US3210724A - Vibratory energy radiating system - Google Patents

Description

Oct. 5, 1965 J. B. JONES ETAL 3,210,724

VIBRATORY ENERGY RADIATING SYSTEM Filed Sept. 15, 1962 2 Sheets-Sheet 1 2E2 F/a/ INVENTORS JAMES BYRON JONES HAROLD L. Mc KAIG,JR. BY NICHOLAS MAROPIS CHARLES A. BOYD ATTORNEY Oct. 5, 1965 J. B. JONES ETAL 3,210,724

VIBRATORY ENERGY RADIATING SYSTEM Filed Sept. 13, 1962 2 Sheets-Sheet 2 srA/vo/A/a m4 v5 0572 6701? CIRCU/T 6 m Esau/170R HAMPL/F/El? H TRANSDUCER INVENTORS JAMES BYRON JONES HAROLD L. MCKA|GQJR- BY NICHOLAS MAROPIS CHARLES A. BOYD wk W ATTORNEY United States Patent VIBRATORY ENERGY RADIATING SYSTEM James Byron Jones, Harold L. McKaig, Ira, and Nicholas Maropis, West Chester, Pa., and Charles A. Boyd,

Dunn Loring, Va., assignors to Aeroprojects Incorporated, West Chester, Pa., a corporation of Pennsylvania Filed Sept. 13, 1962, Ser. No. 223,474 13 Claims. (Cl. 340-11) This invention relates to a vibratory energy radiating system. More particularly, the present invention is directed to a vibratory energy radiating system forming a part of an underwater sound system. The underwater sound system may be an echo-ranging system commonly referred to as sonar. The underwater sound system may be an underwater communication system wherein voice modulated or continuous Wave signals are converted to acoustic energy and then transmitted through water to a remote point where they are picked up by a receiver or reflected back to the system where they are received.

The basic techniques of underwater communication and echo-ranging have been devised heretofore. The present invention is directed to a structural interrelationship and/ or method wherein the vibratory energy radiating system is simple to maintain thereby improving the reliability, permitting flush mounting, and providing a controllable output.

The vibratory energy system of the present invention is particularly adapted for mounting on sea-going vessels. The present invention allows the radiating element to be supported by a stationary member below the surface level within which the member is disposed. Heretofore, the system proposed fell into two catergories. Patent 3,033,158 discloses one category of the prior art wherein the vibratory energy system is supported in the surrounding body of water by a vessel. Such devices are impractical in many circumstances and require very critical impedance matching and are diflicult to maintain since the electrical components are mostly surrounded by a body of water.

Another concept which has been proposed heretofore and adopted for submarines and the like is to physically support the vibratory energy radiator by a portion of the hull of the vessel. As pressure increases due to the depth of the body of water, the pressure on the radiating system increases. The increased pressure may shift the resonant frequency of the radiating system so that it is no longer resonant with the driving signal and operates inefiiciently. Further, clamping the radiator at a nodal point increases the losses from the radiator to the frame structure or hull of the vessel.

The radiating system of the present invention includes a force-insensitive mount, such as described in Patent No. 2,891,180, structurally interrelated with the vibrating radiator and the hull of vessel with a watertight seal therebetween. Such mounts are capable of withstanding tons of force without effective energy losses, or frequency changes, thus making them particularly useful for employment at great depths. As a result of the present invention, all electrical elements subject to maintenance are now inside the vessel.

The radiating system of the present invention also includes a vibratory energy transmission line connecting the transducer system to the vibrating radiator. This transmission line can be of such a length so as to permit location of the transducer system at an accessible site, suitable for maintenace purposes. Hence, the present invention permits one to disconnect or change transducers or to perform maintenance on all the electrical components at sea without interfering with the support of the radiating element or drydocking the vessel.

