US 2429104 A
Description (OCR text may contain errors)
Oct. 14, 1947. H, F, OLSON 2,429,104
SIGNAL TRANSLATING APARATus Fiied uarcn 27, 1945 Inventor Hary f.' Olson f CEM Gttorneg .1' fumrso ysur quencies.
Patented Oct. 14, 1947 SIGNAL 'raANsLArrNG ArrAnA'rUs' Harry F. Olson, Prlncetom-N. J., assignor to Radio Corporation of Delaware This invention relates to signal translating api paratus,V andI more particularly to a loud speaker whichA ls especially useful in submarine signalling. f
VVarious forms of sub-aqueous loud speakers have been provided heretofore for submarine signalling. For successful operation of a loud speaker submerged in water, it is essential not only that the pressureon both sides of thedia;
phragm be the same, but it is highly desirable` that the stiffness thereof be maintained constant, that'is, that the stiffness of the diaphragm be the same under water as it is in air. So far as I am aware, submarine loud speakers of the prior art have failed in this respect.
The primary object of my present invention is to4 provide an improved sub-aqueous loud speaker wherein the diaphragm will always have the same pressure on each side thereof regardl less of the depth to which the loud speaker is submerged in water or other fluid medium.l
More particularly, it is an object of my present America, a corporation of ppueanon- March 27, 1943, serial No. 430,783 101mm. (ci. 11iassi quencies.` vWhen the loud speaker is immersed in -water or other fluid medium, the medium enters the opening in the rigid casing and causes the aforementioned enclosure to collapse partially, thus forcing the air or other fluid entrapped therein through the previously mentioned passageway intoanother fluid-tight chamber which is closed off by thediaphragm. At the same time, since the diaphragm is exposed to the medium on its front surface, the medium also acts directly on the diaphragm. Since the collapsed enclosure forces the entrapped fluid therein into the chamber which backs up the back side of the diaphragm, the same, steady pressure is created on both sides of the diaphragm. At the same time, the collapsible enclosure or equalizer presents a high alternating impedance to the medium because of the fact that the rigid enclosure surinvention to provide a pressure compensator for Vsub-aqueous loud speakers by means of which the same fluid pressure willbe maintained on both provide an improved sub-aqueous loud speaker which will transmit acoustical vibrations with great efficiency.
' sides of the loud speaker diaphragm, while at the Y Still another object of my present invention is to provide an improved sub-aqueous loud speaker the characteristics of which are independent of the depth to which the loud speaker may be immersed in water.
A further object of my present invention is to provide an improved sub-aqueous loud speaker as aforesaidin which the stiffness of the vibratingsystem is maintained at a relatively low value. It is also an object of my present invention to provide an improved sub-aqueous loud speaker as set forth above which is simple in construction, inexpensive in cost, and highly eilicient in use.
In accordance with my present invention, I provide a collapsible enclosure which I couple to the back side of the loud speaker diaphragm through a passageway which offers a high impedance to the passage of fluid at acoustic fre- Around the collapsible enclosure, I provide a rigid enclosure having an opening therein which also affords a high impedance to the passage of fluid therethrough at acoustic frerounds it, and it is coupled to the medium exterior of the rigid casing only through the small aperture or opening in the casing.
The novel features that I consider characteristie of my invention lare set forth with particularity in the appended claim. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be'understood from the following description of one embodiment thereof, when read in connection with the accompanying drawing in which the single figure is a central, sectional View of one embodiment of this invention.
Referring more particularly to the drawing, there is shown a loud speaker comprising a cylindrical magnet l, a back plate 3, a yokeplate 5 and a center pole piece 1 all connected together in fluid-tight relation. The yoke plate 5 is provided With a central opening of larger diameter than that of the pole piece 'l whereby to form an air gap 9 in well known manner. Connected to the yoke plate 5 in fluid-tight relation thereto is a vibratory diaphragm Il provided with a voice coil i3 located in the air gap 9. The magnet I, the back plate 3, and the yoke plate 5 may be coated on the exposed surfaces with a corrosion resistant coating i5, the diaphragm Il being also made of a corrosion resistant material. The structure thus far described provides a fluid-tight chamber I1 within the eld structure constituted by the magnet l and the plates 3 and 5, the air gap 9 affording communication between the chamber I1 and the exterior of the field structure, and the diaphragm I I closing off the chamber l1 from the exterior of the loud speaker.
