Communications – electrical: acoustic wave systems and devices – Signal transducers
Patent
1992-06-01
1994-05-24
Eldred, J. Woodrow
Communications, electrical: acoustic wave systems and devices
Signal transducers
367162, 367176, 310334, H04R 1700
Patent
active
053155653
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase of PCT/EP90/01882 filed Nov. 9, 1990 and based, in turn, upon national applications P 39 37 365.7 filed Nov. 9, 1989 and P 40 20 881.8 filed Jun. 29, 1990 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a resonance oscillator including an active oscillator part which is in contact with a passive, comparatively longer oscillator part, thereby forming a couple oscillator, the passive oscillator part basically determining the resonant frequency and being formed by a liquid column contained in a resonance container or by a solid column the length of which can be varied continuously by means of a movable part in order to change the resonant frequency, the resonance container communicating with an equalizing container which receives and returns, respectively, the liquid being displaced from and drawn into the resonance container, respectively when the movable part is moved.
BACKGROUND OF THE INVENTION
A resonance oscillator of this type is already known from FR-A-374 934. The known resonance oscillator is designed for operations in sea water. As the resonant chamber, it has a cylindrical body which is open on one end and is connected with the surrounding region via openings formed in its holder. The resonant chamber is not filled with a sealed-off liquid volume. Rather, it is filled with the same liquid that is to be sounded. Further, this prior art reference discloses as an acoustic pick-up a cylindrical part attached inside onto the ship's wall, the base thereof, via an outside thread provided at the base, being screwable to an inside thread of the cylindrical pick-up. Also in this case, the resonant chamber is connected with the ambient sea water through an opening in the ship's wall and does not form a sealed-off liquid volume. Thus, in the prior art the density values of sea water and the sound velocity in sea water are effects which have to be accepted from the beginning. Moreover, resonance adaptation takes place only on the side of the receiver while on the side of the transmitter no change in the length of the resonant chamber is provided at all. The application range therefore is restricted.
OBJECT OF THE INVENTION
The object of the invention is to provide a transmitter having a resonance oscillator of the type mentioned initially a whose resonant frequency can be varied continuously and with a high effectiveness of the resonance oscillator.
SUMMARY OF THE INVENTION
The resonance oscillator according to the invention by which this object is achieved comprises a part for setting the resonant frequency in the form of a piston sliding axially in the resonance container, the equalizing container being sealed with respect to the surrounding region by means of a counterpressure diaphragm which enables a change in volume corresponding to the axial displacement of the piston.
As a consequence, in this case the resonance container and the equalizing container form a sealed-off liquid volume. Thereby the filler liquid can be selected freely and independently of the liquid conveying the sound. For example, the liquid column in this structure may be formed by a liquid of a highest possible density, a highest possible sound velocity and a highest possible characteristic acoustic impedance (the product of density and sound velocity). An example therefor is a silocone oil filling. Silicone oil has a low sound absorption coefficient so that the losses in the filler liquid are small. Also, a great latitude for the adaptation to the sound-wave length is obtained.
For this purpose, an axially sliding piston is provided in the resonance container, which makes the adjustability particularly simple. Since, however, the liquid volume in the resonance container and the equalizing container is a fixed volume, additional arrangements for the free sliding movement of the piston have to be made. This is effected with the aid of the counterpressure diaphragm which seals the equalizing container on the side
REFERENCES:
patent: 852647 (1907-05-01), Blake
patent: 2490452 (1949-12-01), Mason
patent: 3219970 (1965-11-01), Sims
patent: 3743446 (1973-07-01), Mandroian
patent: 4671379 (1987-06-01), Kennedy et al.
Dubno Herbert
Eldred J. Woodrow
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