Another feature of the present invention resides in the fact that it permits or allows a direct measurement to be made of the acoustic energy being transmitted into the water by means of a standing wave ratio technique. This feature, in addition to providing direct monitoring of acoustic signal strength, allow operation of the radiating element at a power level just below the cavitation limit existing at the particular depth. The maximum power that can be radiated into water varies with the depth of the radiating element. At sea level, approximately 0.2 watt per square centimeter is the maximum power that can be handled by a radiating element without causing cavitation. When a radiating element produces cavitation, it no longer transmits a signal suitable for echoranging or underwater communication.

In accordance with the systems proposed heretofore, there was no satisfactory way by which one could ascertain the maximum power level which could be utilized. As a result of the present invention, a vibratory energy system is provided which automatically permits the radiating element to operate at power levels just below the cavitation level at any depth. As the operating power level reaches the threshold of the level which will result in cavitation, the operating power level is reduced. Such a system is desirable because variables such as temperature and dissolved gases in the water preclude empirical tables to be formulated so that one may know the maximum power level which may be transmitted by the system merely by ascertaining the depth of the system.

It is an object of the present invention to provide a novel vibratory energy system.

It is another object of the present invention to provide a novel vibratory energy system and method adapted to be associated with a support below liquid level for propagating acoustic energy through water.

It is another object of the present invention to provide a novel vibratory energy system and method which simplifies maintenance and improves reliability.

It is another object of the present invention to provide a vibratory energy system adapted to be coupled to a remote vibratory energy transducer.

It is another object of the present invention to provide a novel vibratory energy system adapted to conform to curvatures in a support vessel.

It is still another object of the present invention to provide a vibratory energy system and method which may be operated at optimum power levels regardless of changes in depth or temperature or gas content of a surrounding body of Water.

It is still another object of the present invention to provide a novel vibratory energy system and method which minimizes energy losses to a frame support and frequency changes in a radiating element as a result of changes in depth of the element with respect to a surrounding body of water.

It is still another object of the present invention to provide a novel vibratory energy system and acoustical method wherein all components except for a radiating element may be disposed within the hull of a vessel.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a sectional view taken through a portion of a hull of a vessel and illustrating the vibratory energy system in accordance with one embodiment of the present invention.

FIGURE 2 is a view similar to FIGURE 1, but illustrating another embodiment using a vibratory energy transmission line in accordance with the present invention.

FIGURE 2a is a partial sectional view illustrating an alternative coupling between two of the components illus trated in FIGURE 2.

FIGURE 3 is a schematic illustration of circuitry in accordance with the system illustrated in FIGURE 2.

FIGURE 4 is a view similar to FIGURE 2, but illustrating another embodiment of the present invention.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIGURE 1 a vibratory energy radiating system designated generally as 10.

The system is is illustrated as being supported by a portion of a wall 12. Wall 12 may be a portion of a hull of a vessel or may be a fixed wall adapted to be disposed below water level. Wall 12 is provided with a well 14. Well 14 is inwardly directed and terminates in a radially outwardly directed flange 16. The flange 16 may be directed radially inwardly if desired. A radiating element 18 is disposed within the well 14. The acoustic radiating surface 20 of the element 18 conforms generally to the outermost surface of the wall 12.

The element 18 is merely illustrative of any one of a wide variety of radiating elements. The details of the element 18, per se, form no part of the present invention since any one of a wide variety of radiating element designs may be utilized with the present invention. The element 18 is provided with a force-insensitive mount 28 adapted to be supported by flange 16 with a watertight seal therebetween.

The force-insensitive mount 20 includes a sleeve 24 having a length of one-half wavelength at the operating frequency and material from which the sleeve is made, or whole number multiples thereof. One end 26 of the sleeve 24 is rigidly attached to the element 18 at an antinode in a manner which provides a watertight seal therebetween. The other end of the sleeve 24 is unattached. The sleeve 24 is provided with a radially outwardly di rected flange 28.

The sleeve 24 is made from metal such as steel, stain less steel, monel or other suitable low hysteresis material. Since the end of the sleeve 24 remote from end 26 is unattached, a true node will develop in sleeve 24 at flange 28, which is one-quarter wavelength distant from the unattached end of sleeve 24.

