US2051866A - Hydrophone - Google Patents

Description

W. KUNZE Aug. 25, 1936.

HYDROPHONE Filed June 24, 1929 /NVENTOR W/fly Kunze y gJM M /1/3 ATTORNEY Patented Aug. 25, 1936 UNITED STATES PATENT OFFICE HYDROPHONE Application June 24, 1929, Serial No. 373,466

r In Germany July 16, 1928 '7 Claims. (Cl. 177-386) The present invention relates to means for detecting sound waves, and more particularly to such means for detecting sound waves in water, though the invention may have application in other media. In particular, it relates to means for the distortionless reception and translation of sound waves'from acoustic to electrical energy, or even from acoustic to mechanical or to acoustic energy.

Apparatus designed for the same purpose in the prior art first used ametallic diaphragm, but since metallic diaphragms are, for the most part, resonant and not aperiodic, they had a resonance peak which intensified out of proportion the sound at the resonance frequency to the sounds at other frequencies. Besides this, the resonant metallic diaphragm responded at its resonance frequency to shocks and blows, not only distorting the character of the noise-if noise was being listened to, as is sometimes done in detecting the presence of other ships, by listening to their propeller noise but also seriously interfering with the detection of resonant signals.

Rubber diaphragm receivers have been used to overcome'the difliculties enumerated above, with remarkably good results.

Also, metallic diaphragms with rubber cushions mounted on the back are used, but apparently while achieving fair results in some cases, they are not as a rule sufficiently aperiodic to provide a suitable receiver. While purely rubber diaphragms have given good results, it seems that the sensitivity of such receivers is not as great as that of receivers using an all metallic diaphragm.

In my inventiomthesound receiver is not only substantially aperiodic, as the purely rubber receiver, but appears to be more sensitive, reliable, durable and in general much better fitted for the work for which it is principally employed,--as a submarine hydrophone,

The purposes and features of the invention will be more clearly understood by a consideration of the following description of the embodiment of the invention, together with the drawings, in which Figure 1 shows a section view of the receiver, and

Figures 2, 3 and 4 show modifications of the inwention.

In Figure 1, represents a casing of the sound eceiver in which there is an electromagnet formed iy the cylindrical shell 2, the core 3 and the coil III. A cylindrical air gap 4 is formed between the me 3 and the shell 2. ,In this air gap is a movable coil 5, which is made fast by an end piece 4| directly to the diaphragm by means of the bolt 8 and nut 42. The diaphragm and coil member is arranged close to the electromagnet so that the coil support may be made as small and light as 5 possible. The core 3 at its end is cupped out at 43 so that the coil 5 may be crowded even closer to its field of useful operation.

In Figure 1, the casing I has an opening 44 and the side wall of the casing is provided with an inwardly extending flange 45, against the inner surface of which a pad of soft rubber H1, or like material, is pressed. The diaphragm, which presses against the ring III, is composed of two. metallic discs 6 and l fastened together at the 5 center by the bolt 8 and nut 42, and has between the discs a soft rubber disc 9, or disc of other suitable material, which extends throughout the whole inner surface of the metallic discs.

On the inner side of the disc I is another ring ll, similar to the ring Ill in structure and size and material, but this may be chosen of such thickness as to space the diaphragm the desired distance from the face of the electromagnet. The

' whole system, as shown in Figure 1, is held in place by means of the cylindrical shell 2, which may be pressed against the ring H by means of an end cap 46 threading in the case I. Between the case and the flange of the cap 46 may be inserted a gasket 41 of suitable material to keep the device watertight. The end cap 46 serves also to obtain the proper pressure desired upon the clamping rings l0 and II, holding the diaphragm in place.

In Figure 2, the electromagnetic system I3 is fixed in the receiving casing l2. The casing 2 has a flange 48 against which the ring II is pressed. The diaphragm in this case is composed of three membranes l4, l5 and I6, between which are rubber discs l1 and Ill. The diaphragm is held together at its center by means of the bolt l9 and nuts 49, 50 and 5|, the nuts 49 and 50 fixing firmly the structure with the central membrane I5. The diaphragm is clamped in place from the front by means of the rubber ring II), the clamping ring 22 and the externally threaded ring 2|, which exerts a pressure against the ring 22. The desired pressure on the diaphragm edge is obtained by tightening to the desired degree the ring 2|.

