with increasing pressure, it is easy'to ?uid to be discharged, in part, by the action of i
70 -raise the frequency very high and to vary the centrifugal force.
‘diaphragm, as distinguished, for instance, from
force acting upon the diaphragm.
Variations relating to the construction may be
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