The flange 28 is juxtaposed to the flange 16 having a re cessed deformable seal 30. A ring 32 overlies flange 28 and has a portion juxtaposed to the radially outwardly disposed portion of flange 16. A plurality of bolts 34 extend through ring 32 and flange 16 to support the element 18 with respect to the wall 12 in a watertight manner. If desired, the flange 28 may be welded or brazed to the flange 16.

A coupler 36 is removably connected to element 18 by means of a threaded stud 38. Stud 38 is threadedly engaged with threads in a bore in the element 18. In order to maintain good impedance characteristics at the joint, a very thin ring of aluminum or other similar material 40 is disposed between the juxtaposed surfaces on the coupler 36 and element 18. Such material is compressed and in intimate contact with the end faces on the coupler 36 and element 18. Such juxtaposed end faces have substantially identical areas.

The end of the coupler 36 remote from the element 18 is fixedly joined to a vibratory energy generator. Such generator includes a transducer 42. The transducer 42 may be of the magnetostrictive type and of conventional construction comprising a laminated core of nickel, nickeliron alloy, Permendur (an iron-cobalt alloy), Alfenol (an aluminum-iron alloy), or other magnetostrictive material. The transducer may also be of the electrostrictive type wherein such materials as barium titanate, lead-zirconatetitanate, etc., are incorporated into compressed stacks of washer-like geometries as well as other types of assemblies. The transducer 42 is properly dimensioned to insure axial resonance with the frequency of alternating current applied thereto by coil 44 so as to cause it to decrease or increase in length according to its coefiicient of magnetostriction. The transducer 42 is provided with a polarizing coil 46. The desirability of magnetically polarizing the magnetostrictive transducer 42 by means of coil 46 in order for the metal laminations in the transducer to efiiciently convert the applied RF energy from excitation coil 44 into elastic vibratory energy will be readily understood by those skilled in the art.

It will be appreciated by those skilled in the art that other known types of transducers may be substituted for the magnetostrictive transducer 42. For example, electrostrictive or piezoelectric transducers, made of barium titanate, quartz crystals, lead titanate, lead zirconate, etc., may be utilized as mentioned above.

When an acoustic wave is being transmitted by the element 18, the transducer 42 will be coupled to a driver comprising an oscillator and an amplifier. When receiving a signal, the transducer 42 will be coupled to a receiver which in turn will be coupled to an audio output and a range indicator. Such components are not illustrated since the same are conventional and well known to those skilled in the art and need not be described in detail herein.

As illustrated in FIGURE 1, the element 18 is supported by the wall 12 in a waterproof manner by the sleeve 24. All other components requiring maintenance or adjustment are internal with respect to the wall 12. If the wall 12 is part of the hull of a submarine, the force-insensitive mount prevents loss of acoustic energy to the hull and also minimizes shifts in resonant frequency of the radiating system due to changes in depth. That is, tons of force may be applied on the radiating system without a change in resonant frequency characteristics thereof.

In FIGURE 2, there is disclosed a system 10' which is identical with system 10 except as will be made clear hereinafter. In system 10, the radiating element 18 is supported in a well on one surface of the wall 12 as described above. However, the transducer coupling system is supported at a point remote from element 18.

The coupler 36 is identical with coupler 36 except that it may be provided with an exponentially tapered portion at the lower end, remote from the end which is metallurgically bonded to the transducer 42'. The coupler 36 is supported from the wall 21 by a force-insensitive mount 33. Mount 33 is identical with the forceinsensitive mount 20. Wall 21 may be a rack-like panel hull, a bulkhead, etc. The coupler 36 is coupled to the radiating element 18 by an acoustic transmission line 19.

