JPH02123900A - Variable tension transducer - Google Patents

Abstract

PURPOSE: To validly allow this device to act at an unlimited depth by providing a medium at which a variable tension transducer is set, and a Helmholtz resonator forming a liquid pressure link and a low frequency acoustic link. CONSTITUTION: An orifice 25 forms a Helmholtz resonator while acting with a hollow in use. Therefore, the compliance of the hollow decided by a shell 11 and a board 11 in use resonates while acting on the fluid mass of the orifice 25, and the size of each orifice 25 controls each Helmholtz resonator in a constant size. A transducer is impregnated to prescribed the depth in sea water in use, a driving signal with a prescribed frequency is transmitted through a cable to a driven element, and the shell element is vibrated. The two orifices 25 allow the sea water to freely intrude into the hollow of the variable tension transducer. Thus, the hollow receives the same water pressure as that of the surrounding sea water regardless of the depth of the variable tension transducer, and the variable tension transducer is nor affected by the change of the depth.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes a known variable tension system.
) relates to a variable tension quadrangle transducer suitable for use at greater depths than the transducer.

A variable tension quadrant transducer is an electromechanical transducer used to generate or detect sound in a fluid medium. An example of a variable tension quadrant juicer of the known type disclosed in European patent application no. It is designed to extend along the main axis of the shell, thereby bending the sides of the shell.

The yield strength of piezoceramics is relatively low, so it is important that the drive deposit is kept in compression or failure will occur during use.

Therefore, the depth at which the variable tension quadrangle juicer can be used is limited. This is because the greater the depth, the greater the hydraulic pressure compressing the sides of the shell, thereby elongating the major axis of the ellipse and reducing the compressive force on the driving deposit.Manufactured today Most variable tension quadrangle juicers available have an inherent service depth of only about 100 meters.

A pressure compensating device for a variable tension quadrant juicer is suggested in European patent application no. An adjustable wedge assembly is used to do this. Another example of a pressure compensator for a variable tension quadrant juicer is Canadian Patent No. 117195.
No. 0, the annular resonator is provided with an air sac communicating with the surrounding medium.

Known pressure compensators complicate the construction of variable tension quadrant transducers.

According to the invention, there is provided a shell defining a cavity and a variable tension quadrangle juicer installed in the cavity to deflect the shell, further comprising a Helmholtz resonator forming a hydrostatic link and a low frequency acoustic link. A quadrant juicer is provided.

Advantageously, the variable tension quadrangle juicer according to the invention is not sensitive to ambient pressure and therefore operates effectively at unlimited depths.

Preferably, the resonant frequency of the Helmholtz resonator is significantly different from the resonant frequency of the cavity.

In an embodiment, the resonant frequency of the Helmholtz resonator is one octave lower than the resonant frequency of the cavity.

Another advantage is that the precise separation of the resonant frequencies of the cavity and Helmholtz resonator produces a wide range of low frequency characteristics in the transducer.

In an embodiment, the shell is an elliptical cylinder with two end plates contacting the ends of the shell, and the Helmholtz resonator having an orifice formed in the plates contacting the ends of the shell. The variable-tension quadrangle juicers are each equipped with a Helmholtz resonator with one double orifice.

During use, the cavity is filled with seawater. This word yields several advantages. These include: the transducer is free to fill and drain through the orifice during deployment, reducing its weight; mechanical seals are no longer a critical design feature; it is the simplest transducer imaginable; , is.

Otherwise, during use the cavity is filled with an elastomer, such as polyurethane. The elastomer is relatively dense, increasing the Helmholtz resonance and decreasing the variable tension resonance.

However, it has a very sturdy structure.

Another advantage is that during use the cavity is filled with oil, and the use of oil facilitates operation at very high voltages.

The diaphragm above the orifice can contain oil, but differential thermal expansion creates mechanical and acoustic problems.

In all cases, the drive assembly only needs to be preloaded due to the amplitude plus safety margin. The stress due to the depth of action is
Once the cavity is filled it becomes irrelevant.

Hereinafter, special embodiments of the present invention will be described based on the drawings.

The drawings show a variable tension quadrangle juicer used to emit high power, low frequency acoustic energy under water.

The transducer has a thick-walled oval cylindrical shell 10 of aluminum sealed and slidably supported between two end plates 11. The drive extends along the main axial plane of the shell 10 and includes six cells of piezoceramic cells 13 arranged in three opposed pairs on either side of the central wedge assembly 14. It has 12 items. The deposits 12 act on opposite wall parts of the shell elements via respective cross-sectional rods 15. The cells may be made of lead zirconate titanate, for example, and are connected in parallel to receive an electrical energization signal. When energized, the deposit vibrates axially, inducing vibrations of the same frequency in the shell elements. Instead of making it from piezoelectric material, the deposit 12
can also be made from magnetostrictive materials.

The central wedge assembly comprises two outer wedge parts 17 each connected to one end of the drive element 13 and an inner inclined part 18 . The thin end of the inclined portion 18 is the screw hole 1
9, into which a bolt 20 is engaged with a washer to hold the inner wedge portion 18 and the ramped portion 17 in a predetermined relative position and to apply a generally constant compressive load to the transducer. The seal ring 22 and the spacer plate 23 are slidably installed between each end face of the shell 10 and the corresponding end plate 11, allowing the shell to vibrate freely relative to the end plate, and preventing fluid from entering. There is. edge + Hz
is held in place by two tension bolts 24 passing through it.