In Figure 3, the outer membrane 23 of the diaphragm is a part of the casing 24. Behind this outer membrane is a rubber disc 25 and the second membrane 26, which is clamped to the first by means of the bolt 21 and nut 28.' The desired it will be noted that the diaphragm operates as .a piston and that the energy picked up by thediaphragm is not first used in compressing the .rubber disc, as in the case of a purely rubber diaphragm. In a purely rubber diaphrag before the whole diaphragm takes up a proper oscillation, some of the energy is first used in compressing the 'rubber nearest the'sound transmitting medium. In the present invention, the diaphragm moves as a whole and is then damped by the rubber between the two metallic membranes to preserve the true characteristic of the note.

The remarkable characteristic of the present diaphragm comes from the fact that, even 2., though aperiodic, it is sensitive to feeble vibrations, that the damping is uniform throughout the'whole diaphragm and less'for feeble vibrations than for large vibrations, that though aperiodic it is rigid, and that its mounting be- :10 tween very yielding clamping rings allows it to move as a real piston diaphragm and still further obtain true aperiodic characteristics without decrease in efficiency of reception.

Besides the above feature, it will be noted that the damping caused by the rubber disc may be adjustable by loose or tight clamping of the membranes.

Further, the system is so constructed that the vibrations are perpendicular to the membrane 4 surface throughout and, therefore, the damping is uniform throughout the entire diaphragm area and bending is also avoided. This relieves edge friction or jamming and consequent distortion of the diaphragm. In the present construction,

the diaphragm is very easily centered and the whole device assembled, since the diaphragm is one unit and is made to fit exactly in the casing and is centered by the casing walls.

It should also be pointed out that the sensitivity to vibrations can be controlled and varied by properly dimensioning the size, shape, thickness and materials used for the diaphragm within suitable limits.

While the description above describes the invention in some of its modifications, it will be understood that the invention may take other .forms. ,Instead.,of using,,a coil for translating the sound wave to electrical energy, other means may be used, such as a microphone, or other reslstance varying device, or purely electromagnetic means. It will also be noted that other materials than rubber may be used, provided they have the same characteristics for the pure pose here specified, and that the diaphragm may take other forms orconstructions, provided it fulfills the same objects and purposes as the present invention.

Having now described my invention, I claim: 1. A sound receiver comprising a diaphragm composed of a plurality of membranes posttioned parallel, having the exterior membranes of metal material and at least one of theinterior membranes of softer yielding material, and means for uniting said membranes together at their centers to form a unitary acting diaphragm, electrodynamic translating means mounted directly on said diaphragm and having a fixed course of oscillation, a casing, said diaphragm fitting in said casing and having free motion only normally to the surface of said diaphragm and means for yieldingly holding the edges of said diaphragm.

2. In a sound receiving structure, a metallic casing having a diaphragm formed as a part thereof, acoustic damping means positioned within the casing behind the diaphragm, a second diaphragm fitting within the casing positioned on the other side of said damping means,

means holding said two diaphragms together and means clamping the edge of the inner diaphragm to the casing.

3. In a sound receiving structure, a metallic casing having a diaphragm formed as a part thereof, a soft rubberdisc filling the portion of the casing directly behind the diaphragm, a second diaphragm positioned on the other side of said disc, means pressing said two diaphragms together andmeans clamping the edge of the inner diaphragm to the casing.

4. In a sound receiving structure, a metallic casing having a diaphragm formed as a part thereof, a soft rubber disc filling the portion of the casing directly behind the diahragm, a second diaphragm positioned on the other side of said disc, a bolt and nut positioned to hold the diaphragms together under tension at their center and'means clamping the edge of the inner diaphragm to the casing.

5. In a sound receiver, a casing, an aperiodic fiat diaphragm composed of' membranes positioned parallel to one another and at one end 01 said casing comprising an exterior membrane oi metallic material, an interior membrane of the same material and a third membrane betweer the two of yielding material abutting agains1 the interior faces of the other membranes, mean: passing through the center of the three membranes and clamping them firmly together ant means bearing upon the periphery of the oute: side of the inner membrane at the wall of sail casing to clamp the membrane firmly against thl yielding material in the casing.

6. A sound receiver comprising a cylindrica casing having an inwardly extending flange a one end of the casing, a diaphragm composer of a plurality of membranes positioned paralle to one another and abutting the said flange in wardly of the casing, said diaphragm compose of two metallic discs and a yielding disc there between, means for clamping said-disc togethe at their centers and clamping means app d a the periphery of the disc against the flange be hind said discs. I

7. A sound receiver comprising a cyllndrics casingwith a flange formed at one end extend ing inwardly, ,a diaphragm composed of two dis elements and a yielding element therebetwee positioned inside said casing on the inner sid of said flange, yielding means positioned on bot external sides of said discs at the edges there and means for clamping said diaphragm firm] in said casing.

WILLY KUNZE.

Images