The acoustic transmission line 19 is preferably made from a low attenuation metal such as monel, aluminum bronze, etc. It need not be particularly thin or narrow of wire-like; its maximum cross sectional dimension is preferably not much more than one-quarter wavelength in the material of which it is made at the frequency of operation. Such acoustical transmission lines can be considered flexible, although bendable or formable is a more precise description. Such acoustical transmission lines can be of substantial length with no immediately evident limits, although due to hysteresis losses in materials, the length of such transmission lines should probably be less than around 15 to 25 feet. The formability of the line 19 enables the same to be bent, thereby circumventing obstructions between walls 12 and 21. For maximum power transmission, the radius of any curvilinear section for the transmission line 19 should be equal to or greater than M4. A minimum bend radius at which attenuation occurs without phase change is M27. The theoretical analysis and experimental data on the application of vibratory energy through elongated acoustical transmission lines is set forth in greater detail in co-pending patent application Serial No. 120,233 filed on June 28, 1961, by Dennison Bancroft et al., and entitled Apparatus and Method for Introducing High Levels of Vibratory Energy to a Work Area now Patent No. 3,166,840. The disclosure in said application is incorporated herein by reference.

For a good impedance match, one end of the transmission line 19 is metallurgically joined to the free end of the coupler 36. At this joint, the cross sectional areas of the transmission line 19 and the end face of the coupler 36' should be identical if they are of the same material. Likewise, the other end of the transmission line 19 is preferably metallurgically joined to the radiating element 18 with a good impedance match. If desired, the lower end of the transmission line 19 may be removably coupled to the radiating element 18 in the manner illustrated in FIGURE 2a.

In FIGURE 3, there is a schematic illustration of circuitry which may be utilized in conjunction with the system to facilitate automatic operation of the system so that the vibratory energy power level is just below the cavitation level regardless of the depth of the system 10. Such circuitry includes an oscillator 84 coupled to an amplifier 86 which in turn is coupled to the transducer 42'. When high power ultrasonic waves are generated in a liquid, cold boiling (cavitation) results. The molecules in the liquid become intensely agitated thereby continuously forming small vapor bubbles which implode, thereby producing tremendous local pressures.

The power level of energy being transmitted by the radiating element 18 must preferably be below the level which results in cavitation. At sea level, the maximum power that can be radiated is approximately 0.2 watts per square centimeter. As the depth of the body of water increases, the maximum power level which the element 18 may be operated at varies with the depth, temperature of the body of liquid, dissolved gases in the liquid, etc. In order to permit the radiating element 18 to operate just below the threshold of cavitation, a standing wave detector circuit 96 is coupled between the amplifier 86 and the transmission line 19.

In co-pending application, Serial No. 66,642 filed on November 1, 1960, by Dennison Bancroft et al., and entitled, fMethodand Apparatus for Measurement of Acoustic Power Transmission and Impedance, there is disclosed an ,embodiment of the standing wave detector circuit 96. The disclosure in the last-mentioned application is incorporated herein by reference.

As described in greater detail in the last-mentioned application, the failure of the energy radiating element to radiate all of its vibratory energy to the surrounding environment, such as when cavitation occurs, causes a wave to be reflected back along the element producing standing waves therein. By coupling two transducers to the transmission line at known spaced points therealong, such as a whole number multiple of one-quarter wavelengths, an electrical signal proportional to the instantaneous displacement of the particle to which the transducers are attached may be generated and coupled together and fed to a circuit which indicates the acoustic power being transmitted by the line. As the threshold of cavitation is approached, the acoustic power being transmitted by the radiating element to the surrounding body of liquid will decrease. Such decrease will be detected by the transducers of circuit 96, which in turn will reduce the power coupled to the transducer 42' through amplifier 86. Hence, the radiating element 18 will always be automatically radiating at its maximum power level without causing cavitation in the surrounding body of liquid.

In FIGURE 4, there is illustrated another embodiment of the present invention, with the system designated generally as 10". The system 10 is identical with the system 10' except as will be made clear hereinafter. In the system 10", a plurality of radiating elements 50, 52, 54, 56 and 58 are supported from a wall 48 in a watertight manner. The wall 48 may be the hull of a vessel. Each of the radiating elements 50-58 is identical with element 18 and is provided with a force-insensitive mount in the same manner as described above.