'I'he back plate 3 is provided with an opening I9 and with a concentrically arranged flange 2| over which is tted a collapsible enclosure 23 of yieldable material, such as relatively soft rubber. The member 23 is relatively less stii than the diaphragm I I and encloses a second chamber 25 which is in communication with the chamber I'I only through the opening I9. The enclosure 23 has fluid-tight connection with the back plate 3, and for this purpose, it may be provided with an outwardly extending iiange 23a which rests against the back plate 3 and which is held tightly thereagainst and against the flange 2| by a ring 2l.
Surrounding the collapsible member 23 preferably, but not necessarily, concentric therewith and in spaced relation thereto, Vwhereby to provide a third chamber 3 I, is a rigid casing 29 which has fluid-tight connection with the ring 21 and the flange 23a. The casing 29 has a small aperture or opening 33 therein which aords communication between the chamber 3| and the exterior of the casing. The opening 33 is of such dimensions that it aifords a high impedance tothe passage of a fluid between the chamber 3| and the exterior of the casing 29 at acoustic frequencies. Y
A loud speaker constructed'as above described will normally have air entrapped within the chambers I'l, 25 and 3 I. When such a loud speaker is immersed in another iluid medium, such as water, the water pressure against the front surface of the diaphragm II would tend to displace the diaphragm from its normal position. However, the water is free to enter the chamber 3| through the opening 33 and to partially collapse the member 23 (for example, to the dot and dash line position shown in the drawing). Thus, some of the air in the chamber 25 is forced into the chamber I1 through the opening I9 until the pressure on the back side of the diaphragm E|| is equal to the water pressure on the front side thereof. Accordingly, the diaphragm |I remains in its normal position and its stiffness is not altered. Consequently, the diaphragm remains free to reproduce faithfully in the form of acoustic vibrations the electrical signal impulses supplied to the voice coil 9 through suitable means (not shown) The high impedance which the passageway I9 offers to vibrations at acoustic frequencies will prevent a transfer of entrapped air between the chambers I1 and 25 during operation of the loud speaker. Also, since the aperture 33 offers a high impedance to the passage of the water therethrough at acoustic frequencies such as are set up therein by the diaphragm II, the collapsed member 23 will remain in the dot and dash line, collapsed condition. 5 From the foregoing description, it will be apparent to those skilled inthe art that I have provided an improved loud speaker having al1 the advantages heretofore enumerated. Although I have shown and described but one embodiment of my invention, it will, -no doubt, be apparent to those skilled in the art that many other modifications thereof are possible. I therefore desire that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claim.
I claim as my invention:
In signal translating apparatus, the combination of a magnetic field structure forming a first chamber and including an air gap affording communication between said first chamberv and the exterior of said field structure, a vibratory member including a voice coil disposed in said air gap. said member having fluid-tight connection with said structure and closing said air gap 01T from the exterior of said apparatus, said field structure including an opening in one wall thereof communicating with said first chamber, a collapsible member having uid-tight connection with said wall and forming a. second chamberfin communication with said opening, and a rigid casing surrounding said collapsible member in.
spaced relation thereto providing a thirdchamber around saidmember, said casing having an opening therein affording communication between said third chamber and the exterior of said apparatus.
HaRRY F. OLSON. REFERENCES CITED file of this patent:
UNITED STATES PATENTS Name Date Dearlove Aug. 11, 1908 Number Country Date France Aug. 24, 1909 Great Britain July 8, 1913 Number The following references are of record inthel Wood June 13, 1922