An orifice 25 is provided in both end plates 11. In use, the orifice interacts with the cavity to form a Helmholtz resonator. Therefore, in use Soel 10 and Kari 11
The compliance of the cavity defined by acts on the fluid mass of the orifice 25 to resonate. The size of each orifice 25 corresponds to each Helmholtz resonator of a constant size.
@Control.

Ideally, the resonant frequency of the Helmholtz resonator is well separated from the resonant 'frequency of the cavity. For example, resonance frequency 8
In the 00112 variable tension quadrangle reducer, the Helmholtz resonator is one octave lower, i.e. 40011z
(with a wavelength of 3.75 m). Typically orifice 25 has a diameter of 1011 mm. An orifice that is small compared to the wavelength has a very low radiation resistance and therefore has little effect on the transducer output. The Helmholtz resonator has a very high Q and the resonance needs to be suppressed to prevent excessive vibration of the shell when the resonance is suddenly excited.

Cushioning is accomplished by placing a cushioning material, such as rubber, in the cavity. Otherwise, ff1di is implemented by a feedback device in which the hydrophone within the cavity generates a signal that controls the drive voltage of the drive deposit 12.

If the resonant frequency of the cavity and the resonant frequency of the Helmholtz resonator are accurately separated, a wide range of low frequency characteristics will be generated in the variable tension quadrangle juicer. FIG. 4 shows the correspondence of a variable tension quadrant reducer with a Helmholtz resonator (solid line) of the present invention compared to a known variable tension quadrant reducer (dashed line).

The drive deposit 12 is electrically encapsulated with an insulating elastomer such as polyurethane.

The cavity has a number of flexible tubes 26 to aid in low frequency Helmholtz resonance. The tube is threaded for immersion to great depths. The tube 26 is a thin metal tube having an oval cross section, sealed at both ends, and filled with air. Other types of flexible tubes can also be used for this purpose, and differently shaped flexible bodies are also suitable.

In use, the transducer is immersed to the required depth in seawater and a drive signal of the required frequency is transmitted to the drive element via the cable 27, causing the shell element to vibrate. Two orifices 25 allow seawater to freely enter the cavity of the variable tension I transducer.

Therefore, regardless of the depth of the variable tension quadrant juicer, the cavity is simultaneously subject to the same water pressure as the surrounding seawater and the variable tension quadrant juicer is not affected by changes in depth.

Although some efficiency loss is to be expected in a variable tension quadrangle juicer because the shell must drive fluid on its inner and outer surfaces, its radiation properties are not significantly affected.

This variable tension quadrangle juicer embodiment operates in some respects similar to a loudspeaker bass reflex cabinet. Radiation from inside the cavity of the variable tension quadrant transducer that is out of phase with radiation from outside the shell 10 at low frequencies and "DC" sound pressures passes through the orifice 25 and responds weakly out of phase. When the orifice 25 is added to the hollow Helmholt resonator, a phase change occurs, and the resonance and internal radiation are in opposite phase and in phase with the external radiation.

In an alternative embodiment to that described above, the variable tension quadrangle juicer has a single orifice to form a Helmholtz resonator. As mentioned above, the cavities can be filled with substances such as oil or elastomers in addition to seawater.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a variable tension quadrant juicer according to the present invention, FIG. 2 is a vertical sectional view of FIG. 1, FIG. 3 is a horizontal sectional view of the variable tension quadrant juicer of FIG. 1, and FIG. FIG. 3 is a diagram showing the frequency response curve of a variable tension quadrangle reducer according to the present invention. lO...-Shell, 11... End plate, 12...
・・Drive deposit 13 ・・・Piezo ceramic cell,
14...(rust aggregate, 15...rod, 17
・−・−・Outer wedge, 18−・・Inner inclined part, 2
2...--ring, 23-...-spacer. 25--・Engraving of the hole drawing (no changes to the content) Fig. 4・ Frequency procedure Japanese official manuscript (self-proposed) November 7, 1999

Claims (11)

[Claims] 1. A variable tension transducer comprising a shell defining a cavity and a drive placed within the cavity for deflecting the shell, further comprising a Helmholtz resonator forming a hydraulic link and a low frequency acoustic link with the medium in which the variable tension transducer is placed. said variable tension transducer. 2. 2. The variable tension transducer of claim 1, wherein the resonant frequency of the Helmholtz resonator is significantly different from the resonant frequency of the cavity. 3. 3. The variable tension transducer of claim 2, wherein the resonant frequency of the Helmholtz resonator is approximately one octave lower than the resonant frequency of the cavity. 4. 4. The shell according to claim 1, wherein the shell is an elliptical cylinder and is provided with two plates contacting the ends of the shell, and the Helmholtz resonator comprises an orifice formed in the plates contacting the ends of the shell. Variable tension transducer as described. 5. 5. A variable tension transducer according to claim 1, wherein each end plate is provided with an orifice to form a Helmholtz resonator. 6. A variable tension transducer according to any preceding claim, wherein the Helmholtz resonator comprises an orifice approximately 10 mm in length. 7. A variable tension transducer according to any preceding claim, wherein the cavity is filled with seawater during use. 8. A variable tension transducer according to any preceding claim, wherein the cavity is filled with oil during use. 9. A variable tension transducer according to any preceding claim, wherein the cavity is filled with an elastomer during use. 10. A variable tension transducer according to any preceding claim, wherein the drive device is housed within an electrically insulating material. 11. A variable tension transducer according to any preceding claim, comprising one or more flexible tubes within the cavity.