Each of the elements 58 is coupled to a single coupler 70 by a formable acoustic transmission line identical with transmission line 19.

Hence, element 50 is coupled to coupler 70 by trans mission line 60. Element 52 is coupled to coupler 70 by transmission line 62. Element 54 is coupled to coupler 70 by transmission line 64. Element 56 is coupled to coupler 70 by transmission line 66. :Element 58 is coupled to coupler 70 by transmission line 68.

The area of the end face of the coupler 70 is substantially equal to the sum of the cross sectional areas of the transmission lines 60-68. The coupler is supported from a wall 74 by a low loss mount or forceinsensitive mount 72. The wall 74 may be a bulkhead, a false hull, etc. The distance between walls 48 and 74 may be any distance up to approximately twenty feet.

The low loss mount 72 is identical with the mount 20. The flange on the mount 72 may be supported from the wall 74 by an overlying ring 76 which is removably se cured to the wall 74 by a plurality of bolts 78. The end of coupler 70 remote from the transmission lines is metallurgically bonded to a transducer 80. Transducer 80 is identical with transducer 42.

The system 10" is particularly adapted for use in a vessel wherein it is desired to have a pressure chamber between the walls 48 and 74. The bendability of the transmission lines 60-68 facilitates the circumvention of any supporting structure or other instrumentation within the pressure chamber. The utilization of a single transducer and coupler for the various radiating elements 50-58 materially reduces the maintenance required for the system 10".

In an array such as is shown in FIGURE 4, each transmission line 60, 62, 64, 66 and 68 shall have an overall length between the end of the coupler 70 to which it is attached and the end of the radiating elements 50, 52, 54, 56 and *58 to which it is also attached equal to an even number of one-quarter wavelengths in the materials from which the transmission lines are made at the frequency of operation. Said equal multiples of one-quarter wavelengths shall be understood to be arrived at by including proper correction for curvatures as described previously.

Hence, it will be seen that the present invention is directed to a vibratory energy system and method wherein the system is automatically operable at its maximum power level without causing cavitation. All parts subject to maintenance except for the radiating elements are internal with respect to the vessel thereby simplifying maintenance and improving reliability. Simplified maintenance and improved reliability are particularly important when the vibratory energy system is incorporated in a submarine. The force-insensitive mounts for the radiating elements enable the system to operate more efficiently at varying depths, which also is of particular significance when the system is associated with a submarine. The present invention may also be utilized with fishing vessels, ocean liners, naval vessels, etc. When the system of the present invention is associated with a vessel, the vessel need not be drydocked when the system malfunctions, since all elements of the system except for the radiating element are internal of the vessel.

As used hereinafter, the mount 20 may be referred to as a force-insensitive or low loss mount. The words flexible transmission line are to be interpreted as referring to an acoustic transmission line which is capable of being bent or geometrically arranged and will remain in any pre-set or arranged disposition.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

It is claimed:

1. Apparatus comprising a vessel, said vessel having a wall adapted to be below the surface level of a body of liquid, an acoustic radiating element, a force-insensitive mount, said element being supported on one side of said wall by said mount, a watertight seal between said element and said mount, means on the other side of said wall for supporting said mount, a watertight seal between said means and mount, and means for generating vibratory energy, said last-mentioned means being on the other side of said wall from said radiating element and coupled to said radiating element.

2. Apparatus in accoradnce with claim 1 wherein said generating means includes a vibratory energy generator, and a flexible acoustic transmission line coupling said generator to said element.

3. Apparatus in accordance with claim 1 wherein said vessel is a submarine, and said wall being a part of the hull of said submarine.

4. Apparatus comprising a wall, a plurality of acoustic transmitters, an acoustically resonant force-insensitive mount supporting each transmitter on one side of said wall, means for generating vibratory energy on the other side of said wall, and a separate flexible acoustic transmission line coupling each transmitter to said means for generating vibratory energy.

5. Apparatus in accordance with claim 4 wherein said transmission lines are capable of being readily bent to facilitate circumvention of obstructions between said transmitters and said means for generating vibratory energy.

6. Apparatus in accordance with claim 4 including a second wall spaced from said first wall, a force-insensitive mount, said means for generating vibratory energy being supported from said second wall by said forceinsensitive mount.

7. In an underwater sound transmission system comprising a wall adapted to be disposed below surface level in a body of liquid, a plurality of acoustic radiating elements, a mount for each element, each mount supporting its element from said wall with all elements being on one side side of said wall for contact with a body of liquid, a waterproof joint between each mount and said wall, a single vibratory energy generating means, means supporting said vibratory enery generating means at a point remote from said wall, a plurality of acoustic transmission lines, each line having one end removably secured to one of said elements and another end coupled to said vibratory energy generating means.

3. Apparatus in accordance with claim 7 wherein the longitudinal axes of said lines are angled with respect to each other, each transmission line being resonant with an antinode occurring at each of its ends.

9. Apparatus in accordance with claim 7 wherein said vibratory energy generating means includes a single coupler, the other end of each transmission line being coupled to one end of said coupler.

10. Apparatus in accordance with claim 7 wherein said elements are disposed within wells on said one side of said wall.

11. Apparatus in accordance with claim 7 wherein said wall is the hull of a vessel.

7 12. Apparatus comprising a vessel, said vessel having a wall adapted to be below surface level of a body of liquid, an acoustic radiating element, a mount, said element being supported on one side of said wall by said mount, a watertight seal between said element and said mount, means on the other side of said wall for supporting said mount, a watertight seal between said support means and mount, and means for generating vibratory energy, said last-mentioned means being on the other side of said wall from said radiating element and coupled to said radiating element, said last-mentioned means including a vibratory energy generator, and a flexible acoustic transmission line coupling said generator to said element.

13. In an underwater sound transmission system comprising a wall adapted to be disposed below surface level in a body of liquid, a plurality of acoustic radiating elements, a force-insensitive mount for each element, each mount supporting its element from said wall with all elements being on one side of said wall for contact with a body of liquid, a waterprool joint between each mount and said wall, a single vibratory energy generating means, means supporting said vibratory energy generating means at a point remote from said wall, a plurality of acoustic transmission lines, each line having one end removably secured to one of said elements and another end coupled to said vibratory energy generating means.

References Cited by the Examiner UNITED STATES PATENTS 1,277,562 9/18 Fessenden 340-6 1,380,869 6/21 Fay.

1,715,831 6/29 Hahnemann 181-0.51 2,435,595 2/48 Mason 340-10 2,714,186 7/55 Henrich 340-11 X 3,029,766 4/62 Jones 310-26 X 3,087,138 4/63 Toulis 340-5 3,121,212 2/64 Weber et al. 340-12 3,129,403 4/64 Harter 340-12 3,142,033 6/64 Flowers et al 340-3 LEWIS H. MYERS, Primary Examiner.

CHESTER L. J'USTUS, Examiner.

Claims (1)

1. APPARATUS COMPRISING A VESSEL, SAID VESSEL HAVING A WALL ADAPTED TO BE BELOW THE SURFACE LEVEL OF A BODY OF LIQUID, AN ACOUSTIC RADIATING ELEMENT, A FORCE-INTENSITIVE MOUNT, SAID ELEMENT BEING SUPPORTED ON ONE SIDE OF SAID WALL BY SAID MOUNT, A WATERTIGHT SEAL BETWEEN SAID ELEMENT AND SAID MOUNT, MEANS ON THE OTHER SIDE OF SAID WALL FOR SUPPORTING SAID MOUNT, A WATERTIGHT SEAL BETWEEN SAID MEANS AND MOUNT, AND MEANS FOR GENERATING VIBRATORY ENERGY, SAID LAST-MENTIONED MEANS BEING ON THE

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